Distant neuroinflammation acutely induced by focal brain injury and its control by endocannabinoid system.

INTRODUCTION: We studied spatiotemporal features of acute transcriptional inflammatory response induced by a focal brain injury in distant uninjured neuronal tissue and a role of endocannabinoid (eCB) system in its control. MATERIALS AND METHODS: A focal excitotoxic lesion was induced by a unilateral injection of kainate in the dorsal hippocampus of awake Wistar rats. During acute post-injury period (3 h and 24 h post-injection), mRNA levels of genes associated with neuroinflammation (Il1b, Il6, Tnf, Ccl2; Cx3cl1, Zc3 h12a, Tgfb1) and eCB receptors of CB1 and CB2 types (Cnr1 and Cnr2) in intact regions of the hippocampus and neocortex were measured using qPCR. Occurrence of acute symptomatic seizures was controlled electrographically. To modulate eCB signaling during injury and acute post-injury period, antagonists (AM251, AM630) and agonist (WIN55-212-2) of eCB receptors were administered before the injury induction. RESULTS: Local intrahippocampal injury triggered widespread time- and region-dependent neuroinflammation in undamaged brain regions remote from the lesion site. The distant areas of the hippocampus and hippocampal meninges exhibited early (3 h) transient upregulation of pro- and anti-inflammatory cytokines simultaneously with occurrence of acute symptomatic seizures. The neocortex and its meninges showed minor neuroinflammation early after injury (3 h) but later (24 h) significantly upregulated several genes, mainly with anti-inflammatory properties. Focal lesion also changed expression of eCB receptors in the distant extra-lesional regions - CB1 receptors at 3 h and both CB1 and CB2 receptors at 24 h. Within the hippocampus, significant regional differences in constitutive and post-injury expression CB1 receptors were found. Pharmacological blockade of eCB receptors during injury and early post-injury period lengthened hippocampal neuroinflammation and reversed upregulation of anti-inflammatory molecules in the neocortex. CONCLUSION: The findings show that focal brain injury rapidly triggers widespread parenchymal and extraparenchymal neuroinflammation. The early injury-induced response is likely to represent neurogenic neuroinflammation produced by network hyperexcitability (acute symptomatic seizures). Activation of eCB signaling during acute phase of the brain injury is important for initiation of adaptive anti-inflammatory processes and prevention of chronic pathologic neuroinflammation in distant uninjured structures. However, the beneficial role of injury-induced eCB activity appears to depend on many factors including time, brain region, eCB tone etc.

Expression of Cytokines and Neurodegeneration in the Rat Hippocampus and Cortex in the Lithium-Pilocarpine Model of Status Epilepticus and the Role of Modulation of Endocannabinoid System.

A significant body of evidence shows that neuroinflammation is one of the key processes in the development of brain pathology in trauma, neurodegenerative disorders, and epilepsy. Various brain insults, including severe and prolonged seizure activity during status epilepticus (SE), trigger proinflammatory cytokine release. We investigated the expression of the proinflammatory cytokines interleukin-1ß (Il1b) and interleukin-6 (Il6), and anti-inflammatory fractalkine (Cx3cl1) in the hippocampus, entorhinal cortex, and neocortex of rats 24 h, 7 days, and 5 months after lithium-pilocarpine SE. We studied the relationship between cytokine expression and neuronal death in the hippocampus and evaluated the effect of modulation of endocannabinoid receptors on neuroinflammation and neurodegeneration after SE. The results of the present study showed that inhibition of endocannabinoid CB1 receptors with AM251 early after SE had a transient neuroprotective effect that was absent in the chronic period and did not affect the development of spontaneous seizures after SE. At the same time, AM251 reduced the expression of Il6 in the chronic period after SE. Higher Cx3cl1 levels were found in rats with more prominent hippocampal neurodegeneration.

Deep Brain Stimulation of the Medial Septal Area Can Modulate Gene Expression in the Hippocampus of Rats under Urethane Anesthesia.

We studied the effects of stimulation of the medial septal area on the gene expression in the dorsal and ventral hippocampus. Rats under urethane anesthesia were implanted with a recording electrode in the right hippocampus and stimulating electrode in the dorsal medial septum (dMS) or medial septal nucleus (MSN). After one-hour-long deep brain stimulation, we collected ipsi- and contralateral dorsal and ventral hippocampi. Quantitative PCR showed that deep brain stimulation did not cause any changes in the intact contralateral dorsal and ventral hippocampi. A comparison of ipsi- and contralateral hippocampi in the control unstimulated animals showed that electrode implantation in the ipsilateral dorsal hippocampus led to a dramatic increase in the expression of immediate early genes (c-fos, arc, egr1, npas4), neurotrophins (ngf, bdnf) and inflammatory cytokines (il1b and tnf, but not il6) not only in the area close to implantation site but also in the ventral hippocampus. Moreover, the stimulation of MSN but not dMS further increased the expression of c-fos, egr1, npas4, bdnf, and tnf in the ipsilateral ventral but not dorsal hippocampus. Our data suggest that the activation of medial septal nucleus can change the gene expression in ventral hippocampal cells after their priming by other stimuli.

CB2 receptors modulate seizure-induced expression of pro-inflammatory cytokines in the hippocampus but not neocortex.

We compared neuroinflammatory responses induced by nonconvulsive and convulsive seizures and analyzed the role that may be played by cannabinoid CB2 receptors in the neuroinflammatory response induced by generalized tonic-clonic seizures (GTCS). Using quantitative PCR, we analyzed expression of interleukin-1b, CCL2, interleukin-6, tumor necrosis factor (TNF), transforming growth factor beta 1 (TGFb1), fractalkine, and cannabinoid receptor type 2 in the neocortex, dorsal and ventral hippocampus, cortical leptomeninges, dura mater, and spleen in 3 and 6 h after induction of GTCS by a high dose of pentylenetetrazole (PTZ, 70 mg/kg) and absence-like activity by a low dose of PTZ (30 mg/kg). The low dose of PTZ had no effect on the gene expression 3 and 6 h after PTZ injection. In 3 and 6 h after high PTZ dose, the expression of CCL2 and TNF increased in the neocortex. Both ventral and dorsal parts of the hippocampus responded to seizures by elevation of CCL2 expression 3 h after PTZ. Cortical leptomeninges but not dura mater also had elevated CCL2 level and decreased TGFb1 expression 3 h after GTCS. Activation of CB2 receptors by HU308 suppressed an inflammatory response only in the dorsal hippocampus but not neocortex. Suppression of CB2 receptors by AM630 potentiated expression of inflammatory cytokines also in the hippocampus but not in the neocortex. Thus, we showed that GTCS, but not the absence-like activity, provoke inflammatory response in the neocortex, dorsal and ventral hippocampus, and cortical leptomeninges. Modulation of CB2 receptors changes seizure-induced neuroinflammation only in the hippocampus but not neocortex.

Micro-evolution of three Streptococcus species: selection, antigenic variation, and horizontal gene inflow.

BACKGROUND: The genus Streptococcus comprises pathogens that strongly influence the health of humans and animals. Genome sequencing of multiple Streptococcus strains demonstrated high variability in gene content and order even in closely related strains of the same species and created a newly emerged object for genomic analysis, the pan-genome. Here we analysed the genome evolution of 25 strains of Streptococcus suis, 50 strains of Streptococcus pyogenes and 28 strains of Streptococcus pneumoniae. RESULTS: Fractions of the pan-genome, unique, periphery, and universal genes differ in size, functional composition, the level of nucleotide substitutions, and predisposition to horizontal gene transfer and genomic rearrangements. The density of substitutions in intergenic regions appears to be correlated with selection acting on adjacent genes, implying that more conserved genes tend to have more conserved regulatory regions. The total pan-genome of the genus is open, but only due to strain-specific genes, whereas other pan-genome fractions reach saturation. We have identified the set of genes with phylogenies inconsistent with species and non-conserved location in the chromosome; these genes are rare in at least one species and have likely experienced recent horizontal transfer between species. The strain-specific fraction is enriched with mobile elements and hypothetical proteins, but also contains a number of candidate virulence-related genes, so it may have a strong impact on adaptability and pathogenicity. Mapping the rearrangements to the phylogenetic tree revealed large parallel inversions in all species. A parallel inversion of length 15 kB with breakpoints formed by genes encoding surface antigen proteins PhtD and PhtB in S. pneumoniae leads to replacement of gene fragments that likely indicates the action of an antigen variation mechanism. CONCLUSIONS: Members of genus Streptococcus have a highly dynamic, open pan-genome, that potentially confers them with the ability to adapt to changing environmental conditions, i.e. antibiotic resistance or transmission between different hosts. Hence, integrated analysis of all aspects of genome evolution is important for the identification of potential pathogens and design of drugs and vaccines.