Abstract
Previous work suggests that vagus nerve disruption reduces hepatocyte and oval cell expansion after liver injury. The role of postneuronal receptor activation in response to liver injury has not been ascertained. We investigated the actions of scopolamine, a nonselective muscarinic receptor antagonist, and specific genetic ablation of a key cholinergic receptor, muscarinic subtype-3 (Chrm3), on azoxymethane (AOM)-induced liver injury in mice. Animal weights and survival were measured as was liver injury using both gross and microscopic examination. To assess hepatocyte proliferation and apoptosis, ductular hyperplasia, and oval cell expansion, we used morphometric analysis of 5-bromo-2′-deoxyuridine-, activated caspase-3-, hematoxylin and eosin-, cytokeratin-19-, and epithelial cell adhesion molecule-stained liver sections. Sirius red staining was used as a measure of collagen deposition and its association with oval cell reaction. In AOM-treated mice, both muscarinic receptor blockade with scopolamine and Chrm3 ablation attenuated hepatocyte proliferation and augmented gross liver nodularity, apoptosis, and fibrosis. Compared with control, scopolamine-treated and Chrm3(−/−) AOM-treated mice had augmented oval cell reaction with increased ductular hyperplasia and oval cell expansion. Oval cell reaction correlated robustly with liver fibrosis. No liver injury was observed in scopolamine-treated and Chrm3(−/−) mice that were not treated with AOM. Only AOM-treated Chrm3(−/−) mice developed ascites and had reduced survival compared with AOM-treated wild-type controls. In AOM-induced liver injury, inhibiting postneuronal cholinergic muscarinic receptor activation with either scopolamine treatment or Chrm3 gene ablation results in prominent oval cell reaction. We conclude that Chrm3 plays a critical role in the liver injury response by modulating hepatocyte proliferation and apoptosis.
Footnotes
This work was supported in part by the Intramural Research Program of the National Institutes of Health National Institute of Diabetes and Digestive and Kidney Diseases; the National Institutes of Health National Cancer Institute [Grants CA107345, CA120407] (to J.-P.R.); the National Institutes of Health National Institute of Diabetes and Digestive and Kidney Diseases [Grant T32-DK067872] (to N.S.; principle investigator J.-P.R.); the National Institutes of Health Institute of Diabetes and Digestive and Kidney Diseases [Grant K08-DK081479] (to S.K.); the Office of Research and Development, Medical Research Service, Department of Veterans Affairs; and the Baltimore Research and Education Foundation.
Parts of this work were previously published in abstract form: Shah N, Samimi R, Cheng K, Drachenberg C, Raufman J-P, and Khurana S (2008) Gastroenterology 134 (Suppl. 1):A-820; Shah N, Belo A, Cheng K, Shant J, Drachenberg C, Raufman J-P, and Khurana S (2009) Hepatology 48 (Suppl):457A; Shah N, Shiu B, Samimi R, Drachenberg C, Shant J, Cheng K, Raufman J-P, and Khurana S (2009) Gastroenterology 136 (Suppl. 1):A-114; Shah N, Shiu B, Drachenberg C, Shant J, Belo A, Cheng K, Raufman J-P, and Khurana S (2009) Gastroenterology 136 (Suppl. 1):A-819; Shah N, Shiu B, Belo A, Drachenberg C, Shant J, Cheng K, Raufman J-P, and Khurana S (2009) Hepatology 50 (Suppl):847A.
Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.
doi:10.1124/jpet.109.165118.
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ABBREVIATIONS:
- Chrm3
- cholinergic receptor, muscarinic subtype-3
- SCOP
- scopolamine
- AOM
- azoxymethane
- PBS
- phosphate-buffered saline
- WT
- wild type
- BrdU
- 5-bromo-2′-deoxyuridine
- H&E
- hematoxylin and eosin
- IHC
- immunohistochemistry
- EpCAM
- epithelial cell adhesion molecule
- HPF
- high-power field
- CK-19
- cytokeratin-19
- VIP
- vasoactive intestinal peptide.
- Received December 21, 2009.
- Accepted March 1, 2010.
- U.S. Government work not protected by U.S. copyright
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