Evaluation of hepatic damage by reactive metabolites--with consideration of circadian variation of murine hepatic glutathione levels.

Generally, reactive metabolites are detoxified by conjugation with glutathione (GSH). A GSH-depleted model was prepared by administering L-buthionine-(S,R)-sulfoximine (BSO), which can be used to detect hepatic damage by reactive metabolites. However, BSO may cause adverse effects on other organs, such as renal damage by reactive metabolites because it depletes GSH in the whole body. The present study was designed to examine whether it was possible to specifically detect hepatic damage by reactive metabolites without reducing renal GSH levels by administering BSO in a time course when hepatic GSH levels are naturally reduced. Male BALB/c mice were administered reverse osmosis (RO) water or 20 mmol/l BSO in drinking water for 4 days. Subsequently, animals in the RO water group were orally administered 500 mg/kg acetaminophen (APAP) at 9:00 or 15:00 and in the BSO group at 9:00 for 4 days. As a result, severe hepatic damage and necrosis of the renal proximal tubules were observed in the BSO/APAP administration at 9:00 group, and all animals died on 1 or 2 days after APAP administration. Hepatic damage was clearly increased in the RO water/APAP administration at 15:00 group compared with the RO water/APAP administration at 9:00 group. However, renal damage and deaths were not observed. This BSO administration model may detect renal damage induced by reactive metabolites. Using an administration time course, whereby hepatic GSH levels were naturally reduced, hepatic damage by reactive metabolites can be detected without secondary renal effects.

Anti-allergic role of cholinergic neuronal pathway via α7 nicotinic ACh receptors on mucosal mast cells in a murine food allergy model.

The prevalence of food allergy (FA) has increased in developed countries over the past few decades. However, no effective drug therapies are currently available. Therefore, we investigated cholinergic anti-inflammatory pathway as a regulatory system to ameliorate disrupted mucosal immune homeostasis in the gut based on the pathophysiological elucidation of mucosal mast cells (MMCs) in a murine FA model. BALB/c mice sensitized with ovalbumin received repeated oral ovalbumin for the development of FA. FA mice developed severe allergic diarrhea and exhibited enhanced type 2 helper T (Th2) cell immune responses in both systemic immunity and mucosal immunity, along with MMCs hyperplasia in the colon. MMCs were localized primarily in the strategic position of the mucosal epithelium. Furthermore, the allergic symptoms did not develop in p85α disrupted phosphoinositide-3 kinase-deficient mice that lacked mast cells in the gut. Vagal stimulation by 2-deoxy-D-glucose and drug treatment with nicotinic ACh receptor (nAChR) agonists (nicotine and α7 nAChR agonist GTS-21) alleviated the allergic symptoms in the FA mice. Nicotine treatment suppressed MMCs hyperplasia, enhanced MPO and upregulated mRNA expression of Th1 and Th2 cytokines in the FA mice colon. MMCs, which are negatively regulated by α7 nAChRs, were often located in close proximity to cholinergic CGRP-immunoreactive nerve fibers in the FA mice colon. The present results reveal that the cholinergic neuroimmune interaction via α7 nAChRs on MMCs is largely involved in maintaining intestinal immune homeostasis and can be a target for a new therapy against mucosal immune diseases with homeostatic disturbances such as FA.

Role of complement in a murine model of peanut-induced anaphylaxis.

Peanut allergy is severe and persisting from childhood to adulthood. However, there is no effective prophylaxis or treatment for peanut allergy. Little is known to about the molecular process in the pathogenesis of peanuts allergy, especially in innate immunity. Thus we investigated the role of complement activation in murine peanut anaphylaxis. Complement component C3 deposition on peanut extract (PE) was evaluated using sera from wild-type (WT), mannose-binding lectin associated serine protease (MASP)-1/3 deficient, MASP-2 deficient, and C4 deficient mice. Sera from interferon regulatory factor-4 (IRF-4) deficient mice, which lack serum immunoglobulin, were also used. In anaphylaxis study, mice were pretreated with propranolol and a long-acting form of IL-4, and injected with PE. Mice were then assessed for plasma C3a levels and hypothermia shock by ELISA and rectal temperature measurement, respectively. C3 deposition on PE was abolished in immunoglobulin- and C4-deficient sera. No difference in C3 deposition levels were observed among WT, MASP-1/3 deficient and MASP-2 deficient sera. IgM, IgG2b, IgG3, C1q, and ficolin-A deposits were detected on PE. In anaphylaxis study, MASP-1/3 deficient mice showed elevation of plasma C3a levels similar to WT mice. However, they were significantly reduced in C4- and MASP-2-deficient mice compared to WT mice. Consistently, PE-induced anaphylactic shock was prevented in C4 deficient mice and partially in MASP-2 deficient mice. In conclusion, PE activates complement via both the lectin and classical pathways in vivo, and the complement activation contributes to hypothermia shock in mice.

Mice deficient in ficolin, a lectin complement pathway recognition molecule, are susceptible to Streptococcus pneumoniae infection.

Mannose-binding lectin (MBL) and ficolin are complexed with MBL-associated serine proteases, key enzymes of complement activation via the lectin pathway, and act as soluble pattern recognition molecules in the innate immune system. Although numerous reports have revealed the importance of MBL in infectious diseases and autoimmune disorders, the role of ficolin is still unclear. To define the specific role of ficolin in vivo, we generated model mice deficient in ficolins. The ficolin A (FcnA)-deficient (Fcna(-/-)) and FcnA/ficolin B double-deficient (Fcna(-/-)b(-/-)) mice lacked FcnA-mediated complement activation in the sera, because of the absence of complexes comprising FcnA and MBL-associated serine proteases. When the host defense was evaluated by transnasal infection with a Streptococcus pneumoniae strain, which was recognized by ficolins, but not by MBLs, the survival rate was significantly reduced in all three ficolin-deficient (Fcna(-/-), Fcnb(-/-), and Fcna(-/-)b(-/-)) mice compared with wild-type mice. Reconstitution of the FcnA-mediated lectin pathway in vivo improved survival rate in Fcna(-/-) but not in Fcna(-/-)b(-/-) mice, suggesting that both FcnA and ficolin B are essential in defense against S. pneumoniae. These results suggest that ficolins play a crucial role in innate immunity against pneumococcal infection through the lectin complement pathway.

Oral tolerance induced by transfer of food antigens via breast milk of allergic mothers prevents offspring from developing allergic symptoms in a mouse food allergy model.

We examined whether maternal exposure to food antigens during lactation and maternal allergic status would affect the development of food allergy in offspring. OVA-sensitized or OVA-nonsensitized BALB/c female mice were exposed or unexposed to OVA during lactation. After weaning, their offspring were systemically sensitized twice with OVA and repeatedly given OVA by oral intubation. While 97.1% of the mice breastfed by OVA-nonsensitized and OVA-unexposed mothers developed allergic diarrhea, 59.7% of the mice breastfed by OVA-exposed nonallergic mothers during lactation and 24.6% of the mice breastfed by OVA-exposed allergic mothers during lactation developed food allergy. Furthermore, OVA was detected in breast-milk from OVA-exposed nonallergic mothers during lactation (4.6 ± 0.5 µg/mL). In addition, OVA-specific IgG1 titers were markedly increased in breast milk from allergic mothers (OVA-sensitized and OVA-unexposed mother: 11.0 ± 0.5, OVA-sensitized and OVA-exposed mother: 12.3 ± 0.3). Our results suggest that oral tolerance induced by breast milk-mediated transfer of dietary antigens along with their specific immunoglobulins to offspring leads to antigen-specific protection from food allergy.