Sitagliptin and Narrow-Band Ultraviolet-B for Moderate Psoriasis (DINUP): A Randomised Controlled Clinical Trial.

BACKGROUND: Sitagliptin, a dipeptidyl peptidase-4 (DPP-4) inhibitor licensed for the treatment of type 2 diabetes mellitus (T2DM), has been reported to improve psoriasis. OBJECTIVE: We compared the effects of sitagliptin treatment, a DPP-4 inhibitor, in combination with narrow-band ultraviolet-B (NB-UVB) phototherapy compared to NB-UVB alone on psoriasis severity, quality of life, cardiovascular disease risk factors and immune parameters in people with moderate psoriasis without T2DM. METHODS: In this 39-week, single-centre, randomised controlled trial, people were allocated randomly to receive sitagliptin for 24 weeks with NB-UVB or NB-UVB alone. The primary endpoint was the change in Psoriasis Area and Severity Index (PASI) from baseline to 24 weeks. We estimated that 120 participants would be needed to have 80% power to find a significant difference between the groups. RESULTS: A total of 118 patients were randomised. The median (IQR) baseline PASI was 8.8 (7.5-11.6). At 24 weeks, the mean difference from baseline in PASI (-1.0 [95% CI -2.0 to 0.0]) was significantly larger in the sitagliptin/NB-UVB arm than in the NB-UVB-alone arm (p = 0.044). There were significant differences in the change in Hospital Anxiety and Depression Scale (-2.5 [95% CI -4.0 to -1.0]; p = 0.002) and EuroQol 5-item questionnaire (0.1 [95% CI 0.0-0.1]; p = 0.036) values from baseline to 24 weeks between the sitagliptin/NB-UVB and the NB-UVB-alone arm. There were no treatment-related serious adverse events. CONCLUSION: Sitagliptin therapy combined with NB-UVB phototherapy significantly improved psoriasis severity, albeit modestly, compared to NB-UVB phototherapy alone in patients with moderate psoriasis without T2DM.

Retinoic acid-induced autoantigen-specific type 1 regulatory T cells suppress autoimmunity.

Regulatory T (Treg) cells help to maintain tolerance and prevent the development of autoimmune diseases. Retinoic acid (RA) can promote peripheral conversion of naïve T cells into Foxp3+ Treg cells. Here, we show that RA can act as an adjuvant to induce antigen-specific type 1 Treg (Tr1) cells, which is augmented by co-administration of IL-2. Immunization of mice with the model antigen KLH in the presence of RA and IL-2 induces T cells that secrete IL-10, but not IL-17 or IFN-γ, and express LAG-3, CD49b and PD-1 but not Foxp3, a phenotype typical of Tr1 cells. Furthermore, immunization of mice with the autoantigen MOG in the presence of RA and IL-2 induces Tr1 cells, which suppress pathogenic Th1 and Th17 cells that mediate the development of experimental autoimmune encephalomyelitis (EAE), an autoimmune disease of the CNS. Furthermore, immunization with a surrogate autoantigen, RA and IL-2 prevents development of spontaneous autoimmune uveitis. Our findings demonstrate that the induction of autoantigen-specific Tr1 cells can prevent the development of autoimmunity.

Naturally derived Heme-Oxygenase 1 inducers attenuate inflammatory responses in human dendritic cells and T cells: relevance for psoriasis treatment.

Psoriasis is a chronic autoimmune disease mediated by dysregulated immune responses in dendritic cells (DC) and T cells. The stress-response enzyme heme oxygenase-1 (HO-1) has been described as protective in animal models of psoriasis, however, implementation of HO-1-based therapies is hindered by the lack of clinically-suitable HO-1 inducers. The plant-derived polyphenols, carnosol and curcumin, have been identified as candidate HO-1 inducers however there has been little investigation into their effects on human immune cells. We demonstrate that treatment of human DC with these polyphenols limits DC maturation, reduces pro-inflammatory cytokine production, and prevents induction of allospecific T cell responses, in a manner partially dependent on carbon monoxide (CO). We also characterised their effects in ex-vivo psoriasis PBMC and report that curcumin, but not carnosol, strongly reduces T cell proliferation and cytokine poly-functionality, with reduced expression of psoriatic cytokines IFNγ, IL-17, GM-CSF and IL-22. This study therefore supports reports highlighting the therapeutic potential of curcumin in psoriasis by providing insight into its immunological effects on healthy human DC and psoriasis PBMC. We also demonstrate, for the first time, the anti-inflammatory effects of carnosol in human immune cells.