Transcriptomic and Histological Analysis of Exacerbated Immune Response in Multidrug-Resistant Pseudomonas aeruginosa in a Murine Model of Endophthalmitis

RNA-Sequencing Reveals the Modulation of the NLRP3 Inflammasome by miR-223-3p in Extracellular Vesicles in Bacterial Endophthalmitis

Purpose

Extracellular vesicles (EVs) are critical mediators of cell-cell communication via transfer of molecular cargo including miRNAs and regulate transcription in various physiological and pathological conditions. This study aimed to investigate the role of EV-derived-microRNAs (EV-miRNAs) in bacterial endophthalmitis, focusing on their regulatory impact on inflammation and host immune responses.

Methods

C57BL/6 mice were infected with Pseudomonas aeruginosa (P. aeruginosa) and Staphylococcus aureus (S. aureus) to induce endophthalmitis. EVs were isolated and characterized followed by miRNA profiling to identify differentially expressed miRNAs. The miRNet platform was used to elucidate potential interactions between exosomal miRNA and retinal mRNA, followed by in vivo and in vitro validation of key miRNAs and their target genes. Additionally, EVs were extracted from vitreous fluid samples of patients with endophthalmitis, and miR-223-3p and NLRP3 expressions were assessed by qPCR.

Results

Bacterial endophthalmitis led to pronounced neutrophil infiltration in the retina of mice. The miRNA profiling identified 651 differentially expressed miRNAs in P. aeruginosa and 29 in S. aureus, with 10 miRNAs shared between both infections. The miR-223-3p, miR-467a-3p, and miR-467d-3p emerged as major regulators of inflammatory pathways, targeting genes such as NLRP3, CXCL5, and IKKα. In patient vitreous samples, miR-223-3p was upregulated in culture-positive samples, correlating with reduced NLRP3 expression. The miRNAs, particularly miR-223-3p, play a critical role in modulating the immune response in bacterial endophthalmitis, largely through the regulation of the NLRP3 inflammasome.

Conclusions

The findings suggest that miR-223-3p could serve as biomarkers in culture-negative cases and therapeutic targets for managing inflammation in bacterial endophthalmitis, potentially guiding treatments aimed at preserving retinal integrity.

Age-Associated Alterations in the Metabolome of Human Vitreous in Bacterial Endophthalmitis

Purpose

Endophthalmitis is a severe inflammatory condition due to intraocular infections that often leads to irreversible blindness. This study aimed to understand the age-dependent metabolic alterations in the vitreous of patients with bacterial endophthalmitis.

Methods

The study included the vitreous metabolome of patients with bacterial endophthalmitis (group 1, n = 15) and uninfected controls (group 2, n = 14), which were further stratified into three groups according to their age: young (0-30 years), middle (31-60 years), and elderly (>60 years). Vitreous samples were subjected to untargeted metabolomic analysis using high-resolution mass spectrometry (HRMS)m and acquired mass spectrometry data were analyzed using MetaboAnalyst 6.0. The altered metabolites with log2FC of ≥2/≤2, P < 0.05, and variable importance in projection > 1 were considered significant.

Results

In a total of 109 endogenous metabolites identified, young and elderly patients with endophthalmitis showed 52 (elevated, 25; reduced, 27; P < 0.05) and 27 (elevated, 19; reduced, 8; P < 0.05) significantly altered metabolites, respectively, compared to their age-matched controls. Additionally, 27 metabolites were differentially expressed in young patients with endophthalmitis compared to the older group. The crucial metabolic pathways dysregulated in the older infected population were de novo purine synthesis and salvage, carnitine, polyamine (spermidine), lipids (prostaglandins), and amino acid (taurine, methionine, histidine) which could possibly be attributed to the increased disease severity and inflammation observed in a clinical setting.

Conclusions

Despite the erratic metabolic changes observed in the younger group infected with endophthalmitis when compared to age-matched controls, dysregulation in the specific pathways such as purine, carnitine, arachidonic acid, and polyamine metabolism could possibly alter the immunological exacerbation observed in the older group.

Unveiling the Innate and Adaptive Immunity Interplay: Global Transcriptomic Profiling of the Host Immune Response in Candida albicans Endophthalmitis in a Murine Model

Intraocular fungal infection poses a significant clinical challenge characterized by chronic inflammation along with vision impairment. Understanding the host defense pathways involved in fungal endophthalmitis will play a pivotal role in identifying adjuvant immunotherapy. Clinical isolates of Candida albicans (15,000 CFU/μL) were intravitreally injected in C57BL/6 mice followed by enucleation at 24 and 72 h postinfection. Histopathological analysis was performed to evaluate the retinal changes and the disease severity. RNA-seq analysis was conducted on homogenized eyeballs to assess the relevant gene profiles and their differentially expressed genes (DEGs). Pathway enrichment analysis was performed to further annotate the functions of the DEGs. Histopathological analysis demonstrated a higher disease severity with increased inflammatory cells at 72 hpi and transcriptome analysis revealed 27,717 DEGs, of which 1493 were significant (adj p value ≤0.05, FC ≥ 1.5). Among these, 924 were upregulated, and 569 were downregulated. Majority of the upregulated genes were associated with the inflammatory/host immune response and signal transduction and enriched in the T-cell signaling pathway, natural killer cell-mediated cytotoxicity, C-type receptor signaling pathway, and NOD-like receptor signaling pathway. Furthermore, inflammation-associated genes such as T-cell surface glycoprotein CD3, cathelicidin antimicrobial peptide, and lymphocyte cell-specific protein tyrosine kinase were enriched, while pathways such as MAPK, cAMP, and metabolic pathways were downregulated. Regulating the T-cell influx could be a potential strategy to modulate excessive inflammation in the retina and could potentially aid in better vision recovery in fungal endophthalmitis.

Global Transcriptomic Profiling of Innate and Adaptive Immunity During Aspergillus flavus Endophthalmitis in a Murine Model

Purpose

Fungal endophthalmitis is characterized by chronic inflammation leading to the partial or complete vision loss. Herein, we analyzed the transcriptomic landscape of Aspergillus flavus (A. flavus) endophthalmitis in C57BL/6 mice to understand the host-pathogen interactions.

Methods

Endophthalmitis was induced by intravitreal injection of A. flavus spores in C57BL/6 mice and monitored for disease progression up to 72 hours. The enucleated eyeballs were subjected to histopathological analysis and mRNA sequencing using the Illumina Nextseq 2000. Pathway enrichment analysis was performed to further annotate the functions of differentially expressed genes (DEGs) and validation of cytokines was performed in vitreous of patients with fungal endophthalmitis using multiplex ELISA.

Results

Transcriptomic landscape of A. flavus endophthalmitis revealed upregulated T-cell receptor signaling, PI3K-AKT, MAPK, NF-κB, JAK-STAT, and NOD like receptor signaling pathways. We observed significant increase in the T-cells during infection especially at 72 hours infection along with elevated expression levels of IL-6, IL-10, IL-12, IL-18, IL-19, IL-23, CCR3, and CCR7. Furthermore, host-immune response associated genes, such as T-cell interacting activating receptor, TNF receptor-associated factor 1, TLR1, TLR9, and bradykinin receptor beta 1, were enriched. Histopathological assessment validated the significant increase in inflammatory cells, especially T-cells at 72 hours post-infection along with increased disruption in the retinal architecture. Additionally, IL-6, IL-8, IL-17, TNF-α, and IL-1β were also significantly elevated, whereas IL-10 was downregulated in vitreous of patients with Aspergillus endophthalmitis.

Conclusions

Regulating T-cell influx could be a potential strategy to modulate the excessive inflammation in the retina and potentially aid in better vision recovery in fungal endophthalmitis.

Temporal Transcriptome Analysis Suggests Modulation of Key Pathways and Hub Genes in a Mice Model of Multi-Drug Resistant (MDR) Pseudomonas aeruginosa Endophthalmitis

PURPOSE

Increasing incidence of multidrug-resistant Pseudomonas aeruginosa (MDR-PA) causing endophthalmitis challenges our ability to manage this vision-threatening condition. In this study, temporal dynamics of immune response in a mouse model of MDR-PA endophthalmitis was investigated by whole transcriptome analysis.

METHODS

C57BL/6 mice were infected with MDR-PA and antibiotic susceptible (S-PA) clinical strains and disease severity were monitored at 6 and 24-h postinfection (p.i), following which eyeballs were enucleated. Microarray analysis was performed using SuperPrint G3 Mouse Gene Expression v2 chip and the differential gene expression analysis was performed with limma package in R (v4.0.0.)/Bioconductor (v3.11).

RESULTS

Histopathological analysis revealed a significant difference in retinal architecture and vitreous infiltrates at 6 and 24 h. In comparison to S-PA, MDR-PA revealed altered expression of 923 genes at 6 h and 2220 genes at 24 h. Further, 23 and 76% of these altered genes and its downstream interacting proteins showed time-specific expression (6 and 24 h respectively), indicating their association with disease progression. At 24 hours, MDR-PA induced endophthalmitis showed aberrant immune response with the enrichment inflammasome signalling, dysregulated ubiquitination, complement cascade, MMPs NF-κβ and IL-1 signalling.

CONCLUSION

The rapid development of transcriptional differences between the two-time points reveals that distinct genes contribute to disease severity. The results from this study highlighted a link between innate and adaptive immune responses and provided novel insights in the pathogenesis of MDR-PA endophthalmitis by extending the number of molecular determinants and functional pathways that underpin host-associated damage.

Proteome profiling of Extracellular Vesicles in Pseudomonas aeruginosa endophthalmitis: Prognostic and therapeutic significance in a mouse model

Endophthalmitis is a sight-threatening infection and a serious consequence of complications during intraocular surgery or penetrating injury of which Pseudomonas aeruginosa is an important etiology. Extracellular vesicles (EVs) have evolved as a promising entity for developing diagnostic and therapeutic biomarkers due to their involvement in intracellular communication and pathogenesis of diseases. We aimed to characterise the protein cargo of extracellular vesicles, isolated from a murine (C57BL/6) model of P. aeruginosa endophthalmitis by LC-MS/MS at 24 h post infection (p.i). EVs were extracted by ultracentrifugation, characterized by Dynamic Light Scattering (DLS) and western blotting with tetraspannin markers, CD9 and CD81 and quantified by the ExoCet quantification kit. Multiplex ELISA was performed to estimate the levels of TNF-α, IL-6, IFN-γ and IL-1β. Proteomic analysis identified 2010 proteins (FDR ≤0.01) in EVs from infected mice eyes, of which 137 were differentially expressed (P-value ≤ 0.05). A total of 101 proteins were upregulated and 36 were downregulated. Additionally, 43 proteins were exclusive to infection set. KEGG and Gene Ontology revealed, Focal adhesion, Phagosome pathway, Complement cascade and IL-17 signalling pathway are crucial upregulated pathways involving proteins such as Tenascin, caveolin 1, caveolin 2, glutamine synthetase, microtubule-associated protein, C1, C8 and IL-17. Tenascin and caveolins are known to suppress anti-inflammatory cytokines further exacerbating the disease. The result of this study provides insight into the global extracellular vesicle proteome of P. aeruginosa endophthalmitis with their functional correlation and distinctive pattern of expression and tenascin, caveolin 1 and caveolin 2 are attractive biomarkers for P. aeruginosa endophthalmitis.