Taiji Hayashi

Mechanism of nephrotoxicity induced by repeated administration of cadmium chloride in rats

To explore the mechanism of Cd nephrotoxicity, CdCl2 was subcutaneously injected to rats, at 3 mg Cd/kg body weight once a day, for 8 d. In the liver, Cd bound to metallothioneins (MTs-Cd) rose from d 1 after the initiation of CdCl2 administration, and reached a plateau after the administration ceased. In the plasma, MTs-Cd rose from d 4, peaked on d 8, and gradually fell thereafter. In the kidneys, leucine aminopeptidase (LAP) and N-acetyl beta-D-glucosaminidase (NAG) fell during d 6-20, and Cd bound to cellular membranes (Mem-Cd) rose from d 1 and reached a plateau during d 6-20. The Mem-Cd levels were significantly correlated with the reduction in the LAP and NAG activity; the values of MTs-Cd plus Mem-Cd were almost equivalent to those of total Cd. These findings showed that the hepatic synthesis of MTs-Cd occurred followed by its release into plasma; the extent of renal injury was aggravated as the plasma level of MTs-Cd rose; and a greater part of the renal Cd distributed intracellularly as the MTs-binding form, while the residual Cd distributed as the cellular membrane-binding form. Also, it was suggested that Cd that occurred as the cellular membrane- binding form in the kidneys was involved in manifestation of renal injury.

Kinetics of Cd2+ in plasma, liver and kidneys after single intravenous injection of Cd-metallothionein-II

To explore the kinetics of Cd2+ in the body, rats received a single intravenous injection of CdCl2 or Cd-saturated metallothionein-II at 0.3 mg Cd/kg body weight. Cd2+ in the two agents was biexponentially eliminated from plasma: rapidly in the first 5 min, and gradually later. Compared with CdCl2, Cd-saturated metallothionein-II showed lower Cd2+ concentrations in plasma during the first 30 min; larger values for parameters concerning distribution of Cd2+, its total body clearance and half-life time in the beta phase. Cd2+ uptake in the liver was higher with CdCl2, and, conversely, in the kidneys it was higher with Cd-saturated metallothionein-II. In Cd-saturated metallothionein-II, the renal content of Cd2+ reached a maximum (8 micrograms Cd2+/g tissue) on day 1, gradually decreasing thereafter; there was a higher area under the Cd2+ content-time curve, and a lower mean residence time of Cd2+; the kidneys showed severe necrosis and defluxion of proximal tubular cells at days 1 and 5, although there were regenerative and reversion signs on day 5. These findings suggested that, in the case of Cd-saturated metallothionein-II, Cd2+ being taken into the cells of proximal tubules was excluded predominantly due to cellular death and the resultant defluxion.

Activation of Stellate Cells Before Induction of Hepatic Fibrosis - Precise Timing in Choline-deficient Diet-fed Rat Model.

Quiescent hepatic stellate cells (HSCs) store vitamin A as lipid droplets in the cytoplasm. The activated HSCs by several stimuli have functions similar to that of myofibroblasts and play key roles in hepatic fibrosis [1-3]. However, precise timing between activation of the HSC and induction of hepatic fibrosis is still unknown. Choline-deficient (CD) diet induces fatty liver and subsequently hepatic fibrosis in rats. We investigated the changes of HSCs in the progress of hepatic fibrosis induced by CD diet in rats, and analyzed the time course from the activation of the HSCs to the induction of hepatic fibrosis.

Abstract C178: TAS-117, a highly potent and selective non-ATP competitive inhibitor of AKT, demonstrates a toxicity profile with manageable hyperglycemia in rats.

Background: TAS-117 is a small molecule which inhibits the PI3K-AKT-mTOR signaling pathway, a critical regulator of cell survival, by stimulating cell proliferation and inhibiting apoptosis. One of the most notable AKT-related adverse events is hyperglycemia which has been a dose limiting toxicity (DLT) in some clinical trials. We elucidate the time-dependent changes of hyperglycemia induced by TAS-117 and try an approach to manage the hyperglycemia in the present study. Materials and Methods: TAS-117 was orally administered to male rats repeatedly for 2 weeks (QD) to evaluate the toxicities of TAS-117. Blood glucose and insulin were measured continuously for 24 hours on the first and last day of dosing. Water intake recording and urinalysis were also performed to monitor for diabetes-related findings. Then, we treated the rats with varying anti-diabetic agents, gliclazide, mitiglinide calcium hydrate, pioglitazone hydrochloride, and metformin hydrochloride, in order to ameliorate the observed diabetes-like effects. Results: In continuous monitoring of blood glucose levels, TAS-117 induced transient elevation of blood glucose and insulin following daily oral administration. The peak level of blood glucose was observed between 4 and/or 8 hours after dosing. TAS-117-induced hyperglycemia reverted to baseline by 24 hours after dosing. Blood insulin levels correlatively increased and decreased with changes in blood glucose levels. Additionally, TAS-117 induced diabetes-like changes including body-weight-gain suppression, increases in water intake, urine volume, and urine glucose level were observed. These changes were deemed to be related to the hyperglycemia caused by TAS-117. However, the hyperglycemic effects of TAS-117 were most ameliorated by one of the anti-diabetic agents given, Metformin hydrochloride, an inhibitor of gluconeogenesis. The peak in blood glucose levels in Metformin medicated rats was suppressed up to 31% as compared with that in TAS-117 alone treated rats. Conclusion: TAS-117’s main toxic effects in rats were diabetes-like, including hyperglycemia and blood insulin elevation due to TAS-117’s dysregulation of carbohydrate metabolism. However, these adverse effects were transient and reversible and were controlled by a particular class of anti-diabetic agent. Therefore, TAS-117 has the potential to be administered on a daily schedule without inducing clinically significant hyperglycemia. Citation Information: Mol Cancer Ther 2013;12(11 Suppl):C178. Citation Format: Kenji Moriyama, Masahiro Yamaguchi, Shigeo Sugimoto, Hirofumi Matsumura, Fumiko Ninomiya, Kazuhiko Besshi, Fumio Morita, Taiji Hayashi, Ryouto Fujita, Hiroto Fukushima, Toshiyasu Shimomura, Kazuhiko Yonekura, Teruhiro Utsugi. TAS-117, a highly potent and selective non-ATP competitive inhibitor of AKT, demonstrates a toxicity profile with manageable hyperglycemia in rats. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr C178.