Transcriptomics of human pleural mesothelial cell line Met-5A infected with Streptococcus pneumoniae

The objectives of the study were to examine the gene expression profile of human pleural mesothelial cells following infection with Streptococcus pneumoniae. The abstract is as follows: Streptococcus pneumoniae (Spn) is a major causative organism of empyema, an inflammatory condition occurring in the pleural sac. In this study, we used human and Spn cDNA microarrays to characterize the transcriptional responses occurring during initial contact between Spn and a human pleural mesothelial cell line (PMC) in vitro. Using stringent filtering criteria, 42 and 23 Spn genes were up-and down-regulated respectively. In particular, genes encoding factors potentially involved in metabolic processes and Spn adherence to eukaryotic cells were up-regulated e.g. glnQ, glnA, aliA, PsaB, LytB and nox. After Spn initial contact, 870 human genes were differentially regulated and the largest numbers of significant gene expression changes were found in canonical pathways for eukaryotic initiation factor 2 signaling (60 genes out of 171), oxidative phosphorylation (32/103), mitochondrial dysfunction (37/164), eIF4 and p70S6K signaling (28/142), mTOR signaling (27/182), NRF2-mediated oxidative stress response (20/177), epithelial adherens junction remodeling (11/66) and ubiquitination (22/254). The cellular response appeared to be directed towards host cell survival and defense. Spn did not activate NF-kB or phosphorylate p38 MAPK or induce cytokine production. Moreover, Spn infection of TNF-α pre-stimulated PMC inhibited production of IL-6 and IL-8 secretion by >50% (p<0.01). In summary, his descriptive study provides datasets and a platform for examining further the molecular mechanisms underlying the pathogenesis of empyema. Met-5A cells were infected with strain D39 at a MOI of 200 for 2h; RNA was extracted from 5 independent experiments and used for microarray analysis as follows: Analysis of gene expression profile of human Met-5A cells. Protocol designi) Human Microarrays: ii) Synthesis and purification of human cDNA and in-vitro transcription to yield amino-allyl RNA (aRNA). iii) Microarray slide hybridisation and data analysis.