Growth, biogenic amine production and tyrDC transcription of Enterococcus faecalis in synthetic medium containing defined amino acid concentrations

AIMS

The tyraminogenic potential of the strains Enterococcus faecalis EF37 and ATCC 29212 was investigated in a synthetic medium containing defined amounts of tyrosine and phenylalanine at different temperatures.

METHODS AND RESULTS

Enterococci growth and the production of biogenic amines (BA) were evaluated in relation to their pre-growth in medium containing tyrosine. Significant differences between the two strains were evidenced at metabolic level. Both the pre-adapted strains grew faster in all the tested conditions, independently of the presence of the precursor. Temperatures of 30 and 40°C positively affected the growth parameters. The tyrosine decarboxylase (tyrDC) activity of the strain EF37 was positively affected by pre-adaptation, while ATCC 29212 showed a faster and higher tyramine accumulation with not-adapted cells. The expression analysis of the gene tyrDC confirmed the influence of the growth conditions on gene transcription.

CONCLUSIONS

The small differences found between the two strains in the maximum transcript level reached rapidly after the inoculum and the different behaviour in the tyramine accumulation suggested the possible involvement of complex regulation mechanisms on the tyrDC or on the membrane transport systems, which could affect the different BA accumulation trend.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study gives deeper insight into the metabolic regulation of tyrDC activity of enterococci.

The antiandrogen flutamide inhibits growth of mcf-7 human breast-cancer cell-line

The antiandrogen flutamide (FLU) has been reported to exert antiproliferative action on both male and postmenopausal breast cancer and to inhibit growth of chemically induced rat breast cancer. We studied the effects of various concentrations of FLU on the growth of the ER+, AR+ and PR+ MCF-7 and the ER-, AR- and PR- MDA-MB-231 human breast cancer cell lines. The growth of MCF-7 cells in both steroid free and estradiol supplemented media was inhibited by FLU. MDA-MB-231 cell growth was not affected by FLU. Our data show a direct inhibitory action of FLU on human breast cancer cells and suggest a different susceptibility to the antiproliferative action of FLU, which seems to be related to the steroid receptor status.

Protective effect of dehydroepiandrosterone against lipid peroxidation in a human liver cell line

OBJECTIVE

Dehydroepiandrosterone (DHEA) is a widely studied steroid hormone with multi-functional properties. Reports suggest that some of the many activities of DHEA are due to its protective effect against lipid peroxidation. Nevertheless, the antioxidant properties of DHEA are still the subject of debate. The aim was to evaluate whether its two opposed effects on lipid peroxidation reported in the literature may be dependent on schedule and doses used.

METHODS

Chang liver cells, a line derived from normal human liver, were grown in media containing either no steroids (control) or DHEA at concentrations ranging from 0.1 micromol/l to 50 micromol/l. At specific times, cultures were halted and cells received a pro-oxidant stimulus (cumene (CuOOH) 0.5 mmol/l), at which time cell viability (by trypan blue staining and lactate dehydrogenase (LDH) release) and thiobarbituric acid reactive substances (TBARS) concentration (spectrophotometrical assay) were evaluated.

RESULTS

At concentrations ranging from 0.1 micromol/l to 1 micromol/l, DHEA protects Chang liver cells against lipid peroxidation and/or death induced by cumene. This effect disappears if the concentration is increased to 10 micromol/l; at higher concentrations (50 micromol/l) a pro-oxidant/cytotoxic effect of DHEA appears.

CONCLUSIONS

DHEA exhibits two opposed effects on lipid peroxidation; depending on its concentration it acts either to limit or to induce oxidative stress. The threshold concentration at which the pro-oxidant activity of DHEA prevails is not far in excess of that having an antioxidant effect. Either effect of DHEA on lipid peroxidation is only evident after a 'lag-phase'.

Dehydroepiandrosterone protects tissues of streptozotocin-treated rats against oxidative stress

Chronic hyperglycemia in diabetes determines the overproduction of free radicals, and evidence is increasing that these contribute to the development of diabetic complications. It has recently been reported that dehydroepiandrosterone possesses antioxidant properties; this study evaluates whether, administered daily for three weeks per os, it may provide antioxidant protection in tissues of rats with streptozotocin-induced diabetes. Lipid peroxidation was evaluated on liver, brain and kidney homogenates from diabetic animals, measuring both steady-state concentrations of thiobarbituric acid reactive substances and fluorescent chromolipids. Hyperglycemic rats had higher thiobarbituric acid reactive substances formation and fluorescent chromolipids levels than controls. Dehydroepiandrosterone-treatment (4 mg/day for 3 weeks) protected tissues against lipid peroxidation: liver, kidney and brain homogenates from dehydroepiandrosterone-treated animals showed a significant decrease of both thiobarbituric acid reactive substances and fluorescent chromolipids formation. The effect of dehydroepiandrosterone on the cellular antioxidant defenses was also investigated, as impaired antioxidant enzyme activities were considered proof of oxygen-dependent toxicity. In kidney and liver homogenates, dehydroepiandrosterone treatment restored to near-control values the cytosolic level of reduced glutathione, as well as the enzymatic activities of superoxide-dismutase, glutathione-peroxidase, catalase. In the brain, only an increase of catalase activity was evident (p < .05), which reverted with dehydroepiandrosterone treatment. The results demonstrate that DHEA treatment clearly reduces oxidative stress products in the tissues of streptozotocin-treated rats.

Dehydroepiandrosterone protects bovine retinal capillary pericytes against glucose toxicity

Pericyte loss is an early feature of diabetic retinopathy and represents a key step in the progression of this disease. This study aimed to evaluate the effect of dehydroepiandro-sterone (DHEA) on glucose toxicity in retinal capillary pericytes. Bovine retinal pericytes (BRP) were cultured in a high glucose concentration, with or without DHEA. After 4 days of incubation the number of BRP was significantly reduced by the high glucose concentration. The addition of DHEA to the medium reversed the adverse effect of high glucose: BRP proliferation partially recovered in the presence of 10 nmol/l DHEA, and completely recovered in the presence of DHEA at concentrations equal to or greater than 100 nmol/l. At physiological glucose concentrations, DHEA had no effect on BRP growth. Data show that DHEA, at concentrations similar to those found in human plasma, protects BRP against glucose toxicity. This effect seems specific for DHEA, since its metabolites, 5-en-androstene-3 beta, 17 beta-diol, dihydrotestosterone and estradiol did not alter BRP growth in normal or high glucose media. Various pieces of evidence link the antioxidant properties of DHEA to its protective effect on glucose-induced toxicity in BRP.

Dehydroepiandrosterone inhibits the growth of DMBA-induced rat mammary carcinoma via the androgen receptor

Dehydroepiandrosterone (DHEA) exerts opposite effects on the growth of mammary carcinoma. A stimulatory effect is observed in absence of estrogens, due to interaction of DHEA metabolite(s) with the estrogen receptor (ER); by contrast, in presence of estrogens DHEA inhibits tumor growth. The mechanism underlying the latter DHEA effect, which might be related to activation of the androgen receptor (AR), is poorly understood. Focusing on this point, we measured over a 20 days period the areas of DMBA-induced mammary tumors in rats given DHEA and/or the anti-androgen flutamide (FLU). Results show that DHEA inhibitory effect on the growth of mammary carcinoma is no longer observed when the ARs are blocked by FLU. Data are consistent with an involvement of ARs in the inhibitory effect of DHEA.

Dehydroepiandrosterone administration prevents the oxidative damage induced by acute hyperglycemia in rats

Free radical overproduction contributes to tissue damage induced by acute hyperglycemia. Dehydroepiandrosterone, which has recently been found to have antioxidant properties, was administered i.p. to rats at different doses (10, 50 or 100 mg/kg body weight) 3 h before treatment with dextrose (5 g/kg). Lipid peroxidation was evaluated on liver, brain and kidney homogenates, measuring both steady-state concentrations of thiobarbituric acid reactive substances, and fluorescent chromolipids, evaluated as hydroxynonenal adducts. Formation of thiobarbituric acid reactive substances was significantly higher in hyperglycemic than in normoglycemic animals. Three hours (but not 1 h) dehydroepiandrosterone-pretreatment protected tissues against lipid peroxidation induced by dextrose; both thiobarbituric acid reactive substances and hydroxynonenal adducts in liver, kidney and brain homogenates were significantly lower in dehydroepiandrosterone-pretreated animals. Dehydroepiandrosterone did not modify the cytosolic level of antioxidants, such as alpha-tocopherol or glutathione, nor the activities of glutathione peroxidase, reductase or transferase. The results of this study indicate that the 'in vivo' administration of dehydroepiandrosterone increases tissue resistance to lipid peroxidation triggered by acute hyperglycemia.

Role of glucose-6-phosphate dehydrogenase inhibition in the antiproliferative effects of dehydroepiandrosterone on human breast cancer cells

Epidemiological and experimental studies suggest that dehydroepiandrosterone (DHEA) exerts a protective effect against breast cancer. It has been proposed that the non-competitive inhibition of glucose-6-phosphate dehydrogenase (G6PD) contributes to DHEA antitumor action. We evaluated the effects of DHEA on G6PD activity and on the in vitro proliferation of two human breast cancer cell lines, MCF-7 (steroid receptor positive) and MDA-MB-231 (steroid receptor negative), in a serum-free assay. DHEA inhibition of G6PD was only found to occur at concentrations above 10 microM; at these high concentrations, the growth curve was parallel to the enzyme inhibition curve in both cell lines. In contrast, at concentrations in the in vivo breast tissue concentration range, neither cell growth nor enzyme activity was inhibited. The results failed to confirm DHEA's putative anti-tumor action on breast cancer through G6PD inhibition, as the enzyme blockade only becomes apparent at pharmacological concentrations of the steroid.

Inhibitory effect of hydroxyflutamide plus tamoxifen on oestradiol-induced growth of MCF-7 breast cancer cells

The antiandrogen flutamide has been reported to exert antiproliferative actions on breast cancer both in vitro and in vivo. Here we study the action of its active metabolite hydroxyflutamide on the oestradiol-induced growth of MCF-7 breast cancer cells. The results show that the antiandrogen inhibits the cell growth. Moreover hydroxyflutamide adds its antiproliferative effect to the action of the antioestrogen tamoxifen. The inhibitory effect is dose-dependent and it is unaffected by tamoxifen concentrations up to levels able to block oestrogen receptors completely. Dihydrotestosterone experiments parallel those on hydroxyflutamide. When the two substances are administered together, neither antagonistic nor additive effects are appreciable. Data are consistent with an androgen-like action of hydroxyflutamide on breast cancer cells. The antiproliferative effect of hydroxyflutamide, without virilizing side-effects, suggests that it is worth exploring its possible employment together with antioestrogens in the treatment of breast cancer patients.

Dihydrotestosterone affects the growth of hormone-unresponsive breast cancer cells: an indirect action

Cell to cell interaction, which plays a crucial role in breast cancer growth, may be regulated by steroid hormones. This study examined dihydrotestosterone (DHT) effects on the interaction between the steroid receptor positive MCF-7 and the steroid receptor negative MDA-MB-231 breast cancer cell lines. The growth of MDA-MB-231 cells was inhibited by medium conditioned by MCF-7 cells grown in presence of DHT but not by medium conditioned by MCF-7 cells grown in presence of both DHT and the antiandrogen hydroxyflutamide. Trypsin pretreatment of conditioned medium abolished its growth-inhibitory effect on hormone-unresponsive cells. DHT itself did not affect the growth of MDA-MB-231 cells when directly added to their culture medium. Data suggest that DHT stimulates, via the androgen receptor, the androgen-responsive breast cancer cells to produce a peptide factor(s) capable of inhibiting the growth of hormone-unresponsive cells.

5-En-androstene-3 beta,17 beta-diol inhibits the growth of MCF-7 breast cancer cells when oestrogen receptors are blocked by oestradiol

Adrenal androgens show a dual and apparently opposite effect on the growth of oestrogen-responsive breast cancer: they stimulate growth on their own, but counteract the growth-stimulatory effect of oestrogens. Focusing on the inhibitory action we have studied the effects of 5-en-androstene-3 beta,17 beta-diol (ADIOL) on the growth of oestrogen-responsive MCF-7 breast cancer cells in the presence of oestrogens (oestradiol and diethylstilboestrol), antiestrogens (tamoxifen) and antiandrogens (hydroxyflutamide). The inhibition of oestrogen-stimulated growth, attained with nanomolar concentrations of ADIOL, was not modified by increasing concentrations of diethylstilboestrol up to 100 nM. This inhibition was counteracted by antiandrogens, which were unable to block the ADIOL stimulatory effect in steroid-free medium. On the other hand, in the presence of tamoxifen ADIOL showed an additive antiproliferative activity also in steroid-free medium, rather than the usual stimulatory effect. These results suggest that ADIOL stimulates breast cancer cell growth via oestrogen receptors, but inhibits oestrogen-stimulated growth via androgen receptors.

Dehydroepiandrosterone antiestrogenic action through androgen receptor in MCF-7 human breast cancer cell line

The possible mechanisms of the inhibitory effect of Dehydroepiandrosterone (DHEA) on the estrogen-induced growth of MCF-7 human breast cancer cells were explored. The impairment of metabolic pathways, via the inhibition of glucose-6-phosphate dehydrogenase (G6PD) activity, was excluded: G6PD activity in MCF-7 homogenate was reduced by DHEA only at a very high concentration (50 microM), while no inhibitory action on the enzyme activity was detected when DHEA was added at the antimitotic concentrations (0.02-0.5 microM). A steroid receptor mediated effect was explored: DHEA might either activate androgen receptors (AR) or partially displace E2 from estrogen receptor (ER). The pure antiandrogens Flutamide and Hydroxyflutamide reversed the inhibitory effect of DHEA on MCF-7 cell growth, whereas both the nonsteroidal estrogen Diethylstilbestrol and the antiestrogen Tamoxifen were ineffective. Results demonstrate that the AR activation plays a pivotal role in the inhibitory action of DHEA on the E2-induced MCF-7 growth.

[Caries receptivity: a modern diagnostic protocol. II. The most important tests]

In this, the second part of the paper, the main clinical tests available today for carrying out early diagnosis of carioreceptivity are reviewed. On its own, measurement of the DMF-T index can classify an individual as carioactive or evaluate his "experience of caries", but it does non determine with any degree of certainty the probability of future caries. Measurement of stimulated salivary flow is important only when this is greatly reduced, as happens, for example, in xerostomy, but the finding of an almost normal flow is not on its own sufficient to make a diagnosis of carioreceptivity certain. Assessment of salivary pH is not a reliable parameter for the screening of carioreceptivity although it may be an indicator of diseases (e.g. diabetes) or bad habits (e.g. heavy smokers) in the patient in question. So examination with very sophisticated methods is of little importance. The buffer potential of saliva, assessed with a colorimetric test, is the most reliable parameter as it measures an important property of saliva at individual level: the capacity to protect from local acidity. Some studies seem to point to the validity of the combined evaluation of DMF, pH, salivary flow and buffer power of saliva in the prediction of caries at the level of groups of individual, but this has little or no validity in the screening of individual carioreceptive subjects. Specific microbiological cultures for cariogenic microorganisms are the most reliable tests for the diagnosis of carioreceptivity, particularly Dentocult for the search for Streptococcus mutans which is the most important factors in caries. The search for lactobacilli also identifies bad hygienic and dietary habits in the patients.

[Sutures and suture technics. Current trends and our method in oral surgery]

Suture techniques are a fundamental aspect of surgical practice in terms of the successful outcome of the operation. Even in dentistry it is important to have a clear idea of the method and the type of thread used. This paper lists the types of suture threads most commonly available today, the main techniques used and, on the basis of the authors' personal experience, explains a method used for oral surgery.

[A case of nickel-induced stomatitis]

Some patients with prostheses or dental material containing nickel have been diagnosed as suffering from stomatitis. These lesions of the oral mucosa are sometimes difficult to interpret since allergies are not always taken into consideration. The paper reports a case of stomatitis due to nickel allergy and describes the diagnostic procedure [correction of iter] followed in order to diagnose the true nature of the pathology.

[Role of direct immunofluorescence in the diagnosis of oral lichen planus]

A series of 25 cases with clinical signs indicative of oral lichen planus was examined. Samples stained with haematoxylin-eosin as for traditional histology and others for DIF were taken in each case. The results obtained by both techniques were then compared with the clinical picture. It is concluded that DIF is a valuable diagnostic aid in doubtful cases.

[Keratotic lesions of the oral cavity. Notes on histopathologic differential diagnosis in leukoplakia, lichen planus, lupus erythematosus. Cases investigation]

A series of 24 white mouth lesions variously diagnosed as leukoplakia, lichen planus and discord lupus erythematosus is examined. A number of histological parameters were investigated using samples stained with haematoxylin-eosin and orcein and by Wohlgemulh's test. The 24 cases were also assessed by direct immunofluorescence (DIF) using the standard techniques. The aim of the study was to discover which of the histological and DIF findings were most helpful for diagnosis. The results confirm the view that histological diagnosis is only possible in some cases and that DIF helps to clarify histologically uncertain ones. Even so, clinical examination of the patient remains essential in order to eliminate the uncertainty created by the histological findings. It therefore follows that close collaboration between clinician and pathologist is essential.

Primary carcinoma of the fallopian tube in an adolescent

Only three cases of adenocarcinoma of the fallopian tube in an adolescent have been reported previously in the literature, and we report the fourth such case. The main presenting symptom in those patients was lower abdominal pain. Type of therapy and outcome of these four cases is reviewed. The small number of patients precludes definitive conclusion on optimal therapy. For this reason, we urge continued reporting of cases to insure the formation of concrete therapeutic recommendations.