Name: trans-tympanic drug delivery for the treatment of ototoxicity
Uploaded: 2018-03-16T12:30:00
Description: Watch this Scientific Journal Video about Trans-Tympanic Drug Delivery for the Treatment of Ototoxicity at JoVE.com

The work described in this article was supported by a NCI RO1 CA166907, NIDCD RO1-DC 002396 and RO3 DC011621.

Male Wistar rats were handled in accordance with the National Institutes of Health animal use guidelines and a protocol approved by the Southern Illinois University School of Medicine Laboratory Animal Care and Use Committee. Auditory brainstem response (ABR) was performed on rats while under anesthesia prior to drug administration and 72 h after to verify the effect of the trans-tympanic drug delivery.
1. Auditory Brainstem Response (ABR)
Note:&#160;...

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The trans-tympanic administration route allows for localized delivery of drugs and other agents to the cochlea which could otherwise produce significant systemic side effects if administered systemically. This method of drug administration allows rapid access of drugs to the site of action at significantly higher doses than would be achieved through the systemic route. Results presented here and published previously showed that trans-tympanic administration of [R]-N-phenyl isopropyl adenosine (R-PIA) pr...

The peripheral auditory system is exquisitely sensitive to drugs such as cisplatin and aminoglycoside antibiotics. Cisplatin is a widely used chemotherapeutic agent for the treatment of a variety of solid tumors, such as ovarian, testicular, and head and neck cancers. Ototoxicity experienced with the use of this drug is dose-limiting and quite common, affecting 75-100% of patients treated1. Other drugs, such as carboplatin and oxaliplatin, have emerged as alternatives to cisplatin2,3,4,5, but their usefulness is limited to a few cancers.
Early studies have shown the critical role of reactive oxygen species (ROS) in mediating the ototoxicity produced by cisplatin and aminoglycosides. Subsequent studies showed that the NOX3 isoform of NADPH oxidase is the primary source of ROS in the cochlea, and is activated by cisplatin6,7. The generation of ROS compromises the antioxidant buffering capacity of cells, leading to increased lipid peroxidation of cellular membranes8. Furthermore, cisplatin increases the production of hydroxyl radicals which generate highly toxic aldehyde 4-hydroxynonenal (4-HNE), an initiator of cell death9,10. Based on these findings, several antioxidants have been examined for the treatment of cisplatin ototoxicity. These include N-acetyl cysteine (NAC), sodium thiosulfate (STS), amifostine, and D-methionine. However, a major concern of antioxidant therapy is that these antioxidants could reduce cisplatin chemotherapeutic efficacy when administered systemically11 through the interaction of cisplatin with thiol groups in the antioxidant molecules.
In view of these problems with antioxidant therapy, the goal of this study was to examine the trans-tympanic route of delivering antioxidants and other drugs to the cochlea to reduce hearing loss. The trans-tympanic route of drug and short interfering (si) RNA, described below, appears particularly promising.

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			<td height="19" style="height:19px;width:423px;">Ketathesia (100 mg/ml) 10 ml</td>
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			<td height="19" style="height:19px;">(&#8722;)-N6-(2-Phenylisopropyl)adenosine</td>
			<td>Sigma Aldrich</td>
			<td>P4532</td>
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			<td height="19" style="height:19px;">8-Cyclopentyl-1,3-dipropylxanthine</td>
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			<td height="22" style="height:22px;">siRNA pSTAT1</td>
			<td>Qiagen</td>
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			<td>Kaur et al. 201120</td>
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			<td height="22" style="height:22px;">siRNA NOX3</td>
			<td>Qiagen</td>
			<td>Custome Made</td>
			<td>Kaur et al. 201120</td>
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			<td>Qiagen</td>
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			<td>Kaur et al. 201120</td>
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trans-tympanic drug delivery for the treatment of ototoxicity

The systemic administration of protective agents to treat drug-induced ototoxicity is limited by the possibility that these protective agents could interfere with the chemotherapeutic efficacy of the primary drugs. This is especially true for the drug cisplatin, whose anticancer actions are attenuated by antioxidants which provide adequate protection against hearing loss. Other current or potential otoprotective agents could pose a similar problem, if administered systemically. The application of various biologicals or protective agents directly to the cochlea would allow for high levels of these agents locally with limited systemic side effects. In this report, we demonstrate a trans-tympanic method of delivery of various drugs or biological reagents to the cochlea, which should enhance basic science research on the cochlea and provide a simple way of directing the use of otoprotective agents in the clinics. This report details a method of trans-tympanic drug delivery and provides examples of how this technique has been used successfully in experimental animals to treat cisplatin ototoxicity.

ABR responses measured in rats at three days following cisplatin administration showed a significant elevation in thresholds. Elevation of these thresholds was significantly reduced in rats administered with trans-tympanic [R]-N-phenylisopropyladenosine (R-PIA), adenosine A1 receptor agonist15, prior to cisplatin. The specificity of the action of R-PIA at the adenosine A1 receptor was demonstrated by the observation ...

Watch this Scientific Journal Video about Trans-Tympanic Drug Delivery for the Treatment of Ototoxicity at JoVE.com

Trans-Tympanic Drug Delivery for the Treatment of Ototoxicity

We present a technique for localized administration of drugs through the trans-tympanic route into the cochlea. Drug delivery through this route would not interfere with the anti-cancer efficacy of the chemotherapeutic drugs such as cisplatin.

The systemic administration of protective agents to treat drug-induced ototoxicity is limited by the possibility that these protective agents could ...

The overall goal of this trans-tympanic procedure, is to locally deliver high concentrations of antioxidants, otoprotective agents, or biological reagents directly into the cochlea for treatment of hearing loss. The trans-tympanic route of drug delivery allows for the localized delivery of drugs and other agents into the cochlea that may cause significant side effects if administered systemically. The main advantage of this matter is that it permits rapid administration of drugs in significantly higher doses into the cochlea than would be achieved by systemic delivery.This technique has the potential for the prophylactic delivery of reagents to prevent against cisplatin-induced hearing loss without interfering with the anti-tumor effect. After confirming a lack of response to toe pinch, apply ointment to the eyes of the rat. To asses the auditory brainstem response, place the rat in the prone position on a 37 degree Celsius heating pad inside a controlled acoustical booth and insert a stainless steel ground electrode into the rear flank, a stainless steel positive electrode into the top of the skull between the ears, and one stainless steal negative electrode below the pinna of each ear.Carefully insert high-frequency transducer tubes into the rat's ears. Then, using high-frequency transducers, apply acoustics stimuli as a five millisecond tone burst at 8, 16, and 32 kilohertz. Place the animal in the left lateral decubitus position.Insert a 2.5 millimeter disposable ear specula into the ear canal and use a surgical scope to position the specula so that the tympanic membrane is visible. It's important to orient the needles so that the ear drum is still visible, because the ear specula is so small and a successful injection requires visualization of all materials and tissue under the microscope. Using a 29 and a half gauge 0.5 milliliter insulin syringe, aspirate 50 microliters of the drug or reagent of interest into the syringe barrel.And use the specula to direct the needle into the anterior inferior of the tympanic membrane. Use the needle to poke a hole through the membrane and administer the entire 50 microliter volume of the drug. Allow the rat to rest in this position for 15 minutes.Then, place the rat in the right lateral decubitus position and administer the drug into the right ear as just demonstrated. For rats receiving cisplatin, place the rat in the supine position on a 37 degree Celsius heating pad and draw cisplatin into a 21 and three-quarter gauge butterfly needle connected to a 12-inch piece of tubing. Then, use a syringe pump to administer one milligram per milliliter of cisplatin via intraperitoneal injection over 30 minutes.When all of the cisplatin has been delivered, place the rat back into its cage in the prone position, taking care that its breathing is not obstructed, and monitor the animal until it is fully recovered. Following the measurement of the post-treatment ABR, sacrifice the rat and dissect out temporal bone. Place the harvested cochlea in a seven milliliter glass scintillation vial containing four percent paraformaldehyde in PBS and store it overnight at four degrees Celsius.The next morning, wash the cochlea in room temperature PBS. Followed by complete immersion in 120 millimolar EDTA. Then, place the vial on a rotator to decalcify the cochlea for two to three weeks at room temperature.Upon completion of the decalcification, place the cochlea in sequential immersions of seven milliliters of sucrose for 24 hours per sucrose solution at four degrees Celsius. After the last submersion, add fresh optimal cutting temperature compound to a 15 by 15 by 5 millimeter disposable embedding mold, and place the cochlea on its side in the mold so that the sample is parallel to the bottom of the mold. Immediately place the mold on dry ice to solidify the OCT and store the mold at negative 80 degrees Celsius overnight.The next morning, transfer the mold onto dry ice and set a cryostat to negative 30 degrees Celsius. Then, use sharp microtone blade to acquire two ten-micrometer sections of cochlea sample per polylysine coated slide. Insert the slides at four degrees Celsius.To analyze the sections by immunohistochemistry, place the slides in a glass microscope slide staining dish on a slide rack and wash the section three times with 350 milliliters of PBS for five minutes per wash. After the last watch, use a lab wipe to remove the excess PBS around each sample, and use hydrophobic barrier pen to surround each section. Block the tissues for one hour at room temperature with 150 microliters of blocking solution per sample.At the end of the incubation, top off the excess blocking solution and incubate the samples with 150 microliters of the primary antibody of interest overnight at four degree Celsius in a humidified chamber. The next morning, return the slides to the staining dish on the side rack and wash the slides three times in PBS as just demonstrated. Incubate the sections with the appropriate secondary antibodies for two to three hours at room temperature in the humidified chamber in the dark.At the end of the incubation, return the slides to the staining dish and wash the slides three times in fresh PBS. After the last wash, tap the slides to remove the excess PBS and dry the slides with a lab wipe. Place a drop of mounting agent supplemented with DAPI directly onto each tissue section and carefully place a cover slip onto each slide taking care not to create bubbles.Then, allow the slides to cure overnight at room temperature in the dark before imaging the samples by confocal microscopy. Auditory brainstem responses measured in rats at three days post-cisplatin administration shows significant elevation in thresholds that is reduced in rats treated with transtympanic delivery of the adenosine A1 receptor agonist, R-PIA, prior to cisplatin administration. Conversely, treatment with DPCPX, an A1 receptor-specific antagonist, potentiates the cisplatin-induced auditory brainstem response threshold shifts, demonstrating the specificity of the R-PIA agonist for the A1 receptor.Cisplatin also increases outer hair cell loss and damage as assessed by scanning electron microscopy, an effect that is significantly reduced by transtympanic R-PIA administration. Further, transtympanic R-PIA reduces basal and cisplatin-induced phospho stat1 immunoreactivity in the outer hair cells of the cochlea, in accordance with the anti inflammatory property of this drug. The transtympanic route can also be used to administer other biologics, such as siRNAs, to reduce stat1 levels and to block the activation of this transcription factor to phospho stat1 by cisplatin, for example.Addition studies show that transtympanic administration of NOX3 siRNA reduces the ability of drugs, such as capsaicin, to increase the expression of some downstream mediators that are implicated in capsaicin-induced hearing loss. When administering this technique in intratympanic injection, it is imperative that the animal be adequately anesthetized so it does not move during the procedure. Once mastered, this drug delivery system could be used to screen a large number of compounds for efficacy against drug-induced hair loss in experimental animals.

Research

JoVE Journal

Medicine

Osmotic Drug Delivery to Ischemic Hindlimbs and Perfusion of Vasculature with Microfil for Micro-Computed Tomography Imaging

Preclinical research in animal models of peripheral arterial disease plays a vital role in testing the efficacy of therapeutic agents designed to ...

Heterotopic Mucosal Engrafting Procedure for Direct Drug Delivery to the Brain in Mice

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Slow-release Drug Delivery through Elvax 40W to the Rat Retina: Implications for the Treatment of Chronic Conditions

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Intraluminal Drug Delivery to the Mouse Arteriovenous Fistula Endothelium

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Pancreatic Duct Infusion: An Effective and Selective Method of Drug and Viral Delivery

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Optimized LC-MS/MS Method for the High-throughput Analysis of Clinical Samples of Ivacaftor, Its Major Metabolites, and Lumacaftor in Biological Fluids of Cystic Fibrosis Patients

Defects in the cystic fibrosis trans-membrane conductance regulator (CFTR) are the cause of cystic fibrosis (CF), a disease with life-threatening ...

Improved Method for the Establishment of an In Vitro Blood-Brain Barrier Model Based on Porcine Brain Endothelial Cells

Improved Method for the Establishment of an In Vitro Blood-Brain Barrier Model Based on Porcine Brain Endothelial Cells

The aim of this protocol presents an optimized procedure for the purification and cultivation of pBECs and to establish in vitro blood-brain barrier (BBB) ...

Novel Methods for Intranasal Administration Under Inhalation Anesthesia to Evaluate Nose-to-Brain Drug Delivery

Intranasal administration has been reported to be a potential pathway for nose-to-brain delivery of therapeutic agents that circumvents the blood-brain ...

Preclinical Model of Hind Limb Ischemia in Diabetic Rabbits

Peripheral vascular disease is a widespread clinical problem that affects millions of patients worldwide. A major consequence of peripheral vascular ...