Browsing by Author "Kumar Abhishek"

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Leishmania donovani activates hypoxia inducible factor-1α and miR-210 for survival in macrophages by downregulation of NF-κB mediated pro-inflammatory immune respons
(Frontiers Media S.A., 2018) Vinod Kumar; Ajay Kumar; Sushmita Das; Ashish Kumar; Kumar Abhishek; Sudha Verma; Abhishek Mandal; Rakesh K. Singh; Pradeep Das
Micro RNAs (miRNAs) have emerged as a critical regulator of several biological processes in both animals and plants. They have also been associated with regulation of immune responses in many human diseases during recent years. Visceral leishmaniasis (VL) is the most severe form of leishmaniasis, which is characterized by impairment of both innate and adaptive immune responses. In the present study, we observed that Leishmania establishes hypoxic environment in host macrophages that induces the expression of hypoxia inducible factor-1α (HIF-1α) and miRNA-210. Further, the expression of miRNA-210 was found to be dependent on activation of HIF-1α expression. The HIF-1α silencing by siRNA resulted in significantly (p < 0.001) decreased expression of miR-210 in parasites infected macrophages. We also observed that in siHIF-1α or antagomir-210 treated L. donovani infected macrophages, the parasitic load and percentage infectivity were significantly (p < 0.001) decreased. Furthermore, we found that inhibition of miR-210 leads to activation of NF-κB subunit p50, and it forms heterodimer with p65 and translocates into the nucleus from the cytoplasm. This significantly (p < 0.05) induced the transcription of pro-inflammatory cytokines genes such as TNF-α and IL-12 in miRNA-210 inhibited macrophages compared to uninhibited macrophages whereas the level of IL-10, an anti-inflammatory cytokine, was found to be significantly decreased (p < 0.001). These findings suggested that L. donovani infection induces hypoxic environment inside the macrophages that activates HIF-1α. Further, HIF-1α upregulates miR-210, which eventually establishes a suitable environment for the survival of parasite inside the host macrophages by downregulating NF-κB mediated pro-inflammatory immune responses. © 2018 Kumar, Kumar, Das, Kumar, Abhishek, Verma, Mandal, Singh and Das.
Leishmania donovani infection induce differential miRNA expression in CD4+ T cells
(Nature Research, 2020) Vinod Kumar; Sushmita Das; Ajay Kumar; Neeraj Tiwari; Ashish Kumar; Kumar Abhishek; Abhishek Mandal; Manjay Kumar; Taj Shafi; Tanvir Bamra; Rakesh Kumar Singh; Saravanan Vijayakumar; Abhik Sen; Pradeep Das
Visceral leishmaniasis is characterized by mixed production of Th1/2 cytokines and the disease is established by an enhanced level of Th2 cytokine. CD4+ T cells are main cell type which produces Th1/2 cytokine in the host upon Leishmania infection. However, the regulatory mechanism for Th1/2 production is not well understood. In this study, we co-cultured mice CD4+ T cells with Leishmania donovani infected and uninfected macrophage for the identification of dysregulated miRNAs in CD4+ T cells by next-generation sequencing. Here, we identified 604 and 613 known miRNAs in CD4+ T cells in control and infected samples respectively and a total of only 503 miRNAs were common in both groups. The expression analysis revealed that 112 miRNAs were up and 96 were down-regulated in infected groups, compared to uninfected control. Nineteen up-regulated and 17 down-regulated miRNAs were statistically significant (p < 0.05), which were validated by qPCR. Further, using insilco approach, we identified the gene targets of significant miRNAs on the basis of CD4+ T cell biology. Eleven up-regulated miRNAs and 9 down-regulated miRNAs were associated with the cellular immune responses and Th1/2 dichotomy upon Leishmania donovani infection. The up-regulated miRNAs targeted transcription factors that promote differentiation of CD4+ T cells towards Th1 phenotype. While down-regulated miRNAs targeted the transcription factors that facilitate differentiation of CD4+ T cells towards Th2 populations. The GO and pathway enrichment analysis also showed that the identified miRNAs target the pathway and genes related to CD4+ T cell biology which plays important role in Leishmania donovani infection. © 2020, The Author(s).
Source of Cr(VI) in the aquatic ecosystem, its genotoxic effects and microbial removal from contaminated water
(Taylor and Francis Ltd., 2023) Veer Singh; Kumar Abhishek; Sachchida Nand Rai; Santosh K. Singh; Emanuel Vamanu; Ashish Kumar
Cr(VI) compounds have important industrial applications and are used in various sectors like tanning, chrome plating, anti-corrosion agents and wood preservation. The Cr(VI) contamination in the wastewater is generally due to several natural and anthropogenic sources. Anthropogenic activities like several industrial operations play a major role in the Cr(VI) contamination in the aquatic ecosystem. Cr(VI) well-known toxic metal ion and its exposure in humans causes several health issues. Cr(VI) enters the cells and gradually reduces into a lower oxidation state and generates oxidative stress in the cell which damages cell organelles. The Cr(VI) mediated genotoxicity has been described as damaging the DNA base pairing, sugar-phosphate backbone, histone modification and chromosomal damage. Water and wastewater must be treated to remove Cr(VI) due to its high toxicity. There are several, physiochemical methods used for Cr(VI) remediation but these approaches are expensive and produce hazardous sludge during the treatment process. Therefore, a suitable environmentally friendly and effective Cr(VI) removal approach is urgently needed. Microbial removal of Cr(VI) is considered an eco-friendly and cost-effective process. In this, the authors focused on sources, genotoxicity and microbial remediation approaches of Cr(VI). © 2023 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.