Regression of Renal Disease by Angiotensin II Antagonism Is Caused by Regeneration of Kidney Vasculature

Influence of genetic polymorphisms in vascular endothelial-related genes on the clinical outcome of axitinib in patients with metastatic renal cell carcinoma

OBJECTIVE

Axitinib is an oral multi-target tyrosine kinase inhibitor used for the treatment of renal cell carcinoma (RCC). Because of the severe adverse events (AEs) associated with axitinib, patients often need dose reductions or discontinue its use, highlighting the need for effective biomarkers to assess efficacy and/or AEs. The aim of this study was to investigate the relationship between single nucleotide polymorphisms (SNPs) in genes involved in the pharmacodynamic action of axitinib and clinical prognosis and AEs in metastatic RCC (mRCC) patients.

METHODS

This study included 80 mRCC patients treated with first-, second-, or third-line axitinib (5 mg orally twice daily). Clinical parameters and genetic polymorphisms were examined in 75 cases (53 males and 22 females). We assessed three SNPs in each of three candidate genes namely, angiotensin-converting enzyme (ACE), nitric oxide synthase 3 (NOS3), and angiotensin II receptor type 1 (AT1R), all of which are involved in axitinib effects on vascular endothelial function.

RESULTS

Axitinib-treated patients carrying the ACE deletion allele suffered more frequently from hand-foot syndrome and a deterioration in kidney function (p  = .045 and p =  0.005, respectively) whereas those carrying the NOS3 G allele suffered more frequently from proteinuria and multiple AEs (p  = .025 and p =  0.036, respectively).

CONCLUSIONS

Our study found that the ACE deletion allele and the NOS3 G allele are associated with increased AEs.

A Prospective, Multicentered, Randomized, Double-Blind, Placebo-Controlled Clinical Trial of Keluoxin Capsules in the Treatment of Microalbuminuria in Patients with Type 2 Early Diabetic Kidney Disease

Background: To evaluate the efficacy and safety of Keluoxin (KLX) capsules and provide validated evidence for the application of KLX in the treatment of diabetic kidney disease (DKD). Methods: A multicenter, randomized, double-blind, placebo-controlled trial design was used to screen 129 patients with DKD (urinary albumin-to-creatinine ratio [UACR]: male, 2.5-30 mg/mmol; female, 3.5-30 mg/mmol) and with Qi and Yin deficiency and blood stasis symptoms. Written informed consent was obtained from all patients. The patients were randomly divided into KLX and control groups. The KLX group was orally administered KLX (6 g/day) and irbesartan tablets (150 mg/day), whereas the control group was administered KLX placebo (6 g/day) and irbesartan tablets (150 mg/day). Patients were observed for 24 weeks to evaluate the natural logarithm of the UACR (log-UACR), the odds ratio (OR) for a sustained increase in the UACR of at least 30% and 40%, estimated glomerular filtration rate (eGFR), changes in symptoms and quality-of-life scores, and adverse events. Results: The changes of the natural log-UACR during the 24 weeks compared with baseline in the KLX group were better than those in the control group (LS mean ± standard error, -0.26 ± 0.10 vs. 0.01 ± 0.09, p = 0.0292). The incidence of a sustained increase in the UACR of at least 30% and 40% was found to be significantly lower in the KLX group (OR, 0.26; 95% confidence interval [CI], 0.09-0.75; OR, 0.29; 95% CI, 0.10-0.82). Changes in symptoms and quality-of-life scores in the KLX group were better than those in the control group. There was no statistically significant difference in eGFR or the incidence of adverse events between the groups. Conclusions: Overall, these results suggest that KLX capsules combined with irbesartan can reduce microalbuminuria, relieve the symptoms, and improve the quality of life for patients with type 2 early DKD compared with the use of irbesartan alone. Trial registration: Chinese Clinical Trial Registry, registration number: ChiCTR2100052764.

Assessment of peritubular capillary rarefaction in kidneys of cats with chronic kidney disease

BACKGROUND

Hypoxia is a key driver of fibrosis and is associated with capillary rarefaction in humans.

OBJECTIVES

Characterize capillary rarefaction in cats with chronic kidney disease (CKD).

ANIMALS

Archival kidney tissue from 58 cats with CKD, 20 unaffected cats.

METHODS

Cross-sectional study of paraffin-embedded kidney tissue utilizing CD31 immunohistochemistry to highlight vascular structures. Consecutive high-power fields from the cortex (10) and corticomedullary junction (5) were digitally photographed. An observer counted and colored the capillary area. Image analysis was used to determine the capillary number, average capillary size, and average percent capillary area in the cortex and corticomedullary junction. Histologic scoring was performed by a pathologist masked to clinical data.

RESULTS

Percent capillary area (cortex) was significantly lower in CKD (median 3.2, range, 0.8-5.6) compared to unaffected cats (4.4, 1.8-7.0; P = <.001) and was negatively correlated with serum creatinine concentrations (r = -.36, P = .0013), glomerulosclerosis (r = -0.39, P = <.001), inflammation (r = -.30, P = .009), and fibrosis (r = -.30, P = .007). Capillary size (cortex) was significantly lower in CKD cats (2591 pixels, 1184-7289) compared to unaffected cats (4523 pixels, 1801-7618; P = <.001) and was negatively correlated with serum creatinine concentrations (r = -.40, P = <.001), glomerulosclerosis (r = -.44, P < .001), inflammation (r = -.42, P = <.001), and fibrosis (r = -.38, P = <.001).

CONCLUSIONS AND CLINICAL IMPORTANCE

Capillary rarefaction (decrease in capillary size and percent capillary area) is present in kidneys of cats with CKD and is positively correlated with renal dysfunction and histopathologic lesions.

Review on Molecular Mechanism of Hypertensive Nephropathy

Hypertension, a prevalent chronic ailment, has the potential to impair kidney function, and thereby resulting in hypertensive nephropathy. The escalating incidence of hypertensive nephropathy attributed to the aging population in urban areas, has emerged as a prominent cause of end-stage renal disease. Nevertheless, the intricate pathogenesis of hypertensive nephropathy poses considerable obstacles in terms of precise clinical diagnosis and treatment. This paper aims to consolidate the research findings on the pathogenesis of hypertensive nephropathy by focusing on the perspective of molecular biology.

Renoprotective Effects of Luteolin: Therapeutic Potential for COVID-19-Associated Acute Kidney Injuries

Acute kidney injury (AKI) has been increasingly reported in critically-ill COVID-19 patients. Moreover, there was significant positive correlation between COVID-19 deaths and renal disorders in hospitalized COVID-19 patients with underlying comorbidities who required renal replacement therapy. It has suggested that death in COVID-19 patients with AKI is 3-fold higher than in COVID-19 patients without AKI. The pathophysiology of COVID-19-associated AKI could be attributed to unspecific mechanisms, as well as COVID-19-specific mechanisms such as direct cellular injury, an imbalanced renin-angiotensin-aldosterone system, pro-inflammatory cytokines elicited by the viral infection and thrombotic events. To date, there is no specific treatment for COVID-19 and its associated AKI. Luteolin is a natural compound with multiple pharmacological activities, including anticoronavirus, as well as renoprotective activities against kidney injury induced by sepsis, renal ischemia and diverse nephrotoxic agents. Therefore, in this review, we mechanistically discuss the anti-SARS-CoV-2 and renoprotective activities of luteolin, which highlight its therapeutic potential in COVID-19-AKI patients.

Add-On Cyclic Angiotensin-(1-7) with Cyclophosphamide Arrests Progressive Kidney Disease in Rats with ANCA Associated Glomerulonephritis

Rapidly progressive crescentic glomerulonephritis associated with anti-neutrophil cytoplasmic antibodies (ANCA-GN) is a major cause of renal failure. Current immunosuppressive therapies are associated with severe side effects, intensifying the need for new therapeutic strategies. The activation of Mas receptor/Angiotensin-(1-7) axis exerted renoprotection in chronic kidney disease. Here, we investigated the effect of adding the lanthionine-stabilized cyclic form of angiotensin-1-7 [cAng-(1-7)] to cyclophosphamide in a rat model of ANCA-GN. At the onset of proteinuria, Wistar Kyoto rats with ANCA-GN received vehicle or a single bolus of cyclophosphamide, with or without daily cAng-(1-7). Treatment with cAng-(1-7) plus cyclophosphamide reduced proteinuria by 85% vs. vehicle, and by 60% vs. cyclophosphamide, and dramatically limited glomerular crescents to less than 10%. The addition of cAng-(1-7) to cyclophosphamide protected against glomerular inflammation and endothelial rarefaction and restored the normal distribution of parietal epithelial cells. Ultrastructural analysis revealed a preserved GBM, glomerular endothelium and podocyte structure, demonstrating that combination therapy provided an additional layer of renoprotection. This study demonstrates that adding cAng-(1-7) to a partially effective dose of cyclophosphamide arrests the progression of renal disease in rats with ANCA-GN, suggesting that cAng-(1-7) could be a novel clinical approach for sparing immunosuppressants.

Current kidney function parameters overestimate kidney tissue repair in reversible experimental kidney disease

Although underlying mechanisms and the clinical course of kidney disease progression are well described, less is known about potential disease reversibility. Therefore, to analyze kidney recovery, we adapted a commonly used murine chronic kidney disease (CKD) model of 2,8- dihydroxyadenine (2,8-DHA) crystal-induced nephropathy to study disease recovery and efficacy of disease-modifying interventions. The recovery phase after CKD was characterized by improved kidney function after two weeks which remained stable thereafter. By contrast, even after eight weeks recovery, tubular injury and inflammation were only partially reduced and fibrosis persisted. Deep-learning-based histologic analysis of 8,604 glomeruli and 596,614 tubular cross sections revealed numerous tubules had undergone either prominent dilation or complete atrophy, leading to atubular glomeruli and irreversible nephron loss. We confirmed these findings in a second CKD model, reversible unilateral ureteral obstruction, in which a rapid improvement of glomerular filtration rate during recovery also did not reflect the permanent histologic kidney injury. In 2,8-DHA nephropathy, increased drinking volume was highly effective in disease prevention. However, in therapeutic approaches, high fluid intake was only effective in moderate but not severe CKD and established tissue injury was again poorly reflective of kidney function parameters. The injury was particularly localized in the medulla, which is often not analyzed. Thus, recovery after crystal- or obstruction-induced CKD is characterized by ongoing tissue injury, fibrosis, and nephron loss, but not reflected by standard measures of kidney function. Hence, our data might aid in designing kidney recovery studies and suggest the need for biomarkers specifically monitoring intra-kidney tissue injury.

Advancements in nanomedicines for the detection and treatment of diabetic kidney disease

In the diabetic kidneys, morbidities such as accelerated ageing, hypertension and hyperglycaemia create a pro-inflammatory microenvironment characterised by extensive fibrogenesis. Radiological techniques are not yet optimised generating inconsistent and non-reproducible data. The gold standard procedure to assess renal fibrosis is kidney biopsy, followed by histopathological assessment. However, this method is risky, invasive, subjective and examines less than 0.01% of kidney tissue resulting in diagnostic errors. As such, less than 10% of patients undergo kidney biopsy, limiting the accuracy of the current diabetic kidney disease (DKD) staging method. Standard treatments suppress the renin-angiotensin system to control hypertension and use of pharmaceuticals aimed at controlling diabetes have shown promise but can cause hypoglycaemia, diuresis and malnutrition as a result of low caloric intake. New approaches to both diagnosis and treatment are required. Nanoparticles (NPs) are an attractive candidate for managing DKD due to their ability to act as theranostic tools that can carry drugs and enhance image contrast. NP-based point-of-care systems can provide physiological information previously considered unattainable and provide control over the rate and location of drug release. Here we discuss the use of nanotechnology in renal disease, its application to both the treatment and diagnosis of DKD. Finally, we propose a new method of NP-based DKD classification that overcomes the current systems limitations.

Comparative analysis of hypertensive nephrosclerosis in animal models of hypertension and its relevance to human pathology. Glomerulopathy

Current research on hypertension utilizes more than fifty animal models that rely mainly on stable increases in systolic blood pressure. In experimental hypertension, grading or scoring of glomerulopathy in the majority of studies is based on a wide range of opinion-based histological changes that do not necessarily comply with lesional descriptors for glomerular injury that are well-established in clinical pathology. Here, we provide a critical appraisal of experimental hypertensive glomerulopathy with the same approach used to assess hypertensive glomerulopathy in humans. Four hypertensive models with varying pathogenesis were analyzed–chronic angiotensin II infused mice, mice expressing active human renin in the liver (TTRhRen), spontaneously hypertensive rats (SHR), and Goldblatt two-kidney one-clip rats (2K1C). Analysis of glomerulopathy utilized the same criteria applied in humans–hyalinosis, focal segmental glomerulosclerosis (FSGS), ischemic, hypertrophic and solidified glomeruli, or global glomerulosclerosis (GGS). Data from animal models were compared to human reference values. Kidneys in TTRhRen mice, SHR and the nonclipped kidneys in 2K1C rats had no sign of hyalinosis, FSGS or GGS. Glomerulopathy in these groups was limited to variations in mesangial and capillary compartment volumes, with mild increases in collagen deposition. Histopathology in angiotensin II infused mice corresponded to mesangioproliferative glomerulonephritis, but not hypertensive glomerulosclerosis. The number of nephrons was significantly reduced in TTRhRen mice and SHR, but did not correlate with severity of glomerulopathy. The most substantial human-like glomerulosclerotic lesions, including FSGS, ischemic obsolescent glomeruli and GGS, were found in the clipped kidneys of 2K1C rats. The comparison of affected kidneys to healthy control in animals produces lesion values that are numerically impressive but correspond to mild damage if compared to humans. Animal studies should be standardized by employing the criteria and classifications established in human pathology to make experimental and human data fully comparable for comprehensive analysis and model improvements.

Catechins: Therapeutic Perspectives in COVID-19-Associated Acute Kidney Injury

Data obtained from several intensive care units around the world have provided substantial evidence of the strong association between impairment of the renal function and in-hospital deaths of critically ill COVID-19 patients, especially those with comorbidities and requiring renal replacement therapy (RRT). Acute kidney injury (AKI) is a common renal disorder of various etiologies characterized by a sudden and sustained decrease of renal function. Studies have shown that 5–46% of COVID-19 patients develop AKI during hospital stay, and the mortality of those patients may reach up to 100% depending on various factors, such as organ failures and RRT requirement. Catechins are natural products that have multiple pharmacological activities, including anti-coronavirus and reno-protective activities against kidney injury induced by nephrotoxic agents, obstructive nephropathies and AKI accompanying metabolic and cardiovascular disorders. Therefore, in this review, we discuss the anti-SARS-CoV-2 and reno-protective effects of catechins from a mechanistic perspective. We believe that catechins may serve as promising therapeutics in COVID-19-associated AKI due to their well-recognized anti-SARS-CoV-2, and antioxidant and anti-inflammatory properties that mediate their reno-protective activities.

Peritubular Capillary Rarefaction: An Underappreciated Regulator of CKD Progression

Peritubular capillary (PTC) rarefaction is commonly detected in chronic kidney disease (CKD) such as hypertensive nephrosclerosis and diabetic nephropathy. Moreover, PTC rarefaction prominently correlates with impaired kidney function and predicts the future development of end-stage renal disease in patients with CKD. However, it is still underappreciated that PTC rarefaction is a pivotal regulator of CKD progression, primarily because the molecular mechanisms of PTC rarefaction have not been well-elucidated. In addition to the established mechanisms (reduced proangiogenic factors and increased anti-angiogenic factors), recent studies discovered significant contribution of the following elements to PTC loss: (1) prompt susceptibility of PTC to injury, (2) impaired proliferation of PTC, (3) apoptosis/senescence of PTC, and (4) pericyte detachment from PTC. Mainly based on the recent and novel findings in basic research and clinical study, this review describes the roles of the above-mentioned elements in PTC loss and focuses on the major factors regulating PTC angiogenesis, the assessment of PTC rarefaction and its surrogate markers, and an overview of the possible therapeutic agents to mitigate PTC rarefaction during CKD progression. PTC rarefaction is not only a prominent histological characteristic of CKD but also a central driving force of CKD progression.

The eye, the kidney, and cardiovascular disease: old concepts, better tools, and new horizons

Chronic kidney disease (CKD) is common, with hypertension and diabetes mellitus acting as major risk factors for its development. Cardiovascular disease is the leading cause of death worldwide and the most frequent end point of CKD. There is an urgent need for more precise methods to identify patients at risk of CKD and cardiovascular disease. Alterations in microvascular structure and function contribute to the development of hypertension, diabetes, CKD, and their associated cardiovascular disease. Homology between the eye and the kidney suggests that noninvasive imaging of the retinal vessels can detect these microvascular alterations to improve targeting of at-risk patients. Retinal vessel-derived metrics predict incident hypertension, diabetes, CKD, and cardiovascular disease and add to the current renal and cardiovascular risk stratification tools. The advent of optical coherence tomography (OCT) has transformed retinal imaging by capturing the chorioretinal microcirculation and its dependent tissue with near-histological resolution. In hypertension, diabetes, and CKD, OCT has revealed vessel remodeling and chorioretinal thinning. Clinical and preclinical OCT has linked retinal microvascular pathology to circulating and histological markers of injury in the kidney. The advent of OCT angiography allows contrast-free visualization of intraretinal capillary networks to potentially detect early incipient microvascular disease. Combining OCT's deep imaging with the analytical power of deep learning represents the next frontier in defining what the eye can reveal about the kidney and broader cardiovascular health.

Targeting the progression of chronic kidney disease

Chronic kidney disease (CKD) is a devastating condition that is reaching epidemic levels owing to the increasing prevalence of diabetes mellitus, hypertension and obesity, as well as ageing of the population. Regardless of the underlying aetiology, CKD is slowly progressive and leads to irreversible nephron loss, end-stage renal disease and/or premature death. Factors that contribute to CKD progression include parenchymal cell loss, chronic inflammation, fibrosis and reduced regenerative capacity of the kidney. Current therapies have limited effectiveness and only delay disease progression, underscoring the need to develop novel therapeutic approaches to either stop or reverse progression. Preclinical studies have identified several approaches that reduce fibrosis in experimental models, including targeting cytokines, transcription factors, developmental and signalling pathways and epigenetic modulators, particularly microRNAs. Some of these nephroprotective strategies are now being tested in clinical trials. Lessons learned from the failure of clinical studies of transforming growth factor β1 (TGFβ1) blockade underscore the need for alternative approaches to CKD therapy, as strategies that target a single pathogenic process may result in unexpected negative effects on simultaneously occurring processes. Additional promising avenues include preventing tubular cell injury and anti-fibrotic therapies that target activated myofibroblasts, the main collagen-producing cells.

Nox1 downregulators: A new class of therapeutics

Chronic non-communicable diseases share the pathomechanism of increased reactive oxygen species (ROS) production by nicotinamide adenine dinucleotide phosphate (NADPH) oxidases, known as Nox. The recent discovery that expression of Nox1, a Nox isoform that has been implicated in the pathogenesis of cardiovascular and kidney disease and cancer is regulated by the expression and activity of G protein-coupled estrogen receptor (GPER) led to the identification of orally active small-molecule GPER blockers as selective Nox1 downregulators (NDRs). Preclinical studies using NDRs have demonstrated beneficial effects in vascular disease, hypertension, and glomerular renal injury. These findings suggest the therapeutic potential of NDRs, which reduce Nox1 protein levels, not only for cardiovascular disease conditions including arterial hypertension, pulmonary hypertension, heart failure with preserved ejection fraction (HFpEF), and chronic renal disease, but also for other non-communicable diseases, such as cerebrovascular disease and vascular dementia, Alzheimer's disease, autoimmune diseases and cancer, in which elevated Nox1-derived ROS production plays a causal role.

MiR-9-5p protects from kidney fibrosis by metabolic reprogramming

MicroRNAs (miRNAs) regulate gene expression posttranscriptionally and control biological processes (BPs), including fibrogenesis. Kidney fibrosis remains a clinical challenge and miRNAs may represent a valid therapeutic avenue. We show that miR-9-5p protected from renal fibrosis in the mouse model of unilateral ureteral obstruction (UUO). This was reflected in reduced expression of pro-fibrotic markers, decreased number of infiltrating monocytes/macrophages, and diminished tubular epithelial cell injury and transforming growth factor-beta 1 (TGF-β1)-dependent de-differentiation in human kidney proximal tubular (HKC-8) cells. RNA-sequencing (RNA-Seq) studies in the UUO model revealed that treatment with miR-9-5p prevented the downregulation of genes related to key metabolic pathways, including mitochondrial function, oxidative phosphorylation (OXPHOS), fatty acid oxidation (FAO), and glycolysis. Studies in human tubular epithelial cells demonstrated that miR-9-5p impeded TGF-β1-induced bioenergetics derangement. The expression of the FAO-related axis peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC-1α)-peroxisome proliferator-activated receptor alpha (PPARα) was reduced by UUO, although preserved by the administration of miR-9-5p. We found that in mice null for the mitochondrial master regulator PGC-1α, miR-9-5p was unable to promote a protective effect in the UUO model. We propose that miR-9-5p elicits a protective response to chronic kidney injury and renal fibrosis by inducing reprogramming of the metabolic derangement and mitochondrial dysfunction affecting tubular epithelial cells.

Translational science in albuminuria: a new view of de novo albuminuria under chronic RAS suppression

The development of de novo albuminuria during chronic renin–angiotensin system (RAS) suppression is a clinical entity that remains poorly recognized in the biomedical literature. It represents a clear increment in global cardiovascular (CV) and renal risk that cannot be counteracted by RAS suppression. Although not specifically considered, it is clear that this entity is present in most published and ongoing trials dealing with the different forms of CV and renal disease. In this review, we focus on the mechanisms promoting albuminuria, and the predictors and new markers of de novo albuminuria, as well as the potential treatment options to counteract the excretion of albumin. The increase in risk that accompanies de novo albuminuria supports the search for early markers and predictors that will allow practising physicians to assess and prevent the development of de novo albuminuria in their patients.

Combined Inhibition of Soluble Epoxide Hydrolase and Renin-Angiotensin System Exhibits Superior Renoprotection to Renin-Angiotensin System Blockade in 5/6 Nephrectomized Ren-2 Transgenic Hypertensive Rats with Established Chronic Kidney Disease

BACKGROUND/AIMS

We found recently that increasing renal epoxyeicosatrienoic acids (EETs) levels by blocking soluble epoxide hydrolase (sEH), an enzyme responsible for EETs degradation, shows renoprotective actions and retards the progression of chronic kidney disease (CKD) in Ren-2 transgenic hypertensive rats (TGR) after 5/6 renal ablation (5/6 NX). This prompted us to examine if additional protection is provided when sEH inhibitor is added to the standard renin-angiotensin system (RAS) blockade, specifically in rats with established CKD.

METHODS

For RAS blockade, an angiotensin-converting enzyme inhibitor along with an angiotensin II type receptor blocker was used. RAS blockade was compared to sEH inhibition added to the RAS blockade. Treatments were initiated 6 weeks after 5/6 NX in TGR and the follow-up period was 60 weeks.

RESULTS

Combined RAS and sEH blockade exhibited additional positive impact on the rat survival rate, further reduced albuminuria, further reduced glomerular and tubulointerstitial injury, and attenuated the decline in creatinine clearance when compared to 5/6 NX TGR subjected to RAS blockade alone. These additional beneficial actions were associated with normalization of the intrarenal EETs deficient and a further reduction of urinary angiotensinogen excretion.

CONCLUSION

This study provides evidence that addition of pharmacological inhibition of sEH to RAS blockade in 5/6 NX TGR enhances renoprotection and retards progression of CKD, notably, when applied at an advanced stage.

A Dual AMPK/Nrf2 Activator Reduces Brain Inflammation After Stroke by Enhancing Microglia M2 Polarization

AIMS

Microglia-mediated neuroinflammation plays an important role in focal ischemic stroke, a disorder with no effective therapeutic agents. Since microglial polarization to the M2 phenotype and reduction of oxidative stress are mediated through AMP-activated protein kinase (AMPK) and nuclear factor erythroid 2-related factor 2 (Nrf2) activation, we assessed the dual therapeutic effect of AMPK and Nrf2 activation by a novel neuroprotectant HP-1c in the treatment of ischemic stroke.

RESULTS

We developed a novel class of hybrids (HP-1a-HP-1f) of telmisartan and 2-(1-hydroxypentyl)-benzoate (HPBA) as a ring-opening derivative of NBP. The most promising hybrid, HP-1c, exhibited more potent anti-inflammatory and neuroprotective effects in vitro and reduced brain infarct volume and improved neurological deficits in a rat model of transient focal cerebral ischemia when compared with telmisartan alone, NBP alone, or a combination of telmisartan and NBP. HP-1c had a therapeutic window of up to 24 h, ameliorated ischemic cerebral injury in permanent focal cerebral ischemia, and improved motor function. The beneficial effects of HP-1c in ischemic stroke were associated with microglial polarization to the M2 phenotype and reduced oxidative stress. HP-1c also shifted the M1/M2 polarization in a mouse neuroinflammatory model. The anti-inflammatory and anti-oxidative effects of HP-1c were associated with AMPK-Nrf2 pathway activation for neuroprotection. We showed that HP-1c penetrates the brain, has a plasma half-life of around 3.93 h, and has no toxicity in mice. Innovation and Conclusion: Our study results suggest that HP-1c, with dual AMPK- and Nrf2-activating properties, may have potential in further studies as a novel therapy for ischemic stroke. Antioxid. Redox Signal. 28, 141-163.

Capillary rarefaction from the kidney point of view

Capillary rarefaction is broadly defined as a reduction in vascular density. Capillary rarefaction in the kidneys is thought to promote hypoxia, impair hemodynamic responses and predispose to chronic kidney disease (CKD) progression and hypertension development. Various mechanisms have been suggested to play a role in the development of capillary rarefaction, including inflammation, an altered endothelial-tubular epithelial cell crosstalk, a relative deficiency in angiogenic growth factors, loss of pericytes, increased activity of Transforming growth factor -β1 and thrombospondin-1, vitamin D deficiency, a link to lymphatic neoangiogenesis and INK4a/ARF (Cylin-dependent kinase inhibitor 2a; CDKN2A). In this review, we summarize the tools available to monitor capillary rarefaction noninvasively in the clinic, the contribution of capillary rarefaction to CKD and hypertension, the known mechanisms of capillary rarefaction, and potential future strategies to attenuate capillary rarefaction and reduce its negative impact. Therapeutic strategies to be explored in more detail include optimization of antihypertensive therapy, vitamin D receptor activators, sirtuin 1 activators, Hypoxia inducible factor prolyl hydroxylase inhibitors and stem cell therapy.

ACE and SGLT2 inhibitors: the future for non-diabetic and diabetic proteinuric renal disease

Most chronic nephropathies progress relentlessly to end-stage kidney disease. Research in animals and humans has helped our understanding of the mechanisms of chronic kidney disease progression. Current therapeutic strategies to prevent or revert renal disease progression focus on reduction of urinary protein excretion and blood pressure control. Blockade of the renin-angiotensin system (RAS) with angiotensin-converting enzyme inhibitors and/or angiotensin II type 1 receptor blockers is the most effective treatment to achieve these purposes in non-diabetic and diabetic proteinuric renal diseases. For those individuals in which nephroprotection by RAS blockade is only partial, sodium-glucose linked cotransporter-2 (SGLT2) inhibitors could be a promising new class of drugs to provide further renoprotective benefit when added on to RAS blockers.

The dilemma of dual renin-angiotensin system blockade in chronic kidney disease: why beneficial in animal experiments but not in the clinic?

Drugs interfering with the renin-angiotensin-aldosterone system (RAAS) improved the prognosis in patients with hypertension, heart failure, diabetes and chronic kidney disease. However, combining different drugs brought no further benefit while increasing the risk of hyperkalemia, hypotension and acute renal failure. This was so with combining angiotensin converting enzyme inhibitors (ACEi) and angiotensin II receptors type 1 antagonists (ARB). Dissimilarly, in animal disease models this dual therapy proved clearly superior to single drug treatment and became the optimal standard regime for comparison with other treatments. This review analyzes the causes of the discrepancy of effects of the dual therapy between animal experiments versus clinical studies, and is focused on the outcomes in chronic kidney disease. Discussed is the role of species differences in RAAS, of the variability of the disease features in humans versus relative stability in animals, of the genetic uniformity in the animals but not in humans, and of the biased publication habits of experimental versus clinical studies. We attempt to understand the causes and reconcile the discordant findings and suggest to what extent dual RAAS inhibition should be continued in animal experiments and why its application in the clinics should be limited to strictly selected groups of patients.

Achieving remission of proteinuria in childhood CKD

BACKGROUND

A multidrug treatment strategy that targets urinary proteins with an angiotensin-converting enzyme (ACE) inhibitor and angiotensin receptor blocker (ARB) up-titrated to the respective maximum tolerated dose combined with intensified blood pressure (BP) control has been found to prevent renal function loss in adults with proteinuric nephropathies. Herein, we investigated the effects of this treatment protocol in the pediatric patient population.

METHODS

From May 2002 to September 2014 we included in this observational, longitudinal, cohort study 20 consecutive children with chronic nephropathies and 24-h proteinuria of >200 mg who had received ramipril and losartan up-titrated to the respective maximum approved and tolerated doses [mean (standard deviation) dose:2.48 (1.37) mg/m² and 0.61 (0.46) mg/kg daily, respectively]. The primary efficacy endpoint was a >50 % reduction in 24-h proteinuria to <200 mg (remission). Secondary outcomes included changes in proteinuria, serum albumin, BP, and glomerular filtration rate (GFR).

RESULTS

Mean (± standard deviation) patient age at inclusion was 13.8 ± 2.8 years, and the median [interquartile range (IQR)] serum creatinine level and proteinuria were 0.7 (0.6-1.0) mg/dl and 690 (379-1270) mg/24 h or 435 (252-711) mg/m²/24 h, respectively. Proteinuria significantly decreased by month 6 of follow-up, and serum albumin levels increased over a median follow-up period of 78 (IQR 39-105) months. In the nine children who achieved remission, proteinuria reduction persisted throughout the whole follow-up without rebounds. The GFR improved in those children who achieved remission and worsened in those who did not. The mean GFR slopes differed significantly between these two groups (p < 0.05), being positive in those children with remission and negative in those without remission (+0.023 ± 0.15 vs.-0.014 ± 0.23 ml/min/1.73 m²/month, respectively), whereas BP control was similar between the two groups. Hyperkalemia was observed in two children.

CONCLUSIONS

Combination therapy with maximum approved doses of ACE inhibitors and ARBs is a safe strategy which may achieve proteinuria remission with kidney function stabilization or even improvement in a substantial proportion of children with proteinuric nephropathies.

Blood capillary rarefaction and lymphatic capillary neoangiogenesis are key contributors to renal allograft fibrosis in an ACE inhibition rat model

Chronic allograft fibrosis is the major cause of graft loss in kidney transplantation. Progression can only be reduced by inhibition of the renin-angiotensin system (RAS). We tested the hypothesis that the protection provided by angiotensin-converting enzyme (ACE) inhibition also decreases capillary rarefaction, lymphangiogenesis, and podocyte injury in allograft fibrosis. Fisher kidneys were transplanted into bilaterally nephrectomized Lewis rats treated with enalapril (60 mg/kg per day) (ACE inhibitor, ACEi) or vehicle. Proteinuria, blood urea nitrogen, and plasma creatinine were regularly assessed, and grafts were harvested for morphological and immunohistological analysis at various times up to 32 wk. In the vehicle group, many new lymphatic capillaries and severe and diffuse mononuclear infiltration of allografts were observed already 1 wk after transplantation. Lymphangiogenesis increased until week 4, by which time inflammatory infiltration became focal. Lymphatic capillaries were often located at sites of inflammation. Progressive interstitial fibrosis, glomerulosclerosis, capillary rarefaction, and proteinuria appeared later, at weeks 4-12 The number of lymphatic capillary cross sections strongly correlated with the interstitial fibrosis score. Podoplanin immunostaining, a marker of healthy podocytes, disappeared from inflamed or sclerotic glomerular areas. ACEi protected from lymphangiogenesis and associated inflammation, preserved glomerular podoplanin protein expression, and reduced glomerulosclerosis, proteinuria, tubulointerstitial fibrosis, and blood capillary rarefaction at 32 wk. In conclusion, ACEi considerably decreased and/or delayed both glomerulosclerosis and tubulointerstitial injury. Prevention of glomerular podoplanin loss and proteinuria could be attributed to the known intraglomerular pressure-lowering effects of ACEi. Reduction of lymphangiogenesis could contribute to amelioration of tubulointerstitial fibrosis and inflammatory infiltration after ACEi.

Ginsenoside Rg1 inhibits angiotensin II-induced podocyte autophagy via AMPK/mTOR/PI3K pathway

Recent researches have reported the extensive pharmacological activities of Ginsenoside Rg1 including antioxidant, anti-inflammatory, and anticancer properties. Furthermore Rg1 was also shown to protect various kinds of cells from self-digestion by its anti-autophagy activity. In previous studies, angiotensin II (Ang II), a key mediator of renin-angiotensin system, has been demonstrated to contribute to the progression of renal injury including abnormal autophagy. However, whether Rg1 can relieve Ang II-induced autophagy in podocyte as well as the underlying molecular mechanism remains to be elucidated. Here, we employed Ang II-treated podocyte as a model to investigate the effect of Rg1 on autophagy and the involved signal pathways. In the present study, we found that Ang II strongly promoted autophagy in immortalized mouse podocyte cells by observing the formation of autophagosomes and detecting the expression of autophagic marker, for example, LC3-II. Notably, compared to the Ang II-treated cells, treatment with Rg1 significantly inhibited the formation of autophagosomes and expression of autophagy-related proteins in Ang II pre-treated podocyte. Meanwhile, Rg1 downregulated the activity of AMPK and GSK-3β and upregulated the activity of P70S6K in Ang II-treated podocyte. In conclusion, these findings demonstrate that Ang II promotes autophagy in podocyte, and Rg1 effectively attenuates this process through AMPK/mTOR/PI3K pathway, suggesting that Rg1 may be beneficial to alleviate podocyte injury.

Capillary Rarefaction Associates with Albuminuria: The Maastricht Study

Albuminuria may be a biomarker of generalized (i.e., microvascular and macrovascular) endothelial dysfunction. According to this concept, endothelial dysfunction of the renal microcirculation causes albuminuria by increasing glomerular capillary wall permeability and intraglomerular pressure, the latter eventually leading to glomerular capillary dropout (rarefaction) and further increases in intraglomerular pressure. However, direct evidence for an association between capillary rarefaction and albuminuria is lacking. Therefore, we examined the cross-sectional association between the recruitment of capillaries after arterial occlusion (capillary density during postocclusive peak reactive hyperemia) and during venous occlusion (venous congestion), as assessed with skin capillaroscopy, and albuminuria in 741 participants of the Maastricht Study, including 211 participants with type 2 diabetes. Overall, 57 participants had albuminuria, which was defined as a urinary albumin excretion ≥30 mg/24 h. After adjustment for potential confounders, participants in the lowest tertile of skin capillary recruitment during postocclusive peak reactive hyperemia had an odds ratio for albuminuria of 2.27 (95% confidence interval, 1.07 to 4.80) compared with those in the highest tertile. Similarly, a comparison between the lowest and the highest tertiles of capillary recruitment during venous congestion yielded an odds ratio of 2.89 (95% confidence interval, 1.27 to 6.61) for participants in the lowest tertile. In conclusion, lower capillary density of the skin microcirculation independently associated with albuminuria, providing direct support for a role of capillary rarefaction in the pathogenesis of albuminuria.

Progression, Remission and Regression of Chronic Renal Diseases

Progression to end-stage renal disease is common in chronic nephropathies, independent of the initial insult. While genetic factors may contribute to susceptibility and progression of renal disease, proteinuria has been documented as an independent predictor of outcome. Reduction of urinary protein levels by restoration of glomerular sieving function with renin-angiotensin system (RAS) blockers has been shown to limit renal function decline in individuals with non-diabetic and diabetic nephropathies to the point that remission of the disease and regression of renal lesions have been observed in experimental animals and even in humans. In animal models, regression of glomerular structural changes is associated with remodeling of glomerular architecture. This review briefly describes our understanding of the mechanism of renal disease progression, the therapeutic advantages of ameliorating glomerular sieving dysfunction and proteinuria of RAS inhibitors and how remission/regression of renal injury can be achieved with multifactorial interventions.