Acetic acid alleviates the inflammatory response and liver injury in septic mice by increasing the expression of TRIM40

Abstract

Sepsis remains a significant health care issue in clinical practice due to its high mortality rate and healthcare cost, despite extensive efforts to better understand the pathophysiology of sepsis. The systemic inflammatory response often leads to severe liver injury, even acute liver dysfunction and failure. Acetic acid, as a type of chemical compound, has been reported to be an emerging drug for improving metabolic syndrome and inhibiting inflammation in rats and human. To verify the effects of acetic acid in protecting the liver and reducing the inflammatory response, a septic mouse model was established by cecal ligation and puncture (CLP), and then the CLP-model mice were treated with acetic acid or PBS. Following the treatment, it was determined that, in CLP-model mice, acetic acid could alleviate the inflammatory response by decreasing the expression of cytokines including interleukin-6 and tumor necrosis factor-α. Additionally, acetic acid also alleviated the liver injury, and the levels of alanine aminotransaminase, aspartate aminotransferase, Toll-like receptor (TLR)4 and nuclear factor-κB (NF-κB) were decreased. The expression of tripartite motif-containing protein (TRIM)40 was also upregulated significantly. Therefore, the authors of the current study hypothesized that acetic acid could decrease the inflammatory response by increasing the expression of TRIM40 and TRIM40 may regulate the activity of the TLR4 signaling pathway. To further illustrate the interaction between TRIM40 and the TLR4 signaling pathway, the authors collected macrophages from the peritoneal cavity by intraperitoneally administering mice with 5 ml ice-cold normal saline. Following the collection, peritoneal macrophages were treated with acetic acid, TRIM40 small interfering RNA or PBS. It was demonstrated that acetic acid upregulated the expression of TRIM40. When TRIM40 was silenced, the protective effect of acetic acid would be reversed as well. The results suggested that TRIM40 could act on and downregulate the activity of the TLR4 signaling pathway. TRIM40 is possibly the major target for acetic acid, which may function as a protective factor in septic mice.

Keywords: acetic acid; liver injury; nuclear factor NF-κB; sepsis; tripartite motif-containing protein 40.

Figure 1.

Acetic acid improves the survival rate of CLP-model mice. Kaplan-Meier survival curves of mice following CLP and the intravenous administration of PBS or 0.1 mmol/kg acetic acid (n=10 mice/group). CLP, cecal ligation and puncture.

Figure 2.

Acetic acid decreases the concentration of inflammatory cytokines in the serum of CLP-model mice. Serum (A) IL-6, (B) IL-10 and (C) TNF-α levels were detected by ELISA 12 h after PBS and acetic acid treatment (n=6 mice/group). Results are presented as mean ± standard deviation. *P<0.05 vs. the CLP + PBS group. ^#P<0.05, ^##P<0.01 vs. the control group. CLP, cecal ligation and puncture; IL, interleukin; TNF-α, tumor necrosis factor α.

Figure 3.

Acetic acid decreases the concentration of liver enzymes in the serum of CLP-model mice. Serum (A) ALT, (B) AST and (C) TBiL levels were detected by a biochemical automatic analyzer 12 h after PBS and acetic acid treatment (n=6 mice/group). Results are presented as mean ± standard deviation. *P<0.05 vs. the CLP + PBS group. ^##P<0.01 vs. the control group. CLP, cecal ligation and puncture; ALT, alanine aminotransferase; AST, aspartate aminotransferase; TBiL, total bilirubin.

Figure 4.

Acetic acid treatment attenuates pathological changes in the livers of CLP-model mice. Liver tissue in the (A) control, (B) CLP + PBS, (C) CLP + acetic acid and (D) control + acetic acid groups. Scale bar=100 µm. CLP, cecal ligation and puncture.

Figure 5.

Acetic acid decreases NF-κB and TLR4, and increases TRIM40 levels in CLP-model mice. The (A) mRNA levels and (B) protein levels of NF-κB, TLR4 and TRIM40 in the livers of CLP-model mice. Results are presented as mean ± standard deviation. **P<0.01 vs. the CLP + PBS group. ^##P<0.01 vs. the control group. CLP, cecal ligation and puncture; TRIM40, tripartite motif-containing protein 40; NF-κB, nuclear factor-κB; TLR4, Toll-like receptor 4.

Figure 6.

Acetic acid reduces supernatant inflammatory factors levels in peritoneal macrophages. Protein concentrations for (A) IL-6, (B) IL-10 and (C) TNF-α were measured using ELISA kits (n=6 mice/group). Results are presented as mean ± standard deviation. *P<0.05, **P<0.01 vs. the LPS group. ^##P<0.01 vs. the control group. IL, interleukin; TNF-α, tumor necrosis factor α; LPS, lipopolysaccharide; TRIM40, tripartite motif-containing protein 40; si, small interfering RNA.

Figure 7.

Acetic acid upregulates the expression of TRIM40 and TRIM40 may inhibit the activity of the TLR4 signaling pathway in peritoneal macrophages. (A) Relative mRNA expression of TRIM40. (B) Relative mRNA and (C) protein expression levels of TRIM40, NF-κB and TLR4 in peritoneal macrophages. Results are presented as mean ± standard deviation. **P<0.01 vs. the LPS group; ^#P<0.05, ^##P<0.01 vs. the control group. TRIM40, tripartite motif 40; NF-κB, nuclear factor-κB; TLR4, Toll-like receptor 4; si, small interfering RNA.