Lens cholesterol biosynthesis inhibition: A common mechanism of cataract formation in laboratory animals by pharmaceutical products

CJ‐12,918, a 5‐lipoxygenase (5‐LO) inhibitor, caused cataracts during a 1‐month safety assessment studies in rats whereas the structurally similar ZD‐2138 was without effect. For CJ‐12,918 analogs, blocking different sites of metabolic liability reduced (CJ‐13,454) and eliminated (CJ‐13,610) cataract formation in both rats and dogs. Using this chemical series as a test set, models and mechanisms of toxicity were first explored by testing the utility of ex vivo rat lens explant cultures as a safety screen. This model overpredicted the cataractogenic potential of ZD‐2138 due to appreciably high lens drug levels and was abandoned in favor of a mechanism‐based screen. Perturbations in lens sterol content, from a decline in lathosterol content, preceded cataract formation suggesting CJ‐12,918 inhibited lens cholesterol biosynthesis (LCB). A 2‐day bioassay in rats using ex vivo LCB assessments showed that the level of LCB inhibition was correlated with incidence of cataract formation in animal studies by these 5‐LO inhibitors. Thereafter, this 2‐day bioassay was applied to other pharmaceutical programs (neuronal nitric oxide synthase, sorbitol dehydrogenase inhibitor, squalene synthetase inhibitor and stearoyl‐CoA desaturase‐1 inhibitors/D₄ antagonists) that demonstrated cataract formation in either rats or dogs. LCB inhibition >40% was associated with a high incidence of cataract formation in both rats and dogs that was species specific. Bioassay sensitivity/specificity were further explored with positive (RGH‐6201/ciglitazone/U18666A) and negative (tamoxifen/naphthalene/galactose) mechanistic controls. This body of work over two decades shows that LCB inhibition was a common mechanism of cataract formation by pharmaceutical agents and defined a level of inhibition >40% that was typically associated with causing cataracts in safety assessment studies typically ≥1 month.     

Dietary umbelliferone attenuates alcohol-induced fatty liver via regulation of PPARα and SREBP-1c in rats

This study investigated the effects of umbelliferone (UF) on alcoholic fatty liver and its underlying mechanism. Rats were fed a Lieber–DeCarli liquid diet with 36% of calories as alcohol with or without UF (0.05 g/L) for 8 weeks. Pair-fed rats received an isocaloric carbohydrate liquid diet. UF significantly reduced the severity of alcohol-induced body weight loss, hepatic lipid accumulation and droplet formation, and dyslipidemia. UF decreased plasma AST, ALT, and γGTP activity. UF significantly reduced hepatic cytochrome P450 2E1 activities and increased alcohol dehydrogenase and aldehyde dehydrogenase 2 activities compared to the alcohol control group, which resulted in a lower plasma acetaldehyde level in the rats that received UF. Chronic alcohol exposure inhibited hepatic AMPK activation compared to the pair-fed rats, which was reversed by UF supplementation. UF also significantly suppressed the lipogenic gene expression (SREBP-1c, SREBP-2, FAS, CIDEA, and PPARγ) and elevated the fatty acid oxidation gene expression (PPARα, Acsl1, CPT, Acox, and Acaa1a) compared to the alcohol control group, which could lead to inhibition of FAS activity and stimulation of CPT and fatty acid β-oxidation activities in the liver of chronic alcohol-fed rats. These results indicated that UF attenuated alcoholic steatosis through down-regulation of SREBP-1c-mediated lipogenesis and up-regulation of PPARα-mediated fatty acid oxidation. Therefore, UF may provide a promising natural therapeutic strategy against alcoholic fatty liver.     

Myeloperoxidase gene polymorphism predicts fibrosis severity in women with hepatitis C

Oxidative stress plays an important role on liver fibrosis progression in the course of hepatitis C virus (HCV) infection. Myeloperoxidase (MPO) is an enzyme released by neutrophils and macrophages, responsible for generating hypochlorous acid and reactive oxygen species (ROS) that may lead to liver injury in HCV infection. On the other hand, antioxidant enzymes such as manganese superoxide dismutase (SOD) controls ROS-mediated damage. The aim of the present study was to investigate the influence of MPO G-463A and SOD2 Ala16Val polymorphisms in the severity of liver fibrosis in individuals with chronic HCV infection. The present study included 270 patients with chronic HCV recruited from the Gastrohepatology Service of the Oswaldo Cruz University Hospital/Liver Institute of Pernambuco (Recife, Northeastern Brazil). All patients underwent liver biopsy, which was classified according METAVIR score. The SNPs were determined by real-time PCR. After multivariate analysis adjustment, the GG genotype of MPO and the presence of metabolic syndrome were independently associated with fibrosis severity in women (P = 0.025 OR 2.25 CI 1.10–4.59 and P = 0.032 OR 2.32 CI 1.07–5.01, respectively). The presence of the GG genotype seems to be a risk factor for fibrosis severity in women with HCV.     

PPARγ激动剂对RSV感染的A549细胞TLR3、TNF-α表达的抑制作用

目的 探讨 A549细胞呼吸道合胞病毒（RSV）感染后Toll样受体3（TLR3）及肿瘤坏死因子-α（TNF-α） mRNA和蛋白表达及PPARγ激动剂15-脱氧前列腺素J2（15d-PGJ2）和罗格列酮的干预作用.方法 建立RSV感染的细胞模型,将传代培养的细胞随机分成6组：15d-PGJ2干预组（A）、罗格列酮干预组（B）、RSV组（C）、PDTC组（D）、GW9662组（E）及对照组（F）.各组在培养12、24和48 h后收获上清液和细胞,实时荧光RT-PCR检测TLR3和TNF-α mRNA表达,Western Blot检测TLR3蛋白表达,ELISA法检测上清中TNF-α蛋白水平.结果 与F组相比,各时间点C组TLR3和TNF-α mRNA及蛋白表达均明显升高（均P＜0.01）;与C组相比,A组、B组和D组TLR3和TNF-α mRNA及蛋白表达均明显降低（均P＜0.01）.15d-PGJ2和罗格列酮对TLR3和TNF-α mRNA和蛋白表达的抑制作用在12 h最明显;同一时间点A组和B组TLR3和TNF-α mRNA和蛋白的表达量均呈剂量依赖性下降.结论 RSV感染后TLR3和TNF-α mRNA及蛋白表达升高;罗格列酮和15d-PGJ2能以剂量依赖性方式抑制TLR3和TNF-α mRNA和蛋白表达.     

Graptopetalum paraguayense and resveratrol ameliorates carboxymethyllysine (CML)-induced pancreas dysfunction and hyperglycemia

Hyperglycemia is associated with advanced glycation end products (AGEs). Recently, AGEs were found to cause pancreatic damage, oxidative stress, and hyperglycemia through the AGE receptor. Carboxymethyllysine (CML) is an AGE but whether it induces pancreatic dysfunction remains unclear. Graptopetalum paraguayense, a vegetable consumed in Taiwan, has been used in folk medicine and is an antioxidant that protects against liver damage. We investigated the protective properties of G. paraguayense 95% ethanol extracts (GPEs) against CML-induced pancreatic damage. The results indicated that resveratrol, GPE, and gallic acid (the active compound of GPE) increased insulin synthesis via upregulation of pancreatic peroxisome proliferator activated-receptor-γ (PPARγ) and pancreatic-duodenal homeobox-1 (PDX-1) but inhibited the expression of CML-mediated CCAAT/enhancer binding protein-β (C/EBPβ), a negative regulator of insulin production. Moreover, resveratrol and GPE also strongly activated nuclear factor-erythroid 2-related factor 2 (Nrf2) to attenuate oxidative stress and improve insulin sensitivity in the liver and muscle of CML-injected C57BL/6 mice and resulted in reduced blood glucose levels. Taken together, these findings suggested that GPE and gallic acid could potentially be used as a food supplement to protect against pancreatic damage and the development of diabetes.     

Role of AMPK in pancreatic beta cell function

Pharmacological activation of AMP activated kinase (AMPK) by metformin has proven to be a beneficial therapeutic approach for the treatment of type II diabetes. Despite improved glucose regulation achieved by administration of small molecule activators of AMPK, the potential negative impact of enhanced AMPK activity on insulin secretion by the pancreatic beta cell is an important consideration. In this review, we discuss our current understanding of the role of AMPK in central functions of the pancreatic beta cell, including glucose-stimulated insulin secretion (GSIS), proliferation, and survival. In addition we discuss the controversy surrounding the role of AMPK in insulin secretion, underscoring the merits and caveats of methods used to date.     

Peroxisome Proliferator-Activated Receptor-γ in Lung Cancer: Defining Specific Versus “Off-Target― Effectors

A large number of studies have indicated that thiazolidinediones (TZDs) such as rosiglitazone and pioglitazone inhibit tumor growth, progression, and metastasis. These agents are specific agonists for the nuclear receptor peroxisome proliferator-activated receptor-γ (PPARγ) but also engage other pathways. In lung cancer, these agents have been shown to induce apoptosis and inhibit tumor growth in xenograft models. Retrospective studies have indicated a significant decrease in lung cancer risk in patients using these agents, suggesting that TZDs may be chemopreventive for lung cancer. However, emerging data suggest that chronic use of these agents is associated with increased risk of adverse cardiovascular events. It is therefore critical to determine the relative contributions of PPARγ-dependent versus PPARγ-independent pathways in mediating both the anti-tumorigenic effects and the cardiovascular effects of TZDs. This review examines these pathways with a specific focus on the role of TZDs and PPARγ in lung cancer.