S-Equol Activates cAMP Signaling at the Plasma Membrane of INS-1 Pancreatic ß-Cells and Protects against Streptozotocin-Induced Hyperglycemia by Increasing ß-Cell Function in Male Mice.

Background:S-equol, which is enantioselectively produced from daidzein by gut microbiota, has been suggested as a chemopreventive agent against type 2 diabetes mellitus (T2DM), but the underlying mechanisms remain unclear.Objective: We investigated the effects of S-equol on pancreatic ß-cell function.Methods: ß-Cell growth and insulin secretion were evaluated with male Institute of Cancer Research mice and isolated pancreatic islets from the mice, respectively. The mechanisms by which S-equol stimulated ß-cell response were examined in INS-1 ß-cells. The effect of S-equol treatment on ß-cell function was assessed in low-dose streptozotocin-treated mice. S-equol was used at 10 µmol/L for in vitro and ex vivo studies and was administered by oral gavage (20 mg/kg, 2 times/d throughout the experimental period) for in vivo studies.Results:S-equol administration for 7 d increased Ki67-positive ß-cells by 27% (P < 0.01) in mice. S-equol enantioselectively enhanced glucose-stimulated insulin secretion in mouse pancreatic islets by 41% (P < 0.001). In INS-1 cells, S-equol exerted stronger effects than daidzein on cell growth, insulin secretion, and cAMP-response element (CRE)-mediated transcription. These S-equol effects were diminished by inhibiting protein kinase A. The effective concentration of S-equol for stimulating cAMP production at the plasma membrane was lower than that for phosphodiesterase inhibition. S-equol-stimulated CRE activation was negatively controlled by the knockdown of G-protein α subunit group S (stimulatory) and positively controlled by that of G-protein-coupled receptor kinase-3 and -6. Compared with vehicle-treated controls, S-equol gavage treatment resulted in an increase in ß-cell mass of 104% (P < 0.05), a trend toward high plasma insulin concentrations (by 118%; P = 0.06), and resistance to hyperglycemia after streptozotocin treatment (78% of AUC after glucose challenge; P < 0.01). S-equol administration significantly increased the number of Ki67-positive proliferating ß-cells by 62% (P < 0.01) and decreased that of terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling-positive apoptotic ß-cells by 75% (P < 0.05).Conclusions: Our results show that S-equol boosts ß-cell function and prevents hypoglycemia in mice, suggesting its potential for T2DM prevention.

A comparative study of ethanol production by Issatchenkia orientalis strains under stress conditions.

The ability of 13 strains of multi-stress-tolerant Issatchenkia orientalis yeast to produce ethanol was examined under different stress conditions, including conditions of elevated Na2SO4 and Na2SO4 concentrations and increased heat. The MF-121 strain produced a significant amount of ethanol after the incubation in acidic media containing high concentrations of salt, e.g., 50 g/l Na2SO4 at pH 2.0, or at high temperatures, e.g., 43°C, when compared with other strains.

Influences of p53 deficiency on the apoptotic response, DNA damage removal and mutagenesis in UVB-exposed mouse skin.

p53 suppresses the genomic instability provoked by genotoxic agents. Ultraviolet (UV) B induces skin cancers by producing DNA damage and mutations in the skin genome, whereas the skin tissue responds to the UVB insult with cell cycle arrest and apoptosis as well as damage exclusion by DNA repair. To address the p53 contribution to these skin responses in vivo, we analyzed the time course of DNA damage removal, apoptosis induction and hyperplasia in the skin after UVB irradiation in p53-knockout mice. We also examined UVB-induced mutations in the skin. We found that p53 deficiency does not abolish the UVB-induced apoptotic response in the epidermis but delays the process and the following hyperplasia 12-24 h. Regardless of the p53 genotype, 1 kJ/m(2) UVB induced a total replacement of the epidermal layer by destroying the damaged epidermis by apoptosis and rebuilding a new one through hyperplasia. We failed to detect a clear defect in removal of UVB-induced DNA photolesions from the genome of the p53-deficient skin except for a delay in the epidermis, which seemed to result from the delay in the apoptotic response. However, we found that p53 deficiency enhanced UVB-induced mutagenesis. Furthermore, in a genetic study using Xpa-knockout mice, we showed that the enhanced mutagenic response depends on the activity of nucleotide excision repair (NER), which was also supported by the mutation spectrum observed in the UVB-exposed p53-knockout mice. These results indicate that p53 protects the skin genome from the UVB genotoxicity by facilitating NER, whereas its contribution to the UVB-induced apoptosis is limited.

Regulation of peroxisome proliferator-activated receptor-gamma expression in human eosinophils by estradiol.

BACKGROUND: Peroxisome proliferator-activated receptor-gamma (PPARgamma) is a nuclear receptor that regulates not only adipogenesis but also immune reaction. We previously demonstrated that human eosinophils expressed functional PPARgamma, although the modulator of PPARgamma expression is less well understood. Because clinical studies have shown that the efficacy of PPARgamma agonists as insulin sensitizers is stronger in women than in men, we investigated whether sex hormones caused any changes in eosinophil PPARgamma expression levels. METHODS: First, purified human peripheral blood eosinophils were cultured with 17beta-estradiol for 24 h, followed by PPARgamma measurement using a flow cytometer. Next, eosinophil PPARgamma expression and serum estradiol were studied in 10 healthy women during the menstrual and follicular phases to identify the physiological significance of estradiol. Eosinophil PPARgamma expression was also compared in 22 men, 21 non-pregnant women, and 15 pregnant women. RESULTS: We observed that PPARgamma protein expression in eosinophils was significantly enhanced by 10(-6)M 17beta-estradiol. Although serum estradiol concentration was increased during the follicular phase, PPARgamma expression levels were not affected by the menstrual cycle. In addition, no significant differences in PPARgamma expression were observed in terms of sex and pregnancy. CONCLUSIONS: These findings suggest that estradiol potentially upregulates eosinophil PPARgamma expression in vitro, although some other mechanisms might be involved in its regulation in vivo.

Procaterol upregulates peroxisome proliferator-activated receptor-gamma expression in human eosinophils.

Peroxisome proliferator-activated receptor-gamma (PPARgamma) is a nuclear receptor that regulates immune reaction. We have previously demonstrated that human eosinophils express PPARgamma and that stimulation with a synthetic agonist for PPARgamma attenuated the factor-induced eosinophil activations. However, the modulator of PPARgamma expression in eosinophils has not yet been studied. In this study, we investigated the effect of procaterol, the synthetic beta2-adrenoceptor agonist widely used as bronchodilators in asthma, on the PPARgamma expression in eosinophils. Purified human peripheral blood eosinophil and the eosinophilic cell line EoL-1 were cultured with procaterol. This was followed by PPARgamma measurement using flow cytometer and quantitative real-time RT-PCR. We observed that PPARgamma was constitutively expressed by EoL-1 and the purified eosinophils and that the therapeutic concentration (10(-9)M) of procaterol markedly enhanced PPARgamma protein expression, which was reversed by the selective beta2-adrenoceptor antagonist ICI-118551. The PPARgamma mRNA expression in EoL-1 and eosinophils was also induced by procaterol. These findings suggest that procaterol could modulate the eosinophil function by increasing the expression of PPARgamma.

Theophylline and dexamethasone induce peroxisome proliferator-activated receptor-gamma expression in human eosinophils.

Eosinophils are major effector cells in allergic diseases including asthma. Peroxisome proliferator-activated receptor-gamma (PPARgamma) is a nuclear receptor that regulates immune reaction. We have previously demonstrated that human eosinophils express PPARgamma and that stimulation with a synthetic agonist for PPARgamma attenuated the factor-induced eosinophil survival and chemotaxis. However, the modulator of the eosinophil PPARgamma expression has not yet been studied. In this study, we investigated the effect of theophylline and dexamethasone (widely used drugs in the treatment of asthma) on PPARgamma expression in eosinophils. Purified human peripheral blood eosinophils were cultured, and therapeutic concentrations of theophylline and dexamethasone were added. Subsequently, PPARgamma was measured using quantitative real-time RT-PCR and flow cytometry. Theophylline and dexamethasone markedly enhanced both mRNA and protein levels of PPARgamma. These findings suggest that the increase in PPARgamma expression on eosinophils may play a role in the anti-inflammatory effects of theophylline and dexamethasone.

Peroxisome proliferator-activated receptor gamma regulates eosinophil functions: a new therapeutic target for allergic airway inflammation.

Peroxisome proliferator-activated receptor gamma (PPARgamma) is a nuclear receptor that regulates lipid metabolism and glucose homeostasis. PPARgamma is not only highly expressed in adipose tissue but also in cells involved in the immune system, and it exerts anti-inflammatory activities. We showed that eosinophils, a major inflammatory cell in allergic inflammation, express PPARgamma. PPARgamma negatively modulates eosinophil functions, such as survival, chemotaxis, antibody-dependent cellular cytotoxicity and degranulation. Recently, three independent groups have demonstrated that PPARgamma agonists inhibit airway inflammation in an animal model of asthma. This evidence suggests that PPARgamma agonists may be a new therapeutic modality for the treatment of allergic diseases including asthma.