Background/Purpose: Progressive functional and structural vascular disorder is one of the hallmark features of Systemic Sclerosis (Scleroderma, SSc). Vascular dysfunction lead to dysregulated vascular tone control and activation of vascular smooth muscle cells (vSMCs) resulting in enhanced vasospasm and intimal hyperplasia. It is believed that vascular dysfunction results from imbalance in endothelial signals with increase vasoconstrictors and defective release of vasodilators and vSMCs inhibitors. In this study, we examine the expression levels of prostacyclin synthase (PTGIS) and prostacyclin receptor (IP) in normal and SSc skin, microvascular endothelial cells (MVECs) and vSMCs. We also investigated the effects of the DNA methyltransferase inhibitor 5-Aza-2′-deoxycytidine (Aza), and the histone deacetylase inhibiter trichostatin (TSA) on PTGIS and IP gene expression in SSc and normal MVECs and vSMCs.

Methods: MVECs and vSMCs were isolated from SSc patients’ skin and matched healthy subjects. The mRNA and protein expression levels of IP and PTGIS were measured by qPCR and Western blot analysis (WB).  In addition, epigenetic inhibitors were added to cell cultures to assess the role of epigenetic regulation on IP and PTGIS expression levels. MVECs and VSMCs were treated with Aza at 5uM for 5 days and TSA at 100nM for 1 day, and mRNA and protein expression levels were measured.

Results: The mRNA expression levels of PTGIS and IP were significantly downregulated in SSc-skin to 0.183‑fold ± 0.03 for PTGIS (P< 0.01) and to 0.54‑fold ± 0.06 for IP (P< 0.01), compared to control skin. The mRNA expression levels of PTGIS and IP were also decreased in SSc-vSMCs, compared to control (to 0.29‑fold ± 0.04, P< 0.01 for PTGIS; to 0.46‑fold ± 0.06 for IP, P< 0.01). WB analysis demonstrated similar reduction on the protein levels in SSc -vSMCs. Addition of Aza and TSA resulted in increased expression of IP and PTGIS to almost normal levels in SSc-vSMCs. SSc-MVECs also exhibited lower expression levels of PTGIS than control MVECs at both mRNA level (0.214‑fold ± 0.03, P< 0.01) and protein level (0.49‑fold ± 0.05, P< 0.05). The addition of Aza and TSA corrected the reduced mRNA and protein expression levels of PTGIS in SSc-MVECs.

Conclusion: These data demonstrate a defective prostacyclin (PGI2)-IP pathway in MVECs and vSMCs from SSc patients. This defect may contribute to the vascular dysfunction observed in SSc by decreasing the vasodilatory PGI2/IP signaling pathway, resulting in enhanced vasospasm and vascular remodeling. The addition of Aza and TSA corrected the reduced PTGIS and IP expression levels, suggesting an epigenetic regulation. Augmenting IP and PTGIS expression, either independent of or combined with the use of PGI2 analogues, may be an important new therapeutic strategy for SSc.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/epigenetic-regulation-mediated-reduction-in-the-expression-of-prostacyclin-receptor-and-prostacyclin-synthase-in-scleroderma-skin-vascular-smooth-muscle-cells-and-microvascular-endothelial-cells/