Temporal retinal transcriptome and systems biology analysis identifies key pathways and hub genes in Staphylococcus aureus endophthalmitis.

Deepa Rajamani,Ashok Kumar,Natasha Singh,Manoj K. Bhasin,Bruce G. Rottmann,Pawan Kumar Singh

doi:10.1038/srep21502

Abstract

Bacterial endophthalmitis remains a devastating inflammatory condition associated with permanent vision loss. Hence, assessing the host response in this disease may provide new targets for intervention. Using a mouse model of Staphylococcus aureus (SA) endophthalmitis and performing retinal transcriptome analysis, we discovered progressive changes in the expression of 1,234 genes. Gene ontology (GO) and pathway analyses revealed the major pathways impacted in endophthalmitis includes: metabolism, inflammatory/immune, antimicrobial, cell trafficking, and lipid biosynthesis. Among the immune/inflammation pathways, JAK/Stat and IL-17A signaling were the most significantly affected. Interactive network-based analyses identified 13 focus hub genes (IL-6, IL-1β, CXCL2, STAT3, NUPR1, Jun, CSF1, CYR61, CEBPB, IGF-1, EGFR1, SPP1, and TGM2) within these important pathways. The expression of hub genes confirmed by qRT-PCR, ELISA (IL-6, IL-1β, and CXCL2), and Western blot or immunostaining (CEBP, STAT3, NUPR1, and IGF1) showed strong correlation with transcriptome data. Since TLR2 plays an important role in SA endophthalmitis, counter regulation analysis of TLR2 ligand pretreated retina or the use of retinas from TLR2 knockout mice showed the down-regulation of inflammatory regulatory genes. Collectively, our study provides, for the first time, a comprehensive analysis of the transcriptomic response and identifies key pathways regulating retinal innate responses in staphylococcal endophthalmitis.

Highlights

Bacteria, such as Bacillus cereus[15,16,17,18] and S. aureus[3,19,20,21,22,23], results in severe intraocular inflammation, retina tissue damage, and loss of vision within 24 to 96 h post-infection, respectively
Principal component analysis (PCA) demonstrated that 12 h and 24 h post-infection samples are separated from controls and 3 h post-infection samples along Principal Component 1 (PC1), which accounts for 65.7% of the variance in transcriptome data
Endophthalmitis is an inflammatory disease caused by intraocular microbial infections, which result in blindness in some patients

Summary

Introduction

Bacteria, such as Bacillus cereus[15,16,17,18] and S. aureus[3,19,20,21,22,23], results in severe intraocular inflammation, retina tissue damage, and loss of vision within 24 to 96 h post-infection, respectively. Regardless of the nature of the pathogens, the common host response to an infection, including endophthalmitis, is the generation of inflammatory responses. The role of TLRs has been well-established in ocular infections[27], including bacterial endophthalmitis[19,20,28,29,30,31]. TLR2 ligand Pam3Cys (Pam3) pretreatment was found to reduce the inflammatory response and enhance the phagocytic activity of microglial cells following SA challenge[19]. How Pam[3] pretreatment modulates global retinal innate responses in bacterial endophthalmitis is not known. Considering the complex nature of host-pathogen interactions, we performed genome wide transcriptome analysis of SA-infected retinal tissue. We established a molecular signature of staphylococcal endophthalmitis, revealed several key pathways, and identified 13 master regulator genes whose expression is modulated by TLR2 signaling

Methods

Results

Conclusion