17(R)‐Resolvin D1 differentially regulates TLR4‐mediated responses of primary human macrophages to purified LPS and live E. coli

Detection and clearance of bacterial infection require balanced effector and resolution signals to avoid chronic inflammation. Detection of GNB LPS by TLR4 on mϕ induces inflammatory responses, contributing to chronic inflammation and tissue injury. LXs and Rvs are endogenous lipid mediators that enhance resolution of inflammation, and their actions on primary human mϕ responses toward GNB are largely uncharacterized. Here, we report that LXA4, LXB4, and RvD1, tested at 0.1–1 μM, inhibited LPS‐induced TNF production from primary human mϕ, with ATL and 17(R)‐RvD1, demonstrating potent inhibition at 0.1 μM. In addition, 17(R)‐RvD1 inhibited LPS‐induced primary human mϕ production of IL‐7, IL‐12p70, GM‐CSF, IL‐8, CCL2, and MIP‐1α without reducing that of IL‐6 or IL‐10. Remarkably, when stimulated with live Escherichia coli, mϕ treated with 17(R)‐RvD1 demonstrated increased TNF production and enhanced internalization and killing of the bacteria. 17(R)‐RvD1‐enhanced TNF, internalization, and killing were not evident for an lpxM mutant of E. coli expressing hypoacylated LPS with reduced inflammatory activity. Furthermore, 17(R)‐RvD1‐enhanced, E. coli‐induced TNF production was evident in WT but not TLR4‐deficient murine mϕ. Thus, Rvs differentially modulate primary human mϕ responses to E. coli in an LPS‐ and TLR4‐dependent manner, such that this Rv could promote resolution of GNB/LPS‐driven inflammation by reducing mϕ proinflammatory responses to isolated LPS and increasing mϕ responses important for clearance of infection.