Dataset Information

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 [Ca2+]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 [Ca2+]i, and decreased depolarisation-induced Ca2+ rise, with the latter two effects being abolished with nimodipine blocking the L-type Ca2+ 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 [Ca2+]i in the soma, and along with CaV1.2 may also regulate presynaptic Ca2+ levels and, perhaps at least serotonergic, neurotransmission in the SCN.

SUBMITTER: Cheng PC

PROVIDER: S-EPMC6478949 | biostudies-literature | 2019 Apr

REPOSITORIES: biostudies-literature

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

Cheng Pi-Cheng PC Lin Hsin-Yi HY Chen Ya-Shuan YS Cheng Ruo-Ciao RC Su Hung-Che HC Huang Rong-Chi RC

Scientific reports 20190423 1

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 [Ca2+]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 ...[more]

PMID: 31015514

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Project description:Introduction: Safranal, which endows saffron its unique aroma, causes vasodilatation and has a hypotensive effect in animal studies, but the mechanisms of these effects are unknown. In this study, we investigated the mechanisms of safranal vasodilation. Methods: Isolated rat endothelium-intact or -denuded aortic rings were precontracted with phenylephrine and then relaxed with safranal. To further assess the involvement of nitric oxide, prostaglandins, guanylate cyclase, and phospholipase A2 in safranal-induced vasodilation, aortic rings were preincubated with L-NAME, indomethacin, methylene blue, or quinacrine, respectively, then precontracted with phenylephrine, and safranal concentration-response curves were established. To explore the effects of safranal on Ca2+ influx, phenylephrine and CaCl2 concentration-response curves were established in the presence of safranal. Furthermore, the effect of safranal on aortic rings in the presence of ouabain, a Na+-K+ ATPase inhibitor, was studied to explore the contribution of Na+/Ca2+ exchanger to this vasodilation. Results: Safranal caused vasodilation in endothelium-intact and endothelium-denuded aortic rings. The vasodilation was not eliminated by pretreatment with L-NAME, indomethacin, methylene blue, or quinacrine, indicating the lack of a role for NO/cGMP. Safranal significantly inhibited the maximum contractions induced by phenylephrine, or by CaCl2 in Ca2+-free depolarizing buffer. Safranal also relaxed contractions induced by ouabain, but pretreatment with safranal totally abolished the development of ouabain contractions. Discussion/Conclusion: Inhibition of Na+-K+ ATPase by ouabain leads to the accumulation of Na+ intracellularly, forcing the Na+/Ca2+ exchanger to work in reverse mode, thus causing a contraction. Inhibition of the development of this contraction by preincubation with safranal indicates that safranal inhibited the Na+/Ca2+ exchanger. We conclude that safranal vasodilation is mediated by the inhibition of calcium influx from extracellular space through L-type Ca2+ channels and by the inhibition of the Na+/Ca2+ exchanger.

Dataset Information

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

Publications

The Na<sup>+/</sup>H<sup>+</sup>-Exchanger NHE1 Regulates Extra- and Intracellular pH and Nimodipine-sensitive [Ca<sup>2+</sup>]<sub>i</sub> in the Suprachiasmatic Nucleus.

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