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• W2050824773 abstract "Reactive oxygen species play a key role in pathophysiology of cardiovascular diseases by modulating G-protein-coupled receptor signaling. We have shown that treatment of animal models of diabetes and aging with tempol decreases oxidative stress and restores renal dopamine D1 receptor (D1R) function. In present study, we determined whether oxidation of D1R and upregulation of mitogen-activated protein kinases (MAPK) were responsible for decreased D1R signaling in obese animals. Male lean and obese Zucker rats were supplemented with antioxidants tempol or lipoic acid for 2 weeks. Compared to lean, obese animals were hyperglycemic and hyperinsulinemic with increased oxidative stress, D1R oxidation and decreased glutathione levels. These animals had decreased renal D1R affinity and basal coupling to G-proteins. SKF-38393, a D1R agonist failed to stimulate G-proteins and adenylyl cyclase. Obese animals showed marked increase in renal MAPK activities. Treatment of obese rats with tempol or lipoic acid decreased blood glucose, reduced oxidative stress, and restored the basal D1R G-protein coupling. Antioxidants also normalized MAPK activities and restored D1R affinity and SKF-38393 induced D1R G-protein coupling and adenylyl cyclase stimulation. These studies show that D1R oxidation and MAPK upregulation contribute to D1R dysfunction in obese animals. Consequently, antioxidants while reducing the oxidative stress normalize the MAPK activities and restore D1R signaling. Reactive oxygen species play a key role in pathophysiology of cardiovascular diseases by modulating G-protein-coupled receptor signaling. We have shown that treatment of animal models of diabetes and aging with tempol decreases oxidative stress and restores renal dopamine D1 receptor (D1R) function. In present study, we determined whether oxidation of D1R and upregulation of mitogen-activated protein kinases (MAPK) were responsible for decreased D1R signaling in obese animals. Male lean and obese Zucker rats were supplemented with antioxidants tempol or lipoic acid for 2 weeks. Compared to lean, obese animals were hyperglycemic and hyperinsulinemic with increased oxidative stress, D1R oxidation and decreased glutathione levels. These animals had decreased renal D1R affinity and basal coupling to G-proteins. SKF-38393, a D1R agonist failed to stimulate G-proteins and adenylyl cyclase. Obese animals showed marked increase in renal MAPK activities. Treatment of obese rats with tempol or lipoic acid decreased blood glucose, reduced oxidative stress, and restored the basal D1R G-protein coupling. Antioxidants also normalized MAPK activities and restored D1R affinity and SKF-38393 induced D1R G-protein coupling and adenylyl cyclase stimulation. These studies show that D1R oxidation and MAPK upregulation contribute to D1R dysfunction in obese animals. Consequently, antioxidants while reducing the oxidative stress normalize the MAPK activities and restore D1R signaling. Renal dopamine system is recognized as an important modulator of sodium balance and blood pressure.1.Jose P.A. Eisner G.M. Felder R.A. Renal dopamine receptors in health and hypertension.Pharmacol Ther. 1998; 80: 149-182Crossref PubMed Scopus (204) Google Scholar During increased sodium intake, dopamine causes more than 50% of sodium excretion and participates in maintaining sodium homeostasis.2.Hegde S.S. Jadhav A.L. Lokhandwala M.F. Role of kidney dopamine in the natriuretic response to volume expansion in rats.Hypertension. 1989; 13: 828-834Crossref PubMed Scopus (98) Google Scholar Dopamine exerts its natriuretic and diuretic actions via activation of D1 receptors in the renal proximal tubules.3.Sibley D.R. New insights into dopaminergic receptor function using antisense and genetically altered animals.Annu Rev Pharmacol Toxicol. 1999; 39: 313-341Crossref PubMed Scopus (174) Google Scholar,4.Missale C. Nash S.R. Robinson S.W. et al.Dopamine receptors: from structure to function.Physiol Rev. 1998; 78: 189-225Crossref PubMed Scopus (2737) Google Scholar In proximal tubules, D1 receptors inhibit activities of Na/H exchanger 3 (NHE3) and Na/phosphate (Pi) co-transporter in luminal membrane and Na/HCO co-transporter and Na/K ATPase (NKA) in basolateral membrane (BLM).1.Jose P.A. Eisner G.M. Felder R.A. Renal dopamine receptors in health and hypertension.Pharmacol Ther. 1998; 80: 149-182Crossref PubMed Scopus (204) Google Scholar, 4.Missale C. Nash S.R. Robinson S.W. et al.Dopamine receptors: from structure to function.Physiol Rev. 1998; 78: 189-225Crossref PubMed Scopus (2737) Google Scholar, 5.Aperia A.C. Intrarenal dopamine: a key signal in the interactive regulation of sodium metabolism.Annu Rev Physiol. 2000; 62: 621-647Crossref PubMed Scopus (229) Google Scholar, 6.Felder C.C. Campbell T. Albrecht F. et al.Dopamine inhibits Na(+)–H+ exchanger activity in renal BBMV by stimulation ofadenylate cyclase.Am J Physiol. 1990; 259: F297-F303PubMed Google Scholar This action of dopamine on NHE3 and Na/HCO co-transporter activities is due to activation of cyclic adenosine mono phosphate (cAMP)/protein kinase A pathway.1.Jose P.A. Eisner G.M. Felder R.A. Renal dopamine receptors in health and hypertension.Pharmacol Ther. 1998; 80: 149-182Crossref PubMed Scopus (204) Google Scholar, 6.Felder C.C. Campbell T. Albrecht F. et al.Dopamine inhibits Na(+)–H+ exchanger activity in renal BBMV by stimulation ofadenylate cyclase.Am J Physiol. 1990; 259: F297-F303PubMed Google Scholar, 7.Ominato M. Satoh T. Katz A.I. Regulation of Na-K-ATPase activity in the proximal tubule: role of the protein kinase C pathway and of eicosanoids.J Membrane Biol. 1996; 152: 235-243Crossref PubMed Scopus (119) Google Scholar, 8.Kunimi M. Seki G. Hara C. et al.Dopamine inhibits renal Na+:HCO3−cotransporter in rabbits and normotensive rats but not in spontaneously hypertensive rats.Kidney Int. 2000; 57: 534-543Abstract Full Text Full Text PDF PubMed Scopus (83) Google Scholar Dopamine can inhibit NKA activity by activating G-protein-linked pathway independent of protein kinase A while involving protein kinase C (PKC) and phosphatidylinositol 3 kinase.7.Ominato M. Satoh T. Katz A.I. Regulation of Na-K-ATPase activity in the proximal tubule: role of the protein kinase C pathway and of eicosanoids.J Membrane Biol. 1996; 152: 235-243Crossref PubMed Scopus (119) Google Scholar, 9.Bertorello A.M. Hopfield J.F. Aperia A. et al.Inhibition by dopamine of (Na(+)+K+)ATPase activity in neostriatal neurons through D1 and D2 dopamine receptor synergism.Nature. 1990; 347: 386-388Crossref PubMed Scopus (262) Google Scholar, 10.Bek M.J. Eisner G.M. Felder R.A. et al.Dopamine receptors in hypertension.Mt Sinai J Med. 2001; 68: 362-369PubMed Google Scholar Abnormalities in renal dopamine receptor function are described in human genetic hypertension and abnormal renal D1 receptor function contributes to the development of genetic hypertension and hypertension associated with obesity and diabetes in animals.1.Jose P.A. Eisner G.M. Felder R.A. Renal dopamine receptors in health and hypertension.Pharmacol Ther. 1998; 80: 149-182Crossref PubMed Scopus (204) Google Scholar, 10.Bek M.J. Eisner G.M. Felder R.A. et al.Dopamine receptors in hypertension.Mt Sinai J Med. 2001; 68: 362-369PubMed Google Scholar, 11.Umrani D.N. Banday A.A. Hussain T. et al.Rosiglitazone treatment restores renal dopamine receptor function in obese Zucker rats.Hypertension. 2002; 40: 880-885Crossref PubMed Scopus (43) Google Scholar, 12.Sanada H. Jose P.A. Hazen-Martin D. et al.Dopamine-1 receptor coupling defect in renal proximal tubule cells in hypertension.Hypertension. 1999; 33: 1036-1042Crossref PubMed Scopus (136) Google Scholar, 13.Banday A.A. Marwaha A. Tallam L.S. et al.Tempol reduces oxidative stress, improves insulin sensitivity, decreases renal dopamine D1 receptor hyperphosphorylation, and restores D1 receptor-G-protein coupling and function in obese Zucker rats.Diabetes. 2005; 54: 2219-2226Crossref PubMed Scopus (91) Google Scholar The failure of renal dopamine system is not caused by decreased renal dopamine production but by a defective D1 receptor G-protein coupling.1.Jose P.A. Eisner G.M. Felder R.A. Renal dopamine receptors in health and hypertension.Pharmacol Ther. 1998; 80: 149-182Crossref PubMed Scopus (204) Google Scholar,10.Bek M.J. Eisner G.M. Felder R.A. et al.Dopamine receptors in hypertension.Mt Sinai J Med. 2001; 68: 362-369PubMed Google Scholar Although the reduced receptor expression and/or increased receptor phosphorylation have been shown to cause receptor G-protein uncoupling, the exact mechanism is still elusive.10.Bek M.J. Eisner G.M. Felder R.A. et al.Dopamine receptors in hypertension.Mt Sinai J Med. 2001; 68: 362-369PubMed Google Scholar, 11.Umrani D.N. Banday A.A. Hussain T. et al.Rosiglitazone treatment restores renal dopamine receptor function in obese Zucker rats.Hypertension. 2002; 40: 880-885Crossref PubMed Scopus (43) Google Scholar, 12.Sanada H. Jose P.A. Hazen-Martin D. et al.Dopamine-1 receptor coupling defect in renal proximal tubule cells in hypertension.Hypertension. 1999; 33: 1036-1042Crossref PubMed Scopus (136) Google Scholar, 13.Banday A.A. Marwaha A. Tallam L.S. et al.Tempol reduces oxidative stress, improves insulin sensitivity, decreases renal dopamine D1 receptor hyperphosphorylation, and restores D1 receptor-G-protein coupling and function in obese Zucker rats.Diabetes. 2005; 54: 2219-2226Crossref PubMed Scopus (91) Google Scholar Previously, we have shown that in obese Zucker rats, an animal model of obesity and type II diabetes, the defect in renal dopamine D1 receptor was associated with increased oxidative stress.13.Banday A.A. Marwaha A. Tallam L.S. et al.Tempol reduces oxidative stress, improves insulin sensitivity, decreases renal dopamine D1 receptor hyperphosphorylation, and restores D1 receptor-G-protein coupling and function in obese Zucker rats.Diabetes. 2005; 54: 2219-2226Crossref PubMed Scopus (91) Google Scholar Treatment of these animals with tempol, a superoxide dismutase (SOD) mimetic compound or with insulin sensitizer rosiglitazone decreased oxidative stress and restored D1 receptor G-protein coupling and function.11.Umrani D.N. Banday A.A. Hussain T. et al.Rosiglitazone treatment restores renal dopamine receptor function in obese Zucker rats.Hypertension. 2002; 40: 880-885Crossref PubMed Scopus (43) Google Scholar,13.Banday A.A. Marwaha A. Tallam L.S. et al.Tempol reduces oxidative stress, improves insulin sensitivity, decreases renal dopamine D1 receptor hyperphosphorylation, and restores D1 receptor-G-protein coupling and function in obese Zucker rats.Diabetes. 2005; 54: 2219-2226Crossref PubMed Scopus (91) Google Scholar Similar observations were made in streptozotocin treated Sprague–Dawley rats and old Fisher 344 rats where antioxidant tempol decreased oxidative stress and restored D1 receptor function, thus indicating that oxidative stress contributes to decreased D1 receptor functioning.14.Marwaha A. Lokhandwala M.F. Tempol reduces oxidative stress and restores renal dopamine D1-like receptor G-protein coupling and function in hyperglycemic rats.Am J Physiol. 2006; 291: F58-F66Google Scholar,15.Asghar M. Lokhandwala M.F. Antioxidant supplementation normalizes elevated protein kinase C activity in the proximal tubules of old rats.Exp Biol Med. 2004; 229: 270-275Google Scholar However, the precise mechanisms responsible for oxidative stress-associated D1 receptor defect remained to be elucidated. Reactive oxygen species serve as second messengers in various signal transduction pathways.16.Kim S. Iwao H. Molecular and cellular mechanisms of angiotensin II-mediated cardiovascular and renal diseases.Pharmacol Rev. 2000; 52: 11-34PubMed Google Scholar, 17.Yoshizumi M. Tsuchiya K. Tamaki T. Signal transduction of reactive oxygen species and mitogen-activated protein kinases in cardiovascular disease.J Med Invest. 2001; 48: 11-24PubMed Google Scholar, 18.Griendling K.K. Sorescu D. Ushio-Fukai M. NAD(P)H oxidase: role in cardiovascular biology and disease.Circ Res. 2000; 86: 494-501Crossref PubMed Scopus (2604) Google Scholar, 19.Nishiyama A. Yoshizumi M. Hitomi H. et al.The SOD mimetic tempol ameliorates glomerular injury and reduces mitogen-activated protein kinase activity in Dahl salt-sensitive rats.J Am Soc Nephrol. 2004; 15: 306-315Crossref PubMed Scopus (79) Google Scholar Among many intracellular signaling molecules, reactive oxygen species-induced cellular events have been implicated in part to activation of mitogen-activated protein kinases (MAPK), including the extracellular signal regulated kinase (ERK) 1/ERK2, c-jun NH2-terminal kinase (JNK), and p38 MAPK.16.Kim S. Iwao H. Molecular and cellular mechanisms of angiotensin II-mediated cardiovascular and renal diseases.Pharmacol Rev. 2000; 52: 11-34PubMed Google Scholar, 17.Yoshizumi M. Tsuchiya K. Tamaki T. Signal transduction of reactive oxygen species and mitogen-activated protein kinases in cardiovascular disease.J Med Invest. 2001; 48: 11-24PubMed Google Scholar, 18.Griendling K.K. Sorescu D. Ushio-Fukai M. NAD(P)H oxidase: role in cardiovascular biology and disease.Circ Res. 2000; 86: 494-501Crossref PubMed Scopus (2604) Google Scholar, 19.Nishiyama A. Yoshizumi M. Hitomi H. et al.The SOD mimetic tempol ameliorates glomerular injury and reduces mitogen-activated protein kinase activity in Dahl salt-sensitive rats.J Am Soc Nephrol. 2004; 15: 306-315Crossref PubMed Scopus (79) Google Scholar Studies have shown that MAPK are activated in cardiovascular diseases such as diabetes and hypertension.16.Kim S. Iwao H. Molecular and cellular mechanisms of angiotensin II-mediated cardiovascular and renal diseases.Pharmacol Rev. 2000; 52: 11-34PubMed Google Scholar, 17.Yoshizumi M. Tsuchiya K. Tamaki T. Signal transduction of reactive oxygen species and mitogen-activated protein kinases in cardiovascular disease.J Med Invest. 2001; 48: 11-24PubMed Google Scholar, 18.Griendling K.K. Sorescu D. Ushio-Fukai M. NAD(P)H oxidase: role in cardiovascular biology and disease.Circ Res. 2000; 86: 494-501Crossref PubMed Scopus (2604) Google Scholar, 19.Nishiyama A. Yoshizumi M. Hitomi H. et al.The SOD mimetic tempol ameliorates glomerular injury and reduces mitogen-activated protein kinase activity in Dahl salt-sensitive rats.J Am Soc Nephrol. 2004; 15: 306-315Crossref PubMed Scopus (79) Google Scholar Furthermore, it is shown that MAPK can modulate dopamine receptor function in various organs including kidneys.20.Chen J. Rusnak M. Luedtke R.R. et al.D1 dopamine receptor mediates dopamine-induced cytotoxicity via the ERK signal cascade.J Biol Chem. 2004; 279: 39317-39330Crossref PubMed Scopus (83) Google Scholar The present study was conducted to elucidate the role of MAPK in renal proximal tubular D1 receptor dysfunction of obese Zucker rats. As shown in Table 1, body weight and blood glucose were significantly higher in obese rats compared to lean rats. Treatment with tempol or lipoic acid showed no effect on the body weight of obese animals but markedly reduced their blood glucose. As shown in Table 2, tempol or lipoic acid showed no effect on body weight and blood glucose of lean rats. Tempol and lipoic acid did not change the water or food intake in lean or obese animals (data not shown).Table 1Effect of tempol and lipoic acid on body weight, glucose, and oxidative markers in lean and obese Zucker ratsLeanObeseObese-tempolObese-lipoic acidBody weight, g280.5±12.0490.0±16.2aSignificantly different from lean rats.540.5±30.2aSignificantly different from lean rats.533±20.9aSignificantly different from lean rats.Blood glucose, mg/dl109.1±6.2209.0±8.2aSignificantly different from lean rats.149.0±4.3aSignificantly different from lean rats.,bObese-tempol and obese-lipoic acid significantly different from obese rats.139.3±3.8aSignificantly different from lean rats.,bObese-tempol and obese-lipoic acid significantly different from obese rats.8-isoprostane, urine (pg/mg creatinine)593.0±29.2992.0±32.1aSignificantly different from lean rats.625.0±26.3bObese-tempol and obese-lipoic acid significantly different from obese rats.670.0±31.6bObese-tempol and obese-lipoic acid significantly different from obese rats.8-isoprostane, plasma (pg/mg creatinine)32.1±2.249.1±2.4aSignificantly different from lean rats.36.1±2.0bObese-tempol and obese-lipoic acid significantly different from obese rats.37.9±2.0bObese-tempol and obese-lipoic acid significantly different from obese rats.CML (optical density/μg protein)0.38±0.061.4±0.1aSignificantly different from lean rats.0.54±0.08bObese-tempol and obese-lipoic acid significantly different from obese rats.0.59±0.1bObese-tempol and obese-lipoic acid significantly different from obese rats.GSH nmol/mg protein0.89±0.050.44±0.03aSignificantly different from lean rats.1.0±0.1bObese-tempol and obese-lipoic acid significantly different from obese rats.0.99±0.09bObese-tempol and obese-lipoic acid significantly different from obese rats.GSSG pmol/mg protein28.0±1.150.0±3.1aSignificantly different from lean rats.32.0±2.9bObese-tempol and obese-lipoic acid significantly different from obese rats.34.0±2.3bObese-tempol and obese-lipoic acid significantly different from obese rats.CML, carboxymethyl lysine; GSH, reduced glutathione; GSSG, oxidized glutathione.Data (mean±s.e.m. of 6–8 different animals) were analyzed by ANOVA and post hoc Newman–Keuls multiple comparison test.P<0.05 was considered statistically significant.a Significantly different from lean rats.b Obese-tempol and obese-lipoic acid significantly different from obese rats. Open table in a new tab Table 2Effect of tempol and lipoic acid on body weight, glucose, and oxidative markers in lean Zucker ratsLeanLean-tempolLean-lipoic acidBody weight, g280.5±12.0310.5±10.0308.5±11.2Blood glucose, mg/dl109.1±6.2104.1±6.9100.1±5.38-isoprostane, urine (pg/mg creatinine)593.0±29.2543.0±22.3545.0±34.38-isoprostane, plasma (pg/mg creatinine)32.1±2.230.1±3.129.9±1.6CML (optical density/μg protein)0.38±0.060.35±0.050.34±0.07GSH nmol/mg protein0.89±0.050.95±0.071.0±0.2GSSG pmol/mg protein28.0±1.122.0±1.923.0±1.3CML, carboxymethyl lysine; GSH, reduced glutathione; GSSG, oxidized glutathione.Data (mean±s.e.m. of 6–8 different animals) were analyzed by ANOVA and post hoc Newman–Keuls multiple comparison test.P<0.05 was considered statistically significant. Open table in a new tab CML, carboxymethyl lysine; GSH, reduced glutathione; GSSG, oxidized glutathione. Data (mean±s.e.m. of 6–8 different animals) were analyzed by ANOVA and post hoc Newman–Keuls multiple comparison test. P<0.05 was considered statistically significant. CML, carboxymethyl lysine; GSH, reduced glutathione; GSSG, oxidized glutathione. Data (mean±s.e.m. of 6–8 different animals) were analyzed by ANOVA and post hoc Newman–Keuls multiple comparison test. P<0.05 was considered statistically significant. Compared to lean rats, obese animals had significantly higher plasma and urinary 8-isoprostane levels (Table 1). Renal proximal tubules from obese rats showed significant decrease in reduced glutathione along with increased levels of oxidized glutathione compared to lean rats (Table 1). In addition, the renal nitrotyrosine (Figure 1) and carboxymethyl lysine (Table 1) levels were significantly higher in obese compared to lean rats. As illustrated in Figure 1b, renal D1 receptors from obese rats have increased carbonyl content compared to lean rats. The Western blotting analysis of various subunits of renal nicotinamide adenine dinucleotide phosphate (NAD(P)H) oxidase in obese animals did not show any upregulation of this enzyme compared to lean rats (Figure 2a–d). In addition, the low-temperature sodium dodecyl sulfate-polyacrylamide gel electrophoresis immunoblotting of endothelial nitric oxide synthase (NOS) showed similar monomer vs dimer expression in lean and obese rats (data not shown). Furthermore, incubation of homogenates with dihydroethidium and NAD(P)H oxidase or NOS substrates caused similar O2− production (fluorescence units/min/mg protein) in lean and obese animals, NAD(P)H oxidase – lean: 891.0±121.0, obese: 1049.0±117.0; NOS – lean: 651.0±85, obese: 819.0±113.0. Taken together, these data suggest that NAD(P)H oxidase and NOS are not the predominant source of superoxide production in obese animals. Treatment of obese animals with tempol or lipoic acid significantly decreased the plasma and urinary 8-isoprostane levels, renal nitrotyrosine and carboxymethyllysine levels, and D1 receptor carbonyl content and also restored the renal glutathione levels in obese animals (Table 1 and Figure 1 a and b). In lean rats, antioxidant supplementation showed no effect on either oxidative or antioxidative markers (Table 2). To determine the affinity of D1 receptors with agonist, we used fenoldopam (FD) to displace [3H]SCH-23390 binding in proximal tubular membranes from lean and obese rats. The agonist affinity for both high- and low-affinity receptors was reduced by a one-log unit of FD concentration in obese compared with lean rats (Figure 3, inset). Treatment with tempol or lipoic acid restored the affinity of renal D1 receptors in obese animals (Figure 3 and inset). Tempol or lipoic acid had no effect on D1 receptor affinity in lean rats (Table 3).Table 3Effect of tempol and lipoic acid on basal D1 receptor affinity, NKA, and NHE3 activity and SKF-38393-induced adenylyl cyclase activation in renal proximal tubular membranes from lean ratsLeanLean-tempolLean-lipoic acidEC5015.92 × 10−114.58 × 10−113.78 × 10−11EC5024.72 × 10−73.85 × 10−74.22 × 10−7NKA activity Basal288.6±20.6269.2±22.1255.1±27.9NHE3 Basal2.3±0.22.5±0.22.1±0.3Adenylyl cyclase activity Basal55.2±4.450.2±3.453.2±3.2 SKF-38393 (100 μM)78.2±4.9aSignificantly different from respective basal.80.0±4.9aSignificantly different from respective basal.74.1±3.2aSignificantly different from respective basal. Forskolin (10 μM)188.2±12.3aSignificantly different from respective basal.201.2±11.3aSignificantly different from respective basal.195.0±16.4aSignificantly different from respective basal.cAMP, cyclic adenosine mono phosphate; NHE3, Na/H exchanger 3; NKA, Na/K ATPase.Effective concentration (EC50) is expressed as [M], NKA and NHE3 are expressed as nmol pi/mg protein/min and nmol 22Na+/mg protein/min, respectively. Adenylyl cyclase activity was determined as cAMP accumulation (fmol/mg protein). Data (mean±s.e.m. of 6–8 different animals) were analyzed by ANOVA and post hoc Newman-Keuls multiple comparison test. P<0.05 was considered statistically significant.a Significantly different from respective basal. Open table in a new tab cAMP, cyclic adenosine mono phosphate; NHE3, Na/H exchanger 3; NKA, Na/K ATPase. Effective concentration (EC50) is expressed as [M], NKA and NHE3 are expressed as nmol pi/mg protein/min and nmol 22Na+/mg protein/min, respectively. Adenylyl cyclase activity was determined as cAMP accumulation (fmol/mg protein). Data (mean±s.e.m. of 6–8 different animals) were analyzed by ANOVA and post hoc Newman-Keuls multiple comparison test. P<0.05 was considered statistically significant. In assessing specific coupling of D1 receptors to G-proteins, we employed direct [3H]SCH-23390 binding in immunoprecipitates of Gαs proteins obtained from solubilized membranes of renal proximal tubules. The results shown in Figure 4a demonstrate that Gαs antiserum immunoprecipitated [3H]SCH-23390 binding sites in obese Zucker rats are significantly reduced compared to lean. In obese animals treated with tempol or lipoic acid, the co-immunoprecipitated D1 binding sites with Gαs antiserum were similar to lean rats. Gαi antiserum failed to co-immunoprecipitate significant D1 binding sites. Immunoprecipitates of Gαs antisera were also blotted with a specific D1A and Gαs antibodies. The data presented in Figure 4b shows that the D1A protein that co-immunoprecipitated with Gαs was significantly reduced in obese rats compared to lean rats and treatment with tempol or lipoic acid restored the co-immunoprecipitation of D1α with Gαs proteins. Gαs antisera immunoprecipitated similar amount of Gαs protein both in lean, obese, and antioxidant-supplemented obese rats (Figure 4c). Tempol and lipoic acid showed no effect on basal D1 receptor G-protein coupling in lean rats (data not shown). Incubation of membranes with SKF-38393 followed by immunoprecipitation with Gαs antiserum showed significant increase in [35S]GTPγS membrane binding in lean rats (Figure 5). However, SKF-38393 failed to increase [35S]GTPγS membrane binding in obese rats. Treatment with tempol or lipoic acid restored the SKF-38393-induced [35S]GTPγS binding in obese rats. In contrast, co-immunoprecipitation with Gαi failed to show the SKF-38393-induced increase in [35S]GTPγS. The activation of G-proteins was D1 receptor specific as the effect of D1 agonist SKF-38393 was completely blocked by D1 antagonist SCH-23390. In lean rats neither tempol or lipoic acid had any effect on SKF-38393-induced GTPγS binding (data not shown). Incubation of proximal tubular membranes with D1 selective agonist SKF-38393 from lean rats resulted in significant elevations in cAMP production. The results summarized in Table 4 indicate that adenylyl cyclase activation in response to SKF-38393 was minimal in membranes from obese rats. Treatment with tempol or lipoic acid restored the SKF-38393-dependent cAMP accumulation in obese rats. Direct enzyme stimulation with forskolin was similar in lean and obese rats (Table 4). Tempol and lipoic acid did not effect the basal or forskolin-induced adenylyl cyclase stimulation (Table 3).Table 4Effect of tempol and lipoic acid on SKF-38393-induced adenylyl cyclase activation in renal proximal tubular membranes from lean and obese animalsLeanObeseLean-tempolObese-lipoic acidBasal55.2±4.453.2±2.250.0±4.252.1±3.9SKF-38393 (100 μM)78.2±4.9aSignificantly different from respective basal.64.1±3.870.0±4.2aSignificantly different from respective basal.73.1±3.6aSignificantly different from respective basal.Forskolin (10 μM)188.2±12.3aSignificantly different from respective basal.209.0±16.9aSignificantly different from respective basal.216.6±14.3aSignificantly different from respective basal.206.2±17.9aSignificantly different from respective basal.Adenylyl cyclase activity was expressed as cAMP accumulation (fmol/mg protein). Data (mean±s.e.m. of 6–8 different animals) were analyzed by ANOVA and post hoc Newman–Keuls multiple comparison test. P<0.05 was considered statistically significant.a Significantly different from respective basal. Open table in a new tab Adenylyl cyclase activity was expressed as cAMP accumulation (fmol/mg protein). Data (mean±s.e.m. of 6–8 different animals) were analyzed by ANOVA and post hoc Newman–Keuls multiple comparison test. P<0.05 was considered statistically significant. We measured the basal expression and activities of NKA and NHE3, the major sodium transporters of renal proximal tubules in BLM and brush border (apical) membrane (BBM), respectively. No difference was observed in protein abundance (data not shown) or activities of these transporters between lean and obese animals, NKA activity (ouabain-sensitive inorganic phosphate release, nmol/mg protein/min) – lean: 269.0±22.0, obese: 248.0±19.0; NHE3 activity (amiloride-sensitive 22Na+ uptake, nmol/mg protein/min) – lean: 2.3±0.2, obese: 2.6±0.3. As shown in Figure 6a–c, the activities of ERK1/2, p38, and JNK were significantly higher in obese rats compared to lean rats. To investigate the role of oxidative stress on MAPK activation, we studied the effect of tempol and lipoic acid on ERK1/2, p38, and JNK activation. As illustrated in Figure 6a–c, tempol and lipoic acid normalized the ERK1/2, p38, and JNK activities to basal levels in obese animals. Incubation of proximal tubules from lean and obese animals with 25 μM H2O2 for 30 min caused significant increase in malondialdehyde levels; however, the increase was more pronounced in lean proximal tubules compared to obese (Figure 7a). Interestingly, incubation of proximal tubules from lean rats with H2O2 caused significant increase in ERK1/2 (Figure 7b) and D1 receptor downregulation and uncoupling from G-proteins (Figure 8a and b). Inhibition of H2O2-induced ERK1/2 kinase activation with U-0126 (Figure 7b) attenuated H2O2-mediated D1 receptor desensitization (Figure 8a and b). H2O2 failed to reduce D1 receptor expression and coupling or upregulate ERK1/2 in proximal tubules from obese animals (Figures 7 and 8). Also, U-0126 failed decrease ERK1/2 activity or restore D1 receptor signaling in proximal tubules of these animals (Figures 7 and 8).Figure 8Effect of H2O2 on renal D1 receptor expression and G-protein coupling. Effect of H2O2 on (a) [3H]SCH-23390 binding and (b) SKF-38393-induced [35S]GTPγS binding in proximal tubular membranes from lean and obese animals. Data were analyzed by ANOVA followed by Newman–Keuls multiple test; P<0.05 was considered statistically significant. *Significantly different from H2O2-lean and -obese (vehicle or H2O2) groups.View Large Image Figure ViewerDownload (PPT) These results show that defect in D1 receptor function in obese Zucker rats is associated with increased D1 receptor oxidation and upregulation of ERK1/2, JNK, and p38 MAPK activities. Treatment with antioxidants tempol and lipoic acid reduced oxidative stress and normalized ERK1/2, JNK, and p38 MAPK activities. The present study demonstrates that in obese animals the D1 receptors have reduced affinity and are uncoupled from G-proteins in basal state. SKF-38393, a D1 receptor agonist failed to eli" @default.
• W2050824773 created "2016-06-24" @default.
• W2050824773 creator A5021765152 @default.
• W2050824773 creator A5070571502 @default.
• W2050824773 creator A5075725520 @default.
• W2050824773 creator A5085220617 @default.
• W2050824773 date "2007-03-01" @default.
• W2050824773 modified "2023-10-17" @default.
• W2050824773 title "Mitogen-activated protein kinase upregulation reduces renal D1 receptor affinity and G-protein coupling in obese rats" @default.
• W2050824773 cites W1573628824 @default.
• W2050824773 cites W1925492557 @default.
• W2050824773 cites W1970838158 @default.
• W2050824773 cites W1982046698 @default.
• W2050824773 cites W1991639351 @default.
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• W2050824773 cites W2123799914 @default.
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• W2050824773 cites W2193548141 @default.
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