Rapid Degradation of Poly(ADP-ribose) after Injection into the Mouse Bloodstream

Abstract

Extensive DNA damage leads to the activation of poly(ADP-ribose) polymerase and subsequently to the formation of poly(ADP-ribose). When the damage is severe or leads to cell death, poly(ADP-ribose) may leak into the blood circulation. The metabolism of poly(ADP-ribose) in the bloodstream is not well understood. Thus, in the present study, the metabolism of 32 P-labeled poly(ADP-ribose) was followed in mice after injection of this labeled compound into the tail vein. The results showed that 5 min after injection more than half of the radioactivity was concentrated in acid-soluble fractions, namely in low molecular weight compounds in the blood, liver, and kidneys. Most of this radioactivity was in the form of inorganic phosphate, detected 5 min post-injection in the blood, kidneys, and urine. By contrast, the metabolites ADP-ribose and phosphoribosyl-AMP were not detected in any of the tissues nor in blood or urine. Taken together, these findings suggest that once poly(ADP-ribose) enters the bloodstream it is rapidly degraded, thereby preventing its accumulation in the blood.

Measurement of Poly(ADP-ribose) Level with Enhanced Slot Blot Assay with Crosslinking

“…Additionally, for an optimized PD assay, studies to detect PARP activity levels with cancer cells less than 10 3 −10 5 cells, obtained from biopsy, surgery, or circulating tumor cells [26], and PBMCs would be necessary for the precise monitoring of PARP inhibition levels. Because PAR is easily degraded in the presence of blood components [27], an ex vivo assay system should contain a minimum level of contaminated blood components.…”