Effect of AZT on thymidine phosphorylation in cultured H9c2, U-937, and Raji cell lines.
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 (IC50) ranging from 4.4 to 21.9muM. 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.
Lynx
Matthew D
MD
Indiana University School of Medicine-South Bend, South Bend, 1234 Notre Dame Avenue, IN 46617, United States.
Kang
Bae-Kwang
BK
McKee
Edward E
EE
D000818:Animals; D019380:Anti-HIV Agents / Q000494:pharmacology*; D002460:Cell Line; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D006801:Humans; D010766:Phosphorylation / Q000187:drug effects; D051381:Rats; D013936:Thymidine / Q000378:metabolism*; D020298:U937 Cells; D015215:Zidovudine / Q000494:pharmacology*
D019380:Anti-HIV Agents; D015215:Zidovudine; D013936:Thymidine