Thromboxane promotes smooth muscle phenotype commitment but not remodeling of hypoxic neonatal pulmonary artery

The Functional Interaction of EGFR with AT1R or TP in Primary Vascular Smooth Muscle Cells Triggers a Synergistic Regulation of Gene Expression

In vivo, cells are simultaneously exposed to multiple stimuli whose effects are difficult to distinguish. Therefore, they are often investigated in experimental cell culture conditions where stimuli are applied separately. However, it cannot be presumed that their individual effects simply add up. As a proof-of-principle to address the relevance of transcriptional signaling synergy, we investigated the interplay of the Epidermal Growth Factor Receptor (EGFR) with the Angiotensin-II (AT1R) or the Thromboxane-A2 (TP) receptors in murine primary aortic vascular smooth muscle cells. Transcriptome analysis revealed that EGFR-AT1R or EGFR-TP simultaneous activations led to different patterns of regulated genes compared to individual receptor activations (qualitative synergy). Combined EGFR-TP activation also caused a variation of amplitude regulation for a defined set of genes (quantitative synergy), including vascular injury-relevant ones (Klf15 and Spp1). Moreover, Gene Ontology enrichment suggested that EGFR and TP-induced gene expression changes altered processes critical for vascular integrity, such as cell cycle and senescence. These bioinformatics predictions regarding the functional relevance of signaling synergy were experimentally confirmed. Therefore, by showing that the activation of more than one receptor can trigger a synergistic regulation of gene expression, our results epitomize the necessity to perform comprehensive network investigations, as the study of individual receptors may not be sufficient to understand their physiological or pathological impact.

Altered expression of PPAR‑γ and TRPC in neonatal rats with persistent pulmonary hypertension

Persistent pulmonary hypertension of the newborn (PPHN) is a life-threatening disease that is commonly observed in the neonatal intensive care unit. PPHN is pathologically characterized by pulmonary vascular remodeling and, in particular, pulmonary artery smooth muscle cell (PASMC) proliferation. Decreased expression levels of peroxisome proliferator-activated receptor γ (PPAR-γ), which is a member of the nuclear receptor hormone superfamily, in combination with elevated expressions of transient receptor potential cation channel, subfamily C, member 1 (TRPC1) and TRPC6 contributes to the PASMC proliferation and excessive pulmonary vascular remodeling in adult pulmonary hypertension (PH). Whether PPAR-γ, TRPC1 and TRPC6 affect the development of vascular remodeling in PPHN model rats remains unknown. The aim of the present study was to investigate the roles of PPAR-γ, TRPC1 and TRP6 on the pathogenesis of PPHN in rats. The rat model of PPHN was established by exposure to hypoxic conditions and indomethacin treatment. Lung tissues, hearts and blood from PPHN model and Control rats were collected and examined. Parameters, including the percentage of medial wall thickness (WT %), the percentage of medial wall area (WA %), right ventricular hypertrophy (RVH) and the plasma concentration of B-type natriuretic peptide (BNP) were used to estimate the development of PPHN. The expression levels of PPAR-γ, TRPC1 and TRPC6 in lung tissues were detected by immunohistochemistry, western blotting and reverse transcription-quantitative polymerase chain reaction. Significant increases were observed in the WT %, WA %, RVH and plasma BNP in the PPHN group compare with the Control group (P<0.01). In addition, the mRNA and protein expression levels of PPAR-γ were markedly downregulated (P<0.05 vs. Control). In the PPHN group, the protein expression levels of TRPC1 and TRPC6 were higher compared to the control group; however, there was no difference in the mRNA expression levels (P>0.05). In conclusion, the present study successfully established a PPHN rat model, and the altered expressions of PPAR-γ, TRPC1 and TRPC6 in the pulmonary artery located in the lungs of newborn rats with PPHN suggested that these proteins may be important mediators of PPHN.