OBJECTIVETo investigate the expression of loricrin (LOR) and cytochrome P450 3A5 (CYP 3A5) in oral submucous fibrosis (OSF) and to evaluate their roles in the defending ability of epithelium mucosae.

METHODSThe expression of LOR and CYP 3A5 was examined in the specimens of 66 OSF and 14 normal buccal mucosa samples by immunohistochemistry, and the protein and mRNA expression of them was detected by Western blot and reverse transcriptase-PCR (RT-PCR).

RESULTSLOR was overexpressed in 42 (63.6%) cases of OSF, and showed a significant difference only between the early and moderately stages of OSF (P < 0.05), but no clear difference between moderately and advanced stages (P > 0.05). All normal buccal mucosa tissues showed positive immunoreactivity for CYP 3A5 protein in the membrane and cytoplasm of spinous epithelial cells and cytoplasm of endothelial cells, 5 (7.6%) cases of OSF showed weak staining of CYP 3A5 in spinous epithelial cells and 33 (50%) showed faint in cytoplasm of endothelial cells. A negative relationship between its expression and pathological stages was found in OSF (P < 0.05). RT-PCR results were fully consistent with the immunohistochemical data. But the results of Western blot only showed the expression of CYP 3A5 was significantly higher in normal buccal mucosa samples than OSF.

CONCLUSIONThe results suggest that the LOR and CYP 3A5 might play a vital role in the change of defending ability of epithelium mucosae as well as the pathopoiesis and carcinogenesis of OSF.