ARQ 092, an orally-available, selective AKT inhibitor, attenuates neutrophil-platelet interactions in sickle cell disease

Human vascular organoids with a mosaic AKT1 mutation recapitulate Proteus syndrome

Vascular malformation, a key clinical phenotype of Proteus syndrome, lacks effective models for pathophysiological study and drug development due to limited patient sample access. To bridge this gap, we built a human vascular organoid model replicating Proteus syndrome's vasculature. Using CRISPR/Cas9 genome editing and gene overexpression, we created induced pluripotent stem cells (iPSCs) embodying the Proteus syndrome-specific AKTE17K point mutation for organoid generation. Our findings revealed that AKT overactivation in these organoids resulted in smaller sizes yet increased vascular connectivity, although with less stable connections. This could be due to the significant vasculogenesis induced by AKT overactivation. This phenomenon likely stems from boosted vasculogenesis triggered by AKT overactivation, leading to increased vascular sprouting. Additionally, a notable increase in dysfunctional PDGFRβ+ mural cells, impaired in matrix secretion, was observed in these AKT-overactivated organoids. The application of AKT inhibitors (ARQ092, AZD5363, or GDC0068) reversed the vascular malformations; the inhibitors' effectiveness was directly linked to reduced connectivity in the organoids. In summary, our study introduces an innovative in vitro model combining organoid technology and gene editing to explore vascular pathophysiology in Proteus syndrome. This model not only simulates Proteus syndrome vasculature but also holds potential for mimicking vasculatures of other genetically driven diseases. It represents an advance in drug development for rare diseases, historically plagued by slow progress.

Mechanism of Tao Hong Decoction in the treatment of atherosclerosis based on network pharmacology and experimental validation

Background

Atherosclerosis (AS) has long been recognized as a cardiovascular disease and stroke risk factor. A well-known traditional Chinese medicine prescription, Tao Hong decoction (THD), has been proven effective in treating AS, but its mechanism of action is still unclear.

Objective

To assess the effects, explore THD's primary mechanism for treating AS, and provide a basis for rational interpretation of its prescription compatibility.

Methods

Based on network pharmacology, we evaluated the mechanism of THD on AS by data analysis, target prediction, the construction of PPI networks, and GO and KEGG analysis. AutoDockTools software to conduct Molecular docking. Then UPLC-Q-TOF-MS was used to identify significant constituents of THD. Furthermore, an AS mice model was constructed and intervened with THD. Immunofluorescence, RT-qPCR, and Western blot were used to verify the critical targets in animal experiments.

Results

The network pharmacology results indicate that eight core targets and seven core active ingredients play an essential role in this process. The GO and KEGG analysis results suggested that the mechanism is mainly involved in Fluid shear stress and atherosclerosis and Lipid and atherosclerosis. The molecular docking results indicate a generally strong affinity. The animal experiment showed that THD reduced plaque area, increased plaque stability, and decreased the levels of inflammatory cytokines (NF-κB, IL-1α, TNF-α, IL-6, IL-18, IL-1β) in high-fat diet -induced ApoE-/-mice. Decreased levels of PTGS2, HIF-1α, VEGFA, VEGFC, FLT-4, and the phosphorylation of PI3K, AKT, and p38 were detected in the THD-treated group.

Conclusion

THD plays a vital role in treating AS with multiple targets and pathways. Angiogenesis regulation, oxidative stress regulation, and immunity regulation consist of the crucial regulation cores in the mechanism. This study identified essential genes and pathways associated with the prognosis and pathogenesis of AS from new insights, demonstrating a feasible method for researching THD's chemical basis and pharmacology.

Neutrophil DREAM promotes neutrophil recruitment in vascular inflammation

The interaction between neutrophils and endothelial cells is critical for the pathogenesis of vascular inflammation. However, the regulation of neutrophil adhesive function remains not fully understood. Intravital microscopy demonstrates that neutrophil DREAM promotes neutrophil recruitment to sites of inflammation induced by TNF-α but not MIP-2 or fMLP. We observe that neutrophil DREAM represses expression of A20, a negative regulator of NF-κB activity, and enhances expression of pro-inflammatory molecules and phosphorylation of IκB kinase (IKK) after TNF-α stimulation. Studies using genetic and pharmacologic approaches reveal that DREAM deficiency and IKKβ inhibition significantly diminish the ligand-binding activity of β2 integrins in TNF-α-stimulated neutrophils or neutrophil-like HL-60 cells. Neutrophil DREAM promotes degranulation through IKKβ-mediated SNAP-23 phosphorylation. Using sickle cell disease mice lacking DREAM, we show that hematopoietic DREAM promotes vaso-occlusive events in microvessels following TNF-α challenge. Our study provides evidence that targeting DREAM might be a novel therapeutic strategy to reduce excessive neutrophil recruitment in inflammatory diseases.

Rho signaling inhibition mitigates lung injury via targeting neutrophil recruitment and selectin-AKT signaling

Neutrophils, the early responders of the immune system, eliminate intruders, but their over-activation can also instigate tissue damage leading to various autoimmune and inflammatory disease conditions. As approaches causing neutropenia are associated with immunodeficiency, targeting aberrant neutrophil infiltration offers an attractive strategy in neutrophil-centered diseases including acute lung injury. Rho GTPase family proteins Rho, Rac and Cdc42 play important role as regulators of chemotaxis in diverse systems. Rho inhibitors protected against lung injuries, while genetic Rho-deficiency exhibited neutrophil hyperactivity and exacerbated lung injury. These differential outcomes might be due to distinct effects on different cell types or activation/ inhibition of specific signaling pathways responsible for neutrophil polarity, migration and functions. In this study, we explored neutrophil centric effects of Rho signaling mitigation. Consistent with previous reports, Rho signaling inhibitor Y-27632 provided protection against acute lung injury, but without regulating LPS mediated systemic increase of neutrophils in the circulation. Interestingly, the adoptive transfer approach identified a specific defect in neutrophil migration capacity after Rho signaling mitigation. These defects were associated with loss of polarity and altered actin dynamics identified using time-lapse in vitro studies. Further analysis revealed a rescue of stimulation-dependent L-selectin shedding on neutrophils with Rho signaling inhibitor. Surprisingly, functional blocking of L-selectin (CD62L) led to defective recruitment of neutrophils into inflamed lungs. Further, single-cell level analyses identified MAPK signaling as downstream mechanism of Rho signaling and L-selectin mediated effects. p-AKT levels were diminished in detergent resistance membrane-associated signalosome upon Rho signaling inhibition and blockade of selectin. Moreover, inhibition of AKT signaling as well as selectin blocking led to defects in neutrophil polarity. Together, this study identified Rho-dependent distinct L-selectin and AKT signaling mediated regulation of neutrophil recruitment to inflamed lung tissue.

Sickle cell vaso-occlusion: The dialectic between red cells and white cells

The pathophysiology of sickle cell anemia, a hereditary hemoglobinopathy, has fascinated clinicians and scientists alike since its description over 100 years ago. A single gene mutation in the HBB gene results in the production of abnormal hemoglobin (Hb) S, whose polymerization when deoxygenated alters the physiochemical properties of red blood cells, in turn triggering pan-cellular activation and pathological mechanisms that include hemolysis, vaso-occlusion, and ischemia-reperfusion to result in the varied and severe complications of the disease. Now widely regarded as an inflammatory disease, in recent years attention has included the role of leukocytes in vaso-occlusive processes in view of the part that these cells play in innate immune processes, their inherent ability to adhere to the endothelium when activated, and their sheer physical and potentially obstructive size. Here, we consider the role of sickle red blood cell populations in elucidating the importance of adhesion vis-a-vis polymerization in vaso-occlusion, review the direct adhesion of sickle red cells to the endothelium in vaso-occlusive processes, and discuss how red cell- and leukocyte-centered mechanisms are not mutually exclusive. Given the initial clinical success of crizanlizumab, a specific anti-P selectin therapy, we suggest that it is appropriate to take a holistic approach to understanding and exploring the complexity of vaso-occlusive mechanisms and the adhesive roles of the varied cell types, including endothelial cells, platelets, leukocytes, and red blood cells.

Complement in Sickle Cell Disease: Are We Ready for Prime Time?

Sickle cell disease (SCD) is a widely spread inherited hemoglobinopathy that includes a group of congenital hemolytic anemias, all characterized by the predominance of sickle hemoglobin (HbS). Its features are anemia, predisposal to bacterial infections and complications such as vaso-occlusive crisis (VOC) or delayed hemolytic transfusion reaction (DHTR), which lead to increased rate of morbidity and mortality even in the era of hydroxyurea. The interaction between sickle cells, neutrophils, platelets or endothelial cells in small vessels results in hemolysis and has been considered the disease’s main pathophysiological mechanism. Complement activation has been reported in small cohorts of SCD patients, but the governing mechanism has not been fully elucidated. This will be important to predict the patient group that would benefit from complement inhibition. Until now, eculizumab-mediated complement inhibition has shown beneficial effects in DHTR, with limited reports in patients with VOC. In the meantime, several innovative agents are under clinical development Our state-of-the-art review summarizes current data on 1) complement activation in SCD both in steady state and crisis, 2) underlying mechanisms of complement over-activation for the clinician in the context of SCD, 3) actions of hydroxyurea and new therapeutic approaches including indirect involvement in complement activation, and 4) novel paradigms in complement inhibition.

Complement in sickle cell disease and targeted therapy: I know one thing, that I know nothing

Sickle cell disease (SCD) is a common inherited clinical syndrome, characterized by the presence of hemoglobin S. Anemia, susceptibility to infections and episodes of vaso-occlusive crisis (VOC) are among its features. Since SCD complications (VOC or delayed hemolytic transfusion reaction/DHTR) lead to significant morbidity and mortality, a number of studies have addressed their pathophysiology Although SCD pathophysiology has been mainly attributed to the interaction between sickle cells and neutrophils, platelets or endothelial cells in small vessels leading to hemolysis, the role of complement activation has been increasingly investigated. Importantly, complement inhibition with eculizumab has shown beneficial effects in DHTR. Given the unmet clinical need of novel therapeutics in SCD, our review summarizes current understanding of (a) complement system for the clinician, (b) complement activation in SCD both in asymptomatic state and severe clinical manifestations, (c) probable underlying mechanisms of complement activation in SCD, and (d) new therapeutic perspective of complement inhibition.

Combating TKI resistance in CML by inhibiting the PI3K/Akt/mTOR pathway in combination with TKIs: a review

Chronic myeloid leukemia (CML), a myeloproliferative hematopoietic cancer, is caused by a genetic translocation between chromosomes 9 and 22. This translocation produces a small Philadelphia chromosome, which contains the Bcr-Abl oncogene. The Bcr-Abl oncogene encodes the BCR-ABL protein, upregulates various signaling pathways (JAK-STAT, MAPK/ERK, and PI3K/Akt/mTOR), and out of which the specifically highly active pathway is the PI3K/Akt/mTOR pathway. Among early treatments for CML, tyrosine kinase inhibitors (TKIs) were found to be the most effective, but drug resistance against kinase inhibitors led to the discovery of novel alternative therapies. At this point, the PI3K/Akt/mTOR pathway components became new targets due to stimulation of this pathway in TKIs-resistant CML patients. The current review article deals with reviewing the scientific literature on the PI3K/Akt/mTOR pathway inhibitors listed in the National Cancer Institute (NCI) drug dictionary and proved effective against multiple cancers. And out of those enlisted inhibitors, the US FDA has also approved some PI3K inhibitors (Idelalisib, Copanlisib, and Duvelisib) and mTOR inhibitors (Everolimus, Sirolimus, and Temsirolimus) for cancer therapy. So far, several inhibitors have been tested, and further investigations are still ongoing. Even in Imatinib, Nilotinib, and Ponatinib-resistant CML cells, a dual PI3K/mTOR inhibitor, BEZ235, showed antiproliferative activity. Therefore, by considering the literature data of these reviews and further examining some of the reported inhibitors, which proved effective against the PI3K/Akt/mTOR signaling pathway in multiple cancers, may improve the therapeutic approaches towards TKI-resistant CML cells where the respective signaling pathway gets upregulated.

Repurposing pyridoxamine for therapeutic intervention of intravascular cell-cell interactions in mouse models of sickle cell disease

Adherent neutrophils on vascular endothelium positively contribute to cell-cell aggregation and vaso-occlusion in sickle cell disease. In the present study, we demonstrated that pyridoxamine, a derivative of vitamin B6, might be a therapeutic agent to alleviate intravascular cell-cell aggregation in sickle cell disease. Using real-time intravital microscopy, we found that one oral administration of pyridoxamine dose-dependently increased the rolling influx of neutrophils and reduced neutrophil adhesion to endothelial cells in cremaster microvessels of sickle cell disease mice challenged with hypoxia-reoxygenation. Short-term treatment also mitigated neutrophil-endothelial cell and neutrophil-platelet interactions in the microvessels and improved the survival of sickle cell disease mice challenged with tumor necrosis factor-α. The inhibitory effects of pyridoxamine on intravascular cell-cell interactions were potentiated by co-treatment with hydroxyurea. We observed that long-term (5.5 months) oral treatment with pyridoxamine significantly diminished the adhesive function of neutrophils and platelets and down-regulated the expression of E-selectin and intercellular adhesion molecule-1 on the vascular endothelium in tumor necrosis factor-α-challenged sickle cell disease mice. Ex vivo studies revealed that the surface amount of αMβ2 integrin was significantly decreased in stimulated neutrophils isolated from sickle cell disease mice treated with pyridoxamine-containing water. Studies using platelets and neutrophils from sickle cell disease mice and patients suggested that treatment with pyridoxamine reduced the activation state of platelets and neutrophils. These results suggest that pyridoxamine may be a novel therapeutic and a supplement to hydroxyurea to prevent and treat vaco-occlusion events in sickle cell disease.

Thromboinflammatory mechanisms in sickle cell disease - challenging the hemostatic balance

Sickle cell disease (SCD) is an inherited hemoglobinopathy that is caused by the presence of abnormal hemoglobin S (HbS) in red blood cells, leading to alterations in red cell properties and shape, as the result of HbS dexoygenation and subsequent polymerization. SCD pathophysiology is characterized by chronic inflammatory processes, triggered by hemolytic and vaso-occlusive events, which lead to the varied complications, organ damage and elevated mortality seen in individuals with the disease. In association with activation of the endothelium and leukocytes, hemostatic alterations and thrombotic events are well-documented in SCD. Here we discuss the role for inflammatory pathways in modulating coagulation and inducing platelet activation in SCD, due to tissue factor activation, adhesion molecule expression, inflammatory mediator production and the induction of innate immune responses, amongst other mechanisms. Thromboinflammatory pathways may play a significant role in some of the major complications of SCD, such as stroke, venous thromboembolism and possibly acute chest syndrome, besides exacerbating the chronic inflammation and cellular interactions that trigger vaso-occlusion, ischemia-reperfusion processes, and eventually organ damage.

The clinical consequences of neutrophil priming

PURPOSE OF REVIEW

Neutrophils priming has been long studied in vitro. Recent studies describe it in vivo. In pathophysiological conditions, complex, heterogeneous characteristics of priming are described in the last few years.

RECENT FINDINGS

Priming can occur systemically when insults such as sepsis or trauma result in an array of circulating mediators and circulating primed neutrophils seem to exert detrimental effects either directly, or indirectly by interacting with other cells, thereby contributing to the development of organ dysfunction. Local priming of neutrophils augments their ability to clear infection, but may also lead to local bystander tissue injury, for example, in the inflamed joint. The complexity, heterogeneity and dynamic nature of inflammatory responses and the accessibility of cells from local sites make neutrophil priming challenging to study in human disease; however, recent advances have made significant progress to this field.

SUMMARY

Herein, we summarize the literature regarding neutrophil priming in selected conditions. In some diseases and in the setting of specific genetic influences, the priming repertoire seems to be restricted, with only some neutrophil functions upregulated. A greater understanding of the nature of neutrophil priming and its role in human disease is required before this process becomes tractable to therapeutic intervention.

Innate immune cells, major protagonists of sickle cell disease pathophysiology

Sickle cell disease (SCD), considered the most common monogenic disease worldwide, is a severe hemoglobin disorder. Although the genetic and molecular bases have long been characterized, the pathophysiology remains incompletely elucidated and therapeutic options are limited. It has been increasingly suggested that innate immune cells, including monocytes, neutrophils, invariant natural killer T cells, platelets and mast cells, have a role in promoting inflammation, adhesion and pain in SCD. Here we provide a thorough review of the involvement of these novel, major protagonists in SCD pathophysiology, highlighting recent evidence for innovative therapeutic perspectives.

Platelet Protein Disulfide Isomerase Promotes Glycoprotein Ibα-Mediated Platelet-Neutrophil Interactions Under Thromboinflammatory Conditions

BACKGROUND

Platelet-neutrophil interactions contribute to vascular occlusion and tissue damage in thromboinflammatory disease. Platelet glycoprotein Ibα (GPIbα), a key receptor for the cell-cell interaction, is believed to be constitutively active for ligand binding. Here, we established the role of platelet-derived protein disulfide isomerase (PDI) in reducing the allosteric disulfide bonds in GPIbα and enhancing the ligand-binding activity under thromboinflammatory conditions.

METHODS

Bioinformatic analysis identified 2 potential allosteric disulfide bonds in GPIbα. Agglutination assays, flow cytometry, surface plasmon resonance analysis, a protein-protein docking model, proximity ligation assays, and mass spectrometry were used to demonstrate a direct interaction between PDI and GPIbα and to determine a role for PDI in regulating GPIbα function and platelet-neutrophil interactions. Also, real-time microscopy and animal disease models were used to study the pathophysiological role of PDI-GPIbα signaling under thromboinflammatory conditions.

RESULTS

Deletion or inhibition of platelet PDI significantly reduced GPIbα-mediated platelet agglutination. Studies using PDI-null platelets and recombinant PDI or Anfibatide, a clinical-stage GPIbα inhibitor, revealed that the oxidoreductase activity of platelet surface-bound PDI was required for the ligand-binding function of GPIbα. PDI directly bound to the extracellular domain of GPIbα on the platelet surface and reduced the Cys4-Cys17 and Cys209-Cys248 disulfide bonds. Real-time microscopy with platelet-specific PDI conditional knockout and sickle cell disease mice demonstrated that PDI-regulated GPIbα function was essential for platelet-neutrophil interactions and vascular occlusion under thromboinflammatory conditions. Studies using a mouse model of ischemia/reperfusion-induced stroke indicated that PDI-GPIbα signaling played a crucial role in tissue damage.

CONCLUSIONS

Our results demonstrate that PDI-facilitated cleavage of the allosteric disulfide bonds tightly regulates GPIbα function, promoting platelet-neutrophil interactions, vascular occlusion, and tissue damage under thromboinflammatory conditions.

Esculetin, a Coumarin Derivative, Prevents Thrombosis: Inhibitory Signaling on PLCγ2-PKC-AKT Activation in Human Platelets

Esculetin, a bioactive 6,7-dihydroxy derivative of coumarin, possesses pharmacological activities against obesity, diabetes, renal failure, and cardiovascular disorders (CVDs). Platelet activation plays a major role in CVDs. Thus, disrupting platelet activation represents an attractive therapeutic target. We examined the effect of esculetin in human platelet activation and experimental mouse models. At 10–80 μM, esculetin inhibited collagen- and arachidonic acid-induced platelet aggregation in washed human platelets. However, it had no effects on other agonists such as thrombin and U46619. Esculetin inhibited adenosine triphosphate release, P-selectin expression, hydroxyl radical (OH·) formation, Akt activation, and phospholipase C (PLC)γ2/protein kinase C (PKC) phosphorylation, but did not diminish mitogen-activated protein kinase phosphorylation in collagen-activated human platelets. Platelet function analysis indicated that esculetin substantially prolonged the closure time of whole blood. In experimental mice, esculetin significantly increased the occlusion time in thrombotic platelet plug formation and reduced mortality associated with acute pulmonary thromboembolism. However, it did not prolong the bleeding time. This study demonstrates that esculetin inhibits human platelet activation via hindering the PLCγ2–PKC cascade, hydroxyl radical formation, Akt activation, and ultimately suppressing platelet activation. Therefore, esculetin may act as an essential therapeutic agent for preventing thromboembolic diseases.

[Neutrophil respiratory burst and the state of hemostasis in patients with ischemic and hemorrhagic stroke]

AIM

To study the relationship between the state of the respiratory burst of neutrophils and the indices of hemostasis in patients with ischemic (IS) and hemorrhagic (HS) strokes.

MATERIAL AND METHODS

Thirty-three patients with IS and 31 patients with HS were examined in the first 24 hours after an acute cerebrovascular accident (ACA). The diagnosis of ASA was confirmed by neuroimaging methods: computed tomography and magnetic resonance imaging. The determination of the respiratory burst state of blood neutrophils was carried out using chemiluminescence analysis. Indicators of vascular-platelet and coagulation hemostasis were determined in all patients.

RESULTS AND CONCLUSION

There were changes in the kinetics and activity of neutrophil respiratory burst in stroke patients. Patients with HS had higher (compared to those of patients with IS) level of spontaneous and induced synthesis of secondary ROS but with a decrease in metabolic resources for their synthesis. Activation of spontaneous and ADP-induced platelet aggregation was detected only in HS. Patients with HS had a higher level of fibrinolytic activity as compared to the patients with IS. There were positive correlations between the kinetic parameters of blood coagulation and the synthesis of primary ROS by neutrophils in patients with HS, whereas the intensity of all ROS synthesis negatively correlated with activated partial thromboplastin time. Therefore, in patients with HS the synergistic relationship between the respiratory burst of neutrophils (pro-inflammatory activity) and coagulation hemostasis was more pronounced compared to patients with IS.

Targeting allosteric site of AKT by 5,7-dimethoxy-1,4-phenanthrenequinone suppresses neutrophilic inflammation

BACKGROUND

Acute lung injury (ALI) is a severe life-threatening inflammatory disease. Neutrophil activation is a major pathogenic factor in ALI. Protein kinase B (PKB)/AKT regulates diverse cellular responses, but the significance in neutrophilic inflammation and ALI remains unknown.

METHODS

Human neutrophils and neutrophil-like differentiated HL-60 (dHL-60) cells were used to examine the anti-inflammatory effects of 5,7-dimethoxy-1,4-phenanthrenequinone (CLLV-1). The therapeutic potential of CLLV-1 was determined in a mouse model of lipopolysaccharide (LPS)-induced ALI.

FINDINGS

CLLV-1 inhibited respiratory burst, degranulation, adhesion, and chemotaxis in human neutrophils and dHL-60 cells. CLLV-1 inhibited the phosphorylation of AKT (Thr308 and Ser473), but not of ERK, JNK, or p38. Furthermore, CLLV-1 blocked AKT activity and covalently reacted with AKT Cys310 in vitro. The AKT_309-313 peptide-CLLV-1 adducts were determined by NMR or mass spectrometry assay. The alkylation agent-conjugated AKT (reduced form) level was also inhibited by CLLV-1. Significantly, CLLV-1 ameliorated LPS-induced ALI, neutrophil infiltration, and AKT activation in mice.

INTERPRETATION

Our results identify CLLV-1 as a covalent allosteric AKT inhibitor by targeting AKT Cys310. CLLV-1 shows potent anti-inflammatory activity in human neutrophils and LPS-induced mouse ALI. Our findings provide a mechanistic framework for redox modification of AKT that may serve as a novel pharmacological target to alleviate neutrophilic inflammation.

The Akt pathway in oncology therapy and beyond (Review)

Protein kinase B (Akt), similar to many other protein kinases, is at the crossroads of cell death and survival, playing a pivotal role in multiple interconnected cell signaling mechanisms implicated in cell metabolism, growth and division, apoptosis suppression and angiogenesis. Akt protein kinase displays important metabolic effects, among which are glucose uptake in muscle and fat cells or the suppression of neuronal cell death. Disruptions in the Akt-regulated pathways are associated with cancer, diabetes, cardiovascular and neurological diseases. The regulation of the Akt signaling pathway renders Akt a valuable therapeutic target. The discovery process of Akt inhibitors using various strategies has led to the identification of inhibitors with great selectivity, low side-effects and toxicity. The usefulness of Akt emerges beyond cancer therapy and extends to other major diseases, such as diabetes, heart diseases, or neurodegeneration. This review presents key features of Akt structure and functions, and presents the progress of Akt inhibitors in regards to drug development, and their preclinical and clinical activity in regards to therapeutic efficacy and safety for patients.

Myeloperoxidase Negatively Regulates Neutrophil-Endothelial Cell Interactions by Impairing αMβ2 Integrin Function in Sterile Inflammation

Interactions of neutrophils with endothelial cells (ECs) and platelets contribute to tissue damage and vascular occlusion under sterile inflammatory conditions. However, the molecular mechanisms regulating the cell–cell interactions remain poorly understood. Previous studies suggest that reactive oxygen species, such as hydrogen peroxide (H₂O₂), produced from NADPH oxidase 2 play a critical role in platelet–neutrophil interactions by regulating the function of neutrophil αMβ2 integrin during sterile inflammation. In this study, we further demonstrate a crucial role for myeloperoxidase (MPO) in regulating the adhesive function of neutrophils through αMβ2 integrin. Using real-time fluorescence intravital microscopy and in vitro assays, we showed that loss of MPO promoted neutrophil–EC interactions and neutrophil emigration but did not affect neutrophil–platelet interactions under inflammatory conditions. Using genetic and pharmacologic approaches, we found that following agonist stimulation, MPO knockout (KO) neutrophils exhibited a significant increase in extracellular H₂O₂ and surface level of αMβ2 integrin and that these effects were dependent on MPO activity. Our in vivo studies using an ischemia/reperfusion-induced hepatic inflammation model revealed that compared to wild-type mice, neutrophils from MPO KO mice—displayed a pro-migratory phenotype while ameliorating tissue damage. These results suggest that MPO plays a negative role in the adhesive and migratory function of neutrophils by impairing αMβ2 integrin function under sterile inflammatory conditions.

Combination of AKT inhibitor ARQ 092 and sorafenib potentiates inhibition of tumor progression in cirrhotic rat model of hepatocellular carcinoma

The prognosis of patients with advanced hepatocellular carcinoma (HCC) is very poor. The AKT pathway is activated in almost half of HCC cases and in addition, long term exposure to conventional drug treatment of HCC, sorafenib, often results in over-activation of AKT, leading to HCC resistance. Therefore, it is important to assess the safety and the efficacy of selective allosteric AKT inhibitor ARQ 092 (Miransertib) in combination with sorafenib.

Here, we demonstrated in vitro that the combination of ARQ 092 with sorafenib synergistically suppressed proliferation, promoted apoptosis, and reduced migration. To test the effect of the combination in vivo, rats with diethylnitrosamine-induced cirrhosis and fully developed HCC were randomized and treated with vehicle, sorafenib, ARQ 092 or the combination of ARQ 092 with sorafenib; (n=7/group) for 6 weeks. Tumor progression, size of tumors and the mean tumor number were significantly reduced by the combination treatment compared to the control or single treatments. This effect was associated with a significant increase in apoptotic response and reduction in proliferation and angiogenesis. Sirius red staining showed a decrease in liver fibrosis. Moreover, treatments improved immune response in blood and in tumor microenvironment.

Thus, the combination of ARQ 092 with sorafenib potentiates inhibition of tumor progression and gives the possibility of therapeutic improvement for patients with advanced HCC.

Ser/Thr protein kinase Bβ-NADPH oxidase 2 signaling in thromboinflammation

PURPOSE OF REVIEW

Interactions between neutrophils and platelets contribute to the progression of thromboinflammatory disease. However, the regulatory mechanism governing these interactions is poorly understood. The present review focuses on the crucial role of Ser/Thr protein kinase B (AKT)β-NADPH oxidase 2 (NOX2) signaling in regulating neutrophil and platelet activation and their heterotypic interactions under thromboinflammatory conditions.

RECENT FINDINGS

Growing evidence has shown that platelets, leukocytes, and blood coagulation need to be considered to treat thromboinflammatory disease in which inflammation and thrombosis occur concurrently. In addition to plasma proteins and intracellular signaling molecules, extracellular reactive oxygen species (ROS) produced from activated leukocytes could be an important factor in the pathophysiology of thromboinflammatory disease. Recent studies reveal that AKT2-NOX2 signaling has critical roles in Ca mobilization, ROS generation, degranulation, and control of the ligand-binding function of cell surface molecules, thereby promoting heterotypic cell-cell interactions in thromboinflammation. These findings have provided novel insights into attractive therapeutic targets for the prevention and treatment of thromboinflammatory disease.

SUMMARY

Recent discoveries concerning molecular mechanisms regulating neutrophil-platelet interactions have bridged some gaps in our knowledge of the complicated signaling pathways exacerbating thromboinflammatory conditions.