The role of GPD2 on ferroptosis in sepsis-induced acute lung injury.

Background: Sepsis-induced acute lung injury (ALI) is a clinical syndrome characterized by excessive uncontrolled inflammation. Photobiomodulation such as light-emitting diode (LED) irradiation has been used to attenuate inflammatory disease. Objective: The protective effect of 630 nm LED irradiation on sepsis-induced ALI remains unknown. The purpose of this study was to investigate the role of 630 nm LED irradiation in sepsis-induced ALI and its underlying mechanism. Methods and results: C57BL/6 mice were performed cecal ligation and puncture (CLP) for 12 h to generate experimental sepsis models. Histopathology analysis showed that alveolar injury, inflammatory cells infiltration, and hemorrhage were suppressed in CLP mice after 630 nm LED irradiation. The ratio of wet/dry weigh of lung tissue was significantly inhibited by irradiation. The number of leukocytes was reduced in bronchoalveolar lavage fluid. Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) results and enzyme-linked immunosorbent assay showed that 630 nm LED irradiation significantly inhibited the mRNA and protein levels of M1 macrophage-related genes in the lung of CLP-induced septic mice. Meanwhile, LED irradiation significantly inhibited signal transducer and activator of transcription 1 (STAT1) phosphorylation in the lung of septic mice. In vitro experiments showed that 630 nm LED irradiation significantly inhibited M1 genes mRNA and protein expression in THP-1-derived M1 macrophages without affecting the cell viability. LED irradiation also significantly inhibited the level of STAT1 phosphorylation in THP-1-derived M1 macrophages. Conclusions: We concluded that 630 nm LED is promising as a treatment against ALI through inhibiting M1 macrophage polarization, which is associated with the downregulation of STAT1 phosphorylation.

Objective To investigate the effects of penehyclidine hydrochloride (PHCD) pretreatment on β-arrestin-1 expression during sepsis-induced acute lung injury in mice.Methods Thirty female Kunming mice,weighing 18-20 g,were randomly divided into 3 groups (n =10 each):sham operation group (S group),sepsis group (CLP group) and PHCD group.Sepsis was induced by cecal ligation and puncture (CLP).In PHCD group,PHCD 0.45 mg/kg was injected intraperitoneally 1 h before CLP.The equal volume of normal saline was given instead in groups S and CLP.The mice were sacrificed at 12 h after CLP,bronchoalveolar lavage fluid (BALF) was collected for measurement of the total protein concentration,and the lungs were removed for determination of wet/dry lung weight ratio and expression of myosin light chain kinase (MLCK),vascular endothelial cadherin (VE-cad-herin) and β-arrestin-1 in lung tissues.The pathological changes of the lung were scored.Results Compared with group S,the lung injury score,wet/dry lung weight ratio and total protein concentration in BALF were significantly increased,MLCK expression was up-regulated and VE-cadherin expression was down-regulated in groups CLP and PHCD,β-arrestin-1 expression was down-regulated in group CLP and β-arrestin-1 expression was up-regulated in group PHCD (P ＜ 0.05 or 0.01).The lung injury score,wet/dry lung weight ratio,total protein concentration in BALF,and MLCK expression were significantly lower,while the expression of VE-cadherin and β-arrestin-1 was higher in PHCD group than in CLP group (P ＜ 0.05 or 0.01).Conclusion PHCD pretreatment can ameliorate acute lung injury through up-regulating β-arrestin-1 expression and reducing microvascular permeability in septic mice. Key words: Cholinergic antagonists ; Arrestins ; ; Respiratory distress syndrome, adult ; Sepsis

ABSTRACTAim of the study: Kaempferol is a flavonoid and important part of the diet. Kaempferol has shown antioxidant, antiinflammatory and antidiabetic activities in various studies. However, protective potential of kaempferol in acute lung injury induced by sepsis and its mechanism remains unclear. The present study was undertaken to evaluate the effect of kaempferol in sepsis-induced acute lung injury in mice and its possible mechanism of action. Materials and methods: Acute lung injury was induced by CLP surgery in mice. Kaempferol (100 mg/kg bw) was administered orally one hour before caecal ligation and puncture surgery in mice. Mice were divided into four groups sham, KEM+sham, sepsis (CLP), and KEM+sepsis. Assessment of lung injury was done by estimation of protein content in lung tissue, lung edema, proinflammatory cytokines in plasma and lung tissue, oxidative stress, antioxidant enzymes, nitrite production, and histopathology. Results: Kaempferol pretreated mice showed significant (P < 0.001) decrease in water content in lungs. Kaempferol pretreatment showed reduction in cytokines IL-6, IL-1β, and TNF-α in plasma as well as in lung tissue in comparison with septic mice without pretreatment. Pretreatment with kaempferol did not show any reduction in MDA level in comparison with septic mice. Antioxidant enzymes SOD and catalase and nonenzymatic antioxidant GSH activities were also increased with kaempferol pretreatment in septic mice. Further, kaempferol pretreatment reduced the lung tissue nitrite level (P < 0.01) and iNOS (P < 0.05) level in septic mice. A significant (P < 0.01) downregulation of mRNA expression of ICAM-1 and iNOS was observed with this pretreatment. Kaempferol pretreatment did not decrease bacterial load in septic mice. Mice pretreated with kaempferol followed by sepsis showed lesser infiltration of cells and more arranged alveolar structure in histopathological analysis. Conclusions: The study suggests that kaempferol showed attenuation in sepsis-induced acute lung injury in mice through suppression of oxidative stress, iNOS, and ICAM-1 pathways.

BackgroundMesenchymal stem cells (MSCs) therapy for sepsis has been extensively studied in the past decade; however, the treatment regimen and mechanism of action of MSCs remain elusive. Here, we attempted to understand the efficacy and mechanism of action of MSCs on rescuing mice with sepsis.MethodsA mouse model of sepsis was produced by cecal ligation and puncture (CLP). Allogeneic adipose-derived MSCs (ADSCs) were administered by intravenous infusion at 6 h after CLP, and dose-related effects of ADSCs on these mice were determined by survival rate, histopathological changes, biochemical and coagulation parameters, bacterial load, and plasma levels of endotoxin and inflammatory cytokines. The tissue distribution of intravenously infused ADSCs in septic mice was investigated by pre-labeling ADSCs with the lipophilic membrane dye PKH26. RNA sequencing analysis was performed to assess the transcriptional changes in peripheral blood mononuclear cells (PBMCs) and the liver.ResultsA significant therapeutic effect of ADSCs at a dose of 2 × 107 cells/kg in septic mice was evidenced by a remarkable reduction in mortality (35.89% vs. 8.89% survival rate), blood bacterial burden, systemic inflammation, and multiple organ damage. In contrast, ADSCs at a lower dose (1 × 107 cells/kg) failed to achieve any beneficial outcomes, while ADSCs at a higher dose (4 × 107 cells/kg) caused more early death within 24 h after CLP, retaining a steady survival rate of 21.42% thereafter. PKH26-labeled ADSCs were predominantly localized in the lungs of septic mice after intravenous infusion, with only a smaller proportion of PKH26-positive signals appearing in the liver and spleen. RNA sequencing analysis identified that insufficient phagocytic activity of PBMCs in addition to a hyperactivation of the hepatic immune response was responsible for the ineffectiveness of low-dose ADSCs therapy, and acute death caused by high-dose ADSCs infusion was associated with impaired coagulation signaling in PBMCs and exacerbated hepatic hypoxic injury.ConclusionsOur findings demonstrate a dose-specific effect of ADSCs on the treatment of sepsis due to dose-related interactions between exogenous stem cells and the host’s microenvironment. Therefore, a precise dosing regimen is a prerequisite for ADSCs therapy for sepsis.

Dysregulation of matrix metalloproteinase- (MMP-) 9 is implicated in the pathogenesis of acute lung injury (ALI). However, it remains controversial whether MMP-9 improves or deteriorates acute lung injury of different etiologies. The receptor for advanced glycation end products (RAGE) plays a critical role in the pathogenesis of acute lung injury. MMPs are known to mediate RAGE shedding and release of soluble RAGE (sRAGE), which can act as a decoy receptor by competitively inhibiting the binding of RAGE ligands to RAGE. Therefore, this study is aimed at clarifying whether and how pulmonary knockdown of MMP-9 affected sepsis-induced acute lung injury as well as the release of sRAGE in a murine cecal ligation and puncture (CLP) model. The analysis of GEO mouse sepsis datasets GSE15379, GSE52474, and GSE60088 revealed that the mRNA expression of MMP-9 was significantly upregulated in septic mouse lung tissues. Elevation of pulmonary MMP-9 mRNA and protein expressions was confirmed in CLP-induced mouse sepsis model. Intratracheal injection of MMP-9 siRNA resulted in an approximately 60% decrease in pulmonary MMP-9 expression. It was found that pulmonary knockdown of MMP-9 significantly increased mortality of sepsis and exacerbated sepsis-associated acute lung injury. Pulmonary MMP-9 knockdown also decreased sRAGE release and enhanced sepsis-induced activation of the RAGE/nuclear factor-κB (NF-κB) signaling pathway, meanwhile aggravating sepsis-induced oxidative stress and inflammation in lung tissues. In addition, administration of recombinant sRAGE protein suppressed the activation of the RAGE/NF-κB signaling pathway and ameliorated pulmonary oxidative stress, inflammation, and lung injury in CLP-induced septic mice. In conclusion, our data indicate that MMP-9-mediated RAGE shedding limits the severity of sepsis-associated pulmonary edema, inflammation, oxidative stress, and lung injury by suppressing the RAGE/NF-κB signaling pathway via the decoy receptor activities of sRAGE. MMP-9-mediated sRAGE production may serve as a self-limiting mechanism to control and resolve excessive inflammation and oxidative stress in the lung during sepsis.

Macrophage Sprouty4 deficiency diminishes sepsis-induced acute lung injury in mice

RETRACTED: Macrophage SAMSN1 protects against sepsis-induced acute lung injury in mice

This study aimed to investigate the effects of lidocaine on sepsis-induced acute lung injury and its underlying mechanisms. Thirty C57BL/6 mice were divided into three groups: SHAM, CLP, and LD. The sepsis-induced acute lung injury model was established using cecal ligation and puncture (CLP) surgery, while SHAM mice underwent a sham operation without ligation or puncture. Mice in the LD group were administered lidocaine (10 mg/kg) intravenously through the tail vein. The SHAM and CLP groups were treated with an equal volume of 0.9% sterile saline solution. All mice were sacrificed 24 hours after surgery, and lung tissue and blood samples were collected for subsequent analysis. The wet/dry weight ratio (W/D ratio) was measured to evaluate lung edema. Lung injury and apoptosis were assessed using HE staining and TUNEL assay. The concentrations of inflammatory cytokines IL-6, TNF-α, and HMGB1 were measured by ELISA. The expression of JAK2, STAT3, p-STAT3, Bcl-2, HMGB1, and Bax was analyzed by western blot. The W/D ratio in the CLP group was significantly higher than the SHAM group, indicating increased lung edema. Pathological examination revealed obvious lung injury, and apoptosis was evident in the CLP group. The expression of HMGB1, IL-6, and TNF-α in lung tissue increased by 24 hours after CLP surgery. Additionally, the levels of JAK2, STAT3, p-STAT3, HMGB1, and Bax were significantly increased, while Bcl-2 expression was reduced. However, lidocaine administration reversed these changes. Intravenous lidocaine effectively alleviated acute lung injury in septic mice. The anti-inflammatory effects of lidocaine may be attributed to its suppression of the JAK2/STAT3 signaling pathway and its anti-apoptotic effects.

Excessive neutrophil extracellular trap (NET) formation is an important contributor to sepsis-induced acute lung injury (ALI). Recent reports indicate that platelets can induce neutrophil extracellular trap formation. However, the specific mechanism remains unclear. Tph1 gene, which encodes the rate-limiting enzyme for peripheral 5-hydroxytryptophan (5-HT) synthesis, was knocked out in mice to simulate peripheral 5-HT deficiency. Cecal ligation and puncture (CLP) surgery was performed to induce sepsis. We found that peripheral 5-HT deficiency reduced NET formation in lung tissues, alleviated sepsis-induced lung inflammatory injury, and reduced the mortality rate of CLP mice. In addition, peripheral 5-HT deficiency was shown to reduce the accumulation of platelets and NETs in the lung of septic mice. We found that platelets from wild-type (WT), but not Tph1 knockout (Tph1 −/− ), mice promote lipopolysaccharide (LPS)-induced NET formation. Exogenous 5-HT intervention increased LPS-induced NET formation when Tph1 −/− platelets were co-cultured with WT neutrophils. Therefore, our study uncovers a mechanism by which peripheral 5-HT aggravated sepsis-induced ALI by promoting NET formation in the lung of septic mice.

Indirect acute lung injury is associated with high morbidity and mortality. We investigated the link between Rho kinase (ROCK) activation and apoptotic cell death in sepsis induced acute lung injury. This hypothesis was tested by administering a specific, selective inhibitor of ROCK (Y-27632) to rats subjected to cecal ligation and puncture (CLP). Rats were randomly divided into 4 groups as; sham-operated, sham + Y-27632, CLP and CLP + Y-27632. Twenty-four hours later, each experiment was terminated and lungs analyzed. Histopathology was assessed by hematoxylin-eosin staining and the presence of apoptosis was evaluated through the TUNEL assay. Pulmonary activity of caspase 3 and ROCK 1 & 2 were measured by western blot. Interstitial edema, severely damaged pulmonary architecture with massive infiltration of the inflammatory cells and an increase in lung tissue TBARS levels as well as 3-NT to total tyrosine ratios were observed in untreated CLP animals. Pretreatment of animals with Y-27632, reduced lung injury in the CLP induced septic rats in each of these parameters of lung injury (p<0.05). Western immunoblot revealed active caspase cleavage and increased expression of active fragment of ROCK 1 & 2 in the CLP group. TUNEL assay showed an increase in percentage of apoptotic cells when comparing the CLP group with the CLP + Y-27632 group. These results suggest an important role of Rho kinase in sepsis induced lung injury by a mechanism that might be related to oxidative and/or nitrosative stress mediated caspase cleavage leading to apoptosis.

Clinical pearls in infectious diseases

SIRT4 knockout exacerbates lung injury in septic mice by activating TLR4/MYD88/NFκB pathway.

During sepsis, systemic inflammation is observed and is associated with multiple organ failure. Activation of NF-κB is crucial for inducing inflammation, which is controlled by degradation of inhibitor molecules (IκB). The ubiquitination proteasome pathway is responsible for the regulation of protein turnover. In this study, we hypothesized that administration of 4[4-(5-nitro-furan-2-ylmethylene)-3, -dioxo-pyrazolidin-1-yl]-benzoic acid ethyl ester (PYR-41), an inhibitor of ubiquitination, could reduce inflammation and organ injury in septic mice. PYR-41 prevented the reduction of IκB protein levels and inhibited release of tumor necrosis factor (TNF)-α in mouse macrophage RAW264.7 cells at 4 h after lipopolysaccharide stimulation dose-dependently. Male C57BL/6 mice were subjected to cecal ligation and puncture (CLP) to induce sepsis. PYR-41 (5 mg/kg) or dimethyl sulfoxide in saline (vehicle) was injected intravenously immediately after CLP. At 20 h after CLP, PYR-41 treatment significantly decreased serum levels of proinflammatory cytokines (TNF-α, interleukin [IL]-1β, and IL-6) and organ injury markers (aspartate aminotransferase, alanine aminotransferase, and lactate dehydrogenase). PYR-41 significantly improved microscopic structure, and reduced myeloperoxidase activity, number of apoptotic cells and caspase-3 degradation in the lungs of septic mice. The reduced protein levels of IκB in the lungs after CLP were restored by PYR-41 treatment. PYR-41 inhibited the expression of cytokines (IL-1β and IL-6), chemokines (keratinocyte-derived chemokine and macrophage inflammatory protein 2), and inflammatory mediators (cyclooxygenase-2 and inducible nitric oxide synthase) in the lungs of septic mice. Importantly, PYR-41 significantly increased 10-day survival in septic mice from 42% to 83%. Therefore, targeting ubiquitination by PYR-41 to inhibit NF-κB activation may represent a potential strategy of sepsis therapeutics.

Introduction: Sepsis can cause acute lung injury (ALI), one of the leading causes of death in critically ill patients. The underlying mechanisms of sepsis-induced acute lung injury include excessive inflammation, oxidative stress, cell apoptosis, pulmonary edema, and lung tissue dysfunction. Recent studies have shown that miRNA-21 (miR-21) plays a vital role in sepsis-induced acute kidney injury. Relatively few studies have focused on the protective effects of ALI. This study aimed to determine the potential role of miR-21 in sepsis-induced ALI. Methods: We performed quantitative real-time polymerase chain reaction in a septic mouse model induced by cecal ligation and puncture (CLP) and found that miR-21 expression was upregulated. We then transfected the miR-21 precursor to upregulate miR-21 expression and miR-21 inhibitor to downregulate miR-21 expression. The sham group was exposed only to the cecum. ALI was induced by CLP, and the pre-miR-21+ALI and anti-miR-21+ALI groups were treated with miR-21 precursor or miR-21 inhibitor in the caudal vein before CLP. Pre-miR-21+ALI+PTEN inhibition (Pre-miR-21+ALI+PI) and anti-miR-21+ALI+PTEN inhibition (Anti-miR-21+ALI+PI) groups were treated with PTEN inhibition into the caudal vein after miR-21 transfection. Inflammatory cytokines, oxidative stress indicators, lung tissue cell apoptosis, oxygenation index (OI), lung wet/dry weight ratio, and lung pathological changes in the lung were observed in each group. Results: Compared with ALI mice, inflammatory response, oxidative stress indicators, lung tissue cell apoptosis, and the degree of lung injury were remarkably alleviated in Pre-miR-21+ALI mice and aggravated in Anti-miR-21+ALI mice. Western blot analysis showed that phosphatase and tensin homolog (PTEN) protein expression was decreased in CLP-treated mics. PTEN protein expression was decreased in the Pre-miR-21+ALI group but increased in the Anti-miR-21+ALI group. Moreover, the effect of miR-21 on anti-inflammatory, anti-oxidative stress, and anti-apoptosis enhanced after PTEN inhibition. Conclusion: This study revealed that miR-21 has a protective effect in sepsis-induced ALI by regulating PTEN in mice.

Hydrogen sulfide attenuates ferroptosis and stimulates autophagy by blocking mTOR signaling in sepsis-induced acute lung injury