Fibrosis may also be stimulated by upregulating the MDA/4-HNE pathway; this pathway will, in turn, upregulate pro-fibrogenic matrix metalloproteinase-2 (MMP2) and downregulate matrix metalloproteinase-1 (MMP1), two enzymes responsible for remodeling the hepatic extracellular matrix [9, 191, 192, 216]. The gene discussed is MMP1; the disease is fibrosis.