Increase in cytosolic Ca2+ levels through the activation of non-selective cation channels induced by oxidative stress causes mitochondrial depolarization leading to apoptosis-like death in Leishmania donovani promastigotes

New insights into the pro-oxidant mechanism of dehydroleucodine on Trypanosoma cruzi

Chagas disease, caused by Trypanosoma cruzi (T. cruzi), is one of the most important neglected diseases in Latin America. The limited use of the current nitro-derivative-based chemotherapy highlights the need for alternative drugs and the identification of their molecular targets. In this study, we investigated the trypanocidal effect of the sesquiterpene lactone dehydroleucodine (DhL) and its derivatives, focusing on the antioxidative defense of the parasites. DhL and two derivatives, at lesser extent, displayed antiproliferative effect on the parasites. This effect was blocked by the reducing agent glutathione (GSH). Treated parasites exhibited increased intracellular ROS concentration and trypanothione synthetase activity, accompanied by mitochondrial swelling. Although molecular dynamics studies predicted that GSH would not interact with DhL, 1H-NMR analysis confirmed that GSH could protect parasites by interacting with the lactone. When parasites overexpressing mitochondrial tryparedoxin peroxidase were incubated with DhL, its effect was attenuated. Overexpression of cytosolic tryparedoxin peroxidase also provided some protection against DhL. These findings suggest that DhL induces oxidative imbalance in T. cruzi, offering new insights into potential drug targets against this parasite.

Compounds with potentialities as novel chemotherapeutic agents in leishmaniasis at preclinical level

Leishmaniasis are neglected infectious diseases caused by kinetoplastid protozoan parasites from the genus Leishmania. These sicknesses are present mainly in tropical regions and almost 1 million new cases are reported each year. The absence of vaccines, as well as the high cost, toxicity or resistance to the current drugs determines the necessity of new treatments against these pathologies. In this review, several compounds with potentialities as new antileishmanial drugs are presented. The discussion is restricted to the preclinical level and molecules are organized according to their chemical nature, source and molecular targets. In this manner, we present antimicrobial peptides, flavonoids, withanolides, 8-aminoquinolines, compounds from Leish-Box, pyrazolopyrimidines, and inhibitors of tubulin polymerization/depolymerization, topoisomerase IB, proteases, pteridine reductase, N-myristoyltransferase, as well as enzymes involved in polyamine metabolism, response against oxidative stress, signaling pathways, and sterol biosynthesis. This work is a contribution to the general knowledge of these compounds as antileishmanial agents.

Acylated ghrelin protection inhibits apoptosis in the remote myocardium post-myocardial infarction by inhibiting calcineurin and activating ARC

This study investigated if acylated ghrelin (AG) could inhibit myocardial infarction (MI)-induced apoptosis in the left ventricles (LV) of male rats and tested if this protection involves modulating ARC anti-apoptotic protein. Rats (n = 12/group) were assigned as a sham-operated, a sham + AG (100 µg/kg, 2x/d, S.C.), MI, and MI + AG. With no antioxidant activity or expression of FAS, AG inhibited caspase-3, 8, and 9 and decreased cytosolic/mitochondrial levels of cytochrome-c, Bax, Bad, and Bad-BCL-2 complex in the LVs of the sham-operated and MI-treated rats. Concomitantly, AG preserved the mitochondria structure, decreased mtPTP, and enhanced state-3 respiration in the LVs of both treated groups. These effects were associated with increased mitochondrial levels of ARC and a reduction in the activity of calcineurin. Overall, AG suppresses MI-induced ventricular apoptosis by inhibition of calcineurin, activation of ARC, and preserving mitochondria integrity.

Casiopeina III-ia: A Copper Compound with Potential Use for Treatment of Infections Caused by Leishmania mexicana

INTRODUCTION

Casiopeina III-ia (CasIII-ia) is a mixed chelate copper (II) compound capable of interacting with free radicals generated in the respiratory chain through redox reactions, producing toxic reactive oxygen species (ROS) that compromise the viability of cancer cells, bacteria and protozoa. Due to its remarkable effect on protozoa, this study evaluated the effect of CasIII-ia on Leishmania mexicana amastigotes and its potential use as a treatment for cutaneous leishmaniasis in the murine model.

METHODS

We analyzed the leishmanicidal effect of CasIII-ia on L. mexicana amastigotes and on their survival in bone marrow-derived macrophages. Furthermore, we evaluated the production of ROS in treated parasites and the efficacy of CasIII-ia in the treatment of mice infected with L. mexicana.

RESULTS

Our results show that CasIII-ia reduces parasite viability in a dose-dependent manner that correlates with increased ROS production. A decrease in the size of footpad lesions and in parasite loads was observed in infected mice treated with the intraperitoneal administration of CasIII-ia.

CONCLUSIONS

We propose CasIII-ia as a potential drug for the treatment of cutaneous leishmaniasis.

Chronic exposure to mercury increases arrhythmia and mortality post-acute myocardial infarction in rats

Introduction: Mercury (Hg) is a heavy metal that causes a variety of toxic effects in eukaryotic cells. Previous studies have reported detrimental effects of mercury toxicity in the cardiovascular system. Given the importance of understanding the relationship between Hg and cardiovascular disease, we sought to investigate if the Hg could worsen the myocardial repercussions following ischemic injury. We demonstrated that once mercury toxicity is established, it can influence the outcome of myocardial infarction (MI). Methods: Male Wistar rats received intramuscular injections of either saline (NaCl 0.9%) or mercuric chloride (HgCl2, first dose of 4.6 μg/kg, and subsequent doses of 0.07 μg/kg/day) for 4 weeks. Three weeks post-exposure, we induced transmural infarction in the left ventricle free wall through coronary artery occlusion surgery. Results: ECG recordings obtained from MI groups demonstrated alterations in the rhythm of the heartbeat/heart electrical activity, as expected, including ventricular extrasystoles and ventricular tachycardia. However, the MI group exposed to Hg (MI-Hg) exhibited augmented ventricular extrasystoles and ventricular tachycardia compared to the MI group. Also, Basckó coefficient revealed that the arrhythmic events-after MI-were aggravated by Hg exposure. Discussion: Our results indicate that the significantly increased mortality in MI-Hg groups when compared to MI (21%, MI vs 32%, MI-Hg) is correlated with greater occurrence of arrhythmias. In conclusion, this study further supports the idea that exposure to mercury (Hg) should be recognized as a significant risk factor that exacerbates the impact of cardiac ischemic injury, potentially leading to an increased mortality rate among patients experiencing acute MI.

Enyne acetogenins from Porcelia macrocarpa displayed anti-Trypanosoma cruzi activity and cause a reduction in the intracellular calcium level

Natural products are a promising source of new compounds with a wide spectrum of pharmacological properties, including antiprotozoal activities. Chagas disease, caused by the protozoan parasite Trypanosoma cruzi, is one of several neglected tropical diseases with reduced options for treatment, which presents limitations such as toxicity and ineffectiveness in the chronic stage of the disease. Aiming to investigate the Brazilian flora for the discovery of new anti-T. cruzi compounds, the MeOH extract from Porcelia macrocarpa R.E. Fries (Annonaceae) fruit peels displayed potent activity against trypomastigotes and intracellular amastigotes and was subjected to bioactivity-guided fractionation. Using different chromatographic steps, a fraction composed of a mixture of four new chemically related acetogenins was obtained. The compounds were characterized as (2S*,3R*,4R*)-3-hydroxy-4-methyl-2-(n-octadeca-13',17'-dien-11'-inil)butanolide (1), (2S*,3R*,4R*)-3-hydroxy-4-methyl-2-(n-eicosa-13',19'-dien-11'-inil)butanolide (2), (2S*,3R*,4R*)-3-hydroxy-4-methyl-2-(n-octadec-13'-en-11'-inil)butanolide (3), and (2S*,3R*,4R*)-3-hydroxy-4-methyl-2-(n-eicosa-13'-en-11'-inil)butanolide (4) by NMR analysis and UHPLC/ESI-HRMS data. The mixture of compounds 1-4, displayed an EC50 of 4.9 and 2.5 µg/mL against trypomastigote and amastigote forms of T. cruzi, respectively, similar to the standard drug benznidazole (EC50 of 4.8 and 1.4 µg/mL). Additionally, the mixture of compounds 1-4 displayed no mammalian toxicity for murine fibroblasts (CC50 > 200 µg/mL), resulting in a SI > 40.8 and > 83.3 against trypomastigotes and amastigotes, respectively. Based on these results, the mechanism of action of this bioactive fraction was investigated. After a short-time incubation with the trypomastigotes, no alterations in the cell membrane permeability were observed. However, it was verified a decrease in the intracellular calcium of the parasites, without significant pH variations of the acidocalcisomes. The intracellular damages were followed by an upregulation of the reactive oxygen species and ATP, but no depolarization effects were observed in the mitochondrial membrane potential. These data suggest that the mixture of compounds 1-4 caused an irreversible oxidative stress in the parasites, leading to death. If adequately studied, these acetogenins can open new insights for the discovery of new routes of death in T. cruzi.

Down the membrane hole: Ion channels in protozoan parasites

Parasitic diseases caused by protozoans are highly prevalent around the world, disproportionally affecting developing countries, where coinfection with other microorganisms is common. Control and treatment of parasitic infections are constrained by the lack of specific and effective drugs, plus the rapid emergence of resistance. Ion channels are main drug targets for numerous diseases, but their potential against protozoan parasites is still untapped. Ion channels are membrane proteins expressed in all types of cells, allowing for the flow of ions between compartments, and regulating cellular functions such as membrane potential, excitability, volume, signaling, and death. Channels and transporters reside at the interface between parasites and their hosts, controlling nutrient uptake, viability, replication, and infectivity. To understand how ion channels control protozoan parasites fate and to evaluate their suitability for therapeutics, we must deepen our knowledge of their structure, function, and modulation. However, methodological approaches commonly used in mammalian cells have proven difficult to apply in protozoans. This review focuses on ion channels described in protozoan parasites of clinical relevance, mainly apicomplexans and trypanosomatids, highlighting proteins for which molecular and functional evidence has been correlated with their physiological functions.

Quinolinyl β-enaminone derivatives exhibit leishmanicidal activity against Leishmania donovani by impairing the mitochondrial electron transport chain complex and inducing ROS-mediated programmed cell death

OBJECTIVES

Previously, a series of side chain-modified quinolinyl β-enaminones was identified to possess significant activity against chloroquine-sensitive or -resistant Plasmodium falciparum and Brugia malayi microfilariae. The present study evaluates in vitro and in vivo activity of the series against Leishmania donovani and reports their mode of action.

METHODS

The in vitro activity of 15 quinolinyl β-enaminone derivatives against Leishmania promastigotes and amastigotes was assessed by luciferase assay. The reduction of organ parasite burden was assessed by Giemsa staining in L. donovani-infected BALB/c mice and hamsters. Intracellular Ca2+ and ATP level in active derivative (3D)-treated promastigotes were determined by fluorescence and luminescence assays. Flow cytometry was performed to determine loss of mitochondrial membrane potential (MMP) using JC-1 dye, reactive oxygen species (ROS) generation using 2',7'-dichlorodihydrofluorescein diacetate (DCFDA) dye, phosphatidylserine externalization by Annexin V-FITC staining and cell-cycle arrest by propidium iodide (PI) staining.

RESULTS

Compounds 3A, 3B and 3D showed significant in vitro efficacy against L. donovani with IC50 < 6 µM and mild cytotoxicity (∼75% viability) at 25 µM on J774 macrophages. 3A and 3D at 50 mg/kg and 100 mg/kg reduced parasite burden (>84%) in infected mice and hamsters, respectively, whereas 3D-treated animals demonstrated maximum parasite burden reduction without organ toxicity. Mode-of-action analysis revealed that 3D induced apoptosis by inhibiting mitochondrial complex II, reducing MMP and ATP levels, increasing ROS and Ca2+ levels, ultimately triggering phosphatidylserine externalization and sub-G0/G1 cell-cycle arrest in promastigotes.

CONCLUSIONS

Compound 3D-mediated inhibition of L. donovani mitochondrial complex induces apoptosis, making it a promising therapeutic candidate for visceral leishmaniasis.

MFN2 mediates ER-mitochondrial coupling during ER stress through specialized stable contact sites

Endoplasmic reticulum (ER) functions critically depend on a suitable ATP supply to fuel ER chaperons and protein trafficking. A disruption of the ability of the ER to traffic and fold proteins leads to ER stress and the unfolded protein response (UPR). Using structured illumination super-resolution microscopy, we revealed increased stability and lifetime of mitochondrial associated ER membranes (MAM) during ER stress. The consequent increase of basal mitochondrial Ca2+ leads to increased TCA cycle activity and enhanced mitochondrial membrane potential, OXPHOS, and ATP generation during ER stress. Subsequently, OXPHOS derived ATP trafficking towards the ER was increased. We found that the increased lifetime and stability of MAMs during ER stress depended on the mitochondrial fusion protein Mitofusin2 (MFN2). Knockdown of MFN2 blunted mitochondrial Ca2+ effect during ER stress, switched mitochondrial F1FO-ATPase activity into reverse mode, and strongly reduced the ATP supply for the ER during ER stress. These findings suggest a critical role of MFN2-dependent MAM stability and lifetime during ER stress to compensate UPR by strengthening ER ATP supply by the mitochondria.

Mitochondrial Imbalance of Trypanosoma cruzi Induced by the Marine Alkaloid 6-Bromo-2'-de-N-Methylaplysinopsin

Chagas disease, caused by Trypanosoma cruzi, affects seven million people worldwide and lacks effective treatments. Using bioactivity-guided fractionation, NMR, and electrospray ionization-high resolution mass spectrometry (ESI-HRMS) spectral analysis, the indole alkaloid 6-bromo-2'-de-N-methylaplysinopsin (BMA) was isolated and chemically characterized from the marine coral Tubastraea tagusensis. BMA was tested against trypomastigotes and intracellular amastigotes of T. cruzi, resulting in IC₅₀ values of 62 and 5.7 μM, respectively, with no mammalian cytotoxicity. The mechanism of action studies showed that BMA induced no alterations in the plasma membrane permeability but caused depolarization of the mitochondrial membrane potential, reducing ATP levels. Intracellular calcium levels were also reduced after the treatment, which was associated with pH alteration of acidocalcisomes. Using matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF)/MS analysis, alterations of mass spectral signals were observed after treatment with BMA, suggesting a different mechanism from benznidazole. In silico pharmacokinetic-pharmacodynamic (PKPD) parameters suggested a drug-likeness property, supporting the promising usefulness of this compound as a new hit for optimizations.

D-pinitol attenuates isoproterenol induced myocardial infarction by alleviating cardiac inflammation, oxidative stress and ultrastructural changes in Swiss Albino mice

Cardiovascular diseases are the most disturbing problems throughout the world. The side effects of existing drugs are continuously compelling the scientist to look for better options in terms of safety, efficacy and cost-effectiveness. Our study is also a move in this direction. We have chosen D-pinitol to see its cardioprotective role in isoproterenol-induced myocardial infarction in Swiss Albino mice. Grouping was made by dividing mice into eight groups (n = 6). Group I - control; Group II - Isoproterenol (ISO) (150 mg/kg, i.p.); Group III - D-pinitol (PIN) (25 mg), Group IV - PIN (50 mg), Group V - PIN (100 mg) per kg per oral, respectively with ISO; Group VI - PIN _{per se} (100 mg D-pinitol only); Group VII - Propranolol (PRO) (20 mg/kg/oral) with ISO; and Group VIII - PRO _{per se} (20 mg/kg, p.o.). After 24 hrs of the last dose, the blood sample was collected for biochemical parameters, then mice were, euthanised through cervical dislocation under anesthesia and cardiac tissue was collected for biochemical, histopathological and ultrastructural evaluation. Administration of ISO in mice altered the level of antioxidant markers, cardiac injury markers and inflammatory markers, which were significantly restored towards normal by D-pinitol at the dose of 50 and 100 mg. 25 mg of D-pinitol dosage, did not produce significant cardio protection. The histopathological and ultrastructural analysis further confirmed these findings. Our study showed that D-pinitol significantly protected myocardial damage which was induced by ISO and reverted oxidative stress and inflammation considerably.

Functionalized 1,2,3-triazolium salts as potential agents against visceral leishmaniasis

Visceral leishmaniasis (VL) is the most severe clinical form of leishmaniasis, being fatal if untreated. In search of a more effective treatment for VL, one of the main strategies is the development and screening of new antileishmanial compounds. Here, we reported the synthesis of seven new acetyl functionalized 1,2,3-triazolium salts, together with four 1,2,3-triazole precursors, and investigated their effect against different strains of L. infantum from dogs and humans. The 1,2,3-triazolium salts exhibited better activity than the 1,2,3-triazole derivatives with IC₅₀ range from 0.12 to 8.66 μM and, among them, compound 5 showed significant activity against promastigotes (IC₅₀ from 4.55 to 5.28 μM) and intracellular amastigotes (IC₅₀ from 5.36 to 7.92 μM), with the best selective index (SI ~ 6-9) and reduced toxicity. Our findings, using biochemical and ultrastructural approaches, demonstrated that compound 5 targets the mitochondrion of L. infantum promastigotes, leading to the formation of reactive oxygen species (ROS), increase of the mitochondrial membrane potential, and mitochondrial alteration. Moreover, quantitative transmission electron microscopy (TEM) revealed that compound 5 induces the reduction of promastigote size and cytoplasmic vacuolization. Interestingly, the effect of compound 5 was not associated with apoptosis or necrosis of the parasites but, instead, seems to be mediated through a pathway involving autophagy, with a clear detection of autophagic vacuoles in the cytoplasm by using both a fluorescent marker and TEM. As for the in vivo studies, compound 5 showed activity in a mouse model of VL at 20 mg/kg, reducing the parasite load in both spleen and liver (59.80% and 26.88%, respectively). Finally, this compound did not induce hepatoxicity or nephrotoxicity and was able to normalize the altered biochemical parameters in the infected mice. Thus, our findings support the use of 1,2,3-triazolium salts as potential agents against visceral leishmaniasis.

Cristae junction as a fundamental switchboard for mitochondrial ion signaling and bioenergetics

OPA1 and MICU1 are both involved in the regulation of mitochondrial Ca2+ uptake and the stabilization of the cristae junction, which separates the inner mitochondrial membrane into the interboundary membrane and the cristae membrane. In this mini-review, we focus on the synergetic control of OPA1 and MICU1 on the cristae junction that serves as a fundamental regulator of multiple mitochondrial functions. In particular, we point to the critical role of an adaptive cristae junction permeability in mitochondrial Ca2+ signaling, spatial H+ gradients and mitochondrial membrane potential, metabolic activity, and apoptosis. These characteristics bear on a distinct localization of the oxidative phosphorylation machinery, the FoF1-ATPase, and mitochondrial Ca2+uniporter (MCU) within sections of the inner mitochondrial membrane isolated by the cristae junction and regulated by proteins like OPA1 and MICU1. We specifically focus on the impact of MICU1-regulated cristae junction on the activity and distribution of MCU within the complex ultrastructure of mitochondria.

β-carbolines RCC and C5 induce death of Leishmania amazonensis intracellular amastigotes

Background: Cutaneous leishmaniasis is caused by Leishmania spp., and its treatment is limited. The β-carbolines have shown activity against kinetoplastids. Aim: To evaluate the activity and effects of the β-carbolines, N-{2-[(4,6-bis(isopropylamino)-1,3,5-triazin-2-yl)amino]ethyl}-1-(4-methoxyphenyl)-β-carboline-3-carboxamide (RCC) and N-benzyl-1-(4-methoxy)phenyl-9H-beta-carboline-3-carboxamide (C5), against L. amazonensis intracellular amastigotes and to suggest their mechanism of action. Methods: We analyzed the activity and cytotoxicity of β-carbolines and the morphological alterations by electron microscopy. Mitochondrial membrane potential, production nitric oxide, reactive oxygen species, lipidic bodies, autophagic vacuoles and ATP were also evaluated. Results & conclusion: The results showed that RCC and C5 are active against intracellular amastigotes and were able to induce oxidative stress and ultrastructural alterations such as accumulation of lipid bodies and autophagic vacuoles, leading to parasite death.

ASSESSMENT OF THE OXIDATIVE AND NITROSATIVE STRESS IN THE SERUM OF SAUDI PATIENTS WITH CUTANEOUS LEISHMANIASIS BEFORE AND AFTER TREATMENT

Macrophages, within which Leishmania species replicate, generate large amounts of reactive oxygen species (ROS) and reactive nitrogen species (RNS) to kill these parasites. The present study assessed the oxidative and nitrosative stress, and specific immune enzymes in the serum of patients with cutaneous leishmaniasis (Cl) before and after treatment and in the control individuals. Serum activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), L-arginase, myeloperoxidase (MPO), and adenosine deaminase (ADA) and the levels of reduced glutathione, malondialdehyde (MDA), and nitric oxide (NO) were studied. The activities of L-arginase, MPO, and ADA and the levels of MDA and NO were significantly elevated (P < 0.001), while the activities of SOD, CAT, and GSH-Px, and the levels of reduced glutathione (GSH) were significantly (P < 0.001) reduced in untreated patients as compared with values of patients after treatment and of control individuals. The treatment, which included intramuscular injection of sodium stibogluconate and meglumine antimoniate, ameliorated these factors in comparison to the untreated group. These results suggest that oxidative and nitrosative stress may play an important role in the pathogenesis of untreated cutaneous leishmaniasis. Furthermore, the reduction in oxidative and nitrosative stress in the treated Cl patients may be due to the drug decreasing energy production by the parasite, which eventually leads to its death.

Mesenchymal Stem Cell-Conditioned Medium Protects Hippocampal Neurons From Radiation Damage by Suppressing Oxidative Stress and Apoptosis

Objective

To investigate the effects of mesenchymal stem cell-conditioned medium (MSC-CM) on radiation-induced oxidative stress, survival and apoptosis in hippocampal neurons.

Methods

The following groups were defined: Control, radiation treatment (RT), RT+MSC-CM, MSC-CM, RT + N-Acetylcysteine (RT+NAC), and RT + MSC-CM + PI3 K inhibitor (LY294002). A cell Counting Kit-8 (CCK-8) was used to measure cell proliferation. Apoptosis was examined by AnnexinV/PI flow cytometric analyses. Intracellular reactive oxygen species (ROS) were detected by DCFH-DA. Intracellular glutathione (GSH), malondialdehyde (MDA) content, and superoxide dismutase (SOD) activity were detected by colorimetric assays. Protein levels of γ-H2AX, PI3K-AKT, P53, cleaved caspase-3, Bax, and BCl-2 were analyzed by Western blotting.

Results

The proliferation of HT22 cells was significantly inhibited in the RT group, but was significantly preserved in the RT + MSC-CM group (P < 0.01). Apoptosis was significantly higher in the RT group than in the RT+ MSC-CM group (P < 0.01). MSC-CM decreased intracellular ROS and MDA content after irradiation (P < 0.01). GSH level and SOD activity were higher in the RT + MSC-CM group than in the RT group, as was MMP (P < 0.01). MSC-CM decreased expression of γ-H2AX, P53, Bax, and cleaved-caspase-3, but increased Bcl-2 expression (P < 0.01).

Conclusion

MSC-CM attenuated radiation-induced hippocampal neuron cell line damage by alleviating oxidative stress and suppressing apoptosis.

Qingda granule attenuates angiotensin II-induced cardiac hypertrophy and apoptosis and modulates the PI3K/AKT pathway

Qingda granule (QDG), simplified from Qingxuan Jiangya Decoction, is a well-known traditional Chinese medicine formula that has been used for decades to treat hypertension. However, the cardioprotective effects of QDG on Ang II-induced hypertension remain unknown. This study aimed to investigate the effects of QDG on hypertension-induced cardiac hypertrophy and apoptosis, as well as explore its underlying mechanisms. Mice were infused with Ang II (500 ng/kg/min) or saline solution as control, then administered oral QDG (1.145 g/kg/day) or saline for two weeks. QDG treatment attenuated the elevation in blood pressure caused by Ang II, as well as the decreased left ventricle ejection fractions and fractional shortening. Moreover, QDG treatment significantly alleviated the Ang II-induced elevation of the ratio of heart weight to tibia length, as well as cardiac injury, hypertrophy, and apoptosis. In cultured H9C2 cells stimulated with Ang II, QDG partially reversed the increase in cell surface area and number of apoptotic cells, up-regulation of hypertrophy markers ANP and BNP, and activation of caspases-9 and -3. QDG also partially reversed Ang II-induced accumulation of reactive oxygen species (ROS), depolarization of the mitochondrial membrane, release of cytochrome C, up-regulation of Bax, and decrease in levels of p-PI3K, p-AKT, and Bcl-2. These results suggest that QDG can significantly attenuate Ang II-induced hypertension, cardiac hypertrophy and apoptosis, and it may exert these effects in part by suppressing ROS production and activating the PI3K/AKT signaling pathway.

Leishmania donovani chaperonin TCP1γ subunit protects miltefosine induced oxidative damage

T-complex protein-1 (TCP1) is a chaperonin protein known to fold various proteins like actin and tubulin. In Leishmania donovani only one subunit of TCP1 that is gamma subunit (LdTCP1γ) has been functionally characterized. It not only performs ATP dependent protein folding but is also essential for survival and virulence. The present work demonstrates that LdTCP1γ also has a role in miltefosine resistance. Overexpression of LdTCP1γ in L. donovani promastigotes results in decreased sensitivity of parasites towards miltefosine, while single-allele replacement mutants exhibited increased sensitivity as compared to wild-type promastigotes. This response was specific to miltefosine with no cross-resistance to other drugs. The LdTCP1γ-mediated drug resistance was directly related to miltefosine-induced apoptotic death of the parasite, as was evidenced by 2 to 3-fold decrease in cell death parameters in overexpressing cells and >2-fold increase in single-allele replacement mutants. Further, deciphering the mechanism revealed that resistance of overexpressing cells was associated with efficient ROS neutralization due to increased levels of thiols and upregulation of cytosolic tryparedoxin peroxidase (cTxnPx). Further, modulation of LdTCP1γ expression in parasite also modulates the levels of proinflammatory cytokine (TNF-α) and anti-inflammatory cytokine (IL-10) of the host macrophages. The study provides evidence for the involvement of a chaperonin protein LdTCP1γ in the protection against miltefosine induced oxidative damage and reveals the fundamental role of LdTCP1γ in parasite biology.

Antiproliferative activity of the dibenzylideneacetone derivate (E)-3-ethyl-4-(4-nitrophenyl)but‑3-en-2-one in Trypanosoma cruzi

Chagas disease is one of the most prevalent neglected diseases in the world. The illness is caused by Trypanosoma cruzi, a protozoan parasite with a complex life cycle and three morphologically distinct developmental stages. Nowadays, the only treatment is based on two nitro-derivative drugs, benznidazole and nifurtimox, which cause serious side effects. Since the treatment is limited, the search for new treatment options for patients with Chagas disease is highly necessary. In this study we analyzed the substance A11K3, a dibenzylideneacetone (DBA). DBAs have an acyclic dienone attached to aryl groups in both β-positions and studies have shown that they have biological activity against tumors cells, bacteria, and protozoa such as T. cruzi and Leishmania spp. Here we show that A11K3 is active against all three T. cruzi evolutionary forms: the epimastigote (IC₅₀ = 3.3 ± 0.8), the trypomastigote (EC₅₀ = 24 ± 4.3) and the intracellular amastigote (IC₅₀ = 9.3 ± 0.5 µM). A cytotoxicity assay in LLCMK₂ cells showed a CC₅₀ of 239.2 ± 15.7 µM giving a selectivity index (CC₅₀/IC₅₀) of 72.7 for epimastigotes, 9.9 for trypomastigotes and 25.9 for intracellular amastigotes. Morphological and ultrastructural analysis of the parasites treated with A11K3 by TEM and SEM revealed alterations in the Golgi complex, mitochondria, plasma membrane and cell body, with an increase of autophagic vacuoles and lipid bodies. Biochemical assays of A11K3-treated T. cruzi showed an increase of ROS, plasma membrane ruptures, lipid peroxidation, mitochondrial membrane depolarization with a decrease in ATP and accumulation of autophagic vacuoles. The results lead to the hypothesis that A11K3 causes death of the protozoan through events such as plasma membrane and mitochondrial alterations and autophagy, characteristic of cell collapse.

Halictine-2 antimicrobial peptide shows promising anti-parasitic activity against Leishmania spp

The protozoan parasite Leishmania spp. causes leishmaniases, a group of diseases creating serious health problems in many parts of the world with significant resistance to existing drugs. Insect derived antimicrobial peptides are promising alternatives to conventional drugs against several human disease-causing pathogens because they do not generate resistance. Halictine-2, a novel antimicrobial peptide from the venom of eusocial honeybee, Halictus sexcinctus showed significant anti-leishmanial activity in vitro, towards two life forms of the dimorphic parasite, the free-swimming infective metacyclic promastigotes and the intracellular amastigotes responsible for the systemic infection. The anti-leishmanial activity of the native peptide (P^5S) was significantly enhanced by serine to threonine substitution at position 5 (P^5T). The peptide showed a propensity to form α-helices after substitution at position-5, conferring amphipathicity. Distinct pores observed on the promastigote membrane after P^5T exposure suggested a mechanism of disruption of cellular integrity. Biochemical alterations in the promastigotes after P^5T exposure included generation of increased oxygen radicals with mitochondrial Ca²⁺ release, loss of mitochondrial membrane potential, reduction in total ATP content and increased mitochondrial mass, resulting in quick bioenergetic and chemiosmotic collapse leading to cell death characterized by DNA fragmentation. P^5T was able to reduce intracellular amastigote burden in an in vitro model of Leishmania infection but did not alter the proinflammatory cytokines like TNF-α and IL-6. The ability of the P^5T peptide to kill the Leishmania parasite with negligible haemolytic activity towards mouse macrophages and human erythrocytes respectively, demonstrates its potential to be considered as a future antileishmanial drug candidate.

Effects on photosynthesis and polyphenolic compounds in crop plant mung bean (Vigna radiata) following simulated accidental exposure to hydrogen peroxide

Hydrogen peroxide (H₂O₂) is a strong oxidizer and bleaching agent included in the list of substances requiring accident preparedness by the National Chemical Information System, Korea. Although chemical accidents related to H₂O₂ frequently occur globally, few studies have evaluated its toxicity and risk to soil ecosystems. Herein, accidental exposure to H₂O₂ was simulated in a microcosm including crop plant mung bean (Vigna radiata), and its long-term effects on photosynthetic activities and polyphenolic compounds were measured. Plants were evaluated based on the concentration and amount of H₂O₂ exposure, distance from H₂O₂ source, and duration post exposure. Plants exposed to high concentrations and large amounts of H₂O₂ at a close distance were most damaged; their photosynthetic activities and polyphenolic compound levels significantly decreased compared to the controls. H₂O₂ consistently damaged plants and affected their activities, but plants with minor damage recovered their photosynthetic activities and polyphenolic compound levels. Additionally, moderate oxidative stress from H₂O₂ exposure induced the synthesis of polyphenolic antioxidants including flavonol and anthocyanin. Thus, we suggest that flavonol and anthocyanin levels are the most sensitive indicators of adverse effects of H₂O₂ exposure in V. radiata. Our results highlight the risk of H₂O₂ and serve as a reference for chemical accidents.

In vitro activity of 1H-phenalen-1-one derivatives against Leishmania spp. and evidence of programmed cell death

Background

The in vitro activity against Leishmania spp. of a novel group of compounds, phenalenone derivatives, is described in this study. Previous studies have shown that some phenalenones present leishmanicidal activity, and induce a decrease in the mitochondrial membrane potential in L. amazonensis parasites, so in order to elucidate the evidence of programmed cell death occurring inside the promastigote stage, different assays were performed in two different species of Leishmania.

Methods

We focused on the determination of the programmed cell death evidence by detecting the characteristic features of the apoptosis-like process, such as phosphatidylserine exposure, mitochondrial membrane potential, and chromatin condensation among others.

Results

The results showed that four molecules activated the apoptosis-like process in the parasite. All the signals observed were indicative of the death process that the parasites were undergoing.

Conclusions

The present results highlight the potential use of phenalenone derivatives against Leishmania species and further studies should be undertaken to establish them as novel leishmanicidal therapeutic agents.

Ascorbate-Dependent Peroxidase (APX) from Leishmania amazonensis Is a Reactive Oxygen Species-Induced Essential Enzyme That Regulates Virulence

The molecular mechanisms underlying biological differences between two Leishmania species that cause cutaneous disease, L. major and L. amazonensis, are poorly understood. In L. amazonensis, reactive oxygen species (ROS) signaling drives differentiation of nonvirulent promastigotes into forms capable of infecting host macrophages. Tight spatial and temporal regulation of H₂O₂ is key to this signaling mechanism, suggesting a role for ascorbate-dependent peroxidase (APX), which degrades mitochondrial H₂O₂ Earlier studies showed that APX-null L. major parasites are viable, accumulate higher levels of H₂O₂, generate a greater yield of infective metacyclic promastigotes, and have increased virulence. In contrast, we found that in L. amazonensis, the ROS-inducible APX is essential for survival of all life cycle stages. APX-null promastigotes could not be generated, and parasites carrying a single APX allele were impaired in their ability to infect macrophages and induce cutaneous lesions in mice. Similar to what was reported for L. major, APX depletion in L. amazonensis enhanced differentiation of metacyclic promastigotes and amastigotes, but the parasites failed to replicate after infecting macrophages. APX expression restored APX single-knockout infectivity, while expression of catalytically inactive APX drastically reduced virulence. APX overexpression in wild-type promastigotes reduced metacyclogenesis, but enhanced intracellular survival following macrophage infection or inoculation into mice. Collectively, our data support a role for APX-regulated mitochondrial H₂O₂ in promoting differentiation of virulent forms in both L. major and L. amazonensis Our results also uncover a unique requirement for APX-mediated control of ROS levels for survival and successful intracellular replication of L. amazonensis.

A synthetic peptide derived of the β2-β3 loop of the plant defensin from Vigna unguiculata seeds induces Leishmania amazonensis apoptosis-like cell death

For medical use of proteins and peptide-based drugs, it is desirable to have small biologically active sequences because they improve stability, reduce side effects, and production costs. Several plant defensins have their biological activities imparted by a sequence named γ-core. Vu-Def, a Vigna unguiculata defensin, has activity against Leishmania amazonensis, which is one etiological agent of leishmaniasis and for which new drugs are needed. Our intention was to understand if the region comprising the Vu-Def γ-core is responsible for the biological activity against L. amazonensis and to unveil its mechanism of action. Different microbiological assays with L. amazonensis in the presence of the synthetic peptide A₃₆,₄₂,₄₄γ_32-46Vu-Def were done, as well as ultrastructural and fluorescent analyses. A₃₆,₄₂,₄₄γ_32-46Vu-Def showed biological activity similar to Vu-Def. A₃₆,₄₂,₄₄γ_32-46Vu-Def (74 µM) caused 97% inhibition of L. amazonensis culture and parasites were unable to regrow in fresh medium. The cells of the treated parasites showed morphological alterations by ultrastructural analysis and fluorescent labelings that corroborate with the data of the organelles alterations. The general significance of our work is based on the description of a small synthetic peptide, A₃₆,₄₂,₄₄γ_32-46Vu-Def, which has activity on L. amazonensis and that the interaction between A₃₆,₄₂,₄₄γ_32-46Vu-Def-L. amazonensis results in parasite inhibition by the activation of an apoptotic-like cell death pathway.

Activity and Cell-Death Pathway in Leishmania infantum Induced by Sugiol: Vectorization Using Yeast Cell Wall Particles Obtained From Saccharomyces cerevisiae

Visceral leishmaniasis, caused by Leishmania infantum, is a neglected tropical disease, to which efforts in the innovation of effective and affordable treatments remain limited, despite the rising incidence in several regions of the world. In this work, the antileishmanial effects of sugiol were investigated in vitro. This compound was isolated from the bark of Cupressus lusitanica and showed promising activity against L. infantum. In spite of the positive results, it is known that the compound is a poorly water-soluble diterpene molecule, which hinders further investigation, especially in preclinical animal studies. Thus, in an alternative delivery method, sugiol was entrapped in glucan-rich particles obtained from Saccharomyces cerevisiae yeast cell walls (YCWPs). To evaluate the activity of sugiol, the experiments were divided into two parts: (i) the in vitro investigation of antileishmanial activity of free sugiol against L. infantum promastigotes after 24, 48, and 72 h of treatment and (ii) the evaluation of antileishmanial activity of sugiol entrapped in glucan-rich particles against intracellular L. infantum amastigotes. Free sugiol induced the cell-death process in promastigotes, which was triggered by enhancing cytosolic calcium level and promoting the autophagy up to the first 24 h. Over time, the presence of autophagic vacuoles became rarer, especially after treatment with lower concentrations of sugiol, but other cellular events intensified, like ROS production, cell shrinkage, and phosphatidylserine exposure. Hyperpolarization of mitochondrial membrane potential was found at 72 h, induced by the mitochondria calcium uptake, causing an increase in ROS production and lipid peroxidation as a consequence. These events resulted in the cell death of promastigotes by secondary necrosis. Sugiol entrapped in glucan-rich particles was specifically recognized by dectin-1 receptor on the plasma membrane of macrophages, the main host cell of Leishmania spp. Electron micrographs revealed particles containing sugiol within the infected macrophages and these particles were active against the intracellular L. infantum amastigotes without affecting the host cell. Therefore, the YCWPs act like a Trojan horse to successfully deliver sugiol into the macrophage, presenting an interesting strategy to deliver water-insoluble drugs to parasitized cells.

(De)glutamylation and cell death in Leishmania parasites

Trypanosomatids are flagellated protozoan parasites that are very unusual in terms of cytoskeleton organization but also in terms of cell death. Most of the Trypanosomatid cytoskeleton consists of microtubules, forming different substructures including a subpellicular corset. Oddly, the actin network appears structurally and functionally different from other eukaryotic actins. And Trypanosomatids have an apoptotic phenotype under cell death conditions, but the pathways involved are devoid of key mammal proteins such as caspases or death receptors, and the triggers involved in apoptotic induction remain unknown. In this article, we have studied the role of the post-translational modifications, deglutamylation and polyglutamylation, in Leishmania. We have shown that Leishmania apoptosis was linked to polyglutamylation and hypothesized that the cell survival process autophagy was linked to deglutamylation. A balance seems to be established between polyglutamylation and deglutamylation, with imbalance inducing microtubule or other protein modifications characterizing either cell death if polyglutamylation was prioritized, or the cell survival process of autophagy if deglutamylation was prioritized. This emphasizes the role of post-translational modifications in cell biology, inducing cell death or cell survival of infectious agents.

Leishmania are unique unicellular organisms in terms of cytoskeleton organization and mechanisms of cell death. For example, the major cytoskeletal components of these parasites are microtubules, which form a subpellicular corset. In terms of cell death, an apoptotic phenotype has been characterized in Leishmania but the pathways remain unknown, being devoid of key mammal cell death proteins. In a previous article, we demonstrated that the cytoskeleton of this parasite is extensively glutamylated but, paradoxically, overexpression or inhibition of polyglutamylase expression have limited visible cellular consequences. In this manuscript, we have highlighted the link between polyglutamylation and Leishmania cell death, suggesting the importance of the polyglutamylation/deglutamylation balance in this parasite. Further, we have identified, for the first time in Leishmania, deglutamylases, among which one that, in an original manner, deglutamylates glutamates at branching points but also long glutamate side chains. This work emphasizes the role of post-translational modifications as essential regulators of protein function, not only of mammal cells such as neurons or ciliated/flagellated cells, but also of infectious agents. This work suggests an important and discernible “live or die”—“cell death or autophagy” balance pathway and the conceptual mechanism that is involved in cellular decision making.

A semi-synthetic neolignan derivative from dihydrodieugenol B selectively affects the bioenergetic system of Leishmania infantum and inhibits cell division

Leishmaniasis is a neglected disease that affects more than 12 million people, with a limited therapy. Plant-derived natural products represent a useful source of anti-protozoan prototypes. In this work, four derivatives were prepared from neolignans isolated from the Brazilian plant Nectandra leucantha, and their effects against intracellular amastigotes of Leishmania (L.) infantum evaluated in vitro. IC₅₀ values between 6 and 35 µM were observed and in silico predictions suggested good oral bioavailability, no PAINS similarities, and ADMET risks typical of lipophilic compounds. The most selective (SI > 32) compound was chosen for lethal action and immunomodulatory studies. This compound caused a transient depolarization of the plasma membrane potential and induced an imbalance of intracellular Ca²⁺, possibly resulting in a mitochondrial impairment and leading to a strong depolarization of the membrane potential and decrease of ATP levels. The derivative also interfered with the cell cycle of Leishmania, inducing a programmed cell death-like mechanism and affecting DNA replication. Further immunomodulatory studies demonstrated that the compound eliminates amastigotes via an independent activation of the host cell, with decrease levels of IL-10, TNF and MCP-1. Additionally, this derivative caused no hemolytic effects in murine erythrocytes and could be considered promising for future lead studies.

Cell death pathways in pathogenic trypanosomatids: lessons of (over)kill

Especially in tropical and developing countries, the clinically relevant protozoa Trypanosoma cruzi (Chagas disease), Trypanosoma brucei (sleeping sickness) and Leishmania species (leishmaniasis) stand out and infect millions of people worldwide leading to critical social-economic implications. Low-income populations are mainly affected by these three illnesses that are neglected by the pharmaceutical industry. Current anti-trypanosomatid drugs present variable efficacy with remarkable side effects that almost lead to treatment discontinuation, justifying a continuous search for alternative compounds that interfere with essential and specific parasite pathways. In this scenario, the triggering of trypanosomatid cell death machinery emerges as a promising approach, although the exact mechanisms involved in unicellular eukaryotes are still unclear as well as the controversial biological importance of programmed cell death (PCD). In this review, the mechanisms of autophagy, apoptosis-like cell death and necrosis found in pathogenic trypanosomatids are discussed, as well as their roles in successful infection. Based on the published genomic and proteomic maps, the panel of trypanosomatid cell death molecules was constructed under different experimental conditions. The lack of PCD molecular regulators and executioners in these parasites up to now has led to cell death being classified as an unregulated process or incidental necrosis, despite all morphological evidence published. In this context, the participation of metacaspases in PCD was also not described, and these proteases play a crucial role in proliferation and differentiation processes. On the other hand, autophagic phenotype has been described in trypanosomatids under a great variety of stress conditions (drugs, starvation, among others) suggesting that this process is involved in the turnover of damaged structures in the protozoa and is not a cell death pathway. Death mechanisms of pathogenic trypanosomatids may be involved in pathogenesis, and the identification of parasite-specific regulators could represent a rational and attractive alternative target for drug development for these neglected diseases.

Screening and analysis of key active constituents in Guanxinshutong capsule using mass spectrum and integrative network pharmacology

Guanxinshutong capsule (GXSTC) is an effective and safe traditional Chinese medicine used in the treatment of cardiovascular diseases (CVDs) for many years. However, the targets of this herbal formula and the underlying molecular mechanisms of action involved in the treatment of CVDs are still unclear. In the present study, we used a systems pharmacology approach to identify the active ingredients of GXSTC and their corresponding targets in the calcium signaling pathway with respect to the treatment of CVDs. This method integrated chromatographic techniques, prediction of absorption, distribution, metabolism, and excretion, analysis using Kyoto Encyclopedia of Genes and Genomes, network construction, and pharmacological experiments. 12 active compounds and 33 targets were found to have a role in the treatment of CVDs, and four main active ingredients, including protocatechuic acid, cryptotanshinone, eugenol, and borneol were selected to verify the effect of (GXSTC) on calcium signaling system in cardiomyocyte injury induced by hypoxia and reoxygenation. The results from the present study revealed the active components and targets of GXSTC in the treatment of CVDs, providing a new perspective to enhance the understanding of the role of the calcium signaling pathway in the therapeutic effect of GXSTC.

Apoptosis in angiotensin II-stimulated hypertrophic cardiac cells -modulation by phenolics rich extract of Boerhavia diffusa L

Herein, we investigated the effects of B. diffusa (BDE), a well-known cardiotonic edible medicinal plant against apoptosis in Angiotensin II (Ang II)-stimulated hypertrophic cardiac cells (H9c2). The cells were analyzed for viability, markers of hypertrophy, apoptosis, and the expression of various proteins related to apoptosis. Ang II (100 nM for 48 h)-exposed H9c2 cells treated with BDE (75 μg/ml) showed a significant reduction in apoptosis (58.60%↓) compared to Ang II-alone treated cells. BDE treatment significantly reduced the up-regulation of Bax and cytosolic cytochrome-C caused by Ang II as well as reduced the degree of Ang II- induced down-regulation of Bcl-2. A reduction in caspase-3 activity (33.77%↓) and down-regulation of TNF-α was also observed in BDE treated cells stimulated with Ang II. Furthermore, the up-regulation of phospho-p38 MAPK was attenuated by BDE treatment. Bioactive components in the extract were identified as boeravinone B, quercetin, kaempferol, and caffeic acid as evident from high-performance liquid chromatography (HPLC). Overall, our study shows that B. diffusa is effective in attenuating apoptosis in cardiac cells, which is a major contributor to sudden cardiac death in addition to its nutraceutical properties.

Temporal analysis of the autophagic and apoptotic phenotypes in Leishmania parasites

The leishmaniases are worldwide neglected tropical diseases caused by parasitic protozoa of the Leishmania genus. Different stimuli induce Leishmania cell death, but the proteins involved remain poorly understood. Furthermore, confusion often appears between cell death and the cell survival process autophagy, whose phenotype is not clearly defined. In this article, we present a comprehensive and temporal analysis of the cellular events occurring during miltefosine-induced cell death and autophagy in L. major. We also provide a list of features in order to clearly identify apoptotic cells, autophagic cells and to distinguish both processes. Furthermore, we demonstrate that autophagy is followed by apoptosis in the absence of nutrients. Finally, we show that cells treated with the generic kinase inhibitor staurosporine express apoptotic as well as autophagic markers and therefore cannot be used as an apoptosis inducer in Leishmania. These descriptions lead to a better recognition and understanding of apoptosis and autophagy, enabling their targeting in the development of new anti-leishmanial drugs. These researches also make it possible to better understand these processes in general, through the study of an ancestral eukaryote.

Grandiflorenic acid promotes death of promastigotes via apoptosis-like mechanism and affects amastigotes by increasing total iron bound capacity

BACKGROUND

American tegumentary leishmaniasis (ATL) is a zoonotic disease caused by protozoa of the genus Leishmania. The high toxicity, high costs and resistance of some strains to current drugs has prompted the search for therapeutic alternatives for the management of this disease. Sphagneticola trilobata is a plant that has diterpenes as main constituents, including grandiflorenic acid (GFA) that has antiinflammatory, antiprotozoal, antibacterial and antinociceptive activity.

PURPOSE

The aim of our study was to determine the effect of GFA on both the promastigotes and the amastigotes of Leishmania amazonensis.

METHODS

Isolation by chromatographic methods and chemical identification of GFA, then evaluation of the in vitro leishmanicidal activity of this compound against Leishmania amazonensis promastigotes and L. amazonensis infected peritoneal Balb/c macrophages, as well its action and microbicide mechanisms.

RESULTS

GFA treatment significantly inhibited the proliferation of promastigotes. This antiproliferative effect was accompanied by morphological changes in the parasite with 25 nM GFA. Afterwards, we investigated the mechanisms involved in the death of the protozoan; there was an increase in the production of reactive oxygen species (ROS), phosphatidylserine exposure, permeabilization of the plasma membrane and decreased mitochondrial depolarization. In addition, we observed that the treatment caused a reduction in the percentage of infected cells and the number of amastigotes per macrophage, without showing cytotoxicity in low doses to peritoneal macrophages and sheep erythrocytes. GFA increased IL-10 and total iron bound to transferrin in infected macrophages. Our results showed that GFA treatment acts on promastigote forms through an apoptosis-like mechanism and on intracellular amastigote forms, dependent of regulatory cytokine IL-10 modulation with increase in total iron bound to transferrin.

CONCLUSION

GFA showed in vitro antileishmanial activity on L. amazonensis promastigotes forms and on L. amazonensis-infected macrophages.

Trichomonas vaginalis Macrophage Migration Inhibitory Factor Mediates Parasite Survival during Nutrient Stress

Trichomonas vaginalis is responsible for the most prevalent non-viral sexually transmitted disease worldwide, and yet the mechanisms used by this parasite to establish and maintain infection are poorly understood. We previously identified a T. vaginalis homologue (TvMIF) of a human cytokine, human macrophage migration inhibitory factor (huMIF). TvMIF mimics huMIF’s role in increasing cell growth and inhibiting apoptosis in human host cells. To interrogate a role of TvMIF in parasite survival during infection, we asked whether overexpression of TvMIF (TvMIF-OE) confers an advantage to the parasite under nutrient stress conditions by comparing the survival of TvMIF-OE parasites to that of empty vector (EV) parasites. We found that under conditions of serum starvation, overexpression of TvMIF resulted in increased parasite survival. Serum-starved parasites secrete 2.5-fold more intrinsic TvMIF than unstarved parasites, stimulating autocrine and paracrine signaling. Similarly, we observed that addition of recombinant TvMIF increased the survival of the parasites in the absence of serum. Recombinant huMIF likewise increased the parasite survival in the absence of serum, indicating that the parasite may use this host survival factor to resist its own death. Moreover, TvMIF-OE parasites were found to undergo significantly less apoptosis and reactive oxygen species (ROS) generation under conditions of serum starvation, consistent with increased survival being the result of blocking ROS-induced apoptosis. These studies demonstrated that a parasitic MIF enhances survival under adverse conditions and defined TvMIF and huMIF as conserved survival factors that exhibit cross talk in host-pathogen interactions.

Macrophage migration inhibitory factor (MIF) is a conserved protein found in most eukaryotes which has been well characterized in mammals but poorly studied in other eukaryotes. The limited analyses of MIF proteins found in unicellular eukaryotes have focused exclusively on the effect of parasitic MIF on the mammalian host. This was the first study to assess the function of a parasite MIF in parasite biology. We demonstrate that the Trichomonas vaginalis MIF functions to suppress cell death induced by apoptosis, thereby enhancing parasite survival under adverse conditions. Our research reveals a conserved survival mechanism, shared by a parasite and its host, and indicates a role for a conserved protein in mediating cross talk in host-pathogen interactions.

Chemoprevention of Leishmaniasis: In-vitro antiparasitic activity of dibenzalacetone, a synthetic curcumin analog leads to apoptotic cell death in Leishmania donovani

Curcumin is the major phenolic compound found in turmeric, a dry powder of rhizomes and roots of the plant, Curcuma longa L., which is widely used as spice and food colorant around the world, and in herbal medicinal practice in Asian countries. The present study reports the leishmanicidal activity of trans-dibenzalacetone (DBA), a synthetic monoketone analog of curcumin, against Leishmania donovani parasites. We for the first time report the antiproliferative effect of a curcumin analog (DBA) on the intracellular amastigotes of L. donovani, the clinically more relevant stage of the parasite than its promastigotes stage. The leishmanicidal effect of DBA was further confirmed by scanning and transmission electron microscopies. Cell growth was arrested in G0/G1 phase with increased concentration of cytosolic calcium and dissipation of mitochondrial membrane potential. Further, the unique trypanothione/trypanothione reductase (TR) system of Leishmania cells was significantly inhibited by DBA. This economically synthesizable simple monoketone analog of curcumin has the potential for field use against visceral leishmaniasis which is currently widespread in tropical and subtropical developing countries of the world. In conclusion, we have identified an analog of curcumin for potential applications against leishmaniasis, based on its strong antiparasitic activity and low toxicity. This curcumin analog compares favorably, at least in vitro, with the existing medication miltefosine.

Sestrin2 facilitates glutamine-dependent transcription of PGC-1α and survival of liver cancer cells under glucose limitation

Differential utilization of metabolites and metabolic plasticity can confer adaptation to cancer cells under metabolic stress. Glutamine is one of the vital and versatile nutrients that cancer cells consume avidly for their proliferation, and therefore mechanisms related to glutamine metabolism have been identified as targets. Recently, sestrin2 (SESN2), a stress-inducible protein, has been reported to regulate survival in glutamine-depleted cancer cells; based on this, we explored if SESN2 could regulate glutamine metabolism during glucose starvation. This report highlights the role of SESN2 in the regulation of glutamine-dependent activation of the mitochondrial biogenesis marker peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) under glucose scarcity in liver cancer cells (HepG2). We demonstrate that down-regulation of SESN2 induces a decrease in the levels of intracellular glutamine and PGC-1α under glucose deprivation, concomitant with a decline in cell survival, but no effect was observed on the invasive or migration potential of the cells. Under similar metabolic conditions, SESN2 forms a complex with c-Jun N-terminal kinase (JNK) and forkhead box protein O1 (FOXO1). Absence of SESN2 or inhibition of JNK reduces nuclear translocation of FOXO1, consequently causing transcriptional inhibition of PGC-1α. Notably, our observations demonstrate a reduction in cell viability under high glutamine and low glucose conditions during SESN2 down-regulation that could be rescued on JNK inhibition. To recover from acetaminophen-induced mitochondrial damage, SESN2 was crucial for glutamine-mediated activation of PGC-1α in HepG2 cells. Collectively, we demonstrate a novel role of SESN2 in mediating activation of PGC-1α by modulating glutamine metabolism that facilitates cancer cell survival under glucose-limited metabolic conditions.

Leishmania mexicana can utilize amino acids as major carbon sources in macrophages but not in animal models

Leishmania parasites target macrophages in their mammalian hosts and proliferate within the mature phagolysosome compartment of these cells. Intracellular amastigote stages are dependent on sugars as a major carbon source in vivo, but retain the capacity to utilize other carbon sources. To investigate whether amastigotes can switch to using other carbon sources, we have screened for suppressor strains of the L. mexicana Δlmxgt1-3 mutant which lacks the major glucose transporters LmxGT1-3. We identified a novel suppressor line (Δlmxgt1-3^s2 ) that has restored growth in rich culture medium and virulence in ex vivo infected macrophages, but failed to induce lesions in mice. Δlmxgt1-3^s2 amastigotes had lower rates of glucose utilization than the parental line and primarily catabolized non-essential amino acids. The increased mitochondrial metabolism of this line was associated with elevated levels of intracellular reactive oxygen species, as well as increased sensitivity to inhibitors of the tricarboxylic acid (TCA) cycle, including nitric oxide. These results suggest that hardwired sugar addiction of Leishmania amastigotes contributes to the intrinsic resistance of this stage to macrophage microbicidal processes in vivo, and that these stages have limited capacity to switch to using other carbon sources.

A3K2A3-induced apoptotic cell death of Leishmania amazonensis occurs through caspase- and ATP-dependent mitochondrial dysfunction

Leishmaniasis is a neglected tropical disease that affects millions of people worldwide. Current therapies mainly rely on antimonial drugs that are inadequate because of their high toxicity and increased drug resistance. An urgent need exists to discover new, more effective, more affordable, and more target-specific drugs. Pathways that are associated with apoptosis-like cell death have been identified in unicellular eukaryotes, including protozoan parasites. In the present study, we studied the mechanism of cell death that is induced by A3K2A3 against L. amazonensis. A3K2A3 is a dibenzylideneacetone that has an acyclic dienone that is attached to aryl groups in both β-positions, which is similar to curcuminoids and chalcone structures. This compound was previously shown to be safe with regard to cytotoxicity and active against the parasite. Biochemical and morphological approaches were used in the present study. The results suggested that A3K2A3 caused mitochondrial dysfunction in L. amazonensis promastigotes, leading to mechanisms of cell death that share some common phenotypic features with metazoan apoptosis, such as an increase in reactive oxygen species production, a decrease in the adenosine triphosphate ratio, phosphatidylserine exposure, a decrease in cell volume, caspase production, and DNA fragmentation. Altogether, these findings indicate that apoptosis can indeed be triggered by chemotherapeutic agents.

Ammonium trichloro [1,2-ethanediolato-O,O']-tellurate cures experimental visceral leishmaniasis by redox modulation of Leishmania donovani trypanothione reductase and inhibiting host integrin linked PI3K/Akt pathway

In an endeavor to search for affordable and safer therapeutics against debilitating visceral leishmaniasis, we examined antileishmanial potential of ammonium trichloro [1,2-ethanediolato-O,O']-tellurate (AS101); a tellurium based non toxic immunomodulator. AS101 showed significant in vitro efficacy against both Leishmania donovani promastigotes and amastigotes at sub-micromolar concentrations. AS101 could also completely eliminate organ parasite load from L. donovani infected Balb/c mice along with significant efficacy against infected hamsters (˃93% inhibition). Analyzing mechanistic details revealed that the double edged AS101 could directly induce apoptosis in promastigotes along with indirectly activating host by reversing T-cell anergy to protective Th1 mode, increased ROS generation and anti-leishmanial IgG production. AS101 could inhibit IL-10/STAT3 pathway in L. donovani infected macrophages via blocking α4β7 integrin dependent PI3K/Akt signaling and activate host MAPKs and NF-κB for Th1 response. In silico docking and biochemical assays revealed AS101's affinity to form thiol bond with cysteine residues of trypanothione reductase in Leishmania promastigotes leading to its inactivation and inducing ROS-mediated apoptosis of the parasite via increased Ca2+ level, loss of ATP and mitochondrial membrane potential along with metacaspase activation. Our findings provide the first evidence for the mechanism of action of AS101 with excellent safety profile and suggest its promising therapeutic potential against experimental visceral leishmaniasis.

SESN2 facilitates mitophagy by helping Parkin translocation through ULK1 mediated Beclin1 phosphorylation

Mitophagy, the selective degradation of mitochondria by autophagy, is crucial for the maintenance of healthy mitochondrial pool in cells. The critical event in mitophagy is the translocation of cytosolic Parkin, a ubiquitin ligase, to the surface of defective mitochondria. This study elucidates a novel role of SESN2/Sestrin2, a stress inducible protein, in mitochondrial translocation of PARK2/Parkin during mitophagy. The data demonstrates that SESN2 downregulation inhibits BECN1/Beclin1 and Parkin interaction, thereby preventing optimum mitochondrial accumulation of Parkin. SESN2 interacts with ULK1 (unc-51 like kinase 1) and assists ULK1 mediated phosphorylation of Beclin1 at serine-14 position required for binding with Parkin prior to mitochondrial translocation. The trigger for SESN2 activation and regulation of Parkin translocation is the generation of mitochondrial superoxide. Scavenging of mitochondrial superoxide lower the levels of SESN2, resulting in retardation of Parkin translocation. Importantly, we observe that SESN2 mediated cytosolic interaction of Parkin and Beclin1 is PINK1 independent but mitochondrial translocation of Parkin is PINK1 dependent. Together, these findings suggest the role of SESN2 as a positive regulator of Parkin mediated mitophagy.

Plumbagin, a plant-derived naphthoquinone metabolite induces mitochondria mediated apoptosis-like cell death in Leishmania donovani: an ultrastructural and physiological study

Naphthoquinones are known to exhibit a broad range of biological activities against microbes, cancer and parasitic diseases and have been widely used in Indian traditional medicine. Plumbagin is a plant-derived naphthoquinone metabolite (5-hydroxy-2-methyl-1,4-naphthoquinone) reported to inhibit trypanothione reductase, the principal enzyme and a validated drug target involved in detoxification of oxidative stress in Leishmania. Here, we report the mechanistic aspects of cell death induced by plumbagin including physiological effects in the promastigote form and ultrastructural alterations in both promastigote and amastigote forms of Leishmania donovani which till now remained largely unknown. Our observations show that oxidative stress induced by plumbagin resulted in depolarization of the mitochondrial membrane, depletion in ATP levels, elevation of cytosolic calcium, increase in caspase 3/7-like protease activity and lipid peroxidation in promastigotes. Apoptosis-like cell death induction post plumbagin treatment was confirmed by biochemical assays like Annexin V/FITC staining, TUNEL as well as morphological and ultrastructural studies. These findings collectively highlight the mode of action and importance of oxidative stress inducing agents in effectively killing both forms of the Leishmania parasite and opens up the possibility of exploring plumbagin and its derivatives as promising candidates in the chemotherapy of Leishmaniasis.

Functional Involvement of Leishmania donovani Tryparedoxin Peroxidases during Infection and Drug Treatment

The parasite Leishmania donovani causes visceral leishmaniasis, a potentially fatal disease. The parasites survive within mammalian macrophages and express a unique set of enzymes, the tryparedoxin peroxidases, for their defense against oxidative stress generated by the host. In this study, we demonstrate different roles of two distinct enzymes, the mitochondrial tryparedoxin peroxidase (mTXNPx) and the cytosolic tryparedoxin peroxidase (cTXNPx), in defending the parasites against mitochondrial and exogenous oxidative stress during infection and drug treatment. Our findings indicate a greater increase in cTXNPx expression in response to exogenous oxidative stress and a higher elevation of mTXNPx expression in response to mitochondrial or endogenous stress created by respiratory chain complex inhibitors. Overexpression of cTXNPx in Leishmania showed improved protection against exogenous stress and enhanced protection against mitochondrial stress in parasites overexpressing mTXNPx. Further, parasites overexpressing cTXNPx infected host cells with increased efficiency at early times of infection compared to control parasites or parasites overexpressing mTXNPx. The mTXNPx-overexpressing parasites maintained higher infection at later times. Higher mTXNPx expression occurred in wild-type parasites on exposure to miltefosine, while treatment with antimony elevated cTXNPx expression. Parasites resistant to miltefosine or antimony demonstrated increased expression of mTXNPx, as well as cTXNPx. In summary, this study provides evidence of distinct roles of the two enzymes defined by virtue of their localization during infection and drug treatment.

Zinc depletion promotes apoptosis-like death in drug-sensitive and antimony-resistance Leishmania donovani

Micronutrients are essential for survival and growth for all the organisms including pathogens. In this manuscript, we report that zinc (Zn) chelator N,N,N’,N’-tetrakis(2-pyridinylmethyl)-1,2-ethylenediamine (TPEN) affects growth and viability of intracellular pathogen Leishmania donovani (LD) by a concentration and time dependent manner. Simultaneous addition of zinc salt reverses the effect of TPEN. Further experiments provide evidence of apoptosis-like death of the parasite due to Zn-depletion. TPEN treatment enhances caspase-like activity suggesting increase in apoptosis-like events in LD. Specific inhibitors of cathepsin B and Endoclease G block TPEN-induced leishmanial death. Evidences show involvement of reactive oxygen species (ROS) potentially of extra-mitochondrial origin in TPEN-induced LD death. Pentavalent antimonials remained the prime source of treatment against leishmaniasis for several decades; however, antimony-resistant Leishmania is now common source of the disease. We also reveal that Zn-depletion can promote apoptosis-like death in antimony-resistant parasites. In summary, we present a new finding about the role of zinc in the survival of drug sensitive and antimony-resistant LD.

Amphotericin B induces apoptosis-like programmed cell death in Naegleria fowleri and Naegleria gruberi

Naegleria fowleri and Naegleria gruberi belong to the free-living amoebae group. It is widely known that the non-pathogenic species N. gruberi is usually employed as a model to describe molecular pathways in this genus, mainly because its genome has been recently described. However, N. fowleri is an aetiological agent of primary amoebic meningoencephalitis, an acute and fatal disease. Currently, the most widely used drug for its treatment is amphotericin B (AmB). It was previously reported that AmB has an amoebicidal effect in both N. fowleri and N. gruberi trophozoites by inducing morphological changes that resemble programmed cell death (PCD). PCD is a mechanism that activates morphological, biochemical and genetic changes. However, PCD has not yet been characterized in the genus Naegleria. The aim of the present work was to evaluate the typical markers to describe PCD in both amoebae. These results showed that treated trophozoites displayed several parameters of apoptosis-like PCD in both species. We observed ultrastructural changes, an increase in reactive oxygen species, phosphatidylserine externalization and a decrease in intracellular potassium, while DNA degradation was evaluated using the TUNEL assay and agarose gels, and all of these parameters are related to PCD. Finally, we analysed the expression of apoptosis-related genes, such as sir2 and atg8, in N. gruberi. Taken together, our results showed that AmB induces the morphological, biochemical and genetic changes of apoptosis-like PCD in the genus Naegleria.

Protective effects of Xinji'erkang on myocardial infarction induced cardiac injury in mice

BACKGROUND

Myocardial infarction (MI) is a major risk factor responsible for morbidity and mortality. Xinji'erkang (XJEK) has been clinically used as an effective medication in the treatment of coronary heart disease and myocarditis. The purpose of this study was to investigate the cardioprotective effect of Xinji'erkang on MI mice.

METHODS

Forty male mice were randomly assigned into four groups as follows (n = 10): sham, model, MI with administration of XJEK and fosinopril for four weeks. At the end of studies, hemodynamic parameters and electrocardiography (ECG) were recorded. Heart and body mass were measured and heart weight/body weight (HW/BW) ratio was calculated as index of hypertrophy. The hypertrophy of heart and aorta was examined using the hematoxylin and eosin (HE) staining, and the collagen deposition was evaluated using Van Gieson (VG) staining. Serum nitric oxide level (NO), superoxide dismutase (SOD) activity and malondialdehyde (MDA) concentration were assayed by colorimetric analysis. The expressions of endothelial NO synthetase (eNOS) expression in serum and cardiac tissues were determined using ELISA assay and immunohistochemistry. Angiotensin II (Ang II) in serum and cardiac tissues was measured using ELISA assay. Besides, tumor necrosis factor-α (TNF-α), interleukin1β (IL-1β) and interleukin10 (IL-10) were observed in cardiac tissues with ELISA assay as well.

RESULTS

The administration of XJEK significantly improved cardiac dysfunction and abnormal ECG with reduced HW/BW ratio and ameliorated cardiomyocyte hypertrophy and collagen deposition compared to MI, which was partly due to the decreased SOD and increased MDA in serum. Moreover, XJEK treatment also improved endothelial dysfunction (ED) with not only enhanced eNOS activities in serum and cardiac tissues and elevated NO levels in serum, but also decreased Ang II content in serum and cardiac tissues. Finally, protein expressions of pro-inflammation cytokines, TNF-α and IL-1β in the cardiac tissues with XJEK treatment were significantly decreased compared to model. On the contrary, IL-10, an anti-inflammatory cytokine concentrated in cardiac tissues was significantly enhanced compared to model.

CONCLUSION

Xinji'erkang exerts cardioprotective effect on myocardial infarction in mice, which may be due to the improvement of endothelial dysfunction and the reduction of oxidative stress and inflammation response.