Homozygous (ZZ) alpha-1-antitrypsin (alpha1AT) deficiency is an important cause of liver disease in children, and can also cause chronic liver disease and hepatocellular carcinoma in adults. There is no specific treatment for alpha1AT associated liver disease. The alpha1AT mutant Z gene encodes a mutant protein which accumulates in the endoplasmic reticulum of hepatocytes rather than being secreted appropriately into the serum. Liver injury is thought to be caused by the accumulation of a1AT mutant Z protein within hepatocytes, which then triggers downstream intracellular injury pathways. Recent studies in our laboratory have focused on understanding the relationship between alpha1AT mutant Z intracellular accumulation and the downstream effects, including ER stress, autophagy, mitochondrial injury, and caspase activation. The accumulated mutant Z protein can also adopt a unique polymerized conformation within hepatocytes, which may play an important role in triggering the cellular injury. We have recently published the first biochemical method to quantitatively isolate these polymers from liver. In this project, we propose to develop specific treatment strategies for alpha1AT deficiency by testing the following hypothesis: alpha1AT deficiency associated liver injury can be reduced by blocking specific cell injury mechanisms in hepatocytes that are triggered by alpha1AT mutant Z intracellular accumulation, or by reducing accumulation of the mutant Z protein itself within liver cells. To test this central hypothesis and to further delineate the mechanisms of cell injury in this disease, we have proposed two aims, each designed to test a different hypothetical therapeutic strategy for alpha1AT associated liver disease and each involving available pharmacologic agents. We will evaluate these therapeutic strategies in tissue culture systems and in transgenic mouse models using quantitative assays of the cellular injury pathways involved. These studies will test the suitability of these therapeutic strategies for future human trials, examine the mechanisms involved in inhibiting liver cell injury, and add to the understanding of the basic mechanisms of cellular injury in liver disease
