Immune complex formation in human diabetic retina enhances toxicity of oxidized LDL towards retinal capillary pericytes

Recently it has been shown that levels of circulating oxidized LDL immune complexes (ox-LDL-IC) predict the development of diabetic retinopathy (DR). This study aimed to investigate whether ox-LDL-IC are actually present in the diabetic retina, and to define their effects on human retinal pericytes vs. ox-LDL. In retinal sections from people with type 2 diabetes, co-staining for ox-LDL and IgG was present, proportionate to DR severity, and detectable even in the absence of clinical DR. In contrast, no such staining was observed in retinas from non-diabetic subjects. In vitro, human retinal pericytes were treated with native (N-) LDL, ox-LDL, and ox-LDL-IC (0-200 mg protein/l), and measures of viability, receptor expression, apoptosis, ER and oxidative stresses, and cytokine secretion were evaluated. Ox-LDL-IC exhibited greater cytotoxicity than ox-LDL towards retinal pericytes. Acting through the scavenger (CD36) and IgG (CD64) receptors, low concentrations of ox-LDL-IC triggered apoptosis mediated by oxidative and ER stresses, and enhanced inflammatory cytokine secretion. The data suggest that IC formation in the diabetic retina enhances the injurious effects of ox-LDL. These findings offer new insights into pathogenic mechanisms of DR, and may lead to new preventive measures and treatments.

Gold nanoparticle cellular uptake, toxicity and radiosensitisation in hypoxic conditions

Background and purpose: Gold nanoparticles (GNPs) are novel agents that have been shown to cause radiosensitisation in vitro and in vivo. Tumour hypoxia is associated with radiation resistance and reduced survival in cancer patients. The interaction of GNPs with cells in hypoxia is explored.

Materials and methods: GNP uptake, localization, toxicity and radiosensitisation were assessed in vitro under oxic and hypoxic conditions.

Results: GNP cellular uptake was significantly lower under hypoxic than oxic conditions. A significant reduction in cell proliferation in hypoxic MDA-MB-231 breast cancer cells exposed to GNPs was observed. In these cells significant radiosensitisation occurred in normoxia and moderate hypoxia. However, in near anoxia no significant sensitisation occurred.

Conclusions: GNP uptake occurred in hypoxic conditions, causing radiosensitisation in moderate, but not extreme hypoxia in a breast cancer cell line. These findings may be important for the development of GNPs for cancer therapy.

Nanoencapsulation of ABT-737 and camptothecin enhances their clinical potential through synergistic antitumor effects and reduction of systemic toxicity

The simultaneous delivery of multiple cancer drugs in combination therapies to achieve optimal therapeutic effects in patients can be challenging. This study investigated whether co-encapsulation of the BH3-mimetic ABT-737 and the topoisomerase I inhibitor camptothecin (CPT) in PEGylated polymeric nanoparticles (NPs) was a viable strategy for overcoming their clinical limitations and to deliver both compounds at optimal ratios. We found that thrombocytopenia induced by exposure to ABT-737 was diminished through its encapsulation in NPs. Similarly, CPT-associated leukopenia and gastrointestinal toxicity were reduced compared with the administration of free CPT. In addition to the reduction of dose-limiting side effects, the co-encapsulation of both anticancer compounds in a single NP produced synergistic induction of apoptosis in both in vitro and in vivo colorectal cancer models. This strategy may widen the therapeutic window of these and other drugs and may enhance the clinical efficacy of synergistic drug combinations.

Mechanistic and toxicity studies of the photocatalytic oxidation of microcystin-LR

Cyanobacterial toxins present in drinking water sources pose a considerable threat to human health. Conventional water treatment systems have proven unreliable for the removal of these toxins and hence new techniques have been investigated. Previous work has shown that TiO₂ photocatalysis effectively destroys microcystin-LR in aqueous solutions, however, a variety of by-products were generated. In this paper, we report a mechanistic study of the photocatalytic destruction of microcystin-LR. In particular, the toxicity by-products of the process have been studied using both brine shrimp and protein phosphatase bioassays. 

Predictors of Chest Wall Toxicity after Lung Stereotactic Ablative Radiotherapy

AIMS: To determine the incidence and predictive factors of rib fracture and chest wall pain after lung stereotactic ablative radiotherapy (SABR).

MATERIALS AND METHODS: Patients were treated with lung SABR of 48-60 Gy in four to five fractions. The treatment plan and follow-up computed tomography scans of 289 tumours in 239 patients were reviewed. Dose-volume histogram (DVH) metrics and clinical factors were evaluated as potential predictors of chest wall toxicity.

RESULTS: The median follow-up was 21.0 months (range 6.2-52.1). Seventeen per cent (50/289) developed a rib fracture, 44% (22/50) were symptomatic; the median time to fracture was 16.4 months. On univariate analysis, female gender, osteoporosis, tumours adjacent (within 5 mm) to the chest wall and all of the chest wall DVH metrics predicted for rib fracture, but only tumour location adjacent to the chest wall remained significant on the multivariate model (P < 0.01). The 2 year fracture-free probability for those adjacent to the chest wall was 65.6%. Among those tumours adjacent to the chest wall, only osteoporosis (P = 0.02) predicted for fracture, whereas none of the chest wall DVH metrics were predictive. Eight per cent (24/289) experienced chest wall pain without fracture.

CONCLUSIONS: None of the chest wall DVH metrics independently predicted for SABR-induced rib fracture when tumour location is taken into account. Patients with tumours adjacent (within 5 mm) to the chest wall are at greater risk of rib fracture after lung SABR, and among these, an additional risk was observed in osteoporotic patients.

Biosensor based toxicity dissection of tannery and associated environmental samples

Kenyan tannery and associated environmental samples were selected for ecotoxicological assessment. A tool-kit of techniques was developed, including whole-cell biosensor and chemical assays. A luminescence based bacterial biosensor (Escherichia coli HB101 pUCD607) (via a multi-copy plasmid) was used for toxicity assessment. Samples were manipulated prior to biosensor interrogation to identify the nature of the toxic contaminants. Untreated samples (before any manipulations) showed a strong toxic effect at the discharge point in comparison to other sampling points. Sparging was used to identify toxicity associated with volatile organics. The toxicity of contaminants, removed by treatment with activated charcoal was identified for all the sampling points except for those upstream of effluent discharges. Filtration identified toxicity associated with suspended solids. Changes in availability of toxic contaminants due to pH adjustment of most samples from the tannery effluent treatment pits were also associated with the extreme pH values (4.0 and 8.0). The approach used has highlighted the complexicity of toxic pollutants in effluent from the tanning industry and the dissection of toxicity points to possible remediation strategies for effluents from the tanning industry.

Relative toxicity of arsenite and arsenate on germination and early seedling growth of rice (Oryza sativa L.)

Elevated soil arsenic levels resulting from long-term use of arsenic contaminated ground for irrigation in Bangladesh may inhibit seed germination and seedling establishment of rice, the country's main food crop. A germination study on rice seeds and a short-term toxicity experiment with different concentrations of arsenite and arsenate on rice seedlings were conducted. Percent germination over control decreased significantly with increasing concentrations of arsenite and arsenate. Arsenite was found to be more toxic than arsenate for rice seed germination. There were varietal differences among the test varieties in response to arsenite and arsenate exposure. The performance of the dry season variety Purbachi was the best among the varieties. Germination of Purbachi was not inhibited at all up to 4 mg l^-1 arsenite and 8 mg l^-1 arsenate treatment. Root tolerance index (RTI) and relative shoot height (RSH) for rice seedlings decreased with increasing concentrations of arsenite and arsenate. Reduction of RTI caused by arsenate was higher than that of arsenite. In general, dry season varieties have more tolerance to arsenite or arsenate than the wet season varieties.

Interactions between soil, toxicant, and a lux-marked bacterium during solid phase-contact toxicity testing

Bioluminescence-based, solid-contact toxicity assays allow test bacterium and toxicant to interact at the solid-solution interface. A lux- marked bacterium, Burkholderia sp. RASC, and 2,4-dichlorophenol (2,4-DCP) were used to characterize these interactions. In the basic bioassay, cells were added to soil slurries containing 2,4-DCP (0-120 μg ml^-1). After 15 min, soil was removed by centrifugation, and bioluminescence in the supernatant was determined. Investigation of 2,4-DCP adsorption to soil revealed that sorption was linear and not significantly (p > 0.1) affected by the presence of Burkholderia cells. The numbers of culturable Burkholderia cells in the assay supernatant were 48.2 to 64.8% of the inoculum and independent of the soil weight. The effect of soil on 2,4-DCP toxicity was investigated by comparing soil aqueous extract and contact assays. The percentage bioluminescence for the contact assay was consistently higher than the extract assay at all test concentrations, and counts of viable Burkholderia cells were enhanced by the presence of 2,4-DCP in the contact assay. Expressing results as specific bioluminescence decreased the variability in response and the discrepancy in results between the two protocols. We suggest that solid-contact assays need improvement to ensure defined contact between cells and solid phase, and that the reporting of specific activity should be emphasized.

Biosensing 2,4-dichlorophenol toxicity during biodegradation by Burkholderia sp. RASC c2 in soil

Biodegradation of the model pollutant, 2,4-dichlorophenol (2,4-DCP) by Burkholderia sp. RASC c2, in contaminated soil was assessed by combining chemical analysis with a toxicity test using Escherichia coli HB101 pUCD607. E. coli HB101 pUCD607 was previously marked with luxCDABE genes, encoding bacterial bioluminescence and was used as an alternative to Microtox. Mineralization of ¹⁴C-2,4-DCP (196.2 μg g^-1 dry wt) in soil occurred rapidly after a 24 h lag. Correspondingly, 2,4-DCP concentrations in soil and soil water extracts decreased with time and concentrations in the latter were at background levels (<0.12 μg mL^-1) after day 2. Toxicity of soil water extracts to the lux-based biosensor also decreased with time. Mean light output of E. coli was stimulated by ~1.5 X control values in soil water extracts when concentrations of 2,4-DCP were approaching the limit of detection by HPLC but returned to values equivalent to those of controls when soil water 2,4-DCP concentrations were below the detection limit. No mineralization or microbial growth was detected in noninoculated microcosms. 2,4-DCP concentration in sterile controls decreased significantly with time as did toxicity to E. coli Lux-based E. coli was a sensitive biosensor of 2,4-DCP toxicity during biodegradation and results complemented chemical analysis.

Toxicity of chlorobenzenes to a lux-marked terrestrial bacterium, Pseudomonas fluorescens

Insertion of lux genes, encoding for bioluminescence in naturally bioluminescent marine bacteria, into the genome of Pseudomonas fluorescens resulted in a bioluminescent strain of this terrestrial bacterium. The lux- marked bacterium was used to toxicity test the chlorobenzene series. By correlating chlorobenzenes 50% effective concentration (EC50) values against physiochemical parameters, the physiochemical properties of chlorobenzenes that elicit toxic responses were investigated. The results showed that the more chlorinated the compounds, the more toxic they were to lux-marked P. fluorescens. Furthermore, it was shown that the more symmetrical the compound, the greater its toxicity to P. fluorescens. In general, the toxicity of a chlorobenzene was inversely proportional to its solubility (S) and directly proportional to its lipophilicity (K(ow). By correlating lux- marked P. fluorescens EC50 values, determined for chlorobenzenes, with toxicity values determined using Pimephales promelas (fathead minnow), Cyclotella meneghiniana (diatom), and Vibrio fischeri (marine bacterium), it was apparent that lux-marked P. fluorescens correlated well with freshwater species such as the diatoms and fathead minnow but not with the bioluminescent marine bacterium V. fischeri. The implications of these findings are that a terrestrial bacterium such as P. fluorescens should be used for toxicity testing of soils and freshwaters rather than the marine bacterium V. fischeri.

Edaphic factors affecting the toxicity and accumulation of arsenate in the earthworm Lumbricus terrestris

The toxicity and accumulation of arsenate was determined in the earthworm Lumbricus terrestris in soil from different layers of a forest profile. Toxicity increased fourfold between 2 and 10 d. Edaphic factors (pH, soil organic matter, and depth in soil profile) also affected toxicity with a three fold decrease in the concentration that causes 50% mortality with increasing depth in soil (from 0-70 mm to 500-700 mm). In a 4-d exposure study, there was no evidence of arsenic bioconcentration in earthworm tissue, although bioaccumulation was occurring. There was a considerable difference in tissue residues between living and dead earthworms, with dead worms having higher concentrations. This difference was dependent on both soil arsenate concentration and on soil type. Over a wide range of soil arsenate concentrations, earthworm arsenic residues are homeostatically maintained in living worms, but this homeostasis breaks down during death. Alternatively, equilibration with soil residues may occur via accumulation after death. In long-term accumulation studies in soils dosed with a sublethal arsenate concentration (40 μg/g dry weight), bioconcentration of arsenate did not occur until day 12, after which earthworm concentrations rose steadily above the soil concentration, with residues in worms three fold higher than soil concentrations by the termination of the study (23 d). This bioconcentration only occurred in depurated worms over the time period of the study. Initially, depurated worms had lower arsenic concentrations than undepurated until tissue concentrations were equivalent to the soil concentration. Once tissue concentration was greater than soil concentration, depurated worms had higher arsenic residues than undepurated.

Galleria mellonella as a novel in vivo model for assessment of the toxicity of 1-alkyl-3-methylimidazolium chloride ionic liquids

The larval form of the Greater Wax Moth (Galleria mellonella) was evaluated as a model system for the study of the acute in vivo toxicity of 1-alkyl-3-methylimidazolium chloride ionic liquids. 24-h median lethal dose (LD50) values for nine of these ionic liquids bearing alkyl chain substituents ranging from 2 to 18 carbon atoms were determined. The in vivo toxicity of the ionic liquids was found to correlate directly with the length of the alkyl chain substituent, and the pattern of toxicity observed was in accordance with previous studies of ionic liquid toxicity in other living systems, including a characteristic toxicity ‘cut-off’ effect. However, G. mellonella appeared to be more susceptible to the toxic effects of the ionic liquids tested, possibly as a result of their high body fat content. The results obtained in this study indicate that G. mellonella represents a sensitive, reliable and robust in vivo model organism for the evaluation of ionic liquid toxicity.