Role of EP3 and EP4 prostaglandin receptors in reorganization of the cytoskeleton in mature human osteoclasts

OBJECTIVE: Osteoclasts are central to the pathophysiology of several bone diseases. Prostaglandin E2 (PGE2) is well known to influence osteoclasts indirectly, but its direct action on osteoclasts is still controversial and the relevant receptors are unknown. We investigated the distribution and function of EP receptors in human mature osteoclasts. METHODS: Osteoclasts were extracted from femurs and tibias of human fetuses obtained from legal abortions. In situ hybridization and immunohistochemistry were used to detect the presence of EP1, EP2, EP3, and EP4 receptors on these cells. Actin staining and fluorescent microscopy were used to detect the effects of receptor activation on the cytoskeleton. RESULTS: Only EP3 and EP4 receptors were detected at the RNA and protein level in osteoclasts. These receptors were functional: PGE2 decreased the number of osteoclasts presenting an actin ring; 11-deoxy-PGE1, an EP2 and EP4 agonist, also decreased the number of tartrate-resistant acid phosphatase-positive cells with an actin ring; sulprostone, an EP3-specific agonist, had no effect on this variable but increased the number of cells with lamellipodia. CONCLUSION: Mature human osteoclasts present 2 subtypes of EP receptors, namely EP3 and EP4, that mediate different actions of PGE2 on these cells: activation of the EP4 receptors inhibits actin ring formation and activation of the EP3 receptors increases the number of lamellipodia. Activation or inhibition of these receptors by specific agents could be used to study and influence osteoclast function.     

Revisiting the physiological effects of methylene blue as a treatment of cyanide intoxication

Background: Although methylene blue (MB) had long been proposed to counteract the effects of cyanide (CN) intoxication, research on its mechanisms of action and efficacy has been abandoned for decades. Recent studies on the benefits of MB in post-anoxic injuries have prompted us to reexamine the relevance of this historical observation.

Methods: Our study was performed in adult male Sprague–Dawley rats and on HEK293T epithelial cells. First, the effects and toxicity of MB (0–80?mg/kg) on circulation and metabolism were established in four urethane-anesthetized rats. Then nine rats received a lethal infusion of a solution of KCN (0.75?mg/kg/min) and were treated by either saline or MB, at 20?mg/kg, a dose that we found to be innocuous in rat and to correspond to a dose of about 4?mg/kg in humans. MB was also administered 5?min after the end of a sub-lethal exposure to CN in a separate group of 10 rats. In addition, ATP/ADP ratio, ROS production, mitochondrial membrane potential (Δψm) and cellular O₂ consumption rate (OCR) were determined in HEK293T cells exposed to toxic levels of CN (200?µM for 10?min) before and after applying a solution containing MB (1–100?µM for 10?min).

Results: Methylene blue was found to be innocuous up to 50?mg/kg. KCN infusion (0.75?mg/kg/min) killed all animals within 7–8?min. MB (20?mg/kg) administered at the same time restored blood pressure, cardiac contractility and limited O₂ deficit, allowing all the animals to survive, without any significant methemoglobinemia. When administered 5?min after a non-lethal CN intoxication, MB sped up the recovery of lactate and O₂ deficit. Finally, MB was able to decrease the production of ROS and restore the ATP/ADP ratio, Δψm as well as OCR of epithelial cells intoxicated by CN.

Conclusions: The present observations should make us consider the potential interest of MB in the treatment of CN intoxication. The mechanisms of the antidotal properties of MB cannot be accounted for by the creation of a cyanomethemoglobinemia, rather its protective effects appears to be related to the unique properties of this redox dye, which, depending on the dose, could directly oppose some of the consequences of the metabolic depression produced by CN at the cellular level.     

Toxicity profiles and solvent–toxicant interference in the planarian Schmidtea mediterranea after dimethylsulfoxide (DMSO) exposure

To investigate hydrophobic test compounds in toxicological studies, solvents like dimethylsulfoxide (DMSO) are inevitable. However, using these solvents, the interpretation of test compound‐induced responses can be biased. DMSO concentration guidelines are available, but are mostly based on acute exposures involving one specific toxicity endpoint. Hence, to avoid solvent–toxicant interference, we use multiple chronic test endpoints for additional interpretation of DMSO concentrations and propose a statistical model to assess possible synergistic, antagonistic or additive effects of test compounds and their solvents. In this study, the effects of both short‐ (1 day) and long‐term (2 weeks) exposures to low DMSO concentrations (up to 1000 µl l^?1) were studied in the planarian Schmidtea mediterranea. We measured different biological levels in both fully developed and developing animals. In a long‐term exposure set‐up, a concentration of 500 µl l^?1 DMSO interfered with processes on different biological levels, e.g. behaviour, stem cell proliferation and gene expression profiles. After short exposure times, 500 µl l^?1 DMSO only affected motility, whereas the most significant changes on different parameters were observed at a concentration of 1000 µl l^?1 DMSO. As small sensitivity differences exist between biological levels and developmental stages, we advise the use of this solvent in concentrations below 500 µl l^?1 in this organism. In the second part of our study, we propose a statistical approach to account for solvent–toxicant interactions and discuss full‐scale solvent toxicity studies. In conclusion, we reassessed DMSO concentration limits for different experimental endpoints in the planarian S. mediterranea. Copyright © 2014 John Wiley & Sons, Ltd.     

Characterization of visual manifestations and identification of risk factors for permanent vision loss in patients with giant cell arteritis

Clinical Rheumatology - Permanent vision loss (PVL) is a feared complication and a leading cause of morbidity in giant cell arteritis (GCA). The objective of this study is to describe visual...     

Ankylosing spondylitis: how should the disease be assessed?

The four clinical features of spondyloarthropathy, i.e. axial involvement, peripheral articular involvement, enthesopathy and extra-articular features, must be assessed in each patient suffering from spondyloarthropathy at each visit.The ASsessment in Ankylosing Spondylitis working group is establishing recommendations to facilitate the short- and long-term monitoring of patients suffering from spondyloarthropathies.Several relevant instruments are available for assessing the main domains, allowing evaluation of such patients - for example, pain, functional disability and spinal mobility. Other investigations are required in order to obtain relevant instruments for other domains, such as structural severity.     

Familial and genetic aspects of spondyloarthropathy

Predisposition to SpA is largely determined by genetic factors including HLA-B27 and other as yet unknown genes that might be tracked by a positional cloning approach. Analysis performed on a large cohort of SpA multiplex families revealed that the different articular and extra-articular inflammatory manifestations comprising the SpA spectrum were linked together, implying that they were determined by a shared set of factors, including HLA-B27. The variety of phenotypes appeared to be related to ubiquitous and secondary factors. Hence, SpA appeared to be more homogenous than previously thought and should be regarded as a unique disease. This conclusion also implies that genetic studies should be performed on the whole group. Such an approach allowed identification of HLA-DR4 as a gene contributing to SpA predisposition independently of linkage disequilibrium with HLA-B27. A significant role for CARD15/NOD2 gene in predisposition to SpA was ruled out, in agreement with the hypothesis that the inflammatory bowel disease in SpA is determined by factors different than those responsible for isolated Crohn's disease.