Hypoxic regulation of nitric oxide signaling in vascular smooth muscle

Thomas C. Resta

Vascular Physiology Group, Department of Cell Biology and Physiology, University of New Mexico Health Sciences Center, Albuquerque, New Mexico 87131-0001

THE CURRENT ARTICLE IN FOCUS by Mingone and colleagues (Ref. 16, see p. L296 in this issue) describes a novel permissive effect of hypoxia on cGMP-independent relaxation to nitric oxide (NO) in bovine pulmonary and coronary arteries. Interestingly, whereas NO-mediated vasorelaxation appeared to be largely a function of cGMP at ambient PO2, a cGMP-independent mechanism involving activation of the sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA) was revealed during hypoxic exposure. This study emphasizes the emerging complexity of NO signaling in vascular smooth muscle and raises important new questions regarding mechanisms by which PO2 regulates cGMP-independent actions of NO.

Both cGMP-dependent and -independent mechanisms of NO signaling have been implicated in vascular smooth muscle (1, 2, 48, 10, 13, 15, 16, 19, 20, 31, 32). It is well established that soluble guanylyl cyclase is an important target of NO in both the pulmonary and systemic circulations (8, 10, 13, 15, 19). Activation of soluble guanylyl cyclase by NO leads to increased cGMP synthesis and stimulation of protein kinase G (PKG) (8, 15, 19). PKG, in turn, elicits relaxation of vascular smooth muscle through a myriad of signaling pathways, leading to a decrease in the intracellular free Ca2+ concentration ([Ca2+]i) and desensitization of the contractile apparatus to Ca2+ (8, 15). Those pathways involving a decrease in [Ca2+]i are, for the most part, poorly understood. However, evidence exists for PKG-dependent activation of large-conductance Ca2+-activated K+ (BK) channels and associated membrane hyperpolarization, inhibition of L-type voltage-gated Ca2+ channels, stimulation of Ca2+-ATPases on both the plasma membrane and sarcoplasmic reticulum, inhibition of inositol trisphosphate receptors, and decreased inositol trisphosphate synthesis (8, 15). Those mechanisms involving a decrease in sensitivity of the contractile apparatus to Ca2+ in response to PKG activation are even less well defined but appear to be predominantly mediated by regulation of myosin light chain phosphorylation subsequent to activation of myosin light chain phosphatase (8, 15, 19, 21, 22).

In addition, NO signals through cGMP-independent mechanisms in many tissues by nitrosylation of cysteine thiol groups or transition metals to posttranslationally modify enzymatic activity (3, 11, 12, 18, 2325, 29). Many cGMP-independent influences of NO in vascular smooth muscle appear to involve an increase in sarcolemmal K+ permeability. For example, NO has been reported to activate BK channels either directly (7) or indirectly via inhibition of 20-hydroxyeicosatet-raenoic (20-HETE) production (4, 5, 31) or increased calcium spark activity (20). Additional evidence supports a role for cGMP-independent activation of delayed rectifier K+ channels in pulmonary arterial smooth muscle cells (32). Other direct effects of NO include stimulation of SERCA in rabbit aortic smooth muscle, leading to increased Ca2+ reuptake by intracellular stores, a fall in [Ca2+]i, and consequent inhibition of store-operated Ca2+ influx (1, 2, 9). This latter mechanism of cGMP-independent activation of SERCA is consistent with the findings of Mingone et al. (16), which identify regulatory influences of hypoxia on this pathway.

Although the mechanism by which NO mediates cGMP-independent Ca2+ sequestration by the sarcoplasmic reticulum is not understood, it is possible that NO modulates SERCA activity by S-nitrosylation of the enzyme (25). It is also unclear how hypoxia functions to modify SERCA activity. Although current debate exists as to whether hypoxia increases the production of reactive oxygen species or instead leads to a more reduced cellular state in pulmonary vascular smooth muscle (14, 17, 2630), one possible explanation for the permissive effect of hypoxia on NO-dependent stimulation of SERCA is via an alteration in the redox state of the pump. In agreement with this hypothesis, Adachi et al. (2) have demonstrated that impaired NO-dependent relaxation and SERCA activity in aortas from hypercholesterolemic rabbits are prevented by long-term administration of the antioxidant t-butylhydroxytoluene, suggesting that increased oxidative stress associated with hypercholesterolemia impairs SERCA function. A more reduced state imposed by hypoxia may, therefore, enhance refilling of intracellular Ca2+ stores through disinhibition of SERCA. Whether oxidative stress impairs SERCA activity by preventing S-nitrosylation of the pump remains to be investigated. However, a recent report by Sun et al. (24) has demonstrated a similar inhibitory effect of increasing PO2 on both NO-dependent activation and S-nitrosylation of the skeletal muscle ryanodine receptor. Whereas stimulation of channel activity by NO is inhibited at ambient PO2 (~150 mmHg), an apparently lower oxidative stress associated with a more physiological tissue PO2 (~10 mmHg) permits S-nitrosylation at a specific cysteine residue (Cys-3635) via an allosteric mechanism and subsequent channel activation. It is noteworthy that this lower PO2 is similar to the oxygen tension used as a hypoxic stimulus (8–10 mmHg) by Mingone et al. (16), and thus an analogous mechanism may account for the observed cGMP-independent stimulation of SERCA by NO under hypoxic conditions. In contrast to potential influences of hypoxia on the redox state and allosteric regulation of the target enzyme (e.g., SERCA), it is alternatively possible that hypoxia limits NO bioinactivation by oxygen-derived free radicals, thus facilitating S-nitrosylation reactions through increases in the concentration of NO within relevant microcellular domains.

In conclusion, the observations of Mingone and colleagues (16) will likely provide the basis for intriguing new avenues of investigation to understand mechanisms of hypoxic modulation of NO signal transduction in vascular smooth muscle. Challenges of future studies include defining the potential role of S-nitrosylation of SERCA in regulating pump activity as well as the mechanism by which hypoxia facilitates cGMP-independent stimulation of SERCA by NO. The concept of hypoxia as a redox effector of second messenger signaling has potentially broad physiological and pathophysiological implications for not only NO regulation of vascular, immunological, and neural function, but for hypoxic modulation of a diverse spectrum of intracellular signaling pathways.


    FOOTNOTES
 

Address for reprint requests and other correspondence: T. C. Resta, Vascular Physiology Group, Dept. of Cell Biology and Physiology, Univ. of New Mexico Health Sciences Center, MSC08 4750, 1 Univ. of New Mexico, Albuquerque, NM 87131-0001 (E-mail: tresta{at}salud.unm.edu).


    REFERENCES
 TOP
 REFERENCES
 

  1. Adachi T, Matsui R, Weisbrod RM, Najibi S, and Cohen RA. Reduced sarco/endoplasmic reticulum Ca2+ uptake activity can account for the reduced response to NO, but not sodium nitroprusside, in hypercholesterolemic rabbit aorta. Circulation 104: 1040–1045, 2001.[Abstract/Free Full Text]
  2. Adachi T, Matsui R, Xu S, Kirber M, Lazar HL, Sharov VS, Schoneich C, and Cohen RA. Antioxidant improves smooth muscle sarco/endoplasmic reticulum Ca2+-ATPase function and lowers tyrosine nitration in hypercholesterolemia and improves nitric oxide-induced relaxation. Circ Res 90: 1114–1121, 2002.[Abstract/Free Full Text]
  3. Ahern GP, Klyachko VA, and Jackson MB. cGMP and S-nitrosylation: two routes for modulation of neuronal excitability by NO. Trends Neurosci 25: 510–517, 2002.[ISI][Medline]
  4. Alonso-Galicia M, Hudetz AG, Shen H, Harder DR, and Roman RJ. Contribution of 20-HETE to vasodilator actions of nitric oxide in the cerebral microcirculation. Stroke 30: 2727–2734, 1999.[Abstract/Free Full Text]
  5. Alonso-Galicia M, Sun CW, Falck JR, Harder DR, and Roman RJ. Contribution of 20-HETE to the vasodilator actions of nitric oxide in renal arteries. Am J Physiol Renal Physiol 275: F370–F378, 1998.[Abstract/Free Full Text]
  6. Archer SL, Huang JM, Hampl V, Nelson DP, Shultz PJ, and Weir EK. Nitric oxide and cGMP cause vasorelaxation by activation of a charybdotoxin-sensitive K channel by cGMP-dependent protein kinase. Proc Natl Acad Sci USA 91: 7583–7587, 1994.[Abstract]
  7. Bolotina VM, Najibi S, Palacino JJ, Pagano PJ, and Cohen RA. Nitric oxide directly activates calcium-dependent potassium channels in vascular smooth muscle. Nature 368: 850–853, 1994.[ISI][Medline]
  8. Carvajal JA, Germain AM, Huidobro-Toro JP, and Weiner CP. Molecular mechanism of cGMP-mediated smooth muscle relaxation. J Cell Physiol 184: 409–420, 2000.[ISI][Medline]
  9. Cohen RA, Weisbrod RM, Gericke M, Yaghoubi M, Bierl C, and Bolotina VM. Mechanism of nitric oxide-induced vasodilatation: refilling of intracellular stores by sarcoplasmic reticulum Ca2+ ATPase and inhibition of store-operated Ca2+ influx. Circ Res 84: 210–219, 1999.[Abstract/Free Full Text]
  10. Fouty B, Komalavilas P, Muramatsu M, Cohen A, Mc-Murtry IF, Lincoln TM, and Rodman DM. Protein kinase G is not essential to NO-cGMP modulation of basal tone in rat pulmonary circulation. Am J Physiol Heart Circ Physiol 274: H672–H678, 1998.[Abstract/Free Full Text]
  11. Gaston B, Reilly J, Drazen JM, Fackler J, Ramdev P, Arnelle D, Mullins ME, Sugarbaker DJ, Chee C, Singel DJ, Loscalco J, and Stamler JS. Endogenous nitrogen oxides and bronchodilator S-nitrosothiols in human airways. Proc Natl Acad Sci USA 90: 10957–10961, 1993.[Abstract]
  12. Gow AJ, Chen Q, Hess DT, Day BJ, Ischiropoulos H, and Stamler JS. Basal and stimulated protein S-nitrosylation in multiple cell types and tissues. J Biol Chem 277: 9637–9640, 2002.[Abstract/Free Full Text]
  13. Jernigan NL and Resta TC. Chronic hypoxia attenuates cGMP-dependent pulmonary vasodilation. Am J Physiol Lung Cell Mol Physiol 282: L1366–L1375, 2002.[Abstract/Free Full Text]
  14. Killilea DW, Hester R, Balczon R, Babal P, and Gillespie MN. Free radical production in hypoxic pulmonary artery smooth muscle cells. Am J Physiol Lung Cell Mol Physiol 279: L408–L412, 2000.[Abstract/Free Full Text]
  15. Lincoln TM, Dey N, and Sellak H. Invited review: cGMP-dependent protein kinase signaling mechanisms in smooth muscle: from the regulation of tone to gene expression. J Appl Physiol 91: 1421–1430, 2001.[Abstract/Free Full Text]
  16. Mingone CJ, Gupte SA, Iesaki T, and Wolin MS. Hypoxia enhances a cGMP-independent nitric oxide relaxing mechanism in pulmonary arteries. Am J Physiol Lung Cell Mol Physiol 285: L296–L304, 2003.
  17. Mohazzab KM and Wolin MS. Oxidant signalling and vascular oxygen sensing. Role of H2O2 in responses of the bovine pulmonary artery to changes in PO2. Adv Exp Med Biol 475: 249–258, 2000.[ISI][Medline]
  18. Perkins WJ, Pabelick C, Warner DO, and Jones KA. cGMP-independent mechanism of airway smooth muscle relaxation induced by S-nitrosoglutathione. Am J Physiol Cell Physiol 275: C468–C474, 1998.[Abstract/Free Full Text]
  19. Pfitzer G. Invited review: regulation of myosin phosphorylation in smooth muscle. J Appl Physiol 91: 497–503, 2001.[Abstract/Free Full Text]
  20. Pucovsky V, Gordienko DV, and Bolton TB. Effect of nitric oxide donors and noradrenaline on Ca2+ release sites and global intracellular Ca2+ in myocytes from guinea-pig small mesenteric arteries. J Physiol 539: 25–39, 2002.[Free Full Text]
  21. Sauzeau V, Le Jeune H, Cario-Toumaniantz C, Smolenski A, Lohmann SM, Bertoglio J, Chardin P, Pacaud P, and Loirand G. Cyclic GMP-dependent protein kinase signaling pathway inhibits RhoA-induced Ca2+ sensitization of contraction in vascular smooth muscle. J Biol Chem 275: 21722–21729, 2000.[Abstract/Free Full Text]
  22. Sawada N, Itoh H, Yamashita J, Doi K, Inoue M, Masatsugu K, Fukunaga Y, Sakaguchi S, Sone M, Yamahara K, Yurugi T, and Nakao K. cGMP-dependent protein kinase phosphorylates and inactivates RhoA. Biochem Biophys Res Commun 280: 798–805, 2001.[ISI][Medline]
  23. Stamler JS, Lamas S, and Fang FC. Nitrosylation, the prototypic redox-based signaling mechanism. Cell 106: 675–683, 2001.[ISI][Medline]
  24. Sun J, Xu L, Eu JP, Stamler JS, and Meissner G. Nitric oxide, NOC-12, and S-nitrosoglutathione modulate the skeletal muscle calcium release channel/ryanodine receptor by different mechanisms. An allosteric function for O2 in S-nitrosylation of the channel. J Biol Chem 278: 8184–8189, 2003.[Abstract/Free Full Text]
  25. Viner RI, Williams TD, and Schoneich C. Nitric oxide-dependent modification of the sarcoplasmic reticulum Ca-ATPase: localization of cysteine target sites. Free Radic Biol Med 29: 489–496, 2000.[ISI][Medline]
  26. Waypa GB, Chandel NS, and Schumacker PT. Model for hypoxic pulmonary vasoconstriction involving mitochondrial oxygen sensing. Circ Res 88: 1259–1266, 2001.[Abstract/Free Full Text]
  27. Waypa GB, Marks JD, Mack MM, Boriboun C, Mungai PT, and Schumacker PT. Mitochondrial reactive oxygen species trigger calcium increases during hypoxia in pulmonary arterial myocytes. Circ Res 91: 719–726, 2002.[Abstract/Free Full Text]
  28. Weir EK and Archer SL. The mechanism of acute hypoxic pulmonary vasoconstriction: the tale of two channels. FASEB J 9: 183–189, 1995.[Abstract/Free Full Text]
  29. Wolin MS. Interactions of oxidants with vascular signaling systems. Arterioscler Thromb Vasc Biol 20: 1430–1442, 2000.[Abstract/Free Full Text]
  30. Wolin MS, Burke-Wolin TM, and Mohazzab H. Roles for NAD(P)H oxidases and reactive oxygen species in vascular oxygen sensing mechanisms. Respir Physiol 115: 229–238, 1999.[ISI][Medline]
  31. Yu M, Sun CW, Maier KG, Harder DR, and Roman RJ. Mechanism of cGMP contribution to the vasodilator response to NO in rat middle cerebral arteries. Am J Physiol Heart Circ Physiol 282: H1724–H1731, 2002.[Abstract/Free Full Text]
  32. Yuan XJ, Tod ML, Rubin LJ, and Blaustein MP. NO hyperpolarizes pulmonary artery smooth muscle cells and decreases the intracellular Ca2+ concentration by activating voltage-gated K+ channels. Proc Natl Acad Sci USA 93: 10489–10494, 1996.[Abstract/Free Full Text]




This Article
Full Text (PDF)
Alert me when this article is cited
Alert me if a correction is posted
Citation Map
Services
Email this article to a friend
Similar articles in this journal
Similar articles in ISI Web of Science
Similar articles in PubMed
Alert me to new issues of the journal
Download to citation manager
Google Scholar
Articles by Resta, T. C.
Articles citing this Article
PubMed
PubMed Citation
Articles by Resta, T. C.


HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
Visit Other APS Journals Online
Copyright © 2003 by the American Physiological Society.