title: Investigation of synergistic mechanism and identification of interaction site of aldose reductase with the combination of gigantol and syringic acid for prevention of diabetic cataract.
abstract: BACKGROUND
  Gigantol and syringic acid (SA) have been shown to synergistically prevent formation of diabetic cataract (DC). However, the exact mechanism of this effect is unknown. Here, we investigate the effect of these compounds on the activity of aldose reductase (AR) and cataract formation.
  
  
  METHODS
  We examined the synergistic anti-cataract efficacy of gigantol and SA in the high glucose- and streptozotocin -induced DC rat model; synergism was evaluated using Jin's formula. We investigated possible mechanisms of action by measuring AR expression and activity and levels of sorbitol using enzyme kinetics, Western blot, and RT-PCR. Finally, we examined binding interaction between AR and both compounds using a combination of site-directed mutagenesis, recombinant expression of wild-type and mutant proteins, and enzyme kinetics.
  
  
  RESULTS
  Combination treatment of gigantol and SA synergistically protected both HLECs(human lens epithelial cells) grown in vitro and DC formation in STZ-induced rats in vivo. Synergism was attributed to inhibition of AR activity, downregulation of AR expression via impaired transcription, and decreased sorbitol levels. Enzyme kinetics studies showed that the activity of an AR Asn160Ala mutant protein was significantly decreased compared to wild-type AR, confirming that Asn160 is a key residue for interaction between AR and both compounds.
  
  
  CONCLUSIONS
  Combined administration of gigantol and SA synergize to enhance anti-cataract efficacy. The synergistic effect is mainly attributed to disruption of the polyol pathway and inhibition of AR activity.
authors: Department of Histology and Embryology, Guangzhou University of Chinese Medicine, 510006, Guangzhou, China.
authors: Jie
authors: J
authors: Wu
authors: Department of Histology and Embryology, Guangzhou University of Chinese Medicine, 510006, Guangzhou, China.
authors: Xue
authors: X
authors: Li
authors: Department of Histology and Embryology, Guangzhou University of Chinese Medicine, 510006, Guangzhou, China. hlfh@gzucm.edu.cn.
authors: Hua
authors: H
authors: Fang
authors: Department of Histology and Embryology, Guangzhou University of Chinese Medicine, 510006, Guangzhou, China.
authors: Yanqun
authors: Y
authors: Yi
authors: Department of Histology and Embryology, Guangzhou University of Chinese Medicine, 510006, Guangzhou, China.
authors: Dan
authors: D
authors: Chen
authors: Department of Histology and Embryology, Guangzhou University of Chinese Medicine, 510006, Guangzhou, China.
authors: Yan
authors: Y
authors: Long
authors: Department of Histology and Embryology, Guangzhou University of Chinese Medicine, 510006, Guangzhou, China.
authors: Xinxin
authors: X
authors: Gao
authors: Department of Histology and Embryology, Guangzhou University of Chinese Medicine, 510006, Guangzhou, China. yaojidewxy@sina.com.|Antioxidants Research Laboratory, Jean Mayer USDA Human Nutrition Research Center on Aging, Tufts University, 02111, Boston, MA, USA. yaojidewxy@sina.com.
authors: Xiaoyong
authors: X
authors: Wei
authors: Antioxidants Research Laboratory, Jean Mayer USDA Human Nutrition Research Center on Aging, Tufts University, 02111, Boston, MA, USA.
authors: C-Y Oliver
authors: CY
authors: Chen
mesh_terms: D000449:Aldehyde Reductase / Q000187:drug effects* / Q000378:metabolism; D000818:Animals; D001632:Bibenzyls / Q000737:chemistry / Q000494:pharmacology*; D002386:Cataract / Q000517:prevention & control*; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D048909:Diabetes Complications / Q000517:prevention & control*; D004195:Disease Models, Animal; D004357:Drug Synergism; D005260:Female; D005707:Gallic Acid / Q000031:analogs & derivatives* / Q000737:chemistry / Q000494:pharmacology; D006139:Guaiacol / Q000031:analogs & derivatives* / Q000737:chemistry / Q000494:pharmacology; D006801:Humans; D008297:Male; D051381:Rats; D017208:Rats, Wistar
chemical_list: D001632:Bibenzyls; D005707:Gallic Acid; C478099:gigantol; D006139:Guaiacol; C001945:syringic acid; D000449:Aldehyde Reductase
keywords: Aldose reductase; Diabetic cataract; Gigantol; Site-directed mutagenesis; Synergism; Syringic acid