As the body's main detoxifying organ, the liver is exposed to high levels of toxicity and has developed the ability to regenerate following even severe injury. However, chronic alcohol consumption completely inhibits this regenerative ability. Proper function of the innate immune cells and hepatic stellate cells resident within the liver has been shown to be critical in modulating hepatocytes'ability to replicate following tissu damage. Therefore, it is likely that chronic alcohol consumption affects both non-parenchymal cells and hepatocytes. To synthesize this complex system, I have developed a mathematical model of cellular interactions and transcriptional regulation between Kupffer cells, hepatic stellate cells, and hepatocytes during regeneration. The model predicts that alterations to any one component in the system may impair, but not completely inhibit, regeneration. However, if certain combinations of alterations are made to the system, regeneration can be completely inhibited. Specifically, I predicts that altered inflammation following partial hepatectomy coupled with hypersensitive or hyperactive hepatic stellate cells leads to complete inhibition of regeneration. Additionally, model simulations suggest that these effects should be observable during and shortly after the priming phase of regeneration (0-6 hrs post-hepatectomy). Although these mechanisms have not been previously studied in the context of chronic alcohol consumption's inhibition of liver repair, chronic alcohol consumption has been shown to alter the inflammatory state of the liver and may progress to cirrhosis, a diseased characterized by highly activated stellate cells. Therefore the goal of this project is to characterize and understand how dynamic alterations in cytokine microenvironment and hepatic stellate cell activation within the liver during the early phases of regeneration contribute to deficient liver regeneration by testing the following hypotheses: (1) chronic alcohol consumption dynamically shifts the balance of pro-inflammatory and anti-inflammatory liver cytokines following partial hepatectomy (PHx), leading to reduced hepatocyte priming, and (2) chronic alcohol consumption dynamically shifts hepatic stellate cells (HSCs) into a distinguishable anti-regenerative activation phenotype post-partial hepatectomy, thereby altering the balance between pro-regenerative and anti- regenerative hepatic stellate cells. Based on model predictions and preliminary results, we expect to find that chronic alcohol consumption increases IL-10 production and decreases or delays IL-6 production leading to a reduction in hepatocyte priming during the priming phase of regeneration. We also expect that chornic alcohol consumption shifts the balance of HSC from a mainly pro-regenerative activation state to a mainly anti-regenerative activation state in the earl phases of regeneration (observable by 6 hrs and peaking at 12 hrs post-PHx). Using systems-tools to investigate the contributions of non-parenchymal cells to an animal model of liver repair will allow integration of these less-studied aspects of liver adaptation to alcohol with the larger field of liver alcohol-adaptation including genome-scale gene expression, hepatocyte signaling, and miRNA-based studies. Additionally, the computational modeling-based approach used in this study will allow for interpretation of our molecular mechanistic findings in the context of alcohol-induced changes to non-parenchymal cell activation phenotype impacting regeneration at a whole-tissue scale.
For approximately 20% of chronic drinkers, alcohol induces cirrhosis inducing the need for liver transplant;for the other 80% of chronic drinkers, the liver'adaptation to chronic alcohol consumption sensitizes it to attack by other diseases, including cancer and Hepatitis C. This project applies a systems biology perspective to investigate key changes in molecular regulation and cell phenotype caused by adaptation to chronic alcohol consumption at the levels of tissue and of single cells, giving a level of precision not previously applied to in vivo liver. The results of these experiments will be interpreted in the systems context of cellular communication and will lead to novel insights into targets for treatment of the liver during chronic alcohol abuse.