Aims To investigate the effect of succinic acid on the development of experimental autoimmune uveitis (EAU) and the underlying mechanism.
Methods Succinic acid was administrated intraperitoneally to evaluate its effects on immune response and EAU in mice. Intraocular inflammation was evaluated by histopathological scoring. Frequencies of Th1/Th17 cells were measured by flow cytometry. Concentrations of IFN-γ/IL-17A, neutrophil elastase (NE) and myeloperoxidase (MPO) were determined by enzyme-linked immunosorbent test. Infiltration of neutrophils and generation of neutrophil extracellular traps (NETs) within the eye were assessed by immumofluorescence. NETs formation in extracellular matrix was visualised by laser scanning confocal microscopy. Succinate receptor (SUCNR1) antagonist was used to investigate its effect on the generation of NETs.
Results Intraperitoneal injection of succinic acid exacerbated EAU severity as evidenced by severe histological changes in association with elevated frequencies of splenic Th1/Th17 cells, and upregulated levels of IFN-γ/IL-17A and NETs in plasma. In vitro experiments showed that succinic acid could promote the generation of NETs by neutrophils as shown by increased expression of NE and MPO.NETs could increase the frequencies of Th1/Th17 cells in CD4+ T cells and their expression of IFN-γ/IL-17A. In the experiment of receptor antagonism, the upregulatory effect of succinic acid on NETs could be significantly blocked by SUCNR1 antagonist.
Conclusions Succinic acid could worsen EAU induced by IRBP in mice. This effect was possibly mediated by its upregulation on NETs generation and frequencies of Th1/Th17 cells in affiliation with increased production of IFN-γ/IL-17A through succinic acid-SUCNR1 axis.
- Experimental – animal models
- Experimental – laboratory
Data availability statement
All data relevant to the study are included in the article or uploaded as online supplemental information. Not applicable.
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HL, HT and ZL contributed equally.
Contributors PY, HL and HT conceived and designed the study. HL, SP, ST and YZ performed all the experiments. HL, ZL and SP analysed the data. SP and QW contributed to FCM test and immunofluorescence. SP and ZL contributed to animal modeling. HL, HT and ZL wrote the manuscript. CZ and QC contributed to experimental equipment. PY and GS interpreted the data and revised the manuscript. PY is the guarantor.
Funding This study was supported by the National Natural Science Foundation Key Programme (81720108009), Natural Science Foundation Major International (Regional) Joint Research Project (81930023), Chongqing Outstanding Science Project (2019) (no grant number), Chongqing Chief Medical Scientist Project (2018)(no grant number), Chongqing Key Laboratory of Ophthalmology (CSTC, 2008CA5003), Chongqing Science and Technology Platform and Base Construction Programme (cstc2014pt-sy10002).
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.
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