Low-Chloride Diet Prevents the Development of Arterial Hypertension and Protects Kidney Function in Angiotensin II-Infused Mice

INTRODUCTION

A comprehensive pathophysiological mechanism to explain the relationship between high-salt intake and hypertension remains undefined. Evidence suggests that chloride, as the accompanying anion of sodium in dietary salt, is necessary to develop hypertension. We evaluated whether reducing dietary Cl- while keeping a standard Na+ intake modified blood pressure, cardiac hypertrophy, renal function, and vascular contractility after angiotensin II (AngII) infusion.

METHODS

C56BL/6J mice fed with standard Cl- diet or a low-Cl- diet (equimolar substitution of Cl- by a mixture of Na+ salts, both diets with standard Na+ content) received AngII (infusion of 1.5 mg/kg/day) or vehicle for 14 days. We measured systolic blood pressure (SBP), glomerular filtration rate (GFR), natriuretic response to acute saline load, and contractility of aortic rings from mice infused with vehicle and AngII, in standard and low-Cl- diet.

RESULTS

The mice fed the standard diet presented increased SBP and cardiac hypertrophy after AngII infusion. In contrast, low-Cl- diet prevented the increase of SBP and cardiac hypertrophy. AngII-infused mice fed a standard diet presented hampered natriuretic response to saline load, meanwhile the low-Cl- diet preserved natriuretic response in AngII-infused mice, without change in GFR. Aortic rings from mice fed with standard diet or low-Cl- diet and infused with AngII presented a similar contractile response.

CONCLUSION

We conclude that the reduction in dietary Cl- as the accompanying anion of sodium in salt is protective from AngII pro-hypertensive actions due to a beneficial effect on kidney function and preserved natriuresis.

Neutrophil gelatinase-associated lipocalin as an immunomodulator in endocrine hypertension

In recent studies, primary aldosteronism (PA) has been reported as the most common etiology for secondary hypertension of endocrine origin, accounting for approximately 10% of cases. In PA, excess aldosterone production can lead to deleterious effects at the cardiovascular (CV) and renal levels by activating mineralocorticoid receptors, which involves an increase in pro-inflammatory and pro-fibrotic mediators. Among these mediators, neutrophil gelatinase-associated lipocalin (NGAL), a secretion glycoprotein belonging to the lipocalin superfamily, has been closely linked to CV and renal damage in several pathological conditions. Because NGAL can be detected in biofluids such as plasma and urine, it has been proposed as a damage biomarker for target tissues and has also been studied for its role in hypertension and associated with PA. NGAL is produced by many different cell types, can be carried on extracellular vesicles, and is modulated by microRNAs, which would support its use as a biomarker for endocrine hypertension due to PA. Over the last decade, studies have shown that NGAL is necessary for the development of aldosterone-induced hypertension and that is associated with end-organ damage. In addition, it has been proposed that some mechanisms are dependent on the activation of immune cells, such as dendritic cells and macrophages, where the release of specific cytokines (i.e., interleukin [IL]-23) or chemokines (i.e., CCL-5) induced by aldosterone would depend on NGAL. Subsequently, this activates the T helper (Th) lymphocytes, such as Th₁₇ and Th₂, resulting in CV and renal fibrosis due to the high aldosterone levels. Although the immune system has been closely associated with essential hypertension, its participation in endocrine hypertension has not been fully elucidated. This review discusses the link between NGAL and endocrine hypertension, particularly in the context of PA, and their possible regulators and mechanisms, with a focus on its role as an immunomodulator.

Hydrochlorothiazide Reduces Cardiac Hypertrophy, Fibrosis and Rho-Kinase Activation in DOCA-Salt Induced Hypertension

BACKGROUND

Thiazides are one of the most common antihypertensive drugs used for hypertension treatment and hydrochlorothiazide (HCTZ) is the most frequently used diuretic for hypertension treatment. The Rho/Rho-kinase (ROCK) path plays a key function in cardiovascular remodeling. We hypothesized that in preclinical hypertension HCTZ reduces myocardial ROCK activation and consequent myocardial remodeling.

METHODS

The preclinical model of deoxycorticosterone (DOCA)-salt hypertension was used (Sprague-Dawley male rats). After 3 weeks, in 3 different groups: HCTZ, the ROCK inhibitor fasudil or spironolactone was added (3 weeks). After 6 weeks myocardial hypertrophy and fibrosis, cardiac levels of profibrotic proteins, mRNA levels (RT PCR) of pro remodeling and pro oxidative molecules and ROCK activity were determined.

RESULTS

Blood pressure, myocardial hypertrophy and fibrosis were reduced significantly by HCTZ, fasudil and spironolactone. In the heart, increased levels of the pro-fibrotic proteins Col-I, Col-III and TGF-β1 and gene expression of pro-remodeling molecules TGF-β1, CTGF, MCP-1 and PAI-1 and the pro-oxidative molecules gp91phox and p22phox were significantly reduced by HCTZ, fasudil and spironolactone. ROCK activity in the myocardium was increased by 54% (P < 0.05) as related to the sham group and HCTZ, spironolactone and fasudil, reduced ROCK activation to control levels.

CONCLUSIONS

HCTZ reduced pathologic LVH by controlling blood pressure, hypertrophy and myocardial fibrosis and by decreasing myocardial ROCK activation, expression of pro remodeling, pro fibrotic and pro oxidative genes. In hypertension, the observed effects of HCTZ on the myocardium might explain preventive outcomes of thiazides in hypertension, specifically on LVH regression and incident heart failure.

[Role of inflammation in hypertension]

Even though the mechanisms that mediate essential hypertension (HT) are not fully understood, an immunological-inflammatory mechanism could be the common pathway for diverse pathophysiological mechanisms. We analyze in a simplified way the participation of the immune system in HT. T lymphocytes (TL) and antigen presenting cells (APCs) are components of the immune system capable of generating proinflammatory cytokines. They cause endothelial damage, vasoconstriction, and decreased urinary sodium excretion. CD4+ and CD8+ TL are effector cells, causally implicated in the development of HT, whereas type γδ TL play their pathogenic role in HT enhancing endothelial dysfunction. Additionally, a immunomodulation decrease by regulatory TL, worsens endothelial dysfunction and reduces vasodilation in experimental HT. Results of recent studies indicate that lymphocyte activation would be mediated by antigens captured by antigen APCs for subsequent presentation to "naive" TL. On the other hand, proinflammatory states such as obesity, the change of the intestinal microbiota and the increase in salt intake favors TL and APC activation, contributing to HT development.

α-Ketoglutarate Upregulates Collecting Duct (Pro)renin Receptor Expression, Tubular Angiotensin II Formation, and Na+ Reabsorption During High Glucose Conditions

Diabetes mellitus (DM) causes high glucose (HG) levels in the plasma and urine. The (pro)renin receptor (PRR) is a key regulator of renal Na+ handling. PRR is expressed in intercalated (IC) cells of the collecting duct (CD) and binds renin to promote angiotensin (Ang) II formation, thereby contributing to Na+ reabsorption. In DM, the Kreb's cycle is in a state of suppression in most tissues. However, in the CD, expression of glucose transporters is augmented, boosting the Kreb's cycle and consequently causing α-ketoglutarate (αKG) accumulation. The αKG receptor 1 (OXGR1) is a Gq-coupled receptor expressed on the apical membrane of IC cells of the CD. We hypothesize that HG causes αKG secretion and activation of OXGR1, which increases PRR expression in CD cells. This effect then promotes intratubular AngII formation and Na+ reabsorption. To test this hypothesis, streptozotocin (STZ)-induced diabetic mice were treated with or without montelukast (ML), an OXGR1 antagonist, for 6 days. STZ mice had higher urinary αKG and PRR expression along with augmented urinary AngII levels and Na+ retention. Treatment with ML prevented all these effects. Similarly, primary cultured inner medullary CD cells treated with HG showed increased PRR expression, while OXGR1 antagonist prevented this effect. αKG increases PRR expression, while treatments with ML, PKC inhibition, or intracellular Ca2+ depletion impair this effect. In silico analysis suggested that αKG binds to mouse OXGR1. These results indicate that HG conditions promote increased levels of intratubular αKG and OXGR1-dependent PRR upregulation, which impact AngII formation and Na+ reabsorption.

Oxidized Albumin as a Mediator of Kidney Disease

Renal diseases are a global health concern, and nearly 24% of kidney disease patients are overweight or obese. Particularly, increased body mass index has been correlated with oxidative stress and urinary albumin excretion in kidney disease patients, also contributing to increased cardiovascular risk. Albumin is the main plasma protein and is able to partially cross the glomerular filtration barrier, being reabsorbed mainly by the proximal tubule through different mechanisms. However, it has been demonstrated that albumin suffers different posttranslational modifications, including oxidation, which appears to be tightly linked to kidney damage progression and is increased in obese patients. Plasma-oxidized albumin levels correlate with a decrease in estimated glomerular filtration rate and an increase in blood urea nitrogen in patients with chronic kidney disease. Moreover, oxidized albumin in kidney disease patients is independently correlated with higher plasma levels of transforming growth factor beta (TGF-β1), tumor necrosis factor (TNF-α), and interleukin (IL)-1β and IL-6. In addition, oxidized albumin exerts a direct effect on neutrophils by augmenting the levels of neutrophil gelatinase-associated lipocalin, a well-accepted biomarker for renal damage in patients and in different experimental settings. Moreover, it has been suggested that albumin oxidation occurs at early stages of chronic kidney disease, accelerating the patient requirements for dialytic treatment during disease progression. In this review, we summarize the evidence supporting the role of overweight- and obesity-induced oxidative stress as a critical factor for the progression of renal disease and cardiovascular morbimortality through albumin oxidation.

The Role of Neutrophils in Hypertension

It is well accepted that the immune system and some cells from adaptive and innate immunity are necessary for the initiation/perpetuation of arterial hypertension (AH). However, whether neutrophils are part of this group remains debatable. There is evidence showing that the neutrophil/lymphocyte ratio correlates with AH and is higher in non-dipper patients. On the other hand, the experimental neutrophil depletion in mice reduces basal blood pressure. Nevertheless, their participation in AH is still controversial. Apparently, neutrophils may modulate the microenvironment in blood vessels by increasing oxidative stress, favoring endothelial disfunction. In addition, neutrophils may contribute to the tissue infiltration of immune cells, secreting chemoattractant chemokines/cytokines and promoting the proinflammatory phenotype, leading to AH development. In this work, we discuss the potential role of neutrophils in AH by analyzing different mechanisms proposed from clinical and basic studies, with a perspective on cardiovascular and renal damages relating to the hypertensive phenotype.

Myeloid CD11c+ Antigen-Presenting Cells Ablation Prevents Hypertension in Response to Angiotensin II Plus High-Salt Diet

Increasing evidence shows that antigen-presenting cells (APCs) are involved in the development of inflammation associated to hypertension. However, the potential role of APCs in the modulation of renal sodium transport has not been addressed. We hypothesized that APCs participate in renal sodium transport and, thus, development of high blood pressure in response to angiotensin II plus a high-salt diet. Using transgenic mice that allow the ablation of CD11c^high APCs, we studied renal sodium transport, the intrarenal renin-angiotensin system components, blood pressure, and cardiac/renal tissue damage in response to angiotensin II plus a high-salt diet. Strikingly, we found that APCs are required for the development of hypertension and that the ablation/restitution of APCs produces rapid changes in the blood pressure in mice with angiotensin II plus a high-salt diet. Moreover, APCs were necessary for the induction of intrarenal renin-angiotensin system components and affected the modulation of natriuresis and tubular sodium transporters. Consistent with the prevention of hypertension, the ablation of APCs also prevented cardiac hypertrophy and the induction of several indicators of renal and cardiac damage. Thus, our findings indicate a prominent role of APCs as modulators of blood pressure by mechanisms including renal sodium handling, with kinetics that suggest the involvement of tubular cell functions in addition to the modulation of inflammation and adaptive immune response.

Differences in the Rates of Drug Polyconsumption and Psychiatric Comorbidity among Patients with Cocaine Use Disorders According to the Mental Health Service

Cocaine continues to be a worldwide public health concern in Europe. To improve prognosis and intervention, it is necessary to understand the characteristics of the patients who depend on the services where they receive care. The objective is to analyze the differences among patients who use cocaine and between ambulatory and residential resources to better adapt treatment. This is a descriptive, observational study of two populations of cocaine users in treatment: the ambulatory therapeutic community (ATC) and the therapeutic community (TC). The PRISM diagnostic interview was used for both groups. An analysis of both populations indicates a high prevalence of cocaine, heroin, cannabis, sedative, psychostimulant, and hallucinogen use disorders in the TC population compared to the ATC. In alcohol use disorder, differences between both mental health services were not observed. The degree of severity of cocaine use disorders (CUD) is greater in the TC population. The prevalence of psychiatric comorbidity is not statistically significant between the two populations, except for primary psychotic disorders, which are more prevalent in the TC population. This difference in the prevalence of psychotic disorders may be related to the high prevalence of cannabis use disorders in TC patients. Differences in the prevalence of substance use disorders, severity of CUD, and psychiatric comorbidity may limit the efficiency of mental health services involved in substance use disorder therapeutics. These results suggest the need for careful and extensive phenotyping of patients to improve intervention and prognosis in a clinical resource-dependent manner.

Diuretics prevent Rho-kinase activation and expression of profibrotic/oxidative genes in the hypertensive aortic wall

BACKGROUND

Diuretics are current antihypertensive drugs since they reduce blood pressure and cardiovascular risk. Increased vascular tone is modulated in a relevant way by the RhoA/Rho-kinase (ROCK) pathway, by acting on vascular smooth muscle cell contraction. This pathway has also proremodeling vascular effects. There are few data on the role of diuretics on both vascular ROCK activation and on proremodeling effects. We assessed the effects of hydrochlorothiazide (HCTZ) and spironolactone (spiro) alone and in combination with the ROCK inhibitor fasudil (FAS) on ROCK activation, gene expression of proremodeling markers and on hypertrophy in the aortic wall of hypertensive rats.

METHODS

Deoxycorticosterone acetate (DOCA)-salt hypertensive rats (male, Sprague-Dawley) were randomized to the specific ROCK inhibitor FAS, HCTZ, spiro or the combinations of FAS/HCTZ or FAS/spiro for 3 weeks. At the end of the study, ROCK activation (by western blot), gene expression of proremodeling markers (by reverse transcription polymerase chain reaction, RT-PCR) and vascular hypertrophy (by morphometry) were determined in the aortic wall.

RESULTS

All treatments significantly reduced blood pressure. In the DOCA rats the p-myosin phosphatase target protein-1 (MYPT1)/t-MYPT1 ratio, index of ROCK activation was higher by 2.8 fold (p < 0.05) compared with control rats. All treatments reduced ROCK activation in the aortic wall to control levels (p < 0.05). Besides, significantly increased protein levels of transforming growth factor β1 (TGF-β₁), gene expression of TGF-β₁, connective tissue growth factor (CTGF), p22 phox and gp91 phox subunits of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, as well as increased media thickness and aortic media area/lumen area (AM/LA) in the untreated hypertensive rats were significantly reduced (p < 0.05) to control levels by all treatments. Similar effects were observed using both diuretics alone or in combination with FAS.

CONCLUSIONS

In the aortic wall, both HCTZ and spiro in antihypertensive doses reduce ROCK activation, subsequent expression of genes that promote vascular remodeling and hypertrophy in this experimental model of hypertension. These effects could explain some of their clinical benefits in hypertensive patients.