Calcineurin (Protein phosphatase 2B, PP2B) is a calcium-dependent serine/threonine phosphatase that regulates cellular survival and stress responses; however, its role in ultraviolet B (UVB)–induced skin damage remains incompletely understood. In the study, we investigated whether PP2B activity modulates UVB-induced apoptosis in skin. Normal epidermal keratinocytes (NHEKs) were exposed to UVB irradiation, followed by the assessment of intracellular Ca²⁺ levels, PP2B activity, and cell viability. At 8-12h post-irradiation, UVB significantly reduced intracellular Ca²⁺ concentration and PP2B activity in NHEKs, accompanied by a decrease in cell viability in NHEKs. Treatment with baicalein markedly attenuated UVB-induced apoptosis and restored PP2B activity. Notably, pharmacological inhibition of PP2B abrogated the cytoprotective effects of baicalein, as evidenced by reduced cell viability and increased caspase-3 activity. In an in vivo mouse model, baicalein administration significantly reduced epidermal thickness and the number of TUNEL-positive cells in UVB-irradiated dorsal skin. Consistently, caspase-3 expression was markedly decreased in baicalein-treated skin tissues following UVB exposure. Collectively, these findings demonstrate that UVB-induced keratinocyte apoptosis is associated with reduced PP2B activity, and that baicalein attenuates UVB-induced skin damage at least in part by preserving PP2B homeostasis. Our results identify PP2B as a critical regulator of UVB-induced skin injury, suggesting it as a potential therapeutic target for preventing photodamage.

To Cite This Article: Yin H, Munna AN, Kim JH, Choi J, Seol JW and Park SY, 2026. Ultraviolet B–induced skin damage is mediated by suppression of protein phosphatase 2B activity. Pak Vet J, 46(4): 972-981. http://dx.doi.org/10.29261/pakvetj/2026.082