A Screening Approach to Assess the Impact of Various Commercial Sources of Crude Marine λ-Carrageenan on the Production of Oligosaccharides with Anti-heparanase and Anti-migratory Activities.

Oligosaccharides derived from λ-carrageenan (λ-COs) are gaining interest in the cancer field. They have been recently reported to regulate heparanase (HPSE) activity, a protumor enzyme involved in cancer cell migration and invasion, making them very promising molecules for new therapeutic applications. However, one of the specific features of commercial λ-carrageenan (λ-CAR) is that they are heterogeneous mixtures of different CAR families, and are named according to the thickening-purpose final-product viscosity which does not reflect the real composition. Consequently, this can limit their use in a clinical applications. To address this issue, six commercial λ-CARs were compared and differences in their physiochemical properties were analyzed and shown. Then, a H2O2-assisted depolymerization was applied to each commercial source, and number- and weight-averaged molar masses (Mn and Mw) and sulfation degree (DS) of the λ-COs produced over time were determined. By adjusting the depolymerization time for each product, almost comparable λ-CO formulations could be obtained in terms of molar masses and DS, which ranged within previously reported values suitable for antitumor properties. However, when the anti-HPSE activity of these new λ-COs was screened, small changes that could not be attributed only to their small length or DS changes between them were found, suggesting a role of other features, such as differences in the initial mixture composition. Further structural MS and NMR analysis revealed qualitative and semi-quantitative differences between the molecular species, especially in the proportion of the anti-HPSE λ-type, other CARs types and adjuvants, and it also showed that H2O2-based hydrolysis induced sugar degradation. Finally, when the effects of λ-COs were assessed in an in vitro migration cell-based model, they seemed more related to the proportion of other CAR types in the formulation than to their λ-type-dependent anti-HPSE activity.

A Marine λ-Oligocarrageenan Inhibits Migratory and Invasive Ability of MDA-MB-231 Human Breast Cancer Cells through Actions on Heparanase Metabolism and MMP-14/MMP-2 Axis.

Sugar-based molecules such as heparins or natural heparan sulfate polysaccharides have been developed and widely studied for controlling heparanase (HPSE) enzymatic activity, a key player in extracellular matrix remodelling during cancer pathogenesis. However, non-enzymatic functions of HPSE have also been described in tumour mechanisms. Given their versatile properties, we hypothesized that sugar-based inhibitors may interfere with enzymatic but also non-enzymatic HPSE activities. In this work, we assessed the effects of an original marine λ-carrageenan derived oligosaccharide (λ-CO) we previously described, along with those of its native counterpart and heparins, on cell viability, proliferation, migration, and invasion of MDA-MB-231 breast cancer cells but also of sh-MDA-MB-231 cells, in which the expression of HPSE was selectively downregulated. We observed no cytotoxic and no anti-proliferative effects of our compounds but surprisingly λ-CO was the most efficient to reduce cell migration and invasion compared with heparins, and in a HPSE-dependent manner. We provided evidence that λ-CO tightly controlled a HPSE/MMP-14/MMP-2 axis, leading to reduced MMP-2 activity. Altogether, this study highlights λ-CO as a potent HPSE "modulator" capable of reducing not only the enzymatic activity of HPSE but also the functions controlled by the HPSE levels.

λ-Carrageenan Oligosaccharides of Distinct Anti-Heparanase and Anticoagulant Activities Inhibit MDA-MB-231 Breast Cancer Cell Migration.

In tumor development, the degradation of heparan sulfate (HS) by heparanase (HPSE) is associated with cell-surface and extracellular matrix remodeling as well as the release of HS-bound signaling molecules, allowing cancer cell migration, invasion and angiogenesis. Because of their structural similarity with HS, sulfated polysaccharides are considered a promising source of molecules to control these activities. In this study, we used a depolymerisation method for producing λ-carrageenan oligosaccharides (λ-CO), with progressive desulfation over time. These were then used to investigate the influence of polymeric chain length and degree of sulfation (DS) on their anti-HPSE activity. The effects of these two features on λ-CO anticoagulant properties were also investigated to eliminate a potential limitation on the use of a candidate λ-CO as a chemotherapeutic agent. HPSE inhibition was mainly related to the DS of λ-CO, however this correlation was not complete. On the other hand, both chain length and DS modulated λ-CO activity for factor Xa and thrombin IIa inhibition, two enzymes that are involved in the coagulation cascade, and different mechanisms of inhibition were observed. A λ-carrageenan oligosaccharide of 5.9 KDa was identified as a suitable anticancer candidate because it displayed one of the lowest anticoagulant properties among the λ-CO produced, while showing a remarkable inhibitory effect on MDA-MB-231 breast cancer cell migration.

Family of Bioactive Heparin-Coated Iron Oxide Nanoparticles with Positive Contrast in Magnetic Resonance Imaging for Specific Biomedical Applications.

Unfractionated heparin (UFH) and low-molecular-weight heparins (LMWH) are well-known for their anticoagulant properties. There is also currently a growing interest in using LMWH in targeted cancer therapy. In particular, several types inhibit heparanase, a key enzyme overexpressed in the tumor microenvironment that promotes angiogenesis progression and metastasis spreading. Here, we propose iron oxide nanoparticles (HEP-IONP) coated with different heparins of distinct anticoagulant/anti-heparanase activity ratios and suitable for positive contrast in magnetic resonance imaging. As a proof of concept, magnetic resonance angiography (MRA) was conducted in mice up to 3 h after intravenous administration. This new IONP-based positive contrast appropriate for clinic together with the long vascular circulating times can enable innovative theranostic applications if combined with the various bioactivities of the heparins. Indeed, we showed, using advanced in vitro tests, how HEP-IONP anticoagulant or anti-heparanase activities were maintained depending on the heparin species used for the coating. Overall, the study allowed presenting an IONP coated with a commercial LMWH (Lovenox) suggested as a theranostic translational probe for MRA diagnostic and treatment of thrombosis, and an antitumor IONP coated with a specific depolymerized heparin to be used in targeted therapy and diagnostic modalities.

Assessment of Heparanase-Mediated Angiogenesis Using Microvascular Endothelial Cells: Identification of λ-Carrageenan Derivative as a Potent Anti Angiogenic Agent.

Heparanase is overexpressed by tumor cells and degrades the extracellular matrix proteoglycans through cleavage of heparan sulfates (HS), allowing pro-angiogenic factor release and thus playing a key role in tumor angiogenesis and metastasis. Here we propose new HS analogs as potent heparanase inhibitors: Heparin as a positive control, Dextran Sulfate, λ-Carrageenan, and modified forms of them obtained by depolymerization associated to glycol splitting (RD-GS). After heparanase activity assessment, 11 kDa RD-GS-λ-Carrageenan emerged as the most effective heparanase inhibitor with an IC50 of 7.32 ng/mL compared to 10.7 ng/mL for the 16 kDa unfractionated heparin. The fractionated polysaccharides were then tested in a heparanase-rich medium-based in vitro model, mimicking tumor microenvironment, to determine their effect on microvascular endothelial cells (HSkMEC) angiogenesis. As a preliminary study, we identified that under hypoxic and nutrient poor conditions, MCF-7 cancer cells released much more mature heparanase in their supernatant than in normal conditions. Then a MatrigelTM assay using HSkMEC cultured under hypoxic conditions in the presence (or not) of this heparanase-rich supernatant was realized. Adding heparanase-rich media strongly enhanced angiogenic network formation with a production of twice more pseudo-vessels than with the control. When sulfated polysaccharides were tested in this angiogenesis assay, RD-GS-λ-Carrageenan was identified as a promising anti-angiogenic agent.

Hemorphin 7 reflects hemoglobin proteolysis in abdominal aortic aneurysm.

OBJECTIVE: In human abdominal aortic aneurysm, the accumulation of blood-derived cells and proteases within the mural thrombus plays a pivotal role in the evolution toward vessel wall rupture. We sought to identify peptides released from abdominal aortic aneurysm specimens, characterized by an intraluminal thrombus. METHODS AND RESULTS: Intraluminal thrombus samples were analyzed by differential proteomics, using surface-enhanced laser desorption/ionization time-of-flight mass spectrometry. A 1309-Da peptide was detected in larger amounts in the newly formed luminal thrombus layer relative to older layers. It was identified as being LVVYPWTQRF (known as LVV-Hemorphin 7), a peptide generated from hemoglobin by cathepsin D. By immunohistochemical analysis, we showed that Hemorphin 7 (H7) colocalizes with cathepsin D and cathepsin G in the luminal layer of the intraluminal thrombus. In vitro, cathepsin G was able to generate H7 peptides at pH 7.4, whereas cathepsin D was only active in acidic conditions. Finally, H7 peptides were shown to be increased 3- to 4-fold in sera of abdominal aortic aneurysm patients relative to controls, and their levels were positively correlated with the volume of the thrombus. CONCLUSIONS: Our results suggest that circulating H7 peptides may reflect proteolysis of hemoglobin in the aneurysmal intraluminal thrombus and may be used as a biological marker of pathological vascular remodeling.

Antiproliferative activity of violaxanthin isolated from bioguided fractionation of Dunaliella tertiolecta extracts.

Dunaliella tertiolecta (DT) was chemically investigated to isolate molecules inhibiting cancer cell proliferation and inducing apoptosis in vitro. The potency to inhibit cell growth was used for the bio-guided fractionation and isolation of active compounds using chromatographic techniques. The DT dichloromethane extract exhibited a strong anti-proliferative activity on MCF-7 and LNCaP cells, and was further fractionated and sub-fractionated by RP-HPLC. High resolution mass spectrometry and spectrophotometric analysis unequivocally identified violaxanthin as the most antiproliferative molecule present in DT DCM extract. Violaxanthin purified from DT induced MCF-7 dose-dependent growth inhibition in continuous and discontinuous treatments, at concentrations as low as 0.1 µg·mL⁻¹ (0.17 µM). Phosphatidylserine exposure, typical of early apoptosis, was observed after 48 h treatment at 8 µg·mL⁻¹ (13.3 µM) but no DNA fragmentation, characteristic of late apoptosis steps, could be detected even after 72 h treatment at 40 µg·mL⁻¹ (66.7 µM). Taken together, our results demonstrate the strong antiproliferative activity of violaxanthin on one human mammary cancer cell line, and suggest that studying the pharmacology of violaxanthin and pharmacomodulated derivatives on cancer cells may allow potent antiproliferative drugs to be obtained.

Heparin length in the coating of extremely small iron oxide nanoparticles regulates in vivo theranostic applications.

The positive contrast of extremely small iron oxide nanoparticles (ESIONP) in magnetic resonance imaging (MRI) rejuvenates this class of metal nanoparticles (NP).Yet, the current synthesis often lacks the possibility of adjusting the core size (while it is a key element for ESIONP-based MRI contrast behaviour), and also involved multiple complex steps before obtaining a ready-to-use probe for medical applications. In this study, we faced these challenges by applying heparin oligosaccharides (HO) of different lengths as coatings for the preparation of HEP-ESIONP with a one-pot microwave method. We demonstrated that the HO length could control the core size during the synthesis to achieve optimal positive MRI contrast, and that HEP-ESIONP were endowed directly with anticoagulant properties and/or a specific antitumor activity, according to the HO used. Relevantly, positron emission tomography (PET)-based in vivo biodistribution study conducted with 68Ga core-doped HEP-ESIONP analogues revealed significant changes in the probe behaviours, the shortening of HO promoting a shift from hepatic to renal clearance. The different conformations of HO coatings and a thorough in vitro characterisation of the probes' protein coronas provided insight into this crucial impact of HO length on opsonization-mediated immune response and elimination. Overall, we were able to identify a precise HO length to get an ESIONP probe showing prolonged vascular lifetime and moderate accumulation in a tumor xenograft, balanced with a low uptake by non-specific organs and favourable urinary clearance. This probe met all prerequisites for advanced theranostic medical applications with a dual MRI/PET hot spot capability and potential antitumor activity.

Impact of ultrafiltration and nanofiltration of an industrial fish protein hydrolysate on its bioactive properties.

BACKGROUND: Numerous studies have demonstrated that in vitro controlled enzymatic hydrolysis of fish and shellfish proteins leads to bioactive peptides. Ultrafiltration (UF) and/or nanofiltration (NF) can be used to refine hydrolysates and also to fractionate them in order to obtain a peptide population enriched in selected sizes. This study was designed to highlight the impact of controlled UF and NF on the stability of biological activities of an industrial fish protein hydrolysate (FPH) and to understand whether fractionation could improve its content in bioactive peptides. RESULTS: The starting fish protein hydrolysate exhibited a balanced amino acid composition, a reproducible molecular weight (MW) profile, and a low sodium chloride content, allowing the study of its biological activity. Successive fractionation on UF and NF membranes allowed concentration of peptides of selected sizes, without, however, carrying out sharp separations, some MW classes being found in several fractions. Peptides containing Pro, Hyp, Asp and Glu were concentrated in the UF and NF retentates compared to the unfractionated hydrolysate and UF permeate, respectively. Gastrin/cholecystokinin-like peptides were present in the starting FPH, UF and NF fractions, but fractionation did not increase their concentration. In contrast, quantification of calcitonin gene-related peptide (CGRP)-like peptides demonstrated an increase in CGRP-like activities in the UF permeate, relative to the starting FPH. The starting hydrolysate also showed a potent antioxidant and radical scavenging activity, and a moderate angiotensin-converting enzyme (ACE)-1 inhibitory activity, which were not increased by UF and NF fractionation. CONCLUSION: Fractionation of an FPH using membrane separation, with a molecular weight cut-off adapted to the peptide composition, may provide an effective means to concentrate CGRP-like peptides and peptides enriched in selected amino acids. The peptide size distribution observed after UF and NF fractionation demonstrates that it is misleading to characterize the fractions obtained by membrane filtration according to the MW cut-off of the membrane only, as is currently done in the literature.

Goat whey fermentation by Kluyveromyces marxianus and Lactobacillus rhamnosus release tryptophan and tryptophan-lactokinin from a cryptic zone of alpha-lactalbumin.

Angiotensin-I-Converting Enzyme (ACE) inhibitors peptides were produced from unsupplemented acid goat whey fermented aerobically for 168 h by Kluyveromyces marxianus and Lactobacillus rhamnosus. This yeast-lactobacillus association is GRAS. Two novel lactokinins were identified: NYW and W with IC50 of 20 and 0.86 mum respectively. They both were resistant toward simulated gastrointestinal digestion. In addition, WLAHK was found in the hydrolysate. These three sequences belong to f(99-110) of alpha-la which seems to be a lactokinin cryptic zone. W was the major molecule released by the fermentation process. Considering that W is the precursor of serotonin, the hydrolysate produced could be of interest for the generation of functional health ingredient involved in regulation of affective disorders and hypertension.

Crude goat whey fermentation by Kluyveromyces marxianus and Lactobacillus rhamnosus: contribution to proteolysis and ACE inhibitory activity.

Unsupplemented acid goat whey containing 0.96% protein and 2.76% lactose was fermented aerobically with 32 microflora extracted from various raw milk cheeses and dairy products. These microflora were screened for their ability to hydrolyse whey proteins (alpha-lactalbumin and/or beta-lactoglobulin) and to generate peptides inhibitors of Angiotensin I Converting Enzyme. Five microflora were able to degrade whey protein. The most efficient microflora was able to fully hydrolyse alpha-lactalbumin and to a lesser extend beta-lactoglobulin. It was extracted from Bamalou des Pyrenées cheese. Micro-organisms involved consisted of yeast Kluyveromyces marxianus and lactobacillus Lactobacillus rhamnosus. Both were able to produce ACE inhibitory peptides after whey fermentation.

Production of heparin and λ-carrageenan anti-heparanase derivatives using a combination of physicochemical depolymerization and glycol splitting.

Strongly associated with tumor angiogenesis and metastasis, the enzyme heparanase is an endo-ß-d-glucuronidase which is overexpressed in the tumor microenvironment. Its inhibition could be one of the most promising anti-angiogenic approaches to date. Although heparin is known as a good heparanase inhibitor, it also possesses major anticoagulant properties that may be incompatible with its use as an anti-angiogenic agent, hence the considerable interest for other sources of sulfated polysaccharides. Recent investigations point to λ-carrageenans, highly sulfated galactans with a tremendous potential that are found in red algae. This study describes the production of low-molecular-weight (LMW) heparins and λ-carrageenans, using a combination of glycol splitting and ultrasonically-assisted radical hydrolysis using hydrogen-peroxide. The structural characteristics, as well as the anticoagulant and antiheparanase activities of the resulting products were assessed. The best candidate was a LMW glycol-split λ-carrageenan that displayed major anti-heparanase properties, with an IC50 of 7.32ng/mL and a close-to-zero anticoagulant activity.

Brain processing of hemorphin-7 peptides in various subcellular fractions from rats.

Hemorphins are multifunctional peptides derived from hemoglobin or blood processing. They have been found at high levels within the central nervous system where they have a direct effect on neuronal cells via peptidergic receptors. As relatively few studies have examined their metabolic stability in the brain, such investigation was performed to locate the cellular distribution of enzymatic activity against these peptides. High-performance liquid chromatography (HPLC) combined with electrospray ionisation mass spectrometry (ESI-MS) allows identification of degradation products resulting from incubation of hemorphin-7 peptides (LVV-hemorphin-7, VV-hemorphin-7 and hemorphin-7) with subcellular fractions isolated from rat brain tissue. Metabolic activities were found against the three peptides in brain homogenate and subcellular fractions with the highest metabolic activity (<3% peptide remaining after 10 min) observed in the microsomal fraction which processed hemorphin-7 peptides mainly into N-terminal fragments (giving LVVH5) suggesting action of brain-membrane enzymes with C-terminal specificity. Incubation of the ACE inhibitor captopril (0.2 microM) with microsomal fraction, together with LVVH7, decreased the processing of LVVH7 to form LVVH5 by 85%.

Anti-heparanase activity of ultra-low-molecular-weight heparin produced by physicochemical depolymerization.

Heparanase is an endo-ß-D-glucuronidase that plays an important role in cancer progression, in particular during tumor angiogenesis and metastasis. Inhibiting this enzyme is considered as one of the most promising approaches in cancer therapy. Heparin is a complex glycoaminoglycan known as a strong inhibitor of heparanase. It is primarily used in clinical practice for its anticoagulant activities, which may not be compatible with its use as anti-angiogenic agent. In this study, we described the production of ultra-low-molecular-weight heparins (ULMWH) by a physicochemical method that consists in a hydrogen peroxide-catalyzed radical hydrolysis assisted by ultrasonic waves. We assessed the structural characteristics, anticoagulant and anti-heparanase activities of the obtained heparin derivatives and compared them with three commercial low-molecular-weight heparins (LMWH), glycol-split non-anticoagulant heparins and heparins produced by enzymatic methods. ULMWH generated by the physicochemical method were characterized by high anti-heparanase and moderate anticoagulant activities. These heparin derivatives might be potential candidates for cancer therapy when a compromise is needed between anti-heparanase and anticoagulant activities.

Alteration of cathepsin D trafficking induced by hypoxia and extracellular acidification in MCF-7 breast cancer cells.

The microenvironment that surrounds tumor cells is characterized by hypoxic conditions and extracellular acidity. These hostile conditions induce crucial changes in cell behavior and can promote the secretion of many soluble factors such as growth factors, cytokines and enzymes. The lysosomal aspartyl-endopeptidase cathepsin D (CD) is a marker of poor prognosis in breast cancer and is associated with a metastatic risk. In this study, the transport of CD was investigated in a model of breast cancer cells line (MCF-7) cultivated under hypoxia and acidification of media. CD secretion was assessed using Western blot analysis and protease activity was measured in conditioned culture media. We demonstrate that cultured MCF-7 cells secrete an active 52 kDa pCD precursor and report that under hypoxia there was an increased amount of pCD secreted. More surprisingly, extracellular acidification (pH 6 and 5.6) induced the secretion of the fully-mature and active (34 kDa + 14 kDa) double chain CD. Our findings reflect the fact that chemical anomalies influence the secretion path of CD in a breast cancer cell model, resulting in altered trafficking of the mature form. This important result may provide new arguments in favor of the role of extracellular CD in the degradation of the matrix proteins that constitute the breast tumor microenvironment.

Comparative effects of angiotensin IV and two hemorphins on angiotensin-converting enzyme activity.

The role of angiotensin IV (AngIV) in the regulation of angiotensin-converting enzyme (ACE) was studied in vitro. This study demonstrates that this active fragment appeared as a novel endogenous ACE inhibitor. Inhibitory kinetic studies revealed that AngIV acts as a purely competitive inhibitor with a K(i) value of 35 microM. AngIV was found to be quite resistant to ACE hydrolysis opposite to hemorphins which are both ACE inhibitors and substrates. In order to confirm a putative role of AngIV and hemorphins in the Renin-Angiotensin system (RAS) regulation, we studied their influence on AngI conversion. We noticed that 16.7 microM of both peptides decreased more than 50% of AngI conversion to AngII in vitro. The capacity of hemorphins, particularly LVVH-7, and AngIV to inhibit ACE activity here suggests a synergistic relation between these two peptides and the regulation of RAS.

Serum levels of Hemorphin-7 peptides in patients with breast cancer.

BACKGROUND: Increased expression of cathepsin D (CD) and B (CB) is found in some cancers and correlates with the development of clinical metastases. It was suggested that these cathepsins could be used as prognostic markers, especially CD in breast cancer. Because serum level of Hemorphin-7 (H7) peptides could reflect CD activity, we have hypothesised that it could be used as a prognostic factor in breast cancer. METHODS: To verify this hypothesis, H7 serum levels from 62 breast cancer patients and 25 healthy controls were measured by ELISA. RESULTS: The mean serum concentration of H7 was 2.27+/-0.63 mumol/l in breast cancer patients in comparison with 4.09+/-1.05 mumol/l in controls (p=0.002). This reduced level of H7 in breast cancer could be due to the over-expression of CB, which exhibits strong interaction with H7 in vitro, with a ratio K(cat)/K(m) estimated at 18000 s(-1) M(-1). CONCLUSIONS: Because H7 serum levels did not correlate with other parameters including age, CA15-3 and ACE markers, it seems that they might be used as independent markers for the diagnosis of breast cancer.

Cathepsin D activity and selectivity in the acidic conditions of a tumor microenvironment: Utilization in the development of a novel Cathepsin D substrate for simultaneous cancer diagnosis and therapy.

Pro-Cathepsin D (pCD) is an aspartyl endopeptidase which is over expressed in many cancers. This over expression generally led to its secretion into the extracellular culture medium of cancer cells. Moreover, pCD can auto activate and cleave its substrates at an acidic pH compatible with that found in tumor microenvironments (TME). Thus, exploiting these two pathological characteristics of TME offers the opportunity to develop new protease-activated vector on the basis of their specific substrate structures. The aim of this study was to validate new pCD substrates in the extracellular pH conditions of TME. As a first step, we investigated the effect of pH on the catalytic activity and selectivity of mature Cathepsin D (CD). It was found that the increase in the pH of the media led to a decrease in the reaction rate. However, the specificity of mature CD was not affected by a variation in pH. In the second step, the effect of the substrate structure was studied. We demonstrated that the substrate structure had a significant effect on the catalytic activity of CD. In fact, some modifications in peptide structure induced a change in the catalytic behavior that involved a substrate activation phenomenon. We suggest that this activation may be related to the amphiphilic nature of the modified peptide that may induce an interfacial activation mechanism. Finally, pCD, which is the major form found in the extracellular culture medium of cancer cells, was used. We demonstrated that the proform of CD cleave the modified peptide 5 at pH 6.5 with the same cleavage selectivity obtained with the mature form of the protease. These data provide a better understanding of CD behavior in tumor microenvironment conditions and this knowledge can be used to develop more specific tools for diagnosis and drug delivery.

Ultrasonic-assisted preparation of a low molecular weight heparin (LMWH) with anticoagulant activity.

Low molecular weight heparin (LMWH) is currently used as an anticoagulant agent and constitutes an alternative to unfractionated heparin, which is the cause of serious adverse drug reaction such as heparin-induced thrombocytopenia (HIT). Commercially available LMWH is produced by enzymatic depolymerization that is costly or by chemical methods that are generally carried out under conditions that could imply side reactions that reduce final product efficiency and yields. In this work, we present the use of a physicochemical method for the production of LMWH. This method consists in the use of hydrogen peroxide-catalyzed radical hydrolysis assisted by ultrasonic waves. LMWH that are produced using this physicochemical method have an average molecular weight and anticoagulant properties (Anti-Xa and Anti-IIa) that are comparable to some of commercial LMWH that are currently used. Ultrasonic-assisted radical depolymerization of heparin leads to products with a remarkably low polydispersity index. Moreover, in comparison to other LMWH such as those produced by enzymatic ß-elimination, this physicochemical depolymerization of heparin induces fewer oligosaccharides with less than five monosaccharide units. This contributes to the better preservation of the ATIII pentasaccharide binding sequence, which results in a high Anti-Xa/Anti-IIa ratio (1.86). However, LMWH obtained using this physicochemical method have a lower degree of sulfation than other LMWH, which seems to be the cause of a lower Anti-Xa and Anti-IIa activity (143.62±5.42 and 77.07±4.4, respectively).

Measuring angiotensin-I converting enzyme inhibitory activity by micro plate assays: comparison using marine cryptides and tentative threshold determinations with captopril and losartan.

To determine the angiotensin-I converting enzyme (ACE) inhibitory activity of marine cryptides, different methods were tested. ACE inhibition was measured using two synthetic substrates, (N-[3-(2-furyl) acryloyl]-Phe-Gly-Gly (FAPGG) and N-hippuryl-His-Leu hydrate salt (HHL)), and a natural one, angiotensin-I. The IC50 value (defined as the concentration of inhibitory molecule needed to inhibit 50% of the ACE activity) of the reference synthetic inhibitor captopril was in the nanomolar range (1.79-15.1 nM) when synthetic substrates were used, whereas it exhibited IC50 of micromolar range (16.71 µM) with angiotensin-I. We chose losartan, an antagonist of angiotensin-II receptor as negative control for the ACE inhibition. Losartan was also able to inhibit ACE whatever the substrate tested, with IC50 of micromolar range (17.13-146 µM). We defined this value as a limit above which molecules are not showing in vitro ACE inhibitory activity. Val-Trp (VW), Val-Tyr (VY), Lys-Tyr (KY), Lys-Trp (KW), Ile-Tyr (IY), Ala-Pro (AP), Val-Ile-Tyr (VIY), Leu-Lys-Pro (LKP), Gly-Pro-Leu (GPL), Ala-Lys-Lys (AKK), and Val-Ala-Pro (VAP) were tested as inhibitors of ACE with synthetic and natural substrates. IC50 displayed were substrate-dependent. With FAPGG as substrate, IW, VAP, KY, IY, AP, AKK, and VIY show IC50 values over the IC50 value of losartan and should not be considered as inhibitors of ACE. VY, VW, KW, and LKP exhibited IC50 value lower than the IC50 value of losartan for all substrates tested and were thus considered as good candidates for effectively decreasing hypertension. It appears that the comparison of IC50 is not consistent when IC50 values are obtained with different substrates and different methods. In vitro ACE inhibitory activity assays should always include various ACE substrates and references such as captopril and a negative control to obtain data reliable to discriminate ACE inhibitory peptides.