Significance: Photobiomodulation (PBM) refers to the beneficial effects of low-energy light absorption. Although there is a large body of literature describing downstream physiological benefits of PBM, there is a limited understanding of the molecular mechanisms underlying these effects. At present, the most popular hypothesis is that light absorption induces release of nitric oxide (NO) from the active site of cytochrome c oxidase (COX), allowing it to bind O2 instead. This is believed to increase mitochondrial respiration, and result in greater overall health of the cell due to increased adenosine triphosphate production. Aim: Although NO itself is a powerful signaling molecule involved in a host of biological responses, less attention has been devoted to NO mechanisms in the context of PBM. The purpose of our work is to investigate wavelength-specific effects on intracellular NO release in living cells. Approach: We have conducted in-depth dosimetry analyses of NO production and function in an in vitro retinal model in response to low-energy exposure to one or more wavelengths of laser light. Results: We found statistically significant wavelength-dependent elevations (10% to 30%) in intracellular NO levels following laser exposures at 447, 532, 635, or 808 nm. Sequential or simultaneous exposures to light at two different wavelengths enhanced the NO modulation up to 50% of unexposed controls. Additionally, the immediate increases in cellular NO levels were independent of the function of NO synthase, depended greatly on the substrate source of electrons entering the electron transport chain, and did not result in increased levels of cyclic guanosine monophosphate. Conclusions: Our study concludes the simple model of light-mediated release of NO from COX is unlikely to explain the wide variety of PBM effects reported in the literature. Our multiwavelength method provides a novel tool for studying immediate and early mechanisms of PBM as well as exploring intracellular NO signaling networks.

中文翻译：

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细胞内一氧化氮水平的波长和辐照度依赖性变化。

意义：光生物调节 (PBM) 是指低能量光吸收的有益效果。尽管有大量文献描述了 PBM 的下游生理益处，但对这些作用背后的分子机制的了解有限。目前，最流行的假设是光吸收诱导一氧化氮 (NO) 从细胞色素 c 氧化酶 (COX) 的活性位点释放，使其与 O2 结合。这被认为会增加线粒体呼吸，并由于三磷酸腺苷产量增加而导致细胞整体健康。目的：虽然 NO 本身是一种强大的信号分子，涉及许多生物反应，但在 PBM 背景下对 NO 机制的关注较少。我们工作的目的是研究波长对活细胞中细胞内 NO 释放的影响。方法：我们在体外视网膜模型中对 NO 的产生和功能进行了深入的剂量学分析，以响应低能量暴露于一种或多种波长的激光。结果：我们发现，在 447、532、635 或 808 nm 激光照射后，细胞内 NO 水平出现统计学显着的波长依赖性升高（10% 至 30%）。连续或同时暴露于两种不同波长的光可增强高达 50% 的未暴露对照的 NO 调制。此外，细胞 NO 水平的立即增加与 NO 合酶的功能无关，很大程度上取决于进入电子​​传递链的电子底物来源，并且不会导致环磷酸鸟苷水平增加。结论：我们的研究得出结论，光介导 COX 释放 NO 的简单模型不太可能解释文献中报道的各种 PBM 效应。我们的多波长方法为研究 PBM 的直接和早期机制以及探索细胞内 NO 信号网络提供了一种新工具。