Abstract
IntroductionGastrointestinal ulceration is associated with high mortality despite advanced management, therefore, understanding of the mucosal protective mechanisms is important. Somatostatin is present in the endocrine cells and sensory nerves, and its analogues were shown to reduce mucosal blood flow, pepsin and gastric acid secretion. Our group discovered that its anti‐inflammatory and analgesic actions are exerted via the somatostatin receptor subtype 4 (sst4). Therefore, we investigated its expression and role in gastrointestinal injury.MethodsSst4 gene‐deleted (sst4−/−) and wildtype mice were treated s.c. with indomethacine (IDM; 35 mg/kg) or vehicle. RNA scope in situ hybridization was performed to localize, qPCR to quantify sst4 and somatostatin mRNA. Macroscopic and microscopic lesions in the stomach and small intestine were evaluated after 4 and 48 h. Plasma protein extravasation was measured by fluorescent, neutrophil myeloperoxidase (MPO) activity bioluminescent ex vivo imaging, TNFα, IL‐1 and COX2 mRNA by qPCR.ResultsSomatostatin mRNA is present in the neuroendocrine D‐cells and significantly upregulated 48 h after IDM. Sst4 mRNA in located in the myenteric plexus neurons, it’s expression did not change in response to mucosal injury.IDM‐induced gastric and small intestinal macroscopic lesions (4, 24 h), gastric MPO activity (24, 48 h) and plasma extravasation (30 min) were significantly greater in sst4−/− mice. TNFα, IL‐1, COX2 expressions significantly increased after 4 h in the stomach of sst4−/− mice, but in wild‐types the same pattern was observed only later, at the 48 h time‐point. IDM‐evoked histopathological alterations and small intestinal length reduction were not altered by the sst4 deletion.ConclusionThis is the first evidence for sst4 expression in myenteric plexus neurons and its protective roles against chemically‐induced gastrointestinal mucosal damage and inflammation. This suggests the safety of sst4 agonist drug candidates in the gastrointestinal tract, and even their potential use for gastroprotective indication.Support or Funding InformationSupported by: GINOP‐2.3.2‐15‐2016‐00050 – PEPSYS, GINOP‐2.3.2 STAY ALIVE, EFOP‐3.6.2‐16‐2017‐00008, ÚNKP‐19‐3‐III‐PTE‐211
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