title: Paricalcitol attenuates 4-hydroxy-2-hexenal-induced inflammation and epithelial-mesenchymal transition in human renal proximal tubular epithelial cells.
abstract: 4-Hydroxy-2-hexenal (HHE), the aldehyde product of lipid peroxidation, may be responsible for the pathogenesis of progressive renal disease. Recently, paricalcitol (19-nor-1,25-dihydroxyvitamin D2) was shown to be renoprotective through its anti-inflammatory and antifibrotic effects in various experimental nephropathy models. In this study, we investigated the effects of paricalcitol on inflammation and epithelial-mesenchymal transition (EMT) after HHE-induced renal tubular epithelial cell injury. To investigate the molecular mechanisms underlying HHE-induced renal tubular cell injury, the human proximal tubular epithelial (HK-2) cells cultured with 10 µM HHE in the presence or absence of paricalcitol. In HK-2 cells, paricalcitol attenuated the HHE-induced expression of extracellular signal-regulated kinase, c-Jun N-terminal kinase, and p38 mitogen-activated protein kinase, and prevented nuclear factor-κB (NF-κB) activation. The expression of the inflammatory proteins inducible nitric oxide synthase and cyclooxygenase-2 was attenuated by paricalcitol pretreatment. In addition, HHE increased the expression of the transforming growth factor (TGF)-β/Smad signaling proteins and fibrotic proteins, such as α-smooth muscle actin and connective tissue growth factor; this inducible expression was suppressed by pretreatment with paricalcitol. Treatment with HHE resulted in the activation of the β-catenin signaling pathway, and paricalcitol pretreatment reduced the expression of β-catenin in HHE-treated HK-2 cells. Coimmunoprecipitation shows that paricalcitol induced vitamin D receptor (VDR)/β-catenin complex formation in HK-2 cells. Also immunofluorescence staining revealed that co-localization of VDR and β-catenin in the nuclei. ICG-001, an inhibitor of β-catenin, decreased the expression of TGF-β1 and attenuated HHE-induced tubular EMT. These results show that paricalcitol attenuated HHE-induced renal tubular cell injury by suppressing inflammation and EMT process through inhibition of the NF-κB, TGF-β/Smad, and β-catenin signaling pathways.
authors.affiliation: Department of Physiology, Chonnam National University Medical School, Gwangju, Korea.
authors.forename: Chang Seong
authors.initials: CS
authors.lastname: Kim
authors.forename: Soo Yeon
authors.initials: SY
authors.lastname: Joo
authors.forename: Ko Eun
authors.initials: KE
authors.lastname: Lee
authors.forename: Joon Seok
authors.initials: JS
authors.lastname: Choi
authors.forename: Eun Hui
authors.initials: EH
authors.lastname: Bae
authors.forename: Seong Kwon
authors.initials: SK
authors.lastname: Ma
authors.forename: Suhn Hee
authors.initials: SH
authors.lastname: Kim
authors.forename: Jongun
authors.initials: J
authors.lastname: Lee
authors.forename: Soo Wan
authors.initials: SW
authors.lastname: Kim
mesh_terms: D000447:Aldehydes / Q000633:toxicity*; D015153:Blotting, Western; D002460:Cell Line; D051546:Cyclooxygenase 2 / Q000378:metabolism; D004847:Epithelial Cells / Q000378:metabolism*; D058750:Epithelial-Mesenchymal Transition / Q000187:drug effects*; D004872:Ergocalciferols / Q000494:pharmacology* / Q000627:therapeutic use; D005455:Fluorescent Antibody Technique; D006801:Humans; D007150:Immunohistochemistry; D047468:Immunoprecipitation; D007249:Inflammation / Q000139:chemically induced* / Q000188:drug therapy*; D007687:Kidney Tubules, Proximal / Q000166:cytology*; D019001:Nitric Oxide Synthase / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D051176:beta Catenin / Q000378:metabolism
chemical_list: D000447:Aldehydes; D004872:Ergocalciferols; D051176:beta Catenin; C045934:4-hydroxy-2-hexenal; C084656:paricalcitol; D019001:Nitric Oxide Synthase; D051546:Cyclooxygenase 2