BACKGROUND: Owing to the increased incidence of photodermatosis caused by ultraviolet light in recent years, it is necessary to clarify the mechanisms potential photodamage to the skin and reveal possible therapeutic targets. Heat shock protein 27 (Hsp27) is well known for suppressing apoptosis. The aim of present study was to elucidate possible photoprotective mechanism between Hsp27 and p21 on ultraviolet B (UVB)-induced photodamage.

MATERIAL AND METHODS: The Hsp27 gene was interfered to assess the expression of its downstream effectors, cell apoptosis, and cell proliferation ability. The cell apoptosis was tested using flow cytometry method. The cell proliferation ability was tested using Cell Counting Kit-8 (CCK-8) assay. The expression of protein was tested using western-blotting method. The expression of mRNA was detected using quantitative reverse transcription polymerase chain reaction (qRT-PCR). The subcellular localization was elucidated using immunofluorescence.

RESULTS: Hsp27 knockdown decreased cell viability and increased the incidence of UVB-induced apoptosis. Compared with control group, activation of phosphorylated-Akt (p-Akt)-dependent pathway resulted in the nuclear accumulation of p21 and suppression of cell proliferation, while promoting apoptosis in Hsp27 knockdown group. In addition, Hsp27 knockdown increased p53 expression and the Bax: Bcl-2 ratio, which further accelerated the apoptotic process.

CONCLUSIONS: These findings complemented the mechanism of skin photodamage and demonstrated the photoprotective mechanisms of Hsp27 in HaCaT cells, which might implicate a potential therapeutic target of photodamage and photodermatosis.

Keywords: Cyclin-Dependent Kinase Inhibitor p21, Dermatitis, Phototoxic, HSP27 Heat-Shock Proteins, Keratinocytes, Ultraviolet Rays