Cardiovascular pharmacologyHydrogen peroxide increases nerve-evoked contractions in mouse tail artery by an endothelium-dependent mechanism
Introduction
Reactive oxygen species are produced in both vascular smooth muscle and endothelial cells, and are generated by NADPH oxidases, xanthine oxidases, mitochondrial respiration and uncoupled nitric oxide synthases (Ardanaz and Pagano, 2006). The reactive oxygen species produced include unstable free radicals such as superoxide (O2•−), and longer-lived non-free radical oxidants, such as hydrogen peroxide (H2O2). Because it is relatively stable, H2O2 has been considered to function as both an intracellular second messenger and a paracrine factor that modifies vascular contractions (Ardanaz and Pagano, 2006).
This study investigated the actions of H2O2 on nerve-evoked constrictions of the mouse tail artery. No studies have reported effects of H2O2 on neurovascular transmission, but H2O2 elicits vasoconstriction that depends on activity of cyclooxygenases and the generation of constrictor prostanoids that activate vascular muscle via thromboxane A2/prostaglandin H2 receptors (Tang and Vanhoutte, 2009). This action of H2O2 has been reported to be mediated either via a direct action on vascular muscle (Gao and Lee, 2005) or by triggering release of constrictor prostanoids from the endothelium (Katusic et al., 1993). Importantly, low concentrations of the thromboxane A2/prostaglandin H2 receptor agonist U-46619 that do not produce a contraction, increase neurovascular transmission (Vila et al., 2001). It therefore seems possible that H2O2 will increase nerve-evoked contractions of mouse tail artery. In addition to prostanoid-mediated contraction, H2O2 can contract vascular muscle by releasing Ca2+ from intracellular stores (Pourmahram et al., 2008) and by increasing extracellular Ca2+ influx (Lin et al., 2007, Shen et al., 2000).
The mouse tail artery is a thermoregulatory vessel and cooling increases its sensitivity to α2-adrenoceptor agonists (Chotani et al., 2000). This effect of cooling on reactivity to α2-adrencoeptor agonists depends on reactive oxygen species signalling (Bailey et al., 2005). This conclusion is based on observations that cooling stimulates mitochondrial production of reactive oxygen species and that the cold-induced increase in reactivity to the α2-adrenoceptor agonist UK 14304 was prevented by inhibiting mitochondrial generation of reactive oxygen species (Bailey et al., 2005). This increased sensitivity to α2-adrenoceptor agonists is suggested to contribute to cold-induced vasoconstriction by amplifying nerve-evoked contractions (Chotani et al., 2000).
The cold-induced increase in sensitivity to α2-adrenoceptor agonists in mouse tail artery depends on activity of Rho kinase and recruitment of previously “silent” α2C-adrenoceptors (Bailey et al., 2004, Jeyaraj et al., 2012). Rho kinase inhibition reduces H2O2-induced contractions of tracheal smooth muscle (Kojima et al., 2007) and pulmonary arteries (Pourmahram et al., 2008). Therefore activation of Rho kinase by H2O2 may contribute to modifying nerve-evoked contractions. In pulmonary arteries, H2O2-induced contractions were also reduced by inhibition of protein kinase C (Pourmahram et al., 2008).
The present study tested the hypothesis that H2O2 increases nerve-evoked contractions of mouse tail artery and demonstrated that this was the case. Further studies investigated involvement of the endothelium in this facilitatory effect of H2O2 and whether it involved the production of prostanoids. In addition, we investigated whether H2O2 increased the contribution of α2-adrenoceptors to neural activation of vascular muscle and whether the augmentation of nerve-evoked contractions depends on Ca2+ influx and on the activity of Rho kinase or protein kinase C.
Section snippets
Animals and tissue preparation
All procedures conformed to the Australian Code of Practice for the Care and Use of Animals for Scientific Purposes and were approved by the animal ethics committee at the University of Melbourne. Male C57Bl/6 mice aged 9–13 weeks were obtained from the Animal Resource Centre (Perth, Australia). Mice were deeply anaesthetised with isoflurane and then killed by cervical dislocation. Segments of ventral tail artery ∼1.75 mm in length were dissected from 60 to 80 mm along the tail. Vessels were
H2O2 increases the amplitude of nerve-evoked contractions
All concentrations of H2O2 tested (10–100 μM) increased the amplitude of nerve-evoked contractions (Fig. 1A). For all the following experiments investigating the mechanisms underlying the facilitatory effect of H2O2 on nerve-evoked contractions 100 μM was used. Fig. 1B shows a representative trace of nerve-evoked contractions in a tissue treated with 100 μM H2O2 after the second contraction. A small increase in resting tension was also observed following H2O2 application (0.04±0.01 mN/mm, P<0.05; n
Discussion
This study demonstrates that H2O2 produces a marked enhancement of nerve-evoked contractions in mouse tail artery that is dependent on the endothelium. Stimulation of the endothelium with H2O2 appears to increase the excitability of the vascular muscle via a mechanism that is dependent on Ca2+ influx through SKF-96365-sensitive channels and is mediated, at least in part, by activation of a cyclooxygenase and production of constrictor prostanoids.
The facilitatory effect of H2O2 on nerve-evoked
Acknowledgements
The work was supported by a grant from the National Health and Medical Research Council of Australia (grant number 568850).
References (28)
- et al.
Estimation of H2O2 gradients across biomembranes
FEBS Lett.
(2000) - et al.
Oxidative stress disrupts nitric oxide synthase activation in liver endothelial cells
Free Radic. Biol. Med.
(2005) - et al.
Direct effects of hydrogen peroxide on airway smooth muscle tone: Roles of Ca2+ influx and Rho-kinase
Eur. J. Pharmacol.
(2007) - et al.
Inhibition of rostral medullary raphé neurons prevents cold-induced activity in sympathetic nerves to rat tail and rabbit ear arteries
Neurosci. Lett.
(2004) - et al.
Constriction of pulmonary artery by peroxide: role of Ca2+ release and PKC
Free Radic. Biol. Med.
(2008) - et al.
Hydrogen peroxide as an endogenous mediator and exogenous tool in cardiovascular research: issues and considerations
Curr. Opin. Pharmacol.
(2008) - et al.
Prostanoids and reactive oxygen species: team players in endothelium-dependent contractions
Pharmacol. Ther.
(2009) - et al.
Hydrogen peroxide as a paracrine vascular mediator: regulation and signaling leading to dysfunction
Exp. Biol. Med.
(2006) - et al.
Rho kinase mediates cold-induced constriction of cutaneous arteries
Circ. Res.
(2004) - et al.
Reactive oxygen species from smooth muscle mitochondria initiate cold-induced constriction of cutaneous arteries
Am. J. Physiol. Heart Circ. Physiol.
(2005)
Enhancement of α2-adrenoceptor-mediated vasoconstriction by the thromboxane-mimetic U46619 in the porcine isolated ear artery: role of the ERK–MAP kinase signal transduction cascade
Br. J. Pharmacol.
Neuronal nitric oxide synthase-derived hydrogen peroxide is a major endothelium-dependent relaxing factor
Am. J. Physiol. Heart Circ. Physiol.
Silent α2C-adrenergic receptors enable cold-induced vasoconstriction in cutaneous arteries
Am. J. Physiol. Heart Circ. Physiol.
Biphasic effect of hydrogen peroxide on skeletal muscle arteriolar tone via activation of endothelial and smooth muscle signaling pathways
J. Appl. Physiol.
Cited by (1)
Angiotensin II increases nerve-evoked contractions in mouse tail artery by a T-type Ca<sup>2+</sup> channel-dependent mechanism
2015, European Journal of PharmacologyCitation Excerpt :As observed in the current study, we have previously reported that removing the endothelium increases nerve-evoked contractions of the mouse tail artery (Reardon and Brock, 2013). As blockade of nitric oxide synthase similarly increased nerve-evoked contractions (see Reardon and Brock, 2013), we assume nitric oxide tonically released from endothelium inhibits nerve-evoked contractions. The increment in the size of nerve-evoked contractions produced by 0.3 nM Ang II was similar in vessels with or without an intact endothelium.