MicroRNA‐7 inhibits melatonin synthesis by acting as a linking molecule between leptin and norepinephrine signaling pathways in pig pineal gland

Abstract

MicroRNAs, including microRNA‐7 (miR‐7), are important modulators of numerous gene expressions and the related biological processes. Melatonin is a key hormone regulating daily and seasonal rhythms, in which a variety of positive and negative regulatory factors, such as norepinephrine (NE) and leptin, are involved. However, the interactions among these factors and the mechanisms remain to be elucidated. The aims of the present study were to identify the functions and the related mechanisms of miR‐7 in regulating melatonin synthesis and secretion through in vitro and in vivo experiments in pineal gland of pigs, which is an important animal model for agricultural and biomedical studies. Our results firstly show that miR‐7 is specifically expressed in porcine pinealocytes and negatively regulates melatonin synthesis. The further functional studies show that the dynamic expression levels of miR‐7 are contrary to the melatonin levels throughout the day, and the forced inhibition of endogenous miR‐7 in porcine pinealocytes sharply increases arylalkylamine N‐acetyltransferase (AANAT) expression by 80.0% (P = 0.0031) and melatonin levels by 81.0% (P = 0.0421), whereas miR‐7 over‐expression down‐regulates AANAT expression by 38.6% (P = 0.0004) and melatonin levels by 37.6% (P = 0.0212). In addition, the miR‐7 expression is up‐regulated by leptin through the JAK/STAT3 signaling pathway, and the in vivo intracerebroventricular injection of leptin increases miR‐7 expression by 80.0% (P = 0.0044) in porcine pineal glands and reduces melatonin levels by 57.1% (P = 0.0060) compared with the controls. This functional inhibition of melatonin synthesis by miR‐7 is accomplished by its binding to the 3′‐UTR of Raf1. Further, our results demonstrate that the RAF1/MEK/ERK signaling pathway mediates NE‐induced AANAT expression, whereas leptin attenuates NE's function through miR‐7. Taken together, the results demonstrated that leptin activates the JAK/STAT3 signaling pathway to increase the expression of miR‐7, which acts as a negative regulatory molecule inhibiting NE‐activated RAF1/MEK/ERK signaling pathway by targeting Raf1, resulting in decreased AANAT expression and melatonin synthesis. These findings suggest that miR‐7 is a novel negative regulator of melatonin synthesis and links leptin‐ and NE‐mediated signaling pathways in porcine pineal glands, which will contribute to our understanding in the establishment of the biological rhythms resulting from melatonin.

LIM homeodomain transcription factor Isl1 affects urethral epithelium differentiation and apoptosis via Shh

“…Our results showed that Isl1 deficiency resulted in GT morphological abnormalities and complete absence of the male urethra at E18.5. In support, our results are in agreement with reports that Isl1 is expressed in mesenchymal cells derived from mesoderm, which subsequently forms the prepuce 41,42 .Thus, ISL1 is crucial for several aspects of urethral formation, as in the nervous system 23,24,50 , digestive system 25,26 , and endocrine glands systems 39,40 .…”

“…Expression and function of the LIM homeobox protein ISL1 has been extensively studied in the nervous system 23,26,50 , digestive system 24,25 , and endocrine glands 39,40 . Results of the present study demonstrated that Isl1 was expressed in urethral epithelial cells throughout urethral development, and that ablation of Isl1 just prior to GT development in Isl1 MCM/Del mutants led to GT morphological abnormalities and urethral hypoplasia.…”

“…The LIM homeobox gene Isl1 plays critical roles in multiple tissues in mouse embryonic development, including the nerve 23,24 , stomach 25,26 , limb 27,28 , and heart 29–32 , by functioning in cell proliferation, apoptosis 33 , and differentiation 34,35 . ISL1 is also involved in hormone biosynthesis and secretion in endocrine tissues such as pancreatic islets 36,37 , pituitary 38 , and pineal glands 39,40 . Isl1 expression has been detected in genital mesenchyme, and Isl1 knockout in mesenchyme results in urogenital malformations, although urethral development in these Isl1 mutants was unaffected 41 .…”

A meta‐analysis of microRNA networks regulated by melatonin in cancer: Portrait of potential candidates for breast cancer treatment

“…Among the 46 differentially expressed miRNAs, 29 were upregulated, and 17 were downregulated (Table S2). Table 1 shows the upregulated miRNAs found in breast (18), oral (3), hepatic (1), gastric (1), colorectal (2), and prostate (2) cancer cell lines. Downregulated miRNAs were found in breast (14), oral (1), and prostate (1) cancer cell lines and in glioma cell lines (1); all miRNAs were validated by RT-PCR.…”

“…15,16 In this context, circadian oscillators and melatonergic signaling molecules can be reciprocally affected by miRNAs. [17][18][19] Although the molecular mechanisms whereby melatonin interacts with miRNAs are only partially known, new information is available regarding its direct or indirect actions on regulatory miRNAs in cancer. 20 In addition to the spread of mutated cells and aberrant expression of miRNAs and their targets in cancer cells, dysregulated miRNAs can be transmitted via exosomes and ectosomes to other cells.…”