No abstract

Background and purpose: Traumatic brain injury (TBI) triggers a complex series of inflammatory responses that contribute to secondary tissue damage. The aim of this study was to investigate the effect of baicalein, a flavonoid possessing potent antiinflammatory properties, on functional and histological outcomes and inflammatory cytokine expression, following TBI in rats. Experimental approach: Rats subjected to controlled cortical impact injury were injected with baicalein (30 mg kg À1 ) or vehicle immediately after injury or daily for 4 days. Neurological status was evaluated using the rotarod, adhesive removal, modified neurological severity scores and beam walk tests. Contusion volume and neuronal degeneration were measured using cresyl violet and FluoroJade B (FJB) histochemistry. Levels of tumour necrosis factor-a (TNF-a), interleukin-1b (IL-1b) and interleukin-6 (IL-6) mRNA and protein were assessed by real-time quantitative reverse transcriptase-PCR, enzyme-linked immunosorbent assay and immunohistochemistry. Key results: Single-dose and multiple-dose treatment with baicalein significantly improved functional recovery and reduced contusion volumes up to day 28 post-injury, although multiple-dose baicalein was the more effective treatment. Single-dose baicalein also significantly reduced the number of degenerating neurons (31%) on post-injury day 1 as indicated by FJB staining. These changes were associated with significantly decreased levels, at the contusion site, of TNF-a, IL-1b and IL-6 mRNA at 6 h, and cytokine protein on day 1 post-injury. Conclusions and implications: Post-injury treatment with baicalein improved functional and histological outcomes and reduced induction of proinflammatory cytokines in rat TBI. The neuroprotective effect of baicalein may be related to a decreased inflammatory response following the injury.

Microglia, the resident immune cells in the brain, play a pivotal role in immune surveillance, host defense, and tissue repair in the CNS. In response to immunological challenges, microglia readily become activated as characterized by morphological changes, expression of surface antigens, and production of immune modulators that impact on neurons to induce neurodegeneration. However, little is known concerning the fate of activated microglia. In the present study, stimulation of cultured rat primary microglia with 1 ng/mL of the inflammagen lipopolysaccharide (LPS) resulted in a maximal activation as measured by the release of tumor necrosis factor alpha (TNF alpha). However, treatment with higher concentrations of LPS resulted in significantly lower quantities of detectable TNF alpha. Further analysis revealed that overactivation of microglia with higher concentrations of LPS (> 1 ng/mL) resulted in a time- and dose-dependent apoptotic death of microglia as defined by DNA strand breaks, surface expression of apoptosis-specific markers (phosphatidylserine), and activation of caspase-3. In contrast, astrocytes were insensitive to LPS-induced cytotoxicity. In light of the importance of microglia and the limited replenishment mechanism, depletion of microglia from the brain may severely hamper its capacity for combating inflammatory challenges and tissue repair. Furthermore, overactivation-induced apoptosis of microglia may be a fundamental self-regulatory mechanism devised to limit bystander killing of vulnerable neurons.

BackgroundThe treatment of traumatic brain injury (TBI) represents an unmet medical need, as no effective pharmacological treatment currently exists. The development of such a treatment requires a fundamental understanding of the pathophysiological mechanisms that underpin the sequelae resulting from TBI, particularly the ensuing neuronal cell death and cognitive impairments. Tumor necrosis factor-alpha (TNF-α) is a cytokine that is a master regulator of systemic and neuroinflammatory processes. TNF-α levels are reported to become rapidly elevated post TBI and, potentially, can lead to secondary neuronal damage.MethodsTo elucidate the role of TNF-α in TBI, particularly as a drug target, the present study evaluated (i) time-dependent TNF-α levels and (ii) markers of apoptosis and gliosis within the brain and related these to behavioral measures of ‘well being’ and cognition in a mouse closed head 50 g weight drop mild TBI (mTBI) model in the presence and absence of post-treatment with an experimental TNF-α synthesis inhibitor, 3,6′-dithiothalidomide.ResultsmTBI elevated brain TNF-α levels, which peaked at 12 h post injury and returned to baseline by 18 h. This was accompanied by a neuronal loss and an increase in astrocyte number (evaluated by neuronal nuclei (NeuN) and glial fibrillary acidic protein (GFAP) immunostaining), as well as an elevation in the apoptotic death marker BH3-interacting domain death agonist (BID) at 72 h. Selective impairments in measures of cognition, evaluated by novel object recognition and passive avoidance paradigms - without changes in well being, were evident at 7 days after injury. A single systemic treatment with the TNF-α synthesis inhibitor 3,6′-dithiothalidomide 1 h post injury prevented the mTBI-induced TNF-α elevation and fully ameliorated the neuronal loss (NeuN), elevations in astrocyte number (GFAP) and BID, and cognitive impairments. Cognitive impairments evident at 7 days after injury were prevented by treatment as late as 12 h post mTBI but were not reversed when treatment was delayed until 18 h.ConclusionsThese results implicate that TNF-α in mTBI induced secondary brain damage and indicate that pharmacologically limiting the generation of TNF-α post mTBI may mitigate such damage, defining a time-dependent window of up to 12 h to achieve this reversal.

Proinflammatory cytokines IL-1beta, tumor necrosis factor alpha, IL-6; T helper 1 cytokines INF-gamma and IL-2 receptor; and chemokines IL-8, monocyte chemoattractant protein 1, and RANTES are increased in patients with exertional heatstroke. T helper 2 cytokines may play a role as anti-inflammatory cytokines. IL-6, interferon gamma, IL-2 receptor, and monocyte chemoattractant protein 1 may serve as prognostic indicators of disease severity in exertional heatstroke.

No abstract

The efficacy of glioblastoma chemotherapy is not satisfactory; therefore, a new medication is expected to improve outcomes. As much evidence shows that antidepressants decrease cancer incidence and improve patients' quality of life, we therefore attempted to explore the potential for fluoxetine to be used to treat GBM and its possible underlying mechanism. The expression level of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) was determined using immunohistochemical staining and PCR analysis. The mechanism of fluoxetine-induced apoptosis of gliomas was elucidated. Computer modeling and a binding assay were conducted to investigate the interaction of fluoxetine with the AMPAR. The therapeutic effect of fluoxetine was evaluated using an animal model. We found that fluoxetine directly bound to AMPAR, thus inducing transmembrane Ca2+ influx. The rise in the intracellular calcium concentration ([Ca2+]i) causes mitochondrial Ca2+ overload, thereby triggering apoptosis. AMPARs are excessively expressed in glioma tissues, suggesting that fluoxetine specifically executes glioma cells. Our in vivo study revealed that fluoxetine suppressed the growth of glioblastomas in brains of Nu/Nu mice, an effect similar to that produced by temozolomide. Our preclinical studies suggest fluoxetine, a commonly used antidepressant, might be selectively toxic to gliomas and could provide a new approach for managing this disease.

With parallels to concussive mild traumatic brain injury (mTBI) occurring in humans, anesthetized mice subjected to a single 30 g weight drop mTBI event to the right parietal cortex exhibited significant diffuse neuronal degeneration that was accompanied by delayed impairments in recognition and spatial memory. To elucidate the involvement of reversible p53-dependent apoptosis in this neuronal loss and associated cognitive deficits, mice were subjected to experimental mTBI followed by the systemic administration of the tetrahydrobenzothiazole p53 inactivator, PFT-α, or vehicle. Neuronal loss was quantified immunohistochemically at 72 hr. post-injury by the use of fluoro-Jade B and NeuN within the dentate gyrus on both sides of the brain, and recognition and spatial memory were assessed by novel object recognition and Y-maze paradigms at 7 and 30 days post injury. Systemic administration of a single dose of PFT-α 1 hr. post-injury significantly ameliorated both neuronal cell death and cognitive impairments, which were no different from sham control animals. Cellular studies on human SH-SY5Y cells and rat primary neurons challenged with glutamate excitotoxicity and H2O2 induced oxidative stress, confirmed the ability of PFT-α and a close analog to protect against these TBI associated mechanisms mediating neuronal loss. These studies suggest that p53-dependent apoptotic mechanisms underpin the neuronal and cognitive losses accompanying mTBI, and that these are potentially reversible by p53 inactivation.