Toll-like receptors and damage-associated molecular patterns: novel links between inflammation and hypertension

Antagonism of major histocompatibility complex class II invariant chain peptide during chronic lipopolysaccharide treatment rescues autoregulatory behavior

Toll-like receptor 4 (TLR4) activation contributes to vascular dysfunction in pathological conditions such as hypertension and diabetes, but the role of chronic TLR4 activation on renal autoregulatory behavior is unknown. We hypothesized that subclinical TLR4 stimulation with low-dose lipopolysaccharide (LPS) infusion increases TLR4 activation and blunts renal autoregulatory behavior. We assessed afferent arteriolar autoregulatory behavior in male Sprague-Dawley rats after prolonged LPS (0.1 mg·kg^-1·day^-1 sq) infusion via osmotic minipump for 8 or 14 days. Some rats also received daily cotreatment with either anti-TLR4 antibody (1 μg ip), competitive antagonist peptide (CAP; 3 mg/kg ip) or tempol (2 mmol/l, drinking water) throughout the 8-day LPS treatment period. Autoregulatory behavior was assessed using the in vitro blood-perfused juxtamedullary nephron preparation. Selected physiological measures, systolic blood pressure and baseline diameters were normal and similar across groups. Pressure-dependent vasoconstriction averaged 72 ± 2% of baseline in sham rats, indicating intact autoregulatory behavior. Eight-day LPS-treated rats exhibited significantly impaired pressure-mediated vasoconstriction (96 ± 1% of baseline), whereas it was preserved in rats that received anti-TLR4 antibody (75 ± 3%), CAP (84 ± 2%), or tempol (82 ± 2%). Using a 14-day LPS (0.1 mg·kg^-1·day^-1 sq) intervention protocol, CAP treatment started on day 7, where autoregulatory behavior is already impaired. Systolic blood pressures were normal across all treatment groups. Fourteen-day LPS treatment retained the autoregulatory impairment (95 ± 2% of baseline). CAP intervention starting on day 7 rescued pressure-mediated vasoconstriction with diameters decreasing to 85 ± 1% of baseline. These data demonstrate that chronic subclinical TLR4 activation impairs afferent arteriolar autoregulatory behavior through mechanisms involving reactive oxygen species and major histocompatibility complex class II activation.

Bioinformatics analysis of gene expression profile data to screen key genes involved in intracranial aneurysms

Intracranial aneurysm (IA) is a cerebrovascular disease with a high mortality rate. The pathogenesis of IA remains unclear and the treatment limited. The purpose of the present study was to identify the key genes expressed in IAs and provide the basis for further research and treatment. The raw dataset GSE75436 was downloaded from Gene Expression Omnibus, including 15 IA samples and 15 matched superficial temporal artery (STA) samples. Then, differentially expressed genes (DEGs) were identified using the limma package in R software. Hierarchical clustering analysis was performed on the DEGs using the gplot2 package in R. Database for Annotation, Visualization, and Integrated Discovery (DAVID) online tools were used to perform gene ontology (GO) functional enrichment analysis. DAVID and gene set enrichment analysis were separately used to perform the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses. The intersections of the two results were selected as common KEGG pathways. Protein-protein interaction (PPI) analysis among the DEGs involved in the common KEGG pathways was performed using Search Tool for the Retrieval of Interacting Genes online tools, and visualized with Cytoscape software. A total of 782 DEGs were identified, comprising 392 upregulated and 390 downregulated DEGs. Hierarchical clustering demonstrated that the DEGs could precisely distinguish the IAs from the STAs. The GO enrichment analysis demonstrated that the upregulated DEGs were mainly involved in the inflammatory response and the management of extracellular matrix, and the downregulated DEGs were mainly involved in the process of vascular smooth muscle contraction. The KEGG pathway enrichment analysis demonstrated that the common pathways were ‘leishmaniasis’, ‘Toll-like receptor signaling pathway’ and ‘vascular smooth muscle contraction’. In the PPI network, tumor necrosis factor (TNF), interleukin 8 and Toll-like receptor 4 had the highest degrees; they were associated with the inflammatory response. The Toll-like receptor signaling pathway and TNF gene may serve as targets for future research and treatment.

Hypertension: a new treatment for an old disease? Targeting the immune system

Arterial hypertension represents a serious public health problem, being a major cause of morbidity and mortality worldwide. The availability of many antihypertensive therapeutic strategies still fails to adequately treat around 20% of hypertensive patients, who are considered resistant to conventional treatment. In the pathogenesis of hypertension, immune system mechanisms are activated and both the innate and adaptive immune responses play a crucial role. However, what, when and how the immune system is triggered during hypertension development is still largely undefined. In this context, this review highlights scientific advances in the manipulation of the immune system in order to attenuate hypertension and end-organ damage. Here, we discuss the potential use of immunosuppressants and immunomodulators as pharmacological tools to control the activation of the immune system, by non-specific and specific mechanisms, to treat hypertension and improve end-organ damage. Nevertheless, more clinical trials should be performed with these drugs to establish their therapeutic efficacy, safety and risk-benefit ratio in hypertensive conditions. LINKED ARTICLES: This article is part of a themed section on Immune Targets in Hypertension. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.12/issuetoc.

C-Reactive Protein Promotes Inflammation through FcγR-Induced Glycolytic Reprogramming of Human Macrophages

C-reactive protein (CRP) is an acute-phase protein produced in high quantities by the liver in response to infection and during chronic inflammatory disorders. Although CRP is known to facilitate the clearance of cell debris and bacteria by phagocytic cells, the role of CRP in additional immunological functions is less clear. This study shows that complexed CRP (phosphocholine [PC]:CRP) (formed by binding of CRP to PC moieties), but not soluble CRP, synergized with specific TLRs to posttranscriptionally amplify TNF, IL-1β, and IL-23 production by human inflammatory macrophages. We identified FcγRI and IIa as the main receptors responsible for initiating PC:CRP-induced inflammation. In addition, we identified the underlying mechanism, which depended on signaling through kinases Syk, PI3K, and AKT2, as well as glycolytic reprogramming. These data indicate that in humans, CRP is not only a marker but also a driver of inflammation by human macrophages. Therefore, although providing host defense against bacteria, PC:CRP-induced inflammation may also exacerbate pathology in the context of disorders such as atherosclerosis.

Gut Microbiota Disorder, Gut Epithelial and Blood-Brain Barrier Dysfunctions in Etiopathogenesis of Dementia: Molecular Mechanisms and Signaling Pathways

Emerging evidences indicate a critical role of the gut microbiota in etiopathogenesis of dementia, a debilitating multifactorial disorder characterized by progressive deterioration of cognition and behavior that interferes with the social and professional functions of the sufferer. Available data suggest that gut microbiota disorder that triggers development of dementia is characterized by substantial reduction in specific species belonging to the Firmicutes and Bacteroidetes phyla and presence of pathogenic species, predominantly, pro-inflammatory bacteria of the Proteobacteria phylum. These changes in gut microbiota microecology promote the production of toxic metabolites and pro-inflammatory cytokines, and reduction in beneficial substances such as short chain fatty acids and other anti-inflammatory factors, thereby, enhancing destruction of the gut epithelial barrier with concomitant activation of local and distant immune cells as well as dysregulation of enteric neurons and glia. This subsequently leads to blood-brain barrier dysfunctions that trigger neuroinflammatory reactions and predisposes to apoptotic neuronal and glial cell death, particularly in the hippocampus and cerebral cortex, which underlie the development of dementia. However, the molecular switches that control these processes in the histo-hematic barriers of the gut and brain are not exactly known. This review integrates very recent data on the molecular mechanisms that link gut microbiota disorder to gut epithelial and blood-brain barrier dysfunctions, underlying the development of dementia. The signaling pathways that link gut microbiota disorder with impairment in cognition and behavior are also discussed. The review also highlights potential therapeutic options for dementia.

Comparative Transcriptomics Reveals the Role of the Toll-Like Receptor Signaling Pathway in Fluoride-Induced Cardiotoxicity

Many studies have shown that fluorosis due to long-term fluoride intake has damaging effects on the heart. However, the mechanisms underlying cardiac fluorosis have not been illuminated in detail. We performed high-throughput transcriptome sequencing (RNA-Seq) on rat cardiac tissue to explore the molecular effects of NaF exposure. In total, 372 and 254 differentially expressed genes (DEGs) were identified between a group given 30 mg/L NaF and control and between a group given 90 mg/L NaF and control, respectively. The transcript levels of most of these genes were significantly down-regulated and many were distributed in the Toll-like receptor signaling pathway. Transcriptome analysis revealed that herpes simplex infection, ECM-receptor interaction, influenza A, cytokine-cytokine receptor interaction, apoptosis, and Toll-like receptor signaling pathway were significantly affected. IL-6 and IL-10 may play a crucial role in the cardiac damage caused by NaF as external stimuli according to protein-protein interaction (PPI) network analysis. The results of qRT-PCR and Western blotting showed a marked decreased mRNA and protein levels of IL-1, IL-6, and IL-10 in the low concentration fluoride (LF) and high concentration fluoride (HF) groups, which was in agreement with RNA-Seq results. This is the first study to investigate NaF-induced cardiotoxicity at a transcriptome level.

Effects of pre-hatch thermal manipulation and post-hatch acute heat stress on the mRNA expression of interleukin-6 and genes involved in its induction pathways in 2 broiler chicken breeds

In response to heat stress, interleukin-6 (IL-6) expression is upregulated in broiler chickens. The main aim of the present study was to evaluate the cumulative effects of thermal manipulation (TM) and subsequent acute heat stress (AHS) on the mRNA expression of IL-6 and genes involved in its induction pathways. The studied genes include IL-6, IL-1β, TNF-α, TLR2, TLR4, NFκB50, NFκB65, Hsp70, and HSF3 in the spleen and liver tissues. TM was carried out at 39°C for 18 h and 65% relative humidity during days 10 to 18 of embryonic development, while AHS was stimulated by raising the temperature to 40°C for 7 h on post-hatch day 28. During AHS at 0, 1, 3, 5, and 7 h, the spleen and liver were collected from all groups to measure the mRNA expression by relative-quantitation real-time RT-PCR, and the blood was collected to measure plasma IL-6 level. TM significantly reduced Tc during AHS for both breeds from 1 to 7 h time intervals. TM resulted in enhanced basal mRNA expression of IL-6, HSF3, and Hsp70, but decreased the basal mRNA level of TLR4. During heat stress, TM enhanced the expression dynamics of Hsp70, HSF3, IL-6, IL-1β, TNF-α, TLR2, TLR4, NFκB50, and NFκB65. The results of the current study indicate that TM enhanced the heat tolerance through improving the protective immunological response to heat stress by enhancing the expression of IL-6 and modulating the expression of genes important in its induction pathways.

Genetic disruption of Npr1 depletes regulatory T cells and provokes high levels of proinflammatory cytokines and fibrosis in the kidneys of female mutant mice

The present study was designed to determine the effects of gene knockout of guanylyl cyclase/natriuretic peptide receptor-A (GC-A/NPRA) on immunogenic responses affecting kidney function and blood pressure (BP) in Npr1 (coding for GC-A/NPRA)-null mutant mice. We used female Npr1 gene-disrupted (Npr1^-/-, 0 copy), heterozygous (Npr1^+/-, 1 copy), wild-type (Npr1^+/+, 2 copy), and gene-duplicated (Npr1^++/++, 4 copy) mice. Expression levels of Toll-like receptor (TLR)2/TLR4 mRNA were increased 4- to 5-fold in 1-copy mice and 6- to 10-fold in 0-copy mice; protein levels were increased 2.5- to 3-fold in 1-copy mice and 4- to 5-fold in 0-copy mice. Expression of proinflammatory cytokines and BP was significantly elevated in 1-copy and 0-copy mice compared with 2-copy and 4-copy mice. In addition, 0-copy and 1-copy mice exhibited drastic reductions in regulatory T cells (Tregs). After rapamycin treatment, Tregs were increased by 17% (P < 0.001) in 0-copy mice and 8% (P < 0.001) in 1-copy mice. Renal mRNA and protein levels of TLR2 and TLR4 were decreased by 70% in 0-copy mice and 50% in 1-copy mice. There were significantly higher levels of Tregs and very low levels of TLR2/TLR4 expression in 4-copy mice (P < 0.001). These findings indicate that the disruption of Npr1 in female mice triggers renal immunogenic pathways, which transactivate the expression of proinflammatory cytokines and renal fibrosis with elevated BP in mutant animals. The data suggest that rapamycin treatment attenuates proinflammatory cytokine expression, dramatically increases anti-inflammatory cytokines, and substantially reduces BP and renal fibrosis in mutant animals.

Lactobacillus rhamnosus GG strain mitigated the development of obstructive sleep apnea-induced hypertension in a high salt diet via regulating TMAO level and CD4+ T cell induced-type I inflammation

Obstructive sleep apnea (OSA) and high salt content in modern diet has been particularly implicated in systemic hypertension, leading to increased morbidity and mortality. Gut dysbiosis, associated with increased risk of systemic immunological imbalance, plays a causal role in the development of cardiovascular diseases. Here, we investigated the effect of Lactobacillus rhamnosus GG strain (LGG) on the development of hypertension induced by OSA and high salt diet. In this study, hypertension was modeled in rats by feeding a high salt diet (HSD) for 6 wk and exposuring to chronic intermittent hypoxia (CIH) during the sleep cycle. We found that OSA combined with HSD increased the severity of hypertension through increasing level of blood Trimethylamine-Oxide (TMAO), release of Th1-related cytokine (IFN-γ) and inhibition of anti-inflammatory cytokine (TGF-β1), and affected the gut microbiome in rats, particularly by depleting Lactobacillus. In addition, expression of PERK1/2, PAkt and PmTOR increased in the aorta from rats with a CIH exposure and HSD. Consequently, treatment of model rats with LGG prevented aggravation of hypertension by reducing blood TMAO levels, modulating Th1/Th2 cytokine imbalance and suppressing phosphorylation levels of ERK1/2, Akt and mTOR. In line with these findings, our results connect high salt diet to the gut-immune axis and highlight the gut microbiome as a potential therapeutic target to counteract the development of OSA-induced hypertension basing on a high salt diet.

Recent clinical trends in Toll-like receptor targeting therapeutics

Toll‐like receptors (TLRs) are germline‐encoded receptors that are central to innate and adaptive immune responses. Owing to their vital role in inflammation, TLRs are rational targets in clinics; thus, many ligands and biologics have been reported to overcome the progression of various inflammatory and malignant conditions and support the immune system. For each TLR, at least one, and often many, drug formulations are being evaluated. Ligands reported as stand‐alone drugs may also be reported based on their use in combinatorial therapeutics as adjuvants. Despite their profound efficacy in TLR‐modulation in preclinical studies, multiple drugs have been terminated at different stages of clinical trials. Here, TLR modulating drugs that have been evaluated in clinical trials are discussed, along with their mode of action, suggestive failure reasons, and ways to improve the clinical outcomes. This review presents recent advances in TLR‐targeting drugs and provides directions for more successful immune system manipulation.

Mechanisms of isolevuglandin-protein adduct formation in inflammation and hypertension

Inflammation has been implicated in the pathogenesis of hypertension and recent evidence suggests that isolevuglandin (IsoLG)-protein adducts play a role. Several hypertensive stimuli contribute to formation of IsoLG-protein adducts including excess dietary salt and catecholamines. The precise intracellular mechanisms by which these hypertensive stimuli lead to IsoLG-protein adduct formation are still not well understood; however, there is now evidence implicating NADPH-oxidase derived reactive oxygen species (ROS) in this process. ROS oxidize arachidonic acid leading to formation of IsoLGs, which non-covalently adduct to lysine residues and alter protein structure and function. Recent studies suggest that these altered proteins act as neo-antigens leading to an autoimmune state that results in hypertension. The goal of this mini-review is to highlight some of the hypertensive stimuli and the mechanisms contributing to IsoLG-protein adduct formation leading to inflammation and hypertension.

Effects of Acute and Chronic Exercise on Immunological Parameters in the Elderly Aged: Can Physical Activity Counteract the Effects of Aging?

Immunosenescence is characterized by deterioration of the immune system caused by aging which induces changes to innate and adaptive immunity. Immunosenescence affects function and phenotype of immune cells, such as expression and function of receptors for immune cells which contributes to loss of immune function (chemotaxis, intracellular killing). Moreover, these alterations decrease the response to pathogens, which leads to several age-related diseases including cardiovascular disease, Alzheimer's disease, and diabetes in older individuals. Furthermore, increased risk of autoimmune disease and chronic infection is increased with an aging immune system, which is characterized by a pro-inflammatory environment, ultimately leading to accelerated biological aging. During the last century, sedentarism rose dramatically, with a concomitant increase in certain type of cancers (such as breast cancer, colon, or prostate cancer), and autoimmune disease. Numerous studies on physical activity and immunity, with focus on special populations (i.e., people with diabetes, HIV patients) demonstrate that chronic exercise enhances immunity. However, the majority of previous work has focused on either a pathological population or healthy young adults whilst research in elderly populations is scarce. Research conducted to date has primarily focused on aerobic and resistance exercise training and its effect on immunity. This review focuses on the potential for exercise training to affect the aging immune system. The concept is that some lifestyle strategies such as high-intensity exercise training may prevent disease through the attenuation of immunosenescence. In this context, we take a top-down approach and review the effect of exercise and training on immunological parameters in elderly at rest and during exercise in humans, and how they respond to different modes of training. We highlight the impact of these different exercise modes on immunological parameters, such as cytokine and lymphocyte concentration in elderly individuals.

Inflammation as a Regulator of the Renin-Angiotensin System and Blood Pressure

PURPOSE OF REVIEW

Mechanisms facilitating progression of hypertension via cross stimulation of the renin-angiotensin system (RAS) and inflammation have been proposed. Accordingly, we review and update evidence for regulation of RAS components by pro-inflammatory factors.

RECENT FINDINGS

Angiotensin II (Ang II), which is produced by RAS, induces vasoconstriction and consequent blood pressure elevation. In addition to this direct action, chronically elevated Ang II stimulates several pathophysiological mechanisms including generation of oxidative stress, stimulation of the nervous system, alterations in renal hemodynamics, and activation of the immune system. In particular, an activated immune system has been shown to contribute to the development of hypertension. Recent studies have demonstrated that immune cell-derived pro-inflammatory cytokines regulate RAS components, further accelerating systemic and local Ang II formation. Specifically, regulation of angiotensinogen (AGT) production by pro-inflammatory cytokines in the liver and kidney is proposed as a key mechanism underlying the progression of Ang II-dependent hypertension.

Toll-like receptors signaling network in pre-eclampsia: An updated review

Toll-like receptors (TLRs) are innate immune cells receptors. They are expressed on leukocytes, epithelial cells, and more particularly on placental immune cells and chorion trophoblast. Upregulation of innate immune response occurs during normal pregnancy, but its excessive activity is involved in the pathology of pregnancy complications including pregnancy-induced hypertension and pre-eclampsia (PE). The recent studies about the overmuch inflammatory responses and aberrant placentation are associated with increased expression of TLRs in PE patients. This review has tried to focus on the relationship between some activities of TLRs and the risk of preeclampsia development.

Current Perspectives and Mechanisms of Relationship between Intestinal Microbiota Dysfunction and Dementia: A Review

BACKGROUND

Accumulating data suggest a crucial role of the intestinal microbiota in the development and progression of neurodegenerative diseases. More recently, emerging reports have revealed an association between intestinal microbiota dysfunctions and dementia, a debilitating multifactorial disorder, characterized by progressive deterioration of cognition and behavior that interferes with the social and professional life of the sufferer. However, the mechanisms of this association are not fully understood.

SUMMARY

In this review, I discuss recent data that suggest mechanisms of cross-talk between intestinal microbiota dysfunction and the brain that underlie the development of dementia. Potential therapeutic options for dementia are also discussed. The pleiotropic signaling of the metabolic products of the intestinal microbiota together with their specific roles in the maintenance of both the intestinal and blood-brain barriers as well as regulation of local, distant, and circulating immunocytes, and enteric, visceral, and central neural functions are integral to a healthy gut and brain.

KEY MESSAGES

Research investigating the effect of intestinal microbiota dysfunctions on brain health should focus on multiple interrelated systems involving local and central neuroendocrine, immunocyte, and neural signaling of microbial products and transmitters and neurohumoral cells that not only maintain intestinal, but also blood brain-barrier integrity. The change in intestinal microbiome/dysbiome repertoire is crucial to the development of dementia.

Targeting toll-like receptor 4 signalling pathways: can therapeutics pay the toll for hypertension?

The immune system plays a prominent role in the initiation and maintenance of hypertension. The innate immune system, via toll-like receptors (TLRs), identifies distinct signatures of invading microbes and damage-associated molecular patterns and triggers a chain of downstream signalling cascades, leading to secretion of pro-inflammatory cytokines and shaping the adaptive immune response. Over the past decade, a dysfunctional TLR-mediated response, particularly via TLR4, has been suggested to support a chronic inflammatory state in hypertension, inducing deleterious local and systemic effects in host cells and tissues and contributing to disease progression. While the underlying mechanisms triggering TLR4 need further research, evidence suggests that sustained elevations in BP disrupt homeostasis, releasing endogenous TLR4 ligands in hypertension. In this review, we discuss the emerging role of TLR4 in the pathogenesis of hypertension and whether targeting this receptor and its signalling pathways could offer a therapeutic strategy for management of this multifaceted disease. LINKED ARTICLES: This article is part of a themed section on Immune Targets in Hypertension. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.12/issuetoc.

Extracellular histones activate autophagy and apoptosis via mTOR signaling in human endothelial cells

Circulating histones have been proposed as targets for therapy in sepsis and hyperinflammatory symptoms. However, the proposed strategies have failed in clinical trials. Although different mechanisms for histone-related cytotoxicity are being explored, those mediated by circulating histones are not fully understood. Extracellular histones induce endothelial cell death, thereby contributing to the pathogenesis of complex diseases such as sepsis and septic shock. Therefore, the comprehension of cellular responses triggered by histones is capital to design effective therapeutic strategies. Here we report how extracellular histones induce autophagy and apoptosis in a dose-dependent manner in cultured human endothelial cells. In addition, we describe how histones regulate these pathways via Sestrin2/AMPK/ULK1-mTOR and AKT/mTOR. Furthermore, we evaluate the effect of Toll-like receptors in mediating autophagy and apoptosis demonstrating how TLR inhibitors do not prevent apoptosis and/or autophagy induced by histones. Our results confirm that histones and autophagic pathways can be considered as novel targets to design therapeutic strategies in endothelial damage.

Specific Transcriptome Changes Associated with Blood Pressure Reduction in Hypertensive Patients After Relaxation Response Training

OBJECTIVE

Mind-body practices that elicit the relaxation response (RR) have been demonstrated to reduce blood pressure (BP) in essential hypertension (HTN) and may be an adjunct to antihypertensive drug therapy. However, the molecular mechanisms by which the RR reduces BP remain undefined.

DESIGN

Genomic determinants associated with responsiveness to an 8-week RR-based mind-body intervention for lowering HTN in 13 stage 1 hypertensive patients classified as BP responders and 11 as nonresponders were identified.

RESULTS

Transcriptome analysis in peripheral blood mononuclear cells identified 1771 genes regulated by the RR in responders. Biological process- and pathway-based analysis of transcriptome data demonstrated enrichment in the following gene categories: immune regulatory pathways and metabolism (among downregulated genes); glucose metabolism, cardiovascular system development, and circadian rhythm (among upregulated genes). Further in silico estimation of cell abundance from the microarray data showed enrichment of the anti-inflammatory M2 subtype of macrophages in BP responders. Nuclear factor-κB, vascular endothelial growth factor, and insulin were critical molecules emerging from interactive network analysis.

CONCLUSIONS

These findings provide the first insights into the molecular mechanisms that are associated with the beneficial effects of the RR on HTN.

Tumor inherent interferons: Impact on immune reactivity and immunotherapy

Immunotherapy has revolutionized cancer treatment, with sustained responses to immune checkpoint inhibitors reported in a number of malignancies. Such therapeutics are now being trialed in aggressive or advanced cancers that are heavily reliant on untargeted therapies, such as triple negative breast cancer. However, responses have been underwhelming to date and are very difficult to predict, leading to an inability to accurately weigh up the benefit-to-risk ratio for their implementation. The tumor immune microenvironment has been closely linked to immunotherapeutic response, with superior responses observed in patients with T cell-inflamed or 'hot' tumors. One class of cytokines, the type I interferons, are a major dictator of tumor immune infiltration and activation. Tumor cell inherent interferon signaling dramatically influences the immune microenvironment and the expression of immune checkpoint proteins, hence regulators and targets of this pathway are candidate biomarkers of immunotherapeutic response. In support of a link between IFN signaling and immunotherapeutic response, the combination of type I interferon inducers with checkpoint immunotherapy has recently been demonstrated critical for a sustained anti-tumor response in aggressive breast cancer models. Here we review evidence that links type I interferons with a hot tumor immune microenvironment, response to checkpoint inhibitors and reduced risk of metastasis that supports their use as biomarkers and therapeutics in oncology.

Toll-Like Receptor 9-Dependent AMPKα Activation Occurs via TAK1 and Contributes to RhoA/ROCK Signaling and Actin Polymerization in Vascular Smooth Muscle Cells

Traditionally, Toll-like receptor 9 (TLR9) signals through an MyD88-dependent cascade that results in proinflammatory gene transcription. Recently, it was reported that TLR9 also participates in a stress tolerance signaling cascade in nonimmune cells. In this noncanonical pathway, TLR9 binds to and inhibits sarcoplasmic/endoplasmic reticulum Ca2+-ATPase 2 (SERCA2), modulating intracellular calcium handling, and subsequently resulting in the activation of 5'-AMP-activated protein kinase α (AMPKα). We have previously reported that TLR9 causes increased contraction in isolated arteries; however, the mechanisms underlying this vascular dysfunction need to be further clarified. Therefore, we hypothesized that noncanonical TLR9 signaling was also present in vascular smooth muscle cells (VSMCs) and that it mediates enhanced contractile responses through SERCA2 inhibition. To test these hypotheses, aortic microsomes, aortic VSMCs, and isolated arteries from male Sprague-Dawley rats were incubated with vehicle or TLR9 agonist (ODN2395). Despite clear AMPKα activation after treatment with ODN2395, SERCA2 activity was unaffected. Alternatively, ODN2395 caused the phosphorylation of AMPKα via transforming growth factor β-activated kinase 1 (TAK1), a kinase involved in TLR9 inflammatory signaling. Downstream, we hypothesized that that TLR9 activation of AMPKα may be important in mediating actin cytoskeleton reorganization. ODN2395 significantly increased the filamentous-to-globular actin ratio, as well as indices of RhoA/Rho-associated protein kinase (ROCK) activation, with the latter being prevented by AMPKα inhibition. In conclusion, AMPKα phosphorylation after TLR9 activation in VSMCs appears to be an extension of traditional inflammatory signaling via TAK1, as opposed to SERCA2 inhibition and the noncanonical pathway. Nonetheless, TLR9-AMPKα signaling can mediate VSMC function via RhoA/ROCK activation and actin polymerization.

Radiation-induced inflammation and autoimmune diseases

Currently, ionizing radiation (IR) plays a key role in the agricultural and medical industry, while accidental exposure resulting from leakage of radioactive sources or radiological terrorism is a serious concern. Exposure to IR has various detrimental effects on normal tissues. Although an increased risk of carcinogenesis is the best-known long-term consequence of IR, evidence has shown that other diseases, particularly diseases related to inflammation, are common disorders among irradiated people. Autoimmune disorders are among the various types of immune diseases that have been investigated among exposed people. Thyroid diseases and diabetes are two autoimmune diseases potentially induced by IR. However, the precise mechanisms of IR-induced thyroid diseases and diabetes remain to be elucidated, and several studies have shown that chronic increased levels of inflammatory cytokines after exposure play a pivotal role. Thus, cytokines, including interleukin-1(IL-1), tumor necrosis factor (TNF-α) and interferon gamma (IFN-γ), play a key role in chronic oxidative damage following exposure to IR. Additionally, these cytokines change the secretion of insulin and thyroid-stimulating hormone(TSH). It is likely that the management of inflammation and oxidative damage is one of the best strategies for the amelioration of these diseases after a radiological or nuclear disaster. In the present study, we reviewed the evidence of radiation-induced diabetes and thyroid diseases, as well as the potential roles of inflammatory responses. In addition, we proposed that the mitigation of inflammatory and oxidative damage markers after exposure to IR may reduce the incidence of these diseases among individuals exposed to radiation.

Role of Toll-like receptors and interferon regulatory factors in different experimental heart failure models of diverse etiology: IRF7 as novel cardiovascular stress-inducible factor

Heart failure (HF) is a leading cause of morbidity and mortality in the western world. Although optimal medical care and treatment is widely available, the prognosis of patients with HF is still poor.

Toll-like receptors (TLRs) are important compartments of the innate immunity. Current studies have identified TLRs as critical mediators in cardiovascular diseases. In the present study, we investigated the involvement of TLRs and interferon (IFN) regulatory factors (IRFs) in different experimental HF models including viral myocarditis, myocardial ischemia, diabetes mellitus, and cardiac hypertrophy. In addition, we investigated for the first time comprehensive TLR and IRF gene and protein expression under basal conditions in murine and human cardiac tissue. We found that Tlr4, Tlr9 and Irf7 displayed highest gene expression under basal conditions, indicating their significant role in first-line defense in the murine and human heart. Moreover, induction of TLRs and IRFs clearly differs between the various experimental HF models of diverse etiology and the concomitant inflammatory status. In the HF model of acute viral-induced myocarditis, TLR and IRF activation displayed the uppermost gene expression in comparison to the remaining experimental HF models, indicating the highest amount of myocardial inflammation in myocarditis. In detail, Irf7 displayed by far the highest gene expression during acute viral infection. Interestingly, post myocardial infarction TLR and IRF gene expression was almost exclusively increased in the infarct zone after myocardial ischemia (Tlr2, Tlr3, Tlr6, Tlr7, Tlr9, Irf3, Irf7). With one exception, Irf3 showed a decreased gene expression in the remote zone post infarction. Finally, we identified Irf7 as novel cardiovascular stress-inducible factor in the pathologically stressed heart. These findings on TLR and IRF function in the inflamed heart highlight the complexity of inflammatory immune response and raise more interesting questions for future investigation.

The Activation of Human Dermal Microvascular Cells by Poly(I:C), Lipopolysaccharide, Imiquimod, and ODN2395 Is Mediated by the Fli1/FOXO3A Pathway

Endothelial cell (EC) dysfunction has been associated with inflammatory and autoimmune diseases; however, the factors contributing to this dysfunction have not been fully explored. Because activation of TLRs has been implicated in autoimmune diseases, the goal of this study was to determine the effects of TLR ligands on EC function. Human dermal microvascular ECs (HDMECs) treated with TLR3 [Poly(I:C)], TLR4 (LPS), and TLR7 (imiquimod) agonists showed decreased proliferation and a reduced total number of branching tubules in three-dimensional human dermal organoid ex vivo culture. In contrast, the TLR9 ligand class C, ODN2395, increased angiogenesis. The antiproliferative effects of TLR3, TLR4, and TLR7 ligands correlated with significant downregulation of a key regulator of vascular homeostasis, Fli1, whereas TLR9 increased Fli1 levels. Furthermore, Poly(I:C) and LPS induced endothelial to mesenchymal transition that was reversed by the pretreatment with TGF-β neutralizing Ab or re-expression of Fli1. We showed that Fli1 was required for the HDMEC proliferation by transcriptionally repressing FOXO3A. In contrast to TLR9, which suppressed activation of the FOXO3A pathway, TLR3, TLR4, and TLR7 ligands activated FOXO3A as indicated by decreased phosphorylation and increased nuclear accumulation. The inverse correlation between Fli1 and FOXO3A was also observed in the vasculature of scleroderma patients. This work revealed opposing effects of TLR9 and TLR3, TLR4, and TLR7 on the key angiogenic pathways, Fli1 and FOXO3A. Our results provide a mechanistic insight into the regulation of angiogenesis by TLRs and confirm a central role of Fli1 in regulating vascular homeostasis.

Out of the frying pan and into the fire: damage-associated molecular patterns and cardiovascular toxicity following cancer therapy

Cardio-oncology is a new and rapidly expanding field that merges cancer and cardiovascular disease. Cardiovascular disease is an omnipresent side effect of cancer therapy; in fact, it is the second leading cause of death in cancer survivors after recurrent cancer. It has been well documented that many cancer chemotherapeutic agents cause cardiovascular toxicity. Nonetheless, the underlying cause of cancer therapy-induced cardiovascular toxicity is largely unknown. In this review, we discuss the potential role of damage-associated molecular patterns (DAMPs) as an underlying contributor to cancer therapy-induced cardiovascular toxicity. With an increasing number of cancer patients, as well as extended life expectancy, understanding the mechanisms underlying cancer therapy-induced cardiovascular disease is of the utmost importance to ensure that cancer is the only disease burden that cancer survivors have to endure.

Poly (I:C) impairs NO donor-induced relaxation by overexposure to NO via the NF-kappa B/iNOS pathway in rat superior mesenteric arteries

Recent studies have suggested a link between vascular dysfunction and innate immune activation including toll-like receptors (TLRs), but the detailed mechanism remains unclear. Here we investigated whether poly (I:C) [a synthetic double-strand RNA recognized by TLR3, melanoma differentiation-associated gene 5 (MDA5), and retinoic acid-inducible gene I (RIG-I)] affected nitric oxide (NO)/cGMP-related vascular relaxation, one of the major cascades of relaxation, in rat superior mesenteric arteries. Using organ-cultured arteries, we found that poly (I:C) (30μg/mL for approximately 1 day) markedly reduced sodium nitroprusside (SNP)-induced relaxation (vs. vehicle); this was prevented by co-treatment with a TLR3 inhibitor. Relaxation induced by 8-Br cGMP (a phosphodiesterase (PDE)-resistant cGMP analogue) and the expression of proteins related to NO/cGMP signaling did not differ between vehicle- and poly (I:C)-treated groups. When PDEs were inhibited by IBMX (a nonselective PDE inhibitor), the SNP-induced relaxation was still greatly reduced in poly (I:C)-treated arteries (vs. vehicle). Poly (I:C) reduced SNP-stimulated cGMP production, but increased NO production and iNOS expression (vs. vehicle). The impairment of SNP-induced relaxation by poly (I:C) was prevented by co-treatment with either iNOS or a nuclear factor-kappa B (NF-κB) inhibitor. This effect induced by poly (I:C) appeared to be independent of oxidative stress. The SNP-induced relaxation was reduced in freshly isolated arteries by pre-incubation with SNP in a concentration-dependent manner. Poly (I:C) did not alter protein levels of TLR3, TRIF/TICAM-1, or phospho-IRF3/IRF3, whereas RIG-I and MDA5 were significantly upregulated (vs. vehicle). These results suggest that poly (I:C) impairs NO donor-induced relaxation in rat superior mesenteric arteries via overexposure to NO produced by the NF-κB/iNOS pathway.

Acute toll-like receptor 4 activation impairs rat renal microvascular autoregulatory behaviour

AIM

Little is known about how toll-like receptor 4 (TLR4) influences the renal microvasculature. We hypothesized that acute TLR4 stimulation with lipopolysaccharide (LPS) impairs afferent arteriole autoregulatory behaviour, partially through reactive oxygen species (ROS).

METHODS

We assessed afferent arteriole autoregulatory behaviour after LPS treatment (1 mg kg^-1 ; i.p.) using the in vitro blood-perfused juxtamedullary nephron preparation. Autoregulatory behaviour was assessed by measuring diameter responses to stepwise changes in renal perfusion pressure. TLR4 expression was assessed by immunofluorescence, immunohistochemistry and Western blot analysis in the renal cortex and vasculature.

RESULTS

Baseline arteriole diameter at 100 mmHg averaged 15.2 ± 1.2 μm and 12.2 ± 1.0 μm for control and LPS groups (P < 0.05) respectively. When perfusion pressure was increased in 15 mmHg increments from 65 to 170 mmHg, arteriole diameter in control kidneys decreased significantly to 69 ± 6% of baseline diameter. In the LPS-treated group, arteriole diameter remained essentially unchanged (103 ± 9% of baseline), indicating impaired autoregulatory behaviour. Pre-treatment with anti-TLR4 antibody or the TLR4 antagonist, LPS-RS, preserved autoregulatory behaviour during LPS treatment. P2 receptor reactivity was normal in control and LPS-treated rats. Pre-treatment with Losartan (angiotensin type 1 receptor blocker; (AT₁ ) 2 mg kg^-1 ; i.p.) increased baseline afferent arteriole diameter but did not preserve autoregulatory behaviour in LPS-treated rats. Acute exposure to Tempol (10^-3 mol L^-1 ), a superoxide dismutase mimetic, restored pressure-mediated vasoconstriction in kidneys from LPS-treated rats.

CONCLUSION

These data demonstrate that TLR4 activation impairs afferent arteriole autoregulatory behaviour, partially through ROS, but independently of P2 and AT₁ receptor activation.

The Role of Toll-Like Receptors and Vitamin D in Cardiovascular Diseases-A Review

Cardiovascular diseases are the leading cause of mortality worldwide. Therefore, a better understanding of their pathomechanisms and the subsequent implementation of optimal prophylactic and therapeutic strategies are of utmost importance. A growing body of evidence states that low-grade inflammation is a common feature for most of the cardiovascular diseases in which the contributing factors are the activation of toll-like receptors (TLRs) and vitamin D deficiency. In this article, available data concerning the association of cardiovascular diseases with TLRs and vitamin D status are reviewed, followed by a discussion of new possible approaches to cardiovascular disease management.

Transcription analysis of the responses of porcine heart to Erysipelothrix rhusiopathiae

Erysipelothrix rhusiopathiae (E. rhusiopathiae) is the causative agent of swine erysipelas. This microbe has caused great economic losses in China and in other countries. In this study, high-throughput cDNA microarray assays were employed to evaluate the host responses of porcine heart to E. rhusiopathiae and to gain additional insights into its pathogenesis. A total of 394 DE transcripts were detected in the active virulent E. rhusiopathiae infection group compared with the PBS group at 4 days post-infection. Moreover, 262 transcripts were upregulated and 132 transcripts were downregulated. Differentially expressed genes were involved in many vital functional classes, including inflammatory and immune responses, signal transduction, apoptosis, transport, protein phosphorylation and dephosphorylation, metabolic processes, chemotaxis, cell adhesion, and innate immune responses. Pathway analysis demonstrated that the most significant pathways were Chemokine signaling pathway, NF-kappa B signaling pathway, TLR pathway, CAMs, systemic lupus erythematosus, chemokine signaling pathway, Cytokine–cytokine receptor interaction, PI3K-Akt signaling pathway, Phagosome, HTLV-I infection, Measles, Rheumatoid arthritis and natural-killer-cell-mediated cytotoxicity. The reliability of our microarray data was verified by performing quantitative real-time PCR. This study is the first to document the response of piglet heart to E. rhusiopathiae infection. The observed gene expression profile could help screen potential host agents that can reduce the prevalence of E. rhusiopathiae. The profile might also provide insights into the underlying pathological changes that occur in pigs infected with E. rhusiopathiae.

The role of hyperuricemia on vascular endothelium dysfunction

Hyperuricemia appears to be associated with an increased risk for cardiovascular disease and associated mortality. Population epidemiological data support a causal link between hyperuricemia and cardiovascular disease. Endothelium injury could be one of the potential mechanisms in hyperuricemia-induced cardiovascular disease. However, the specific role of uric acid (UA) in the impairment of vascular relaxation and its signal transduction pathway has not been examined. The authors investigated the role of UA on vascular relaxation, nitric oxide (NO) production and expression of proinflammatory cytokines. Brachial flow-mediated dilation and nitroglycerine-mediated dilation were measured by B-mode ultrasound with 10 megahertz linear-array transducer from 21 patients with hyperuricemia and 16 control subjects. Human umbilical vein endothelial cells (ECs) were incubated with UA (5-15 mg/dl) with or without nuclear factor (NF)-κB inhibitor II. Hyperuricemia inhibited brachial flow-mediated dilation. While UA significantly inhibited NO expression with time course- and dose- dependent manner in the cultured ECs, 10 mg/dl UA also increased expression of inflammation cytokine interleukin (IL)-6, IL-8 and tumor necrosis factor-α in vitro. These abnormalities were associated with UA-induced activation of transcription factor NF-κB. Furthermore, NF-κB inhibitor II prevented UA-induced reduction of NO and increased inflammation cytokines. These data suggested hyperuricemia-induced endothelium injury and vascular dysfunction by a reduction of NO and expression of inflammatory cytokines through the NF-κB pathway.

Inhibition of Toll-Like Receptor Signaling as a Promising Therapy for Inflammatory Diseases: A Journey from Molecular to Nano Therapeutics

The recognition of invading pathogens and endogenous molecules from damaged tissues by toll-like receptors (TLRs) triggers protective self-defense mechanisms. However, excessive TLR activation disrupts the immune homeostasis by sustained pro-inflammatory cytokines and chemokines production and consequently contributes to the development of many inflammatory and autoimmune diseases, such as systemic lupus erythematosus (SLE), infection-associated sepsis, atherosclerosis, and asthma. Therefore, inhibitors/antagonists targeting TLR signals may be beneficial to treat these disorders. In this article, we first briefly summarize the pathophysiological role of TLRs in the inflammatory diseases. We then focus on reviewing the current knowledge in both preclinical and clinical studies of various TLR antagonists/inhibitors for the prevention and treatment of inflammatory diseases. These compounds range from conventional small molecules to therapeutic biologics and nanodevices. In particular, nanodevices are emerging as a new class of potent TLR inhibitors for their unique properties in desired bio-distribution, sustained circulation, and preferred pharmacodynamic and pharmacokinetic profiles. More interestingly, the inhibitory activity of these nanodevices can be regulated through precise nano-functionalization, making them the next generation therapeutics or “nano-drugs.” Although, significant efforts have been made in developing different kinds of new TLR inhibitors/antagonists, only limited numbers of them have undergone clinical trials, and none have been approved for clinical uses to date. Nevertheless, these findings and continuous studies of TLR inhibition highlight the pharmacological regulation of TLR signaling, especially on multiple TLR pathways, as future promising therapeutic strategy for various inflammatory and autoimmune diseases.

Loss of MD1 exacerbates pressure overload-induced left ventricular structural and electrical remodelling

Myeloid differentiation protein 1 (MD1) has been implicated in numerous pathophysiological processes, including immune regulation, obesity, insulin resistance, and inflammation. However, the role of MD1 in cardiac remodelling remains incompletely understood. We used MD1-knockout (KO) mice and their wild-type littermates to determine the functional significance of MD1 in the regulation of aortic banding (AB)-induced left ventricular (LV) structural and electrical remodelling and its underlying mechanisms. After 4 weeks of AB, MD1-KO hearts showed substantial aggravation of LV hypertrophy, fibrosis, LV dilation and dysfunction, and electrical remodelling, which resulted in overt heart failure and increased electrophysiological instability. Moreover, MD1-KO-AB cardiomyocytes showed increased diastolic sarcoplasmic reticulum (SR) Ca²⁺ leak, reduced Ca²⁺ transient amplitude and SR Ca²⁺ content, decreased SR Ca²⁺-ATPase2 expression, and increased phospholamban and Na⁺/Ca²⁺-exchanger 1 protein expression. Mechanistically, the adverse effects of MD1 deletion on LV remodelling were related to hyperactivated CaMKII signalling and increased impairment of intracellular Ca²⁺ homeostasis, whereas the increased electrophysiological instability was partly attributed to exaggerated prolongation of cardiac repolarisation, decreased action potential duration alternans threshold, and increased diastolic SR Ca²⁺ leak. Therefore, our study on MD1 could provide new therapeutic strategies for preventing/treating heart failure.

Role of the Immune System in Hypertension

High blood pressure is present in more than one billion adults worldwide and is the most important modifiable risk factor of death resulting from cardiovascular disease. While many factors contribute to the pathogenesis of hypertension, a role of the immune system has been firmly established by a large number of investigations from many laboratories around the world. Immunosuppressive drugs and inhibition of individual cytokines prevent or ameliorate experimental hypertension, and studies in genetically-modified mouse strains have demonstrated that lymphocytes are necessary participants in the development of hypertension and in hypertensive organ injury. Furthermore, immune reactivity may be the driving force of hypertension in autoimmune diseases. Infiltration of immune cells, oxidative stress, and stimulation of the intrarenal angiotensin system are induced by activation of the innate and adaptive immunity. High blood pressure results from the combined effects of inflammation-induced impairment in the pressure natriuresis relationship, dysfunctional vascular relaxation, and overactivity of the sympathetic nervous system. Imbalances between proinflammatory effector responses and anti-inflammatory responses of regulatory T cells to a large extent determine the severity of inflammation. Experimental and human studies have uncovered autoantigens (isoketal-modified proteins and heat shock protein 70) of potential clinical relevance. Further investigations on the immune reactivity in hypertension may result in the identification of new strategies for the treatment of the disease.

Toll-like receptor-4 signaling pathway in aorta aging and diseases: "its double nature"

Recent advances in the field of innate immunity have revealed a complex role of innate immune signaling pathways in both tissue homeostasis and disease. Among them, the Toll-like receptor 4 (TLR-4) pathways has been linked to various pathophysiological conditions, such as cardiovascular diseases (CVDs). This has been interrogated by developing multiple laboratory tools that have shown in animal models and clinical conditions, the involvement of the TLR-4 signaling pathway in the pathophysiology of different CVDs, such as atherosclerosis, ischemic heart disease, heart failure, ischemia-reperfusion injury and aorta aneurysm. Among these, aorta aneurysm, a very complex pathological condition with uncertain etiology and fatal complications (i.e. dissection and rupture), has been associated with the occurrence of high risk cardiovascular conditions, including thrombosis and embolism. In this review, we discuss the possible role of TLR-4 signaling pathway in the development of aorta aneurysm, considering the emerging evidence from ongoing investigations. Our message is that emphasizing the role of TLR-4 signaling pathway in aorta aneurysm may serve as a starting point for future studies, leading to a better understanding of the pathophysiological basis and perhaps the effective treatment of this difficult human disease.

Chemical Tools for Studying TLR Signaling Dynamics

The detection of infectious pathogens is essential for the induction of antimicrobial immune responses. The innate immune system detects a wide array of microbes using a limited set of pattern-recognition receptors (PRRs). One family of PRRs with a central role in innate immunity are the Toll-like receptors (TLRs). Upon ligation, these receptors initiate signaling pathways culminating in the release of pro-inflammatory cytokines and/or type I interferons (IFN-I). In recent years, it has become evident that the specific subcellular location and timing of TLR activation affect signaling outcome. The subtlety of this signaling has led to a growing demand for chemical tools that provide the ability to conditionally control TLR activation. In this review, we survey current models for TLR signaling in time and space, discuss how chemical tools have contributed to our understanding of TLR ligands, and describe how they can aid further elucidation of the dynamic aspects of TLR signaling.

T-cell involvement in sex differences in blood pressure control

Hypertension affects one-third of adults in the Western world and is the most common independent risk factor for cardiovascular disease, and the leading cause of premature death globally. Despite available therapeutic options, approximately half of the hypertensive population taking medication does not achieve adequate blood pressure (BP) control leaving them at increased risk of chronic kidney disease, renal failure, stroke, congestive heart failure, myocardial infarction, aneurysm and peripheral artery disease. New therapeutic options need to be identified for the treatment of hypertension in order to increase the percentage of individuals with controlled BP. There is a growing basic science literature regarding the role of T-cells in the pathogenesis of hypertension and BP control; however, the majority of this literature has been performed exclusively in males despite the fact that both men and women develop hypertension. This is especially problematic since hypertension is well recognized as having distinct sex differences in the prevalence, absolute BP values and molecular mechanisms contributing to the pathophysiology of the disease. The purpose of this article is to review the available literature regarding sex differences in T-cells in hypertension followed by highlighting the potential pathways that may result in sex-specific effects on T-cell activation and differentiation.

Toll-like receptor 4 mediates vascular remodeling in hyperhomocysteinemia

Although hyperhomocysteinemia (HHcy) is known to promote downstream pro-inflammatory cytokine elevation, the precise mechanism is still unknown. One of the possible receptors that could have significant attention in the field of hypertension is toll-like receptor 4 (TLR-4). TLR-4 is a cellular membrane protein that is ubiquitously expressed in all cell types of the vasculature. Its mutation can attenuate the effects of HHcy-mediated vascular inflammation and mitochondria- dependent cell death that suppresses hypertension. In this review, we observed that HHcy induces vascular remodeling through immunological adaptation, promoting inflammatory cytokine up-regulation (IL-1β, IL-6, TNF-α) and initiation of mitochondrial dysfunction leading to cell death and chronic vascular inflammation. The literature suggests that HHcy promotes TLR-4-driven chronic vascular inflammation and mitochondria-mediated cell death inducing peripheral vascular remodeling. In the previous studies, we have characterized the role of TLR-4 mutation in attenuating vascular remodeling in hyperhomocysteinemia. This review includes, but is not limited to, the physiological synergistic aspects of the downstream elevation of cytokines found within the vascular inflammatory cascade. These events subsequently induce mitochondrial dysfunction defined by excessive mitochondrial fission and mitochondrial apoptosis contributing to vascular remodeling followed by hypertension.

Strain-Specific Single-Nucleotide Polymorphisms in Hypertensive ISIAH Rats

Single-nucleotide polymorphisms (SNPs) in the coding and regulatory regions of genes can affect transcription rate and translation efficiency, modify protein function, and, in some cases, cause the development of diseases. In the current study, the RNA-Seq approach has been used to discover strain-specific SNPs in ISIAH (inherited stress-induced arterial hypertension) rats, which are known as a model of stress-induced arterial hypertension. The comparison of the ISIAH SNPs with genome sequencing data available for another 42 rat strains and substrains, 11 of them known as hypertensive, showed a considerable genetic distance between the genotypes of ISIAH and all other rat strains and substrains. The study revealed 1849 novel SNPs specific for ISIAH rats and 158 SNPs present only in the genotypes of hypertensive rats. Amino acid substitutions with possible deleterious effect on protein function were detected. Several of them were found in the genes associated with hypertension. These SNPs may be considered as novel molecular targets for further studies aimed at assessing their potential in the therapy of stress-induced hypertension.

The interplay between Angiotensin II, TLR4 and hypertension

Hypertension is a multifactorial disease. Although a number of different underlying mechanisms have been learned from the various experimental models of the disease, hypertension still poses challenges for treatment. Angiotensin II plays an unquestionable role in blood pressure regulation acting through central and peripheral mechanisms. During hypertension, dysregulation of the Renin-Angiotensin System is associated with increased expression of pro-inflammatory cytokines and reactive oxygen species causing kidney damage, endothelial dysfunction, and increase in sympathetic activity, among other damages, eventually leading to decline in organ function. Recent studies have shown that these effects involve both the innate and the adaptive immune response. The contribution of adaptive immune responses involving different lymphocyte populations in various models of hypertension has been extensively studied. However, the involvement of the innate immunity mediating inflammation in hypertension is still not well understood. The innate and adaptive immune systems intimately interact with one another and are essential to an effectively functioning of the immune response; hence, the importance of a better understanding of the underlying mechanisms mediating innate immune system during hypertension. In this review, we aim to discuss mechanisms linking Angiotensin II and the innate immune system, in the pathogenesis of hypertension. The newest research investigating Angiotensin II triggering toll like receptor 4 activation in the kidney, vasculature and central nervous system contributing to hypertension will be discussed. Understanding the role of the innate immune system in the development of hypertension may bring to light new insights necessary to improve hypertension management.

Choline ameliorates cardiovascular damage by improving vagal activity and inhibiting the inflammatory response in spontaneously hypertensive rats

Autonomic dysfunction and abnormal immunity lead to systemic inflammatory responses, which result in cardiovascular damage in hypertension. The aim of this report was to investigate the effects of choline on cardiovascular damage in hypertension. Eight-week-old male spontaneously hypertensive rats (SHRs) and Wistar-Kyoto rats were intraperitoneally injected with choline or vehicle (8 mg/kg/day). After 8 weeks, choline restored the cardiac function of the SHRs, as evidenced by decreased heart rate, systolic blood pressure, left ventricle systolic pressure, and ±dp/dt_max and increased ejection fraction and fractional shortening. Choline also ameliorated the cardiac hypertrophy of the SHRs, as indicated by reduced left ventricle internal dimensions and decreased cardiomyocyte cross-sectional area. Moreover, choline improved mesenteric arterial function and preserved endothelial ultrastructure in the SHRs. Notably, the protective effect of choline may be due to its anti-inflammatory effect. Choline downregulated expression of interleukin (IL)-6 and tumour necrosis factor-α and upregulated IL-10 in the mesenteric arteries of SHRs, possibly because of the inhibition of Toll-like receptor 4. Furthermore, choline restored baroreflex sensitivity and serum acetylcholine level in SHRs, thus indicating that choline improved vagal activity. This study suggests that choline elicits cardiovascular protective effects and may be useful as a potential adjunct therapeutic approach for hypertension.

Chloroquine Suppresses the Development of Hypertension in Spontaneously Hypertensive Rats

BACKGROUND

Innate immune system responses to damage-associated molecular patterns (DAMPs) are involved in hypertension. However, the mechanisms of this contribution are not well understood. Circulating mitochondrial DNA is a DAMP that activates Toll-like receptor (TLR) 9 and is elevated in spontaneously hypertensive rats (SHR). Therefore, we hypothesized that lysosomotropic agent chloroquine (CQ) would impair TLR9 signaling, as well as prevent the development of hypertension and immune cell recruitment to the vasculature, in SHR.

METHODS

Initially, adult SHR and Wistar-Kyoto (WKY) rats (12 weeks old), as well as a group of young SHR (5 weeks old), were treated with CQ (40mg/kg/day) or vehicle (saline) via intraperitoneal injections for 21 days and then TLR9-myeloid differentiation primary response protein (MyD88) signaling proteins were assessed in mesenteric resistance arteries (MRA) via western blot. Subsequently, young SHR and WKY were treated from 5-8 weeks of age and then were allowed to mature without further treatment. Blood pressure was measured pretreatment, posttreatment, and after maturation, and immune cell recruitment to the vasculature was measured via flow cytometry after maturation.

RESULTS

In MRA from adult SHR, CQ increased the expression of MyD88-dependent proteins, whereas young SHR MRA exhibited a decrease. This inhibition was subsequently associated with suppression of blood pressure, as well as decreased counts of circulating T cells and vascular infiltrating leukocytes in SHR, when CQ was administered during the prehypertensive phase.

CONCLUSIONS

These data bring into question the participation of TLRs during the maintenance phase of hypertension and promote the exploration of innate immune system therapy during the critical developmental phase.

Are the innate and adaptive immune systems setting hypertension on fire?

Hypertension is the most common chronic cardiovascular disease and is associated with several pathological states, being an important cause of morbidity and mortality around the world. Low-grade inflammation plays a key role in hypertension and the innate and adaptive immune systems seem to contribute to hypertension development and maintenance. Hypertension is associated with vascular inflammation, increased vascular cytokines levels and infiltration of immune cells in the vasculature, kidneys and heart. However, the mechanisms that trigger inflammation and immune system activation in hypertension are completely unknown. Cells from the innate immune system express pattern recognition receptors (PRR), which detect conserved pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs) that induce innate effector mechanisms to produce endogenous signals, such as inflammatory cytokines and chemokines, to alert the host about danger. Additionally, antigen-presenting cells (APC) act as sentinels that are activated by PAMPs and DAMPs to sense the presence of the antigen/neoantigen, which ensues the adaptive immune system activation. In this context, different lymphocyte types are activated and contribute to inflammation and end-organ damage in hypertension. This review will focus on experimental and clinical evidence demonstrating the contribution of the innate and adaptive immune systems to the development of hypertension.

Dendritic cells and isolevuglandins in immunity, inflammation, and hypertension

Hypertension is the major risk factor for morbidity and mortality from myocardial infarction, stroke, heart failure, and chronic kidney disease. Despite its importance, the pathogenesis of essential hypertension is poorly understood. During the past several years, it has become evident that T cells contribute to hypertension. Activated T cells accumulate in the perivascular space and the kidney and release cytokines that promote vascular dysfunction and end-organ damage. Although dendritic cells play a pivotal role in initiating adaptive immune responses, T cells have taken center stage in studies implicating the immune system in the genesis of hypertension. The mechanisms by which T cells are activated and the antigens involved are poorly understood. We recently showed that hypertension is associated with increased dendritic cell production of the T_H17 polarizing cytokines, IL-6, IL-1β, and IL-23. This occurs in part by increased superoxide production via NADPH oxidase and protein modification by highly reactive isolevuglandins (IsoLGs). IsoLGs are produced via the isoprostane pathway of free radical-mediated lipid peroxidation and, when adducted to proteins, have the potential to act as neoantigens. In this review, we discuss recent advances in our understanding of the role of antigen-presenting dendritic cells in the pathophysiology of hypertension and highlight potential neoantigens that may contribute to this disease.