Increased CaSR and TRPC6 pulmonary vascular expression in the nitrofen-induced model of congenital diaphragmatic hernia

Abstract

Aims and objectives

The high morbidity and mortality rates in congenital diaphragmatic hernia (CDH) are attributed primarily to severe lung hypoplasia and/or persistent pulmonary hypertension (PPH). PPH in CDH is characterized by abnormal vascular remodeling with thickening of medial and adventitial layers and extension of smooth muscle into previously nonmuscularized arteries. Excessive proliferation of pulmonary arterial smooth muscle cells (PASMC) is an important contributor to the concentric pulmonary arterial remodeling. An increase in cytosolic-free Ca²⁺ concentration in PASMC is a major trigger for pulmonary vasoconstriction and a key stimulus for PASMC proliferation and migration. Calcium-sensing receptor (CaSR), a member of the G-protein coupled receptor family, is activated by cations (e.g., Ca²⁺, Mg²⁺) and polyamines. Under normal physiological conditions, the expression levels of CaSR in the pulmonary vasculature are very low. Canonical transient receptor potential channels (TRPCs) constitute a series of nonselective cation channels with variable degree of Ca²⁺ selectivity. TRPC6 has been reported to play a crucial role in the regulation of neo-muscularization, vasoreactivity, and vasomotor tone in the pulmonary vasculature. We hypothesized that CaSR and TRPC6 expression is upregulated in the pulmonary vasculature of nitrofen-induced CDH rats.

Materials and methods

Following ethical approval (REC1103), time-pregnant Sprague Dawley rats received nitrofen or vehicle on gestational day (D) 9. D21 fetuses were divided into CDH and control (n = 12). Quantitative real-time polymerase chain reaction (QRT-PCR), western blotting, and confocal-immunofluorescence microscopy were performed to detect lung gene and protein expression of CaSR and TRPC6.

Results

QRT-PCR and western blot analysis revealed that CaSR and TPRC6 expression was significantly increased in the CDH group compared to controls (p < 0.05). Confocal-immunofluorescence microscopy revealed that CaSR and TRPC6 lung expression was markedly increased in CDH group compared to controls.

Conclusion

Increased CaSR and TRPC6 expression in CDH lung suggests that CaSR interacting with TRPC6 may contribute to abnormal vascular remodeling resulting in pulmonary vasoconstriction and development of PPH.