Fluorescent histochemical techniques for analysis of intracellular signaling

AOP report: Development of an adverse outcome pathway for deposition of energy leading to abnormal vascular remodeling

Cardiovascular diseases (CVDs) are complex, encompassing many types of heart pathophysiologies and associated etiologies. Radiotherapy studies have shown that fractionated radiation exposure at high doses (3-17 Gy) to the heart increases the incidence of CVD. However, the effects of low doses of radiation on the cardiovascular system or the effects from space travel, where radiation and microgravity are important contributors to damage, are not clearly understood. Herein, the adverse outcome pathway (AOP) framework was applied to develop an AOP to abnormal vascular remodeling from the deposition of energy. Following the creation of a preliminary pathway with the guidance of field experts and authoritative reviews, a scoping review was conducted that informed final key event (KE) selection and evaluation of the Bradford Hill criteria for the KE relationships (KERs). The AOP begins with a molecular initiating event of deposition of energy; ionization events increase oxidative stress, which when persistent concurrently causes the release of pro-inflammatory mediators, suppresses anti-inflammatory mechanisms and alters stress response signaling pathways. These KEs alter nitric oxide levels leading to endothelial dysfunction, and subsequent abnormal vascular remodeling (the adverse outcome). The work identifies evidence needed to strengthen understanding of the causal associations for the KERs, emphasizing where there are knowledge gaps and uncertainties in both qualitative and quantitative understanding. The AOP is anticipated to direct future research to better understand the effects of space on the human body and potentially develop countermeasures to better protect future space travelers.

Cytoprotective Effects of Dinitrosyl Iron Complexes on Viability of Human Fibroblasts and Cardiomyocytes

Nitric oxide (NO) is an important signaling molecule that plays a key role in maintaining vascular homeostasis. Dinitrosyl iron complexes (DNICs) generating NO are widely used to treat cardiovascular diseases. However, the involvement of DNICs in the metabolic processes of the cell, their protective properties in doxorubicin-induced toxicity remain to be clarified. Here, we found that novel class of mononuclear DNICs with functional sulfur-containing ligands enhanced the cell viability of human lung fibroblasts and rat cardiomyocytes. Moreover, DNICs demonstrated remarkable protection against doxorubicin-induced toxicity in fibroblasts and in rat cardiomyocytes (H9c2 cells). Data revealed that the DNICs compounds modulate the mitochondria function by decreasing the mitochondrial membrane potential (ΔΨm). Results of flow cytometry showed that DNICs were not affected the proliferation, growth of fibroblasts. In addition, this study showed that DNICs did not affect glutathione levels and the formation of reactive oxygen species in cells. Moreover, results indicated that DNICs maintained the ATP equilibrium in cells. Taken together, these findings show that DNICs have protective properties in vitro. It was further suggested that DNICs may be uncouplers of oxidative phosphorylation in mitochondria and protective mechanism is mainly provided by the leakage of excess charge through the mitochondrial membrane. It is assumed that the DNICs have the therapeutic potential for treating cardiovascular diseases and for decreasing of chemotherapy-induced cardiotoxicity in cancer survivors.

Obesity Mediates Apoptosis and Extracellular Matrix Metabolic Imbalances via MAPK Pathway Activation in Intervertebral Disk Degeneration

Obesity may promote intervertebral disc degeneration (IDD) by non-mechanical means, by influencing levels of free fatty acids which could impair cell metabolism. This study aims to establish metabolic factors in obesity-related IDD independent of mechanical loading. In clinical study, we retrospectively reviewed 128 volunteers (73 males, 55 females, aged 29-88 years) and compared their grades of disk degeneration with obesity-related factors such as body weight, BMI, and serum lipid levels. Clinically, the IDD group showed increased age, BMI and serum triglyceride. Triglyceride was a significant risk factor for IDD even after correction for BMI and age (P = 0.007). In obesity animal model, rats were fed a high-fat diet (HFD) in order to study its effects on disk metabolism and apoptosis. HFD rats had significantly higher serum levels of lipids, including triglyceride and non-esterified fatty acid, and showed significantly decreased markers of anabolism, increased catabolism and apoptosis in disk. Finally, rat nucleus pulposus (NP) cells were stimulated in vitro with a fatty acid (palmitic acid, PA) to gauge its effects on cell metabolism and apoptosis. Cell culture studies showed that NP cells exposed to PA showed increased apoptosis for activation of caspase 3, 7, 9, and PARP, which was primarily via the MAPK signal pathway, especially ERK pathway. In conclusion, hypertriglyceridemia can lead to IDD, independently of age and BMI. Hypertriglyceridemia appears to mediate disk cell apoptosis and matrix catabolism primarily via the ERK pathway.

Hypoxia-induced reactive oxygen species mediate N-cadherin and SERPINE1 expression, EGFR signalling and motility in MDA-MB-468 breast cancer cells

One of the hallmarks of the tumour microenvironment is hypoxia resulting from increased oxygen consumption by proliferative cancer cells and altered vasculature. Hypoxic tension initiates various cellular signals and can drive epithelial to mesenchymal transition (EMT), a process important in cancer progression. In this study, using the antioxidant N-acetylcysteine (NAC), we show that hypoxia-induced reactive oxygen species (ROS) in MDA-MB-468 breast cancer cells, selectively regulate hypoxia-induced increases in N-cadherin and SERPINE1, two proteins involved in cell adhesion. Treatment of cells with NAC also attenuated hypoxia-mediated activation of EGFR, but did not have any effect on hypoxia-mediated induction of HIF1α. Exogenous hydrogen peroxide phenocopied the effects of hypoxia on N-cadherin and SERPINE1 expression and EGFR activation, suggesting its possible involvement in these hypoxia-mediated events. Reflective of their effect on cell adhesion proteins and EGFR (associated with migratory phenotypes), NAC also reduced cell migration under hypoxic conditions, a crucial event in metastasis. Our findings suggest a selective role for redox signalling in the regulation of specific components of the responses to hypoxia and induction of EMT in breast cancer cells. This study provides new evidence supporting the potential of targeting ROS as a therapeutic strategy for the control of breast cancer metastasis.

Use of combined scanning electrochemical and fluorescence microscopy for detection of reactive oxygen species in prostate cancer cells

Release of ROS from prostate cancer (PC3) cells was studied using scanning electrochemical microscopy (SECM) and fluorescence microscopy. One-directional lateral scan SECM was used as a rapid and reproducible tool for simultaneous mapping of cell topography and reactive oxygen species (ROS) release. Fluorescence microscopy was used in tandem to monitor the tip position, in addition to providing information on intracellular ROS content via the use of ROS-reactive fluorescent dyes. A unique tip current (iT) vs lateral distance profile was observed when the tip potential (ET) was set at -0.65 V. This profile reflects the combined effects of topographical change and ROS release at the PC3 cell surfaces. Differentiation between topographical-related and ROS-induced current change was achieved by comparing the scans collected at -0.65 and -0.85 V. The effects of other parameters such as tip to cell distance, solvent oxygen content, and scan direction on the profile of the scan were systematically evaluated. Cells treated with tert-butyl hydroperoxide, a known ROS stimulus, were also evaluated using the lateral scanning approach. Overall, the SECM results correlate well with the fluorescence results. The extracellular ROS level detected at the SECM tip was found to be similar to the intracellular ROS level monitored using fluorescence microscopy. While the concentration of each contributing ROS species has not been determined and is thus part of the future study, here we have successfully demonstrated the use of a simple two-potential lateral scan approach for analysis of ROS released by living cells under real physiological conditions.

Endosomal trafficking of the ligated FcvarepsilonRI receptor

In addition to initiating signaling cascades leading to mast cell mediator release, aggregation of the high affinity IgE receptor (FcvarepsilonRI) leads to rapid internalization of the cross-linked receptor. However, little is known about the trafficking of the internalized FcvarepsilonRI. Here we demonstrate that in RBL-2H3 cells, aggregated FcvarepsilonRI appears in the early endosomal antigen 1 (EEA1(+)) domains of the early endosomes within 15min after ligation. Minimal co-localization of FcvarepsilonRI with Rab5 was observed by 30min, followed by its appearance in the Rab7(+) late endosomes and lysosomes at later time points. During endosomal sorting, FcvarepsilonRIalpha and gamma subunits remain associated. In Syk-deficient RBL-2H3 cells, the rate of transport to lysosomes is markedly increased. Taken together, our data demonstrate time-dependent sorting of aggregated FcvarepsilonRI within the endosomal-lysosomal network, and that Syk may play an essential role in regulating the trafficking and retention of FcvarepsilonRI in endosomes.

Multivariate image analysis in biomedicine

In recent years, multivariate imaging techniques are developed and applied in biomedical research in an increasing degree. In research projects and in clinical studies as well m-dimensional multivariate images (MVI) are recorded and stored to databases for a subsequent analysis. The complexity of the m-dimensional data and the growing number of high throughput applications call for new strategies for the application of image processing and data mining to support the direct interactive analysis by human experts. This article provides an overview of proposed approaches for MVI analysis in biomedicine. After summarizing the biomedical MVI techniques the two level framework for MVI analysis is illustrated. Following this framework, the state-of-the-art solutions from the fields of image processing and data mining are reviewed and discussed. Motivations for MVI data mining in biology and medicine are characterized, followed by an overview of graphical and auditory approaches for interactive data exploration. The paper concludes with summarizing open problems in MVI analysis and remarks upon the future development of biomedical MVI analysis.