Name: using caco-2 cells to study lipid transport by the intestine
Uploaded: 2015-08-20T14:00:00.000+00:00
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Description: Watch this Scientific Journal Video about Using Caco-2 Cells to Study Lipid Transport by the Intestine at JoVE.com

This work was supported by the Seed Grant Award from California Northstate University College of Pharmacy (to AMN). The authors would like to thank California Northstate University College of Pharmacy for covering the publication cost of this article, and George Talbott for his help in editing this manuscript.

CACO-2 hücrelerinin 1. Bakım <ol><li> Düzenli doku kültürü yemekleri kullanma <ol><li> (FBS, 37 ° C su banyosu içinde şişe yerleştirerek bir dondurulmuş şişesinden alınan Caco-2 hücreleri çözülme ve hemen önceden ısıtılmış büyüme ortamı (% 15 fetal bovin serumu, 10 ml içeren 10 cm&#39;lik bir doku kültürü kabı eklemek ) Dulbecco Modifiye Edilmiş Eagle Ortamı (DMEM)) &#39;de. <ol><li> Caco-2 hücreleri% 50-70 kaynaşmaya ulaştığı zaman, onları 1 bölünmüş: müstakil kadar 37 ° C&#39;de% 0.05 tripsin / 0.53 mM etilendiamintetraasetik asit (EDTA), 3 ml ile hücrelerin inkübe edilmesi ile 6 (15 dk) . Hücre topaklaşmayı önlemek yumuşak pipetleme hücreler karıştırmak için birkaç kez. Önceden ısıtılmış büyüme ortamı 10 ml içeren 10 cm&#39;lik bir doku kültürü kabı tripsinize edilmiş hücre 0.5 ml ilave edilir. </li></ol></li><li> Yavaşça bir sola ve sağa yön ardından ileri ve geri yönde yemeklere birkaç kez sallayın. Yemekler dönen kaçınıngibi eşit olmayan bir hücre dispersiyonu ile sonuçlanabilir. </li><li> % 5 CO 2 ile birlikte 37 ° C inkübatör düz bir yüzeye yerleştirin yemekleri. Eğimli yüzeyler de eşit olmayan bir hücre dispersiyonu ile sonuçlanabilir. </li><li> Inkübasyon başladıktan sonra büyüme Ortam bir gün değiştirin. </li><li> Hücreleri izlemek ve izdiham ulaşmak günü kaydedin. Hücreler bölünür günden itibaren izdiham ulaşmak için yaklaşık 1 hafta sürer. </li><li> Hücreler izdiham ulaşmadan haftada iki kez büyüme ortamı değiştirin. Hücreler izdiham ulaştığınızda, her gün büyüme ortamı değiştirmek. Hücreler 7-günler sonrası konfluent olduktan sonra, günlük büyüme ortamı değiştirmek. Not: 13-günler sonrası konfluent (Şekil 1) olduğunda hücreler deneyler için hazırız. Hücreler sonunda lipoproteinlerin üreten daha az etkili hale gelecektir yana, 8 sonrası birleşik 13-17-gün arasında olan hücreleri kullanır. Deney yapmak için nasıl adım 3&#39;e gidin.</li></ol></li><li> Geçirgen zar sistemi kullanılarak <ol><li> Aşama 1.1.1.1 tarif edildiği gibi geçirgen zar ekinde Caco-2 hücreleri, tohum. Yukarıda. Onların hücre büyümesi (iyileşme dönemi) normalde yavaş çünkü dondurulmuş şişesinden alınan hücreler kullanılarak kaçının. Kısaca, önceden ısıtılmış büyüme ortamı 10 ml içeren apikal (üst bölmesi) tripsinize edilmiş hücre 0.5 ml ilave ediniz. Ayrıca, bazolateral bölme (alt bölmesi) önceden ısıtılmış büyüme ortamı 10 ml. Not: En iyi uygulama için, bazolateral odasına ilk ve daha sonra apikal odasına büyüme ortamı ekleyin. Eski medya çıkartırken, apikal medya önünde bazolateral ortamı çıkarın. Bu membran rüptürü olabilir polikarbonat membran alay kaçının. </li><li> Nedeniyle polikarbonat zardan kötü hücre görünürlüğe, benzer yoğunlukta düzenli bir doku kültürü çanak Caco-2 hücreleri tohum ve hücre izdiham yargılamak için bu yemeğin kullanın. </li><li> S izleyinTeps&#39;in 1.1.2-1.1.6, yukarıda. </li></ol></li></ol> 2. Gene overekspresyonu <ol><li> Normal transfeksiyon yaklaşımı kullanarak <ol><li> Yukarıda 1.1.1.1.-1.1.4 de tarif edildiği gibi bir doku kültürü tabağına Caco-2 hücreleri, tohum. Not: hücreler yaklaşık% 40-50 konfluent olduğunda, transfekte hazırdır. </li><li> Mikrosantrifüj tüpü içinde düşük serum ortamında 472 ul transfeksiyon reaktifi 67 ul ekle. Tüp duvar ile sulandırılmamış transfeksiyon reaktif temasından kaçının. </li><li> PLL3.7 23 ug transfeksiyon reaktifi / düşük serum ortamında karışımına, yeşil flüoresan protein (EGFP) 9 Geliştirilmiş ekleyin. </li><li> Oda sıcaklığında 20 dakika süreyle inkübe karışımı. </li><li> DMEM içinde% 10 FBS 8 ml Caco-2 hücreleri, büyüme ortamı değiştirin. </li><li> Damla damla çanak DNA / transfeksiyon reaktif / azaltılmış serum medya karışımı ekleyin. </li><li> Yavaşça ileri ve ba yemekleri birkaç kez sallayınBir sola ve sağa yönde takip ckward yön. </li><li> 37 ° C inkübatör çanak yerleştirin. </li><li> Kuluçka başladıktan sonra büyüme ortamı 10 ml her gün bir çanak ortamı değiştirin. </li><li> Gen ifadesini izleyin. <ol><li> 4 &#39;, 6-diamidino-2-fenilindol (DAPI) ile boyanmamış olan gen ekspresyonunu izlemek. Floresan mikroskobu kullanılarak, yeşil hücrelerin yüzde belirler. yüzde transfeksiyon verimini gösterir. </li><li> DAPI boyama ile gen ifadesini izleyin. <ol><li> Fosfat tamponlu salin (PBS) ile üç kez hücreler yıkanır. </li><li> PBS (oda sıcaklığında 10 dakika inkübasyon) içinde% 4 formaldehit, 10 ml ekleyerek hücreleri saptamak. </li><li> PBS üç kez hücreleri yıkayın. </li><li> 500 DAPI,% 1 BSA,% 0.01 digitonin: 1 içeren PBS 8 ml ile oda sıcaklığında 15 dakika süreyle karanlıkta inkübe hücreleri. </li><li> PBS üç kez hücreleri yıkayın. </li><li> U, bir flüoresan mikroskop şarkı, mavi (Şekil 2 üst panel) ki bu yeşil / mavi göreli hücre sayısını belirler. hesaplanan yüzde transfeksiyon verimini gösterir. </li></ol></li></ol></li></ol></li><li> Lentivirüs aşırı sistemi 10 kullanılarak <ol><li> 15 cm&#39;lik bir doku kültürü çanağı içinde Tohum, insan embriyonik böbrek (HEK) 293T hücreleri (DMEM içinde% 10 FBS büyüme ortamı olarak). Not: hücreler yaklaşık% 60-70 konfluent olduğunda, transfekte hazırdır. </li><li> Mikrosantrifüj tüpü 11 düşük serum ortamı 1133 ul transfeksiyon reaktifi 162 ul ekle. Tüp duvar ile sulandırılmamış transfeksiyon reaktif temasından kaçının. </li><li> Ekle 24 pLL3.7 eGFP (ya da başka bir yapı) ug, 15.6 REV karşılık elemanının ug (RRE), REV 6.0 ug, ve transfeksiyon reaktifi / r içine veziküler stomatit virüsü glikoprotein 8.4 ug (VSVG)educed serum ortamında karışımı ile gerçekleştirilmektedir. </li><li> Oda sıcaklığında 20 dakika süreyle inkübe karışımı. </li><li> DMEM içinde% 10 FBS ve 16 ml büyüme ortamı değiştirin. </li><li> Damla damla çanak DNA / transfeksiyon reaktif / azaltılmış serum medya karışımı ekleyin. </li><li> Yavaşça bir sola ve sağa yön ardından ileri ve geri yönde yemeklere birkaç kez sallayın. Bu noktada müstakil HEK293T hücrelerinin bazılarını görmek için normaldir. </li><li> Inkübatör çanak yerleştirin. </li><li> Kuluçkalamadan 24 saat sonra, büyüme ortamı, 25 ml çanak ortamı değiştirin. </li><li> Ertesi gün, lentivirüs (birinci toplama) içeren büyüme ortamı toplar. </li><li> Adımı yineleyin 2.2.10 fazla lentivirüs (ikinci toplama) toplamak için. </li><li> (5 dakika boyunca 2.500 xg) birinci ve ikinci toplama havuzu ve santrifüj hücre enkaz kaldırmak. </li><li> Tek kullanımlık şişe üstü filtre (0.45 mikron gözenek) ile toplama Filtre veRT (JA-20 rotor) 2 saat süre ile 31.400 x g&#39;de santrifüje toplama virüsü konsantre edilir. Pelet bulunduğu santrifüj tüpünün dibine işaretleyin. Süpernatant tortusundan ayırma, ve yaklaşık 15 dakika boyunca oda sıcaklığında ters tüpü terk. </li><li> 1X PBS, 100 ul virüs içeren pelletini. Kabarcıkları kaçının. </li><li> -80 ° C &#39;de konsantre edilir virüs saklayın. Donma-çözülme döngüleri kaçının. </li><li> Titrasyon ile, Caco-2 hücreleri nakletmek için gerekli virüs optimal miktarının belirlenmesi. Maliyet tasarrufu için, 24-çukurlu plaka (iyi büyüme ortamı / 0.3 ml) kullanılarak titrasyonu için 10 cm&#39;lik bir doku kültürü çanağı kullanın. <ol><li> Konsantre edilmiş virüs artan miktarlarda ekleyin (0, 1, 2, 5, 10, 25, ve 50 ul / kuyucuk)% 40-70 konfluent Caco-2 hücreleri için polibren (nihai konsantrasyon = 5 ug / ml) ile takviye edilmiştir. 1.1.2 tarif edildiği gibi hafifçe 24 oyuklu plaka çalkalayın. </li><li> Onların gen ifadesini Monitör (Adım 2.1.10.) (Şekil 2 alt4 paneller). </li></ol></li><li> Transgen ifadesi genellikle sürekli olduğundan, gelecek deneyler için transdüse hücreleri korumak ve sürekli olarak gen ifadesini izlemek (Adım 2.1.10.). </li></ol></li></ol> 3. Lipoprotein salgılanmasını uyararak <ol><li> Düzenli doku kültürü çanak kullanma <ol><li> Oleik asit, 50 mg, lesitin, 40 mg, ve sodyum taurokolat ve 48 mg karıştırılarak bir 100X yağ karışım hazırlayın. (8 yemekler için yeterli) PBS ile 900 ul hacim kazandırın. Kuvvetli bir şekilde lipit karışımı karıştırın. </li><li> Büyüme ortamı 89.1 ml 100X lipit karışımı 900 ul ekleyin. Mix ve lipid içeren medya filtre. oleik asit, lesitin, ve sodyum taurokolat ve nihai konsantrasyonlar (1X) 2.0 mM, 1.36 mM ve sırası ile 1.0 mM vardır. </li><li> Hücrelere lipid içeren ortam, 10 ml ilave edilir. </li><li> 37 4 saat boyunca lipit-içeren ortam ile inkübe hücreleriC inkübatör °. </li><li> PBS üç kez hücreleri yıkayın. </li><li> Lipoprotein salgılanmasını toplamak için hücrelerin büyüme ortamı 10 ml ilave edilir. </li><li> 37 ° C kuluçka makinesi içinde 2 saat süreyle inkübe edin. </li><li> Lipoprotein içeren medya toplayın. </li></ol></li><li> Geçirgen zar sistemi kullanılarak <ol><li> Adımları 3.1.1-3.1.2 lipit karışımı hazırlamak için. </li><li> Apikal bölmeye lipid içeren ortam 10 ml ve bazolateral bölmeye büyüme ortamı 10 ml ilave edilir. </li><li> 37 ° C kuluçka makinesi içinde 4 saat süreyle inkübe edin. Bazolateral bölme lipoprotein ihtiva eden ortam toplayın. </li></ol></li></ol> 4. lipoprotein İzolasyon (Şekil 3) <ol><li> Santrifüj (5 dakika boyunca 2.000 xg) lipoprotein içeren medyanın hücre enkaz kaldırmak. </li><li> 50 ml&#39;lik bir tüp içine ortamı süzün. </li><li> Ortam, sodyum klorür 5.95 g ekleyin. </li><li> Sa Eğermple TEM ile analiz edilecektir, lipoproteinlerin bütünlüğünü korumak için 1 proteaz önleyici kokteyl tablet ekleyin. </li><li> Su ile 23 ml hacmi (1.2 g / ml NaCI yoğunluk çözeltisi) getirin. </li><li> Tamamen çözünmüş çözülür. </li><li> Polikarbonat ultrasantrifüjdeki tüp içine çözeltinin Tümünü süzün. </li><li> Yavaşça, 0.5 ml, su (1.0 ug / ml yoğunlukta), 1.2 ug / ml yoğunlukta çözelti kaplar. </li><li> Hacimce ağırlıkça değil tüp dengeleyin. </li><li> Yavaşça T865 rotor tüpler yükleyin. </li><li> 4 ° C&#39;de 24 saat boyunca 429.460 x g&#39;de ultrasantrifüjdeki örnekleri dönerler. </li><li> Hemen Nazik pipetleme üst 0.5 ml solüsyon izole. Mümkün olduğunca hareketsiz tüp tutun. </li></ol> 5. TEM analizi <ol><li> (A / h) ile pH 6,0&#39;a ayarlanır% 2 fosfotungstik asit 5 ml hazırlayın. </li><li> (: 0.2 mikron gözenek boyutu) bir şırınga filtresi ile% 2 fosfotungstik asit Filtre. </li><li> Steril bir çanak lipoprotein numunenin 20 ul bırakın. </li><li> Bir sonraki aynı yemeğin üzerine örnek süzülmüş% 2 fosfotungstik asit 20 ul bırakın. </li><li> Yavaşça donuk yan numune üzerinde oturan bir EM ızgara bırakın. </li><li> 1 dakika süre ile, oda sıcaklığında inkübe edilir. </li><li> Yavaşça ızgara örneği kaldırmak için bir filtre kağıdına EM ızgara tarafı dokunun. </li><li> Yavaşça donuk tarafı% 2 fosfotungstik asit dayayarak EM ızgara bırakın. </li><li> 1 dakika süre ile, oda sıcaklığında inkübe edilir. </li><li> Yavaşça ızgara fosfotungstik asit ayrılması için bir filtre kağıdı üzerinde EM ızgara yan dokunun. </li><li> Bir TEM kullanarak, lipoproteinler (Şekil 4) görüntüleri yakalamak. </li></ol>

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The author has nothing to disclose.

Bu yazıda, kullanılabilecek iki sistem Caco-2 hücreleri, yani düzenli doku kültürü çanak ve geçirgen zar açıklanmıştır korumak için. geçirgen zar sistemi kullanmanın faydaları apikal ayrılmasını ve bazolateral bölmeleri ve lipid karışımı inkübe ve aynı zamanda lipoprotein salgılanmasını toplamak için yeteneği vardır. Ancak, geçirgen zar ekler pahalıdır, ve polikarbonat membran iyi bir hücre görünürlüğü izin vermez. Bu in vitro modelin avantajlarından biri genetik man...

4 - diyet yağ ve lipid içinde çözünür ilaçlar ve vitaminler intestinal çalışmaları lenf fistül MODEL 1 kullanılarak in vivo olarak gerçekleştirilebilir. Ancak, ilgili cerrahi teknikler sadece zor değil, aynı zamanda pahalı değil. In vivo kullanılabilmektedir dışkı analizi dayalı yaklaşımlar da, mide-barsak sisteminde 2,5 yüzdesi alımını belirlemek için temel olarak kullanılmaktadır. Bu yazıda anlatılan in vitro model daha düşük maliyetli olduğunu ve ilgili teknikler tartışmalı az zorlayıcı bulunmaktadır. Genetik modifikasyonlar çalışmaları da zaman alıcı, bu in vitro bir model kullanılarak gerçekleştirilmiştir zaman daha ekonomik ve daha az bulunmaktadır. Enterositler tarafından alınır lipit çözünür malzeme lipoproteinler 6,7 içine paketlenmiş olduğundan, lipoproteinlerin üretmek için bu in vitro modelin etkinliği çok önemlidir. iki ana intestinal lipoproteinler kilomikronlar, çok düşük yoğunluklu lipoproteinler (VLDL) vardır. Lipidler mide-bağırsak lümeninde bol mevcut olduğunda çapı 80 nm ya da daha fazlası ile lipoproteinler olarak tanımlanan kilomikronlar, küçük bağırsak tarafından sıkı bir şekilde üretilir. Onlar büyük lipoproteinler olduğundan, şilomikronlar makul en verimli lipit taşıyıcıları vardır. Şilomikron 8 üretebilen bu in vitro modeli, diyet yağ emme, gut lipid çözünür vitamini emme ve oral lipofilik ilaç biyo-incelemek için kullanılabilir. lipoprotein fraksiyonuna lipid çözünür moleküller, vitaminler ya da ilaçların bulunması, ince bağırsakta kendi emilme bir göstergesidir. Daha önce ele alındığı gibi, bu model, oral lipofilik ilaç biyo-6 geliştirmek için de kullanılabilir. Bu kağıt Caco-2 hücreleri geçirgen zar veya normal doku kültürü yemekleri, nasıl lipit mi muhafaza edilmelidir açıklanırLipoprotein üretimini stimüle etmek için soğutun lentivirüs sentezleme sisteminin etkin aşırı ekspresyonunu gerçekleştirmek için kullanılabilir nasıl hazırlanmalı ve izole lipoproteinler kadar analiz edilmelidir.

<table><tbody><tr><td>DMEM</td><td>VWR</td><td>16750-112</td><td>Pre-warm the growth media in individual tissue culture dish before adding cells</td></tr><tr><td>FBS</td><td>Fisher</td><td>3600511</td><td>We do not heat inactivate our serum</td></tr><tr><td>Trypsin</td><td>VWR</td><td>45000-660</td><td>Cells can be washed with PBS prior to trypsin treatment&amp;nbsp;</td></tr><tr><td>Permeable membrane system</td><td>Fisher</td><td>7200173</td><td>10-cm dish, 3-mm pore size, polycarbonate membrane</td></tr><tr><td>10 cm dish</td><td>Fisher</td><td>08-772-E</td><td>Tissue culture dish</td></tr><tr><td>15 cm dish</td><td>Fisher</td><td>08-772-24</td><td>Tissue culture dish</td></tr><tr><td>24 well plate</td><td>Fisher</td><td>12565163</td><td>Tissue culture plate</td></tr><tr><td>Lipid-based transfection reagent</td><td>Fisher</td><td>PRE2691</td><td>Can be substituted with other transfection reagent</td></tr><tr><td>Reduced serum media</td><td>Invitrogen</td><td>11058021</td><td>For transfection</td></tr><tr><td>pLL3.7 eGFP</td><td>Addgene</td><td>11795</td><td>&lt;a href=&quot;https://www.addgene.org/11795/&quot;&gt;https://www.addgene.org/11795/&lt;/a&gt;</td></tr><tr><td>Bottle-top filter</td><td>Fisher</td><td>9761120</td><td>0.45 mm pore</td></tr><tr><td>Polybrene</td><td>Fisher</td><td>NC9840454</td><td>10 mg/ml</td></tr><tr><td>Oleic acid</td><td>Sigma</td><td>01383-5G</td><td>Prevent freeze-thaw cycle</td></tr><tr><td>Lecithin&amp;nbsp;</td><td>Fisher</td><td>IC10214625</td><td>Egg lecithin&amp;nbsp;</td></tr><tr><td>Sodium taurocholate</td><td>Fisher</td><td>NC9620276</td><td>Product discontinued; alternative catalog number: 50-121-7956</td></tr><tr><td>Protease inhibitor cocktail tablet (EDTA-free)</td><td>Fisher</td><td>5892791001</td><td>Used mainly for samples that need TEM analysis</td></tr><tr><td>Polycarbonate ultracentrifuge tube</td><td>Fisher</td><td>NC9696153</td><td>Reusing it multiple times will collapse the tube</td></tr><tr><td>Lid for ultracentrifuge tube</td><td>Fisher</td><td>NC9796914</td><td>A tool is required to remove the tube/lid from rotor</td></tr><tr><td>Syringe</td><td>Fisher</td><td>50-949-261</td><td>Disposable</td></tr><tr><td>Syringe filter</td><td>Fisher</td><td>09-719C</td><td>Pore size = 0.2 mm; nylon</td></tr><tr><td>Phosphotungstic acid</td><td>Fisher</td><td>AC208310250</td><td>For preparing 2% phosphotungstic acid, pH 6.0</td></tr><tr><td>Tweezer</td><td>Fisher</td><td>50-238-62</td><td>Extra fine and strong tips</td></tr><tr><td>Formvar/carbon grid</td><td>Fisher</td><td>50-260-34</td><td>Formvar/carbon film square grid 400 Copper</td></tr></tbody></table>

using caco-2 cells to study lipid transport by the intestine

Studies of dietary fat absorption are generally conducted by using an animal model equipped with a lymph cannula. Although this animal model is widely accepted as the in vivo model of dietary fat absorption, the surgical techniques involved are challenging and expensive. Genetic manipulation of the animal model is also costly and time consuming. The alternative in vitro model is arguably more affordable, timesaving, and less challenging. Importantly, the in vitro model allows investigators to examine the enterocytes as an isolated system, reducing the complexity inherent in the whole organism model. This paper describes how human colon carcinoma cells (Caco-2) can serve as an in vitro model to study the enterocyte transport of lipids, and lipid-soluble drugs and vitamins. It explains the proper maintenance of Caco-2 cells and the preparation of their lipid mixture; and it further discusses the valuable option of using the permeable membrane system. Since differentiated Caco-2 cells are polarized, the main advantage of using the permeable membrane system is that it separates the apical from the basolateral compartment. Consequently, the lipid mixture can be added to the apical compartment while the lipoproteins can be collected from the basolateral compartment. In addition, the effectiveness of the lentivirus expression system in upregulating gene expression in Caco-2 cells is discussed. Lastly, this paper describes how to confirm the successful isolation of intestinal lipoproteins by transmission electron microscopy (TEM).

1 görüntüler, normal 13-gün sonrası birleşik Caco-2 hücreleri Şekil. Kubbe-şekilli yapılar ve hücre içi lipid damlacıkları görünümü farklılaşmış Caco-2 hücreleri için karakteristiktir. Caco-2 hücreleri tohumlama sırasında eşit dağılmış değil, onlar kümelenir ve yemeğin belirli alanlarda sarmak olacaktır; ve herhangi bir hücrelerde olmadan çanak birkaç alanları olacaktır. Swirling ve eğimli bir yüzeye çanak yerleştirilmesi kaçınılmalıdır....

Watch this Scientific Journal Video about Using Caco-2 Cells to Study Lipid Transport by the Intestine at JoVE.com

Using Caco-2 Cells to Study Lipid Transport by the Intestine

Caco-2 cells can serve as an in vitro model to study the enterocyte transport of lipids, and lipid-soluble drugs/vitamins. The permeable membrane system separates the apical from the basolateral compartment, while the lentivirus expression system offers an effective gene overexpression method. The isolation of lipoproteins is confirmed by TEM.

Bağırsak tarafından Lipit Transport Eğitim için Caco-2 hücreleri kullanarak

Studies of dietary fat absorption are generally conducted by using an animal model equipped with a lymph cannula. Although this animal model is widely ...

using-caco-2-cells-to-study-lipid-transport-by-the-intestine

Research

JoVE Journal

Biology

18.7K Görüntüleme.  California Northstate University. Caco-2 cells can serve as an in vitro model to study the enterocyte transport of lipids, and lipid-soluble drugs/vitamins. The permeable membrane system separates the apical from the basolateral compartment, while the lentivirus expression system offers an effective gene overexpression method. The isolation of lipoproteins is confirmed by TEM.

Video: Using Caco-2 Cells to Study Lipid Transport by the Intestine

Cholesterol Efflux Assay

Cholesterol content of cells must be maintained within the very tight limits, too much or too little cholesterol in a cell results in disruption of cellular membranes, apoptosis and necrosis 1. Cells can source cholesterol from intracellular synthesis and from plasma lipoproteins, both sources are sufficient to fully satisfy cells' requirements for cholesterol. The processes of cholesterol synthesis and uptake are tightly regulated and deficiencies of cholesterol are rare 2. Excessive cholesterol is more common problem 3. With the exception of hepatocytes and to some degree adrenocortical cells, cells are unable to degrade cholesterol. Cells have two options to reduce their cholesterol content: to convert cholesterol into cholesteryl esters, an option with limited capacity as overloading cells with cholesteryl esters is also toxic, and cholesterol efflux, an option with potentially unlimited capacity. Cholesterol efflux is a specific process that is regulated by a number of intracellular transporters, such as ATP binding cassette transporter proteins A1 (ABCA1) and G1 (ABCG1) and scavenger receptor type B1. The natural acceptor of cholesterol in plasma is high density lipoprotein (HDL) and apolipoprotein A-I. 
The cholesterol efflux assay is designed to quantitate the rate of cholesterol efflux from cultured cells. It measures the capacity of cells to maintain cholesterol efflux and/or the capacity of plasma acceptors to accept cholesterol released from cells. The assay consists of the following steps. Step 1: labelling cellular cholesterol by adding labelled cholesterol to serum-containing medium and incubating with cells for 24-48 h. This step may be combined with loading of cells with cholesterol. Step 2: incubation of cells in serum-free medium to equilibrate labelled cholesterol among all intracellular cholesterol pools. This stage may be combined with activation of cellular cholesterol transporters. Step 3: incubation of cells with extracellular acceptor and quantitation of movement of labelled cholesterol from cells to the acceptor. If cholesterol precursors were used to label newly synthesized cholesterol, a fourth step, purification of cholesterol, may be required.
The assay delivers the following information: (i) how a particular treatment (a mutation, a knock-down, an overexpression or a treatment) affects the capacity of cell to efflux cholesterol and (ii) how the capacity of plasma acceptors to accept cholesterol is affected by a disease or a treatment. This method is often used in context of cardiovascular research, metabolic and neurodegenerative disorders, infectious and reproductive diseases.

The cholesterol assay is designed to quantitate the rate of cholesterol efflux from cultured cells and the capacity of plasma acceptors to accept cholesterol released from cells. The assay consists of labelling cells with cholesterol, equilibration of cholesterol among intracellular pools and release of cholesterol to an extracellular acceptor.

Kolesterol akışı Testi

Cholesterol content of cells must be maintained within the very tight limits, too much or too little cholesterol in a cell results in disruption of ...

Tıp

Models and Methods to Evaluate Transport of Drug Delivery Systems Across Cellular Barriers

Sub-micrometer carriers (nanocarriers; NCs) enhance efficacy of drugs by improving solubility, stability, circulation time, targeting, and release. Additionally, traversing cellular barriers in the body is crucial for both oral delivery of therapeutic NCs into the circulation and transport from the blood into tissues, where intervention is needed. NC transport across cellular barriers is achieved by: (i) the paracellular route, via transient disruption of the junctions that interlock adjacent cells, or (ii) the transcellular route, where materials are internalized by endocytosis, transported across the cell body, and secreted at the opposite cell surface (transyctosis). Delivery across cellular barriers can be facilitated by coupling therapeutics or their carriers with targeting agents that bind specifically to cell-surface markers involved in transport. Here, we provide methods to measure the extent and mechanism of NC transport across a model cell barrier, which consists of a monolayer of gastrointestinal (GI) epithelial cells grown on a porous membrane located in a transwell insert. Formation of a permeability barrier is confirmed by measuring transepithelial electrical resistance (TEER), transepithelial transport of a control substance, and immunostaining of tight junctions. As an example, ~200&#160;nm polymer NCs are used, which carry a therapeutic cargo and are coated with an antibody that targets a cell-surface determinant. The antibody or therapeutic cargo is labeled with 125I for radioisotope tracing and labeled NCs are added to the upper chamber over the cell monolayer for varying periods of time. NCs associated to the cells and/or transported to the underlying chamber can be detected. Measurement of free 125I allows subtraction of the degraded fraction. The paracellular route is assessed by determining potential changes caused by NC transport to the barrier parameters described above. Transcellular transport is determined by addressing the effect of modulating endocytosis and transcytosis pathways.

Many therapeutic applications require safe and efficient transport of drug carriers and their cargoes across cellular barriers in the body. This article describes an adaptation of established methods to evaluate the rate and mechanism of transport of drug nanocarriers (NCs) across cellular barriers, such as the gastrointestinal (GI) epithelium.

Modelleri ve Hücresel Engeller Arasında İlaç Taşıyıcı Sistemlerin Transport Değerlendirmesinde Yöntemleri

Sub-micrometer carriers (nanocarriers; NCs) enhance efficacy of drugs by improving solubility, stability, circulation time, targeting, and release. ...

Biyomühendislik

Exploring the Regulation of Lipid Droplet Catabolism through Lipophagy

Macroautophagy, commonly referred to as autophagy, is a highly conserved cellular process responsible for the degradation of cellular components. This process is particularly prominent under conditions such as fasting, cellular stress, organelle damage, cellular damage, or aging of cellular components. During autophagy, a segment of the cytoplasm is enclosed within double-membrane vesicles known as autophagosomes, which then fuse with lysosomes. Following this fusion, the contents of autophagosomes undergo non-selective bulk degradation facilitated by lysosomes. However, autophagy also exhibits selective functionality, targeting specific organelles, including mitochondria, peroxisomes, lysosomes, nuclei, and lipid droplets (LDs). Lipid droplets are enclosed by a phospholipid monolayer that isolates neutral lipids from the cytoplasm, protecting cells from the harmful effects of excess sterols and free fatty acids (FFAs). Autophagy is implicated in various conditions, including neurodegenerative diseases, metabolic disorders, and cancer. Specifically, lipophagy -- the autophagy-dependent degradation of lipid droplets -- plays a crucial role in regulating intracellular FFA levels across different metabolic states. This regulation supports essential processes such as membrane synthesis, signaling molecule formation, and energy balance. Consequently, impaired lipophagy increases cellular vulnerability to death stimuli and contributes to the development of diseases such as cancer. Despite its significance, the precise mechanisms governing lipid droplet metabolism regulated by lipophagy in cancer cells remain poorly understood. This article aims to describe confocal imaging acquisition and quantitative imaging analysis protocols that enable the investigation of lipophagy associated with metabolic changes in cancer cells. The results obtained through these protocols may shed light on the intricate interplay between autophagy, lipid metabolism, and cancer progression. By elucidating these mechanisms, novel therapeutic targets may emerge for combating cancer and other metabolic-related diseases.

Lipophagy is a selective form of autophagy that involves the degradation of lipid droplets. Dysfunctions in this process are associated with cancer development. However, the precise mechanisms are not yet fully understood. This protocol describes quantitative imaging approaches to better understand the interplay between autophagy, lipid metabolism, and cancer progression.

Lipofaji Yoluyla Lipid Damlacık Katabolizmasının Düzenlenmesinin Araştırılması

Macroautophagy, commonly referred to as autophagy, is a highly conserved cellular process responsible for the degradation of cellular components. This ...

Kanser Araştırmaları

A Co-culture Method to Investigate the Crosstalk Between X-ray Irradiated Caco-2 Cells and PBMC

The protocol adopted in this work aims at unraveling how X-rays perturb the functioning of the intestinal barrier, focusing on the interplay between colorectal tumor cells and the immune system. Colorectal carcinoma is among the most common type of cancer, typically treated by surgery, chemotherapy, and radiotherapy. Advantages of radiotherapy in targeting the tumor are well known. However, even limited exposures of healthy tissues are of great concern, particularly regarding the effects on the intestinal barrier and the immune system. The adopted setup allows to study the interplay between two cell populations in a condition more similar to the physiological one, when compared to normal cell cultures. For this purpose, we resort to different techniques and we used an in vitro co-culture model, based on Caco-2 cells differentiated as a monolayer and PBMC, sharing the same culture medium. This protocol has been developed to focus on both macroscopic effects, i.e. cell viability and Trans-Epithelial Electrical Resistance (TEER), and, through western blot, molecular alterations, i.e. the activation of inflammatory pathway in immune cells and the tight junction protein expression in Caco-2 cells. Initial evaluation of radiation effects on Caco-2 cell viability was assessed via the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and Trypan blue assays, while TEER was measured at fixed time intervals through an ohmmeter specifically designed for co-culture systems. In this way, the effects due to radiation, the presence of Peripheral Blood Mononuclear Cells (PBMC), and eventually their synergistic effect, can be demonstrated. Through these complementary techniques, we observed a high radio-resistance of Caco-2 within the range of 2 - 10 Gy of X-rays and an increased Caco-2 monolayer permeability when PBMCs were added. In particular, PBMC presence was found to be associated with the variation in the tight junction scaffold proteins expression.

We present a protocol to investigate the crosstalk between X-ray-irradiated Caco-2 and peripheral blood mononuclear cells (PBMC). The protocol starts with Caco-2 irradiation and set-up of the co-culture with PBMC; subsequently, trans-epithelial electrical resistance is measured regularly over 48 h and western blot performed in both Caco-2 and PBMC.

X-ışını arasında çapraz karışma araştırmak için bir ortak kültür yöntemi Caco-2 hücreleri ve PBMC radyasyona maruz

The protocol adopted in this work aims at unraveling how X-rays perturb the functioning of the intestinal barrier, focusing on the interplay between ...

İmmünoloji ve Enfeksiyon

Lipid Exchange Assay in Living Cells

Lipid rafts are dynamic, ordered domains in the plasma membrane often formed during membrane protein clustering and signaling. The lipid identity of the outer leaflet drives the membrane&#39;s propensity to form lipid rafts. The transient nature of lipid rafts makes it difficult to study in living cells. Therefore, methods that add or remove raft-forming lipids at&#160;the outer leaflet of living cells facilitate studying the characteristics of rafts, such as their effects on membrane proteins. Lipid exchange experiments developed in our lab utilize lipid-loaded cyclodextrins to remove and add exogenous phospholipids to change the lipid constitution of the plasma membrane. Substituting the membrane with a raft or non-raft-forming lipid can aid in studying the effects on transmembrane protein activity. Here, we describe a method for lipid exchange on the outer leaflet of the plasma membrane using lipid-loaded cyclodextrin. We demonstrate the preparation of the exchange media and the subsequent treatment of attached mammalian cells. We also showcase how to measure the efficiency of exchange using HP-TLC. This protocol yields a nearly complete replacement of the outer leaflet with exogenous lipids without altering cellular viability, permitting further experimentation on modified intact plasma membranes.

We describe a method for using cyclodextrin to mediate exchange between lipids of the plasma membrane with exogenous lipids. This technique can be paired with experiments studying transmembrane proteins, which behave differently in lipid raft-like environments than they do in non-raft-like environments.

Canlı Hücrelerde Lipid Değişim Testi

Lipid rafts are dynamic, ordered domains in the plasma membrane often formed during membrane protein clustering and signaling. The lipid identity of the ...

Biyokimya

A Fluorescence-based Assay for Characterization and Quantification of Lipid Droplet Formation in Human Intestinal Organoids

Dietary lipids are taken up as free fatty acids (FAs) by the intestinal epithelium. These FAs are intracellularly converted into triglyceride (TG) molecules, before they are packaged into chylomicrons for transport to the lymph or into cytosolic lipid droplets (LDs) for intracellular storage. A crucial step for the formation of LDs is the catalytic activity of diacylglycerol acyltransferases (DGAT) in the final step of TG synthesis. LDs are important to buffer toxic lipid species and regulate cellular metabolism in different cell types. Since the human intestinal epithelium is regularly confronted with high concentrations of lipids, LD formation is of great importance to regulate homeostasis. Here we describe a simple assay for the characterization and quantification of LD formation (LDF) upon stimulation with the most common unsaturated fatty acid, oleic acid, in human intestinal organoids. The LDF assay is based on the LD-specific fluorescent dye LD540, which allows for quantification of LDs by confocal microscopy, fluorescent plate reader, or flow cytometry. The LDF assay can be used to characterize LD formation in human intestinal epithelial cells, or to study human (genetic) disorders that affect LD metabolism, such as DGAT1 deficiency. Furthermore, this assay can also be used in a high-throughput pipeline to test novel therapeutic compounds, which restore defects in LD formation in intestinal or other types of organoids.

This protocol describes an assay for the characterization of lipid droplet (LD) formation in human intestinal organoids upon stimulation with fatty acids. We discuss how this assay is used for quantification of LD formation, and how it can be used for high throughput screening for drugs that affect LD formation.

İnsan Bağırsak Organoidlerinde Lipid Damlacık Oluşumunun Karakterizasyonu ve Niceliği için Floresan Esaslı Bir Test

Dietary lipids are taken up as free fatty acids (FAs) by the intestinal epithelium. These FAs are intracellularly converted into triglyceride (TG) ...

A Proteoliposome-Based Efflux Assay to Determine Single-molecule Properties of Cl- Channels and Transporters

The last 15 years have been characterized by an explosion in the ability to overexpress and purify membrane proteins from prokaryotic organisms as well as from eukaryotes. This increase has been largely driven by the successful push to obtain structural information on membrane proteins. However, the ability to functionally interrogate these proteins has not advanced at the same rate and is often limited to qualitative assays of limited quantitative value, thereby limiting the mechanistic insights that they can provide. An assay to quantitatively investigate the transport activity of reconstituted Cl- channels or transporters is described. The assay is based on the measure of the efflux rate of Cl- from proteoliposomes following the addition of the K+ ionophore valinomycin to shunt the membrane potential. An ion sensitive electrode is used to follow the time-course of ion efflux from proteoliposomes reconstituted with the desired protein. The method is highly suited for mechanistic studies, as it allows for the quantitative determination of key properties of the reconstituted protein, such as its unitary transport rate, the fraction of active protein and the molecular mass of the functional unit. The assay can also be utilized to determine the effect of small molecule compounds that directly inhibit/activate the reconstituted protein, as well as to test the modulatory effects of the membrane composition or lipid-modifying reagents. Where possible, direct comparison between results obtained using this method were found to be in good agreement with those obtained using electrophysiological approaches. The technique is illustrated using CLC-ec1, a CLC-type H+/Cl- exchanger, as a model system. The efflux assay can be utilized to study any Cl- conducting channel/transporter and, with minimal changes, can be adapted to study any ion-transporting protein.

A Proteoliposome-Based Efflux Assay to Determine Single-molecule Properties of Cl- Channels and Transporters

Proteoliposomes are used to study purified channels and transporters reconstituted in a well-defined biochemical environment. An experimental procedure to measure efflux mediated by these proteins is illustrated. The steps to prepare proteoliposomes, perform the recordings, and analyze data to quantitatively determine the functional properties of the reconstituted protein are described.

Bir Proteoliposome Tabanlı effluks Deney Cl Tek-molekül Properties belirleme<sup&gt; -</sup&gt; Kanallar ve Nakliyeciler

The last 15 years have been characterized by an explosion in the ability to overexpress and purify membrane proteins from prokaryotic organisms as well as ...

Biyoloji

Endothelial Cell Transcytosis Assay as an In Vitro Model to Evaluate Inner Blood-Retinal Barrier Permeability

Dysfunction of the blood-retinal barrier (BRB) contributes to the pathophysiology of several vascular eye diseases, often resulting in retinal edema and subsequent vision loss. The inner blood-retinal barrier (iBRB) is mainly composed of retinal vascular endothelium with low permeability under physiological conditions. This feature of low permeability is tightly regulated and maintained by low rates of paracellular transport between adjacent retinal microvascular endothelial cells, as well as transcellular transport (transcytosis) through them. The assessment of retinal transcellular barrier permeability may provide fundamental insights into iBRB integrity in health and disease. In this study, we describe an endothelial cell (EC) transcytosis assay, as an in vitro model for evaluating iBRB permeability, using human retinal microvascular endothelial cells (HRMECs). This assay assesses the ability of HRMECs to transport transferrin and horseradish peroxidase (HRP) in receptor- and caveolae-mediated transcellular transport processes, respectively. Fully confluent HRMECs cultured on porous membrane were incubated with fluorescent-tagged transferrin (clathrin-dependent transcytosis) or HRP (caveolae-mediated transcytosis) to measure the levels of transferrin or HRP transferred to the bottom chamber, indicative of transcytosis levels across the EC monolayer. Wnt signaling, a known pathway regulating iBRB, was modulated to demonstrate the caveolae-mediated HRP-based transcytosis assay method. The EC transcytosis assay described here may provide a useful tool for investigating the molecular regulators of EC permeability and iBRB integrity in vascular pathologies and for screening drug delivery systems.

Endothelial Cell Transcytosis Assay as an In Vitro Model to Evaluate Inner Blood-Retinal Barrier Permeability

This protocol illustrates an in vitro endothelial cell transcytosis assay as a model to evaluate inner blood-retinal barrier permeability by measuring the ability of human retinal microvascular endothelial cells to transport horseradish peroxidase across cells in caveolae-mediated transcellular transport processes.

İç Kan-Retinal Bariyer Geçirgenliğini Değerlendirmek için In Vitro Model Olarak Endotel Hücre Transsitozu Testi

Dysfunction of the blood-retinal barrier (BRB) contributes to the pathophysiology of several vascular eye diseases, often resulting in retinal edema and ...

Methods to Study Epithelial Transport Protein Function and Expression in Native Intestine and Caco-2 Cells Grown in 3D

The intestinal epithelium has important transport and barrier functions that play key roles in normal physiological functions of the body while providing a barrier to foreign particles. Impaired epithelial transport (ion, nutrient, or drugs) has been associated with many diseases and can have consequences that extend beyond the normal physiological functions of the transporters, such as by influencing epithelial integrity and the gut microbiome. Understanding the function and regulation of transport proteins is critical for the development of improved therapeutic interventions. The biggest challenge in the study of epithelial transport is developing a suitable model system that recapitulates important features of the native intestinal epithelial cells. Several in vitro cell culture models, such as Caco-2, T-84, and HT-29-Cl.19A cells are typically used in epithelial transport research. These cell lines represent a reductionist approach to modeling the epithelium and have been used in many mechanistic studies, including their examination of epithelial-microbial interactions. However, cell monolayers do not accurately reflect cell-cell interactions and the in vivo microenvironment. Cells grown in 3D have shown to be promising models for drug permeability studies. We show that Caco-2 cells in 3D can be used to study epithelial transporters. It is also important that studies in Caco-2 cells are complemented with other models to rule out cell specific effects and to take into account the complexity of the native intestine. Several methods have been previously used to assess the functionality of transporters, such as everted sac and uptake in isolated epithelial cells or in isolated plasma membrane vesicles. Taking into consideration the challenges in the field with respect to models and the measurement of transport function, we demonstrate here a protocol to grow Caco-2 cells in 3D and describe the use of an Ussing chamber as an effective approach to measure serotonin transport, such as in intact polarized intestinal epithelia.

We describe simple methods to study the regulation of intestinal serotonin transporter (SERT) function and expression using an in vitro cell culture model of Caco-2 cells grown in 3D&#160;and an ex vivo model of mouse intestines. These methods are applicable to the study of other epithelial transporters.

Yöntem 3D Yetiştirilen Yerli Barsak ve Caco-2 Hücreler Epitel Ulaşım Protein Fonksiyonu ve Anlatım Eğitim için

The intestinal epithelium has important transport and barrier functions that play key roles in normal physiological functions of the body while providing ...

In Vitro and In Vivo Approaches to Determine Intestinal Epithelial Cell Permeability

The intestinal barrier defends against pathogenic microorganism and microbial toxin. Its function is regulated by tight junction permeability and epithelial cell integrity, and disruption of the intestinal barrier function contributes to progression of gastrointestinal and systemic disease. Two simple methods are described here to measure the permeability of intestinal epithelium. In vitro, Caco-2BBe cells are plated in tissue culture wells as a monolayer and transepithelial electrical resistance (TER) can be measured by an epithelial (volt/ohm) meter. This method is convincing because of its user-friendly operation and repeatability. In vivo, mice are gavaged with 4 kDa fluorescein isothiocyanate (FITC)-dextran, and the FITC-dextran concentrations are measured in collected serum samples from mice to determine the epithelial permeability. Oral gavage provides an accurate dose, and therefore is the preferred method to measure the intestinal permeability in vivo. Taken together, these two methods can measure the permeability of the intestinal epithelium in vitro and in vivo, and hence be used to study the connection between diseases and barrier function.

In Vitro and In Vivo Approaches to Determine Intestinal Epithelial Cell Permeability

Two methods are presented here to determine intestinal barrier function. An epithelial meter (volt/ohm) is used for measurements of transepithelial electrical resistance of cultured epithelia directly in tissue culture wells. In mice, the FITC-dextran gavage method is used to determine the intestinal permeability in vivo.

Bağırsak tarafından Lipit Transport Eğitim için Caco-2 hücreleri kullanarak

Özet

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