Introduction/Rational: Military personnel engaged in combat operation are often exposed to desert storm resulting in silica dust (SiO2 nanoparticles) intoxication. In addition, combat stress, sleep deprivation and continuous attention for enemy group results in mild to moderate hypertension. Under such situations, any traumatic brain or spinal cord injury could result in massive brain pathology due to stress induced hypertension and possibly SiO2 nanoparticles intoxication. However, effects of trauma in hypertension and SiO2 intoxication are still not well known. In present study we investigated the effects of hypertension and SiO2 intoxication of the pathophysiology of traumatic brain injury (TBI).

Method/Approach: Male Wistar rats (250-300 g) were made renal hypertensive by 2kidney 1clip (2K1C) procedure allowing mean arterial blood pressure (MABP) reaching 180 ± 8 torr over 6 weeks. These hypertensive rats were exposed to SiO2NPs (40-50 nm) once daily (50 mg/kg, i.p.) for 8 days. On the 9^th day these hypertensive and SiO2NPs intoxicated animals were subjected to TBI under anesthesia by making an incision (3 mm long and 2.5 mm deep) on the right parietal cerebral cortex after opening the skull (4mmOD) on both sides. The animas were allowed to survive 48 h after TBI.

Results/Effects: TBI in hypertensive and SiO2 nanoparticles intoxicated rats showed 4-to-6 fold higher breakdown of the blood-brain barrier (BBB) to Evans blue albumin (EBA) and [131]-Iodine, edema formation and neuronal injuries as compared to TBI in normal animals at 48 h. Treatment with a multimodal drug Cerebrolysin-containing balanced composition of neurotrophic factors and active peptide fragments (10 ml/kg, i.v.) started 4 h after TBI followed by 4 injections at every 8 h markedly reduced brain pathologies. Whereas only 5 ml/kg of the drug is needed to achieve identical neuroprotection in normal rats after TBI.

Conclusions/Limitations: These observations are the first to show that a combination of hypertension and SiO2 nanoparticles worsens brain pathology in TBI. Under these situations almost double dose of drugs is needed to induce neuroprotection, not reported earlier. Our laboratory is engaged to see whether nanodelivery of cerebrolysin could have an added therapeutic value in this complicated situation of brain injury, a subject that is currently being investigated in our laboratory.