Tight junction proteins vary in the choroid plexus of ewes according to photoperiod

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Supernatant of Bifidobacterium breve induces dendritic cell maturation, activation, and survival through a Toll-like receptor 2 pathway

International audienceBackground: Commensal gut bacteria are essential for the development and maintenance of the gut's immune system. Some bacteria strains, such as Lactobacillus and Bifidobacterium species, have been reported to provide protection from allergic and inflammatory bowel diseases. However, the interactions between these commensal bacteria and the immune system are largely unknown. Objective: We studied the effects of a supernatant from the culture of B breve C50 (BbC50) on the maturation, activation, and survival of human dendritic cells (DCs). Methods: DCs were differentiated from human monocytes with IL-4 and GM-CSF for 5 days and cultured with BbC50 supernatant (BbC50 SN) or LPS for 2 days. Results: BbC50 SN induced DC maturation, with increase in CD83, CD86, and HLA-DR expression. We also showed, for the first time, that BbC50 SN prolonged DC survival, with high IL-10 and low IL-12 production compared with that seen in LPS-DCs. Moreover, BbC50 SN inhibited the effects of LPS on DCs, both in terms of IL-12 production and in terms of survival. The prolonged DC survival was independent of IL-10 production and nuclear factor kB pathway but was associated with an upregulation of Bcl-x L and Phospho-Bad. Finally, BbC50 SN induced activation of Toll-like receptor 2 (TLR2)–transfected cells in contrast to TLR4-, TLR7-, and TLR9-transfected cells. Conclusion: The supernatant of B breve C50 can induce DC maturation and prolonged DC survival through TLR2, with high IL-10 production. These properties might correspond to a regulatory DC profile, which could limit the excessive T H 1 response and control the excessive T H 2 polarization observed in atopic newborns. (J Allergy Clin Immunol 2006;117:696-702.) Live commensal microflora is essential for the development of the gut's immune system. 1 Some bacteria, such as Lactobacillus and Bifidobacterium species, described as ''living microorganisms exerting health benefit,'' 2 define the concept of probiotics. These bacteria have been reported to prevent and treat rotavirus infections and postantibiotic diarrhea, 3,4 allergic diseases, 5-7 and recurrence of inflammatory bowel disease. 8,9 These studies suggest that the intestinal immune system could be a privileged target of probiotics. Nevertheless, despite several studies reporting modifications of immunologic parameters induced by probiotic bacteria, the interactions between the cells of the intestinal immune system and bacteria remain largely unknown. 10 However, it has been shown that killed probiotic bacteria can affect the maturation and cytokine secretion profile of dendritic cells (DCs), 11,12 which represent potent antigen-presenting cells. DCs also have properties to induce negative regulation , with generation of regulatory T cells. 13 DCs can be activated by bacterial components through the interaction between pathogen-derived immunostimulatory molecules from bacteria and membrane receptors called pattern-recognition receptors, including the Toll-like receptor (TLR) family. 14 The different TLRs recognize a broad spectrum of highly conserved microbial structures, such as proteins, lipids, glycoproteins, and nucleic acid motifs, contained in the wall, cytoplasm, and nucleus of bacteria. TLR engagement could therefore have different types of effects on DC activation according to the bacteria strain. 15 Because of these properties, DCs represent a potential target of probi-otic bacteria. Menard et al 16 recently reported that active bacterial products from Bifidobacterium breve C50 (BbC50) could cross an intestinal monolayer of epithelial cells. We therefore studied the effects of a supernatant of BbC50 (BbC50 SN) on human monocyte-derived DCs in vitro to define the interactions with the immune system. In our model BbC50 SN was able to mature and fully activate DCs, inducing a particular cytokine synthesis profile and prolonged DC survival through a TLR2 pathway. Abbreviations used 7-AAD: 7-Amino actinomycin D BbC50: Bifidobacterium breve C50 BbC50 SN : Supernatant of Bifidobacterium breve C50 BbC50 SN-DC: DC treated with BbC50 SN DC: Dendritic cell NF: Nuclear factor PE: Phycoerythrin TLR: Toll-like recepto

Targeting MT1 and MT2 melatonin receptors with fluorescent ligands: assay on cell cultures and brain tissues

National audienc

Effect of a two-week treatment with a low dose of 2,2'4,4' 5,5'-hexacholorobiphenyl (PCB153) on tight junction protein expression in ovine choroid plexus during long and short photoperiods

Ortho-substituted polychlorinated biphenyls (PCBs) preferentially accumulate in the brain and cerebrospinal fluid (CSF) compared to other PCBs. We previously reported that the same dose of 2,2',4,4',5,5'-hexachlorobiphenyl (PCB153) induced higher concentrations in the CSF of treated animals compared to controls during short days (SD), while no differences were observed during long days (LD). Similarly, the plasma concentration of PCB153 in treated ewes was higher during SD than LD. To understand the structural and molecular events explaining the photoperiodically different concentration of PCBs in the CSF in sheep, we studied the effect of photoperiod on PCB153 action on tight junction (TJ) proteins expression in the choroid plexus (CP) of ewes. For that purpose, we collected CP from ovariectomised, estradiol-treated ewes maintained under artificial LD or SD and orally administered low dose (0.33 mg/kg/day, 3 times per week for 3 weeks) of PCB153 or vehicle. Exposure to PCB153 affected TJ proteins only during SD, and the levels of claudin-1, zonula occludens-2 (ZO-2), and afadin (AF-6) were significantly lower when compared to vehicle-treated animals. No differences were observed for occludin, junctional adhesion molecule-1 (JAM-1), claudin-5, ZO-1 and ZO-3. There was no effect of PCB153 treatment on TJ-mRNA levels. These results indicate that PCB153 selectively alters TJ proteins in the ovine CP. These alterations appear to be associated with the level of PCB153 in the blood plasma, which is modulated by the photoperiod. This study emphasises the importance of photoperiod in the susceptibility of adult sheep to PCBs

PCB153 (2,2′,4,4′,5,5′-hexachlorobiphenyl) differentially affects the VEGF/VEGFR system depending on photoperiod in the ovine choroid plexus

Ortho-substituted polychlorinated biphenyls (PCBs) preferentially accumulate in the brain and cerebrospinal fluid (CSF) compared with other PCBs. We previously demonstrated in ewes that an identical dose of PCB153, the most environmentally prevalent congener, resulted in a higher plasma concentration during short days (SD: 1200 pg/ml) than during long days (LD: 200 pg/ml). Moreover, PCB153 treatment only reduced the SD tight junction protein content in the choroid plexus (CP), which was followed by a significant increase of the PCB153 concentration in the CSF. The aim of the present study was to evaluate how PCB153 treatment affects the VEGF/VEGFR system that maintains CSF homoeostasis and CP function. To do so, we collected CPs from ovariectomised, oestradiol-replaced adult ewes maintained under artificial LD or SD and treated them per os with low doses of PCB153 (0.3 mg/kg, 3 times a week for 3 weeks). Exposure to PCB153 significantly affected (P<0.05) the VEGF/VEGFR system during the SD period, provoking increases in VEGF164 mRNA and protein levels and decreases in VEGFR-1 mRNA levels and VEGFR-2 mRNA and protein levels. These results suggest that exposure to environmentally relevant dose of PCB153 affects the VEGF/VEGFR system, which is involved in the fenestration of the CP endothelium and therefore in CSF production

Fluorescent ligands to target MT1 and MT2 melatonin receptors

International audienc

Brain passage of PCB 153 under different photoperiods and effects on ovine reproductive axis

National audienc

Development of fluorescent molecules to study MT1 and MT2 melatonin receptors

International audienc

Pattern of expression of vascular endothelial growth factor and its receptors in the ovine choroid plexus during long and short photoperiods

Vascular endothelial growth factor (VEGF-A) plays an important role in maintaining cerebrospinal fluid (CSF) homeostasis and the function of the choroid plexuses (CPs). The objective of the study was to determine the expression of vascular endothelial growth factor (VEGF-A), tyrosine kinase receptors Flt-1 and KDR and KDR co-receptor neuropilin 1 (NRP-1) in ovine CPs during different photoperiods. CPs were collected from the lateral brain ventricles from ovariectomized, estradiol-treated ewes during long day (LD; 16L:8D, n = 5) and short day (SD; 8L:16D, n = 5) photoperiods. We analyzed mRNA expression levels of two VEGF-A isoforms, VEGF-A (120) and VEGF-A (164) and our results indicate that VEGF-A (164) was the predominant isoform. Expression levels of VEGF-A and Flt-1 were similar during the SD and LD photoperiods. There were significant increases in KDR mRNA and protein expression (p < 0.05) and NRP-1 mRNA expression (p < 0.05) during SD. These data show that expression of KDR and its co-receptor NRP-1 are up-regulated by short photoperiod and that this effect is not dependent on ovarian steroids. Our results suggest that the VEGF-A-system may be involved in photoperiodic plasticity of CP capillaries and may therefore be responsible for photoperiodic changes in the CSF turnover rate in ewes