T-type Ca2+ channels elicit pro-proliferative and anti-apoptotic responses through impaired PP2A/Akt1 signaling in PASMCs from patients with pulmonary arterial hypertension

Abstract

Idiopathic pulmonary arterial hypertension (iPAH) is characterized by obstructive hyperproliferation and apoptosis resistance of distal pulmonary artery smooth muscle cells (PASMCs). T-type Ca channel blockers have been shown to reduce experimental pulmonary hypertension, although the impact of T-type channel inhibition remains unexplored in PASMCs from iPAH patients. Here we show that T-type channels Cav3.1 and Cav3.2 are present in the lung and PASMCs from iPAH patients and control subjects. The blockade of T-type channels by the specific blocker, TTA-A2, prevents cell cycle progression and PASMCs growth. In iPAH cells, T-type channel signaling fails to activate phosphatase PP2A, leading to an increase in ERK1/2, P38 activation. Moreover, T-type channel signaling is redirected towards the activation of the kinase Akt1, leading to increased expression of the anti-apoptotic protein survivin, and a decrease in the pro-apoptotic mediator FoxO3A. Finally, in iPAH cells, Akt1 is no longer able to regulate caspase 9 activation, whereas T-type channel overexpression reverses PP2A defect in iPAH cells but reinforces the deleterious effects of Akt1 activation. Altogether, these data highlight T-type channel signaling as a strong trigger of the pathological phenotype of PASMCs from iPAH patients (hyper-proliferation/cells survival and apoptosis resistance), suggesting that both T-type channels and PP2A may be promising therapeutic targets for pulmonary hypertension.

Ion Channels in Pulmonary Hypertension: A Therapeutic Interest?

“…In PASMC, two main types of VGCC are expressed, the high voltage-activated (HVA) L-type and low voltage-activated (LVA) T-type channels that represent the major pathways for voltage-mediated Ca 2+ entry involved in cell function such as excitation–contraction coupling [ 79 ], excitation–transcription coupling and cell proliferation [ 80 , 81 , 82 ].…”

“…In PASMC, the L-type channel, Ca v 1.2 is widely accepted as the source for depolarization Ca 2+ concentration [ 86 ] whereas T-type channels Ca v 3.1 and Ca v 3.2 are involved in cell proliferation [ 81 , 82 ]. Recent studies showed, by immunostaining and confocal imaging, that both Ca v 3.1 and Ca v 3.2 isoforms are revealed in human lung tissue and cultured PASMCs; Ca v 3.1 labeling is mainly in the cytoplasm, whereas Ca v 3.2 labeling is strongly localized in the nucleus [ 82 ].…”

Proteomic Analysis of KCNK3 Loss of Expression Identified Dysregulated Pathways in Pulmonary Vascular Cells

“…The overactivation of the mTOR pathway is well known to contribute to PAH pathogenesis, and the in vivo inhibition of mTOR by rapamycin reduces the development experimental PH [ 52 ]. Moreover, mTOR is a part of the PI3K/AKT/mTOR pathway, which we found to be increased in lungs from Kcnk3 -mutated rats as well as in human PAH [ 8 , 10 ].…”

“…Pulmonary arteries were excised at a distance from tumor areas. hPAECs and hPASMCs were cultured as previously described [ 10 , 11 ], and were used for the study at passage 4. The patients studied were part of a program approved by the institutional Ethics Committee, and had given their written informed consent (ID RCB: 2018-A01252-53, approved on June 18, 2006).…”

Silencing PDK1 limits hypoxia‑induced pulmonary arterial hypertension in mice via the Akt/p70S6K signaling pathway

“…It has been previously reported that the excessive proliferation of pVSMCs and pVECs is mediated by various signaling molecules, including protein kinase B (Akt) and transforming growth factor (TGF)β (1). The Akt/mechanistic target of rapamycin (mTOR) signaling pathway is associated with the differentiation of myofibroblasts and extracellular remodeling, which are critical for organ fibrosis.…”