Interindividual variation contributes to differential PCB 126 induced gene expression in primary breast epithelial cells and tissues.

PCB 126 is a pervasive, dioxin-like chemical pollutant which can activate the aryl hydrocarbon receptor (AhR). Despite being banned from the market, PCB 126 can be detected in breast milk to this day. The extent to which interindividual variation impacts the adverse responses to this chemical in the breast tissue remains unclear. This study aimed to investigate the impact of 3 nM PCB 126 on gene expression in a panel of genetically diverse benign human breast epithelial cell (HBEC) cultures and patient derived breast tissues. Six patient derived HBEC cultures were treated with 3 nM PCB 126. RNAseq was used to interrogate the impact of exposure on differential gene expression. Gene expression changes from the top critical pathways were confirmed via qRT-PCR in a larger panel of benign patient derived HBEC cultures, as well as in patient-derived breast tissue explant cultures. RNAseq analysis of HBEC cultures revealed a signature of 144 genes significantly altered by 3 nM PCB 126 treatment. Confirmation of 8 targets using a panel of 12 HBEC cultures and commercially available breast cell lines demonstrated that while the induction of canonical downstream target gene, CYP1A1, was consistent across our primary HBECs, other genes including AREG, S100A8, IL1A, IL1B, MMP7, and CCL28 exhibited significant variability across individuals. The dependence on the activity of the aryl hydrocarbon receptor was confirmed using inhibitors. PCB 126 can induce significant and consistent changes in gene expression associated with xenobiotic metabolism in benign breast epithelial cells. Although the induction of most genes was reliant on the AhR, significant variability was noted between genes and individuals. These data suggest that there is a bifurcation of the pathway following AhR activation that contributes to the variation in interindividual responses.

The use of patient-derived breast tissue explants to study macrophage polarization and the effects of environmental chemical exposure.

Ex vivo mammary explant systems are an excellent model to study interactions between epithelium and stromal cell types because they contain physiologically relevant heterotypic interactions in the background of genetically diverse patients. The intact human mammary tissue, termed patient-derived explant (PDE), can be used to investigate cellular responses to a wide variety of external stimuli in situ. For this study, we examined the impact of cytokines or environmental chemicals on macrophage phenotypes. We demonstrate that we can polarize macrophages within human breast tissue PDEs toward M1 or M2 through the addition of interferon-γ (IFNγ) + lipopolysaccharide (LPS) or interleukin (IL)-4 + IL-13, respectively. Elevated expression levels of M(IFNγ + LPS) markers (HLADRA and CXCL10) or M(IL-4 + IL-13) markers (CD209 and CCL18) were observed in cytokine-treated tissues. We also examined the impact of the endocrine-disrupting chemical, benzophenone-3, on PDEs and measured significant, yet varying effects on macrophage polarization. Furthermore, a subset of the PDEs respond to IL-4 + IL-13 through downregulation of E-cadherin and upregulation of vimentin which is reminiscent of epithelial-to-mesenchymal transition (EMT) changes. Finally, we were able to show immortalized nonmalignant breast epithelial cells can exhibit EMT characteristics when exposed to growth factors secreted by M(IL-4 + IL-13) macrophages. Taken together, the PDE model system is an outstanding preclinical model to study early tissue-resident immune responses and effects on epithelial and stromal responses to stimuli found both endogenously in the breast and exogenously as a result of exposures.

Fit αß T-cell receptor suppresses leukemogenesis of Pten-deficient thymocytes.

Signaling through the αßT cell receptor (TCR) is a crucial determinant of T-cell fate and can induce two opposite outcomes during thymocyte development: cell death or survival and differentiation. To date, the role played by T-cell receptor in the oncogenic transformation of developing T cells remains unclear. Here we show that human primary T-cell acute lymphoblastic leukemias expressing an αßT cell receptor are frequently deficient for phosphatase and tensin homolog protein (PTEN), and fail to respond strongly to T-cell receptor activation. Using Pten-deficient T-cell acute lymphoblastic leukemia mouse models, we confirm that T-cell receptor signaling is involved in leukemogenesis. We show that abrogation of T-cell receptor expression accelerated tumor onset, while enforced expression of a fit transgenic T-cell receptor led to the development of T-cell receptor-negative lymphoma and delayed tumorigenesis. We further demonstrate that pre-tumoral Pten-deficient thymocytes harboring fit T-cell receptors undergo early clonal deletion, thus preventing their malignant transformation, while cells with unfit T-cell receptors that should normally be deleted during positive selection, pass selection and develop T-cell acute lymphoblastic leukemias. Altogether, our data show that fit T-cell receptor signaling suppresses tumor development mediated by Pten loss-of-function and point towards a role of Pten in positive selection.

Inhaling xenon ameliorates l-dopa-induced dyskinesia in experimental parkinsonism.

Parkinson's disease motor symptoms are treated with levodopa, but long-term treatment leads to disabling dyskinesia. Altered synaptic transmission and maladaptive plasticity of corticostriatal glutamatergic projections play a critical role in the pathophysiology of dyskinesia. Because the noble gas xenon inhibits excitatory glutamatergic signaling, primarily through allosteric antagonism of the N-methyl-d-aspartate receptors, we aimed to test its putative antidyskinetic capabilities. We first studied the direct effect of xenon gas exposure on corticostriatal plasticity in a murine model of levodopa-induced dyskinesia We then studied the impact of xenon inhalation on behavioral dyskinetic manifestations in the gold-standard rat and primate models of PD and levodopa-induced dyskinesia. Last, we studied the effect of xenon inhalation on axial gait and posture deficits in a primate model of PD with levodopa-induced dyskinesia. This study shows that xenon gas exposure (1) normalized synaptic transmission and reversed maladaptive plasticity of corticostriatal glutamatergic projections associated with levodopa-induced dyskinesia, (2) ameliorated dyskinesia in rat and nonhuman primate models of PD and dyskinesia, and (3) improved gait performance in a nonhuman primate model of PD. These results pave the way for clinical testing of this unconventional but safe approach. © 2018 The Authors. Movement Disorders published by Wiley Periodicals, Inc. on behalf of International Parkinson and Movement Disorder Society.

Individual-specific variation in the respiratory activities of HMECs and their bioenergetic response to IGF1 and TNFα.

Metabolic reprograming is a hallmark of cancer cells. However, the roles of pre-existing differences in normal cells metabolism toward cancer risk is not known. In order to assess pre-existing variations in normal cell metabolism, we have quantified the inter-individual variation in oxidative metabolism of normal primary human mammary epithelial cells (HMECs). We then assessed their response to selected cytokines such as insulin growth factor 1 (IGF1) and tumor necrosis factor alpha (TNFα), which are associated with breast cancer risk. Specifically, we compared the oxidative metabolism of HMECs obtained from women with breast cancer and without cancer. Our data show considerable inter-individual variation in respiratory activities of HMECs from different women. A bioenergetic parameter called pyruvate-stimulated respiration (PySR) was identified as a key distinguishing feature of HMECs from women with breast cancer and without cancer. Samples showing PySR over 20% of basal respiration rate were considered PySR+ve and the rest as PySR-ve . By this criterion, HMECs from tumor-affected breasts (AB) and non-tumor affected breasts (NAB) of cancer patients were mostly PySR-ve (88% and 89%, respectively), while HMECs from non-cancer patients were mostly PySR+ve (57%). This suggests that PySR-ve/+ve phenotypes are individual-specific and are not caused by field effects due to the presence of tumor. The effects of IGF1 and TNFα treatments on HMECs revealed that both suppressed respiration and extracellular acidification. In addition, IGF1 altered PySR-ve/+ve phenotypes. These results reveal individual-specific differences in pyruvate metabolism of normal breast epithelial cells and its association with breast cancer risk.

Regulation of early growth response 2 expression by secreted frizzled related protein 1.

BACKGROUND: Secreted frizzled-related protein 1 (SFRP1) expression is down-regulated in a multitude of cancers, including breast cancer. Loss of Sfrp1 also exacerbates weight gain as well as inflammation. Additionally, loss of SFRP1 enhances TGF-ß signaling and the downstream MAPK pathway. TGF-ß has been shown to increase the expression of Early Growth Response 2 (EGR2), a transcription factor implicated in immune function in a wide variety of cell types. The work described here was initiated to determine whether SFRP1 modulation affects TGF-ß mediated EGR2 expression in mammary tissues as well as macrophage polarization. METHODS: Real-time PCR analysis was performed to examine EGR2 expression in human and murine mammary epithelial cells and tissues in response to SFRP1 modulation. Chemical inhibition was employed to investigate the roles TGF-ß and MAPK signaling play in the control of EGR2 expression in response to SFRP1 loss. Primary murine macrophages were isolated from Sfrp1-/- mice and stimulated to become either M1 or M2 macrophages, treated with recombinant SFRP1, and real-time PCR was used to measure the expression of murine specific M1/M2 markers [Egr2 (M2) and Gpr18 (M1)]. Immunohistochemical analysis was used to measure the expression of human specific M1/M2 markers [CD163 (M2) and HLA-DRA (M2)] in response to rSFRP1 treatment in human mammary explant tissue. RESULTS: Knockdown of SFRP1 expression increases the expression of EGR2 mRNA in human mammary epithelial cells and addition of rSFRP1 decreases the expression of EGR2 when added to explant mammary gland tissues. Chemical inhibition of both TGF-ß and MAPK signaling in Sfrp1-/- or knockdown mammary epithelial cells results in decreased expression of EGR2. Stimulated murine macrophages obtained from Sfrp1-/- mice and treated with rSFRP1 exhibit a reduction in Egr2 expression and an increase in Gpr18 mRNA expression. Human mammary explant tissue treated with rSFRP1 decreases CD163 protein expression whereas there was no effect on the expression of HLA-DRA. CONCLUSIONS: Loss of SFRP1 likely contributes to tumor progression by altering the expression of a critical transcription factor in both the epithelium and the immune system.

Prototypic and arkypallidal neurons in the dopamine-intact external globus pallidus.

Studies in dopamine-depleted rats indicate that the external globus pallidus (GPe) contains two main types of GABAergic projection cell; so-called "prototypic" and "arkypallidal" neurons. Here, we used correlative anatomical and electrophysiological approaches in rats to determine whether and how this dichotomous organization applies to the dopamine-intact GPe. Prototypic neurons coexpressed the transcription factors Nkx2-1 and Lhx6, comprised approximately two-thirds of all GPe neurons, and were the major GPe cell type innervating the subthalamic nucleus (STN). In contrast, arkypallidal neurons expressed the transcription factor FoxP2, constituted just over one-fourth of GPe neurons, and innervated the striatum but not STN. In anesthetized dopamine-intact rats, molecularly identified prototypic neurons fired at relatively high rates and with high regularity, regardless of brain state (slow-wave activity or spontaneous activation). On average, arkypallidal neurons fired at lower rates and regularities than prototypic neurons, and the two cell types could be further distinguished by the temporal coupling of their firing to ongoing cortical oscillations. Complementing the activity differences observed in vivo, the autonomous firing of identified arkypallidal neurons in vitro was slower and more variable than that of prototypic neurons, which tallied with arkypallidal neurons displaying lower amplitudes of a "persistent" sodium current important for such pacemaking. Arkypallidal neurons also exhibited weaker driven and rebound firing compared with prototypic neurons. In conclusion, our data support the concept that a dichotomous functional organization, as actioned by arkypallidal and prototypic neurons with specialized molecular, structural, and physiological properties, is fundamental to the operations of the dopamine-intact GPe.

In the absence of its cytosolic domain, the CD28 molecule still contributes to T cell activation.

The CD28 costimulatory receptor has a pivotal role in T cell biology as this molecule amplifies T cell receptor (TCR) signals to provide an efficient immune T cell response. There is a large debate about how CD28 mediates these signals. Here, we designed a CD28 gene-targeted knock-in mouse strain lacking the cytoplasmic tail of CD28. As is the case in CD28-deficient (CD28 knock-out) mice, regulatory T cell homeostasis and T cell activation are altered in these CD28 knock-in mice. Unexpectedly, the presence of a CD28 molecule deprived of its cytoplasmic tail could partially induce some early activation events in T cells such as signaling events or expression of early activation markers. These results unravel a new mechanism of T cell costimulation by CD28, independent of its cytoplasmic tail.

Dopamine-dependent long-term depression at subthalamo-nigral synapses is lost in experimental parkinsonism.

Impairments of synaptic plasticity are a hallmark of several neurological disorders, including Parkinson's disease (PD) which results from the progressive loss of dopaminergic neurons of the substantia nigra pars compacta leading to abnormal activity within the basal ganglia (BG) network and pathological motor symptoms. Indeed, disrupted plasticity at corticostriatal glutamatergic synapses, the gateway of the BG, is correlated to the onset of PD-related movement disorders and thus has been proposed to be a key neural substrate regulating information flow and motor function in BG circuits. However, a critical question is whether similar plasticity impairments could occur at other glutamatergic connections within the BG that would also affect the inhibitory influence of the network on the motor thalamus. Here, we show that long-term plasticity at subthalamo-nigral glutamatergic synapses (STN-SNr) sculpting the activity patterns of nigral neurons, the main output of the network, is also affected in experimental parkinsonism. Using whole-cell patch-clamp in acute rat brain slices, we describe a molecular pathway supporting an activity-dependent long-term depression of STN-SNr synapses through an NMDAR-and D1/5 dopamine receptor-mediated endocytosis of synaptic AMPA glutamate receptors. We also show that this plastic property is lost in an experimental rat model of PD but can be restored through the recruitment of dopamine D1/5 receptors. Altogether, our findings suggest that pathological impairments of subthalamo-nigral plasticity may enhance BG outputs and thereby contribute to PD-related motor dysfunctions.

Inhibiting subthalamic D5 receptor constitutive activity alleviates abnormal electrical activity and reverses motor impairment in a rat model of Parkinson's disease.

Burst firing has been reported as a pathological activity of subthalamic nucleus (STN) neurons in Parkinson's disease. However, the origin of bursts and their causal link with motor deficits remain unknown. Here we tested the hypothesis that dopamine D5 receptors (D5Rs), characterized by a high constitutive activity, may contribute to the emergence of burst firing in STN. We tested whether inhibiting D5R constitutive activity depresses burst firing and alleviates motor impairments in the 6-OHDA rat model of Parkinson's disease. Intrasubthalamic microinjections of either an inverse agonist of D5Rs, flupenthixol, or a D2R antagonist, raclopride, were applied. Behavioral experiments, in vivo and in vitro electrophysiological recordings, and ex vivo functional neuroanatomy studies were performed. Using [(5)S]GTPγ binding autoradiography, we show that application of flupenthixol inhibits D5R constitutive activity within the STN. Furthermore, flupenthixol reduced evoked burst in brain slices and converted pathological burst firing into physiological tonic, single-spike firing in 6-OHDA rats in vivo. This later action was mimicked by calciseptine, a Cav1 channel blocker. Moreover, the same treatment dramatically attenuated motor impairment in this model and normalized metabolic hyperactivity in both STN and substantia nigra pars reticulata, the main output structure of basal ganglia in rats. In contrast, raclopride as well as saline did not reverse burst firing and motor deficits, confirming the selective action of flupenthixol on D5Rs. These results are the first to demonstrate that subthalamic D5Rs are involved in the pathophysiology of Parkinson's disease and that administering an inverse agonist of these receptors may lessen motor symptoms.

Benzophenone-3 exposure alters composition of tumor infiltrating immune cells and increases lung seeding of 4T1 breast cancer cells.

Environmental chemicals are a persistent and pervasive part of everyday life. A subset of environmental chemicals are xenoestrogens, compounds that bind to the estrogen receptor (ER) and drive estrogen-related processes. One such chemical, benzophenone-3 (BP3), is a common chemical in sunscreen. It is a potent UV protectant but also is quickly absorbed through the skin. While it has been approved by the FDA, there is a renewed interest in the safety of BP3, particularly in relation to breast cancer. The focus of this study was to examine the impact that BP3 has on triple negative breast cancer (TNBC) through alterations to cells in the immune microenvironment. In this study, we exposed female mice to one of two doses of BP3 before injecting them with a TNBC cell line. Several immune endpoints were examined both in the primary tissues and from in vitro studies of T cell behavior. Our studies revealed that in the lung tumor microenvironment, exposure to BP3 not only increased the number of metastases, but also the total area of tumor coverage. We also found that BP3 caused alterations in immune populations in a tissue-dependent manner, particularly in T cells. Taken together, our data suggest that while BP3 may not directly affect the proliferation of TNBC, growth and metastasis of TNBC-derived tumors can be altered by BP3 exposures via the alterations in the immune populations of the tumor microenvironment.

Altered pallido-pallidal synaptic transmission leads to aberrant firing of globus pallidus neurons in a rat model of Parkinson's disease.

The pattern of activity of globus pallidus (GP) neurons is tightly regulated by GABAergic inhibition. In addition to extrinsic inputs from the striatum (STR-GP) the other source of GABA to GP neurons arises from intrinsic intranuclear axon collaterals (GP-GP). While the contribution of striatal inputs has been studied, notably its hyperactivity in Parkinson's disease (PD), the properties and function of intranuclear inhibition remain poorly understood. Our objective was therefore to test the impact of chronic dopamine depletion on pallido-pallidal transmission. Using patch-clamp whole-cell recordings in rat brain slices, we combined electrical and optogenetic stimulations with pharmacology to differentiate basic synaptic properties of STR-GP and GP-GP GABAergic synapses. GP-GP synapses were characterized by activity-dependent depression and insensitivity to the D(2) receptor specific agonist quinpirole and STR-GP synapses by frequency-dependent facilitation and quinpirole modulation. Chronic dopamine deprivation obtained in 6-OHDA lesioned animals boosted the amplitude of GP-GP IPSCs but did not modify STR-GP transmission and increased the amplitude of miniature IPSCs. Replacement of calcium by strontium confirmed that the quantal amplitude was increased at GP-GP synapses. Finally, we demonstrated that boosted GP-GP transmission promotes resetting of autonomous activity and rebound-burst firing after dopamine depletion. These results suggest that GP-GP synaptic transmission (but not STR-GP) is augmented by chronic dopamine depletion which could contribute to the aberrant GP neuronal activity observed in PD.

Emerging dysfunctions consequent to combined monoaminergic depletions in Parkinsonism.

The loss of dopamine (DA) neurons has been the pathophysiological focus of the devastating conditions of Parkinson's disease, but depletion of DA alone in animal models has failed to simultaneously elicit both the motor and non-motor deficits of PD. The present study aimed to investigate, in rats, the respective role of dopamine (DA), noradrenaline (NA) and serotonin (5-HT) depletions on motor and non-motor behaviors and on subthalamic (STN) neuronal activity. We show that NA or DA depletion significantly decreased locomotor activity and enhanced the proportion of bursty and irregular STN neurons. Anxiety-like states required DA depletion plus the depletion of 5-HT or NA. Anhedonia and "depressive-like" behavior emerged only from the combined depletion of all three monoamines, an effect paralleled by an increase in the firing rate and the proportion of bursty and irregular STN neurons. Here, we provide evidence for the exacerbation of behavioral deficits when NA and/or 5-HT depletions are combined with DA depletion, bringing new insight into the combined roles of the three monoamines in PD.

Vitamin D Controls Tumor Growth and CD8+ T Cell Infiltration in Breast Cancer.

Women with low levels of vitamin D have a higher risk of developing breast cancer. Numerous studies associated the presence of a CD8+ T cell infiltration with a good prognosis. As vitamin D may play a key role in the modulation of the immune system, the objective of this work was to evaluate the impact of vitamin D on the breast cancer progression and mammary tumor microenvironment. We show that vitamin D decreases breast cancer tumor growth. Immunomonitoring of the different immune subsets in dissociated tumors revealed an increase in tumor infiltrating CD8+ T cells in the vitamin D-treated group. Interestingly, these CD8+ T cells exhibited a more active T cell (TEM/CM) phenotype. However, in high-fat diet conditions, we observed an opposite effect of vitamin D on breast cancer tumor growth, associated with a reduction of CD8+ T cell infiltration. Our data show that vitamin D is able to modulate breast cancer tumor growth and inflammation in the tumor microenvironment in vivo. Unexpectedly, this effect is reversed in high-fat diet conditions, revealing the importance of diet on tumor growth. We believe that supplementation with vitamin D can in certain conditions represent a new adjuvant in the treatment of breast cancers.

D5 dopamine receptors control glutamatergic AMPA transmission between the motor cortex and subthalamic nucleus.

Corticofugal fibers target the subthalamic nucleus (STN), a component nucleus of the basal ganglia, in addition to the striatum, their main input. The cortico-subthalamic, or hyperdirect, pathway, is thought to supplement the cortico-striatal pathways in order to interrupt/change planned actions. To explore the previously unknown properties of the neurons that project to the STN, retrograde and anterograde tools were used to specifically identify them in the motor cortex and selectively stimulate their synapses in the STN. The cortico-subthalamic neurons exhibited very little sag and fired an initial doublet followed by non-adapting action potentials. In the STN, AMPA/kainate synaptic currents had a voltage-dependent conductance, indicative of GluA2-lacking receptors and were partly inhibited by Naspm. AMPA transmission displayed short-term depression, with the exception of a limited bandpass in the 5 to 15 Hz range. AMPA synaptic currents were negatively controlled by dopamine D5 receptors. The reduction in synaptic strength was due to postsynaptic D5 receptors, mediated by a PKA-dependent pathway, but did not involve a modified rectification index. Our data indicated that dopamine, through post-synaptic D5 receptors, limited the cortical drive onto STN neurons in the normal brain.

GAT-3 Dysfunction Generates Tonic Inhibition in External Globus Pallidus Neurons in Parkinsonian Rodents.

The external globus pallidus (GP) is a key GABAergic hub in the basal ganglia (BG) circuitry, a neuronal network involved in motor control. In Parkinson's disease (PD), the rate and pattern of activity of GP neurons are profoundly altered and contribute to the motor symptoms of the disease. In rodent models of PD, the striato-pallidal pathway is hyperactive, and extracellular GABA concentrations are abnormally elevated in the GP, supporting the hypothesis of an alteration of neuronal and/or glial clearance of GABA. Here, we discovered the existence of persistent GABAergic tonic inhibition in GP neurons of dopamine-depleted (DD) rodent models. We showed that glial GAT-3 transporters are downregulated while neuronal GAT-1 function remains normal in DD rodents. Finally, we showed that blocking GAT-3 activity in vivo alters the motor coordination of control rodents, suggesting that GABAergic tonic inhibition in the GP contributes to the pathophysiology of PD.

Modulation of T Cell Activation in Obesity.

SIGNIFICANCE: Immune T cells are present in adipose tissues (AT), and the stoichiometry of the different T cell subsets is altered during diet-induced obesity (DIO). T cells contribute to the early steps of AT inflammation during DIO. Recent Advances: Many factors could potentially be responsible for this altered pro-inflammatory versus anti-inflammatory T cell balance. CRITICAL ISSUES: T cells are potentially activated in AT, which vitamin D might contribute to, as will be discussed in this article. In addition, we will review the different possible contributors to T cell activation in AT, such as the CD28 and CD154 T cell costimulatory molecules in AT. FUTURE DIRECTIONS: The potential antigen presentation capacities of adipocytes should be further investigated. Moreover, the properties of these AT resident (or migrating to AT) T cells must be further assessed. Antioxid. Redox Signal. 26, 489-500.

Neonatal mono-colonization of germ-free mice with Lactobacillus casei enhances casein immunogenicity after oral sensitization to cow's milk.

SCOPE: Food allergy is an increasing global health problem and perinatal administration of probiotic bacteria is currently under investigation in order to prevent the development of allergic diseases. Here, we investigated the impact of neonatal mono-colonization of mice with Lactobacillus casei BL23 on an oral sensitization to cow's milk. METHODS AND RESULTS: Mono-colonized (LC) mice were obtained by inoculating L. casei to germ-free (GF) parents. Nine-week-old GF, LC, and conventional (CV) mice were orally sensitized to cow's milk with cholera toxin as adjuvant. Compared to GF and CV mice, LC mice developed higher casein-specific IgG responses. In contrast, no significant differences between GF and LC mice were observed for the humoral responses against whey proteins. Immunoblotting experiments performed on αS1-casein hydrolysates revealed the presence of small peptides immunoreactive with sera from LC mice but not from GF mice. After in vitro reactivation of splenocytes, secretion of IL-17 was higher in LC mice than in GF and CV mice. CONCLUSION: Neonatal mono-colonization by L. casei BL23 modulated the allergic sensitization toward food antigens. Furthermore, our data suggest that casein-specific humoral responses in LC mice were enhanced because of casein hydrolysis by L. casei into immunogenic peptides.

Delayed bacterial colonization of the gut alters the host immune response to oral sensitization against cow's milk proteins.

SCOPE: Cow's milk allergy is the most prevalent food allergy in infants whose immune system development is critically stimulated during postnatal gut colonization by commensal bacteria. Allergenic potential of cow's milk ß-lactoglobulin (BLG) and caseins (CAS) was investigated in germ-free (GF) BALB/c mice and in GF mice conventionalized (CVd) at 6 weeks of age. METHODS AND RESULTS: Oral sensitization to cow's milk in the presence of cholera toxin led to higher BLG-specific IgE, IgG1, and IgG2a responses in GF mice than in conventional (CV) mice. No significant difference was observed for CAS-specific IgE responses although IgG1 responses to αS1- and κ-caseins were higher in GF mice than in CV mice. CVd mice, orally inoculated with fecal preparations from CV mice, also displayed biased antibody responses compared to CV mice. Secretion of Th2 cytokines by BLG- and CAS-reactivated splenocytes of CVd mice was similar to that of GF mice whereas cytokine production by reactivated cells from mesenteric lymph nodes of CVd mice was equivalent to that of CV mice. CONCLUSION: Oral sensitization to BLG and CAS was differentially affected by the absence of gut microbiota and delayed bacterial colonization altered persistently the host immune response to oral sensitization against food antigens.

Allergenic and immunogenic potential of cow's milk ß-lactoglobulin and caseins evidenced without adjuvant in germ-free mice.

SCOPE: In most animal models of allergy, the development of an IgE response requires the use of an adjuvant. Germ-free (GF) mice exhibit Th2-polarized antibody responses combined with defective immunosuppressive mechanisms. The sensitizing potential of milk proteins was investigated in GF mice in the absence of adjuvant. METHODS AND RESULTS: ß-lactoglobulin (BLG) and whole casein (CAS) allergenicity was evaluated by means of intraperitoneal injections without adjuvant. Injections of BLG induced significant IgE and IgG1 responses in GF mice, while CAS injections provoked the production of IgG1 toward κ- and αS1-caseins. No significant antibody response was evidenced in conventional (CV) mice. After in vitro BLG-reactivation, IL-4, IL-5, IL-13 and IFN-γ productions by splenocytes were higher in GF mice than in CV mice. Heat-treatment decreased BLG allergenicity as indicated by the absence of IgE production in GF mice. However, heat-treatment increased protein immunogenicity and led to the production of anti-BLG and anti-κ-casein IgG1 in both GF and CV mice. This correlated with enhanced productions of IL-4, IL-5 and IL-13 in BLG-reactivated splenocytes from CV mice. CONCLUSION: Gut colonization by commensal bacteria appeared then to significantly reduce the susceptibility of mice toward the intrinsic allergenic and immunogenic potential of milk proteins.