Lee Napierata

IL-22 is required for Th17 cell–mediated pathology in a mouse model of psoriasis-like skin inflammation

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.

Inter-Regulation of Th17 Cytokines and the IL-36 Cytokines In Vitro and In Vivo: Implications in Psoriasis Pathogenesis

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.

Tumor necrosis factor α blockade exacerbates murine psoriasis‐like disease by enhancing Th17 function and decreasing expansion of Treg cells

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.

Attenuating Janus Kinases (JAK) by Tofacitinib Effectively Prevented Psoriasis Pathology in Various Mouse Skin Inflammation Models

Background: Tofacitinib is a Janus kinase (JAK) inhibitor that preferentially inhibits signaling by JAK1 and JAK3 that blocks the signaling of type I interferons, IL-6 as well as IL-2, IL-4, IL-7, IL-9, IL-15, and IL-21. Together these cytokines are important to lymphocyte function and therefore regulate multiple aspects of the immune response. Tofacitinib has demonstrated efficacy in clinical trials of various autoimmune diseases including psoriasis.Objectives: To understand the mechanisms of action of tofacitinib in improving psoriasis.Methods: Tofacitinib was evaluated in several IL-23/Th17 pathway-dependent, psoriasis-like skin inflammation models.Results: We demonstrate that similar to mice that received mouse IL-12/23 p40 antibody (anti-p40), treatment with tofacitinib also reduced clinical signs of skin inflammation. Histologic analysis confirmed the clinical data: skin inflammation, the number of cells expressing pSTAT3 were significantly decreased in affected skin of mice treated with tofacitinib and with anti-p40 Ab relative to vehicle/isotype-treated mice. Gene expression analysis of the affected skin revealed that tofacitinib also significantly down-modulated various pro-inflammatory mediators including CXCL10, IL-1β, IL-6, IL-7, IL-17A, IL-22 and S100A8.Conclusion: These results suggest the mechanism of action of tofacitinib is likely due to its ability to block multiple cytokines and attenuate immune response that contribute to the positive clinical efficacy in psoriasis.

CRTH2 is Critical to the Development of Colitis Induced by Dextran Sodium Sulfate (DSS)

Chemoattractant Receptor-homologous molecule expressed on Th2 cells [CRTH2] is expressed on granulocytes (eosinophils, basophils and neutrophils), Th2 cells and monocytes. CRTH2 has been implicated in the development of cutaneous inflammation as CRTH2+ CD4+ T cells and CRTH2+ eosinophils are increased in the blood of atopic dermatitis patients. CRTH2 is also up-regulated in circulating neutrophils of psoriatic patients. Interestingly, CRTH2 is detected in the mucosa of patients with Inflammatory Bowel Disease (IBD) ulcerative colitis, where the CRTH2 positive cells localize within and adjacent to regions of inflamed mucosa suggesting that CRTH2 may play a role in IBD. However, the exact downstream inflammatory pathways resulting from CRTH2 activation in colitis are not well characterized. To gain a better understanding of the effects of CRTH2 activation in the pathogenesis of colitis, we have generated a small molecule inhibitor against CRTH2 and its potency was first validated in an oxazolone induced contact dermatitis model. We investigated the consequences of inhibiting CRTH2 in the development of IBD using a Dextran Sodium Sulfate (DSS)-induced colitis mouse model. Compared to the vehicle control group, mice treated with a selective CRTH2 antagonist had reduced disease severity as measured by weight loss, as well as serum acute phase protein, haptoglobin. Furthermore, pro-inflammatory cytokine gene expression for TNFα, IL-1β, IL-6, IL-17A, and IFNγ were reduced in colons of mice that had been treated with the CRTH2 antagonist compared with DSS treated controls that received vehicle. Taken together, our data identify a previously unrecognized role for CRTH2 in the initiation/amplification and/or stabilization of colon inflammation.