Adenosine deaminase inhibition alterates glucose metabolism in a human astrocytoma cell line

Adenosine deaminase, which catalyzes the deamination of adenosine and deoxyadenosine, plays a central role in purine metabolism. Indeed, its deficiency is associated with severe immunodeficiency and abnormalities in the functioning of many organs, including nervous system. We have mimicked an adenosine deaminase-deficient situation by incubating a human astrocytoma cell line (ADF) in the presence of deoxycoformycin, a strong adenosine deaminase inhibitor, and deoxyadenosine, which accumulates in vivo when the enzyme is deficient. We have previously demonstrated that, after 15 h of treatment, this combination increases both mitochondrial reactive oxygen species and mitochondrial mass, induces apoptosis as indicated by cytochrome c release from mitochondria and activation of caspase-3. These events are preceded by reduction in lactacte release in the medium [1]. In this work we demonstrate that after 8 h of incubation with deoxyadenosine and deoxycoformycin, caspase-8 is activated, mitochondrial mass increases and mitochondrial reactive oxygen species decrease. The addition of baicalein to the incubation medium reduces cell death and caspase-3 activity induced by deoxycoformycin and deoxyadenosine in combination. This protective effect is correlated to an increase of lactate released in the medium, a decrease in the intracellular levels of dATP, and an increase in ATP levels, as compared to the cells subjected to the treatment with deoxycoformycin and deoxyadenosine in combination without any further addition. The effect of baicalein appears to be related to an inhibition of deoxyadenosine phosphorylation, rather than or in addition to the well known antioxidant activity of the compound.