The Cratylia mollis Seed Lectin Induces Membrane Permeability Transition in Isolated Rat Liver Mitochondria and a Cyclosporine A-Insensitive Permeability Transition in Trypanosoma cruzi Mitochondria

Biosensor Characterization from Cratylia mollis Seed Lectin (Cramoll)-MOF and Specific Carbohydrate Interactions in an Electrochemical Model

Biosensors are small devices known for their selectivity, high specificity and sensitivity to the respective analyte, at low concentrations. We developed an electrochemical biosensor using the crystalline polymer MOF-[Cu3 (BTC)2 (H2 O)2 ]n to characterize Cratylia mollis seed lectin (Cramoll) and its interaction with free carbohydrate (glucose) and carbohydrates on the surface of rabbit erythrocytes. The electrochemical potentials presented by the exponential curves that vary from 96 to 142 mV in relation to concentrations of 10 to 20 mM of glucose are decisive for the use of the system containing gold electrode/MOF/Cramoll for the characterization of biological models due to its high sensitivity. As well as the kinetic behavior presented in the cyclic voltammograms, with a cathodic current response of 0.000 3 A for a glucose concentration of 15 mM. These results were due to the high specificity of Cramoll under these conditions, promoting stability of surface charges at the Cramoll/electrode interface. This phenomenon facilitates the monitoring of the interaction with free glucose present in the electrolyte medium by potentiometric and amperometric methods and with carbohydrates present on the surface of rabbit erythrocytes through the potentiometric method. Through scanning electron microscopy (SEM) it was possible to observe Cramoll immobilized on the MOF surface, proving the specificity of the ligand (glucose-lectin) through the morphological lectin changes in this process. This electrochemical model, Cramoll/MOF biosensor, is effective for evaluating free lectin/carbohydrate or in the erythrocyte membrane.

Mitochondrial Ca2+ homeostasis in trypanosomes

Mitochondrial calcium ion (Ca2+) uptake is important for buffering cytosolic Ca2+ levels, for regulating cell bioenergetics, and for cell death and autophagy. Ca2+ uptake is mediated by a mitochondrial Ca2+ uniporter (MCU) and the discovery of this channel in trypanosomes has been critical for the identification of the molecular nature of the channel in all eukaryotes. However, the trypanosome uniporter, which has been studied in detail in Trypanosoma cruzi, the agent of Chagas disease, and T. brucei, the agent of human and animal African trypanosomiasis, has lineage-specific adaptations which include the lack of some homologues to mammalian subunits, and the presence of unique subunits. Here, we review newly emerging insights into the role of mitochondrial Ca2+ homeostasis in trypanosomes, the composition of the uniporter, its functional characterization, and its role in general physiology.

Mitochondrial calcium transport and the redox nature of the calcium-induced membrane permeability transition

Mitochondria possess a Ca²⁺ transport system composed of separate Ca²⁺ influx and efflux pathways. Intramitochondrial Ca²⁺ concentrations regulate oxidative phosphorylation, required for cell function and survival, and mitochondrial redox balance, that participates in a myriad of signaling and damaging pathways. The interaction between Ca²⁺ accumulation and redox imbalance regulates opening and closing of a highly regulated inner membrane pore, the membrane permeability transition pore (PTP). In this review, we discuss the regulation of the PTP by mitochondrial oxidants, reactive nitrogen species, and the interactions between these species and other PTP inducers. In addition, we discuss the involvement of mitochondrial redox imbalance and PTP in metabolic conditions such as atherogenesis, diabetes, obesity and in mtDNA stability.

Lectins as antimicrobial agents

The resistance of micro-organisms to antimicrobial agents has been a challenge to treat animal and human infections, and for environmental control. Lectins are natural proteins and some are potent antimicrobials through binding to carbohydrates on microbial surfaces. Oligomerization state of lectins can influence their biological activity and maximum binding capacity; the association among lectin polypeptide chains can alter the carbohydrate-lectin binding dissociation rate constants. Antimicrobial mechanisms of lectins include the pore formation ability, followed by changes in the cell permeability and latter, indicates interactions with the bacterial cell wall components. In addition, the antifungal activity of lectins is associated with the chitin-binding property, resulting in the disintegration of the cell wall or the arrest of de novo synthesis from the cell wall during fungal development or division. Quorum sensing is a cell-to-cell communication process that allows interspecies and interkingdom signalling which coordinate virulence genes; antiquorum-sensing therapies are described for animal and plant lectins. This review article, among other approaches, evaluates lectins as antimicrobials.

Piperine induces autophagy by enhancing protein phosphotase 2A activity in a rotenone-induced Parkinson's disease model

Parkinson's disease (PD) is the second most common neurodegenerative disorder, but there are few treatments currently available. The autophagy pathway plays an important role in the pathogenesis of PD; modulating this pathway is considered to be a promising treatment strategy. Piperine (PIP) is a Chinese medicine with anti-inflammatory and antioxidant effects. The present study investigated the neuroprotective effects of PIP on rotenone-induced neurotoxicity in SK-N-SH cells, primary rat cortical neurons, and in a mouse model. Mice were administered rotenone (10mg/kg) for 6 weeks; PIP (25mg/kg, 50mg/kg) was subsequently administered for 4 weeks. We found that PIP treatment attenuated rotenone-induced motor deficits, and rescued the loss of dopaminergic neurons in the substantia nigra. PIP increased cell viability and restored mitochondrial functioning in SK-N-SH cells and primary neurons. In addition, PIP induced autophagy by inhibiting mammalian target of rapamycin complex 1(mTORC1) via activation of protein phosphotase 2A (PP2A). However, inhibiting PP2A activity with okadaic acid reduced these protective effects, suggesting that PP2A is a target of PIP. These findings demonstrate that PIP exerts neuroprotective effects in PD models via induction of autophagy, and may be an effective agent for PD treatment.

A homolog of cyclophilin D is expressed in Trypanosoma cruzi and is involved in the oxidative stress-damage response

Mitochondria have an important role in energy production, homeostasis and cell death. The opening of the mitochondrial permeability transition pore (mPTP) is considered one of the key events in apoptosis and necrosis, modulated by cyclophilin D (CyPD), a crucial component of this protein complex. In Trypanosoma cruzi, the protozoan parasite that causes Chagas disease, we have previously described that mitochondrial permeability transition occurs after oxidative stress induction in a cyclosporin A-dependent manner, a well-known cyclophilin inhibitor. In the present work, a mitochondrial parasite cyclophilin, named TcCyP22, which is homolog to the mammalian CyPD was identified. TcCyP22-overexpressing parasites showed an enhanced loss of mitochondrial membrane potential and loss of cell viability when exposed to a hydrogen peroxide stimulus compared with control parasites. Our results describe for the first time in a protozoan parasite that a mitochondrial cyclophilin is a component of the permeability transition pore and is involved in regulated cell death induced by oxidative stress.

Protection effect of piperine and piperlonguminine from Piper longum L. alkaloids against rotenone-induced neuronal injury

Currently available treatment approaches for Parkinson׳s disease (PD) are limited in terms of variety and efficacy. Piper longum L. (PLL; Piperaceae) is used in traditional medicine in Asia and the Pacific Islands, with demonstrated anti-inflammatory and antioxidant activities in preclinical studies, and alkaloid extracts of PLL have shown protective effects in PD models. The present study investigated the mechanistic basis for the observed protective effects of PLL. Rats treated with PLL-derived alkaloids showed improvement in rotenone-induced motor deficits, while reactive oxygen species (ROS) production was decreased, mitochondrial membrane potential was stabilized, and the opening of the mitochondrial permeability transition pore (mPTP)-which is involved in ROS production-was inhibited. In addition, rotenone-induced apoptosis was abrogated in the presence of these alkaloids, while a pretreatment stimulated autophagy, likely mitigating neuronal injury by the removal of damaged mitochondria. These findings provide novel insight into the neuroprotective function of PLL as well as evidence in favor of its use in PD treatment. This article is part of a Special Issue entitled SI: Neuroprotection.

Trypanosoma cruzi mitochondrial tryparedoxin peroxidase is located throughout the cell and its pull down provides one step towards the understanding of its mechanism of action

Trypanosoma cruzi depends on the effectiveness of redox metabolism to survive and ensure infection in the host. Homeostasis of redox metabolism in T. cruzi is achieved by the actions of several proteins that differ in many aspects from host proteins. Although extensive research has been performed examining hydroperoxide cytosolic antioxidant defense centered on trypanothione, the mechanisms of mitochondrial antioxidant defense are not yet known. The aim of this study was to elucidate the partners of TcMPx antioxidant pathway and to determine the influence of the cellular context (physiological versus oxidative stress). Through co-precipitation coupled with a mass spectrometry approach, a variety of proteins were detected under physiological and oxidative stress conditions. Interestingly, functional category analysis of the proteins identified under physiological conditions showed that they were involved in the stress response, oxidoreduction, thiol transfer, and metabolic processes; this profile is distinct under oxidative stress conditions likely due to structural alterations. Our findings help to elucidate the reactions involving TcMPx and most importantly also reveal that this protein is present throughout the cell and that its interaction partners change following oxidative stress exposure. The involvement and significance of the proteins found to interact with TcMPx and other possible functions for this protein are discussed widening our knowledge regarding T. cruzi mitochondrial antioxidant defenses.

Effect of Syzygium cumini and Bauhinia forficata aqueous-leaf extracts on oxidative and mitochondrial parameters in vitro

Aqueous-leaf extract of Syzygium cumini and Bauhinia forficata are traditionally used in the treatment of diabetes and cancer, especially in South America, Africa, and Asia. In this study, we analyzed the effects of these extracts on oxidative and mitochondrial parameters in vitro, as well as their protective activities against toxic agents. Phytochemical screenings of the extracts were carried out by HPLC analysis. The in vitro antioxidant capacities were compared by DPPH radical scavenging and Fe(2+) chelating activities. Mitochondrial parameters observed were swelling, lipid peroxidation and dehydrogenase activity. The major chemical constituent of S. cumini was rutin. In B. forficata were predominant quercetin and gallic acid. S. cumini reduced DPPH radical more than B. forficata, and showed iron chelating activity at all tested concentrations, while B. forficata had not similar property. In mitochondria, high concentrations of B. forficata alone induced a decrease in mitochondrial dehydrogenase activity, but low concentrations of this extract prevented the effect induced by Fe(2+)+H2O2. This was also observed with high concentrations of S. cumini. Both extracts partially prevented the lipid peroxidation induced by Fe(2+)/citrate. S. cumini was effective against mitochondrial swelling induced by Ca(2+), while B. forficata alone induced swelling more than Ca(2+). This study suggests that leaf extract of S. cumini might represent a useful therapeutic for the treatment of diseases related with mitochondrial dysfunctions. On the other hand, the consumption of B. forficata should be avoided because mitochondrial damages were observed, and this possibly may pose risk to human health.

Mitochondrial calcium transport in trypanosomes

The biochemical peculiarities of trypanosomes were fundamental for the recent molecular identification of the long-sought channel involved in mitochondrial Ca(2+) uptake, the mitochondrial Ca(2+) uniporter or MCU. This discovery led to the finding of numerous regulators of the channel, which form a high molecular weight complex with MCU. Some of these regulators have been bioinformatically identified in trypanosomes, which are the first eukaryotic organisms described for which MCU is essential. In trypanosomes MCU is important for buffering cytosolic Ca(2+) changes and for activation of the bioenergetics of the cells. Future work on this pathway in trypanosomes promises further insight into the biology of these fascinating eukaryotes, as well as the potential for novel target discovery.

A lectin from Bothrops leucurus snake venom raises cytosolic calcium levels and promotes B16-F10 melanoma necrotic cell death via mitochondrial permeability transition

BlL, a galactose-binding C-type lectin purified from Bothrops leucurus snake venom, exhibits anticancer activity. The current study was designed to elucidate the cellular mechanisms by which BlL induces melanoma cell death. The viabilities of B16-F10 melanoma cells and HaCaT keratinocytes treated with BlL were evaluated. Necrotic and apoptotic cell death, cytosolic Ca(2+) levels, mitochondrial Ca(2+) transport and superoxide levels were assessed in B16-F10 melanoma cells exposed to BlL. We found that treatment with BlL caused dose-dependent necrotic cell death in B16-F10 melanoma cells. Conversely, the viability of non-tumorigenic HaCaT cells was not affected by similar doses of BlL. BlL-induced B16-F10 necrosis was preceded by a significant (2-fold) increase in cytosolic calcium concentrations and a significant (3-fold) increase in mitochondrial superoxide generation. It is likely that BlL treatment triggers B16-F10 cell death via mitochondrial permeability transition (MPT) pore opening because the pharmacological MPT inhibitors bongkrekic acid and Debio 025 greatly attenuated BlL-induced cell death. Experiments evaluating mitochondrial Ca(2+) transport in permeabilized B16-F10 cells strongly supported the hypothesis that BlL rapidly stimulates cyclosporine A-sensitive Ca(2+)-induced MPT pore opening. We therefore conclude that BlL causes selective B16-F10 melanoma cell death via dysregulation of cellular Ca(2+) homeostasis and Ca(2+)-induced opening of MPT pore.