scholarly journals Hydroxycobalamin Reveals the Involvement of Hydrogen Sulfide in the Hypoxic Responses of Rat Carotid Body Chemoreceptor Cells

Antioxidants ◽  
2019 ◽  
Vol 8 (3) ◽  
pp. 62
Author(s):  
Teresa Gallego-Martin ◽  
Jesus Prieto-Lloret ◽  
Philip Aaronson ◽  
Asuncion Rocher ◽  
Ana Obeso
Keyword(s):  
Hydrogen Sulfide ◽  
Carotid Body ◽  
Oxygen Sensor ◽  
Catecholamine Release ◽  
Glomus Cells ◽  
Arterial Blood ◽  
Carotid Bodies ◽  
High K ◽  
Chemoreceptor Cells ◽  
Ca2 Channels

Carotid body (CB) chemoreceptor cells sense arterial blood PO2, generating a neurosecretory response proportional to the intensity of hypoxia. Hydrogen sulfide (H2S) is a physiological gaseous messenger that is proposed to act as an oxygen sensor in CBs, although this concept remains controversial. In the present study we have used the H2S scavenger and vitamin B12 analog hydroxycobalamin (Cbl) as a new tool to investigate the involvement of endogenous H2S in CB oxygen sensing. We observed that the slow-release sulfide donor GYY4137 elicited catecholamine release from isolated whole carotid bodies, and that Cbl prevented this response. Cbl also abolished the rise in [Ca2+]i evoked by 50 µM NaHS in enzymatically dispersed CB glomus cells. Moreover, Cbl markedly inhibited the catecholamine release and [Ca2+]i rise caused by hypoxia in isolated CBs and dispersed glomus cells, respectively, whereas it did not alter these responses when they were evoked by high [K+]e. The L-type Ca2+ channel blocker nifedipine slightly inhibited the rise in CB chemoreceptor cells [Ca2+]i elicited by sulfide, whilst causing a somewhat larger attenuation of the hypoxia-induced Ca2+ signal. We conclude that Cbl is a useful and specific tool for studying the function of H2S in cells. Based on its effects on the CB chemoreceptor cells we propose that endogenous H2S is an amplifier of the hypoxic transduction cascade which acts mainly by stimulating non-L-type Ca2+ channels.

scholarly journals CaV3.2 T-type Ca2+ channels in H2S-mediated hypoxic response of the carotid body

2015 ◽  
Vol 308 (2) ◽  
pp. C146-C154 ◽  
Author(s):  
Vladislav V. Makarenko ◽  
Ying-Jie Peng ◽  
Guoxiang Yuan ◽  
Aaron P. Fox ◽  
Ganesh K. Kumar ◽  
...  
Keyword(s):  
Carotid Body ◽  
Sensory Nerve ◽  
Wild Type ◽  
Glomus Cells ◽  
Arterial Blood ◽  
Carotid Bodies ◽  
Intracellular Ca ◽  
Ca2 Channels ◽  
Body Response

Arterial blood O2 levels are detected by specialized sensory organs called carotid bodies. Voltage-gated Ca2+ channels (VGCCs) are important for carotid body O2 sensing. Given that T-type VGCCs contribute to nociceptive sensation, we hypothesized that they participate in carotid body O2 sensing. The rat carotid body expresses high levels of mRNA encoding the α1H-subunit, and α1H protein is localized to glomus cells, the primary O2-sensing cells in the chemoreceptor tissue, suggesting that CaV3.2 is the major T-type VGCC isoform expressed in the carotid body. Mibefradil and TTA-A2, selective blockers of the T-type VGCC, markedly attenuated elevation of hypoxia-evoked intracellular Ca2+ concentration, secretion of catecholamines from glomus cells, and sensory excitation of the rat carotid body. Similar results were obtained in the carotid body and glomus cells from CaV3.2 knockout ( Cacna1h−/−) mice. Since cystathionine-γ-lyase (CSE)-derived H2S is a critical mediator of the carotid body response to hypoxia, the role of T-type VGCCs in H2S-mediated O2 sensing was examined. Like hypoxia, NaHS, a H2S donor, increased intracellular Ca2+ concentration and augmented carotid body sensory nerve activity in wild-type mice, and these effects were markedly attenuated in Cacna1h−/− mice. In wild-type mice, TTA-A2 markedly attenuated glomus cell and carotid body sensory nerve responses to hypoxia, and these effects were absent in CSE knockout mice. These results demonstrate that CaV3.2 T-type VGCCs contribute to the H2S-mediated carotid body response to hypoxia.

scholarly journals Oxygen sensing by ion channels and chemotransduction in single glomus cells.

1996 ◽  
Vol 107 (1) ◽  
pp. 133-143 ◽  
Author(s):  
R J Montoro ◽  
J Ureña ◽  
R Fernández-Chacón ◽  
G Alvarez de Toledo ◽  
J López-Barneo
Keyword(s):  
Carotid Body ◽  
Initial Period ◽  
Threshold Value ◽  
Second Phase ◽  
Dependent Manner ◽  
Cellular Mechanisms ◽  
Transmitter Secretion ◽  
Glomus Cells ◽  
Arterial Blood ◽  
Ca2 Channels

We have monitored cytosolic [Ca2+] and dopamine release in intact fura-2-loaded glomus cells with microfluoroimetry and a polarized carbon fiber electrode. Exposure to low PO2 produced a rise of cytosolic [Ca2+] with two distinguishable phases: an initial period (with PO2 values between 150 and approximately 70 mm Hg) during which the increase of [Ca2+] is very small and never exceeds 150-200 nM, and a second phase (with PO2 below approximately 70 mm Hg) characterized by a sharp rise of cytosolic [Ca2+]. Secretion occurs once cytosolic [Ca2+] reaches a threshold value of 180 +/- 43 nM. The results demonstrate a characteristic relationship between PO2 and transmitter secretion at the cellular level that is comparable with the relation described for the input (O2 tension)output (afferent neural discharges) variables in the carotid body. Thus, the properties of single glomus cells can explain the sensory functions of the entire organ. In whole-cell, patch-clamped cells, we have found that in addition to O2-sensitive K+ channels, there are Ca2+ channels whose activity is also regulated by PO2. Ca2+ channel activity is inhibited by hpoxia, although in a strongly voltage-dependent manner. The average hypoxic inhibition of the calcium current in 30% +/- 10% at -20 mV but only 2% +/- 2% at +30 mV. The differential inhibition of K+ and Ca2+ channels by hypoxia helps to explain why the secretory response of the cells is displaced toward PO2 values (below approximately 70 mm Hg) within the range of those normally existing in arterial blood. These data provide a conceptual framework for understanding the cellular mechanisms of O2 chemotransduction in the carotid body.

Acetylcholine release from the carotid body by hypoxia: evidence for the involvement of autoinhibitory receptors

2004 ◽  
Vol 96 (1) ◽  
pp. 376-383 ◽  
Author(s):  
Dong-Kyu Kim ◽  
Nanduri R. Prabhakar ◽  
Ganesh K. Kumar
Keyword(s):  
Carotid Body ◽  
Ex Vivo ◽  
Primary Cultures ◽  
Acetylcholinesterase Activity ◽  
Electrochemical Analysis ◽  
Ach Release ◽  
Glomus Cells ◽  
Carotid Bodies ◽  
High K ◽  
Hydrolysis Of

The purpose of the present study was to investigate whether hypoxia influences acetylcholine (ACh) release from the rabbit carotid body and, if so, to determine the mechanism(s) associated with this response. ACh is expressed in the rabbit carotid body (5.6 ± 1.3 pmol/carotid body) as evidenced by electrochemical analysis. Immunocytochemical analysis of the primary cultures of the carotid body with antibody specific to ACh further showed that ACh-like immunoreactivity is localized to many glomus cells. The effect of hypoxia on ACh release was examined in ex vivo carotid bodies harvested from anesthetized rabbits. The basal release of ACh during normoxia (∼150 Torr) averaged 5.9 ± 0.5 fmol·min-1·carotid body-1. Lowering the Po2 to 90 and 20 Torr progressively decreased ACh release by ∼15 and ∼68%, respectively. ACh release returned to the basal value on reoxygenation. Simultaneous monitoring of dopamine showed a sixfold increase in dopamine release during hypoxia. Hypercapnia (21% O2 + 10% CO2) as well as high K+ (100 mM) facilitated ACh release from the carotid body, suggesting that hypoxia-induced inhibition of ACh release is not due to deterioration of the carotid body. Hypoxia had no significant effect on acetylcholinesterase activity in the medium, implying that increased hydrolysis of ACh does not account for hypoxia-induced inhibition of ACh release. In the presence of either atropine (10 μM) or domperidone (10 μM), hypoxia stimulated ACh release. These results demonstrate that glomus cells of the rabbit carotid body express ACh and that hypoxia overall inhibits ACh release via activation of muscarinic and dopaminergic autoinhibitory receptors in the carotid body.

Autocrine and paracrine actions of ATP in rat carotid body

2012 ◽  
Vol 90 (6) ◽  
pp. 705-711 ◽  
Author(s):  
Amy Tse ◽  
Lei Yan ◽  
Andy K. Lee ◽  
Frederick W. Tse
Keyword(s):  
Carotid Body ◽  
Cellular Damage ◽  
Type I ◽  
Glomus Cells ◽  
Sustentacular Cells ◽  
Arterial Blood ◽  
Carotid Bodies ◽  
Intracellular Ca ◽  
Paracrine Actions ◽  
I Cells

Carotid bodies are peripheral chemoreceptors that detect lowering of arterial blood O2 level. The carotid body comprises clusters of glomus (type I) cells surrounded by glial-like sustentacular (type II) cells. Hypoxia triggers depolarization and cytosolic [Ca2+] ([Ca2+]i) elevation in glomus cells, resulting in the release of multiple transmitters, including ATP. While ATP has been shown to be an important excitatory transmitter in the stimulation of carotid sinus nerve, there is considerable evidence that ATP exerts autocrine and paracrine actions in carotid body. ATP acting via P2Y1 receptors, causes hyperpolarization in glomus cells and inhibits the hypoxia-mediated [Ca2+]i rise. In contrast, adenosine (an ATP metabolite) triggers depolarization and [Ca2+]i rise in glomus cells via A2A receptors. We suggest that during prolonged hypoxia, the negative and positive feedback actions of ATP and adenosine may result in an oscillatory Ca2+ signal in glomus cells. Such mechanisms may allow cyclic release of transmitters from glomus cells during prolonged hypoxia without causing cellular damage from a persistent [Ca2+]i rise. ATP also stimulates intracellular Ca2+ release in sustentacular cells via P2Y2 receptors. The autocine and paracrine actions of ATP suggest that ATP has important roles in coordinating chemosensory transmission in the carotid body.

Fine Structure of Carotid Body: Normal and Anoxic Cats

1967 ◽  
Vol 25 ◽  
pp. 150-151
Author(s):  
Fadhil Al-Lami ◽  
R.G. Murray
Keyword(s):  
Fine Structure ◽  
Adrenal Medulla ◽  
Carotid Body ◽  
Uranyl Acetate ◽  
Lead Citrate ◽  
Glomus Cells ◽  
Sustentacular Cells ◽  
Carotid Bodies

Although the fine structure of the carotid body has been described in several recent reports, uncertainties remain, and the morphological effects of anoxia on the carotid body cells of the cat have never been reported. We have, therefore, studied the fine structure of the carotid body both in normal and severely anoxic cats, and to test the specificity of the effects, have compared them with the effects on adrenal medulla, kidney, and liver of the same animals. Carotid bodies of 50 normal and 15 severely anoxic cats (9% oxygen in nitrogen) were studied. Glutaraldehyde followed by OsO4 fixations, Epon 812 embedding, and uranyl acetate and lead citrate staining, were the technics employed.We have called the two types of glomus cells enclosed and enclosing cells. They correspond to those previously designated as chemoreceptor and sustentacular cells respectively (1). The enclosed cells forming the vast majority, are irregular in shape with many processes and occasional peripheral densities (Fig. 1).

scholarly journals Nitric Oxide Inhibits L-Type Ca2+ Current in Glomus Cells of the Rabbit Carotid Body Via a cGMP-Independent Mechanism

1999 ◽  
Vol 81 (4) ◽  
pp. 1449-1457 ◽  
Author(s):  
Beth A. Summers ◽  
Jeffrey L. Overholt ◽  
Nanduri R. Prabhakar
Keyword(s):  
Nitric Oxide ◽  
Carotid Body ◽  
Channel Blocker ◽  
Adult Rabbit ◽  
Subsequent Formation ◽  
No Donors ◽  
Glomus Cells ◽  
Channel Proteins ◽  
Carotid Bodies ◽  
Independent Mechanism

Nitric oxide inhibits L-type Ca2+ current in glomus cells of the rabbit carotid body via a cGMP-independent mechanism. Previous studies have shown that nitric oxide (NO) inhibits carotid body sensory activity. To begin to understand the cellular mechanisms associated with the actions of NO in the carotid body, we monitored the effects of NO donors on the macroscopic Ca2+ current in glomus cells isolated from rabbit carotid bodies. Experiments were performed on freshly dissociated glomus cells from adult rabbit carotid bodies using the whole cell configuration of the patch-clamp technique. The NO donors sodium nitroprusside (SNP; 600 μM, n = 7) and spermine nitric oxide (SNO; 100 μM, n = 7) inhibited the Ca2+ current in glomus cells in a voltage-independent manner. These effects of NO donors were rapid in onset and peaked within 1 or 2 min. In contrast, the outward K+ current was unaffected by SNP (600 μM, n = 6), indicating that the inhibition by SNP was not a nonspecific membrane effect. 2-(4-carboxyphenyl)-4,4,5,5-tetramethyl-imidazoline-1-oxyl-3-oxide (carboxy-PTIO; 500 μM), an NO scavenger, prevented inhibition of the Ca2+ current by SNP ( n = 7), whereas neither superoxide dismutase (SOD; 2,000 U/ml, n = 4), a superoxide scavenger, nor sodium hydrosulfite (SHS; 1 mM, n = 7), a reducing agent, prevented inhibition of the Ca2+ current by SNP. However, SNP inhibition of the Ca2+ current was reversible in the presence of either SOD or SHS. These results suggest that NO itself inhibits Ca2+current in a reversible manner and that subsequent formation of peroxynitrites results in irreversible inhibition. SNP inhibition of the Ca2+ current was not affected by 30 μM LY 83,583 ( n = 7) nor was it mimicked by 600 μM 8-bromoguanosine 3′:5′-cyclic monophosphate (8-Br-cGMP; n = 6), suggesting that the effects of NO on the Ca2+ current are mediated, in part, via a cGMP-independent mechanism. N-ethylmaleimide (NEM; 2.5 mM, n= 6) prevented the inhibition of the Ca2+ current by SNP, indicating that SNP is acting via a modification of sulfhydryl groups on Ca2+ channel proteins. Norepinephrine (NE; 10 μM) further inhibited the Ca2+ current in the presence of NEM ( n = 7), implying that NEM did not nonspecifically eliminate Ca2+ current modulation. Nisoldipine, an L-type Ca2+ channel blocker (2 μM, n = 6), prevented the inhibition of Ca2+ current by SNP, whereas ω-conotoxin GVIA, an N-type Ca2+ channel blocker (1 μM, n = 9), did not prevent the inhibition of Ca2+ current by SNP. These results demonstrate that NO inhibits L-type Ca2+ channels in adult rabbit glomus cells, in part, due to a modification of calcium channel proteins. The inhibition might provide one plausible mechanism for efferent inhibition of carotid body activity by NO.

scholarly journals Simulated Sleep Apnea Alters Hydrogen Sulfide Regulation of Blood Flow and Pressure

2020 ◽  
Author(s):  
Adelaeda Barrera ◽  
Humberto Morales-Loredo ◽  
Joshua Garcia ◽  
Gisel Fregoso ◽  
Carolyn E. Pace ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Hydrogen Sulfide ◽  
Sleep Apnea ◽  
Vascular Resistance ◽  
Carotid Body ◽  
Animal Studies ◽  
Mesenteric Arteries ◽  
Carotid Bodies ◽  
Inner Diameter ◽  
Induced Changes

In sleep apnea, airway obstruction causes intermittent hypoxia (IH). In animal studies, IH-dependent hypertension is associated with loss of vasodilator hydrogen sulfide (H2S), and increased H2S activation of sympathetic nervous system (SNS) activity in the carotid body. We previously reported that inhibiting cystathionine γ-lyase (CSE) to prevent H2S synthesis augments vascular resistance in control rats. The goal of this study was to evaluate the contribution of IH-induced changes in CSE signaling to increased blood pressure and vascular resistance. We hypothesized that chronic IH exposure eliminates CSE regulation of blood pressure (BP) and vascular resistance. In rats instrumented with venous catheters, arterial telemeters, and flow probes on the main mesenteric artery, the CSE inhibitor DL-propargylglycine (PAG, 50 mg/kg/day i.v. for 5 days) increased BP in Sham rats but decreased BP in IH rats (in mmHg, Sham (n = 11): 114±4 to 131±6; IH (n = 8): 131±8 to 115±7 mmHg, p<0.05). PAG treatment increased mesenteric vascular resistance in Sham rats but decreased it in IH rats (Day 5/Day 1: Sham: 1.50 ± 0.07; IH: 0.85 ± 0.19, p<0.05). Administration of the ganglionic blocker hexamethonium (to evaluate SNS activity) decreased mesenteric resistance in PAG-treated Sham rats more than in saline-treated Sham rats or PAG-treated IH rats. CSE immunoreactivity in IH carotid bodies compared to those from Sham rats. However, CSE staining in small mesenteric arteries was less in arteries from IH compared to Sham rats but not different in larger arteries (inner diameter > 200 mm). These results suggest endogenous H2S regulates blood pressure and vascular resistance but this control is lost after IH exposure with decreased CSE expression in resistance size arteries. IH exposure concurrently increases carotid body CSE expression and relative SNS control of blood pressure suggesting both vascular and carotid body H2S generation contribute to blood pressure regulation.

scholarly journals Gasotransmitter Regulation of Ion Channels: A Key Step in O2 Sensing By the Carotid Body

Physiology ◽  
2014 ◽  
Vol 29 (1) ◽  
pp. 49-57 ◽  
Author(s):  
Nanduri R. Prabhakar ◽  
Chris Peers
Keyword(s):  
Ion Channels ◽  
Carotid Body ◽  
Physiological Responses ◽  
Current Understanding ◽  
Body Function ◽  
Arterial Blood ◽  
Carotid Bodies ◽  
Review Current ◽  
O2 Sensing

Carotid bodies detect hypoxia in arterial blood, translating this stimulus into physiological responses via the CNS. It is long established that ion channels are critical to this process. More recent evidence indicates that gasotransmitters exert powerful influences on O2 sensing by the carotid body. Here, we review current understanding of hypoxia-dependent production of gasotransmitters, how they regulate ion channels in the carotid body, and how this impacts carotid body function.

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