High Mobility Group Protein 1 Reverses Immune System Paralysis in Late-Phase Sepsis

Rab26 alleviates sepsis-induced immunosuppression as a master regulator of macrophage ferroptosis and polarization shift

Macrophage dysfunction is a significant contributor to more than 70 % of sepsis-related deaths, specifically secondary bacterial infections, during the immunosuppression stage of sepsis. Nevertheless, the role of Rab26 in this context remains unclear. In this study, we observed a substantial decrease in Rab26 expression in macrophages during the immunosuppressive phase of sepsis, which was also found to be suppressed by high extracellular levels of HMGB1. During the progression of sepsis, Rab26 deficiency promotes a polarization shift from the M1 to the M2-like phenotype in macrophages, rendering them susceptible to ferroptosis. Subsequent experimentation has revealed that Rab26 deficiency facilitates the degradation of GPX4, thereby aggravating macrophage ferroptosis through the upregulation of levels of lipid ROS, MDA, and ferrous iron induced by RSL3, a ferroptosis inducer. Additionally, Rab26-deficient mice in the immunosuppressed phase of sepsis exhibit heightened susceptibility to secondary infections, leading to exacerbated lung tissue damage and increased mortality rate. Overall, these findings indicate that Rab26 plays a crucial role in sepsis-induced macrophage immunosuppression by regulating macrophage ferroptosis and polarization. Hence, it represents a potential novel target for sepsis therapy.

Role of metformin in inflammation

BACKGROUND

Metformin has good anti-hyperglycemic effectiveness, but does not induce hypoglycemia，is very safe, and has become the preferred drug for the treatment of type 2 diabetes. Recently, the other effects of metformin, such as being anti-inflammatory and delaying aging, have also attracted increased attention.

METHODS AND RESULTS

The relevant literatures on pubmed and other websites for reading, classification and sorting, and did not involve any animal experiments.

CONCLUSION

Metformin has anti-inflammatory effects through multiple routes, which provides potential therapeutic targets for certain inflammatory diseases, such as neuroinflammation and rheumatoid arthritis. In addition, inflammation is a key component of tumor occurrence and development ; thus, targeted inflammatory intervention is a significant benefit for both cancer prevention and treatment. Therefore, metformin may have further potential for inflammation-related disease prevention and treatmen. However, the inflammatory mechanism is complex; various molecules are connected and influence each other. For example, metformin significantly inhibits p65 nuclear translocation, but pretreatment with compound C, an AMPK inhibitor, abolishes this effect, and silencing of HMGB1 inhibits NF-κB activation . SIRT1 deacetylates FoxO, increasing its transcriptional activity . mTOR in dendritic cells regulates FoxO1 via AKT. The interactions among various molecules should be further explored to clarify their specific mechanisms and provide more direction for the treatment of inflammatory diseases, as well as cancer.

HMGB1: An overview of its roles in the pathogenesis of liver disease

High-mobility group box 1 (HMGB1) is an abundant architectural chromosomal protein that has multiple biologic functions: gene transcription, DNA replication, DNA-damage repair, and cell signaling for inflammation. HMGB1 can be released passively by necrotic cells or secreted actively by activated immune cells into the extracellular milieu after injury. Extracellular HMGB1 acts as a damage-associated molecular pattern to initiate the innate inflammatory response to infection and injury by communicating with neighboring cells through binding to specific cell-surface receptors, including Toll-like receptors (TLRs) and the receptor for advanced glycation end products (RAGE). Numerous studies have suggested HMGB1 to act as a key protein mediating the pathogenesis of chronic and acute liver diseases, including nonalcoholic fatty liver disease, hepatocellular carcinoma, and hepatic ischemia/reperfusion injury. Here, we provide a detailed review that focuses on the role of HMGB1 and HMGB1-mediated inflammatory signaling pathways in the pathogenesis of liver diseases.

Interleukin-1β Protection Against Experimental Sepsis in Mice

The inflammatory response involving interleukin-1β (IL-1β) has been thought to play an important role in the development of late-phase sepsis. However, in this study, we wanted to explore the possibility of using IL-1β to improve the prognosis of sepsis by triggering local differentiation of bone marrow cells (BMCs) into regulatory dendritic cells (DCs) in vivo, thereby reversing the immune paralysis in late-phase sepsis. Sepsis mouse models were induced by cecal ligation and puncture (CLP) and lethal Escherichia coli O18 infection. Mice were injected intraperitoneally with IL-1β after CLP and after the lethal infection. Septic BMCs and liver immune cells were isolated at 0, 3, 6, 9, and 14 days post-CLP. BMCs and liver cells isolated from septic mice treated with IL-1β were adoptively transferred into CLP mice. GFP⁺-C57BL/6 parabiosis models were established. Serum IL-1β levels were determined by enzyme-linked immunosorbent assay (ELISA) kit, and the number, ratio, and phenotype of immune cells were observed by flow cytometry. IL-1β treatment improved the survival of sepsis and increased the numbers of BMCs and liver immune cells in septic mice. Moreover, IL-1β stimulation increased the number and the percentage of CD11c⁻CD45RB^high DCs in septic BM and liver. Adoptive transfer of septic BMCs, liver immune cells, and CD11c⁻CD45RB^high DCs treated with IL-1β into CLP mice attenuated sepsis. IL-1β triggered the redistribution of CD11c⁻CD45RB^high DCs as well as BMCs in parabiosis models. IL-1β protects against sepsis by stimulating local proliferation and differentiation of BMCs into CD11c⁻CD45RB^high DCs at immune organs and non-immune organs.