Synergistic regulation of microglia differentiation by CD93 and integrin ß1 in the rat pneumococcal meningitis model.

Streptococcus pneumoniae is the main bacterial pathogen of meningitis worldwide, which has a high mortality rate and survivors are prone to central nervous system (CNS) sequelae. In this regard, microglia activation has been associated with injury to the CNS. The aim of this study was to investigate the relationship between CD93, integrin ß1, and microglia activation. In the rat pneumococcal meningitis model, we found significant increases of CD93 and integrin ß1 expression and differentiation of M1 phenotype microglia. Furthermore, we showed in vitro siRNA-mediated downregulation of CD93 and integrin ß1 expression after infecting highly aggressive proliferating immortalized (HAPI) microglia cells with S. pneumoniae. We observed differentiation of S. pneumonia-infected HAPI microglia cells to the M1 phenotype and significant release of soluble CD93 (sCD93) and integrin ß1 expression. Complement C1q and metalloproteinases promoted sCD93 release. We also showed that downregulation of CD93 significantly reduced differentiation to M1 microglia and increased differentiation to M2 microglia. However, addition of recombinant CD93 may regulate microglia differentiation to the M1 phenotype. Furthermore, the downregulation of integrin ß1 resulted in downregulation of the CD93 protein. In conclusion, interaction between integrin ß1 and CD93 promotes differentiation of microglia to the M1 phenotype, increases the release of pro-inflammatory factors, and leads to nervous system injury in pneumococcal meningitis.

Crosstalk between CD93, C1q and GIPC in the Regulation of Pneumococcal Meningitis Inflammation.

OBJECTIVE: Pneumococcal meningitis is a common and serious infectious disease that threatens human health worldwide. Recent studies have shown that various regulatory proteins of the immune system may be potential targets for adjuvant therapy. The aim of this study was to investigate CD93 expression and potential signaling pathways in rat models of pneumococcal meningitis. METHODS: The levels of sCD93 (soluble CD93), IL-6 (Interleukin-6) and TNF-α (tumor necrosis factor-α) in cerebrospinal fluid were assessed by ELISA, and the levels of iNOS (inducible nitric oxide synthase), CD93, complement C1q, and GIPC (C-terminal of the regulator of G protein signaling-G alpha interacting protein) in the brain tissue were evaluated by Western Blotting. The interaction between CD93 and complement C1q was investigated by co-immunoprecipitation, and the interaction between CD93 and GIPC was detected by immunofluorescence colocalization. RESULTS: Our results showed a significant increase in the levels of IL-6, TNF-α, sCD93, CD93, complement C1q, GIPC, and iNOS in the Streptococcus pneumoniae infection group. CD93 interacted with complement C1q, and CD93 and GIPC colocalized on the cell membrane of the cerebral cortex. CONCLUSIONS: This study suggests that CD93 may be a new inflammatory factor in pneumococcal meningitis. C1q and GIPC may mediate downstream signaling pathways of CD93 in pneumococcal meningitis.

Nuclear translocation of GluA2/ GAPDH promotes neurotoxicity after pilocarpine-induced epilepsy.

Recent studies have identified that glyceraldehyde-3-phosphate dehydrogenase (GAPDH) exerts multiple functions besides its role in energy metabolism. It can form a protein complex with GluA2 subunit of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs), translocate into nucleus and confer neurotoxicity in a cerebral ischemia model. We postulate that GAPDH may also induce neurotoxicity by forming a coupling with GluA2 in pilocarpine-induced epileptic model, and disruption of the GluA2/GAPDH coupling can protect against neuronal injury. In this study, induced status epilepticus (SE) in rats by the systemic administration of pilocarpine, collected hippocampal tissues at different time points after SE, and assessed the relationship between GluA2/GAPDH coupling and neuronal apoptosis in SE rats. Then, we interrupted the GluA2/GAPDH coupling by a special interfering peptide and determined whether neuronal injury can be rescued and hippocampus-depended memory function can be improved. We also evaluated the concentrations of GAPDH in nuclear and cytoplasmatic proteins in SE group, non-SE group and after interruption of GluA2/GAPDH coupling, to verify the nuclear translocation of GAPDH in SE model. We found that the apoptosis of hippocampal neurons was most significant at 72 h after SE, which was also the peak time of GluA2/GAPDH coupling expression and GluA2 consumption. After interruption of GluA2/GAPDH coupling, the apoptosis and memorial function of hippocampal neurons were improved and nuclear translocation of GluA2/GAPDH coupling was reduced. In conclusion, GAPDH can be translocated into nucleus in the form of GluA2/GAPDH, which plays an important role in regulating pilocarpine-induced epilepsy via neurotoxicity pathway.

The protective effect of PPARγ in sepsis-induced acute lung injury via inhibiting PTEN/ß-catenin pathway.

The present study aims to reveal the molecular mechanism of peroxisome proliferator-activated receptor γ (PPARγ) on sepsis-induced acute lung injury (ALI). To do that, the rat injury model was established using cecal ligation and perforation (CLP) method, followed by different treatments, and the rats were divided into Sham group, CLP group, CLP + rosiglitazone (PPARγ agonist) group, CLP + GW9662 (PPARγ inhibitor) group, CLP + bpV (phosphatase and tensin homolog (PTEN) inhibitor) group, CLP + GW9662 + bpV group. Compared with Sham group, the mRNA and protein expression levels of PPARγ were down-regulated, the inflammation levels were elevated, and the apoptosis was increased in CLP group. After treatment with rosiglitazone, the protein expression level of PPARγ was significantly up-regulated, the phosphorylation level of PTEN/ß-catenin pathway was decreased, the PTEN/ß-catenin pathway was inhibited, the lung injury, inflammation and apoptosis were reduced. The opposite effect was observed after treatment with GW9662. Besides, bpV inhibited PTEN/ß-catenin pathway, and relieved the lung tissue injury. The overexpression of PPARγ reduced inflammatory response and inhibited apoptosis in sepsis-induced ALI. Furthermore, PPARγ relieved the sepsis-induced ALI by inhibiting the PTEN/ß-catenin pathway.

Disruption of the GluA2/GAPDH complex using TAT-GluA2NT1-3-2 peptide protects against AMPAR-mediated excitotoxicity after epilepsy.

Excitotoxicity and neuronal death following epilepsy involve α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs). It forms a protein complex with glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and co-internalizes upon activation of AMPA receptors after epilepsy. Disruption of the GluA2/GAPDH complex with an interfering peptide, TAT-GluA2NT1-3-2, protects cells against AMPAR-mediated excitotoxicity, which have been identified in in-vitro and in-vivo models of brain ischemia. We postulated that disruption of the GluA2/GAPDH interaction with the TAT-GluA2NT1-3-2 peptide would also protect against AMPAR-induced neuronal injury in an in-vivo model of status epilepticus (SE). In the present study, we divided pilocarpine-induced SE Wistar rats into three main groups: the TAT-GluA2NT1-3-2 peptide group, the TAT-GluA2NT-scram peptide group, and the normal saline group, and injected different doses of peptides stereotaxically into the hippocampus of SE rats to investigate whether the GluA2/GAPDH interaction could be disrupted by our TAT-GluA2NT1-3-2 peptide and determine its most appropriate dose. Then, the dose was administered stereotaxically at different time points after SE to determine the best administration time of neuronal protection. We found that the TAT-GluA2NT1-3-2 peptide can disrupt the GluA2/GAPDH interaction and protects against epilepsy-induced neuronal damage. The GluA2/GAPDH interaction may be a novel therapeutic target for epilepsy.

[Etiology of anti-N-methyl-D-aspartate receptor encephalitis].

Anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis is a type of newly recognized autoimmune encephalitis which is commonly seen in children, but its precise etiology is still uncertain. To reveal the etiology of anti-NMDAR encephalitis is very necessary for understanding its pathology, and for starting immune-related therapy as early as possible to improve its prognosis. In the initial literature, tumor, especially teratoma is more related with the anti-NMDAR encephalitis. In recent research, its etiology is related to infection and heredity. This article reviews the recognition and variation of the etiology of anti-NMDAR encephalitis.

Amelioration of ß-amyloid-induced cognitive dysfunction and hippocampal axon degeneration by curcumin is associated with suppression of CRMP-2 hyperphosphorylation.

The Alzheimer's disease (AD) brain is characterized by ß-amyloid deposition, hyperphosphorylation of microtubule-associated proteins, formation of senile plaques and neurofibrillary tangles, and degeneration of specific neuronal populations. Collapsin response mediator protein 2 (CRMP-2) hyperphosphorylation has been implicated in AD-associated neural process regression and neurofibrillary tangle formation. Curcumin is a promising AD drug with incompletely defined therapeutic mechanisms. One possibility is that curcumin prevents ß-amyloid-induced CRMP-2 hyperphosphorylation, thereby protecting against axonal regression and (or) promoting axonal regrowth. We examined spatial learning in the Morris water maze, hippocampal expression levels of CRMP-2 and phosphorylated CRMP-2 (p-CRMP-2) by Western blot, and NF-200 (an axon-specific marker) by immunohistochemistry in Sprague-Dawley rats subjected to a single intrahippocampal injection of Aß1-40 alone or Aß1-40 followed by curcumin (i.p. daily for 7 days). Compared to controls, spatial learning was significantly impaired in these Aß1-40-injected AD model rats (P<0.05). In addition, hippocampal expression levels of CRMP-2 and NF-200 were reduced while p-CRMP-2 expression was significantly enhanced (P<0.05 for all). Overexpression of p-CRMP-2 was correlated with NF-200 underexpression (r(2)=-0.67308, P<0.05), suggesting that Aß1-40 damaged hippocampal axons. Spatial learning deficits were reversed, CRMP-2 and NF-200 expression levels increased, and p-CRMP-2 expression reduced in curcumin-treated rats (all P<0.05). We propose that curcumin improves spatial learning by inhibiting CRMP-2 hyperphosphorylation, thus protecting against ß-amyloid-induced hippocampal damage or promoting regeneration.

Prenatal immune challenge in rats increases susceptibility to seizure-induced brain injury in adulthood.

Maternal infection during pregnancy is associated with an increased risk of neurodevelopmental injury. Our aim was to investigate whether prenatal immune challenge could alter susceptibility to seizure-induced brain injury in adulthood. Pregnant Wistar rats were injected intraperitoneally with lipopolysaccharide (LPS) or normal saline (NS) at days 15 and 16 of gestation. At postnatal day 45, seizure susceptibility was assessed in response to lithium-pilocarpine (LiPC) in adult offspring. Four groups were studied, including normal control (NS-NS), prenatal inflammation (LPS-NS), adult seizure (NS-LiPC), and "two-hit" (LPS-LiPC) groups. Our results demonstrated that adult rat offspring of LPS-exposed dams showed significantly greater susceptibility to LiPC-induced seizures, as well as enhanced hippocampal neuronal injury after seizures. Furthermore, animals in the "two-hit" group performed significantly worse than those from the NS-LiPC group in the open field test and Morris water maze. Our findings suggest that prenatal immune activation can cause a long-lasting increase in seizure susceptibility and predispose the brain to the damaging effect of seizures later in life.

Neonatal immune challenge exacerbates seizure-induced hippocampus-dependent memory impairment in adult rats.

Our aim was to examine whether neonatal lipopolysaccharide (LPS) exposure is associated with changes in microglia and whether these alternations could influence later seizure-induced neurobehavioral outcomes. Male pups were first injected intraperitoneally with either LPS or saline on postnatal day 3 (P3) and postnatal day 5 (P5). Immunohistochemical analysis showed that LPS-treated animals exhibited increased microglia activation that persisted into adolescence. At P45, seizures were induced in rats by intraperitoneal injection of kainic acid (KA). Rats treated with LPS neonatally showed significantly greater proinflammatory responses and performed significantly worse in the Y-maze, Morris water maze, and inhibitory avoidance tasks after KA insult. Treatment with minocycline at the time of neonatal LPS exposure to block LPS-induced microglia alternation attenuated the exaggerated neuroinflammatory responses and alleviated memory impairment associated with the KA insult. Our findings suggest that neonatal immune activation can predispose the brain to exacerbated behavioral deficits following seizures in adulthood, possibly by priming microglia.