title: Beta-casomorphin-7 prevents epithelial-mesenchymal transdifferentiation of NRK-52E cells at high glucose level: Involvement of AngII-TGF-β1 pathway.
abstract: BACKGROUND
  Hyperglycemia is the most important risk factor in the progression of renal fibrosis in diabetic kidney. Based on previous studies, β-casomorphin-7 may exert anti-fibrotic activities in diabetic rats. However, the role of β-casomorphin-7 in the pathogenesis of renal tubulointerstitial fibrosis remains unclear. Thus, this study was designed to investigate the protective effect of β-casomorphin-7 on epithelial-mesenchymal transition (EMT) of NRK-52E cells treated under hyperglycemic condition and to explore the possible mechanism.
  
  
  METHODS
  NRK-52E cells were cultured in high glucose (30 mM) for 3 days. Different concentrations of β-casomorphin-7, naloxone (antagonist of opioid receptor) and losartan (antagonist of angiotensin II type I receptor) were added in the culture. Expression of α-smooth muscle actin (α-SMA), E-cadherin, vimentin and cytokeratin19 mRNA were determined by real-time PCR. Protein levels of E-cadherin and α-SMA were analyzed by Western blotting. The concentrations of angiotensin (Ang) II and transforming growth factor β1 (TGF-β1) in the culture medium were determined.
  
  
  RESULTS
  High glucose-induced up-regulation of vimentin mRNA and α-SMA mRNA and protein were significantly inhibited by β-casomorphin-7. On the contrary, high glucose-induced down-regulation of cytokeratin19 mRNA and E-cad mRNA and protein was significantly reversed by β-casomorphin-7. β-casomorphin-7 significantly alleviate high glucose induced increase of AngII and TGF-β1 in the culture. Moreover, losartan significantly attenuated the expression of TGF-β1 and EMT of NRK-52E cells treated under hyperglycemic condition. But naloxone did not affect the EMT of NRK-52E cells treated by high glucose and β-casomorphin-7.
  
  
  CONCLUSIONS
  We demonstrate that β-casomorphin-7 has the potential to inhibit high glucose-induced renal proximal tubular EMT partly by modulating AngII-TGF-β1 pathway, but not by opioid receptor.
authors.affiliation: Key Lab of Animal Physiology and Biochemistry, Ministry of Agriculture, Nanjing Agriculture University, Nanjing, 210095, People's Republic of China; Key Lab of Human Function Genomics Jiangsu Province, Nanjing Medical University, Nanjing, 210029, People's Republic of China.
authors.forename: Wei
authors.initials: W
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Meat Processing and Quality Control, Ministry of Education, Nanjing Agricultural University, Nanjing 210095, People's Republic of China; Key Laboratory of Agricultural and Animal Products Processing and Quality Control, Ministry of Agriculture, Nanjing Agricultural University, Nanjing 210095, People's Republic of China.
authors.forename: Shangxin
authors.initials: S
authors.lastname: Song
authors.affiliation: Key Lab of Animal Physiology and Biochemistry, Ministry of Agriculture, Nanjing Agriculture University, Nanjing, 210095, People's Republic of China.
authors.forename: Fei
authors.initials: F
authors.lastname: Liu
authors.affiliation: Key Lab of Animal Physiology and Biochemistry, Ministry of Agriculture, Nanjing Agriculture University, Nanjing, 210095, People's Republic of China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Key Lab of Animal Physiology and Biochemistry, Ministry of Agriculture, Nanjing Agriculture University, Nanjing, 210095, People's Republic of China. Electronic address: zhangyuanshu@njau.edu.cn.
authors.forename: Yuanshu
authors.initials: Y
authors.lastname: Zhang
mesh_terms: D000804:Angiotensin II / Q000378:metabolism*; D000818:Animals; D002460:Cell Line; D004723:Endorphins / Q000494:pharmacology*; D004847:Epithelial Cells / Q000187:drug effects / Q000502:physiology*; D058750:Epithelial-Mesenchymal Transition / Q000187:drug effects / Q000502:physiology*; D005947:Glucose / Q000494:pharmacology*; D007687:Kidney Tubules, Proximal / Q000187:drug effects / Q000503:physiopathology*; D010446:Peptide Fragments / Q000494:pharmacology*; D051381:Rats; D053773:Transforming Growth Factor beta1 / Q000378:metabolism*
chemical_list: D004723:Endorphins; D010446:Peptide Fragments; D053773:Transforming Growth Factor beta1; D000804:Angiotensin II; C041128:beta-casomorphin 7; D005947:Glucose
keywords: Angiotensin II; Diabetic nephropathy; Epithelial-mesenchymal transdifferentiation; NRK-52E; TGF-β1; β-casomorphin-7