Inhibition of STAT3 phosphorylation by colchicine regulates NLRP3 activation to alleviate sepsis-induced acute lung injury

Macrophage‑driven pathogenesis in acute lung injury/acute respiratory disease syndrome: Harnessing natural products for therapeutic interventions (Review)

Acute lung injury (ALI) or acute respiratory distress syndrome (ARDS) is a common respiratory disease characterized by hypoxemia and respiratory distress. It is associated with high morbidity and mortality. Due to the complex pathogenesis of ALI, the clinical management of patients with ALI/ARDS is challenging, resulting in numerous post‑treatment sequelae and compromising the quality of life of patients. Macrophages, as a class of innate immune cells, play an important role in ALI/ARDS. In recent years, the functions and phenotypes of macrophages have been better understood due to the development of flow cytometry, immunofluorescence, single‑cell sequencing and spatial genomics. However, no macrophage‑targeted drugs for the treatment of ALI/ARDS currently exist in clinical practice. Natural products are important for drug development, and it has been shown that numerous natural compounds from herbal medicine can alleviate ALI/ARDS caused by various factors by modulating macrophage abnormalities. In the present review, the natural products from herbal medicine that can modulate macrophage abnormalities in ALI/ARDS to treat ALI/ARDS are introduced, and their mechanisms of action, discovered in the previous five years (2019‑2024), are presented. This will provide novel ideas and directions for further research, to develop new drugs for the treatment of ALI/ARDS.

PKM2-mediated STAT3 phosphorylation promotes acute liver failure via regulating NLRP3-dependent pyroptosis

Acute liver failure (ALF) is a life-threatening clinical syndrome characterized by high-grade inflammation and multi-organ failure. Our previous study shows that targeting the M2 isoform of pyruvate kinase (PKM2) to inhibit macrophage inflammation may be a promising strategy for ALF treatment. however, the mechanism by which PKM2 regulates the inflammatory response is unclear. Here we demonstrate that PKM2 contributes to ALF by modulating NLRP3-mediated pyroptosis activation in liver macrophages. The specific knockout of PKM2 in myeloid cells reduces mortality and alleviates hepatic injury in D-galactosamine/LPS-induced ALF mice. Single-cell transcriptome analysis suggests that NLRP3 inflammasome activation of macrophages involves in ALF, knockout of PKM2 in macrophages reduces the expression of NLRP3, and activation of pyroptosis. Pharmacological inhibition of the PKM2 nuclear translocation, but not glycolytic activity, protects mice from ALF. Pharmacological and genetic inhibition of PKM2 attenuates NLRP3-mediated pyroptosis activation and consequently reduces the release of IL-1β and IL-18 by macrophages. Mechanistically, PKM2 translocates into the nucleus and combines with STAT3, enhancing its phosphorylation and recruitment to the NLRP3 promoter region, thereby increasing NLRP3 expression. This work defines PKM2 acts as an important nonmetabolic regulator of NLRP3 that modulates pyroptosis activation in macrophages and guides future therapeutic strategies development for ALF.

CircHipk3 serves a dual role in macrophage pyroptosis by promoting NLRP3 transcription and inhibition of autophagy to induce abdominal aortic aneurysm formation

AIMS

CircRNAs could regulate macrophage pyroptosis, which has the potential in promoting the synergistic effect of inflammation and matrix metalloproteinase (MMP) activity in abdominal aortic aneurysm (AAA). But the roles of circRNAs in modulating macrophage pyroptosis in the AAA remain unknown. This study explored the contribution to AAA of circHipk3, which was macrophage pyroptosis promoter, and the underlying mechanism.

METHODS AND RESULTS

CircHipk3 was markedly upregulated in aortic aneurysms compared with that in normal arteries. In mice treated with circHipk3 contributed to macrophage pyroptosis, subsequently promoting the synergistic effect of inflammation and MMP synthesis, and significantly accelerated angiotensin (Ang) II- and porcine pancreatic elastase (PPE)-induced AAA formation. Mechanically, chromatin isolation by RNA purification (ChIRP) indicated that circHipk3 facilitated macrophage pyroptosis by interaction with Stat3, increase the NLRP3 level in the aorta, and by binding Snd1 to promote Ptbp1 mRNA degradation to inhibit autophagy. Therefore, our study revealed the important role of circHipk3 in macrophage pyroptosis and thus significantly improved the outcome of AAA.

CONCLUSIONS

CircHipk3 serves a dual role in augmenting macrophage pyroptosis by interaction with Stat3, increase the NLRP3 level, and by binding Snd1 to promote Ptbp1 mRNA degradation to inhibit autophagy, thereby inducing aneurysm formation and progression.

KEY POINTS

CircHipk3 is significantly upregulated in abdominal aortic aneurysms (AAA) compared to normal arteries, contributing to macrophage pyroptosis. CircHipk3 promotes the synergistic effect of inflammation and matrix metalloproteinase (MMP) activity, accelerating Angiotensin II- and porcine pancreatic elastase-induced AAA formation in mice. Mechanistically, CircHipk3 interacts with Stat3 to elevate NLRP3 levels and binds Snd1 to promote Ptbp1 mRNA degradation, inhibiting autophagy. CircHipk3's dual role in enhancing NLRP3 inflammasome activation and inhibiting autophagy makes it a critical regulator in AAA development and rupture. Targeting CircHipk3 may offer a novel therapeutic strategy to prevent pyroptosis and AAA development, positioning it as a potential treatment target.

Placental mesenchymal stem cells suppress inflammation and promote M2-like macrophage polarization through the IL-10/STAT3/NLRP3 axis in acute lung injury

INTRODUCTION

Acute lung injury (ALI) is a clinically severe respiratory disorder that currently lacks specific and effective pharmacotherapy. The imbalance of M1/M2 macrophage polarization is pivotal in the initiation and progression of ALI. Shifting macrophage polarization from the proinflammatory M1 phenotype to the anti-inflammatory M2 phenotype could be a potential therapeutic strategy. The intratracheal administration of placental mesenchymal stem cells (pMSCs) has emerged as a novel and effective treatment for ALI. This study aimed to investigate the role and downstream mechanisms of pMSCs in reprogramming macrophage polarization to exert anti-inflammatory effects in ALI.

METHODS

The study used lipopolysaccharide (LPS) to induce inflammation in both cell and rat models of ALI. Intratracheal administration of pMSCs was tested as a therapeutic intervention. An expression dataset for MSCs cultured with LPS-treated macrophages was collected from the Gene Expression Omnibus database to predict downstream regulatory mechanisms. Experimental validation was conducted through in vitro and in vivo assays to assess pMSCs effects on macrophage polarization and inflammation.

RESULTS

Both in vitro and in vivo experiments validated that pMSCs promoted M2 macrophage polarization and reduced the release of inflammatory factors. Further analyses revealed that pMSCs activated the signal transducer and activator of transcription (STAT)3 signaling pathway by secreting interleukin (IL)-10, leading to increased STAT3 phosphorylation and nuclear translocation. This activation inhibited NLRP3 inflammasome activation, promoting M2 macrophage polarization and suppressing the inflammatory response.

CONCLUSION

The study concluded that pMSCs alleviated lung injury in an LPS-induced ALI model by inhibiting M1 macrophage polarization and proinflammatory factor secretion, while promoting M2 macrophage polarization. This effect was mediated via the IL-10/STAT3/NLRP3 axis, presenting a novel therapeutic pathway for ALI treatment.

The regulation of pyroptosis by post-translational modifications: molecular mechanisms and therapeutic targets

Pyroptosis, a type of programmed cell death mediated by gasdermin family proteins, releases a large amount of immune stimulatory substances, which further contribute to inflammation and elicit an adaptive immune response against tumours and pathogens. And it occurs through multiple pathways that involve the activation of specific caspases and the cleavage of gasdermins. Post-translational modifications (PTMs) could influence the chemical properties of the modified residues and neighbouring regions, ultimately affecting the activity, stability, and functions of proteins to regulate pyroptosis. Many studies have been conducted to explore the influence of PTMs on the regulation of pyroptosis. In this review, we provide a comprehensive summary of different types of PTMs that influence pyroptosis, along with their corresponding modifying enzymes. Moreover, it elaborates on the specific contributions of different PTMs to pyroptosis and delves into how the regulation of these modifications can be leveraged for therapeutic interventions in cancer and inflammatory diseases.

The ubiquitin-specific protease 21 is critical for cancer cell mitochondrial function and regulates proliferation and migration

Ubiquitin-specific proteases (USPs) are the main members of deubiquitinases (DUBs) that catalyze removing ubiquitin chains from target proteins, thereby modulating their half-life and function. Enzymatic activity of USP21 regulates protein degradation which is critical for maintaining cell homeostasis. USP21 determines the stability of oncogenic proteins and therefore is implicated in carcinogenesis. In this study, we investigated the effect of USP21 deletion on cancer cell metabolism. Transcriptomic and proteomic analysis of USP21 KO HAP-1 cells revealed that endogenous USP21 is critical for the expression of genes and proteins involved in mitochondrial function. Additionally, we have found that the deletion of USP21 reduced STAT3 activation and STAT3-dependent gene and protein expression in cancer cells. Genetic deletion of USP21 impaired mitochondrial respiration and disturbed ATP production. This resulted in cellular consequences such as inhibition of cell proliferation and migration. Presented results provide new insights into the biology of USP21, suggesting novel mechanisms for controlling STAT3 activity and mitochondrial function in tumor cells. Taken together, our findings indicate that targeting USP21 dysregulates the energy status of cancer cells offering new perspectives for anticancer therapy.

NLRP3 Inflammasomes: Dual Function in Infectious Diseases

The Nod-like receptor family pyrin domain containing 3 (NLRP3) inflammasome has been the most distinctive polymer protein complex. After recognizing the endogenous and exogenous danger signals, NLRP3 can cause inflammation by pyroptosis and secretion of mature, bioactive forms of IL-1β and IL-18. The NLRP3 inflammasome is essential in the genesis and progression of infectious illnesses. Herein, we provide a comprehensive review of the NLRP3 inflammasome in infectious diseases, focusing on its two-sided effects. As an essential part of host defense with a protective impact, abnormal NLRP3 inflammasome activation, however, result in a systemic high inflammatory response, leading to subsequent damage. In addition, scientific evidence of small molecules, biologics, and phytochemicals acting on the NLRP3 inflammasome has been reviewed. We believe that the NLRP3 inflammasome helps us understand the pathological mechanism of different stages of infectious diseases and that inhibitors targeting the NLRP3 inflammasome will become a new and valuable research direction for the treatment of infectious diseases.

Peficitinib alleviated acute lung injury by blocking glycolysis through JAK3/STAT3 pathway

Peficitinib is a selective Janus kinase (JAK3) inhibitor recently developed and approved for the treatment of rheumatoid arthritis in Japan. Glycolysis in macrophages could induce NOD-like receptor (NLR) family and pyrin domain-containing protein 3 (NLRP3) inflammasome activation, thus resulting in pyroptosis and acute lung injury (ALI). The aim of our study was to investigate whether Peficitinib could alleviate lipopolysaccharide (LPS)-induced ALI by inhibiting NLRP3 inflammasome activation. Wild type C57BL/6J mice were intraperitoneally injected with Peficitinib (5 or 10 mg·kg-1·day-1) for 7 consecutive days before LPS injection. The results showed that Peficitinib pretreatment significantly relieved LPS-induced pulmonary edema, inflammation, and apoptosis. NLRP3 inflammasome and glycolysis in murine lung tissues challenged with LPS were also blocked by Peficitinib. Furthermore, we found that the activation of JAK3/signal transducer and activator of transcription 3 (STAT3) was also suppressed by Peficitinib in mice with ALI. However, in Jak3 knockout mice, Peficitinib did not show obvious protective effects after LPS injection. In vitro experiments further showed that Jak3 overexpression completely abolished Peficitinib-elicited inhibitory effects on pyroptosis and glycolysis in LPS-induced RAW264.7 macrophages. Finally, we unveiled that LPS-induced activation of JAK3/STAT3 was mediated by toll-like receptor 4 (TLR4) in RAW264.7 macrophages. Collectively, our study proved that Peficitinib could protect against ALI by blocking JAK3-mediated glycolysis and pyroptosis in macrophages, which may serve as a promising candidate against ALI in the future.

Targeting epigenetic and post-translational modifications regulating pyroptosis for the treatment of inflammatory diseases

Inflammatory diseases, including infectious diseases, diabetes-related diseases, arthritis-related diseases, neurological diseases, digestive diseases, and tumor, continue to threaten human health and impose a significant financial burden despite advancements in clinical treatment. Pyroptosis, a pro-inflammatory programmed cell death pathway, plays an important role in the regulation of inflammation. Moderate pyroptosis contributes to the activation of native immunity, whereas excessive pyroptosis is associated with the occurrence and progression of inflammation. Pyroptosis is complicated and tightly controlled by various factors. Accumulating evidence has confirmed that epigenetic modifications and post-translational modifications (PTMs) play vital roles in the regulation of pyroptosis. Epigenetic modifications, which include DNA methylation and histone modifications (such as methylation and acetylation), and post-translational modifications (such as ubiquitination, phosphorylation, and acetylation) precisely manipulate gene expression and protein functions at the transcriptional and post-translational levels, respectively. In this review, we summarize the major pathways of pyroptosis and focus on the regulatory roles and mechanisms of epigenetic and post-translational modifications of pyroptotic components. We also illustrate these within pyroptosis-associated inflammatory diseases. In addition, we discuss the effects of novel therapeutic strategies targeting epigenetic and post-translational modifications on pyroptosis, and provide prospective insight into the regulation of pyroptosis for the treatment of inflammatory diseases.

Mechanisms of Sepsis-Induced Acute Lung Injury and Advancements of Natural Small Molecules in Its Treatment

Sepsis-induced acute lung injury (ALI), characterized by widespread lung dysfunction, is associated with significant morbidity and mortality due to the lack of effective pharmacological treatments available clinically. Small-molecule compounds derived from natural products represent an innovative source and have demonstrated therapeutic potential against sepsis-induced ALI. These natural small molecules may provide a promising alternative treatment option for sepsis-induced ALI. This review aims to summarize the pathogenesis of sepsis and potential therapeutic targets. It assembles critical updates (from 2014 to 2024) on natural small molecules with therapeutic potential against sepsis-induced ALI, detailing their sources, structures, effects, and mechanisms of action.

Long noncoding RNA MCM3AP-AS1 attenuates sepsis-induced cardiomyopathy by improving inflammation, oxidative stress, and mitochondrial function through mediating the miR-501-3p/CADM1/STAT3 axis

Oxidative stress and inflammation are highly important for sepsis-mediated myocardial damage. The long noncoding RNA (lncRNA) MCM3AP-AS1 is involved in inflammatory diseases, but its function in acute myocardial injury during sepsis has not been fully elucidated. LPS and cecal ligation and puncture (CLP) were used to construct in vitro and in vivo sepsis-induced myocardial damage models, respectively. qRT-PCR was used to evaluate alterations in MCM3AP-AS1 and miR-501-3p alterations. After the MCM3AP-AS1 and miR-501-3p knockdown or overexpression models were established, the viability, apoptosis, inflammation, oxidative stress, and mitochondrial function of the myocardial cells were examined. Dual luciferase activity assay, RNA immunoprecipitation, and fluorescence in situ hybridization (FISH) confirmed the correlation among MCM3AP-AS1, miR-501-3p, and CADM1. Previous studies revealed that MCM3AP-AS1 was downregulated in sepsis patients, myocardial cells treated with LPS, and in the CLP mouse sepsis model, whereas miR-501-3p expression was increased. MCM3AP-AS1 overexpression hampered myocardial damage mediated by LPS and abated inflammation, oxidative stress, and mitochondrial dysfunction in myocardial cells and THP-1 cells. In contrast, MCM3AP-AS1 knockdown or miR-501-3p overexpression promoted all the effects of LPS. In vivo, MCM3AP-AS1 overexpression increased the survival rate of CLP mice; ameliorated myocardial injury; decreased the levels of TNF-α, IL-1β, IL-6, iNOS, COX2, ICAM1, VCAM1, PGE2, and MDA; and increased the levels of SOD, GSH-PX, Nrf2, and HO-1. Mechanistic studies demonstrated that MCM3AP-AS1 acted as a competitive endogenous RNA to repress miR-501-3p, enhance CADM1 expression, and dampen STAT3/nuclear factor-kappaB (NF-κB) activation. MCM3AP-AS1 suppresses myocardial injury elicited by sepsis by mediating the miR-501-3p/CADM1/STAT3/NF-κB axis.

Exploration of the role of oxidative stress-related genes in LPS-induced acute lung injury via bioinformatics and experimental studies

During the progression of acute lung injury (ALI), oxidative stress and inflammatory responses always promote each other. The datasets analyzed in this research were acquired from the Gene Expression Omnibus (GEO) database. The Weighted Gene Co-expression Network Analysis (WGCNA) and limma package were used to obtain the ALI-related genes (ALIRGs) and differentially expressed genes (DEGs), respectively. In total, two biological markers (Gch1 and Tnfaip3) related to oxidative stress were identified by machine learning algorithms, Receiver Operator Characteristic (ROC), and differential expression analyses. The area under the curve (AUC) value of biological markers was greater than 0.9, indicating an excellent power to distinguish between ALI and control groups. Moreover, 15 differential immune cells were selected between the ALI and control samples, and they were correlated to biological markers. The transcription factor (TF)-microRNA (miRNA)-Target network was constructed to explore the potential regulatory mechanisms. Finally, based on the quantitative reverse transcription polymerase chain reaction (qRT-PCR), the expression of Gch1 and Tnfaip3 was significantly higher in ALI lung tissue than in healthy controls. In conclusion, the differences in expression profiles between ALI and normal controls were found, and two biological markers were identified, providing a research basis for further understanding the pathogenesis of ALI.

Mitigation of Sepsis-Induced Acute Lung Injury by BMSC-Derived Exosomal miR-125b-5p Through STAT3-Mediated Suppression of Macrophage Pyroptosis

Introduction

Sepsis is a syndrome characterized by high morbidity and mortality rates. One of its most severe complications is acute lung injury, which exhibits a multitude of clinical and biological features, including macrophage pyroptosis. This study investigates the regulatory effects of exosomes derived from Bone Marrow-Derived Mesenchymal Stem Cells (BMSCs) on sepsis-associated acute lung injury (ALI) and explores the potential mechanisms mediated by exosomal miRNAs.

Methods

Exosomes were isolated from primary BMSCs of adult C57BL/6J mice using differential centrifugation. Their uptake and distribution in both in vitro and in vivo contexts were validated. Key sepsis-associated hub gene signal transducer and activator of transcription 3 (STAT3) and its upstream non-coding miR-125b-5p were elucidated through a combination of bioinformatics, machine learning, and miRNA sequencing. Subsequently, the therapeutic potential of BMSC-derived exosomes in alleviating sepsis-induced acute lung injury was substantiated. Moreover, the functionalities of miR-125b-5p and STAT3 were corroborated through miR-125b-5p inhibitor and STAT3 agonist interventions, employing gain and loss-of-function strategies both in vitro and in vivo. Finally, a dual-luciferase reporter assay reaffirmed the interaction between miR-125b-5p and STAT3.

Results

We isolated exosomes from primary BMSCs and confirmed their accumulation in the mouse lung as well as their uptake by macrophages in vitro. This study identified the pivotal sepsis-associated hub gene STAT3 and demonstrated that exosomes derived from BMSCs can target STAT3, thereby inhibiting macrophage pyroptosis. MiR-125b-5p inhibition experiments showed that exosomes mitigate macrophage pyroptosis and lung injury by delivering miR-125b-5p. STAT3 overexpression experiments validated that miR-125b-5p reduces macrophage pyroptosis and lung injury by suppressing STAT3. Furthermore, a dual-luciferase reporter assay confirmed the binding interaction between miR-125b-5p and STAT3.

Conclusion

Exosomes derived from BMSCs, serving as carriers for delivering miR-125b-5p, can downregulate STAT3, thereby inhibiting macrophage pyroptosis and alleviating sepsis-associated ALI. These significant findings provide valuable insights into the potential development of ALI therapies centred around exosomes derived from BMSC.