Differential Expression of TGF-β Isoforms in Human Kerationocytes by Narrow Band UVB

Salvianolic acid A prevents UV-induced skin damage by inhibiting the cGAS-STING pathway

DNA damage resulting from UV irradiation on the skin has been extensively documented in numerous studies. In our prior investigations, we demonstrated that UVB-induced DNA breakage from keratinocytes can activate the cGAS-STING pathway in macrophages. The cGAS-STING signaling pathway serves as the principal effector for detecting and responding to abnormal double-stranded DNA in the cytoplasm. Expanding on our previous findings, we have further validated that STING knockout significantly diminishes UVB-induced skin damage, emphasizing the critical role of cGAS-STING activation in this context. Salvianolic acid A, a principal active constituent of Salvia miltiorrhiza Burge, has been extensively studied for its therapeutic effects in conditions such as coronary heart disease, angina pectoris, and diabetic peripheral neuropathy. However, its effect on cGAS-STING pathway and its ability to alleviate skin damage have not been previously reported. In a co-culture system, supernatant from UVB-treated keratinocytes induced IRF3 activation in macrophages, and this activation was inhibited by salvianolic acid A. Our investigation, employing photodamage and photoaging models, establishes that salvianolic acid A effectively mitigates UV-induced epidermal thickening and collagen degeneration. Treatment with salvianolic acid A significantly reduced skin damage, epidermal thickness increase, and keratinocyte hyperproliferation compared to the untreated photo-damage and photoaging model groups. In summary, salvianolic acid A emerges as a promising candidate for preventing UV-induced skin damage by inhibiting cGAS-STING activation. This research enhances our understanding of the intricate mechanisms underlying skin photodamage and provides a potential avenue for the development of therapeutic interventions.

DNA-PKcs Mediates An Epithelial-Mesenchymal Transition Process Promoting Cutaneous Squamous Cell Carcinoma Invasion And Metastasis By Targeting The TGF-β1/Smad Signaling Pathway

Purpose

DNA-dependent protein kinase catalytic subunit (DNA-PKcs) has attracted extensive attention in various types of malignant tumors. However, the role of DNA-PKcs in cutaneous squamous cell carcinoma (cSCC) development has not been elucidated. In this study, we investigated the role of DNA-PKcs in cSCC and the molecular mechanisms of TGF-β1-induced cSCC progression mediated by DNA-PKcs.

Methods

We performed bioinformatic analysis and RT-PCR to examine the DNA-PKcs expression level in cSCC. Then, we downregulated DNA-PKcs using a DNA-PK-specific inhibitor or small interfering RNA (siRNA) to explore the effects of DNA-PKcs on SCL-1 cell migration and invasion. To further investigate the mechanism by which DNA-PKcs promotes cSCC progression, TGF-β1 and the TGF-β receptor (TGF-βR) I/II dual inhibitor LY2109761 were used to examine whether DNA-PKcs participates in TGF-β1/Smad signaling.

Results

DNA-PKcs expression was upregulated in cSCC. DNA-PK inhibition or expression knockdown resulted in inhibited migration and invasion and altered epithelial-mesenchymal transition (EMT) marker expression patterns in SCL-1 cells. Importantly, TGF-β1 mediated EMT induction in cSCC cells, and DNA-PKcs was identified as a TGF-β1-responsive gene. TGF-β1 promoted DNA-PKcs transcription, and DNA-PKcs enhanced the TGF-β1-induced EMT program involved in cSCC invasion and metastasis by phosphorylating Smad3.

Conclusion

This study is the first to show that DNA-PKcs mediates EMT to promote cSCC aggressiveness by targeting the TGF-β1/Smad signaling pathway, which provides insight into how DNA-PKcs impacts cSCC progression and identifies a new therapeutic target.