Stabilization of Graphene Oxide Dispersion in Plasma-like Isotonic Solution Containing Aggregating Concentrations of Bivalent Cations

Graphene oxide's (GO) intravascular applications and biocompatibility are not fully explored yet, although it has been proposed as an anticancer drug transporter, antibacterial factor or component of wearable devices. Bivalent cations and the number of particles' atom layers, as well as their structural oxygen content and pH of the dispersion, all affect the GO size, shape, dispersibility and biological effects. Bovine serum albumin (BSA), an important blood plasma protein, is expected to improve GO dispersion stability in physiological concentrations of the precipitating calcium and magnesium cations to enable effective and safe tissue perfusion.

METHODS

Four types of GO commercially available aqueous dispersions (with different particle structures) were diluted, sonicated and studied in the presence of BSA and physiological cation concentrations. Nanoparticle populations sizes, electrical conductivity, zeta potential (Zetasizer NanoZS), structure (TEM and CryoTEM), functional groups content (micro titration) and dispersion pH were analyzed in consecutive preparation stages.

RESULTS

BSA effectively prevented the aggregation of GO in precipitating concentrations of physiological bivalent cations. The final polydispersity indexes were reduced from 0.66-0.91 to 0.36-0.43. The GO-containing isotonic dispersions were stable with the following Z-ave results: GO1 421.1 nm, GO2 382.6 nm, GO3 440.2 nm and GO4 490.1 nm. The GO behavior was structure-dependent.

CONCLUSION

BSA effectively stabilized four types of GO dispersions in an isotonic dispersion containing aggregating bivalent physiological cations.

In vitro effects of cobalt and chromium nanoparticles on human platelet function

Nanoparticles (NPs) are released from orthopedic and neurosurgical prostheses and can interact with a number of blood components once in the bloodstream. Potential toxic effects of Co and Cr NPs on blood platelets have not been thoroughly investigated. The aim of this study was to analyze the effect of Co and Cr NPs on platelet function in vitro. The ability of the tested NPs to induce platelet activation and aggregation was measured using light transmission aggregometry, flow cytometry, and quartz crystal balance with dissipation (QCM-D). This was confirmed by transmission electron microscopy (TEM), scanning electron microscopy, and optical and immunofluorescence microscopy. Perfusion of QCM-D sensor crystals with platelet-rich-plasma in the presence of Co 28 nm, CoO 50 nm, Co₂O₃ 50 nm, Co₃O₄ 30-50nm, Cr 35-45nm, Cr₂O₃ 60 nm NPs (0.5-5.0 µg/mL) resulted in significant changes in frequency and dissipation, indicating that these NPs caused platelet microaggregation. Transmission electron microscopy also revealed that Cr NPs led to platelet swelling and lysis. Our study shows that both Co and Cr NPs affect platelet function in vitro with two distinct mechanisms. While Co NPs result in standard platelet aggregation, Cr NPs cause both platelet aggregation and decreased platelet membrane integrity and lysis. Based on these findings, monitoring serum NP levels and platelet-mediated hemostasis can be advised in patients with metal-on-metal Co-Cr prostheses.

Novel Barbiturate-Nitrate Compounds Inhibit the Upregulation of Matrix Metalloproteinase-9 Gene Expression in Intestinal Inflammation through a cGMP-Mediated Pathway

Matrix metalloproteinase-9 is upregulated in inflammatory bowel disease. Barbiturate nitrate hybrid compounds have been designed to inhibit MMP secretion and enzyme activity. In this study, we investigated the mechanism of action of barbiturate-nitrate hybrid compounds and their component parts using models of intestinal inflammation in vitro. Cytokine-stimulated Caco-2 cells were used in all in vitro experiments. The NO donors SNAP and DETA-NONOate were used to study the effect of NO on MMP-9 mRNA. Mechanistic elucidation was carried out using the soluble guanylate cyclase (sGC) inhibitor, ODQ, and the cGMP analogue, 8-Bromo-cGMP. Further experiments were carried out to elucidate the role of NF-κB. NO donors exerted an inhibitory effect on MMP-9 mRNA in cytokine-stimulated cells. While the non-nitrate barbiturates had a limited effect on MMP-9 expression, the hybrid compounds inhibited MMP-9 expression through its NO-mimetic properties. No effect could be observed on mRNA for MMP-1 or MMP-2. The sGC inhibitior, ODQ, abolished the nitrate-barbiturate inhibition of MMP-9 gene expression, an effect which was reversed by 8-Br-cGMP. This study shows that the barbiturate scaffold is suitable for hybrid design as an MMP-9 inhibitor in cytokine-stimulated Caco-2 cells. The inhibition of MMP-9 levels was largely mediated through a reduction in its mRNA by a sGC/cGMP pathway mediated mechanism.

Differential eNOS-signalling by platelet subpopulations regulates adhesion and aggregation

Aims

In addition to maintaining haemostasis, circulating blood platelets are the cellular culprits that form occlusive thrombi in arteries and veins. Compared to blood leucocytes, which exist as functionally distinct subtypes, platelets are considered to be relatively simple cell fragments that form vascular system plugs without a differentially regulated cellular response. Hence, investigation into platelet subpopulations with distinct functional roles in haemostasis/thrombosis has been limited. In our present study, we investigated whether functionally distinct platelet subpopulations exist based on their ability to generate and respond to nitric oxide (NO), an endogenous platelet inhibitor.

Methods and results

Utilizing highly sensitive and selective flow cytometry protocols, we demonstrate that human platelet subpopulations exist based on the presence and absence of endothelial nitric oxide synthase (eNOS). Platelets lacking eNOS (approximately 20% of total platelets) fail to produce NO and have a down-regulated soluble guanylate cyclase-protein kinase G (sGC-PKG)-signalling pathway. In flow chamber and aggregation experiments eNOS-negative platelets primarily initiate adhesion to collagen, more readily activate integrin αIIbβ3 and secrete matrix metalloproteinase-2, and form larger aggregates than their eNOS-positive counterparts. Conversely, platelets having an intact eNOS-sGC-PKG-signalling pathway (approximately 80% of total platelets) form the bulk of an aggregate via increased thromboxane synthesis and ultimately limit its size via NO generation.

Conclusion

These findings reveal previously unrecognized characteristics and complexity of platelets and their regulation of adhesion/aggregation. The identification of platelet subpopulations also has potentially important consequences to human health and disease as impaired platelet NO-signalling has been identified in patients with coronary artery disease.

Role of matrix metalloproteinases 2 and 9, toll-like receptor 4 and platelet-leukocyte aggregate formation in sepsis-associated thrombocytopenia

Background

The development of thrombocytopenia in sepsis is a poor prognostic indicator associated with a significantly increased mortality risk. Mechanisms underlying this phenomenon remain to be clearly elucidated. Matrix metalloproteinases (MMPs) are enzymes that regulate the turnover of the extra-cellular matrix. MMP-2 is recognised as a platelet agonist with MMP-9 proposed as an inhibitor of platelet activation. The existence of MMP-9 in platelets is a subject of debate. There is limited evidence thus far to suggest that toll-like receptor 4 (TLR-4) and platelet-leukocyte aggregate (PLA) formation may be implicated in the development of sepsis-associated thrombocytopenia.

Objectives

To investigate whether MMP -2/-9, toll-like receptor 4 (TLR-4) or platelet-leukocyte aggregate (PLA) formation are implicated in a decline in platelet numbers during septic shock.

Methods

This was an observational study which recruited healthy controls, non-thrombocytopenic septic donors and thrombocytopenic septic donors. MMP-2, MMP-9 and TLR-4 platelet surface expression as well as PLA formation was examined using flow cytometry. In addition MMP-2 and MMP-9 were examined by gelatin zymography and enzyme-linked immunosorbent assay (ELISA) using a 3 compartment model (plasma, intraplatelet and platelet membrane).

Results

There was no difference found in MMP-2, MMP-9 or TLR-4 levels between non-thrombocytopenic and thrombocytopenic septic donors. PLA formation was increased in thrombocytopenic patients. MMP-9 was detected in platelets using flow cytometry, gelatin zymography and ELISA techniques.

Conclusions

Platelet consumption into PLAs may account for the development of thrombocytopenia in septic shock. MMP-9 is found in platelets and it is upregulated during septic shock.

The Role of Mucin in the Toxicological Impact of Polystyrene Nanoparticles

The development of novel oral drug delivery systems is an expanding area of research and both new approaches for improving their efficacy and the investigation of their potential toxicological effect are crucial and should be performed in parallel. Polystyrene nanoparticles (NPs) have been used for the production of diagnostic and therapeutic nanosystems, are widely used in food packaging, and have also served as models for investigating NPs interactions with biological systems. The mucous gel layer that covers the epithelium of the gastrointestinal system is a complex barrier-exchange system that it is mainly constituted by mucin and it constitutes the first physical barrier encountered after ingestion. In this study, we aimed to investigate the effect of polystyrene NPs on mucin and its potential role during NP–cell interactions. For this purpose, we evaluated the interaction of polystyrene NPs with mucin in dispersion by dynamic light scattering and with a deposited layer of mucin using a quartz crystal microbalance with dissipation technology. Next, we measured cell viability and the apoptotic state of three enterocyte-like cell lines that differ in their ability to produce mucin, after their exposure to the NPs. Positive charged NPs showed the ability to strongly interact and aggregate mucin in our model. Positive NPs affected cell viability and induced apoptosis in all cell lines independently of their ability of produce mucin.

Pharmacokinetics and bio-distribution of novel super paramagnetic iron oxide nanoparticles (SPIONs) in the anaesthetized pig

Manufactured nanomaterials have a variety of medical applications, including diagnosis and targeted treatment of cancer. A series of experiments were conducted to determine the pharmacokinetic, biodistribution and biocompatibility of two novel magnetic nanoparticles (MNPs) in the anaesthetized pig. Dimercaptosuccinic acid (DMSA) coated superparamagnetic iron oxide nanoparticles (MF66-labelled 12 nm, core nominal diameter and OD15 15 nm); at 0.5, or 2.0 mg/kg) were injected intravenously. Particles induced a dose-dependent decrease in blood pressure following administration which recovered to control levels several minutes after injection. Blood samples were collected for a 5-h period and stored for determination of particle concentration using particle electron paramagnetic resonance (pEPR). Organs were harvested post-mortem for magnetic resonance imaging (MRI at 1.5 T field strength) and histology. OD15 (2.0 mg/kg) MNP had a plasma half-life of approximately 15 min. Both doses of the MF66 (0.5 and 2.0 mg/kg) MNP were below detection limits. MNP accumulation was observed primarily in the liver and spleen with MRI scans which was confirmed by histology. MRI also showed that both MNPs were present in the lungs. The results show that further modifications may be required to improve the biocompatibility of these particles for use as diagnostic and therapeutic agents.

miR-134 in extracellular vesicles reduces triple-negative breast cancer aggression and increases drug sensitivity

Exosomes (EVs) have relevance in cell-to-cell communication carrying pro-tumorigenic factors that participate in oncogenesis and drug resistance and are proposed to have potential as self-delivery systems. Advancing on our studies of EVs in triple-negative breast cancer, here we more comprehensively analysed isogenic cell line variants and their EV populations, tissues cell line variants and their EV populations, as well as breast tumour and normal tissues. Profiling 384 miRNAs showed EV miRNA content to be highly representative of their cells of origin. miRNAs most substantially down-regulated in aggressive cells and their EVs originated from 14q32. Analysis of miR-134, the most substantially down-regulated miRNA, supported its clinical relevance in breast tumours compared to matched normal breast tissue. Functional studies indicated that miR-134 controls STAT5B which, in turn, controls Hsp90. miR-134 delivered by direct transfection into Hs578Ts(i)₈ cells (in which it was greatly down-regulated) reduced STAT5B, Hsp90, and Bcl-2 levels, reduced cellular proliferation, and enhanced cisplatin-induced apoptosis. Delivery via miR-134-enriched EVs also reduced STAT5B and Hsp90, reduced cellular migration and invasion, and enhanced sensitivity to anti-Hsp90 drugs. While the differing effects achieved by transfection or EV delivery are likely to be, at least partly, due to specific amounts of miR-134 delivered by these routes, these EV-based studies identified miRNA-134 as a potential biomarker and therapeutic for breast cancer.

The Nanopharmacology and Nanotoxicology of Nanomaterials: New Opportunities and Challenges

The very dynamic growth of nanotechnology, nanomaterials (sized 1-100 nm) and their medical applications over the past 10 years has promised to add a new impetus to the diagnostics and therapeutics of a wide range of human pathologies, including cancer, cardiovascular diseases and diseases of the central nervous system. This growth in nanomedicine also fuels advances in bioengineering, regenerative medicine and the development of medical devices. However, as with all new pharmaceuticals and medical devices, new opportunities are inherently accompanied by new challenges due to the ability of nanomaterials to interact with the body on the cellular, subcellular and molecular levels. This article reviews some of the most compelling problems related to the nanopharmacology and nanotoxicology of nanomaterials. The overview focuses on opportunities emerging from the development of multifunctional nanomaterials and nanotheranostics for the diagnostics and therapy of both major and rare diseases. Challenges related to the hemocompatibility of nanomaterials are also discussed.

Magnetic Nanoparticles in Cancer Theranostics

In a report from 2008, The International Agency for Research on Cancer predicted a tripled cancer incidence from 1975, projecting a possible 13-17 million cancer deaths worldwide by 2030. While new treatments are evolving and reaching approval for different cancer types, the main prevention of cancer mortality is through early diagnosis, detection and treatment of malignant cell growth. The last decades have seen a development of new imaging techniques now in widespread clinical use. The development of nano-imaging through fluorescent imaging and magnetic resonance imaging (MRI) has the potential to detect and diagnose cancer at an earlier stage than with current imaging methods. The characteristic properties of nanoparticles result in their theranostic potential allowing for simultaneous detection of and treatment of the disease. This review provides state of the art of the nanotechnological applications for cancer therapy. Furthermore, it advances a novel concept of personalized nanomedical theranostic therapy using iron oxide magnetic nanoparticles in conjunction with MRI imaging. Regulatory and industrial perspectives are also included to outline future perspectives in nanotechnological cancer research.

Pharmacological characterization of nanoparticle-induced platelet microaggregation using quartz crystal microbalance with dissipation: comparison with light aggregometry

BACKGROUND

Engineered nanoparticles (NPs) can induce platelet activation and aggregation, but the mechanisms underlying these interactions are not well understood. This could be due in part to use of devices that study platelet function under quasi-static conditions with low sensitivity to measure platelet microaggregation. Therefore, in this study we investigated the pharmacological pathways and regulators of NP-induced platelet microaggregation under flow conditions at nanoscale using quartz crystal microbalance with dissipation (QCM-D) and compared the data thus obtained with those generated by light aggregometry.

METHODS

Blood was collected from healthy volunteers, and platelet-rich plasma was obtained. Thrombin receptor-activating peptide, a potent stimulator of platelet function, and pharmacological inhibitors were used to modulate platelet microaggregation in the presence/absence of silica (10 nm and 50 nm) and polystyrene (23 nm) NPs. Light aggregometry was used to study platelet aggregation in macroscale. Optical, immunofluorescence, and scanning electron microscopy were also used to visualize platelet aggregates.

RESULTS

Platelet microaggregation was enhanced by thrombin receptor-activating peptide, whereas prostacyclin, nitric oxide donors, acetylsalicylic acid, and phenanthroline, but not adenosine diphosphate (ADP) blockers, were able to inhibit platelet microaggregation. NPs caused platelet microaggregation, an effect not detectable by light aggregometry. NP-induced microaggregation was attenuated by platelet inhibitors.

CONCLUSION

NP-induced platelet microaggregation appears to involve classical proaggregatory pathways (thromboxane A2-mediated and matrix metalloproteinase-2-mediated) and can be regulated by endogenous (prostacyclin) and pharmacological (acetylsalicylic acid, phenanthroline, and nitric oxide donors) inhibitors of platelet function. Quartz crystal microbalance with dissipation, but not light aggregometry, is an appropriate method for studying NP-induced microaggregation.

Biodistribution and pharmacokinetic studies of SPION using particle electron paramagnetic resonance, MRI and ICP-MS

Aim: Superparamagnetic iron oxide nanoparticles (SPIONs) may play an important role in nanomedicine by serving as drug carriers and imaging agents. In this study, we present the biodistribution and pharmacokinetic properties of SPIONs using a new detection method, particle electron paramagnetic resonance (pEPR). Materials & methods: The pEPR technique is based on a low-field and low-frequency electron paramagnetic resonance. pEPR was compared with inductively coupled plasma mass spectrometry and MRI, in in vitro and in vivo. Results: The pEPR, inductively coupled plasma mass spectrometry and MRI results showed a good correlation between the techniques. Conclusion: The results indicate that pEPR can be used to detect SPIONs in both preclinical and clinical studies.

Nanodiagnostics, nanopharmacology and nanotoxicology of platelet–vessel wall interactions

In physiological conditions, the interactions between blood platelets and endothelial cells play a major role in vascular reactivity and hemostasis. By contrast, increased platelet activation contributes to the pathogenesis of vascular pathology such as atherosclerosis, thrombosis, diabetes mellitus, hypertension and carcinogenesis. Nanomedicine, including nanodiagnostics and nanotherapeutics is poised to be used in the management of vascular diseases. However, the inherent risk and potential toxicity resultant from the use of nanosized (<100 nm) materials need to be carefully considered. This review, basing on a systematic search of literature provides state-of-the-art and focuses on new discoveries, as well as the potential benefits and threats in the field of nanodiagnostics, nanopharmacology and nanotoxicology of platelet–vessel wall interactions.

CdTe quantum dots induce activation of human platelets: implications for nanoparticle hemocompatibility

New nanomaterials intended for systemic administration have raised concerns regarding their biocompatibility and hemocompatibility. Quantum dots (QD) nanoparticles have been used for diagnostics, and recent work suggests their use for in vivo molecular and cellular imaging. However, the hemocompatibility of QDs and their constituent components has not been fully elucidated. In the present study, comprehensive investigation of QD–platelet interactions is presented. These interactions were shown using transmission electron microscopy. The effects of QDs on platelet function were investigated using light aggregometry, quartz crystal microbalance with dissipation, flow cytometry, and gelatin zymography. Platelet morphology was also analyzed by phase-contrast, immunofluorescence, atomic-force and transmission electron microscopy. We show that the QDs bind to platelet plasma membrane with the resultant upregulation of glycoprotein IIb/IIIa and P-selectin receptors, and release of matrix metalloproteinase-2. These findings unravel for the first time the mechanism of functional response of platelets to ultrasmall QDs in vitro.

Blood biocompatibility of surface-bound multi-walled carbon nanotubes

Blood clots when it contacts foreign surfaces following platelet activation. This can be catastrophic in clinical settings involving extracorporeal circulation such as during heart-lung bypass where blood is circulated in polyvinyl chloride tubing. Studies have shown, however, that surface-bound carbon nanotubes may prevent platelet activation, the initiator of thrombosis. We studied the blood biocompatibility of polyvinyl chloride, surface-modified with multi-walled carbon nanotubes in vitro and in vivo. Our results show that surface-bound multi-walled carbon nanotubes cause platelet activation in vitro and devastating thrombosis in an in vivo animal model of extracorporeal circulation. The mechanism of the pro-thrombotic effect likely involves direct multi-walled carbon nanotube-platelet interaction with Ca(2+)-dependant platelet activation. These experiments provide evidence, for the first time, that modification of surfaces with nanomaterials modulates blood biocompatibility in extracorporeal circulation.

Nitric oxide-matrix metaloproteinase-9 interactions: biological and pharmacological significance--NO and MMP-9 interactions

Nitric oxide (NO) and matrix metalloproteinase 9 (MMP-9) levels are found to increase in inflammation states and in cancer, and their levels may be reciprocally modulated. Understanding interactions between NO and MMP-9 is of biological and pharmacological relevance and may prove crucial in designing new therapeutics. The reciprocal interaction between NO and MMP-9 have been studied for nearly twenty years but to our knowledge, are yet to be the subject of a review. This review provides a summary of published data regarding the complex and sometimes contradictory effects of NO on MMP-9. We also analyse molecular mechanisms modulating and mediating NO-MMP-9 interactions. Finally, a potential therapeutic relevance of these interactions is presented.

Pharmacological and toxicological effects of co-exposure of human gingival fibroblasts to silver nanoparticles and sodium fluoride

Background

Silver nanoparticles (AgNPs) and fluoride (F) are pharmacological agents widely used in oral medicine and dental practice due to their anti-microbial/anti-cavity properties. However, risks associated with the co-exposure of local cells and tissues to these xenobiotics are not clear. Therefore, we have evaluated the effects of AgNPs and F co-exposure on human gingival fibroblast cells.

Methods

Human gingival fibroblast cells (CRL-2014) were exposed to AgNPs and/or F at different concentrations for up to 24 hours. Cellular uptake of AgNPs was examined by transmission electron microscopy. Downstream inflammatory effects and oxidative stress were measured by real-time quantitative polymerase chain reaction (PCR) and reactive oxygen species (ROS) generation. Cytotoxicity and apoptosis were measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and real-time quantitative PCR and flow cytometry, respectively. Finally, the involvement of mitogen-activated protein kinases (MAPK) was studied using Western blot.

Results

We found that AgNPs penetrated the cell membrane and localized inside the mitochondria. Co-incubation experiments resulted in increased oxidative stress, inflammation, and apoptosis. In addition, we found that co-exposure to both xenobiotics phosphorylated MAPK, particularly p42/44 MAPK.

Conclusion

A combined exposure of human fibroblasts to AgNPs and F results in increased cellular damage. Further studies are needed in order to evaluate pharmacological and potentially toxicological effects of AgNPs and F on oral health.

Exosomes from triple-negative breast cancer cells can transfer phenotypic traits representing their cells of origin to secondary cells

BACKGROUND

Triple-negative breast cancer (TNBC) accounts for 15-20% of breast cancers but is responsible for a disproportionate number of deaths. We investigated the relevance, in TNBC, of nano-sized exosomes expelled from cells. Specifically, we compared effects of exosomes derived from the claudin-low TNBC cell line Hs578T and its more invasive Hs578Ts(i)8 variant, as well as exosomes from TNBC patient sera compared to normal sera.

METHODS

Exosomes were isolated from conditioned media (CM) of Hs578T and Hs578Ts(i)8 cells and from sera by filtration and ultracentrifugation. Successful isolation was confirmed by transmission electron microscopy and immunoblotting. Subsequent analysis, of secondary/recipient cells in response to exosomes, included proliferation; motility/migration; invasion; anoikis assays and endothelial tubule formation assays.

RESULTS

Hs578Ts(i)8-exosomes versus Hs578T-exosomes significantly increased the proliferation, migration and invasion capacity of all three recipient cell lines evaluated i.e. SKBR3, MDA-MB-231 and HCC1954. Exosomes from Hs578Ts(i)8 cells also conferred increased invasiveness to parent Hs578T cells. Hs578Ts(i)8-exosomes increased sensitivity of SKBR3, MDA-MB-231 and HCC1954 to anoikis when compared to the effects of Hs578T-exosomes reflecting the fact that Hs578Ts(i)8 cells are themselves innately more sensitive to anoikis. In relation to vasculogenesis and subsequent angiogenesis, Hs578Ts(i)8-exosomes versus Hs578T-exosomes stimulated significantly more endothelial tubules formation. Finally, our pilot translational study showed that exosomes from TNBC patients' sera significantly increased recipient cells' invasion when compared to those derived from age- and gender-matched healthy control sera.

CONCLUSION

This study supports the hypothesis that TNBC exosomes may be involved in cancer cell-to-cell communication, conferring phenotypic traits to secondary cells that reflect those of their cells of origin.

Platelets increase survival of adenocarcinoma cells challenged with anticancer drugs: mechanisms and implications for chemoresistance

BACKGROUND AND PURPOSE

Cancer cells grow without the restraints of feedback control mechanisms, leading to increased cancer cell survival. The treatment of cancer is often complicated by the lack of response to chemotherapy leading to chemoresistance and persistent survival of tumour cells. In this work we studied the role of platelets in chemotherapy-induced cancer cell death and survival.

EXPERIMENTAL APPROACH

Human adenocarcinoma cells, colonic (Caco-2) and ovarian (59 M) cells, were incubated with 5-fluorouracil (1-300 µg·mL(-1) ) or paclitaxel (1-200 µg·mL(-1) ) in the presence or absence of platelets (1.5 × 10(8) mL(-1) ) for 1, 24 or 72 h. Following incubation, cancer cells were harvested and cell survival/death was assayed using flow cytometry, Western blotting, real-time PCR, TaqMan® Gene Expression Assays and proteomics.

KEY RESULTS

Human platelets increased the survival of colonic and ovarian adenocarcinoma cells treated with two standard anticancer drugs, 5-fluorouracil and paclitaxel. In the presence of platelets, cancer cells up-regulated anti-apoptotic and down-regulated pro-apoptotic genes, increased the number of cells in the synthesis of DNA and decreased the number in the quiescent phase, increased expression of cyclins, DNA repair proteins and MAPKs. The analysis of platelet-Caco-2 secretome demonstrated the release of the chemokine RANTES, thrombospondin-1, TGF-β and clusterin. Finally, human recombinant RANTES and thrombospondin-1 improved survival of Caco-2 cells challenged with paclitaxel.

CONCLUSIONS AND IMPLICATIONS

These data demonstrate that platelets increase adenocarcinoma cells survival, proliferation and chemoresistance to standard anticancer drugs. Modulating cancer cell-platelet interactions may offer a new strategy to improve the efficacy of chemotherapy.

Differential inhibition of tumour cell-induced platelet aggregation by the nicotinate aspirin prodrug (ST0702) and aspirin

BACKGROUND AND PURPOSE

Tumour cell-induced platelet aggregation (TCIPA) facilitates cancer cell invasion, angiogenesis and the formation of metastatic foci. TCIPA can be modulated by pharmacological inhibitors of MMP-2 and ADP; however, the COX inhibitor aspirin did not prevent TCIPA. In this study, we have tested the pharmacological effects of a new group of isosorbide-based aspirin prodrugs on TCIPA.

EXPERIMENTAL APPROACH

TCIPA was induced in human platelets by mixing with human adenocarcinoma or fibrosarcoma cells under no flow and flow conditions. The release of gelatinases and P-selectin expression during TCIPA were studied by zymography and flow cytometry respectively.

KEY RESULTS

Tumour cells caused platelet aggregation. This aggregation resulted in the release of MMP-2 and a significant up-regulation of P-selectin on platelets, indicative of platelet activation. Pharmacological modulation of TCIPA revealed that ST0702, one of the aspirin prodrugs, down-regulated TCIPA while aspirin was ineffective. The deacetylated metabolite of ST0702, 5-nicotinate salicylate (ST0702 salicylate), down-regulated both ADP-stimulated platelet aggregation and TCIPA.

CONCLUSIONS AND IMPLICATIONS

Our results show that ST0702 was an effective inhibitor of TCIPA in vitro. Its deacetylated metabolite may contribute to the effects of ST0702 by inhibiting ADP-mediated TCIPA.

Mechanisms of toxicity of amorphous silica nanoparticles on human lung submucosal cells in vitro: protective effects of fisetin

There is growing evidence that amorphous silica nanoparticles (SiO₂-NP) can cause an inflammatory response in the lung. We studied in vitro the effects of exposing human lung submucosal cells to SiO₂-NP of various sizes (10, 150, and 500 nm) for 2-24 h. Cell survival, reactive oxygen species (ROS), malondialdehyde (MDA) levels, cytokine production, inflammatory gene expression, and genotoxicity were measured after exposure of Calu-3 cells to 10SiO₂-NP in the presence or absence of the flavanoid fisetin and an antioxidant enzyme catalase. The exposure of Calu-3 cells to 10SiO₂-NP resulted in (1) increased cytotoxicity and cell death in a time- and concentration-dependent manner, with a lethal concentration (LC₅₀) of 9.7 μg/mL after 24 h; (2) enhanced gene expression of interleukin (IL)-6, IL-8, and matrix metalloproteinase-9; (3) a significant correlation between increases in MDA and cytotoxicity at 18 h; (4) ROS production; (5) IL-6 and IL-8 release; and (6) up-regulation of the pro-apoptotic genes, p53 and caspase-3. Cell death and inflammatory reactions were attenuated by fisetin and catalase. We observed that 150- and 500SiO₂-NP exerted no toxic effects on Calu-3 cells. In conclusion, the nanotoxicity of amorphous 10SiO₂-NP on submucosal cells is associated with inflammation, the release of ROS leading to apoptosis, and decreased cell survival. The nanotoxic effects of 10SiO₂-NP can be decreased by fisetin and catalase treatment, implicating oxidative stress in this injury.

Targeted delivery of transferrin-conjugated liposomes to an orthotopic model of lung cancer in nude rats

BACKGROUND

Lung cancer is the leading cause of cancer death worldwide. Pulmonary anticancer therapy might offer several advantages over systemic delivery, leading to an increased exposure of the lung tumor to the drug, while minimizing side effects, due to regional containment. Here, we studied if a combination of inhalation therapy and drug targeting holds potential as an even more efficient lung cancer therapy.

METHODS

Transferrin (Tf )-conjugated PEG liposomes loaded with doxorubicin (DOX) were administered using an intracorporeal nebulizing catheter to an orthotopic lung cancer model established in athymic Rowett nude rats. Different DOX formulations and doses (0.2 and 0.4 mg/kg) were tested and the influence on tumor progression and life span of rats was evaluated in comparison with the i.v. administration of Tf-PEG-liposomes loaded with DOX at a therapeutic dose of 2 mg/kg.

RESULTS

Rats in the untreated control group showed significant weight loss 2 weeks after tumor induction and died between days 19 and 29. Lungs of these animals showed multiple foci of neoplastic deposits, ranging up to 20 mm replacing the entire lobe. Empty Tf-liposomes showed a significant effect on survival time. This might be caused by the secondary cytotoxicity via stimulation of pulmonary macrophages. All animal treated intravenously also perished before the end of the study. No significant (p<0.05) improvement in survival was observed between the groups treated with aerosols of free drug, DOX encapsulated in plain and in Tf-modified liposomes. However, more animals survived in the Tf-liposome groups than in the other treatment regimes, and their lung tissue generally had fewer and smaller tumors. Nevertheless, the size of the groups, and the duration of the trial render it impossible to come to a definite conclusion.

CONCLUSIONS

Drug targeting demonstrated potential for improving the aerosol treatment of lung cancer.

Design of barbiturate-nitrate hybrids that inhibit MMP-9 activity and secretion

We describe a new type of barbiturate-based matrix metalloproteinase (MMP) inhibitor incorporating a nitric oxide (NO) donor/mimetic group (series 1). The compounds were designed to inhibit MMP at enzyme level and to attenuate MMP-9 secretion arising from inflammatory signaling. To detect effects related to the nitrate, we prepared and studied an analogous series of barbiturate C5-alkyl alcohols that were unable to release NO (series 2). Both series inhibited recombinant human MMP-2/9 activity with nanomolar potency. Series 1 consistently inhibited the secretion of MMP-9 from TNFα/IL1β stimulated Caco-2 cells at 10 μM, which could be attributed to NO related effects because the non-nitrate panel did not affect enzyme levels. Several compounds from series 1 (10 μM) inhibited tumor cell invasion but none from the non-nitrate panel did. The work shows that MMP-inhibitory barbiturates are suitable scaffolds for hybrid design, targeting additional facets of MMP pathophysiology, with potential to improve risk-benefit ratios.

Amorphous silica nanoparticles aggregate human platelets: potential implications for vascular homeostasis

Background

Amorphous silica nanoparticles (SiNP) can be used in medical technologies and other industries leading to human exposure. However, an increased number of studies indicate that this exposure may result in cardiovascular inflammation and damage. A high ratio of nitric oxide to peroxynitrite concentrations ([NO]/[ONOO⁻]) is crucial for cardiovascular homeostasis and platelet hemostasis. Therefore, we studied the influence of SiNP on the platelet [NO]/[ONOO⁻] balance and platelet aggregation.

Methods

Nanoparticle–platelet interaction was examined using transmission electron microscopy. Electrochemical nanosensors were used to measure the levels of NO and ONOO⁻ released by platelets upon nanoparticle stimulation. Platelet aggregation was studied using light aggregometry, flow cytometry, and phase contrast microscopy.

Results

Amorphous SiNP induced NO release from platelets followed by a massive stimulation of ONOO⁻ leading to an unfavorably low [NO]/[ONOO⁻] ratio. In addition, SiNP induced an upregulation of selectin P expression and glycoprotein IIb/IIIa activation on the platelet surface membrane, and led to platelet aggregation via adenosine diphosphate and matrix metalloproteinase 2-dependent mechanisms. Importantly, all the effects on platelet aggregation were inversely proportional to nanoparticle size.

Conclusions

The exposure of platelets to amorphous SiNP induces a critically low [NO]/[ONOO⁻] ratio leading to platelet aggregation. These findings provide new insights into the pharmacological profile of SiNP in platelets.

Fisetin prevents fluoride- and dexamethasone-induced oxidative damage in osteoblast and hippocampal cells

Fluoride intoxication and dexamethasone treatment produce deleterious effects in bone and brain. The aim of this study was to evaluate the effect of fluoride (F) and dexamethasone (Dex) co-exposure on oxidative stress and apoptosis in osteoblast-like MC3T3-E1 and hippocampal HT22 cell lines. Co-exposure to F and Dex resulted in a concentration-dependent decrease in cell viability, induction of apoptosis and increased generation of reactive oxygen species (ROS) and nitric oxide (NO) following 72 h of incubation. Fluoride-induced apoptosis in MC3T3-E1 and HT22 cells was attenuated by catalase and L-NNMA, indicating a role for H2O2 and NO as mediators of cytotoxicity. Dexamethasone-induced apoptosis was associated with H2O2 generation in both cell lines and it was attenuated during co-incubation with catalase. These data indicate that co-exposure to F and Dex amplifies their respective cytotoxicity in H2O2- and NO-dependent manner. As flavonoid fisetin prevented F- and Dex-induced cytotoxicity the potential role of this product in pharmacology and diet may be considered.

Mechanisms of aggregation inhibition by aspirin and nitrate-aspirin prodrugs in human platelets

Objectives

Aspirin is the mainstay of anti-platelet therapy in the secondary prevention of cardiovascular disease. However, problems with aspirin safety and resistance demand clinical strategies based on multiple pharmacological approaches. Prodrugs of aspirin may offer beneficial effects in terms of gastro-intestinal safety and multiple pharmacological approaches. However, the pharmacological profile of aspirin prodrugs in human platelets has not been completed yet. We aimed to compare the effects of aspirin and prodrugs of aspirin (1–5) on human platelet aggregation stimulated by ADP and collagen and associated receptor expression (GPIIb/IIIa and P-selectin) in platelet-rich plasma (PRP) and washed platelets (WP).

Methods

As aspirin is released from prodrugs following esterase hydrolysis we studied the expression and activity of butyrylcholineterase (BuChE) and carboxyesterase (CE) in plasma and platelets. The mechanism of prodrug-induced platelet aggregation inhibition was explored by studying the effects of plasma and purified human BuChE on aggregation. Finally, the relative contribution of nitric oxide (NO) bioactivity to nitrate-containing prodrugs of aspirin-induced inhibition of aggregation was determined using 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ,) a selective inhibitor of the soluble guanylyl cyclase.

Key findings

ST0702, 2, a nicotinic acid-aspirin codrug was equipotent with aspirin with respect to inhibition of collagen-induced platelet aggregation. Compound 4, a NO releasing aspirin was the most potent inhibitor of ADP-induced platelet aggregation, an effect partially reversed by ODQ. The platelet inhibitory effects of aspirin prodrugs were time-dependent as the maximal inhibitory effects against collagen-induced aggregation were achieved by aspirin at 2 min, 1 at 5 min and ST0702 at 15 min. The aspirin prodrugs were significantly less potent in WP than in PRP and the reverse was true of aspirin. In the presence of complete BuChE inhibition in PRP, there was almost complete loss of aspirin prodrug, but not aspirin anti-aggregatory activity. Interestingly, CE activity was observed in WP and platelet lysate with pNPA substrate. Accordingly, 1 and ST0702 retained 50% and 100% anti-aggregatory activity at maximal concentrations in WP, which was attenuated in the presence of esterase inhibitor phenylmethylsulphonyl fluoride.

Conclusions

The inhibitory effect of aspirin prodrugs in PRP is due to prodrug activation by BuChE. In contrast, the platelet-inhibitory effects of aspirin prodrugs in WP may be mediated through the activity of platelet CE. Compound 4, a NO-containing aspirin prodrug, may exert dual inhibitory effects in platelets. Thus, aspirin prodrugs effectively inhibit human platelet aggregation and as such may be an alternative to conventional aspirin.

Amorphous silica nanoparticles trigger nitric oxide/peroxynitrite imbalance in human endothelial cells: inflammatory and cytotoxic effects

Background

The purpose of this study was to investigate the mechanism of noxious effects of amorphous silica nanoparticles on human endothelial cells.

Methods

Nanoparticle uptake was examined by transmission electron microscopy. Electrochemical nanosensors were used to measure the nitric oxide (NO) and peroxynitrite (ONOO⁻) released by a single cell upon nanoparticle stimulation. The downstream inflammatory effects were measured by an enzyme-linked immunosorbent assay, real-time quantitative polymerase chain reaction, and flow cytometry, and cytotoxicity was measured by lactate dehydrogenase assay.

Results

We found that the silica nanoparticles penetrated the plasma membrane and rapidly stimulated release of cytoprotective NO and, to a greater extent, production of cytotoxic ONOO⁻. The low [NO]/[ONOO⁻] ratio indicated increased nitroxidative/oxidative stress and correlated closely with endothelial inflammation and necrosis. This imbalance was associated with nuclear factor κB activation, upregulation of key inflammatory factors, and cell death. These effects were observed in a nanoparticle size-dependent and concentration-dependent manner.

Conclusion

The [NO]/[ONOO⁻] imbalance induced by amorphous silica nanoparticles indicates a potentially deleterious effect of silica nanoparticles on vascular endothelium.

Elucidation of flow-mediated tumour cell-induced platelet aggregation using an ultrasound standing wave trap

BACKGROUND AND PURPOSE

Tumour cells activate and aggregate platelets [tumour cell-induced platelet aggregation (TCIPA)] and this process plays an important role in the successful metastasis of cancer cells. To date, most studies on TCIPA have been conducted under no-flow conditions. In this study, we have investigated TCIPA in real time under flow conditions, using an ultrasound standing wave trap that allows formation and levitation of cancer cell clusters in suspension, thus mimicking the conditions generated by flowing blood.

EXPERIMENTAL APPROACH

Using 59M adenocarcinoma and HT1080 fibrosarcoma cells and human platelets, cancer cell cluster-platelet aggregates were imaged in real time using epi-fluorescence microscopy (F-actin) and investigated in detail using confocal microscopy (matrix metalloproteinase-2-GPIIb/IIIa co-localization) and scanning electron and helium-ion microscopy (<1 nm resolution). The release of gelatinases from aggregates was studied using zymography.

KEY RESULTS

We found that platelet activation and aggregation takes place on the surface of cancer cells (TCIPA), leading to time-dependent disruption of cancer cell clusters. Pharmacological modulation of TCIPA revealed that EDTA, prostacyclin, o-phenanthroline and apyrase significantly down-regulated TCIPA and, in turn, delayed cell cluster disruption, However, EGTA and aspirin were ineffective. Pharmacological inhibition of TCIPA correlated with the down-regulation of platelet activation as shown by flow-cytometry assay of platelet P-selectin.

CONCLUSION AND IMPLICATIONS

Our results show for the first time, that during TCIPA, platelet activation disrupts cancer cell clusters and this can contribute to metastasis. Thus, selective targeting of platelet aggregate-cancer cell clusters may be an important strategy to control metastasis.

Isolation of exosomes for subsequent mRNA, MicroRNA, and protein profiling

Exosomes are nano-sized, cell membrane surrounded structures that are released from many cell types. These exosomes are believed to transport a range of molecules, including mRNAs, miRNAs, and proteins; the contents depending on their cell of origin. The physiological and pathological relevance of exosomes has yet to be fully elucidated. Exosomes have been implicated in cell-to-cell communication. For example, in relation to the immune system, such exosomes may enable exchange of antigen or major histocompatibility complex-peptide complexes between antigen-bearing cells and antigen-presenting cells; in cancer, they may contain molecules that not only have relevance as biomarkers, but may also be taken up and cause adverse effects on secondary cells. Furthermore, exosomes have been proposed as autologous delivery systems that could be exploited for personalised delivery of therapeutics. In order to explore the contents and functional relevance of exosomes from medium conditioned by culture cells or from other biological fluids, prior to extensive molecular profiling, they must be isolated and purified. Here, we describe differential centrifugation methods suitable for isolating exosomes from conditioned medium and from other biological fluids, including serum, saliva, tumour ascites, and urine. We also detail Western blotting and transmission electron microscopy methods suitable for basic assessment of their presence, size, and purity, prior to progressing to global mRNA, miRNA, or protein profiling.

Platelet compatibility of PLGA, chitosan and PLGA-chitosan nanoparticles

AIM

The increasing interest in biodegradable nanoparticles containing biomaterials such as poly(D,L-lactide-co-glycolide) (PLGA) and chitosan for drug delivery raises issues regarding the blood compatibility of these nanoparticles, since some nanoparticles, including carbon nanoparticles, can affect human platelet aggregation and cause vascular thrombosis. Therefore, the aim of this work was to investigate the effect of polymeric nanoparticles on human platelet function by measuring aggregation and receptor expression in vitro.

MATERIALS & METHOD

PLGA, chitosan-PLGA and a series of chitosan nanoparticles were prepared by the single emulsion technique and ionotropic gelation method. The effects of these nanoparticles (0.01-100 microg/ml) on resting platelets, as well as on platelet aggregation and expression of receptors (GPIIb/IIIa and P-selectin) induced by agonists in platelet-rich plasma were examined using light aggregometry and flow cytometry.

RESULTS & CONCLUSION

All tested nanoparticles at concentrations below 10 microg/ml did not modify platelet aggregation, showing that they may be used for the delivery of active molecules to the bloodstream.

Characterisation of the R3/1 cell line as an alveolar epithelial cell model for drug disposition studies

The rat cell line R3/1 displays several phenotypical features of alveolar epithelial type I cells. In order to evaluate this cell line as potential in vitro model for drug disposition studies, R3/1 cells were cultured on Transwell filters and the transepithelial electrical resistance (TEER) was measured to test the integrity of cell layers. The mRNA expression of cell junctional components including E-cadherin, occludin, ZO-1 and ZO-2 was studied using reverse transcriptase-polymerase chain reaction (RT-PCR) and the corresponding proteins by immunofluorescence microscopy (IFM). Moreover, the expression pattern of catabolic peptidases, carboxypeptidase M, aminopeptidases (AP): A, B, N and P, gamma-glutamyltransferase (GGT), dipeptidylpeptidase IV, angiotensin-converting enzyme (ACE), and endopeptidases (EP) 24.11 and 24.15 was analysed in R3/1 cells and compared to rat alveolar epithelial I-like cells in primary culture. TEER peaked at 99+/-17Omegacm(2) after 5 days in culture. Addition of 0.1muM dexamethasone (DEX) with 20% foetal bovine serum further increased TEER by 65%. However, none of the culture conditions used in our study yielded monolayers with TEER values comparable to those of primary cultures of rat pneumocytes. No transcripts encoding for E-cadherin and occludin were detected by RT-PCR. However, ZO-1 and -2 mRNA transcripts were found. IFM using a monoclonal antibody against occludin confirmed the absence of the protein in R3/1 cells. Of the investigated proteolytic enzymes, mRNA transcripts encoding APA and APB as well as EP 24.11 and EP 24.15 were detected; a pattern similar to that of rat alveolar epithelial I-like cells in primary culture. Thus, although R3/1 cells express certain markers typical for type I pneumocytes (e.g., T1alpha, ICAM-1, connexin-43, caveolins-1 and -2) they do not form electrically tight monolayers. This excludes R3/1 cells from being used as an in vitro model for alveolar absorption. However, the cell line may be suitable to study stability of inhaled and endogenous proteins.

Ceramide promotes apoptosis in chronic myelogenous leukemia-derived K562 cells by a mechanism involving caspase-8 and JNK

Ceramide is a sphingolipid that activates stress kinases such as p38 and c-JUN N-Terminal Kinase (JNK). Though Chronic Myelogenous Leukemia (CML) derived K562 cells resist killing by short chain C2-ceramide, we report here that longer chain C6-ceramide promotes apoptosis in these cells. C6-ceramide induces cleavage of Caspase-8 and Caspase-9, but only Caspase-8 is required for apoptosis. The sphingolipid killed CML derived KBM5 cells and, to a lesser extent, imatinib-resistant KBM5-STI cells suggesting that BCR-ABL can not completely block C6-ceramide-induced apoptosis but the kinase may regulate the process. BCR-ABL is known to suppress Protein Phosphatase 2A (PP2A) in CML cells. While C6-ceramide can activate PP2A in acute leukemia cells, the sphingolipid did not activate the phosphatase in K562 cells. C6-ceramide did not activate p38 kinase but did promote JNK activation and phosphorylation of JUN. Inhibition of JNK by pharmacological agent protected K562 cells from C6-ceramide suggesting that JNK plays an essential role in C6-ceramide mediated apoptosis. Furthermore, the sphingolipid promoted MCL-1 phosphorylation by a mechanism that, at least in part, involves JNK. The findings presented here suggest that Caspase-8, JNK, and perhaps MCL-1 may play important roles in regulating cell death and may represent new targets for therapeutic strategies for CML.

Long-term doxycycline is more effective than atenolol to prevent thoracic aortic aneurysm in marfan syndrome through the inhibition of matrix metalloproteinase-2 and -9

Beta-blockers, eg, atenolol, are the cornerstone therapy for thoracic aortic aneurysm (TAA) in patients with Marfan syndrome; however, continued aortic dilatation has been reported. We have demonstrated that matrix metalloproteinase (MMP)-2 and -9 were upregulated during progression of TAA in Marfan syndrome, accompanied with degenerated elastic fibers and vasomotor dysfunction. We hypothesized that doxycycline, a nonspecific inhibitor of MMPs, would ameliorate TAA by attenuating elastic fiber degeneration and improving vasomotor function. A well-characterized mouse model of Marfan syndrome (Fbn1(C1039G/+)) was used. Mice were untreated (n=40), given doxycycline (0.24 g/L, n=30), or given atenolol (0.5 g/L, n=30) in drinking water at 6 weeks of age. The Fbn1(+/+) mice served as control (n=40). At 3, 6, and 9 months, aortic segments from the ascending, arch, and descending portions were used to obtain the "average" value of the whole thoracic aorta. TAA was prevented in the doxycycline group, whereas mild aneurysm was evident in the atenolol group. Doxycycline improved elastic fiber integrity, normalized aortic stiffness, and prevented vessel weakening. The impairment of vasocontraction and endothelium-dependent relaxation in the untreated and atenolol groups were improved by doxycycline. The upregulation of transforming growth factor-beta in the Marfan aorta was suppressed by doxycycline. Doxycycline augmented expression ratios of tissue inhibitors of MMP to MMPs. Intraperitoneally injected neutralizing antibodies against MMP-2 and -9 yielded similar effects to doxycycline. We concluded that long-term treatment with doxycycline, through the inhibition of MMP-2 and -9, is more effective than atenolol in preventing TAA in Marfan syndrome by preserving elastic fiber integrity, normalizing vasomotor function, and reducing transforming growth factor-beta activation.

Role of metalloproteinases in platelet function

Platelets contain and release matrix metalloproteinases (MMPs), their inhibitors (TIMPs) and disintegrin metalloproteinases (ADAMs) including MMP-1, MMP-2, MMP-3, MMP-9, MT1-MMP (MMP-14), ADAM-10, ADAM-17, ADAMTS-13, TIMP-1, TIMP-2 and TIMP-4. These proteins exert several effects regulating platelet functions such as agonist-stimulated platelet adhesion and aggregation, tumour cell-induced platelet aggregation and platelet-leukocyte aggregation. In this review, mechanisms of MMPs, TIMPs and ADAMs on platelets are discussed.

Nanoparticles: pharmacological and toxicological significance

Nanoparticles are tiny materials (<1000 nm in size) that have specific physicochemical properties different to bulk materials of the same composition and such properties make them very attractive for commercial and medical development. However, nanoparticles can act on living cells at the nanolevel resulting not only in biologically desirable, but also in undesirable effects. In contrast to many efforts aimed at exploiting desirable properties of nanoparticles for medicine, there are limited attempts to evaluate potentially undesirable effects of these particles when administered intentionally for medical purposes. Therefore, there is a pressing need for careful consideration of benefits and side effects of the use of nanoparticles in medicine. This review article aims at providing a balanced update of these exciting pharmacological and potentially toxicological developments. The classes of nanoparticles, the current status of nanoparticle use in pharmacology and therapeutics, the demonstrated and potential toxicity of nanoparticles will be discussed.

Selectins--potential pharmacological targets?

Recent advances in our (patho)physiological understanding have underpinned the frequent involvement of the protein family of selectins in the progression of serious illnesses, including cancer and cancer metastasis, and immunological diseases, such as asthma, allergy and autoimmune reactions. Moreover, selectins seem to have a role in post-ischemic damage and during transplant failures (e.g. in graft-versus-host disease). Although the interplay between selectins and their counter-receptors and ligands is not always primarily involved in the development of these pathological conditions, selectins have been investigated as potential therapeutic targets for therapeutic intervention. This review focuses on the latest trends and developments in anti-selectin antibodies, anti-selectin receptor antibodies, recombinant selectin counter-receptors, low molecular weight selectin antagonists (glycomimetics), induction of selectin tolerance and selectin-targeted imaging agents.

Increased Alveolar and Plasma Gelatinases Activity during Postpump Syndrome: Inhibition by Inhaled Nitric Oxide

Postpump syndrome is associated with systemic inflammation. Matrix metalloproteinases (MMP)-2 and -9 contribute to proinflammatory and platelet-activator reactions. Nitric oxide (NO) is involved in the regulation of MMPs. The objectives of our study were to investigate the intensity of inflammation induced by 3 different surgical procedures, the effects of inflammation on the activity of MMPs, and the regulation of inflammation by inhaled NO (20 ppm). Inhaled NO was initiated immediately after tracheal intubation and maintained for the total duration of the experiments. Thirty pigs were equally randomized into 6 groups [sham; sham + NO; cardiopulmonary bypass; bypass + NO; bypass + lipopolysaccharide (1 microg/kg for 50 min); bypass + lipopolysaccharide + NO] and animals were subjected to anesthesia and mechanical ventilation up to 24 h. The levels of MMP-2 and MMP-9 in plasma and bronchoalveolar lavage were measured using zymography. Bypass resulted in a time-dependent rise in MMP activity, an effect potentiated by lipopolysaccharide. Inhaled NO attenuated the effects of bypass + lipopolysaccharide. These results confirm that MMP-2 and MMP-9 are associated with the inflammatory process causing the postpump syndrome. Preemptive and continuous administration of inhaled NO helps to prevent increased MMP-2 and MMP-9 activity.

Alteration of decreased plasma NO metabolites and platelet NO synthase activity by paroxetine in depressed patients

Although major depression (MD) and cardiovascular disease (CVD) have been conclusively linked in the literature, the mechanism associating MD and CVD is yet undetermined. The purpose of this paper is to further investigate a potential mechanism involving nitric oxide (NO) and to examine the effect of the selective serotonin reuptake inhibitor paroxetine on NO production by both platelets and the endothelium. In total, 17 subjects with MD and 12 healthy controls (HCs) with no known history of cardiovascular illness completed the study. Paroxetine was administered to both the MD patients and HCs over an 8-week period, and then medication was discontinued. Blood samples were taken at various times throughout paroxetine treatment and after discontinuation. Plasma NO metabolite (NOx) levels were measured by a chemiluminescence method. Platelet endothelial NO synthase (eNOS) activity was examined through the conversion of L-[14C]arginine to L-[(14)C]citrulline. Data were analyzed using t-tests and a linear mixed effects model. Baseline levels of both plasma NOx and platelet NOS activity were significantly lower in subjects with MD compared to HCs. Throughout paroxetine treatment, plasma NOx levels increased in both HCs and MD patients. However, platelet eNOS activity decreased in HCs, while no statistically significant change was evidenced in MD patients. These data suggest that, in MD patients, decreased peripheral production of NO, a potential contributor to increased cardiovascular risk, is modified by administration of the antidepressant paroxetine.

Generation of platelet angiostatin mediated by urokinase plasminogen activator: effects on angiogenesis

BACKGROUND

Angiogenesis, the growth of new capillaries from pre-existing blood vessels, is regulated by a balance between its promoters and inhibitors. Platelets are an important circulating store of angiogenesis regulators. We have previously identified the angiogenesis inhibitor angiostatin in human platelets.

AIM

To identify the mechanism of platelet angiostatin generation and its pharmacological regulation.

METHODS

Platelet aggregometry, flow cytometry, Western blot, zymography, immunofluorescence microscopy, matrigel-induced angiogenesis of human umbilical vein endothelial cells (HUVECs), and a panel of selective proteinase inhibitors were used to study the mechanism of angiostatin generation by platelets, its pharmacological regulation, and effects on angiogenesis. Release of pro-MMP-2 by HUVECs was also used to quantify angiogenesis.

RESULTS

Platelet membranes were identified as the site of angiostatin generation from plasminogen. Generation of angiostatin by platelet membranes was not affected by a matrix metalloproteinase (MMP) inhibitor, phenanthroline, but was inhibited by serine proteinase inhibitors aprotinin, leupeptin, plasminogen activator inhibitor-1, and selective inhibitor of urokinase plasminogen activator (uPA), uPA-STOP(TM). Angiostatin generation by intact platelets was inhibited by aprotinin, and the resulting incubate promoted angiogenesis to a greater extent than incubate where angiostatin generation occurred. Furthermore, HUVECs incubated with reaction mixture, where angiostatin generation was inhibited, released more pro-MMP-2 than HUVECs incubated with supernatants, where angiostatin generation occurred.

CONCLUSIONS

We conclude that; (i) platelets constitutively generate angiostatin on their membranes; (ii) this mechanism is dependent on uPA, but not, MMPs; and (iii) inhibition of platelet angiostatin generation can further promote angiogenesis.