Engin ŞAHNA, Elif ONAT, Murat KARA, Selçuk İLHAN, Emre MUTLU

The effects of novokinin, an AT2 agonist, on blood pressure, vascular responses, and levels of ADMA, NADPH oxidase, and Rho kinase in hypertension induced by NOS inhibition and salt

Background/aim: The effects of AT2receptor agonist novokinin on blood pressure, eNOS, NADPH oxidase, protein arginine methyltransferases (PRMTs), and Rho kinase in hypertension were investigated. Furthermore, in isolated thoracic aorta rings, contractile and dilator responses were studied. Materials and methods: To develop hypertension, L-NAME was administered intraperitoneally and salt was given with tap water (1%) for 4 weeks. Novokinin was administered intraperitoneally for the last 2 weeks. Blood pressures were measured using the tail-cuff method and enzyme levels by real-time polymerase chain reaction in aortic tissues. Results: Blood pressure increased significantly in hypertensive rats. Novokinin reduced the blood pressure in the hypertensive group. While the contractile responses to increasing doses of angiotensin II were increased, vascular reactivity (Emax) and sensitivity (EC50) to acetylcholine were decreased in hypertensive rats. In novokinin-treated hypertensive groups, the EC50 value decreased and the Emax value for acetylcholine significantly increased. The levels of Rho kinase and PRMT expression increased and the level of eNOS expression decreased in the hypertensive group. In novokinin-treated rats, ADMA, NADPH oxidase, and Rho kinase tended to decreased, but these changes did not reach statistical significance. Conclusion: Although further studies are needed to determine its effectiveness, the AT2 agonist novokinin may be a novel agent that is promising in terms of protective effects for the treatment of hypertension.

PDF

___

1. Muller DN, Luft FC. Direct renin inhibition with aliskiren in hypertension and target organ damage. Clin J Am Soc Nephrol 2006; 1: 221-228.
2. Ilhan S, Oktar S, Sahna E, Aksulu HE. Salt and nitric oxide inhibition induced hypertension: the role of prostacycline and 8-isoprostane. Clin Exp Hypertens 2011; 33: 84-88.
3. Epstein BJ. Aliskiren and valsartan combination therapy for the management of hypertension. Vasc Health Risk Manag 2010; 6: 711-722.
4. Savoia C, Tabet F, Yao G, Schiffrin EL, Touyz RM. Negative regulation of RhoA/Rho kinase by angiotensin II type 2 receptor in vascular smooth muscle cells: role in angiotensin II-induced vasodilation in stroke-prone spontaneously hypertensive rats. J Hypertens 2005; 23: 1037-1045.
5. Volpe M, Musumeci B, De Paolis P, Savoia C, Morganti A. Angiotensin II AT2 receptor subtype: an uprising frontier in cardiovascular disease? J Hypertens 2003; 21: 1429-1443.
6. Gelosa P, Pignieri A, Fandriks L, de Gasparo M, Hallberg A, Banfi C, Castiglioni L, Turolo L, Guerrini U, Tremoli E et al. Stimulation of AT2 receptor exerts beneficial effects in strokeprone rats: focus on renal damage. J Hypertens 2009; 27: 2444- 2451.
7. Berry C, Touyz R, Dominiczak AF, Webb RC, Johns DG. Angiotensin receptors: signaling, vascular pathophysiology, and interactions with ceramide. Am J Physiol Heart Circ Physiol 2001; 281: 2337-2365.
8. Maas R. Pharmacotherapies and their influence on asymmetric dimethylargine (ADMA). Vasc Med 2005; 10 (Suppl. 1): 49-57. 9. Matsuguma K, Ueda S, Yamagishi S, Matsumoto Y, Kaneyuki U, Shibata R, Fujimura T, Matsuoka H, Kimoto M, Kato S et al. Molecular mechanism for elevation of asymmetric dimethylarginine and its role for hypertension in chronic kidney disease. J Am Soc Nephrol 2006; 17: 2176-2183.
10. Zhou Q, Gensch C, Liao JK. Rho-associated coiled-coilforming kinases (ROCKs): potential targets for the treatment of atherosclerosis and vascular disease. Trends Pharmacol Sci 2011; 32: 167-173.
11. Sartori C, Lepori M, Scherrer U. Interaction between nitric oxide and the cholinergic and sympathetic nervous system in cardiovascular control in humans. Pharmacol Ther 2005; 106: 209-220.
12. Pollock DM, Rekito A. Hypertensive response to chronic NO synthase inhibition is different in Sprague-Dawley rats from two suppliers. Am J Physiol 1998; 275: 1719-1723.
13. Yamada SS, Sassaki AL, Fujihara CK, Malheiros DM, De Nucci G, Zatz R. Effect of salt intake and inhibitor dose on arterial hypertension and renal injury induced by chronic nitric oxide blockade. Hypertension 1996; 27: 1165-1172.
14. De Gennaro Colonna V, Fioretti S, Rigamonti A, Bonomo S, Manfredi B, Muller EE, Berti F, Rossoni G. Angiotensin II type 1 receptor antagonism improves endothelial vasodilator function in L-NAME-induced hypertensive rats by a kinindependent mechanism. J Hypertens 2006; 24: 95-102.
15. Forstermann U. Nitric oxide and oxidative stress in vascular disease. Pflugers Arch 2010; 459: 923-939.
16. Veresh Z, Racz A, Lotz G, Koller A. ADMA impairs nitric oxide-mediated arteriolar function due to increased superoxide production by angiotensin II-NAD(P)H oxidase pathway. Hypertension 2008; 52: 960-966.
17. Van Assche R, Temmerman L, Dias DA, Boughton B, Boonen K, Braeckman BP, Schoofs L, Roessner U. Metabolic profiling of a transgenic Caenorhabditis elegans Alzheimer model. Metabolomics 2015; 11: 477-486.
18. Antoniades C, Shirodaria C, Leeson P, Antonopoulos A, Warrick N, Van-Assche T, Cunnington C, Tousoulis D, Pillai R, Ratnatunga C et al. Association of plasma asymmetrical dimethylarginine (ADMA) with elevated vascular superoxide production and endothelial nitric oxide synthase uncoupling: implications for endothelial function in human atherosclerosis. Eur Heart J 2009; 30: 1142-1150.
19. Satoh K, Fukumoto Y, Shimokawa H. Rho-kinase: important new therapeutic target in cardiovascular diseases. Am J Physiol Heart Circ Physiol 2011; 301: H287-296.
20. Yamada Y, Yamauchi D, Yokoo M, Ohinata K, Usui H, Yoshikawa M. A potent hypotensive peptide, novokinin, induces relaxation by AT2- and IP-receptor-dependent mechanism in the mesenteric artery from SHRs. Biosci Biotechnol Biochem 2008; 72: 257-259.
21. Yoshikawa M, Ohinata K, Yamada Y. The pharmacological effects of novokinin; a designed peptide agonist of the angiotensin AT2 receptor. Curr Pharm Des 2013; 19: 3009- 3012.
22. Kalliovalkama J, Jolma P, Tolvanen JP, Kähönen M, HutriKähönen N, Wu X, Holm P, Pörsti I. Arterial function in nitric oxide-deficient hypertension: influence of long-term angiotensin II receptor antagonism. Cardiovasc Res 1999; 42: 773-782.
23. Lopez RM, Ortiz CS, Ruiz A, Velez JM, Castillo C, Castillo EF. Impairment of smooth muscle function of rat thoracic aorta in an endothelium-independent manner by long-term administration of N(G)-nitro-L-arginine methyl ester. Fundam Clin Pharmacol 2004; 18: 669-677.
24. Yayama K, Okamoto H. Angiotensin II-induced vasodilation via type 2 receptor: role of bradykinin and nitric oxide. Int Immunopharmacol 2008; 8: 312-318.
25. De Gennaro Colonna V, Rigamonti A, Fioretti S, Bonomo S, Manfredi B, Ferrario P, Bianchi M, Berti F, Muller EE, Rossoni G. Angiotensin-converting enzyme inhibition and angiotensin AT1-receptor antagonism equally improve endothelial vasodilator function in L-NAME-induced hypertensive rats. Eur J Pharmacol 2005; 516: 253-259.
26. Takai S, Kirimura K, Jin D, Muramatsu M, Yoshikawa K, Mino Y, Miyazaki M. Significance of angiotensin II receptor blocker lipophilicities and their protective effect against vascular remodeling. Hypertens Res 2005; 28: 593-600.
27. Park YM, Lim BH, Touyz RM, Park JB. Expression of NAD(P) H oxidase subunits and their contribution to cardiovascular damage in aldosterone/salt-induced hypertensive rat. J Korean Med Sci 2008; 23: 1039-1045.
28. Wirth A. Rho kinase and hypertension. Biochim Biophys Acta 2010; 1802: 1276-1284.
29. Seko T, Ito M, Kureishi Y, Okamoto R, Moriki N, Onishi K, Isaka N, Hartshorne DJ, Nakano T. Activation of RhoA and inhibition of myosin phosphatase as important components in hypertension in vascular smooth muscle. Circ Res 2003; 92: 411-418.
30. Stegbauer J, Coffman TM. New insights into angiotensin receptor actions: from blood pressure to aging. Curr Opin Nephrol Hypertens 2011; 20: 84-88.