Abstract
Purpose :
Recently, we performed global metabolomics and transcriptomic analyses to determine key signaling pathways perturbed during experimental Staphylococcus (S) aureus endophthalmitis. The integrated data approach revealed increased glycolysis in infected mouse retina and bone marrow-derived macrophages (BMDMs). As pyruvate kinase isozyme type M2 (PKM2) is a key regulator of glycolysis and oxidative phosphorylation, the aim of this study is to investigate the role of PKM2 in bacterial endophthalmitis.
Methods :
Bacterial endophthalmitis was induced in C57BL/6 mice by intravitreal (IVT) injection of S. aureus (SA) strain, RN6390. The physiological roles of PKM2 isoforms were determined by using its activator ML265 which promotes the tetrameric form of PKM2. ML265 is injected in the mouse eye at 6h post-SA infection. Disease progression was evaluated by a daily eye exam, ERG analysis, and bacterial burden and inflammatory cytokines assessment. Mechanistic studies were performed using cultured human retinal Müller glia, BMDMs, and neutrophils by challenging them with S. aureus in the presence or absence of ML265.
Results :
Our temporal transcriptomic and metabolomics analyses revealed a time-dependent increase in genes and metabolites regulating glycolysis, respectively. Interestingly, intravitreal administration of PKM2 activator (ML265) resulted in diminished the severity of endophthalmitis as evidenced by decreased corneal haze, opacity, and hypopyon. The ML265-treated mice eyes exhibited reduced bacterial burden, neutrophil infiltration, and inflammatory mediators resulting in preserved retinal function. Moreover, PKM2 activator treatment in BMDMs, neutrophils, and Müller glia showed attenuated HIF-1α expression and inflammatory cytokines milieu.
Conclusions :
Our study demonstrates that PKM2-mediated glycolytic reprogramming influences the innate immune response and its small molecule activator (ML265), negatively regulates the inflammation, and ameliorates the endophthalmitis severity. Therefore, modulation of the glycolytic enzyme “PKM2” could be used as an anti-inflammatory therapy to improve visual outcomes in bacterial endophthalmitis.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.