Thromb Haemost 2005; 94(05): 1012-1018
DOI: 10.1160/TH05-02-0125
Platelets and Blood Cells
Schattauer GmbH

Biphasic effects of angiotensin II and receptor antagonism on aggregability and protein kinase C phosphorylation in human platelets

Kimiaki Utsugisawa
1   Department of Neurology, Iwate Medical University, Morioka, Japan
,
Hideki Kizawa
1   Department of Neurology, Iwate Medical University, Morioka, Japan
,
Yuriko Nagane
1   Department of Neurology, Iwate Medical University, Morioka, Japan
,
Ryushi Kondoh
1   Department of Neurology, Iwate Medical University, Morioka, Japan
,
Yoko Iwa
1   Department of Neurology, Iwate Medical University, Morioka, Japan
,
Hitomi Akutsu
2   High-Tech Research Center, Iwate Medical University, Morioka, Japan
,
Hideo Tohgi
1   Department of Neurology, Iwate Medical University, Morioka, Japan
,
Yasuo Terayama
1   Department of Neurology, Iwate Medical University, Morioka, Japan
› Author Affiliations
Further Information

Publication History

Received: 20 February 2005

Accepted after resubmission: 22 August 2005

Publication Date:
14 December 2017 (online)

Summary

In order to define the role of angiotensin II (AngII) receptor subtypes, AT1 and AT2, in platelet activation, we examined the effects of AngII and receptor antagonists on both aggregability and phosphorylation status of protein kinase C (PKC) isoforms in human platelets obtained from 56 healthy volunteers. AngII promoted both spontaneous and agonist (collagen and ADP) stimulated platelet aggregation at concentrations of 10 nM or less, but the promotion effects were lost at 100 nM. Antagonism of AT1 receptor inhibited the promotion effects of AngII at 10 nM or less. On the other hand, antagonism of AT2 receptor enhanced platelet aggregability modestly with AngII at 10 nM or less, and markedly with 100 nM AngII. Furthermore, with 10 nM AngII, phospho-PKCα/βII expression in platelets was increased after collagen stimulation and was inhibited by antagonism of AT1 receptor. With 100 nM AngII, expression levels of phospho-PKCα/ βII remained low even after collagen stimulation but were markedly enhanced by antagonism of AT2 receptor. These findings suggest that at 10 nM or below, AngII promotes aggregability and PKC phosphorylation in human platelets through the AT1 receptor, which can be inhibited by AT1 receptor antagonists, but at higher concentrations, the promotion effects were lost through the opposing action of the AT2 receptor. The present study may provide an additional mechanism for AT1 receptor antagonism, which would provide clinical benefit to patients with stroke or cardiovascular disease accompanied by hypertension.

 
  • References

  • 1 Ito H, Takemori K, Suzuki T. Role of angiotensin II type 1 receptor in the leucocytes and endothelial cells of brain microvessels in the pathogenesis of hypertensive cerebral injury. J Hypertension 2001; 19: 591-7.
  • 2 Ito T, Yamakawa H, Bregonzio C. et al. Protection against ischemia and improvement of cerebral blood flow in genetically hypertensive rats by chronic pretreatment with an angiotensin II AT1 antagonist. Stroke 2002; 33: 2297-303.
  • 3 Nishimura Y, Ito T, Saavedra JM. Angiotensin II AT1 blockade normalizes cerebrovascular autoregulation and reduces cerebral ischemia in spontaneously hypertensive rats. Stroke 2000; 31: 2478-86.
  • 4 Yamanaka H, Jezova M, Ando H. et al. Normalization of endothelial and inducible nitric oxide synthase expression in brain microvessels of spontaneously hypertensive rats by angiotensin II AT1 receptor inhibition. J Cereb Blood Flow Metab 2003; 23: 371-80.
  • 5 Lorell BH. Role of angiotensin AT1 and AT2 receptors in cardiac hypertrophy and disease. Am J Cardiol 1999; 83: 48H-42H.
  • 6 Dai W-J, Funk A, Herdegen T. et al. Blockade of central angiotensin AT1 receptors improves neurological outcome and reduces expression of AP-1 transcription factors after focal brain ischemia in rats. Stroke 1999; 30: 2391-9.
  • 7 Walther T, Olah L, Harms C. et al. Ischemic injury in experimental stroke depends on angiotensin II. FASEB J 2002; 16: 169-76.
  • 8 Utsugisawa K, Nagane Y, Utsugisawa T. et al. Candesartan prevents angiotensin II-induced facilitation of hypoxic neuronal damage through PKCδ inhibition. Mol Brain Res 2005; 135: 134-40.
  • 9 Ding Y-A, Mac Intire E, Kenyon CJ. et al. Angiotensin II effects on platelet function. J Hypertension 1985; 3 (03) S251-S253.
  • 10 Montón M, Jiménez A, Núñez A. et al. Comparative effects of angiotensin II AT-1-type receptor antagonists in vitro on human platelet activation. J Cardiovasc Pharmacol 2000; 35: 906-13.
  • 11 Siess W, Lapetina EG. Ca2+ mobilization primes protein kinase C in human platelets: Ca2+ and phorbol ester stimulate platelet aggregation and secretion synergistically through protein kinase C. Biochem J 1988; 255: 309-18.
  • 12 Gerrard JM, Beattie LL, Park J. et al. A role for protein kinase C in the membrane fusion necessary for platelet granule secretion. Blood 1989; 74: 2405-13.
  • 13 Walker TR, Watson SP. Synergy between Ca2+ and protein kinase C is the major factor in determining the level of secretion from human platelets. Biochem J 1993; 289: 277-82.
  • 14 Pulcinelli FM, Ashby B, Gazzaniga PP. et al. Protein kinase C activation is not a key step in ADP-mediated exposure of fibrinogen receptors on human platelets. FEBS lett 1995; 364: 87-90.
  • 15 Toullec D, Pianetti P, Coste H. et al. The bisindolylmaleimide GF 109203X is a potent and selective inhibitor of protein kinase C. J Biol Chem 1991; 266: 15771-81.
  • 16 Crosby D, Poole AW. Physical and functional interaction between protein kinase Cδ and Fyn tyrosine kina-se in human platelets. J Biol Chem 2003; 278: 24533-41.
  • 17 Tohgi H, Takahashi H, Kashiwaya M. et al. Effect of plasma fibrinogen concentration on inhibition of platelet aggregation after ticlopidine compared with aspirin. Stroke 1994; 25: 2017-21.
  • 18 Tohgi H, Takahashi H, Watanabe K. et al. Development of large platelet aggregates from small aggregates as determined by laser-light scattering: effects of aggregant concentration and antiplatelet medication. Thromb Haemostasis 1996; 75: 838-43.
  • 19 Satoh K, Ozaki Y, Qi R. et al. Factors that affect the size of platelet aggregates in epinephrine-induced activation: a study using the particle counting method based upon light scattering. Thromb Res 1996; 81: 515-23.
  • 20 Serebruany VL, Malinin AI, Lowry DR. et al. Effects of valsartan and valeryl 4-hydroxy valsartan on human platelets: a possible additional mechanism for clinical benefits. J Cardiovasc Pharmacol 2004; 43: 677-84.
  • 21 Li W, Zhang J, Bottaro DP. et al. Identification of serine 643 of protein kinase C-δ as an important autophosphorylation site for its enzymatic activity. J Biol Chem 1997; 272: 24550-5.
  • 22 Murugappan S, Tuluc F, Dorsam RT. et al. Differential role of protein kinase C isoform in agonist-induced dense granule secretion in human platelets. J Biol Chem 2004; 279: 2360-7.
  • 23 Santucci A, Ferri C, Luparini RL. et al. Effect of angiotensin converting enzyme inhibition on platelet angiotensin II content. Am J Med 1988; 84 (Suppl 3A) 119-21.
  • 24 Motley ED, Eguchi K, Gardner C. et al. Insulin-induced Akt activation is inhibited by angiotensin II in the vasculature through protein kinase C-α. Hypertension 2003; 41: 775-80.
  • 25 Ishii K, Takekoshi K, Shibuya S. et al. Angiotensin subtype-2 receptor (AT2) negatively regulates subtype- 1 receptor (AT1) in signal transduction pathways in cultured porcine adrenal medullary chromaffin cells. J Hypertension 2001; 19: 1991-9.
  • 26 Horiuchi M, Hayashida W, Akishita M. et al. Stimulation of different subtypes of angiotensin II receptors, AT1 and AT2 receptors, regulates STAT activation by negative crosstalk. Circ Res 1999; 84: 876-82.
  • 27 Huang X-C, Richards EM, Sumners C. Mitogenactivated protein kinases in rat brain neuronal cultures are activated by angiotensin II type1 receptors and inhibited by angiotensin II type2 receptors. J Biol Chem 1996; 271: 15635-41.
  • 28 Kumar V, Knowle D, Gavini N. et al. Identification of the region of AT2 receptor needed for inhibition of the AT1 receptor-mediated inositol 1,4,5-triphosphate generation. FEBS Lett 2002; 532: 379-86.
  • 29 Miura S, Karnik SS. Angiotensin II type1 and type2 receptors bind angiotensin II through different types of epitope recognition. J Hypertension 1999; 17: 397-404.
  • 30 Yoshioka A, Shirakawa R, Nishioka H. et al. Identification of protein kinase C-α as an essential, but not sufficient, cytosolic factor for Ca2+-induced α- and dense-core granule secretion in platelets. J Biol Chem 2001; 276: 39379-85.
  • 31 The ACCESS Study Group. The ACCESS study. Evaluation of acute candesartan cilexetil therapy in stroke survivors. Stroke 2003; 34: 1699-703.