Effects of probiotics on the survival of sepsis mice and their mechanism

Abstract

Objective To investigate the effects of probiotics on the survival of sepsis mice and their mechanism. Methods A total of 60 male C57BL6 mice were randomly divided into 3 groups, respectively, the sham operation group (n = 20), the control group (n = 20) and the experimental group (n = 20). After feeding 2 d, mice in the experimental group were given 200 μL probiotics solution daily; mice in the control and sham operation groups were given 200 μL NaCl solution, with continuous intragastric administration for 4 weeks. Cecal ligation and puncture (CLP) was performed on the mice in the experimental and control groups, while mice in the sham operation group were performed with the same procedures of CLP except for cecal puncture. Ten mice in each group were used to observe their activity and survival of 7 d, and the blood and colon tissues were taken in the other 10 mice in each group after 24 hours. The expression levels of serum inflammatory factor interleukin 22 (IL-22), IL-2 and tumor necrosis factor alpha (TNF-α) were detected by enzyme-linked immunosorbent assay, the colon tissues were measured by the hematoxylin and eosin (HE) staining method, and the expression of colonic mucosa (Occludin) in each group was observed by the immunohistochemical method. Results Mice in the sham operation group grew well, mice in the control group curled up in a corner of the cage and trembled, and mice in the experimental group were more active than the experimental group, without obvious tremor. At 7 d, there were still 3 survived mice in the experimental group which were given euthanasia; the 7 d survival was significantly higher than that of the control group (P = 0.020). At 7 d, 10 mice in the sham operation group all survived and were given euthanasia. The expressions of serum IL-22 [(103 ± 23) ng/L vs. (27 ± 9) ng/L, t = 7.590, P < 0.001], IL-2 [(328 ± 27) ng/L vs. (77 ± 21) ng/L, t = 21.368, P < 0.001] and TNF-α [(94 ± 22) ng/L vs. (56 ± 9) ng/L, t = 4.734, P < 0.001] in the control group were significantly different as compared to the sham operation group. Meanwhile, the expressions of serum IL-22 [(75 ± 33) ng/L vs. (27 ± 9) ng/L, t = 3.755, P = 0.001], IL-2 [(217 ± 30) ng/L vs. (77 ± 21) ng/L, t = 10.850, P < 0.001] and TNF-α [(107 ± 20) ng/L vs. (56 ± 9) ng/L, t = 5.956, P < 0.001] in the experimental and sham operation groups all showed statistically significant differences. Compared with the control group, the expressions of serum IL-22 [(103 ± 23) ng/L vs. (75 ± 33) ng/L, t = 2.185, P = 0.042] and IL-2 [(328 ± 27) ng/L vs. (217 ± 30) ng/L, t = 8.371, P < 0.001] in the experimental group were significantly different, while the TNF-α [(94 ± 22) ng/L vs. (107 ± 20) ng/L, t = 1.363, P = 0.188] expression showed no statistically significant difference. In the sham operation group, the colonic mucosa was intact and the glands were regularly arranged with little or no inflammatory cell infiltration. However, mice in the control group appeared derangement, deformation and lack of colonic mucosal epithelial glands, fuzzy connected structures of enterocytes, and extensive infiltration of inflammatory cells some of which had crypt abscess. The colonic epithelia of mice in the experimental group were basically complete without erosion and loss, glands were normally arranged, and the infiltration of inflammatory cells decreased more as compared to the control group. The results of immunohistochemistry showed that mice in the sham operation group had complete acinar structures of colonic epithelial cells and more Occludin proteins. The acinar structures of colonic epithelial cells in the control group were destructed and disappeared, and there were infiltration of inflammatory cells and less Occludin proteins. The acinar structures of colonic epithelial cells in the experimental group were complete with widened interacinar gaps, and the expression of Occludin protein increased as compared to the control group. Conclusion Probiotics can inhibit the reduction of Occludin of intestinal epithelial cells and stabilize barrier structures of intestinal mucosas, thus effectively improving the survival of septic mice. Key words: Probiotics; Sepsis; Occludin