Ghrelin upregulates PepT1 activity in the small intestine epithelium of rats with sepsis

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.

Cx43-Delivered miR-181b Negatively Regulates Sirt1/FOXO3a Signalling Pathway-Mediated Apoptosis on Intestinal Injury in Sepsis

INTRODUCTION

Gap junctions can transmit signals between cells, including miRNAs, leading to the amplification of adjacent cell damage. No previous study has addressed gap junctions and miRNAs in sepsis because the internal mechanism of sepsis-induced intestinal injury is complex. Therefore, we studied the relationship between connexin43 (Cx43) and miR-181b and provided a research direction for further study of sepsis.

METHODS

A mouse caecal ligation and puncture method was used to construct a mouse sepsis model. Firstly, damage to intestinal tissues at different time points was analysed. The levels of Cx43, miR-181b, Sirt1, and FOXO3a in intestinal tissues and the transcription and translation of the apoptosis-related genes Bim and puma, which are downstream of FOXO3a were analysed. Secondly, the effect of Cx43 levels on miR-181b and Sirt1/FOXO3a signalling pathway activity was explored by using the Cx43 inhibitor heptanol. Finally, luciferase assays were used to determine miR-181b binding to the predicted target sequence.

RESULTS

The results show that during sepsis, intestinal injury becomes increasingly worse with time, and the expression of Cx43 and miR-181b increase. In addition, we found that heptanol could significantly reduce intestinal injury. This finding indicates that inhibiting Cx43 regulates the transfer of miR-181b between adjacent cells, thereby reducing the activity of the Sirt1/FOXO3a signalling pathway and reducing the degree of intestinal injury during sepsis.

CONCLUSIONS

In sepsis, the enhancement of Cx43 gap junctions leads to an increase in miR-181b intercellular transfer, affects the downstream SIRT1/FOXO3a signalling pathway and causes cell and tissue damage.

PTX3 Protects Intestinal Mucosal Barrier Damage in Sepsis Through Toll-Like Receptor Signaling Pathway

This study aims to confirm the protective effect of Pentraxin 3 (PTX3) on intestinal mucosal barrier damage in sepsis in animal and cell models and explore its mechanism. Analysis of the GSE147775 gene set revealed that the level of PTX3 was upregulated in the lipopolysaccharide (LPS)-induced rat sepsis model. The mice sepsis model was established by cecal ligation perforation (CLP), and the cell inflammation model was induced by LPS. Cell apoptosis and the expression of apoptosis-related protein were detected by flow cytometry and Western blotting. The PTX3 level was significantly upregulated in the mice sepsis model. Intestinal mucosal barrier damage was aggravated and inflammatory factor expression was upregulated after PTX3 downregulation in sepsis mice. After upregulation of PTX3, intestinal mucosal barrier damage was alleviated and inflammatory factor expression was decreased in sepsis mice. Further data mining suggested that the anti-inflammatory effect of PTX3 might be realized through inhibition of the toll-like receptor (TLR) signaling pathway. Moreover, compared with the LPS group, downregulation of PTX3 increased cell apoptosis and the levels of BCL2-associated X (Bax), myeloperoxidase (MPO), tumor necrosis factor-alfa (TNF-α), interleukin 1 beta (IL-1β), and interferon-gamma (IFN-γ), and decreased the levels of B-cell lymphoma-2 (Bcl-2), zona occludens (ZO)-1, and occludin. On the contrary, overexpression of PTX3 reduced cell apoptosis and the levels of Bax, MPO, TNF-α, IL-1β, and IFN-γ. Moreover, downregulation of PTX3 reversed the inhibitive effects on cell apoptosis and inflammation and promotive effects on the levels of Zo-1 and occludin induced by CLI-095 (a TLR signaling pathway inhibitor). In the CLP-induced mice sepsis model and LPS-induced cell inflammation model, PTX3 inhibits inflammatory response and reduces intestinal mucosal barrier damage through the TLR signaling pathway.

Expression, Regulation, and Role of an Oligopeptide Transporter: PEPT1 in Tumors

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PEPT1 is a vital member of the proton-dependent oligopeptide transporters family (POTs). Many studies have confirmed that PEPT1 plays a critical role in the absorption of dipeptides, tripeptides, and pseudopeptides in the intestinal tract. In recent years, several studies have found that PEPT1 is highly expressed in malignant tumor tissues and cells. The abnormal expression of PEPT1 in tumors may be closely related to the progress of tumors, and hence, could be considered as a potential molecular biomarker for the diagnosis, treatment, and prognosis in malignant tumors. Furthermore, PEPT1 can be used to mediate the targeted delivery of anti-tumor drugs. Herein, the expression, regulation, and role of PEPT1 in tumors in recent years have been reviewed.

Counteraction of perforated cecum lesions in rats: Effects of pentadecapeptide BPC 157, L-NAME and L-arginine

AIM

To study the counteraction of perforated cecum lesion using BPC 157 and nitric oxide (NO) system agents.

METHODS

Alongside with the agents’ application (after 1 min, medication (/kg, 10 mL/2 min bath/rat) includes: BPC 157 (10 μg), L-NAME (5 mg), L-arginine (100mg) alone or combined, and saline baths (controls)) on the rat perforate cecum injury, we continuously assessed the gross reappearance of the vessels (USB microcamera) quickly propagating toward the defect at the cecum surface, defect contraction, bleeding attenuation, MDA- and NO-levels in cecum tissue at 15 min, and severity of cecum lesions and adhesions at 1 and 7 d.

RESULTS

Post-injury, during/after a saline bath, the number of vessels was significantly reduced, the defect was slightly narrowed, bleeding was significant and MDA-levels increased and NO-levels decreased. BPC 157 bath: the vessel presentation was markedly increased, the defect was noticeably narrowed, the bleeding time was shortened and MDA- and NO-levels remained normal. L-NAME: reduced vessel presentation but not more than the control, did not change defect and shortened bleeding. L-arginine: exhibited less vessel reduction, did not change the defect and prolonged bleeding. In combination, mutual counteraction occurred (L-NAME + L-arginine) or the presentation was similar to that of BPC 157 rats (BPC 157 + L-NAME; BPC 157 + L-arginine; BPC 157 + L-NAME + L-arginine), except the defect did not change. Thereby at day 1 and 7, saline, L-NAME, L-arginine and L-NAME + L-arginine failed (defect was still open and large adhesions present).

CONCLUSION

The therapeutic effect was achieved with BPC 157 alone or in combination with L-NAME and L-arginine as it was able to consolidate the stimulating and inhibiting effects of the NO-system towards more effective healing recruiting vessels.

Regulation profile of the intestinal peptide transporter 1 (PepT1)

The intestinal peptide transporter 1 (PepT1) was first identified in 1994. It plays a crucial role in the absorption of small peptides including not only >400 different dipeptides and 8,000 tripeptides digested from dietary proteins but also a repertoire of structurally related compounds and drugs. Owing to its critical role in the bioavailability of peptide-like drugs, such as the anti-cancer agents and anti-virus drug, PepT1 is increasingly becoming a striking prodrug-designing target. Therefore, the understanding of PepT1 gene regulation is of great importance both for dietary adaptation and for clinical drug treatment. After decades of research, it has been recognized that PepT1 could be regulated at the transcriptional and post-transcriptional levels by numerous factors. Therefore, the present review intends to summarize the progress made in the regulation of PepT1 and provide insights into the PepT1's potential in clinical aspects of nutritional and drug therapies.