Effect of AZT on thymidine phosphorylation in cultured H9c2, U-937, and Raji cell lines

• Published in: Biochemical pharmacology 2008-04, Vol.75 (8), p.1610-1615
• Main Authors: Lynx, Matthew D., Kang, Bae-Kwang, McKee, Edward E.
• Format: Article
• Language: English
• Subjects: Animals; Anti-HIV Agents - pharmacology; AZT; Biological and medical sciences; Cell Line; Cell Line, Tumor; Cell Proliferation - drug effects; Cultured cells; Humans; Medical sciences; Mitochondrial toxicity; Pharmacology. Drug treatments; Phosphorylation - drug effects; Rats; Reverse transcriptase inhibitors; Thymidine; Thymidine - metabolism; U937 Cells; Zidovudine - pharmacology
• ISSN: 0006-2952; 1873-2968
• DOI: 10.1016/j.bcp.2008.01.006

3′-Azido-3′-deoxythymidine (AZT) has been shown to be a potent inhibitor of thymidine kinase 2 in work from this laboratory. Inhibition results in decreased salvage of thymidine to TTP, which may lead to depletion of the TTP pool and result in the mitochondrial dysfunction and mt-DNA depletion observed with AZT toxicity. The effect of AZT on thymidine phosphorylation in growing cells expressing thymidine kinase 1 has not been shown. Three cell lines were used in these experiments: H9c2, derived from rat cardiomyoblasts; U-937, derived from human monocytes; and Raji, derived from human lymphoblasts. AZT inhibited growth in a concentration-dependent manner in U-937 cells, but not the other cell lines. The phosphorylation of [ 3H]-thymidine or [ 3H]-AZT was determined during log growth. All cell lines salvaged and phosphorylated thymidine to TTP, with TTP the major product. The U-937 cells had a much more active salvage pathway than the other cells. All cell lines phosphorylated AZT to the triphosphate, but the major product was AZTMP. The AZT inhibition of growth of the U-937 cells did not correlate with levels of the phosphorylated AZT. In contrast, pro-drug AZT was shown to inhibit thymidine phosphorylation in all lines with 50% inhibition concentrations (IC 50) ranging from 4.4 to 21.9 μM. Since the U-937 cells expressed higher activity of the salvage pathway than the other cell lines, the U-937 cells may rely more heavily on the salvage pathway for TTP synthesis, accounting for AZT inhibition of growth.