Publications (34) View all
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Article: Renal microvascular dysfunction, hypertension and CKD progression.
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ABSTRACT: PURPOSE OF REVIEW: Despite apparent blood pressure (BP) control and renin-angiotensin system (RAS) blockade, the chronic kidney disease (CKD) outcomes have been suboptimal. Accordingly, this review is addressed to renal microvascular and autoregulatory impairments that underlie the enhanced dynamic glomerular BP transmission in CKD progression. RECENT FINDINGS: Clinical data suggest that failure to achieve adequate 24-h BP control is likely contributing to the suboptimal outcomes in CKD. Whereas evidence continues to accumulate regarding the importance of preglomerular autoregulatory impairment to the dynamic glomerular BP transmission, emerging data indicate that nitric oxide-mediated efferent vasodilation may play an important role in mitigating the consequences of glomerular hypertension. By contrast, the vasoconstrictor effects of angiotensin II are expected to potentially reduce glomerular barotrauma and possibly enhance ischemic injury. When adequate BP measurement methods are used, the evidence for BP-independent injury initiating mechanisms is considerably weaker and the renoprotection by RAS blockade largely parallels its antihypertensive effectiveness. SUMMARY: Adequate 24-h BP control presently offers the most feasible intervention for reducing glomerular BP transmission and improving suboptimal outcomes in CKD. Investigations addressed to improving myogenic autoregulation and/or enhancing nitric oxide-mediated efferent dilation in addition to the more downstream mediators may provide additional future therapeutic targets.Current opinion in nephrology and hypertension 11/2012; · 3.96 Impact Factor -
Article: Hypertension and chronic kidney disease progression: why the suboptimal outcomes?
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ABSTRACT: Current therapeutic interventions to retard the progression of chronic kidney disease have yielded disappointing outcomes despite adequate renin-angiotensin system blockade. The parameters to gauge the adequacy of blood pressure control need to be reassessed because clinic blood pressure constitutes a poor gauge of such control. The biologically relevant parameter for hypertensive target organ damage is total blood pressure burden, and reliance on isolated clinic blood pressure measurements per se does not accurately reflect the total blood pressure burden. This is particularly relevant to the population with chronic kidney disease in whom masked daytime or nocturnal hypertension and blood pressure lability are both widely prevalent and more difficult to control. Consequently, it is possible that the limited success currently being achieved in preventing or attenuating chronic kidney disease progression may be attributable in part to suboptimal 24-hour blood pressure control. Recent data and analyses also indicate that blood pressure variability, instability, episodic and nocturnal blood pressure elevations, and maximum systolic blood pressure may constitute additional strong predictors of the risk of target organ damage independently of mean systolic blood pressure. Accordingly, we suggest that future research should include the development of safe and effective strategies to achieve around-the-clock blood pressure control in addition to targeting mechanisms that reduce intrarenal blood pressure transmission or interrupt subsequent downstream pathways. Meanwhile, more aggressive use of patient education and home blood pressure monitoring with selection of longer-acting antihypertensive agents or nocturnal dosing should be considered to improve the current suboptimal results.The American journal of medicine 08/2012; 125(11):1057-62. · 4.47 Impact Factor -
Article: PTEN loss defines a TGF-β-induced tubule phenotype of failed differentiation and JNK signaling during renal fibrosis.
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ABSTRACT: We investigated the signaling basis for tubule pathology during fibrosis after renal injury. Numerous signaling pathways are activated physiologically to direct tubule regeneration after acute kidney injury (AKI) but several persist pathologically after repair. Among these, transforming growth factor (TGF)-β is particularly important because it controls epithelial differentiation and profibrotic cytokine production. We found that increased TGF-β signaling after AKI is accompanied by PTEN loss from proximal tubules (PT). With time, subpopulations of regenerating PT with persistent loss of PTEN (phosphate and tension homolog) failed to differentiate, became growth arrested, expressed vimentin, displayed profibrotic JNK activation, and produced PDGF-B. These tubules were surrounded by fibrosis. In contrast, PTEN recovery was associated with epithelial differentiation, normal tubule repair, and less fibrosis. This beneficial outcome was promoted by TGF-β antagonism. Tubule-specific induction of TGF-β led to PTEN loss, JNK activation, and fibrosis even without prior AKI. In PT culture, high TGF-β depleted PTEN, inhibited differentiation, and activated JNK. Conversely, TGF-β antagonism increased PTEN, promoted differentiation, and decreased JNK activity. Cre-Lox PTEN deletion suppressed differentiation, induced growth arrest, and activated JNK. The low-PTEN state with JNK signaling and fibrosis was ameliorated by contralateral nephrectomy done 2 wk after unilateral ischemia, suggesting reversibility of the low-PTEN dysfunctional tubule phenotype. Vimentin-expressing tubules with low-PTEN and JNK activation were associated with fibrosis also after tubule-selective AKI, and with human chronic kidney diseases of diverse etiology. By preventing tubule differentiation, the low-PTEN state may provide a platform for signals initiated physiologically to persist pathologically and cause fibrosis after injury.AJP Renal Physiology 02/2012; 302(9):F1210-23. · 4.42 Impact Factor -
Article: Large BP-dependent and -independent differences in susceptibility to nephropathy after nitric oxide inhibition in Sprague-Dawley rats from two major suppliers.
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ABSTRACT: The N(ω)-nitro-l-arginine methyl ester (l-NAME) model is widely employed to investigate the role of nitric oxide (NO) in renal injury. The present studies show that Sprague-Dawley rats from Harlan (H) and Charles River (CR) exhibit strikingly large differences in susceptibility to l-NAME nephropathy. After 4 wk of l-NAME (∼50 mg·kg(-1)·day(-1) in drinking water), H rats (n = 13) exhibited the expected hypertension [average radiotelemetric systolic blood pressure (BP), 180 ± 3 mmHg], proteinuria (136 ± 17 mg/24 h), and glomerular injury (GI) (12 ± 2%). By contrast, CR rats developed less hypertension (142 ± 4), but surprisingly no proteinuria or GI, indicating a lack of glomerular hypertension. Additional studies showed that conscious H, but not CR, rats exhibit dose-dependent renal vasoconstriction after l-NAME. To further investigate these susceptibility differences, l-NAME was given 2 wk after 3/4 normotensive nephrectomy (NX) and comparably impaired renal autoregulation in CR-NX and H-NX rats. CR-NX rats, nevertheless, still failed to develop proteinuria and GI despite moderate hypertension (144 ± 2 mmHg, n = 29). By contrast, despite an 80-90% l-NAME dose reduction and lesser BP increases (169 ± 4 mmHg), H-NX rats (n = 20) developed greater GI (26 ± 3%) compared with intact H rats. Linear regression analysis showed significant (P < 0.01) differences in the slope of the relationship between BP and GI between H-NX (slope 0.56 ± 0.14; r = 0.69; P < 0.008) and CR-NX (slope 0.09 ± 0.06; r = 0.29; P = 0.12) rats. These data indicate that blunted BP responses to l-NAME in the CR rats are associated with BP-independent resistance to nephropathy, possibly mediated by a resistance to the renal (efferent arteriolar) vasoconstrictive effects of NO inhibition.AJP Renal Physiology 09/2011; 302(1):F173-82. · 4.42 Impact Factor -
Article: Chronic kidney disease: blood-pressure targets in chronic kidney disease.
Nature Reviews Nephrology 12/2010; 7(3):128-30. · 7.09 Impact Factor
