Deletion of STAT5a/b in vascular smooth muscle abrogates the male bias in hypoxic pulmonary hypertension in mice: implications in the human disease.

Yang-Ming Yang,Kanta Ochani,Huijuan Yuan,Yester Skayian,Edmund J Miller,Pravin B Sehgal,John G Edwards

doi:10.2119/molmed.2014.00180

Abstract

Chronic hypoxia typically elicits pulmonary hypertension (PH) in mice with a male-dominant phenotype. There is an opposite-sex bias in human PH, with a higher prevalence in women, but greater survival (the "estrogen paradox"). We investigated the involvement of the STAT5a/b species, previously established to mediate sexual dimorphism in other contexts, in the sex bias in PH. Mice with heterozygous or homozygous deletions of the STAT5a/b locus in vascular smooth muscle cells (SMCs) were generated in crosses between STAT5a/b(fl/fl) and transgelin (SM22α)-Cre(+/+) parents. Wild-type (wt) males subjected to chronic hypoxia showed significant PH and pulmonary arterial remodeling, with wt females showing minimal changes (a male-dominant phenotype). However, in conditional STAT5(+/-) or STAT5(-/-) mice, hypoxic females showed the severest manifestations of PH (a female-dominant phenotype). Immunofluorescence studies on human lung sections showed that obliterative pulmonary arterial lesions in patients with idiopathic pulmonary arterial hypertension (IPAH) or hereditary pulmonary arterial hypertension (HPAH), both male and female, overall had reduced STAT5a/b, reduced PY-STAT5 and reduced endoplasmic reticulum (ER) GTPase atlastin-3 (ATL3). Studies of SMCs and endothelial cell (EC) lines derived from vessels isolated from lungs of male and female IPAH patients and controls revealed instances of coordinate reductions in STAT5a, STAT5b and ATL3 in IPAH-derived cells, including SMCs and ECs from the same patient. Taken together, these data provide the first definitive evidence for a contribution of STAT5a/b to the sex bias in PH in the hypoxic mouse and implicate reduced STAT5 in the pathogenesis of the human disease.

Highlights

There is an unusual “estrogen paradox” in the pathogenesis of pulmonary arterial hypertension (PAH) [1,2,3,4,5]
There was a marked reduction in transcripts for STAT5a and STAT5b in RNA isolated from the aorta of homozygous knockout mice (Supplementary Figure S3C and Table S3), and a marked reduction in STAT5 species by Western blotting in extracts of smooth muscle cells (SMCs) isolated from the aorta of homozygous knockout mice (Supplementary Figure S3D) as well as in extracts of aortas of heterozygous knockout mice
We have previously shown that acute siRNA-mediated knockdown of STAT5a/b in pulmonary vascular cells led to the development of a unique cystic endoplasmic reticulum (ER) and dilated and fragmented Golgi apparatus phenotype with deposition of RTN4 and ATL3 at the cystzone boundaries, with one to three large juxta-nuclear cysts comprising dilation of the ER space between the inner and outer nuclear membranes resulting in a lunate distortion of the nuclei [45,46]

Summary

Introduction

There is an unusual “estrogen paradox” in the pathogenesis of pulmonary arterial hypertension (PAH) [1,2,3,4,5]. In a converse example, female mice overexpressing the serotonin transporter (SERT) or the S100 calcium-binding protein S100A4/mts, but not male mice, spontaneously developed PH, with modest increases in right ventricular pressure at 5 months of age [3,7]. The mechanisms for these variations in sex dependence of this disease in humans and rodent models, and the underlying estrogen paradox, remain incompletely understood. A perplexing question has remained: what are the differences between a female mouse (or female rat) and a female human?

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