CD36 Is a Matrix Metalloproteinase-9 Substrate That Stimulates Neutrophil Apoptosis and Removal During Cardiac Remodeling

Circ Cardiovasc Genet. 2016 Feb;9(1):14-25. doi: 10.1161/CIRCGENETICS.115.001249. Epub 2015 Nov 17.

Abstract

Background: After myocardial infarction, the left ventricle undergoes a wound healing response that includes the robust infiltration of neutrophils and macrophages to facilitate removal of dead myocytes as well as turnover of the extracellular matrix. Matrix metalloproteinase (MMP)-9 is a key enzyme that regulates post-myocardial infarction left ventricular remodeling.

Methods and results: Infarct regions from wild-type and MMP-9 null mice (n=8 per group) analyzed by glycoproteomics showed that of 541 N-glycosylated proteins quantified, 45 proteins were at least 2-fold upregulated or downregulated with MMP-9 deletion (all P<0.05). Cartilage intermediate layer protein and platelet glycoprotein 4 (CD36) were identified as having the highest fold increase in MMP-9 null mice. By immunoblotting, CD36 but not cartilage intermediate layer protein decreased steadily during the time course post-myocardial infarction, which identified CD36 as a candidate MMP-9 substrate. MMP-9 was confirmed in vitro and in vivo to proteolytically degrade CD36. In vitro stimulation of day 7 post-myocardial infarction macrophages with MMP-9 or a CD36-blocking peptide reduced phagocytic capacity. Dual immunofluorescence revealed concomitant accumulation of apoptotic neutrophils in the MMP-9 null group compared with wild-type group. In vitro stimulation of isolated neutrophils with MMP-9 decreased neutrophil apoptosis, indicated by reduced caspase-9 expression.

Conclusions: Our data reveal a new cell-signaling role for MMP-9 through CD36 degradation to regulate macrophage phagocytosis and neutrophil apoptosis.

Keywords: extracellular matrix; immunoblotting; infarction; inflammation; myocardial; proteomics.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Apoptosis*
  • CD36 Antigens / genetics
  • CD36 Antigens / metabolism*
  • Female
  • Gene Expression Regulation, Enzymologic
  • Heart Ventricles / metabolism
  • Heart Ventricles / pathology
  • Male
  • Matrix Metalloproteinase 9 / biosynthesis*
  • Matrix Metalloproteinase 9 / genetics
  • Mice
  • Mice, Mutant Strains
  • Myocardial Infarction / genetics
  • Myocardial Infarction / metabolism*
  • Myocardial Infarction / pathology
  • Myocytes, Cardiac / metabolism*
  • Myocytes, Cardiac / pathology
  • Neutrophils / metabolism*
  • Proteolysis*
  • Signal Transduction

Substances

  • CD36 Antigens
  • Matrix Metalloproteinase 9
  • Mmp9 protein, mouse