The immune system and hypertension (original) (raw)
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Proceedings of the National Academy of Sciences, 2007
Calcitonin gene-related peptide (CGRP) is thought to be a prominent neuropeptide in cardiovascular regulation and neuroimmune modulation. There are two isoforms of CGRP (␣CGRP and CGRP), and the main CGRP receptors are probably composed of a calcitonin receptor-like receptor (CLR) and a receptor activity-modifying protein (RAMP)1. However, the physiological functions of CGRP that are mediated through the CLR/RAMP1 receptors remain to be clarified. For an improved understanding of the functions, we generated mice deficient in RAMP1, a specific subunit of CGRP receptors, by a conditional gene-targeting technique. The RAMP1deficient mice (RAMP1 ؊/؊ ) exhibited high blood pressure, with no changes in heart rate. ␣CGRP was found to have a potent vascular relaxant activity compared with CGRP in the artery of the WT (RAMP1 ؉/؉ ) mice. The activities of both CGRP isoforms were remarkably suppressed in the arteries of the RAMP1 ؊/؊ mice. The LPS-induced inflammatory responses of the RAMP1 ؊/؊ mice revealed a transient and significant increase in the serum CGRP levels and high serum levels of proinflammatory cytokines compared with the RAMP1 ؉/؉ mice. ␣CGRP and CGRP equally suppressed the production of TNF-␣ and IL-12 in bone marrow-derived dendritic cells stimulated with lipopolysaccharide. Their inhibitory effects were not observed in the bone marrow-derived dendritic cells of the RAMP1 ؊/؊ mice. These results indicate that CGRP signaling through CLR/RAMP1 receptors plays a crucial role in the regulation of both blood pressure by vascular relaxation and proinflammatory cytokine production from dendritic cells. HR, heart rate; MCP, macrophage chemoattractant protein; RAMP, receptor activitymodifying protein; SBP, systolic blood pressure.
Innate Immune Response in Hypertension
Current Pharmaceutical Design
: Even though an association between inflammation and hypertension has been known for many years, it has not been simple to ascertain the role of several physiological responses involved. The innate immune response plays a critical role in these physiological responses. Innate immune cells can be activated directly by shear stress, activate the inflammasome and produce numerous cytokines and soluble mediators essential in hypertension. NFkB activation is mainly involved in the activation of innate immune cells. Shear stress also stimulates the expression of DAMP and PAMP receptors, enhancing pathogen and danger signals and magnifying inflammation. The adaptative immune response is activated with the increased antigen presentation resulting from the insults mentioned. Chronic inflammation may lead to autoimmunity. Peripheral hypoxia, a consequence of hypertension, activates hypoxia-inducing factors 1-α and 1-β (HIF-1α, HIF-1β), which modulate innate immune cells and promote inflammation. HIF-1α is involved in the upregulation of oxygen and nitrogen radical production proteins. HIF-1β down-regulates antioxidant enzymes. However, the critical evidence of the role of innate immune cells in hypertension came from the results of clinical trials involving therapies blocking inflammatory cytokines and Toll-like receptor expression. Several lines of research have been conducted on this complex disease. Pro-tolerogenic innate immune cells, myeloid suppressor cells, and M2 macrophages may play a crucial role in promoting or resolving inflammation, cardiovascular diseases and hypertension, and should be studied in detail.
Sympathetic-mediated activationversussuppression of the immune system: consequences for hypertension
The Journal of Physiology, 2015
It is generally well-accepted that the immune system is a significant contributor in the pathogenesis of hypertension. Specifically, activated and pro-inflammatory T-lymphocytes located primarily in the vasculature and kidneys appear to have a causal role in exacerbating elevated blood pressure. It has been proposed that increased sympathetic nerve activity and noradrenaline outflow associated with hypertension may be primary contributors to the initial activation of the immune system early in the disease progression. However, it has been repeatedly demonstrated in many different human and experimental diseases that sympathoexcitation is immunosuppressive in nature. Moreover, human hypertensive patients have demonstrated increased susceptibility to secondary immune insults like infections. Thus, it is plausible, and perhaps even likely, that in diseases like hypertension, specific immune cells are activated by increased noradrenaline, while others are in fact suppressed. We propose a model in which this differential regulation is based upon activation status of the immune cell as well as the resident organ. With this, the concept of global immunosuppression is obfuscated as a viable target for hypertension treatment, and we put forth the concept of focused organ-specific immunotherapy as an alternative option.
International Journal of Molecular Sciences, 2021
Essential hypertension (EH) is a highly heterogenous disease with a complex etiology. Recent evidence highlights the significant contribution of subclinical inflammation, triggered and sustained by excessive innate immune system activation in the pathogenesis of the disease. Toll-like receptors (TLRs) have been implied as novel effectors in this inflammatory environment since they can significantly stimulate the production of pro-inflammatory cytokines, the migration and proliferation of smooth muscle cells and the generation of reactive oxygen species (ROS), facilitating a low-intensity inflammatory background that is evident from the very early stages of hypertension. Furthermore, the net result of their activation is oxidative stress, endothelial dysfunction, vascular remodeling, and finally, vascular target organ damage, which forms the pathogenetic basis of EH. Importantly, evidence of augmented TLR expression and activation in hypertension has been documented not only in immun...
Journal of Neuroinflammation, 2015
Background: Despite the availability of several antihypertensive medications, the morbidity and mortality caused by hypertension is on the rise, suggesting the need for investigation of novel signaling pathways involved in its pathogenesis. Recent evidence suggests the role of toll-like receptor (TLR) 4 in various inflammatory diseases, including hypertension. The role of the brain in the initiation and progression of all forms of hypertension is well established, but the role of brain TLR4 in progression of hypertension has never been explored. Therefore, we investigated the role of TLR4 within the paraventricular nucleus (PVN; an important cardioregulatory center in the brain) in an animal model of human essential hypertension. We hypothesized that a TLR4 blockade within the PVN causes a reduction in mean arterial blood pressure (MAP), inflammatory cytokines and sympathetic drive in hypertensive animals. Methods: Spontaneously hypertensive rats (SHR) and normotensive Wistar Kyoto (WKY) rats were administered either a specific TLR4 blocker, viral inhibitory peptide (VIPER), or control peptide in their PVN for 14 days. MAP was recorded continuously by radiotelemetry. PVN and blood were collected for the measurement of pro-inflammatory cytokines (Tumor Necrosis Factor (TNF)-α, interleukin (IL)-1β), anti-inflammatory cytokine IL-10, inducible nitric oxide synthase (iNOS), TLR4, nuclear factor (NF) κB activity and plasma norepinephrine (NE) and high mobility group box (HMGB)1 expression, respectively. Results: Hypertensive rats exhibited significantly higher levels of TLR4 in the PVN. TLR4 inhibition within the PVN attenuated MAP, improved cardiac hypertrophy, reduced TNF-α, IL-1β, iNOS levels, and NFκB activity in SHR but not in WKY rats. These results were associated with a reduction in plasma NE and HMGB1 levels and an increase in IL-10 levels in SHR. Conclusions: This study demonstrates that TLR4 upregulation in PVN plays an important role in hypertensive response. Our results provide mechanistic evidence that hypertensive response in SHR are mediated, at least in part, by TLR4 in the PVN and that inhibition of TLR4 within the PVN attenuates blood pressure and improves inflammation, possibly via reduction in sympathetic activity.
Targeting the immune system to treat hypertension
Current Opinion in Nephrology and Hypertension, 2014
Purpose of review Research over the past decade has significantly deepened our understanding of mechanisms that drive the development of hypertension. In particular, a novel paradigm of inflammation as a common mediator of cardiovascular and kidney disease has emerged. This review will summarize the role of the immune system in cardiovascular disease, explore some of the most promising new therapeutic directions and consider their potential as new treatments for hypertension. Recent findings Recent data continue to demonstrate that targeting the immune system can prevent hypertension in a variety of experimental models. Tempering the enthusiasm for a long-awaited new approach to treating hypertension is decades of clinical data, showing that classic immunosuppression regimens are associated with significant side-effects-including cardiovascular disease-that effectively preclude their use in the setting of chronic hypertension. New, more specific therapies are being developed that target cytokines including IL-17, IL-6 and TNFa.
Vagal-Immune Interactions in the Control of Hypertension
Journal of Neurology & Neuromedicine, 2018
There is a consensus in the literature that the autonomic dysfunction in arterial hypertension involves the increase of sympathetic activity and, also, reduction of vagal tone. In the last years, the role played by inflammation in the development of hypertension and target organs injuries, such as heart and blood vessels, has been emphasized. Although the clinical importance of sympathetic hyperactivity and its treatment of arterial hypertension is recognized, the therapeutic benefit of increasing parasympathetic activity in hypertensive patients still requires an in-depth investigation. The increased vagal activity may produce beneficial effects on cardiovascular modulation and inflammation, preventing target organ damage. Parasympathetic neurotransmission can be improved by the inhibition of acetylcholinesterase action. Anticholinesterase agents prevent the hydrolysis of acetylcholine by acetylcholinesterase, prolonging its availability within the cholinergic cleft. This article will highlight the key concepts of the cardiac autonomic imbalance and the increase of acetylcholine availability under inflammation and control of arterial hypertension. In conclusion, significant evidence exists associating the reduction of parasympathetic activity and the occurrence of inflammation involving the pathophysiology of hypertension; suggesting that the improvement of vagal activity by the increased availability of acetylcholine has a remarkable potential for the therapeutic intervention on arterial hypertension.
The Immunological Basis of Hypertension
American Journal of Hypertension, 2014
A large number of investigations have demonstrated the participation of the immune system in the pathogenesis of hypertension. Studies focusing on macrophages and Toll-like receptors have documented involvement of the innate immunity. The requirements of antigen presentation and co-stimulation, the critical importance of T cell-driven inflammation, and the demonstration, in specific conditions, of agonistic antibodies directed to angiotensin II type 1 receptors and adrenergic receptors support the role of acquired immunity. Experimental findings support the concept that the balance between T cell-induced inflammation and T cell suppressor responses is critical for the regulation of blood pressure levels. Expression of neoantigens in response to inflammation, as well as surfacing of intracellular immunogenic proteins, such as heat shock proteins, could be responsible for autoimmune reactivity in the kidney, arteries, and central nervous system. Persisting, low-grade inflammation in these target organs may lead to impaired pressure natriuresis, an increase in sympathetic activity, and vascular endothelial dysfunction that may be the cause of chronic elevation of blood pressure in essential hypertension.