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V. Enzmann, C. Meier, G.-M. Sarra, S. Eigeldinger-Berthou; Rasagiline Modulates Apoptosis Differently in Normal and Degenerated Retina. Invest. Ophthalmol. Vis. Sci. 2009;50(13):690.
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The Prph2/rds mouse, a well-characterized animal model for retinitis pigmentosa (RP), was used to evaluate the neuroprotective potential of rasagiline, a second generation of propargylamine compounds. Rasagiline acts by modifying activation of caspase-3 and expression of Bcl-2 family members and exerts a dose-dependent anti-apoptotic effect in neurons. To assess its effect on the pathogenic mechanisms causing retinal degeneration in the Prph2/rds mouse, we examined morphologically and biochemically the time course of photoreceptor cell (PRC) death.
Animals were treated orally with various doses of rasagiline (2, 5, 25, 50 mg /kg/day) starting at post-natal day 1 (P1) till euthanasia at P10, 14, 18, 28 and 56. Morphological analysis consisted of H&E staining followed by morphometric measurement of the outer nuclear layer (ONL) thickness of the neuroretina. Apoptotic cells were identified during retinal development and degeneration by TUNEL-assay, immunoblotting and immunohistochemistry.
Differences in apoptotic events were apparent beginning at P14. In wild type retinae, oral rasagiline treatment delays down-regulation of caspase-3, and slightly increases the expression level of Bcl-2 and Bcl-XL. However, that effect was not measurable morphologically. In the Prph2/rds mouse, treatment results at P56 in an inverse dose dependent PRC rescue measurable by an increase of the ONL thickness highest (~18%) at the concentration of 2 mg/kg/day (p < 0.01). In non-treated degenerated retinae, cleaved caspase-3 and TUNEL positive PRC were detected in the ONL at P14, which overlaps with a rapid caspase-3 and downregulation of anti-apoptotic proteins. When treated with rasagiline, a shift in PRC degeneration is observed, pro-caspases downregulation starting at P18 and anti-apoptotic protein level remaining high, even at P28.
In the Prph2/rds mice, characterized by retinal degeneration due to aberrant expression and activation of caspases, rasagiline has a morphologically significant neuroprotective effect. It is seen as delayed photoreceptor cell death. That effect is probably mediated by interfering in the cleavage and/or the expression of several caspase precursors. Rasagiline treatment also discloses the possibility of an alternative caspase-3 independent apoptotic pathway that leads ultimatively to retinal degeneration.
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