Andrew T. Tsin, Ph.D.
Professor of Biochemistry and Physiology
Office: BSB 1.03.36
Phone: (210) 458-5480
Andrew.Tsin@utsa.edu
Research Interests
The focus of our Vision Research Laboratory is to understand the biochemical and cellular/molecular events in the eye related to normal visual functions and to abnormal/disease conditions.
A major emphasis of our laboratory is to investigate the mechanism of pigment regeneration in the cone visual system. Upon light adaptation, cone pigments are bleached to initiate electrical signals in the cone photoreceptors. These signals are then transmitted by neurons to the brain for color visual perception. In order to sustain such visual function, cone pigment must be regenerated in-situ but the underlying mechanism of this cone pigment regeneration is not known. Using animals models, the kinetics of cone pigment bleaching and regeneration are studied in details using biochemical methods. The cellular mechanisms of cone pigment regeneration are also studied using Muller cells and retinal pigment epithelial cells in culture. Specifically, we focus on the abilities of these cells to esterify, isomerize and oxidize the vitamin A (retinoid) chromophore of cone visual pigments.
An additional emphasis of our vision research laboratory is to learn how hyperglycemia and/or insulin induce vascular endothelial growth factor (VEGF) secretion by retinal cells. Retinal pigment epithelial cells, retinal pericytes, and endothelial cells are maintained in culture. Growth factors such as VEGF, transforming growth factor (TGF), and bone morphological proteins (BMP) are assayed for protein end-product using ELISA. The expression of these proteins is measured by RNA protection assays. We are particularly interested in the effect of BMP-4, TGB-β, and PEDF on the secretion of VEGF by retinal cells. Our long term goal is to learn how cytokines mediate angiogenesis leading to diabetic retinopathy or age-related macular degeneration.
Recent Publications
Sardar DK, Swanland GY, Yow RM, Thomas RJ, Tsin AT. Optical properties of ocular tissues in the near infrared region. Lasers Med Sci. 2007 Mar;22(1):46-52.
Muniz A, Villazana-Espinoza ET, Thackeray B, Tsin AT. 11-cis-Acyl-CoA:retinol O-acyltransferase activity in the primary culture of chicken Muller cells. Biochemistry. 2006 Oct 10;45(40):12265-73.
Villazana-Espinoza ET, Hatch AL, Tsin AT. Effect of light exposure on the accumulation and depletion of retinyl ester in the chicken retina. Exp Eye Res. 2006 Oct;83(4):871-6.
Vogt RR, Unda R, Yeh LC, Vidro EK, Lee JC, Tsin AT. Bone morphogenetic protein-4 enhances vascular endothelial growth factor secretion by human retinal pigment epithelial cells. J Cell Biochem. 2006 Aug 1;98(5):1196-202.
Sardar DK, Yow RM, Tsin AT, Sardar R. Optical scattering, absorption, and polarization of healthy and neovascularized human retinal tissues. J Biomed Opt. 2005 Sep-Oct;10(5):051501.
Trevino SG, Villazana-Espinoza ET, Muniz A, Tsin AT. Retinoid cycles in the cone-dominated chicken retina. J Exp Biol. 2005 Nov;208(Pt 21):4151-7.
Sardar DK, Salinas FS, Perez JJ, Tsin AT. Optical characterization of bovine retinal tissues. J Biomed Opt. 2004 May-Jun;9(3):624-31.
Chen M, Thomson AB, Tsin AT, Basu TK. The hepatic retinyl ester hydrolase activity is depressed at the onset of diabetes in BB rats. Br J Nutr. 2003 Feb;89(2):231-8.
Lu J, Dixon WT, Tsin AT, Basu TK. The metabolic availability of vitamin A is decreased at the onset of diabetes in BB rats. J Nutr. 2000 Aug;130(8):1958-62.
Tsin AT, Mata NL, Ray JA, Villazana ET. Substrate specificities of retinyl ester hydrolases in retinal pigment epithelium. Methods Enzymol. 2000;316:384-400.
Gamble MV, Mata NL, Tsin AT, Mertz JR, Blaner WS. Substrate specificities and 13-cis-retinoic acid inhibition of human, mouse and bovine cis-retinol dehydrogenases. Biochim Biophys Acta. 2000 Jan 3;1476(1):3-8.