Hepatocytes express nerve growth factor during liver injury: evidence for paracrine regulation of hepatic stellate cell apoptosis.
A key feature of recovery from liver fibrosis is hepatic stellate cell (HSC) apoptosis, which serves the dual function of removing the major source of neomatrix and tissue inhibitors of metalloproteinases thereby facilitating matrix degradation. The mechanisms regulating HSC apoptosis remain undefined but may include the interaction of nerve growth factor (NGF) with its receptor, p75, on HSC. In this study, by TaqMan polymerase chain reaction in situ hybridization and immunohistochemistry, we demonstrate that NGF is expressed by hepatocytes during fibrotic injury. Peak hepatocyte expression of NGF (48 hours after CCl(4) injection) coincides with maximal rate of apoptosis of HSC by terminal dUTP nick-end labeling staining. Addition of recombinant NGF to HSC in tissue culture causes a dose-dependent increase in apoptosis. NGF regulates nuclear factor (NF)-kappaB activity, reducing p50/p65 binding detected by electromobility shift assay and reduced NF-kappaB CAT reporter activities from both basal unstimulated levels and after NF-kappaB induction by tumor necrosis factor. In each case, a relative reduction in NF-kappaB binding was associated with a significant increase in caspase 3 activity. These data provide evidence that NGF is expressed during fibrotic liver injury and may regulate number of activated HSCs via induction of apoptosis.
Liver Research Group, IIR Division, School of Medicine, Southampton General Hospital, Tremona Road, Southampton SO16 6YD, United Kingdom.
Fiona
F
Oakley
Nathan
N
Trim
Christothea M
CM
Constandinou
Weilan
W
Ye
Alane M
AM
Gray
Gretchen
G
Frantz
Kenneth
K
Hillan
Tim
T
Kendall
R Christopher
RC
Benyon
Derek A
DA
Mann
John P
JP
Iredale
D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D002251:Carbon Tetrachloride / Q000633:toxicity; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D022781:Hepatocytes / Q000378:metabolism; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D020287:In Situ Nick-End Labeling; D008103:Liver Cirrhosis / Q000139:chemically induced / Q000378:metabolism / Q000473:pathology*; D008297:Male; D051379:Mice; D016328:NF-kappa B / Q000378:metabolism; D020932:Nerve Growth Factor / Q000096:biosynthesis* / Q000494:pharmacology; D019899:Paracrine Communication; D016133:Polymerase Chain Reaction
D016328:NF-kappa B; D020932:Nerve Growth Factor; D002251:Carbon Tetrachloride; C505409:Casp3 protein, mouse; D053148:Caspase 3; D020169:Caspases