Activation of TLR4 induces severe acute pancreatitis-associated spleen injury via ROS-disrupted mitophagy pathway

Involvement of circ_0029407 in Caerulein-Evoked Cytotoxicity in Human Pancreatic Cells via the miR-579-3p/TLR4/NF-κB Pathway

Acute pancreatitis (AP) is the most prevalent gastrointestinal inflammatory disease. Circular RNAs (circRNAs) are implicated in the development of AP. Here, we identified the precise action of circ_0029407 in AP development. Human pancreatic epithelial cells (HPECs) were stimulated with caerulein. Cell viability, proliferation, and apoptosis were gauged by Cell Counting Kit-8 (CCK-8), 5-ethynyl-2'-deoxyuridine (EdU), and flow cytometry assays, respectively. Circ_0029407, microRNA (miR)-579-3p, and toll-like receptor 4 (TLR4) were quantified by a qRT-PCR or western blot assay. Dual-luciferase reporter and RNA pull-down assays were performed to evaluate the direct relationship between miR-579-3p and circ_0029407 or TLR4. Our results indicated that circ_0029407 was markedly overexpressed in AP serum samples and caerulein-stimulated HPECs. Reduction of circ_0029407 attenuated caerulein-imposed HPEC damage by promoting cell proliferation and repressing cell apoptosis and inflammation. Mechanistically, circ_0029407 contained a miR-579-3p binding site, and miR-579-3p downregulation reversed the effect of circ_0029407 reduction on caerulein-imposed HPEC damage. TLR4 was identified as a direct and functional target of miR-579-3p, and TLR4 overexpression reversed the impact of miR-579-3p upregulation on attenuating caerulein-imposed HPEC damage. Moreover, circ_0029407 regulated the TLR4/nuclear factor NF-kappaB (NF-κB) signaling by acting as a competing endogenous RNA (ceRNA) for miR-579-3p. Our study suggests that circ_0029407 regulates caerulein-imposed cell injury in human pancreatic cells at least in part via the TLR4/NF-κB signaling pathway by functioning as a ceRNA for miR-579-3p.

Esculetin and Phloretin Combination Mitigates Acute Kidney Injury-Diabetes Comorbidity via Regulating Mitophagy and Inflammation: A Dual-Pronged Approach

Induction of PINK1/Parkin-mediated mitophagy and reducing inflammation via targeting the TLR4/NF-κB axis simultaneously could be a promising therapy for the complex pathophysiology of AKI-diabetes comorbidity. Earlier, esculetin by mitophagy activation and phloretin by inhibiting inflammation have shown promising renoprotection. Therefore, we aimed to evaluate the synergistic renoprotective ability of esculetin and phloretin combination against AKI-diabetes comorbidity. AKI-diabetes comorbidity was mimicked in vivo by bilateral ischemia/reperfusion injury (IRI) in diabetic rats and in vitro by sodium azide-induced hypoxia/reperfusion injury (HRI) under hyperglycemic conditions. The cells were pretreated with esculetin (50 μM) and phloretin (50 μM) for 24 h. Similarly, the diabetic AKI rats received esculetin (50 mg/kg/day, p.o.) and phloretin (50 mg/kg/day, p.o.) pretreatment for 4 days and 1 h before surgery. Further, the obtained samples were utilized for different experiments. Esculetin and phloretin in diabetic AKI rats preserved kidney function and prevented kidney injury, indicated by reduced plasma creatinine, blood urea nitrogen, and kidney injury molecule 1. Esculetin improved mitophagy, indicated by increased mitophagosome formation, increased PINK1, Parkin, LC3B, and decreased p62 expression. Similarly, phloretin suppressed the diabetic AKI-related increased expression of inflammatory mediators including NF-κB, TLR4, TNF-α, and MCP-1. Moreover, combination therapy showed a more pronounced effect via synergistically improving mitophagy, maintaining ΔΨm, preventing mitochondrial dysfunction, reducing inflammation, and apoptosis. Esculetin and phloretin combination ameliorated AKI-diabetes comorbidity more effectively than their monotherapies. Esculetin upregulated the PINK1/Parkin-mediated mitophagy, and phloretin reduced inflammation by inhibiting the TLR4/NF-κB axis, thereby synergistically preventing kidney dysfunction.

Timing, initiation and function: An in-depth exploration of the interaction network among neutrophil extracellular traps related genes in acute pancreatitis

BACKGROUND

Exogenous inhibition of neutrophil extracellular traps (NETs) was believed to alleviate acute pancreatitis (AP). This study aimed to comprehensively explore the key biological behavior of NETs including timing and pathogenesis in AP by integrating of single cell RNA sequencing(scRNA-seq) and bulk RNA-seq.

METHODS

Differentially expressed NETs-related genes and the hub genes of NETs were screened by bulk RNA-seq. ScRNA-seq was used to identify the cell types in pancreas of AP mice and to depict the transcriptomic maps in neutrophils. The mouse AP models were build to verify the timing of initiation of NETs and underlying pathogenesis of damage on pancreas acinar cells.

RESULTS

Tlr4 and Ccl3 were screened for hub genes by bulk RNA-seq. The trajectory analysis of neutrophils showed that high expression of Ccl3, Cybb and Padi4 can be observed in the middle stage during AP. Macrophages might be essential in the biological behavior of neutrophils and NETs. Through animal models, we presented that extensive NETs structures were formed at mid-stage of inflammation, accompanied by more serious pancreas and lung damage. NETs might promote necroptosis and macrophage infiltration in AP, and the damage on pancreatic injury could be regulated by Tlr4 pathway. Ccl3 was considered to recruit neutrophils and promote NETs formation.

CONCLUSION

The findings explored the underlying timing and pathogenesis of NETs in AP for the first time, which provided gene targets for further studies.

The current status of early nursing for emergency pancreatitis and analysis of factors influencing prognosis: A retrospective study

This study is to investigate the incidence of pain and the influencing factors of prognostic complications in early admission care of pancreatitis in the emergency department patients. This provides a basis for clinical nursing management and prognosis improvement. Hundred patients with acute pancreatitis admitted to the tertiary hospital between January 2021 and December 2023 were selected according to the inclusion and exclusion criteria. It collected basic baseline data and medical data of patients during admission, clarifies whether patients have complications, and analyzed the length of hospital stay. Comparing hospital stays >7 days with <7 days. A questionnaire on patient psychological status was collected, and single factor analysis was conducted on different prognostic factors. Binary logistic regression was used for single factor analysis, and P < .05 was considered statistically significant. The presence or absence of complications during treatment is the main criterion for determining the prognostic impact of pancreatitis in the emergency department patients. Among 100 patients, 26 (26%) had complications during hospitalization, 74 (74%) had no complications during hospitalization, and 64 (64%) had a stay of >7 days. There were statistically significant differences (P < .05) in smoking status and history of hypertension between the complication group and the non-complication group. In the comparison between the group with <7 days of hospitalization and the group with >7 days of hospitalization, age, education level, smoking status, and history of hyperlipidemia showed statistical significance (P < .05). The fasting days, BISAP score, first bowel movement time, C-reactive protein, blood urea nitrogen, albumin, duration of severe pain within 24 hours of admission, and duration of severe pain within 24 to 48 hours of admission were all statistically significant (P < .05). Pancreatitis in the emergency department patients are prone to exacerbation and prolonged pain during early hospitalization. In nursing, timely attention should be paid to the patient's pain issues, timely pain relief measures should be taken, and the occurrence of complications should be reduced, reducing the patient's hospitalization time. Meanwhile, it is necessary to constantly pay attention to changes in the patient's gastrointestinal function and experimental indicators.

Molecular mechanism and potential role of mitophagy in acute pancreatitis

Acute pancreatitis (AP) is a multifaceted inflammatory disorder stemming from the aberrant activation of trypsin within the pancreas. Despite the contribution of various factors to the pathogenesis of AP, such as trypsin activation, dysregulated increases in cytosolic Ca2+ levels, inflammatory cascade activation, and mitochondrial dysfunction, the precise molecular mechanisms underlying the disease are still not fully understood. Mitophagy, a cellular process that preserves mitochondrial homeostasis under stress, has emerged as a pivotal player in the context of AP. Research suggests that augmenting mitophagy can mitigate pancreatic injury by clearing away malfunctioning mitochondria. Elucidating the role of mitophagy in AP may pave the way for novel therapeutic strategies. This review article aims to synthesize the current research findings on mitophagy in AP and underscore its significance in the clinical management of the disorder.

Ultrasmall polyvinylpyrrolidone-modified iridium nanoparticles with antioxidant and anti-inflammatory activity for acute pancreatitis alleviation

Acute pancreatitis (AP) is a common and serious acute inflammatory disease with high severity rate and mortality. Inflammation and oxidative stress play an extremely important role in the development of AP disease. Polyvinylpyrrolidone-modified iridium nanoparticles (IrNP-PVP) have multienzyme mimetic activity, and the aim of this article is to discuss the therapeutic alleviative effects of the ultrasmall nanozymes IrNP-PVP on AP through their antioxidant and anti-inflammatory effects. IrNP-PVP were proved to inhibit inflammation and scavenge reactive oxygen species (ROS) at the cellular level. The synthetic IrNP-PVP exhibit remarkable antioxidant and anti-inflammatory activities in the prevention and treatment of AP mice by establishing murine AP model, which can reduce the oxidative stress and inflammatory response. The results of this article indicated that the ultrasmall nanozymes IrNP-PVP effectively alleviate AP via scavenging ROS as well as suppressing inflammation both in vivo and in vitro, which might provide enormous promise for the AP management.

Protective effect of Xixin-Ganjiang herb pair for warming the lungs to dissolve phlegm in chronic obstructive pulmonary disease rats based on integrated network pharmacology and metabolomics

Xixin-Ganjiang herb pair (XGHP) is a classic combination for warming the lungs to dissolve phlegm and is often used to treat a variety of chronic lung diseases; it can treat the syndrome of cold phlegm obstruction of lungs. First, ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was used to examine the composition of XGHP, and network pharmacology was used to predict its potential core targets and signaling pathways in the current study. Second, a rat model of chronic obstructive pulmonary disease (COPD) was established for assessing the anti-COPD activity of XGHP, and metabolomics was used to explore the biomarkers and metabolic pathways. Finally, the sample was validated using molecular docking and Western blotting. The integration of metabolomics and network pharmacology results identified 11 targets, 3 biomarkers, 3 pathways, and 2 metabolic pathways. Western blotting showed that XGHP effectively regulated the expression of core proteins via multiple signaling pathways (downregulation of toll-like receptor 4 [TLR4] and upregulation of serine/threonine-protein kinase 1 [p-AKT1] and nitric oxide synthase 3 [NOS3]). Molecular docking results showed that the 10 potentially active components of XGHP have good affinity with tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), matrix metalloproteinase 9 (MMP-9), TLR4, p-AKT1, and NOS3. Our findings suggest that XGHP may regulate glucolipid metabolism, improve energy supply, and inhibit inflammatory responses (TNF-α, IL-6, and MMP-9) via the PI3K-Akt signaling pathway and HIF-1 signaling pathway in the management of COPD.

The Pathogenesis of Pancreatitis and the Role of Autophagy

The pathogenesis of acute and chronic pancreatitis has recently evolved as new findings demonstrate a complex mechanism operating through various pathways. In this review, the current evidence indicating that several mechanisms act in concert to induce and perpetuate pancreatitis were presented. As autophagy is now considered a fundamental mechanism in the pathophysiology of both acute and chronic pancreatitis, the fundamentals of the autophagy pathway were discussed to allow for a better understanding of the pathophysiological mechanisms of pancreatitis. The various aspects of pathogenesis, including trypsinogen activation, ER stress and mitochondrial dysfunction, the implications of inflammation, and macrophage involvement in innate immunity, as well as the significance of pancreatic stellate cells in the development of fibrosis, were also analyzed. Recent findings on exosomes and the miRNA regulatory role were also presented. Finally, the role of autophagy in the protection and aggravation of pancreatitis and possible therapeutic implications were reviewed.

PD-1/PD-L1 axis induced host immunosuppression via PI3K/Akt/mTOR signalling pathway in piglets infected by Glaesserella Parasuis

Glaesserella parasuis, an important respiratory bacterial pathogen, causes Glässer's disease in piglets, with potential immunosuppression. We established a piglet infection model and explored the immunosuppression mechanism to improve our understanding of the host immune response to G. parasuis. Twenty piglets were randomly divided into two groups (n = 10). The infection group was intraperitoneally challenged with 2 × 108 CFU of G. parasuis in 2 mL TSB. The control group was intraperitoneally injected with equivalent TSB. After 72 h, the piglets were sacrificed, and spleen tissue was collected. PD-1/PD-L1 expression was determined. The splenocytes were isolated to detect CD3+ T, CD3+CD4+ T, CD3+CD8+ T and CD3-CD21+cell differentiation. Via data-independent acquisition (DIA), we compared the proteomics of healthy and infected spleen tissues. Glaesserella parasuis modified CD3+ T, CD3+CD4+ T, CD3+CD8+ T and CD3-CD21+ cell differentiation and PD-1/PD-L1 expression in the spleen. The infection group had 596 proteins with significant differences in expression, of which 301 were significantly upregulated and 295 downregulated. Differentially expressed proteins (DEPs) were mainly related to immune responses. This is the first study on PD-1/PD-L1 expression in the spleen associated with immunosuppression in a piglet model to explore the protein changes related to immune responses via DIA.

The mitochondria-targeted Kaempferol nanoparticle ameliorates severe acute pancreatitis

Kaempferol (KA), an natural antioxidant of traditional Chinese medicine (TCM), is extensively used as the primary treatment for inflammatory digestive diseases with impaired redox homeostasis. Severe acute pancreatitis (SAP) was exacerbated by mitochondrial dysfunction and abundant ROS, which highlights the role of antioxidants in targeting mitochondrial function. However, low bioavailability and high dosage of KA leading to unavoidable side effects limits clinical transformation. The mechanisms of KA with poor bioavailability largely unexplored, hindering development of the efficient strategies to maximizing the medicinal effects of KA. Here, we engineered a novel thioketals (TK)-modified based on DSPE-PEG2000 liposomal codelivery system for improving bioavailability and avoiding side effects (denotes as DSPE-TK-PEG2000-KA, DTM@KA NPs). We demonstrated that the liposome exerts profound impacts on damaging intracellular redox homeostasis by reducing GSH depletion and activating Nrf2, which synergizes with KA to reinforce the inhibition of inadequate fission, excessive mitochondrial fusion and impaired mitophagy resulting in inflammation and apoptosis; and then, the restored mitochondrial homeostasis strengthens ATP supply for PAC renovation and homeostasis. Interestingly, TK bond was proved as the main functional structure to improve the above efficacy of KA compared with the absence of TK bond. Most importantly, DTM@KA NPs obviously suppresses PAC death with negligible side effects in vitro and vivo. Mechanismly, DTM@KA NPs facilitated STAT6-regulated mitochondrial precursor proteins transport via interacting with TOM20 to further promote Drp1-dependent fission and Pink1/Parkin-regulated mitophagy with enhanced lysosomal degradation for removing damaged mitochondria in PAC and then reduce inflammation and apoptosis. Generally, DTM@KA NPs synergistically improved mitochondrial homeostasis, redox homeostasis, energy metabolism and inflammation response via regulating TOM20-STAT6-Drp1 signaling and promoting mitophagy in SAP. Consequently, such a TCM's active ingredients-based nanomedicine strategy is be expected to be an innovative approach for SAP therapy.

Toll-like receptor 2 deficiency alleviates acute pancreatitis by inactivating the NF-κB/NLRP3 pathway

The early aseptic immune response is the key factor leading to the aggravation of acute pancreatitis (AP). Toll-like receptor (TLR) 2 is an important member of the TLR family, but the role of TLR2 in AP remains to be investigated. In the present study, we found that TLR2 expression was significantly increased in AP patients. In a mouse model of cerulein-induced AP, TLR2 deficiency resulted in reduced inflammation, reduced infiltration of pancreatic neutrophils and macrophages, and decreased expression of proinflammatory cytokines such as interleukin (IL)-1β, IL-6, IL-17 and IL-18. In addition, transcriptomic analysis revealed that nod-like receptor family pyrin domain-containing 3 (NLRP3) expression was increased in AP, and there was a significant correlation between NLRP3 and TLR2. This study found that TLR2 deficiency can lead to a decrease in the activation of the NF-κB/NLRP3 signalling pathway, and the NLRP3 inhibitor MCC950 can alleviate AP in mice. Therefore, this study confirmed that TLR2 participates in the development of AP by activating the NF-κB/NLRP3 pathway. This study suggested that TLR2 might be a novel therapeutic target for AP.

Molecular characterization, immune expression, and functional delineation of peroxiredoxin 1 in Epinephelus akaara

Peroxiredoxin 1 is a member of the typical 2-Cys peroxiredoxin family, which serves diverse functions in gene expression, immune and inflammatory responses, and tumor progression. In this study, we aimed to analyze the structural, functional, and immunomodulatory properties of peroxiredoxin 1 from Epinephelus akaara (EaPrx1). The open reading frame of EaPrx1 is 597 base pairs in length, encoding 198 amino acids, with a molecular weight of approximately 22 kDa. The in silico analysis revealed that EaPrx1 shares a conserved thioredoxin fold and signature motifs that are critical for its catalytic activity and oligomerization. Further, EaPrx1 is closely related to Epinephelus lanceolatus Prx1 and clustered in the Fishes group of the vertebrate clade, revealing that EaPrx1 was conserved throughout evolution. In terms of tissue distribution, a high level of EaPrx1 expression was observed in the spleen, brain, and blood tissues. Likewise, in immune challenge experiments, significant transcriptional modulations of EaPrx1 upon lipopolysaccharide, polyinosinic:polycytidylic acid, and nervous necrosis virus injections were noted at different time points, indicating the immunological role of EaPrx1 against pathogenic infections. In the functional analysis, rEaPrx1 exhibited substantial DNA protection, insulin disulfide reduction, and tissue repair activities, which were concentration-dependent. EaPrx1/pcDNA™ 3.1 (+)-transfected fathead minnow cells revealed high cell viability upon arsenic toxicity, indicating the heavy metal detoxification activity of EaPrx1. Taken together, the transcriptional and functional studies imply critical roles of EaPrx1 in innate immunity, redox regulation, apoptosis, and tissue-repair processes in E. akaara.

Xanthohumol alleviates oxidative stress and impaired autophagy in experimental severe acute pancreatitis through inhibition of AKT/mTOR

Severe acute pancreatitis (SAP) is a lethal gastrointestinal disorder, yet no specific and effective treatment is available. Its pathogenesis involves inflammatory cascade, oxidative stress, and autophagy dysfunction. Xanthohumol (Xn) displays various medicinal properties, including anti-inflammation, antioxidative, and enhancing autophagic flux. However, it is unclear whether Xn inhibits SAP. This study investigated the efficacy of Xn on sodium taurocholate (NaT)-induced SAP (NaT-SAP) in vitro and in vivo. First, Xn attenuated biochemical and histopathological responses in NaT-SAP mice. And Xn reduced NaT-induced necrosis, inflammation, oxidative stress, and autophagy impairment. The mTOR activator MHY1485 and the AKT activator SC79 partly reversed the treatment effect of Xn. Overall, this is an innovative study to identify that Xn improved pancreatic injury by enhancing autophagic flux via inhibition of AKT/mTOR. Xn is expected to become a novel SAP therapeutic agent.

Molecular mechanism analysis of m6A modification-related lncRNA-miRNA-mRNA network in regulating autophagy in acute pancreatitis

This study aims to explore the molecular mechanism of N6-methyladenosine (m6A) modification-related long noncoding RNA (lncRNA)-microRNA (miRNA)-messenger RNA (mRNA) network in regulating autophagy and affecting the occurrence and development of acute pancreatitis (AP). RNA-seq datasets related to AP were obtained from Gene Expression Omnibus (GEO) database and merged after batch effect removal. lncRNAs significantly related to m6A in AP, namely candidate lncRNA, were screened by correlation analysis and differential expression analysis. In addition, candidate autophagy genes were screened through the multiple databases. Furthermore, the key pathways for autophagy to play a role in AP were determined by functional enrichment analysis. Finally, we predicted the miRNAs binding to genes and lncRNAs through TargetScan, miRDB and DIANA TOOLS databases and constructed two types of lncRNA-miRNA-mRNA regulatory networks mediated by upregulated and downregulated lncRNAs in AP. Nine lncRNAs related to m6A were differentially expressed in AP, and 21 candidate autophagy genes were obtained. Phosphoinositide 3-kinase (PI3K)-Akt signaling pathway and Forkhead box O (FoxO) signaling pathway might be the key pathways for autophagy to play a role in AP. Finally, we constructed a lncRNA-miRNA-mRNA regulatory network. An upregulated lncRNA competitively binds to 13 miRNAs to regulate 6 autophagy genes, and a lncRNA-miRNA-mRNA regulatory network in which 2 downregulated lncRNAs competitively bind to 7 miRNAs to regulate 2 autophagy genes. m6A modification-related lncRNA Pvt1, lncRNA Meg3 and lncRNA AW112010 may mediate the lncRNA-miRNA-mRNA network, thereby regulating autophagy to affect the development of AP.

Quercetin improves pancreatic cancer chemo-sensitivity by regulating oxidative-inflammatory networks

Chemotherapy is the main method for controlling pancreatic cancer metastasis but the prevalent chemotherapy resistance limits its utilization. The response of oxidation and inflammation often promotes pancreatic cancer progression and chemo-resistance. It is critical to explore the potential natural products with few side effects to control inflammatory responses and understand the related mechanisms. Quercetin is a flavonoid widely found in numerous vegetables, fruits, and foods and is thought to have antioxidant and anti-inflammatory properties, which may be associated with improvement of chemotherapy sensitivity during pancreatic cancer treatment. Quercetin may sensitize pancreatic cancer cells to the chemotherapeutic agents, including bromodomain and extraterminal domain inhibitors (BETI), daunorubicin, gemcitabine, sulforaphane, doxorubicin, and tumor necrosis factor-related signaling apoptosis-inducing ligand (TRAIL). Meanwhile, during the chemo-resistance therapy, many signaling molecules are involved with toll-like receptor 4 (TLR4)-mediated oxidative and inflammatory pathway. The effects of quercetin on other oxidative and inflammatory pathways were also explored. Quercetin may exert antitumor activity during the prevention of pancreatic cancer progression by regulating oxidative and inflammatory networks, which can promote immune escape of cancer cells by inducing immunosuppressive cytokines. Studying these patterns will help us to better understand the functional role of quercetin in the improvement of pancreatic cancer chemo-sensitivity. PRACTICAL APPLICATIONS: Chemotherapy is the major way for treating pancreatic cancer metastasis but the prevalent chemotherapy resistance caused by oxidative and inflammatory responses limits its utilization. It is necessary to explore the potential natural products with few side effects to prevent the oxidative and inflammatory responses. Quercetin is a flavonoid widely found in numerous vegetables, fruits, and foods and is thought to have antioxidant and anti-inflammatory properties, which may be associated with improvement of chemotherapy sensitivity of pancreatic cancer treatment by sensitizing pancreatic cancer cells to various chemotherapeutic agents via the regulation of oxidative and inflammatory networks. Studying these patterns will help us to better understand the functional role of quercetin in the improvement of pancreatic cancer chemo-sensitivity.

Effect and Mechanism of PINK1/Parkin-Mediated Mitochondrial Autophagy in Rat Lung Injury Induced by Nano Lanthanum Oxide

Nano lanthanum oxide particles (La2O3 NPs) are important nanoparticle materials which are widely used in photoelectric production, but their potential health hazards to the respiratory system are not clear. The purpose of this study was to explore the possible mechanism of lung injury induced by La2O3 NPs. In this study, 40 SPF male SD rats were randomly divided into low-, medium-, and high-dose groups and control groups, with 10 animals in each group. Rats were poisoned by tracheal injection. The low-, medium-, and high-dose groups were given La2O3 NPs suspension of 25, 50, and 100 mg/kg, respectively, and the control group was given an equal volume of high-temperature sterilized ultrapure water. The rats in each group were exposed once a week for 12 consecutive times. The gene transcription and protein expression levels of PINK1 and parkin in rat lung tissue were mainly detected. Compared with the control group, the gene transcription and protein expression levels of PINK1 and Parkin in the exposed group were significantly higher (p < 0.05). La2O3 NPs may activate PINK1/parkin-induced mitochondrial autophagy.

The gut-lung axis in severe acute Pancreatitis-associated lung injury: The protection by the gut microbiota through short-chain fatty acids

The role of gut microbiota in regulating the intestinal homeostasis, as well as the pathogenesis of severe acute pancreatitis-associated lung injury (PALI) is widely recognized. The bioactive functions of metabolites with small molecule weight and the detail molecular mechanisms of PALI mediated by "gut-lung axis" have gradually raised the attentions of researchers. Several studies have proved that short-chain fatty acids (SCFAs) produced by gut microbiome play crucial roles and varied activities in the process of PALI. However, relevant reviews reporting SCFAs in the involvement of PALI is lacking. In this review, we firstly introduced the synthetic and metabolic pathways of SCFAs, as well as the transport and signal transduction routes in brief. Afterwards, we focused on the possible mechanisms and clues of SCFAs to participate in the fight against PALI which referred to the inhibition of pathogen proliferation, anti-inflammatory effects, enhancement of intestinal barrier functions, and the maintenance and regulation of immune homeostasis via pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs). In addition, the latest reported pathological and physiological mechanisms of the gut-lung axis involved in PALI were reviewed. Finally, we summarized the potential therapeutic interventions of PALI by targeting SCFAs, including dietary fiber supplementation, direct supplementation of SCFAs/prebiotics/probiotics, and drugs administration, which is expected to provide new sights for clinical use in the future.

Activation of TLR4 induces inflammatory muscle injury via mTOR and NF-κB pathways in experimental autoimmune myositis mice

Idiopathic inflammatory myopathy (IIM) is an autoimmune disease that invades skeletal muscle; however, the etiology of IIM is still poorly understood. Toll-like receptor (TLR) 4 has been widely reported to take part in the autoimmune inflammation of IIMs. The mammalian target of rapamycin, mTOR, is a key central substance which mediates immune responses and metabolic changes, and also has been confirmed to be involved in the pathogenesis of IIMs. However, the interconnectedness between TLR4 and mTOR in IIM inflammation has not been fully elucidated. We hypothesized that TLR4 may play an important role in IIM inflammatory muscle injury by regulating mTOR. Mice were divided into four groups: a normal control group, IIM animal model (experimental autoimmune myositis, EAM) group, TAK242 intervention group and rapamycin (RAPA) intervention group. The results of EAM mice showed that TLR4, mTOR, nuclear factor-kappa B (NF-κB) and inflammatory factors interleukin-17A (IL-17A) and interferon γ (IFN-γ) mRNA levels were significantly upregulated. These factors were positively correlated with the degree of muscle inflammatory injury. When EAM mice were given the antagonist TAK242 to inhibit the TLR4 pathway, the results demonstrated that both mTOR and NF-κB were downregulated in the muscle of the mice. Muscle staining showed that the inflammatory injury was alleviated and the EAM mouse muscle strength was improved. Then, RAPA was used to inhibit the mTOR pathway, and the inflammatory factors IL-17A and IFN-γ were downregulated in EAM mouse muscle and serum. Consistently, muscle inflammatory injury was significantly reduced, and muscle strength was significantly improved. Our results suggest that TLR4 may regulate inflammatory muscle injury in EAM by activating the mTOR and NF-κB pathways, which provides both an experimental complement for the pathological mechanism of IIM and an encouraging target for the selection of effective treatments.