Induction of the stress response after inflicted and non-inflicted traumatic brain injury in infants and children

Rapid induction of 72-kD heat shock protein (Hsp70) is a key component of the stress response and is seen after a variety of insults to the brain including experimental hyperthermia, ischemia, seizures, and traumatic brain injury (TBI). Little is known about the endogenous stress response in pediatric patients after brain injury. Accordingly, the concentration of Hsp70 was determined in 61 cerebrospinal fluid (CSF) samples from 20 infants and children after TBI. Peak Hsp70 level were increased in TBI patients vs. controls.(4.60 [1.49-78.99] vs. 2.18 [1.38-4.25] ng/mL, respectively, median (range), p = 0.01) and occurred most often on day 1 after injury. Strikingly, CSF levels of Hsp70 were positively and independently associated with inflicted vs. non-inflicted TBI (7.03 [2.30-27.22] vs. 2.06 [1.06-78.99] ng/mL, respectively, p = 0.05). Endogenous Hsp70 expression was confirmed by Western blot and immunocytochemistry using brain tissue samples removed from patients who underwent decompressive craniotomy for refractory intracranial hypertension or at autopsy. These data suggest that the endogenous stress response, as measured and quantified by the Hsp70 concentration in CSF, occurs in infants and children after TBI. The endogenous stress response is more robust in victims of child abuse, compared with patients with accidental TBI, supporting age-dependence or a difference in either injury frequency, duration, severity, or mechanism in this subgroup of TBI patients. Further studies are needed to determine the role of Hsp70 in both non-inflicted and inflicted TBI in infants and children.