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OBJECTIVE: Patients with psoriasis and psoriatic arthritis respond well to tumor necrosis factor alpha (TNFalpha) blockers in general; however, there is now mounting evidence that a small cohort of patients with rheumatoid arthritis who receive TNFalpha blockers develop psoriasis. This study was undertaken to explore the mechanisms underlying TNFalpha blockade-induced exacerbation of skin inflammation in murine psoriasis-like skin disease. METHODS: Skin inflammation was induced in BALB/c scid/scid mice after they received CD4+CD45RB(high)CD25- (naive CD4) T cells from donor mice. These mice were treated with either anti-interleukin-12 (anti-IL-12)/23p40 antibody or murine TNFRII-Fc fusion protein and were examined for signs of disease, including histologic features, various cytokine levels in the serum, and cytokine or FoxP3 transcripts in the affected skin and draining lymph node (LN) cells. In a separate study, naive CD4+ T cells were differentiated into Th1 or Th17 lineages with anti-CD3/28 magnetic beads and appropriate cytokines in the presence or absence of TNFalpha. Cytokine gene expression from these differentiated cells was also determined. RESULTS: Neutralization of TNFalpha exacerbated skin inflammation and markedly enhanced the expression of the proinflammatory cytokines IL-1beta, IL-6, IL-17, IL-21, and IL-22 but suppressed FoxP3 expression in the skin and reduced the number of FoxP3-positive Treg cells in the draining LNs. TNFalpha also demonstrated a divergent role during priming and reactivation of naive T cells. CONCLUSION: These results reveal a novel immunoregulatory role of TNFalpha on Th17 and Treg cells in some individuals, which may account for the exacerbation of skin inflammation in some patients who receive anti-TNF treatments. [ABSTRACT FROM AUTHOR]

The nuclear hormone receptor retinoic acid receptor-related orphan C2 (RORC2, also known as RORγt) is a promising target for the treatment of autoimmune diseases. A small molecule, inverse agonist of the receptor is anticipated to reduce production of IL-17, a key proinflammatory cytokine. Through a high-throughput screening approach, we identified a molecule displaying promising binding affinity for RORC2, inhibition of IL-17 production in Th17 cells, and selectivity against the related RORA and RORB receptor isoforms. Lead optimization to improve the potency and metabolic stability of this hit focused on two key design strategies, namely, iterative optimization driven by increasing lipophilic efficiency and structure-guided conformational restriction to achieve optimal ground state energetics and maximize receptor residence time. This approach successfully identified 3-cyano- N-(3-(1-isobutyrylpiperidin-4-yl)-1-methyl-4-(trifluoromethyl)-1 H-pyrrolo[2,3- b]pyridin-5-yl)benzamide as a potent and selective RORC2 inverse agonist, demonstrating good metabolic stability, oral bioavailability, and the ability to reduce IL-17 levels and skin inflammation in a preclinical in vivo animal model upon oral administration.

Accumulating evidence indicates that IL-1 family members and Th17 cytokines have a pathogenic role in psoriasis. We investigated the regulatory interactions of the IL-1-like IL-36 cytokine family and the Th17 cytokines in the context of skin inflammation. We observed increased gene expression of all three IL-36 cytokines in a Th17-dominant psoriasis-like animal model. The induction was downregulated by neutralizing IL-22. Expression of the IL-36s was also induced in cultured primary human keratinocytes (KC) by IL-17A and tumor necrosis factor (TNF)-α, and IL-22 synergized with IL-17A and TNF-α. Furthermore, the IL-36s directly induced their own expression and the production of proinflammatory mediators (TNF-α, IL-6, IL-8) in KC. These functions were markedly enhanced with the addition of IL-17A or TNF-α to the cultures. Similarly, IL-36α and IL-36β augmented IL-17A-mediated induction of antibacterial peptides. Finally, we show that the increased gene expression of IL-36 correlated with Th17 cytokines in the lesions of psoriatic patients. Our results indicate that the IL-36 cytokines are not only regulated by Th17 cytokines, but that they themselves can regulate the expression and enhance the function of Th17 cytokines. We propose that a feedback loop between the IL-36 and Th17 cytokines is involved in driving cytokine expression in psoriatic tissues.

Methylphenidate (MPH) is one of the few psychotropic agents approved for use in pediatric populations, underscoring the importance of elucidating any long-term consequences following exposure to this agent. Here, we examined the influence of several variables (i.e. age of assessment, age of exposure, sex, route of administration) on the effect of chronic low-dose MPH (2 mg/kg, twice daily) exposure on place conditioning to cocaine. Juvenile exposure to MPH, but not later exposure, resulted in aversions to cocaine-paired environments when assessed in young adult male rats, but not those entering adolescence. Juvenile MPH enhanced place preferences for cocaine-paired environments in female adolescent rats. The route of administration (i.p. injection or oral ingestion) did not produce enduring differential effects on behavior, and D-MPH was confirmed as the active enantiomer. These observations add to the growing literature on the enduring effects of MPH exposure, and highlight the need for more research in females., (2009 S. Karger AG, Basel.)

Attention deficit hyperactivity disorder is associated with reduced cortical blood flow that is reversible with exposure to the psychostimulant methylphenidate (MPH). D3 dopamine receptors modulate stimulant-induced changes in blood flow and are associated with reward processing during young adulthood, but their role in the enduring effects of MPH during development is unknown. Rats were given vehicle (VEH) or MPH (2 mg/kg between postnatal days 20-35) and assessed in young adulthood for regional cerebral blood volume (rCBV) after MPH challenge and mRNA expression levels of dopamine receptors. To probe D3 receptor involvement, juvenile subjects were exposed to VEH, MPH, the D3-preferring agonist +/-7-OHDPAT (0.3 mg/kg), the D3 antagonist nafadotride (Naf; 0.05, 0.5 or 5.0 mg/kg) or a Naf (0.05 mg/kg)/MPH combination, and assessed biochemically and behaviorally. Juvenile MPH exposure increased MPH-induced rCBV in the cingulate and medial prefrontal cortex and thalamus in adulthood. Behaviorally, juvenile MPH- or +/-7-OHDPAT-exposed subjects demonstrated an aversion to cocaine-associated environments, which was prevented by juvenile co-treatment with MPH and Naf, or with adult cortical microinjections of +/-7-OHDPAT. Cortical D3 mRNA levels significantly decreased by 23.8 +/- 6.7% in MPH-treated subjects and normalized with combined Naf/MPH treatment, with no change in the other dopamine receptors. Enhanced cortical responsiveness to psychostimulants may occur through a reduction in D3 receptors, which in turn reduces drug-seeking behavior. These data provide evidence for a postnatal sensitive period when juvenile MPH exposure is able to alter cortical development.

Psoriasis is a chronic skin disease resulting from the dysregulated interplay between keratinocytes and infiltrating immune cells. We report on a psoriasis-like disease model, which is induced by the transfer of CD4(+)CD45RB(hi)CD25(-) cells to pathogen-free scid/scid mice. Psoriasis-like lesions had elevated levels of antimicrobial peptide and proinflammatory cytokine mRNA. Also, similar to psoriasis, disease progression in this model was dependent on the p40 common to IL-12 and IL-23. To investigate the role of IL-22, a Th17 cytokine, in disease progression, mice were treated with IL-22-neutralizing antibodies. Neutralization of IL-22 prevented the development of disease, reducing acanthosis (thickening of the skin), inflammatory infiltrates, and expression of Th17 cytokines. Direct administration of IL-22 into the skin of normal mice induced both antimicrobial peptide and proinflammatory cytokine gene expression. Our data suggest that IL-22, which acts on keratinocytes and other nonhematopoietic cells, is required for development of the autoreactive Th17 cell-dependent disease in this model of skin inflammation. We propose that IL-22 antagonism might be a promising therapy for the treatment of human psoriasis.