Modulation of late apoptotic events by ammonia in glutaminedeprived mouse hybridoma cells

Abstract

Highly proliferating cells reprogram their metabolism in order to fulfill their requirements in biosynthetic precursors. One consequence of this metabolic adaptation is glutamine (Gln) addiction, a phenomenon whereby cells become dependent on Gln for their survival. Using Sp2/0‐Ag14 (Sp2/0) hybridoma cells, we examined the effect of ammonium ions, a product of glutaminolysis, on the viability of Gln‐deprived cells. Supplementing Gln‐deprived Sp2/0 cells with 5 mM ammonium acetate (NH4+ acetate) or 5 mM ammonium chloride (NH4+ chloride) resulted in a significant increase in cell viability. Both ammonium salts also protected Sp2/0 cells treated with the toxic Gln analog azaserine. Supplementing Gln‐starved Sp2/0 cells with either ammonium salt did not alter cytosolic cytochrome c release or caspase‐3 activation, indicating that the mechanisms triggering the apoptotic machinery remained intact. Interestingly, a significant reduction in the number of cells with apoptotic nuclear condensation and fragmentation was observed. However, neither NH4+ acetate nor NH4+ chloride interfered with DNA fragmentation and nuclear lamin A/C cleavage, two key events observed in apoptotic nuclear condensation and fragmentation. All together, these data suggest that the pro‐survival effect of ammonium salts are linked with an inhibition of late apoptotic events. Funded by NSERC‐CANADA (to ERG).