title: CaV3.2 T-type Ca2+ channels mediate the augmented calcium influx in carotid body glomus cells by chronic intermittent hypoxia.
abstract: Chronic intermittent hypoxia (CIH) is a hallmark manifestation of sleep apnea. A heightened carotid body activity and the resulting chemosensory reflex mediate increased sympathetic nerve activity by CIH. However, the mechanisms underlying heightened carotid body activity by CIH are not known. An elevation of intracellular calcium ion concentration ([Ca(2+)]i) in glomus cells, the primary oxygen-sensing cells, is an essential step for carotid body activation by hypoxia. In the present study, we examined the effects of CIH on the glomus cell [Ca(2+)]i response to hypoxia and assessed the underlying mechanisms. Glomus cells were harvested from adult rats or wild-type mice treated with 10 days of either room air (control) or CIH (alternating cycles of 15 s of hypoxia and 5 min of room air; 9 episodes/h; 8 h/day). CIH-treated glomus cells exhibited an enhanced [Ca(2+)]i response to hypoxia, and this effect was absent in the presence of 2-(4-cyclopropylphenyl)-N-((1R)-1-[5-[(2,2,2-trifluoroethyl)oxo]-pyridin-2-yl]ethyl)acetamide (TTA-A2), a specific inhibitor of T-type Ca(2+) channels, and in voltage-gated calcium channel, type 3.2 (CaV3.2), null glomus cells. CaV3.2 knockout mice exhibited an absence of CIH-induced hypersensitivity of the carotid body. CIH increased reactive oxygen species (ROS) levels in glomus cells. A ROS scavenger prevented the exaggerated TTA-A2-sensitive [Ca(2+)]i response to hypoxia. CIH had no effect on CaV3.2 mRNA levels. CIH augmented Ca(2+) currents and increased CaV3.2 protein in plasma membrane fractions of human embryonic kidney-293 cells stably expressing CaV3.2, and either a ROS scavenger or brefeldin-A, an inhibitor of protein trafficking, prevented these effects. These findings suggest that CIH leads to an augmented Ca(2+) influx via ROS-dependent facilitation of CaV3.2 protein trafficking to the plasma membrane.
authors.affiliation: Institute for Integrative Physiology and Center for Systems Biology of Oxygen Sensing, University of Chicago, Chicago, Illinois.
authors.forename: Vladislav V
authors.initials: VV
authors.lastname: Makarenko
authors.affiliation: Institute for Integrative Physiology and Center for Systems Biology of Oxygen Sensing, University of Chicago, Chicago, Illinois.
authors.forename: Gias U
authors.initials: GU
authors.lastname: Ahmmed
authors.affiliation: Institute for Integrative Physiology and Center for Systems Biology of Oxygen Sensing, University of Chicago, Chicago, Illinois.
authors.forename: Ying-Jie
authors.initials: YJ
authors.lastname: Peng
authors.affiliation: Institute for Integrative Physiology and Center for Systems Biology of Oxygen Sensing, University of Chicago, Chicago, Illinois.
authors.forename: Shakil A
authors.initials: SA
authors.lastname: Khan
authors.affiliation: Institute for Integrative Physiology and Center for Systems Biology of Oxygen Sensing, University of Chicago, Chicago, Illinois.
authors.forename: Jayasri
authors.initials: J
authors.lastname: Nanduri
authors.affiliation: Institute for Integrative Physiology and Center for Systems Biology of Oxygen Sensing, University of Chicago, Chicago, Illinois.
authors.forename: Ganesh K
authors.initials: GK
authors.lastname: Kumar
authors.affiliation: Institute for Integrative Physiology and Center for Systems Biology of Oxygen Sensing, University of Chicago, Chicago, Illinois.
authors.forename: Aaron P
authors.initials: AP
authors.lastname: Fox
authors.affiliation: Institute for Integrative Physiology and Center for Systems Biology of Oxygen Sensing, University of Chicago, Chicago, Illinois nanduri@uchicago.edu.
authors.forename: Nanduri R
authors.identifier: http://orcid.org/0000-0003-4570-1380
authors.initials: NR
authors.lastname: Prabhakar
mesh_terms: D000818:Animals; D044482:Benzeneacetamides / Q000008:administration & dosage; D002118:Calcium / Q000378:metabolism*; D020747:Calcium Channels, T-Type / Q000378:metabolism* / Q000502:physiology; D002344:Carotid Body / Q000187:drug effects / Q000378:metabolism*; D015687:Cell Hypoxia; D057809:HEK293 Cells; D006801:Humans; D000860:Hypoxia / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D021381:Protein Transport; D011725:Pyridines / Q000008:administration & dosage; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000378:metabolism
chemical_list: C553486:2-(4-cyclopropylphenyl)-N-(1-(5-((2,2,2-trifluoroethyl)oxo)pyridin-2-yl)ethyl)acetamide; D044482:Benzeneacetamides; C504883:Cacna1h protein, mouse; D020747:Calcium Channels, T-Type; D011725:Pyridines; D017382:Reactive Oxygen Species; D002118:Calcium
keywords: hypertension; oxidative stress; protein trafficking; sleep apnea; voltage-gated Ca2+ channels