miR-379-5P INHIBITION ENHANCES INTESTINAL EPITHELIAL PROLIFERATION AND BARRIER FUNCTION RECOVERY AFTER ISCHEMIA/REPERFUSION BY TARGETING EIF4G2

ABSTRACT

Gut barrier dysfunction caused by intestinal ischemia/reperfusion (I/R) injury is associated with substantial death and morbidity. In this research, the role of microRNAs (miRNAs) in regulating intestinal I/R injury was investigated. We used miRNA sequencing to analyze clinical ischemic and normal intestinal samples. Through bioinformatics analysis based on sequencing results, we found that upregulated miRNAs inhibited epithelial barrier function and cell proliferation, with miR-379-5p being the most significantly upregulated in the ischemic intestine. Further studies confirmed the role of miR-379-5p through experiments in the human ischemic intestine, the mouse I/R injury model in vivo , and cell hypoxia/reoxygenation models in vitro . Inhibiting miR-379-5p increased epithelial cell proliferation and improved barrier function after I/R injury. We also identified eukaryotic translation initiation factor 4 gamma 2 (EIF4G2) as a downstream target gene of miR-379-5p through bioinformatics prediction and experimental verification. The findings suggest that inhibiting miR-379-5p could improve intestinal epithelial cell proliferation and barrier function by targeting EIF4G2. The goal of this study was to find a potential target for treating I/R injury in the intestine, as well as to prevent and mitigate the damage caused.

cGAS-STING signaling pathway in intestinal homeostasis and diseases

The intestinal mucosa is constantly exposed to commensal microbes, opportunistic pathogens, toxins, luminal components and other environmental stimuli. The intestinal mucosa consists of multiple differentiated cellular and extracellular components that form a critical barrier, but is also equipped for efficient absorption of nutrients. Combination of genetic susceptibility and environmental factors are known as critical components involved in the pathogenesis of intestinal diseases. The innate immune system plays a critical role in the recognition and elimination of potential threats by detecting pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs). This host defense is facilitated by pattern recognition receptors (PRRs), in which the cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) pathway has gained attention due to its role in sensing host and foreign double-stranded DNA (dsDNA) as well as cyclic dinucleotides (CDNs) produced by bacteria. Upon binding with dsDNA, cGAS converts ATP and GTP to cyclic GMP-AMP (cGAMP), which binds to STING and activates TANK binding kinase 1 (TBK1) and interferon regulatory factor 3 (IRF3), inducing type I interferon (IFN) and nuclear factor kappa B (NF-κB)-mediated pro-inflammatory cytokines, which have diverse effects on innate and adaptive immune cells and intestinal epithelial cells (IECs). However, opposite perspectives exist regarding the role of the cGAS-STING pathway in different intestinal diseases. Activation of cGAS-STING signaling is associated with worse clinical outcomes in inflammation-associated diseases, while it also plays a critical role in protection against tumorigenesis and certain infections. Therefore, understanding the context-dependent mechanisms of the cGAS-STING pathway in the physiopathology of the intestinal mucosa is crucial for developing therapeutic strategies targeting the cGAS-STING pathway. This review aims to provide insight into recent findings of the protective and detrimental roles of the cGAS-STING pathway in intestinal diseases.

6-Shogaol from Dried Ginger Protects against Intestinal Ischemia/Reperfusion by Inhibiting Cell Apoptosis via the BDNF/TrkB/PI3K/AKT Pathway

SCOPE

Intestinal ischemia-reperfusion (II/R) injury is a common pathological process with high morbidity and mortality. Effective prevention and treatment therapies for II/R are clinically necessary. 6-Shogaol (6-SG), the main active ingredient in dried ginger, behaviors multiple biological activities, including anti-inflammation, antioxidation, and anti-apoptosis. This study aims to elucidate the protective effects and mechanism of 6-SG against II/R-induced injury.

METHODS AND RESULTS

Sprague-Dawley rats are pre-treated orally with 6-SG and subjected to II/R injury by clamping superior mesenteric artery for 1 h and reperfusion for 2 h. Caco-2 cells are challenged by hypoxia/reoxygenation to mimic II/R in vitro. 6-SG pre-treatment protects against II/R injury by reducing intestinal morphological damage and intestinal barrier injury via inhibiting cell apoptosis. Network pharmacology and molecular docking analyses reveal that 6-SG has a high affinity with brain-derived neurotrophic factor (BDNF) formed homodimer or heterodimer with NT4 instead of the monomer, and thus the dimer configuration is stabilized, activating BDNF/TrkB/PI3K/AKT signaling pathway and inhibiting II/R-induced cell apoptosis. The outcome is further validated both in vivo and in vitro.

CONCLUSION

6-Shogaol protects against II/R injury by inhibiting cell apoptosis through the BDNF/TrkB/PI3K/AKT pathway. This study offers a new understanding of the protection mechanism of 6-SG against II/R-induced injury.

Activation of GPR81 aggravated intestinal ischemia/reperfusion injury-induced acute lung injury via HMGB1-mediated neutrophil extracellular traps formation

INTRODUCTION

Intestinal ischemia/reperfusion (II/R) injury is a life-threatening situation accompanied by severe organ injury, especially acute lung injury (ALI). A great body of evidence indicates that II/R injury is usually associated with hyperlactatemia. G-protein-coupled receptor 81 (GPR81), a receptor of lactate, has been recognized as a regulatory factor in inflammation, but whether it was involved in II/R injury-induced ALI is still unknown.

METHODS

To establish the II/R injury model, the superior mesenteric artery of the mice was occluded gently by a microvascular clamp for 45 min to elicit intestinal ischemia and then a 90-min reperfusion was performed. Broncho-alveolar lavage fluid (BALF) and lung tissues were obtained to evaluate the lung injury after II/R. The pulmonary histopathological alteration was evaluated by H&E staining. The concentration of proteins, the number of infiltrated cells, and the level of IL-6 were measured in BALF. The formation of neutrophil extracellular traps (NETs) was evaluated by the level of double-stranded DNA (dsDNA) and myeloperoxidase- double-stranded DNA (MPO-dsDNA) complex in BALF, and the content of citrullinated histone H3 (Cit-H3) in lung tissue. The level of HMGB1 in the BALF and plasma was measured by enzyme linked immunosorbent assay (ELISA).

RESULTS

Administration of the GPR81 agonist 3,5-dihydroxybenzoic acid (DHBA) aggravated II/R injury-induced lung histological abnormalities, upregulated the concentration of proteins, the number of infiltrated cells, and the level of IL-6 in BALF. In addition, DHBA treatment increased the level of dsDNA and MPO-dsDNA complex in BALF, and promoted the elevation of Cit-H3 in lung tissue and the release of HMGB1 in BALF and plasma.

CONCLUSION

After induction of ALI by II/R, the administration of DHBA aggravated ALI through NETs formation in the lung.

H151, A SMALL MOLECULE INHIBITOR OF STING AS A NOVEL THERAPEUTIC IN INTESTINAL ISCHEMIA-REPERFUSION INJURY

BACKGROUND

Intestinal ischemia-reperfusion (I/R) injury is a severe disease associated with high mortality. Stimulator of interferon genes (STING) is an intracellular protein that is activated by cytosolic DNA and is implicated in I/R injury, resulting in transcription of type I interferons (IFN-α and IFN-β) and other proinflammatory molecules. Extracellular cold-inducible RNA-binding protein (eCIRP), a damage-associated molecular pattern, induces STING activation. H151 is a small molecule inhibitor of STING that has not yet been studied as a potential therapeutic. We hypothesize that H151 reduces inflammation, tissue injury, and mortality after intestinal I/R. Methods: In vitro, RAW264.7 cells were pretreated with H151 then stimulated with recombinant murine (rm) CIRP, and IFN-β levels in the culture supernatant were measured at 24 hours after stimulation. In vivo, male C57BL/6 mice were subjected to 60-minute intestinal ischemia via superior mesenteric artery occlusion. At the time of reperfusion, mice were intraperitoneally instilled with H151 (10 mg/kg BW) or 10% Tween-80 in PBS (vehicle). Four hours after reperfusion, the small intestines, lungs, and serum were collected for analysis. Mice were monitored for 24 hours after intestinal I/R to assess survival. Results: In vitro, H151 reduced rmCIRP-induced IFN-β levels in a dose-dependent manner. In vivo, intestinal levels of pIRF3 were increased after intestinal I/R and decreased after H151 treatment. There was an increase in serum levels of tissue injury markers (lactate dehydrogenase, aspartate aminotransferase) and cytokine levels (interleukin 1β, interleukin 6) after intestinal I/R, and these levels were decreased after H151 treatment. Ischemia-reperfusion-induced intestinal and lung injury and inflammation were significantly reduced after H151 treatment, as evaluated by histopathologic assessment, measurement of cell death, chemokine expression, neutrophil infiltration, and myeloperoxidase activity. Finally, H151 improved the survival rate from 41% to 81% after intestinal I/R. Conclusions: H151, a novel STING inhibitor, attenuates the inflammatory response and reduces tissue injury and mortality in a murine model of intestinal I/R. H151 shows promise as a potential therapeutic in the treatment of this disease.

Gut-Derived Exosomes Induce Liver Injury After Intestinal Ischemia/Reperfusion by Promoting Hepatic Macrophage Polarization

Liver injury induced by intestinal ischemia/reperfusion (I/R) is accompanied by the polarization of Kupffer cells, which are specialized macrophages located in the liver. However, the causes of hepatic macrophage polarization after intestinal I/R remain unknown. This study investigated whether gut-derived exosomes contribute to the pathogenesis of liver injury triggered by intestinal I/R in a murine model and explored the underlying mechanisms. Intestinal I/R models were established by temporally clamping the superior mesenteric arteries of mice. Exosomes were isolated from the intestinal tissue of mice that underwent intestinal I/R or sham surgery according to a centrifugation-based protocol. Exosomes were co-cultured with RAW 264.7 macrophages or injected intravenously in mice. Liposomal clodronate was administered intraperitoneally to deplete the macrophages. Macrophage polarization was determined by flow cytometry, immunohistochemistry, and quantitative polymerase chain reaction. Liver injury was assessed by histological morphology and increased serum aspartate aminotransferase and alanine aminotransferase levels. Exosomes from mice intestines subjected to I/R (IR-Exo) promoted macrophage activation in vitro. Intravenous injection of IR-Exo caused hepatic M1 macrophage polarization and led to liver injury in mice. Depleting macrophages ameliorated liver injury caused by intestinal I/R or the injection of IR-Exo. Furthermore, inhibiting exosome release improved intestinal injury, liver function, and survival rates of mice subjected to intestinal I/R. Our study provides evidence that gut-derived exosomes induce liver injury after intestinal I/R by promoting hepatic M1 macrophage polarization. Inhibition of exosome secretion could be a therapeutic target for preventing hepatic impairment after intestinal I/R.

Tofacitinib protects intestinal epithelial cells against oxygen-glucose deprivation/reoxygenation injury by inhibiting the JAK/STAT3 signaling pathway

The present study aimed to investigate the role and potential mechanism of action of tofacitinib (Tofa) in intestinal ischemia/reperfusion (I/R) injury. The normal rat small intestine epithelial cell line, IEC-6, was used to establish an I/R injury model by inducing oxygen-glucose deprivation/reoxygenation (OGD/R). Cells were divided into the following five groups: Control, OGD/R, OGD/R with 50, 100 and 200 nM Tofa. Following Tofa administration, cell viability was measured using Cell Counting Kit-8 assay and a lactate dehydrogenase detection kit. The expression levels of cell apoptosis-related proteins, Bcl-2, cleaved-caspase-3 and cleaved-caspase-9 were detected using western blot analysis. Additionally, the levels of oxidative stress-related markers, such as reactive oxygen species (ROS), malondialdehyde (MDA) and superoxide dismutase (SOD), and inflammatory cytokines, TNF-α, IL-6 and IL-1β were assessed using the colorimetric method. Western blot analysis was also used to measure the expression levels of the Janus kinase (JAK)/STAT3 signaling pathway-related proteins, including phosphorylated (p)-JAK1, p-JAK3 and p-STAT3. Subsequently, colivelin, an agonist of the JAK/STAT3 pathway, was used to investigate whether the effects of Tofa on intestinal I/R injury were mediated by this signaling pathway. The results showed that Tofa dose-dependently elevated cell viability compared with that in the OGD/R group. By contrast, Tofa attenuated cell apoptosis, which was coupled with upregulated Bcl-2 expression, downregulated cleaved-caspase-3 and downregulated cleaved-caspase-9 levels, in OGD/R-induced IEC-6 cells. Furthermore, the contents of ROS and MDA were significantly increased following exposure to OGD/R, which were accompanied by the decreased activity of SOD. These effects were reversed following cell treatment with Tofa. Consistently, Tofa intervention reduced the secretion levels of TNF-α, IL-6 and IL-1β in a dose-dependent manner. Additionally, Tofa markedly downregulated the phosphorylation levels of JAK1, JAK3 and STAT3 in OGD/R-induced IEC-6 cells. However, treatment with colivelin markedly reversed the inhibitory effects of Tofa on cell viability, cell apoptosis, oxidative stress and inflammation. Overall, the findings of the present study suggested that Tofa could protect against intestinal I/R injury by inhibiting the JAK/STAT3 signaling pathway, which may hold promise as a therapeutic agent for intestinal I/R injury.

MicroRNA-146a overexpression alleviates intestinal ischemia/reperfusion-induced acute lung injury in mice

Previous studies have shown that microRNAs (miRs), such as miR-146a play an important role in the pathogenesis of intestinal ischemia/reperfusion (I/R)-induced injury; however, the role of miR-146a in intestinal I/R-induced acute lung injury has not been elucidated. An intestinal I/R-induced injury mouse model was established in the present study by clamping the superior mesenteric artery and expression levels of miR-146a in intestinal and lung tissue samples were evaluated using reverse transcription-quantitative PCR (RT-qPCR). Intestinal and lung histopathological characteristics in mice with intestinal I/R-induced injury were assessed by hematoxylin and eosin staining, and mRNA and protein expression levels in intestinal and lung tissue samples were evaluated using RT-qPCR and western blotting, respectively. miR-146a expression was significantly downregulated in the intestinal and lung tissue samples of mice with intestinal I/R-induced injury. Intestinal I/R injury-induced histopathological changes in the lung and intestines, and pulmonary edema in mice transduced with an adenoviral miR-146a-overexpression vector (the miR-146a overexpression group) were alleviated. mRNA expression levels of TNF-α, IL-1β, IFN-γ and TGF-β1, and protein expression levels of TNF receptor-associated factor 6, phosphorylated-p65 NF-κB, cleaved caspase-3 and cleaved caspase-9 in lung and intestinal tissue samples were downregulated in I/R-miR-146a-overexpressing mice, compared with those from the I/R-negative control group. Thus, the present study identified that pre-treatment with the miR-146a overexpression vector alleviated intestinal I/R-induced acute lung injury in mice.

Gut Ischemia Reperfusion Injury Induces Lung Inflammation via Mesenteric Lymph-Mediated Neutrophil Activation

Gut ischemia/reperfusion (I/R) injury is a common clinical problem associated with significant mortality and morbidities that result from systemic inflammation and remote organ dysfunction, typically acute lung injury. The mechanisms underlying the dissemination of gut-derived harmful mediators into the circulation are poorly understood. The objective of our study was to determine the role of mesenteric lymphatic circulation in the systemic and pulmonary inflammatory response to gut I/R. Using a murine intestinal I/R model, we evaluated whether and how blocking mesenteric lymph flow affects the inflammatory response in local tissues (gut) and remote organs (lungs). We further explored the mechanisms of post-I/R lymph-induced systemic inflammation by examining neutrophil activity and interaction with endothelial cells in vitro. Mice subjected to intestinal I/R displayed a significant inflammatory response in local tissues, evidenced by neutrophil infiltration into mucosal areas, as well as lung inflammation, evidenced by increased myeloperoxidase levels, neutrophil infiltration, and elevated microvascular permeability in the lungs. Mesenteric lymph duct ligation (MLDL) had no effect on gut injury per se, but effectively attenuated lung injury following gut I/R. Cell experiments showed that lymph fluid from post-I/R animals, but not pre-I/R, increased neutrophil surface CD11b expression and their ability to migrate across vascular endothelial monolayers. Moreover, post-I/R lymph upregulated neutrophil expression of pro-inflammatory cytokines and chemokines, which was mediated by a mechanism involving nuclear factor (NF)-κB signaling. Consistently, gut I/R activated NF-κB in lung neutrophils, which was alleviated by MLDL. In conclusion, all these data indicate that mesenteric lymph circulation contributes to neutrophil activation and lung inflammation following gut I/R injury partly through activating NF-κB.

circ-PRKCB acts as a ceRNA to regulate p66Shc-mediated oxidative stress in intestinal ischemia/reperfusion

Background: Oxidative stress has emerged as an essential factor in the pathogenesis of intestinal ischemia/reperfusion (I/R) injury. The adaptor protein p66Shc is a key regulator of reactive oxygen species (ROS) generation and a mediator of I/R damage in the intestine, but the upstream mechanisms that directly regulate p66Shc expression during intestinal I/R remain largely unknown. Recent studies have suggested that noncoding RNAs, such as circular RNAs (circRNAs), are important players in physiological and pathological processes based on their versatile regulatory roles in gene expression. The aim of this study was to elucidate the contribution of p66Shc to oxidative damage in intestinal I/R and to investigate the regulation of p66Shc by circRNA sponges.

Methods: Intestinal I/R was induced in mice via superior mesenteric artery (SMA) occlusion. A miR-339-5p agomir or circ-protein kinase C beta (PRKCB) siRNA was injected intravenously before I/R challenge. In addition, Caco-2 cells were subjected to hypoxia/reoxygenation (H/R) in vitro to simulate an in vivo I/R model.

Results:In vitro, p66Shc deficiency significantly reduced H/R-induced ROS overproduction by attenuating mitochondrial superoxide anion (O₂^-) levels, suppressing NADPH oxidase activity and enhancing antioxidant enzyme expression. Moreover, miR-339-5p was identified to directly regulate p66Shc expression in the intestine. Furthermore, we found that a circRNA transcribed from the PRKCB gene, named circ-PRKCB, acted as an endogenous miR-339-5p sponge to regulate p66Shc expression. circ-PRKCB silencing or miR-339-5p overexpression significantly downregulated p66Shc expression and attenuated oxidative stress levels and I/R injury in vivo and in vitro. Notably, the increased circ-PRKCB levels and decreased miR-339-5p levels associated with murine intestinal I/R were consistent with those in patients with intestinal infarction.

Conclusions: Our findings reveal a crucial role for the circ-PRKCB/miR-339-5p/p66Shc signaling pathway in regulating oxidative stress in the I/R intestine. This pathway may be a potential therapeutic target for intestinal I/R injury.

HB-EGF improves intestinal microcirculation after hemorrhagic shock

BACKGROUND

The goal of this study was to determine the role of heparin-binding epidermal growth factor-like growth factor (HB-EGF) as a mediator of gut microcirculation after hemorrhagic shock and resuscitation (HS/R) in mice.

MATERIALS AND METHODS

HS/R was induced in HB-EGF knockout (KO) and wild type (WT) mice. Ink-gelatin injection and vascular corrosion casting were performed to visualize the gut microvasculature. The degree of gut microcirculatory injury was graded using five patterns of injury (1-5) according to the severity of microvascular hypoperfusion. Statistical analyses were performed using linear mixed models with P < 0.05 considered statistically significant.

RESULTS

HB-EGF KO mice subjected to HS/R had significantly decreased perfusion of the gut microvasculature compared with WT mice subjected to HS/R (P = 0.0001). HB-EGF KO mice subjected to HS/R and treated with exogenous HB-EGF had significantly increased gut microvascular perfusion compared with non-HB-EGF treated KO mice (P = 0.01). Lastly, WT mice subjected to HS/R and treated with HB-EGF had significantly increased gut microvascular perfusion compared with non-HB-EGF-treated WT mice (P = 0.04).

CONCLUSIONS

HB-EGF improves gut microcirculation after HS/R. These findings support the clinical use of HB-EGF in protection of the intestines from disease states associated with intestinal hypoperfusion injury.