Gut microbe-derived milnacipran enhances tolerance to gut ischemia/reperfusion injury.

There are significant differences in the susceptibility of populations to intestinal ischemia/reperfusion (I/R), but the underlying mechanisms remain elusive. Here, we show that mice exhibit significant differences in susceptibility to I/R-induced enterogenic sepsis. Notably, the milnacipran (MC) content in the enterogenic-sepsis-tolerant mice is significantly higher. We also reveal that the pre-operative fecal MC content in cardiopulmonary bypass patients, including those with intestinal I/R injury, is associated with susceptibility to post-operative gastrointestinal injury. We reveal that MC attenuates mouse I/R injury in wild-type mice but not in intestinal epithelial aryl hydrocarbon receptor (AHR) gene conditional knockout mice (AHRflox/flox) or IL-22 gene deletion mice (IL-22-/-). Collectively, our results suggest that gut microbiota affects susceptibility to I/R-induced enterogenic sepsis and that gut microbiota-derived MC plays a pivotal role in tolerance to intestinal I/R in an AHR/ILC3/IL-22 signaling-dependent manner, revealing the pathological mechanism, potential prevention and treatment drugs, and treatment strategies for intestinal I/R.

Gut microbiota-derived succinate aggravates acute lung injury after intestinal ischaemia/reperfusion in mice.

INTRODUCTION: Acute lung injury (ALI) is a major cause of morbidity and mortality after intestinal ischaemia/reperfusion (I/R). The gut microbiota and its metabolic byproducts act as important modulators of the gut-lung axis. This study aimed to define the role of succinate, a key microbiota metabolite, in intestinal I/R-induced ALI progression. METHODS: Gut and lung microbiota of mice subjected to intestinal I/R were analysed using 16S rRNA gene sequencing. Succinate level alterations were measured in germ-free mice or conventional mice treated with antibiotics. Succinate-induced alveolar macrophage polarisation and its effects on alveolar epithelial apoptosis were evaluated in succinate receptor 1 (Sucnr1)-deficient mice and in murine alveolar macrophages transfected with Sucnr1-short interfering RNA. Succinate levels were measured in patients undergoing cardiopulmonary bypass, including intestinal I/R. RESULTS: Succinate accumulated in lungs after intestinal I/R, and this was associated with an imbalance of succinate-producing and succinate-consuming bacteria in the gut, but not the lungs. Succinate accumulation was absent in germ-free mice and was reversed by gut microbiota depletion with antibiotics, indicating that the gut microbiota is a source of lung succinate. Moreover, succinate promoted alveolar macrophage polarisation, alveolar epithelial apoptosis and lung injury during intestinal I/R. Conversely, knockdown of Sucnr1 or blockage of SUCNR1 in vitro and in vivo reversed the effects of succinate by modulating the phosphoinositide 3-kinase-AKT/hypoxia-inducible factor-1α pathway. Plasma succinate levels significantly correlated with intestinal I/R-related lung injury after cardiopulmonary bypass. CONCLUSION: Gut microbiota-derived succinate exacerbates intestinal I/R-induced ALI through SUCNR1-dependent alveolar macrophage polarisation, identifying succinate as a novel target for gut-derived ALI in critically ill patients.

Gut microbiota dysbiosis is associated with sepsis-induced cardiomyopathy in patients: A case-control study.

BACKGROUND: Myocardial injury is a major complication of sepsis and a key factor affecting prognosis. Therefore, early and accurate diagnosis and timely management of sepsis-induced cardiomyopathy (SICM) are of great significance for the prevention and treatment of sepsis. The gut microbiota has been shown to be closely associated with sepsis or myocardial injury, but the association between the gut microbiota and SICM is not fully understood. This study aimed to explore the link between gut microbiota composition and SICM. METHODS: A case-control and single-center study of clinical features and gut microbiota profiles by Metagenome and Virome was conducted in SICM patients (n = 15) and sepsis-uninduced cardiomyopathy patients (SNICM, n = 16). RESULTS: Compared with SNICM patients, SICM patients showed significant myocardial injury and higher 28-day mortality, SOFA scores, lactate levels, and infection levels on admission. Meanwhile, differences in the composition of gut bacteria, archaea, fungi, and viruses were analyzed between the two groups. Differential gut bacteria or viruses were found to have a good predictive effect on SICM. Furthermore, gut bacteria and viruses that differed between the two groups were strongly related. The abundance of Cronobacter and Cronobacter phage was higher in the SICM group than in the SNICM group, and the receiver operating characteristic curve showed that Cronobacter and Cronobacter phage both had a good predictive effect on SICM. CONCLUSIONS: SICM patients may have specific gut microbiota signatures, and Cronobacter and Cronobacter phages have a good ability to identify and diagnose SICM.

Use of dexmedetomidine to alleviate intestinal ischemia-reperfusion injury via intestinal microbiota modulation in mice.

Background: Intestinal ischemia-reperfusion (I/R) injury is a serious condition with unacceptable mortality rates. Our previous study revealed a protective effect of dexmedetomidine (DEX) on intestinal I/R injury, but its underlying mechanism remains unclear. Gut microbiota imbalance is associated with the progression of I/R injury. We hypothesized that DEX would attenuate intestinal I/R injury via modulating gut microbiota. Methods: An I/R injury model was established in C57BL/6 mice in the presence or absence of DEX preconditioning. Some mice were treated with antibiotics to deplete intestinal bacteria. Fecal microbiota transplantation (FMT) was performed by transplanting the feces of DEX-pretreated mice into a new batch of I/R mice. We analyzed the expression of Bacteroidetes and Firmicutes in feces, survival rate, and inflammatory cytokines. Results: DEX reversed I/R-induced bacterial abnormalities by increasing the ratio of Firmicutes to Bacteroidetes [DEX + I/R 3.02±0.36 vs. normal saline (NS) + I/R 0.82±0.15; 95% CI: 0.80-3.60; P<0.05] and was accompanied by increased 72-hour survival (0.40±0.16 vs. 0.10±0.09; P<0.05). The protective effect of DEX did not significantly differ from that of DEX + antibiotics. Furthermore, the bacteria of the DEX-pretreated mice decreased the release of inflammatory factors. Conclusions: This study revealed that DEX can alleviate intestinal I/R injury through a microbiota-related mechanism, providing a potential avenue for the management of intestinal I/R injury.

Gut microbiota-derived indole 3-propionic acid partially activates aryl hydrocarbon receptor to promote macrophage phagocytosis and attenuate septic injury.

Sepsis is associated with a high risk of death, and the crosstalk between gut microbiota and sepsis is gradually revealed. Indole 3-propionic acid (IPA) is a gut microbiota-derived metabolite that exerts immune regulation and organ protective effects. However, the role of IPA in sepsis is not clear. In this study, the role of IPA in sepsis-related survival, clinical scores, bacterial burden, and organ injury was assessed in a murine model of cecal ligation and puncture-induced polymicrobial sepsis. Aryl hydrocarbon receptor (AhR) highly specific inhibitor (CH223191) was used to observe the role of AhR in the protection of IPA against sepsis. The effects of IPA on bacterial phagocytosis by macrophages were investigated in vivo and vitro. The levels of IPA in feces were measured and analyzed in human sepsis patients and patient controls. First, we found that gut microbiota-derived IPA was associated with the survival of septic mice. Then, in animal model, IPA administration protected against sepsis-related mortality and alleviated sepsis-induced bacterial burden and organ injury, which was blunted by AhR inhibitor. Next, in vivo and vitro, IPA enhanced the macrophage phagocytosis through AhR. Depletion of macrophages reversed the protective effects of IPA on sepsis. Finally, on the day of ICU admission (day 0), septic patients had significantly lower IPA level in feces than patient controls. Also, septic patients with bacteremia had significantly lower IPA levels in feces compared with those with non-bacteremia. Furthermore, in septic patients, reduced IPA was associated with worse clinical outcomes, and IPA in feces had similar prediction ability of 28-day mortality with SOFA score, and increased the predictive ability of SOFA score. These findings indicate that gut microbiota-derived IPA can protect against sepsis through host control of infection by promoting macrophages phagocytosis and suggest that IPA may be a new strategy for sepsis treatment.

The role of intestinal microbiota and its metabolites in intestinal and extraintestinal organ injury induced by intestinal ischemia reperfusion injury.

Intestinal ischemia/reperfusion (I/R) is a common pathophysiological process in clinical severe patients, and the effect of intestinal I/R injury on the patient's systemic pathophysiological state is far greater than that of primary intestinal injury. In recent years, more and more evidence has shown that intestinal microbiota and its metabolites play an important role in the occurrence, development, diagnosis and treatment of intestinal I/R injury. Intestinal microbiota is regulated by host genes, immune response, diet, drugs and other factors. The metabolism and immune potential of intestinal microbiota determine its important significance in host health and diseases. Therefore, targeting the intestinal microbiota and its metabolites may be an effective therapy for the treatment of intestinal I/R injury and intestinal I/R-induced extraintestinal organ injury. This review focuses on the role of intestinal microbiota and its metabolites in intestinal I/R injury and intestinal I/R-induced extraintestinal organ injury, and summarizes the latest progress in regulating intestinal microbiota to treat intestinal I/R injury and intestinal I/R-induced extraintestinal organ injury.

Association Between Gut Dysbiosis and Sepsis-Induced Myocardial Dysfunction in Patients With Sepsis or Septic Shock.

Objective: Sepsis-induced myocardial dysfunction (SIMD) seriously affects the evolution and prognosis of the sepsis patient. The gut microbiota has been confirmed to play an important role in sepsis or cardiovascular diseases, but the changes and roles of the gut microbiota in SIMD have not been reported yet. This study aims to assess the compositions of the gut microbiota in sepsis or septic patients with or without myocardial injury and to find the relationship between the gut microbiota and SIMD. Methods: The prospective, observational, and 1:1 matched case-control study was conducted to observe gut microbiota profiles from patients with SIMD (n = 18) and matched non-SIMD (NSIMD) patients (n = 18) by 16S rRNA gene sequencing. Then the relationship between the relative abundance of microbial taxa and clinical indicators and clinical outcomes related to SIMD was analyzed. The receiver operating characteristic (ROC) curves were used to evaluate the predictive efficiencies of the varied gut microbiota to SIMD. Results: SIMD was associated with poor outcomes in sepsis patients. The beta-diversity of the gut microbiota was significantly different between the SIMD patients and NSIMD subjects. The gut microbiota profiles in different levels significantly differed between the two groups. Additionally, the abundance of some microbes (Klebsiella variicola, Enterobacteriaceae, and Bacteroides vulgatus) was correlated with clinical indicators and clinical outcomes. Notably, ROC analysis indicated that K. variicola may be a potential biomarker of SIMD. Conclusion: Our study indicates that SIMD patients may have a particular gut microbiota signature and that the gut microbiota might be a potential diagnostic marker for evaluating the risk of developing SIMD.

Propionate alleviates myocardial ischemia-reperfusion injury aggravated by Angiotensin II dependent on caveolin-1/ACE2 axis through GPR41.

Myocardial ischemia/reperfusion (I/R) injury is still a lack of effective therapeutic drugs, and its molecular mechanism is urgently needed. Studies have shown that the intestinal flora plays an important regulatory role in cardiovascular injury, but the specific mechanism has not been fully elucidated. In this study, we found that an increase in Ang II in plasma was accompanied by an increase in the levels of myocardial injury during myocardial reperfusion in patients with cardiopulmonary bypass. Furthermore, Ang II treatment enhanced mice myocardial I/R injury, which was reversed by caveolin-1 (CAV-1)-shRNA or strengthened by angiotensin-converting enzyme 2 (ACE2)-shRNA. The results showed that CAV-1 and ACE2 have protein interactions and inhibit each other's expression. In addition, propionate, a bacterial metabolite, inhibited the elevation of Ang II and myocardial injury, while GPR41-shRNA abolished the protective effects of propionate on myocardial I/R injury. Clinically, the propionate content in the patient's preoperative stool was related to Ang II levels and myocardial I/R injury levels during myocardial reperfusion. Taken together, propionate alleviates myocardial I/R injury aggravated by Ang II dependent on CAV-1/ACE2 axis through GPR41, which provides a new direction that diet to regulate the intestinal flora for treatment of myocardial I/R injury.

Predictive and Preventive Potential of Preoperative Gut Microbiota in Chronic Postoperative Pain in Breast Cancer Survivors.

BACKGROUND: Evidence suggests a potential relationship between gut microbiota and chronic postoperative pain (CPP). This study aimed to explore the predictive and preventive potential of preoperative gut microbiota in CPP in breast cancer survivors. METHODS: In the clinical experiments, we designed a nested case-control study to compared preoperative gut microbiota of breast cancer survivors with and without CPP using 16s rRNA sequencing. The primary outcome was clinically meaningful pain in or around the operative area 3 months after surgery. Logistic prediction models based on previously identified risk factors for CPP in breast cancer survivors were tested with and without differential bacteria to evaluate the model's potential for improvement with the addition of gut microbiota information. In the animal experiments, preoperative fecal microbiota was transplanted from patients with and without CPP to mice, and a spared nerve injury (SNI) model was used to mimic neuropathic pain in CPP. Mechanical hyperalgesia and the expression of markers of spinal microglia and peroxisome proliferator-activated receptor-γ (PPAR-γ) were assessed. RESULTS: Sixty-six CPP patients and 66 matched controls were analyzed. Preoperative gut microbiota composition was significantly different in the 2 groups at phylus, family, and genera levels. The discrimination of the clinical prediction model (determined by area under the receiver operating characteristic curve) improved by 0.039 and 0.099 after the involvement of differential gut microbiota at the family and genus levels, respectively. After fecal microbiota transplantation (FMT), "CPP microbiota" recipient mice exhibited significantly increased mechanical hyperalgesia and decreased expression of Ppar-γ and arginase-1 (Arg-1) in the spinal cord. CONCLUSIONS: Preoperative gut microbiota has the potential to predict and prevent the development of CPP and plays a causal role in its development via the PPAR-γ-microglia pathway in the spinal cord. Thus, it could be targeted to develop a prevention strategy for CPP in breast cancer survivors.

Gut Microbial Metabolite Pravastatin Attenuates Intestinal Ischemia/Reperfusion Injury Through Promoting IL-13 Release From Type II Innate Lymphoid Cells via IL-33/ST2 Signaling.

Intestinal ischemia/reperfusion (I/R) injury is a grave condition with high morbidity and mortality. We previously confirmed that intestinal I/R induces intestinal flora disorders and changes in metabolites, but the role of different metabolites in intestinal I/R injury is currently unclear. Based on targeted metabolic sequencing, pravastatin (PA) was determined to be a metabolite of the gut microbiota. Further, intestinal I/R model mice were established through superior mesenteric artery obstruction. In addition, a co-culture model of small intestinal organoids and type II innate lymphoid cells (ILC2s) was subjected to hypoxia/reoxygenation (H/R) to simulate an intestinal I/R model. Moreover, correlation analysis between the PA level in preoperative feces of patients undergoing cardiopulmonary bypass and the indices of postoperative intestinal I/R injury was carried out. IL-33-deficient mice, ILC2-deleted mice, and anti-IL-13 neutralizing antibodies were also used to explore the potential mechanism through which PA attenuates intestinal I/R injury. We demonstrated that PA levels in the preoperative stool of patients undergoing cardiopulmonary bypass were negatively correlated with the indices of postoperative intestinal I/R injury. Furthermore, PA alleviated intestinal I/R injury and improved the survival of mice. We further showed that PA promotes IL-13 release from ILC2s by activating IL-33/ST2 signaling to attenuate intestinal I/R injury. In addition, IL-13 promoted the self-renewal of intestinal stem cells by activating Notch1 and Wnt signals. Overall, results indicated that the gut microbial metabolite PA can attenuate intestinal I/R injury by promoting the release of IL-13 from ILC2s via IL-33/ST2 signaling, revealing a novel mechanism of and therapeutic strategy for intestinal I/R injury.

The gut microbiota metabolite capsiate promotes Gpx4 expression by activating TRPV1 to inhibit intestinal ischemia reperfusion-induced ferroptosis.

Ferroptosis, a new type of cell death has been found to aggravate intestinal ischemia/reperfusion (I/R) injury. However, little is known about the changes of gut microbiota and metabolites in intestinal I/R and the role of gut microbiota metabolites on ferroptosis-induced intestinal I/R injury. This study aimed to establish a mouse intestinal I/R model and ileum organoid hypoxia/reoxygenation (H/R) model to explore the changes of the gut microbiota and metabolites during intestinal I/R and protective ability of capsiate (CAT) against ferroptosis-dependent intestinal I/R injury. Intestinal I/R induced disturbance of gut microbiota and significant changes in metabolites. We found that CAT is a metabolite of the gut microbiota and that CAT levels in the preoperative stool of patients undergoing cardiopulmonary bypass were negatively correlated with intestinal I/R injury. Furthermore, CAT reduced ferroptosis-dependent intestinal I/R injury in vivo and in vitro. However, the protective effects of CAT against ferroptosis-dependent intestinal I/R injury were abolished by RSL3, an inhibitor of glutathione peroxidase 4 (Gpx4), which is a negative regulator of ferroptosis. We also found that the ability of CAT to promote Gpx4 expression and inhibit ferroptosis-dependent intestinal I/R injury was abrogated by JNJ-17203212, an antagonist of transient receptor potential cation channel subfamily V member 1 (TRPV1). This study suggests that the gut microbiota metabolite CAT enhances Gpx4 expression and inhibits ferroptosis by activating TRPV1 in intestinal I/R injury, providing a potential avenue for the management of intestinal I/R injury.

Ribonuclease attenuates acute intestinal injury induced by intestinal ischemia reperfusion in mice.

Ribonuclease (RNase) reportedly exerts organ-protective effects in several pathological conditions, including ischemia reperfusion (I/R), but whether it can exhibit protective effect on intestinal I/R injury and potential mechanisms remain unknown. The present study was aimed to evaluate the effects of RNase on intestinal I/R injury and explore the underlying mechanisms. Thirty-two wild-type C57BL/6J adult male mice were evenly divided into a sham group, a sham + RNase group, an I/R group and an I/R + RNase group. Intestinal I/R was produced by clamping the superior mesenteric artery for 1 h followed by reperfusion for 2 h. All mice were treated with 3 doses of RNase or the same dosage of normal saline at different points. It was found that intestinal I/R caused significant intestinal injury and an increase in levels of extracellular RNAs (exRNAs). Treatment with RNase significantly reduced the inflammatory cytokine production, inhibited intestinal apoptosis and down-regulated the expression of toll like receptor 3 in intestinal tissues. In conclusion, increased exRNAs may contribute to intestinal I/R injury in adult mice, and RNase treatment during perioperative window is effective for attenuating intestinal I/R injury.