Mel1c Mediated Monochromatic Light-Stimulated IGF-I Synthesis through the Intracellular Gαq/PKC/ERK Signaling Pathway.

Shujie Ning,Zixu Wang,Yulan Dong,Jing Cao,Yaoxing Chen

doi:10.3390/ijms20071682

Abstract

Previous studies have demonstrated that monochromatic light affects plasma melatonin (MEL) levels, which in turn regulates hepatic insulin-like growth factor I (IGF-I) secretion via the Mel1c receptor. However, the intracellular signaling pathway initiated by Mel1c remains unclear. In this study, newly hatched broilers, including intact, sham operation, and pinealectomy groups, were exposed to either white (WL), red (RL), green (GL), or blue (BL) light for 14 days. Experiments in vivo showed that GL significantly promoted plasma MEL formation, which was accompanied by an increase in the MEL receptor, Mel1c, as well as phosphorylated extracellular regulated protein kinases (p-ERK1/2), and IGF-I expression in the liver, compared to the other light-treated groups. In contrast, this GL stimulation was attenuated by pinealectomy. Exogenous MEL elevated the hepatocellular IGF-I level, which is consistent with increases in cyclic adenosine monophosphate (cAMP), Gαq, phosphorylated protein kinase C (p-PKC), and p-ERK1/2 expression. However, the Mel1c selective antagonist prazosin suppressed the MEL-induced expression of IGF-I, Gαq, p-PKC, and p-ERK1/2, while the cAMP concentration was barely affected. In addition, pretreatment with Ym254890 (a Gαq inhibitor), Go9863 (a PKC inhibitor), and PD98059 (an ERK1/2 inhibitor) markedly attenuated MEL-stimulated IGF-I expression and p-ERK1/2 activity. These results indicate that Mel1c mediates monochromatic GL-stimulated IGF-I synthesis through intracellular Gαq/PKC/ERK signaling.

Highlights

The characteristics of light, including its source, spectra, intensity, and regimen, play important roles in avian growth and reproduction
We investigated the pathway of activation of monochromatic photostimulated insulin-like growth factor I (IGF-I) synthesis in broiler livers by Mel1c, and found that a signaling cascade of Gαq/protein kinase C (PKC)/extracellular regulated protein kinases (ERK) is involved
In this study, following exposure to different light treatments, the plasma and livers of intact, sham, or pinealectomy broilers were collected for measurement of the MEL concentration as well as Mel1c and IGF-I mRNA detection at P14

Summary

Introduction

The characteristics of light, including its source, spectra, intensity, and regimen, play important roles in avian growth and reproduction. Green light (GL) stimulation has been shown to accelerate muscle growth in broilers [4], and enhance the secretion of insulin-like growth factor I (IGF-I) by chick embryo hepatocytes [5,6]. Liu et al [10] have shown that GL illumination promoted chick satellite cell myogenic processes during early posthatch stages, and IGF-I played a central role. Previous studies have shown that monochromatic light influenced the secretion of MEL [15], which was involved in IGF-I synthesis [5,16]. We investigated the pathway of activation of monochromatic photostimulated IGF-I synthesis in broiler livers by Mel1c, and found that a signaling cascade of Gαq/protein kinase C (PKC)/extracellular regulated protein kinases (ERK) is involved

Monochromatic Green Light-Regulated Hepatic IGF-I Expression through Mel1c

Animals and Treatment

Primary Hepatocytes Isolation and Culture

Western Blot Analysis

Data Analysis

Conclusions