Fibulin-3 Attenuates Phosphate-Induced Vascular Smooth Muscle Cell Calcification by Inhibition of Oxidative Stress.

BACKGROUND/AIMS: Fibulin-3, an extracellular matrix glycoprotein, inhibits vascular oxidative stress and remodeling in hypertension. Oxidative stress is prevalent in chronic kidney disease (CKD) patients and is an important mediator of osteo-/chondrogenic transdifferentiation and calcification of vascular smooth muscle cells (VSMCs) during hyperphosphatemia. Therefore, the present study explored the effects of Fibulin-3 on phosphate-induced vascular calcification.

METHODS

Experiments were performed in primary human aortic smooth muscle cells (HAoSMCs) treated with control or with phosphate without or with additional treatment with recombinant human Fibulin-3 protein or with hydrogen peroxide as an exogenous source of oxidative stress.

RESULTS

Treatment with calcification medium significantly increased calcium deposition in HAoSMCs, an effect significantly blunted by additional treatment with Fibulin-3. Moreover, phosphate-induced alkaline phosphatase activity and mRNA expression of osteogenic and chondrogenic markers MSX2, CBFA1, SOX9 and ALPL were all significantly reduced by addition of Fibulin-3. These effects were paralleled by similar regulation of oxidative stress in HAoSMCs. Phosphate treatment significantly up-regulated mRNA expression of the oxidative stress markers NOX4 and CYBA, down-regulated total antioxidant capacity and increased the expression of downstream effectors of oxidative stress PAI-1, MMP2 and MMP9 as well as BAX/BLC2 ratio in HAoSMCs, all effects blocked by additional treatment with Fibulin-3. Furthermore, the protective effects of Fibulin-3 on phosphate-induced osteogenic and chondrogenic markers expression in HAoSMCs were reversed by additional treatment with hydrogen peroxide.

CONCLUSIONS

Fibulin-3 attenuates phosphate-induced osteo-/ chondrogenic transdifferentiation and calcification of VSMCs, effects involving inhibition of oxidative stress. Up-regulation or supplementation of Fibulin-3 may be beneficial in reducing the progression of vascular calcification during hyperphosphatemic conditions such as CKD.