Protective effect of ethyl pyruvate on gut barrier function through regulations of ROS-related NETs formation during sepsis

Phellodendrine inhibits oxidative stress and promotes autophagy by regulating the AMPK/mTOR pathway in burn sepsis-induced intestinal injury

Intestinal injury is an important complication of burn sepsis with limited therapeutic choices. Phellodendrine is a promising compound for gastrointestinal inflammatory diseases and is extracted from the traditional Chinese medicine phellodendron bark. The study aimed to explore the role of phellodendrine against oxidative stress and autophagy in burn sepsis-induced intestinal injury. A mouse model of burn sepsis model was established by intraperitoneally injecting 10 mg/kg lipopolysaccharide (LPS) to mice burned by boiled water. Phellodendrine (30 mg/kg) was injected into mice in the drug group after scalding and before LPS injection. Hematoxylin and eosin staining was performed to observe histopathological changes in murine small intestines. TdT-mediated dUTP Nick-End Labeling (TUNEL) assay was performed to evaluate intestinal cell apoptosis. Immunofluorescence staining was performed to measure the expression and distribution of autophagy markers, light chain 3II (LC3II) and p62 in intestinal tissues. Oxidative stress indicators were detected using corresponding commercial kits. Protein levels of apoptotic markers, autophagy markers, and factors involved in adenosine monophosphate-activated protein kinase (AMPK)/mechanistic target of rapamycin (mTOR) pathway in intestines were quantified by western blotting. Phellodendrine attenuated bun sepsis-induced intestinal pathological changes. Meanwhile, aggravated cell apoptosis, reduction of antioxidant enzymes, and downregulation of autophagy markers in intestinal tissues of burn sepsis group were all improved by phellodendrine. In addition, phellodendrine activated the phosphorylation (p) of AMPK and inhibited p-mTOR signaling in intestines of burn septic mice. In conclusion, phellodendrine suppresses oxidative stress and activates autophagy in burn sepsis-induced intestinal injury by activating AMPK and inhibiting mTOR signaling.

Electron transfer-based antioxidant nanozymes: Emerging therapeutics for inflammatory diseases

Inflammatory diseases are usually featured with relatively high level of reactive oxygen species (ROS). The excess ROS facilitate the polarization of microphages into proinflammatory M1 phenotype, and cause DNA damage, protein carbonylation, and lipid peroxidation, resulting in further deterioration of inflammatory diseases. Therefore, alleviating oxidative stress by ROS scavenging has been an effective strategy for reversing inflammation. Inspired by the natural antioxidant enzymes, electron transfer-based artificial antioxidant nanozymes have been emerging therapeutics for the treatment of inflammatory diseases. The present review starts with the basic knowledge of ROS and diseases, followed by summarizing the possible active centers for the preparation of antioxidant nanozymes. The strategies for the design of antioxidant nanozymes on the purpose of higher catalytic activity are provided, and the applications of the developed antioxidant nanozymes on the therapy of inflammatory diseases are discussed. A perspective is included for the design and applications of artificial antioxidant nanozymes in biomedicine as well.

Selenium mitigates the inhibitory effect of TBBPA on NETs release by regulating ROS/MAPK pathways-induced carp neutrophil apoptosis and necroptosis

Tetrabromobisphenol A (TBBPA) is one of the most common and persistent organic pollutants found in the environment. When TBBPA is ingested by organisms through various pathways and stored in the body, it shows obvious harmful effects. Selenium (Se) works as an antioxidant in the body, allowing it to withstand the poisonous effects of dangerous substances. The effects and mechanisms of Se and TBBPA on carp neutrophil immune function, apoptosis, and necroptosis, however, are unknown. As a result, we created TBBPA exposure and Se antagonism models using carp neutrophils as study objects, and we investigated the expression of genes implicated in extracellular traps (NETs), cytokines, apoptosis, and necroptosis. The findings demonstrated that extracellular traps neutrophils in the TBBPA group displayed the inhibition of NETs, apoptosis, and necrosis, as well as an increase in Reactive oxygen species (ROS) levels and activation of the MAPK pathway. The expression of genes related to the mitochondrial apoptosis pathway (Bax, Cyt-c, Bcl-2 and Caspase-3) and necroptosis pathway (MLKL, RIPK1, RIPK3, Caspase-8 and FADD) were activated. The expression of inflammatory factors IL-1 and TNF-α were increased, and the expression of IL-2 and IFN-γ were decreased. But an appropriate concentration of Se can mitigate the effects of TBBPA. Our results suggest that Se can mitigate the inhibitory effect of TBBPA on NETs release by regulating apoptosis and necroptosis of carp neutrophil via ROS/MAPK pathways. These results provide a basis information for exploring the toxicity of TBBPA, and enrich the anti-toxicity mechanism of trace element Se in the body.

Inhibition of PFKFB Preserves Intestinal Barrier Function in Sepsis by Inhibiting NLRP3/GSDMD

Intestinal barrier dysfunction is associated with the occurrence and development of sepsis. Further, aerobic glycolysis plays an essential role in inflammation and cell death. This study is aimed at investigating the protective effect and mechanism of PFKFB3 inhibition on intestinal barrier dysfunction in sepsis mice. Sepsis mouse models were established by cecal ligation and puncture (CLP) in wild-type mice and Gsdmd^-/- mice. The results showed that the expression of 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 3 (PFKFB3) in the small intestines was significantly upregulated in sepsis. 3-(3-Pyridinyl)-1-(4-pyridinyl)-2-propen-1-one (3PO), the specific inhibitor of PFKFB3, and Gsdmd gene knockout significantly inhibited the inflammatory response and cell death caused by sepsis, thus alleviating intestinal damage and barrier dysfunction. 3PO was also shown to significantly inhibit oxidative stress and NLRP3/caspase-1/GSDMD-dependent cell pyroptosis in the small intestines. The in vitro studies revealed that 3PO reduced NLRP3/caspase-1/GSDMD-dependent cell pyroptosis by inhibiting ROS. Taken together, our results suggest that PFKFB3 is involved in inflammation, oxidative stress, and pyroptosis during sepsis and enhances intestinal damage, which may provide important clues about the potential targets to be exploited in this highly lethal disease.

Ethyl pyruvate, a versatile protector in inflammation and autoimmunity

Ethyl pyruvate (EP) has potent influence on redox processes, cellular metabolism, and inflammation. It has been intensively studied in numerous animal models of systemic and organ-specific disorders whose pathogenesis involves a strong immune component. Here, basic chemical and biological properties of EP are discussed, with an emphasis on its redox and metabolic activity. Further, its influence on myeloid and T cells is considered, as well as on intracellular signaling beyond its effect on immune cells. Also, the effects of EP on animal models of chronic inflammatory and autoimmune disorders are presented. Finally, a possibility to apply EP as a treatment for such diseases in humans is discussed. Scientific papers cited in this review were identified using the PubMed search engine that relies on the MEDLINE database. The reference list covers the most important findings in the field in the past twenty years.

Neutrophil Extracellular Traps (NETs) and Covid-19: A new frontiers for therapeutic modality

Coronavirus disease 2019 (Covid-19) is a worldwide infectious disease caused by severe acute respiratory coronavirus 2 (SARS-CoV-2). In severe SARS-CoV-2 infection, there is severe inflammatory reactions due to neutrophil recruitments and infiltration in the different organs with the formation of neutrophil extracellular traps (NETs), which involved various complications of SARS-CoV-2 infection. Therefore, the objective of the present review was to explore the potential role of NETs in the pathogenesis of SARS-CoV-2 infection and to identify the targeting drugs against NETs in Covid-19 patients. Different enzyme types are involved in the formation of NETs, such as neutrophil elastase (NE), which degrades nuclear protein and release histones, peptidyl arginine deiminase type 4 (PADA4), which releases chromosomal DNA and gasdermin D, which creates pores in the NTs cell membrane that facilitating expulsion of NT contents. Despite of the beneficial effects of NETs in controlling of invading pathogens, sustained formations of NETs during respiratory viral infections are associated with collateral tissue injury. Excessive development of NETs in SARS-CoV-2 infection is linked with the development of acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) due to creation of the NETs-IL-1β loop. Also, aberrant NTs activation alone or through NETs formation may augment SARS-CoV-2-induced cytokine storm (CS) and macrophage activation syndrome (MAS) in patients with severe Covid-19. Furthermore, NETs formation in SARS-CoV-2 infection is associated with immuno-thrombosis and the development of ALI/ARDS. Therefore, anti-NETs therapy of natural or synthetic sources may mitigate SARS-CoV-2 infection-induced exaggerated immune response, hyperinflammation, immuno-thrombosis, and other complications.

De-escalation antibiotic therapy alleviates organ injury through modulation of NETs formation during sepsis

Empiric broad-spectrum antimicrobials therapy is suggested to be started immediately for sepsis patients. Empiric antimicrobial therapy should be narrowed once pathogen identification and sensitivities are established. However, the detailed mechanisms of de-escalation strategy are still unclear. Here we hypothesized neutrophil extracellular traps (NETs) played an essential role and de-escalation strategy might alleviate organs injury through regulation of NETs formation in sepsis. We evaluated the effect of imipenem and ceftriaxone on NETs formation in vitro and examined the role of reactive oxygen species (ROS). Next, we designed de-escalation and escalation strategy in cecum ligation and puncture (CLP) models. Organ injury, inflammatory cytokines, NETs levels were compared and evaluated. In CLP models, de-escalation therapy resulted in an increased serum MPO-DNA level during the early stage and decreased MPO-DNA level during late stage, which exerted the reverse effects in escalation therapy. Inflammatory response and organ injury exacerbated when eliminated NETs with DNAse I during the early stage of sepsis (p < 0.01). Histopathological analysis showed decreased injury in lung, liver, and intestine in de-escalation therapy compared with escalation therapy (p < 0.01). De-escalation therapy results in the highest 6-day survival rate compared with the control group (p < 0.01), however, no significant difference was found between de-escalation and escalation group (p = 0.051). The in vitro study showed that the imipenem could promote, while the ceftriaxone could inhibit the formation of NETs in PMA-activated PMNs through a ROS-dependent manner. We firstly demonstrate that de-escalation, not escalation, therapy reduces organ injury, decreases inflammatory response by promoting NETs formation in the early stage, and inhibiting NETs formation in the late stage of sepsis.

Neutrophil extracellular traps and organ dysfunction in sepsis

Sepsis is a clinical syndrome resulting from infection followed by inflammation and is one of the significant causes of mortality worldwide. The underlying reason is the host's uncontrolled inflammatory response due to an infection led to multiple organ dysfunction/failure. Neutrophils, an innate immune cell, are forerunners to reach the site of infection/inflammation for clearing the infection and resolute the inflammation during sepsis. A relatively new neutrophil effector function, neutrophil extracellular traps (NETs), have been demonstrated to kill the pathogens by releasing DNA decorated with histone and granular proteins. A growing number of pieces of shreds of evidence suggest that unregulated incidence of NETs have a significant influence on the pathogenesis of sepsis-induced multiple organ damage, including arterial hypotension, hypoxemia, coagulopathy, renal, neurological, and hepatic dysfunction. Thus, excessive production and improper resolution of NETs are of significant therapeutic value in combating sepsis-induced multiple organ failure. The purpose of this review is intended to highlight the role of NETs in sepsis-induced organ failure. Furthermore, the current status of therapeutic strategies to intersect the harmful effects of NETs to restore organ functions is discussed.