A New Stereocontrolled Total Synthesis of the Mast Cell inhibitory Alkaloid, (+)-Monanchorin, via the Wittig Reaction of a Stabilized Ylide with a Cyclic Guanidine Hemiaminal

Abstract Image

An asymmetric total synthesis of the mast cell inhibitor (+)-monanchorin is reported in which a Sharpless AD on 11 and a cyclic sulfate ring opening with an azide feature as key steps. After further manipulation, a novel guanidine-controlled ester reduction provided the guanidine-hemiaminal 25 which underwent Wittig olefination to give 27. Hydrogenation and a second guanidine-controlled reduction of the ester in 28, to obtain aldehyde 29, then set up a trifluoroacetic acid mediated cyclization to give (+)-monanchorin TFA salt.

Topical antihistamines and mast cell stabilisers for treating seasonal and perennial allergic conjunctivitis

BACKGROUND: Seasonal/perennial allergic conjunctivitis is the most common allergic conjunctivitis, usually with acute manifestations when a person is exposed to allergens and with typical signs and symptoms including itching, redness, and tearing. The clinical signs and symptoms of allergic conjunctivitis are mediated by the release of histamine by mast cells. Histamine antagonists (also called antihistamines) inhibit the action of histamine by blocking histamine H1 receptors, antagonising the vasoconstrictor, and to a lesser extent, the vasodilator effects of histamine. Mast cell stabilisers inhibit degranulation and consequently the release of histamine by interrupting the normal chain of intracellular signals. Topical treatments include eye drops with antihistamines, mast cell stabilisers, non-steroidal anti-inflammatory drugs, combinations of the previous treatments, and corticosteroids. Standard treatment is based on topical antihistamines alone or topical mast cell stabilisers alone or a combination of treatments. There is clinical uncertainty about the relative efficacy and safety of topical treatment.

OBJECTIVES: The objective of this review was to assess the effects of topical antihistamines and mast cell stabilisers, alone or in combination, for use in treating seasonal and perennial allergic conjunctivitis.

SEARCH METHODS: We searched CENTRAL (which contains the Cochrane Eyes and Vision Trials Register) (2014, Issue 7), Ovid MEDLINE, Ovid MEDLINE In-Process and Other Non-Indexed Citations, Ovid MEDLINE Daily, Ovid OLDMEDLINE (January 1946 to July 2014), EMBASE (January 1980 to July 2014), the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com), ClinicalTrials.gov (www.clinicaltrials.gov) and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en). We did not use any date or language restrictions in the electronic searches for trials. We last searched the electronic databases on 17 July 2014. We also searched the reference lists of review articles and relevant trial reports for details of further relevant publications.

SELECTION CRITERIA: We included randomised controlled trials (RCTs) comparing topical antihistamine and mast cell stabilisers, alone or in combination, with placebo, no treatment or to any other antihistamine or mast cell stabiliser, or both, that examined people with seasonal or perennial allergic conjunctivitis, or both. The primary outcome was any participant-reported evaluation (by questionnaire) of severity of four main ocular symptoms: itching, irritation, watering eye (tearing), and photophobia (dislike of light), both separately and, if possible, by an overall symptom score. We considered any follow-up time between one week and one year.

DATA COLLECTION AND ANALYSIS: Two review authors independently extracted data and assessed risk of bias. Disagreements were resolved by discussion among review authors and the involvement of a third review author. We followed standard methodological approaches used by Cochrane.

MAIN RESULTS: We identified 30 trials with a total of 4344 participants randomised, with 17 different drugs or treatment comparisons. The following antihistamines and mast cell stabilisers were evaluated in at least one RCT: nedocromil sodium or sodium cromoglycate, olopatadine, ketotifen, azelastine, emedastine, levocabastine (or levocabastine), mequitazine, bepotastine besilate, combination of antazoline and tetryzoline, combination of levocabastine and pemirolast potassium. The most common comparison was azelastine versus placebo (nine studies).We observed a large variability in reporting outcomes. The quality of the studies and reporting was variable, but overall the risk of bias was low. Trials evaluated only short-term effects, with a range of treatment of one to eight weeks. Meta-analysis was only possible in one comparison (olopatadine versus ketotifen). There was some evidence to support that topical antihistamines and mast cell stabilisers reduce symptoms and signs of seasonal allergic conjunctivitis when compared with placebo. There were no reported serious adverse events related to the use of topical antihistamine and mast cell stabilisers treatment.

AUTHORS' CONCLUSIONS: It seems that all reported topical antihistamines and mast cell stabilisers reduce symptoms and signs of seasonal allergic conjunctivitis when compared with placebo in the short term. However, there is no long-term data on their efficacy. Direct comparisons of different antihistamines and mast cell stabilisers need to be interpreted with caution. Overall, topical antihistamines and mast cell stabilisers appear to be safe and well tolerated. We observed a large variability in outcomes reported. Poor quality of reporting challenged the synthesis of evidence.

Mast cell tryptase controls paracellular permeability of the intestine: role of protease-activated receptor 2 and beta-arrestins

Tight junctions between intestinal epithelial cells prevent ingress of luminal macromolecules and bacteria and protect against inflammation and infection. During stress and inflammation, mast cells mediate increased mucosal permeability by unknown mechanisms. We hypothesized that mast cell tryptase cleaves protease-activated receptor 2 (PAR2) on colonocytes to increase paracellular permeability. Colonocytes expressed PAR2 mRNA and responded to PAR2 agonists with increased [Ca2+]i. Supernatant from degranulated mast cells increased [Ca2+]i in colonocytes, which was prevented by a tryptase inhibitor, and desensitized responses to PAR2 agonist, suggesting PAR2 cleavage. When applied to the basolateral surface of colonocytes, PAR2 agonists and mast cell supernatant decreased transepithelial resistance, increased transepithelial flux of macromolecules, and induced redistribution of tight junction ZO-1 and occludin and perijunctional F-actin. When mast cells were co-cultured with colonocytes, mast cell degranulation increased paracellular permeability of colonocytes. This was prevented by a tryptase inhibitor. We determined the role of ERK1/2 and of beta-arrestins, which recruit ERK1/2 to PAR2 in endosomes and retain ERK1/2 in the cytosol, on PAR2-mediated alterations in permeability. An ERK1/2 inhibitor abolished the effects of PAR2 agonist on permeability and redistribution of F-actin. Down-regulation of beta-arrestins with small interfering RNA inhibited PAR2-induced activation of ERK1/2 and suppressed PAR2-induced changes in permeability. Thus, mast cells signal to colonocytes in a paracrine manner by release of tryptase and activation of PAR2. PAR2 couples to beta-arrestin-dependent activation of ERK1/2, which regulates reorganization of perijunctional F-actin to increase epithelial permeability. These mechanisms may explain the increased epithelial permeability of the intestine during stress and inflammation.

Mast cell tryptase and proteinase-activated receptor 2 induce hyperexcitability of guinea-pig submucosal neurons

Mast cells that are in close proximity to autonomic and enteric nerves release several mediators that cause neuronal hyperexcitability. This study examined whether mast cell tryptase evokes acute and long-term hyperexcitability in submucosal neurons from the guinea-pig ileum by activating proteinase-activated receptor 2 (PAR2) on these neurons. We detected the expression of PAR2 in the submucosal plexus using RT-PCR. Most submucosal neurons displayed PAR2 immunoreactivity, including those colocalizing VIP. Brief (minutes) application of selective PAR2 agonists, including trypsin, the activating peptide SL-NH2 and mast cell tryptase, evoked depolarizations of the submucosal neurons, as measured with intracellular recording techniques. The membrane potential returned to resting values following washout of agonists, but most neurons were hyperexcitable for the duration of recordings (> 30 min-hours) and exhibited an increased input resistance and amplitude of fast EPSPs. Trypsin, in the presence of soybean trypsin inhibitor, and the reverse sequence of the activating peptide (LR-NH2) had no effect on neuronal membrane potential or long-term excitability. Degranulation of mast cells in the presence of antagonists of established excitatory mast cell mediators (histamine, 5-HT, prostaglandins) also caused depolarization, and following washout of antigen, long-term excitation was observed. Mast cell degranulation resulted in the release of proteases, which desensitized neurons to other agonists of PAR2. Our results suggest that proteases from degranulated mast cells cleave PAR2 on submucosal neurons to cause acute and long-term hyperexcitability. This signalling pathway between immune cells and neurons is a previously unrecognized mechanism that could contribute to chronic alterations in visceral function.

In vitro inhibitory effect of trichostatin A on canine grade 3 mast cell tumor

Mast cell tumor (MCT) is one of the most prevalent neoplasms that affect skin and soft tissue in dogs. Because mast cell tumors present a great variety of clinical appearance and behavior, their treatment becomes a challenge. Trichostatin A (TSA), an antifungal antibiotic, has shown inhibitory effects on the proliferation and induction of apoptosis in various types of cancer cells. In order to evaluate the potential of trichostatin A as a therapeutic drug, cells of grade 3 MCT were cultured and treated with concentrations of 1 nM to 400 nM of TSA. MTT assay and trypan blue exclusion assays were performed to estimate cell growth and cell viability, and cell cycle analysis was evaluated. TSA treatment showed a reduction in numbers of viable cells and an increase of cell death by apoptosis. The cell cycle analysis showed an increase of hypodiploid cells and a reduction of G0/G1 and G2/M -phases. According to these results, trichostatin A may be an interesting potential chemotherapeutic agent for the treatment of canine MCT.

Mast cell and eosinophils in the wall of the gut and eosinophils in the blood stream during Toxocara vitulorum infection of the water buffalo calves (Bubalus bubalis)

Toxocara vitulorum is a pathogenic nematode from the small intestine of very young buffalo calves. To understand the development of the inflammatory responses in the wall of the gut, samples of tissues were removed from the duodenum, jejunum and ileum of buffalo calves naturally infected with T. vitulorum during the beginning of the infection, at the peak of egg output, as well as during the periods of rejection of the worms and post-rejection. Two additional control groups of uninfected calves (by anti-helminthic therapy of their mothers and after the birth) were also necropsied on days 30 and 50 after birth. Blood samples were fortnightly collected from birth to 174 days post-birth. Blood smears were prepared and stained with Giemsa for eosinophils. The parasitological status of buffalo calves was evaluated through weekly fecal egg counts (EPG) from 1 to 106 days after birth, which revealed that T. vitulorum egg shedding started on day 11, reached the peak of the infection on day 49 and finally expelled the parasites between days 50 and 85 after birth. In the infected buffalo calves, the mast cell population increased significantly, by two-fold in the mucosa (villus-crypt unit (VCU)) of the duodenum and four-fold in the proximal jejunum; but these increases were statistically significant only at the peak of the infection. Although mast cell numbers increased in the mucosa of the ileum as well as in both the submucosal and muscle tissues of the duodenum, proximal jejunum and ileum, the data was not significantly different from the controls. Eosinophil numbers increased in the mucosa of the duodenum (two-five times higher than the control) and proximal jejunum (three-five-fold) during the period of the infection (beginning, peak and rejection). The relative numbers of eosinophils increased in the blood stream from the second to the seventh week. In conclusion, T. vitulorum infection elicited mastocytosis and tissue eosinophilia in the duodenum and proximal jejunum, as well as eosinophilia in the blood stream, during the beginning, at the peak and during the rejection of the worm. After the rejection of the worms, the numbers of these cells returned to normal levels suggesting that these cells may have a role in the process of rejection of T. vitulorum by the host. (C) 2003 Elsevier B.V. B.V. All rights reserved.

Ileal mucosal mast cell, eosinophil, and goblet cell populations during Hymenolepis diminuta infection of the rat

The population dynamics in the enteric connective tissues of eosinophils, mucosal mast cells (MMC), and in the mucosal epithelium of goblet cells were examined morphometrically in fixed ileal tissue of outbred Sprague Dawley rats during the first 32 days of infection with the tapeworm Hymenolepis diminuta. MMC and eosinophils were present in the lamina propria and submucosa; however, only eosinophils were also present in the muscularis externa. Eosinophilic infiltrate was first observed in the lamina propria at 15 days postinfection (dpi) and the numbers of eosinophils remained elevated through 32 dpi. Initial mucosal mastocytosis was detected on 6 dpi and MC numbers continued to rise over the study period without reaching a plateau. Goblet cell hyperplasia occurred only at 32 dpi. In contrast to some intestinal nematode infections where these same 3 cell types are associated with the host's expulsion responses, H. diminuta is not lost by a rapid host response in the outbred Sprague Dawley rat strain used in these experiments. We suggest that either the induction of hyperplasia of these host effector cells in ileum tissue during H. diminuta infection is not capable of triggering parasite rejection mechanisms, or the function of the induced hyperplasia is necessary for some as yet unassociated physiological or tissue architecture change in the host's intestine.

Canine Subcutaneous Mast Cell Tumors: Cellular Proliferation and KIT Expression as Prognostic Indices

Molecular assays are widely used to prognosticate canine cutaneous mast cell tumors (MCT). There is limited information about these prognostic assays used on MCT that arise in the subcutis. The aims of this study were to evaluate the utility of KIT immunohistochemical labeling pattern, c-KIT mutational status (presence of internal tandem duplications in exon 11), and proliferation markers-including mitotic index, Ki67, and argyrophilic nucleolar organizing regions (AgNOR)-as independent prognostic markers for local recurrence and/or metastasis in canine subcutaneous MCT. A case-control design was used to analyze 60 subcutaneous MCT from 60 dogs, consisting of 24 dogs with subsequent local recurrence and 12 dogs with metastasis, as compared to dogs matched by breed, age, and sex with subcutaneous MCT that did not experience these events. Mitotic index, Ki67, the combination of Ki67 and AgNOR, and KIT cellular localization pattern were significantly associated with local recurrence and metastasis, thereby demonstrating their prognostic value for subcutaneous MCT. No internal tandem duplication mutations were detected in exon 11 of c-KIT in any tumors. Because c-KIT mutations have been demonstrated in only 20 to 30% of cutaneous MCT and primarily in tumors of higher grade, the number of subcutaneous MCT analyzed in this study may be insufficient to draw conclusions on the role c-KIT mutations in these tumors.

Effects of myenteric denervation on extracellular matrix fibers and mast cell distribution in normal stomach and gastric lesions

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Pharmacological modulation of allergic inflammation in the rat airways and association with mast cell heterogeneity

Administration of ovalbumin by aerosol to sensitised rats produced a rapid (15 min) protein exudation in different airway tissues, as determined by Evans blue staining. This was associated with marked mast cell degranulation determined by histological examination, with there being no difference between mucosal and connective tissue mast cells. A 5-day administration regimen with compound 48/80 selectively depleted connective tissue mast cell (Positive to berberine staining) without modifying ovalbumin-induced plasma protein extravasation. Treatment of rats with dexamethasone (1 mg/kg, - 12 h) or nor-dihydroguaiaretic acid (30 mg/kg i.p., - 30 min) significantly reduced ovalbumin-induced protein extravasation and preserved mucosal mast cell morphology. Indomethacin (4 mg/kg i.v., - 30 min) exerted no effect on either parameter. In conclusion, we propose the mucosal mast cell as a target cell responsible at least partly for the inhibitory actions of known anti-inflammatory drugs. We suggest an involvement of endogenous leukotriene(s), but not prostanoid(s), in mucosal mast cell activation/degranulation. (C) 2001 Published by Elsevier B.V. B.V.

Dermal mast cell counts in F2 Holstein x Gir crossbred cattle artificially infested with the tick Boophilus microplus (Acari : Ixodidae)

The role of dermal mast cells (DMC) in the host resistance to ticks has been studied but it is not totally explained yet. Studies have proposed that zebuine cattle breeds, known as highly resistant to ticks, have more DMC than taurine breeds. In the present study, we compared the number of adult female ticks Boophilus microplus and the mast cells' countings in the skin of F-2 crossbred Gir x Holstein cattle, before and after tick infestation. F-2 crossbred cattle (n = 148) were divided into seven groups and artificially infested with 1.0 x 10(4) B. nticroplus larvae and, 21 days afterwards, adult female-fed ticks attached to the skin were counted. Skin biopsies were taken and examined under light microscopy with a square-lined ocular reticulum in a total area of 0.0625 mm(2) in both the superficial and deep dermis. Results demonstrated that infested F-2 crossbred cattle acquired resistance against the cattle-tick B. microplus probably associated to an increase in the dermal mast cell number. It is concluded that the tick infestation may lead to an environmental modification in the dermis of parasitized hosts due to the massive migration of mast cells or their local proliferation.

ULTRASTRUCTURAL SIMILARITY BETWEEN BAT AND HUMAN MAST-CELL SECRETORY GRANULES

Mast cells in the tongue of the bat (Artibeus lituratus) show a well-developed Golgi area and abundant mitochondria in the granule-free perinuclear cytoplasm. Rough endoplasmic reticulum profiles, free ribosomes, mitochondria, bundles of filaments and a great number of secretory granules are found throughout the remaining cytoplasm. The granules, of various shapes and sizes, are simple containing an electron-dense, homogeneous matrix, coarse particles or cylindrical scrolls, or combinations (cylindrical scrolls with either electron-dense, homogeneous matrix or coarse particle contents). Up to now, scroll-containing granules have been considered to be a unique feature of human mast cells.

Immunohistochemical evaluation of prostaglandin E2 and vascular endothelial growth factor in canine cutaneous mast cell tumours

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)