Lili Nimri

Orally administered glucans from the edible mushroom Pleurotus pulmonarius reduce acute inflammation in dextran sulfate sodium-induced experimental colitis.

Polysaccharides are one of the most potent mushroom-derived substances exhibiting anti-inflammatory and immunomodulatory properties. The aims of the present study were to determine whether orally administered glucans from the edible mushroom Pleurotus pulmonarius could attenuate or prevent the development of experimental colitis in mice. Colonic inflammation was induced in mice by treatment with 3.5 % dextran sulfate sodium (DSS) for 18 d. Before or after DSS administration, mice were given hot water solubles (HWS) or mycelium extract (ME) (2 or 20 mg per mouse) daily in their food. Colonic damage was macroscopically and histologically evaluated. Inflammation was assessed by changes in colon length, TNF-alpha levels released by colonic samples in organ culture and myeloperoxidase (MPO) activity. mRNA levels of pro-inflammatory (IL-1beta) and anti-inflammatory (IL-10) cytokines in colonic samples were determined by quantitative real-time RT-PCR. P. pulmonarius glucans attenuated and prevented the development of symptoms associated with DSS-induced colitis. High doses of HWS and ME blocked colon shortening, suppressed MPO activity and improved macroscopic score in all treatment groups. In addition, histological damage from colitis was reduced by HWS and ME at all doses. The tissue levels of TNF-alpha protein were significantly decreased and correlated with degree of inflammation and macroscopic score. All treatments significantly attenuated the increased DSS-mediated expression levels of IL-1beta. We conclude that the different glucan preparations (HWS or ME) harvested from P. pulmonarius when orally administered to DSS-treated mice attenuate the development of colonic inflammation, suggesting putative clinical utility for these extracts in the treatment of colitis.

Secreted Human Adipose Leptin Decreases Mitochondrial Respiration in HCT116 Colon Cancer Cells

Obesity is a key risk factor for the development of colon cancer; however, the endocrine/paracrine/metabolic networks mediating this connection are poorly understood. Here we hypothesize that obesity results in secreted products from adipose tissue that induce malignancy-related metabolic alterations in colon cancer cells. Human HCT116 colon cancer cells, were exposed to conditioned media from cultured human adipose tissue fragments of obese vs. non-obese subjects. Oxygen consumption rate (OCR, mostly mitochondrial respiration) and extracellular acidification rate (ECAR, mostly lactate production via glycolysis) were examined vis-à-vis cell viability and expression of related genes and proteins. Our results show that conditioned media from obese (vs. non-obese) subjects decreased basal (40%, p<0.05) and maximal (50%, p<0.05) OCR and gene expression of mitochondrial proteins and Bax without affecting cell viability or expression of glycolytic enzymes. Similar changes could be recapitulated by incubating cells with leptin, whereas, leptin-receptor specific antagonist inhibited the reduced OCR induced by conditioned media from obese subjects. We conclude that secreted products from the adipose tissue of obese subjects inhibit mitochondrial respiration and function in HCT116 colon cancer cells, an effect that is at least partly mediated by leptin. These results highlight a putative novel mechanism for obesity-associated risk of gastrointestinal malignancies, and suggest potential new therapeutic avenues.

Restoration of caveolin‐1 expression suppresses growth, membrane‐type‐4 metalloproteinase expression and metastasis‐associated activities in colon cancer cells

Caveolin‐1 (cav‐1) and flotillin‐1 are two major structural proteins associated with lipid rafts in mammalian cells. The membrane‐type matrix metalloproteinases (MT‐MMPs) are expressed at the cell surface, hydrolyze extracellular matrix, and play an important role in cancer cell migration and metastasis. Expression of cav‐1, flotillin‐1, and MT4‐MMP in lysates and lipid rafts of LS174T and HM‐7 colon cancer cells was determined. The impact of restoration of cav‐1 expression on proliferation, adhesion, motility in vitro, and growth of implanted tumors in vivo was characterized. Cav‐1 is not expressed in lipid rafts of the highly metastatic colon cancer cell line (HM‐7), but expressed in cytosolic fractions of the parental lower metastatic cell line (LS174T). In contrast, MT4‐MMP was expressed in lipid rafts of HM‐7 cells but not in LS174T cells. Overexpression of cav‐1 in HM‐7 cells down‐regulate proliferation, viability, wound closure, adhesion to laminin, invasion, and development of filopodial and lamellipodial structures in a dose‐dependent manner. Cav‐1 positive HM‐7 clones ceased to express MT4‐MMP in their lipid rafts. Comparative proteomic analyses of lipid rafts from cav‐1 positive and cav‐1 negative cells demonstrated de novo expression of flotillin‐1 only on the cells expressing cav‐1. Xenografting control cells devoid of cav‐1 in nude mice induced development of bigger tumors expressing higher levels of proliferating cell nuclear antigen as compared to mice injected with cells expressing the highest cav‐1 levels. We conclude that cav‐1 orchestrates and reorganize several proteins in lipid rafts, activities directly associated with reduced tumorigenic and metastatic ability of colon cancer cells.

Mechanisms linking obesity to altered metabolism in mice colon carcinogenesis.

There are an increasing number of reports on obesity being a key risk factor for the development of colon cancer. Our goal in this study was to explore the metabolic networks and molecular signaling pathways linking obesity, adipose tissue and colon cancer. Using in-vivo experiments, we found that mice fed a high-fat diet (HFD) and injected with MC38 colon cancer cells develop significantly larger tumors than their counterparts fed a control diet. In ex-vivo experiments, MC38 and CT26 colon cancer cells exposed to conditioned media (CM) from the adipose tissue of HFD-fed mice demonstrated significantly lower oxygen consumption rate as well as lower maximal oxygen consumption rate after carbonyl cyanide-4-trifluoromethoxy-phenylhydrazone treatment. In addition, in-vitro assays showed downregulated expression of mitochondrial genes in colon cancer cells exposed to CM prepared from the visceral fat of HFD-fed mice or to leptin. Interestingly, leptin levels detected in the media of adipose tissue explants co-cultured with MC38 cancer cells were higher than in adipose tissue explants cultures, indicating cross talk between the adipose tissue and the cancer cells. Salient findings of the present study demonstrate that this crosstalk is mediated at least partially by the JNK/STAT3-signaling pathway.

A recombinant fungal compound induces anti-proliferative and pro-apoptotic effects on colon cancer cells

Finding intracellular pathways and molecules that can prevent the proliferation of colon cancer cells can provide significant bases for developing treatments for this disease. Ostreolysin (Oly) is a protein found in the mushroom Pleurotus ostreatus, and we have produced a recombinant version of this protein (rOly). We measured the viability of several colon cancer cells treated with rOly. Xenografts and syngeneic colon cancer cells were injected into in vivo mouse models, which were then treated with this recombinant protein. rOly treatment induced a significant reduction in viability of human and mouse colon cancer cells. In contrast, there was no reduction in the viability of normal epithelial cells from the small intestine. In the search for cellular targets of rOly, we showed that it enhances the anti-proliferative activity of drugs targeting cellular tubulin. This was accompanied by a reduction in the weight and volume of tumours in mice injected with rOly as compared to their respective control mice in two in vivo models. Our results advance the functional understanding of rOly as a potential anti-cancer treatment associated with pro-apoptotic activities preferentially targeting colon cancer cells.

Ostreolysin induces browning of adipocytes and ameliorates hepatic steatosis: Ostreolysin induces browning of adipocytes and ameliorates hepatic steatosis

Non‐alcoholic fatty liver disease (NAFLD) is associated with all features of the metabolic syndrome. Deposition of excess triglycerides in liver cells, a hallmark of NAFLD, is associated with loss of insulin sensitivity. Ostreolysin (Oly) is a 15‐kDa fungal protein known to interact with cholesterol‐enriched raft‐like membrane domains. We aim to test whether a recombinant version of Oly (rOly) can induce functional changes in vitro in adipocytes or in vivo in mice fed a high‐fat diet (HFD).

Recombinant ostreolysin induces brown fat‐like phenotype in HIB‐1B cells

SCOPE Brown adipose tissue (BAT) is the main regulator of thermogenesis by increasing energy expenditure through the uncoupling of oxidative metabolism from ATP synthesis. There is a growing body of evidence for BAT being the key responsible organ in combating obesity and its related disorders. Herein we propose the fungal protein ostreolysin (Oly), which has been previously shown to bind to cholesterol-enriched raft-like membrane domains (lipid rafts) of mammalian cells, as a suitable candidate for interaction with brown preadipocytes. The aim of the present study was therefore to characterize the mechanism by which a recombinant version of ostreolysin (rOly) induces brown adipocyte differentiation. METHODS AND RESULTS Primary isolated brown preadipocytes or HIB-1B brown preadipocyte cells were treated with rOly and the effects on morphology, lipid accumulation, respiration rate, and associated gene and protein expression were measured. rOly upregulated mRNA and protein levels of factors related to brown adipocyte differentiation, induced lipid droplet formation, and increased cellular respiration rate due to expression of uncoupling protein 1. rOly also upregulated β-tubulin expression, and therefore microtubules might be involved in its mechanism of action. CONCLUSION rOly promotes brown adipocyte differentiation, suggesting a new mechanism for rOlys contribution to the battle against obesity.

Erratum to: Glucans from the edible mushroom Pleurotus pulmonarius

On page 510, Fig. 2, the legend should be as follows: ‘‘Fig. 2. Effects of treatments on formation of aberrant crypt foci (ACF) in mice. On day 40, the colons of 5 mice per group (1–8) were removed and fixed flat. The colon was stained with methylene blue (0.1 %). The mucosal side of the colon was examined for ACF under a light microscope, and these were counted when identified. a Number of ACF/cm colon was assessed. *P \ 0.01 as compared to AOM/DSS group (group 2). b Representative picture from control mice. c Representative picture from AOM ? DSStreated mice. d Immunohistochemical analyses of PCNA staining: quantification of proliferating cell nuclear antigen (PCNA) staining, which was determined in colon tissues in mice of experimental groups 1 through 8 (see ’Materials and methods’). *P \ 0.05 as compared to AOM/DSS group (group 2). e Representative pictures from control mice. f Representative pictures from AOM ? DSS-treated mice. Bars in the pictures indicate magnification (100 lm). FBE fruiting body extract; ME mycelia extract of the edible mushroom Pleurotus pulmonarius; CMC carboxymethylcellulose.’’