Pharmacologic targeting of Cdc42 GTPase by a small molecule Cdc42 activity-specific inhibitor prevents platelet activation and thrombosis

Intravital Imaging of Thrombosis Models in Mice

Intravital microscopy is a powerful tool to study thrombosis in real time. The kinetics of thrombus formation and progression in vivo is studied after inflicting damage to the endothelium through mechanical, chemical, or laser injury. Mouse models of atherosclerosis are also used to induce thrombus formation. Vessels of different sizes and from different vascular beds such as carotid artery or vena cava, mesenteric or cremaster arterioles, can be targeted. Using fluorescent dyes, antibodies, or reporter mouse strains allows to visualize key cells and factors mediating the thrombotic processes. Here, we review the latest literature on using intravital microscopy to study thrombosis as well as thromboinflammation following transient middle cerebral artery occlusion, infection-induced immunothrombosis, and liver ischemia reperfusion.

CDC42 Might Be a Molecular Signature of DWI-FLAIR Mismatch in a Nonhuman Primate Stroke Model

No definitive blood markers of DWI-FLAIR mismatch, a pivotal indicator of salvageable ischemic penumbra brain tissue, are known. We previously reported that CDC42 and RHOA are associated with the ischemic penumbra. Here, we investigated whether plasma CDC42 and RHOA are surrogate markers of DWI-FLAIR mismatch. Sixteen cynomolgus macaques (3 as controls and 13 for the stroke model) were included. Guided by digital subtraction angiography (DSA), a middle cerebral artery occlusion (MCAO) model was established by occluding the middle cerebral artery (MCA) with a balloon. MRI and neurological deficit scoring were performed to evaluate postinfarction changes. Plasma CDC42 and RHOA levels were measured by enzyme-linked immunosorbent assay (ELISA). The stroke model was successfully established in eight monkeys. Based on postinfarction MRI images, experimental animals were divided into a FLAIR (-) group (N = 4) and a FLAIR (+) group (N = 4). Plasma CDC42 in the FLAIR (-) group showed a significant decrease compared with that in the FLAIR (+) group (p < 0.05). No statistically significant difference was observed for plasma RHOA. The FLAIR (-) group showed a milder neurological function deficit and a smaller infarct volume than the FLAIR (+) group (p < 0.05). Therefore, plasma CDC42 might be a new surrogate marker for DWI-FLAIR mismatch.

Role of a small GTPase Cdc42 in aging and age-related diseases

A small GTPase, Cdc42 is evolutionarily one of the most ancient members of the Rho family, which is ubiquitously expressed and involved in a wide range of fundamental cellular functions. The crucial role of Cdc42 includes regulation of the actin cytoskeleton, cell polarity, morphology and migration, endocytosis and exocytosis, cell cycle, and proliferation in many different cell types. Many studies have provided compelling yet contradicting evidence that Cdc42 dysregulation plays an important role in cellular and tissue aging. Furthermore, Cdc42 is a critical factor in the development and progression of aging-related pathologies, such as neurodegenerative and cardiovascular disorders, diabetes type 2, and aging-related disorders of the joints and bones, and the inhibition of the Cdc42 demonstrates potentially significant therapeutic and anti-aging effects in animal models of aging and disease. However, regulation of Cdc42 expression and activity is very complex and depends on many factors, such as the origin and complexity of the tissues, hormonal status, etc. Therefore, this review is focused on current advances in understanding the underlying cellular and molecular mechanisms associated with Cdc42 activity and regulation of senescence in different cell types since they may provide a foundation for novel therapeutic strategies and targeted drugs to reverse the aging process and treat aging-associated disorders.

Rho GTPase Signaling in Platelet Regulation and Implication for Antiplatelet Therapies

Platelets play a vital role in regulating hemostasis and thrombosis. Rho GTPases are well known as molecular switches that control various cellular functions via a balanced GTP-binding/GTP-hydrolysis cycle and signaling cascade through downstream effectors. In platelets, Rho GTPases function as critical regulators by mediating signal transduction that drives platelet activation and aggregation. Mostly by gene targeting and pharmacological inhibition approaches, Rho GTPase family members RhoA, Rac1, and Cdc42 have been shown to be indispensable in regulating the actin cytoskeleton dynamics in platelets, affecting platelet shape change, spreading, secretion, and aggregation, leading to thrombus formation. Additionally, studies of Rho GTPase function using platelets as a non-transformed model due to their anucleated nature have revealed valuable information on cell signaling principles. This review provides an updated summary of recent advances in Rho GTPase signaling in platelet regulation. We also highlight pharmacological approaches that effectively inhibited platelet activation to explore their possible development into future antiplatelet therapies.

Danshensu prevents thrombosis by inhibiting platelet activation via SIRT1/ROS/mtDNA pathways without increasing bleeding risk

BACKGROUND

Coronary thrombosis and its correlated disorders are main healthcare problems globally. The therapeutic effects of current treatments involving antiplatelet drugs are not fully satisfactory. Danshensu (DSS) is an important monomer obtained from Salvia miltiorrhiza roots that have been widely employed for vascular diseases in medicinal practices. Nonetheless, the underlying mechanisms of DSS are not fully unraveled.

PURPOSE

The objective of this study was to penetrate the antithrombotic and antiplatelet mechanisms of DSS.

METHODS

Network pharmacology assay was used to forecast the cellular mechanisms of DSS for treating thrombosis. The work focused the impacts of DSS on platelet activation by analyzing aggregation and adhesion in vitro. Flow cytometry, western blotting, CM-H2DCFDA staining and mitochondrial function assays were performed to reveal the molecular mechanisms. The model of common carotid artery thrombus induced by ferric chloride was established. The wet weight of thrombus was measured, and the thrombosis was observed by hematoxylin and eosin (H&E) staining, in order to support the inhibitory effect of DSS on thrombosis.

RESULTS

Data mining found the antithrombotic effect of DSS is related to platelet activation and the core target is silent information regulator 1 (SIRT1). We confirmed that DSS dose-dependently inhibited platelet activation in vitro. DSS was further demonstrated to induce the expression of SIRT1 and decreased reactive oxygen species (ROS) burden and thereby prevented mitochondrial dysfunction. Mitochondrial function tests further indicated that DSS prevented mitochondrial DNA (mtDNA) release, which induced activation of platelet in a dendritic cell specific intercellular-adhesion-molecule-3 grabbing non-integrin (DC-SIGN)-dependent manner. In carotid artery injury model induced by ferric chloride, DSS inhibited the development of carotid arterial thrombosis. More encouragingly, in tail bleeding time assay, DSS did not augment bleeding risk.

CONCLUSION

These findings indicated that DSS effectively inhibited platelet activation by depressing the collection of ROS and the release of platelet mtDNA without arousing hemorrhage risk. DSS might represent a promising candidate drug for thrombosis and cardiovascular disease therapeutics.

Longitudinal Variations of CDC42 in Patients With Acute Ischemic Stroke During 3-Year Period: Correlation With CD4+ T Cells, Disease Severity, and Prognosis

Objective

Cell division cycle 42 (CDC42) modulates CD4⁺ T-cell differentiation, blood lipids, and neuronal apoptosis and is involved in the pathogenesis of acute ischemic stroke (AIS); however, the clinical role of CDC42 in AIS remains unanswered. This study aimed to evaluate the expression of CDC42 in a 3-year follow-up and its correlation with disease severity, T helper (Th)1/2/17 cells, and the prognosis in patients with AIS.

Methods

Blood CDC42 was detected in 143 patients with AIS at multiple time points during the 3-year follow-up period and in 70 controls at admission by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). In addition, blood Th1, Th2, and Th17 cells and their secreted cytokines (interferon-γ (IFN-γ), interleukin-4 (IL-4), and interleukin-17A (IL-17A)) in patients with AIS were detected by flow cytometry and enzyme-linked immunosorbent assay (ELISA), respectively.

Results

Compared with controls (p < 0.001), CDC42 was reduced in patients with AIS. CDC42 was negatively correlated with the National Institutes of Health Stroke Scale (NIHSS) score (p < 0.001), whereas, in patients with AIS (all p < 0.050), it was positively associated with Th2 cells and IL-4 but negatively correlated with Th17 cells and IL-17A. CDC42 was decreased from admission to 3 days and gradually increased from 3 days to 3 years in patients with AIS (P<0.001). In a 3-year follow-up, 24 patients with AIS recurred and 8 patients died. On the 3rd day, 7th day, 1st month, 3rd month, 6th month, 1st year, 2nd year, and 3rd year, CDC42 was decreased in recurrent patients than that in non-recurrent patients (all p < 0.050). CDC42 at 7 days (p = 0.033) and 3 months (p = 0.023) was declined in reported deceased patients than in survived patients.

Conclusion

CDC42 is used as a biomarker to constantly monitor disease progression and recurrence risk of patients with AIS.