Abstract 604: Loss of PCPE2 Alternates Bone Marrow-derived Macrophage Functions

Procollagen C-endopeptidase enhancer 2 (PCPE2), an extracellular matrix protein was recently found to positively correlate with triglyceride storage in response to Western diet (WD) consumption and obesity in mice (p< 2.5 x 10 -25 ) and in humans (p<1.0 x 10 -5 ). Our lab showed that deficiency in PCPE2 promoted the development of atherosclerosis in WD-fed Ldlr -/- Pcpe2 -/- vs. Ldlr -/- mice. Cholesterol levels in PCPE2-deficient mice decreased in adipose tissue while increased in plasma. This was accompanied by increased atherosclerotic lesion formation. Interestingly, a significant increase of macrophage infiltration into the atherosclerotic lesions was also observed in the PCPE2-deficient mice. To probe the link between PCPE2 and macrophage functions, bone marrow-derived macrophages (BMDM) from Ldlr -/- and Ldlr -/- Pcpe2 -/- mice were used. Flow cytometry analysis of bone marrow (BM) cell surface markers by CyTOF showed an overall reduction in CD45 + cells in PCPE2-knockout BM. In addition, there were reduced neutrophil progenitor cells as well as neutrophils but increased monocytes in PCPE2-deficient BM. These BM were harvested and induced into BMDM, some of which were further polarized into M1 or M2 phenotypes. Differentiation and polarization of macrophages from BM were confirmed by flow cytometry and RT-PCR. Surprisingly, CD36 expressions were greatly suppressed (> 8 fold) in PCPE2-knockout M0, M1 and M2 BMDM. This was consistent with the CyTOF data showing a trend of reduced cell surface CD36 levels in PCPE2-knockout BM F4/80 hi macrophages. Further, Western Blot analysis of BMDM protein extracts confirmed that CD36 protein was almost diminished in PCPE2-knockout BMDM. Interestingly, RNA array analysis of BM showed a reduced PPARγ expression in PCPE2-knockout mice, indicating the reduced CD36 expression may due to the suppressed PPARγ expression, an upstream transcription factor of CD36. In summary, our studies demonstrate that loss of PCPE2 results in loss of CD36 in BMDM, which may alternate the functions of macrophages.