Yuta Ohira

Inhibition of small-conductance Cl− channels by the interleukin-1β-stimulated production of superoxide in rabbit gastric parietal cells

We have shown previously that the G protein‐coupled production of superoxide anion (O2−) leads to closure of small‐conductance Cl− channels (0.3–0.4 pS) in the basolateral membrane of rabbit parietal cells. In the present study, effects of interleukin‐1β (IL‐1β) on the Cl− channel were investigated. In the whole‐cell patch‐clamp recording, IL‐1β (0.3–10 ng ml−1) inhibited the whole‐cell Cl− current recorded from a parietal cell within isolated rabbit gastric glands. Variance noise analysis of the whole‐cell Cl− current showed that the single channel conductance of the Cl− channel that is sensitive to IL‐1β is 0.37 pS. The IL‐1β (1 ng ml−1)‐induced decrease of the Cl− current was abolished by anti‐IL‐1β antibody (2 μg ml−1), recombinant IL‐1 receptor antagonist (500 ng ml−1), GDPβS (500 μM) and superoxide dismutase (100 units ml−1), a scavenger of O2−. Northern blot analysis showed that the mRNA of the IL‐1 receptor was selectively expressed in rabbit gastric parietal cells. In the dihydrofluorescein diacetate‐loaded single parietal cells in gastric glands, IL‐1β (0.3–10 ng ml−1) stimulated the production of oxygen radicals. Y‐27632 (1–10 μM), a specific Rho‐kinase inhibitor, and fluvastatin (10 μM), an indirect inhibitor for Rho proteins, significantly inhibited the IL‐1β‐induced effects on the channel activity and production of oxygen radicals. IL‐1β (0.3–10 ng ml−1) activated Rho in the parietal cells. These results indicate that IL‐1β binds to the IL‐1 receptor of gastric parietal cells and inhibits the small‐conductance Cl− channel via the G protein‐mediated Rho/Rho‐kinase‐dependent production of O2−.

Z-505 hydrochloride, an orally active ghrelin agonist, attenuates the progression of cancer cachexia via anabolic hormones in Colon 26 tumor-bearing mice

Cancer cachexia is a progressive wasting syndrome characterized by anorexia and weight loss, specifically muscle wasting and fat depletion. There is no therapeutic agent for treatment of this syndrome. We investigated the anti-cachexia effects of Z-505 hydrochloride (Z-505), a new oral growth hormone secretagogue receptor 1a (GHSR1a) agonist, using a mouse model of cancer cachexia. We performed a calcium flux assay in Chinese hamster ovary (CHO-K1) cells stably expressing human GHSR1a to quantify the agonistic activity of Z-505. In Colon 26 tumor-bearing mice, Z-505 (300mg/kg, p.o., twice daily) was administered for 7 days to assess its anti-cachexia effects. Body weight and food intake were monitored during the period, and the skeletal muscle and epididymal fat weights were measured. Serum levels of insulin, insulin-like growth factor 1 (IGF-1), interleukin-6 (IL-6), and corticosterone were measured to confirm the mechanism of the anti-cachexia action of Z-505. Z-505 showed strong agonistic activity similar to that of human ghrelin, with a half maximal effective concentration (EC50) value of 0.45nM. Z-505 treatment significantly increased food intake and inhibited the progression of weight loss. Z-505 also significantly attenuated muscle wasting and fat loss, and increased circulating levels of anabolic factors such as insulin and IGF-1, but not catabolic factors such as IL-6 and corticosterone. These findings suggest that Z-505 might be effective in the treatment of cachexia via the increased anabolic hormone levels stimulated by the activation of the ghrelin receptor, GHSR1a.

Z-505 hydrochloride ameliorates chemotherapy-induced anorexia in rodents via activation of the ghrelin receptor, GHSR1a

Abstract Despite its therapeutic advantages, chemotherapy with anti‐cancer drugs can cause adverse effects, including anorexia and weight loss. Although most patients with cancer suffer from anorexia during chemotherapy, resulting in the need to suspend or cease treatment and thereby worsening prognosis, treatment options for anorexia remain limited. Ghrelin is an orexigenic hormone that has been proposed to prevent anorexia. To investigate the potential of ghrelin receptor agonists, synthetic small‐molecule compounds, as preventive therapies for chemotherapy‐induced anorexia, we studied the effects of Z‐505 hydrochloride (Z‐505), a new oral growth hormone secretagogue receptor 1a (GHSR1a) agonist, in cisplatin‐ and 5‐fluorouracil (5‐FU)‐induced anorexia animal models. The agonistic activity of Z‐505 was examined using calcium flux assays in Chinese hamster ovary (CHO‐K1) cells stably expressing rat or mouse GHSR1a. Z‐505 showed agonistic activity for rat GHSR1a and mouse GHSR1a, with a half maximal effective concentration (EC50) of 2.08 nM and 5.46 nM, respectively. In a cisplatin‐induced anorexia rat model, administration of Z‐505 (30, 100 or 300 mg/kg, p.o., once daily) significantly improved the cisplatin‐induced reduction in food intake and body weight. In addition, treatment with Z‐505 (100 or 300 mg/kg, p.o., once daily) prevented the 5‐FU‐induced decrease in food intake and body weight in the 5‐FU‐induced mouse model. Our results demonstrate that Z‐505 ameliorates cisplatin‐ and 5‐FU‐induced anorexia through the activation of the ghrelin receptor, GHSR1a, suggesting its usefulness in the preventive treatment of anorexia during chemotherapy.