40 INABILITY OF POLY-ADP-RIBOSYLATION INHIBITORS TO PROTECT PERIPHERAL BLOOD LYMPHOCYTES FROM THE TOXIC EFFECTS OF ADA INHIBITION

Abstract

The effectiveness of two inhibitors of poly-ADP-ribosylation, nicotinamide and 3-aminobenzamide to rescue resting and PHA-stimulated lymphocytes damaged by the combination of deoxycoformycin (dCF) and deoxyadenosine (dAdo), has been evaluated. Incubation with dCF (10⁻⁵M) and dAdo (10⁻⁴M) for 18h inhibited protein and RNA synthesis in unstimulated lymphocytes and impaired the cells to respond to PHA stimulation or to give rise to T-cell colonies in methyl-cellulose. Viability studies showed predominantly dead cells at day 4 in both the unstimulated and PHA-stimulated lymphocytes, whether or not the drugs were removed at 18h. Cell viability at day 4 increased from 13.7% to 41.1% with 3mM nicotinamide and to 28.8% with 5mM 3-aminobenzamide. Although nicotinamide was able to sustain the levels of NAD and reduce the fall in cell ATP concentration, the inhibition by dCF plus dAdo of protein synthesis, RNA synthesis and ability of cells to form colonies in cellulose or to respond to PHA was not reversed. Use of physiological concentrations of dCF (10⁻⁶M) and dAdo (10⁻⁶M), though producing less pronounced effects on cell viability, protein and RNA synthesis still caused toxicity even in the presence of nicotinamide. We conclude that inhibition of ADP-ribosylation with nicotinamide or 3-aminobenzamide does not protect cells in vitro from dAdo toxicity with ADA inhibition and is thus not likely to give significant clinical benefit in ADA deficiency.

Log in or create a free account to read this content

Gain free access to this article, as well as selected content from this journal and more on nature.com

Access through your institution

or

Sign in or create an account

Continue with Google

Continue with ORCiD