Probiotics: A non-conventional therapy for oral lichen planus.

Oral lichen planus (OLP) is a common T-cell mediated chronic inflammatory disease. Although the etiology is still unclear, present studies suggest that the composition of the oral microbiota and psychological problems are implicated in the etiology of OLP. The pathogenesis of OLP includes mainly antigen-specific and non-specific mechanisms. Antigen-specific mechanisms involve T-cell activation following antigen presentation and apoptosis of basal keratinocytes triggered by CD8+ cytotoxic T cells, while non-specific mechanisms consist of matrix metalloproteinase over-expression and mast cell degranulation in OLP lesions. Therapies for OLP are mainly used to control symptoms and a specific cure is not yet available. Probiotics are capable of modulating the immune response in a strain-specific manner. They are able to alleviate microbial infection and suppress T-cell activation, infiltration and proliferation, as well as suppress keratinocyte apoptosis and nuclear factor-kappa B signaling. Furthermore, probiotics can also modulate the production of inflammatory cytokines and microRNAs, inhibit MMP-9 expression and mast cell degranulation, and ameliorate psychological problems, all of which are involved in the pathogenesis of OLP. Therefore, we hypothesize that probiotics may be applicable to OLP as a safe, inexpensive and non-conventional therapy.