Resolvin D1 in the Lipopolysaccharide-Induced Inflammatory Microenvironment Mediates Resolution in Human Monocytic THP-1 Cells

Objectives: An infectious trigger can initiate a systemic inflammatory response, which in turn activates immune cells and causes the release of various mediators. Local mediators, such as resolvin D1 (RvD1), actively interact with immune cells to promote the resolution of inflammation. This study aimed to determine the impact of RvD1 on the inflammatory response mediated by monocytes in response to LPS. Methods: To investigate the mechanism by which RvD1 affects the monocyte-mediated inflammatory response to LPS, human THP-1 monocytic cells were treated with LPS, RvD1, or vehicle for 24 h. Inflammatory cytokines, interleukin-1β (IL-1β) and tumor necrosis factor (TNF-α), were measured using enzyme-linked immunosorbent assay (ELISA). RNA sequencing (RNA-seq) was used to identify differentially expressed genes (DEGs). The NF-κB and MAPK p38 signaling pathways were validated using real-time quantitative PCR (RT-qPCR) and Western blotting (WB). Results: RvD1 diminished the levels of IL-1β and TNF-α in LPS-induced inflammation. RvD1 significantly enhanced the mRNA expression of CREB, NRF2, and BCL-2. In addition, RvD1 significantly decreased the mRNA expression of CASP3. RvD1 regulated the inflammatory process in human monocytic THP-1 cells via the NF-κB p65 (MyD88, p65) and p38 MAPK signaling pathways (p38, BCL-2) and further suppressed the expression of apoptotic factors (PI3K, caspase-3). Conclusions: RvD1 has been shown to exert pro-resolving effects by regulating the anti-apoptotic gene BCL-2 and activating the NF-κB p65 and MAPK p38 signaling pathways.