Mechanisms of joint destruction in rheumatoid arthritis

Oral Escherichia coli colonization factor antigen I fimbriae ameliorate arthritis via IL-35, not IL-27

A Salmonella therapeutic expressing enterotoxigenic Escherichia coli colonization factor Ag I (CFA/I) fimbriae protects against collagen-induced arthritis (CIA) by eliciting two regulatory T cell (Treg) subsets: TGF-β-producing Foxp3(-)CD39(+)CD4(+) T cells and IL-10-producing Foxp3(+)CD39(+)CD4(+) T cells. However, it is unclear whether CFA/I fimbriae alone are protective and whether other regulatory cytokines are involved, especially in the context for the EBI3-sharing cytokines, Treg-derived IL-35 and APC-derived IL-27, both capable of suppressing Th17 cells and regulating autoimmune diseases. Subsequent evaluation revealed that a single oral dose of purified, soluble CFA/I fimbriae protected against CIA as effectively as did Salmonella-CFA/I and found that Foxp3(+)CD39(+)CD4(+) T cells were the source of secreted IL-35, whereas IL-27 production by CD11c(+) cells was inhibited. Inquiring into their relevance, CFA/I fimbriae-treated IL-27R-deficient (WSX-1(-/-)) mice were equally protected against CIA as were wild-type mice, suggesting a limited role for IL-27. In contrast, CFA/I fimbriae-mediated protection was abated in EBI3(-/-) mice, accompanied by the loss of TGF-β- and IL-10-producing Tregs. Adoptive transfer of C57BL/6 CD39(+)CD4(+) T cells to EBI3(-/-) mice with concurrent CFA/I plus IL-35 treatment effectively stimulated Tregs suppressing proinflammatory collagen II-specific Th cells. In contrast, recipients cotransferred with C57BL/6 and EBI3(-/-) CD39(+)CD4(+) T cells and treated with CFA/I plus IL-35 were not protected, implicating the importance of endogenous IL-35 for conferring CFA/I-mediated protection. Thus, CFA/I fimbriae stimulate IL-35 required for the coinduction of TGF-β and IL-10.

In vitro evaluation of orthopedic composite cytotoxicity: assessing the potential for postsurgical production of hydroxyl radicals

Hydroxyl radical (*OH)-induced inflammation is a primary mode for in vivo cytotoxicity. A legitimate concern is whether particulate wear debris from orthopedic composites can stimulate inflammation via ferrous ion (Fe2+)-mediated production of *OH. The purpose of this research was to utilize electron paramagnetic resonance (EPR) spin trapping in investigating and comparing the potential for postsurgical cytotoxicity induced specifically by *OH in the presence of two composites: Simplex P and the novel, hybrid, CORTOSS. Cytotoxicity is evaluated based on the composites competitively chelating catalytic Fe2+ or readily reducing ferric ions (Fe3+), in facilitating the Fenton reaction (FR). *OH that are produced were then validated by a radical scavenger to confirm a genuine radical signal and mechanism. Spin adduct peak areas decreased in the presence of CORTOSS as opposed to increasing in the presence of Simplex P, evaluated against their respective controls. A plausible theory elucidating this finding is that CORTOSS may sequester the Fe form, by virtue of its monomers. Principally, direct comparison of composites indicated that Simplex P had greater tendency to produce *OH, yielding 25.6 and 48.7% greater spin adduct peak areas when chelated and non-chelated Fe2+ are used, respectively. Moreover, the rate of FR accelerated when chelated Fe2+ was used, leading to the formation of a ternary complex with the composites. This was more prominent in Simplex P, as coordination of chelated Fe2+ occurs on its surface via an electrostatic attraction to allow a seventh coordination site for ligand exchange in the ternary complex, stabilized by Ba2+. Conversely, the silica found in CORTOSS possesses radical quenching abilities that deactivate generated *OH in impeding the efficiency of FR. Neither composite demonstrated a capacity to readily reduce Fe3+ to the relevant Fe2+, as validated by a non-radical pathway. Instead, the artificial spin adduct signal attained when employing chelated Fe3+ was due to the nucleophilic addition of water onto DMPO. Simplex P may also serve as a template for surface catalysis of the nucleophilic addition of water onto DMPO involving chelated Fe3+. CORTOSS is thought not to induce cytotoxicity, whereas the propensity of Simplex P in promoting Fenton chemistry is a serious issue that must be addressed.

Electron paramagnetic resonance analyses of surface radical chemistries of γ-sterilized orthopedic materials: Implications pointing to cytotoxicity via wear debris-induced inflammation

In this research, electron paramagnetic resonance (EPR) spin-trapping was utilized to determine if surface radical chemistries occur for gamma (gamma)-sterilized orthopedic materials-ultra-high molecular weight polyethylene (UHMWPE) and the novel, hybrid, diurethane dimethacrylate (DUDMA)-based RHAKOSS. The materials' ability to competitively chelate catalytic ferrous ions (Fe(2+)) or readily reduce ferric ions (Fe(3+)), and hydrogen peroxide (H(2)O(2)) directly, in facilitating the Fenton reaction (FR), is indicative of cytotoxicity. Validations with a radical scavenger aids to confirm a radical mechanism. In conjunction, materials were thermally annealed and characterized by attenuated total reflectance-Fourier-transform infrared (ATR-FTIR) spectroscopy in order to explore accelerated oxidative degradation induced by residual radicals evolving from gamma-sterilization. Particularly, there was a significant decrease in spin-adduct peak areas obtained from the reduction of H(2)O(2) in the presence of RHAKOSS or UHMWPE, evaluated against their respective controls. Additionally, chelated Fe(2+) accelerated the rate of FR. This phenomenon suggests that the materials are not better chelators than the Fe-activating chelator, edta. Neither material had the propensity to readily reduce Fe(3+) to the relevant Fe(2+), as certified by a nonradical mechanism. Alternatively, the false spin-adduct signal acquired when chelated Fe(3+) is employed arises via the nucleophilic addition of water onto the DMPO spin trap. Residual radicals in UHMWPE did not recombine/terminate following thermal annealing in an inert atmosphere. The radicals in RHAKOSS, however, did recombine under mild heating in an oxidizing or inert atmosphere. Both materials displayed quenching of ( )OH; however, for UHMWPE, this mechanism was jointly accountable for its accelerated degradation, evidenced by ATR-FTIR. Quenching of ( )OH by the silica found in RHAKOSS manifested in a competing effect that counterbalanced the observed FR. Implanted RHAKOSS is not likely to promote cytotoxicity and should not degrade, but the damaging effect of gamma sterilization on UHMWPE is a serious dilemma confronting its long-term durability and biocompatibility.