Retinal regeneration mechanisms linked to multiple cancer molecules: A therapeutic conundrum

Over the last decade, a large number of research articles have been published demonstrating regeneration and/or neuroprotection of retinal ganglion cells following manipulation of specific genetic and molecular targets. Interestingly, of the targets that have been identified to promote repair following visual system damage, many are genes known to be mutated in different types of cancer. This review explores recent literature on the potential for modulating cancer genes as a therapeutic strategy for visual system repair and looks at the potential clinical challenges associated with implementing this type of therapy. We also discuss signalling mechanisms that have been implicated in cancer and consider how similar mechanisms may improve axonal regeneration in the optic nerve.

Cardiotrophin-1 decreases intestinal sugar uptake in mice and in Caco-2 cells

AIM

Cardiotrophin-1 (CT-1) is a member of the IL-6 family of cytokines with a key role in glucose and lipid metabolism. In the current investigation, we examined the in vivo and in vitro effects of CT-1 treatment on intestinal sugar absorption in different experimental models.

METHODS

rCT-1 effects on α-Methyl-D-glucoside uptake were assessed in everted intestinal rings from wild-type and CT-1(-/-) mice and in Caco-2 cells. rCT-1 actions on SGLT-1 expression in brush border membrane vesicles and the identification of the potential signalling pathways involved were determined by Western blot.

RESULTS

In vivo administration (0.2 mg kg(-1) ) of rCT-1 caused a significant decrease on α-Methyl-D-glucoside uptake in everted intestinal rings from wild-type and CT-1(-/-) mice after short-term and long-term treatments. Similarly, in vitro treatment (1-50 ng mL(-1) ) with rCT-1 reduced α-Methyl-D-glucoside uptake in everted intestinal rings. In Caco-2 cells, rCT-1 treatment (20 ng mL(-1) , 1 and 24 h) lowered apical uptake of α-Methyl-D-glucoside in parallel with a decrease on SGLT-1 protein expression. rCT-1 promoted the phosphorylation of STAT-3 after 5 and 15 min treatment, but inhibited the activation by phosphorylation of AMPK after 30 and 60 min. Interestingly, pre-treatment with the JAK/STAT inhibitor (AG490) and with the AMPK activator (AICAR) reversed the inhibitory effects of rCT-1 on α-Methyl-D-glucoside uptake. AICAR also prevented the inhibition of SGLT-1 observed in rCT-1-treated cells.

CONCLUSIONS

CT-1 inhibits intestinal sugar absorption by the reduction of SGLT-1 levels through the AMPK pathway, which could also contribute to explain the hypoglycaemic and anti-obesity properties of CT-1.

Leptin regulates sugar and amino acids transport in the human intestinal cell line Caco-2

AIM

Studies in rodents have shown that leptin controls sugars and glutamine entry in the enterocytes by regulating membrane transporters. Here, we have examined the effect of leptin on sugar and amino acids absorption in the human model of intestinal cells Caco-2 and investigated the transporters involved.

METHODS

Substrate uptake experiments were performed in Caco-2 cells, grown on plates, in the presence and the absence of leptin, and the expression of the different transporters in brush border membrane vesicles was analysed by Western blot.

RESULTS

Leptin inhibited 0.1 mm α-methyl-D-glucoside uptake after 5 or 30 min treatment and decreased SGLT1 protein abundance in the apical membrane. Uptake of 20 μm glutamine and 0.1 mm phenylalanine was also inhibited by leptin, indicating sensitivity to the hormone of the Na(+) -dependent neutral amino acid transporters ASCT2 and B(0) AT1. This inhibition was accompanied by a reduction in the transporters expression at the brush border membrane. Leptin also inhibited 1 mm proline and β-alanine uptake in Na(+) medium at pH 6, conditions for optimal activity of the H(+) -dependent neutral amino acid transporter PAT1. In this case, abundance of PAT1 in the brush border membrane after leptin treatment was not modified. Interestingly, leptin inhibitory effect on β-alanine uptake was reversed by the PKA inhibitor H-89 suggesting involvement of PKA pathway in leptin's regulation of PAT1 activity.

CONCLUSION

These data show in human intestinal cells that leptin can rapidly control the activity of physiologically relevant transporters for rich-energy molecules, that is, D-glucose (SGLT1) and amino acids (ASCT2, B(0) AT1 and PAT1).

Treatment of multiple myeloma with adoptively transferred chimeric NKG2D receptor-expressing T cells

Multiple myeloma causes approximately 10% of all hematologic malignancies. We have previously shown that human T cells expressing chimeric NKG2D receptors (chNKG2D) consisting of NKG2D fused to the CD3ζ cytoplasmic domain secrete proinflammatory cytokines and kill human myeloma cells. In this study, we show chNKG2D T cells are effective in a murine model of multiple myeloma. Mice with established 5T33MM-green fluorescent protein tumors were treated with one or two infusions of chNKG2D T cells. Compared with mice treated with T cells expressing wild type (wt)NKG2D receptors, a single dose of chNKG2D T cells increased survival, with half of the chNKG2D T-cell-treated mice surviving long term. Two infusions of chNKG2D T cells led to tumor-free survival in all mice. ChNKG2D T cells were located at sites of tumor growth, including the bone marrow and spleen after intravenous injection. There was an increase in activated host T cells and NK cells at tumor sites and in serum interferon-γ after chNKG2D T-cell injection. Surviving mice were able to resist a rechallenge with 5T33MM cells but not RMA lymphoma cells, indicating that the mice developed a protective, specific memory response. These data demonstrate that chNKG2D T cells may be an effective adoptive cellular therapy for multiple myeloma.

Lipoic acid prevents body weight gain induced by a high fat diet in rats: effects on intestinal sugar transport

Several studies have suggested that oxidative stress might cause and aggravate the inflammatory state associated with obesity and could be the link between excessive weight gain and its related disorders such as insulin resistance and cardiovascular diseases. Thus, antioxidant treatment has been proposed as a therapy to prevent and manage obesity and associated complications. Therefore, the aim of the present study was to investigate the effects of supplementation of a standard or high fat diet with the antioxidant lipoic acid (LA) during 56 days, on body weight gain, adiposity, feed efficiency and intestinal sugar absorption, in male Wistar rats. LA supplementation induced a lower body weight gain and adipose tissue size in both control or high fat fed rats accompanied by a reduction in food intake. The group fed on a high fat diet and treated with LA (OLIP group) showed a lower body weight gain than its corresponding Pair-Fed (PF) group (P < 0.05), which received the same amount of food than LA-treated animals but with no LA. In fact, LA induced a reduction on feed efficiency and also significantly decreased intestinal alpha-methylglucoside (alpha-MG) absorption both in lean and obese rats. These results suggest that the beneficial effects of dietary supplementation with LA on body weight gain are mediated, at least in part, by the reduction observed in food intake and feed efficiency. Furthemore, the inhibitory action of LA on intestinal sugar transport could explain in part the lower feed efficiency observed in LA-treated animals and therefore, highlighting the beneficial effects of LA on obesity.

Luminal leptin inhibits intestinal sugar absorption in vivo

AIM

We have previously demonstrated that leptin inhibits galactose absorption in rat intestinal everted rings and that leptin receptors are present in the apical membrane of the enterocytes. This adipocyte-derived hormone is also secreted by gastric mucosal cells and is able to reach the intestinal lumen. The goal of the present study was to prove whether luminal leptin acts on intestinal sugar absorption in vivo both at low (basal state) and high sugar concentration (post-prandial state).

METHODS

In vivo intestinal sugar absorption in rat was measured with recirculating and single-pass perfusion systems. Sugar disappearance in the perfusate was measured by radioactivity and biochemical methods. Luminal leptin effect on intestinal absorption mediated by sodium-dependent glucose transporter 1 (SGLT1) and glucose transporter 2 (GLUT2) as well as intestinal permeability (mannitol absorption) was determined.

RESULTS

Luminal leptin inhibited intestinal sugar absorption at low galactose concentrations, which indicates that leptin regulates SGLT1 activity in vivo. The inhibition was reversed in the absence of hormone in the intestinal lumen, suggesting that it was produced by post-translational regulation processes. At high luminal glucose concentrations, leptin also inhibited the phloretin-insensitive component of sugar absorption mediated by SGLT1. There was no significant effect on the apical GLUT2 component of absorption. Leptin did not modify in vivo intestinal permeability determined with (14)C-mannitol.

CONCLUSION

These observations support the view that gastric leptin exerts a regulatory role on intestinal sugar absorption in the postprandial state by modifying the active component of absorption.

Na+ and pH dependence of proline and beta-alanine absorption in rat small intestine

AIMS

Early characterization of intestinal absorption of imino acids in mammals has demonstrated the existence of a Na+-dependent, Cl- -independent transport system in rat small intestine, which is the only carrier for beta-alanine. Based on the substrate selectivity, it was proposed that the Proton Amino Acid Transporter 1 (PAT1) could be the same as this imino acid carrier. The present study characterizes the pH and Na+ dependence of proline and beta-alanine uptake in rat small intestine.

METHODS

Intestinal uptake of radiolabelled l-proline or beta-alanine was measured in brush border membrane vesicles and everted intestinal rings, in the presence and absence of Na+ and at different pH values.

RESULTS

The existence of an inwardly directed H+ gradient in the absence of Na+ enhanced the initial entry of proline and beta-alanine in brush border membrane vesicles, that reached a transient overshoot with maximal value around 30 s. In the absence of pH gradient, no overshoot was shown. In entire tissue, there was an increase of proline and beta-alanine uptake at acidic pH that was higher in the presence of Na+ than in its absence. This ion dependence and pH effect of the amino acids uptake also increased with the incubation period. Substrate inhibition studies confirmed that intestinal proline absorption in rat occurs mainly by system B and PAT1-like transporter.

CONCLUSIONS

There is a Na+ -independent, H+ -dependent transporter of amino acids at the apical membrane of the rat enterocytes.

Transport of d-galactose by the gastrointestinal tract of the locust, Locusta migratoria

Due to exoskeleton, the absorption of nutrients in adult insects takes place across the gastrointestinal tract epithelium. In most physiological studies, sugar intestinal absorption has been described as a diffusional process and to date no sugar transporter has been cloned from the digestive tract of insects. In the present work, the existence of a saturable transport system for galactose in the gastric caeca of Locusta migratoria is clearly demonstrated. This transport shows a relatively high affinity for galactose (apparent K0.5=2-3 mM) and is inhibited by glucose, 2-deoxyglucose and with less potency by fructose and alpha-methyl-d-glucoside. The absence of sodium or the presence of phloridzin hardly affects galactose absorption, indicating that it is not mediated by a SGLT1-like transporter. The absence of K+, Cl-, Mg2+ and Ca2+ or changes in the pH do not modify galactose absorption either. Nevertheless, phloretin, cytochalasin B and theophylline (inhibitors of facilitative transporters) decrease sugar uptake around 50%. Xenopus laevis oocytes microinjected with poly A+ RNA isolated from gastric caeca show sodium-independent galactose uptake that is three times higher than in non-injected oocytes, further supporting the existence of a mRNA coding for at least one equilibrative sugar transporter in L. migratoria gastric caeca.

The GAIN (Geriatric Anorexia Nutrition) registry: the impact of appetite and weight on mortality in a long-term care population

PURPOSE

To investigate nursing home residents at high nutritional risk to determine: 1) which baseline nutrition or health status indicators correlated with subsequent weight gain or appetite improvement; and, 2) whether a continued weight loss correlated with higher mortality.

METHODS

At study entry, nutritional, health status, and demographic data were extracted from the nursing home chart or the MDS. Each subject was tracked for 6 months with survival, weight gain of 5%, and appetite improvement the primary outcome measures.

RESULTS

During the 6-month study, younger age was the strongest correlate of appetite improvement. The odds of gaining weight were negatively correlated with BMI, age, and feeding dependency. Subjects who were receiving appetite stimulants (orexigenics) at study entry had a 70% greater probability of gaining weight than those who were not. A weight loss during the 6-month period was associated with a nearly two-fold increase in the likelihood of dying (adjusted RR: 1.95, 95% CI 1.43 to 2.66).

CONCLUSION

The course of nutritional problems within nursing homes is highly variable. Continued weight loss, however, appears to have ominous implications for mortality. Younger residents who are not dependent on others for feeding assistance, and who receive orexigenics tend to experience weight gain.

Effect of adrenomedullin and proadrenomedullin N-terminal 20 peptide on sugar transport in the rat intestine

Previous studies have shown immunostaining of adrenomedullin (AM) and proadrenomedullin N-terminal 20 peptide (PAMP) throughout the gastrointestinal tract. Based on these data, we decided to investigate the effect of these peptides on intestinal sugar absorption using everted rings from Wistar rat intestine. PAMP increases alpha-methylglucoside (MG) uptake at concentrations ranging from 10(-12) to 10(-7) M. AM shows a dual effect inhibiting sugar absorption at low concentrations (10(-12) to 10(-11) M) and increasing MG uptake at higher concentrations (10(-8) to 10(-6) M). In all cases, the effect is phloridzin-sensitive, indicating that the peptides alter SGLT1 function without modifying the non-mediated component of absorption. The enhancing effect of 10(-8) M AM and PAMP seems to be mediated by elevation of cAMP and is accompanied by an increase on SGLT1 expression in the brush-border membrane of the enterocytes. The inhibitory effect of 10(-12) M AM could be mediated by either cAMP reduction or, more probably, by other second messenger able to inhibit sugar absorption. PKC is not involved in the action of either AM or PAMP. These results demonstrate that both peptides play a role in the regulation of the active transport of sugars in the intestine.

Novel developments with selective, non-peptidic kappa-opioid receptor agonists

Despite the recent introduction of a number of new compounds, there has of late been a cooling of interest by pharmaceutical companies in the development of centrally-active, selective kappa opioid agonists for therapeutic purposes. This is reflected in the discontinuation of a number of clinical trials, for reasons that are often not completely clear to outside observers. Spiradoline and enadoline have apparently been abandoned as potential analgesics because they induce dose-limiting central side-effects (i.e., dysphoria) in models of post-surgical pain. The development of niravoline as an aquaretic for the treatment of cirrhosis with ascites and other hyponatraemic disorders has also been halted. Enadoline may yet find some application against ischaemic stroke and severe head injury, presumably in comatose patients in whom psychiatric side-effects are taken to be immaterial, while apadoline and TRK 820 remain in Phase II clinical testing against cancer pain. The peripherally-selective kappa agonists, asimadoline, and the atypical compound, fedotozine, are well-tolerated in man. Results of Phase III trials of fedotozine against irritable bowel syndrome and dyspepsia have, however, ultimately been disappointing, whereas asimadoline is currently in Phase II clinical trials against pain of rheumatic and osteoarthritic origin. The results of these trials are eagerly awaited.

The use of a European telemedicine system to examine the effects of pollutants and allergens on asthmatic respiratory health

The experience of using a telemedicine feasibility study to integrate respiratory health response and environmental stimuli information is presented. The effects of ambient air quality, pollen and local environment conditions on asthmatic patients' lung function were investigated through the use of a novel European health telematic system. The Medical Diagnosis, Communication and Analysis Throughout Europe (MEDICATE) project developed and tested the feasibility of using a telemedicine system for chronic asthmatics in London, UK, and Barcelona, Spain. The key to this was the determination of the real time health (lung function) response to the ambient environment and allergens. Air quality, pollen and environmental lifestyle information were related to respiratory measurements for recruited asthmatic patients in the study through the design of a dedicated environmental management system (EMS) database. In total, 28 patients completed the study trial, subject to ambulatory monitoring of spirometric lung function (PEF, FEV(1) and FVC) up to four times a day over a 2-week period recorded during the year 2000. Alongside this, ambient air quality and pollen counts were used to represent local exposure to potential environmental stimuli. Personal questionnaire interviewing collected additional data about patient lifestyles, social-economic conditions and quality of life perceptions. The methods and indicative results of integrating environmental and health data in this respect are examined. Assessment tools such as GIS and object-orientated databases were designed to locate and compile environmental information about the patients' locations and lifestyles in the study areas (London and Barcelona). Socioeconomic and lifestyle factors, such as exposure to smoking, pets, personal journey lengths and modes, income, household occupancy and domestic fuel use, were found to have limited detectable effects on the patients' basic lung function levels. Patients' gender, age and predicted PEFR were significantly associated with the 2-week mean and minimum respiratory measurements. Lung function data were compared with air quality and pollen indicators to examine relationships on a daily or lagged-day basis controlling for confounding factors. The paper discusses the new methodology and the practicalities of using the telemedical system as a tool for assessing the impacts of environmental stimuli on respiratory health.

Leptin effect on intestinal galactose absorption in ob/ob and db/db mice

Our previous works demonstrated that leptin inhibits galactose absorption in rat and mice intestinal rings. Here, we have studied the effect of exogenous leptin on intestinal galactose absorption in the genetically obese db/db (leptin-resistant) and ob/ob (leptin-deficient) mice. Assays were performed by incubating the intestinal rings in saline solution containing 5 mM galactose in the absence or presence of 0.2 or 0.4 nM leptin. Basal galactose uptake was similar in the wild-type and the two obese groups. Contrarily to what happens in wild-type mice, leptin increased galactose uptake in db/db animals; since these mice lack the functional long leptin receptor, the measured effect may be due to the short receptor signaling. In the ob/ob mice, 0.2 nM leptin also increased galactose absorption whereas 0.4 nM did not have any effect, suggesting that in the genetically obese animals the expression and regulation of leptin receptors may be altered.

Transport of proline and hydroxyproline by the neutral amino-acid exchanger ASCT1

ASCT1 is a member of the glutamate transporter superfamily cloned from human brain and characterized as a Na(+)-dependent neutral amino-acid exchanger, which displays substrate-induced chloride-channel activity and mediates concentrative transport of alanine. Initial studies in ASCT1-expressing Xenopus laevis oocytes showed that proline did not elicit measurable currents, in contrast to what occurred with alanine, serine or cysteine, suggesting that proline was not an ASCT1 substrate, although it induced the release of alanine from preloaded oocytes. Here, we have studied the uptake of proline and hydroxyproline by ASCT1-expressing oocytes in order to investigate the ability of ASCT1 to translocate these imino acids. The results demonstrate ASCT1-mediated proline transport that is Na(+)-dependent, saturable, inhibited by the reported ASCT1 substrates as well as by hydroxyproline and can drive the imino acid against its concentration gradient. The apparent kinetic constants for the transport of alanine and the imino acids, obtained with oocytes from the same batch, showed maximal transport rate for proline and hydroxyproline to be half of that for alanine. However, K(0.5) for proline was 704 +/- 86 microM, about three times higher than alanine K(0.5) (203.3 +/- 36.4 microM), whereas hydroxyproline K(0.5) was 33.2 +/- 4.3 microM, indicating that the hydroxylation on carbon 4 of proline strongly increases the affinity of ASCT1 for this proline derivative. In summary, the present work demonstrates for the first time the ability of ASCT1 to transport proline and hydroxyproline.

Perfusion thresholds in acute stroke thrombolysis

BACKGROUND AND PURPOSE

Perfusion-weighted MRI has been shown to be useful in the early identification of cerebral tissue at risk of infarction during acute ischemia. Identification of threshold perfusion measures that predict infarction may assist in the selection of patients for thrombolysis.

METHODS

Mean transit time (MTT), regional cerebral blood flow (rCBF), and regional cerebral blood volume (rCBV) maps were generated in 35 acute stroke patients (17 treated with tissue plasminogen activator and 18 control patients) imaged within 6 hours from symptom onset. Day 90 outcome infarcts (T2-weighted MRI) were superimposed on acute MTT, rCBF, and rCBV maps. Perfusion-weighted MRI measures were then calculated for 2 regions: infarcted and salvaged tissue.

RESULTS

MTT was prolonged by 22% in infarcted regions relative to salvaged tissue (P<0.001). rCBF was 10% lower in infarcted tissue than in salvaged regions (P<0.01). rCBV did not differ significantly between infarcted and salvaged regions. When reperfusion occurred, tissue with more severely prolonged MTT was salvaged from infarction relative to patients with persistent hypoperfusion (P<0.05). In contrast, rCBF in salvaged regions did not differ between patients with and without reperfusion. In reperfused patients, an inverse correlation (R=0.93, P<0.001) was found between time of initial MRI scan and MTT delay in salvaged tissue.

CONCLUSIONS

Both increases in MTT and decreases in rCBF predict infarction. Differences in MTT also predict salvage in more severely hypoperfused tissue after reperfusion, suggesting that it is the most clinically useful quantitative perfusion measure. Perfusion thresholds for infarction need to be assessed in the context of symptom duration.

Functional expression of the short isoform of the murine leptin receptor Ob-Rc (muB1.219) inXenopus laevis oocytes

Leptin, a hormone mainly secreted by the adipose tissue, acts on the hypothalamus to regulate food intake and thermogenesis. Six leptin receptor isoforms have been identified and localized in different tissues. While it is clear that leptin action in the brain occurs by binding to the long receptor isoform, several studies have shown that the short isoforms could be involved in the transcellular transport of the hormone from the blood to the brain. Based on these works, we decided to investigate whether the murine short leptin receptor isoform Ob-Rc (muB1.219) could transport leptin when expressed in Xenopus laevis oocytes. MuB1.219 cRNA was injected into the oocytes and functional studies were performed by incubating the oocytes in the presence of 2.5 nM [125I]-leptin, under different conditions. Results showed that leptin binding to the injected oocytes was four to eight-fold higher than the binding to the non-injected oocytes. This was blocked by 250 nM of non-radiolabeled leptin, suggesting that the binding was specific. Leptin internalization was observed from 30 min incubation onwards. Coexpression of the human Na+/glucose cotransporter and the leptin receptor showed that leptin increased sugar uptake into the oocytes. These results demonstrate that the short leptin receptor Ob-Rc is able to mediate binding and internalization of the hormone when expressed in oocytes and that it may perform intracellular signaling.

Distribution of the long leptin receptor isoform in brush border, basolateral membrane, and cytoplasm of enterocytes

BACKGROUND AND AIM

Leptin, a hormone mainly produced by fat cells, acts primarily on the hypothalamus regulating energy expenditure and food intake. Leptin receptors are expressed in several tissues and the possible physiological role of leptin is being extensively investigated, with the result that important peripheral actions of the hormone in the organism are being discovered. Recent studies have demonstrated leptin and leptin receptor expression in gastric epithelial cells. In the present study, we report the presence of the long leptin receptor isoform (OB-Rb) in human, rat, and mouse small intestine, supporting the hypothesis of leptin as a hormone involved in gastrointestinal function.

METHODS

The presence of the leptin receptor was determined by immunocytochemical methods using antibodies against the peptide corresponding to the carboxy terminus of the long isoform of the leptin receptor. Human duodenal biopsies from normal individuals undergoing gastrointestinal endoscopy, and intestinal fragments of Wistar rats and Swiss mice were processed for the study.

RESULTS

Immunoreactivity for the long leptin receptor isoform was observed in the three studied species. Staining was located throughout the cytoplasm of the enterocytes, of both villi and crypts, and in the basolateral plasma membrane. Immunolabelling for OB-Rb protein was also found in the brush border of human enterocytes of formol and paraformaldehyde fixed samples.

CONCLUSION

This report demonstrates the presence of the long leptin receptor isoform in the absorptive cells of rat, mouse, and human small intestine, suggesting that leptin could have a physiological role in the regulation of nutrient absorption.

Transforming growth factor beta expression in human placenta and placental bed during early pregnancy

Normal human pregnancy depends on physiological transformation of spiral arteries. Pre-eclampsia and fetal growth restriction are associated with impaired trophoblast invasion and spiral artery transformation. Recent data obtained from studies on placenta suggest that temporal changes in expression of TGF-beta3 play a key role in trophoblast invasion and that over-expression of TGF-beta3 in pre-eclampsia is responsible for inadequate trophoblast invasion. There are, however, no studies of specific TGF-betas in the placental bed throughout pregnancy although this is where the invasive trophoblast and spiral arteries are located. In this study we have used immunohistochemistry, Western blot analysis, ELISA and RT-PCR to examine the expression of TGF-beta1, TGF-beta2 and TGF-beta3 in placental bed biopsies and placentas from 7--19 weeks' gestation. The results show that TGF-beta1, 2 and 3 are expressed in the placenta throughout this time but the striking temporal changes in TGF-beta3 expression previously reported were not observed. Extravillous trophoblast within the placental bed expressed TGF-beta2 but not TGF-beta1 or TGF-beta3 while extracellular TGF-beta1 and cytoplasmic TGF-beta2 were detected in decidua. These data suggest that TGF-beta1 and TGF-beta2 but not TGF-beta3 may play a role in trophoblast invasion.

Active transport of alanine by the neutral amino-acid exchanger ASCT1

ASCT1 protein is a member of the glutamate transporter superfamily, which shows system ASC selectivity and properties and has been characterized as a Na+-dependent neutral amino-acid exchanger. Here, by using ASCT1-expressing oocytes, the uptake of alanine and glutamate was measured to investigate ASCT1's ability to mediate a concentrative transport of alanine, ASCT1's sodium dependence, and the influence of pH on the mutual inhibition between alanine and glutamate. Alanine uptake was measured after 30 min incubation. Kinetic analysis of the Na+ dependence of alanine uptake showed an apparent K0.5 (affinity constant) value for Na+ of 23.1 ± 4.3 mM (mean ± SE). Concentration dependence of alanine uptake was tested at 100 and 1 mM Na+, with apparent K0.5 values of 0.16 ± 0.04 and 1.8 ± 0.4 mM, respectively, at pH 7.5, and 0.21 ± 0.06 and 1.9 ± 0.3 mM at pH 6. Vmax was not modified between 100 and 1 mM Na+ at either pH. ASCT1 actively transports alanine and accumulates it in the cytosol even when the Na+ concentration in the medium was as low as 1–3 mM. 22Na uptake studies revealed that Na+ transport was stimulated by the presence of alanine in the medium. Our results demonstrate that ASCT1 is able to mediate a concentrative transport of alanine, which is Na+-dependent but not coupled to the Na+ gradient.Key words: ASCT1, sodium, Xenopus laevis oocytes, concentrative transport, alanine.

Active transport of alanine by the neutral amino-acid exchanger ASCT1

ASCT1 protein is a member of the glutamate transporter superfamily, which shows system ASC selectivity and properties and has been characterized as a Na+-dependent neutral amino-acid exchanger. Here, by using ASCT1-expressing oocytes, the uptake of alanine and glutamate was measured to investigate ASCT1's ability to mediate a concentrative transport of alanine, ASCT1's sodium dependence, and the influence of pH on the mutual inhibition between alanine and glutamate. Alanine uptake was measured after 30 min incubation. Kinetic analysis of the Na+ dependence of alanine uptake showed an apparent K0.5 (affinity constant) value for Na+ of 23.1 +/- 4.3 mM (mean +/- SE). Concentration dependence of alanine uptake was tested at 100 and 1 mM Na+, with apparent K0.5 values of 0.16 +/- 0.04 and 1.8 +/- 0.4 mM, respectively, at pH 7.5, and 0.21 +/- 0.06 and 1.9 +/- 0.3 mM at pH 6. Vmax was not modified between 100 and 1 mM Na+ at either pH. ASCT1 actively transports alanine and accumulates it in the cytosol even when the Na+ concentration in the medium was as low as 1-3 mM. 22Na uptake studies revealed that Na+ transport was stimulated by the presence of alanine in the medium. Our results demonstrate that ASCT1 is able to mediate a concentrative transport of alanine, which is Na+-dependent but not coupled to the Na+ gradient.

Transforming growth factor-beta expression in human placenta and placental bed in third trimester normal pregnancy, preeclampsia, and fetal growth restriction

Normal human pregnancy depends on physiological transformation of spiral arteries by invasive trophoblasts. Preeclampsia (PE) and fetal growth restriction (FGR) are associated with impaired trophoblast invasion and spiral artery transformation. Recent studies have suggested that transforming growth factor (TGF)-beta3 is overexpressed in the placenta of PE patients and that this may be responsible for failed trophoblast invasion. There are, however, no studies on TGF-betas in the placenta in FGR or in the placental bed in PE or FGR. In this study we have used immunohistochemistry, Western blot analysis, and enzyme-linked immunosorbent assay to examine the expression of TGF-beta1, TGF-beta2, and TGF-beta3 in placenta and placental bed of pregnancies complicated by PE and FGR and matched control pregnancies. The results show that TGF-beta1, -beta2, and -beta3 are not expressed in villous trophoblasts but are present within the placenta. TGF-beta1, -beta2, and, to a much lesser extent, TGF-beta3 were present within the placental bed but only TGF-beta2 was present in extravillous trophoblast. No changes in expression of either isoform were found in placenta or placental bed in PE or FGR compared with normal pregnancy. These data are not consistent with overexpression of TGF-beta3 being responsible for failed trophoblast invasion in PE. Our findings suggest that the TGF-betas do not have a pathophysiological role in either PE or FGR.

Heme oxygenase expression in human placenta and placental bed: reduced expression of placenta endothelial HO-2 in preeclampsia and fetal growth restriction

In this study we tested the hypothesis that expression of heme oxygenases HO-1 and HO-2, which are responsible for the production of carbon monoxide, are reduced in the placenta and placental bed of pregnancies complicated by preeclampsia (PE) and fetal growth restriction (FGR) compared with control third-trimester pregnancies. Placental protein expression was determined by Western blotting (n=10 in each group) and immunohistochemistry (controls n=18, PE n=19, FGR n=10). Extravillous trophoblast expression was determined by immunohistochemistry of placental bed biopsy samples (controls n=17, PE n=19, FGR n=10). Western blot analysis of placental homogenates showed no overall differences in HO-2 among groups. However, immunohistochemical analysis showed a reduction in HO-2 expression in endothelial cells in both abnormal groups (PE P<0.01; FGR P<0.0005 vs. control group) but no differences in villous trophoblast staining. HO-1 was undetectable by Western blotting in control and abnormal pregnancies and immunoreactivity was very low, suggesting that there is little HO-1 in the placenta. Within the placental bed, HO-2 but not HO-1 was detected on all populations of extravillous trophoblast, but expression of HO-2 or HO-1 did not change in PE or FGR. The reduced expression of HO-2 on endothelial cells in PE and FGR may be responsible for reduced placental blood flow in these conditions. The data do not show changes in HO in the placental bed in PE or FGR.

Fallopian tube necrosis after postpartum sterilization

Because it usually presents with nonspecific symptoms and occurs rarely, the diagnosis of fallopian tube torsion and necrosis is usually done at laparotomy. A 32 year-old woman returned to the hospital with right lower quadrant pain three days after a postpartum tubal sterilization procedure. Clinical, laboratory and imaging findings did not assist with the diagnosis. At laparotomy, after dissection of adhesions, a necrotic right fallopian tube was found. A salpingectomy was performed and the patient had an uneventful postoperative course. Fallopian tube torsion should be included in the differential diagnosis of pelvic pain in women. This patient has a good prognosis.

Cytoskeleton involvement on intestinal absorption processes

It has been recently demonstrated in the laboratory that the cytoskeletal inhibitor cytochalasin E has an indirect inhibitory effect on the function of the intestinal Na+-sugar cotransporter (SGLT1). The present work confirms that cytochalasin E inhibits SGLT1 activity through cytoskeleton disruption, showing that in anaerobic conditions (N2 bubbling), which implies low cytosolic ATP levels, the inhibition is not observed. As it occurs in sugar transport, the Na+-dependent intestinal transport of phenylalanine decreases if cytochalasin E is present in the incubation medium. However, the activity of the brush border enzymes sucrase, amino peptidase N and gamma-glutamyl transferase is not affected by the inhibitor. These enzymes only have one transmembrane domain and the active center is projected to the intestinal lumen. Therefore, cytoskeleton changes that could modify the transmembrane enzyme segment do not alter the activity of these enzymes. Examination of the intestine morphology after 30 min incubation with cytochalasin E shows only light modifications which do not seem to explain the inhibitory effects of the toxin on Na+-sugar or Na+-phenylalanine cotransporters function. On the whole, these results indicate that the inhibition of cytochalasin E on galactose and phenylalanine intestinal transport is secondary to its action on cytoskeleton through protein structure modifications.

Hemeoxygenase expression in human placenta and placental bed implies a role in regulation of trophoblast invasion and placental function

The purpose of this study was to examine the expression of hemeoxygenases HO-1 and HO-2, which are responsible for the production of carbon monoxide (CO), in the human placenta and placental bed and to determine the role of inhibitors of HO on placental perfusion pressure. We hypothesized that HO is expressed within the placenta and that invading cytotrophoblast cells (CTB) express HO isoforms. The expression of HO-1 and HO-2 was studied on placenta and placental bed biopsies, obtained using a transcervical sampling technique, from normal human pregnancies between 8 and 19 wk gestation and at term. In the placenta, HO-2 immunostaining was prominent in syncytiotrophoblast in the first trimester and reduced toward term (P<0.0005). HO-2 endothelial immunostaining was weak in the first trimester, but increased by term (P<0.0005). Within the placental bed, HO-2 was expressed by CTB in cell columns, the cytotrophoblast shell, and cell islands. Both intravascular CTB and interstitial CTB expressed HO-2. HO-1 immunostaining was low in the placenta but intense on the CTB within the placental bed. A striking feature was the absence of HO-1 from the proximal layers of cell columns, with strong expression on the more distal CTB layers of the cell columns. In placental perfusion studies, a significant dose-dependent increase in perfusion pressure was observed in the presence of zinc protoporphyrin, an inhibitor of HO. These results suggest a role for CO in placental function, trophoblast invasion, and spiral artery transformation. Hemeoxygenase expression in human placenta and placental bed implies a role in regulation of trophoblast invasion and placental function.