Ghrelin Alleviates Intestinal Dysfunction in Sepsis Through the KLF4/MMP2 Regulatory Axis by Activating SIRT1

PLASMA PROTEOME, METABOLOME MENDELIAN RANDOMIZATION IDENTIFIES SEPSIS THERAPEUTIC TARGETS

ABSTRACT

Background : The interrelation between the plasma proteome and plasma metabolome with sepsis presents a multifaceted dynamic that necessitates further research to elucidate the underlying causal mechanisms. Methods : Our investigation used public genome-wide association study data to explore the relationships among the plasma proteome, metabolome, and sepsis, considering different sepsis subgroup. Initially, two-sample Mendelian randomization established causal connections between the plasma proteome and metabolome with sepsis. Subsequently, multivariate and iterative Mendelian randomization analyses were performed to understand the complex interactions in plasma during sepsis. The validity of these findings was supported by thorough sensitivity analyses. Result : The study identified 25 plasma proteins that enhance risk and 34 that act as protective agents in sepsis. After P value adjustment (0.05/1306), ICAM5 emerged with a positive correlation to sepsis susceptibility ( P value = 2.14E-05, OR = 1.10, 95% CI = 1.05-1.15), with this significance preserved across three sepsis subgroup examined. Additionally, 29 plasma metabolites were recognized as risk factors, and 15 as protective factors for sepsis outcomes. After P value adjustment (0.05/997), elevated levels of 1,2,3-benzenetriol sulfate (2) was significantly associated with increased sepsis risk ( P value = 3.37E-05, OR = 1.18, 95% CI = 1.09-1.28). Further scrutiny revealed that this plasma metabolite notably augments the abundance of ICAM5 protein ( P value = 3.52E-04, OR = 1.11, 95% CI = 1.04-1.17), devoid of any detected heterogeneity, pleiotropy, or reverse causality. Mediated Mendelian randomization revealed ICAM5 mediated 11.9% of 1,2,3-benzenetriol sulfate (2)'s total effect on sepsis progression. Conclusion : This study details the causal link between the plasma proteome and metabolome with sepsis, highlighting the roles of ICAM5 and 1,2,3-benzenetriol sulfate (2) in sepsis progression, both independently and through crosstalk.

AQP3 mediates autophagy through SIRT1/p62 signal to alleviate intestinal epithelial cell damage caused by sepsis

BACKGROUND

Autophagy damage will aggravate intestinal damage caused by sepsis. Studies have shown that the activation of AQP3 and SIRT1 signals can reduce the inflammatory response of sepsis. However, their role and mechanism in intestinal injury in the late stage of sepsis are not deeply studied.

OBJECTIVE

To explore whether AQP3 can mediate autophagy by regulating the SIRT1/P62 signaling pathway to alleviate intestinal epithelial cell damage caused by sepsis.

METHODS

Caco-2 cells were transfected with plasmid to overexpress AQP3. Western blot and RT-qPCR were used to detect the expression of cell protein, ELISA was used to detect the level of cytokines, DCFH-DA probe was added to quantify the ROS level, and the integrity of cell barrier was evaluated by measuring the transepithelial resistance (TEER). The autophagy levels were observed by MDC staining, and the levels of ZO-1 and Occludin were detected by immunofluorescence.

RESULTS

AQP3 was down-regulated in the Caco-2 cell injury model induced by LPS in vitro. Overexpression of AQP3 inhibited the production of inflammatory factors and ROS, thus relieving LPS-induced intestinal epithelial cell damage; restored the TEER of cells; up-regulated the expression of claudin-1, TJP-1, Occludin, and ZO-1, thus alleviating the cell barrier injury; increased autophagy bodies in cells; and increased the expression of Beclin1 and the ratio of LC3-II/LC3-I while inhibiting the expression of p62, thus restoring the autophagy level of cells. However, autophagy inhibitor 3-MA and SIRT1 inhibitor EX 527 offset these effects of AQP3 overexpression.

CONCLUSION

AQP3 regulated the autophagy level of Caco-2 cells induced by LPS through SIRT1/p62 signal and relieved intestinal epithelial cell damage caused by sepsis.

Ghrelin alleviates intestinal ischemia-reperfusion injury by activating the GHSR-1α/Sirt1/FOXO1 pathway

Ischemia-reperfusion (IR) injury is primarily characterized by the restoration of blood flow perfusion and oxygen supply to ischemic tissue and organs, but it paradoxically leads to tissue injury aggravation. IR injury is a challenging pathophysiological process that is difficult to avoid clinically and frequently occurs during organ transplantation, surgery, shock resuscitation, and other processes. The major causes of IR injury include increased levels of free radicals, calcium overload, oxidative stress, and excessive inflammatory response. Ghrelin is a newly discovered brain-intestinal peptide with anti-inflammatory and antiapoptotic effects that improve blood supply. The role and mechanism of ghrelin in intestinal ischemia-reperfusion (IIR) injury remain unclear. We hypothesized that ghrelin could attenuate IIR-induced oxidative stress and apoptosis. To investigate this, we established IIR by using a non-invasive arterial clip to clamp the root of the superior mesenteric artery (SMA) in mice. Ghrelin was injected intraperitoneally at a dose of 50 μg/kg 20 min before IIR surgery, and [D-Lys3]-GHRP-6 was injected intraperitoneally at a dose of 12 nmol/kg 20 min before ghrelin injection. We mimicked the IIR process with hypoxia-reoxygenation (HR) in Caco-2 cells, which are similar to intestinal epithelial cells in structure and biochemistry. Our results showed that ghrelin inhibited IIR/HR-induced oxidative stress and apoptosis by activating GHSR-1α. Moreover, it was found that ghrelin activated the GHSR-1α/Sirt1/FOXO1 signaling pathway. We further inhibited Sirt1 and found that Sirt1 was critical for ghrelin-mediated mitigation of IIR/HR injury. Overall, our data suggest that pretreatment with ghrelin reduces oxidative stress and apoptosis to attenuate IIR/HR injury by binding with GHSR-1α to further activate Sirt1.

Intestinal epithelial Krüppel-like factor 4 alleviates endotoxemia and atherosclerosis through improving NF-κB/miR-34a-mediated intestinal permeability

Maintenance of intestinal barrier function contributes to gastrointestinal homeostasis and therefore cardiovascular diseases. A number of studies show that intestinal permeability is affected by excessive inflammatory responses. Krüppel-like factor (KLF) 4 is one of the critical transcriptional factors, which controls multiple immune responses. In this study we investigated the role of KLF4 in regulating intestinal inflammation and permeability during the atherosclerotic process. Atherosclerotic model was established in ApoE-/- mice by feeding a high fat high cholesterol (HFHC) diet. We showed that colon expression levels of KLF4 and tight junction proteins were significantly decreased whereas inflammatory responses increased in atherosclerotic mice. Overexpression of colon epithelial Klf4 decreased atherosclerotic plaque formation and vascular inflammation in atherosclerotic mice, accompanied by remarkable suppression of intestinal NF-κB activation. We found that overexpression of epithelial Klf4 in atherosclerotic mice significantly increased intestinal tight junction expression and ameliorated endotoxemia, whereas replenishment of LPS abolished these benefits. Overexpression of Klf4 reversed LPS-induced permeability and downregulation of ZO-1 and Occludin in Caco-2 cells in vitro. HFHC diet stimulated the expression of epithelial microRNA-34a, whereas silence of epithelial Klf4 abolished the benefits of microRNA-34a sponge, a specific miR-34a inhibitor, on intestinal permeability and atherosclerotic development. A clinical cohort of 24 atherosclerotic patients supported colon KLF4/NF-κB/tight junction protein axis mediated intestine/cardiovascular interaction in patients with atherosclerosis. Taken together, intestinal epithelial KLF4 protects against intestinal inflammation and barrier dysfunction, ameliorating atherosclerotic plaque formation.

SNP-SNP positive interaction between MMP2 and MMP12 increases the risk of COPD

Determining SNP-SNP interaction of the disease has become important for further investigation of pathogenesis and experimental research. Although many studies have been published on the effect of MMPs gene polymorphisms on chronic obstructive pulmonary disease (COPD), there is a lack of information on SNP-SNP and SNP-environment interactions. This study aimed to investigate the interaction between the polymorphisms of MMP1, MMP2, MMP9 and MMP12 genes and its combined effect with smoking on the risk of developing COPD. Totally 181 COPD patients and 292 healthy individuals were involved. Blood samples from the participants were tested for genotyping and data were collected through questionnaires. Genotyping was performed with nested allele-specific polymerase chain reaction (AS-PCR) and polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). SNP-SNP and SNP-environment interactions were investigated using multifactor dimensionality reduction and logistic regression analysis. The result showed that participants with high nicotine dependence and heavy smokers had a higher risk of COPD than non-smokers. Also, G/G genotype (cOR = 5.83; 95% CI, 1.19-28.4, p = 0.029) of MMP2 rs243864 and T/T genotype (cOR = 1.79; 95% CI, 1.16-2.76, p = 0.008) of MMP12 rs652438 independently contributes to the susceptibility of COPD. For SNP-SNP interaction, the positive interaction between rs243864 G/G genotype of MMP2 and rs652438 T/T genotype of MMP12 was found, and the combination of risk genotypes has a high risk of COPD (OR = 12.92; 95% CI, 1.46-114.4, p = 0.021). Moreover, the combination of T/T genotype of MMP12 rs652438 and smoking-related factors increases the risk of COPD approximately 4.5 to 6-fold. The results suggests that there is a combination of MMP2, MMP12, and smoking-related factors may increase the risk of developing COPD.

Ghrelin in Focus: Dissecting Its Critical Roles in Gastrointestinal Pathologies and Therapies

This review elucidates the critical role of ghrelin, a peptide hormone mainly synthesized in the stomach in various gastrointestinal (GI) diseases. Ghrelin participates in diverse biological functions ranging from appetite regulation to impacting autophagy and apoptosis. In sepsis, it reduces intestinal barrier damage by inhibiting inflammatory responses, enhancing GI blood flow, and modulating cellular processes like autophagy and apoptosis. Notably, in inflammatory bowel disease (IBD), serum ghrelin levels serve as markers for distinguishing between active and remission phases, underscoring its potential in IBD treatment. In gastric cancer, ghrelin acts as an early risk marker, and due to its significant role in increasing the proliferation and migration of gastric cancer cells, the ghrelin-GHS-R axis is poised to become a target for gastric cancer treatment. The role of ghrelin in colorectal cancer (CRC) remains controversial; however, ghrelin analogs have demonstrated substantial benefits in treating cachexia associated with CRC, highlighting the therapeutic potential of ghrelin. Nonetheless, the complex interplay between ghrelin's protective and potential tumorigenic effects necessitates a cautious approach to its therapeutic application. In post-GI surgery scenarios, ghrelin and its analogs could be instrumental in enhancing recovery and reducing complications. This article accentuates ghrelin's multifunctionality, shedding light on its influence on disease mechanisms, including inflammatory responses and cancer progression, and examines its therapeutic potential in GI surgeries and disorders, advocating for continued research in this evolving field.

Ghrelin/GHSR Axis Induced M2 Macrophage and Alleviated Intestinal Barrier Dysfunction in a Sepsis Rat Model by Inactivating E2F1/NF-κB Signaling

Sepsis is an inflammatory reaction disorder state that is induced by infection. The activation and regulation of the immune system play an essential role in the development of sepsis. Our previous studies have shown that ghrelin ameliorates intestinal dysfunction in sepsis. Very little is known about the mechanism of ghrelin and its receptor (GHSR) on the intestinal barrier and the immune function of macrophage regulation. Our research is to investigate the regulatory effect and molecular mechanism of the ghrelin/GHSR axis on intestinal dysfunction and macrophage polarization in septic rats. A rat model of sepsis was established by cecal ligation and puncture (CLP) operation. Then, the sepsis rats were treated with a ghrelin receptor agonist (TZP-101) or ghrelin inhibitor (obestatin). The results suggested that TZP-101 further enhanced ghrelin and GHSR expressions in the colon and spleen of septic rats and obestatin showed the opposite results. Ghrelin/GHSR axis ameliorated colonic structural destruction and intestinal epithelial tight junction injury in septic rats. In addition, the ghrelin/GHSR axis promoted M2-type polarization of macrophages, which was characterized by the decreases of IL-1β, IL-6, and TNF-α, as well as the increase of IL-10. Mechanistically, the ghrelin/GHSR axis promoted E2F2 expression and suppressed the activation of the NF-κB signaling pathway in septic rats. Collectively, targeting ghrelin/GHSR during sepsis may represent a novel therapeutic approach for the treatment of intestinal barrier injury.

Inhibition of PFKFB Preserves Intestinal Barrier Function in Sepsis by Inhibiting NLRP3/GSDMD

Intestinal barrier dysfunction is associated with the occurrence and development of sepsis. Further, aerobic glycolysis plays an essential role in inflammation and cell death. This study is aimed at investigating the protective effect and mechanism of PFKFB3 inhibition on intestinal barrier dysfunction in sepsis mice. Sepsis mouse models were established by cecal ligation and puncture (CLP) in wild-type mice and Gsdmd^-/- mice. The results showed that the expression of 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 3 (PFKFB3) in the small intestines was significantly upregulated in sepsis. 3-(3-Pyridinyl)-1-(4-pyridinyl)-2-propen-1-one (3PO), the specific inhibitor of PFKFB3, and Gsdmd gene knockout significantly inhibited the inflammatory response and cell death caused by sepsis, thus alleviating intestinal damage and barrier dysfunction. 3PO was also shown to significantly inhibit oxidative stress and NLRP3/caspase-1/GSDMD-dependent cell pyroptosis in the small intestines. The in vitro studies revealed that 3PO reduced NLRP3/caspase-1/GSDMD-dependent cell pyroptosis by inhibiting ROS. Taken together, our results suggest that PFKFB3 is involved in inflammation, oxidative stress, and pyroptosis during sepsis and enhances intestinal damage, which may provide important clues about the potential targets to be exploited in this highly lethal disease.

Synergistic effect of GF9 and streptomycin on relieving gram-negative bacteria-induced sepsis

Triggering receptor expressed on myeloid cells-1 (TREM-1) regulates inflammation and promotes a vigorous immune response. GF9 is one of the peptides that inhibit the mTREM-1 signaling pathway, thus reducing the inflammatory mediators in diseases including sepsis. Nanotechnology could offer a new complementary strategy for diseases. Streptomycin is also one treatment of sepsis. However, the role of nanoparticles delivered GF9 combined with streptomycin on sepsis had never been discovered. In the present study, cecal ligation and puncture (CLP) and lipopolysaccharide [LPS, Escherichia coli (E. coli) O111:B4] sepsis models were constructed. SDS-PAGE was used to evaluate the size of nano drugs; Western blot was used to detect the protein levels of MMP2 and TREM-1 in cells. The levels of TNF-α and IL-6 were detected by ELISA. Histopathological changes were observed by HE staining. And the nanomedicines of GF9-HFn/Str were successfully constructed. The size of GF9-HFn/Str is 36 kD. The ferritin-based nanoparticle plays a vital role in delivering streptomycin into cells and tissues. GF9 (1.6 μM) and streptomycin (40 μM) co-delivery nanomedicine showed a better effect on promoting overall survival, decreasing E. coli, significantly suppressed the expression levels of inflammatory factors (TNF-α and IL-6), and can reduce lung injury. Our study demonstrated that combination delivery of nanomedicine GF9 and streptomycin have a better effect on overall survival rate, anti-inflammatory, and anti-bacterial in sepsis. Our present study revealed a new potential therapeutic method for sepsis.

HSA-miR-34a-5p regulates the SIRT1/TP53 axis in prostate cancer

SIRT1 is tightly associated with the progression of prostate cancer while the role of Hsa-miR-34a-5p in SIRT1-mediated prostate cancer is not fully understood. We have thoroughly mined the data from two databases, namely the Lipidemia and the cancer genome atlas (TCGA) and found that SIRT1 was highly expressed in human carcinoma tissues as compared to normal tissues, and patients with high SIRT1 expression level had a shorter survival time. The online tool "Gene-RADAR" was applied to investigate the interaction among SIRT1, the TP53 gene and miR-34a-5p. We found that SIRT1 was up-regulated in cancer tissues from patients diagnosed with prostate and castration-resistant prostate cancer when compared to healthy controls. Pearson analysis indicated a positive correlation between SIRT1 and miR-34a-5p, while data mining on the TargetScan database predicted the binding site between the two. An apoptosis assay of prostate cancer cells (PRAD) confirmed that the overexpression of miR-34a-5p inhibited paclitaxel-induced apoptosis and promoted cell proliferation. Cell cycle analysis verified that miR-34a-5p overexpression blocked PRAD cells in the G2/S phase of the cell cycle. Moreover, the Western blotting (WB) and quantitative PCR (qPCR) assays demonstrated that the overexpression of miR-34a-5p induced down-regulation of the SIRT-related proteins HIF2α and PGC1α, while on the contrary, it up-regulated the expression of two tumour suppressor genes, TP53 and VEGF. In conclusion, we have shown that miR-34a-5p is involved in the oncogenesis of PRAD cells via the SIRT1/TP53 axis.

GIST and Ghrelin: To Be or Not to Be?

BACKGROUND

Ghrelin is the orexigenic hormone secreted mainly by the stomach. Its involvement in neoplastic development has been studied in gastrointestinal adenocarcinomas. Our paper aims to evaluate the influence of the ghrelin axis in gastrointestinal stromal tumors (GISTs).

MATERIALS AND METHODS

The study design included two groups of patients, 46 with gastric GISTs and 30 with obesity. Archived tissue samples were evaluated for the presence of gastritis and H. pylori. Immunohistochemical expression of ghrelin and its receptor (GHS-R) was assessed.

RESULTS

All GISTs showed absent immunohistochemical expression for ghrelin, while GHS-R displayed a particular pattern, with notable differences in intensity (p = 0.0256) and percentage of stained cells (p < 0.00001) in the periphery vs. core of tumors. Positive ghrelin expression was lower in the gastric mucosa of the first group compared to the second group (p < 0.001).

CONCLUSION

The ghrelin axis can influence GISTs carcinogenesis through activation of GHS-R. A previously described direct autocrine/paracrine mechanism is not supported by our findings.