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Stimulation of macrophage function by interphotoreceptor retinoid-binding protein: production of nitric oxide
1Department of Ophthalmology, Taejon St. Mary's Hospital, College of Medicine, Catholic University of Korea, Korea.
Abstract:
In this study, we investigated whether retinal soluble proteins, such as interphotoreceptor retinoid-binding protein(IRBP), 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 evaluated for nitric oxide production using the Griess reaction. IRBP induced significant, dose-dependent nitrite production in both RAW 264.7 and rat peritoneal macrophages. Induction of inducible nitric oxide synthase (iNOS) by retinal proteins was inhibited by the iNOS-specific inhibitor, aminoguanidine, and the tyrosine inhibitor, genistein. These results show that soluble retinal proteins significantly induce 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
Soluble retinal proteins, including interphotoreceptor retinoid-binding protein (IRBP), significantly induce nitric oxide production in macrophages. This finding suggests a potential role in inflammatory eye diseases like 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 in inflammation and tissue regulation.
- The role of retinal soluble proteins in modulating macrophage activity is not fully understood.
Purpose of the Study:
- To investigate the effect of retinal soluble proteins on nitric oxide production by macrophages.
- To determine if interphotoreceptor retinoid-binding protein (IRBP) induces nitric oxide synthesis.
- To explore the mechanisms underlying nitric oxide induction by retinal proteins.
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.
- Inhibition studies using aminoguanidine (iNOS inhibitor) and genistein (tyrosine inhibitor).
Main Results:
- Retinal soluble proteins, including IRBP, induced significant, dose-dependent nitrite production in macrophages.
- The induction of nitric oxide synthase (iNOS) by retinal proteins was confirmed through inhibition studies.
- These results demonstrate that soluble retinal proteins are potent stimulators of macrophage nitric oxide production.
Conclusions:
- Soluble retinal proteins, notably IRBP, effectively induce nitric oxide production in macrophages.
- This macrophage activation by retinal proteins may contribute to photoreceptor damage in conditions like uveitis.
- Further in vivo studies are warranted to elucidate the role of these proteins in inflammatory eye diseases.