LED Light-Induced ROS Differentially Regulates Focal Adhesion Kinase Activity in HaCaT Cell Viability.

Jun-Sub Kim,Ssang-Taek Lim

doi:10.3390/cimb44030082

Abstract

In this study, changes in cell signaling mechanisms in skin cells induced by various wavelengths and intensities of light-emitting diodes (LED) were investigated, focusing on the activity of focal adhesion kinase (FAK) in particular. We examined the effect of LED irradiation on cell survival, the generation of intracellular reactive oxygen species (ROS), and the activity of various cell-signaling proteins. Red LED light increased cell viability at all intensities, whereas strong green and blue LED light reduced cell viability, and this effect was reversed by NAC or DPI treatment. Red LED light caused an increase in ROS formation according to the increase in the intensity of the LED light, and green and blue LED lights led to sharp increases in ROS formation. In the initial reaction to LEDs, red LED light only increased the phosphorylation of FAK and extracellular-signal regulated protein kinase (ERK), whereas green and blue LED lights increased the phosphorylation of inhibitory-κB Kinase α (IKKα), c-jun N-terminal kinase (JNK), and p38. The phosphorylation of these intracellular proteins was reduced via FAK inhibitor, NAC, and DPI treatments. Even after 24 h of LED irradiation, the activity of FAK and ERK appeared in cells treated with red LED light but did not appear in cells treated with green and blue LED lights. Furthermore, the activity of caspase-3 was confirmed along with cell detachment. Therefore, our results suggest that red LED light induced mitogenic effects via low levels of ROS–FAK–ERK, while green and blue LED lights induced cytotoxic effects via cellular stress and apoptosis signaling resulting from high levels of ROS.

Highlights

The scientific basis of photodynamic therapy (PDT) was defined at the beginning of the twentieth century [1], and currently, the main dermatological application of PDT is as a low-level laser therapy [2]
We found that red light-emitting diode (LED) light elicited a distinct pattern of focal adhesion kinase (FAK) activation and downstream signaling, as compared to blue LED light in HaCaT cells
We observed that LEDs induced reactive oxygen species (ROS) formation and activated FAK

Summary

Introduction

The scientific basis of photodynamic therapy (PDT) was defined at the beginning of the twentieth century [1], and currently, the main dermatological application of PDT is as a low-level laser therapy [2]. Evidence has increasingly suggested beneficial effects of LEDs in the treatment of many conditions such as skin inflammatory conditions, aging, and disorders linked to hair growth [1]. Despite these beneficial effects, the therapeutic potential of LED irradiation remains controversial due to the divergence of protocols used [2,3]. Mechanistic studies have shown that LEDs at 625 nm had the potential to treat skin disorders via reactive oxygen species (ROS) and/or inflammatory signaling through the SPHK1/NF-κB pathway [4]. LEDs at 655 nm have promoted human hair growth by activating Wnt/β-catenin signaling [5], and LEDs at 660 nm have reversed collagen downregulation and matrix metalloproteinase-1 upregulation in human skin [6]

Methods

Results

Conclusion