Evidence of mast-cell histamine being mitogenic in intact tissue

On Connective Tissue Mast Cells as Protectors of Life, Reproduction, and Progeny

The connective tissue mast cell (MC), a sentinel tissue-residing secretory immune cell, has been preserved in all vertebrate classes since approximately 500 million years. No physiological role of the MC has yet been established. Considering the power of natural selection of cells during evolution, it is likely that the MCs exert essential yet unidentified life-promoting actions. All vertebrates feature a circulatory system, and the MCs interact readily with the vasculature. It is notable that embryonic MC progenitors are generated from endothelial cells. The MC hosts many surface receptors, enabling its activation via a vast variety of potentially harmful exogenous and endogenous molecules and via reproductive hormones in the female sex organs. Activated MCs release a unique composition of preformed and newly synthesized bioactive molecules, like heparin, histamine, serotonin, proteolytic enzymes, cytokines, chemokines, and growth factors. MCs play important roles in immune responses, tissue remodeling, cell proliferation, angiogenesis, inflammation, wound healing, tissue homeostasis, health, and reproduction. As recently suggested, MCs enable perpetuation of the vertebrates because of key effects-spanning generations-in ovulation and pregnancy, as in life-preserving activities in inflammation and wound healing from birth till reproductive age, thus creating a permanent life-sustaining loop. Here, we present recent advances that further indicate that the MC is a specific life-supporting and progeny-safeguarding cell.

Peritoneal cell response during adhesion formation

BACKGROUND

We estimated a number of cell populations of peritoneal fluid in rats with experimentally developed peritoneal adhesions.

MATERIALS AND METHODS

The fluid was taken in standarized conditions at the first operation and during reoperation. Animals were divided into four groups. The first group was the control group (n = 20) on which the abdomen was opened and closed without any manipulations (group 1a), and the reoperation was done after 72 hr (group 1b). The other groups (2, 3, 4; n = 20 for each group) were operated, and scarification of the parietal peritoneum and serosa of the bowel was performed. The rats were reoperated after 24, 72, and 168 hr, respectively, after the first surgery. The peritoneal cavity was washed with the 0.9% saline solution. The number of the peritoneal adhesions and populations of the cells were counted.

RESULTS

The highest number of peritoneal adhesions was observed in the group of animals reoperated after 72 hr. After 72 and 168 hr, the higher number of mast cells (MC) and neutrophils was observed. The difference was statistically significant. The percentage of mast cells (MC) increased during the experiment. It was different from other cell populations which decreased after 168 hr. The highest change in number was observed for MC. The highest number of MC was observed on the seventh day after the laparotomy.

CONCLUSIONS

MC influence peritoneal adhesion formation and probably take part in adhesion remodeling. MC and neutrophils changed significantly after manipulations in the peritoneal cavity. Probably, they play an important role in peritoneal adhesion formation.

Mast cells in peritoneal fluid in rats with experimentally induced peritoneal adhesions

Mast cells (MC) produce, store and release many biologically active substances, especially inflammatory factors, chemotactic substances for neutrophiles, cytokines and prostaglandins. They play very important role in fibrinosis and they are an important factor in peritoneal adhesions formation and lysis. In this study we tried to evaluate role of mast cells in peritoneal adhesions formation. We estimated number of mast cells in peritoneal fluid in rats with experimentally developed peritoneal adhesions. The number of mast cells per ml was counted in flow cytometry in specimens of peritoneal fluid taken from operated rats. The fluid was taken in standardized conditions the same for each group at the first operation and during reoperation. Peritoneal cavity was washed with 0.9% Saline solution. MC were visualized using indirect immunohistochemical method LSAB with mouse antibody. The animals were divided into 4 groups. 1 st group was control group (n=20) on which the abdomen was opened and closed without any manipulations, and the reoperation was done after 72 hours. The other groups (2, 3, 4; n=20 for each group) were operated and scarification of the partial peritoneum and serosa was performed. The rats were brought back to conscious and then were reoperated respectively after 24, 72 and 168 hours after first surgery. After the laparotomy and damage of the peritoneum we observed formation of the peritoneal adhesions between intestine loops and between intestines and damaged parietal peritoneum. Also the higher number of mast cells was observed in the groups of animals with damaged peritoneum. The highest number of peritoneal adhesions was observed in the group of animals reoperated after 72 hours. After 72 and 168 hours the higher number of MC and neutrophils was observed. The difference was statistically significant. The percentage of mast cells was increasing during the experiment duration. It was different from other cells populations which decreased after 168 hours. The MC and neutrophils were cell population which changed significantly after manipulations in peritoneal cavity. It is very probable that they play an important role in peritoneal adhesions formation.

Decreased histamine catabolism in the colonic mucosa of patients with colonic adenoma

INTRODUCTION

Alterations in mucosal histamine degradation play an important role in various gastrotinestinal diseases including colonic adenoma. In humans, histamine can be catabolized either by oxidative deamination by diamine oxidase (DAO) or by ring methylation by histamine N-methyltransferase (HNMT). The significance of HNMT in this context was investigated for the first time in this project.

METHODS

About 94 colonic biopsies were endoscopically obtained from 23 patients suffering from colonic adenoma and 26 biopsies from six healthy individuals. Each sample was mechanically homogenized, homogenates were cleared by centrifugation and used for determination of protein and histamine concentrations and enzyme activities of DAO and HNMT by radiometric assay.

RESULTS

In adenoma patients DAO activities were slightly and HNMT activities were significantly decreased in normal mucosa compared to controls. Activities of both enzymes were significantly lower in adenoma tissue than in healthy mucosa in the same patients. A significant correlation was found between HNMT and DAO in all investigated samples. Histamine concentrations were elevated in adenoma patients.

CONCLUSIONS

Histamine catabolism is decreased in the colonic mucosa of patients with colonic adenoma.

Abundant eosinophil infiltration in a neurofibroma

We report a case of sporadic cutaneous neurofibroma showing diffuse eosinophil infiltration in a 72-year-old woman. The neurofibroma had been on the skin of the left anterior shoulder for approximately 10 years. The presence of mast cells is well known in neurofibroma. However, infiltration of neurofibromas by eosinophils has not yet been documented. We propose that eosinophil infiltration is mediated by the effects of mast cells. We suggest that this is indirect evidence that mast cells in some neurofibromas are not quiescent but active. We also reintroduce the notion that acid-fast stains are a useful method to discriminate between mast cell granules and eosinophil granules.

Sclerosed hemangioma and sclerosing cavernous hemangioma of the liver: a comparative clinicopathologic and immunohistochemical study with emphasis on the role of mast cells in their histogenesis

BACKGROUND/AIMS

Sclerosed hemangiomas of the liver are rare. To date, their histopathology, immunohistochemistry, and the role of mast cells (MC) in their histogenesis have not been systematically studied.

PATIENTS/METHODS

Clinical, histopathologic and immunohistochemical features of 20 sclerosed hemangiomas were compared with those of 18 sclerosing cavernous hemangiomas. The number of MC was quantified and compared in all cases, using a tryptase immunostain.

RESULTS

Compared to patients with sclerosed hemangiomas, those with sclerosing hemangiomas were younger (mean age, 63 versus 71 years); had larger tumors (mean 6 +/- 4.73 versus 3 +/- 2.2 cm); presented with a mass more frequently, and epigastric pain less frequently. Sclerosing hemangiomas, but not sclerosed hemangiomas, were more frequent in males than in females. Sclerosing hemangiomas occurred much more frequently in the right lobe than sclerosed hemangiomas. Sclerosing hemangiomas had less fibrosis, hyalinization, and elastic fibers than sclerosed hemangiomas (p = 0.00004). Numerous thick-walled blood vessels were a feature of sclerosed hemangiomas but not of sclerosing hemangiomas. Collagen IV, and laminin were more uniformly positive in sclerosing hemangiomas than in sclerosed hemangiomas. Increased immunoreactivity for smooth muscle actin was present in sclerosed hemangiomas more often than in sclerosing hemangiomas. FVIII-R Ag, CD34, and CD31 were more diffusely positive in sclerosing hemangiomas than in sclerosed hemangiomas. In sclerosing hemangiomas, the mean number of tryptase-positive MC per high power field (MC/HPF) varied from 8.25 +/- 6.23 in vascular areas to 1.6 +/- 4.01 in sclerotic areas. In comparison, the mean number of MC in sclerosed hemangiomas, was 4.3 +/- 5.01 in vascular areas, and 0.86 +/- 0.58 in sclerotic areas (p = 0.0095). The number of MC was significantly correlated with vascular proliferation and inversely related to the degree of fibrosis (p < 0.0001).

CONCLUSIONS

This study demonstrates certain distinct clinical and histopathologic differences between sclerosing cavernous hemangiomas and sclerosed hemangiomas of the liver. We have established the presence of MC in those tumors, and suggest possible involvement of the MC in angiogenesis, and the regression process and development of fibrosis.

Role of mast cells in early and delayed radiation injury in rat intestine

Mast cell hyperplasia is a characteristic feature of many inflammatory and fibrotic conditions, including intestinal radiation injury (radiation enteropathy). This study used mast cell-deficient rats to define the role of mast cells in the mechanisms underlying early radiation-induced mucosal injury and delayed intestinal wall fibrosis. Mast cell-deficient (Ws/Ws) mutant rats and mast cell-competent (+/+) littermates were used. A 4-cm loop of ileum was exposed to 21 Gy single-dose radiation. Irradiated and unirradiated intestine were examined at 2 or 26 weeks using quantitative histology and morphometry. Quantitative immunohistochemistry was used to assess transforming growth factor beta (Tgfb), myeloperoxidase, and epithelial and smooth muscle cell proliferation. Collagen content was measured colorimetrically, and steady-state Tgfb1 mRNA was determined with fluorogenic probe RT-PCR. Compared to +/+ rats, Ws/Ws animals exhibited strikingly exacerbated mucosal injury but minimal reactive intestinal wall fibrosis. Ws/Ws rats exhibited less radiation-induced intestinal smooth muscle cell proliferation and collagen accumulation than +/+ littermates. Tgfb expression increased to a similar extent in Ws/Ws and +/+ rats. Unirradiated intestine from Ws/Ws and +/+ rats did not differ significantly. Mast cells protected the intestinal mucosa during the early phase of radiation enteropathy and promoted intestinal fibrosis after the breakdown of the mucosal barrier. Mast cells may be required for Tgfb to exert its full fibrogenic effect in radiation enteropathy.

Histamine effects on conjunctival fibroblasts from patients with vernal conjunctivitis

Histamine, an important mast cell mediator in allergic disorders, may affect extracellular matrix production and cell growth in vernal keratoconjunctivitis (VKC). In the present study, the histamine reactivity of conjunctival fibroblasts derived from VKC patients was investigated in vitro. Conjunctival fibroblast cultures were derived from biopses of 8 tarsal VKC patients and 5 normal subjects. These cells were maintained in vitro and stimulated with different concentrations of histamine with and without H1 (clorpheniramine) and H2 (cimetidine) receptor antagonists. Comparisons were made to fibroblasts grown in the same media without histamine and to fibroblasts stimulated with just antihistamine. The effects of histamine were evaluated by: (1) the MTT test to assess cell proliferation; (2) an in vitro wound model for cell migration and (3) the measurement of procollagen I (PIP) and procollagen III (PIIIP) in supernatants for collagen production. Results showed: (1) While VKC-derived fibroblasts proliferated at a faster rate than normal cells in unstimulated media, after histamine stimulation, VKC and normal cells grew at a similar rate. Both H1 and H2 antagonists significantly inhibited (P<0.05) histamine-induced cell proliferation. (2) Histamine enhanced cell migration after wounding; this effect was inhibited only by H2 antagonism. (3) When stimulated with histamine, VKC fibroblasts produced significantly more PIP than those in control media. Furthermore, VKC-derived fibroblasts were more sensitive to histamine challenge, producing significantly more PIP than normal fibroblasts. H1 and H2 antagonists did not modify histamine-stimulated PIP production. The enhanced proliferative and productive capacity of VKC fibroblasts may be the result of a selective overgrowth of one or more fibroblast subpopulations in a chronically inflamed tissue. Histamine increased proliferation, migration and collagen production in both normal and VKC fibroblasts. Since H2 antagonism modulated both cell growth and migration, but not histamine-induced collagen production, the latter may be mediated by a different receptor. These results showed that histamine is at least partially responsible for fibroblast stimulation.

Distribution of histamine in laying hen ovary

In a laying hen, histamine was found to be present in all compartments of the ovary, i.e. stroma with follicles < 1 mm, small white (1-4 mm), large white (4-8 mm), atretic white, yellow preovulatory (8-35 mm) and postovulatory follicles. Stroma containing non-yolky follicles exhibited the highest histamine concentration (6080 +/- 331 ng/g wet wt. tissue) which differed significantly (P < 0.01) from histamine levels observed in all examined classes of ovarian follicles. High histamine concentration was found in small, large and atretic white follicles as well as in older postovulatory follicles whereas low levels of histamine contained yellow preovulatory and younger postovulatory follicles. Population of yolky white follicles presented significant (P < 0.01) differences in histamine level among small (4280 +/- 333), atretic (2940 +/- 193) and large (2010 +/- 110 ng/g) follicles. Within hierarchy of yellow preovulatory (F7-F1) follicles initial decrease in histamine concentration, from 859.3 +/- 51.5 ng/g in F7 follicle to 363.9 +/- 28.3 ng/g in F4 follicle, was followed by the increase as follicle matured, reaching the highest level in F1 follicle (711.4 +/- 35.9 ng/g). In postovulatory (P1-P5) follicles histamine concentration gradually increased as they were getting older, from 604.3 +/- 49.3 ng/g in P1 follicle to 2253 +/- 197 ng/g in P5 follicle. Determination of histamine in relation to ovulation revealed significant (P < 0.01) difference both in histamine concentration and content between the largest preovulatory F1 follicle and the largest postovulatory P1 follicle, being 0.5 h before and 0.5 h after ovulation, respectively. It is suggested that in chicken, ovarian histamine may play a role in the follicular development and/or the ovulatory process.

Mast cells, eosinophils and fibrosis

We have presented results that increase our understanding of the roles MC and EOS play in modulating fibrotic processes. In vitro studies have provided clear-cut evidence for the direct involvement of these two inflammatory cells in enhancing proliferation, and either enhancing or decreasing collagen synthesis in human fibroblasts isolated from different anatomical locations. In addition, we have shown that MC and EOS interactions can also take part in modulating fibrosis. In vivo studies in murine and human cGVHD showed that MC activation is detrimental, and that MC stabilization therapy may be helpful in treating the fibrotic outcome of this disease. Much is still obscure. It is, for example, important to define the MC and EOS mediators involved in the modulation of fibroblast properties, and their pattern of influence, keeping in mind the ultimate goal of defining new therapeutic targets for the treatment of fibrotic diseases.

Mast cell interaction with tumor cells in small early gastric cancer: ultrastructural observations

The authors studied the mast cells by light and electron microscopy in four small intramucosal early gastric cancers (EGC). Mast cells were found in the tumor stroma and among neoplastic cells of adenocarcinoma glands. Stromal and adenocarcinoma-infiltrating mast cells were ultrastructurally identified as T mast cells, and exhibited anaphylactic or piecemeal degranulation. Tumor cells in intimate contact with mast cells showed no cytopathic changes. These data do not support a mast cell-mediated cancer lysis, such as that reported in some systems in vitro. The interepithelial localization of T mast cell in adenocarcinoma glands is similar to that observed in some disease states, including interstitial cystitis, fibrotic lung disorders, and mucosal allergic reaction. The findings suggest that T mast cells may be involved in the pathophysiology of the host reaction to small intramucosal EGC.

The role of mast cell-derived histamine in the closure of an in vitro wound

We have previously reported that mast cells (MC) stimulate 3T3 fibroblast migration and proliferation into an in vitro model of wound obtained by producing in a confluent 3T3 monolayer, a midline cut and by scraping the cells from half of the monolayer. The purpose of the present study was to determine the contribution of mast cell-derived histamine to this MC increasing effect. Histamine levels in supernatants of MC/ 3T3 cultures unactivated or activated with either compound 48/80 or anti-IgE antibodies (10 min) did not correlate to the degree of fibroblast migration and proliferation into the wound space (42 h). Various concentrations of histamine were added to 3T3 fibroblast monolayers in the absence of cocultured MC, and fibroblasts beyond the wound line were counted (42 h). Addition of 100 ng/ml histamine had the highest stimulating effect on fibroblast numbers. This effect was abrogated by the addition of cimetidine (an H-2 antagonist). Addition of cimetidine to unactivated MC/ 3T3 cultures did not affect the increasing activity of MC presence on the wounded monolayer, although it diminished the enhancing effect obtained after MC activation with compound 48/80. These results indicate that histamine is partially responsible for the mast cell enhancing effect on fibroblast migration and proliferation in an in vitro model of wound.

Interleukin-2 inhibits 3T3 fibroblast proliferation

In order to clarify the role played by interleukin-2 (IL-2) in the regulation of fibroblast function, we investigated the effect of rat IL-2 and human recombinant IL-2 on 3T3 fibroblast proliferation and collagen synthesis. Fibroblasts were incubated with various concentrations of IL-2 for different periods of time. IL-2 was found to decrease in time- and dose-dependent manner the proliferation of 3T3 fibroblasts. This effect correlated with ability of IL-2 to enhance PGE2 production by 3T3 fibroblasts. When 3T3 fibroblasts were cocultured with rat peritoneal mast cells (MC), the growth-inhibiting effect of IL-2 was significantly less pronounced. Treatment of the cultures with IL-2 had no effect on collagen production by both 3T3 fibroblasts and fibroblasts cocultured with MC. In conclusion, in this study we provide evidence that IL-2, the key cytokine in T-cell growth and differentiation, can affect fibroblast functions.

Mast cells as modulators of hair follicle cycling

While the central role of mast cells (MC) in allergy and inflammation is well-appreciated, much less is known about their physiological functions. The impressive battery of potent growth modulatory MC products, and increasing evidence of MC involvement in hyperproliferative and fibrotic disorders suggest that tissue remodelling may be one of those, namely in the skin. Here, we delineate why this may best be studied by analysing the potential role of MC in hair growth regulation. On the background of numerous, yet widely under-appreciated hints from the older literature, we summarize and discuss our recent observations from the C57BL/6 mouse model for hair research which support the concept that MC are functionally important modulators of hair follicle cycling, specifically during anagen development. This invites to exploit the murine hair cycle as a model for dissecting the physiological growth modulatory functions of MC and encourages the exploration of MC-targeting pharmaceutical strategies for the treatment of hair growth disorders.

Activated mast cells are fibrogenic for 3T3 fibroblasts

The extent of mast cell direct involvement in fibrosis is not defined as yet. In the present study we assessed whether long-term co-culture (up to 7 d) of functionally active rat peritoneal mast cells with 3T3 mouse fibroblasts and mass cell activation can affect fibroblast proliferation and collagen production. Co-culture of subconfluent 3T3 fibroblasts with resting mast cells or with mast cells stimulated by alpha IgE (1:35) or repeatedly activated by low concentrations of compound 48/80 (0.25-0.75 microgram/ml) did not alter fibroblast proliferation. However, fibroblast proliferation was increased significantly (100-130%) when mast cells were repeatedly activated with higher concentrations of compound 48/80 (1-3 micrograms/ml). Repeated mast cell activation by compound 48/80 (0.25 microgram/ml) caused a twofold increase in collagen production and this was reduced by 63% by the mast cell stabilizer nedocromil sodium (10(-5) M). At the same time, co-culture of 3T3 fibroblasts with unstimulated or immunologically activated mast cells did not modulate their collagen production. In conclusion, we have demonstrated that mast cell activation, under certain conditions, can enhance significantly 3T3 fibroblast proliferation and collagen production, thus indicating a direct mast cell involvement in the fibrotic processes.

Hypothalamic tissue stimulates hippocampal pyramidal neuron survival during development: evidence from intraocular double transplants

The present study was undertaken to evaluate innervation and possible growth promotion by posterior hypothalamic tissue on different areas that are, or are not, interactive with this brain region during development. Posterolateral hypothalamus was dissected from embryonic day 17 rat fetuses, and inserted into the anterior chamber of the eye of adult rat hosts. Two weeks postgrafting, a second transplant consisting of either fetal hippocampal, cerebellar, or lung tissue was placed adjacent to the first graft. Growth of the intraocular double transplants was monitored weekly by measurements through the cornea. Fetal hippocampal tissue grew significantly larger when placed together with a hypothalamic graft, as compared to single hippocampal transplants. Cerebellar or lung tissue growth was not stimulated by a hypothalamic cograft. Pyramidal neuron cell counts demonstrated a significantly higher final number of these neurons in growth-stimulated hippocampal grafts, as compared to non-stimulated single hippocampal grafts. Immunohistochemistry with antibodies directed against histamine or histidine decarboxylase revealed that hippocampal transplants received the most dense histaminergic innervation. Cerebellar transplants contained occasional histaminergic neurites, and lung tissue never exhibited any histaminergic innervation from the adjacent hypothalamic graft. Taken together, these results demonstrate a growth-promoting effect of posterior hypothalamic tissue on developing hippocampal tissue, as well as target specificity of histaminergic innervation patterns.

Mast cells and fibroblasts: two interacting cells

Mast cell (MC) fibroblast interactions may have a role in health and disease. We analyzed the relationships between these cells by utilizing our in vitro model in which mucosal (MMC) and connective tissue (CTMC) type MC were cocultured long-term with different fibroblasts. Mouse 3T3 fibroblasts were used to provide a normal microenvironment for MC, while fibroblasts derived from mouse with chronic graft-versus-host disease (cGVHD) provided a fibrotic one. We found that both 3T3 and cGVHD fibroblasts maintain CTMC viability, phenotype and functional activity. When MMC were cocultured with 3T3 or cGVHD fibroblasts, they changed their phenotype towards that of CTMC. On the other hand, MCs were found to affect fibroblast properties. Coculture of MMC on 3T3 monolayers was shown to increase Forsmann antigen production and collagen synthesis and stimulate fibroblast proliferation. Resting CTMC or CTMC activated by anaphylactic stimuli induced 3T3 and cGVHD fibroblasts to proliferate more. In addition, CTMC activation increased collagen production by 3T3 fibroblasts. In conclusion, fibroblasts were found to regulate MC survival and differentiation, whereas MCs were shown to affect the biochemical properties of fibroblasts, which can lead to fibrosis.

Histamine and histidine decarboxylase are correlated with mucosal repair in rat small intestine after ischemia-reperfusion

The aim of this experiment was to demonstrate whether histamine and histidine decarboxylase (HDC) contribute to mucosal repair in small intestine subjected to ischemia-reperfusion (I/R). The superior mesenteric artery was occluded for 15 min followed by reperfusion. In jejunal mucosa, histamine content and HDC activity increased after I/R. Histamine output in mesenteric lymph was also elevated after I/R. These increases in HDC activity, and mucosal and lymph histamine levels were suppressed by pretreatment of alpha-fluoromethylhistidine (alpha-FMH), a suicide inhibitor of HDC. alpha-FMH also attenuated the increase of ornithine decarboxylase (ODC) activity normally observed after I/R. Transport of dietary lipid into lymph markedly decreased at 24 h after I/R, yet it was restored to normal at 48 h after I/R. alpha-FMH inhibitor led to a sustained deficit in lipid transport at 48 h after I/R. This sustained functional impairment in alpha-FMH treated animals was associated with blunted responses of HDC activity and histamine content to I/R. Our results suggest that histamine and HDC contribute to the restoration in mucosal function observed at 48 h after I/R. This response may be related, at least in part, to stimulation of ODC activity by histamine.

Temporal sequence of early alterations in rat lung following thoracic X-irradiation

The temporal patterns of several responses in the lungs of groups of rats administered two different thoracic doses of X-rays (7.5 and 15 Gy) were examined during a time frame within which radiation pneumonitis develops (1-13-week period) in order to assess for potential interrelationships among the responses. Endpoints surveyed included lung gravimetric and volumetric changes, changes in lavaged alveolar macrophage (AM) numbers, interstitial accumulations of mast cells (MC), and alterations in the amounts of lavaged phospholipids (PL), protein (P), and histamine (H). Sham-irradiated rats served as controls. Early (1 week), dose-dependent increases in lavageable PL were not accompanied by increases in lung weights or lavageable P. Elevations in lavaged PL continued for at least 5 weeks after exposure. By this time, lung weights, AM numbers, MC, and lavageable P, but not lavageable H, were all substantially increased in lungs that received the 15 Gy dose, whereas these changes were not observed at the lower dose. At later times (weeks 7 and 9), the hyperpermeability response following the 15 Gy exposure became less pronounced and the PL response also subsided, while lung MC continued to further increase and lavageable H became abnormally elevated. Maximal increases in the lung's permeability status after the 15 Gy exposure was coincidental with maximal increases in AM. An association of increases in AM and lung hyperpermeability, however, was not evident as of week 13 after the 7.5 Gy dose when lung weights and lavageable P were significantly elevated. For the X-ray doses examined, our results suggest that: (1) the early PL response to X-rays is independent of, and precedes, permeability changes in the lung; (2) the time to onset of an X-irradiation-induced increase in lung permeability is dose-dependent; (3) the progressive accumulation of MC in the lung following X-irradiation is dose-dependent; (4) excessive accumulations of interstitial MC after X-irradiation do not necessarily result in an increase in free H; and (5) free H in the lung does not appear to play a prominent role in the hyperpermeable response. Additionally, in conjunction with the findings of other investigators, our study suggests that the MC response to X-rays may be a fundamental component of the fibrogenic response.

Mast cell modulation of tumour cell proliferation in rat mammary adenocarcinoma 13762NF

Mast cells were shown to accumulate around the periphery of the invasive and metastatic rat mammary adenocarcinoma (MTLn3), and histological evidence of mast cell degranulation was observed during the later stages of this model. To assess the physiological role of mast cells in vivo we have used the mast cell-stabilising compound FPL 55618 applied i.p. daily at 1 mg kg-1 for 23 days. Using groups of 12 rats we have found that this compound inhibited tumour growth at the primary site by as much as 70% in most of the treated animals compared with the control group which received equivalent volumes of saline. When the drug treatment was stopped after 23 days, tumour growth of the test group accelerated over the next 7 days and reached a similar tumour size to that of control animals. Histological studies of the tumour and contiguous host tissue at day 24 of the experiment revealed numerous extra-tumoural mast cells often showing signs of degranulation at several sites around the tumour periphery in the control animals. Such observations were not seen in those animals receiving FPL 55618 where, in contrast to controls, numerous intact mast cells were often seen within the tumour mass. Following cessation of the MC-stabilising treatment progressive mast cell activation was evident within 2-4 days, primarily at the tumour periphery. In vitro studies have shown that drug concentrations equivalent to five times the in vivo dose had no effect on the proliferative rate or viability of the MTLn3 cells. Moreover, the proliferative rate of these cells in culture was significantly increased when exposed to soluble mast cell products. Thus our data indicate that a mast cell-stabilising compound has significant benefits in reducing tumour growth in vivo, an observation which supports the concept that mast cell:tumour cell interactions are important for the growth and invasive properties demonstrated by this model of breast carcinoma.

Hyaluronan reflects the pre-fibrotic inflammation in irradiated rat lung: concomitant analysis of parenchymal tissues and bronchoalveolar lavage

The pathogenesis of pulmonary fibrosis is a complicated chain of interactions between cells and molecules. During recent years bronchoalveolar lavage (BAL) in patients with various interstitial lung disorders has increased our knowledge of the fibrosis process and focused on new interesting interactions. Here we present an animal model which makes it possible to apply both morphological and immunohistochemical tissue staining to perform bronchoalveolar lavage in the same animal. Irradiation is an established method for experimentally evoking lung fibrosis in animals. Rats received irradiation (30 Gy) to the lower parts of both lungs. Bronchoalveolar lavage was performed in the right lung. The biochemical determination of lavage concentration of hyaluronan (HA) and cellular differential counts were compared with interstitial morphology. Animals were sacrificed and analysed 2, 4, 6, 8 and 10 weeks after irradiation. After 6 weeks a massive increase in connective tissue mast cells was seen in the peribronchial and alveolar-interstitial tissue. This mastocytosis was closely related to a marked increase in HA. It became obvious that, in this model, cellular analysis of BAL fluid did not correctly reflect the cellular changes in the lung interstitium. While BAL revealed a pronounced increase of neutrophils with no--or only very few--mast cells, a concomitant increase in mononuclear cells and mast cells was seen in the lung interstitium. In contrast an increase in HA in BAL correlated well with an increase in HA-deposition in the lung interstitium, indicating that measurement of a non-cellular component, such as HA, may better reflect the tissue inflammation.

Mast cells enhance migration and proliferation of fibroblasts into an in vitro wound

The effects of mast cells (MC) in an in vitro wound model were studied. The model consisted of rat peritoneal MC cultured on confluent monolayers of 3T3 fibroblasts (MC/3T3). A linear wound was performed by cutting along the midline and scraping one half of the monolayer. After 42 h fibroblasts were counted in the scraped area of the wound. In the MC/3T3 cocultures 27.6 +/- 2.1 fibroblasts were found compared to 16.6 +/- 0.9 in the 3T3 cultures. The most significant increase in the number of fibroblasts was obtained upon activation of the MC with anti-IgE antibodies immediately after wound production (39.9 +/- 2.1). Stimulation with compound 48/80 had a weaker effect (32.7 +/- 1.5). Incubation of 3T3 wounded monolayers with supernatants of anti-IgE- or compound 48/80-activated MC, or with sonicated MC, induced an increase in fibroblast number similar to that found in unactivated MC/3T3. [3H]Thymidine incorporation followed by autoradiography was performed to assess fibroblast mitosis. The highest number of labeled fibroblasts beyond the wound line was found in immunologically activated MC/3T3 (29.7 +/- 4.4), followed by compound 48/80-activated MC/3T3 (18.4 +/- 1.5), MC/3T3 (15.1 +/- 3.6), and 3T3 (10.6 +/- 2.6). After addition of aphidicolin, which inhibited fibroblast mitosis, MC were still effective in enhancing fibroblast migration. In all the cocultures MC were observed to have migrated alongside fibroblasts. Thus merely the presence of MC adhering to wounded fibroblast monolayers significantly enhanced migration and proliferation of the fibroblasts. A further increase was achieved by immunological activation of the MC. We therefore suggest that MC have a facilitating role in this in vitro wound model.

A mast cell secretagogue, compound 48/80, prevents the accumulation of hyaluronan in lung tissue injured by ionizing irradiation

Irradiation with a single dose of 30 Grey on the basal regions of the lungs of Sprague-Dawley rats induced a peribronchial and alveolar inflammation. Infiltration of mast cells in the edematous alveolar interstitial tissue and also in the peribronchial tissue were characteristic features of the lesion. The appearance of mast cells was already seen 4 wk after irradiation and by weeks 6 to 8 there was a heavy infiltration. The staining properties suggested that they were connective tissue-type mast cells. The infiltration of mast cells was paralleled by an accumulation of hyaluronan (hyaluronic acid) in the alveolar interstitial tissue 6 and 8 wk after irradiation. The recovery of hyaluronan (HA) during bronchoalveolar lavage (BAL) of the lungs also increased at this time. Treatment with a mast cell secretagogue, compound 48/80, induced a distinct reduction of granulated mast cells in the alveolar tissue. Regular treatment with compound 48/80 from the time of irradiation considerably reduced the HA recovery during BAL and the HA accumulation in the interstitial tissue but did not affect the interstitial infiltration of mononuclear cells and polymorphonuclear leukocytes. By contrast, an accumulation of HA in the alveolar interstitial space was induced when compound 48/80 was given not until mast cell infiltration of the lung had started. The effects of compound 48/80 indicate that the connective tissue response after lung irradiation is dependent on whether or not mast cell degranulation is induced before or after the mast cell infiltration of the alveolar tissue.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of Treponema hyodysenteriae infection on mucosal mast cells and T cells in the murine cecum

The pathogenic mechanisms responsible for the development of lesions in swine and mice after infection with Treponema hyodysenteriae have not been fully characterized. The release of inflammatory mediators from mast cells has been postulated to play a role in lesion development during swine dysentery. Therefore, C3H/HeN mice were infected with T. hyodysenteriae, and mucosal mast cell (MMC) numbers were examined in cecal sections. An initial increase in MMC numbers from 13 to 22 per 50 crypt villus units was observed, but at 20 days postinfection the numbers significantly decreased (P less than 0.05) to 5 MMC per 50 crypt villus units. Immunohistochemical analysis performed on cecal sections failed to show a significant change in lamina proprial T-lymphocyte subsets. Numbers of T. hyodysenteriae CFU recovered from the cecum were stable throughout the experimental time period. Mast cell-deficient W/Wv mice and their mast cell-sufficient littermates were also infected to determine whether MMCs were necessary for the occurrence of T. hyodysenteriae-induced lesions. W/Wv mice were as susceptible to infection as their normal littermates and developed similar macroscopic and microscopic lesions. These results indicate that changes in MMC numbers can be detected after an infection with T. hyodysenteriae; however, on the basis of observations of infected W/Wv mice, mast cells are not required for lesion development in the murine model.

Effect of histamine on the development of astroglial cells in culture

The effect of histamine on different aspects of the growth of astrocytes was studied using primary cultures derived either from forebrain or from cerebellum of the rat. The influence on general growth and differentiation was monitored in terms of the activities of ornithine decarboxylase and glutamine synthetase enzymes, whereas [3H]thymidine incorporation into DNA was used as a specific index of cell proliferation. Treatment with 500 nM histamine of cells grown for 6 days in vitro, caused a time-dependent significant increase in ornithine decarboxylase activity of astrocytes from both sources. The maximum increase was observed at 4 h after histamine treatment, at that time the elevation in ornithine decarboxylase activity being about 80% and 300% over control values in the forebrain and the cerebellar astrocytes, respectively. Under similar experimental conditions, addition of histamine (500 nM) to medium resulted in a significant increase in [3H]thymidine incorporation into DNA in both types of cultures: in comparison with control, the elevation was about 45% at 48 h in forebrain astrocytes and at 24 h in cerebellar astrocytes. On the other hand, the specific activity of glutamine synthetase in cerebellar astrocytes was markedly enhanced (about 100%) by treatment with histamine (500 nM) for 4 days, but forebrain astrocytes were little affected. Addition of histamine to the culture medium produced no significant alteration in the activity of lactate dehydrogenase and protein content of either type of astroglial cells. The present findings, which support our earlier proposal that the biochemical properties of astrocytes differ between various brain regions, provide direct evidence for the involvement of histamine in the regulation of growth and development of astrocytes.

Mast-cell secretion and angiogenesis, a quantitative study in rats and mice

The activation of the autogenous mast cells (MCs) in situ in intact mesenterial windows was elicited by the intraperitoneal injection of the MC secretagogue Compound 48/80 over a period of 1, 3 and 5 days in Sprague-Dawley rats and in C57 BL/6 and CBA/Ca mice. As a probe of MC secretion, the release of histamine was quantified fluorometrically at predetermined intervals during the treatment. Fourteen days after the start of the treatment, the angiogenic response was quantified histologically as the number of vessel profiles per unit length of mesenteric window. Both the MC-activating and the angiogenic effect of the 48/80-treatment was greater in the rats than in the mice. The occurrence of MC-mediated angiogenesis in the mouse is demonstrated here for the first time. In the rat, 48/80-induced MC mediated angiogenesis increased in a distinctly dose-dependent manner. Two daily doses of 48/80 was the most efficient angiogenic protocol tested; a single day's treatment increased the number of vessels almost fivefold. The remarkable potency of the angiogenic reaction following MC secretion supports our previous notion that MC-mediated angiogenesis may have therapeutic implications in poorly vascularized tissues.

Evidence of an acquired increase in mitogenesis in streptozotocin-diabetic rats, apparently relating to some tissue factor

We have previously reported that rats which have been suffering from streptozotocin-diabetes for 4 weeks show a supranormal mast cell mediated mitogenesis in mesenteric windows and in the skin; this late emerging, augmented mitogenic responsiveness appears, to be unaffected by insulin per se. To test whether this increased proliferogenic response is effected by some acquired quality within the tissue rather than a systemic factor in the blood, we studied mast cell mediated mitogenesis in organ-cultured intact mesenteric windows from rats with diabetes of 4 weeks' duration, using a biochemically-defined serum-free growth medium. Mast cells were activated by Compound 48/80 and their secretion was quantified biochemically in terms of histamine release. The mast cell-dependent mitogenic reaction in the predominant, morphologically discrete fibroblasts and mesothelial cells was quantified photometrically using Feulgen-absorption analysis of individual cell nuclei, and by determination of the mitotic index. Both types of target cell responded to a significantly greater degree mitogenically in diabetic compared with control tissue. This finding suggests that a considerable part of the increased mitogenic responsiveness previously observed in diabetic animals in vivo is causally related to some tissue-bound, i.e., cellular and/or extracellular factor(s) acquired during the course of the disease.

Molecular aspects of mast-cell-mediated mitogenesis in fibroblasts and mesothelial cells in situ

Mast-cell-mediated mitogenesis in intact tissues is a paracrine reaction the molecular mechanisms of which still have to be elucidated. One strategy worth exploring is to study the mitogenic reaction under as defined conditions as possible. The present study demonstrates that in the virtually avascular rat mesentery, organ-cultured in a biochemically-defined medium, activation of mast cells induced a mitogenic reaction in fibroblasts and mesothelial cells, the two predominant, morphologically distinct neighboring cell types. Thus the system provides a means of studying the influence of defined molecules in the growth medium on the outcome of a mitogenic response in these two cell types in situ. It was further observed that exogenous platelet-derived growth factor (PDGF) was not essential for this mast-cell-mediated mitogenic reaction to occur in the tissue-bound fibroblasts and mesothelial cells.

Mast cells in the ovary of Gallus gallus domesticus

1. Histamine or mast cells are involved in mammalian ovary function. Their role in the avian ovary is not known. In the present study mast cell distribution in the ovary of the domestic fowl was studied. 2. Mast cells were distributed throughout the ovary, both in the stroma of medullary and cortical regions as well as in the thecae of normal and atretic follicles. In the stroma, mast cells were especially abundant in the area just below the germinal epithelium (GE) and followed the contours of the GE. 3. In the follicles, mast cells were more obvious in the thecae of small non-yolky follicles, whereas they were compressed and scattered in the larger yolky follicles. They were more frequently seen in the theca externa than in the theca interna and in their ultrastructure showed characteristic mast cell granules. 4. Some of the atretic follicles showed increased mast cells in their thecae. Postovulatory follicles had very few mast cells. 5. The possible role of the mast cells in the ovarian activity of domestic fowl is discussed.

Demonstration of histamine H2 receptors on human melanoma cells

Histamine induced a concentration-dependent increase in intracellular cyclic-AMP of the two human melanoma cell lines SK23 and DX3.LT5.1; maximal stimulation was obtained with 17.8 microM histamine which consistently produced greater than 50-fold increases in the cyclic AMP content of both cell lines. The dose-response curve for histamine in each culture was progressively displaced to the right with increasing concentrations of the histamine H2 receptor antagonist cimetidine. Ranitidine, another H2 receptor antagonist also prevented the histamine-induced cyclic AMP elevation, but the H1 receptor antagonists mepyramine and tripelennamine had no significant effect. These findings indicate that human melanoma cells express histamine H2 receptors, stimulation of which activates adenylate cyclase with a subsequent rise in intracellular cyclic AMP. Mast cell:melanoma interactions mediated by histamine in vivo might therefore be expected to modify some aspects of melanoma cell behaviour.

Histamine H2-receptor mediated activation of neonatal rat brain ornithine decarboxylase in vivo

The effect of histamine (HA) administered via intracerebroventricular injection on ornithine decarboxylase (ODC) activity was studied in neonatal rat brain. The HA effect was dose and time dependent. Maximal increase in ODC activity was achieved 2 hr after administration of 10 micrograms HA (38% over control levels). Impromidine (HA H2-agonist) mimicked the effect of HA on ODC and ranitidine (HA H2-antagonist) inhibited the response to HA. Neither 2-thiazolylethylamine (HA H1-agonist) nor mepyramine (HA H1-antagonist) modified control ODC activity. The HA-releasers, compound 48/80 and polymixin B sulfate, elicited an increase in brain ODC activity of 35% and 32%, respectively, over the control value.

Mast-cell-mediated angiogenesis: a novel experimental model using the rat mesentery

The angiogenic effect of autogenous secreting mast cells (MCs) was studied using a novel experimental approach. The virtually avascular membranous rat mesentery was used as test tissue. The activation of MCs was elicited by repeated intraperitoneal injections of the MC-secretagogue compound 48/80, which per se appears inert from the proliferogenic and angiogenic point of view. Angiogenesis was quantitated histologically and expressed the number of vessels/unit length of mesentery. The smallest vessels recognized had a luminal area of approximately 7-8 microns 2 (corresponding to a circular diameter of 3.0-3.2 microns). Seven to ten days after MC-activation ended, the number of blood vessels had increased 7- to 6-fold. A retrogressive reaction occurred between days 21 and 38 after treatment, when the number of vessels had essentially normalized, as compared to vehicle-treated controls. The present study, introducing the membranous mesentery as a model for quantitative angiogenetic studies, provides evidence that MCs can induce angiogenesis, which is new. The possible therapeutic implication of this finding is noteworthy.

Mast cells and matrix degradation at sites of tumour invasion in rat mammary adenocarcinoma

Significant numbers of mast cells have been demonstrated histologically around the periphery of the invasive rat mammary adenocarcinoma 13672NF. The number of mast cells at microfoci along the tumour:host tissue junction was significantly greater than that found in normal mammary tissues, and few mast cells were detected within the tumour itself. Mast cell degranulation, often associated with disruption and lysis of the connective tissue matrix, was a common feature in later stages of tumour proliferation. When soluble products derived from purified rat peritoneal mast cells were added to monolayer cultures of rat stromal fibroblasts or tumour cells they stimulated a significant increase in total collagenase production, and the mast cell products were also capable of activating the latent collagenases thus produced. Histological examination indicated that degradation of local collagenous matrix was a common feature of mast cell degranulation, an observation possibly explained by the release of mast cell enzymes and/or the potential of this cell to modulate the expression of collagenolytic activity by surrounding cells. These observations suggest that, at least in some tumours, mast cells contribute to the connective tissue breakdown commonly associated with tumour invasiveness and metastatic spread.