Activation of Mast Cells by Neuropeptides: The Role of Pro-Inflammatory and Anti-Inflammatory Cytokines.

Mast cells (MCs) are tissue cells that are derived from bone marrow stem cells that contribute to allergic reactions, inflammatory diseases, innate and adaptive immunity, autoimmunity, and mental disorders. MCs located near the meninges communicate with microglia through the production of mediators such as histamine and tryptase, but also through the secretion of IL-1, IL-6 and TNF, which can create pathological effects in the brain. Preformed chemical mediators of inflammation and tumor necrosis factor (TNF) are rapidly released from the granules of MCs, the only immune cells capable of storing the cytokine TNF, although it can also be produced later through mRNA. The role of MCs in nervous system diseases has been extensively studied and reported in the scientific literature; it is of great clinical interest. However, many of the published articles concern studies on animals (mainly rats or mice) and not on humans. MCs are known to interact with neuropeptides that mediate endothelial cell activation, resulting in central nervous system (CNS) inflammatory disorders. In the brain, MCs interact with neurons causing neuronal excitation with the production of neuropeptides and the release of inflammatory mediators such as cytokines and chemokines. This article explores the current understanding of MC activation by neuropeptide substance P (SP), corticotropin-releasing hormone (CRH), and neurotensin, and the role of pro-inflammatory cytokines, suggesting a therapeutic effect of the anti-inflammatory cytokines IL-37 and IL-38.

Mast Cell Cytokines in Acute and Chronic Gingival Tissue Inflammation: Role of IL-33 and IL-37.

Much evidence suggests autoimmunity in the etiopathogenesis of periodontal disease. In fact, in periodontitis, there is antibody production against collagen, DNA, and IgG, as well as increased IgA expression, T cell dysfunction, high expression of class II MHC molecules on the surface of gingival epithelial cells in inflamed tissues, activation of NK cells, and the generation of antibodies against the azurophil granules of polymorphonuclear leukocytes. In general, direct activation of autoreactive immune cells and production of TNF can activate neutrophils to release pro-inflammatory enzymes with tissue damage in the gingiva. Gingival inflammation and, in the most serious cases, periodontitis, are mainly due to the dysbiosis of the commensal oral microbiota that triggers the immune system. This inflammatory pathological state can affect the periodontal ligament, bone, and the entire gingival tissue. Oral tolerance can be abrogated by some cytokines produced by epithelial cells and activated immune cells, including mast cells (MCs). Periodontal cells and inflammatory-immune cells, including mast cells (MCs), produce cytokines and chemokines, mediating local inflammation of the gingival, along with destruction of the periodontal ligament and alveolar bone. Immune-cell activation and recruitment can be induced by inflammatory cytokines, such as IL-1, TNF, IL-33, and bacterial products, including lipopolysaccharide (LPS). IL-1 and IL-33 are pleiotropic cytokines from members of the IL-1 family, which mediate inflammation of MCs and contribute to many key features of periodontitis and other inflammatory disorders. IL-33 activates several immune cells, including lymphocytes, Th2 cells, and MCs in both innate and acquired immunological diseases. The classic therapies for periodontitis include non-surgical periodontal treatment, surgery, antibiotics, anti-inflammatory drugs, and surgery, which have been only partially effective. Recently, a natural cytokine, IL-37, a member of the IL-1 family and a suppressor of IL-1b, has received considerable attention for the treatment of inflammatory diseases. In this article, we report that IL-37 may be an important and effective therapeutic cytokine that may inhibit periodontal inflammation. The purpose of this paper is to study the relationship between MCs, IL-1, IL-33, and IL-37 inhibition in acute and chronic inflamed gingival tissue.

Mast Cell Cytokines IL-1, IL-33, and IL-36 Mediate Skin Inflammation in Psoriasis: A Novel Therapeutic Approach with the Anti-Inflammatory Cytokines IL-37, IL-38, and IL-1Ra.

Psoriasis (PS) is a skin disease with autoimmune features mediated by immune cells, which typically presents inflammatory erythematous plaques, and is associated with many comorbidities. PS exhibits excessive keratinocyte proliferation, and a high number of immune cells, including macrophages, neutrophils, Th1 and Th17 lymphocytes, and mast cells (MCs). MCs are of hematopoietic origin, derived from bone marrow cells, which migrate, mature, and reside in vascularized tissues. They can be activated by antigen-provoking overexpression of proinflammatory cytokines, and release a number of mediators including interleukin (IL)-1 and IL-33. IL-1, released by activated keratinocytes and MCs, stimulates skin macrophages to release IL-36-a powerful proinflammatory IL-1 family member. IL-36 mediates both innate and adaptive immunity, including chronic proinflammatory diseases such as psoriasis. Suppression of IL-36 could result in a dramatic improvement in the treatment of psoriasis. IL-36 is inhibited by IL-36Ra, which binds to IL-36 receptor ligands, but suppression can also occur by binding IL-38 to the IL-36 receptor (IL-36R). IL-38 specifically binds only to IL-36R, and inhibits human mononuclear cells stimulated with IL-36 in vitro, sharing the effect with IL-36Ra. Here, we report that inflammation in psoriasis is mediated by IL-1 generated by MCs-a process that activates macrophages to secrete proinflammatory IL-36 inhibited by IL-38. IL-37 belongs to the IL-1 family, and broadly suppresses innate inflammation via IL-1 inhibition. IL-37, in murine models of inflammatory arthritis, causes the suppression of joint inflammation through the inhibition of IL-1. Therefore, it is pertinent to think that IL-37 can play an inhibitory role in inflammatory psoriasis. In this article, we confirm that IL-38 and IL-37 cytokines emerge as inhibitors of inflammation in psoriasis, and hold promise as an innovative therapeutic tool.

Powerful anti-inflammatory action of luteolin: Potential increase with IL-38.

Luteolin belongs to the flavone family originally present in some fruits and vegetables, including olives, which decrease intracellular levels of reactive oxygen species (ROS) following the activation of various stimuli. Luteolin inhibits inflammation, a complex process involving immune cells that accumulate at the site of infectious or non-infectious injury, with alteration of the endothelium leading to recruitment of leukocytes. Cytokines have been widely reported to act as immune system mediators, and IL-1 family members evolved to assist in host defense against infections. Interleukin (IL)-1 and Toll-like receptor (TLR) are involved in the innate immunity in almost all living organisms. After being synthesized, IL-1 induces numerous inflammatory mediators including itself, other pro-inflammatory cytokines/chemokines, and arachidonic acid products, which contribute to the pathogenesis of immune diseases. Among the 11 members of the IL-1 family, there are two new cytokines that suppress inflammation, IL-37 and IL-38. IL-38 binds IL-36 receptor (IL-1R6) and inhibits several pro-inflammatory cytokines, including IL-6, through c-Jun N-terminal kinase (JNK) induction and reducing AP1 and nuclear factor kappa-light-chain-enhancer of activated B cells (NFκB) activity, alleviating inflammatory diseases. Therefore, since luteolin, IL-37 and IL-38 are all anti-inflammatory molecules with different signaling pathways, it is pertinent to recommend the combination of luteolin with these anti-inflammatory cytokines in inflammation.

Advances in Mast Cell Activation by IL-1 and IL-33 in Sjögren's Syndrome: Promising Inhibitory Effect of IL-37.

Sjögren's syndrome (SS) is a chronic autoimmune inflammatory disease that affects primarily older women and is characterized by irreversible damage of the exocrine glands, including tear (xerophthalmia) and salivary glands (xerostomia). Secretory glands lose their functionality due to the infiltration of immune cells, which produce cytokines and cause inflammation. Primary SS is characterized by dry syndrome with or without systemic commitment in the absence of other pathologies. Secondary SS is accompanied by other autoimmune diseases with high activation of B lymphocytes and the production of autoantibodies, including the rheumatoid factor. Other cells, such as CD4+ T cells and mast cells (MCs), participate in SS inflammation. MCs are ubiquitous, but are primarily located close to blood vessels and nerves and can be activated early in autoimmune diseases to express a wide variety of cytokines and chemokines. In the SS acute phase, MCs react by generating chemical mediators of inflammation, tumor necrosis factor (TNF), and other pro-inflammatory cytokines such as interleukin (IL)-1 and IL-33. IL-33 is the specific ligand for ST2 capable of inducing some adaptive immunity TH2 cytokines but also has pro-inflammatory properties. IL-33 causes impressive pathological changes and inflammatory cell infiltration. IL-1 family members can have paracrine and autocrine effects by exacerbating autoimmune inflammation. IL-37 is an IL-1 family cytokine that binds IL-18Rα receptor and/or Toll-like Receptor (TLR)4, exerting an anti-inflammatory action. IL-37 is a natural inhibitor of innate and acquired immunity, and the level is abnormal in patients with autoimmune disorders. After TLR ligand activation, IL-37 mRNA is generated in the cytoplasm, with the production of pro-IL-37 and later mature IL-37 caspase-1 mediated; both precursor and mature IL-37 are biologically active. Here, we discuss, for the first time, the current knowledge of IL-37 in autoimmune disease SS and propose a new therapeutic role.

Sodium chromo-glycate and palmitoylethanolamide: A possible strategy to treat mast cell-induced lung inflammation in COVID-19.

A novel human coronavirus SARS-CoV-2 (also referred to as CoV-19) that emerged in late 2019 causes Covid-19 disease a respiratory tract infection which provokes about 4 million deaths per year. Unfortunately, to date, there is no specific antiviral treatment for COVID-19. Mast cells (MCs) are immune cells implicated in the pathogenesis of viral infections, where they mediate inflammation. Microbes, including virus, activate MCs through TLR releasing chemical pro-inflammatory compounds and cytokines. Although, in biomedical literature there are only few reports on MCs activation by SARS-CoV-2 infection. The production of pro-inflammatory cytokines by MC viral activation leads to increase pulmonary inflammation and fibrosis. Sodium Chromo-Glycate (SCG) described as a MC stabilizer, prevents the release of inflammatory chemical compounds, improve mouse survival and respiratory pathological changes in lung viral infection and suppresses inflammation. Furthermore, palmitoylethanolamide (PEA) a nuclear factor agonist, an endogenous fatty acid amide, which exerts a variety of biological effects, related to chronic inflammation and pain, is involved also in MCs homeostasis with an inhibitory and protective effect on the respiratory tract during viral infections. Here, we hypothesize for the first time, that SCG and/or PEA suppress MC activation and pro-inflammatory mediators release, playing an anti-inflammatory therapeutic role in the inflamed lung of patients with COVID-19.

New aspect of allergic contact dermatitis, an inflammatory skin disorder mediated by mast cells: Can IL-38 help?

Atopic dermatitis (AD) is an inflammatory reaction of the skin that can occur in several parts of the body and can be provoked or exacerbated by food and/or environmental compounds. Allergic contact dermatitis (ACD) is a potential enhancer of AD, and an epidermal barrier breaker which induces greater penetration of allergens and other compounds. ACD presents an eczematous rash, red and itchy, with inflammation mediated by cytokines. ACD is an immunological disorder caused by contact with an allergic substance (haptens) that involves immunotoxicity, irritation and inflammation. Mast cells (MCs) are important immune cells that intervene, as effector cells, in allergic and anaphylactic reactions, asthma, autoimmune diseases and cancer. In dermatitis, activated MCs release inflammatory chemical mediators and secrete pro-inflammatory cytokines, including interleukin (IL)-1, TNF, and IL-33. In addition, IL-1 activates MCs to generate a number of cytokines and chemokines, which aggravate inflammation. IL-38 cytokine, an IL-1 family member, is secreted by activated immune cells, including macrophages and lymphocytes, and possesses anti-inflammatory activity. IL-38, by binding IL-36 receptor (IL-36R), provokes suppression of inflammation in many immune diseases. In particular, IL-38 inhibits the generation of IL-1, IL-6 and IL-8 along with other cytokines/chemokines. Here, we hypothesize for the first time that IL-38 may suppresses the inflammatory response in dermatitis, exerting beneficial therapeutic effect.

Impact of mast cells in fibromyalgia and low-grade chronic inflammation: Can IL-37 play a role?

Fibromyalgia (FM) is a disease characterized by chronic widespread pain, fatigue, aches, joint stiffness, depression, cognitive dysfunction, and nonrestorative sleep. In FM, neurotransmission and glial activation can occur with an increase in inflammatory cytokines and involvement of mast cells (MCs) in the skin. FM skin biopsies show an increase in the number of MCs, as well as the production of corticotropin releasing hormone and substance P (SP) by the neurons, which in turn activate MCs to release neurosensitizing proinflammatory substances, such as cytokines, secreted preformed mediators, and lipids, which can exacerbate low-grade inflammation. In fact, certain proinflammatory cytokines are higher in FM and mediate muscle pain, the mechanism of which is not yet clear. MC-derived tumor necrosis factor (TNF) induces nerve growth factor (NGF) and participates in nerve fiber elongation in skin hypersensitivity. IL-37 is an inhibitor of proinflammatory IL-1 family members, which are generated and released by MCs. The goal of this article is to demonstrate that inflammatory cytokines and MC products play a role in FM and that inflammation may be inhibited by IL-37. Here, we propose IL-37 as a cytokine that contributes to improve the pathogenesis of FM by blocking IL-1 family members.

New insight into systemic mastocytosis mediated by cytokines IL-1ß and IL-33: Potential inhibitory effect of IL-37.

Systemic mastocytosis in various forms is characterized by mast cell (MC) infiltration of the bone marrow and other internal organs. The most common form is the indolent one with life expectancy similar to the normal population, while the systemic aggressive myeloproliferative type presents serious damage to various organs and is associated with mature and immature atypical mast cells. In systemic mastocytosis patients, MCs could be activated with consequent severe anaphylactic reactions, along with other symptoms. MCs, which are reactive to a variety of external factors such as allergens or other inflammatory or physical stimuli, derive from pluripotent cellular progenitor CD34+ which leaves the bone marrow as CD34+/CD17+ for implantation in the tissues where they reach maturation. MCs participate in the innate and adaptive immune system where they play a role in host defense. Activation of MCs occurs through the binding of IgE to FcεRI receptor, and initiates the phosphorylation and activation of the p38 tyrosine MAP kinase. After various reactions there is a subsequent translation and generation of pro-inflammatory cytokines which are strongly linked to allergic inflammation and mastocytosis. Human cytokine interleukin-37 (IL-37), a unique IL-1ß family member, has strong protective and anti-inflammatory properties, influencing cellular metabolism. We investigated the effect of IL-37 on inflammation in mastocytosis and report that the hematopoietic expression of IL-37 can reduce the inflammatory state in this disease. IL-37 limits excessive inflammation, which suggests that IL-37 may be beneficial to the metabolic and inflammatory process and is a candidate as a potential new therapeutic agent.

Activation of mast cells mediates inflammatory response in psoriasis: Potential new therapeutic approach with IL-37.

Psoriasis (PS) is an autoimmune disorder characterized by chronic inflammatory skin immune-mediated disease which occurs in 2-4% of the worldwide population. PS is associated with an increased risk of cardiovascular disease and depression, and 30% of PS patients are affected with psoriatic arthritis. PS presents excessive keratinocyte proliferation, abnormal differentiation, and elevated mast cell (MC) number. In PS, there are enhanced type I interferon (IFN), angiogenesis, and over-expression of several proinflammatory cytokines, such as tumor necrosis factor and interleukin (IL)-1 family members generated by several immune cells including MCs. MCs are hematopoietic cells that reside in vascularized tissues, which, upon appropriate activation, release proinflammatory cytokines, an effect worsened by acute stress and PS. In recent years, IL-37 emerged as an anti-inflammatory cytokine which binds to alpha chain of the IL-18 receptor alpha (IL-18Rα) and downregulates MyD88. This effect leads to the inhibition of nuclear factor-κB (NF-κB) and mitogen activation protein kinase, with the suppression of inflammatory response. These observations candidate IL-37 as a potential new therapeutic cytokine for inflammatory disorders including PS.

Some microbiological aspects of rats captured alive at the port city of Piraeus, Greece.

The aim was to investigate the presence of leptospira infection and the antibiotic resistance of Enterobacteriaceae among wild rats living in a densely populated area. For this purpose 3-4 large traps were placed daily across the commercial port-front of Piraeus for the duration of two months. The rats captured were transferred in the laboratory alive, where samples were freshly collected. None of the 25 rats captured was found to be infected with leptospira. Only one rat was infected with Salmonella. Other predominant members of the family of Enterobacteriaceae were Escherichia coli, Proteus spp. and Klebsiella spp. Resistance to antimicrobial agents commonly used in veterinary treatment was very high for spectinomycin, erythromycin, neomycin and tetracycline in all tested species of Enterobacteriaceae. It appears that port rats living in the densely populated area of the city of Piraeus could become a source of infection for man and animals with microorganisms highly resistant to antimicrobial agents.