Opsin 3 and 4 mediate light-induced pulmonary vasorelaxation that is potentiated by G protein-coupled receptor kinase 2 inhibition

Abstract

We recently demonstrated that blue light induces vasorelaxation in the systemic mouse circulation, a phenomenon mediated by the nonvisual G protein-coupled receptor melanopsin (Opsin 4; Opn4). Here we tested the hypothesis that nonvisual opsins mediate photorelaxation in the pulmonary circulation. We discovered Opsin 3 (Opn3), Opn4, and G protein-coupled receptor kinase 2 (GRK2) in rat pulmonary arteries (PAs) and in pulmonary arterial smooth muscle cells (PASMCs), where the opsins interact directly with GRK2, as demonstrated with a proximity ligation assay. Light elicited an intensity-dependent relaxation of PAs preconstricted with phenylephrine (PE), with a maximum response between 400 and 460 nm (blue light). Wavelength-specific photorelaxation was attenuated in PAs from Opn4 mice and further reduced following shRNA-mediated knockdown of Opn3. Inhibition of GRK2 amplified the response and prevented physiological desensitization to repeated light exposure. Blue light also prevented PE-induced constriction in isolated PAs, decreased basal tone, ablated PE-induced single-cell contraction of PASMCs, and reversed PE-induced depolarization in PASMCs when GRK2 was inhibited. The photorelaxation response was modulated by soluble guanylyl cyclase but not by protein kinase G or nitric oxide. Most importantly, blue light induced significant vasorelaxation of PAs from rats with chronic pulmonary hypertension and effectively lowered pulmonary arterial pressure in isolated intact perfused rat lungs subjected to acute hypoxia. These findings show that functional Opn3 and Opn4 in PAs represent an endogenous "optogenetic system" that mediates photorelaxation in the pulmonary vasculature. Phototherapy in conjunction with GRK2 inhibition could therefore provide an alternative treatment strategy for pulmonary vasoconstrictive disorders.

The human non-visual opsin OPN3 regulates pigmentation of epidermal melanocytes through interaction with MC1R

“…This is particularly intriguing considering that OPN3 homologues absorb light in the visible spectrum [24][25][26]. In addition, unlike two recent reports suggesting that human OPN3 functions in a blue light-dependent manner in human skin [41,42] and in rat and human pulmonary vasorelaxation [41,42], we did not detect OPN3 sensitivity to blue light by either spectrophotometric analysis or by monitoring Ca 2+ levels in melanocytes. One possible scenario is that OPN3 absorbs light outside the range covered by conventional UV-visible spectroscopy (200-700 nm) or that its absorption overlaps with protein absorption (λmax=280 nm) and is masked by the large protein peak [43].…”

Differential response of human dermal fibroblast subpopulations to visible and near‐infrared light: Potential of photobiomodulation for addressing cutaneous conditions

“…Traditionally, cytochrome c oxidase and nitrozated proteins were considered as the major targets of light . Recently, there has been increasing evidence that cryptochromes and opsins , mediate the cell's response to visible and UV light. All this suggests that there are several molecular targets, which could intercept a photon of light and trigger multiple signaling cascades.…”

Regulation of Melanopsin Signaling: Key Interactions of the Nonvisual Photopigment

“… noticed substantial similarity of this system with that of photoreceptive neurones of invertebrates involving Go coupled to particulate guanylyl cyclase and cGMP‐dependent gating of K + channels. GRK2 role in desensitization of blue light‐induced melanopsin‐mediated response was demonstrated in further studies of the same group in rat pulmonary arteries and pulmonary arterial smooth muscle cells . Data described above suggest that melanopsin also plays a role outside the eye and the signaling cascade involved differs between different tissues.…”

“…Melanopsin is also present in blood vessels, where it plays a crucial role in photorelaxation. Sikka et al (15) hypothesized that melanopsin was probably localized in vascular smooth muscle cells (VSMCs), which was confirmed very recently by demonstrating the presence of melanopsin in pulmonary arterial smooth muscle cells (PASMCs) and rat pulmonary arteries (19). The occurrence of melanopsin mRNA in arteries was also reported by platform Expression Atlas (20) including both microarray and RNA-seq data as well as by Genevisible platform collecting data from Affymetrix Human Genome U133 Plus 2.0 Array (21).…”

“…In HEK293 cells, murine Opn4-L interacted with GRK2 and GRK3 (29); however, other studies showed that even though GRK2 was present in vivo, it did not play a major role in the regulation of murine melanopsin activity (66). In contrast, GRK2 was demonstrated to be strongly involved in the melanopsin-triggered photorelaxation of blood vessels upon illumination in rodents (15,19). It indicates that the regulation of melanopsin signaling by protein kinases might vary depending on the cell type or the specific process.…”