Tannin is the major agent present in cotton mill dust responsible for human platelet 5-hydroxytryptamine secretion and thromboxane formation

Dexamethasone attenuates grain sorghum dust extract-induced increase in macromolecular efflux in vivo

The purpose of this study was to determine whether dexamethasone attenuates grain sorghum dust extract-induced increase in macromolecular efflux from the in situ hamster cheek pouch and, if so, whether this response is specific. By using intravital microscopy, we found that an aqueous extract of grain sorghum dust elicited significant, concentration-dependent leaky site formation and increase in clearance of FITC-labeled dextran (FITC-dextran; mol mass, 70 kDa) from the in situ hamster cheek pouch (P < 0.05). This response was significantly attenuated by dexamethasone (10 mg/kg iv). Dexamethasone also attenuated substance P-induced leaky site formation and increase in clearance of FITC-dextran from the cheek pouch but had no significant effects on adenosine-induced responses. Dexamethasone had no significant effects on arteriolar diameter in the cheek pouch. On balance, these data indicate that dexamethasone attenuates grain sorghum dust extract- and substance P-induced increases in macromolecular efflux from the in situ hamster cheek pouch in a specific fashion.

Tannic acid elicits neurogenic plasma exudation from the in situ hamster cheek pouch

The purpose of this study was to determine whether tannic acid elicits neurogenic plasma exudation from the oral mucosa in vivo and, if so, whether this response is transduced in part by the L-arginine-nitric oxide (NO) biosynthetic pathway. Using intravital microscopy, we found that suffusion of tannic acid elicits significant concentration-dependent leaky site formation and increase in clearance of fluorescein isothiocyanate-dextran (molecular mass 70 kDa) from the in situ hamster cheek pouch (P < 0.05). These effects are significantly attenuated by two selective, but structurally distinct, nonpeptide neurokinin-1 (NK1) receptor antagonists, CP-96,345 and RP-67580, but not by CP-96,344, the 2R,3R enantiomer of CP-96,345. NG-nitro-L-arginine methyl ester (L-NAME), an NO synthase inhibitor, but not D-NAME, significantly attenuates tannic acid-induced responses. L-Arginine, but not D-arginine, reverses the attenuating effects of L-NAME. We conclude that tannic acid elicits L-arginine-NO biosynthetic pathway-dependent neurogenic plasma exudation from the in situ hamster cheek pouch.

Tannin inhibition of protein kinase C in airway epithelium

Tannin, a polydisperse polyphenol extracted from cotton bracts (CBE), has been implicated in the pathogenesis of byssinosis, a lung disease of mill workers. CBE tannin inhibits chloride secretion in airway epithelial cells by means of an unknown mechanism(s). Activation of protein kinase C (PKC) by PMA (phorbol 12-myristate 13-acetate) in airway cells increases chloride secretion. The effect of tannin on this PKC pathway was examined, using canine tracheal epithelium mounted in Ussing chambers. PMA addition (10 nM) to the mucosal bath resulted in a 0.36 +/- 0.07 microEq/cm2.h (mean +/- SEM, n = 20) increase in short-circuit current (Isc) and a 0.38 +/- 0.17 microEq/cm2.h increase in net chloride secretion (Jnet). The inactive 4 alpha-phorbol had no effect. Tannin addition to the mucosal bath produced a dose-dependent decrease in Isc and Jnet. In tissues pretreated with 2-50 micrograms/ml tannin, and subsequently stimulated with PMA, tannin inhibited PMA stimulation of chloride secretion beginning at a tannin concentration of 10 micrograms/ml (0.09 +/- 0.05 microEq/cm2.h [n = 10] increase in Isc and 0.08 +/- 0.03 microEq/cm2.h increase in Jnet with PMA after tannin pretreatment). At 50 micrograms/ml tannin, the stimulatory effect of PMA was completely abolished. The known PKC inhibitor, H-7 (20 microM), inhibited PMA stimulation, while chelerythrine (2 microM) had not effect on PMA-stimulated Isc and Jnet, and calphostin C was toxic to the airway epithelium. In membrane fragments, 2.5 micrograms/ml tannin inhibited the rate of histone III phosphorylation by PMA from 32.1 +/- 4.4 nmol/mg protein per min to 20.1 +/- 2.7 nmol/mg protein per min (n = 7). In bovine airway cells, tannin pretreatment (2.5 micrograms/ml) decreased the cytosolic activity of PKC but had no effect on PKC translocation to the membrane. We conclude that tannin inhibits chloride secretion in airway epithelial cells in part by inhibiting PKC.

Organic dust disease of airways

Exposure to aerosols of organic dusts such as coffee, tea, spices, soy, fur, and animal food in an occupational setting can affect the respiratory health of industrial workers. Based on our experience with workers from many small industries processing organic materials, we discuss the clinical features and possible mechanisms responsible for the respiratory impairment associated with these types of dust exposure. Significantly higher prevalences for most chronic respiratory symptoms were found among exposed workers than among control workers. Smoking appears to aggravate these symptoms. A large number of exposed workers complained of acute symptoms which developed during the work shift. In exposed workers, significant across-shift reductions in lung function were recorded for all spirometric tests, but particularly for the flow rates at 50% and 25% of vital capacity on maximum expiratory flow-volume curves. Comparison of preshift measured ventilatory capacity tests with predicted normal values indicates that these workers demonstrate obstructive changes affecting primarily flow rate at low lung volumes. The data suggest that exposure to organic aerosols in industrial settings, particularly in conjunction with smoking, may be associated with the development of chronic obstructive lung disease.

Cotton condensed tannin: a potent modulator of alveolar macrophage host-defense function

Alveolar macrophages are the resident airway cells primarily responsible for the protection of the lungs against inhaled toxins and other biologically active material. A number of functional capabilities constitute their host-defense function. They can phagocytize and inactivate foreign material by production of reactive oxygen intermediates or the action of hydrolytic enzymes. In the absence of phagocytosis, macrophages can secrete reactive oxygen intermediates or enzymes that inactivate extracellular biologically active material. They also can secrete metabolites of arachidonic acid and other cytokines that contribute to the inflammatory response of the lungs. Macrophages also secrete a variety of peptide and lipid chemotactic factors that lead to the recruitment of other inflammatory cells into the airways. The condensed tannins, which constitute a significant percentage of the water soluble compounds present in respirable cotton mill dust, dramatically alter the host-defense function of alveolar macrophages in vitro. Tannin inhibits both phagocytosis and production of reactive oxidants in a dose-dependent manner with EC50's of 16 micrograms/mL and 3 micrograms/mL, respectively. This inhibition dramatically decreases the ability of resident alveolar macrophages to clear and detoxify potentially harmful inhaled particles. However, at similar concentrations, tannin stimulates the dose-dependent secretion (EC50 = 15 micrograms/mL) of a low molecular weight lipid neutrophil chemotactic factor that could result in an inflammatory reaction with the recruitment of neutrophils into the lungs. At slightly higher concentrations, tannin promotes the dose-dependent release of arachidonic acid from the macrophage membranes (EC50 = 65 micrograms/mL), which could also contribute to the local inflammatory reaction. Finally, tannin also causes secretion of the cytokine, interleukin-1, from the monocyte precursors of macrophages with an EC50 of 32 micrograms/mL. Interleukin-1 has been implicated as one of the causative agents in the development of fever.

Signal transducing mechanisms in human platelets stimulated by cotton bract tannin

Cotton bract tannin is a potent stimulus for platelet aggregation and secretion. Tannin has been shown to stimulate the phosphorylation of two 19-kD and 47-kD cytosolic proteins in platelets, but earlier steps in signal transducing mechanisms of platelet activation are unknown. In this study, measurements of 32P-labeled phospholipids, 14C-labeled arachidonic acid, and levels of intracellular free calcium (Ca2+) were performed before and after the addition of thrombin (1 U/ml) or various concentrations of tannin to human platelets. The results showed that tannin induced a dose-dependent synthesis of phosphatidic acid, an early and transient hydrolysis of phosphatidylinositol monophosphate and bisphosphate, a transient synthesis of diacylglycerol, and a release of arachidonic acid metabolites. The kinetics of phosphatidic acid, diacylglycerol, and arachidonic acid metabolite synthesis were similar after platelet stimulation by tannin (75 micrograms/ml) or thrombin. Tannin also induced a reversible rise of intracellular Ca2+ due to a mobilization of the internal stores and an influx of extracellular Ca2+. These results suggest that cotton bract tannin, as thrombin, activates human platelets by phospholipase C and A2 activations, release of diacylglycerol, and mobilization of intracellular free Ca2+.

Activation of platelets by eosinophil granule proteins

Two of the four principal cationic proteins of the eosinophil granule, major basic protein (MBP) and eosinophil peroxidase (EPO), were shown to be platelet agonists. Both MBP and EPO evoked a dose-dependent nonlytic secretion of platelet 5-hydroxytryptamine in unstirred platelet suspensions even in the presence of 10 microM indomethacin. MBP also evoked secretion of platelet alpha granule and lysosome components. Secretion by MBP and EPO was inhibited by 1 microM PGE1, but the nature of the inhibition differed from that observed with thrombin. Thus, MBP and EPO can be classified as strong platelet agonists with a distinct mechanism of activation.

Modulation of inflammatory cell function by cotton bract tannin: changes in the capacity of alveolar macrophages and neutrophils to produce hydrogen peroxide

Inhalation of cotton mill dust leads to the development of the occupational lung disease byssinosis in a portion of the exposed workers. Condensed tannins present in the dust have biologic activities consistent with the hypothesis that they are one of the etiologic agents for the disease. Inhalation of either cotton dust or tannin provokes an acute inflammatory response characterized by the influx of neutrophils into the airways. The secretion of a low-molecular-weight, lipid neutrophil chemotactic factor from the alveolar macrophages in response to tannin stimulation appears to be important in this inflammatory process. In these studies, the effect of tannin the ability of alveolar macrophages and neutrophils to produce hydrogen peroxide was examined. Low concentrations of tannin itself induced a modest production of hydrogen peroxide from conditioned rabbit alveolar macrophages, while higher concentrations failed to induce peroxide production. In the presence of an independent stimulator of peroxide production (concanavalin A), tannin inhibited peroxide production at all concentrations examined. Aqueous extracts of cotton mill dust (CDE) had an identical effect on peroxide production in a manner that indicated that the tannin present in the dust was responsible for the effect. Like its direct effect on macrophage peroxide production, tannin induced modest peroxide production in human neutrophils. However, unlike its effect on macrophages, tannin enhanced the peroxide production induced by the presence of an independent stimulator (phorbol myristate acetate). CDE had a similar effect on peroxide production, but the dose-response curves suggested that only the high-molecular-weight polymers of tannin present in the CDE were able to enhance peroxide production.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of tannins from different sources on airway epithelial and platelet function

The uniqueness of tannin isolated from aqueous extracts of cotton bracts (CBE) on the electrophysiological and ion transport properties of the canine tracheal epithelium and on 5-hydroxytryptamine (5-HT) release from platelets was investigated. The effect of CBE from Deltapine 41 cotton picked before (green, containing high-concentration, high-molecular-weight tannin) and after (brown, containing low-concentration, low-molecular-weight tannin) senescence and Darjeeling tea extracts and tannin isolated from Darjeeling tea were compared to the effects of Acala SJ-2 CBE and Acala SJ-2 tannin. Green Deltapine 41 CBE was similar to Acala SJ-2 CBE in decreasing short-circuit current (Isc) and net chloride secretion and in producing a dose-response release of 5-HT from platelets. Both Green and Brown Deltapine 41 CBE altered the paracellular pathway, but were less potent than Acala SJ-2 CBE. Brown Deltapine 41 CBE stimulated chloride transport in the airway epithelium and did not produce 5-HT release from human platelets. Darjeeling tea and tea tannin increased Isc and net chloride secretion and caused 5-HT release from platelets only at high concentrations. These studies demonstrate that all tannins are not alike; they suggest that molecular weight and concentration may be important for tannin activity and that the tannin in cotton bracts extract may be unique to cotton in its effect on the airway epithelium and on platelets.

Respiratory findings in spice factory workers

The respiratory consequences of working in the spice industry were studied in 92 female spice factory workers (mean age, 36 yr; mean exposure, 12 yr). A control group of 104 female workers employed in a nondusty industry was also studied. The prevalence of chronic respiratory symptoms was significantly higher in the exposed than in the control group. In particular, the prevalence of dyspnea (57.6%), chronic cough (22.8%), chronic phlegm and chronic bronchitis (19.6%), nasal catarrh (37.0%), and sinusitis (22.2%) was high when compared to controls (p less than .01). Among spice factory workers, a high prevalence of acute symptoms during the workshift was recorded. Acute reductions in lung function were statistically significant over the workshift for forced vital capacity (FVC), -2.0%; forced expiratory volume in one second (FEV1.0), -3.0%; and for maximum expiratory flow rates at 50% (FEF50), -8.3% and at 25% (FEF25), -15.2% measured on maximum expiratory flow-volume (MEFV) curves. No difference was found in across-shift ventilatory function in workers with or without chronic respiratory symptoms, except for FEF25 (with symptoms, 16.7%; without symptoms, 9.6%). Preshift administration of 40 mg of disodium cromoglycate (DSC) inhaled 15 min before the workshift significantly diminished acute reductions in FEF50 and FEF25 in exposed workers. Monday preshift FEF50 and FEF25 in exposed workers were significantly lower than in control workers (p less than .01), which suggests an early irreversible component to this illness.