Treatment Of Acute Brain Injury Research Articles

Estrogen and progesterone as neuroprotective agents in the treatment of acute brain injuries

Estrogen and progesterone are often thought of as steroid hormones that strongly influence reproductive and maternal behaviours. However, the steroids are now showing considerable promise as neuroprotective and neuroregenerative agents in stroke and traumatic brain injuries. Collectively, these two hormones have been reported to reduce the consequences of the injury cascade by enhancing anti-oxidant mechanisms, reducing excitotoxicity: altering glutamate receptor activity, reducing immune inflammation, providing neurotrophic support, stimulating axonal remyelinization and enhancing synaptogenesis and dendritic arborization. Estrogen has often been tried as a prophylactic treatment in females for ischemic brain injury, while progesterone has, thus far, been given as a post-injury treatment for both male and female subjects with acute, ischemic and traumatic injuries of the brain and spinal cord. This review compares and evaluates estrogen and progesterone as neuroactive agents in the acute treatment of brain damage caused by stroke and trauma.

The role of mononuclear phagocytes in wound healing after traumatic injury to adult mammalian brain

We monitor cellular responses to a penetrating wound in the cerebral cortex of adult rat during the first weeks after injury. Two classes of activated mononuclear phagocytes containing acetylated low-density lipoprotein (ac-LDL) receptors appear within hours at the wound site. One type of cell surrounding the lesion edge had thin, delicate processes and is identical in appearance to ramified microglia found in developing brain. Within the lesion, round cells are recognized as blood-borne macrophages when labeled by intravenous injection of carbon particles. Thus, both process-bearing reactive microglia and invading macrophages respond to brain trauma. The greatest number of ac-LDL(+) or nonspecific esterase(+) mononuclear phagocytes appears 2 days after injury within the wound site and are associated with a peak production of the cytokine interleukin-1 (IL-1). Because intracerebral infusion of IL-1 is known to stimulate astrogliosis and neovascularization (Giulian et al., 1988), we examine the time course of injury-induced reactive astrogliosis and angiogenesis. A 5-fold increase in the number of reactive astroglia is found at 3 d and a marked neovascularization at 5 d after injury. During the first week, mononuclear phagocytes engulf particles and clear them from the wound site either by migrating to the brain surface or by entering newly formed brain vasculature. To investigate further the role of reactive brain mononuclear phagocytes in CNS injury, we use drugs to inhibit trauma-induced inflammation. When applied in vivo, chloroquine or colchicine reduce the number of mononuclear phagocytes in damaged brain, help to block reactive astrogliosis and neovascularization, and slow the rate of debris clearance from sites of traumatic injury. In contrast, the glucocorticoid dexamethasone neither reduces the number of brain inflammatory cells nor hampers such responses as phagocytosis, astrogliosis, neovascularization, or debris clearance in vivo. Our observations show that mononuclear phagocytes play a major role in wound healing after CNS trauma with some events controlled by secretion of cytokines. Moreover, certain classes of immunosuppressive drugs may be useful in the treatment of acute brain injury.