Tuning the endothelial response: differential release of exocytic cargos from Weibel‐Palade bodies

Essentials

• Endothelial activation initiates multiple processes, including hemostasis and inflammation.
• The molecules that contribute to these processes are co‐stored in secretory granules.
• How can the cells control release of granule content to allow differentiated responses?
• Selected agonists recruit an exocytosis‐linked actin ring to boost release of a subset of cargo.

Summary

Background

Endothelial cells harbor specialized storage organelles, Weibel‐Palade bodies (WPBs). Exocytosis of WPB content into the vascular lumen initiates primary hemostasis, mediated by von Willebrand factor (VWF), and inflammation, mediated by several proteins including P‐selectin. During full fusion, secretion of this large hemostatic protein and smaller pro‐inflammatory proteins are thought to be inextricably linked.

Objective

To determine if secretagogue‐dependent differential release of WPB cargo occurs, and whether this is mediated by the formation of an actomyosin ring during exocytosis.

Methods

We used VWF string analysis, leukocyte rolling assays, ELISA, spinning disk confocal microscopy, high‐throughput confocal microscopy and inhibitor and siRNA treatments to demonstrate the existence of cellular machinery that allows differential release of WPB cargo proteins.

Results

Inhibition of the actomyosin ring differentially effects two processes regulated by WPB exocytosis; it perturbs VWF string formation but has no effect on leukocyte rolling. The efficiency of ring recruitment correlates with VWF release; the ratio of release of VWF to small cargoes decreases when ring recruitment is inhibited. The recruitment of the actin ring is time dependent (fusion events occurring directly after stimulation are less likely to initiate hemostasis than later events) and is activated by protein kinase C (PKC) isoforms.

Conclusions

Secretagogues differentially recruit the actomyosin ring, thus demonstrating one mechanism by which the prothrombotic effect of endothelial activation can be modulated. This potentially limits thrombosis whilst permitting a normal inflammatory response. These results have implications for the assessment of WPB fusion, cargo‐content release and the treatment of patients with von Willebrand disease.

     

Morphometric observations on the effects of ischemia in the isolated perfused rat heart.

The design of the experiment was to observe the changes which took place in the isolated perfused rat heart, that was made ischemic according to the technique of Neely et al. [16], using quantitative stereological techniques. The results showed that 24 min after myocardial failure there was a significant decrease in the fractional volume of myofibrils, mitochondria, T-system, and sarcoplasmic reticulum. The decrease in fractional volume of subcellular organelles can most probably be explained by myocardial cell swelling secondary to intercellular edema. There was also a decrease in the sarcoplasmic reticulum membrane area, and quantitative measurements indicated that this compartment was dilated. Observations on the intercalated disc indicated that there was a migration of acid phosphatase positive multivesicular bodies toward the disc interspace in ischemic hearts. This was found to be associated with the dissolution of gap junctions. Stereological measurements indicated that in ischemic hearts there was a 5-fold increase in the percentage of membrane area of the disc made up of open gap junctions, and that the number of vesicles from multivesicular bodies observed per μm³ of disc interspace was also proportionately higher. It is suggested that the multivesicular bodies represent elements of the lysosomal system and are responsible for the dissociation of the intercalated disc in ischemic hearts.     

鱼刺穿透胃窦形成胃周脓肿1例

病例：患者男，45岁，工人。因“中上腹痛1周，加重伴反复呕吐2d”于2007年7月7日入院。患者入院前一周无明显诱因出现中上腹持续闷痛，阵发性加剧。疼痛与饮食、体位无明显关系。2d前中上腹痛加剧，呈持续性，能忍受，其他部位无放射痛，伴呕吐宿食，呕吐后腹痛无明显缓解，有低热．体温最高38．2℃，无眼黄、尿黄，无呕血、黑便等。     

Diabetic coma: Serum growth hormone before and during treatment

Summary Serum growth hormone values in 37 patients with diabetic ketoacidosis were 5.4±0.8 ng/ml (S.E.M.) in males and 6.7±1.1 ng/ml in females before treatment; while in five hyperosmolar non-ketotic patients the HGH concentration was 3.9±0.5 ng/ml. One hour after insulin 90% of patients showed a rise in HGH, to a mean of 33.7±9.8 ng/ml for males and 25.5±6.0 ng/ml for females in ketoacidosis; and to 27.1±9.9 ng/ml for hyperosmolar coma patients. The rise, which was transient, was inversely correlated with pretreatment plasma glucose, the l h plasma glucose concentration and plasma urea, and directly proportional to the % fall in blood glucose after 1 h. When the ketoacidosis patients were divided into two groups according to HGH response, those with a small response had the greater disturbances of plasma glucose, blood ketone bodies, blood lactate, plasma urea, blood pH, and blood pressure, the smaller 1 h fall in blood glucose, and the higher mortality. Thus the most severely ketoacidotic patients had the poorest growth hormone response. Growth hormone is probably of little importance as an insulin antagonist in diabetic coma.Presented in part at the Spring Meeting of the British Diabetic Association, York, April 1972.     

Nanobacteria and Psammoma Bodies: Ultrastructural Observations in a Case of Pathological Placental Calcification

Nanobacteria are controversial infectious agents with nanometric size, the capacity to nucleate hydroxyapatite and grow in culture, and present in human diseases associated with calcification and psammoma bodies. The authors report a case of pathological placental calcifications associated with nanobacteria. Electron microscopy and electron energy loss spectroscopy imaging were used to recognize 160-nm-sized calcium-free bodies mainly presenting as extracellular fibrillary tangles and 500-nm-sized calcified bodies; they encrusted the syncito-trophoblast basal membrane and aggregated into miniaturized psammoma bodies. Nanobacteria may be composed of a prionoid protein with self-assembling and self-propagating abilities whose growth is associated with the formation of psammoma bodies.     

Infection resistance of degradable versus non-degradable biomaterials: An assessment of the potential mechanisms

Extended life expectancy and medical development has led to an increased reliance on biomaterial implants and devices to support or restore human anatomy and function. However, the presence of an implanted biomaterial results in an increased susceptibility to infection. Due to the severity of the potential outcomes of biomaterial-associated infection, different strategies have been employed to reduce the infection risk. Interestingly, degradable biological materials demonstrate increased resistance to bacterial infection compared to non-degradable synthetic biomaterials. Current knowledge about the specific mechanisms of how degradable biological materials are afforded increased resistance to infection is limited. Therefore, in this paper a number of hypotheses to explain the decreased infection risk associated with the use of degradable versus non-degradable biomaterials are evaluated and discussed with reference to the present state of knowledge.     

Modulation of the foreign body response to implanted sensor models through device-based delivery of the tyrosine kinase inhibitor,masitinib

The host foreign body response (FBR) adversely effects the performance of numerous implanted biomaterials especially biosensors, including clinically popular glucose-monitoring sensors. Reactive formation of a fibrous capsule around implanted sensors hinders the transport of essential analytes to the sensor from the surrounding tissue, resulting in loss of glucose response sensitivity and eventual sensor failure. Several strategies have sought to mitigate the foreign body response's effects on CGM sensors through the use of local delivery of pharmaceuticals and biomolecules with limited success. This study describes release of a tyrosine kinase inhibitor – masitinib – from the sensor implant to target tissue resident mast cells as key mediators of the FBR. Model implants are coated with a composite polymer hydrophilic matrix that rapidly dissolves upon tissue implantation to deposit slower-degrading polymer microparticles containing masitinib. Matrix dissolution limits coating interference with sensor function while establishing a local controlled-release delivery depot formulation to alter implant tissue pharmacology and addressing the FBR. Drug efficacy was evaluated in a murine subcutaneous pocket implant model. Drug release extends to more than 30 days in vitro. The resulting FBR in vivo, evaluated by implant capsule thickness and inflammatory cell densities at 14, 21, and 28 days, displays statistically significant reduction in capsule thickness around masitinib-releasing implant sites compared to control implant sites.     

Default network is not hypoactive in dementia with fluctuating cognition: an Alzheimer disease/dementia with Lewy bodies comparison

Default mode network resting state activity in posterior cingulate cortex is abnormally reduced in Alzheimer disease (AD) patients. Fluctuating cognition and electroencephalogram abnormalities are established core and supportive elements respectively for the diagnosis of dementia with Lewy bodies (DLB). Our aim was to assess whether patients with DLB with both of these features have different default mode network patterns during resting state functional magnetic resonance imaging compared with AD. Eighteen patients with DLB, 18 AD patients without fluctuating cognition, and 15 control subjects were selected after appropriate matching and followed for 2–5 years to confirm diagnosis. Independent component analysis with functional connectivity (FC) and Granger causality approaches were applied to isolate and characterize resting state networks. FC was reduced in AD and DLB patients compared with control subjects. Posterior cingulate cortex activity was lower in AD than in control subjects and DLB patients (p < 0.05). Right hemisphere FC was reduced in DLB patients in comparison with control subjects but not in patients with AD, and was correlated with severity of fluctuations (ρ = −0.69; p < 0.01). Causal flow analysis showed differences between patients with DLB and AD and control subjects.