Ischemic Preconditioning Preserves Dystrophin Through Matrix Metalloproteinase-2 Inhibition

pp. 7-13

Abstract

Background
Ischemia/reperfusion injury produces cell death through different pathways, some of which induce plasma membrane rupture. In cardiac cells, dystrophin and spectrin provide cell membrane stability and link the intracellular and extracellular environments. Dystrophin breakdown causes membrane fragility. Ischemic preconditioning has been suggested to attenuate this injury, but the mechanism is still unknown.

Objective
To determine whether ischemic preconditioning prevents dystrophin breakdown through matrix metalloproteinase-2 (MMP-2) inhibition. 

Methods
Isolated rabbit hearts were treated as follows: G1 (n=5): 30 min perfusion (Nx); G2 (n=6): 30 min global ischemia (GI) without reperfusion; G3: same as G2, followed by 180 min reperfusion (I/R); G4 (n=5): doxycycline (MMP inhibitor) before GI; G5 ( n=6): normoxic hearts treated with SIN-1 (which stimulates ONOO production) with 30 min left ventricular function monitoring; G6 (n=5): doxycycline during 5 min, before SIN-1 administration; G7 and G8 (n=5): ischemic preconditioning (n=5) before 30 min GI with/without reperfusion, respectively.

Results
Dystrophin expression decreased during ischemia, reaching 21% of control values (p < 0.05); spectrin expression remained unchanged. MMP-2 activity increased 71% during ischemia compared to control values (p < 0.05). Doxycycline administered
before ischemia prevented dystrophin breakdown. In normoxic hearts, SIN-1 increased thiobarbituric acid reactive substances (TBARS) by 33% (p<0.05) and MMP-2 activity by 36% (p<0.05), and reduced dystrophin expression to 23% of control values (p<0.05). Ischemic preconditioning attenuated dystrophin breakdown significantly by inhibiting MMP-2 activity.

Conclusions
Activation of MMP-2 due to increased oxidative stress is responsible for dystrophin breakdown. Ischemic preconditioning attenuates dystrophin breakdown by inhibiting MMP-2 activity.