Endostatin modulates VEGF-mediated barrier dysfunction in the retinal microvascular endothelium

Recent evidence indicates that the anti-angiogenic peptide endostatin may modulate some of the vasomodulatory effects of vascular endothelial growth factor (VEGF) in the retina, including reduction of blood retinal barrier function although it remains uncertain how endostatin promotes endothelial barrier properties. The current study has sought to examine how physiological levels of endostatin alters VEGF-induced inner BRB function using an in vitro model system and evaluation of occludin and ZO-1 regulatory responses. In addition, the ability of exogenous endostatin to regulate VEGF-mediated retinal vascular permeability in vivo was investigated.

Retinal microvascular endothelial cells (RMEC's) were exposed to various concentrations of endostatin. In parallel studies, RMEC monolayers were treated with vascular endothelial growth factor (VEGF165). Vasopermeability of RMEC monolayers and occludin expression were determined.

Blood retinal barrier integrity was quantified in mouse retina using Evans Blue assay following intravitreal delivery of VEGF165, endostatin or a VEGF/endostatin combination.

Endostatin increased the levels of expression of occludin whilst causing no significant change in FITC-dextran flux across the RMEC monolayer. Endostatin reversed the effects of VEGF165-enhanced permeability between microvascular endothelial cells and induced phosphorylation of occludin. Evans Blue leakage from retinas treated with VEGF was 2.0 fold higher than that of contra-lateral untreated eyes (P<0.05) while leakage of eyes from endostatin treated animals was unchanged. When eyes were injected with a combination of VEGF165 and endostatin there was a significant reduction in retinal vasopermeability when compared to VEGF-injected eyes (P<0.05).

We conclude that endostatin can promote integrity of the retinal endothelial barrier, possibly by preventing VEGF-mediated alteration of tight junction integrity. This suggests that endostatin may be of clinical benefit in ocular disorders where significant retinal vasopermeability changes are present.

Advanced glycation end products induce blood-retinal barrier dysfunction in normoglycemic rats

Advanced glycation end products (AGEs) have been implicated in the progressive vascular dysfunction which occurs during diabetic retinopathy. In the current study we have examined the role of these adducts in blood-retinal barrier (BRB) breakdown and investigated expression of the vasopermeabilizing agent vascular endothelial growth factor (VEGF) in the retina. When normoglycemic rats were injected with AGE-modified albumin daily for up to 10 days there was widespread leakage of FITC-dextran and serum albumin from the retinal vasculature when compared to control animals treated with nonmodified albumin. Ultrastructural examination of the vasculature revealed areas of attenuation of the retinal vascular endothelium and increased vesicular organelles only in the AGE-exposed rats. Quantitative RT-PCR and in situ hybridization demonstrated a significant increase in retinal VEGF mRNA expression (P <0.05). These results suggest that AGEs can initiate BRB dysfunction in nondiabetic rats and a concomitant increase in retinal VEGF expression. These findings may have implications for the role of AGEs in the pathogenesis of diabetic retinopathy.

Predisposition to arrhythmia and autonomic dysfunction in Nhlh1-deficient mice.

Nhlh1 is a basic helix-loop-helix transcription factor whose expression is restricted to the nervous system and which may play a role in neuronal differentiation. To directly study Nhlh1 function, we generated null mice. Homozygous mutant mice were predisposed to premature, adult-onset, unexpected death. Electrocardiograms revealed decreased total heart rate variability, stress-induced arrhythmia, and impaired baroreceptor sensitivity. This predisposition to arrhythmia is a likely cause of the observed death in the mutant mice. Heterozygosity for the closely related transcription factor Nhlh2 increased the severity of the Nhlh1-null phenotype. No signs of primary cardiac structural or conduction abnormalities could be detected upon necropsy of the null mice. The pattern of altered heart rhythm observed in basal and experimental conditions (stress and pharmacologically induced) suggests that a deficient parasympathetic tone may contribute to the arrhythmia in the Nhlh1-null mouse. The expression of Nhlh1 in the developing brain stem and in the vagal nuclei in the wild-type mouse further supports this hypothesis. The Nhlh1 mutant mouse may thus provide a model to investigate the contribution of the autonomic nervous system to arrhythmogenesis.

A comparison of mitochondrial and nuclear DNA status in testicular sperm from fertile men and those with obstructive azoospermia

Background: Mitochondria are vital to sperm as their motility powerhouses. They are also the only animal organelles with their own unique genome; encoding subunits for the complexes required for the electron transfer chain. Methods: A modified long PCR technique was used to study mitochondrial DNA (mtDNA) in ejaculated and testicular sperm samples from fertile men (n=11) and testicular sperm from men with obstructive azoospermia (n=25). Nuclear DNA fragmentation was measured by an alkaline single cell gel electrophoresis (COMET) assay. Results: Wild-type mtDNA was detected in only 60% of fertile mens�??�?�¢?? testicular sperm, 50% of their ejaculated sperm and 46% of testicular sperm from men with obstructive azoospermia. The incidence of mitochondrial deletions in testicular sperm of fertile and infertile men was not significantly different but the mean size of the deletions was significantly less in testicular sperm from fertile men compared with men with obstructive azoospermia (p<0.02). Nuclear DNA fragmentation in testicular sperm from fertile men and men with obstructive azoospermia was not significantly different. Conclusion: Multiple mtDNA deletions are common in testicular and ejaculated sperm from both fertile and infertile men. However, in males with obstructive azoospermia the mtDNA deletions in testicular sperm are of a larger scale.

Accommodative dysfunction in children with cerebral palsy: a population based study

Purpose. To determine the prevalence, nature, and degree of accommodative dysfunction among children with different types and severities of cerebral palsy (CP) in Northern Ireland. Methods. Ninety subjects with CP (aged 4–15 years) were recruited through the Northern Ireland CP Register (NICPR). Modified Nott dynamic retinoscopy was used to measure lag and lead of accommodation at three test distances: 25 cm (4 D), 16.7 cm (6 D), and 10 cm (10 D) with the distance correction in place. Accommodative function was also assessed in an age-matched control group (n = 125) for comparison. Each subject’s neurologic status was derived from the NICPR. Results. Children with CP demonstrate significantly reduced accommodative responses compared with their neurologically normal peers. Of the subjects with CP, 57.6% demonstrated an accommodative lag outside normal limits at one or more distances. Reduced accommodative responses were significantly associated with more severe motor and intellectual impairments (ANOVA P = 0.001, P < 0.01, respectively). Conclusions. Brain injury such as that present in CP has a significant impact on accommodative function. These findings have implications for the optometric care of children with CP and inform our understanding of the impact of early brain injury on visual development.

Cytoplasmic Irradiation Induces Mitochondrial-Dependent 53BP1 Protein Relocalization in Irradiated and Bystander Cells

The accepted paradigm for radiation effects is that direct DNA damage via energy deposition is required to trigger the downstream biological consequences. The radiation-induced bystander effect is the ability of directly irradiated cells to interact with their nonirradiated neighbors, which can then show responses similar to those of the targeted cells. p53 binding protein 1 (53BP1) forms foci at DNA double-strand break sites and is an important sensor of DNA damage. This study used an ionizing radiation microbeam approach that allowed us to irradiate specifically the nucleus or cytoplasm of a cell and quantify response in irradiated and bystander cells by studying ionizing radiation-induced foci (IRIF) formation of 53BP1 protein. Our results show that targeting only the cytoplasm of a cell is capable of eliciting 53BP1 foci in both hit and bystander cells, independently of the dose or the number of cells targeted. Therefore, direct DNA damage is not required to trigger 53BP1 IRIF. The use of common reactive oxygen species and reactive nitrogen species (RNS) inhibitors prevent the formation of 53BP1 foci in hit and bystander cells. Treatment with filipin to disrupt membrane-dependent signaling does not prevent the cytoplasmic irradiation-induced 53BP1 foci in the irradiated cells, but it does prevent signaling to bystander cells. Active mitochondrial function is required for these responses because pseudo-rho(0) cells, which lack mitochondrial DNA, could not produce a bystander signal, although they could respond to a signal from normal rho(+) cells.