title: Deciphering the potential efficacy of acetyl-L-carnitine (ALCAR) in maintaining connexin-mediated lenticular homeostasis.
abstract: OBJECTIVE
  To determine the putative role of acetyl-L-carnitine (ALCAR) in maintaining normal intercellular communication in the lens through connexin.
  
  
  METHODS
  In the present study, Wistar rat pups were divided into 3 groups of eight each. On postpartum day ten, Group I rat pups received an intraperitoneal injection (50 µl) of 0.89% saline. Rats in Groups II and III received a subcutaneous injection (50 µl) of sodium selenite (19 µmol/kg bodyweight); Group III rat pups also received an intraperitoneal injection of ALCAR (200 mg/kg bodyweight) once daily on postpartum days 9-14. Both eyes of each pup were examined from day 16 up to postpartum day 30. Alterations in the mean activity of the channel pumps, calcium-ATPase and sodium/potassium-ATPase, were determined. The expression of genes encoding key lenticular gap junctions (connexin 46 and connexin 50) and a channel pump (plasma membrane Ca(2+)-ATPase [PMCA1]) was evaluated by reverse transcription-PCR. Immunoblot analysis was also performed to confirm the differential expression of key lenticular connexin proteins. In addition, bioinformatics analysis was performed to determine the interacting residues of the connexin proteins with ALCAR.
  
  
  RESULTS
  Significantly lower mean activities of Ca(2+)-ATPase and Na(+)/K(+) -ATPase were observed in the lenses of Group II rats than those in Group I rat lenses. However, the observed mean activities of Ca(2+)-ATPase and Na(+)/K(+)-ATPase in Group III rat lenses were significantly higher than those in Group II rat lenses. The mean mRNA transcript levels of the connexin 46 and connexin 50 genes were significantly lower, while the mean levels of PMCA1 gene transcripts were significantly higher, in Group II rat lenses than in Group I rat lenses. Immunoblot analysis also confirmed the altered expression of connexin proteins in lysates of whole lenses of Group II rats. However, the expression of connexin 46 and connexin 50 proteins in lenses from group III rats was essentially similar to that noted in lenses from normal (Group I) rats. Hydrogen bond-interaction between ALCAR and amino acid residues at the functional domain regions of connexin 46 and connexin 50 proteins was also demonstrated through bioinformatics tools.
  
  
  CONCLUSIONS
  The results suggest that ALCAR plays a key role in maintaining lenticular homeostasis by promoting gap junctional intercellular communication.
authors.affiliation: Department of Animal Science, School of Life Sciences, Bharathidasan University, Tiruchirappalli, Tamilnadu, India.
authors.forename: Arumugam Ramachandran
authors.initials: AR
authors.lastname: Muralidharan
authors.forename: George
authors.initials: G
authors.lastname: Leema
authors.forename: Thangaraj
authors.initials: T
authors.lastname: Annadurai
authors.forename: Thirugnanasambandhar Sivasubramanian
authors.initials: TS
authors.lastname: Anitha
authors.forename: Philip A
authors.initials: PA
authors.lastname: Thomas
authors.forename: Pitchairaj
authors.initials: P
authors.lastname: Geraldine
mesh_terms: D000108:Acetylcarnitine / Q000008:administration & dosage*; D000818:Animals; D000831:Animals, Newborn; D001665:Binding Sites; D002450:Cell Communication / Q000187:drug effects; D017630:Connexins / Q000235:genetics / Q000378:metabolism*; D003459:Crystallins / Q000235:genetics / Q000378:metabolism; D005136:Eye Proteins / Q000235:genetics / Q000378:metabolism*; D015870:Gene Expression / Q000187:drug effects; D006706:Homeostasis; D006860:Hydrogen Bonding; D007274:Injections, Intraperitoneal; D007908:Lens, Crystalline / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D008958:Models, Molecular; D053499:Plasma Membrane Calcium-Transporting ATPases / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D051381:Rats; D017208:Rats, Wistar; D020133:Reverse Transcriptase Polymerase Chain Reaction; D018038:Sodium Selenite / Q000008:administration & dosage; D000099264:Connexin 50
chemical_list: D000108:Acetylcarnitine; D017630:Connexins; D003459:Crystallins; D005136:Eye Proteins; D053499:Plasma Membrane Calcium-Transporting ATPases; D018038:Sodium Selenite; D000099264:Connexin 50; C487370:Gja3 protein, rat