Abstract
Purpose :
Increasing incidences of multidrug-resistant bacteria in endophthalmitis threaten our ability to treat and manage this condition. Host immunity is an important, but often-overlooked factor in the clearance of drug-resistant infections and little information is available on inflammation induced by resistant bacteria. In this study, we compared the immune responses of susceptible and multidrug-resistant (MDR) strains of Pseudomonas aeruginosa isolated from patients with endophthalmitis in microglial cells
Methods :
Human microglial cells (CHME-3) were exposed to susceptible and MDR P. aeruginosa strains for different time points and analyzed for expression of TLRs, MMPs, inflammatory cytokines and chemokines by real-time quantitative PCR (RT-qPCR). Data are expressed as the mean ratio of cytokine over housekeeping gene (b-actin) expression pooled from three independent experiments. The mRNA expression was confirmed by ELISA and/or fluorescence microscopy. STRING analysis was used to assess the involved biological pathways of the altered cytokines.
Results :
Assessment of growth dynamics revealed higher bacterial counts (log CFU/mL) in the MDR strain of P. aeruginosa compared with the susceptible strain, being most significant at 12 h (p = 0.008). In the MDR strain challenged microglial cells, there was a time-dependent increased expression (p <0.05) of IL-6, TNF-α, IFN-γ, MMP-9, TLR-4, TLR-5, and TLR-9 compared to cells inoculated with the susceptible strain of P. aeruginosa. Most strikingly, significantly upregulated expression was observed with IL-10 (0.004), IL-8 (p=0.0006), IL-1β (p=0.02) and GM-CSF (p=0.0006) in cells infected with the resistant strain. The increased expression of TLR-4, IL-1β, and IFN-γ was confirmed by immunohistochemical staining while the protein expression of IL-10, IL-6, IL-8, GM-CSF, and MMP-9 was confirmed by ELISA. String analysis revealed that microglia initiates a defense response to P. aeruginosa through the inflammatory and cytokine-mediated signaling pathway thus playing an important role in the etiopathogenesis of endophthalmitis.
Conclusions :
These findings highlight that IL-10, IL-8, IL-1β, and GM-CSF play a critical role in MDR P. aeruginosa infection in microglial cells. These differentially expressed genes may serve as therapeutic and prognostic targets in endophthalmitis.
This is a 2020 ARVO Annual Meeting abstract.