Sacubitril/valsartan ameliorates renal tubulointerstitial injury through increasing renal plasma flow in a mouse model of type 2 diabetes with aldosterone excess

Sacubitril/valsartan reduces proteinuria depending on blood pressure in patients with stage 4-5 chronic kidney disease

BACKGROUND

Blood pressure (BP) control is an important factor in the management of chronic kidney disease (CKD). Several studies have shown that BP in many patients with CKD remained uncontrolled even with multiple medications. Sacubitril/valsartan, an angiotensin receptor neprilysin inhibitor (ARNI), has been newly approved for treating hypertension in Japan. However, the renoprotective effects remain unclear, particularly in patients with advanced CKD. Here, we investigated the effects on proteinuria of this ARNI in patients with stage 4-5 CKD.

METHODS

We retrospectively collected data from outpatients with stage 4-5 CKD who started ARNI from January until December 2023. The primary outcome was the change in urine protein creatinine ratio (UPCR) at 6 months after ARNI initiation. Secondary outcomes were systolic and diastolic BP, estimated glomerular filtration rate (eGFR), serum potassium, and serum uric acid (UA). We analyzed factors associated with 50% UPCR reduction by multivariate analysis.

RESULTS

In total, 47 patients were analyzed. ARNI reduced UPCR from 2.14 g/gCr (interquartile range; 1.09-2.91) to 1.05 g/gCr (0.42-1.95; p < 0.001). Systolic BP fell from 150.0 mmHg (139.5-160.0) to 134.0 mmHg (124.5-140.0; p < 0.001). No significant changes in eGFR, serum potassium, and serum uric acid were observed, except for a slight decrease in eGFR among patients with conversion from a renin-angiotensin system inhibitor to ARNI. In multivariate regression analysis, higher systolic BP (per 10-mmHg increase) was significantly associated with reduced proteinuria (odds ratio 2.51, 95% confidence interval 1.35-4.66; p = 0.004).

CONCLUSIONS

ARNI reduced proteinuria in patients with stage 4-5 CKD, particularly for those with uncontrolled hypertension.

Glomerular pressure and tubular oxygen supply: a critical dual target for renal protection

The primary treatment goal of chronic kidney disease (CKD) is preserving renal function and preventing its progression to end-stage renal disease. Glomerular hypertension and tubular hypoxia are critical risk factors in CKD progression. However, the renal hemodynamics make it difficult to avoid both factors due to the existence of peritubular capillaries that supply oxygen to the renal tubules downstream from the glomerulus through the efferent arteriole. In the treatment strategies for balancing glomerular pressure and tubular oxygen supply, afferent and efferent arterioles of the glomerulus determine glomerular filtration rate and blood flow to the peritubular capillaries. Therefore, sodium-glucose cotransporter 2 inhibitors and angiotensin receptor-neprilysin inhibitors as well as classical renin-angiotensin system inhibitors, which can change the diameter of afferent and/or efferent arterioles, are promising options for balancing this dual target and achieving renal protection. This review focuses on the clinical importance of glomerular pressure and tubular oxygen supply and proposes an effective treatment modality for this dual target.

Real-time imaging of cGMP signaling shows pronounced differences between glomerular endothelial cells and podocytes

Recent clinical trials of drugs enhancing cyclic guanosine monophosphate (cGMP) signaling for cardiovascular diseases have renewed interest in cGMP biology within the kidney. However, the role of cGMP signaling in glomerular endothelial cells (GECs) and podocytes remains largely unexplored. Using acute kidney slices from mice expressing the FRET-based cGMP biosensor cGi500 in endothelial cells or podocytes enabled real-time visualization of cGMP. Stimulation with atrial natriuretic peptide (ANP) or SNAP (NO donor) and various phosphodiesterase (PDE) inhibitors elevated intracellular cGMP in both cell types. GECs showed a transient cGMP response upon particulate or soluble guanylyl cyclase activation, while the cGMP response in podocytes reached a plateau following ANP administration. Co-stimulation (ANP + SNAP) led to an additive response in GECs. The administration of PDE inhibitors revealed a broader basal PDE activity in GECs dominated by PDE2a. In podocytes, basal PDE activity was mainly restricted to PDE3 and PDE5 activity. Our data demonstrate the existence of both guanylyl cyclase pathways in GECs and podocytes with cell-specific differences in cGMP synthesis and degradation, potentially suggesting new therapeutic options for kidney diseases.

Angiotensin Receptor-Neprilysin Inhibitor for Chronic Kidney Disease: Strategies for Renal Protection

BACKGROUND

Chronic kidney disease (CKD) and hypertension are significant global health challenges that often coexist and aggravate each other. Renin-angiotensin system inhibitors are important to the management of these conditions; however, their efficacy for advanced CKD remains uncertain.

SUMMARY

Angiotensin receptor-neprilysin inhibitors (ARNIs) have superior efficacy for heart failure (HF) management, as evidenced by landmark trials such as the PARADIGM-HF and PARAGON-HF, thus leading to its endorsement by various guidelines. Although direct evidence supporting the renal-protective effects of ARNI is lacking, post hoc analyses have suggested its potential to mitigate the decline of the estimated glomerular filtration rate and renal events, particularly in patients with HF with a relatively preserved ejection fraction. Mechanistically, ARNI augments the glomerular filtration rate by dilating glomerular arterioles, relaxing mesangial cells, and improving renal medullary blood flow, thereby mitigating interstitial fibrosis progression. ARNI also effectively addresses nondipper hypertension, particularly in salt-sensitive individuals, thereby reducing the cardiovascular risk.

KEY MESSAGES

Uncertainties regarding the efficacy and safety of ARNI for advanced renal failure (estimated glomerular filtration rate <30 mL/min) exist. Excessive hypotension associated with ARNI use may exacerbate the renal function decline, especially in older patients with comorbid HF with a reduced ejection fraction. Hence, vigilant blood pressure monitoring is essential to optimizing the renal benefits of ARNI and minimizing adverse effects. Evidence supporting the renal benefits of ARNI continues to evolve; therefore, ARNI could mitigate renal dysfunction in select patient populations. Further research should be performed to clarify the efficacy of ARNI for advanced renal failure and refine its therapeutic application for patients with concurrent HF and renal dysfunction.

Addition of Sacubitril/Valsartan to Mineralocorticoid Receptor Antagonist Therapy in Primary Aldosteronism: Effects on Plasma Aldosterone Concentration and Plasma Renin Activity

In the pharmacologic treatment of primary aldosteronism (PA), titration of mineralocorticoid receptor antagonist (MRA) dosing is necessary to reverse the renin suppression caused by high aldosterone levels. However, we often encounter cases in which the plasma renin activity (PRA) does not achieve the target level, even with the maximum dose of MRA. In this setting, sacubitril/valsartan, a combination of a neprilysin inhibitor and an angiotensin II type 1 receptor blocker that is approved for use as adjunctive therapy with an MRA, has been reported to inhibit aldosterone secretion both in vitro and in vivo. If sacubitril/valsartan proves to be effective in this context, it may offer a promising treatment for PA. However, there are few reports on the use of sacubitril/valsartan in this disease. We used add-on sacubitril/valsartan in three patients with PA, in whom blood pressure was insufficiently reduced and PRA remained suppressed despite administering the maximum dose of MRA. With the addition of sacubitril/valsartan, the decrease in plasma aldosterone concentration (PAC) was more marked than the increase in PRA. Because MRAs do not suppress aldosterone production but instead act by blocking mineralocorticoid receptors, use of these agents actually promotes the renin-angiotensin system and leads to increased PAC resulting from positive feedback. The pathological significance of the phenomenon whereby PAC increases with MRA administration but decreases with the addition of sacubitril/valsartan is unclear. In PA, more effective treatment may be possible by suppressing aldosterone with sacubitril/valsartan and blocking the action of aldosterone with MRAs.

Exploring the protective effect and mechanism of icariside II on the bladder in a rat model of radiation cystitis based on transcriptome sequencing

PURPOSE

Radiation cystitis (RC) is a complex and common complication after radiotherapy for pelvic cancer. Icariside II (ICAII) is a flavonoid compound extracted from Epimedium, a traditional Chinese medicine, with various pharmacological activities. The aim of the present study was to investigate the cysto-protective effects of ICAII in RC rats and its possible mechanisms.

MATERIALS AND METHODS

A rat model of induced radiation cystitis using pelvic X-ray irradiation was used, and bladder function was assessed by bladder volume and bladder leakage point pressure (LPP) after ICAII treatment. HE and Masson stains were used to assess the histopathological changes in the bladder. IL-6, TNF-α, IL-10, IL-4 and IL-1β were measured by ELISA to assess the level of inflammation. The gene-level changes in ICAII-treated RC were observed by transcriptome sequencing, and then the potential targets of action and biological mechanisms were explored by PPI, GO and KEGG enrichment analysis of the differentially expressed genes. Finally, the predicted targets of action were experimentally validated using immunohistochemistry, RT-qPCR, molecular docking and CETSA.

RESULTS

ICAII significantly increased bladder volume and the LPP, ameliorated pathological damage to bladder tissues, decreased the levels of IL-6, TNF-α, and IL-1β, and increased the levels of IL-10 and IL-4 in radiation-injured rats. A total of 90 differentially expressed genes were obtained by transcriptome sequencing, and PPI analysis identified H3F3C, ISG15, SPP1, and LCN2 as possible potential targets of action. GO and KEGG analyses revealed that these differentially expressed genes were mainly enriched in the pathways metabolism of xenobiotics by cytochrome P450, arachidonic acid metabolism, Staphylococcus aureus infection and chemical carcinogenesis - reactive oxygen species. Experimental validation showed that ICAII could significantly increase the expression of H3F3C and ISG15 and inhibit the expression of SPP1 and LCN2. ICAII binds well to H3F3C, ISG15, SPP1 and LCN2, with the best binding ability to H3F3C. Furthermore, ICAII inhibited the protein degradation of H3F3C in bladder epithelial cells.

CONCLUSIONS

ICAII may alleviate the bladder inflammatory response and inhibit the fibrosis process of bladder tissues through the regulation of H3F3C, ISG15, SPP1, and LCN2 targets and has a protective effect on the bladder of radioinjured rats. In particular, H3F3C may be one of the most promising therapeutic targets.

Study on the Effects of Angiotensin Receptor/Neprilysin Inhibitors on Renal Haemodynamics in Healthy Dogs

An angiotensin receptor/neprilysin inhibitor (ARNI), a heart failure treatment, is a combination drug made up of sacubitril, a neprilysin inhibitor, and valsartan, a vascular receptor blocker. No human or veterinary studies regarding the effect of ARNI on renal haemodynamics in the absence of cardiac or renal issues exist. Therefore, we investigated the effect of ARNI on renal haemodynamics in five healthy dogs. ARNI was administered to all five dogs at an oral dose of 20 mg/kg twice daily for 4 weeks. Renal haemodynamics were assessed on the day before ARNI administration (BL), on Day 7, and on Day 28. The glomerular filtration rate (GFR) significantly increased on Day 28 compared to BL and Day 7, whereas renal plasma flow increased on Day 7 and Day 28 compared to BL. Systolic blood pressure significantly decreased between BL and Day 28. Plasma atrial natriuretic peptide (ANP) concentrations increased on Day 7 compared to BL. Additionally, ANP concentrations increased on Day 28 in three of the five dogs. Different ANP concentrations were observed in the remaining two dogs. Both urine output volume and heart rate remained relatively stable and did not exhibit significant change. In conclusion, ARNI may enhance renal haemodynamics in healthy dogs. ARNI could be a valuable drug for treating both heart and kidney disease in dogs.

Neprilysin Inhibition Promotes Skeletal Growth via the CNP/NPR-B Pathway

C-type natriuretic peptide (CNP) plays a crucial role in enhancing endochondral bone growth and holds promise as a therapeutic agent for impaired skeletal growth. To overcome CNP's short half-life, we explored the potential of dampening its clearance system. Neprilysin (NEP) is an endopeptidase responsible for catalyzing the degradation of CNP. Thus, we investigated the effects of NEP inhibition on skeletal growth by administering sacubitril, a NEP inhibitor, to C57BL/6 mice. Remarkably, we observed a dose-dependent skeletal overgrowth phenotype in mice treated with sacubitril. Histological analysis of the growth plate revealed a thickening of the hypertrophic and proliferative zones, mirroring the changes induced by CNP administration. The promotion of skeletal growth observed in wild-type mice treated with sacubitril was nullified by the knockout of cartilage-specific natriuretic peptide receptor B (NPR-B). Notably, sacubitril promoted skeletal growth in mice only at 3 to 4 weeks of age, a period when endogenous CNP and NEP expression was higher in the lumbar vertebrae. Additionally, sacubitril facilitated endochondral bone growth in organ culture experiments using tibial explants from fetal mice. These findings suggest that NEP inhibition significantly promotes skeletal growth via the CNP/NPR-B pathway, warranting further investigations for potential applications in people with short stature.

Sacubitril/valsartan ameliorates tubulointerstitial fibrosis by restoring mitochondrial homeostasis in diabetic kidney disease

BACKGROUND

Tubulointerstitial fibrosis plays an important role in the progression of diabetic kidney disease (DKD). Sacubitril/valsartan (Sac/Val) exerts a robust beneficial effect in DKD. However, the potential functional effect of Sac/Val on tubulointerstitial fibrosis in DKD is still largely unclear.

METHODS

Streptozotocin-induced diabetic mice were given Sac/Val or Val by intragastric administration once a day for 12 weeks. The renal function, the pathological changes of tubule injury and tubulointerstitial fibrosis, as well as mitochondrial morphology of renal tubules in mice, were evaluated. Genome-wide gene expression analysis was performed to identify the potential mechanisms. Meanwhile, human tubular epithelial cells (HK-2) were cultured in high glucose condition containing LBQ657/valsartan (LBQ/Val). Further, mitochondrial functions and Sirt1/PGC1α pathway of tubular epithelial cells were assessed by Western blot, Real-time-PCR, JC-1, MitoSOX or MitoTracker. Finally, the Sirt1 specific inhibitor, EX527, was used to explore the potential effects of Sirt1 signaling in vivo and in vitro.

RESULTS

We found that Sac/Val significantly ameliorated the decline of renal function and tubulointerstitial fibrosis in DKD mice. The enrichment analysis of gene expression indicated metabolism as an important modulator in DKD mice with Sac/Val administration, in which mitochondrial homeostasis plays a pivotal role. Then, the decreased expression of Tfam and Cox IV;, as well as changes of mitochondrial function and morphology, demonstrated the disruption of mitochondrial homeostasis under DKD conditions. Interestingly, Sac/Val administration was found to restore mitochondrial homeostasis in DKD mice and in vitro model of HK-2 cells. Further, we demonstrated that Sirt1/PGC1α, a crucial pathway in mitochondrial homeostasis, was activated by Sac/Val both in vivo and in vitro. Finally, the beneficial effects of Sac/Val on mitochondrial homeostasis and tubulointerstitial fibrosis was partially abolished in the presence of Sirt1 specific inhibitor.

CONCLUSIONS

Taken together, we demonstrate that Sac/Val ameliorates tubulointerstitial fibrosis by restoring Sirt1/PGC1α pathway-mediated mitochondrial homeostasis in DKD, providing a theoretical basis for delaying the progression of DKD in clinical practice.