Mitochondria as Potential Targets and Initiators of the Blue Light Hazard to the Retina

Table 1

Features of major chromophores or pigments in the mitochondria or the retina.

Chromophores or pigments			Wavelength absorption maxima (nm)	Molecular or cellular localizations	Roles in the blue light hazard	References
Mitochondria	Flavin	FMN	450	Complex I	Pro-^†	[128, 216]
		FAD		Complex II
	Porphyrin	Hemes	400-410	Complex III		[135, 217, 218]
				Cytochrome c oxidase (complex IV)
				Cytochrome P450
Retina	Blue-cone opsin^‡ (OPN1SW)		430	Outer segments of cones		[79, 219]
	Rhodopsin (OPN2)		500	Outer segments of rods		[220, 221]
	Melanopsin (OPN4)		479	Cell membrane of ipRGCs		[222, 223]
	All-trans-retinal		382	POS; phagocytosed POS in RPE		[78, 224]
	A2E^§		336, 430-439	Lipofuscin in RPE cells		[225, 226]
	Melanin		335	Melanosomes in RPE cells	Anti-/pro-	[86, 98, 227]
	Carotenoid	Lutein	450	HL and OPL in the peripheral retina	Anti-^†	[228–231]
		Zeaxanthin		HL and OPL in the macula

Abbreviations: FMN: flavin mononucleotide; FAD: flavin adenine dinucleotide; complex I: NADH dehydrogenase; complex II: succinate dehydrogenase (SDH); complex III: coenzyme Q – cytochrome c reductase; OPN: opsin; POS: photoreceptor outer segments; HL: Henle’s nerve fiber layer, composed of photoreceptor axons; OPL: outer plexiform layer. The (part of the) molecule that absorbs the radiation and accounts for its color is dubbed the chromophore. ^†Pro- refers to the corresponding chromophore or pigment that can mediate the blue light hazard, while anti- refers to a protective effect against the blue light hazard. ^‡Cone opsins include three visual pigments, which are sensitive to blue light (peak at 430 nm), green light (peak at 540 nm), and red light (peak at 570 nm), respectively. ^§A2E is one of the components and the potent photosensitizers of lipofuscin. Absorption spectrum of A2E is featured by two maxima at 336 and 430–439 nm.