Renal microcirculation and calcium channel subtypes

New Insights into the Nephroprotective Potential of Lercanidipine

Kidneys are responsible for many crucial biological processes in the human body, including maintaining the water-electrolyte balance, pH, and blood pressure (BP), along with the elimination of toxins. Despite this, chronic kidney disease (CKD), which affects more and more people, is a disease that develops insidiously without causing any symptoms at first. The main purpose of this article is to summarize the existing literature on lercanidipine, with a particular focus on its nephroprotective properties. Lercanidipine is a third-generation dihydropyridine (DHP) blocker of calcium channels, and as such it possesses unique qualities such as high lipophilicity and high vascular selectivity. Furthermore, it acts by reversibly inhibiting L-type and T-type calcium channels responsible for exerting positive renal effects. It has been shown to reduce tissue inflammation and tubulointerstitial fibrosis, contributing to a decrease in proteinuria. Moreover, it exhibited antioxidative effects and increased expression of molecules responsible for repairing damaged tissues. It also decreased cell proliferation, preventing thickening of the vascular lumen. This article summarizes studies simultaneously comparing the effect of lercanidipine with other antihypertensive drugs. There is still a lack of studies on the medications used in patients with CKD, and an even greater lack of studies on those used in patients with concomitant hypertension. Therefore, further studies on lercanidipine and its potential in hypertensive patients with coexisting CKD are required.

A nationwide cohort study comparing the effectiveness of diuretics and calcium channel blockers on top of renin-angiotensin system inhibitors on chronic kidney disease progression and mortality

It is unknown whether initiating diuretics on top of renin-angiotensin system inhibitors (RASi) is superior to alternative antihypertensive agents such as calcium channel blockers (CCBs) in patients with chronic kidney disease (CKD). For this purpose, we emulated a target trial in the Swedish Renal Registry 2007-2022 that included nephrologist-referred patients with moderate-advanced CKD and treated with RASi, who initiated diuretics or CCB. Using propensity score-weighted cause-specific Cox regression, we compared risks of major adverse kidney events (MAKE; composite of kidney replacement therapy [KRT], experiencing over a 40% eGFR decline from baseline, or an eGFR under 15 ml/min per 1.73m2), major cardiovascular events (MACE; composite of cardiovascular death, myocardial infarction or stroke), and all-cause mortality. We identified 5875 patients (median age 71 years, 64% men, median eGFR 26 ml/min per 1.73m2), of whom 3165 started a diuretic and 2710 a CCB. After a median follow-up of 6.3 years, 2558 MAKE, 1178 MACE and 2299 deaths occurred. Compared to CCB, diuretic use was associated with a lower risk of MAKE (weighted hazard ratio 0.87 [95% confidence interval: 0.77-0.97]), consistent across single components (KRT: 0.77 [0.66-0.88], over 40% eGFR decline: 0.80 [0.71-0.91] and eGFR under 15ml/min/1.73m2: 0.84 [0.74-0.96]). The risks of MACE (1.14 [0.96-1.36]) and all-cause mortality (1.07 [0.94-1.23]) did not differ between therapies. Results were consistent when modeling the total time drug exposure, across sub-groups and a broad range of sensitivity analyses. Thus, our observational study suggests that in patients with advanced CKD, using a diuretic rather than a CCB on top of RASi may improve kidney outcomes without compromising cardioprotection.

N-/T-Type vs. L-Type Calcium Channel Blocker in Treating Chronic Kidney Disease: A Systematic Review and Meta-Analysis

Renin-angiotensin system (RAS) inhibitors and calcium channel blockers (CCB) are often used together in chronic kidney disease (CKD). The PubMed, EMBASE, and Cochrane Library databases were searched to identify randomized controlled trials (RCTs) in order to explore better subtypes of CCB for the treatment of CKD. This meta-analysis of 12 RCTs with 967 CKD patients who were treated with RAS inhibitors demonstrated that, when compared with L-type CCB, N-/T-type CCB was superior in reducing urine albumin/protein excretion (SMD, −0.41; 95% CI, −0.64 to −0.18; p < 0.001) and aldosterone, without influencing serum creatinine (WMD, −3.64; 95% CI, −11.63 to 4.35; p = 0.37), glomerular filtration rate (SMD, 0.06; 95% CI, −0.13 to 0.25; p = 0.53), and adverse effects (RR, 0.95; 95% CI, 0.35 to 2.58; p = 0.93). In addition, N-/T-type CCB did not decrease the systolic blood pressure (BP) (WMD, 0.17; 95% CI, −1.05 to 1.39; p = 0.79) or diastolic BP (WMD, 0.64; 95% CI, −0.55 to 1.83; p = 0.29) when compared with L-type CCB. In CKD patients treated with RAS inhibitors, N-/T-type CCB is more effective than L-type CCB in reducing urine albumin/protein excretion without increased serum creatinine, decreased glomerular filtration rate, and increased adverse effects. The additional benefit is independent of BP and may be associated with decreased aldosterone (PROSPERO, CRD42020197560).

Renal haemodynamic and protective effects of renoactive drugs in type 2 diabetes: Interaction with SGLT2 inhibitors

Diabetic kidney disease remains the leading cause of end‐stage kidney disease and a major risk factor for cardiovascular disease. Large cardiovascular outcome trials and dedicated kidney trials have shown that sodium‐glucose cotransporter (SGLT)2 inhibitors reduce cardiovascular morbidity and mortality and attenuate hard renal outcomes in patients with type 2 diabetes (T2D). Underlying mechanisms explaining these renal benefits may be mediated by decreased glomerular hypertension, possibly by vasodilation of the post‐glomerular arteriole. People with T2D often receive several different drugs, some of which could also impact the renal vasculature, and could therefore modify both renal efficacy and safety of SGLT2 inhibition. The most commonly prescribed drugs that could interact with SGLT2 inhibitors on renal haemodynamic function include renin‐angiotensin system inhibitors, calcium channel blockers and diuretics. Herein, we review the effects of these drugs on renal haemodynamic function in people with T2D and focus on studies that measured glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) with gold‐standard techniques. In addition, we posit, based on these observations, potential interactions with SGLT2 inhibitors with an emphasis on efficacy and safety.

This invited review describes the renal haemodynamic and protective effects of commonly prescribed drugs in people with type 2 diabetes and their interaction with SGLT2 inhibitors.

PAIT-Survey Follow-Up: Changes in Albuminuria in Hypertensive Diabetic Patients with Mild-Moderate Chronic Kidney Disease

INTRODUCTION

Albuminuria is an early marker of kidney disease and reduction of albuminuria translates into a decreased occurrence of cardiovascular and renal outcomes.

AIMS

To evaluate the changes in the prevalence of albuminuria in diabetic hypertensive patients treated with several combinations of renin-angiotensin aldosterone system with calcium channel blockers.

METHODS

We analysed data from 668 unselected patients from the PAIT survey (mean age 60.4 ± 10.2 years, prevalence of males 38%), with and without albuminuria, maintained for 6 months with the previous treatment with amlodipine-valsartan, amlodipine perindopril, lercanidipine-enalapril, verapamil-trandolapril, nitrendipine-enalapril and felodipine-ramipril Albuminuria was assessed, as urinary albumin-creatinine ratio, using a Multistic-Clinitek device analyzer. Microalbuminuria was defined as a loss of 3.4-33.9 mg albumin/mmol creatinine (30-300 mg/g) and macroalbuminuria as a loss of > 33.9 mg albumin/mmol creatinine (> 300 mg/g). Blood pressure was measured with a validated digital device.

RESULTS

At baseline, albuminuria was present in 310 subjects (46.4%) (microalbuminuria in 263 (84.8%), macroalbuminuria in 15.2%), and normoalbuminuria in 53.6% 358. After 6 months, the prevalence of subjects with albuminuria was significantly lowered (p < 0.01) by 23.5% (microalbuminuria - 23.9%, p < 0.01 and macroalbuminuria - 21.3%). The prevalence of subjects with microalbuminuria was reduced with all treatments: amlodipine-valsartan - 15.6%, amlodipine-perindopril - 11.8%, lercanidipine-enalapril - 41.3% and verapamil-trandolapril - 19.2%. Data with nitrendipine-enalapril and felodipine-ramipril were not analyzed, due to the low number of patients. The frequency of patients with normoalbuminuria was significantly higher (p < 0.01) with lercanidipine-enalapril compared with any other treatment. Blood pressure was significantly (p < 0.01) reduced, with a similar effect between treatments.

CONCLUSIONS

The treatments decrease the prevalence of subjects with albuminuria, showing a significant difference among the different drug combinations, favoring the use of new dihydropyridine calcium channel blockers, such as lercanidipine, combined with RAAS inhibitors, to control albuminuria in diabetic hypertensive patients.

Comprehensive miRNA Analysis of Human Umbilical Cord-Derived Mesenchymal Stromal Cells and Extracellular Vesicles

BACKGROUND/AIMS

Mesenchymal stromal cells (MSCs) participate in the tissue-specific repair of many different organs, especially the kidney. Their effects are primarily mediated by the paracrine release of factors including extracellular vesicles (EVs), which are composed of micro-vesicles and exosomes. The corresponding microRNAs (miRNAs) of EVs are considered important for their biological functions.

METHODS

MSCs were cultured from the human umbilical cord, and EVs were isolated from the medium. The expression levels of miRNAs in MSCs and EVs were determined by microarray analysis, and gene ontology (GO) was used to analyze the functions of their target genes.

RESULTS

MSCs and EVs had similar miRNA expression profiles, with the exception of a small number of selectively enriched miRNAs. GO analysis indicated that, unlike MSCs, the target genes of EV-enriched miRNAs were associated with calcium channel regulation and cell junction activities, which may indicate that MSC and EVs have different regulatory properties. Angiogenesis, oxidative stress, and inflammatory signaling pathways related to the repair of renal injury were also analyzed, and EV-enriched miRNAs targeted genes associated with oxidative stress, T cell activation, and Toll-like receptor signaling. The miRNAs enriched in both MSCs and EVs targeted different genes in signaling pathways regulating angiogenesis and chemokine release.

CONCLUSION

MSCs and their EVs shared similar miRNA component, and some selectively enriched miRNAs observed in MSCs and EVs may affect different target genes through some specific signaling pathways.

Calcium channel blockade blunts the renal effects of acute nitric oxide synthase inhibition in healthy humans

Our aim was to investigate whether blockade of calcium channels (CCs) or angiotensin II type 1 receptors (AT1R) modulates renal responses to nitric oxide synthesis inhibition (NOSI) in humans. Fourteen sodium-replete, healthy volunteers underwent 90-min infusions of 3.0 μg·kg−1·min−1 NG-nitro-l-arginine methyl ester (l-NAME) on 3 occasions, preceded by 3 days of either placebo (PL), 10 mg of manidipine (MANI), or 50 mg of losartan (LOS). At each phase, mean arterial pressure (MAP), glomerular filtration rate (GFR; inulin), renal blood flow (RBF; p-aminohippurate), urinary sodium (UNaV), and 8-isoprostane (U8-iso-PGF2αV; an oxidative stress marker) were measured. With PL + l -NAME, the following changes were observed: +6% MAP ( P < 0.005 vs. baseline), −10% GFR, −20% RBF, −49% UNaV ( P < 0.001), and +120% U8-iso-PGF2αV ( P < 0.01). In contrast, MAP did not increase during LOS + l-NAME or MANI + l-NAME ( P > 0.05 vs. baseline), whereas renal changes were the same during LOS + l-NAME vs. PL + l-NAME (ANOVA, P > 0.05). However, during MANI + l-NAME, changes vs. baseline in GFR (−6%), RBF (−12%), and UNaV (−34%) were blunted vs. PL + l-NAME and LOS + l-NAME ( P < 0.005), and the rise in U8-iso-PGF2αV was almost abolished (+37%, P > 0.05 vs. baseline; P < 0.01 vs. PL + l-NAME or LOS + l-NAME). We conclude that, since MANI blunted l-NAME-induced renal hemodynamic changes, CCs participate in the renal responses to NOSI in healthy, sodium-replete humans independent of changes in MAP and without the apparent contribution of the AT1R. Because the rise in U8-iso-PGF2αV was essentially prevented during MANI + l-NAME, CC blockade may oppose the renal effects of NOSI in part by counteracting oxidative stress responses to acutely impaired renal NO bioavailability.

Ablation of the N-type calcium channel ameliorates diabetic nephropathy with improved glycemic control and reduced blood pressure

Pharmacological blockade of the N- and L-type calcium channel lessens renal injury in kidney disease patients. The significance of specific blockade of α1 subunit of N-type calcium channel, Ca_v2.2, in diabetic nephropathy, however, remains to be clarified. To examine functional roles, we mated Ca_v2.2^−/− mice with db/db (diabetic) mice on the C57BLKS background. Ca_v2.2 was localized in glomeruli including podocytes and in distal tubular cells. Diabetic Ca_v2.2^−/− mice significantly reduced urinary albumin excretion, glomerular hyperfiltration, blood glucose levels, histological deterioration and systolic blood pressure (SBP) with decreased urinary catecholamine compared to diabetic Ca_v2.2^+/+ mice. Interestingly, diabetic heterozygous Ca_v2.2^+/− mice also decreased albuminuria, although they exhibited comparable systolic blood pressure, sympathetic nerve activity and creatinine clearance to diabetic Ca_v2.2^+/+ mice. Consistently, diabetic mice with cilnidipine, an N-/L-type calcium channel blocker, showed a reduction in albuminuria and improvement of glomerular changes compared to diabetic mice with nitrendipine. In cultured podocytes, depolarization-dependent calcium responses were decreased by ω-conotoxin, a Ca_v2.2-specific inhibitor. Furthermore, reduction of nephrin by transforming growth factor-β (TGF-β) in podocytes was abolished with ω-conotoxin, cilnidipine or mitogen-activated protein kinase kinase inhibitor. In conclusion, Ca_v2.2 inhibition exerts renoprotective effects against the progression of diabetic nephropathy, partly by protecting podocytes.

Effect of N- and T-type calcium channel blocker on proteinuria, blood pressure and kidney function in hypertensive patients: a meta-analysis

The combination of a calcium channel blocker (CCB) and a blocker of the renin-angiotensin-aldosterone system (RAAS) is recommended in clinical practice guidelines. L/N- and L/T-type CCBs might provide an additional effect on lowering proteinuria. Therefore, we conducted a meta-analysis to assess the efficacy of L/N- and L/T-type CCBs in hypertensive patients with proteinuria. We searched MEDLINE, Scopus, Cochrane Central Register of Controlled Trials and ClinicalTrials.gov for single-arm studies and randomized controlled trials (RCTs) that examined the effect of L/N- and L/T-type CCBs as add-on therapy compared with standard antihypertensive regimen for proteinuria on hemodynamic and kidney-related parameters in hypertensive patients with proteinuria. Random-effect model meta-analyses were used to compute changes in the outcomes of interest. We identified 17 RCTs, representing 1905 patients. By meta-analysis, L/N- and L/T-type CCB add-on therapy did not yield significant changes in systolic and diastolic blood pressure compared with standard treatment, but there was a significant lowering of the pulse rate. However, L/N- and L/T-type CCBs resulted in a significant standardized net decrease in albuminuria and proteinuria (-1.01; 95% confidence interval (CI), -1.78 to -0.23; P=0.01), and a standardized net improvement in the estimated glomerular filtration rate and serum creatinine (0.23; 95% CI, 0.11 to 0.35, P<0.001; and -0.25; 95% CI, -0.46 to -0.03; P=0.02, respectively). Despite no additional lowering effect on blood pressure, L/N- and L/T-type CCBs combined with a blocker of the RAAS provided a decrease in proteinuria and improvement in kidney function. Further studies are required to establish the long-term kidney benefits of this combination therapy.

Renal autoregulation in health and disease

Intrarenal autoregulatory mechanisms maintain renal blood flow (RBF) and glomerular filtration rate (GFR) independent of renal perfusion pressure (RPP) over a defined range (80-180 mmHg). Such autoregulation is mediated largely by the myogenic and the macula densa-tubuloglomerular feedback (MD-TGF) responses that regulate preglomerular vasomotor tone primarily of the afferent arteriole. Differences in response times allow separation of these mechanisms in the time and frequency domains. Mechanotransduction initiating the myogenic response requires a sensing mechanism activated by stretch of vascular smooth muscle cells (VSMCs) and coupled to intracellular signaling pathways eliciting plasma membrane depolarization and a rise in cytosolic free calcium concentration ([Ca(2+)]i). Proposed mechanosensors include epithelial sodium channels (ENaC), integrins, and/or transient receptor potential (TRP) channels. Increased [Ca(2+)]i occurs predominantly by Ca(2+) influx through L-type voltage-operated Ca(2+) channels (VOCC). Increased [Ca(2+)]i activates inositol trisphosphate receptors (IP3R) and ryanodine receptors (RyR) to mobilize Ca(2+) from sarcoplasmic reticular stores. Myogenic vasoconstriction is sustained by increased Ca(2+) sensitivity, mediated by protein kinase C and Rho/Rho-kinase that favors a positive balance between myosin light-chain kinase and phosphatase. Increased RPP activates MD-TGF by transducing a signal of epithelial MD salt reabsorption to adjust afferent arteriolar vasoconstriction. A combination of vascular and tubular mechanisms, novel to the kidney, provides for high autoregulatory efficiency that maintains RBF and GFR, stabilizes sodium excretion, and buffers transmission of RPP to sensitive glomerular capillaries, thereby protecting against hypertensive barotrauma. A unique aspect of the myogenic response in the renal vasculature is modulation of its strength and speed by the MD-TGF and by a connecting tubule glomerular feedback (CT-GF) mechanism. Reactive oxygen species and nitric oxide are modulators of myogenic and MD-TGF mechanisms. Attenuated renal autoregulation contributes to renal damage in many, but not all, models of renal, diabetic, and hypertensive diseases. This review provides a summary of our current knowledge regarding underlying mechanisms enabling renal autoregulation in health and disease and methods used for its study.

Functional importance of T-type voltage-gated calcium channels in the cardiovascular and renal system: news from the world of knockout mice

Over the years, it has been discussed whether T-type calcium channels Cav3 play a role in the cardiovascular and renal system. T-type channels have been reported to play an important role in renal hemodynamics, contractility of resistance vessels, and pacemaker activity in the heart. However, the lack of highly specific blockers cast doubt on the conclusions. As new T-type channel antagonists are being designed, the roles of T-type channels in cardiovascular and renal pathology need to be elucidated before T-type blockers can be clinically useful. Two types of T-type channels, Cav3.1 and Cav3.2, are expressed in blood vessels, the kidney, and the heart. Studies with gene-deficient mice have provided a way to investigate the Cav3.1 and Cav3.2 channels and their role in the cardiovascular system. This review discusses the results from these knockout mice. Evaluation of the literature leads to the conclusion that Cav3.1 and Cav3.2 channels have important, but different, functions in mice. T-type Cav3.1 channels affect heart rate, whereas Cav3.2 channels are involved in cardiac hypertrophy. In the vascular system, Cav3.2 activation leads to dilation of blood vessels, whereas Cav3.1 channels are mainly suggested to affect constriction. The Cav3.1 channel is also involved in neointima formation following vascular damage. In the kidney, Cav3.1 regulates plasma flow and Cav3.2 plays a role setting glomerular filtration rate. In conclusion, Cav3.1 and Cav3.2 are new therapeutic targets in several cardiovascular pathologies, but the use of T-type blockers should be specifically directed to the disease and to the channel subtype.