The pasteurized Weissella cibaria alleviates sepsis-induced acute lung injury by modulation of intestinal mucus barrier and gut microbiota

Abstract

Background: Dysbiosis of intestinal microecology caused by sepsis plays a crucial role in the onset and progression of sepsis-induced acute lung injury (SALI). As a postbiotic type, inactivated probiotic bacteria can regulate the gut microbiome. Pasteurized bacteria are considered safer than live bacteria in immune dysregulation disorders. Weissella cibaria (W. cibaria) is considered a candidate probiotic with certain beneficial functions. However, whether inactivated W. cibaria can alleviate SALI and the underlying mechanisms remain unclear. This study aimed to investigate whether inactivated W. cibaria can regulate intestinal mucosal barrier function and gut microbiota, thereby improving SALI.

Methods: Following gavage of pasteurized W. cibaria in septic mice, lung tissue damage and inflammation levels were assessed. Circulating LPS levels and inflammatory cytokine concentrations in the blood were measured. Additionally, colonic tissue inflammation, intestinal mucosal barrier integrity, and alterations in the gut microbiota were evaluated.

Result: Pasteurized W. cibaria increases survival rates in SALI mice and improves pathological damage and cell apoptosis in lung tissue. Pasteurized W. cibaria also reduces the lung inflammatory response in septic mice by lowering pro-inflammatory cytokine levels and increasing anti-inflammatory cytokine levels. Pasteurized W. cibaria appears to exert its effects by improving the intestinal mucosal barrier and reversing gut microbiota dysbiosis caused by sepsis. Specifically, pasteurized W. cibaria alleviates intestinal barrier damage and inflammation in SALI mice, enhancing the integrity of the intestinal mucosal barrier. Additionally, pasteurized W. cibaria increases the abundance of anti-inflammatory bacteria such as Muribaculaceae. Pasteurized W. cibaria also decreases the levels of LPS-producing bacteria, including Escherichia-Shigella and Helicobacter, leading to significant attenuation in metabolic endotoxemia, which in turn alleviates excessive lung inflammation in septic mice.

Conclusions: Pasteurized W. cibaria has the potential to act as a postbiotic agent, improving sepsis-induced gut microbiota dysbiosis and acute lung injury, and providing a novel strategy for treating SALI.

Keywords: Weissella cibaria; Gut microbiota; Intestinal mucosal barrier; Postbiotic; Sepsis-induced acute lung injury.

Fig. 1

Pasteurized D-2 ameliorates lung injury of sepsis mice. (A) The survival curve of mice; (B) The lung W/D weight ratios; (C) Protein concentration in bronchoalveolar lavage fluid (BALF); (D-E) Representative H&E staining and damage scores of lung tissue; (F-G) TUNEL-positive cells in the lungs of septic mice. *p < 0.05; **p < 0.01; ***p < 0.001; ****p < 0.0001

Fig. 2

Pasteurized D-2 ameliorates inflammation in mice with SALI. (A) The levels of leukocytes in the BALF; (B) The levels of neutrophils in the BALF; (C-H) Inflammatory cytokines MPO, IL-6, IL-1β, TNF-α, IFN-γ, and IL-10 levels in lung; (I-J) Immunohistochemistry analysis of iNOS in lung; (K-L) Immunohistochemistry analysis of COX-2 in lung. *p < 0.05; **p < 0.01; ***p < 0.001; ****p < 0.0001

Fig. 3

Pasteurized D-2 ameliorates systemic inflammation and LPS level. (A-E) Inflammatory cytokines IL-6, IL-1β, TNF-α, IFN-γ, and IL-10 levels in serum; (F) The levels of LPS in serum. **p < 0.01; ***p < 0.001; ****p < 0.0001

Fig. 4

Pasteurized D-2 ameliorates colonic injury and inflammation. (A-B) Representative H&E staining and damage scores of the colon; (C-D) TUNEL-positive cells in the lungs of septic mice; (E-I) Inflammatory cytokines IL-6, IL-1β, TNF-α, IFN-γ, and IL-10 levels in colon. *p < 0.05; **p < 0.01; ***p < 0.001; ****p < 0.0001

Fig. 5

Pasteurized D-2 improves intestinal mucosal barrier function. (A-B) Representative images of the Alcian blue staining; (C-D) Immunofluorescence images of Occludin; (E-F) Immunofluorescence images of Claudin-1; (G-H) Fluorescence quantitative RT-PCR of Claudin-1 and Occludin. *p < 0.05; **p < 0.01; ****p < 0.0001

Fig. 6

Pasteurized D-2 altered the gut microbial diversity of SALI mice. (A-D) Alpha diversity analysis of gut microbiota; (E-F) Beta diversity analysis (PCoA and NMDS) of gut microbiota. *p < 0.05; **p < 0.01; ***p < 0.001

Fig. 7

Pasteurized D-2 alters gut microbial abundance at the phylum level of SALI mice. (A) The relative abundance of the top 15 bacteria at the phylum level; (B) Heatmap analysis at the phylum level; (C-F) Relative abundance of Proteobacteria, Campylobacterota, Bacteroidota, and Firmicutes. ns: not significant; *p < 0.05; **p < 0.01

Fig. 8

Pasteurized D-2 alters gut microbial abundance at the genus level of SALI mice. (A) The relative abundance of the top 15 bacteria at the genus level; (B) Heatmap analysis at the genus level; (C-F) Relative abundance of Escherichia-Shigella, Helicobacter, Muribaculaceae, and Alloprevotella. ns: not significant; *p < 0.05; **p < 0.01; ***p < 0.001

Fig. 9

Pasteurized D-2 ameliorates LPS induced lung injury. (A) The lung W/D weight ratios; (B) Protein concentration in bronchoalveolar lavage fluid (BALF); (C, E) Representative H&E staining and damage scores of lung tissue; (D, F) TUNEL-positive cells in the lungs of septic mice; (G) The levels of leukocytes in the BALF; (H) The levels of neutrophils in the BALF; (I-J) Immunohistochemistry analysis of iNOS in lung; (K-L) Immunohistochemistry analysis of COX-2 in lung. *p < 0.05; **p < 0.01; ***p < 0.001; ****p < 0.0001

Fig. 10

Pasteurized D-2 does not exhibit toxicity on the body. (A-B) The levels of ALT and AST in serum; (C-D) The levels of UREA and CREA-s in serum; (E) The serum aldolase activity; (F) The HE- stained images of the heart, liver, spleen, lung, and kidney tissues. ns: not significant