Anti-Inflammatory Activity of Lobaric Acid via Suppressing NF-κB/MAPK Pathways or NLRP3 Inflammasome Activation.

Lobaric acid (LA) is a constituent of the lichen . LA has multiple biological activities, including antibacterial and antioxidant ones. The purpose of this study was to investigate the effect of LA and its mechanism on lipopolysaccharide (LPS)-induced inflammatory responses in macrophages. Macrophages were pretreated with different concentrations of LA (0.2 - 20 µM), followed by LPS stimulation. LA treatment of LPS stimulated macrophages decreased their nitric oxide production and the expression of cyclooxygenase-2 and prostaglandin E2. LA also significantly reduced the production of tumor necrosis factor- and interleukin (IL)-6 by inhibiting the activation of mitogen-activated protein kinases (MAPKs) and nuclear factor-kappa B (NF-B). Additionally, LA inhibited the production of IL-1 and IL-18, as well as caspase-1 maturation, by inhibition of NLRP3 inflammasome activation in LPS/ATP-stimulated cells. These results strongly suggest that LA could inhibit inflammation by downregulating NF-B/MAPK pathways and NLRP3 inflammasome activation in activated macrophages. These results reveal a new therapeutic approach to modulate inflammatory diseases linked to deregulated inflammasome activities.