Inflammatory cytokines facilitate neurotoxicity by encouraging excitotoxicity and the inflammatory response, but simultaneously they facilitate the neurotrophic mechanisms and induction of cell growth Selleck C188-9 factors which are neuroprotective . It has also been shown by Vuylsteke et al that there is an increased gradient of inflammatory marker IL-8 in the brain after cardiopulmonary bypass, which is attenuated
by hypothermia . This gradient continued into the postoperative period. The primary insult also results in an immediate disturbance of the cerebral circulation, resulting in cerebral ischaemia and which contributes significantly to about 90% of deaths after closed head injuries. . Ischaemic brain damage is perpetuated by factors such as hypotension, hypoxia, raised intracranial pressure, oedema, focal tissue compression, damage to microvasculature, and in late phases, vasospasm in the remaining vessels [16, 17]. The time sequence after TBI can be arbitrarily divided into an early
(phase 1, immediate, with hypoperfusion), intermediate (phase 2, on days 1–3, when hyperaemia can be seen) and a late vasospastic phase (phase 3, on days 4–15, with a marked reduction in blood flow) . These different phases are associated with marked regional variations in cerebral blood flow, with a reduction in blood flow to the surrounding of the ischaemic core, which does not respond to augmentation of cerebral perfusion pressure . Surviving apoptosis Programmed cell death (which is often referred to as apoptosis 17DMAG cell line although strictly speaking this refers to the distinct morphological changes after programmed cell death) is a genetic mechanism by which cells are eliminated during development, and is the physiological mechanism by which cells are normally removed in the adult animal . This involves specific genes and proteins which were first described in neuronal development
of the round worm . Following TBI there is increased expression of two main sets of genes which are genes encoding for the caspase family of cysteine proteases [including interleukin-1β converting enzyme (ICE) and cpp32] and a family of genes that are Wilson disease protein homologous to the oncogene Bcl-2 that either Ruboxistaurin in vitro promote or suppress cell death. The Bcl-2 gene family controls both caspase dependent and independent apoptosis. [19, 21–23]. The endpoint of all these steps is fragmentation of cellular DNA with collapse of the nuclear structure, followed by the formation of membrane-wrapped apoptotic bodies, cleared by macrophages . Apoptosis is now recognised as an important factor in secondary brain injury . Following TBI, two different types of cells are visible; type 1 and 2 cells. The type 1 cells show a classic necrotic pattern (this follows the primary brain injury) and type 2 cells shows a classic apoptotic pattern on microscopy [25, 19]. Cells undergoing apoptosis die without membrane rupture and therefore elicit less inflammatory reactions.