Search research articles

ABOUT JoVE

Overview Leadership Blog JoVE Help Center

AUTHORS

Publishing Process Editorial Board Scope & Policies Peer Review FAQ Submit

LIBRARIANS

Testimonials Subscriptions Access Resources Library Advisory Board FAQ

RESEARCH

JoVE Journal Methods Collections JoVE Encyclopedia of Experiments Archive

EDUCATION

JoVE Core JoVE Business JoVE Science Education JoVE Lab Manual Faculty Resource Center Faculty Site

Terms & Conditions of Use

Related Concept Videos

Anticoagulant Drugs: Low-Molecular-Weight Heparins

Anticoagulant Drugs: Low-Molecular-Weight Heparins

Hemostasis is a crucial process that prevents excessive blood loss from damaged blood vessels. It involves various mechanisms such as vasoconstriction, platelet adhesion and activation, and fibrin formation. The importance of each mechanism depends on the type of vessel injury. In contrast, thrombosis is the abnormal formation of a blood clot within the blood vessels, leading to potential complications if the clot obstructs blood flow. Thrombosis can be caused by increased coagulability of the...

Structure and Function of Platelets

Structure and Function of Platelets

The cell fragments known as platelets are disc-shaped, with an average diameter of about 3 μm and a thickness of roughly 1 μm. They play a crucial role in the body's vascular clotting system, which also involves plasma proteins, blood cells, and blood vessel tissues.
Platelets are continually replenished, circulating in the bloodstream for 9-12 days before being removed by phagocytes, primarily in the spleen. A microliter of circulating blood contains between 150,000 and 450,000...

Formation of the Platelet Plug

Formation of the Platelet Plug

The platelet phase, the second stage of hemostasis, commences around 15-20 seconds after an injury. It follows and overlaps with the vascular phase, during which blood vessels constrict to minimize blood loss.
As the injured blood vessel contracts, endothelial cells undergo contraction, revealing collagen fibers in the basement membrane and underlying connective tissue. Furthermore, the plasma membrane of endothelial cells becomes adhesive, preparing the site for platelet adhesion. Platelets...

Clot Retraction and Fibrinolysis

Clot Retraction and Fibrinolysis

After a fibrin clot is formed, the next step is clot retraction, a vital process facilitated by platelet contractile proteins, such as actin and myosin. These proteins pull the fibrin strands closer together and condense the clot. This action reduces the size of the clot, creating a smaller, denser structure that effectively seals off the damaged vessel. Clot retraction consolidates the clot and helps with wound healing by bringing the edges of the damaged blood vessel closer together.

Extrinsic and Intrinsic Pathways of Hemostasis

Extrinsic and Intrinsic Pathways of Hemostasis

Blood clotting or coagulation involves extrinsic and intrinsic pathways, which ultimately merge into the common pathway, forming a fibrin clot.
The Extrinsic Pathway
The extrinsic pathway of coagulation is typically initiated by tissue damage that exposes blood to tissue factor (TF), a protein released by the damaged tissue cells outside the blood vessels—this interaction with TF triggers biochemical reactions involving specific clotting factors. The key player here is Factor VII, which...

Inflammation

Inflammation

You might also read

Related Articles

Articles linked to this work by shared authors, journal, and citation graph.

Sort by

Same author

Integrative assessment of high-sensitivity C-reactive protein and lipid levels in predicting 20-year atherosclerotic cardiovascular disease risk, in a Mediterranean population: The ATTICA study (2002-2022).

American heart journal·2026

Same author

Neuroimmune Regulation of Microvascular Inflammation: The Heart-Brain Axis, Mast Cells, and the Protective Role of Flavonoids-A Comprehensive Review.

Biomedicines·2026

Same author

Natural Molecules for Brain Health and Resilience.

International journal of molecular sciences·2026

Same author

The Mediterranean Diet and Cardiovascular Protection: Biochemical Mechanisms with Emphasis on Platelet-Activating Factor.

Nutrients·2026

Same author

Long COVID neuropathy: The role of mast cells.

Journal of neuropathology and experimental neurology·2026

Same author

Gut-Brain Inflammation and Disrupted Homeostasis Due to Activation of Mast Cells and Microglia.

International journal of molecular sciences·2026

Search research articles

Related Experiment Video

Updated: Nov 26, 2025

Flow Cytometry Analysis of Tissue Factor Expression in Human Platelets

Flow Cytometry Analysis of Tissue Factor Expression in Human Platelets

Published on: November 22, 2024

COVID-19, microthromboses, inflammation, and platelet activating factor.

Constantinos Demopoulos¹, Smaragdi Antonopoulou², Theoharis C Theoharides^3,4,5

¹Laboratory of Biochemistry, Faculty of Chemistry, National & Kapodistrian University, Athens, Greece.

Biofactors (Oxford, England)

|December 9, 2020

Summary

Platelet activating factor (PAF) may drive COVID-19 coagulation and inflammation. The drug rupatadine, an anti-PAF agent, could be repurposed for COVID-19 prevention, potentially with natural compounds like quercetin.

Keywords:

COVID-19 PAF coagulation flavonoids inflammation mast cells rupatadine

More Related Videos

Procoagulant Platelet Characterization by Measuring Phosphatidylserine Exposure and Microvesicle Release from Human Purified Platelets

Procoagulant Platelet Characterization by Measuring Phosphatidylserine Exposure and Microvesicle Release from Human Purified Platelets

Published on: November 29, 2024

Comprehensive Analysis of Procoagulant Platelets Exhibiting Features of Necrosis, Apoptosis and Platelet Activation

Comprehensive Analysis of Procoagulant Platelets Exhibiting Features of Necrosis, Apoptosis and Platelet Activation

Published on: May 23, 2025

Related Experiment Videos

Last Updated: Nov 26, 2025

Flow Cytometry Analysis of Tissue Factor Expression in Human Platelets

Flow Cytometry Analysis of Tissue Factor Expression in Human Platelets

Published on: November 22, 2024

Procoagulant Platelet Characterization by Measuring Phosphatidylserine Exposure and Microvesicle Release from Human Purified Platelets

Procoagulant Platelet Characterization by Measuring Phosphatidylserine Exposure and Microvesicle Release from Human Purified Platelets

Published on: November 29, 2024

Comprehensive Analysis of Procoagulant Platelets Exhibiting Features of Necrosis, Apoptosis and Platelet Activation

Comprehensive Analysis of Procoagulant Platelets Exhibiting Features of Necrosis, Apoptosis and Platelet Activation

Published on: May 23, 2025

Area of Science:

Immunology
Virology
Pharmacology

Background:

COVID-19 patients exhibit elevated coagulation and endothelial injury markers.
The role of platelet activating factor (PAF) in inducing intravascular coagulation in COVID-19 remains underexplored.
PAF is a potent platelet activator involved in host defense and inflammation.

Purpose of the Study:

To explore the potential role of PAF in COVID-19 pathogenesis.
To investigate rupatadine and natural compounds as potential treatments for COVID-19.

Main Methods:

Review of existing literature on PAF, COVID-19, and mast cell activation.
Analysis of PAF's biological actions and similarities to COVID-19 manifestations.
Evaluation of rupatadine's anti-PAF and mast cell inhibitory properties.

Main Results:

PAF production by host defense cells and its pro-inflammatory actions align with COVID-19 symptoms.
PAF stimulates mast cells, releasing cytokines like IL-1β and IL-6, implicated in severe COVID-19 and SARS.
Rupatadine exhibits anti-PAF activity and inhibits mast cell activation.

Conclusions:

PAF is a potential key mediator of intravascular coagulation and inflammation in COVID-19.
Rupatadine, an existing drug, shows promise for repurposing in COVID-19 prophylaxis.
Combination therapy with natural PAF inhibitors (quercetin, luteolin) may enhance efficacy.