Ethyl pyruvate modulates adhesive and secretory reactions in human lung epithelial cells

Ethyl pyruvate ameliorates acute respiratory distress syndrome in mice

Acute respiratory distress syndrome (ARDS) became a focus of intensive research due to its death toll during the Covid-19 pandemic. An uncontrolled and excessive inflammatory response mediated by proinflammatory molecules such as high mobility group box protein 1 (HMGB1), IL-6, and TNF mounts as a response to infection. In this study, ethyl pyruvate (EP), a known inhibitor of HMGB1, was tested in the model of murine ARDS induced in C57BL/6 mice by intranasal administration of polyinosinic:polycytidylic acid (poly(I:C)). Intraperitoneal administration of EP ameliorated the ARDS-related histopathological changes in the lungs of poly(I:C)-induced ARDS and decreased numbers of immune cells in the lungs, broncho-alveolar lavage fluid and draining lymph nodes (DLN). Specifically, fewer CD8+ T cells and less activated CD4+ T cells were observed in DLN. Consequently, the lungs of EP-treated animals had fewer damage-inflicting CD8+ cells and macrophages. Additionally, the expression and production of proinflammatory cytokines, IL-17, IFN-γ and IL-6 were downregulated in the lungs. The expression of chemokine CCL5 which recruits immune cells into the lungs was also reduced. Finally, EP downregulated the expression of HMGB1 in the lungs. Our results imply that EP should be further evaluated as a potential candidate for ARDS therapy.

Ethyl pyruvate and analogs as potential treatments for acute pancreatitis: A review of in vitro and in vivo studies

Ethyl pyruvate (EP) has been shown to improve outcomes from multiple organ dysfunction syndrome (MODS) in experimental animal models of critical illness. This review aimed to summarise in vitro and in vivo effects of EP analogs on acute pancreatitis (AP) with the objective of proposing medicinal chemistry modifications of EP for future research. In vitro studies showed that both sodium pyruvate and EP significantly reduced pancreatic acinar necrotic cell death pathway activation induced by multiple pancreatic toxins. In vivo studies using different murine AP models showed that EP (usually at a dose of 40 mg/kg every 6 h) consistently reduced pain, markers of pancreatic injury, systemic inflammation and MODS. There was also a significant increase in survival rate, even when EP was administered 12 h after disease induction (compared with untreated groups or those treated with Ringer's lactate solution). Experimental studies suggest that EP and analogs are promising drug candidates for treating AP. EP or analogs can undergo medicinal chemistry modifications to improve its stability and deliverability. EP or analogs could be evaluated as a supplement to intravenous fluid therapy in AP.

Ethyl pyruvate inhibits oxidation of LDL in vitro and attenuates oxLDL toxicity in EA.hy926 cells

Background

Ethyl pyruvate (EP) exerts anti-inflammatory and anti-oxidative properties. The aim of our study was to investigate whether EP is capable of inhibiting the oxidation of LDL, a crucial step in atherogenesis. Additionally, we examined whether EP attenuates the cytotoxic effects of highly oxidized LDL in the human vascular endothelial cell line EA.hy926.

Methods

Native LDL (nLDL) was oxidized using Cu²⁺ ions in the presence of increasing amounts of EP. The degree of LDL oxidation was quantified by measuring lipid hydroperoxide (LPO) and malondialdehyde (MDA) concentrations, relative electrophoretic mobilities (REMs), and oxidation-specific immune epitopes. The cytotoxicity of these oxLDLs on EA.hy926 cells was assessed by measuring cell viability and superoxide levels. Furthermore, the cytotoxicity of highly oxidized LDL on EA.hy926 cells under increasing concentrations of EP in the media was assessed including measurements of high energy phosphates (ATP).

Results

Oxidation of nLDL using Cu²⁺ ions was remarkably inhibited by EP in a concentration-dependent manner, reflected by decreased levels of LPO, MDA, REM, oxidation-specific epitopes, and diminished cytotoxicity of the obtained oxLDLs in EA.hy926 cells. Furthermore, the cytotoxicity of highly oxidized LDL on EA.hy926 cells was remarkably attenuated by EP added to the media in a concentration-dependent manner reflected by a decrease in superoxide and an increase in viability and ATP levels.

Conclusions

EP has the potential for an anti-atherosclerotic drug by attenuating both, the oxidation of LDL and the cytotoxic effect of (already formed) oxLDL in EA.hy926 cells. Chronic administration of EP might be beneficial to impede the development of atherosclerotic lesions.

Effects of ethyl pyruvate on leukocyte-endothelial interactions in the mesenteric microcirculation during early sepsis treatment

OBJECTIVES

Experimental studies on sepsis have demonstrated that ethyl pyruvate is endowed with antioxidant and anti-inflammatory properties. This study aimed to investigate the effects of ethyl pyruvate on leukocyte-endothelial interactions in the mesenteric microcirculation in a live Escherichia coli-induced sepsis model in rats.

METHODS

Male Wistar rats were administered an intravenous suspension of E. coli bacteria or were subjected to a sham procedure. Three hours after bacterial infusion, the rats were randomized into the following groups: a control group without treatment, a group treated with lactated Ringer's solution (4 mL/kg, i.v.), and a group treated with lactated Ringer's solution (4 mL/kg, i.v.) plus ethyl pyruvate (50 mg/kg). At 24 h after bacterial infusion, leukocyte-endothelial interactions were investigated using intravital microscopy, and the expression of P-selectin and intercellular adhesion molecule-1 was evaluated via immunohistochemistry. White blood cell and platelet counts were also determined at baseline and 3 h and 24 h after E. coli inoculation.

RESULTS

The non-treated and lactated Ringer's solution-treated groups exhibited increases in the numbers of rolling leukocytes (∼2.5-fold increase), adherent cells (∼3.0-fold), and migrated cells (∼3.5-fold) compared with the sham group. In contrast, treatment with Ringer's ethyl pyruvate solution reduced the numbers of rolling, adherent and migrated leukocytes to the levels observed in the sham group. Additionally, the expression of P-selectin and intercellular adhesion molecule-1 was significantly increased on mesenteric microvessels in the non-treated group compared with the sham group (p<0.001). The expression of both adhesion molecules was reduced in the other groups, with ethyl pyruvate being more effective than lactated Ringer's solution. Infusion of bacteria caused significant leukopenia (3 h), followed by leukocytosis with granulocytosis (24 h). There was also an intense and progressive reduction in the number of platelets. However, no differences were observed after treatment with the different solutions.

CONCLUSIONS

The presented data suggest that ethyl pyruvate efficiently reduces the inflammatory response in the mesenteric microcirculation in an experimental model of sepsis induced by live E. coli and is associated, at least in part, with down-regulation of P-selectin and intercellular adhesion molecule-1.

Decreased inflammatory responses of human lung epithelial cells after ethanol exposure are mimicked by ethyl pyruvate

Background and Purpose. Leukocyte migration into alveolar space plays a critical role in pulmonary inflammation resulting in lung injury. Acute ethanol (EtOH) exposure exerts anti-inflammatory effects. The clinical use of EtOH is critical due to its side effects. Here, we compared effects of EtOH and ethyl pyruvate (EtP) on neutrophil adhesion and activation of cultured alveolar epithelial cells (A549). Experimental Approach. Time course and dose-dependent release of interleukin- (IL-) 6 and IL-8 from A549 were measured after pretreatment of A549 with EtP (2.5–10 mM), sodium pyruvate (NaP, 10 mM), or EtOH (85–170 mM), and subsequent lipopolysaccharide or IL-1beta stimulation. Neutrophil adhesion to pretreated and stimulated A549 monolayers and CD54 surface expression were determined. Key Results. Treating A549 with EtOH or EtP reduced substantially the cytokine-induced release of IL-8 and IL-6. EtOH and EtP (but not NaP) reduced the adhesion of neutrophils to monolayers in a dose- and time-dependent fashion. CD54 expression on A549 decreased after EtOH or EtP treatment before IL-1beta stimulation. Conclusions and Implications. EtP reduces secretory and adhesive potential of lung epithelial cells under inflammatory conditions. These findings suggest EtP as a potential treatment alternative that mimics the anti-inflammatory effects of EtOH in early inflammatory response in lungs.

High-mobility-group box protein 1A box reduces development of sodium laurate-induced thromboangiitis obliterans in rats

OBJECTIVE

High-mobility-group box protein 1 (HMGB1), as a late mediator of inflammation, plays a key role in inflammatory responses by inducing and extending the production of proinflammatory cytokines. The effect of HGMB1 in the inflammatory disease thromboangiitis obliterans (TAO) is unknown. We aimed to investigate the role of HMGB1 in sodium laurate-induced TAO in rats.

METHODS

Male Wistar rats were randomly divided into five groups (n=8 each) for treatment: normal, sham-operated, TAO model, and low-dose (15 mg/kg) or high-dose (30 mg/kg) recombinant A box (rA box) infection (administered intraperitoneally once daily for 15 days). The TAO model was induced by sodium laurate and graded by gross appearance on day 15 after femoral artery injection. Histologic changes were measured by histopathology in rat femoral arteries. Plasma levels of HMGB1, thromboxane B2, 6-keto-prostaglandin F1-α, and blood cell counts and blood coagulation levels were measured. Expression of HMGB1, receptor for advanced glycation end-products (RAGE), interleukin-6, intercellular adhesion molecule-1, and vascular cell adhesion molecule-1 was assessed by immunohistochemistry and immunofluorescence, Western blot analysis, and quantitative reverse-transcription polymerase chain reaction.

RESULTS

The typical signs and symptoms of TAO were observed on day 15 after sodium laurate injection. The expression of HMGB1, RAGE, interleukin-6, intercellular adhesion molecule-1, and vascular cell adhesion molecule-1 was markedly increased in rat femoral arteries. Plasma levels of HMGB1 and thromboxane B2 were elevated, but the level of 6-keto-prostaglandin F1-α was decreased. Blood was in a hypercoagulable state, and prothrombin, thrombin, and activated partial thromboplastin times were all significantly shortened, whereas fibrinogen level was increased in TAO rats compared with sham-operated rats. These effects were terminated by the HMGB1 antagonist rA box.

CONCLUSIONS

HMGB1 is involved in the inflammatory state in a model of TAO induced by sodium laurate in rats, probably via its receptor RAGE. As the antagonist of HMGB1, rA box can attenuate the development of TAO, which may be a potential therapeutic target for the treatment of TAO.

Staphylococcus aureus enterotoxin B augments granulocyte migration and survival via airway epithelial cell activation

BACKGROUND

Staphylococcus aureus enterotoxin B (SEB) has recently been postulated to be involved in the pathology of granulocyte-dominated disease. Studying the immunologic interaction between SEB and airway epithelial cells in immortalized cell lines or long-term epithelial cell cultures has obvious disadvantages.

METHODS

We used a novel technique of freshly isolated and purified human nasal epithelial cells (HNEC) from healthy, nonallergic individuals, which were incubated for 24 h without/with SEB at different concentrations. Chemokine production was evaluated in the supernatant using Cytometric Bead Array. The chemotactic activity of the supernatant was studied in vitro using a Boyden chamber. Survival was evaluated with flow cytometry, using propidium iodide to identify dead cells.

RESULTS

Staphylococcus aureus enterotoxin B showed a dose-dependent induction of interferon-inducible protein-10, monokine induced by interferon-gamma, regulated upon activation normal T cell expressed and secreted, monocyte chemoattractant protein 1 (MCP-1) and granulocyte colony stimulating factor production by epithelial cells in vitro. The supernatant of epithelial cells had chemotactic activity for granulocytes in vitro, which was enhanced in the supernatant of SEB-stimulated epithelial cells. Reduced number of propidium iodide positive granulocytes was found in the conditions where supernatant of SEB-stimulated epithelial cells was applied.

CONCLUSION

Staphylococcus aureus enterotoxin B exerts a direct pro-inflammatory effect on HNEC, with induction of chemokine and growth factor release, resulting in the migration and prolonged survival of granulocytes in vitro.

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.

Ethyl pyruvate protects against hypoxic-ischemic brain injury via anti-cell death and anti-inflammatory mechanisms

Ethyl pyruvate (EP) is protective in experimental models of many illnesses. This study investigates whether EP can protect against neonatal hypoxic-ischemic (H-I) brain injury. Pre-treatment with EP significantly reduced brain damage at 7 days post-H-I, with 50 mg/kg EP achieving over 50% recovery in tissue loss compared to vehicle-treated animals. Delayed treatment with EP until 30 min after H-I was still neuroprotective. EP-afforded brain protection, together with neurological function improvement, was observed up to 2 months after H-I. We further demonstrated an inhibitory effect of EP on cell death, both in an in vivo model of H-I and in in vitro neuronal cultures subjected to OGD, by reducing calpain activation and calcium dysregulation. Moreover, EP exerted an anti-inflammatory effect in microglia by inhibiting NF-kappaB activation and subsequent release of inflammatory mediators. Taken together, our results suggest that EP confers potent neuroprotection against neonatal H-I brain injury via its anti-cell death and anti-inflammatory actions. EP is a potential novel therapeutic agent for neonatal H-I brain injury.