Psoriasis (Ps) is an autoimmune disease characterized by keratinocyte hyperproliferation and chronic inflammation, with increased expression of tumor necrosis factor (TNF) and vascular endothelial growth factor (VEGF). Anti-TNF biologic agents are effective in treating Ps, but are associated with increased risk of infections and blood malignancies. Moreover, keratinocyte hyperproliferation and activation have yet to be addressed. Flavonoids, such as luteolin, are natural compounds with potent anti-inflammatory properties, but their actions on keratinocytes remain unknown. We show that TNF (50 ng/mL) triggers significant production of inflammatory mediators interleukin-6, interleukin-8 and VEGF from both human HaCaT and primary keratinocytes. Pretreatment with the flavonoid luteolin (10–100 µM) significantly inhibits mRNA expression and release of all three mediators in a concentration-dependent manner. More importantly, luteolin decreases TNF-induced phosphorylation, nuclear translocation and DNA binding of the nuclear factor-kappa B (NF-κB) typically involved in inflammatory mediator transcription. We also report that luteolin reduces TNF-induced mRNA expression of two genes (NFKB1 and RELA) encoding two NF-κB subunits (NF-κB p50 and NF-κB p65, respectively). Interestingly, we show that gene expression of RELA is increased in human psoriatic skin. Keratinocyte proliferation, which is a characteristic feature of psoriatic skin, is effectively reduced by luteolin in HaCaT cells, but not in primary keratinocytes. Finally, luteolin does not affect intracellular ATP production or viability. Appropriate formulations of luteolin and related flavones may be promising candidates to be developed into local and systemic treatments for Ps and other inflammatory skin diseases.

Mast cells are important in the development of allergic and anaphylactic reactions, but also in acquired and innate immunity. There is also increasing evidence that mast cells participate in inflammatory diseases, where they can be activated by non-allergic triggers, such as neuropeptides and cytokines, often having synergistic effects as in the case of substance P (SP) and IL-33. Secretion of vasoactive mediators, cytokines and proteinases contribute to the development of coronary artery disease (CAD), as well as to diet-induced obesity and the metabolic syndrome. Mast cells may be able to orchestrate such different biological processes through their ability to release pro-inflammatory mediators selectively without the degranulation typical of allergic reactions. Recent evidence suggests that mitochondrial uncoupling protein 2 (UCP2) and mitochondrial translocation regulate mast cell degranulation, but not selective mediator release. Better understanding of these two processes and how mast cells exert both immunostimulatory and immunosuppressive actions could lead to the development of inhibitors of release of specific mediators with novel therapeutic applications.

Interleukin 9 (IL-9) has been implicated in mast cell-related inflammatory diseases, such as asthma, where vascular endothelial growth factor (VEGF) is involved. Here we report that IL-9 (10–20 ng/ml) induces gene expression and secretion of VEGF from human LAD2. IL-9 does not induce mast cell degranulation or the release of other mediators (IL-1, IL-8, or TNF). VEGF production in response to IL-9 involves STAT-3 activation. The effect is inhibited (about 80%) by the STAT-3 inhibitor, Stattic. Gene-expression of IL-9 and IL-9 receptor is significantly increased in lesional skin areas of atopic dermatitis (AD) patients as compared to normal control skin, while serum IL-9 is not different from controls. These results imply that functional interactions between IL-9 and mast cells leading to VEGF release contribute to the initiation/propagation of the pathogenesis of AD, a skin inflammatory disease.

There is increased serum CRH with decreased lesional skin CRHR-1 gene expression in psoriasis and atopic dermatitis, suggesting possible involvement in stress-induced worsening of symptoms.

Psoriasis is characterized by keratinocyte proliferation and chronic inflammation, but the pathogenesis is still unclear. Dysregulated mitochondria (mt) could lead to reduced apoptosis and extracellular secretion of mtDNA, acting as “innate pathogen” triggering inflammation. Serum was obtained from healthy volunteers and psoriatic patients. Mitochondrial DNA was extracted from the serum and amplified with quantitative PCR (qPCR). Punch biopsies were obtained from lesional and non‐lesional psoriatic skin (10 cm apart) and from healthy volunteers, were placed in RNA later and were stored at −80°C until RNA was extracted and cDNA was synthesized; gene expression of uncoupling protein 2 (UCP2), Dynamin‐related protein 1 (Drp1) and calcineurin, involved in the regulation of mitochondria function, was detected with qPCR. Mitochondrial DNA was significantly increased (7s, P = 0.0496 and Cytochrome B, CytB, P = 0.0403) in the serum of psoriatic patients (n = 63) as compared to controls (n = 27). Gene expression was significantly reduced for UCP2 (P = 0.0218), Drp1 (P = 0.0001) and calcineurin (P = 0.0001) in lesional psoriatic skin, as compared to non‐lesional or control skin. Increased serum extracellular mtDNA in psoriatic patients and decreased expression of mitochondrial regulatory proteins in psoriatic skin suggest increased inflammation and reduced keratinocyte apoptosis, respectively. Inhibitors of mtDNA secretion and/or UCP2 stimulants may be potential treatment options.

Summary Vitiligo is a disorder of depigmentation, for which the pathogenesis is as yet unclear. Interleukin (IL)-8 is a key inflammatory chemokine. We investigated the regulation of IL-8 production in human melanocytes, and the IL-8 serum levels and skin gene expression in patients with vitiligo and in controls. Cultured melanocytes were stimulated for 24 h with tumour necrosis factor (TNF) 100 ng/mL and IL-1β 10 ng/mL, with or without pretreatment with luteolin 50 μmol/L for 30 min, and IL-8 release was measured by ELISA. Serum cytokines were measured by a microbead array. Skin biopsies were taken from healthy subjects (n = 14) as well as from marginal lesional and nonlesional skin from patients with vitiligo (n = 15). IL-8 gene expression was evaluated by quantitative reverse transcriptase PCR. Both TNF and IL-1β stimulated significant IL-8 release (P < 0.01) from melanocytes, whereas pretreatment with luteolin significantly inhibited this effect (P < 0.01). IL-8 gene expression was significantly increased in vitiligo compared with control skin (P < 0.05). IL-8 may be involved in vitiligo inflammation. Inhibition by luteolin of IL-8 release could be useful for vitiligo therapy.

Background: Mast cells are immune cells derived from hematopoietic precursors that mature in the tissue microenvironment. Mast cells are critical for allergic, immune and inflammatory processes, many of which involve tumor necrosis factor (TNF). These cells uniquely store TNF in their secretory granules. Upon stimulation, mast cells rapidly (30 min) secrete β-hexosaminidase and granule-stored TNF through degranulation, but also increase TNF mRNA and release de novo synthesized TNF 24 h later. The regulation of these two distinct pathways is poorly understood. Methods: Human LAD2 leukemic mast cells are stimulated by substance P. TNF secretion and gene expression were measured by ELISA and real-time PCR, and mitochondrial dynamics was observed in live cells under confocal microscopy. Cell energy consumption was measured in terms of oxygen consumption rate. Results: Here, we show that granule-stored TNF is preformed, and its secretion from LAD2 mast cells stimulated by substance P (1) exhibits higher energy consumption and is inhibited by the mitochondrial ATP pump blocker oligomycin, (2) shows rapid increase in intracellular calcium levels, and (3) exhibits reversible mitochondrial translocation, from a perinuclear distribution to the cell surface, as compared to de novo synthesized TNF release induced by lipopolysaccharide. This mitochondrial translocation is confirmed using primary human umbilical cord blood-derived mast cells stimulated by an allergic trigger (IgE/streptavidin). Conclusion: Our findings indicate that unique mitochondrial functions distinguish granule-stored from newly synthesized TNF release from human mast cells, thus permitting the versatile involvement of mast cells in different biological processes.

Summary Background Psoriasis involves skin inflammation that often worsens with stress, but the mechanism of this effect remains obscure. We have shown that corticotrophin- releasing hormone (CRH) is increased in the serum of patients with psoriasis. A peptide, neurotensin (NT), can trigger skin histamine release and augment the ability of CRH to increase skin vascular permeability. Objectives To investigate the serum level of NT, and the expression of genes for NT and NT receptor-1 (NTR-1) in lesional and nonlesional skin of patients with psoriasis, compared with normal controls. Also, to study the effect of NT on human mast cell release of vascular endothelial growth factor (VEGF), which is increased in psoriasis skin. Methods Serum was obtained from patients with psoriasis (n = 56) and controls (n = 33); NT levels were measured with the Milliplex microbead assay. Biopsies were obtained from the lesional and nonlesional skin of patients with chronic plaque psoriasis (n = 40), who had not received any treatment for at least 15 days and were free of any systemic inflammatory diseases. Control skin samples were obtained from healthy subjects (n = 30). Expression of genes for NT and NTR-1 in the skin was evaluated by quantitative reverse transcriptase–polymerase chain reaction. LAD2 human mast cells were stimulated by NT (1 μmol L−1) for 24 h and VEGF was measured by enzyme-linked immunosorbent assay. Results Serum NT was increased in patients with psoriasis, while expression of genes for NT and NTR-1 in lesional skin was decreased compared with controls. NT induced VEGF release from mast cells and was augmented by interleukin-33. Conclusion NT may play a role in psoriasis pathogenesis and its worsening by stress, at least in part through activation of skin mast cells.