Essential hypertension has a heritability as high as 30 -50%, but its genetic cause(s) has not been determined despite intensive investigation. The renal dopaminergic system exerts a pivotal role in maintaining fluid and electrolyte balance and participates in the pathogenesis of genetic hypertension. In genetic hypertension, the ability of dopamine and D1-like agonists to increase urinary sodium excretion is impaired. A defective coupling between the D1 dopamine receptor and the G protein͞effector enzyme complex in the proximal tubule of the kidney is the cause of the impaired renal dopaminergic action in genetic rodent and human essential hypertension. We now report that, in human essential hypertension, single nucleotide polymorphisms of a G protein-coupled receptor kinase, GRK4␥, increase G protein-coupled receptor kinase (GRK) activity and cause the serine phosphorylation and uncoupling of the D1 receptor from its G protein͞effector enzyme complex in the renal proximal tubule and in transfected Chinese hamster ovary cells. Moreover, expressing GRK4␥A142V but not the wild-type gene in transgenic mice produces hypertension and impairs the diuretic and natriuretic but not the hypotensive effects of D1-like agonist stimulation. These findings provide a mechanism for the D1 receptor coupling defect in the kidney and may explain the inability of the kidney to properly excrete sodium in genetic hypertension.L ong-term regulation of blood pressure is vested in the organ responsible for the control of body fluid volume, the kidney (1, 2). Dopamine facilitates the antihypertensive function of the kidney because it is both vasodilatory and natriuretic (3). Dopamine (produced by renal proximal tubules) via D 1 -like receptors is responsible for over 50% of incremental sodium excretion when sodium intake is increased (3-6). The paracrine͞ autocrine dopaminergic regulation of sodium excretion is mediated by tubular but not by hemodynamic mechanisms (6). The ability of dopamine and D 1 -like agonists to decrease renal proximal tubular sodium reabsorption is impaired in genetic rodent hypertension and human essential hypertension (3,5,(7)(8)(9)(10)(11)(12)(13)(14)(15). Indeed, the aberrant D 1 -like receptor function in the kidney precedes and cosegregates with high blood pressure in spontaneously hypertensive rats. In addition, disruption of the D 1 receptor in mice produces hypertension (12, 13). The pivotal role of dopamine in the excretion of sodium after increased sodium intake has led to the hypothesis that an aberrant renal dopaminergic system is important in the pathogenesis of some forms of genetic hypertension (3,5,(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17). Several mechanisms potentially responsible for the failure of endogenous renal dopamine to engender a natriuretic effect in genetic hypertension have been investigated and ruled out, including decreased renal dopamine production and receptor expression, aberrant nephron segment distribution of dopamine receptors, defective effector enzymes (adenylyl cyclase or...

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Extracellular vesicles (EVs) carry signals within or at their limiting membranes, providing a mechanism by which cells can exchange more complex information than what was previously thought. In addition to mRNAs and microRNAs, there are DNA fragments in EVs. Solexa sequencing indicated the presence of at least 16434 genomic DNA (gDNA) fragments in the EVs from human plasma. Immunofluorescence study showed direct evidence that acridine orange-stained EV DNAs could be transferred into the cells and localize to and inside the nuclear membrane. However, whether the transferred EV DNAs are functional or not is not clear. We found that EV gDNAs could be homologously or heterologously transferred from donor cells to recipient cells, and increase gDNA-coding mRNA, protein expression, and function (e.g. AT1 receptor). An endogenous promoter of the AT1 receptor, NF-κB, could be recruited to the transferred DNAs in the nucleus, and increase the transcription of AT1 receptor in the recipient cells. Moreover, the transferred EV gDNAs have pathophysiological significance. BCR/ABL hybrid gene, involved in the pathogenesis of chronic myeloid leukemia, could be transferred from K562 EVs to HEK293 cells or neutrophils. Our present study shows that the gDNAs transferred from EVs to cells have physiological significance, not only to increase the gDNA-coding mRNA and protein levels, but also to influence function in recipient cells.

Elevated arterial pressure is a major risk factor for progression to ESRD in diabetic nephropathy. However, the component of arterial pressure and level of BP control for optimal renal outcomes are disputed. Data from 1590 hypertensive patients with type 2 diabetes in the Irbesartan Diabetic Nephropathy Trial (IDNT), a randomized, double-blind, placebo-controlled trial performed in 209 clinics worldwide, were examined, and the effects of baseline and mean follow-up systolic BP (SBP) and diastolic BP and the interaction of assigned study medications (irbesartan, amlodipine, and placebo) on progressive renal failure and all-cause mortality were assessed. Other antihypertensive agents were added to achieve predetermined BP goals. Entry criteria included elevated baseline serum creatinine concentration up to 266 mol/L (3.0 mg/dl) and urine protein excretion >900 mg/d. Baseline BP averaged 159/87 ؎ 20/11 mmHg. Median patient follow-up was 2.6 yr. Follow-up achieved SBP most strongly predicted renal outcomes. SBP >149 mmHg was associated with a 2.2-fold increase in the risk for doubling serum creatinine or ESRD compared with SBP <134 mmHg. Progressive lowering of SBP to 120 mmHg was associated with improved renal and patient survival, an effect independent of baseline renal function. Below this threshold, all-cause mortality increased. An additional renoprotective effect of irbesartan, independent of achieved SBP, was observed down to 120 mmHg. There was no correlation between diastolic BP and renal outcomes. We recommend a SBP target between 120 and 130 mmHg, in conjunction with blockade of the renin-angiotensin system, in patients with type 2 diabetic nephropathy.

Since dopamine receptors are important in the regulation of renal and cardiovascular function, we studied the cardiovascular consequences of the disruption of the D 3 receptor, a member of the family of D 2 -like receptors, expressed in renal proximal tubules and juxtaglomerular cells. Systolic and diastolic blood pressures were higher ( ‫ف‬ 20 mmHg) in heterozygous and homozygous than in wild-type mice. An acute saline load increased urine flow rate and sodium excretion to a similar extent in wild-type and heterozygous mice but the increase was attenuated in homozygous mice. Renal renin activity was much greater in homozygous than in wild-type mice; values for heterozygous mice were intermediate. Blockade of angiotensin II subtype-1 receptors decreased systolic blood pressure for a longer duration in mutant than in wild-type mice. Thus, disruption of the D 3 receptor increases renal renin production and produces renal sodium retention and renin-dependent hypertension. ( J .

Abnormalities in dopamine production and receptor function have been described in human essential hypertension and rodent models of genetic hypertension. Under normal conditions, D 1-like receptors (D1 and D5) inhibit sodium transport in the kidney and intestine. However, in the Dahl salt-sensitive and spontaneously hypertensive rats (SHRs) and in humans with essential hypertension, the D 1-like receptor-mediated inhibition of epithelial sodium transport is impaired because of an uncoupling of the D1-like receptor from its G protein/effector complex. The uncoupling is receptor specific, organ selective, nephron-segment specific, precedes the onset of hypertension, and cosegregates with the hypertensive phenotype. The defective transduction of the renal dopaminergic signal is caused by activating variants of G protein-coupled receptor kinase type 4 (GRK4: R65L, A142V, A486V). The GRK4 locus is linked to and GRK4 gene variants are associated with human essential hypertension, especially in saltsensitive hypertensive subjects. Indeed, the presence of three or more GRK4 variants impairs the natriuretic response to dopaminergic stimulation in humans. In genetically hypertensive rats, renal inhibition of GRK4 expression ameliorates the hypertension. In mice, overexpression of GRK4 variants causes hypertension either with or without salt sensitivity according to the variant. GRK4 gene variants, by preventing the natriuretic function of the dopaminergic system and by allowing the antinatriuretic factors (e.g., angiotensin II type 1 receptor) to predominate, may be responsible for salt sensitivity. Subclasses of hypertension may occur because of additional perturbations caused by variants of other genes, the quantitative interaction of which may vary depending upon the genetic background. dopamine; D 1 dopamine receptor; G protein-coupled receptor kinase type 4 THE LONG-TERM REGULATION of blood pressure rests on renal and nonrenal mechanisms (22, 34, 41,82,85,138,143,172). The sympathetic nervous (48,91,133,198,240) and the reninangiotensin (48,62,64,81,82,122,132,143,171,205,221) systems have been shown to be important in the pathogenesis of essential hypertension, including that associated with obesity (43). However, there are several counter-regulatory pathways (39,76,135,142,169,174,184,205,219) (e.g., dopamine pathway), aberrations of which are involved in the pathogenesis of essential hypertension (3, 4, 8-18, 20, 21, 23-26, 29-33, 35, 37, 42, 44-46, 52-60, 67-70, 73-75, 77, 79, 80, 84, 86, 93-95, 97-103, 106-111, 114, 116, 118, 119, 124, 126-128, 130, 131, 136, 140, 141, 144-146, 148-156, 159-161, 163-166, 176-179, 182, 183, 186, 189, 192, 193, 195, 197, 203, 207, 209-216, 218, 224, 226-239), including that associated with obesity (16, 37,201). Dopamine can regulate blood pressure by renal and nonrenal mechanisms (e.g., intestines and central nervous system) (93,130,131,207) that also involve the renin-angiotensin system (12, 29, 46,209,211,212,226,235,236).Because the kidney is important in the long-term regu...

Since dopamine produced by the kidney is an intrarenal regulator of sodium transport, an abnormality of the dopaminergic system may be important in the pathogenesis of hypertension. In the spontaneously hypertensive rat (SHR), in spite of normal renal production of dopamine and receptor density, there is defective transduction of the D 1 receptor signal in renal proximal tubules, resulting in decreased inhibition of sodium transport (Na

Complex interactions between genes and environment result in a sodium-induced elevation in blood pressure (salt sensitivity) and/or hypertension that lead to significant morbidity and mortality affecting up to 25% of the middle-aged adult population worldwide. Determining the etiology of genetic and/or environmentally-induced high blood pressure has been difficult because of the many interacting systems involved. Two main pathways have been implicated as principal determinants of blood pressure since they are located in the kidney (the key organ responsible for blood pressure regulation), and have profound effects on sodium balance: the dopaminergic and renin-angiotensin systems. These systems counteract or modulate each other, in concert with a host of intracellular second messenger pathways to regulate sodium and water balance. In particular, the G protein-coupled receptor kinase type 4 (GRK4) appears to play a key role in regulating dopaminergic-mediated natriuresis. Constitutively activated GRK4 gene variants (R65L, A142V, and A486V), by themselves or by their interaction with other genes involved in blood pressure regulation, are associated with essential hypertension and/or salt-sensitive hypertension in several ethnic groups. GRK4γ 142V transgenic mice are hypertensive on normal salt intake while GRK4γ 486V transgenic mice develop hypertension only with an increase in salt intake. GRK4 gene variants have been shown to hyperphosphorylate, desensitize, and internalize two members of the dopamine receptor family, the D1 (D1R) and D3 (D3R) dopamine receptors, but also increase the expression of a key receptor of the renin-angiotensin system, the angiotensin type 1 receptor (AT1R). Knowledge of the numerous blood pressure regulatory pathways involving angiotensin and dopamine may provide new therapeutic approaches to the pharmacological regulation of sodium excretion and ultimately blood pressure control.