QSAR and molecular docking modelling of anti-leishmanial activities of organic selenium and tellurium compounds

Leishmaniasis affects mainly rural areas and the poorest people in the world. A computational study of the antileishmanial activity of organic selenium and tellurium compounds was performed. The 3D structures of the compounds were optimized at the wb97xd/lanl2dz level and used in the quantitative structure-activity relationship (QSAR) analysis. The antileishmanial activity was measured by L. donovani β carbonic anhydrase inhibition (Ki) and the half-maximal inhibitory concentration (IC₅₀) against L. infantum amastigotes. The dataset was divided into training (75%) and test sets (25%) by using a k-means clustering algorithm. For pKi prediction, model M3 with seven 3D topographic descriptors was characterized by the following statistical parameters: r ² = 0.879, Q ² _LOO = 0.822, and Q ² _ext = 0.840. For pIC₅₀ prediction, model M12 with six attributes was characterized by the following statistical parameters: r ² = 0.907, Q ² _LOO = 0.824, and Q ² _ext = 0.795. Both models met all the requirements of Tropsha´s test, which implies predictions of pIC₅₀ and pKi activities with high accuracy. Concomitantly, favourable interactions of the sulphonamide group with the Zn atom in the protein were revealed by the docking analysis.

FRI0460 SAFETY OF BIOLOGICAL AGENTS IN JUVENILE IDIOPATHIC ARTHRITIS: A META-ANALYSIS OF OBSERVATIONAL STUDIES

Background:

Follow-up cohorts (observational studies) were initiated consecutively or simultaneously to the development of randomised controlled trials (RCTs) in JIA patients(1,2). They help to identify many complications observed only in clinical practice related to off label use, coadministration of treatments, drug misuse, and occurrence of rare or unexpected event. In addition, observational studies include a higher number of patients with a longer duration of follow-up compared to randomised trials. Hence, they have a higher power to capture the occurrence of serious adverse events (SAE) in daily clinical practice3.

Objectives:

To estimate the incidence of serious adverse events (SAEs) including serious infections, malignancies, and death in patients with juvenile idiopathic arthritis (JIA) treated with biological agents (BAs) in daily clinical practice, using meta-analysis techniques.

Methods:

We systematically searched, up to May 2019, Medline and Embase databases for observational studies performed in JIA disease under BAs treatment. Outcomes were SAEs, serious infections, malignancies and all-cause mortality. Complementary, the incidence of SAEs in randomised controlled trials (RCTs) with withdrawal and parallel designs was performed by meta-analysis.

Results:

A total of 31 observational studies were included (6811 patients totalizing 17530 patients-years [PY] of follow-up). The incidence rate of SAEs was similar in observational cohorts and withdrawal RCTs (4.46 events per 100 PY, 95% CI 2.85- 6.38, I2= 95%) and 3.71 events per 100 PY (95%CI 0.0-13.34), I2= 56%, respectively). The incidence of SAE was lower in parallel RCT. The incidence rate of serious infections, malignancies and death in observational cohorts was estimated at 0.74 events per 100 PY (95%CI 0.32-1.30, I2=83%), 0.10 events per 100 PY (95% CI 0.06-0.16, I2=0%) and 0.09 events per 100 PY (95% CI 0.05-0.14, I2=0%), respectively. Infections were the known cause of death in 8 of the 14 deaths. In meta-regression and subgroup analysis, variation of serious infections rates were partially explained by follow-up time (R2= 30.3%, p= 0.0008), JIA categories (all JIA versus polyarticular versus systemic JIA categories, p= 0.001) and cohort quality (Newcastle-Ottawa score ≥ to 6 versus ≤ to 5 stars, p= 0.0025).

Conclusion:

Our results suggest that the incidence rate of SAEs related to BAs in JIA disease is similar to those observed in randomised withdrawal trials. The overall incidence remained low. However, unsatisfactory description of SAEs prevents analysis of hospitalisation causes. Infection and, to a lesser extent, cancer and death, explain only part of burden of BAs.

References:

[1]Berard RA, Laxer RM. Learning the hard way: clinical trials in juvenile idiopathic arthritis. Ann Rheum Dis. 2018;77(1):1–2.

[2]Swart J, Giancane G, Horneff G, Magnusson B, Hofer M, Alexeeva Е, et al. Pharmacovigilance in juvenile idiopathic arthritis patients treated with biologic or synthetic drugs: combined data of more than 15,000 patients from Pharmachild and national registries. Arthritis Res Ther. 2018 27;20(1):285.

[3]Monti S, Grosso V, Todoerti M, Caporali R. Randomized controlled trials and real-world data: differences and similarities to untangle literature data. Rheumatol Oxf Engl. 2018 01;57(57 Suppl 7):vii54–

Disclosure of Interests:

None declared

Comparison of a new chemiluminescent immunoassay for von Willebrand factor activity with the ristocetin cofactor-induced platelet agglutination method

Measuring von Willebrand factor (VWF) activity is essential for the diagnosis of von Willebrand disease (VWD). The VWF activity is usually assessed based on measurement of the ristocetin cofactor (VWF:RCo). However, that test is technically challenging and has high intra- and inter-assay variabilities. A new automated chemiluminescent immunoassay VWF activity has recently become commercially available (HemosIL AcuStar von Willebrand Factor Ristocetin Cofactor Activity). The main objective of this study was to evaluate this new method and to compare it with the VWF:RCo assay as the reference method. We studied 91 samples, 18 healthy volunteers samples and 73 samples from patients (VWF:RCo level <50 IU dL(-1) ): 29 type 1 VWD, 13 type 2A, 5 type 2B, 5 type 2M, 3 type 2N, 5 type 3, 4 type 3 under treatment, 5 type 3 carriers and 4 samples with other pathologies. The HemosIL AcuStar VWF:RCo assay was 96% sensitive and 100% specific for detecting VWF abnormalities. The good analytical performance, and the sensitivity and specificity of HemosIL AcuStar VWF:RCo to detect VWF deficiency renders it a suitable method for VWD screening.

A multicommuted flow system for the determination of copper, chromium, iron and lead in lubricating oils with detection by flame AAS

In this work, a flow analysis procedure for the determination of copper, chromium, iron and lead in lubricating oils using flame AAS as detection technique is described. The flow manifold was designed to implement the multicommutation approach and it comprised three 3-way solenoid valves controlled by a personal computer. The flow system presented allowed to process the oil samples to determine wear metals without any prior preparation. Aiming to assess accuracy the results were compared with those obtained by manual procedure using flame AAS. Applying the joint-confidence ellipse test, no significant difference at the 95% confidence level was observed. Other profitable features such as a sample throughput of 50 determinations per hour; relative standard deviations (n = 5) below 2% for Cu, and below 8% for Cr, Fe and Pb; and linear responses in the range 0-40ppm (w/w) (Cu, Fe) and 0-15ppm (w/w) (Cr, Pb) were also achieved.

Inhibitor development in one patient and laboratory discrepancies in several families with both mild haemophilia and Arg531Cys mutation

Certain mutations in mild haemophilia A have been associated with a greater risk of inhibitor development, especially when associated with intense treatment. We present a patient with both mild haemophilia A and Arg531Cys mutation, which developed lowtitre inhibitors and was not seen to be related to the intense substitute treatment. The inhibitor has a greater effect on the exogenous factor VIII, permiting an adequate response to treatment with desmopressin. A discrepancy exists in the factor VIII activity in this our patient and in the haemophiliacs of another two families with the same mutation when determination is performed with one-stage or chromogenic method.

Factors that control the reactivity of the interface cysteine of triosephosphate isomerase from Trypanosoma brucei and Trypanosoma cruzi

The amino acid sequences and X-ray structures of homodimeric triosephosphate isomerase from the pathogenic parasites Trypanosoma brucei (TbTIM) and Trypanosoma cruzi (TcTIM) are markedly similar. In the two TIMs, the side chain of the only interface cysteine (Cys14) of one subunit docks into loop 3 of the other subunit. This portion of the interface is also markedly similar in the two enzymes. Nonetheless, Cys14 of TcTIM is nearly 2 orders of magnitude more susceptible to the thiol reagent methylmethane thiosulfonate (MMTS) than Cys14 of TbTIM. The causes of this difference were explored by measuring the second-order rate constant of inactivation by MMTS (k(2)) under various conditions. At pH 7.4, k(2) in TcTIM is 70 times higher than in TbTIM. The difference decreases to 30 when the amino acid sequence of loop 3 and adjoining residues of TbTIM are conferred to TcTIM (triple mutant). The pK(a) values of the thiol group of the interface cysteine of TcTIM and the triple mutant were 0.7 pH unit lower than in TbTIM. Because this difference could account for the different sensitivity of the enzymes to thiol reagents, we determined the k(2) of inactivation at equal levels of ionization of their interface cysteines. Under these conditions, the difference in k(2) between TcTIM and TbTIM became 8-fold, whereas that of the triple mutant to TbTIM was 1.5 times. The substrate analogue phosphoglycolate did not modify the pK(a) of the thiol group of the interface, albeit it diminished the rate of its derivatization by MMTS. In the presence of phosphoglycolate, under conditions in which the interface cysteines of the enzymes had equal levels of protonation, the difference in k(2) of TcTIM and TbTIM became smaller, whereas k(2) of the triple mutant was almost equal to that of TbTIM. Thus, from measurements of the reactivity of the interface cysteine in various conditions, it was possible to obtain information on the factors that control the dynamics of a portion of the dimer interface.

Cleavage of the TrkA neurotrophin receptor by multiple metalloproteases generates signalling-competent truncated forms

The ectodomain of the neurotrophin receptor TrkA has been recovered as a soluble fragment from the culture media of cells by a process that involves endoproteolytic cleavage. This cleavage may be upregulated by several treatments, including NGF treatment or protein kinase C activation. In this report we have investigated the cellular site and proteolytic activities involved in TrkA cleavage, and the effects of ectodomain truncation on signalling. Cleavage occurs when the receptor is at, or near, the cell surface, and it can be prevented by agents that affect protein sorting. Cleavage generates several cell-bound fragments, and their generation can be differentially blocked by inhibitors, documenting the involvement of multiple plasma membrane metalloendoproteases. The major cell-bound receptor fragment (i) is tyrosine-phosphorylated in vivo; (ii) does autophosphorylate in vitro; and (iii) is able to associate with intracellular signalling substrates. Artificial deletion of the TrkA ectodomain results in an active receptor that induced neurite outgrowth in pheochromocytoma cells. Cleavage by this natural cellular mechanism appears thus to serve not only as an outlet of receptor binding fragments, but also to generate signalling-competent cell-bound receptor fragments. In the nervous system this ligand-independent receptor activation could play important roles in the development and survival of neurons.

[New species of Aeromonas isolated in Cuba]

One hundred and fifty-five strains of Aeromonas isolated in the stools of children under 5 years presenting with acute diarrheal disease were studied. Using the Aerokey II system for the identification of species, 47 strains were identified as Aeromonas caviae, 58 as Aeromonas hydrophila, 23 as Aeromonas veronii biovar sobria, 14 as Aeromonas trota, 9 as Aeromonas veronii biovar veronii, 2 as Aeromonas jandaei and 2 as Aeromonas shubertii, Emphasis is placed on the advantages of this method which allowed for the classification of new species not identified previously in our country.

Differences in the intersubunit contacts in triosephosphate isomerase from two closely related pathogenic trypanosomes

The aligned amino acid sequences of TIM from Trypanosoma cruzi (TcTIM) and Trypanosoma brucei (TbTIM) have a positional identity of 68%. The two enzymes have markedly similar catalytic properties. Agents that interact with their interface Cys inhibit TcTIM and TbTIM; and those TIMs that lack this Cys (such as human TIM) are largely or completely insensitive to these agents. The susceptibility of TcTIM to the agents is approximately 100 times higher than that of TbTIM. To ascertain the cause of this large difference, the crystal structure of TcTIM was solved at 1.83 A resolution. The two enzymes are very similar homodimers. In TcTIM and TbTIM their respective Cys, 15 or 14, forms part of the dimer interface. In both, the contacts of the Cys with residues of the other subunit are almost identical. Nevertheless, there are noteworthy differences between the two; the existence of glutamine 18 in TbTIM instead of glutamic acid in TcTIM at the beginning of helix 1 decreases the contacts between this portion of the protein and helix 3 of the other subunit. In addition, TcTIM has proline at position 24 in the first helix of the TIM barrel; this is absent in the other TIM. Pro24 disrupts the regular helix arrangement, making the pitch of this helix 1.2 A longer than in TbTIM. When Pro24 of TcTIM was substituted for Glu, the sensitivity of TcTIM to sulfhydryl reagents increased about fivefold, possibly as a consequence of an increase in the space between the first portion of helix 1 and helix 3 of the other subunit. Therefore, it may be concluded that the geometry of the latter region is central in the accessibility to agents that perturb the interface Cys. In human TIM this region is more compact.

Reactivation of triosephosphate isomerase from three trypanosomatids and human: effect of suramin

The reactivation of the homodimeric triosephosphate isomerases (TIMs) from Trypanosoma brucei, T. cruzi, Leishmania mexicana and humans was determined after their denaturation with guanidine hydrochloride. In the range of 2-32 microg of T. brucei TIM per ml and 0.2-5 microg of the other enzymes per ml, the rate and extent of TIM reactivation depended on protein concentration, indicating that at these protein concentrations, the rate-limiting step of reactivation is monomer association and not monomer folding. The rate of monomer association was more than one order of magnitude lower in the T. brucei enzyme than in the other three enzymes. Suramin is a drug of choice in the treatment of sleeping sickness, but its mechanism of action is not known. At micromolar concentrations, Suramin inhibited the reactivation of the four enzymes, but the extent of inhibition by Suramin decreased with increasing protein concentration as consequence of a diminution of the life time of the folded monomer. Since the life time of the monomer of T. brucei TIM is longer than that of the other enzymes, Suramin is a more effective inhibitor of the reactivation of TIM from T. brucei, particularly at monomer concentrations above 1 microg of protein per ml (monomer concentration approx. 37 nM). Compounds that are structurally related to Suramin also inhibit TIM reactivation; their effect was about five times more pronounced in the enzyme from T. brucei than in human TIM.

Sulfhydryl reagent susceptibility in proteins with high sequence similarity--triosephosphate isomerase from Trypanosoma brucei, Trypanosoma cruzi and Leishmania mexicana

The amino acid sequence of triosephosphate isomerase from Trypanosoma brucei, Trypanosoma cruzi, and Leishmania mexicana have an identity of 68%. Using the numbering system for the T. brucei enzyme, in their aligned sequences, the T. cruzi and leishmanial enzymes have cysteine residues at positions 14, 40, 117 and 126. T. brucei triosephosphate isomerase has cysteine residues at positions 14, 40 and 126, and a valine residue at position 117. Dithionitrobenzoic acid and methylmethane thiosulfonate inhibited the three enzymes, but T. cruzi triosephosphate isomerase was more than 100-fold more sensitive. The sensitivity of wild type triosephosphate isomerase from T. cruzi and T. brucei to the reagents was equal to that of the Cys117Val and Val117Cys mutant enzymes, respectively. Triosephosphate isomerases that have cysteine residues at positions 40 and 126, but lack a cysteine residue at position 14 are insensitive to methylmethane thiosulfonate. Thus, sulfhydryl reagents act on Cys14. At stoichiometric concentrations, the reagents inhibited the three enzymes as a consequence of structural alterations as measured by binding of 8-anilino-1-napthalenesulfonic acid to previously buried hydrophobic regions. However, the times for half-maximal alterations were 10 min, 15 hours and over 30 hours for T. cruzi, T. brucei and L. mexicana triosephosphate isomerase, respectively. The effect of pH on the action of the sulfhydryl reagents and molecular modeling showed no differences in the solvent accessibility of Cys14. As Cys14 forms part of the dimer interface, the data indicate that, in the three enzymes, barriers of different magnitude hinder the interaction between the sulfhydryl reagents and Cys14. The barrier is lower in T. cruzi triosephosphate isomerase which makes its dimer interface more susceptible for perturbation.

Purification of alcohol dehydrogenase from Entamoeba histolytica and Saccharomyces cerevisiae using zinc-affinity chromatography

We have developed a single-step method for the purification of NADP(+)-dependent alcohol dehydrogenase from Entamoeba histolytica and NAD(+)-dependent alcohol dehydrogenase from Saccharomyces cerevisiae. It is based on the affinity for zinc of both enzymes. The amebic enzyme was purified almost 800 times with a recovery of 54% and the yeast enzyme was purified 30 times with a recovery of 100%. The kinetic constants of the purified enzymes were similar to those reported for other purification methods. With mammalian alcohol dehydrogenase, we obtained a 40-kDa band suggestive of purified alcohol dehydrogenase, but we failed to retain enzymatic activity in this preparation. Our results suggest that the described method is more applicable to the purification of tetrameric alcohol dehydrogenases.

A mechanism of acquired resistance to complement-mediated lysis by Entamoeba histolytica

Some Entamoeba histolytica strains resist complement-mediated lysis by serum. Susceptible and resistant strains activate the complement system equivalently, but resistant amebas evade killing by membrane attack complexes. Our objective was to determine the mechanism by which trophozoites of E. histolytica resist lysis by human serum. Amebas were made resistant to lysis by incubation with increasing concentrations of normal human serum. The possibility that resistant cells ingest membrane attack complexes was explored by subcellular fractionation of susceptible and resistant trophozoites treated with sublytic concentrations of human serum containing radiolabeled C9. In both cases, most of the label was in the fractions containing plasma membrane. The susceptible strain consistently showed more label associated with these fractions than the resistant strain. Thus, the possibility that the membrane attack complexes were released to the medium was explored. Both resistant and susceptible trophozoites release to the medium similar amounts of material excluded by Sepharose CL-2B in the presence or absence of normal human serum. Labeled C9 elutes together with the main bulk of proteins from the medium: this indicates that it is not in vesicles or high molecular weight aggregates. Coincubation of susceptible amebas with lysates of resistant trophozoites confers resistance to susceptible cells within 30 min. Resistance to lysis by serum can also be acquired by susceptible amebas after coincubation with lysates from human erythrocytes or after feeding them with whole human red blood cells. Resistant but not susceptible trophozoites show intense immunofluorescent staining on their surface with anti-human erythrocytic membrane antibody. These results suggest that amebas acquire resistance to lysis by serum by incorporating into their membranes complement regulatory proteins.

Isolation and characterization of mutants as an approach to a transformation system in Kluyveromyces marxianus

A method to obtain K. marxianus mutants has been developed. Different auxotrophic mutants were isolated by nystatin and snail-enzyme enrichment procedures using an incubation time of 2 h before adding the antibiotic or the enzyme respectively. All his mutants analyzed by complementation tests turned out to belong to the same complementation group. Some of them were transformed and complemented by the S. cerevisiae HIS3 gene. These non-reverting his3 mutants contain no heterologous sequence, which is essential to make them acceptable for application in the food industry.

TrkA receptor ectodomain cleavage generates a tyrosine-phosphorylated cell-associated fragment

The extracellular domain of several membrane-anchored proteins can be released as a soluble fragment by the action of a cell surface endoproteolytic system. This cleavage results in the generation of a soluble and a cell-bound fragment. In the case of proteins with signaling capability, such as tyrosine kinase receptors, the cleavage process may have an effect on the kinase activity of the cell-bound receptor fragment. By using several cell lines that express the TrkA neurotrophin receptor, we show that this receptor tyrosine kinase is cleaved by a proteolytic system that mimics the one that acts at the cell surface. TrkA cleavage is regulated by protein kinase C and several receptor agonists (including the TrkA ligand NGF), occurs at the ectodomain in a membrane-proximal region, and is independent of lysosomal function. TrkA cleavage results in the generation of a cell-associated fragment that is phosphorylated on tyrosine residues. Tyrosine phosphorylation of this fragment is not detected in TrkA mutants devoid of kinase activity, suggesting that phosphorylation requires an intact TrkA kinase domain, and is not due to activation of an intermediate intracellular tyrosine kinase. The increased phosphotyrosine content of the cell-bound fragment may thus reflect higher catalytic activity of the truncated fragment. We postulate that cleavage of receptor tyrosine kinases by this naturally occurring cellular mechanism may represent an additional mean for the regulation of receptor activity.

Proteolytic activity in extracts of invasive cervical carcinoma and precursor lesions

In this preliminary report, we showed that proteolytic activity of extracts from 85 cervical samples of patients with normal cervix, low and high-grade squamous intra-epithelial lesions and invasive carcinoma, increased according to the natural history of the cervical cancer when measured with three different substrates. Inhibitor assays for four different catalytic classes of endopeptidases indicated that the predominant catalytic class in extracts of all groups was that of metalloproteinases. Substrate gel electrophoresis revealed that invasive carcinoma extracts had two bands with proteolytic activity (with M(r) of 72 and 52 kDa) which were not present in normal tissue or biopsies with precursor lesions. Immunological and molecular characterization of these bands may provide information relevant to cervical cancer biology and clinical applications.

Stanozolol and danazol, unlike natural androgens, interact with the low affinity glucocorticoid-binding sites from male rat liver microsomes

Some 17 alpha-alkylated androgens used as anabolic agents, such as stanozolol (ST) and danazol (DA), have specific effects on the liver that are not exerted by testosterone. This gives rise to the possibility that a steroid-binding protein, other than the androgen receptor, could modulate the intracellular actions of these agents. Male rat liver microsomes contain a homogeneous population of [3H]dexamethasone ([3H]DEX)-binding sites which we have denominated low affinity glucocorticoid-binding sites (LAGS). Because glucocorticoids, progestagens, and the synthetic estrogen ethynyl estradiol compete with [3H]DEX for binding to the LAGS, we aimed to study the possible interactions between androgens and the LAGS. To investigate whether several androgens had the capability of interacting with the LAGS, we performed competition experiments. The LAGS had no affinity for testosterone or methyltrienolone (R1881). However, some 17 alpha-alkylated androgens (DA (IC50, 116 nM) > ST >> fluoxymesterone > mestaline > methandriol >> methandrostenolone > methyltestosterone) were able to compete with [3H]DEX binding to liver microsomes. ST and DA were potent inhibitors of [3H]DEX binding to liver microsomes. They decreased both the affinity and the number of [3H]DEX-binding sites, increased the dissociation rate of [3H]DEX from the LAGS, and provoked a time- and dose-dependent inactivation of the [3H]DEX-binding site. These results strongly suggest that ST and DA exert a negative allosteric modulation on [3H]DEX binding to the LAGS. The in vivo administration of ST (but not other androgens) to male rats provoked a time- and dose-dependent decrease in the LAGS level. Full recovery of the LAGS concentration required at least 8 h and was blocked by protein synthesis inhibitors. Such results suggest that ST irreversibly inactivates the [3H]DEX-binding site in vivo as it does in vitro. Taken together, these observations are indicative of an irreversible interaction between some 17 alpha-alkylated androgens and the LAGS both in vitro and in vivo and suggest that ST may be an important pharmacological tool that can be used in the elucidation of the molecular structure of the LAGS. These results also mean that the LAGS are a steroid-binding entity able to distinguish between natural androgens and 17 alpha-alkylated testosterone derivatives used as anabolic agents.

Proteinases of Entamoeba histolytica associated with different subcellular fractions

Crude lysates of Entamoeba histolytica (strain HM 1:IMSS) analyzed by substrate gel electrophoresis in 12.5% acrylamide separating gels with reducing agents showed six hydrolysis zones with apparent molecular weights of 73,000 (high), 45,000, 36,000 (intermediate), 30,000, 26,000 and 23,000 (low molecular weight proteinases). Amebic lysates fractionated using the procedure of Aley et al. or the procedure of Rosenberg and Gitler and analyzed by the same method show all enzymes in the fractions with the soluble components and only the intermediate and low molecular weight proteinases in the fraction containing internal vesicles or membranes and plasma membrane. Some of these proteinases seem to be integral membrane proteins since they resist treatment with high salt, high urea buffer. All fractions are capable of digesting azocasein. Fractionation of amebic lysates by hydrophobic chromatography using phenyl-Sepharose or phase separation of amebic extracts with Triton X-114 show that proteinases with high, intermediate and low molecular weight behave as hydrophilic proteins while only proteinases of intermediate and low molecular weight behave as hydrophobic proteins. These results suggest that some proteinases are segregated in different compartments of the cell.

Double early epidermoid carcinoma of the esophagus in columnar epithelium

Two epidermoid, identical but independent tumors of the middle esophagus, arising in columnar lined esophagus (Barrett's esophagus or endobrachyesophagus) are reported. Both were diagnosed endoscopically and resected. The upper tumor involved only the mucosa, the aboral one the mucosa and submucosa.