Quantification of Poly(ADP-Ribose)-Modified Proteins in Cerebrospinal Fluid from Infants and Children after Traumatic Brain Injury

Abstract

Poly-ADP-ribosylation (PAR) of proteins by poly(ADP-ribose) polymerases (PARP) occurs after experimental traumatic brain injury (TBI) and modulates neurologic outcome. Several promising pharmacological PARP inhibitors have been developed for use in humans, but there is currently no clinically relevant means of monitoring treatment effects. We therefore used an enzyme-linked immunosorbent assay to measure PAR-modified proteins in cerebrospinal fluid (CSF). Cerebrospinal fluid samples from 17 pediatric TBI patients and 15 controls were plated overnight and then incubated with polyclonal antibody against PAR. Histone-1, a PARP substrate, was incubated with active PARP, NAD, and nicked DNA, and served as the standard. Both peak and mean CSF PAR-modified proteins were increased in TBI patients versus controls. Peak CSF PAR-modified protein levels occurred on day 1 and levels remained increased on day 2 after TBI. Increases in peak CSF PAR-modified protein concentrations were independently associated with age and male sex, but not initial Glasgow Coma Scale score, Glasgow outcome score, or mechanism of injury. The increase in PAR-modified proteins in CSF after TBI may be because of increased PARP activation, decreased PAR degradation, or both. As PAR-modified protein concentration correlated with age and male sex, developmental and sex-dependent roles for PARP after TBI are implicated.