T. Bani Sacchi

Relaxin influences the growth of MCF-7 breast cancer cells. Mitogenic and antimitogenic action depends on peptide concentration.

Background. The effects of relaxin (RLX) on the human breast adenocarcinoma cell line MCF‐7 have been evaluated.

Histamine release from rat mast cells induced by the metabolic activation of drugs of abuse into free radicals

BACKGROUND The metabolic activation of morphine, cocaine and methadone into free radicals could have pathophysiological relevance in the organic injuries of drug addiction. METHODS Isolated purified rat serosal mast cells were incubated with morphine, cocaine and methadone (10(-7) M-10(-4) M) with oxidative enzymes (prostaglandin-H-synthetase, 25 mU; rat liver homogenate fraction S 10-mix, 400 microl), and with the drugs of abuse in the presence of oxidative enzymes. Histamine and lactate dehydrogenase (LDH) were analysed with a fluorimetric and spectrophotometric assay, respectively; the generation of malonyldialdehyde (MDA) was measured by a spectrophotometric assay. RESULTS The release of mast cell histamine and the generation of MDA are present only when mast cells were incubated with the drugs of abuse in the presence of oxidative enzymes. This release was dependent on the concentration of the drug in question and showed a maximum value at 10(-4) M. Moreover, in parallel experiments we demonstrated that, under the same experimental conditions, the release of LDH was always less than 20% of the total, suggesting that this effect is due to a selective exocytotic process. Histamine release and MDA generation were abated by the free radical scavengers: reduced glutathione, 10(-4) M GSH and alpha-tocopherol, 10(-4) M and by the spin trapper 5.5-dimethyl-1-pyrroline-N-oxide, 10(-4) M DMPO. The light and electron microscopic features are consistent with exocytotic secretion in the cases of morphine and methadone and with cell lysis in the case of cocaine. CONCLUSION These results suggest that morphine, cocaine and methadone are activated into free radicals which produce membrane lipid perturbation and histamine release, suggesting that a massive release of mast cell histamine could be an additional risk factor in heroin and cocaine overdoses.

Helicobacter pylori potentiates histamine release from rat serosal mast cells induced by bile acids

In the present study we have experimentally addressed the effects ofHelicobacter pylori on the bile acid capability of histamine release. Bile acids alone were confirmed to be able to inducein vitro histamine release from rat serosal and mucosal mast cells. On the contrary, no significant histamine release was obtained when incubating anyHelicobacter pylori preparations alone with mast cells. However, histamine release induced by bile acids was significantly enhanced, without any significant increase in lactate dehydrogenase activity, when whole washed or formalin-killed bacterial cells or crude cell walls were incubated with mast cells in the presence of cholic (0.3 mM), deoxycholic (0.3 mM), or lithocholic (0.3 mM) acids, chenodeoxycholylglycine (0.3 mM), and deoxycholyltaurine (3 mM). The electron microscopic features of mast cells incubated withHelicobacter pylori were consistent with an exocytotic secretion. The release of histamine induced by 0.3 mM deoxycholic acid in the presence ofHelicobacter pylori was inhibited by the preincubation of the cells with dimaprit (an H2 agonist) and potentiated by the H2 antagonist, ranitidine. The current results suggest a link between humanHelicobacter pylori infection and histamine release and a possible involvement of gastric mucosal mast cells in the pathogenesis ofHelicobacter pylori-associated gastritis.

Differentiation of breast cancer cells in vitro is promoted by the concurrent influence of myoepithelial cells and relaxin.

Our previous studies showed that relaxin promotes differentiation of MCF-7 breast adenocarcinoma cells. In the current investigation, we aimed to elucidate whether the effect of the hormone is potentiated when MCF-7 cells are grown together with myoepithelial cells, thus creating a microenvironment reminiscent of the organised tissue architecture of the mammary parenchyma in vivo. The findings obtained reveal that most MCF-7 cells cultured alone have an undifferentiated, blast-like phenotype, only a minority showing a more differentiated phenotype with more organelles and rudimentary intercellular junctions. When co-cultured with myoepithelial cells more MCF-7 cells acquire ultrastructural features consistent with a more differentiated phenotype, such as a rich organellular complement, apical microvilli and intercellular junctions. When relaxin was added to the co-cultures, the ultrastructural signs of differentiation could be observed in even more MCF-7 cells and became more pronounced than in the absence of the hormone, judged by the appearance of a clear-cut polarisation of cytoplasmic organelles, an almost continuous coat of apical microvilli and numerous intracellular pseudolumina.

Relaxin promotes differentiation of human breast cancer cells MCF-7 transplanted into nude mice.

Previous studies showed that the hormone relaxin acts on human breast cancer MCF-7 cells in vitro by modulating cell proliferation and promoting cell differentiation toward a duct epithelial phenotype. The present study was designed to investigate whether relaxin retains these properties when acting in vivo on MCF-7 cell tumors developed in athymic nude mice. Mice bearing MCF-7 cell tumors transplanted under the mammary fat pad and estrogenized to sustain tumor growth were treated systemically with relaxin (10 µg/day) for 19 days. Vehicle-treated mice were used as controls. Thirty days later, the mice were sacrificed and tumor fragments were analyzed by light and electron microscopy and immunocytochemistry. Measurements of tumor volume were recorded weekly for the overall experimental period. The results obtained indicate that relaxin treatment promotes differentiation of tumor cells towards both myoepithelial-like and epithelial-like cells, as judged by the ultrastructural features of the cells and by the increased expression of smooth muscle actin and cadherins. Measurements of tumor size and of the number of cycling cells show that relaxin, at the doses and times of exposure used in this study, does not significantly influence tumor growth and cell proliferation.

Nesidioblastosis and islet cell changes related to endogenous hypergastrinemia.

SummaryThe endocrine pancreas from four hypergastrinemic patients with recurrent peptic ulceration has been studied by light and electron microscopy. Greatly increased numbers of ducts and centroacinar cells have been observed associated with a striking increase in the number of islets and endocrine cells scattered in the acinar tissue (nesidioblastosis). The islet cells scattered throughout the exocrine parenchyma are of all the known islet cell types, with a prevalence of B and especially A cells. Many islets, probably formed de novo, are of a considerable size, have irregular contours and are in close apposition to centroacinar cells and ducts. The degree of nesidioblastosis and islet hyperplasia does not seem to be related to the plasma gastrin levels.Cytological changes have also been found in the islet cells of the hypergastrinemic patients compared with controls. These changes mainly affect the B cells and consist of a striking decrease in the number of mature secretory granules associated with a fairly extended ergastoplasm and Golgi apparatus and with a relevant increase in the number of immature granules. In two of the four patients examined, who had more severe hypergastrinemia, cytological signs of enhanced secretion are also recognized in A cells. The features indicating hypersecretion of B and A cells seem to be related to the plasma gastrin levels.The above findings indicate that chronic endogenous hypergastrinemia promotes proliferation and differentiation of islet cells and stimulates the secretory function of B cells and, to a lesser extent, of A cells, thus providing evidence for a trophic and secretagogue action of gastrin on the endocrine pancreas.

Histamine release by platelet aggregation.

Coincubation of rat serosal mast cells with human platelets leads to a significant release of histamine, which dose-dependently increases when platelet aggregation is induced by various concentrations of arachidonic acid. In turn, histamine enhances platelet aggregation induced by different agonists, this effect being mimicked by pyridyl-ethyl-amine (PEA), blocked by mepyramine and amplified by ranitidine. The data suggest the existence of a platelet-derived histamine releasing factor (PDHRF) and indicate the presence of platelet H1 and H2 receptors, capable of modulating platelet aggregation.

Relaxin: a possible future preventive therapy for cardiovascular disease in postmenopausal women and men?

Myocardial infarction, stroke, peripheral vascular disease, thrombosis and hypertension are the main manifestations of cardiovascular disease (CVD), which represents the most frequent cause of death and disability in most civilized countries. In 1997, CVD accounted for 43% of all deaths in women in the USA1. It has been calculated that, for the nearly 50 million American women who will be aged over 50 years this year, the greatest healthrelated issue is the prevention of CVD1,2. Attempts at prevention include drugs, diet and life-style modification, which act on various pathogenic factors, some of which are sex-linked3. Clinical and epidemiological studies have shown that men and women suffering from CVD differ in terms of pathophysiology, time of presentation of disease and outcome of therapy. The incidence of CVD in women is very low until the menopause, when it increases sharply to reach an incidence similar to that in men, albeit with a 10–20-year delay4. The loss of protection against CVD has been attributed to the deficiency of ovarian steroids, and, consequently, menopausal hormone replacement therapy has been widely advocated for primary and secondary prevention5. However, estrogen or progesterone has not been clearly identified as the protective agent in women. The results of estrogen replacement therapy trials are still controversial and under discussion6,7. Furthermore, the administration of sex steroids to fertile women may interfere with normal physiological protection against CVD, as the contraceptive pill is associated with an increased risk of thrombosis8. This apparent paradox may be explained by the fact that these opposing hormonal conditions share an important biological event: the failure, absence or loss of ovulation, either natural or pharmacological. Loss of ovarian function at the menopause does not mean cessation of only estrogen and progestogen production; the ovary produces many other active hormones and agents. Hence, protection of the cardiovascular system against CVD may be attributed to an active substance other than estrogen and progesterone, possibly produced by the corpus luteum. Ovarian steroids are the most widely recognized hormones of the corpus luteum but are not the only ones: relaxin is also secreted by the corpus luteum and, at variance with estrogens, it circulates in the blood of cycling and pregnant women but it is not present in the blood of normal men9–11. Could this rather mysterious hormone represent a natural or physiological protective shield against CVD in the fertile woman? CLIMACTERIC 2001;4:137–143

Storage and release of histamine in human platelets

A key-note of inflammatory cells is the presence of cytoplasmic granules which can be mobilized towards the plasmalemmal membrane during the exocytotic release of preformed mediators of inflammation. Human platelets share with inflammatory cells the presence of cytoplasmic granules (c~-granules; dense granules; lysosomal granules) which release inflammatory mediators (phospholipase A2 [1]; platelet factor 4 [2]; superoxide radicals [3]) when platelets aggregate. Another key-note of some inflammatory cells (mast cells, basophils, monocytes) is the presence of histamine within the cytoplasmic granules, and the release of histamine from the granular matrix in response to a variety of stimuli [4]. Human platelets share with inflammatory cells the presence of histamine and the release of histamine in response to aggregatory stimuli [5]. Our present aim is to study whether platelet histamine is stored in granules and to investigate the release of platelet histamine in response to immunological stimuli.

Nesidioblastosis and intermediate cells in the pancreas of patients with hyperinsulinemic hypoglycemia

SummaryThe pancreases of three patients with hyperinsulinemic hypoglycemia were studied : one of these patients was a child born to a diabetic mother, the other two were adults with insulinomas. All the patients had nesidioblastosis, namely the presence of a number of pancreatic endocrine cells spread throughout the exocrine tissue singly or clustered in small groups. In the hypoglycemic child the endocrine cells scattered in the acinar tissue were mostly A cells, whereas in the patients with insulinomas both A and B cells were found with a similar frequency. Intermediate cells (acinar-islet cells) were found in all the cases. These findings suggest that nesidioblastosis and the de novo formation of intermediate cells are associated phenomena.Possible mechanisms for the genesis of the islet cell types spread throughout the exocrine parenchyma and of the intermediate cells are discussed and their possible clinical implications are suggested.