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

Abstract

Abstract 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.