Pyruvate inhibits hepatic ischemia-reperfusion injury in rats

Antibiotic-induced microbiome depletion alters renal glucose metabolism and exacerbates renal injury after ischemia-reperfusion injury in mice

Recent studies have revealed the impact of antibiotic-induced microbiome depletion (AIMD) on host glucose homeostasis. The kidney has a critical role in systemic glucose homeostasis; however, information regarding the association between AIMD and renal glucose metabolism remains limited. Hence, we aimed to determine the effects of AIMD on renal glucose metabolism by inducing gut microbiome depletion using an antibiotic cocktail (ABX) composed of ampicillin, vancomycin, and levofloxacin in mice. The results showed that bacterial 16s rRNA expression, luminal concentrations of short-chain fatty acids and bile acids, and plasma glucose levels were significantly lower in ABX-treated mice than in vehicle-treated mice. In addition, ABX treatment significantly reduced renal glucose and pyruvate levels. mRNA expression levels of glucose-6-phosphatase and phosphoenolpyruvate carboxykinase in the renal cortex were significantly higher in ABX-treated mice than in vehicle-treated mice. We further examined the impact of AIMD on the altered metabolic status in mice after ischemia-induced kidney injury. After exposure to ischemia for 60 min, renal pyruvate concentrations were significantly lower in ABX-treated mice than in vehicle-treated mice. ABX treatment caused a more severe tubular injury after ischemia-reperfusion. Our findings confirm that AIMD is associated with decreased pyruvate levels in the kidney, which may have been caused by the activation of renal gluconeogenesis. Thus, we hypothesized that AIMD would increase the vulnerability of the kidney to ischemia-reperfusion injury.NEW & NOTEWORTHY This study aimed to determine the impact of antibiotic-induced microbiome depletion (AIMD) on renal glucose metabolism in mice. This is the first report confirming that AIMD is associated with decreased levels of pyruvate, a key intermediate in glucose metabolism, which may have been caused by activation of renal gluconeogenesis. We hypothesized that AIMD can increase the susceptibility of the kidney to ischemia-reperfusion injury.

Hepatoprotective effects of ethyl pyruvate against carbon tetrachloride-induced oxidative stress, biochemical and histological alterations in rats

This study investigated the protective effects of ethyl pyruvate (EP) against carbon tetrachloride (CCl₄)-induced acute hepatic injury in rats. The administration of a single dose of CCl₄ (1.6 g/kg body weight) significantly elevated the levels of malondialdehyde, nitric oxide, alanine transaminase, aspartate transaminase, and alkaline phosphatase, cholesterol, low-density lipoprotein cholesterol, and triglycerides. In addition, CCl₄ was found to significantly suppress the activity of superoxide dismutase, catalase, and glutathione peroxidase. All of these parameters were restored to their normal levels by the administration of EP before and after the CCl₄ injection. Moreover, the number of positive apoptotic hepatocytes had significantly increased in the CCl₄ group but decreased in rats treated with EP along with CCl₄. Histopathological changes induced by CCl₄ were also ameliorated by EP treatment. These findings provided evidence that EP, because of its antioxidant and anti-apoptotic action, could protect rat liver against CCl₄-induced acute liver injury.

Ethyl Pyruvate Directly Attenuates Active Secretion of HMGB1 in Proximal Tubular Cells via Induction of Heme Oxygenase-1

Renal ischemia reperfusion (IR) is a main cause of acute kidney injury leading to high morbidity and mortality during postoperative periods. This study investigated whether ethyl pyruvate (EP) protects the kidney against renal IR injury. Male C57BL/6 mice were treated with vehicle or EP (40 mg/kg) 1 h before ischemia and the plasma creatinine (Cr) levels and tubular damage were evaluated after reperfusion. EP attenuated the IR-induced plasma Cr levels, renal inflammation and apoptotic cell death, but the effect of EP was abolished by pretreating Zinc protoporphyrin (ZnPP), a heme oxygenase (HO)-1 inhibitor. HO-1 is a stress-induced protein and protects the kidney against IR injury. EP increased significantly HO-1 expression in the proximal tubular cells in vivo and HK-2 cells in vitro. Inhibition of PI3K/Akt pathway and knockdown of Nrf2 blocked HO-1 induction by EP. High mobility group box 1 (HMGB1) secretion was assessed as an early mediator of IR injury; plasma HMGB1 were significantly elevated as early as 2 h to 24 h after reperfusion and these were attenuated by EP, but the effect of EP was abolished by ZnPP. EP also reduced HMGB1 secretion stimulated by TNF-α in HK-2 cells, and the inhibition of PI3K/Akt and knockdown of HO-1 blocked the effect of EP. Conclusively, EP inhibits the active secretion of HMGB1 from proximal tubular cells during IR injury by inducing HO-1 via activation of PI3K/Akt and Nrf2 pathway.

Ethyl pyruvate ameliorates hepatic injury following blunt chest trauma and hemorrhagic shock by reducing local inflammation, NF-kappaB activation and HMGB1 release

BACKGROUND

The treatment of patients with multiple trauma including blunt chest/thoracic trauma (TxT) and hemorrhagic shock (H) is still challenging. Numerous studies show detrimental consequences of TxT and HS resulting in strong inflammatory changes, organ injury and mortality. Additionally, the reperfusion (R) phase plays a key role in triggering inflammation and worsening outcome. Ethyl pyruvate (EP), a stable lipophilic ester, has anti-inflammatory properties. Here, the influence of EP on the inflammatory reaction and liver injury in a double hit model of TxT and H/R in rats was explored.

METHODS

Female Lewis rats were subjected to TxT followed by hemorrhage/H (60 min, 35±3 mm Hg) and resuscitation/R (TxT+H/R). Reperfusion was performed by either Ringer`s lactated solution (RL) alone or RL supplemented with EP (50 mg/kg). Sham animals underwent all surgical procedures without TxT+H/R. After 2h, blood and liver tissue were collected for analyses, and survival was assessed after 24h.

RESULTS

Resuscitation with EP significantly improved haemoglobin levels and base excess recovery compared with controls after TxT+H/R, respectively (p<0.05). TxT+H/R-induced significant increase in alanine aminotransferase levels and liver injury were attenuated by EP compared with controls (p<0.05). Local inflammation as shown by increased gene expression of IL-6 and ICAM-1, enhanced ICAM-1 and HMGB1 protein expression and infiltration of the liver with neutrophils were also significantly attenuated by EP compared with controls after TxT+H/R (p<0.05). EP significantly reduced TxT+H/R-induced p65 activation in liver tissue. Survival rates improved by EP from 50% to 70% after TxT+H/R.

CONCLUSIONS

These data support the concept that the pronounced local pro-inflammatory response in the liver after blunt chest trauma and hemorrhagic shock is associated with NF-κB. In particular, the beneficial anti-inflammatory effects of ethyl pyruvate seem to be regulated by the HMGB1/NF-κB axis in the liver, thereby, restraining inflammatory responses and liver injury after double hit trauma in the rat.

Association between high mobility group box‑1 protein expression and cell death in acute pancreatitis

The present study used caerulein stimulation of AR42J rat pancreatic cells as an in vitro acute pancreatitis (AP) model to investigate proteins differentially expressed in apoptosis and necrosis. AR42J cells were stimulated with 10‑8mol/l caerulein and incubated for 24 h. Apoptosis and necrosis were detected using flow cytometry. The sorted Annexin V‑positive cells (apoptotic) and the Annexin V/propidium iodide double‑positive cells (necrotic) were analysed using proteomics. Results showed that numerous proteins were differentially expressed in these 2 groups. Functional enrichment analysis was performed on the differentially expressed genes using the Database for Annotation, Visualization and Integrated Discovery. High mobility group box‑1 protein (HMGB1) was specifically expressed in the necrosis group. Models of varying degrees of AP were established using caerulein at concentrations of 10‑9, 10‑8, 10‑7, 10‑6 and 10‑5 mol/l. The percentage of apoptotic and necrotic cells in each group was determined using flow cytometry. Protein expression levels of HMGB1 were detected by western blot analysis. The present study showed that as the concentration of caerulein increased, the percentage of necrotic cells and the protein expression levels of HMGB1 increased. HMGB1 is involved in many biological processes, including the chromosomal protein glycyl lysine isopeptide cross‑link. HMGB1 may be involved in the early stage of pancreatitis, potentially by inducing the development of cell death by necrosis. These results provide an experimental basis for clinical intervention in AP.

Anti-apoptotic and myocardial protective effects of ethyl pyruvate after regional ischaemia/reperfusion myocardial damage in an in vivo rat model

INTRODUCTION

The integration of reactive oxygen species is strongly associated with important pathophysiological mechanisms that mediate myocardial ischaemia/reperfusion (I/R) damage. Pyruvate is an efficacious scavenger of reactive oxygen species and a previous study has shown that ethyl pyruvate (EP) has a myocardial protective effect against regional I/R damage in an in vivo rat model. The purpose of this study was to determine whether the myocardial protective effect of EP is associated with anti-apoptosis.

METHODS

Rats were allocated to receive EP dissolved in lactated Ringer's solution or lactated Ringer's solution alone, via intraperitoneal infusion one hour before ischaemia. They were exposed to 30 minutes of ischaemia followed by reperfusion of the left coronary artery territory over two hours. Anti-apoptotic effects were checked using several biochemical parameters after two hours of reperfusion. Apoptosis was analysed using measured caspase-3 activity, Western blotting of B-cell lymphoma 2 (Bcl-2) family protein cleaved by caspase-3, and assessment of DNA laddering patterns and the terminal deoxynucleotidyl transferase dUTP nick end labelling (TUNEL) staining test.

RESULTS

In ischaemic myocardium, EP increased Bcl-2 expression, but reduced Bcl-2-associated X protein and cleaved caspase-3 expressions. EP reduced the expression of DNA laddering and the number of myocardial I/R-damaged TUNEL-positive cells.

CONCLUSION

This study demonstrated that EP has an anti-apoptotic effect after regional I/R damage in an in vivo rat heart model. The myocardial protective effect of EP may be related to its anti-apoptotic effect.

Impact of ethyl pyruvate on Adriamycin-induced cardiomyopathy in rats

Ethyl pyruvate (EP), a derivative of pyruvic acid, is known to have protective effects against ischemic cardiomyopathy and other disorders. However, little is known about its role in Adriamycin (ADR)-induced cardiomyopathy. The present study was designed to investigate the impact of EP on ADR-induced cardiomyopathy in an animal model. Sixty male Sprague-Dawley (SD) rats were divided into four groups: Normal control, EP, ADR and ADR + EP groups (n=15/group). Rats in the ADR and ADR + EP groups were treated with ADR (2.5 mg/kg/week intraperitoneally) for 6 weeks. From the eighth week, rats in the EP and ADR + EP groups received EP via gastric lavage at a dose of 50 mg/kg/day for 30 days. After completing the EP treatment, cardiac function was assessed by echocardiography and then rats were sacrificed. Hearts were harvested for subsequent analysis. Compared with rats in the normal control and EP groups (without ADR treatment), rats in the ADR and ADR + EP groups showed significant impairments in terms of cardiac function, apoptosis, severe oxidative stress and fibrosis in the heart. However, these impairments were alleviated by EP treatment in the ADR + EP group. Upon EP treatment, cardiac function was significantly improved. The levels of oxidative stress, fibrosis and apoptosis in the myocardial tissues were also significantly reduced. These findings indicated that EP treatment attenuated, at least partially, ADR-induced cardiomyopathy in rats.

Erythropoietin: powerful protection of ischemic and post-ischemic brain

Ischemic brain injury inflicted by stroke and cardiac arrest ranks among the leading causes of death and long-term disability in the United States. The brain consumes large amounts of metabolic substrates and oxygen to sustain its energy requirements. Consequently, the brain is exquisitely sensitive to interruptions in its blood supply, and suffers irreversible damage after 10-15 min of severe ischemia. Effective treatments to protect the brain from stroke and cardiac arrest have proven elusive, due to the complexities of the injury cascades ignited by ischemia and reperfusion. Although recombinant tissue plasminogen activator and therapeutic hypothermia have proven efficacious for stroke and cardiac arrest, respectively, these treatments are constrained by narrow therapeutic windows, potentially detrimental side-effects and the limited availability of hypothermia equipment. Mounting evidence demonstrates the cytokine hormone erythropoietin (EPO) to be a powerful neuroprotective agent and a potential adjuvant to established therapies. Classically, EPO originating primarily in the kidneys promotes erythrocyte production by suppressing apoptosis of proerythroid progenitors in bone marrow. However, the brain is capable of producing EPO, and EPO's membrane receptors and signaling components also are expressed in neurons and astrocytes. EPO activates signaling cascades that increase the brain's resistance to ischemia-reperfusion stress by stabilizing mitochondrial membranes, limiting formation of reactive oxygen and nitrogen intermediates, and suppressing pro-inflammatory cytokine production and neutrophil infiltration. Collectively, these mechanisms preserve functional brain tissue and, thus, improve neurocognitive recovery from brain ischemia. This article reviews the mechanisms mediating EPO-induced brain protection, critiques the clinical utility of exogenous EPO to preserve brain threatened by ischemic stroke and cardiac arrest, and discusses the prospects for induction of EPO production within the brain by the intermediary metabolite, pyruvate.

Multiphoton microscopy can visualize zonal damage and decreased cellular metabolic activity in hepatic ischemia-reperfusion injury in rats

Ischemia-reperfusion (I/R) injury is a common occurrence in liver surgery. In orthotopic transplantation, the donor liver is exposed to periods of ischemia and when oxygenated blood is reintroduced to the liver, oxidative stress may develop and lead to graft failure. The aim of this project was to investigate whether noninvasive multiphoton and fluorescence lifetime imaging microscopy, without external markers, were useful in detecting early liver damage caused by I/R injury. Localized hepatic ischemia was induced in rats for 1 h followed by 4 h reperfusion. Multiphoton and fluorescence lifetime imaging microscopy was conducted prior to ischemia and up to 4 h of reperfusion and compared to morphological and biochemical assessment of liver damage. Liver function was significantly impaired at 2 and 4 h of reperfusion. Multiphoton microscopy detected liver damage at 1 h of reperfusion, manifested by vacuolated cells and heterogeneous spread of damage over the liver. The damage was mainly localized in the midzonal region of the liver acinus. In addition, fluorescence lifetime imaging showed a decrease in cellular metabolic activity. Multiphoton and fluorescence lifetime imaging microscopy detected evidence of early I/R injury both structurally and functionally. This provides a simple noninvasive technique useful for following progressive liver injury without external markers.

Pyruvate attenuates cardiac dysfunction and oxidative stress in isoproterenol-induced cardiotoxicity

Pyruvate, a potent endogenous antioxidant and an important metabolic fuel is essential for the cardiac function and tissue defense mechanism. The present study was evaluated to investigate whether pyruvate attenuates the development of cardiotoxicity in isoproterenol (ISO)-induced myocardial infarction by assessing hemodynamic, biochemical and histopathological parameters. Subcutaneous injection of ISO (85 mg/kg) administered for 2 days at an interval of 24h was used for induction of cardiotoxicity. ISO administration significantly decreased arterial pressure indices, heart rate, contractility {(+)LVdP/dt} and relaxation {(-)LVdP/dt} and increased left ventricular end-diastolic pressure. In addition, a significant reduction in activities of myocardial creatine phosphokinase-MB, lactate dehydrogenase, superoxide dismutase, catalase, glutathione peroxidase and reduced glutathione levels along with increase in thiobarbituric acid reactive substances were also observed following ISO administration. However, pretreatment with pyruvate (0.25, 0.5 and 1.0 g/kg, p.o.) favorably modulated all most every studied parameters in ISO-induced myocardial injury. Furthermore, protective effect of pyruvate was confirmed by histopathological studies. Rats pretreated only with pyruvate did not produce significant change in hemodynamic, biochemical and histopathological parameters. Pyruvate at 0.50 and 1.0 g/kg doses was found to exert optimal cardioprotective effect against ISO-induced myocardial infarction. The results of our study suggest that pyruvate possessing antioxidant activity has a significant cardioprotective effect against ISO-induced myocardial injury.

Ethyl pyruvate has anti-inflammatory and delayed myocardial protective effects after regional ischemia/reperfusion injury

PURPOSE

Ethyl pyruvate has anti-inflammatory properties and protects organs from ischemia/reperfusion (I/R)-induced tissue injury. The aim of this study was to determine whether ethyl pyruvate decreases the inflammatory response after regional I/R injury and whether ethyl pyruvate protects against delayed regional I/R injury in an in vivo rat heart model after a 24 hours reperfusion.

MATERIALS AND METHODS

Rats were randomized to receive lactated Ringer's solution or ethyl pyruvate dissolved in Ringer's solution, which was given by intraperitoneal injection 1 hour prior to ischemia. Rats were subjected to 30 min of ischemia followed by reperfusion of the left coronary artery territory. After a 2 hours reperfusion, nuclear factor κB, myocardial myeloperoxidase activity, and inflammatory cytokine levels were determined. After the 24 hours reperfusion, the hemodynamic function and myocardial infarct size were evaluated.

RESULTS

At 2 hours after I/R injury, ethyl pyruvate attenuated I/R-induced nuclear factor κB translocation and reduced myeloperoxidase activity in myocardium. The plasma circulating levels of inflammatory cytokines decreased significantly in the ethyl pyruvate-treated group. At 24 hours after I/R injury, ethyl pyruvate significantly improved cardiac function and reduced infarct size after regional I/R injury.

CONCLUSION

Ethyl pyruvate has the ability to inhibit neutrophil activation, inflammatory cytokine release, and nuclear factor κB translocation. Ethyl pyruvate is associated with a delayed myocardial protective effect after regional I/R injury in an in vivo rat heart model.

The biochemical basis for the anti-inflammatory and cytoprotective actions of ethyl pyruvate and related compounds

Pyruvate is an important metabolic intermediate, and also is an effective scavenger of hydrogen peroxide and other reactive oxygen species (ROS). Pharmacological administration of pyruvate has been shown to improve organ function in animal models of oxidant-mediated cellular injury. However, pyruvate is relatively unstable in aqueous solutions, which could limit the therapeutic potential of this compound. Ethyl pyruvate (EP), a simple derivative of pyruvic acid, is also an ROS scavenger, but seems to exert pharmacological effects, such as suppression of inflammation, which are at least quantitatively different and in some instances are qualitatively distinct from those exerted by pyruvate anion. Treatment with EP has been shown to improve survival and/or ameliorate organ dysfunction in a wide variety of pre-clinical models of acute illnesses, such as severe sepsis, acute pancreatitis and stroke. Using other animal models, some studies have demonstrated that more prolonged treatment with EP can ameliorate inflammatory bowel disease or slow the rate of growth of malignant tumors. In a clinical trial of patients undergoing cardiac surgery, treatment with EP was shown to be safe, but it failed to improve outcome. The true therapeutic potential of EP and related compounds remains to be elucidated. In this review, some of the biochemical mechanisms, which might be responsible for the pharmacological effects of EP, are discussed.

The strategy of combined ischemia preconditioning and salvianolic acid-B pretreatment to prevent hepatic ischemia-reperfusion injury in rats

BACKGROUND

Ischemia-reperfusion injury (IRI) is a serious complication of liver surgery, especially for extended hepatectomy and liver transplantation. The aim of this study was to evaluate the protective effect of combined ischemic preconditioning (IPC) and salvianolic acid-B (Sal-B) pretreatment against IRI-induced hepatocellular injury.

METHODS

Sixty male Wistar rats weighing around 200 g were randomized into five groups (n=12): sham group: only anesthesia and laparotomy; IR group: 90 min sustained ischemia by blocking the left ortal vessels; IPC group: 10 min ischemia and 10 min reperfusion prior to the sustained ischemia; Sal-B group: 10 mg/kg injection of Sal-B intravenously 10 min prior to the sustained ischemia; IPC+Sal-B group: same IPC procedure as in IPC group, but proceeded by intravenous administration of Sal-B 10 min prior to sustained ischemia. After 5 h of reperfusion, serum levels of ALT and AST were measured; the amount of malondialdehyde (MDA) and adenine nucleotides in liver tissue was determined; the expression of Bcl-2 and caspase-3 was detected by immunofluorescent and western blotting techniques; the severity of apoptosis and pathological alterations was evaluated by TUNEL and H&E staining, respectively.

RESULTS

The serum aminotransferases, hepatic MDA concentration, and apoptotic index in groups IPC, Sal-B, and IPC+Sal-B were significantly lower than those in the IR group (P<0.001), while the IPC+Sal-B group had the lowest values among these groups (P<0.05). Compared with the IR group, groups IPC and Sal-B not only had statistically higher ATP levels and energy charge (EC) values (P<0.01), but also had upregulated Bcl-2 expression and downregulated cleaved caspase-3 expression in liver tissue. All these effects were further augmented in the IPC+Sal-B group. Liver histopathological findings were consistent with these results.

CONCLUSIONS

Based on these results, the combined IPC and Sal-B pretreatment had a synergistically protective effect on liver tissue against IRI, which might be due to decreased post-ischemic oxidative stress, improved energy metabolism, and reduced hepatocellular apoptosis.

Molecular Biology of Apoptosis in Ischemia and Reperfusion

This study reviews the current understanding of the mechanisms that mediate the complex processes involved in apoptosis secondary to ischemia and reperfusion (I/R) and is not intended as a complete literature review of apoptosis. Several biochemical reactions trigger a cascade of events, which activate caspases. These caspases exert their effect through downstream proteolysis until the final effector caspases mediate the nuclear features characteristic of apoptosis, DNA fragmentation and condensation. Within the context of ischemia, the hypoxic environment initiates the expression of several genes involved in inflammation, the immune response, and apoptosis. Many of these same genes are activated during reperfusion injury in response to radical oxygen species generation. It is plausible that inhibition of specific apoptotic pathways via inactivation or downregulation of those genes responsible for the initiation of inflammation, immune response, and apoptosis may provide promising molecular targets for ameliorating reperfusion injury in I/R-related processes. Such inhibitory mechanisms are discussed in this review. Important targets in I/R-related pathologies include the brain during stroke, the heart during myocardial infarction, and the organs during harvesting and/or storage for transplantation. In addition, we present data from our ongoing research of specific signal transduction-related elements and their role in ischemia/reperfusion injury. These data address the potential therapeutic application of anti-inflammatory and anti-ischemic compounds in the prevention of I/R damage.

Ethyl pyruvate protects colonic anastomosis from ischemia-reperfusion injury

Ethyl pyruvate is a simple derivative in Ca(+2)- and K(+)-containing balanced salt solution of pyruvate to avoid the problems associated with the instability of pyruvate in solution. It has been shown to ameliorate the effects of ischemia-reperfusion (I/R) injury in many organs. It has also been shown that I/R injury delays the healing of colonic anastomosis. In this study, the effect of ethyl pyruvate on the healing of colon anastomosis and anastomotic strength after I/R injury was investigated. Anastomosis of the colon was performed in 32 adult male Wistar albino rats divided into 4 groups of 8 individuals: (1) sham-operated control group (group 1); (2) 30 minutes of intestinal I/R by superior mesenteric artery occlusion (group 2); (3) I/R+ ethyl pyruvate (group 3), ethyl pyruvate was administered as a 50-mg/kg/d single dose; and (4) I/R+ ethyl pyruvate (group 4), ethyl pyruvate administration was repeatedly (every 6 hours) at the same dose (50 mg/kg). On the fifth postoperative day, animals were killed. Perianastomotic tissue hydroxyproline contents and anastomotic bursting pressures were measured in all groups. When the anastomotic bursting pressures and tissue hydroxyproline contents were compared, it was found that they were decreased in group 2 when compared with groups 1, 3, and 4 (P < .05). Both anastomotic bursting pressure (P = .005) and hydroxyproline content (P < .001) levels were found to be significantly increased with ethyl pyruvate administration when compared with group 2. When ethyl pyruvate administration doses were compared, a significant difference was not observed (P > .05). Ethyl pyruvate significantly prevents the delaying effect of I/R injury on anastomotic strength and healing independent from doses of administration.

Ethyl pyruvate decreased early nuclear factor-kappaB levels but worsened survival in lipopolysaccharide-challenged mice

BACKGROUND

Ethyl pyruvate (EP) treatment inhibits nuclear factor (NF)-kappaB-mediated inflammation and has been considered for sepsis. However, NF-kappaB is also protective, and its inhibition may have adverse effects.

METHODS

We studied EP in lipopolysaccharide-challenged mice and systematically analyzed its efficacy in published sepsis models.

RESULTS

After lipopolysaccharide, compared with placebo (n = 68), each of six doses of EP (0.01-100 mg/kg, n = 204) increased the hazards ratio of death. Although these increases were individually not significant (p = .13 to .37), when combined, they were (log mean +/- SEM, 0.26 +/- 0.13; p = .01). At 3 and 9 hrs after challenge, lipopolysaccharide increased lung NF-kappaB and 12 serum cytokines (p < or = .05 vs. phosphate-buffered saline challenge, except for interleukin-4 at 9 hrs). With lipopolysaccharide, although EP (100 mg/kg) decreased NF-kappaB and 11 of 12 cytokines at 3 hrs, it increased NF-kappaB and 11 of 12 cytokines at 9 hrs in patterns that differed (p < or = .05) across time points. In 14 published comparisons, EP's effects on the odds ratio of death varied (I2 = 85% [95% confidence interval, 74-91%], p < .0001), decreasing it significantly in five of the studies but not the other nine. In three of the latter, it increased time to death.

CONCLUSION

Although EP has had promising effects in some preclinical sepsis models, it has not in others, and in the present model, it worsened outcome. Based on the complex role NF-kappaB has regulating both maladaptive and protective host responses, further defining factors that influence EP's effects is important if this agent is considered for patients with or at risk of sepsis.

The effect of ethyl pyruvate on oxidative stress in intestine and bacterial translocation after thermal injury

BACKGROUND

Thermal injury causes a breakdown in the intestinal mucosal barrier due to ischemia reperfusion injury, which can induce bacterial translocation (BT), sepsis, and multiple organ failure in burn patients. The aim of this study was to investigate the effect of ethyl pyruvate (EP) on intestinal oxidant damage and BT in burn injury.

MATERIALS AND METHODS

Thirty-two rats were randomly divided into four groups. The sham group was exposed to 21 degrees C water and injected intraperitoneal with saline (1 mL/100 g). The sham + EP group received EP (40 mg/kg) intraperitoneally 6 h after the sham procedure. The burn group was exposed to thermal injury and given intraperitoneal saline injection (1 mL/100 g). The burn + EP group received EP (40 mg/kg) intraperitoneally 6 h after thermal injury. Twenty-four hours later, tissue samples were obtained from mesenteric lymph nodes, spleen, and liver for microbiological analysis and ileum samples were harvested for biochemical analysis.

RESULTS

Thermal injury caused severe BT in burn group. EP supplementation decreased BT in mesenteric lymph nodes and spleen in the burn + EP group compared with the burn group (P < 0.05). Also, burn caused BT in liver, but this finding was not statistically significant among all groups. Thermal injury caused a statistically significant increase in malondialdehyde and myeloperoxidase levels, and EP prevented this effects in the burn + EP group compared with the burn group (P < 0.05).

CONCLUSION

Our data suggested that EP can inhibit the BT and myeloperoxidase and malondialdehyde production in intestine following thermal injury, suggesting anti-inflammatory and anti-oxidant properties of EP.

Ethyl pyruvate: a novel anti-inflammatory agent

Ethyl pyruvate (EP) is a simple derivative of the endogenous metabolite, pyruvic acid. Treatment with EP has been shown to improve survival and/or ameliorate organ dysfunction in a wide variety of preclinical models of critical illnesses, such as severe sepsis, acute respiratory distress syndrome, acute pancreatitis and stroke. EP was originally regarded as simply a way to administer pyruvate anion, whilst avoiding some of the problems associated with the instability of pyruvate in aqueous solutions. Increasingly, however, it is becoming apparent that certain pyruvate esters, including EP, have pharmacological effects, such as suppression of inflammation, that are quite distinct from those exerted by pyruvate anion. EP has been tested in human volunteers and shown to be safe at clinically relevant doses. It remains to be determined whether EP can be used successfully to treat human diseases.

Effect of bilateral in vivo ischemia/reperfusion on the activities of superoxide dismutase and catalase: Response to a standardized grape suspension

PURPOSE

Ischemia/reperfusion (I/R) is a major etiological factor in the bladder dysfunctions observed in men with lower tract obstruction, women with postmenopausal incontinence and with aging. A standardized grape suspension protects the rabbit urinary bladder from both the contractile dysfunctions and the morphologic changes mediated by I/R. Using a model of in vivo bilateral ischemia/reperfusion, the current study investigated the effect of this grape suspension on the endogenous antioxidant defense systems.

MATERIALS AND METHODS

24 NZW rabbits were separated into 6 groups of 4. Groups 1-3 were treated by gavage with aqueous grape suspensions; groups 4-6 received sugar-water vehicle. Groups 3 and 6 were controls. Groups 1 and 4 were subjected to bilateral ischemia for 2 h (I). Groups 2 and 5 underwent bilateral ischemia for 2 h and reperfusion for 1 week (I/R). For all rabbit bladders, the muscle and mucosa were separated by blunt dissection and analyzed separately. The effects of the various treatments on bladder antioxidant systems of cytoplasmic superoxide dismutase (Cu-Zn superoxide dismutase; SOD), and catalase (CAT) were evaluated.

RESULTS

The standardized grape suspension up-regulated both SOD and CAT activity of bladder muscle and mucosa in control animals. There were few differences in the grape suspension treated animals after ischemia, and in general the activities decreased following I/R.

CONCLUSIONS

Increases of SOD and CAT activity in control animals as a result of grape suspension suggest a greater antioxidant capacity. This increase in the antioxidant defense system may explain the increased protection of grape suspension in the face of ischemia and I/R. However, the activities of both enzyme systems decreased in the smooth muscle subjected to I/R showing that reperfusion damages these systems probably via oxidation damage to the enzymes themselves.

Interstitial Lactic Acidosis in the Graft During Organ Harvest, Cold Storage, and Reperfusion of Human Liver Allografts Predicts Subsequent Ischemia Reperfusion Injury

BACKGROUND

The impact of the process of liver transplantation on glucose metabolism in the graft was studied using microdialysis.

METHODS

Microdialysis catheters were inserted into 15 human livers to monitor metabolic changes that took place during organ harvest, the process of backtable preparation of the graft, and following implantation in the recipient where it remained in situ for 48 hours. The cannula was perfused with isotonic solution and hourly samples of perfusate were collected and analyzed.

RESULTS

Six livers showed serum biochemical evidence of ischemia/reperfusion (IR) injury with 24 hours aspartate transaminase (AST) levels >2000 IU/L (Group A) whereas the remaining patients showed little evidence of IR injury (Group B). In Group A, lactate levels in the donor microdialysate rose to >6 mM (P < 0.05), were significantly higher during backtable preparation of the liver (>15 mM; P < 0.03), and took longer to normalize in the recipient following implantation (18 vs. 8 hours, P < 0.03) than lactate levels of the livers of patients in Group B who did not develop ischemia reperfusion injury. No significant differences were observed in glucose, pyruvate, or glycerol concentrations between the two groups.

CONCLUSIONS

Interstitial lactic acidosis in the donor allograft is associated with significant reperfusion injury on implantation.

Ethyl pyruvate ameliorates liver ischemia-reperfusion injury by decreasing hepatic necrosis and apoptosis

BACKGROUND

Hepatic ischemia-reperfusion injury (I/R) occurs in the settings of transplantation, trauma, and elective liver resections. Reactive oxygen species (ROS) have been shown to play a major role in organ I/R injury. Pyruvate, a key intermediate in cellular metabolism, is an effective scavenger of ROS. The purpose of this study was to test the hypothesis that ethyl pyruvate (EP), a soluble pyruvate derivative, is effective in preventing hepatic I/R injury.

METHODS

Lewis rats underwent 60 minutes of partial warm hepatic ischemia. Three doses of EP dissolved in lactated Ringer's solution or lactated Ringer's solution (LR) alone were given by intravenous injection. Serum and tissue samples were obtained at 1 to 24 hours postreperfusion.

RESULTS

Serum transaminases, degree of hepatic necrosis, and neutrophil infiltration were all significantly decreased in the EP-treated rats compared with control animals. The amount of hepatic lipid peroxidation was also significantly decreased in EP-treated animals. Both circulating levels and hepatic expression of inflammatory cytokines were significantly decreased in the EP-treated animals. Furthermore, EP inhibited activation of extracellular signal-regulated kinase, p38, and c-Jun N-terminal kinase mitogen-activated protein kinases, as well as nuclear factor-kappaB, signaling pathways involved in cytokine release. Treatment with EP also inhibited hepatic apoptosis.

CONCLUSION

EP has a protective effect on hepatic I/R injury, mediated in part by decreasing lipid peroxidation, down-regulation of inflammatory mediators, and inhibition of apoptosis. Strategies using this additive to LR solution should be considered in clinical settings of ischemic liver injury to decrease organ damage.

Pyruvate in the correction of intracellular acidosis: a metabolic basis as a novel superior buffer

The review focuses on biochemical metabolisms of conventional buffers and emphasizes advantages of sodium pyruvate (Pyr) in the correction of intracellular acidosis. Exogenous lactate (Lac) as an alternative of natural buffer, bicarbonate, consumes intracellular protons on an equimolar basis, regenerating bicarbonate anions in plasma while the completion of gluconeogenesis and/or oxidation occurs via tricarboxylic-acid cycle in mitochondria mainly in liver and kidney, or heart. The general assumption that Lac is 'metabolized to bicarbonate' in liver to serve as a buffer has been questioned. Pyr as a novel buffer would be superior to conventional ones in the correction of metabolic acidosis. Several likely biochemical mechanisms of Pyr action are discussed. Experimental evidence, in vivo, strongly suggested that Pyr would be particularly efficient in the correction of severe acidemia: type A lactic acidosis, hypercapnia with cardiac arrest, and diabetic and alcoholic ketoacidosis in animal experiments and clinic settings. Because of its multi-cytoprotection, Pyrs not only correct acidosis, but also benefit theunderlying dysfunction of vital organs. In addition, Pyr is also a potential buffer component of dialysis solutions. However, the instability of Pyr in aqueous solutions restricts its clinical applications as a therapeutic agent. Attempts to create a stable Pyr preparation are needed.

Possible involvement of pyruvate kinase in acquisition of tolerance to hypoxic stress in glial cells

Neurons are highly vulnerable to ischemic/hypoxic stress, while glial cells show tolerance to such stress. However, the mechanisms for tolerance acquisition in glial cells have yet to be established. We attempted to isolate and identify a stress protein that is upregulated in response to hypoxia in human astrocytoma CCF-STTG1 cells. In particular, pyruvate kinase (PK) was upregulated by hypoxia in CCF-STTG1 cells. Hypoxia-inducible factor 1 (HIF-1), the primary transcription factor that is responsible for multiple gene activation under hypoxia, plays a critical role in PK expression during hypoxic challenge. To determine whether newly synthesized PK is involved in tolerance to hypoxic stress, we established the PK-overexpressing neuronal cells. Overexpression of the wild-type, but not the kinase-negative mutant, resulted in attenuation of the loss of cell viability and the typical apoptotic features by hypoxia or oxidative stress in SK-N-MC cells. These findings suggest that upregulation of PK may result in acquisition of tolerance against hypoxic stress, and that the antioxidant effect may be involved in the protective effect of PK.

Role of mitochondria in cell apoptosis during hepatic ischemia-reperfusion injury and protective effect of ischemic postconditioning

AIM: To investigate the role of mitochondria in cell apoptosis during hepatic ischemia-reperfusion injury and protective effect of ischemic postconditioning (IPC).

METHODS: A rat model of acute hepatic ischemia-reperfusion was established, 24 healthy male Wistar rats were randomly divided into sham-operated group, ischemia-reperfusion group (IR) and IPC group. IPC was achieved by several brief pre-reperfusions followed by a persistent reperfusion. Concentration of malondialdehyde (MDA) and activity of several antioxidant enzymes in hepatic tissue were measured respectively. Apoptotic cells were detected by TdT-mediated dUTP-biotin nick end labeling (TUNEL) and expression of Bcl-2 protein was measured by immunohistochemical techniques. Moreover, mitochondrial ultrastructure and parameters of morphology of the above groups were observed by electron microscope.

RESULTS: Compared with IR group, the concentration of MDA and the hepatocellular apoptotic index in IPC group was significantly reduced (P < 0.05), while the activity of antioxidant enzymes and OD value of Bcl-2 protein were markedly enhanced (P < 0.05). Moreover, the injury of mitochondrial ultrastructure in IPC group was also obviously relieved.

CONCLUSION: IPC can depress the synthesis of oxygen free radicals to protect the mitochondrial ultrastructure and increase the expression of Bcl-2 protein that lies across the mitochondrial membrane. Consequently, IPC can reduce hepatocellular apoptosis after reperfusion and has a protective effect on hepatic ischemia-reperfusion injury.

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

Ethyl pyruvate dissolved in a calcium-containing balanced salt solution--Ringer's ethyl pyruvate solution (REPS)--ameliorates ileal mucosal hyperpermeability and decreases the expression of several proinflammatory genes when it is used instead of Ringer's 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.

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-1beta, interferon-gamma, 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.

Dose-dependent effects of ethyl pyruvate in mice subjected to mesenteric ischemia and reperfusion

OBJECTIVE

We previously showed that infusing rats with a solution of ethyl pyruvate ameliorates intestinal mucosal injury after mesenteric ischemia and reperfusion. Ethyl pyruvate also has been shown to inhibit the expression of various pro-inflammatory cytokines in several animal models of critical illness, but dose-response relationships have not been investigated.

DESIGN

Anesthetized C57BL/6 mice were subjected to 60 min of mesenteric ischemia followed by 60 min of reperfusion. After 55 min of ischemia, groups of mice were treated with normal saline or graded bolus doses of ethyl pyruvate dissolved in a calcium-containing balanced salt solution. Some animals (i.e., those in the sham group) were subjected to the anesthetic, but not mesenteric ischemia/reperfusion. Gut mucosal permeability was assessed using an everted gut sac technique.

SETTING

University research laboratory.

MEASUREMENTS AND RESULTS

Mesenteric ischemia/reperfusion significantly increased ileal mucosal permeability to the hydrophilic macromolecule, fluorescein isothiocyanate dextran (molecular mass 4,000 Da). Whereas the lowest dose of ethyl pyruvate evaluated (17 mg/kg) had no effect on gut mucosal permeability, the two highest doses tested (50 and 150 mg/kg) significantly ameliorated the development of ischemia/reperfusion-induced mucosal hyperpermeability to about the same extent. The two highest doses of ethyl pyruvate also significantly ameliorated deficits in ileal serosal and mucosal and hepatic surface microvascular perfusion induced by mesenteric ischemia/reperfusion. Ethyl pyruvate inhibited post-ischemia/reperfusion hepatic NF-kappaB activation and TNF mRNA expression in a dose-dependent fashion.

CONCLUSION

Doses of ethyl pyruvate equal to or greater than 50 mg/kg ameliorate inflammation, microvascular hypoperfusion and gut mucosal damage induced by mesenteric ischemia/reperfusion in mice.

Enhanced energy metabolism during cold hypoxic organ preservation: studies on rat liver after pyruvate supplementation

Previous studies have indicated that pyruvate is able to reduce ischaemia/reperfusion (I/R) injury in a variety of tissues, but a full understanding of the effects is lacking. In this current preliminary study, magnetic resonance spectroscopy (MRS) was used to investigate the biochemical effects of differing concentrations of pyruvate (3 and 15mM) on liver metabolism during the cold hypoxic preservation period itself, in order to gain insight into possible mechanisms. Hepatic lactate, alanine, and succinate levels were increased in livers preserved with 15mM pyruvate added to the University of Wisconsin (UW) solution and were generally elevated (but to a lesser degree) in livers flushed with 3mM pyruvate, compared to those cold stored in UW alone. Further, from enzymatic assays of adenine nucleotides, 15mM levels of pyruvate were found to maintain higher ATP levels during short periods (up to 4h) of cold hypoxic storage than in UW stored livers, whilst energy charge ratios (after 4 and 24h) were also higher (P<0.01 in each case). This may arise from enhanced glycolysis secondary to an improved redox status in the pyruvate-treated livers, as evident by the increase in the levels of lactate.

Ethyl pyruvate: a novel anti-inflammatory agent

Pyruvate plays a central role in intermediary metabolism. Pyruvate, however, is also a potent antioxidant and free radical scavenger, and numerous studies have shown that treatment with this compound can be salutary in numerous pathologic conditions that are thought to be mediated, at least in part, by redox-dependent phenomena. Unfortunately, aqueous solutions of pyruvate rapidly undergo an aldol-like condensation reaction to form 2-hydroxy-2-methyl-4-ketoglutarate (parapyruvate), a compound that is a potent inhibitor of a critical step in the mitochondrial tricarboxylic acid cycle. To circumvent this issue, our laboratory formulated a derivative of pyruvic acid, ethyl pyruvate, in a calcium- and potassium-containing balanced salt solution. We showed that treatment with this fluid could ameliorate much of the structural and functional damage to the intestinal mucosa caused by mesenteric ischemia and reperfusion in rats. In subsequent studies, we showed that treatment with ethyl pyruvate solution could improve survival in rodent models of hemorrhagic shock and resuscitation and also down-regulate a number of proinflammatory genes. Recently, ethyl pyruvate was also shown to improve survival in murine models of acute endotoxemia and bacterial peritonitis. Although the biochemical basis for the anti-inflammatory actions of pyruvate remain to be elucidated, this simple compound warrants further evaluation as a treatment for a number of conditions commonly encountered in the practice of critical care medicine.

Ethyl pyruvate ameliorates intestinal epithelial barrier dysfunction in endotoxemic mice and immunostimulated caco-2 enterocytic monolayers

Ethyl pyruvate (EP) solution ameliorates ileal mucosal hyperpermeability and decreases the expression of several proinflammatory genes in ileal and/or colonic mucosa when it is used instead of Ringer's lactate solution (RLS) to resuscitate mice from hemorrhagic shock. To test the hypothesis that EP can ameliorate gut barrier dysfunction induced by other forms of inflammation, we incubated Caco-2 monolayers for 24 to 48 h with cytomix (a mixture of interferon-gamma, tumor necrosis factor-alpha, and interleukin-1beta) in the presence or absence of graded concentrations of EP or sodium pyruvate. Cytomix increased the permeability of Caco-2 monolayers to fluorescein isothiocyanate-labeled dextran (FD4; average molecular mass 4 kDa), but this effect was inhibited by adding 0.1 to 10 mM EP (but not similar concentrations of sodium pyruvate) to the culture medium. EP inhibited several other cytomix-induced phenomena, including nuclear factor-kappaB activation, inducible nitric oxide synthase mRNA expression, and nitric oxide production. Cytomix altered the expression and localization of the tight junctional proteins, ZO-1 and occludin, but this effect was prevented by EP. Delayed treatment with EP solution instead of RLS ameliorated ileal mucosal hyperpermeability to FD4 and bacterial translocation to mesenteric lymph nodes in mice challenged with lipopolysaccharide (LPS). These data support the view that EP ameliorates cytokine- and/or LPS-induced derangements in intestinal epithelial barrier function.