cAMP signaling regulates platelet myosin light chain (MLC) phosphorylation and shape change through targeting the RhoA-Rho kinase-MLC phosphatase signaling pathway

Protein Kinase A Regulates Platelet Phosphodiesterase 3A through an A-Kinase Anchoring Protein Dependent Manner

Platelet activation is critical for haemostasis, but if unregulated can lead to pathological thrombosis. Endogenous platelet inhibitory mechanisms are mediated by prostacyclin (PGI2)-stimulated cAMP signalling, which is regulated by phosphodiesterase 3A (PDE3A). However, spatiotemporal regulation of PDE3A activity in platelets is unknown. Here, we report that platelets possess multiple PDE3A isoforms with seemingly identical molecular weights (100 kDa). One isoform contained a unique N-terminal sequence that corresponded to PDE3A1 in nucleated cells but with negligible contribution to overall PDE3A activity. The predominant cytosolic PDE3A isoform did not possess the unique N-terminal sequence and accounted for >99% of basal PDE3A activity. PGI2 treatment induced a dose and time-dependent increase in PDE3A phosphorylation which was PKA-dependent and associated with an increase in phosphodiesterase enzymatic activity. The effects of PGI2 on PDE3A were modulated by A-kinase anchoring protein (AKAP) disruptor peptides, suggesting an AKAP-mediated PDE3A signalosome. We identified AKAP7, AKAP9, AKAP12, AKAP13, and moesin expressed in platelets but focussed on AKAP7 as a potential PDE3A binding partner. Using a combination of immunoprecipitation, proximity ligation techniques, and activity assays, we identified a novel PDE3A/PKA RII/AKAP7 signalosome in platelets that integrates propagation and termination of cAMP signalling through coupling of PKA and PDE3A.

Salvia miltiorrhiza ameliorates endometritis in dairy cows by relieving inflammation, energy deficiency and blood stasis

Introduction: According to traditional Chinese veterinary medicine, endometritis is caused by a combination of Qi deficiency, blood stasis, and external evil invasion. Salvia miltiorrhiza is a traditional Chinese medicine that counteracts blood stasis and has additional demonstrated effects in boosting energy and restraining inflammation. Salvia miltiorrhiza has been employed in many traditional Chinese prescriptions that have proven effective in healing clinical dairy cow endometritis. Methods: the in vivo effect of Salvia miltiorrhiza in treating endometritis was evaluated in dairy cows. In addition, bovine endometrial epithelium cell inflammation and rat blood stasis models were employed to demonstrate the crosstalk between energy, blood circulation and inflammation. Network analysis, western blotting, qRT-PCR and ELISA were performed to investigate the molecular mechanism of Salvia miltiorrhiza in endometritis treatment. Results: The results demonstrate that treatment with Salvia miltiorrhiza relieves uterine inflammation, increases blood ATP concentrations, and prolongs blood clotting times. Four of the six Salvia miltiorrhiza main components (SMMCs) (tanshinone IIA, cryptotanshinone, salvianolic acid A and salvianolic acid B) were effective in reversing decreased ATP and increased IL-1β, IL-6, and IL-8 levels in an in vitro endometritis model, indicating their abilities to ameliorate the negative energy balance and external evil invasion effects of endometritis. Furthermore, in a blood stasis rat model, inflammatory responses were induced in the absence of external infection; and all six SMMCs inhibited thrombin-induced platelet aggregation. Network analysis of SMMC targets predicted that Salvia miltiorrhiza may mediate anti-inflammation via the Toll-like receptor signaling pathway; anti-aggregation via the Platelet activation pathway; and energy balance via the Thermogenesis and AMPK signaling pathways. Multiple molecular targets within these pathways were verified to be inhibited by SMMCs, including P38/ERK-AP1, a key molecular signal that may mediate the crosstalk between inflammation, energy deficiency and blood stasis. Conclusion: These results provide mechanistic understanding of the therapeutic effect of Salvia miltiorrhiza for endometritis achieved through Qi deficiency, blood stasis, and external evil invasion.

Activation of Dopamine Receptor D1 and Downstream Cellular Functions by Polydopamine

Polydopamine is a remarkable molecule that has gained considerable attention for its role in material surface modification, leading to an abundance of research in the biomaterial domain. While its widespread use is well documented, the molecule's potential cellular interactions have been less explored. In particular, dopamine serves as a neurotransmitter and a hormone that interacts with dopamine receptors in cells. Our study sheds light on the previously unexamined interaction between polydopamine and dopamine receptor D1 (DRD1). We discovered that polydopamine, along with its derivatives, such as levodopa and catechol, can activate DRD1─a function previously attributed solely to dopamine. Moreover, we found that polydopamine has the ability to influence cell behavior through the cAMP/PKA pathway, thereby affecting RhoA activity and stress fiber formation. These observations invite further consideration regarding the biological safety of polydopamine in biomedical contexts and also open avenues for new research directions in designing bioactive functional materials.

Platelet zinc status regulates prostaglandin-induced signaling, altering thrombus formation

BACKGROUND

Approximately 17.3% of the global population exhibits an element of zinc (Zn2+) deficiency. One symptom of Zn2+ deficiency is increased bleeding through impaired hemostasis. Platelets are crucial to hemostasis and are inhibited by endothelial-derived prostacyclin (prostaglandin I2 [PGI2]), which signals via adenylyl cyclase (AC) and cyclic adenosine monophosphate signaling. In other cell types, Zn2+ modulates cyclic adenosine monophosphate concentrations by changing AC and/or phosphodiesterase activity.

OBJECTIVES

To investigate if Zn2+ can modulate platelet PGI2 signaling.

METHODS

Platelet aggregation, spreading, and western blotting assays with Zn2+ chelators and cyclic nucleotide elevating agents were performed in washed platelets and platelet-rich plasma conditions. In vitro thrombus formation with various Zn2+ chelators and PGI2 was assessed in whole blood.

RESULTS

Incubation of whole blood or washed platelets with Zn2+ chelators caused either embolization of preformed thrombi or reversal of platelet spreading, respectively. To understand this effect, we analyzed resting platelets and identified that incubation with Zn2+ chelators elevated pVASPser157, a marker of PGI2 signaling. In agreement that Zn2+ affects PGI2 signaling, addition of the AC inhibitor SQ22536 blocked Zn2+ chelation-induced platelet spreading reversal, while addition of Zn2+ blocked PGI2-mediated platelet reversal. Moreover, Zn2+ specifically blocked forskolin-mediated AC reversal of platelet spreading. Finally, PGI2 inhibition of platelet aggregation and in vitro thrombus formation was potentiated in the presence of low doses of Zn2+ chelators, increasing its effectiveness in inducing platelet inhibition.

CONCLUSION

Zn2+ chelation potentiates platelet PGI2 signaling, elevating PGI2's ability to prevent effective platelet activation, aggregation, and thrombus formation.

MTH1 protects platelet mitochondria from oxidative damage and regulates platelet function and thrombosis

Human MutT Homolog 1 (MTH1) is a nucleotide pool sanitization enzyme that hydrolyzes oxidized nucleotides to prevent their mis-incorporation into DNA under oxidative stress. Expression and functional roles of MTH1 in platelets are not known. Here, we show MTH1 expression in platelets and its deficiency impairs hemostasis and arterial/venous thrombosis in vivo. MTH1 deficiency reduced platelet aggregation, phosphatidylserine exposure and calcium mobilization induced by thrombin but not by collagen-related peptide (CRP) along with decreased mitochondrial ATP production. Thrombin but not CRP induced Ca2+-dependent mitochondria reactive oxygen species generation. Mechanistically, MTH1 deficiency caused mitochondrial DNA oxidative damage and reduced the expression of cytochrome c oxidase 1. Furthermore, MTH1 exerts a similar role in human platelet function. Our study suggests that MTH1 exerts a protective function against oxidative stress in platelets and indicates that MTH1 could be a potential therapeutic target for the prevention of thrombotic diseases.

Monensin synergizes with chemotherapy in uveal melanoma through suppressing RhoA

OBJECTIVE

Uveal melanoma (UM) is the common primary cancer of the eye and new treatments are needed. Substantial evidence has shown that an antibiotic monensin is an attractive candidate for the development of anti-cancer drug. In this study, we investigated the potential of repositioning monensin for the treatment of UM in the pre-clinical setting.

MATERIALS AND METHODS

Cellular activity assays were performed using multiple cell lines representing UM models with different cellular origins and genetic profiling and normal cells as control. Combination studies were performed using Chou-Talalay method. Mechanism studies were performed using immunoblotting and ELISA.

RESULTS

Monensin was effective against all tested UM cell lines and less effective against normal fibroblast cells. Monensin induced G0/G1 arrest and thus decreased S phase, leading to UM cell growth inhibition. It also inhibited migration and induced apoptosis in UM cells. In addition, the combination of monensin and dacarbazine was synergistic in targeting UM cells. Our mechanistic studies showed that monensin specifically decreased activity of RhoA without affecting other small GTPases, such as Ras and Rac1. Consistently, monensin decreased phosphorylation of downstream effectors of RhoA signaling, including ROCK, MYPT1 and MLC. Rescue studies using RhoA activator calpeptin showed that calpeptin significantly abolished the inhibitory effects of monensin on RhoA activity, proliferation, migration and survival, confirming that RhoA is the target of monensin in UM cells.

CONCLUSIONS

Our study demonstrates that monensin is a potent inhibitor of UM and synergizes with chemotherapy, via suppressing RhoA activity and RhoA-mediated signaling. Our findings suggest that monensin may be a potential lead compound for further development into a drug for UM treatment.

The Role of NO/sGC/cGMP/PKG Signaling Pathway in Regulation of Platelet Function

Circulating blood platelets are controlled by stimulatory and inhibitory factors, and a tightly regulated equilibrium between these two opposing processes is essential for normal platelet and vascular function. NO/cGMP/ Protein Kinase G (PKG) pathways play a highly significant role in platelet inhibition, which is supported by a large body of studies and data. This review focused on inconsistent and controversial data of NO/sGC/cGMP/PKG signaling in platelets including sources of NO that activate sGC in platelets, the role of sGC/PKG in platelet inhibition/activation, and the complexity of the regulation of platelet inhibitory mechanisms by cGMP/PKG pathways. In conclusion, we suggest that the recently developed quantitative phosphoproteomic method will be a powerful tool for the analysis of PKG-mediated effects. Analysis of phosphoproteins in PKG-activated platelets will reveal many new PKG substrates. A future detailed analysis of these substrates and their involvement in different platelet inhibitory pathways could be a basis for the development of new antiplatelet drugs that may target only specific aspects of platelet functions.

Ceramide Synthase 6 Mediates Triple-Negative Breast Cancer Response to Chemotherapy Through RhoA- and EGFR-Mediated Signaling Pathways

PURPOSE

Limited treatment options and lack of treatment sensitivity biomarkers make the clinical management of triple-negative breast cancer (TNBC) challenging. Ceramide synthase 6 (CERS6) generates ceramides, which are key intermediates in sphingolipid biosynthesis and play important roles in cancer progression and resistance.

METHODS

CERS6 was analyzed to determine its potential as a treatment sensitivity biomarker. CERS6 levels were determined in patients with breast cancer, and the roles and downstream signaling of CERS6 were analyzed using cellular and biochemical assays.

RESULTS

Analysis of CERS6 expression in 195 patients with TNBC and their clinical response to chemotherapy revealed that individuals with CERS6 overexpression experienced significantly inferior responses to chemotherapy than those without CERS6 overexpression. Functional analysis demonstrated that although CERS6 overexpression did not affect TNBC cell growth and migration, it conferred chemoresistance. CERS6 inhibition significantly reduced growth, migration, and survival by suppressing the RhoA- and EGFR-mediated signaling pathways. Compared to control cells, CERS6-depleted cells were consistently less viable at different concentrations of chemotherapeutic agents.

CONCLUSION

Our study is the first to demonstrate that CERS6 may serve as a treatment sensitivity biomarker in patients with TNBC in response to chemotherapy. In addition, our findings suggested that CERS6 may be a therapeutic target for TNBC treatment.

ROS-Mediated Enamel Formation Disturbance Characterized by Alternative Cervical Loop Cell Proliferation and Downregulation of RhoA/ROCK in Ameloblasts

Reactive oxygen stress (ROS) is generally accepted as a signal transducer for coordinating the growth and differentiation of tissues and organs in the oral and maxillofacial region. Although ROS has been confirmed to affect the development of enamel, it is not yet known that the specific mechanism of ROS accumulation induced enamel defects. Given the lack of knowledge of the role of ROS in enamel, the aim of the study is to determine how oxidative stress affects cervical cells and ameloblast cells. Using SOD1 knockout mice, we identified a relationship between ROS fluctuations and abnormal enamel structure with HE staining, micro-CT, and scanning electron microscope. Increased ROS induced by H2O2, certified by the DCFH probe, has resulted in a dual effect on the proliferation and differentiation of cervical cells, indicating a higher tendency to proliferate at low ROS concentrations. Ameloblasts transfected with SOD1 siRNA showed a significant reduction of RhoA and ROCK. This study investigates for the first time that SOD1-mediated ROS accumulation disrupted normal enamel structure through alternative cervical loop cell proliferation and downregulation of RhoA and ROCK in ameloblasts, demonstrating the convoluted role of ROS in monitoring the progress of enamel defects.

Morphine stimulates cervical cancer cells and alleviates cytotoxicity of chemotherapeutic drugs via opioid receptor-dependent and -independent mechanisms

Morphine is frequently applied in cancer patients for pain management. However, its effects on cancer are not well understood but observed to be specific to certain cancer types. We previously revealed the stimulatory properties of morphine in esophageal carcinoma. This work addressed the effects of morphine and its underlying mechanisms in cervical cancer. Proliferation, apoptosis, and migration assays were performed to examine the effects of morphine alone and its combinatory effects with chemotherapeutic drugs. Immunoblotting and biochemical analysis were performed to determine the underlying mechanisms of morphine's action. Morphine promoted proliferation in opioid receptor-dependent manner and stimulated migration in opioid receptor-independent manner. However, morphine did not affect cervical cancer cell survival. Morphine also interfered with all tested chemotherapeutic drugs (e.g., cisplatin, 5-FU, and paclitaxel) and alleviates their efficacy. Mechanistically, morphine-stimulated growth via activating EGFR-mediated signaling pathways and is opioid-receptor-dependent; morphine-stimulated migration via activating RhoA-mediated signaling pathways and this is opioid receptor-independent. Our work suggests a strong correlation of this opioid receptor on growth factor signaling to stimulate growth and opioid receptor-independent activation of RhoA and consequent migration. Our findings have the potential to guide the clinical use of morphine for patients with cervical cancer.

Complex Transcriptional Profiles of the PPP1R12A Gene in Cells of the Circulatory System as Revealed by In Silico Analysis and Reverse Transcription PCR

The myosin light chain phosphatase target subunit 1 (MYPT1), encoded by the PPP1R12A gene, is a key component of the myosin light chain phosphatase (MLCP) protein complex. MYPT1 isoforms have been described as products of the cassette-type alternative splicing of exons E13, E14, E22, and E24. Through in silico analysis of the publicly available EST and mRNA databases, we established that PPP1R12A contains 32 exons (6 more than the 26 previously reported), of which 29 are used in 11 protein-coding transcripts. An in silico analysis of publicly available RNAseq data combined with validation by reverse transcription (RT)-PCR allowed us to determine the relative abundance of each transcript in three cell types of the circulatory system where MYPT1 plays important roles: human umbilical vein endothelial cells (HUVEC), human saphenous vein smooth muscle cells (HSVSMC), and platelets. All three cell types express up to 10 transcripts at variable frequencies. HUVECs and HSVSMCs predominantly express the full-length variant (58.3% and 64.3%, respectively) followed by the variant skipping E13 (33.7% and 23.1%, respectively), whereas in platelets the predominant variants are those skipping E14 (51.4%) and E13 (19.9%), followed by the full-length variant (14.4%). Variants including E24 account for 5.4% of transcripts in platelets but are rare (<1%) in HUVECs and HSVSMCs. Complex transcriptional profiles were also found across organs using in silico analysis of RNAseq data from the GTEx project. Our findings provide a platform for future studies investigating the specific (patho)physiological roles of understudied MYPT1 isoforms.

The protective effect of Escherichia coli Nissle 1917 on the intestinal barrier is mediated by inhibition of RhoA/ROCK2/MLC signaling via TLR-4

AIMS

This study investigated the protective effect of Escherichia coli Nissle 1917 (EcN) on intestinal barrier and the mechanism in the context of acute severe inflammation.

MATERIALS AND METHODS

In this study, mice received lipopolysaccharide (LPS) intraperitoneal injection with or without EcN administration to construct a mouse model of endotoxemia. Clinical scores, intestinal permeability, inflammatory cytokines and histopathological analysis of four main organs from different groups were assessed. The expression of tight junction proteins and activation of RhoA/ROCK2/MLC signaling were examined using western blotting. The localization of tight junction proteins was examined by immunofluorescence. Caco-2 monolayers with or without TLR-4 knockdown were incubated with EcN or TNF-α/IFN-γ and the monolayer barrier function was assessed by transepithelial electrical resistance (TER) and FITC-dextran 4000 Da (FD-4) flux. The expression of tight junction proteins and activation of RhoA/ROCK2/MLC signaling were examined by western blotting. The localization of tight junction proteins was examined by immunofluorescence.

KEY FINDINGS

We found that EcN downregulated the RhoA/ROCK2/MLC signaling pathway to preserve barrier function and alleviated systemic inflammation in mouse model. And EcN also protected barrier function of Caco-2 monolayers by inhibiting the activation of RhoA/ROCK2/MLC signaling via TLR-4.

SIGNIFICANCE

The results indicated that EcN protected the intestinal barrier function in endotoxemia through inhibiting the activation of RhoA/ROCK2/MLC signaling via TLR-4.

Inhibition of USP11 sensitizes gastric cancer to chemotherapy via suppressing RhoA and Ras-mediated signaling pathways

BACKGROUND

The poor outcomes in advanced gastric cancer (GC) necessitate alternative therapeutic strategy. Ubiquitin-specific protease 11 (USP11) has recently garnered attention as a therapeutic target in cancer because of its important regulatory role in cancer cell functions. Here, we revealed the expression, function and underlying molecular interactions of USP11 in gastric cancer.

METHODS

The expression of USP11 was analyzed using immunohistochemistry and ELISA. The loss-of function and gain-of function analysis of USP11 was performed using siRNA knockdown and plasmid overexpression approaches. The downstream molecules regulated by USP11 were determined using immunoblotting analysis.

RESULTS

USP11 was upregulated in ∼80% of gastric cancer patients, and the upregulation was associated with HER3 overexpression. In addition, USP11 level was not regulated by HER3 and vice versa. Functional studies demonstrated that USP11 overexpression promoted gastric cancer growth and migration, and alleviated toxicity-induced by chemotherapeutic drug. In contrast, USP11 depletion significantly inhibited gastric cancer growth, migration and survival, and augmented chemotherapeutic drug's efficacy. Gastric cancer cells with higher USP11 levels were more sensitive to USP11 inhibitions than cells with lower USP11 levels. Mechanism studies showed that USP11 depletion suppressed migration via RhoA-mediated pathway and inhibited growth and survival likely via Ras-mediated pathway.

CONCLUSIONS

Our work highlights the important role of USP11 in gastric cancer and therapeutic value of inhibiting USP11 to sensitize gastric cancer to chemotherapy.

The putative roles of FSH and AMH in the regulation of oocyte developmental competence: from fertility prognosis to mechanisms underlying age-related subfertility

BACKGROUND

Fertility loss during female ageing is associated with increasing basal FSH and decreasing anti-Müllerian hormone (AMH) concentrations, together with compromised oocyte quality, presumably due to increased oxidative stress (OS) and DNA damage, as well as reduced metabolic and meiotic competences. Basal FSH and AMH circulatory concentrations have been broadly utilized as IVF success predictors, regardless of fluctuations in prognostic accuracy; basal FSH and AMH perform better in pre-advanced maternal age (AMA: >35 years) and AMA patients, respectively. The relationships between FSH and AMH intrafollicular levels and IVF outcomes suggest, nevertheless, that both hormones regulate oocyte competence, supporting the hypothesis that changes in FSH/AMH levels cause, at least in part, oocyte quality degradation during ageing. To understand the reasons behind the fluctuations in FSH and AMH prognostic accuracies and to clarify their participation in mechanisms determining oocyte competence and age-related subfertility, a deeper knowledge of the regulation of FSH and AMH intrafollicular signalling during the female reproductive lifespan, and of their effects on the cumulus-oocyte complex, is required.

OBJECTIVE AND RATIONALE

An extensive body of information on the regulation of FSH and AMH intrafollicular availability and signalling, as well as on the control of folliculogenesis and oocyte metabolism, has been accumulated. However, these datasets have been explored within the relatively narrow boundaries of their specific subjects. Given the aforementioned gaps in knowledge and their clinical relevance, herein we integrate clinical and basic data, within a wide biological perspective, aiming to shed light on (i) the reasons for the variability in the accuracy of serum FSH and AMH as fertility markers, and on (ii) the potential roles of these hormones in mechanisms regulating oocyte quality, particularly those associated with ageing.

SEARCH METHODS

The PubMed database encompassing the period between 1960 and 2021 was searched. Principal search terms were FSH, FSH receptor, AMH, oocyte, maternal age, cumulus, transzonal projections (TZPs), actin, OS, redox, reactive oxygen species, mitochondria, DNA damage, DNA repair, aneuploidy, spindle, meiosis, gene expression, transcription, translation, oocyte secreted factors (OSFs), cAMP, cyclic guanosine monophosphate, natriuretic peptide C, growth differentiation factor 9, bone morphogenetic protein 15 and fibroblast growth factor.

OUTCOMES

Our analysis suggests that variations in the accuracy of fertility prognosis reflect a modest association between circulatory AMH levels and oocyte quality as well as increasing basal FSH inter-cycle variability with age. In addition, the basic and clinical data articulated herein support the hypothesis that increased intrafollicular FSH levels, as maternal age advances, may override the physiological protective influences of AMH and OSFs against excessive FSH signalling in cumulus cells. This would result in the disruption of oocyte homeostasis via reduced TZP-mediated transfer of cumulus-derived molecules essential for meiotic competence, gene expression, redox activity and DNA repair.

WIDER IMPLICATIONS

In-depth data analysis, encompassing a wide biological perspective has revealed potential causative mechanisms of age-related subfertility triggered by alterations in FSH/AMH signalling during the female reproductive life. Insights from new mechanistic models arising from this analysis should contribute to advancing our comprehension of oocyte biology in humans and serve as a valuable reference for novel AMA subfertility treatments aimed at improving oocyte quality through the modulation of AMH/FSH action.

Inhaled β2 Adrenergic Agonists and Other cAMP-Elevating Agents: Therapeutics for Alveolar Injury and Acute Respiratory Disease Syndrome?

Inhaled long-acting β-adrenergic agonists (LABAs) and short-acting β-adrenergic agonists are approved for the treatment of obstructive lung disease via actions mediated by β2 adrenergic receptors (β2-ARs) that increase cellular cAMP synthesis. This review discusses the potential of β2-AR agonists, in particular LABAs, for the treatment of acute respiratory distress syndrome (ARDS). We emphasize ARDS induced by pneumonia and focus on the pathobiology of ARDS and actions of LABAs and cAMP on pulmonary and immune cell types. β2-AR agonists/cAMP have beneficial actions that include protection of epithelial and endothelial cells from injury, restoration of alveolar fluid clearance, and reduction of fibrotic remodeling. β2-AR agonists/cAMP also exert anti-inflammatory effects on the immune system by actions on several types of immune cells. Early administration is likely critical for optimizing efficacy of LABAs or other cAMP-elevating agents, such as agonists of other Gs-coupled G protein-coupled receptors or cyclic nucleotide phosphodiesterase inhibitors. Clinical studies that target lung injury early, prior to development of ARDS, are thus needed to further assess the use of inhaled LABAs, perhaps combined with inhaled corticosteroids and/or long-acting muscarinic cholinergic antagonists. Such agents may provide a multipronged, repurposing, and efficacious therapeutic approach while minimizing systemic toxicity. SIGNIFICANCE STATEMENT: Acute respiratory distress syndrome (ARDS) after pulmonary alveolar injury (e.g., certain viral infections) is associated with ∼40% mortality and in need of new therapeutic approaches. This review summarizes the pathobiology of ARDS, focusing on contributions of pulmonary and immune cell types and potentially beneficial actions of β2 adrenergic receptors and cAMP. Early administration of inhaled β2 adrenergic agonists and perhaps other cAMP-elevating agents after alveolar injury may be a prophylactic approach to prevent development of ARDS.

Multidimensional flow cytometry reveals novel platelet subpopulations in response to prostacyclin

BACKGROUND

Robust platelet activation leads to the generation of subpopulations characterized by differential expression of phosphatidylserine (PS). Prostacyclin (PGI2 ) modulates many aspects of platelet function, but its influence on platelet subpopulations is unknown.

OBJECTIVES AND METHODS

We used fluorescent flow cytometry coupled to multidimensional fast Fourier transform-accelerated interpolation-based t-stochastic neighborhood embedding analysis to examine the influence of PGI2 on platelet subpopulations.

RESULTS

Platelet activation (SFLLRN/CRP-XL) in whole blood revealed three platelet subpopulations with unique combinations of fibrinogen (fb) binding and PS exposure. These subsets, PSlo /fbhi (68%), PShi /fblo (23%), and PShi /fbhi (8%), all expressed CD62P and partially shed CD42b. PGI2 significantly reduced fibrinogen binding and prevented the majority of PS exposure, but did not significantly reduce CD62P, CD154, or CD63 leading to the generation of four novel subpopulations, CD62Phi /PSlo /fblo (64%), CD62Phi /PSlo /fbhi (22%), CD62Phi /PShi /fblo (3%), and CD62Plo /PSlo /fblo (12%). Mechanistically this was linked to PGI2 -mediated inhibition of mitochondrial depolarization upstream of PS exposure. Combining phosphoflow with surface staining, we showed that PGI2 -treated platelets were characterized by both elevated vasodilator-stimulated phosphoprotein phosphorylation and CD62P. The resistance to cyclic AMP signaling was also observed for CD154 and CD63 expression. Consistent with the functional role of CD62P, exposure of blood to PGI2 failed to prevent SFLLRN/CRP-XL-induced platelet-monocyte aggregation despite reducing markers of hemostatic function.

CONCLUSION

The combination of multicolor flow cytometry assays with unbiased computational tools has identified novel platelet subpopulations that suggest differential regulation of platelet functions by PGI2 . Development of this approach with increased surface and intracellular markers will allow the identification of rare platelet subtypes and novel biomarkers.

H2S protects hippocampal neurons against hypoxia-reoxygenation injury by promoting RhoA phosphorylation at Ser188

Inhibition of RhoA-ROCK pathway is involved in the H₂S-induced cerebral vasodilatation and H₂S-mediated protection on endothelial cells against oxygen-glucose deprivation/reoxygenation injury. However, the inhibitory mechanism of H₂S on RhoA-ROCK pathway is still unclear. The aim of this study was to investigate the target and mechanism of H₂S in inhibition of RhoA/ROCK. GST-RhoA^wild and GST-RhoA^S188A proteins were constructed and expressed, and were used for phosphorylation assay in vitro. Recombinant RhoA^wild-pEGFP-N1 and RhoA^S188A-pEGFP-N1 plasmids were constructed and transfected into primary hippocampal nerve cells (HNCs) to evaluate the neuroprotective mechanism of endothelial H₂S by using transwell co-culture system with endothelial cells from cystathionine-γ-lyase knockout (CSE^-/-) mice and 3-mercaptopyruvate sulfurtransferase knockout (3-MST^-/-) rats, respectively. We found that NaHS, exogenous H₂S donor, promoted RhoA phosphorylation at Ser188 in the presence of cGMP-dependent protein kinase 1 (PKG1) in vitro. Besides, both exogenous and endothelial H₂S facilitated the RhoA phosphorylation at Ser188 in HNCs, which induced the reduction of RhoA activity and membrane transposition, as well as ROCK₂ activity and expression. To further investigate the role of endothelial H₂S on RhoA phosphorylation, we detected H₂S release from ECs of CSE^+/+ and CSE^-/- mice, and 3-MST^+/+ and 3-MST^-/- rats, respectively, and found that H₂S produced by ECs in the culture medium is mainly catalyzed by CSE synthase. Moreover, we revealed that both endothelial H₂S, mainly catalyzed by CSE, and exogenous H₂S protected the HNCs against hypoxia-reoxygenation injury via phosphorylating RhoA at Ser188.

Gentiopicroside Produces Endothelium-Independent Vasodilation by Deactivating the PI3K/Akt/Rho-Kinase Pathway in Isolated Rat Thoracic Aorta

Gentiopicroside (GPS), a main active secoiridoid glucoside derived from the roots of perennial herbs in the Gentianaceae family, has antispasmodic and relaxant effects. However, the vasorelaxant effects of GPS on aortic rings and the molecular mechanisms involved in these effects are not yet clear. Therefore, we investigated whether GPS inhibits phenylephrine- (PE-) or KCl-induced contractions in isolated rat thoracic aortic rings. The present study found that GPS produced a dose-dependent relaxation in aortic rings precontracted with PE or KCl and significantly reduced CaCl₂-, narciclasine- (Rho-kinase activator-), and phorbol-12,13-diacetate- (PKC activator-) induced vasocontractions. Pretreatment with NG-Nitroarginine methyl ester hydrochloride (L-NAME, NOS inhibitor), methylene blue (sGC inhibitor), indomethacin (COX inhibitor), 4-aminopyridine (K_V channel inhibitor), and glibenclamide (K_ATP channel inhibitor) had no influence on the vasorelaxant effect of GPS, while BaCl₂ (K_ir channel inhibitor), tetraethylammonium chloride (K_Ca channel inhibitor), ruthenium red (RYR inhibitor), and heparin (IP₃R inhibitor) significantly reduced GPS-induced vasorelaxation. Moreover, GPS pretreatment remarkably inhibited the influx of Ca²⁺ in vascular smooth muscle cells stimulated using KCl or PE-containing CaCl₂ solution. Western blot analysis confirmed that GPS treatment inhibited PE-induced increases in the protein levels of p-Akt, p-myosin light chain (MLC), and p-myosin-binding subunit of myosin phosphatase 1 (MYPT1) in the aortic rings. Additionally, the vasorelaxation activity of GPS was attenuated upon pretreatment with LY294002 (PI3K/Akt inhibitor), Y27632 (Rho-kinase inhibitor), and verapamil (L-type Ca²⁺ channel inhibitor). These findings demonstrate that GPS exhibits endothelium-independent vasorelaxant effects through inhibition of voltage-dependent, receptor-operated, and inositol triphosphate receptor (IP₃R)/ryanodine receptor- (RYR-) mediated Ca²⁺ channels as well as the PI3K/Akt/Rho-kinase signaling pathway.

Multidrug Resistance Protein 4 (MRP4/ABCC4): A Suspected Efflux Transporter for Human's Platelet Activation

The main role of platelets is to contribute to hemostasis. However, under pathophysiological conditions, platelet activation may lead to thrombotic events of cardiovascular diseases. Thus, anti-thrombotic treatment is important in patients with cardiovascular disease. This review focuses on a platelet receptor, a transmembrane protein, the Multidrug Resistance Protein 4, MRP4, which contributes to platelet activation by extruding endogenous molecules responsible for their activation and accumulation. The regulation of the intracellular concentration levels of these molecules by MRP4 turned to make the protein suspicious and, at the same time, an interesting regulatory factor of normal platelet function. Especially, the possible role of MRP4 in the excretion of xenobiotic and antiplatelet drugs such as aspirin is discussed, thus imparting platelet aspirin tolerance and correlating the protein with the ineffectiveness of aspirin antiplatelet therapy. Based on the above, this review finally underlines that the development of a highly selective and targeted strategy for platelet MRP4 inhibition will also lead to inhibition of platelet activation and accumulation.

Proteomics: A Tool to Study Platelet Function

Platelets are components of the blood that are highly reactive, and they quickly respond to multiple physiological and pathophysiological processes. In the last decade, it became clear that platelets are the key components of circulation, linking hemostasis, innate, and acquired immunity. Protein composition, localization, and activity are crucial for platelet function and regulation. The current state of mass spectrometry-based proteomics has tremendous potential to identify and quantify thousands of proteins from a minimal amount of material, unravel multiple post-translational modifications, and monitor platelet activity during drug treatments. This review focuses on the role of proteomics in understanding the molecular basics of the classical and newly emerging functions of platelets. including the recently described role of platelets in immunology and the development of COVID-19.The state-of-the-art proteomic technologies and their application in studying platelet biogenesis, signaling, and storage are described, and the potential of newly appeared trapped ion mobility spectrometry (TIMS) is highlighted. Additionally, implementing proteomic methods in platelet transfusion medicine, and as a diagnostic and prognostic tool, is discussed.

Conceptus metabolomic profiling reveals stage-specific phenotypes leading up to pregnancy recognition in cattle†

Reproductive efficiency in livestock is a major driver of sustainable food production. The poorly understood process of ruminant conceptus elongation (a) prerequisites maternal pregnancy recognition, (b) is essential to successful pregnancy establishment, and (c) coincides with a period of significant conceptus mortality. Conceptuses at five key developmental stages between Days 8-16 were recovered and cultured in vitro for 6 h prior to conditioned media analysis by untargeted ultrahigh-performance liquid chromatography tandem mass spectroscopy. This global temporal biochemical interrogation of the ex situ bovine conceptus unearths two antithetical stage-specific metabolic phenotypes during tubular (metabolically retentive) vs. filamentous (secretory) development. Moreover, the retentive conceptus phenotype on Day 14 coincides with an established period of elevated metabolic density in the uterine fluid of heifers with high systemic progesterone-a model of accelerated conceptus elongation. These data, combined, suggest a metabolic mechanism underpinning conceptus elongation, thereby enhancing our understanding of the biochemical reciprocity of maternal-conceptus communication, prior to maternal pregnancy recognition.

Rho GTPase regulation of reactive oxygen species generation and signalling in platelet function and disease

Platelets are master regulators and effectors of haemostasis with increasingly recognized functions as mediators of inflammation and immune responses. The Rho family of GTPase members Rac1, Cdc42 and RhoA are known to be major components of the intracellular signalling network critical to platelet shape change and morphological dynamics, thus playing a major role in platelet spreading, secretion and thrombus formation. Initially linked to the regulation of actomyosin contraction and lamellipodia formation, recent reports have uncovered non-canonical functions of platelet RhoGTPases in the regulation of reactive oxygen species (ROS), where intrinsically generated ROS modulate platelet function and contribute to thrombus formation. Platelet RhoGTPases orchestrate oxidative processes and cytoskeletal rearrangement in an interconnected manner to regulate intracellular signalling networks underlying platelet activity and thrombus formation. Herein we review our current knowledge of the regulation of platelet ROS generation by RhoGTPases and their relationship with platelet cytoskeletal reorganization, activation and function.

Morphine Stimulates Migration and Growth and Alleviates the Effects of Chemo Drugs via AMPK-Dependent Induction of Epithelial-Mesenchymal Transition in Esophageal Carcinoma Cells

The role of morphine, an opioid analgesic drug, in cancer biology has increasingly garnered attention due to its frequent usage in postoperative period for pain management in cancer patients. In this work, we demonstrated that morphine, at clinically relevant concentrations, stimulated migration and growth, and alleviated chemo drugs' efficacy in esophageal carcinoma cells. Although morphine did not affect survival, it protected esophageal carcinoma cells from chemo drugs-induced apoptosis. Mechanistical studies showed that morphine increased RhoA but not Rac1 activity. In addition, morphine activated AMP-activated protein kinase (AMPK) pathway, induced epithelial-mesenchymal transition (EMT) via upregulating Snail and Slug levels, and increased oxidative stress in esophageal carcinoma cells. Rescue studies further demonstrated that the stimulatory effects of morphine in esophageal carcinoma cells are through activation of AMPK pathway but not RhoA or opioid receptor. In addition, morphine induced EMT in an AMPK-dependent manner whereas increased RhoA activity in an AMPK-independent manner. Our work demonstrates the protective role of morphine on esophageal carcinoma cells via AMPK activation, which may provide a new guide in clinical use of morphine for patients with esophageal carcinoma.

Ceramide kinase mediates intrinsic resistance and inferior response to chemotherapy in triple-negative breast cancer by upregulating Ras/ERK and PI3K/Akt pathways

Background

Clinical management of triple-negative breast cancer (TNBC) patients remain challenging because of the development of chemo-resistance. Identification of biomarkers for risk stratification of chemo-resistance and therapeutic decision-making to overcome such resistance is thus necessary.

Methods

Retrospective analysis was performed to identify potential stratification biomarkers. The levels of ceramide kinase (CERK) was determined in breast cancer patients. The roles of CERK and its downstream signaling pathways were analysed using cellular and biochemical assays.

Results

CERK upregulation was identified as a biomarker for chemotherapeutic response in TNBC. A > 2-fold change in CERK (from tumor)/CERK (from normal counterpart) was significantly associated with chemo-resistance (OR = 2.66, 95% CI 1.18–7.34), P = 0.04. CERK overexpression was sufficient to promote TNBC growth and migration, and confer chemo-resistance in TNBC cell lines, although this resistance could be overcome via CERK inhibition. Mechanistic studies suggest that CERK mediates intrinsic resistance and inferior response to chemotherapy in TNBC by regulating multiple oncogenic pathways such as Ras/ERK, PI3K/Akt/mTOR, and RhoA.

Conclusions

Our work provides an explanation for the heterogeneity of chemo-response across TNBC patients and demonstrates that CERK inhibition offers a therapeutic strategy to overcome treatment resistance.

The role of phospho-tyrosine signaling in platelet biology and hemostasis

Platelets are small enucleated cell fragments specialized in the control of hemostasis, but also playing a role in angiogenesis, inflammation and immunity. This plasticity demands a broad range of physiological processes. Platelet functions are mediated through a variety of receptors, the concerted action of which must be tightly regulated, in order to allow specific and timely responses to different stimuli. Protein phosphorylation is one of the main key regulatory mechanisms by which extracellular signals are conveyed. Despite the importance of platelets in health and disease, the molecular pathways underlying the activation of these cells are still under investigation. Here, we review current literature on signaling platelet biology and in particular emphasize the newly emerging role of phosphatases in these processes.

Recent Advances in β2-Agonists for Treatment of Chronic Respiratory Diseases and Heart Failure

β₂-Adrenoceptor (β₂-AR) agonists are widely used as bronchodilators. The emerge of ultralong acting β₂-agonists is an important breakthrough in pulmonary medicine. In this review, we will provide mechanistic insights into the application of β₂-agonists in asthma, chronic obstructive pulmonary disease (COPD), and heart failure (HF). Recent studies in β-AR signal transduction have revealed opposing functions of the β₁-AR and the β₂-AR on cardiomyocyte survival. Thus, β₂-agonists and β-blockers in combination may represent a novel strategy for HF management. Allosteric modulation and biased agonism at the β₂-AR also provide a theoretical basis for developing drugs with novel mechanisms of action and pharmacological profiles. Overlap of COPD and HF presents a substantial clinical challenge but also a unique opportunity for evaluation of the cardiovascular safety of β₂-agonists. Further basic and clinical research along these lines can help us develop better drugs and innovative strategies for the management of these difficult-to-treat diseases.

The RhoA regulators Myo9b and GEF-H1 are targets of cyclic nucleotide-dependent kinases in platelets

BACKGROUND

Circulating platelets are maintained in an inactive state by the endothelial lining of the vasculature. Endothelium-derived prostacyclin and nitric oxide stimulate cAMP- and cGMP-dependent kinases, PKA and PKG, to inhibit platelets. PKA and PKG effects include the inhibition of the GTPase RhoA, which has been suggested to involve the direct phosphorylation of RhoA on serine 188.

OBJECTIVES

We wanted to confirm RhoA S188 phosphorylation by cyclic nucleotide-dependent kinases and to identify possible alternative mechanisms of RhoA regulation in platelets.

METHODS

Phosphoproteomics data of human platelets were used to identify candidate PKA and PKG substrates. Phosphorylation of individual proteins was studied by Western blotting and Phos-tag gel electrophoresis in human platelets and transfected HEK293T cells. Pull-down assays were performed to analyze protein interaction and function.

RESULTS

Our data indicate that RhoA is not phosphorylated by PKA in platelets. Instead, we provide evidence that cyclic nucleotide effects are mediated through the phosphorylation of the RhoA-specific GTPase-activating protein Myo9b and the guanine nucleotide exchange factor GEF-H1. We identify Myo9b S1354 and guanine nucleotide exchange factor-H1 (GEF-H1) S886 as PKA and PKG phosphorylation sites. Myo9b S1354 phosphorylation enhances its GTPase activating protein function leading to reduced RhoA-GTP levels. GEF-H1 S886 phosphorylation stimulates binding of 14-3-3β and has been shown to inhibit GEF function by facilitating binding of GEF-H1 to microtubules. Microtubule disruption increases RhoA-GTP levels confirming the importance of GEF-H1 in platelets.

CONCLUSION

Phosphorylation of RhoA regulatory proteins Myo9b and GEF-H1, but not RhoA itself, is involved in cyclic nucleotide-mediated control of RhoA in human platelets.

Cx43 and Associated Cell Signaling Pathways Regulate Tunneling Nanotubes in Breast Cancer Cells

Connexin 43 (Cx43) forms gap junctions that mediate the direct intercellular diffusion of ions and small molecules between adjacent cells. Cx43 displays both pro- and anti-tumorigenic properties, but the mechanisms underlying these characteristics are not fully understood. Tunneling nanotubes (TNTs) are long and thin membrane projections that connect cells, facilitating the exchange of not only small molecules, but also larger proteins, organelles, bacteria, and viruses. Typically, TNTs exhibit increased formation under conditions of cellular stress and are more prominent in cancer cells, where they are generally thought to be pro-metastatic and to provide growth and survival advantages. Cx43 has been described in TNTs, where it is thought to regulate small molecule diffusion through gap junctions. Here, we developed a high-fidelity CRISPR/Cas9 system to knockout (KO) Cx43. We found that the loss of Cx43 expression was associated with significantly reduced TNT length and number in breast cancer cell lines. Notably, secreted factors present in conditioned medium stimulated TNTs more potently when derived from Cx43-expressing cells than from KO cells. Moreover, TNT formation was significantly induced by the inhibition of several key cancer signaling pathways that both regulate Cx43 and are regulated by Cx43, including RhoA kinase (ROCK), protein kinase A (PKA), focal adhesion kinase (FAK), and p38. Intriguingly, the drug-induced stimulation of TNTs was more potent in Cx43 KO cells than in wild-type (WT) cells. In conclusion, this work describes a novel non-canonical role for Cx43 in regulating TNTs, identifies key cancer signaling pathways that regulate TNTs in this setting, and provides mechanistic insight into a pro-tumorigenic role of Cx43 in cancer.

Biased signaling in platelet G-protein coupled receptors

Platelets are small megakaryocyte-derived, anucleate, disk-like structures that play an outsized role in human health and disease. Both a decrease in the number of platelets and a variety of platelet function disorders result in petechiae or bleeding that can be life threatening. Conversely, the inappropriate activation of platelets, within diseased blood vessels, remains the leading cause of death and morbidity by affecting heart attacks and stroke. The fine balance of the platelet state in healthy individuals is controlled by a number of receptor-mediated signaling pathways that allow the platelet to rapidly respond and maintain haemostasis. G-protein coupled receptors (GPCRs) are particularly important regulators of platelet function. Here we focus on the major platelet-expressed GPCRs and discuss the roles of downstream signaling pathways (e.g., different G-protein subtypes or β-arrestin) in regulating the different phases of the platelet activation. Further, we consider the potential for selectively targeting signaling pathways that may contribute to platelet responses in disease through development of biased agonists. Such selective targeting of GPCR-mediated signaling pathways by drugs, often referred to as biased signaling, holds promise in delivering therapeutic interventions that do not present significant side effects, especially in finely balanced physiological systems such as platelet activation in haemostasis.

Impaired iloprost-induced platelet inhibition and phosphoproteome changes in patients with confirmed pseudohypoparathyroidism type Ia, linked to genetic mutations in GNAS

Patients diagnosed with pseudohypoparathyroidism type Ia (PHP Ia) suffer from hormonal resistance and abnormal postural features, in a condition classified as Albright hereditary osteodystrophy (AHO) syndrome. This syndrome is linked to a maternally inherited mutation in the GNAS complex locus, encoding for the GTPase subunit Gsα. Here, we investigated how platelet phenotype and omics analysis can assist in the often difficult diagnosis. By coupling to the IP receptor, Gsα induces platelet inhibition via adenylyl cyclase and cAMP-dependent protein kinase A (PKA). In platelets from seven patients with suspected AHO, one of the largest cohorts examined, we studied the PKA-induced phenotypic changes. Five patients with a confirmed GNAS mutation, displayed impairments in Gsα-dependent VASP phosphorylation, aggregation, and microfluidic thrombus formation. Analysis of the platelet phosphoproteome revealed 2,516 phosphorylation sites, of which 453 were regulated by Gsα-PKA. Common changes in the patients were: (1) a joint panel of upregulated and downregulated phosphopeptides; (2) overall PKA dependency of the upregulated phosphopeptides; (3) links to key platelet function pathways. In one patient with GNAS mutation, diagnosed as non-AHO, the changes in platelet phosphoproteome were reversed. This combined approach thus revealed multiple phenotypic and molecular biomarkers to assist in the diagnosis of suspected PHP Ia.

Glucagon-like peptide 1 reverses myocardial hypertrophy through cAMP/PKA/RhoA/ROCK2 signaling

Myocardial hypertrophy is a major pathological and physiological process during heart failure. Glucagon-like peptide 1 (GLP-1) is a glucagon incretin hormone released from the gut endocrine L-cells that has protective effects on various cardiovascular diseases, including hypertension, atherosclerosis, and myocardial hypertrophy. However, the protective mechanisms of GLP-1 in myocardial hypertrophy remain unclear. Here, we showed that the GLP-1 agonist liraglutide and dipeptidyl peptidase 4 inhibitor alogliptin decreased heart weight and cardiac muscle cell volume in spontaneously hypertensive rats (SHR). In H9C2 cell hypertensive models induced by angiotensin II, GLP-1 treatment reduced myocardial cell volume, inhibited the expressions of atrial natriuretic peptide, brain/B-type natriuretic peptide, β-myosin heavy chain, RhoA, and ROCK2, and decreased MLC and MYPT1 phosphorylation. When H9C2 cells were treated with H89, a PKA inhibitor, the inhibitory effect of GLP-1 disappeared, while the inhibitory role was enhanced under the treatment of Y-27632, a ROCK2 inhibitor. These results suggested that GLP-1 might reverse myocardial hypertrophy through the PKA/RhoA/ROCK2 signaling pathway.

Platelets: emerging facilitators of cellular crosstalk in rheumatoid arthritis

Rheumatoid arthritis (RA) is an autoimmune disease in which a variety of circulating pro-inflammatory cells and dysregulated molecules are involved in disease aetiology and progression. Platelets are an important cellular element in the circulation that can bind several dysregulated molecules (such as collagen, thrombin and fibrinogen) that are present both in the synovium and the circulation of patients with RA. Platelets not only respond to dysregulated molecules in their environment but also transport and express their own inflammatory mediators, and serve as regulators at the boundary between haemostasis and immunity. Activated platelets also produce microparticles, which further convey signalling molecules and receptors to the synovium and circulation, thereby positioning these platelet-derived particles as strategic regulators of inflammation. These diverse functions come together to make platelets facilitators of cellular crosstalk in RA. Thus, the receptor functions, ligand binding potential and dysregulated signalling pathways in platelets are becoming increasingly important for treatment in RA. This Review aims to highlight the role of platelets in RA and the need to closely examine platelets as health indicators when designing effective pharmaceutical targets in this disease.

Coenzyme Q10 attenuates platelet integrin αIIbβ3 signaling and platelet hyper-reactivity in ApoE-deficient mice

CoQ10 supplementation in ApoE^−/− mice attenuates high-fat diet-induced platelet hyper-reactivity via down-regulating platelet αIIbβ3 signaling, and thus protecting against atherothrombosis.

Dipeptidyl peptidase-4 inhibitor sitagliptin induces vasorelaxation via the activation of Kv channels and PKA

The present study investigated the vasorelaxant effects of sitagliptin, which is a dipeptidyl peptidase-4 (DPP-4) inhibitor in aortic rings pre-contracted with phenylephrine (Phe). Sitagliptin induced vasorelaxation in a concentration-dependent manner but the inhibition of voltage-dependent K⁺ (Kv) channels by pretreatment with 4-aminopyridine (4-AP) effectively reduced this effect. By contrast, the inhibition of inward rectifier K⁺ (Kir) channels by pretreatment with barium (Ba²⁺), large-conductance calcium (Ca²⁺)-activated K⁺ (BK_Ca) channels with paxilline, and adenosine triphosphate (ATP)-sensitive K⁺ (K_ATP) channels with glibenclamide did not change this effect. Although the application of SQ 22536, which is an adenylyl cyclase inhibitor, also did not change this effect, treatment with KT 5720, a protein kinase A (PKA) inhibitor, effectively reduced the vasorelaxant effects of sitagliptin. ODQ, which is a guanylyl cyclase inhibitor, and KT 5823, a protein kinase G (PKG) inhibitor, did not impact the effect. Furthermore, neither the inhibition of Ca²⁺ channels by pretreatment with nifedipine nor the inhibition of sarcoplasmic/endoplasmic reticulum Ca²⁺-ATPase (SERCA) pumps by pretreatment with thapsigargin changed the effect. Similarly, the effects of sitagliptin were not altered by eliminating the endothelium, by pretreatment with a nitric oxide (NO) synthase inhibitor (L-NAME), or by inhibition of small- and intermediate-conductance Ca²⁺-activated K⁺ channels (SK_Ca and IK_Ca) using apamin and TRAM-34. Taken together, these results suggest that sitagliptin induces vasorelaxation by inhibiting both membrane potential (Em)-dependent and -independent vasoconstriction and activating PKA and Kv channels independently of PKG signaling pathways, other K⁺ channels, SERCA pumps, and the endothelium.

Coenzyme Q10 Upregulates Platelet cAMP/PKA Pathway and Attenuates Integrin αIIbβ3 Signaling and Thrombus Growth

SCOPE

Platelet integrin αIIbβ3 is the key mediator of atherothrombosis. Supplementation of coenzyme Q10 (CoQ10), a fat-soluble molecule that exists in various foods, exerts protective cardiovascular effects. This study aims to investigate whether and how CoQ10 acts on αIIbβ3 signaling and thrombosis, the major cause of cardiovascular diseases.

METHODS AND RESULTS

Using a series of platelet functional assays in vitro, it is demonstrated that CoQ10 reduces human platelet aggregation, granule secretion, platelet spreading, and clot retraction. It is further demonstrated that CoQ10 inhibits platelet integrin αIIbβ3 outside-in signaling. These inhibitory effects are mainly mediated by upregulating cAMP/PKA pathway, where CoQ10 stimulates the A_2A adenosine receptor and decreases phosphodiesterase 3A phosphorylation. Moreover, CoQ10 attenuates murine thrombus growth and vessel occlusion in a ferric chloride (FeCl₃ )-induced thrombosis model in vivo. Importantly, the randomized, double-blind, placebo-controlled clinical trial in dyslipidemic patients demonstrates that 24 weeks of CoQ10 supplementation increases platelet CoQ10 concentrations, enhances the cAMP/PKA pathway, and attenuates αIIbβ3 outside-in signaling, leading to decreased platelet aggregation and granule release.

CONCLUSION

Through upregulating the platelet cAMP/PKA pathway, and attenuating αIIbβ3 signaling and thrombus growth, CoQ10 supplementation may play an important protective role in patients with risks of cardiovascular diseases.

Isoprenylcysteine carboxylmethyltransferase is associated with nasopharyngeal carcinoma chemoresistance and Ras activation

Development of chemo-resistance in nasopharyngeal carcinoma (NPC) poses the therapeutic challenge and its mechanisms are still poorly understood. In this work, we demonstrate that targeting isoprenylcysteine carboxylmethyltransferase (Icmt) is a therapeutic strategy to overcome NPC chemo-resistance. We found that Icmt mRNA and protein levels were increased in NPC cells after prolonged exposure to chemotherapy. Using pharmacological inhibitor cysmethynil or genetic siRNA approaches, we showed that Icmt inhibition was more effective against chemoresistant compared to chemosensitive NPC cells, suggesting that chemoresistant NPC cells is more dependent on Icmt function. The combination of Icmt inhibition with 5-FU or cisplatin resulted in greater efficacy than single chemotherapeutic agent alone in NPC. Notably, we demonstrated that the in vitro observations were translatable to in vivo NPC cancer xenograft mouse model. Mechanism analysis indicated that Icmt inhibition decreased Ras and RhoA activities, leading to the suppression of Ras and RhoA-mediated downstream signaling in NPC cells. The reverse of the inhibitory effects of cysmethynil by constitutively active Ras suggests that Ras is the critical effector of Icmt in NPC cells. Our work is the first to show that Icmt plays an important role in the development of NPC chemoresistance. Our findings also suggest that targeting Icmt represents a promising strategy to inhibit Ras function.

Simvastatin enhances chemotherapy in cervical cancer via inhibition of multiple prenylation-dependent GTPases-regulated pathways

Aberrant activation of GTPases is common in cervical cancer, and their proper biological functions largely depend on a post-translational modification termed prenylation. Simvastatin is a cholesterol-lowering drug via inhibiting HMG-CoA reductase, thereby inhibiting protein prenylation. In this study, we show that simvastatin selectively inhibits proliferation and induces apoptosis in cervical cancer cells while sparing normal cervical epithelial cells. This is achieved by depleting geranylgeranyl pyrophosphate, inhibiting prenylation, decreasing GTPases activities and suppressing the activation of downstream Ras and RhoA signaling. The combination of simvastatin and paclitaxel remarkably augments in vitro as well as in vivo efficacy of either drug alone in cellular system and xenograft mouse model. Importantly, we show that cervical cancer cells have higher level of HMG-CoA reductase and elevated activities of GTPases, suggesting that cervical cancer cells may be more dependent on prenylation than normal cervical epithelial cells. This might explain the selective inhibitory effects of simvastatin in cervical cancer. Since simvastatin is already available for clinic use, these results suggest that simvastatin is a promising drug candidate in combination with chemotherapy for the treatment of cervical cancer. Our findings also emphasize the therapeutic value of prenylation inhibition and provide preclinical evidence to evaluate prenylation-targeted drugs in cervical cancer.

Clinically relevant concentration of sevoflurane suppresses cervical cancer growth and migration through targeting multiple oncogenic pathways

The biological effects of sevoflurane, a volatile anesthetics, on cancer cells seem to be contradictory and are not fully understood. While some studies demonstrate that sevoflurane promotes tumor growth, other studies report that sevoflurane displays anti-cancer activities. In this work, we systematically investigated the effects of sevoflurane at clinically relevant dose on the multiple biological aspects of cervical cancer cells and analyzed the underlying mechanism. Using a panel of cell lines, we found that sevoflurane significantly inhibited proliferation and migration of cervical cancer cells regardless of cellular origin and genetic background. In contrast, sevoflurane did not affect cervical cancer survival. Additionally, sevoflurane significantly enhanced chemosensitivity of cervical cancer cells. Mechanistically, we show that sevoflurane inhibits Ras and RhoA GTPase activities, leading to the blockade of their downstream signaling pathways, such as Ras/Erk/Akt and Rho/MYPT1/MLC. The rescue studies using Rho activator calpeptin or constitutively active Ras further confirm that Ras and RhoA are the targets of sevoflurane in cervical cancer. Interestingly, we found that the anti-proliferative effect of sevoflurane was via targeting Ras whereas the anti-migratory effect of sevoflurane was mediated via targeting RhoA. Our data clearly demonstrates the anti-cancer effects of sevoflurane. These findings provide preclinical evidence into the potential mechanisms by which sevoflurane may negatively affect cervical cancer growth and metastasis.

Cholera toxin B induces interleukin-1β production from resident peritoneal macrophages through the pyrin inflammasome as well as the NLRP3 inflammasome

Cholera toxin B (CTB) is a subunit of cholera toxin, a bacterial enterotoxin secreted by Vibrio cholerae and also functions as an immune adjuvant. However, it remains unclear how CTB activates immune cells. We here evaluated whether or how CTB induces production of a pro-inflammatory cytokine, interleukin-1β (IL-1β). CTB induced IL-1β production not only from bone marrow-derived macrophages (BMMs) but also from resident peritoneal macrophages in synergy with O111:B4-derived lipopolysaccharide (LPS O111:B4) that can bind to CTB. Meanwhile, when prestimulated with O55:B5-derived LPS (LPS O55:B5) that fails to bind to CTB, resident peritoneal macrophages, but not BMMs, produced IL-1β in response to CTB. The CTB-induced IL-1β production in synergy with LPS in both peritoneal macrophages and BMMs was dependent on ganglioside GM1, which is required for internalization of CTB. Notably, not only the NLRP3 inflammasome but also the pyrin inflammasome were involved in CTB-induced IL-1β production from resident peritoneal macrophages, while only the NLRP3 inflammasome was involved in that from BMMs. In response to CTB, a Rho family small GTPase, RhoA, which activates pyrin inflammasome upon various kinds of biochemical modification, increased its phosphorylation at serine-188 in a GM1-dependent manner. This phosphorylation as well as CTB-induced IL-1β productions were dependent on protein kinase A (PKA), indicating critical involvement of PKA-dependent RhoA phosphorylation in CTB-induced IL-1β production. Taken together, these results suggest that CTB, incorporated through GM1, can activate resident peritoneal macrophages to produce IL-1β in synergy with LPS through novel mechanisms in which pyrin as well as NLRP3 inflammasomes are involved.

Phospholipase Cγ2 signalling contributes to the haemostatic effect of Notoginsenoside Ft1

OBJECTIVES

The drawback of bleeding caused by chronic antiplatelet therapy is persecuting patients with thrombotic diseases severely. Based on the dual-directional regulatory effect of Panax notoginseng on platelet, the present study focused on the effect of Notoginsenoside Ft1, a saponin with effect in promoting platelet aggregation.

KEY FINDINGS

According to the present study, Notoginsenoside Ft1 cannot stimulate platelet aggregation independently. However, the effect in enhancing aggregation induced by thrombin, collagen and ADP is peaked at 5-10 μm. In addition, thrombin-induced activation of PLCγ2-IP₃ /DAG-[Ca²⁺ ]/PKC-TXA₂ signalling was potentiated by Notoginsenoside Ft1, as well. Furthermore, the mice tail bleeding time was shortened by administration of Notoginsenoside Ft1 significantly. And the bleeding time prolonged by aspirin was also restored by Ft1.

CONCLUSIONS

The haemostatic effect of Notoginsenoside Ft1 was exerted through potentiation of PLCγ2-IP₃ /DAG-[Ca²⁺ ]/PKC-TXA₂ signalling pathway stimulated by other stimulators. Notoginsenoside Ft1 has the potential to be developed into supplements in antiplatelet therapy to prevent the drawback of bleeding.

Rho-Associated Coiled-Coil Kinase (ROCK) in Molecular Regulation of Angiogenesis

Identified as a major downstream effector of the small GTPase RhoA, Rho-associated coiled-coil kinase (ROCK) is a versatile regulator of multiple cellular processes. Angiogenesis, the process of generating new capillaries from the pre-existing ones, is required for the development of various diseases such as cancer, diabetes and rheumatoid arthritis. Recently, ROCK has attracted attention for its crucial role in angiogenesis, making it a promising target for new therapeutic approaches. In this review, we summarize recent advances in understanding the role of ROCK signaling in regulating the permeability, migration, proliferation and tubulogenesis of endothelial cells (ECs), as well as its functions in non-ECs which constitute the pro-angiogenic microenvironment. The therapeutic potential of ROCK inhibitors in angiogenesis-related diseases is also discussed.

Multi-omics analysis points to altered platelet functions in severe food-associated respiratory allergy

BACKGROUND

Prevalence and severity of allergic diseases have increased worldwide. To date, respiratory allergy phenotypes are not fully characterized and, along with inflammation progression, treatment is increasingly complex and expensive. Profilin sensitization constitutes a good model to study the progression of allergic inflammation. Our aim was to identify the underlying mechanisms and the associated biomarkers of this progression, focusing on severe phenotypes, using transcriptomics and metabolomics.

METHODS

Twenty-five subjects were included in the study. Plasma samples were analyzed using gas and liquid chromatography coupled to mass spectrometry (GC-MS and LC-MS, respectively). Individuals were classified in four groups-"nonallergic," "mild," "moderate," and "severe"-based on their clinical history, their response to an oral challenge test with profilin, and after a refinement using a mathematical metabolomic model. PBMCs were used for microarray analysis.

RESULTS

We found a set of transcripts and metabolites that were specific for the "severe" phenotype. By metabolomics, a decrease in carbohydrates and pyruvate and an increase in lactate were detected, suggesting aerobic glycolysis. Other metabolites were incremented in "severe" group: lysophospholipids, sphingosine-1-phosphate, sphinganine-1-phosphate, and lauric, myristic, palmitic, and oleic fatty acids. On the other hand, carnitines were decreased along severity. Significant transcripts in the "severe" group were found to be downregulated and were associated with platelet functions, protein synthesis, histone modification, and fatty acid metabolism.

CONCLUSION

We have found evidence that points to the association of severe allergic inflammation with platelet functions alteration, together with reduced protein synthesis, and switch of immune cells to aerobic glycolysis.

Cyclic nucleotide-dependent inhibitory signaling interweaves with activating pathways to determine platelet responses

Platelets are regulated by extracellular cues that impact on intracellular signaling. The endothelium releases prostacyclin and nitric oxide which stimulate the synthesis of cyclic nucleotides cAMP and cGMP leading to platelet inhibition. Other inhibitory mechanisms involve immunoreceptor tyrosine-based inhibition motif-containing receptors, intracellular receptors and receptor desensitization. Inhibitory cyclic nucleotide pathways are traditionally thought to represent a passive background system keeping platelets in a quiescent state. In contrast, cyclic nucleotides are increasingly seen to be dynamically involved in most aspects of platelet regulation. This review focuses on crosstalk between activating and cyclic nucleotide-mediated inhibitory pathways highlighting emerging new hub structures and signaling mechanisms. In particular, interactions of plasma membrane receptors like P2Y12 and GPIb/IX/V with the cyclic nucleotide system are described. Furthermore, differential regulation of the RGS18 complex, second messengers, protein kinases, and phosphatases are presented, and control over small G-proteins by guanine-nucleotide exchange factors and GTPase-activating proteins are outlined. Possible clinical implications of signaling crosstalk are discussed.

Image-guided chemotherapy with specifically tuned blood brain barrier permeability in glioma margins

Blood-brain barrier (BBB) disruption is frequently observed in the glioma region. However, the tumor uptake of drugs is still too low to meet the threshold of therapeutic purpose.

Method: A tumor vasculature-targeted nanoagonist was developed. Glioma targeting specificity of the nanoagonist was evaluated by in vivo optical imaging. BBB permeability at the glioma margin was quantitatively measured by dynamic contrast enhanced magnetic resonance imaging (DCE-MRI). Single-photon emission computed tomography imaging/computed tomography (SPECT/CT) quantitatively determined the glioma uptake of the radiolabeled model drug. T2-weighted MRI monitored the tumor volume.

Results: Immunostaining studies demonstrated that the BBB remained partially intact in the invasive margin of patients' gliomas regardless of their malignancies. DCE-MRI showed that vascular permeability in the glioma margin reached its maximum at 45 min post nanoagonist administration. In vivo optical imaging indicated the high glioma targeting specificity of the nanoagonist. SPECT/CT showed the significantly enhanced glioma uptake of the model drug after pre-treatment with the nanoagonist. Image-guided paclitaxel injection after nanoagonist-mediated BBB modulation more efficiently attenuated tumor growth and extended survival than in animal models treated with paclitaxel or temozolomide alone.

Conclusion: Thus, image-guided drug delivery following BBB permeability modulation holds promise to enhance the efficacy of chemotherapeutics to glioma.

Effects of the NO/soluble guanylate cyclase/cGMP system on the functions of human platelets

Platelets are circulating sentinels of vascular integrity and are activated, inhibited, or modulated by multiple hormones, vasoactive substances or drugs. Endothelium- or drug-derived NO strongly inhibits platelet activation via activation of the soluble guanylate cyclase (sGC) and cGMP elevation, often in synergy with cAMP-elevation by prostacyclin. However, the molecular mechanisms and diversity of cGMP effects in platelets are poorly understood and sometimes controversial. Recently, we established the quantitative human platelet proteome, the iloprost/prostacyclin/cAMP/protein kinase A (PKA)-regulated phosphoproteome, and the interactions of the ADP- and iloprost/prostacyclin-affected phosphoproteome. We also showed that the sGC stimulator riociguat is in vitro a highly specific inhibitor, via cGMP, of various functions of human platelets. Here, we review the regulatory role of the cGMP/protein kinase G (PKG) system in human platelet function, and our current approaches to establish and analyze the phosphoproteome after selective stimulation of the sGC/cGMP pathway by NO donors and riociguat. Present data indicate an extensive and diverse NO/riociguat/cGMP phosphoproteome, which has to be compared with the cAMP phosphoproteome. In particular, sGC/cGMP-regulated phosphorylation of many membrane proteins, G-proteins and their regulators, signaling molecules, protein kinases, and proteins involved in Ca²⁺ regulation, suggests that the sGC/cGMP system targets multiple signaling networks rather than a limited number of PKG substrate proteins.

Novel phosphorylated TAK1 species with functional impact on NF-κB and β-catenin signaling in human Cutaneous T-cell lymphoma

Cutaneous T-cell lymphomas (CTCLs) represent different subtypes of lymphoproliferative disorders with no curative therapies for the advanced forms of the disease (namely mycosis fungoides and the leukemic variant, Sézary syndrome). Molecular events leading to CTCL progression are heterogeneous, however recent DNA and RNA sequencing studies highlighted the importance of NF-κB and β-catenin pathways. We here show that the kinase TAK1, known as essential in B-cell lymphoma, is constitutively activated in CTCL cells, but tempered by the MYPT1/PP1 phosphatase complex. Blocking PP1 activity, both pharmacologically and genetically, resulted in TAK1 hyperphosphorylation at residues T344, S389, T444, and T511, which have functional impact on canonical NF-κB signaling. Inhibition of TAK1 precluded NF-κB and β-catenin signaling and induced apoptosis of CTCL cell lines and primary Sézary syndrome cells both in vitro and in vivo. Detection of phosphorylated TAK1 at T444 and T344 is associated with the presence of lymphoma in a set of 60 primary human samples correlating with NF-κB and β-catenin activation. These results identified TAK1 as a potential biomarker and therapeutic target for CTCL therapy.