TNF-alpha inhibition reduces renal injury in DOCA-salt hypertensive rats

Amiloride lowers plasma TNF and interleukin-6 but not interleukin-17A in patients with hypertension and type 2 diabetes

Interleukin (IL)-17A contributes to hypertension in preclinical models. T helper 17 and dendritic cells are activated by NaCl, which could involve the epithelial Na+ channel (ENaC). We hypothesized that the ENaC blocker amiloride reduces plasma IL-17A and related cytokines in patients with hypertension. Concentrations of IL-17A, IFN-γ, TNF, IL-6, IL-1β, and IL-10 were determined by immunoassays in plasma from two patient cohorts before and after amiloride treatment: 1) patients with type 2 diabetes mellitus (T2DM) and treatment-resistant hypertension (n = 69, amiloride 5-10 mg/day for 8 wk) and 2) patients with hypertension and type 1 diabetes mellitus (T1DM) (n = 29) on standardized salt intake (amiloride 20-40 mg/day, 2 days). Plasma and tissue from ANG II-hypertensive mice with T1DM treated with amiloride (2 mg/kg/day, 4 days) were analyzed. The effect of amiloride and benzamil on macrophage cytokines was determined in vitro. Plasma cytokines showed higher concentrations (IL-17A ∼40-fold) in patients with T2DM compared with T1DM. In patients with T2DM, amiloride had no effect on IL-17A but lowered TNF and IL-6. In patients with T1DM, amiloride had no effect on IL-17A but increased TNF. In both cohorts, blood pressure decline and plasma K+ increase did not relate to plasma cytokine changes. In mice, amiloride exerted no effect on IL-17A in the plasma, kidney, aorta, or left cardiac ventricle but increased TNF in cardiac and kidney tissues. In lipopolysaccharide-stimulated human THP-1 macrophages, amiloride and benzamil (from 1 nmol/L) decreased TNF, IL-6, IL-10, and IL-1β. In conclusion, inhibition of ENaC by amiloride reduces proinflammatory cytokines TNF and IL-6 but not IL-17A in patients with T2DM, potentially by a direct action on macrophages.NEW & NOTEWORTHY ENaC activity may contribute to macrophage-derived cytokine release, since amiloride exerts anti-inflammatory effects by suppression of TNF and IL-6 cytokines in patients with resistant hypertension and type 2 diabetes and in THP-1-derived macrophages in vitro.

Immunomodulatory Activity of Cytokines in Hypertension: A Vascular Perspective

Cytokines play a crucial role in the structure and function of blood vessels in hypertension. Hypertension damages blood vessels by mechanisms linked to shear forces, activation of the renin-angiotensin-aldosterone and sympathetic nervous systems, oxidative stress, and a proinflammatory milieu that lead to the generation of neoantigens and damage-associated molecular patterns, ultimately triggering the release of numerous cytokines. Damage-associated molecular patterns are recognized by PRRs (pattern recognition receptors) and activate inflammatory mechanisms in endothelial cells, smooth muscle cells, perivascular nerves, and perivascular adipose tissue. Activated vascular cells also release cytokines and express factors that attract macrophages, dendritic cells, and lymphocytes to the blood vessels. Activated and differentiated T cells into Th1, Th17, and Th22 in secondary lymphoid organs migrate to the vessels, releasing specific cytokines that further contribute to vascular dysfunction and remodeling. This chronic inflammation alters the profile of endothelial and smooth muscle cells, making them dysfunctional. Here, we provide an overview of how cytokines contribute to hypertension by impacting the vasculature. Furthermore, we explore clinical perspectives about the modulation of cytokines as a potential therapeutic intervention to specifically target hypertension-linked vascular dysfunction.

Mechanisms of inflammation modulation by different immune cells in hypertensive nephropathy

Hypertensive nephropathy (HTN) is the second leading cause of end-stage renal disease (ESRD) and a chronic inflammatory disease. Persistent hypertension leads to lesions of intrarenal arterioles and arterioles, luminal stenosis, secondary ischemic renal parenchymal damage, and glomerulosclerosis, tubular atrophy, and interstitial fibrosis. Studying the pathogenesis of hypertensive nephropathy is a prerequisite for diagnosis and treatment. The main cause of HTN is poor long-term blood pressure control, but kidney damage is often accompanied by the occurrence of immune inflammation. Some studies have found that the activation of innate immunity, inflammation and acquired immunity is closely related to the pathogenesis of HTN, which can cause damage and dysfunction of target organs. There are more articles on the mechanism of diabetic nephropathy, while there are fewer studies related to immunity in hypertensive nephropathy. This article reviews the mechanisms by which several different immune cells and inflammatory cytokines regulate blood pressure and renal damage in HTN. It mainly focuses on immune cells, cytokines, and chemokines and inhibitors. However, further comprehensive and large-scale studies are needed to determine the role of these markers and provide effective protocols for clinical intervention and treatment.

Circulating cytokines and risk of developing hypertension: A systematic review and meta-analysis

BACKGROUND

Immune responses play a significant role in hypertension, though the importance of key inflammatory mediators remains to be defined. We used a systematic literature review and meta-analysis to study the associations between key cytokines and incident hypertension.

METHODS

We performed a systematic search of Pubmed/Medline, Embase, Web of Science, and the Cochrane Central Register of Controlled Trials (CENTRAL), for peer-reviewed studies published up to August 2022. Incident hypertension was defined as systolic blood pressure ≥ 140 mmHg or diastolic blood pressure ≥ 90 mmHg and/or the use of antihypertensive medications. Random effects meta-analyses were used to calculate pooled hazard ratios (HRs)/risk ratios (RRs) and 95% confidence intervals by cytokine levels (highest vs. lowest quartile).

RESULTS

Only IL-6 and IL-1β levels have evidence allowing for quantitative evaluation concerning the onset of hypertension. Six studies (10406 participants, 2932 incident cases) examined the association of IL-6 with incident hypertension. The highest versus lowest quartile of circulating IL-6 was associated with a significant HR/RR of hypertension (1.61, 95% CI: 1.00 to 2.60; I2 =87%). After adjusting for potential confounders, including body mass index (BMI), HR/RR was no longer significant (HR/RR: 1.24; 95% CI, 0.96 to 1.61; I2 = 56%). About IL-1β, neither the crude (HR/RR: 1.03; 95% CI, 0.60 to 1.76; n = 2) nor multivariate analysis (HR/RR: 0.97, 95% CI, 0.60 to 1.56; n = 2) suggested a significant association with the risk of developing hypertension.

CONCLUSIONS

A limited number of studies suggest that higher IL-6, but not IL-1β, might be associated with the development of hypertension.

The Role of Pro-Inflammatory Cytokines in the Pathogenesis of Cardiovascular Disease

With cardiovascular disease (CVD) being a primary source of global morbidity and mortality, it is crucial that we understand the molecular pathophysiological mechanisms at play. Recently, numerous pro-inflammatory cytokines have been linked to several different CVDs, which are now often considered an adversely pro-inflammatory state. These cytokines most notably include interleukin-6 (IL-6),tumor necrosis factor (TNF)α, and the interleukin-1 (IL-1) family, amongst others. Not only does inflammation have intricate and complex interactions with pathophysiological processes such as oxidative stress and calcium mishandling, but it also plays a role in the balance between tissue repair and destruction. In this regard, pre-clinical and clinical evidence has clearly demonstrated the involvement and dynamic nature of pro-inflammatory cytokines in many heart conditions; however, the clinical utility of the findings so far remains unclear. Whether these cytokines can serve as markers or risk predictors of disease states or act as potential therapeutic targets, further extensive research is needed to fully understand the complex network of interactions that these molecules encompass in the context of heart disease. This review will highlight the significant advances in our understanding of the contributions of pro-inflammatory cytokines in CVDs, including ischemic heart disease (atherosclerosis, thrombosis, acute myocardial infarction, and ischemia-reperfusion injury), cardiac remodeling (hypertension, cardiac hypertrophy, cardiac fibrosis, cardiac apoptosis, and heart failure), different cardiomyopathies as well as ventricular arrhythmias and atrial fibrillation. In addition, this article is focused on discussing the shortcomings in both pathological and therapeutic aspects of pro-inflammatory cytokines in CVD that still need to be addressed by future studies.

C-atrial natriuretic peptide (ANP)4-23 attenuates renal fibrosis in deoxycorticosterone-acetate-salt hypertensive mice

Epithelial-mesenchymal transition (EMT) plays a critical role in hypertension-induced renal fibrosis, a final pathway that leads to end-stage renal failure. C-Atrial natriuretic peptide (ANP)4-23, a specific agonist of natriuretic peptide receptor-C (NPR-C), has been reported to have protective effects against hypertension. However, the role of C-ANP4-23 in hypertension-associated renal fibrosis has not yet been elucidated. In this study, mice were randomly divided into SHAM group, DOCA-salt group and DOCA-salt + C-ANP4-23 group. Renal morphology changes, renal function and fibrosis were detected. Human proximal tubular epithelial cells (HK2) stimulated by aldosterone were used for cell function and mechanism study. The DOCA-salt treated mice exhibited hypertension, kidney fibrosis and renal dysfunction, which were attenuated by C-ANP4-23. Moreover, C-ANP4-23 inhibited DOCA-salt treatment-induced renal EMT as evidenced by decrease of the mesenchymal marker alpha-smooth muscle actin (ACTA2) and vimentin and increase of epithelial cell marker E-cadherin. In HK2 cells, aldosterone induced EMT response, which was also suppressed by C-ANP4-23. The key transcription factors (twist, snail, slug and ZEB1) involved in EMT were increased in the kidney of DOCA-salt-treated mice, which were also suppressed by C-ANP4-23. Mechanistically, C-ANP4-23 inhibited the aldosterone-induced translocation of MR from cytosol to nucleus without change of MR expression. Furthermore, C-ANP4-23 rescued the enhanced expression of NADPH oxidase (NOX) 4 and oxidative stress after aldosterone stimulation. Aldosterone-induced Akt and Erk1/2 activation was also suppressed by C-ANP4-23. Our data suggest that C-ANP4-23 attenuates renal fibrosis, likely through inhibition of MR activation, enhanced oxidative stress and Akt and Erk1/2 signaling pathway.

A new immune disease: systemic hypertension

Systemic hypertension is the most common medical comorbidity affecting the adult population globally, with multiple associated outcomes including cerebrovascular diseases, cardiovascular diseases, vascular calcification, chronic kidney disease, metabolic syndrome and mortality. Despite advancements in the therapeutic field approximately one in every five adult patients with hypertension is classified as having treatment-resistant hypertension, indicating the need for studies to provide better understanding of the underlying pathophysiology and the need for more therapeutic targets. Recent pre-clinical studies have demonstrated the role of the innate and adaptive immune system including various cell types and cytokines in the pathophysiology of hypertension. Moreover, pre-clinical studies have indicated the potential beneficial effects of immunosuppressant medications in the control of hypertension. Nevertheless, it is unclear whether such pathophysiological mechanisms and therapeutic alternatives are applicable to human subjects, while this area of research is undoubtedly a rapidly growing field.

Downregulation of inflammatory erectile dysfunction by Mantisa religiosa egg-cake through NO-cGMP-PKG dependent NF-kB signaling cascade activated by mixture of salt intake

We hypothesized whether 10% praying-mantis-egg-cake (10% PMEC) can be applied against inflammatory-erectile-dysfunction and whether it could be linked to NO-cGMP-dependent PKG signaling cascade. Ninety male albino-rats were randomly distributed into nine (n = 10) groups. Group I was given distilled water. Group II and III were pre-treated with 80 mg/kg NaCl and 75 mg/kg MSG, respectively. Group IV was pre-treated with 80 mg/kg NaCl + 75 mg/kg MSG. Group V was administered with 80 mg/kg NaCl+ 3 mg/kg Amylopidin. Group VI was given 80 mg/kg NaCl + 10% PMEC. Group VII was treated with 75 mg/kg MSG + 10% PMEC. Group VIII was treated with 80 mg/kg NaCl+ 75 mg/kg MSG + 10% PMEC. Group IX was post-treated with 10% PMEC for 14 days. Penile PDE-5¹, arginase, ATP hydrolytic, cholinergic, dopaminergic (MAO-A) and adenosinergic (ADA) enzymes were hyperactive on intoxication with NaCl and MSG. The erectile dysfunction caused by inflammation was linked to alteration of NO-cGMP-dependent PKG signaling cascade via up-regulation of key cytokines and chemokine (MCP-1). These lesions were prohibited by protein-rich-cake (10% PMEC). Thus, protein-rich-cake (10% PMEC) by a factor of 4 (25%) inhibited penile cytokines/MCP-1 on exposure to mixture of salt-intake through NO-cGMP-PKG dependent-NF-_KB signaling cascade in rats.

Bioactive lipids in hypertension

Hypertension is a major healthcare issue that afflicts one in every three adults worldwide and contributes to cardiovascular diseases, morbidity and mortality. Bioactive lipids contribute importantly to blood pressure regulation via actions on the vasculature, kidney, and inflammation. Vascular actions of bioactive lipids include blood pressure lowering vasodilation and blood pressure elevating vasoconstriction. Increased renin release by bioactive lipids in the kidney is pro-hypertensive whereas anti-hypertensive bioactive lipid actions result in increased sodium excretion. Bioactive lipids have pro-inflammatory and anti-inflammatory actions that increase or decrease reactive oxygen species and impact vascular and kidney function in hypertension. Human studies provide evidence that fatty acid metabolism and bioactive lipids contribute to sodium and blood pressure regulation in hypertension. Genetic changes identified in humans that impact arachidonic acid metabolism have been associated with hypertension. Arachidonic acid cyclooxygenase, lipoxygenase and cytochrome P450 metabolites have pro-hypertensive and anti-hypertensive actions. Omega-3 fish oil fatty acids eicosapentaenoic acid and docosahexaenoic acid are known to be anti-hypertensive and cardiovascular protective. Lastly, emerging fatty acid research areas include blood pressure regulation by isolevuglandins, nitrated fatty acids, and short chain fatty acids. Taken together, bioactive lipids are key contributors to blood pressure regulation and hypertension and their manipulation could decrease cardiovascular disease and associated morbidity and mortality.

Responses to Ang II (Angiotensin II), Salt Intake, and Lipopolysaccharide Reveal the Diverse Actions of TNF-α (Tumor Necrosis Factor-α) on Blood Pressure and Renal Function

TNF-α (tumor necrosis factor-alpha) is the best known as a proinflammatory cytokine; yet, this cytokine also has important immunomodulatory and regulatory functions. As the effects of TNF-α on immune system function were being revealed, the spectrum of its activities appeared in conflict with each other before investigators defined the settings and mechanisms by which TNF-α contributed to both host defense and chronic inflammation. These effects reflect self-protective mechanisms that may become harmful when dysregulated. The paradigm of physiological and pathophysiological effects of TNF-α has since been uncovered in the lung, colon, and kidney where its role has been identified in pulmonary edema, electrolyte reabsorption, and blood pressure regulation, respectively. Recent studies on the prohypertensive and inflammatory effects of TNF-α in the cardiovascular system juxtaposed to those related to NaCl and blood pressure homeostasis, the response of the kidney to lipopolysaccharide, and protection against bacterial infections are helping define the mechanisms by which TNF-α modulates distinct functions within the kidney. This review discusses how production of TNF-α by renal epithelial cells may contribute to regulatory mechanisms that not only govern electrolyte excretion and blood pressure homeostasis but also maintain the appropriate local hypersalinity environment needed for optimizing the innate immune response to bacterial infections in the kidney. It is possible that the wide range of effects mediated by TNF-α may be related to severity of disease, amount of inflammation and TNF-α levels, and the specific cell types that produce this cytokine, areas that remain to be investigated further.

Should Renal Inflammation Be Targeted While Treating Hypertension?

Despite extensive research and a plethora of therapeutic options, hypertension continues to be a global burden. Understanding of the pathological roles of known and underexplored cellular and molecular pathways in the development and maintenance of hypertension is critical to advance the field. Immune system overactivation and inflammation in the kidneys are proposed alternative mechanisms of hypertension, and resistant hypertension. Consideration of the pathophysiology of hypertension in chronic inflammatory conditions such as autoimmune diseases, in which patients present with autoimmune-mediated kidney inflammation as well as hypertension, may reveal possible contributors and novel therapeutic targets. In this review, we 1) summarize current therapies used to control blood pressure and their known effects on inflammation; 2) provide evidence on the need to target renal inflammation, specifically, and especially when first-line and combinatory treatment efforts fail; and 3) discuss the efficacy of therapies used to treat autoimmune diseases with a hypertension/renal component. We aim to elucidate the potential of targeting renal inflammation in certain subsets of patients resistant to current therapies.

Treatment of male and female spontaneously hypertensive rats with TNF-α inhibitor etanercept increases markers of renal injury independent of an effect on blood pressure

Hypertension remains the leading risk factor for cardiovascular disease. Young females tend to be protected from hypertension compared with age-matched males. Although it has become increasingly clear that the immune system plays a key role in the development of hypertension in both sexes, few studies have examined how cytokines mediate hypertension in males versus females. We previously published that there are sex differences in the levels of the cytokine tumor necrosis factor (TNF)-α in spontaneously hypertensive rats (SHR). The goal of this study was to test the hypothesis that TNF-α inhibition with etanercept will lower BP in male and female SHR. However, as male SHR have a more pro-inflammatory status than female SHR, we further hypothesize that males will have a greater decrease in BP with TNF-α inhibition than females. Young adult male and female SHR were administered increasing doses of the TNF-α inhibitor etanercept or vehicle twice weekly for 31 days and BP was continuously measured via telemetry. Following treatment, kidneys and urine were collected and analyzed for markers of inflammation and injury. Despite significantly decreasing renal TNF-α levels, renal phospho-NFκB and urinary MCP-1 excretion, etanercept did not alter BP in either male or female SHR. Interestingly, treatment with etanercept increased urinary excretion of protein, creatinine and KIM-1 in both sexes. These results indicate that TNF-α does not contribute to sex differences in BP in SHR but may be vital in the maintenance of renal health.

Novel nanoliposomes alleviate contrast-induced acute kidney injury in New Zealand rabbits by mediating inflammatory response

Background

The purpose of the research was to investigate the preventive effect of nanoliposomes on contrast-induced nephropathy (CIN) in New Zealand rabbits and to provide a theoretical basis for clinically effective prevention and treatment of CIN and the development of new contrast agents.

Methods

A total of 48 New Zealand rabbits were divided into four groups randomly, there were 12 rabbits in eacj group: (I) control group; (II) contrast group; (III) hydration prevention group; and (IV) nanoliposome group. The changes of serum creatinine (SCr) and blood urea nitrogen (BUN) were messured before and after injection of iopromide. Enzyme-linked immunosorbent assay (ELISA) was used to detect inflammatory and oxidative stress indexes, including neutrophil gelatinase-associated lipoprotein (NGAL), tumor necrosis factor-α (TNF-α), superoxide dismutase (SOD), and malondialdehyde (MDA). Twenty-four hours after injection of the contrast medium, the rabbits were killed and the pathological changes were observed under an electron microscope.

Results

There were statistical significances in sCr and BUN values among the four groups at both 8 hours and 24 hours after injection of the contrast medium. Serum NGAL and TNF-α levels were also significantly different among the four groups (P<0.05) 24 hours after injection of the contrast medium. The incidence rate of CIN in each group was statistically significant. Nanoliposomes had obvious advantages over hydration prevention in NGAL and TNF-α levels.

Conclusions

Nanoliposomes can prevent the occurrence of CIN and reduce the damage of contrast agent to the kidney by reducing inflammatory reaction.

Angiotensin II-induced renal angiotensinogen formation is enhanced in mice lacking tumor necrosis factor-alpha type 1 receptor

In hypertension induced by angiotensin II (AngII) administration with high salt (HS) intake, intrarenal angiotensinogen (AGT) and tumor necrosis factor-alpha (TNF-α) levels increase. However, TNF-α has been shown to suppress AGT formation in cultured renal proximal tubular cells. We examined the hypothesis that elevated AngII levels during HS intake reduces TNF-α receptor type 1 (TNFR1) activity in the kidneys, thus facilitating increased intrarenal AGT formation. The responses to HS diet (4% NaCl) with chronic infusion of AngII (25 ng/min) via implanted minipump for 4 weeks were assessed in wild-type (WT) and knockout (KO) mice lacking TNFR1 or TNFR2 receptors. Blood pressure was measured by tail-cuff plethysmography, and 24-h urine samples were collected using metabolic cages prior to start (0 day) and at the end of 2nd and 4th week periods. The urinary excretion rate of AGT (uAGT; marker for intrarenal AGT) was measured using ELISA. HS +AngII treatment for 4 weeks increased mean arterial pressure (MAP) in all strains of mice. However, the increase in MAP in TNFR1KO (77 ± 2 to 115 ± 3 mmHg; n = 7) was significantly greater (p < 0.01) than in WT (76 ± 1 to 102 ± 2 mmHg; n = 7) or in TNFR2KO (78 ± 2 to 99 ± 5 mmHg; n = 6). The increase in uAGT at 4th week was also greater (p < 0.05) in TNFR1KO mice (6 ± 2 to 167 ± 75 ng/24 h) than that in WT (6 ± 3 to 46 ± 16 ng/24 h) or in TNFR2KO mice (8 ± 7 to 65 ± 44 ng/24 h). The results indicate that TNFR1 exerts a protective role by mitigating intrarenal AGT formation induced by elevated AngII and HS intake.

Role of inflammatory chemokines in hypertension

Hypertension is associated with immune cells activation and their migration into the kidney, vasculature, heart and brain. These inflammatory mechanisms are critical for blood pressure regulation and mediate target organ damage, creating unique novel targets for pharmacological modulation. In response to angiotensin II and other pro-hypertensive stimuli, the expression of several inflammatory chemokines and their receptors is increased in the target organs, mediating homing of immune cells. In this review, we summarize the contribution of key inflammatory chemokines and their receptors to increased accumulation of immune cells in target organs and effects on vascular dysfunction, remodeling, oxidative stress and fibrosis, all of which contribute to blood pressure elevation. In particular, the role of CCL2, CCL5, CXCL8, CXCL9, CXCL10, CXCL11, CXCL16, CXCL1, CX3CL1, XCL1 and their receptors in the context of hypertension is discussed. Recent studies have tested the efficacy of pharmacological or genetic targeting of chemokines and their receptors on the development of hypertension. Promising results indicate that some of these pathways may serve as future therapeutic targets to improve blood pressure control and prevent target organ consequences including kidney failure, heart failure, atherosclerosis or cognitive impairment.

A pilot study on gene expression of endoplasmic reticulum unfolded protein response in chronic kidney disease

BACKGROUND

Chronic kidney disease (CKD) is a worldwide public health problem due to its increasing prevalence worldwide. Endoplasmic reticulum (ER) stress has been shown to play a role in the pathogenesis of various renal diseases in humans. It leads to the activation of the unfolded protein response (UPR) which triggers three known trans membrane sensors in the ER: activating transcription factor 6 (ATF6), inositol-requiring enzyme I (IRE1), and PKR (double-stranded RNA-dependent protein kinase)-like ER protein kinase (PERK). The activation of these signal transduction pathways can result in cell death, inflammation, and fibrosis in the context of CKD.

OBJECTIVES

The aim of this study was to detect the level of gene expression of activating transcription factor 6 (ATF6), inositol-requiring enzyme I (IRE1), and PKR (double-stranded RNA-dependent protein kinase)-like ER protein kinase (PERK) in chronic kidney disease patients.

SUBJECTS AND METHODS

This study was carried out on eighty subjects, 50 patients with CKD (25 with hypertension and 25 without hypertension) and 30 healthy subjects served as controls. All studied subjects underwent laboratory investigations, including CBC, Serum Lipid profile: Total cholesterol, Triglycerides, HDL-cholesterol and LDL-cholesterol, liver and kidney functions, fasting and 2 h postprandial blood glucose and HbA1C, serum level of IL6 and gene expression of ATF6, IRE1 and PERK using real time PCR technique.

RESULTS

There was a significant increase in relative quantitation (RQ) of gene expression of IRE1, ATF6 and PERK in chronic kidney patient groups with hypertension and without hypertension compared to control group. Also, there was a significant positive correlation of PERK and ATF6 gene expressions and a significant negative correlation of PERK gene expressions and GFR in groups I&II.

CONCLUSION

Endoplasmic reticulum (ER) stress occurs in CKD with activation of gene expression of three trans-membrane sensors in the ER: activating transcription factor 6 (ATF6), inositol-requiring enzyme I (IRE1), and PKR (double-stranded RNA-dependent protein kinase)-like ER protein kinase (PERK).

Triptolide attenuates renal damage by limiting inflammatory responses in DOCA-salt hypertension

BACKGROUND

Triptolide (TP), a principal bioactive component of traditional Chinese medicine Tripterygium wilfordii Hook. F., has been shown to have immunosuppressive/anti-inflammatory actions in vitro. Moreover, it is well established that inflammatory mechanisms contribute to the progression of hypertension-induced renal injury. Therefore, this study was performed to determine the protective effects of TP on renal injury in salt-sensitive hypertension and to identify the possible mechanisms for TP-induced protection.

METHODS

Ten-week-old male C57BL/6 mice were subjected to uninephrectomy and deoxycorticosterone acetate (DOCA)-salt treatment with or without intraperitoneal administration of various concentrations of TP.

RESULTS

Five weeks after the treatment, systolic blood pressure measured by tail-cuff plethysmography increased in DOCA-salt-treated mice, but no difference was found between DOCA-salt-treated mice with or without TP treatment. Treatment with TP dose-dependently attenuated increments in urinary albumin and 8-isoprostane excretion, and glomerulosclerosis and tubulointerstitial injury and fibrosis in DOCA-salt-treated mice. Moreover, our data showed that treatment with TP dose-dependently inhibited DOCA-salt-induced interstitial monocyte/macrophage infiltration associated with decreases in renal levels of proinflammatory cytokine/chemokine and adhesion molecule, as well as renal activated NF-κB concentrations. Our results also demonstrated that suppression of inflammatory responses with dexamethasone, an immunosuppressive agent, alleviated DOCA-salt hypertension-induced renal injury.

CONCLUSIONS

TP treatment induced renal protection associated with inhibition of monocyte/macrophage-mediated inflammatory responses without lowering blood pressure. Thus, our data for the first time indicate that TP treatment ameliorates renal injury possibly via attenuating inflammatory responses in salt-sensitive hypertension.

ADAM17-Mediated Shedding of Inflammatory Cytokines in Hypertension

The increase of Angiontesin-II (Ang-II), one of the key peptides of the renin-angiotensin system (RAS), and its binding to the Ang-II type 1 receptor (AT1R) during hypertension is a crucial mechanism leading to AD\AM17 activation. Among the reported membrane anchored proteins cleaved by ADAM17, immunological cytokines (TNF-α, IFN-γ, TGF-β, IL-4, IL-10, IL-13, IL-6, FKN) are the major class of substrates, modulation of which triggers inflammation. The rise in ADAM17 levels has both central and peripheral implications in inflammation-mediated hypertension. This narrative review provides an overview of the role of ADAM17, with a special focus on its cellular regulation on neuronal and peripheral inflammation-mediated hypertension. Finally, it highlights the importance of ADAM17 with regards to the biology of inflammatory cytokines and their roles in hypertension.

Greater T Regulatory Cells in Females Attenuate DOCA-Salt-Induced Increases in Blood Pressure Versus Males

Hypertension is the most common risk factor for cardiovascular disease, causing over 18 million deaths a year. Although the mechanisms controlling blood pressure (BP) in either sex remain largely unknown, T cells play a critical role in the development of hypertension. Further evidence supports a role for the immune system in contributing to sex differences in hypertension. The goal of the current study was to first, determine the impact of sex on the renal T-cell profiles in DOCA-salt hypertensive males and females and second, test the hypothesis that greater numbers of T regulatory cells (Tregs) in females protect against DOCA-salt-induced increases in BP and kidney injury. Male rats displayed greater increases in BP than females following 3 weeks of DOCA-salt treatment, although increases in renal injury were comparable between the sexes. DOCA-salt treatment resulted in an increase in proinflammatory T cells in both sexes; however, females had more anti-inflammatory Tregs than males. Additional male and female DOCA-salt rats were treated with anti-CD25 to decrease Tregs. Decreasing Tregs significantly increased BP only in females, thereby abolishing the sex difference in the BP response to DOCA-salt. This data supports the hypothesis that Tregs protect against the development of hypertension and are particularly important for the control of BP in females.

Tumor Necrosis Factor Alpha Deficiency Improves Endothelial Function and Cardiovascular Injury in Deoxycorticosterone Acetate/Salt-Hypertensive Mice

It has been shown that the inflammatory cytokine tumor necrosis factor α (TNFα) plays a role in the development of hypertension and end-stage renal diseases. We hypothesize that TNFα contributes to endothelial dysfunction and cardiac and vascular injury in deoxycorticosterone acetate (DOCA)/salt-hypertensive mice. The wild-type or TNFα-deficient mice were uninephrectomized and implanted with DOCA pellet treatment for 5 weeks; the mice were given either tap water or 1% NaCl drinking water. DOCA mice developed hypertension (systolic blood pressure (SBP): 167 ± 5 vs. 110 ± 4 mmHg in control group, p < 0.05), cardiac and vascular hypertrophy, and the impairment of endothelium-dependent relaxation to acetylcholine (EDR). TNFα deficiency improved EDR and lowered cardiac and vascular hypertrophy with a mild reduction in SBP (152 ± 4 vs. 167 ± 5 mmHg in DOCA group, p < 0.05) in DOCA mice. The mRNA expressions of the inflammatory cytokines, including TNFα, interleukin 1β (IL1β), monocyte chemotactic protein 1 (MCP1), and monocyte/macrophage marker F4/80 were significantly increased in the aorta of DOCA-hypertensive mice; TNFα deficiency reduced these inflammatory gene expressions. DOCA-hypertensive mice also exhibited an increase in the vascular oxidative fluorescence intensities, the protein expressions of gp91phox and p22phox, and the fibrotic factors transforming growth factor β and fibronectin. TNFα deficiency reduced oxidative stress and fibrotic protein expressions. The DOCA mice also showed a decrease in the protein expression of eNOS associated with increased miR155 expression; TNFα deficiency prevented a decrease in eNOS expression and an increase in miR155 expression in DOCA mice. These results support the idea that TNFα significantly contributes to vascular inflammation, vascular dysfunction, and injury in hypertension.

Renal Inflammation in DOCA-Salt Hypertension

Recent reports indicate that, in addition to treating hypertension, renal denervation (RDN) also mitigates renal inflammation. However, because RDN decreases renal perfusion pressure, it is unclear whether these effects are because of the direct effects of RDN on inflammatory signaling or secondary to decreased arterial pressure (AP). Therefore, this study was conducted to elucidate the contribution of renal nerves to renal inflammation in the deoxycorticosterone (DOCA)-salt rat, a model in which RDN decreases AP and abolishes renal inflammation. In Experiment 1, we assessed the temporal changes in renal inflammation by measuring renal cytokines and AP in DOCA-salt rats. Uninephrectomized (1K) adult male Sprague Dawley rats that received surgical RDN or sham (Sham) were administered DOCA (100 mg, SC) and 0.9% saline for 21 days. AP was measured by radiotelemetry, and urinary cytokine excretion was measured repeatedly. In Experiment 2, the contribution of renal nerves in renal inflammation was assessed in a 2-kidney DOCA-salt rat to control for renal perfusion pressure. DOCA-salt treatment was administered after unilateral (U-)RDN. In Experiment 1, DOCA-salt-induced increases in AP and renal inflammation (assessed by urinary cytokines) were attenuated by RDN versus Sham. In Experiment 2, GRO/KC (growth-related oncogene/keratinocyte chemoattractant), MCP (monocyte chemoattractant protein)-1, and macrophage infiltration were lower in the denervated kidney versus the contralateral Sham kidney. No differences in T-cell infiltration were observed. Together, these data support the hypothesis that renal nerves mediate, in part, the development of renal inflammation in the DOCA-salt rat independent of hypertension. The mechanisms and cell-specificity mediating these effects require further investigation.

Triptolide attenuates lipopolysaccharide-induced inflammatory responses in human endothelial cells: involvement of NF-κB pathway

BACKGROUND

Endothelial cell inflammation is a central event in the pathogenesis of numerous cardiovascular diseases, including sepsis and atherosclerosis. Triptolide, a principal bioactive ingredient of Traditional Chinese Medicine Tripterygium wilfordii Hook.F., displays anti-inflammatory actions in vivo. However, the mechanisms underlying these beneficial effects remain undetermined. The present study investigated the effects and possible mechanisms of triptolide on lipopolysaccharide (LPS)-induced inflammatory responses in human umbilical vein endothelial cells (HUVECs).

METHODS

The effects of triptolide on the LPS-induced production and expression of inflammatory molecules, monocyte adhesion and activation of nuclear factor (NF)-κB pathway were examined in cultured HUVECs.

RESULTS

In cultured HUVECs, pre-treatment with triptolide dose-dependently attenuated LPS-induced cytokine and chemokine production, adhesion molecule expression and monocyte adhesion. Mechanistically, triptolide was found to dose-dependently inhibit the LPS-induced increases in the DNA binding activity of NF-κB p65 associated with attenuating IκBα phosphorylation and its degradation. Additionally, the present study revealed that triptolide inhibited LPS-triggered NF-κB transcriptional activation in a dose-dependent manner.

CONCLUSIONS

The results of the present study indicated that triptolide suppresses the inflammatory response of endothelial cells possibly via inhibition of NF-κB activation.

Adaptive Immunity in Hypertension

PURPOSE OF REVIEW

In recent years, a vast body of evidence has accumulated indicating the role of the immune system in the regulation of blood pressure and modulation of hypertensive pathology. Numerous cells of the immune system, both innate and adaptive immunity, have been indicated to play an important role in the development and maintenance of hypertension. The purpose of this review was to summarize the role of adaptive immunity in experimental models of hypertension (genetic, salt-sensitive, and Angiotensin (Ang) II induced) and in human studies. In particular, the role of T and B cells is discussed.

RECENT FINDINGS

In response to hypertensive stimuli such as Ang II and high salt, T cells become pro-inflammatory and they infiltrate the brain, blood vessel adventitia and periadventitial fat, heart, and the kidney. Pro-inflammatory T cell-derived cytokines such as IFN-γ and TNF-α (from CD8+ and CD4+Th1) and IL-17A (from the γδ-T cell and CD4+Th17) exacerbate hypertensive responses mediating both endothelial dysfunction and cardiac, renal, and neurodegenerative injury. The modulation of adaptive immune activation in hypertension has been attributed to target organ oxidative stress that leads to the generation of neoantigens, including isolevuglandin-modified proteins. The role of adaptive immunity is sex-specific with much more pronounced mechanisms in males than that in females. Hypertension is also associated with B cell activation and production of autoantibodies (anti-Hsp70, anti-Hsp65, anti-Hsp60, anti-AT1R, anti-α1AR, and anti-β1AR). The hypertensive responses can be inhibited by T regulatory lymphocytes (Tregs) and their anti-inflammatory IL-10. Adaptive immunity and its interface with innate mechanisms may represent valuable targets in the modulation of blood pressure, as well as hypertension-related residual risk.

The protective effects of polysaccharide extract from Xin-Ji-Er-Kang formula on Ang II-induced HUVECs injury, L-NAME-induced hypertension and cardiovascular remodeling in mice

Background

Xin-Ji-Er-Kang (XJEK) is a Chinese herbal formula, which has been reported to exert effective protection against cardiovascular diseases, including hypertension and myocarditis.

Methods

Cultured human umbilical vascular endothelial cells (HUVECs) were treated with angiotensin II (Ang II) and different concentrations of aqueous layer extracts (AqE). Subsequently nitric oxide (NO) and endothelial nitric oxide synthase (eNOS) expression levels were detected. In addition, fifty Kunming mice were randomized into control, Nω-nitro-L-arginine methyl ester (L-NAME), L-NAME+AqE, L-NAME+XJEK and L-NAME+fosinopril treatment groups. Following 8 weeks of treatment, the cardiac hemodynamic index was measured, relaxation of the aorta was examined and pathological changes were observed. Colorimetric analysis and enzyme linked immunosorbent assay (ELISA) were applied to determine the relevant indicators in plasma and cardiac tissues.

Results

The in vitro study results demonstrated that AqE could preserve endothelial function (NO, 21.05 ± 2.03 vs. 8.64 ± 0.59; eNOS, 1.08 ± 0.17 vs.0.73 ± 0.06). In addition, the in vivo results demonstrated that compared with the control group, treatment with AqE could enhance a high hemodynamic state (left ventricular systolic pressure, 116.76 ± 9.96 vs.114.5 ± 15.16), improve endothelial function (NO, 7.98 ± 9.64 vs. 1.66 ± 3.11; eNOS, 19.78 ± 3.18 vs.19.38 ± 3.85), suppress oxidative stress (OS) (superoxide dismutase, 178.17 ± 13.78 vs. 159.38 ± 18.86; malondialdehyde, 0.77 ± 0.13 vs.1.25 ± 0.36) and reverse cardiovascular remodeling.

Conclusion

Polysaccharide from XJEK exerts protective effects against Ang II-induced injury in HUVECs and L-NAME-induced hypertension in mice and the underlying mechanism may be attributed to improving endothelial dysfunction, OS and the inflammation status in mice.

Autonomic regulation of T-lymphocytes: Implications in cardiovascular disease

The nervous and immune systems both serve as essential assessors and regulators of physiological function. Recently, there has been a great interest in how the nervous and immune systems interact to modulate both physiological and pathological states. In particular, the autonomic nervous system has a direct line of communication with immune cells anatomically, and moreover, immune cells possess receptors for autonomic neurotransmitters. This circumstantial evidence is suggestive of a functional interplay between the two systems, and extensive research over the past few decades has demonstrated neurotransmitters such as the catecholamines (i.e. dopamine, norepinephrine, and epinephrine) and acetylcholine have potent immunomodulating properties. Furthermore, immune cells, particularly T-lymphocytes, have now been found to express the cellular machinery for both the synthesis and degradation of neurotransmitters, which suggests the ability for both autocrine and paracrine signaling from these cells independent of the nervous system. The details underlying the functional interplay of this complex network of neuroimmune communication are still unclear, but this crosstalk is suggestive of significant implications on the pathogenesis of a number of autonomic-dysregulated and inflammation-mediated diseases. In particular, it is widely accepted that numerous forms of cardiovascular diseases possess imbalanced autonomic tone as well as altered T-lymphocyte function, but a paucity of literature exists discussing the direct role of neurotransmitters in shaping the inflammatory microenvironment during the progression or therapeutic management of these diseases. This review seeks to provide a fundamental framework for this autonomic neuroimmune interaction within T-lymphocytes, as well as the implications this may have in cardiovascular diseases.

Tauroursodeoxycholic acid (TUDCA) abolishes chronic high salt-induced renal injury and inflammation

AIM

Chronic high salt intake exaggerates renal injury and inflammation, especially with the loss of functional ET_B receptors. Tauroursodeoxycholic acid (TUDCA) is a chemical chaperone and bile salt that is approved for the treatment of hepatic diseases. Our aim was to determine whether TUDCA is reno-protective in a model of ET_B receptor deficiency with chronic high salt-induced renal injury and inflammation.

METHODS

ET_B -deficient and transgenic control rats were placed on normal (0.8% NaCl) or high salt (8% NaCl) diet for 3 weeks, receiving TUDCA (400 mg/kg/d; ip) or vehicle. Histological and biochemical markers of kidney injury, renal cell death and renal inflammation were assessed.

RESULTS

In ET_B -deficient rats, high salt diet significantly increased glomerular and proximal tubular histological injury, proteinuria, albuminuria, excretion of tubular injury markers KIM-1 and NGAL, renal cortical cell death and renal CD4⁺ T cell numbers. TUDCA treatment increased proximal tubule megalin expression as well as prevented high salt diet-induced glomerular and tubular damage in ET_B -deficient rats, as indicated by reduced kidney injury markers, decreased glomerular permeability and proximal tubule brush border restoration, as well as reduced renal inflammation. However, TUDCA had no significant effect on blood pressure.

CONCLUSIONS

TUDCA protects against the development of glomerular and proximal tubular damage, decreases renal cell death and inflammation in the renal cortex in rats with ET_B receptor dysfunction on a chronic high salt diet. These results highlight the potential use of TUDCA as a preventive tool against chronic high salt induced renal damage.

Emerging Roles of Sympathetic Nerves and Inflammation in Perivascular Adipose Tissue

Perivascular adipose tissue (PVAT) is no longer recognised as simply a structural support for the vasculature, and we now know that PVAT releases vasoactive factors which modulate vascular function. Since the discovery of this function in 1991, PVAT research is rapidly growing and the importance of PVAT function in disease is becoming increasingly clear. Obesity is associated with a plethora of vascular conditions; therefore, the study of adipocytes and their effects on the vasculature is vital. PVAT contains an adrenergic system including nerves, adrenoceptors and transporters. In obesity, the autonomic nervous system is dysfunctional; therefore, sympathetic innervation of PVAT may be the key mechanistic link between increased adiposity and vascular disease. In addition, not all obese people develop vascular disease, but a common feature amongst those that do appears to be the inflammatory cell population in PVAT. This review will discuss what is known about sympathetic innervation of PVAT, and the links between nerve activation and inflammation in obesity. In addition, we will examine the therapeutic potential of exercise in sympathetic stimulation of adipose tissue.

The TNF-derived TIP peptide activates the epithelial sodium channel and ameliorates experimental nephrotoxic serum nephritis

In mice, the initial stage of nephrotoxic serum-induced nephritis (NTN) mimics antibody-mediated human glomerulonephritis. Local immune deposits generate tumor necrosis factor (TNF), which activates pro-inflammatory pathways in glomerular endothelial cells (GECs) and podocytes. Because TNF receptors mediate antibacterial defense, existing anti-TNF therapies can promote infection; however, we have previously demonstrated that different functional domains of TNF may have opposing effects. The TIP peptide mimics the lectin-like domain of TNF, and has been shown to blunt inflammation in acute lung injury without impairing TNF receptor-mediated antibacterial activity. We evaluated the impact of TIP peptide in NTN. Intraperitoneal administration of TIP peptide reduced inflammation, proteinuria, and blood urea nitrogen. The protective effect was blocked by the cyclooxygenase inhibitor indomethacin, indicating involvement of prostaglandins. Targeted glomerular delivery of TIP peptide improved pathology in moderate NTN and reduced mortality in severe NTN, indicating a local protective effect. We show that TIP peptide activates the epithelial sodium channel(ENaC), which is expressed by GEC, upon binding to the channel's α subunit. In vitro, TNF treatment of GEC activated pro-inflammatory pathways and decreased the generation of prostaglandin E2 and nitric oxide, which promote recovery from NTN. TIP peptide counteracted these effects. Despite the capacity of TIP peptide to activate ENaC, it did not increase mean arterial blood pressure in mice. In the later autologous phase of NTN, TIP peptide blunted the infiltration of Th17 cells. By countering the deleterious effects of TNF through direct actions in GEC, TIP peptide could provide a novel strategy to treat glomerular inflammation.

Renal Effects of Cytokines in Hypertension

Preclinical studies point to a key role for immune cells in hypertension via augmenting renal injury and/or hypertensive responses. Blood pressure elevation in rheumatologic patients is attenuated by anti-inflammatory therapies. Both the innate and adaptive immune systems contribute to the pathogenesis of hypertension by modulating renal sodium balance, blood flow, and functions of the vasculature and epithelial cells in the kidney. Monocytes/macrophages and T lymphocytes are pivotal mediators of hypertensive responses, while dendritic cells and B lymphocytes can regulate blood pressure indirectly by promoting T lymphocytes activation. Pro-inflammatory cytokines, such as tumor necrosis factor-α (TNF), interleukin-1 (IL-1), interleukin-17 (IL-17), and interferon-γ (IFN), amplify blood pressure elevation and/or renal injury. By contrast, interleukin-10 (IL-10) protects against renal and vascular function when produced by T helper 2 cells (Th2) and regulatory T cells (Treg). Thus, understanding the renal effects of cytokines in hypertension will provide targets for precise immunotherapies to inhibit targeted organ damage while preserving necessary immunity.

Pharmacological potentiation of the efferent vagus nerve attenuates blood pressure and renal injury in a murine model of systemic lupus erythematosus

Recent evidence suggests hypertension may be secondary to chronic inflammation that results from hypoactive neuro-immune regulatory mechanisms. To further understand this association, we used systemic lupus erythematosus (SLE) as a model of inflammation-induced hypertension. In addition to prevalent inflammatory kidney disease and hypertension, SLE patients suffer from dysautonomia in the form of decreased efferent vagal tone. Based on this, the cholinergic anti-inflammatory pathway, an endogenous vagus-to-spleen mechanism that, when activated results in decreases in systemic inflammation, may be compromised in SLE. We hypothesized that stimulation of the cholinergic anti-inflammatory pathway via pharmacological potentiation of the efferent vagus nerve would reduce inflammation and halt the development of hypertension and renal injury in SLE. Female NZBWF1 mice, an established model of murine SLE, and female control mice were treated with galantamine (4 mg/kg daily ip), an acetylcholinesterase inhibitor, or saline for 14 days. At the end of therapy, carotid catheters were surgically implanted and were used to measure mean arterial pressure before the animals were euthanized. Chronic galantamine administration attenuated both splenic and renal cortical inflammation, which likely explains why the hypertension and renal injury (i.e., glomerulosclerosis and fibrosis) typically observed in murine SLE was attenuated following therapy. Based on this, the anti-inflammatory, antihypertensive, and renoprotective effects of galantamine may be mediated through activation of the cholinergic anti-inflammatory pathway. It is possible that dysfunction of the cholinergic anti-inflammatory pathway exists in SLE at the level of the efferent vagus nerve and promoting restoration of its activity through central cholinergic receptor activation may be beneficial.

Angiotensin receptor and tumor necrosis factor-α activation contributes to glucose intolerance independent of systolic blood pressure in obese rats

Pathological activation of the renin-angiotensin system and inflammation are associated with hypertension and the development of metabolic syndrome (MetS). The contributions of angiotensin receptor type 1 (AT1) activation, independent of blood pressure, and inflammation to glucose intolerance and renal damage are not well defined. Using a rat model of MetS, we hypothesized that the onset of glucose intolerance is primarily mediated by AT1 activation and inflammation independent of elevated systolic blood pressure (SBP). To address this hypothesis, we measured changes in SBP, adiposity, plasma glucose and triglyceride levels, and glucose tolerance in six groups of rats: 1) lean, strain control Long-Evans Tokushima Otsuka (LETO; n = 5), 2) obese Otsuka Long-Evans Tokushima Fatty (OLETF; n = 8), 3) OLETF + angiotensin receptor blocker (ARB; 10 mg olmesartan/kg; n = 8), 4) OLETF + tumor necrosis factor-α (TNF-α) inhibitor (ETAN; 1.25 mg etanercept/kg; n = 6), 5) OLETF + TNF-α inhibitor + angiotensin receptor blocker (ETAN+ARB; 1.25 mg etanercept/kg + 10 mg olmesartan/kg; n = 6), and 6) OLETF + calcium channel blocker (CCB; 5 mg amlodipine/kg; n = 7). ARB and ETAN+ARB were most effective at decreasing SBP in OLETF, and ETAN did not offer any additional reduction. Glucose tolerance improved in ARB, ETAN, and ETAN+ARB compared with OLETF, whereas CCB had no detectable effect. Furthermore, all treatments reduced adiposity, whereas ETAN alone normalized urinary albumin excretion. These results suggest that AT1 activation and inflammation are primary factors in the development of glucose intolerance in a setting of MetS and that the associated increase in SBP is primarily mediated by AT1 activation.

Renal effects of cytokines in hypertension

PURPOSE OF REVIEW

Inflammatory cytokines contribute to the pathogenesis of hypertension through effects on renal blood flow and sodium handling. This review will update recent advances that explore the renal actions of immune cells and cytokines in the pathogenesis of hypertension.

RECENT FINDINGS

Populations of cells from both the innate and adaptive immune systems contribute to hypertension by modulating functions of the vasculature and epithelial cells in the kidney. Macrophages and T lymphocytes can directly regulate the hypertensive response and consequent target organ damage. Dendritic cells and B lymphocytes can alter blood pressure (BP) indirectly by facilitating T-cell activation. Proinflammatory cytokines, including tumor necrosis factor-α, interleukin 17, interleukin 1, and interferon-γ augment BP and/or renal injury when produced by T helper 1 cells, T helper 17 cells, and macrophages. In contrast, interleukin 10 improves vascular and renal functions in preclinical hypertension studies. The effects of transforming growth factor-β are complex because of its profibrotic and immunosuppressive functions that also depend on the localization and concentration of this pleiotropic cytokine.

SUMMARY

Preclinical studies point to a key role for cytokines in hypertension via their actions in the kidney. Consistent with this notion, anti-inflammatory therapies can attenuate BP elevation in human patients with rheumatologic disease. Conversely, impaired natriuresis may further polarize both T lymphocytes and macrophages toward a proinflammatory state, in a pathogenic, feed-forward loop of immune activation and BP elevation. Understanding the precise renal actions of cytokines in hypertension will be necessary to inhibit cytokine-dependent hypertensive responses while preserving systemic immunity and tumor surveillance.

Na+-Cl- cotransporter-mediated chloride uptake contributes to hypertension and renal damage in aldosterone-infused rats

Recently, in addition to epithelial sodium channel alpha-subunit (αENaC), the thiazide-sensitive sodium-chloride cotransporter (NCC) and pendrin, also known as sodium-independent chloride/iodide transporter, were reported to be activated by aldosterone. Here, we investigated whether chloride (Cl^-) is responsible for hypertension, inflammation, and renal damage in aldosterone-infused rats. Following left nephrectomy, 8-wk-old male Sprague-Dawley rats were allocated into four groups: 1) drinking 1.0% sodium chloride solution with aldosterone infusion (Aldo/NaCl rats); 2) drinking 1.44% sodium bicarbonate solution with aldosterone infusion (Aldo/NaHCO₃ rats); 3) drinking distilled water with aldosterone infusion (Aldo/water rats); and 4) drinking distilled water without aldosterone infusion (sham rats). Additionally, heminephrectomized rats with aldosterone infusion were fed a 0.26% NaCl diet (control); 8.0% NaCl diet (high-Na/high-Cl); or a 4.0% NaCl 6.67% sodium citrate diet (high-Na/half-Cl). Last, Aldo/NaCl rats were treated with or without hydrochlorothiazide. Blood pressure in the Aldo/NaCl rats was significantly higher than in the Aldo/NaHCO₃ rats, which was associated with the increased expression of NCC. Expression of markers of inflammation (CD3, CD68, interleukin-17A) and fibrosis (α-smooth muscle actin, collagen 1) were also increased in Aldo/NaCl rats. Similarly, aldosterone-infused rats fed a high-Na/half-Cl diet had lower blood pressure than those fed a high-Na/high-Cl diet, with a reduction of phosphorylated NCC, but not αENaC and pendrin. NCC inhibition with hydrochlorothiazide attenuated interleukin-17A protein expression along with the phosphorylation of NCC in Aldo/NaCl rats. These findings suggest that NCC-mediated Cl^- uptake plays important roles in the development of aldosterone-induced hypertension and renal injury.

Inflammatory Signaling in Hypertension: Regulation of Adrenal Catecholamine Biosynthesis

The immune system is increasingly recognized for its role in the genesis and progression of hypertension. The adrenal gland is a major site that coordinates the stress response via the hypothalamic-pituitary-adrenal axis and the sympathetic-adrenal system. Catecholamines released from the adrenal medulla function in the neuro-hormonal regulation of blood pressure and have a well-established link to hypertension. The immune system has an active role in the progression of hypertension and cytokines are powerful modulators of adrenal cell function. Adrenal medullary cells integrate neural, hormonal, and immune signals. Changes in adrenal cytokines during the progression of hypertension may promote blood pressure elevation by influencing catecholamine biosynthesis. This review highlights the potential interactions of cytokine signaling networks with those of catecholamine biosynthesis within the adrenal, and discusses the role of cytokines in the coordination of blood pressure regulation and the stress response.

Antihypertensive and antioxidant effects of protocatechuic acid in deoxycorticosterone acetate-salt hypertensive rats

Protocatechuic acid (PCA) is a natural antioxidant with beneficial cardiovascular properties. In this study, the effect of supplementation with PCA was investigated in deoxycorticosterone acetate (DOCA)-salt hypertension. Male Wistar rats received DOCA (25 mg/kg, s.c.) twice weekly and 1% NaCl in drinking water and simultaneously treated with PCA (50, 100 and 200 mg/kg, p.o.) for 4 weeks. Systolic blood pressure (SBP) was detected using tail-cuff method. Electrolytes including Na⁺, K⁺ and chloride, catalase activity, glutathione, total antioxidant capacity, malondialdehyde (MDA) and hydroperoxides concentration were measured in serum samples. Body and organs weight, water intake and, kidney and heart histopathology were also evaluated. Administration of PCA reversed the changes caused by DOCA-salt approximately at all doses. At the lowest dose, PCA significantly decreased SBP (132.5 ± 4.0 vs 152.3 ± 4.5 mmHg, P < .05), serum sodium (138.5  ± 1.52 vs 141 ± 1.50, P < .05) and chloride level (101.6 ± 1.47 vs 110 ± 1.39, P < .01) and raised serum potassium level (3.8 ± 0.09 vs 3.1 ± 0.17, P < .05) compared with DOCA-salt hypertensive rats. PCA increased serum catalase activity, total antioxidant capacity and glutathione concentration and reduced MDA and hydroperoxides levels. PCA also improved organ weight changes, reduced water intake and moderately prevented histopathological changes of kidney and heart upon DOCA-salt administration. The present study indicates the antihypertensive and antioxidant effects of PCA against DOCA-salt hypertension.

Redox system and phospholipid metabolism in the kidney of hypertensive rats after FAAH inhibitor URB597 administration

Primary and secondary hypertension is associated with kidney redox imbalance resulting in enhanced reactive oxygen species (ROS) and enzymes dependent phospholipid metabolism. The fatty acid amide hydrolase inhibitor, URB597, modulates the levels of endocannabinoids, particularly of anandamide, which is responsible for controlling blood pressure and regulating redox balance. Therefore, this study aimed to compare the effects of chronic URB597 administration to spontaneously hypertensive rats (SHR) and rats with secondary hypertension (DOCA-salt rats) on the kidney metabolism associated with the redox and endocannabinoid systems. It was shown fatty acid amide hydrolase (FAAH) inhibitor decreased the activity of ROS-generated enzymes what resulted in a reduction of ROS level. Moreover varied changes in antioxidant parameters were observed with tendency to improve antioxidant defense in SHR kidney. Moreover, URB597 administration to hypertensive rats decreased pro-inflammatory response, particularly in the kidneys of DOCA-salt hypertensive rats. URB597 had tendency to enhance ROS-dependent phospholipid oxidation, estimated by changes in neuroprostanes in the kidney of SHR and reactive aldehydes (4-hydroxynonenal and malondialdehyde) in DOCA-salt rats, in particular. The administration of FAAH inhibitor resulted in increased level of endocannabinoids in kidney of both groups of hypertensive rats led to enhanced expression of the cannabinoid receptors type 1 and 2 in SHR as well as vanilloid receptor 1 receptors in DOCA-salt rats. URB597 given to normotensive rats also affected kidney oxidative metabolism, resulting in enhanced level of neuroprostanes in Wistar Kyoto rats and reactive aldehydes in Wistar rats. Moreover, the level of endocannabinoids and cannabinoid receptors were significantly higher in both control groups of rats after URB597 administration.

In conclusion, because URB597 disturbed the kidney redox system and phospholipid ROS-dependent and enzymatic-dependent metabolism, the administration of this inhibitor may enhance kidney disorders depending on model of hypertension, but may also cause kidney disturbances in control rats. Therefore, further studies are warranted.

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URB597 has tendency to decrease kidney oxidative conditions.

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URB597 differentiates Nrf2 pathway response in kidney of SHR and DOCA-salt rats.

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URB597 enhances level of phospholipid peroxidation products and endocannabinoids.

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URB597 reduces pro-inflammatory response particularly in kidney of DOCA-salt rats.

Tumor necrosis factor-α, kidney function, and hypertension

Hypertension is considered to be a low-grade inflammatory condition characterized by the presence of various proinflammatory cytokines. Tumor necrosis factor-α (TNF-α) is a constituent of the proinflammatory cytokines that is associated with salt-sensitive hypertension (SSH) and related renal injury. Elevated angiotensin II (ANG II) and other factors such as oxidative stress conditions promote TNF-α formation. Many recent studies have provided evidence that TNF-α exerts a direct renal action by regulating hemodynamic and excretory function in the kidney. The cytokine incites a strong natriuretic response and plays a part in regulation of the intrarenal renin-angiotensin system. The exact mechanistic role of TNF-α in the development of SSH is as yet poorly understood. While TNF-α antagonism has been shown to attenuate hypertensive responses in many hypertensive animal models, contrasting findings demonstrate that the direct systemic administration of TNF-α usually induces hypotensive as well as natriuretic responses, indicating a counterregulatory role of TNF-α in SSH. Differential activities of two cell surface receptors of TNF-α (receptor type 1 and type 2) may explain the contradictory functions of TNF-α in the setting of hypertension. This short review will evaluate ongoing research studies that investigate the action of TNF-α within the kidney and its role as an influential pathophysiological variable in the development of SSH and renal injury. This information may help to develop specific TNF-α receptor targeting as an effective treatment strategy in this clinical condition.

Circulating Th1, Th2, and Th17 Levels in Hypertensive Patients

Background

Evidence from experimental studies showed that Th1, Th2, and Th17 play a pivotal role in hypertension and target organ damage. However, whether changes in the circulating Th1, Th2, and Th17 levels are associated with nondipper hypertension and carotid atherosclerotic plaque in hypertension has yet to be investigated.

Methods

Th1, Th2, and Th17 levels were detected using a flow cytometric analysis, and their related cytokines were measured by enzyme-linked immunosorbent assay in 45 hypertensive patients and 15 normotensive subjects.

Results

The frequencies of Th1 and Th17 in hypertensive patients, especially in nondipper patients and patients with carotid atherosclerotic plaque, were markedly higher than those in the control group; this was accompanied by higher IFN-γ and IL-17 levels. In contrast, the Th2 frequencies and IL-4 levels in hypertensive patients, especially in nondipper patients and patients with carotid atherosclerotic plaque, were significantly lower than those in the control group.

Conclusions

The changes in Th1, Th2, and Th17 activity are associated with the onset of the nondipper type and carotid atherosclerotic plaque in hypertensive patients.

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.

Role of renal transporters and novel regulatory interactions in the TAL that control blood pressure

Hypertension (HTN), a major public health issue is currently the leading factor in the global burden of disease, where associated complications account for 9.4 million deaths worldwide every year. Excessive dietary salt intake is among the environmental factors that contribute to HTN, known as salt sensitivity. The heterogeneity of salt sensitivity and the multiple mechanisms that link high salt intake to increases in blood pressure are of upmost importance for therapeutic application. A continual increase in the kidney's reabsorption of sodium (Na+) relies on sequential actions at various segments along the nephron. When the distal segments of the nephron fail to regulate Na+, the effects on Na+ homeostasis are unfavorable. We propose that the specific nephron region where increased active uptake occurs as a result of variations in Na+ reabsorption is at the thick ascending limb of the loop of Henle (TAL). The purpose of this review is to urge the consideration of the TAL as contributing to the pathophysiology of salt-sensitive HTN. Further research in this area will enable development of a therapeutic application for targeted treatment.

Single-trait and multi-trait genome-wide association analyses identify novel loci for blood pressure in African-ancestry populations

Hypertension is a leading cause of global disease, mortality, and disability. While individuals of African descent suffer a disproportionate burden of hypertension and its complications, they have been underrepresented in genetic studies. To identify novel susceptibility loci for blood pressure and hypertension in people of African ancestry, we performed both single and multiple-trait genome-wide association analyses. We analyzed 21 genome-wide association studies comprised of 31,968 individuals of African ancestry, and validated our results with additional 54,395 individuals from multi-ethnic studies. These analyses identified nine loci with eleven independent variants which reached genome-wide significance (P < 1.25×10-8) for either systolic and diastolic blood pressure, hypertension, or for combined traits. Single-trait analyses identified two loci (TARID/TCF21 and LLPH/TMBIM4) and multiple-trait analyses identified one novel locus (FRMD3) for blood pressure. At these three loci, as well as at GRP20/CDH17, associated variants had alleles common only in African-ancestry populations. Functional annotation showed enrichment for genes expressed in immune and kidney cells, as well as in heart and vascular cells/tissues. Experiments driven by these findings and using angiotensin-II induced hypertension in mice showed altered kidney mRNA expression of six genes, suggesting their potential role in hypertension. Our study provides new evidence for genes related to hypertension susceptibility, and the need to study African-ancestry populations in order to identify biologic factors contributing to hypertension.

Upregulation of nuclear factor-κB activity mediates CYP24 expression and reactive oxygen species production in indoxyl sulfate-induced chronic kidney disease

AIM

Chronic kidney disease (CKD) is associated with an inflammation-mediated process, and the vitamin D (3) catabolizing enzyme, CYP24, is frequently overexpressed in CKD, where it may play a crucial role in kidney disease.

METHODS

Herein, in this study, we investigated CYP24, reactive oxygen species (ROS), and inflammatory responses in an indoxyl sulfate (IS)-induced CKD model to elucidate the role of CYP24 in CKD.

RESULTS

Our results showed that IS upregulates proinflammatory cytokine, CYP24 and nuclear factor-κB (NF-κB) expression in human renal proximal tubule epithelial cells. In addition, IS treatment increased ROS production and simultaneously upregulated CYP24 expression and NF-κB translocation. Moreover, the IS-induced upregulation of CYP24 expression was alleviated by an inhibitor of NF-κB, as well as a siRNA specific to NF-κB p65. Furthermore, the renal cortex of DN (Dahl salt-resistant normotensive) + IS, DH (Dahl salt-sensitive hypertensive), and DH + IS rats showed increased expression of NF-κB p65, CYP24, 8-hydroxydeoxyguanosine (8-OHdG), a marker of ROS and macrophage infiltration compared with DN rats.

CONCLUSIONS

These results provide evidence that administration of IS in human renal tubular epithelial cells upregulates NF-κB, which leads to increase CYP24 expression and ROS production. They also suggest that suppressing NF-κB signalling is promising for the development into a strategy for CKD treatment.

Influence of Endothelin 1 Receptor Blockers and a Nitric Oxide Synthase Inhibitor on Reactive Oxygen Species Formation in Rat Lungs

This study was designated to estimate protective role of ETA and ETB receptor antagonist against endothelin 1 (ET-1)-induced oxidative stress in lungs and determine whether these effects are mediated by nitric oxide (NO) synthase. Experiments were performed on Wistar rats divided into the following groups: I – saline (0.9 % NaCl); II – ET-1 (3 μg/kg b.w.), III – BQ123 (1 mg/kg b.w.) + ET-1 (3 μg/kg b.w.), IV – BQ788 (3 mg/kg b.w.) + ET-1 (3 μg/kg b.w.), V – N-nitro-L-arginine methyl ester (L-NAME) (5 mg/kg b.w.) + ET-1 (3 μg/kg b.w.). ETA and ETB receptor antagonists or L-NAME were administered 30 min before ET-1 injection. The levels of the following substances were measured in the lungs homogenates: thiobarbituric acid reactive substances (TBARS), hydrogen peroxide (H2O2), reduced glutathione (GSH) and tumor necrosis factor-alpha (TNF-α). The results showed that ET-1 significantly increased TBARS, H2O2 (respectively: p<0.001, p<0.02) and TNF-α levels (p<0.02) and decreased the GSH level (p<0.01) vs. control group. On the other hand, prior administration of ETA receptor blocker (BQ123) significantly attenuated TBARS (p<0.01), H2O2 (p<0.02), TNF-α (p<0.02) and increased GSH (p<0.02) levels vs. ET-1. However, prior administration of ETB receptor blocker BQ788 did not cause significant changes in the: TBARS, H2O2 and TNF-α (p>0.05) levels, but significantly increased the GSH level and GSH/GSSG ratio (p<0.05). Administration of L-NAME significantly attenuated TBARS (p<0.001), H2O2 (p<0.05), TNF-α (p<0.01) and increased GSH (p<0.05) levels vs. ET-1. In conclusion, we demonstrated that ET-1 induced oxidative stress in the lungs is mediated by ETA receptors. ETA receptor blockage inhibited generation of free radicals and TNF-α and ameliorated antioxidant properties. Moreover, generation of reactive oxygen species is mediated by NOS in the lungs.

Role of Tumor Necrosis Factor-α and Natural Killer Cells in Uterine Artery Function and Pregnancy Outcome in the Stroke-Prone Spontaneously Hypertensive Rat

Women with chronic hypertension are at increased risk of maternal and fetal morbidity and mortality. We have previously characterized the stroke-prone spontaneously hypertensive rat (SHRSP) as a model of deficient uterine artery function and adverse pregnancy outcome compared with the control Wistar-Kyoto. The activation of the immune system plays a role in hypertension and adverse pregnancy outcome. Therefore, we investigated the role of tumor necrosis factor-α in the SHRSP phenotype in an intervention study using etanercept (0.8 mg/kg SC) at gestational days 0, 6, 12, and 18 in pregnant SHRSP compared with vehicle-treated controls (n=6). Etanercept treatment significantly lowered systolic blood pressure after gestational day 12 and increased litter size in SHRSP. At gestational day 18, etanercept improved the function of uterine arteries from pregnant SHRSP normalizing the contractile response and increasing endothelium-dependent relaxation, resulting in increased pregnancy-dependent diastolic blood flow in the uterine arteries. We identified that the source of excess tumor necrosis factor-α in the SHRSP was a pregnancy-dependent increase in peripheral and placental CD3^- CD161⁺ natural killer cells. Etanercept treatment also had effects on placental CD161⁺ cells by reducing the expression of CD161 receptor, which was associated with a decrease in cytotoxic granzyme B expression. Etanercept treatment improves maternal blood pressure, pregnancy outcome, and uterine artery function in SHRSP by antagonizing signaling from excess tumor necrosis factor-α production and the reduction of granzyme B expression in CD161⁺ natural killer cells in SHRSP.

Interleukin-6 inhibition attenuates hypertension and associated renal damage in Dahl salt-sensitive rats

Immune cells in the kidney are implicated in the development of hypertension and renal damage in the Dahl salt-sensitive (SS) rat. Interestingly, interleukin 6 (IL-6) mRNA is 54-fold higher in T-lymphocytes isolated from the kidney compared with circulating T-lymphocytes. The present experiments assessed the role of IL-6 in the development of SS hypertension by treating rats (n = 13-14/group) with an IL-6 neutralizing antibody or normal IgG during an 11-day period of high-salt (4.0% NaCl chow) intake. The mean arterial pressure (MAP) and urine albumin excretion rates (Ualb) were not different between the groups fed low salt (0.4% NaCl). Following 11 days of drug treatment and high salt, however, the rats receiving anti-IL-6 demonstrated a 47% reduction of IL-6 in the renal medulla compared with control SS. Moreover, the increase in MAP following 11 days of high-NaCl intake was significantly attenuated in SS administered anti-IL-6 compared with the control group (138 ± 3 vs. 149 ± 3 mmHg) as was the salt-induced increase in Ualb and glomerular and tubular damage. To investigate potential mechanisms of action, a flow cytometric analysis of immune cells in the kidney (n = 8-9/group) demonstrated that the total number of monocytes and macrophages was significantly lower in the treatment vs. the control group. The total number of T- and B-lymphocytes in the kidneys was not different between groups. These studies indicate that IL-6 production may participate in the development of SS hypertension and end-organ damage by mediating increased infiltration or proliferation of macrophages into the kidney.

Longitudinal genome-wide methylation study of Roux-en-Y gastric bypass patients reveals novel CpG sites associated with essential hypertension

BACKGROUND

Essential hypertension is a significant risk factor for cardiovascular diseases. Emerging research suggests a role of DNA methylation in blood pressure physiology. We aimed to investigate epigenetic associations of promoter related CpG sites to essential hypertension in a genome-wide methylation approach.

METHODS

The genome-wide methylation pattern in whole blood was measured in 11 obese patients before and six months after Roux-en-Y gastric bypass surgery using the Illumina 450 k beadchip. CpG sites located within 1500 bp of the transcriptional start site of adjacent genes were included in our study, resulting in 124 199 probes investigated in the subsequent analysis. Percent changes in methylation states and SBP measured before and six months after surgery were calculated. These parameters were correlated to each other using the Spearman's rank correlation method (Edgeworth series approximation). To further investigate the detected relationship between candidate CpG sites and systolic blood pressure levels, binary logistic regression analyses were performed in a larger and independent cohort of 539 individuals aged 19-101 years to elucidate a relationship between EH and the methylation state in candidate CpG sites.

RESULTS

We identified 24 promoter associated CpG sites that correlated with change in SBP after RYGB surgery (p < 10(-16)). Two of these CpG loci (cg00875989, cg09134341) were significantly hypomethylated in dependency of EH (p < 10(-03)). These results were independent of age, BMI, ethnicity and sex.

CONCLUSIONS

The identification of these novel CpG sites may contribute to a further understanding of the epigenetic regulatory mechanisms underlying the development of essential hypertension.

Crosstalk between liver antioxidant and the endocannabinoid systems after chronic administration of the FAAH inhibitor, URB597, to hypertensive rats

Hypertension is accompanied by perturbations to the endocannabinoid and antioxidant systems. Thus, potential pharmacological treatments for hypertension should be examined as modulators of these two metabolic systems. The aim of this study was to evaluate the effects of chronic administration of the fatty acid amide hydrolase (FAAH) inhibitor [3-(3-carbamoylphenyl)phenyl]N-cyclohexylcarbamate (URB597) on the endocannabinoid system and on the redox balance in the livers of DOCA-salt hypertensive rats. Hypertension caused an increase in the levels of endocannabinoids [anandamide (AEA), 2-arachidonoyl-glycerol (2-AG) and N-arachidonoyl-dopamine (NADA)] and CB1 receptor and the activities of FAAH and monoacylglycerol lipase (MAGL). These effects were accompanied by an increase in the level of reactive oxygen species (ROS), a decrease in antioxidant activity/level, enhanced expression of transcription factor Nrf2 and changes to Nrf2 activators and inhibitors. Moreover, significant increases in lipid, DNA and protein oxidative modifications, which led to enhanced levels of proapoptotic caspases, were also observed. URB597 administration to the hypertensive rats resulted in additional increases in the levels of AEA, NADA and the CB1 receptor, as well as decreases in vitamin E and C levels, glutathione peroxidase and glutathione reductase activities and Nrf2 expression. Thus, after URB597 administration, oxidative modifications of cellular components were increased, while the inflammatory response was reduced. This study revealed that chronic treatment of hypertensive rats with URB597 disrupts the endocannabinoid system, which causes an imbalance in redox status. This imbalance increases the levels of electrophilic lipid peroxidation products, which later participate in metabolic disturbances in liver homeostasis.

Renal Tumor Necrosis Factor α Contributes to Hypertension in Dahl Salt-Sensitive Rats

Tumor necrosis factor α (TNFα) is a major proinflammatory cytokine and its level is elevated in hypertensive states. Inflammation occurs in the kidneys during the development of hypertension. We hypothesized that TNFα specifically in the kidney contributes to the development of hypertension and renal injury in Dahl salt-sensitive (SS) rats, a widely used model of human salt-sensitive hypertension and renal injury. SS rats were chronically instrumented for renal interstitial infusion and blood pressure measurement in conscious, freely moving state. Gene expression was measured using real-time PCR and renal injury assessed with histological analysis. The abundance of TNFα in the renal medulla of SS rats, but not the salt-insensitive congenic SS.13^BN26 rats, was significantly increased when rats had been fed a high-salt diet for 7 days (n = 6 or 9, p < 0.01). The abundance of TNFα receptors in the renal medulla was significantly higher in SS rats than SS.13^BN26 rats. Renal interstitial administration of Etanercept, an inhibitor of TNFα, significantly attenuated the development of hypertension in SS rats on a high-salt diet (n = 7–8, p < 0.05). Glomerulosclerosis and interstitial fibrosis were also significantly ameliorated. These findings indicate intrarenal TNFα contributes to the development of hypertension and renal injury in SS rats.