Mice, double deficient in lysosomal serine carboxypeptidases Scpep1 and Cathepsin A develop the hyperproliferative vesicular corneal dystrophy and hypertrophic skin thickenings

Xuefang Pan,Aleksander Hinek,Yanting Wang,Alexey V Pshezhetsky,Torben Lübke

doi:10.1371/journal.pone.0172854

Abstract

Vasoactive and mitogenic peptide, endothelin-1 (ET-1) plays an important role in physiology of the ocular tissues by regulating the growth of corneal epithelial cells and maintaining the hemodynamics of intraocular fluids. We have previously established that ET-1 can be degraded in vivo by two lysosomal/secreted serine carboxypeptidases, Cathepsin A (CathA) and Serine Carboxypeptidase 1 (Scpep1) and that gene-targeted CathAS190A /Scpep1-/- mice, deficient in CathA and Scpep1 have a prolonged half-life of circulating ET-1 associated with systemic hypertension. In the current work we report that starting from 6 months of age, ~43% of CathAS190A /Scpep1-/- mice developed corneal clouding that eventually caused vision impairment. Histological evaluation of these mice demonstrated a selective fibrotic thickening and vacuolization of the corneas, resembling human hyperproliferative vesicular corneal stromal dystrophy and coexisting with a peculiar thickening of the skin epidermis. Moreover, we found that cultured corneal epithelial cells, skin fibroblasts and vascular smooth muscle cells derived from CathA/Scpep1-deficient mice, demonstrated a significantly higher proliferative response to treatment with exogenous ET-1, as compared with cells from wild type mice. We also detected increased activation level of ERK1/2 and AKT kinases involved in cell proliferation in the ET-1-treated cultured cells from CathA/Scpep1 deficient mice. Together, results from our experimental model suggest that; in normal tissues the tandem of serine carboxypeptidases, Scpep1 and CathA likely constitutes an important part of the physiological mechanism responsible for the balanced elimination of heightened levels of ET-1 that otherwise would accumulate in tissues and consequently contribute to development of the hyper-proliferative corneal dystrophy and abnormal skin thickening.

Highlights

Endothelin-1 (ET-1) is recognized as one of the most potent vasoactive regulators known to date
CathAS190A /Serine Carboxypeptidase 1 (Scpep1)-/- mice with a combined deficiency of Cathepsin A (CathA) and Scpep1 (CathAS190A /Scpep1-/mice) were generated by crossing CathAS190A and Scpep1-/- mouse strains each in C57BL/6NCrl genetic background [21]
In contrast to WT mice that normally extend their front legs in order to get hold of the box while approaching its edge, the CathAS190A /Scpep1-/mice, having visible corneal clouding, extended legs only after their noses or vibrissae physically contacted with the hard edge

Summary

Introduction

Endothelin-1 (ET-1) is recognized as one of the most potent vasoactive regulators known to date. It modulates blood pressure by inducing constriction of arterial vascular smooth muscle cells (SMCs). ET-1 is known as a potent mitogen of vascular endothelium and SMCs[1, 2]. In human patients high levels of ET-1 have been associated with systemic and pulmonary hypertension, as well as with diverse cardiovascular disorders [3]. In mice overexpression of human ET-1 resulted in vascular remodelling and endothelial dysfunction[4, 5], whereas ET-1 deficient mice showed respiratory failure at birth and morphological abnormalities of the pharyngeal-arch-derived craniofacial tissues and organs[6]

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Conclusion