Mast cells are well known for their role in allergic and anaphylactic reactions, as well as their involvement in acquired and innate immunity. Increasing evidence now implicates mast cells in inflammatory diseases where they are activated by non-allergic triggers, such as neuropeptides and cytokines, often exerting synergistic effects as in the case of IL-33. Mast cells can also release pro-inflammatory mediators selectively without degranulation. In particular, IL-1 induces selective release of IL-6, while corticotropin-releasing hormone secreted under stress induces the release of vascular endothelial growth factor. Many inflammatory diseases involve mast cells in cross-talk with T cells, such as atopic dermatitis, psoriasis and multiple sclerosis, which all worsen by stress. How mast cell differential responses are regulated is still unresolved. Preliminary evidence suggests that mitochondrial function and dynamics control mast cell degranulation, but not selective release. Recent findings also indicate that mast cells have immunomodulatory properties. Understanding selective release of mediators could explain how mast cells participate in numerous diverse biologic processes, and how they exert both immunostimulatory and immunosuppressive actions. Unraveling selective mast cell secretion could also help develop unique mast cell inhibitors with novel therapeutic applications.

The peptide substance P (SP) has been implicated in inflammatory conditions, such as psoriasis, where mast cells and VEGF are increased. A relationship between SP and VEGF has not been well studied, nor has any interaction with the proinflammatory cytokines, especially IL-33. Here we report that SP (0.1-10 μM) induces gene expression and secretion of VEGF from human LAD2 mast cells and human umbilical core blood-derived cultured mast cells (hCBMCs). This effect is significantly increased by coadministration of IL-33 (5-100 ng/mL) in both cell types. The effect of SP on VEGF release is inhibited by treatment with the NK-1 receptor antagonist 733,060. SP rapidly increases cytosolic calcium, and so does IL-33 to a smaller extent; the addition of IL-33 augments the calcium increase. SP-induced VEGF production involves calcium-dependent PKC isoforms, as well as the ERK and JNK MAPKs. Gene expression of IL-33 and histidine decarboxylase (HDC), an indicator of mast cell presence/activation, is significantly increased in affected and unaffected (at least 15 cm away from the lesion) psoriatic skin, as compared with normal control skin. Immunohistochemistry indicates that IL-33 is associated with endothelial cells in both the unaffected and affected sites, but is stronger and also associated with immune cells in the affected site. These results imply that functional interactions among SP, IL-33, and mast cells leading to VEGF release contribute to inflammatory conditions, such as the psoriasis, a nonallergic hyperproliferative skin inflammatory disorder with a neurogenic component.inflammation | cytokines | IL-1 | innate immunity | stress

Background Mast cells derive from hematopoietic cell precursors and participate in tissue allergic, immune, and inflammatory processes. They secrete many mediators, including preformed TNF, in response to allergic, neuropeptide, and environmental triggers. However, regulation of mast cell degranulation is not well understood. Objective We investigated the role of mitochondrial dynamics in degranulation of human cultured mast cells. Methods Human umbilical cord blood–derived mast cells (hCBMCs) and Laboratory of Allergic Diseases 2 (LAD2) mast cells were examined by confocal and differential interference contrast microscopy during activation by IgE/antigen and substance P (SP). Mast cells in control and atopic dermatitis (AD) skin were evaluated by transmission electron microscopy. LAD2 cells were pretreated with mitochondrial division inhibitor, a dynamin-related protein 1 (Drp1) inhibitor, and small interfering RNA for Drp1, which is necessary for mitochondrial fission and translocation. Calcineurin and Drp1 gene expression was analyzed in stimulated LAD2 cells and AD skin biopsies. Results Stimulation of hCBMCs with IgE/antigen or LAD2 cells with SP leads to rapid (30 minutes) secretion of preformed TNF. Degranulation is accompanied by mitochondrial translocation from a perinuclear location to exocytosis sites. Extracellular calcium depletion prevents these effects, indicating calcium requirement. The calcium-dependent calcineurin and Drp1 are activated 30 minutes after SP stimulation. Reduction of Drp1 activity by mitochondrial division inhibitor and decrease of Drp1 expression using small interfering RNA inhibit mitochondrial translocation, degranulation, and TNF secretion. Mitochondrial translocation is also evident by transmission electron microscopy in skin mast cells from AD biopsies, in which gene expression of calcineurin, Drp1, and SP is higher than in normal skin. Conclusion Human mast cell degranulation requires mitochondrial dynamics, also implicated in AD. (J Allergy Clin Immunol 2011;127:1522-31.)

Background and purpose: Allergic inflammation and autoimmune diseases, such as atopic dermatitis, psoriasis and multiple sclerosis (MS), involve both mast cell and T‐cell activation. However, possible interactions between the two and the mechanism of such activations are largely unknown. Experimental approach: Human umbilical cord blood‐derived cultured mast cells (hCBMCs) and Jurkat T cells were incubated separately or together, following activation with myelin basic protein (MBP), as well as with or without pretreatment with the flavonoid luteolin for 15 min. The supernatant fluid was assayed for inflammatory mediators released from mast cells and interleukin (IL)‐2 release from Jurkat cells. Key results: MBP (10 μM) stimulates hCBMCs to release IL‐6, IL‐8, transforming growth factor (TGF)‐β1, tumour necrosis factor‐α (TNF‐α), vascular endothelial growth factor (VEGF), histamine and tryptase (n=6, P<0.05). Addition of mast cells to Jurkat cells activated by anti‐CD3/anti‐CD28 increases IL‐2 release by 30‐fold (n=3, P<0.05). MBP‐stimulated mast cells and their supernatant fluid further increase Jurkat cell IL‐2 release (n=3, P<0.05). Separation of mast cells and activated Jurkat cells by a Transwell permeable membrane inhibits Jurkat cell stimulation by 60%. Pretreatment of Jurkat cells with a TNF‐neutralizing antibody reduces IL‐2 release by another 40%. Luteolin pretreatment inhibits mast cell activation (n=3–6, P<0.05), Jurkat cell activation and mast cell‐dependent Jurkat cell stimulation (n=3, P<0.05). Conclusions and implications: Mast cells can stimulate activated Jurkat cells. This interaction is inhibited by luteolin, suggesting that this flavonoid may be useful in the treatment of autoimmune diseases. British Journal of Pharmacology (2008) 155, 1076–1084; doi:; published online 22 September 2008

Autism spectrum disorders (ASD) are neurodevelopmental disorders characterized by difficulties in communication, cognitive and learning deficits, as well as stereotypic behaviors. For the majority of cases there are no reliable biomarkers or distinct pathogenesis. However, increasing evidence indicates ASD may be associated with some immune dysregulation, and may have a neuroimmune component. We recently showed that the peptide neurotensin (NT) is increased in autistic children. We now show that NT induces release of extracellular mitochondrial DNA (mtDNA) that could act as "autoimmune" trigger. We further show that serum from young autistic patients contains mtDNA (n = 20; cytochrome B, p = 0.0002 and 7S, p = 0.006), and anti-mitochondrial antibody Type 2 (n = 14; p = 0.001) as compared to normally developing, unrelated controls (n = 12). Extracellular blood mtDNA and other components may characterize an autistic endophenotype and may contribute to its pathogenesis by activating autoimmune responses.

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 involved in allergic reactions, where they secrete numerous vasoactive, inflammatory and nociceptive mediators in response to immunoglobulin E (IgE) and antigen. However, they have also been implicated in inflammatory conditions, such as painful bladder syndrome/interstitial cystitis (PBSIIC), irritable bowel syndrome (IBS) and migraines, all of which occur more often in women and are exacerbated during ovulation, but are suppressed during pregnancy. Mast cells express high affinity estrogen receptors and estradiol augments their secretion, while tamoxifen inhibits it. Here we report that progesterone (100 nM), but not the structurally related cholesterol, inhibits histamine secretion from purified rat peritoneal mast cells stimulated immunologically or by substance P (SP), an effect also documented by electron microscopy. These results suggest that mast cell secretion may be regulated by progesterone and may explain the reduced symptoms of certain inflammatory conditions during pregnancy.

Acetaminophen is a leading cause of acute liver failure (ALF). Genetic differences might predispose some individuals to develop ALF. In this exploratory study, we evaluated genotype frequency differences among patients enrolled by the ALF Study Group who had developed ALF either intentionally from a singletime-point overdose of acetaminophen (n = 78), unintentionally after chronic high doses of acetaminophen (n = 79), or from causes other than acetaminophen (n = 103). The polymorphisms evaluated included those in genes encoding putative acetaminophenmetabolizing enzymes (UGT1A1, UGT1A6, UGT1A9, UGT2B15, SULT1A1, CYP2E1, and CYP3A5) as well as CD44 and BHMT1. Individuals carrying the CYP3A5 rs776746 A allele were overrepresented among ALF patients who had intentionally overdosed with acetaminophen, with an odds ratio of 2.3 (95% confidence interval, 1.1-4.9; P = 0.034) compared with all other ALF patients.This finding is consistent with the enhanced bioactivation of acetaminophen by the CYP3A5 enzyme. Persons homozygous for the CD44 rs1467558 A allele were also overrepresented among patients who had unintentionally developed ALF from chronic acetaminophen use, with an odds ratio of 4.0 (1.0-17.2, P = 0.045) compared with all other ALF subjects. This finding confirms a prior study that found elevated serum liver enzyme levels in healthy volunteers with the CD44 rs1467558 AA genotype who had consumed high doses of acetaminophen for up to 2 weeks. However, both genetic associations were considered relatively weak, and they were not statistically significant after adjustment for multiple comparisons testing. Nevertheless, both CYP3A5 rs776746 and CD44 rs1467558 warrant further investigation as potential genomic markers of enhanced risk of acetaminopheninduced ALF.