Desulfovibrio vulgaris exacerbates sepsis by inducing inflammation and oxidative stress in multiple organs

Abstract

Introduction: Sepsis is a life-threatening condition that often leads to organ dysfunction and systemic inflammation, with gut microbiota dysbiosis playing a crucial role in its pathogenesis. The role of Desulfovibrio vulgaris (D. vulgaris), a potentially pathogenic bacterium, in sepsis remains unclear.

Methods: We first assessed the abundance of D. vulgaris in the feces of septic mice and patients using qPCR. Mice were then orally gavaged with D. vulgaris (2 × 10⁸ CFU/mouse/day) for 7 consecutive days followed by cecal ligation and puncture (CLP) surgery. We monitored survival, assessed organ damage, and measured inflammation. Peritoneal macrophages were isolated to analyze the phosphorylation of key MAPK and NF-κB signaling pathways. Finally, oxidative stress levels in the liver, lungs, and kidneys were evaluated, measuring markers such as GSH, CAT, and SOD.

Results: The abundance of D. vulgaris was significantly increased in the feces of both septic mice and patients. Supplementation with D. vulgaris exacerbated sepsis in mice, resulting in lower survival rates, more severe organ damage, and heightened inflammation. Phosphorylation of MAPK and NF-κB pathways in peritoneal macrophages was significantly enhanced. Additionally, D. vulgaris amplified oxidative stress across multiple organs, as indicated by increased ROS levels and decreased antioxidant enzyme activity.

Conclusion: Our findings suggest that D. vulgaris exacerbates the progression of sepsis by enhancing inflammation, activating key immune signaling pathways, and increasing oxidative stress. These processes contribute to organ dysfunction and increased mortality, highlighting the potential pathogenic role of D. vulgaris in sepsis.

Keywords: Desulfovibrio vulgaris; inflammation; macrophage; oxidative stress; sepsis.

Figure 1

Increased abundance of D. vulgaris in the gut microbiota of septic mice and patients. (A) Cecal contents were collected from septic mice 12 h post-CLP surgery, and bacterial DNA was extracted. (B) qPCR analysis of the abundance of Desulfovibrio genus in the cecal microbiota of septic mice. n = 6. (C) qPCR analysis revealing increased D. vulgaris abundance in septic mouse cecal microbiota. n = 6. (D) qPCR analysis of the abundance of D. piger, D. intestinalis, D. fairfieldensis, and D. desulfuricans in the cecal microbiota of septic mice. n = 6. (E) Cecal contents were collected 12 h post-intraperitoneal LPS injection (25 mg/kg), with bacterial DNA extraction. (F) qPCR analysis showing increased D. vulgaris abundance in the cecal microbiota of endotoxemic mice. n = 7. (G) Comparison of D. vulgaris abundance in the cecal microbiota of septic versus non-septic patients. n = 15–16. Data are presented as mean ± SEM. Statistical comparisons were performed using two-tailed unpaired Student’s t-test. *p < 0.05.

Figure 2

D. vulgaris exacerbates mortality and organ dysfunction in septic mice. (A) Experimental design for D. vulgaris administration: mice were gavaged with D. vulgaris (2 × 10⁸ CFU/mouse) daily for 7 days before CLP surgery. Survival was monitored for 36 h, and tissues were collected 12 h post-CLP. (B) Survival rates of D. vulgaris-treated mice after CLP. n = 17–18. (C) Serum ALT, AST, Cr, and BUN levels in septic mice after D. vulgaris gavage. n = 6. (D) The relative mRNA levels of Zo-1, Occludin, and Claudin-1 in the colon. n = 6. (E) The protein expression levels of ZO-1, Occludin, and Claudin-1 in the colon. n = 4. Data are presented as mean ± SEM. Survival rates were analyzed using the Kaplan–Meier method with the log-rank test (B). Statistical comparisons were performed using two-tailed unpaired Student’s t-tests (C–E). *p < 0.05, **p < 0.01, ***p < 0.001.

Figure 3

D. vulgaris promotes multi-organ pathological damage in septic mice. (A) Representative H&E-stained histological images and quantitative analysis of liver, kidney, and lung tissue damage in septic mice after D. vulgaris administration. n = 6. (B) TUNEL staining (red: TUNEL-positive cells, blue: cell nuclei) showing apoptosis in liver, kidney, and lung tissues of septic mice after D. vulgaris gavage. n = 4. Data are presented as mean ± SEM. Statistical comparisons were performed using two-tailed unpaired Student’s t-test. *p < 0.05, **p < 0.01. Scale bars, 100 μm.

Figure 4

D. vulgaris induces inflammation in septic mice. (A) ELISA measurement of TNF-α, IL-1β, and IL-6 levels in the serum of D. vulgaris-treated septic mice. n = 6. (B,C) Immunohistochemical staining showing CD11b⁺ cell infiltration in liver, kidney, and lung tissues. n = 5–6. (D) qPCR analysis of inflammatory cytokines and chemokines in liver, kidney, and lung tissues. Data are presented as mean ± SEM. Statistical comparisons were performed using two-tailed unpaired Student’s t-test. *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001. Scale bars, 100 μm.

Figure 5

D. vulgaris promotes the activation of MAPK and NF-κB pathways in peritoneal macrophages of septic mice. (A,B) Western blot analysis of phosphorylated MAPK and NF-κB in peritoneal macrophages isolated from septic mice treated with D. vulgaris. n = 3. Data are presented as mean ± SEM. Statistical comparisons were performed using two-tailed unpaired Student’s t-test. *p < 0.05.

Figure 6

D. vulgaris induces oxidative stress in septic mice. (A) ROS levels in liver, kidney, and lung tissues of septic mice treated with D. vulgaris. n = 4. (B) Antioxidant levels (GSH, CAT, and SOD) in liver, kidney, and lung tissues of septic mice. n = 6. Data are presented as mean ± SEM. Statistical comparisons were performed using two-tailed unpaired Student’s t-test. *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001. Scale bars, 100 μm.

Figure 7

D. vulgaris promotes inflammation and oxidative stress in septic mice. Model illustrating the effects of increased D. vulgaris abundance in the gut during sepsis, leading to activated macrophage MAPK and NF-κB pathways, heightened inflammation, and increased oxidative stress in multiple organs.