Mannose-binding lectin is expressed after clinical and experimental traumatic brain injury and its deletion is protective

Objective: Mannose-binding lectin protein is the activator of the lectin complement pathway. Goals were 1) to investigate mannose-binding lectin expression after human and experimental traumatic brain injury induced by controlled cortical impact and 2) to evaluate whether mannose-binding lectin deletion is associated with reduced sequelae after controlled cortical impact. Design: Translational research, combining a human/experimental observational study and a prospective experimental study. Setting: University hospital/research laboratory. PATIENTS AND Subjects: Brain-injured patients, C57Bl/6 mice, and mannose-binding lectin-A and mannose-binding lectin-C double-knockout (-/-) mice. Interventions: Using anti-human mannose-binding lectin antibody, we evaluated mannose-binding lectin expression in tissue samples from six patients who underwent surgery for a cerebral contusion. Immunohistochemistry was also performed on tissues obtained from mice at 30 minutes; 6, 12, 24, 48, and 96 hours; and 1 week after controlled cortical impact using anti-mouse mannose-binding lectin-A and mannose-binding lectin-C antibodies. We evaluated the effects of mannose-binding lectin deletion in wild-type and mannose-binding lectin-A and mannose-binding lectin-C double-knockout mice. Functional outcome was evaluated using the neuroscore and beam walk tests for 4 weeks postinjury (n = 11). Histological injury was evaluated by comparing neuronal cell counts in the cortex adjacent to the contusion (n = 11). Measurements and main results: Following human traumatic brain injury, we observed mannose-binding lectin-positive immunostaining in the injured cortex as early as few hours and up to 5 days postinjury. Similarly in mice, we observed mannose-binding lectin-C-positive immunoreactivity in the injured cortex beginning 30 minutes and persisting up to 1 week postinjury. The extent of mannose-binding lectin-A expression was lower when compared with that of mannose-binding lectin-C. We observed attenuated sensorimotor deficits in mannose-binding lectin (-/-) mice compared with wild-type mice at 2-4 weeks postinjury. Furthermore, we observed reduced cortical cell loss at 5 weeks postinjury in mannose-binding lectin (-/-) mice compared with wild-type mice. Conclusions: Mannose-binding lectin expression was documented after traumatic brain injury. The reduced sequelae associated with mannose-binding lectin absence suggest that mannose-binding lectin modulation might be a potential target after traumatic brain injury. Copyright © 2014 by the Society of Critical Care Medicine and Lippincott Williams & Wilkins.