Topical anti-inflammatory activity of Polygonum cuspidatum extract in the TPA model of mouse ear inflammation

BACKGROUND: This study tested the ability of a characterized extract of Polygonum cuspidatum (PCE) to inhibit mouse ear inflammation in response to topical application of 12-O-tetradecanoylphorbol-13-acetate (TPA). METHODS: A 50% (wt:vol) ethanolic solution of commercial 200:1 PCE was applied to both ears of female Swiss mice (n = 8) at 0.075, 0.15, 0.3, 1.25 and 2.5 mg/ear 30 min after TPA administration (2 μg/ear). For comparison, 3 other groups were treated with TPA and either 1) the vehicle (50% ethanol) alone, 2) indomethacin (0.5 mg/ear), or 3) trans-resveratrol (0.62 mg/ear). Ear thickness was measured before TPA and at 4 and 24 h post-TPA administration to assess ear edema. Ear punch biopsies were collected at 24 h and weighed as a second index of edema. Myeloperoxidase activity was measured in each ear punch biopsy to assess neutrophil infiltration. RESULTS: PCE treatment at all doses significantly reduced ear edema compared to the TPA control. The PCE response was dose-dependent and 2.5 mg PCE significantly inhibited all markers of inflammation to a greater extent than indomethacin (0.5 mg). MPO activity was inhibited at PCE doses ≥ 1.25 mg/ear. Trans-resveratrol inhibited inflammation at comparable doses. CONCLUSION: PCE inhibits development of edema and neutrophil infiltration in the TPA-treated mouse ear model of topical inflammation.