AB0111 Monosodium Urate Crystals Promote an Oxidative State Which Induces Apoptosis in Human Synoviocytes

Background

The gout is the most common inflammatory arthropathy, is caused by a metabolic disorder in which monosodium urate crystals (MSU) are deposed in the joints and in particular soft tissues. Usually the models designed for the study of the gout focus on inflammatory process rather than the role of the oxidative/anti-oxidative system.

Objectives

The objective of this research was to evaluate the effect of the MSU crystals in the oxidative-antioxidant system to identify possible molecular mechanisms of oxidative stress in gout.

Methods

A primary cell culture of human synoviocytes were exposed to 75 μg/mL of MSU crystals for 24 hours, cell viability was evaluated as well as apoptosis and the oxidative stress (OS), trough the oxidation of proteins, generated by reactive oxygen species (O₂^–, H₂O₂) and nitrogen reactive species (ON^–). Additionally, the genetic expression was evaluated by qRT-PCR and the protein expression by Western Blot of p22^Phox, the hipoxia inducible factor (HIF-1α), the receptor for advanced glycation end products (RAGE), superoxide dismutase (SOD -1) and the glutathione peroxidase (GPX).

Results

The cell viability of the synoviocytes exposed to MSU crystals decreased a 30% (p<0.05) and the apoptosis increases in a 40% (p=0.01). The synoviocytes exposed to MSU crystals induced the production of H₂O₂ in 2.1106 (p<0.05) in comparison with the synoviocytes that were not exposed to MSU crystals. However, the production of O₂^– and ON^– had an increment of 0.5 times. The amount of total oxidative proteins were higher in synoviocytes exposed to MSU crystals. The genetic expression of p22^Phox and HIF-1α increased 0.5 times (p=0.0009 and p<0.05) in the synoviocytes exposed to MSU crystals. In the other hand, RAGE increased 0.8 times (p=0.0010) in comparison with the culture cells without MSU crystals. In the protein expression the amount of p22^Phox (p=0.0004) decreased, as well as a negative tendency of the amount of SOD-1 and GPX.

Conclusions

The induction of H₂O₂, O₂^– and ON^– originated a OS which promoted an apoptotic state as well as a decrement in cell viability of synoviocytes exposed to MSU crystals. Additionally, the identification of RAGE and HIF-1α in the molecular pathways that triggered the physiological findings previously described, is of high relevance for its possible participation of therapeutic targets that allow an action against the progression of this disease.

References

Martillo et al., 2014. The crystallization of monosodium urate. Curr Rheumatol Rep. 16: 400. DOI 10.1007/s11926-013-0400-9. Martinon et al., 2006. Gout associated uric acid crystals activate the NALP3 inflammasome. Nature. 440: 237-241. Malemud et al., 2012. Monosodium urate and tumor necrosis factor-α increase apoptosis in human chondrocyte cultures. Rheumatol Curr Res, 2:3.

Acknowledgements

The authors thanks Daniel Medina for his assistance with the technical work details and language advice.

Disclosure of Interest

None declared