Inhibition of PHA and NalO 4 mitogenesis by the adenosine deaminase inhibitors erythro-9-(2-hydroxy-3-nonyl) adenine (EHNA) and 2-deoxycoformycin (2-dCF)

Abstract

Two adenosine deaminase inhibitors, erythro-9-(2-hydroxy-3-nonyl) adenine (EHNA) and 2-deoxycoformycin (2-dCF), significantly inhibit the normal mitogenic response of dog peripheral blood mononuclear cells to phytohemagglutinin (PHA) and sodium periodate (NaIO 4) oxidation. The addition of excess PHA does not reverse the inhibitory effects of EHNA on the normal PHA response. However, it was further observed that if EHNA (10 −3, 10 −4 M) or 2-dCF (10 −3 M) were added to fresh cultures of murine P388 leukemia cells or Novikoff rat hepatoma cells, cellular proliferation, in general, was markedly inhibited. We then pretreated dog cells with 2-dCF and observed that even a brief exposure of cells to this compound was sufficient to inhibit the increased [ 3H]thymidine uptake of these cells in response to PHA or NaIO 4 treatment. In contrast, similar pretreatment of Novikoff or P388 cells did not alter the normal logarithmic growth phase. Therefore, we conclude that EHNA and 2-dCF may have an overall inhibitory effect on cellular proliferation when continuously present in cultures of dog mononuclear cells, P388 mouse leukemia cells, and Novikoff rat hepatoma cells. However, unlike continuous cell lines which grow normally after pretreatment with 2-dCF, it appears that there is a specific requirement for normal ADA function early in the initiation of DNA synthesis in dog cells which are responding to the nonimmunologic mitogenic stimulation of PHA and NaIO 4.