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V. Ganapathy, H. Hu, M.E. Ganapathy, S.B. Smith; Upregulation of xCT (x–c transporter) expression in HIV–1 Tat–transgenic mouse eyes . Invest. Ophthalmol. Vis. Sci. 2004;45(13):1134.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: There is evidence for visual deficits in AIDS patients in the absence of secondary infections with opportunistic pathogens such as CMV and HSV. These retinal complications, caused solely by HIV–1 infection, are collectively called non–infectious AIDS retinopathy. The purpose of the present study was to generate a transgenic mouse line which expresses the HIV–1 Tat gene exclusively in MHC class II–positive immune cells and use it as a model for non–infectious AIDS retinopathy. Since there is evidence for a role of the amino acid transport system x–c in glutamate–induced oxidative stress and excitotoxicity, we specifically wanted to use this animal model to study the influence of HIV–1 Tat protein on the expression of this amino acid transport system in ocular tissues. Methods: The HIV–1 Tat cDNA containing the first exon was inserted into pDOI–5 vector under the control of the promoter specific for the murine MHC class II gene Ea. This construct was used to generate the transgenic mouse line. Expression of the transgene was analyzed in macrophages by RT–PCR and western blot. Influence of HIV–1 Tat on the expression of the transport system x–c in mouse eyes was examined by assessing the mRNA levels for the two subunits of the transport system (xCT and 4F2hc) by RT–PCR. Results: Western blot analysis with macrophages isolated from control and transgenic mice indicated the expression of the Tat protein in transgenic mice but not in control mice. RT–PCR with Tat–specific primers and RNA isolated from control and transgenic mouse eyes showed that Tat mRNA was present in the ocular tissues from the transgenic mice. Analyses of mRNA levels for xCT and 4F2hc in eyes from control mice and transgenic mice revealed that the expression of xCT, but not that of 4F2hc, was upregulated in transgenic mouse eyes. Conclusions: We have generated a transgenic mouse line which expresses the HIV–1 Tat protein exclusively in MHC class II–positive immune cells. The expression of HIV–1 Tat protein in these mice leads to the upregulation of xCT in ocular tissues. Since x–c mediates the release of glutamate from the cells in exchange for extracellular cystine, we speculate that the expression of HIV–1 Tat will lead to an increase in the extracellular levels of the excitotoxin glutamate in ocular tissues. These findings may have relevance to the molecular mechanisms involved in the pathogenesis of non–infectious AIDS retinopathy.
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