Introduction: Sepsis is a life-threatening syndrome which can progress to multiple organ dysfunction with high mortality. Intestinal barrier failure exerts a central role in the pathophysiological sequence of events that lead from sepsis to multiple organ dysfunction. The present study investigated the role of hydrocortisone (HC) administration and fecal microbiota transplantation (FMT) in several parameters of the gut barrier integrity, immune activation, and survival, in a model of polymicrobial sepsis in rats. Methods: Forty adults male Wistar rats were randomly divided into four groups: sham (group I), cecal ligation and puncture (CLP) (group II), CLP + HC (2.8 mg/kg, intraperitoneally single dose at 6 h) (group III), and CLP + FMT at 6 h (group IV). At 24 h post-CLP, ileal tissues were harvested for histological and immunohistochemical analyses while endotoxin, IL-6, and IL-10 levels in systemic circulation were determined. In a second experiment the same groups were observed for 7 days for mortality, with daily administration of hydrocortisone (group III) and FMT (group IV) in surviving rats. Results: HC administration and FMT significantly reduced mortality of septic rats by 50%. These interventions totally reversed intestinal mucosal atrophy by increasing villous density and mucosal thickness (mu m, mean +/- SD: Group I: 620 +/- 35, Group II: 411 +/- 52, Group III: 622 +/- 19, Group IV: 617 +/- 44). HC and FMT reduced the apoptotic body count in intestinal crypts whereas these increased the mitotic/apoptotic index. Activated caspase-3 expression in intestinal crypts was significantly reduced by HC or FMT (activated caspase-3 (+) enterocytes/10 crypts, mean +/- SD: Group I: 1.6 +/- 0.5, Group II: 5.8 +/- 2.4, Group III: 3.6 +/- 0.9, Group IV: 2.3 +/- 0.6). Both treatments increased Paneth cell count and decreased intraepithelial CD3(+) T lymphocytes and inflammatory infiltration of lamina propria to control levels. In the sham group almost the total of intestinal epithelial cells expressed occludin (92 +/- 8%) and claudin-1 (98 +/- 4%) and CLP reduced this expression to 34 +/- 12% for occludin and 35 +/- 7% for claudin-1. Administration of HC significantly increased occludin (51 +/- 17%) and claudin-1 (77 +/- 9%) expression. FMT exerted also a significant restoring effect in tight junction by increasing occludin (56 +/- 15%) and claudin-1 (84 +/- 7%) expression. The beneficial effects of these treatments on gut barrier function led to significant reduction of systemic endotoxemia (EU/mL, mean +/- SD: Group I: 0.93 +/- 0.36, Group II: 2.14 +/- 1.74, Group III: 1.48 +/- 0.53, Group IV: 1.61 +/- 0.58), while FMT additionally decreased IL-6 and IL-10 levels. Conclusion: Fecal microbiota transplantation and stress dose hydrocortisone administration in septic rats induce a multifactorial improvement of the gut mechanical and immunological barriers, preventing endotoxemia and leading to improved survival.
