Exposure to Secondhand Smoke Extract Increases Cisplatin Resistance in Head and Neck Cancer Cells.

Chemotherapy and radiotherapy resistance are major obstacles in the long-term efficacy of head and neck squamous cell carcinoma (HNSCC) treatment. Secondhand smoke (SHS) exposure is common and has been proposed as an independent predictor of HNSCC recurrence and disease-free survival. However, the underlying mechanisms responsible for these negative patient outcomes are unknown. To assess the effects of SHS exposure on cisplatin efficacy in cancer cells, three distinct HNSCC cell lines were exposed to sidestream (SS) smoke, the main component of SHS, at concentrations mimicking the nicotine level seen in passive smokers' saliva and treated with cisplatin (0.01-100 µM) for 48 h. Compared to cisplatin treatment alone, cancer cells exposed to both cisplatin and SS smoke extract showed significantly lower cisplatin-induced cell death and higher cell viability, IC50, and indefinite survival capacity. However, SS smoke extract exposure alone did not change cancer cell viability, cell death, or cell proliferation compared to unexposed control cancer cells. Mechanistically, exposure to SS smoke extract significantly reduced the expression of cisplatin influx transporter CTR1, and increased the expression of multidrug-resistant proteins ABCG2 and ATP7A. Our study is the first to document that exposure to SHS can increase cisplatin resistance by altering the expression of several proteins involved in multidrug resistance, thus increasing the cells' capability to evade cisplatin-induced cell death. These findings emphasize the urgent need for clinicians to consider the potential role of SHS on treatment outcomes and to advise cancer patients and caregivers on the potential benefits of avoiding SHS exposure.

Platelet and endothelial cell responses under concurrent shear stress and tensile strain.

Thrombosis can lead to significant mortality and morbidity. Both platelets and vascular endothelial cells play significant roles in thrombosis. Platelets' response to blood flow-induced shear stress can vary greatly depending on shear stress magnitude, pattern and shear exposure time. Endothelial cells are also sensitive to the biomechanical environment. Endothelial cell activation and dysfunction can occur under low oscillatory shear stress and low tensile strain. Platelet and endothelial cell interaction can also be affected by mechanical conditions. The goal of this study was to investigate how blood flow-induced shear stress, vascular wall tensile strain, platelet-endothelial cell stress history, and platelet-endothelial cell interaction affect platelet thrombogenicity. Platelets and human coronary artery endothelial cells were pretreated with physiological and pathological shear stress and/or tensile strain separately. The pretreated cells were then put together and exposed to pulsatile shear stress and cyclic tensile strain simultaneously in a shearing-stretching device. Following treatment, platelet thrombin generation rate, platelet and endothelial cell activation, and platelet adhesion to endothelial cells was measured. The results demonstrated that shear stress pretreatment of endothelial cells and platelets caused a significant increase in platelet thrombin generation rate, cell surface phosphatidylserine expression, and adhesion to endothelial cells. Shear stress pretreatment of platelets and endothelial cells attenuated endothelial cell ICAM-1 expression under stenosis conditions, as well as vWF expression under recirculation conditions. These results indicate that platelets are sensitized by prior shearing, while in comparison, the interaction with shear stress-pretreated platelets may reduce endothelial cell sensitivity to pathological shear stress and tensile strain.

Complement component C1q initiates extrinsic coagulation via the receptor for the globular head of C1q in adventitial fibroblasts and vascular smooth muscle cells.

BACKGROUND: Vascular diseases are highly associated with inflammation and thrombosis. Elucidating links between these two processes may provide a clearer understanding of these diseases, allowing for the design of more effective treatments. The activation of complement component 1 (C1) is a crucial contributor to innate immunity and is associated with significant concentrations of circulating C1q. Many pathological pathways initiate when C1q interacts with gC1qR. This interaction plays a major role in inflammation observed during atherosclerosis and the initiation of intrinsic coagulation. However, the effects of C1 and the role of C1q/gC1qR on extrinsic coagulation, which is the more physiologically relevant coagulation arm, has not been studied. We hypothesized that C1q binding to gC1qR enhances the expression of tissue factor (TF) in adventitial fibroblasts and vascular smooth muscle cells, the primary TF bearing cells in the body. METHODS: Using an enzyme-linked immunosorbent assay approach, TF expression and the role of gC1qR was observed. Cells were conditioned for 1 h with C1q or a gC1qR blocker and C1q, to assess the role of gC1qR. Additionally, cell growth characteristics were monitored to assess changes in viability and metabolic activity. RESULTS: Our results indicate that the expression of TF increased significantly after incubation with C1q as compared with unconditioned cells. Cells conditioned with gC1qR blockers and C1q exhibited no change in TF expression when compared with cells conditioned with the blocking antibodies alone. Our results show no significant differences in metabolic activity or cell viability under these conditions. CONCLUSIONS: This indicates that gC1qR association with C1q induces TF expression and may initiate extrinsic coagulation. Overall, this data illustrates a role for C1q in the activation of extrinsic coagulation and that gC1qR activity may link inflammation and thrombosis.

An in situ inferior vena cava ligation-stenosis model to study thrombin generation rates with flow.

BACKGROUND: Blood flow-induced shear stress affects platelet participation in coagulation and thrombin generation. We aimed to develop an in vivo model to characterize thrombin generation rates under flow. METHODS: An in situ inferior vena cava (IVC) ligation-stenosis model was established using C57BL/6 mice. Wild type C57BL/6 mice were fed normal chow diet for two weeks before experiments. On the day of experiments, mice were anesthetized, followed by an incision through the abdominal skin to expose the IVC, which was then ligated (followed by reperfusion through a stenosis for up to 2 h). IVC blood flow rate was monitored using a Transonic ultrasound flow meter. In sham animals, the IVC was exposed following the same procedure, but no ligation was applied. Thrombin generation following IVC ligation was estimated by measuring mouse plasma prothrombin fragment 1-2 concentration. Mouse plasma factor Va concentration was measured using phospholipids and a modified prothrombinase assay. Blood vessel histomorphology, vascular wall ICAM-1, von Willebrand Factor, tissue factor, and PECAM-1 expression were measured using immunofluorescence microscopy. RESULTS: IVC blood flow rate increased immediately following ligation and stenosis formation. Sizable clots formed in mouse IVC following ligation and stenosis formation. Both plasma factor Va and prothrombin fragment 1-2 concentration reduced significantly following IVC ligation/stenosis, while no changes were observed with ICAM-1, von Willebrand Factor, tissue factor and PECAM-1 expression. CONCLUSION: Clot formation was successful. However, the prothrombin-thrombin conversion rate constant in vivo cannot be determined as local thrombin and FVa concentration (at the injury site) cannot be accurately measured. Modification to the animal model is needed to further the investigation.

Development of 3D Printed Electrospun Scaffolds for the Fabrication of Porous Scaffolds for Vascular Applications.

Over the past two decades, electrospinning has emerged as a common technique to produce biomedical scaffolds composed of ultrafine fibers formed from many natural and synthetic polymers. A major advantage of this technique is the ability to produce scaffolds that resemble the native extracellular matrix in physical, chemical, and topological properties. However, scaffolds fabricated via electrospinning are not formed with a controlled architecture and typically do a poor job of directing cell growth into prescribed structures for tissue/organ development. To address these weaknesses, 3D bioprinting has recently been used to develop scaffolds that have a highly organized and precise global topology. Unfortunately, these 3D bioprinted scaffolds do not typically resemble the native extracellular matrix in physical properties, such as porosity, fiber diameter, and pore size (e.g., the microarchitecture). Thus, the goal of the current study was to develop a technique that harnesses the intrinsic advantages of both conventional electrospinning and 3D bioprinting techniques to produce scaffolds that have the potential to be used within biomedical applications. The physical properties of formed 3D printed electrospun scaffolds were compared with conventional electrospun and 3D printed scaffolds. Further, we conducted initial proof-of-concept biocompatibility studies to illustrate the applicability of the scaffolds within vascular applications. Our results illustrate that 3D printed electrospun scaffolds can be developed, via our technique, that have highly tailored and organized arbitrary geometries with scaffold properties in the range of the innate extracellular matrix. In addition, these scaffolds were shown to support endothelial cell growth. Therefore, we illustrate the development and testing of a novel bioscaffold fabrication technique that may be used for many tissue engineering and regenerative medicine applications, which allows for the direct printing of electrospun scaffolds into well-defined macro-scale geometries that also retain the micro-structures commonly observed in electrospun scaffolds.

SARS-CoV-2 Structural Proteins Exposure Alter Thrombotic and Inflammatory Responses in Human Endothelial Cells.

Introduction: We have experienced a pandemic induced by the interaction of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) structural proteins with innate structures. These interactions are especially prevalent for patients with underlying pathologies, such as cardiovascular diseases. However, there has been limited work to uncover the range of responses induced by SARS-CoV-2 structural proteins. Thus, our objective was to investigate how endothelial cell pro-thrombotic and pro-inflammatory responses are altered after exposure to SARS-CoV-2 spike, nucleocapsid, and membrane-envelope proteins. We hypothesized that after a short duration exposure, endothelial cells would have a heightened thrombotic and inflammatory potential. With longer exposures, this may lead to altered disease progression and the observed increased mortality and morbidity rates in patients with underlying vascular pathologies. Methods: To test this hypothesis, human endothelial cells were exposed to SARS-CoV-2 structural proteins. After the exposure, the expression of thrombomodulin, PECAM-1, connexin-43, and gC1qR were assessed. In parallel, standard cell culture readouts were assessed to determine if these incubations altered cell growth and metabolism. Results and Conclusions: We observed significant increases in thrombotic and inflammatory marker expression, with no change to the cell culture parameters (with the exception of a reduction in cell density in response to one SARS-CoV-2 structural protein). Importantly, these observations were dependent on the viral structural protein the cells were exposed to, suggesting that the interactions of SARS-CoV-2 with innate cells is complex and must be uncovered. Combined, this suggests that SARS-CoV-2 structural proteins can regulate inflammatory and thrombotic responses that underlie common pathologies observed during COVID-19.

gC1qR Antibody Can Modulate Endothelial Cell Permeability in Angioedema.

Angioedema is characterized by swelling of the skin or mucous membranes. Overproduction of the vasodilator bradykinin (BK) is an important contributor to the disease pathology, which causes rapid increase in vascular permeability. BK formation on endothelial cells results from high molecular weight kininogen (HK) interacting with gC1qR, the receptor for the globular heads of C1q, the first component of the classical pathway of complement. Endothelial cells are sensitive to blood-flow-induced shear stress and it has been shown that shear stress can modulate gC1qR expression. This study aimed to determine the following: (1) how BK or angioedema patients' (HAE) plasma affected endothelial cell permeability and gC1qR expression under shear stress, and (2) if monoclonal antibody (mAb) 74.5.2, which recognizes the HK binding site on gC1qR, had an inhibitory effect in HK binding to endothelial cells. Human dermal microvascular endothelial cells (HDMECs) grown on Transwell inserts were exposed to shear stress in the presence of HAE patients' plasma. Endothelial cell permeability was measured using FITC-conjugated bovine serum albumin. gC1qR expression and HK binding to endothelial cell surface was measured using solid-phase ELISA. Cell morphology was quantified using immunofluorescence microscopy. The results demonstrated that BK at 1 µg/mL, but not HAE patients' plasma and/or shear stress, caused significant increases in HDMEC permeability. The mAb 74.5.2 could effectively inhibit HK binding to recombinant gC1qR, and reduce HAE patients' plasma-induced HDMEC permeability change. These results suggested that monoclonal antibody to gC1qR, i.e., 74.5.2, could be potentially used as an effective therapeutic reagent to prevent angioedema.

Platelet adhesion potential estimation in a normal and diseased coronary artery model: effects of shear stress magnitude versus shear stress history.

Platelets play a salient role in the pathogenesis of coronary diseases; primarily through their adhesion to other platelets, endothelial cells and plasma proteins. It is necessary for platelets to activate in order for them to adhere to these different substrates. One of the key regulatory mechanical factors in platelet activation is shear stress, which has been shown to alter multiple platelet functions through the activation of mechanoreceptors. Our goal was to investigate how different numerical shear stress tracking techniques affect platelet adhesion estimates within physiologically relevant computational models. Previously, we developed a physiological coronary artery computational fluid dynamics model. Shear stress waveforms, obtained from these models, were used to monitor in vitro platelet and endothelial cell adhesion marker expression. In this work, the adhesion marker expression data was regressed to obtain numerical functions for receptor expression predictions. These functions were input into a customized adhesion model utilizing different shear stress tracking techniques. For the normal vascular conditions and minimal pathological disease models, shear stress tracking did not significantly affect the adhesion estimates. However, for the severe pathological model, the two shear stress tracking methods had vastly different estimates. Therefore, shear stress tracking methods must be chosen accurately to predict platelet adhesion potentials for accurate modeling techniques.

SARS-CoV-2 Exacerbates COVID-19 Pathology Through Activation of the Complement and Kinin Systems.

Infection with SARS-CoV-2 triggers the simultaneous activation of innate inflammatory pathways including the complement system and the kallikrein-kinin system (KKS) generating in the process potent vasoactive peptides that contribute to severe acute respiratory syndrome (SARS) and multi-organ failure. The genome of SARS-CoV-2 encodes four major structural proteins - the spike (S) protein, nucleocapsid (N) protein, membrane (M) protein, and the envelope (E) protein. However, the role of these proteins in either binding to or activation of the complement system and/or the KKS is still incompletely understood. In these studies, we used: solid phase ELISA, hemolytic assay and surface plasmon resonance (SPR) techniques to examine if recombinant proteins corresponding to S1, N, M and E: (a) bind to C1q, gC1qR, FXII and high molecular weight kininogen (HK), and (b) activate complement and/or the KKS. Our data show that the viral proteins: (a) bind C1q and activate the classical pathway of complement, (b) bind FXII and HK, and activate the KKS in normal human plasma to generate bradykinin and (c) bind to gC1qR, the receptor for the globular heads of C1q (gC1q) which in turn could serve as a platform for the activation of both the complement system and KKS. Collectively, our data indicate that the SARS-CoV-2 viral particle can independently activate major innate inflammatory pathways for maximal damage and efficiency. Therefore, if efficient therapeutic modalities for the treatment of COVID-19 are to be designed, a strategy that includes blockade of the four major structural proteins may provide the best option.

SARS-CoV-2 proteins regulate inflammatory, thrombotic and diabetic responses in human arterial fibroblasts.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is responsible for many pathological processes, including altered vascular disease development, dysfunctional thrombosis and a heightened inflammatory response. However, there is limited work to determine the underlying cellular responses induced by exposure to SARS-CoV-2 structural proteins. Thus, our objective was to investigate how human arterial adventitial fibroblasts inflammation, thrombosis and diabetic disease markers are altered in response to Spike, Nucleocapsid and Membrane-Envelope proteins. We hypothesized that after a short-term exposure to SARS-CoV-2 proteins, adventitial fibroblasts would have a higher expression of inflammatory, thrombotic and diabetic proteins, which would support a mechanism for altered vascular disease progression. After incubation, the expression of gC1qR, ICAM-1, tissue factor, RAGE and GLUT-4 was significantly up-regulated. In general, the extent of expression was different for each SARS-CoV-2 protein, suggesting that SARS-CoV-2 proteins interact with cells through different mechanisms. Thus, SARS-CoV-2 protein interaction with vascular cells may regulate vascular disease responses.

Endothelial Cell Biomechanical Responses are Dependent on Both Fluid Shear Stress and Tensile Strain.

INTRODUCTION: The goal of this study was to investigate how concurrent shear stress and tensile strain affect endothelial cell biomechanical responses. METHODS: Human coronary artery endothelial cells were exposed to concurrent pulsatile shear stress and cyclic tensile strain in a programmable shearing and stretching device. Three shear stress-tensile strain conditions were used: (1) pulsatile shear stress at 1 Pa and cyclic tensile strain at 7%, simulating normal stress/strain conditions in a healthy coronary artery; (2) shear stress at 3.7 Pa and tensile strain at 3%, simulating pathological stress/strain conditions near a stenosis; (3) shear stress at 0.7 Pa and tensile strain at 5%, simulating pathological stress/strain conditions in a recirculation zone. Cell morphology was quantified using immunofluorescence microscopy. Cell surface PECAM-1 phosphorylation, ICAM-1 expression, ERK1/2 and NF-κB activation were measured using ELISA or Western blot. RESULTS: Simultaneous stimulation from pulsatile shear stress and cyclic tensile strain induced a significant increase in cell area, compared to that induced by shear stress or tensile strain alone. The combined stimulation caused significant increases in PECAM-1 phosphorylation. The combined stimulation also significantly enhanced EC surface ICAM-1 expression (compared to that under shear stress alone) and transcriptional factor NF-κB activation (compared to that under control conditions). CONCLUSION: Pulsatile shear stress and cyclic tensile strain could induce increased but not synergistic effect on endothelial cell morphology or activation. The combined mechanical stimulation can be relayed from cell membrane to nucleus. Therefore, to better understand how mechanical conditions affect endothelial cell mechanotransduction and cardiovascular disease development, both shear stress and tensile strain need to be considered.

A comprehensive fluid-structure interaction model of the left coronary artery.

A fluid structure interaction model of a left anterior descending (LAD) coronary artery was developed, incorporating transient blood flow, cyclic bending motion of the artery, and myocardial contraction. The 3D geometry was constructed based on a patient's computed tomography angiography data. To simulate disease conditions, a plaque was placed within the LAD to create a 70% stenosis. The bending motion of the blood vessel was prescribed based on the LAD spatial information. The pressure induced by myocardial contraction was applied to the outside of the blood vessel wall. The fluid domain was solved using the Navier-Stokes equations. The arterial wall was defined as a nonlinear elastic, anisotropic, and incompressible material, and the mechanical behavior was described using the modified hyper-elastic Mooney-Rivlin model. The fluid (blood) and solid (vascular wall) domains were fully coupled. The simulation results demonstrated that besides vessel bending/stretching motion, myocardial contraction had a significant effect on local hemodynamics and vascular all stress/strain distribution. It not only transiently increased blood flow velocity and fluid wall shear stress, but also changed shear stress patterns. The presence of the plaque significantly reduced vascular wall tensile strain. Compared to the coronary artery models developed previously, the current model had improved physiological relevance.

Platelet-Activation Mechanisms and Vascular Remodeling.

This overview article for the Comprehensive Physiology collection is focused on detailing platelets, how platelets respond to various stimuli, how platelets interact with their external biochemical environment, and the role of platelets in physiological and pathological processes. Specifically, we will discuss the four major functions of platelets: activation, adhesion, aggregation, and inflammation. We will extend this discussion to include various mechanisms that can induce these functional changes and a discussion of some of the salient receptors that are responsible for platelets interacting with their external environment. We will finish with a discussion of how platelets interact with their vascular environment, with a special focus on interactions with the extracellular matrix and endothelial cells, and finally how platelets can aid and possibly initiate the progression of various vascular diseases. Throughout this overview, we will highlight both the historical investigations into the role of platelets in health and disease as well as some of the more current work. Overall, the authors aim for the readers to gain an appreciation for the complexity of platelet functions and the multifaceted role of platelets in the vascular system. © 2017 American Physiological Society. Compr Physiol 8:1117-1156, 2018.

Electronic cigarette aerosols suppress cellular antioxidant defenses and induce significant oxidative DNA damage.

BACKGROUND: Electronic cigarette (EC) aerosols contain unique compounds in addition to toxicants and carcinogens traditionally found in tobacco smoke. Studies are warranted to understand the public health risks of ECs. OBJECTIVE: The aim of this study was to determine the genotoxicity and the mechanisms induced by EC aerosol extracts on human oral and lung epithelial cells. METHODS: Cells were exposed to EC aerosol or mainstream smoke extracts and DNA damage was measured using the primer anchored DNA damage detection assay (q-PADDA) and 8-oxo-dG ELISA assay. Cell viability, reactive oxygen species (ROS) and total antioxidant capacity (TAC) were measured using standard methods. mRNA and protein expression were evaluated by RT-PCR and western blot, respectively. RESULTS: EC aerosol extracts induced DNA damage in a dose-dependent manner, but independently of nicotine concentration. Overall, EC aerosol extracts induced significantly less DNA damage than mainstream smoke extracts, as measured by q-PADDA. However, the levels of oxidative DNA damage, as indicated by the presence of 8-oxo-dG, a highly mutagenic DNA lesion, were similar or slightly higher after exposure to EC aerosol compared to mainstream smoke extracts. Mechanistically, while exposure to EC extracts significantly increased ROS, it decreased TAC as well as the expression of 8-oxoguanine DNA glycosylase (OGG1), an enzyme essential for the removal of oxidative DNA damage. CONCLUSIONS: Exposure to EC aerosol extracts suppressed the cellular antioxidant defenses and led to significant DNA damage. These findings emphasize the urgent need to investigate the potential long-term cancer risk of exposure to EC aerosol for vapers and the general public.

Glycated albumin modifies platelet adhesion and aggregation responses.

A diabetic vasculature is detrimental to cardiovascular health through the actions of advanced glycation end products (AGEs) on endothelial cells and platelets. Platelets activated by AGEs agonize endothelial responses promoting cardiovascular disease (CVD) development. While it has been established that AGEs can alter platelet functions, little is known about the specific platelet pathways that AGEs modify. Therefore, we evaluated the effects of AGEs on specific salient platelet pathways related to CVDs and whether the effects that AGEs elicit are dependent on glycation extent. To accomplish our objective, platelets were incubated with reversibly or irreversibly glycated albumin. A time course for adhesion and aggregation agonist receptor expression was assessed. Optical platelet aggregometry was used to confirm the functional activity of platelets after AGE exposure. In general, platelets subjected to glycated albumin had a significantly enhanced adhesion and aggregation potential. Furthermore, we observed an enhancement in dense body secretion and intracellular calcium concentration. This was especially prevalent for platelets exposed to irreversibly glycated albumin. Additionally, functional aggregation correlated well with receptor expression, suggesting that AGE-induced altered receptor sensitivity translated to altered platelet functions. Our findings indicate that under diabetic vascular conditions platelets become more susceptible to activation and aggregation due to an overall enhanced receptor expression, which may act to promote CVD development.

Endothelial Cell Inflammatory Reactions Are Altered in the Presence of E-Cigarette Extracts of Variable Nicotine.

Exposure to tobacco smoke has been associated with heightened endothelial cell activities associated with cardiovascular diseases (CVD). Conversely, the exposure to nicotine both activates and inhibits particular endothelial cell functions. However, which constituent(s) of tobacco smoke is responsible for these changes is unknown, since toxic gases and fine particulate matter cannot be isolated. Electronic cigarette vapor allows us to isolate these constituents, providing us the ability to evaluate individual constituents. Here, we used e-cigarettes to (1) identify which constituents of tobacco products are most responsible for altered CVD functions and (2) elucidate the underlying risk of e-cigarette exposure. To accomplish this goal, endothelial cells were exposed to extracts produced from tobacco cigarettes or e-cigarettes. Endothelial cell inflammatory processes, viability, density and metabolic activity were observed. In general, a significant increase in complement deposition, the expression of the receptors for C1q, coupled with a decrease in cell proliferation and metabolic activity was observed. These results were independent of nicotine and the exposure to e-vapor was just as harmful as tobacco smoke extracts. Thus, the exposure to fine particulate matter and not toxic combustion gases or nicotine may be the most critical for regulating CVD progression.

Platelets modulate endothelial cell response to dynamic shear stress through PECAM-1.

INTRODUCTION: Both vascular endothelial cells and platelets are sensitive to blood flow induced shear stress. We have recently reported that platelet-endothelial cell interaction could greatly affect platelet activation under flow. In the present study, we aimed to investigate how platelet-endothelial cell interaction affected endothelial cell inflammatory responses under flow. MATERIALS AND METHODS: Human coronary artery endothelial cells were exposed to normal or low pulsatile shear stress with or without the presence of platelets. Following shear exposure, endothelial cell ICAM-1 expression was measured using ELISA, Western blot and PCR; cell surface PECAM-1 expression/phosphorylation was measured using ELISA. Platelet adhesion to endothelial cells was quantified using immunofluorescence microscopy. To determine the role of PECAM-1 in platelet-endothelial cell interaction, endothelial cell PECAM-1 expression was suppressed using siRNA. RESULTS: Pathological low shear stress induced a significant increase in endothelial cell ICAM-1 expression, at both protein and mRNA levels. Platelet adhesion to endothelial cells increased significantly under low shear stress, co-localizing with PECAM-1 at endothelial cell junctions. The presence of platelets inhibited low shear stress-induced ICAM-1 upregulation. When endothelial cell PECAM-1 expression was suppressed, platelet adhesion to endothelial cells under low shear stress decreased significantly; endothelial cell ICAM-1 expression was not affected by shear stress, with or without platelets. CONCLUSIONS: These results suggested that PECAM-1 could mediate platelet adhesion to endothelial cells under shear stress. Platelets binding to endothelial cells interfered with endothelial cell mechanotransduction through PECAM-1, affecting endothelial cell inflammatory responses towards pathological shear flow.

Biocompatible and target specific hydrophobically modified glycol chitosan nanoparticles.

Cardiovascular disease is the leading cause of death in the United States. Atherosclerosis is a major cause for cardiovascular diseases. Drugs that treat atherosclerosis usually act nonspecifically. To enhance drug delivery specificity, the authors developed a hydrophobically modified glycol chitosan (HGC) nanoparticle that can specifically target activated endothelial cells. The biocompatibility of these nanoparticles toward red blood cells and platelets was evaluated through hemolysis, platelet activation, platelet thrombogenicity, and platelet aggregation assays. The biocompatibility of these nanoparticles toward vascular endothelial cells was evaluated by their effects on endothelial cell growth, metabolic activity, and activation. The results demonstrated that HGC nanoparticles did not cause hemolysis, or affect platelet activation, thrombogenicity, and aggregation capability in vitro. The nanoparticles did not impair vascular endothelial cell growth or metabolic activities in vitro, and did not cause cell activation either. When conjugated with intercellular adhesion molecular 1 antibodies, HGC nanoparticles showed a significantly increased targeting specificity toward activated endothelial cells. These results suggested that HGC nanoparticles are likely compatible toward red blood cells, platelets, and endothelial cells, and they can be potentially used to identify activated endothelial cells at atherosclerotic lesion areas within the vasculature, and deliver therapeutic drugs.