[Live-combined Bifidobacterium, Lactobacillus, and Enterococcus improves heat tolerance and attenuates systemic inflammatory injury in heat-stroke rats via modulation of gut microbiota and intestinal barrier].

OBJECTIVES

To investigate the ameliorative effects of live combined Bifidobacterium, Lactobacillus and Enterococcus (LCBLE) preparation on heat tolerance and systemic inflammatory injury in rats with heat stroke, and to explore its underlying mechanisms.

METHODS

Rats were randomly divided into blank control, LCBLE control, model control, and LCBLE treatment groups. Rats in the LCBLE control and LCBLE treatment groups were administered LCBLE by gavage for 7 consecutive days prior to heat stroke modeling, while those in the blank control and model control groups received an equal volume of physiological saline. On day 8, heat stroke was induced in the model control and LCBLE treatment groups. Core body temperature, body weight and survival rate were monitored. Serum levels of inflammatory factors and intestinal fatty acid-binding protein (I-FABP) were measured by enzyme-linked immunosorbent assay; D-lactate levels were detected by lactate colorimetry; endotoxin levels were measured by limulus amebocyte lysate test; histopathological morphology of intestinal tissues was observed by hematoxylin-eosin staining and scored; tight junction proteins and E-cadherin in colonic tissues were localized by immunofluorescence staining; colonic epithelial ultrastructure was observed by transmission electron microscope; and the composition and structural characteristics of the intestinal flora were analyzed by 16S rRNA sequencing.

RESULTS

Compared with the model control group, LCBLE treatment significantly reduced peak core body temperature [(43.21±0.33) ℃ vs. (42.03±0.43) ℃, P<0.01], attenuated weight loss [(286.68±12.61) g vs. (307.76±11.29) g, P<0.05 ], and improved survival rate (55.6% vs. 77.8%, P<0.05). Furthermore, serum levels of tumor necrosis factor-α, IL-6, and IL-1β were significantly reduced in the LCBLE treatment group (all P<0.01); indicators of intestinal barrier dysfunction, including D-lactate, I-FABP, and endotoxin, were also significantly decreased (all P<0.05); histopathological injury in various intestinal segments was alleviated, with reduced injury scores (all P<0.01), and the expression of tight junction proteins (zonula occludens protein 1, occludin), and E-cadherin as well as the ultrastructural integrity of colonic epithelium were restored. 16S rRNA sequencing revealed that LCBLE significantly increased the relative abundances of Bifidobacterium and Lactobacillus in the gut.

CONCLUSIONS

Prophylactic administration of LCBLE improves heat tolerance and alleviates systemic inflammatory injury in heat stroke rats, likely through maintaining intestinal barrier integrity and regulating gut microbiota.