Reduction of estrogen production by interleukin-6 in a human granulosa tumor cell line may have implications for endometriosis-associated infertility.
OBJECTIVE
To examine the effect of interleukin-6 (IL-6) on estrogen production and aromatase activity using a human granulosa tumor cell line (KGN cells). The involvement of the mitogen-activated protein kinase (MAPK) cascade in the inhibitory effects of IL-6 on estrogen production was also evaluated.


METHODS
Molecular and biological studies of KGN cells.


METHODS
Department of Obstetrics and Gynecology, Tottori University Hospital, Yonago, Japan.


METHODS
Gene expression of IL-6 and the IL-6 receptor was analyzed by reverse transcription-polymerase chain reaction and Southern blot analysis. KGN cells were cultured for 48 hours with IL-6 (0.1-10 ng/mL) or IL-6 (10 ng/mL) plus a mitogen activated protein kinase-extracellular signal regulated kinase kinase 1/2 (MEK1/2) inhibitor U0126 (10 microM). Estradiol concentration in the culture supernatants was measured by means of enzyme immunoassay, [1beta-(3)H] androstenedione was added to the cell lysate supernatant, and aromatase activity was determined by measuring the amount of [(3)H] H(2)O released upon the conversion of [1beta-(3)H] androstenedione to estrone. To examine the activation of intracellular signal transduction molecules induced by IL-6, the phosphorylation of Stat3, p38 MAPK, and extracellular signal-regulated kinase 1/2 (ERK1/2) was examined by Western blotting.


RESULTS
Gene expression of IL-6 and its receptor was detected in KGN cells. Estradiol secretion was significantly inhibited by adding IL-6, which also suppressed aromatase activity to 50% of the control. In addition, pretreatment with U0126 restored the IL-6-induced suppression of aromatase activity. IL-6 markedly enhanced the phosphorylation of ERK1/2, but not Stat3 and p38 MAPK. U0126 markedly reduced the level of the IL-6-induced phosphorylation of ERK1/2.


CONCLUSIONS
These findings demonstrate that IL-6 may reduce estrogen production via the MAPK signal pathway in human granulosa cells. The results may support the notion that IL-6 is related to impaired estrogen biosynthesis in patients with endometriosis.
Deura
Imari
I
Department of Obstetrics and Gynecology, Tottori University School of Medicine, 36-1 Mishimachi, Yonago 683-8504, Japan. imari@grape.med.tottori-u.ac.jp
Harada
Tasuku
T
Taniguchi
Fuminori
F
Iwabe
Tomio
T
Izawa
Masao
M
Terakawa
Naoki
N
D015703:Antigens, CD / Q000235:genetics; D001141:Aromatase / Q000378:metabolism; D045744:Cell Line, Tumor; D050822:Cytokine Receptor gp130; D004715:Endometriosis / Q000378:metabolism / Q000503:physiopathology*; D004789:Enzyme Activation / Q000187:drug effects; D004958:Estradiol / Q000378:metabolism*; D005260:Female; D006801:Humans; D007247:Infertility, Female / Q000378:metabolism / Q000503:physiopathology*; D015850:Interleukin-6 / Q000235:genetics* / Q000494:pharmacology; D008184:Luteal Cells / Q000166:cytology / Q000378:metabolism*; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology; D008562:Membrane Glycoproteins / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis; D019947:Receptors, Interleukin-6 / Q000235:genetics
D015703:Antigens, CD; C494199:IL6ST protein, human; D015850:Interleukin-6; D008562:Membrane Glycoproteins; D012333:RNA, Messenger; D019947:Receptors, Interleukin-6; D050822:Cytokine Receptor gp130; D004958:Estradiol; D001141:Aromatase