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Vivian K. Lee, Jaimie Hoh Kam, Glen Jeffery; Vitamin D Reduce Retinal Inflammation And Clears Amyloid Beta Systemically In Aged Mice. Invest. Ophthalmol. Vis. Sci. 2012;53(14):1238.
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Vitamin D3 plays a key role in immune regulation and may protect against ageing. Excess amyloid beta deposition and inflammation have been known as risk factors leading to age-related macular degeneration (AMD), the largest cause of blindness in those over 50 years in developed countries. Vitamin D3 has been shown to significantly reduce retinal macrophage numbers, reduce inflammation and clear amyloid beta in the eye and brain. These changes were reflected in a significant improvement in visual function. Vitamin D3 has also been linked to longer leukocyte telomeres, and epidemiologically to possible protection against AMD. Here, we examine the outer retina following vitamin D3 treatment to specifically look at its inflammatory properties on outer segments. We also examine its impact on amyloid beta in retinal and major systemic blood vessels in aged mice.
Ultrastructure examination of the outer retina was analysed with scanning electron microscopy (SEM). Cone density was estimated with peanut agglutinin staining. Levels of proinflammatory cytokine, tumour necrosis factor-α (TNF-α) were also assessed using immunohistochemistry (IHC). Amyloid beta deposition was also studied using IHC in retinal and aortic blood vessels.
Aged vitamin D3 treated mice had markedly decreased deposition on their photoreceptor outer segments as revealed in SEM images. These appeared clean with a relatively regular alignment. However, a greater level of deposition was present on controls and in the majority of cases they appeared to be less regular in their alignment, although no quantitative measures of these were made. Together with decreased deposition, the IHC revealed that levels of TNF-α, a pro-inflammatory cytokine also were significantly reduced. Estimates of cone photoreceptor numbers did not reveal significant differences between the groups, although numbers in vitamin D3 treated animals were slightly higher. Analysis of amyloid beta levels in blood vessels revealed reductions in the vitamin D3 treated animals in both the retina and the aorta.
Vitamin D3 may have a range of therapeutic effects in its immune protective role and its impact on inflammation may be significant for AMD. Supplementation may be a route to reducing inflammation in aged human retina, delay photoreceptor degeneration and clear amyloid beta systemically.
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