Chloride Ions, Vascular Function and Hypertension

Pharmacological profiling of small molecule modulators of the TMEM16A channel and their implications for the control of artery and capillary function

BACKGROUND AND PURPOSE

TMEM16A chloride channels constitute a depolarising mechanism in arterial smooth muscle cells (SMCs) and contractile cerebral pericytes. TMEM16A pharmacology is incompletely defined. We elucidated the mode of action and selectivity of a recently identified positive allosteric modulator of TMEM16A (PAM_16A) and of a range of TMEM16A inhibitors. We also explore the consequences of selective modulation of TMEM16A activity on arterial and capillary function.

EXPERIMENTAL APPROACH

Patch-clamp electrophysiology, isometric tension recordings, live imaging of cerebral cortical capillaries and assessment of cell death were employed to explore the effect of selective pharmacological control of TMEM16A on vascular function.

KEY RESULTS

In low intracellular free Ca2+ concentrations ([Ca2+]i), nanomolar concentrations of PAM_16A activated heterologous TMEM16A channels, while being almost ineffective on the closely related TMEM16B channel. In either the absence of Ca2+ or in saturating [Ca2+]i, PAM_16A had no effect on TMEM16A currents at physiological potentials. PAM_16A selectively activated TMEM16A currents in SMCs and enhanced aortic contraction caused by phenylephrine or angiotensin-II and capillary (pericyte) constriction evoked by endothelin-1 or oxygen-glucose deprivation (OGD) to simulate cerebral ischaemia. Conversely, selective TMEM16A inhibition with Ani9 facilitated aortic, mesenteric and pericyte relaxation, and protected against OGD-mediated pericyte cell death. Unlike PAM_16A and Ani9, a range of other available modulators were found to interfere with endogenous cationic currents in SMCs.

CONCLUSIONS AND IMPLICATIONS

Arterial tone and capillary diameter can be controlled with TMEM16A modulators, highlighting TMEM16A as a target for disorders with a vascular component, including hypertension, stroke, Alzheimer's disease and vascular dementia.

Hypochloremia is an underutilised prognostic marker in patients with advanced liver cirrhosis and liver failure

Patients with advanced liver cirrhosis and liver failure frequently experience abnormalities in their serum electrolyte levels. In such patients, hyponatremia has been identified as a predictor of poor outcomes. However, emerging evidence suggests that serum chloride may provide even better prognostic information in similar situations. Hypochloremia, characterised by low serum chloride levels, has been linked to increased mortality, exacerbated organ dysfunction, and higher requirements for renal replacement therapy and vasopressors in various critical conditions, including advanced liver diseases. The pathophysiological mechanisms underlying the association between low serum chloride levels and poor outcomes in liver disease appear to involve complex interactions among electrolyte imbalances, renal function, and systemic hemodynamics. Chloride dysregulation can influence renal salt-sensing mechanisms, disrupt acid-base homeostasis, and exacerbate complications such as hepatic encephalopathy and hepatorenal syndrome. This article aims to elucidate the prognostic significance of lower serum chloride levels in patients with advanced liver disease. By reviewing recent literature and analysing clinical data, we seek to establish serum chloride as an underutilised but valuable prognostic marker. Understanding the role of serum chloride in liver disease could enhance prognostic accuracy, refine treatment strategies, and ultimately improve patient outcomes.

Associations of serum sodium, potassium and chloride levels with the all-cause and cardiovascular diseases mortality among patients with depression

BACKGROUND

Electrolyte disturbances are relatively common in patients with depression, but they are often overlooked, and the relationship between electrolyte changes and adverse outcomes in depression is not yet clear. This study aims to explore the impact of serum electrolyte levels on the all-cause and cardiovascular disease (CVD) mortality rates in patients with depression.

METHODS

This prospective cohort study included 3127 patients with depression who participated in the National Health and Nutrition Examination Survey (NHANES) from 2005 through 2018. Depression was assessed using the Patient Health Questionnaire (PHQ-9), with a PHQ-9 score ≥10 defined as depression. The data were analyzed from April 1 to July 30, 2024. Multivariable Cox proportional hazards regression model was used to calculate the hazard ratios (HRs) and 95% confidence intervals (CIs) between serum sodium, potassium, and chloride levels and the CVD risk and all-cause mortality in patients with depression. Three multivariable models were constructed. We further stratified the analysis by age, gender, hypertension, smoking, alcohol consumption, diabetes, and drinking status. Interaction significance was estimated using P-values for the product terms between serum sodium, potassium, chloride, and stratification factors.

RESULTS

This cohort study included data from 2946 participants in the analysis (mean [SD] age, 50.13 [16.48] years; 1116 men [37.88]); During a median (IQR) follow-up of 7.2 (3.6-10.5) years, 398 deaths were recorded, of which 117 were attributed to CVD.After multivariable adjustment, compared with participants in the first quartile of serum sodium levels, the HRs of CVD mortality were 0.90(95% CI, 0.53-1.53) in the fourth quartile (p for trend = 0.484). The HRs of all-cause mortality were 0.73(95% CI, 0.55-0.99) for the fourth quartile (p for trend = 0.003). A nonlinear association was observed between serum sodium levels and all-cause mortality in patients with depression (p for overall = 0.003, p for nonlinear = 0.047). Compared with participants in the first quartile of serum potassium levels, the HRs of CVD mortality were and 1.58(95% CI, 0.98-2.54) in the fourth quartile (p for trend = 0.050), the HRs of all-cause mortality were 1.52(95% CI, 1.16-1.99) for the fourth quartile (p for trend <0.001). A nonlinear association was observed between serum potassium levels and all-cause (p for overall<0.001, p for nonlinear = 0.005) and CVD (p for nonlinear = 0.003) mortality in patients with depression. Compared with participants in the first quartile of serum chlorine levels, the HRs of CVD mortality were 0.84(95% CI, 0.49-1.46) in the fourth quartile(p for trend = 0.284). The HRs of all-cause mortality were 0.70(95% CI, 0.51-0.95) for the fourth quartile(p for trend <0.001). A nonlinear association was observed between serum chlorine levels and all-cause (p for nonlinear<0.001) and CVD (p for nonlinear<0.001) mortality in patients with depression.

CONCLUSION AND CORRELATIONS

This cohort study found that in patients with depression, higher sodium is significantly correlated with lower all-cause mortality, higher potassium is significantly correlated with higher all-cause and CVD mortality, and higher chloride is significantly correlated with lower all-cause and CVD mortality.

5,7-Dihydroxyflavone acts on eNOS to achieve hypotensive effects in spontaneously hypertensive rats

Hypertension is one of the most serious chronic diseases. This study will focus on the systemic antihypertensive mechanisms of 5,7-dihydroxyflavone from in silico simulations to in vivo validations. In-silico studies were applied by network pharmacology, molecular docking, and molecular dynamic simulation. Based on the information of network pharmacology, 5,7-dihydroxyflavone could act on several different blood pressure regulating pathways, molecular docking results confirmed it might direct binding on the active pocket of eNOS, and the average molecular distance between 5,7-dihydroxyflavone -eNOS is less than 0.4 Å by molecular dynamic simulation. The in vivo studies were carried by SHRs oral administrated with 10 mg/kg 5,7-dihydroxyflavone that could alleviate hypertensive symptoms within 30 min, but if SHRs pretreated with L-NAME (10 mg/kg, an eNOS inhibitor) can erase the anti-hypertensive effects of 5,7-dihydroxyflavone, but no affected by aminoguanidine pretreatment (100 mg/kg, the selective antagonist of iNOS). Furthermore, oral administration of 5,7-dihydroxyflavone does not affect the heart rate and pulse pressure difference in SHR rats. In conclusion, the effects of 5,7-dihydroxyflavone on blood pressure regulation may act on eNOS as an agonist to achieve its acute antihypertensive effects. These acute antihypertensive effects suggest that 5,7-dihydroxyflavone has the potential to be a candidate medication for urgently lowering blood pressure requirements without posing hypertensive risks.

Calcium signaling in endothelial and vascular smooth muscle cells: sex differences and the influence of estrogens and androgens

Calcium signaling in vascular endothelial cells (ECs) and smooth muscle cells (VSMCs) is essential for the regulation of vascular tone. However, the changes to intracellular Ca2+ concentrations are often influenced by sex differences. Furthermore, a large body of evidence shows that sex hormone imbalance leads to dysregulation of Ca2+ signaling and this is a key factor in the pathogenesis of cardiovascular diseases. In this review, the effects of estrogens and androgens on vascular calcium-handling proteins are discussed, with emphasis on the associated genomic or nongenomic molecular mechanisms. The experimental models from which data were collected were also considered. The review highlights 1) in female ECs, transient receptor potential vanilloid 4 (TRPV4) and mitochondrial Ca2+ uniporter (MCU) enhance Ca2+-dependent nitric oxide (NO) generation. In males, only transient receptor potential canonical 3 (TRPC3) plays a fundamental role in this effect. 2) Female VSMCs have lower cytosolic Ca2+ levels than males due to differences in the activity and expression of stromal interaction molecule 1 (STIM1), calcium release-activated calcium modulator 1 (Orai1), calcium voltage-gated channel subunit-α1C (CaV1.2), Na+-K+-2Cl- symporter (NKCC1), and the Na+/K+-ATPase. 3) When compared with androgens, the influence of estrogens on Ca2+ homeostasis, vascular tone, and incidence of vascular disease is better documented. 4) Many studies use supraphysiological concentrations of sex hormones, which may limit the physiological relevance of outcomes. 5) Sex-dependent differences in Ca2+ signaling mean both sexes ought to be included in experimental design.

The TMEM16A channel as a potential therapeutic target in vascular disease

PURPOSE OF REVIEW

The transmembrane protein 16A (TMEM16A) Ca 2+ -activated Cl - channel constitutes a key depolarising mechanism in vascular smooth muscle and contractile pericytes, while in endothelial cells the channel is implicated in angiogenesis and in the response to vasoactive stimuli. Here, we offer a critical analysis of recent physiological investigations and consider the potential for targeting TMEM16A channels in vascular disease.

RECENT FINDINGS

Genetic deletion or pharmacological inhibition of TMEM16A channels in vascular smooth muscle decreases artery tone and lowers systemic blood pressure in rodent models. Inhibition of TMEM16A channels in cerebral cortical pericytes protects against ischemia-induced tissue damage and improves microvascular blood flow in rodent stroke models. In endothelial cells, the TMEM16A channel plays varied roles including modulation of cell division and control of vessel tone through spread of hyperpolarisation to the smooth muscle cells. Genetic studies implicate TMEM16A channels in human disease including systemic and pulmonary hypertension, stroke and Moyamoya disease.

SUMMARY

The TMEM16A channel regulates vascular function by controlling artery tone and capillary diameter as well as vessel formation and histology. Preclinical and clinical investigations are highlighting the potential for therapeutic exploitation of the channel in a range of maladaptive states of the (micro)circulation.

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.

L-Shaped Association of Serum Chloride Level With All-Cause and Cause-Specific Mortality in American Adults: Population-Based Prospective Cohort Study

BACKGROUND

Chloride is the most abundant anion in the human extracellular fluid and plays a crucial role in maintaining homeostasis. Previous studies have demonstrated that hypochloremia can act as an independent risk factor for adverse outcomes in various clinical settings. However, the association of variances of serum chloride with long-term mortality risk in general populations has been rarely investigated.

OBJECTIVE

This study aims to assess the association of serum chloride with all-cause and cause-specific mortality in the general American adult population.

METHODS

Data were collected from 10 survey cycles (1999-2018) of the National Health and Nutrition Examination Survey. All-cause mortality, cardiovascular disease (CVD) mortality, cancer mortality, and respiratory disease mortality data were obtained by linkage to the National Death Index through December 31, 2019. After adjusting for demographic factors and relevant lifestyle, laboratory items, and comorbid factors, weighted Cox proportional risk models were constructed to estimate hazard ratios and 95% CIs for all-cause and cause-specific mortality.

RESULTS

A total of 51,060 adult participants were included, and during a median follow-up of 111 months, 7582 deaths were documented, 2388 of CVD, 1639 of cancer, and 567 of respiratory disease. The weighted Kaplan-Meier survival analyses showed consistent highest mortality risk in individuals with the lowest quartiles of serum chloride. The multivariate-adjusted hazard ratios from lowest to highest quartiles of serum chloride (≤101.2, 101.3-103.2, 103.2-105.0, and ≥105.1 mmol/L) were 1.00 (95% CI reference), 0.77 (95% CI 0.67-0.89), 0.72 (95% CI 0.63-0.82), and 0.77 (95% CI 0.65-0.90), respectively, for all-cause mortality (P for linear trend<.001); 1.00 (95% CI reference), 0.63 (95% CI 0.51-0.79), 0.56 (95% CI 0.43-0.73), and 0.67 (95% CI 0.50-0.89) for CVD mortality (P for linear trend=.004); 1.00 (95% CI reference), 0.67 (95% CI 0.54-0.84), 0.65 (95% CI 0.50-0.85), and 0.65 (95% CI 0.48-0.87) for cancer mortality (P for linear trend=.004); and 1.00 (95% CI reference), 0.68 (95% CI 0.41-1.13), 0.59 (95% CI 0.40-0.88), and 0.51 (95% CI 0.31-0.84) for respiratory disease mortality (P for linear trend=.004). The restricted cubic spline analyses revealed the nonlinear and L-shaped associations of serum chloride with all-cause and cause-specific mortality (all P for nonlinearity<.05), in which lower serum chloride was prominently associated with higher mortality risk. The associations of serum chloride with mortality risk were robust, and no significant additional interaction effect was detected for all-cause mortality and CVD mortality (P for interaction>.05).

CONCLUSIONS

In American adults, decreased serum chloride concentrations were independently associated with increased all-cause mortality, CVD mortality, cancer mortality, and respiratory disease mortality. Our findings suggested that serum chloride may serve as a promising cost-effective health indicator in the general adult population. Further studies are warranted to explore the potential pathophysiological mechanisms underlying the association between serum chloride and mortality.