Ethyl pyruvate: a novel anti-inflammatory agent

Asbestos-induced chronic inflammation in malignant pleural mesothelioma and related therapeutic approaches-a narrative review

Objective:

The aim of this review is addressing the mechanisms of asbestos carcinogenesis, including chronic inflammation and autophagy-mediated cell survival, and propose potential innovative therapeutic targets to prevent mesothelioma development or improve drug efficacy by reducing inflammation and autophagy.

Background:

Diffuse malignant pleural mesothelioma is an aggressive cancer predominantly related to chronic inflammation caused by asbestos exposure. Millions of individuals have been exposed to asbestos or to other carcinogenic mineral fibers occupationally or environmentally, resulting in an increased risk of developing mesothelioma. Overall patient survival rates are notably low (about 8–14 months from the time of diagnosis) and mesothelioma is resistant to existing therapies. Additionally, individuals carrying inactivating germline mutations in the BRCA-associated protein 1 (BAP1) gene and other genes are predisposed to developing cancers, prevalently mesothelioma. Their risk of developing mesothelioma further increases upon exposure to asbestos. Recent studies have revealed the mechanisms and the role of inflammation in asbestos carcinogenesis. Biomarkers for asbestos exposure and malignant mesothelioma have also been identified. These findings are leading to the development of novel therapeutic approaches to prevent or delay the growth of mesothelioma.

Methods:

Review of full length manuscripts published in English from January 1980 to February 2021 gathered from PubMed.gov from the National Center of Biotechnology Information and the National Library of Medicine were used to inform this review.

Conclusion:

Key regulators of chronic inflammation mediate asbestos-driven mesothelial cell transformation and survival through autophagic pathways. Recent studies have elucidated some of the key mechanisms involved in asbestos-induced chronic inflammation, which are largely driven by extracellular high mobility group box 1 (HMGB1). Upon asbestos exposure, mesothelial cells release HMGB1 from the nucleus to the cytoplasm and extracellular space, where HMGB1 initiates an inflammatory response. HMGB1 translocation and release also activates autophagy and other pro-survival mechanisms, which promotes mesothelioma development. HMGB1 is currently being investigated as a biomarker to detect asbestos exposure and to detect mesothelioma development in its early stage when therapy is more effective. In parallel, several approaches inhibiting HMGB1 activities have been studied and have shown promising results. Moreover, additional cytokines, such as IL-1β and TNF-α are being targeted to interfere with the inflammatory process that drives mesothelioma growth. Developing early detection methods and novel therapeutic strategies is crucial to prolong overall survival of patients with mesothelioma. Novel therapies targeting regulators of asbestos-induced inflammation to reduce mesothelioma growth may lead to clinical advancements to benefit patients with mesothelioma.

Activation of PKM2 metabolically controls fulminant liver injury via restoration of pyruvate and reactivation of CDK1

Accumulating evidence indicates that metabolic events profoundly modulate the progression of various diseases. Pyruvate is a central metabolic intermediate in glucose metabolism. In the present study, the metabolic status of pyruvate and its pharmacological significance has been investigated in mice with lipopolysaccharide/D-galactosamine (LPS/D-Gal)-induced fulminant liver injury. Our results indicated that LPS/D-Gal exposure decreased the activity of pyruvate kinase and the content of pyruvate, which were reversed by the PKM2 activator TEPP-46. Pretreatment with TEPP-46 or supplementation with the cell-permeable pyruvate derivate ethyl pyruvate (EP) attenuated LPS/D-Gal-induced liver damage. Interestingly, post-insult intervention of pyruvate metabolism also resulted in beneficial outcomes. The phospho-antibody microarray analysis and immunoblot analysis found that the inhibitory phosphorylation of cyclin dependent kinase 1 (CDK1) was reversed by TEPP-46, DASA-58 or EP. In addition, the therapeutic benefits of PKM2 activator or EP were blunted by the CDK1 inhibitor Ro 3306. Our data suggests that LPS/D-Gal exposure-induced decline of pyruvate might be a novel metabolic mechanism underlies the development of LPS/D-Gal-induced fulminant liver injury, PKM2 activator or pyruvate derivate might have potential value for the pharmacological intervention of fulminant liver injury.

Anti-Inflammatory and Neuroprotective Effects of DIPOPA (N,N-Diisopropyl-2-Oxopropanamide), an Ethyl Pyruvate Bioisoster, in the Postischemic Brain

Ethyl pyruvate (EP) is a simple aliphatic ester of pyruvic acid and has been shown to have protective properties, which have been attributed to its anti-inflammatory, anti-oxidative, and anti-apoptotic functions. In an effort to develop better derivatives of EP, we previously synthesized DEOPA (N,N-diethyl-2-oxopropanamide, a novel isoster of EP) which has greater neuroprotective effects than EP, probably due to its anti-inflammatory and anti-excitotoxic effects. In the present study, we synthesized 3 DEOPA derivatives, in which its diethylamino group was substituted with diisopropylamino, dipropylamino, or diisobutylamino groups. Among them, DIPOPA (N,N-diisopropyl-2-oxopropanamide) containing diisopropylamino group had a greater neuroprotective effect than DEOPA or EP when administered intravenously to a rat middle cerebral artery occlusion (MCAO) model at 9 h after MCAO. Furthermore, DIPOPA had a wider therapeutic window than DEOPA and a marked reduction of infarct volume was accompanied by greater neurological and behavioral improvements. In particular, DIPOPA exerted robust anti-inflammatory effects, as evidenced by marked suppressions of microglia activation and neutrophil infiltration in the MCAO model, in microglial cells, and in neutrophil-endothelial cocultures at lower concentration, and did so more effectively than DEOPA. In particular, DIPOPA remarkably suppressed neutrophil infiltration into brain parenchyma, and this effect was attributed to the expressional inhibitions of cell adhesion molecules in neutrophils of brain parenchyma and in circulating neutrophils via NF-κB inhibition. Together, these results indicate the robust neuroprotective effects of DIPOPA are attributable to its anti-inflammatory effects and suggest that DIPOPA offers a potential therapeutic means of ameliorating cerebral ischemic injury and other inflammation-related pathologies.

Cold Tolerance Regulated by the Pyruvate Metabolism in Vibrio parahaemolyticus

Vibrio parahaemolyticus is a common foodborne pathogen found in seafood, and represents a major threat to human health worldwide. Low-temperature storage is an important seafood processing method, but is not sufficient to completely eliminate the bacteria and avoid foodborne illness. To determine the mechanisms behind such cold tolerance, RNA-seq and iTRAQ analyses were first performed to obtain the global transcriptomic and proteomic patterns of frozen squid and clinical V. parahaemolyticus isolates under cold conditions. The integrated analysis revealed the modulation of multiple pathways such as the co-occurrence of down-regulated pyruvate metabolism and up-regulated fatty acid biosynthesis, which likely contribute to V. parahaemolyticus cold tolerance. Furthermore, we found that increasing concentrations of pyruvate can reduce the fatty acid content to influence V. parahaemolyticus growth in cold conditions. Thus, regulation of pyruvate concentration may be an effective method to control this seafood-borne pathogen.

Parapyruvate, an Impurity in Pyruvate Supplements, Induces Senescence in Human Fibroblastic Hs68 Cells via Inhibition of the α-Ketoglutarate Dehydrogenase Complex

Commercial dietary supplements of calcium pyruvate claim to be beneficial for losing weight, increasing muscle endurance, and regulating metabolism. Most industrial preparations have some impurities, including parapyruvate. Parapyruvate is an inhibitor of the α-ketoglutarate dehydrogenase complex (KGDHC). However, the effect and mechanism of parapyruvate on cell senescence and the content of parapyruvate in the dietary supplements of calcium pyruvate are unknown. In this study, we prepared pure parapyruvate with a purity of 99.8 ± 0.1% and investigated its ability to inhibit KGDHC activity and affect fibroblast senescence. Parapyruvate dose-dependently decreased KGDHC activity, with an IC₅₀ of 4.13 mM and induced Hs68 cell senescence. Calcium ions, a KGDHC activator, antagonized the senescent effects of parapyruvate. The parapyruvate content was 1.4 ± 0.1% to 10.6 ± 0.2% in five brands of calcium pyruvate supplements. In this study, we showed that parapyruvate strongly induces Hs68 cell senescence by inhibiting KGDHC activity. Because of its KGDHC inhibition activity, the parapyruvate content should be an important issue for the food safety of calcium pyruvate supplements.

Ethyl pyruvate reverses development of Pseudomonas aeruginosa pneumonia during sepsis-induced immunosuppression

Sepsis is characterized by an innate immune response and the following immune dysfunction which can increase the emergence of secondary infections. Ethyl pyruvate (EP) has multiple immunoregulation functions in several serious illnesses, such as burn injury, severe sepsis and acute respiratory syndrome. However, little data was shown the effect of EP administration on immunosuppression post-CLP and the following secondary infection. The cecal ligation and puncture (CLP) followed by the induction of Pseudomonas aeruginosa (PA) was used as a clinically relevant two-hit model of sepsis. We assessed the survival rate, lung damage and lung bacterial clearance in vehicle or EP treatment group to demonstrate the lung response to Pseudomonas aeruginosa of septic mice. Then cytokines including lung IL-6, IL-1β, IL-10 and plasma HMGB1, apoptosis of splenic immune cells and Foxp3 level on regulatory T cells (Tregs) were studied to demonstrate the mechanisms of EP administration on two-hit mice. We found that the susceptibility of septic mice to Secondary Pseudomonas aeruginosa pneumonia could be down-regulated by ethyl pyruvate treatment and the protective effects of EP may via decreasing lung IL-10 and plasma HMGB1 expression, inhibiting the function of Tregs and relieving the apoptosis of splenic immune cells. The "immune paralysis" post-sepsis still remains a rigorous challenge for curing sepsis, our study may aid in the development of new therapeutic strategies to this problem.

Anti-inflammatory and anti-excitoxic effects of diethyl oxopropanamide, an ethyl pyruvate bioisoster, exert robust neuroprotective effects in the postischemic brain

Ethyl pyruvate (EP) is a simple aliphatic ester of pyruvic acid and has been shown to have robust neuroprotective effects via its anti-inflammatory, anti-oxidative, and anti-apoptotic functions. In an effort to develop novel EP derivatives with greater protective potencies than EP, we generated four EP isosteres, among them the neuroprotective potency of N,N-diethyl-2-oxopropanamide (DEOPA), in which the ethoxy group of EP was replaced with diethylamine, was far greater than that of EP. When DEOPA was administered intravenously (5 mg/kg) to rat middle cerebral artery occlusion (MCAO) model at 6 hrs post-surgery, it suppressed infarct formation, ameliorated neurological and sensory/motor deficits, and inhibited microglial activation and neutrophil infiltrations in the postischemic brain more effectively than EP. In particular, DEOPA markedly suppressed LPS-induced nitrite production and cytokine/chemokine inductions in microglia, neutrophils, and endothelial cells and these effects are attributable to inhibition of the activity of NF-κB by suppressing IκB-α degradation and p65 to DNA binding. In addition, DEOPA suppressed NMDA-induced neuronal cell death in primary cortical neuron cultures by NAD replenishment and suppression of NF-κB activity. Together, these results indicate DEOPA has multi-modal protective effects against ischemic brain damage targeting numerous cell types in the brain and also against other inflammation-related diseases.

The effect of antioxidant supplementation on bacterial translocation after intestinal ischemia and reperfusion

The intestine is highly sensitive to ischemia/reperfusion (I/R) injury. Intestinal I/R may cause local tissue injury and disruption of the intestinal mucosal barrier, allowing the passage of viable bacteria and endotoxins from the gastrointestinal lumen to distant organs. This phenomenon, known as bacterial translocation (BT), may lead to systemic disorders with high morbidity and mortality. Oxidative stress mediators such as reactive oxygen species, polymorphonuclear neutrophils and nitric oxide are believed to contribute to the intestinal I/R injury. Many antioxidants have shown protective effects against I/R injury of various organs. The present article provides an overview of studies investigating the effect of antioxidant supplementation on BT after intestinal I/R.

A review of equine sepsis

Sepsis is defined as an exaggerated, systemic inflammatory response to infection and is a common condition in horses. Systemic inflammatory response syndrome (SIRS) associated with bacterial infection is a hallmark of sepsis. Sepsis in neonatal foals is a common sequela of failure of passive transfer and, in addition to development of SIRS, may be characterised by bacteraemia, pneumonia, enterocolitis, omphalophlebitis, meningoencephalitis or arthritis. Sepsis in mature horses is most commonly observed secondary to gastrointestinal lesions that result in disrupted mucosa and bacterial translocation into circulation (endotoxaemia). Pleuropneumonia and metritis may also cause sepsis in mature horses. Diagnosis of sepsis is based on SIRS criteria as well as suspected or confirmed infection. Due to the relatively low sensitivity of microbial culture and the subjectivity of sepsis scoring, many sepsis biomarkers are being studied for their usefulness in diagnosis and prognostication of sepsis in horses. Treatment of sepsis requires an intensive care approach that includes antimicrobial drug administration, fluid resuscitation and pressure support, and treatment for inflammation, endotoxaemia and coagulopathy. Early recognition of sepsis and prompt antimicrobial drug treatment are critical for a successful outcome. Multiple organ dysfunction syndrome may occur in severe cases of sepsis, with common manifestations including laminitis and coagulopathies. Although prognosis for septic mature horses depends highly on the primary disease process, the overall survival rate in septic neonatal foals ranges from 26 to 86%, with most studies indicating a survival rate of 45-60%.

NADPH oxidases: an overview from structure to innate immunity-associated pathologies

Oxygen-derived free radicals, collectively termed reactive oxygen species (ROS), play important roles in immunity, cell growth, and cell signaling. In excess, however, ROS are lethal to cells, and the overproduction of these molecules leads to a myriad of devastating diseases. The key producers of ROS in many cells are the NOX family of NADPH oxidases, of which there are seven members, with various tissue distributions and activation mechanisms. NADPH oxidase is a multisubunit enzyme comprising membrane and cytosolic components, which actively communicate during the host responses to a wide variety of stimuli, including viral and bacterial infections. This enzymatic complex has been implicated in many functions ranging from host defense to cellular signaling and the regulation of gene expression. NOX deficiency might lead to immunosuppression, while the intracellular accumulation of ROS results in the inhibition of viral propagation and apoptosis. However, excess ROS production causes cellular stress, leading to various lethal diseases, including autoimmune diseases and cancer. During the later stages of injury, NOX promotes tissue repair through the induction of angiogenesis and cell proliferation. Therefore, a complete understanding of the function of NOX is important to direct the role of this enzyme towards host defense and tissue repair or increase resistance to stress in a timely and disease-specific manner.

Redox modulation of HMGB1-related signaling

SIGNIFICANCE

In the cells' nuclei, high-mobility group box protein 1 (HMGB1) is a nonhistone chromatin-binding protein involved in the regulation of transcription. Extracellularly, HMGB1 acts as a danger molecule with properties of a proinflammatory cytokine. It can be actively secreted from myeloid cells or passively leak from any type of injured, necrotic cell. Increased serum levels of active HMGB1 are often found in pathogenic inflammatory conditions and correlate with worse prognoses in cancer, sepsis, and autoimmunity. By damaging cells, superoxide and peroxynitrite promote leakage of HMGB1.

RECENT ADVANCES

The activity of HMGB1 strongly depends on its redox state: Inflammatory-active HMGB1 requires an intramolecular disulfide bond (Cys23 and Cys45) and a reduced Cys106. Oxidation of the latter blocks its stimulatory activity and promotes immune tolerance.

CRITICAL ISSUES

Reactive oxygen and nitrogen species create an oxidative environment and can be detoxified by superoxide dismutase (SOD), catalase, and peroxidases. Modifications of the oxidative environment influence HMGB1 activity.

FUTURE DIRECTIONS

In this review, we hypothesize that manipulations of an oxidative environment by SOD mimics or by hydrogen sulfide are prone to decrease tissue damage. Both the concomitant decreased HMGB1 release and its redox chemical modifications ameliorate inflammation and tissue damage.

Regulation of pyruvate metabolism and human disease

Pyruvate is a keystone molecule critical for numerous aspects of eukaryotic and human metabolism. Pyruvate is the end-product of glycolysis, is derived from additional sources in the cellular cytoplasm, and is ultimately destined for transport into mitochondria as a master fuel input undergirding citric acid cycle carbon flux. In mitochondria, pyruvate drives ATP production by oxidative phosphorylation and multiple biosynthetic pathways intersecting the citric acid cycle. Mitochondrial pyruvate metabolism is regulated by many enzymes, including the recently discovered mitochondria pyruvate carrier, pyruvate dehydrogenase, and pyruvate carboxylase, to modulate overall pyruvate carbon flux. Mutations in any of the genes encoding for proteins regulating pyruvate metabolism may lead to disease. Numerous cases have been described. Aberrant pyruvate metabolism plays an especially prominent role in cancer, heart failure, and neurodegeneration. Because most major diseases involve aberrant metabolism, understanding and exploiting pyruvate carbon flux may yield novel treatments that enhance human health.

Neuroprotective profile of pyruvate against ethanol-induced neurodegeneration in developing mice brain

Exposure to ethanol during developmental stages leads to several types of neurological disorders. Apoptotic neurodegeneration due to ethanol exposure is a main feature in alcoholism. Exposure of developing animals to alcohol induces apoptotic neuronal death and causes fetal alcohol syndrome. In the present study, we observed the possible protective effect of pyruvate against ethanol-induced neurodegeneration. Exposure of developing mice to ethanol (2.5 g/kg) induces apoptotic neurodegeneration and widespread neuronal cell death in the cortex and thalamus. Co-treatment of pyruvate (500 mg/kg) protects neuronal cell against ethanol by the reduced expression of caspase-3 in these brain regions. Immunohistochemical analysis and TUNNEL at 24 h showed that apoptotic cell death induced by ethanol in the cortex and thalamus is reduced by pyruvate. Histomorphological analysis at 24 h with cresyl violet staining also proved that pyruvate reduced the number of neuronal cell loss in the cortex and thalamus. The results showed that ethanol increased the expression of caspase-3 and thus induced apoptotic neurodegeneration in the developing mice cortex and thalamus, while co-treatment of pyruvate inhibits the induction of caspase-3 and reduced the cell death in these brain regions. These findings, therefore, showed that treatment of pyruvate inhibits ethanol-induced neuronal cell loss in the postnatal seven (P7) developing mice brain and may appear as a safe neuroprotectant for treating neurodegenerative disorders in newborns and infants.

Neuroprotective effects of alpha-ketoglutarate and ethyl pyruvate against motor dysfunction and oxidative changes caused by repeated 1-methyl-4-phenyl-1,2,3,6 tetrahydropyridine exposure in mice

1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) is a neurotoxin associated with drug abuse and causes permanent symptoms of Parkinson's disease (PD) by destroying dopaminergic neurons in the substantia nigra of the brain. In the present study, the neuroprotective effects of two carboxylic acid compounds, viz. alpha-ketoglutarate (A-KG), a Kreb’s cycle intermediate and ethyl pyruvate (EP), a lipid-soluble analogue of pyruvate, were evaluated against MPTP intoxication in mice and compared with madopar (MD; combination of levodopa plus benserazide), a standard drug. Animals received oral treatment of A-KG (500 mg/kg), EP (100 mg/kg) or MD (5 mg/kg) daily for 5 days followed by intraperitoneal administration of MPTP (20 mg/kg) and posttreatment (+10 min) of A-KG, EP or MD daily for the remaining 5 days. MPTP caused the inhibition of complex I of electron transport chain accompanied by oxidative stress in the brain. It also caused cytotoxicity in the midbrain region as characterized by histology and immunohistochemistry. Treatments of A-KG and EP were found to resolve the loss of motor coordination, oxidative stress, diminished complex I activity and tyrosine hydroxylase–positive neurons in midbrain. A-KG and EP also regressed the histological damage in the brain and minimized the accumulation of alpha-synuclein in the midbrain region. The data suggest that A-KG and EP which are nontoxic carboxylic acid compounds could be of potential therapeutic value in the treatment of PD.

It Is Not Just Folklore: The Aqueous Extract of Mung Bean Coat Is Protective against Sepsis

Mung bean (Vigna Radiata) has been traditionally used in China both as nutritional food and herbal medicine against a number of inflammatory conditions since the 1050s. A nucleosomal protein, HMGB1, has recently been established as a late mediator of lethal systemic inflammation with a relatively wider therapeutic window for pharmacological interventions. Here we explored the HMGB1-inhibiting capacity and therapeutic potential of mung bean coat (MBC) extract in vitro and in vivo. We found that MBC extract dose-dependently attenuated LPS-induced release of HMGB1 and several chemokines in macrophage cultures. Oral administration of MBC extract significantly increased animal survival rates from 29.4% (in saline group, N = 17 mice) to 70% (in experimental MBC extract group, N = 17 mice, P < 0.05). In vitro, MBC extract stimulated HMGB1 protein aggregation and facilitated both the formation of microtubule-associatedprotein-1-light-chain-3-(LC3-)containing cytoplasmic vesicles, and the production of LC3-II in macrophage cultures. Consequently, MBC extract treatment led to reduction of cellular HMGB1 levels in macrophage cultures, which was impaired by coaddition of two autophagy inhibitors (bafilomycin A1 and 3-methyladenine). Conclusion. MBC extract is protective against lethal sepsis possibly by stimulating autophagic HMGB1 degradation.

Ethyl pyruvate promotes spinal cord repair by ameliorating the glial microenvironment

BACKGROUND AND PURPOSE

Spinal cord injury (SCI) triggers a series of endogenous processes, including neuroinflammation and reactive astrogliosis, which may contribute to the failure of neural regeneration and functional recovery. In the present study, the effect of ethyl pyruvate on spinal cord repair was explored.

EXPERIMENTAL APPROACH

Functional assessment and histological analyses of astrogliosis, neuroinflammation, neuronal survival and axonal regeneration were performed to investigate the effects of ethyl pyruvate (0.086, 0.215, 0.431 or 0.646 mmol·kg(-1) ·day(-1) ) on spinal cord repair in a rat model of SCI. The effect of ethyl pyruvate (5, 10 or 15 mM) on astrocytic activation was also evaluated in an in vitro'scratch-wound' model.

KEY RESULTS

Functional assessment showed evident improvement of behavioural functions in the ethyl pyruvate-treated rats. Reactive astrogliosis was significantly inhibited in vivo, after injection of ethyl pyruvate (0.431 mmol·kg(-1) day(-1) ), and in vitro'scratch-wound' model in the presence of 10 or 15 mM ethyl pyruvate. The difference between effective concentration in vitro and in vivo suggests that the inhibitory effect of ethyl pyruvate on astrogliosis in damaged spinal cord is indirect. In addition, ethyl pyruvate (0.431 mmol·kg(-1) day(-1) ) attenuated SCI-induced neuroinflammation; it decreased the Iba-1-, ED-1- and CD11b-positive cells at the lesion site. Importantly, histological analyses showed a significantly greater number of surviving neurons and regenerative axons in the ethyl pyruvate-treated rats.

CONCLUSIONS AND IMPLICATIONS

Ethyl pyruvate was shown to inhibit astrogliosis and neuroinflammation, promote neuron survival and neural regeneration, and improve the functional recovery of spinal cord, indicating a potential neuroprotective effect of ethyl pyruvate against SCI.

Ethyl pyruvate diminishes the inflammatory response to lipopolysaccharide infusion in horses

REASONS FOR PERFORMING THE STUDY

Endotoxaemia contributes to morbidity and mortality in horses with colic due to inflammatory cascade activation. Effective therapeutic interventions are limited for these horses. Ethyl pyruvate (EP), an anti-inflammatory agent that alters the expression of proinflammatory cytokines, improved survival and organ function in sepsis and gastrointestinal injury in rodents and swine. Therapeutic efficacy of EP is unknown in endotoxaemic horses.

OBJECTIVES

Determine the effects of EP on signs of endotoxaemia and expression of proinflammatory cytokines following administration of lipopolysaccharide (LPS) in horses.

METHODS

Horses received 30 ng/kg bwt LPS in saline to induce signs of endotoxaemia. Next, horses received lactated Ringer's solution (LRS), (n = 6), 150 mg/kg bwt EP in LRS, (n = 6), or 1.1 mg/kg bwt flunixin meglumine (FM), (n = 6). Controls received saline followed by LRS (n = 6). Physical examinations, behaviour pain scores and blood for clinical pathological testing and gene expression were obtained at predetermined intervals for 24 h.

RESULTS

Lipopolysaccharide infusion produced clinical and clinicopathological signs of endotoxaemia and increased expression of tumour necrosis factor alpha (TNFα), interleukin 6 (IL-6) and IL-8 (P<0.001) compared with controls. Leucopenia and neutropenia occurred in all horses that received LPS. Horses treated with EP and FM had significantly (P<0.0001) reduced pain scores compared with horses receiving LPS followed by LRS. Flunixin meglumine was significantly more effective at ameliorating fever compared with EP. Both EP and FM significantly diminished TNFα expression. Ethyl pyruvate significantly decreased, but FM significantly increased, IL-6 expression. Neither EP nor FM altered IL-8 expression.

CONCLUSIONS AND POTENTIAL RELEVANCE

Ethyl pyruvate administered following LPS diminished the clinical effects of endotoxaemia and decreased proinflammatory gene expression in horses. Ethyl pyruvate suppressed expression of proinflammatory cytokines better than FM. However, FM was a superior anti-pyretic compared with EP. Ethyl pyruvate may have therapeutic applications in endotoxaemic horses.

Ethyl pyruvate improves healing of colonic anastomosis in a rat model of peritonitis

BACKGROUND

This study was designed to evaluate the effects of ethyl pyruvate (EP) on wound healing in primary colonic anastomoses in intraperitoneal sepsis.

METHODS

Standard left colon resection and end-to-end anastomosis were performed on 30 rats. They were grouped as control (C)--no further treatment; sepsis (S)--received 2 mL Escherichia coli (ATCC 25922) intraperitoneally (IP), and after 5 hours, standard resection and anastomosis were performed; or sepsis-group treated with EP (S-EP)--received 2 mL E coli IP, after 5 hours, standard resection and anastomosis were performed and treated with EP 50 mg/kg IP for 7 days. On the postoperative day 7, the animals were sacrificed.

RESULTS

The anastomosis bursting pressure in group S was significantly lower than in the other groups. There were no differences between groups C and S-EP. Tissue hydroxyproline concentrations in group C were significantly higher than in group S.

CONCLUSIONS

EP administration prevented intraperitoneal sepsis-induced impaired anastomotic healing of colon.

Pitfalls in the quest of neuroprotectants for the perinatal brain

Sick preterm and term newborns are highly vulnerable to neural injury, and thus there has been a major search for new, safe and efficacious neuroprotective interventions in recent decades. Preclinical studies are essential to select candidate drugs for clinical trials in humans. This article focuses on 'negative' preclinical studies, i.e. studies where significant differences cannot be detected. Such findings are critical to inform both clinical and preclinical investigators, but historically they have been difficult to publish. A significant amount of time and resources is lost when negative results or nonpromising therapeutics are replicated in separate laboratories because these negative results were not shared with the research community in an open and accessible format. In this article, we discuss approaches to strengthen conclusions from negative preclinical studies and, conversely, to reduce false-negative preclinical evaluations of potential therapeutic compounds. Without being exhaustive, we address three major issues in conducting and interpreting preclinical experiments, including: (a) the choice of animal models, (b) the experimental design, and (c) issues concerning statistical analyses of the experiments. This general introduction is followed by synopses of negative data obtained from studies of three potential therapeutics for perinatal brain injury: (1) the somatostatin analog octreotide, (2) an AMPA/kainate receptor antagonist, topiramate, and (3) a pyruvate derivative, ethyl pyruvate.

Hypertonic sodium pyruvate solution is more effective than Ringer's ethyl pyruvate in the treatment of hemorrhagic shock

Hypertonic sodium pyruvate (HSP), as well as ethyl pyruvate solutions, has been proposed as resuscitative fluids in the treatment of hemorrhagic shock (HS) because of their anti-inflammatory and antioxidant properties. The effectiveness of one pyruvate preparation over the other in the treatment of HS has not been evaluated. The authors aimed to compare two pyruvate solutions for resuscitation and their mechanisms of action in rats during HS. The effects of infusion of low-volume HSP were compared against high-volume Ringer's ethyl pyruvate on hemodynamic parameters, inflammatory cascade, and regulation of stress and apoptosis-related proteins in the liver. Sprague-Dawley rats were either treated as sham animals or subjected to computer-controlled arterial hemorrhage (40 mmHg) for 60 min followed by resuscitation with isotonic sodium chloride solution, hypertonic saline, Ringer's lactate solution, Ringer's ethyl pyruvate, or HSP for 60 min. Animals were continuously monitored for hemodynamic and biochemical parameters in blood. At the end of the experiment, animals were killed, and liver samples were taken for the evaluation of inflammatory and anti-inflammatory markers and mediators of oxidative stress, liver injury, and expression of apoptotic signaling proteins. In comparison with Ringer's ethyl pyruvate, HSP administration after hemorrhage reduced liver injury, which was associated with increased levels of serum and tissue inflammatory cytokines, inflammatory mediators such as NOS and cyclooxygenase 2, lipid peroxidation, and higher hepatocellular adenosine triphosphate. Cellular apoptotic events related to the activation of caspase-3 and poly(ADP-ribose)polymerase cleavage were also decreased by sodium pyruvate. Resuscitation with small-volume HSP offers significant protection against inflammatory and oxidative stress and in preventing liver injury compared with large-volume Ringer's ethyl pyruvate.

Role of high-mobility group box 1 protein in the pathogenesis of intestinal barrier injury in rats with severe acute pancreatitis

OBJECTIVE

To investigate the role of high-mobility group box 1 (HMGB1) in the development of intestinal barrier injury of severe acute pancreatitis (SAP) and to examine the effect of ethyl pyruvate (EP) on intestinal inflammation in rats with SAP.

METHODS

Rats were randomly divided into the following experimental groups: control, SAP, and EP treated. Then, the distal ileum was harvested for morphological studies, streptavidin-peroxidase immunohistochemistry examination, and Western blot analysis. The concentrations of plasma amylase, endotoxin, and diamine oxidase (DAO) and the activity of myeloperoxidase (MPO) in the intestine were determined.

RESULTS

We found that the expression of HMGB1 was up-regulated in the ileal mucosa within 6 hours and then remained elevated for more than 48 hours after SAP. Meanwhile, the levels of plasma amylase, endotoxin, and DAO and the activity of MPO in the intestinal mucosa were rapidly increased after SAP. Whereas treatment with EP significantly decreased the expression of intestinal HMGB1, the levels of plasma amylase, endotoxin, and DAO ameliorated the activity of MPO in the intestine in SAP rats.

CONCLUSIONS

Our results demonstrate that HMGB1 participates in intestinal barrier injury in SAP and EP might play a therapeutic role in intestinal inflammation in this SAP model.

Ethyl pyruvate reduces mortality in an endotoxin-induced severe acute lung injury mouse model

Background

Ethyl pyruvate (EP) was recently identified as an experimental therapeutic agent in a wide variety of model systems for inflammation-mediated tissue and cellular injury.

Objective

To evaluate the effect of ethyl EP on improving the survival in mice with LPS-induced acute lung injury (ALI).

Methods

ALI was induced by administering lipopolysaccharide (LPS) intratracheally. The mice were treated intraperitoneally (i.p.) with 100, 50 and 10 mg/kg EP immediately before intratracheal instillation of LPS, and 100 mg/kg EP was administered 0, 12, 24 and 48 hours after induction of ALI. The mortality rate was recorded and analyzed by the Kaplan-Meier method. Serum tumor necrosis factor (TNF)-α, interleukin (IL) -6 and IL-1 β were measured in bronchial alveolar lavage fluid using an enzyme-linked immunosorbent assay. High-mobility group box 1 levels were measured by Western immunoblotting.

Results

Treatment with EP significantly inhibited the release of HMGB1, TNF-α, IL-6 and IL-1β into bronchoalveolar lavage (BAL) fluids of ALI mice, and reduced the permeability index of the injured lung. High EP doses reduced the mortality from ALI and the permeability index (100 mg/kg and 50 mg/kg EP versus control; P < 0.0001). Early administration of high-dose EP significantly increased survival rate (0, 12 and 24 h versus control; P < 0.0001, P < 0.0001 and P = 0.01 respectively by log-rank test). There was no survival advantage when EP was initiated at 48 h.

Conclusion

Ethyl pyruvate improves survival and reduces the lung permeability index in mice with LPS-induced ALI.

Recent Developments in the Identification of Novel Therapeutic Targets for the Treatment of Patients with Sepsis and Septic Shock

The overall mortality in patients with sepsis is approximately 30%; this figure increases to 50% or higher in patients with septic shock, and sepsis continues to be seen as a major clinical challenge. The recent success of several important trials has fuelled interest in further therapeutic developments. Here, I review the many different strategies that are being investigated, focusing in particular on those that are in late pre-clinical or early clinical development. These can be broadly divided into three groups: strategies aimed at bacterial targets, strategies aimed at disorders of immune regulation in the host, and finally, other novel strategies based on modifying host response; which, if any, of these will prove successful in large clinical trials is unknown. Nevertheless, the fact that sepsis has finally proved tractable as a target for new drug development lends support to those who believe that at least some of the compounds identified in this paper will prove to have clinical benefit.

Anti-inflammatory resuscitation improves survival in hemorrhage with trauma

BACKGROUND

Hemorrhage is a common cause of death despite the recent advances in resuscitation and critical care. Conventional resuscitation fluids are designed to reestablish tissue perfusion, but they fail to prevent systemic inflammation. Indeed, resuscitation can promote inflammatory responses, which can be more dangerous than the original hemorrhage. This consideration is relevant in critical care where hemorrhage is normally associated with collateral trauma that can exacerbate the inflammatory responses during resuscitation. Here, we analyzed whether ethyl pyruvate could provide a therapeutic anti-inflammatory potential during resuscitation in experimental hemorrhage with trauma.

METHODS

Adult male Sprague-Dawley rats were subjected to trauma induced by closed femur fracture. Then, the animals were immediately subjected to lethal hemorrhage during 15 minutes to reach a mean arterial blood pressure of 35 mm Hg to 40 mm Hg and subsequent maintenance of this mean arterial blood pressure for another 15 minutes. Resuscitation was limited to 15 mL/kg Hextend with or without ethyl pyruvate.

RESULTS

Resuscitation with conventional fluids reestablished normal tissue perfusion, but still more than 60% of the animals died. Resuscitation with ethyl pyruvate protected all the animals from lethal hemorrhage with trauma. Trauma exacerbated tumor necrosis factor (TNF) levels in the serum, the spleen, and the heart. Ethyl pyruvate blunted TNF levels in the serum and all the organs but particularly in the lung and the liver during resuscitation. TNF levels in the lung, spleen, and the liver of those animals resuscitated with ethyl pyruvate were statistically similar to those in control animals.

CONCLUSION

Ethyl pyruvate may attenuate systemic inflammatory responses during resuscitation and improve survival in experimental models of hemorrhage with trauma.

Ethyl pyruvate decreases HMGB1 release and ameliorates murine colitis

Signals from stressed cells and the enteric microbiota activate macrophages and dendritic cells and mediate intestinal inflammation. HMGB1 serves as an immunogenic stimuli causing release of inflammatory cytokines by myeloid cells. Ethyl pyruvate inhibits secretion of HMGB1 and improves survival in models of endotoxemia and hemorrhagic shock. We reasoned that ethyl pyruvate may be protective in colitis, which involves similar inflammatory pathways. In IL-10(-/-) mice with established chronic colitis, ethyl pyruvate administration ameliorated colitis and reduced intestinal cytokine production. IL-10(-/-) mice demonstrated increased intestinal HMGB1 expression and decreased expression of RAGE compared with wild-type mice. Fecal HMGB1 levels were decreased in ethyl pyruvate-treated mice. Furthermore, ethyl pyruvate induced HO-1 expression in intestinal tissue. In TNBS-induced colitis, intrarectal administration of ethyl pyruvate resulted in amelioration of colitis and reduced intestinal cytokine production. In LPS-activated murine macrophages, ethyl pyruvate decreased expression of IL-12 p40 and NO production but did not affect IL-10 levels. Ethyl pyruvate did not inhibit nuclear translocation of NF-kappaB family members but attenuated NF-kappaB DNA binding. Additionally, ethyl pyruvate induced HO-1 mRNA and protein expression and HO-1 promoter activation. Moreover, ethyl pyruvate prevented nuclear-to-cytoplasmic translocation of HMGB1. In conclusion, the HMGB1/RAGE pathway has pathophysiologic and diagnostic significance in experimental colitis. Ethyl pyruvate and other strategies to inhibit HMGB1 release and function represent promising interventions in chronic inflammatory diseases.

Experimental therapeutic strategies for severe sepsis: mediators and mechanisms

Severe sepsis is the leading cause of mortality in intensive care units. The limited ability of current therapies to reduce sepsis mortality rates has fueled research efforts for the development of novel treatment strategies. Through the close collaboration between clinicians and scientists, progress can be seen in the struggle to develop effective therapeutic approaches for the treatment of sepsis and other immune and inflammatory disorders. Indeed, significant advances in intensive care, such as lung protective mechanical ventilation, improved antibiotics, and superior monitoring of systemic perfusion, are improving patient survival. Nonetheless, specific strategies that target the pathophysiological disorders in sepsis patients are essential to further improve clinical outcomes. This article reviews current clinical management approaches and experimental interventions that target pleiotropic or late-acting inflammatory mediators like caspases, C5a, MIF, and HMGB1, or the body's endogenous inflammatory control mechanisms such as the cholinergic anti-inflammatory pathway. These inflammatory mediators and anti-inflammatory mechanisms, respectively, show significant potential for the development of new experimental therapies for the treatment of severe sepsis and other infectious and inflammatory disorders.

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.

Neuroprotective effects of ethyl pyruvate on brain energy metabolism after ischemia-reperfusion injury: a 31P-nuclear magnetic resonance study

The neuroprotective effects of ethyl pyruvate (EP), a stable derivative of pyruvate, on energy metabolism of rat brain exposed to ischemia-reperfusion stress were investigated by (31)P-nuclear magnetic resonance ((31)P-NMR) spectroscopy. Recovery level of phosphocreatine after ischemia was significantly greater when superfused with artificial cerebrospinal fluid (ACSF) with 2 mM EP than when superfused with ACSF without EP. EP was neuroprotective against ischemia only when administered before the ischemic exposure. Intracellular pH during ischemia was less acidic when superfused ahead of time with EP. EP did not show neuroprotective effects in neuron-rich slices pretreated with 100 microM fluorocitrate, a selective glial poison. It was suggested that both the administration of EP before ischemic exposure and the presence of astrocytes are required for EP to exert neuroprotective effects. We suggest the potential involvement of multiple mechanisms of action, such as less acidic intracellular pH, glial production of lactate, and radical scavenging ability.

Fructose-1,6-bisphosphate does not preserve ATP in hypoxic-ischemic neonatal cerebrocortical slices

Fructose-1,6-bisphosphate (FBP), an endogenous intracellular metabolite in glycolysis, was found in many preclinical studies to be neuroprotective during hypoxia-ischemia (HI) when administered exogenously. We looked for HI neuroprotection from FBP in a neonatal rat brain slice model, using 14.1 T (1)H/(31)P/(13)C NMR spectroscopy of perchloric acid slice extracts to ask: 1) if FBP preserves high energy phosphates during HI; and 2) if exogenous [1-(13)C]FBP enters cells and is glycolytically metabolized to [3-(13)C]lactate. We also asked: 3) if substantial superoxide production occurs during and after HI, thinking such might be treatable by exogenous FBP's antioxidant effects. Superfused P7 rat cerebrocortical slices (350 mum) were treated with 2 mM FBP before and during 30 min of HI, and then given 4 h of recovery with an FBP-free oxygenated superfusate. Slices were removed before HI, at the end of HI, and at 1 and 4 h after HI. FBP did not improve high energy phosphate levels or change (1)H metabolite profiles. Large increases in [3-(13)C]lactate were seen with (13)C NMR, but the lactate fractional enrichment was always (1.1+/-0.5)%, implying that all of lactate's (13)C was natural abundance (13)C, that none was from metabolism of (13)C-FBP. FBP had no effect on the fluorescence of ethidium produced from superoxide oxidation of hydroethidine. Compared to control slices, ethidium fluorescence was 25% higher during HI and 50% higher at the end of recovery. Exogenous FBP did not provide protection or enter glycolysis. Its use as an antioxidant might be worth studying at higher FBP concentrations.

Protective effects of ethyl pyruvate treatment on paraquat-intoxicated rats

Although, numerous studies have attempted to reduce the oxygen radical injury induced by the antioxidants in paraquat intoxication, these antioxidant therapies have showed few survival benefits. Ethyl pyruvate (EP) may function as an effective scavenger of oxygen radicals, an anti-inflammatory agent and an energy source in many ischemia reperfusion models. The aim of this study was to evaluate the antioxidant and anti-inflammatory effects of EP on the lung and the liver tissues in paraquat-intoxicated rats. Rats were randomly given either a low (2 mg/kg i.p.) or high (40 mg/kg i.p.) EP dose, 30 min before or 1 h after paraquat (50 mg/kg i.p.) administration, and subsequently killed at 6 and 24 h. Glutathione (GSH) and malondialdehyde (MDA) levels of the lungs and the livers, and plasma nitric oxide (NO) concentrations were measured. Pretreatment of EP significantly decreased the MDA level in the lung and the liver tissues. EP also significantly decreased plasma NO concentrations at 6 h. EP pretreatment, however, failed to show significant change in GSH concentration. In post-treatment of EP, MDA levels in the lung tissue and plasma NO levels were significantly decreased. In conclusion, EP decreased the lipid peroxidation and seemed to exert an anti-inflammatory action in the paraquat intoxication rat model.

Ethyl pyruvate reduces germ cell-specific apoptosis and oxidative stress in rat model of testicular torsion/detorsion

PURPOSE

Testicular torsion/detorsion (T/D) results in enhanced formation of free radical metabolites, which contributes to the pathophysiology of tissue damage. We investigated the protective effects of ethyl pyruvate (EP) against testis tissue damage in an experimental model of testicular torsion.

METHODS

Sprague-Dawley rats were divided into 5 groups. In those animals that underwent T/D, right testes were rotated 720 degrees for 1 hour. Group 1 control rats underwent sham operation. In group 2, the rats underwent T/D. The EP was prepared and injected in the form of Ringer's ethyl pyruvate solution. The rats in group 3, 4, and 5 received 2 doses of 20, 50, and 100 mg/kg EP (30 minutes before and after detorsion), respectively. The right testes of 6 animals from each group were excised 4 hours after detorsion for the measurement of lipid peroxidation, myeloperoxidase (MPO), and antioxidant enzymes activities. Germ cell apoptosis was determined in right testes of 8 animals per group 24 hours after detorsion. The epididymal sperm concentration and motility were evaluated 1 month after treatments.

RESULTS

Germ cell apoptosis indices were significantly higher in group 2 compared with control group. The level of lipid peroxidation and MPO activity increased, whereas antioxidant enzymes activities decreased after T/D. Sperm count and motility were also reduced 1 month after T/D in group 2 rats. However, EP treatment at doses of 50 and 100 mg/kg significantly decreased the early apoptotic damage and improved long-term sperm count and motility. In the same dosing groups, we observed normalization of oxidant/antioxidant balance and decrement of MPO activity. However, administration of 20 mg/kg of EP conferred no protective effect.

CONCLUSIONS

Administration of Ringer's ethyl pyruvate solution (in appropriate doses) is protective against apoptotic tissue damage following testicular torsion and improves long-term testicular function. The antioxidant and anti-inflammatory properties of EP seem responsible for the protective effects. Our findings suggest this resuscitation solution as a possible substitute for fluid and electrolyte maintenance during surgical detorsion.

Ethyl pyruvate improves survival and ameliorates distant organ injury in rats with severe acute pancreatitis

OBJECTIVE

To evaluate the effect of ethyl pyruvate (EP) in improving the survival and ameliorating distant organ damage and to investigate the role of high-mobility group box (HMGB) 1 in rats with established severe acute pancreatitis (SAP).

METHODS

Severe acute pancreatitis was induced by retrograde infusion of sodium taurodeoxycholate (5%, 1 mL/kg) into the biliopancreatic ducts in male Wistar rats. The rats were infused intravenously with EP of 40 mg/kg, 4 mg/kg, and 0.4 mg/kg initiating 12 hours, and EP of 40 mg/kg was administered beginning 2 hours before surgery (-2 hours) and 12, 24, and 36 hours after induction of SAP; then, the mortality was recorded. Serum tumor necrosis factor alpha, interleukin (IL) 6, and IL-1beta were measured using enzyme-linked immunosorbent assay. High-mobility group box 1 levels were measured using Western immunoblotting analysis.

RESULTS

Serum HMGB1 levels were increased dramatically after 12 hours, remained at high levels for 72 hours, and were significantly higher in rats with SAP than in those with mild and moderate pancreatitis (P < 0.01). Treatment with EP (40 mg/kg) conferred protection from lethality of SAP (EP survival [63%] vs vehicle survival [6.3%]; P < 0.001). No survival advantage occurred when treatment was initiated 36 hours after surgery, but administration beginning 2 hours before operation (-2 hours) and 12 and 24 hours after induction of SAP significantly increased survival. Ethyl pyruvate treatment significantly decreased serum HMGB1, tumor necrosis factor alpha, IL-1beta, and IL-6 levels and ameliorated extrapancreatic organ dysfunction in rats with SAP.

CONCLUSIONS

Ethyl pyruvate improves survival and ameliorates distant organ injury of SAP. These beneficial effects of EP are because of the modulation of HMGB1 and other inflammatory cytokine responses.

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 inhibits hypoxic pulmonary vasoconstriction and attenuates pulmonary artery cytokine expression

Hypoxic pulmonary vasoconstriction is a common consequence of acute lung injury and may be mediated by increased local production of proinflammatory cytokines. Ethyl pyruvate is a novel anti-inflammatory agent that has been shown to down-regulate proinflammatory genes following hemorrhagic shock; however, its effects on hypoxic pulmonary vasoconstriction are unknown. We hypothesized that ethyl pyruvate would inhibit hypoxic pulmonary vasoconstriction and down-regulate pulmonary artery cytokine expression during hypoxia. To study this, isometric force displacement was measured in isolated rat pulmonary artery rings (n = 8/group) during hypoxia (95% N(2)/5% CO(2)) with or without prior ethyl pyruvate (10 mm) treatment. Following 60 min of hypoxia, pulmonary artery rings were analyzed for tumor necrosis factor-alpha and interleukin-1 mRNA via reverse transcriptase polymerase chain reaction. Ethyl pyruvate inhibited hypoxic pulmonary artery contraction (4.49 +/- 2.32% versus 88.80 +/- 5.68% hypoxia alone) and attenuated the hypoxic up-regulation of pulmonary artery tumor necrosis factor and interleukin-1 mRNA (P < 0.05). These data indicate that (1) hypoxia increases pulmonary artery vasoconstriction and proinflammatory cytokine gene expression; (2) ethyl pyruvate decreases hypoxic pulmonary vasoconstriction and down-regulates hypoxia-induced pulmonary artery proinflammatory cytokine gene expression; and (3) ethyl pyruvate may represent a novel therapeutic adjunct in the treatment of acute lung injury.

An assessment of serum leptin levels in patients with chronic viral hepatitis: a prospective study

BACKGROUND

The role of leptin in the course of liver disease due to chronic viral hepatitis (CVH) remains controversial. Our aims were to investigate the relationship between serum leptin concentrations and the severity of liver disease in a cohort of subjects with HBeAg negative chronic hepatitis B (CHB) and C (CHC) and to analyze the effect of body composition, the leptin system and insulin resistance together with viral factors on virologic response to antiviral treatment.

METHODS

We studied 50 (36 men) consecutive patients suffering from biopsy-proven CVH due to HBV (n = 25) or HCV (n = 25) infection. Thirty-two (17 men) healthy volunteers served as controls. Levels of serum leptin and insulin were determined by immunoassays at baseline and at the end of the treatment.

RESULTS

A significant association between serum leptin levels and the stage of hepatic fibrosis was noted; patients with cirrhosis presented higher serum leptin levels compared to those with lower fibrosis stage [CHB patients (17436 pg/ml vs 6028.5 pg/ml, p = 0.03), CHC patients (18014 pg/ml vs 4385 pg/ml, p = 0.05]. An inverse correlation between lower leptin levels and response to lamivudine monotherapy was noted in patients with CHB; those with a virologic response presented lower serum leptin levels (5334 vs 13111.5 pg/ml; p-value = 0.003) than non-responders. In genotype 1 CHC patients, insulin resistance played a significant role in the response to antiviral therapy.

CONCLUSION

Our data clearly suggest that cirrhosis due to CHB or CHC is associated with higher leptin levels. Increased serum leptin levels represent a negative prognostic factor for response to lamivudine monotherapy in patients with CHB. In CHC patients insulin resistance strongly influences the response to antiviral treatment in patients infected with genotype 1.

Anti-inflammatory properties of the short-chain fatty acids acetate and propionate: A study with relevance to inflammatory bowel disease

AIM: To compare the anti-inflammatory properties of butyrate with two other SCFAs, namely acetate and propionate, which have less well-documented effects on inflammation.

METHODS: The effect of SCFAs on cytokine release from human neutrophils was studied with ELISA. SCFA-dependent modulation of NF-κB reporter activity was assessed in the human colon adenocarcinoma cell line, Colo320DM. Finally, the effect of SCFAs on gene expression and cytokine release, measured with RT-PCR and ELISA, respectively, was studied in mouse colon organ cultures established from colitic mice.

RESULTS: Acetate, propionate and butyrate at 30 mmol/L decreased LPS-stimulated TNFα release from neutrophils, without affecting IL-8 protein release. All SCFAs dose dependently inhibited NF-κB reporter activity in Colo320DM cells. Propionate dose-dependently suppressed IL-6 mRNA and protein release from colon organ cultures and comparative studies revealed that propionate and butyrate at 30 mmol/L caused a strong inhibition of immune-related gene expression, whereas acetate was less effective. A similar inhibition was achieved with the proteasome inhibitor MG-132, but not the p38 MAPK inhibitor SB203580. All SCFAs decreased IL-6 protein release from organ cultures.

CONCLUSION: In the present study propionate and butyrate were equipotent, whereas acetate was less effective, at suppressing NF-κB reporter activity, immune-related gene expression and cytokine release in vitro. Our findings suggest that propionate and acetate, in addition to butyrate, could be useful in the treatment of inflammatory disorders, including IBD.

Protective effects of ethyl pyruvate against acute lung injury induced by acute necrotizing pancreatitis in rats

AIM: To investigate the effects of ethyl pyruvate (EP) on the levels of tumor necrosis factor-α (TNF-α), interleukin-1b (IL-1β) in serum and mRNA expression of high mobility group box 1 (HMGB1) in lung tissues, and explore the mechanisms of ethyl pyruvate in protecting the lungs against acute injury induced by acute necrotizing pancreatitis (ANP).

METHODS: ANP model was induced by retrograde injection of 50 g/L sodium taurocholate into pancreatic duct. Animals were divided randomly into 3 groups: control group, ANP group, and EP treatment group. EP solution was administered intravenously every 6 hours (40 mg/kg once). The serum levels of TNF-α and IL-1β were measured by enzyme-linked immunosorbent assay (ELISA). The mRNA expression of HMGB1 in lung tissues was detected by reverse transcription-polymerase chain reaction (RT-PCR). The partial pressure of blood oxygen (PaO₂) was measured, and histological examination of the lungs was also performed.

RESULTS: The serum levels of TNF-α and IL-6 were rapidly increased after ANP model was induced, and reached peak at the 6^th hour, but they were decreased at the 12^th hour. In comparison with those in ANP group, the serum levels of TNF-α and IL-1β were markedly lowered in EP group 6 and 12 hours after ANP model was induced (TNF-α: 131.6 ± 29.6 ng/L vs 196.3 ± 16.3 ng/L, 65.0 ± 16.6 ng/L vs 90.2 ± 20.1 ng/L, P < 0.05; IL-1β: 194.9 ± 26.8 ng/L vs 223.0 ± 34.8 ng/L, 105.2 ± 24.0 ng/L vs 130.4 ± 23.0 ng/L, P < 0.05). The mRNA expression of HMGB1 in lung tissues was increased significantly at the 12th hour and maintained to the 24^th hour after ANP model was induced, whereas in EP group, HMGB1 mRNA expression was significantly lower than that in ANP group at each time point (0.68 ± 0.11 vs 0.88 ± 0.11, 0.81 ± 0.11 vs 1.04 ± 0.10, 1.08 ± 0.08 vs 1.33 ± 0.15, all P < 0.05). The injury of lung tissues in EP group was milder than that in ANP group, and the value of PaO₂ was also obviously higher in EP group than that in ANP group (P < 0.05).

CONCLUSION: EP can inhibit the release of TNF-α and IL-1β, down-regulate HMGB1 mRNA expression in lung tissues of ANP rats, and protect lungs from acute injury induced by ANP.

Experimental strategies to improve in vitro models of renal ischemia

Ischemia has elicited a great deal of interest among the scientific community due to its role in life-threatening pathologies such as cancer, stroke, acute renal failure, and myocardial infarction. Oxygen deprivation (hypoxia) associated with ischemia has recently become a subject of intense scrutiny. New investigators may find it challenging to induce hypoxic injury in vitro. Researchers may not always be aware of the experimental barriers that contribute to this phenomenon. Furthermore, ischemia is associated with other major insults, such as excess carbon dioxide (hypercapnia), nutrient deprivation, and accumulation of cellular wastes. Ideally, these conditions should also be incorporated into in vitro models. Therefore, the motivation behind this review is to: i. delineate major in vivo ischemic insults; ii. identify and explain critical in vitro parameters that need to be considered when simulating ischemic pathologies; iii. provide recommendations to improve experiments; and as a result, iv. enhance the validity of in vitro results for understanding clinical ischemic pathologies. Undoubtedly, it is not possible to completely replicate the in vivo environment in an ex vivo model system. In fact, the primary goal of many in vitro studies is to elucidate the role of specific stimuli during in vivo pathological events. This review will present methodologies that may be implemented to improve the applicability of in vitro models for understanding the complex pathological mechanisms of ischemia. Finally, although these topics will be discussed within the context of renal ischemia, many are pertinent for cellular models of other organ systems and pathologies.

Pyruvate improves recovery after PARP-1-associated energy failure induced by oxidative stress in neonatal rat cerebrocortical slices

Previous neuron and glial cell culture studies of excessive poly (ADP-ribose) polymerase (PARP-1) activation found NAD(+) depletion, glycolytic arrest, and cell death that could be avoided by exogenous tricarboxylic acid cycle (TCA) metabolites, especially pyruvate (pyr). Pyruvate neuroprotection has been attributed to cytosolic NAD(+) replenishment, TCA metabolism, and antioxidant activity. We investigated the first two mechanisms in respiring cerebrocortical slices after a 1-h H(2)O(2) exposure to activate PARP-1. H(2)O(2) was followed by a 4-h recovery with oxy-artificial cerebrospinal fluid superfusion having either: (1) no glucose (glc) or pyruvate; (2) 10 mmol/L glc only; (3) 10 mmol/L pyruvate only; (4) both 10 mmol/L glc and 10 mmol/L pyruvate. Poly-ADP-ribosylation was quantified from Western blots and immunohistochemistry. Perchloric acid extracts were quantified with 14.1 T (31)P nuclear magnetic resonance spectroscopy. Just after H(2)O(2) exposure, ATP and NAD(+) decreased by approximately 50%, PCr decreased by 75%, and the ADP/ATP ratio approximately doubled. ATP and NAD(+) changes, but not PCr changes, were nearly eliminated if PARP inhibitors accompanied the H(2)O(2). Recovery with both pyruvate and glc was better than with glc alone, having higher ATP (0.161 versus 0.075, P<0.01) and PCr levels (0.144 versus 0.078, P<0.01), and higher viable cell counts in TUNEL and Fluoro-Jade B staining. Two-dimensional [(1)H-(13)C] HSQC spectra showed metabolism during recovery of (13)C glc or pyr. Pyruvate metabolism was primarily via pyruvate dehydrogenase, with some via pyruvate carboxylation. Pyruvate superfusion of PARP-injured brain slices helps replenish NAD(+) while providing metabolic fuel. Although this augments recovery, a strong antioxidant role for pyruvate has not been ruled out.

Haemodynamic and metabolic effects of resuscitation with Ringer's ethyl pyruvate in the acute phase of porcine endotoxaemic shock

BACKGROUND

Ethyl pyruvate has been shown to possess anti-inflammatory and free radical scavenging properties. However, the haemodynamic effects of ethyl pyruvate have not been studied in detail. We investigated the systemic, regional and microcirculatory haemodynamic and metabolic effects of resuscitation with Ringer's ethyl pyruvate solution (REPS) vs. Ringer's acetate (RA) in an acute model of porcine endotoxaemic shock.

METHODS

Fourteen anaesthetized pigs received an infusion of endotoxin that was increased stepwise over 30 min to a rate of 2.5 microg/kg/h. After 60 min of endotoxaemia, the animals were resuscitated with either ethyl pyruvate 40 mg/kg, given as REPS, or the equivalent volume of RA, administered over 10 min. Thereafter, an infusion of either ethyl pyruvate 40 mg/kg/h, given as REPS, or the equivalent volume of RA, was started, and the maintenance fluid was reduced so that the total amount of fluid given was kept constant. The experiment was terminated after 300 min of endotoxaemia.

RESULTS

Endotoxin infusion led to a hypodynamic state that was reversed by fluid resuscitation after 60 min. Progressive deterioration ensued and, after 300 min, all animals were again hypodynamic. No differences in response to treatment were found between the groups with regard to systemic haemodynamics, renal artery or portal vein flow or microcirculatory flow in the liver, kidney, ileal serosa or mucosa. Metabolic acidosis and increased arterial blood lactate developed in both groups, but, in the REPS group, the base excess was significantly lower from 150 min and the anion gap was significantly higher at 150 and 210 min.

CONCLUSION

We could not demonstrate any difference between REPS and RA for resuscitation in this model of acute porcine endotoxaemic shock.

Hepatic and Pulmonary Apoptosis After Hemorrhagic Shock in Swine Can Be Reduced Through Modifications of Conventional Ringer???s Solution

BACKGROUND

Cytotoxic properties of racemic (D-,L-isomers) lactated Ringer's solution detected in vitro and in small animal experiments, have not been confirmed in large animal models. Our hypothesis was that in a clinically relevant large animal model of hemorrhage, resuscitation with racemic lactated Ringer's solution would induce cellular apoptosis, which can be attenuated by elimination of d-lactate.

METHODS

Yorkshire swine (n = 49, weight 40-58 kg) were subjected to uncontrolled (iliac arterial and venous injuries) and controlled hemorrhage, totaling 40% of estimated blood volume. They were randomized (n = 7/group) to control groups, which consisted of (1) no hemorrhage (NH), (2) no resuscitation (NR), or resuscitation groups, which consisted of (3) 0.9% saline (NS), (4) racemic lactated Ringer's (DL-LR), (5) L-isomer lactated Ringer's (L-LR), (6) Ketone Ringer's (KR), (7) 6% hetastarch in 0.9% saline (Hespan). KR was identical to LR except for equimolar substitution of lactate with beta-hydroxybutyrate. Resuscitation was performed in three phases, simulating (1) prehospital, (2) operative, (3) postoperative/recovery periods. Arterial blood gasses, circulating cytokines (TNF-alpha, IL-1, -6, -10), and markers of organ injury were serially measured. Metabolic activity of brain, and liver, was measured with microdialysis. Four hours postinjury, organs were harvested for Western blotting, ELISA, TUNEL assay, and immunohistochemistry.

RESULTS

All resuscitation strategies restored blood pressure, but clearance of lactic acidosis was impeded following DL-LR resuscitation. Metabolic activity decreased during shock and improved with resuscitation, without any significant inter-group differences. Levels of cytokines in circulation were similar, but tissue levels of TNF in liver and lung increased six- and threefolds (p < 0.05) in NR group. In liver, all resuscitation strategies significantly decreased TNF levels compared with the NR group, but in the lung resuscitation with lactated Ringer (DL and L isomers) failed to decrease tissue TNF levels. DL-LR resuscitation also increased apoptosis (p < 0.05) in liver and lung, which was not seen after resuscitation with other solutions.

CONCLUSIONS

In this large animal model of hemorrhagic shock, resuscitation with conventional (racemic) LR solution increased apoptotic cell death in liver and lung. This effect can be prevented by simple elimination of D-lactate from the Ringer's solution.

Ethyl pyruvate ameliorates ileus induced by bowel manipulation in mice

BACKGROUND

Ethyl pyruvate (EP) improves survival, decreases proinflammatory cytokine expression, and ameliorates organ dysfunction in mice who have lethal sepsis or were subjected to hemorrhagic shock. Herein, we tested the hypothesis that treatment with EP can prevent the development of ileus after bowel manipulation, a phenomenon that is mediated by an inflammatory response in the bowel wall.

METHODS

C57Bl/6 mice underwent operative manipulation of the small intestine or were subjected to a sham procedure. Some of the mice subjected to gut manipulation were pre- and post-treated with 4 doses of EP (40 or 80 mg/kg per dose), whereas others received similar volumes of the vehicle for EP. Gastrointestinal transit of a nonabsorbable marker was assessed by gavaging the mice with the tracer 24 hours after operation and assessing its concentration 90 minutes later in bowel contents from the stomach, 10 equally long segments of small intestine, the cecum, and 2 equally long segments of colon. The contractile responses of ileal circular smooth muscle to graded concentrations of bethanechol were assessed by using standard organ bath methodology. Expression of interleukin-6 and inducible nitric oxide synthase transcripts in ileal muscularis propria was assessed by using the semiquantitative reverse transcriptase-polymerase chain reaction.

RESULTS

In sham-operated controls, the mean (+/- SE) geometric center for the transit marker was 10.0 +/- 0.5, whereas for vehicle-treated mice subject to bowel manipulation, the value for this parameter was 3.5 +/- 0.1 (P < .05). When mice subjected to bowel manipulation were treated with several 40 mg/kg doses of EP, the geometric center was 7.3 +/- 1.0 (P < .05 vs sham-operated group). Gut manipulation impaired intestinal smooth muscle contractility in vitro and increased steady-state levels of interleukin-6 and inducible nitric oxide synthase messenger RNA. Treatment with EP ameliorated these effects of gut manipulation.

CONCLUSIONS

EP warrants further evaluation as a therapeutic agent to ameliorate postoperative ileus.

Hepatic apoptosis after hemorrhagic shock in rats can be reduced through modifications of conventional Ringer's solution

BACKGROUND

Resuscitation with racemic lactated Ringer's solution induces cellular apoptosis. This study was conducted to determine if the elimination of D-lactate isomer would attenuate apoptosis in the liver, and to investigate the possible mechanisms.

STUDY DESIGN

Sprague Dawley rats (n=30, 5 per group) were subjected to modified volume-controlled hemorrhage and randomized to the following groups: no hemorrhage (sham); no resuscitation (NR); resuscitation with racemic lactated Ringer's (DL-LR); L-isomer LR (L-LR); ketone (beta-hydroxybuturate) Ringer's (KR); or pyruvate Ringer's (PR). Animals were sacrificed 2 hours later and expressions of proapoptotic proteins (BAD), antiapoptotic (bcl-2) proteins, and poly-ADP ribose polymerase (PARP) cleavage in liver were analyzed by Western blotting. Contribution of the phosphatidylinositol 3-kinase/serine/threonine kinase (PI3k/Akt) pathway was assessed by measuring total and phosphorylated PI3K, Akt, BAD, and endothelial nitric oxide synthase (eNOS) proteins. The terminal deoxynucleotidyl transferase mediated dUTP nick end labeling (TUNEL) assay was used to detect the apoptotic cells. Liver ATP levels were measured using a luciferase reaction assay.

RESULTS

Hemorrhage significantly decreased the hepatic ATP level and resuscitation improved it, but it returned to normal only in the L-isomer lactated Ringer's and ketone Ringer's groups. Expression of proapoptotic proteins was significantly lower in the pyruvate Ringer's and ketone Ringer's groups; L-isomer lactated Ringer's and pyruvate Ringer's resuscitation significantly increased bcl-2 expression. Poly-ADP ribose polymerase fragmentation and total number of apoptotic cells were significantly increased in the racemic lactated Ringer's group. There was no significant induction of Akt activity or changes in phosphorylated BAD, Akt, or eNOS levels.

CONCLUSIONS

Resuscitation with racemic lactated Ringer's induces hepatic apoptosis, which is decreased if the D-isomer of lactate is eliminated. Apoptosis is reduced even more when lactate is substituted with beta-hydroxybutyrate or pyruvate. The beneficial effects are not through improvements in the energy status or activation of the PI3K/Akt pathway.

Bench-to-bedside review: Amelioration of acute renal impairment using ethyl pyruvate

Inflammation and oxidative stress cause renal impairment. Renal failure exacerbates the effect of oxidative stress on many organ systems. Antioxidants can prevent or treat renal failure in various experimental models and clinical situations. Pyruvate is an endogenous antioxidant with beneficial effects in animal models of oxidative stress. Because sodium pyruvate rapidly degrades in solution, a simple derivative of pyruvic acid, namely ethyl pyruvate, has been investigated as a therapeutic agent in preclinical studies. Ethyl pyruvate reduces organ system damage in ischaemia/reperfusion injury and haemorrhagic and endotoxic shock, at least in part through its antioxidant action. In addition, ethyl pyruvate appears to have direct beneficial effects on cytokine expression and proinflammatory gene regulation. The effect is long lasting and, importantly, even when it is administered after the onset of inflammation it can ameliorate organ damage and improve survival. Ethyl pyruvate is a widely used as a food additive and was shown to be safe in phase I clinical trials. We suggest ethyl pyruvate warrants further evaluation in the management of acute renal impairment.