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Ординатура / Офтальмология / Английские материалы / Retinal Degenerative Diseases Laboratory and Therapeutic Investigations_Anderson_2008.pdf
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50 The Pathophysiology of Cigarette Smoking and AMD

441

50.5 Non-oxidative Chemical Damage by Cigarette Smoke

50.5.1 Nicotine

Of the numerous constituents of cigarette smoke, nicotine is the only known ingredient to possess addictive properties. Nicotine promotes angiogenesis in vitro (Heeschen et al. 2001) and in vivo (Suner et al. 2004) and these biological effects can be applied to AMD. Angiogenesis is likely due to a nicotine-induced increase in expression of Vascular Endothelial Growth Factor (VEGF) in endothelial cells (Conklin et al. 2002). A nicotine-induced increase of VEGF could account for the expedited progression to neovascular AMD seen in smokers.

Nornicotine, a metabolite of nicotine catalyses the metabolism of retinoids to all- E-retinal which can lead to the accumulation of lipofuscin, a constituent of drusen, in RPE cells (Brogan et al. 2005). Nicotine also exerts a vasoconstrictive action via α-adrenergic stimulation which may impair blood flow through the choroid (Zhu and Parmley 1995).

50.5.2 Polycyclic Aromatic Hydrocarbons

Polycyclic aromatic hydrocarbons (PAH) have been linked to the toxicity of cigarette smoke through vascular and carcinogenic effects in cardiovascular and respiratory disease (Ambrose and Barua 2004). Benzo[a]pyrene is a PAH found in cigarette smoke and that damages nuclear and mitochondrial DNA in bovine RPE (Patton et al. 2002) through the formation of a reactive epoxide. Benzo(e)pyrene is a related polycyclic aromatic hydorcarbon molecule cause caspase mediated cell apoptosis of human RPE cells (Sharma et al. 2008) perhaps through the generation of similar epoxides.

50.6 Inflammation

50.6.1 Inflammation and AMD

Drusen deposits in atrophic AMD contain evidence of chronic low grade inflammation supporting the hypothesis that inflammation is central in pathogenesis of AMD (Anderson et al. 2002). The complement cascade may be central this process. A number of genetic risk factors associated with AMD are involved in the activation and regulation of the complement pathway and thus far, SNPs in complement components C3, CFH, C2 and Factor B have been implicated in the pathogenesis of AMD (Haines et al. 2005; Gold et al. 2006; Yates et al. 2007).

Inflammatory mediators also govern the progression from atrophic to neovascular AMD. Depletion of macrophages in a laser-induced animal model of CNV inhibits the immune response and the subsequent neovascularization (Espinosa-Heidmann et al. 2003).