The effect of hyperpolarization-activated cyclic nucleotide-gated ion channel inhibitors on the vagal control of guinea pig airway smooth muscle tone

Airway levels of the endogenous bronchodilator S-nitrosoglutathione (GSNO) are low in children with near-fatal asthma. We hypothesized that GSNO could be broken down in the lung and that this catabolism could inhibit airway smooth muscle relaxation. In our experiments, GSNO was broken down by guinea pig lung homogenates, particularly after ovalbumin sensitization (OS). Two lung protein fractions had catabolic activity. One was NADPH dependent and was more active after OS. The other was NADPH independent and was partially inhibited by aurothioglucose. Guinea pig lung tissue protein fractions with GSNO catabolic activity inhibited GSNO-mediated guinea pig tracheal ring relaxation. The relaxant effect of GSNO was partially restored by aurothioglucose. These observations suggest that catabolism of GSNO in the guinea pig 1) is mediated by lung proteins, 2) is partially upregulated after OS, and 3) may contribute to increased airway smooth muscle tone. We speculate that enzymatic breakdown of GSNO in the lung could contribute to asthma pathophysiology by inhibiting the beneficial effects of GSNO, including its effect on airway smooth muscle tone.

Download Full-text

An in vivo guinea pig preparation for studying the autonomic regulation of airway smooth muscle tone

Autonomic Neuroscience ◽

10.1016/s1566-0702(02)00053-x ◽

2002 ◽

Vol 99 (2) ◽

pp. 91-101 ◽

Cited By ~ 18

Author(s):

Stuart B Mazzone ◽

Brendan J Canning

Keyword(s):

Smooth Muscle ◽

Guinea Pig ◽

Airway Smooth Muscle ◽

Muscle Tone ◽

Autonomic Regulation ◽

Smooth Muscle Tone

Download Full-text

Melatonin MT2 receptor is expressed and potentiates contraction in human airway smooth muscle

AJP Lung Cellular and Molecular Physiology ◽

10.1152/ajplung.00273.2021 ◽

2021 ◽

Author(s):

Haruka Sasaki ◽

Yi Zhang ◽

Charles W Emala ◽

Kentaro Mizuta

Keyword(s):

Smooth Muscle ◽

Guinea Pig ◽

Airway Smooth Muscle ◽

Muscle Tone ◽

Fiber Formation ◽

Melatonin Receptors ◽

Human Airway Smooth Muscle ◽

Nocturnal Asthma ◽

Smooth Muscle Tone ◽

Human Airway

Nocturnal asthma is characterized by heightened bronchial reactivity at night, and plasma melatonin concentrations are higher in patients with nocturnal asthma symptoms. Numerous physiological effects of melatonin are mediated via its specific G protein-coupled receptors (GPCRs) named the MT1 receptor which couples to both Gq and Gi proteins, and the MT2 receptor which couples to Gi. We investigated whether melatonin receptors are expressed on airway smooth muscle, whether they regulate intracellular cyclic AMP (cAMP) and calcium concentrations ([Ca2+]i) which modulate airway smooth muscle tone, and whether they promote airway smooth muscle cell proliferation. We detected the mRNA and protein expression of the melatonin MT2 but not the MT1 receptor in native human and guinea pig airway smooth muscle and cultured human airway smooth muscle (HASM) cells by RT-PCR, immunoblotting, and immunohistochemistry. Activation of melatonin MT2 receptors with either pharmacological concentrations of melatonin (10 - 100 µM) or the non-selective MT1/MT2 agonist ramelteon (10 µM) significantly inhibited forskolin-stimulated cAMP accumulation in HASM cells, which was reversed by the Gαi protein inhibitor pertussis toxin or knockdown of the MT2 receptor by its specific siRNA. Although melatonin by itself did not induce an initial [Ca2+]i increase and airway contraction, melatonin significantly potentiated acetylcholine-stimulated [Ca2+]i increases, stress fiber formation through the MT2 receptor in HASM cells, and attenuated the relaxant effect of isoproterenol in guinea pig trachea. These findings suggest that the melatonin MT2 receptor is expressed in ASM, and modulates airway smooth muscle tone via reduced cAMP production and increased [Ca2+]i.

Download Full-text

A smooth muscle tone-dependent stretch-activated migrating motor pattern in isolated guinea-pig distal colon

The Journal of Physiology ◽

10.1113/jphysiol.2003.049163 ◽

2003 ◽

Vol 551 (3) ◽

pp. 955-969 ◽

Cited By ~ 38

Author(s):

T. K Smith ◽

G. R Oliver ◽

G. W Hennig ◽

D. M O'Shea ◽

P. V. Berghe ◽

...

Keyword(s):

Smooth Muscle ◽

Guinea Pig ◽

Muscle Tone ◽

Motor Pattern ◽

Distal Colon ◽

Smooth Muscle Tone

Download Full-text

Cyclic Nucleotide Phosphodiesterase (PDE) Isoenzymes in the Human Detrusor Smooth Muscle: II. Effect of Various PDE Inhibitors on Smooth Muscle Tone and Cyclic Nucleotide Levels In Vitro

The Journal of Urology ◽

10.1016/s0022-5347(01)63366-4 ◽

1998 ◽

Vol 159 (6) ◽

pp. 2263-2263

Author(s):

M.C. Truss ◽

S. Uckert ◽

C.G. Stief ◽

W.G. Forssmann ◽

U. Jonas

Keyword(s):

Smooth Muscle ◽

Cyclic Nucleotide ◽

Muscle Tone ◽

Cyclic Nucleotide Phosphodiesterase ◽

Detrusor Smooth Muscle ◽

Smooth Muscle Tone ◽

Pde Inhibitors ◽

Human Detrusor

Download Full-text

A GABAergic inhibitory microcircuit controlling cholinergic outflow to the airways

Journal of Applied Physiology ◽

10.1152/japplphysiol.00523.2003 ◽

2004 ◽

Vol 96 (1) ◽

pp. 260-270 ◽

Cited By ~ 29

Author(s):

Constance T. Moore ◽

Christopher G. Wilson ◽

Catherine A. Mayer ◽

Sandra S. Acquah ◽

V. John Massari ◽

...

Keyword(s):

Smooth Muscle ◽

Airway Smooth Muscle ◽

Muscle Tone ◽

Structural Characteristics ◽

Nucleus Ambiguus ◽

Acid Decarboxylase ◽

Electron Microscopic ◽

Synaptic Contacts ◽

Smooth Muscle Tone ◽

Rostral Nucleus

GABA is the main inhibitory neurotransmitter that participates in the regulation of cholinergic outflow to the airways. We have tested the hypothesis that a monosynaptic GABAergic circuit modulates the output of airway-related vagal preganglionic neurons (AVPNs) in the rostral nucleus ambiguus by using a dual-labeling electron microscopic method combining immunocytochemistry for glutamic acid decarboxylase (GAD) with retrograde tracing from the trachea. We also determined the effects of blockade of GABAA receptors on airway smooth muscle tone. The results showed that retrogradely labeled AVPNs received a significant GAD-immunoreactive (GAD-IR) terminal input. Out of a pooled total of 3,161 synaptic contacts with retrogradely labeled somatic and dendritic profiles, 20.2% were GAD-IR. GAD-IR terminals formed significantly more axosomatic synapses than axodendritic synapses ( P < 0.02). A dense population of GABAergic synaptic contacts on AVPNs provides a morphological basis for potent physiological effects of GABA on the excitability of AVPNs. GAD-IR terminals formed exclusively symmetric synaptic specializations. GAD-IR terminals were significantly larger ( P < 0.05) in both length and width than unlabeled terminals synapsing on AVPNs. Therefore, the structural characteristics of certain nerve terminals may be closely correlated with their function. Pharmacological blockade of GABAA receptors within the rostral nucleus ambiguus increased activity of putative AVPNs and airway smooth muscle tone. We conclude that a tonically active monosynaptic GABAergic circuit utilizing symmetric synapses regulates the discharge of AVPNs.

Download Full-text

PI3-kinase/Akt modulates vascular smooth muscle tone via cAMP signaling pathways

Journal of Applied Physiology ◽

10.1152/jappl.2001.91.4.1819 ◽

2001 ◽

Vol 91 (4) ◽

pp. 1819-1827 ◽

Cited By ~ 38

Author(s):

Padmini Komalavilas ◽

Shyamal Mehta ◽

Christopher J. Wingard ◽

Daniel T. Dransfield ◽

Jyoti Bhalla ◽

...

Keyword(s):

Smooth Muscle ◽

Protein Kinase ◽

Vascular Smooth Muscle ◽

Cyclic Nucleotide ◽

Muscle Tone ◽

Pi3 Kinase ◽

Dependent Protein Kinase ◽

Smooth Muscle Tone ◽

Dependent Protein ◽

Vascular Smooth Muscle Tone

Phosphatidylinositol 3-kinase (PI3-kinase) activates protein kinase B (also known as Akt), which phosphorylates and activates a cyclic nucleotide phosphodiesterase 3B. Increases in cyclic nucleotide concentrations inhibit agonist-induced contraction of vascular smooth muscle. Thus we hypothesized that the PI3-kinase/Akt pathway may regulate vascular smooth muscle tone. In unstimulated, intact bovine carotid artery smooth muscle, the basal phosphorylation of Akt was higher than that in cultured smooth muscle cells. The phosphorylation of Akt decreases in a time-dependent manner when incubated with the PI3-kinase inhibitor, LY-294002. Agonist (serotonin)-, phorbol ester (phorbol 12,13-dibutyrate; PDBu)-, and depolarization (KCl)-induced contractions of vascular smooth muscles were all inhibited in a dose-dependent fashion by LY-294002. However, LY-294002 did not inhibit serotonin- or PDBu-induced increases in myosin light chain phosphorylation or total O2 consumption, suggesting that inhibition of contraction was not mediated by reversal or inhibition of the pathways that lead to smooth muscle activation and contraction. Treatment of vascular smooth muscle with LY-294002 increased the activity of cAMP-dependent protein kinase and increased the phosphorylation of the cAMP-dependent protein kinase substrate heat shock protein 20 (HSP20). These data suggest that activation of the PI3-kinase/Akt pathway in unstimulated smooth muscle may modulate vascular smooth muscle tone (allow agonist-induced contraction) through inhibition of the cyclic nucleotide/HSP20 pathway and suggest that cyclic nucleotide-dependent inhibition of contraction is dissociated from the myosin light chain contractile regulatory pathways.

Download Full-text