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: 1200pg/ml) than during long days (LD: 200pg/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 (0.3mg/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.

Effect of a two-week treatment with a low dose of 2,2'4,4',5,5'-hexachlorobiphenyl (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) protein 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 with a 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.

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.

Photoperiod modulates access of 2,2',4,4',5,5'-hexachlorobiphenyl (PCB153) to the brain and its effect on gonadotropin and thyroid hormones in adult ewes.

The effects of photoperiod on the cerebrospinal fluid (CSF) concentration of six ortho-substituted polychlorinated biphenyls (PCBs: PCB28, PCB52, PCB101, PCB138, PCB153, and PCB180), the effects of an orally administered low dose of PCB153 (0.3mg/kg, three times a week for three weeks) on PCBs and thyroid hormones (THs) concentrations in the CSF and plasma, and the release of luteinizing hormone (LH) were determined in ovariectomized, estradiol-implanted ewes (2.5 years old) maintained indoors under artificial long day (LD, 16L: 8D) and short day (SD, 8L: 16D) conditions. Concentrations of two PCBs (PCB28 and PCB153) in the plasma and four PCBs in the CSF (PCB101, PCB138, PCB153, and PCB180) were significantly higher during LD than SD. Following PCB153 treatment, its concentration in the plasma was higher in SD (1.2 ± 0.3 ng/ml) than LD (0.2 ± 0.05 ng/ml), but similar in the CSF (10.2 ± 3.7 pg/ml vs. 13 ± 0.7 pg/ml) under both photoperiods. During SD, the concentration of PCB153 in the CSF was higher in treated animals than controls, while no differences were noted under LD. These findings indicate that in ewes, exposure of the brain to more highly chlorinated, ortho-substituted PCBs may be modulated by photoperiod. PCB153 treatment had no effect on plasma THs, but reduced total triiodothyronine concentration during LD and free thyroxine during SD in the CSF. Under both photoperiods, PCB153 reduced basal plasma LH and reinforced the inhibition of pulsatile LH release during LD. As PCB153 reduced LH and THs (which are involved in the seasonal control of reproduction in ewes), it may have a braking effect on seasonal transitions between active and inactive phases of reproduction.

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

Sheep from temperate latitudes exhibit seasonal variations in many physiological functions such as reproduction, food intake, body weight, and pelage growth. Majority of seasonal changes are controlled by the annual photoperiodic cycle and melatonin secretion. For reproduction, the resulting key event is a modulation of the negative feedback of steroids on gonadotropin secretion. However, this seasonal effect could also depend on variable uptake of steroids by the brain. Seasonal regulation of food intake also involves numerous peripheral hormones, among which the protein hormone leptin informs the brain on the metabolic status of the animal. It has been shown previously that access of progesterone, estradiol and leptin to the cerebrospinal fluid (CSF) increases under long days. This physiological modulation of the passage of hormones to the brain could depend on regulation of the permeability of the blood-CSF barrier. This study therefore compared the tight junction proteins in the choroid plexus of ewes exposed to short days or long days. Levels of occludin, zonula occludens proteins (ZO) ZO-1 and ZO-2, afadin and cadherin were significantly higher during short days, but no statistical difference was observed for junctional adhesion molecule 1 (JAM-1), ZO-3 or claudins 1 and 5. These results are consistent with an increase in the blood-CSF barrier permeability during long days through a regulation of tight junctions and show that the permeability could depend upon physiological conditions such as photoperiodic status.

Induction of human CD4+ regulatory T cells by mycophenolic acid-treated dendritic cells.

Depending on their degree of maturation, costimulatory molecule expression, and cytokine secretion, dendritic cells (DC) can induce immunity or tolerance. DC treated with mycophenolic acid during their maturation (MPA-DC) have a regulatory phenotype and may therefore provide a new approach to induce allograft tolerance. Purified CD4(+) T cells stimulated in a human in vitro model of mixed culture by allogeneic MPA-DC displayed much weaker proliferation than T cells activated by mature DC and were anergic. This hyporesponsiveness was alloantigen-specific. Interestingly, T cells stimulated by MPA-DC during long-term coculture in four 7-day cycles displayed potent, suppressive activity, as revealed by marked inhibition of the proliferation of naive and preactivated control T cells. These regulatory T cells (Tregs) appeared to have antigen specificity and were contact-dependent. Tregs induced by MPA-DC were CD25(+)glucocorticoid-induced TNFR(+)CTLA-4(+)CD95(+), secreted IL-5 and large amounts of IL-10 and TGF-beta, and displayed enhanced forkhead box p3 expression. These results obtained in vitro demonstrate that human MPA-DC can induce allospecific Tregs that may be exploited in cell therapy to induce allograft tolerance.

Anti CD25 treatment of human dendritic cells modulates both their cytokine synthesis profiles and their capacity to activate allogeneic CD4 T cells: a potential tolerogenic effect.

Recently, attention has been focused on the role for dendritic cells (DCs) in the promotion of peripheral tolerance. It is currently believed that the maturation/activation state of DCs might be a control point for the induction of graft tolerance through modifications of the activation state of T cells. We have observed IL-2, and IL-2 receptor gene expression by reverse transcriptase-polymerase chain reaction (RT-PCR) in human DC lysates following bacterial stimulation. It has been demonstrated in the present study IL-2R alpha (CD25) expression on human DCs upon LPS activation. DCs differentiated from monocytes were exposed to anti CD25 during maturation, anti CD25 treatment affected the abilities of human DCs to induce CD4+ T cell proliferation in response to alloantigens, maintained endocytic capacity, Anti CD25 treated DCs produce low levels of IL-12 and IFN and high level of IL-10. All these characteristics suggest that DCs may be used in cellular therapy either to induce allograft tolerance (anti CD25 treated DCs) or to restore immunity against tumors (IL-2 treated DCs).

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

BACKGROUND: 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 (BbC50SN) or LPS for 2 days. RESULTS: BbC50SN induced DC maturation, with increase in CD83, CD86, and HLA-DR expression. We also showed, for the first time, that BbC50SN prolonged DC survival, with high IL-10 and low IL-12 production compared with that seen in LPS-DCs. Moreover, BbC50SN 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 kappaB pathway but was associated with an upregulation of Bcl-xL and Phospho-Bad. Finally, BbC50SN 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 TH1 response and control the excessive TH2 polarization observed in atopic newborns.

Mycophenolic acid-treated human dendritic cells have a mature migratory phenotype and inhibit allogeneic responses via direct and indirect pathways.

Immature dendritic cells (DCs) can induce T-cell hyporesponsiveness, thus interfering with the process of DC maturation in a pro-inflammatory context, may therefore provide a novel approach to inducing allograft tolerance. We have studied the effects of mycophenolic acid (MPA), an immunosuppressive agent currently used in transplantation, using an in vitro model of a mixed human DC/alloreactive CD4(+) T lymphocyte culture. DCs differentiated from monocytes were exposed to MPA during maturation. MPA treatment affected the maturation of DCs, and this was reflected both in the impairment of the up-regulation of co-stimulatory molecule expression and the maintained endocytic capacity. However, MPA-DCs exhibited a distinctive microscopic morphology and secreted IL-10 and so could no longer be regarded as immature DC. Moreover, MPA-DCs had a mature phenotype for chemokine receptor expression, exhibiting down-regulation of CCR5 and up-regulation of CCR7. Interestingly, the abilities of the MPA-DCs to induce CD4(+) T-cell proliferation in response to alloantigens was impaired not only via direct but also via indirect pathways. The maintenance of endocytosis and the inhibition of syngeneic T-cell activation suggest that these cells could have a potential role to avoid chronic rejection. All these characteristics suggest that MPA-DCs may be used in cell therapy to induce allograft tolerance.

Effects of immunosuppressive drugs on dendritic cells and tolerance induction.

Dendritic cells, the most effective antigen-presenting cells for priming naive T cells and initiating immune responses, are also able to induce tolerance. This balance between immunity and tolerance depends on the functional stage of dendritic cells (DC). Activation of naive T cells by immature DC can induce tolerance. It is therefore of interest to summarize the effects of immunosuppressive agents on DC maturation and functions. In contrast to glucocorticosteroids, mycophenolate mofetil, and vitamin D(3) analogs, calcineurin inhibitors do not seem to inhibit DC maturation in in vitro culture systems. However, these molecules all appear to interfere with DC functions.