Abstract 319: Intermedin Attenuates Vascular Calcification by Upregulating Klotho via CRLR/RAMP3 Receptor Complex and cAMP/PKA Signaling Pathway in Rats With Chronic Kidney Disease

Vascular calcification (VC) is highly associated with increased morbidity and mortality in patients with advanced chronic kidney disease(CKD). We previously reported that paracrine/autocrine factor intermedin (IMD) could protect against VC. In the present study we assessed the hypothesis that IMD inhibits VC by upregulating klotho protein. VC in CKD rat was induced by 5/6 nephrectomy plus vitamin D 3 administration and vascular smooth muscle cells (VSMCs) calcification was induced by calcifying media containing β -glycerophosphate and CaCl 2 . IMD (100 ng kg -1 h -1 ) was systemically administered by a mini-osmotic pump. CKD rat aortas showed lower IMD content and increased expression of its receptors (calcitonin receptor-like receptor,CRLR/receptor activity-modifying protein 3, RAMP3), along with increased aortic alkaline phosphatase (ALP) activity and calcium deposition. In vivo administration of IMD significantly reduced aortic ALP activity and calcium deposition in CKD rats when compared with vehicle treatment, which was further confirmed in cultured VSMCs. Concurrently, the loss of smooth muscle lineage markers and klotho protein in aortas was rescued by administering IMD to CKD rats with VC. However, the inhibitory effects of IMD on VC were abolished upon pre-treatment with small interfering RNA to reduce klotho. Moreover, the increased effects of IMD on klotho were abolished upon pretreatment with small interfering RNA to reduce its receptors or with PKA inhibitor H89. These results demonstrated that IMD attenuates VC by upregulating klotho via CRLR/RAMP3-cAMP/PKA signaling pathway in rat with CKD. IMD is an important paracrine/autocrine protective factor for VC.