Milestone Papers on Signal Transduction Mechanisms of Hypertension and Its Complications.

To celebrate 100 years of American Heart Association-supported cardiovascular disease research, this review article highlights milestone papers that have significantly contributed to the current understanding of the signaling mechanisms driving hypertension and associated cardiovascular disorders. This article also includes a few of the future research directions arising from these critical findings. To accomplish this important mission, 4 principal investigators gathered their efforts to cover distinct yet intricately related areas of signaling mechanisms pertaining to the pathogenesis of hypertension. The renin-angiotensin system, canonical and novel contractile and vasodilatory pathways in the resistance vasculature, vascular smooth muscle regulation by membrane channels, and noncanonical regulation of blood pressure and vascular function will be described and discussed as major subjects.

Reprogramming endothelial and vascular smooth muscle cells to prevent and treat hypertension.

The major pathophysiological characteristic of hypertension is the occurrence of small artery remodeling and endothelial dysfunction. There is also solid evidence showing that microcirculation abnormalities occur prior to the onset of hypertension. However, the mechanism(s) that trigger these changes prior to the elevation of blood pressure are unknown, and this may limit our ability to identify the cause of this disease and effectively treat it. In hypertension, as with aging, the vasculature becomes less susceptible to repair. One of the reasons is because endothelial cells start to deteriorate and present with exacerbated endothelial-to-mesenchymal transition (EndMT). Likewise, vascular smooth muscle cells (VSMC) also dedifferentiate into a synthetic phenotype, whereby they start to produce and secrete extracellular vesicles with a high migration and proliferation capacity for repairing vascular injury. Uncontrolled EndMT and/or VSMC phenotype switching contributes to vascular diseases, but the initial trigger for these conditions is unidentified. Importantly, EndMT and synthetic VSMC exhibit plasticity and can return to adopt an endothelial cell-like fate and present contractile phenotype again, respectively. Therefore, in this hypothesis we will take advantage of this plasticity, and we propose to manipulate this fate by inducing partial cellular reprogramming without passing through the pluripotent state. Specifically, we suggest that activation of the three master transcription factors, Oct-4, Sox-2, and Klf-4 (collectively termed OSK) will reprogram endothelial cells and prevent and reduce EndMT and VSMC synthetic phenotype. It was recently shown that activation of OSK was able to restore lost vision in old mice, and cancer risk was reduced by excluding c-Myc. Therefore, OSK treatment could provide new possibilities for vascular rejuvenation and treatment of hypertension.

Soluble and insoluble protein aggregates, endoplasmic reticulum stress, and vascular dysfunction in Alzheimer's disease and cardiovascular diseases.

Dementia refers to a particular group of symptoms characterized by difficulties with memory, language, problem-solving, and other thinking skills that affect a person's ability to perform everyday activities. Alzheimer's disease (AD) is the most common form of dementia, affecting about 6.2 million Americans aged 65 years and older. Likewise, cardiovascular diseases (CVDs) are a major cause of disability and premature death, impacting 126.9 million adults in the USA, a number that increases with age. Consequently, CVDs and cardiovascular risk factors are associated with an increased risk of AD and cognitive impairment. They share important age-related cardiometabolic and lifestyle risk factors, that make them among the leading causes of death. Additionally, there are several premises and hypotheses about the mechanisms underlying the association between AD and CVD. Although AD and CVD may be considered deleterious to health, the study of their combination constitutes a clinical challenge, and investigations to understand the mechanistic pathways for the cause-effect and/or shared pathology between these two disease constellations remains an active area of research. AD pathology is propagated by the amyloid ß (Aß) peptides. These peptides give rise to small, toxic, and soluble Aß oligomers (SPOs) that are nonfibrillar, and it is their levels that show a robust correlation with the extent of cognitive impairment. This review will elucidate the interplay between the effects of accumulating SPOs in AD and CVDs, the resulting ER stress response, and their role in vascular dysfunction. We will also address the potential underlying mechanisms, including the possibility that SPOs are among the causes of vascular injury in CVD associated with cognitive decline. By revealing common mechanistic underpinnings of AD and CVD, we hope that novel experimental therapeutics can be designed to reduce the burden of these devastating diseases. Graphical abstract Alzheimer's disease (AD) pathology leads to the release of Aß peptides, and their accumulation in the peripheral organs has varying effects on various components of the cardiovascular system including endoplasmic reticulum (ER) stress and vascular damage. Image created with BioRender.com.

Vasoconstrictor and hemodynamic effects of a methanolic extract from Rhinella marina toad poison.

Rhinella marina toad is abundant in Brazil. Its poison contains cardiac glycosides called bufadienolides, which are extensively investigated for their bioactivity. Our aim was to characterize the vasoactivity of Rhinella marina poison (RmP) on the aorta of male Wistar rats. For this, the RmP was first collected and processed to obtain an alcoholic extract. To determine cardiovascular effects of RmP, we performed in vivo tests by administering RmP intravenously in doses of 0.1-0.8 mg/kg. Vascular reactivity was also performed through concentration-response curves to RmP (10 ng/mL to 200 µg/mL) in aortic segments with and without endothelium. RmP induced a concentration-dependent contraction in rat aorta which was partly endothelium-mediated. Nitric oxide contributes with this response in view that incubation with L-NAME increased the contractile response. Additionally, treatment with indomethacin [cyclooxygenase, (COX) inhibitor], nifedipine (L-type voltage-gated calcium channels blocker), and BQ-123 (ETA receptors antagonist) decreased maximum response, and ketanserin (5-HT2 receptors antagonist) decreased pEC50, suggesting active participation of these pathways in the contractile response. On the other hand, apocynin (NADPH oxidase inhibitor) did not alter contractility. Incubation with prazosin (α1-adrenergic receptor antagonist) abolished the contractile response, suggesting that the RmP-induced contraction is dependent on the adrenergic pathway. In the Na+/K+ ATPase protocol, a higher Emax was observed in the RmP experimental group, suggesting that RmP potentiated Na+/K+ATPase hyperpolarizing response. When this extract was injected (i.v.) in vivo, increase in blood pressure and decrease in heart rate were observed. The results were immediate and transitory, and occurred in a dose-dependent manner. Overall, these data suggest that the poison extract of R. marina toad has an important vasoconstrictor action and subsequent vasopressor effects, and its use can be investigated to some cardiovascular disorders.

Intrinsic Exercise Capacity and Mitochondrial DNA Lead to Opposing Vascular-Associated Risks.

Exercise capacity is a strong predictor of all-cause morbidity and mortality in humans. However, the associated hemodynamic traits that link this valuable indicator to its subsequent disease risks are numerable. Additionally, exercise capacity has a substantial heritable component and genome-wide screening indicates a vast amount of nuclear and mitochondrial DNA (mtDNA) markers are significantly associated with traits of physical performance. A long-term selection experiment in rats confirms a divide for cardiovascular risks between low- and high-capacity runners (LCR and HCR, respectively), equipping us with a preclinical animal model to uncover new mechanisms. Here, we evaluated the LCR and HCR rat model system for differences in vascular function at the arterial resistance level. Consistent with the known divide between health and disease, we observed that LCR rats present with resistance artery and perivascular adipose tissue dysfunction compared to HCR rats that mimic qualities important for health, including improved vascular relaxation. Uniquely, we show by generating conplastic strains, which LCR males with mtDNA of female HCR (LCR-mtHCR/Tol) present with improved vascular function. Conversely, HCR-mtLCR/Tol rats displayed indices for cardiac dysfunction. The outcome of this study suggests that the interplay between the nuclear genome and the maternally inherited mitochondrial genome with high intrinsic exercise capacity is a significant factor for improved vascular physiology, and animal models developed on an interaction between nuclear and mtDNA are valuable new tools for probing vascular risk factors in the offspring.

TRPM8 channel activation triggers relaxation of pudendal artery with increased sensitivity in the hypertensive rats.

INTRODUCTION: Erectile dysfunction (ED) is frequently encountered in patients with arterial hypertension and there is a recent functional correlation between the expression of thermoreceptor channels TRPM8 (melastatin 8) and alterations in blood pressure in hypertension. The aim of this study was to investigate the function of cold-sensing TRPM8 channel in internal pudendal artery (IPA) in both normotensive and hypertensive rats. METHODS: We performed experiments integrating physiological, pharmacological, biochemical and cellular techniques. RESULTS: TRPM8 channels are expressed in the IPA and in vascular smooth muscle cells from IPA. In addition, TRPM8 activation, by both a cooling compound icilin (82.1 ±â€¯3.0%, n = 6) and cold temperature [thermal stimulus, basal tone (25 °C, 41.2 ±â€¯3.4%, n = 5) or pre-contracted tone induced by phenylephrine (25 °C, 87.0 ±â€¯3.6%, n = 7)], induced relaxation in IPA. Furthermore, the results showed that the concentration-response curve to icilin was significantly shifted to the right in different conditions, such as: the absence of the vascular endothelium, in the presence of L-NAME (10-4 M), or indomethacin (10-5 M) or by a combination of charybdotoxin (10-7 M) and apamin (5 × 10-6 M), and Y27632 (10-6 M). Interestingly, icilin-induced vasodilation was significantly higher in IPA from spontaneously hypertensive (SHR, E10-4M = 75.3 ±â€¯1.7%) compared to wistar rats (E10-4M = 56.4 ±â€¯2.6%), despite no changes in the TRPM8 expression in IPA between the strains, suggesting that the sensitivity of TRPM8 channels is higher in SHR. CONCLUSIONS: These data demonstrate for the first time, the expression and function of TRPM8 channels in the IPA involving, at least in part, endothelium-derived relaxing factors and ROCK inhibition. Overall, this channel could potentially be a new target for the treatment of hypertension associated-ED.

Targeting Endothelial Barrier Dysfunction Caused by Circulating Bacterial and Mitochondrial N-Formyl Peptides With Deformylase.

Despite recent advances in our understanding of the mechanisms underlying systemic inflammatory response syndrome (SIRS) and sepsis, the current therapeutic approach to these critically ill patients is centered around supportive care including fluid resuscitation, vasopressors and source control. The incidence of SIRS and sepsis continues to increase in the United States and patients die due to failure to respond to the traditional therapies of nitric oxide blockade, adrenergic agonists, etc. Bacterial and mitochondrial N-formyl peptides (NFPs) act as damage-associated molecular patterns and activate the innate immune system through formyl peptide receptors (FPR) located in immune and non-immune cells, including the vascular endothelium. The resulting inflammatory response manifests as capillary leak, tissue hypoperfusion and vasoplegia, partially due to endothelium barrier breakdown. Potential strategies to prevent this response include decreasing NFP release, breakdown of NFPs, and blocking NFPs from binding FPR. We propose the use of deformylase, the degrading enzyme for NFPs, as potential therapeutic approach to prevent the deleterious effects of NFPs in SIRS and sepsis.

Mitochondrial N-formyl peptides cause airway contraction and lung neutrophil infiltration via formyl peptide receptor activation.

Respiratory failure is a common characteristic of systemic inflammatory response syndrome (SIRS) and sepsis. Trauma and severe blood loss cause the release of endogenous molecules known as damage-associated molecular patterns (DAMPs). Mitochondrial N-formyl peptides (F-MITs) are DAMPs that share similarities with bacterial N-formylated peptides, and are potent immune system activators. Recently, we observed that hemorrhagic shock-induced increases in plasma levels of F-MITs associated with lung damage, and that antagonism of formyl peptide receptors (FPR) ameliorated hemorrhagic shock-induced lung injury in rats. Corroborating these data, in the present study, it was observed that F-MITs expression is higher in plasma samples from trauma patients with SIRS or sepsis when compared to control trauma group. Therefore, to better understand the role of F-MITs in the regulation of lung and airway function, we studied the hypothesis that F-MITs lead to airway contraction and lung inflammation. We observed that F-MITs induced concentration-dependent contraction in trachea, bronchi and bronchioles. However, pre-treatment with mast cells degranulator or FPR antagonist decreased this response. Finally, intratracheal challenge with F-MITs increased neutrophil elastase expression in lung and inducible nitric oxide synthase and cell division control protein 42 expression in all airway segments. These data suggest that F-MITs could be a putative target to treat respiratory failure in trauma patients.

Mitochondrial N-formyl peptides induce cardiovascular collapse and sepsis-like syndrome.

Fifty percent of trauma patients who present sepsis-like syndrome do not have bacterial infections. This condition is known as systemic inflammatory response syndrome (SIRS). A unifying factor of SIRS and sepsis is cardiovascular collapse. Trauma and severe blood loss cause the release of endogenous molecules known as damage-associated molecular patterns. Mitochondrial N-formyl peptides (F-MIT) are damage-associated molecular patterns that share similarities with bacterial N-formylated peptides and are potent immune system activators. The goal of this study was to investigate whether F-MIT trigger SIRS, including hypotension and vascular collapse via formyl peptide receptor (FPR) activation. We evaluated cardiovascular parameters in Wistar rats treated with FPR or histamine receptor antagonists and inhibitors of the nitric oxide pathway before and after F-MIT infusion. F-MIT, but not nonformylated peptides or mitochondrial DNA, induced severe hypotension via FPR activation and nitric oxide and histamine release. Moreover, F-MIT infusion induced hyperthermia, blood clotting, and increased vascular permeability. To evaluate the role of leukocytes in F-MIT-induced hypotension, neutrophil, basophil, or mast cells were depleted. Depletion of basophils, but not neutrophils or mast cells, abolished F-MIT-induced hypotension. Rats that underwent hemorrhagic shock increased plasma levels of mitochondrial formylated proteins associated with lung damage and antagonism of FPR ameliorated hemorrhagic shock-induced lung injury. Finally, F-MIT induced vasodilatation in isolated resistance arteries via FPR activation; however, F-MIT impaired endothelium-dependent relaxation in the presence of blood. These data suggest that F-MIT may be the link among trauma, SIRS, and cardiovascular collapse.

Inhalation of fine particulate matter during pregnancy increased IL-4 cytokine levels in the fetal portion of the placenta.

This study aimed to verify the development of placental and systemic inflammation in rats exposed to fine particulate matter before or during pregnancy. Wistar rats were exposed to filtered air (control) or to a load of 600 µg/m(3) of fine particles in the air. The gene expression of IL-1ß, IL-4, IL-6, IL-10, INF-γ, TNF-α and Toll-like receptor 4 in the placenta was evaluated. The serum and placental concentrations of IL-1ß, IL-4, IL-6, IL-10, INF-γ and TNF-α were measured. The total and differential blood leukocyte and blood platelet count was assessed. Compared to control animals, IL-4 content was elevated in the fetal portion of the placenta in rats exposed to air pollution before and during pregnancy. Increased IL-4 suggests that a placental inflammatory reaction may have occurred in response to exposure to fine particulate matter and that this cytokine was responsible, among possibly others factors, for resolution of the inflammatory reaction.

Enhanced Na⁺, K⁺-ATPase activity and endothelial modulation decrease phenylephrine-induced contraction in aorta from ouabain-treated normotensive and hypertensive rats.

AIM: The purpose of this study was to compare the effect of long-term ouabain treatment on the vascular reactivity and Na+, K+-ATPase activity of a conductance artery from normotensive and hypertensive rats. METHODS: Male Wistar rats were treated with ouabain (~8.0 µg/day, subcutaneously) or vehicle for 5 and 20 weeks, and spontaneously hypertensive rats (SHRs) for 5 weeks. Vasoconstrictor response to phenylephrine (10-10 to 10-4 M) and relaxation curves to KCl (1-10 mM) were analyzed in thoracic aorta. The effects of endothelial removal, L-NAME (100 µM), and indomethacin (10 µM) were used to evaluate the endothelial, nitric oxide (NO), and cyclooxygenase (COX) modulation of phenylephrine response, respectively. Protein expression of endothelial and neuronal NO synthase (NOS) and COX-2 were also investigated. RESULTS: The phenylephrine-induced contraction was reduced, whereas the relaxation to KCl was enhanced in the aorta of ouabain-treated Wistar rats and SHRs. In both strains, endothelial modulation of α-adrenergic response was enhanced, related to an increased NO and reduced COX-derived vasoconstrictor factor modulation. Aortas from 20-week ouabain-treated Wistar rats showed reduced COX-2 and enhanced eNOS protein expression. In SHRs, 5-week ouabain treatment reduced COX-2 and increased nNOS protein expression. CONCLUSIONS: The results suggest that long-term ouabain treatment reduces the α-adrenergic response of aorta from normotensive rats and SHRs, associated with an increase of NO synthesis, reduced COX-2-derived vasoconstrictor factors, and enhanced ouabain-sensitive Na+, K+-ATPase activity. These aortic mechanisms could be adjustments to the elevated blood pressure induced by ouabain, even in the presence of preexisting hypertension.

Mitochondrial damage-associated molecular patterns and vascular function.

Immune system activation occurs not only due to foreign stimuli, but also due to endogenous molecules. As such, endogenous molecules that are released into the circulation due to cell death and/or injury alarm the immune system that something has disturbed homeostasis and a response is needed. Collectively, these molecules are known as damage-associated molecular patterns (DAMPs). Mitochondrial DAMPs (mtDAMPs) are potent immunological activators due to the bacterial ancestry of mitochondria. Mitochondrial DAMPs are recognized by specific pattern recognition receptors of the innate immune system, some of which are expressed in the cardiovascular system. Cell death leads to release of mtDAMPs that may induce vascular changes by mechanisms that are currently not well understood. This review will focus on recently published evidence linking mtDAMPs and immune system activation to vascular dysfunction and cardiovascular disease.

Long-term ouabain treatment impairs vascular function in resistance arteries.

BACKGROUND/AIMS: The purpose of this study was to examine the cardiovascular effects of long-term ouabain treatment at different time points. METHODS: Systolic blood pressure (SBP) was measured by tail-cuff method in male Wistar rats treated with ouabain (approx. 8.0 µg·day(-1)) or vehicle for 5, 10 and 20 weeks. Afterwards, vascular function was assessed in mesenteric resistance arteries (MRA) using a wire myograph. ROS production and COX-1 and COX-2, TNF-α, and IL-6 protein expression were investigated. RESULTS: SBP was increased by ouabain treatment up to the 6th week and remained stable until the 20th week. However, noradrenaline-induced contraction increased only in MRA in rats treated with ouabain for 20 weeks. NOS inhibition and endothelium removal increased the noradrenaline response, but to a smaller magnitude in MRA in the ouabain group. Moreover, inhibition of COX-2 or incubation with superoxide dismutase restores noradrenaline-induced contraction in the 20-week ouabain group to control levels. ROS production as well as COX-2, IL-6 and TNF-α protein expression increased in MRA in this group. CONCLUSION: Although ouabain treatment induced hypertension in all groups, a larger noradrenaline induced contraction was observed over 20 weeks of treatment. This vascular dysfunction was related to COX-2-derived prostanoids and oxidative stress, increased pro- inflammatory cytokines and reduced NO bioavailability.