Angiotensin II-induced hypertension dose-dependently leads to oxidative stress and DNA damage in mouse kidneys and hearts

DNA damage and arterial hypertension. A systematic review and meta-analysis

Oxidative DNA damage markers (8OHdG, comet assay, gammaH2AX) are becoming widely used in clinical cardiology research. To conduct this review of DNA damage in relation to hypertension in humans, we used databases (e.g. PubMed, Web of Science) to search for English-language publications up to June 30, 2022 and the terms: DNA damage, comet assay, gammaH2AX, 8OHdG, strand breaks, and arterial hypertension. Exclusion criteria were: children, absence of relevant controls, extra-arterial hypertensive issues, animal, cell lines. From a total of 79526, 15 human studies were selected. A total of 902 hypertensive patients (pts): (comet: N=418 pts; 8OHdG: N=484 pts) and 587 controls (comet: N=203; 8OHdG: N=384) were included. DNA damage was significantly higher in hypertensive pts than healthy controls (comet 26.6±11.0 vs 11.7±4.07 arbitrary units /A.U./; P<0.05 and="" 8ohdg="" 13="" 1="" 4="" 12="" vs="" 6="" 97="" 2="" 67="" ng="" mg="" creatinine="" i=""> P<0.05) confirmed with meta-analysis for both. Greater DNA damage was observed in more adverse cases (concentric cardiac hypertrophy 43.4±15.4 vs 15.6±5.5; sustained/untreated hypertension 31.4±12.1 vs 14.2±5/35.0±5.0 vs 25.0 ±5.0; non-dippers 39.2±15.5 vs 29.4±11.1 A.U.; elderly 14.9±4.5 vs 9.3±4.1 ng/mg creatinine; without carvedilol 9.1±4.2 vs 5.7±3.9; with coronary heart disease 0.5±0.1 vs 0.2±0.1 ng/mL) (P<0.05) confirmed with meta-analysis. DNA damage correlated strongly positively with serum glycosylated haemoglobin (r=0.670; P<0.05) and negatively with total antioxidant status (r=-0.670 to -0.933; P<0.05). This is the first systematic review with meta-analysis showing that oxidative DNA damage was increased in humans with arterial hypertension compared to controls.

Collecting duct NCOR1 controls blood pressure by regulating mineralocorticoid receptor

INTRODUCTION

Nuclear receptor corepressor 1(NCOR1) is reported to play crucial roles in cardiovascular diseases, but its function in the kidney has remained obscure.

OBJECTIVE

We aim to elucidate the role of collecting duct NCOR1 in blood pressure (BP) regulation.

METHODS AND RESULTS

Collecting duct NCOR1 knockout (KO) mice manifested increased BP and aggravated vascular and renal injury in an angiotensin II (Ang II)-induced hypertensive model. KO mice also showed significantly higher BP than littermate control (LC) mice in deoxycorticosterone acetate (DOCA)-salt model. Further study showed that collecting duct NCOR1 deficiency aggravated volume and sodium retention after saline challenge. Among the sodium transporter in the collecting duct, the expression of the three epithelial sodium channel (ENaC) subunits was markedly increased in the renal medulla of KO mice. Consistently, BP in Ang II-infused KO mice decreased significantly to the similar level as those in LC mice after amiloride treatment. ChIP analysis revealed that NCOR1 deficiency increased the enrichment of mineralocorticoid receptor (MR) on the promoters of the three ENaC genes in primary inner medulla collecting duct (IMCD) cells. Co-IP results showed interaction between NCOR1 and MR, and luciferase reporter results demonstrated that NCOR1 inhibited the transcriptional activity of MR. Knockdown of MR eliminated the increased ENaC expression in primary IMCD cells isolated from KO mice. Finally, BP was significantly decreased in Ang II-infused KO mice after treatment of MR antagonist spironolactone and the difference between LC and KO mice was abolished.

CONCLUSIONS

NCOR1 interacts with MR to control ENaC activity in the collecting duct and to regulate sodium reabsorption and ultimately BP. Targeting NCOR1 might be a promising tactic to interrupt the volume and sodium retention of the collecting duct in hypertension.

Acute inhibition of nicotinamide adenine dinucleotide phosphate oxidase in the commissural nucleus of the solitary tract reduces arterial pressure and renal sympathetic nerve activity in renovascular hypertension

BACKGROUND

A growing body of evidence suggests that oxidative stress plays a role in the pathophysiology of hypertension. However, the involvement of the reactive oxygen species (ROS) in the commissural nucleus of the solitary tract (commNTS) in development the of hypertension remains unclear.

METHOD

We evaluated the hemodynamic and sympathetic responses to acute inhibition of NADPH oxidase in the commNTS in renovascular hypertensive rats. Under anesthesia, male Holtzman rats were implanted with a silver clip around the left renal artery to induce 2-kidney 1-clip (2K1C) hypertension. After six weeks, these rats were anesthetized and instrumented for recording mean arterial pressure (MAP), renal blood flow (RBF), renal vascular resistance (RVR), and renal sympathetic nerve activity (RSNA) during baseline and after injection of apocynin (nicotinamide adenine dinucleotide phosphate oxidase inhibitor), NSC 23766 (RAC inhibitor) or saline into the commNTS.

RESULTS

Apocynin into the commNTS decreased MAP, RSNA, and RVR in 2K1C rats. NSC 23766 into the commNTS decreased MAP and RSNA, without changing RVR in 2K1C rats.

CONCLUSION

These results demonstrate that the formation of ROS in the commNTS is important to maintain sympathoexcitation and hypertension in 2K1C rats and suggest that NADPH oxidase in the commNTS could be a potential target for therapeutics in renovascular hypertension.

Screening and Management of Coronary Artery Disease in Kidney Transplant Candidates

Cardiovascular disease (CVD) is a major cause of morbidity and mortality in patients with chronic kidney disease (CKD), especially in end-stage renal disease (ESRD) patients and during the first year after transplantation. For these reasons, and due to the shortage of organs available for transplant, it is of utmost importance to identify patients with a good life expectancy after transplant and minimize the transplant peri-operative risk. Various conditions, such as severe pulmonary diseases, recent myocardial infarction or stroke, and severe aorto-iliac atherosclerosis, need to be ruled out before adding a patient to the transplant waiting list. The effectiveness of systematic coronary artery disease (CAD) treatment before kidney transplant is still debated, and there is no universal screening protocol, not to mention that a nontailored screening could lead to unnecessary invasive procedures and delay or exclude some patients from transplantation. Despite the different clinical guidelines on CAD screening in kidney transplant candidates that exist, up to today, there is no worldwide universal protocol. This review summarizes the key points of cardiovascular risk assessment in renal transplant candidates and faces the role of noninvasive cardiovascular imaging tools and the impact of coronary revascularization versus best medical therapy before kidney transplant on a patient's cardiovascular outcome.

Comparative Analysis of Hypertensive Tubulopathy in Animal Models of Hypertension and Its Relevance to Human Pathology

Assessment of hypertensive tubulopathy for more than fifty animal models of hypertension in experimental pathology employs criteria that do not correspond to lesional descriptors for tubular lesions in clinical pathology. We provide a critical appraisal of experimental hypertension with the same approach used to estimate hypertensive renal tubulopathy in humans. Four models with different pathogenesis of hypertension were analyzed-chronic angiotensin (Ang) II-infused and renin-overexpressing (TTRhRen) mice, spontaneously hypertensive (SHR), and Goldblatt two-kidney one-clip (2K1C) rats. Mouse models, SHR, and the nonclipped kidney in 2K1C rats had no regular signs of hypertensive tubulopathy. Histopathology in animals was mild and limited to variations in the volume density of tubular lumen and epithelium, interstitial space, and interstitial collagen. Affected kidneys in animals demonstrated lesion values that are significantly different compared with healthy controls but correspond to mild damage if compared with hypertensive humans. The most substantial human-like hypertensive tubulopathy was detected in the clipped kidney of 2K1C rats. For the first time, our study demonstrated the regular presence of chronic progressive nephropathy (CPN) in relatively young mice and rats with induced hypertension. Because CPN may confound the assessment of rodent models of hypertension, proliferative markers should be used to verify nonhypertensive tubulopathy.

Sex- and age-related differences in renal and cardiac injury and senescence in stroke-prone spontaneously hypertensive rats

BACKGROUND

Sex differences play a critical role in the incidence and severity of cardiovascular diseases, whereby men are at a higher risk of developing cardiovascular disease compared to age-matched premenopausal women. Marked sex differences at the cellular and tissue level may contribute to susceptibility to cardiovascular disease and end-organ damage. In this study, we have performed an in-depth histological analysis of sex differences in hypertensive cardiac and renal injury in middle-aged stroke-prone spontaneously hypertensive rats (SHRSPs) to determine the interaction between age, sex and cell senescence.

METHODS

Kidneys, hearts and urine samples were collected from 6.5- and 8-month-old (Mo) male and female SHRSPs. Urine samples were assayed for albumin and creatinine content. Kidneys and hearts were screened for a suite of cellular senescence markers (senescence-associated β-galactosidase, p16^INK4a, p21, γH2AX). Renal and cardiac fibrosis was quantified using Masson's trichrome staining, and glomerular hypertrophy and sclerosis were quantified using Periodic acid-Schiff staining.

RESULTS

Marked renal and cardiac fibrosis, concomitant with albuminuria, were evident in all SHRSPs. These sequelae were differentially affected by age, sex and organ. That is, the level of fibrosis was greater in the kidney than the heart, males had greater levels of fibrosis than females in both the heart and kidney, and even a 6-week increase in age resulted in greater levels of kidney fibrosis in males. The differences in kidney fibrosis were reflected by elevated levels of cellular senescence in the kidney in males but not females. Senescent cell burden was significantly less in cardiac tissue compared to renal tissue and was not affected by age or sex.

CONCLUSIONS

Our study demonstrates a clear sex pattern in age-related progression of renal and cardiac fibrosis and cellular senescence in SHRSP rats. A 6-week time frame was associated with increased indices of cardiac and renal fibrosis and cellular senescence in male SHRSPs. Female SHRSP rats were protected from renal and cardiac damage compared to age-matched males. Thus, the SHRSP is an ideal model to investigate the effects of sex and aging on organ injury over a short timeframe.

Nrf2 Activation Does Not Protect from Aldosterone-Induced Kidney Damage in Mice

Nuclear factor erythroid 2-related factor 2 (Nrf2) is downregulated in chronic kidney disease (CKD). Activation of Nrf2 might be a therapeutic option in CKD. Here we investigate the effect of Nrf2 activation on aldosterone (Aldo)-induced renal injury. Wild-type (WT) mice, transgenic Keap1 hypomorphic (Nrf2ꜛ, genotype results in upregulation of Nrf2 expression) mice and WT mice treated with the Nrf2 activator sulforaphane (Sulf) received Aldo for 4 weeks. In Aldo-treated mice, kidneys were significantly heavier and pathologically altered, reflected by increased urinary albumin levels and tissue damage. In Nrf2ꜛ-Aldo mice the tubule damage marker NGAL was significantly decreased. Increased oxidative damage markers (8-OHdG, 15-isoprostane F_2t) were measured in all Aldo-treated groups. Aldo-increased Nrf2 amounts were mainly found in the late tubule system. The amount of phosphorylated and thus putatively active Nrf2 was significantly increased by Aldo only in WT mice. However, expression of Nrf2 target genes NQO1 and HO1 was decreased in all Aldo-infused mice. GSK3β, which promotes Nrf2 degradation, was significantly increased in the kidneys of Aldo-treated WT mice. Neither genetic nor pharmacological Nrf2 activation was able to prevent oxidative injury induced by Aldo, probably due to induction of negative regulators of Nrf2.

Activation of the Renin–Angiotensin System Disrupts the Cytoskeletal Architecture of Human Urine-Derived Podocytes

High blood pressure is one of the major public health problems that causes severe disorders in several tissues including the human kidney. One of the most important signaling pathways associated with the regulation of blood pressure is the renin–angiotensin system (RAS), with its main mediator angiotensin II (ANGII). Elevated levels of circulating and intracellular ANGII and aldosterone lead to pro-fibrotic, -inflammatory, and -hypertrophic milieu that causes remodeling and dysfunction in cardiovascular and renal tissues. Furthermore, ANGII has been recognized as a major risk factor for the induction of apoptosis in podocytes, ultimately leading to chronic kidney disease (CKD). In the past, disease modeling of kidney-associated diseases was extremely difficult, as the derivation of kidney originated cells is very challenging. Here we describe a differentiation protocol for reproducible differentiation of sine oculis homeobox homolog 2 (SIX2)-positive urine-derived renal progenitor cells (UdRPCs) into podocytes bearing typical cellular processes. The UdRPCs-derived podocytes show the activation of the renin–angiotensin system by being responsive to ANGII stimulation. Our data reveal the ANGII-dependent downregulation of nephrin (NPHS1) and synaptopodin (SYNPO), resulting in the disruption of the podocyte cytoskeletal architecture, as shown by immunofluorescence-based detection of α-Actinin. Furthermore, we show that the cytoskeletal disruption is mainly mediated through angiotensin II receptor type 1 (AGTR1) signaling and can be rescued by AGTR1 inhibition with the selective, competitive angiotensin II receptor type 1 antagonist, losartan. In the present manuscript we confirm and propose UdRPCs differentiated to podocytes as a unique cell type useful for studying nephrogenesis and associated diseases. Furthermore, the responsiveness of UdRPCs-derived podocytes to ANGII implies potential applications in nephrotoxicity studies and drug screening.

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.

Overexpression of NOX2 Exacerbates AngII-Mediated Cardiac Dysfunction and Metabolic Remodelling

The present study aimed to examine the effects of low doses of angiotensin II (AngII) on cardiac function, myocardial substrate utilization, energetics, and mitochondrial function in C57Bl/6J mice and in a transgenic mouse model with cardiomyocyte specific upregulation of NOX2 (csNOX2 TG). Mice were treated with saline (sham), 50 or 400 ng/kg/min of AngII (AngII₅₀ and AngII₄₀₀) for two weeks. In vivo blood pressure and cardiac function were measured using plethysmography and echocardiography, respectively. Ex vivo cardiac function, mechanical efficiency, and myocardial substrate utilization were assessed in isolated perfused working hearts, and mitochondrial function was measured in left ventricular homogenates. AngII₅₀ caused reduced mechanical efficiency despite having no effect on cardiac hypertrophy, function, or substrate utilization. AngII₄₀₀ slightly increased systemic blood pressure and induced cardiac hypertrophy with no effect on cardiac function, efficiency, or substrate utilization. In csNOX2 TG mice, AngII₄₀₀ induced cardiac hypertrophy and in vivo cardiac dysfunction. This was associated with a switch towards increased myocardial glucose oxidation and impaired mitochondrial oxygen consumption rates. Low doses of AngII may transiently impair cardiac efficiency, preceding the development of hypertrophy induced at higher doses. NOX2 overexpression exacerbates the AngII -induced pathology, with cardiac dysfunction and myocardial metabolic remodelling.

OUP accepted manuscript

Cardiovascular diseases (CVDs) arise from a complex interplay among genomic, proteomic, and metabolomic abnormalities. Emerging evidence has recently consolidated the presence of robust DNA damage in a variety of cardiovascular disorders. DNA damage triggers a series of cellular responses termed DNA damage response (DDR) including detection of DNA lesions, cell cycle arrest, DNA repair, cellular senescence, and apoptosis, in all organ systems including hearts and vasculature. Although transient DDR in response to temporary DNA damage can be beneficial for cardiovascular function, persistent activation of DDR promotes the onset and development of CVDs. Moreover, therapeutic interventions that target DNA damage and DDR have the potential to attenuate cardiovascular dysfunction and improve disease outcome. In this review, we will discuss molecular mechanisms of DNA damage and repair in the onset and development of CVDs, and explore how DDR in specific cardiac cell types contributes to CVDs. Moreover, we will highlight the latest advances regarding the potential therapeutic strategies targeting DNA damage signalling in CVDs.

The severity of SARS-CoV-2 infection is dictated by host factors? Epigenetic perspectives

The emergence of COVID-19, caused by SARS-CoV-2 poses a significant threat to humans as it is highly contagious with increasing mortality. There exists a high degree of heterogeneity in the mortality rates of COVID-19 across the globe. There are multiple speculations on the varying degree of mortality. Still, all the clinical reports have indicated that preexisting chronic diseases like hypertension, diabetes, chronic obstructive pulmonary disease (COPD), kidney disorders, and cardiovascular diseases are associated with the increased risk for high mortality in SARS-CoV-2 infected patients. It is worth noting that host factors, mainly epigenetic factors could play a significant role in deciding the outcome of COVID-19 diseases. Over the recent years, it is evident that chronic diseases are developed due to altered epigenome that includes a selective loss/gain of DNA and histone methylation on the chromatin of the cells. Since, there is a high positive correlation between chronic diseases and elevated mortality due to SARS-CoV-2, in this review; we discuss the overall picture of the aberrant epigenome map in varying chronic ailments and its implications in COVID-19 disease severity and high mortality.

Up-Regulation of DNA Damage Response Signaling in Autosomal Dominant Polycystic Kidney Disease

DNA damage and alterations in DNA damage response (DDR) signaling could be one of the molecular mechanisms mediating focal kidney cyst formation in autosomal dominant polycystic kidney disease (ADPKD). The aim of this study was to test the hypothesis that markers of DNA damage and DDR signaling are increased in human and experimental ADPKD. In the human ADPKD transcriptome, the number of up-regulated DDR-related genes was increased by 16.6-fold compared with that in normal kidney, and by 2.5-fold in cystic compared with that in minimally cystic tissue (P < 0.0001). In end-stage human ADPKD tissue, γ-H2A histone family member X (H2AX), phosphorylated ataxia telangiectasia and radiation-sensitive mutant 3 (Rad3)-related (pATR), and phosphorylated ataxia telangiectasia mutated (pATM) localized to cystic kidney epithelial cells. In vitro, pATR and pATM were also constitutively increased in human ADPKD tubular cells (WT 9-7 and 9-12) compared with control (HK-2). In addition, extrinsic oxidative DNA damage by hydrogen peroxide augmented γ-H2AX and cell survival in human ADPKD cells, and exacerbated cyst growth in the three-dimensional Madin-Darby canine kidney cyst model. In contrast, DDR-related gene expression was only transiently increased on postnatal day 0 in Pkd1^RC/RC mice, and not altered at later time points up to 12 months of age. In conclusion, DDR signaling is dysregulated in human ADPKD and during the early phases of murine ADPKD. The constitutive expression of the DDR pathway in ADPKD may promote survival of PKD1-mutated cells and contribute to kidney cyst growth.

The NADPH Oxidase Isoform 1 Contributes to Angiotensin II-Mediated DNA Damage in the Kidney

In higher concentrations, the blood pressure regulating hormone angiotensin II leads to vasoconstriction, hypertension, and oxidative stress by activating NADPH oxidases which are a major enzymatic source of reactive oxygen species (ROS). With the help of knockout animals, the impact of the three predominant NADPH oxidases present in the kidney, i.e., Nox1, Nox2 and Nox4 on angiotensin II-induced oxidative damage was studied. Male wildtype (WT) C57BL/6 mice, Nox1-, Nox2- and Nox4-deficient mice were equipped with osmotic minipumps, delivering either vehicle (PBS) or angiotensin II, for 28 days. Angiotensin II increased blood pressure and urinary albumin levels significantly in all treated mouse strains. In Nox1 knockout mice these increases were significantly lower than in WT, or Nox2 knockout mice. In WT mice, angiotensin II also raised systemic oxidative stress, ROS formation and DNA lesions in the kidney. A local significantly increased ROS production was also found in Nox2 and Nox4 knockout mice but not in Nox1 knockout mice who further had significantly lower systemic oxidative stress and DNA damage than WT animals. Nox2 and Nox4 knockout mice had increased basal DNA damage, concealing possible angiotensin II-induced increases. In conclusion, in the kidney, Nox1 seemed to play a role in angiotensin II-induced DNA damage.

Aldosterone Induces DNA Damage and Activation of Nrf2 Mainly in Tubuli of Mouse Kidneys

Hypertensive patients have an increased risk of developing chronic kidney disease (CKD). Many of these patients have increased levels of the blood pressure regulating mineralocorticoid aldosterone. As a protection against aldosterone-induced damage, kidney cells can upregulate key regulators of the antioxidant defense, such as nuclear factor-erythroid-2-related factor 2 (Nrf2). In the present study aldosterone-induced kidney damage and Nrf2 activation in kidney cells of mice treated with three different concentrations of aldosterone for 4 weeks was localized. Increased albumin and neutrophil gelatinase-associated lipocalin (NGAL) in urine revealed an impaired kidney function of the aldosterone-infused mice. Localization of aldosterone-induced oxidative damage (in the form of DNA lesions) in specific kidney cells showed an increase in proximal tubuli and to an even greater extend in distal tubuli. Phosphorylated Nrf2 was increased in distal tubule cells after aldosterone-infusion. Nrf2 activation in proximal tubuli or in glomeruli after aldosterone-treatment could not be observed. Nrf2 target genes and proteins analyzed, paradoxically, showed a downregulation in the whole kidney. Aldosterone-treated mice exhibited an increased kidney injury and DNA damage in distal and proximal tubuli. Nrf2 seemed only to be specifically activated in distal tubule cells, where we also detected the highest amount of oxidative damage.

The role of DNA damage as a therapeutic target in autosomal dominant polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) is the most common monogenic kidney disease and is caused by heterozygous germ-line mutations in either PKD1 (85%) or PKD2 (15%). It is characterised by the formation of numerous fluid-filled renal cysts and leads to adult-onset kidney failure in ~50% of patients by 60 years. Kidney cysts in ADPKD are focal and sporadic, arising from the clonal proliferation of collecting-duct principal cells, but in only 1-2% of nephrons for reasons that are not clear. Previous studies have demonstrated that further postnatal reductions in PKD1 (or PKD2) dose are required for kidney cyst formation, but the exact triggering factors are not clear. A growing body of evidence suggests that DNA damage, and activation of the DNA damage response pathway, are altered in ciliopathies. The aims of this review are to: (i) analyse the evidence linking DNA damage and renal cyst formation in ADPKD; (ii) evaluate the advantages and disadvantages of biomarkers to assess DNA damage in ADPKD and finally, (iii) evaluate the potential effects of current clinical treatments on modifying DNA damage in ADPKD. These studies will address the significance of DNA damage and may lead to a new therapeutic approach in ADPKD.

Angiotensin II-induced hypertension increases the mutant frequency in rat kidney

Epidemiological studies revealed an increased risk for kidney cancer in hypertensive patients. In many of these patients, the blood pressure regulating renin-angiotensin-aldosterone system (RAAS) is activated. A stimulated RAAS leads to oxidative stress and increases markers of DNA damage, both in vitro and in animal models of hypertension. However, the mutagenic potential of RAAS activation has not been investigated yet. To quantify hypertension-induced mutations, BigBlue^®+/- rats, which carry a transgenic lacI gene for mutation analysis, were treated for 20 weeks with a mean dose of 400 µg angiotensin II/kg × day. Angiotensin II-treated animals showed significantly increased blood pressure and impaired kidney function. Urinary excretion of oxidized nucleobases was raised. Additionally, in the renal cortex, oxidative stress, oxidatively generated DNA lesions and DNA strandbreaks were significantly increased. Further, a significant elevation of the mutant frequency in kidney DNA was detected. Sequencing revealed the presence of GC → T:A transversions in the mutated lacI genes of the angiotensin II-treated animals as a result of unrepaired oxidatively modified DNA bases, while no such transversions were found in the mutated lacI genes from control animals. The results demonstrate that the oxidative stress and DNA damage previously observed in kidney cells in vitro and in vivo after angiotensin II treatment indeed is associated with the accumulation of mutations in rat kidneys, providing further evidence for a cancer-initiating potential of elevated angiotensin II concentrations.

Cardiomyocyte calcineurin is required for the onset and progression of cardiac hypertrophy and fibrosis in adult mice

Previous studies have demonstrated that activation of calcineurin induces pathological cardiac hypertrophy (CH). In these studies, loss-of-function was mostly achieved by systemic administration of the calcineurin inhibitor cyclosporin A. The lack of conditional knockout models for calcineurin function has impeded progress toward defining the role of this protein during the onset and the development of CH in adults. Here, we exploited a mouse model of CH based on the infusion of a hypertensive dose of angiotensin II (AngII) to model the role of calcineurin in CH in adulthood. AngII-induced CH in adult mice was reduced by treatment with cyclosporin A, without affecting the associated increase in blood pressure, and also by induction of calcineurin deletion in adult mouse cardiomyocytes, indicating that cardiomyocyte calcineurin is required for AngII-induced CH. Surprisingly, cardiac-specific deletion of calcineurin, but not treatment of mice with cyclosporin A, significantly reduced AngII-induced cardiac fibrosis and apoptosis. Analysis of profibrotic genes revealed that AngII-induced expression of Tgfβ family members and Lox was not inhibited by cyclosporin A but was markedly reduced by cardiac-specific calcineurin deletion. These results show that AngII induces a direct, calcineurin-dependent prohypertrophic effect in cardiomyocytes, as well as a systemic hypertensive effect that is independent of calcineurin activity.

Differential Expression of Hypertensive Phenotypes in BXD Mouse Strains in Response to Angiotensin II

BACKGROUND

Besides environmental risk factors, genetic factors play a crucial role in the pathogenesis of primary hypertension. The current study is to unravel whether hypertensive phenotypes vary in mice with different genetic background.

METHODS

Hypertension was induced in C57BL/6J (B6), DBA/2J (D2), and 25 BXD strains by administrating angiotensin (Ang)II (2.5 mg/kg/day infused by osmotic minipump) for 4 weeks. Systolic blood pressure was monitored before (baseline) and after 4 weeks of AngII treatment by tail cuff. Cardiac and renal fibrosis was evaluated by picrosirius red staining and collagen volume fraction (CVF) was quantitated using imaging analyzing system; cardiac transforming growth factor (TGF)-β gene expression was monitored by RT-PCR, and inflammatory response was detected by immunohistochemical ED-1 staining.

RESULTS

AngII infusion caused hypertension in all strains. However, blood pressure elevation was more evident in the D2 strain than the B6 group, while it was widely variable among BXD strains. Furthermore, chronic AngII treatment lead to development of hypertensive cardiac and renal diseases. Cardiac and renal CVF levels in the D2 strain was significantly higher than the B6 cohort, whereas these varied vastly across BXD strains. Moreover, cardiac TGF-β mRNA levels were markedly diverse among various mouse strains.

CONCLUSION

Our study unequivocally demonstrates that in response to AngII, BXDs with different genetic background expressed hypertension phenotypes with varied degree in severity. It implicates that genomics contribute to pathogenesis of primary hypertension. Building upon the genotype and hypertensive phenotypes, the BXD cohort can be further exploited experimentally to identify genes that influence blood pressure.

Development of nonfibrotic left ventricular hypertrophy in an ANG II-induced chronic ovine hypertension model

Hypertension is a major risk factor for many cardiovascular diseases and leads to subsequent concomitant pathologies such as left ventricular hypertrophy (LVH). Translational approaches using large animals get more important as they allow the use of standard clinical procedures in an experimental setting. Therefore, the aim of this study was to establish a minimally invasive ovine hypertension model using chronic angiotensin II (ANG II) treatment and to characterize its effects on cardiac remodeling after 8 weeks. Sheep were implanted with osmotic minipumps filled with either vehicle control (n = 7) or ANG II (n = 9) for 8 weeks. Mean arterial blood pressure in the ANG II‐treated group increased from 87.4 ± 5.3 to 111.8 ± 6.9 mmHg (P = 0.00013). Cardiovascular magnetic resonance imaging showed an increase in left ventricular mass from 112 ± 12.6 g to 131 ± 18.7 g after 7 weeks (P = 0.0017). This was confirmed by postmortem measurement of left ventricular wall thickness which was higher in ANG II‐treated animals compared to the control group (18 ± 4 mm vs. 13 ± 2 mm, respectively, P = 0.002). However, ANG II‐treated sheep did not reveal any signs of fibrosis or inflammatory infiltrates as defined by picrosirius red and H&E staining on myocardial full thickness paraffin sections of both atria and ventricles. Measurements of plasma high‐sensitivity C‐reactive protein and urinary 8‐iso‐prostaglandin F_2α were inconspicuous in all animals. Furthermore, multielectrode surface mapping of the heart did not show any differences in epicardial conduction velocity and heterogeneity. These data demonstrate that chronic ANG II treatment using osmotic minipumps presents a reliable, minimally invasive approach to establish hypertension and nonfibrotic LVH in sheep.

Hearing Loss Controlled by Optogenetic Stimulation of Nonexcitable Nonglial Cells in the Cochlea of the Inner Ear

Light-gated ion channels and transporters have been applied to a broad array of excitable cells including neurons, cardiac myocytes, skeletal muscle cells and pancreatic β-cells in an organism to clarify their physiological and pathological roles. Nonetheless, among nonexcitable cells, only glial cells have been studied in vivo by this approach. Here, by optogenetic stimulation of a different nonexcitable cell type in the cochlea of the inner ear, we induce and control hearing loss. To our knowledge, deafness animal models using optogenetics have not yet been established. Analysis of transgenic mice expressing channelrhodopsin-2 (ChR2) induced by an oligodendrocyte-specific promoter identified this channel in nonglial cells—melanocytes—of an epithelial-like tissue in the cochlea. The membrane potential of these cells underlies a highly positive potential in a K⁺-rich extracellular solution, endolymph; this electrical property is essential for hearing. Illumination of the cochlea to activate ChR2 and depolarize the melanocytes significantly impaired hearing within a few minutes, accompanied by a reduction in the endolymphatic potential. After cessation of the illumination, the hearing thresholds and potential returned to baseline during several minutes. These responses were replicable multiple times. ChR2 was also expressed in cochlear glial cells surrounding the neuronal components, but slight neural activation caused by the optical stimulation was unlikely to be involved in the hearing impairment. The acute-onset, reversible and repeatable phenotype, which is inaccessible to conventional gene-targeting and pharmacological approaches, seems to at least partially resemble the symptom in a population of patients with sensorineural hearing loss. Taken together, this mouse line may not only broaden applications of optogenetics but also contribute to the progress of translational research on deafness.

Cigarette Smoking Attenuates Kidney Protection by Angiotensin-Converting Enzyme Inhibition in Nondiabetic Chronic Kidney Disease

BACKGROUND

Cigarette smoking exacerbates the estimated glomerular filtration rate (eGFR) decline in nondiabetic chronic kidney disease (CKD) despite the kidney protection that is achieved by angiotensin converting enzyme inhibition (ACEI). Whether smoking cessation restores ACEI-related kidney protection is not known.

METHODS

This 5-year, prospective, prevention trial recruited 108 smokers and 108 nonsmokers with stage-2 nondiabetic CKD with primary hypertension and urine albumin-to-creatinine ratio (Ualb) >200 mg/g. All smokers underwent smoking cessation intervention programs. Blood pressure was reduced in all participants toward achieving a goal of <130 mm Hg with regimens including ACEI. The primary outcome was eGFR change, and secondary outcomes included Ualb and urine levels of angiotensinogen (UATG), a surrogate for kidney angiotensin II (AII) levels, and isoprostane 8-isoprostaglandin F2α (U8-iso), an indicator of oxidative stress.

RESULTS

One-year Ualb was lower than baseline in nonsmokers but not in either smoking group, supporting greater ACEI-related kidney protection in nonsmokers than smokers. Higher Ualb at 1 year in continued smokers was associated with higher UATG and higher U8-iso, consistent with smoking-induced AII and increased oxidative stress contributing to less ACEI-related kidney protection in smokers. Baseline eGFR was not different among groups (p = 0.92), but 5-year eGFR was higher in quitters than in continued smokers (62.0 ± 5.4 vs. 52.9 ± 5.6 mL/min/1.73 m2, p < 0.001); this value was lower in quitters than in nonsmokers (64.7 ± 5.6 mL/min/1.73 m2, p = 0.02).

CONCLUSIONS

Smoking cessation compared with continued smoking ameliorates eGFR decline in nondiabetic CKD treated with ACEI, possibly by restoring kidney-protective effects of ACEI through reductions in kidney AII and oxidative stress.

Angiotensin II type 1a receptor-deficient mice develop angiotensin II-induced oxidative stress and DNA damage without blood pressure increase

Hypertensive patients have an increased risk of developing kidney cancer. We have shown in vivo that besides elevating blood pressure, angiotensin II causes DNA damage dose dependently. Here, the role of blood pressure in the formation of DNA damage is studied. Mice lacking one of the two murine angiotensin II type 1 receptor (AT1R) subtypes, AT1aR, were equipped with osmotic minipumps, delivering angiotensin II during 28 days. Parameters of oxidative stress and DNA damage of kidneys and hearts of AT1aR-knockout mice were compared with wild-type (C57BL/6) mice receiving angiotensin II, and additionally, with wild-type mice treated with candesartan, an antagonist of both AT1R subtypes. In wild-type mice, angiotensin II induced hypertension, reduced kidney function, and led to a significant formation of reactive oxygen species (ROS). Furthermore, genomic damage was markedly increased in this group. All these responses to angiotensin II could be attenuated by concurrent administration of candesartan. In AT1aR-deficient mice treated with angiotensin II, systolic pressure was not increased, and renal function was not affected. However, angiotensin II still led to an increase of ROS in kidneys and hearts of these animals. Additionally, genomic damage in the form of double-strand breaks was significantly induced in kidneys of AT1aR-deficient mice. Our results show that angiotensin II induced ROS production and DNA damage even without the presence of AT1aR and independently of blood pressure changes.

Expression of Class I and Class II a/b Histone Deacetylase is Dysregulated in Hypertensive Animal Models

Background and Objectives

Dysregulation of histone deacetylase expression and enzymatic activity is associated with a number of diseases. It has been reported that protein levels of histone deacetylase (HDAC)1 and HDAC5 increase during human pulmonary hypertension, and that the enzymatic activity of HDAC6 is induced in a chronic hypertensive animal model. This study investigated the protein expression profiles of class I and II a/b HDACs in three systemic hypertension models.

Subjects and Methods

We used three different hypertensive animal models: (i) Wistar-Kyoto rats (n=8) and spontaneously hypertensive rats (SHR; n=8), (ii) mice infused with saline or angiotensin II to induce hypertension, via osmotic mini-pump for 2 weeks, and (iii) mice that were allowed to drink L-N^G-nitro-L-arginine methyl ester (L-NAME) to induce hypertension.

Results

SHR showed high systolic, diastolic, and mean blood pressures. Similar increases in systolic blood pressure were observed in angiotensin II or L-NAME-induced hypertensive mice. In SHR, class IIa HDAC (HDAC4, 5, and 7) and class IIb HDAC (HDAC6 and 10) protein expression were significantly increased. In addition, a HDAC3 protein expression was induced in SHR. However, in L-NAME mice, class IIa HDAC protein levels (HDAC4, 5, 7, and 9) were significantly reduced. HDAC8 protein levels were significantly reduced both in angiotensin II mice and in SHR.

Conclusion

These results indicate that dysregulation of class I and class II HDAC protein is closely associated with chronic hypertension.

Transcriptome Pathway Analysis of Pathological and Physiological Aldosterone-Producing Human Tissues

Supplemental Digital Content is available in the text.

Primary aldosteronism is present in ≈10% of hypertensives. We previously performed a microarray assay on aldosterone-producing adenomas and their paired zona glomerulosa and fasciculata. Confirmation of top genes validated the study design and functional experiments of zona glomerulosa selective genes established the role of the encoded proteins in aldosterone regulation. In this study, we further analyzed our microarray data using AmiGO 2 for gene ontology enrichment and Ingenuity Pathway Analysis to identify potential biological processes and canonical pathways involved in pathological and physiological aldosterone regulation. Genes differentially regulated in aldosterone-producing adenoma and zona glomerulosa were associated with steroid metabolic processes gene ontology terms. Terms related to the Wnt signaling pathway were enriched in zona glomerulosa only. Ingenuity Pathway Analysis showed "NRF2-mediated oxidative stress response pathway" and "LPS (lipopolysaccharide)/IL-1 (interleukin-1)–mediated inhibition of RXR (retinoid X receptor) function" were affected in both aldosterone-producing adenoma and zona glomerulosa with associated genes having up to 21- and 8-fold differences, respectively. Comparing KCNJ5-mutant aldosterone-producing adenoma, zona glomerulosa, and zona fasciculata samples with wild-type samples, 138, 56, and 59 genes were differentially expressed, respectively (fold-change >2; P<0.05). ACSS3, encoding the enzyme that synthesizes acetyl-CoA, was the top gene upregulated in KCNJ5-mutant aldosterone-producing adenoma compared with wild-type. NEFM, a gene highly upregulated in zona glomerulosa, was upregulated in KCNJ5 wild-type aldosterone-producing adenomas. NR4A2, the transcription factor for aldosterone synthase, was highly expressed in zona fasciculata adjacent to a KCNJ5-mutant aldosterone-producing adenoma. Further interrogation of these genes and pathways could potentially provide further insights into the pathology of primary aldosteronism.

Measurement of Reactive Oxygen Species, Reactive Nitrogen Species, and Redox-Dependent Signaling in the Cardiovascular System: A Scientific Statement From the American Heart Association

Reactive oxygen species and reactive nitrogen species are biological molecules that play important roles in cardiovascular physiology and contribute to disease initiation, progression, and severity. Because of their ephemeral nature and rapid reactivity, these species are difficult to measure directly with high accuracy and precision. In this statement, we review current methods for measuring these species and the secondary products they generate and suggest approaches for measuring redox status, oxidative stress, and the production of individual reactive oxygen and nitrogen species. We discuss the strengths and limitations of different methods and the relative specificity and suitability of these methods for measuring the concentrations of reactive oxygen and reactive nitrogen species in cells, tissues, and biological fluids. We provide specific guidelines, through expert opinion, for choosing reliable and reproducible assays for different experimental and clinical situations. These guidelines are intended to help investigators and clinical researchers avoid experimental error and ensure high-quality measurements of these important biological species.

Impact of weight loss induced by gastric bypass or caloric restriction on oxidative stress and genomic damage in obese Zucker rats

BACKGROUND

Evidence on bariatric surgery induced weight loss and its possible impact on cancer risk is limited, but also controversial. We used obese Zucker(fa/fa) and lean Zucker(fa/+) to investigate the association between obesity, oxidative stress and genomic damage after weight loss induced either by Roux-en-Y gastric bypass surgery (RYGB) or caloric restriction.

METHODS

Male Zucker(fa/fa) rats underwent RYGB (n=15) or sham surgery (n=17). Five shams were food restricted and body weight matched (BWM) to RYGB. Twelve Zucker(fa/+) rats served as lean controls. Body weight and food intake were measured daily. An oral glucose tolerance test was performed on day 27. DHE staining and western blots of HSP70 and HO-1 were used to evaluate oxidative stress and anti-3-nitrotyrosine antibody staining for nitrative stress detection in colon and kidney. Lipid peroxidation products in urine were quantified by TBARS assay. LC/MS/MS was applied to measure urinary excretion of 8-oxoGua (oxidized DNA derived base), 8-oxodG (oxidized DNA derived nucleoside) and 8-oxoGuo (oxidized RNA derived nucleoside). DNA double strand breaks (DSBs) and cell proliferation (PCNA) were detected by immunohistochemistry.

RESULTS

Sham-operated rats showed impaired glucose tolerance, elevated plasma insulin levels as well as elevated oxidative stress and nitrative stress markers, which were less severe after weight loss by RYGB or caloric restriction. Cell proliferation showed similar trends but no significant alteration. DNA DSBs were more frequent in sham-operated compared to all other groups. DNA damage in Zucker(fa/fa) rats positively correlated with basal plasma insulin values (Spearman's correlation coefficient for colon, 0.634 and for kidney, 0.525).

CONCLUSIONS

RYGB and caloric restriction were sufficient to significantly reduce elevated oxidative/nitrative stress and genomic damage in obese Zucker(fa/fa) rats. Further investigations are needed to elucidate the underlying mechanism of these genome protective effects.

TLR4 mutant mice are protected from renal fibrosis and chronic kidney disease progression

Chronic kidney disease (CKD) is associated with persistent low-grade inflammation and immunosuppression. In this study we tested the role of Toll-like receptor 4, the main receptor for endotoxin (LPS), in a mouse model of renal fibrosis and in a model of progressive CKD that better resembles the human disease. C3HeJ (TLR4 mutant) mice have a missense point mutation in the TLR4 gene, rendering the receptor nonfunctional. In a model of renal fibrosis after folic acid injection, TLR4 mutant mice developed less interstititial fibrosis in comparison to wild-type (WT) mice. Furthermore, 4 weeks after 5/6 nephrectomy with continuous low-dose angiotensin II infusion, C3HeOuJ (TLR4 WT) mice developed progressive CKD with albuminuria, increased serum levels of BUN and creatinine, glomerulosclerosis, and interstitial fibrosis, whereas TLR4 mutant mice were significantly protected from CKD progression. TLR4 WT mice also developed low-grade systemic inflammation, splenocyte apoptosis and increased expression of the immune inhibitory receptor PD-1 in the spleen, which were not observed in TLR4 mutant mice. In vitro, endotoxin (LPS) directly upregulated NLRP3 inflammasome expression in renal epithelial cells via TLR4. In summary, TLR4 contributes to renal fibrosis and CKD progression, at least in part, via inflammasome activation in renal epithelial cells, and may also participate in the dysregulated immune response that is associated with CKD.

Pathogenesis and treatment of the cardiorenal syndrome: Implications of L-arginine-nitric oxide pathway impairment

A highly complex interplay exists between the heart and kidney in the setting of both normal and abnormal physiology. In the context of heart failure, a pathophysiological condition termed the cardiorenal syndrome (CRS) exists whereby dysfunction in the heart or kidney can accelerate pathology in the other organ. The mechanisms that underpin CRS are complex, and include neuro-hormonal activation, oxidative stress and endothelial dysfunction. The endothelium plays a central role in the regulation of both cardiac and renal function, and as such impairments in endothelial function can lead to dysfunction of both these organs. In particular, reduced bioavailability of nitric oxide (NO) is a key pathophysiologic component of endothelial dysfunction. The synthesis of NO by the endothelium is critically dependent on the plasmalemmal transport of its substrate, L-arginine, via the cationic amino acid transporter-1 (CAT1). Impaired L-arginine-NO pathway activity has been demonstrated individually in heart and renal failure. Recent findings suggest abnormalities of the L-arginine-NO pathway also play a role in the pathogenesis of CRS and thus this pathway may represent a potential new target for the treatment of heart and renal failure.

Oxidative DNA damage in kidneys and heart of hypertensive mice is prevented by blocking angiotensin II and aldosterone receptors

Introduction

Recently, we could show that angiotensin II, the reactive peptide of the blood pressure-regulating renin-angiotensin-aldosterone-system, causes the formation of reactive oxygen species and DNA damage in kidneys and hearts of hypertensive mice. To further investigate on the one hand the mechanism of DNA damage caused by angiotensin II, and on the other hand possible intervention strategies against end-organ damage, the effects of substances interfering with the renin-angiotensin-aldosterone-system on angiotensin II-induced genomic damage were studied.

Methods

In C57BL/6-mice, hypertension was induced by infusion of 600 ng/kg • min angiotensin II. The animals were additionally treated with the angiotensin II type 1 receptor blocker candesartan, the mineralocorticoid receptor blocker eplerenone and the antioxidant tempol. DNA damage and the activation of transcription factors were studied by immunohistochemistry and protein expression analysis.

Results

Administration of angiotensin II led to a significant increase of blood pressure, decreased only by candesartan. In kidneys and hearts of angiotensin II-treated animals, significant oxidative stress could be detected (1.5-fold over control). The redox-sensitive transcription factors Nrf2 and NF-κB were activated in the kidney by angiotensin II-treatment (4- and 3-fold over control, respectively) and reduced by all interventions. In kidneys and hearts an increase of DNA damage (3- and 2-fold over control, respectively) and of DNA repair (3-fold over control) was found. These effects were ameliorated by all interventions in both organs. Consistently, candesartan and tempol were more effective than eplerenone.

Conclusion

Angiotensin II-induced DNA damage is caused by angiotensin II type 1 receptor-mediated formation of oxidative stress in vivo. The angiotensin II-mediated physiological increase of aldosterone adds to the DNA-damaging effects. Blocking angiotensin II and mineralocorticoid receptors therefore has beneficial effects on end-organ damage independent of blood pressure normalization.

Renal molecular mechanisms underlying altered Na+ handling and genesis of hypertension during adulthood in prenatally undernourished rats

In the present study, we investigated the development of hypertension in prenatally undernourished adult rats, including the mechanisms that culminate in dysfunctions of molecular signalling in the kidney. Dams were fed a low-protein multideficient diet throughout gestation with or without α-tocopherol during lactation. The time course of hypertension development followed in male offspring was correlated with alterations in proximal tubule Na+-ATPase activity, expression of angiotensin II (Ang II) receptors, and activity of protein kinases C and A. After the establishment of hypertension, Ang II levels, cyclo-oxygenase 2 (COX-2) and NADPH oxidase subunit expression, lipid peroxidation and macrophage infiltration were examined in renal tissue. Lipid peroxidation in undernourished rats, which was very intense at 60 d, decreased at 90 d and returned to control values by 150 d. During the prehypertensive phase, prenatally undernourished rats exhibited elevated renal Na+-ATPase activity, type 2 Ang II receptor down-regulation and altered protein kinase A:protein kinase C ratio. Stable late hypertension coexisted with highly elevated levels of Ang II-positive cells in the cortical tubulointerstitium, enhanced increase in the expression of p47phox (NADPH oxidase regulatory subunit), marked down-regulation of COX-2 expression, expanded plasma volume and decreased creatinine clearance. These alterations were reduced when the dams were given α-tocopherol during lactation. The offspring of well-nourished dams treated with α-tocopherol exhibited most of the alterations encountered in the offspring of undernourished dams not treated with α-tocopherol. Thus, alterations in proximal tubule Na+ transport, subcellular signalling pathways and reactive oxygen species handling in renal tissue underpin the development of hypertension.

Do intravenous and subcutaneous angiotensin II increase blood pressure by different mechanisms?

Angiotensin (Ang) II plays a key role in blood pressure regulation. Mechanisms of the pressor effect of chronic intravenous AngII administration include vasoconstriction, stimulation of the sympathetic nervous system and aldosterone production, as well as direct effects on renal excretion of sodium and water.  Chronic AngII administration by subcutaneous minipump at doses higher than required to increase blood pressure by the intravenous route has identified additional pressor mechanisms, including the immune system, cytokines and matrix metalloproteinases. However, pressor doses of subcutaneous AngII may exceed the angiotensinogen synthesis rate and produce inflammation, fibrosis and necrosis of skin overlying the minipump.  Evidence that chronic subcutaneous and intravenous AngII increase blood pressure by different mechanisms includes the prevention of the pressor effects of subcutaneous, but not intravenous, AngII by angiotensin-converting enzyme inhibition. Furthermore, low doses of subcutaneous AngII reduce blood pressure of female, but not male, rodents and higher doses are less pressor in females than in males, whereas intravenous AngII is equally pressor in males and females.  Pressor doses of chronic subcutaneous AngII produce greater weight loss, anorexia and reduced kidney weight and cause greater vascular, cardiac and renal pathology than equally pressor doses of chronic intravenous AngII.  The different effects of chronic intravenous and subcutaneous AngII suggest that these two models of hypertension give different information and may differ in their relevance to blood pressure regulation in physiological and pathological states such as hypertension in humans.

Reactive oxygen species, vascular Noxs, and hypertension: focus on translational and clinical research

SIGNIFICANCE

Reactive oxygen species (ROS) are signaling molecules that are important in physiological processes, including host defense, aging, and cellular homeostasis. Increased ROS bioavailability and altered redox signaling (oxidative stress) have been implicated in the onset and/or progression of chronic diseases, including hypertension.

RECENT ADVANCES

Although oxidative stress may not be the only cause of hypertension, it amplifies blood pressure elevation in the presence of other pro-hypertensive factors, such as salt loading, activation of the renin-angiotensin-aldosterone system, and sympathetic hyperactivity, at least in experimental models. A major source for ROS in the cardiovascular-renal system is a family of nicotinamide adenine dinucleotide phosphate oxidases (Noxs), including the prototypic Nox2-based Nox, and Nox family members: Nox1, Nox4, and Nox5.

CRITICAL ISSUES

Although extensive experimental data support a role for increased ROS levels and altered redox signaling in the pathogenesis of hypertension, the role in clinical hypertension is unclear, as a direct causative role of ROS in blood pressure elevation has yet to be demonstrated in humans. Nevertheless, what is becoming increasingly evident is that abnormal ROS regulation and aberrant signaling through redox-sensitive pathways are important in the pathophysiological processes which is associated with vascular injury and target-organ damage in hypertension.

FUTURE DIRECTIONS

There is a paucity of clinical information related to the mechanisms of oxidative stress and blood pressure elevation, and a few assays accurately measure ROS directly in patients. Such further ROS research is needed in humans and in the development of adequately validated analytical methods to accurately assess oxidative stress in the clinic.

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.