Disruption of Endothelial-Cell Caveolin-1α/Raft Scaffolding During Development of Monocrotaline-Induced Pulmonary Hypertension

Abstract

Background-In the monocrotaline (MCT)-treated rat, there is marked stimulation of DNA synthesis and megalocytosis of pulmonary arterial endothelial cells (PAECs) within 3 to 4 days, followed by pulmonary hypertension (PH) 10 to 14 days later. Growing evidence implicates caveolin-1 (cav-1) in plasma membrane rafts as a negative regulator of promitogenic signaling. We have investigated the integrity and function of endothelial cell-selective cav-1␣/raft signaling in MCT-induced PH. Methods and Results-Although PH and right ventricular hypertrophy developed by 2 weeks after MCT, a reduction in cav-1␣ levels in the lung was apparent within 48 hours, declining to Ϸ30% by 2 weeks, accompanied by an increase in activation of the promitogenic transcription factor STAT3 (PY-STAT3). Immunofluorescence studies showed a selective loss of cav-1␣ and platelet endothelial cell adhesion molecule-1 in the PAEC layer within 48 hours after MCT but an increase in PY-STAT3. PAECs with cav-1␣ loss displayed high PY-STAT3 and nuclear immunostaining for proliferating cell nuclear antigen (PCNA). Biochemical studies showed a loss of cav-1␣ from the detergent-resistant lipid raft fraction concomitant with hyperactivation of STAT3. Moreover, cultured PAECs treated with MCT-pyrrole for 48 hours developed megalocytosis associated with hypo-oligomerization and reduction of cav-1␣, hyperactivation of STAT3 and ERK1/2 signaling, and stimulation of DNA synthesis. Conclusions-MCT-induced disruption of cav-1␣ chaperone and scaffolding function in PAECs likely accounts for diverse alterations in endothelial cell signaling in this model of PH.

Cytoplasmic provenance of STAT3 and PY-STAT3 in the endolysosomal compartments in pulmonary arterial endothelial and smooth muscle cells: implications in pulmonary arterial hypertension

“…This reciprocal relationship between cav-1 downregulation and PY-STAT3 activation in PAH in the rat/MCT model was later confirmed by Jasmin and colleagues (19). That the increase in PY-STAT3 levels was seen before the onset of PAH in MCT-treated rats (19,24) and that the introduction of a cav-1 scaffolding domain peptide blocked PY-STAT3 hyperactivation and ameliorated MCT-induced PAH (19) indicated that STAT3 played a role in the initiation of PAH, at least in this animal model. Moreover, Park and colleagues (33) reported the hyperactivation of PY-STAT3 in lungs of cav-1 Ϫ/Ϫ mice, which spontaneously developed PAH.…”

“…24). Close examination of individual cells in vivo showed that the specific endothelial cells that had a loss of cav-1 expression were the same cells with hyperactivation of PY-STAT3 and increased DNA synthesis (24). This reciprocal relationship between cav-1 downregulation and PY-STAT3 activation in PAH in the rat/MCT model was later confirmed by Jasmin and colleagues (19).…”

“…The loss of cav-1 and hyperactivation of PY-STAT3 was observed within 2-4 days after administration of MCT to rats (i.e., before the onset of PAH at 10 -14 days; Ref. 24). Close examination of individual cells in vivo showed that the specific endothelial cells that had a loss of cav-1 expression were the same cells with hyperactivation of PY-STAT3 and increased DNA synthesis (24).…”

Pathogenesis of pulmonary hypertension: a case for caveolin-1 and cell membrane integrity

“…In addition, at 1 wk post-MCT before the development of PH, progressive activation of PY-STAT3 and increased expression of Bcl-xL occur (48,78). At 2 wk post-MCT, there is evidence of PH and right ventricular hypertrophy; only 26 Ϯ 3% of the arteries exhibit the presence of endothelial caveolin-1 compared with the controls with intact endothelial caveolin-1 in 100% of arteries (49).…”

“…The expression of the endothelial caveolin-1 was reduced in these cases. In the MCT model, progressive loss of endothelial caveolin-1 and the activation of proliferative and antiapoptotic pathways occur before the onset of PH (48,78). The rescue of caveolin-1 inhibits the proliferative pathways (PY-STAT3, cyclin D1 and D3) and attenuates PH (47,60).…”