Leishmania donovani mitogen-activated protein kinases as a host-parasite interaction interface.

Leishmaniasis, a major globally re-emerging neglected tropical disease, has a restricted repertoire of chemotherapeutic options due to a narrow therapeutic index, drug resistance, or patient non-compliance due to toxicity. The disease is caused by the parasite Leishmania that resides in two different forms in two different environments: as sessile intracellular amastigotes within mammalian macrophages and as motile promastigotes in sandfly gut. As mitogen-activated protein kinases (MAPKs) play important roles in cellular differentiation and survival, we studied the expression of Leishmania donovani MAPKs (LdMAPKs). The homology studies by multiple sequence alignment show that excepting LdMAPK1 and LdMAPK2, all thirteen other LdMAPKs share homology with human ERK and p38 isoforms. Expression of LdMAPK4 and LdMAPK5 is less in avirulent promastigotes and amastigotes. Compared to miltefosine-sensitive L. donovani parasites, miltefosine-resistant parasites have higher LdMAPK1, LdMAPK3-5, LdMAPK7-11, LdMAPK13, and LdMAPK14 expression. IL-4-treatment of macrophages down-regulated LdMAPK11, in virulent amastigotes whereas up-regulated LdMAPK5, but down-regulated LdMAPK6, LdMAPK12-15, expression in avirulent amastigotes. IL-4 up-regulated LdMAPK1 expression in both virulent and avirulent amastigotes. IFN-γ-treatment down-regulated LdMAPK6, LdMAPK13, and LdMAPK15 in avirulent amastigotes but up-regulated in virulent amastigotes. This complex profile of LdMAPKs expression among virulent and avirulent parasites, drug-resistant parasites, and in amastigotes within IL-4 or IFN-γ-treated macrophages suggests that LdMAPKs are differentially controlled at the host-parasite interface regulating parasite survival and differentiation, and in the course of IL-4 or IFN-γ dominated immune response.

Interleukin-7 potentiates MAPK10-elicited host-protective vaccine against Leishmania donovani.

Leishmania donovani causes the potentially fatal disease visceral leishmaniasis for which neither a vaccine nor an adjuvant for human use exists. Although interleukin-7 (IL-7) is implicated in CD4+ T-cell response stabilization, its anti-leishmanial function is uncertain. Therefore, we examined whether IL-7 would potentiate the efficacy of Leishmania major-expressed MAPK10 (LmjMAPK10; M10)-elicited anti-leishmanial host-protective response. We observed that aligning with IL-7R expression, IL-7 increased IFN-γ-secreting TH1 cell but reduced IL-4-producing TH2 cells and production of IL-10 and TGF-ß effectuating anti-leishmanial functions in susceptible BALB/c mouse-derived macrophages. Co-culturing IL-7-pre-treated L. donovani-infected macrophages with L. donovani-infected BALB/c-derived T cells induced IFN-γ-dominated TH1 type anti-leishmanial function. IL-7 treatment of L. donovani-infected BALB/c mice significantly reduced splenic and hepatic parasite loads. Co-culturing CD4+ T cells from IL to 7-treated mice with L. donovani-infected macrophages reduced amastigote numbers suggesting IL-7-elicited host-protective effector T cells. Priming BALB/c with M10 + IL-7 reduced the splenic parasite burden more effectively than that was observed in M10-primed mice. An enhanced protection against L. donovani infection was accompanied by enhanced IL-12 and IFN-γ, but suppressed IL-10 and IL-4, response and host-protective TH1 and memory T cells. These results indicate IL-7-induced leishmanial antigen-specific memory T cell response that protects a susceptible host against L. donovani infection.

Multiconfiguration Pair-Density Functional Theory for Vertical Excitation Energies in Actinide Molecules.

Modeling actinides with electronic structure theories is challenging because these systems present a strong ligand field and metal-ligand covalency. We systematically investigate the effectiveness of pair-density functional theory (PDFT) for the calculation of vertical excitation energies in An(III), [AnIIICl6]3-, and [AnVIO2]2+ (An = U, Np, Pu, and Am). We compare the performance of PDFT, hybrid PDFT, and multistate PDFT with traditional active-space methods followed by perturbation theory, like multistate CASPT2, and with experimental data. Overall, multistate PDFT gives quantitative agreement with multistate CASPT2 at a significantly reduced computational cost.

Understanding Antiferromagnetic and Ligand Field Effects on Spin Crossover in a Triple-Decker Dimeric Cr(II) Complex.

Two possible explanations for the temperature dependence of spin-crossover (SCO) behavior in the dimeric triple-decker Cr(II) complex ([(η5-C5Me5)Cr(µ2:η5-P5)Cr(η5-C5Me5)]+) have been offered. One invokes variations in antiferromagnetic interactions between the two Cr(II) ions, whereas the other posits the development of a strong ligand-field effect favoring the low-spin ground state. We perform multireference electronic structure calculations based on the multiconfiguration pair-density functional theory to resolve these effects. We find quintet, triplet, and singlet electronic ground states, respectively, for the experimental geometries at high, intermediate, and low temperatures. The ground-state transition from quintet to triplet at an intermediate temperature derives from increased antiferromagnetic interactions between the two Cr(II) ions. By contrast, the ground-state transition from triplet to singlet at low temperature can be attributed to increased ligand-field effects, which dominate with continued variations in antiferromagnetic coupling. This study provides quantitative detail for the degree to which these two effects can act in concert for the observed SCO behavior in this complex and others subject to temperature-dependent variations in geometry.

Theoretical study of the formation of metal-oxo species of the first transition series with the ligand 14-TMC: driving factors of the "Oxo Wall".

Terminal metal-oxo species of the early transition metal series are well known, whereas those for the late transition series are rare, and this is related to the "Oxo Wall". Here, we have undertaken a theoretical study on the formation of metal-oxo species from the metal hydroperoxo species of the 3d series (Cr, Mn, Fe, Co, Ni, and Cu) with the ligand 14-TMC (1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane) via O⋯O bond cleavage. DFT calculations reveal that the barrier for O⋯O bond cleavage is higher with the late transition metals (Co, Ni, and Cu) than the early transition metals (Cr, Mn, and Fe), and the formed late metal-oxo species are also thermodynamically less stable. The higher barrier may be due to electronic repulsion because of the pairing of d electrons. In the late transition metal series, the electron goes into an antibonding orbital, which decreases the bond order and hence decreases the possibility of metal-oxo formation. Computed structural parameters and spin densities suggest that valence tautomerism occurs in the late transition metal-oxo species which remain as a metal-oxyl. Our findings support the concept of the "Oxo Wall".

Deciphering phenotyping, DNA barcoding, and RNA secondary structure predictions in eggplant wild relatives provide insights for their future breeding strategies.

Eggplant or aubergine (Solanum melongena L.) and its wild cousins, comprising 13 clades with 1500 species, have an unprecedented demand across the globe. Cultivated eggplant has a narrow molecular diversity that hinders eggplant breeding advancements. Wild eggplants need resurgent attention to broaden eggplant breeding resources. In this study, we emphasized phenotypic and genotypic discriminations among 13 eggplant species deploying chloroplast-plastid (Kim matK) and nuclear (ITS2) short gene sequences (400-800 bp) at DNA barcode region followed by ITS2 secondary structure predictions. The identification efficiency at the Kim matK region was higher (99-100%) than in the ITS2 region (80-90%). The eggplant species showed 13 unique secondary structures with a central ring with various helical orientations. Principal component analysis (PCoA) provides the descriptor-wise phenotypic clustering, which is essential for trait-specific breeding. Groups I and IV are categorized under scarlet complexes S. aethiopicum, S. trilobatum, and S. melongena (wild and cultivated). Group II represented the gboma clade (S. macrocarpon, S. wrightii, S. sisymbriifolium, and S. aculeatissimum), and group III includes S. mammosum, and S. torvum with unique fruit shape and size. The present study would be helpful in genetic discrimination, biodiversity conservation, and the safe utilization of wild eggplants.

Elucidating Actinide-Pertechnetate and Actinide-Perrhenate Bonding via a Family of Th-TcO4 and Th-ReO4 Frameworks and Solutions.

Technetium-99, a ß-emitter produced from 235U fission, poses a challenge for the nuclear industry due to co-extraction of pertechnetate (TcO4-) with the actinides (An) during nuclear fuel reprocessing. Previous studies suggested that direct coordination of pertechnetate with An plays an important role in the coextraction process. However, few studies have provided direct evidence for An-TcO4- bonding in the solid state, and even fewer in solution. The present study describes synthesis and structural elucidation of a family of thorium(IV)-pertechnetate/perrhenate (ReO4-, nonradioactive surrogate) compounds, which is obtained by dissolution of thorium oxyhydroxide in perrhenic/pertechnic acid followed by crystallization, with or without heating. For reaction ratios of 3:1, 4:1, and 6:1 MO4-/Th(IV) (M = Tc, Re), the crystallized compounds reflect the same ratio, suggesting facile and flexible coordination. Nine structures reveal 1-dimensional and 2-dimensional frameworks with varying topologies. While a multitude of compounds isolated from 4:1 (and 6:1) reaction solutions feature Th monomers linked by MO4-, the 3:1 reaction solution yielded the well-known dihydroxide-bridged thorium dimer, linked, and capped by MO4-. Density functional theory calculations on ReO4-/TcO4- isomorphs suggest similar bonding characteristics in the solid state, but experimental solution characterization noted differences. Specifically, small-angle X-ray scattering studies suggest the bonding of Th-TcO4- persists in solution, while Th-ReO4- bonding is less apparent.

Broad Electronic Modulation of Two-Dimensional Metal-Organic Frameworks over Four Distinct Redox States.

Two-dimensional (2D) inorganic materials have emerged as exciting platforms for (opto)electronic, thermoelectric, magnetic, and energy storage applications. However, electronic redox tuning of these materials can be difficult. Instead, 2D metal-organic frameworks (MOFs) offer the possibility of electronic tuning through stoichiometric redox changes, with several examples featuring one to two redox events per formula unit. Here, we demonstrate that this principle can be extended over a far greater span with the isolation of four discrete redox states in the 2D MOFs LixFe3(THT)2 (x = 0-3, THT = triphenylenehexathiol). This redox modulation results in 10,000-fold greater conductivity, p- to n-type carrier switching, and modulation of antiferromagnetic coupling. Physical characterization suggests that changes in carrier density drive these trends with relatively constant charge transport activation energies and mobilities. This series illustrates that 2D MOFs are uniquely redox flexible, making them an ideal materials platform for tunable and switchable applications.

Theoretical Investigation of Single-Molecule-Magnet Behavior in Mononuclear Dysprosium and Californium Complexes.

Early-actinide-based (U, Np, and Pu) single-molecule magnets (SMMs) have yet to show magnetic properties similar to those of highly anisotropic lanthanide-based ones. However, there are not many studies exploring the late-actinides (more than half-filled f shells) as potential candidates for SMM applications. We computationally explored the electronic structure and magnetic properties of a hypothetical Cf(III) complex isostructural to the experimentally synthesized Dy(dbm)3(bpy) complex (bpy = 2,2'-bipyridine; dbm = dibenzoylmethanoate) via multireference methods and compared them to those of the Dy(III) analogue. This study shows that the Cf(III) complex can behave as a SMM and has a greater magnetic susceptibility compared to other experimentally and computationally studied early-actinide-based (U, Np, and Pu) magnetic complexes. However, Cf spontaneously undergoes α-decay and converts to Cm. Thus, we also explored the isostructural Cm(III)-based complex. The computed magnetic susceptibility and g-tensor values show that the Cm(III) complex has poor SMM behavior in comparison to both the Dy(III) and Cf(III) complexes, suggesting that the performance of Cf(III)-based magnets may be affected by α-decay and can explain the poor performance of experimentally studied Cf(III)-based molecular magnets in the literature. Further, this study suggests that the ligand field is dominant in Cf(III), which helps to increase the magnetization blocking barrier by nearly 3 times that of its 4f congener.

Anti-leishmanial therapy: Caught between drugs and immune targets.

Leishmaniasis is an enigmatic disease that has very restricted options for chemotherapy and none for prophylaxis. As a result, deriving therapeutic principles for curing the disease has been a major objective in Leishmania research for a long time. Leishmania is a protozoan parasite that lives within macrophages by subverting or switching cell signaling to the pathways that ensure its intracellular survival. Therefore, three groups of molecules aimed at blocking or eliminating the parasite, at least, in principle, include blockers of macrophage receptor- Leishmania ligand interaction, macrophage-activating small molecules, peptides and cytokines, and signaling inhibitors or activators. Macrophages also act as an antigen-presenting cell, presenting antigen to the antigen-specific T cells to induce activation and differentiation of the effector T cell subsets that either execute or suppress anti-leishmanial functions. Three groups of therapeutic principles targeting this sphere of Leishmania-macrophage interaction include antibodies that block pro-leishmanial response of T cells, ligands that activate anti-leishmanial T cells and the antigens for therapeutic vaccines. Besides these, prophylactic vaccines have been in clinical trials but none has succeeded so far. Herein, we have attempted to encompass all these principles and compose a comprehensive review to analyze the feasibility and adoptability of different therapeutics for leishmaniasis.

Multiconfiguration Pair-Density Functional Theory for Chromium(IV) Molecular Qubits.

Pseudotetrahedral organometallic complexes containing chromium(IV) and aryl ligands have been experimentally identified as promising molecular qubit candidates. Here we present a computational protocol based on multiconfiguration pair-density functional theory for computing singlet-triplet gaps and zero-field splitting (ZFS) parameters in Cr(IV) aryl complexes. We find that two multireference methods, multistate complete active space second-order perturbation theory (MS-CASPT2) and hybrid multistate pair-density functional theory (HMS-PDFT), perform better than Kohn-Sham density functional theory for singlet-triplet gaps. Despite the very small values of the ZFS parameters, both multireference methods performed qualitatively well. MS-CASPT2 and HMS-PDFT performed particularly well for predicting the trend in the ratio of the rhombic and axial ZFS parameters, |E/D|. We have also investigated the dependence and sensitivity of the calculated ZFS parameters on the active space and the molecular geometry. The methodologies outlined here can guide future prediction of ZFS parameters in molecular qubit candidates.

Linker Redox Mediated Control of Morphology and Properties in Semiconducting Iron-Semiquinoid Coordination Polymers.

The emergence of conductive 2D and less commonly 3D coordination polymers (CPs) and metal-organic frameworks (MOFs) promises novel applications in many fields. However, the synthetic parameters for these electronically complex materials are not thoroughly understood. Here we report a new 3D semiconducting CP Fe5 (C6 O6 )3 , which is a fusion of 2D Fe-semiquinoid materials and 3D cubic Fex (C6 O6 )y materials, by using a different initial redox-state of the C6 O6 linker. The material displays high electrical conductivity (0.02 S cm-1 ), broad electronic transitions, promising thermoelectric behavior (S2 σ=7.0×10-9  W m-1 K-2 ), and strong antiferromagnetic interactions at room temperature. This material illustrates how controlling the oxidation states of redox-active components in conducting CPs/MOFs can be a "pre-synthetic" strategy to carefully tune material topologies and properties in contrast to more commonly encountered post-synthetic modifications.

Bidirectional cytokine-microRNA control: A novel immunoregulatory framework in leishmaniasis.

As effector innate immune cells and as a host to the protozoan parasite Leishmania, macrophages play a dual role in antileishmanial immunoregulation. The 2 key players in this immunoregulation are the macrophage-expressed microRNAs (miRNAs) and the macrophage-secreted cytokines. miRNAs, as small noncoding RNAs, play vital roles in macrophage functions including cytokines and chemokines production. In the reverse direction, Leishmania-regulated cytokines alter miRNAs expression to regulate the antileishmanial functions of macrophages. The miRNA patterns vary with the time and stage of infection. The cytokine-regulated macrophage miRNAs not only help parasite elimination or persistence but also regulate cytokine production from macrophages. Based on these observations, we propose a novel immunoregulatory framework as a scientific rationale for antileishmanial therapy.

Siah2-GRP78 interaction regulates ROS and provides a proliferative advantage to Helicobacter pylori-infected gastric epithelial cancer cells.

Helicobacter pylori-mediated gastric carcinogenesis involves upregulation of the E3 ubiquitin ligase Siah2 and its phosphorylation-mediated stabilization. This study elucidates a novel mechanism of oxidative stress regulation by phosphorylated Siah2 in H. pylori-infected gastric epithelial cancer cells (GECs). We identify that H. pylori-mediated Siah2 phosphorylation at the 6th serine residue (P-S6-Siah2) enhances proteasomal degradation of the 78-kDa glucose-regulated protein (GRP78) possessing antioxidant functions. S6 phosphorylation stabilizes Siah2 and P-S6-Siah2 potentiates H. pylori-mediated reactive oxygen species (ROS) generation. However, infected S6A phospho-null Siah2-expressing cells have decreased cellular GRP78 level as surprisingly these cells release GRP78 to a higher extent and accumulate significantly higher ROS than the wild type (WT) Siah2 construct-expressing cells. Ectopic expression of GRP78 prevents the loss of mitochondrial membrane potential and cellular ROS accumulation caused by H. pylori. H. pylori-induced mitochondrial damage and mitochondrial membrane potential loss are potentiated in Siah2-overexpressing cells but these effects are further enhanced in S6A-expressing cells. This study also confirms that while phosphorylation-mediated Siah2 stabilization optimally upregulates aggresome accumulation, it suppresses autophagosome formation, thus decreasing the dependency on the latter mechanism in regulating cellular protein abundance. Disruption of the phospho-Siah2-mediated aggresome formation impairs proliferation of infected GECs. Thus, Siah2 phosphorylation has diagnostic and therapeutic significance in H. pylori-mediated gastric cancer (GC).

What controls the magnetic anisotropy in heptacoordinate high-spin cobalt(II) complexes? A theoretical perspective.

The magnetic anisotropy of sixteen seven-coordinate high-spin CoII complexes with O, N, Cl and I donors was investigated with state-of-the-art ab initio CASSCF/NEVPT2 calculations and compared with experimental data. Based on the nature of the equatorial and axial ligands, which were found to tune the zero-field splitting, the complexes were classified into four groups. The experimental zero-field splitting parameters D which, for the various structures are in a range of +30 to +60 cm-1, as well as the g and E values are well reproduced. The investigation of the electronic structure shows that in these pentagonal bipyramidal complexes the donors and symmetry in the equatorial plane play an important role in the values of the axial zero-field splitting parameter D, and breaking of the horizontal plane of symmetry was found to enhance the magnitude of the D value. Although negative values of D are a desired condition for SIMs, many CoII based SIMs with positive zero-field splitting are fundamentally important to understand the nature of magnetic anisotropy, and seven coordinate CoII complexes with a large overall crystal field splitting might provide a way forward in this class of molecules.

The expression of PD-1 and its ligands increases in Leishmania infection and its blockade reduces the parasite burden.

The expression of programmed cell death protein-1 (PD-1) and its ligands- PD-L1 and PD-L2- on T cells and macrophages', respectively, increases in Leishmania infection. The PD-1/PD-L1 interaction induces T cell anergy, T cell apoptosis and exhaustion, diversion of T cells toward TH2 and T-reg cells but inhibits M1 macrophage activities by suppression of nitric oxide (NO) and reactive oxygen species (ROS) production. These changes exacerbate Leishmania infection. As PD-L1-deficient, but not PD-L2-deficient, mice were protected againstL. mexicanainfection, differential roles have been proposed for PD-L1 and PD-L2 in mouse models of leishmaniasis. Blockade of PD-1/PD-L1 interaction in various in vitro and Leishmania-infected mouse, hamster and dog models enhanced IFN-γ and NO production, reduced IL-10 and TGF-ß generation, promoted T cell proliferation and reduced parasite burden. Therefore, PD-1/PD-L1 blockade is being considered as a potential therapeutic strategy to restore protective immunity during leishmaniasis, particularly, in drug-resistant cases.

Electric-Field-Induced Solid-Gas Interfacial Chemical Reaction in Carbon Nanotube Ensembles: Route toward Ultra-sensitive Gas Detectors.

The electric field at the sharp pointed tips of single wall carbon nanotube ensembles has been utilized to kinetically accelerate hitherto unobserved chemical reactions at the heterogeneous solid-gas interfaces. The principle of ″action-of-points″ drives specific chemical reactions between the defect sites of single wall carbon nanotubes (CNTs) and ppb levels of gaseous hydrogen sulfide. This is manifested as changes in the electrical conductivity of the conductive CNT-ensemble (cCNT) and visually tracked as enthalpic modulations at the site of the reaction through infrared thermometry. Importantly, the principle has been observed for a variety of analytes such as NH3, H2O, and H2S, leading to distinctly correlatable changes in reactivity and conductivity changes. Theoretical calculations based on the density functional theory in the presence and absence of applied electric field reveal that the applied electric field activates the H2S gas molecules by charge polarization, yielding favorable energetics. These results imply the possibility of carrying out site-specific chemical modifications for nanomaterials and also provide transformative opportunities for the development of miniaturized e-nose-based gas analyzers.

Molecular cloning, sequence characterization, and expression analysis of C-type lectin (CTL) and ER-Golgi intermediate compartment 53-kDa protein (ERGIC-53) homologs from the freshwater prawn, Macrobrachium rosenbergii.

Lectin protein families are diverse and multi-functional in crustaceans. The carbohydrate-binding domains (CRDs) of lectins recognize the molecular patterns associated with pathogens and orchestrate important roles in crustacean defense. In this study, two lectin homologs, a single CRD containing C-type lectin (CTL) and an L-type lectin (LTL) domain containing endoplasmic reticulum Golgi intermediate compartment 53 kDa protein (ERGIC-53) were identified from the freshwater prawn, Macrobrachium rosenbergii. The open reading frames of MrCTL and MrERGIC-53 were 654 and 1,515 bp, encoding polypeptides of 217 and 504 amino acids, respectively. Further, MrCTL showed a 20-amino acid transmembrane helix region and 10 carbohydrate-binding residues within the CRD. MrERGIC-53 showed a signal peptide region, a type-I transmembrane region, and a coiled-coil region at the C-terminus. Phylogenetic analysis revealed a close relationship between MrCTL and MrLectin and M. nipponense CTL (MnCTL), whereas MrERGIC-53 shared high sequence identity with Eriocheir sinensis ERGIC-53 and Penaeus vannamei MBL-1. A homology-based model predicted small carbohydrate-combining sites with a metal-binding site for ligand binding (Ca2+ binding site) in MrCTL and beta-sheets connected by short loops and beta-bends forming a dome-shaped beta-barrel structure representing the LTL domain of MrERGIC-53. Quantitative real-time polymerase chain reaction detected MrCTL and MrERGIC-53 transcripts in all examined tissues, with particularly high levels observed in hemocytes, hepatopancreas, and mucosal-associated tissues, such as the stomach and intestine. Further, the expression levels of MrCTL and MrERGIC-53 transcripts were remarkably altered after V. harveyi challenge, suggesting putative function in host innate immunity. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s10499-022-00845-3.

Silent hypoxia in COVID-19: a gut microbiota connection.

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection has triggered the COVID-19 pandemic. Several factors induce hypoxia in COVID-19. Despite being hypoxic, some SARS-CoV-2-infected individuals do not experience any respiratory distress, a phenomenon termed 'silent (or happy) hypoxia'. Prolonged undetected hypoxia could be dangerous, sometimes leading to death. A few studies attempted to unravel what causes silent hypoxia, however, the exact mechanisms are still elusive. Here, we aim to understand how SARS-CoV-2 causes silent hypoxia.

[(VIVO)2MII5] (M = Ni, Co) Anderson wheels.

Heterometallic Anderson wheels of formula [(VIVO)2MII5(hmp)10Cl2](ClO4)2·2MeOH (M = Ni, 1; Co, 2) have been synthesised from the solvothermal reaction of M(ClO4)2·6H2O and VCl3 with hmpH (2-(hydroxymethyl)pyridine). The metallic skeleton describes a centred hexagon, with the two vanadyl ions sitting on opposing sides of the outer ring. Magnetic susceptibility and magnetisation measurements indicate the presence of both ferromagnetic and antiferromagnetic exchange interactions. Theoretical calculations based on density functional methods reproduce both the sign and strength of the exchange interactions found experimentally, and rationalise the parameters extracted.