Nonalcoholic Steatohepatitis: A Search for Factual Animal Models.

Nonalcoholic fatty liver disease (NAFLD) is characterized by hepatic steatosis, which occurs in the absence of alcohol abuse. NAFLD can evolve into progressive liver injury and fibrosis in the form of nonalcoholic steatohepatitis (NASH). Several animal models have been developed to attempt to represent the morphological, biochemical, and clinical features of human NASH. The actual review presents a critical analysis of the most commonly used experimental models of NAFLD/NASH development. These models can be classified into genetic, nutritional, and a combination of genetic and nutritional factors. The main genetic models are ob/ob and db/db mutant mice and Zucker rats. The principal nutritional models employ methionine- and choline-deficient, high-fat, high-cholesterol and high-cholate, cafeteria, and high-fructose diets. Currently, associations between high-fructose and various compositions of high-fat diets have been widely studied. Previous studies have encountered significant difficulties in developing animal models capable of reproducing human NASH. Some models produce consistent morphological findings, but the induction method differs significantly compared with the pathophysiology of human NASH. Other models precisely represent the clinical and etiological contexts of this disease but fail to provide accurate histopathological representations mainly in the progression from steatosis to liver fibrosis.

Rosmarinic acid attenuates hepatic ischemia and reperfusion injury in rats.

Rosmarinic acid (RosmA) demonstrates antioxidant and anti-inflammatory properties. We investigated the effect of RosmA on liver ischemia/reperfusion injury. Rats were submitted to 60 min of ischemia plus saline or RosmA treatment (150 mg/kg BW intraperitoneally) followed by 6 h of reperfusion. Hepatocellular injury was evaluated according to aminotransferase activity and histological damage. Hepatic neutrophil accumulation was also evaluated. Oxidative/nitrosative stress was estimated by measuring the reduced glutathione, lipid hydroperoxide and nitrotyrosine levels. Endothelial and inducible nitric oxide synthase (eNOS/iNOS) and nitric oxide (NO) were assessed with immunoblotting and chemiluminescence assays. Hepatic tumor necrosis factor-alpha (TNF-α) and interleukin-1beta mRNA were assessed using real-time PCR, and nuclear factor-kappaB (NF-κB) activation was estimated by immunostaining. RosmA treatment reduced hepatocellular damage, neutrophil infiltration and all oxidative/nitrosative stress parameters. RosmA decreased the liver content of eNOS/iNOS and NO, attenuated NF-κB activation, and down-regulated TNF-α and interleukin-1beta gene expression. These data indicate that RosmA exerts anti-inflammatory and antioxidant effects in the ischemic liver, thereby protecting hepatocytes against ischemia/reperfusion injury. The mechanisms underlying these effects may be related to the inhibitory potential of RosmA on the NF-κB signaling pathway and the reduction of iNOS and eNOS expressions and NO levels, in addition to its natural antioxidant capability.

NFκB activation in cutaneous lesions of leprosy is associated with development of multibacillary infection.

BACKGROUND: Nuclear factor kappa B (NFκB) transcription factors play a central role in controlling the expression of genes involved in inflammatory reactions, proliferation, and survival of human cells. However, the in situ evaluation of NFκB activity in leprosy has not been completed previously. The aim of this study was to determine whether NFκB activity correlates with susceptibility or resistance to Mycobacterium leprae infection in biopsies from skin lesions of 38 patients with the clinical and laboratory diagnosis of leprosy. METHODS: The NFκB activation profile was evaluated in biopsies from skin lesions of 38 patients with the clinical and laboratory diagnosis of leprosy. NFκB activation was evaluated and quantified by Southwestern histochemistry, and its activation index (range, 0-4) was calculated according to the percentage of nuclear positivity by the histochemistry. Activation index >1 was considered representative of activation of NFκB. RESULTS: Fifteen patients (39.5%) demonstrated activated NFκB. Multibacillary leprosy was associated with activated NFκB (54.5%, P=0.028). Borderline leprosy was most strongly associated with NFκB activation (80%), with an odds ratio of 32.7 (P=0.016). These clinical forms are characterized by increased susceptibility to M. leprae and by immunological instability. Activation of NFκB was absent in the granulomas in tuberculoid leprosy, which represents an effective inflammatory reaction pattern against M. leprae. CONCLUSION: These results indicate that NFκB activation could favor susceptibility and immunological instability to M. leprae infection, potentially by the stimulation of phagocytosis and the regulation of apoptotic mechanisms of infected cells, leading to the proliferation of this intracellular bacillus. Further studies are needed to evaluate if inhibition of NFκB activation in multibacillary leprosy could favor resistance and an effective granulomatous immune response.

Riboflavin (vitamin B-2) reduces hepatocellular injury following liver ischaemia and reperfusion in mice.

Riboflavin has been shown to exhibit anti-inflammatory and antioxidant properties in the settings of experimental sepsis and ischaemia/reperfusion (I/R) injury. We investigated the effect of riboflavin on normothermic liver I/R injury. Mice were submitted to 60 min of ischaemia plus saline or riboflavin treatment (30 µmoles/kg BW) followed by 6 h of reperfusion. Hepatocellular injury was evaluated by aminotransferase levels, reduced glutathione (GSH) content and the histological damage score. Hepatic neutrophil accumulation was assessed using the naphthol method and by measuring myeloperoxidase activity. Hepatic oxidative/nitrosative stress was estimated by immunohistochemistry. Liver endothelial and inducible nitric oxide synthase (eNOS/iNOS) and nitric oxide (NO) amounts were assessed by immunoblotting and a chemiluminescence assay. Riboflavin significantly reduced serum and histological parameters of hepatocellular damage, neutrophil infiltration and oxidative/nitrosative stress. Furthermore, riboflavin infusion partially recovered hepatic GSH reserves and decreased the liver contents of eNOS/iNOS and NO. These data indicate that riboflavin exerts antioxidant and anti-inflammatory effects in the ischaemic liver, protecting hepatocytes against I/R injury. The mechanism of these effects appears to be related to the intrinsic antioxidant potential of riboflavin/dihydroriboflavin and to reduced hepatic expression of eNOS/iNOS and reduced NO levels, culminating in attenuation of oxidative/nitrosative stress and the acute inflammatory response.