1. Academic Validation
  2. Lactate-driven macrophage polarization in the inflammatory microenvironment alleviates intestinal inflammation

Lactate-driven macrophage polarization in the inflammatory microenvironment alleviates intestinal inflammation

  • Front Immunol. 2022 Oct 18;13:1013686. doi: 10.3389/fimmu.2022.1013686.
Hai-Cun Zhou 1 2 Wen-Wen Yu 1 3 Xin-Yan Yan 2 Xiao-Qin Liang 1 Xiu-Feng Ma 2 Jian-Ping Long 2 Xiao-Yan Du 2 Hong-Yan Mao 2 Hong-Bin Liu 1 3
Affiliations

Affiliations

  • 1 The Second Clinical Medical College, Lanzhou University, Lanzhou, China.
  • 2 Department of Breast Surgery, Gansu Maternal and Child Health Care Hospital, Lanzhou, Gansu Province, China.
  • 3 Key Laboratory of Stem Cells and Gene Drugs of Gansu Province, The 940th Hospital of Joint Logistics Support Force of Chinese People's Liberation Army, Lanzhou, China.
Abstract

Background: Lactate has long been considered an intermediate by-product of glucose metabolism. However, in recent years, accumulating evidence reveals that lactate has unique biological activities. In previous studies, lactate signaling was shown to inhibit inflammation. Furthermore, <i>in vitro</i> experiments have shown that lactate can promote the transformation of pro-inflammatory macrophages into anti-inflammatory macrophages. However, no <i>in vivo</i> studies have shown whether lactate can alleviate inflammation.

Methods: RAW 264.7 macrophages were stimulated by LPS to induce an M1 phenotype, and cultured with low and high concentrations of lactate. The cells were then observed for phenotypic transformations and expression of inflammatory mediators and surface markers. The expression of inflammatory factors was also analyzed in the cell-free supernatant fraction. Further, a mouse model of DSS-induced colitis was established and treated with lactate. Colonic tissue injury was monitored by histopathological examinations.

Results: The <i>in vitro</i> experiments showed that lactate promoted the transformation of activated macrophages to M2 phenotype and decreased the expression of TLR4-mediated NF-κB signaling proteins and inflammatory factors. In the DSS-induced colitis mouse model, lactate promoted the phenotypic transformation of macrophages in colonic tissue, reduced inflammation and organ damage, inhibited the activation of TLR4/NF-κB signaling pathway, decreased the serum levels of pro-inflammatory factors, increased the expression of anti-inflammatory factors, promoted the repair of the intestinal mucosal barrier and reduced the severity of colitis.

Conclusions: Lactate inhibits the TLR/NF-κB signaling pathway and the production of pro-inflammatory factors by promoting polarization of macrophages. In addition, lactate promotesthe repair of the intestinal mucosal barrier and protects intestinal tissue in inflammation. Furthermore, lactate is relatively safe. Therefore, lactate is a promising and effective drug for treating inflammation through immunometabolism regulation.

Keywords

colitis; inflammation; inflammatory microenvironment; lactic acid; macrophage polarization.

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