Pio Conti

Differential release of mast cell mediators and the pathogenesis of inflammation.

Summary:  Mast cells are well known for their involvement in allergic and anaphylactic reactions, during which immunoglobulin E (IgE) receptor (FcɛRI) aggregation leads to exocytosis of the content of secretory granules (1000 nm), commonly known as degranulation, and secretion of multiple mediators. Recent findings implicate mast cells also in inflammatory diseases, such as multiple sclerosis, where mast cells appear to be intact by light microscopy. Mast cells can be activated by bacterial or viral antigens, cytokines, growth factors, and hormones, leading to differential release of distinct mediators without degranulation. This process appears to involve de novo synthesis of mediators, such as interleukin‐6 and vascular endothelial growth factor, with release through secretory vesicles (50 nm), similar to those in synaptic transmission. Moreover, the signal transduction steps necessary for this process appear to be largely distinct from those known in FcɛRI‐dependent degranulation. How these differential mast cell responses are controlled is still unresolved. No clinically available pharmacological agents can inhibit either degranulation or mast cell mediator release. Understanding this process could help develop mast cell inhibitors of selective mediator release with novel therapeutic applications.

IL-33 augments substance P–induced VEGF secretion from human mast cells and is increased in psoriatic skin

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.

IL-10, an inflammatory/inhibitory cytokine, but not always.

IL-10 has been previously called cytokine synthesis inhibiting factor, produced mostly by Th2 cells, macrophages and CD8+ cell clones. IL-10 is capable of inhibiting the synthesis of several cytokines from different cells, antigen or mitogen activated. IL-10 exerts its inhibition at the mRNA transcriptional and translational level. In addition, IL-10 is a co-stimulatory cytokine on activated T cells. For example, IL-10 inhibits NK cell activity, the production of Th1 cytokines, cytokines generated by peripheral blood mononuclear cells, and macrophage activity. On the other hand, IL-10 exerts immunostimulatory effects on B cells, cytotoxic T cell development and thymocytes. In mast cells derived from CD4+/CD133+ cells, IL-10 inhibits IL-6 and TNFalpha, and prostaglandin E(1) and E(2) induced by IL-6. Here, we report for the first time that IL-10 fails to inhibit tryptase and IL-6 from human mast cell-1 (HMC-1) and human umbilical cord blood-derived mast cells.

Gut-Microbiota-Brain Axis and Its Effect on Neuropsychiatric Disorders With Suspected Immune Dysregulation

PURPOSE Gut microbiota regulate intestinal function and health. However, mounting evidence indicates that they can also influence the immune and nervous systems and vice versa. This article reviews the bidirectional relationship between the gut microbiota and the brain, termed the microbiota-gut-brain (MGB) axis, and discusses how it contributes to the pathogenesis of certain disorders that may involve brain inflammation. METHODS Articles were identified with a search of Medline (starting in 1980) by using the key words anxiety, attention-deficit hypersensitivity disorder (ADHD), autism, cytokines, depression, gut, hypothalamic-pituitary-adrenal (HPA) axis, inflammation, immune system, microbiota, nervous system, neurologic, neurotransmitters, neuroimmune conditions, psychiatric, and stress. FINDINGS Various afferent or efferent pathways are involved in the MGB axis. Antibiotics, environmental and infectious agents, intestinal neurotransmitters/neuromodulators, sensory vagal fibers, cytokines, and essential metabolites all convey information to the central nervous system about the intestinal state. Conversely, the hypothalamic-pituitary-adrenal axis, the central nervous system regulatory areas of satiety, and neuropeptides released from sensory nerve fibers affect the gut microbiota composition directly or through nutrient availability. Such interactions seem to influence the pathogenesis of a number of disorders in which inflammation is implicated, such as mood disorder, autism-spectrum disorders, attention-deficit hypersensitivity disorder, multiple sclerosis, and obesity. IMPLICATIONS Recognition of the relationship between the MGB axis and the neuroimmune systems provides a novel approach for better understanding and management of these disorders. Appropriate preventive measures early in life or corrective measures such as use of psychobiotics, fecal microbiota transplantation, and flavonoids are discussed.

Treatment with an acetylcholinesterase inhibitor in Alzheimer patients modulates the expression and production of the pro-inflammatory and anti-inflammatory cytokines.

Elevated levels of cytokines have been detected in brains of Alzheimers disease (AD) patients, and altered peripheral levels of IL-1beta, TNFalpha and IL-6 have been reported in these patients. We studied the ability of PBMC from patients with AD, matched with a control group, to release pro- and anti-inflammatory cytokines, and the effect of AChEI treatment on cytokine release. Our data indicates that AChEI treatment down-regulates IL-1, IL-6 and TNF, and up-regulates the expression and production of IL-4 in PBMC in AD patients, and that AChEI leads to the remodelling of the cytokine network, probably acting on the lymphocytic cholinergic system.

IL-10 subfamily members: IL-19, IL-20, IL-22, IL-24 and IL-26

It has been reported that the CD4+ T cell is a very important source of interleukin 10 (IL-10), while CD8+ cells produce low amounts. IL-10 exerts several immune stimulating, as well as inhibitory effects. There are at least five novel human IL-10 family-related molecules: IL-19, IL-20, IL-22, IL-24, and IL-26. Activated T cells produce IL-19, IL-22 and IL-26, while IL-24 is produced by activated monocytes and T-cells. IL-20 induces cheratin proliferation and Stat-3 signal transduction pathway, while IL-22 induces acute-phase production by hepatocytes and neonatal lethality with skin abnormalities reminiscent of psoriasic lesions in humans. In addition, IL-22 mediates inflammation and binds class II cytokine receptor heterodimers IL-22 RA1/CRF2-4. This cytokine is also involved in immuno-regulatory responses. IL-26 (AK155) is a novel cytokine generated by memory cells and is involved in the transformed phenotype of human T cells after infection by herpes virus. All these new IL-10 subfamily member cytokines are strongly involved in immune regulation and inflammatory responses.

Intramuscular injection of hrRANTES causes mast cell recruitment and increased transcription of histidine decarboxylase in mice: lack of effects in genetically mast cell-deficient W/WV mice

RANTES (regulated upon activation, normal T cell expressed and presumably secreted) and other chemoattractant proteins are members of the intercrine or chemokine family of proinflammatory basic polypeptides. RANTES is a prototype of the C‐C chemokine subfamily that acts as a selective chemoattractant for human monocytes and CD4‐positive lymphocytes and increases the adherence of monocytes to endothelial cells. However, the role of RANTES in white cells is still unclear. We report here that hrRANTES at 20 ng/50 µl in mice causes mast cell recruitment 4 h after intramuscular injection, an effect inhibited by anti‐RANTES, as evidenced by 0.1% Toluidine blue, a specific dye for coloring mast cells. Injections of PBS (50 µl) vehicle (negative control) did not produce any appreciable inflammatory response, whereas injection of lipopolysaccharide 20 ng/50 µl (positive control) generated a marked inflammatory state. When RANTES was injected intramuscularly in genetically mast cell‐deficient W/Wv mice, the inflammatory effect was not present. The RANTES injection sites were then excised and studied under an optical and electron microscope. A Northern blot analysis was performed using a probe that was prepared to detect mRNA encoding the histidine decarboxylase (HDC) gene on excised muscle tissue. We found that hrRANTES provoked generation of HDC mRNA from muscle tissue after 4 h. These effects were inhibited by an anti‐RANTES antibody and were absent in genetically mast cell‐deficient mice. The increasing number of mast cells in the RANTES injection sites led to an augmentation of histamine content compared to controls (PBS). The injection of hrRANTES 20 ng/20 µl into the sole of a rat paw confirmed the inflammatory and the mast cell recruitment potential of this chemokine. In these studies, hrRANTES injections in muscle tissue provided direct in vivo evidence that RANTES has a significant effect on mast cell recruitment and HDC mRNA generation.—Conti, P., Reale, M., Barbacane, R. C., Letourneau, R., Theoharides, T. C. Intramuscular injection of hrRANTES causes mast cell recruitment and increased transcription of histidine decarboxylase in mice: lack of effects in genetically mast cell‐deficient W/WV mice. FASEB J. 12, 1693–1700 (1998)

Monocyte Chemotactic Protein 1 (MCP-1) Is a Mitogen for Cultured Rat Vascular Smooth Muscle Cells

The involvement of inflammatory mechanisms in the progression of atherosclerosis has recently been suggested. Monocyte chemotactic protein 1 (MCP-1) is a soluble protein which is implicated in acute and chronic inflammatory processes, including atherosclerosis. We evaluated the effect of human recombinant MCP-1 on the in vitro proliferation of rat vascular smooth muscle cells (VSMCs). Incubation of VSMCs with MCP-1 (50-200 ng/ml) in the presence of 0.5% FCS significantly increased cell proliferation, [3H]-thymidine incorporation and the proliferative S fraction, measured by flow cytometry, compared to control cells. The proliferative effect of MCP-1 was specific, as shown by inhibition with a rabbit polyclonal serum to MCP-1. Moreover, the mitogenic effect of MCP-1 was significantly inhibited by downregulation of protein kinase C (PKC) activity and by incubation with H-7, a protein kinase inhibitor, suggesting the involvement of the PKC system. Verapamil, a Ca2+ channel blocker, also reduced the stimulatory effect of MCP-1 on cell proliferation. This study demonstrates that MCP-1 does not merely have a chemotactic activity, but also a mitogenic effect on cultured rat VSMCs.

Novel therapeutic targets for autism

Autism spectrum disorders (ASDs) are pervasive neurodevelopmental disorders, diagnosed in early childhood when acquired skills are lost or the acquisition of new skills becomes delayed. ASDs are associated with varying degrees of dysfunctional communication and social skills, in addition to repetitive and stereotypic behaviors. The diagnosis has increased considerably to approximately one in 180 people, but it is not clear whether this is because of a higher prevalence of the disorder, improved awareness by clinicians or a combination of both. There are no defined mechanisms of pathogenesis or curative therapy presently available. Oxidative stress, overactivation of the hypothalamic-pituitary-adrenal axis and increased gut-blood-brain-barrier permeability might be involved. The scope of this article is to integrate these findings and present the opinion that non-allergic activation of gastrointestinal and brain mast cells could contribute to many of the pathologic findings and provide unique targets for ASD therapy. We make suggestions for new research directives and possible novel therapies from readily available molecules.

RANTES production and expression is reduced in relapsing-remitting multiple sclerosis patients treated with interferon-β-1b

RANTES (regulated upon activation, normal T-cell expressed and secreted), a CC chemokine, appears to play a role in the pathogenesis of relapsing-remitting multiple sclerosis (RR-MS), enhancing the inflammatory response within the nervous system. We have demonstrated that RANTES production is increased in RR-MS compared to controls. Interferon-beta-1b (IFN-beta-1b) treatment reduces RANTES production in sera and peripheral blood adherent mononuclear cell (PBAM) supernatants both in relapse and remission. IFN-beta-1b also reduces RANTES expression in PBAM. Our results suggest that RANTES modulation might represent one of the mechanisms of action of IFN-beta-1b in RR-MS.