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Stimulation of macrophage function by S-antigen: production of nitric oxide
1Department of Ophthalmology, Taejon St. Mary's Hospital, College of Medicine, Catholic University of Korea, Seoul, Korea.
Abstract:
In this study, we investigated whether retinal soluble proteins, such as S-antigen, play a role in the induction of nitric oxide by macrophages in vitro. Cells from the murine macrophage cell line RAW 264.7 and rat and rabbit peritoneal macrophages were incubated in the presence of retinal soluble protein. The nitrite level in the cultured supernatant was measured to determine nitric oxide production using the Griess reaction. S-antigen induced significant, dose-dependent nitrite production in both RAW 264.7 and rat peritoneal macrophages. The induction of inducible nitric oxide synthase by retinal protein was inhibited by the iNOS-specific inhibitor, aminoguanidine and the tyrosine inhibitor, genistein. These results show that soluble retinal protein significantly induces nitric acid production by macrophages. Increased production of reactive oxygen species by macrophages in the presence of this soluble retinal protein in vivo may accelerate photoreceptor degeneration in uveitis.
Insights
Retinal soluble proteins, like S-antigen, significantly increase nitric oxide production by macrophages. This finding suggests a potential mechanism for photoreceptor damage in uveitis.
Area of Science:
- Immunology
- Ophthalmology
- Cell Biology
Background:
- Macrophages play a crucial role in immune responses within the eye.
- Nitric oxide (NO) is a signaling molecule with diverse functions, including immune modulation.
- Retinal soluble proteins, such as S-antigen, are implicated in autoimmune eye diseases like uveitis.
Purpose of the Study:
- To investigate the role of retinal soluble proteins in nitric oxide (NO) production by macrophages.
- To determine if S-antigen can induce NO synthesis in macrophage cell lines and primary cultures.
- To explore the signaling pathways involved in retinal protein-induced NO production.
Main Methods:
- Incubation of macrophage cell lines (RAW 264.7) and primary macrophages (rat, rabbit) with retinal soluble proteins.
- Quantification of nitric oxide production via the Griess reaction to measure nitrite levels.
- Assessment of inducible nitric oxide synthase (iNOS) pathway involvement using specific inhibitors (aminoguanidine, genistein).
Main Results:
- Retinal soluble proteins, including S-antigen, induced significant, dose-dependent nitrite production in macrophages.
- The induction of NO production was observed in both murine (RAW 264.7) and rat peritoneal macrophages.
- Inhibition studies confirmed the involvement of inducible nitric oxide synthase (iNOS) in this process.
Conclusions:
- Soluble retinal proteins, particularly S-antigen, are potent inducers of nitric oxide production by macrophages.
- This macrophage activation by retinal proteins may contribute to ocular inflammation and photoreceptor damage in uveitis.
- Further in vivo studies are warranted to elucidate the role of reactive oxygen species in this context.