Abstract: Objective: To detect the expression level of cyclooxygenase-2 (COX-2) and phosphorylated P38 mitogen-activated protein kinase (p-P38MAPK) in the lesions of lichen planus (LP) and to explore its role in the pathogenesis of LP. Methods: The expression level of COX-2 and p-P38MAPK in 20 lesions with LP and normal skin of 20 human controls were detected by immunohistochemical technology. Results: The IOD(integrated optical density) of COX-2 and p-P38MAPK in LP lesions were (8.46±1.79)×10³ and (11.54±2.85)×10³, which were both higher than those in the controls, (3.14±2.35)×10³ and (6.26±3.12)×10³, with significant differences (Ps＜0.01). There was a positive correlation between the expression level of COX-2 and p-P38MAPK in LP lesions (r=0.62,P＜0.01). Conclusion: The up-regulation of COX-2 expression may be correlated with the activation of upstream P38MAPK, which may be involved in the pathogenesis of lichen planus.

Key words: lichen planus, COX-2, P38 mitogen-activated protein kinase