Pituitary Actions of EGF on Gonadotropins, Growth Hormone, Prolactin and Somatolactins in Grass Carp

Qiongyao Hu,Cheng Ye,Chuanhui Xia,Huiying Zhang,Xuetao Shi,Shaohua Xu,Guangfu Hu,Lingling Zhou,Qinbo Qin,Zhan Yin,Jingyi Jia

doi:10.3390/biology9090279

Qiongyao Hu, Cheng Ye + Show 9 more

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https://doi.org/10.3390/biology9090279

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Abstract

Simple SummaryIn mammals, the functions of epidermal growth factor (EGF) have been widely studied. However, little is known about the pituitary actions of EGF in teleost. Using primary cultured grass carp pituitary cells as model, we found that EGF could reduce pituitary luteinizing hormone β (LHβ) mRNA expression, but induce pituitary growth hormone (GH), prolactin (PRL) and somatolactins (SL) mRNA expression. Furthermore, we also found that NKB could suppress EGF-induced PRL mRNA expression in grass carp pituitary cells. These results suggested that EGF could directly regulate pituitary hormones expression in teleost.In mammals, epidermal growth factor (EGF) plays a vital role in both pituitary physiology and pathology. However, the functional role of EGF in the regulation of pituitary hormones has rarely reported in teleost. In our study, using primary cultured grass carp pituitary cells as an in vitro model, we examined the effects of EGF on pituitary hormone secretion and gene expression as well as the post-receptor signaling mechanisms involved. Firstly, we found that EGF significantly reduced luteinizing hormone (LHβ) mRNA expression via ErbB1 coupled to ERK1/2 pathway, but had no effect on LH release in grass carp pituitary cells. Secondly, the results showed that EGF was effective in up-regulating mRNA expression of growth hormone (GH), somatolactin α (SLα) and somatolactin β (SLβ) via ErbB1 and ErbB2 and subsequently coupled to MEK1/2/ERK1/2 and PI3K/Akt/mTOR pathways, respectively. However, EGF was not effective in GH release in pituitary cells. Thirdly, we found that EGF strongly induced pituitary prolactin (PRL) release and mRNA expression, which was mediated by ErbB1 and subsequent stimulation of MEK1/2/ERK1/2 and PI3K/Akt/mTOR pathways. Interestingly, subsequent study further found that neurokinin B (NKB) significantly suppressed EGF-induced PRL mRNA expression, which was mediated by neurokinin receptor (NK2R) and coupled to AC/cAMP/PKA signal pathway. These results suggested that EGF could differently regulate the pituitary hormones expression in grass carp pituitary cells.

Highlights

The pituitary is an important endocrine gland, that secrets multiple important pituitary hormones including growth hormone (GH), prolactin (PRL), somatolactin alpha /beta (SLα/β), luteinizing hormone (LH) and follicle-stimulating hormone (FSH) [1,2]
The result showed that the inhibitory effect of epidermal growth factor (EGF) on LHβ mRNA expression was eliminated by simultaneous treatment with the ErbB1 inhibitor AG1478, but the ErbB2 inhibitor AG879 was not effective in this regard (Figure 1D)
Treatment with wortmannin, MK2206 and rapamycin targeting for PI3 K/Akt/mTOR pathway were not involved in the inhibitory effects of EGF on LHβ mRNA expression (Figure 1F)

Summary

Introduction

The pituitary is an important endocrine gland, that secrets multiple important pituitary hormones including growth hormone (GH), prolactin (PRL), somatolactin alpha /beta (SLα/β), luteinizing hormone (LH) and follicle-stimulating hormone (FSH) [1,2]. These pituitary hormones are responsible for the process of endocrine regulation and metabolism, growth and reproduction development within the body [3,4]. Previous studies found that SLα and SLβ were involved in diverse functions in fish models, including melanosome aggregation [10,11], inflation of swim bladder during embryo development [12], reproduction [9], stress responses [13], lipid metabolism [12], and osmoregulation [14]

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