A Quinoxaline Derivative as a New Therapeutic Agent for Sepsis through Suppression of TLR4 Signaling Pathways

Sepsis is a severe systemic inflammatory syndrome and one of the leading causes of global morbidity and mortality. Preclinical studies have identified several quinoxaline-based compounds with anti-inflammatory properties, but their effects in sepsis have not been investigated. This study aimed to identify a quinoxaline derivative with anti-inflammatory properties in sepsis. Examining the inflammatory response of primary mouse macrophages to Lipopolysaccharides (LPS) revealed that 2-methoxy-N-(3-quinoxalin-2-ylphenyl)benzamide (2-MQB) is a promising molecule. It suppressed the production of several inflammatory cytokines, including Interleukin-1β (IL-1β), IL-6, IL-12p70, Interferon-γ (IFN-γ), IFN-β, and Tumor necrosis factor-α (TNF-α). Importantly, 2-MQB inhibited the transcriptional activities of Toll-like receptor 4 (TLR4) signaling pathways, including Nuclear factor-κB (NF-κB) and Interferon regulatory factor 3 (IRF3). This was accompanied by lower expression of TLR4, Myeloid differentiation primary response 88 (MyD88), TIR Domain-containing adaptor molecule 1 (Trif), and TNF Receptor-associated factor 3 (Traf3). Additionally, 2-MQB selectively reduced the expression of genes encoding CD80, CD86, and Programmed death-ligand 1 (PD-L1). In vivo, 2-MQB improved mice survival, mitigated tissue damage in the spleen, kidney, and lung, and reduced pro-inflammatory cytokine levels in both LPS-induced endotoxin shock and Cecal ligation and puncture (CLP) models. Notably, 2-MQB decreased the numbers of CD4⁺ and CD8⁺ T cells in the spleen and inhibited TLR4 signaling pathways in LPS-induced endotoxemia. In conclusion, these results introduce the quinoxaline derivative 2-MQB as a potential therapeutic agent for sepsis by inhibiting TLR4 signaling pathways, paving the way for future clinical applications.