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

In essential hypertension, the defect in renal dopamine (DA) D1 receptor function is intrinsic to proximal tubules as this phenomenon is also seen in primary proximal tubule cultures from spontaneously hypertensive rats (SHR) and essential hypertensive patients. Previously, a defect was reported in renal D1 receptor function in obese Zucker rats. In the present study, we sought to determine whether this D1 receptor dysfunction is intrinsic in these animals. In primary proximal tubular epithelial cells (PTECs) from lean and obese rats, DA inhibited Na-K-ATPase (NKA) activity in PTECs from both groups of rats. Basal NKA activity, D1 receptor protein expression, and their coupling to G proteins were similar in cells from both groups. However, when PTECs from lean and obese rats were cultured in 20% serum from obese rats, DA failed to inhibit NKA activity, which was accompanied by a reduction in D1 receptor expression and a defect in D1 receptor-G protein coupling. No such defects in the inhibitory effect of DA on NKA activity, D1 receptor numbers, or coupling were seen when PTECs from both lean and obese rats were grown in 20% serum from lean or rosiglitazone-treated obese (RTO) rats. RTO rat serum had normal blood glucose and reduced plasma levels of insulin compared with serum from obese rats. Furthermore, chronic insulin treatment of PTECs from lean and obese rats caused an attenuation in DA-induced NKA inhibition, a decrease in D1 receptor expression, and D1 receptor-G protein uncoupling. These results suggest that defective D1 receptor function in obese Zucker rats is not inherited but contributed to by hyperinsulinemia and/or other circulating factors associated with obesity.

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Tempol reduces oxidative stress and restores renal dopamine D1-like receptor- G protein coupling and function in hyperglycemic rats

AJP Renal Physiology ◽

10.1152/ajprenal.00362.2005 ◽

2006 ◽

Vol 291 (1) ◽

pp. F58-F66 ◽

Cited By ~ 23

Author(s):

Aditi Marwaha ◽

Mustafa F. Lokhandwala

Keyword(s):

Oxidative Stress ◽

G Protein ◽

Sodium Excretion ◽

Receptor Activation ◽

Serine Phosphorylation ◽

G Protein Coupling ◽

Protein Coupling ◽

Agonist Stimulation ◽

Renal Dopamine ◽

And Function

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-βI- and -δ-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.

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Glycaemic control with insulin prevents the reduced renal dopamine D1 receptor expression and function in streptozotocin-induced diabetes

Nephrology Dialysis Transplantation ◽

10.1093/ndt/gfq150 ◽

2010 ◽

Vol 25 (9) ◽

pp. 2945-2953 ◽

Cited By ~ 15

Author(s):

M. Moreira-Rodrigues ◽

J. Quelhas-Santos ◽

P. Serrao ◽

C. Fernandes-Cerqueira ◽

B. Sampaio-Maia ◽

...

Keyword(s):

Glycaemic Control ◽

Dopamine D1 Receptor ◽

D1 Receptor ◽

Receptor Expression ◽

Streptozotocin Induced Diabetes ◽

Renal Dopamine ◽

And Function

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Role of oxidative stress in defective renal dopamine D1 receptor-G protein coupling and function in old Fischer 344 rats

AJP Renal Physiology ◽

10.1152/ajprenal.00111.2006 ◽

2006 ◽

Vol 291 (5) ◽

pp. F945-F951 ◽

Cited By ~ 33

Author(s):

Riham Zein Fardoun ◽

Mohammad Asghar ◽

Mustafa Lokhandwala

Keyword(s):

Oxidative Stress ◽

G Protein ◽

D1 Receptor ◽

Serine Phosphorylation ◽

D1 Receptors ◽

Adult Rats ◽

G Protein Coupling ◽

Protein Coupling ◽

Age Related ◽

Old Rats

Aging is associated with an increase in oxidative stress. Previously, we have reported that dopamine failed to inhibit proximal tubular Na-K-ATPase and to promote sodium excretion in old rats (Beheray S, Kansra V, Hussain T, and Lokhandwala MF. Kidney Int 58: 712–720, 2000). This was due to uncoupling of dopamine D1 receptors from G proteins resulting from hyperphosphorylation of D1 receptors. The present study was designed to test the role of oxidative stress in the age-related decline in renal dopamine D1 receptor function. We observed that old animals had increased malondialdehyde (MDA) levels, a biomarker of oxidative stress, and decreased D1 receptor number and protein in the proximal tubules (PT) compared with adult rats. In old rats, there was increased G protein-coupled receptor kinase-2 (GRK-2) abundance, increased basal serine phosphorylation of D1 receptors, and defective D1 receptor-G protein coupling in PT membranes. Interestingly, supplementation with an antioxidant, tempol (1 mmol/l in drinking water for 15 days), lowered MDA levels and normalized D1 receptor number and protein in old rats to the level seen in adult rats. Furthermore, tempol decreased GRK-2 abundance and D1 receptor serine phosphorylation and restored D1 receptor-G protein coupling in PT of old rats. The functional consequence of these changes was the restoration of the natriuretic response to D1 receptor activation in tempol-supplemented old rats. Therefore, in old rats, tempol reduces oxidative stress and prevents GRK-2 membranous abundance and hyperphosphorylation of D1 receptors, resulting in restoration of D1 receptor-G protein coupling and the natriuretic response to SKF-38393. Thus tempol, by lowering oxidative stress, normalizes the age-related decline in dopamine receptor function.

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Abstract P337: Angiotensin 1-7 Mitigates Oxidative Stress, Protects Renal Dopamine D1 Receptor Function and Prevents Development of Hypertension

Hypertension ◽

10.1161/hyp.68.suppl_1.p337 ◽

2016 ◽

Vol 68 (suppl_1) ◽

Author(s):

Mustafa Lokhandwala ◽

Andrea Diaz Diaz ◽

Anees Ahamd Banday

Keyword(s):

Oxidative Stress ◽

Buthionine Sulfoximine ◽

Chronic Administration ◽

Dopamine D1 Receptor ◽

D1 Receptor ◽

Sodium Reabsorption ◽

Sodium Regulation ◽

Renal Dopamine ◽

Renal Sodium Reabsorption

The role of angiotensin in etiology of cardiovascular diseases especially in hypertension is well established. Renin-angiotensin-aldosterone contributes to the development and maintenance of hypertension directly by increases in vascular tone and renal sodium reabsorption or indirectly by increasing oxidative stress and inflammation. Contrary to this pathological arm, angiotensin (Ang) 1-7 via Mas receptors has been reported to protect the cardiovascular function although the exact mechanism is not yet clear. We have previously shown that oxidative stress leads to renal dopamine D1 receptor (D1R) dysfunction which could disrupt sodium regulation and subsequently lead to hypertension. In here we wanted to test whether chronic administration of Ang 1-7 in mice could mitigate oxidative stress, protect renal D1R function and prevent development of hypertension. Mice (C57BL) were implanted with telemetry probes and concomitantly treated with L-buthionine sulfoximine (BSO, in drinking water) and Ang 1-7 (via jugular vein by osmotic pumps). Control (C, no treatment) and shams (implanted with saline filled pumps) exhibited similar behavioral and physiological parameters. Mice treated with BSO alone exhibited increased oxidative stress and high BP as compared to controls. Ang 1-7 treatment did not affect oxidative stress and BP in control mice but prevented the increase in BP and oxidative milieu in BSO treated mice. Mean arterial pressure (mmHg), C: 78.5 ± 2.3*; BSO: 97.3 ± 3.8; Ang 1-7: 80.1* ± 4.1; BSO+Ang 1-7: 83.2 ± 3.4*, *P <0.05 vs BSO. SKF38393, a D1R agonist, increased urine and sodium excretion in control mice but failed to induce diuresis or natriuresis in BSO-treated mice. Treatment with Ang 1-7 protected D1R function as both natriuresis and diuresis was observed in mice treated with BSO plus Ang 1-7. Chronic Ang 1-7 had no effect on D1R function in the absence of BSO. These data show that oxidative stress leads to hypertension by disrupting renal D1R dependent sodium regulation. Ang 1-7 mitigates oxidative stress, protects renal D1R function and prevents increase in BP. This study provides a new insight on how beneficial arm of Ang system could protect renal D1R-mediated sodium regulation and prevent development of hypertension during oxidative stress.

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Oxidative Stress Causes Renal Dopamine D1 Receptor Dysfunction and Hypertension via Mechanisms That Involve Nuclear Factor-κB and Protein Kinase C

Journal of the American Society of Nephrology ◽

10.1681/asn.2006121373 ◽

2007 ◽

Vol 18 (5) ◽

pp. 1446-1457 ◽

Cited By ~ 49

Author(s):

Anees Ahmad Banday ◽

Fatima Rizwan Fazili ◽

Mustafa F. Lokhandwala

Keyword(s):

Oxidative Stress ◽

Protein Kinase C ◽

Protein Kinase ◽

Nuclear Factor Κb ◽

Dopamine D1 Receptor ◽

D1 Receptor ◽

Nuclear Factor ◽

Kinase C ◽

Renal Dopamine

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Exercise reduces oxidative stress but does not alleviate hyperinsulinemia or renal dopamine D1 receptor dysfunction in obese rats

AJP Renal Physiology ◽

10.1152/ajprenal.00386.2010 ◽

2011 ◽

Vol 300 (1) ◽

pp. F98-F104 ◽

Cited By ~ 13

Author(s):

Abdul Bari Muhammad ◽

Mustafa F. Lokhandwala ◽

Anees A. Banday

Keyword(s):

Oxidative Stress ◽

Blood Pressure ◽

Nuclear Translocation ◽

Blood Pressure Reduction ◽

Nuclear Factor Κb ◽

D1 Receptor ◽

Zucker Rats ◽

Insulin Levels ◽

Obese Rats ◽

Renal Dopamine

Impairment of renal dopamine D1 receptor (D1R)-mediated natriuresis is associated with hypertension in humans and animal models, including obese Zucker rats. We have previously reported that treatment of these rats with antioxidants or insulin sensitizers reduced insulin levels and oxidative stress, restored D1R-mediated natriuresis, and reduced blood pressure. Furthermore, the redox-sensitive transcription factor, nuclear factor-κB (NF-κB), has been implicated in impairment of D1R-mediated natriuresis during oxidative stress. In this study, we investigated the effect of exercise on insulin levels, oxidative stress, nuclear translocation of NF-κB, blood pressure, albuminuria, and D1R-mediated natriuresis. The exercise protocol involved treadmill exercise from 3 wk of age for 8 wk. Exercise reduced oxidative stress, nuclear translocation of NF-κB, and albuminuria. However, exercise did not reduce plasma insulin levels or blood pressure. Also, selective D1R agonist (SKF-38393)-mediated increases in sodium excretion and guanosine 5′- O-(3-thiotriphosphate) binding were impaired in obese rats compared with lean rats, and exercise did not restore this defect. We conclude that, while exercise is beneficial in reducing oxidative stress and renal injury, reducing insulin levels may be required to restore D1R-mediated natriuresis in this model of obesity and metabolic syndrome. Furthermore, this study supports previous observations that restoring D1R function contributes to blood pressure reduction in this model.

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Renal proximal tubules from old Fischer 344 rats grow into epithelial cells in cultures and exhibit increased oxidative stress and reduced D1 receptor function

AJP Cell Physiology ◽

10.1152/ajpcell.00367.2008 ◽

2008 ◽

Vol 295 (5) ◽

pp. C1326-C1331 ◽

Cited By ~ 10

Author(s):

Mohammad Asghar ◽

Annirudha Chillar ◽

Mustafa F. Lokhandwala

Keyword(s):

Oxidative Stress ◽

Primary Cultures ◽

D1 Receptor ◽

Zucker Rats ◽

Receptor Function ◽

Adult Rats ◽

Fischer 344 ◽

Old Rats ◽

Obese Zucker Rats ◽

F344 Rats

Earlier we reported defects in D1 receptor function in renal proximal tubules (RPTs) of aged Fischer 344 (F344) and obese Zucker rats. However, the defects in the receptor function in RPTs of obese Zucker rats do not pass onto primary cultures of RPTs from these animals. Here, we determined whether the defects in D1 receptor function in RPTs of aged F344 rats pass onto the primary cultures. RPTs from aged (24-mo) and adult (6-mo) F344 rats were grown into primary cultures. The microscopic studies showed that cells in cultures from adult and old rats were healthy as determined by the shape and size of the cells and nuclei. D1 receptor agonist SKF-38393 produced inhibition of 86Rb (rubidium) uptake, index of Na-K-ATPase activity, in cells from adult rats, but this was reduced in old rats. Also, SKF-38393 increased the [35S]GTPγS binding, index of receptor activation, in the membranes of cells from adult rats but to a lesser extent from old rats. Furthermore, there was a downward trend in the levels of D1 receptor numbers and in the receptor proteins in old rats. Interestingly, gp 91phox subunit of NADPH oxidase and cellular protein carbonyl levels (oxidative stress marker) were higher in cultures from old rats. These results show that RPTs from adult and old F344 rats grow into epithelial cells in cultures. Furthermore, cells in cultures from old rats are at a higher level of oxidative stress, which may be contributing to the reduced D1 receptor function in the cells from old compared with adult rats.

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