Angiotensin Type-1 Receptor A1166C Gene Polymorphism Correlates With Oxidative Stress Levels in Human Heart Failure

Non-HLA Antibodies in Kidney Transplantation: Immunity and Genetic Insights

The polymorphic human leukocyte antigen (HLA) system has been considered the main target for alloimmunity, but the non-HLA antibodies and autoimmunity have gained importance in kidney transplantation (KT). Apart from the endothelial injury, secondary self-antigen exposure and the presence of polymorphic alloantigens, respectively, auto- and allo- non-HLA antibodies shared common steps in their development, such as: antigen recognition via indirect pathway by recipient antigen presenting cells, autoreactive T cell activation, autoreactive B cell activation, T helper 17 cell differentiation, loss of self-tolerance and epitope spreading phenomena. Both alloimmunity and autoimmunity play a synergic role in the formation of non-HLA antibodies, and the emergence of transcriptomics and genome-wide evaluation techniques has led to important progress in understanding the mechanistic features. Among them, non-HLA mismatches between donors and recipients provide valuable information regarding the role of genetics in non-HLA antibody immunity and development.

The Potential Therapeutic Role of Celastrol in Patients With Heart Failure With Preserved Ejection Fraction

Analysis of left ventricular systolic dysfunction remained at the centre of heart failure research for many years (also known as heart failure with reduced ejection fraction, HFrEF). Although more than 50% of all heart failure patients experience a form of heart failure characterised by preserved ejection fraction (HFpEF), the pathophysiological mechanisms leading to this form of heart failure remain not well-understood. Several evidence-based treatments for HFrEF are in routine use, but there are limited evidence-based therapies for HFpEF. The effects of these remain controversial, with current treatment options being limited to managing the associated symptoms and conditions. Accumulating evidence demonstrates that pro-inflammatory and oxidative stress pathways play key roles in the development and progression of HFpEF, such as the Unfolded Protein Response (UPR) and inducible nitric oxide synthase. Celastrol, derived from medicinal plants, is a bioactive compound with strong anti-inflammatory properties, which could deem it as fruitful in overcoming the effects of such dysregulated UPR. This literature review therefore focuses on Celastrol's anti-inflammatory and antioxidant activities, alongside its other potential therapeutic activities, and its ability to impede the pathways that are thought to be involved in the development of HFpEF, such as the JAK2/STAT pathway, to elucidate the potential therapeutic role of this bioactive compound, in the treatment of HFpEF.

Anabolic Hormone Deficiencies in Heart Failure with Reduced or Preserved Ejection Fraction and Correlation with Plasma Total Antioxidant Capacity

BACKGROUND

While anabolic hormone deficit is a common finding in heart failure with reduced ejection fraction (HFrEF), few data are available in heart failure with preserved ejection fraction (HFpEF).

METHODS

Blood samples were collected for metabolic (total cholesterol, HDL cholesterol, LDL cholesterol, creatinine, and glucose) and hormonal (IGF-1, DHEA-S, TSH, fT3, fT4, and T) determination, comparing 30 patients with HFpEF and 20 patients with HFrEF. Total antioxidant capacity was evaluated by using the spectrophotometric method using the latency time in the appearance of the radical species of a chromogen (LAG, sec) as a parameter proportional to antioxidant content of the sample. Echocardiographic parameters were also assessed in the two groups.

RESULTS

A high prevalence of testosterone (32% in HFrEF and 72% in HFpEF, p < 0.05) and DHEA-S deficiencies was observed in HFpEF patients. Echocardiographic parameters did not correlate with hormone values. A significant direct correlation between T (r ² = 0.25, p < 0.05) and DHEA-S (r ² = 0.19, p < 0.05) with LAG was observed only in HFpEF.

CONCLUSION

Anabolic hormone deficiency is clearly shown in HFpEF, as already known in HFrEF. Although longitudinal studies are required to confirm the prognostic value of this observation, our data suggest different mechanisms in modulating antioxidants in the two conditions, with possible therapeutic implications.

The association between angiotensin II type 1 receptor A1166C gene polymorphism and the risk of essential hypertension: a meta-analysis

Background

Since first reported having the association with essential hypertension, angiotensin II type 1 receptor (AT1R) A1166C was globally investigated worldwide. However, controversy was found. Furthermore, previous meta-analyses did not adequate to clarify the precise correlation due to some limitations. Therefore, we aimed to perform a meta-analysis concerning the association between AT1R A1166C single-nucleotide polymorphism (SNP) and the risk of essential hypertension with eliminating the limitations of previous studies.

Methods

A meta-analysis was conducted from February to March 2019. Some information related to sample size of hypertension and control groups and genotype frequencies of hypertension and control groups were extracted from each study. Data were analyzed using fixed or random effect model to determine the overall correlation.

Results

A total of 45 papers consisting of 11911 cases and 1340 controls were enrolled for the study. Our overall analysis showed that C allele and AC genotype of AT1R A1166C was associated with 1.18-fold and 1.15-fold respectively increased risk of essential hypertension, while the decreased risk of essential hypertension was observed in A allele and AA genotype. In sub-group analysis, increased risk of essential hypertension was found in C allele, AC genotype, and CC genotype of both Asian population and PCR-RFLP sub-groups, while decreased risk was observed in A allele and AA genotype.

Conclusions

Our meta-analysis reveals that AT1R A1166C remains a valuable SNP having an association with the risk of essential hypertension.

Common pathways and communication between the brain and heart: connecting post-traumatic stress disorder and heart failure

Psychiatric illnesses and cardiovascular disease (CVD) contribute to significant overall morbidity, mortality, and health care costs, and are predicted to reach epidemic proportions with the aging population. Within the Veterans Administration (VA) health care system, psychiatric illnesses such as post-traumatic stress disorder (PTSD) and CVD such as heart failure (HF), are leading causes of hospital admissions, prolonged hospital stays, and resource utilization. Numerous studies have demonstrated associations between PTSD symptoms and CVD endpoints, particularly in the Veteran population. Not only does PTSD increase the risk of HF, but this relationship is bi-directional. Accordingly, a VA-sponsored conference entitled "Cardiovascular Comorbidities in PTSD: The Brain-Heart Consortium" was convened to explore potential relationships and common biological pathways between PTSD and HF. The conference was framed around the hypothesis that specific common systems are dysregulated in both PTSD and HF, resulting in a synergistic acceleration and amplification of both disease processes. The conference was not intended to identify all independent pathways that give rise to PTSD and HF, but rather identify shared systems, pathways, and biological mediators that would be modifiable in both disease processes. The results from this conference identified specific endocrine, autonomic, immune, structural, genetic, and physiological changes that may contribute to shared PTSD-CVD pathophysiology and could represent unique opportunities to develop therapies for both PTSD and HF. Some recommendations from the group for future research opportunities are provided.

Prolonged exposure to hypoxia induces an autophagy-like cell survival program in human neutrophils

Neutrophils contribute to low oxygen availability at inflammatory sites through the generation of reactive oxidants. They are also functionally affected by hypoxia, which delays neutrophil apoptosis. However, the eventual fate of neutrophils in hypoxic conditions is unknown and this is important for their effective clearance and the resolution of inflammation. We have monitored the survival and function of normal human neutrophils exposed to hypoxia over a 48 h period. Apoptosis was delayed, and the cells remained intact even at 48 h. However, hypoxia promoted significant changes in neutrophil morphology with the appearance of many new cytoplasmic vesicles, often containing cell material, within 5 hours of exposure to low O₂ . This coincided with an increase in LC3B-II expression, indicative of autophagosome formation and an autophagy-like process. In hypoxic conditions, neutrophils preferentially lost myeloperoxidase, a marker of azurophil granules. Short-term (2 h) hypoxic exposure resulted in sustained potential to generate superoxide when O₂ was restored, but the capacity for oxidant production was lost with longer periods of hypoxia. Phagocytic ability was unchanged by hypoxia, and bacterial killing by neutrophils in both normoxic and hypoxic conditions was substantially diminished after 24 hours. However, pre-exposure to hypoxia resulted in an enhanced ability to kill bacteria by oxidant-independent mechanisms. Our data provide the first evidence for hypoxia as a driver of neutrophil autophagy that can influence the function and ultimate fate of these cells, including their eventual clearance and the resolution of inflammation.

Myeloperoxidase - A bridge linking inflammation and oxidative stress with cardiovascular disease

Myeloperoxidase (MPO) is a member of the superfamily of heme peroxidases that is mainly expressed in neutrophils and monocytes. MPO-derived reactive species play a key role in neutrophil antimicrobial activity and human defense against various pathogens primarily by participating in phagocytosis. Elevated MPO levels in circulation are associated with inflammation and increased oxidative stress. Multiple lines of evidence suggest an association between MPO and cardiovascular disease (CVD) including coronary artery disease, congestive heart failure, arterial hypertension, pulmonary arterial hypertension, peripheral arterial disease, myocardial ischemia/reperfusion-related injury, stroke, cardiac arrhythmia and venous thrombosis. Elevated MPO levels are associated with a poor prognosis including increased risk for overall and CVD-related mortality. Elevated MPO may signify an increased risk for CVD for at least 2 reasons. First, low-grade inflammation and increased oxidative stress coexist with many metabolic abnormalities and comorbidities and consequently an elevated MPO level may represent an increased cardiometabolic risk in general. Second, MPO produces a large number of highly reactive species which can attack, destroy or modify the function of every known cellular component. The most common MPO actions relevant to CVD are generation of dysfunctional lipoproteins with an increased atherogenicity potential, reduced NO availability, endothelial dysfunction, impaired vasoreactivity and atherosclerotic plaque instability. These actions strongly suggest that MPO is directly involved in the pathophysiology of CVD. In this regard MPO may be seen as a mediator or an instrument through which inflammation promotes CVD at molecular and cellular level. Clinical value of MPO therapeutic inhibition remains to be tested.

Role and therapeutic potential of G-protein coupled receptors in breast cancer progression and metastases

G-protein-coupled receptors (GPCRs) comprise a large family of cell-surface receptors, which have recently emerged as key players in tumorigenesis, angiogenesis and metastasis. In this review, we discussed our current understanding of the many roles played by GPCRs in general, and particularly Angiotensin II type I receptor (AGTR1), a member of the seven-transmembrane-spanning G-protein coupled receptor superfamily, and its significance in breast cancer progression and metastasis. We have also discussed different strategies for targeting AGTR1, and its ligand Angiotension II (Ang II), which might unravel unique opportunities for breast cancer prevention and treatment. For example, AGTR1 blockers (ARBs) which are already in clinical use for treating hypertension, merit further investigation as a therapeutic strategy for AGTR1-positive cancer patients and may have the potential to prevent Ang II-AGTR1 signalling mediated cancer pathogenesis and metastases.

The protective effect of lipoic acid on selected cardiovascular diseases caused by age-related oxidative stress

Oxidative stress is considered to be the primary cause of many cardiovascular diseases, including endothelial dysfunction in atherosclerosis and ischemic heart disease, hypertension, and heart failure. Oxidative stress increases during the aging process, resulting in either increased reactive oxygen species (ROS) production or decreased antioxidant defense. The increase in the incidence of cardiovascular disease is directly related to age. Aging is also associated with oxidative stress, which in turn leads to accelerated cellular senescence and organ dysfunction. Antioxidants may help lower the incidence of some pathologies of cardiovascular diseases and have antiaging properties. Lipoic acid (LA) is a natural antioxidant which is believed to have a beneficial effect on oxidative stress parameters in relation to diseases of the cardiovascular system.

Protein chlorination in neutrophil phagosomes and correlation with bacterial killing

Neutrophils ingest and kill bacteria within phagocytic vacuoles. We investigated where they produce hypochlorous acid (HOCl) following phagocytosis by measuring conversion of protein tyrosine residues to 3-chlorotyrosine. We also examined how varying chloride availability affects the relationship between HOCl formation in the phagosome and bacterial killing. Phagosomal proteins, isolated following ingestion of opsonized magnetic beads, contained 11.4 Cl-Tyr per thousand tyrosine residues. This was 12 times higher than the level in proteins from the rest of the neutrophil and ~6 times higher than previously recorded for protein from ingested bacteria. These results indicate that HOCl production is largely localized to the phagosomes and a substantial proportion reacts with phagosomal protein before reaching the microbe. This will in part detoxify the oxidant but should also form chloramines which could contribute to the killing mechanism. Neutrophils were either suspended in chloride-free gluconate buffer or pretreated with formyl-Met-Leu-Phe, a procedure that has been reported to deplete intracellular chloride. These treatments, alone or in combination, decreased both chlorination in phagosomes and killing of Staphylococcus aureus by up to 50%. There was a strong positive correlation between the two effects. Killing was predominantly oxidant and myeloperoxidase dependent (88% inhibition by diphenylene iodonium and 78% by azide). These results imply that lowering the chloride concentration limits HOCl production and oxidative killing. They support a role for HOCl generation, rather than an alternative myeloperoxidase activity, in the killing process.

Genetic susceptibility to nosocomial pneumonia, acute respiratory distress syndrome and poor outcome in patients at risk of critical illness

Genetic susceptibility may partially explain the clinical variability observed during the course of similar infections. To establish the contribution of genetic host factors in the susceptibility to critical illness, we genotyped 750 subjects (419 at high risk of critical illness) for 14 single nucleotide polymorphisms (SNPs) in the xenobiotics detoxification/oxidative stress and vascular homeostasis metabolic pathways. In the group of nosocomial pneumonia (NP; 268 patients) the risk of acute respiratory distress syndrome (ARDS) is significantly higher for the carriers of CYP1A1 rs2606345 T/T genotypes and AhR rs2066853 G/A-A/A genotypes. AGTR1 rs5186 allele C is more common among NP non-survivors. The duration of stay in intensive care units (ICU) is higher for NP patients with ABCB1 rs1045642-T allele. The cumulative effect of the risk alleles in the genes comprising two sets of genes partners (xenobiotics detoxification: CYP1A1, AhR and RAS family: ACE, AGT, AGTR1) is associated with the development of both NP and ARDS.

Renin-angiotensin-aldosterone system related gene polymorphisms and urinary total arsenic is related to chronic kidney disease

A recent study demonstrated that an increased risk of chronic kidney disease (CKD) was associated with high urinary total arsenic levels. However, whether genomic instability is related to CKD remains unclear. An association between CKD and genetic polymorphisms of regulation enzymes of the renin-angiotensin-aldosterone system (RAAS), such as angiotensin-converting enzyme (ACE), angiotensinogen (AGT), angiotensin II type I receptor (AT1R), and aldosterone synthase (CYP11B2) has not been shown. The aim of the present study was to investigate the relationship between arsenic, genetic polymorphisms of RAAS enzymes and CKD. A total of 233 patients and 449 age- and gender-matched controls were recruited from the Taipei Medical University Hospital, Taipei Municipal Wan Fang Hospital and the Shin Kong Wu Ho-Su Memorial Hospital. Concentrations of urinary arsenic were determined by a high-performance liquid chromatography-linked hydride generator, and atomic absorption spectrometry. Polymorphisms of ACE(I/D), AGT(A[-20]C), (T174M), (M235T), AT1R(A1166C) and CYP11B2(C[-344]T) were examined by polymerase chain reaction and restriction fragment length polymorphism. Subjects carrying the CYP11B2 TT genotype had a higher odds ratio (OR), 1.39 (0.96-2.01), of CKD; while those with the AGT(A[-20]C) CC genotype had an inverse OR of CKD (0.20 (0.05-0.81)), and a high-risk genotype was defined as A/A+A/C for AGT(A[-20C]) and T/T for CYP11B2(C[-344]T). The trend test showed a higher OR for CKD in patients who had either high urinary total arsenic levels or carried the high-risk genotype, or both, compared to patients with low urinary total arsenic levels, who carried the low-risk genotype, and could also be affected by the hypertension or diabetes status.

Influence of the AGTR1 A1166C genotype on the progression of arterial stiffness: A 16-year longitudinal study

BACKGROUND

We examined the influence of the AGTR1 A1166C genotype on the 16-year evolution of pulse wave velocity (PWV) in a middle-aged population. In a cross-sectional study, we reported that the presence of the AGTR1 1166C allele was associated with higher aortic stiffness compared with the AGTR1 1166AA genotype.

METHODS

The study was conducted in 259 subjects who underwent 3 health check-ups over 16 years at the Centre IPC-Paris: an initial visit in 1992-1993, an intermediate visit in 1998-1999, and a final visit in 2007-2008. Aortic stiffness was assessed during the 3 visits by measuring carotid-femoral PWV. AGTR1 A1166C polymorphism was assayed by allele-specific oligonucleotide hybridization.

RESULTS

AGTR1 1166C allele carriers (AC + CC genotypes) had a 35% more pronounced increase in PWV over this 16-year period when compared with the AGTR1 1166AA subjects (3.01 ± 0.32 vs. 1.92 ± 0.23 m/s; P < 0.001). This increase remained significant after adjustment for age, sex, initial PWV values, and changes in blood pressure (+37%; P < 0.05). The genotype-related differences in PWV were only observed at the last visit (i.e., later in life, after the age of 55 years). The effects of this genotype on PWV were not related to the presence of antihypertensive treatment.

CONCLUSIONS

This is the first long-term longitudinal study indicating that AT1 1166C carriers are at increased risk of pronounced arterial stiffening during aging especially after the age of 55.

Angiotensin II and oxidative stress in the failing heart

SIGNIFICANCE

Despite recent medical advances, cardiovascular disease and heart failure (HF) continue to be major health concerns, and related mortality remains high. As a result, investigation of the mechanisms involved in the development of HF continues to be an active field of study.

RECENT ADVANCES

The renin-angiotensin system (RAS) and its effector molecule, angiotensin (Ang) II, affect cardiac function through both systemic and local actions, and have been shown to play a major role in cardiac remodeling and dysfunction in the failing heart. Many of the downstream effects of AngII signaling are mediated by elevated levels of reactive oxygen species (ROS) and oxidative stress, which have also been implicated in the pathology of HF.

CRITICAL ISSUES

Inhibitors of the RAS have proven beneficial in the treatment of patients at risk for and suffering from HF, but remain only partially effective. ROS can be generated from several different sources, and the oxidative state is normally tightly regulated in the heart. How AngII increases ROS levels and causes dysregulation of the cardiac oxidative state has been the subject of considerable interest in recent years.

FUTURE DIRECTIONS

A better understanding of this process and the mechanisms involved should lead to the development of more effective HF therapies and improved outcomes.

Silibinin protects H9c2 cardiac cells from oxidative stress and inhibits phenylephrine-induced hypertrophy: potential mechanisms

Cardiac hypertrophy is the main response of the heart to various extrinsic and intrinsic stimuli, and it is characterized by specific molecular and phenotypic changes. Recent in vitro and in vivo studies indicate the involvement of reactive oxygen species in the hypertrophic response. In this study, silibinin, a plant flavonolignan extracted from milk thistle with potent antioxidant activity, was evaluated for its effects in (a) preventing hydrogen peroxide (H2O2)-induced cellular damage and (b) blocking the phenylephrine-induced hypertrophic response. Using the in vitro model of embryonic rat heart-derived H9c2 cells, we showed that silibinin has a rather safe profile as concentrations up to 200μM did not affect cell viability. Pretreatment of H9c2 cells with silibinin resulted in better protection of H9c2 cells under conditions of H2O2-induced cellular stress compared to untreated cells as indicated by cell viability and DNA fragmentation assays. Furthermore, silibinin attenuated the phenylephrine-induced hypertrophic response as evidenced by the measurement of cell surface, up-regulation of atrial natriuretic peptide and increase of cellular protein levels. Moreover, silibinin repressed the phenylephrine-induced phosphorylation of ERK1/2 kinases, while it appeared to inhibit the weakly activated by phenylephrine phosphorylation of Akt. Based on our results, silibinin may attenuate the phenylephrine-induced hypertrophic response of H9c2 cells via antioxidant mechanisms involving mainly the inhibition of the intracellular signaling pathways mediated by ERK1/2 MAPKs and Akt.

Cardiovascular redox and ox stress proteomics

SIGNIFICANCE

Oxidative post-translational modifications (OPTMs) have been demonstrated as contributing to cardiovascular physiology and pathophysiology. These modifications have been identified using antibodies as well as advanced proteomic methods, and the functional importance of each is beginning to be understood using transgenic and gene deletion animal models. Given that OPTMs are involved in cardiovascular pathology, the use of these modifications as biomarkers and predictors of disease has significant therapeutic potential. Adequate understanding of the chemistry of the OPTMs is necessary to determine what may occur in vivo and which modifications would best serve as biomarkers.

RECENT ADVANCES

By using mass spectrometry, advanced labeling techniques, and antibody identification, OPTMs have become accessible to a larger proportion of the scientific community. Advancements in instrumentation, database search algorithms, and processing speed have allowed MS to fully expand on the proteome of OPTMs. In addition, the role of enzymatically reversible OPTMs has been further clarified in preclinical models.

CRITICAL ISSUES

The identification of OPTMs suffers from limitations in analytic detection based on the methodology, instrumentation, sample complexity, and bioinformatics. Currently, each type of OPTM requires a specific strategy for identification, and generalized approaches result in an incomplete assessment.

FUTURE DIRECTIONS

Novel types of highly sensitive MS instrumentation that allow for improved separation and detection of modified proteins and peptides have been crucial in the discovery of OPTMs and biomarkers. To further advance the identification of relevant OPTMs in advanced search algorithms, standardized methods for sample processing and depository of MS data will be required.

Cellular dysfunction in diabetes as maladaptive response to mitochondrial oxidative stress

Oxidative stress has been implicated in diabetes long-term complications. In this paper, we summarize the growing evidence suggesting that hyperglycemia-induced overproduction of superoxide by mitochondrial electron transport chain triggers a maladaptive response by affecting several metabolic and signaling pathways involved in the pathophysiology of cellular dysfunction and diabetic complications. In particular, it is our goal to describe physiological mechanisms underlying the mitochondrial free radical production and regulation to explain the oxidative stress derived from a high intracellular glucose concentration and the resulting maladaptive response that leads to a cellular dysfunction and pathological state. Finally, we outline potential therapies for diabetes focused to the prevention of mitochondrial oxidative damage.

A polymorphic miR-155 binding site in AGTR1 is associated with cardiac hypertrophy in Friedreich ataxia

Friedreich ataxia (FRDA) is an autosomal recessive neurodegenerative condition with a heterogeneous cardiac phenotype caused primarily by an expanded GAA trinucleotide repeat in the frataxin gene (FXN). FXN is important in mitochondrial iron efflux, sensitivity to oxidative stress, and cell death. The number of GAA repeats on the smaller FXN allele (GAA1) only accounts for a portion of the observed variability in cardiac phenotype. Genetic modifying factors, such as single nucleotide polymorphisms (SNPs) in genes of the Renin-Angiotensin-Aldosterone system (RAAS), may contribute to phenotype variability. This study investigated genetic variability in the angiotensin-II type-1 receptor (AGTR1), angiotensin-converting enzyme (ACE), and ACE2 genes as cardiac phenotype modifying factors in FRDA patients. Comprehensive review of the AGTR1, ACE and ACE2 genes identified twelve haplotype tagging SNPs. Correlation of these SNPs with left ventricular internal diameter in diastole (LVIDd), interventricular septal wall thickness (SWT) and left ventricular mass (LVM) was examined in a large Australian FRDA cohort (n=79) with adjustments performed for GAA repeats, age, sex, body surface area and diastolic blood pressure. A significant inverse relationship was observed between GAA1 and LVIDd (p=0.010) but not with SWT or LVM after adjustment for covariates. The AGTR1 polymorphism rs5186 was more common in FRDA patients than in a control population (p=0.002). Using a recessive model of inheritance, the C allele of rs5186 was associated with a significant increase in SWT (p=0.003) and LVM (p=0.001). This functional polymorphism increases expression of AGTR1 by altering the binding site for miR-155, a regulatory microRNA. No significant associations with left ventricular structure were observed for the remaining RAAS polymorphisms. The AGTR1 polymorphism rs5186 appears to modify the FRDA cardiac phenotype independently of GAA1. This study supports the role of RAAS polymorphisms as modifiers of cardiac phenotype in FRDA patients.

Trisomy-21 gene dosage over-expression of miRNAs results in the haploinsufficiency of specific target proteins

Down syndrome (DS) or Trisomy 21 (Ts21) is caused by the presence of an extra copy of all or part of human chromosome 21 (Hsa21) and is the most frequent survivable congenital chromosomal abnormality. Bioinformatic annotation has established that Hsa21 harbors more than 400 genes, including five microRNA (miRNA) genes (miR-99a, let-7c, miR-125b-2, miR-155, and miR-802). MiRNAs are endogenous, single-stranded, small non-coding RNA molecules that regulate gene expression by interacting with specific recognition elements harbored within the 3'-untranslated region (3'-UTR) of mRNAs and subsequently target these mRNAs for translational repression or destabilization. MiRNA expression profiling, miRNA RT-PCR, and miRNA in situ hybridization experiments have demonstrated that Hsa21-derived miRNAs were over-expressed in fetal brain and heart specimens isolated from individuals with DS. We now propose that Ts21 gene dosage over-expression of Hsa21-derived miRNAs in DS individuals result in the decreased expression of specific target proteins (i.e. haploinsufficiency) that contribute, in part, to the DS phenotype.

Cardiovascular Disease, Single Nucleotide Polymorphisms; and the Renin Angiotensin System: Is There a MicroRNA Connection?

Essential hypertension is a complex disorder, caused by the interplay between many genetic variants, gene-gene interactions, and environmental factors. Given that the renin-angiotensin system (RAS) plays an important role in blood pressure (BP) control, cardiovascular regulation, and cardiovascular remodeling, special attention has been devoted to the investigation of single-nucleotide polymorphisms (SNP) harbored in RAS genes that may be associated with hypertension and cardiovascular disease. MicroRNAs (miRNAs) are a family of small, ∼21-nucleotide long, and nonprotein-coding RNAs that recognize target mRNAs through partial complementary elements in the 3′-untranslated region (3′-UTR) of mRNAs and inhibit gene expression by targeting mRNAs for translational repression or destabilization. Since miRNA SNPs (miRSNPs) can create, destroy, or modify miRNA binding sites, this review focuses on the hypothesis that transcribed target SNPs harbored in RAS mRNAs, that alter miRNA gene regulation and consequently protein expression, may contribute to cardiovascular disease susceptibility.

MicroRNAs miR-124 and miR-135a are potential regulators of the mineralocorticoid receptor gene (NR3C2) expression

MicroRNAs (miRNAs) comprise a post-transcriptional layer of gene regulation shown to be involved in diverse physiological processes. We aimed to study whether regulatory networks that determine susceptibility to hypertension may involve a miRNA component. Screening of loci, involved in renal water–salt balance regulation, highlighted the mineralocorticoid receptor gene NR3C2 as a potential target for several miRNAs. A luciferase assay demonstrated that miR-124 and miR-135a suppress NR3C2 3′UTR reporter construct activity 1.5- and 2.2-fold, respectively. As the tested miRNAs did not reduce the levels of target mRNA, we suggest that the binding of miR-124 and miR-135a to NR3C2 3′UTR contributes to the translational, not transcriptional regulation of the gene. Co-expression of two different miRNAs did not increase the repression of the reporter gene, indicating no additive or synergistic effects between the tested miRNAs.

Our results demonstrate that by repressing the mineralocorticoid receptor gene NR3C2, miR-124 and miR-135a could participate in the regulation of renin–angiotensin–aldosterone system and thereby might be involved in blood pressure regulation.

Genetic polymorphisms of the angiotensin II type 1 receptor gene and diastolic heart failure

OBJECTIVES

The aim of the study was to investigate the association between angiotensin II type 1 receptor (AGTR1) gene polymorphisms and diastolic heart failure (DHF) in a case controlled study.

METHODS

Of 1752 consecutive patients analyzed, 176 diagnosed with DHF and confirmed by echocardiography were recruited. Controls were matched one-to-one by age, sex, hypertension, diabetes, renal function, and medication use. We genotyped 11 single nucleotide polymorphisms (SNPs) according to the HapMap Han Chinese Beijing databank across the AGTR1 gene to capture 96% of the haplotype variance in all SNPs with minor allele frequencies at least 5%. We also genotyped A1166C (rs5186) SNP with known associations with cardiovascular disease and analyzed associations of SNPs and haplotypes with DHF and linkage disequilibrium structure of the AGTR1 gene.

RESULTS

In a single locus analysis, SNP rs16860760, rs389566, and rs5186 were associated with DHF (allele specific P = 0.004, 0.002, 0.002, respectively; permuted P = 0.045, 0.022, 0.027, respectively). SNP rs389566, with a minor allele frequency of 20.17%, had an odds ratio (OR) 2.03 for the autosomal dominant model [AA + AT: TT, 95% confidence interval (CI) 1.29-3.19; P = 0.0012] and 1.73 for the additive model (95% CI 1.21-2.48; P = 0.0018) corresponding to a population attributable risk fraction of 27.21%. The haplotypes in a linkage disequilibrium block of rs389566 (T-A-G and A-A-G) were also significantly associated with DHF (permuted P = 0.0125 and 0.0105, respectively).

CONCLUSION

We identified risk-conferring genetic variants of the AGTR1 gene for DHF in a Chinese population.

Independent and combined influence of AGTR1 variants and aerobic exercise on oxidative stress in hypertensives

Abstract Angiotensin II (AngII), via the AngII type 1 receptor (AT(1)R), contributes to oxidative stress. Aerobic exercise training (AEXT) reduces the risk of cardiovascular (CV) disease, presumably by reducing the grade of oxidative stress. We investigated the independent and combined influence of the AGTR1 A1166C and -825 T/A polymorphisms on oxidative stress and plasma AngII responses to AEXT in pre- and stage 1 hypertensives. Urinary 8-iso-PGF(2alpha) significantly increased with AEXT (p=0.002); however, there were no significant changes in superoxide dismutase activity or AngII levels. There was a significant difference in the change in AngII levels with AEXT between A1166C genotype groups (p=0.04) resulting in a significant interactive effect of the A1166C polymorphism and AEXT on the change in AngII (p<0.05). Only the TT genotype group of the -825 T/A polymorphism had a significant reduction in plasma AngII (p=0.02). Risk allele analysis revealed a significant reduction in plasma AngII (p=0.04) and a significant increase in urinary 8-iso-PGF(2alpha) (p=0.01) with AEXT in individuals with two risk alleles only. Our findings suggest that variation in the AGTR1 gene is associated with differential changes in plasma AngII but not oxidative stress.

The common G-866A polymorphism of the UCP2 gene and survival in diabetic patients following myocardial infarction

Background

A variant in the promoter of the human uncoupling protein 2 (UCP2) gene, the G-866A polymorphism, has been associated with future risk of coronary heart disease events, in those devoid of traditional risk factors and in those suffering from diabetes. We thus examined the impact of the G-866A polymorphism on 5-year survival in a cohort of 901 post-myocardial infarction patients, and the impact of type-2 diabetes on this relationship. The association of UCP2 with baseline biochemical and hormonal measurements, including levels of the inflammatory marker myeloperoxidase, was also examined.

Methods

UCP2 G-866A genotypes were determined using a polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) protocol. Myeloperoxidase levels were measured in plasma samples taken from 419 cohort patients 24–96 hours after admission.

Results

Genotypes were obtained for 901 patients with genotype frequencies AA 15.5%, GA 45.5%, and GG 39.0%. Genotype was not associated with survival in the overall cohort (mortality: AA 15.6%, GA 16.8%, GG 19.4%, p = 0.541). However, amongst diabetics, AA and GA genotype groups had significantly worse survival than GG diabetic patients (p < 0.05) with an attributable risk of 23.3% and 18.7% for those of AA and GA genotype respectively. Multivariate analysis using a Cox proportional hazards model confirmed that the interaction of diabetes with genotype was significantly predictive of survival (p = 0.031). In the cohort's diabetic subgroup AA/GA patients had higher myeloperoxidase levels than their GG counterparts (GA/AA, n = 51, 63.9 ± 5.23; GG, n = 34, 49.1 ± 3.72 ng/ml, p = 0.041). Further analysis showed that this phenomenon was confined to male patients (GA/AA, n = 36, 64.3 ± 6.23; GG, n = 29, 44.9 ± 3.72 ng/ml, p = 0.015).

Conclusion

Diabetic patients in this post-myocardial infarction cohort with UCP2 -866 AA/GA genotype have poorer survival and higher myeloperoxidase levels than their GG counterparts.

Effects of oral contraception with ethinylestradiol and drospirenone on oxidative stress in women 18-35 years old

BACKGROUND

Oral contraceptives (OCs) with estrogens and progestins may affect oxidative stress (OS) status.

STUDY DESIGN

A group of 32 women using oral contraceptives (OCU) containing 0.03 mg ethinylestradiol and 3 mg drospirenone have been compared to a matched control group of 30 noncontraception users (NCU). Blood levels of antioxidants, trace elements and markers of lipid peroxidation were assessed by biochemical methods. A microarray analysis of whole blood mRNA levels of 200 genes involved in OS-dependant pathway was also performed.

RESULTS

Levels of zinc, vitamin E and antibodies to oxidized low-density lipoproteins (LDLs) were not significantly different between the two groups. On the other hand, significant increases in the mean levels of lipid peroxides (+176%, p<.001), oxidized LDLs (+145%, p<.002), copper (+103%, p<.001), Cu/Zn ratio (+100%, p<.001) and a significant decrease in the mean level of beta-carotene (-41%, p<.01) were observed in the OCU compared to NCU. There was a highly significant positive correlation between the lipid peroxide levels and the copper-to-zinc ratio. From the 200 genes tested by microarray, one coding for HSP70 was significantly up-regulated (log(2) fold change=+ 0.45, p<.02) and one coding for inducible nitric oxide synthase significantly down-regulated (log(2) fold change=-0.24, p<.05) in the OCU compared to the NCU.

CONCLUSIONS

The recently introduced combination of ethinylestradiol and drospirenone induced the heightening of lipid peroxidation correlated with high levels of copper, a situation that could be associated with increased cardiovascular risk.

Effects of Darbepoetin Alfa on plasma mediators of oxidative and nitrosative stress in anemic patients with chronic heart failure secondary to ischemic or idiopathic dilated cardiomyopathy

Increased oxidative and nitrosative stress are important mediators of left ventricular (LV) and vascular dysfunction in patients with chronic heart failure (CHF). This study investigated the effects of darbepoetin alfa on plasma markers of oxidative and nitrosative stress in patients with CHF with anemia. Thirty patients with CHF (LV ejection fraction [LVEF] <40%, hemoglobin <12.5 g/dl, and serum creatinine <2.5 mg/dl) were randomly assigned (1:1) to receive either a 3-month darbepoetin alfa regimen at 1.5 microg/kg every 20 days plus oral iron or placebo plus oral iron. Plasma B-type natriuretic peptide (BNP), markers of oxidative (oxidative, malondialdehyde, carbonyl proteins; antioxidative, glutathione) and nitrosative (nitrotyrosine) stress, LVEF, and 6-minute walked distance were assessed at baseline and after treatment. A significant improvement in LVEF and 6-minute walked distance was observed in only darbepoetin-treated patients. Plasma BNP (F = 14.8, p = 001), malondialdehyde (F = 9.4, p = 0.006), protein carbonyl (F = 9.2, p = 0.006), and nitrotyrosine (F = 4.4, p = 0.045) were significantly decreased, along with an increase in antioxidative glutathione (F = 4.2, p = 0.049) after darbepoetin alfa treatment. These factors were unaffected in placebo-treated patients. Darbepoetin-induced percentages of change in carbonyl protein significantly correlated with respective changes in plasma BNP (r = 0.55, p <0.05) and LVEF (r = -0.46, p <0.05). Finally, a drug-induced percentage of decrease in nitrotyrosine significantly correlated with the respective improvement in 6-minute walked distance (r = -0.63, p <0.05). In conclusion, darbepoetin alfa attenuated deleterious effects of oxidative and nitrosative stress into the cardiovascular system of anemic patients with CHF, improving also cardiac function and exercise capacity.

Up-and-coming markers: myeloperoxidase, a novel biomarker test for heart failure and acute coronary syndrome application?

Myeloperoxidase (MPO) is a mammalian enzyme responsible for generation of hypochlorite. The advantage of myeloperoxidase for use as a biomarker in the setting of heart failure and acute coronary syndrome is the early increase of MPO concentration in response to the acute event. In the setting of heart failure the reported independency of coronary artery disease and general inflammation, as indicated by MPO concentration in comparison to other inflammatory markers or in subgroups of patients with ischemic and non-ischemic cardiomyopathy, has to be highlighted. In terms of ACS, inclusion of MPO into a multiple marker strategy might add to enhance diagnosis and therapy decision making. Therefore, MPO is a biomarker worthwhile of further evaluation in the setting of cardiovascular disease.

Pharmacogenetics of heart failure: evidence, opportunities, and challenges for cardiovascular pharmacogenomics

Heart failure is a significant medical problem affecting more than five million people in the USA alone. Although clinical trials of pharmacological agents have demonstrated significant reductions in the relative risk of mortality across populations, absolute mortality remains high. In addition, individual variation in response is great. Some of this variation may be explained by genetic polymorphism. In this paper, we review the key studies to date in heart failure pharmacogenetics, setting this against a background of recent progress in the genetics of warfarin metabolism. Several polymorphisms that have supporting molecular and clinical data in the heart failure literature are reviewed, among them the beta1-adrenergic receptor variant Arg389Gly and the angiotensin converting enzyme gene insertion/deletion polymorphism. These variants and others are responsible for a fraction of the total variation seen in the treatment response to heart failure. With the dawn of the genomic age, further pharmacogenetic and new pharmacogenomic studies will advance our ability to tailor the treatment of heart failure.

A1166C polymorphism of the angiotensin AT1 receptor (AT1R) gene alters endothelial response to statin treatment

BACKGROUND

The function of vascular endothelium is influenced by several factors: low-density lipoprotein (LDL) cholesterol, oxidative stress and the reninangiotensin system.

METHODS

We tested the hypothesis that polymorphisms A1166C of the angiotensin AT1 receptor (AT1R) gene, C242T and A640G of the pphox22 gene (p22 phox is an essential component of NADH/NADPH oxidases) and G894T of the endothelial nitric oxide (NO) synthase (eNOS) gene influence endothelial function and its reaction to statin treatment. In 44 patients with coronary artery disease or hypercholesterolemia (not on lipid-lowering treatment), lipid profile and endothelial function (brachial artery flow-mediated dilation, FMD) were measured at baseline and after treatment with statins for 8-12 weeks. All subjects were genotyped for the above-mentioned polymorphisms.

RESULTS

None of the polymorphisms significantly predicted baseline FMD. Patients with the C allele of A1166C showed smaller changes in FMD in comparison with patients with the AA genotype (-0.044+/-0.439% vs. 0.386+/-0.599%; p=0.016). None of the other polymorphisms significantly influenced changes in FMD.

CONCLUSIONS

The C allele of AT1R A1166C is associated with significantly lower endothelial response to statin treatment.

The human angiotensin II type 1 receptor +1166 A/C polymorphism attenuates microRNA-155 binding

The adverse effects of angiotensin II (Ang II) are primarily mediated through the Ang II type 1 receptor (AT1R). A silent polymorphism (+1166 A/C) in the human AT1R gene has been associated with cardiovascular disease, possibly as a result of enhanced AT(1)R activity. Because this polymorphism occurs in the 3'-untranslated region of the human AT1R gene, the biological importance of this mutation has always been questionable. Computer alignment demonstrated that the +1166 A/C polymorphism occurred in a cis-regulatory site, which is recognized by a specific microRNA (miRNA), miR-155. miRNAs are noncoding RNAs that silence gene expression by base-pairing with complementary sequences in the 3'-untranslated region of target RNAs. When the +1166 C-allele is present, base-pairing complementarity is interrupted, and the ability of miR-155 to interact with the cis-regulatory site is decreased. As a result, miR-155 no longer attenuates translation as efficiently as demonstrated by luciferase reporter and Ang II radioreceptor binding assays. In situ hybridization experiments demonstrated that mature miR-155 is abundantly expressed in the same cell types as the AT1R (e.g. endothelial and vascular smooth muscle). Finally, when human primary vascular smooth muscle cells were transfected with an antisense miR-155 inhibitor, endogenous human AT1R expression and Ang II-induced ERK1/2 activation were significantly increased. Taken together, our study demonstrates that the AT1R and miR-155 are co-expressed and that miR-155 translationally represses the expression of AT1R in vivo. Therefore, our study provides the first feasible biochemical mechanism by which the +1166 A/C polymorphism can lead to increased AT1R densities and possibly cardiovascular disease.

Plasma Concentrations of Myeloperoxidase Predict Mortality After Myocardial Infarction

OBJECTIVES

This study investigated relationships between plasma myeloperoxidase (MPO), protein oxidation markers, and clinical outcome retrospectively in patients after acute myocardial infarction (MI).

BACKGROUND

Reactive oxidants are implicated in cardiovascular disease, and elevated plasma MPO is reported to predict adverse outcome in acute coronary syndromes.

METHODS

Detailed demographic information, radionuclide ventriculography, neurohormone measurements, and clinical history were obtained for 512 acute MI patients at hospital admission. Plasma levels of MPO and protein carbonyls were measured in patients and 156 heart-healthy control subjects. 3-chlorotyrosine was measured in selected patients. Patient mortality was followed for 5 years.

RESULTS

Plasma MPO and protein carbonyl concentrations were higher in MI patients 24 h to 96 h after admission than in control subjects (medians: MPO 55 ng/ml vs. 39 ng/ml, and protein carbonyls 48 pmol/mg vs. 17 pmol/mg protein, p < 0.001 for each). Both markers were significantly correlated with each other and with cardiovascular hormone levels. Chlorotyrosine was not elevated in patients with high MPO or carbonyl levels. Above-median levels of MPO but not protein carbonyls were independently predictive of mortality (odds ratio 1.8, 95% confidence interval 1.0 to 3.0, p = 0.034). Patients with above-median MPO levels in combination with above-median plasma amino-terminal pro-brain natriuretic peptide (NT-proBNP) or below-median left ventricular ejection fraction (LVEF) had significantly greater mortality compared with other patients.

CONCLUSIONS

Myeloperoxidase and protein carbonyl levels are elevated in plasma after acute MI, apparently via independent mechanisms. High MPO is a risk factor for long-term mortality and adds prognostic value to LVEF and plasma NT-proBNP measurements.