Apoptosis markers in oral lichen planus

Objectives: Oral lichen planus (OLP) is a chronic inflammatory disease with an unclear pathogenesis. The main aim of the present study was to investigate the apoptotic mechanisms in the epidermal layers. Expression of p53, Bax, Bcl-2, caspase-3, p63 and involucrin was evaluated. Methods: Histological specimens were obtained from 97 patients with OLP and 11 controls after surgery and studied using immunohistochemical methods. The samples were labeled with different primary antibodies: mouse monoclonal anti-involucrin; mouse monoclonal anti-p63; mouse monoclonal anti-bax; mouse monoclonal anti-bcl-2; mouse monoclonal anti-caspase3; mouse monoclonal anti-p53. ImageJ software was used to determine the area of each marker expression in ten of randomly selected high-magnification fields and to establish percentages of stained area to total. The results were classified in three categories: no staining: 0%; mild: <25%; strong: 25-50% Results: p53 expression was observed mainly in the basal layers of the epidermis with 68.7% of the samples positive while compared with their respective controls ( 98% mild expression). Pro-apoptotic Bax protein was also localized mostly in the basal layers with 69.5% of the samples being positive (73.9% mild and 18.71% strong expression). On the other hand anti-apoptotic Bcl-2 protein expression was found negative in 95% of OLP cases. Caspase-3 activity was not increased compared with controls, only 4.3% of total cases expressing the marker. The OLP clinical types expressing caspase-3 were the erosive and keratotic types but only with 15% and 6% expression respectively. OLP samples showed an increment in p63 and involucrin markers when compared with their controls. Conclusions: The observed increase of different apoptotic markers but the low expression of caspase-3 indicates that caspase-induced apoptosis may not happen in the pathogenesis of the disease. OLP might have highly resistant to the execution of caspase-induced apoptosis, although the mechanism of such inhibition should be clarified hereafter.