Anamika Gangwar

Cerium oxide nanoparticles promote neurogenesis and abrogate hypoxia-induced memory impairment through AMPK–PKC–CBP signaling cascade

Structural and functional integrity of the brain is adversely affected by reduced oxygen saturation, especially during chronic hypoxia exposure and often encountered by altitude travelers or dwellers. Hypoxia-induced generation of reactive nitrogen and oxygen species reportedly affects the cortex and hippocampus regions of the brain, promoting memory impairment and cognitive dysfunction. Cerium oxide nanoparticles (CNPs), also known as nanoceria, switch between +3 and +4 oxidation states and reportedly scavenge superoxide anions, hydrogen peroxide, and peroxynitrite in vivo. In the present study, we evaluated the neuroprotective as well as the cognition-enhancing activities of nanoceria during hypobaric hypoxia. Using polyethylene glycol-coated 3 nm nanoceria (PEG-CNPs), we have demonstrated efficient localization of PEG-CNPs in rodent brain. This resulted in significant reduction of oxidative stress and associated damage during hypoxia exposure. Morris water maze-based memory function tests revealed that PEG-CNPs ameliorated hypoxia-induced memory impairment. Using microscopic, flow cytometric, and histological studies, we also provide evidences that PEG-CNPs augmented hippocampus neuronal survival and promoted neurogenesis. Molecular studies revealed that PEG-CNPs promoted neurogenesis through the 5′-adenine monophosphate-activated protein kinase–protein kinase C–cyclic adenosine monophosphate response element-binding protein binding (AMPK-PKC-CBP) protein pathway. Our present study results suggest that nanoceria can be translated as promising therapeutic molecules for neurodegenerative diseases.

Size restricted silymarin suspension evokes integrated adaptive response against acute hypoxia exposure in rat lung.

Despite its extraordinary antioxidant capacity, the clinical usage of silymarin has remained restricted to amelioration of hepatic pathology. Perhaps its low bioavailability and uneven bio-distribution, owing to its poor aqueous solubility, are two main causes that have dampened the clinical applicability and scope of this preparation. We took these two challenges and suggested an unexplored application of silymarin. Apart from liver, two of the most susceptible vital organs at the highest risk of oxidative stress are brain and lung, especially during reduced oxygen saturation (hypoxia) at anatomical level. Hypoxia causes excess generation of radicals primarily in the lungs as it is the first organ at the interphase of atmosphere and organism making it the most prone and vulnerable to oxidative stress and the first responder against hypobaric hypoxia. As our first objective, we improved the silymarin formulation by restricting its size to the lower threshold and then successfully tested the prophylactic and therapeutic action in rat lung challenged with simulated hypobaric hypoxia. After dose optimization, we observed that 50mg/kg BW silymarin as size restricted and homogenous aqueous suspension successfully minimized the reactive oxygen species and augmented the antioxidant defense by significant upregulation of catalase and superoxide dismutase and reduced glutathione. Moreover, the well-established hypoxia markers and proteins related to hypoxia adaptability, hif1a and VEGF were differentially regulated conferring significant reduction in the inflammation caused by hypobaric hypoxia. We therefore report,the unexplored potential benefits of silymarin for preventing high altitude associated pathophysiology further paving its road to clinical trials.

STAT3-RXR-Nrf2 activates systemic redox and energy homeostasis upon steep decline in pO2 gradient.

Hypobaric hypoxia elicits several patho-physiological manifestations, some of which are known to be lethal. Among various molecular mechanisms proposed so far, perturbation in redox state due to imbalance between radical generation and antioxidant defence is promising. These molecular events are also related to hypoxic status of cancer cells and therefore its understanding has extended clinical advantage beyond high altitude hypoxia. In present study, however, the focus was to understand and propose a model for rapid acclimatization of high altitude visitors to enhance their performance based on molecular changes. We considered using simulated hypobaric hypoxia at some established thresholds of high altitude stratification based on known physiological effects. Previous studies have focused on the temporal aspect while overlooking the effects of varying pO2 levels during exposure to hypobaric hypoxia. The pO2 levels, indicative of altitude, are crucial to redox homeostasis and can be the limiting factor during acclimatization to hypobaric hypoxia. In this study we present the effects of acute (24 h) exposure to high (3049 m; pO2: 71 kPa), very high (4573 m; pO2: 59 kPa) and extreme altitude (7620 m; pO2: 40 kPa) zones on lung and plasma using semi-quantitative redox specific transcripts and quantitative proteo-bioinformatics workflow in conjunction with redox stress assays. It was observed that direct exposure to extreme altitude caused 100% mortality, which turned into high survival rate after pre-exposure to 59 kPa, for which molecular explanation were also found. The pO2 of 59 kPa (very high altitude zone) elicits systemic energy and redox homeostatic processes by modulating the STAT3-RXR-Nrf2 trio. Finally we posit the various processes downstream of STAT3-RXR-Nrf2 and the plasma proteins that can be used to ascertain the redox status of an individual.

Competing trends of ROS and RNS-mediated protein modifications during hypoxia as an alternate mechanism of NO benefits

Hypoxia, especially altitude associated hypoxia is known to cause severe physiological alterations and life-threatening conditions. Impaired redox balance along with oxidative stress, protein carbonylation and instigation of apoptotic events are common sub-cellular events that follow the hypoxic insult. The role of nitric oxide (NO) is very dynamic and versatile in preventing the ill effects of hypoxia vis-a-vis reacting with oxidative species and causing protein nitrosylation. Although several mechanisms of NO-mediated cytoprotection are known during hypoxic insult, limited pieces of evidence are available to support the relationship between two downstream events of oxidative stress, protein carbonylation (caused by carbonyl; CO radical) and protein nitrosylation/nitration (caused by NO/peroxynitrite; ONOO radical). In this study, we investigated an entirely new aspect of NO protection in hypoxia involving crosstalk between carbonylation and nitrosylation. Using standard NO inhibitor l-NAME and simulated hypoxic conditions in hypoxia-sensitive cell line H9c2, we evaluated the levels of radicals, cell death, mitochondrial membrane potential, levels of protein nitrosylation, protein nitration and carbonylation and glutathione content. The results were then carefully analyzed in light of NO bioavailability. Our study shows that reducing NO during hypoxia caused cell death via the increased degree of carbonylation in proteins. This provides a new aspect of NO benefits which furthers opens new possibilities to explore potential mechanisms and effects of cross-talk between nitrosylation, protein nitration and carbonylation, especially through some common antioxidant mediators such as glutathione and thioredoxin.

Plasma Proteomics of Ladakhi Natives Reveal Functional Regulation Between Renin–Angiotensin System and eNOS–cGMP Pathway

Padhy, Gayatri, Anamika Gangwar, Manish Sharma, Kalpana Bhargava, and Niroj Kumar Sethy. Plasma proteomics of Ladakhi natives reveal functional regulation between renin-angiotensin system and eNOS-cGMP pathway. High Alt Med Biol. 18:27-36, 2017.-Humans have been living in high altitudes for more than 25,000 years but the molecular pathways promoting survival and performance in these extreme environments are not well elucidated. In an attempt to understand human adaptation to high altitudes, we used two-dimensional gel electrophoresis combined with MALDI-TOF/TOF to identify plasma proteins and associated pathways of ethnic Ladakhi natives residing at 3520 m. This resulted in the identification of 36 differential proteins compared with sea-level individuals. Proteins belonging to coagulation cascade and complement activation were found to be less abundant in Ladakhi natives. Interestingly, we observed lower abundance of angiotensinogen (ANGT) and subsequent analysis also revealed lower levels of both ANGT and angiotensin II (Ang II) in Ladakhi natives. Concomitantly, we observed elevated levels of eNOS, phosphorylated eNOS (Ser1177), and plasma biomarkers for nitric oxide (NO) production (nitrate and nitrite) and availability (cGMP). These results suggest that functional interplay between renin-angiotensin system and NO-cGMP pathway contributes to the hypoxia adaptation in Ladakhi natives. These findings will augment the present understanding of higher NO and NO-derived metabolite availability during human adaptation to high altitude.

A glowing antioxidant from tasar silk cocoon

Oxidative stress is associated with a variety of disorders, diseases as well as the natural aging process thus making antioxidant discovery of medical relevance. In the present study, we report the simultaneous antioxidant as well as bio-imaging activities of a fluorescent extract (fluorophore) obtained from the tasar silk cocoons of the silk moth Antheraea mylitta. Using a nanocarrier-based strategy, we were able to localize the fluorophore in the cytosol of cardiomyoblast cell line H9c2 without any alterations to cellular morphology. In search of additional uses of the fluorophore beyond bio-imaging, we evaluated the antioxidant efficacies of the fluorophore against hydrogen peroxide-induced oxidative stress. Using microscopic, flow-cytometry and ELISA based studies; we observed that the silk fluorophore ameliorated hydrogen peroxide-induced reactive oxygen species (ROS) levels and oxidative stress. Moreover, enhanced levels of endogenous antioxidant enzymes were also observed in fluorophore pre-treated cells during oxidative stress. This resulted in significant reduction of oxidative stress-induced cell death. Our cumulative results suggest concomitant antioxidant and bio-imaging activities of the naturally occurring silk fluorophore. Given that a tasar silk fluorophore has never been isolated from cocoons in the silk textile industry, further commercial exploration will provide economic support to silk farmers.

Diagnosis and prophylaxis for high-altitude acclimatization: Adherence to molecular rationale to evade high-altitude illnesses

ABSTRACT Lack of zero side‐effect, prescription‐less prophylactics and diagnostic markers of acclimatization status lead to many suffering from high altitude illnesses. Although not fully translated to the clinical setting, many strategies and interventions are being developed that are aimed at providing an objective and tangible answer regarding the acclimatization status of an individual as well as zero side‐effect prophylaxis that is cost‐effective and does not require medical supervision. This short review brings together the twin problems associated with high‐altitude acclimatization, i.e. acclimatization status and zero side‐effect, easy‐to‐use prophylaxis, for the reader to comprehend as cogs of the same phenomenon. We describe current research aimed at preventing all the high‐altitude illnesses by considering them an assault on redox and energy homeostasis at the molecular level. This review also entails some proteins capable of diagnosing either acclimatization or high‐altitude illnesses. The future strategies based on bioinformatics and systems biology is also discussed. Graphical abstract: Figure. No caption available.

Nanomaterials in Antioxidant Research

Oxidative stress is proposed as leading event in the deterioration of health and basic biological processes. Ever since the Harman’s theory of aging was proposed based on the ill effects of oxidative in the body, the pace of oxidative stress research became rapid. The antioxidants were proposed as putative therapeutic and prophylactic agents for the prevention of oxidative damage and its aftermath. Despite the escalating research publications in the domain of oxidative stress and antioxidant therapy, apparent clinical transitions are fairly low. Perhaps, this should not be looked as question on the studies which were performed on the antioxidants, rather our poor understanding of cross talk of antioxidants and oxidants in the cells and its downstream effects. It seems that decision of considering antioxidants as miracle drugs for aging and similar condition was too early. There is lot more to be explored in this domain, and as we move deeper, we realize that oxidative stress and antioxidant interplay is one of the most complicated biological events that has several fold more complexity than basic cellular processes and metabolism. The scientific questions such as how much antioxidant dose is optimal and which antioxidant is most suitable can only be answered in a context-specific manner. The several anomalies and unfruitful clinical translations of antioxidants have led to the continuation and intensification of antioxidant research. With the advent of a new domain of science named nanotechnology, few exciting possibilities have emerged in the antioxidant researches which are likely to answer some of the issues of conventional antioxidants. This chapter is aimed to discuss the emerging trends in nano-antioxidants with a special focus on much-studied antioxidant nanoceria.