title: Topical application of L-arginine blocks advanced glycation by ascorbic acid in the lens of hSVCT2 transgenic mice.
abstract: OBJECTIVE
  Previous experiments from our laboratory showed that the oral intake of selected guanidino compounds could block the formation of crystallin-bound advanced ascorbylation products. Here we tested whether these were also active when applied as eye drops.
  
  
  METHODS
  Two month old hSVCT2 transgenic mice (n=10) were treated twice daily with one drop of 0.1% L-arginine, γ-guanidinobutyric acid (GBA), penicillamine (PA) or N-acetylcysteine (NAC) in one eye and vehicle only in the other eye. After seven months, lens crystallins were isolated, dialyzed, and proteolytically digested to determine the protein-bound fluorescence at 335/385 and 370/440 nm excitation/emission and the advanced glycation/ascorbylation endproducts carboxymethyl-lysine (CML), carboxyethyl-lysine (CEL), glucosepane, glyoxal, and methylglyoxal hydroimidazolones G-H1 and MG-H1. The topical uptake of L-arginine and NAC was also evaluated in vitro and in vivo in rabbit lens.
  
  
  RESULTS
  In hSVCT2 mice, L-arginine decreased 335/385 and 370/440 nm fluorescence by 40% (p<0.001), CML, CEL, and glucosepane crystallin crosslinks by 35% (p<0.05), 30% (p<0.05), and 37% (p<0.05), respectively, without affecting MG-H1 and G-H1. NAC decreased 335/385 nm fluorescence by 50% (p<0.001) but, like PA and GBA, had no effect on other modifications. L-Arginine uptake into rabbit eyes treated topically reached identical lenticular plateau levels (~400 nmol/g wet weight) at 0.5% and 2.0% but levels remained three times higher at 5 h at 2% versus 0.5% concentration, respectively. In vitro studies showed a 100 fold higher L-arginine level than NAC levels, implicating high affinity uptake of the former.
  
  
  CONCLUSIONS
  L-Arginine when applied both orally and topically is a potent and broad suppressor of advanced ascorbylation in the lens. Its uptake in rabbit lens upon topical application suggests transcorneal uptake into the human lens should be feasible for testing its potential anticataract properties in clinical trials.
authors: Department of Pathology, Case Western Reserve University, Cleveland, OH, USA.
authors: Xingjun
authors: X
authors: Fan
authors: Liu
authors: L
authors: Xiaoqin
authors: Breshey
authors: B
authors: Potts
authors: Christopher M
authors: CM
authors: Strauch
authors: Ina
authors: I
authors: Nemet
authors: Vincent M
authors: VM
authors: Monnier
mesh_terms: D000111:Acetylcysteine / Q000008:administration & dosage; D000287:Administration, Topical; D000375:Aging; D000818:Animals; D001120:Arginine / Q000008:administration & dosage / Q000627:therapeutic use; D001205:Ascorbic Acid / Q000378:metabolism*; D001693:Biological Transport, Active; D002386:Cataract / Q000517:prevention & control*; D003459:Crystallins / Q000378:metabolism*; D055879:Gene Knock-In Techniques; D017127:Glycation End Products, Advanced / Q000378:metabolism*; D006146:Guanidines / Q000008:administration & dosage; D006801:Humans; D007908:Lens, Crystalline / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D013058:Mass Spectrometry; D051379:Mice; D008822:Mice, Transgenic; D009883:Ophthalmic Solutions / Q000008:administration & dosage; D010396:Penicillamine / Q000008:administration & dosage; D011817:Rabbits; D060347:Sodium-Coupled Vitamin C Transporters / Q000235:genetics / Q000378:metabolism*; D013050:Spectrometry, Fluorescence
chemical_list: D003459:Crystallins; D017127:Glycation End Products, Advanced; D006146:Guanidines; D009883:Ophthalmic Solutions; C555163:SLC23A2 protein, human; D060347:Sodium-Coupled Vitamin C Transporters; C001317:gamma-guanidinobutyric acid; D001120:Arginine; D010396:Penicillamine; D001205:Ascorbic Acid; D000111:Acetylcysteine