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Do we kNOw how HSP90 and eNOS mediate lung injury in sickle cell disease? Jeffrey H. Schwartz, Carl A. White and Bruce A. Freeman AJP - Lung 286:701-704, 2004. doi:10.1152/ajplung.00362.2003 You might find this additional information useful... This article cites 43 articles, 27 of which you can access free at: http://ajplung.physiology.org/cgi/content/full/286/4/L701#BIBL Medline items on this article's topics can be found at http://highwire.stanford.edu/lists/artbytopic.dtl on the following topics: Immunology .. Inflammatory Mediators Biochemistry .. Cell Adhesion Molecules Biochemistry .. Free Radicals Oncology .. Oxidative Damage Physiology .. Vasodilation Neuroscience .. Nitric Oxide

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AJP - Lung Cellular and Molecular Physiology publishes original research covering the broad scope of molecular, cellular, and integrative aspects of normal and abnormal function of cells and components of the respiratory system. It is published 12 times a year (monthly) by the American Physiological Society, 9650 Rockville Pike, Bethesda MD 20814-3991. Copyright © 2005 by the American Physiological Society. ISSN: 1040-0605, ESSN: 1522-1504. Visit our website at http://www.the-aps.org/.

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Am J Physiol Lung Cell Mol Physiol 286: L701–L704, 2004; 10.1152/ajplung.00362.2003.

Editorial Focus

Do we kNOw how HSP90 and eNOS mediate lung injury in sickle cell disease? Jeffrey H. Schwartz,1,2 Carl A. White,3 and Bruce A. Freeman1,2,4,5 Departments of 1Pediatrics, 4Anesthesiology, and 5Biochemistry and Molecular Genetics, and 2The University of Alabama at Birmingham Center for Free Radical Biology, University of Alabama at Birmingham, Birmingham, Alabama 35233; and 3 Department of Pediatrics, National Jewish Center for Immunology and Respiratory Medicine, Denver, Colorado 80206

Address for reprint requests and other correspondence: B. A. Freeman, Dept. of Anesthesiology, 946 Tinsley Harrison Tower, 619 So. 19th St., Univ. of Alabama at Birmingham, Birmingham, AL 35233-6810 (E-mail: [email protected]). http://www.ajplung.org

sumption (2, 6, 12). In support of this precept, XO has been shown to be increased in vessel walls and the plasma both clinically and in a transgenic, knockout murine model of SCD that expresses exclusively human HbS (2). Diverse approaches have been employed in quantifying and modifying various aspects of NO signaling in SCD. Basal levels of the amino acid precursor of NO, L-arginine, are decreased in SCD and are suppressed even more so during complications, such as VOC and ACS (20, 23–25, 34). Both inducible and constitutive nitric oxide synthase (NOS) isoforms convert L-arginine to NO. Subsequent tissue reactions of ⫺ NO predominantly yield nitrite (NO⫺ 2 ) and nitrate (NO3 ), with low, but potentially significant levels of nitroso (RNO) and nitro (RNO2) derivatives produced as well. Neuronal NOS is located throughout the lung and remains constitutively activated (7, 21, 42). In SCD, neuronal NOS displays polymorphisms that have been associated with ACS (40). Inducible NOS (iNOS) is located in most vascular cells, with its expression induced by the spectrum of inflammatory mediators associated with SCD. Although differing levels of iNOS expression and activity have been reported in SCD (3, 11, 27), our data support the view that iNOS is generally “upregulated” in multiple organs and vascular beds in SCD (3). Endothelial NOS (eNOS) is located in the vascular endothelium and manifests both increased expression and activity in SCD (11, 16). It is critical to understand that NO derived from iNOS and eNOS displays frequently unique but sometimes overlapping reactivities due to differences in their mechanisms of activation and intracellular compartmentalization. iNOS is induced by cytokines and functions independently of changes in calcium homeostasis. Because of this, it does not appear to play a role in receptor-dependent vasodilation but, rather, in more chronic inflammatory activation and hypotensive states (17). eNOS, on the other hand, is activated by calcium influxes and effects vasodilation (11, 17, 43). Plasma levels of the NO metabolites ⫺ (NOx) NO⫺ 2 and NO3 have been used as a measure of endothelium-dependent NO signaling, but a significant limitation becomes operative upon inflammatory induction of iNOS expression and activity (as in SCD). At this point, NO⫺ 2 and levels become less reliable as a measure of the more NO⫺ 3 salutary endothelium-dependent NO that is produced in response to vasodilatory stimuli and can actually reflect iNOSderived NO and decomposition products of inflammatory oxidants such as nitrogen dioxide (䡠NO2) and ONOO⫺ that can contribute to impaired vascular function (22). Nonetheless, the ⫺ plasma levels of NO⫺ 2 and NO3 are comparable in HbA (control) and HbS (SCD) patients under basal conditions but are decreased in SCD patients during VOC and ACS (18–20, 24, 26, 39) and are inversely related to pain scores during VOC (18).

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(SCD) is an inherited condition involving the ␤-hemoglobin subunit in red blood cells (RBC), where a single ␤6-amino acid mutation results in glutamic acid being switched to valine. Under hypoxic and acidotic conditions, sickle hemoglobin (HbS) molecules polymerize and sickled RBCs are formed. These structurally altered RBCs are unable to traverse distal blood vessels, causing microvascular obstruction and subsequent tissue hypoxia and ischemia. The clinical presentation of this process manifests as a painful vaso-occlusive crisis (VOC), infarction, or acute chest syndrome (ACS), which has multifactorial inciting events that remain an area of investigation and debate. Although these processes are certainly important in SCD, the roles of inflammatory mediators and vascular dysfunction are also now recognized as significant in the pathophysiology of SCD. As evidence of this vascular inflammatory state, cell adhesion molecules on RBC and endothelial surfaces, such as VCAM-1 and ICAM-1, are upregulated (4, 35, 37, 39). Cytokines and reactive inflammatory mediators (e.g., free radicals, oxidants) are also produced in elevated amounts (15, 30, 38). Nitric oxide (NO) is a multifaceted mediator of vascular homeostasis. NO inhibits the upregulation of cell adhesion molecules, platelet aggregation (1), and monocyte adhesion to endothelial cells (5). NO also mediates vasodilation through cGMP-dependent pathways and inhibits endothelin-1-induced vasoconstriction (12, 13). For lipid-derived radicals, NO acts as a beneficial free radical scavenger, and, upon reaction with the oxygen free radical superoxide (O⫺ 2 䡠), the potent oxidizing and nitrating species peroxynitrite (ONOO⫺) is formed. In SCD, NO-mediated inhibition of adhesion molecule expression is impaired (39), as is NO-mediated vasodilation (2). Interestingly, many patients with SCD are also hypotensive (14, 29). Xanthine oxidase (XO) has been shown to be responsible for catalytic inactivation of NO signaling in a variety of vascular diseases, most recently SCD, by playing a role in the dysregulation of both NO-dependent vascular relaxation (2) and neutrophil function (41). XO is a rich source of O⫺ 2 䡠, and hydrogen peroxide (H2O2) is particularly abundant in splanchnic tissues and endothelium and is released into the circulation following a variety of pathogenic events, including tissue ischemia/ reperfusion (28). Once in the circulation, XO binds to and is transcytosed by vascular endothelium to anatomic locations where XO-derived reactive oxygen species contribute to impaired NO signaling via direct O⫺ 2 䡠 reaction with NO or following H2O2-mediated, peroxidase-dependent NO conSICKLE CELL DISEASE

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pertension, and atherosclerosis. The conclusion that pulmonary vascular NO production and signaling have been impaired seems reasonable but is complicated by 1) the similar cGMP contents measured in the posthypoxic lung tissue of the different animal groups and 2) the discrepant clinical measurements ⫺ of plasma NO⫺ 2 and NO3 levels in HbA and HbS patients and the question of how to interpret the meaning of these measurements in terms of guanylate cyclase activation. In any event, the authors’ measurement of increased lung NO2Tyr content affirms increased NO production and/or its secondary oxidative reactions. In the author’s defense, the similar cGMP levels observed in the different posthypoxia experimental groups may also be due to NO-independent effects on cGMP levels or changes in the content of this mediator in nonvascular tissues. A novel and important element of the results of Pritchard et al. (33) is that HSP90-eNOS interactions are diminished in SCD, compared with wild-type control mice, even under normoxic conditions. After a hypoxic episode, the SCD mice revealed an even greater decrease in pulmonary tissue HSP90eNOS interactions, with no changes observed in wild-type controls. The investigators further explored mechanisms underlying altered HSP90-eNOS interactions by evaluating the impact of a stimulus of eNOS activity on PMVEC that had been subjected to oxidants derived from XO plus its substrate xanthine. In support of in vivo observations, there was an XO-dependent decrease in the association of HSP90 with ⫺ eNOS, as well as decreased cell NO⫺ 2 and NO3 production. The authors conclude that the oxidative stress induced by elevations in lung tissue XO impairs the ability of HSP90 and eNOS to associate, leading to a decrease in NO generation. We must be cautious when making this final inference, however, because of the difficulty in interpreting NOx levels as a measure of only eNOS-derived NO. As with every seminal research advance, provocative new questions arise. A crucial aspect of this and other studies that needs further definition is the anatomic source of the elevated XO observed in the vasculature in SCD. Clinical and animal model studies of XO inhibition and cell biological studies such as those utilized in the present report will assist in resolving the clinical significance of the observations made by Pritchard and colleagues (33). It is possible that either enhanced lung parenchymal XO expression or the expression and/or remote organ release of XO, followed by the pulmonary uptake of circulating XO, is the source of this increased oxidative injury. Addressing the question of whether increases in other sources of oxidant production contribute to altered eNOS activity in SCD will also be illuminating and important from a therapeutic perspective. This increased inflammatory oxidant “burden” not only could contribute to altered interactions between eNOS and HSP but could also have an impact on other eNOS regulatory interactions (e.g., caveolar vs. cytoplasmic distribution). In addition, HSP90 also interacts with and enhances iNOS activity (44). It might be possible that HSP90 association with eNOS is decreased in part because of increased oxidant-induced HSP90 interactions with iNOS. By resolving the relative contributions of eNOS- and iNOS-derived NO to both vascular functional defects and inflammatory-oxidant-related actions (or some potentially regulable combination of both sequelae), we will gain better insight into the pathogenesis of SCD. The authors and these editorialists are hopeful that this report will stimulate continued interest in the significance of 286 • APRIL 2004 •

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Because eNOS expression and activity is increased in SCD, this enzyme has gained significant interest in the pathogenesis of SCD complications, such as ACS. Of special significance and the subject of a current article in focus (Ref. 33, see p. L705 in this issue), eNOS binds heat shock protein 90 (HSP90), leading to conformational changes in eNOS and enzyme activation (8, 9, 31, 32, 36). However, if these proteins interact without appropriate conformational changes, electron transfer reactions of eNOS become uncoupled, to yield eNOSderived O⫺ 2 䡠 and H2O2, which concomitantly “inactivate” NO and generate secondary oxides of nitrogen such as 䡠NO2 and ONOO⫺ (31, 32). Despite the important regulatory interactions of HSPs with eNOS, the biochemical and functional actions of HSP90 in SCD have not been previously evaluated. To address this issue, a team of prominent vascular biology investigators led by Kirkwood Pritchard reveal novel insight into the actions of HSP90 and eNOS in acute lung injury in a murine model of SCD (33). This investigation first tested the hypothesis that the “oxidative stress” caused by hypoxiainduced increases in XO activity in pulmonary microvascular endothelial cells (PMVEC) leads to decreased association of HSP90 and eNOS. This in turn would impair NO production by PMVEC and, by extension of this concept to the clinical scenario, could contribute to the acute lung injury seen in SCD during ACS. The mice studied included a SCD model (with HbS, as well as evidence of mild to moderate ␤-thalassemia), a heterozygous SCD mouse (representing sickle trait but expresses mild pathological changes unlike sickle trait in human subjects), and wild-type control mice. These mouse models demonstrated vaso-occlusive events, as evidenced by increased vascular congestion, with these events observed in both SCD and SCD trait mice, but not in wild-type controls. Several measurements revealed enhanced lung injury in this model of SCD. Quantitative immunohistochemical analysis of XO activity showed increased pulmonary XO present in SCD mice but not in trait or control mice under normoxic conditions. After hypoxic exposure, pulmonary XO was increased twofold in SCD mice, only minimally in trait mice, and was unchanged in controls. Pulmonary 3-nitrotyrosine (NO2Tyr) content, an index of the abrogation of salutary signaling actions of NO [e.g., NO-dependent oxidative inflammatory reactions (10)], was also evaluated by immunohistochemical staining, with NO2Tyr levels in SCD mice 2.5 times greater than trait or control mice. Hypoxic conditions led to ⬃50% increases in lung NO2Tyr content in SCD mice, compared with only modest increases in trait and control mice. Finally, the investigators evaluated guanylate cyclase-dependent NO signaling activity by measuring lung tissue cGMP content, an index that was increased under basal conditions only in SCD mice. Interestingly, following hypoxic exposure of mice, cGMP content was significantly decreased from basal conditions in all mice to the same level. From these results, the authors concluded that hypoxic conditions in SCD induce oxidant-mediated lung injury and impaired NO signaling, as evidenced by increased XO activity, lung NO2Tyr content, and the suppression of cGMP levels under hypoxic conditions. The role of XO in the pathogenesis of SCD is thus gaining increased relevance, especially in light of the recent expanding literature supporting the contributions of XO and the benefits of allopurinol (an XO inhibitor) in a variety of clinical vasculopathies including heart failure, hy-

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REFERENCES 1. Alonso D and Radomski MW. The nitric oxide-endothelin-1 connection. Heart Fail Rev 8: 107–115, 2003. 2. Aslan M, Ryan TM, Adler B, Townes TM, Parks DA, Thompson JA, Tousson A, Gladwin MT, Patel RP, Tarpey MM, Batinic-Haberle I, White CR, and Freeman BA. Oxygen radical inhibition of nitric oxidedependent vascular function in sickle cell disease. Proc Natl Acad Sci USA 98: 15215–15220, 2001. 3. Aslan M, Ryan TM, Townes TM, Coward L, Kirk MC, Barnes Alexander CB, Rosenfeld SS, and Freeman BA. Nitric oxide-dependent generation of reactive species in sickle cell disease. Actin tyrosine nitration induces defective cytoskeletal polymerization. J Biol Chem 278: 4194–4204, 2003. 4. Belcher JD, Bryant CJ, Nguyen J, Bowlin PR, Kielbik MC, Bischof JC, Hebbel RP, and Vercellotti GM. Transgenic sickle mice have vascular inflammation. Blood 101: 3953–3959, 2003. 5. De Caterina R, Libby P, Peng H, Thannickal VJ, Rajavashisth TB, Gimbrone MA Jr, Shin WS, and Liao JK. Nitric oxide decreases cytokine-induced endothelial activation. Nitric oxide selectively reduces endothelial expression of adhesion molecules and proinflammatory cytokines. J Clin Invest 96: 60–68, 1995. 6. Eiserich JP, Baldus S, Brennan M, Ma W, Zhang C, Tousson A, Castro L, Lusis AJ, Nauseef WM, White CR, and Freeman BA. Myeloperoxidase, a leukocyte-derived vascular NO oxidase. Science 296: 2391–2394, 2002. 7. Fagan KA, Morrissey B, Fouty BW, Sato K, Harral JW, Morris KG, Hoedt-Miller M, Vidmar S, McMurtry IF, and Rodman DM. Upregulation of nitric oxide synthase in mice with severe hypoxia-induced pulmonary hypertension. Respir Res 2: 306–313, 2001. 8. Garcia-Cardena G, Fan R, Shah V, Sorrentino R, Cirino G, Papapetropoulos A, and Sessa WC. Dynamic activation of endothelial nitric oxide synthase by Hsp90. Nature 392: 821–824, 1998. 9. Gratton J, Fontana J, O’Connor DS, Garcia-Cardena G, McCabe TJ, and Sessa WC. Reconstitution of an endothelial nitric-oxide synthase (eNOS), hsp90, and caveolin-1 complex in vitro. J Biol Chem 275: 22268–22272, 2000. 10. Greenacre SA and Ischiropoulos H. Tyrosine nitration: localization, quantification, consequences for protein function and signal transduction. Free Radic Res 34: 541–581, 2001. AJP-Lung Cell Mol Physiol • VOL

11. Hammerman SI, Klings ES, Hendra KP, Upchurch GR, Rishikof DC, Loscalzo J, and Farber HW. Endothelial cell nitric oxide production in acute chest syndrome. Am J Physiol Heart Circ Physiol 277: H1579– H1592, 1999. 12. Houston M, Estevez A, Chumley P, Aslan M, Marklund S, Parks DA, and Freeman BA. Binding of xanthine oxidase to vascular endothelium. Kinetic characterization and oxidative impairment of nitric oxide-dependent signaling. J Biol Chem 274: 4985–4994, 1999. 13. Hubloue I, Biarent D, Abdel Kafi S, Bejjani G, Kerbaul F, Naeije R, and Leeman M. Endogenous endothelins and nitric oxide in hypoxic pulmonary vasoconstriction. Eur Respir J 21: 19–24, 2003. 14. Johnson CS and Giorgio AJ. Arterial blood pressure in adults with sickle cell disease. Arch Intern Med 141: 891–893, 1981. 15. Kaul DK and Hebbel RP. Hypoxia/reoxygenation causes inflammatory response in transgenic sickle mice but not in normal mice. J Clin Invest 106: 411–420, 2000. 16. Kaul DK, Liu X, Fabry ME, and Nagel RL. Impaired nitric oxidemediated vasodilation in transgenic sickle mouse. Am J Physiol Heart Circ Physiol 278: H1799–H1806, 2000. 17. Kone BC, Kuncewicz T, Zhang W, and Yu Z. Protein interactions with nitric oxide synthases: controlling the right time, right place, and the right amount of nitric oxide. Am J Physiol Renal Physiol 285: F178–F190, 2003. 18. Lopez BL, Barnett J, Ballas SK, Christopher TA, Davis-Moon L, and Ma X. Nitric oxide metabolite levels in acute vaso-occlusive sickle-cell crisis. Acad Emerg Med 3: 1098–1103, 1996. 19. Lopez BL, Davis-Moon L, Ballas SK, and Ma X. Sequential nitric oxide measurements during the emergency department treatment of acute vasoocclusive sickle cell crisis. Am J Hematol 64: 15–19, 2000. 20. Lopez BL, Kreshak AA, Morriss CR, Davis-Moon L, Ballas SK, and Ma X. L-arginine levels are diminished in adult acute vaso-occlusive sickle cell crisis in the emergency department. Br J Haematol 120: 532–534, 2003. 21. Luhrs H, Papadopoulos T, Schmidt HHHW, and Menzel T. Type I nitric oxide synthase in the human lung is predominantly expressed in capillary endothelial cells. Respir Physiol 129: 367–374, 2002. 22. Miranda KM, Espey MG, Jourd’hevil D, Grisham MB, Fukuto JM, Feelisch M, and Wink DA. The chemical biology of nitric oxide. In: Nitric Oxide Biology and Pathobiology, edited by Ignarro J. San Diego, CA: Academic, 2000, p. 41–55. 23. Morris CR, Kuypers FA, Larkin S, Sweeters N, Simon J, Vichinsky EP, and Styles LA. Arginine therapy: a novel strategy to induce nitric oxide production in sickle cell disease. Br J Haematol 111: 498–500, 2000. 24. Morris CR, Kuypers FA, Larkin S, Vichinsky EP, and Styles LA. Patterns of arginine and nitric oxide in patients with sickle cell disease with vaso-occlusive crisis and acute chest syndrome. J Pediatr Hematol Oncol 22: 515–520, 2000. 25. Morris CR, Morris SM Jr, Hagar W, van Warmerdam J, Claster S, Kepka-Lenhart D, Machado L, Kuypers FA, and Vichinsky EP. Arginine therapy: a new treatment for pulmonary hypertension in sickle cell disease? Am J Respir Crit Care Med 168: 63–69, 2003. 26. Morris CR, Vichinsky EP, van Warerdam J, Machado L, KepkaLenhart D, Morris SM, and Kuypers FA. Hydroxyurea and arginine therapy: impact on nitric oxide production in sickle cell disease. J Pediatr Hematol Oncol 25: 629–634, 2003. 27. Nath KA, Shah V, Haggard JJ, Croatt AJ, Smith LA, Hebbel RP, and Katusic ZS. Mechanisms of vascular instability in a transgenic mouse model of sickle cell disease. Am J Physiol Regul Integr Comp Physiol 279: R1949–R1955, 2000. 28. Nielson VG, Tan S, Weinbroum A, McCammon AT, Samuelson PN, Gelman S, and Parks DA. Lung injury after hepatoenteric ischemiareperfusion: role of xanthine oxidase. Am J Respir Crit Care Med 154: 1364–1369, 1996. 29. Pegelow CH, Colangelo L, Steinberg M, Wright EC, Smith J, Phillips G, and Vichinsky E. Natural history of blood pressure in sickle cell disease: risks for stroke and death associated with relative hypertension in sickle cell anemia. Am J Med 102: 171–177, 1997. 30. Platt OS. Sickle cell anemia as an inflammatory disease. J Clin Invest 106: 337–338, 2000. 31. Pritchard KA, Ackerman AW, Gross ER, Stepp DW, Shi Y, Fontana JT, Baker JE, and Sessa WC. Heat shock protein 90 mediates the balance of nitric oxide and superoxide anion from endothelial nitric-oxide synthase. J Biol Chem 276: 17621–17624, 2001. 286 • APRIL 2004 •

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oxidative stress and HSP90-eNOS interactions in SCD, especially as they apply to the clinical setting. Questions do arise regarding the applicability of some SCD mouse model-based findings to humans with SCD. For example, vaso-occlusive events were reported to occur in larger vessels in the murine SCD model, although in humans vaso-occlusion occurs in the microvascular environment. Also, the heterozygous sickle trait mouse showed evidence of vaso-occlusion, whereas humans with sickle cell trait are clinically asymptomatic. Regardless, this report sheds light on an important area of focus in developing new understanding regarding the pathogenesis of SCD. It is also entirely possible that new diagnostic and therapeutic strategies will emanate from the observations of Pritchard et. al. (33). Quantification of HSP90-eNOS interactions could be predictive of the severity of ACS or the potential onset of painful crises and the need for more aggressive clinical management. Could these interactions be affected by XO inhibitors, such as the pyrazolo derivatives oxypurinol and allopurinol, or an NO source, such as inhaled NO, L-arginine, or hydroxyurea, thus altering the clinical course of SCD? In summary, Pritchard and colleagues have elegantly established that HSP90 displays decreased interactions with eNOS in SCD. This finding is significant in that HSP90 enhances eNOS function, and in SCD, NOS function and NO pathways are dysregulated. A better understanding of the altered interactions between HSP90 and eNOS in SCD may hold the key to successful predictive and therapeutic modalities for ACS.

Editorial Focus L704 32. Pritchard KA, Ackerman AW, Ou J, Curtis M, Smalley DM, Fontana JT, Stemerman MB, and Sessa WC. Native low density lipoprotein induces endothelial nitric oxide synthase dysfunction: role of heat shock protein 90 and caveolin-1. Free Radic Biol Med 33: 52–62, 2002. 33. Pritchard KA Jr, Ou J, Ou Z, Shi Y, Franciosi JP, Signorino P, Kaul S, Ackland-Berglund C, Witte K, Holzhauer S, Mohandas N, Guice KS, Oldham KT, and Hillery CA. Hypoxia-induced acute lung injury in murine models of sickle cell disease. Am J Physiol Lung Cell Mol Physiol 286: L705–L714, 2004. 34. Romero JR, Suzuka SM, Nagel RL, and Fabry ME. Arginine supplementation of sickle transgenic mice reduces red cell density and Gardos channel activity. Blood 99: 1103–1108, 2002. 35. Setty BN and Stuart MJ. Vascular cell adhesion molecule-1 is involved in mediating hypoxia-induced sickle red blood cell adherence to endothelium: potential role in sickle cell disease. Blood 88: 2311–2320, 1996. 36. Shah V, Wiest R, Garcia-Cardena G, Cadelina G, Groszmann RJ, and Sessa WC. Hsp90 regulation of endothelial nitric oxide synthase contributes to vascular control in portal hypertension. Am J Physiol Gastrointest Liver Physiol 277: G463–G468, 1999. 37. Space SL, Lane PA, Pickett CK, and Weil JV. Nitric oxide attenuates normal and sickle red blood cell adherence to pulmonary endothelium. Am J Hematol 63: 200–204, 2000.

38. Steinberg MH and Brugnara C. Pathophysiology-based approaches to treatment of sickle cell disease. Annu Rev Med 54: 89–112, 2003. 39. Stuart MJ and Setty BN. Sickle cell acute chest syndrome: pathogenesis and rationale for treatment. Blood 94: 1555–1560, 1999. 40. Sullivan KJ, Kissoon N, Duckworth LJ, Sandler E, Freeman B, Bayne E, Sylvester JE, and Lima JJ. Low exhaled nitric oxide and a polymorphism in the NOS I gene is associated with acute chest syndrome. Am J Respir Crit Care Med 164: 2186–2190, 2001. 41. Terada LS, Hybertson BM, Connelly KG, Weill D, Piermattei D, and Repine JE. XO increases neutrophil adherence to endothelial cells by a dual ICAM-1 and P-selectin-mediated mechanism. J Appl Physiol 82: 866–873, 1997. 42. Vaughan DJ, Brogan TV, Kerr ME, Deem S, Luchtel DL, and Swenson ER. Contributions of nitric oxide synthase isozymes to exhaled nitric oxide and hypoxic pulmonary vasoconstriction in rabbit lungs. Am J Physiol Lung Cell Mol Physiol 284: L834–L843, 2003. 43. Venema RC, Venema VJ, Ju H, Harris MB, Snead C, Jilling T, Dimitropoulou C, Maragoudakis ME, and Catravas JD. Novel complexes of guanylate cyclase with heat shock protein 90 and nitric oxide synthase. Am J Physiol Heart Circ Physiol 285: H669–H678, 2003. 44. Yoshida M and Xia Y. Heat shock protein 90 as an endogenous protein enhancer of inducible nitric-oxide synthase. J Biol Chem 278: 36953– 36958, 2003.

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