title: Age affects ERK1/2 and NRF2 signaling in the regulation of GCLC expression.
abstract: We previously reported that activator protein-1 (AP-1) DNA binding activity was increased in vascular smooth muscle cells (VSMC) from old rats when exposed to high glucose or tumor necrosis factor (TNF-alpha) (Li et al., 2003. J Cell Physiol 197:418-425). We have now examined the relationship between the age-dependent activation of the ERK1/2-AP-1 pathway and modulation of constitutive gene expression of the catalytic subunit of glutamate-cysteine ligase (GCLC) in response to high glucose and TNF-alpha. GCLC mRNA levels were higher in VSMC from old rats compared to young, a pattern consistent with its protein levels. To determine whether age-related activation of ERK1/2-AP-1 signaling is responsible for the up-regulation of GCLC, the MEK inhibitors, PD98059 and U0126, were used to block ERK1/2 in VSMC from old rats. An increase in GCLC with inhibitors was observed, diminishing the likelihood of ERK1/2-AP-1 activation as the up-regulating signal for GCLC. However, the transcription factor Nrf2 was higher in nuclei and accompanied by increased Nrf2-ARE binding in VSMC from old rats. Furthermore, MEK inhibitors increased nuclear Nrf2 and Nrf2/ARE binding. These data suggest opposing effects of Nrf2 and ERK1/2 signaling in the modulation of GCLC expression in old animals.
authors.affiliation: University of Alabama at Birmingham, Birmingham, Alabama, USA [corrected]
authors.forename: Muyao
authors.initials: M
authors.lastname: Li
authors.forename: Rui-Ming
authors.initials: RM
authors.lastname: Liu
authors.forename: Cynthia R
authors.initials: CR
authors.lastname: Timblin
authors.forename: Suzanne G
authors.initials: SG
authors.lastname: Meyer
authors.forename: Brooke T
authors.initials: BT
authors.lastname: Mossman
authors.forename: Naomi K
authors.initials: NK
authors.lastname: Fukagawa
mesh_terms: D000367:Age Factors; D000375:Aging; D000818:Animals; D020134:Catalytic Domain; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D005947:Glucose / Q000494:pharmacology; D005721:Glutamate-Cysteine Ligase / Q000378:metabolism*; D005978:Glutathione / Q000378:metabolism; D020930:MAP Kinase Kinase Kinases; D008297:Male; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism*; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000378:metabolism*; D051267:NF-E2-Related Factor 2 / Q000378:metabolism*; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D051381:Rats; D011916:Rats, Inbred F344; D015398:Signal Transduction; D013997:Time Factors; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D015854:Up-Regulation
chemical_list: D051267:NF-E2-Related Factor 2; D016760:Proto-Oncogene Proteins c-fos; D014409:Tumor Necrosis Factor-alpha; D048052:Mitogen-Activated Protein Kinase 3; D020930:MAP Kinase Kinase Kinases; D005721:Glutamate-Cysteine Ligase; D005978:Glutathione; D005947:Glucose