To further address the mechanism of Didox

To further address the mechanism of Didox’s suppressive effects on mast cell activation, FceRI receptor α-mangostin and downstream transcription factor induction were assessed. We found that Didox had no effect on FceRI surface expression, and thus concluded that Didox effects must be occurring downstream of receptor activation. The transcription factors NFκB and AP-1 have previously been shown to be critical for FceRI-mediated cytokine induction [31], [33], [52]. Lee and Elford have previously shown Didox downregulates NFκB activation in a T-cell model of HIV infection [53], [54]. We found that Didox antagonized the FceRI-induced activity of both transcription factors, confirming and extending this previous report. Because NFκB and AP-1 can be induced by reactive oxygen species [55], [56] and Didox suppressed measures of oxidative stress, the antioxidant effects of Didox are a likely mechanism by which Didox suppresses transcription factor activity. Interestingly, increased antioxidant capacity and suppression of NFκB and AP-1 transcription suggest one explanation for the suppression of inflammatory cytokines, however, our data also showed that Didox is selectively suppressive. We found that Didox has no effect on IgE-mediated MCP-1 expression while studying BMMC from different genetic backgrounds and in peritoneal mast cells. While NFκB- and AP-1-dependent transcription have been linked to production of inflammatory cytokines and chemokines, including MCP-1 [57], [58], [59], these results suggest that MCP-1 induction is unique among IgE-induced cytokines. In fact, Metzger’s group similarly reported that MCP-1 regulation was unusual in mast cells. While most IgE-induced factors are acutely dependent upon continuous signaling from aggregated receptors, MCP-1 secretion is not [60]. They postulated that MCP-1 may be responsive to weak, intermittent calcium fluxes, which are capable of activating NFκB [61]. Since Didox did not completely abrogate NFκB or AP-1 activity, one possible explanation is that MCP-1 transcription requires a lower threshold of NFκB or AP-1 function. Alternatively, additional transcription factors or post-transcriptional modifications could yield redundant control of MCP-1 secretion, giving resistance to NFκB and AP-1 inhibition. This possibility is supported by the demonstration that MCP-1 expression is regulated by p53 in human keratinocytes [62]. On balance, the inability of Didox to suppress MCP-1 secretion is in keeping with other findings that MCP-1 regulation is unusual among inflammatory cytokines. Lastly, our data are the first to show that Didox can attenuate inflammation in an in vivo model. We found that Didox treatment after IgE sensitization reduced antigen-mediated hypothermia in passive systemic anaphylaxis, a mast cell-dependent model. These data support our cell culture findings and suggest that Didox should be further studied using models of allergic disease, asthma, and inflammation. As a potent analog of the clinically approved drugs HU and NAC, Didox shows significant therapeutic potential.
Acknowledgments This work was supported by U.S. National Institutes of Health, National Institute of Allergy and Infectious Diseases Grants 1R01AI101153 and 2R01AI059638 (to J.J.R.).
Introduction Parkinson's disease (PD) is the second most common neurodegenerative disorder after Alzheimer's disease. PD is characterized by tremor at rest, akinesia, rigidity, postural abnormalities, and episodes of motor arrest [1]. The key feature of PD is a massive loss of dopaminergic neurons in the substantia nigra (SN); as a result, the concentration of striatal dopamine drastically decreases [2]. Despite widespread research efforts, the cause of dopaminergic neuronal loss in the SNs of PD patients remains poorly understood. Recent evidence has shown that neuroinflammation is involved in the pathogenesis of PD [3]. The presence of activated T-lymphocytes and microglia proximal to the SN has been observed postmortem in PD patients. These cell populations are believed to contribute to the process of neurodegeneration and the release of pro-inflammatory and cytotoxic factors, including interleukin-1β, tumor necrosis factor-α, nitric oxide and reactive oxygen intermediates [3,4]. Toll-like receptors (TLRs) are a family of innate immunity receptors that play a major role in regulating the host immune system [5]. Recent studies have shown that TLR4 and TLR2 are expressed in the brain and may regulate certain physiological processes. Furthermore, these molecules have also been reported to play key roles in neurodegenerative disorders, such as PD and Alzheimer's disease [5,6]. Recent studies have indicated that TLRs are also involved in the pathogenesis of PD [7]. α-Synuclein transgenic mice exhibit significant up-regulation of TLR2. Conversely, TLR-deficient mice are less vulnerable to MPTP toxicity and show decreased microglial activation in the SN following MPTP treatment [6,8,9].