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M. Schallenberg, S. Thanos; Non-Histone HMGB1 is a Transcriptional Factor Involved in Degeneration of Injured RGCs. Invest. Ophthalmol. Vis. Sci. 2009;50(13):135.
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High mobility group box 1 (HMGB1) is a non-histone chromosomal protein implicated in a variety of biologically important processes, including transcription, DNA repair, differentiation and inflammation. In the present study, we focussed on the proteomic analysis of HMGB-1 protein during retinal ganglion cell (RGC) degeneration and regeneration and we examined its functional role during glaucomatous neurodegeneration.
Two-dimensional (2-D) gel electrophoresis profiles of extracts from normal and glaucomatous rat retina as well as regenerating and non-regenerating rat retina after optic nerve crush and lens injury were compared. HMGB1 was further investigated for a potential role in glaucomatous neurodegeneration. To verify the results of the 2-D gel electrophoresis and to determine cellular localisation, immunochemistry staining and Western blot analysis was performed. RGC-5 cells were incubated either in presence or absence of HMGB1 protein. The supernatant of the medium was collected to examine the cytokine level within the medium after incubation with HMGB1. To examine the expression profiles of apoptosis-related proteins, the cleaved caspase 3 activity and pBad expression of the HMGB1 treated RGC-5 was assessed by Western blot analysis.
HMGB1 was differentially expressed throughout the gels. In glaucomatous retina the HMGB1 expression was strongly up-regulated compared to normal retina. The expression of HMGB1 is nearly abolished, when the retina regenerates after optic nerve crush and lens injury compared to non-regenerative cultivation. The Cytokine Array revealed a decreased CNTF concentration and an increased concentration of TNF- and VEGF within the medium. Western blot analysis of HMGB1 treated RGC showed an increased cleaved caspase 3 activity and a decreased pBad expression indicating a changed expression of apoptosis-related proteins.
Our data suggest that HMGB1 induces cytokine release and participates in the pathogenesis of neurodegenerative disease of the eye by mediating apoptosis in retinal ganglion cells.
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