Interruption of endothelin signaling modifies membrane type 1 matrix metalloproteinase activity during ischemia and reperfusion

The matrix metalloproteinases ( MMPs), in particular, membrane type 1 MMP (MT1-MMP), are increased in the context of myocardial ischemia and reperfusion (I/R) and likely contribute to myocardial dysfunction. One potential upstream induction mechanism for MT1-MMP is endothelin (ET) release and subsequent protein kinase C (PKC) activation. Modulation of ET and PKC signaling with respect to MT1-MMP activity with I/R has yet to be explored. Accordingly, this study examined in vivo MT1-MMP activation during I/R following modification of ET signaling and PKC activation. With the use of a novel fluorogenic microdialysis system, myocardial interstitial MT1-MMP activity was measured in pigs ( 30 kg; n = 9) during I/R (90 min I/120 min R). Local ETA receptor antagonism (BQ-123, 1 mu M) and PKC inhibition (chelerythrine, 1 mu M) were performed in parallel microdialysis probes. MT1-MMP activity was increased during I/R by 122 +/- 10% ( P < 0.05) and was unchanged from baseline with ET antagonism and/or PKC inhibition. Selective PKC isoform induction occurred such that PKC-beta II increased by 198 +/- 31% ( P < 0.05). MT1-MMP phosphothreonine, a putative PKC phosphorylation site, was increased by 121 +/- 8% ( P < 0.05) in the I/R region. These studies demonstrate for the first time that increased interstitial MT1-MMP activity during I/ R is a result of the ET/ PKC pathway and may be due to enhanced phosphorylation of MT1-MMP. These findings identify multiple potential targets for modulating a local proteolytic pathway operative during I/R.