The Expression of Toll-Like Receptors (TLRs) in Cultured Human Skin Fibroblast is Modulated by Histamine

Fibroblasts are responsible for the synthesis and degradation of various connective tissue components and soluble mediators of extracellular matrix metabolism. Few studies have been conducted concerning the expression of toll-like receptors (TLRs) in fibroblasts until now. This study aimed first to determine the quantitative expression of TLRs 1 to 10 in human skin fibroblasts and secondarily to explore any influence of expression by histamine, which is a well-known factor engaged in dermal inflammation. It was found that all 10 TLRs were expressed in fibroblasts. Interestingly, the expression of TLRs 4, 5, and 10 was increased after 2 and 6 hours of histamine treatment during culture. However, the expression of TLRs 2, 3, 6, 7, 8, and 9 was decreased after 6 hours of histamine treatment. Among the TLRs with a decreasing expression pattern, TLRs 7 and 8 showed a persistent tendency to decrease. All of these changes in TLR expression with histamine treatment were antagonized by treatment with diphenhydramine, a well-known antihistamine. Thus, these results suggest a role of histamine in the early phase of the dermal inflammatory reaction mediated by TLRs.