Aging-related increase in store-operated Ca2+ influx in human ventricular fibroblasts

Abstract

Senescence-related fibrosis contributes to cardiac dysfunction. Profibrotic processes are Ca2+ dependent. The effect of aging on the Ca2+ mobilization processes of human ventricular fibroblasts (hVFs) is unclear. Therefore, we tested whether aging altered intracellular Ca2+ release and store-operated Ca2+ entry (SOCE). Disease-free hVFs from 2- to 63-yr-old trauma victims were assessed for cytosolic Ca2+ dynamics with fluo 3/confocal imaging. Angiotensin II or thapsigargin was used to release endoplasmic reticulum Ca2+ in Ca2+-free solution; CaCl2 (2 mM) was then added to assess SOCE, which was normalized to ionomycin-induced maximal Ca2+. The angiotensin II experiments were repeated after phosphoenolpyruvate pretreatment to determine the role of energy status. The expression of genes encoding SOCE-related ion channel subunits was assessed by quantitative PCR, and protein expression was assessed by immunoblot analysis. Age groups of <50 and ≥50 yr were compared using unpaired t-test or regression analysis. Ca2+ release by angiotensin II or thapsigargin was not different between the groups, but SOCE was significantly elevated in the ≥50-yr group. Regression analysis showed an age-dependent phosphoenolpyruvate-sensitive increase in SOCE of hVFs. Aging did not alter the mRNA expression of SOCE-related genes. The profibrotic phenotype of hVFs was evident by sprouty1 downregulation with age. Thus, an age-associated increase in angiotensin II- and thapsigargin-induced SOCE occurs in hVFs, independent of receptor mechanisms or alterations of mRNA expression level of SOCE-related ion channel subunits but related to the cellular bioenergetics status. Elucidation of mechanisms underlying enhanced hVF SOCE with aging may refine SOCE targets to limit aging-related progression of Ca2+-dependent cardiac fibrosis. NEW & NOTEWORTHY Human ventricular fibroblasts exhibit an age-related increase in store-operated Ca2+ influx induced by angiotensin II, an endogenous vasoactive hormone, or thapsigargin, an inhibitor of endoplasmic reticulum Ca2+-ATPase, independent of receptor mechanisms or genes encoding store-operated Ca2+ entry-related ion channel subunits. Selective inhibition of this augmented store-operated Ca2+ entry could therapeutically limit aging-related cardiac fibrosis.