What Causes Increased Liver Enzymes?

I have monthly labs to monitor my post-liver transplant from 2 years ago. I also have untreated HepC. My last lab, 10/31/12, showed a dramatic increase in my liver enzymes; this happened 1-1/2 years ago as well; then, I was hospitalized, biopsyed, and treated for rejection. The only thing that recently changed in the past month is that I stopped smoking and began chewing nicorette gum. I will be getting another biopsy next week to find out whether I am once again in rejection or if the hepC is active again. However, I wonder if perhaps my hepatic functions have been affected by the use of nicorette gum?