miR-208a as a biomarker of isoproterenol-induced cardiac injury in Sod2+/- and C57BL/6J wild-type mice.

This investigation examined microRNA-208a (miR-208a) as a potential biomarker of isoproterenol (ISO)-induced cardiac injury in superoxide dismutase-2 (Sod2(+/-) ) and the wild-type mice, and the potential sensitivity of Sod2(+/-) mice to ISO-induced toxicity. A single intraperitoneal injection of ISO was administered to age-matched wild-type and Sod2(+/-) mice at 0, 80, or 160 mg/kg. Plasma miR-208a, cardiac troponin I (cTnI), and ISO systemic exposure were measured at various time points postdose. Hearts were collected for histopathology examination and for tissue expression of miR-208a and myosin heavy chain 7. ISO administration caused increases in cTnI and miR-208a plasma levels that correlated with myocardial damage; however, the magnitude of increase differed according to the types of mice. At similar ISO systemic exposure, the magnitude of cTnI was greater in wild-type mice compared to Sod2(+/) (-) mice; however, the magnitude of miR-208a was greater in Sod2(+/-) mice than that of the wild-type mice. Myocardial degeneration occurred at ≥3 hr in the wild-type and ≥6 hr in Sod2(+/) (-) mice. At ≥24 hr after ISO administration, miR-208a appeared superior to cTnI in indicating myocardial injury in both wild-type and Sod2(+/-) mice. Sod2(+/-) mice were not more sensitive than wild-type mice to ISO-induced toxicity.

Responses of the steroidogenic pathway from exposure to methyl-tert-butyl ether and tert-butanol.

Methyl tertiary-butyl ether (MTBE) is a solvent and fuel additive included in reformulated gasoline to increase combustion efficiency. While widespread use in motor fuels in the U.S. was discontinued after MTBE was detected in surface and ground waters due to concerns about environmental persistence and water quality, it is still manufactured in the U.S. for export. Questions concerning the etiology of rat Leydig cell and mouse liver tumors identified in extremely high dose cancer studies have led to an interest in evaluating potential hormonal imbalances and endocrine system involvement. To address the possibility that MTBE or its metabolite, tert-butanol (TBA), are interacting with components of the endocrine system that are involved in steroidogenesis a number of targeted experiments were performed focusing mostly on the primary gonadal steroids, estradiol and testosterone. The goal of the experiments was to gain a better understanding of potential interactions with the steroidogenic pathway, including effects specifically on aromatase, the P450 enzyme that converts testosterone to estradiol. In three GLP-compliant in vitro guideline studies, MTBE and TBA were classified as non-binders to the androgen receptor, were classified negative for effects on testosterone and estradiol in the steroidogenesis assay, and were classified as non-inhibitors of aromatase activity. In three 14-day in vivo experiments involving gavaging of male Sprague-Dawley rats with doses of MTBE ranging from 400 to 1,500 mg/kg bw/day, the lack of definitive and consistent supporting statistically significant findings in steroid hormone measurements and aromatase activity and mRNA measured in liver and testis microsomes further suggested that it is unlikely that MTBE is interacting with the endocrine system directly. Evidence of other underlying systemic effects were also seen, including reduced body weight gain, increased adrenal weights, and elevated corticosterone suggestive of a more general stress response. Taken together, the results from these studies suggest that MTBE and TBA do not directly impact the steroidogenic pathways involved in estrogen and androgen production.

First-in-class pan caspase inhibitor developed for the treatment of liver disease.

A series of oxamyl dipeptides were optimized for pan caspase inhibition, anti-apoptotic cellular activity and in vivo efficacy. This structure-activity relationship study focused on the P4 oxamides and warhead moieties. Primarily on the basis of in vitro data, inhibitors were selected for study in a murine model of alpha-Fas-induced liver injury. IDN-6556 (1) was further profiled in additional in vivo models and pharmacokinetic studies. This first-in-class caspase inhibitor is now the subject of two Phase II clinical trials, evaluating its safety and efficacy for use in liver disease.

Characterization of IDN-6556 (3-[2-(2-tert-butyl-phenylaminooxalyl)-amino]-propionylamino]-4-oxo-5-(2,3,5,6-tetrafluoro-phenoxy)-pentanoic acid): a liver-targeted caspase inhibitor.

The potency, efficacy, and pharmacokinetic properties of IDN-6556 (3-[2-[(2-tert-butyl-phenylaminooxalyl)-amino]-propionylamino]-4-oxo-5-(2,3,5,6-tetrafluoro-phenoxy)-pentanoic acid), a first-in-class caspase inhibitor in clinical trials for the treatment of liver diseases, were characterized in vivo in rodent models. In the mouse alpha-Fas model of liver injury, i.p. administration of IDN-6556 resulted in marked reduction of alanine aminotransferase (ALT), apoptosis, and caspase activities at a dose of 3 mg/kg. At this dose, IDN-6556 was also effective when given up to 2 h before alpha-Fas and as late as 4 h after alpha-Fas administration. In both the alpha-Fas and d-galactosamine/lipopolysaccharide (D-Gln/LPS) model, ED(50) values in the sub-milligram per kilogram range were established after a number of routes of administration (i.p., i.v., i.m., or p.o.), ranging from 0.04 to 0.38 mg/kg. Efficacy was also demonstrated in the rat D-Gln/LPS model with 67 and 72% reductions in ALT activities after i.p. and p.o. treatment with IDN-6556 (10 mg/kg), respectively. Pharmacokinetic analysis in the rat demonstrated rapid clearance after i.v., i.p., and s.c. administration with terminal t(1/2) ranging from 46 to 51 min. Low absolute bioavailability after p.o. administration was seen (2.7-4%), but portal drug concentrations after oral administration were 3-fold higher than systemic concentrations with a 3.7-fold increase in the terminal t(1/2), indicating a significant first-pass effect. Liver concentrations remained constant after oral administration for at least a 4-h period, reaching a C(max) of 2558 ng/g liver at 120 min. Last, 51 +/- 20 and 4.9 +/- 3.4% of IDN-6556 was excreted intact in bile after i.v. and p.o. administration, respectively. This evaluation indicates that IDN-6556 has marked efficacy in models of liver disease after oral administration and thus, is an excellent candidate for the treatment of liver diseases characterized by excessive apoptosis.