Mechanisms of carvacrol-induced expression of type I collagen gene

Background: Skin aging is accompanied by wrinkle formation and appears to be principally related to decreases in the levels of type I collagen, the primary component of the dermal layer of skin. Objective: To investigate the effect of carvacrol on collagen gene expression and its mechanisms of action. Methods: To elucidate the effect of carvacrol on collagen expression and its mechanism, several experiments were performed in human dermal fibroblasts. Collagen production, small interference RNA, Ca²⁺ mobilization, COL1A2/AP-1 luciferase reporter assays and Western blots for proteins that are involved in collagen gene expression were used in this study. Results: Carvacrol activated both the human COL1A2 promoter activity and the synthesis of human type I procollagen. Additionally, we attempted to characterize the mechanism of action of carvacrol in type I procollagen synthesis. In a human COL1A2 promoter luciferase assay, the small interference RNA for SP-1 did not reduce the carvacrol-induced promoter activation. Also, Smad 2 phosphorylation was not induced by carvacrol. However, in the AP-1 (activator protein-1) luciferase reporter assay and in the Western blot analysis for mitogen-activated protein kinases (MAPKs), carvacrol induced the activation of the AP-1 promoter and the phosphorylation of JNK and ERK1/2 (p42/44 MAPK), but did not induce the phosphorylation of p38 MAPK. Carvacrol also induced intracellular Ca²⁺ mobilization and phosphorylation of phospholipase Cγ1 (PLCγ1), a molecule upstream of Ca²⁺. In addition, PAO, a PLCγ1 inhibitor, attenuated the carvacrol-induced production of collagen. Conclusion: Our study suggests that the PLCγ1 signaling pathway may be involved in the carvacrol-induced expression of the type I collagen gene.