Pleiotropic effects of clopidogrel

Clopidogrel-induced thrombotic microangiopathy: a case report

Thrombotic microangiopathy is a serious condition that can be precipitated by exposure to certain medications. Although rare, it is life threatening and requires a high index of clinical suspicion, appropriate laboratory testing and immediate cessation of the offending agent. We present a case of a 75-year-old man with a history of ischaemic heart disease treated with clopidogrel and aspirin. One month after initiating the treatment he developed microangiopathic haemolytic anaemia and thrombocytopenia. Extensive clinical and laboratory investigations suggested thrombotic microangiopathy secondary to clopidogrel. The drug was immediately discontinued and treatment with intravenous corticosteroids was started. Within a week the patient's laboratory parameters normalised, indicating successful recovery. This case highlights the role of early detection and immediate discontinuation of suspected medication in the effective management of clopidogrel-induced thrombotic microangiopathy. Healthcare professionals should consider drug-induced thrombotic microangiopathy as a possible diagnosis in patients receiving clopidogrel who present with thrombocytopenia and microangiopathic haemolytic anaemia.

Contribution of platelets to disruption of the blood-brain barrier during arterial baroreflex dysfunction

BACKGROUND

Arterial baroreflex dysfunction, like many other central nervous system disorders, involves disruption of the blood-brain barrier, but what causes such disruption in ABR dysfunction is unclear. Here we explored the potential role of platelets in this disruption.

METHODS

ABR dysfunction was induced in rats using sinoaortic denervation, and the effects on integrity of the blood-brain barrier were explored based on leakage of Evans blue or FITC-dextran, while the effects on expression of CD40L in platelets and of key proteins in microvascular endothelial cells were explored using immunohistochemistry, western blotting and enzyme-linked immunosorbent assay. Similar experiments were carried out in rat brain microvascular endothelial cell line, which we exposed to platelets taken from rats with ABR dysfunction.

RESULTS

Sinoaortic denervation permeabilized the blood-brain barrier and downregulated zonula occludens-1 and occludin in rat brain, while upregulating expression of CD40L on the surface of platelets and stimulating platelet aggregation. Similar effects of permeabilization and downregulation were observed in healthy rats that received platelets from animals with ABR dysfunction, and in rat brain microvascular endothelial cells, but only in the presence of lipopolysaccharide. These effects were associated with activation of NF-κB signaling and upregulation of matrix metalloprotease-9. These effects of platelets from animals with ABR dysfunction were partially blocked by neutralizing antibody against CD40L or the platelet inhibitor clopidogrel.

CONCLUSION

During ABR dysfunction, platelets may disrupt the blood-brain barrier when CD40L on their surface activates NF-kB signaling within cerebral microvascular endothelial cells, leading to upregulation of matrix metalloprotease-9. Our findings imply that targeting CD40L may be effective against cerebral diseases involving ABR dysfunction.

Metabolic crosstalk: Extracellular ATP and the tumor microenvironment in cancer progression and therapy

Adenosine 5'-triphosphate (ATP) is a vital element in energy information. It plays a critical role in transmitting signals inside the body, which is necessary for controlling the life activities of all cells, including tumor cells [1]. Its significance extends from intracellular signaling pathways to tumor regression. Purinergic signaling, a form of extracellular paracrine signaling, relies on purine nucleotides. Extracellular ectonucleotidases convert these purine nucleotides to their respective di and mono-phosphate nucleoside forms, contributing significantly to immune biology, cancer biology, and inflammation studies. ATP functions as a mighty damage-linked molecular pattern when released outside the cell, accumulating in inflammatory areas. In the tumor microenvironment (TME), purinergic receptors such as ATP-gated ion channels P2X1-5 and G protein-coupled receptors (GPCR) (P2Y) interact with ATP and other nucleotides, influencing diverse immune cell activities. CD39 and CD73-mediated extracellular ATP degradation contributes to immunosuppression by diminishing ATP-dependent activation and generating adenosine (ADO), potentially hindering antitumor immunity and promoting tumor development. Unraveling the complexities of extracellular ATP (e-ATP) and ADO effects on the TME poses challenges in identifying optimal treatment targets, yet ongoing investigations aim to devise strategies combating e-ATP/ADO-induced immunosuppression, ultimately enhancing anti-tumor immunity. This review explores e-ATP metabolism, its purinergic signaling, and therapeutic strategies targeting associated receptors and enzymes.

The Signaling Pathway of the ADP Receptor P2Y12 in the Immune System: Recent Discoveries and New Challenges

P2Y12 is a G-protein-coupled receptor that is activated upon ADP binding. Considering its well-established role in platelet activation, blocking P2Y12 has been used as a therapeutic strategy for antiplatelet aggregation in cardiovascular disease patients. However, receptor studies have shown that P2Y12 is functionally expressed not only in platelets and the microglia but also in other cells of the immune system, such as in monocytes, dendritic cells, and T lymphocytes. As a result, studies were carried out investigating whether therapies targeting P2Y12 could also ameliorate inflammatory conditions, such as sepsis, rheumatoid arthritis, neuroinflammation, cancer, COVID-19, atherosclerosis, and diabetes-associated inflammation in animal models and human subjects. This review reports what is known about the expression of P2Y12 in the cells of the immune system and the effect of P2Y12 activation and/or inhibition in inflammatory conditions. Lastly, we will discuss the major problems and challenges in studying this receptor and provide insights on how they can be overcome.

Purinergic signaling: a potential therapeutic target for ischemic stroke

Pathogenesis of ischemic stroke is mainly characterized by thrombosis and neuroinflammation. Purinergic signaling pathway constitutes adenosine triphosphate (ATP), adenosine diphosphate (ADP), adenosine monophosphate (AMP), and adenosine (ADO). ATP is hydrolyzed to ADP and then to AMP by extracellular nucleotidase CD39; AMP is subsequently converted to adenosine by CD73. All these nucleotides and nucleosides act on purinergic receptors protecting against thrombosis and inhibit inflammation. In addition, many physical methods have been found to play a neuroprotective role through purinergic signaling. This review mainly introduces the role and potential mechanism of purinergic signalings in the treatment of ischemic stroke, so as to provide reference for seeking new treatment methods for stroke.