renal-ischaemia-reperfusion-injury-mouse-model-injury

Renal Ischaemia Reperfusion Injury: A Mouse Model of Injury and Regeneration

Renal ischaemia reperfusion injury (IRI) is a common cause of acute kidney injury (AKI) in patients and occlusion of renal blood flow is unavoidable ...

University of Edinburgh

Time-dependent changes in polyamine metabolism and c-Myc expression are reported in kidney of mice treated with cisplatin, a widely used anticancer drug. We show that cisplatin significantly induces the expression of two enzymes critical to proper homeostasis of cellular polyamines, ornithine decarboxylase (ODC) and spermidine/spermine N1-acetyltransferase (SSAT). We also document the cross-talk between signalling pathway(s) induced by cisplatin injury to renal tubules and the testosterone/androgen receptor pathway. Their interaction results in a decrease in testosterone-induced ODC activity and ODC mRNA level, and in differential modulation of SSAT expression. Moreover, cisplatin and antifolate CB 3717, another nephrotoxic drug examined, severalfold up-regulate expression of c-Myc mRNA, albeit with different kinetics. However, cisplatin, contrary to CB 3717, does not induce renal hepatocyte growth factor (HGF)/c-Met expression being without effect on HGF mRNA level and significantly down-regulating c-Met transmembrane receptor message. In conclusion, these in vivo studies document significant cisplatin-induced modulation of polyamine biosynthesis/degradation and up-regulation of c-Myc expression, and suggest that c-Myc transcription factor is involved in the induction of ODC in kidney injured with antifolate, but not with cisplatin.

Cisplatin up-regulates the in vivo biosynthesis and degradation of renal polyamines and c-Myc expression.

The available evidence suggests that metabolic control mechanisms are programmed early in life. Previous studies of pregnant rats fed low-protein diets have suggested that the vegetable oils used in the experimental diets influence the outcome. The present study investigated the offspring of female rats fed semi-synthetic diets containing either 180 or 90g casein/kg with 70 g/kg (w/w) of either corn oil or soya oil during gestation. During lactation, the dams received stock diet, and the offspring were subsequently weaned onto the stock diet. The offspring of dams fed the low-protein diets were smaller at birth. At 25 weeks of age, the offspring were subjected to an oral glucose tolerance test. In the offspring of dams fed the diet containing soya oil, the area under the insulin curve was affected by the protein content of the maternal diet. There was no effect of protein on the area under the insulin curve in the offspring of dams fed the diet prepared with corn oil. There were no differences in plasma glucose concentrations. The levels of mRNA for acetyl-CoA carboxylase- in the livers of female offspring were affected by the protein and oil content of the maternal diet. The level of carnitine palmitoyl transferase mRNA was affected by the protein content of the maternal diet. The present study suggests that PUFA in the maternal diet can interact with protein metabolism to influence the development of the offspring. This may involve the higher content of alpha-linolenic acid in soya oil compared with corn oil.

Interactions between protein and vegetable oils in the maternal diet determine the programming of the insulin axis in the rat.

Iron metabolism during pregnancy is biased toward maintaining the fetal supply, even at the cost of anemia in the mother. The mechanisms regulating this are not well understood. Here, we examine iron deficiency and supplementation on the hierarchy of iron supply and the gene expression of proteins that regulate iron metabolism in the rat. Dams were fed iron-deficient diets for 4 wk, mated, and either continued on the deficient diet or an iron-supplemented diet during either the first half or the second half of their pregnancy. A control group was maintained on normal iron throughout. They were killed at 0.5, 12.5, or 21.5 days of gestation, and tissues and blood samples were collected. Deficiency and supplementation had differential effects on maternal and fetal hematocrit and liver iron levels. From early in pregnancy, a hierarchy of iron supply is established benefiting the fetus to the detriment of the mother. Transferrin receptor, transferrin receptor 2, and hepcidin mRNA expression were regulated by both iron deficiency and supplementation. Expression patterns showed both organ and supplementation protocol dependence. Further analysis indicated that iron levels in the fetal, and not maternal, liver regulate the expression of liver transferrin receptor and hepcidin expression in the mother.

Fetal iron status regulates maternal iron metabolism during pregnancy in the rat.

Components of the insulin receptor signaling pathway are probably some of the best studied ones. Even though methods for studying these components are well established, the in vivo effects of different fasting regimens, and the time course of insulin receptor phosphorylation and that of its downstream components in insulin-sensitive peripheral tissues have not been analyzed in detail.

In vivo differential effects of fasting, re-feeding, insulin and insulin stimulation time course on insulin signaling pathway components in peripheral tissues.

Obesity is associated with induction of the ER (endoplasmic reticulum)-stress response signalling and insulin resistance. PTP1B (protein tyrosine phosphatase 1B) is a major regulator of adiposity and insulin sensitivity. The aim of the present study was to investigate the role of L-PTP1B (liver-specific PTP1B) in chronically HFD (high-fat diet) and pharmacologically induced (tunicamycin and thapsigargin) ER-stress response signalling in vitro and in vivo. We assessed the effects of ER-stress response induction on hepatic PTP1B expression, and consequences of hepatic-PTP1B deficiency, in cells and mouse liver, on components of ER-stress response signalling. We found that PTP1B protein and mRNA expression levels were up-regulated in response to acute and/or chronic ER stress, in vitro and in vivo. Silencing PTP1B in hepatic cell lines or mouse liver (L-PTP1B(-/-)) protected against induction of pharmacologically induced and/or obesity-induced ER stress. The HFD-induced increase in CHOP (CCAAT/enhancer-binding protein homologous protein) and BIP (binding immunoglobulin protein) mRNA levels were partially inhibited, whereas ATF4 (activated transcription factor 4), GADD34 (growth-arrest and DNA-damage-inducible protein 34), GRP94 (glucose-regulated protein 94), ERDJ4 (ER-localized DnaJ homologue) mRNAs and ATF6 protein cleavage were completely suppressed in L-PTP1B(-/-) mice relative to control littermates. L-PTP1B(-/-) mice also had increased nuclear translocation of spliced XBP-1 (X box-binding protein-1) via increased p85α binding. We demonstrate that the ER-stress response and L-PTP1B expression are interlinked in obesity- and pharmacologically induced ER stress and this may be one of the mechanisms behind improved insulin sensitivity and lower lipid accumulation in L-PTP1B(-/-) mice.

Liver-specific deletion of protein tyrosine phosphatase (PTP) 1B improves obesity- and pharmacologically induced endoplasmic reticulum stress.

Protein tyrosine phosphatase 1B (PTP1B), a key negative regulator of leptin and insulin signaling, is positively correlated with adiposity and contributes to insulin resistance. Global PTP1B deletion improves diet-induced obesity and glucose homeostasis via enhanced leptin signaling in the brain and increased insulin signaling in liver and muscle. However, the role of PTP1B in adipocytes is unclear, with studies demonstrating beneficial, detrimental or no effect(s) of adipose-PTP1B-deficiency on body mass and insulin resistance. To definitively establish the role of adipocyte-PTP1B in body mass regulation and glucose homeostasis, adipocyte-specific-PTP1B knockout mice (adip-crePTP1B(-/-)) were generated using the adiponectin-promoter to drive Cre-recombinase expression. Chow-fed adip-crePTP1B(-/-) mice display enlarged adipocytes, despite having similar body weight/adiposity and glucose homeostasis compared to controls. High-fat diet (HFD)-fed adip-crePTP1B(-/-) mice display no differences in body weight/adiposity but exhibit larger adipocytes, increased circulating glucose and leptin levels, reduced leptin sensitivity and increased basal lipogenesis compared to controls. This is associated with decreased insulin receptor (IR) and Akt/PKB phosphorylation, increased lipogenic gene expression and increased hypoxia-induced factor-1-alpha (Hif-1α) expression. Adipocyte-specific PTP1B deletion does not beneficially manipulate signaling pathways regulating glucose homeostasis, lipid metabolism or adipokine secretion in adipocytes. Moreover, PTP1B does not appear to be the major negative regulator of the IR in adipocytes.

Adipocyte-specific protein tyrosine phosphatase 1B deletion increases lipogenesis, adipocyte cell size and is a minor regulator of glucose homeostasis.

Ischemia reperfusion injury (IRI) contributes to partial flap and solid organ transplant failure. Heme-oxygenase 1 (HO-1) is an inducible, cytoprotective enzyme which protects against IRI in solid organ transplant models. Heme arginate (HA), a HO-1 inducer, is a promising, translatable, preconditioning agent. This study investigated the effects of preconditioning with HA on the clinical outcome of a myocutaneous IRI model. Forty male Lewis rats were randomized to intravenously receive 1) Control-NaCl, 2) HA, 3) HA and tin mesoporphyrin (SnMP), a HO-1 inhibitor; and 4) SnMP alone. Twenty-four hours later, an in situ transverse rectus abdominis myocutaneous flap was performed under isoflurane anesthesia. Viability of flaps was measured clinically and by laser-Doppler perfusion scanning. In vitro work on human epidermal keratinocytes (HEKa) assessed the effects of HA, SnMP, and the iron chelator desferrioxamine on 1) cytotoxicity, 2) intracellular reactive oxygen species (ROS) concentration, and 3) ROS-mediated DNA damage. In contrast to our hypothesis, HA preconditioning produced over 30% more flap necrosis at 48 h compared with controls (P = 0.02). HA-containing treatments produced significantly worse flap perfusion at all postoperative time points. In vitro work showed that HA is cytotoxic to keratinocytes. This cytotoxicity was independent of HO-1 and was mediated by the generation of ROS by free heme. In contrast to solid organ data, pharmacological preconditioning with HA significantly worsened clinical outcome, thus indicating that this is not a viable approach in free flap research.

Paradoxical effects of heme arginate on survival of myocutaneous flaps.

Protein tyrosine phosphatase-1B (PTP1B) negatively regulates insulin and leptin signaling, rendering it an attractive drug target for treatment of obesity-induced insulin resistance. However, some studies suggest caution when targeting macrophage PTP1B, due to its potential anti-inflammatory role. We assessed the role of macrophage PTP1B in inflammation and whole-body metabolism using myeloid-cell (LysM) PTP1B knockout mice (LysM PTP1B). LysM PTP1B mice were protected against lipopolysaccharide (LPS)-induced endotoxemia and hepatic damage associated with decreased proinflammatory cytokine secretion in vivo. In vitro, LPS-treated LysM PTP1B bone marrow-derived macrophages (BMDMs) displayed increased interleukin (IL)-10 mRNA expression, with a concomitant decrease in TNF-α mRNA levels. These anti-inflammatory effects were associated with increased LPS- and IL-10-induced STAT3 phosphorylation in LysM PTP1B BMDMs. Chronic inflammation induced by high-fat (HF) feeding led to equally beneficial effects of macrophage PTP1B deficiency; LysM PTP1B mice exhibited improved glucose and insulin tolerance, protection against LPS-induced hyperinsulinemia, decreased macrophage infiltration into adipose tissue, and decreased liver damage. HF-fed LysM PTP1B mice had increased basal and LPS-induced IL-10 levels, associated with elevated STAT3 phosphorylation in splenic cells, IL-10 mRNA expression, and expansion of cells expressing myeloid markers. These increased IL-10 levels negatively correlated with circulating insulin and alanine transferase levels. Our studies implicate myeloid PTP1B in negative regulation of STAT3/IL-10-mediated signaling, highlighting its inhibition as a potential anti-inflammatory and antidiabetic target in obesity.

Myeloid-cell protein tyrosine phosphatase-1B deficiency in mice protects against high-fat diet and lipopolysaccharide-induced inflammation, hyperinsulinemia, and endotoxemia through an IL-10 STAT3-dependent mechanism.

Alicja Czopek

MRC Centre for Inflammation Research

University of Edinburgh

Renal Ischaemia Reperfusion Injury: A Mouse Model of Injury and Regeneration

Alicja Czopek

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}MRC Centre for Inflammation Research

University of Edinburgh

Renal Ischaemia Reperfusion Injury: A Mouse Model of Injury and Regeneration

MRC Centre for Inflammation Research