Analysis of autophagy and inflammasome regulation in neuronal cells and monocytes infected with Chlamydia Pneumoniae: Implications for Alzheimer’s disease

Philadelphia Campus

Objectives: Our laboratory has been studying the role of infection with the obligate intracellular bacterium Chlamydia pneumoniae in sporadic late-onset Alzheimer disease (LOAD). This infection may be a trigger for the pathology observed in LOAD as a function of initiating changes in gene regulation following entry of the organism into the brain. As such, we are analyzing how this infection can promote changes in autophagy and inflammasome gene regulation as both have been shown to be altered in LOAD. Methods: Human SKNMC neuronal cells and THP1 monocytes were infected in vitro for 24-72 hrs with a laboratory strain of Chlamydia pneumoniae followed by RNA extraction, cDNA synthesis and analysis using Real-Time PCR microarrays for autophagy and inflammasome genes. Results: Gene expression for autophagy and inflammasome pathways was altered dramatically following infection. Genes encoding for co-regulation of autophagy, apoptosis, and the cell cycle that were significantly changed included: BCL2L1, FAS, PIK3CG, APP, and TP53. In addition, ATG3, and GABARAP, genes encoding for protein transport & ubiquitination and autophagic vacuole formation were significantly deregulated. Of the inflammasome genes, 4 NOD-like receptor genes were significantly up-regulated. IL-1beta, AIM2, CCL2, and CCL7 genes were all dramatically up-regulated in monocytes during the 72 hrs of infection. Conclusions: Our data suggest that Chlamydia pneumoniae-infected human SKNMC neuronal cells and THP1 monocytes exhibit specific changes in gene regulation for both autophagy and inflammasome pathways. These gene changes appear to correlate with pathologic changes previously reported in AD and further support the contention that infection with Chlamydia pneumoniae plays a role in LOAD pathogenesis.