4. Discussion
CAS remains a serious clinical problem because, despite recent progress including apparent improvement in the diagnostic process (Elbadawi et al. , 2019), it remains under-diagnosed, its epidemiology is poorly understood, there is no consensus as to its precise pathogenesis, and because the only well-validated prophylactic treatment modality, that of calcium antagonists, yields only moderate symptomatic improvement. The importance of constrictor hyperactivity, in general, to the pathophysiology of CAS, and its link to vascular endothelial dysfunction, has recently been summarized (Ong et al. , 2015a) and is beyond dispute. However, there is also increasing evidence that platelet-based impairment of circulatory homeostasis may be involved (Robertson et al. , 1980; Ogasawara et al. , 1986; Murakami et al. , 1998). In the current study, we investigated whether abnormal platelet reactivity is present in CAS patients and whether symptomatic crises reflect platelet-endothelial interactions. In the current study, we sought to delineate the demographics of patients with CAS, to understand its pathophysiology, and that of the episodic crises which characterize the condition, and to identify a potential “screening test” for acute episodes (to distinguish such episodes from “non-cardiac chest pain”).
A central basis for our undertaking the current study was continuing uncertainty about the pathogenesis of CAS, despite increasing evidence of vascular hyporesponsiveness to NO (Folts et al. , 1991; Yamada et al. , 2013), inflammatory activation (Ong et al. , 2015b) (sometimes involving mast cell activation (Forman et al. , 1985; Kounis et al. , 1991)), a tendency for intracoronary thrombi to be formed at sites of (ill-defined) plaque “erosion” (Shin et al. , 2015), and potentially activation of platelet aggregation (Hamm et al. , 1987; Miyamoto et al. , 2000).
In a series of ex vivo and in vitro experiments, we have now shown that patients with CAS have hyperaggregable platelets which exhibit marked impairment of the anti-aggregatory effects of the NO donor SNP, even during the chronic phases of the disorder. This finding almost certainly has parallels within coronary vascular smooth muscle, which represent the basis for the precipitation of CAS by intracoronary ACh injection (Goto et al. , 1999) . Thus our findings provide a basis for regarding CAS as a combined, biochemically-based disorder of NO signaling (rather than of NO generation in most cases), differentially affecting both the coronary vasculature and circulating platelets in individual patients (Crea et al. , 2017). Importantly, the current findings appear to apply equally for patients with macrovascular (PA) or microvascular (CSFP) types of CAS.
Platelet aggregatory responses to ADP were greater, and their inhibition by SNP was impaired, in chronic CAS patients relative to control subjects. During symptomatic crises, platelet responses to SNP tended to decrease further, together with substantial release of SD-1 (implying acute damage to the vascular glycocalyx as a contributing factor incremental to endothelial dysfunction). The damaged glycocalyx provides an environment favouring platelet adhesion/activation, with consequent release of pro-constrictor autacoids, such as thromboxane A2 and serotonin, which in turn may contribute to coronary vasoconstriction. This is accompanied by elevated plasma tryptase concentrations (implying mast cell activation) and formation of PMPs, the most abundant type of circulating microparticles, the generation of which implies platelet activation and apoptosis (Rosinska et al. , 2017) . Overall, these data provide strong evidence that CAS crises are associated with mast cell activation and both vascular and platelet damage, and thus provide a basis for the potential diagnostic utility of SD-1 assay for exclusion of “non-cardiac pain” in patients presenting with acute episodes of CAS.
The finding that intravenous infusion of GTN/NAC reversed the anomalies of platelet SNP responses and of plasma SD-1 concentrations was novel, even though a therapeutic effect based on potentiation of responses to NO was certainly consistent with previous clinical (Pasupathy et al. , 2017) and physiological (Horowitz et al. , 1983; Loscalzo, 1985) studies with GTN/NAC. Although no controlled clinical observations were made of the impact of GTN/NAC infusion on resolution of symptoms, it seems, from the rapid fall in plasma SD-1 concentrations associated with this treatment, that there was associated cessation of acute vascular damage (Mulivor et al. , 2004). These data are reminiscent of the findings of (Foltset al. , 1991) in a canine model of intimal injury to the circumflex coronary artery. These investigators demonstrated that NAC potentiated the effects of GTN in reversing cyclical coronary flow reductions, which resulted from periodic platelet adhesion to the injured vessel wall.
The performance of exploratory in vitro studies shed completely new light on the mechanism of beneficial effect of NAC in a number of acute cardiovascular disease states, with the revelation that potentiation of SNP anti-aggregatory effects by NAC was inhibited in the presence of antagonists (Paul et al. , 2012) of the enzymatic release of H2S from cysteine. Although NAC is known to be a potential donor of H2S (DiNicolantonio et al. , 2017; Bankhele et al. , 2018), and there is also some evidence that H2S and NO may have synergistic effects under some circumstances (Altaany et al. , 2013; Zhou et al. , 2016) , the current findings represent the first data to suggest that previously described potentiation of the effects of NO donors by high doses of NAC (Horowitz et al. , 1983; Loscalzo, 1985) may be primarily mediated by H2S release.
In this regard, the current results reinforce those of recent studies suggesting that disordered microvascular reactivity (Levy et al. , 2019) and overt CAS (Ong et al. , 2008) may contribute to the pathogenesis of many forms of acute coronary syndrome. Indeed, the concept that CAS is associated with coronary plaque erosion and associated focal coronary thrombus formation in a substantial minority of cases (Ong et al. , 2015a) suggests that at least the acute phases of the disorder are pivotally related to vssel wall: platelet interactions. The current clinically used definition of plaque erosion (Jiaet al. , 2017) includes the presence of thrombus on an apparently intact coronary plaque , but such erosions have been associated with the release into blood of vascular glycocalyx products (Quillard et al. , 2017). These data therefore are consistent with our current findings for acute CAS.
The study has a number of limitations. First, the role of adventitial and/or systemic mast cell activation in precipitation of acute crises remains incompletely delineated. Aggravation of platelet NO resistance during acute crises should be studied in larger cohorts of patients. The precise mechanism(s) whereby NTG/NAC infusion rapidly reverses the glycocalyx shedding which underlies SD-1 release remain uncertain (although there is an implication of decreased generation of at least one “sheddase” enzyme) (Mulivor et al. , 2004), and need both to be correlated with symptomatic effects of this treatment modality and with changes within the cascade of matrix metalloproteinase release associated with mast cell activation. In this regard, it is unfortunate that optical coherence tomography was not performed in CAS patients during acute presentations, in order that plaque erosion and associated focal coronary thrombosis could be diagnosed. The precise mechanisms underlying potentiation of platelet NO signaling by H2S also remain to be elucidated, although a recent report (Miyamoto et al. , 2017) suggests that combination of H2S and NO may lead to synergistic vascular effects via polysulphide formation. Finally, the possibility that CAS might fundamentally represent a disorder of H2S generation remains to be explored.
The importance of the current findings therefore rests in three main areas:-
The results reinforce previous, less definitive data, to suggest that fluctuating severity of symptoms in CAS patients reflects, at least in parts, episodic platelet aggregation at sites of vessel wall damage and emphasize that the pathogenesis of CAS is fundamentally related to combined impairment of vasodilator and anti-aggregatory mechanisms. These findings, in the acute context, probably represent an indirect reflection of the phenomenon of plaque erosion and associated thrombosis. Clinical findings of plaque erosion (Crea et al. , 2019) and hospital admissions with CAS crises (Elbadawiet al. , 2019) are occurring more frequently. It is also likely that there is a “grey area” of pathogenesis across the whole spectrum of acute coronary syndromes, with plaque erosion increasingly implicated in the pathogenesis of S-T segment elevation acute myocardial infarction (Crea et al. , 2019).
(2) The findings of substantial elevation of SD-1 concentrations during acute attacks could be utilized as a means for provisional diagnosis of CAS in patients with prolonged chest pain who have no definitive changes on ECG or cardiac troponin concentrations. This would reduce the possibility that CAS patients will continue to remain undiagnosed, simply because there is no available screening test.
(3) The finding that there is likely to be an impaired H2S generation and/or a deficient NO/H2S interaction during both the chronic and acute phases of the disorder, could be a basis for new therapeutic modalities, both for prophylaxis and treatment of crises. Similarly, the finding of acute mast cell activation carries many potential therapeutic implications (Siebenhaar et al. , 2018). Exploration of such therapeutic options for CAS, coupled with an improvement in diagnostic efficiency, represents a considerable therapeutic priority.
REFERENCES
Altaany Z, Yang G, Wang R (2013). Crosstalk between hydrogen sulfide and nitric oxide in endothelial cells. J Cell Mol Med 17: 879-888.
Bankhele P, Salvi A, Jamil J, Njie-Mbye F, Ohia S, Opere CA (2018). Comparative Effects of Hydrogen Sulfide-Releasing Compounds on [(3)H]D-Aspartate Release from Bovine Isolated Retinae. Neurochem Res 43: 692-701.
Beltrame JF, Limaye SB, Horowitz JD (2002). The coronary slow flow phenomenon–a new coronary microvascular disorder. Cardiology 97: 197-202.
Beltrame JF, Limaye SB, Wuttke RD, Horowitz JD (2003). Coronary hemodynamic and metabolic studies of the coronary slow flow phenomenon. Am Heart J 146: 84-90.
Chirkov YY, Horowitz JD (2007). Impaired tissue responsiveness to organic nitrates and nitric oxide: a new therapeutic frontier? Pharmacol Ther 116: 287-305.
Chirkov YY, Holmes AS, Willoughby SR, Stewart S, Wuttke RD, Sage PR, et al. (2001). Stable angina and acute coronary syndromes are associated with nitric oxide resistance in platelets. J Am Coll Cardiol 37: 1851-1857.
Closs EI, Ostad MA, Simon A, Warnholtz A, Jabs A, Habermeier A, et al. (2012). Impairment of the extrusion transporter for asymmetric dimethyl-L-arginine: a novel mechanism underlying vasospastic angina. Biochem Biophys Res Commun 423: 218-223.
Crea F, Libby P (2017). Acute Coronary Syndromes: The Way Forward From Mechanisms to Precision Treatment.Circulation 136: 1155-1166.
Crea F, Vergallo R (2019). Plaque erosion: Towards precision medicine in acute coronary syndromes.Int J Cardiol 288: 22-24.
DiNicolantonio JJ, JH OK, McCarty MF (2017). Boosting endogenous production of vasoprotective hydrogen sulfide via supplementation with taurine and N-acetylcysteine: a novel way to promote cardiovascular health. Open Heart 4:e000600.
Elbadawi A, Elgendy IY, Naqvi SY, Mohamed AH, Ogunbayo GO, Omer MA, et al. (2019). Temporal Trends and Outcomes of Hospitalizations With Prinzmetal Angina: Perspectives From a National Database. Am J Med .
Folts JD, Stamler J, Loscalzo J (1991). Intravenous nitroglycerin infusion inhibits cyclic blood flow responses caused by periodic platelet thrombus formation in stenosed canine coronary arteries. Circulation 83: 2122-2127.
Forman MB, Oates JA, Robertson D, Robertson RM, Roberts LJ, 2nd, Virmani R (1985). Increased adventitial mast cells in a patient with coronary spasm. N Engl J Med313: 1138-1141.
Goto A, Ito S, Kondo H, Nomura Y, Yasue N, Suzumura H, et al. (1999). Evaluation of adjunctive intracoronary administration of acetylcholine following intravenous infusion of ergonovine to provoke coronary artery spasm. J Cardiol 34: 309-316.
Hamm CW, Lorenz RL, Bleifeld W, Kupper W, Wober W, Weber PC (1987). Biochemical evidence of platelet activation in patients with persistent unstable angina. J Am Coll Cardiol 10: 998-1006.
Horowitz JD, Antman EM, Lorell BH, Barry WH, Smith TW (1983). Potentiation of the cardiovascular effects of nitroglycerin by N-acetylcysteine. Circulation 68:1247-1253.
Jia H, Dai J, Hou J, Xing L, Ma L, Liu H, et al. (2017). Effective anti-thrombotic therapy without stenting: intravascular optical coherence tomography-based management in plaque erosion (the EROSION study). Eur Heart J 38:792-800.
Kopetz V, Kennedy J, Heresztyn T, Stafford I, Willoughby SR, Beltrame JF (2012). Endothelial function, oxidative stress and inflammatory studies in chronic coronary slow flow phenomenon patients. Cardiology 121: 197-203.
Kounis NG, Zavras GM (1991). Histamine-induced coronary artery spasm: the concept of allergic angina.Br J Clin Pract 45: 121-128.
Levy BI, Heusch G, Camici PG (2019). The many faces of myocardial ischaemia and angina. Cardiovasc Res115: 1460-1470.
Lewy RI, Wiener L, Smith JB, Walinsky P, Silver MJ, Saia J (1979). Comparison of plasma concentrations of thromboxane B2 in Prinzmetal’s variant angina and classical angina pectoris. Clin Cardiol 2: 404-406.
Loscalzo J (1985). N-Acetylcysteine potentiates inhibition of platelet aggregation by nitroglycerin. J Clin Invest 76: 703-708.
Miyamoto R, Koike S, Takano Y, Shibuya N, Kimura Y, Hanaoka K, et al. (2017). Polysulfides (H2Sn) produced from the interaction of hydrogen sulfide (H2S) and nitric oxide (NO) activate TRPA1 channels. Sci Rep 7:45995.
Miyamoto S, Ogawa H, Soejima H, Takazoe K, Sakamoto T, Yoshimura M, et al. (2000). Formation of platelet aggregates after attacks of coronary spastic angina pectoris.Am J Cardiol 85: 494-497, A410.
Morikawa Y, Mizuno Y, Harada E, Kuboyama O, Yoshimura M, Yasue H (2010). Nitrate tolerance as a possible cause of multidrug-resistant coronary artery spasm. Int Heart J51: 211-213.
Mulivor AW, Lipowsky HH (2004). Inflammation- and ischemia-induced shedding of venular glycocalyx.Am J Physiol Heart Circ Physiol 286: H1672-1680.
Murakami Y, Shimada T, Ishinaga Y, Kinoshita Y, Kin H, Kitamura J, et al. (1998). Transcardiac 5-hydroxytryptamine release and impaired coronary endothelial function in patients with vasospastic angina. Clin Exp Pharmacol Physiol25: 999-1003.
Nhek S, Clancy R, Lee KA, Allen NM, Barrett TJ, Marcantoni E, et al. (2017). Activated Platelets Induce Endothelial Cell Activation via an Interleukin-1beta Pathway in Systemic Lupus Erythematosus. Arterioscler Thromb Vasc Biol37: 707-716.
Nieuwdorp M, van Haeften TW, Gouverneur MC, Mooij HL, van Lieshout MH, Levi M, et al. (2006). Loss of endothelial glycocalyx during acute hyperglycemia coincides with endothelial dysfunction and coagulation activation in vivo.Diabetes 55: 480-486.
Ninomiya Y, Hamasaki S, Saihara K, Ishida S, Kataoka T, Ogawa M, et al. (2008). Comparison of effect between nitrates and calcium channel antagonist on vascular function in patients with normal or mildly diseased coronary arteries. Heart Vessels 23: 83-90.
Nooney VB, Hurst NL, Chirkov YY, De Caterina R, Horowitz JD (2015). Post receptor determinants of acute platelet response to clopidogrel in patients with symptomatic myocardial ischemia. Vascul Pharmacol 65-66: 17-22.
Ogasawara K, Aizawa T, Nishimura K, Satoh H, Fujii J, Katoh K (1986). Beta-thromboglobulin release within coronary circulation–a potential role of platelets in ergonovine-induced coronary vasospasm. Int J Cardiol 10:15-22.
Ong P, Athanasiadis A, Hill S, Vogelsberg H, Voehringer M, Sechtem U (2008). Coronary artery spasm as a frequent cause of acute coronary syndrome: The CASPAR (Coronary Artery Spasm in Patients With Acute Coronary Syndrome) Study. J Am Coll Cardiol 52: 523-527.
Ong P, Athanasiadis A, Borgulya G, Mahrholdt H, Kaski JC, Sechtem U (2012). High prevalence of a pathological response to acetylcholine testing in patients with stable angina pectoris and unobstructed coronary arteries. The ACOVA Study (Abnormal COronary VAsomotion in patients with stable angina and unobstructed coronary arteries). J Am Coll Cardiol 59:655-662.
Ong P, Aziz A, Hansen HS, Prescott E, Athanasiadis A, Sechtem U (2015a). Structural and Functional Coronary Artery Abnormalities in Patients With Vasospastic Angina Pectoris.Circ J 79: 1431-1438.
Ong P, Carro A, Athanasiadis A, Borgulya G, Schaufele T, Ratge D, et al. (2015b). Acetylcholine-induced coronary spasm in patients with unobstructed coronary arteries is associated with elevated concentrations of soluble CD40 ligand and high-sensitivity C-reactive protein. Coron Artery Dis 26: 126-132.
Pasupathy S, Tavella R, Grover S, Raman B, Procter NEK, Du YT, et al. (2017). Early Use of N-acetylcysteine With Nitrate Therapy in Patients Undergoing Primary Percutaneous Coronary Intervention for ST-Segment-Elevation Myocardial Infarction Reduces Myocardial Infarct Size (the NACIAM Trial [N-acetylcysteine in Acute Myocardial Infarction]).Circulation 136: 894-903.
Paul BD, Snyder SH (2012). H(2)S signalling through protein sulfhydration and beyond. Nat Rev Mol Cell Biol 13: 499-507.
Picard F, Sayah N, Spagnoli V, Adjedj J, Varenne O (2019). Vasospastic angina: A literature review of current evidence. Arch Cardiovasc Dis 112: 44-55.
Pope CA, 3rd, Bhatnagar A, McCracken JP, Abplanalp W, Conklin DJ, O’Toole T (2016). Exposure to Fine Particulate Air Pollution Is Associated With Endothelial Injury and Systemic Inflammation. Circ Res 119: 1204-1214.
Prinzmetal M, Kennamer R, Merliss R, Wada T, Bor N (1959). Angina pectoris. I. A variant form of angina pectoris; preliminary report. Am J Med 27: 375-388.
Quillard T, Franck G, Mawson T, Folco E, Libby P (2017). Mechanisms of erosion of atherosclerotic plaques.Curr Opin Lipidol 28: 434-441.
Robertson RM, Robertson D, Friesinger GC, Timmons S, Hawiger J (1980). Platelet aggregates in peripheral and coronary-sinus blood in patients with spontaneous coronary-artery spasm.Lancet 2: 829-831.
Rosinska J, Lukasik M, Kozubski W (2017). The Impact of Vascular Disease Treatment on Platelet-Derived Microvesicles. Cardiovasc Drugs Ther 31: 627-644.
Sakata K, Yoshida H, Hoshino T, Kurata C (1996). Sympathetic nerve activity in the spasm-induced coronary artery region is associated with disease activity of vasospastic angina. J Am Coll Cardiol 28: 460-464.
Shin ES, Ann SH, Singh GB, Lim KH, Yoon HJ, Hur SH, et al. (2015). OCT-Defined Morphological Characteristics of Coronary Artery Spasm Sites in Vasospastic Angina.JACC Cardiovasc Imaging 8: 1059-1067.
Siebenhaar F, Redegeld FA, Bischoff SC, Gibbs BF, Maurer M (2018). Mast Cells as Drivers of Disease and Therapeutic Targets. Trends Immunol 39: 151-162.
Siljander PR (2011). Platelet-derived microparticles - an updated perspective. Thromb Res 127 Suppl 2: S30-33.
Teragawa H, Oshita C, Ueda T (2018). Coronary spasm: It’s common, but it’s still unsolved. World J Cardiol 10: 201-209.
Waters DD, Bouchard A, Theroux P (1983). Spontaneous remission is a frequent outcome of variant angina.J Am Coll Cardiol 2: 195-199.
Willoughby SR, Stewart S, Holmes AS, Chirkov YY, Horowitz JD (2005). Platelet nitric oxide responsiveness: a novel prognostic marker in acute coronary syndromes. Arterioscler Thromb Vasc Biol 25: 2661-2666.
Willoughby SR, Rajendran S, Chan WP, Procter N, Leslie S, Liberts EA, et al. (2012). Ramipril sensitizes platelets to nitric oxide: implications for therapy in high-risk patients. J Am Coll Cardiol 60: 887-894.
Yamada S, Saitoh S, Machii H, Mizukami H, Hoshino Y, Misaka T, et al. (2013). Coronary artery spasm related to thiol oxidation and senescence marker protein-30 in aging. Antioxid Redox Signal 19: 1063-1073.
Zhou Z, Martin E, Sharina I, Esposito I, Szabo C, Bucci M, et al. (2016). Regulation of soluble guanylyl cyclase redox state by hydrogen sulfide. Pharmacol Res111: 556-562.