Simvastatin decreases endothelial progenitor cell apoptosis in the kidney of hypertensive hypercholesterolemic pigs

Potentials of Natural Antioxidants in Reducing Inflammation and Oxidative Stress in Chronic Kidney Disease

Chronic kidney disease (CKD) presents a substantial global public health challenge, with high morbidity and mortality. CKD patients often experience dyslipidaemia and poor glycaemic control, further exacerbating inflammation and oxidative stress in the kidney. If left untreated, these metabolic symptoms can progress to end-stage renal disease, necessitating long-term dialysis or kidney transplantation. Alleviating inflammation responses has become the standard approach in CKD management. Medications such as statins, metformin, and GLP-1 agonists, initially developed for treating metabolic dysregulation, demonstrate promising renal therapeutic benefits. The rising popularity of herbal remedies and supplements, perceived as natural antioxidants, has spurred investigations into their potential efficacy. Notably, lactoferrin, Boerhaavia diffusa, Amauroderma rugosum, and Ganoderma lucidum are known for their anti-inflammatory and antioxidant properties and may support kidney function preservation. However, the mechanisms underlying the effectiveness of Western medications and herbal remedies in alleviating inflammation and oxidative stress occurring in renal dysfunction are not completely known. This review aims to provide a comprehensive overview of CKD treatment strategies and renal function preservation and critically discusses the existing literature's limitations whilst offering insight into the potential antioxidant effects of these interventions. This could provide a useful guide for future clinical trials and facilitate the development of effective treatment strategies for kidney functions.

The impact of hypoxia preconditioning on mesenchymal stem cells performance in hypertensive kidney disease

BACKGROUND

Autologous mesenchymal stem cells (MSCs) have emerged as a therapeutic option for many diseases. Hypertensive kidney disease (HKD) might impair MSCs' reparative ability by altering the biomolecular properties, but the characteristics of this impairment are unclear. In our previous pre-clinical studies, we found hypoxic preconditioning (HPC) enhanced angiogenesis and suppressed senescence gene expression. Thus, we hypothesize that HPC would improve human MSCs by enhancing their functionality and angiogenesis, creating an anti-inflammatory and anti-senescence environment.

METHODS

MSC samples (n = 12 each) were collected from the abdominal fat of healthy kidney donors (HC), hypertensive patients (HTN), and patients with hypertensive kidney disease (HKD). MSCs were harvested and cultured in Normoxic (20% O2) or Hypoxic (1% O2) conditions. MSC functionality was measured by proliferation assays and cytokine released in conditioned media. Senescence was evaluated by senescence-associated beta-galactosidase (SA-beta-gal) activity. Additionally, transcriptome analysis using RNA-sequencing and quantitative PCR (qPCR) were performed.

RESULTS

At baseline, normoxic HTN-MSCs had higher proliferation capacity compared to HC. However, HPC augmented proliferation in HC. HPC did not affect the release of pro-angiogenic protein VEGF, but increased EGF in HC-MSC, and decreased HGF in HC and HKD MSCs. Under HPC, SA-β-gal activity tended to decrease, particularly in HC group. HPC upregulated mostly the pro-angiogenic and inflammatory genes in HC and HKD and a few senescence genes in HKD.

CONCLUSIONS

HPC has a more favorable functional effect on HC- than on HKD-MSC, reflected in increased proliferation and EGF release, and modest decrease in senescence, whereas it has little effect on HTN or HKD MSCs.

Kidney Intrinsic Mechanisms as Novel Targets in Renovascular Hypertension

Almost a hundred years have passed since obstruction of the renal artery has been recognized to raise blood pressure. By now chronic renovascular disease (RVD) due to renal artery stenosis is recognized as a major source of renovascular hypertension and renal disease. In some patients, RVD unaccompanied by noteworthy renal dysfunction or blood pressure elevation may be incidentally identified during peripheral angiography. Nevertheless, in others, RVD might present as a progressive disease associated with diffuse atherosclerosis, leading to loss of renal function, renovascular hypertension, hemodynamic compromise, and a magnified risk for cardiovascular morbidity and mortality. Atherosclerotic RVD leads to renal atrophy, inflammation, and hypoxia but represents a potentially treatable cause of chronic renal failure because until severe fibrosis sets in the ischemic kidney, it retains a robust potential for vascular and tubular regeneration. This remarkable recovery capacity of the kidney begs for early diagnosis and treatment. However, accumulating evidence from both animal studies and randomized clinical trials has convincingly established the inadequate efficacy of renal artery revascularization to fully restore renal function or blood pressure control and has illuminated the potential of therapies targeted to the ischemic renal parenchyma to instigate renal regeneration. Some of the injurious mechanisms identified as potential therapeutic targets included oxidative stress, microvascular disease, inflammation, mitochondrial injury, and cellular senescence. This review recapitulates the intrinsic mechanisms that orchestrate renal damage and recovery in RVD and can be harnessed to introduce remedial opportunities.

Effect of Hypoxia Preconditioning on the Regenerative Capacity of Adipose Tissue Derived Mesenchymal Stem Cells in a Model of Renal Artery Stenosis

Atherosclerotic renal artery stenosis (ARAS) is associated with irreversible parenchymal renal disease and regenerative stem cell therapies may improve renal outcomes. Hypoxia preconditioning (HPC) may improve the regenerative functions of adipose tissue-derived mesenchymal stem cells (AMSC) by affecting DNA 5-hydroxymethylcytosine (5hmC) marks in angiogenic genes. Here, we investigated using a porcine ARAS model, whether growth of ARAS AMSCs in hypoxia (Hx) versus normoxia (Nx) would enhance renal tissue repair, and comprehensively analyze how HPC modifies DNA hydroxymethylation compared to untreated ARAS and healthy/normal pigs (n=5 each). ARAS pigs exhibited elevated serum cholesterol, serum creatinine and renal artery stenosis, with a concomitant decrease in renal blood flow (RBF) and increased blood pressure (BP) compared to healthy pigs. Renal artery injection of either autologous Nx or Hx AMSCs improved diastolic BP, reduced kidney tissue fibrosis, and inflammation (CD3+ T-cells) in ARAS pigs. In addition, renal medullary hypoxia significantly lowered with Nx but not Hx AMSC treatment. Mechanistically, levels of epigenetic 5hmC marks (which reflect gene activation) estimated using DNA immunoprecipitation technique were elevated in profibrotic and inflammatory genes in ARAS compared with normal AMSCs. HPC significantly reduced 5hmC levels in cholesterol biosynthesis and oxidative stress response pathways in ARAS AMSCs. Thus, autologous AMSCs improve key renovascular parameters and inflammation in ARAS pigs, with HPC mitigating pathological molecular effects on inflammatory and profibrotic genes which may play a role in augmenting regenerative capacity of AMSCs.

Natural products in the treatment of pulmonary emphysema: Therapeutic effects and mechanisms of action

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is a class of lung diseases including chronic bronchitis, asthma, and emphysema. Long-time smoking is considered the main reason for developing emphysema. Emphysema can be defined as damage to the walls of the air sacs (alveoli) of the lung. It has been demonstrated that natural compounds with antioxidant and anti-inflammatory effects can effectively improve or protect the lung against this disease. This paper is dedicated to systematically review the effective natural compounds in the treatment of pulmonary emphysema.

PURPOSE

This is the first systematic and comprehensive review on the role of plant-derived secondary metabolites in managing and/or treating pulmonary emphysema STUDY DESIGN AND METHODS: A systematic and comprehensive review was done based on Scopus, PubMed, and Cochrane Library databases were searched using the "emphysema", "plant", "herb", and "phytochemical" keywords. Non-English, review, and repetitive articles were excluded from the study. Search results were included in the Prisma diagram.

RESULTS

From a total of 1285 results, finally, 22 articles were included in the present study. The results show that some herbs such as Scutellaria baicalensis Georgi and Monascus adlay and some phytochemicals such as gallic acid and quercetin and blackboard tree indole alkaloids affect more factors in improving the lung emphysema. Also, some natural compounds such as marijuana smoke and humic acid also play an aggravating role in this disease. It also seems that some of the medicinal plants such as PM014 herbal formula, pomegranate juice and açaí berry sometimes have side effects that are inconsistent with their therapeutic effects.

CONCLUSION

We concluded that natural compounds can effectively improve pulmonary emphysema due to their antioxidant, anti-inflammatory, and anti-apoptotic properties. However, additional studies are suggested to prove efficacy and side effects.

Emergent players in renovascular disease

Renovascular disease (RVD) remains a common etiology of secondary hypertension. Recent clinical trials revealed unsatisfactory therapeutic outcomes of renal revascularization, leading to extensive investigation to unravel key pathophysiological mechanisms underlying irreversible functional loss and structural damage in the chronically ischemic kidney. Research studies identified complex interactions among various players, including inflammation, fibrosis, mitochondrial injury, cellular senescence, and microvascular remodeling. This interplay resulted in a shift of our understanding of RVD from a mere hemodynamic disorder to a pro-inflammatory and pro-fibrotic pathology strongly influenced by systemic diseases like metabolic syndrome (MetS), hypertension, diabetes mellitus, and hyperlipidemia. Novel diagnostic approaches have been tested for early detection and follow-up of RVD progression, using new imaging techniques and biochemical markers of renal injury and dysfunction. Therapies targeting some of the pathological pathways governing the development of RVD have shown promising results in animal models, and a few have moved from bench to clinical research. This review summarizes evolving understanding in chronic ischemic kidney injury.

Diabetic Kidney Disease Alters the Transcriptome and Function of Human Adipose-Derived Mesenchymal Stromal Cells but Maintains Immunomodulatory and Paracrine Activities Important for Renal Repair

Mesenchymal stem/stromal cells (MSCs) facilitate repair in experimental diabetic kidney disease (DKD). However, the hyperglycemic and uremic milieu may diminish regenerative capacity of patient-derived therapy. We hypothesized that DKD reduces human MSC paracrine function. Adipose-derived MSC from 38 participants with DKD and 16 control subjects were assessed for cell surface markers, trilineage differentiation, RNA sequencing (RNA-seq), in vitro function (coculture or conditioned medium experiments with T cells and human kidney cells [HK-2]), secretome profile, and cellular senescence abundance. The direction of association between MSC function and patient characteristics were also tested. RNA-seq analysis identified 353 differentially expressed genes and downregulation of several immunomodulatory genes/pathways in DKD-MSC versus Control-MSC. DKD-MSC phenotype, differentiation, and tube formation capacity were preserved, but migration was reduced. DKD-MSC with and without interferon-γ priming inhibited T-cell proliferation greater than Control-MSC. DKD-MSC medium contained higher levels of anti-inflammatory cytokines (indoleamine 2,3-deoxygenase 1 and prostaglandin-E2) and prorepair factors (hepatocyte growth factor and stromal cell-derived factor 1) but lower IL-6 versus control-MSC medium. DKD-MSC medium protected high glucose plus transforming growth factor-β-exposed HK-2 cells by reducing apoptotic, fibrotic, and inflammatory marker expression. Few DKD-MSC functions were affected by patient characteristics, including age, sex, BMI, hemoglobin A_1c, kidney function, and urine albumin excretion. However, senescence-associated β-galactosidase activity was lower in DKD-MSC from participants on metformin therapy. Therefore, while DKD altered the transcriptome and migratory function of culture-expanded MSCs, DKD-MSC functionality, trophic factor secretion, and immunomodulatory activities contributing to repair remained intact. These observations support testing of patient-derived MSC therapy and may inform preconditioning regimens in DKD clinical trials.

Chitosan Coated Microparticles Enhance Simvastatin Colon Targeting and Pro-Apoptotic Activity

This work aimed at improving the targeting and cytotoxicity of simvastatin (SMV) against colon cancer cells. SMV was encapsulated in chitosan polymers, followed by eudragit S100 microparticles. The release of SMV double coated microparticles was dependent on time and pH. At pH 7.4 maximum release was observed for 6 h. The efficiency of the double coat to target colonic tissues was confirmed using real-time X-ray radiography of iohexol dye. Entrapment efficiency and particle size were used in the characterization of the formula. Cytotoxicity of SMV microparticles against HCT-116 colon cancer cells was significantly improved as compared to raw SMV. Cell cycle analysis by flow cytomeric technique indicated enhanced accumulation of colon cancer cells in the G2/M phase. Additionally, a significantly higher cell fraction was observed in the pre-G phase, which highlighted enhancement of the proapoptotic activity of SMV prepared in the double coat formula. Assessment of annexin V staining was used for confirmation. Cell fraction in early, late and total cell death were significantly elevated. This was accompanied by a significant elevation of cellular caspase 3 activity. In conclusion, SMV-loaded chitosan coated with eudragit S100 formula exhibited improved colon targeting and enhanced cytotoxicity and proapoptotic activity against HCT-116 colon cancer cells.

Novel therapeutic strategies for renovascular disease

PURPOSE OF REVIEW

Renovascular disease (RVD) remains an important cause of hypertension and renal dysfunction. Given the failure of renal revascularization to provide consistent clinical benefit in the Cardiovascular Outcomes for Renal Artery Lesions trial among others, further research has underscored the need for mechanistically targeted interventions to improve renal outcomes in patients in RVD. This review discusses novel therapeutic approaches for RVD in the post-Cardiovascular Outcomes for Renal Artery Lesions era.

RECENT FINDINGS

Emerging evidence indicates that renal inflammation, microvascular remodeling, and mitochondrial damage accelerate progression of renal injury and are important determinants of the response to revascularization. Experimental studies have identified interventions capable of ameliorating renal inflammation (e.g., cytokine inhibitors, mesenchymal stem cells), microvascular remodeling (proangiogenic interventions), and mitochondrial injury (mito-protective drugs), alone or combined with renal revascularization, to preserve the structure and function of the poststenotic kidney. Recent prospective pilot studies in patients with atherosclerotic RVD demonstrate the safety and feasibility of some of such interventions to protect the kidney.

SUMMARY

Experimental studies and pilot clinical trials suggest that therapies targeting renal inflammation, microvascular remodeling, and mitochondrial damage have the potential to preserve the structure and function of the stenotic kidney. Further studies in larger cohorts are needed to confirm their renoprotective effects and clinical role in human RVD.

Effect of Simvastatin on Lipid Accumulation and the Expression of CXCL16 and Nephrin in Podocyte Induced by Oxidized LDL

OBJECTIVE

To investigate the effect of simvastatin on lipid accumulation and the expression of CXCL16 and Nephrin in murine podocytes induced by oxidized LDL (OxLDL) in order to explore the mechanism of protection.

METHODS

Murine podocytes (MPC5) were incubated with OxLDL (80 μg/ml) at different concentrations of simvastatin (0, 1.0, and 2.0 μg/ml) for 48 hours. Oil red O staining was used for the assessment of lipid accumulation in podocytes, and colorimetric cholesterol detection kit was used for the quantitative measurement. CXCL16 and Nephrin expression were detected by using Western blot.

RESULTS

OxLDL-treated MPC5 cells exhibited significantly higher intracellular lipid accumulations compared with the untreated group. Colorimetric detection found that total cholesterol was 90.3 ± 30.1 μg/ml in untreated cells and 226.5 ± 21.6 μg/ml in OxLDL-treated cells. The difference was statistically significant (p < .01). While cells were treated with both OxLDL and simvastatin, we observed little lipid accumulation. Total cholesterol in OxLDL + simvastatin cells were 151.8 ± 6.8 μg/ml and 135.5 ± 26.9 μg/ml under 1.0 μg/ml or 2.0 μg/ml of simvastatin treatment, respectively. Both were statistically significantly lower than that of the OxLDL treated cells (p < .05). Western blot analysis showed that CXCL16 expression was significantly increased (p < .05) in OxLDL-treated cells compared with the untreated cells, and was significantly inhibited by application of simvastatin (p < .05). The analysis of nephrin expression showed that there were no changes in group simvastatin compared with that of control group (p > .05). Nephrin expression was significantly reduced by treatment with OxLDL (p < .01), and was significantly increased by application of simvastatin (p < .05).

CONCLUSION

Simvastatin treatment could significantly decrease lipid accumulation in murine podocytes and this protective effect was realized through inhibition of the expression of CXCL16 and increase in the expression of nephrin.

Role of the Renal Microcirculation in Progression of Chronic Kidney Injury in Obesity

BACKGROUND

Obesity is largely responsible for the growing incidence and prevalence of diabetes, cardiovascular and renal diseases. Current strategies to prevent and treat obesity and its consequences have been insufficient to reverse the ongoing trends. Lifestyle modification or pharmacological therapies often produce modest weight loss which is not sustained and recurrence of obesity is frequently observed, leading to progression of target organ damage in many obese subjects. Therefore, research efforts have focused not only on the factors that regulate energy balance, but also on understanding mechanisms of target organ injury in obesity. Summary and Key Message: Microvascular (MV) disease plays a pivotal role in progressive kidney injury from different etiologies such as hypertension, diabetes, and atherosclerosis, which are all important consequences of chronic obesity. The MV networks are anatomical units that are closely adapted to specific functions of nutrition and removal of waste in every organ. Damage of the small vessels in several tissues and organs has been reported in obesity and may increase cardio-renal risk. However, the mechanisms by which obesity and its attendant cardiovascular and metabolic consequences interact to cause renal MV injury and chronic kidney disease are still unclear, although substantial progress has been made in recent years. This review addresses potential mechanisms and consequences of obesity-induced renal MV injury as well as current treatments that may provide protection of the renal microcirculation and slow progressive kidney injury in obesity.

Hypercholesterolemia Impairs Nonstenotic Kidney Outcomes After Reversal of Experimental Renovascular Hypertension

BACKGROUND

Revascularization of a stenotic renal artery improves kidney function only in select patients with renovascular hypertension (HT) secondary to atherosclerosis. However, the effects of reversal of renovascular HT (RRHT) on the nonstenotic kidney are unclear. We hypothesized that concurrent hypercholesterolemia (HC) attenuates nonstenotic kidney recovery.

METHODS

Female domestic pigs were randomized as Normal, renovascular HT, HT+RRHT, HTC (renovascular HT and HC), and HTC+RHT (n = 7 each). RRHT or sham was performed after 6 weeks of HT. Nonstenotic renal blood flow, glomerular filtration rate, and injurious pathways were studied 4 weeks later.

RESULTS

Mean arterial pressure increased similarly in HT and HTC and decreased after RRHT. Oxidative stress increased in HT and HTC kidneys, and decreased in HT+RRHT, but remained elevated in HTC+RRHT. Renal interstitial fibrosis, glomerulosclerosis, and tubular injury were all attenuated in HT+RRHT, but not HTC+RRHT. Endothelin-1 signaling and PGF2α isoprostane levels were elevated in both HTC and HTC+RRHT pigs.

CONCLUSIONS

RRHT reverses nonstenotic kidney injury in experimental renovascular HT, but concurrent HC blunts regression of kidney injury, possibly due to predominant vasoconstrictors and oxidative stress. These findings reinforce the contribution of the nonstenotic kidney and of prevailing cardiovascular risk factors to irreversibility of kidney dysfunction after revascularization.

Use of Statins to Augment Progenitor Cell Function in Preclinical and Clinical Studies of Regenerative Therapy: a Systematic Review

BACKGROUND

Mesenchymal stromal cells (MSCs) and endothelial progenitor cells (EPCs) are used in cell-based regenerative therapy. HMG CoA reductase inhibitors (statins) appear promising in blocking apoptosis, prolonging progenitor cell survival and improving their capacity to repair organ function.

METHODS

We performed a systematic review of preclinical and clinical studies to clarify whether statins can improve cell-based repair of organ injury. MEDLINE, EMBASE, and PUBMED databases were searched (1947 to June 25, 2013). Controlled clinical and pre-clinical studies were included that evaluated statin therapy used alone or in combination with MSCs or EPCs in patients or animals with organ injury.

RESULTS

After screening 771 citations, 100 records underwent full eligibility screening of which 38 studies met eligibility and were included in the review: Studies were grouped into pre-clinical studies that involved statin treatment in combination with cell therapy (18 studies), preclinical studies of statin therapy alone (13 studies) and clinical studies of statin therapy (7 studies). Studies addressed cardiac injury (14 studies), vascular disorders (15 studies), neurologic conditions (8 studies) and bone fractures (1 study). Pre-clinical studies of statins in combination with MSC infusion (15 studies) or EPC therapy (3 studies) were described and despite marked heterogeneity in reporting outcomes of cellular analysis and organ function, all of these cell-based pre-clinical studies reported improved organ recovery with the addition of statin therapy. Moreover, 13 pre-clinical studies involved the administration of a statin drug alone to animals. An increase in EPC number and/or function (no studies of MSCs) was reported in 11 of these studies (85 %) and improved organ function in 12 studies (92 %). We also identified 7 clinical studies and none involved the administration of cells but described an increased number and/or function of EPCs (no studies of MSCs) and improved organ function with statin therapy (1.2-fold to 35-fold improvement over controls) in all 7 studies.

CONCLUSION

Our systematic review provides a foundation of encouraging results that support further study of statins in regenerative therapy to augment the number and/or function of MSCs used in cell-based repair and to augment the number and function of EPCs in vivo to repair damaged tissues. Larger studies are needed to ensure safety and confirm clinical benefits.

Chronic renal ischemia in humans: can cell therapy repair the kidney in occlusive renovascular disease?

Occlusive renovascular disease caused by atherosclerotic renal artery stenosis (ARAS) elicits complex biological responses that eventually lead to loss of kidney function. Recent studies indicate a complex interplay of oxidative stress, endothelial dysfunction, and activation of fibrogenic and inflammatory cytokines as a result of atherosclerosis, hypoxia, and renal hypoperfusion in this disorder. Human studies emphasize the limits of the kidney adaptation to reduced blood flow, eventually leading to renal hypoxia with activation of inflammatory and fibrogenic pathways. Several randomized prospective clinical trials show that stent revascularization alone in patients with atherosclerotic renal artery stenosis provides little additional benefit to medical therapy once these processes have developed and solidified. Experimental data now support developing adjunctive cell-based measures to support angiogenesis and anti-inflammatory renal repair mechanisms. These data encourage the study of endothelial progenitor cells and/or mesenchymal stem/stromal cells for the repair of damaged kidney tissue.

Obesity and renovascular disease

Obesity remains a prominent public health concern. Obesity not only contributes greatly to cardiovascular events but has also been identified to initiate and affect the progression of preexisting chronic kidney disease. The prevalence of renal artery stenosis is growing world-wide, especially in the elderly population and in individuals with atherosclerotic risk factors such as obesity. Prolonged renovascular disease causes inflammation and microvascular remodeling within the post-stenotic kidney, which promote tissue scarring and may account for irreversible renal damage. Obesity has been shown to aggravate kidney damage via several pathways, including exacerbation of microvascular regression and renal cell injury mediated by adipocytes and insulin resistance, thereby worsening the structural and functional outcomes of the kidney in renovascular disease. Dietary modification and inhibition of the renin-angiotensin-aldosterone system have been shown to alleviate obesity-induced tissue injury and remodeling. Possibly, angiogenic factors may boost microvascular repair in the ischemic kidney in the obesity milieu. Novel therapeutic interventions targeting deleterious pathways that are activated by obesity and responsible for kidney damage need to be explored in future studies.

Ex vivo exposure of bone marrow from chronic kidney disease donor rats to pravastatin limits renal damage in recipient rats with chronic kidney disease

Introduction

Healthy bone marrow cell (BMC) infusion improves renal function and limits renal injury in a model of chronic kidney disease (CKD) in rats. However, BMCs derived from rats with CKD fail to retain beneficial effects, demonstrating limited therapeutic efficacy. Statins have been reported to improve cellular repair mechanisms.

Methods

We studied whether exposing CKD rat BMCs ex vivo to pravastatin improved their in vivo therapeutic efficacy in CKD and compared this to systemic in vivo treatment. Six weeks after CKD induction, healthy BMCs, healthy pravastatin-pretreated BMCs, CKD BMCs or CKD pravastatin-pretreated BMCs were injected into the renal artery of CKD rats.

Results

At 6 weeks after BMC injection renal injury was reduced in pravastatin-pretreated CKD BMC recipients vs. CKD BMC recipients. Effective renal plasma flow was lower and filtration fraction was higher in CKD BMC recipients compared to all groups whereas there was no difference between pravastatin-pretreated CKD BMC and healthy BMC recipients. Mean arterial pressure was higher in CKD BMC recipients compared to all other groups. In contrast, 6 weeks of systemic in vivo pravastatin treatment had no effect. In vitro results showed improved migration, decreased apoptosis and lower excretion of pro-inflammatory Chemokine (C-X-C Motif) Ligand 5 in pravastatin-pretreated CKD BMCs.

Conclusions

Short ex vivo exposure of CKD BMC to pravastatin improves CKD BMC function and their subsequent therapeutic efficacy in a CKD setting, whereas systemic statin treatment did not provide renal protection.

Paradigm Shifts in Atherosclerotic Renovascular Disease: Where Are We Now?

Results of recent clinical trials and experimental studies indicate that whereas atherosclerotic renovascular disease can accelerate both systemic hypertension and tissue injury in the poststenotic kidney, restoring vessel patency alone is insufficient to recover kidney function for most subjects. Kidney injury in atherosclerotic renovascular disease reflects complex interactions among vascular rarefication, oxidative stress injury, and recruitment of inflammatory cellular elements that ultimately produce fibrosis. Classic paradigms for simply restoring blood flow are shifting to implementation of therapy targeting mitochondria and cell-based functions to allow regeneration of vascular, glomerular, and tubular structures sufficient to recover, or at least stabilize, renal function. These developments offer exciting possibilities of repair and regeneration of kidney tissue that may limit progressive CKD in atherosclerotic renovascular disease and may apply to other conditions in which inflammatory injury is a major common pathway.

Therapeutic potential of traditional chinese medicine on inflammatory diseases

Increased oxidative stress induces inflammation to several tissues/organs leading to cell death and long-term injury. Traditional Chinese Medicine (TCM) with antioxidant, anti-inflammatory, anti-apoptotic, and autophagic regulatory functions has been widely used as preventive or therapeutic strategy in modern medicine. Oxidative stress and inflammation have been widely reported to contribute to cigarette smoke-induced lung inflammation, hepatotoxicity, or sympathetic activation-induced liver inflammation, lipopolysaccharide-induced renal inflammation, and substance P-mediated neurogenic hyperactive bladder based on clinical findings. In this review, we introduce several evidences for TCM treatment including Monascus adlay (MA) produced by inoculating adlay (Cois lachrymal-jobi L. var. ma-yuen Stapf) with Monascus purpureus on lung injury, Amla (Emblica officinalis Gaertn. of Euphorbiaceae family) on hepatotoxin-induced liver inflammation, Virgate Wormwood Decoction (Yīn Chén Hāo tāng) and its active component genipin on sympathetic activation–induced liver inflammation, and green tea extract and its active components, catechins, or a modified TCM formula Five Stranguries Powder (Wǔ Lén Sǎn) plus Crataegi Fructus (Shān Zhā) on hyperactive bladder. The pathophysiologic and molecular mechanisms of TCM on ameliorating inflammatory diseases are discussed in the review.

Endothelial dysfunction in conduit arteries and in microcirculation. Novel therapeutic approaches

The vascular endothelium not only is a single monolayer of cells between the vessel lumen and the intimal wall, but also plays an important role by controlling vascular function and structure mainly via the production of nitric oxide (NO). The so called "cardiovascular risk factors" are associated with endothelial dysfunction, that reduces NO bioavailability, increases oxidative stress, and promotes inflammation contributing therefore to the development of atherosclerosis. The significant role of endothelial dysfunction in the development of atherosclerosis emphasizes the need for efficient therapeutic interventions. During the last years statins, angiotensin-converting enzyme inhibitors, angiotensin-receptor antagonists, antioxidants, beta-blockers and insulin sensitizers have been evaluated for their ability to restore endothelial function (Briasoulis et al., 2012). As there is not a straightforward relationship between therapeutic interventions and improvement of endothelial function but rather a complicated interrelationship between multiple cellular and sub-cellular targets, research has been focused on the understanding of the underlying mechanisms. Moreover, the development of novel diagnostic invasive and non-invasive methods has allowed the early detection of endothelial dysfunction expanding the role of therapeutic interventions and our knowledge. In the current review we present the available data concerning the contribution of endothelial dysfunction to atherogenesis and review the methods that assess endothelial function with a view to understand the multiple targets of therapeutic interventions. Finally we focus on the classic and novel therapeutic approaches aiming to improve endothelial dysfunction and the underlying mechanisms.

Sildenafil ameliorates oxidative stress and DNA damage in the stenotic kidneys in mice with renovascular hypertension

Background

Oxidative stress and DNA damage have been implicated in the pathogenesis of renovascular hypertension induced by renal artery stenosis in the two-kidney, one-clip (2K1C) Goldblatt model. Considering our previous report indicating that the chronic blockade of phosphodiesterase 5 with sildenafil (Viagra®) has marked beneficial effects on oxidative stress and DNA damage, we tested the hypothesis that sildenafil could also protect the stenotic kidneys of 2K1C hypertensive mice against oxidative stress and genotoxicity.

Methods

The experiments were performed with C57BL6 mice subjected to renovascular hypertension by left renal artery clipping. Two weeks after clipping, the mice were treated with sildenafil (40 mg/kg/day for 2 weeks, 2K1C-sildenafil group) or the vehicle (2K1C). These mice were compared with control mice not subjected to renal artery clipping (Sham). After hemodynamic measurements, the stenotic kidneys were assessed using flow cytometry to evaluate cell viability and the comet assay to evaluate DNA damage. Measurements of intracellular superoxide anions and hydrogen peroxide levels as well as nitric oxide bioavailability were also obtained.

Results

Sildenafil treatment significantly reduced mean arterial pressure (15%), heart rate (8%), intrarenal angiotensin II (50%) and renal atrophy (36%). In addition, it caused a remarkable decrease of reactive oxygen species production. On the other hand, sildenafil increased nitric oxide levels relative to those in the nontreated 2K1C mice. Sildenafil treatment also significantly reduced the high level of kidney DNA damage that is a characteristic of renovascular hypertensive mice.

Conclusions

Our data reveal that sildenafil has a protective effect on the stenotic kidneys of 2K1C mice, suggesting a new use of phosphodiesterase 5 inhibitors for protection against the DNA damage observed in the hypoperfused kidneys of individuals with renovascular hypertension. Further translational research is necessary to delineate the mechanisms involved in the prevention of renal stenosis in the clinical setting.

Renovascular hypertension leads to DNA damage and apoptosis in bone marrow cells

Angiotensin II (Ang II), which plays a pivotal role in the pathophysiology of the two-kidney, one-clip (2K1C) Goldblatt hypertension, has been associated with augmented generation of reactive oxygen species (ROS) in some cells and tissues. In the present study, we evaluated the influence of 2K1C hypertension on oxidative stress, DNA fragmentation, and apoptosis of bone marrow (BM) cells. Two weeks after the renal artery clipping or Sham operation, flow cytometry analysis showed a higher production of superoxide anions (approximately sixfold) and hydrogen peroxide (approximately twofold) in 2K1C hypertensive than in Sham normotensive mice. 2K1C mice also showed an augmented DNA fragmentation (54%) and apoptotic cells (21%). Our data show that the 2K1C renovascular hypertension is characterized by an increased production of ROS, DNA damage, and apoptosis of BM, which is a fundamental source of the cells involved in tissue repair.

Stem cell recruitment after injury: lessons for regenerative medicine

Tissue repair and regeneration are thought to involve resident cell proliferation as well as the selective recruitment of circulating stem and progenitor cell populations through complex signaling cascades. Many of these recruited cells originate from the bone marrow, and specific subpopulations of bone marrow cells have been isolated and used to augment adult tissue regeneration in preclinical models. Clinical studies of cell-based therapies have reported mixed results, however, and a variety of approaches to enhance the regenerative capacity of stem cell therapies are being developed based on emerging insights into the mechanisms of progenitor cell biology and recruitment following injury. This article discusses the function and mechanisms of recruitment of important bone marrow-derived stem and progenitor cell populations following injury, as well as the emerging therapeutic applications targeting these cells.

Dietary Monascus adlay supplements facilitate suppression of cigarette smoke-induced pulmonary endoplasmic reticulum stress, autophagy, apoptosis and emphysema-related PLGF in the rat

Cigarette smoke (CS) exposure may cause oxidative stress in the lung, leading to cell death and long-term injury. Monascus adlay (MA) with antioxidant components produced by inoculating adlay (Cois lachrymal-jobi L. var. ma-yuen Stapf) with Monascus purpureus may protect lung against CS-induced lung injuries in rats. MA and lovastatin had higher antioxidant activities than either M. purpureus or adlay. CS exposure caused significant lung damage, as evidenced by higher levels of reactive oxygen species (ROS), neutrophil infiltration, dityrosine and 4-HNE, as well as lower levels of Mn-superoxide dismutase and catalase expression. Lung tissues with CS exposure had higher levels of ER stress, apoptosis, autophagy and emphysema-related placenta growth factor (PlGF) expressions. All CS-induced injuries were significantly suppressed by MA supplements. MA would be a beneficial nutritional therapy to ameliorate CS-induced lung injury via preserving antioxidant defense mechanisms, decreasing oxidative stress and inhibiting ER stress, autophagy, apoptosis and emphysema-related risk factor.

Adipose tissue-derived mesenchymal stem cells improve revascularization outcomes to restore renal function in swine atherosclerotic renal artery stenosis

Reno-protective strategies are needed to improve renal outcomes in patients with atherosclerotic renal artery stenosis (ARAS). Adipose tissue-derived mesenchymal stem cells (MSCs) can promote renal regeneration, but their potential for attenuating cellular injury and restoring kidney repair in ARAS has not been explored. We hypothesized that replenishment of MSC as an adjunct to percutaneous transluminal renal angioplasty (PTRA) would restore renal cellular integrity and improve renal function in ARAS pigs. Four groups of pigs (n = 7 each) were studied after 16 weeks of ARAS, ARAS 4 weeks after PTRA and stenting with or without adjunct intrarenal delivery of MSC (10 × 10(6) cells), and controls. Stenotic kidney blood flow (renal blood flow [RBF]) and glomerular filtration rate (GFR) were measured using multidetector computer tomography (CT). Renal microvascular architecture (micro-CT), fibrosis, inflammation, and oxidative stress were evaluated ex vivo. Four weeks after successful PTRA, mean arterial pressure fell to a similar level in all revascularized groups. Stenotic kidney GFR and RBF remained decreased in ARAS (p = .01 and p = .02) and ARAS + PTRA (p = .02 and p = .03) compared with normal but rose to normal levels in ARAS + PTRA + MSC (p = .34 and p = .46 vs. normal). Interstitial fibrosis, inflammation, microvascular rarefaction, and oxidative stress were attenuated only in PTRA + MSC-treated pigs. A single intrarenal delivery of MSC in conjunction with renal revascularization restored renal hemodynamics and function and decreased inflammation, apoptosis, oxidative stress, microvascular loss, and fibrosis. This study suggests a unique and novel therapeutic potential for MSC in restoring renal function when combined with PTRA in chronic experimental renovascular disease.

Oxidized low density lipoprotein, stem cells, and atherosclerosis

Oxidized low density lipoprotein (ox-LDL), a risk factor of atherosclerosis, facilitates the formation and vulnerability of atherosclerotic plaque, thus contributing to several clinical complications. Stem cells participate in vascular repair after damage and atherosclerosis is a process of inflammation accompanied with vascular injury. Researchers have proposed that stem cells participate in the formation of atherosclerotic plaque. Also, because ox-LDL is capable of inducing toxic effects on stem cells, it is reasonable to postulate that ox-LDL promotes the progress of atherosclerosis via acting on stem cells. In the present article, we review the relationship between ox-LDL, stem cells, and atherosclerosis and a portion of the associated mechanisms.

Deciphering the pathways of death of Histoplasma capsulatum-infected macrophages: implications for the immunopathogenesis of early infection

Apoptosis of leukocytes is known to strongly influence the immunopathogenesis of infection. In this study, we dissected the death pathways of murine macrophages (MΦs) infected with the intracellular pathogen Histoplasma capsulatum. Yeast cells caused apoptosis of MΦs at a wide range of multiplicity of infection, but smaller inocula resulted in delayed detection of apoptosis. Upon infection, caspases 3 and 1 were activated, and both contributed to cell death; however, only the former was involved in apoptosis. The principal driving force for apoptosis involved the extrinsic pathway via engagement of TNFR1 by TNF-α. Infected MΦs produced IL-10 that dampened apoptosis. The chronology of TNF-α and IL-10 release differed in vitro. The former was detected by 2 h postinfection, and the latter was not detected until 8 h postinfection. In vivo, the lungs of TNFR1(-/-) mice infected for 1 d contained fewer apoptotic MΦs than wild-type mice, whereas the lungs of IL-10(-/-) mice exhibited more. Blockade of apoptosis by a pan-caspase inhibitor or by simvastatin sharply reduced the release of TNF-α but enhanced IL-10. However, these treatments did not modify the fungal burden in vitro over 72 h. Thus, suppressing cell death modulated cytokine release but did not alter the fungal burden. These findings provide a framework for the early pathogenesis of histoplasmosis in which yeast cell invasion of lung MΦs engenders apoptosis, triggered in part in an autocrine TNF-α-dependent manner, followed by release of IL-10 that likely prevents apoptosis of newly infected neighboring phagocytes.

Increased glomerular filtration rate in early metabolic syndrome is associated with renal adiposity and microvascular proliferation

Metabolic syndrome (MetS) is associated with glomerular hyperfiltration and is a risk factor for chronic kidney disease, but the underlying mechanisms are poorly defined. This study tested the hypothesis that increased glomerular filtration rate (GFR) in early MetS is associated with renal adiposity and microvascular proliferation. Twelve MetS-prone Ossabaw pigs were randomized to 10 wk of a standard (lean, n = 6) or atherogenic (MetS, n = 6) diet. Kidney hemodynamics and function, perirenal fat volume, and tubular dynamics were assessed in vivo by multidetector computed tomography (CT) and blood oxygen level-dependent (BOLD)-MRI. Microvascular architecture was assessed ex vivo with micro-CT. Candidate injury mechanisms were evaluated in kidney tissue by Western blotting and histology. Basal GFR, renal blood flow, and renal cortical perfusion and volume were elevated in the MetS group. Perirenal and kidney tissue fat, proximal-nephron intratubular fluid concentration, and endothelial nitric oxide synthase expression were increased in MetS. GFR levels correlated with tissue triglyceride levels. Elevated spatial density of 20- to 40-μm cortical microvessels was accompanied by mild oxidative stress, inflammation, and with proximal tubular vacuolization. Medullary size and perfusion were relatively preserved, and BOLD-MRI showed intact medullary tubular response to furosemide. Increased GFR in early MetS is associated with renal adiposity and microvascular proliferation, which involve mainly the renal cortex and precede significant activation of oxidative stress and inflammation. Renal adiposity and proliferative microvessels may represent novel therapeutic targets for preserving renal function in early MetS.

Noninvasive In vivo assessment of renal tissue elasticity during graded renal ischemia using MR elastography

OBJECTIVES

: Magnetic resonance elastography (MRE) allows noninvasive assessment of tissue stiffness in vivo. Renal arterial stenosis (RAS), a narrowing of the renal artery, promotes irreversible tissue fibrosis that threatens kidney viability and may elevate tissue stiffness. However, kidney stiffness may also be affected by hemodynamic factors. This study tested the hypothesis that renal blood flow (RBF) is an important determinant of renal stiffness as measured by MRE.

MATERIAL AND METHODS

: In 6 anesthetized pigs MRE studies were performed to determine cortical and medullary elasticity during acute graded decreases in RBF (by 20%, 40%, 60%, 80%, and 100% of baseline) achieved by a vascular occluder. Three sham-operated swine served as time control. Additional pigs were studied with MRE 6 weeks after induction of chronic unilateral RAS (n = 6) or control (n = 3). Kidney fibrosis was subsequently evaluated histologically by trichrome staining.

RESULTS

: During acute RAS the stenotic cortex stiffness decreased (from 7.4 ± 0.3 to 4.8 ± 0.6 kPa, P = 0.02 vs. baseline) as RBF decreased. Furthermore, in pigs with chronic RAS (80% ± 5.4% stenosis) in which RBF was decreased by 60% ± 14% compared with controls, cortical stiffness was not significantly different from normal (7.4 ± 0.3 vs. 7.6 ± 0.3 kPa, P = 0.3), despite histologic evidence of renal tissue fibrosis.

CONCLUSION

: Hemodynamic variables modulate kidney stiffness measured by MRE and may mask the presence of fibrosis. These results suggest that kidney turgor should be considered during interpretation of elasticity assessments.

Persistent kidney dysfunction in swine renal artery stenosis correlates with outer cortical microvascular remodeling

Percutaneous transluminal renal stenting (PTRS) does not consistently improve renal function in patients with atherosclerotic renovascular disease, but the mechanisms underlying irreversible kidney injury have not been fully elucidated. We hypothesized that renal dysfunction after PTRS is linked to ongoing renal microvascular (MV) remodeling. Pigs were studied after 10 wk of atherosclerosis and renal artery stenosis (ARAS), ARAS treated with PTRS 4 wk earlier, and normal controls (n = 10 each). Renal blood flow (RBF) and glomerular filtration rate (GFR) were studied using multidetector computer tomography. Renal microvascular architecture (micro-CT), angiogenic activity, oxidative stress, and fibrosis were evaluated ex vivo. Four weeks after PTRS, blood pressure was normalized. However, GFR and RBF remained similarly decreased in untreated ARAS and ARAS+PTRS (P < 0.05 vs. normal). MV rarefaction was unaltered after revascularization, and the spatial density of outer cortical microvessels correlated with residual GFR. Interstitial fibrosis and altered expression of proangiogenic and profibrotic factors persisted after PTRS. Tubulointerstitial injury in ARAS persisted 4 wk after mechanically successful PTRS, and vessel loss correlated with residual renal dysfunction. MV loss and fibrosis in swine ARAS might account for persistent renal dysfunction after PTRS and underscore the need to assess renal parenchymal disease before revascularization.

Statins and renovascular disease in the elderly: a population-based cohort study

AIMS

More than 90% of cases of renovascular disease (RVD) are caused by atherosclerosis; thus patients with this condition are at high risk for vascular events. We examined the association of statins with prognosis in patients with RVD.

METHODS AND RESULTS

We performed a population-based cohort study in 4040 patients with RVD older than 65 years using province-wide health data in Ontario, Canada. The primary outcome was time to first cardiorenal event, specifically myocardial infarction, stroke, heart failure, acute renal failure, dialysis or death; the primary analysis used a time-dependent covariate for statin exposure. Despite having a greater burden of cardiovascular and renal comorbidity, the risk of the primary outcome was significantly lower in statin users than in non-users [unadjusted hazard ratio (HR) 0.51, 95% confidence interval (CI) 0.47-0.57; P < 0.0001]. This association was materially unchanged after adjusting for demographic characteristics, cardiovascular risk factors, other comorbidities, measures of health-care utilization, screening, and concomitant medications (adjusted HR 0.51, 95% CI 0.46-0.57). An analysis using the same endpoint in a propensity-matched cohort without time-dependent statin exposure revealed a lower risk of the primary outcome in statin-treated patients but with a substantially more conservative point estimate (HR 0.82, 95% CI 0.71-0.95).

CONCLUSION

These data suggest that statins are associated with improved prognosis in elderly patients with RVD.