Number Of Weibel-Palade Bodies Research Articles

Coronary microthrombi in the failing human heart: the role of von Willebrand factor and PECAM-1.

The recognition of microthrombi in the heart microcirculation has recently emerged from studies in COVID-19 decedents. The present study investigated the ultrastructure of coronary microthrombi in heart failure (HF) due to cardiomyopathies that are unrelated to COVID-19 infection. In addition, we have investigated the role of von Willebrand factor (VWF) and PECAM-1 in microthrombus formation. We used electron microscopy to investigate the occurrence of microthrombi in patients with HF due to dilated (DCM, n = 7), inflammatory (MYO, n = 6) and ischemic (ICM, n = 7) cardiomyopathy and 4 control patients. VWF and PECAM-1 was studied by quantitative immunohistochemistry and Western blot. In comparison to control, the number of microthrombi was increased 7-9 times in HF. This was associated with a 3.5-fold increase in the number of Weibel-Palade bodies (WPb) in DCM and MYO compared to control. A fivefold increase in WPb in ICM was significantly different from control, DCM and MYO. In Western blot, VWF was increased twofold in DCM and MYO, and more than threefold in ICM. The difference between ICM and DCM and MYO was statistically significant. These results were confirmed by quantitative immunohistochemistry. Compared to control, PECAM-1 was by approximatively threefold increased in all groups of patients. This is the first study to demonstrate the occurrence of microthrombi in the failing human heart. The occurrence of microthrombi is associated with increased expression of VWF and the number of WPb, being more pronounced in ICM. These changes are likely not compensated by increases in PECAM-1 expression.

VWF Exocytosis and Biogenesis of Weibel Palade Bodies in Endothelial Cells Are Differentially Controlled By Interactions between Bloc-2 and the Exocyst Complex

Italiano: Platelet Biogenesis: Employment, Equity Ownership; Ionis Research Funding: Research Funding. Flaumenhaft:PlateletDiagnostics: Consultancy, Other: Founder; Relay Therapeutics: Consultancy.

Effect of laminar shear stress on the distribution of Weibel-Palade bodies in endothelial cells

BackgroundVascular endothelial cells (ECs) provide a highly interactive barrier between blood and the underlying tissues. It is well established that ECs exposed to laminar flow align in the direction of flow and also arrange their actin stress fibers in a parallel manner in the direction of flow. Also the organization of the microtubule network is altered in response to flow with repositioning of the microtubule-organizing centre (MTOC) in the direction of flow. Weibel-Palade bodies (WPBs) are endothelial cell specific storage organelles that contain a number of important homeostatic and inflammatory components. Dynamics of WPBs are controlled by microtubules and the actin cytoskeleton. ObjectivesHere, we monitored flow-induced changes in distribution of WPBs. MethodsECs were exposed for five days to laminar shear stress of 10 dyne/cm2. Subsequently we measured the distance of individual WPBs with respect to the centre of the nucleus using Image Pro Plus. ResultsECs aligned in the direction of flow under these conditions. After 5days the MTOC was positioned downstream of the nucleus in the direction of the flow. The number of WPBs per cell was slightly reduced as a result of the application of flow. Unexpectedly, only minor differences in the distribution of WPBs in ECs cultured under laminar flow were observed when compared to that of cells grown under static conditions. ConclusionsOur findings suggest that laminar flow does not induce major changes in number and distribution of WPBs in ECs.

The Shear Stress-Induced Transcription Factor KLF2 Affects Dynamics and Angiopoietin-2 Content of Weibel-Palade Bodies

BackgroundThe shear-stress induced transcription factor KLF2 has been shown to induce an atheroprotective phenotype in endothelial cells (EC) that are exposed to prolonged laminar shear. In this study we characterized the effect of the shear stress-induced transcription factor KLF2 on regulation and composition of Weibel-Palade bodies (WPBs) using peripheral blood derived ECs.Methodology and Principal FindingsLentiviral expression of KLF2 resulted in a 4.5 fold increase in the number of WPBs per cell when compared to mock-transduced endothelial cells. Unexpectedly, the average length of WPBs was significantly reduced: in mock-transduced endothelial cells WPBs had an average length of 1.7 µm versus 1.3 µm in KLF2 expressing cells. Expression of KLF2 abolished the perinuclear clustering of WPBs observed following stimulation with cAMP-raising agonists such as epinephrine. Immunocytochemistry revealed that WPBs of KLF2 expressing ECs were positive for IL-6 and IL-8 (after their upregulation with IL-1β) but lacked angiopoietin-2 (Ang2), a regular component of WPBs. Stimulus-induced secretion of Ang2 in KLF2 expressing ECs was greatly reduced and IL-8 secretion was significantly lower.Conclusions and SignificanceThese data suggest that KLF2 expression leads to a change in size and composition of the regulated secretory compartment of endothelial cells and alters its response to physiological stimuli.

Formation and function of Weibel-Palade bodies

Weibel-Palade bodies (WPBs) are secretory organelles used for post-synthesis storage in endothelial cells that can, very rapidly, be triggered to release their contents. They carry a variety of bioactive molecules that are needed to mount a rapid response to the complex environment of cells that line blood vessels. They store factors that are essential to haemostasis and inflammation, as well as factors that modulate vascular tonicity and angiogenesis. The number of WPBs and their precise content vary between endothelial tissues, reflecting their differing physiological circumstances. The particular functional demands of the highly multimerised haemostatic protein von Willebrand Factor (VWF), which is stored in WPBs as tubules until release, are responsible for the cigar shape of these granules. How VWF tubules drive the formation of these uniquely shaped organelles, and how WPB density increases during maturation, has recently been revealed by EM analysis using high-pressure freezing and freeze substitution. In addition, an AP1/clathrin coat has been found to be essential to WPB formation. Following recruitment of cargo at the TGN, there is a second wave of recruitment that delivers integral and peripheral membrane proteins to WPBs, some of which is AP3 dependent.

The Enhancement of Preproendothelin-1 Synthesis and the Acceleration of Endothelin-1 Processing in the Acute Hypoxic Rat Aorta

Wistar rats were deeply anesthetized and perfused by Hanks' solution bubbled with either 95% air and 5% CO2 (normoxic group) or 95% N2 and 5% CO2 (hypoxic group) from the thoracic aorta for 30 minutes. The isolated abdominal aortas were used for electron microscopy, immunocytochemistry of endothelin-1 (ET-1) and endothelin-converting enzyme-1 (ECE-1), and in situ hybridization of preproendothelin-1 mRNA. A remarkable increase in the number of Weibel-Palade bodies, storage sites of ET-1 and ECE-1, occurred in the hypoxic group when compared with the normoxic group. Immunoreactivities for ET-1 and ECE-1, and signals for preproendothelin-1 mRNA were seen along the endothelia of both groups, but the intensities were significantly elevated in the hypoxic group. The increase in the number of ECE-1 immunoreactive gold particles was noticed in Weibel-Palade bodies in the hypoxic group. These findings indicate the enhancement of preproendothelin-1 synthesis in the rat aortic endothelial cells and the acceleration of ET-1 processing in Weibel-Palade bodies of such cells in an acute hypoxic condition.

Increase in number of Weibel-Palade bodies and endothelin-1 release from endothelial cells in the cadmium-treated rat thoracic aorta.

Male rats received daily intraperitoneal injections of cadmium sulphate (2.0 mg/kg) for 3 (Cd-3 group), 6 (Cd-6 group) and 8 days (Cd-8 group). The blood samples were prepared for endothelin (ET)-1 assay, and the thoracic aorta was investigated by both electron microscopy and immunoelectron microscopy using anti ET-1 sera. The plasma ET-1 concentrations of both Cd-6 and Cd-8 groups increased significantly in a cumulative dose-dependent manner. The cadmium-treated rat aorta showed an increase in the number of Weibel-Palade (WP) bodies in endothelial cells, and degranulation and exocytosis of WP bodies occurred exclusively in the Cd-8 group. Immunoreaction for ET-1 was localized preferentially in WP bodies of both cadmium-treated and control groups, and in the rough endoplasmic reticulum of the cadmium-treated groups only. Reactivity was also found on the WP bodies undergoing exocytosis in the Cd-8 group. Cadmium intoxication induces an increase in number of ET-1-storing WP bodies in the rat aorta endothelium. The enhancement of extracellular release of their contents by exocytosis results in elevation of the plasma ET-1 concentration.

Rickettsia rickettsii Infection of Cultured Endothelial Cells Induces Release of Large von Willebrand Factor Multimers From Weibel-Palade Bodies

AbstractThe clinical manifestations of Rocky Mountain spotted fever (RMSF) result from Rickettsia rickettsii [R rickettsii) infection of endothelial cells and are mediated by pathologic changes localized to the vessel, including in situ thrombosis and tissue ischemia. This study uses in vitro infection of cultured human umbilical vein endothelial cells with R rickettsii to test the hypothesis that such infection induces von Willebrand factor (vWF) release from Weibel-Palade bodies, a process that could contribute to thrombotic changes. At 24 hours postinfection, there was an increase in metabolically prelabeled large multimers of vWF in the culture medium, with a concomitant decrease of these forms in the cell lysate samples. This release reaction was specific for the large multimer pool of vWF, localized to Weibel-Palade bodies, because no change in the distribution of dimeric forms between cells and culture medium was detected. Double-label immunofluorescence staining showed an inverse correlation between the number of R rickettsii and the number of Weibel-Palade bodies in infected cells. Cell lysis was minimal at 24 hours postinfection, as no detectable intracellular precursor forms (molecular weight 260,000) of vWF were released into the culture medium, there was no decrease in cell viability as measured by trypan blue exclusion, and no increase in 51Cr-release into the culture medium was observed when compared with uninfected controls. Release was likely a direct effect of the intracellular presence of the organism, rather than due to a noxious soluble factor such as endotoxin, because culture medium conditioned by infected endothelial cells was ineffective at inducing release in uninfected endothelial cell cultures. In summary, in vitro infection of endothelial cells by R rickettsii induces release of Weibel-Palade body contents, a process that may contribute to the pathogenesis of RMSF.

Effect of vasoactive amines on Weibel-Palade bodies in capillary endothelial cells

The presence and distribution of Weibel-Palade bodies in stomach and colonic mucosal microvessels after the administration of vasoactive amines (serotonin and histamine), the serotonin depletor reserpine, and the von Willebrand factor secretagogue thrombin, was studied by transmission electron microscopy. These agents elevated the number of Weibel-Palade bodies in all microvascular endothelial cells and especially in capillaries. It is concluded that vasoactive amines enhance the synthesis and secretion of large von Willebrand protein multimers by endothelial cells.

Ultrastructural development of Kaposi's sarcoma in relation to the dermal microvasculature

Ultrastructural subtypes of endothelial cells in Kaposi's sarcoma were compared with lymphatics and the normal dermal microcirculation in different stages of lesional development. In the earliest patch stage, lymphatic channels, recognised by their dissecting growth pattern and a lack of a basal lamina and pericytes, were prominent. Venous endothelium was recognised by virtue of its multilaminated basal lamina and often showed markedly irregular luminal and abluminal cytoplasmic projections. As the histological stage progressed toward spindle cells, venous endothelium showed a tetrad of changes: dissolution of the basal lamina; fragmentation and disappearance of the pericyte sheath, decreased and often rudimentary intercellular junctions and markedly reduced numbers of Weibel-Palade bodies. These were also features of spindle cells, which were rarely seen to emerge from narrow vascular channels of indeterminate type. Spindle cells showed sparse intercellular junctions and minimal basal lamina but no Weibel-Palade bodies. These progressive venous alterations thus resulted in a mixed intermediate subtype of endothelium with the morphological traits resembling lymphatics as well as venous blood vessels. The mixed subtype included endothelial tubes surrounded by a complete basal lamina but lacking pericytes, and much more commonly, tubes with pericytes but a scanty basal lamina. Both forms had remarkably few or no Weibel-Palade bodies. In the spindle cell stage, normal vessels were largely replaced by the mixed subtype and an indeterminate type of frequently disrupted endothelial tube which lacked a basal lamina as well as a pericytic investment. Dissecting lymphatic channels could not be confidently distinguished from the latter vessels.(ABSTRACT TRUNCATED AT 250 WORDS)

Relationship Between the Early Arterial Reaction to Hypertension and the Development of Intimal Proliferation

Malignant renal hypertension was induced in male Wistar rats. In the early phase of the disease, ie. the 1st week, a transient and generalized activation of arterial cellular functions was observed, while later, on day 21 widespread intimal proliferations developed in the arteries. This early activation included an increase in transmural permeability, DNA-, protein, collagen, elastin and ground substance synthesis, a rise in mural PGI2 content and an increase in number of Weibel-Palade bodies. An activation of platelets and monocytes could also be detected during the 1st week. In a group of rats the development of malignant hypertension was interrupted following the early activation of arteries and the incidence of intimal proliferations was compared with that of rats with maintained hypertension. No intimal proliferation was observed on day 21 in the rats with interrupted hypertension. It is concluded that the early activation of the artery does not furnish enough stimulus for triggering intimal proliferations and intimal plaques are not direct sequelae of the early arterial reaction. Furthermore the entrance of plasma materials during transmural permeability increase can not induce smooth muscle proliferation if the hypertension is interrupted.