The adrenal gland is an important endocrine gland in balancing homeostasis and the response to stress by synthesizing and secreting catecholamines (CATs), and it has been confirmed that microRNA-375 (miR-375) is highly expressed in adrenal medulla. However, up to now there are few reports about the functions and related mechanisms in adrenal medulla. The present study was thus designed to study the roles and related mechanisms in rat adrenal medulla. Our results showed that miR-375 was specifically expressed in rat adrenal medulla chromaffin cells, and its expression was downregulated when rats were exposed to stress. The further functional studies demonstrated that the inhibition of endogenous miR-375 induced the secretion of CATs in primary rat medulla chromaffin cells and PC12 cells, whereas miR-375 overexpression resulted in a decline of CAT secretion. In addition, our results showed that miR-375 negatively regulated tyrosine hydroxylase (TH) and dopamine-β-hydroxylase (DBH) and mediated adrenomedullary CAT biosynthesis. These functions of miR-375 were accomplished by its binding to the 3'-untranslated region of Sp1, which was involved in the regulation of TH and DBH expressions. These novel findings suggest that miR-375 acts as a potent negative mediator in regulating the synthesis and secretion of CATs in the adrenal medulla during the maintenance of homeostasis under stress.
Donkey milk is consumed by humans for its nutritional and therapeutic properties. MicroRNAs (miRNAs) and messenger RNAs (mRNAs) have been implicated in the regulation of milk component synthesis and mammary gland development. However, the regulatory profile of the miRNAs and mRNAs involved in lactation in donkeys is unclear. We performed mRNA-seq and miRNA-seq and constructed coexpression regulatory networks for the mammary glands during the lactating and nonlactating period of jennies. We identified 3144 differentially expressed (DE) mRNAs (987 upregulated mRNAs and 2157 downregulated mRNAs) and 293 DE miRNAs (231 upregulated miRNAs and 62 downregulated miRNAs) in the lactating group compared to the nonlactating group. The DE miRNA target mRNA were significantly associated with pathways related to RNA polymerase, glycosphingolipid biosynthesis, mRNA surveillance, ribosome biogenesis in eukaryotes, glycerophospholipid metabolism, Ras signaling, and the fly hippo signaling pathway. The mRNA–miRNA coregulation analysis showed that novel-m0032-3p, miR-195, miR-26-5p, miR-23-3p, miR-674-3p, and miR-874-3p are key miRNAs that target mRNAs involved in immunity and milk lipid, protein, and vitamin metabolism in the jenny mammary gland. Our results improve the current knowledge of the molecular mechanisms regulating bioactive milk component metabolism in the mammary glands and could be used to improve milk production in donkeys.
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