Na(+)/K(+)/Cl(-) cotransporter activates mitogen-activated protein kinase in fibroblasts and lymphocytes

Somatic growth outcomes in response to an individualized neonatal sodium supplementation protocol

OBJECTIVE

Evaluate the impact of a sodium (Na) supplementation protocol based upon urine Na concentration on growth parameters and morbidities.

STUDY DESIGN

Retrospective cohort study of infants 260/7-336/7 weeks gestational age (GA) cared for before (2012-15, n = 310) and after (2016-20, n = 382) implementation of the protocol. Within- and between-group changes over time were assessed using repeated measures generalized linear models.

RESULTS

For infants 260/7-296/7 weeks GA, utilization of the protocol was associated with increased mean body weight z-score at 8-weeks postnatal age, increased mean head circumference z-score at 16-weeks postnatal age, and decreased time on mechanical ventilation (all p < 0.02). No impact on growth was identified for infants 30-336/7 weeks GA. Incidences of hypertension, hypernatremia, bronchopulmonary dysplasia, necrotizing enterocolitis, and culture positive sepsis were unaffected by the protocol.

CONCLUSION

Protocolized Na supplementation is associated with improved growth and reduced time on invasive mechanical ventilation in extremely preterm infants without increasing incidence of morbidities.

Somatic growth outcomes in response to an individualized neonatal sodium supplementation protocol

Objective

Evaluate the impact of a sodium (Na) supplementation protocol based upon urine Na concentration on growth parameters and morbidities.

Study Design

Retrospective cohort study of infants 260/7-336/7 weeks gestational age (GA) cared for before (2012-15, n = 225) and after (2016-20, n = 157) implementation of the protocol. Within- and between-group changes over time were assessed using repeated measures generalized linear models.

Results

For infants 260/7-296/7 weeks GA, utilization of the protocol was associated with increased mean body weight z-score at 8-weeks postnatal age, increased mean head circumference z-score at 16-weeks postnatal age, and decreased time on mechanical ventilation (all p < 0.02). No impact on growth was identified for infants 30-336/7 weeks GA. Incidences of hypertension, hypernatremia, bronchopulmonary dysplasia, and culture positive sepsis were unaffected by the protocol.

Conclusion

Protocolized Na supplementation results in improved growth and reduced time on invasive mechanical ventilation in extremely preterm infants without increasing incidence of morbidities.

Novel γ-sarcoglycan interactors in murine muscle membranes

BACKGROUND

The sarcoglycan complex (SC) is part of a network that links the striated muscle cytoskeleton to the basal lamina across the sarcolemma. The SC coordinates changes in phosphorylation and Ca⁺⁺-flux during mechanical deformation, and these processes are disrupted with loss-of-function mutations in gamma-sarcoglycan (Sgcg) that cause Limb girdle muscular dystrophy 2C/R5.

METHODS

To gain insight into how the SC mediates mechano-signaling in muscle, we utilized LC-MS/MS proteomics of SC-associated proteins in immunoprecipitates from enriched sarcolemmal fractions. Criteria for inclusion were co-immunoprecipitation with anti-Sgcg from C57BL/6 control muscle and under-representation in parallel experiments with Sgcg-null muscle and with non-specific IgG. Validation of interaction was performed in co-expression experiments in human RH30 rhabdomyosarcoma cells.

RESULTS

We identified 19 candidates as direct or indirect interactors for Sgcg, including the other 3 SC proteins. Novel potential interactors included protein-phosphatase-1-catalytic-subunit-beta (Ppp1cb, PP1b) and Na⁺-K⁺-Cl^--co-transporter NKCC1 (SLC12A2). NKCC1 co-localized with Sgcg after co-expression in human RH30 rhabdomyosarcoma cells, and its cytosolic domains depleted Sgcg from cell lysates upon immunoprecipitation and co-localized with Sgcg after detergent permeabilization. NKCC1 localized in proximity to the dystrophin complex at costameres in vivo. Bumetanide inhibition of NKCC1 cotransporter activity in isolated muscles reduced SC-dependent, strain-induced increases in phosphorylation of extracellular signal-regulated kinases 1 and 2 (ERK1/2). In silico analysis suggests that candidate SC interactors may cross-talk with survival signaling pathways, including p53, estrogen receptor, and TRIM25.

CONCLUSIONS

Results support that NKCC1 is a new SC-associated signaling protein. Moreover, the identities of other candidate SC interactors suggest ways by which the SC and NKCC1, along with other Sgcg interactors such as the membrane-cytoskeleton linker archvillin, may regulate kinase- and Ca⁺⁺-mediated survival signaling in skeletal muscle.

CNS pharmacology of NKCC1 inhibitors

The Na-K-2Cl cotransporter NKCC1 and the neuron-specific K-Cl cotransporter KCC2 are considered attractive CNS drug targets because altered neuronal chloride regulation and consequent effects on GABAergic signaling have been implicated in numerous CNS disorders. While KCC2 modulators are not yet clinically available, the loop diuretic bumetanide has been used off-label in attempts to treat brain disorders and as a tool for NKCC1 inhibition in preclinical models. Bumetanide is known to have anticonvulsant and neuroprotective effects under some pathophysiological conditions. However, as shown in several species from neonates to adults (mice, rats, dogs, and by extrapolation in humans), at the low clinical doses of bumetanide approved for diuresis, this drug has negligible access into the CNS, reaching levels that are much lower than what is needed to inhibit NKCC1 in cells within the brain parenchyma. Several drug discovery strategies have been initiated over the last ∼15 years to develop brain-permeant compounds that, ideally, should be selective for NKCC1 to eliminate the diuresis mediated by inhibition of renal NKCC2. The strategies employed to improve the pharmacokinetic and pharmacodynamic properties of NKCC1 blockers include evaluation of other clinically approved loop diuretics; development of lipophilic prodrugs of bumetanide; development of side-chain derivatives of bumetanide; and unbiased high-throughput screening approaches of drug discovery based on large chemical compound libraries. The main outcomes are that (1), non-acidic loop diuretics such as azosemide and torasemide may have advantages as NKCC1 inhibitors vs. bumetanide; (2), bumetanide prodrugs lead to significantly higher brain levels than the parent drug and have lower diuretic activity; (3), the novel bumetanide side-chain derivatives do not exhibit any functionally relevant improvement of CNS accessibility or NKCC1 selectivity vs. bumetanide; (4) novel compounds discovered by high-throughput screening may resolve some of the inherent problems of bumetanide, but as yet this has not been achieved. Thus, further research is needed to optimize the design of brain-permeant NKCC1 inhibitors. In parallel, a major challenge is to identify the mechanisms whereby various NKCC1-expressing cellular targets of these drugs within (e.g., neurons, oligodendrocytes or astrocytes) and outside the brain parenchyma (e.g., the blood-brain barrier, the choroid plexus, and the endocrine system), as well as molecular off-target effects, might contribute to their reported therapeutic and adverse effects.

Molecular features and physiological roles of K+-Cl- cotransporter 4 (KCC4)

A K⁺-Cl^- cotransport system was documented for the first time during the mid-seventies in sheep and goat red blood cells. It was then described as a Na⁺-independent and ouabain-insensitive ion carrier that could be stimulated by cell swelling and N-ethylmaleimide (NEM), a thiol-reacting agent. Twenty years later, this system was found to be dispensed by four different isoforms in animal cells. The first one was identified in the expressed sequence tag (EST) database by Gillen et al. based on the assumption that it would be homologous to the Na⁺-dependent K⁺-Cl^- cotransport system for which the molecular identity had already been uncovered. Not long after, the three other isoforms were once again identified in the EST databank. Among those, KCC4 has generated much interest a few years ago when it was shown to sustain distal renal acidification and hearing development in mouse. As will be seen in this review, many additional roles were ascribed to this isoform, in keeping with its wide distribution in animal species. However, some of them have still not been confirmed through animal models of gene inactivation or overexpression. Along the same line, considerable knowledge has been acquired on the mechanisms by which KCC4 is regulated and the environmental cues to which it is sensitive. Yet, it is inferred to some extent from historical views and extrapolations.

NKCC1-Deficiency Results in Abnormal Proliferation of Neural Progenitor Cells of the Lateral Ganglionic Eminence

The proliferative pool of neural progenitor cells is maintained by exquisitely controlled mechanisms for cell cycle regulation. The Na-K-Cl cotransporter (NKCC1) is important for regulating cell volume and the proliferation of different cell types in vitro. NKCC1 is expressed in ventral telencephalon of embryonic brains suggesting a potential role in neural development of this region. The ventral telencephalon is a major source for both interneuron and oligodendrocyte precursor cells. Whether NKCC1 is involved in the proliferation of these cell populations remains unknown. In order to assess this question, we monitored several markers for neural, neuronal, and proliferating cells in wild-type (WT) and NKCC1 knockout (KO) mouse brains. We found that NKCC1 was expressed in neural progenitor cells from the lateral ganglionic eminence (LGE) at E12.5. Mice lacking NKCC1 expression displayed reduced phospho-Histone H3 (PH3)-labeled mitotic cells in the ventricular zone (VZ) and reduced cell cycle reentry. Accordingly, we found a significant reduction of Sp8-labeled immature interneurons migrating from the dorsal LGE in NKCC1-deficient mice at a later developmental stage. Interestingly, at E14.5, NKCC1 regulated also the formation of Olig2-labeled oligodendrocyte precursor cells. Collectively, these findings show that NKCC1 serves in vivo as a modulator of the cell cycle decision in the developing ventral telencephalon at the early stage of neurogenesis. These results present a novel mechanistic avenue to be considered in the recent proposed involvement of chloride transporters in a number of developmentally related diseases, such as epilepsy, autism, and schizophrenia.

Inhibition of Na(+)-K(+)-2Cl(-) Cotransporter-1 attenuates traumatic brain injury-induced neuronal apoptosis via regulation of Erk signaling

Traumatic brain injury (TBI) is the leading cause of mortality and morbidity worldwide and is characterized by immediate brain damage and secondary injuries, such as brain edema and ischemia. However, the exact pathological mechanisms that comprise these associated secondary injuries have not been fully elucidated. This study aimed to investigate the role of the Na(+)-K(+)-2Cl(-) cotransporter-1 (NKCC1) in the disruption of ion homeostasis and neuronal apoptosis in TBI. Using a traumatic neuron injury (TNI) model in vitro and a controlled cortex injury (CCI) model in vivo, the present study investigated changes in the expression and effects of NKCC1 in TBI using western blot, RNA interference, a lactate dehydrogenase (LDH) release assay, TdT-mediated dUTP Nick end-labeling (TUNEL) analysis, sodium imaging, brain water content, and neurological severity scoring. TBI induced the expression of NKCC1 to be significantly upregulated in the cortex, both in vitro and in vivo. Pharmacological inhibitor bumetanide (Bume) or NKCC1 RNA interference significantly attenuated TBI-induced intracellular Na(+) increase, inhibited neuronal apoptosis, and improved brain edema and neurological function. Furthermore, NKCC1 inhibition also significantly inhibited TBI-induced extracellular signal-regulated kinase (Erk) activation. Erk inhibition significantly protected neurons from TBI injury; however, Erk inhibition had no effect on NKCC1 expression or the neuroprotective effect of NKCC1 inhibition against TBI. This study demonstrates the role of NKCC1 in TBI-induced brain cortex injury, establishing that NKCC1 may play a neurotoxic role in TBI and that the inhibition of NKCC1 may protect neurons from TBI via the regulation of Erk signaling.

NKCC1 mediates traumatic brain injury-induced hippocampal neurogenesis through CREB phosphorylation and HIF-1α expression

Traumatic brain injury (TBI) is one of the most prevalent causes of worldwide mortality and morbidity. We previously had evidenced that TBI induced Na-K-2Cl co-transporter (NKCC1) upregulation in hippocampus. Here, we aim to investigate the role of NKCC1 in TBI-induced neurogenesis and the detailed mechanisms. The TBI-associated alternations in the expression of NKCC1, HIF-1α, VEGF, MAPK cascade, and CREB phosphorylation were analyzed by Western blot. TBI-induced neurogenesis was determined by immuno-fluorescence labeling. Chromatin immunoprecipitation was used to elucidate whether HIF-1α would activate VEGF gene after TBI. We found that the level of hippocampal NKCC1 and VEGF began to rise 8 h after TBI, and both of them reached maxima at day 7. Along with the upregulation of NKCC1 and VEGF, MAPK cascade was activated and hippocampal neurogenesis was promoted. Administration of CREB antisense oligonucleotide significantly attenuated the expression of HIF-1α, while HIF-1α antisense oligonucleotide exhibited little effect on the expression of CREB. However, HIF-1α antisense oligonucleotide administration did effectively suppress the expression of VEGF. Our results of the chromosome immunoprecipitation also indicated that HIF-1α could directly act on the VEGF promoter and presumably would elevate the VEGF expression after TBI. All these results have illustrated the correlation between NKCC1 upregulation and TBI-associated neurogenesis. The pathway involves the activation of Raf/MEK/ERK cascade, CREB phosphorylation, and HIF-1α upregulation, and finally leads to the stimulation of VEGF expression and the induction of neurogenesis.

Expression of GABA receptors subunits in peripheral blood mononuclear cells is gender dependent, altered in pregnancy and modified by mental health

AIM

The concept of nerve-driven immunity recognizes a link between the nervous and the immune system. γ-aminobutyric acid (GABA) is the main inhibitory neurotransmitter in the brain, and receptors activated by GABA can be expressed by immune cells. Here, we examined whether the expression of GABA receptors and chloride transporters in human peripheral blood mononuclear cells (PBMCs) was influenced by gender, pregnancy or mental health.

METHODS

We used RT-qPCR to determine the mRNA expression level in PBMCs from men (n = 16), non-pregnant women (n = 19), healthy pregnant women (n = 27) and depressed pregnant women (n = 15).

RESULTS

The ρ2 subunit had the most prominent expression level of the GABA-A receptor subunits in all samples. The δ and ρ2 subunits were up-regulated by pregnancy, whereas the ε subunit was more frequently expressed in healthy pregnant women than non-pregnant women who, in turn, commonly expressed the α6 and the γ2 subunits. The β1 and ε subunits expression was altered by depression in pregnant women. The GABA-B1 receptor was up-regulated by depression in pregnant women, while the transporters NKCC1 and KCC4 were down-regulated by pregnancy. The changes recorded in the mRNA expression levels imply participation of GABA receptors in establishing and maintaining tolerance in pregnancy. Importantly, the correlation of mental health with the expression of specific receptor subunits reveals a connection between the immune cells and the brain. Biomarkers for mental health may be identified in PBMCs.

CONCLUSION

The results demonstrate the impact gender, pregnancy and mental health have on the expression of GABA receptors and chloride transporters expressed in human PBMCs.

Ion transporter NKCC1, modulator of neurogenesis in murine olfactory neurons

Olfaction is one of the most crucial senses for vertebrates regarding foraging and social behavior. Therefore, it is of particular interest to investigate the sense of smell, its function on a molecular level, the signaling proteins involved in the process and the mechanism of required ion transport. In recent years, the precise role of the ion transporter NKCC1 in olfactory sensory neuron (OSN) chloride accumulation has been a controversial subject. NKCC1 is expressed in OSNs and is involved in chloride accumulation of dissociated neurons, but it had not been shown to play a role in mouse odorant sensation. Here, we present electro-olfactogram recordings (EOG) demonstrating that NKCC1-deficient mice exhibit significant defects in perception of a complex odorant mixture (Henkel100) in both air-phase and submerged approaches. Using next generation sequencing (NGS) and RT-PCR experiments of NKCC1-deficient and wild type mouse transcriptomes, we confirmed the absence of a highly expressed ion transporter that could compensate for NKCC1. Additional histological investigations demonstrated a reduced number of cells in the olfactory epithelium (OE), resulting in a thinner neuronal layer. Therefore, we conclude that NKCC1 is an important transporter involved in chloride ion accumulation in the olfactory epithelium, but it is also involved in OSN neurogenesis.

Both NKCC1 and anion exchangers contribute to Cl⁻ accumulation in postnatal forebrain neuronal progenitors

Neuronal progenitors are continuously generated in the postnatal rodent subventricular zone and migrate along the rostral migratory stream to supply interneurons in the olfactory bulb. Nonsynaptic GABAergic signaling affects the postnatal neurogenesis by depolarizing neuronal progenitors, which depends on an elevated intracellular Cl(-) concentration. However, the molecular mechanism responsible for Cl(-) accumulation in these cells still remains elusive. Using confocal Ca(2+) imaging, we found that GABA depolarization-induced Ca(2+) increase was either abolished by bumetanide, a specific inhibitor of the Na(+) -K(+) -2Cl(-) cotransporter, or reduced by partial replacement of extracellular Na(+) with Li(+) , in the HEPES buffer but not in the CO(2)/HCO₃⁻ buffer. GABA depolarization-induced Ca(2+) increase in CO(2)/HCO₃⁻ buffer was abolished by a combination of bumetanide with the anion exchanger inhibitor DIDS or with the carbonic anhydrase inhibitor acetozalimide. Using gramicidin-perforated patch-clamp recording, we further confirmed that bumetanide, together with DIDS or acetozalimide, reduced the intracellular chloride concentration in the neuronal progenitors. In addition, with BrdU labeling, we demonstrated that blocking of the Na(+) -K(+) -2Cl(-) cotransporter, but not anion exchangers, reduced the proliferation of neuronal progenitors. Our results indicate that both the Na(+) -K(+) -2Cl(-) cotransporter and anion exchangers contribute to the elevated intracellular chloride responsible for the depolarizing action of GABA in the postnatal forebrain neuronal progenitors. However, the Na(+) -K(+) -2Cl(-) cotransporter displays an additional effect on neuronal progenitor proliferation.

Enhanced insulin secretion and improved glucose tolerance in mice with homozygous inactivation of the Na(+)K(+)2Cl(-) co-transporter 1

The intracellular chloride concentration ([Cl(-)](i)) in β-cells plays an important role in glucose-stimulated plasma membrane depolarisation and insulin secretion. [Cl(-)](i) is maintained above equilibrium in β-cells by the action of Cl(-) co-transporters of the solute carrier family 12 group A (Slc12a). β-Cells express Slc12a1 and Slc12a2, which are known as the bumetanide (BTD)-sensitive Na(+)-dependent K(+)2Cl(-) co-transporters 2 and 1 respectively. We show that mice lacking functional alleles of the Slc12a2 gene exhibit better fasting glycaemia, increased insulin secretion in response to glucose, and improved glucose tolerance when compared with wild-type (WT). This phenomenon correlated with increased sensitivity of β-cells to glucose in vitro and with increased β-cell mass. Further, administration of low doses of BTD to mice deficient in Slc12a2 worsened their glucose tolerance, and low concentrations of BTD directly inhibited glucose-stimulated insulin secretion from β-cells deficient in Slc12a2 but expressing intact Slc12a1 genes. Together, our results suggest for the first time that the Slc12a2 gene is not necessary for insulin secretion and that its absence increases β-cell secretory capacity. Further, impairment of insulin secretion with BTD in vivo and in vitro in islets lacking Slc12a2 genes unmasks a potential new role for Slc12a1 in β-cell physiology.

Dependence of corneal epithelial cell proliferation on modulation of interactions between ERK1/2 and NKCC1

Epidermal growth factor (EGF) receptor stimulation or protein kinase C (PKC) activation enhances corneal epithelial cell proliferation. This response is needed to maintain corneal transparency and vision. We clarify here in human corneal epithelial cells (HCEC) the cause and effect relationships between ERK1/2 and NKCC1 phosphorylation induced by EGF receptor or PKC activation. Furthermore, the roles are evaluated of NF-κB and ERK1/2 in mediating negative feedback control of ERK1/2 and NKCC1 phosphorylation through modulating DUSP1 and DUSP6 expression levels. Intracellular Ca(2+) rises induced by EGF elicited NKCC1 phosphorylation through ERK1/2 activation. Bumetanide suppressed EGF-induced NKCC1 phosphorylation, transient cell swelling and cell proliferation. This cause and effect relationship is similar to that induced by PKC stimulation. NKCC1 activation occurred through time-dependent increases in protein-protein interaction between ERK1/2 and NKCC1, which were proportional to EGF concentration. DUSP6 upregulation obviated EGF and PKC-induced NKCC1 phosphorylation. NF-κB inhibition by PDTC prolonged ERK1/2 activation through GSK-3 inactivation leading to declines in DUSP1 expression levels. These results show that EGF receptor and PKC activation induce increases in HCEC proliferation through ERK1/2 interaction with NKCC1. This response is modulated by changes in DUSP1- and DUSP6-mediated negative feedback control of ERK1/2-induced NKCC1 phosphorylation.

Effects of furosemide on allergic asthmatic responses in mice

BACKGROUND

The syndrome of allergic asthma features reversible bronchoconstriction, airway inflammation and hyperresponsiveness as well as airway remodelling, including goblet cell hyperplasia. Managing severe asthma is still a clinical challenge. Numerous studies report that furosemide, an inhibitor of Na(+)-K(+)-Cl(-) cotransporter (NKCC) reduces airway hyperresponsiveness (AHR) in asthmatic patients. However, the mechanism by which furosemide exerts anti-asthmatic action remains unclear.

OBJECTIVE

This study sought to investigate the cellular profile of NKCC1 expression in the lung and examine the effects of furosemide on several outcome measurements in a mouse model of allergic asthma.

METHODS

Mice were sensitized and challenged with ovalbumin (OVA). Before challenge, the OVA-sensitized mice were treated with furosemide (4.0 mg/kg/day, via daily intraperitoneal injection for 5 days). Outcome measurements in naïve, OVA-exposure, furosemide-treated naïve and furosemide-treated OVA-exposed mice included the slope of the relationship between inhaled methacholine (MCh) concentration and respiratory system resistance (Slope·R(RS)), bronchoalveolar lavage (BAL) cell counts and immunohistochemical and immunoblotting assays of lung tissues.

RESULTS

NKCC1 immunoreactivity was observed in airway epithelial cells (AECs) and alveolar type II (ATII) cells of the control mice. OVA exposure enhanced the expression of NKCC1 in AECs and ATII cells, and increased the infiltration of NKCC1-expressing T lymphocytes in the lung. NKCC1 immunoreactivity was not detected in the airway smooth muscle (ASM) cells. Furosemide treatment reduced the Slope·R(RS) in both naïve and OVA-exposed mice by about 50%. Furosemide treatment also increased T lymphocyte infiltration to the lung in OVA-exposed mice by approximately 53%, but had no effect on pulmonary goblet cell hyperplasia.

CONCLUSIONS AND CLINICAL RELEVANCE

Furosemide decreases basal airway responsiveness, thereby reducing the extent of allergen-induced AHR. However, the same treatment also increases T lymphocytes infiltration in the course of allergic asthma. Further studies are necessary to address the usefulness of furosemide in the clinical treatment of asthma.

Effect of different antihypertensive treatments on Ras, MAPK and Akt activation in hypertension and diabetes

Ras GTPases function as transducers of extracellular signals regulating many cell functions, and they appear to be involved in the development of hypertension. In the present study, we have investigated whether antihypertensive treatment with ARBs (angiotensin II receptor blockers), ACEi (angiotensin-converting enzyme inhibitors) and diuretics induce changes in Ras activation and in some of its effectors [ERK (extracellular-signal-regulated kinase) and Akt] in lymphocytes from patients with hypertension without or with diabetes. ACEi treatment transiently reduced Ras activation in the first month of treatment, but diuretics induced a sustained increase in Ras activation throughout the 3 months of the study. In patients with hypertension and diabetes, ARB, ACEi and diuretic treatment increased Ras activation only during the first week. ACEi treatment increased phospho-ERK expression during the first week and also in the last 2 months of the study; however, diuretic treatment reduced phospho-ERK expression during the last 2 months of the study. In patients with hypertension and diabetes, antihypertensive treatments did not induce changes in phospho-ERK expression in lymphocytes. ACEi treatment reduced phospho-Akt expression in patients with hypertension and diabetes only in the first month of treatment. In conclusion, these findings show that antihypertensive treatments with ACEi, and diuretics to a lesser extent, modify Ras activation and some of its signalling pathways, although in different directions, whereas ARBs do not appear to have any influence on Ras signalling pathways.

NKCC-1 and ENaC are down-regulated in nitrofen-induced hypoplastic lungs with congenital diaphragmatic hernia

Congenital diaphragmatic hernia (CDH) is accompanied by pulmonary hypoplasia and pulmonary hypertension. Fetal lung growth is dependent on the secretion of lung liquid, which normally is absorbed at partus. The ion channel NKCC-1 is involved in this secretory process, but has recently also been reported to be implicated in absorption. CDH patients show a disturbed transition from secretion to absorption. alpha- and beta-ENaC are essential for lung liquid absorption. Common for all transcellular ion transport is the need for Na/K-ATPase as a primary driving force. The aim of the study was first to map the normal pulmonary expression of the above proteins during late gestation and secondly to see if the expression was affected in a CDH rat model. Pregnant Sprague-Dawley rat dams were given nitrofen on gestational day 9.5 to induce CDH. The fetuses were removed on gestational days E18 and E21. In addition, newborn rats were harvested postpartum on day P2. The fetuses were put into one of two groups: hypoplastic lungs without CDH (N-CDH) and hypoplastic lungs with CDH (N+CDH). The pulmonary expression of NKCC-1, alpha-/beta-ENaC and Na/K-ATPase was then analyzed using Western blot. We found that the protein levels of NKCC-1 on gestational days E18 and E21 were significantly lower among fetuses with N+CDH as well as N-CDH compared to controls. The expression of beta-ENaC was also significantly down-regulated in both the groups on E18 and E21. The protein levels of alpha-ENaC and Na/K-ATPase were not found to be significantly decreased, but both showed a tendency towards down-regulation. The marked down-regulation of NKCC-1 in fetal hypoplastic lungs with CDH indicates a possibly decreased lung liquid production. This may be one of the mechanisms behind the disturbed pulmonary development in CDH. We also show that beta-ENaC is down-regulated. Down-regulation of beta-ENaC may result in abnormal lung liquid absorption, which could be one of the mechanisms behind the respiratory distress seen in CDH patients postpartum.

Interleukin-1beta upregulates Na+-K+-2Cl- cotransporter in human middle ear epithelia

Disruption of periciliary fluid homeostasis is the main pathogenesis of otitis media with effusion (OME), one of the most common childhood diseases. Although the underlying molecular mechanisms are unclear, it has been suggested that the altered functions of ion channels and transporters are involved in the fluid collection of middle ear cavity of OME patients. In the present study, we analyzed the effects of a major cytokine interleukin (IL)-1beta, which was known to be involved in the pathogenesis of OME, on Na(+)-K(+)-2Cl(-) cotransporter (NKCC) in human middle ear cells. Intracellular pH (pH(i)) was measured in primary cultures of normal human middle ear epithelial (NHMEE) cells using a double perfusion chamber, which enabled us to analyze the membrane-specific transporter activities. NKCC activities were estimated by the pH(i) reduction due to bumetanide-sensitive intracellular uptake of NH(4) (+). In NHMEE cells, NKCC activities were observed only in the basolateral membrane, and immunoblotting using specific antibodies revealed the expression of NKCC1. Interestingly, IL-1beta treatments augmented the basolateral NKCC activities and increased NKCC1 expression. In addition, IL-1beta treatments stimulated bumetanide-sensitive fluid transport across the NHMEE cell monolayers. Furthermore, an elevated NKCC1 expression was observed in middle ear cells from OME patients when compared to those from control individuals. The above results provide in vitro and in vivo evidence that the inflammatory cytokine IL-1beta upregulates NKCC1 in middle ear epithelial cells, which would be one of the important underlying mechanisms of excess fluid collection in OME patients.

Intracellular monovalent ions as second messengers

It is generally accepted that electrochemical gradients of monovalent ions across the plasma membrane, created by the coupled function of pumps, carriers and channels, are involved in the maintenance of resting and action membrane potential, cell volume adjustment, intracellular Ca(2+ )handling and accumulation of glucose, amino acids, nucleotides and other precursors of macromolecular synthesis. In the present review, we summarize data showing that side-by-side with these classic functions, modulation of the intracellular concentration of monovalent ions in a physiologically reasonable range is sufficient to trigger numerous cellular responses, including changes in enzyme activity, gene expression, protein synthesis, cell proliferation and death. Importantly, the engagement of monovalent ions in regulation of the above-listed cellular responses occurs at steps upstream of Ca(2+) (i) and other key intermediates of intracellular signaling, which allows them to be considered as second messengers. With the exception of HCO (3) (-) -sensitive soluble adenylyl cyclase, the molecular origin of sensors involved in the function of monovalent ions as second messengers remains unknown.

Topical furosemide versus oral steroid in preoperative management of nasal polyposis

The efficacy of topical nasal furosemide treatment has been shown in the protection of nasal polyp recurrence. The aim of the study was to compare the effect of oral steroid, as standard preoperative treatment, and inhaled furosemide, as alternative treatment, for 7 days preoperatively in terms of subjective improvement of nasal symptoms, polyp size reduction, inflammation in the polyp tissue, and intraoperative blood loss. A group of 40 patients with nasal polyposis entered the study and they were randomly allocated to 7-day preoperative treatment with either oral methylprednisolon (1 mg/kg/day) or topical furosemide by inhalation (6.6 mmol/l solution). Subjective scores of rhinosinusitis symptoms, polyp scores at endoscopy, and biopsy of the most superficial polyp were taken at inclusion. All procedures were repeated on day 7. Intraoperative blood loss was estimated (scores 0-10) by the surgeon at the operation. Eosinophils, mastocytes, and oedema were quantified by histomorphometry. Subjective symptoms and endoscopy scores did not differ significantly between the groups after the treatment although improvement of olfaction was insignificantly better in the steroid group. Steroid treatment significantly reduced eosinophil count, with no effect on mastocytes and oedema. Furosemide treatment did not affect inflammatory cells count significantly, but it has significantly reduced oedema in previously unoperated patients. No difference in intraoperative bleeding was observed between the groups.

Physiology and pathophysiology of Na+/H+ exchange and Na+ -K+ -2Cl- cotransport in the heart, brain, and blood

Maintenance of a stable cell volume and intracellular pH is critical for normal cell function. Arguably, two of the most important ion transporters involved in these processes are the Na+/H+ exchanger isoform 1 (NHE1) and Na+ -K+ -2Cl- cotransporter isoform 1 (NKCC1). Both NHE1 and NKCC1 are stimulated by cell shrinkage and by numerous other stimuli, including a wide range of hormones and growth factors, and for NHE1, intracellular acidification. Both transporters can be important regulators of cell volume, yet their activity also, directly or indirectly, affects the intracellular concentrations of Na+, Ca2+, Cl-, K+, and H+. Conversely, when either transporter responds to a stimulus other than cell shrinkage and when the driving force is directed to promote Na+ entry, one consequence may be cell swelling. Thus stimulation of NHE1 and/or NKCC1 by a deviation from homeostasis of a given parameter may regulate that parameter at the expense of compromising others, a coupling that may contribute to irreversible cell damage in a number of pathophysiological conditions. This review addresses the roles of NHE1 and NKCC1 in the cellular responses to physiological and pathophysiological stress. The aim is to provide a comprehensive overview of the mechanisms and consequences of stress-induced stimulation of these transporters with focus on the heart, brain, and blood. The physiological stressors reviewed are metabolic/exercise stress, osmotic stress, and mechanical stress, conditions in which NHE1 and NKCC1 play important physiological roles. With respect to pathophysiology, the focus is on ischemia and severe hypoxia where the roles of NHE1 and NKCC1 have been widely studied yet remain controversial and incompletely elucidated.

Interleukin-2-dependent regulation of Na/K pump in human lymphocytes

The present study provides the first evidence that the abundance of catalytic alpha1-subunit of Na,K-ATPase increases in the course of T cell blast transformation. Immunodepressant cyclosporin A at anti-proliferative doses diminished the induction of alpha1 protein in activated lymphocytes. Furthermore, in competent T cells, IL-2 increases both the transport activity of Na/K pump and the content of Na,K-ATPase alpha1 protein in a time-dependent manner. A correlation was found between the long-term elevation in ouabain-sensitive Rb influxes and the increase in alpha1 protein content in late activated T cells. These results suggest that (1) the increased expression of Na,K-ATPase proteins underlie the cell cycle-dependent upregulation of ion pump during T cell transformation, and (2) IL-2 is involved in the regulated expression of Na,K-ATPase in human lymphocytes.

A pharmacological examination of Na+ and Cl- transport in two species of freshwater fish

We examined branchial Na(+) and Cl(-) uptake in two species of stenohaline, freshwater fish (goldfish and the Amazonian neon tetra). Kinetic analysis revealed that the two species had similar uptake capacities and affinities for Na(+) and Cl(-). However, while uptakes of Na(+) and Cl(-) (JNain and JClin, respectively) by goldfish were completely inhibited at pH 4.5 and below, uptake in tetras was unaffected by pH down to 3.25. Examination of Cl(-) transport with blockers indicated that goldfish and neon tetras utilize Cl(-)/HCO-3 exchange; SITS and SCN(-) inhibited Cl(-) uptake in both species. In contrast, large differences in Na(+) transport were indicated between the species. In goldfish, exposure to four Na(+)/H(+) exchange blockers, as well as the Na(+) channel blocker phenamil, strongly inhibited JNain. Further, Na(+) and Cl(-) uptake were strongly inhibited by the Na(+)/K(+)/Cl(-) cotransport inhibitor furosemide, as was JNain in "Cl(-)-free" water and JClin in "Na(+)-free" water. This suggests the presence of multiple transporters and possibly even a direct linkage between the transport of Na(+) and Cl(-) in goldfish. In contrast, none of these drugs strongly reduced Na(+) transport in neon tetras, which raises the possibility of a significantly different Na(+) transport mechanism in this acid-tolerant species.

Na+/K+/Cl− cotransporter activates MAP-kinase cascade downstream to protein kinase C, and upstream to MEK

In this study, we demonstrated that the specific inhibitors of the Na+/K+/Cl- cotransporter (NKCC1), bumetanide and furosemide, inhibited extracellular regulated kinase (ERK) phosphorylation in Balb/c 3T3 fibroblasts, stimulated with a variety of mitogens. In addition to fibroblast growth factor (FGF) shown before, the various mitogens tested in the present study (endothelial growth factor (EGF), platelet-derived growth factor (PDGF), insulin, thrombin, and the phorbol ester, 12-O-tetradecanoyl-phorbol-13-acetate (TPA)). Enter, the Ras/Raf/MEK/ERK cascade via different growth factors receptors and through one of the two main routes. The results of the present study provide evidence that have led us to conclude that the target protein which is controlled by the Na+/K+/Cl- cotransporter, is downstream of tyrosine kinase receptors, as well as of the G-protein-coupled receptor (GPCR). Several additional lines of evidence supported the above conclusion: (i) furosemide inhibits phosphorylation of MAPK kinase (MEK) induced by receptor tyrosine kinase (RTK) ligands, such as PDGF, FGF, and EGF. (ii) Furosemide also inhibited ERK phosphorylation, induced by thrombin, a GPCR. (iii) Furosemide inhibited MEK and ERK phosphorylation even when ERK phosphorylation was induced by direct activation of protein kinase C (PKC) by TPA, which bypasses early steps of the mitogenic cascade. In addition, we found that furosemide did not affect PKC phosphorylation induced directly by TPA. Taken together, the results of the present study indicate that the signal transduction protein, controlled by the Na+/K+/Cl- cotransporter, must be downstream of the PKC, and at/or upstream to MEK in the Ras/Raf/MEK/ERK cascade.