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P.A. Kumar, P. Suryanarayana, G. Bhanuprakash Reddy; Elevated Expression of –Crystallin Subunits in Diabetic Rat Lens: Possible Role of Heat Shock Factors . Invest. Ophthalmol. Vis. Sci. 2006;47(13):2560.
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αA and αB crystallins are the members of sHSP family and their chaperone function has been shown to be critical in preventing the protein aggregation thus favoring the cell survival in response to various stress stimuli. In the present study, we investigated the influence of diabetes induced oxidative stress on expression of αA and αB crystallin and also the heat shock factors involved.
Diabetes was induced in WNIN rats by i.p. injection of streptozotocin (STZ; 35mg/kg b.w), while control rats received only vehicle. Progression of cataract in diabetic rats was monitored by slit lamp biomicroscope. After 8 weeks of STZ treatment animals were sacrificed and tissues were collected. Antioxidant status was estimated by measuring the activity of various antioxidant enzymes, protein carbonyls and lipid peroxidation products. To study the expression of αA, αB subunits and HSFs, gene specific primers were designed and quantified using semi–quantitative RT–PCR. Changes at protein level were estimated using corresponding polyclonal antibodies by western blot.
Lenses isolated from diabetic animals showed reduced glutathione, increased protein carbonyls and lipid peroxidation together with decline in antioxidant enzyme activity. Furthermore, increased oxidative stress in these animals led to the development of cataract. Interestingly, lenses of diabetic animals showed elevated levels of αA and αB crystallins, both at transcript and protein level. Furthermore, increase in the expression of HSF1 and HSF2 observed in these tissues
Diabetic oxidative stress resulted in elevated expression of αA and αB crystallins and possibly b HSF1 and HSF2 mediated gene transcription. Understanding the possible role of HSF mediated sHSP expression against diabetes induced oxidative stress may help in treating diabetic ocular complications more effectively.
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