Regulation and Function of C-Type Natriuretic Peptide (CNP) in Gonadotrope-Derived Cell Lines.

Mirczuk Mirczuk,Childs Childs,Mcardle Mcardle,Read Read,Catterick Catterick,Perrett Perrett,Lessey Lessey,Fowkes Fowkes,Scudder Scudder,Lipscomb Lipscomb,Mcgonnell Mcgonnell,Niessen Niessen

doi:10.3390/cells8091086

Mirczuk Mirczuk, Childs Childs + Show 10 more

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https://doi.org/10.3390/cells8091086

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Abstract

C-type natriuretic peptide (CNP) is the most conserved member of the mammalian natriuretic peptide family, and is implicated in the endocrine regulation of growth, metabolism and reproduction. CNP is expressed throughout the body, but is particularly abundant in the central nervous system and anterior pituitary gland. Pituitary gonadotropes are regulated by pulsatile release of gonadotropin releasing hormone (GnRH) from the hypothalamus, to control reproductive function. GnRH and CNP reciprocally regulate their respective signalling pathways in αT3-1 gonadotrope cells, but effects of pulsatile GnRH stimulation on CNP expression has not been explored. Here, we examine the sensitivity of the natriuretic peptide system in LβT2 and αT3-1 gonadotrope cell lines to continuous and pulsatile GnRH stimulation, and investigate putative CNP target genes in gonadotropes. Multiplex RT-qPCR assays confirmed that primary mouse pituitary tissue express Nppc, Npr2 (encoding CNP and guanylyl cyclase B (GC-B), respectively) and Furin (a CNP processing enzyme), but failed to express transcripts for Nppa or Nppb (encoding ANP and BNP, respectively). Pulsatile, but not continuous, GnRH stimulation of LβT2 cells caused significant increases in Nppc and Npr2 expression within 4 h, but failed to alter natriuretic peptide gene expression in αT3-1 cells. CNP enhanced expression of cJun, Egr1, Nr5a1 and Nr0b1, within 8 h in LβT2 cells, but inhibited Nr5a1 expression in αT3-1 cells. Collectively, these data show the gonadotrope natriuretic peptide system is sensitive to pulsatile GnRH signalling, and gonadotrope transcription factors are putative CNP-target genes. Such findings represent additional mechanisms by which CNP may regulate reproductive function.

Highlights

The natriuretic peptides are a highly conserved group of peptide hormones, comprising of Atrial, B-type and C-type natriuretic peptides (ANP, BNP and CNP, respectively)
Our previous studies have identified an intact, and functional, natriuretic peptide system in gonadotrope cell lines, mouse and rat pituitaries, and a range of human pituitary adenomas [7,8,9,17,18]. These qualitative studies in pituitary cells lines and pituitary tissue did not examine all components of the natriuretic peptide system, nor did it compare expression of these components in other endocrine tissues
Initial expression profiling studies identified the anterior pituitary as a major source of CNP [5], with subsequent investigations highlighting the importance of pituitary gonadotrope cells [8,17,18]

Summary

Introduction

The natriuretic peptides are a highly conserved group of peptide hormones, comprising of Atrial-, B-type and C-type natriuretic peptides (ANP, BNP and CNP, respectively). They are structurally related, sharing a common 17-membered disulphide ring, which imparts biological activity at their respective particulate guanylyl cyclase receptors, GC-A and GC-B [1,2,3]. Our subsequent pharmacological and molecular investigations revealed gonadotropes to be major sources of both expression and function for CNP in the pituitary [8], and demonstrated expression of both CNP and GC-B in normal human fetal pituitaries and a range of pituitary adenomas [9]. The elegant mouse models of CNP/GC-B disruption revealed severe achondroplasia and early death, and suggested impaired fertility and reduced growth hormone secretion, phenotypes that strongly implicate a pituitary role for CNP/GC-B signalling [10,11]

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