Abstract
Purpose :
Corneal epithelium is subjected to biological, chemical, and physical stressors from the environment, many of which are known activators or modulators of TRPV4 channel. TRPV4 signaling has been linked to nociception and release of inflammatory molecules which might contribute to tissue damage but the role of TRPV4 in corneal epithelial pathophysiology is not understood well. Here, we investigate the involvement of TRPV4 in ultraviolet light-mediated injury, G-protein receptor-dependent signaling and cytokine release.
Methods :
Corneas from C57BL/6 and TRPV4-/- mice were enzymatically detached from the stroma and used for in situ experiments. They were subjected to assorted agonists and antagonists as well as to UVB radiation, mimicking UVB damage inflicted to the cornea. For cytokine release assay, epithelial cells were dissociated, subjected to the UV stimuli or the selective TRPV4 agonist GSK1016790A and supernatants were evaluated by chemiluminescence reaction. Optical imaging assessed the properties of Ca2+ homeostasis under different experimental conditions.
Results :
UVB radiation reversibly elevated [Ca2+]i in mouse corneal epithelial cells, an effect that was slightly attenuated by TRPV4 ablation or inhibition. UV-evoked increases in [Ca2+]i principally reflected release of calcium from the pool stored intracellularly within the endoplasmic reticulum. Pharmacological activation of the protease-activated receptor-2 (PAR-2) sensitized TRPV4 for agonist activation. UVB radiation and TRPV4 activation evoked stimulus-specific release of proinflammatory cytokines and inflammatory substances, effects that were antagonized by pharmacological blockade of TRPV4.
Conclusions :
Our data suggest that corneal epithelial cells respond to harmful UVB radiation with parallel and additive activation of TRPV4 channels and release of calcium from intracellular stores. It is possible that substances residing in tears contribute to PAR-2-mediated TRPV4 regulation in corneal epithelial cells under pathological conditions. In addition, the corneal milieu is likely to be influenced by TRPV4- and/or UVB-dependent release of cytokines and inflammatory substances, with potential effects on transparency, would healing and nociception. Overall, this study identifies TRPV4 as a potential target of ocular surface inflammation and tissue damage.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.