[Degradation of proteins by ubiquitin proteasome pathway]. / Degradace proteinu ubikvitinproteazomovou dráhou.

All intracellular and some extracellular proteins are continually degraded and replaced by synthesis of new proteins. Both these processes need to stay in equilibrium since their balance may lead to emergence of diseases. Cells contain many proteolytic systems that ensure highly specific and controlled degradation of proteins. One of these systems is the proteasome, a very complex molecular engine allowing degradation of proteins conjugated to ubiquitin. Since the first isolation of proteasome in 1968, many details about its function have been uncovered. In 2004, Nobel Prize for chemistry was awarded for these discoveries. In our review article, we aimed to summarize information about the mechanism of highly selective degradation of proteins by the ubiquitin proteasome pathway. Individual parts of the paper summarize current knowledge about highly selective degradation of proteins by the ubiquitin proteasome system, mechanisms of protein degradation regulation and bio-logical effects of proteasome inhibitors.

[Comparative plasma proteomic analysis of patients with multiple myeloma treated with bortezomib-based regimens]. / Srovnávací proteomická analýza krevní plazmy pacientu s mnohocetným myelomem lécených rezimy s bortezomibem.

BACKGROUNDS: Recently, the term biomarker has become, especially in connection with the term clinical proteomics, one of the most frequent terms in the field of biomedical research. The aim of this work was to select an appropriate pre-fractionation method of blood plasma prior to a subsequent proteomic analysis of low-abundant fraction of proteins by two dimensional gel electrophoresis (2-DE) and mass spectrometry to improve the resolution of 2-DE maps and protein identification. MATERIALS AND METHODS: First, we compared two prefractionation methods (MARS versus ProteoMiner) preceding 2-DE analysis using 10 blood plasma samples. Based on the results of the comparative experiments, low-abundant plasma protein fractions from 18 multiple myeloma patients treated with bortezomib were analyzed. Patients were divided into two groups: a group resistant to chemotherapy (9 patients--disease progression, stable disease) and a group with positive clinical response (9 patients--complete and partial remission). RESULTS AND CONCLUSION: Samples prefractioned by ProteoMiner method yielded 2-DE maps with a significantly increased number of detected protein spots, as compared to immunodepletion method MARS (Multiple Affinity Removal System). Between groups of chemoresistant and sensitive patients treated with bortezomib, 15 differently intense spots were revealed by image analysis. These spots were found to correspond to 10 proteins, as confirmed by mass spectrometry. Seven proteins had significantly lower protein level in the group of chemosensitive patients (serum amyloid P, fibrinogen--gamma chain, retinol-binding protein 4, complement factor C4-A, apolipoprotein E, carboxypeptidase N and complement factor H-related protein 1) and 3 proteins showed significantly higher levels of protein (or were only detected) in the group of chemosensitive patients (serum paraoxonase 1, alpha-1-antitrypsin and complement factor B).

Sample processing and methodological pitfalls in multiple myeloma research.

In this paper, initial processing of biological material, cell separation algorithms and other procedures are discussed. For samples with initial infiltration of plasma cells > 5%, CD138 MicroBeads and Auto-Magnetic-Activated Cell Sorting program are used. Fluorescence-Activated Cell Sorting is used exclusively for cell populations with low-abundance; these samples are detected using fluorescently labeled antibodies only. Isolated plasma cells are further processed for molecular biological studies, for cytogenetics and protein analyses. Furthermore, this work examines the pitfalls of research related to multiple myeloma; some of them we have overcome, while the others are still problematic.

Impact of nestin analysis in multiple myeloma.

Nestin, a marker of multipotent precursor cells, is an important dynamic structure; its polymerization/depolymerization influences intracellular signaling and participates in key cell processes such as proliferation, migration and cell survival. It is presumed that nestin plays a central role in carcinogenesis. It is suggested that nestin might be a suitable diagnostic and prognostic indicator of malignancy and a potential marker of cancer stem cells. Unexpectedly, nestin has been identified in mature CD138+CD38+ plasma cells (PC) of multiple myeloma patients (MM). Expression of nestin, a marker of stem/progenitor cells, in malignant PC, that are considered to be terminally differentiated, indicates that nestin might play a unique role in pathology of MM.

Optimization of immunomagnetic selection of myeloma cells from bone marrow using magnetic activated cell sorting.

Plasma cells (PCs) enrichment from bone marrow samples of multiple myeloma (MM) patients is frequently performed by immunomagnetic separation (magnetic activated cell sorting, MACS) using anti-CD138 MicroBeads. The aim of our work was to find optimal strategy for immunomagnetic separation of PCs and determine optimal algorithm of separation techniques for samples with various percentage of neoplastic cells. From 2007 to 2008, selection of PCs using separation programs Possels and Posseld(2) was carried out on 234 bone marrow samples obtained from 208 MM patients. In 2008, an optimal algorithm for separation programs was introduced based on the analysis of the previous experiments. The Possels program is applicable for samples with >10% PCs in the mononuclear fraction, while the Posseld(2) program is used for samples with 5-10% PCs in the mononuclear fraction. Median purity of 92.6% for the positive fraction of cells (range 14.5-99.6%) and median recovery of 60.4% (range 25.7-99.5%) were obtained when the Possels program was applied (n = 45). A total of 80% (36/45) of processed samples had purity of >70%. Median purity for the positive fraction of 83.7% (range 14.3-99.7%) and median recovery of 14.3% (range 3.6-50.0%) were achieved using the Posseld(2) program (n = 99). A total of 68% (67/99) of processed samples reached >70% purity. This separation strategy enabled us to obtain sufficient amounts of highly purified PCs required for subsequent research purposes. The MACS method has been unsuccessful if the percentage of PCs in the initial sample was <5%. These samples were processed by fluorescence activated cell sorting (FACS).

Cardiac remodeling and MMPs on the model of chronic daunorubicin-induced cardiomyopathy in rabbits.

The matrix metalloproteinases (MMPs) play a key role during cardiac remodeling. The aim of the study was to investigate the changes in collagenous proteins and MMPs in the model of non-ischemic, anthracycline-induced chronic cardiomyopathy in rabbits using both biochemical and histological approaches. The study was carried out in three groups of Chinchilla male rabbits: 1) daunorubicin (3 mg/kg, once weekly for 10 weeks), 2) control (saline in the same schedule), 3) daunorubicin with the cardioprotectant dexrazoxane (60 mg/kg, before each daunorubicin). Morphological changes in the myocardium of daunorubicin-treated animals were characterized by focal myocardial interstitial fibrosis of different intensity. The subsequent proliferation of the fibrotic tissue was marked by an increased content of both collagen types I and III, which resulted in their typical coexpression in the majority of bundles of fibers forming either smaller or larger scars. Biochemical analysis showed a significantly increased concentration of hydroxyproline, mainly in the pepsin-insoluble fraction of collagenous proteins, in the daunorubicin-treated group (1.42+/-0.12 mg/g) as compared with the control (1.03+/-0.04 mg/g) and dexrazoxane (1.07+/-0.07 mg/g) groups. Dexrazoxane co-administration remarkably reduced the cardiotoxic effects of daunorubicin to the extent comparable with the controls in all evaluated parameters. Using zymography, it was possible to detect only a gelatinolytic band corresponding to MMP-2 (MMP-9 activity was not detectable). However, no significant changes in MMP-2 activity were determined between individual groups. Immunohistochemical analysis revealed increased MMP-2 expression in both cardiomyocytes and fibroblasts. Thus, this study has revealed specific alterations in the collagen network in chronic anthracycline cardiotoxicity in relationship to the expression and activity of major MMPs.

Regression of left ventricular hypertrophy and aortic remodelling in NO-deficient hypertensive rats: effect of L-arginine and spironolactone.

AIM: We investigated, whether the substrate for nitric oxide (NO) formation -L-arginine - and the aldosterone receptor antagonist - spironolactone - are able to reverse alterations of the left ventricle (LV) and aorta in N(omega)-nitro-L-arginine methyl ester (L-NAME)-induced hypertension. METHODS: Six groups of male adult Wistar rats were investigated: controls after 4 and 7 weeks of experiment, rats treated with L-NAME for 4 weeks and three recovery groups: spontaneous-reversion (4 weeks L-NAME + 3 weeks placebo), spironolactone-induced reversion (4 weeks L-NAME + 3 weeks spironolactone) and L-arginine-induced reversion (4 weeks L-NAME+ 3 weeks L-arginine). Blood pressure was measured by tail-cuff plethysmography. Relative weight of the LV, myocardial fibrosis (based upon histomorphometry and hydroxyproline determination) and conjugated dienes in the LV and aortic cross-sectional area, inner diameter and wall thickness were determined. NO-synthase activity was investigated in the LV and aorta. RESULTS: L-NAME administration induced hypertension, left ventricular hypertrophy (LVH), LV fibrosis, aortic thickening and diminution of NO-synthase activity in the LV and aorta. Reduction in blood pressure and regression of LVH were observed in all recovery groups, yet reduction in LV fibrosis and aortic thickening were not. NO-synthase activity was restored only in the L-arginine and spironolactone group. CONCLUSION: In our study, the reversion of hypertension and LVH was not dependent on the restoration of NO-synthase activity. Moreover, LV fibrosis and aortic remodelling seem to be more resistant to conditions resulting in regression of LVH. Preserved level of fibrosis in the initial period of LVH regression might result in loss of structural homogeneity and possible functional alterations of the LV.

Spontaneous, L-arginine-induced and spironolactone-induced regression of protein remodeling of the left ventricle in L-NAME-induced hypertension.

N(G)-nitro-L-arginine-methyl ester (L-NAME)-induced hypertension is associated with protein remodeling of the left ventricle. The aim of the study was to show, whether aldosterone receptor blocker spironolactone and precursor of NO-production L-arginine were able to reverse the protein rebuilding of the left ventricle. Six groups of male Wistar rats were investigated: control 4 (4 weeks placebo), L-NAME (4 weeks L-NAME), spontaneous-regression (4 weeks L-NAME + 3 weeks placebo), spironolactone-regression (4 weeks L-NAME + 3 weeks spironolactone), L-arginine-regression (4 weeks L-NAME + 3 weeks arginine), control 7 (7 weeks placebo). L-NAME administration induced hypertension, hypertrophy of the left ventricle (LV), and the increase of metabolic and contractile as well as soluble and insoluble collagenous protein concentration. The systolic blood pressure and relative weight of the LV decreased in all three groups with regression, while the most prominent attenuation of the LVH was observed after spironolactone treatment. In the spontaneous-regression and L-arginine-regression groups the concentrations of individual proteins were not significantly different from the control value. However, in the spironolactone-regression group the concentration of metabolic, contractile and insoluble collagenous proteins remained significantly increased in comparison with the control group. The persistence of the increased protein concentration in the spironolactone group may be related to the more prominent reduction of myocardial water content by spironolactone.

Evaluation of ECG time intervals in a rabbit model of anthracycline-induced cardiomyopathy: a useful tool for assessment of cardioprotective agents.

The aim of this study was to analyze the ECG time intervals in the course of the development of chronic anthracycline cardiomyopathy in rabbits. Furthermore, this approach was employed to study the effects of a model cardioprotective drug (dexrazoxane) and two novel iron chelating compounds--salicylaldehyde isonicotinoyl hydrazone (SIH) and pyridoxal 2-chlorobenzoyl hydrazone (o-108). Repeated daunorubicin administration induced a significant and progressive prolongation of the QRS complex commencing with the eighth week of administration. At the end of the study, we identified a significant correlation between QRS duration and the contractility index dP/dt(max) (r = -0.81; P<0.001) as well as with the plasma concentrations of cardiac troponin T (r = 0.78; P<0.001). In contrast, no alterations in ECG time intervals were revealed in the groups co-treated with either dexrazoxane or both novel cardioprotective drugs (SIH, o-108). Hence, in this study, the QRS duration is for the first time shown as a parameter suitable for the non-invasive evaluation of the anthracycline cardiotoxicity and cardioprotective effects of both well established and investigated drugs. Moreover, our results strongly suggest that novel iron chelators (SIH and o-108) merit further study as promising cardioprotective drugs against anthracycline cardiotoxicity.

Early detection of anthracycline cardiotoxicity in a rabbit model: left ventricle filling pattern versus troponin T determination.

Anthracycline cardiotoxicity represents a serious risk of anticancer chemotherapy. The aim of the present pilot study was to compare the potential of both the left ventricular (LV) filling pattern evaluation and cardiac troponin T (cTnT) plasma levels determination for the early detection of daunorubicin-induced cardiotoxicity in rabbits. The echocardiographic measurements of transmitral LV inflow as well as cTnT determinations were performed weekly for 10 weeks in daunorubicin (3 mg/kg weekly) and control groups (n=5, each). Surprisingly, no significant changes in LV-filling pattern were observed through the study, most likely due to the xylazine-containing anesthesia, necessary for appropriate resolving of the E and A waves. In contrast to the echographic measurement, the dP/dt(min) index obtained invasively at the end of the study revealed a significant impairment in LV relaxation, which was further supported by observed disturbances in myocardial collagen content and calcium homeostasis. However, at the same time cTnT plasma levels were progressively rising in the daunorubicin-treated animals from the fifth week (0.024+/-0.008 microg/l) until the end of the experiment (0.186+/-0.055 microg/l). Therefore, in contrast to complicated non-invasive evaluation of diastolic function, cTnT is shown to be an early and sensitive marker of anthracycline-induced cardiotoxicity in the rabbit model.