Integrative metabolomics and transcriptomics analysis reveals a Krebs cycle metabolite “itaconate” in promoting inflammation resolution in bacterial endophthalmitis
Singh S, Singh PK, Giri S, and Kumar A. Integrative metabolomics and transcriptomics analysis reveals a Krebs cycle metabolite “itaconate” in promoting inflammation resolution in bacterial endophthalmitis. Invest Ophthalmol Vis Sci 2019; 60(9).
Invest Ophthalmol Vis Sci
Purpose: While recent advances in “omics” technologies have been dramatic, extracting biological insight from complex me taboolic and trans criptom e profiles re mains a cha llenge. This site uses c ookies. By co ntinuing to use ur web site, you are ag reeing t o our priva y policy. We integrated these two high throughput screening approaches, to determine key signaling pathways perturbed in bacterial endophthalmitis. This led to the identification of an endogenous metabolite “itaconate” which is altered in this disease. Hence, this study is designed to determine the role of itaconate in bacterial endophthalmitis. Methods: Staphylococcal endophthalmitis was induced in, C57BL/6 or Irg1 -/-mice. The therapeutic efficacy of itaconate was evaluated by intravitreal injections of dimethyl itaconate (DMI) or 4-octyl itaconate (OI) in infected eyes. In vitro studies were performed using human Müller glia and mouse bone marrow-derived macrophages (BMDMs) and challenging them with S. aureus in the presence or absence of DMI or OI. The proinflammatory cytokines were measured by qRT-PCR and ELISA. Western blot was performed to assess the activation of itaconate-mediated signaling pathways. Results: Metabolomics analysis revealed a time-dependent increase in the production of itaconate in S. aureus-infected retina. This coincided with induced expression of Irg1 as revealed by transcriptomics approach. In comparison with C57BL/6, Irg1 -/- mice exhibited the exacerbated endophthalmitis with increased inflammation and retinal tissue damage. Administration of DMI or OI significantly reduced intraocular inflammation resulting in preserved retinal architecture and function. Similarly, itaconate attenuated bacterial-induced inflammation in Müller glia and mouse BMDMs, potentially by activating antioxidant pathways (NRF2, HO-1, and Keap1). Activation of this signaling cascade was also observed in retina in vivo. Most importantly, co-administration of itaconate with vancomycin at sub-MIC levels resulted in ameliorated disease severity. Conclusions: Our findings demonstrate retinal metabolism is altered in endophthalmitis, leading to the production of itaconate, which exerts anti-inflammatory actions to limit tissue damage by promoting inflammation resolution. Moreover, itaconate can be used as an adjunct anti-inflammatory therapy along with antibiotics to improve visual outcome in endophthalmitis.