Extrinsic nitric oxide donor partially reverses arginine deiminase induced cell growth inhibition through NFκB and Bcl-X_L

Arginine deiminase (ADI) is known to be an inducer of apoptosis in vitro and an anti-tumor agent in vivo in some cancers. ADI causes the enzymatic depletion of arginine which may inhibit nitric oxide (NO) synthesis. However, the effect of ADI treatment on NO synthesis has not been clearly elucidated. With the goal of understanding the role of ADI in NO synthesis, we used the Ramos human lymphoma cell line, which is known to be ADI-sensitive. After determining an optimal experimental ADI concentration (0.001 U/ml), we studied the effects of ADI treatment when combined with different concentrations of the extrinsic NO donor, sodium nitroprusside (SNP) (i.e., control, ADI only, ADI with 10 μM/ml SNP, ADI with 50 μM/ml SNP, and ADI with 100 μM/ml SNP). An MTT assay was used to assess cell survival after treatment, nitric oxide assays to determine nitrite levels and Western blot analysis to determine the expression of the NO mediators, NFκB and Bcl-X _L . Interestingly, we found that the extrinsic NO donor only partially reversed ADI-induced inhibition of cell growth in a dose-dependent pattern and resulted in an induction of NFκB and Bcl-X _L expression. In conclusion, we suggest that there might be an association between reversal of cell growth inhibition by extrinsic NO donor with Bcl-X_L and NFκB expression in ADI-treated Ramos cell.