title: Cyclic stretch induces proliferation and TGF-beta1-mediated apoptosis via p38 and ERK in ureteric bud cells.
abstract: We previously reported that p38 mitogen-activated protein kinase (p38) and phosphorylated ERK are upregulated in cyst epithelium of human renal dysplasia and obstructive uropathy in fetal lambs (Omori S, Fukuzawa R, Hida M, Awazu M. Kidney Int 61: 899-906, 2002; Omori S, Kitagawa H, Koike J, Fujita H, Hida M, Pringle KC, Awazu M. Kidney Int 73: 1031-1037, 2008). Dysplastic epithelium is characterized by proliferation, apoptosis, and upregulation of Pax2 and transforming growth factor (TGF)-beta1. In the present study, we investigated whether cyclic mechanical stretching of ureteric bud cells, a mimic of the hydrodynamic derangement after fetal urinary tract obstruction, reproduces events seen in vivo. Cyclic stretch activated p38 and ERK and upregulated Pax2 expression in a time-dependent manner in ureteric bud cells. Stretch-stimulated Pax2 expression was suppressed by a p38 inhibitor, SB203580, or a MEK inhibitor, PD98059. 5-Deoxyuridine incorporation was increased by stretch at 24 h, which was also abolished by SB203580 or PD98059. On the other hand, apoptosis was not induced at 24 h by stretch but was significantly increased at 48 h. TGF-beta1 secretion was increased by stretch at 24 h, which was inhibited by SB203580 or PD98059. Inhibition of p38 or ERK as well as anti-TGF-beta antibody abolished the stretch-induced apoptosis. Finally, exogenous TGF-beta1 induced apoptosis of ureteric bud cells, which was inhibited by SB203580 and PD98059. In conclusion, cyclic stretch induces Pax2 upregulation, proliferation, and TGF-beta1-mediated apoptosis, features characteristic of dysplastic epithelium, via p38 and ERK in ureteric bud cells.
authors.affiliation: Dept. of Pediatrics, Keio Univ. School of Medicine, Tokyo, Japan.
authors.forename: Hisayo
authors.initials: H
authors.lastname: Fujita
authors.forename: Mariko
authors.initials: M
authors.lastname: Hida
authors.forename: Katsuyoshi
authors.initials: K
authors.lastname: Kanemoto
authors.forename: Keiichi
authors.initials: K
authors.lastname: Fukuda
authors.forename: Michio
authors.initials: M
authors.lastname: Nagata
authors.forename: Midori
authors.initials: M
authors.lastname: Awazu
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D002453:Cell Cycle / Q000502:physiology; D002460:Cell Line; D049109:Cell Proliferation; D004195:Disease Models, Animal; D004791:Enzyme Inhibitors / Q000494:pharmacology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D005419:Flavonoids / Q000494:pharmacology; D007093:Imidazoles / Q000494:pharmacology; D051379:Mice; D008822:Mice, Transgenic; D051762:PAX2 Transcription Factor / Q000378:metabolism; D011725:Pyridines / Q000494:pharmacology; D015398:Signal Transduction / Q000502:physiology; D013314:Stress, Mechanical; D013997:Time Factors; D053773:Transforming Growth Factor beta1 / Q000378:metabolism*; D014513:Ureter / Q000166:cytology* / Q000196:embryology / Q000378:metabolism*; D014517:Ureteral Obstruction / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D004791:Enzyme Inhibitors; D005419:Flavonoids; D007093:Imidazoles; D051762:PAX2 Transcription Factor; C497319:Pax2 protein, mouse; D011725:Pyridines; D053773:Transforming Growth Factor beta1; D048049:Extracellular Signal-Regulated MAP Kinases; D048051:p38 Mitogen-Activated Protein Kinases; C093642:SB 203580; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one