The nitric oxide donor molsidomine improves survival and reduces hepatocyte apoptosis in cholestasis and endotoxemia

Molsidomine alleviates acetic acid-induced colitis in rats by reducing oxidative stress, inflammation and apoptosis

Ulcerative colitis (UC) is a subcategory of intestinal inflammatory bowel disease characterized by up-regulation of proinflammatory cytokines and oxidative stress. The current study was designed to assess the probable protective effect of the nitric oxide (NO) donor, molsidomine, in experimental colitis model in rats. Rats were haphazardly classified into four groups: control, acetic acid, acetic acid + molsidomine (1 mg/kg) and acetic acid + molsidomine (2 mg/kg). Molsidomine (1 and 2 mg/kg/day) was administered by intra-peritoneal injection for 7 days prior to induction of UC. On the 8th day, colitis was induced by intra-rectal instillation of 2 ml of (4% v/v) acetic acid in normal saline using a pediatric plastic catheter. The rats were sacrificed 1 day following colitis induction, blood samples were obtained; colons and livers were isolated then underwent macroscopic, biochemical, histopathological and immunohistochemical examination. Pretreatment with molsidomine significantly reduced disease activity index, colon mass index, colonic macroscopic and histological damage. Besides, molsidomine significantly reduced the serum levels of alanine transaminase (ALT) (58.7 ± 8.9 & 59.7 ± 8 vs 288.75 ± 31.4 in AA group) and aspartate transaminase (AST) (196.2 ± 37.4 & 204 ± 30 vs 392.7 ± 35.6 in AA group). Moreover, molsidomine effectively decreased malondialdehyde (MDA) and total nitrate/nitrite (NOx) contents, and up regulated the enzymatic activity of superoxide dismutase (SOD) and glutathione level (GSH) in colonic and hepatic tissues. With regard to anti-inflammatory mechanisms, molsidomine suppressed tumor necrosis factor-alpha (TNF-α) (792.5 ± 16.7 & 448 ± 12.1 vs 1352.5 ± 45.8 in AA group) in colonic tissues and (701 ± 19 & 442.5 ± 22.5 vs 1501 ± 26 in AA group) in hepatic tissues as well as nuclear transcription factor kappa B (NF-kB/p65) levels (416.2 ± 4.1 & 185.5 ± 14.2 vs 659.2 ± 11.5 in AA group) in colonic tissues and (358 ± 6.2 & 163.5 ± 9.6 vs 732.5 ± 5.5 in AA group) in hepatic tissues. In addition, molsidomine significantly decreased inducible nitric oxide synthase (iNOS) levels (8.1 ± 0.1 & 4.9 ± 0.1 vs 16 ± 0.1 in AA group) in colonic tissues and (8.6 ± 0.3 & 6.1 ± 0.1 vs 17.8 ± 0.1 in AA group) in hepatic tissues, and myeloperoxidase (MPO) contents (10.5 ± 0.4 & 6.6 ± 0.3 vs 20.9 ± 0.6 in AA group) in colonic tissues and (13.1 ± 0.2 & 6.3 ± 0.06 vs 23.9 ± 1.4 in AA group) in hepatic tissues at p > 0.05. Furthermore, it suppressed apoptosis by reducing expression of Caspase 3 and Bax in colonic and hepatic tissues. Therefore, molsidomine might be a promising candidate for the treatment of UC.

Nitric oxide synthase 2 enhances the survival of mice during Salmonella Typhimurium infection-induced sepsis by increasing reactive oxygen species, inflammatory cytokines and recruitment of neutrophils to the peritoneal cavity

Sepsis, a leading cause of death in intensive care units, is primarily caused due to an exaggerated immune response. The hyperactive inflammatory response mediated by immune cells against infectious organisms and their toxins results in host cell death and tissue damage, the hallmarks of septic shock. Therefore, molecules that modulate inflammatory responses are attractive therapeutic targets for sepsis. Nitric oxide (NO) is a signaling molecule, which is implicated in regulating diverse immune functions. Although, the protective roles of NO in infectious diseases are well documented, its importance in sepsis is controversial. In the present study, the effects of intra-peritoneal injection of mice with Salmonella Typhimurium, a Gram-negative intracellular pathogen, were studied which leads to a rapid upregulation of serum cytokines and infiltration of neutrophils to the peritoneal cavity. Surprisingly, the induction of inflammatory cytokines and chemokines, e.g. IL6 and CCL2, and the infiltration of neutrophils into the peritoneal cavity are mitigated in mice lacking Nitric oxide synthase 2 (NOS2). The reduced inflammatory response in Nos2^-/- mice is accompanied by greater bacterial burden in the peritoneal cavity, lower thymic atrophy, higher liver damage and cardiovascular dysfunction followed by decreased survival. However, no significant differences are observed in other responses between C57BL/6 wild type (WT) and Nos2^-/- mice: induction of glucocorticoids, phagocytic ability and apoptosis of peritoneal cells. This study clearly highlights the NOS2-dependent and -independent responses in this mouse model of peritonitis induced sepsis. Importantly, pre-treatment of Nos2^-/- mice with DETA-NO, a NO donor, upon infection, restores neutrophil recruitment, reduces bacterial numbers in the peritoneal cavity, improves liver and cardio-vascular function and enhances survival. Interestingly, DETA-NO treatment does not significantly increase the survival of infected WT mice. The implications of these results and the complex roles of NO as a target molecule during sepsis are discussed.

Reduced hepatic arterial perfusion impairs the recovery from focal hepatic venous outflow obstruction in liver-resected rats

BACKGROUND

Extended partial hepatectomy (PH) in patients is leading to portal hyperperfusion but reduced hepatic arterial perfusion (HAP), and is invariably causing focal hepatic venous outflow obstruction (FHVOO). We observed in a rat model that PH in combination with right median hepatic vein ligation (RMHV-L) caused confluent parenchymal necrosis interspersed with viable portal tracts in the obstructed territory and large sinusoidal vascular canals in the border zone. Lack of HAP impaired the spontaneous course of recovery in terms of enlarged parenchymal necrosis, delayed regeneration, and the absence of draining vascular canals. We aimed to investigate whether pharmacological intervention modulates the imbalance between portal venous and hepatic arterial inflow, aggravates the liver damage, and delays the recovery process after FHVOO in liver-resected rats.

METHODS

Male Lewis rats were subjected to 70% PH and RMHV-L. Molsidomine or NG-nitro-L-arginine methyl ester (L-NAME) or saline were applied daily. Hepatic damage, microcirculation, regeneration, and vascular remodeling were evaluated at postoperative days 1, 2, and 7. Animals subjected to RMHV-L only were used as "no HAP" control.

RESULTS

Significant increase of portal venous inflow with a concomitant decrease in HAP was observed in all groups after PH. Molsidomine treatment did neither affect hepatic hemodynamics nor the spontaneous recovery. In contrast, L-NAME treatment further decreased HAP which impaired hepatic microcirculation, aggravated parenchymal damage, decelerated recovery, and impaired the formation of sinusoidal canals.

CONCLUSIONS

Reduction of HAP through inhibition of nitric oxide production worsened the recovery from FHVOO. Drugs increasing HAP need to be evaluated to reverse the hyperperfusion-induced impairment of the spontaneous course after FHVOO.

Anti-inflammatory and vasoprotective activity of a retroviral-derived peptide, homologous to human endogenous retroviruses: endothelial cell effects

Malignant and inflammatory tissues sometimes express endogenous retroviruses or their proteins. A highly-conserved sequence from retroviral transmembrane (TM) proteins, termed the “immunosuppressive domain (ID)”, is associated with inhibition of immune and inflammatory functions. An octadecapeptide (MN10021) from the ID of retroviral TM protein p15E inhibits in vitro release of pro-inflammatory cytokines and increases synthesis of anti-inflammatory IL-10. We sought to determine if MN10021 has significant in vivo effects. MN10021, prepared by solid-phase synthesis, was dimerized through a naturally-occurring, carboxy-terminal cysteine. In vivo anti-inflammatory activity was determined using a murine model of sodium periodate (NaIO₄)-induced peritonitis. In vivo vasoprotective effects were determined using: (1) a carrageenan-induced model of disseminated intravascular coagulation (DIC) in mice; (2) a reverse passive Arthus model in guinea pigs; and (3) vasoregulatory effects in spontaneously hypertensive rats (SHR). In vitro studies included: (1) binding/uptake of MN10021 using human monocytes, cultured fibroblasts, and vascular endothelial cells (VEC); (2) gene expression by RT-PCR of MN10021-treated VEC; and (3) apoptosis of MN10021-treated VEC exposed to staurosporine or TNF-α. One-tenth nmol MN10021 inhibits 50 percent of the inflammatory response in the mouse peritonitis model. Furthermore, 73 nmol MN10021 completely protects mice in a lethal model of carrageenan-induced DIC and inhibits vascular leak in both the mouse DIC model and a guinea pig reverse passive Arthus reaction. MN10021 binds to and is taken up in a specific manner by both human monocytes and VEC but not by cultured human fibroblasts. Surprisingly, orally-administered MN10021 lowers blood pressure in SHR rats by 10–15% within 1 h suggesting a direct or indirect effect on the vascular endothelium. MN10021 and derived octapeptides induce iNOS (inducible nitric oxide synthase) mRNA in VEC and nitrate in VEC cell culture supernatants and protect VEC from induced apoptosis or necrosis. However, pretreatment of VEC with nitro-L-arginine methyl ester (L-NAME), while inhibiting the release of nitrate, does not block the anti-apoptotic effect of MN10021 and derived octapeptides suggesting that their potent vasoprotective and anti-inflammatory activity is not nitric oxide dependent.

Nitric oxide donors in sepsis: a systematic review of clinical and in vivo preclinical data

An abundant literature in the field of sepsis focuses on the role of NO. Inhibiting NO synthesis corrects certain hemodynamic parameters of septic shock but failed to improve outcome in patients. Conversely, administration of NO donors lowers blood pressure but restores microcirculatory flow in patients with sepsis. We undertook a systematic review of the literature to comprehensively summarize the results of studies exploring the effects of systemic NO donors in sepsis. We included both clinical and preclinical data. We described the details surrounding NO donor administration, and the results obtained in each study were regrouped in broad categories. In the case of animal research, we limited our data collection to in vivo protocols and described the sepsis model. Finally, we critically appraised all the studies included in the review. Overall, the reviewed publications aimed for physiopathological description rather than clinical relevance and did not meet the required criteria for extrapolation to clinical practice. With this reserve, NO donors usually improved the outcomes measured (e.g., mortality, pulmonary hypertension, tissue/organ perfusion, etc.) but also lowered blood pressure. We conclude that our findings warrant further animal experimentation designed to maximize clinical relevance.

Nitric oxide administration restores the hepatic artery buffer response during porcine endotoxemia

The hepatic artery buffer response, which is lost during endotoxemia, plays a central role in the autoregulation of liver perfusion. A temporarily decreased synthesis of nitric oxide during early endotoxemia might be responsible for this dysfunction; hence exogenous administration of nitric oxide could reestablish the autoregulation of hepatic blood flow and help prevent hepatic damage later in septic shock. Fifteen pigs were treated with lipopolysaccharide +/- the nitric oxide donor nitroprusside-sodium via the portal vein. Hemodynamics were measured, and serum chemistry and liver biopsies for nitric oxide synthase expression were obtained. Lipopolysaccharide decreased arterial liver perfusion after 5 hours by 38% (p = .012), which was reversed by addition of nitroprusside (8%). Administration of nitroprusside preserved an increase of 28% in hepatic arterial upon portal vein flow reduction (p < .001). Nitroprusside maintained mRNA levels of constitutive nitric oxide synthase in liver tissue which were decreased by lipopolysaccharide (p = .026 vs. p = .114) and tempered the burst in inducible nitric oxide synthase expression at t = 3 hours. The early administration of the nitric oxide donor sodium nitroprusside during endotoxemia is able to reestablish the autoregulatory response of the hepatic artery following reduction of hepatic blood flow. This beneficial effect might help to prevent subsequent hepatic damage in the course of abdominal sepsis.

Effect of antioxidant treatments on the gut-liver axis oxidative status and function in bile duct-ligated rats

BACKGROUND

Experimental and clinical studies have demonstrated the pivotal role of oxidative stress in the promotion of hepatic and intestinal injury in obstructive jaundice. The present study was undertaken to investigate the effect of well known antioxidant treatments on the gut-liver axis oxidative status and function in bile duct-ligated rats.

METHODS

A total of 60 male Wistar rats were randomly divided into six groups of 10 animals each: controls, sham operated, bile duct ligated (BDL), and BDL treated with either N-acetylcysteine (NAC), allopurinol, or alpha-tocopherol (alpha-TC). Ten days after treatment, the hepatic and intestinal oxidative status was estimated by measuring lipid peroxidation and a battery of biochemical markers comprising the organ's thiol redox state (i.e., glutathione, cysteine, protein thiols, oxidized glutathione, nonprotein mixed disulfides, oxidized cysteine derivatives, protein symmetrical disulfides, and protein mixed disulfides). Portal and aortic endotoxin concentrations and alanine aminotransferase (ALT) levels were also determined.

RESULTS

All antioxidant treatments significantly improved intestinal barrier function and protected from cholestatic liver injury, as evidenced by reduction of the portal and aortic endotoxin concentration and ALT levels, respectively. This effect accompanied their significant antioxidant action in both organs, mediated by a certain influence profile on the thiol redox state by each treatment.

CONCLUSION

NAC, allopurinol, and alpha-TC, exerting a potent combined antioxidant effect on the intestine and liver in experimental obstructive jaundice, significantly prevented intestinal barrier dysfunction and liver injury. The variety of results depending on the antioxidant agent that was administered and the marker of oxidative stress that was estimated, indicates that a battery of biomarkers would be more appropriate in assessing pharmacologic responses to therapeutic interventions.

New preservation strategies for preventing liver grafts against cold ischemia reperfusion injury

BACKGROUND

In spite of improvements in University of Wisconsin (UW) preservation solution, the injury from grafts during cold storage is an unresolved problem in liver transplantation. The aim of the present study was to evaluate the beneficial effect on ischemia-reperfusion injury associated with liver transplantation of the inversion of K(+) and Na(+) concentrations and the replacement of hydroxyethyl starch (HES) by polyethylene glycol (PEG) in UW preservation solution.

METHODS

Using an orthotopic liver transplantation model, the effects on rat liver preservation of a modified preservation solution (UW-PEG) were evaluated, based on the inversion of K(+) and Na(+) concentration and the replacement of HES by PEG 35 kDa (0.03 mmol/L) in UW preservation solution.

RESULTS

The use of UW-PEG preservation solution ameliorated the biochemical and histological parameters of hepatic damage. Thus, at 24 h after transplantation, transaminase levels were reduced significantly when livers were preserved during 8 h in UW-PEG preservation solution compared with the original UW solution. In addition, histological findings revealed fewer and smaller areas of hepatocyte necrosis. The benefits of UW-PEG solution cannot be explained by modifications in oxidative stress or neutrophil accumulation associated with liver transplantation. However, the results of hepatic and portal blood flow indicated that the benefits of this modified preservation solution, UW-PEG were associated with improvements in the microcirculatory disorders after reperfusion.

CONCLUSIONS

The UW-PEG solution, while retaining all the advantages of UW solution, improved hepatic ischemia-reperfusion injury associated with liver transplantation.

Hepatic guanylate cyclase activity is decreased in a model of cirrhosis: a quantitative cytochemistry study

The production of nitric oxide (NO) in liver disease and its role in vascular control has been a subject of much interest in recent years. However, the activity of guanylate cyclase (GC), the enzyme activated by NO has received little attention with regard to liver disease. In this study we have utilised a quantitative cytochemical technique to examine the activity of GC on a per cell basis in a rat model of cirrhosis. Our results show a significant reduction in GC activity, indicating that vascular regulation is likely to be substantially affected irrespective of NO generation in this disease model.

Gut regulatory peptides bombesin and neurotensin reduce hepatic oxidative stress and histological alterations in bile duct ligated rats

Gut regulatory peptides bombesin (BBS) and neurotensin (NT) exert a wide spectrum of biological actions on gastrointestinal tissues and we have previously shown that they improve intestinal barrier function and oxidative stress in experimentally jaundiced rats. In the present study, we explored their potential action on liver histology and oxidative status in bile duct ligated rats. Seventy male Wistar rats were randomly divided into five groups: controls, sham operated, bile duct ligated (BDL), BDL + BBS (10 microg/kg, s.c. x3), BDL + NT (300 microg/kg, i.p.). At the end of the experiment, on day 10, serum total bilirubin and alanine aminotransferase (ALT) levels were determined and endotoxin was measured in portal and aortic blood. Liver tissue samples were examined histologically for evaluation of the ratio of portal tracts presenting changes of obstructive cholangiopathy and neutrophils' number in portal tracts. In addition, hepatic oxidative status was estimated on liver homogenates by measurements of lipid peroxidation (malondialdehyde), protein oxidation (protein carbonyl groups) and thiol redox state [reduced glutathione (GSH), oxidized glutathione (GSSG), total non-protein mixed disulfides (NPSSR) and protein thiols (PSH)]. Administration of BBS or NT significantly reduced portal and aortic endotoxaemia observed in obstructive jaundice. Both agents significantly ameliorated liver injury, as demonstrated by improvement of obstructive cholangiopathy and reduction of ALT. This effect was accompanied by prevention of lipid peroxidation, protein oxidation and decrease of the oxidized forms GSSG and NPSSR. Moreover, neutrophil accumulation in portal tracts was significantly decreased. In conclusion, this study shows that gut regulatory peptides BBS and NT reduce cholestatic liver injury, exerting protective effects on portal tract architecture, neutrophil infiltration and hepatic oxidative stress in bile duct ligated rats.

Is ischemic preconditioning a useful strategy in steatotic liver transplantation?

This study examined the effect of preconditioning on steatotic livers for transplantation and attempted to identify the underlying protective mechanisms. Blood flow alterations, neutrophil accumulation, tumor necrosis factor alpha release and lipid peroxidation were observed in nonsteatotic livers after transplantation. Steatotic and nonsteatotic liver grafts were similar in their blood flow, neutrophil accumulation, and TNF release after transplantation. However, in the presence of steatosis, lipid peroxidation and hepatic injury increased. In addition, recipients of steatotic liver grafts were more vulnerable to lung damage associated with transplantation. The conversion of xanthine dehydrogenase to xanthine oxidase and the accumulation of xanthine during cold ischemia was greater in steatotic than in nonsteatotic liver grafts. The results obtained with xanthine oxidase inhibitors indicated that xanthine/xanthine oxidase could be responsible for the increased lipid peroxidation as well as the exacerbated liver and lung damage associated with transplantation of steatotic livers. Preconditioning reduced the xanthine accumulation and percentage of xanthine oxidase seen in steatotic liver grafts during cold ischemia, and conferred protection against liver and lung damage following transplantation. The benefits of preconditioning could be mediated by nitric oxide. These findings suggest that preconditioning could be a relevant new strategy to protect against the inherent risk of steatotic liver failure following transplantation.