In vitro activation of extracellular signal-regulated kinase1/2 in the inner ear of guinea pigs.
Growth factors such as vascular endothelial growth factor (VEGF) exert their proliferative properties partly through activation of mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK1/2). Although both VEGF and inactive ERK could be detected in the inner ear of guinea pigs, under normal conditions activated ERK (phospho-ERK) was found only sparely. Cochleae of adult guinea pigs were removed, incubated with VEGF in a carbogen-gased organ-bath for 5, 15, 30 and 60 min (n=6 in each group), fixed with PFA 4%, embedded in paraffin and sectioned, followed by immunohistochemical staining to inactive and active ERK. Whereas inactive ERK was found in all cochleae, in sensory and supporting cells of the apex activated ERK was strongly detected after 5-min VEGF-incubation. After 15 min all Corti-organs showed clear staining corresponding to activated ERK, which decreased again after 30 min. Faint staining in endothelial cells of the spring-coil-vessels and in the spiral ganglion cells was found after 30 min and was increased after 60 min, while the staining in the Corti-organs vanished. Addition of the MEK-inhibitor PD 98059 to the organ-bath led to diminished phospho-ERK1/2 immunostaining. These findings provide evidence for a VEGF-dependent phosphorylation of ERK1/2 in the cochlea. Activated ERK1/2 is thought to support axonal outgrowth, enhancement of cell survival and to regulate the turnover of the NO/cGMP-pathway.
Hess
Alexander
A
Department of Oto-Rhino-Laryngology, University of Cologne, Joseph-Stelzmannstr 9, D-50924 Cologne, Germany.
Labbé
Daniel
D
Michel
Olaf
O
Teranishi
Masa-aki
MA
Orzechowska
Olga
O
Schmidt
Annette
A
Addicks
Klaus
K
Bloch
Wilhelm
W
D000818:Animals; D015153:Blotting, Western; D003051:Cochlea / Q000378:metabolism*; D016228:Endothelial Growth Factors / Q000008:administration & dosage / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D005419:Flavonoids / Q000494:pharmacology; D006168:Guinea Pigs; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D036341:Intercellular Signaling Peptides and Proteins / Q000008:administration & dosage / Q000378:metabolism*; D008222:Lymphokines / Q000008:administration & dosage / Q000378:metabolism*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D009925:Organ of Corti / Q000378:metabolism*; D010766:Phosphorylation; D013997:Time Factors; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors
D016228:Endothelial Growth Factors; D004791:Enzyme Inhibitors; D005419:Flavonoids; D036341:Intercellular Signaling Peptides and Proteins; D008222:Lymphokines; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; D020928:Mitogen-Activated Protein Kinases; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one