title: Estrogen regulates transcription factors STAT-1 and NF-kappaB to promote inducible nitric oxide synthase and inflammatory responses.
abstract: Estrogen regulation of inflammatory responses has broad physiological and pathological consequences. However, the molecular mechanism of estrogen regulation of inflammation is still poorly understood. In this study, we report that activation of both STAT-1 and NF-kappaB signaling is essential for Con A-induced inducible NO synthase (iNOS) and NO in murine splenocytes. Estrogen enhances STAT-1 DNA-binding activity without increasing the expression of phosphorylated and total STAT-1 protein. We have recently reported that estrogen blocks the nuclear expression of NF-kappaB p65 and modifies nuclear NF-kappaBp50. Here, we demonstrated that both nuclear STAT-1 and NF-kappaB are modified by serine protease-mediated proteolysis, which resulted in altered STAT-1 and NF-kappaB activity/signaling in splenocytes from estrogen-treated mice. Inhibition of serine protease activity with 4-(2-aminoethyl)benzenesulfonyl fluoride hydrochloride (AEBSF) restores the nuclear expression of full-length STAT-1 and NF-kappaB proteins, and resulted in decreased STAT-1 DNA-binding activity and formation of NF-kappaB p65/p50 binding complexes in nuclei of splenocytes from estrogen-treated mice. Consequently, there is significantly decreased iNOS and IFN-gamma production in AEBSF-treated splenocytes from estrogen-treated mice, which suggests a positive regulatory role of truncated STAT-1 and/or NF-kappaB. Interestingly, there is increased production of MCP-1 in STAT-1 or NF-kappaB small interfering RNA-transfected cells, as well as in AEBSF-treated splenocytes from estrogen-treated mice. These data suggest a differential role of truncated STAT-1 and NF-kappaB in regulation of various inflammatory molecules in splenocytes from estrogen-treated mice. Together, our data reveal a novel molecular mechanism of estrogen-mediated promotion of inflammatory responses, which involves posttranslational modification of STAT-1 and NF-kappaB proteins.
authors.affiliation: Center for Molecular Medicine and Infectious Diseases, Department of Biomedical Sciences and Pathobiology, Virginia-Maryland Regional College of Veterinary Medicine, Virginia Polytechnic Institute and State University, Blacksburg, VA 24060, USA.
authors.forename: Rujuan
authors.initials: R
authors.lastname: Dai
authors.forename: Rebecca A
authors.initials: RA
authors.lastname: Phillips
authors.forename: Ebru
authors.initials: E
authors.lastname: Karpuzoglu
authors.forename: Deena
authors.initials: D
authors.lastname: Khan
authors.forename: S Ansar
authors.initials: SA
authors.lastname: Ahmed
mesh_terms: D000818:Animals; D015153:Blotting, Western; D024202:Electrophoretic Mobility Shift Assay; D004797:Enzyme-Linked Immunosorbent Assay; D004967:Estrogens / Q000494:pharmacology*; D015870:Gene Expression; D005786:Gene Expression Regulation / Q000187:drug effects; D007249:Inflammation / Q000276:immunology*; D007371:Interferon-gamma / Q000276:immunology / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D016328:NF-kappa B / Q000187:drug effects* / Q000276:immunology / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II / Q000187:drug effects* / Q000276:immunology / Q000378:metabolism; D011499:Protein Processing, Post-Translational / Q000187:drug effects*; D050794:STAT1 Transcription Factor / Q000187:drug effects* / Q000276:immunology / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000276:immunology; D014162:Transfection
chemical_list: D004967:Estrogens; D016328:NF-kappa B; D050794:STAT1 Transcription Factor; C494080:Stat1 protein, mouse; D007371:Interferon-gamma; D052247:Nitric Oxide Synthase Type II