Cis‐urocanic acid, a novel anti‐inflammatory and cytoprotective drug, decreases effectively UVB‐induced IL‐6 secretion and cytotoxicity in human corneal and conjunctival epithelial cells in vitro

Abstract

Abstract Purpose Urocanic acid (UCA) is a major UV‐absorbing chromophore in the epidermis and has been suggested to act as one of the initiators of UV‐induced immunosuppression. The anti‐inflammatory and cytoprotective effects of cis‐UCA were studied in human corneal and conjunctival epithelial cells in response to UVB‐irradiation in vitro. Methods Human corneal epithelial cells (HCE‐2) and human conjunctival epithelial cells (HCEC) were exposed to 10, 100, 1000, and 5000 µg/ml concentrations of cis‐UCA (BioCis Pharma, Turku, Finland) with and without UVB‐radiation (4 x Philips TL 20W/12 lamps; total irradiation dose 153 mJ/cm2). Secreted interleukin‐6 (IL‐6) levels were analyzed with ELISA assay. Cell viability was measured by a colorimetric MTT (3‐(4,5‐dimethyldiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide) assay. Results The 100 µg/ml and 1000 µg/ml concentrations of cis‐UCA significantly suppressed IL‐6 secretion induced by UVB‐irradiation in both cell types. In addition, the same concentrations improved the viability of the UVB‐irradiated cells when analyzed by MTT assay. No significant alterations in IL‐6 expression levels or viability were observed in response to 10, 100, and 1000 µg/ml cis‐UCA only, while 5000 µg/ml cis‐UCA evoked cytotoxicity in both cell types. Conclusion Our findings suggest that cis‐UCA is a promising novel drug to suppress UVB‐induced inflammation and cellular damage in human corneal and conjunctival epithelial cells.