Introduction

Ultraviolet A (UVA) radiation, comprising 95% of UV radiation reaching the Earth’s surface, induces skin damage primarily through oxidative stress. The Hippo signalling pathway, involving YAP and kinases such as LATS1/2, plays a crucial role in skin homeostasis and carcinogenesis. However, the interaction between UVA-induced stress signalling and the Hippo pathway remains unclear.

Aim

This study aimed to investigate how UVA exposure alters mRNA expression of canonical Hippo pathway kinases (LATS1/2) and upstream regulators (JNK1/2, ERK2, and ABL1) in human keratinocytes with preserved and silenced YAP expression.

Material and methods

Primary epidermal keratinocytes (PEK) were irradiated with increasing doses of UVA (5, 10, 15, and 20 J/cm²). YAP expression was silenced via siRNA transfection (siYAP PEK). Quantitative real-time PCR (RT-qPCR) assessed mRNA expression levels. Statistical analyses were performed using GraphPad Prism 10.0, with significance set at p < 0.05.

Results

UVA irradiation did not significantly affect mRNA expression of YAP, LATS1, JNK1/2, ERK2, or ABL1 in either PEK or siYAP-PEK. A dose-dependent LATS2 expression pattern was noted in PEK, with siYAP-PEK exhibiting significantly higher LATS2 expression after 10 J/cm² (p < 0.05). JNK1 expression was reduced in siYAP-PEK compared to PEK, with a significant difference at 10 J/cm² (p < 0.05).

Conclusions

UVA radiation did not significantly impact mRNA expression of Hippo pathway kinases or upstream regulators, except for dose-dependent LATS2 expression and reduced JNK1 expression in YAP-silenced keratinocytes, suggesting a limited role of YAP in UVA-induced gene regulation.