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Interferon (IFN)-gamma-induced protein 10 (IP-10/CXCL10), a CXC chemokine, has been documented in several inflammatory and autoimmune disorders including atopic dermatitis and bronchial asthma. Although CXCL10 could be induced by IFN-gamma depending on cell type, the mechanisms regulating CXCL10 production following treatment with combination of IFN-gamma and TNF-alpha have not been adequately elucidated in human monocytes. In this study, we showed that TNF-alpha had more potential than IFN-gamma to induce CXCL10 production in THP-1 monocytes. Furthermore, IFN-gamma synergistically enhanced the production of CXCL10 in parallel with the activation of NF-kappaB in TNF-alpha-stimulated THP-1 cells. Blockage of STAT1 or NF-kappaB suppressed CXCL10 production. JAKs inhibitors suppressed IFN-gamma plus TNF-alpha-induced production of CXCL10 in parallel with activation of STAT1 and NF-kappaB, while ERK inhibitor suppressed production of CXCL10 as well as activation of NF-kappaB, but not that of STAT1. IFN-gamma-induced phosphorylation of JAK1 and JAK2, whereas TNF-alpha induced phosphorylation of ERK1/2. Interestingly, IFN-gamma alone had no effect on phosphorylation and degradation of IkappaB-alpha, whereas it significantly promoted TNF-alpha-induced phosphorylation and degradation of IkappaB-alpha. These results suggest that TNF-alpha induces CXCL10 production by activating NF-kappaB through ERK and that IFN-gamma induces CXCL10 production by increasing the activation of STAT1 through JAKs pathways. Of note, TNF-alpha-induced NF-kappaB may be the primary pathway contributing to CXCL10 production in THP-1 cells. IFN-gamma potentiates TNF-alpha-induced CXCL10 production in THP-1 cells by increasing the activation of STAT1 and NF-kappaB through JAK1 and JAK2.

Silicon dioxide (SiO 2 ) nanoparticles (NPs) have been widely used in the biomedical field, such as in drug delivery and gene therapy. However, little is known about the biological effects and potential hazards of SiO 2 . Herein, the colloidal SiO 2 NPs with two different sizes (20 nm and 100 nm) and different charges (L-arginine modified: SiO 2 EN20[R] , SiO 2 EN100[R] ; and negative: SiO 2 EN20[−] , SiO 2 EN100[−] were orally administered (750 mg/kg/day) in female C57BL/6 mice for 14 days. Assessments of immunotoxicity include hematology profiling, reactive oxygen species generation and their antioxidant effect, stimulation assays for B- and T-lymphocytes, the activity of natural killer (NK) cells, and cytokine profiling. In vitro toxicity was also investigated in the RAW 264.7 cell line. When the cellularity of mouse spleen was evaluated, there was an overall decrease in the proliferation of B- and T-cells for all the groups fed with SiO 2 NPs. Specifically, the SiO 2 EN20(−) NPs showed the most pronounced reduction. In addition, the nitric oxide production and NK cell activity in SiO 2 NP-fed mice were significantly suppressed. Moreover, there was a decrease in the serum concentration of inflammatory cytokines such as interleukin (IL)-1β, IL-12 (p70), IL-6, tumor necrosis factor-α, and interferon-γ. To elucidate the cytotoxicity mechanism of SiO 2 in vivo, an in vitro study using the RAW 264.7 cell line was performed. Both the size and charge of SiO 2 using murine macrophage RAW 264.7 cells decreased cell viability dose-dependently. Collectively, our data indicate that different sized and charged SiO 2 NPs would cause differential immunotoxicity. Interestingly, the small-sized and negatively charged SiO 2 NPs showed the most potent in vivo immunotoxicity by way of suppressing the proliferation of lymphocytes, depressing the killing activity of NK cells, and decreasing proinflammatory cytokine production, thus leading to immunosuppression.

The increased generation of reactive oxygen species (ROS) induces inflammation in different cell types. However, it is unclear whether ROS play an essential role in the production of thymus and activation-regulated chemokine (TARC/CCL17) and macrophage-derived chemokine (MDC/CCL22) in keratinocytes. Here, we investigated the function of ROS in the production of these two Th2 chemokines in interferon-gamma (IFN-γ)-treated HaCaT keratinocytes. We found that IFN-γ-induced production of both chemokines in parallel with the increased generation of intracellular ROS. A ROS scavenger, N-acetyl cysteine (NAC), significantly inhibited the IFN-γ-induced production of chemokines as well as the activation of I kappa-B (IκB)-nuclear factor-kappa B (NF-κB). Inhibitors of Janus family kinases (JAKs), p38 mitogen-activated kinase (MAPK), and NF-κB suppressed IFN-γ-induced production of TARC and MDC. NF-κB activation was inhibited by both inhibitors of JAKs and p38 MAPK. Importantly, IFN-γ-stimulated phosphorylation of p38 MAPK was significantly suppressed by JAKs inhibitors, but not significantly affected by NAC or L-buthionine sulfoximine (L-BSO). However, IFN-γ-stimulated activation of IκB and NF-κB was suppressed by NAC but enhanced by BSO. Furthermore, inhibition of p38 MAPK and JAKs did not affect ROS generation in IFN-γ-stimulated HaCaT cells. These results indicate that intracellular ROS and JAKs/p38 MAPK both contribute independently to IFN-γ-stimulated production of TARC and MDC in HaCaT keratinocytes, by increasing NF-κB activation.

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