Tempol reduces oxidative stress and restores renal dopamine D1-like receptor- G protein coupling and function in hyperglycemic rats.
Dopamine via activation of renal D1-like receptors inhibits the activities of Na-K-ATPase and Na/H exchanger and subsequently increases sodium excretion. Decreased renal dopamine production and sodium excretion are associated with hyperglycemic conditions. We have earlier reported D1-like receptor-G protein uncoupling and reduced response to D1-like receptor activation in streptozotocin (STZ)-treated hyperglycemic rats (Marwaha A, Banday AA, and Lokhandwala MF. Am J Physiol Renal Physiol 286: F451-F457, 2004). The present study was designed to test the hypothesis that oxidative stress associated with hyperglycemia increases basal D1-like receptor serine phosphorylation via activation of the PKC-G protein receptor kinase (GRK) pathway, resulting in loss of D1-like receptor-G protein coupling and function. We observed that STZ-treated rats exhibited oxidative stress as evidenced by increased lipid peroxidation. Furthermore, PKC activity and expression of PKC-betaI- and -delta-isoforms were increased in STZ-treated rats. In addition, in STZ-treated rats there was increased GRK2 translocation to proximal tubular membrane and increased basal serine D1-like receptor phosphorylation. Supplementation with the antioxidant tempol lowered oxidative stress in STZ-treated rats, led to normalization of PKC activity, and prevented GRK2 translocation. Furthermore, tempol supplementation in STZ-treated rats restored D1-like receptor-G protein coupling and inhibition of Na-K-ATPase activity on D1-like receptor agonist stimulation. The functional consequence was the restoration of the natriuretic response to D1-like receptor activation. We conclude that oxidative stress associated with hyperglycemia causes an increase in activity and expression of PKC. This leads to translocation of GRK2, subsequent phosphorylation of the D1-like receptor, its uncoupling from G proteins and loss of responsiveness to agonist stimulation.
Marwaha
Aditi
A
Heart and Kidney Institute, College of Pharmacy, University of Houston, Houston, TX 77204-5041, USA.
Lokhandwala
Mustafa F
MF
D015647:2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine / Q000494:pharmacology; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology*; D001786:Blood Glucose / Q000032:analysis; D001835:Body Weight / Q000187:drug effects / Q000502:physiology; D002319:Cardiovascular System / Q000187:drug effects / Q000503:physiopathology; D003497:Cyclic N-Oxides / Q000494:pharmacology*; D004326:Drinking / Q000187:drug effects / Q000502:physiology; D054769:G-Protein-Coupled Receptor Kinase 2; D019204:GTP-Binding Proteins / Q000032:analysis / Q000378:metabolism / Q000502:physiology*; D006943:Hyperglycemia / Q000139:chemically induced / Q000503:physiopathology*; D007328:Insulin / Q000097:blood; D007684:Kidney Tubules / Q000737:chemistry / Q000187:drug effects / Q000502:physiology*; D015227:Lipid Peroxidation / Q000187:drug effects / Q000502:physiology; D008297:Male; D009318:Natriuresis / Q000187:drug effects / Q000502:physiology; D018384:Oxidative Stress / Q000187:drug effects* / Q000502:physiology; D011485:Protein Binding; D011493:Protein Kinase C / Q000032:analysis / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D017447:Receptors, Dopamine D1 / Q000032:analysis / Q000378:metabolism / Q000502:physiology*; D000254:Sodium-Potassium-Exchanging ATPase / Q000032:analysis / Q000037:antagonists & inhibitors / Q000502:physiology; D013113:Spin Labels; D013311:Streptozocin / Q000009:adverse effects; D051552:beta-Adrenergic Receptor Kinases / Q000378:metabolism
D000975:Antioxidants; D001786:Blood Glucose; D003497:Cyclic N-Oxides; D007328:Insulin; D017447:Receptors, Dopamine D1; D013113:Spin Labels; C098593:dopamine D1A receptor; D013311:Streptozocin; D015647:2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine; D011493:Protein Kinase C; C496569:Grk2 protein, rat; D051552:beta-Adrenergic Receptor Kinases; D054769:G-Protein-Coupled Receptor Kinase 2; D019204:GTP-Binding Proteins; D000254:Sodium-Potassium-Exchanging ATPase; C001803:tempol