Synergistic effect of tolfenamic acid and glycyrrhizic acid on TPA-induced skin inflammation in mice
Tolfenamic acid (TA) and glycyrrhizic acid (GA) are well-known components with anti-inflammatory properties. However, their combined effects on inflammation have not been well studied. The present study aimed to investigate the in vivo anti-inflammatory effects of TA combined with GA using a 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced mouse ear edema model, as well as the underlying mechanisms thereof. The results indicated that TA combined with GA led to a stronger inhibition on TPA-induced mouse ear edema compared to the singular treatments. In addition, the combined treatment significantly alleviated subcutaneous tissue inflammation caused by TPA. Further mechanistic investigations demonstrated that TA combined with GA decreased the levels of TPA-induced interleukin-1β (IL-1β), interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α). Furthermore, the combined treatment effectively inhibited nuclear factor-κB (NF-κB), extracellular signal-regulated kinase (ERK1/2), c-Jun N-terminal kinase (JNK), phosphor-ERK1/2 and phosphor-JNK, which was accompanied by blocking of the activation and the phosphorylation in mitogen-activated protein kinase (MAPK) and phosphoinositide 3-kinase (PI3K)/Akt signaling pathways. Collectively, our findings revealed that different anti-inflammatory components used in combination lead to enhanced inhibitory effects against inflammation.