Ethanol affects calmodulin and the calmodulin-binding proteins neuronal nitric oxide synthase and alphaII-spectrin (alpha-fodrin) in the nucleus of growing and differentiated rat astrocytes in primary culture

Addressing the needs of traumatic brain injury with clinical proteomics

Background

Neurotrauma or injuries to the central nervous system (CNS) are a serious public health problem worldwide. Approximately 75% of all traumatic brain injuries (TBIs) are concussions or other mild TBI (mTBI) forms. Evaluation of concussion injury today is limited to an assessment of behavioral symptoms, often with delay and subject to motivation. Hence, there is an urgent need for an accurate chemical measure in biofluids to serve as a diagnostic tool for invisible brain wounds, to monitor severe patient trajectories, and to predict survival chances. Although a number of neurotrauma marker candidates have been reported, the broad spectrum of TBI limits the significance of small cohort studies. Specificity and sensitivity issues compound the development of a conclusive diagnostic assay, especially for concussion patients. Thus, the neurotrauma field currently has no diagnostic biofluid test in clinical use.

Content

We discuss the challenges of discovering new and validating identified neurotrauma marker candidates using proteomics-based strategies, including targeting, selection strategies and the application of mass spectrometry (MS) technologies and their potential impact to the neurotrauma field.

Summary

Many studies use TBI marker candidates based on literature reports, yet progress in genomics and proteomics have started to provide neurotrauma protein profiles. Choosing meaningful marker candidates from such ‘long lists’ is still pending, as only few can be taken through the process of preclinical verification and large scale translational validation. Quantitative mass spectrometry targeting specific molecules rather than random sampling of the whole proteome, e.g., multiple reaction monitoring (MRM), offers an efficient and effective means to multiplex the measurement of several candidates in patient samples, thereby omitting the need for antibodies prior to clinical assay design. Sample preparation challenges specific to TBI are addressed. A tailored selection strategy combined with a multiplex screening approach is helping to arrive at diagnostically suitable candidates for clinical assay development. A surrogate marker test will be instrumental for critical decisions of TBI patient care and protection of concussion victims from repeated exposures that could result in lasting neurological deficits.

Helicobacter pylori induces demethylation of the Calmodulin gene promoter in gastric cancer cells

AIM: To explore the expression of Calmodulin (CaM) gene in gastric cancer tissue and the relationship between the methylation level of the CaM gene promoter and Helicobacter pylori (H. pylori) infection.

METHODS: The expression of the CaM gene in 30 cases of gastric cancer and matched tumor-adjacent gastric tissue and metastatic lymph nodes was assessed by real-time fluorescence quantitative PCR. The relationship between CaM gene expression and H. pylori infection was analyzed. Methylation of CpG islands in the CaM gene promoter was measured by bisulfite modified sequencing method in gastric cancer cells infected with H. pylori and stably transfected with the H. pylori cytotoxin-associated protein A (cagA) gene.

RESULTS: The relative expression level of the CaM gene in cancer tissue was 2.08 times higher than that in tumor-adjacent gastric tissue (P < 0.05). The relative expression level of the CaM gene in H. pylori-positive gastric cancer was 6.11 times higher than that in the H. pylori-negative group (P < 0.05). The demethylation at -276 bp in the CaM gene promoter was detected in H. pylori-infected and cagA-overexpressed gastric cancer cells.

CONCLUSION: H. pylori, though secreting the virulence factor CagA, up-regulates the expression of the CaM gene in gastric cancer possibly by inducing the demethylation of the CaM promoter.

Mapping the distributions and quantifying the labelling intensities of cell compartments by immunoelectron microscopy: progress towards a coherent set of methods

An important tool in cell biology is the combination of immunogold labelling and transmission electron microscopy (TEM) by which target molecules (e.g. antigens) are bound specifically to affinity markers (primary antibodies) and then detected and localised with visualisation probes (e.g. colloidal gold particles bound to protein A). Gold particles are electron-dense, punctate and available in different sizes whilst TEM provides high-resolution images of particles and cell compartments. By virtue of these properties, the combination can be used also to quantify one or more defined targets in cell compartments. During the past decade, new ways of quantifying gold labelling within cells have been devised. Their efficiency and validity rely on sound principles of specimen sampling, event counting and inferential statistics. These include random selection of items at each sampling stage (e.g. specimen blocks, thin sections, microscopical fields), stereological analysis of cell ultrastructure, unbiased particle counting and statistical evaluation of a suitable null hypothesis (no difference in the intensity or pattern of labelling between compartments or groups of cells). The following approaches are possible: (i) A target molecule can be tested for preferential labelling by mapping the localisation of gold particles across a set of compartments. (ii) Data from wild-type and knockdown/knockout control cells can be used to correct raw gold particle counts, estimate specific labelling densities and then test for preferential labeling. (iii) The same antigen can be mapped in two or more groups of cells to test whether there are experimental shifts in compartment labelling patterns. (iv) A variant of this approach uses more than one size of gold particle to test whether or not different antigens colocalise in one or more compartments. (v) In studies involving antigen translocation, absolute numbers of gold particles can be mapped over compartments at specific positions within polarised, oriented or dividing cells. Here, the current state of the art is reviewed and approaches are illustrated with virtual datasets.

Inhibition of nitric oxide-induced nuclear localization of CAPON by NMDA receptor antagonist in cultured rat primary astrocytes

Astrocytes play a key role in regulating aspects of inflammation in the central nervous system. It was observed that nNOS had located in the nucleus of cultured cerebral cortical astrocytes of 7 days. In the present study, we found that carboxy-terminal PDZ ligand of nNOS (CAPON) mainly located in the nucleus of astrocytes stimulated with NO donor sodium nitroprusside (SNP) or GSNO or N-methyl-d-aspartate (NMDA) receptor agonist-NMDA. However, originally, it was localized mostly in the cytoplasm of normal astrocytes. Immunocytochemistry showed that nNOS was co-localized with CAPON in the nucleus of astrocytes stimulated with SNP. In addition to the nuclear localization, treatment with SNP increased the mRNA and protein expression of CAPON. When SNP was removed from media, CAPON accumulated in nucleus transported back to cytoplasm. MK801, an inhibitor of NMDA receptor, was able to reverse the nuclear localization of CAPON resulted from SNP, suggesting that there is a functional relationship of NO with NMDA receptor in the regulation of the nuclear localization of CAPON. These findings provide a new insight in the understanding of the physical and pathological significances of CAPON/nNOS/NMDA receptor.

Developments in cell biology for quantitative immunoelectron microscopy based on thin sections: a review

Quantitative immunoelectron microscopy uses ultrathin sections and gold particle labelling to determine distributions of molecules across cell compartments. Here, we review a portfolio of new methods for comparing labelling distributions between different compartments in one study group (method 1) and between the same compartments in two or more groups (method 2). Specimen samples are selected unbiasedly and then observed and expected distributions of gold particles are estimated and compared by appropriate statistical procedures. The methods can be used to analyse gold label distributed between volume-occupying (organelle) and surface-occupying (membrane) compartments, but in method 1, membranes must be treated as organelles. With method 1, gold counts are combined with stereological estimators of compartment size to determine labelling density (LD). For volume-occupiers, LD can be expressed simply as golds per test point and, for surface-occupiers, as golds per test line intersection. Expected distributions are generated by randomly assigning gold particles to compartments and expressing observed/expected counts as a relative labelling index (RLI). Preferentially-labelled compartments are identified from their RLI values and by Chi-squared analysis of observed and expected distributions. For method 2, the raw gold particle counts distributed between compartments are simply compared across groups by contingency table and Chi-squared analysis. This identifies the main compartments responsible for the differences between group distributions. Finally, we discuss labelling efficiency (the number of gold particles per target molecule) and describe how it can be estimated for volume- or surface-occupiers by combining stereological data with biochemical determinations.