Streptococcus pneumoniae Damages the Ciliated Ependyma of the Brain during Meningitis

Abstract

Streptococcus pneumoniae meningitis remains a disease with a poor outcome for the patient. A region of the brain that has been neglected in the study of meningitis is the ependyma, which has been identified as a location of adult pluripotent cells. In this study we have used a rat model of meningitis to examine whether the ependymal layer is affected by S. pneumoniae. The effects included localized loss of cilia, a decrease of the overall ependymal ciliary beat frequency, and damage to the ependymal ultrastructure during meningitis. In conclusion, loss of ependymal cells and ciliary function exposes the underlying neuronal milieu to host and bacterial cytotoxins and this is likely to contribute to the neuropathology commonly observed in pneumococcal meningitis.Despite modern intensive care, antibiotic treatment, and the use of dexamethasone, the morbidity and mortality associated with Streptococcus pneumoniae meningitis remain high (15). Vaccines against this bacterium show no evidence of reducing the number of cases (17). The mechanisms by which S. pneumoniae causes neuronal damage (once it infects the cerebrospinal fluid [CSF]) are yet to be fully deciphered. To investigate the effect of S. pneumoniae and its virulence factors, we established an ex vivo method for the culture and differentiation of brain tissue into a monolayer of ciliated ependymal cells. Ependymal cells line the ventricular cavities and the cerebral aqueduct separating the CSF that is infected in meningitis and ventriculitis from neuronal tissue. Using this model, investigators have previously shown that both pneumolysin (4, 12) and pneumococcal hydrogen peroxide (H 2 O 2 ) (5) cause damage to ependymal cells. In addition, when clinically relevant concentrations of bacteria were added to brain slices prepared from the fourth ventricle there was a rapid inhibition of ependymal ciliary beat frequency (CBF) (5).The CBF of ependymal cilia may be measured directly and continually to assess the functioning and integrity of ependymal cells. The ependyma is thought to act as a filter relaying macromolecules to and from the CSF, and it also plays a role in controlling CSF volume (3). Recently, both ependymal (8) and subventricular zone (1) cells have been identified as adult neuronal stem cells, stressing the potential importance of the thin cellular layer that lines the ventricles and aqueducts of the brain.It was essential to determine whether our ex vivo findings (determined using the ciliated ependymal cells) were also observed during pneumococcal meningitis. We therefore established a modification of the rat meningitis model described by Pfister and colleagues (14). In this paper we show that during pneumococcal meningitis and as predicted from our ex vivo studies, ependymal CBF is inhibited and the integrity of the ependymal layer is compromised.Overview. A cannula was surgically implanted onto the atlanto-occipital membrane prior to perforation, according to the method of Huang and colleagues (6). The CSF was then infected with the desired bac...

Hydrogen peroxide at a concentration used during neurosurgery disrupts ciliary function and causes extensive damage to the ciliated ependyma of the brain

“…Small animals with primary ciliary dyskinesia (PCD) commonly develop hydrocephalus and hydrocephalus is also occasionally seen in humans with PCD [9,10]. It is known that bacteria and their toxins adversely affect ciliary function [4,5,11] and it has been shown that viral or bacterial infection of the CSF, in animal models, may cause ependymal damage and hydrocephalus [7,8].…”

PACAP27 regulates ciliary function in primary cultures of rat brain ependymal cells

“…Ependymal cilia also have been shown to play an important role in host defence against pathogens (Hirst et al, 2003;Hirst et al, 2000;Mohammed et al, 1999). In addition, a recent study (Sawamoto et al, 2006) has shown that ependymal cilia are responsible for the formation of gradients of CSF guidance molecules that direct neuroblast movement in the brain parenchyma.…”

Streptococcus pneumoniae -Induced Inhibition of Rat Ependymal Cilia Is Attenuated by Antipneumolysin Antibody

“…The rapid release of pneumolysin on antibiotic-induced bacterial lysis (23) is thought to contribute to toxic shock and local tissue damage and may partially be responsible for causing deafness (7). Recently we have shown that pneumococci and pneumolysin cause rapid ependymal ciliary stasis in ependymal brain slices and cultured primary ependymal cells (12), an effect that is mirrored in experimental meningitis in rats (11).…”

“…We established an ex vivo model that allowed measurement of the ependymal ciliary beat frequency (CBF), by high-speed video photography, during exposure to bacteria and bacterial toxins. Our initial studies using this model targeted pneumococcal meningitis, for which new, improved therapeutic strategies are urgently required to reduce mortality and neurological damage (11,12,13,16). Currently, only dexamethasone has widely been used as an adjunctive therapy to antibiotic treatment (8).…”