Abstract
Previously, we have shown that primary afferent neurons are necessary for disease activity in immune-mediated liver injury in mice. These nerve fibers are detectable by substance P (SP) immunocytochemistry in the portal tract of rodent liver. Antagonists of the neurokinin-1 receptor (NK-1R), which is the prime receptor of SP, prevented liver damage by suppressing the synthesis of proinflammatory cytokines. Here, we investigated the influence of primary afferent nerve fibers, SP, and NK-1 receptor antagonists on hepatocyte apoptosis in vivo induced by administration of activating anti-CD95 monoclonal antibody (mAb) to mice. Depletion of primary afferent nerve fibers by neonatal capsaicin treatment prevented CD95-mediated activation of caspase-3, measured as enzymatic activity in liver homogenates or by demonstration of hepatocellular immunoreactivity for active caspase-3 in liver slices, and liver damage. This effect was reversed by administration of SP to anti-CD95 mAb-treated mice depleted from primary afferent neurons. The presence of the NK-1R on mouse hepatocytes was demonstrated by immunocytochemistry and flow cytometry. Intraperitoneal pretreatment with the NK-1 receptor antagonists (2S,3S)-cis-2-(diphenylmethyl)-N-([2-methoxyphenyl]-methyl)-1-azabicyclo(2.2.2.)-octan-3-amine (CP-96,345) or (2S,3S)3-([3,5-bis(trifluoromethyl)phenyl]methoxy)-2-phenylpiperadine (L-733,060) dose dependently protected mice from CD95-mediated liver injury. Similar results were obtained when apoptotic liver damage was induced by administration of tumor necrosis factor-α to d-galactosamine-sensitized mice. In conclusion, SP, probably by binding to its receptor on hepatocytes, might aggravate apoptotic signals in these cells. Because NK-1 receptor antagonists not only suppress the proinflammatory cytokine response in the liver but also prevent liver cell apoptosis in vivo, they might be suitable drugs for treatment of immune-mediated liver disease.
Footnotes
-
This work was supported by the Deutsche Forschungsgemeinschaft (DFG) Grant NE 534/1.
-
DOI: 10.1124/jpet.103.059329.
-
ABBREVIATIONS: SP, substance P; NK-1R, neurokinin-1 receptor; SEB, Staphylococcus enterotoxin B; LPS, lipopolysaccharide; CHAPS, (3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate); GaIN, d-galactosamine; TNFα, tumor necrosis factor-α; TNFR1, tumor necrosis factor-α receptor 1; mAb, monoclonal antibody; PBS, phosphate-buffered saline; CP-96,345, (2S,3S)-cis-2-(diphenylmethyl)-N-([2-methoxyphenyl]-methyl)-1-azabicyclo(2.2.2.)-octan-3-amine; L-73,060, (2S,3S)3-([3,5-bis(trifluoromethyl)phenyl]methoxy)-2-phenylpiperadine; ALT, alanine aminotransferase; AST, aspartate aminotransferase; BSA, bovine serum albumin.
- Received August 29, 2003.
- Accepted November 11, 2003.
- The American Society for Pharmacology and Experimental Therapeutics
JPET articles become freely available 12 months after publication, and remain freely available for 5 years.Non-open access articles that fall outside this five year window are available only to institutional subscribers and current ASPET members, or through the article purchase feature at the bottom of the page.
|