Class differences in the effects of calcium channel blockers in the rat remnant kidney model

Dihydropyridine Calcium Channel Blockers and Kidney Outcomes

BACKGROUND

Early trials of dihydropyridine calcium channel blockers (DCCBs) suggest a detrimental effect on intraglomerular pressure and an association with albuminuria.

OBJECTIVE

We sought to evaluate the associations of DCCB initiation with albuminuria and kidney failure with replacement therapy (KFRT) and to determine whether renin-angiotensin system (RAS) blockade modified these associations.

DESIGN

We conducted a target trial emulation study using a new user, active comparator design and electronic health record data from Geisinger Health.

PARTICIPANTS

We included patients without severe albuminuria or KFRT who were initiated on a DCCB or thiazide (active comparator) between January 1, 2004, and December 31, 2019.

MAIN MEASURES

Using inverse probability of treatment weighting, we performed doubly robust Cox proportional hazards regression to estimate the association of DCCB initiation with incident severe albuminuria (urine albumin to creatinine ratio > 300 mg/g) and KFRT, overall and stratified by RAS blocker use.

KEY RESULTS

There were 11,747 and 26,758 eligible patients initiating a DCCB and thiazide, respectively, with a weighted baseline mean age of 60 years, systolic blood pressure of 143 mm Hg, and eGFR of 86 mL/min/1.73 m2, and with a mean follow-up of 8 years. Compared with thiazides, DCCBs were significantly associated with the development of severe albuminuria (hazard ratio [HR], 1.29; 95% confidence interval [CI], 1.16-1.43), with attenuation of risk in the presence of RAS blockade (P for interaction < 0.001). The risk of KFRT was increased among patients without RAS blockade (HR, 1.66; 95% CI, 1.19-2.31), but not with RAS blockade (P for interaction = 0.005).

CONCLUSIONS

DCCBs were associated with increased risk of albuminuria and, in the absence of RAS blockade, KFRT. These findings suggest coupling DCCB therapy with RAS blockade may mitigate adverse kidney outcomes.

Predicting chronic responses to calcium channel blockade with a virtual population of African Americans with hypertensive chronic kidney disease

Chronic kidney disease (CKD) is associated with the progressive loss of functional nephrons and hypertension (HTN). Clinical studies demonstrate calcium channel blocker (CCB) therapy mitigates the decline in renal function in humans with essential HTN. However, there are few long-term clinical studies that determine the impact of CCBs in patients with hypertensive CKD. African Americans (AA) have a higher prevalence of CKD and a faster progression to total kidney failure as compared to the white population but the mechanisms are poorly understood. Both clinical evidence (the African American Study of Kidney Disease and Hypertension, or AASK trial) and experimental studies have demonstrated that CCB may expose glomerular capillaries to high systemic pressures and exacerbate CKD progression. Therefore, using a large physiological model, we set out to replicate the AASK trial findings, predict renal hemodynamic responses and the role of the renin-angiotensin system during CCB antihypertensive therapy in a virtual population, and hypothesize mechanisms underlying those findings. Our current mathematical model, HumMod, is comprised of integrated systems that play an integral role in long-term blood pressure (BP) control such as neural, endocrine, circulatory, and renal systems. Parameters (n=341) that control these systems were randomly varied and resulted in 1400 unique models that we define as a virtual population. We calibrated these models to individual patient level data from the AASK trial: BP and glomerular filtration rate (GFR) before and after 3 years of amlodipine (10 mg/day). After calibration, the new virtual population (n=165) was associated with statistically similar BP and GFR before and after CCB. Baseline factors such as elevated single nephron GFR and low tubuloglomerular feedback were correlated with greater declines in renal function and increased glomerulosclerosis after 3 years of CCB. Blocking the renin-angiotensin system (RAS) in the virtual population decreased glomerular pressure, limited glomerular damage, and further decreased BP (-14 ± 8 mmHg) as compared to CCB alone (-11 ± 9 mmHg). Our simulations echo the potential risk of CCB monotherapy in AA CKD patients and support blockade of the renin angiotensin system as a valuable tool in renal disease treatment when combined with CCB therapy.

Questioning the renoprotective role of L-type calcium channel blockers in chronic kidney disease using physiological modeling

Chronic kidney disease (CKD) is characterized by the progressive functional loss of nephrons and hypertension (HTN). Some antihypertensive regimens attenuate the progression of CKD (blockers of the renin-angiotensin system). Although studies have suggested that calcium channel blocker (CCB) therapy mitigates the decline in renal function in humans with essential HTN, there are few long-term clinical studies that have determined the impact of CCBs in patients with hypertensive CKD. Dihydropyridine (DHP) or L-type CCBs preferentially vasodilate the afferent arteriole and have been associated with glomerular HTN and increases in proteinuria in animal models with low renal function. Small clinical studies in vulnerable populations with renal disease such as African Americans, children, and diabetics have also suggested that DHP CCBs exacerbate glomerular injury, which questions the renoprotective effect of this class of antihypertensive drug. We used an established integrative mathematical model of human physiology, HumMod, to test the hypothesis that DHP CCB therapy exacerbates pressure-induced glomerular injury in hypertensive CKD. Over a simulation of 3 yr, CCB therapy reduced mean blood pressure by 14-16 mmHg in HTN both with and without CKD. Both impaired tubuloglomerular feedback and low baseline renal function exacerbated glomerular pressure, glomerulosclerosis, and the decline in renal function during L-type CCB treatment. However, simulating CCB therapy that inhibited both L- and T-type calcium channels increased efferent arteriolar vasodilation and alleviated glomerular damage. These simulations support the evidence that DHP (L-type) CCBs potentiate glomerular HTN during CKD and suggest that T/L-type CCBs are valuable in proteinuric renal disease treatment.NEW & NOTEWORTHY Our physiological model replicates clinical trial results and provides unique insights into possible mechanisms that play a role in glomerular injury and hypertensive kidney disease progression during chronic CCB therapy. Specifically, these simulations predict the temporal changes in renal function with CCB treatment and demonstrate important roles for tubuloglomerular feedback and efferent arteriolar conductance in the control of chronic kidney disease progression.

L-type calcium channel blocker use and proteinuria among children with chronic kidney diseases

BACKGROUND

Hypertension is common among children with chronic kidney disease (CKD), and dihydropyridine calcium channel blockers (dhCCBs) are frequently used as treatment. The impact of dhCCBs on proteinuria in children with CKD is unclear.

METHODS

Data from 722 participants in the Chronic Kidney Disease in Children (CKiD) longitudinal cohort with a median age of 12 years were used to assess the association between dhCCBs and log transformed urine protein/creatinine levels as well as blood pressure control measured at annual visits. Angiotensin-converting enzyme inhibitor (ACEi) and angiotensin receptor blocker (ARB) use was evaluated as an effect measure modifier.

RESULTS

Individuals using dhCCBs had 18.8% higher urine protein/creatinine levels compared to those with no history of dhCCB or ACEi and ARB use. Among individuals using ACEi and ARB therapy concomitantly, dhCCB use was not associated with an increase in proteinuria. Those using dhCCBs had higher systolic and diastolic blood pressures.

CONCLUSIONS

Use of dhCCBs in children with CKD and hypertension is associated with higher levels of proteinuria and was not found to be associated with improved blood pressure control.

Pharmacotherapy of hypertension in patients with pre-dialysis chronic kidney disease

INTRODUCTION

Hypertension is the most common co-morbidity in patients with chronic kidney disease (CKD), with prevalence gradually increasing across CKD Stages to the extent that about 90% of end-stage renal disease (ESRD) patients are hypertensives. Several factors contribute to blood pressure (BP) elevation and guide the therapeutic interventions that should be employed in these patients.

AREAS COVERED

This review summarizes the existing data for the management of hypertension, regarding optimal BP targets and the use of major antihypertensive classes in patients with CKD.

EXPERT OPINION

Management of hypertension in CKD requires both lowering BP levels and reducing proteinuria to minimize the risk of both CKD progression and cardiovascular disease. In this respect, aggressive control of office BP to levels <130/80 mmHg has long been proposed for patients with proteinuric nephropathies. Following evidence from recent studies that confirmed significant reductions in renal and cardiovascular outcomes with strict BP control, most, but not all, of international guidelines, suggest such BP goals for all hypertensive patients, including those with CKD. Use of renin-angiotensin system (RAS) blockers is the treatment of choice for patients with proteinuric nephropathies, while, in most patients with CKD, combination treatment with two, three, or more antihypertensive agents is often required to control BP.

Treatment with enalapril and not diltiazem ameliorated progression of chronic kidney disease in rats, and normalized renal AT1 receptor expression as measured with PET imaging

ACE inhibitors are considered first line of treatment in patients with many forms of chronic kidney disease (CKD). Other antihypertensives such as calcium channel blockers achieve similar therapeutic effectiveness in attenuating hypertension-related renal damage progression. Our objective was to explore the value of positron emission tomography (PET) imaging of renal AT1 receptor (AT1R) to guide therapy in the 5/6 subtotal-nephrectomy (Nx) rat model of CKD. Ten weeks after Nx, Sprague-Dawley rats were administered 10mg/kg/d enalapril (NxE), 30mg/kg/d diltiazem (NxD) or left untreated (Nx) for an additional 8-10 weeks. Kidney AT1R expression was assessed using in vivo [18F]fluoropyridine-losartan PET and in vitro autoradiography. Compared to shams, Nx rats exhibited higher systolic blood pressure that was reduced by both enalapril and diltiazem. At 18-20 weeks, plasma creatinine and albuminuria were significantly increased in Nx, reduced to sham levels in NxE, but enhanced in NxD rats. Enalapril treatment decreased kidney angiotensin II whereas diltiazem induced significant elevations in plasma and kidney levels. Reduced PET renal AT1R levels in Nx were normalized by enalapril but not diltiazem, and results were supported by autoradiography. Reduction of renal blood flow in Nx was restored by enalapril, while no difference was observed in myocardial blood flow amongst groups. Enhanced left ventricle mass in Nx was not reversed by enalapril but was augmented with diltiazem. Stroke volume was diminished in untreated Nx compared to shams and restored with both therapies. [18F]Fluoropyridine-Losartan PET allowed in vivo quantification of kidney AT1R changes associated with progression of CKD and with various pharmacotherapies.

Renoprotective Effect of the Combination of Renin-angiotensin System Inhibitor and Calcium Channel Blocker in Patients with Hypertension and Chronic Kidney Disease

BACKGROUND

Renin-angiotensin system inhibitor and calcium channel blocker (CCB) are widely used in controlling blood pressure (BP) in patients with chronic kidney disease (CKD). We carried out a meta-analysis to compare the renoprotective effect of the combination of angiotensin-converting enzyme inhibitor (ACEI) or angiotensin receptor blocker (ARB) and CCB (i.e., ACEI/ARB + CCB) with ACEI/ARB monotherapy in patients with hypertension and CKD.

METHODS

Publications were identified from PubMed, Embase, Medline, and Cochrane databases. Only randomized controlled trials (RCTs) of BP lowering treatment for patients with hypertension and CKD were considered. The outcomes of end-stage renal disease (ESRD), cardiovascular events, BP, urinary protein measures, estimated glomerular filtration rate (GFR), and adverse events were extracted.

RESULTS

Based on seven RCTs with 628 patients, ACEI/ARB + CCB did not show additional benefit for the incidence of ESRD (risk ratio [RR] = 0.84; 95% confidence interval [CI]: 0.52-1.33) and cardiovascular events (RR = 0.58; 95% CI: 0.21-1.63) significantly, compared with ACEI/ARB monotherapy. There were no significant differences in change from baseline to the end points in diastolic BP (weighted mean difference [WMD] = -1.28 mmHg; 95% CI: -3.18 to -0.62), proteinuria (standard mean difference = -0.55; 95% CI: -1.41 to -0.30), GFR (WMD = -0.32 ml/min; 95% CI: -1.53 to -0.89), and occurrence of adverse events (RR = 1.05; 95% CI: 0.72-1.53). However, ACEI/ARB + CCB showed a greater reduction in systolic BP (WMD = -4.46 mmHg; 95% CI: -6.95 to -1.97), compared with ACEI/ARB monotherapy.

CONCLUSION

ACEI/ARB + CCB had no additional renoprotective benefit beyond than what could be achieved with ACEI/ARB monotherapy.

Relative antihypertensive and glomeruloprotective efficacies of enalapril and candesartan cilexetil in the remnant kidney model

The present studies were performed to investigate whether the differences described between the two modalities for interruption of the renin-angiotensin-aldosterone system (RAAS), angiotensin-converting enzyme inhibitors (ACE-I) and angiotensin AT 1receptor antagonists (AIIA) result in differences in renoprotective efficacy in the rat remnant kidney model. Male Sprague-Dawley rats with an initial body weight of 225—300 g, underwent 5/6 renal ablation and had radiotransmitters installed for radiotelemetric blood pressure (BP) measurements, owing to the known limitations of periodic tail-cuff BP measurements to adequately reflect ambient BP profiles. After renal ablation surgery, the rats received no treatment (n=10); enalapril (n=11) or candesartan (n=9) after the first week, both administered initially at a dose of 50 mg/l of drinking water (~10 mg/kg). However, the dose of candesartan had to be reduced to 10—25 mg/l in 4/9 rats to avoid excessive hypotension. Both enalapril and candesartan produced significant reductions in average systolic BP during the subsequent approximately six weeks of observations as compared with untreated rats (187±4 mmHg, p<0.001), but candesartan was significantly more effective at these relative doses (121±3 vs. 133±4 mmHg, p<0.05). At approximately seven weeks, serum creatinine and proteinuria were measured before sacrifice for morphologic assessment of percentage glomerulosclerosis (GS). Despite the described differences between ACE-I and AIIA after acute administration, the percentage GS was reduced similarly by enalapril (down to 6.8±2.8%) and candesartan (down to 2.9±1.5%) as compared with untreated rats (37.2±4.3%). Moreover, GS in individual animals paralleled the BP reductions achieved. Proteinuria was reduced in parallel to the decrease in % GS. These data indicate that, at least in the 5/6 renal ablation model, RAAS blockade by either ACE-I or AIIA provides protection by BPdependent rather than BP-independent mechanisms. This may reflect the primarily hypertensive pathogenesis of GS in this model, and the fact that hypertension is also very angiotensin II-dependent in this model. Thus, these data suggest that models other than the 5/6 ablation model may be more appropriate to demonstrate the BP-independent protective effects of RAAS blockade.

The Gomez' equations and renal hemodynamic function in kidney disease research

Diabetic kidney disease (DKD) remains the leading cause of end-stage renal disease. A major challenge in preventing DKD is the difficulty in identifying high-risk patients at an early, pre-clinical stage. Albuminuria and eGFR as measures of renal function in DKD research and clinical practice are limited by regression of one-third of patients with microalbuminuria to normoalbuminuria and eGFR is biased and imprecise in the normal-elevated range. Moreover, existing methods that are used to assess renal function do not give detailed insight into the location of the renal hemodynamic effects of pharmacological agents at the segmental level. To gain additional information about the intrarenal circulation in-vivo in humans, mathematical equations were developed by Gomez et al in the 1950s. These equations used measurements of GFR, renal blood flow (RBF), effective renal plasma flow (ERPF), renal vascular resistance (RVR), hematocrit and serum protein to calculate afferent and efferent arteriolar resistances, glomerular hydrostatic pressure and filtration pressure. Although indirect and based on physiological assumptions, these techniques have the potential to improve researchers' ability to identify early pre-clinical changes in renal hemodynamic function in patients with a variety of conditions including DKD, thereby offering tremendous potential in mechanistic human research studies. In this review, we focus on the application of Gomez' equations and summarize the potential and limitations of this technique in DKD research. We also summarize illustrative data derived from Gomez' equations in patients with type 1 (T1D) and type 2 diabetes (T2D) and hypertension.

Molecular mechanisms of renal blood flow autoregulation

Diabetes and hypertension are the leading causes of chronic kidney disease and their incidence is increasing at an alarming rate. Both are associated with impairments in the autoregulation of renal blood flow (RBF) and greater transmission of fluctuations in arterial pressure to the glomerular capillaries. The ability of the kidney to maintain relatively constant blood flow, glomerular filtration rate (GFR) and glomerular capillary pressure is mediated by the myogenic response of afferent arterioles working in concert with tubuloglomerular feedback that adjusts the tone of the afferent arteriole in response to changes in the delivery of sodium chloride to the macula densa. Despite intensive investigation, the factors initiating the myogenic response and the signaling pathways involved in the myogenic response and tubuloglomerular feedback remain uncertain. This review focuses on current thought regarding the molecular mechanisms underlying myogenic control of renal vascular tone, the interrelationships between the myogenic response and tubuloglomerular feedback, the evidence that alterations in autoregulation of RBF contributes to hypertension and diabetes-induced nephropathy and the identification of vascular therapeutic targets for improved renoprotection in hypertensive and diabetic patients.

Effects of T-type calcium channel blockers on renal function and aldosterone in patients with hypertension: a systematic review and meta-analysis

Background

High blood pressure can cause kidney damage, which can increase blood pressure, leading to a vicious cycle. It is not clear whether the protective effects of T-type calcium channel blockers (T-type CCBs) on renal function are better than those of L-type CCBs or renin-angiotensin system (RAS) antagonists in patients with hypertension.

Methods and Findings

PUBMED, MEDLINE, EMBASE, OVID, Web of Science, Cochrane, CNKI, MEDCH, VIP, and WANFANG databases were searched for clinical trials published in English or Chinese from January 1, 1990, to December 31, 2013. The weighted mean difference (WMD) and 95% confidence interval (CI) were calculated and reported. A total of 1494 reports were collected, of which 24 studies with 1,696 participants (including 809 reports comparing T-type CCBs versus L-type CCBs and 887 reports comparing T-type CCB versus RAS antagonists) met the inclusion criteria. Compared with L-type CCBs, T-type CCBs resulted in a significant decline in aldosterone (mean difference = −15.19, 95% CI −19.65–−10.72, p<1×10⁻⁵), proteinuria (mean difference = −0.73, 95% CI −0.88–−0.57, p<1×10⁻⁵), protein to creatinine ratio (mean difference = −0.22, 95% CI −0.41–−0.03, p = 0.02), and urinary albumin to creatinine ratio (mean difference = −55.38, 95% CI −86.67–−24.09, p = 0.0005); no significant difference was noted for systolic blood pressure (SBP) (p = 0.76) and diastolic blood pressure (DBP) (p = 0.16). The effects of T-type CCBs did not significantly differ from those of RAS antagonists for SBP (p = 0.98), DBP (p = 0.86), glomerular filtration rate (p = 0.93), albuminuria (p = 0.97), creatinine clearance rate (p = 0.24), and serum creatinine (p = 0.27) in patients with hypertension.

Conclusion

In a pooled analysis of data from 24 studies measuring the effects of T-type CCBs on renal function and aldosterone, the protective effects of T-type CCBs on renal function were enhanced compared with L-type CCBs but did not differ from RAS antagonists. Their protective effects on renal function were independent of blood pressure.

Effects of manidipine vs. amlodipine on intrarenal haemodynamics in patients with arterial hypertension

AIMS

Intraglomerular pressure is one of the main drivers of progression of renal failure. Experimental data suggest that there are important differences between calcium channel blockers (CCBs) in their renal haemodynamic effects: manidipine reduces, whereas amlodipine increases intraglomerular pressure. The aim of this study was to investigate the effects of manidipine and amlodipine treatment on intragomerular pressure (P(glom)) in patients with mild to moderate essential hypertension.

METHODS

In this randomized, double-blind, parallel group study, hypertensive patients were randomly assigned to receive manidipine 20 mg (n = 54) or amlodipine 10 mg (n = 50) for 4 weeks. Renal plasma flow (RPF) and glomerular filtration rate (GFR) were determined by constant-infusion input-clearance technique with p-aminohippurate (PAH) and inulin. P(glom) and resistances of the afferent (R(A)) and efferent (R(E)) arterioles were calculated according to the model established by Gomez.

RESULTS

P(glom) did not change in the manidipine group (P = 0.951), whereas a significant increase occurred in the amlodipine group (P = 0.009). There was a significant difference in the change of P(glom) by 1.2 mmHg between the manidipine and amlodipine group (P = 0.042). In both treatment arms, R(A) was reduced (manidipine P = 0.018; amlodipine P < 0.001). The reduction of R(A) was significantly more pronounced with amlodipine compared with manidipine treatment (P < 0.001). R(E) increased in both treatment arms (manidipine P = 0.012; amlodipine P = 0.002), with no difference between the treatment arms. Both CCBs significantly reduced systolic and diastolic blood pressure (BP) (both P < 0.001). However, amlodipine treatment resulted in a significantly greater decrease of BP compared with manidipine (P < 0.001).

CONCLUSIONS

In accordance with experimental data after antihypertensive treatment of 4 weeks, intraglomerular pressure was significantly lower with the CCB manidipine than with amlodipine, resulting and explaining their disparate effects on albuminuria.

Amlodipine Reduces Inflammation despite Promoting Albuminuria in the Streptozotocin-Induced Diabetic Rat

Amlodipine reduces blood pressure; however, its effect in the diabetic kidney irrespective of its blood pressure-lowering effects is unclear. This study examined the effects of amlodipine (0, 5, 10 and 20 mg/kg; D_A0, D_A5, D_A10 and D_A20, respectively) for 12 weeks on renal functional and structural changes in the streptozotocin-induced diabetic rat, a nonhypertensive model of diabetes-associated hyperfiltration. Compared with nondiabetic rats, diabetes (D) was associated with increased urine albumin excretion (UAE, 12.6 ± 3.40 vs. 3.73 ± 1.14 mg/day), glomerular filtration rate (2.17 ± 0.09 vs. 1.64 ± 0.12 ml/min/g kidney weight), glomerulosclerosis (0.21 ± 0.03 vs. 0.05 ± 0.01 AU) and infiltration of inflammatory cells (18.5 ± 2.78 vs. 6.92 ± 0.70 cells/cm²), but did not affect mean arterial pressure (MAP, 110 ± 4.70 vs. 109 ± 5.33 mm Hg). While D_A20 abolished glomerular hyperfiltration (1.49 ± 0.05 ml/min/g kidney weight) and inflammatory cell abundance (6.0 ± 0.79 cells/cm²), it exacerbated UAE (43.5 ± 8.49 mg/day) and increased MAP (132 ± 3.76 mm Hg), but had no effect on renal pathology. These data suggest that amlodipine reduces renal inflammation and abolished glomerular hyperfiltration, but increases blood pressure and exacerbates albuminuria in the rat model of normotensive diabetic kidney disease. We conclude that amlodipine may have limited renoprotective effects in the face of hyperfiltration and absence of elevated blood pressure.

NKCC1 and hypertension: role in the regulation of vascular smooth muscle contractions and myogenic tone

High-ceiling diuretics (HCD), known potent inhibitors of housekeeping Na(+),K(+),2Cl cotransporter (NKCC1) and renal-specific NKCC2, decrease [Cl(-)](i), hyperpolarize vascular smooth muscle cells (VSMC), and suppress contractions evoked by modest depolarization, phenylephrine, angiotensin II, and UTP. These actions are absent in nkcc1 (/) knock-out mice, indicating that HCD interact with NKCC1 rather than with other potential targets. These findings also suggest that VSMC-specific inhibitors of NKCC1 may be considered potential pharmacological therapeutic tools in treatment of hypertension. It should be underlined that side by side with attenuation of peripheral resistance and systemic blood pressure, HCD blocked myogenic tone (MT) in renal afferent arterioles. Keeping this in mind, attenuation of MT might be a mechanism underlying the prevalence of end-stage renal disease documented in hypertensive African-Americans with decreased NKCC1 activity and in hypertensive patients subjected to chronic HCD treatment. The role of NKCC1-mediated MT in protection of the brain, heart, and other encapsulated organs deserves further investigation.

Differential effects of strict blood pressure lowering by losartan/hydrochlorothiazide combination therapy and high-dose amlodipine monotherapy on microalbuminuria: the ALPHABET study

We investigated the effects of losartan/hydrochlorothiazide (HCTZ) fixed combination therapy and high-dose amlodipine monotherapy on BP measurements and target organ protection. In this open-label multicenter trial, hypertensive patients were randomly allocated to receive losartan 50 mg or amlodipine 5 mg for 4 weeks, and the treatments were changed to combination of losartan 50 mg/HCTZ 12.5 mg or amlodipine 10 mg for a further 4 weeks. A total of 91 hypertensive patients (age 63.6 years), 47 in the losartan/HCTZ group and 44 in amlodipine group, were enrolled. After 8 weeks, the clinic BP, home BP, and 24-hour ambulatory BP were successfully controlled to the same level in both treatment groups (P < .001). Furthermore, both groups showed the same degree of BP reduction in the 24-hour, daytime, and nighttime (P < .001). B-type natriuretic peptide (BNP) also significantly decreased to the same level in both groups, whereas the reduction of urinary albumin/creatinine ratio (UACR) was greater in the losartan/HCTZ group than in the high-dose amlodipine group (-47.6% vs 2.4%, P < .001). Losartan/HCTZ combination and high-dose amlodipine have similar effects on clinic, home, and ambulatory BP control and BNP reduction, whereas losartan/HCTZ has superior effect on UACR reduction when compared with high-dose amlodipine.

Treatment of proteinuria with lercanidipine associated with reninangiotensin axis-blocking drugs

Aim. Most calcium antagonists do not seem to reduce microalbuminuria or proteinuria. We have tried to assess the antiproteinuric effect of a calcium channel blocker, lercanidipine, in patients previously treated with ACE inhibitors or angiotensin receptor blockers.Design and methods. The study included 68 proteinuric (>500 mg/day) patients (age 63,1±12,9 years, 69,1 % males and 30,9 % females). All patients were receiving ACE inhibitors (51,4 %) or angiotensin II receptor blockers (48,6 %) therapy but had higher blood pressure (BP) than recommended for proteinuric patients (<130/80 mm Hg). Patients were clinically evaluated one, three, and six months after starting treatment with lercanidipine (20 mg/day). Samples for urine and blood examination were taken during the examination. When needed, a third drug was added to treatment. Creatinine clearance was measured using 24 h urine collection.Results. BP significantly decreased from 152±15/86±11 mm Hg to 135±12/77±10 mm Hg at six months of follow-up (p<0,001). After six months of treatment, the percentage of normalized patients (BP <130/80 mm Hg) was 42,5 %, and the proportion of patients whose BP was below 140/90 mm Hg was 58,8 %. Plasmatic creatinine did not change nor did creatinine clearance. Plasmatic cholesterol also decreased from 210±48 to 192±34 mg/dL (p<0,001), as did plasma triglycerides (from 151±77 to 134±72 mg/dL,p=0,022). Basal proteinuria was 1,63±1,34 g/day; it was significantly (p<0,001) reduced by 23 % at the first month, 37 % at three months, and 33 % at the last visit.

Conclusion. Lercanidipine at 20 mg dose, associated with renin-angiotensin axis-blocking drugs, showed a high antihypertensive and antiproteinuric effect. This antiproteinuric effect seems to be dose-dependent as compared with previous reports and proportionally higher than blood pressure reduction.

T-type Ca channel blockade as a determinant of kidney protection

Voltage-dependent Ca channels are classified into several subtypes based on the isoform of their α1 subunits. Traditional Ca channels blockers (CCBs), including nifedipine and amlodipine, act predominantly on L-type Ca channels, whereas novel CCBs such as efonidipine, benidipine and azelnidipine inhibit both L-type and T-type Ca channels. Furthermore, cilnidipine blocks L-type and N-type Ca channels. These CCBs exert divergent actions on renal microvessels. L-type CCBs preferentially dilate afferent arterioles, whereas both L-/T-type and L-/N-type CCBs potently dilate afferent and efferent arterioles. The distinct actions of CCBs on the renal microcirculation are reflected by changes in glomerular capillary pressure and subsequent renal injury: L-type CCBs favor an increase in glomerular capillary pressure, whereas L-/T-type and L-/N-type CCBs alleviate glomerular hypertension. The renal protective action of L-/T-type CCBs is also mediated by non-hemodynamic mechanisms, i.e., inhibition of the inflammatory process and inhibition of Rho kinase and aldosterone secretion. Finally, a growing body of evidence indicates that T-type CCBs offer more beneficial action on proteinuria and renal survival rate than L-type CCBs in patients with chronic kidney disease (CKD). Similarly, in CKD patients treated with renin-angiotensin blockers, add-on therapy with N-type CCBs is more potent in reducing proteinuria than that with L-type CCBs, although no difference is found in the subgroup with diabetic nephropathy. Thus, the strategy for hypertension treatment with CCBs has entered a new era: treatment selection depends not only on blood pressure control but also on the subtypes of CCBs.

Treatment of proteinuria with lercanidipine associated with renin-angiotensin axis-blocking drugs

OBJECTIVE

Most calcium antagonists do not seem to reduce microalbuminuria or proteinuria. We have tried to assess the antiproteinuric effect of a calcium channel blocker, lercanidipine, in patients previously treated with ACE inhibitors or angiotensin receptor blockers.

DESIGN AND METHODS

The study included 68 proteinuric (> 500 mg/day) patients (age 63.1 +/- 12.9 years, 69.1% males and 30.9 females). All patients were receiving ACE inhibitors (51.4%) or angiotensin II receptor blockers (48.6%) therapy but had higher blood pressure than recommended for proteinuric patients (<130/80 mmHg). Patients were clinically evaluated one, three, and six months after starting treatment with lercanidipine (20 mg/day). Samples for urine and blood examination were taken during the examination. When needed, a third drug was added to treatment. Creatinine clearance was measured using 24 h urine collection.

RESULTS

BP significantly decreases from 152 +/- 15/86 +/- 11 mmHg to 135 +/- 12/77 +/- 10 mmHg at six months of follow-up (p < 0.001). After six months of treatment, the percentage of normalized patients (BP < 130/80 mmHg) was 42.5%, and the proportion of patients whose BP was below 140/90 mmHg was 58.8%. Plasmatic creatinine did not change nor did creatinine clearance. Plasmatic cholesterol also decreased from 210 +/- 48 to 192 +/- 34 mg/dL (p < 0.001), as did plasma triglycerides (from 151 +/- 77 to 134 +/- 72 mg/dL, p = 0.022). Basal proteinuria was 1.63 +/- 1.34 g/day; it was significantly (p < 0.001) reduced by 23% at the first month, 37% at three months, and 33% at the last visit.

CONCLUSIONS

Lercanidipine at 20 mg dose, associated to renin-angiotensin axis-blocking drugs, showed a high antihypertensive and antiproteinuric effect. This antiproteinuric effect seems to be dose-dependent as compared with previous reports and proportionally higher than blood pressure reduction.

Prevalence and risk factors of microalbuminuria in Thai nondiabetic hypertensive patients

PURPOSE

To assess the prevalence and risk factors of microalbuminuria in nondiabetic hypertensive patients in Thailand.

PATIENTS AND METHODS

A cross-sectional study was performed during January to December 2007 at outpatients departments of Bhumibol Adulyadej hospital. Nondiabetic hypertensive patients without a history of pre-existing kidney diseases participated in this study. A questionnaire was used for collecting information on demographics, lifestyle, and family history of cardiovascular and kidney disease. Spot morning urine samples were collected for albuminuria estimation. Albuminuria thresholds were evaluated and defined using albumin-creatinine ratio (ACR).

RESULTS

A total of 559 hypertensive patients (283 males, 276 females), aged 58.0 +/- 11.6 years were enrolled in this study. Microalbuminuria (ACR 17 to 299 mg/g in males and 25 to 299 mg/g in females) was found in 93 cases (16.6%) [15.0%-18.2%]. The independent determinants of elevated urinary albumin excretion in a multiple logistic regression model were; body mass index > or =30 (odds ratio (OR) = 2.24, 95% confidence intervals (CI): 1.33-3.76) and dihydropyridine calcium channel blockers (DCCB) use (OR = 1.92, 95% CI: 1.22-3.02).

CONCLUSION

In Thai nondiabetic hypertensive patients, microalbuminuria was not uncommon. Obesity and use of dihydropyridine calcium channel blocker were found to be the important predictors. Prognostic value of the occurrence of microalbuminuria in this population remains to be determined in prospective cohort studies.

Verapamil Reverts Acute Renal Functional Impairment Induced by Angiotensin II Converting Enzyme Inhibitors

Angiotensin converting enzyme inhibitors (ACEI) reduce blood pressure (BP) and provide end-organ protection, but may induce renal function deterioration. In these cases, serum creatinine (SCr) can be normalized by ACEI withdrawn. In some patients, it could be desirable to maintain the ACEI for the protection of the kidney and heart. The objective of the study was to evaluate the effect of Verapamil (V) on renal function added to patients with elevated SCr due to ACEI treatment. In 46 hypertensive patients without previous renal failure, in which ACEI treatment induced an acute increase in SCr (> or = 20% or 0.5 mg/dL), ACEI treatment was maintained and 180 mg/day of V was added for 12 weeks. Those patients showing further SCr increase or no BP control at four weeks were withdrawn. Patients under BP control were moved on the combination V 180 + Trandolapril 2 mg/day for eight weeks more. SCr decreased from 136 +/- 49 micromol/L at baseline to 126 +/- 49 at 12 weeks after adding V (p < 0.001) and to 111 +/- 31 micromol/L at 20 weeks (p < 0.01). Creatinine clearance increased from 62 +/- 22 mL/min at baseline to 68 +/- 28 after 12 weeks of V (p < 0.001). This article demonstrates than in patients with acute renal function impairment secondary to ACEI treatment, the addition of 180 mg/day of verapamil to ACEI reverses SCr towards previous values.

Potential risks of calcium channel blockers in chronic kidney disease

Antihypertensive therapy remains the most effective strategy for slowing the progression of chronic kidney disease (CKD). However, in proteinuric nephropathies, calcium channel blockers (CCBs) are less effective than other antihypertensives unless normotension is achieved. This is because the glomerular capillaries, rather than larger vessels, are the primary site of hypertensive injury in proteinuric nephropathies. CCBs impair renal autoregulation, which protects glomerular capillaries against the transmission of systemic pressures. CCBs' renoprotective inferiority in the comparator group likely accounts for the greater renoprotection observed with renin-angiotensin system blockade rather than blood pressure (BP)-independent renoprotective superiority. Nevertheless, CKD patients are at greater absolute risk for cardiovascular events rather than end-stage renal disease. Therefore, if the needed BP reductions cannot be achieved with other agents, it may be appropriate to use CCBs because of their antihypertensive effectiveness, provided care is taken to ensure normotension and to closely monitor proteinuria and renal disease progression.

Renoprotective effect of calcium channel blockers

The advancing chronic renal failure is at most the consequence of secondary haemodynamic and metabolic factors as intraglomerular hypertension and glomerular hypertrophy. Although tight blood pressure control is the major preventive mechanism for progressive renal failure, ACE inhibitors and angiotensin receptor blockers have some other renoprotective mechanisms beyond the blood pressure control. That is why these two groups of antihypertensive drugs traditionally have advantages in treating renal patients especially those with proteinuria over 400-1000 mg/day. Even if earlier experimental studies have shown renoprotective effect of calcium channel blockers, later clinical studies did not prove that calcium channel blockers have any advantages in renal protection over ACE inhibitors given as monotherapy or in combination with ACE inhibitors. It was explained by action of calcium channel blockers on afferent but not on efferent glomerular arterioles; a well known mechanism that leads to intraglomerular hypertension. New generations of dihydropiridine calcium channel blockers can dilate even efferent arterioles not causing unfavorable haemodynamic disturbances. This finding was confirmed in clinical studies which showed that renoprotection established by calcium channel blockers was not inferior to that of ACE inhibitors and that calcium channel blockers and ACE inhibitors have additive effect on renoprotection. Newer generation of dihydropiridine calcium channel blockers seem to offer more therapeutic possibilities in renoprotection by their dual action on afferent and efferent glomerular arterioles and, possibly by other effects beyond the blood pressure control.

Are differences in calcium antagonists relevant across all stages of nephropathy or only proteinuric nephropathy?

PURPOSE OF REVIEW

The main effects of classic calcium antagonists are mediated by the inhibition of L-type calcium channels broadly distributed within the renal vascular bed. Calcium antagonists act predominantly on the afferent arterioles, and dihydropyridines can favour the increase in glomerular hypertension and progression of kidney diseases, in particular when systemic blood pressure remains uncontrolled.

RECENT FINDINGS

Calcium antagonists have been widely used in clinical practice because of their antihypertensive capacity. The prevention of renal damage is a very important aim of antihypertensive therapy. This is particularly so taking into account the high prevalence of chronic kidney disease in the general population. Non-dihydropyridines such as verapamil have been shown to possess an antiproteinuric effect that could be particularly relevant.

SUMMARY

Recent data from clinical trials have confirmed that, in hypertensive patients with preserved renal function or with chronic kidney disease, calcium antagonists are effective antihypertensive drugs to be considered alone or in combination with an angiotensin-converting enzyme inhibitor or an angiotensin receptor blocker. In those patients presenting with proteinuric kidney disease, non-dihydropyridines could reduce proteinuria to a greater degree than dihydropyridines.

Ca2+ channel subtypes and pharmacology in the kidney

A large body of evidence has accrued indicating that voltage-gated Ca(2+) channel subtypes, including L-, T-, N-, and P/Q-type, are present within renal vascular and tubular tissues, and the blockade of these Ca(2+) channels produces diverse actions on renal microcirculation. Because nifedipine acts exclusively on L-type Ca(2+) channels, the observation that nifedipine predominantly dilates afferent arterioles implicates intrarenal heterogeneity in the distribution of L-type Ca(2+) channels and suggests that it potentially causes glomerular hypertension. In contrast, recently developed Ca(2+) channel blockers (CCBs), including mibefradil and efonidipine, exert blocking action on L-type and T-type Ca(2+) channels and elicit vasodilation of afferent and efferent arterioles, which suggests the presence of T-type Ca(2+) channels in both arterioles and the distinct impact on intraglomerular pressure. Recently, aldosterone has been established as an aggravating factor in kidney disease, and T-type Ca(2+) channels mediate aldosterone release as well as its effect on renal efferent arteriolar tone. Furthermore, T-type CCBs are reported to exert inhibitory action on inflammatory process and renin secretion. Similarly, N-type Ca(2+) channels are present in nerve terminals, and the inhibition of neurotransmitter release by N-type CCBs (eg, cilnidipine) elicits dilation of afferent and efferent arterioles and reduces glomerular pressure. Collectively, the kidney is endowed with a variety of Ca(2+) channel subtypes, and the inhibition of these channels by their specific CCBs leads to variable impact on renal microcirculation. Furthermore, multifaceted activity of CCBs on T- and N-type Ca(2+) channels may offer additive benefits through nonhemodynamic mechanisms in the progression of chronic kidney disease.

A review of calcium channel antagonists in the treatment of pediatric hypertension

All children aged > or = 3 years should have an annual blood pressure (BP) measurement taken during a routine physical examination. Physicians should become familiar with recommended pediatric normative BP tables. BP above the 95th percentile may require drug therapy. There are several categories of antihypertensives available to the clinician. Calcium channel antagonists (CCAs) are a class of drugs that exert their antihypertensive effect by inhibiting the influx of calcium ions across the cell membranes. This results in dilatation of peripheral arterioles. When given orally, CCAs are metabolised in the liver by cytochrome P450 (CYP) enzyme CYP3A4; hence, some CCAs will affect the half-life of drugs that share this enzyme system for their metabolism. CCAs can be safely used in children with renal insufficiency or failure and as a general rule there is no need to modify drug dosage in this population. CCAs are generally well tolerated; most adverse effects appear to be dose related. Headache, flushing, gastrointestinal upset, and edema of the lower extremities are the most common symptoms reported with the use of CCAs. Pediatric data regarding safety and efficacy of CCAs have mostly been obtained from retrospective analyses. Extended-release nifedipine and amlodipine are the two most commonly used oral CCAs in the management of pediatric hypertension. These drugs can be given once a day, although many children require twice-daily administration. Extended-release nifedipine has to be swallowed whole; hence, its use in younger children who cannot swallow pills is limited. Amlodipine can be made into a solution without compromising its long duration of action; therefore, it is the CCA of choice for very young children. Oral short-acting nifedipine and intravenous nicardipine are safe and effective CCAs for the management of hypertensive crisis in children. Short-acting nifedipine can cause unpredictable changes in BP; hence, it should be used cautiously and in low doses. Intravenous nicardipine has a rapid onset of action and a short half-life. Intravenous infusion of nicardipine can be titrated for effective control of BP. Intravenous nicardipine has been used safely in hospitalized children and newborns for the management of hypertensive crisis, and for controlled hypotension during surgery. CCAs are a class of antihypertensives that are safe and effective in pediatric patients. They have relatively few adverse effects and are well tolerated by children. This article reviews CCAs as antihypertensives in the management of pediatric hypertension.

Protection of Swiss albino mice against whole-body gamma irradiation by diltiazem

The aim of the present study was to evaluate the radioprotective effect of diltiazem (DTZ) on Swiss albino mice exposed to gamma radiation. In the present study, radioprotective efficacy of DTZ (a calcium channel blocker) was studied against radiation induced haematological and biochemical alterations. Swiss albino mice of 6-8 weeks old were administered diltiazem (100 mg kg(-1) by weight) intraperitoneally prior to whole body gamma-irradiation (7.5 Gy). Radiation exposure resulted in a significant decline in different bone marrow cells (pro- and normoblasts) and blood constituents (erythrocytes, leukocytes, differential leukocyte count, haematocrit, haemoglobin and erythrocyte sedimentation rate). Pro- and normoblasts, erythrocytes, leukocytes, haematocrit and haemoglobin values showed a significant (p<0.0051) decline until day 3, following a gradual recovery from day 7, but normal values were not recorded until 28 days post-exposure. In contrast, erythropoietin levels increased significantly and reached a maximum on day 3. In DTZ pre-treated irradiated animals, a significant increase in pro- and normoblasts, erythrocytes, leukocytes, differential leukocyte count, haematocrit and haemoglobin values, and a significant decrease in erythropoietin values, were observed compared with control. A significant elevation above normal in lipid peroxidation level was recorded in gamma irradiated mice, whereas this increase was considerably less in DTZ pre-treated animals. Similarly, pre-treatment of DTZ caused a significant increase in erythropoietin and glutathione levels in serum in comparison with irradiated animals. From our study it is clear that DTZ provides protection against radiation-induced haematological and biochemical alterations in Swiss albino mice.

Antihypertensive Therapy in the Presence of Proteinuria

The presence of proteinuria is a well-known risk factor for both the progression of renal disease and cardiovascular morbidity and mortality, and decreases in urine protein excretion level were associated with a slower decrease in renal function and decrease in risk of cardiovascular events. Increased blood pressure has a major role in the development of proteinuria in patients with either diabetic or nondiabetic kidney disease, and all recent guidelines recommend a blood pressure goal less than 130/80 mm Hg in patients with proteinuria to achieve maximal renal and cardiovascular protection. Drugs interfering with the renin-angiotensin system, ie, angiotensin-converting enzyme inhibitors and angiotensin receptor blockers, should be used as first-line antihypertensive therapy in patients with proteinuria because they seem to have a blood pressure-independent antiproteinuric effect, and if blood pressure levels are still out of goal, a diuretic should be added to this regimen. A combination of an angiotensin-converting enzyme inhibitor with an angiotensin receptor blocker or other classes of medications shown to decrease protein excretion, such as nondihydropyridine calcium antagonists or aldosterone receptor blockers, should be considered to decrease proteinuria further. This review provides an extended summary of current evidence regarding the associations of blood pressure with proteinuria, the rationale for currently recommended blood pressure goals, and the use of various classes of antihypertensive agents in proteinuric patients.

Progression of renal disease: renoprotective specificity of renin-angiotensin system blockade

Recent guidelines for management of patients with chronic kidney disease recommend both lower optimal BP targets and agents that block the renin-angiotensin system (RAS) for specific additional BP-independent renoprotection. Although there are other compelling rationales to use RAS blockade in patients with chronic kidney disease, including its antihypertensive effectiveness and ability to counteract the adverse effects of diuretics, a critical review of the available scientific evidence suggests that the specificity of renoprotection that is provided by RAS blockade has been greatly overemphasized. Little evidence of truly BP-independent renoprotection is observed in experimental animal models when ambient BP is assessed adequately by chronic continuous BP radiotelemetry. Although the clinical trial evidence is somewhat stronger, nevertheless, even when interpreted favorably, the absolute magnitude of the BP-independent component of the renoprotection that is observed with RAS blockade is much smaller than what is due to its antihypertensive effects.

Renal autoregulation: new perspectives regarding the protective and regulatory roles of the underlying mechanisms

When the kidney is subjected to acute increases in blood pressure (BP), renal blood flow (RBF) and glomerular filtration rate (GFR) are observed to remain relatively constant. Two mechanisms, tubuloglomerular feedback (TGF) and the myogenic response, are thought to act in concert to achieve a precise moment-by-moment regulation of GFR and distal salt delivery. The current view is that this mechanism insulates renal excretory function from fluctuations in BP. Indeed, the concept that renal autoregulation is necessary for normal renal function and volume homeostasis has long been a cornerstone of renal physiology. This article presents a very different view, at least regarding the myogenic component of this response. We suggest that its primary purpose is to protect the kidney against the damaging effects of hypertension. The arguments advanced take into consideration the unique properties of the afferent arteriolar myogenic response that allow it to protect against the oscillating systolic pressure and the accruing evidence that when this response is impaired, the primary consequence is not a disturbed volume homeostasis but rather an increased susceptibility to hypertensive injury. It is suggested that redundant and compensatory mechanisms achieve volume regulation, despite considerable fluctuations in distal delivery, and the assumed moment-by-moment regulation of renal hemodynamics is questioned. Evidence is presented suggesting that additional mechanisms exist to maintain ambient levels of RBF and GFR within normal range, despite chronic alterations in BP and severely impaired acute responses to pressure. Finally, the implications of this new perspective on the divergent roles of the myogenic response to pressure vs. the TGF response to changes in distal delivery are considered, and it is proposed that in addition to TGF-induced vasoconstriction, vasodepressor responses to reduced distal delivery may play a critical role in modulating afferent arteriolar reactivity to integrate the regulatory and protective functions of the renal microvasculature.

Morphometric evidence for impairment of renal autoregulation in advanced essential hypertension

A morphometric study was performed on 22 renal biopsies from hypertensive patients with proteinuria and/or azotemia, with no evidence of other renal disease. These results were compared with our earlier study of normotensive aging kidneys. Afferent arterioles in hypertensive kidneys showed a significant increase in lumen diameter (15.7+/-4.9 vs 13.4+/-4.7 microm, P=0.0007) and wall area (1234+/-769 vs 998+/-445 microm(2), P=0.037), due primarily to shift in the distribution of arteriolar types, from predominantly normal toward predominantly hyaline arterioles in hypertension. Glomeruli were divided into four basic types: normal, hypertrophic, focal segmental glomerulosclerosis (FSGS) type, and sclerosing. Overall, glomeruli in hypertensive kidneys were much larger than in normotensive aging kidneys, for example, total capillary area (16 247+/-10 681 vs 11 624+/-5702 microm(2), P<0.00001). This increase was due primarily to an increase in size of each type, for example, for hypertrophic glomeruli: total capillary area (22 205+/-10 426 vs 15 349+/-4577 microm(2), P=0.0038). There was an excellent correlation between arteriolar lumen diameter and mean glomerular capillary area for hypertrophic/FSGS-type glomeruli (r=0.4778, P=0.0013), such that as arteriolar diameter increases the mean glomerular capillary area increases, consistent with loss of autoregulation. The morphologic correlates of loss of autoregulation, with afferent arteriolar dilatation and increase in glomerular capillary size, glomerular hypertrophy, and subsequent FSGS, are present on a focal basis in aging kidneys and, much more extensively, although still focally, in hypertensive kidneys.

Systolic blood pressure as the trigger for the renal myogenic response: protective or autoregulatory?

PURPOSE OF REVIEW

The ability of the kidney to autoregulate renal blood flow and glomerular filtration rate has long been viewed as existing to prevent fluctuations in blood pressure from causing parallel fluctuations in renal function and distal delivery of filtrate. This review, however, points out that the primary consequence of the loss of this autoregulatory capacity is not a disturbance in volume regulation, but rather an increased susceptibility to hypertensive injury. Moreover, the kinetic requirements for renal protection indicate that current views of dynamic autoregulation cannot explain how the kidney is normally protected against acute elevations in systolic blood pressure.

RECENT FINDINGS

Recent findings suggest that the kinetics of the myogenic mechanism of the afferent arteriole are uniquely suited to protect against acute elevations in the systolic blood pressure, in that this vessel not only senses this rapidly oscillating blood pressure component, but that its response is exclusively dependent on this signal.

SUMMARY

These new findings are consistent with recent data indicating that it is the systolic blood pressure elevations that most closely correlate with target organ damage. The fact that the myogenic mechanism is also a necessary component of renal autoregulation may explain the strong linkage between autoregulatory impairment and increased susceptibility to hypertensive injury.

Calcium Antagonists

Calcium antagonists comprise 2 main subclasses, dihydropyridines and nondihydropyridines, and have been studied extensively in hypertensive patients. Early meta-analyses suggested that short-acting calcium antagonists were associated with higher mortality rates resulting from cardiovascular events and other etiologies. Recent meta-analyses failed to show any substantive difference between long acting calcium antagonists and other antihypertensive drug classes with regard to cardiovascular outcomes in those with low to moderate cardiovascular risk or kidney disease progression among those with stage 2 or 3 nonproteinuric kidney diseases. The data from calcium antagonist trials are consistent in that they decrease stroke incidence but fail to protect against new-onset heart failure. In people with proteinuric kidney disease, that is > 300 mg protein/gram creatinine, use of dihydropyridine calcium antagonists to lower blood pressure without the use of agents that block the renin angiotensin aldosterone system does not provide optimal slowing of nephropathy progression. This relates directly to lack of antiproteinuric effects with this subclass and not seen with nondihydropyridine agents that reduce proteinuria to a greater degree than dihydropyridines. Thus, calcium antagonists are safe and as efficacious as other antihypertensive agents to reduce cardiovascular risk. They should be avoided in people with systolic dysfunction but may be used for blood pressure lowering in people with preserved systolic function. Dihydropyridine calcium antagonists should only be used in conjunction with angiotensin-converting enzyme inhibitors or angiotensin receptor blockers in proteinuric kidney disease because they will not optimally slow kidney function loss in their absence.

Blood Pressure Control, Drug Therapy, and Kidney Disease

The African American Study of Kidney Disease and Hypertension examined the effect on renal function decline of 2 blood pressure (BP) goals (low mean arterial pressure [MAP] ≤92 versus usual MAP 102 to 107 mm Hg) and 3 antihypertensives (ramipril versus amlodipine versus metoprolol). We previously reported that in all drug groups combined the BP intervention had similar effects on the primary outcome of glomerular filtration rate (GFR) slope or the main secondary clinical composite outcome of end-stage renal disease (ESRD), death, or GFR decline by 50% or 25 mL/min per 1.73 m 2 . This report examines the effect of the BP intervention separately in the 3 drug groups. The BP effect was similar among the drug groups for either GFR slope or the main clinical composite. However, the BP effect differed significantly among the drug groups for the composite of ESRD or death ( P =0.035) and ESRD alone ( P =0.021). Higher event rates for amlodipine patients assigned to the usual BP goal (0.087 per patient-year for ESRD or death and 0.064 per patient-year for ESRD) were seen compared with the remaining groups of the factorial design (range, 0.041 to 0.050 for ESRD or death; and range, 0.027 to 0.036 for ESRD). The low BP goal was associated with reduced risk of ESRD or death (risk reduction 51%; 95% confidence interval, 13% to 73%) and ESRD (54%; 8% to 77%) for amlodipine patients, but not for patients assigned to the other drug groups. These secondary analyses suggest a benefit of the low BP goal among patients assigned to amlodipine, but they must be interpreted cautiously.

ACE inhibitors improve nephrin expression in Zucker rats with glomerulosclerosis

BACKGROUND

Podocyte injury is associated with many forms of human and experimental proteinuric glomerular disease. The aim of this study was to investigate the level of nephrin expression in a model of obesity and type II diabetes mellitus, the obese Zucker rat, as well as to investigate whether nephrin expression is influenced by treatment with quinapril or diltiazem, 2 drugs frequently used in type II diabetes mellitus.

METHODS

Obese Zucker rats were treated with either quinapril or diltiazem at a dose of 10 mg/kg body weight per day and 100 mg/kg body weight per day, respectively, for 6 months. Real time reverse transcription-polymerase chain reaction (RT-PCR) and immunoperoxidase assays were used to assess and quantify nephrin gene expression and other markers of podocyte damage, such as desmin and synaptopodin protein.

RESULTS

Quinapril treatment prevented the reduction of nephrin levels compared with the control group, while diltiazem treatment did not prevent the reduction. Similar results were obtained when other phenotypic markers, such as desmin, were assessed. Similarly, synaptodin showed this tendency, although it did not achieve statistically significant differences.

CONCLUSION

The podocyte phenotypic changes assessed in a model of obesity and type II diabetes mellitus were corrected by an angiotensin-converting enzyme (ACE) inhibitor. These results could be associated with an improvement in the slit diaphragm, and therefore, in the maintenance of the filtration barrier. Diltiazem did not achieve similar results.

Differential effects of antihypertensive drugs on renal and glomerular hemodynamics and injury in the chronic nitric-oxide-suppressed rat

BACKGROUND/AIMS

Prolonged nitric oxide synthase (NOS) inhibition with N(omega)-nitro-L-arginine methylester in normotensive and hypertensive rats has been demonstrated to produce severe systemic and glomerular hypertension with glomerular sclerosis, and these changes have become a useful experimental model of hypertensive nephrosclerosis. This review summarizes data from our serial studies as well as work of others who are also investigating the effects of the commonly used antihypertensive drugs (including calcium antagonist, angiotensin-converting enzyme inhibitor, angiotensin II type 1 receptor blocker, aldosterone antagonist and thiazide diuretic) on renal and glomerular hemodynamics, renal function and glomerular histopathology using this model.

METHODS

A Medline search was performed to identify the relevant literature describing renal effects of antihypertensive drugs in models of hypertension and nephrosclerosis produced or exacerbated by NOS inhibition.

RESULTS

Existing data have indicated that most of these drug classes have produced dramatic renoprotective effects, structurally or functionally, on nephrosclerosis induced by prolonged NOS inhibition.

CONCLUSION

This review of experimental studies has provided strong evidence supporting the clinical benefits of antihypertensive drugs for hypertensive patients with renal impairment particularly those with endothelial dysfunction associated with NOS deficiency.

Angiotensin-converting enzyme inhibitors and angiotensin receptor blockers in chronic renal disease: safety issues

Reducing the actions of the renin-angiotensin-aldosterone system with angiotensin-converting enzyme inhibitors (ACE inhibitors) and angiotensin receptor blockers (ARBs) slows nephropathy progression in patients with or without diabetes. These drug classes have proven therapeutic benefits, particularly in patients with renal insufficiency (ie, serum creatinine level 133-265 micromol/L [1.5-3.0 mg/dL]). This class of drugs could also provide renoprotective effects that are nonblood pressure-dependent when used as part of combination antihypertensive therapy in patients with more advanced renal disease. Although many studies demonstrate the use of ACE inhibitors and ARBs to delay the decline in renal function and reduce proteinuria, many physicians fail to use these drug classes in patients with renal insufficiency for fear that either serum creatinine or potassium levels will rise. Thus, because of these issues, patients are deprived of known strategies that delay progression of renal disease. A strong association exists between acute increases in serum creatinine of up to 30% to 35% after initiating ACE inhibitor therapy and long-term preservation of renal function. This association is predominantly present in people with a baseline serum creatinine of up to 3 mg/dL and usually stablizes within 2 to 3 months of therapy given blood pressure is reduced to goal. Moreover, the appropriate use of diuretics mitigates against profound increases in serum potassium. Thus, withdrawal of an ACE inhibitor in such patients should occur only when the rise in creatinine exceeds this threshold over a shorter period of time or hyperkalemia develops, ie, serum potassium level of 5.6 mmol/L or greater.

Disturbances in Renal Autoregulation and the Susceptibility to Hypertension-Induced Chronic Kidney Disease

The risk of developing chronic kidney disease in the setting of hypertension varies among patient populations. Black hypertensive patients have an increased risk of developing hypertension-induced chronic kidney disease even after taking into account socioeconomic factors. There is evidence to suggest that the kidney is intrinsically more susceptible to the damaging effects of hypertension in black patients. This susceptibility can be traced to disturbances in the way the kidney autoregulates. Impaired renal autoregulation may be the renal manifestation of a more widespread abnormality in endothelial function. Other conditions that can impair renal autoregulation and add to the risk of chronic kidney disease include low birth weight, obesity, insulin resistance, hyperuricemia, and hypercholesterolemia. To minimize the risk of chronic kidney disease in patients with impaired renal autoregulatory capability, strict blood pressure control is required. There is indirect evidence that blocking the renin-angiotensin system may improve renal autoregulation.

Hypertensive renal damage: insights from animal models and clinical relevance

Investigations using chronic blood pressure (BP) radiotelemetry in conscious animals have provided substantial insights into the pathophysiology of hypertensive renal damage. Normal renal autoregulation protects the renal microvasculature from significant injury in most patients with primary hypertension, unless BP exceeds a certain threshold, when malignant nephrosclerosis develops. However, if autoregulation is impaired, as in chronic renal disease and/or diabetes models, the threshold for renal damage is lowered and glomerulosclerosis (GS) increases linearly with increasing BP. Modest BP reductions are predicted to prevent malignant nephrosclerosis, but prevention of GS in patients with diabetes and chronic renal disease requires that BP be lowered well into the normotensive range, as recognized in the currently recommended BP goals. When BP load is accurately assessed in these experimental models, renal protection is proportional to the achieved BP reductions, and there is little evidence of BP-independent protection, even with agents that block the renin-angiotensin system (RAS). Recent clinical data also suggest that achieving lower BP targets might be vastly more important than the choice of therapeutic regimens. Nevertheless, because aggressive diuretic use is usually necessary to achieve such BP goals, RAS blockade should be included as initial therapy both for antihypertensive synergy and to minimize the potassium and magnesium depletion associated with diuretics.

Clinical importance of microalbuminuria in diabetes and hypertension

Numerous studies document an almost linear association between the level of albuminuria and risk for a cardiovascular event. Recent data also demonstrate a strong association between the presence of microalbuminuria and elevations in C-reactive protein. Therefore, the increased membrane permeability that generates microalbuminuria might be secondary to an inflammatory process. Progression from microalbuminuria to macroalbuminuria indicates worsening of vascular disease and presence of kidney disease. Recent pharmacologic interventions have resulted in significant delay and even arrest of progression of microalbuminuria to macroalbuminuria as well as kidney disease progression. Therefore, focus should be placed on use of antihypertensive agents that not only lower blood pressure but also lower or normalize albuminuria levels. All recent guideline statements support the use of angiotensin-converting enzyme (ACE) inhibitors or angiotensin receptor blockers (ARBs). Further lowering of albuminuria may be achieved by adding verapamil, diltiazem, or an ARB to an ACE inhibitor.

Blood pressure control and nephroprotection in diabetes

Achievement of recommended levels of blood pressure as prescribed by guidelines (i.e., systolic blood pressure of < 130 mmHg in people with nephropathy secondary to type 2 diabetes) generally requires three or more different antihypertensive agents that have complementary modes of action. This systolic goal blood pressure, recommended by generally all international guideline committees, was derived from largely observational studies demonstrating a greater reduction of cardiovascular risk and preservation of kidney function at these levels. Commonly used antihypertensive combinations include angiotensin-converting enzyme (ACE) inhibitors or angiotensin receptor blockers, which have compelling indications for use in people with kidney disease and/or diabetes, combined with a diuretic, generally a thiazide-type agent. If additional therapy is required, either a beta-blocker or a calcium antagonist may be added to this antihypertensive "cocktail." Beta-blockers are particularly effective in people with a high sympathetic drive (i.e., high pulse rates) to lower blood pressure and reduce cardiovascular risk. Moreover, in recent studies, their benefits on kidney function, both by reducing macroalbuminuria and slowing the decline of kidney function, make them good agents to add in the appropriate clinical setting. With all these potential benefits of achieving blood pressure goals, it is unfortunate that only 11% of people being treated for hypertension with diabetic kidney disease achieve the blood pressure goal of < 130 mmHg, likely contributing to the climbing incidence of people starting dialysis. Physicians need to work harder and educate patients on the importance of achieving these lower blood pressure guidelines.