Dual action of leptin on rest-firing and stimulated catecholamine release via phosphoinositide 3-kinase-riven BK channel up-regulation in mouse chromaffin cells Journal Article


Author(s): Gavello, Daniela; Vandael, David H; Gosso, Sara; Carbone, Emilio; Carabelli, Valentina
Article Title: Dual action of leptin on rest-firing and stimulated catecholamine release via phosphoinositide 3-kinase-riven BK channel up-regulation in mouse chromaffin cells
Affiliation IST Austria
Abstract: Leptin is an adipokine produced by the adipose tissue regulating body weight through its appetite-suppressing effect. Besides being expressed in the hypothalamus and hippocampus, leptin receptors (ObRs) are also present in chromaffin cells of the adrenal medulla. In the present study, we report the effect of leptin on mouse chromaffin cell (MCC) functionality, focusing on cell excitability and catecholamine secretion. Acute application of leptin (1 nm) on spontaneously firing MCCs caused a slowly developing membrane hyperpolarization followed by complete blockade of action potential (AP) firing. This inhibitory effect at rest was abolished by the BK channel blocker paxilline (1 μm), suggesting the involvement of BK potassium channels. Single-channel recordings in 'perforated microvesicles' confirmed that leptin increased BK channel open probability without altering its unitary conductance. BK channel up-regulation was associated with the phosphoinositide 3-kinase (PI3K) signalling cascade because the PI3K specific inhibitor wortmannin (100 nm) fully prevented BK current increase. We also tested the effect of leptin on evoked AP firing and Ca2+-driven exocytosis. Although leptin preserves well-adapted AP trains of lower frequency, APs are broader and depolarization-evoked exocytosis is increased as a result of the larger size of the ready-releasable pool and higher frequency of vesicle release. The kinetics and quantal size of single secretory events remained unaltered. Leptin had no effect on firing and secretion in db-/db- mice lacking the ObR gene, confirming its specificity. In conclusion, leptin exhibits a dual action on MCC activity. It dampens AP firing at rest but preserves AP firing and increases catecholamine secretion during sustained stimulation, highlighting the importance of the adipo-adrenal axis in the leptin-mediated increase of sympathetic tone and catecholamine release.
Keywords: Male; Exocytosis; Signal Transduction; nonhuman; priority journal; mouse; protein function; large conductance calcium activated potassium channel; Hyperpolarization; cell vacuole; upregulation; EMTREE drug terms: calcium ion; catecholamine; leptin; paxilline; phosphatidylinositol 3 kinase; wortmannin; catecholamine release; chromaffin cell; nerve cell excitability; nerve cell membrane potential; nerve cell membrane steady potential
Journal Title: Journal of Physiology
Volume: 593
Issue 22
ISSN: 1469-7793
Publisher: Wiley-Blackwell  
Date Published: 2015-11-15
Start Page: 4835
End Page: 4853
Sponsor: This work was supported by the Compagnia di San Paolo Foundation ‘Neuroscience Program’ to VC and ‘Progetto di Ateneo 2011-13’ to EC.
URL:
DOI: 10.1113/JP271078
Notes: We thank Dr Claudio Franchino for cell preparation and for providing excellent technical support.
Open access: yes (repository)