The intracellular signaling that triggers the development of cytotoxic edema is multifactorial and
includes, besides events secondary to cerebral ischaemia, mitochondrial dysfunction due to direct
mechanical injury. As a consequence, energetic depletion, excessive Ca2þ-overload and ionic
imbalance due to failure of membrane pumps (e.g. ATP-dependent Naþ/Kþ-pumps) occur, with
subsequent cell swelling due to intracellular accumulation of osmotic active ions (in particular Naþ)
[for a review see Ref.140].
Other potentially critical mediators of posttraumatic edema include aquaporins, integral membrane
proteins which form pores in cellular membranes, matrix metalloproteinases, enzymes, which degrade
extracellular matrix proteins, including components of the BBB, and proinflammatory, vasoactive
agents which are capable of increasing BBB permeability, for example bradykinins and neuropeptides
(e.g. calcitonin gene-related peptide or substance P).138 Signaling cascades of these recently discovered
mediators of posttraumatic brain edema are rather complex and have not yet been completely elucidated.
However, insight into these mechanisms might offer new therapeutic strategies for improving
the prognosis of patients suffering from TBI.