ecent evidence (in the B6 background) for a role of MC in this model [51], which may be further explained by the model of arthritis induction and future experiments will be directed towards such studies, including using the CIA model in the MC-deficient mice. The strategy for these studies was to first determine which PND-1186 manufacturer fullerene derivatives inhibited human and mouse MC through arthritis�relevant stimulation. In addition, the ability of fullerene derivatives to inhibit synovial fibroblast cytokine production and osteoclast development were considered important prerequisites for predicting in vivo efficacy, as an amalgam of cell types govern the degree and severity of arthritis [19,54]. To this end, a panel of fullerene derivatives were tested for their ability to inhibit MC FcR-mediated responses [55]. A clear structure-activity relationship between fullerene derivatives and inhibitory function was not defined. However, in general, the fullerene derivatives that were most efficient at inhibiting MC mediator release had side chain moieties that induced maximum water solubility, a zeta potential between 37 and -146 mV, and particle sizes between 50 to 200 nM. Of these, both TGA and ALM have been shown previously to inhibit IgE-mediated degranulation and cytokine production [25] and in response to other non-IgE-mediated secretagogues [46]. The TGA (tetra-glycolic 
acid) is a C70 series with four carboxyl groups, which confers water solubility. It is postulated that the mechanism by which TGA exerts its effect via an interaction between the carboxyl groups and the electrons on the fullerene cage. To examine this point, a similar fullerene derivative that presented a triethylene glycol spacer between the carboxyl groups and the cage was prepared. TEG-TGA (-25 mV zeta potential; 94 nM particle size) did not block MC mediator release nor did it interfere with cytokine release (not shown). This result is consistent with the hypothesis that proximity of the carboxyl groups to the cage is necessary for activity. The mitochondrial electron transport is the machinery that orchestrates one of the most fundamental of chemical processes; the generation of cellular energy from oxygen resulting in the fuel that supports all eukaryotic life. However, it is a highly sensitive process and, unbalanced, leads to the generation of free radicals or ROS which have been linked as a mechanism underlying many chronic human diseases including MC activation and inflammatory arthritis [56,57]. ALM is a mitochondria- targeting fullerene derivative that has been previously shown to home to mitochondria and inhibit inflammation [27,28]. ALM was designed to accumulate in the internal mitochondrial membrane bilayers positioned to neutralize superoxide molecules, reactive lipid radicals, and radicals that have formed on transmembrane proteins 21593435 at the site where they are generated. Subsequently, this is predicted to impact diseases whose pathologies stem from radical injury. To this end both fullerene derivatives significantly block ROS production and mitochondrial membrane potential. While it has been shown previously that human MC degranulation in response to FcRI and Fc-signaling involves ROS [58,59], it is not clear if blocking ROS directly blocks degranulation and cytokine production. Results here suggest that blocking ROS using ALM and TGA in response to IC (an FcRIIA-dependent stimuli [35]) parallels inhibition of mediator release. This is in line with previous work sugge
