Heat shock protein 70 is necessary to improve mitochondrial bioenergetics and reverse diabetic sensory neuropathy following KU-32 therapy.

Impaired neuronal mitochondrial bioenergetics contributes to the pathophysiologic progression of diabetic peripheral neuropathy (DPN) and may be a focal point for disease management. We have demonstrated that modulating heat shock protein (Hsp) 90 and Hsp70 with the small-molecule drug KU-32 ameliorates psychosensory, electrophysiologic, morphologic, and bioenergetic deficits of DPN in animal models of type 1 diabetes. The current study used mouse models of type 1 and type 2 diabetes to determine the relationship of changes in sensory neuron mitochondrial bioenergetics to the onset of and recovery from DPN. The onset of DPN showed a tight temporal correlation with a decrease in mitochondrial bioenergetics in a genetic model of type 2 diabetes. In contrast, sensory hypoalgesia developed 10 weeks before the occurrence of significant declines in sensory neuron mitochondrial bioenergetics in the type 1 model. KU-32 therapy improved mitochondrial bioenergetics in both the type 1 and type 2 models, and this tightly correlated with a decrease in DPN. Mechanistically, improved mitochondrial function following KU-32 therapy required Hsp70, since the drug was ineffective in diabetic Hsp70 knockout mice. Our data indicate that changes in mitochondrial bioenergetics may rapidly contribute to nerve dysfunction in type 2 diabetes, but not type 1 diabetes, and that modulating Hsp70 offers an effective approach toward correcting sensory neuron bioenergetic deficits and DPN in both type 1 and type 2 diabetes.

Rapid and sensitive high-performance liquid chromatographic assay for novobiocin in human serum.

In this paper we present a new HPLC method for the determination of novobiocin in human serum. The assay uses mitomycin C as an internal standard, protein precipitation with acetonitrile, an ODS reversed-phase column with an isocratic mobile phase of acetonitrile-0.01 M phosphoric acid (80:20, v/v), and UV detection at 340 nm. The assay has a lower limit of quantitation of 1 microgram/ml and is linear over the range of 1-1000 micrograms/ml. The assay is ideally suited for use in clinical trials as it requires minimal amounts of serum, is highly sensitive and reproducible, is performed with minimal sample preparation, and involves a short run time. It should prove important in evaluating the potential of novobiocin as a means to modulate resistance to antineoplastic chemotherapy and in therapeutic drug monitoring of the growing number of patients receiving novobiocin to control methicillin-resistant Staphylococcus aureus infections.

Determination of plasma novobiocin levels by a reversed-phase high-performance liquid chromatographic assay.

A simple and specific reversed-phase high-performance liquid chromatographic (HPLC) assay for the determination of novobiocin levels in human plasma has been developed. The sample preparation was performed by deproteinization with methanol. Prednisone was used as an internal standard. Both novobiocin and prednisone were separated on a C8 column with a gradient elution of acidic water (pH 3.0)-methanol. The recovery of novobiocin from plasma was nearly complete. The linear range was 5-1000 microM in 0.5 ml of plasma with a minimum limit of determination of 2.25 fmol of novobiocin at 254 nm. The method has been implemented and validated in an ongoing clinical trial.

Cisplatin and novobiocin in the treatment of non-small cell lung cancer. A Southwest Oncology Group study.

Novobiocin, a commercially available oral antibiotic, inhibits DNA topoisomerase II in a manner shown in cell culture to enhance the cytotoxicity of alkylating agents and cisplatin. Thirty-six patients were entered on a Phase II trial using high-dose cisplatin (100 mg/m2 on days 1 and 8 for four cycles) after steady-state dosing with novobiocin (1000 mg or four 250-mg capsules every 12 hours for six doses, four of which were administered before each dose of cisplatin). One patient remains on study and cannot be evaluated for response. No complete responses were seen. Three patients (8%) had partial responses and an additional patient had an unconfirmed partial response. The median survival time of all patients was just less than 7 months. These results are comparable with those of other concurrent Southwest Oncology Group (SWOG) Phase II and III trials of high-dose cisplatin in non-small cell lung cancer (NSCLC). Novobiocin plasma levels were obtained for three patients and were approximately 50% of the optimal concentration as reported in cell culture for potentiation of cytotoxicity. It was concluded that an optimum test of novobiocin as a modulator of cytotoxicity may require the availability of an intravenous preparation.

Determination of novobiocin residues in milk, blood, and tissues by liquid chromatography.

Residues of novobiocin in milk, blood, and tissues can be detected by microbiological tests but cannot be distinguished from other antibiotics. A simple liquid chromatographic (LC) method was developed for identification of residues. Tissues were blended and milk and blood serum were mixed with 0.2M NH4H2PO4. The mixture was deproteinized by adding aqueous methanol and filtering. The LC apparatus consisted of a variable wavelength detector, set at 340 nm, an automatic loop injector, and a C18 column with guard cartridge. The flow rate was 1 mL/min and the solvent mixture of 0.01M H3PO4-acetonitrile-methanol was programmed from 50 + 0 + 50 (0-1 min) to 20 + 80 + 0 (20 min). Novobiocin was concentrated directly by solid-phase extraction on the analytical column. Five or more 200 microL aliquots of the filtrate in water-methanol (1 + 1) (adjusted if necessary) were injected with the column solvent at 50 + 0 + 50. After the final injection, the program was run to completion. Recoveries were 90-100% with sensitivities of 0.05 ppm or less. The procedure should be adaptable for use with formulations and feeds.

Steady-state serum pharmacokinetics of novobiocin and rifampin alone and in combination.

Because of the potential of novobiocin-rifampin for oral therapy of methicillin-resistant Staphylococcus aureus infection, we evaluated the pharmacokinetics of novobiocin and rifampin, alone and in combination, in a randomized, crossover, multiple-dose evaluation (500 mg of novobiocin and 300 mg of rifampin administered orally, twice a day, for 27 doses) in 10 volunteers. The half-lives of novobiocin and rifampin when administered alone were 5.85 +/- 1.20 and 1.46 +/- 0.30 h, respectively; when administered in combination, the half-lives were 2.66 +/- 0.65 and 1.43 +/- 0.29 h, respectively. This difference was significant for novobiocin. The area under the curve also differed significantly for novobiocin when administered in combination. No significant differences were seen in the maximum concentration of drug in serum, the time to maximum concentration of drug in serum, or both for either drug when single and combination therapy groups were compared. A change in clearance of novobiocin rather than a change in absorption is the more likely explanation for these findings. The mechanism remains to be elucidated. Nevertheless, the trough serum concentrations of both novobiocin and rifampin were in excess of the MIC for 90% of strains tested of methicillin-resistant S. aureus, even when coadministered.

Studies on protein binding of antibiotics. III. Effect of novobiocin on protein binding and pharmacokinetics of cefoperazone and cefazolin.

The drug-protein interactions between cefoperazone (CPZ) and novobiocin (NB), and between cefazolin (CEZ) and NB were investigated. Though there was a remarkable reduction of CPZ or CEZ binding to rabbit serum and human serum albumin with increases in drug concentrations above 3.0x10-4M (CPZ: 200 microgram/ml, CEZ: 140 microgram/ml), NB binding was not affected. In addition, when CPZ or CEZ was added to the NB solution, NB binding was not altered and remained above 90%. Therefore, it was evident that NB had a high capacity for binding to protein, compared with CPZ or CEZ. From the competitive study, the main binding site of NB to protein appeared to differ from that of CPZ or CEZ. The CPZ or CEZ serum levels in rabbits for the simultaneous adminstration of NB were significantly higher than those for the control experiments, however, the NB serum levels were not greatly affected by CPZ or CEZ.