Lactobacillus acidophilus versus placebo in the symptomatic treatment of irritable bowel syndrome: the LAPIBSS randomized trial.

Irritable bowel syndrome is a chronic functional gastrointestinal disorder characterized by abdominal pain/discomfort and altered bowel habits. The use of Lactobacilli as probiotics during irritable bowel syndrome is based on their interesting mechanisms of action and their excellent safety profile but little is known about their clinical efficacy due to the lack of adequately designed clinical trials. The current clinical trial protocol aims to determine the effects of a mixture of Lactobacillus acidophilus NCFM and LAFTI L10 as probiotics to improve irritable bowel syndrome symptoms (LAPIBSS). Eighty patients with a positive diagnosis of irritable bowel syndrome according to Rome III criteria were recruited to a multicentre, double-blinded, in parallel groups, placebo-controlled randomized trial. Patients were provided with a daily dose of two capsules with two strains of Lactobacilli (5x109cfu/capsule) or placebo for 8 weeks on a 1:1 ratio. The primary outcome is to obtain scores of abdominal pain/discomfort assessed with a 100-mm visual analogue scale. The secondary outcome is to obtain scores of bloating, flatus and rumbling tested with a 100-mm visual analogue scale, composite score, stool frequency and stool consistency/appearance assessed with the Bristol Stool Form scale. According to the hypothesis that abdominal pain is mainly the result of a visceral hypersensitivity, the current study protocol aims to provide high quality proof of concept data to elucidate the efficacy of a consumption of a mixture of Lactobacillus acidophilus probiotic strains after 8 weeks, for decreasing abdominal pain. Ethical approval was given by ethics committee French Consultative Committee for the Protection of Individuals in Biomedical Research of the South West (Number CPP08-014a) and ANSM (French National Agency for Medicines and Health Products Safety - Number B80623-40). The findings from LAPBISS will be disseminated through peer-reviewed publications and at scientific conferences. TRIAL REGISTRATION: EudraCT N°2008-A00844-51.

Sodium calcium exchanger operates in the reverse mode in metastatic human melanoma cells.

Cytosolic Ca2+ ([Ca2+]cyt) is important in the regulation of several cellular functions involved in metastasis. We hypothesize that distinct [Ca2+]cyt regulation explains the acquisition of a more metastatic phenotype. To test this hypothesis, we used highly and lowly metastatic human melanoma cells and [Ca2+]cyt was monitored using Fura—2AM and fluorescence spectroscopy. Stimulation with ATP elicited a sustained increase in [Ca2+]cyt in highly metastatic cells, but a transient increase in lowly metastatic cells. Na+ substitution revealed Na+/Ca2+ exchanger (NCX) activity in reverse mode in highly, but not in lowly metastatic cells. In highly metastatic cells, addition of Na+ in the plateau phase of [Ca2+]cyt increase elicited with ATP, in the absence of Na+, resulted in a rapid return to basal, indicating that NCX can operate in both reverse and forward modes. Inhibition and knockdown of NCX, using KB—R7943 and siRNA NCX—1 respectively, supported the significance of NCX in [Ca2+]cyt regulation in highly metastatic cells. Stimulation with UTP triggered a rapid increase in highly metastatic cells [Ca2+]cyt, but not in lowly metastatic cells suggesting that highly and lowly metastatic cells exhibit distinct purinergic receptors. These data indicate that following agonist—stimulation, NCX operates preferentially in the reverse mode to enable a sustained [Ca2+]cyt increase in highly metastatic cells. The forward mode of NCX operation to extrude Ca2+ is preferred in lowly metastatic cells. The acquisition of a more metastatic phenotype involves a switch in NCX activity from forward to reverse mode that is favorable to maintain elevated [Ca2+]cyt in response to agonist stimulation.

Vacuolar H+-ATPase is down-regulated by the angiogenesis-inhibitory pigment epithelium-derived factor in metastatic prostate cancer cells.

The Vacuolar H+-ATPases (V-ATPases), a multi-subunits nanomotor present in all eukaryotic cells resides in the endomembranes of exocytotic and endocytotic pathways. Plasmalemmal V-ATPases have been shown to be involved in tumor cell metastasis. Pigment epithelium-derived factor (PEDF), a potent endogenous inhibitor of angiogenesis, is down-regulated in prostate cancer cells. We hypothesized that the transduction of PEDF in prostate cancer cells will down-regulate V-ATPase function; that in turn will decrease the expression of the V-ATPase accessory protein ATP6ap2 and a-subunit isoforms that target V-ATPase to the cell surface. To test these hypotheses, we used the human androgen-sensitive prostate cancer cells LNCaP, and its castration-refractory-derivative CL1 that were engineered to stably co-express the DsRed Express Fluorescent Protein with or without PEDF. To determine if PEDF down-regulates the function of V-ATPase, we measured the rate of proton fluxes (JH+) of the cytosolic and endosome/lysosome compartments. The mRNA levels for subunit-a isoforms and the ATP6ap2 were measured using quantitative reverse transcription-PCR. The results showed that PEDF expression decreased the rate of JH+ in metastatic CL1 cells without affecting JH+ in non-metastatic LNCaP cells, when studying pH(cyt). Interestingly, PEDF did not affect JH+ in endosomes/lysosomes either in metastatic cells or in non-metastatic cells. We also showed that PEDF significantly decreases the levels of a4 isoform and ATP6ap2 in metastatic CL1 cells, without affecting the levels of a4 isoform in the non-metastatic LNCaP cells. These data identify PEDF as a novel regulator of V-ATPase suggesting a new way by which PEDF may inhibit prostate tumor growth.

V-ATPase regulates communication between microvascular endothelial cells and metastatic cells.

To metastasize distant organs, tumor cells and endothelial cells lining the blood vessels must crosstalk. The nature of this communication that allows metastatic cells to intravasate and travel through the circulation and to extravasate to colonize different organs is poorly understood. In this study, we evaluated one of the first steps in this process­the proximity and physical interaction of endothelial and metastatic cells. To do this, we developed a cell separator chamber that allows endothelial and metastatic cells to grow side by side. We have shown in our previous studies that V-ATPases at the cell surface (pmV-ATPase) are involved in angiogenesis and metastasis. Therefore, we hypothesized that the physical proximity/interaction between endothelial and metastatic cells expressing pmV-ATPase will increase its activity in both cell types, and such activity in turn will increase pmV-ATPase expression on the membranes of both cell types. To determine pmV-ATPase activity we measured the proton fluxes (JH+) across the cell membrane. Our data indicated that interaction between endothelial and metastatic cells elicited a significant increase of JH+ via pmV-ATPase in both cell types. Bafilomycin, a V-ATPase inhibitor, significantly decrease JH+. In contrast, JH+ of the non-metastatic cells were not affected by the endothelial cells and vice-versa. Altogether, our data reveal that one of the early consequences of endothelial and metastatic cell interaction is an increase in pmV-ATPase that helps to acidify the extracellular medium and favors protease activity. These data emphasize the significance of the acidic tumor microenvironment enhancing a metastatic and invasive phenotype.

A high calorie diet induces type 2 diabetes in the desert sand rat (Psammomys obesus).

Diabetes mellitus type 2 is a major factor for cardiovascular diseases. The toxic effects of chronic hyperglycemia involve many alterations in the vascular tissue, including atherosclerosis. The pathogenesis of atherosclerosis in the diabetic syndrome (DS-II) has not been fully elucidated. A better understanding of the progress of DS-II at the level of the aorta could help us to identify inhibitors of atherosclerosis. Studies have shown that obesity and high calorie diet (HCD) are associated with the development of DS-II, however the lack of naturally occurring experimental models of DS-II have impaired to directly address these issues. We hypothesize that a HCD induces DS-II. This study (15 months duration) is designed to determine if HCD induces DS-II in the desert sand rat (Psammomys obesus; P. obesus). We also evaluated the histopathology of the aorta in animals fed with a laboratory chow pellets ad libitum (hypercaloric) and in control (animals fed with the naturally occurring hypocaloric diet; halophile plants). The weight and blood chemistry (glucose, lipids, and insulin levels) were evaluated periodically (once per week), and the histology of the aortas of these animals were assessed every 3 months for up to 12 months, during the development of DS-II. This study demonstrates that 40% of the animals in HCD develop DS-II at 3 months. Histological characterization demonstrates the typical alterations observed in atherosclerosis, i.e., alteration of the elastic fibers of the media layer and enrichment in collagen and glucosaminoglycans. This study demonstrates that P. obesus is an excellent animal model to study the progression of DS-II and the development of atherosclerosis.

Vacuolar-type H+-ATPases at the plasma membrane regulate pH and cell migration in microvascular endothelial cells.

Microvascular endothelial cells involved in angiogenesis are exposed to an acidic environment that is not conducive for growth and survival. These cells must exhibit a dynamic intracellular (cytosolic) pH (pHcyt) regulatory mechanism to cope with acidosis, in addition to the ubiquitous Na+/H+ exchanger and HCO3--based H+-transporting systems. We hypothesize that the presence of plasmalemmal vacuolar-type proton ATPases (pmV-ATPases) allows microvascular endothelial cells to better cope with this acidic environment and that pmV-ATPases are required for cell migration. This study indicates that microvascular endothelial cells, which are more migratory than macrovascular endothelial cells, express pmV-ATPases. Spectral imaging microscopy indicates a more alkaline pHcyt at the leading than at the lagging edge of microvascular endothelial cells. Treatment of microvascular endothelial cells with V-ATPase inhibitors decreases the proton fluxes via pmV-ATPases and cell migration. These data suggest that pmV-ATPases are essential for pHcyt regulation and cell migration in microvascular endothelial cells.