An Intracellular Matrix Metalloproteinase-2 Isoform Induces Tubular Regulated Necrosis: Implications for Acute Kidney Injury
Published online on March 22, 2017
Abstract
Acute kidney injury (AKI) causes severe morbidity, mortality, and chronic kidney disease (CKD). Mortality is particularly marked in the elderly and with pre-existing CKD. Oxidative stress is a common theme in models of AKI induced by ischemia/reperfusion (I/R) injury. We recently characterized an intracellular isoform of matrix metalloproteinase-2 (MMP-2) induced by oxidative stress-mediated activation of an alternate promoter in the first intron of the MMP-2 gene. This generates an N-terminal truncated MMP-2 isoform (NTT-MMP-2) that is intracellular and associated with mitochondria. The NTT-MMP-2 isoform is expressed in kidneys of 14 month old mice and in a mouse model of coronary atherosclerosis and heart failure with CKD. We recently determined that NTT-MMP-2 is induced in human renal transplants with delayed graft function and correlated with tubular cell necrosis. To determine mechanism(s) of action, we generated proximal tubule cell-specific NTT-MMP-2 transgenic mice. While morphologically normal at the light microscopic level at 4 months, ultrastructural studies revealed foci of tubular epithelial cell necrosis, the mitochondrial permeability transition and mitophagy. To determine if NTT-MMP-2 expression enhances sensitivity to I/R injury, we performed unilateral I/R to induce mild tubular injury in wild type mice. In contrast, expression of the NTT-MMP-2 isoform resulted in a dramatic increase in tubular cell necrosis, inflammation and fibrosis. NTT-MMP-2 mice had enhanced expression of innate immunity genes and release of danger-associated molecular pattern molecules. We conclude that NTT-MMP-2 "primes" the kidney to enhanced susceptibility to I/R injury via induction of mitochondrial dysfunction. NTT-MMP-2 may be a novel AKI treatment target.