Role of protein kinase a pathway in epidermal growth factor-induced liver cell repair.
To gain a better understanding of the mechanisms that control the repair process in the injured liver, the actions of epidermal growth factor (EGF) and protein kinase A (PKA) were studied. Normal rat liver cells (clone 9) were grown to confluence. Standardized excisional wounds were made with a razor blade. The extent of hepatocyte migration into the wound was measured and determined at specific time intervals using a computerized digital analyzing system. Immunostaining of F-actin was performed with a fluorescein-labeled phalloidin. EGF significantly stimulated liver cell migration, whereas specific EGF-neutralizing antibody inhibited the EGF-induced migration. Agents that activate PKA at different stages of the PKA activation pathway, including 3-isobutyl-1-methylxanthine (IBMX), forskolin, and cholera toxin, inhibited EGF-induced migration. EGF triggered formation of actin stress fibers. PKA-activating agents inhibited actin stress fiber formation and stretching of cells at the wound margin. The following conclusions were drawn: (1) In excisional wounds of hepatocyte monolayers, both EGF and PKA exert action on actin microfilaments, which are stretched by EGF and inhibited by PKA; (2) the enhanced repair of wounded hepatocyte monolayers by EGF is blocked by activation of the PKA pathway at various levels; and (3) these actions of EGF and PKA indicate their important regulatory roles in controlling the rate of hepatocyte migration and restitution following the creation of excisional wounds.
Kikuchi
M
M
Department of Surgery and Medicine, Department of Veterans Affairs Medical Center, Long Beach, CA 90822, USA.
Ma
T Y
TY
Tarnawski
A S
AS
Shimada
H
H
Sarfeh
I J
IJ
D000818:Animals; D002465:Cell Movement; D002478:Cells, Cultured; D004815:Epidermal Growth Factor / Q000502:physiology*; D008099:Liver / Q000166:cytology* / Q000293:injuries*; D008115:Liver Regeneration; D008297:Male; D011494:Protein Kinases / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction
D004815:Epidermal Growth Factor; D011494:Protein Kinases