| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
|
FJ
EXPRESS SUMMARY ARTICLE The Full-length version of this article is also available, published online April 28, 2005 as doi:10.1096/fj.04-3508fje. |
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
,1,1
,2
* INSERM U652/367, Paris, France;
Département de Pharmacologie, Faculté de Médecine Paris-Sud, Le Kremlin-Bicêtre, France; and
INSERM U388, IFR31, Institut Louis Bugnard, Toulouse, France
2 Correspondence: E-mail: christine.giudicelli{at}kb.u-psud.fr
SPECIFIC AIMS
We tested the hypothesis that tissue kallikrein (TK), a serine protease and a major kinin-forming enzyme, has a cardioprotective role in myocardial ischemia. We studied TK-deficient mice and wild-type littermates, in an in vivo model of ischemia-reperfusion injury, with and without ischemic preconditioning (IPC) or ACE inhibitor treatment. We also attempted to establish the respective roles of each of the two kinin receptors, B1 and B2, in these cardioprotective effects, by using specific pharmacological blockers, as well as B2 receptor-deficient mice.
PRINCIPAL FINDINGS
1. The cardioprotective effect of IPC is reduced by 39% in TK-deficient mice
The area of myocardium placed at risk by left anterior coronary artery occlusion was similar in TK–/– and wild-type mice. Ischemia-reperfusion (30 min coronary occlusion, followed by 180 min reperfusion) induced similar infarcts in wild-type and TK–/– mice. IPC (3 cycles of 3 min occlusion followed by 5 min reperfusion) reduced infarct size by 65% in wild-type mice, and by 40% in TK-deficient mice (P<0.05, TK–/– vs. wild-type, Fig. 1
A). This loss of cardioprotection was observed in the absence of any preexisting anatomical and hemodynamic abnormalities in TK-deficient mice
|
2. The cardioprotective effect of ramiprilat, an ACE inhibitor, is abolished in TK-deficient mice
Ramiprilat injection (50 µg/kg IV, 5 min before reperfusion) reduced infarct size by 29% during ischemia-reperfusion (30 min coronary occlusion, followed by 180 min reperfusion) in wild-type mice, but in TK-deficient mice, ramiprilat had no effect (Fig. 1B
). Ramiprilat had no detectable effect on heart rate and blood pressure in these experimental conditions.
3. The B2 receptor is the only kinin receptor involved in the cardioprotective effects of IPC and ramiprilat in normal mice. In B2-deficient mice however, the B1 receptor is induced and takes over this function of the B2 receptor
In wild-type mice, blockade of the B2 receptor with the specific antagonist icatibant (500 µg/kg IV 5 min before IPC, or 30 min before ramiprilat) reduced the beneficial effects of IPC by 45% and abolished the effect of ramiprilat. Infarct sizes in icatibant-treated wild-type mice were the same as in TK-deficient mice. The specific B1 antagonist SSR 240612 (300 µg/kg IV 5 min before IPC or 30 min before ramiprilat) had no effect alone or in combination with icatibant. To confirm the involvement of the B2 receptor, B2 receptor-deficient mice were studied. Unexpectedly, these mice responded like wild-type mice to IPC or ramiprilat treatment. However, treatment of the B2-deficient mice with SSR 240612 suppressed the cardioprotective effects of IPC and ramiprilat.
4. Both B2 and B1 receptor cardiac mRNA levels increase during ischemia-reperfusion and IPC
B2 and B1 receptor mRNAs were quantified in the heart by real time PCR. In wild-type mice, both B2 and B1 mRNA levels increased by 130 and 250%, respectively, during ischemia-reperfusion, and to a significantly greater extent (350 and 535%) during IPC + ischemia-reperfusion. In B2-deficient mice, B1 mRNA level was elevated in basal conditions compared with wild-type mice (Fig. 2
).
|
CONCLUSIONS AND SIGNIFICANCE
Ischemic heart disease is a leading cause of mortality in developed countries. The deleterious and the protective mechanisms activated in the heart by ischemia are not all known, but this question can be studied in animal models. Ischemic preconditioning (IPC) enhances the ability of the heart to tolerate ischemia-reperfusion injury in animals, and probably plays a beneficial role in human coronary heart disease. Ischemia-reperfusion injury can also be prevented pharmacologically, by using ACE inhibitors, which suppress the formation of angiotensin II and reduce kinin inactivation.
We show here for the first time that tissue kallikrein plays a critical role in the cardioprotection afforded by both IPC and ACE inhibitors in ischemia-reperfusion. Data obtained by a combined genetic and pharmacological approach indicate that the tissue kallikrein-kinin system accounts for 
one-third of the infarct size reducing effect of IPC. It entirely mediates the cardioprotective effects of ACE inhibition in ischemia-reperfusion injury. The study identifies TK as the major enzyme responsible for the activation of the kallikrein kinin system in the ischemic heart, and suggests that plasma kallikrein and other potential kinin-forming enzymes play little, if any, role in this activation (Fig. 3
). Partial genetic deficiency in TK activity occurs in humans as the result of an amino-acid mutation, and affects 5–7% of white subjects. The present data obtained in TK-deficient mice suggest that the TK-deficient subjects may be at increased risk for myocardial infarction, a hypothesis that needs to be tested in clinical studies. We also show that an activation of the kallikrein-kinin system occurs at the receptor level in the ischemic heart. The B2 receptor is generally considered as being constitutively synthesized whereas the B1 receptor is induced by ischemia. The large increase in B2 receptor gene expression during ischemia-reperfusion and its potentiation by ischemic preconditioning is an unexpected finding, and its mechanism remains unknown. This receptor entirely mediates the cardioprotective effects of the kallikrein-kinin system in normal mice in our experimental conditions. These data suggest a potential therapeutic approach based on B2 receptor agonists.
|
FOOTNOTES
1 These authors contributed equally to this work. 
To read the full text of this article, go to http://www.fasebj.org/cgi/doi/10.1096/fj.04-3508fje; doi: 10.1096/fj.04-3508fje
This article has been cited by other articles:
|
|
 |
|
  D. C. Isbell, S. Voros, Z. Yang, J. M. DiMaria, S. S. Berr, B. A. French, F. H. Epstein, S. P. Bishop, H. Wang, R. J. Roy, et al. Interaction between bradykinin subtype 2 and angiotensin II type 2 receptors during post-MI left ventricular remodeling Am J Physiol Heart Circ Physiol, December 1, 2007; 293(6): H3372 - H3378. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 E. Messadi-Laribi, V. Griol-Charhbili, A. Pizard, M.-P. Vincent, D. Heudes, P. Meneton, F. Alhenc-Gelas, and C. Richer Tissue Kallikrein Is Involved in the Cardioprotective Effect of AT1-Receptor Blockade in Acute Myocardial Ischemia J. Pharmacol. Exp. Ther., October 1, 2007; 323(1): 210 - 216. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. Kakoki, R. W. McGarrah, H.-S. Kim, and O. Smithies Bradykinin B1 and B2 receptors both have protective roles in renal ischemia/reperfusion injury PNAS, May 1, 2007; 104(18): 7576 - 7581. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
