Gene Expression Analysis Reveals New Possible Mechanisms of Vancomycin-Induced Nephrotoxicity and Identifies Gene Markers Candidates

Vancomycin, one of few effective treatments against methicillin-resistant Staphylococcus aureus, is nephrotoxic. The goals of this study were to (1) gain insights into molecular mechanisms of nephrotoxicity at the genomic level, (2) evaluate gene markers of vancomycin-induced kidney injury, and (3) compare gene expression responses after iv and ip administration. Groups of six female BALB/c mice were treated with seven daily iv or ip doses of vancomycin (50, 200, and 400 mg/kg) or saline, and sacrificed on day 8. Clinical chemistry and histopathology demonstrated kidney injury at 400 mg/kg only. Hierarchical clustering analysis revealed that kidney gene expression profiles of all mice treated at 400 mg/kg clustered with those of mice administered 200 mg/kg iv. Transcriptional profiling might thus be more sensitive than current clinical markers for detecting kidney damage, though the profiles can differ with the route of administration. Analysis of transcripts whose expression was changed by at least twofold compared with vehicle saline after high iv and ip doses of vancomycin suggested the possibility of oxidative stress and mitochondrial damage in vancomycin-induced toxicity. In addition, our data showed changes in expression of several transcripts from the complement and inflammatory pathways. Such expression changes were confirmed by relative real-time reverse transcription–polymerase chain reaction. Finally, our results further substantiate the use of gene markers of kidney toxicity such as KIM-1/Havcr1, as indicators of renal injury

Characterization of the lipid composition of washed and percoll gradient centrifuged epididymal mouse sperm.

Capacitation is an important yet poorly understood process during which the fluidity of the sperm membrane increases to prepare sperm for the acrosome reaction (AR) and subsequent sperm-egg binding. While cholesterol efflux may be partially responsible for this increase, modification of lipid components, such as remodeling of specific phospholipid (PL) bound unsaturated fatty acyl chains, may also be involved, since no change in the cholesterol:PL molar ratio following capacitation in mouse has been previously described. In this study, lipid classes (cholesterol, PL, sulfogalactosylglycerolipid (SGG), diacylglycerol and triacylglycerol) were quantified and the fatty acyl chain compositions of phosphatidylcholine (PC) and phosphatidylethanolamine (PE) were characterized in washed non-capacitated (WS), washed capacitated (WCS), and Percoll gradient centrifuged (PGC) capacitated (PGCS) epididymal mouse sperm. Fatty acid methyl esters were generated from PC and PE by acid methanolysis and their identity was analyzed by gas chromatography. (Abstract shortened by UMI.

Evaluation of Antitrypanosomal Dihydroquinolines for Hepatotoxicity, Mutagenicity, and Methemoglobin Formation In Vitro

N1-Benzylated dihydroquinolin-6-ols and their corresponding esters display exceptional activity against African trypanosomes in vitro, and administration of members of this class of compounds to trypanosome-infected mice results in cures in a first-stage African trypanosomiasis model. Since a quinone imine intermediate has been implicated in the antiparasitic mechanism of action of these compounds, evaluation of the hepatotoxic, mutagenic, and methemoglobin-promoting effects of these agents was performed. 1-Benzyl-1,2-dihydro-2,2,4-trimethylquinolin-6-ol hydrochloride and 1-benzyl-1,2-dihydro-2,2,4-trimethylquinolin-6-yl acetate showed outstanding in vitro selectivity for Trypanosoma brucei compared to the HepG2, Hep3B, Huh7, and PLC5 hepatocyte cell lines. 1-Benzyl-1,2-dihydro-2,2,4-trimethylquinolin-6-ol hydrochloride and 1-(2-methoxybenzyl)-1,2-dihydro-2,2,4-trimethylquinolin-6-yl acetate were not mutagenic when screened in the Ames assay, with or without metabolic activation. The latter 2 compounds promoted time- and dose-dependent formation of methemoglobin when incubated in whole human blood, but such levels were below those typically required to produce symptoms of methemoglobinemia in humans. Although compounds capable of quinone imine formation require careful evaluation, these in vitro studies indicate that antitrypanosomal dihydroquinolines merit further study as drug candidates against the neglected tropical disease human African trypanosomiasis. </jats:p

Pharmacokinetics and Metabolism of 4R-Cembranoid.

4R-cembranoid (4R) is a natural cyclic diterpenoid found in tobacco leaves that displays neuroprotective activity. 4R protects against NMDA, paraoxon (POX), and diisopropylfluorophosphate (DFP) damage in rat hippocampal slices and against DFP in rats in vivo. The purpose of this study was to examine the metabolism and pharmacokinetics of 4R as part of its preclinical development as a neuroprotective drug. 10 µM 4R was found to be very stable in plasma for up to 1 hr incubation. 4R metabolism in human microsomes was faster than in the rat. Ten metabolites of 4R were detected in the microsomal samples; 6 dihydroxy and 4 monohydroxy forms of 4R. Male rats received a single dose of 4R at 6 mg/kg i.v., i.m., or s.c. The i.v. group had the highest plasma concentration of 1017 ng/mL. The t1/2 was 36 min and reached the brain within 10 min. The brain peak concentration was 6516 ng/g. The peak plasma concentration in the i.m. group was 163 ng/mL compared to 138 ng/mL in the s.c. group. The t1/2 of 4R after i.m. and s.c. administration was approximately 1.5 hr. The brain peak concentration was 329 ng/g in the i.m. group and 323 ng/g for the s.c. group. The brain to plasma ratio in the i.v. group was 6.4, reached 10 min after dose, whereas in the i.m. and s.c. groups was 2.49 and 2.48, respectively, at 90 min after dose. Our data show that 4R crosses the BBB and concentrates in the brain where it exerts its neuroprotective effect

In Vitro Metabolism and Stability of the Actinide Chelating Agent 3,4,3‐LI(1,2‐HOPO)

The hydroxypyridinonate ligand 3,4,3-LI(1,2-HOPO) is currently under development for radionuclide chelation therapy. The preclinical characterization of this highly promising ligand comprised the evaluation of its in vitro properties, including microsomal, plasma, and gastrointestinal fluid stability, cytochrome P450 inhibition, plasma protein binding, and intestinal absorption using the Caco-2 cell line. When mixed with active human liver microsomes, no loss of parent compound was observed after 60 min, indicating compound stability in the presence of liver microsomal P450. At the tested concentrations, 3,4,3-LI(1,2-HOPO) did not significantly influence the activities of any of the cytochromal isoforms screened. Thus, 3,4,3-LI(1,2-HOPO) is unlikely to cause drug-drug interactions by inhibiting the metabolic clearance of coadministered drugs metabolized by these enzymes. Plasma protein-binding assays revealed that the compound is protein-bound in dogs and less extensively in rats and humans. In the plasma stability study, the compound was stable after 1 h at 37°C in mouse, rat, dog, and human plasma samples. Finally, a bidirectional permeability assay demonstrated that 3,4,3-LI(1,2-HOPO) is not permeable across the Caco-2 monolayer, highlighting the need to further evaluate the effects of various compounds with known permeability enhancement properties on the permeability of the ligand in future studies

Abstract 731: SRI-28731, a highly potent and selective MAP4K4 (HGK) inhibitor for cancer therapy

Abstract MAP4K4, a Ser/Thr kinase, was identified as an important pro-migratory kinase in an siRNA screen, targeting 5,234 human genes for modulators of tumor cell motility. MAP4K4 siRNA potently suppressed cell invasion and migration of multiple cancer cell lines, indicating a broad role in cell motility. There are no drugs in the clinic that are known to specifically target MAP4K4 for cancer therapy. We have successfully developed an orally active, highly effective and selective MAP4K4 inhibitor (SRI-28731) with potent in vitro and in vivo anticancer activity. SRI-28731 is more potent than Paclitaxel (Taxol) against most of the breast cancer cell lines tested. SRI-28731 exhibits more potent activities against triple negative (MDA-MB-231, BT549 and Hs578T) than estrogen-dependent (T47D and MCF-7) breast cancer cell lines, and its potency is positively correlated with MAP4K4 expression in cancer cell lines. SRI-28731 is also more potent than Docetaxel against both androgen-dependent (LNCaP) and -independent (PC-3 and DU-145) prostate cancer cell lines. In vitro mechanistic studies showed that SRI-28731 induced apoptosis and a time-dependent M phase arrest. Treatment with SRI-28731 (12.5, 25 and 50 mg/kg/day) caused a significant dose-dependent growth reduction of PC-3 tumors (30%, 61% and 88% growth inhibition, respectively), while Docetaxel at its MTD (7.5 mg/kg; Q3Dx2) produced only 10-15% growth inhibition. At the end of PC-3 tumor xenograft studies, we conducted an ex vivo invasion assay using PC-3 tumor cells isolated from tumor-bearing mice. SRI-28731 significantly reduced ex vivo tumor cell invasion by ∼80%. Pharmacokinetic studies showed that SRI-28731 could be detected in plasma up to 8 hours after oral dosing, and drug plasma concentrations remained above the IC50 values needed to inhibit prostate or breast cancer proliferation. To quantitatively define the kinase selectivity of SRI-28731, we tested the interaction of SRI-28731 with 456 kinase protein kinases (KINOMEscan), followed by in vitro pharmacology studies. Our data indicated that SRI-28731 is a highly selective Type-II MAP4K4 inhibitor. Type II kinase inhibitors bind to both the ATP site and an adjacent hydrophobic site exposed in the non-activated kinase state. Generally, type II inhibitors show higher selectivity for targets, and act primarily by locking the equilibrium switch between conformational states in a way that prevents kinase activation, rather than directly inhibiting it. Elevated MAP4K4 expression is strongly associated with higher rate of metastasis, and is regarded as an independent predictor of overall survival in cancer patients. Since MAP4K4 is overexpressed in many human cancer cell lines but is undetectable in non-transformed epithelial cells, targeting MAP4K4 may provide effective anti-metastatic therapy with limited side effects on normal tissues. Citation Format: Chih-Tsung Chang, Jaehyeon Park, Wei Zhou, Xiaohe Liu, Barbara Sato, Dominic Dinh, Anna Furimsky, Lucia Beviglia, Lidia Sambucetti, Ling Jong. SRI-28731, a highly potent and selective MAP4K4 (HGK) inhibitor for cancer therapy. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 731. doi:10.1158/1538-7445.AM2014-731</jats:p

In vitro metabolic stability of 4R.

<p>10 μM 4R was incubated with human and rat liver microsomes at selected time points (0, 5, 15, 30 and 60 min). As positive control, 10 μM midazolam was incubated with human and rat microsomes at 0, 15, 30 and 60 min. 4R levels were determined by LC-MS/MS. All samples were assayed in duplicate.</p