title: Role of JNK-1 regulation in the protection of contact-inhibited fibroblasts from oxidative stress.
abstract: The molecular signaling events leading to protection from oxidative stress-induced apoptosis upon contact inhibition have not been fully investigated. Previous research has indicated a role for mitogen-activated protein kinases (MAPKs) in the regulation of contact inhibition, and these proteins have also been associated with cell cycle regulation and stress-induced apoptosis. The potential role of the MAPK JNK-1 in the stress-response of actively proliferating and contact-inhibited cells was investigated. Actively proliferating normal fibroblasts (BJ) and fibrosarcoma cells (HT-1080) were stressed with H2O2, and levels of activated JNK-1 and cleaved PARP were ascertained. Similarly, these results were compared with levels of activated JNK-1 and cleaved PARP detected in H2O2-stressed confluent fibrosarcoma or contact-inhibited fibroblast cells. Contact-inhibited fibroblasts were protected from apoptosis in comparison to subconfluent fibroblasts, concurrent with decreased JNK-1 activation. Increased culture density of fibrosarcoma cells was not protective against apoptosis, and these cells did not demonstrate density-dependent alterations in the JNK-1 stress response. This decreased activation of JNK-1 in stressed, contact-inhibited cells did not appear to be dependent upon increased expression of MKP-1; however, over-expression of MKP-1 was sufficient to result in a slight decrease in H2O2-stimulated PARP cleavage. Increasing the antioxidant capacity of fibroblasts through NAC-treatment not only lessened H2O2-stimulated JNK-1 activation, but also did not influence the expression of MKP-1. Taken together, these results suggest that regulation of negative regulation of JNK-1 upon contact inhibition is protective against apoptosis, and that this regulation is independent of MKP-1.
authors.affiliation: Department of Biology, Monmouth University, 400 Cedar Avenue, West Long Branch, NJ 07764, USA.
authors.forename: Marian
authors.initials: M
authors.lastname: Gaballah
authors.forename: Michael
authors.initials: M
authors.lastname: Slisz
authors.forename: Dorothy
authors.initials: D
authors.lastname: Hutter-Lobo
mesh_terms: D017209:Apoptosis; D002460:Cell Line; D003260:Contact Inhibition; D054638:Dual Specificity Phosphatase 1; D005347:Fibroblasts / Q000166:cytology / Q000502:physiology*; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D048055:Mitogen-Activated Protein Kinase 8 / Q000502:physiology*; D018384:Oxidative Stress; D011065:Poly(ADP-ribose) Polymerases
chemical_list: D006861:Hydrogen Peroxide; D011065:Poly(ADP-ribose) Polymerases; D048055:Mitogen-Activated Protein Kinase 8; C517019:DUSP1 protein, human; D054638:Dual Specificity Phosphatase 1