Context: Pain-relieving plaster (PRP) is a traditional Chinese medicine (TCM) that has been widely used with satisfactory results in the treatment of some diseases related to inflammation, such as bruises, chronic arthritis.
Objective: The mechanisms underlying the anti-inflammatory actions of PRP are investigated in this study for the first time.
Materials and methods: The anti-inflammatory effects of PRP extracts were evaluated in lipopolysaccharide (LPS) or calcium ionophore A23187-treated murine peritoneal macrophages (PMs). Tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), prostaglandin E₂ (PGE₂), and leukotrienes B₄ (LTB₄) were evaluated by ELISA assays. Reverse transcriptase-polymerase chain reaction (RT-PCR) and western blot analysis were used to detect the expression of cyclooxygenase-2 (COX-2) and 5-lipoxygenase (5-LOX). Nuclear factor-kappa B (NF-κB)-DNA-binding activity was determined by gel mobility shift assay.
Results: PRP extracts were found to inhibit the production of TNF-α, IL-1β, and PGE(2), reduce the expressions of COX-2 at the mRNA and protein levels induced by LPS, and reduced the production of LTB₄ induced by A23187. Furthermore, PRP extracts significantly attenuated LPS-induced NF-κB-DNA-binding activity.
Discussion and conclusion: The anti-inflammatory effects of PRP possibly are related to reduction of inflammatory cytokines (TNF-α and IL-1β), inducible inflammatory enzyme (COX-2), and its metabolite PGE₂ via NF-κB signal pathway. Moreover, PRP extracts also notably inhibited the production of LTB₄, indicating that PRP inhibited the 5-LOX pathway, which may be the other mechanism for its anti-inflammatory action.