Deletion of toll-like receptor-4 downregulates protein kinase C-zeta and attenuates liver injury in experimental pancreatitis.
BACKGROUND
Toll-like receptor-4 (TLR4) and protein kinase C-zeta (PKC-zeta) play a role in macrophage activation. We hypothesized that deletion of TLR4 downregulates PKC-zeta and attenuates liver cell apoptosis in experimental pancreatitis.


METHODS
Acute pancreatitis was induced by choline-deficient ethionine diet in C57/BL6 (TLR4+/+ and TLR4-/-) mice.


RESULTS
During pancreatitis, staining for TLR4 and PKC-zeta, which colocalized in Kupffer cells but not in hepatocytes, increased in TLR4+/+ mice and decreased in TLR4-/- mice. In TLR4+/+ mice, pancreatitis increased TLR4 protein and mRNA and PKC-zeta protein and activity, nuclear factor (NF)-kappaB, ERK1/2, caspase-3 cleavage, and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) staining; all P < .01 versus controls. In TLR4-/- mice with pancreatitis, PKC-zeta mRNA and activity were reduced, ERK1/2 and caspase-3 did not increase, and NF-kappaB and TUNEL (mostly in hepatocytes) increased mildly (all P < .01 vs control). PKC-zeta did not interact directly with NF-kappaB; however, during pancreatitis, coimmunoprecipitation of PKC-zeta with ERK1/2 was increased in TLR4+/+ mice and was attenuated in TLR4-/- mice (all P < .01 vs control), indicating that PKC-zeta interacts with ERK1/2.


CONCLUSIONS
Acute pancreatitis upregulates TLR4, PKC-zeta, NF-kappaB, and ERK1/2, and increases apoptosis in mice livers. PKC-zeta induces nuclear translocation of NF-kappaB via ERK1/2-dependent mechanisms. Deletion of TLR4 downregulates PKC-zeta, NF-kappaB, and ERK1/2, and attenuates pancreatitis-induced liver cell apoptosis.
Peng
Yanhua
Y
Department of Surgery, James A. Haley Veterans Affairs Medical Center, University of South Florida Health Sciences Center, Tampa, Fla, USA.
Sigua
Celia A
CA
Rideout
Drew
D
Murr
Michel M
MM
D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D053148:Caspase 3 / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D005260:Female; D022781:Hepatocytes / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D010195:Pancreatitis / Q000201:enzymology / Q000378:metabolism*; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism*; D051197:Toll-Like Receptor 4 / Q000378:metabolism*; D051996:Transcription Factor RelA / Q000378:metabolism; D015854:Up-Regulation; D000099221:Protein Kinase C zeta
D053148:Caspase 3; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D011493:Protein Kinase C; D051197:Toll-Like Receptor 4; D051996:Transcription Factor RelA; D000099221:Protein Kinase C zeta; C498144:Rela protein, mouse; C493487:Tlr4 protein, mouse