2,3,7,8-Tetrachlorodibenzo-p-dioxin-induced oxidative stress in female rats

Oxidative stress may play a role in the toxic manifestations of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Therefore, the time-dependent effects of 100 micrograms TCDD/kg on various indices of oxidative stress including lipid peroxidation. DNA damage, membrane fluidity, calcium homeostasis, nonprotein sulfhydryl content, and NADPH content of hepatic subcellular fractions of female rats were followed for 12 days. Increases in lipid peroxidation of 400-500% occurred in mitochondrial and microsomal membranes and nuclei, with maximum increases occurring 5-6 days post-treatment. Decreases in the nonprotein sulfhydryl content of mitochondrial and microsomal fractions of approximately 80% were observed by Day 12 posttreatment. Membrane fluidity gradually decreased following administration of TCDD, with decreases of 30-40% being observed in mitochondria, microsomes, and plasma membranes. A sharp increase in the incidence of hepatic nuclear DNA single strand breaks was observed 3 days after treatment with an increase of approximately 600% by Day 9. Following the administration of TCDD, increases of 70-80% occurred in the calcium content of mitochondria and microsomes. An 18% increase in cytosolic calcium was present 12 days after the administration of TCDD. Cytosol and mitochondria both exhibited an initial increase in NADPH content following administration of TCDD, but by Day 12 both had decreased to approximately two-thirds of control values. The results clearly demonstrate that TCDD administration induces an oxidative stress in rat liver. The most pronounced effects were observed in membrane lipid peroxidation and DNA damage with gradual changes being observed in calcium and nonprotein sulfhydryl contents and membrane fluidity.     

Protective Effects of Antioxidants Against Uraemia-Induced Lipid Peroxidation and Glutathione Depletion in Humans

Abstract: The effects of uraemias and antioxidant therapy for 40 days with vitamin A, vitamin C and vitamin E on blood and erythrocyte sulfhydryl (glutathione, GSH) content and on erythrocyte glutathione-S transferase (GST), glutathione reductase (GSR) and glutathione peroxidase activities were studied in six uraemic patients maintained on haemodialysis. In addition, the effect of antioxidant therapy on erythrocyte lipid peroxidation was determined, and erythrocyte haemoglobin content was measured. Uraemic patients in dialysis exhibited significant decreases in blood and erythrocyte GSH content as well as significant decreases in the activities of GST, GSR and GSH-peroxidase relative to control subjects. Furthermore, the uraemic patients had elevated erythrocyte malondialdehyde levels. Blood and erythrocyte GSH content from uraemic patients was significantly elevated after 20 days of antioxidant treatment and remained elevated thereafter throughout the remaining 20 days of the study (130% and 173%, respectively). Antioxidant therapy also produced significant increases in GSR and GSH-peroxidase activities after 20 days of treatment which remained relatively constant thereafter. No significant change in GST activity was observed. Erythrocyte malondialdehyde levels, as an index of oxidative tissue damage, exhibited a significant decrease (70%) in the patients after 40 days of antioxidant therapy. A gradual increase in erythrocyte haemoglobin content was observed following treatment of the uraemic subjects (45% at day 40). The results suggest that antioxidant therapy may protect against oxidative stress associated with uraemia.     

Chitosan-Gelatin Hydrogel Crosslinked With Oxidized Sucrose for the Ocular Delivery of Timolol Maleate

Ocular hypertension due to increased intraocular pressure is a major risk factor for the development of glaucoma. Rapid clearance and low ocular bioavailability are drawbacks of conventional ocular treatments. This requires frequent and long-term application of antiglaucoma drugs which in turn cause local side effects and are a major cause of therapeutic failure due to loss of persistence in using glaucoma therapy. In this study, a semisynthetic, biocompatible, oxidized sucrose crosslinker was developed and used in the formulation of chitosan-gelatin hydrogel for the sustained release of timolol to control ocular hypertension. The swelling properties of the hydrogel showed a strong relationship with the oxidized sucrose concentration. Mucoadhesive properties of the hydrogel were studied and the in vitro release profiles demonstrated that crosslinking with oxidized sucrose reduced the release rate of the entrapped timolol. The results of both in vitro and in vivo studies supported that the formulated hydrogel maintained the release and in turn the efficacy of timolol for a longer period of time compared to the conventional eye drops. This is expected to reduce the frequency of drug application onto the eye surface and in turn enhances patients’ convenience. In conclusion, the developed formulation represents a promising platform for an effective and compliant treatment of ocular hypertension.     

Utilizing mixer torque rheometer in the prediction of optimal wet massing parameters for pellet formulation by extrusion/spheronization

In this study, we aimed to optimize theophylline pellet formulations using a two-factor three-level full-factorial design (3²) by monitoring the concentration of two pellet excipients, polyvinyl pyrrolidone K30 (PVP) binder solution (X1) and the hydrophilic excipient mannitol (X2). Their impact on pellet characteristics (responses) were evaluated. Increasing PVP concentration in the binder solution resulted in an increase in the wet mass torque value. The effect of mannitol, however, was antagonistic. Moreover, the pellet particle size was significantly influenced by the level of mannitol, PVP solution, and quadratic effect of mannitol. Mannitol significantly antagonized the pellet particle size. Furthermore, increased mannitol concentrations significantly enhanced drug dissolution rate from the pellets, whereas PVP concentration in the binder solution significantly reduced the drug dissolution rate. In conclusion, wet granulations can be controlled by monitoring the composition of the binder solution and pellet composition.     

Protective effects of vitamin A and vitamin E succinate against 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-induced body wasting, hepatomegaly, thymic atrophy, production of reactive oxygen species and DNA damage in C57BL/6J mice

The protective effect of vitamin A and vitamin E succinate against 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-induced acute toxicity and measures of oxidative stress was studied. Ten mice were treated with either vitamin A (50 mg/kg every other day for eight days) or vitamin E succiante (150 mg/kg/day followed by a dose of 40 mg/kg/day for five additional days). Half of each of the above groups of animals received TCDD on day 4. Five mice received corn oil or TCDD alone. After five days of TCDD treatment, antioxidant combination treatment with vitamin A and TCDD or vitamin E succinate and TCDD resulted in a significant reduction in indicators of acute toxicity including the decrease in total body and thymus weight as compared to TCDD alone (P<0.05). The combination treatment produced also a significant reduction in the increase in liver weight as compared to TCDD only (P<0.05). Following one day of treatment with 50 microg TCDD/kg, vitamin A and vitamin E succinate produced a significant decrease in the production of superoxide anion by peritoneal lavage cells (P<0.05) and in DNA-single strand breaks in the same cells (P<0.05) as assessed by the reduction of cytochrome c and the alkaline elution technique, respectively. A significant decrease in DNA-single strand breaks in peritoneal lavage cells was observed following 5 days treatment with 50 microg TCDD/kg (P<0.05). The results indicate a potential role for oxidative stress in the acute toxicity of TCDD and a protective effect for vitamin A and vitamin E succinate in the overall toxicity of TCDD including measures of oxidative stress.     

Genetic investigation of 93 families with microphthalmia or posterior microphthalmos

Microphthalmia is a developmental eye defect that is highly variable in severity and in its potential for systemic association. Despite the discovery of many disease genes in microphthalmia, at least 50% of patients remain undiagnosed genetically. Here, we describe a cohort of 147 patients (93 families) from our highly consanguineous population with various forms of microphthalmia (including the distinct entity of posterior microphthalmos) that were investigated using a next‐generation sequencing multi‐gene panel (i‐panel) as well as whole exome sequencing and molecular karyotyping. A potentially causal mutation was identified in the majority of the cohort with microphthalmia (61%) and posterior microphthalmos (82%). The identified mutations (55 point mutations, 15 of which are novel) spanned 24 known disease genes, some of which have not or only very rarely been linked to microphthalmia (PAX6, SLC18A2, DSC3 and CNKSR1). Our study has also identified interesting candidate variants in 2 genes that have not been linked to human diseases (MYO10 and ZNF219), which we present here as novel candidates for microphthalmia. In addition to revealing novel phenotypic aspects of microphthalmia, this study expands its allelic and locus heterogeneity and highlights the need for expanded testing of patients with this condition.