Colonization of the pilosebaceous follicle by P. acnes stimulates the expression of IL-1β, TNF-α, IL-6 and IL-8 through activating Toll-like receptors (TLRs) and induces the expression of nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) in human sebocytes, thereby amplifying the inflammatory cascade and deteriorating acne vulgaris [26,27]. Here, PTGS2 is linked to acne.