Kayoko Ishimaru

Lactobacillus bulgaricus OLL1181 activates the aryl hydrocarbon receptor pathway and inhibits colitis

Increasing evidence suggests that the aryl hydrocarbon receptor (AhR) pathway has an important role in the regulation of inflammatory responses. Most recently, we have shown that the activation of the AhR pathway by a potent AhR agonist inhibits the development of dextran sodium sulfate (DSS)‐induced colitis, a model of human ulcerative colitis, by the induction of prostaglandin E2 (PGE2) in the large intestine. Because several strains of probiotic lactic acid bacteria have been reported to inhibit DSS‐induced colitis by unidentified mechanisms, we hypothesized that particular strains of lactic acid bacterium might have the potential to activate the AhR pathway, thereby inhibiting DSS‐induced colitis. This study investigated whether there are specific lactic acid bacterial strains that can activate the AhR pathway, and if so, whether this AhR‐activating potential is associated with suppression of DSS‐induced colitis. By using AhR signaling reporter cells, we found that Lactobacillus bulgaricus OLL1181 had the potential to activate the AhR pathway. OLL1181 also induced the mRNA expression of cytochrome P450 family 1A1 (CYP1A1), a target gene of the AhR pathway, in human colon cells, which was inhibited by the addition of an AhR antagonist, α‐naphthoflavon (αNF). In addition, mice treated orally with OLL1181 showed an increase in CYP1A1 mRNA expression in the large intestine and amelioration of DSS‐induced colitis. Thus, OLL1181 can induce activation of the intestinal AhR pathway and inhibit DSS‐induced colitis in mice. This strain of lactic acid bacterium has therefore the potential to activate the AhR pathway, which may be able to suppress colitis.

Identification of a probiotic bacteria-derived activator of the aryl hydrocarbon receptor that inhibits colitis

The aryl hydrocarbon receptor (AhR) recognizes environmental xenobiotics and is originally thought to be involved in the metabolism (detoxification) of the substances. Recently, AhR is highlighted as an important regulator of inflammation. Notably, accumulating evidence suggests that activation of the AhR suppresses inflammatory bowel diseases (IBDs). Therefore, non‐toxic AhR activators become attractive drug candidates for IBD. This study identified 1,4‐dihydroxy‐2‐naphthoic acid (DHNA), a precursor of menaquinone (vitamin K2) abundantly produced by Propionibacterium freudenreichii ET‐3 isolated from Swiss‐type cheese, as an AhR activator. DHNA activated the AhR pathway in human intestinal epithelial cell line Caco2 cells and in the mouse intestine. Oral treatment of mice with DHNA induced anti‐microbial proteins RegIIIβ and γ in the intestine, altered intestinal microbial flora and inhibited dextran sodium sulfate (DSS)‐induced colitis, which recapitulated the phenotypes of AhR activation in the gut. As DHNA is commercially available in Japan as a prebiotic supplement without severe adverse effects, DHNA or its derivatives might become a promising drug candidate for IBD via AhR activation. The results also implicate that intestinal AhR might act not only as a sensor for xenobiotics in diet and water but also for commensal bacterial activity because DHNA is a precursor of vitamin K2 produced by vitamin K2‐synthesizing commensal bacteria as well as propionic bacteria. Hence, DHNA might be a key bacterial metabolite in the host–microbe interaction to maintain intestinal microbial ecosystem.

Circadian clock gene Period2 regulates a time-of-day–dependent variation in cutaneous anaphylactic reaction

BACKGROUND IgE-mediated immediate-type skin reaction shows a diurnal rhythm, although the precise mechanisms remain uncertain. Period2 (Per2) is a key circadian gene that is essential for endogenous clockworks in mammals. OBJECTIVE This study investigated whether Per2 regulates a time-of-day-dependent variation in IgE-mediated immediate-type skin reaction. METHODS The kinetics of a passive cutaneous anaphylactic reaction were compared between wild-type mice and mice with a loss-of-function mutation of Per2 (mPer2(m/m) mice). The effects of adrenalectomy, aging, and dexamethasone on the kinetics of a passive cutaneous anaphylactic reaction were also examined. In addition, the extent of IgE-mediated degranulation in bone marrow-derived mast cells (BMMCs) was compared between wild-type and mPer2(m/m) mice. RESULTS A time-of-day-dependent variation in a passive cutaneous anaphylactic reaction observed in wild-type mice was absent in mPer2(m/m) mice and in adrenalectomized and aged mice associated with the loss of rhythmic secretion of corticosterone. In addition, mPer2(m/m) mice showed decreased sensitivity to the inhibitory effects of dexamethasone on the passive cutaneous anaphylactic reactions. IgE-mediated degranulation in BMMCs was comparable between wild-type and mPer2(m/m) mice, but Per2 mutation decreased sensitivity to the inhibitory effects of dexamethasone on IgE-mediated degranulation in BMMCs. CONCLUSION A circadian oscillator, Per2, regulates a time-of-day-dependent variation in a passive cutaneous anaphylactic reaction in mice. Per2 may do so by controlling the rhythmic secretion of glucocorticoid from adrenal glands and/or by gating the glucocorticoid responses of mast cells to certain times of the day (possibly when Per2 levels are high in mast cells).

Circadian regulation of allergic reactions by the mast cell clock in mice

BACKGROUND It remains elusive how allergic symptoms exhibit prominent 24-hour variations. In mammals the circadian clocks present in nearly all cells, including mast cells, drive the daily rhythms of physiology. Recently, we have shown that the circadian clocks drive the daily rhythms in IgE/mast cell-mediated allergic reactions. However, the precise mechanisms, particularly the specific roles of the mast cell-intrinsic clockwork in temporal regulation, remain unclear. OBJECTIVE We determined whether the mast cell clockwork contributes to the temporal regulation of IgE/mast cell-mediated allergic reaction. METHODS The kinetics of a time of day-dependent variation in passive cutaneous anaphylactic reactions were compared between mast cell-deficient mice reconstituted with bone marrow-derived cultured mast cells generated from mice with a wild-type allele and a dominant negative type mutation of the key clock gene Clock. We also examined the temporal responses of wild-type and Clock-mutated bone marrow-derived cultured mast cells to IgE stimulation in vitro. Furthermore, factors influencing the mast cell clockwork were determined by using in vivo imaging. RESULTS The Clock mutation in mast cells resulted in the absence of temporal variations in IgE-mediated degranulation in mast cells both in vivo and in vitro associated with the loss of temporal regulation of FcεRI expression and signaling. Additionally, adrenalectomy abolished the mast cell clockwork in vivo. CONCLUSION The mast cell-intrinsic clockwork, entrained by humoral factors from the adrenal gland, primarily contributes to the temporal regulation of IgE/mast cell-mediated allergic reactions. Our results reveal a novel regulatory mechanism for IgE-mediated mast cell responses that might underlie the circadian pathophysiology in patients with allergic diseases.

Dietary Resveratrol Prevents the Development of Food Allergy in Mice

Background Resveratrol is a bioactive polyphenol enriched in red wine that exhibits many beneficial health effects via multiple mechanisms. However, it is unclear whether resveratrol is beneficial for the prevention of food allergy. This study investigated whether resveratrol inhibited the development of food allergy by using a mouse model of the disease. Methodology/Principal Findings Mice fed standard diet or standard diet plus resveratrol were sensitized by intragastric administration of ovalbumin (OVA) and mucosal adjuvant cholera toxin (CT). Several manifestations of food allergy were then compared between the mice. The effects of resveratrol on T cells or dendritic cells were also examined by using splenocytes from OVA-specific T cell-receptor (TCR) transgenic DO11.10 mice or mouse bone marrow-derived dendritic cells (BMDCs) in vitro. We found that mice fed resveratrol showed reduced OVA-specific serum IgE production, anaphylactic reaction, and OVA-induced IL-13 and IFN-ã production from the mesenteric lymph nodes (MLNs) and spleens in comparison to the control mice, following oral sensitization with OVA plus CT. In addition, resveratrol inhibited OVA plus CT-induced IL-4, IL-13, and IFN-ã production in splenocytes from DO11.10 mice associated with inhibition of GATA-3 and T-bet expression. Furthermore, resveratrol suppressed the OVA plus CT-induced CD25 expression and IL-2 production in DO11.10 mice-splenocytes in association with decreases in CD80 and CD86 expression levels. Finally, resveratrol suppressed CT-induced cAMP elevation in association with decreases in CD80 and CD86 expression levels in BMDCs. Conclusions/Significance Ingestion of resveratrol prevented the development of a food allergy model in mice. Given the in vitro findings, resveratrol might do so by inhibiting DC maturation and subsequent early T cell activation and differentiation via downregulation of CT-induced cAMP activation in mice. These results suggest that resveratrol may have potential for prophylaxis against food allergy.

Maternal psychosocial factors determining the concentrations of transforming growth factor-beta in breast milk

To cite this article: Kondo N, Suda Y, Nakao A, Oh‐Oka K, Suzuki K, Ishimaru K, Sato M, Tanaka T, Nagai A, Yamagata Z. Maternal psychosocial factors determining the concentrations of transforming growth factor‐beta in breast milk. Pediatr Allergy Immunology 2011: 22: 853–861.

Expressions of Tight Junction Proteins Occludin and Claudin-1 Are under the Circadian Control in the Mouse Large Intestine: Implications in Intestinal Permeability and Susceptibility to Colitis

Background & Aims The circadian clock drives daily rhythms in behavior and physiology. A recent study suggests that intestinal permeability is also under control of the circadian clock. However, the precise mechanisms remain largely unknown. Because intestinal permeability depends on tight junction (TJ) that regulates the epithelial paracellular pathway, this study investigated whether the circadian clock regulates the expression levels of TJ proteins in the intestine. Methods The expression levels of TJ proteins in the large intestinal epithelium and colonic permeability were analyzed every 4, 6, or 12 hours between wild-type mice and mice with a mutation of a key clock gene Period2 (Per2; mPer2m/m). In addition, the susceptibility to dextran sodium sulfate (DSS)-induced colitis was compared between wild-type mice and mPer2m/m mice. Results The mRNA and protein expression levels of Occludin and Claudin-1 exhibited daily variations in the colonic epithelium in wild-type mice, whereas they were constitutively high in mPer2m/m mice. Colonic permeability in wild-type mice exhibited daily variations, which was inversely associated with the expression levels of Occludin and Claudin-1 proteins, whereas it was constitutively low in mPer2m/m mice. mPer2m/m mice were more resistant to the colonic injury induced by DSS than wild-type mice. Conclusions Occludin and Claudin-1 expressions in the large intestine are under the circadian control, which is associated with temporal regulation of colonic permeability and also susceptibility to colitis.

Allergen-specific basophil reactivity exhibits daily variations in seasonal allergic rhinitis

It remains poorly understood how symptoms in allergic rhinitis are most severe during overnight or early in the morning. The circadian clock consisting of a network of several ‘clock genes’ including Clock drives daily rhythms in physiology. This study showed that allergen‐induced surface CD203c expression on basophils in seasonal allergic rhinitis caused by Japanese cedar pollen exhibited a time‐of‐day‐dependent variation associated with temporal variations in canonical circadian clock gene expression. We also found that bone‐marrow‐derived basophils (BM basophils) generated from wild‐type mice exhibited a time‐of‐day‐dependent variation in IgE‐mediated IL‐4 and histamine production, which was not observed in BM basophils generated from Clock‐mutated mice. Therefore, allergen‐specific basophil reactivity shows daily variations depending on the circadian clock activity in basophils, which could partly explain temporal symptomatic variations in allergic rhinitis. Additionally, circadian variations in CD203c expression should be considered for interpretation of this biomarker in clinical research.

Circadian Gene Clock Regulates Psoriasis-Like Skin Inflammation in Mice

There are several reports suggesting that the pathophysiology of psoriasis may be associated with aberrant circadian rhythms. However, the mechanistic link between psoriasis and the circadian time-keeping system, “the circadian clock,” remains unclear. This study determined whether the core circadian gene, Clock, had a regulatory role in the development of psoriasis. For this purpose, we compared the development of psoriasis-like skin inflammation induced by the Toll-like receptor 7 ligand imiquimod (IMQ) between wild-type mice and mice with a loss-of-function mutation of Clock. We also compared the development of IMQ-induced dermatitis between wild-type mice and mice with a loss-of-function mutation of Period2 (Per2), another key circadian gene that inhibits CLOCK activity. We found that Clock mutation ameliorated IMQ-induced dermatitis, whereas the Per2 mutation exaggerated IMQ-induced dermatitis, when compared with wild-type mice associated with decreased or increased IL-23 receptor (IL-23R) expression in γ/δ+ T cells, respectively. In addition, CLOCK directly bound to the promoter of IL-23R in γ/δ+ T cells, and IL-23R expression in the mouse skin was under circadian control. These findings suggest that Clock is a novel regulator of psoriasis-like skin inflammation in mice via direct modulation of IL-23R expression in γ/δ+ T cells, establishing a mechanistic link between psoriasis and the circadian clock.

Inhibition of IgE-mediated allergic reactions by pharmacologically targeting the circadian clock

BACKGROUND The circadian clock temporally gates signaling through the high-affinity IgE receptor (FcεRI) in mast cells, thereby generating a marked day/night variation in allergic reactions. Thus manipulation of the molecular clock in mast cells might have therapeutic potential for IgE-mediated allergic reactions. OBJECTIVE We determined whether pharmacologically resetting the molecular clock in mast cells or basophils to times when FcεRI signaling was reduced (ie, when core circadian protein period 2 [PER2] is upregulated) resulted in suppression of IgE-mediated allergic reactions. METHODS We examined the effects of PF670462, a selective inhibitor of the key clock component casein kinase 1δ/ε, or glucocorticoid, both of which upregulated PER2 in mast cells, on IgE-mediated allergic reactions both in vitro and in vivo. RESULTS PF670462 or corticosterone (or dexamethasone) suppressed IgE-mediated allergic reactions in mouse bone marrow-derived mast cells or basophils and passive cutaneous anaphylactic reactions in mice in association with increased PER2 levels in mast cells or basophils. PF670462 or dexamethasone also ameliorated allergic symptoms in a mouse model of allergic rhinitis and downregulated allergen-specific basophil reactivity in patients with allergic rhinitis. CONCLUSION Pharmacologically resetting the molecular clock in mast cells or basophils to times when FcεRI signaling is reduced can inhibit IgE-mediated allergic reactions. The results suggest a new strategy for controlling IgE-mediated allergic diseases. Additionally, this study suggests a novel mechanism underlying the antiallergic actions of glucocorticoids that relies on the circadian clock, which might provide a novel insight into the pharmacology of this drug in allergic patients.