In vitro testing of anthelmintic efficacy of Flemingia vestita (Fabaceae) on carbohydrate metabolism in Rallietina echinobothrida

Antioxidant activity of Flemingia praecox and Mucuna pruriens and their implications for male fertility improvement

Globally, 15-24% couples are unable to conceive naturally and 50% of cases of this problem are due to infertility in males. Of this, about 50% of male infertility problems are developed due to unknown reasons called as idiopathic infertility. It is well established that, reactive oxygen species (ROS) have negative impact on male fertility and are involved in 80% of total idiopathic male infertility cases. Medicinal plants are considered as an alternative approach for mitigating the health problems. The plants with good antioxidant capacity can improve the male infertility symptoms generated by ROS. Such medicinal plants can be used to alleviate the symptoms of male infertility with their diverse phytoconstituents. Mucuna pruriens is a well-accepted herb, with its seeds being used to improve the male fertility in various ways and one of the ways is by eliminating the ROS. In our field survey, another plant, Flemingia praecox, although less known, its roots are used in all problems related to the male fertility by tribal people of the Gadchiroli district of Maharashtra, India. The study was conducted to determine in vitro antioxidant potential of F. praecox and compared the results with the well-established male fertility improving plant M. pruriens with special emphasis on medicinally important roots of F. praecox and seeds of M. pruriens. The objective of the study was investigated by studying their total phenol (TPC) and flavonoid (TFC) content, antioxidant parameters (DPPH, FRAP, ABTS, DMPD, β-carotene bleaching and TAA) and finally DNA damage protection capacity of the plant extracts was studied. The plant parts used for the medicinal purposes have been investigated along with other major parts (leaves, stem and roots of both the plants) and compared with synthetic antioxidants, BHA, BHT and ascorbic acid. Moreover, the inhibition of two male infertility enzyme markers, PDE5 and arginase by F. praecox root and M. pruriens seed extract was also studied in vitro. The results showed that F. praecox possesses higher antioxidant activity than M. pruriens in the majority of studies as observed in TFC, DPPH, TAA, ABTS and DMPD assays. However, M. pruriens seeds showed best results in TPC, FRAP and DNA damage protection assay. F. praecox root extract also gave better PDE5 inhibition value than M. pruriens seeds. This study will help to establish the authenticity of F. praecox used by tribal people and will encourage its further use in managing the male infertility problems.

Antiparasitic Effects of Selected Isoflavones on Flatworms

Medicinal plants have been successfully used in the ethno medicine for a wide range of diseases since ancient times. The research on natural products has allowed the discovery of biologically relevant compounds inspired by plant secondary metabolites, what contributed to the development of many chemotherapeutic drugs. Flavonoids represent a group of therapeutically very effective plant secondary metabolites and selected molecules were shown to exert also antiparasitic activity. This work summarizes the recent knowledge generated within past three decades about potential parasitocidal activities of several flavonoids with different chemical structures, particularly on medically important flatworms such as Schistosoma spp., Fasciola spp., Echinococcus spp., Raillietina spp., and model cestode Mesocestoides vogae. Here we focus on curcumin, genistein, quercetin and silymarin complex of flavonolignans. All of them possess a whole spectrum of biological activities on eukaryotic cells which have multi-therapeutic effects in various diseases. In vitro they can induce profound alterations in the tegumental architecture and its functions as well as their activity can significantly modulate or damage worm´s metabolism directly by interaction with enzymes or signaling molecules in dose-dependent manner. Moreover, they seem to differentially regulate the RNA activity in numbers of worm´s genes. This review suggests that examined flavonoids and their derivates are promising molecules for antiparasitic drug research. Due to lack of toxicity, isoflavons could be used directly for therapy, or as adjuvant therapy for diseases caused by medically important cestodes and trematodes.

Intricate Regulation of Phosphoenolpyruvate Carboxykinase (PEPCK) Isoforms in Normal Physiology and Disease

BACKGROUND

The phosphoenolpyruvate carboxykinase (PEPCK) isoforms are considered as rate-limiting enzymes for gluconeogenesis and glyceroneogenesis pathways. PEPCK exhibits several interesting features such as a) organelle-specific isoforms (cytosolic and a mitochondrial) in vertebrate clade, b) tissue-specific expression of isoforms and c) organism-specific requirement of ATP or GTP as a cofactor. In higher organisms, PEPCK isoforms are intricately regulated and activated through several physiological and pathological stimuli such as corticoids, hormones, nutrient starvation and hypoxia. Isoform-specific transcriptional/translational regulation and their interplay in maintaining glucose homeostasis remain to be fully understood. Mounting evidence indicates the significant involvement of PEPCK isoforms in physiological processes (development and longevity) and in the progression of a variety of diseases (metabolic disorders, cancer, Smith-Magenis syndrome).

OBJECTIVE

The present systematic review aimed to assimilate existing knowledge of transcriptional and translational regulation of PEPCK isoforms derived from cell, animal and clinical models.

CONCLUSION

Based on current knowledge and extensive bioinformatics analysis, in this review we have provided a comparative (epi)genetic understanding of PCK1 and PCK2 genes encompassing regulatory elements, disease-associated polymorphisms, copy number variations, regulatory miRNAs and CpG densities. We have also discussed various exogenous and endogenous modulators of PEPCK isoforms and their signaling mechanisms. A comprehensive review of existing knowledge of PEPCK regulation and function may enable identification of the underlying gaps to design new pharmacological strategies and interventions for the diseases associated with gluconeogenesis.

Identification of small molecule enzyme inhibitors as broad-spectrum anthelmintics

Targeting chokepoint enzymes in metabolic pathways has led to new drugs for cancers, autoimmune disorders and infectious diseases. This is also a cornerstone approach for discovery and development of anthelmintics against nematode and flatworm parasites. Here, we performed omics-driven knowledge-based identification of chokepoint enzymes as anthelmintic targets. We prioritized 10 of 186 phylogenetically conserved chokepoint enzymes and undertook a target class repurposing approach to test and identify new small molecules with broad spectrum anthelmintic activity. First, we identified and tested 94 commercially available compounds using an in vitro phenotypic assay, and discovered 11 hits that inhibited nematode motility. Based on these findings, we performed chemogenomic screening and tested 32 additional compounds, identifying 6 more active hits. Overall, 6 intestinal (single-species), 5 potential pan-intestinal (whipworm and hookworm) and 6 pan-Phylum Nematoda (intestinal and filarial species) small molecule inhibitors were identified, including multiple azoles, Tadalafil and Torin-1. The active hit compounds targeted three different target classes in humans, which are involved in various pathways, including carbohydrate, amino acid and nucleotide metabolism. Last, using representative inhibitors from each target class, we demonstrated in vivo efficacy characterized by negative effects on parasite fecundity in hamsters infected with hookworms.

Genistein: is the multifarious botanical a natural anthelmintic too?

Genistein (4',5,7-trihydroxyisoflavone) is naturally present in plants of the soy family and is known to have various pharmacological activities, such as anti-cancer, anti-diabetic, anti-oxidant, etc. The phytoestrogen is one of the major isoflavones found in some medicinal plants having anthelmintic properties. This review describes the putative role of genistein as an anthelmintic, which has been tested on some helminth parasites in vitro. Genistein has been shown to cause paralysis and alterations in the tegument and tegumental enzymes (acid phosphatase, alkaline phosphatase, adenosine triphosphatase, and 5'-nucleotidase) of helminth parasites. Alterations in the activities of several enzymes associated with the coordination system (specifically non-specific esterases, acetylcholine esterase, and nitric oxide synthase), and changes in the concentration of nitric oxide, cGMP, free amino acid pool, and tissue ammonia are observed in helminth parasites treated with genistein. The phytoestrogen also affects the carbohydrate metabolism by altering the activities of key enzymes involved in glycogen- and glucose-metabolism of a cestode parasite. Considering the significance of phosphoenolpyruvate carboxykinase (PEPCK) in glycolysis of the cestode parasite, Ki of the phytoestrogen for PEPCK in the parasite has been determined, and molecular docking of genistein into the active site of the enzyme has also been described. The potential beneficial role of genistein as a natural alternative in management of helminth parasites needs to be further explored, particularly considering its in vivo efficacy and pharmacokinetics.

Biological significance of phosphoenolpyruvate carboxykinase in a cestode parasite, Raillietina echinobothrida and effect of phytoestrogens on the enzyme from the parasite and its host, Gallus domesticus

Phosphoenolpyruvate carboxykinase (PEPCK) is involved in glycolysis in the cestode parasite, Raillietina echinobothrida; whereas, it executes a gluconeogenic role in its host, Gallus domesticus. Because of its differing primary function in the cestode parasite and its host, this enzyme is regarded as a plausible anthelmintic target. Hence, the biological significance of PEPCK in the parasite was analysed using siRNA against PEPCK from R. echinobothrida (RePEPCK). In order to find out the functional differences between RePEPCK and GdPEPCK (PEPCK from its host, G. domesticus), PEPCK genes from both sources were cloned, over-expressed, characterized, and some properties of the purified enzymes were compared. RePEPCK and GdPEPCK showed a standard Michaelis-Menten kinetics with K mapp of 46.9 and 22.9 µ m, respectively, for phosphoenolpyruvate and K mapp of 15.4 µ m for oxaloacetate in GdPEPCK decarboxylation reaction. Here, we report antagonist behaviours of recombinant PEPCKs derived from the parasite and its host. In search of possible modulators for PEPCK, few phytoestrogens were examined on the purified enzymes and their inhibitory constants were determined and discussed. This study stresses the potential of these findings to validate PEPCK as the anthelmintic drug target for parasitism management.

Biocomputational analysis of phosphoenolpyruvate carboxykinase from Raillietina echinobothrida, a cestode parasite, and its interaction with possible modulators

Phosphoenolpyruvate carboxykinase (PEPCK) involved in gluconeogenesis in higher vertebrates opposedly plays a significant role in glucose oxidation of the cestode parasite, Raillietina echinobothrida. Considering the importance of the enzyme in the parasite and lack of its structural details, there exists an urgent need for understanding the molecular details and development of possible modulators. Hence, in this study, PEPCK gene was obtained using rapid amplification of cDNA ends, and various biocomputational analyses were performed. Homology model of the enzyme was generated, and docking simulations were executed with its substrate, co-factor, and modulators. Computer hits were generated after structure- and ligand-based screening using Discovery Studio 4.1 software; the predicted interactions were compared with those of the existing structural information of PEPCK. In order to evaluate the docking simulation results of the modulators, PEPCK gene was cloned and the overexpressed protein was purified for kinetic studies. Enzyme kinetics and in vitro studies revealed that out of the modulators tested, tetrahydropalmatine (THP) inhibited the enzyme with lowest inhibition constant value of 93 nm. Taking the results together, we conclude that THP could be a potential inhibitor for PEPCK in the parasite.

Cloning and expression of phosphoenolpyruvate carboxykinase from a cestode parasite and its solubilization from inclusion bodies using l-arginine

Phosphoenolpyruvate carboxykinase is an essential regulatory enzyme of glycolysis in the cestode parasite, Raillietina echinobothrida, and is considered a potential target for anthelmintic action because of its differential activity from that of its avian host. However, due to the unavailability of its structure, the mechanism of regulation of PEPCK from R. echinobothrida (rePEPCK) and its interaction with possible modulators remain unclear. Hence, in this study, the rePEPCK gene was cloned into pGEX-4T-3 and overexpressed for its characterization. On being induced by IPTG, the recombinant rePEPCK was expressed as inclusion bodies (IBs); hence, various agents, like different inducer concentrations, temperature, time, host cell types, culture media, pH, and additives, were used to bring the protein to soluble form. Finally, a significant amount (∼46%) of rePEPCK was solubilized from IBs by adding 2M l-arginine. Near-UV circular dichroism spectra analysis indicated that l-arginine (2M) had no effect on the conformation of the protein. In this study, we have reported a yield of ∼73mg of purified rePEPCK per 1L of culture. The purified rePEPCK retained its biological activity, and Km of the enzyme for its substrate was determined and discussed. The availability of recombinant rePEPCK may help in biochemical- and biophysical-studies to explore its molecular mechanisms and regulations.

Differential kinetics at PK/PEPCK branch point in the cestode, Raillietina echinobothrida

Pyruvate kinase (PK; EC 2.7.1.40) and phosphoenolpyruvate carboxykinase (PEPCK; EC 4.1.1.32) are essential regulatory enzymes of glucose oxidation in helminths, the PK/PEPCK branch point being the first divergent step between carbohydrate catabolism of the parasites and their hosts. Recently, PEPCK from the cestode parasite, Raillietina echinobothrida, has been purified and characterized. In order to find out the differential kinetics, if any, at PK/PEPCK branch point in the parasite, in this study, we purified and characterized the parasite PK and compared it with the parasite PEPCK. The purified PK displayed standard Michaelis-Menten kinetics with Kmapp of 77.8 µM for its substrate PEP, whereas the Kmapp was 46.9 µM for PEPCK. PEP exhibited differential kinetics at PK/PEPCK branch point of the parasite and behaved as a homotropic effector for PEPCK, but not for PK. The inhibitory constant (Ki) for genistein and daidzein (phytochemicals from Flemingia vestita) was determined and discussed. From these results, we hypothesize that PK/PEPCK branch point is a probable site for anthelmintic action.

Purification and characterization of phosphoenolpyruvate carboxykinase from Raillietina echinobothrida, a cestode parasite of the domestic fowl

Phosphoenolpyruvate carboxykinase (PEPCK, EC 4.1.1.32) is an essential regulatory enzyme of glycolysis in helminths in contrast to its role in gluconeogenesis in their host. Previously we have reported that phytochemicals from Flemingia vestita (Family: Fabaceae), genistein in particular, have vermifugal action and are known to affect carbohydrate metabolism in the cestode, Raillietina echinobothrida. In order to determine the functional differences of PEPCK from the parasite and its avian host (Gallus domesticus), we purified the parasite enzyme apparently to homogeneity, and characterized it. The native PEPCK is a monomer with a subunit molecular weight of 65 kDa. The purified enzyme displayed standard Michaelis-Menten kinetics with Km value of 42·52 μM for its substrate PEP. The Ki for the competitive inhibitors GTP, GMP, ITP and IMP for the carboxylation reaction were determined and discussed. In order to identify putative modulators from plant sources, phytochemicals from F. vestita and Stephania glabra were tested on the purified PEPCK, which resulted in alteration of its activity. From our results, we hypothesize that PEPCK may be a potential target site for anthelmintic action.

Anthelmintic efficacy of ethanolic shoot extract of Alpinia nigra on tegumental enzymes of Fasciolopsis buski, a giant intestinal parasite

Ethanolic shoot extract of Alpinia nigra, a traditionally used anthelmintic medicinal plant among the Tripuri tribes of north-east India, was tested in vitro to determine its anthelmintic efficacy in gastrointestinal trematode Fasciolopsis buski, using alterations in the activity of vital tegumental enzymes viz. acid phosphatase (AcPase), alkaline phosphatase (AlkPase) and adenosine triphosphatase (ATPase). Live adult F. buski treated in vitro with different concentrations of the plant extract showed significant decline in the visible stain histochemically and enzyme activities. Quantitatively, the total enzyme activity of AcPase, AlkPase and ATPase was found to be reduced by 45, 41 and 43%, respectively compared to the control. The reference drug, praziquantel also showed more or less similar effect like that of the plant extract. The results suggest that the tegumental enzymes of the parasite may be an important target of action for active component(s) of A. nigra, which appears to act transtegumentally.

Phytochemicals from Flemingia vestita (Fabaceae) and Stephania glabra (Menispermeaceae) alter cGMP concentration in the cestode Raillietina echinobothrida

Cyclic GMP (cGMP) mediates various physiological functions of nitric oxide (NO) synthesized by nitric oxide synthase (NOS). A crude peel extract and purified fraction of Flemingia vestita, as well as a crude rhizome extract of Stephania glabra and fractions were tested with respect to the activity of NOS, NO efflux and cGMP concentration in the cestode Raillietina echinobothrida in order to find out the possible mode of anthelmintic action of these plant-derived components. For comparison purposes, the parasites were also treated with pure genistein, sodium nitroprusside (SNP-a known NO donor), and the reference drug, praziquantel (PZQ). At the time of onset of paralysis in the parasites, a significant increase (32%-87%) in the NOS activity and a two to three fold increase of NO efflux into the incubation medium were observed in the treated parasites in comparison to their respective controls. The cGMP concentration in the treated parasites' tissue was also increased by 44%-103%. However, in the presence of NG-nitro-L-arginine methyl ester, a potent inhibitor of NOS, there was no increase in the cGMP concentration in the parasite tissue. This study indicates that the phytochemicals, in particular genistein and tetrahydropalmatine, from F. vestita and S. glabra, respectively, disturb the downstream signalling pathway of NO, as indicated by the change in cGMP concentration in the parasite tissue.

Ultrastructural observations on tegumental surface of Raillietina echinobothrida and its alterations caused by root-peel extract of Millettia pachycarpa

Millettia pachycarpa Benth (Leguminosae) has a usage in traditional medicine system practiced among the Lushai tribes of Mizoram, a state in North East India, who customarily consume the aqueous extract of the root peel of the plant to get rid of intestinal worm infections. The crude ethanol, methanol, and acetone fractions of the plant were assayed against Raillietina echinobothrida, the intestinal cestode parasite of domestic fowl, to authenticate the putative anthelmintic efficacy and cestocidal potential in particular of the plants. In vitro exposure of the worm to the extract at a concentration of 25 mg/mL phosphate buffered saline (at 37 degrees C +/- 1 degrees C) revealed distortion and disruption of mitochondria, nucleus, nucleolus, nuclear membrane, basal lamina, and tegumental vacuolization in the distal cytoplasm leading to scar formation in the surface. The possible use of the plant as a potential anthelmintic against cestode parasite is discussed.

Genistein from Flemingia vestita (Fabaceae) enhances NO and its mediator (cGMP) production in a cestode parasite, Raillietina echinobothrida

Cyclic GMP (cGMP) is responsible for various cellular functions including signal pathways and it acts as a mediator for nitric oxide (NO). In order to evaluate the anthelmintic efficacy of the plant-derived isoflavones, the crude peel extract of Flemingia vestita and pure genistein were tested with respect to the activity of nitric oxide synthase (NOS), NO efflux and the cGMP concentration in Rallietina echinobothrida, the cestode parasite of domestic fowl. For comparison, the parasites were also treated with genistein (the major isoflavone present in the crude peel extract), sodium nitroprusside (SNP), a known NO donor, and praziquantel (PZQ), the reference drug. At the time of onset of paralysis in the parasite, the activity of NOS showed a significant increase (35-46%) and a 2-fold increase of NO efflux into the incubation medium in the treated worms in comparison to the respective controls. The cGMP concentration in the parasite tissue increased by 46-84% in the treated test worms in comparison to the controls. The results show that the isoflavones, genistein in particular, from the crude peel extract of F. vestita influence the cGMP concentration in the parasite tissue, which plays a major role in the downstream signal pathways.