The long term objective of this research proposal is to determine the molecular mechanisms of vascular calcification in order to identify novel target(s) for the treatment of chronic kidney disease (CKD)-dependent vascular calcification. Vascular calcification is closely associated with cardiovascular mortality in patients with CKD. More than half of all deaths in CKD subjects can be attributed to cardiovascular diseases. Our previous study revealed that stearate derived from de novo lipogenesis promotes aortic calcification. Recently, we found that levels of one of the stearate metabolites, distearoyl-phosphatidic acid (18:0/18:0-PA) are significantly increased in subjects with CKD due to lower stearoyl-CoA desaturase (SCD) activity. The pro-calcific and pro- osteogenic effects of stearate were highly correlated with levels of distearoyl-phosphatidic acid (18:0/18:0-PA) and NF-??-mediated TNF? expression. We hypothesized that a central event in the pathogenesis of vascular calcification is increased expression of TNF? through PKC?/IKK?/NF-?B signaling in vascular smooth muscle cells (VSMCs). Our hypothesis is based on the following evidence derived from a series of preliminary results from our lab: 1) CKD increased serum and aortic TNF? 2) 18:0/18:0-PA synthesized through the GPAT4-AGPAT3 pathway of de novo glycerolipid synthesis is a critical metabolite in the pathogenesis of vascular calcification. 3) TNF? increased mineralization of VSMCs and 18:0/18:0-PA in humans and mice, resulting in activation of the IKK?/NF?B pathway. 4) CKD activated aortic PKC?. 5) PA is known to activate PKC?, which in turn phosphorylates and activates IKK?. 6) Active NF-?B proteins were increased in the aortas of murine models of vascular calcification such as DBA2/J mice with 5/6 nx and VSMC-specific SCD1/2 knockout mice. 7) Treatment with a TNF? monoclonal antibody (Infliximab) completely attenuated CKD-dependent vascular calcification. To determine the pivotal role of the PA-PKC?-IKK?-NF-?B-TNF? axis in the pathogenesis of vascular calcification, we propose three specific aims.
Specific Aim 1 : Determine whether activation of PKC?-IKK?-NF-?B by 18:0/18:0-PA is required for osteoblastic differentiation and mineralization of VSMCs.
Specific Aim 2 : A) Determine whether the modulation of de novo 18:0/18:0-PA synthesis affects the PKC?-IKK?-NF-?B - TNF? axis and vascular calcification in vivo and B) determine whether SMC-specific activation and inhibition of the PKC?-IKK?-NF-?B axis influences vascular calcification in vivo.
Vascular calcification is common in chronic kidney disease (CKD) and associated with increased morbidity and mortality. This research project will enhance our understanding of the molecular mechanisms of vascular calcification, and identify novel target(s) for treatment of CKD-dependent vascular calcification.
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