Role of mast cells in gastrointestinal mucosal defense

The purpose of this review, based on studies from our laboratory as well as from others, is to summarize salient features of mast cell immunobiology and to describe their associations with gastrointestinal mucosal defense. Gastrointestinal mast cells are involved in many pathologic effects, such as food hypersensitivity. On the other hand, they also play a protective role in defense against parasitic and microbial infections. Thus, they have both positive and negative effects, but presently the mechanisms that control the balance of these various effects are poorly known. It has been suggested that stabilization of mast cells may be a key mechanism to protect the gastrointestinal tract from injury. Few molecules are known to possess both mast cell stabilizing and gastrointestinal cytoprotective activity. These include zinc compounds, sodium cromoglycate, FPL 52694, ketotifen, aloe vera, certain flavonoids such as quercetin, some sulfated proteoglycans such as chondroitin sulfate and dehydroleucodine. Dehydroleucodine, a sesquiterpene lactone isolated from Artemisia douglasiana Besser, exhibits anti-inflammatory and gastrointestinal cytoprotective action. The lactone stimulates mucus production, and inhibits histamine and serotonin release from intestinal mast cells. The lactone could act as a selective mast cell stabilizer by releasing cytoprotective factors and inhibiting pro-inflammatory mast cell mediators.

Role of mast cells in gastrointestinal mucosal defense

The purpose of this review, based on studies from our laboratory as well as from others, is to summarize salient features of mast cell immunobiology and to describe their associations with gastrointestinal mucosal defense. Gastrointestinal mast cells are involved in many pathologic effects, such as food hypersensitivity. On the other hand, they also play a protective role in defense against parasitic and microbial infections. Thus, they have both positive and negative effects, but presently the mechanisms that control the balance of these various effects are poorly known. It has been suggested that stabilization of mast cells may be a key mechanism to protect the gastrointestinal tract from injury. Few molecules are known to possess both mast cell stabilizing and gastrointestinal cytoprotective activity. These include zinc compounds, sodium cromoglycate, FPL 52694, ketotifen, aloe vera, certain flavonoids such as quercetin, some sulfated proteoglycans such as chondroitin sulfate and dehydroleucodine. Dehydroleucodine, a sesquiterpene lactone isolated from Artemisia douglasiana Besser, exhibits anti-inflammatory and gastrointestinal cytoprotective action. The lactone stimulates mucus production, and inhibits histamine and serotonin release from intestinal mast cells. The lactone could act as a selective mast cell stabilizer by releasing cytoprotective factors and inhibiting pro-inflammatory mast cell mediators. (AU)

Cell populations in the pineal gland of the viscacha (Lagostomus maximus). Seasonal variations.

Pineal samples of the viscacha, which were taken in winter and in summer, were analysed using both light and electron microscopy. The differences found between the two seasons were few in number but significant. The parenchyma showed two main cell populations. Type I cells occupied the largest volume of the pineal and showed the characteristics of typical pinealocytes. Many processes, some of which were filled with vesicles, could be seen in intimate contact with the neighbouring cells. The presence in the winter samples of "synaptic" ribbons and spherules, which were almost absent in the summer pineals, suggests a seasonal rhythm. These synaptic-like structures, as well as the abundant subsurface cisterns present in type I cells, appeared as basic differential features which allowed these cells to be distinguished from type II cells. These latter cells, which can be classified as interstitial cells, showed some other distinguishing features, such as irregular-shaped nuclei, abundant deposits of glycogen-like particles and structures of unknown function consisting of concentric cisterns surrounding a dense body. In the summer, interstitial cells displayed numerous large round bodies, which contributed to increase the cellular volume slightly. Regarding other constituents, like glial cell processes, vessels of non-fenestrated endothelium and sympathetic innervation, no qualitative differences were observed between the two seasons studied. We have presented here some morphological evidences of the circannual rhythm of the viscacha pineal, as well as ultrastructural criteria for distinguishing the main cell populations of this organ, which could be useful for studies carried out in other mammals.

Effect of dehydroleucodine on histamine and serotonin release from mast cells in the isolated mouse jejunum.

OBJECTIVE AND DESIGN: DhL, a lactone isolated from Artemisia douglasiana, prevents gastrointestinal damage elicited by necrosis-inducing agents and exhibits antiinflammatory action. This work examines the effect of DhL on compound 48/80-induced histamine and serotonin release in the isolated mouse jejunum, to determine whether DhL inhibits mediator release from mast cells at the enteric level. MATERIAL: Thirty jejuna from male Balb-c mice were used for the studies. TREATMENT: Samples were incubated sequentially in 9 test tubes containing RBS or 10 microg/ml compound 48/80 or 1.6 mmol/l + 10 microg/ml compound 48/80 at 37 degrees C for 90 minutes (10 min per tube). METHODS: Histamine and serotonin release studies, quantification of granulated mast cells, and evaluation of mast cell ultrastructure were carried out. Differences between groups were determined using analysis of variance followed by Tukey-Kramer multiple comparisons test. RESULTS: Compound 48/80 increased histamine and serotonin release by the tissue (141.95 +/- 62.58 pg/mg tissue vs basal 5.45 +/- 1.04, P<0.01 and 20.04 +/- 2.81 vs basal 9.24 +/- 1.56 ng/ mg tissue, P<0.01, respectively), decreased the number of granulated submucosal mast cells (0.077 +/- 0.0035 vs basal 0.14 +/- 0.015, P<0.05), and elicited evident granule ultrastructural changes. These effects were reduced by dehydroleucodine (19.51 +/- 7.88, P<0.01; 12.69 +/- 1, P<0.05 and 0.143 +/- 0.014, P<0.05, respectively). CONCLUSION: The lactone inhibits compound 48/80-induced histamine and serotonin release from mast cells in the isolated mouse jejunum.

Ultrastructural and morphometric study of the Sertoli cell of the viscacha (Lagostomus maximus maximus) during the annual reproductive cycle.

Changes in the morphology of viscacha Sertoli cells were studied during the annual reproductive cycle. Sertoli cells exhibited marked nuclear and cytoplasmic changes. Seasonal variation in nuclear size and shape, chromatin texture, and nucleolus characteristics was observed. The seasonal patterns of the volume densities of the endoplasmic reticulum (ER), mitochondria, Golgi complex, dense bodies and lipid inclusions were distinct. Morphometric analysis revealed that the Golgi complex is the organelle most sensitive to seasonal change. It declined drastically in the regressed testes and its recovery was slow. The ER and mitochondria exhibited seasonal variations in their pattern and content, that was minimal during winter. In contrast, an accumulation of lipid and dense bodies, such as primary and secondary lysosomes, accompanied the spermatogenic arrest. The volume densities of both organelles were maximum during the restoration of spermatogenesis. The length and organization of the inter-Sertoli junctions also changed with the reproductive cycle. The Sertoli cell number per tubular cross section decreased significantly during the testicular regression, coincident with the presence of Sertoli cells with marked signs of involution. The degree of regression and recovery exhibited by the viscacha Sertoli cells was closely related to that shown by the associated germ cells. Therefore, seasonal endocrine fluctuations and local factors could be involved in the regulation of the morphological and functional characteristics of the viscacha Sertoli cells. These hormonal fluctuations are synchronized by the photoperiod through the pineal gland and its hormone, melatonin.

Changes in gastroduodenal 5-hydroxytryptamine-containing cells induced by dehydroleucodine.

In previous work, we demonstrated that dehydroleucodine (DhL), a lactone isolated from Artemisia douglasiana Besser, prevents gastroduodenal damage induced by absolute ethanol (EtOH). The present study examined the effects of DhL - applied alone or before EtOH - on gastroduodenal cells containing 5-hydroxytryptamine (5-HT), to clarify the mechanism of action of the drug. Mice were divided into four groups: (I) control; (II) DhL; (III) EtOH, and (IV) DhL + EtOH. Stomachs and duodena were studied by immunohistochemistry and image analysis. EtOH decreased the immunopositive cell number and the area occupied by these cells. This effect was prevented by DhL. DhL alone did not affect the gastric immunopositive cell number and area. Duodena treated only with DhL exhibited a reduction of immunopositive cell number, but no change in area was observed. We propose that the drug probably inhibits the release of the inflammatory mediator 5-HT from endocrine cells, acting as a 'cell stabilizer' in response to injury.

Colloid in the pituitary pars distalis of viscacha (Lagostomus maximus maximus): ultrastructure and occurrence in relation to season, sex, and growth.

Randomly distributed extracellular colloidal accumulations were observed in the pars distalis of viscacha (Lagostomus maximus maximus). They were preferentially located in the peripheral zone of the gland and showed variability in shape and size. Two different types of colloidal accumulations were found by electron microscopy: 1) those surrounded by nongranulated follicular cells that correspond to characteristic follicles, and 2) those surrounded by granulated cells. In the follicles lined by nongranulated follicular cells, long, prominent microvilli and cytoplasmic processes protruded into the lumen. The frequency of these accumulations varies during the year in adult male animals, showing an increase in number during summer and a decrease during winter. The lowest value was registered in August (winter). The mean follicular diameter did not vary seasonally. The number of colloidal accumulations did not vary seasonally in adult female viscachas, but a significant difference in the mean follicular diameter between pregnant and non-pregnant females was observed. Pituitaries of immature animals contain fewer colloidal accumulations than those of adults. In fetuses, these accumulations were absent. The administration of melatonin provoked a decrease in the number of these structures. The numeric changes of the colloidal accumulations observed in this study are associated with: 1) the seasonal reproductive activity in adult males, and 2) the reproductive condition, body weight and sexual maturity in males and females. The fact that melatonin administration decreases the population of colloidal accumulations in males suggests participation of the pineal gland in these changes.

Probable effect of photoperiod on seasonal variation in the nuclear volume of the adrenal cortex of viscacha (Lagostomus maximus maximus)

The neuroendocrine system regulates several organic functions such as reproduction, metabolism and adaptation to the environment. This system shows seasonal changes linked to the environment. The experimental model used in the present study was Lagostomus maximus maximus (viscacha). The reproduction of males of this species is photoperiod dependent. Twenty-four adult male viscachas were captured in their habitat at different times during one year. The adrenal glands were processed for light microscopy. Serial cuts were stained with hematoxylin-eosin for the morphometric study, and 100 nuclei of each zone of the adrenal cortex were counted per animal. Data were analyzed statistically by ANOVA and the Tukey test. The cells of the glomerulosa zone are arranged in a tube-shaped structure. The fasciculata zone has large cells with central nuclei and clearly visible nucleoli and with a vacuolar cytoplasm. In the reticularis zone there are two of types of cells, one with a nucleus of fine chromatin and a clearly visible nucleolus and the other with nuclear pycnosis. Morphometric analysis showed maximum nuclear volumes during the February-March period with values of 133 percet 7.3 µm3 for the glomerulosa, 286.4 percent 14.72 µm3 for the fasciculata, and 126.3 percent 9.49 µm3 for the reticularis. Minimum nuclear volumes were observed in August with values of 88.24 + or - 9.9 µm3 for the glomerulosa, 163.7 percent 7.78 µm3 for the fasciculata and 64.58 + or - 4.53 µm3 for the reticularis. The short winter photoperiod to which viscacha is subjected could inhibit the adrenal cortex through a melatonin increase which reduces the nuclear volume as well as the cellular activity

Probable effect of photoperiod on seasonal variation in the nuclear volume of the adrenal cortex of viscacha (Lagostomus maximus maximus).

The neuroendocrine system regulates several organic functions such as reproduction, metabolism and adaptation to the environment. This system shows seasonal changes linked to the environment. The experimental model used in the present study was Lagostomus maximus maximus (viscacha). The reproduction of males of this species is photoperiod dependent. Twenty-four adult male viscachas were captured in their habitat at different times during one year. The adrenal glands were processed for light microscopy. Serial cuts were stained with hematoxylin-eosin for the morphometric study, and 100 nuclei of each zone of the adrenal cortex were counted per animal. Data were analyzed statistically by ANOVA and the Tukey test. The cells of the glomerulosa zone are arranged in a tube-shaped structure. The fasciculata zone has large cells with central nuclei and clearly visible nucleoli and with a vacuolar cytoplasm. In the reticularis zone there are two of types of cells, one with a nucleus of fine chromatin and a clearly visible nucleolus and the other with nuclear pycnosis. Morphometric analysis showed maximum nuclear volumes during the February-March period with values of 133 +/- 7.3 microm3 for the glomerulosa, 286.4 +/- 14.72 microm3 for the fasciculata, and 126.3 +/- 9.49 microm3 for the reticularis. Minimum nuclear volumes were observed in August with values of 88.24 +/- 9.9 microm3 for the glomerulosa, 163.7 +/- 7.78 microm3 for the fasciculata and 64.58 +/- 4.53 microm3 for the reticularis. The short winter photoperiod to which viscacha is subjected could inhibit the adrenal cortex through a melatonin increase which reduces the nuclear volume as well as the cellular activity.

Effect of dehydroleucodine on mucus production: a quantitative study.

We have demonstrated that dehydroleucodine (DhL), a lactone isolated from Artemisia douglasiana Besser, prevents gastroduodenal damage induced by necrosis-inducing agents such as absolute ethanol. We have also reported, in a qualitative study, that this effect is related to the ability of the drug to stimulate mucus production. The present study was designed to quantitatively evaluate the effect of DhL on adherent mucus layer thickness, to obtain a more objective approach to the mechanism of action of the drug. Mice were divided into two groups: (I) controls were treated with orally administered carboxymethylcellulose (CMC) and (II) experimental animals received DhL in CMC. The thickness of the mucus gel layer was measured in unfixed stomachs and duodena, using an image analysis system. We observed an increase in the adherent mucus layer thickness in the experimental samples. This confirms that one of the main mechanisms involved in the cytoprotective action of the drug is mucus secretion.

Stages of the cycle of the seminiferous epithelium of the viscacha (Lagostomus maximus maximus).

The adult male viscacha (Lagostomus maximus maximus) is a seasonal rodent. It exhibits a short period of testicular regression with partial arrest of spermatogenesis during winter (July-August). The present study provides the first description of the viscacha spermatogenic cycle during the period of maximum gonadal activity (summer-autumn). The testes were processed by using conventional techniques of light and electron microscopy. One-micrometer-thick sections stained with toluidine blue were used to clearly define the different cell associations. Spermatogenesis in this rodent is well organized and synchronized and has been divided into nine stages. The present classification is based on the morphogenesis of the acrosomal system (stages I-V) and the degree of elongation and condensation of the heads of the differentiating spermatids (stages VI-IX). Stage I is principally defined by round spermatids with a well-developed, juxtanuclear Golgi complex and without acrosomal components that are visible under the light microscope. Sperm release from the viscacha seminiferous epithelium occurs either in late stage III or in early stage IV. Stage IX is characterized by diplotene spermatocytes, figures of meiosis I or II, and secondary spermatocytes.

Gastroduodenal mucosal protection induced by dehydroleucodine: mucus secretion and role of monoamines.

In previous work we have demonstrated that dehydroleucodine (DhL) prevents gastric damage induced by necrosis-inducing agents such as absolute ethanol (EtOH). In this study we examine the effects of DhL on gastroduodenal morphology and monoamine levels by histological and biochemical methods, respectively, as an approach to elucidating the cytoprotective mechanism of the drug. Histological evidence shows that DhL prevents formation of gastroduodenal mucosal lesions induced by EtOH and that this protective effect is related to the ability of the drug to stimulate mucus production. DhL itself does not affect the tissue concentration of NE, DA and 5-HT. However, it prevents the depletion of DA and 5-HT provoked by EtOH. We propose that the abundant mucoid blanket secreted after treatment with DhL acts as a diffusion barrier against EtOH. It is also possible that DhL could act as a "cell stabilizer," by inhibiting the degranulation of cells containing monoamines.

Seasonal changes of the Leydig cells of viscacha (Lagostomus maximus maximus). A light and electron microscopy study.

The Leydig cells of viscacha (seasonal rodent) show cytoplasmic hypertrophy and regional distribution during the breeding period (summer-autumn). The dominant organelles are smooth endoplasmic reticulum (SER) and mitochondria. A moderately well-developed Golgi, abundant lipid inclusions, dense bodies like lysosomes in different stages, and centrioles are observed. Extensive or focal desmosome and gap-like junctions between neighbouring Leydig cells are present. These cells exhibit an evident hypotrophy and an increase in the number of dense bodies during the gonadal regression in winter (July and August). Cells in different stages of involution are observed in this period. Their nuclei are irregular and heterochromatic. The cytoplasm contains few mitochondria. The vesicular SER is scarse. Irregular and large intercellular spaces with microvilli and amorphous material are present. The junctional complexes are absent. The nuclear and cytoplasmic volume and development of SER and mitochondria increase during the recovery period (spring). The lipid inclusions decrease. Dilatations of the intercellular space with microvilli and limited by focal desmosome-like junctions are observed. In conclusion, the Leydig cells of Lagostomus maximus maximus show deep changes alongside the reproductive cycle. The photoperiod variations, through pineal hypothalamus pituitary axis and the hormone melatonin, are probably responsible for them. Moreover, the fall of serum and tubular testosterone would be one of the factors responsible for gonadal regression.

Dehydroleucodine prevents ethanol-induced necrosis in the rat gastric mucosa. A histological study.

The aerial part of Artemisia douglasiana Besser (6) has been used in folk medicine as a cytoprotective agent against the development of peptic ulcer. The dehydroleucodine (DhL), its active principle, significantly prevents the formation of gastric lesions induced by the exposure of the rats to absolute ethanol orally administered. The stomachs of control and experimental rats (after ethanol and pretreated with DhL) were removed, opened along the greater curvature and studied under stereo microscope and with light and scanning electron microscope. Absolute ethanol produced focal visible hemorrhagic lesions, extensive hyperemia, vascular stasis, cell disruption, and necrosis of the mucosa. Abundant mass of mucus was observed with scanning. The stomachs of rats pretreated with DhL showed a reduction of lesions. No hemorrhage and hyperemia were observed. The epithelia of the mucosa had a cobblestone appearance, similar to control rats and was covered by a fine layer of mucus. The mechanism of the protective action of DhL is unknown although it seems to be related to endogenous prostaglandins (PG).

Dehydroleucodine prevents ethanol-induced necrosis in the rat gastric mucosa. A histological study

The aerial part of Artemisia douglasiana Besser (6) has been used in folk medicine as a cytoprotective agent against the development of peptic ulcer. The dehydroleucodine (DhL), its active principle, significantly prevents the formation of gastric lesions induced by the exposure of the rats to absolute ethanol orally administered. The stomachs of control and experimental rats (after ethanol and pretreated with DhL) were removed, opened along the greater curvature and studied under stereo microscope and with light and scanning electron microscope. Absolute ethanol produced focal visible hemorrhagic lesions, extensive hyperemia, vascular stasis, cell disruption, and necrosis of the mucosa. Abundant mass of mucus was observed with scanning. The stomachs of rats pretreated with DhL showed a reduction of lesions. No hemorrhage and hyperemia were observed. The epithelia of the mucosa had a cobblestone appearance, similar to control rats and was covered by a fine layer of mucus. The mechanism of the protective action of DhL is unknown although it seems to be related to endogenous prostaglandins (PG).

Dehydroleucodine prevents ethanol-induced necrosis in the rat gastric mucosa. A histological study

The aerial part of Artemisia douglasiana Besser (6) has been used in folk medicine as a cytoprotective agent against the development of peptic ulcer. The dehydroleucodine (DhL), its active principle, significantly prevents the formation of gastric lesions induced by the exposure of the rats to absolute ethanol orally administered. The stomachs of control and experimental rats (after ethanol and pretreated with DhL) were removed, opened along the greater curvature and studied under stereo microscope and with light and scanning electron microscope. Absolute ethanol produced focal visible hemorrhagic lesions, extensive hyperemia, vascular stasis, cell disruption, and necrosis of the mucosa. Abundant mass of mucus was observed with scanning. The stomachs of rats pretreated with DhL showed a reduction of lesions. No hemorrhage and hyperemia were observed. The epithelia of the mucosa had a cobblestone appearance, similar to control rats and was covered by a fine layer of mucus. The mechanism of the protective action of DhL is unknown although it seems to be related to endogenous prostaglandins (PG).

Dehydroleucodine prevents ethanol-induced necrosis in the rat gastric mucosa. A histological study.

The aerial part of Artemisia douglasiana Besser (6) has been used in folk medicine as a cytoprotective agent against the development of peptic ulcer. The dehydroleucodine (DhL), its active principle, significantly prevents the formation of gastric lesions induced by the exposure of the rats to absolute ethanol orally administered. The stomachs of control and experimental rats (after ethanol and pretreated with DhL) were removed, opened along the greater curvature and studied under stereo microscope and with light and scanning electron microscope. Absolute ethanol produced focal visible hemorrhagic lesions, extensive hyperemia, vascular stasis, cell disruption, and necrosis of the mucosa. Abundant mass of mucus was observed with scanning. The stomachs of rats pretreated with DhL showed a reduction of lesions. No hemorrhage and hyperemia were observed. The epithelia of the mucosa had a cobblestone appearance, similar to control rats and was covered by a fine layer of mucus. The mechanism of the protective action of DhL is unknown although it seems to be related to endogenous prostaglandins (PG).

Dehydroleucodine prevents ethanol-induced necrosis in the rat gastric mucosa. A histological study.

The aerial part of Artemisia douglasiana Besser (6) has been used in folk medicine as a cytoprotective agent against the development of peptic ulcer. The dehydroleucodine (DhL), its active principle, significantly prevents the formation of gastric lesions induced by the exposure of the rats to absolute ethanol orally administered. The stomachs of control and experimental rats (after ethanol and pretreated with DhL) were removed, opened along the greater curvature and studied under stereo microscope and with light and scanning electron microscope. Absolute ethanol produced focal visible hemorrhagic lesions, extensive hyperemia, vascular stasis, cell disruption, and necrosis of the mucosa. Abundant mass of mucus was observed with scanning. The stomachs of rats pretreated with DhL showed a reduction of lesions. No hemorrhage and hyperemia were observed. The epithelia of the mucosa had a cobblestone appearance, similar to control rats and was covered by a fine layer of mucus. The mechanism of the protective action of DhL is unknown although it seems to be related to endogenous prostaglandins (PG).