Inhibition of tumour necrosis factor-alpha (TNF-alpha) release from mast cells by the anti-inflammatory drugs, sodium cromoglycate and nedocromil sodium

TNF-Alpha as an Initiator of Allodynia and Anxiety-Like Behaviors in a Preclinical Model of PTSD and Comorbid Pain

Post-Traumatic Stress Disorder (PTSD) is a debilitating mental health disorder that occurs after exposure to a traumatic event. Patients with comorbid chronic pain experience affective distress, worse quality of life, and poorer responses to treatments for pain or PTSD than those with either condition alone. FDA-approved PTSD treatments are often ineffective analgesics, requiring additional drugs to treat co-morbid symptoms. Therefore, development of new treatment strategies necessitate a better understanding of the pathophysiology of PTSD and comorbid pain. The single prolonged stress (SPS) model of PTSD induces the development of persistent mechanical allodynia and thermal hyperalgesia. Increased Nociceptin/Orphanin FQ (N/OFQ) levels in serum and CSF accompany these exaggerated nociceptive responses, as well as increased serum levels of the pro-inflammatory cytokine tumor necrosis factor (TNF-α). Therefore, the primary goal was to determine the role of TNF-α in the development of SPS-induced allodynia/hyperalgesia and elevated serum and CNS N/OFQ using two approaches: TNF-α synthesis inhibition, and blockade with anti-TNF-α antibody that acts primarily in the periphery. Administration of TNF-α synthesis blocker, thalidomide (THL), immediately after SPS prevented increased TNF-α and development of allodynia and hyperalgesia. The THL effect lasted at least 21 days, well after thalidomide treatment ended (day 5). THL also prevented SPS-induced increases in serum N/OFQ and reversed regional N/OFQ mRNA expression changes in the CNS. Serum TNF-α increases detected at 4 and 24 h post SPS were not accompanied by blood brain barrier disruption. A single injection of anti-TNF-α antibody to male and female rats during the SPS procedure prevented the development of allodynia, hyperalgesia, and elevated serum N/OFQ, and reduced SPS-induced anxiety-like behaviors in males. Anti-TNFα treatment also blocked development of SPS-induced allodynia in females, and blocked increased hypothalamic N/OFQ in males and females. This suggests that a peripheral TNF-α surge is necessary for the initiation of allodynia associated with SPS, as well as the altered central and peripheral N/OFQ that maintains nociceptive sensitivity. Therefore, early alleviation of TNF-α provides new therapeutic options for investigation as future PTSD and co-morbid pain treatments.

Visnagin and benzofuran scaffold-based molecules as selective cyclooxygenase-2 inhibitors with anti-inflammatory and analgesic properties: design, synthesis and molecular docking

A series of new visnagin and benzofuran scaffold-based molecules was designed and synthesized as anti-inflammatory and analgesic agents. Biological screening of these compounds showed that they exhibit potent anti-inflammatory/analgesic activity with a safer side effect profile in in vivo mouse models. In vitro cyclooxygenase (COX) inhibition assay showed that the compounds elicit their function through selective COX-2 inhibition. Molecular docking study also revealed the ability of the compounds to correctly recognize the active site and achieve noncovalent binding interactions with key residues therein. The best combined profile of anti-inflammatory, analgesic and COX-2 selective inhibition properties in association with low gastrotoxicity was displayed by the analogs 8, 11b and 19d, which can be considered as promising leads for further future optimization.

Natural chromones as potential anti-inflammatory agents: Pharmacological properties and related mechanisms

Chromones are a group of natural substances with a diversity of biological activities. Herein we assessed the pharmacological potential of three chromones (1, 2 and 3) isolated from Dictyoloma vandellianum as anti-inflammatory agents using in vitro and in vivo approaches. During in vitro screening, the production of NO and cytokines by macrophages stimulated with LPS and IFN-γ was inhibited by all chromones at concentrations (5-20 μM) that did not induce cytotoxicity. Analysis of pharmacokinetic parameters (in vitro half-life and intrinsic clearance) using human liver microsomes revealed that 3 has a superior pharmacokinetic profile, compared to 1 and 2. Treatment with 3 (100 mg/kg, ip) did not affect the mice motor performance, while 1 and 2 induced motor deficit. Taking into account the pharmacokinetic profile and absence of motor impairment, 3 was selected for further pharmacological characterization. Corroborating the data from in vitro screening, treatment of cell cultures with 3 (5-20 μM) reduced TNF-α, IL-6 and IL-1β production by stimulated macrophages. In the complete Freund's adjuvant-induced paw inflammation model in mice, 3 (25 and 50 mg/kg, ip) inhibited mechanical hyperalgesia, edema and cytokine production/release (IL-1β, IL-6 and TNF-α). 3 (5-20 μM) also reduced the transcriptional activity of NF-κB in stimulated macrophages. Furthermore, treatment with RU486, a glucocorticoid receptor (GR) antagonist, partially prevented the inhibitory effect of 3 on macrophages, indicating that this chromone exerts its anti-inflammatory effects in part through the activation of GR. The results presented herein demonstrate the pharmacological potential of natural chromones, highlighting 3 as a possible candidate for the drug discovery process targeting new anti-inflammatory drugs.

The Glucocorticoid Receptor Is a Critical Regulator of HIV Latency in Human Microglial Cells

We have developed models of HIV latency using microglia derived from adult human patient brain cortex and transformed with the SV40 T large and hTERT antigens. Latent clones infected by HIV reporter viruses display high levels of spontaneous HIV reactivation in culture. BrainPhys, a medium highly representative of the CNS extracellular environment, containing low glucose and 1% FBS, reduced, but did not prevent, HIV reactivation. We hypothesized that spontaneous HIV reactivation in culture was due to the expression of pro-inflammatory genes, such as TNF-α, taking place in the absence of the natural inhibitory signals from astrocytes and neurons. Indeed, expression and secretion of TNF-α is strongly reduced in HIV-latently infected microglia compared to the subset of cells that have undergone spontaneous HIV reactivation. Whereas inhibitors of NF-κB or of macrophage activation only had a short-term silencing effect, addition of dexamethasone (DEXA), a glucocorticoid receptor (GR) agonist and mediator of anti-inflammation, silenced the HIV provirus in a long-term, and shRNA-mediated knock-down of GR activated HIV. DEXA also decreased secretion of a number of cytokines, including TNF-α. Chromatin immunoprecipitation analysis revealed that DEXA strongly increased GR occupancy at the HIV promoter, and reduced histone 3 acetylated levels. Moreover, TNF-α expression inhibitors in combination with DEXA induced further HIV silencing and increased the histone 3 lysine 27 tri-methylated epigenetic mark of repression at the HIV promoter region. We conclude that GR is a critical repressor of HIV transcription in microglia, and a novel potential pharmacological target to restrict HIV expression in the CNS.

Daily Onset of Light and Darkness Differentially Controls Hematopoietic Stem Cell Differentiation and Maintenance

Hematopoietic stem and progenitor cells (HSPCs) tightly couple maintenance of the bone marrow (BM) reservoir, including undifferentiated long-term repopulating hematopoietic stem cells (LT-HSCs), with intensive daily production of mature leukocytes and blood replenishment. We found two daily peaks of BM HSPC activity that are initiated by onset of light and darkness providing this coupling. Both peaks follow transient elevation of BM norepinephrine and TNF secretion, which temporarily increase HSPC reactive oxygen species (ROS) levels. Light-induced norepinephrine and TNF secretion augments HSPC differentiation and increases vascular permeability to replenish the blood. In contrast, darkness-induced TNF increases melatonin secretion to drive renewal of HSPCs and LT-HSC potential through modulating surface CD150 and c-Kit expression, increasing COX-2/αSMA+ macrophages, diminishing vascular permeability, and reducing HSPC ROS levels. These findings reveal that light- and darkness-induced daily bursts of norepinephrine, TNF, and melatonin within the BM are essential for synchronized mature blood cell production and HSPC pool repopulation.

The Anti-allergic Cromones: Past, Present, and Future

The anti-allergic cromones were originally synthesized in the 1960s by Fisons Plc, and the first drug to emerge from this program, disodium cromoglycate was subsequently marketed for the treatment of asthma and other allergic conditions. Whilst early studies demonstrated that the ability of the cromones to prevent allergic reactions was due to their 'mast cell stabilizing' properties, the exact pharmacological mechanism by which this occurred, remained a mystery. Here, we briefly review the history of these drugs, recount some aspects of their pharmacology, and discuss two new explanations for their unique actions. We further suggest how these findings could be used to predict further uses for the cromones.

Mesalazine Has No Effect on Mucosal Immune Biomarkers in Patients with Diarrhea-Dominant Irritable Bowel Syndrome Referred to Shariati Hospital: A Randomized Double-Blind, Placebo-Controlled Trial

BACKGROUND

Intestinal mast cells may cause gastrointestinal symptoms in patients with diarrhea-dominant irritable bowel syndrome (IBS). The objective of this study was to determine the effect of mesalazine on the number of lamina propria mast cells and clinical manifestations of patients with diarrhea-dominant IBS referred to Shariati Hospital affiliated to Tehran University of Medical Sciences.

METHODS

This was a randomized placebo-controlled double-blind trial conducted on 49 patients with diarrhea-dominant IBS. The patients were randomly assigned to one of the experiment or control groups. The patients in experiment group took 2400 mg mesalazine daily in three divided doses for 8 weeks and the patient in control group took placebo on the same basis. Our first targeted outcome was an assigned downturn of mast cells number to the safe colonic baseline and the next one was a marked palliation of disease symptoms. Data were analyzed conforming intention-to-treat method. We used MANCOVA test to compare our both assigned outcomes in the two groups. We also compared the data with baseline values in both groups.All statistical tests were performed at the significance level of 0.05.

RESULTS

There was no significant difference between Mesalazine and placebo groups regarding the number of mast cells (p value=0.396), abdominal pain (p value=0.054), bloating (p value=0.365), defecation urgency (p value=0.212), and defecation frequency (p value=0.702).

CONCLUSION

Mesalazine had no significant effect either on the number of mast cells or on the severity of disease symptoms. This finding seems to be inconsistent with the hypothesis indicating immune mechanisms as potential therapeutic targets in IBS. The possible difference in this effect of Mesalazine should be evaluated in further studies among populations varying in race, ethnic, and geographical characteristics.

Negative Feed-forward Control of Tumor Necrosis Factor (TNF) by Tristetraprolin (ZFP36) Is Limited by the Mitogen-activated Protein Kinase Phosphatase, Dual-specificity Phosphatase 1 (DUSP1): IMPLICATIONS FOR REGULATION BY GLUCOCORTICOIDS

TNF is central to inflammation and may play a role in the pathogenesis of asthma. The 3'-untranslated region of the TNF transcript contains AU-rich elements (AREs) that are targeted by the RNA-binding protein, tristetraprolin (also known as zinc finger protein 36 (ZFP36)), which is itself up-regulated by inflammatory stimuli, to promote mRNA degradation. Using primary human bronchial epithelial and pulmonary epithelial A549 cells, we confirm that interleukin-1β (IL1B) induces expression of dual-specificity phosphatase 1 (DUSP1), ZFP36, and TNF. Whereas IL1B-induced DUSP1 is involved in feedback control of MAPK pathways, ZFP36 exerts negative (incoherent) feed-forward control of TNF mRNA and protein expression. DUSP1 silencing increased IL1B-induced ZFP36 expression at 2 h and profoundly repressed TNF mRNA at 6 h. This was partly due to increased TNF mRNA degradation, an effect that was reduced by ZFP36 silencing. This confirms a regulatory network, whereby DUSP1-dependent negative feedback control reduces feed-forward control by ZFP36. Conversely, whereas DUSP1 overexpression and inhibition of MAPKs prevented IL1B-induced expression of ZFP36, this was associated with increased TNF mRNA expression at 6 h, an effect that was predominantly due to elevated transcription. This points to MAPK-dependent feed-forward control of TNF involving ZFP36-dependent and -independent mechanisms. In terms of repression by dexamethasone, neither silencing of DUSP1, silencing of ZFP36, nor silencing of both together prevented the repression of IL1B-induced TNF expression, thereby demonstrating the need for further repressive mechanisms by anti-inflammatory glucocorticoids. In summary, these data illustrate why understanding the competing effects of feedback and feed-forward control is relevant to the development of novel anti-inflammatory therapies.

The influence of age and weaning on permeability of the gastrointestinal tract in Holstein bull calves

Fourteen Holstein bull calves were used in a randomized complete block design to investigate the effect of calf age and weaning on permeability of the gastrointestinal tract (GIT). Calves were randomly assigned to 1 of 2 treatments: (1) a weaning protocol that was initiated on d 35; WN; n=7), or (2) a control treatment where calves were not weaned (CON; n=7). Calves were bottle-fed milk replacer (150 g/L), in 3 equal portions/d targeting 15% of their body weight (BW) in liquid milk intake [approximately 21.1g/kg of BW/d, dry matter (DM) basis]. On d 35, the amount of milk replacer offered to WN calves was reduced to 7.5% of BW for 7 d before calves were weaned on d 42. On d 14, 28, and 42, calves were orally dosed with 500 mL of Cr-EDTA (179 mM Cr-EDTA solution) and housed in a metabolism crate to enable total urine collection and determination of total urinary Cr recovery as an indicator of total-tract permeability. On d 44, calves were killed and tissues from the rumen, omasum, duodenum, jejunum, ileum, cecum, and proximal and distal colon were collected, rinsed, and transported in buffer solution (pH 7.4 at 38.5°C). Tissues were incubated in Ussing chambers under short-circuit conditions with buffer solutions designed to mimic the mucosal and serosal energy source that would be available in vivo (glucose for tissues from the small intestine and short-chain fatty acids for tissues that would be exposed to fermentation; rumen, omasum, and large intestinal tissues). The serosal to mucosal flux of (14)C-mannitol and (3)H-inulin was measured for each region. Although we detected treatment × period interactions for BW and starter intake, dietary treatments did not differ within a week. Overall, the time that ruminal pH was <5.5 was less before weaning than after weaning. We observed a differential response for the appearance of Cr in urine for WN and CON calves, where the appearance of Cr (mg/48 h) in urine decreased for both treatments from d 14 to 28, but increased from d 28 to 42 for WN, whereas Cr appearance continued to decrease for CON. The flux of mannitol and inulin did not differ between treatments but did differ among region of the GIT, with rumen, duodenum, and jejunum having the greatest permeability. These data suggest that permeability of the GIT decreases with age but weaning may disrupt this process. The rumen, duodenum, and jejunum appear to be the regions with greatest permeability.

Nasal sodium cromoglycate (Lomusol) modulates the early phase reaction of mild to moderate persistent allergic rhinitis in patients mono-sensitized to house dust mite: a preliminary study

We evaluated the clinical improvement of patients with mild to moderate persistent allergic rhinitis (AR) due to mono-sensitization to house dust mite (HDM) allergen, by sodium cromoglycate nasal spray (Lomusol 4%). Lomusol was used as a single agent treatment, and its anti-inflammatory effects, in the early phase reaction were evaluated. Herein we showed that Lomusol significantly improved the subjective nasal symptom scores especially nasal obstruction. This was associated with significant and specific reduction in neutrophils influx in nasal cytology but had no effect on other cell types. This selective anti-inflammatory effect on nasal cytology was associated with significant reduction in the levels of platelet activating factor (PAF) and histamine in nasal secretions but had no effect on PGD2, LTC4 or CysLt levels. Lomusol was also able to induce significant reduction in eosinophil cationic protein (ECP) levels in nasal secretions without altering the percentage of eosinophil influx in nasal cytology. Taken collectively, we showed the first evidence that nasal sodium cromoglycate possesses a selective inhibition on neutrophil recruitment into nasal cytology in the early phase reaction of AR patients mono-sensitized to HDM. This may be attributed to the ability of Lomusol to significantly reduce the amount of PAF recovered in nasal secretion. These results were associated with significant improvement in subjective symptom scores especially nasal obstruction that may in addition, be due to the ability of Lomusol to down-regulate eosinophil degranulation activity as well.

PF-04886847 (an inhibitor of plasma kallikrein) attenuates inflammatory mediators and activation of blood coagulation in rat model of lipopolysaccharide (LPS)-induced sepsis

The plasma kallikrein-mediated proteolysis regulates both thrombosis and inflammation. Previous study has shown that PF-04886847 is a potent and competitive inhibitor of kallikrein, suggesting that it might be useful for the treatment of kallikrein-kinin mediated inflammatory and thrombotic disorders. In the rat model of lipopolysaccharide (LPS) -induced sepsis used in this study, pretreatment of rats with PF-04886847 (1 mg/kg) prior to LPS (10 mg/kg) prevented endotoxin-induced increase in granulocyte count in the systemic circulation. PF-04886847 significantly reduced the elevated plasma 6-keto PGF1α levels in LPS treated rats, suggesting that PF-04886847 could be useful in preventing hypotensive shock during sepsis. PF-04886847 did not inhibit LPS-induced increase in plasma TNF-α level. Pretreatment of rats with PF-04886847 prior to LPS did not attenuate endotoxin-induced decrease in platelet count and plasma fibrinogen levels as well as increase in plasma D-dimer levels. PF-04886847 did not protect the animals against LPS-mediated acute hepatic and renal injury and disseminated intravascular coagulation (DIC). Since prekallikrein (the zymogen form of plasma kallikrein) deficient patients have prolonged activated partial thromboplastin time (aPTT) without having any bleeding disorder, the anti-thrombotic property and mechanism of action of PF-04886847 was assessed. In a rabbit balloon injury model designed to mimic clinical conditions of acute thrombotic events, PF-04886847 reduced thrombus mass dose-dependently. PF-04886847 (1 mg/kg) prolonged both aPTT and prothrombin time (PT) in a dose-dependent manner. Although the findings of this study indicate that PF-04886847 possesses limited anti-thrombotic and anti-inflammatory effects, PF-04886847 may have therapeutic potential in other kallikrein-kinin mediated diseases.

Quercetin is more effective than cromolyn in blocking human mast cell cytokine release and inhibits contact dermatitis and photosensitivity in humans

Mast cells are immune cells critical in the pathogenesis of allergic, but also inflammatory and autoimmune diseases through release of many pro-inflammatory cytokines such as IL-8 and TNF. Contact dermatitis and photosensitivity are skin conditions that involve non-immune triggers such as substance P (SP), and do not respond to conventional treatment. Inhibition of mast cell cytokine release could be effective therapy for such diseases. Unfortunately, disodium cromoglycate (cromolyn), the only compound marketed as a mast cell "stabilizer", is not particularly effective in blocking human mast cells. Instead, flavonoids are potent anti-oxidant and anti-inflammatory compounds with mast cell inhibitory actions. Here, we first compared the flavonoid quercetin (Que) and cromolyn on cultured human mast cells. Que and cromolyn (100 µM) can effectively inhibit secretion of histamine and PGD(2). Que and cromolyn also inhibit histamine, leukotrienes and PGD(2) from primary human cord blood-derived cultured mast cells (hCBMCs) stimulated by IgE/Anti-IgE. However, Que is more effective than cromolyn in inhibiting IL-8 and TNF release from LAD2 mast cells stimulated by SP. Moreover, Que reduces IL-6 release from hCBMCs in a dose-dependent manner. Que inhibits cytosolic calcium level increase and NF-kappa B activation. Interestingly, Que is effective prophylactically, while cromolyn must be added together with the trigger or it rapidly loses its effect. In two pilot, open-label, clinical trials, Que significantly decreased contact dermatitis and photosensitivity, skin conditions that do not respond to conventional treatment. In summary, Que is a promising candidate as an effective mast cell inhibitor for allergic and inflammatory diseases, especially in formulations that permit more sufficient oral absorption.

Different roles of mast cells in obesity and diabetes: lessons from experimental animals and humans

Mast cells (MCs) play an important role in allergic hyperresponsiveness and in defending microorganism infections. Recent studies of experimental animals and humans have suggested that MCs participate in obesity and diabetes. MC distribution and activities in adipose tissues may vary, depending on the locations of different adipose tissues. In addition to releasing inflammatory mediators to affect adipose tissue extracellular matrix remodeling and to promote inflammatory cell recruitment and proliferation, MCs directly and indirectly interact and activate adipose tissue cells, including adipocytes and recruited inflammatory cells. Plasma MC protease levels are significantly higher in obese patients than in lean subjects. Experimental obese animals lose body weight after MC inactivation. MC functions in diabetes are even more complicated, and depend on the type of diabetes and on different diabetic complications. Both plasma MC proteases and MC activation essential immunoglobulin E levels are significant risk factors for human pre-diabetes and diabetes mellitus. MC stabilization prevents diet-induced diabetes and improves pre-established diabetes in experimental animals. MC depletion or inactivation can improve diet-induced type 2 diabetes and some forms of type 1 diabetes, but also can worsen other forms of type 1 diabetes, at least in experimental animals. Observations from animal and human studies have suggested beneficial effects of treating diabetic patients with MC stabilizers. Some diabetic patients may benefit from enhancing MC survival and proliferation – hypotheses that merit detailed basic researches and clinical studies.

Bresol inhibits phosphodiesterase 4 gene expression and modulates the levels of select mediators of inflammation in human monocytic cells

Bresol-a poly-herbal formulation, has been reported to be effective against bronchial asthma and allergic rhinitis in children. In vivo studies have supported the anti-histaminic and anti-anaphylactic action of bresol. However, the mechanism of action of bresol in modulation of inflammation has not been studied at the cellular and molecular level. The present study was aimed to elucidate the mechanism(s) of action of bresol at the cellular and molecular levels, using human monocyte leukemia cells. The effects of bresol on phosphodiesterase 4B (PDE4B) gene expression were analyzed using human monocytic U937 leukemia cells. The ability of bresol to stimulate cAMP formation in these cells, as well as its effects on mediators of inflammation like tumor necrosis factor-α (TNFα), nitric oxide (NO), and cycloxygenase-2 (COX-2) in lipopolysaccharide (LPS)-stimulated U937 cells, were also studied. The results here indicated that bresol exhibited potential anti-inflammatory properties by inhibiting LPS-induced PDE4B gene expression in the cells. Bresol also dose dependently activated cAMP formation, and inhibited TNFα, NO, as well as COX-2 formation in the LPS-stimulated cells. Based upon the results, we concluded that the reported anti-inflammatory activity of bresol might be attributed to its abilities to inhibit PDE4B and thus elevate cAMP levels in human monocytes. The anti-inflammatory effects of bresol might also be a result of the capacity of bresol to modulate the formation of TNFα, NO, and COX-2 in monocytes.

Biosurfactant mannosyl-erythritol lipid inhibits secretion of inflammatory mediators from RBL-2H3 cells

BACKGROUND

Biosurfactant mannosyl-erythritol lipids (MELs) are glycolipids produced by microbes that have various biological activities. It has been reported that MELs exhibit excellent surface-activity and also various bioactivities, such as induction of cell differentiation and apoptosis. However, little is known about their action related to drug discovery or drug seeds.

METHODS

We investigated the effects of MELs on the secretion of inflammatory mediators from mast cells that play a central role in allergic responses. Mast cells secrete three kinds of inflammatory mediators and we quantified these secreted mediators by photometer or ELISA. The action mechanisms of MELs were studied by Ca(2+)-sensitive fluorescence dye and Western blotting of phosphorylated proteins.

RESULTS

MELs inhibited exocytotic release by antigen stimulation in a dose-dependent manner. We also found that MELs inhibited antigen-induced secretion of leukotriene C(4) and cytokine TNF-α (tumor necrosis factor-α). The inhibitory action of MELs on mediator secretion was mediated by inhibition of Ca(2+) increase, phosphorylation of MAP kinases and SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) that serve as a molecular machinery for exocytotic membrane fusion.

CONCLUSIONS

MELs have anti-inflammatory action inhibiting the secretion of inflammatory mediators from mast cells.

GENERAL SIGNIFICANCE

MELs affects two of major intracellular signaling pathways including Ca(2+) increase and MAP kinases. MELs also inhibited the phosphorylation of SNARE proteins that is crucial for not only exocytosis but also intracellular vesicular trafficking.

Do resident renal mast cells play a role in the pathogenesis of diabetic nephropathy?

Diabetic nephropathy is associated with high morbidity and mortality and the prevalence of this disease is continuously increasing world wide. Though, the major risk factors like hyperglycemia and hypertension play a pivotal role in the pathogenesis of diabetic nephropathy, the etiology of this insidious disorder is not well understood. Mast cells are pluripotent bone marrow derived cells that play a key role in inflammation. Degranulation of mast cells releases various mediators including inflammatory cytokines, endothelins, growth factors, and proteolytic enzymes. Infiltration of mast cells has been noted to occur in renal diseases. In addition, the renal density of mast cells is significantly increased in diabetic patients with nephropathy. It remains unclear whether resident renal mast cells derived mediators play a role in the pathogenesis of diabetic nephropathy. Recent studies suggest the involvement of renal mast cell infiltration and degranulation in diabetic nephropathy. The present review focuses on the role of resident renal mast cells in diabetic nephropathy.

Gastrointestinal dysfunction induced by early weaning is attenuated by delayed weaning and mast cell blockade in pigs

Our previous work has demonstrated that weaning at 19 days of age has deleterious effects on mucosal barrier function in piglet intestine that are mediated through peripheral CRF receptor signaling pathways. The objectives of the present study were to assess the impact of piglet age on weaning-associated intestinal dysfunction and to determine the role that mast cells play in weaning-induced breakdown of mucosal barrier function. Nursing Yorkshire-cross piglets were either weaned at 19 days of age (early-weaned, n = 8) or 28 days of age (late-weaned, n = 8) and housed in nursery pens. Twenty-four hours postweaning, segments of midjejunum and ascending colon from piglets within each weaning age group were harvested and mounted on Ussing chambers for measurements of transepithelial electrical resistance and serosal-to-mucosal [(3)H]mannitol fluxes. Early weaning resulted in reductions in transepithelial electrical resistance and increases in mucosal permeability to [(3)H]mannitol in the jejunum and colon (P < 0.01). In contrast, postweaning reductions in intestinal barrier function were not observed in piglets weaned at 28 days of age. Early-weaned piglet intestinal mucosa had increased expression of CRF receptor 1 protein, increased mucosal mast cell tryptase levels, and evidence of enhanced mast cell degranulation compared with late-weaned intestinal mucosa. Pretreatment of piglets with the mast cell stabilizer drug cromolyn, injected intraperitoneally 30 min prior to weaning, abolished the early-weaning-induced intestinal barrier disturbances. Our results indicate that early-weaning stress induces mucosal dysfunction mediated by intestinal mast cell activation and can be prevented by delaying weaning.

Sodium cromoglycate inhibits absorption of the major soybean allergen, Gly m Bd 30K, in mice and human intestinal Caco-2 cells

Our previous data showed that Gly m Bd 30K was absorbed from the gastrointestinal tract and circulated in blood in mice. This study was conducted to determine the mechanism and identify the inhibitor of such absorption. Using sandwich ELISA and immunoblotting, we found that intact Gly m Bd 30K was absorbed from apical to basolateral solutions and intracellularly accumulated by Caco-2 cells in a dose- and time-dependent manner. The absorption and intracellular accumulation of Gly m Bd 30K were significantly suppressed when Caco-2 cells were treated with sodium cromoglycate (SCG) (0-50 mmol/L) in a dose-dependent manner. In 24-d-old mice orally treated with SCG (10-1000 mg/kg body weight), plasma Gly m Bd 30K concentration decreased significantly 30-120 min after Gly m Bd 30K (2000 mg/kg body weight) administration. Moreover, inhibitors that suppress the clathrin-dependent endocytosis dansylcadaverine, the caveolae-dependent endocytosis nystatin and clathrin, and the caveolae-dependent endocytosis methyl-beta-cyclodextrin had inhibitory effects on the absorption and intracellular accumulation of Gly m Bd 30K by Caco-2 cells. These data indicate that Gly m Bd 30K is absorbed and intracellularly accumulated in Caco-2 cells via clathrin- or caveolae-dependent endocytosis. We propose that the absorption and intracellular accumulation of Gly m Bd 30K are inhibited by SCG via clathrin- or caveolae-dependent endocytosis.

Pharmacologic inhibition of mast cell degranulation prevents left ventricular remodeling induced by chronic volume overload in rats

BACKGROUND

Left ventricular (LV) hypertrophy and dilation are important compensatory responses to chronic volume overload; however, the mechanisms responsible for this LV remodeling have not been well characterized. Previous observations that the number of myocardial mast cells are increased in congestive heart failure (CHF) suggested the hypothesis that mast cells might be involved in the ventricular remodeling induced by a chronic volume overload.

METHODS AND RESULTS

Accordingly, the intent of this study was to determine the contribution of mast cells to LV remodeling, dysfunction, and morbidity/mortality secondary to CHF in the infrarenal aortocaval fistula model of sustained volume overload. To this end, LV end-diastolic pressure, size, and function (ie, isovolumetric pressure-volume relations in the blood-perfused isolated heart) were assessed in both nedocromil sodium treated and untreated rats at 8 weeks after fistula and compared with age-matched controls. Nedocromil, a mast cell-stabilizing drug, effectively prevented the LV dilation and decreased contractility seen in the untreated fistula group in a dose-dependent fashion, resulting in a significant reduction in the incidence of morbidity/mortality from CHF.

CONCLUSION

The ability of mast cell stabilization to prevent ventricular dilation induced by chronic volume overload identifies a key role for mast cells in the regulation of myocardial remodeling.

Suppression of matrix metalloproteinase production in nasal fibroblasts by tranilast, an antiallergic agent, in vitro

Allergic rhinitis is an inflammatory disease characterized by nasal wall remodeling with intense infiltration of eosinophils and mast cells/basophils. Matrix metalloproteinases (MMPs), MMP-2 and MMP-9, are the major proteolytic enzymes that induce airway remodeling. These enzymes are also important in the migration of inflammatory cells through basement membrane components. We evaluated whether tranilast (TR) could inhibit MMP production from nasal fibroblasts in response to tumor necrosis factor-alpha (TNF-alpha) stimulation in vitro. Nasal fibroblasts (NF) were established from nasal polyp tissues taken from patients with allergic rhinitis. NF (2 x 10(5) cells/mL) were stimulated with TNF-alpha in the presence of various concentrations of TR. After 24 hours, the culture supernatants were obtained and assayed for MMP-2, MMP-9, TIMP-1, and TIMP-2 levels by ELISA. The influence of TR on mRNA expression of MMPs and TIMPs in cells cultured for 12 hours was also evaluated by RT-PCR. TR at more than 5 x 10(-5) M inhibited the production of MMP-2 and MMP-9 from NF in response to TNF-alpha stimulation, whereas TIMP-1 and TIMP-2 production was scarcely affected. TR also inhibited MMP mRNA expression in NF after TNF-alpha stimulation. The present data suggest that the attenuating effect of TR on MMP-2 and MMP-9 production from NF induced by inflammatory stimulation may underlie the therapeutic mode of action of the agent in patients with allergic diseases, including allergic rhinitis.

Flavonols inhibit proinflammatory mediator release, intracellular calcium ion levels and protein kinase C theta phosphorylation in human mast cells

Mast cells participate in allergies, and also in immunity and inflammation by secreting proinflammatory cytokines. Flavonoids are naturally occurring polyphenolic plant compounds, one group of which -- the flavonols, inhibits histamine and some cytokine release from rodent basophils and mast cells. However, the effect of flavonols on proinflammatory mediator release and their possible mechanism of action in human mast cells is not well defined. Human umbilical cord blood-derived cultured mast cells (hCBMCs) grown in the presence of stem cell factor (SCF) and interleukin (IL)-6 were preincubated for 15 min with the flavonols quercetin, kaempferol, myricetin and morin (0.01, 0.1, 1, 10 or 100 microM), followed by activation with anti-IgE. Secretion was quantitated for IL-6, IL-8, tumor necrosis factor-alpha (TNF-alpha), histamine and tryptase levels. Release of IL-6, IL-8 and TNF-alpha was inhibited by 82-93% at 100 microM quercetin and kaempferol, and 31-70% by myricetin and morin. Tryptase release was inhibited by 79-96% at 100 microM quercetin, kampferol and myricetin, but only 39% by morin; histamine release was inhibited 52-77% by the first three flavonols, but only 28% by morin. These flavonols suppressed intracellular calcium ion elevations in a dose-response manner, with morin being the weakest; they also inhibited phosphorylation of the calcium-insensitive protein kinase C theta (PKC theta). Flavonol inhibition of IgE-mediated proinflammatory mediator release from hCBMCs may be due to inhibition of intracellular calcium influx and PKC theta signaling. Flavonols may therefore be suitable for the treatment of allergic and inflammatory diseases.

Involvement of mast cells in basal and neurotensin-induced intestinal absorption of taurocholate in rats

Neurotensin (NT), a hormone released from intestine by ingested fat, facilitates lipid digestion by stimulating pancreatic secretion and slowing the movement of chyme. In addition, NT can contract the gall bladder and enhance the enterohepatic circulation (EHC) of bile acids to promote micelle formation. Our recent finding that NT enhanced and an NT antagonist inhibited [(3)H]taurocholate ([(3)H]TC) absorption from proximal rat small intestine indicated a role for endogenous NT in the regulation of EHC. Here, we postulate the involvement of intestinal mast cells in the TC uptake process and in the stimulatory effect of NT. In anesthetized rats with the bile duct cannulated for bile collection, infusion of NT (10 pmol.kg(-1).min(-1)) enhanced the [(3)H]TC recovery rate from duodenojejunum by 2.2-fold. This response was abolished by pretreatment with mast cell stabilizers (cromoglycate, doxantrazole) and inhibitors of mast cell mediators (diphenhydramine, metergoline, zileuton). In contrast, mast cell degranulators (compound 48/80, substance P) and mast cell mediators (histamine, leukotriene C(4)) reproduced the effect of NT. N(G)-nitro-l-arginine methyl ester enhanced and l-arginine inhibited basal and NT-induced TC uptake, consistent with the known inhibitory effect of nitric oxide (NO) on mast cell reactivity. These results argue that basal and NT-stimulated TC uptake in rat jejunum are similarly dependent on mast cells, are largely mediated by release of mast cell mediators, and are subject to regulation by NO.

Fisetin, a flavonol, inhibits TH2-type cytokine production by activated human basophils

BACKGROUND

Activation of mast cells and basophils through allergen stimulation releases chemical mediators and synthesizes cytokines. Among these cytokines, IL-4, IL-13, and IL-5 have major roles in allergic inflammation.

OBJECTIVE

We sought to determine the potency of flavonoids (astragalin, fisetin, kaempferol, myricetin, quercetin, and rutin) for the inhibition of cytokine expression and synthesis by human basophils.

METHODS

The inhibitory effect of flavonoids on cytokine expression by stimulated KU812 cells, a human basophilic cell line, and freshly purified peripheral blood basophils was measured by means of semiquantitative RT-PCR and ELISA assays. The effects of flavonoids on transcriptional activation of the nuclear factor of activated T cells were assessed by means of electrophoretic mobility shift assays.

RESULTS

Fisetin suppressed the induction of IL-4, IL-13, and IL-5 mRNA expression by A23187-stimulated KU812 cells and basophils in response to cross-linkage of the IgE receptor. Fisetin reduced IL-4, IL-13, and IL-5 synthesis (inhibitory concentration of 50% [IC(50)] = 19.4, 17.7, and 17.4 micromol/L, respectively) but not IL-6 and IL-8 production by KU812 cells. In addition, fisetin inhibited IL-4 and IL-13 synthesis by anti-IgE antibody-stimulated human basophils (IC(50) = 5.1 and 6.2 micromol/L, respectively) and IL-4 synthesis by allergen-stimulated basophils from allergic patients (IC(50) = 4.8 micromol/L). Among the flavonoids examined, kaempferol and quercetin showed substantial inhibitory activities in cytokine expression but less so than those of fisetin. Fisetin inhibited nuclear localization of nuclear factor of activated T cells c2 by A23187-stimulated KU812 cells.

CONCLUSION

These results provide evidence of a novel activity of the flavonoid fisetin that suppresses the expression of T(H)2-type cytokines (IL-4, IL-13, and IL-5) by basophils.

Corticotropin-releasing hormone and brain mast cells regulate blood-brain-barrier permeability induced by acute stress

Stress activates the hypothalamic-pituitary-adrenal axis through release of corticotropin releasing hormone (CRH), leading to production of glucocorticoids that down-regulate immune responses. Acute stress, however, also has proinflammatory effects that seem to be mediated through the activation of mast cells. Stress and mast cells have been implicated in the pathophysiology of various inflammatory conditions, including some in the central nervous system, such as multiple sclerosis in which disruption of the blood-brain barrier (BBB) precedes clinical symptoms. We previously showed that acute restraint stress increases rat BBB permeability to intravenous 99Tc gluceptate and that administration of the "mast cell stabilizer" disodium cromoglycate (cromolyn) inhibits this effect. In this study, we show that the CRH-receptor antagonist Antalarmin blocks stress-induced 99Tc extravasation, whereas site-specific injection of CRH in the paraventricular nucleus (PVN) of the hypothalamus mimics acute stress. This latter effect is blocked by pretreatment of the PVN with cromolyn; moreover, restraint stress cannot disrupt the BBB in the diencephalon and cerebellum of W/W(v) mast cell-deficient mice. These results demonstrate that CRH and mast cells are involved in regulating BBB permeability and, possibly, brain inflammatory disorders exacerbated by acute stress.

Sodium cromoglycate attenuates pulmonary inflammation without influencing bronchial responsiveness in healthy subjects exposed to organic dust

BACKGROUND

Inhalation of organic dust from a pig house induces airway inflammation and increases bronchial responsiveness to methacholine in healthy subjects.

OBJECTIVE

To study whether sodium cromoglycate influences the airway inflammatory reaction and the increase in airway responsiveness induced by inhalation of organic dust.

METHODS

Bronchoalveolar and nasal lavages, and bronchial methacholine challanges were performed and blood samples were drawn in 32 healthy subjects before and after exposure to dust in a pig farm. Sodium cromoglycate was inhaled (20 mg, twice a day) and administered intranasally (5.2 mg, twice a day) by 16 and a corresponding placebo was given to the other 16 healthy controls for two weeks prior to exposure.

RESULTS

Exposure induced a significant increase in inflammatory cells and soluble components (pro-inflammatory cytokines, inflammatory mediators) in bronchoalveolar and nasal lavage fluid in both groups. The increase in neutrophils, interleukin (IL)-6 and tumour necrosis factor (TNF)-alpha as well as myeloperoxidase and soluble intracellular adhesion molecule (ICAM)-1 in bronchoalveolar lavage (BAL) fluid was significantly reduced by treatment with sodium cromoglycate. Although sodium cromoglycate inhalation largely influenced a variety of inflammatory indices in bronchoalveolar lavage fluid it had no effect on the increase in bronchial responsiveness to methacholine.

CONCLUSION

Sodium cromoglycate alters the airway inflammatory response to inhaled organic dust without influencing the dust-induced increase in bronchial responsiveness to methacholine.

Chondroitin sulphate inhibits connective tissue mast cells

1. Mast cells derive from the bone marrow and are responsible for the development of allergic and possibly inflammatory reactions. Mast cells are stimulated by immunoglobulin E (IgE) and specific antigen, but also by a number of neuropeptides such as neurotensin (NT), somatostatin or substance P (SP), to secrete numerous pro-inflammatory molecules that include histamine, cytokines and proteolytic enzymes. 2. Chondroitin sulphate, a major constituent of connective tissues and of mast cell secretory granules, had a dose-dependent inhibitory effect on rat peritoneal mast cell release of histamine induced by the mast cell secretagogue compound 48/80 (48/80). This inhibition was stronger than that of the clinically available mast cell 'stabilizer' disodium cromoglycate (cromolyn). Inhibition by chondroitin sulphate increased with the length of preincubation and persisted after the drug was washed off, while the effect of cromolyn was limited by rapid tachyphylaxis. 3. Immunologic stimulation of histamine secretion from rat connective tissue mast cells (CTMC) was also inhibited, but this effect was weaker in umbilical cord-derived human mast cells and was absent in rat basophilic leukemia (RBL) cells which are considered homologous to mucosal mast cells (MMC). Oligo- and monosaccharides were not as effective as the polysaccharides. 4. Inhibition, documented by light and electron microscopy, involved a decrease of intracellular calcium ion levels shown by confocal microscopy and image analysis. Autoradiography at the ultrastructural level showed that chondroitin sulphate was mostly associated with plasma and perigranular membranes. 5. Chondroitin sulphate appears to be a potent mast cell inhibitor of allergic and nonimmune stimulation with potential clinical implications.

Comparison of topical nedocromil sodium and oral terfenadine for the treatment of seasonal allergic conjunctivitis

This double-masked, comparative, multicenter study was conducted to assess the onset of action and tolerability of nedocromil sodium 2% ophthalmic solution BID, 60-mg terfenadine tablets BID, and placebo in the treatment of seasonal allergic conjunctivitis. Two hundred sixty-eight patients in whom seasonal allergic conjunctivitis was diagnosed were assigned to 1 of 3 groups and administered study medication for 4 weeks. Patients' mean age was 33 years (range, 12 to 68 years); 57.8% (155 of 268) were female. Demographic characteristics were similar in all 3 groups. Although all 3 groups showed improvement in ocular symptoms, nedocromil sodium was associated with a statistically significantly faster onset of action than was terfenadine or placebo (P = 0.038). During the study, 29 nedocromil sodium-treated patients (36.7%) achieved control of symptoms in < or =2 minutes, and 61 (77.2%) achieved control in < or =15 minutes. The corresponding numbers were 21 (24.7%) and 50 (58.8%) in the terfenadine group and 25 (29.1%) and 48 (55.8%) in the placebo group. The frequency of adverse events was low and similar between groups (nedocromil sodium, 26; terfenadine, 32; placebo, 32). No severe treatment-related adverse events were reported. In conclusion, nedocromil sodium had a significantly faster onset of action than did terfenadine or placebo.

Interferon-gamma regulates the interaction of RBL-2H3 cells with fibronectin through production of nitric oxide

Interferon-gamma (IFN-gamma) is an important regulatory cytokine in cell proliferation, differentiation, adhesion, mediator release, and gene induction. This diversity of effector roles is achieved by a variety of incompletely understood mechanisms. In the mast cell (MC), IFN-gamma downregulates mediator synthesis and secretion. The present study demonstrates and characterizes for the first time IFN-gamma inhibition of adhesion of the MC analogue RBL-2H3 to the extracellular matrix protein fibronectin (FN). Inhibition requires preincubation of the cells with IFN-gamma for 20 hr, and is statistically significant at 100 U/ml IFN-gamma. Flow cytometry indicates that cell surface expression of very late antigen-4 (VLA-4), VLA-5, and the vitronectin receptor (VNR) remain constant following IFN-gamma treatment, indicating the inhibitory effect of IFN-gamma on adhesion to FN is not achieved through a reduction in integrin receptors for FN. Fluorescent labelling with Texas red phalloidin demonstrated rearrangement of the actin cytoskeleton in response to IFN-gamma was not significant. The tyrosine phosphatase inhibitor vanadate, and the nitric oxide (NO) synthase inhibitor L-NAME, reduced the IFN-gamma effect on adhesion to FN by 62 and 70%, respectively, demonstrating that the IFN-gamma effect is dependent upon the production of NO, potentially though a tyrosine phosphatase dependent mechanism. The NO donors sodium nitroprusside and S-nitrosoglutathione mimicked the effect of IFN-gamma. Thus, following stimulation with IFN-gamma, NO plays an autocrine role in the MC, and is able to modulate integrin function. This adds to the pathways NO is able to inhibit in the mast cell, shows that endogenous NO is able to inhibit these pathways, and suggests NO is impinging upon an element common to many signalling mechanisms in the MC.

Role of intestinal mast cells in modulating gastrointestinal pathophysiology

OBJECTIVE

This article reviews the current understanding of the pathophysiologic role of intestinal mast cells.

DATA SOURCE

Up to date English language publications on mast cell characteristics, heterogeneity and functions were used. Recent articles were used to develop and extend novel concepts about the role of intestinal mast cells.

STUDY SELECTION

Reference sources were selected because of their pertinence to the pathophysiological effects of mast cells in intestinal hypersensitivity. Recent publications on the following topics were emphasized: mast cell proteases in intestinal anaphylaxis; effects of nitric oxide in gastrointestinal pathophysiology; involvement of cytokines derived from mast cells in tissue damage and repair.

RESULTS

Mast cells are clearly implicated in the pathology of intestinal disease. Growing evidence suggests physiological roles for mast cells in the protection of tissues from inflammatory damage, and in intestinal maturation. Mast cells can release cytokines, such as tumour necrosis factor-alpha and interleukin-10, which were originally thought to contribute to inflammatory damage, but which may also have anti-inflammatory properties. Interestingly, mast cell function can be regulated by nitric oxide, and mast cells themselves are sources of this important mediator. Nitric oxide has protective as well as detrimental effects in the intestine.

CONCLUSIONS

Intestinal mast cells have physiologic regulatory effects in addition to their pathologic effects. However, relatively little is known about the mechanisms of these regulatory effects. Mast cells are likely in an ongoing fluctuating balance between physiological functions and pathological effects in normal individuals. Poorly known factors can create an imbalance and lead to pathologic reactions.

Leflunomide, a novel immunomodulating agent, prevents the development of allergic sensitization in an animal model of allergic asthma

BACKGROUND

Leflunomide is a new anti-inflammatory and immunomodulating agent which is showing promise in several immune disorders, especially rheumatoid arthritis. Its activity profile suggests it may be of use in modulating allergic sensitization.

OBJECTIVE

To investigate the effectiveness of leflunomide in preventing the development of allergic sensitization.

METHODS

Fifty-three brown Norway rats were sensitized by intraperitoneal injection of ovalbumin and adjuvant (ricin) on day 0. To determine the ability of leflunomide to inhibit primary allergic sensitization six rats were treated with A77 1726, the active metabolite of leflunomide, from day 0 through day 5, six were treated from day 5 through day 10, and nine rats acted as controls. On day 14, ovalbumin-specific serum antibody levels and the magnitude of the early-phase airway response (EAR) after inhalation allergen challenge were assessed. To determine the ability of acute topical treatment with leflunomide to inhibit mast cell degranulation, three groups of five animals received either vehicle, 100 microg A77 1726, or 1000 g A77 1726 60 min prior to aerosol allergen challenge. To determine the effects of leflunomide treatment in vivo on mast cell function in vitro, mast cells were obtained by bronchoalveolar lavage from 17 rats (nine treated with leflunomide and eight controls). Allergen-specific and non-specific degranulation (48/80 induced) were studied.

RESULTS

In the leflunomide treated rats both ovalbumin-specific IgE and IgG levels were significantly reduced, and the increases in lung resistance and lung elastance were essentially abolished, compared to those of the control group. Non significant differences were found in any of the parameters between the two leflunomide treated groups. Topical pre-treatment with leflunomide did not prevent the allergen-induced EAR. Treatment with leflunomide in vivo prevented allergen-induced mast cell degranulation in vitro because the mast cells lacked IgE on their surface. Non allergen-specific degranulation was normal and allergen-induced degranulation could be restored by passive sensitization.

CONCLUSIONS

These data suggests that leflunomide can prevent primary allergic sensitization and prevent allergen-induced EAR by inhibiting production of allergen-specific IgE antibodies. Further studies in atopic conditions are warranted.

Cromolyn sodium prophylaxis inhibits pulmonary proinflammatory cytokines in infants at high risk for bronchopulmonary dysplasia

An imbalance of proinflammatory cytokines such as TNF-alpha, IL-1 beta, and the neutrophil chemotactic factor IL-8 and inhibitors (e.g., soluble TNF receptors and IL-1ra) in the lung during the first week of life may contribute to prolonged pulmonary inflammation and fibrosis in bronchopulmonary dysplasia (BPD). Disodium cromoglycate (DSCG) has anti-inflammatory effects in asthma, a disease with many similarities with BPD. In a prospective, randomized, blinded study, we examined whether early DSCG therapy inhibits proinflammatory cytokines in infants at risk for BPD. Twenty-six infants who were identified as high risk (> or = 75% probability) for oxygen-dependency at 28 d by a 12-h predictive score and survived 48 h were randomized to nebulized DSCG 20 mg (n = 13) or 2 cc NS (control, n = 13) every 6 h from Day 3 to Day 28. Lung lavage was collected on Day 3 (pre-study) and Day 7 and analyzed for cell count and differential and TNF-alpha, sTNFR1, sTNFR2, IL-1 beta, IL-1ra, and IL-8 concentrations. The groups' pre-study lavage cytokine concentrations were similar, but TNF-alpha and IL-8 concentrations were 3.6- and 4.9-fold lower in the DSCG group on Day 7 compared with levels in the control group. Soluble TNF receptors were unaffected by DSCG. There was a trend towards lower IL-1 beta levels in DSCG-treated infants on Day 7, but IL-1ra levels were unaffected by DSCG therapy. Three control subjects, but no DSCG-treated infants, died during the study period (p = 0.07). There were no significant differences between survivors of the two groups for oxygen-dependency at 28 d (100% control subjects; 85% DSCG). These results suggest that nebulized DSCG may exert an anti-inflammatory effect in the lungs of infants < or = 1,000 g at risk for BPD.