Brain-derived neurotrophic factor is regulated via MyD88/NF-?B signaling in experimental Streptococcus pneumoniae meningitis.
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ABSTRACT:
SUBMITTER: Xu D
PROVIDER: S-EPMC5471242 | biostudies-literature | 2017 Jun
REPOSITORIES: biostudies-literature
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Brain-derived neurotrophic factor is regulated via MyD88/NF-κB signaling in experimental Streptococcus pneumoniae meningitis.
Xu Danfeng D Lian Di D Zhang Zhijie Z Liu Ying Y Sun Jiaming J Li Ling L
Scientific reports 20170614 1
Streptococcus pneumoniae meningitis is an intractable disease of the central nervous system (CNS). Brain-derived neurotrophic factor (BDNF) is a member of the neurotrophic family and found to participate in the immune inflammatory response. In this study, we investigated if activation of the classical inflammatory signaling pathway, myeloid differentiation factor 88 (MyD88)/nuclear factor-kappa B (NF-κB), regulates BDNF expression in experimental S. pneumoniae meningitis. MyD88 knockout (myd88-/ ...[more]
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Project description:Streptococcus pneumoniae meningitis is a serious inflammatory disease of the central nervous system (CNS) and is associated with high morbidity and mortality rates. The inflammatory processes initiated by recognition of bacterial components contribute to apoptosis in the hippocampal dentate gyrus. Brain-derived neurotrophic factor (BDNF) has long been recommended for the treatment of CNS diseases due to its powerful neuro-survival properties, as well as its recently reported anti-inflammatory and anti-apoptotic effects in vitro and in vivo.In this study, we investigated the effects of BDNF-related signaling on the inflammatory response and hippocampal apoptosis in experimental models of pneumococcal meningitis. Pretreatment with exogenous BDNF or the tropomyosin-receptor kinase B (TrkB) inhibitor k252a was performed to assess the activation or inhibition of the BDNF/TrkB-signaling axis prior to intracisternal infection with live S. pneumoniae. At 24 h post-infection, rats were assessed for clinical severity and sacrificed to harvest the brains. Paraffin-embedded brain sections underwent hematoxylin and eosin staining to evaluate pathological severity, and cytokine and chemokine levels in the hippocampus and cortex were evaluated by enzyme-linked immunosorbent assay. Additionally, apoptotic neurons were detected in the hippocampal dentate gyrus by terminal deoxynucleotidyl transferase dUTP-nick-end labeling, key molecules associated with the related signaling pathway were analyzed by real-time polymerase chain reaction and western blot, and the DNA-binding activity of nuclear factor kappa B (NF-κB) was measured by electrophoretic mobility shift assay.Rats administered BDNF exhibited reduced clinical impairment, pathological severity, and hippocampal apoptosis. Furthermore, BDNF pretreatment suppressed the expression of inflammatory factors, including tumor necrosis factor α, interleukin (IL)-1β, and IL-6, and increased the expression of the anti-inflammatory factor IL-10. Moreover, BDNF pretreatment increased TrkB expression, activated downstream phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT) signaling, and inhibited the myeloid differentiation primary response gene 88 (MyD88)/NF-κB-signaling pathway.These data suggested that BDNF administration exerted anti-inflammatory and anti-apoptotic effects on an experimental pneumococcal meningitis model via modulation of MyD88/NF-κB- and PI3K/AKT-signaling pathways. Our results indicated that treatment with exogenous BDNF might constitute a potential therapeutic strategy for the treatment of bacterial meningitis.
| S-EPMC5545027 | biostudies-other
Project description:Streptococcus pneumoniae meningitis is a life-threatening bacterial infection of the central nervous system (CNS), and its unfavorable prognosis usually results from an intense inflammatory response. Recent studies have shown that brain-derived neurotrophic factor (BDNF) mediates anti-inflammatory and neuroprotective effects in CNS diseases; however, the distinct contribution of BDNF to pneumococcal meningitis (PM) remains unknown. In this study, we sought to investigate the effects of endogenous BDNF on the inflammatory response and brain damage in experimental PM. We used Camk2a-CreERT2 mice to delete Bdnf from the cerebral cortex and hippocampus, and meningitis was induced by intracisternal infection with S. pneumoniae. Clinical parameters were assessed during acute meningitis. At 24 h post-infection, histopathology, neutrophil granulocytes infiltration, and microglia/macrophage proliferation of brain tissues were evaluated. Additionally, cortical damage and hippocampal apoptosis were assessed using Nissl staining and terminal deoxynucleotidyl transferase dUTP-nick-end labeling (TUNEL), respectively. Pro-inflammatory cytokine levels were determined using real-time polymerase chain reaction (RT-PCR). Key molecules associated with the related signaling pathways were analyzed by RT-PCR and western blot. To investigate the role of microglia/macrophage in infected BDNF conditional knockout mice, GW2580 was used for microglia/macrophage depletion. Here, we, for the first time, found that BDNF conditional knockouts exhibited more profound clinical impairment, pathological severity, and neuron injury and enhanced microglia/macrophage proliferation than were observed in their littermate controls. Furthermore, the BDNF conditional knockouts showed an obviously increase in the expression of pro-inflammatory factors (Tnf-α, Il-1β, and Il-6). Mechanistically, loss of BDNF activated TLR2- and NOD2-mediated downstream nuclear factor kappa B (NF-κB) p65 and p38 mitogen-activated protein kinase (MAPK) pathways associated with S. pneumoniae infection. Furthermore, targeted depletion of microglia/macrophage population decreased the resistance of mice to PM with diminishing neuroinflammation in BDNF conditional knockouts. Our findings suggest that loss of BDNF may enhance the inflammatory response and contribute to brain injury during PM at least partially by modulating TLR2- and NOD2-mediated signaling pathways, thereby providing a potential therapeutic target for future interventions in bacterial meningitis pathologies.
| S-EPMC7333737 | biostudies-literature
Project description:Streptococcus pneumoniaebacteria can be characterized into over 90 serotypes according to the composition of their polysaccharide capsules. Some serotypes are common in nasopharyngeal carriage whereas others are associated with invasive disease, but when carriage serotypes do invade disease is often particularly severe. It is unknown whether disease severity is due directly to the capsule type or to other virulence factors. Here, we used a clinical pneumococcal isolate and its capsule-switch mutants to determine the effect of capsule, in isolation from the genetic background, on severity of meningitis in an infant rat model. We found that possession of a capsule was essential for causing meningitis. Serotype 6B caused significantly more mortality than 7F and this correlated with increased capsule thickness in the cerebrospinal fluid (CSF), a stronger inflammatory cytokine response in the CSF and ultimately more cortical brain damage. We conclude that capsule type has a direct effect on meningitis severity. This is an important consideration in the current era of vaccination targeting a subset of capsule types that causes serotype replacement.
| S-EPMC4821241 | biostudies-literature
Project description:We applied genomic array footprinting (GAF) in the search for genes of S. pneumoniae essential during the establishment and progression of experimental meningitis. Four libraries with a total of 6,000 independent TIGR4 marinerT7 transposon mutants were injected intra-cisternally in rabbits, and cerebrospinal fluid (CSF) was collected after three, nine, and fifteen hours. Microarray analysis of mutant-specific probes from CSF samples and inocula identified 82 genes of which mutants had become attenuated and eleven genes of which mutants had become enriched during infection. Screening results particularly point to an essential role for capsular polysaccharides (cps), nutrient uptake, and metabolism in meningitis. Detailed study on directed mutants of a subset of sixteen GAF targets in an experimental model of rat meningitis revealed that ten were significantly attenuated or enriched during competitive infection. Furthermore, we showed that mutants of adenylosuccinate synthetase (purA), flavodoxin (fld), and the substrate binding protein (livJ) of a branched chain amino acid ABC-transporter were essential for full blown meningitis in a mono-infection setup of rat meningitis. Overall, the GAF screen revealed the general restraint on nutrients encountered by the pneumococcus in CSF, while, except for cps genes, no ‘classic’ virulence factors appeared to be required for infection. This knowledge will contribute to a better understanding of the molecular pathogenesis of pneumococcal meningitis.
2010-11-16 | GSE21729 | GEO
Project description:Meningitis is the most serious of invasive infections caused by the Gram-positive bacterium Streptococcus pneumoniae. Vaccines protect only against a limited number of serotypes, and evolving bacterial resistance to antimicrobials impedes treatment. Further insight into the molecular pathogenesis of invasive pneumococcal disease is required in order to enable the development of new or adjunctive treatments and/or pneumococcal vaccines that are efficient across serotypes. We applied genomic array footprinting (GAF) in the search for S. pneumoniae genes that are essential during experimental meningitis. A total of 6,000 independent TIGR4 marinerT7 transposon mutants distributed over four libraries were injected intracisternally into rabbits, and cerebrospinal fluid (CSF) was collected after 3, 9, and 15 h. Microarray analysis of mutant-specific probes from CSF samples and inocula identified 82 and 11 genes mutants of which had become attenuated or enriched, respectively, during infection. The results point to essential roles for capsular polysaccharides, nutrient uptake, and amino acid biosynthesis in bacterial replication during experimental meningitis. The GAF phenotype of a subset of identified targets was followed up by detailed studies of directed mutants in competitive and noncompetitive infection models of experimental rat meningitis. It appeared that adenylosuccinate synthetase, flavodoxin, and LivJ, the substrate binding protein of a branched-chain amino acid ABC transporter, are relevant as targets for future therapy and prevention of pneumococcal meningitis, since their mutants were attenuated in both models of infection as well as in competitive growth in human cerebrospinal fluid in vitro.
| S-EPMC3019918 | biostudies-literature
Project description:Streptococcus pneumoniae (the pneumococcus) is a Gram-positive bacterium and the predominant cause of bacterial meningitis. Meningitis is thought to occur as the result of pneumococci crossing the blood-brain barrier to invade the Central Nervous System (CNS); yet little is known about the steps preceding immediate disease development. To study the interactions between pneumococci and the vascular endothelium of the blood-brain barrier prior to meningitis we used an established bacteremia-derived meningitis model in combination with immunofluorescent imaging. Brain tissue of mice infected with S. pneumoniae strain TIGR4, a clinical meningitis isolate, was investigated for the location of the bacteria in relation to the brain vasculature in various compartments. We observed that S. pneumoniae adhered preferentially to the subarachnoid vessels, and subsequently, over time, reached the more internal cerebral areas including the cerebral cortex, septum, and choroid plexus. Interestingly, pneumococci were not detected in the choroid plexus till 8 hours-post infection. In contrast to the lungs, little to no leukocyte recruitment to the brain was observed over time, though Iba-1 and GFAP staining showed that microglia and astrocytes were activated as soon as 1 hour post-infection. Our results imply that i) the local immune system of the brain is activated immediately upon entry of bacteria into the bloodstream and that ii) adhesion to the blood brain barrier is spatiotemporally controlled at different sites throughout the brain. These results provide new information on these two important steps towards the development of pneumococcal meningitis.
| S-EPMC3713044 | biostudies-literature
Project description:We applied genomic array footprinting (GAF) in the search for genes of S. pneumoniae essential during the establishment and progression of experimental meningitis. Four libraries with a total of 6,000 independent TIGR4 marinerT7 transposon mutants were injected intra-cisternally in rabbits, and cerebrospinal fluid (CSF) was collected after three, nine, and fifteen hours. Microarray analysis of mutant-specific probes from CSF samples and inocula identified 82 genes of which mutants had become attenuated and eleven genes of which mutants had become enriched during infection. Screening results particularly point to an essential role for capsular polysaccharides (cps), nutrient uptake, and metabolism in meningitis. Detailed study on directed mutants of a subset of sixteen GAF targets in an experimental model of rat meningitis revealed that ten were significantly attenuated or enriched during competitive infection. Furthermore, we showed that mutants of adenylosuccinate synthetase (purA), flavodoxin (fld), and the substrate binding protein (livJ) of a branched chain amino acid ABC-transporter were essential for full blown meningitis in a mono-infection setup of rat meningitis. Overall, the GAF screen revealed the general restraint on nutrients encountered by the pneumococcus in CSF, while, except for cps genes, no ‘classic’ virulence factors appeared to be required for infection. This knowledge will contribute to a better understanding of the molecular pathogenesis of pneumococcal meningitis. The rabbit meningitis model was performed as previously described by Østergaard (PMID: 9661008 ). Briefly, 10E6 CFU of a S. pneumoniae mutant library was suspended in 20 µl beef-broth and injected into cisterna magna of four groups of four outbred New Zealand White rabbits of app. 2.5 kg (in one group one rabbit died). CSF (0.3 ml) samples were repeatedly obtained from the same rabbit by aspiration from indwelling spinal- and arterial cannules. Samples were collected before pleocytosis developed (three hrs), at the time of maximal pleocytosis (nine hrs), and at a time of slowing bacterial growth and abating pleocytosis (fifteen hrs ). Until further processing in the GAF protocol, CSF and inocula were stored with 15% glycerol at -80ºC. The GAF technology was performed as described previously (PMID: 17261526 ). Briefly, stored inocula and CSF obtained during the experimental rabbit meningitis experiments were defrosted, diluted in GM17 medium supplemented with spectinomycin, and grown to mid-log phase. Chromosomal DNA was isolated, digested with AluI endonuclease, and used as a template for in vitro transcription initiated from the T7 promoters of the marinerT7 transposon that is present in each mutant. After removal of template DNA by DNAseI treatment, mutant-specific T7 RNA was reverse transcribed in the presence of fluorescent Cy3/Cy5-labeled dUTP nucleotides. Labeled Cy3/Cy5-cDNA from the CSF samples and oppositely labeled Cy5/Cy3 cDNA from the inocula were combined, purified, and washed by ultrafiltration. The cDNA was hybridized to pneumococcal microarrays containing, 2,087 ORFs of Streptococcus pneumoniae TIGR4 and 70-mer oligo's specific for the non-homologous ORFs in the R6, D39, 23F, INV104B, INV200, OXC141, and G54 strains, all spotted in duplicate (PMID: 18174343) . Dual channel array images were acquired on a GenePix 4200AL microarray scanner (Axon Instruments, Union City, CA). Microarray image files were analyzed with GenePix Pro software (Axon Instruments, Union City, CA). Spots were screened visually to identify those of low quality and removed from the data set prior to analysis. A net mean intensity filter based on hybridization signals obtained with R6-specific spots was applied in all experiments. Slide data were processed and normalized using MicroPreP (PMID: 15907200). Further analysis was performed using a CyberT implementation of the Student’s t test (cybert.microarray.ics.uci.edu). This web-based program lists the ratios of all intra-replicates (duplicate spots) and inter-replicates (different slides), the mean ratios per gene, and standard deviations and (Bayesian) p values assigned to the mean ratios. For identification of conditionally essential genes, only genes with a minimum of 6/8 (for groups of four rabbits) or 5/6 for the group of three rabbits) reliable measurements and a Bayesian p-value < 0.001 were included. Further selection criteria were applied, as only mutants displaying an average fold-change of >2.5 at a minimum of two time-points, or >4.0 at one time-point were accepted as significantly attenuated or enriched. The microarray data have been deposited in the NCBI Gene Expression Omnibus (GEO) database (www.ncbi.nlm.nih.gov/geo/) under GEO Series accession number ...
2010-11-16 | E-GEOD-21729 | biostudies-arrayexpress
Project description:BackgroundStreptococcus pneumoniae meningitis is a destructive central nervous system (CNS) infection with acute and long-term neurological disorders. Previous studies suggest that p75NTR signaling influences cell survival, apoptosis, and proliferation in brain-injured conditions. However, the role of p75NTR signaling in regulating pneumococcal meningitis (PM)-induced neuroinflammation and altered neurogenesis remains largely to be elucidated.Methodsp75NTR signaling activation in the pathological process of PM was assessed. During acute PM, a small-molecule p75NTR modulator LM11A-31 or vehicle was intranasally administered for 3 days prior to S. pneumoniae exposure. At 24 h post-infection, clinical severity, histopathology, astrocytes/microglia activation, neuronal apoptosis and necrosis, inflammation-related transcription factors and proinflammatory cytokines/mediators were evaluated. Additionally, p75NTR was knocked down by the adenovirus-mediated short-hairpin RNA (shRNA) to ascertain the role of p75NTR in PM. During long-term PM, the intranasal administration of LM11A-31 or vehicle was continued for 7 days after successfully establishing the PM model. Dynamic changes in inflammation and hippocampal neurogenesis were assessed.ResultsOur results revealed that both 24 h (acute) and 7, 14, 28 day (long-term) groups of infected rats showed increased p75NTR expression in the brain. During acute PM, modulation of p75NTR through pretreatment of PM model with LM11A-31 significantly alleviated S. pneumoniae-induced clinical severity, histopathological injury and the activation of astrocytes and microglia. LM11A-31 pretreatment also significantly ameliorated neuronal apoptosis and necrosis. Moreover, we found that blocking p75NTR with LM11A-31 decreased the expression of inflammation-related transcription factors (NF-κBp65, C/EBPβ) and proinflammatory cytokines/mediators (IL-1β, TNF-α, IL-6 and iNOS). Furthermore, p75NTR knockdown induced significant changes in histopathology and inflammation-related transcription factors expression. Importantly, long-term LM11A-31 treatment accelerated the resolution of PM-induced inflammation and significantly improved hippocampal neurogenesis.ConclusionOur findings suggest that the p75NTR signaling plays an essential role in the pathogenesis of PM. Targeting p75NTR has beneficial effects on PM rats by alleviating neuroinflammation and promoting hippocampal neurogenesis. Thus, the p75NTR signaling may be a potential therapeutic target to improve the outcome of PM.
| S-EPMC8561879 | biostudies-literature
Project description:Streptococcus pneumoniae meningitis is one of the most common disorders seen in clinical practice. It is believed that the brain tissue immune injury is caused by the expression of pattern-recognition receptors (PRR) which can further induce the release of other cytokines and inflammatory cascades. The aim of this study is to investigate the expression of nucleotide-binding oligomerization domain 2 (NOD2) and inflammatory factors in rat brain tissues infected with Streptococcus pneumoniae and its influence on the blood-brain barrier (BBB) permeability. Rats were given an intracranial injection of Streptococcus pneumoniae to construct the Streptococcus pneumoniae meningitis rat models. The expression change curves of NOD2 and inflammatory factors at different time points (0 h, 12 h, 24 h, 48 h, and 7 d) after Streptococcus pneumoniae were evaluated by enzyme-linked immunosorbent assay (ELISA). Western blotting analysis and quantitative real-time polymerase chain reaction (qRT-PCR) were engaged to examine the expression of NOD2. Furthermore, the changing processes of pathological characteristics, nervous system score, cerebral oedema, and BBB permeability were observed. Our results showed that NOD2 expression began to increase in the 12 h after Streptococcus pneumoniae infection group, while the remaining inflammatory factors were not obviously increased. Meanwhile, the levels of NOD2, as well as inflammatory factors IL-1β, TNF-α, and IL-6 were markedly elevated in 24 h and 48 h infection groups, which were consistent with the increases in BBB permeability and BWC, and the positive expression of NOD2 in the infected rat brain tissues was observed using immunohistochemistry (IHC). This study suggests that NOD2 might be related to the activation of inflammation pathways and the damage to the blood-brain barrier. NOD2 and inflammatory factors have played vital roles in the pathogenesis of Streptococcus pneumoniae meningitis.
| S-EPMC6109993 | biostudies-literature
Project description:BackgroundStatus epilepticus (SE) is an acute, prolonged epileptic crisis with a mortality rate of 20-30%; the underlying mechanism is not completely understood. We assessed the hypothesis that brain stem cardiovascular dysregulation occurs during SE because of oxidative stress in rostral ventrolateral medulla (RVLM), a key nucleus of the baroreflex loop; to be ameliorated by brain-derived neurotrophic factor (BDNF) via an antioxidant action.Methodology/principal findingsIn a clinically relevant experimental model of temporal lobe SE (TLSE) using Sprague-Dawley rats, sustained hippocampal seizure activity was accompanied by progressive hypotension that was preceded by a reduction in baroreflex-mediated sympathetic vasomotor tone; heart rate and baroreflex-mediated cardiac responses remained unaltered. Biochemical experiments further showed concurrent augmentation of superoxide anion, phosphorylated p47(phox) subunit of NADPH oxidase and mRNA or protein levels of BDNF, tropomyosin receptor kinase B (TrkB), angiotensin AT1 receptor subtype (AT1R), nitric oxide synthase II (NOS II) or peroxynitrite in RVLM. Whereas pretreatment by microinjection bilaterally into RVLM of a superoxide dismutase mimetic (tempol), a specific antagonist of NADPH oxidase (apocynin) or an AT1R antagonist (losartan) blunted significantly the augmented superoxide anion or phosphorylated p47(phox) subunit in RVLM, hypotension and the reduced baroreflex-mediated sympathetic vasomotor tone during experimental TLSE, pretreatment with a recombinant human TrkB-Fc fusion protein or an antisense bdnf oligonucleotide significantly potentiated all those events, alongside peroxynitrite. However, none of the pretreatments affected the insignificant changes in heart rate and baroreflex-mediated cardiac responses.Conclusions/significanceWe conclude that formation of peroxynitrite by a reaction between superoxide anion generated by NADPH oxidase in RVLM on activation by AT1R and NOS II-derived NO leads to a reduction in baroreflex-mediated sympathetic vasomotor tone during experimental TLSE; to be ameliorated by the upregulated BDNF/TrkB signaling via inhibition of p47(phox) phosphorylation. This information offers a new vista in devising therapeutic strategy towards minimizing mortality associated with TLSE.
| S-EPMC3307740 | biostudies-literature