Abstract
Purpose::
Tobacco smoke is one of the few factors known to be linked to age-related macular degeneration (AMD). Recent studies indicate that levels of cadmium, a toxic metal found in tobacco smoke, are approximately fourfold higher in the retinal tissue of smokers compared to nonsmokers (Erie et al. Am. J. Ophthalm. 2005, 139: 888-893). Presently it is unknown whether cadmium accumulates with age in the human eye and if cadmium levels are elevated in AMD-afflicted eyes.
Methods::
In this study we used graphite furnace atomic absorption spectrometry and inductively-coupled plasma mass spectrometry to assess the distribution of cadmium in the human neural retina, retinal pigment epithelium and choroid in eyes from young (<55 years) and older (≥ 55 yrs) human donors.
Results::
Cadmium levels were highest in the retinal pigment epithelium (RPE) and lowest in the neural retina. In young eyes (n=15), Cd averaged 5.2 ± 1.4 ng/mg protein, 1.0 ± 0.5 ng/mg protein, and 2.1 ± 0.5 ng/mg protein in the RPE, neural retina, and choroid, respectively. In older eyes (n=16), these values were over twofold higher (10.6 ± 2.0 ng/mg protein, 2.5 ± 0.4 ng/mg protein, and 7.6 ± 1.3 ng/mg protein, for RPE, neural retina, and choroid). Cadmium uptake and toxic effects of this metal were determined in cultured human RPE cells. Overnight incubation with Cd altered cell morphology and decreased the density of RPE cells. However, these changes did not occur when the anti-oxidative agent N-Acetyl-L-cysteine (NAC) was present in the incubation solution.
Conclusions::
These findings indicate that cadmium accumulates in retinal tissues during aging. The identification of mechanism(s) of cadmium uptake and toxicity in the RPE and other retinal tissues is needed to elucidate the effects of this metal in the aging retina.
Keywords: aging • drug toxicity/drug effects • retinal pigment epithelium