Role of cAMP-response element-binding protein phosphorylation in hepatic apoptosis under protein kinase C alpha suppression during sepsis.
Previous studies have shown that a decrease in protein kinase C (PKC) alpha levels contributes to hepatic failure and/or apoptosis during sepsis, and suppression of PKCalpha plays a critical role in triggering caspase-dependent apoptosis, which can modulate expression of Bcl-xL. However, the underlying molecular mechanism remains uncertain. In the present study, we examined whether a decrease in the nuclear PKCalpha levels causes hepatic apoptosis via modulation of cAMP-response element-binding protein (CREB) or nuclear factor-kappaB (NFkappaB), the crucial factors regulating the expression of prosurvival Bcl-xL. For polymicrobial sepsis induction, a cecal ligation and puncture model was used; at 9 or 18 h after CLP, experiments were terminated, referring as early or late sepsis, respectively. Additionally, PKCalpha was suppressed by stable transfection of antisense PKCalpha plasmid into a Clone-9 rat hepatic epithelial cell. The results showed that the nuclear PKCalpha was significantly decreased in the liver during sepsis, which was accompanied by decreases in phospho-CREB content, DNA-binding activity of CREB, and Bcl-xL expression. Likewise, the binding activity of NFkappaB increased significantly, which was associated with a decrease in cytosolic inhibitory-kappaBalpha content. The in vitro suppression of PKCalpha also resulted in decreases in the phospho-CREB content and DNA-binding activity, which were accompanied by down-regulation of Bcl-xL and apoptosis, but no significant alteration in NFkappaB-binding activity. The in vivo and in vitro results suggest that the suppression of PKCalpha results in a decreased CREB phosphorylation and subsequent down-regulation of Bcl-xL, which may contribute to the hepatic apoptosis during sepsis.
Hsieh
Ya-Ching
YC
Department of Physiology, Kaohsiung Medical University, Kaohsiung, 807 Taiwan.
Chen
Yen-Hsu
YH
Jao
Hsiao-Ching
HC
Hsu
Hseng-Kuang
HK
Huang
Li-Ju
LJ
Hsu
Chin
C
D000818:Animals; D017209:Apoptosis; D015153:Blotting, Western; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D017362:Cyclic AMP Response Element-Binding Protein / Q000737:chemistry*; D003600:Cytosol / Q000378:metabolism; D004247:DNA / Q000737:chemistry; D053938:DNA Fragmentation; D015536:Down-Regulation; D004847:Epithelial Cells / Q000166:cytology; D020287:In Situ Nick-End Labeling; D008099:Liver / Q000378:metabolism / Q000473:pathology; D008297:Male; D016328:NF-kappa B / Q000378:metabolism; D016376:Oligonucleotides, Antisense / Q000737:chemistry / Q000494:pharmacology; D010766:Phosphorylation; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D051571:Protein Kinase C-alpha / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D018805:Sepsis / Q000473:pathology; D013997:Time Factors; D014162:Transfection; D051020:bcl-X Protein / Q000378:metabolism
D017362:Cyclic AMP Response Element-Binding Protein; D016328:NF-kappa B; D016376:Oligonucleotides, Antisense; D012333:RNA, Messenger; D051020:bcl-X Protein; D004247:DNA; D051571:Protein Kinase C-alpha