Hidehiko Kondo

Percutaneous sensitization with allergens through barrier-disrupted skin elicits a Th2-dominant cytokine response.

We investigated whether percutaneous sensitization with different allergens through barrier‐disrupted skin regulates the balance of Th1/Th2 cytokine expression. When mice were sensitized with the typical hapten picryl chloride (PiCl) by a single topical application to intact skin, there was an up‐regulation in the lymph nodes (LN) of mRNA expression for the Th1 cytokines IL‐2 or IFN‐γ, and for the Th2 cytokine IL‐4. In contrast, sensitization with PiCl after barrier disruption of the skin down‐regulated the expression of mRNA for IFN‐γ in a tape‐stripping number‐dependent manner without changing the expression of mRNA for IL‐4. When mice were sensitized with house dust mite antigens (MA) by a single topical application to barrier‐disrupted abdominal skin, there was a tape‐stripping number‐dependent up‐regulation in the LN of mRNA expression for IL‐4 but not for IL‐2 or IFN‐γ. In the LN, mRNA for the IL‐4‐inducible immunoglobulins IgE and IgG1, but not for the IFN‐γ‐inducible IgG2a, were up‐regulated after sensitization with MA, while all three immunoglobulin mRNA were augmented after PiCl sensitization through intact skin. Antigenic elicitation by a topical application of PiCl in aural skin of mice sensitized through intact skin consistently increased the expression of mRNA for all three cytokines in the challenged skin, whereas elicitation in mice sensitized through barrier‐disrupted skin decreased the expression of mRNA for IL‐2 and IFN‐γ, but not for IL‐4. Antigenic elicitation by subcutaneous injection of MA in aural skin consistently increased the expression of mRNA for IL‐4, but not for IL‐2 or IFN‐γ in the challenged skin. Infiltration of eosinophils in the dermis was more prominent following elicitation with MA in mice sensitized through barrier disruption than with PiCl in mice sensitized through intact skin. These findings suggest that the percutaneous entry of environmental allergens through barrier‐disrupted skin is strongly associated with the induction of Th2‐dominant immunological responses, as is seen in atopic dermatitis.

Digestion and assimilation features of dietary DAG in the rat small intestine.

Several recent studies have demonstrated that dietary DAG oil rich in 1,3-species suppresses the postprandial increase of serum TAG level and decreases body fat accumulation, compared with TAG oil. To clarify the mechanisms underlying the beneficial effects of DAG, we investigated the metabolic features of DAG in the small intestine with regard to the digestion pathway in the lumen and the TAG-synthesis pathway in the mucosa. When intraduodenally infused as an emulsion, TAG was digested to 1,2-DAG, 2-MAG, and FFA, whereas 1,3-DAG was digested to 1(3)-MAG and FFA. When assessed by the incorporation of [1-14C]linoleic acid in lipids, the mucosal TAG-synthesis was significantly reduced by DAG infusion compared with TAG infusion. However, the mucosal 1,3-DAG synthesis was remarkably increased in the DAG-infused rats. The total amount of mucosal 1,3-DAG was also increased (4.5-fold) after DAG infusion compared with that after TAG infusion. Next, we examined the synthesis pathway of 1,3-DAG. In cultures of the everted intestinal sacs, 1,3-DAG production required the presence of 1-MAG, suggesting that the 1,3-DAG synthesis was due to acylation of 1(3)-MAG in the DAG-infused rats. Furthermore, measurements of DAG acyltransferase activity indicated that 1,3-DAG was little utilized in TAG synthesis. These findings suggest that features of 1,3-DAG digestion and assimilation in the intestine may be responsible for the reduction of the postprandial serum TAG level by dietary DAG.

Cloning of cDNAs for New Subtypes of Murine Low-Affinity Fc Receptor for IgE (FcεRII/CD23)

In humans, two subtypes of the low-affinity Fc receptor for IgE, Fc epsilon RIIa and Fc epsilon RIIb, have been identified. The two forms differ only in a short stretch of amino acids at the cytoplasmic amino terminus. On the other hand, only one Fc epsilon RIIa-like receptor was reported in the mouse, although the existence of another subtype of transcript has been suggested. A new cDNA subtype for murine Fc epsilon RII that has amino acid homology to the human subtype b at the amino terminus was cloned by polymerase chain reaction. When expressed transiently in COS cells, the cDNA is capable of generating a functional cell surface protein that is recognized by an anti-Fc epsilon RII antibody and that has affinity to IgE. In the spleen, although the expression level is considerably lower than that of subtype a, the transcript appears in B cells and in non-B cells upon stimulation with IL-4 and LPS, in contrast to the constitutive expression of the conventional Fc epsilon RII transcript. It is also detectable in several cell lines of B- or T-cell lineages. These results suggest that this gene may be the murine counterpart of human Fc epsilon RII subtype b. Another cDNA clone for the distinct Fc epsilon RII transcript has also been isolated. The cDNA also encodes a surface protein functional on COS cells, but its human counterpart has not been found.

Abundant expression of uncoupling protein-2 in the small intestine: up-regulation by dietary fish oil and fibrates.

Mitochondrial uncoupling protein-2 (UCP-2) is widely expressed in various mammalian tissues, although its physiological functions are not well understood. We examined the effects of dietary fish oil on UCP-2 expression in the rat small intestine, in which UCP-2 mRNA levels are higher than in other organs. Feeding with fish oil (20%) up-regulated UCP-2 mRNA within 6 days in the small intestine as well as the liver, compared to feeding with soybean oil. This was mimicked by feeding with agonists for peroxisome proliferator-activated receptor alpha (PPARalpha) such as fenofibrate and bezafibrate, but not the PPARgamma agonist troglitazone. The bezafibrate-induced increase in UCP-2 expression was found within 2 days in the small intestine, but only after 6 days in the liver. The up-regulation of UCP-2 was also found in cultured intestinal epithelial cells (IEC-6) treated for 24 h with various long-chain fatty acids and PPARalpha agonists. These results indicated that intestinal UCP-2 is up-regulated through direct activation of PPARalpha by dietary fatty acids.

Dietary Phospholipids Ameliorate Fructose-Induced Hepatic Lipid and Metabolic Abnormalities in Rats

Overconsumption of fructose results in hepatic dyslipidemia, which has a documented correlation with metabolic syndrome. We examined whether the ingestion of phospholipids (PL) from soybeans prevents fructose-induced metabolic abnormalities. Rats were fed either a fructose-free diet (C), a 60% fructose diet (F), or a 60% fructose plus 3% PL diet (F-PL) for 10 wk. At wk 8, plasma glucose concentrations after glucose loading were significantly higher in rats fed the F diet than in rats fed the C and F-PL diets, which did not differ from one another. The concentrations of hepatic TG, diglycerides, ceramides, and oleates in rats fed the F diet for 10 wk was significantly higher than those in rats fed the C diet. The increases were prevented by concurrent PL ingestion; concentrations did not differ between the F-PL and C groups. Dietary fructose increased the mRNA expression of SREBP1, ChREBP, and genes related to lipogenesis. PL completely inhibited these increases. Furthermore, reflecting the difference at the mRNA level, lipogenic enzyme activities were greater in rats fed the F diet than in rats fed the C diet, and PL ingestion suppressed the increased activities by fructose feeding. Treatment of cultured Hep-G2 cells with fructose for 24 h increased the levels of SREBP1 and ChREBP nuclear proteins, which were suppressed by culture with purified PL components, especially phosphatidylethanolamine and phosphatidylinositol. These findings indicate that PL prevents fructose-induced metabolic abnormalities in association with alterations of the hepatic lipid profile by inhibiting de novo lipogenesis.

Effects of coumestrol on lipid and glucose metabolism as a farnesoid X receptor ligand

In the course of an effort to identify novel agonists of the farnesoid X receptor (FXR), coumestrol was determined to be one such ligand. Reporter and in vitro coactivator interaction assays revealed that coumestrol bound and activated FXR. Treatment of Hep G2 cells with coumestrol stimulated the expression of FXR target genes, thereby regulating the expression of target genes of the liver X receptor and hepatocyte nuclear factor-4alpha. Through these actions, coumestrol is expected to exert beneficial effects on lipid and glucose metabolism.

Alteration of amiloride-sensitive salt taste nerve responses in aldosterone/NaCl-induced hypertensive rats.

Salt taste sensitivity is related to physiological condition, and declined in hypertensive patients. However, little is known about the mechanism underlying changes in salt taste sensitivity during the development of hypertension. This is largely due to lack of an appropriate animal model which shows the decline of salt taste sensitivity caused by hypertension. Previous studies have suggested that one of main causes of salt-sensitive hypertension is dysfunction of the renin-angiotensin-aldosterone system (RAAS). To examine the involvement of RAAS in modulation of salt taste sensitivity, we utilized aldosterone/NaCl-treated rats as a well-established model of salt-sensitive hypertension caused by RAAS dysfunction. Amount of sodium intake in aldosterone/NaCl-treated rats was higher than that in control rats. In addition to behavioral changes, the amiloride-sensitive salt taste nerve responses in aldosterone/NaCl-treated rats were remarkably lower by approximately 90% than those in the other groups. Moreover, αENaC mRNA expression in the epithelium of circumvallate papillae was significantly low in aldosterone/NaCl-treated rats. Thus, RAAS modulates salt taste system as is case in hypertensive patients. This report is to our knowledge the first to describe an animal model with decline of amiloride-sensitive salt taste nerve responses by RAAS dysfunction-mediated salt-sensitive hypertension.

Perilla extract improves frequent urination in spontaneously hypertensive rats with enhancement of the urothelial presence and anti-inflammatory effects

To investigate the effects of perilla extract on urinary symptoms in spontaneously hypertensive rats as a model of spontaneous overactive bladder.