understanding-development-compensatory-pathways-mutant-malaria

Understanding the Development of Compensatory Pathways in a Mutant Malaria Parasite Harbouring Hypomorphic Allele of Plant-Like Kinases

One of the mechanisms for subverting the effect of drugs by&#160;the malaria parasite is through rewiring of its transcriptome. The effect is more ...

Jawaharlal Nehru University

Radiotherapy is the biggest force acting behind cancer treatment, yet the vast majority of patients get only modest benefit. The successive failure of targeted therapies in radiotherapy lies in the non-discriminative killing of both normal and cancer cells. However, there is still a reason for optimism due to recent advancement made in cancer biology which unrevealed many new deregulated pathways in cancer and their response towards drug and radiation. In this review, we comprehensively discussed novel and promising druggable target which can be exploited for tumor radiosensitization in addition to normal tissue radioprotection in radiotherapy, for better tumor controllability and patient quality of life. In the last part, we also discussed the radiation countermeasure agents in brief.

Emerging targets for radioprotection and radiosensitization in radiotherapy.

Aqueous bark extract of Terminalia arjuna (TA) has been in use as an ethnomedicine for cardiovascular ailments in the Indian subcontinent for centuries. Studies using hemodynamic, ROS scavenging and anti-inflammatory parameters in animal models have shown its anti-atherogenic, hypotensive, inotropic, anti-inflammatory effects. However, details analysis on its effects on established molecular and cell biological markers are a prerequisite for its wider acceptance to the medical community.

Proteomic analysis of the protective effects of aqueous bark extract of Terminalia arjuna (Roxb.) on isoproterenol-induced cardiac hypertrophy in rats.

Present study was designed to investigate the role of acemannan acetyl group in murine radioprotection. Acemannan, extracted from Aloe vera gel, has molecular weight of 1.02 × 10 Da and mainly composed of mannose (84.9%), glucose (7.2%), and galactose (3.9%), with backbone of (1→4)-linked mannose and glucose. Acemannan was over-acetylated and deacetylated to investigate the role of acetyl group. Acetylation enhances acemannan viscosity and thermal stability. Free radicals scavenging and Fenton reaction inhibition was mediated by acemannan acetyl and hydroxyl group respectively. Native or over-acetylated or deacetylated acemannan pre-treatment to mice has shown to reduce the γ-radiation-induced oxidative damage, and hematopoietic injuries by free radical scavenging and microphage activation (secretes pro-hematopoietic factors through TLR-4) respectively. Over-acetylated acemannan has stronger effects on immunomodulation/radioprotection. In summary, acemannan acetyl-group modulates immune system, while hydroxyl-group participate in free radical scavenging, and present finding can be employed in food and pharma industries for enhancing polysaccharide bioactivity.

Role of acemannan O-acetyl group in murine radioprotection.

Mental health in old age is of great concern due to the increased incidence of neurological and psychiatric diseases. With age, probability of cognitive and behavioral deficits increase and the prognosis deteriorates. Although a few in vitro studies have reported that flavonoid fisetin is beneficial for healthy aging, its effect on deteriorating mental health with aging in vivo is very limited and poorly understood. The brain aging is physiologically characterized by electroencephalograph (EEG) wave frequency, power, and distribution. Brain oscillatory waves from neural tissue get altered by various sensory-cognitive inputs. Besides, the fast-wave α(8-12 Hz)- and β(12-28 Hz)-oscillations are associated with coordination and indeed deal with complex behavioral performances. Therefore, the effect of fisetin supplementation on age-associated EEG mean cortical spectral power in α- and β-oscillations, multi-unit activity (MUA) count were studied in vivo which was not addressed so far. Besides, age-associated cognitive and behavioral alterations were also studied. The relative spectral power of α and β declined along with the MUA count in aged rats compared to young. However, supplementing fisetin for four weeks has improved relative α-power, β-power, and MUA count in aged rats. Also, fisetin supplemented aged rats showed significantly improved cognitive and behavioral performances than aged controls. These findings demonstrated the relative cortical spectral power in α-, β-oscillations, and MUA count change in aged rats and that some of these changes and behavioral alterations may be partly as a result of oxidative stress, which was prevented significantly in fisetin supplemented aged rats. Thus, fisetin boosted mental health in the aged animals.

Fisetin prevents the aging-associated decline in relative spectral power of α, β and linked MUA in the cortex and behavioral alterations.

Calcium ions are used as important signals during various physiological processes. In malaria parasites,  spp., calcium dependent protein kinases (CDPKs) have acquired the unique ability to sense and transduce calcium signals at various critical steps during the lifecycle, either through phosphorylation of downstream substrates or mediating formation of high molecular weight protein complexes. Calcium signaling cascades establish important crosstalk events with signaling pathways mediated by other secondary messengers such as cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP). CDPKs play critical roles at various important physiological steps during parasite development in vertebrates and mosquitoes. They are also important for transmission of the parasite between the two hosts. Combined with the fact that CDPKs are not present in humans, they continue to be pursued as important targets for development of anti-malarial drugs.

CDPKs: The critical decoders of calcium signal at various stages of malaria parasite development.

Protozoan parasitic diseases pose a substantial global health burden. Understanding the pathogenesis of these diseases is crucial for developing intervention strategies in the form of vaccine and drugs. Manipulating the parasite's genome is essential for gaining insights into its fundamental biology. Traditional genomic manipulation methods rely on stochastic homologous recombination events, which necessitates months of maintaining the cultured parasites under drug pressure to generate desired transgenics. The introduction of mega-nucleases (MNs), zinc-finger nucleases (ZFNs), and transcription activator-like effector nucleases (TALENs) greatly reduced the time required for obtaining a desired modification. However, there is a complexity associated with the design of these nucleases. CRISPR (Clustered regularly interspaced short palindromic repeats)/Cas (CRISPR associated proteins) is the latest gene editing tool that provides an efficient and convenient method for precise genomic manipulations in protozoan parasites. In this chapter, we have elaborated various strategies that have been adopted for the use of CRISPR-Cas9 system in Plasmodium, Leishmania and Trypanosoma. We have also discussed various applications of CRISPR-Cas9 pertaining to understanding of the parasite biology, development of drug resistance mechanism, gene drive and diagnosis of the infection.

Recent development in CRISPR-Cas systems for human protozoan diseases.

Conditional regulation is a highly beneficial system for studying the function of essential genes in Plasmodium falciparum and dimerizable Cre recombinase (DiCre) is a recently adapted conditional regulation system suitable for this purpose. In the DiCre system, two inactive fragments of Cre are reconstituted to form a functionally active enzyme in the presence of rapamycin. Different loci have been targeted to generate parasite lines that express the DiCre enzyme. Here, we have used marker-free CRISPR-Cas9 gene editing to integrate the DiCre cassette in a redundant cg6 locus. We have shown the utility of the newly generated ∆cg6DC4 parasites in mediating robust, rapid, and highly specific excision of exogenously encoded gfp sequence. The ∆cg6DC4 parasites are also capable of conditional excision of an endogenous parasite gene, PF3D7_1246000. Conditional deletion of PF3D7_1246000 did not cause any inhibition in the asexual proliferation of the parasites. Furthermore, the health and morphology of the mutant parasites were comparable to that of the control parasites in Giemsa smears. The availability of another stable DiCre parasite strain competent for conditional excision of target genes will expedite functional characterization and validation of novel drug and vaccine targets against malaria.

Article	Year
Emerging targets for radioprotection and radiosensitization in radiotherapy. Tumour biology : the journal of the International Society for Oncodevelopmental Biology and Medicine\| PubMed ID: 27318945	2016
Proteomic analysis of the protective effects of aqueous bark extract of Terminalia arjuna (Roxb.) on isoproterenol-induced cardiac hypertrophy in rats. Journal of ethnopharmacology\| PubMed ID: 28063919	2017
Role of acemannan O-acetyl group in murine radioprotection. Carbohydrate polymers\| PubMed ID: 30600029	2019
Fisetin prevents the aging-associated decline in relative spectral power of α, β and linked MUA in the cortex and behavioral alterations. Experimental gerontology\| PubMed ID: 32592831	2020
CDPKs: The critical decoders of calcium signal at various stages of malaria parasite development. Computational and structural biotechnology journal\| PubMed ID: 34589185	2021
Recent development in CRISPR-Cas systems for human protozoan diseases. Progress in molecular biology and translational science\| PubMed ID: 39266180	2024
Generation of a new DiCre expressing parasite strain for functional characterization of Plasmodium falciparum genes in blood stages. Scientific reports\| PubMed ID: 39402380	2024

Himashree Choudhury

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