Pro-inflammatory cytokines from Kupffer cells downregulate hepatocyte expression of adrenomedullin binding protein-1.
Polymicrobial sepsis is characterized by an early, hyperdynamic phase followed by a late hypodynamic phase. Adrenomedullin (AM), a vasodilatory peptide, inhibits this transition from the early phase to the late phase. Adrenomedullin binding protein-1 (AMBP-1) enhances AM-mediated activities. The decrease of AMBP-1 levels in late sepsis reduces the vascular response to AM and produces the hypodynamic phase. Studies have indicated that the administration of LPS downregulates AMBP-1 production in the liver. Since hepatocytes are the primary source of AMBP-1 biosynthesis in the liver, we employed a co-culture strategy using hepatocyte and Kupffer cells to determine whether LPS directly or by increasing pro-inflammatory cytokines from Kupffer cells downregulates AMBP-1 production. Hepatocytes and Kupffer cells isolated from rats were co-cultured and treated with LPS for 24 h. LPS significantly attenuated AMBP-1 protein expression in a dose-dependent manner. Since AMBP-1 is basically a secretory protein, cell supernatants from co-culture cells treated with LPS were examined for AMBP-1 protein levels. LPS treatment caused a dose related decrease in AMBP-1 protein secretion. Similarly, LPS treatment produced a significant decrease in AMBP-1 protein expression in hepatocytes and Kupffer cells cultured using transwell inserts. LPS had no direct effect on AMBP-1 levels in cultured hepatocytes or Kupffer cells alone. To confirm that the observed effects in co-culture were due to the cytokines released from Kupffer cells, hepatocytes were treated with IL-1beta or TNF-alpha for 24 h and AMBP-1 expression was examined. The results indicated that both cytokines significantly inhibited AMBP-1 protein levels. Thus, pro-inflammatory cytokines released from Kupffer cells are responsible for downregulation of AMBP-1.
Jacob
Asha
A
Department of Surgery, North Shore University Hospital and Long Island Jewish Medical Center, Manhasset, NY 11030, USA.
Zhou
Mian
M
Wu
Rongqian
R
Halpern
Vivienne J
VJ
Ravikumar
Thanjavur S
TS
Wang
Ping
P
D000818:Animals; D018920:Coculture Techniques; D017242:Complement Factor H / Q000502:physiology*; D016207:Cytokines / Q000494:pharmacology*; D015536:Down-Regulation / Q000187:drug effects*; D022781:Hepatocytes / Q000187:drug effects* / Q000378:metabolism; D018836:Inflammation Mediators / Q000494:pharmacology*; D007375:Interleukin-1 / Q000494:pharmacology; D007728:Kupffer Cells / Q000187:drug effects* / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
D016207:Cytokines; D018836:Inflammation Mediators; D007375:Interleukin-1; D014409:Tumor Necrosis Factor-alpha; C481978:adrenomedullin-binding protein 1, rat; D017242:Complement Factor H