Rosemary Extract-Induced Autophagy and Decrease in Accumulation of Collagen Type I in Osteogenesis Imperfecta Skin Fibroblasts

Osteogenesis imperfecta (OI) is a heterogeneous connective tissue disease mainly caused by structural mutations in type I collagen. Mutant collagen accumulates intracellularly, causing cellular stress that has recently been shown to be phenotype-related. Therefore, the aim of the study was to search for potential drugs reducing collagen accumulation and improving OI fibroblast homeostasis. We found that rosemary extract (RE), which is of great interest to researchers due to its high therapeutic potential, at concentrations of 50 and 100 µg/mL significantly reduced the level of accumulated collagen in the fibroblasts of four patients with severe and lethal OI. The decrease in collagen accumulation was associated with RE-induced autophagy as was evidenced by an increase in the LC3-II/LC3-I ratio, a decrease in p62, and co-localization of type I collagen with LC3-II and LAMP2A by confocal microscopy. The unfolded protein response, activated in three of the four tested cells, and the level of pro-apoptotic markers (Bax, CHOP and cleaved caspase 3) were attenuated by RE. In addition, the role of RE-modulated proteasome in the degradation of unfolded procollagen chains was investigated. This study provides new insight into the beneficial effects of RE that may have some implications in OI therapy targeting cellular stress.

Elevated plasma 20S proteasome chymotrypsin-like activity is correlated with IL-8 levels and associated with an increased risk of death in glial brain tumor patients

INTRODUCTION

In cancer treatment an attempt has been made to pharmacologically regulate the proteasome functions, thus the aim was to test whether 20S proteasome chymotrypsin-like (ChT-L) activity has a role in glial brain tumors. Furthermore, we analyzed the correlation between proteasome activity and IL-8, CCL2, NF-κB1 and NF-κB2 concentrations, which impact on brain tumors has already been indicated.

METHODS

Plasma 20S proteasome ChT-L activity was assayed using the fluorogenic peptide substrate Suc-Leu-Leu-Val-Tyr-AMC in the presence of SDS. IL-8, CCL2, NF-κB1 and NF-κB2 concentration was analyzed with the use of ELISA method. Immunohistochemistry for IDH1-R132H was done on 5-microns-thick formalin-fixed, paraffin-embedded tumor sections with the use of antibody specific for the mutant IDH1-R132H protein. Labelled streptavidin biotin kit was used as a detection system.

RESULTS

Brain tumor patients had statistically higher 20S proteasome ChT-L activity (0.649 U/mg) compared to non-tumoral individuals (0.430 U/mg). IDH1 wild-type patients had statistically higher 20S proteasome ChT-L activity (1.025 U/mg) compared to IDH1 mutants (0.549 U/mg). 20S proteasome ChT-L activity in brain tumor patients who died as the consequence of a tumor (0.649) in the following 2 years was statistically higher compared to brain tumor patients who lived (0.430 U/mg). In brain tumor patients the 20S proteasome ChT-L activity positively correlated with IL-8 concentration.

CONCLUSIONS

Elevated 20S proteasome ChT-L activity was related to the increased risk of death in glial brain tumor patients. A positive correlation between 20S proteasome ChT-L activity and IL-8 concentration may indicate the molecular mechanisms regulating glial tumor biology. Thus research on proteasomes may be important and should be carried out to verify if this protein complexes may represent a potential therapeutic target to limit brain tumor invasion.

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.

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.

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.

Challenging of AS160/TBC1D4 Alters Intracellular Lipid milieu in L6 Myotubes Incubated With Palmitate

The Akt substrate of 160 kDa (AS160) is a key regulator of GLUT4 translocation from intracellular depots to the plasma membrane in myocytes. Likely, AS160 also controls LCFAs transport, which requires relocation of fatty acid transporters. The aim of the present study was to determine the impact of AS160 knockdown on lipid milieu in L6 myotubes incubated with palmitate (PA). Therefore, we compared two different settings, namely: 1) AS160 knockdown prior to palmitate incubation (pre-PA-silencing, AS160^- /PA); 2) palmitate incubation with subsequent AS160 knockdown (post-PA-silencing, PA/AS160^- ). The efficiency of AS160 silencing was checked at mRNA and protein levels. The expression and localization of FA transporters were determined using Western Blot and immunofluorescence analyses. Intracellular lipid content (FFA, DAG, TAG, and PL) and FA composition were estimated by GLC, whereas basal palmitate uptake was analyzed by means of scintigraphy. Both groups with silenced AS160 were characterized by a greater expression of FA transporters (FAT/CD36, FATP-1, 4) which had contributed to an increased FA cellular influx. Accordingly, we observed that post-PA-silencing of AS160 resulted in a marked decrement in DAG, TAG, and PL contents, but increased FFA content (PA/AS160^- vs. PA). The opposite effect was observed in the group with pre-PA-silencing of AS160 in which AS160 knockdown did not affect the lipid pools (AS160^- /PA vs. PA). Our results indicate that post-PA-silencing of AS160 has a capacity to decrease the lipotoxic effect(s) of PA by decreasing the content of lipids (DAG and PL) that promote insulin resistance in myotubes. J. Cell. Physiol. 232: 2373-2386, 2017. © 2016 The Authors. Journal of Cellular Physiology Published by Wiley Periodicals Inc.

Low glucose dependent decrease of apoptosis and induction of autophagy in breast cancer MCF-7 cells

Cancer cells have developed a number of adaptation mechanisms involving the signal activation of the transduction pathways, which promotes the progression and metastasis. Our results showed that the percentage of apoptotic MCF-7 cells incubated in the low glucose medium for 48 h was lower in comparison to those cultured in the high glucose medium, despite the high expression of the proapoptotic transcription factor-CHOP. Furthermore, the MCF-7 cells incubated in the low glucose medium for 48 h showed a higher expression of NF-κB p100/p52 subunits compared to cells incubated in the high glucose medium. Moreover, our findings demonstrated that the shortage of glucose strongly induces autophagy in MCF-7 cells. The activation of this process is not associated with the changes in the expression of mTOR kinase. We suggest, that the antiapoptotic chaperone ORP150 induction, transcription factor NF-κB2 activation, and increased autophagy constitute mechanisms protecting the MCF-7 cells against apoptosis.

Peroxynitrite may affect fibrinolysis via the reduction of platelet-related fibrinolysis resistance and alteration of clot structure

We tested the hypothesis that in vitro peroxynitrite (ONOO(-), a product of activated inflammatory cells) may affect fibrinolysis in human blood through the reduction of platelet-related fibrinolysis resistance. It was found that ONOO(-) (25-300 µM) accelerated lysis of platelet-fibrin clots (in PRP) dose-dependently, whereas fibrinolysis of platelet-free clots was slightly inhibited by ≥ 1000 µM stressor. Concentrations of ONOO(-) affecting the lysis of platelet-rich clots, inhibited clot retraction (CR) in a dose-dependent manner. Thromboelastometry (ROTEM) measurements performed in PRP showed that treatment with ONOO(-) (threshold conc. 100 µM) prolongs clotting time, and reduces alpha angle, and clot formation velocity parameters indicating for reduced thrombin formation rate. In PRP, ONOO(-) (threshold conc. 100 µM) reduced the collagen-evoked exposure of phosphatidylserine (PS) on platelets' plasma membrane, the shedding of platelet-derived microparticles (PMP), and inhibited platelet-dependent thrombin generation (measured in artificial system), dose-dependently. As judged by confocal microscopy, similar ONOO(-) concentrations altered the architecture of clots formed in collagen-treated PRP. Clots formed in the presence of ONOO(-) were less dense and were composed of thicker fibers, which make them more susceptible to lysis. In platelet-depleted plasma, ONOO(-) (up to milimolar concentration) did not alter clot structure. Blockage of PS exposed on platelets resulted in an alteration of clot architecture toward more prone to lysis. ONOO(-), at lysis-affecting concentrations, inhibited the collagen-evoked secretion of fibrinolytic inhibitors from platelets. We conclude that physiologically relevant ONOO(-) concentrations may accelerate the lysis of platelet-fibrin clots predominantly via downregulation of platelet-related mechanisms including: platelet secretion, clot retraction, platelet procoagulant response, and the alteration in clot architecture associated with it.

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.

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.

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.

SPR imaging biosensor for the 20S proteasome: sensor development and application to measurement of proteasomes in human blood plasma

The 20S proteasome is a multicatalytic enzyme complex responsible for intracellular protein degradation in mammalian cells. Its antigen level or enzymatic activity in blood plasma are potentially useful markers for various malignant and nonmalignant diseases. We have developed a method for highly selective determination of the 20S proteasome using a Surface Plasmon Resonance Imaging (SPRI) technique. It is based on the highly selective interaction between the proteasome's catalytic β5 subunit and immobilized inhibitors (the synthetic peptide PSI and epoxomicin). Inhibitor concentration and pH were optimized. Analytical responses, linear ranges, accuracy, precision and interferences were investigated. Biosensors based on either PSI and epoxomicin were found to be suitable for quantitative determination of the proteasome, with a precision of ±10% for each, and recoveries of 102% and 113%, respectively, and with little interference by albumin, trypsin, chymotrypsin, cathepsin B and papain. The proteasome also was determined in plasma of healthy subjects and of patients suffering from acute leukemia. Both biosensors gave comparable results (2860 ng·mL-1 on average for control, and 42300 ng·mL-1 on average for leukemia patients).FigureThe synthetic peptide aldehyde Z-Ile-Glu(OBut)-Ala-Leu-H (PSI) and a microbial α',β' epoxyketone peptide epoxomicin was used to develop SPRI biosensor for the highly selective determination of the 20S proteasome concentration, and to evaluate the sensor applicability for the determination of 20S proteasome in human blood plasma.

Increased plasma proteasome chymotrypsin-like activity in patients with advanced solid tumors

The chymotrypsin-like (ChT-L) activity is one of the key regulators of intracellular protein degradation. Elevated proteasome ChT-L activity has recently been reported in plasma of patients with leukemia and myelodysplastic syndrome and suggested to have a prognostic significance. The aim of the present study was to evaluate plasma proteasome ChT-L activity in patients with newly diagnosed solid tumors at early and advanced stages of the disease. The activity was assayed using the fluorogenic peptide substrate, Suc-Leu-Leu-Val-Tyr-AMC, in a cohort of 155 patients with early/advanced rectal (n=43/29), gastric (n=6/13), and breast (n=37/27) cancer and compared with that in normal individuals (n=55). The median plasma proteasome ChT-L activity was elevated by 20-32% in patients with advanced stage of rectal, gastric, and breast cancer compared with healthy donors. The difference turned out to be statistically significant (P<0.001). By contrast, values in patients with early stage of malignancies were not significantly different from those observed in normal individuals. We also found that plasma proteasome activity correlated with serum carcinoembryonic antigen levels in the group of patients with rectal cancer (r=0.433, P<0.05). Elevated plasma proteasome ChT-L activity is indicative of advanced stage of rectal, gastric, and breast cancer. However, the activity does not seem to be a parameter with clinically relevant potential in terms of early detection of cancer in this subset of patients.

Cathepsin A-like activity is possibly the main acidic carboxypeptidase in human platelets

Human platelets were investigated for activity of the acidic carboxypeptidases: cathepsin A, lysosomal carboxypeptidase B and prolyl-carboxypeptidase. It was found that the main acidic carboxypeptidase in human platelets had cathepsin A activity. No activity of lysosomal carboxypeptidase B and prolyl-carboxypeptidase in human platelets was detectable using their specific substrates. Human platelet cathepsin A-type enzyme hydrolyzed at the highest rate Cbz-Phe-Ala, Cbz-Phe-Met and Cbz-Phe-Leu, did not require sulfhydryl activator and was inhibited by serine protease inhibitors (DFP, DCI) and inhibitors that react with the SH group (mersalyl acid, PCMS, PCMB, HgCl2). Cbz-Phe-Ala and Cbz-Glu-Tyr were hydrolyzed at a broad pH range with optimum at pH 5.0-6.0. The chromatographic analysis on Con A-Sepharose and DEAE-Sephacel showed different forms of Cbz-Phe-Ala-hydrolyzing enzyme in human platelets. The multiple forms of this enzyme were probably due to heterogeneity of carbohydrate moiety.

[Plasma proteasome 20S activity in children treated for acute lymphoblastic leukaemia]

THE AIM of our study was: to determine the proteasome 20S activity in plasma of patients treated for acute lymphoblastic leukaemia.

METHODS

Plasma proteasome activity was measured in children (n=16) at two points: at diagnosis and on the 33rd day using the spectrophotometric method with peptidic substrate and selective proteasome activator 0.03% SDS.

RESULTS

1. At diagnosis we observed high activity of the proteasome 20S in comparison to control (p<0.005). After haematological remission the proteasome 20S activity lowered by about 50% (p<0.05). 3. We did not find the influence of immunophenotype, initial leucocytosis, LDH activity and hepatosplenomegaly on initial proteasome values.

CONCLUSIONS

Dynamic changes of the proteasome 20S activity confirm its participation in cancerogenic process. Proteasome 20S activity may be an effective indicator in the monitoring of anticancer treatment.

Immuno-proteasome subunit LMP7 is up-regulated in the ischemic kidney in an experimental model of renovascular hypertension

Immuno-proteasome is thought to be responsible for the processing of intracellular antigens and is induced when cells are treated with the inflammatory cytokines promoting cellular immunity. We tested the possibility that immuno-proteasome can be up-regulated in renal cells exposed to a long-lasting ischemia and inflammation in an experimental model of two-kidney, one-clip renovascular hypertension in the rat. Western blotting showed that immuno-proteasome subunit, LMP7, was up-regulated in the clipped ischemic kidney that was atrophic, but not in the contralateral unclipped kidney that underwent compensatory hypertrophy. Immunohistochemical analysis revealed that LMP7 was highly expressed in cortical epithelial and endothelial cells of the ischemic kidney. Surprisingly, the second immuno-subunit, LMP2, was almost undetectable, indicating that renal ischemia may induce exclusively the LMP7 subunit. We also found that renal ischemia neither reduced the SDS-stimulated proteasomal activity nor affected a high level of the PA28 activator. Thus, the results provide evidence that LMP7 immuno-subunit is induced in renal cells exposed to a long-lasting renal ischemia and inflammation, and that there is a direct link between LMP induction and renal atrophy. This opens an opportunity to study a role for LMP-containing proteasomes in the kidneys and other organs undergoing reduction in mass in diseases accompanied by a long-lasting ischemia and inflammatory responses.

Ebelactone B, an Inhibitor of Extracellular Cathepsin A-Type Enzyme, Suppresses Platelet Aggregation Ex Vivo in Renovascular Hypertensive Rats

The present study was undertaken to investigate whether ebelactone B, an inhibitor of bradykinin and angiotensin I hydrolysis by serine carboxypeptidase Y-like enzymes, could influence platelet aggregation ex vivo in renovascular hypertensive rats (2-kidney, 1-clip Goldblatt model, 2K1C). We found that ebelactone B (5 mg/kg) administrated subcutaneously once a day for 5 days, 5 weeks after the development of hypertension, or a single dose of ebelactone B (0.5 mg/kg) injected intravenously into 2K1C hypertensive rats before the induction of arterial thrombosis, both markedly suppressed collagen-induced platelet aggregation in whole blood. In contrast, inhibition of collagen-induced platelet aggregation was not evident in vitro after pretreatment of the blood with ebelactone B, indicating that ex vivo the antiaggregatory action of this compound can proceed through an indirect mechanism. The injection of ebelactone B did not affect the mean blood pressure of 2K1C hypertensive rats but lowered an elevated extracellular serine carboxypeptidase cathepsin A-like activity. Thus, the data indicate that ebelactone B may be a promising antiaggregatory agent in renovascular hypertension and suggest that 1 of the possible mechanisms through which it exerts this effect may be related to the suppression of cathepsin A-like activity released locally during the development of renovascular hypertension.

Proteasome inhibitor prevents experimental arterial thrombosis in renovascular hypertensive rats

Recent studies indicate that highly selective proteasome inhibitors can be useful in prevention of some cardiovascular events. Here we demonstrate that proteasome inhibitor, Z-Ile-Glu (Ot-Bu) Ala-Leucinal (PSI), is active in the prevention of platelet-dependent arterial thrombosis induced in renovascular hypertensive rats (two-kidney, one clip Goldblatt model, and 2K1C, n=5). The administration of PSI intravenously at a single dose of 0.3 mg/kg before induction of arterial thrombosis markedly increased carotid final flow rate, as compared to control (vehicle) group (10.36 +/- 1.8 ml/min and 1.2 +/- 1.2 ml/min, respectively), significantly decreased the wet (1.23 +/- 0.23 mg and 4.1 +/- 0.94 mg, respectively), and dry (0.46 +/- 0.145 mg and 1.46 +/- 0.39, respectively) thrombus weight, and completely prevented arterial occlusion. Moreover, platelets from PSI - treated thrombotic 2K1C rats, showed in response to collagen a significant inhibition of aggregation in the whole blood (10.26 +/- 0.6 ohms vs. 15.51 +/- 0.91 ohms in the control group). In contrast, collagen-induced platelet aggregation was not inhibited in vitro, after pre-treatment of the blood with PSI at the concentration of 10 microM that effectively inhibited the 20S proteasome activity in platelets, indicating that ex vivo anti-aggregatory effect of PSI proceeds through an indirect mechanism not associated with suppression of 20S proteasome activity in platelets. In conclusion, our in vivo findings demonstrate that proteasome inhibitor, Z-Ile-Glu(Ot-Bu)Ala-Leucinal, prevents the development of arterial thrombosis in renovascular hypertensive rats and effectively suppresses platelet aggregation by an indirect mechanism. Thus the data provide a new insight into the potential role for the proteasome-dependent pathway in cardiovascular events.

Lysosomal high molecular weight multienzyme complex

Three acidic glycosidases: beta-galactosidase (beta-GAL, EC 3.2.1.23), alpha-neuraminidase (NEUR, sialidase, EC 3.2.1.18), N-acetylaminogalacto-6-sulfate sulfatase (GALNS, EC 3.1.6.4) and serine carboxypepidase cathepsin A (EC 3.4.16.1) form a functional high molecular weight complex in the lysosomes. The major constituent of this complex is cathepsin A, the so-called "lysosomal protective protein" (PPCA). By forming a multienzyme complex, it protects the glycosidases from rapid intralysosomal proteolysis, and it is also required for the intracellular sorting and proteolytic processing of their precursors. In man, a deficiency of cathepsin A leads to a combined deficiency of beta-GAL and NEUR activities, called "galactosialidosis". Multiple mutations identified in the cathepsin A gene are the molecular basis of this lysosomal storage disease. This review describes the structural organization of the lysosomal high molecular weight multienzyme complex and the importance of the protective protein/cathepsin A in physiology and pathology.

Changes in proteasome activity in the ischemic kidney of rat with experimental renovascular hypertension

A long-lasting renal ischemia, followed by the left renal artery clipping (two-kidney, one clip Goldblatt model in rats) led to a marked decrease in proteasome chymotrypsin-like activity in the ischemic kidney. This activity was, however, significantly raised upon the stimulation with an artificial 20S proteasome activator SDS (0.025%). No changes were observed in either the levels of the constitutive 20S proteasome subunit (alpha5) or of its protein activator, PA28alpha, in the kidneys by Western blot. These preliminary results indicate that an inhibition of proteasome activity may result from a dissociation of the active proteasome complexes into the inactive 20S proteasome and its endogenous activators after a long-lasting renal ischemia.

Pulmonary neuroendocrine cells in chronic renal failure

In patients with chronic renal failure, mechanical and haemodynamic changes could occur in the lungs without obvious pulmonary symptoms and findings, and their effects could pave the way to pulmonary functional disorders. Numerous studies have demonstrated that the respiratory system is a site of synthesis of many compounds, which play biological roles ascribed to hormones. The present article is an attempt to make a synthesis of current opinions and views, based on the world literature survey and on our own studies, concerning the effect of homeostatic dysfunction of the kidneys on the morphology and action of DNES cells in the lung.

Human platelet 20S proteasome: inhibition of its chymotrypsin-like activity and identification of the proteasome activator PA28. A preliminary report

Earlier studies have demonstrated that human platelets contain the 20S proteasome, and its protein activator. However, understanding the potential role of the proteasome in human platelets requires a detailed knowledge about its chymotryptic-like activity, a crucial one for protein degradation in all eukaryotic cells. In this communication we have shown that human platelet 20S proteasome exhibited chymotryptic-like activity towards succinyl-Leu-Leu-Val-Tyr-7-amido-4-methylcoumarin as substrate at a broad pH range, with optimum between pH 7.5-8.0 and 5.0-5.5. These two activities were markedly inhibited by a 10 micromol/l concentration of two structurally unrelated proteasome inhibitors: lactacystin/beta-lactone or benzyloxycarbonyl-Ile-Glu(O-tert.-butyl)-Ala-leucinal, but not by ebelactone B, an inhibitor of lysosomal cathepsin A/deamidase. The chymotryptic-like activity of the 20S proteasome against succinyl-Leu-Leu-Val-Tyr-7-amido-4-methylcoumarin was also significantly inhibited in platelets, after exposure of platelet-rich plasma to 10 micromol/l lactacystin and benzyloxycarbonyl-Ile-Glu(O-tert.-butyl)-Ala-leucinal for up to 60 min. This indicates that these inhibitors can enter platelets and selectively inhibit 20S proteasome activity. We also demonstrated for the first time by Western blot analysis that human platelets contain a proteasome activator, PA28, which is known to play a key role in antigen processing by significant stimulation of the proteasomal chymotryptic-like activity. Since the platelet 20S proteasome was also present in a latent form, this suggests that its activity may be regulated in vivo in human platelets. All these results can therefore be beneficial in future studies on the role of the 20S proteasome in platelet biology.

Effects of ebelactone B on cathepsin A activity in intact platelets and on platelet activation

PURPOSE

Previous in vitro studies have demonstrated that a potent antihypertensive agent ebelactone B inhibits cathepsin A/deamidase activity. The aim of our studies was to assess the effects of this inhibitor on cathepsin A activity in intact platelets and on platelet activation events.

MATERIAL AND METHODS

PRP or washed human platelets from healthy volunteers were pre-incubated with different concentrations of ebelactone B (1-10 microM) for 10-60 min. Cathepsin A activity in platelets was assayed colorimetrically using Cbz-Phe-Ala at pH 5.5. Expression of platelet activation markers GpIIb/IIIa and P-selectin on non-activated or agonist-activated platelets (ADP, TRAP) was measured by flow cytometry.

RESULTS

Pre-treatment of platelets for up to 60 minutes with 10 mumol/l ebelactone B, that effectively inhibits cathepsin A activity in platelet lysate, did not affect this activity in intact platelets. Exposure of PRP to 10 mumol/l ebelactone B alone, or before platelet activation with ADP or TRAP caused only a small but non-significant increase in P-selectin and GpIIb/IIIa expression on the platelet surface, as demonstrated by flow cytometry analysis.

CONCLUSIONS

The lack of cathepsin A inhibition by ebelactone B in intact platelets indicates that this inhibitor does not enter cells. Therefore, a potential antihypertensive significance of this compound may be through the inhibition of cathepsin A/deamidase released from activated or damaged cells. In vitro ebelactone B seems to exert no effect on platelet activation. Further studies are underway to determine whether ebelactone B administration affects platelet activation events in experimental model of hypertension in rats.

Chymotrypsin-like activity in rat tissues in experimental acute pancreatitis

PURPOSE

Increase in intracellular chymotrypsin activity was reported during acute pancreatitis. Beside chymotrypsin, there are at least two enzymes with chymotrypsin-like activity: proteasome and lysosomal cathepsin A. Until now it is not known whether and to what extent they contribute to increases in chymotrypsin activity in acute pancreatitis. Our aim was to study organ chymotrypsin-like activities during experimental acute pancreatitis.

MATERIAL AND METHODS

Rat cerulein model of acute pancreatitis was used. The chymotrypsin-like activities were assessed in pancreas, liver, lung, heart, spleen and kidney using highly selective synthetic substrates of the proteasome and the cathepsin A, at neutral and acidic pH. Determinations after addition of selective inhibitor were also performed.

RESULTS

During acute pancreatitis we found in the pancreas an increase only in neutral chymotrypsin-like activity, as compared to the control animals. In other organs neutral chymotrypsin-like activity did not increase, and in kidney it even decreased. There were no changes in acidic chymotrypsin-like activity in any of organs studied. The studies using the inhibitor of the proteasome showed that the neutral chymotrypsin-like activity in the pancreas of the rats with acute pancreatitis should not be attributed to the proteasome activity, but rather to the chymotrypsin.

CONCLUSIONS

Our results did not confirm any significant contribution of proteasome or cathepsin A to increased chymotrypsin-like activity in acute pancreatitis. We showed a decrease in neutral chymotrypsin-like activity of proteasome in the kidney, but the significance of this finding remains to be established.

Lactacystin inhibits cathepsin A activity in melanoma cell lines

We describe the inhibitory effect of the proteasome inhibitor, lactacystin, on cathepsin A activity in murine melanoma cell lines. In vitro lactacystin metabolite, beta-lactone, at a concentration of 1 microM, significantly suppressed cathepsin A activity in B78 melanoma cell lysates by about 50%. Exposure of three murine melanoma cell lines with different metastatic potential to lactacystin at a concentration of 5 microM for 6 h caused a significant reduction in the carboxypeptidase activity of this enzyme, while the inhibitory activity remained unchanged for at least 12 h. Other proteasome-specific inhibitors, e.g. epoxomicin and N-benzyloxycarbonyl-Ile-Glu(O-tert-Bu)-Ala-leucinal (PSI) at a concentration of 1 microM did not affect cathepsin A activity in melanoma cell line lysates. These data support our previous proposal that lactacystin is not a specific inhibitor of the proteasome. Since cathepsin A is also a tumor-associated enzyme, further research is needed to clarify its role and the significance of its inhibition by lactacystin in tumor biology.

Separation of cathepsin A-like enzyme and the proteasome: evidence that lactacystin/beta-lactone is not a specific inhibitor of the proteasome

Previous studies have described a human platelet cathepsin A-like enzyme with a number of similarities to the "acidic" and "neutral" chymotrypsin-like activities of the proteasome. This includes its strong inhibition by the highly specific proteasome inhibitor Lactacystin/beta-lactone, suggesting that either the Cbz-Phe-Ala-hydrolyzing activity attributed to cathepsin A was due to the chymotrypsin-like activity of the proteasome or that lactacystin was not a specific inhibitor of the proteasome. In the present study we discard the first possibility on the basis of the following findings: (a) human platelet cathepsin A, unlike proteasome, binds to concanavalin A, and does not bind to Heparin-Sepharose at pH 7.4; (b) neither the chymotrypsin-like activity of the proteasome, nor proteasome antigens are detected in the cathepsin A preparation; (c) purified proteasome does not exhibit Cbz-Phe-Ala-hydrolyzing activity; (d) Z-lle-Glu-(Ot-Bu)Ala-leucinal (PSI), a compound that selectively inhibits the chymotrypsin-like activity of the proteasome at a concentration of 10 microM has no inhibitory effect on the carboxypeptidase activity of cathepsin A; (e) cathepsin A, free of the proteasome, is completely inhibited by micromolar concentrations of lactacystin/beta-lactone. It is therefore concluded that lactacystin/beta-lactone is not a specific inhibitor of the proteasome.

Cathepsin A activity in primary and metastatic human melanocytic tumors

Several lysosomal proteases including cathepsins B, D, H and L have been found to play a role in the metastasis of tumor cells. However, up to now no information on the role of cathepsin A, a lysosomal multifunctional peptidase, in the proliferative, invasive, and metastatic potential of malignant tumors has been available. In the present study we compared the activity of cathepsin A in lysates of 34 human melanocytic tumors: primary (n = 12) and metastatic (n = 5) malignant melanoma, dysplastic pigmented nevi (n = 6) and pigmented nevi without evidence of dysplastic melanocytes (n = 11). The carboxypeptidase activity of cathepsin A was assayed at pH 5.0 with its specific substrate Cbz-Phe-Ala. The amount of released C-terminal alanine was measured by the ninhydrin method. We found that lysates of primary malignant melanoma lesions exhibited significantly higher cathepsin A activity than lysates of dysplastic and normal pigmented nevi. The cathepsin A activity in lysates of metastatic lesions of malignant melanoma was significantly higher than in primary focus lysates. It seems that cathepsin A may play a role in malignant transformation and metastatic dissemination of malignant melanoma.

[The role of proteolytic enzymes in apoptosis]

The literature review dealing with participation of proteolytic enzymes in initiation and execution of apoptosis was done. Cysteine proteases with Asp-X cleavage specificity, called caspases, play the main role in this process. The other proteases such calpains and proteasomes take also part in apoptosis. The proteases degrade proteins of cytoskeleton and structural proteins of nucleus, they also activate proendonucleases.

Cellular serine carboxypeptidases

The literature on serine carboxypeptidases of cells is reviewed. These proteases occur in the vacuoles of fungi and higher plants and in the lysosomes of animals and man cells. Physico-chemical properties, chemical structure, catalytic mechanism and substrate specificity of these enzymes are presented.

Activity of lysosomal and nonlysosomal proteases of fibrosarcoma induced by methylcholanthrene

Activity of lysosomal (cathepsins A,B,C,D and E) and nonlysosomal proteases (cathepsin G, elastase, collagenase, prolidase, prolinase) was evaluated in fibrosarcoma induced in rats by methylcholanthrene. No differences were found in the activity of the examined proteases in tumours of different size in the external, intermediate and central spheres of these tumours. Activity of cathepsins A,B,C,D,E and G, prolidase and prolinase was higher in the fibrosarcoma and activity of collagenase and elastase was lower than in the rat skin.

Activity and tissue localization of cathepsin G in non small cell lung cancer

Activity and tissue localization of cathepsin G were examined in tumors deriving from 73 patients with non small cell lung cancer. Activity of cathepsin G was highest in adenocarcinoma, lower in planoepitheliale cancer, the lowest in macrocellular cancer. In all histological types of tumors cathepsin G activity in supernatants was lower than in sediments. The enzyme immunohistochemically was localized in neutrophils. There is evident correlation between neutrophil numbers and cathepsin G activity in examined cancer types. Result of our examinations indicate a relationship between cathepsin G activity, grade of tumor differentiation and particular clinical stages of disease.

Activity and tissue localization of cathepsin D in non small cell lung cancer

Activity and tissue localization of cathepsin D were examined in tumors deriving from 80 patients with non small cell lung cancer. Activity of the enzyme was higher in sediments and supernatants of tumors than in non invaded lung parenchyma. In all histological types of tumors cathepsin D activity in sediments was three times lower and in lung parenchyma five times lower than in supernatants. The immunohistochemical technique was used for enzyme localization. We observed seemingly the lack of correlation between activity of cathepsin D examined in tumors and immunohistochemical reaction intensity in neoplasm cells. Different numbers of macrophages and quantity of tumor stroma could explain this effect in examined histological types of cancer. Results of our explanations indicates for relations between cathepsin D activity versus histological type and degree of tumor differentiation. We did not observe correlation between cathepsin D activity versus lymph node metastases and clinical stages.

Cathepsin A-like activity in thrombin-activated human platelets. Substrate specificity, pH dependence, and inhibitory profile

Cathepsin A-like enzyme released from human platelets by thrombin hydrolyzed at the highest rate Cbz-Phe-Ala, Cbz-Phe-Met and Cbz-Phe-Leu, did not require activators and was inhibited by DFP, DCI and mercurial compounds (mersalyl acid, PCMS, PCMB and HgCl2). The optimum activity of secreted enzyme was at pH 5.0-6.0. Cbz-Glu-Tyr was also hydrolyzed at lower pH with optimum at pH 3.5. These enzymatic properties are the same as those of cathepsin A solubilized from whole platelets and purified from other mammalian cells and tissues. High specific activity of secreted cathepsin A, and a broad pH range of activity may have a significance in extracellular proteolysis in local sites of ischemia. Large portion of cathepsin A-like activity was not secretable by high concentration of thrombin and was sedimented with platelet aggregates. No activity of lysosomal carboxypeptidases B and prolylcarboxypeptidase was detectable in supernatants and pellets of thrombin-stimulated platelets.

Lactacystin, a specific inhibitor of the proteasome, inhibits human platelet lysosomal cathepsin A-like enzyme

Lactacystin, the most specific inhibitor of the proteasome, strongly inhibited at pH 5.5 the activity of human platelet lysosomal cathepsin A-like enzyme. At a concentration as low as 1-5 microM it almost completely decreased the hydrolysis rate of cathepsin A specific substrates: Cbz-Phe-Ala and FA-Phe-Phe. This inhibition was probably due to the lactacystin intermediate beta-lactone formed during 10 min hydrolysis at pH 8.0 since nonhydrolyzed inhibitor did not affect cathepsin A activity. Basing on similarities in the inhibitor sensitivity, pH optimum, and substrate preferences it is suggested that the cathepsin A-like activity may be involved in chymotrypsin-like activity of the proteasome.

Activity of lysosomal and nonlysosomal proteases and contents of protein and its degradation products in the blood serum of rats with fibrosarcoma induced by methylcholanthrene

Activity of lysosomal and nonlysosomal proteases and contents of protein and its degradation products in the blood serum of rats with methylcholantrene fibrosarcoma were evaluated. Activity of lysosomal proteases and prolidase and prolinase as well in the blood serum of rats with methylcholanthrene tumour did not differ from the activity of these enzymes in the blood serum of control rats. Only the activity of elastase and collagenase in the blood serum of rats with methylcholanthrene tumour especially with tumour of intermediate and big mass was increased. Content of total protein was decreased in the blood serum of rats with tumour of intermediate and big mass and contents of glycoproteins and alfa-amin nitrogen were increased in comparison to the blood serum of control rats.

Inhibition of human platelet cathepsin A by non-steroidal anti-inflammatory drugs--in vitro study

Since the lysosomal proteases appear at site of inflammation they may be a target for non-steroidal anti-inflammatory drugs (NSAIDs). In in vitro study the inhibition of human platelet cathepsin A by NSAIDs was found. Indomethacin, phenacetin and aminophenazone were the most potent inhibitors of cathepsin A. Acetylsalicylic acid added to platelet lysate inhibited cathepsin A in the same extent as salicylate. The inhibition was time-dependent and reversed after dialysis. Mixed type of inhibition by salicylate was shown.

Pig platelet acidic carboxypeptidases

Pig platelet acidic carboxypeptidases hydrolyzed only N-blocked dipeptides with bulky aromatic and aliphatic hydrophobic amino acids. The optimum hydrolysis of these substrates was at pH 5.0. The main acidic carboxypeptidase in pig platelet lysate was lysosomal carboxypeptidase A (1CPA), which hydrolyzed Cbz-Phe-Ala at the highest rate. A lower activity of this enzyme was found on Cbz-Glu-Tyr and Cbz-Glu-Phe. 1CPA also hydrolyzed Cbz-Glu-Tyr at pH 3.5. No activity of lysosomal carboxypeptidase B in platelet lysate was detectable using Bz-Gly-Arg. Pig platelet acidic carboxypeptidase hydrolyzed Cbz-Pro-Phe and Cbz-Pro-Ala, which are specific substrates of lysosomal prolylcarboxypeptidase, more slowly. The incubation of platelet lysate with plasma did not influence the rate of hydrolysis of Cbz-Glu-Tyr, whereas no hydrolysis of Cbz-Pro-Phe was observed.