We reported earlier that closed head injury (CHI) in mice causes a sharp elevation of brain 2-arachidonoylglycerol (2-AG) levels, and that exogenous 2-AG reduces brain edema, infarct volume and hippocampal death and improved clinical recovery after CHI. The beneficial effect of 2-AG was attenuated by SR141716A, a CB 1 cannabinoid receptor antagonist, albeit at relatively high doses. In the present study, we further explored the role of CB 1 receptors in mediating 2-AG neuroprotection. CB 1 receptor knockout mice (CB 1 (À/À)) showed minor spontaneous recovery at 24 h after CHI, in contrast to the significant improvement in neurobehavioral function seen in wild-type (WT) mice. Moreover, administration of 2-AG did not improve neurological performance and edema formation in the CB 1 (À/À) mice. In addition, 2-AG abolished the three-to four-fold increase of nuclear factor jB (NF-jB) transactivation, at 24 h after CHI in the WT mice, while it had no effect on NF-jB in the CB 1 (À/À) mice, which was as high as in the WT vehicle-treated mice. We thus propose that 2-AG exerts its neuroprotection after CHI, at least in part, via CB 1 receptor-mediated mechanisms that involve inhibition of intracellular inflammatory signaling pathways.

Traumatic brain injury (TBI) is followed by massive production of reactive oxygen species (ROS), which mediate secondary cellular damage. Low molecular weight antioxidants (LMWA) constitute one of the defense mechanisms of the brain, and their levels correlate with post-TBI outcome. Melatonin, the main pineal hormone, possesses antioxidant properties. We investigated the effects of melatonin on neurobehavioral recovery, brain LMWA, and activation of the redox-sensitive transcription factors nuclear factor-kappaB (NF-kappaB) and AP-1 in mice subjected to closed head injury (CHI). Given 1 h after CHI, melatonin facilitated recovery during at least 1 wk (P<0.05) and decreased lesion size by approximately twofold (P<0.01). The dose response displayed a bell-shape, i.e., neuroprotection was achieved with 5 but not 1 or 10 mg/kg. At the neuroprotective dose, melatonin treatment was associated with sustained (4 days) elevation of brain LMWA, including ascorbic acid (P<0.05). In contrast, LMWA were unaffected by the administration of the neuroprotective endocannabinoid 2-arachidonoyl glycerol. Furthermore, melatonin did not alter early phase (24 h) CHI-induced activation of NF-kappaB and AP-1; however, it blocked the robust late-phase (8 days) activation of NF-kappaB and decreased that of AP-1 to below basal levels. Our results demonstrate that melatonin induces neuroprotection, presumably via potentiation of brain antioxidants and attenuation of NF-kappaB and AP-1 activation.

The acute inflammatory response following traumatic brain injury (TBI) has been shown to play an important role in the development of secondary tissue damage. The proinflammatory cytokines interleukin-1 (IL-1) and tumor necrosis factor-alpha (TNFalpha), are induced early after brain injury and have been implicated in the delayed damage. The IL-1 receptor antagonist (IL-1ra) has been shown to modulate the proinflammatory cytokine cascade by blocking the binding of IL-1 to its signaling receptor. In this study, we investigated the effect of transgenic overexpression of IL-1ra on the cytokine expression and neurological damage in a closed head injury (CHI) model of TBI. The neurological recovery, as analyzed by neurological severity score (NSS), was significantly higher in transgenic mice overexpressing the human secreted form of IL-1ra in astrocytes, directed by the murine glial fibrillary acidic protein promoter, as compared to wild-type mice. Analysis of tissue levels of cytokines by ELISA showed increased levels of TNFalpha in the cerebral cortex from the wild type mice 1 h after injury. After 4 h significant increases in the levels of IL-1beta and IL-6 were observed in the wild type mice. In the transgenic mice, on the other hand, no effect on TNFalpha levels was observed and no significant increases in IL-1beta and IL-6 levels could be detected until 6 h after injury. Thus, it can be concluded that blockage of IL-1 signaling by elevated levels of IL-1ra has a neuroprotective effect, in agreement with previous reports, and that central overexpression of IL-1ra results in delayed proinflammatory cytokine induction and improved neurological recovery after traumatic brain injury.

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Activity-dependent neuroprotective protein (ADNP), a crucial brain development factor, contains a unique sequence, termed NAPVSIPQ, which protects mice against closed head injury (CHI). The aim of this study was to determine whether CHI affects ADNP mRNA expression in the injured brain hemisphere. Male C57JBL/6J mice were subjected to CHI. Brains were removed 5 h, 24 h, 7 d, and 29 d post-CHI. A comparison was made between ADNP mRNA in the injured versus the noninjured hemisphere using real-time polymerase chain reaction. A nonsignificant change (p >0.05) was found 5 h, 24 h, and 7 d post-CHI. However, a significant increase (p <0.05) in ADNP mRNA expression was detected in the injured cerebral hemisphere 29 d post-CHI. The data presented may be associated with ADNP's crucial involvement in brain development and response to injury.