Effects Of L-NAME On Blood-Brain Barrier Permeability And MMP-9 Expression In Rats At The Early Stages Of Severe Scald

Objective: To observe the effects of L-NAME on blood-brain barrier permeability and MMP-9 expression in rats at the early stages of severe scald in order to address whether BBB dysfunction caused by scald is associated with MMP-9 overexpression. Methods: To establish model of a third-degree burn affecting 30% of the total body surface area. Healthy adult Sprague Dawlay rats were divided into four groups as following: normal control(A), sham-scalded group(B), scald group(C), scald+L-NA ME group(D), the later two groups were quantified at 3, 6, 12, 24,and 48 h post thermal injury. The ultrastructural change of blood-brain barrier was observed by transmission electron microscope; Brain Evans blue content was examined with the ultraviolet spectrophotometer; Brain water content was detected by caculating dry/wet weight; The change of brain MMP-9 expression after severe scald was determined by immunohistochemical method.Results: Brain water content and Evans blue content were significantly increased after burn. Expression of brain MMP-9 in rats after severe scald was higher than that of sham control group's, and the difference was considered significantly (P<0.01). Under transmission electron microscope, mitochondrion of some neurons of the cerebral cortex were swollen or dissolved, the number of synapes vescile decreased and synaptic cleft broadened.There were vacuolated, swollen endothelium, abnormity of capillary basement membranes of BBB. Brain water content and Evans blue content decreased in serious scalded rats after they were treated with L-NAME. The changes of ultrastructure of BBB rats' brain with severe scald nearly returned to normal after they were treated with L-NAME, and the expression of MMP-9 was returned to basal level.Conclusions: The increase in MMP-9 expression, associated with increased BBB permeability following thermal injury, indicates that MMP-9 may contribute to observed BBB disruption in peripheral thermal injury. The increases of BBB permeability after severe scald, which can be significantly restricted by L-NAME at the early stage, may be linked to restrain MMP-9 expression in rats after severe scald.