Na+/H+ antiporter plays an important role in mechanisms of the plant salt tolerance, it extrudes Na+ from cell energized by the proton gradient generated by the plasm membrane H(+)-ATPase and/or compartmentalizes Na+ in vacuole energized by the proton gradient generated by the vacuolar membrane H(+)-ATPase and H(+)-PPiase. This review mainly discusses the latest progress in the study of Na+/H+ antiporter in plant and yeast at molecular level.
Phylogeny ; Plants ; metabolism ; Salts ; metabolism ; Sodium ; metabolism ; Sodium-Hydrogen Exchangers ; classification ; metabolism ; Vacuoles ; physiology

This study was aimed to investigate the expression of Na(+)/H(+) exchanger 1 (NHE1) in K562 and HL-60 cells undergoing DNA damage induced by etoposide and to elucidate the regulating mechanism. Real-time quantitative PCR (RQ-PCR) and Western blot methods were used to determine the expression of NHE1 in K562 cells after the treating with etoposide. Meanwhile, the flow cytometry was used to detect the apoptosis of leukemic cells. The luciferase reporter vector containing NHE1 promoter was constructed to measure relative luciferase activity after treating with different etoposide concentrations. The results showed that the mRNA and protein of NHE1 increased in accordance with apoptosis ratio in HL-60 cells after treated with etoposide (p < 0.05), but no such obvious increase in K562 cells. Treatment with NHE1 specific inhibitor could block etoposide induced alkalization and reduce the apoptosis ratio of HL-60 cells. The expression pattern and apoptosis alteration was not similar in K562 cells. Relative luciferase activity of reporter vector containing NHE1 promoter however increased in K562 cells after treated with etoposide. It is concluded that the expression of NHE1 is up-regulated in the process of apoptosis of HL-60 cells induced by etoposide and depends on the pHi increasing caused by NHE1 up-regulation which is not found in K562 cells although the transcriptional activity increased.
Apoptosis ; Cation Transport Proteins ; metabolism ; DNA Damage ; Etoposide ; HL-60 Cells ; Humans ; K562 Cells ; Promoter Regions, Genetic ; Sodium-Hydrogen Exchanger 1 ; Sodium-Hydrogen Exchangers ; metabolism

This study was purposed to investigate the effect of hypoxia microenvironment on K562 leukemic cell differentiation, and characteristics of NHE1 involvement in this process. The K562 cells were treated with hypoxia-mimical agent CoCl₂ or under actual hypoxia culture, and the specific NHE1 inhibitor Cariporide was used to inhibit NHE1 activity. The fluorescent probe BCECF was used for pH(i) measurements. Gene expression was analyzed by RT-PCR. The morphological characteristics was determined by Wright's staining. Signaling pathways were detected by Western blot using phosphospecific antibodies. The results indicated that the hypoxia or mimetic hypoxia favored K562 cells differentiation with up-regulation of C/EBPα. Moreover, treatment with Cariporide under hypoxia synergistically enhanced leukemia cell differentiation. Treatment with Cariporide increased levels of phosphorylated ERK5 and P38 mitogen-activated protein kinase (MAPK). It is concluded that the hypoxia or mimetic hypoxia can induce the differentiation of K562 cells, the inhibition of NHE1 activity can promote the hypoxia-induced K562 cell differentiation. The enhancement of hypoxia-induced K562 differentiation by Cariporide via MAPK signal pathway suggests a possible therapeutic target of NHE1 under hypoxia microenvironment in the treatment of leukemias.
Cation Transport Proteins ; metabolism ; Cell Differentiation ; Cell Hypoxia ; Humans ; K562 Cells ; MAP Kinase Signaling System ; Sodium-Hydrogen Exchanger 1 ; Sodium-Hydrogen Exchangers ; metabolism

BACKGROUNDRecent studies showed the central Na+/H+ exchanger type 3 (NHE3) has a close relationship with ventilation control. The objective of the study is to investigate the role of NHE3 in sleep apnea in Sprague-Dawley (SD) rats.

METHODSA sleep study was performed on 20 male SD rats to analyze the correlation between the sleep apneic events and total NHE3 protein content and inactive NHE3(pS552) in the brainstem measured by Western blotting. Another 20 adult male SD rats received 3 days of sleep and respiration monitoring for 6 hours a day, with adaption on the first day, 0.5% DMSO microinjection into the fourth ventricle on the second day, and AVE0657 (specific inhibitor of NHE3) microinjection on the third day. Rats were divided into two groups with injection of 5 µmol/L or 8 µmol/L AVE0657 before the sleep study. The effects of AVE0657 on sleep apnea and sleep structure of rats were analyzed through self-control.

RESULTSThe total post-sigh apnea index (TPSAI) and post-sigh apnea index in non-rapid eye movement (NREM) sleep (NPSAI) and total apnea index (AI) in NREM sleep (NAI) were negatively correlated with NHE3(pS552) protein contents in the brainstem (r = -0.534, -0.547 and -0.505, respectively, P < 0.05). The spontaneous apnea index in REM sleep (RSPAI) was positively correlated with the level of NHE3(pS552) protein expression in the brainstem (r = 0.556, P < 0.05). However, the sleep AI had no relationship with total NHE3 protein. Compared with the blank control and microinjection of 0.5% DMSO, 5 µmol/L AVE0657 significantly reduced the total AI and NPSAI (both P < 0.05) without a significant effect on sleep architecture. In contrast to blank control and microinjection of 0.5% DMSO, injection of 8 µmol/L AVE0657 significantly reduced the AI and PSAI in NREM and REM sleep (all P < 0.05).

CONCLUSIONSThe severity of sleep apnea was negatively correlated with central inactive NHE3. A specific inhibitor of NHE3 decreased the sleep AI. Thus, our results indicate that central NHE3 might be a molecular target for sleep apnea treatment, whose inhibitors may be potential therapeutic drugs for sleep apnea.

Animals ; Male ; Rats ; Rats, Sprague-Dawley ; Sleep Apnea Syndromes ; metabolism ; physiopathology ; Sleep, REM ; physiology ; Sodium-Hydrogen Exchanger 3 ; Sodium-Hydrogen Exchangers ; antagonists & inhibitors ; metabolism

HCO3(-) reabsorption in the renal tubules plays a critically important role in maintaining the global acid-base balance. Loss of HCO3(-) causes metabolic acidosis. Proximal renal tubule is the major site for HCO3(-) reabsorption, accounting for more than 80% of total HCO3(-) reabsorption along the nephron. Over the past more than half centuries, tremendous progresses have been made on understanding the molecular mechanisms underlying the HCO3(-) reabsorption in proximal tubules. The transepithelial movement of HCO3(-) involves the coordinated operation of machineries on both the apical and the basolateral membranes of the epithelial cells. On the apical domain, Na(+)-H(+) exchanger NHE3 and the vacuolar H(+)-ATPase are two major pathways mediating the apical uptake of HCO3(-)-related species. Taken together, NHE3 and H(+)-ATPase are responsible for about 80% of HCO3(-) reabsorption in the proximal tubule. The remaining 20% is likely mediated by pathways yet to be characterized. On the basolateral membrane, NBCe1 represents the only major known pathway mediating the extrusion of HCO3(-) coupled with Na(+) into the interstitial space. In the present article, we provide a historical view about the studies on the mechanisms of HCO3(-) reabsorption since 1940s. Moreover, we summarize the latest progresses emerging over the past decade in the physiological as well as pathological roles of acid-base transporters underlying the HCO3(-) reabsorption in proximal tubules.
Acidosis ; physiopathology ; Animals ; Bicarbonates ; metabolism ; Humans ; Kidney Tubules, Proximal ; physiopathology ; Sodium-Hydrogen Exchangers ; physiology ; Vacuolar Proton-Translocating ATPases ; physiology

OBJECTIVETo investigate the protective effects of Cariporide on immature rabbit heart, and to search for the protective mechanism of the Na(+)/H(+) exchange inhibitor on immature rabbit hearts.

METHODSNew Zealand immature rabbits were randomly divided into two groups (n = 12 in each group). The isolated rabbit heart model was involved in this study. The hearts were submitted to 60 minutes of normothermic ischemia with cardioplegia per 20 minutes of reperfusion. Group I received St. Thomas No2 as cardioprotective solution. Group II received St. Thomas No2 with addition of cariporide (10 micro mol/L). The left ventricular function was recorded, including left ventricular systolic pressure (LVSP), left ventricular dystolic pressure (LVDP), coronary artery flow (CAF), mean aortic pressure (MAP), aortic flow (AF) and dp/dt max. The levels of creatine phosphokinase (CK), lactic dehydrogenase (LDH) of coronary sinus venous solution were measured. The ventricular cardiomyocytes isolated from other 6 immature rabbit hearts were subdivided into 3 groups of each heart, which were attained by means of collagenase-perfusion. All cells were incubated with calcium fluoresence indicator Fluo-3/AM, and then the intracellular free calcium was measured under the laser scanning con-focal microscopy. The baseline was measured after isolation without anoxic/re-oxygenation. The control group received anoxic conditions for 60 minutes and re-oxygenation for 30 minutes, then was measured. The experiment group received the same conditions as control group with addition of Cariporide (1 micromol/L).

RESULTSAfter ischaemia/reperfusion, the percentage of recovery of myocardial function in group II was much better than group I; the LVDP, LVSP, MAP, AF, CAF and dp/dt max showed markedly better recovery in group II. The release of CK, LDH was significantly increased in Group I. After anoxic/re-oxygenation, the intracellular free calcium of isolated immature rabbit ventricular myocytes in control group increased significantly than baseline (P < 0.01); there were no significant difference of immature myocardial [Ca(2+)]i between experiment group and baseline (P > 0.05); and the experiment group myocardial [Ca(2+)]i reduced significantly than control (P < 0.01).

CONCLUSIONSCariporide demonstrates significant cardio-protective effects for immature myocardium ischemia/reperfusion, and the protective mechanism may be due to the inhibition of the intracellular free calcium overload.

Animals ; Arrhythmias, Cardiac ; etiology ; Calcium ; metabolism ; Female ; Guanidines ; pharmacology ; Male ; Myocardial Reperfusion Injury ; prevention & control ; Rabbits ; Sodium ; metabolism ; Sodium-Hydrogen Exchangers ; antagonists & inhibitors ; Sulfones ; pharmacology

Na(+)-H(+) exchangers (NHE) are major membrane proteins that have been identified as signal transduction mediators in the regulation of cell differentiation and important membrane ion transporters in the regulation of the intercellular pH and the cell volume. NHE are composed of at least six isoforms and activated in growth factor-regulated cell differentiation. However, little is known about the differential regulation of NHE expression in the development. In the present study, we studied developmental regulation of the expression of NHE isoforms in human fetal tissues by comparing the expression of various isoforms between two developmental stages, i.e., week 11 (11 W) and week 16 (16 W). The results demonstrated that NHE1 transcripts were expressed ubiquitously. In comparison to the expression at 16 W, the level of NHE1 transcripts was low and varied significantly in a tissue-specific pattern at 11 W, suggesting that the house-keeping function of MHE1 occurs at 11 W or earlier and becomes well established at least as early as at 16 W. The tissue-specifically restricted expression of NHE2 and NHE3 was regulated at 11 W and 16 W in an opposite tendency, supporting the overlapping relationship between NHE2 and NHE3 in the tissue distribution as reported in adults. NHE5 expression was relatively ubiquitous at 11 W and became restricted in the cerebellum at 16 W, suggesting that the restrictive expression of NHE5 in the brain occurs later than that of other isoforms. The present study demonstrates a space time-dependent regulation of the tissue-specific expression pattern of NHE isoforms during human development between 11 W and 16 W. The results also suggest that at 16 W or earlier the expression pattern of developing tissues becomes similar to that of adult tissues. The observed developmental regulation of NHE expression provides a molecular basis for further study of the function and regulation of NHE gene during development.
Fetus ; embryology ; metabolism ; Gene Expression Regulation, Developmental ; physiology ; Humans ; Organ Specificity ; Protein Isoforms ; metabolism ; physiology ; RNA, Messenger ; metabolism ; physiology ; Sodium-Hydrogen Exchangers ; metabolism ; physiology ; Tissue Distribution

OBJECTIVETo investigate the effect of adenosine and its agonist on hypoxia-induced right ventricular hypertrophy (RVH) and explore the underlying mechanism.

METHODSFifty-six rats were randomly divided into normoxia group, hypoxia group, and treated hypoxia groups (with different treatments with adenosine, A1 receptor agonist CPA, A2 receptor agonist NECA, CPA plus A1 receptor inhibitor DPCPX, or NECA plus A2B receptor inhibitor MRS1754). The rats except for those in normoxia group were exposed to normobaric chronic hypoxia (9.5%-10.5% oxygen) for 21 days, and the corresponding treatments were administered since the 7th day of hypoxia till day 21 via implantable capsule with a pressure pump. After the treatments, the right ventricles were then removed and weighed for evaluation of hypertrophy, and the expressions of NHE-1 and CnAβ mRNA in the myocardial tissue were detected using RT-PCR.

RESULTSAfter a 21-day hypoxia, the rats showed significantly increased RV/(LV+S) ratio (0.369∓0.033) and RV/BW ratio (0.75∓0.095) compared to those in normoxia group (0.271∓0.010 and 0.59∓0.039, respectively; P<0.001), adenosine treatment group (0.281∓0.022 and 0.65∓0.077, respectively; P<0.001, P=0.025), hypoxia with CPA group (0.313∓0.021 and 0.66∓0.067, respectively P<0.001), and hypoxia with NECA group(0.333∓0.019, and 0.68∓0.074, respectively P<0.001). The NHE-1 and CnAβ mRNA levels in hypoxia group were significantly higher than those in normoxia group, adenosine treatment group, hypoxia with CPA group, and hypoxia with NECA group(P<0.001).

CONCLUSIONAdenosine and its agonist can inhibit hypoxia-induced RVH in rats through the NHE-1/CaN signal pathway.

Adenosine ; agonists ; pharmacology ; Animals ; Hypertrophy, Right Ventricular ; metabolism ; Hypoxia ; metabolism ; Male ; Rats ; Rats, Sprague-Dawley ; Signal Transduction ; drug effects ; Sodium-Hydrogen Exchangers ; metabolism

OBJECTIVETo determine the expression of Na+/H+ exchanger 1(NHE1) in human gastric carcinoma tissue and to investigate the association between NHE1 expression and clinicopathological characteristics.

METHODSThe expressions of NHE1 mRNA and protein were detected in both gastric carcinoma tissue (n=60) and adjacent gastric mucosa tissue (n=30) by reverse transcription polymerase chain reaction (RT-PCR) and Western blot. The association between the expression and the clinicopathological characteristics was analyzed.

RESULTSThe relative expression levels of NHE1 mRNA and protein in gastric carcinoma tissue were 0.786+/-0.291 and 1.442+/-0.175, which were significantly higher than those in adjacent gastric mucosa tissue (0.369+/-0.052 and 0.348+/-0.029) (P<0.01). The expression of NHE1 mRNA was positively correlated with NHE1 protein in the gastric carcinoma tissue (r=0.264, P<0.05). The expressions of NHE1 mRNA and protein were associated with the depth of invasion, lymph node metastasis, and TNM staging (P<0.05). However, no statistical difference was found in age, gender, and tumor differentiation (P>0.05).

CONCLUSIONThe expression levels of NHE1 mRNA and protein are significantly up-regulated in gastric carcinoma tissue, which may be involved in the development of gastric carcinoma.

Adult ; Aged ; Carcinoma ; metabolism ; pathology ; Cation Transport Proteins ; metabolism ; Female ; Humans ; Male ; Middle Aged ; Prognosis ; RNA, Messenger ; metabolism ; Sodium-Hydrogen Exchanger 1 ; Sodium-Hydrogen Exchangers ; metabolism ; Stomach ; metabolism ; pathology ; Stomach Neoplasms ; metabolism ; pathology

This study was aimed to investigate the role of Na(+)/H(+) exchanger 1 (NHE1) in apoptosis of HL-60 cells induced by etoposide. Real-time quantitative PCR (RQ-PCR) and Western blot methods were used to determine the expression of NHE1 in HL-60 cells after the treatment with etoposide. Meanwhile, laser scanning confocal microscopy was used to test the intracellular pH (pHi) of HL-60 cells. Cell apoptosis was measured by DNA fragmentation and terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) assay. The results showed that etoposide induced cell apoptosis after treatment for 24 hours. The expression level of NHE1 mRNA increased by 2.848 +/- 0.886 times after treatment with etoposide for 12 hours (p < 0.01), and the expression of NHE1 protein was also up-regulated (p < 0.01). The pHi of HL-60 cells increased from 7.11 to 7.46 after treatment with etoposide for 24 hours. Treatment with cariporide could block etoposide-induced alkalinisation and enhance the apoptosis HL-60 cells. It is concluded that the expression of NHE1 is up-regulated in process of apoptosis of HL-60 cells induced by etoposide and the apoptosis depends on the pH increase caused by NHE1 higher expression.
Apoptosis ; drug effects ; Cation Transport Proteins ; genetics ; metabolism ; DNA Fragmentation ; Etoposide ; pharmacology ; Gene Expression Regulation, Leukemic ; HL-60 Cells ; Humans ; RNA, Messenger ; genetics ; Sodium-Hydrogen Exchanger 1 ; Sodium-Hydrogen Exchangers ; genetics ; metabolism