Abstract TP404: A Novel Adipokine DPPIV Induces Inflammation and Apoptosis of Carotid Artery Smooth Muscle Cells: Implications for Atherosclerotic Plaque Instability

Abstract

Background: Carotid Atherosclerotic (CA) plaque rupture is associated with ischemic stroke. Smooth muscle cells (SMC) play key role in plaque development. SMC also produce collagen fibers and maintain the fibrous cap thickness and strength, and SMC apoptosis and inflammation can lead to plaque rupture. Molecular mechanisms leading to plaque instability and stroke are not completely understood. Our study has shown that an adipokine dipeptidyl peptidase (DPPIV) is significantly upregulated in post-stroke rat brain, and in the plasma of over 75% of CA patients, suggesting a role for DPPIV in CA and stroke. In this study, we examined the effects of DPPIV on SMC viability, apoptosis, and identified responsible signaling pathways. Methods: Mouse carotid artery SMC were exposed to oxygen glucose deprivation (OGD). Cells were treated with either physiological (200-500 ng/ml) or high (1000-2000 ng/ml) dose of DPPIV. Using transcriptome array, we examined the expression profile of apoptotic and inflammatory pathway specific genes in these cells. DPPIV levels were examined by PCR and immunofluorescence staining. MTT assay was used to assess cell viability. Live/dead cell assay detected apoptosis. Mitochondrial membrane potential was detected using tetra-methyl-rhodamine ethyl ester (TMRE). Results: Ischemia/hypoxia upregulates DPPIV mRNA and protein levels in association with increased pro-apoptotic genes including caspase 7, Nod1, and Gadd45a. Transcriptome array data demonstrated that higher dose of exogenous DPPIV results in significant increase in same pro-apoptotic pathway genes including caspase 3,7, Nod1, Trp63, and Gadd45a. On the other hand, DPPIV decreased the expression of anti-apoptotic genes including Atf5 and Birc3. Levels of pro-inflammatory cytokines including IL1-beta and Ccl26/Eotaxin were increased in both DPPIV and ischemic SMCs. Higher dose of DPPIV increased apoptosis, decreased viability and mitochondrial membrane potential in SMCs. Conclusion: Higher levels of DPP4 activates the inflammatory and apoptotic signaling cascade resulting in the apoptosis of SMC. Further research in this area will enhance our understanding of the mechanism of CA progression and may provide clues to efficient therapeutic intervention for CA.