Overexpression of brain natriuretic peptide facilitates neutrophil infiltration and cardiac matrix metalloproteinase-9 expression after acute myocardial infarction.
BACKGROUND
Recent clinical trials have shown that systemic infusion of nesiritide, a recombinant human brain natriuretic peptide (BNP), improves hemodynamic parameters in acutely decompensated hearts. This suggests that BNP exerts a direct cardioprotective effect and might thus be a useful therapeutic agent with which to treat acute myocardial infarction (MI). In the present study, we used BNP-transgenic (BNP-Tg) mice with elevated plasma BNP to determine whether and how BNP contributes to left ventricular remodeling and healing after MI.


RESULTS
We examined the accumulation of neutrophils and the expression and activation of matrix metalloproteinase (MMP)-9 in the ventricles of male BNP-Tg mice and their nontransgenic (non-Tg) littermates during the early phase after acute MI. The numbers of neutrophils infiltrating the infarcted area were significantly increased in BNP-Tg mice 3 days after MI. In addition, both the gene expression and zymographic activity of MMP-9, but not MMP-2, were significantly higher in BNP-Tg than non-Tg mice. Double immunostaining revealed that neutrophils are the main source of the MMP-9, although doxycycline, an MMP inhibitor, had no effect on neutrophil infiltration of the infarcted area in BNP-Tg mice.


CONCLUSIONS
These results demonstrate that elevated plasma BNP facilitates neutrophil infiltration of the infarcted area after MI and increases the activity of the MMP-9 they produce. This suggests that BNP plays a key role in the processes of extracellular matrix remodeling and wound-healing during the early phase after acute MI.
Kawakami
Rika
R
Department of Medicine and Clinical Science, Kyoto University Graduate School of Medicine, Kyoto, Japan.
Saito
Yoshihiko
Y
Kishimoto
Ichiro
I
Harada
Masaki
M
Kuwahara
Koichiro
K
Takahashi
Nobuki
N
Nakagawa
Yasuaki
Y
Nakanishi
Michio
M
Tanimoto
Keiji
K
Usami
Satoru
S
Yasuno
Shinji
S
Kinoshita
Hideyuki
H
Chusho
Hideki
H
Tamura
Naohisa
N
Ogawa
Yoshihiro
Y
Nakao
Kazuwa
K
D000818:Animals; D002634:Chemotaxis, Leukocyte / Q000502:physiology*; D004318:Doxycycline / Q000494:pharmacology / Q000627:therapeutic use; D004789:Enzyme Activation; D004790:Enzyme Induction / Q000502:physiology; D020869:Gene Expression Profiling; D006352:Heart Ventricles; D008297:Male; D020780:Matrix Metalloproteinase 9 / Q000096:biosynthesis* / Q000235:genetics; D051379:Mice; D008822:Mice, Transgenic; D009203:Myocardial Infarction / Q000097:blood / Q000473:pathology*; D020097:Natriuretic Peptide, Brain / Q000096:biosynthesis / Q000097:blood / Q000235:genetics / Q000502:physiology*; D009504:Neutrophils / Q000201:enzymology / Q000502:physiology*; D009195:Peroxidase / Q000032:analysis; D011993:Recombinant Fusion Proteins / Q000097:blood / Q000502:physiology
D011993:Recombinant Fusion Proteins; D020097:Natriuretic Peptide, Brain; D009195:Peroxidase; D020780:Matrix Metalloproteinase 9; D004318:Doxycycline