D-NMAPPD is potent inhibitor of the acid ceramidase inhibitor.

Acid ceramidase is the lipid hydrolase responsible for the degradation of ceramide into sphingosine and free fatty acids within lysosomes. Aberrant AC activity has been observed in several human cancers and Alzheimer's disease. Overexpression of AC may prevent insulin resistant (Type II) diabetes induced by free fatty acids [2].

In vitro: D-NMAPPD was a potent inhibitor of acid ceramidase with an IC50 of ～10 μmol/l. D-NMAPPD (500 μmol/l) reduced the alkaline ceramidase activity. Treatment of melanoma cells with D-NMAPPD elevated endogenous ceramide levels in all melanoma cell populations. In HaCaT keratinocytes and A375 melanoma cells, D-NMAPPD triggered Bcl-2 overexpression abolished apoptosis. High concentrations of D-NMAPPD showed significant cytotoxic effects on HaCaT and melanoma cells. In melanoma cell lines A375, M186, Mel2A, M221, treatment of with 25 μM D-NMAPPD for 24 h resulted in a strong accumulation of ceramide. D-NMAPPD inhibited cell proliferation in a concentration-dependent manner in HaCaT keratinocytes with an IC50 of ～7 μM. D-NMAPPD exhibited no antiproliferative effect on ceramide-resistant melanoma cells.

References:
[1] Raisova M, Goltz G, Bektas M, et al.  Bcl‐2 overexpression prevents apoptosis induced by ceramidase inhibitors in malignant melanoma and HaCaT keratinocytes[J]. FEBS letters, 2002, 516(1-3): 47-52.
[2] Park J H, Schuchman E H.  Acid ceramidase and human disease[J]. Biochimica et Biophysica Acta (BBA)-Biomembranes, 2006, 1758(12): 2133-2138.