Chlamydia pneumoniae infection of brain cells: An in vitro study
Introduction
Previous data provided a strong link between infectious agents, like human immunodeficiency virus (HIV), herpes simplex virus or cytomegalovirus and diseases of the central nervous system [5], [15], [17], [22], [36]. More recent data then suggested that Chlamydia pneumoniae (Cpn) should be added to the candidate list of microbes responsible for several of these diseases [34]. Cpn, an obligate intracellular bacterium, is a widespread respiratory pathogen able to infect a diversity of eukaryotic cell types [20]. Cpn infections mainly result in acute respiratory tract infections, including pneumonia, sinusitis, bronchitis and pharyngitis [10], [11]. Furthermore, Cpn has been associated with various chronic diseases like asthma [39], atherosclerosis [6], [19] and rheumatoid arthritis. Interestingly, previous studies suggested a potential link between Cpn and several disorders of the central nervous system as well [42].
One of the neurological diseases associated with Cpn is Alzheimer's disease (AD). When post-mortem brain samples were analysed, Cpn was found in 17 out of 19 late-onset AD patients using PCR, immunohistochemistry and electron microscopy while Cpn could be detected in only 1 out of 19 controls [2]. Similarly, Cpn could be detected in other areas of neuropathology in the brain [1]. Additional evidence for a role of Cpn in neurological disorders comes from animal experiments as Balb/c mice develop AD-like pathology after infection with Cpn [23]. However, others failed to identify an association between Cpn and AD [4], [9], [26], [30], [37] and discrepancies exist regarding the presence of Cpn inside the brain in neurological diseases. Nonetheless, it is well recognised that Cpn can traffic towards the brain and cause a local inflammatory reaction [34]. Whether this is induced by direct infection of brain cells or rather by an indirect response is still ambiguous. Therefore, it is important to investigate the susceptibility of specific brain cells to Cpn infection. For this purpose three brain cell lines were selected: neurons (NB41A3), microglial cells (BV-2) and astrocytes (C8D1A). Neurons are particularly involved in intracellular communication, while neuronal death is often connected with a variety of brain disorders like AD and Parkinson's disease. Next, astrocytes play a role in maintaining an appropriate chemical content of the extracellular space for neuronal signaling. Finally, microglial cells have been termed the tissue macrophages of the central nervous system; they proliferate following brain injury and presumably help repair neural damage [32].
In this study, it was our aim to examine the susceptibility of these murine brain cells to Cpn infection by immunohistochemical techniques and real-time polymerase chain reaction (RT-PCR). Furthermore, a productive infection was assessed by using a susceptible cell line (epithelial cell line). Finally, we determined the occurrence of cell death and its nature – apoptotic versus necrotic – in these cell lines following Cpn infection.
Section snippets
C. pneumoniae (Cpn)
The Cpn strain, TWAR 2043, was obtained from the American Type Tissue collection (ATCC VR-1355) and continuously propagated on Hep2 cells as described previously [31]. Bacterial titres, expressed as the number of inclusion forming units per millilitre (IFU/ml), were determined by titration in Hep2 cells as described by Ezzahiri [6] and stained with a Chlamydia LPS-specific, FITC-conjugated mononuclear Antibody (RR402, DAKO, Glostrup, Denmark).
Cell cultures
Murine microglial cells (MMC—BV-2) [3] were kindly
Results
Thus, a reference epithelial cell layer and three brain cell lines were infected with C. pneumoniae (MOI 5). The presence of Cpn antigens and DNA in these cell lines was determined, using immunofluorescent techniques and real-time PCR respectively. A productive Cpn infection was also analyzed. Therefore, Cpn fluorescent signal was investigated in a “susceptible cell layer” after transferring medium of infected cells. Finally, a double-staining with Hoechst 33258 and propidium iodide revealed
Discussion
C. pneumoniae (Cpn), an obligate intracellular gram-negative bacterium, has been associated with both acute (meningitis–encephalitis) as well as chronic diseases (multiple sclerosis) of the central nervous system [12], [33], [34], [40]. Also, recent evidence suggests a role for Cpn in AD [2]. Nevertheless, the data published so far do not prove any causative role for Cpn in AD and many questions have to be answered before we can attribute a definite role to Cpn in the pathogenesis of AD. For
Acknowledgement
This research was funded by the Departments of Medical Microbiology and Cellular Neuroscience of the Maastricht University.
References (42)
- et al.
Immortalization of murine microglial cells by a v-raf/v-myc carrying retrovirus
J Neuroimmunol
(1990) - et al.
Herpes simplex virus type 1 and Alzheimer's disease
Neurobiol Aging
(1999) - et al.
Chlamydia pneumoniae infection induces an unstable atherosclerotic plaque phenotype in LDL-receptor, ApoE double knockout mice
Eur J Vasc Endovasc Surg
(2003) - et al.
Cytomegalovirus is present in a very high proportion of brains from vascular dementia patients
Neurobiol Dis
(2002) - et al.
Chlamydia pneumoniae induces Alzheimer-like amyloid plaques in brains of BALB/c mice
Neurobiol Aging
(2004) - et al.
Association of Chlamydia pneumoniae with central nervous system disease
Microbes Infect
(2003) - et al.
Infectious agents and multiple sclerosis—are Chlamydia pneumoniae and human herpes virus 6 involved?
J Neuroimmunol
(2003) Respiratory infections and asthma: current treatment strategies
Drug Discov Today
(2004)- et al.
Role of infection in Alzheimer's disease
J Am Osteopath Assoc
(2001) - et al.
Identification and localization of Chlamydia pneumoniae in the Alzheimer's brain
Med Microbiol Immunol (Berl)
(1998)
Proinflammatory cytokines, antibodies to Chlamydia pneumoniae and age-associated diseases in Danish centenarians: is there a link?
Scand J Infect Dis
Replication of Chlamydia pneumoniae in vitro in human macrophages, endothelial cells, and aortic artery smooth muscle cells
Infect Immun
Chlamydia pneumoniae infection in circulating human monocytes is refractory to antibiotic treatment
Circulation
Failure to detect Chlamydia pneumoniae in brain sections of Alzheimer's disease patients
J Clin Microbiol
Evidence that Chlamydia pneumoniae causes pneumonia and bronchitis
J Infect Dis
A new respiratory tract pathogen: Chlamydia pneumoniae strain TWAR
J Infect Dis
Severe meningoencephalitis: an unusual manifestation of Chlamydia pneumoniae infection
Clin Infect Dis
Replication of murine cytomegalovirus in differentiated macrophages as a determinant of viral pathogenesis
J Virol
Chlamydia pneumoniae infection of alveolar macrophages: a model
J Infect Dis
Herpesviruses in brains in Alzheimer's and Parkinson's diseases
Ann Neurol
The r131 gene of rat cytomegalovirus encodes a proinflammatory CC chemokine homolog which is essential for the production of infectious virus in the salivary glands
Virus Genes
Cited by (40)
Olfactory dysfunction in the pathophysiological continuum of dementia
2019, Ageing Research ReviewsCitation Excerpt :As for HSV-1, the load of C. Pneumoniae in the Alzheimer’s brain varies with APOE genotype with ApoEε4 carriers showing higher copy numbers of C. Pneumoniae as compared to subjects lacking the risk variant (Gérard et al., 2005). Chlamydial LPS and other membrane proteins induce the secretion of proinflammatory cytokines (IL-6 and MCP-1) and reactive oxygen species from astrocytes with neurotoxic activity (Boelen et al., 2007). Spirochetes, such as Borrelia Burgdorferi (B. burgdorferi) and Treponema denticola, cause latent or persistent infection throughout life (Miklossy, 2008b).
Chlamydia pneumoniae seropositivity in Iranian patients with multiple sclerosis: A pilot study
2011, Neurologia i Neurochirurgia PolskaCitation Excerpt :C. pneumoniae has been reported to be associated with neurological diseases such as ischaemic stroke in young adults [18], Alzheimer disease and MS. One study showed that the neuronal cell line may be markedly sensitive to C. pneumoniae [19] and it may play an important role in the aetiology of MS. However, the results of other studies are inconsistent, neither confirming nor excluding a possible role for C. pneumoniae in MS development and progression [20]. Another study investigating the serum and cerebrospinal fluid of MS cases for C. pneumoniae showed the production of C. pneumoniae oligoclonal band IgG only in a minority of MS patients [21].
Inhibitory effect of the natural product betulin and its derivatives against the intracellular bacterium Chlamydia pneumoniae
2010, Biochemical PharmacologyCitation Excerpt :It has been estimated that C. pneumoniae infection is the causative agent in 5–10% of community-acquired pneumonia, bronchitis and sinusitis cases [1]. This intracellular bacterium also causes a chronic infection that has been associated with atherosclerosis [2,3], asthma [4,5], lung cancer [6] and Alzheimer's disease [7,8]. In these diseases, C. pneumoniae seems to act as a triggering factor, although comprehensive data in this respect is yet to be gathered.
Chlamydia pneumoniae infection enhances microglial activation in atherosclerotic mice
2010, Neurobiology of AgingCitation Excerpt :In humans activated microglia were demonstrated in autopsied brains from patients with Binswanger's disease (Rosenberg et al., 2001), which is characterized by diffuse ischemic white matter damage due to hypoperfusion. Human astrocytic and microglial cell lines can be infected with C. pneumoniae, as well as murine astrocytes and microglial cells, although in the latter, microglia were more resistant to infection (Boelen et al., 2006; Dreses-Werringloer et al., 2006). Whether infection of these cells lead to activation has not been described yet.
Detection of Chlamydia Pneumoniae in Lung Tissues Derived from Lung Tumor-Bearing Iraqi Patients
2021, Iraqi Journal of Science