Recent studies have demonstrated nicotinamide (NAM), a soluble B-group vitamin, to be an effective treatment in experimental models of TBI. However, research on this compound has been limited to administration regimens starting shortly after injury. This study was conducted to establish the window of opportunity for NAM administration following controlled cortical impact (CCI) injury to the frontal cortex. Groups of rats were assigned to NAM (50 mg/kg), saline (1 ml/kg), or sham conditions and received contusion injuries or sham procedures. Injections of NAM or saline were administered at 15 min, 4 hrs, or 8 hrs post-injury, followed by five boosters at 24 hr intervals. Following the last injection, blood was taken for serum NAM analysis. Animals were tested on a variety of tasks to assess somatosensory performance (bilateral tactile adhesive removal and vibrissae-forelimb placement) and cognitive performance (reference and working memory) in the Morris water maze. The results of the serum NAM analysis showed that NAM levels were significantly elevated in treated animals. Behavioral analysis on the tactile removal test showed that all NAM-treated groups facilitated recovery of function compared to saline treatment. On the vibrissae-forelimb placing test all NAM-treated groups also were significantly different from the saline-treated group. However, the acquisition of reference memory was only significantly improved in the 15-min and 4-hr groups. In the working memory task both the 15-min and 4-hr groups also improved working memory compared to saline treatment. The window of opportunity for NAM treatment is task-dependent and extends to 8 hrs for the sensorimotor tests but only extends to 4 hrs post-injury in the cognitive tests. These results suggest that a 50 mg/kg treatment regimen starting at the clinically relevant time point of 4 hrs may result in attenuated injury severity in the human TBI population.

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It has previously been shown that small peptide molecules derived from the apolipoprotein E (ApoE) receptor binding region are anti-inflammatory in nature and can improve outcome following head injury. The present study evaluated the preclinical efficacy of COG1410, a small molecule ApoE-mimetic peptide (1410 daltons), following cortical contusion injury (CCI). Animals were prepared with a unilateral CCI of the sensorimotor cortex (SMC) or sham procedure. Thirty mins post-CCI the animals received i.v. infusions of 0.8 mg/kg COG1410, 0.4 mg/kg COG1410, or vehicle. Starting on day 2, the animals were tested on a battery of behavioral measures to assess sensorimotor (vibrissae-forelimb placing and forelimb use-asymmetry), and motor (tapered balance beam) performance. Administration of the 0.8 mg/kg dose of COG1410 significantly improved recovery on the vibrissae-forelimb and limb asymmetry tests. However, no facilitation was observed on the tapered beam. The low dose (0.4 mg/kg) of COG1410 did not show any significant differences compared to vehicle. Lesion analysis revealed that the 0.8 mg/kg dose of COG1410 significantly reduced the size of the injury cavity compared to the 0.4 mg/kg dose and vehicle. The 0.8 mg/kg dose also reduced the number of glial fibrillary acid protein (GFAP+) reactive cells in the injured cortex. These results suggest that a single dose of COG1410 facilitates behavioral recovery and provides neuroprotection in a dose and task-dependent manner. Thus, the continued clinical development of ApoE based therapeutics is warranted and could represent a novel strategy for the treatment of traumatic brain injuries.

Previous studies in our laboratory have demonstrated the preclinical efficacy of nicotinamide (NAM; vitamin B3) treatment following fluid percussion injury (FPI). At a dose of 500 or 50 mg/kg, NAM significantly facilitated recovery of function on a variety of motor and sensorimotor tasks in rodents, and the 500 mg/kg dose improved cognitive performance. The purpose of the present study was to examine the acute neuroprotective ability of NAM following FPI. Rats were given a moderate FPI (1.8 atm) or sham injury. NAM (500 or 50 mg/kg) or saline was administered 15 min and 20 h after FPI. Rats were sacrificed at 24 h or 7 days following injury and prepared for histological analysis. Systematic volumetric measurements were conducted to examine cortical loss in a series of cresyl violet stained slices to examine the development of the injury cavity. To assess the extent of astrocytic activity and neurodegeneration, triple labeling with glial fibrillary acidic protein (GFAP), Fluoro-Jade B (FJ), and DAPI was performed. GFAP(+) astrocytes and FJ(+) neurons in the ipsilateral and contralateral cortex, and ipsilateral hippocampus and thalamus were assessed. While not significant at 24 h, NAM significantly attenuated cortical tissue loss at 7 days. At 24 h, the number of GFAP(+) astrocytes was significantly reduced by NAM. However, the inverse was observed at 7 days where NAM treatment significantly increased the number of GFAP(+) astrocytes. Both doses of NAM also significantly reduced FJ expression at the 24-h and 7-day time intervals. The results of this study suggest that NAM has strong neuroprotective abilities in the injured brain and may have therapeutic potential for brain injury.

Microcystis aeruginosa (M. aeruginosa) is a cosmopolitan Gram-negative cyanobacterium that may contaminate freshwater by releasing toxins, such as lipopolysaccharide (LPS) during aquatic blooms, affecting environmental and human health. The putative toxic effects of cyanobacterial LPS on brain microglia, a glial cell type that constitutes the main leukocyte-dependent source of reactive oxygen species in the central nervous system, are presently unknown. We tested the hypothesis that in vitro concentration- and time-dependent exposure to M. aeruginosa LPS strain UTCC 299 would activate rat microglia and the concomitant generation of superoxide anion (O₂⁻). After a 17-h exposure of microglia to M.aeruginosa LPS, the following concentration-dependent responses were observed: 0.1-100 ng/ml M. aeruginosa LPS enhanced O₂⁻ generation, with limited inflammatory mediator generation; 1000-10,000 ng/ml M. aeruginosa LPS caused thromboxane B₂ (TXB₂), matrix metalloproteinase-9 (MMP-9), and macrophage inflammatory protein-2 (MIP-2/CXCL2) release, concurrent with maximal O₂⁻ generation; 100,000 ng/mL M. aeruginosa LPS deactivated O₂⁻ production but maintained elevated levels of TXB₂, MMP-9, tumor necrosis factor-α (TNF-α), interleukin 1-α (IL-1α), and interleukin-6 (IL-6), macrophage inflammatory protein 1α (MIP-1α/CCL3), and MIP-2/CXCL2, with concomitant lactic dehydrogenase release. Although M. aeruginosa LPS was consistently less potent than Escherichia coli LPS, with the exception of O₂⁻, TXB₂, and MCP-1/CCL2 generation, it was more efficacious because higher levels of MMP-9, TNF-α, IL-1α, IL-6, MIP-1α/CCL3, and MIP-2/CXCL2 were produced. Our in vitro studies suggest that one or more of the inflammatory mediators released during M. aeruginosa LPS stimulation of microglia may play a critical role in the subsequent ability of microglia to generate O₂⁻. To our knowledge, this is the first experimental evidence that LPS isolated from a M. aeruginosa strain, can activate brain microglia in vitro, as well as the release of O₂⁻, and other inflammatory mediators hypothesized to be involved in neuroinflammation and neurodegeneration.