Effects of vasopeptidase inhibition on renal function and tubuloglomerular feedback in spontaneously hypertensive rats

Calcium channel blocker in patients with chronic kidney disease

BACKGROUND

Chronic kidney disease (CKD) is involved in a progressive deterioration in renal function over the years and is now a global public health problem. Currently, reducing the number of patients progressing to end-stage renal failure is urgently necessary. Hypertension and CKD interact with each other, and good control of blood pressure (BP) can improve CKD patients' prognosis. With the current global trend for more strict BP control, the importance of BP management and the need for medication to achieve this strict goal are increasing. Calcium channel blockers (CCBs), which target voltage-dependent calcium channels, are frequently used in combination with renin-angiotensin-aldosterone system inhibitors for CKD patients because of their strong BP-lowering properties and relatively few adverse side effects. Calcium channels have several subtypes, including L, N, T, P/Q, and R, and three types of CCBs, L-type CCBs, L-/T-type CCBs, and L-/N-type CCBs, that are available. Nowadays, the new functions and effects of the CCBs are being elucidated.

CONCLUSION

We should use different types of CCBs properly depending on their pharmacological effects, such as the strength of antihypertensive effects and the organ protection effects, taking into account the pathophysiology of the patients. In this article, the role and the use of CCBs in CKD patients are reviewed.

TaleNeprilysin and Neprilysin inhibition in chronic kidney disease

PURPOSE OF REVIEW

Chronic kidney disease (CKD) is associated with increased risk of progression to end-stage kidney disease and cardiovascular events. There is limited evidence that available treatments have beneficial effects on cardiorenal outcomes in all people with nondiabetic CKD. Neprilysin inhibition (NEPi) is a new therapeutic strategy with potential to improve outcomes for patients with CKD.

RECENT FINDINGS

NEPi enhances the activity of the natriuretic peptide system producing natriuresis, diuresis and inhibition of the renin-angiotensin system and sympathetic nervous system. Sacubitril/valsartan is the first Angiotensin receptor-neprilysin inhibitor (ARNI) to be produced and has been shown to substantially improve cardiovascular outcomes in heart failure and delay progression of kidney disease in this population. Although ARNIs have not shown similar effects on kidney function in the short-to-medium term in people with CKD, they are associated with substantial reductions in cardiac biomarkers and blood pressure in CKD.

SUMMARY

These data suggest that NEPi with an ARNI could benefit patients with CKD by reducing the risk of cardiovascular disease and have the possibility of retarding the progression of CKD (hence delaying the need for renal replacement therapy).

Importance of endogenous compensatory vasoactive peptides in broadening the effects of inhibitors of the renin-angiotensin system for the treatment of heart failure

The magnitude of the clinical benefits produced by inhibitors of the renin-angiotensin system in heart failure has been modest, possibly because of the ability of renin-angiotensin activity to escape from suppression during long-term treatment. Efforts to intensify pharmacological blockade by use of dual inhibitors that interfere with the renin-angiotensin system at multiple sites have not yielded consistent incremental clinical benefits, but have been associated with serious adverse reactions. By contrast, potentiation of endogenous compensatory vasoactive peptides can act to enhance the survival effects of inhibitors of the renin-angiotensin system, as evidenced by trials that have compared angiotensin-converting enzyme inhibitors with drugs that inhibit both the renin-angiotensin system and neprilysin. Several endogenous vasoactive peptides act as adaptive mechanisms, and their augmentation could help to broaden the benefits of renin-angiotensin system inhibitors for patients with heart failure.

Concurrent activation of multiple vasoactive signaling pathways in vasoconstriction caused by tubuloglomerular feedback: a quantitative assessment

Tubuloglomerular feedback (TGF) describes the negative relationship between (a) NaCl concentration at the macula densa and (b) glomerular filtration rate or glomerular capillary pressure. TGF-induced vasoconstriction of the afferent arteriole results from the enhanced effect of several vasoconstrictors with an effect size sequence of adenosine = 20-HETE > angiotensin II > thromboxane = superoxide > renal nerves > ATP. TGF-mediated vasoconstriction is limited by the simultaneous release of several vasodilators with an effect size sequence of nitric oxide > carbon monoxide = kinins > adenosine. The sum of the constrictor effects exceeds that of the dilator effects by the magnitude of the TGF response. The validity of the additive model used in this analysis can be tested by determining the effect of combined inhibition of some or all agents contributing to TGF. Multiple independent contributors to TGF are consistent with the variability of TGF and of the factors contributing to TGF resetting.

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.

Novel concepts in the genesis of hypertension: role of LOX-1

Hypertension is a common disease and a potent risk factor for cardiovascular disease. Tremendous strides have been made in understanding its genesis in the last 2 decades. Hypertension is often clustered with other cardiovascular risk factors, such as dyslipidemia and diabetes. The state of hypertension is often associated with increased vascular oxidative stress. Oxidative stress promotes proliferation and hypertrophy of vascular smooth muscle cell and collagen deposition, leading to thickening of the vascular media and narrowing of the vascular lumen. Oxidative stress also injures endothelium, impairs endothelium-dependent vascular relaxation and increases vascular contractile activity. Further, oxidative stress also oxidizes LDL-cholesterol. It has been shown that oxidized low-density lipoprotein (ox-LDL) activates renin-angiotensin system (RAS) and angiotensin II via its type 1 receptor activates ox-LDL receptor LOX-1. This mutually facilitative cross-talk between ox-LDL and RAS may be an important component in the development of hypertension. Lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) is a receptor for ox-LDL. This review summarizes the role of LOX-1 in the pathogenesis of hypertension.

Sympathetic regulation of the renal functions in rats reciprocally congenic for chromosome 1 blood pressure quantitative trait locus

The role of the chromosome 1 blood pressure quantitative trait locus (QTL) on the sympathorenal interaction was studied using congenic strains. The two reciprocal congenic strains, WKYpch1.0 and SHRSPwch1.0, were respectively constructed by introgressing the stroke-prone spontaneously hypertensive rat (SHRSP)-derived fragment for the QTL into a Wistar-Kyoto rat (WKY) and vice versa. The role of the sympathetic nervous system in the kidney was evaluated by comparing the renal functions between denervated and sham-operated kidneys under anesthesia. The denervation was performed by stripping the adventitia off and applying 10% phenol to the blood vessels at the left renal hilus. Polyfructosan was continuously injected intravenously to determine the renal plasma flow and the glomerular filtration rate. A reciprocal and significant alteration in the renal norepinephrine (NE) content was observed between WKY and WKYpch1.0 and between SHRSP and SHRSPwch1.0. Concomitantly, the renal vascular resistance differed significantly between the congenic and the background parental strains. By contrast, no significant difference was observed in the fractional excretion of sodium, an index of the tubular function. While the denervation elicited a significant decrease of the renal NE content in all of the four strains studied, the significant effects of the denervation on the renal functions were observed only in SHRSP and WKYpch1.0, both of which harbored the SHRSP-derived QTL fragment. These results indicated that the chromosome 1 blood pressure QTL modulated the renal functions through the sympathetic nerve activity in the kidney.

Vasopeptidase inhibition normalizes blood pressure and restores endothelial function in renovascular hypertension

BACKGROUND/AIMS

Vasopeptidase inhibitors by definition inhibit both angiotensin-converting enzyme (ACE) and neutral endopeptidase (NEP), therefore they may exceed the effect of ACE inhibitors in the treatment of hypertension. The present study investigated the effect of the vasopeptidase inhibitor AVE7688 in comparison to the ACE inhibitor ramipril on systolic blood pressure (SBP) and endothelial function in renovascular hypertension.

METHODS

Wistar-Kyoto rats with renovascular hypertension (two-kidney one-clamp-model) were randomized 2 weeks after unilateral clamping of the right renal artery for 3 weeks' oral treatment with either AVE7688 (30 mg/kg/day), ramipril (1 mg/kg/day) or placebo. SBP was measured by the tail-cuff method and endothelium-dependent and -independent vascular function was assessed in isolated preconstricted (norepinephrine 10(-7) mol/l) aortic rings as relaxation to acetylcholine (10(-10)-10(-4) mol/l) and sodium nitroprusside (10(-10)-10(-4) mol/l), respectively.

RESULTS

Two weeks after clamping, SBP was significantly elevated (196 +/- 16 vs. 145 +/- 8 mm Hg for sham-operated rats; p < 0.01) and further increased in placebo-treated animals to 208 +/- 19 mm Hg. Treatment with AVE7688 and ramipril had a similar blood pressure-lowering effect (119 +/- 8 and 124 +/- 10 mm Hg, respectively; p < 0.01 vs. placebo). Maximum endothelium-dependent relaxation was reduced in hypertensive rats (72 +/- 6 vs. 99 +/- 7% in control rats; p < 0.05). Endothelium-dependent relaxation was restored by AVE7688 (101 +/- 6%) and ramipril (94 +/- 8%), respectively, whereas endothelium-independent relaxation was comparable in all groups.

CONCLUSION

In renovascular hypertension the vasopeptidase inhibitor AVE7688 exhibited similar blood pressure-lowering and endothelial protective properties as compared to the ACE inhibitor ramipril. Therefore, in high renin models of hypertension, vasopeptidase inhibition may be considered an alternative treatment option to ACE inhibition.