title: Hypoxia‑inducible adrenomedullin ameliorates the epithelial-to-mesenchymal transition in human proximal tubular epithelial cells.
abstract: Renal tubular epithelial cells can enter the epithelial‑to‑mesenchymal transition (EMT) in response to chronic hypoxia. EMT is a process which involves the phenotypic conversion of epithelial cells, that is believed to have an important role in renal fibrosis. However, the underlying mechanisms of the involvement of EMT in renal fibrosis remain to be elucidated. Adrenomedullin (AMD) has been implicated in renal fibrosis and is induced by hypoxia. The aims of the present study were to determine whether ADM signaling was active in human proximal tubular epithelial cells cultured under hypoxic conditions, and to observe the activity of ADM during EMT. The expression levels of ADM were significantly increased, in a time‑dependent manner, in HK‑2 and HKC human proximal tubular epithelial cells, cultured under hypoxic conditions. Overexpression of exogenous ADM was accompanied by increased expression levels of the epithelial markers E‑cadherin and tight junction protein‑1, and decreased expression levels of the mesenchymal markers vimentin and α‑smooth muscle actin, during hypoxia. Knock‑down of ADM expression by small hairpin RNA, or co‑administration of an ADM peptide inhibitor, in HK‑2 cells significantly exacerbated hypoxia‑induced EMT, as compared to the lack of effect observed in the untransfected controls. ADM was shown to suppress EMT by inhibiting the activation of extracellular signal‑regulated kinase (ERK), and this effect was prevented by the ERK activator apigenin. The results of the present study suggest that ADM has an important role in promoting EMT in hypoxic human proximal tubular epithelial cells. ADM may therefore represent a novel therapeutic target in the treatment of injured kidneys.
authors.affiliation: Department of Nephrology, First Affiliated Hospital of Xinxiang Medical University, Xinxiang, Henan 453100, P.R. China.
authors.forename: Tiechui
authors.initials: T
authors.lastname: Zhu
authors.affiliation: Department of Nephrology, First Affiliated Hospital of Xinxiang Medical University, Xinxiang, Henan 453100, P.R. China.
authors.forename: Jun
authors.initials: J
authors.lastname: Yang
authors.affiliation: Department of Nephrology, First Affiliated Hospital of Xinxiang Medical University, Xinxiang, Henan 453100, P.R. China.
authors.forename: Xiangdong
authors.initials: X
authors.lastname: Liu
authors.affiliation: Department of Nephrology, First Affiliated Hospital of Xinxiang Medical University, Xinxiang, Henan 453100, P.R. China.
authors.forename: Lianyun
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Department of Nephrology, First Affiliated Hospital of Xinxiang Medical University, Xinxiang, Henan 453100, P.R. China.
authors.forename: Jie
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Department of Nephrology, First Affiliated Hospital of Xinxiang Medical University, Xinxiang, Henan 453100, P.R. China.
authors.forename: Yongtao
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Department of Nephrology, First Affiliated Hospital of Xinxiang Medical University, Xinxiang, Henan 453100, P.R. China.
authors.forename: Haijun
authors.initials: H
authors.lastname: Ma
authors.affiliation: Department of Nephrology, First Affiliated Hospital of Xinxiang Medical University, Xinxiang, Henan 453100, P.R. China.
authors.forename: Zhenhui
authors.initials: Z
authors.lastname: Ren
mesh_terms: D053607:Adrenomedullin / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D004789:Enzyme Activation; D004847:Epithelial Cells / Q000378:metabolism* / Q000473:pathology*; D058750:Epithelial-Mesenchymal Transition / Q000235:genetics; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D055785:Gene Knockdown Techniques; D006801:Humans; D000860:Hypoxia / Q000378:metabolism*; D007687:Kidney Tubules, Proximal / Q000166:cytology*; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics; D014158:Transcription, Genetic
chemical_list: D034741:RNA, Small Interfering; D053607:Adrenomedullin; D048049:Extracellular Signal-Regulated MAP Kinases