Tumor necrosis factor alpha (TNF-␣) is a potent cytokine which regulates inflammation via the induction of adhesion molecules and chemokine expression. Its expression is known to be regulated in a complex manner with transcription, message turnover, message splicing, translation, and protein cleavage from the cell surface all being independently regulated. This study examined both cell lines and primary cells to understand the developmental regulation of epigenetic changes at the TNF-␣ locus. We demonstrate that epigenetic modifications of the TNF-␣ locus occur both developmentally and in response to acute stimulation and, importantly, that they actively regulate expression. DNA demethylates early in development, beginning with the hematopoietic stem cell. The TNF-␣ locus migrates from heterochromatin to euchromatin in a progressive fashion, reaching euchromatin slightly later in differentiation. Finally, histone modifications characteristic of a transcriptionally competent gene occur with myeloid differentiation and progress with differentiation. Additional histone modifications characteristic of active gene expression are acquired with stimulation. In each case, manipulation of these epigenetic variables altered the ability of the cell to express TNF-␣. These studies demonstrate the importance of epigenetic regulation in the control of TNF-␣ expression. These findings may have relevance for inflammatory disorders in which TNF-␣ is overproduced.

Background:The signaling mechanisms involved in PGE2-induced MMP-9 expression in DCs are unknown. Results: PGE2-induced MMP-9 expression is mediated through the EP2/EP4 3 cAMP 3 PKA/PI3K 3 ERK signaling pathway. Conclusion: PGE2-induced ERK activation is required for the binding of AP-1 to the MMP-9 promoter. Significance: ERK inhibitors can be used to regulate DC migration.

Administration of cannabinoid receptor 2 (CB2R) agonists in inflammatory and autoimmune disease and CNS injury models results in significant attenuation of clinical disease, and reduction of inflammatory mediators. Previous studies reported that CB2R signaling also reduces leukocyte migration. Migration of dendritic cells (DCs) to various sites is required for their activation and for the initiation of adaptive immune responses. Here, we report for the first time that CB2R signaling affects DC migration in vitro and in vivo, primarily through the inhibition of matrix metalloproteinase 9 (MMP-9) expression. Reduced MMP-9 production by DCs results in decreased migration to draining lymph nodes in vivo and in vitro in the matrigel migration assay. The effect on Mmp-9 expression is mediated through CB2R, resulting in reduction in cAMP levels, subsequent decrease in ERK activation, and reduced binding of c-Fos and c-Jun to Mmp-9 promoter activator protein 1 sites. We postulate that, by dampening production of MMP-9 and subsequent MMP-9-dependent DC migration, cannabinoids contribute to resolve acute inflammation and to reestablish homeostasis. Selective CB2R agonists might be valuable future therapeutic agents for the treatment of chronic inflammatory conditions by targeting activated immune cells, including DCs. IntroductionThe cannabinoid system consists of cannabinoid receptors and their ligands, including endocannabinoids, synthetic cannabinoid receptor agonists and antagonists, and phytocannabinoids. Several cannabinoid receptors have been described, that is, the classic cannabinoid receptor 1 (GPR) and GPR, the previously orphaned G-protein receptors GPR18 and GPR55, various ion channels, and intracellular peroxisome proliferator-activated receptor-␥ (reviewed in Pertwee et al 1 and Console-Bram 2 ). The 2 classic cannabinoid receptors, CB1R and CB2R, have different distribution and functions (reviewed in Kubajewska and Constantinescu 3 and Basu and Dittel 4 ). CB1R is abundantly expressed on CNS and peripheral neurons and involved in neural functions. In contrast, CB2R is mostly expressed on immune cells and involved in immunoregulation. Administration of CB2R-selective agonists in models of inflammatory and autoimmune diseases such as systemic sclerosis, experimental autoimmune uveoretinitis, inflammatory bowel diseases, and experimental autoimmune encephalomyelitis (EAE) resulted in attenuation of clinical disease (reviewed in Basu and Dittel 4 ). CB2R agonists also have been reported to have a beneficial effect in models of CNS injury such as cerebral infarction and spinal cord injury. [5][6][7][8] In addition to effects on clinical outcome, CB2R agonists reduced the levels of inflammatory mediators in various experimental models. [8][9][10] A possible mechanism for the anti-inflammatory effect of CB2R signaling is the direct action of CB2R agonists on immune cells. In vitro studies indicated that CB2R signaling inhibited the production of proinflammatory cytokines such as TNF␣, IL-6, IL-2, and IFN-␥ by ac...

Background:The molecular mechanisms involved in IL-23 up-regulation by PGE2 are not elucidated. Results: PGE2 induces IL-23p19 through the EP4 cAMP-PKA/EPAC-CREB/C/EBP␤ signaling pathway. Conclusion: PGE2 synergizes with TLR ligands and with proinflammatory cytokines such as TNF␣ to up-regulate Il23a gene expression. Significance: Understanding is gained of one of the major functions of PGE2 leading to activation of pathogenic Th17 cells.

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Neuroinflammation characterizes various neurological disorders. Peripheral immune cells and CNS-resident glia contribute to neuroinflammation and impact CNS degeneration, recovery and regeneration. Recently, the role of dendritic cells in neuroinflammation received special attention. The function of infiltrating immune cells and resident glia is affected by various factors, including lipid mediators. Polyunsaturated fatty acids, especially n-6 arachidonic acid and n-3 docosahexaenoic acid (DHA), the most abundant in the CNS, play an important role in neuroinflammation. The major arachidonic acid bioactive derivative in immune cells, PGE2, and DHA have been reported to have opposite effects on dendritic cells in terms of cytokine production and activation/differentiation of CD4+ T cells. Here we review the existing information on PGE2 and DHA modulation of dendritic cell function and the potential impact of these lipid mediators of dendritic cells in CNS inflammatory disorders.

This study analyzed the antigen-specific (Gag, Nef, Rev, and Tat) IgM, IgG, and IgA humoral responses during the first 200 days of SIVmac251 infection in cynomolgus macaques. These responses were tested for correlation with the CD4(+) T-cell-related hematologic parameters and viral load throughout the course of the study (acute and chronic infection, during and after antiretroviral therapy). Strong inverse correlations were observed between the percentage of CD4(+) T cells at almost every timepoint of the study and the levels of IgM (but not IgG and IgA) against Gag, Nef, and Rev (but not Tat) measured after, but not during, the primary peak of IgM response. Significant levels of persistent antigen-specific IgMs may reflect the prevalence of mature plasma cells that have not undergone immunoglobulin class switching, possibly due to defects in helper T-cell function. Strong correlations were observed between the preinfection CD4(+) T-cell count or CD4/CD8 ratio and the same parameters measured throughout the study, suggesting the importance of preinfection immune status as a determinant of disease progression. The negative correlations between the post-acute-phase IgM levels and the percentage of CD4(+) T cells at later times during the study suggest the potential prognostic value of this measurement.

Dendritic Cells (DCs) play an important role in the initiation of the immune response. Immature DCs take up antigen, mature and migrate to the regional lymph nodes where they activate antigen-specific naïve T cells. Prostaglandins such as PGE2 are essential for the migration of DCs to lymph nodes. Matrix metalloproteinases (MMPs) play an essential role in DC migration, through the degradation of extracellular matrix (ECM) and basement membranes. MMP2, and particularly MMP9, are essential for dendritic cell migration in vitro, as well as in vivo to the draining lymph nodes. In this study, we show that PGE2-induced MMP9 expression is mediated through the EP2/EP4-cAMP-PKA/PI3K-ERK signaling pathway. EP2 and EP4 receptors as well as cAMP analog mimic the effect of PGE2 to upregulate MMP-9. In the presence of PKA, PI3K or ERK inhibitors, PGE2-induced MMP-9 production is abolished. Furthermore, PGE2-induced c-Fos expression mediated through ERK activation is required for the binding of AP-1 transcription factor to the MMP-9 promoter. In the presence of ERK inhibitors, PGE2-induced AP-1 binding is abrogated. Our results describe a new molecular mechanism for the effect of PGE on MMP-9 production in DCs, which could lead to a new therapeutic approach by using ERK inhibitors to regulate DC migration.