The Na+/H+-Exchanger NHE1 Regulates Extra- and Intracellular pH and Nimodipine-sensitive [Ca2+]i in the Suprachiasmatic Nucleus

Abstract

The central clock in the suprachiasmatic nucleus (SCN) has higher metabolic activity than extra-SCN areas in the anterior hypothalamus. Here we investigated whether the Na + /H + exchanger (NHE) may regulate extracellular pH (pHe), intracellular pH (pHi) and [Ca 2+ ] i in the SCN. In hypothalamic slices bathed in HEPES-buffered solution a standing acidification of ~0.3 pH units was recorded with pH-sensitive microelectrodes in the SCN but not extra-SCN areas. The NHE blocker amiloride alkalinised the pHe. RT-PCR revealed mRNA for plasmalemmal-type NHE1, NHE4, and NHE5 isoforms, whereas the NHE1-specific antagonist cariporide alkalinised the pHe. Real-time PCR and western blotting failed to detect day-night variation in NHE1 mRNA and protein levels. Cariporide induced intracellular acidosis, increased basal [Ca 2+ ] i , and decreased depolarisation-induced Ca 2+ rise, with the latter two effects being abolished with nimodipine blocking the L-type Ca 2+ channels. Immunofluorescent staining revealed high levels of punctate colocalisation of NHE1 with serotonin transporter (SERT) or CaV1.2, as well as triple staining of NHE1, CaV1.2, and SERT or the presynaptic marker Bassoon. Our results indicate that NHE1 actively extrudes H + to regulate pHi and nimodipine-sensitive [Ca 2+ ] i in the soma, and along with CaV1.2 may also regulate presynaptic Ca 2+ levels and, perhaps at least serotonergic, neurotransmission in the SCN.

Empagliflozin restores chronic kidney disease–induced impairment of endothelial regulation of cardiomyocyte relaxation and contraction

“…Cariporide is highly specific for NHE1, showing 50% inhibition on NHE1 at w0.03 to 3 mM concentration. 66 However, in the presence of 10 mM cariporide, empagliflozin still reduced endothelial ROS level by 75%, indicating that the effect of empagliflozin in CMECs is largely independent of NHE1. This is in line with a recent report showing no inhibition of NHE1 activity by empagliflozin or other SGLT2 inhibitors in CMs.…”

Role of Intracellular Na+ in the Regulation of [Ca2+]i in the Rat Suprachiasmatic Nucleus Neurons

“…Nevertheless, it should be noted that monensin also alkalinizes intracellular pH, which could potentially alter [Ca 2+ ] i in view of our recent finding showing that intracellular pH also plays a role in the regulation of [Ca 2+ ] i in rat SCN neurons [26].…”

Precise Cancer Anti-acid Therapy Monitoring Using pH-Sensitive MnO2@BSA Nanoparticles by Magnetic Resonance Imaging

“…14 Fluorescence imaging is an alternative in vivo approach that enables the measurement of subcellular pH gradients with a high spatial resolution (<1 μm); however, low tissue penetration is an important limitation in whole animal and clinical imaging. 15 Magnetic resonance spectroscopy (MRS) allows the detection of pH-dependent chemical shifts of MRS-visible nuclei such as 1 H, 31 P, and 19 F in endogenous or exogenous compounds. However, the poor spatial and temporal resolutions of 1 H magnetic resonance spectroscopic imaging (MRSI), 31 P MRS, and 19 F MRS preclude measurement of pH changes and limit their clinical applications.…”