title: Sex bias in experimental immune-mediated, drug-induced liver injury in BALB/c mice: suggested roles for Tregs, estrogen, and IL-6.
abstract: OBJECTIVE
  Immune-mediated, drug-induced liver injury (DILI) triggered by drug haptens is more prevalent in women than in men. However, mechanisms responsible for this sex bias are not clear. Immune regulation by CD4+CD25+FoxP3+ regulatory T-cells (Tregs) and 17β-estradiol is crucial in the pathogenesis of sex bias in cancer and autoimmunity. Therefore, we investigated their role in a mouse model of immune-mediated DILI.
  
  
  METHODS
  To model DILI, we immunized BALB/c, BALB/cBy, IL-6-deficient, and castrated BALB/c mice with trifluoroacetyl chloride-haptenated liver proteins. We then measured degree of hepatitis, cytokines, antibodies, and Treg and splenocyte function.
  
  
  RESULTS
  BALB/c females developed more severe hepatitis (p<0.01) and produced more pro-inflammatory hepatic cytokines and antibodies (p<0.05) than did males. Castrated males developed more severe hepatitis than did intact males (p<0.001) and females (p<0.05). Splenocytes cultured from female mice exhibited fewer Tregs (p<0.01) and higher IL-1β (p<0.01) and IL-6 (p<0.05) than did those from males. However, Treg function did not differ by sex, as evidenced by absence of sex bias in programmed death receptor-1 and responses to IL-6, anti-IL-10, anti-CD3, and anti-CD28. Diminished hepatitis in IL-6-deficient, anti-IL-6 receptor α-treated, ovariectomized, or male mice; undetectable IL-6 levels in splenocyte supernatants from ovariectomized and male mice; elevated splenic IL-6 and serum estrogen levels in castrated male mice, and IL-6 induction by 17β-estradiol in splenocytes from naïve female mice (p<0.05) suggested that 17β-estradiol may enhance sex bias through IL-6 induction, which subsequently discourages Treg survival. Treg transfer from naïve female mice to those with DILI reduced hepatitis severity and hepatic IL-6.
  
  
  CONCLUSIONS
  17β-estradiol and IL-6 may act synergistically to promote sex bias in experimental DILI by reducing Tregs. Modulating Treg numbers may provide a therapeutic approach to DILI.
authors.affiliation: Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University, Baltimore, MD, USA.
authors.forename: Joonhee
authors.initials: J
authors.lastname: Cho
authors.forename: Lina
authors.initials: L
authors.lastname: Kim
authors.forename: Zhaoxia
authors.initials: Z
authors.lastname: Li
authors.forename: Noel R
authors.initials: NR
authors.lastname: Rose
authors.forename: Monica Vladut
authors.initials: MV
authors.lastname: Talor
authors.forename: Dolores B
authors.initials: DB
authors.lastname: Njoku
mesh_terms: D000818:Animals; D002369:Castration; D056486:Chemical and Drug Induced Liver Injury / Q000276:immunology* / Q000378:metabolism* / Q000503:physiopathology / Q000601:surgery; D004958:Estradiol / Q000378:metabolism*; D004967:Estrogens / Q000378:metabolism*; D005260:Female; D007114:Immunization; D020381:Interleukin-17 / Q000378:metabolism; D015850:Interleukin-6 / Q000378:metabolism*; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D012727:Sex Characteristics; D013154:Spleen / Q000276:immunology; D050378:T-Lymphocytes, Regulatory / Q000276:immunology*
chemical_list: D004967:Estrogens; D020381:Interleukin-17; D015850:Interleukin-6; D004958:Estradiol