Dual blockade of the renin-angiotensin system with angiotensin-converting enzyme inhibitors and angiotensin II receptor blockers in chronic kidney disease

Therapeutic approaches and novel antifibrotic agents in renal fibrosis: A comprehensive review

Renal fibrosis (RF) is one of the underlying pathological conditions leading to progressive loss of renal function and end-stage renal disease (ESRD). Over the years, various therapeutic approaches have been explored to combat RF and prevent ESRD. Despite significant advances in understanding the underlying molecular mechanism(s), effective therapeutic interventions for RF are limited. Current therapeutic strategies primarily target these underlying mechanisms to halt or reverse fibrotic progression. Inhibition of transforming growth factor-β (TGF-β) signaling, a pivotal mediator of RF has emerged as a central strategy to manage RF. Small molecules, peptides, and monoclonal antibodies that target TGF-β receptors or downstream effectors have demonstrated potential in preclinical models. Modulating the renin-angiotensin system and targeting the endothelin system also provide established approaches for controlling fibrosis-related hemodynamic changes. Complementary to pharmacological strategies, lifestyle modifications, and dietary interventions contribute to holistic management. This comprehensive review aims to summarize the underlying mechanisms of RF and provide an overview of the therapeutic strategies and novel antifibrotic agents that hold promise in its treatment.

Preventing microalbuminuria with benazepril, valsartan, and benazepril-valsartan combination therapy in diabetic patients with high-normal albuminuria: A prospective, randomized, open-label, blinded endpoint (PROBE) study

BACKGROUND

Angiotensin converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARBs) prevent microalbuminuria in normoalbuminuric type 2 diabetic patients. We assessed whether combined therapy with the 2 medications may prevent microalbuminuria better than ACE inhibitor or ARB monotherapy.

METHODS AND FINDINGS

VARIETY was a prospective, randomized, open-label, blinded endpoint (PROBE) trial evaluating whether, at similar blood pressure (BP) control, combined therapy with benazepril (10 mg/day) and valsartan (160 mg/day) would prevent microalbuminuria more effectively than benazepril (20 mg/day) or valsartan (320 mg/day) monotherapy in 612 type 2 diabetic patients with high-normal albuminuria included between July 2007 and April 2013 by the Istituto di Ricerche Farmacologiche Mario Negri IRCCS and 8 diabetology or nephrology units in Italy. Time to progression to microalbuminuria was the primary outcome. Analyses were intention to treat. Baseline characteristics were similar among groups. During a median [interquartile range, IQR] follow-up of 66 [42 to 83] months, 53 patients (27.0%) on combination therapy, 57 (28.1%) on benazepril, and 64 (31.8%) on valsartan reached microalbuminuria. Using an accelerated failure time model, the estimated acceleration factors were 1.410 (95% CI: 0.806 to 2.467, P = 0.229) for benazepril compared to combination therapy, 0.799 (95% CI: 0.422 to 1.514, P = 0.492) for benazepril compared to valsartan, and 1.665 (95% CI: 1.007 to 2.746, P = 0.047) for valsartan compared to combination therapy. Between-group differences in estimated acceleration factors were nonsignificant after adjustment for predefined confounders. BP control was similar across groups. All treatments were safe and tolerated well, with a slight excess of hyperkalemia and hypotension in the combination therapy group. The main study limitation was the lower than expected albuminuria at inclusion.

CONCLUSIONS

Risk/benefit profile of study treatments was similar. Dual renin-angiotensin system (RAS) blockade is not recommended as compared to benazepril or valsartan monotherapy for prevention of microalbuminuria in normoalbuminuric type 2 diabetic patients.

TRIAL REGISTRATION

EudraCT 2006-005954-62; ClinicalTrials.gov NCT00503152.

Sympathetic Hyperactivity—A Hidden Enemy in Chronic Kidney Disease Patients

Chronic kidney disease is often characterized by the presence of sympathetic hyperactivity. The aim of this brief review is to summarize available knowledge on the pathogenesis of sympathetic hyperactivity and to discuss its clinical relevance, the consequences of this knowledge for the choice of treatment, and the yet unresolved issues.

The effect of aliskiren on urinary cytokine/chemokine responses to clamped hyperglycaemia in type 1 diabetes

AIMS/HYPOTHESIS

Acute clamped hyperglycaemia activates the renin-angiotensin-aldosterone system (RAAS) and increases the urinary excretion of inflammatory cytokines/chemokines in patients with uncomplicated type 1 diabetes mellitus. Our objective was to determine whether blockade of the RAAS would blunt the effect of acute hyperglycaemia on urinary cytokine/chemokine excretion, thereby giving insights into potentially protective effects of these agents prior to the onset of clinical nephropathy.

METHODS

Blood pressure, renal haemodynamic function (inulin and para-aminohippurate clearances) and urinary cytokines/chemokines were measured after 6 h of clamped euglycaemia (4-6 mmol/l) and hyperglycaemia (9-11 mmol/l) on two consecutive days in patients with type 1 diabetes mellitus (n = 27) without overt nephropathy. Measurements were repeated after treatment with aliskiren (300 mg daily) for 30 days.

RESULTS

Before aliskiren, clamped hyperglycaemia increased filtration fraction (from 0.188 ± 0.007 to 0.206 ± 0.007, p = 0.003) and urinary fibroblast growth factor-2 (FGF2), IFN-α2 and macrophage-derived chemokine (MDC) (p < 0.005). After aliskiren, the filtration fraction response to hyperglycaemia was abolished, resulting in a lower filtration fraction after aliskiren under clamped hyperglycaemic conditions (p = 0.004), and none of the biomarkers increased in response to hyperglycaemia. Aliskiren therapy also reduced levels of urinary eotaxin, FGF2, IFN-α2, IL-2 and MDC during clamped hyperglycaemia (p < 0.005).

CONCLUSIONS/INTERPRETATION

The increased urinary excretion of inflammatory cytokines/chemokines in response to acute hyperglycaemia is blunted by RAAS blockade in humans with uncomplicated type 1 diabetes mellitus.

Treatment with valsartan stimulates endothelial progenitor cells and renal label-retaining cells in hypertensive rats

OBJECTIVE

The pathogenesis of hypertension is dependent on tissue angiotensin (Ang) II, which induces cardiovascular and renal remodeling. The presence of label-retaining cells (LRCs) as renal stem cells has been reported in nephrotubulus. We examined effects of treatment with valsartan on endothelial progenitor cells (EPCs) and renal LRCs in stroke-prone spontaneously hypertensive rats (SHR-SP).

METHODS

SHR-SP were salt-loaded and treated with hydralazine or valsartan. Peripheral blood mononuclear cells (MNCs) were cultured to assess EPC colony formation and migration. LRCs were labeled for 1 week with bromodeoxyuridine (BrdU) and were detected after a 2-week chase period. We measured expression of c-kit and Pax-2 mRNAs in renal medulla.

RESULTS

Colony formation and migration of EPCs were suppressed in salt-loaded SHR-SP. Treatment with valsartan markedly stimulated these EPC functions. There was no difference in the number of renal LRCs in normotensive Wistar-Kyoto rats and SHR-SP. Treatment with valsartan significantly improved renal tubular degeneration and increased the number of LRCs in renal medulla from salt-loaded SHR-SP. Treatment with valsartan significantly increased expression of c-kit and Pax-2 mRNAs in renal medulla from salt-loaded SHR-SP.

CONCLUSION

These findings suggest that ARBs have cardiovascular and renal protective effects through an antioxidative action that stimulates ECP function and increases the number of the self-repairing renal LRCs.

Cardiovascular risk reduction with Renin-Angiotensin aldosterone system blockade

This paper examines the evidence supporting treatments within the renin-angiotensin aldosterone system (RAS), the role cardioprotection plays within the management of hypertension, considerations around medication adherence, and the role of the nurse or nurse practitioner in guiding patients to achieve higher hypertension control rates. A large body of data now exists to support the use of angiotensin receptor blockers (ARBs) and angiotensin-converting enzyme inhibitors (ACEIs) which act on RAS, in the management of hypertension and their effect on cardiovascular risk reduction. Current evidence suggests that inhibition of the RAS is an important target for cardioprotection. RAS inhibition controls blood pressure and also reduces target-organ damage. This is especially important in populations at high-risk for damage including patients with diabetes and those with chronic kidney disease. Both ARBs and ACEIs target the RAS offering important reductions in both BP and target organ damage.

ADAM-17 is activated by the mitogenic protein kinase ERK in a model of kidney fibrosis

Chronic kidney disease affects 1 of 9 Americans. Recent studies showed increased activation of the metalloenzyme disintegrin ADAM-17 during the development of the disease and that threonine phosphorylation of ADAM-17 may be an important regulator of the enzyme activity. Using kidney mesangial cells we investigated whether profibrotic serotonin (5-HT) induces phosphorylation of ADAM-17 with concomitant increase in the enzyme activity. We found that 5-HT treatment (1 mM for 10 minutes) induced a significant 3-fold increase in ADAM-17 phosphorylation and employing a fluorogenic enzyme activity assay we showed 2.3-fold activation of ADAM-17, both of which was inhibited by PD98059 (1 mM), an inhibitor of extracellular signal regulated kinase (ERK) activation. In coimmunoprecipitation analysis, we observed increased (2.7-fold) binding of activated ERK to ADAM-17 during 5-HT stimulation. We concluded that, during profibrotic stimulus, ERK phosphorylates ADAM-17 in kidney cells which induces concomitant increase in the enzyme activity.

Effect of mineralocorticoid receptor blockade on the renal renin-angiotensin system in Dahl salt-sensitive hypertensive rats

BACKGROUND

The (pro)renin receptor exists in the kidney, blood vessels and the heart. (Pro)renin binds to the receptor and induces tissue injuries directly, completely independent of angiotensin II (Ang II). The renal renin-angiotensin-aldosterone system is activated in salt-sensitive hypertensive rats with in-vitro studies showing aldosterone increases angiotensin-converting enzyme (ACE) activity, renin production and angiotensin II type 1 receptor (AT1R) activity. However, the effect of blockade of mineralocorticoid receptor on the renal (pro)renin receptor, angiotensinogen, ACE and AT1R in Dahl salt-sensitive rats is unknown.

METHODS

The following parameters were measured in Dahl salt-sensitive rats and in Dahl salt-resistant rats fed high-salt or low-salt diets and treated for 8 weeks with or without eplerenone (100 mg/kg per day, orally): blood pressure, plasma renin activity, plasma aldosterone concentration, kidney weight and Ang II contents, urinary protein excretion, glomerular injury (assessed by semiquantitative morphometric analysis) and levels of expression in the kidney of (pro)renin receptor protein and messenger RNA (mRNA) for angiotensinogen, ACE and AT1R.

RESULTS

Dahl salt-sensitive rats fed a high-salt diet had increased kidney/body weight (175%) and urinary protein excretion (886%) and decreased plasma renin activity and plasma aldosterone concentration. The rats developed progressive sclerotic and proliferative glomerular changes, concomitant with increased expression of renal (pro)renin receptor protein and mRNA levels of angiotensinogen, ACE and AT1R and kidney Ang II content. Treatment with eplerenone in Dahl salt-sensitive rats was associated with significant improvements in kidney to body weight ratio, urinary protein excretion and renal injury scores and decreased renal (pro)renin receptor protein expression and angiotensinogen and AT1R mRNA levels and kidney Ang II content.

CONCLUSION

A high salt diet increased the renal renin-angiotensin system, whereas blockade of mineralocorticoid receptors attenuated renal injuries by decreasing the activity of tissue renin-angiotensin system in Dahl salt-sensitive rats.

Renin-angiotensin system revisited

New components and functions of the renin-angiotensin system (RAS) are still being unravelled. The classical RAS as it looked in the middle 1970s consisted of circulating renin, acting on angiotensinogen to produce angiotensin I, which in turn was converted into angiotensin II (Ang II) by angiotensin-converting enzyme (ACE). Ang II, still considered the main effector of RAS was believed to act only as a circulating hormone via angiotensin receptors, AT1 and AT2. Since then, an expanded view of RAS has gradually emerged. Local tissue RAS systems have been identified in most organs. Recently, evidence for an intracellular RAS has been reported. The new expanded view of RAS therefore covers both endocrine, paracrine and intracrine functions. Other peptides of RAS have been shown to have biological actions; angiotensin 2-8 heptapeptide (Ang III) has actions similar to those of Ang II. Further, the angiotensin 3-8 hexapeptide (Ang IV) exerts its actions via insulin-regulated amino peptidase receptors. Finally, angiotensin 1-7 (Ang 1-7) acts via mas receptors. The discovery of another ACE2 was an important complement to this picture. The recent discovery of renin receptors has made our view of RAS unexpectedly complex and multilayered. The importance of RAS in cardiovascular disease has been demonstrated by the clinical benefits of ACE inhibitors and AT1 receptor blockers. Great expectations are now generated by the introduction of renin inhibitors. Indeed, RAS regulates much more and diverse physiological functions than previously believed.

LR-90 prevents dyslipidaemia and diabetic nephropathy in the Zucker diabetic fatty rat

AIMS/HYPOTHESIS

Previous studies have shown that LR-90, a new inhibitor of AGE formation, prevented the development of experimental type 1 diabetic nephropathy. In this study, we examined the effects of LR-90 in the Zucker diabetic fatty (ZDF) rat, a model of type 2 diabetes and metabolic syndrome, and investigated the mechanisms by which it may protect against renal injury.

METHODS

Male ZDF rats were treated without or with LR-90 from age 13 to 40 weeks. Metabolic and kidney functions and renal histology were evaluated. AGE accumulation and the production of the receptor for AGE (AGER) were measured. Profibrotic growth factors, extracellular matrix proteins and intracellular signalling pathways associated with glomerular and tubular damage were also analysed.

RESULTS

LR-90 dramatically reduced plasma lipids in ZDF rats, with only modest effects on hyperglycaemia. Renal AGE, AGER and lipid peroxidation were all attenuated by LR-90. LR-90 significantly retarded the increase in albuminuria and proteinuria. This was associated with reduction in glomerulosclerosis and tubulointerstitial fibrosis, concomitant with marked inhibition of renal overproduction of TGF-beta1, connective tissue growth factor, fibronectin and collagen IV. Additionally, LR-90 downregulated the activation of key mitogen-activated protein kinases (MAPKs) and nuclear factor kappa B (NF-kappaB) in the renal cortex.

CONCLUSIONS/INTERPRETATION

These results support our earlier studies on the renoprotective effects of LR-90 on type 1 diabetic nephropathy and provide further evidence that LR-90, an AGE inhibitor with pleiotrophic effects, may also be beneficial for the prevention of type 2 diabetic nephropathy, where multiple risk factors, such as hyperglycaemia, dyslipidaemia, obesity, insulin resistance and hypertension, contribute to renal injury.

New opportunities in cardiovascular patient management: a survey of clinical data on the combination of angiotensin-converting enzyme inhibitors and angiotensin receptor blockers

Angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARBs) differ in their actions on the renin-angiotensin-aldosterone system (RAAS). ACE inhibitors prevent the formation of angiotensin II, although angiotensin II may still be generated by alternative pathways. However, ACE inhibitors interrupt bradykinin breakdown, which in turn potentially enhances nitric oxide and prostacyclin mechanisms. In contrast, ARBs selectively prevent the binding of angiotensin II to the angiotensin type 1 (AT(1)) receptor while leaving the potentially beneficial effects of the AT(2) receptor unaffected. The supposition is that dual blockade of the RAAS effectively overcomes the harmful effects of angiotensin II mediated by the AT(1) receptor while offering the additional effects of the ACE inhibitor. This concept was first evaluated clinically more than a decade ago in small-scale studies that were not sufficiently powered to conclusively demonstrate benefits from dual blockade. Subsequently, larger-scale trials have been conducted to determine the effects of a combination of an ACE inhibitor and an ARB in combating the effects of angiotensin II at different stages of cardiovascular and renal disease. This review explores these data in areas, such as hypertension, renal disease, and cardiovascular disease, and draws on this preliminary evidence to support the rationale for the Ongoing Telmisartan Alone in Combination with Ramipril Global Endpoint Trial (ONTARGET) program, which aims to fully explore the clinical end points and effects of dual RAAS blockade in patients at high risk for cardiovascular outcomes.

Angiotensin II activates plasminogen activator inhibitor-I promoter in renal tubular epithelial cells via the AT1receptor

BACKGROUND

Plasminogen activator inhibitor-1 (PAI-1) regulates normal extracellular matrix (ECM) metabolism and it is a key regulator of the fibrotic process. Both angiotensin II (Ang II) and angiotensin IV (Ang IV) have been reported to stimulate PAI-1 expression. It is not known how PAI-1 expression is regulated by the renin-angiotensin system (RAS) in renal tubular cells.

METHODS

To dissect signaling mechanisms contributing to the up-regulation of the PAI-1 promoter, porcine proximal tubular cells stably expressing the rabbit AT1 receptor (LLC-PK/AT1) were transiently transfected with a luciferase reporter construct containing the PAI-1 promoter. Promoter activation was assessed by measuring luciferase activity from cell lysates.

RESULTS

Ang II dose-dependently stimulated the transcriptional activity of the PAI-1 promoter in renal proximal tubular cells whereas Ang IV had no consistent effect on the promoter activity. Neither inhibition of the Extracellular Signal Regulated Kinase (ERK) cascade nor inhibition of the c-Jun-N-terminal Kinase (JNK) pathway did reduce the stimulation of the PAI-1 promoter by Ang II. However, genistein, a tyrosine kinase inhibitor blocked the effect of Ang II.

CONCLUSION

Ang II but not Ang IV activates the PAI-1 promoter in renal proximal tubular cells and this effect is mediated by tyrosine kinases.

Treating patients for cardiovascular protection: combination therapy to achieve complete renin-angiotensin system blockade

Inhibition of the renin-angiotensin system (RAS) with angiotensin-converting enzyme (ACE) inhibitors or angiotensin receptor blockers (ARBs) is a proven antihypertensive strategy. Understanding of the pathophysiologic effects of chronic RAS activation and clinical data indicate that RAS inhibition may exert beneficial effects in addition to blood pressure reduction. Studies indicate that monotherapy with ACE inhibitors and ARBs slows progression of diabetic and non-diabetic renal disease. Vascular protective effects of RAS inhibition have also been demonstrated in patients at high risk for cardiovascular events in the absence of significant blood pressure elevation or left ventricular dysfunction. Combining the complementary effects of ACE inhibitors and ARBs to achieve more complete RAS blockade is a promising approach to further reducing cardiovascular risk. This review will present the rationale for dual RAS inhibition, clinical data relating to its efficacy, and ongoing studies designed to evaluate its utility in patients at high risk for cardiovascular events.