A study of the calcium-induced morphological transistions of human erythrocytes

An examination was made of the morphological transitions induced in human erythrocytes by the elevation of cytosolic calcium, and of the biochemical mechanisms responsible. The loss of the discocyte morphology and the sequential progression of cells through the echinocyte stages 1, 2, 3 and sphereo-echinocyte was found to occur in both a calcium concentration- and a time-dependent manner. SDS-PAGE analysis of cytoskeletal proteins prepared from intact cells loaded with 150uM or 1mM calcium revealed the partial proteolytic loss of proteins 2.1, 2.2 and 4.1. The rate of proteolysis was not paralleled by that of echinocytosis, making a causative relationship unlikely. Cytoskeletal integrity did appear to influence shape reversal from the echinocyte to the discocyte morphology after removal of the calcium and ionophore A23187. The loss of 80% protein 4.1, 40% 2.1 and 30% 2.2 was associated with, although not necessarily the sole cause, of irreversible sphereo-echinocytosis. Pre-treatment of cells with wheat germ agglutinin preserved the discocyte morphology despite continued cytoskeletal proteolysis during calcium-loading. All observations were made on cells incubated either in the presence or absence of glycolytic substrates, effectively altering cell metabolic status. This influenced the rate of progression of cells through the echinocyte stages, the rate of proteolysis of cytoskeletal proteins, and the extent and kinetics of shape reversal from cells transformed to the sphereo-echinocyte morphology. The stage 1 to discocyte transition was the rate limiting step of this shape recovery. In contrast the rate of loss of the discocyte morphology was independent of cell metabolic status during exposure to calcium, as was the extent of restoration of the discocyte morphology from cells transformed to stage 1 echinocytes. An hypothesis is presented that echinocytosis is a discontinuous process with discrete steps initiated by different biochemical mechanisms varying in their dependence on metabolic energy

Status and future directions of anti-metastatic cancer nanomedicines for the inhibition of cathepsin L

Angiogenesis, tissue invasion and metastasis in the tumour microenvironment are all critical hallmarks of cancer. Upregulation of cathepsin L plays an important role in angiogenesis and metastasis through its ability to degrade the extracellular matrix, facilitating tissue remodeling and tumour cell invasion. Thus, cathepsin L is a potential therapeutic target for anticancer nanomedicine, with its inhibition emerging as an innovative and potentially promising therapeutic intervention for the development of anti-invasion and anti-metastatic enzyme therapies. Nanotechnology-based platforms have been extensively tested in the anti-cancer nanomedicine field with effective anti-tumour efficacy. These nanodrugs can suppress tumour cell proliferation, thereby reducing tumour growth. Recently, nanomedicinal approaches have also emerged as effective anti-metastatic strategies, including the use of graphene oxide and gold nanoparticles. With a focus on recent advances in developing nanotechnology to inhibit cathepsin L, this review provides an in-depth examination of this stimulating field in the context of tumour microenvironments. Innovative anti-metastatic agents may lead to new options for the treatment of cancers

Endoplasmic reticulum stress-induced release and binding of calreticulin from human ovarian cancer cells

BACKGROUND: Calreticulin (CRT) is an endoplasmic reticulum (ER) chaperone, but can appear surface bound on cancers cells, including ovarian cancers (OC). We investigated at what stage of cell viability, CRT appeared associated with surface of human OC cells. CRT on pre-apoptotic tumour cells is thought to initiate their eradication via a process termed immunogenic cell death (ICD). METHODS: We treated OC cells with the chemotherapeutic-doxorubicin (DX) known to induce translocation of CRT to some tumour cell surfaces, with and without the ER stressor-thapsigargin (TG)-and/or an ER stress inhibitor-TUDCA. We monitored translocation/release of CRT in pre-apoptotic cells by flow cytometry, immunoblotting and ELISA. We investigated the difference in binding of FITC-CRT to pre-apoptotic, apoptotic and necrotic cells and the ability of extracellular CRT to generate immature dendritic cells from THP-1 monocytes. RESULTS: Dx-treatment increased endogenously released CRT and extracellular FITC_CRT binding to human pre-apoptotic OC cells. DX and TG also promoted cell death in OC cells which also increased CRT release. These cellular responses were significantly inhibited by TUDCA, suggesting that ER stress is partially responsible for the changes in CRT cellular distribution. Extracellular CRT induces maturation of THP-1 towards a imDC phenotype, an important component of ICD. CONCLUSION: Collectively, these cellular responses suggest that ER stress is partially responsible for the changes in CRT cellular distribution. ER-stress regulates in part the release and binding of CRT to human OC cells where it may play a role in ICD

Non‐invasive measurement of retinal permeability in a diabetic rat model

Objective: The gold standard for measuring blood-retinal barrier permeability is the Evans blue assay. However, this technique has limitations in vivo, including non-specific tissue binding and toxicity. This study describes a non-toxic, high throughput and cost effective alternative technique that minimizes animal usage. Methods: Sodium fluorescein fundus angiography was performed in non- and diabetic Brown Norway rats on days 0, 7, 14, 21 and 28. Sodium fluorescein intensity in the retinal interstitium and a main retinal vessel were measured over time. The intensity gradients were used to quantify retinal vascular permeability. Post study eyes were fixed, dissected and stained (isolectin B4) to measure required parameters for permeability quantification including: Total vessel length per retinal volume, radius and thickness. Results: In the non-diabetic cohort retinal permeability remained constant over the 28-day study period. However, in the diabetic cohort there was a significant and progressive increase in retinal permeability from day 14 to 28 (p [less than] 0.01, p [less than] 0.001, p [less than] 0.0001). Conclusions: This novel imaging methodology in combination with mathematical quantification allows retinal permeability to be non-invasively and accurately measured at multiple time points in the same animal. In addition, this technique is a non-toxic, rapid, sensitive and cost-effective alternative to the Evans blue assay

Graphene Oxide-Based Targeting of Extracellular Cathepsin D and Cathepsin L As A Novel Anti-Metastatic Enzyme Cancer Therapy

This is the final version. Available from the publisher via the DOI in this record.Overexpression and secretion of the enzymes cathepsin D (CathD) and cathepsin L (CathL) is associated with metastasis in several human cancers. As a superfamily, extracellularly, these proteins may act within the tumor microenvironment to drive cancer progression, proliferation, invasion and metastasis. Therefore, it is important to discover novel therapeutic treatment strategies to target CathD and CathL and potentially impede metastasis. Graphene oxide (GO) could form the basis of such a strategy by acting as an adsorbent for pro-metastatic enzymes. Here, we have conducted research into the potential of targeted anti-metastatic therapy using GO to adsorb these pro-tumorigenic enzymes. Binding of CathD/L to GO revealed that CathD/L were adsorbed onto the surface of GO through its cationic and hydrophilic residues. This work could provide a roadmap for the rational integration of CathD/L-targeting agents into clinical settings.Engineering and Physical Sciences Research Council (EPSRC)FORCE Cancer Charit

Microstructural characterisation of resistance artery remodelling in diabetes mellitus

Introduction: Microvascular remodelling is a symptom of cardiovascular disease. Despite the mechanical environment being recognized as a major contributor to the remodelling process, it is currently only understood in a rudimentary way. Objective: A morphological and mechanical evaluation of the resistance vasculature in health and diabetes mellitus. Methods: The cells and extracellular matrix of human subcutaneous resistance arteries from abdominal fat biopsies were imaged using two-photon fluorescence and second harmonic generation at varying transmural pressure. The results informed a two-layer mechanical model. Results: Diabetic resistance arteries reduced in wall area as pressure was increased. This was attributed to the presence of thick, straight collagen fibre bundles that braced the outer wall. The abnormal mechanical environment caused the internal elastic lamina and endothelial and vascular smooth muscle cell arrangements to twist. Conclusions: Our results suggest diabetic microvascular remodelling is likely to be stress-driven, comprising at least 2 stages: (1) Laying down of adventitial bracing fibres that limit outward distension, and (2) Deposition of additional collagen in the media, likely due to the significantly altered mechanical environment. This work represents a step towards elucidating the local stress environment of cells, which is crucial to build accurate models of mechanotransduction in disease

The novel mitochondria-targeted hydrogen sulfide (H2S) donors AP123 and AP39 protect against hyperglycemic injury in microvascular endothelial cells in vitro.

The development of diabetic vascular complications is initiated, at least in part, by mitochondrial reactive oxygen species (ROS) production in endothelial cells. Hyperglycemia induces superoxide production in the mitochondria and initiates changes in the mitochondrial membrane potential that leads to mitochondrial dysfunction. Hydrogen sulfide (H2S) supplementation has been shown to reduce the mitochondrial oxidant production and shows efficacy against diabetic vascular damage in vivo. However, the half-life of H2S is very short and it is not specific for the mitochondria. We have therefore evaluated two novel mitochondria-targeted anethole dithiolethione and hydroxythiobenzamide H2S donors (AP39 and AP123 respectively) at preventing hyperglycemia-induced oxidative stress and metabolic changes in microvascular endothelial cells in vitro. Hyperglycemia (HG) induced significant increase in the activity of the citric acid cycle and led to elevated mitochondrial membrane potential. Mitochondrial oxidant production was increased and the mitochondrial electron transport decreased in hyperglycemic cells. AP39 and AP123 (30-300nM) decreased HG-induced hyperpolarisation of the mitochondrial membrane and inhibited the mitochondrial oxidant production. Both H2S donors (30-300nM) increased the electron transport at respiratory complex III and improved the cellular metabolism. Targeting H2S to mitochondria retained the cytoprotective effect of H2S against glucose-induced damage in endothelial cells suggesting that the molecular target of H2S action is within the mitochondria. Mitochondrial targeting of H2S also induced >1000-fold increase in the potency of H2S against hyperglycemia-induced injury. The high potency and long-lasting effect elicited by these H2S donors strongly suggests that these compounds could be useful against diabetic vascular complications

ARF1-regulated phospholipase D in human neutrophils is enhanced by PMA and MgATP

AbstractHuman neutrophil PLD activity stimulated with GTP-γ-S was reconstituted with recombinant ARF1 in cytosol-depleted cells. PMA-pretreatment of intact cells greatly enhanced the subsequent reconstitution of the ARF1-regulated PLD activity. This enhancement was only observed provided that the intact cells were pretreated with PMA, suggesting the stable recruitment of a cytosolic component, presumably protein kinase C, to the membranes. rARF1-reconstituted PLD activity was not dependent on MGATP, but could be considerably enhanced by MgATP. Maximal effects of MgATP were seen at 1 mM. This enhancement by MgATP could not be attributed to protein kinase C. Neomycin was found to inhibit ARF1-regulated PLD activity suggesting the requirement for polyphosphoinositides. We conclude: (i) that many of the observed effects of PMA may be dependent on the presence of the small GTP-binding protein, ARF, and (ii) polyphosphoinositides are required for ARF1-stimulated PLD activity

Loss of the endothelial glycocalyx is associated with increased E-selectin mediated adhesion of lung tumour cells to the brain microvascular endothelium

Open access journalBACKGROUND: Arrest of metastasising lung cancer cells to the brain microvasculature maybe mediated by interactions between ligands on circulating tumour cells and endothelial E-selectin adhesion molecules; a process likely to be regulated by the endothelial glycocalyx. Using human cerebral microvascular endothelial cells and non-small cell lung cancer (NSCLC) cell lines, we describe how factors secreted by NSCLC cells i.e. cystatin C, cathepsin L, insulin-like growth factor-binding protein 7 (IGFBP7), vascular endothelial growth factor (VEGF) and tumour necrosis factor-alpha (TNF-α), damage the glycocalyx and enhance initial contacts between lung tumour and cerebral endothelial cells. METHODS: Endothelial cells were treated with tumour secreted-proteins or lung tumour conditioned medium (CM). Surface levels of E-selectin were quantified by ELISA. Adhesion of A549 and SK-MES-1 cells was examined under flow conditions (1 dyne/cm(2)). Alterations in the endothelial glycocalyx were quantified by binding of fluorescein isothiocyanate-linked wheat germ agglutinin (WGA-FITC). RESULTS: A549 and SK-MES-1 CM and secreted-proteins significantly enhanced endothelial surface E-selectin levels after 30 min and 4 h and tumour cell adhesion after 30 min, 4 and 24 h. Both coincided with significant glycocalyx degradation; A549 and SK-MES-1 CM removing 55 ± 12 % and 58 ± 18.7 % of WGA-FITC binding, respectively. Inhibition of E-selectin binding by monoclonal anti-E-selectin antibody completely attenuated tumour cell adhesion. CONCLUSION: These data suggest that metastasising lung cancer cells facilitate their own adhesion to the brain endothelium by secreting factors that damage the endothelial glycocalyx, resulting in exposure of the previously shielded adhesion molecules and engagement of the E-selectin-mediated adhesion axis.FORCE Cancer Charity, Exete