Regulatory control of the Na-Cl co-transporter NCC and its therapeutic potential for hypertension

Navigating the multifaceted intricacies of the Na+-Cl- cotransporter, a highly regulated key effector in the control of hydromineral homeostasis

The Na+-Cl- cotransporter (NCC; SLC12A3) is a highly regulated integral membrane protein that is known to exist as three splice variants in primates. Its primary role in the kidney is to mediate the cosymport of Na+ and Cl- across the apical membrane of the distal convoluted tubule. Through this role and the involvement of other ion transport systems, NCC allows the systemic circulation to reclaim a fraction of the ultrafiltered Na+, K+, Cl-, and Mg+ loads in exchange for Ca2+ and [Formula: see text]. The physiological relevance of the Na+-Cl- cotransport mechanism in humans is illustrated by several abnormalities that result from NCC inactivation through the administration of thiazides or in the setting of hereditary disorders. The purpose of the present review is to discuss the molecular mechanisms and overall roles of Na+-Cl- cotransport as the main topics of interest. On reading the narrative proposed, one will realize that the knowledge gained in regard to these themes will continue to progress unrelentingly no matter how refined it has now become.

Hereditary causes of hypertension due to increased sodium transport

PURPOSE OF REVIEW

Hypertension, commonly known as high blood pressure, is a widespread health condition affecting a large number of individuals across the globe. Although lifestyle choices and environmental factors are known to have a significant impact on its development, there is growing recognition of the influence of genetic factors in the pathogenesis of hypertension. This review specifically focuses on the hereditary causes of hypertension that are associated with increased sodium transport through the thiazide-sensitive NaCl cotransporter (NCC) or amiloride-sensitive epithelial sodium channel (ENaC), crucial mechanisms involved in regulating blood pressure in the kidneys. By examining genetic mutations and signaling molecules linked to the dysregulation of sodium transport, this review aims to deepen our understanding of the hereditary causes of hypertension and shed light on potential therapeutic targets.

RECENT FINDINGS

Liddle syndrome (LS) is a genetic disorder that typically manifests early in life and is characterized by hypertension, hypokalemic metabolic alkalosis, hyporeninemia, and suppressed aldosterone secretion. This condition is primarily caused by gain-of-function mutations in ENaC. In contrast, Pseudohypoaldosteronism type II (PHAII) is marked by hyperkalemia and hypertension, alongside other clinical features such as hyperchloremia, metabolic acidosis, and suppressed plasma renin levels. PHAII results from overactivations of NCC, brought about by gain-of-function mutations in its upstream signaling molecules, including WNK1 (with no lysine (K) 1), WNK4, Kelch-like 3 (KLHL3), and cullin3 (CUL3).

SUMMARY

NCC and ENaC are integral components, and their malfunctions lead to disorders like LS and PHAII, hereditary causes of hypertension. Current treatments for LS involve ENaC blockers (e.g., triamterene and amiloride) in conjunction with low-sodium diets, effectively normalizing blood pressure and potassium levels. In PHAII, thiazide diuretics, which inhibit NCC, are the mainstay treatment, albeit with some limitations and potential side effects. Ongoing research in developing alternative treatments, including small molecules targeting key regulators, holds promise for more effective and tailored hypertension solutions.

Utilizing systematic Mendelian randomization to identify potential therapeutic targets for mania

Background

Mania has caused incalculable economic losses for patients, their families, and even society, but there is currently no effective treatment plan for this disease without side effects.

Methods

Using bioinformatics and Mendelian randomization methods, potential drug target genes and key substances associated with mania were explored at the mRNA level. We used the chip expression profile from the GEO database to screen differential genes and used the eQTL and mania GWAS data from the IEU database for two-sample Mendelian randomization (MR) to determine core genes by colocalization. Next, we utilized bioinformatics analysis to identify key substances involved in the mechanism of action and determined related gene targets as drug targets.

Results

After differential expression analysis and MR, a causal relationship between the expression of 46 genes and mania was found. Colocalization analysis yielded six core genes. Five key substances were identified via enrichment analysis, immune-related analysis, and single-gene GSVA analysis of the core genes. MR revealed phenylalanine to be the only key substance that has a unidirectional causal relationship with mania. In the end, SBNO2, PBX2, RAMP3, and QPCT, which are significantly associated with the phenylalanine metabolism pathway, were identified as drug target genes.

Conclusion

SBNO2, PBX2, RAMP3, and QPCT could serve as potential target genes for mania treatment and deserve further basic and clinical research. Medicinal target genes regulate the phenylalanine metabolism pathway to achieve the treatment of mania. Phenylalanine is an important intermediate substance in the treatment of mania that is regulated by drug target genes.

Sex differences in blood pressure regulation and hypertension: renal, hemodynamic, and hormonal mechanisms

The teleology of sex differences has been argued since at least as early as Aristotle's controversial Generation of Animals more than 300 years BC, which reflects the sex bias of the time to contemporary readers. Although the question "why are the sexes different" remains a topic of debate in the present day in metaphysics, the recent emphasis on sex comparison in research studies has led to the question "how are the sexes different" being addressed in health science through numerous observational studies in both health and disease susceptibility, including blood pressure regulation and hypertension. These efforts have resulted in better understanding of differences in males and females at the molecular level that partially explain their differences in vascular function and renal sodium handling and hence blood pressure and the consequential cardiovascular and kidney disease risks in hypertension. This review focuses on clinical studies comparing differences between men and women in blood pressure over the life span and response to dietary sodium and highlights experimental models investigating sexual dimorphism in the renin-angiotensin-aldosterone, vascular, sympathetic nervous, and immune systems, endothelin, the major renal sodium transporters/exchangers/channels, and the impact of sex hormones on these systems in blood pressure homeostasis. Understanding the mechanisms governing sex differences in blood pressure regulation could guide novel therapeutic approaches in a sex-specific manner to lower cardiovascular risks in hypertension and advance personalized medicine.

Neuronal K+-Cl- cotransporter KCC2 as a promising drug target for epilepsy treatment

Epilepsy is a prevalent neurological disorder characterized by unprovoked seizures. γ-Aminobutyric acid (GABA) serves as the primary fast inhibitory neurotransmitter in the brain, and GABA binding to the GABAA receptor (GABAAR) regulates Cl- and bicarbonate (HCO3-) influx or efflux through the channel pore, leading to GABAergic inhibition or excitation, respectively. The neuron-specific K+-Cl- cotransporter 2 (KCC2) is essential for maintaining a low intracellular Cl- concentration, ensuring GABAAR-mediated inhibition. Impaired KCC2 function results in GABAergic excitation associated with epileptic activity. Loss-of-function mutations and altered expression of KCC2 lead to elevated [Cl-]i and compromised synaptic inhibition, contributing to epilepsy pathogenesis in human patients. KCC2 antagonism studies demonstrate the necessity of limiting neuronal hyperexcitability within the brain, as reduced KCC2 functioning leads to seizure activity. Strategies focusing on direct (enhancing KCC2 activation) and indirect KCC2 modulation (altering KCC2 phosphorylation and transcription) have proven effective in attenuating seizure severity and exhibiting anti-convulsant properties. These findings highlight KCC2 as a promising therapeutic target for treating epilepsy. Recent advances in understanding KCC2 regulatory mechanisms, particularly via signaling pathways such as WNK, PKC, BDNF, and its receptor TrkB, have led to the discovery of novel small molecules that modulate KCC2. Inhibiting WNK kinase or utilizing newly discovered KCC2 agonists has demonstrated KCC2 activation and seizure attenuation in animal models. This review discusses the role of KCC2 in epilepsy and evaluates its potential as a drug target for epilepsy treatment by exploring various strategies to regulate KCC2 activity.

CAB39 promotes cisplatin resistance in bladder cancer via the LKB1-AMPK-LC3 pathway

Systemic therapy for muscle-invasive bladder cancer (BC) remains dominated by cisplatin-based chemotherapy. However, resistance to cisplatin therapy greatly limits long-term survival. Resistance to cisplatin-based chemotherapy still needs to be addressed. In this study, we established three cisplatin-resistant BC cell lines by multiple cisplatin pulse treatments. Interestingly, after exposure to cisplatin, all cisplatin-resistant cell lines showed lower reactive oxygen species (ROS) levels than the corresponding parental cell lines. Using proteomic analysis, we identified 35 proteins that were upregulated in cisplatin-resistant BC cells. By knocking down eleven of these genes, we found that after CAB39 knockdown, BC cisplatin-resistant cells were more sensitive to cisplatin. Overexpression of CAB39 had the opposite effect. Then, the knockdown of six genes downstream of CAB39 revealed that CAB39 promoted cisplatin resistance in BC through LKB1. Moreover, a key cause of cisplatin-induced cell death is damage to mitochondria and increased ROS levels. In our study, cisplatin-resistant cells exhibited higher autophagic flux and healthier mitochondrial status after cisplatin exposure. We demonstrated that the CAB39-LKB1-AMPK-LC3 pathway plays a critical role in enhancing autophagy to maintain the health of mitochondria and reduce ROS levels. In addition, the autophagy inhibitor chloroquine (CQ) can significantly enhance the killing effect of cisplatin on BC cells. Compared with gemcitabine plus cisplatin (GC), GC plus CQ significantly reduced tumor burden in vivo. In conclusion, our study shows that CAB39 counteracts the killing of cisplatin by enhancing the autophagy of BC cells to damaged mitochondria and other organelles to alleviate the damage of cells caused by harmful substances such as ROS.

Insights into the diverse mechanisms and effects of variant CUL3-induced familial hyperkalemic hypertension

Familial hyperkalemic hypertension (FHHt), also known as Pseudohypoaldosteronism type II (PHAII) or Gordon syndrome is a rare Mendelian disease classically characterized by hyperkalemia, hyperchloremic metabolic acidosis, and high systolic blood pressure. The most severe form of the disease is caused by autosomal dominant variants in CUL3 (Cullin 3), a critical subunit of the multimeric CUL3-RING ubiquitin ligase complex. The recent identification of a novel FHHt disease variant of CUL3 revealed intricacies within the underlying disease mechanism. When combined with studies on canonical CUL3 variant-induced FHHt, these findings further support CUL3's role in regulating renal electrolyte transport and maintaining systemic vascular tone. However, the pathophysiological effects of CUL3 variants are often accompanied by diverse systemic disturbances in addition to classical FHHt symptoms. Recent global proteomic analyses provide a rationale for these systemic disturbances, paving the way for future mechanistic studies to reveal how CUL3 variants dysregulate processes outside of the renovascular axis. Video Abstract.

A Spanish Family with Gordon Syndrome Due to a Variant in the Acidic Motif of WNK1

(1) Background: Gordon syndrome (GS) or familial hyperkalemic hypertension is caused by pathogenic variants in the genes WNK1, WNK4, KLHL3, and CUL3. Patients presented with hypertension, hyperkalemia despite average glomerular filtration rate, hyperchloremic metabolic acidosis, and suppressed plasma renin (PR) activity with normal plasma aldosterone (PA) and sometimes failure to thrive. GS is a heterogeneous genetic syndrome, ranging from severe cases in childhood to mild and sometimes asymptomatic cases in mid-adulthood. (2) Methods: We report here a sizeable Spanish family of six patients (four adults and two children) with GS. (3) Results: They carry a novel heterozygous missense variant in exon 7 of WNK1 (p.Glu630Gly). The clinical presentation in the four adults consisted of hypertension (superimposed pre-eclampsia in two cases), hyperkalemia, short stature with low body weight, and isolated hyperkalemia in both children. All patients also presented mild hyperchloremic metabolic acidosis and low PR activity with normal PA levels. Abnormal laboratory findings and hypertension were normalized by dietary salt restriction and low doses of thiazide or indapamide retard. (4) Conclusions: This is the first Spanish family with GS with a novel heterozygous missense variant in WNK1 (p.Glu630Gly) in the region containing the highly conserved acidic motif, which is showing a relatively mild phenotype, and adults diagnosed in mild adulthood. These data support the importance of missense variants in the WNK1 acidic domain in electrolyte balance/metabolism. In addition, findings in this family also suggest that indapamide retard or thiazide may be an adequate long-standing treatment for GS.

Association study of WNK1 genetic variants and essential hypertension risk in the Northern Han Chinese in Beijing

Background: Essential hypertension (EH) is a complex disorder resulting from interaction of genetic and environmental factors. Lysine deficient protein kinase 1 (WNK1) plays a very important role in maintaining renal potassium, sodium and chlorine ions balance as well as the regulation of blood pressure, so the WNK1 gene is considered a key gene for EH. This study thus sought to evaluate possible genetic associations between the WNK1 genetic variants and EH risk in the Northern Han Chinese population in Beijing. Methods: This study included 476 hypertensive subjects and 491 normotensive subjects. A total of 12 tag SNVs of WNK1 gene were genotyped successfully by TaqMan assay. Comparisons of the genotypic and allelic frequency between cases and controls were made by using the chi-square test. Logistic regression analyses were performed under different genetic models, and haplotype analysis was also conducted. Results: A total of 12 SNVs were identified as the tag SNVs for WNK1 gene. Significant associations were observed between WNK1 gene rs7305099 variant and EH risk, and T allele influenced hypertension risk in a protective manner. After correcting for multiple testing using Bonferroni, the significance remained for the SNV of rs7305099 in three genetic models [allele comparison, p < 0.0002, OR = 0.627, 95%CI (0.491-0.801); homozygote comparison, p < 0.0003, OR = 0.278, 95%CI (0.140-0.552); additive model, p < 0.0003, OR = 0.279, 95%CI (0.140-0.553)]. In the haplotype analyses, we found that the haplotype A-A-A-C-G-G-G was significantly associated with increased risk for EH (p = 0.043, OR = 1.23). Conclusion: Our data suggested that the rs7305099 genetic variant and the haplotype A-A-A-C-G-G-G on WNK1 gene might be associated with the susceptibility of EH in the Northern Han Chinese population. These could provide evidences to the risk assessment, early prevention and individualized therapy of EH to some extent.

Intrarenal Mechanisms of Sodium-Glucose Cotransporter-2 Inhibitors on Tubuloglomerular Feedback and Natriuresis

When sodium-glucose cotransporter-2 (SGLT2) inhibitors were first introduced a decade ago, no one expected them to have substantial effects beyond their known glucose-lowering effects, until the emergence of evidence of their robust renal and cardiovascular benefits showing that they could attenuate progression of kidney disease, irrespective of diabetes, as well as prevent the development of acute kidney injury. Still, the precise and elaborate mechanisms underlying the major organ protection of SGLT2 inhibitors remain unclear. SGLT2 inhibitors inhibit the reabsorption of sodium and glucose in the proximal tubule of the kidney and then recovers tubuloglomerular feedback, whereby SGLT2 inhibitors reduce glomerular hyperfiltration. This simple demonstration of their beneficial effects has perplexed experts in seeking more plausible and as yet undisclosed explanations for the whole effects of SGLT2 inhibitors, including metabolism reprogramming and the modulation of hypoxia, inflammation, and oxidative stress. Given that the renal benefits of SGLT2 inhibitors in patients with kidney disease but without diabetes were comparable to those seen in patients with diabetes, it may be reasonable to keep the emphasis on their hemodynamic actions. In this context, the aim of the present review is to provide a comprehensive overview of renal hemodynamics in individuals with diabetes who are treated with SGLT2 inhibitors, with a focus on natriuresis associated with the regulation of tubuloglomerular feedback and potential aquaresis. Throughout the discussion of alterations in renal sodium and water transports, particular attention will be given to the potential enhancement of adenosine and its receptors following SGLT2 inhibition.

Dietary sodium enhances the expression of SLC4 family transporters, IRBIT, L-IRBIT, and PP1 in rat kidney: Insights into the molecular mechanism for renal sodium handling

The kidney plays a central role in maintaining the fluid and electrolyte homeostasis in the body. Bicarbonate transporters NBCn1, NBCn2, and AE2 are expressed at the basolateral membrane of the medullary thick ascending limb (mTAL). In a previous study, NBCn1, NBCn2, and AE2 are proposed to play as a regulatory pathway to decrease NaCl reabsorption in the mTAL under high salt condition. When heterologously expressed, the activity of these transporters could be stimulated by the InsP3R binding protein released with inositol 1,4,5-trisphosphate (IRBIT), L-IRBIT (collectively the IRBITs), or protein phosphatase PP1. In the present study, we characterized by immunofluorescence the expression and localization of the IRBITs, and PP1 in rat kidney. Our data showed that the IRBITs were predominantly expressed from the mTAL through the distal renal tubules. PP1 was predominantly expressed in the TAL, but is also present in high abundance from the distal convoluted tubule through the medullary collecting duct. Western blotting analyses showed that the abundances of NBCn1, NBCn2, and AE2 as well as the IRBITs and PP1 were greatly upregulated in rat kidney by dietary sodium. Co-immunoprecipitation study provided the evidence for protein interaction between NBCn1 and L-IRBIT in rat kidney. Taken together, our data suggest that the IRBITs and PP1 play an important role in sodium handling in the kidney. We propose that the IRBITs and PP1 stimulates NBCn1, NBCn2, and AE2 in the basolateral mTAL to inhibit sodium reabsorption under high sodium condition. Our study provides important insights into understanding the molecular mechanism for the regulation of sodium homeostasis in the body.

Two-pore channel protein TPC1 is a determining factor for the adaptation of proximal tubular phosphate handling

AIM

Two-pore channels (TPCs) constitute a small family of cation channels expressed in endo-lysosomal compartments. TPCs have been characterized as critical elements controlling Ca²⁺ -mediated vesicular membrane fusion and thereby regulating endo-lysosomal vesicle trafficking. Exo- and endocytotic trafficking and lysosomal degradation are major mechanisms of adaption of epithelial transport. A prime example of highly regulated epithelial transport is the tubular system of the kidney. We therefore studied the localization of TPC protein 1 (TPC1) in the kidney and its functional role in the dynamic regulation of tubular transport.

METHODS

Immunohistochemistry in combination with tubular markers were used to investigate TPC1 expression in proximal and distal tubules. The excretion of phosphate and ammonium, as well as urine volume and pH were studied in vivo, in response to dynamic challenges induced by bolus injection of parathyroid hormone or acid-base transitions via consecutive infusion of NaCl, Na₂ CO₃ , and NH₄ Cl.

RESULTS

In TPC1-deficient mice, the PTH-induced rise in phosphate excretion was prolonged and exaggerated, and its recovery delayed in comparison with wildtype littermates. In the acid-base transition experiment, TPC1-deficient mice showed an identical rise in phosphate excretion in response to Na₂ CO₃ compared with wildtypes, but a delayed NH4Cl-induced recovery. Ammonium-excretion decreased with Na₂ CO₃ , and increased with NH₄ Cl, but without differences between genotypes.

CONCLUSIONS

We conclude that TPC1 is expressed subapically in the proximal but not distal tubule and plays an important role in the dynamic adaptation of proximal tubular phosphate reabsorption towards enhanced, but not reduced absorption.

Structural Pharmacology of Cation-Chloride Cotransporters

Loop and thiazide diuretics have been cornerstones of clinical management of hypertension and fluid overload conditions for more than five decades. The hunt for their molecular targets led to the discovery of cation-chloride cotransporters (CCCs) that catalyze electroneutral movement of Cl^- together with Na⁺ and/or K⁺. CCCs consist of two 1 Na⁺-1 K⁺-2 Cl^- (NKCC1-2), one 1 Na⁺-1 Cl^- (NCC), and four 1 K⁺-1 Cl^- (KCC1-4) transporters in human. CCCs are fundamental in trans-epithelia ion secretion and absorption, homeostasis of intracellular Cl^- concentration and cell volume, and regulation of neuronal excitability. Malfunction of NKCC2 and NCC leads to abnormal salt and water retention in the kidney and, consequently, imbalance in electrolytes and blood pressure. Mutations in KCC2 and KCC3 are associated with brain disorders due to impairments in regulation of excitability and possibly cell volume of neurons. A recent surge of structures of CCCs have defined their dimeric architecture, their ion binding sites, their conformational changes associated with ion translocation, and the mechanisms of action of loop diuretics and small molecule inhibitors. These breakthroughs now set the stage to expand CCC pharmacology beyond loop and thiazide diuretics, developing the next generation of diuretics with improved potency and specificity. Beyond drugging renal-specific CCCs, brain-penetrable therapeutics are sorely needed to target CCCs in the nervous system for the treatment of neurological disorders and psychiatric conditions.

Cryo-EM structure of the human sodium-chloride cotransporter NCC

The sodium-chloride cotransporter NCC mediates the coupled import of sodium and chloride across the plasma membrane, playing vital roles in kidney extracellular fluid volume and blood pressure control. Here, we present the full-length structure of human NCC, with 2.9 Å for the transmembrane domain and 3.8 Å for the carboxyl-terminal domain. NCC adopts an inward-open conformation and a domain-swap dimeric assembly. Conserved ion binding sites among the cation-chloride cotransporters and the Na2 site are observed in our structure. A unique His residue in the substrate pocket in NCC potentially interacts with Na1 and Cl1 and might also mediate the coordination of Na2 through a Ser residue. Putative observed water molecules are indicated to participate in the coordination of ions and TM coupling. Together with transport activity assays, our structure provides the first glimpse of NCC and defines ion binding sites, promoting drug development for hypertension targeting on NCC.

HIV-1 Vpr suppresses expression of the thiazide-sensitive sodium chloride co-transporter in the distal convoluted tubule

HIV-associated nephropathy (HIVAN) impairs functions of both glomeruli and tubules. Attention has been previously focused on the HIVAN glomerulopathy. Tubular injury has drawn increased attention because sodium wasting is common in hospitalized HIV/AIDS patients. We used viral protein R (Vpr)-transgenic mice to investigate the mechanisms whereby Vpr contributes to urinary sodium wasting. In phosphoenolpyruvate carboxykinase promoter-driven Vpr-transgenic mice, in situ hybridization showed that Vpr mRNA was expressed in all nephron segments, including the distal convoluted tubule. Vpr-transgenic mice, compared with wild-type littermates, markedly increased urinary sodium excretion, despite similar plasma renin activity and aldosterone levels. Kidneys from Vpr-transgenic mice also markedly reduced protein abundance of the Na⁺-Cl^- cotransporter (NCC), while mineralocorticoid receptor (MR) protein expression level was unchanged. In African green monkey kidney cells, Vpr abrogated the aldosterone-mediated stimulation of MR transcriptional activity. Gene expression of Slc12a3 (NCC) in Vpr-transgenic mice was significantly lower compared with wild-type mice, assessed by both qRT-PCR and RNAScope in situ hybridization analysis. Chromatin immunoprecipitation assays identified multiple MR response elements (MRE), located from 5 kb upstream of the transcription start site and extending to the third exon of the SLC12A3 gene. Mutation of MRE and SP1 sites in the SLC12A3 promoter region abrogated the transcriptional responses to aldosterone and Vpr, indicating that functional MRE and SP1 are required for the SLC12A3 gene suppression in response to Vpr. Thus, Vpr attenuates MR transcriptional activity and inhibits Slc12a3 transcription in the distal convoluted tubule and contributes to salt wasting in Vpr-transgenic mice.

Kelch-like protein 3 in human disease and therapy

Kelch-like protein 3 (KLHL3) is a substrate adaptor of Cullin3-RING ubiquitin ligase (CRL3), and KLHL3-CUL3 complex plays a vital role in the ubiquitination of specific substrates. Mutations and abnormal post-translational modifications of KLHL3-CUL3 affect substrate ubiquitination and may related to the pathogenesis of Gordon syndrome (GS), Primary Hyperparathyroidism (PHPT), Diabetes Mellitus (DM), Congenital Heart Disease (CHD), Pre-eclampsia (PE) and even cancers. Therefore, it is essential to understand the function and molecular mechanisms of KLHL3-CUL3 for the treatment of related diseases. In this review, we summary the structure and function of KLHL3-CUL3, the effect of KLHL3-CUL3 mutations and aberrant modifications in GS, PHPT, DM, CHD and PE. Moreover, we noted a possible role of KLHL3-CUL3 in carcinogenesis and provided ideas for targeting KLHL3-CUL3 for related disease treatment.

Targeting the WNK-SPAK/OSR1 Pathway and Cation-Chloride Cotransporters for the Therapy of Stroke

Stroke is one of the major culprits responsible for morbidity and mortality worldwide, and the currently available pharmacological strategies to combat this global disease are scanty. Cation-chloride cotransporters (CCCs) are expressed in several tissues (including neurons) and extensively contribute to the maintenance of numerous physiological functions including chloride homeostasis. Previous studies have implicated two CCCs, the Na+-K+-Cl- and K+-Cl- cotransporters (NKCCs and KCCs) in stroke episodes along with their upstream regulators, the with-no-lysine kinase (WNKs) family and STE20/SPS1-related proline/alanine rich kinase (SPAK) or oxidative stress response kinase (OSR1) via a signaling pathway. As the WNK-SPAK/OSR1 pathway reciprocally regulates NKCC and KCC, a growing body of evidence implicates over-activation and altered expression of NKCC1 in stroke pathology whilst stimulation of KCC3 during and even after a stroke event is neuroprotective. Both inhibition of NKCC1 and activation of KCC3 exert neuroprotection through reduction in intracellular chloride levels and thus could be a novel therapeutic strategy. Hence, this review summarizes the current understanding of functional regulations of the CCCs implicated in stroke with particular focus on NKCC1, KCC3, and WNK-SPAK/OSR1 signaling and discusses the current and potential pharmacological treatments for stroke.

Role of the Cation-Chloride-Cotransporters in Cardiovascular Disease

The SLC12 family of cation-chloride-cotransporters (CCCs) is comprised of potassium chloride cotransporters (KCCs), which mediate Cl- extrusion and sodium-potassium chloride cotransporters (N[K]CCs), which mediate Cl- loading. The CCCs play vital roles in cell volume regulation and ion homeostasis. The functions of CCCs influence a variety of physiological processes, many of which overlap with the pathophysiology of cardiovascular disease. Although not all of the cotransporters have been linked to Mendelian genetic disorders, recent studies have provided new insights into their functional role in vascular and renal cells in addition to their contribution to cardiovascular diseases. Particularly, an imbalance in potassium levels promotes the pathogenesis of atherosclerosis and disturbances in sodium homeostasis are one of the causes of hypertension. Recent findings suggest hypothalamic signaling as a key signaling pathway in the pathophysiology of hypertension. In this review, we summarize and discuss the role of CCCs in cardiovascular disease with particular emphasis on knowledge gained in recent years on NKCCs and KCCs.