Plasmepsin inhibitors: design,synthesis, inhibitory studies and crystal structure analysis

Abstract: Plasmepsin group of enzymes are key enzymes in the life cycle of malarial parasites. As inhibition of plasmepsins leads to the parasite's death, these enzymes can be utilized as potential drug targets. Although many drugs are available, it has been observed that Plasmodium falciparum, the species that causes most of the malarial infections and subsequent death, has developed resistance against most of the drugs. Based on the cleavage sites of hemglobin, the substrate for plasmepsins, we have designed two compounds (p‐nitrobenzoyl‐leucine‐β‐alanine and p‐nitrobenzoyl‐leucine‐isonipecotic acid), synthesized them, solved their crystal structures and studied their inhibitory effect using experimental and theoretical (docking) methods. In this paper, we discuss the synthesis, crystal structures and inhibitory nature of these two compounds which have a potential to inhibit plasmepsins.     

Multistage antiplasmodial activity of hydroxyethylamine compounds,in vitro and in vivo evaluations

Malaria, a global threat to the human population, remains a challenge partly due to the fast-growing drug-resistant strains of Plasmodium species. New therapeutics acting against the pathogenic asexual and sexual stages, including liver-stage malarial infection, have now attained more attention in achieving malaria eradication efforts. In this paper, two previously identified potent antiplasmodial hydroxyethylamine (HEA) compounds were investigated for their activity against the malaria parasite''s multiple life stages. The compounds exhibited notable activity against the artemisinin-resistant strain of P. falciparum blood-stage culture with 50% inhibitory concentrations (IC₅₀) in the low micromolar range. The compounds'' cytotoxicity on HEK293, HepG2 and Huh-7 cells exhibited selective killing activity with IC₅₀ values > 170 μM. The in vivo efficacy was studied in mice infected with P. berghei NK65, which showed a significant reduction in the blood parasite load. Notably, the compounds were active against liver-stage infection, mainly compound 1 with an IC₅₀ value of 1.89 μM. Mice infected with P. berghei sporozoites treated with compound 1 at 50 mg kg⁻¹ dose had markedly reduced liver stage infection. Moreover, both compounds prevented ookinete maturation and affected the developmental progression of gametocytes. Further, systematic in silico studies suggested both the compounds have a high affinity towards plasmepsin II with favorable pharmacological properties. Overall, the findings demonstrated that HEA and piperidine possessing compounds have immense potential in treating malarial infection by acting as multistage inhibitors.

Malaria, a global threat to the human population, remains a challenge partly due to the fast-growing drug-resistant strains of Plasmodium species.     

Purification and properties of hyaluronidase from Hippasa partita (funnel web spider) venom gland extract.

Spider venom is a complex mixture of protein and peptide toxins. Hyaluronidase a 'spreading factor' has not been studied extensively in spider venom. In this paper, we describe the purification and characterization of a hyaluronidase from Hippasa partita venom gland extract. Hyaluronidase (HPHyal) has been purified by the successive chromatography on a Sephadex G-100 and on CM-Sephadex C-25 columns. HPHyal has been purified to an extent of about approximately 20-folds. The molecular mass was found to be 42.26 kDa by matrix-assisted laser desorption ionization time of flight (MALDI-TOF) mass spectrometry. HPHyal was optimally active at pH 5.8 at 37 degrees C and in the presence of 300 mM NaCl in the reaction mixture. HPHyal showed absolute specificity for hyaluronan and belongs to neutral active group of enzymes. HPHyal revealed single-precipitin line, while venom gland extract revealed multiple bands in Western blotting with the antiserum prepared against venom gland extract. HPHyal indirectly potentiates the myotoxicity of VRV-PL-VIII myotoxin and also the hemorrhagic potency of hemorrhagic complex-I. Cations, Na(+) and K(+) enhanced the activity and chloride ions do not have any effect while, divalent cations, inhibited the enzyme activity.     

Influence of dietary spices on the fluidity of erythrocytes in hypercholesterolaemic rats

In rats rendered hypercholesterolaemic by maintaining them on a cholesterol-enriched diet (0.5 %) for 8 weeks, as a result of alteration in membrane structural lipids, erythrocytes were observed to be deformed and become more fragile. This deformity and fragility was partially reversed by the two dietary spice principles, curcumin and capsaicin, and the spice, garlic, by virtue of their ability to lower the extent of hypercholesterolaemia. A further insight into the factors that might have reduced the fluidity of erythrocytes in hypercholesterolaemic rats revealed changes in fatty acid profile of the membranes, phospholipid composition of the membrane bilayer, reduced Ca(2+),Mg(2+)-ATPase, and reduction in the sensitivity of erythrocytes to concanavaline A. Dietary capsaicin appeared to counter these changes partially in hypercholesterolaemic rats. Electron spin resonance (ESR) spectra and fluorescence anisotropy parameters also revealed altered fluidity of erythrocytes in hypercholesterolaemic rats. Dietary capsaicin and curcumin significantly reversed this alteration. Scanning electron microscopic examination revealed that the echinocyte population was increased in the erythrocytes of hypercholesterolaemic rats, and this was significantly countered by dietary capsaicin. The membrane protein profile and the active cation efflux appeared to be unaffected in the hypercholesterolaemic situation.     

Yttrium<Superscript>90</Superscript> synovectomy in the management of chronic knee arthritis: a single institution experience

Radiation synovectomy (RS) has been used to treat chronically inflamed joints refractory to treatment using conventional agents. In RS, the radioactive isotope is concentrated in the synovial membrane from the injected colloid suspension, where it exerts its activity. However, despite numerous reports confirming its safety and efficacy, this procedure is not widely practised. In the Singleton Hospital NHS Trust, yttrium(90) (Y(90)) RS has been practised since 1990 for refractory synovitis. In this study, we analyse the results of therapy and complications in 38 joints so treated. Doses of 10 mCi were used in the majority of patients. Most responses were apparent by 6 months following the procedure. Altogether, 68% of the treated joints showed satisfactory response at 3 years, with 29% having all symptoms under control beyond 3 years. In three patients, there was evidence of minor pigmentation at the injection site. Two patients had extravasation of the isotope and needle track ulcers, which were recorded as major toxicity. We find Y(90) radiosynovectomy to be safe, quick, and effective in the management of patients with refractory synovitis. The efficacy of RS should be tested in randomised clinical trials involving large numbers of patients.     

Facile syntheses of O(2)-[4-(3-pyridyl-4-oxobut-1-yl]thymidine, the major adduct formed by tobacco specific nitrosamine 4-methylnitrosamino-1-(3-pyridyl)-1-butanone (NNK) in vivo, and its site-specifically adducted oligodeoxynucleotides

O(2)-[4-(3-Pyridyl)-4-oxobut-1-yl]thymidine (O(2)-POB-dThd) is the most persistent adduct detected in the lung and liver of rats treated with tobacco specific nitrosamines: N'-nitrosonornicotine (NNN), 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), and its metabolite 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL). It is an important biomarker to assess the human exposure to these carcinogens. The only synthetic method reported for O(2)-POB-dThd requires repeated HPLC purifications and could only be used to prepare an analytical standard due to very low yield (0.4%). We have developed for the first time a regioselective and efficient method for the total synthesis of O(2)-POB-dThd and its site-specifically adducted oligonucleotides. The main step in the synthesis of O(2)-POB-dThd was achieved by a novel method. The treatment of O(2)-5'-anhydrothymidine with the sodium salt of 4-(1,3-dithian-2-yl)-4-(3-pyridyl)butan-1-ol gave exclusively the O(2)-alkylated adduct, which was deprotected in one step to furnish the desired O(2)-POB-dThd in excellent yield. The product was characterized by NMR ((1)H and (13)C), high-resolution MS, and HPLC analysis. This work provided for the first time a reliable method for large scale total synthesis of O(2)-POB-dThd that allowed for solid state site-specifically adducted oligomer synthesis. The O(2)-POB-dThd was converted to its phosphoramidite and subsequently used for the synthesis of oligodeoxynucleotides by standard methods. The oligomers were characterized by MS and HPLC analysis. These oligomers will facilitate the elucidation of the mutagenic potential of the O(2)-POB-dThd adduct, which will provide further insight into the role of tobacco-specific nitrosamines in inducing cancers in smokers.     

Development of novel naphthalimide derivatives and their evaluation as potential melanoma therapeutics

Synthesis and anti-melanoma activity of various naphthalimide analogs, rationally modified by introducing isothiocyanate (ITC) and thiourea (TU) functionalities, found in well-known anti-cancer agents, is described. The structure-activity relationship comparison of the novel agents in inhibiting cancer cell growth was evaluated in various melanoma cell lines. Both ITC and TU analogs effectively inhibited cell viability and induced apoptosis in various human melanoma cells. Nitro substitution and increase in alkyl chain length, in general, enhanced the apoptotic activity of ITC derivatives. All the new compounds were well tolerated when injected intraperitoneal (i.p.) in mice at effective doses at which both the ITC and TU derivatives inhibited melanoma tumor growth in mice following i.p. xenograft. The nitro substituted naphthalimide-ITC derivative 3d was found to be the most effective in inducing apoptosis, and in inhibiting melanoma cell and tumor growth.     

Testing-Related and Geo-Demographic Indicators Strongly Predict COVID-19 Deaths in the United States during March of 2020

The COVID-19 pandemic has wreaked havoc around the globe and caused significant disruptions across multiple domains[1]. Moreover, different countries have been differentially impacted by COVID-19 — a phenomenon that is due to a multitude of complex and often interacting determinants[2]. Understanding such complexity and interacting factors requires both compelling theory and appropriate data analytic techniques. Regarding data analysis, one question that arises is how to analyze extremely non-normal data, such as those variables evidencing L-shaped distributions. A second question concerns the appropriate selection of a predictive modelling technique when the predictors derive from multiple domains (e.g., testing-related variables, population density), and both main effects and interactions are examined.     

Melatonin restores neutrophil functions and prevents apoptosis amid dysfunctional glutathione redox system

Melatonin is a chronobiotic hormone, which can regulate human diseases like cancer, atherosclerosis, respiratory disorders, and microbial infections by regulating redox system. Melatonin exhibits innate immunomodulation by communicating with immune system and influencing neutrophils to fight infections and inflammation. However, sustaining redox homeostasis and reactive oxygen species (ROS) generation in neutrophils are critical during chemotaxis, oxidative burst, phagocytosis, and neutrophil extracellular trap (NET) formation. Therefore, endogenous antioxidant glutathione (GSH) redox cycle is highly vital in regulating neutrophil functions. Reduced intracellular GSH levels and glutathione reductase (GR) activity in the neutrophils during clinical conditions like autoimmune disorders, neurological disorders, diabetes, and microbial infections lead to dysfunctional neutrophils. Therefore, we hypothesized that redox modulators like melatonin can protect neutrophil health and functions under GSH and GR activity–deficient conditions. We demonstrate the dual role of melatonin, wherein it protects neutrophils from oxidative stress-induced apoptosis by reducing ROS generation; in contrast, it restores neutrophil functions like phagocytosis, degranulation, and NETosis in GSH and GR activity–deficient neutrophils by regulating ROS levels both in vitro and in vivo. Melatonin mitigates LPS-induced neutrophil dysfunctions by rejuvenating GSH redox system, specifically GR activity by acting as a parallel redox system. Our results indicate that melatonin could be a potential auxiliary therapy to treat immune dysfunction and microbial infections, including virus, under chronic disease conditions by restoring neutrophil functions. Further, melatonin could be a promising immune system booster to fight unprecedented pandemics like the current COVID-19. However, further studies are indispensable to address the clinical usage of melatonin.