Limits...
Apoptosis is essential for neutrophil functional shutdown and determines tissue damage in experimental pneumococcal meningitis.

Koedel U, Frankenberg T, Kirschnek S, Obermaier B, Häcker H, Paul R, Häcker G - PLoS Pathog. (2009)

Bottom Line: We here show that transgenic expression of Bcl-2 in haematopoietic cells blocks the resolution of inflammation following antibiotic therapy in a mouse model of pneumococcal meningitis.The persistence of neutrophil brain infiltrates was accompanied by high levels of IL-1beta and G-CSF as well as reduced levels of anti-inflammatory TGF-beta.In wild type mice treated with antibiotics, roscovitine significantly improved the resolution of the inflammation after pneumococcal infection and accelerated recovery.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurology, Clinic of the University of Munich, Munich, Germany.

ABSTRACT
During acute bacterial infections such as meningitis, neutrophils enter the tissue where they combat the infection before they undergo apoptosis and are taken up by macrophages. Neutrophils show pro-inflammatory activity and may contribute to tissue damage. In pneumococcal meningitis, neuronal damage despite adequate chemotherapy is a frequent clinical finding. This damage may be due to excessive neutrophil activity. We here show that transgenic expression of Bcl-2 in haematopoietic cells blocks the resolution of inflammation following antibiotic therapy in a mouse model of pneumococcal meningitis. The persistence of neutrophil brain infiltrates was accompanied by high levels of IL-1beta and G-CSF as well as reduced levels of anti-inflammatory TGF-beta. Significantly, Bcl-2-transgenic mice developed more severe disease that was dependent on neutrophils, characterized by pronounced vasogenic edema, vasculitis, brain haemorrhages and higher clinical scores. In vitro analysis of neutrophils demonstrated that apoptosis inhibition completely preserves neutrophil effector function and prevents internalization by macrophages. The inhibitor of cyclin-dependent kinases, roscovitine induced apoptosis in neutrophils in vitro and in vivo. In wild type mice treated with antibiotics, roscovitine significantly improved the resolution of the inflammation after pneumococcal infection and accelerated recovery. These results indicate that apoptosis is essential to turn off activated neutrophils and show that inflammatory activity and disease severity in a pyogenic infection can be modulated by targeting the apoptotic pathway in neutrophils.

Show MeSH

Related in: MedlinePlus

Reduction of CSF leucocyte count and induction of apoptosis by roscovitine in vivo.Wild type mice were subjected to pneumococcal meningitis by bacterial injection into the cisterna magna and treated either with a combination of ceftriaxone (100 mg/kg, intraperitoneally) and roscovitine (50 mg/kg intraperitoneally) or ceftriaxone and the vehicle of roscovitine (PBS+20% DMSO). In the case of the 24 h experiments (n = 10 per group), treatment was initiated 18 hours after infection, whereas drugs were given at 24 h and 48 h after infection in the 72 h experiments (n = 11 per group). CSF samples were obtained by puncture of the cisterna magna and analyzed for leucocyte counts (A) as well as the relative proportions of leucocyte subpopulations (B) and apoptotic leucocytes (B,C). (A) Roscovitine treatment significantly reduces CSF leukocyte counts at both observation times. *P<0.05, roscovitine-treated mice compared to vehicle-treated mice. (B,C) CSF samples from untreated, infected mice (n = 6) were used as controls to assess the effect of antibiotic therapy on leucocyte differential counts and apoptosis. (B) Roscovitine therapy increases the proportion of apoptotic leucocytes and decreases the proportion of neutrophils in the CSF. (C) Representative CSF smears of the 24 h time point are shown. Arrows indicate typically apoptotic leucocyte morphology, showing condensed nuclei (filled arrows) and karyorhexis (open arrows).
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2682662&req=5

ppat-1000461-g005: Reduction of CSF leucocyte count and induction of apoptosis by roscovitine in vivo.Wild type mice were subjected to pneumococcal meningitis by bacterial injection into the cisterna magna and treated either with a combination of ceftriaxone (100 mg/kg, intraperitoneally) and roscovitine (50 mg/kg intraperitoneally) or ceftriaxone and the vehicle of roscovitine (PBS+20% DMSO). In the case of the 24 h experiments (n = 10 per group), treatment was initiated 18 hours after infection, whereas drugs were given at 24 h and 48 h after infection in the 72 h experiments (n = 11 per group). CSF samples were obtained by puncture of the cisterna magna and analyzed for leucocyte counts (A) as well as the relative proportions of leucocyte subpopulations (B) and apoptotic leucocytes (B,C). (A) Roscovitine treatment significantly reduces CSF leukocyte counts at both observation times. *P<0.05, roscovitine-treated mice compared to vehicle-treated mice. (B,C) CSF samples from untreated, infected mice (n = 6) were used as controls to assess the effect of antibiotic therapy on leucocyte differential counts and apoptosis. (B) Roscovitine therapy increases the proportion of apoptotic leucocytes and decreases the proportion of neutrophils in the CSF. (C) Representative CSF smears of the 24 h time point are shown. Arrows indicate typically apoptotic leucocyte morphology, showing condensed nuclei (filled arrows) and karyorhexis (open arrows).

Mentions: To test for apoptosis induction by roscovitine and its consequences in vivo, we used a different, more virulent strain of S. pneumoniae (D39, serogroup 2). In experiments with this strain, 4 out of 11 wt mice and 9 out of 12 Bcl-2-transgenic mice died despite treatment after 24 h (Fig. S6B). This result in wt mice is a good approximation of the lethality of human pneumococcal meningitis. We first tested for the effect of roscovitine on the CSF infiltrate. Wild type mice were infected and treated with antibiotics at 18 h (the earlier treatment was chosen to keep the point of analysis at 24 h; this change also resulted in higher number of mice surviving, see below). One group of mice received roscovitine at the same time point, the other one vehicle (DMSO). As shown in Fig. 5A, roscovitine treatment significantly reduced CSF leucocyte counts as early as 24 h post infection, and a difference was still detectable at 72 h. Analysis of cell composition in CSF in these mice showed enhanced relative numbers of lymphocytes following antibiotic treatment (Fig. 5B). Clearly increased numbers of apoptotic neutrophils, identified by their nuclear pyknosis and karyrhexis were seen in the CSF of roscovitine treated mice (Fig. 5C). Combined treatment with antibiotics and roscovitine thus induces apoptosis in situ and very likely by this mechanism reduces the absolute number of neutrophils in the CSF.


Apoptosis is essential for neutrophil functional shutdown and determines tissue damage in experimental pneumococcal meningitis.

Koedel U, Frankenberg T, Kirschnek S, Obermaier B, Häcker H, Paul R, Häcker G - PLoS Pathog. (2009)

Reduction of CSF leucocyte count and induction of apoptosis by roscovitine in vivo.Wild type mice were subjected to pneumococcal meningitis by bacterial injection into the cisterna magna and treated either with a combination of ceftriaxone (100 mg/kg, intraperitoneally) and roscovitine (50 mg/kg intraperitoneally) or ceftriaxone and the vehicle of roscovitine (PBS+20% DMSO). In the case of the 24 h experiments (n = 10 per group), treatment was initiated 18 hours after infection, whereas drugs were given at 24 h and 48 h after infection in the 72 h experiments (n = 11 per group). CSF samples were obtained by puncture of the cisterna magna and analyzed for leucocyte counts (A) as well as the relative proportions of leucocyte subpopulations (B) and apoptotic leucocytes (B,C). (A) Roscovitine treatment significantly reduces CSF leukocyte counts at both observation times. *P<0.05, roscovitine-treated mice compared to vehicle-treated mice. (B,C) CSF samples from untreated, infected mice (n = 6) were used as controls to assess the effect of antibiotic therapy on leucocyte differential counts and apoptosis. (B) Roscovitine therapy increases the proportion of apoptotic leucocytes and decreases the proportion of neutrophils in the CSF. (C) Representative CSF smears of the 24 h time point are shown. Arrows indicate typically apoptotic leucocyte morphology, showing condensed nuclei (filled arrows) and karyorhexis (open arrows).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2682662&req=5

ppat-1000461-g005: Reduction of CSF leucocyte count and induction of apoptosis by roscovitine in vivo.Wild type mice were subjected to pneumococcal meningitis by bacterial injection into the cisterna magna and treated either with a combination of ceftriaxone (100 mg/kg, intraperitoneally) and roscovitine (50 mg/kg intraperitoneally) or ceftriaxone and the vehicle of roscovitine (PBS+20% DMSO). In the case of the 24 h experiments (n = 10 per group), treatment was initiated 18 hours after infection, whereas drugs were given at 24 h and 48 h after infection in the 72 h experiments (n = 11 per group). CSF samples were obtained by puncture of the cisterna magna and analyzed for leucocyte counts (A) as well as the relative proportions of leucocyte subpopulations (B) and apoptotic leucocytes (B,C). (A) Roscovitine treatment significantly reduces CSF leukocyte counts at both observation times. *P<0.05, roscovitine-treated mice compared to vehicle-treated mice. (B,C) CSF samples from untreated, infected mice (n = 6) were used as controls to assess the effect of antibiotic therapy on leucocyte differential counts and apoptosis. (B) Roscovitine therapy increases the proportion of apoptotic leucocytes and decreases the proportion of neutrophils in the CSF. (C) Representative CSF smears of the 24 h time point are shown. Arrows indicate typically apoptotic leucocyte morphology, showing condensed nuclei (filled arrows) and karyorhexis (open arrows).
Mentions: To test for apoptosis induction by roscovitine and its consequences in vivo, we used a different, more virulent strain of S. pneumoniae (D39, serogroup 2). In experiments with this strain, 4 out of 11 wt mice and 9 out of 12 Bcl-2-transgenic mice died despite treatment after 24 h (Fig. S6B). This result in wt mice is a good approximation of the lethality of human pneumococcal meningitis. We first tested for the effect of roscovitine on the CSF infiltrate. Wild type mice were infected and treated with antibiotics at 18 h (the earlier treatment was chosen to keep the point of analysis at 24 h; this change also resulted in higher number of mice surviving, see below). One group of mice received roscovitine at the same time point, the other one vehicle (DMSO). As shown in Fig. 5A, roscovitine treatment significantly reduced CSF leucocyte counts as early as 24 h post infection, and a difference was still detectable at 72 h. Analysis of cell composition in CSF in these mice showed enhanced relative numbers of lymphocytes following antibiotic treatment (Fig. 5B). Clearly increased numbers of apoptotic neutrophils, identified by their nuclear pyknosis and karyrhexis were seen in the CSF of roscovitine treated mice (Fig. 5C). Combined treatment with antibiotics and roscovitine thus induces apoptosis in situ and very likely by this mechanism reduces the absolute number of neutrophils in the CSF.

Bottom Line: We here show that transgenic expression of Bcl-2 in haematopoietic cells blocks the resolution of inflammation following antibiotic therapy in a mouse model of pneumococcal meningitis.The persistence of neutrophil brain infiltrates was accompanied by high levels of IL-1beta and G-CSF as well as reduced levels of anti-inflammatory TGF-beta.In wild type mice treated with antibiotics, roscovitine significantly improved the resolution of the inflammation after pneumococcal infection and accelerated recovery.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurology, Clinic of the University of Munich, Munich, Germany.

ABSTRACT
During acute bacterial infections such as meningitis, neutrophils enter the tissue where they combat the infection before they undergo apoptosis and are taken up by macrophages. Neutrophils show pro-inflammatory activity and may contribute to tissue damage. In pneumococcal meningitis, neuronal damage despite adequate chemotherapy is a frequent clinical finding. This damage may be due to excessive neutrophil activity. We here show that transgenic expression of Bcl-2 in haematopoietic cells blocks the resolution of inflammation following antibiotic therapy in a mouse model of pneumococcal meningitis. The persistence of neutrophil brain infiltrates was accompanied by high levels of IL-1beta and G-CSF as well as reduced levels of anti-inflammatory TGF-beta. Significantly, Bcl-2-transgenic mice developed more severe disease that was dependent on neutrophils, characterized by pronounced vasogenic edema, vasculitis, brain haemorrhages and higher clinical scores. In vitro analysis of neutrophils demonstrated that apoptosis inhibition completely preserves neutrophil effector function and prevents internalization by macrophages. The inhibitor of cyclin-dependent kinases, roscovitine induced apoptosis in neutrophils in vitro and in vivo. In wild type mice treated with antibiotics, roscovitine significantly improved the resolution of the inflammation after pneumococcal infection and accelerated recovery. These results indicate that apoptosis is essential to turn off activated neutrophils and show that inflammatory activity and disease severity in a pyogenic infection can be modulated by targeting the apoptotic pathway in neutrophils.

Show MeSH
Related in: MedlinePlus