Narrow Results

Excitotoxicity has been proposed to play a pivotal role in retinal ischemia. Retinal ischemia-associated ocular disorders are vision threatening. The aim was to also examine whether and how S-allyl L-cysteine (SAC) can protect the retina against kainate excitotoxicity. In vivo retinal excitotoxicity was induced by an intravitreous injection of 100 μM kainate into a Wistar rat eye for 1 day. The management and mechanisms involved in the processes were evaluated by electrophysiology, immunohistochemistry, histopathology, and various biochemical approaches. In the present study, the cultured retinal cells were shown to possess kainate receptors. The defined retinal excitotoxic changes were characterized by a decrease in electroretinogram (ERG) b-wave amplitudes, a loss of the fluorogold retrograde labeled retinal ganglion cells (RGCs), an increase in the apoptotic cells in the RGC layer, and an increase in vimentin or glial fibrillary acidic protein (GFAP) immunoreactivity, a marker for Müller cells. An up-regulation in the mRNA levels of inducible nitric oxide synthase (iNOS) and matrix metalloproteinases-9 (MMPs-9) was also detected in the retina subjected to kainate excitoxicity. Importantly, the excitotoxicity-induced alterations were significantly blunted when 100 μM SAC and/or the kainate receptor antagonist CNQX was applied. Conclusively, SAC would seem to protect the retina against kainate excitotoxicity via an inhibition of the up-regulation of iNOS and MMP-9 as well as a modulation of glial activation and apoptosis.

Endothelial dysfunction plays an important role in the pathogenesis of atherogenesis. 2,3,5,4′-tetrahydroxystilbene-2-O-β-D-glucoside (TSG), an active component of the rhizome extract from Polygonum multiflorum (PM), exhibits significant anti-atherosclerotic activity. Here, we used human umbilical vein endothelial cells (HUVECs) induced by tumor necrosis factor-α (TNF-α) in vitro to investigate the cytoprotective effects of TSG on TNF-α-induced endothelial injury and the related mechanisms. Pretreatment with 50 and 100 μM TSG markedly attenuated TNF-α-induced loss of cell viability and release of lactate dehydrogenase (LDH) and inhibited TNF-α-induced cell apoptosis. The inhibition of vimentin expression was involved in the cytoprotection afforded by TSG. Using inhibitors for PI3K and TGFβ or siRNA for Akt and Smad2, we found that vimentin production in HUVECs is regulated by TGFβ/Smad signaling, but not by PI3K–Akt–mTOR signaling. Meanwhile, TSG inhibited both the expression of TGFβ1 and the phosphorylation of Smad2 and Smad3, and TSG suppressed the nuclear translocation of Smad4 induced by TNF-α. These results suggest that TSG protects HUVECs against TNF-α-induced cell damage by inhibiting vimentin expression via the interruption of the TGFβ/Smad signaling pathway.