Antibiotic therapy prevents, in part, the oxidative stress in the rat brain after meningitis induced by Streptococcus pneumoniae

Sink or swim: Does a worm paralysis phenotype hold clues to neurodegenerative disease?

Receiving a neurodegenerative disease (NDD) diagnosis, such as Alzheimer's disease, Parkinson's disease, Huntington's disease, or amyotrophic lateral sclerosis, is devastating, particularly given the limited options for treatment. Advances in genetic technologies have allowed for efficient modeling of NDDs in animals and brought hope for new disease-modifying medications. The complexity of the mammalian brain and the costs and time needed to identify and develop therapeutic leads limits progress. Modeling NDDs in invertebrates, such as the fruit fly Drosophila melanogaster and the nematode Caenorhabditis elegans, offers orders of magnitude increases in speed of genetic analysis and manipulation, and can be pursued at substantially reduced cost, providing an important, platform complement and inform research with mammalian NDD models. In this review, we describe how our efforts to exploit C. elegans for the study of neural signaling and health led to the discovery of a paralytic phenotype (swimming-induced paralysis) associated with altered dopamine signaling and, surprisingly, to the discovery of a novel gene and pathway whose dysfunction in glial cells triggers neurodegeneration. Research to date on swip-10 and its putative mammalian ortholog MBLAC1, suggests that a tandem analysis will offer insights into NDD mechanisms and insights into novel, disease-modifying therapeutics.

Dysfunctional Glymphatic System with Disrupted Aquaporin 4 Expression Pattern on Astrocytes Causes Bacterial Product Accumulation in the CSF during Pneumococcal Meningitis

Pneumococcal meningitis, inflammation of the meninges due to an infection of the Central Nervous System caused by Streptococcus pneumoniae (the pneumococcus), is the most common form of community-acquired bacterial meningitis globally. Aquaporin 4 (AQP4) water channels on astrocytic end feet regulate the solute transport of the glymphatic system, facilitating the exchange of compounds between the brain parenchyma and the cerebrospinal fluid (CSF), which is important for the clearance of waste away from the brain. Wistar rats, subjected to either pneumococcal meningitis or artificial CSF (sham control), received Evans blue-albumin (EBA) intracisternally. Overall, the meningitis group presented a significant impairment of the glymphatic system by retaining the EBA in the CSF compartments compared to the uninfected sham group. Our results clearly showed that during pneumococcal meningitis, the glymphatic system does not function because of a detachment of the astrocytic end feet from the blood-brain barrier (BBB) vascular endothelium, which leads to misplacement of AQP4 with the consequent loss of the AQP4 water channel's functionality. IMPORTANCE The lack of solute drainage due to a dysfunctional glymphatic system leads to an increase of the neurotoxic bacterial material in the CSF compartments of the brain, ultimately leading to brain-wide neuroinflammation and neuronal damage with consequent impairment of neurological functions. The loss of function of the glymphatic system can therefore be a leading cause of the neurological sequelae developing post-bacterial meningitis.

Gut microbiota depletion from early adolescence alters anxiety and depression-related behaviours in male mice with Alzheimer-like disease

The gut-microbiota-brain axis plays an important role in stress-related disorders, and dysfunction of this complex bidirectional system is associated with Alzheimer's disease. This study aimed to assess the idea that whether gut microbiota depletion from early adolescence can alter anxiety- and depression-related behaviours in adult mice with or without Alzheimer-like disease. Male C57BL/6 mice were treated with an antibiotic cocktail from weaning to adulthood. Adult mice received an intracerebroventricular injection of amyloid-beta (Aβ)1-42, and were subjected to anxiety and depression tests. We measured, brain malondialdehyde and glutathione following anxiety tests, and assessed brain oxytocin and the hypothalamic-pituitary-adrenal (HPA) axis function by measuring adrenocorticotrophic hormone (ACTH) and corticosterone following depression tests. Healthy antibiotic-treated mice displayed significant decreases in anxiety-like behaviours, whereas they did not show any alterations in depression-like behaviours and HPA axis function. Antibiotic treatment from early adolescence prevented the development of anxiety- and depression-related behaviours, oxidative stress and HPA axis dysregulation in Alzheimer-induced mice. Antibiotic treatment increased oxytocin in the brain of healthy but not Alzheimer-induced mice. Taken together, these findings suggest that gut microbiota depletion following antibiotic treatment from early adolescence might profoundly affect anxiety- and depression-related behaviours, and HPA axis function in adult mice with Alzheimer-like disease.

Cerebroprotective Effects of 2-Ethyl-6-methyl-3-hydroxypyridine-2,6-dichlorophenyl(amino)phenylethanoic Acid in the Treatment of Purulent Meningitis

Purulent meningitis (PM) is a severe disease, characterized by high mortality and a formation of a residual neurological deficit. Loss of treatment of PM leads to the lethal outcome in 100% of cases. In addition, death and the development of residual neurological complications are possible despite adequate therapy. The aim of the study was to evaluate the cerebroprotective effects of a new pharmacological compound 2-ethyl-6-methyl-3-hydroxypyridine-2,6-dichlorophenyl(amino)phenylethanoic acid (EMHDPA) on the bacterial purulent meningitis in a model of experimental pneumococcal meningitis. Meningitis was simulated by intrathecal injection of the suspension containing Streptococcus pneumoniae at the concentration of 5 × 10⁹ CFU/mL. The cerebroprotective effect was evaluated by survival rates, the severity of neurological deficit, investigatory behaviors, and results of short-term and long-term memory tests. The group administered with EMHDPA showed high survival rates, 80%. Animals treated with the studied compound showed a higher clinical assessment of the rat health status and specific force, and a lesser intensity of neurological deficit compared to the control group (p < 0.05). Locomotor activity of the animals treated with EMHDPA was significantly higher compared to the control group (p < 0.05). There is a decrease in the activity of all estimated indicators of oxidative stress in the group administered with 2-ethyl-6-methyl-3-hydroxypyridine-2,6-dichlorophenyl(amino)phenylethanoic acid relative to the control group: a decrease in the activity of catalase—17%, superoxide dismutase—34%, malondialdehyde and acetylhydroperoxides—50%, and nitric oxide—85% (p < 0.05). Analysis of the data obtained during the experiment leads to the conclusion about the effectiveness of 2-ethyl-6-methyl-3-hydroxypyridine-2,6-dichlorophenyl(amino)phenylethanoic acid in the treatment of the experimental PM.

The Potentials of Melatonin in the Prevention and Treatment of Bacterial Meningitis Disease

Bacterial meningitis (BM) is an acute infectious central nervous system (CNS) disease worldwide, occurring with 50% of the survivors left with a long-term serious sequela. Acute bacterial meningitis is more prevalent in resource-poor than resource-rich areas. The pathogenesis of BM involves complex mechanisms that are related to bacterial survival and multiplication in the bloodstream, increased permeability of blood-brain barrier (BBB), oxidative stress, and excessive inflammatory response in CNS. Considering drug-resistant bacteria increases the difficulty of meningitis treatment and the vaccine also has been limited to several serotypes, and the morbidity rate of BM still is very high. With recent development in neurology, there is promising progress for drug supplements of effectively preventing and treating BM. Several in vivo and in vitro studies have elaborated on understanding the significant mechanism of melatonin on BM. Melatonin is mainly secreted in the pineal gland and can cross the BBB. Melatonin and its metabolite have been reported as effective antioxidants and anti-inflammation, which are potentially useful as prevention and treatment therapy of BM. In bacterial meningitis, melatonin can play multiple protection effects in BM through various mechanisms, including immune response, antibacterial ability, the protection of BBB integrity, free radical scavenging, anti-inflammation, signaling pathways, and gut microbiome. This manuscript summarizes the major neuroprotective mechanisms of melatonin and explores the potential prevention and treatment approaches aimed at reducing morbidity and alleviating nerve injury of BM.

Myeloid-Related Protein 8/14 Participates in the Progression of Experimental Pneumococcal Meningitis by Augmentation of Inflammation

It has been reported that myeloid-related protein 8/14 (MRP8/14) participates in the progression of inflammation after release from neutrophils and monocytes. This study aimed to clarify the mechanism(s) of the MRP8/14-augmented inflammatory response in mice with pneumococcal meningitis. Streptococcus pneumoniae (SP) meningitis was established by intracerebral injection of SP suspension. Balb/c mice were randomly divided into four groups and received the following injections: phosphate-buffer saline (PBS), MRP8/14 alone, SP alone, and SP plus MRP8/14. At 6 h, 24 h and 48 h postinfection, the clinical disease status was measured by the modified neurological severity score test, body weight loss and degree of cerebral edema; mice were anaesthetized, blood samples and brain samples were collected and brain inflammation was detected by haematoxylin and eosin (HE) staining; tumour necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), C-reactive protein (CRP) and monocyte chemoattractant protein-1 (MCP-1) levels in serum and brain homogenates were assessed by an enzyme-linked immunosorbent assay (ELISA), and the mRNA levels of the above cytokines in brain homogenates were measured by polymerase chain reaction (PCR); and the expression of nuclear factor-kappa B (NF-κB) p65 in brain tissues was determined by immunohistochemical assay. In this study, we identified that MRP8/14 substantially augmented the SP-stimulated inflammatory response, aggravated clinical disease status and exacerbated SP-induced brain edema in a murine model of pneumococcal meningitis. Exogenous administration of MRP8/14 significantly enhanced mRNA and protein expression of the proinflammatory cytokines and chemokines TNF-α, CRP, IL-6 and MCP-1 in brain homogenates and serum from mice with pneumococcal meningitis, which may be related to the NF-κB signalling pathway. We further found that MRP8/14 strongly augmented SP-induced phosphorylation of NF-κB p65 in brain tissue slices from the same model. In conclusion, our results indicated that MRP8/14 augmented the inflammatory response in mice with pneumococcal meningitis and contributed to the development of disease, which was probably through NF-κB signalling pathway activation.

Association between Experimental Bacterial Meningitis and Periapical Lesion

INTRODUCTION

Mortality and morbidity from bacterial meningitis in African adults is significantly higher than those in better resourced settings. At the same time, the periodontal diseases are highly prevalent and can affect up to 90% of the population. Dental caries in Uganda was recorded in 40% and 62.5% of the children and adults, respectively. We hypothesize that pneumococcal meningitis could interfere in the development of periapical lesion. The aim of this study was to evaluate periapical lesion in Wistar rats subjected to pneumococcal meningitis.

MATERIALS AND METHODS

The animals were divided in control, control/periapical lesion, meningitis, and meningitis/periapical lesion groups. The surgical exposure of molars and the infection of the dental pulp were from the oral environment. Pulp necrosis was induced on the left mandibular first molars during adulthood. Dental pulps were exposed by drilling cavities on the central portion of the occlusal surface with a 1011 HL round bur in high speed to a depth nearly equal to the bur diameter. Animals were subjected to behavioral task and evaluation of the size of periodontal ligament. Data from periodontal ligament space and open field task were reported as mean ± SEM and analysed by Two-way ANOVA and paired Student's t-test, respectively.

RESULTS AND CONCLUSION

Meningitis/periapical increased the periodontal ligament space by 61% when compared with control/periapical. In the open-field task, there were no differences in the number of crossings and rearing movements between training and test session in meningitis and periapical lesion groups demonstrating habituation memory impairment. Bacterial meningitis and periapical lesion may play an important role in development of cognitive impairment.

Vitamin B6 prevents cognitive impairment in experimental pneumococcal meningitis

Streptococcus pneumoniae is the relevant cause of bacterial meningitis, with a high-mortality rate and long-term neurological sequelae, affecting up to 50% of survivors. Pneumococcal compounds are pro-inflammatory mediators that induce an innate immune response and tryptophan degradation through the kynurenine pathway. Vitamin B6 acts as a cofactor at the active sites of enzymes that catalyze a great number of reactions involved in the metabolism of tryptophan, preventing the accumulation of neurotoxic intermediates. In the present study, we evaluated the effects of vitamin B6 on memory and on brain-derived neurotrophic factor (BDNF) expression in the brain of adult Wistar rats subjected to pneumococcal meningitis. The animals received either 10 µL of artificial cerebral spinal fluid (CSF) or an equivalent volume of S. pneumoniae suspension. The animals were divided into four groups: control, control treated with vitamin B6, meningitis, and meningitis treated with vitamin B6. Ten days after induction, the animals were subjected to behavioral tests: open-field task and step-down inhibitory avoidance task. In the open-field task, there was a significant reduction in both crossing and rearing in the control group, control/B6 group, and meningitis/B6 group compared with the training session, demonstrating habituation memory. However, the meningitis group showed no difference in motor and exploratory activity between training and test sessions, demonstrating memory impairment. In the step-down inhibitory avoidance task, there was a difference between training and test sessions in the control group, control/B6 group, and meningitis/B6 group, demonstrating aversive memory. In the meningitis group, there was no difference between training and test sessions, demonstrating impairment of aversive memory. In the hippocampus, BDNF expression decreased in the meningitis group when compared to the control group; however, adjuvant treatment with vitamin B6 increased BDNF expression in the meningitis group. Thus, vitamin B6 attenuated the memory impairment in animals subjected to pneumococcal meningitis.

Erythropoietin prevents cognitive impairment and oxidative parameters in Wistar rats subjected to pneumococcal meningitis

Pneumococcal meningitis is characterized by a severe inflammatory reaction in the subarachnoid and ventricular space of the brain, disruption of the blood-brain barrier, hearing loss, and neurologic sequelae in as many as 27% of surviving patients. Several experimental studies have shown that erythropoietin (EPO) and its receptor are expressed in the central nervous system and have neuroprotective properties through the inhibition of apoptosis, as well as anti-inflammatory, antioxidant, angiogenic, and neurotrophic effects. In the current study, we demonstrated the effect of erythropoietin (EPO) on lipid peroxidation, protein carbonylation, superoxide dismutase (SOD), catalase (CAT), myeloperoxidase (MPO), and behavioral parameters in rats with pneumococcal meningitis. EPO decreased lipid peroxidation and protein carbonylation, and it prevented protein degradation in the hippocampus and frontal cortex. MPO activity was decreased, and both SOD and CAT activity were increased in the first 6 hours after pneumococcal meningitis induction. Novel object recognition memory was impaired in the meningitis group; however, adjuvant treatment with EPO prevented memory impairment during both the short- and long-term retention tests. The meningitis group showed no difference in motor and exploratory activity between training and test sessions in the open-field task, which indicates that habituation memory was impaired; however, adjuvant treatment with EPO prevented habituation memory impairment. Although there are some limitations with respect to the animal model of pneumococcal meningitis, this study suggests that adjuvant treatment with EPO contributed to decreased oxidative stress and prevented cognitive impairment.

Inhibition of matrix metalloproteinases-2 and -9 prevents cognitive impairment induced by pneumococcal meningitis in Wistar rats

Pneumococcal meningitis is a relevant clinical disease characterized by an intense inflammatory reaction into the subarachnoid and ventricular spaces, leading to blood–brain barrier breakdown, hearing loss, and cognitive impairment. Matrix metalloproteinases (MMPs) are capable of degrading components of the basal laminin, thus contributing to BBB damage and neuronal injury. In the present study, we evaluated the effects of MMP-2, MMP-9, and MMP-2/9 inhibitors on BBB integrity, learning, and memory in Wistar rats subjected to pneumococcal meningitis. The animals underwent a magna cistern tap and received either 10 µL sterile saline as a placebo or an equivalent volume of a Streptococcus pneumoniae suspension at a concentration of 5 × 109 cfu/mL. The rats were randomized into different groups that received adjuvant treatment with MMP-2, MMP-9 or MMP-2/9 inhibitors. The BBB integrity was evaluated, and the animals were habituated to open-field and object recognition tasks 10 days after meningitis induction. Adjuvant treatments with inhibitors of MMP-2 or MMP-2/9 prevented BBB breakdown in the hippocampus, and treatments with inhibitors of MMP-2, MMP-9 or MMP-2/9 prevented BBB breakdown in the cortex. Ten days after meningitis induction, the animals that received adjuvant treatment with the inhibitor of MMP-2/9 demonstrated that animals habituated to the open-field task faster and enhanced memory during short-term and long-term retention test sessions in the object recognition task. Further investigation is necessary to provide support for MMP inhibitors as an alternative treatment for bacterial meningitis; however, these findings suggest that the meningitis model could be a good research tool for studying the biological mechanisms involved in the behavioral alterations associated with pneumococcal meningitis.

Inhibition of indoleamine 2,3-dioxygenase prevented cognitive impairment in adult Wistar rats subjected to pneumococcal meningitis

Streptococcus pneumoniae is a common cause of forms of bacterial meningitis that have a high mortality rate and cause long-term neurologic sequelae. We evaluated the effects of an indoleamine 2,3-dioxygenase (IDO) inhibitor on proinflammatory mediators and memory in Wistar rats subjected to pneumococcal meningitis. The animals were divided into 4 groups: sham, sham treated with IDO inhibitor, meningitis, and meningitis treated with IDO inhibitor. During the first experiment, the animals were killed 24 hours later, and the hippocampus was isolated for the analysis of tumor necrosis factor (TNF)-α, interleukin (IL)-4, IL-6, IL-10, and cytokine-induced neutrophil chemoattractant 1 (CINC-1) levels. The survival rate was 56.296% in the meningitis group and 29.616% in the meningitis group with IDO inhibitor. In the control group, we found a mean of 14.29 white blood cells/mL cerebrospinal fluid, whereas the mean was 80.00 white blood cells/mL cerebrospinal fluid in the sham IDO inhibitor group, 1167.00 white blood cells/mL cerebrospinal fluid in the meningitis group, and 286.70 white blood cells/mL cerebrospinal fluid in the meningitis IDO inhibitor group. In the meningitis group with IDO inhibitor, the levels of TNF-α and CINC-1 were reduced. In the second experiment, animals were subjected to a behavioral task and cytokine analysis 10 days after meningitis induction. In the meningitis group, there was an impairment of aversive memory. However, in the meningitis group that received adjuvant treatment with the IDO inhibitor, animals demonstrated preservation of aversive memory. These findings showed dual effects of the IDO inhibitor on a pneumococcal meningitis animal model because the inhibitor impaired survival but also produced beneficial effects, including anti-inflammatory activity and neuroprotection against the latter behavioral deficits.

Klebsiella pneumoniae meningitis induces memory impairment and increases pro-inflammatory host response in the central nervous system of Wistar rats

Klebsiella pneumoniae meningitis has recently become an increasingly common cause of central nervous system infection. The invasion of bacteria within the subarachnoid space stimulates the release of pro-inflammatory cytokines and chemokines, triggering a host immune response. The aim of the present study was to evaluate memory and pro-inflammatory mediators at different times in the brains of adult Wistar rats with K. pneumoniae meningitis. The animals were sacrificed at 6, 12, 24, 48 and 96 h after meningitis induction. The hippocampus, frontal cortex and cerebrospinal fluid were isolated to determine the cytokine, chemokine and brain-derived neurotrophic factor (BDNF) levels. In the first 6 and 24 h following meningitis induction, there was a significant increase of the TNF-α, IL-1β, IL-6, cytokine-induced neutrophil chemoattractant-1 and BDNF levels in the central nervous system. Ten days after meningitis induction, cognitive memory was evaluated using an open-field task and step-down inhibitory avoidance task. In the control group, significant differences in behaviour were observed between the training and testing sessions for both tasks, demonstrating habituation and aversive memory. However, the meningitis group did not exhibit any difference between the training and testing sessions in either task, demonstrating memory impairment. As a result of these observations, we believe that the meningitis model may be a good research tool to study the biological mechanisms involved in the pathophysiology of this illness, while recognizing that animal models should be interpreted with caution before extrapolation to the clinic.

Evaluation of energetic metabolism in the rat brain after meningitis induction by Klebsiella pneumoniae

BACKGROUND

Bacterial meningitis is an infection of the central nervous system characterised by strong inflammatory response. The brain is highly dependent on ATP, and the cell energy is obtained through oxidative phosphorylation, a process which requires the action of various respiratory enzyme complexes and creatine kinase (CK) as an effective buffering system of cellular ATP levels in tissues that consume high energy.

OBJECTIVES

Evaluate the activities of mitochondrial respiratory chain complexes I, II, III, IV and CK activity in hippocampus and cortex of the Wistar rat submitted to meningitis by Klebsiella pneumoniae.

METHODS

Adult Wistar rats received either 10 µl of sterile saline as a placebo or an equivalent volume of K. pneumoniae suspension. The animals were killed in different times at 6, 12, 24 and 48 h after meningitis induction. Another group was treated with antibiotic, starting at 16 h and continuing daily until their decapitation at 24 and 48 h after induction.

RESULTS

In the hippocampus, the meningitis group without antibiotic treatment, the complex I was increased at 24 and 48 h, complex II was increased at 48 h, complex III was inhibited at 6, 12, 24 and 48 h and in complex IV all groups with or without antibiotic treatment were inhibited after meningitis induction, in the cortex there was no alteration. Discussion Although descriptive, our results show that antibiotic prevented in part the changes of the mitochondrial respiratory chain. The meningitis model could be a good research tool to study the biological mechanisms involved in the pathophysiology of the K. pneumoniae meningitis.

Pathophysiology of acute meningitis caused by Streptococcus pneumoniae and adjunctive therapy approaches

Pneumococcal meningitis is a life-threatening disease characterized by an acute purulent infection affecting piamater, arachnoid and the subarachnoid space. The intense inflammatory host's response is potentially fatal and contributes to the neurological sequelae. Streptococcus pneumoniae colonizes the nasopharynx, followed by bacteremia, microbial invasion and blood-brain barrier traversal. S. pneumoniae is recognized by antigen-presenting cells through the binding of Toll-like receptors inducing the activation of factor nuclear kappa B or mitogen-activated protein kinase pathways and subsequent up-regulation of lymphocyte populations and expression of numerous proteins involved in inflammation and immune response. Many brain cells can produce cytokines, chemokines and others pro-inflammatory molecules in response to bacteria stimuli, as consequence, polymorphonuclear are attracted, activated and released in large amounts of superoxide anion and nitric oxide, leading to the peroxynitrite formation, generating oxidative stress. This cascade leads to lipid peroxidation, mitochondrial damage, blood-brain barrier breakdown contributing to cell injury during pneumococcal meningitis.

Antioxidant treatment prevents cognitive impairment and oxidative damage in pneumococcal meningitis survivor rats

Pneumococcal meningitis is associated with the highest fatality case ratios in the world. Most of patients that survive present neurologic sequelae at later times as well as biochemicals alterations such as oxidative stress in both earlier and later times after central nervous system infection. In this context, we evaluated the effect of antioxidant treatment on memory and oxidative parameters in the hippocampus of meningitis survivor rats 10 days after infection. To this aim, the animals underwent a magna cistern tap receiving either 10 μL sterile saline as a placebo or an equivalent volume of a Streptococcus pneumoniae suspension at the concentration 5x10(9) cfu/mL. The animals submitted to meningitis were divided into the following groups: 1) treated with antibiotic, 2) treated with basic support plus N-acetylcysteine, 3) treated with basic support plus deferoxamine, 4) treated with basic support plus N-acetylcysteine and deferoxamine, or 5) treated with N-acetylcysteine plus deferoxamine. Ten days after meningitis, the animals underwent inhibitory avoidance and habituation to an open field tasks and, immediately after, were assessed for oxidative damage in the hippocampus and cortex. The meningitis group showed significantly decreased performance in latency retention compared with the sham group in the inhibitory avoidance task. In the open-field task, the meningitis group presented memory impairment after meningitis. All these memory impairments were prevented by N-acetylcysteine plus deferoxamine with or without basic support and its isolate use. In addition, there was an increase of lipid phosphorylation in cortex and hippocampus and all the combined antioxidants attenuated lipid phosphorylation in both structures. On the other hand, there was an increase of protein phosphorylation in cortex and N-acetylcysteine plus deferoxamine with or without basic support prevented it. Thus, we hypothesize that oxidative stress may be related to cognitive impairment in pneumococcal meningitis.

Increased Na+,K+-ATPase activity in the rat brain after meningitis induction by Streptococcus pneumoniae

Barichello T, Generoso JS, Cipriano AL, Casagrande R, Collodel A, Savi GD, Scherer EBS, Kolling J, Wyse ATS. Increase Na+,K+-ATPase activity in the rat brain after meningitis induction byStreptococcus pneumoniae.

Background: Pneumococcal meningitis is the most severe infection of the central nervous system with a mortality rate up to 20% and an adverse neurological result in up to 50% of survivors. A complicated series of interactions among the host immune response and oxidants seems to be responsible for meningitis associated brain dysfunctions. Na+,K+-ATPase is an essential enzyme responsible for generating and maintaining the membrane potential necessary for neural excitability, however, the Na+,K+-ATPase activity is altered in several illness;

Objective: The aim of this study is to evaluate the Na+,K+-ATPase activity in hippocampus and cortex of the rats submitted to pneumococcal meningitis.

Methods: Animals received 10 µl sterile saline as a placebo or an equivalent volume ofStreptococcus pneumoniaeto the concentration of 5 × 109cfu/ml and were killed at 24, 48, 72 and 96 h after meningitis induction. The brain structures, hippocampus and cortex, were immediately isolated on dry ice and stored at −80°C to analyse Na+,K+-ATPase activity.

Results: In the hippocampus, we verified the increase of Na+,K+-ATPase activity at 48, 72 and 96 h (p< 0.05) and in the cortex at 24 h (p< 0.05) after pneumococcal meningitis induction.

Conclusion: The Na+,K+-ATPase activity is under the control of a diversity of intracellular messengers that are able to modulate the function of the particular isozymes in a precise way. Furthermore, we verified that pneumococcal meningitis increased the Na+,K+-ATPase activity in hippocampus and cortex; this increase can be correlated with a compensatory mechanism in illness pathophysiology.

Brain-blood barrier breakdown and pro-inflammatory mediators in neonate rats submitted meningitis by Streptococcus pneumoniae

Neonatal meningitis is an illness characterized by inflammation of the meninges and occurring within the birth and the first 28 days of life. Invasive infection by Streptococcus pneumoniae, meningitis and sepsis, in neonate is associated with prolonged rupture of membranes; maternal colonization/illness, prematurity, high mortality and 50% of cases have some form of disability. For this purpose, we measured brain levels of TNF-α, IL-1β, IL-6, IL-10, CINC-1, oxidative damage, enzymatic defense activity and the blood-brain barrier (BBB) integrity in neonatal Wistar rats submitted to pneumococcal meningitis. The cytokines increased prior to the BBB breakdown and this breakdown occurred in the hippocampus at 18 h and in the cortex at 12h after pneumococcal meningitis induction. The time-dependent association between the complex interactions among cytokines, chemokine may be responsible for the BBB breakdown and neonatal pneumococcal severity.

Microvesicles at the crossroads between infection and cardiovascular diseases

Observational and experimental studies continue to support the association of infection and infection-stimulated inflammation with development of cardiovascular disease (CVD) including atherosclerosis and thrombosis. Microvesicles (MV) are heterogeneous populations of sealed membrane-derived vesicles shed into circulation by activated mammalian cells and/or pathogenic microbes that may represent an interface between bacterial/microbial infection and increased risk of CVD. This review evaluates how MV act to modulate and intersect immunological and inflammatory responses to infection with particular attention to progression of CVD. Although infection-related stimuli provoke release of MV from blood and vascular cells, MV express phosphatidylserine and other procoagulant factors on their surface, which initiate and amplify blood coagulation. In addition, MV mediate cell-cell adhesion, which may stimulate production of pro-inflammatory cytokines in vascular cells, which in turn aggravate progression of CVD and propagate atherothrombosis. MV transfer membrane receptors, RNA and proteins among cells, and present auto-antigens from their cells of origin to proximal or remote target cells. Because MV harbor cell surface proteins and contain cytoplasmic components of the parent cell, they mediate biological messages and play a pivotal role in the crossroad between infection-stimulated inflammation and CVDs.

Oxidative stress, cytokine/chemokine and disruption of blood-brain barrier in neonate rats after meningitis by Streptococcus agalactiae

We verify the levels of cytokine/chemokine, myeloperoxidase activity, oxidative stress and disruption of BBB in hippocampus and cortex of the neonate Wistar rats after meningitis by S. agalactiae. In the hippocampus the levels were increased of CINC-1 at 6 h and 12 h, IL-1β at 6, 12 and 24 h, IL-6 at 6, 24 and 96 h, IL-10 at 24, 48 and 96 h and TNF-α at 24 h and 96 h. In the cortex the CINC-1 and IL-1β levels were found increased at 6 h. The MPO activity was significantly elevated at 24, 48 and 98 h in hippocampus and at 6, 12, 24, 48 and 96 h in the cortex. The breakdown of BBB started at 12 h.TBARS levels were elevated in the hippocampus at 6, 12, 24, 48, 72 and 96 h and cortex at 72 and 96 h. Protein carbonyls were elevated in the hippocampus and cortex at 6, 24, 48, 72 and 96 h. There was a decrease of SOD activity in hippocampus and in cortex. Catalase activity was elevated in hippocampus at 6 h and in the cortex at 12 and 96 h. Neonatal bacterial infections of the CNS are severe, the interference with the complex network of cytokines/chemokine, other inflammatory mediators and oxidants tend to aggravate the illness and can be involved in the breakdown of the BBB.