Expression Microarray Analysis Implicates Apoptosis and Interferon-Responsive Mechanisms in Susceptibility to Experimental Cerebral Malaria

Abstract

Specific local brain responses, influenced by parasite sequestration and host immune system activation, have been implicated in the development of cerebral malaria. This study assessed whole-brain transcriptional responses over the course of experimental cerebral malaria by comparing genetically resistant and susceptible inbred mouse strains infected with Plasmodium berghei ANKA. Computational methods were used to identify differential patterns of gene expression. Overall, genes that showed the most transcriptional activity were differentially expressed in susceptible mice 1 to 2 days before the onset of characteristic symptoms of cerebral malaria. Most of the differentially expressed genes identified were associated with immune-related gene ontology categories. Further analysis to identify interaction networks and to examine patterns of transcriptional regulation within the set of identified genes implicated a central role for both interferon-regulated processes and apoptosis in the pathogenesis of cerebral malaria. Biological relevance of these genes and pathways was confirmed using quantitative RT-PCR and histopathological examination of the brain for apoptosis. The application of computational biology tools to examine systematically the disease progression in cerebral malaria can identify important transcriptional programs activated during its pathogenesis and may serve as a methodological approach to identify novel targets for therapeutic intervention.

Cerebral Malaria Pathogenesis

“…The expression microarray findings were again confirmed: CM-susceptible mice showed a higher number of terminal dUTP nick-end labeling-positive cells, primarily in the neurons of the cerebral cortex and cells of the leptomeninges. 4 The corroborative studies performed by Lovegrove and colleagues 4 add significantly to the data from initial microarray analysis and convincingly suggest a role for IFN-related processes and neuronal apoptosis in murine CM pathogenesis. Although other studies have suggested the importance of IFN, particularly IFN-␥, in murine CM, 19 only two very recent studies have documented neuronal apoptosis in murine CM.…”

“…18 The methods of microarray analysis are as important as the microarray testing itself: appropriate and rigorous statistical analysis is key to accurate interpretation of results, and the methods and presentation of data analysis can make a big difference in communicating the main findings from within the many. In this regard, the inclusion of a gene-gene interaction network to create an "interactome" that identified hubs of interconnectivity is a major strength of the study by Lovegrove and colleagues, 4 allowing them to identify factors that appear to be particularly important in directing the overall transcriptional response to PbA infection. The finding that expression of several genes involved in regulation of IFN were up-regulated in CM-susceptible mice led to assessment of brain tissue by quantitative real-time reverse transcriptase (RT)-PCR directed at a number of immune-related genes.…”

“…Expression microarray and PCR analyses correlated well for most genes, and the majority of up-regulated genes documented by RT-PCR were either involved in IFN signaling or were IFNinducible. 4 In addition, the identification of several caspase genes and Fas (CD95) as prominent hubs in the interactome led the investigators to assess the brains of CM-susceptible and CM-resistant mice for evidence of apoptosis by terminal dUTP nick-end labeling immunohistochemistry. The expression microarray findings were again confirmed: CM-susceptible mice showed a higher number of terminal dUTP nick-end labeling-positive cells, primarily in the neurons of the cerebral cortex and cells of the leptomeninges.…”

“…In an elegant and carefully designed series of experiments in this issue of The American Journal of Pathology, Lovegrove and colleagues 4 use microarray analysis of whole brain tissue gene expression in CM-susceptible and CM-resistant mice to define potential pathways involved in murine CM pathogenesis. Their microarray analysis and confirmatory quantitative real-time polymerase chain reaction (PCR) and immunohistochemistry studies demonstrate that interferon (IFN)-regulated processes and neuronal apoptosis appear to be important in murine CM pathogenesis.…”

Molecular profiling of the gilthead sea bream (Sparus aurata L.) response to chronic exposure to the myxosporean parasite Enteromyxum leei

“…These apoptotic adjustments may also reflect the host's attempt to reduce immunopathology associated with unwanted activity of effector leukocytes and return to a status of cell/tissue homeostasis. An overcompensated host immune response which includes elevated apoptotic transcriptomic signals has been implicated in the immunopathology associated with infection with the malarial parasite Plasmodium falciparum (Lovegrove et al, 2007).…”