Achieving abiotic stress tolerance in plants through antioxidative defense mechanisms

Climate change has increased the overall impact of abiotic stress conditions such as drought, salinity, and extreme temperatures on plants. Abiotic stress adversely affects the growth, development, crop yield, and productivity of plants. When plants are subjected to various environmental stress conditions, the balance between the production of reactive oxygen species and its detoxification through antioxidant mechanisms is disturbed. The extent of disturbance depends on the severity, intensity, and duration of abiotic stress. The equilibrium between the production and elimination of reactive oxygen species is maintained due to both enzymatic and non-enzymatic antioxidative defense mechanisms. Non-enzymatic antioxidants include both lipid-soluble (α-tocopherol and β-carotene) and water-soluble (glutathione, ascorbate, etc.) antioxidants. Ascorbate peroxidase (APX), superoxide dismutase (SOD), catalase (CAT), and glutathione reductase (GR) are major enzymatic antioxidants that are essential for ROS homeostasis. In this review, we intend to discuss various antioxidative defense approaches used to improve abiotic stress tolerance in plants and the mechanism of action of the genes or enzymes involved

Post-implementation Review of the Himalaya Home Care Project for Home Isolated COVID-19 Patients in Nepal

Background: The emergence of coronavirus disease 2019 (COVID-19) has resulted in a pandemic that has significantly impacted healthcare systems at a global level. Health care facilities in Nepal, as in other low- and middle-income countries, have limited resources for the treatment and management of COVID-19 patients. Only critical cases are admitted to the hospital resulting in most patients in home isolation. Methods: Himalaya Home Care (HHC) was initiated to monitor and provide counseling to home isolated COVID-19 patients for disease prevention, control, and treatment. Counselors included one physician and four nurses. Lists of patients were obtained from district and municipal health facilities. HHC counselors called patients to provide basic counseling services. A follow-up check-in phone call was conducted 10 days later. During this second call, patients were asked about their perceptions of the HHC program. Project objects were: (1) To support treatment of home isolated persons with mild to moderate COVID-19, decrease burden of hospitalizations, and decrease risks for disease transmission; and, (2) To improve the health status of marginalized, remote, and vulnerable populations in Nepal during the COVID-19 pandemic. Results: Data from 5823 and 3988 patients from May 2021-February 2022 were entered in initial and follow-up forms on a REDCap database. The majority of patients who received counseling were satisfied. At follow-up, 98.4% of respondents reported that HHC prevented hospitalization, 76.5% reported they could manage their symptoms at home, and 69.5% reported that counseling helped to limit the spread of COVID-19 in their household. Conclusions: Telehealth can be an essential strategy for providing services while keeping patients and health providers safe during the COVID-19 pandemic

Microbial exposure during early human development primes fetal immune cells

Human fetal immune system begins to develop early during gestation, however factors responsible for fetal immune-priming remain elusive. We explored potential exposure to microbial agents in-utero and their contribution towards activation of memory T cells in fetal tissues. We profiled microbes across fetal organs using 16S-rRNA gene sequencing and detected low but consistent microbial signal in fetal gut, skin, placenta and lungs, in 2nd trimester of gestation. We identified several live bacterial strains including Staphylococcus and Lactobacillus in fetal tissues, which induced in vitro activation of memory T cells in fetal mesenteric lymph-node, supporting the role of microbial exposure in fetal immune-priming. Finally, using SEM and RNA-ISH, we visualised discrete localisation of bacteria-like structures and eubacterial-RNA within 14th week fetal gut lumen. These findings indicate selective presence of live-microbes in fetal organs during 2nd trimester of gestation and have broader implications towards establishment of immune competency and priming before birt

Biochemical characterization of argininosuccinate lyase from M-tuberculosis: significance of a c-terminal cysteine in catalysis and thermal stability

Arginine biosynthesis pathway is crucial to the survival and pathogenesis of Mycobacterium tuberculosis (Mtb). Arginine is a critical amino acid that contributes to the inflection of cellular immune responses during pathogenesis. Argininosuccinate lyase from Mtb (MtArgH), the last enzyme in the pathway, catalyzes the production of arginine from argininosuccinic acid. MtArgH is an essential enzyme for the growth and survival of M. tuberculosis. We biochemically characterized MtArgH and deciphered the role of a previously unexplored cysteine (Cys(441)) residue at the C-terminal region of the protein. Chemical modification of Cys(441) completely abrogated the enzymatic activity suggesting its involvement in the catalytic mechanism. Replacement of Cys(441) to alanine showed a striking decrease in the enzymatic activity, while retaining the overall secondary to quaternary structure of the protein, hence corroborating the involvement of Cys(441) in the process of catalysis. Interestingly, replacement of Cys(441) to serine, showed significant increase in activity, as compared to the wild-type MtArgH. Inactivity of C(441)A and elevated activity of its conservative mutant ((CS)-S-441) confirmed the participation of Cys(441) in the MtArgH activity. We also, observed that (CS)-S-441 mutant has higher thermal stability and maintains significant activity at high temperatures. This is in concordance with our observation that Cys(441) in Mtb is replaced by a serine in the ArgH from thermophilic microorganisms. Furthermore, we also propose a potential feedback mechanism, wherein the Cys(441) is covalently modified to S-(2-succinyl) cysteine (succination) by one of the products, fumarate, thereby inactivating MtArgH. These insights into the mechanism of MtArgH activity unravel novel regulations of arginine biosynthetic pathway in Mtb. (c) 2017 IUBMB Life, 69(11):896-907, 201

Mycobacterium tuberculosis: Surviving and Indulging in an Unwelcoming Host

More than a century has passed since the identification of Mycobacterium tuberculosis (Mtb) as the causative agent of tuberculosis (TB), we still are nowhere close to eradicating this deadly disease. Moreover, emergence of new drug-resistant strains has further complicated the situation, making it even more difficult to treat by conventional therapy regimens. Humans are the only reservoir for the existence and propagation of Mtb, which suggests that its latent forms will be most difficult to eradicate, till the human race lasts. Mtb has been associated with us for ages and its evolution is strictly guided to exploit its human host for survival and spread. The strategies employed by Mtb are unique and host specific, thereby making it hard to break this association without accurate understanding of this host-pathogen interaction. Metabolic pathways have always been at the heart of Mtb pathogenesis, with a continuous cross-talk between the pathogen and the host. Over the years, Mtb has mastered the art of manipulating the host machinery, along with modulating its own metabolism for survival in the hostile conditions. Here we aim to summarize the history of tuberculosis, its pathology and recent advances in basic understanding of the machinery, with eventual gape on the novel therapeutic strategies emerged in the past decade. (c) 2018 IUBMB Life, 70(9):917-925, 201

Structural studies on M-tuberculosis argininosuccinate lyase and its liganded complex: Insights into catalytic mechanism

Argininosuccinate lyase catalyses the reversible breakdown of argininosuccinate into arginine and fumarate and is known to form tetramers in its quaternary association. The absence of structures involving competent enzymes bound to substrate/products came in the way of the precise elucidation of the catalytic mechanism of this family of proteins. Crystal structures of the enzyme from Mycobacterium tuberculosis in an unliganded form and its complex with the substrate/products have now been determined at 2.2 and 2.7 angstrom, respectively. The refinement of the structure of the complex was bedevilled by the presence of a lattice translocation defect. The two tetramers in the apo-crystals and the one in the crystals of the liganded protein, have the same structure except for the movements associated with enzyme action. Each molecule consists of an N-domain, an M-domain, and a C-domain. The molecule consists of four binding sites, each made up of peptide stretches from three subunits. Three binding sites appear to be occupied by the ligand in the transition state, while the products occupy the fourth site. The structure exhibits the movement of a loop in the M-domain and parts of the C-domain. This is the first instance when the appropriate movements are observed in a complex with bound substrate/product. The detailed picture of the binding site, active site residues and the movements associated with catalysis thus obtained, enabled a revisit of the mechanism of action of the enzyme. (c) 2019 IUBMB Life, 71(5):643-652, 201

Targeting human telomeric G-quadruplex DNA with curcumin and its synthesized analogues under molecular crowding conditions

The formation of telomeric G-quadruplexes has been shown to inhibit telomerase activity. Indeed, a number of small molecules capable of p-stacking with G-tetrads have shown the ability to inhibit telomerase activity through the stabilization of G-quadruplexes. Curcumin displays a wide spectrum of medicinal properties ranging from anti-bacterial, anti-viral, anti-protozoal, anti-fungal and anti-inflammatory to anti-cancer activity. We have investigated the interactions of curcumin and its structural analogues with the human telomeric sequence AG(3)(T(2)AG(3))(3) under molecular crowding conditions. Experimental studies indicated the existence of a AG(3)(T(2)AG(3))(3)/curcumin complex with binding affinity of 0.72 x 10(6) M-1 under molecular crowding conditions. The results from UV-visible absorption spectroscopy, a fluorescent TO displacement assay, circular dichroism and molecular docking studies, imply that curcumin and their analogues interact with G-quadruplex DNA via groove binding. While other analogs of curcumin studied here bind to G-quadruplexes in a qualitatively similar manner their affinities are relatively lower in comparison to curcumin. The Knoevenagel condensate, a methoxy-benzylidene derivative of curcumin, also exhibited significant binding to G-quadruplex DNA, although with two times decreased affinity. Our study establishes the potential of curcumin as a promising natural product for G-quadruplex specific ligands

Experimental Osteoporosis Induced in Female Albino Rats and its Antagonism by Indian Black Scorpion (Heterometrus Bengalensis C.L.Koch) Venom.

The present study was designed to explore the antiosteoporosis activity of the Indian black scorpion (Heterometrus bengalensis) venom on experimental osteoporosis female albino rats. Sham operated control rats were designated as Gr I, Gr II animals served as osteoporosis control, Gr III osteoporosis rats were treated with SV (1/25th of MLD), Gr IV osteoporosis rats were treated with 1/50th of MLD of SV and Gr V osteoporosis rats were treated with standard (calcium and vit-D3). As compared with the Gr I rats, the Gr II rats showed typical osteoporosis changes in increased of urinary Ca2þ, PO43�, CRE, OH-P levels, serum/plasma Ca2þ, PO4 3�, TRAP, IL1, IL6, TNFa and PTH level, bone Ca2þ, PO4 3�, Mg2þ, Zn2þ and decreased level of serum/plasma ALP, EST and PTH, bone Naþ. In Gr III, Gr IV and Gr V rats, the osteoporosis changes of urine, serum and bone, were significantly restored as compared with the Gr II rats. The bone dimensions, morphology and histological changes observed in Gr II rats were restored in Gr III, Gr IV and Gr V rats. This study confirms that the Indian black scorpion venom may influence bone remodeling process by stimulating bone formation and reducing bone resorption process of osteogenesis

An allosteric inhibitor of Mycobacterium tuberculosis ArgJ: Implications to a novel combinatorial therapy

The existing treatment regime against tuberculosis is not adequate, and novel therapeutic interventions are required to target Mycobacterium tuberculosis (Mtb) pathogenesis. We report Pranlukast (PRK) as a novel allosteric inhibitor of Mtb's arginine biosynthetic enzyme, Ornithine acetyltransferase (MtArgJ). PRK treatment remarkably abates the survival of free as well as macrophage-internalized Mtb, and shows enhanced efficacy in combination with standard-of-care drugs. Notably, PRK also reduces the 5-lipoxygenase (5-LO) signaling in the infected macrophages, thereby surmounting an enhanced response against intracellular pathogen. Further, treatment with PRK alone or with rifampicin leads to significant decrease in Mtb burden and tubercular granulomas in Mtb-infected mice lungs. Taken together, this study demonstrates a novel allosteric inhibitor of MtArgJ, which acts as a dual-edged sword, by targeting the intracellular bacteria as well as the bacterial pro-survival signaling in the host. PRK is highly effective against invitro and invivo survival of Mtb and being an FDA-approved drug, it shows a potential for development of advanced combinatorial therapy against tuberculosis