The effect of exenatide (a GLP-1 analogue) and sitagliptin (a DPP-4 inhibitor) on asymmetric dimethylarginine (ADMA) metabolism and selected biomarkers of cardiac fibrosis in rats with fructose-induced metabolic syndrome.

Asymmetric dimethylarginine (ADMA), an endogenous inhibitor of nitric oxide (NO) synthesis, is a risk factor for endothelial dysfunction, a common pathophysiological denominator for both atherogenesis and cardiac fibrosis. We aimed to investigate whether the cardioprotective and antifibrotic effects of incretin drugs, exenatide and sitagliptin, may be associated with their ability to affect circulating and cardiac ADMA metabolism. Normal and fructose-fed rats were treated with sitagliptin (5.0/10 mg/kg) or exenatide (5/10 µg/kg) for 4 weeks. The following methods were used: LC-MS/MS, ELISA, Real-Time-PCR, colorimetry, IHC and H&E staining, PCA and OPLS-DA projections. Eight-week fructose feeding resulted in an increase in plasma ADMA and a decrease in NO concentration. Exenatide administration into fructose-fed rats reduced the plasma ADMA level and increased NO level. In the heart of these animals exenatide administration increased NO and PRMT1 level, reduced TGF-ß1, α-SMA levels and COL1A1 expression. In the exenatide treated rats renal DDAH activity positively correlated with plasma NO level and negatively with plasma ADMA level and cardiac α-SMA concentration. Sitagliptin treatment of fructose-fed rats increased plasma NO concentration, reduced circulating SDMA level, increased renal DDAH activity and reduced myocardial DDAH activity. Both drugs attenuated the myocardial immunoexpression of Smad2/3/P and perivascular fibrosis. In the metabolic syndrome condition both sitagliptin and exenatide positively modulated cardiac fibrotic remodeling and circulating level of endogenous NOS inhibitors but had no effects on ADMA levels in the myocardium.

The role of PPAR gamma agonists - rosiglitazone and 15-deoxy-Δ12,14-prostaglandin J2 in experimental cyclosporine A hepatotoxicity.

Cyclosporine A (CsA) is an immunosuppressive drug used in transplantation and treatment of autoimmune diseases. Experimental studies revealed impairments in liver function and morphology among cyclosporine-treated animals. The aim of the study was to evaluate hepatoprotective activity of peroxisome-proliferator-activated receptors γ (PPARγ) ligands: rosiglitazone and 15-deoxy-Δ12,14-prostaglandin J2 (PGDJ2) on CsA-induced hepatotoxicity in experimental animals. CsA was administered subcutaneously at a dose of 15 mg/kg/day for 28 days. Both PPARγ agonists were given for 28 days 0.5 hour before the administration of CsA. Rosiglitazone was administered orally at a dose of 8 mg/kg/day and PGDJ2 was given intraperitoneally at a dose of 30 µg/kg/day. CsA induced liver injury was evidenced by increased serum levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT), and bilirubin. Concentrations of glutathione (GSH) and glutathione disulfide (GSSG), lipid peroxidation products, nicotinamide adenine dinucleotide+/nicotinamide adenine dinucleotide hydrogen (NAD+/NADH), nicotinamide adenine dinucleotide phosphate+/nicotinamide adenine dinucleotide phosphate hydrogen (NADP+/NADPH) and adenosine diphosphate/adenosine triphosphate (ADP/ATP) ratios and caspase 3 activity that were measured in the liver tissue showed, that CsA induced oxidative stress, evoked an imbalanced redox state and apoptosis in the liver. Microscope examination showed sinusoidal dilatation, mononuclear cell infiltration, necrosis of hepatocytes, intracellular vacuolar degeneration and microvesicular steatosis and apoptopic cells. The biochemical and morphological changes induced by CsA were limited by administration of both PPARγ agonist - rosiglitazone and PGDJ2. Our biochemical and liver histopathological examination indicate that both PPARγ agonists may play an important role in protecting against CsA-induced hepatotoxicity.

The effect of the angiotensin II receptor, type 1 receptor antagonists, losartan and telmisartan, on thioacetamide-induced liver fibrosis in rats.

It has been reported previously that the density of angiotensin II receptors is increased in the rat liver in experimentally-induced fibrosis. We hypothesized that pharmacological blockade of angiotensin receptors may produce beneficial effects in models of liver fibrosis. In this study, we used the widely used thioacetamide (TAA)-induced model of liver fibrosis (300 mg/L TAA ad libitum for 12 weeks). Rats received daily injections (i.p), lasting 4 weeks of the angiotensin II type 1 receptor antagonists, losartan 30 mg/kg (TAA + L) or telmisartan 10 mg/kg (TAA + T) and were compared to rat that received TAA alone. Chronic treatment with losartan and telmisartan was associated with a significant reduction in the activity of alkaline phosphatase, and decreased concentrations of tumor necrosis factor-alpha and transforming growth factor beta-1 compared to controls. We also found a significant reduction interleukin-6 in rats receiving telmisartan (P < 0.05) but not losartan. Both treatments increased the concentration of liver glutathione along with a concomitant decrease of GSSG compared to controls. In addition, increased paraoxonase 1 activity was observed in the serum of rats receiving telmisartan group compared to the TAA alone controls. Finally, histological evaluation of liver sections revealed losartan and telmisartan treatment was associated with reduced inflammation and liver fibrosis. Taken together, these results indicate that both telmisartan and losartan have anti-inflammatory and anti-oxidative properties in the TAA model of liver fibrosis. These finding add support to a growing body of literature indicating a potentially important role for the angiotensin system in liver fibrosis and indicate angiotensin antagonists may be useful agents for fibrosis treatment.

Protective effects of melatonin against thioacetamide-induced liver fibrosis in rats.

The aim of this study was to determine the effect of melatonin on thioacetamide (TAA) induced liver fibrosis in rats. The antifibrotic effects of melatonin were assessed by determining activity indirect markers of fibrosis: aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (AP), and proinflammatory cytokines: interleukin 6 (IL-6), interleukin-1beta (IL-1ß), tumour necrosis factor alpha (TNF-α), transforming growth factor-beta (TGF-ß) and platelet-derived growth factor (PDGF). Parameters of oxidative stress: oxidised glutathione (GSSG), reduced glutathione (GSH) and presaged activity of paraoxonase 1 (PON-1), an antioxidative enzyme were determined. Inflammatory changes and fibrosis extent were evaluated histologically. Experiments were carried out in Wistar rats. Animals were divided into 4 groups: I - controls, water ad libitum for 12 weeks, group II - TAA, 300 mg/L ad libitum for 12 weeks, III - melatonin, 10 mg/kg b.w. intraperitoneally (i.p.) daily for 4 weeks, IV - TAA, 300 mg/L ad libitum for 12 weeks followed by melatonin, 10 mg/kg/b.w. i.p. daily for 4 weeks. Results of serum determinations demonstrated significantly lower activity of AST, ALT and AP in the group receiving TAA followed by melatonin compared to the group receiving only TAA. Immunoenzymatic findings on effect of melatonin on concentration of proinflammatory cytokines confirmed these data. Biochemical examinations in liver homogenates revealed statistically significant improvement (concentration of GSH increases and concentration of GSSG decreases) in animals with TAA-induced liver damage receiving melatonin. Moreover, the activity of PON-1 toward phenyl acetate and paraoxon was increased in liver homogenates and serum in the group receiving TAA followed by melatonin compared to the TAA group without melatonin treatment. Microscopic evaluation disclosed inhibitory effects of melatonin on inflammatory changes and extent of liver fibrosis.

Effects of treatment with melatonin and tryptophan on liver enzymes, parameters of fat metabolism and plasma levels of cytokines in patients with non-alcoholic fatty liver disease--14 months follow up.

Non-alcoholic fatty liver disease (NAFLD), most common chronic hepatic pathology, that occurs in the developed countries is estimated at 1/3 of the population. Amongst the numerous pathogenetic factors, oxidative stress and apoptosis of hepatocytes initiate many inflammatory processes and are involved in the progression of disease, particularly in transformation of non-alcoholic steatohepatitis (NASH) to cirrhosis. The aim of our study was to determine the effects of tryptophan and melatonin on the selected biochemical parameters in patients with NAFLD, and additionally, to evaluate the effects of tryptophan and melatonin in improvement of liver tissue in selected NAFLD patients. Seventy four patients with NAFLD confirmed by histopathological examination of liver biopsy samples, were admitted to the study. They were randomly assigned to three groups. Group I received the preparation Essentiale forte in the dose of 3 x 1 tablet per day and tryptophan 2 x 500 mg/day over the period of 14 months, group II received Essentiale forte and melatonin 2 x 5 mg/day over 14 months and group III received only Essentiale over the period of 14 months. In nine patients of groups I, II, and III, the liver biopsy was performed after 14-months of treatment period. Out of nine patients whom biopsy was performed, three of them were from group I, four from group II and two of them were from group III, respectively. After the 14-month treatment period, gamma-glutamyl transferase (GGPT) activity and levels of triglycerides and LDL-cholesterol were found to be significantly reduced in group I and II. The level of melatonin after the therapy was significantly elevated in group I and II and did not change in group III. Statistically significantly lower levels of IL-1, IL-6 and TNF-α were observed in patients receiving melatonin and tryptophan, comparing with group III treated with Essentiale forte only. These study findings demonstrate that melatonin and tryptophan substantially reduce the levels of pro-inflammatory cytokines and improve some parameters of fat metabolism in patients with NAFLD. In few patients with NASH melatonin and tryptophan reduced the inflammation in liver. We conclude that melatonin is worth considering for the therapy of NAFLD, particularly in patients with impaired fat metabolism accompanied by hypertriglyceridemia and hyper-LDL cholesterolemia.

The role of peroxisome-proliferator-activating receptor gamma agonists: rosiglitazone and 15-deoxy-delta12,14-prostaglandin J2 in chronic experimental cyclosporine A-induced nephrotoxicity.

Cyclosporine A(CsA) is an immunosuppressor frequently used in the transplant surgery and in the treatment of autoimmune diseases. The therapeutic benefits of CsA are often limited by it's main side effect-nephrotoxicity. Mechanisms of chronic CsA- induced renal damage include: activation of renin-angiotensin-aldosterone system, upregulation of transforming growth factor beta (TGF-ß), oxidative stress. This study was undertaken to investigate the protective effect of the peroxisome-proliferator-activated receptors gamma (PPARs-γ) agonists: rosiglitazone and 15-deoxy-Δ12,14-prostaglandin J2 (PGDJ2), against CsA-induced kidney injury in male Wistar rats. CsA was administered subcutaneously at a dose of 15 mg/kg/day for 28 days. Both PPAR-γ agonists were given for 28 days 0.5 hour before the administration of CsA. Rosiglitazone was administered orally at a dose of 8 mg/kg/day and PGDJ2 was given intraperitoneally at a dose of 30 µg/kg/day. CsA induced renal failure was evidenced by increased serum levels of urea, uric acid and creatinine. Serum concentrations of GSH and GSSG, lipid peroxidation products as well as NAD+/NADH, NADP+/NADPH and ADP/ATP ratios showed, that CsA induced oxidative stress and evoked an imbalanced red-ox state in the kidney. Light and electron microscope studies showed degenerative changes within renal tubules with damage to their mitochondria, interstitial fibrosis and arteriolopathy. Immunohistochemical expression of profibrotic TGF-ß was assessed. The biochemical and morphological changes induced by CsA were limited by administration of both rosiglitazone and PGDJ2. Ultrastructural examination of renal tubular epithelial cells showed marked improvement within mitochondria. Our results indicate that both PPAR-γ agonists used in the experiment may play an important role in protecting against CsA-induced damage in the kidney.

Comparison of anti-inflammatory properties of peroxisome proliferator-activated receptor gamma agonists rosiglitazone and troglitazone in prophylactic treatment of experimental colitis.

Non-specific inflammatory bowel disease (IBD), including ulcerative colitis and Crohn`s disease, is a chronic noninfectious inflammatory disease whose incidence is increasingly high, especially in the developed countries. Effective methods of its treatment and prevention of recurrences are still under investigation. Amongst the options to control effectively the inflammatory processes of the gastrointestinal tract are thiazolidinediones - peroxisome proliferator-activated receptors gamma (PPAR-γ) agonists, whose beneficial effects on macroscopic and histopathological features of colitis have been confirmed in numerous studies. In the present study, possible effects of PPAR-γ agonists rosiglitazone and troglitazone enhancing the resistance of colonic tissues to the damaging factor were examined and compared. Rats received the food with 0.01% rosiglitazone or troglitazone for 4 weeks; during the final 2 weeks, colitis-inducing 1.5% DSS (dextran sodium sulfate) was additionally administered in the drinking water. The large intestine specimens were microscopically evaluated and the levels of Th1- (IL-2, INF) and Th2-dependent (IL-4, IL-10) cytokines were determined in the serum and intestinal homogenates. Prophylactic treatment with rosiglitazone and troglitazone ameliorated colitis substantially down-regulating the microscopic inflammatory parameters. Rosiglitazone and troglitazone administered before the induction of colitis exerted comparable effects on colitis. Both substances significantly reduced the levels of pro-inflammatory cytokines and increased the levels of inflammation-limiting cytokines. We conclude that thiazolidinedione drugs are likely to be successfully used for therapy and prevention of non-specific bowel diseases.

Comparison of the anti-inflammatory and therapeutic actions of PPAR-gamma agonists rosiglitazone and troglitazone in experimental colitis.

Non-specific inflammatory bowel diseases, including ulcerative colitis and Crohn`s disease, are chronic non-infectious diseases that showed an increase in prevalence in recent years, particularly in the developed countries. The effective methods of their treatment and prevention of recurrences are currently under investigation. One type of therapy that can prevent the inflammatory recurrence in the gastrointestinal tract is the PPAR-γ agonists thiazolidinediones. Numerous studies available in literature have confirmed the beneficial effects of thiazolidinediones (glitazones), namely rosiglitazone and troglitazone in the gut. The objective of the present study was to compare the possible effects of rosiglitazone 10 mg/kg b.w. or 30 mg/kg b.w. and troglitazone 30 mg/kg b.w. on experimental colitis induced by administration of 1.5% dextran sodium sulphate (DSS) administered in drinking water to rats. Specimens collected from the large intestine were microscopically evaluated, and concentrations of Th1- dependent (IL-2, INF) and Th2-dependent (IL-4, IL-10) cytokines were determined in the serum and intestinal homogenates. Both rosiglitazone and troglitazone have demonstrated significant anti-inflammatory properties. This observation was confirmed by histopathological and immunoenzymatic tests. The therapeutic efficacy of rosiglitazone was dose-dependent. Troglitazone resulted in significantly stronger enhancement of anti-inflammatory cytokine expression than rosiglitazone and comparable downregulation of pro-inflammatory cytokine expression compared to rosiglitazone used in a higher dose.

Effects of peroxisome proliferator-activated receptors-gamma ligands on dextran sodium sulphate-induced colitis in rats.

Recent studies indicate the involvement of peroxisone proliferator-activated receptor-γ (PPAR-γ) in the inflammatory reaction. The exact mechanism of PPAR-γ action has not been elucidated. It is supposed that PPAR-γ regulates transcription of genes responsible for encoding cytokines involved in the inflammatory response. The latest studies, carried out to explain the pathogenesis of non-specific colitis, confirm beneficial effects of PPAR-γ agonists on attenuation of colon inflammation. The aim of the present study was to assess the effects of nuclear PPAR-γ activity on the course of experimental acute colitis induced by intragastric administration of dextran sodium sulphate (DSS) using the PPAR-γ agonist rosiglitazone and the antagonist BADGE in rats. Colitis in Wistar rats was induced by 1.5% DSS administered in drinking water for 8 days. Animals with induced colitis received rosiglitazone, bisphenol A diglycidyl ether (BADGE) or both substances. After decapitation, colons were macroscopically and histopathologically evaluated. Levels of interleukin-1ß (IL-1ß), interleukin-6 (IL-6), interleukin-10 (IL-10), tumor necrosis factor-α (TNF-α) and myeloperoxidase (MPO) were determined in serum and colon homogenates using ELISA. In rats with experimentally induced colitis receiving rosiglitazone, the inflammatory reaction was found to be markedly limited; ulceration, oedema and infiltration activity were reduced. The activated PPAR-γ inhibit the expression of proinflammatory factors, such as IL-6, TNF-α, and neutrophil chemotaxis, which was evidenced by MPO reduction in serum and colon homogenates mediated by rosiglitazone. The positive effects of rosiglitazone on expression of IL-10 were also demonstrated. During the short period of observation, BADGE did not increase histopathological inflammatory markers.

Influence of the peroxisome proliferator-activated receptor gamma (PPAR-γ) agonist, rosiglitazone and antagonist, biphenol-A-diglicydyl ether (BADGE) on the course of inflammation in the experimental model of colitis in rats.

PPAR-γ plays a role in the development of immune response, particularly in inflammation. The inflammatory reaction may be stimulated or suppressed by the presence of PPAR ligands. Some researchers suggest positive influence of the PPAR-γ agonist on suppression of the intestinal inflammatory process, yet there has not been much evidence showing that the antagonist of PPAR-γ can affect the inflammatory process. The aim of the present study was to define the mechanism by which PPAR-γ ligands affect the course of experimentally induced colitis in rats. Colitis was induced in rats by rectal administration of TNBS (trinitrobenzene sulfonate). Rosiglitazone was administrated to animals at the dose of 8 mg/kg four times via an intra-gastric probe. Biphenol-A-diglicydyl ether (BADGE) was administrated intraperitoneally at the dose of 120 mg/kg, three times every second day. One group of animals received rosiglitazone together with BADGE before the induction of inflammation. Histological and ELISA examinations of large intestine samples were performed. Levels of IL-1ß, IL-6, TNF-α cytokines were determined in serum and homogenates. Rats exposed to rosiglitazone had higher body weight yet lower large intestine weight. Histological findings showed less ulceration, lower expression of crypts' loss and smaller oedema. Animals, which did not receive rosiglitazone, and those receiving it together with BADGE, developed more severe inflammatory changes. Rosiglitazone decreased the expression of inflammatory cytokines, such as IL-6 and TNF-α, both in serum and in intestinal homogenates. BADGE used with TNBS did not increase the expression of inflammatory cytokines; however, applied together with rosiglitazone, it caused inflammation similar to that observed among rats with experimentally induced colitis. Rosiglitazone reduces inflammation by decreasing the expression of IL-6 and TNF-α. BADGE administered with rosiglitazone blocks the activity of PPAR-γ and abolishes the protective effects of PPAR-γ agonist.

RAS inhibitors decrease apoptosis of acinar cells and increase elimination of pancreatic stellate cells after in the course of experimental chronic pancreatitis induced by dibutyltin dichloride.

Chronic pancreatitis (CP) is a progressive disease, in which the exocrine function of the gland is gradually lost and fibrosis develops due to repeated episodes of acute pancreatitis. The aim of the study was to investigate the effects of RAS inhibitors on the apoptosis of acinar cells and pancreatic stellate cells (PSCs) elimination in experimental CP induced by dibutyltin dichloride (DBTC). CP was induced by administration of DBTC to the femoral vein. Simultaneously captopril, losartan, enalapril and lisinopril were administered intraperitoneally. The rats were decapitated after 60 days and tissue of pancreas was collected. In rats treated by DBTC the features of inflammatory infiltration, ductal lumen dilatation, fibrosis were found. Strong reactivity with caspase2(L) and clusterin-beta antibodies was observed in areas of fibrosis. In animals treated with RAS inhibitors inflammatory changes and fibrosis were less severe. In groups of rats treated with DBTC and RAS inhibitors immunoreactivity of caspase(2L) and clusterin-beta was weak. Positive immunostaining against smooth muscle actine and desmin was observed in the elongated cells (PSC-s). This reaction was weak in groups of rat treated with DBTC and RAS inhibitors. Treatment of CP rats with RAS inhibitors alleviate apoptosis of pancreatic acinar cells and induces PSCs elimination.

The role of adenosine A2a receptors in experimental acute pancreatitis.

PURPOSE: The role of adenosine and its receptors in acute pancreatitis remains unelucidated. The aim was to evaluate the effects of the adenosine A2a receptor agonist and antagonist in the severe, taurocholate-induced experimental acute pancreatitis (EAP). MATERIAL AND METHODS: The experiments were performed on 80 male Wistar rats, subdivided into 4 groups: C--the control rats, I--the EAP group, IIA--EAP group treated with the A2a adenosine receptor agonist CGS 21680, IIB--EAP group treated with the A2a adenosine receptor antagonist ZM 241385. The blood for alpha-amylase and lipase and tissues samples for the morphological examinations and immunohistochemistry for A2a receptors were collected in 2, 6, 24 hours of the experiment. RESULTS: The serum alpha-amylase tended to decrease in the group IIA as compared to EAP untreated after 6 and 24 h. No significant effect of both treatments on serum lipase was noted. The administration of CGS 21680 resulted in favorable decrease of the inflammatory cell infiltration, hemorrhagic changes, necrosis and vacuolization of acinar cells, without an evident effect on the edema of the interstitial tissue. The administration of ZM 241385 did not affect the scores of necro-hemorrhagic changes and inflammatory infiltration, whereas it decreased the scores of vacuolization and edema. In all groups the expression of A2a receptors was similar. CONCLUSIONS: Our findings suggest, that A2a adenosine receptors are involved in the course of sodium taurocholate EAP. It is probable that the modulation of some subgroups of adenosine receptors could alleviate the course of severe experimental AP.