''Ex vivo'' release of eicosanoid from human brain tissue: Its relevance in the development of brain edema

The specific mechanism underlying the genesis of vasogenic brain edema is still debated: the role of arachidonic acid is considered extremely important, as it is a possible activator of self-maintaining reactions enhancing the release of vasoactive and cytotoxic compounds. The relationship between arachidonic acid metabolism and brain edema has been studied primarily in brain tissue samples or in the extracellular fluid, whereas the residual capacity of perilesional tissue to synthesize and release eicosanoids has not been investigated. In the present study, perilesional samples of brain tissue were available from 4 patients operated on for brain metastasis, from 8 patients who had malignant neuroepithelial tumors, from 4 with meningiomas, and from 5 with subarachnoid hemorrhage. A brain edema index was calculated from the preoperative computed tomographic scan. The ''ex vivo'' method allowed determination of the residual capacity of endogenous arachidonic acid metabolism. The edema index is significantly higher in patients with brain metastasis (6.5 ± 0.8) and neuroepithelial tumors (3.6 ± 0.2) than in those with meningiomas (1.5 ± 0.06), subarachnoid hemorrhage (1.7 ± 0.18), and in controls. In patients with metastatic and neuroepithelial tumors there is a significant correlation between peritumoral brain edema and the capacity to synthesize leukotriene C₄ (P <0.05); the capacity to synthesize leukotriene C₄ is also significantly elevated after subarachnoid hemorrhage (13.91 ± 2.6 ng/ml of incubation medium) when compared with control cases (5.56 ± 0.91). The capacity to synthesize prostacyclin is significantly higher in patients with brain metastasis than in those with neuroepithelial tumors and meningiomas (P <0.05). The ex vivo capacity to synthesize PGD₂ and PGE₂ are not significantly different in each subgroup when compared with control cases. These results suggest that in perilesional brain tissue, the release of specific eicosanoids may be correlated with the extent of edema.