Circulating proteasome levels are an independent prognostic factor for survival in multiple myeloma

Functional and quantitative evaluation of the 20S proteasome in serum and intracellular in145 moroccan patients with hematologic malignancies

BACKGROUND

Regulatory degradation of intracellular proteins plays an essential role in most biological processes, particularly in the control of cell proliferation and differentiation. In eukaryotes, intracellular proteolysis is largely provided by the Ubiquitin / Proteasome system. Alterations and dysfunction of protein degradation by the Ubiquitin / Proteasome system, such as transcription factors, cell cycle regulators or tumor suppressor proteins, have been linked to human. Pathologies, including blood cancers. Mainly localized in the nucleus and cytoplasm of cells, the proteasome can be detected in the cell culture supernatant or in the peripheral blood of patients. This study deals with the problems of the search for serum markers specific to certain pathologies and which would be useful in the prevention, diagnosis and monitoring of cancers and which could be used as a therapeutic tool.

METHODS

The functional and quantitative analysis of the proteasome is carried out at the serum and subcellular level during a pathological phenomenon in a population of 145 Moroccan patients (sex ratio: 1.10 / average age: 47.9 ± 15, 3 years) using an indirect ELISA test and a follow-up of the fluorescence emitted after enzymatic digestion of specific peptides by proteolytic activity (chymotrypsin-like).

RESULTS

The evolutionary trend proteasome subcellular is significantly linked to the rate of chymotrypsin-like activity. The entire population of 60 patients called back for a second blood test. After three months of treatment reported a significant drop in the rate and the activity of the proteasome in serum and intracellular level.

CONCLUSIONS

Although the serum proteasome level is a potential new tool for the monitoring of. Patientswithliquid cancer.

TRIAL REGISTRATION

retrospectively registered.

Extracellular Vesicles in Multiple Myeloma-Cracking the Code to a Better Understanding of the Disease

Multiple myeloma (MM) is a plasma cell-derived malignancy that stands for around 1.5% of newly discovered cancer cases. Despite constantly improving treatment methods, the disease is incurable with over 13,000 deaths in the US and over 30,000 in Europe. Recent studies suggest that extracellular vesicles (EVs) might play a significant role in the pathogenesis and evolution of MM. Further investigation of their role could prove to be beneficial in establishing new therapies and hence, improve the prognosis of MM patients. What is more, EVs might serve as novel markers in diagnosing and monitoring the disease. Great advancements concerning the position of EVs in the pathophysiology of MM have recently been shown in research and in this review, we would like to delve into the still expanding state of knowledge.

UCHL1 and Proteasome in Blood Serum in Relation to Dietary Habits, Concentration of Selected Antioxidant Minerals and Total Antioxidant Status among Patients with Alzheimer's Disease

Alzheimer's disease (AD) is an incurable neurodegenerative disease. It is the most common form of dementia among the elderly population. So far, no effective methods of its treatment have been found. Research to better understand the mechanism of pathology may provide new methods for early diagnosis. This, in turn, could enable early intervention that could slow or halt disease progression and improve patients' quality of life. Therefore, minimally invasive markers, including serum-based markers, are being sought to improve the diagnosis of AD. One of the important markers may be the concentration of UCHL1 and the proteasome in the blood serum. Their concentration can be affected by many factors, including eating habits. This study was conducted in 110 patients with early or moderate AD, with a mean age of 78.0 ± 8.1 years. The patients were under the care of the Podlasie Center of Psychogeriatrics and the Department of Neurology (Medical University of Białystok, Poland). The control group consisted of 60 healthy volunteers, matched for gender and age. The concentration of UCHL1 and the 20S proteasome subunit were measured by surface plasmon resonance imaging (SPRI). In addition, a nutritional interview was conducted with patients with AD, which assessed the frequency of consumption of 36 groups of products. In the group of patients with AD, compared to the control group, we showed a significantly higher concentration of UCHL1 (56.05 vs. 7.98 ng/mL) and the proteasome (13.02 vs. 5.72 µg/mL). Moreover, we found a low negative correlation between UCHL1 and the proteasome in the control group, and positive in the AD group. The analysis of eating habits showed that the consumption of selected groups of products may affect the concentration of the tested components, and therefore may have a protective effect on AD.

Carfilzomib: A Promising Proteasome Inhibitor for the Treatment of Relapsed and Refractory Multiple Myeloma

The proteasome is crucial for the degradation of intracellular proteins and plays an important role in mediating a number of cell survival and progression events by controlling the levels of key regulatory proteins such as cyclins and caspases in both normal and tumor cells. However, compared to normal cells, cancer cells are more dependent on the ubiquitin proteasome pathway (UPP) due to the accumulation of proteins in response to uncontrolled gene transcription, allowing proteasome to become a potent therapeutic target for human cancers such as multiple myeloma (MM). Up to date, three proteasome inhibitors namely bortezomib (2003), carfilzomib (2012) and ixazomib (2015) have been approved by the US Food and Drug Administration (FDA) for the treatment of patients with relapsed and/or refractory MM. This review mainly focuses on the biochemical properties, mechanism of action, toxicity profile and pivotal clinical trials related to carfilzomib, a second-generation proteasome inhibitor that binds irreversibly with proteasome to overcome the major toxicities and resistance associated with bortezomib.

Concept and application of circulating proteasomes

Proteostasis is primarily a function of protein synthesis and degradation. Although the components and processes involved in intracellular proteostasis have been studied extensively, it is apparent that extracellular proteostasis is equitably crucial for the viability of organisms. The 26S proteasome, a unique ATP-dependent proteolytic complex in eukaryotic cells, contributes to the majority of intracellular proteolysis. Accumulating evidence suggests the presence of intact 20S proteasomes in the circulatory system (c-proteasomes), and similar to other plasma proteins, the levels of these c-proteasomes may vary, potentially reflecting specific pathophysiological conditions. Under normal conditions, the concentration of c-proteasomes has been reported to be in the range of ~0.2-2 μg/mL, which is ~2-4-fold lower than that of functional plasma proteins but markedly higher than that of signaling proteins. The characterization of c-proteasomes, such as their origin, structure, role, and clearance, has been delayed mainly due to technical limitations. In this review, we summarize the current perspectives pertaining to c-proteasomes, focusing on the methodology, including our experimental understanding. We believe that once the pathological relevance of c-proteasomes is revealed, these unique components may be utilized in the diagnosis and prognosis of diverse human diseases.

Proteasome Activity in the Plasma as a Novel Biomarker in Mild Cognitive Impairment with Chronic Tinnitus

BACKGROUND

Although the existence of proteasomes in human blood, termed circulating proteasomes (c-proteasomes), has been reported previously, their origin and pathophysiological functions remain largely unknown.

OBJECTIVE

Given that c-proteasome activity was significantly reduced in Alzheimer's disease model mice and relatively high frequency of mild cognitive impairment (MCI) is accompanied by chronic tinnitus in aged patients, we examined whether c-proteasome activity in human plasma was associated with cognitive function in patients with chronic tinnitus.

METHODS

c-Proteasome activity in the plasma of tinnitus patients (N = 55) was measured with fluorogenic reporter substrate, suc-LLVY-AMC. To assess MCI, the Montreal Cognitive Assessment was conducted with a cut-off score of 22/23. All patients underwent audiological and psychoacoustic analyses. Levels of c-proteasomes, Aβ42, and Aβ40 were measured using ELISA, and their association with c-proteasome activity was evaluated.

RESULTS

The activity of circulating proteasomes was significantly lower in patients with chronic tinnitus and MCI (p = 0.042), whereas activities of other plasma enzymes showed little correlation. In addition, c-proteasome activity was negatively associated with the level of plasma Aβ and was directly dependent on its own concentration in the plasma of patients with chronic tinnitus.

CONCLUSION

Our current work provides a new perspective for understanding the potential relationship between circulating proteasomes in the plasma and cognitive dysfunction, suggesting a novel, non-invasive biomarker in the context of MCI diagnosis.

Beyond cells: The extracellular circulating 20S proteasomes

Accumulating evidence arising from numerous clinical studies indicate that assembled and functional 20S proteasome complexes circulate freely in plasma. Elevated levels of this core proteolytic complex have been found in the plasma of patients suffering from blood, skin and solid cancers, autoimmune disorders, trauma and sepsis. Moreover, in various diseases, there is a positive correlation between circulating 20S proteasome (c20S) levels and treatment efficacy and survival rates, suggesting the involvement of this under-studied c20S complex in pathophysiology. However, many aspects of this system remain enigmatic, as we still do not know the origin, biological role or mechanisms of extracellular transport and regulation of c20S proteasomes. In this review, we provide an overview of the current understanding of the c20S proteasome system and discuss the remaining gaps in knowledge.

Serum 20S proteasome levels are associated with disease activity in MPO-ANCA-associated microscopic polyangiitis

Background

Proteasomes are found in both the cell nucleus and cytoplasm and play a major role in the ubiquitin-dependent and -independent non-lysosomal pathways of intracellular protein degradation. Proteasomes are also involved in the turnover of various regulatory proteins, antigen processing, cell differentiation, and apoptosis. To determine the diagnostic value of serum proteasome in antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV), we investigated patients with AAV at various stages of the disease.

Methods

Serum 20S-proteasome was measured by ELISA in 44 patients with MPO-ANCA-associated microscopic polyangiitis (MPA) and renal involvement. Thirty of the patients provided serum samples before the initial treatment, and 30 provided samples during remission; 16 provided samples at both time points.

Results

The mean serum 20S-proteasome level was significantly higher in the active-vasculitis patients (3414.6 ± 2738.9 ng/mL; n = 30) compared to the inactive-vasculitis patients (366.4 ± 128.4 ng/mL; n = 30; p <  0.0001) and 40 controls (234.9 ± 90.1 ng/mL; p <  0.0001). There were significant positive correlations between the serum 20S-proteasome level and the Birmingham Vasculitis Activity Score (BVAS) (r = 0.581, p <  0.0001), the ANCA titer (r = 0.384, p <  0.0001), the white blood cell (WBC) count (r = 0.284, p = 0.0042), the platelet count (r = 0.369, p = 0.0002), and the serum C-reactive protein (CRP) level (r = 0.550, p < 0.0001). There were significant negative correlations between the serum 20S-proteasome level and both the hemoglobin concentration (r = - 0.351, p = 0.0003) and the serum albumin level (r = - 0.460, p < 0.0001). In a multiple regression analysis, there was a significant positive correlation between the serum 20S-proteasome level and only the BVAS results (β = 0.851, p = 0.0009). In a receiver operating curve analysis, the area under the curve for the serum 20S-proteasome level was 0.996, which is higher than those of the WBC count (0.738) and the serum CRP level (0.963).

Conclusion

The serum level of 20S-proteasome may be a useful marker for disease activity in AAV.

Circulating 20S proteasome for assessing protein energy wasting syndrome in hemodialysis patients

Protein energy wasting (PEW) including muscle atrophy is a common complication in chronic hemodialysis patients. The ubiquitin proteasome system (UPS) is the main proteolytic system causing muscle atrophy in chronic kidney disease and proteasome 20S is the catalytic component of the UPS. Circulating proteasome 20S (c20S proteasome) is present in the blood and its level is related to disease severity and prognosis in several disorders. We hypothesized that c20S proteasome could be related with muscle mass, other PEW criteria and their evolution in hemodialysis patients. Stable hemodialysis patients treated at our center for more than 3 months were followed over 2 years. C20S proteasome assay was performed at baseline. Biological and clinical data were collected, muscle mass was assessed by multi-frequency bio-impedancemetry, and nutritional scores were calculated at baseline, 1 year and 2 years. Hospitalizations and mortality data were collected over the 2 years. Forty-nine patients were included. At baseline, the c20S proteasome level was 0.40[0.26–0.55] μg/ml. Low muscle mass as defined by a lean tissue index (LTI) < 10th in accordance with the International Society of Renal Nutrition and Metabolism guidelines was observed in 36% and PEW in 62%. Increased c20S proteasome levels were related with LTI at baseline (R = 0.43, p = 0.004) and with its 2 year-variation (R = -0.56, p = 0.003). Two-year survival rate was not different between higher and lower c20S proteasome values (78.9 vs 78.4%, p = 0.98 log-rank test). C20S proteasome is not a good marker for assessing nutritional status in hemodialysis patients and predicting patient outcomes.

Post-Translational Modifications of Extracellular Proteasome

The ubiquitin-proteasome system (UPS) is one of the major protein degradation pathways in eukaryotic cells. Abnormal functioning of this system has been observed in cancer and neurological diseases. The 20S proteasomes, essential components of the UPS, are present not only within the cells but also in the extracellular space, and their concentration in blood plasma has been found to be elevated and dependent upon the disease state, being of prognostic significance in patients suffering from cancer, liver diseases, and autoimmune diseases. However, functions of extracellular proteasomes and mechanisms of their release by cells remain largely unknown. The main mechanism of proteasome activity regulation is provided by modulation of their composition and post-translational modifications (PTMs). Moreover, diverse PTMs of proteins are known to participate in the loading of specific elements into extracellular vesicles. Since previous studies have revealed that the transport of extracellular proteasomes may occur via extracellular vesicles, we have set out to explore the PTMs of extracellular proteasomes in comparison to cellular counterparts. In this work, cellular and extracellular proteasomes were affinity purified and separated by SDS-PAGE for subsequent trypsinization and matrix-assisted laser desorption/ionization (MALDI) Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry (MS) analysis. In total, we could identify 64 and 55 PTM sites in extracellular and cellular proteasomes, respectively, including phosphorylation, ubiquitination, acetylation, and succinylation. We observed novel sites of acetylation at K238 and K192 of the proteasome subunits β2 and β3, respectively, that are specific for extracellular proteasomes. Moreover, cellular proteasomes show specific acetylation at K227 of α2 and ubiquitination at K201 of β3. Interestingly, succinylation of β6 at the residue K228 seems not to be present exclusively in extracellular proteasomes, whereas both extracellular and cellular proteasomes may also be acetylated at this site. The same situation takes place at K201 of the β3 subunit where ubiquitination is seemingly specific for cellular proteasomes. Moreover, crosstalk between acetylation, ubiquitination, and succinylation has been observed in the subunit α3 of both proteasome populations. These data will serve as a basis for further studies, aimed at dissection of the roles of extracellular proteasome-specific PTMs in terms of the function of these proteasomes and mechanism of their transport into extracellular space.

Targeting Ubiquitin-Proteasome Pathway by Natural Products: Novel Therapeutic Strategy for Treatment of Neurodegenerative Diseases

Misfolded proteins are the main common feature of neurodegenerative diseases, thereby, normal proteostasis is an important mechanism to regulate the neural survival and the central nervous system functionality. The ubiquitin-proteasome system (UPS) is a non-lysosomal proteolytic pathway involved in numerous normal functions of the nervous system, modulation of neurotransmitter release, synaptic plasticity, and recycling of membrane receptors or degradation of damaged and regulatory intracellular proteins. Aberrant accumulation of intracellular ubiquitin-positive inclusions has been implicated to a variety of neurodegenerative disorders such as Alzheimer's disease (AD), Parkinson's disease (PD), Huntington disease (HD), Amyotrophic Lateral Sclerosis (ALS), and Multiple Myeloma (MM). Genetic mutation in deubiquitinating enzyme could disrupt UPS and results in destructive effects on neuron survival. To date, various agents were characterized with proteasome-inhibitory potential. Proteins of the ubiquitin-proteasome system, and in particular, E3 ubiquitin ligases, may be promising molecular targets for neurodegenerative drug discovery. Phytochemicals, specifically polyphenols (PPs), were reported to act as proteasome-inhibitors or may modulate the proteasome activity. PPs modify the UPS by means of accumulation of ubiquitinated proteins, suppression of neuronal apoptosis, reduction of neurotoxicity, and improvement of synaptic plasticity and transmission. This is the first comprehensive review on the effect of PPs on UPS. Here, we review the recent findings describing various aspects of UPS dysregulation in neurodegenerative disorders. This review attempts to summarize the latest reports on the neuroprotective properties involved in the proper functioning of natural polyphenolic compounds with implication for targeting ubiquitin-proteasome pathway in the neurodegenerative diseases. We highlight the evidence suggesting that polyphenolic compounds have a dose and disorder dependent effects in improving neurological dysfunctions, and so their mechanism of action could stimulate the UPS, induce the protein degradation or inhibit UPS and reduce protein degradation. Future studies should focus on molecular mechanisms by which PPs can interfere this complex regulatory system at specific stages of the disease development and progression.

A Translational Physiologically Based Pharmacokinetics/Pharmacodynamics Framework of Target-Mediated Disposition, Target Inhibition and Drug-Drug Interactions of Bortezomib

Bortezomib is a potent 20S proteasome inhibitor approved for the treatment of multiple myeloma and mantle cell lymphoma. Despite the extensive clinical use of bortezomib, the mechanism of the complex time-dependent pharmacokinetics of bortezomib has not been fully investigated in context of its pharmacodynamics (PD) and drug-drug interaction (DDI) profiles. Here, we aimed to develop a mechanistic physiologically based (PB) PK/PD model to project PK, blood target inhibition and DDI of bortezomib in patients. A minimal PBPK/PD model consisting of six compartments was constructed using a bottom-up approach with pre-clinical data and human physiological parameters. Specifically, the target-mediated drug disposition (TMDD) of bortezomib in red blood cells (RBC), which determines target inhibition in blood, was characterized by incorporating the proteasome binding affinity of bortezomib and the proteasome concentration in RBC. The hepatic clearance and fraction metabolized by different CYP isoforms were estimated from in vitro metabolism and phenotyping experiments. The established model adequately characterized the multi-exponential and time-dependent plasma pharmacokinetics, target binding and blood proteasome inhibition of bortezomib. Further, the model was able to accurately predict the impact of a strong CYP3A inducer (rifampicin) and inhibitor (ketoconazole) on bortezomib exposure. In conclusion, the mechanistic PBPK/PD model successfully described the complex pharmacokinetics, target inhibition and DDIs of bortezomib in patients. This study illustrates the importance of incorporating target biology, drug-target interactions and in vitro clearance parameters into mechanistic PBPK/PD models and the utility of such models for pharmacokinetic, pharmacodynamic and DDI predictions.

A Peptidomimetic Fluorescent Probe to Detect the Trypsin β2 Subunit of the Human 20S Proteasome

This work describes the chemical synthesis, combinatorial selection, and enzymatic evaluation of peptidomimetic fluorescent substrates specific for the trypsin-like (β2) subunit of the 20S human proteasome. After deconvolution of a library comprising nearly 6000 compounds composed of peg substituted diaminopropionic acid DAPEG building blocks, the sequence ABZ–Dap(O2(Cbz))–Dap(GO1)–Dap(O2(Cbz))–Arg–ANB–NH₂, where ABZ is 2-aminobenzoic acid, and ANB- 5 amino 2- nitro benzoic acid was selected. Its cleavage followed sigmoidal kinetics, characteristic for allosteric enzymes, with K_m = 3.22 ± 0.02 μM, k_cat = 245 s⁻¹, and k_cat/K_m = 7.61 × 10⁷ M⁻¹ s⁻¹. This process was practically halted when a selective inhibitor of the β2 subunit of the 20S human proteasome was supplemented to the reaction system. Titration of the substrate resulting in decreased amounts of proteasome 20S produced a linear signal up to 10⁻¹¹ M. Using this substrate, we detected human proteasome 20S in human urine samples taken from the bladders of cancer patients. This observation could be useful for the noninvasive diagnosis of this severe disease.

Population-based meta-analysis of bortezomib exposure-response relationships in multiple myeloma patients

Bortezomib (Velcade®) is a reversible proteasome inhibitor that shows potent antineoplastic activity, by inhibiting the constitutively increased proteasome activity in myeloma cells, and is approved as a first-line therapy for multiple myeloma (MM). Although clinically successful, bortezomib exhibits a relatively narrow therapeutic index and can induce dose-limiting toxicities such as thrombocytopenia. This study aims to develop a quantitative and predictive pharmacodynamic model to investigate bortezomib dosing-regimens in a rational and efficient manner. Mean temporal profiles of bortezomib pharmacokinetics, proteasome activity, M-protein concentrations, and platelet counts following bortezomib monotherapy were extracted from published clinical studies. A population-based meta-analysis of bortezomib anti-myeloma activity and thrombocytopenia was conducted sequentially with a Stochastic Approximation Expectation Maximization algorithm in Monolix. The final pharmacodynamic model integrates drug-target interactions and cell signaling dynamics with temporal biomarkers of clinical efficacy and toxicity. Bortezomib pharmacokinetics, disease progression, and platelet dynamic profiles were well characterized in MM patients, and a local sensitivity analysis of the final model suggests that increased proteasome concentration could ultimately attenuate bortezomib antineoplastic activity in MM patients. In addition, model simulations confirm that a once-weekly dosing schedule represents an optimal therapeutic regimen with comparable antineoplastic activity but significantly reduced risk of thrombocytopenia. In conclusion, a pharmacodynamic model was successfully developed, which provides a quantitative, mechanism-based platform for probing bortezomib dosing-regimens. Further research is needed to determine whether this model could be used to individualize bortezomib regimens to maximize antineoplastic efficacy and minimize thrombocytopenia during MM treatment.

Genes related to maintenance of autophagy and successful aging

Considering aging as a phenomenon in which there is a decline in essential processes for cell survival, we investigated the autophagic and proteasome pathways in three different groups: young, older and oldest old male adults. The expression profile of autophagic pathway-related genes was carried out in peripheral blood, and the proteasome quantification was performed in plasma. No significant changes were found in plasma proteasome concentrations or in correlations between proteasome concentrations and ages. However, some autophagy- and/or apoptosis-related genes were differentially expressed. In addition, the network and enrichment analysis showed an interaction between four of the five differentially expressed genes and an association of these genes with the transcriptional process. Considering that the oldest old individuals maintained both the expression of genes linked to the autophagic machinery, and the proteasome levels, when compared with the older group, we concluded that these factors could be considered crucial for successful aging.

Injury derived autoimmunity: Anti-perlecan/LG3 antibodies in transplantation

Ischemic, immunologic or pharmacological stressors can induce vascular injury and endothelial apoptosis in organ donors, in transplant candidates due to the impact of end stage organ failure on the vasculature, and in association with peri-transplantation events. Vascular injury may shape innate and adaptive immune responses, leading to dysregulation in the balance between tolerance and immunoreactivity to vascular-derived antigens. Mounting evidence shows that the early stages of apoptosis, characterized by the absence of membrane permeabilization, are prone to trigger various modes of intercellular communication allowing neoantigen production, exposure, or both. In this review, we present the evidence for the release of LG3, an immunogenic fragment of perlecan, as a consequence of caspase-3 dependent vascular apoptosis leading to the genesis of anti-LG3 autoantibodies and the consequences of these autoantibodies in native and transplanted kidneys.

Lactacystin: first-in-class proteasome inhibitor still excelling and an exemplar for future antibiotic research

Lactacystin exemplifies the role that serendipity plays in drug discovery and why “finding things without actually looking for them” retains such a pivotal role in the search for the useful properties of chemicals. The first proteasome inhibitor discovered, lactacystin stimulated new possibilities in cancer control. New and innovative uses are regularly being found for lactacystin, including as a model to study dementia, while new formulations and delivery systems may facilitate its use clinically as an anticancer agent. All this provides yet more evidence that we need a comprehensive, collaborative and coordinated programme to fully investigate all new and existing chemical compounds, especially those of microbial origin. We need to do so in order to avoid failing to detect and successfully exploit unsought yet potentially life-saving or extremely advantageous properties of microbial metabolites.

High chymotrypsin-like activity in the plasma of patients with newly diagnosed multiple myeloma treated with bortezomib is predictive of a better response and longer PFS

Proteasome inhibitors (PIs) such as bortezomib constitute an important part of the modern standard therapy for multiple myeloma (MM). In this study, we set out to assess whether proteasome concentration and chymotrypsin-like (ChT-L) activity could serve as potential biomarkers defining the likelihood of response to treatment with bortezomib, in order to identify patients who are more likely to respond to treatment with PI. We analysed proteasome concentration and ChT-L activity in the plasma of 78 patients with newly diagnosed MM during treatment with or without proteasome inhibitors. Values of all the studied parameters in the group of responders decreased sharply from the initial levels already after the third cycle of chemotherapy and remained significantly lower until the end of treatment. On the other hand, in the group of non-responders, there was an increase in the measured proteasome parameters already after the third cycle, and they remained high during the next cycles of therapy. We also showed that high baseline proteasome ChT-L activity values might prognosticate longer progression-free survival (PFS) in patients treated with PI. Our findings demonstrate that measuring plasma proteasome ChT-L activity can be used as a powerful biomarker for predicting clinical response to treatment and PFS in patients with newly diagnosed MM.

Concentration of Proteasome in the Blood Plasma of Children with Acute Appendicitis, Before and After Surgery, and Its Correlation with CRP

OBJECTIVE

The determination of 20S proteasome concentration in the blood plasma of children with appendicitis and its correlation with CRP.

DESIGN AND SETTING

Thirty-one children with acute appendicitis, were randomly included into the study (age 5 years up to 17 years, mean age 11.5 + 1 years).

PARTICIPANTS

There were 17 girls and 14 boys. Eighteen healthy, age-matched subjects, admitted for planned surgeries served as controls. Exclusion criteria were: severe preexisting infections, immunological or cardiovascular diseases that required long-term medication, and complicated cases of appendicitis with perforation of appendix and/or peritonitis.

MAIN OUTCOME MEASURES

The 20S proteasome concentrations in the blood plasma of patients with acute appendicitis were highest before the surgery and were above the range of concentrations measured in controls, and the difference was statistically significant.

RESULTS

The 20S proteasome concentration measured 24 and 72 h after the operation, slowly decreased over time, and still did not reach the normal range, when compared with the concentration measured in controls (p < 0.05).

CONCLUSIONS

20S proteasome concentration may reflect the metabolic response to acute state inflammation, and the process of gradual ebbing of the inflammation. The method of operation-classic open appendectomy, or laparoscopic appendectomy, does not influence the general trend in 20S proteasome concentration.

A specific QSAR model for proteasome inhibitors from Oleaeuropaea and Ficuscarica

Oleaeuropaea and Ficuscarica are widely used in traditional medicine for the treatment of cancer. Therefore, it is of interest to develop a QSAR model for screening proteasome inhibitors from plant source. Hence, a QSAR model was developed using multiple linear regressions; partial least squares regression and principal component regression methods. Results of QSAR modeling and docking demonstrate that compounds derived from both plants have great potentiality to be proteasome inhibitors. The developed QSAR model highlights a strong structure-effect relationship. The predicted correlation of comparative molecular field analysis, and comparative molecular similarity indexes are 0.963 and 0.919, respectively. Computed absorption, distribution, metabolism, excretion and toxicity studies on these derivatives showed encouraging results with very low toxicity, distribution and absorption.

Evaluation of serum insulin-like growth factor-1 and 26S proteasome concentrations in healthy dogs and dogs with chronic diseases depending on body condition score

In patients suffering from chronic diseases, the objective assessment of metabolic states could be of interest for disease prognosis and therapeutic options. Therefore, the aim of this study was to assess insulin-like growth factor-1 (IGF-1) and 26S proteasome (26SP) in healthy dogs and dogs suffering from chronic diseases depending on their body condition score (BCS) and to examine their potential for objective assessment of anabolic and catabolic states. Serum concentrations of IGF-1, an anabolic hormone, and 26SP, a multiprotein complex which is part of the ubiquitin-proteasome pathway, by which the majority of endogenous proteins including the muscle proteins are degraded, were measured in 21 healthy dogs and 20 dogs with chronic diseases by canine ELISA. The concentrations of IGF-1, 26SP and their ratio (IGF-1/26SP) were set in relationship to the BCS of the dogs. When examining healthy and chronically diseased dogs separately, a positive correlation between IGF-1 and the BCS was observed in the healthy group and a negative correlation between 26SP and the BCS was noted in dogs with chronic diseases. Further, dogs suffering from chronic diseases showed higher 26SP concentrations and lower values for IGF-1/26SP than the healthy dogs. Overall, we detected a negative correlation between 26SP and the BCS and a positive correlation between IGF-1/26SP and the BCS. The results of our study indicate usability of IGF-1 for description of anabolic states, while 26SP could be useful for detection and description of catabolic states. Finally, the ratio IGF-1/26SP seems to be promising for assessment of metabolic states.

Proteasome 20S in multiple myeloma: comparison of concentration and chymotrypsin-like activity in plasma and serum

The ubiquitin-proteasome system is relevant in the pathobiology of many haematological malignancies, including multiple myeloma. The assessment of proteasome concentration and chymotrypsin-like (ChT-L) activity might constitute a new approach to diagnosis, prognosis and monitoring of anticancer treatment of patients with haematological malignancies and other diseases. The aim of our study was to determine which material, plasma or serum, is better for measuring chymotrypsin-like (ChT-L) activity and proteasome concentration. We analysed proteasome concentration and chymotrypsin-like (ChT-L) activity in 70 plasma and serum samples drawn from 28 patients at different treatment stages for multiple myeloma (MM) and 31 healthy volunteers. Proteasome ChT-L activity and concentration in multiple myeloma patients were significantly higher in plasma compared to serum. In this group we observed significant and positive correlations both between the plasma and serum proteasome ChT-L activity and plasma and serum proteasome concentration. The higher values of proteasome concentration and ChT-L activity in plasma than in serum and their better correlations with parameters of tumour load and prognosis suggest that plasma constitutes a better biological material for measuring ChT-L activity and proteasome concentration than serum in multiple myeloma patients.

Proteomic analysis of affinity-purified extracellular proteasomes reveals exclusively 20S complexes

Proteasome-mediated proteolysis is important for many basic cellular processes. In addition to their functions in the cell, proteasomes have been found in physiological fluids of both healthy and diseased humans including cancer patients. Higher levels of these proteasomes are associated with higher cancer burden and stage. The etiology and functions of these proteasomes, referred to as circulating, plasmatic, or extracellular proteasomes (ex-PSs), are unclear. Here we show that human cancer cell lines, as well as human endometrium-derived mesenchymal stem cells (hMESCs), release proteasome complexes into culture medium (CM). To define ex-PS composition, we have affinity purified them from CM conditioned by human leukemia cell line K562. Using matrix-assisted laser desorption/ionization (MALDI) Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry (MS), we have identified core 20S proteasome subunits and a set of 15 proteasome-interacting proteins (PIPs), all previously described as exosome cargo proteins. Three of them, PPIase A, aldolase A, and transferrin, have never been reported as PIPs. The study provides compelling arguments that ex-PSs do not contain 19S or PA200 regulatory particles and are represented exclusively by the 20S complex.

Immunoproteasome in the blood plasma of children with acute appendicitis, and its correlation with proteasome and UCHL1 measured by SPR imaging biosensors

The aim of this study was to determinate the immunoproteasome concentration in the blood plasma of children with appendicitis, and its correlation with circulating proteasome and ubiquitin carboxyl-terminal hydrolase L1 (UCHL1). Twenty-seven children with acute appendicitis, managed at the Paediatric Surgery Department, were included randomly into the study (age 2 years 9 months up to 14 years, mean age 9·5 ± 1 years). There were 10 girls and 17 boys; 18 healthy, age-matched subjects, admitted for planned surgeries served as controls. Mean concentrations of immunoproteasome, 20S proteasome and UCHL1 in the blood plasma of children with appendicitis before surgery 24 h and 72 h after the appendectomy were higher than in the control group. The immunoproteasome, 20S proteasome and UCHL1 concentrations in the blood plasma of patients with acute appendicitis were highest before surgery. The immunoproteasome, 20S proteasome and UCHL1 concentration measured 24 and 72 h after the operation decreased slowly over time and still did not reach the normal range (P < 0·05). There was no statistical difference between immunoproteasome, 20S proteasome and UCHL1 concentrations in children operated on laparoscopically and children after classic appendectomy. The immunoproteasome concentration may reflect the metabolic response to acute state inflammation, and the process of gradual ebbing of the inflammation may thus be helpful in the assessment of the efficacy of treatment. The method of operation - classic open appendectomy or laparoscopic appendectomy - does not influence the general trend in immunoproteasome concentration in children with appendicitis.

Proteasome and C-reactive protein inflammatory response in children undergoing shorter and longer lasting laparoscopic cholecystectomy

Operations of varying duration cause the release of a number of inflammatory mediators, in particular cytokines which lead to proteasome and acute-phase reactions. The purpose of this novel human study, was to characterize inflammatory response in children undergoing laparoscopic cholecystectomy, by analyzing changes in selected inflammatory mediators: C-reactive protein concentration and circulating 20S proteasome activity following surgical injury and to correlate them with the duration of the surgical procedure. Plasma C-reactive protein concentration (CRP) was determined by standard biochemical laboratory procedures. Proteasome activity in the plasma of children was assessed using Suc-Leu-Leu-Val-Tyr-AMC peptide substrate. Statistically significant increase in the plasma proteasome activity and C-reactive protein concentration, was noted (p < .05) in children after laparoscopic cholecystectomy. We found the correlation between the 20S proteasome activity and the length of the procedure. In children undergoing longer lasting laparoscopic cholecystectomy the proteasome activity was much higher than in patients having shorter surgical procedure. The CRP concentration and 20S proteasome activity significantly increase after surgery, but only 20S proteasome activity correlate with the length of the surgery. This may confirm that CRP is only an indicator of pathological state, while the function of the proteasomes is more complex because of their participation in the processes of repair and wound healing, and in the removal of damaged proteins.

Pathways towards indolent B-cell lymphoma - Etiology and therapeutic strategies

Although patients with indolent B-cell lymphomas have a relatively good survival rate, conventional chemotherapy is not curative. Disease courses are typically characterized by multiple relapses and progressively shorter response duration with subsequent lines of therapy. There has been an explosion of innovative targeted agents in the past years. This review discusses current knowledge on the etiology of indolent B-cell lymphomas with respect to the role of micro-organisms, auto-immune diseases, and deregulated pathways caused by mutations. In particular, knowledge on the mutational landscape of indolent B-cell lymphomas has strongly increased in recent years and harbors great promise for more accurate decision making in the current wide range of therapeutic options. Despite this promise, only in chronic lymphocytic leukemia the detection of TP53 mutations and/or del17p currently have a direct effect on treatment decisions. Nevertheless, it is expected that in the near future the role of genetic testing will increase for prediction of response to targeted treatment as well as for more accurate prediction of prognosis in indolent B-cell lymphomas.

Secretomic profiling of cells from hollow fiber bioreactor reveals PSMA3 as a potential cholangiocarcinoma biomarker

Cholangiocarcinoma (CCA), derived from the bile duct, occurs with a relatively high incidence in Northeast Thailand. Early diagnosis is still hampered by the lack of sufficient biomarkers. In recent years, biomarker discovery using secretomes has provided interesting results, including our studies on CCA secretomes, especially with three-dimensional cell cultures. Thus, cells cultured using the hollow fiber bioreactor (HFB) with 20 kDa molecular weight cut-off (MWCO) yielded higher quality and quantity of secretomes than those from conditioned media of the monolayer culture (MNC) system. In this study, we employed the HFB culture system with 5 kDa MWCO and compared conditioned media from the HFB and MNC systems using two-dimensional gel electrophoresis, followed by identifying proteins of interest by liquid chromatography and mass spectrometry (LC/MS/MS). Two out of 4 spots of NGAL or lipocalin-2 were found to show highest increase in expression of 19.93-fold and 18.79-fold in HFB compared to MNC. Interestingly, all 14 proteasome subunits including proteasome subunit α type-1 to type-7 and β type-1 to type-7 showed 2.92-fold to 12.13-fold increased expression in HFB. The protein-protein interactions of upregulated proteins were predicted, and one of the main interaction clusters involved 20S proteasome subunits. Proteasome activity in the HFB conditioned media was also found to be higher than that in MNC conditioned media. Three types of proteasome subunit were also validated by immunoblotting and showed higher expression in the HFB system compared to MNC system. Proteasome subunit α type-3 (PSMA3) showed the highest level in plasma of cholangiocarcinoma patients compared to normal and hepatocellular carcinoma patients by immunodetection, and is of interest as a potential biomarker for cholangiocarcinoma.

Carfilzomib boosted combination therapy for relapsed multiple myeloma

Carfilzomib is a proteasome inhibitor that binds selectively and irreversibly to the 20S proteasome, the proteolytic core particle within the 26S proteasome, resulting in the accumulation of proteasome substrates and ultimately growth arrest and apoptosis of tumor cells. The development and ultimate approval of this medication by regulatory agencies has been an important step toward improving clinical outcomes in multiple myeloma. Although initially approved as a single agent for the treatment of multiply relapsed and/or refractory myeloma, in the USA, it is now widely used in the early relapse setting in combination with lenalidomide and dexamethasone. Carfilzomib has also been studied in combination with second-generation immunomodulatory drugs, histone deacetylase inhibitors, alkylating agents and other novel medications. In this review article, we will discuss the efficacy, safety, tolerability and quality of life of carfilzomib-based combination therapies, as well as novel agents, for relapsed multiple myeloma.

Enzymatic activities of circulating plasma proteasomes in newly diagnosed multiple myeloma patients treated with carfilzomib, lenalidomide and dexamethasone

The proteasome inhibitor carfilzomib is highly effective in the treatment of multiple myeloma. It irreversibly binds the chymotrypsin-like active site in the β5 subunit of the 20S proteasome. Despite impressive response rates when carfilzomib is used in combination with immunomodulatory agents in newly diagnosed multiple myeloma patients; no biomarker exists to accurately predict response and clinical outcomes. We prospectively assessed the activity in peripheral blood of the chymotrypsin-like (CHYM), caspase-like (CASP) and trypsin-like (TRYP) proteolytic sites in 45 newly diagnosed multiple myeloma patients treated with eight cycles of carfilzomib, lenalidomide and dexamethasone (CRd) (NCT01402284). Samples were collected per protocol and proteasome activity measured through a fluorogenic assay. Median CHYM levels after one dose of carfilzomib decreased by >70%. CHYM and CASP activity decreased throughout treatment reaching a minimum after eight cycles of treatment. Higher levels of proteasome activity associated with higher disease burden (r > 0.30; p < 0.05) and higher disease stage (0.10 < p <0.20). No association was found with the probability of achieving a complete response, minimal residual disease negativity or time to best response. Further studies evaluating proteasome activity in malignant plasma cells may help elucidate how proteasome activity can be used as a biomarker in multiple myeloma.

Bladder cancer detection using a peptide substrate of the 20S proteasome

The 20S catalytic core of the human 26S proteasome can be secreted from cells, and high levels of extracellular 20S proteasome have been linked to many types of cancers and autoimmune diseases. Several diagnostic approaches have been developed that detect 20S proteasome activity in plasma, but these suffer from problems with efficiency and sensitivity. In this report, we describe the optimization and synthesis of an internally quenched fluorescent substrate of the 20S proteasome, and investigate its use as a potential diagnostic test in bladder cancer. This peptide, 2-aminobenzoic acid (ABZ)-Val-Val-Ser-Tyr-Ala-Met-Gly-Tyr(3-NO2 )-NH2 , is cleaved by the chymotrypsin 20S proteasome subunit and displays an excellent specificity constant value (9.7 × 10(5)  m(-1) ·s(-1) ) and a high kcat (8 s(-1) ). Using this peptide, we identified chymotrypsin-like proteasome activity in the majority of urine samples obtained from patients with bladder cancer, whereas the proteasome activity in urine samples from healthy volunteers was below the detection limit (0.5 pm). These findings were confirmed by an inhibitory study and immunochemistry methods.

Mammalian proteasome subtypes: Their diversity in structure and function

The 20S proteasome is a multicatalytic proteinase catalysing the degradation of the majority of intracellular proteins. Thereby it is involved in almost all basic cellular processes, which is facilitated by its association with various regulator complexes so that it appears in different disguises like 26S proteasome, hybrid-proteasome and others. The 20S proteasome has a cylindrical structure built up by four stacked rings composed of α- and β-subunits. Since the three active site-containing β-subunits can all or in part be replaced by immuno-subunits, three main subpopulations exist, namely standard-, immuno- and intermediate-proteasomes. Due to posttranslational modifications or/and genetic variations all α- and β-subunits occur in multiple iso- or proteoforms. This leads to the fact that each of the three subpopulations is composed of a variety of 20S proteasome subtypes. This review summarizes the knowledge of proteasome subtypes in mammalian cells and tissues and their possible biological and medical relevancy.

Bortezomib modulates CHIT1 and YKL40 in monocyte-derived osteoclast and in myeloma cells

Osteolytic bone disease is a common manifestation of multiple myeloma (MM) that leads to progressive skeleton destruction and is the most severe cause of morbidity in MM patients. It results from increased osteolytic activity and decrease osteoblastic function. Activation of mammalian chitinases chitotriosidase (CHIT1) and YKL40 is associated with osteoclast (OCs) differentiation and bone digestion. In the current study, we investigated the effect of two Bortezomib’s concentration (2.5 and 5 nM) on osteoclastogenesis by analyzing regulation of chitinase expression. OCs exposition to bortezomib (BO) was able to inhibit the expression of different OCs markers such as RANK, CTSK, TRAP, and MMP9. In addition BO-treatment reduced CHIT1 enzymatic activity and both CHIT1 and YKL40 mRNA expression levels and cytoplasmatic and secreted protein. Moreover, immunofluorescence evaluation of mature OCs showed that BO was able to translocate YKL40 into the nucleus, while CHIT1 remained into the cytoplasm. Since MM cell lines such as U266, SKM-M1 and MM1 showed high levels of CHIT1 activity, we analyzed bone resorption ability of U266 using dentin disk assay resorption pits. Silencing chitinase proteins in U266 cell line with specific small interfering RNA, resulted in pits number reduction on dentine disks. In conclusion, we showed that BO decreases osteoclastogenesis and reduces bone resorption in OCs and U266 cell line by modulating the chitinases CHIT1 and YKL40. These results indicate that chitinases may be a therapeutic target for bone disease in MM patients.

The comparison of C-proteasome activity in the plasma of children after burn injury, mild head injury and blunt abdominal trauma

PURPOSE

We aimed to evaluate and compare the changes in circulating 20S proteasome activity in the plasma of children suffering from blunt abdominal trauma, thermal injury and mild head injury.

PATIENTS AND METHODS

The study population comprised 40 patients with burns, 35 children admitted due to mild head injury, and 30 children suffering from blunt abdominal trauma, who were admitted to Pediatric Surgery Department of Medical University of Bialystok Poland, between 2010 and 2014, and their parents gave informed consent, were included into the study. Patients were aged 9 months to 17 years (median=5.73±1.91y). The girls to boys ratio was nearly 1:2 (34 girls and 106 boys). Plasma proteasome activity was assessed using Suc-Leu-Leu-Val-Tyr-AMC peptide substrate, 2-6h, 12-16h, and 48h after the injury. 20 healthy children admitted for planned inguinal hernia repair served as controls.

RESULTS

In our series of patients, the C-proteasome activity was much higher 12-16h after burns, than after mild head injuries, or blunt abdominal injuries, and the difference was statistically significant (p<0.05).

CONCLUSIONS

Circulating 20S proteasome is probably released from damaged tissues in response to the injury and is a biomarker of tissue damage - more severe in the group of burnt patients in comparison to the patients with mild head injury and blunt abdominal trauma. Therefore detection of 20S proteasome may represent a novel marker of immunological activity and cellular degradation in trauma patients.

Novel internally quenched substrate of the trypsin-like subunit of 20S eukaryotic proteasome

This article describes the synthesis, using combinatorial chemistry, of internally quenched substrates of the trypsin-like subunit of human 20S proteasome. Such substrates were optimized in both the nonprime and prime regions of the peptide chain. Two were selected as the most susceptible for proteasomal proteolysis with excellent kinetic parameters: (i) ABZ-Val-Val-Ser-Arg-Ser-Leu-Gly-Tyr(3-NO2)-NH2 (kcat/KM = 934,000 M(-1) s(-1)) and (ii) ABZ-Val-Val-Ser-GNF-Ala-Met-Gly-Tyr(3-NO2)-NH2 (kcat/KM = 1,980,000 M(-1) s(-1)). Both compounds were efficiently hydrolyzed by the 20S proteasome at picomolar concentrations, demonstrating significant selectivity over other proteasome entities.

FV-162 is a novel, orally bioavailable, irreversible proteasome inhibitor with improved pharmacokinetics displaying preclinical efficacy with continuous daily dosing

Approved proteasome inhibitors have advanced the treatment of multiple myeloma but are associated with serious toxicities, poor pharmacokinetics, and most with the inconvenience of intravenous administration. We therefore sought to identify novel orally bioavailable proteasome inhibitors with a continuous daily dosing schedule and improved therapeutic window using a unique drug discovery platform. We employed a fluorine-based medicinal chemistry technology to synthesize 14 novel analogs of epoxyketone-based proteasome inhibitors and screened them for their stability, ability to inhibit the chymotrypsin-like proteasome, and antimyeloma activity in vitro. The tolerability, pharmacokinetics, pharmacodynamic activity, and antimyeloma efficacy of our lead candidate were examined in NOD/SCID mice. We identified a tripeptide epoxyketone, FV-162, as a metabolically stable, potent proteasome inhibitor cytotoxic to human myeloma cell lines and primary myeloma cells. FV-162 had limited toxicity and was well tolerated on a continuous daily dosing schedule. Compared with the benchmark oral irreversible proteasome inhibitor, ONX-0192, FV-162 had a lower peak plasma concentration and longer half-life, resulting in a larger area under the curve (AUC). Oral FV-162 treatment induced rapid, irreversible inhibition of chymotrypsin-like proteasome activity in murine red blood cells and inhibited tumor growth in a myeloma xenograft model. Our data suggest that oral FV-162 with continuous daily dosing schedule displays a favorable safety, efficacy, and pharmacokinetic profile in vivo, identifying it as a promising lead for clinical evaluation in myeloma therapy.

Particulate cytoplasmic structures with high concentration of ubiquitin-proteasome accumulate in myeloid neoplasms

Background

Increased plasma levels of proteasome have been associated with various neoplasms, especially myeloid malignancies. Little is known of the cellular origin and release mechanisms of such proteasome. We recently identified and characterized a novel particulate cytoplasmic structure (PaCS) showing selective accumulation of ubiquitin-proteasome system (UPS) components. PaCSs have been reported in some epithelial neoplasms and in two genetic disorders characterized by hematopoietic cell dysplasia and increased risk of leukemia. However, no information is available about PaCSs in hematopoietic neoplasms.

Methods

PaCSs were investigated by ultrastructural, immunogold, and immunofluorescence analysis of bone marrow (BM) biopsies and peripheral blood (PB) cell preparations of 33 consecutive, untreated, or relapsed patients affected by different hematopoietic neoplasms. BM and PB samples from individuals with non-neoplastic BM or healthy donors were studied as controls. Granulocytes and platelet proteasome content was measured by immunoblotting and plasma proteasome levels by ELISA.

Results

PaCSs with typical, selective immunoreactivity for polyubiquitinated proteins and proteasome were widespread in granulocytic cells, megakaryocytes, and platelets of patients with myeloproliferative neoplasms (MPN). In acute myeloid leukemia and myelodysplastic syndromes (MDS), PaCSs were only occasionally detected in blast cells and were found consistently in cells showing granulocytic and megakaryocytic maturation. Conversely, PaCSs were poorly represented or absent in non-neoplastic hematopoietic tissue or lymphoid neoplasms. In MPN granulocytes and platelets, the presence of PaCSs was associated with increased amounts of proteasome in cell lysates. PaCSs were often localized in cytoplasmic blebs generating PaCSs-filled plasma membrane vesicles observable in the BM intercellular space. In MPN and MDS, accumulation of PaCSs was associated with significant increase in plasma proteasome. Immunogold analysis showed that PaCSs of myeloid neoplasia selectively concentrated the chaperone proteins Hsp40, Hsp70, and Hsp90.

Conclusions

PaCSs accumulate in cells of myeloid neoplasms in a lineage- and maturation-restricted manner; in particular, they are widespread in granulocytic and megakaryocytic lineages of MPN patients. PaCSs development was associated with excess accumulation of polyubiquitinated proteins, proteasome, and chaperone molecules, indicating impairment of the UPS-dependent protein homeostasis and a possible link with Hsp90-related leukemogenesis. A mechanism of PaCSs discharge by leukemic cells could contribute to increased plasma proteasome of MPN and MDS.

Electronic supplementary material

The online version of this article (doi:10.1186/s13045-015-0169-6) contains supplementary material, which is available to authorized users.

Circulating 20S proteasome is independently associated with abdominal muscle mass in hemodialysis patients

Protein-energy wasting is highly prevalent in hemodialysis patients, and it contributes to patient morbidity and mortality. The ubiquitin-proteasome system is the major pathway for intracellular protein degradation and it is involved in the regulation of basic cellular processes. However, the role of this system in the determination of nutritional status is largely unknown. To examine a relationship between protein-energy wasting and the ubiquitin-proteasome system, a cross-sectional study of 76 hemodialysis patients was performed. Plasma concentrations of 20S proteasome were studied to evaluate its association with muscle and fat mass, which were investigated by abdominal muscle and fat areas measured using computed tomography and by creatinine production estimated using the creatinine kinetic model. Plasma 20S proteasome concentrations significantly and negatively correlated with abdominal muscle areas and creatinine production (rho = -0.263, P < 0.05 and rho = -0.241, P < 0.05, respectively), but not abdominal subcutaneous and visceral fat areas. Multiple regression analyses showed that 20S proteasome was a significant independent predictor of abdominal muscle area (P < 0.05). In conclusion, plasma 20S proteasome concentrations were independently associated with abdominal muscle mass in hemodialysis patients. Our findings indicate a relationship between circulating 20S proteasomes and muscle metabolism in these patients.

A preliminary study of the effect of curcumin on the expression of p53 protein in a human multiple myeloma cell line

Curcumin is an inexpensive, natural plant ingredient with protease inhibitor effects. The present study aimed to analyze the inhibitory effects of curcumin on the multiple myeloma (MM) RPMI 8226 cell line, and examine the underlying mechanism that promotes the apoptosis of RPMI 8226 cells. A growth curve was constructed in order to observe the relative growth velocity, and MTT was used to analyze the effect of different concentrations of curcumin on inhibiting the proliferation of the RPMI 8226 cells. The mRNA expression of the p53, Bax and MDM2 genes was detected using quantitative polymerase chain reaction. The expression of p53 protein in the MM RPMI 8226 cells following treatment with curcumin was detected by western blotting and ELISA. Curcumin inhibited the proliferation of the MM RPMI 8226 cells in a dose- and time-dependent manner. In the MM RPMI 8226 cells treated with curcumin, the expression of the p53 and Bax genes was upregulated, while the expression of the MDM2 gene was downregulated. p53 protein expression was higher in the curcumin experimental group compared with the control group. Subsequent to treatment with curcumin, the growth of the MM RPMI 8226 cell line was inhibited in a concentration- and time-dependent manner. In the MM RPMI 8226 cells treated with curcumin, p53 protein levels were upregulated, which suggested that curcumin may promote the apoptosis of MM cells by upregulating p53 protein expression.

Increased proteasome activator 28 gamma (PA28γ) levels are unspecific but correlate with disease activity in rheumatoid arthritis

BACKGROUND

PA28γ (also known as Ki, REG gamma, PMSE3), a member of the ubiquitin-and ATP-independent proteasome activator family 11S, has been proved to show proteasome-dependent and -independent effects on several proteins including tumor suppressor p53, cyclin-dependent kinase inhibitor p21 and steroid receptor co-activator 3 (SCR-3). Interestingly, PA28γ is overexpressed in pathological tissue of various cancers affecting e. g. breast, bowl and thyroids. Furthermore, anti-PA28γ autoantibodies have been linked to several autoimmune disorders. The aim of this study was to develop and evaluate a novel and sensitive PA28γ sandwich ELISA for the quantification of PA28γ serum levels in patients with cancer and autoimmune diseases for diagnostic and prognostic purposes.

METHODS

PA28γ-specific polyclonal antibodies and recombinant His-tagged PA28γ were purified and used to develop a sandwich ELISA for the detection of circulating PA28γ. With this new assay, PA28γ serum levels of patients with various cancers, rheumatoid arthritis (RA), Sjögren's syndrome (SS), adult-onset Still's disease (AOSD) and different connective-tissue diseases (CTD) were compared with healthy control subjects. Anti-PA28γ autoantibodies were additionally confirmed using a newly developed microbead assay.

RESULTS

The developed PA28γ sandwich ELISA showed a high specificity with a detection limit of 3 ng/ml. A significant up-regulation of circulating PA28γ was detected in the sera of patients with cancer, RA, SS and CTD. A significant correlation was observed dependent on age as well as anti-PA28γ autoantibody levels with circulating PA28γ protein levels. Furthermore, PA28γ serum levels showed a correlation with disease activity in patients with RA under treatment with the T-cell directed biological compound abatacept according to disease activity score 28 (DAS28) and erythrocyte sedimentation rate (ESR).

CONCLUSION

The application of PA28γ as a novel biomarker for diagnostic purposes of a specific disease is limited, since elevated levels were observed in different disorders. However, the correlation with disease activity in patients with RA suggests a prognostic value, which needs to be addressed by further studies. Therefore our results show that PA28γ is a useful marker which should be included in studies related to novel treatments, e.g. abatacept.

The amazing ubiquitin-proteasome system: structural components and implication in aging

Proteome quality control (PQC) is critical for the maintenance of cellular functionality and it is assured by the curating activity of the proteostasis network (PN). PN is constituted of several complex protein machines that under conditions of proteome instability aim to, firstly identify, and then, either rescue or degrade nonnative polypeptides. Central to the PN functionality is the ubiquitin-proteasome system (UPS) which is composed from the ubiquitin-conjugating enzymes and the proteasome; the latter is a sophisticated multi-subunit molecular machine that functions in a bimodal way as it degrades both short-lived ubiquitinated normal proteins and nonfunctional polypeptides. UPS is also involved in PQC of the nucleus, the endoplasmic reticulum and the mitochondria and it also interacts with the other main cellular degradation axis, namely the autophagy-lysosome system. UPS functionality is optimum in the young organism but it is gradually compromised during aging resulting in increasing proteotoxic stress; these effects correlate not only with aging but also with most age-related diseases. Herein, we present a synopsis of the UPS components and of their functional alterations during cellular senescence or in vivo aging. We propose that mild UPS activation in the young organism will, likely, promote antiaging effects and/or suppress age-related diseases.

Circulating proteasome activity following mild head injury in children

PURPOSE

The aim of the study is to characterize changes in circulating proteasome (c-proteasome) activity following mild traumatic brain injury in children.

METHODS

Fifty children managed at the Department of Pediatric Surgery because of concussion-mild head injury was randomly included into the study. The children were aged 11 months to 17 years (median = 10.07 + -1.91 years). Plasma proteasome activity was assessed using Suc-Leu-Leu-Val-Tyr-AMC peptide substrate, 2-6 h, 12-16 h, and 2 days after injury. Twenty healthy children admitted for planned inguinal hernia repair served as controls.

RESULTS

Statistically significant elevation of plasma c-proteasome activity was noted in children with mild head injury 2-6 h, 12-16 h, and 2 days after the injury.

CONCLUSIONS

Authors observed a statistically significant upward trend in the c-proteasome activity between 2-6 and 12-16 h after the mild head injury, consistent with the onset of the symptoms of cerebral concussion and a downward trend in the c-proteasome activity in the plasma of children with mild head injury between 12-16 h and on the second day after the injury, consistent with the resolving of the symptoms of cerebral concussion. Further studies are needed to demonstrate that the proteasome activity could be a prognostic factor, which can help in further diagnostic and therapeutic decisions in patients with head injury.

The proteasome: mechanisms of biology and markers of activity and response to treatment in multiple myeloma

Since the early 1990s, the synthesis and subsequent clinical application of small molecule inhibitors of the ubiquitin proteasome pathway (UPP) has revolutionized the treatment and prognosis of multiple myeloma. In this review, we summarize important aspects of the biology of the UPP with a focus on its structure and key upstream/downstream regulatory components. We then review current knowledge of plasma cell sensitivity to proteasome inhibition and highlight new proteasome inhibitors that have recently entered clinical development. Lastly, we address the putative role of circulating proteasomes as a novel biomarker in multiple myeloma and provide guidance for future clinical trials using proteasome inhibitors.

Current understanding on the role of standard and immunoproteasomes in inflammatory/immunological pathways of multiple sclerosis

The ubiquitin-proteasome system is the major intracellular molecular machinery for protein degradation and maintenance of protein homeostasis in most human cells. As ubiquitin-proteasome system plays a critical role in the regulation of the immune system, it might also influence the development and progression of multiple sclerosis (MS). Both ex vivo analyses and animal models suggest that activity and composition of ubiquitin-proteasome system are altered in MS. Proteasome isoforms endowed of immunosubunits may affect the functionality of different cell types such as CD8⁺ and CD4⁺ T cells and B cells as well as neurons during MS development. Furthermore, the study of proteasome-related biomarkers, such as proteasome antibodies and circulating proteasomes, may represent a field of interest in MS. Proteasome inhibitors are already used as treatment for cancer and the recent development of inhibitors selective for immunoproteasome subunits may soon represent novel therapeutic approaches to the different forms of MS. In this review we describe the current knowledge on the potential role of proteasomes in MS and discuss the pro et contra of possible therapies for MS targeting proteasome isoforms.

Correlation between circulating proteasome activity, total protein and c-reactive protein levels following burn in children

AIM OF THE STUDY

To characterize burn-induced changes following burn in children by analyzing circulating proteasome (c-proteasome) activity in the plasma in correlation with total protein and c-reactive protein levels in the plasma, and the severity of the burn.

METHODS

Fifty consecutive children scalded by hot water who were managed at the Department of Pediatric Surgery after primarily presenting with burns in 4-20% TBSA were included into the study. The children were aged 9 months up to 14 years (mean age 2.5±1 years). Patients were divided into groups according to the pediatric injury severity score used by American Burns Association. Plasma proteasome activity was assessed using Suc-Leu-Leu-Val-Tyr-AMC peptide substrate, 2-6 h, 12-16 h, 3 days, 5 days, and 7 days after injury. 20 healthy children consecutively admitted for planned inguinal hernia repair served as controls.

RESULTS

Statistically significant elevation of plasma c-proteasome activity was noted in all groups of burned children 12-16 h after the injury. We found a strong negative correlation of c-proteasome activity with total protein levels, and positive correlation with CRP levels 12-16 h after burn. We also found stronger correlation between c-proteasome activity and severity of burn, than CRP level and severity of burn 12-16 h, and 3 days after the burn. Correlations were statistically significant.

CONCLUSIONS

This study characterized circulating 20S proteasome activity levels after burn. C-proteasome activity elevate after burn and correlate negatively with plasma total protein level, thus plasma 20S proteasome activity could be additional biomarker of tissue damage in burn in pediatric population.

T lymphocytes export proteasomes by way of microparticles: a possible mechanism for generation of extracellular proteasomes

The 20S proteasome is almost exclusively localized within cells. High levels of extracellular proteasomes are also found circulating in the blood plasma of patients suffering from a variety of inflammatory, autoimmune and neoplastic diseases. However, the origin of these proteasomes remained enigmatic. Since the proteome of microparticles, small membrane enclosed vesicles released from cells, was shown to contain proteasomal subunits, we studied whether intact proteasomes are actively released into the extracellular space. Using human primary T lymphocytes stimulated with CaCl2 and the calcium ionophore A23187 to induce membrane blebbing we demonstrate that microparticles contain proteolytically active 20S proteasomes as well as the proteasome activator PA28 and subunits of the 19S proteasome regulator. Furthermore, our experiments reveal that incubation of in vitro generated T lymphocyte-microparticles with sphingomyelinase results in the hydrolysis of the microparticle membranes and subsequent release of proteasomes from the vesicles. Thus, we here show for the first time that functional proteasomes can be exported from activated immune cells by way of microparticles, the dissolution of which may finally lead to the generation of extracellular proteasomes.

Targeting the ubiquitin proteasome system in haematological malignancies

The ubiquitin proteasome system (UPS) plays a central role in cellular protein homeostasis through the targeted destruction of damaged/misfolded proteins and regulatory proteins that control critical cellular functions. The UPS comprises a sequential series of enzymatic activities to covalently attach ubiquitin to proteins to target them for degradation through the proteasome. Aberrancies within this system have been associated with transformation and tumourigenesis and thus, the UPS represents an attractive target for the development of anti-cancer therapies. The use of the first-in-class proteasome inhibitor, bortezomib, in the treatment of Plasma Cell Myeloma and Mantle Cell Lymphoma has validated the UPS as a therapeutic target. Following on its success, efforts are focused on the development of second-generation proteasome inhibitors and small molecule inhibitors of other components of the UPS. This review will provide an overview of the UPS and discuss current and novel therapies targeting the UPS.