TLR4 and its adaptor protein MyD88 in inflammatory and noninflammatory lesions of acne vulgaris

Background Acne is a disorder of the pilosebaceous unit resulting from multiple factors. One factor believed to be important in the pathogenesis of acne is Propionobacterium acnes. Toll-like receptors (TLRs) have been studied extensively over the past decade particularly with respect to infectious microbial pathogens. P. acnes (Gram-positive anaerobic bacterium) was found capable of inducing TLR4 expression in vivo in the epidermis of acne lesions. Objective To evaluate the level and role of TLR4 and its adaptor molecule MyD88 (myeloid differentiation primary response protein 88) expression during the inflammatory and noninflammatory stages of acne development. Patients and methods This study included 60 patients with acne vulgaris and 30 apparently healthy controls. Patients were classified into two groups: the inflammatory group including 30 patients with inflammatory lesions on the back and the noninflammatory group including 30 patients with comedonal lesions on the back. A 2mm punch skin biopsy was obtained from the upper back from all individuals. Results TLR4 mRNA and MyD88 levels were significantly higher in patients compared with controls (Po0.001 for each). The mean values of TLR4 mRNA and MyD88 mRNA were significantly higher in inflammatory lesions than in comedones (Po0.001). The mean values of TLR4 mRNA for both comedonal and inflammatory groups were significantly higher in patients with progressive disease than in those with stationary disease (Po0.001). There was a statistically significant correlation between TLR4 and MyD88 mRNA in all patients (r = 0.456, Po0.01). Conclusion We propose that TLR4 may be directly involved in the pathogenesis and progression of acne vulgaris lesions. On the basis of the present results, we suggest that MyD88 is also upregulated in acne lesions, corresponding, even though weakly, to the TLR4 amplification.