Preparation and evaluation of tributyrin emulsion as a potent anti-cancer agent against melanoma

Histone deacetylase inhibitors such as butyrate are known to exhibit anti-cancer activities in a wide range of cancer including melanoma. In spite of these potencies, butyrate is not practically used for cancer treatment due to its rapid metabolism and very short plasma half-life. Tributyrin, a triglyceride analog of butyrate, can act as a pro-drug of butyrate after being cleaved by intracellular enzymes. The present study sought to investigate a possibility to develop tributyrin emulsion as a potent anti-cancer agent against melanoma. Mixture of Tween80 and 1, 2-dimyristoyl-sn-glycero-3-phosphocholine as a surfactant to disperse tributyrin produced homogeneous emulsions with nanometer sizes, even without a harsh homogenization procedure. Tributyrin emulsion was more potent than butyrate in inhibiting the growth of B16-F10 melanoma cells. Accumulation of cells at sub G(0)/G(1) phase and the DNA fragmentation induced by tributyrin emulsion treatment revealed that tributyrin emulsion inhibited the growth of B16-F10 cells by inducing apoptosis. Treatment with tributyrin emulsion suppressed the colony formation of melanoma cells in a dose-dependent manner. Furthermore, after intraperitoneal administration into mice, tributyrin emulsion inhibited the formation of tumor colonies in the lung following intravenous injection of melanoma cells. Taken together, our data suggests that tributyrin emulsion may be developed as a potent anti-cancer agent against melanoma.

Comparison of the apoptosis-inducing capability of sulforaphane analogues in human colon cancer cells

The anticancer activity of sulforaphane is known to be mediated at least partly by apoptosis induction and associated with the presence of the -N=C=S moiety. The present study explored how oxidation of sulphur in the side chain of sulforaphane affected apoptosis induction to provide the chemical basis of sulforaphane effects. Sulforaphane analogues containing oxidised sulphur (alyssin, sulforaphane, erysolin and alyssin sulfone) exerted a superior growth inhibitory effect compared with sulforaphane analogues with nonoxidised sulphur (erucin and berteroin) in human colon cancer cell lines. Furthermore, erysolin was a more potent inducer of reactive oxygen species (ROS) and apoptosis compared with erucin. Erysolin-induced ROS generation and subsequent apoptosis were inhibited by pretreatment with the antioxidant N-acetyl-cysteine. Erysolin induced caspase-8 activation, while blockade of caspsase 8 activation inhibited apoptosis induced by erysolin. Taken together, sulforaphane analogues with oxidised sulphur were the most efficient apoptosis inducers, likely due to high-level ROS induction.

Nanoscaled iodized oil emulsion as a CT contrast agent for the detection of experimental liver tumors in a rat model

RATIONALE AND OBJECTIVES

To characterize an iodized oil emulsion for computed tomography (CT) imaging of experimental hepatic tumors in rat models.

MATERIALS AND METHODS

For characterizing the agents in normal rats, three rats were intravenously infused and imaged with clinical CT up to 1 week. Iopamidol solution was also used as controls (n = 3). For evaluating the feasibility of diagnosis of hepatic tumors, 12 rats were injected with C6 glial tumor cells into the liver 11, 9, 7, and 5 days before CT (n = 3 per day). After CT imaging, gross and histopathologic correlation of liver tumors with CT images were performed.

RESULTS

CT numbers of aorta and inferior vena cava (IVC) increased immediately after injection of the emulsion and remained above 200 Hounsfield units for 1 hour (maximum: 295.67 +/- 27.65 in aorta and 347.07 +/- 10.58 in IVC). The mean attenuation in liver and spleen was relatively stable between 30 and 180 minutes (maximum: 188.84 +/- 18.70 in liver and 210.97 +/- 15.83 in spleen). All 20 tumors later confirmed by pathology were detected as hypodense lesions on CT (sensitivity: 100%; range, 2.0-16.4 mm). The mean enhancement ratios of liver at all time points were significantly higher than those of tumors (P < .05).

CONCLUSION

The hepatic enhancement achieved by the iodized oil emulsion is reticuloendothelial system-specific with the property of blood pool enhancement and longer lasting than that achievable with the current water soluble agents. Thus, this agent may offer significant advantages for diagnosis of hepatic metastases.

A structure-based virtual screening approach toward the discovery of histone deacetylase inhibitors: identification of promising zinc-chelating groups

The inhibitors of histone deacetylases (HDACs) have drawn a great deal of attention due to their promising potential as small-molecule therapeutics for the treatment of cancer. By means of virtual screening with docking simulations under consideration of the effects of ligand solvation, we were able to identify six novel HDAC inhibitors with IC(50) values ranging from 1 to 100 muM. These newly identified inhibitors are structurally diverse and have various chelating groups for the active site zinc ion, including N-[1,3,4]thiadiazol-2-yl sulfonamide, N-thiazol-2-yl sulfonamide, and hydroxamic acid moieties. The former two groups are included in many drugs in current clinical use and have not yet been reported as HDAC inhibitors. Therefore, they can be considered as new inhibitor scaffolds for the development of anticancer drugs by structure-activity relationship studies to improve the inhibitory activities against HDACs. Interactions with the HDAC1 active site residues responsible for stabilizing these new inhibitors are addressed in detail.

Alpha-tocopheryl succinate potentiates the paclitaxel-induced apoptosis through enforced caspase 8 activation in human H460 lung cancer cells

Paclitaxel is one of the chemotherapeutic drugs widely used for the treatment of nonsmall cell lung cancer (NSCLC) patients. Here, we tested the ability of alpha-tocopheryl succinate (TOS), another promising anticancer agent, to enhance the paclitaxel response in NSCLC cells. We found that sub-apoptotic doses of TOS greatly enhanced paclitaxel-induced growth suppression and apoptosis in the human H460 NSCLC cell lines. Our data revealed that this was accounted for primarily by an augmented cleavage of poly(ADP-ribose) polymerase (PARP) and enhanced activation of caspase-8. Pretreatment with z-VAD-FMK (a pan-caspase inhibitor) or z-IETD-FMK (a caspase-8 inhibitor) blocked TOS/paclitaxel cotreatment-induced PARP cleavage and apoptosis, suggesting that TOS potentiates the paclitaxel-induced apoptosis through enforced caspase 8 activation in H460 cells. Furthermore, the growth suppression effect of TOS/paclitaxel combination on human H460, A549 and H358 NSCLC cell lines were synergistic. Our observations indicate that combination of paclitaxel and TOS may offer a novel therapeutic strategy for improving paclitaxel drug efficacy in NSCLC patient therapy as well as for potentially lowering the toxic side effects of paclitaxel through reduced drug dosage.

Liposome composition is important for retention of liposomal rhodamine in P-glycoprotein-overexpressing cancer cells

Multidrug resistance (MDR) caused by high expression of P-glycoprotein (Pgp) in cancer patients remains one of the major obstacles to successful therapy of cancer. Earlier studies have shown that the incorporation of Pgp-substrate drugs in liposomes may provide a strategy to circumvent Pgp-mediated drug efflux. The present study investigated the impact of liposome composition on the efflux of Pgp-substrate incorporated in liposomes. Liposomes with varying compositions were loaded with rhodamine 123, a fluorescent probe frequently used as a Pgp-substrate, and the retention of rhodamine was compared in two breast cancer cell lines: wild-type cells with no detectable Pgp expression (MCF-7/WT) and Pgp-expressing cells resulting from stable transfection of the MDR1 gene (MCF-7/Pgp). Pgp-expression decreased the rhodamine retention in MCF-7 cells, suggesting that Pgp is functional. Liposome loading increased rhodamine retention in MCF-7/Pgp cells, but not in MCF-7/WT cells. Surface charge of liposomes did not affect the rhodamine retention, whereas the incorporation of cholesterol and polyethyleneglycol-attached lipids was effective in further increasing the rhodamine retention in MCF-7/Pgp cells. Since further study demonstrated that the rate of rhodamine release from liposomes tended to be inversely correlated with rhodamine retention by cells, it seems likely that more rigid liposomes are able to sequester rhodamine more efficiently, thereby inhibiting direct interactions of rhodamine with Pgp proteins. Taken together, these findings suggest that Pgp-mediated MDR in cancer cells may be more effectively modulated by optimizing the composition of liposomes for loading Pgp-substrate anti-cancer drugs.

Topical administration of cyclosporin A in a solid lipid nanoparticle formulation

Cyclosporin A (CsA)-loaded solid lipid nanoparticles (SLN) were developed for improved skin penetration. CsA-loaded SLN, prepared using a hot homogenization method, were nano-sized (about 73 nm) with a slightly negative surface charge (about -16 mV) and stable under physiological conditions regardless of CsA incorporation. In vitro permeation studies using murine skin mounted in the Franz-type vertical diffusion assembly revealed that the skin permeation efficiency of CsA-loaded SLN was 2-fold higher than that of CsA-oil mixture in viable skin. Furthermore, topically administered CsA-loaded SLN relieved symptoms of atopic dermatitis (AD) in an in vivo murine model of AD by decreasing the T helper (Th) 2 cell-related cytokines interleukin (IL)-4 and -5. These results suggest that SLN are effective drug carriers for topical delivery andthat CsA-loaded SLN can be therapeutically applied in allergy-related skin disorders.

Biological nutrient and organic removal from meat packing wastewater with a unique sequence of suspended growth and fixed-film reactors

A unique sequence of anaerobic filter/suspended anaerobic/aerobic (AO) reactor/aerobic filter system was developed to alleviate the drawbacks of conventional suspended growth and fixed growth systems. An anaerobic filter (AF) was used to efficiently produce volatile fatty acids (VFAs) prior to the aerobic suspended growth. A second anaerobic reactor was installed in the A/O return activated sludge line to improve phosphorus uptake by potentially controlling glycogen accumulating organisms (GAOs). One biological aerobic filter (BAF) was used for nitrification followed by an anoxic filter for denitrification and a second BAF was used for effluent polishing. The meat packing wastewater had a biochemical oxygen demand (BOD) of 853 mg/L and total nitrogen (T-N) and total phosphorus (T-P) concentrations of 61.1 mg/L and 5.8 mg/L, respectively. The BOD removal efficiency was 99.0-99.7% and the suspended solids (SS) concentration in the effluent was below 10 mg/L. The T-N removal efficiency was maintained at greater than 75.0% except at low C/N ratios. A high T-P removal efficiency, 74.7-83.9%, was also obtained when the system was operated at a hydraulic retention time of 15.7 hrs. The AF successfully produced VFAs that aided in phosphorus removal. Additionally, recycled concrete aggregate used as attachment media in the biological filters continuously provided micronutrients and stabilized the pH.

Metabolic inhibition and kinetics of raloxifene by pharmaceutical excipients in human liver microsomes

This study was originally undertaken to establish the in vitro metabolic conditions and then evaluate the effect of pharmaceutical excipients (PEs) on drug metabolism in uridine diphosphoglucuronic acid-supplemented human liver microsomes. Poorly bioavailable raloxifene was chosen as a model drug. Intact drug and its two glucuronide metabolites were successfully isolated using gradient HPLC analysis and LC/MS analysis. Formation of raloxifene metabolites was affected by buffer compositions, incubation time and initial raloxifene concentrations. Under optimized metabolic conditions, 41.0% of raloxifene was converted to its metabolites after 2h incubation. This metabolic inhibition of raloxifene by the PEs occurred in a dose-dependent manner and accordingly formed two glucuronide metabolites. In the metabolic kinetics using Lineweaver-Burk analyses, Cremophor EL competitively inhibited formation of metabolites while sodium lauryl sulfate (SLS), polyvinylpyrrolidone K30 (PVP) and Tween 80 significantly inhibited in a mixed competition. Although some PEs showed inhibition on glucuronidation of raloxifene in vitro, their effects on in vivo bioavailability of raloxifene need to be confirmed directly due to the dilution factors and other complicated situations influencing the bioavailability.

Differential effects of selective cyclooxygenase-2 inhibitors in inhibiting proliferation and induction of apoptosis in oral squamous cell carcinoma

Cyclooxygenase-2 (COX-2), an enzyme that catalyzes the synthesis of prostaglandins, is made inducible by various stimuli such as inflammation. Although COX-2 is commonly overexpressed in a variety of premalignant and malignant conditions including oral leukoplakia and squamous cell carcinoma, relatively little research has compared the effects of various COX-2 inhibitors (celecoxib, NS-398, nimesulide and meloxicam). Therefore, we investigated the effects of four different selective COX-2 inhibitors on the growth of KB cells, derived from oral squamous cell carcinoma (OSCC) and its mechanisms. Celecoxib and NS-398 strongly suppressed the proliferation of KB cells at 10-100 microM, whereas nimesulide and meloxicam are less potent proliferation inhibitors. Only celecoxib induced apoptosis of the KB cells, as detected on the basis of DNA fragmentation, caspase-3/7 activation and cleaved poly(ADP-ribose) polymerase (PARP) fragmentation. All four COX-2 inhibitors increased COX-2 protein expression but suppressed prostaglandin (PG) E2 production in the KB cells, suggesting that the pro-apoptotic effect of celecoxib was unrelated to the inhibition of COX-2. Mechanistically, a high level of p53 protein and a low level of multidrug-resistant protein 1 (MRP1) and breast cancer resistant protein (BCRP) mRNA in KB cells with celecoxib may explain the differential effect of these selective COX-2 inhibitors in KB cells. Taken together, celecoxib is a good therapeutic candidate for treating OSCC through the suppression of cell proliferation and the induction of apoptosis in a COX-2 independent manner.

Novel cationic solid lipid nanoparticles enhanced p53 gene transfer to lung cancer cells

Mutations in the p53 tumor suppressor gene are the most common molecular genetic abnormalities to be described in lung cancer. However, there have been few reports of nonviral vector-mediated p53 gene delivery in lung cancer. A new formulation of cationic solid lipid nanoparticles (SLNs) for gene delivery was produced by the melt homogenization method with slight modification, and the SLNs were formulated by mixing tricaprin (TC) as a core, 3beta[N-(N', N'-dimethylaminoethane) carbamoyl] cholesterol (DC-Chol), dioleoylphosphatidylethanolamine (DOPE) and Tween 80 in various ratios. Plasmid DNA (pp53-EGFP)/SLNs complexes were transfected into human non-small cell lung cancer cells (H1299 cells) and transfection efficiency was determined by FACS analysis. The gene expression was determined by reverse transcription-polymerase chain reaction (RT-PCR) and Western blot analysis. The cellular growth inhibition and apoptosis of treated cells with pp53-EGFP/SLNs complexes were assessed by trypan blue exclusion assay and annexin V staining, respectively. In vivo biodistribution of plasmid DNA was investigated by PCR and RT-PCR. The transfection efficiency of SLN1 (TC:DC-Chol:DOPE:Tween 80=0.3:0.3:0.3:1), which showed the highest transfection efficiency among the SLN formulations, was higher than that of commercially available Lipofectin. The SLNs-mediated transfection of the p53 gene resulted in efficient high levels of wild-type p53 mRNA and protein expression levels in H1299 cells. The efficient reestablishment of wild-type p53 function in lung cancer cells restored the apoptotic pathway. Taken together, our results reveal that cationic SLN-mediated p53 gene delivery may have potential for clinical application as a nonviral vector-mediated lung cancer therapy due to its effective induction of apoptosis and tumor growth inhibition.

Preparation, characterization and in vitro cytotoxicity of paclitaxel-loaded sterically stabilized solid lipid nanoparticles

In an effort to develop an alternative formulation of paclitaxel suitable for parenteral administration, paclitaxel-loaded sterically stabilized solid lipid nanoparticles (SLNs) were prepared, characterized and examined for in vitro cytotoxicity. The SLNs, comprising trimyristin (TM) as a solid lipid core and egg phosphatidylcholine and pegylated phospholipid as stabilizers, were prepared using a hot homogenization method. Regardless of paclitaxel loading, the particle sizes and zeta potentials of the prepared SLNs were around 200nm and -38mV, respectively, suggesting that they would be suitable as a parenteral formulation. Cryo-scanning electron microscopy showed that the SLNs were homogeneous and spherical in shape, while differential scanning calorimetry measurement of the melting peak revealed that the TM exists as a solid in our formulation. Paclitaxel was loaded to the solid cores at a w/w ratio of 6%. Gel column chromatography showed that paclitaxel co-eluted with the phospholipids, indicating that paclitaxel was incorporated in the SLNs. An in vitro drug release study showed that paclitaxel was released from the SLNs in a slow but time-dependent manner. Furthermore, treatment of the OVCAR-3 human ovarian cancer cell line and the MCF-7 breast cancer cell line with paclitaxel-loaded SLNs yielded cytotoxicities comparable to those of a commercially available Cremophor EL-based paclitaxel formulation. These results collectively suggest that our optimized SLN formulation may have a potential as alternative delivery system for parenteral administration of paclitaxel.

Alpha-tocopheryl succinate sensitizes human colon cancer cells to exisulind-induced apoptosis

Sulindac sulfone (also known as exisulind) and its chemical derivatives are promising anticancer agents capable of inducing apoptosis in a variety of malignant cell types with minimal toxicity to normal cells. Here, we tested the ability of alpha-tocopheryl succinate (TOS), another promising anticancer agent, to sensitize colon cancer cells to exisulind-induced apoptosis. We found that sub-apoptotic doses of TOS greatly enhanced exisulind-induced growth suppression and apoptosis in the HCT116, LoVo and SNU-C4 human colon cancer cell lines. Our results revealed that this was accounted for primarily by an augmented cleavage of poly(ADP-ribose) polymerase (PARP) and enhanced activation of caspase-8, -9 and -3. Pretreatment with z-VAD-FMK (a pan-caspase inhibitor), z-IETD-FMK (a caspase-8 inhibitor) or z-LEHD-FMK (a caspase-9 inhibitor) blocked TOS and exisulind cotreatment-induced PARP cleavage and apoptosis. Furthermore, TOS/exisulind cotreatment induced JNK phosphorylation, while pretreatment with SP600151 (a JNK inhibitor) partially blocked cotreatment-induced caspase-dependent PARP cleavage and apoptosis. Taken together, these findings indicate that TOS sensitizes human colon cancer cells to exisulind-induced apoptosis. Apoptotic synergy induced by exisulind plus TOS seems likely to be mediated through a mechanism involving activation of caspases and JNK.

The association of increased lung resistance protein expression with acquired etoposide resistance in human H460 lung cancer cell lines

Chemoresistance remains the major obstacle to successful therapy of cancer. In order to understand the mechanism of multidrug resistance (MDR) that is frequently observed in lung cancer patients, here we studied the contribution of MDR-related proteins by establishing lung cancer cell lines with acquired resistance against etoposide. We found that human H460 lung cancer cells responded to etoposide more sensitively than A549 cells. Among MDR-related proteins, the expression of p-glycoprotein (Pgp) and lung resistance protein (LRP) were much higher in A549 cells compared with that in H460 cells. When we established H460-R1 and -R2 cell lines by progressive exposure of H460 cells to increasing doses of etoposide, the response against etoposide as well as doxorubicin was greatly reduced in R1 and R2 cells, suggesting MDR induction. Induction of MDR was not accompanied by a decrease in the intracellular accumulation of etoposide and the expression of MDR-related proteins that function as drug efflux pumps such as Pgp and MRP1 was not changed. We found that the acquired resistance paralleled an increased expression of LRP in H460 cells. Taken together, our data suggest the implicative role of LRP in mediating MDR in lung cancer.

p38MAPK inhibitor SB203580 sensitizes human SNU-C4 colon cancer cells to exisulind-induced apoptosis

Sulindac sulfone (exisulind), is a promising anticancer agent because of its ability to induce apoptosis in a variety of malignant cell types and its minimal toxicity to normal cells. The induction of apoptosis is thought to account for the growth inhibitory effect of exisulind. The mitogen-activated protein kinase (MAPK) cascade has been implicated in the regulation of apoptosis in response to exisulind. With human SNU-C4 colon cancer cells that were much more resistant to exisulind than other colon cancer cells, in this study, we investigated whether the modulation of MAPK activity by using selective MAPK inhibitors can contribute to sensitizing SNU-C4 cells to exisulind. Exisulind (400 and 600 microM) slightly increased the phosphorylation of pERK1/2 but pretreatment with the pERK1/2 inhibitor PD98059 did not significantly change the apoptotic response of SNU-C4 cells. The same doses of exisulind increased the phosphorylation of p38MAPK, and pretreatment with the p38MAPK inhibitor SB203580 significantly potentiated growth inhibition and apoptosis induced by exisulind in SNU-C4 cells. We further found that apoptosis induced by a combination of exisulind and SB203580 was mediated through caspase activation. Collectively, our findings indicate that selective p38MAPK inhibitors potentiate apoptosis induction by exisulind in SNU-C4 cells. Such combinations may provide a more effective and less toxic strategy for the prevention or treatment of colon cancer.

Improvement of bioavailability and photostability of amlodipine using redispersible dry emulsion

To improve the bioavailability and photostability of poorly water-soluble and photosensitive amlodipine, dry emulsion (DE) was prepared by spray-drying the oil-in-water emulsion of amlodipine. Labrafil M 1944 CS and dextrin were employed as oil phase and matrix material, respectively. Dispersing DE in distilled water formed an emulsion with a mean droplet size 1.4-fold larger than that of the homogenized amlodipine emulsion before spray-drying (0.24 +/- 0.30 microm versus 0.17 +/- 0.02 microm). The mean droplet size of DE remained unchanged during 6-month storage at room temperature. 94.4% versus 33.1% of amlodipine remained intact after 24-h UV irradiation of amlodipine as DE formulation or as powder. These data suggest that DE formulation greatly improved the photostability of amlodipine, as well as increasing the physical stability of emulsion systems. In vitro release of DE was higher than that of amlodipine powder (66% versus 48% release at 60 min). Consequently, DE formulation resulted in 2.6- and 2.9-fold higher Cmax and AUC0-24 h of amlodipine compared after oral administration of amlodipine powder in rats. Our data suggest that the DE may be a potential oral dosage form for amlodipine to improve its bioavailability.

Stabilization of all-trans retinol by loading lipophilic antioxidants in solid lipid nanoparticles

Loading of drugs into the solid matrix of solid lipid nanoparticles (SLNs) can be one of effective means to protect them against chemical degradation. In this study, the SLNs for all-trans retinol (AR) were formulated to improve the stability of AR, whose chemical instability has been a limiting factor in its clinical use. First of all, the physicochemical properties of AR-loaded SLNs, including mean particle diameter and zeta potential, were modulated by changing the total amount of surfactant mixture and the mixing ratio of eggPC and Tween 80 as surfactant mixture. The AR-loaded SLNs formulation was irradiated with a 60-W bulb to investigate the photostability. The extent of photodegradation was measured by high-performance liquid chromatography. The mean particle diameter and zeta potential of the smallest SLNs were 96 nm and -28 mV, respectively. The loading of AR in optimized SLNs formulations rather decelerated the degradation of AR, compared with AR solution dissolved in methanol. Our subsequent study showed that the co-loading of antioxidants greatly enhanced the stability of AR loaded in SLNs, compared with those loaded in SLNs without antioxidant. The photostability at 12 h of AR in SLNs was enhanced folds (43% approximately) higher than that in methanol solution (about 11%). Furthermore, the protecting effect of antioxidants was greatly dependent on the type of antioxidant. Taken together, AR could be effectively stabilized by being loaded in SLNs together with an antioxidant BHT-BHA.

Alpha-tocopheryl succinate, in contrast to alpha-tocopherol and alpha-tocopheryl acetate, inhibits prostaglandin E2 production in human lung epithelial cells

The production of prostaglandin E2 (PGE2), a key proinflammatory mediator, is regulated by the availability of its substrate, arachidonic acid (AA), and the activity of the enzyme cyclooxygenase (COX). Increased PGE2 production and COX-2 expression have been observed frequently in specimens from lung cancer patients. Agents that decrease PGE2 production may prevent the initiation and progression of lung cancer. We, therefore, tested the effects of alpha-tocopherol (alphaTOL) analogs on PGE2 production in human lung epithelial cells. Alpha-tocopheryl succinate (alphaTOS), but not alphaTOL or alpha-tocopheryl acetate (alphaTOA), inhibited the phorbol 12-myristate 13-acetate (PMA)-stimulated PGE2 production in three human lung epithelial cell lines (BEAS-2B, H460 and A549 cells). The effect of these compounds on PGE2 production was not correlated with their antioxidant activities, since alphaTOS alone did not inhibit PMA-induced generation of reactive oxygen species. alphaTOS had no effect on PMA-induced AA release or COX-2 expression, although post-incubation with alphaTOS inhibited COX activity and prostaglandin (PGE2 and PGF(2alpha)) production in PMA-stimulated cells. alphaTOS also blocked the COX activity in A549 cells with endogenous high levels of COX enzymes in the absence of PMA stimulation. In addition, the ability of alphaTOS to inhibit COX was affected by AA concentration, suggesting that alphaTOS may compete with AA for interaction with COX proteins. These results suggest that alphaTOS inhibits COX activity, thereby inhibiting PGE2 production in human lung epithelial cells, despite the lack of antioxidant activity. Administration of alphaTOS may block inflammatory responses mediated by PGE2, thereby inhibiting the initiation and progression of lung cancer.

Ionizing radiation induces astrocyte gliosis through microglia activation

The aim of this study was to investigate the role of microglia in radiation-induced astrocyte gliosis. We found that a single dose of 15 Gy radiation to a whole rat brain increased immunostaining of glial fibrillary acidic protein in astrocytes 6 h later, and even more so 24 h later, indicating the initiation of gliosis. While irradiation of cultured rat astrocytes had little effect, irradiation of microglia-astrocyte mixed-cultures displayed altered astrocyte phenotype into more processed, which is another characteristic of gliosis. Experiments using microglia-conditioned media indicated this astrocyte change was due to factors released from irradiated microglia. Irradiation of cultured mouse microglial cells induced a dose-dependent increase in mRNA levels for cyclooxygenase-2 (COX-2), interleukin (IL)-1beta, IL-6, IL-18, tumor necrosis factor-alpha and interferon-gamma-inducible protein-10, which are usually associated with microglia activation. Consistent with these findings, irradiation of microglia activated NF-kappaB, a transcription factor that regulates microglial activation. Addition of prostaglandin E2 (PGE2: a metabolic product of the COX-2 enzyme) to primary cultured rat astrocytes resulted in phenotypic changes similar to those observed in mixed-culture experiments. Therefore, it appears that PGE(2) released from irradiated microglia is a key mediator of irradiation-induced gliosis or astrocyte phenotype change. These data suggest that radiation-induced microglial activation and resultant production of PGE2 seems to be associated with an underlying cause of inflammatory complications associated with radiation therapy for malignant gliomas.