Matrix metalloproteinase-7 and epidermal growth factor receptor mediate hypoxia-induced extracellular signal-regulated kinase 1/2 mitogen-activated protein kinase activation and subsequent proliferation in bladder smooth muscle cells.
Low oxygen tension (hypoxia) has been implicated in proliferation of vascular smooth muscle cells (SMCs) of the lung. Tissue hypoxia also occurs in the obstructed bladder. The extracellular-regulated kinase mitogen-activated protein kinase 1/2 (Erk1/2) pathway is induced in many cell types during hypoxia. We examined whether hypoxia (3% O2), compared with normoxia (21% O2), induces proliferation responses and activation of the Erk1/2 pathways in primary rat bladder smooth muscle cells (BSMCs). We show that hypoxia induces proliferation of BSMCs at 18 h and, although reduced at 22 h, still remained above normoxic levels. Hypoxia induced a strikingly transient activation of Erk1/2 that lasted only 10-30 min. However, inhibition of the transient Erk1/2 activity with a specific mitogen-activated protein kinase kinase 1 (MEK-1) inhibitor PD 98059 prevented subsequent hypoxia-induced proliferation at 18 h. Interestingly, inhibition of general matrix metalloproteinase (MMP) activity, using either doxycycline or GM 6001, prevented both transient Erk1/2 activity and subsequent proliferation in response to hypoxia. Furthermore, MMP-7 (matrilysin) is activated in the conditioned medium (CM) of BSMCs at 10-20 min of hypoxia. In addition, MMP-7 was also transcriptionally induced at 6 h of hypoxia in an Erk1/2-dependent manner. Moreover, transient Erk1/2 activation and BSMC proliferation were both dependent on epidermal growth factor receptor (EGFR/HER1) but not neu receptor (HER2/ERB2) autophosphorylation. We conclude that hypoxia leads to Erk1/2 activation, which appears to modulate BSMC proliferation through MMP-7-and EGFR-mediated mechanisms.
Sabha
Nesrin
N
Division of Infection, Immunity, Injury, & Repair, The Research Institute, The Hospital for Sick Children and Institute for Medical Sciences, University of Toronto, Toronto, Ontario, Canada.
Aitken
Karen
K
Lorenzo
Armando J
AJ
Szybowska
Marta
M
Jairath
Ashish
A
Bägli
Darius J
DJ
D000818:Animals; D015687:Cell Hypoxia; D049109:Cell Proliferation / Q000187:drug effects; D004789:Enzyme Activation; D066246:ErbB Receptors / Q000378:metabolism* / Q000502:physiology; D005419:Flavonoids / Q000494:pharmacology; D005786:Gene Expression Regulation; D048369:MAP Kinase Kinase 1 / Q000037:antagonists & inhibitors; D020935:MAP Kinase Signaling System / Q000502:physiology; D020783:Matrix Metalloproteinase 7 / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism*; D009130:Muscle, Smooth / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D010766:Phosphorylation; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D001743:Urinary Bladder / Q000166:cytology*
D005419:Flavonoids; D012333:RNA, Messenger; D066246:ErbB Receptors; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D048369:MAP Kinase Kinase 1; D020783:Matrix Metalloproteinase 7; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one