Neutrophil trapping and nexocytosis, mast cell-mediated processes for inflammatory signal relay.

Neutrophils are sentinel immune cells with essential roles for antimicrobial defense. Most of our knowledge on neutrophil tissue navigation derived from wounding and infection models, whereas allergic conditions remained largely neglected. Here, we analyzed allergen-challenged mouse tissues and discovered that degranulating mast cells (MCs) trap living neutrophils inside them. MCs release the attractant leukotriene B4 to re-route neutrophils toward them, thus exploiting a chemotactic system that neutrophils normally use for intercellular communication. After MC intracellular trap (MIT) formation, neutrophils die, but their undigested material remains inside MC vacuoles over days. MCs benefit from MIT formation, increasing their functional and metabolic fitness. Additionally, they are more pro-inflammatory and can exocytose active neutrophilic compounds with a time delay (nexocytosis), eliciting a type 1 interferon response in surrounding macrophages. Together, our study highlights neutrophil trapping and nexocytosis as MC-mediated processes, which may relay neutrophilic features over the course of chronic allergic inflammation.

Image quality assessment in low-dose COVID-19 chest CT examinations.

BACKGROUND: Low-dose thoracic protocols were developed massively during the COVID-19 outbreak. PURPOSE: To study the impact on image quality (IQ) and the diagnosis reliability of COVID-19 low-dose chest computed tomography (CT) protocols. MATERIAL AND METHODS: COVID-19 low-dose protocols were implemented on third- and second-generation CT scanners considering two body mass index (BMI) subgroups (<25 kg/m2 and >25 kg/m2). Contrast-to-noise ratios (CNR) were compared with a Catphan phantom. Next, two radiologists retrospectively assessed IQ for 243 CT patients using a 5-point Linkert scale for general IQ and diagnostic criteria. Kappa score and Wilcoxon rank sum tests were used to compare IQ score and CTDIvol between radiologists, protocols, and scanner models. RESULTS: In vitro analysis of Catphan inserts showed in majority significantly decreased CNR for the low dose versus standard acquisition protocols on both CT scanners. However, in vivo, there was no impact on the diagnosis: sensitivity and specificity were ≥0.8 for all protocols and CT scanners. The third-generation scanner involved a significantly lower dose compared to the second-generation scanner (CTDIvol of 1.8 vs. 2.6 mGy for BMI <25 kg/m2 and 3.3 vs. 4.6 mGy for BMI >25 kg/m2). Still, the third-generation scanner showed a significantly higher IQ with the low-dose protocol compared to the second-generation scanner (30.9 vs. 28.1 for BMI <25 kg/m2 and 29.9 vs. 27.8 for BMI >25 kg/m2). Finally, the two radiologists had good global inter-reader agreement (kappa ≥0.6) for general IQ. CONCLUSION: Low-dose protocols provided sufficient IQ independently of BMI subgroups and CT models without any impact on diagnosis reliability.

Fecal microbiota transplantation in patients with irritable bowel syndrome: an overview of current studies.

As dysbiosis is a key factor associated with irritable bowel syndrome (IBS), modulation of the intestinal microbiota could improve IBS symptoms and quality of life. Fecal microbiota transplantation (FMT) could be one efficient way to restore bacterial composition in IBS patients. This review comprises 12 clinical trials published from 2017 to 2021. Inclusion criteria were the assessment of IBS symptoms using the IBS symptom severity score, quality of life measured by the lBS quality of life scale, and gut microbiota analysis. Improved symptoms were reported in all 12 studies, paralleling with an increased quality of life after FMT, but also partly after placebo treatment. The use of oral capsules showed that the placebo treatment can have similar or even stronger positive effects on IBS patients than FMT. Gastroscopic FMT appears to link modulation of the gut microbiome to significant symptom reduction in patients. The patient's microbiota profile shifted toward their respective donors. Symptom worsening or decreased quality of life after FMT was not reported. The results show that FMT could be a therapeutic approach in IBS patients. Further research is needed to investigate whether FMT has a more beneficial effect on IBS patient than placebo treatment with the patient's own stool, placebo capsules, or bowel cleansing. Moreover, optimal donor selection, frequency, dosage, and route of delivery still need to be defined.

Resveratrol Treatment Prevents Increase of Mast Cells in Both Murine OVA Enteritis and IL-10-/- Colitis.

Mast cells are involved in allergic and other inflammatory diseases. The polyphenol resveratrol is known for its anti-inflammatory properties and may be used as nutraceutical in mast cell associated diseases. We analyzed the effect of resveratrol on mast cells in vivo in ovalbumin-induced allergic enteritis as well as experimental colitis in IL-10-/- mice which received resveratrol via drinking water. Treatment with resveratrol prevented the increase in mast cells in both allergic enteritis and chronic colitis in duodenum as well as in colon. Further, it delayed the onset of diseases symptoms and ameliorated diseases associated parameters such as tissue damage as well as inflammatory cell infiltration in affected colon sections. In addition to the findings in vivo, resveratrol inhibited IgE-dependent degranulation and expression of pro-inflammatory cytokines such as TNF-α in IgE/DNP-activated as well as in LPS-activated bone marrow-derived mast cells. These results indicate that resveratrol may be considered as an anti-allergic and anti-inflammatory plant-derived component for the prevention or treatment of mast cell-associated disorders of the gastrointestinal tract.

Probiotic Potential of Lactobacillus Species in Allergic Rhinitis.

Since conventional allergy medication for asthma or allergic rhinitis (AR) can cause side effects which limit the patients' quality of life, it is of interest to find other forms of therapy. In particular, probiotic bacteria, such as Lactobacillus species, have shown anti-allergic effects in various mouse and human studies. For instance, administration of some Lactobacillus species resulted in nasal and ocular symptom relief and improvement of quality of life in children and adults suffering from rhinitis. Different changes in cytokine profiles, such as elevated Th1 and decreased Th2 cytokines, reduced allergy-related immunoglobulins and cell immigration have been found in both human and murine studies. Positive effects on patients like less activity limitations or fewer rhinitis episodes and longer periods free from asthma or rhinitis were also described following oral administration of Lactobacillus bacteria. However, it is still unclear how this type of lactic acid bacteria leads to changes in the immune system and thus inhibits the development of allergies or relieves their symptoms. This review gives an overview of current studies and draws conclusions concerning the usage of probiotic Lactobacillus strains in AR.

Resveratrol Is a Natural Inhibitor of Human Intestinal Mast Cell Activation and Phosphorylation of Mitochondrial ERK1/2 and STAT3.

Mast cells play a critical role as main effector cells in allergic and other inflammatory diseases. Usage of anti-inflammatory nutraceuticals could be of interest for affected patients. Resveratrol, a natural polyphenol found in red grapes, is known for its positive properties. Here, we analyzed the effects of resveratrol on FcεRI-mediated activation of mature human mast cells isolated from intestinal tissue (hiMC). Resveratrol inhibited degranulation and expression of cytokines and chemokines such as CXCL8, CCL2, CCL3, CCL4, and TNF-α in a dose-dependent manner. Further, resveratrol inhibited the phosphorylation of extracellular signal-regulated kinase (ERK) 1/2 and signal transducer and activator of transcription (STAT) 3. ERK1/2 is known to be involved in cytokine expression of hiMC and to directly interact with STAT3. Mitochondrial STAT3 is phosphorylated by ERK1/2 and contributes to mast cell degranulation. We were able to isolate mitochondrial fractions from small hiMC numbers and could show that activation of mitochondrial STAT3 and ERK1/2 in hiMC was also inhibited by resveratrol. Our results indicate that resveratrol inhibits hiMC activation by inhibiting the phosphorylation of mitochondrial and nuclear ERK1/2 and STAT3, and it could be considered as an anti-inflammatory nutraceutical in the treatment of mast cell-associated diseases.

Nobiletin acts anti-inflammatory on murine IL-10-/- colitis and human intestinal fibroblasts.

PURPOSE: Inflammatory bowel disease (IBD) shows increasing prevalence over the last years. We propose that anti-inflammatory plant substances could be used as additional or alternative agents with good compliance in prevention and/or therapy of IBD and its complication intestinal fibrosis. We could recently show that the citrus flavonoid nobiletin acts anti-inflammatory on activation of intestinal mast cells. Here, we analysed the effects of nobiletin on inflammation and fibrosis in IL-10-/- colitis. METHODS: IL-10-/- and wild-type (WT) mice were orally treated with/without vehicle or nobiletin. Clinical symptoms of colitis and disease activity index (DAI) were assessed, and colon tissue was analysed for tissue damage, cellular infiltration, bowel wall thickness, mast cell number and degranulation, as well as collagen deposition as marker for fibrosis. Human intestinal fibroblasts (hiFB) were treated with nobiletin and the expression of collagen and pro-inflammatory cytokines was measured. RESULTS: Nobiletin treatment of IL-10-/- mice resulted in a reduction of clinical colitis symptoms and a longer survival time. In addition, histological scores of colitis were reduced compared to control groups. Mast cell number and degranulation was lower in nobiletin treated IL-10-/- mice, and correlated positively with DAI. As well, fibrotic marker of collagen deposition was reduced by nobiletin. In hiFB, the expression of collagen as well as of pro-inflammatory cytokines IL-6, TNF and CCL2 was down-regulated by nobiletin treatment. CONCLUSIONS: Nobiletin decreases inflammatory symptoms and markers in murine colitis as well as fibrotic collagen deposition and expression. Thus, nobiletin could be a potential new agent in therapy of chronic colitis.

Increased IL-17RA and IL-17RC in End-Stage COPD and the Contribution to Mast Cell Secretion of FGF-2 and VEGF.

Mast cells are accumulated in advanced chronic obstructive pulmonary disease (COPD), and interleukin (IL)-17 signaling plays a role in disease progression. The expression, localization and functional relevance of IL-17 receptor (R)A and IL-17RC was explored in COPD by immunodetection, and functional assays.IL-17RA and IL-17RC was increased in very severe COPD, and expressed by mast cells. Increased secretion of the pro-angiogenic basic fibroblast growth factor and vascular endothelial growth factor was observed in vitro-maintained mast cells stimulated with IL-17A. Expression of these mediators was confirmed in end-stage COPD. Thus, accumulation of mast cells in COPD may contribute to vascular remodeling.

Citrus peel polymethoxyflavones nobiletin and tangeretin suppress LPS- and IgE-mediated activation of human intestinal mast cells.

PURPOSE: Allergic diseases with mast cells (MC) as main effector cells show an increased prevalence. MC also play an essential role in other inflammatory conditions. Therapeutical use of anti-inflammatory nutraceuticals directly targeting MC activation could be of interest for afflicted patients. Nobiletin and tangeretin are citrus peel polymethoxyflavones, a group of citrus flavonoids, possessing anticancer, antimetastatic, and anti-inflammatory activities. Here, we analyzed the effects of nobiletin/tangeretin on LPS- and IgE-mediated stimulation of human intestinal mast cells (hiMC). METHODS: MC isolated from human intestinal tissue were treated with different concentrations of nobiletin or tangeretin prior to stimulation via LPS/sCD14 or IgE-dependently. Degranulation, pro-inflammatory cytokine expression and phosphorylation of ERK1/2 were examined. RESULTS: Expression of CXCL8, CCL3, CCL4 and IL-1ß in response to LPS-mediated stimulation was inhibited by nobiletin/tangeretin. hiMC activated IgE-dependently showed a reduced release of ß-hexosaminidase and cysteinyl LTC4 in response to nobiletin, but not in response to tangeretin. Expression of CXCL8, CCL2, CCL3, CCL4 and TNF in IgE-dependently activated hiMC was decreased in a dose-dependent manner following treatment with nobiletin/tangeretin. IL-1ß expression was only reduced by tangeretin. Compared to treatment with NF-κB inhibitor BMS345541 or MEK-inhibitor PD98059, nobiletin and tangeretin showed similar effects on mediator production. Phosphorylation of ERK1/2 upon IgE-mediated antigen stimulation was significantly suppressed by nobiletin and tangeretin. CONCLUSIONS: Nobiletin and, to a lesser extent, tangeretin could be considered as anti-inflammatory nutraceuticals by reducing release and production of proinflammatory mediators in MC.

Cinnamaldehyde is the main mediator of cinnamon extract in mast cell inhibition.

PURPOSE: In terms of their involvement in allergic and inflammatory conditions, mast cells (MC) can be promising targets for medical agents in therapy. Because of their good compliance and effectiveness, phytochemicals are of great interest as new therapeutic tools in form of nutraceuticals. We found recently that cinnamon extract (CE) inhibits mast cell activation. Here, we analysed the effects of a major compound of CE, cinnamaldehyde (CA), on mast cell activation. METHODS: Release of prestored and de novo synthesised mediators as well as expression of pro-inflammatory cytokines and mast cell-specific proteases were analysed in RBL-2H3 cells or in human mast cells isolated from intestinal tissue (hiMC) treated with CA prior to stimulation by FcεRI crosslinking or IONO/PMA. The results were compared with the corresponding effects of CE. RESULTS: Following treatment with CA, release of ß-hexosaminidase in IgE-dependent or IgE-independent activated RBL-2H3 cells was down-regulated in a dose-dependent manner to about 10%. In hiMC, release of ß-hexosaminidase was also significantly reduced, and release of LTC4 and CXCL8 was almost completely inhibited by CA. Moreover, IgE-mediated expression of CXCL8, CCL2, CCL3 and CCL4 in hiMC was significantly down-regulated by CA. With the exception of the expression of the mast cell proteases tryptase and chymase, the inhibitory effects of CA were very similar to the effects shown for CE treatment. The reducing effect of CA on mast cell mediators-seen for long- and for short-term incubations-could be related to particular signalling pathways as CA caused a down-regulation in ERK as well as PLCγ1 phosphorylation. CONCLUSIONS: CA decreases release and expression of pro-inflammatory mast cell mediators. This inhibitory action is similar to the effects observed for CE indicating CA as the main active compound in CE leading to its anti-allergic properties.

Soluble CD14 is essential for lipopolysaccharide-dependent activation of human intestinal mast cells from macroscopically normal as well as Crohn's disease tissue.

Mast cells are now considered sentinels in immunity. Given their location underneath the gastrointestinal barrier, mast cells are entrusted with the task of tolerating commensal microorganisms and eliminating potential pathogens in the gut microbiota. The aim of our study was to analyse the responsiveness of mast cells isolated from macroscopically normal and Crohn's disease-affected intestine to lipopolysaccharide (LPS). To determine the LPS-mediated signalling, human intestinal mast cells were treated with LPS alone or in combination with soluble CD14 due to their lack of surface CD14 expression. LPS alone failed to stimulate cytokine expression in human intestinal mast cells from both macroscopically normal and Crohn's disease tissue. Upon administration of LPS and soluble CD14, there was a dose- and time-dependent induction of cytokine and chemokine expression. Moreover, CXCL8 and interleukin-1ß protein expression was induced in response to activation with LPS plus soluble CD14. Expression of cytokines and chemokines was at similar levels in mast cells from macroscopically normal and Crohn's disease-affected intestine after LPS/soluble CD14 treatment. In conclusion, human intestinal mast cells appear to tolerate LPS per se. The LPS-mediated activation in mast cells may be provoked by soluble CD14 distributed by other LPS-triggered cells at the gastrointestinal barrier.

Interferon-γ regulates growth and controls Fcγ receptor expression and activation in human intestinal mast cells.

BACKGROUND: Development and function of tissue resident mast cells (MCs) is tightly controlled by various cytokines, most of which belong to the typical T helper (Th) 2-type cytokines such as IL-3 and IL-4. The effects of the Th1-type cytokine IFN-γ on human MCs is less clear. RESULTS: Here, we analyzed the effects of IFN-γ on tissue-derived, mature human MCs. We found that INF-γ decreases proliferation, without affecting apoptosis in human intestinal MCs cultured in the presence of optimal concentrations of stem cell factor (SCF) or SCF and IL-4. However, in the absence of growth factors or at suboptimal concentrations of SCF, INF-γ promotes survival through inhibition of MC apoptosis. Interestingly, we found that INF-γ has no effect on FcϵRI expression and FcϵRI-mediated release of histamine and leukotriene (LT)C4, while it has profound effects on FcγR expression and activation. We show that intestinal MCs express FcγRI, FcγRIIa, and FcγRIIc, whereas FcγRIIb expression was found in only 40% of the isolates and FcγRIII was never detectable. INF-γ strongly increases FcγRI and decreases FcγRIIa expression. INF-γ-naïve MCs produce LTC4 but fail to degranulate upon crosslinking of surface-bound monomeric IgG. In contrast, INF-γ-treated MCs rapidly release granule-stored histamine in addition to de novo-synthesized LTC4. CONCLUSION: In summary, we identify INF-γ as an important regulator of tissue-resident human MCs. IFN-γ displays a dual function by blocking extensive MC proliferation, while decreasing apoptosis in starving MCs and enhancing FcγRI expression and activation. These results emphasize the involvement of mucosal MCs in Th1-mediated disorders.

The circadian clock is functional in eosinophils and mast cells.

Allergic diseases are frequently exacerbated between midnight and early morning, suggesting a role for the biological clock. Mast cells (MC) and eosinophils are the main effector cells of allergic diseases and some MC-specific or eosinophil-specific markers, such as tryptase or eosinophil cationic protein, exhibit circadian variation. Here, we analysed whether the circadian clock is functional in mouse and human eosinophils and MC. Mouse jejunal MC and polymorphonuclear cells from peripheral blood (PMNC) were isolated around the circadian cycle. Human eosinophils were purified from peripheral blood of non-allergic and allergic subjects. Human MC were purified from intestinal tissue. We found a rhythmic expression of the clock genes mPer1, mPer2, mClock and mBmal1 and eosinophil-specific genes mEcp, mEpo and mMbp in murine PMNC. We also found circadian variations for hPer1, hPer2, hBmal1, hClock, hEdn and hEcp mRNA and eosinophil cationic protein (ECP) in human eosinophils of both healthy and allergic people. Clock genes mPer1, mPer2, mClock and mBmal1 and MC-specific genes mMcpt-5, mMcpt-7, mc-kit and mFcεRI α-chain and protein levels of mMCPT5 and mc-Kit showed robust oscillation in mouse jejunum. Human intestinal MC expressed hPer1, hPer2 and hBmal1 as well as hTryptase and hFcεRI α-chain, in a circadian manner. We found that pre-stored histamine and de novo synthesized cysteinyl leukotrienes, were released in a circadian manner by MC following IgE-mediated activation. In summary, the biological clock controls MC and eosinophils leading to circadian expression and release of their mediators and, hence it might be involved in the pathophysiology of allergy.

Obesity - a promoter of allergy?

The prevalence of both obesity and allergy has been increasing throughout the world, leading to the hypothesis that the two are linked to one another. This overview summarizes the results of 34 studies from 2002 to 2012 that investigated a possible contributing effect of increasing body mass on the development and prevalence of various atopic diseases. Obesity was found to clearly affect bronchial asthma. However, the correlation was stronger in the nonatopic asthma phenotype. Obesity was found to be associated with the development of atopic dermatitis in children only. No clear association was found between obesity and the prevalence of allergic rhinitis or allergic conjunctivitis or increased sensitization to food allergens. This review sums up our study results and discusses a possible role of obesity in the promotion of allergy and asthma.

Combined arginine and glutamine decrease release of de novo synthesized leukotrienes and expression of proinflammatory cytokines in activated human intestinal mast cells.

PURPOSE: Glutamine and arginine modulate inflammatory responses of epithelial cells and monocytes. Here, we studied the response of human mast cells to pharmacological doses of arginine and glutamine. METHODS: Mast cells isolated from intestinal tissue were incubated with physiological doses of arginine (0.1 mmol/L) and glutamine (0.6 mmol/L) or with pharmacological doses of arginine (2 mmol/L) and glutamine (10 mmol/L) for 18 h. Following stimulation by IgE receptor crosslinking mast cell mediators were measured by enzymatic assay, ELISA, multiplex bead immunoassay, or real-time RT-PCR, and activation of intracellular signaling molecules was determined using proteome profiler array or immunoblotting. RESULTS: We found that the combined challenge of mast cells with pharmacological doses of arginine and glutamine caused a decrease in induced release of de novo synthesized leukotriene C(4) but not of pre-stored ß-hexosaminidase. Moreover, we found reduced expression of chemokines monocyte chemoattractant protein-1 (CCL2), macrophage inflammatory protein-1ß (CCL4), IL-8 (CXCL8), and TNF in response to high doses of both amino acids. The anti-inflammatory effects of arginine and glutamine were associated with decreased activation levels of signaling molecules known to be involved in mast cell cytokine expression such as MAPK family members extracellular signal-regulated kinase, c-Jun N-terminal kinase, and p38, and the protein kinase B (Akt). CONCLUSION: Arginine and glutamine attenuate IgE-dependent human mast cell activation by decreasing lipid mediator release and expression of proinflammatory cytokines.

Relationship between the Biological Clock and Inflammatory Bowel Disease.

The biological clock is a molecular oscillator that generates a 24-hour rhythm in accordance with the earth's rotation. Physiological functions and pathophysiological processes such as inflammatory bowel diseases (IBD) are closely linked to the molecular clock. This review summarizes 14 studies in humans and mice on the interactions between the biological clock and IBD. It provides evidence that IBD negatively affect core clock gene expression, metabolism and immune functions. On the other hand, disruption of the clock promotes inflammation. Overexpression of clock genes can lead to inhibition of inflammatory processes, while silencing of clock genes can lead to irreversible disease activity. In both human and mouse studies, IBD and circadian rhythms have been shown to influence each other. Further research is needed to understand the exact mechanisms and to develop potential rhythm-related therapies to improve IBD.

Effects of Dietary Components on Mast Cells: Possible Use as Nutraceuticals for Allergies?

Allergic diseases affect an estimated 30 percent of the world's population. Mast cells (MC) are the key effector cells of allergic reactions by releasing pro-inflammatory mediators such as histamine, lipid mediators, and cytokines/chemokines. Components of the daily diet, including certain fatty acids, amino acids, and vitamins, as well as secondary plant components, may have effects on MC and thus may be of interest as nutraceuticals for the prevention and treatment of allergies. This review summarizes the anti-inflammatory effects of dietary components on MC, including the signaling pathways involved, in in vitro and in vivo models. Butyrate, calcitriol, kaempferol, quercetin, luteolin, resveratrol, curcumin, and cinnamon extract were the most effective in suppressing the release of preformed and de novo synthesized mediators from MC or in animal models. In randomized controlled trials (RCT), vitamin D, quercetin, O-methylated epigallocatechin gallate (EGCG), resveratrol, curcumin, and cinnamon extract improved symptoms of allergic rhinitis (AR) and reduced the number of inflammatory cells in patients. However, strategies to overcome the poor bioavailability of these nutrients are an important part of current research.

Human intestinal mast cells are a potent source of multiple chemokines.

Mast cells are key effector cells of immediate type allergic reactions. Upon activation they release a broad array of pre-stored and de novo synthesized mediators including immunoregulatory cytokines and chemokines. Here, we analyzed the chemokine profile expressed by mature human mast cells. Human mast cells were isolated from intestinal tissue and cultured with stem cell factor (SCF) in the presence or absence of IL-4 for 10d. Cells were stimulated by cross-linking of the high affinity IgE receptor (FcεRI) and/or by SCF. Chemokine and chemokine receptor mRNA expression was determined by real-time RT-PCR and chemokine release was measured by multiplex bead immunoassay. Out of 43 chemokines and 19 chemokine receptors human intestinal mast cells express 27 chemokines and nine chemokine receptors. Twelve chemokines (CCL1, CCL2, CCL3, CCL4, CCL5, CCL7, CCL18, CCL20, CXCL2, CXCL3, CXCL8, and XCL1) were more than four-fold up-regulated in response to FcεRI cross-linking. Combination of pre-culture with IL-4 and/or stimulation with SCF in addition to FcεRI cross-linking further increased the antigen-dependent expression of mRNA for most chemokines. In contrast, the expression of CCL20, CXCL2, and CXCL3 was strongly inhibited by IL-4 treatment. In conclusion, human intestinal mast cells express a broad spectrum of different chemokines underlining their important role as immunoregulatory cells. Furthermore, combined treatment with IL-4 and SCF increases the antigen-mediated expression and release of multiple chemokines, but IL-4 priming inhibits the expression of CCL20, CXCL2, and CXCL3.

Relationship between allergy and cancer: an overview.

Allergic diseases and malignancies cause a lot of morbidity, mortality and high costs for healthcare systems. An inverse association between allergy and cancer has been suspected for a long time, but even despite extensive research no general relationship has been determined. This review comprises 32 epidemiological studies published between 1960 and 2011 and draws conclusions regarding relationships between specific types of cancer and allergic diseases. On the one hand, inflammatory reactions in the course of allergy can support carcinogenesis but are limited to specific areas, whereas on the other hand systemic effects in terms of enhanced immunosurveillance can prevent cancer.