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The formyl peptide receptor like-1 and scavenger receptor MARCO are involved in glial cell activation in bacterial meningitis.

Braun BJ, Slowik A, Leib SL, Lucius R, Varoga D, Wruck CJ, Jansen S, Podschun R, Pufe T, Brandenburg LO - J Neuroinflammation (2011)

Bottom Line: Furthermore, we demonstrated a functional interaction between FPRL1 and MARCO in NM-induced signalling by real-time RT-PCR, ERK1/2 phosphorylation and cAMP level measurement and show differences between NM- or SP-induced signal transduction.We propose that NM and SP induce glial cell activation and rCRAMP expression also via FPRL1 and MARCO.Thus the receptors contribute an important part to the host defence against infection.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Anatomy and Cell Biology, RWTH Aachen University, Germany.

ABSTRACT

Background: Recent studies have suggested that the scavenger receptor MARCO (macrophage receptor with collagenous structure) mediates activation of the immune response in bacterial infection of the central nervous system (CNS). The chemotactic G-protein-coupled receptor (GPCR) formyl-peptide-receptor like-1 (FPRL1) plays an essential role in the inflammatory responses of host defence mechanisms and neurodegenerative disorders such as Alzheimer's disease (AD). Expression of the antimicrobial peptide cathelicidin CRAMP/LL-37 is up-regulated in bacterial meningitis, but the mechanisms underlying CRAMP expression are far from clear.

Methods: Using a rat meningitis model, we investigated the influence of MARCO and FPRL1 on rCRAMP (rat cathelin-related antimicrobial peptide) expression after infection with bacterial supernatants of Streptococcus pneumoniae (SP) and Neisseria meningitides (NM). Expression of FPRL1 and MARCO was analyzed by immunofluorescence and real-time RT-PCR in a rat meningitis model. Furthermore, we examined the receptor involvement by real-time RT-PCR, extracellular-signal regulated kinases 1/2 (ERK1/2) phosphorylation and cAMP level measurement in glial cells (astrocytes and microglia) and transfected HEK293 cells using receptor deactivation by antagonists. Receptors were inhibited by small interference RNA and the consequences in NM- and SP-induced Camp (rCRAMP gene) expression and signal transduction were determined.

Results: We show an NM-induced increase of MARCO expression by immunofluorescence and real-time RT-PCR in glial and meningeal cells. Receptor deactivation by antagonists and small interfering RNA (siRNA) verified the importance of FPRL1 and MARCO for NM- and SP-induced Camp and interleukin-1β expression in glial cells. Furthermore, we demonstrated a functional interaction between FPRL1 and MARCO in NM-induced signalling by real-time RT-PCR, ERK1/2 phosphorylation and cAMP level measurement and show differences between NM- or SP-induced signal transduction.

Conclusions: We propose that NM and SP induce glial cell activation and rCRAMP expression also via FPRL1 and MARCO. Thus the receptors contribute an important part to the host defence against infection.

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Strongly increased MARCO expression in astrocytes after Neisseria meningitides infection in an infant rat model of meningitis. Coronal brain sections from rats infected with Neisseria meningitidis (NM) or Streptococcus pneumoniae (SP) were fixed at defined time-points after infection and immunolabeled using anti-MARCO (green) and anti-glial fibrillary acidic protein (anti-GFAP) antibodies to identify astrocytes with nuclear counterstaining (blue). Sections were examined by double fluorescence microscopy. The figures show representative results from one of three independent experiments. Scale bar = 200 μm for overview and 20 μm for the other images. (B) Shows a detail of (A). Please note that the detail shows a strong colocalization between GFAP and MARCO in the sub-cortical layer after NM infection.
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Figure 3: Strongly increased MARCO expression in astrocytes after Neisseria meningitides infection in an infant rat model of meningitis. Coronal brain sections from rats infected with Neisseria meningitidis (NM) or Streptococcus pneumoniae (SP) were fixed at defined time-points after infection and immunolabeled using anti-MARCO (green) and anti-glial fibrillary acidic protein (anti-GFAP) antibodies to identify astrocytes with nuclear counterstaining (blue). Sections were examined by double fluorescence microscopy. The figures show representative results from one of three independent experiments. Scale bar = 200 μm for overview and 20 μm for the other images. (B) Shows a detail of (A). Please note that the detail shows a strong colocalization between GFAP and MARCO in the sub-cortical layer after NM infection.

Mentions: In order to validate our previous in vitro findings in vivo, we used double fluorescence microscopy with receptor specific antibodies to examine the localization of MARCO and GFAP in astrocytes from infant rats with bacterial meningitis with NM or SP. Control rat brains showed a very low positive GFAP staining, since GFAP is a marker for activated astrocytes [22]. In correspondence with real-time RT-PCR and immunofluorescence results, MARCO expression shows a strong increase after 24 h of infection with NM as seen in Figure 3A, with visible co-localization of MARCO and GFAP in the sub-cortical area; Figure 3B. In addition the meninges showed an increase of MARCO expression after NM infection. Positive MARCO staining and MARCO/GFAP co-localization were also shown after 12, 22, 39 h of infection with SP, albeit weaker than in meningitis by NM (Figure 3A). After SP infection an increase of MARCO expression in meninges was also detected. Interestingly we could show an increase of MARCO expression after treatment with NM and SP in meningeal cells. For FPRL1 however, only SP induced increased expression (see Figure 1E and 1F).


The formyl peptide receptor like-1 and scavenger receptor MARCO are involved in glial cell activation in bacterial meningitis.

Braun BJ, Slowik A, Leib SL, Lucius R, Varoga D, Wruck CJ, Jansen S, Podschun R, Pufe T, Brandenburg LO - J Neuroinflammation (2011)

Strongly increased MARCO expression in astrocytes after Neisseria meningitides infection in an infant rat model of meningitis. Coronal brain sections from rats infected with Neisseria meningitidis (NM) or Streptococcus pneumoniae (SP) were fixed at defined time-points after infection and immunolabeled using anti-MARCO (green) and anti-glial fibrillary acidic protein (anti-GFAP) antibodies to identify astrocytes with nuclear counterstaining (blue). Sections were examined by double fluorescence microscopy. The figures show representative results from one of three independent experiments. Scale bar = 200 μm for overview and 20 μm for the other images. (B) Shows a detail of (A). Please note that the detail shows a strong colocalization between GFAP and MARCO in the sub-cortical layer after NM infection.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3040686&req=5

Figure 3: Strongly increased MARCO expression in astrocytes after Neisseria meningitides infection in an infant rat model of meningitis. Coronal brain sections from rats infected with Neisseria meningitidis (NM) or Streptococcus pneumoniae (SP) were fixed at defined time-points after infection and immunolabeled using anti-MARCO (green) and anti-glial fibrillary acidic protein (anti-GFAP) antibodies to identify astrocytes with nuclear counterstaining (blue). Sections were examined by double fluorescence microscopy. The figures show representative results from one of three independent experiments. Scale bar = 200 μm for overview and 20 μm for the other images. (B) Shows a detail of (A). Please note that the detail shows a strong colocalization between GFAP and MARCO in the sub-cortical layer after NM infection.
Mentions: In order to validate our previous in vitro findings in vivo, we used double fluorescence microscopy with receptor specific antibodies to examine the localization of MARCO and GFAP in astrocytes from infant rats with bacterial meningitis with NM or SP. Control rat brains showed a very low positive GFAP staining, since GFAP is a marker for activated astrocytes [22]. In correspondence with real-time RT-PCR and immunofluorescence results, MARCO expression shows a strong increase after 24 h of infection with NM as seen in Figure 3A, with visible co-localization of MARCO and GFAP in the sub-cortical area; Figure 3B. In addition the meninges showed an increase of MARCO expression after NM infection. Positive MARCO staining and MARCO/GFAP co-localization were also shown after 12, 22, 39 h of infection with SP, albeit weaker than in meningitis by NM (Figure 3A). After SP infection an increase of MARCO expression in meninges was also detected. Interestingly we could show an increase of MARCO expression after treatment with NM and SP in meningeal cells. For FPRL1 however, only SP induced increased expression (see Figure 1E and 1F).

Bottom Line: Furthermore, we demonstrated a functional interaction between FPRL1 and MARCO in NM-induced signalling by real-time RT-PCR, ERK1/2 phosphorylation and cAMP level measurement and show differences between NM- or SP-induced signal transduction.We propose that NM and SP induce glial cell activation and rCRAMP expression also via FPRL1 and MARCO.Thus the receptors contribute an important part to the host defence against infection.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Anatomy and Cell Biology, RWTH Aachen University, Germany.

ABSTRACT

Background: Recent studies have suggested that the scavenger receptor MARCO (macrophage receptor with collagenous structure) mediates activation of the immune response in bacterial infection of the central nervous system (CNS). The chemotactic G-protein-coupled receptor (GPCR) formyl-peptide-receptor like-1 (FPRL1) plays an essential role in the inflammatory responses of host defence mechanisms and neurodegenerative disorders such as Alzheimer's disease (AD). Expression of the antimicrobial peptide cathelicidin CRAMP/LL-37 is up-regulated in bacterial meningitis, but the mechanisms underlying CRAMP expression are far from clear.

Methods: Using a rat meningitis model, we investigated the influence of MARCO and FPRL1 on rCRAMP (rat cathelin-related antimicrobial peptide) expression after infection with bacterial supernatants of Streptococcus pneumoniae (SP) and Neisseria meningitides (NM). Expression of FPRL1 and MARCO was analyzed by immunofluorescence and real-time RT-PCR in a rat meningitis model. Furthermore, we examined the receptor involvement by real-time RT-PCR, extracellular-signal regulated kinases 1/2 (ERK1/2) phosphorylation and cAMP level measurement in glial cells (astrocytes and microglia) and transfected HEK293 cells using receptor deactivation by antagonists. Receptors were inhibited by small interference RNA and the consequences in NM- and SP-induced Camp (rCRAMP gene) expression and signal transduction were determined.

Results: We show an NM-induced increase of MARCO expression by immunofluorescence and real-time RT-PCR in glial and meningeal cells. Receptor deactivation by antagonists and small interfering RNA (siRNA) verified the importance of FPRL1 and MARCO for NM- and SP-induced Camp and interleukin-1β expression in glial cells. Furthermore, we demonstrated a functional interaction between FPRL1 and MARCO in NM-induced signalling by real-time RT-PCR, ERK1/2 phosphorylation and cAMP level measurement and show differences between NM- or SP-induced signal transduction.

Conclusions: We propose that NM and SP induce glial cell activation and rCRAMP expression also via FPRL1 and MARCO. Thus the receptors contribute an important part to the host defence against infection.

Show MeSH
Related in: MedlinePlus