Interleukin-1ß Receptor Antagonism Prevents Cognitive Impairment Following Experimental Bacterial Meningitis.

Pneumococcal meningitis is characterized by high rates of mortality and long-term cognitive impairment. In this study, we evaluated the effects of interleukin (IL)-1ß receptor antagonist (IL-1Ra) on memory, cytokine, and brain-derived neurotrophic factor (BDNF) levels in hippocampus after experimental pneumococcal meningitis. In a first experiment the animals were divided into four groups: control/saline, control treated with IL-1Ra, meningitis/saline, and meningitis treated with IL-1Ra. In the meningitis/saline group IL-1ß and cytokine-induced neutrophil chemoattractant-1 (CINC-1) levels increased at 24 h post-infection; adjuvant treatment with IL-1Ra reversed the increased levels in the hippocampus. The levels of tumour necrosis factor-alpha (TNF-α), IL-4, IL-6, IL-10, and BDNF did not change in all groups at 24 h post-infection. In a second experiment, the animals were subjected to behavioural tasks (open field, step-down inhibitory avoidance task, and object recognition task), cytokine, and BDNF levels analysis 10 days after experimental meningitis induction. In the open-field task, the meningitis/saline group did not exhibit difference between the training and test sessions, in the motor and exploratory activity indicating memory injury. The meningitis/IL-1Ra group presented difference between training and test session indicating habituation memory. The meningitis/saline group showed impairment in long-term memory for novel object recognition and in aversive memory. The adjuvant treatment with IL-1Ra prevented memory impairment. After behavioural tasks the hippocampus was evaluated. The levels of IL-4, IL-6, IL-10, and BDNF were maintained elevated 10 days post-infection. CINC-1 levels were elevated only in meningitis/saline group and IL-1ß decreased in meningitis/IL-Ra group. The levels of TNF-α did not change at 10 days post-infection. These findings illustrate the anti-inflammatory activity of IL-1Ra inhibitor in the first hours after meningitis induction. Adjuvant treatment with IL-1ß receptor antagonist could be a new avenue as therapeutic target during bacterial meningitis.

Environmental enrichment restores cognitive deficits induced by experimental childhood meningitis

Objective: To evaluate the influence of environmental enrichment (EE) on memory, cytokines, and brain-derived neurotrophic factor (BDNF) in the brain of adult rats subjected to experimental pneumococcal meningitis during infancy. Methods: On postnatal day 11, the animals received either artificial cerebrospinal fluid (CSF) or Streptococcus pneumoniae suspension intracisternally at 1 × 106 CFU/mL and remained with their mothers until age 21 days. Animals were divided into the following groups: control, control + EE, meningitis, and meningitis + EE. EE began at 21 days and continued until 60 days of age (adulthood). EE consisted of a large cage with three floors, ramps, running wheels, and objects of different shapes and textures. At 60 days, animals were randomized and subjected to habituation to the open-field task and the step-down inhibitory avoidance task. After the tasks, the hippocampus and CSF were isolated for analysis. Results: The meningitis group showed no difference in performance between training and test sessions of the open-field task, suggesting habituation memory impairment; in the meningitis + EE group, performance was significantly different, showing preservation of habituation memory. In the step-down inhibitory avoidance task, there were no differences in behavior between training and test sessions in the meningitis group, showing aversive memory impairment; conversely, differences were observed in the meningitis + EE group, demonstrating aversive memory preservation. In the two meningitis groups, IL-4, IL-10, and BDNF levels were increased in the hippocampus, and BDNF levels in the CSF. Conclusions: The data presented suggest that EE, a non-invasive therapy, enables recovery from memory deficits caused by neonatal meningitis. .

Environmental enrichment restores cognitive deficits induced by experimental childhood meningitis.

OBJECTIVE: To evaluate the influence of environmental enrichment (EE) on memory, cytokines, and brain-derived neurotrophic factor (BDNF) in the brain of adult rats subjected to experimental pneumococcal meningitis during infancy. METHODS: On postnatal day 11, the animals received either artificial cerebrospinal fluid (CSF) or Streptococcus pneumoniae suspension intracisternally at 1 × 10(6) CFU/mL and remained with their mothers until age 21 days. Animals were divided into the following groups: control, control + EE, meningitis, and meningitis + EE. EE began at 21 days and continued until 60 days of age (adulthood). EE consisted of a large cage with three floors, ramps, running wheels, and objects of different shapes and textures. At 60 days, animals were randomized and subjected to habituation to the open-field task and the step-down inhibitory avoidance task. After the tasks, the hippocampus and CSF were isolated for analysis. RESULTS: The meningitis group showed no difference in performance between training and test sessions of the open-field task, suggesting habituation memory impairment; in the meningitis + EE group, performance was significantly different, showing preservation of habituation memory. In the step-down inhibitory avoidance task, there were no differences in behavior between training and test sessions in the meningitis group, showing aversive memory impairment; conversely, differences were observed in the meningitis + EE group, demonstrating aversive memory preservation. In the two meningitis groups, IL-4, IL-10, and BDNF levels were increased in the hippocampus, and BDNF levels in the CSF. CONCLUSIONS: The data presented suggest that EE, a non-invasive therapy, enables recovery from memory deficits caused by neonatal meningitis.

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-1ß, 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.

Late anxiety-like behavior and neuroinflammation in mice subjected to sublethal polymicrobial sepsis.

Sepsis can lead to long-term cognitive changes, including memory and learning deficits, which are known as septic encephalopathy (SE). SE also includes behavioral changes. The underlying mechanism of SE is unknown, and several mechanisms have been proposed. This study investigated late anxiety-like behavior, serum cytokine levels and brain cytokine production in C57BL/6 mice subjected to polymicrobial sepsis induced by sublethal cecum ligature and puncture (CLP). Anxiety-like behavior and locomotor activity were assessed in mice 10 days after sham operation or CLP procedure using the elevated plus maze, contextual fear conditioning, and open field test. Brain and serum concentrations of the cytokines TNF-α, IFN-γ, IL-1ß, IL-6, and IL-10 were determined by ELISA. We found that mice subjected to polymicrobial sepsis presented anxiety-like behavior, which was accompanied by increased serum TNF-α and brain TNF-α, IFN-γ, IL-1ß, and IL-6 levels, 10 days after the surgical procedure. These findings suggest an involvement of central nervous system inflammatory mediators in the anxiety-like symptoms found in SE.

Platelet-activating factor receptor is essential for the development of experimental cerebral malaria.

Cerebral malaria is a severe form of the disease that may result, in part, from an overt inflammatory response during infection by Plasmodium falciparum. The understanding of the pathogenesis of cerebral malaria may aid in the development of better therapeutic strategies for patients. The immune response in cerebral malaria involves elevation of circulating levels of cytokines and chemokines associated with leukocyte accumulation and breakdown of the blood-brain barrier in the central nervous system. Platelet-activating factor (PAF) is a mediator of inflammation shown to orchestrate inflammatory processes, including recruitment of leukocytes and increase of vascular permeability. Using mice lacking the PAF receptor (PAFR(-/-)), we investigated the relevance of this molecule for the outcome and the neuroinflammatory process triggered by P. berghei ANKA, an experimental model of cerebral malaria. In PAFR(-/-) mice, lethality was markedly delayed and brain inflammation was significantly reduced, as demonstrated by histology, accumulation, and activation of CD8(+) T cells, changes in vascular permeability and activation of caspase-3 on endothelial cells and leukocytes. Similarly, treatment with the PAFR antagonist UK-74,505 delayed lethality. Taken together, the results suggest that PAFR signaling is crucial for the development of experimental cerebral malaria. Mechanistically, PAFR activation is crucial for the cascade of events leading to changes in vascular permeability, accumulation, and activation of CD8(+) T cells and apoptosis of leukocytes and endothelial cells.

Intracerebral infection with dengue-3 virus induces meningoencephalitis and behavioral changes that precede lethality in mice.

BACKGROUND: Dengue, one of the most important arboviral diseases of humans, may cause severe systemic disease. Although dengue virus (DENV) has been considered to be a non-neurotropic virus, dengue infection has been associated recently with a series of neurological syndromes, including encephalitis. In this work, we evaluated behavioral changes and inflammatory parameters in C57BL/6 mice infected with non-adapted dengue virus 3 (DENV-3) genotype I. METHODS: C57BL/6 mice received 4×10(3) PFU of DENV-3 by an intracranial route. We evaluated the trafficking of leukocytes in brain microvasculature using intravital microscopy, and evaluated chemokine and cytokine profiling by an ELISA test at 3 and 6 days post infection (p.i.). Furthermore, we determined myeloperoxidase activity and immune cell populations, and also performed histopathological analysis and immunostaining for the virus in brain tissue. RESULTS: All animals developed signs of encephalitis and died by day 8 p.i. Motor behavior and muscle tone and strength parameters declined at day 7 p.i. We observed increased leukocyte rolling and adhesion in brain microvasculature of infected mice at days 3 and 6 p.i. The infection was followed by significant increases in IFN-γ, TNF-α, CCL2, CCL5, CXCL1, and CXCL2. Histological analysis showed evidence of meningoencephalitis and reactive gliosis. Increased numbers of neutrophils, CD4+ and CD8+ T cells were detected in brain of infected animals, notably at day 6 p.i. Cells immunoreactive for anti-NS-3 were visualized throughout the brain. CONCLUSION: Intracerebral infection with non-adapted DENV-3 induces encephalitis and behavioral changes that precede lethality in mice.

Traffic of leukocytes and cytokine up-regulation in the central nervous system in sepsis.

PURPOSE: To evaluate the effects of sepsis on brain microvasculature leukocyte rolling and adherence, myeloperoxidase (MPO) activity, cytokine and chemokine concentrations, and behavioral screening 6, 12, and 24 h after sepsis induction. METHODS: C57BL/6 mice or Wistar rats underwent cecal ligation and perforation (CLP) or sham operation. At 6, 12, and 24 h after sepsis induction, intravital microscopy was performed in the mice brain microvasculature to evaluate leukocyte rolling and adherence. Animals were killed and had the brain removed to determine MPO activity and the levels of cytokines and chemokines. A behavioral screening was also performed in a separate cohort of animals. Blood-brain barrier (BBB) permeability and cytokines and chemokines were determined in different brain regions in Wistar rats. RESULTS: There was a decrease in circulating leukocyte levels at 6, 12, and 24 h, an increase in rolling and adhesion of leukocytes in the brain microvasculature, followed by an increase in brain MPO activity. In addition, there was an increase in both brain cytokines and chemokines at different times. There was a decrease in the neuropsychiatric state muscle tone and strength only at 6 h, and a decrease in the autonomous function at 6 and 12 h. The pattern of brain cytokines and chemokines, and BBB permeability between the analyzed regions seemed to be similar with minor differences. CONCLUSIONS: During sepsis the brain's production of cytokines and chemokines is an early event and it seemed to participate both in central nervous system (CNS) dysfunction and BBB permeability alterations, reinforcing the role of brain inflammatory response in the acute CNS dysfunction associated with sepsis.

Using intravital microscopy to study the role of chemokines during infection and inflammation in the central nervous system.

The interaction between a microorganism and a potential host may modify each other in multiple ways. Because of their central role in controlling leukocyte trafficking and activation, chemokines may be essential in defining these interactions. Here, we describe potential uses of intravital microscopy to define the role of chemokines and their receptors in the context of HSV-1 infection and EAE. We show that CCL5 plays a major role in driving neuropathology by mediating leukocyte adhesion and consequent migration in HSV-1 encephalitis. In contrast, CCR5 is important to attract cell types that modulate negatively CNS damage at the cost of allowing greater viral replication in the brain. Finally, intravital microscopy studies were crucial to determine that induction of leukocyte adhesion and subsequent emigration into the CNS is a major mechanism of action of CCL2 in EAE.

Intramuscular immunization with p36(LACK) DNA vaccine induces IFN-gamma production but does not protect BALB/c mice against Leishmania chagasi intravenous challenge.

Acute visceral leishmaniasis is a progressive disease caused by Leishmania chagasi in South America. The acquisition of immunity following infection suggests that vaccination is a feasible approach to protect against this disease. Since Leishmania homologue of receptors for activated C kinase (LACK) antigen is of particular interest as a vaccine candidate because of the prominent role it plays in the pathogenesis of experimental Leishmania major infection, we evaluated the potential of a p36(LACK) DNA vaccine in protecting BALB/c mice challenged with L. chagasi. In this study, mice received intramuscular (i.m.) or subcutaneous (s.c.) doses of LACK DNA vaccine. We evaluated the production of vaccine-induced cytokines and whether this immunization was able to reduce parasite load in liver and spleen. We detected a significant production of interferon gamma by splenocytes from i.m. vaccinated mice in response to L. chagasi antigen and to rLACK protein. However, we did not observe a reduction in parasite load neither in liver nor in the spleen of vaccinated animals. The lack of protection observed may be explained by a significant production of IL-10 induced by the vaccine.