Downloaded on June 21, 2014. The Journal of Clinical Investigation. More information at www.jci.org/articles/view/113999 Accumulation of PiZ a1-Antitrypsin Causes Liver Damage in Transgenic Mice
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Abstract
Circulating a,-antitrypsin is synthesized primarily in the liver and secreted into the bloodstream, where it serves as the major protease inhibitor. The PiZ variant of a1-antitrypsin is associated with decreased levels of the protein in sera as a result of its retention within hepatocytes. Homozygosity for the variant allele predisposes individuals to the development of pulmonary emphysema and an increased risk for liver disease. We and others have previously demonstrated that the normal PiM human a,-antitrypsin gene can be properly expressed in the livers of transgenic mice. The PiZ variant of the human a,-antitrypsin gene was introduced into the germline of mice to determine whether the mutant protein would accumulate in mouse hepatocytes and if such accumulation would result in the development of liver damage in an animal model. As expected, the mutant human protein was abundantly synthesized in the livers of the transgenic animals and accumulated within the rough endoplasmic reticulum of hepatocytes as it does in human patients. PiZ mice developed significantly more liver necrosis and inflammation than PiM transgenic mice or control littermates. The degree of liver damage was correlated with the amount of PiZ a,-antitrypsin accumulated in the liver of the different pedigrees of mice. Although 40 % of PiZ mice tested were seropositive for mouse hepatitis virus (MHV), the degree of liver damage was not influenced by the MHV seropositivity; rather, it was related only to the presence of accumulated PiZ protein