Selective overexpression of human SIRT1 in adipose tissue enhances energy homeostasis and prevents the deterioration of insulin sensitivity with ageing in mice

SIRT1, a longevity regulator and NAD(+)-dependent deacetylase, plays a critical role in promoting metabolic fitness associated with calorie restriction and healthy ageing. Using a tissue-specific transgenic approach, the present study demonstrates that over-expression of human SIRT1 selectively in adipose tissue of mice prevents ageing-induced deterioration of insulin sensitivity and ectopic lipid distribution, reduces whole body fat mass and enhances locomotor activity. During ageing, the water-soluble vitamin biotin is progressively accumulated in adipose tissue. Over-expression of SIRT1 alleviates ageing-associated biotin accumulation and reduces the amount of biotinylated proteins, including acetyl CoA carboxylase, a major reservoir of biotin in adipose tissues. Chronic biotin supplementation increases adipose biotin contents and abolishes adipose SIRT1-mediated beneficial effects on insulin sensitivity, lipid metabolism and locomotor activity. Biochemical, spectrometric and chromatographic analysis revealed that biotin and its metabolites act as competitive inhibitors of SIRT1-mediated deacetylation. In summary, these results demonstrate that adipose SIRT1 is a key player in maintaining systemic energy homeostasis and insulin sensitivity; enhancing its activity solely in adipose tissue can prevent ageing-associated metabolic disorders.

Herpes simplex virus (HSV)-mediated ICAM-1 gene transfer abrogates tumorigenicity and induces anti-tumor immunity

BACKGROUND

Costimulatory and cellular adhesion molecules are thought to be essential components of antigen presentation in the immune response to cancer. The current studies examine gene transfer utilizing herpes viral amplicon vectors (HSV) to direct surface expression of adhesion molecules, and specifically evaluate the potential of a tumor-expressing intercellular adhesion molecule-1 (ICAM-1) to elicit an anti-tumor response.

MATERIALS AND METHODS

The human ICAM-1 (hICAM1) gene was inserted into an HSV amplicon vector and tested in a transplantable rat hepatocellular carcinoma and in a human colorectal cancer cell line. Cell surface ICAM-1 expression was assessed by flow cytometry. Lymphocyte binding to HSV-hICAM1-transduced cells was compared with that to cells transduced with HSV not carrying the ICAM gene. Tumorigenicity of HSV-hICAM1-transduced tumor cells were tested in syngeneic Buffalo rats. Additionally, immunization with irradiated (10,000 rads) HSV-hICAM1-transduced tumor cells was performed to determine its effect on tumor growth.

RESULTS

A 20-min exposure of tumor cells at a multiplicity of infection (MOI) of 1 resulted in high-level cell surface expression of human ICAM in approximately 25% of tumor cells. Transduced rat or human tumor cells exhibited significantly enhanced binding of lymphocytes (p < 0.05). HSV-hICAM1-transduced cells elicited an increase in infiltration by CD4(+) lymphocytes in vivo and exhibited decreased tumorigenicity. Immunization with irradiated HSV-hICAM1-transduced cells protected against growth of subsequent injected parental tumor cells.

CONCLUSIONS

HSV amplicon-mediated gene transfer is an efficient method for modifying the cell surface expression of adhesion molecules. Increased tumor expression of ICAM-1 represents a promising immune anti-cancer strategy.

Management of high-risk subsets in unstable angina

This article focuses on the optimal treatment of postinfarction, refractory, or recurrent angina based on the results of recent clinical trials. Many of our recommendations hold true for the general management of unstable angina, but special considerations for the high-risk subsets are emphasized. Specifically, we discuss acute medical management and suggest that an early aggressive strategy that leads to early coronary angiography with the goal of revascularization when feasible best serves this subset. A special emphasis on the emerging role of glycoprotein IIb-IIIa antagonists is made because the important role of platelets in coronary thrombosis has dominated recent views on the pathophysiology of unstable angina.

Rapid production of interleukin-2-secreting tumor cells by herpes simplex virus-mediated gene transfer: implications for autologous vaccine production

Production of autologous tumor vaccines would be facilitated by the development of a rapid and efficient method for the transfer of genes into freshly isolated cells. To evaluate the potential of replication defective herpes simplex viral (HSV) amplicon vectors as gene transfer vehicles for tumor vaccine generation, a vector that expresses the human interleukin-2 (IL-2) gene (HSV-IL2) and one that expresses Escherichia coli beta-galactosidase (HSVlac) were tested in hepatoma cells of both murine and human origin. Gene transfer into murine hepatoma cells (HEPA 1-6) was both rapid and highly efficient: greater than 50% of cells expressed beta-Gal when infected at a multiplicity of infection (m.o.i.) of 1 with an exposure period of 20 min. Moreover, gene transfer was as efficient in tumor cells after irradiation with 10,000 rads as in nonirradiated tumor cells. Irradiated HEPA 1-6 cells infected with HSV-IL2 for 20 min secreted IL-2 at a rate of 1,200 +/- 160 ng/10(6) cells per day. C57B1/6J mice immunized with irradiated, HSV-IL-2-transduced tumor cells produced in this way demonstrated specific tumor immunity by in vitro splenocyte tumoricidal activity and by in vivo protection against tumor challenge. Human hepatobiliary tumor specimens harvested at the time of operation, irradiated, and infected with HSV-IL-2 also produced nanogram quantities of IL-2/10(6) cells per 24 hr. These results indicate that the HSV amplicon vector is a good candidate vehicle for gene transfer in the production of autologous tumor vaccines. By allowing rapid gene transfer to freshly harvested tumor specimens, these vectors bypass the requirement for cell culture and make feasible reinfusion of genetically modified and irradiated autologous cells within hours of tumor harvest.

Interferon gamma protects against hepatic tumor growth in rats by increasing Kupffer cell tumoricidal activity

An increasing number of hepatic resections are being performed as potentially curative surgery for malignant liver neoplasms. Hepatectomy and subsequent liver regeneration produce a local environment that enhances growth of microscopic residual tumor. To determine if pretreatment with murine interferon gamma (IFN-gamma) can protect against such enhanced tumor growth, Buffalo rats were randomized to receive a 3-day treatment of IFN-gamma (50,000 U/qD intraperitoneally) or saline. Groups then underwent intrasplenic injection of 10(6) Morris hepatoma cells, followed 1 hour later by sham (control) or partial hepatectomy (PH) of 70%. PH significantly enhanced tumor growth within the liver (control, 8 +/- 3 nodules per liver; PH, 73 +/- 12 nodules per liver; P < .001). This enhancement was attenuated by prior administration of IFN-gamma IFN-gamma/PH, 16 +/- 3; P < .001 vs. PH). Growth factor release and liver regeneration were not affected significantly by pretreatment with IFN-gamma. The effect of IFN-gamma on tumor growth is associated with a significant enhancement of Kupffer cell (KC)-mediated tumoricidal activity (percentage of specific lysis, 55 +/- 10% control, 78 +/- 11% IFN-gamma, P < .01) but not lymphocyte-mediated tumoricidal activity. Because microscopic residual disease may be present after hepatectomies for cancer, IFN-gamma may be useful agent in retarding growth of residual tumors.

Effects of inhibition of the B subunit of DNA gyrase on conjugation in Escherichia coli

Antagonism of the DNA gyrase B subunit in the donor bacterium by coumermycin or thermal inactivation inhibited transfer of plasmid R64drd-11. Coumermycin also inhibited Hfr transfer, with kinetics after drug removal suggesting that transfer resumed from the point of inhibition, in contrast to inhibition with nalidixic acid, after which transfer reinitiated from the origin of transfer.

Genetic and biochemical characterization of norfloxacin resistance in Escherichia coli

In Escherichia coli the frequency of spontaneous single-step mutation to high levels of resistance to the newer 4-quinolone agent norfloxacin was confirmed to be over 300-fold lower than that to the older agent nalidixic acid. Serial passage on incremental concentrations of drug was necessary to produce mutants highly resistant to norfloxacin. Genetic analysis of one such highly resistant strain identified two mutations conferring drug resistance. One mutation, nfxA, mapped around 48 min on the E. coli genetic map and was shown to be an allele of gyrA by studies demonstrating an increased drug resistance of DNA gyrase reconstituted with the gyrase A subunit isolated from the mutant strain. These findings also identified the DNA gyrase A subunit as a target of norfloxacin. The second mutation, nfxB, mapped between 20 and 22 min was associated with additional resistances to tetracycline, chloramphenicol, and cefoxitin and with decreases in outer membrane porin protein OmpF. The nfxA and nfxB mutations together accounted for most, but not all, of the norfloxacin resistance phenotype of this strain.

Elimination of plasmid pMG110 from Escherichia coli by novobiocin and other inhibitors of DNA gyrase

The ability of novobiocin to eliminate (cure) the wild-type plasmid pMG110 from Escherichia coli has been compared with that of other inhibitors of the gyrase B subunit and of the gyrase A subunit. Novobiocin eliminated pMG110 , producing over 99% plasmid loss at concentrations two- to eightfold below the MIC for bacterial growth. Structurally related compounds ( clorobiocin , coumermycin A1, isobutyryl novenamine , and decarbamyl novobiocin) varied in their ability to eliminate pMG110 . Higher concentrations of drugs were required to eliminate pMG110 from a gyrB( Cour ) strain, implicating DNA gyrase in the curing phenomenon. For these drugs, the ratio of the concentration effecting maximal plasmid elimination to the MIC varied from 0.16 to 1.1, indicating that curing cannot be explained simply by inhibition of a pool of DNA gyrase equally available for replication of the bacterial chromosome and the plasmid DNA molecule. Inhibitors of the gyrase A subunit, nalidixic acid and oxolinic acid, eliminated pMG110 only to variable low levels. The differences in the ability of the gyrase A and B subunit antagonists to eliminate plasmids are discussed.

The pharmacokinetics of chlorbutol in man

The pharmacokinetics of chlorbutol were studied after oral administration in 4 healthy subjects on two occasions. Following the rapid attainment of peak concentrations, plasma concentrations fell by approximately 50 per cent in 24 h. After the first dose of chlorbutol, the terminal elimination half-life was 10.3 +/-1.3 days (mean +/- S.E.M), the volume of distribution was 233 +/- 141 and the plasma clearance was 11.6 +/- 1.0 ml min-1. The binding to plasma proteins was 57 +/- 3 per cent. In 3 of the 4 subjects, there was a small but significant decrease in the terminal half-life of chlorbutol after the second dose. The mean urinary recovery over 17 days in two of the subjects accounted for only 9.6 per cent of the dose, 7.4 per cent of the total as the glucuronide and sulphate conjugates and 2.2 per cent as unchanged chlorbutol. A significant factor in the elimination of chlorbutol may be its instability under physiological conditions. Its half-life in vitro is 37 days at pH 7.4. The long terminal half-life of chlorbutol makes it unsuitable as a sedative drug because of the considerable accumulation which will occur when the drug is taken in multiple doses.