Runkuan Yang

Ethyl pyruvate prevents lethality in mice with established lethal sepsis and systemic inflammation

Sepsis, a potentially fatal clinical syndrome, is mediated by an early (e.g., tumor necrosis factor and IL-1) and late [e.g., high mobility group B-1 (HMGB1)] proinflammatory cytokine response to infection. Specifically targeting early mediators has not been effective clinically, in part because peak mediator activity often has passed before therapy can be initiated. Late-acting downstream effectors, such as HMGB1, that mediate sepsis lethality may be more relevant therapeutic targets. Ethyl pyruvate (EP) recently was identified as an experimental therapeutic that significantly protects against lethal hemorrhagic shock. Here, we report that EP attenuates lethal systemic inflammation caused by either endotoxemia or sepsis even if treatment begins after the early tumor necrosis factor response. Treatment with EP initiated 24 h after cecal puncture significantly increased survival (vehicle survival = 30% vs. EP survival = 88%, P < 0.005). EP treatment significantly reduced circulating levels of HMGB1 in animals with established endotoxemia or sepsis. In macrophage cultures, EP specifically inhibited activation of p38 mitogen-activated protein kinase and NF-κB, two signaling pathways that are critical for cytokine release. This report describes a new strategy to pharmacologically inhibit HMGB1 release with a small molecule that is effective at clinically achievable concentrations. EP now warrants further evaluation as an experimental “rescue” therapeutic for sepsis and other potentially fatal systemic inflammatory disorders.

Increased iNOS activity is essential for intestinal epithelial tight junction dysfunction in endotoxemic mice

We tested the hypothesis that increased production of nitric oxide (NO·) associated with lipopolysaccharide (LPS)-induced systemic inflammation leads to functionally significant alterations in the expression and/or targeting of key tight junction (TJ) proteins in ileal and colonic epithelium. Wild-type or inducible NO· synthase (iNOS) knockout male C57B1/6J mice were injected intraperitoneally with 2 mg/kg Escherichia coli O111:B4 LPS. iNOS was inhibited using intraperitoneal L-N(6)-(1-iminoethyl)lysine (L-NIL; 5 mg/kg). Immunoblotting of total protein and NP-40 insoluble proteins revealed decreased expression and decreased TJ localization, respectively, of the TJ proteins, zonula occludens (ZO)-1, ZO-2, ZO-3, and/or occludin in ileal mucosa and colonic mucosa (total protein only) after injection of C57B1/6J mice with LPS. Immunohistochemistry showed deranged distribution of ZO-1 and occludin in both tissues from endotoxemic mice. Endotoxemia was associated with evidence of gut epithelial barrier dysfunction evidenced by increased ileal mucosal permeability to fluorescein isothiocyanate-dextran (Mr = 4 kDa) and increased bacterial translocation to mesenteric lymph nodes. Pharmacologic inhibition of iNOS activity using L-NIL or genetic ablation of the iNOS gene ameliorated LPS-induced changes in TJ protein expression and gut mucosal barrier function. These results support the view that at least one mechanism contributing to the pathogenesis of gastrointestinal epithelial dysfunction secondary to systemic inflammation is increased iNOS-dependent NO· production leading to altered expression and localization of key TJ proteins.

Increased iNOS activity is essential for hepatic epithelial tight junction dysfunction in endotoxemic mice.

We tested the hypothesis that increased production of nitric oxide (NO*) by inducible NO* synthase (iNOS) is a key factor responsible for alterations in the expression, localization, and function of key tight junction (TJ) proteins in mice challenged with lipopolysaccharide (LPS, endotoxin). Endotoxemia was associated with hepatobiliary epithelial barrier dysfunction, as evidenced by increased plasma-to-bile leakage of FITC-labeled dextran (relative molecular mass 40 kDa) and increased circulating levels of bile acids and conjugated bilirubin. Immunoblotting revealed decreased expression of zonula occludens (ZO)-1, ZO-2, ZO-3, and occludin in liver after injection of C57Bl/6J mice with 2 mg/kg Escherichia coli 0111:B4 LPS. Nonidet P-40-insoluble (i.e., TJ-associated) occludin and ZO-1 were virtually undetectable 12 and 18 h after injecting LPS. Immunofluorescence microscopy also revealed deranged subcellular localization of ZO-1 and occludin in endotoxemic mice. Pharmacological inhibition of iNOS activity using l-N6-(1-iminoethyl)lysine (5 mg/kg) or genetic ablation of iNOS ameliorated LPS-induced changes in hepatobiliary barrier function, and these strategies partially preserved TJ protein expression and localization. Steady-state levels of occludin and ZO-3 transcripts decreased transiently after injecting LPS but returned toward normal by 12 and 24 h after induction of endotoxemia, respectively. These results support the view that iNOS-dependent NO* production is an important factor contributing to hepatobiliary epithelial barrier dysfunction resulting from systemic inflammation and suggest that iNOS induction may play a role in the development of cholestatic jaundice in patients with severe sepsis.

Ethyl pyruvate ameliorates distant organ injury in a murine model of acute necrotizing pancreatitis.

Objective:Ethyl pyruvate has been shown to be an effective anti-inflammatory agent in a variety of in vitro and in vivo model systems. Herein, we used a murine model of acute pancreatitis to compare the effects of treatment with either Ringer’s lactate solution or ethyl pyruvate solution on several physiologic and biochemical variables related to disease severity. Design:Experimental animal study. Setting:University laboratory. Subjects:C57Bl/6 mice. Interventions:Pancreatitis was induced by feeding the animals a choline-deficient diet supplemented with 0.5% ethionine for 24 hrs and then challenging the animals with seven hourly 50 μg/kg intraperitoneal injections of cerulein and a single intraperitoneal injection of Escherichia coli lipopolysaccharide (4 mg/kg). Measurements and Main Results:When mice were treated with ethyl pyruvate (40 mg/kg intraperitoneally every 6 hrs for 48 hrs) instead of Ringer’s lactate solution starting 2 hrs after the injection of lipopolysaccharide, long-term survival was improved from one of ten to six of ten (p = .057). When mice were treated with a 40 mg/kg dose of ethyl pyruvate just before the first dose of cerulein and then injected with a second 40 mg/kg dose 6 hrs later, serum concentrations of alanine aminotransferase measured 10 hrs after the first cerulein dose were significantly lower than in mice with pancreatitis treated with Ringer’s lactate solution. In this model of acute pancreatitis, the same dosing regimen for ethyl pyruvate also ameliorated bacterial translocation to mesenteric lymph nodes and leakage of fluorescein isothiocyanate-labeled albumin from blood into bronchoalveolar lavage fluid. Treatment with ethyl pyruvate decreased pancreatic expression of tumor necrosis factor and interleukin-6 messenger RNA and nuclear factor-κB DNA binding in nuclear extracts prepared from pancreatic tissue. Conclusion:Treatment with ethyl pyruvate ameliorated the local inflammatory response and decreased local and distant organ injury in a murine model of necrotizing pancreatitis.

Ethyl pyruvate ameliorates acute alcohol-induced liver injury and inflammation in mice

Ethyl pyruvate dissolved in a calcium-containing balanced salt solution--Ringers ethyl pyruvate solution (REPS)--ameliorates ileal mucosal hyperpermeability and decreases the expression of several proinflammatory genes when it is used instead of Ringers lactate solution (RLS) to resuscitate mice from hemorrhagic shock. Herein, we sought to determine whether delayed treatment with REPS would be beneficial in a murine model of acute alcoholic liver injury associated with binge drinking. Mice were gavaged with 3 doses of ethanol (5 g/kg each dose) over a 12-hour period and then randomized to treatment with 3 intraperitoneal doses of REPS or RLS over 12 hours. Compared with sham-treated controls not subjected to alcohol intoxication, RLS-treated mice demonstrated histologic evidence of fatty change and piecemeal necrosis of hepatocytes in the liver, as well as a significant increase in the plasma concentration of alanine aminotransferase. Biochemical changes induced by alcohol administration included increased hepatic lipid peroxidation, nuclear factor-kappaB activation, and tumor necrosis factor-alpha messenger RNA expression. All of these alcohol-induced effects were ameliorated by treatment with REPS instead of RLS. These data support the view that treatment with REPS ameliorates the hepatic inflammatory response and decreases hepatocellular injury in mice subjected to acute alcohol intoxication.

Prolonged treatment with N-acetylcystine delays liver recovery from acetaminophen hepatotoxicity

IntroductionAcetaminophen (APAP) toxicity is the most common cause of acute liver failure in the US and Europe. Massive hepatocyte necrosis is the predominant feature of APAP-induced acute liver injury (ALI). Liver regeneration is a vital process for survival after a toxic insult, it occurs at a relative late time point after the injurious phase. Currently, N-acetylcysteine (NAC), a glutathione precursor, is the antidote for acetaminophen overdose. However, NAC is effective only for patients who present within hours of an acute overdose, and is less effective for late-presenting patients. It is possible that in delayed patients, previously reduced endogenous glutathione (GSH) level has restored and prolonged treatment with NAC might be toxic and impair liver regeneration. Therefore, we hypothesize that prolonged treatment with NAC impairs liver regeneration in ALI induced by APAP.MethodsALI was induced in C57BL/6 male mice by a single dose of APAP (350 mg/kg) by intraperitoneal injection. After two hours of APAP challenge, the mice were given 100 mg/kg NAC dissolved in 0.6 mL saline, or saline treatment every 12 hours for a total of 72 hours.ResultsSeventy-two hours after APAP challenge, compared with saline treatment, NAC treatment significantly increased serum transaminases (alanine transaminase/aspartate aminotransferase), induced evident hepatocyte vacuolation in the periportal area and delayed liver regeneration seen in histopathology. This detrimental effect was associated with reduced hepatic nuclear factor (NF)-κB DNA binding and decreased expression of cell cycle protein cyclin D1, two important factors in liver regeneration.ConclusionsProlonged treatment with NAC impairs liver regeneration in ALI induced by APAP.

Ethyl pyruvate provides durable protection against inflammation-induced intestinal epithelial barrier dysfunction.

Ethyl pyruvate (EP) has been shown to be an effective anti-inflammatory agent. Herein, we sought to test the following hypotheses: 1) the pharmacological effects of EP persist after cells have been exposed to the compound in vitro, even if the cultures are washed to minimize the amount of EP that is retained in the media; 2) the pharmacological effects of EP persist in vivo, even after waiting a prolonged period (i.e., 6 h) after the last dose of the compound; and 3) the in vivo pharmacological effects of EP are distinct from those of the closely related compound, sodium pyruvate. Incubation of Caco-2 human enterocyte-like monolayers with cytomix, a mixture of interleukin-1&bgr;, interferon-&ggr;, and tumor necrosis factor, increased permeability to the fluorescent macromolecule, FITC-labeled Dextran (mol wt 4,000 Da). Co-incubation of the cells with 5 mM EP ameliorated cytomix-induced hyperpermeability and induction of iNOS mRNA expression. EP was associated with similar pharmacological effects when cells were pre-incubated with the compound for 24 h prior and then washed extensively prior to adding the cytokine cocktail. Injecting C57Bl/6 mice with lipopolysaccharide (LPS) resulted in gut barrier dysfunction and hepatocellular injury. Although equivalent doses of both EP and sodium pyruvate ameliorated these phenomena, EP was more efficacious than pyruvate. Pretreatment with EP ameliorated the deleterious effects of LPS, even when the duration between the last dose of EP and the endotoxic challenge was 6 h. We conclude that EP provides durable protection against some of the deleterious effects of LPS or pro-inflammatory cytokines.

Bile high-mobility group box 1 contributes to gut barrier dysfunction in experimental endotoxemia

Lipopolysaccharide (LPS) is an important factor in sepsis. LPS given by intraperitoneal injection induces intestinal hyperpermeability and bacterial translocation in animals and stimulates hepatic Kupffer cells to release TNF-alpha into the bile. This study aims to test the hypothesis that in response to LPS stimulation, hepatic Kupffer cells and extrahepatic macrophages release a large amount of the inflammatory cytokine high-mobility group box 1 (HMGB1) into the bile and that bile containing HMGB1 contributes to gut barrier dysfunction in experimental endotoxemia. To test this, rat common bile ducts were catheterized and bile flow rate was monitored before and during the LPS administration. Eight hours after LPS challenge, anti-HMGB1 neutralizing antibody or nonimmune (sham) IgG was injected into the duodenal lumen of endotoxemic rats; normal mice were also gavaged with normal or endotoxemic rat bile (bile collected from LPS-treated rats). We found that after LPS challenge, the bile flow rate in rats was significantly decreased at the 4- to 12-h time points, TNF-alpha concentration in the bile was markedly elevated at the 3- to 4-h time points, and bile HMGB1 levels were significantly increased at the 8- to 12-h time points. Duodenal injection with anti-HMGB1 antibody reversed LPS-induced gut barrier dysfunction in rats. In addition, feeding endotoxemic rat bile to normal mice significantly increased both mucosal permeability and bacterial translocation. The increase in permeability and bacterial translocation was reversible following removal of HMGB1 from the endotoxemic rat bile. These findings document that bile HMGB1 mediates gut barrier dysfunction in experimental endotoxemia.

Vascular adhesion protein‐1 and syndecan‐1 in septic shock

Constituents of vascular endothelial surface layer (glycocalyx), e.g. an anchor protein syndecan‐1 (SDC‐1), can be detected in plasma in many inflammatory conditions. In inflammation, vascular adhesion protein‐1 (VAP‐1) is rapidly translocated to the apical side of the endothelial cells and may be released to plasma in a soluble form. We hypothesized that glycocalyx injury coincides with VAP‐1 activation on endothelial cells. To test the hypothesis, we measured SDC‐1 and VAP‐1 levels in 20 patients with septic shock.

Ethyl pyruvate reduces liver injury in a murine model of extrahepatic cholestasis.

Ethyl pyruvate has been shown to ameliorate liver injury and decrease expression of several proinflammatory cytokines when used to treat mice with hemorrhagic shock or alcoholic hepatitis. Herein we sought to determine whether delayed treatment with ethyl pyruvate dissolved in a Ringer’s-type balanced salt solution—Ringer’s ethyl pyruvate solution (REPS)—would be beneficial in a murine model of common bile duct ligation (CBDL)-induced liver injury. Male C57BL/6 mice were subjected to a sham (n = 6) procedure or CBDL (n = 27). Twenty-four hours after operation, mice subjected to CBDL were randomized to receive treatment with either REPS (40 mg/kg of ethyl pyruvate per dose) or Ringer’s lactate solution (RLS) every 8 h over a 72 h period. Compared with sham-treated controls, CBDL in RLS-treated mice was associated with histological evidence of hepatocellular necrosis as well as significant increases in the plasma concentrations of alanine aminotransferase and total bilirubin. Relative to sham-treated controls, CBDL in RLS-treated mice also was associated with increased hepatic lipid peroxidation and increased hepatic expression of transcripts for TNF, IL-6, and iNOS. All of these changes were significantly attenuated by delayed treatment with REPS after CBDL. In the RLS-treated group, CBDL was associated with increased NF-κB DNA binding in nuclear extracts prepared from liver tissue. Treatment with REPS increased NF-κB DNA binding still further. CBDL was associated with increased hepatocellular apoptosis in both the RLS- and REPS-treated groups. These data support the view that ethyl pyruvate ameliorates hepatic inflammation, lipid peroxidation, and necrosis in mice subjected to CBDL. Ethyl pyruvate warrants further evaluation as an adjunctive treatment to ameliorate liver injury from extrahepatic biliary obstruction.