Doxycycline improves traumatic brain injury outcomes in a murine survival model.

BACKGROUND:Traumatic brain injury (TBI) has significant morbidity and cost implications. Primary treatment modalities aim to decrease intracranial pressure; however, therapies targeting the underlying pathophysiology of a TBI are limited. The TBI-induced microvascular leak and secondary injury are largely due to proteolysis of the blood-brain barrier (BBB) by matrix metalloproteinase-9. We previously observed doxycycline's inhibitory affinity on matrix metalloproteinase-9 resulting in preserved BBB integrity in nonsurvival murine studies. This study sought to determine the effect of doxycycline on functional motor and behavioral outcomes in the setting of a TBI murine survival model. METHODS:C57BL/6J mice were assigned to a sham, TBI, or TBI with doxycycline arm. A moderate TBI was induced utilizing a controlled cortical impactor. The TBI with doxycycline cohort received a dose of doxycycline (20 mg/kg) 2 hours after injury and every 12 hours until postoperative day (POD) 6. All mice underwent preoperative testing for weight, modified neurological severity score, wire grip, and ataxia analysis (DigiGait). Postoperative testing was performed on POD 1, POD 3, and POD 6 for the same measures. SAS 9.4 was used for comparative analysis. RESULTS:Fifteen sham mice, 15 TBI mice, and 10 TBI with doxycycline mice were studied. Mice treated with doxycycline had significantly improved modified neurological severity score and wire grip scores at POD 1 (all p < 0.05). Mice treated with doxycycline had significantly improved ataxia scores by POD 3 and POD 6 (all p < 0.05). There was no significant difference in rate of weight change between the three groups. CONCLUSION:Mice treated with doxycycline following TBI demonstrated improved behavioral and motor function suggesting doxycycline's role in preserving murine BBB integrity. Examining the role of doxycycline in human TBIs is warranted given the relative universal accessibility, affordability, and safety profile of doxycycline.