Fig. 4

Epithelial glutathione-associated genes are activated in response to pneumococcal ROS. a We clustered epithelial working libraries exposed to wild-type pneumococci and found a cluster of 242 co-expressed genes showing sustained upregulation (p < 0.05, FC > 2) at 60 mpi compared with 30 mpi. Gene ontology (GO) analysis showed that “oxidation reduction” was enriched in 17 genes. b GPX2, encoding glutathione peroxidase-2, is one of the enriched genes. Eight genes are associated with glutathione (GSH), an important antioxidant. The main glutathione-associated processes are biosynthesis of glutathione and detoxification of ROS assisted by ligand and glutathione recycling. c Between 30 and 60 mpi, expression of GCLC increased 2.7 ± 1.1 times and of GCLM 2.3 ± 1.2 times. Expression of GPX2, the main detoxification gene, increased 18.1 ± 1.3 times while that of the gene encoding its ligand, MGST2, increased 3.1 ± 1.2 times. Genes involved in the recycling of glutathione were activated: IDH1, 4.5 ± 1.2; IDH2, 2.3 ± 1.2; PGD, 2.9 ± 1.2; and G6PD, 6.5 ± 1.2. d We validated GPX2, GSR, IDH1, and PGD expression using qRT-PCR. Epithelial incubation with pneumococcal supernatant showed similar upregulation of glutathione-associated genes. Addition of resveratrol (100 μM) into the model diminished the upregulation (FC < 2) altogether