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Biology subjects

Khanna, K.

Publications and source records attributed to Khanna, K..

2 recordsLinked to original sources

Simvastatin mediates inhibition of exosome synthesis, localization, and secretion via multicomponent interventions.

Discovery of exosomes as modulator of cellular communication has added a new dimension to our understanding of biological processes. Exosomes influence the biological systems by mediating trans-communication across tissues and cells, which has important implication for health and disease. Identification of strategies for exosome modulation may pave the way towards better understanding of exosome biology and development of novel therapeutics. In absence of well-characterized modulators of exosome biogenesis, an alternative option is to target pathways generating important exosomal components. Cholesterol represents one such essential component required for exosomal biogenesis. We initiated this study to test the hypothesis that owing to its cholesterol lowering effect, simvastatin, a HMG CoA inhibitor, might be able to alter exosome formation and secretion. Using previously established protocols for detecting secreted exosomes in biological fluids, simvastatin was tested for its effect on exosome secretion under various in-vitro and in-vivo settings. Murine model of AAI was used for further validation of our findings. Utilizing aforementioned systems, we demonstrate exosome-lowering potential of simvastatin in various in-vivo and in-vitro models, of AAI and atherosclerosis. We believe that the knowledge acquired in this study holds potential for extension to other exosome dominated pathologies and model systems.

cell biology

DNA damage response decreases during induced pluripotent and embryonic stem cell differentiation

Genomic integrity is critical for preservation of stem cell function and is, maintained through a robust DNA damage response (DDR) with systemized DNA DSB repair by either the non-homologous end joining (NHEJ) pathway or the homologous recombination (HR) pathway. To examine DDR during stem cell differentiation, human embryonic (hES) and induced pluripotent stem (IPS) cells were exposed to DNA damaging agents and DNA damage signaling/repair measured. Differentiated cells displayed a higher frequency of residual DNA damage, chromosomal aberrations, cells with delayed {gamma}-H2AX foci disappearance and a reduced number of RAD51 foci. Factors impacting DNA DSB repair by HR formed reduced foci in differentiated cells. The reduction in repairosome foci formation after DNA damage was not due to changes in HR protein levels, which were unchanged by differentiation. Differentiated cells also displayed a higher frequency of stalled DNA replication forks and decreased firing of new replication origins from transient inhibition of DNA synthesis by hydroxyurea treatment. In addition, we observed that differentiated cells exhibit a higher frequency of R-loops. A similar decline in DDR was observed as early stage mouse astrocytes differentiated into later stage astrocytes. Our studies thus suggest that DSB repair by homologous recombination is increasingly impaired during stem cell differentiation while the NHEJ pathway is minimally altered.

cell biology