Aside from nicotinamide, natural occurring inhibitors of PARP-1 include tryptophan-related compounds, purines, unsaturated fatty-acids (including linoleic acid and arachidonic acid), and carotenoids (Banasik et al., 1992) the levels of which are reportedly low in CF patients (Wetmore et al., 2010, Galli et al., 2012). Here, PARP1 is linked to cystic fibrosis.