TNF-a??Activin A??????????CML?????????? The molecular mechanism of TNF-a inhibited ActivinA-mediated erythropoiesis in CML cells

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TNF-a??Activin A??????????CML??????????The
molecular mechanism of TNF-a inhibited
ActivinA-mediated erythropoiesis in CML cells

• TNF-a?pro-inflammatory cytokine?TNF-a???????????,?
  ???????????Activin A?transforming growth factor
  (TGF)-ß superfamily???????,??????????????????PDTC
  (NF-?B???) ???CML?????K562???TNF-a???NF-?B????c-Ju
  n?????Activin A??????????????,??transient
  transfection??????????NF-?B p50?NF-?B
  p65???????K562???NF-?B?TNF-a??c-Jun???????????????
  ?K562???,NF-?B p65???c-Jun promoter
  activity,NF-?B p50???c-Jun promoter
  activity?c-Jun?NF-?B p65??AP-1 binding
  site???c-Jun promoter,????NF-?B p65??c-Jun???AP-1
  binding site,????TNF-a?????????????JNK???SP600125?
  ???TNF-a???c-Jun promoter??,?????TNF-a?????JNK????
  c-Jun??????,NF-?B p65??c-Jun promoter???????JNK???
  ????????TNF-a?????JNK??NF-?B????????c-Jun????RT-PC
  T?????Activin A???K562???erythroid
  genes(a-globin, ?-globin, NF-E2p45 and
  GATA-1)???TNF-a?????genes?????NF-E2????????Activi
  n A???-globin reporter???,?c-Jun?????,????????????
  ????TNF-a??NF-?B???c-Jun?????NF-E2??Activin
  A???????????,???ChIP assay??NF-?B p65?????c-Jun
  promoter ?AP-1 binding site?c-Jun???c-Jun
  promoter???

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• The pro-inflammatory cytokine, tumor necrosis
  factor (TNF)-a, is linked to erythropoietic
  inhibition and may contribute to different forms
  of anemia. Activin A, a member of the
  transforming growth factor (TGF)-ß superfamily,
  is an erythroid differentiation factor. In our
  previous study, we demonstrated that TNF-a
  up-regulated c-Jun expression through the NF-?B
  pathway to inhibit Activin A-mediated
  erythropoiesis with NF-?B inhibitor PDTC in
  chronic myeloid leukemia (CML)-derived K562
  cells. In this study, we carry out the
  over-expression of different NF-?B family
  members, p50 and p65, by transient transfection
  or stable expression in K562 cells to further
  explore the role of NF-?B on TNF-a-induced c-Jun
  expression. Our data show that p65 activates
  c-Jun promoter however, p50 represses c-Jun
  promoter. The c-Jun or NF-?B p65 activates c-Jun
  promoter through AP-1 binding site, suggesting
  NF-?B p65 act on AP-1 binding site through c-Jun
  which may lead to erythropoietic inhibition in
  TNF-a signaling. The JNK inhibitor SP600125
  represses the TNF-a-activated c-Jun promoter,
  indicating that TNF-a?n also exerts its effect
  through JNK activation. Furthermore,
  p65-activated c-Jun promoter is partly inhibited
  by JNK inhibitor, suggesting TNF-a ?nregulates
  the c-Jun promoter through both NF-?B and JNK
  pathways. The results of RT-PCR show that activin
  A up-regulates the expression of erythroid genes
  (a-globin, ?-globin, NF-E2p45 and GATA-1) and
  TNF-a?n down-regulates these genes. The
  over-expression of NF-E2 enhances Activin
  A-induced ?-globin reporter activity,
  co-expression of c-Jun and NF-E2 can inhibit
  these effects. These results indicate that TNF-a
  up-regulates c-Jun through NF-?B pathway to
  antagonize the NF-E2 transcriptional activity by
  Activin A in erythroid differentiation. In the
  future work, whether NF-?B p65 binding to c-Jun
  on the AP-1 binding site of c-Jun promoter to
  enhance the c-Jun promoter activity will be
  investigated by ChIP assay.