Question:

Vascular calcification is observed in chronic kidney disease (CKD) and a predictor of cardiovascular mortality. Aldosterone is increased in CKD patients and klotho-hypomorphic mice. We therefore investigated the effect of aldosterone and of the moderately selective mineralocorticoid receptor antagonist spironolactone on vascular calcification in primary human aortic smooth muscle cells (HAoSMCs) and in the klotho-hypomorphic mouse model of phosphate-induced calcification.

Methods & Results:

Aldosterone induced the TNFα, MSX2, RUNX2/CBFA1 cascade of vascular calcification signaling and stimulated alkaline phosphatase expression and activity in HAoSMCs, effects blocked by cotreatment with spironolactone. Aldosterone dose-dependently increased PiT-1 mRNA expression, while spironolactone abrogated this effect. Under high phosphate conditions, addition of aldosterone to the high phosphate medium significantly increased the expression of RUNX2/CBFA1 and PiT-1, while spironolactone reversed this effect. FGF-23 attenuated the effect of aldosterone in HAoSMCs in a KLOTHO-dependent manner. Silencing of PiT-1 abrogated the effects of aldosterone on TNFα, MSX2, RUNX2/CBFA1 and alkaline phosphatase mRNA expression, as well as alkaline phosphatase activity. In the klotho-hypomorphic mouse model, spironolactone treatment mitigated vascular osteoinduction and reduced aortic Pit-1, Tnfα and alkaline phosphatase mRNA expression, accompanied by a reduction of Msx2, Runx2/Cbfa1 and Osterix mRNA and protein expression.

Conclusions:

Aldosterone stimulates the expression of PiT-1, which is essential for the aldosterone-induced vascular calcification signaling in aortic smooth muscle cells. Despite the associated risks, spironolactone treatment could provide beneficial cardiovascular effects in chronic kidney disease.