Effects of luteolin, quercetin and baicalein on immunoglobulin E-mediated mediator release from human cultured mast cells

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.

Role of Intestinal First-Pass Metabolism of Baicalein in its Absorption Process

PURPOSE

The aim of the present study was to investigate the role of intestinal first-pass metabolism of baicalein (B) in its absorption process.

METHODS

The intestinal absorption of B was characterized using Caco-2 cell monolayer model and rat in situ single-pass intestinal perfusion model. In addition, preliminary metabolic kinetics of B was evaluated in both rat and human intestinal S9 fractions.

RESULTS

B was well absorbed and extensively metabolized to baicalin (BG), baicalein-7-O-beta-glucuronide, in rat intestinal perfusion model, whereas less extent of metabolism was observed in the Caco-2 cell monolayer model. Moreover, BG generated in the intestinal epithelium during the absorption of B also rapidly transported to both the apical side (the apical chamber of Caco-2 model and the perfusate of the intestinal perfusion model) as well as the basolateral side of the small intestine (the basal chamber of Caco-2 model and the mesenteric vein of the intestinal perfusion model). From the preliminary metabolic studies, it was found that a higher loading dose of B resulted in a less extent of metabolism in intestine. In addition, the extent of metabolism of B was similar in jejunum and ileum when 50 microM of B was perfused through different sections of rat small intestine.

CONCLUSION

The first-pass metabolism of B in small intestine may play an important role in its low oral bioavailability.

Antiallergic and antihistaminic effect of two extracts of Capparis spinosa L. flowering buds

The antiallergic properties of two lyophilized extracts obtained from Capparis spinosa L. flowering buds (capers) by methanol extraction, carried out at room temperature (CAP-C) or with heating at 60 degrees C (CAP-H), were investigated. The protective effects of CAP-H and CAP-C, orally administered (14.28 mg[sol ]kg), were evaluated against Oleaceae antigen challenge-induced and histamine-induced bronchospasm in anaesthetized guinea-pigs. Furthermore, the histamine skin prick test was performed on humans, applying a gel formulation containing 2% CAP-C (the only extract able to protect against histamine-induced bronchospasm) on the skin for 1 h before histamine application and monitoring the erythema by reflectance spectrophotometry. The CAP-H showed a good protective effect against the bronchospasm induced by antigen challenge in sensitized guinea-pigs; conversely, a significant decrease in the responsiveness to histamine was seen only in CAP-C pretreated animals. Finally, the CAP-C gel formulation possessed a marked inhibitory effect (46.07%) against histamine-induced skin erythema. These two caper extracts displayed marked antiallergic effectiveness; however, the protective effect of CAP-H was very likely due to an indirect mechanism (for example, inhibition of mediator release from mast cells or production of arachidonic acid metabolites); conversely, CAP-C is endowed with direct antihistaminic properties. The different mechanisms of action of CAP-H and CAP-C may be related to a difference in the extraction procedure and, thus, in their qualitative[sol ]quantitative chemical profile.

Inhibitory effects of flavonol glycosides from Cinnamomum osmophloeum on inflammatory mediators in LPS/IFN-γ-activated murine macrophages

Four kaempferol glycosides were isolated from the leaves of Cinnamomum osmophloeum Kaneh, a Taiwan endemic tree. These compounds namely, kaempferitrin (1), kaempferol 3-O-beta-D-glucopyranosyl-(1-->4)-alpha-L-rhamnopyranosyl-7-O-alpha-L-rhamnopyranoside (2), kaempferol 3-O-beta-D-apiofuranosyl-(1-->2)-alpha-L-arabinofuranosyl-7-O-alpha-L-rhamnopyranoside (3), and kaempferol 3-O-beta-D-apiofuranosy-(1-->4)-alpha-L-rhamnopyranosyl-7-O-alpha-L-rhamnopyranoside (4). The structure of compound 2 was determined by spectroscopic analyses and acid hydrolysis. The isolates 1-4 were evaluated as inhibitors of some macrophage functions involved in the inflammatory process. These four compounds inhibited lipopolysaccharide (LPS) and interferon (IFN)-gamma-induced nitric oxide (NO), and cytokines [tumor necrosis factor (TNF)-alpha and interleukin (IL)-12] in a dose-dependent manner. The concentration of 50% inhibition (IC(50)) of NO by compounds 1, 3, 4 were 40, 15, 20microM, respectively. In parallel, these concentrations were approximately in a similar manner to that observed for TNF-alpha and IL-12 production. However, compound 2 inhibited NO and cytokines production by 30% at 100microM concentration. On the other hand, compounds 3 and 4 showed no inhibitory effect on the production of NO from macrophages, when inducible NO synthase was already expressed by the stimulation with LPS and IFN-gamma. Taken together, our results provide evidence that isolates of C. osmophloeum possess an anti-inflammatory potential which constitutes a previously unrecognized biological activity.

Inhibition of syk activity and degranulation of human mast cells by flavonoids

To investigate the effect of flavonoids on the activation of p72(syk) (Syk) protein tyrosine kinase which plays a pivotal role in the high affinity IgE receptor-mediated degranulation of mast cells, we picked out 10 flavonoids, classified them into 4 series, and examined their effects on the activation of Syk and on the degranulation of human mast cells. Flavones and flavonols showed clear inhibition, whereas flavanones and isoflavones had either weak or no effect on Syk enzymatic activity induced by amino acid peptide corresponding to the activation loop domain and on IgE-dependent degranulation of human cultured mast cells (HCMC). On the basis of calculated logP (ClogP) values as a prediction of compound lipophilicity, some flavonoids were speculated to have low lipophilicity, the reason for poor cell permeability. A significant relationship was observed between the inhibition of Syk activity and HCMC degranulation attributable to flavonoids when the ClogP values of the compounds were taken into account (r(2)=0.89). These results suggested that the impairment of mast cell degranulation by several flavonoids classified into flavones and flavonols might be mediated via inhibition of the intracellular activation of Syk.

Inhibitory effect of luteolin on TNF-α-induced IL-8 production in human colon epithelial cells

Interleukin (IL)-8 plays a central role in the initiation and maintenance of inflammatory responses in the inflammatory bowel disease. The proinflammatory cytokine-mediated production of IL-8 requires activation of various kinases, which leads to the IkappaB degradation and NF-kappaB activation. In this study, we investigated the role of luteolin, a major flavonoid of Lonicera japonica, on TNF-alpha-induced IL-8 production in human colonic epithelial cells. HT29 cells were stimulated with TNF-alpha in the presence or absence of luteolin. IL-8 production was measured by enzyme-linked immunosorbent assay (ELISA) and reverse transcriptase-polymerase chain reaction (RT-PCR) analysis, and the mitogen-activated protein kinases (MAPKs) activation and IkappaB degradation were determined by Western blot analysis. NF-kappaB activation was assessed by the electrophoretic motility shift assay (EMSA). Luteolin suppressed TNF-alpha-induced IL-8 production in dose-dependent manner. In addition, luteolin inhibited TNF-alpha-induced phosphorylation of p38 MAPK and extracellular-regulated kinases (ERK), IkappaB degradation, and NF-kappaB activation. These results suggest that luteolin has the inhibitory effects on TNF-alpha-induced IL-8 production in the intestinal epithelial cells through blockade in the phosphorylation of MAPKs, following IkappaB degradation and NF-kappaB activation.

Flavones inhibit proliferation and increase mediator content in human leukemic mast cells (HMC-1)

OBJECTIVE

Mast cells are involved in allergic and inflammatory reactions. These cells are also increased in the bone marrow, skin, and other organs in systemic mastocytosis. Flavonoids are naturally occurring molecules with antioxidant, cytoprotective, and anti-inflammatory activities. Some flavonoids, like quercetin, inhibit the growth of certain malignant cells in culture. Quercetin also inhibits histamine release and induces accumulation of secretory granules in rat basophilic leukemia cells.

METHOD

We investigated the effect of five flavonoids: flavone, kaempferol, morin, myricetin, and quercetin at 1, 10, and 100 microM on proliferation and secretory mediator content (beta-hexosaminidase, histamine, and tryptase) in human leukemic mast cells (HMC-1), the doubling time of which was about 2 d.

RESULTS

Flavone and kaempferol at 100 microM inhibited cell proliferation over 80% on either day 3, 4, or 5 of culture. Quercetin showed this level of inhibition only on day 5, myricetin inhibited by 50% at days 3-5, whereas morin's inhibition was < 20%. All flavonoids (except morin) at 100 microm increased histamine and tryptase content, but not beta-hexosaminidase, equally at days 3 and 4 of culture quercetin also increased the development of secretory granules.

CONCLUSION

These results indicate that certain flavonoids can inhibit HMC-1 proliferation, induce secretory granule development and the accumulation of mediators.

Lafoensia pacari extract inhibits IL-5 production in toxocariasis

Toxocariasis is an infection induced by Toxocara canis, an intestinal parasite of dogs. In this study, an experimental murine model of toxocariasis was used to evaluate the anti-inflammatory activity of an ethanolic extract of Lafoensia pacari stem bark. Mice infected with T. canis were treated with L. pacari extract (200 mg/kg, p.o.). Subsequently, we observed a reduction in the number of eosinophils in the peritoneal cavity, bronchoalveolar fluid, blood and bone marrow. Production of interleukin (IL)-5, a major cytokine involved in eosinophilic differentiation, proliferation and activation, is also an important marker for infection. The reduced levels of IL-5 observed in serum, lung homogenates and bronchoalveolar fluid demonstrated the anti-inflammatory mechanisms of L. pacari. Larvae recovery from infected mice treated with L. pacari was comparable with that from untreated mice, suggesting that L. pacari is not toxic to the parasite. Nonetheless, our results demonstrate a potential therapeutic effect of L. pacari extract in IL-5-mediated inflammatory diseases and provide new prospects for the development of drugs to treat IL-5-dependent allergic diseases such as parasite infection and asthma.

The antioxidative and antihistaminic properties of quercetin in ethanol-induced gastric lesions

The role of reactive oxygen species in the pathogenesis of acute ethanol-induced gastric mucosal lesions and the effects of quercetin were evaluated in an experimental model. In addition, the effects of quercetin on gastric damage were evaluated histopathologically. Rats were divided into three groups as control rats, ethanol treated rats and ethanol+quercetin treated rats. Ethanol group was given a gastric gavage containing 1 ml of 80% ethanol (v/v) prepared in distilled water. Quercetin (200 mg/kg body wt.) was given by intragastric gavage 120 min before the administration of ethanol. Gastric tissue thiobarbituric acid reactive substance levels, carbonyl compounds, histamine levels and myeloperoxidase activities were found to be increased in ethanol treated rats and quercetin treatment reversed these increases. No statistically significant changes were found between all groups in catalase activity. The superoxide dismutase activity dropped significantly after ethanol treatment and quercetin treatment increased this enzyme activity. Gastric damage was confirmed histomorphometrically by significant increases in the number of mast cells and gastric erosions in ethanol treated rats. It was also confirmed that quercetin treatment significantly decreased the number of mast cells and reduced the area of gastric erosions. The results suggest that the gastroprotective effect of quercetin in this experimental model could be due to its antiperoxidative, antioxidant and antihistaminic effects.

Luteolin, an emerging anti-cancer flavonoid, poisons eukaryotic DNA topoisomerase I

Luteolin, a naturally occurring flavonoid, is abundant in our daily dietary intake. It exhibits a wide spectrum of pharmacological properties, but little is known about its biochemical targets other than the fact that it induces topoisomerase II-mediated apoptosis. In the present study, we show that luteolin completely inhibits the catalytic activity of eukaryotic DNA topoisomerase I at a concentration of 40 microM, with an IC50 of 5 microM. Preincubation of enzyme with luteolin before adding a DNA substrate increases the inhibition of the catalytic activity (IC50=0.66 microM). Treatment of DNA with luteolin before addition of topoisomerase I reduces this inhibitory effect. Subsequent fluorescence tests show that luteolin not only interacts directly with the enzyme but also with the substrate DNA, and intercalates at a very high concentration (>250 microM) without binding to the minor groove. Direct interaction between luteolin and DNA does not affect the assembly of the enzyme-DNA complex, as evident from the electrophoretic mobility-shift assays. Here we show that the inhibition of topoisomerase I by luteolin is due to the stabilization of topoisomerase-I DNA-cleavable complexes. Hence, luteolin is similar to camptothecin, a class I inhibitor, with respect to its ability to form the topoisomerase I-mediated 'cleavable complex'. But, unlike camptothecin, luteolin interacts with both free enzyme and substrate DNA. The inhibitory effect of luteolin is translated into concanavalin A-stimulated mouse splenocytes, with the compound inducing SDS-K+-precipitable DNA-topoisomerase complexes. This is the first report on luteolin as an inhibitor of the catalytic activity of topoisomerase I, and our results further support its therapeutic potential as a lead anti-cancer compound that poisons topoisomerases.

Flavonoid phytochemicals regulate activator protein-1 signal transduction pathways in endometrial and kidney stable cell lines

Phytochemicals bind to and regulate the human estrogen receptors (ERalpha and ERbeta), mimicking actions of the endogenous estrogen, 17beta-estradiol, and known antiestrogens such as ICI 182,780. Recently, however, some of these estrogenic phytochemicals have been shown to affect other signal transduction pathways, such as receptor tyrosine kinases and mitogen-activated protein kinases (MAPK). Previously, we found that certain phytochemicals, such as flavone, apigenin, kaempferide and chalcone, have potent antiestrogenic activity. However, the antiestrogenicity of these compounds does not correlate with their ER binding capacity, suggesting alternative signaling as a mechanism for their antagonistic effects. In this study, we examined the effects of these compounds on the transcription factor activator protein-1 (AP-1). Using AP-1-luciferase stable human endometrial adenocarcinoma Ishikawa and human embryonic kidney (HEK) 293 cells, chalcone, flavone and apigenin all stimulated AP-1 activity. Additionally, we determined the effects of the phytochemicals on transcription factors that are downstream targets of various MAPK pathways. To test this, we used HEK 293 cells stably cointegrated with GAL4 transcriptional activation systems of Elk-1, c-Jun or C/EBP homologous protein (CHOP). Chalcone was the only phytochemical that activated all three transcription factors [Elk-1, 2.7-fold (P < 0.001); c-Jun, 2.7-fold (P = 0.025); CHOP, 3.0-fold (P = 0.002)], whereas apigenin stimulated CHOP (3.9-fold; P < 0.001), but inhibited phorbol myristoyl acetate-induced c-Jun activity (71%;P = 0.006). This work suggests that phytochemicals affect multiple signaling pathways that converge at the level of transcriptional regulation. The ability of flavonoids to regulate MAPK-responsive pathways in a selective manner indicates a mechanism by which phytochemicals may influence human health and disease.

Azelastine is more potent than olopatadine n inhibiting interleukin-6 and tryptase release from human umbilical cord blood-derived cultured mast cells

BACKGROUND

Mast cells are involved in early- and late-phase reactions by releasing vasoactive molecules, proteases, and cytokines. Certain histamine-1 receptor antagonists and other antiallergic drugs seem to inhibit the release of mediators from rat and human mast cells.

OBJECTIVE

Azelastine and olopatadine are antiallergic agents present in the ophthalmic solutions azelastine hydrochloride (Optivar, Asta Medica/Muro Pharmaceuticals, Tewksbury, MA), and olopatadine hydrochloride (Patanol, Alcon Laboratories, Fort Worth, TX), respectively. We investigated the effect of these drugs on interleukin-6 (IL-6), tryptase, and histamine release from cultured human mast cells (CHMCs).

METHODS

CHMCs were grown from human umbilical cord blood-derived CD34+ cells in the presence of stem cell factor and IL-6 for 14 to 16 weeks. Sensitized CHMCs were pretreated with various concentrations of azelastine or olopatadine for 5 minutes. CHMCs were then challenged with anti-immunoglobulin E, and the released mediators were quantitated.

RESULTS

The greatest inhibition of mediator release was seen with 24 microM azelastine; this level of inhibition was matched with the use of 133 microM olopatadine. At this concentration, these drugs inhibited IL-6 release by 83% and 74%, tryptase release by 55% and 79%, and histamine release by 41% and 45%, respectively. Activated CHMCs were characterized by numerous filopodia that were inhibited by both drugs as shown by electron microscopy.

CONCLUSIONS

These results indicate that azelastine and olopatadine can inhibit CHMCs activation and release of IL-6, tryptase, and histamine. On an equimolar basis, azelastine was a more potent inhibitor than olopatadine.

The Chinese herbal formulation biminne in management of perennial allergic rhinitis: a randomized, double-blind, placebo-controlled, 12-week clinical trial

BACKGROUND

Herbal therapies have been widely used in allergic rhinitis (AR), but none have been shown to be effective in controlled scientific clinical trials.

OBJECTIVE

The aim of this study was to test the effects of the Chinese herbal formulation Biminne in patients with moderate to severe perennial AR.

METHODS

In a randomized, double-blind, placebo-controlled clinical trial, 58 patients were randomized to receive either Biminne capsules (n = 26) or placebo (n = 32) in doses of five capsules twice a day for 12 weeks. Main outcomes were measured by changes in symptom diaries, quality of life scores, patients' evaluations of improvement on visual analog scores, and physicians' overall evaluation. Total serum immunoglobulin E was measured in all patients without knowledge of which group they were in. After 1 year we performed a randomized, double-blind, dose-response study in 22 patients who had previously received placebo.

RESULTS

The trial outcomes evaluated by four instruments showed a statistically significant improvement in some of the symptoms of AR, whereas others exhibited a positive trend that did not reach statistical significance. Followup 1 year after completion of the trial suggested that benefit of the treatment persisted. A pilot dose-response study showed both half and full strengths were effective. Total serum immunoglobulin E was reduced after the herbal treatment.

CONCLUSIONS

Our results suggest the Biminne formulation is effective in treatment of perennial AR. Its mode of action is unknown.

Antiallergic effect of flavonoid glycosides obtained from Mentha piperita L

Six flavonoid glycosides, eriocitrin (1), narirutin (2), hesperidin (3), luteolin-7-O-rutinoside (4), isorhoifolin (5), diosmin (6), rosmarinic acid (7) and 5,7-dihydroxycromone-7-O-rutinoside (8), were isolated from the aerial part of Mentha piperita L. Among these compounds, compound 4 showed a potent inhibitory effect on histamine release induced by compound 48/80 and antigen-antibody reaction. This compound was more effective than luteolin and luteolin-7-O-glucoside in inhibiting histamine release from rat peritoneal mast cells. Compound 4 also caused a dose-related inhibition of the antigen-induced nasal response and significant effects were observed at doses of 100 and 300 mg/kg. These results indicate that compound 4 may be clinically useful in alleviating the nasal symptoms of allergic rhinitis.

Dietary antioxidants and asthma in adults: population-based case-control study

A protective role for dietary antioxidants in asthma has been proposed. However, epidemiological evidence to implicate antioxidant vitamins is weak, and data on the role of flavonoid-rich foods and antioxidant trace elements are lacking. We carried out a population-based case-control study in South London, UK, to investigate whether asthma is less common and less severe in adults who consume more dietary antioxidants. Participants were aged 16-50 yr and registered with 40 general practices. Asthma was defined by positive responses to a standard screening questionnaire in 1996, and complete information about usual diet was obtained by food frequency questionnaire from 607 cases and 864 controls in 1997. After controlling for potential confounding factors and total energy intake, apple consumption was negatively associated with asthma (odds ratio [OR] per increase in frequency group 0.89 [95% confidence interval [CI]: 0.82 to 0.97]; p = 0.006). Intake of selenium was also negatively associated with asthma (OR per quintile increase 0.84 [0.75 to 0.94]; p = 0.002). Red wine intake was negatively associated with asthma severity. The associations between apple and red wine consumption and asthma may indicate a protective effect of flavonoids. The findings for dietary selenium could have implications for health policy in Britain where intake has been declining.

Immunotoxicity of a standardized citrus polymethoxylated flavone extract

Polymethoxylated flavones (PMFs) from citrus inhibit production of TNF-alpha and other pro-inflammatory cytokines. As TNF-alpha also modulates NK cell activity, the current studies were conducted to assess the potential for a standardized citrus PMF mixture to suppress humoral and innate immune functions. PMFs were isolated from orange peel oil using a procedure that obtained a consistent mixture of PMFs both in identity and proportion. The mixture consisted of nobiletin (30.7%), 3,3',4',5,6,7,8-heptamethoxyflavone (27.9%), trimethylscutellarein (14.5%), tangeretin (10.4%), sinensetin (5.8%), 5-demethyl-nobiletin (2.0%), hexa-O-methylquercetagetin (1.3%), 5-demethyl-tetramethylscutellarein (0.6%), and other flavonoids (2.7%). To assess the effect of the PMF mixture on humoral immune responses, female B(6)C(3)F(1) mice (n=8) were exposed to the PMF by gavage at 5, 50, 150 and 500 mg/kg/day for 28 days. On day 25, mice were sensitized to sRBC by tail vein injection and AFC response determined 4 days later. Humoral immunity was insensitive to suppression following exposure to all concentrations of the PMF mixture. Suppression of NK cell activity was observed only following 500 mg/kg/day for 28 days. Body weights were not affected by exposure to any concentration of the PMF mixture in sRBC immunized or non-immunized mice. However, in sRBC-immunized mice, higher concentrations of PMF were associated with a statistically insignificant increase in spleen weight (P>0.05). No change in spleen weight was observed in non-immunized mice. As anticipated, based on previously published in vitro observations, long-term, high-dose exposure to a standardized mixture of citrus PMFs caused a mild suppression of NK cell activity; however, humoral immunity was not sensitive to suppression at the same exposure levels.

New agents for the medical treatment of interstitial cystitis

Interstitial cystitis (IC) is a painful, sterile, disorder of the urinary bladder characterised by urgency, frequency, nocturia and pain. IC occurs primarily in women but also in men with recent findings indicating that chronic, abacterial prostatitis may be a variant of this condition. The prevalence of IC has ranged from about 8 - 60 cases/100,000 female patients depending on the population evaluated. About 10% of patients have severe symptoms that are associated with Hunner's ulcers on bladder biopsy; the rest could be grouped in those with or without bladder inflammation. Symptoms of IC are exacerbated by stress, certain foods and ovulatory hormones. Many patients also experience allergies, irritable bowel syndrome (IBS) and migraines. There have been various reports indicating dysfunction of the bladder glycosaminoglycan (GAG) protective layer and many publications showing a high number of activated bladder mast cells. Increasing evidence suggests that neurogenic inflammation and/or neuropathic pain is a major component of IC pathophysiology. Approved treatments so far include intravesical administration of dimethylsulphoxide (DMSO) or oral pentosanpolysulphate (PPS). New treatments focus on the combined use of drugs that modulate bladder sensory nerve stimulation (neurolytic agents), inhibit neurogenic activation of mast cells, or provide urothelial cytoprotection, together with new drugs with anti-inflammatory activity.