Homocysteine– A Stealth Mediator of Impaired Wound Healing: A Preliminary Study
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The results of this preliminary clinical study suggest a correlation exists between elevated serum Hcy and impaired chronic wound healing with patients receiving dermal substitute therapy. Furthermore, the preliminary data indicate that elevated serum Hcy may also be correlated with significantly decreased wound NO bioactivity as determined by wound fluid NOx assay, and left untreated, elevated Hcy may become common among patients with chronic wounds (50% incidence). Additionally, the observations of a single case report suggest that successful treatment of elevated Hcy in a patient with impaired wound healing may promote the restoration of normal wound healing.
Nitric oxide, a key mediator of cutaneous physiology, is formed by the enzymatic combination of molecular oxygen and the semi-essential amino acid L-arginine. Nitric oxide provides cellular signaling by activation of its target molecule, guanylate cyclase, which elevates intracellular concentrations of cyclic guanosine monophosphate (cGMP).21 Increased cGMP causes vascular smooth muscle relaxation, which constitutes a significant mechanism of homeostasis for microcirculation, and modulates the cardiovascular response to vasoconstrictors, cytokines, and endotoxin. Nitric oxide may alter key enzymes, affecting subcellular systems, the Krebs cycle, or RNA/DNA synthesis. This activity is performed without the need for signal transduction. Nitric oxide crosses cell membranes without mediation of channels or receptors—it diffuses across cellular membranes isotropically.21 Because of its high diffusion coefficient, short half-life (approximately 5 seconds), and prompt decomposition, NO is ideal because it acts as a cellular signal for wound repair. Nitric oxide is generated by 3 isoforms of nitric oxide synthase (NOS) that metabolize L-arginine and molecular oxygen to citrulline and NO.22 Two of the 3 isoforms are constitutive enzyme systems (cNOS) that are described in neuronal cells (nNOS) and endothelial cells (eNOS). With these enzymes, increased levels of intracellular calcium activate the cNOS via calmodulin. The calcium-dependent cNOS systems produce low (picomolar) quantities of NO. The third system is the inducible isoform (iNOS), which is calcium independent. Expression of iNOS is controlled by tissue-specific stimuli, such as inflammatory cytokines or exogenous materials, ie, bacterial lipopolysaccharide (LPS). Once induced, production of NO within tissue can increase as much as 1,000-fold, thereby producing an environment that is toxic to invading microorganisms. Currently, it appears that the cNOS enzymes are involved in maintaining skin homeostasis and providing regulatory function.22 The iNOS enzymes appear to be mainly associated with inflammatory and immune responses that are also implicated in certain skin diseases. In human skin, keratinocytes, fibroblasts, and endothelial cells possess both the cNOS and iNOS isoforms. The wound macrophage and keratinocyte possess the iNOS isoform.23 Epithelial migration,4 wound angiogenesis,2 and granulation tissue formation3 are primarily mediated by the activation and upregulation of the iNOS isoform.
The major metabolic pathway for NO is through nitrate (NO3–) and nitrite (NO2–), collectively termed NOx, which are stable metabolites within tissue, plasma, and urine.21 Tracer studies in humans have demonstrated that perhaps 50% of the total body NOx originates from the NO synthesis substrate, L-arginine, although this percentage will vary with the dietary intake of NOx.24,25 Fasting plasma and urine samples allow clinicians to use variations in NOx values as a means of evaluating changes in NO production and bioactivity.26
1. Schwentker A, Billiar TR. Nitric oxide and wound repair. Surg Clin North Am. 2003;83(3):521–530.
2. Fukumura D, Gohongi T, Kadambi A, et al. Predominant role of endothelial nitric oxide synthase in vascular endothelial growth factor-induced angiogenesis and vascular permeability. Proc Natl Acad Sci USA. 2001;98(5):2604–2609.
3. Pollock JS, Webb W, Callaway D, Sathyanarayana, O’Brien W, Howdieshell TR. Nitric oxide synthase isoform expression in a porcine model of granulation tissue formation. Surgery. 2001;129(3):341–350.
4. Noiri E, Peresleni T, Srivastava N, et al. Nitric oxide is necessary for a switch from stationary to locomoting phenotype in epithelial cells. Am J Physiol. 1996;270(3 Pt 1):C794–802.
5. Most D, Efron DT, Shi HP, Tantry US, Barbul A. Characterization of incisional wound healing in inducible nitric oxide synthase knockout mice. Surgery. 2002;132(5):866–876.
6. Schaffer MR, Tantry U, Efron PA, Ahrendt GM, Thornton FJ, Barbul A. Diabetes-impaired healing and reduced wound nitric oxide synthesis: a possible pathophysiologic correlation. Surgery. 1997;121(5):513–519.
7. Boykin JV, Kalns JE, Shawler LG, Sommer VL, Crossland M. Diabetes-impaired wound healing predicted by urinary nitrate assay: a preliminary, retrospective study. WOUNDS. 1999;11(3):62–69.
8. Stallmeyer B, Anhold M, Wetzler C, Kahlina K, Pfeilschifter J, Frank S. Regulation of eNOS in normal and diabetes-impaired skin repair: implications for tissue regeneration. Nitric Oxide. 2002;6(2):168–177.
9. Witte MB, Thornton FJ, Tantry U, Barbul A. L-arginine supplementation enhances diabetic wound healing: involvement of the nitric oxide synthase and arginase pathways. Metabolism. 2002;51(10):1269–1273.
10. Schaffer MR, Tantry U, Ahrendt GM, Wasserkrug HL, Barbul A. Acute protein-calorie malnutrition impairs wound healing: a possible role of decreased wound nitric oxide synthesis. J Am Coll Surg. 1997;184(1):37–43.
11. Schaffer M, Weimer W, Wider S, et al. Differential expression of inflammatory mediators in radiation-impaired wound healing. J Surg Res. 2002;107(1):93–100.
12. Ulland AE, Shearer JD, Coulter C, Caldwell MD. Altered wound arginine metabolism by corticosterone and retinoic acid. J Surg Res. 1997;70(1):84–88.
13. Schaffer MR, Tantry U, Thornton FJ, Barbul A. Inhibition of nitric oxide synthesis in wounds: pharmacology and effect on accumulation of collagen in wounds in mice. Eur J Surg. 1999;165(3):262–267.
14. Schaffer MR, Tantry U, Gross SS, Wasserburg HL, Barbul A. Nitric oxide regulates wound healing. J Surg Res. 1996;63(1):237–240.
15. Witte MB, Kiyama T, Barbul A. Nitric oxide enhances experimental wound healing in diabetes. Br J Surg. 2002;89(12):1594–1601.
16. Pollock JS, Webb W, Callaway D, Sathyanarayana, O’Brien W, Howdieshell TR. Nitric oxide synthase isoform expression in a porcine model of granulation tissue formation. Surgery. 2001;129(3):341–350.
17. Welch GN, Loscalzo J. Homocysteine and atherothrombosis. N Engl J Med. 1998;338(15):1042–1050.
18. Green LC, Wagner DA, Glogowski J, Skipper PL, Wishnok JS, Tannenbaum SR. Analysis of nitrate, nitrite, and 15N-nitrate in biological fluids. Anal Biochem. 1982;126(1):131–138.
19. US patents 6,312,663B1, 6,344,181B2, and 6,436,366B2.
20. Eikelboom JW, Lonn E, Genest J Jr, Hankey G, Yusuf S. Homocyst(e)ine and cardiovascular disease: a critical review of the epidemiologic evidence. Ann Intern Med. 1999;131(5):363–375.
21. Beckman JS. The physiological and pathological chemistry of nitric oxide. In: Lancaster J, ed. Nitric Oxide. New York, NY: Academic Press; 1996:1–71.
22. Moncada S, Higgs A. The L-arginine-nitric oxide pathway. N Engl J Med. 1993;329(27):2002–2012.
23. Schaffer MR, Tantry U, van Wesep RA, Barbul A. Nitric oxide metabolism in wounds. J Surg Res. 1997;71(1):25–31.
24. Rhodes P, Leone AM, Francis PL, Struthers AD, Moncada S. The L-arginine:nitric oxide pathway is the major source of plasma nitrite in fasted humans. Biochem Biophys Res Commun. 1995;209(2):590–596.
25. Castillo L, deRojas TC, Chapman TE, Vogt J, Burke JF, Tannenbaum SR, Young VR. Splanchnic metabolism of dietary arginine in relation to nitric oxide synthesis in normal adult man. Proc Natl Acad Sci USA. 1993;90(1):193–197.
26. Baylis C, Vallance P. Measurement of nitrite and nitrate levels in plasma and urine—what does this measure tell us about the activity of the endogenous nitric oxide system? Curr Opin Nephrol Hypertens. 1998;7(1):59–67.
27. Lefer AM, Lefer DJ. The role of nitric oxide and cell adhesion molecules on the microcirculation in ischaemia-reperfusion. Cardiovasc Res. 1996;32(4):743–751.
28. Um SC, Suzuki S, Toyokuni S, et al. Involvement of nitric oxide in survival of random pattern skin flap. Plast Reconstr Surg. 1998;101(3):785–792.
29. Fukumura D, Gohongi T, Kadambi A, et al. Predominant role of endothelial nitric oxide synthase in vascular endothelial growth factor-induced angiogenesis and vascular permeability. Proc Natl Acad Sci USA. 2001;98(5):2604–2609.
30. Dhaunsi GS, Ozand PT. Nitric oxide promotes mitogen-induced DNA synthesis in human dermal fibroblasts through cGMP. Clin Exp Pharmacol Physiol. 2004;31(1-2):46–49.
31. Howdieshell TR, Webb WL, Sathyanarayana, McNeil PL. Inhibition of inducible nitric oxide synthase results in reductions in wound vascular endothelial growth factor expression, granulation tissue formation, and local perfusion. Surgery. 2003;133(5):528–537.
32. Hayden MR, Tyagi SC. Homocysteine and reactive oxygen species in metabolic syndrome, type 2 diabetes mellitus, and atheroscleropathy: the pleiotropic effects of folate supplementation. Nutr J. 2004;3:4.
33. Nygard O, Vollset SE, Refsum H, Brattstrom L, Ueland PM. Total homocysteine and cardiovascular disease. J Intern Med. 1999;246(5):425–454.
34. Petchkrua W, Burns SP, Stiens SA, James JJ, Little JW. Prevalence of vitamin B12 deficiency in spinal cord injury. Arch Phys Med Rehabil. 2003;84(11):1675–1679.
35. Brosnan JT. Homocysteine and cardiovascular disease: interactions between nutrition, genetics and lifestyle. Can J Appl Physiol. 2004;29(6):773–780.
36. Venn BJ, Green TJ, Moser R, Mann JI. Comparison of the effect of low-dose supplementation with L-5-methyltetrahydrofolate or folic acid on plasma homocysteine: a randomized placebo-controlled study. Am J Clin Nutr. 2003;77(3):658–662.
37. Deloughery TG, Evans A, Sadeghi A, et al. Common mutation in methylenetetrahydrofolate reductase. Correlation with homocysteine metabolism and late-onset vascular disease. Circulation. 1996;94(12):3074–3078.
38. Klerk M, Verhoef P, Clarke R, Blom HJ, Kok FJ, Schouten EG; MTHFR Studies Collaboration Group. MTHFR 677C-->T polymorphism and risk of coronary heart disease: a meta analysis. JAMA. 2002;288(16):2023–2031.
39. Willems FF, Boers GH, Blom HJ, Aengevaeren WR, Verheugt FW. Pharmacokinetic study on the utilisation of 5-methyltetrahydrofolate and folic acid in patients with coronary artery disease. Br J Pharmacol. 2004;141(5):825–830.
40. Yaqub BA, Siddique A, Sulimani R. Effects of methylcobalamin on diabetic neuropathy. Clin Neurol Neurosurg. 1992;94(2):105–111.
41. Zhang X, Li H, Jin H, Ebin Z, Brodsky S, Goligorsky MS. Effects of homocysteine on endothelial nitric oxide production. Am J Physiol Renal Physiol. 2000;279(4):F671–678.
42. Nihei S, Tasaki H, Yamashita K, et al. Hyperhomocysteinemia is associated with human coronary atherosclerosis through the reduction of the ratio of endothelium-bound to basal extracellular superoxide dismutase. Circ J. 2004;68(9):822–828.
43. Stuhlinger MC, Tsao PS, Her JH, Kimoto M, Balint RF, Cooke JP. Homocysteine impairs the nitric oxide synthase pathway: role of asymmetric dimethylarginine. Circulation. 2001;104(21):2569–2575.
44. Stallmeyer B, Kampfer H, Kolb N, Pfeilschifter J, Frank S. The function of nitric oxide in wound repair: inhibition of inducible nitric oxide-synthase severely impairs wound reepithelialization. J Invest Dermatol. 1999;113(6):1090–1098.
45. Majors AK, Sengupta S, Willard B, Kinter MT, Pyeritz RE, Jacobsen DW. Homocysteine binds to human plasma fibronectin and inhibits its interaction with fibrin. Arterioscler Thromb Vasc Biol. 2002;22(8):1354–1359.
46. Singer AJ, Clark RA. Cutaneous wound healing. N Engl J Med. 1999;341(10):738–746.
47. Duan J, Murohara T, Ikeda H, et al. Hyperhomocysteinemia impairs angiogenesis in response to hindlimb ischemia. Arterioscler Thromb Vasc Biol. 2000;20(12):2579–2585.
48. Rekhter MD. Collagen synthesis in atherosclerosis: too much and not enough. Cardiovasc Res. 1999;41(2):376–384.