Marie-Chantal Farges

Effects of Enriched Environment on COX-2, Leptin and Eicosanoids in a Mouse Model of Breast Cancer

Cyclooxygenase-2 (COX-2) and adipokines have been implicated in breast cancer. This study investigated a possible link between COX-2 and adipokines in the development of mammary tumors. A model of environmental enrichment (EE), known to reduce tumor growth was used for a syngeneic murine model of mammary carcinoma. 3-week-old, female C57BL/6 mice were housed in standard environment (SE) or EE cages for 9 weeks and transplanted orthotopically with syngeneic EO771 adenocarcinoma cells into the right inguinal mammary fat pad. EE housing influenced mammary gland development with a decrease in COX-2 expressing cells and enhanced side-branching and advanced development of alveolar structures of the mammary gland. Tumor volume and weight were decreased in EE housed mice and were associated with a reduction in COX-2 and Ki67 levels, and an increase in caspase-3 levels. In tumors of SE mice, high COX-2 expression correlated with enhanced leptin detection. Non-tumor-bearing EE mice showed a significant increase in adiponectin levels but no change in those of leptin, F2-isoprostanes, PGF2α, IL-6, TNF-α, PAI-1, and MCP-1 levels. Both tumor-bearing groups (SE and EE housing) had increased resistin, IL-6, TNF-α, PAI-1 and MCP-1 levels irrespective of the different housing environment demonstrating higher inflammatory response due to the presence of the tumor. This study demonstrates that EE housing influenced normal mammary gland development and inhibited mammary tumor growth resulting in a marked decrease in intratumoral COX-2 activity and an increase in the plasma ratio of adiponectin/leptin levels.

Leptin, adipocytes and breast cancer: Focus on inflammation and anti-tumor immunity

More than one million new cases of breast cancer are diagnosed worldwide each year and more than 400,000 deaths are caused by the disease. The origin of this pathology is multifactorial and involved genetic, hormonal, environmental and nutritional factors including obesity in postmenopausal women. The role played by the adipose tissue and their secretions, ie adipokines, is beginning to be recognized. Plasma adipokine levels, which are modulated during obesity, could have “remote” effects on mammary carcinogenesis. Breast cancer cells are surrounded and locally influenced by an adipocyte microenvironment, which is probably more extensive in obese people. Hence, leptin appears to be strongly involved in mammary carcinogenesis and may contribute to the local pro-inflammatory mechanisms, especially in obese patients, who have increased metastatic potential and greater risk of mortality. This review presents the multifaceted role of leptin in breast cancer development and the different molecular pathways involved such as inflammation, oxidative stress and antitumor immunity.

Leptin modulates dose-dependently the metabolic and cytolytic activities of NK-92 cells.

Leptin, a hormone‐cytokine produced primarily in the adipose tissue, has pleiotropic effects on many biological systems and in several cell types, including immune cells. Hyperleptinemia is associated with immune dysfunction and carcinogenesis. Natural killer (NK) cells are critical mediators of anti‐tumor immunity, and leptin receptor deficiency in mice leads to impaired NK function. It was thus decided to explore the in vitro effects of leptin on human NK cell function. NK‐92 cells were cultured during 48u2009h with different leptin concentrations [absence, 10 (physiological), 100 (obesity), or 200u2009ng/ml (pharmacology)]. Their metabolic activity was assessed using the resazurin test. NK‐92 cell cytotoxicity and intracellular IFN‐γ production were analyzed by flow cytometry. NK‐92 cell mRNA and protein expression levels of cytotoxic effectors were determined by RT‐qPCR and Western blot. In our conditions, leptin exerted a dose‐dependent stimulatory effect on NK‐92 cell metabolic activity. In addition, high leptin concentrations enhanced NK‐92 cell cytotoxicity against K562‐EGFP and MDA‐MB‐231‐EGFP target cells and inversely reduced cytotoxicity against the MCF‐7‐EGFP target. At 100u2009ng/ml, leptin up‐regulated both NK cell granzyme B and TRAIL protein expressions and concomitantly down‐regulated perforin expression without affecting Fas‐L expression. In response to PMA/ionomycin stimulation, the proportion of IFN‐γ expressing NK‐92 cells increased with 100 and 200u2009ng/ml of leptin. In conclusion, leptin concentration, at obesity level, variably increased NK‐92 cell metabolic activity and modulated NK cell cytotoxicity according to the target cells. The underlying mechanisms are partly due to an up‐regulation of TRAIL and IFN‐γ expression and a down‐regulation of perforin. J. Cell. Physiol. 228: 1202–1209, 2013.

Free amino acid concentrations in milk: Effects of microwaveversus conventional heating

SummaryMicrowave effects on free amino acid concentrations in milkversus a water bath heating were investigated in view of their importance for infant growth. Concentrations of few amino acids, such as aspartate, serine or lysine, are unchanged whatever the way and the temperature of heating. In contrast, tryptophan concentrations decreased similarly whatever the way of heating (110 ± 3µmol/l before heatingvs 84 ± 4µmol/l after 30°C microwave heating, p < 0.05). On the contrary, concentrations of glutamate and glycine increased more after water bath heating at 90°C (325 ± 4 and 101 ± 1µmol/l, respectively) than after microwave heating (312 ± 4 and 95 ± 1µmol/l, respectively, p < 0.05) suggesting milk proteolysis. Moreover, the accumulation of ammonia observed at 90°C with the water bath together with increase Glu levels might reflect a degradation of glutamine. An ornithine enrichment, more evident with microwave heating, was shown and could be of interest as it is a polyamine precursor. Also, considering few variations of free amino acid concentrations and the time saved, microwave heating appears to be an appropriate method to heat milk.

l-Arginine and TNFα Production in Macrophages: A Focus on Metabolism, Aging, Metabolic Syndrome, and Type 2 Diabetes

Arginine (Arg) has long been known to be a major regulator of immunity via its metabolic and physiological functions. In the 1950s, it was classified as a non-essential amino acid by Rose since Arg could be synthesized at the whole body level, mainly in the kidneys, after the conversion of intestinal citrulline (Cit) via argininosuccinate synthase (ASS) and argininosuccinate lyase (ASL). But things changed when Barbul et al. (Surg Forum 28:101–103, 1977) observed, surprisingly, that Arg was an immunomodulator via a thymic effect. At the same time, they observed that Arg could be essential in several situations, like growth or sepsis. Finally in the 1990s, Albina et al. (J Immunol 147:144–148, 1991) demonstrated that macrophages were able to produce nitric oxide (NO). These pioneering observations opened a new field of research focused on the regulation of macrophage functions by Arg.

Enhancement of Lytic Activity by Leptin Is Independent From Lipid Rafts in Murine Primary Splenocytes

Leptin, a pleiotropic adipokine, is known as a regulator of food intake, but it is also involved in inflammation, immunity, cell proliferation, and survival. Leptin receptor is integrated inside cholesterol‐rich microdomains called lipid rafts, which, if disrupted or destroyed, could lead to a perturbation of lytic mechanism. Previous studies also reported that leptin could induce membrane remodeling. In this context, we studied the effect of membrane remodeling in lytic activity modulation induced by leptin. Thus, primary mouse splenocytes were incubated with methyl‐β‐cyclodextrin (β‐MCD), a lipid rafts disrupting agent, cholesterol, a major component of cell membranes, or ursodeoxycholic acid (UDCA), a membrane stabilizer agent for 1u2009h. These treatments were followed by splenocyte incubation with leptin (absence, 10 and 100u2009ng/ml). Unlike β‐MCD or cholesterol, UDCA was able to block leptin lytic induction. This result suggests that leptin increased the lytic activity of primary spleen cells against syngenic EO771 mammary cancer cells independently from lipid rafts but may involve membrane fluidity. Furthermore, natural killer cells were shown to be involved in the splenocyte lytic activity. To our knowledge it is the first publication in primary culture that provides the link between leptin lytic modulation and membrane remodeling. J. Cell. Physiol. 232: 101–109, 2017.

L’activité physique spontanée ralentit la croissance tumorale chez la souris C57/bl6 en situation d’obésité

Introduction et but de l’etude L’obesite est reconnue comme etant un facteur de risque du cancer du sein et de sa recidive apres la menopause. Il est etabli que les secretions adipokiniques modulent la capacite de proliferation des cellules epitheliales mammaires en culture. Par ailleurs, l’activite physique est un element regulateur des secretions adipokiniques. Ainsi, le but de cette etude etait de caracteriser in vivo l’impact de l’activite physique sur la secretion de leptine et le metabolisme energetique de l’animal, lors de la croissance tumorale en situation d’obesite. Materiel et methodes Des souris femelles C57/bl6xa0âgees (28xa0semaines) ovariectomisees placees ou non en environnement enrichi pour favoriser l’activite physique et les interactions sociales ( n xa0=xa010), ont ete nourries pendant 12xa0semaines avec un regime hyperlipidique (HLxa0: 4,3xa0kcal/g, lipides 45xa0% des AET). Apres 8xa0semaines, les cellules tumorales mammaires syngeniques (lignee EO 771) ont ete implantees dans la quatrieme paire de glande mammaire par la technique fat pad . La prise alimentaire, la prise de poids, l’activite physique, la composition corporelle des animaux et la croissance tumorale ont ete mesurees tout au long de l’experimentation. Au sacrifice des animaux (12xa0semaines), un bilan metabolique et hormonal a ete realise sur le plasma. Resultats La prise energetique journaliere etait de 12,8xa0±xa00,4xa0calories par jour et s’accompagnait d’une prise de masse grasse significative ( p 3 xa0contre 1222xa0±xa0482xa0mm 3 ( p p p Conclusion Un regime hyperlipidique associe a l’ovariectomie favorise l’augmentation de masse grasse et la croissance tumorale. Dans ce contexte, l’augmentation de l’activite physique spontanee due a l’environnement enrichi limite a la fois la prise de masse grasse et la croissance tumorales. Ces modifications s’accompagnent d’une amelioration de l’insulinoresistance, d’une diminution de l’inflammation a bas bruit associee a l’obesite.