MRI-guided intracerebral convection-enhanced injection of gliotoxins to induce focal demyelination in swine

Demyelinating disorders such as multiple sclerosis (MS) or transverse myelitis are devastating neurological conditions with no effective cure. Prevention of myelin loss or restoration of myelin are key for successful therapy. To investigate the disease and develop cures animal models with good clinical relevance are essential. The goal of the current study was to establish a model of focal demyelination in the brain of domestic pig using MRI-guided gliotoxin delivery. The rationale for developing a new myelin disease model in the domestic pig was based on the fact that the brain in pigs is anatomically and histologically much more similar to that of humans compared to the rodent brain. For MRI-assisted gliotoxin injection, eight 30 kg pigs were subjected to treatment with lysolecithin (20, 30 mg/ml); or with ethidium bromide (0.0125, 0.05, 0.2 mg/ml). Animals were placed in an MRI scanner for intraparenchymal targeting of gliotoxin into the corona radiata (250 μl over 1h), with real-time monitoring of toxin distribution on T1 scans and monitoring of lesion evolution over seven days using both T1 and T2 scans. After the last MRI, animals were transcardially perfused and brains were processed for histological and immunofluorescent analysis. Gadolinium-enhanced T1 MRI during injection demonstrated biodistribution of the contrast (as a surrogate marker for toxin distribution) and its diffusion through the brain parenchyma. Lesion induction was confirmed on T2-weighted MRI and histopathology, thus enabling the establishment of optimal doses of gliotoxins. To conclude, MRI-guided focal demyelination in swine is accurate and provides real-time confirmation of gliotoxin, thus facilitating placement of focal lesions with high precision. This new model of focal demyelination can be used for further investigation and development of novel therapeutic approaches.

Polymer functionalized single walled carbon nanotubes mediated drug delivery of gliotoxin in cancer cells

During recent years, significant development has been achieved in carbon nanotube conjugated with polymer system for drug delivery system (DDS). In the present study, we have prepared functionalized single walled carbon nanotube conjugated with chitooligosaccharide (f-SWNT-COS) as a Drug Delivery System. In addition, drug Gliotoxin (GTX) and targeting molecules (Lysozyme, p53 and Folic acid) have been incorporated into f-SWNT-COS. f-SWNTs-COS-GTX-p53, f-SWNTs-COS-GTX-lysozyme, f-SWNTs-COS-GTX-FA have been physiochemically characterized for DDS. FT-IR, SEM and TEM analysis confirmed the formation of chemical interaction and polymer coating. FT-IR result clearly confirmed the interaction between f-SWNT and COS. The effective drug release was monitored against cervical cancer (HeLa) cells and Breast Cancer (MCF-7) cells and it was found that all the three drug delivery systems showed significant cytotoxicity. f-SWNTs-COS-GTX-p53 delivery vehicle and its effective cytotoxicity on HeLa cells was further checked with fluorescent activated cell sorter analysis. Our results suggest that the f-SWNTs-COS-GTX-p53 is the most effective delivery vehicle with a controlled release and enhanced cytotoxicity rendered through apoptosis in human cervical cancer (HeLa) cells. These systems can further be used for the delivery of other commercially available anti cancer drugs as well.

Mechanism of action of the antifibrogenic compound gliotoxin in rat liver cells

Gliotoxin has been shown to promote a reversal of liver fibrosis in an animal model of the disease although its mechanism of action in the liver is poorly defined. The effects of gliotoxin on activated hepatic stellate cells (HSCs) and hepatocytes have therefore been examined. Addition of gliotoxin (1.5 microM) to culture-activated HSCs resulted in its rapid accumulation, resulting in increased levels of glutathione and apoptosis without any evidence of oxidative stress. In contrast, although hepatocytes also rapidly sequestered gliotoxin, cell death only occurred at high (50-microM) concentrations of gliotoxin and by necrosis. At high concentrations, gliotoxin was metabolized by hepatocytes to a reduced (dithiol) metabolite and glutathione was rapidly oxidized. Fluorescent dye loading experiments showed that gliotoxin caused oxidative stress in hepatocytes. Antioxidants--but not thiol redox active compounds--inhibited both oxidative stress and necrosis in hepatocytes. In contrast, HSC apoptosis was not affected by antioxidants but was potently abrogated by thiol redox active compounds. The adenine nucleotide transporter (ANT) is implicated in mitochondrial-dependent apoptosis. HSCs expressed predominantly nonliver ANT isoform 1, and gliotoxin treatment resulted in a thiol redox-dependent alteration in ANT mobility in HSC extracts, but not hepatocyte extracts. In conclusion, these data suggest that gliotoxin stimulates the apoptosis of HSCs through a specific thiol redox-dependent interaction with the ANT. Further understanding of this mechanism of cell death will aid in finding therapeutics that specifically stimulate HSC apoptosis in the liver, a promising approach to antifibrotic therapy.

Targeting hepatic stellate cells for cell-specific treatment of liver fibrosis

Since hepatic stellate cells (HSC) play a crucial role in the development of liver fibrosis, this cell is the major target for anti-fibrotic drugs. Most of the experimental drugs that influenced the HSC activity showed however low efficacy in vivo. Either a low uptake of the compounds in the cells that cause disease might account for this lack of effect, or side-effects in other cells may limit the dosage of the drugs. These side-effects may even counteract the beneficial effects. Therefore a selective delivery of drugs to the HSC may comprise a promising new way to improve liver fibrosis. The targeting to HSC has become a feasible option, because albumin-based carriers have been developed that preferentially distribute to HSC in fibrotic rat livers. In addition to the targeting of drugs, also the selective delivery of genes to HSC in fibrotic livers is of interest for therapeutic purposes and a start is made in this respect. The present review discusses the drugs to be targeted to HSC and summarizes some of the problems encountered during this novel strategy in the treatment of liver fibrosis.

Nuclear factor-kappa B activity and intestinal inflammation in dextran sulphate sodium (DSS)-induced colitis in mice is suppressed by gliotoxin

In acute DSS-induced colitis nuclear factor (NF)-kappaB-dependent inflammatory cytokines including IL-1 and tumour necrosis factor-alpha (TNF-alpha) are up-regulated. Here we examined the effects of gliotoxin, a fungal metabolite known to inhibit NF-kappaB activity, on cytokine production by a mouse cell system in vitro and on intestinal inflammation and NF-kappaB activation in vivo. In vitro gliotoxin decreased TNF-alpha gene expression and protein production by RAW-264.7 mouse macrophage-like cells stimulated with lipopolysaccharide. In vivo, gliotoxin treatment of mice was begun on day 3 of 5% DSS application dissolved in the drinking water and continued until day 8. Gliotoxin treatment dose-dependently down-regulated colonic inflammation as assessed histologically and in parallel there was a suppression of colonic TNF-alpha and IL-1alpha mRNA expression on day 8 as analysed by semiquantitative reverse transcriptase-polymerase chain reaction (P < 0.01). Furthermore, colonic NF-kappaB DNA-binding activity was increased in DSS-induced colitis and was suppressed by gliotoxin. These results demonstrate the essential role of NF-kappaB in DSS-induced colitis and indicate a molecular approach to the treatment of intestinal inflammatory disorders.

Inhibition of corneal inflammation by the topical use of Ras farnesyltransferase inhibitors: selective inhibition of macrophage localization

PURPOSE

Ras farnesyltransferase inhibitors are known to block the membrane translocalization of oncogenic Ras protein. They inhibit the cytoplasmic mitogen-activated protein kinase signaling cascade related to Ras protein. Thus far, Ras farnesyltransferase inhibitors have been exclusively regarded with the anticancer drugs. The object of this study was to elucidate the role of Ras farnesyltransferase inhibitors on the corneal opacity induced by an inflammatory stimulus.

METHODS

We used a cauterization-induced corneal inflammation model. The central corneas of BALB/c mice were cauterized with silver nitrate (1 mm in diameter). Ras farnesyltransferase inhibitors, either manumycin or gliotoxin eye drops (each drug dissolved in balanced salt solution [BSS] at concentrations of 1 mM), were topically delivered to the cauterized cornea every 8 hours; BSS eye drops were used as a control. Clinical signs such as corneal edema, opacity, and corneal neovascularization, which are major causes of visual disturbance, were then examined 96 hours after the cauterization. The corneal edema and opacity were clinically scored under a stereoscopic microscope. The corneal neovascularization was evaluated by the length of the blood vessels from the limbus and the sum of extension central angle of vascularized limbus. Furthermore, the corneas were examined histologically, and the phenotypes of the cornea-infiltrating cells were analyzed by flow cytometry.

RESULTS

The control corneas showed prominent edema, neovascularization, and opacity. Histologic analysis revealed corneal epithelial and endothelial cell loss and a large amount of inflammatory cell infiltration into the corneal stroma. Flow cytometric analysis revealed that most of the infiltrating cells were neutrophils and macrophages. In contrast, the degree of corneal edema, neovascularization, and opacity was significantly less in the manumycin- or gliotoxin-treated corneas than in the control corneas. Histologically, the manumycin- and gliotoxin-treated corneas showed minimum edema and good epithelialization. Flow cytometric analysis showed corneal infiltration of macrophages to be selectively and clearly inhibited. Neither manumycin nor gliotoxin produced any side effects in the noncauterized normal cornea either clinically or histologically.

CONCLUSIONS

Ras proteins play an important role in cauterization-induced corneal inflammation and the opacity it induces. Ras farnesyltransferase inhibitors thus have a great potential for improving the treatment of corneal opacity induced by a corneal inflammatory stimulus.