Biology subjects

Rajabi, H.

Publications and source records attributed to Rajabi, H..

6 recordsLinked to original sources

bioRxiv2025

PM2.5 Exposure Facilitates SARS-CoV-2 Infection through ACE2/TMPRSS2 Regulation and Suppression of Anti-Viral Response

BackgroundEpidemiological studies suggest an interaction between air pollution including particulate matter <2.5 {micro}m (PM2.5) and coronavirus disease 2019 (COVID-19) mortality and morbidity; however, the underlying mechanisms are not clear. The aim of our study was to investigate effects of PM2.5 on viability, epithelial integrity, and cellular entry of SARS-CoV-2 into airway epithelial cells, and the mechanisms involved. MethodsWe exposed Calu-3 airway epithelial cell cultures to PM2.5 (10, 50, and100 {micro}g/ml) and SARS-CoV-2 (MOI 0.01) for 24 h. The viability of Calu-3 cells and epithelial barrier integrity were determined using MTT assay and immunofluorescence staining for Zonula Occludens-1, respectively. mRNA expression for viral entry-related genes such as angiotensin converting enzyme (ACE)2 and transmembrane protease, serine (TMPRSS)2, and inflammatory and inflammasomal genes, including interleukin (IL)-8,IL-6, nuclear factor (NF)-{kappa}B p65 (RELA), JNK, c-JUN, Caspase-1, IL-1{beta}, NLRP3, was analyzed by qRT-PCR. Intracellular viral spike protein intensity and RNA-dependent RNA polymerase (RdRP) expression were determined using immunofluorescence staining and qRT-PCR, respectively. ELISA was used to analyze the release of inflammatory cytokines (IL-8, IL-6, and GM-CSF). ResultsHigher concentrations of 100{micro}g/ml PM2.5 decreased Calu-3 cell viability (p=0.02) and deteriorated epithelial barrier integrity, while 50 {micro}g/ml of PM2.5 (p<0.01) induced mRNA expression for ACE2 and TMPRSS2. Although PM2.5 alone decreased c-JUN, it did not alter the expression of mRNA for JNK and RELA. In contrast, a combination of SARS-CoV-2 and PM2.5 led to a significant increase in mRNA for both JNK and RELA (p < 0.05 and p < 0.01, respectively) and attenuated c-JUN expression. Moreover, our results indicated an increase in the expression of IL-1{beta}, IL-6, and GM-CSF following exposure to PM2.5 and PM2.5 + SARS-CoV-2, whereas IL-8 was induced only by SARS-CoV-2 exposure. Co-incubation of Calu-3 cells with PM2.5 and SARS-CoV-2 leads to a decrease in IL-8, IL-1{beta}, Caspase-1 (CASP-1), and Interferon gamma (IFNG) expression. Finally, the viral load (RdRP) also increased in the presence of both PM2.5 and the SARS-CoV-2 group. ConclusionOur findings have demonstrated that PM2.5 impaired epithelial integrity and cell viability, whereas it increased the mRNA expression for ACE2 and TMPRSS2, and induced inflammatory changes in Calu-3 cells incubated with SARS-CoV-2. These findings suggest that PM2.5 can facilitate the entry of SARS-CoV-2 into airway epithelial cells, and that both PM2.5 and SARS-CoV-2 can decrease the inflammatory and antiviral responses of the host cell.

cell biology↗

bioRxiv2025

A neural basis for flexible perceptual inference

What seems obvious in one context can take on an entirely different meaning if that context shifts. While context-dependent inference has been widely studied, a fundamental question remains: how does the brain simultaneously infer both the meaning of sensory input and the underlying context itself, especially when the context is changing? Here, we study flexible perceptual inference--the ability to adapt rapidly to implicit contextual shifts without trial and error. We introduce a novel change-detection task in dynamic environments that requires tracking latent state and context. We find that mice exhibit first-trial behavioral adaptation to latent context shifts driven by inference rather than reward feedback. By deriving the Bayes-optimal policy under a partially observable Markov decision process, we show that rapid adaptation emerges from sequential updates of an internal belief state. In addition, we show that artificial neural networks trained via reinforcement learning achieve near-optimal performance, implementing Bayesian inference-like mechanisms within their recurrent dynamics. These networks develop flexible internal representations that enable real-time adjustments to the inference model. Our findings establish flexible perceptual inference as a core principle of cognitive flexibility, offering computational and neural-mechanistic insights into adaptive behavior in uncertain environments.

neuroscience↗

bioRxiv2025

Endurance training restores ageing-impaired lysosomal biogenesis factors in rest and response to acute exercise in rat skeletal muscle

PurposeLysosomes, crucial for autophagy, play a pivotal role in cellular processes influenced by exercise. This study investigates the impact of ageing on lysosomal function, focusing on Transcription Factor E3 and its regulators, mTORC1 and Calcineurin, emphasizing their response and adaptation to endurance training MethodsTwenty-five male Sprague-Dawley rats were categorised into Young (2 months), Aged sedentary and Aged sedentary single session (18 months), Aged long-term trained, and Aged trained-single session (17 months). Changes in variables were explored concerning sarcopenia by Soleus muscle fibre diameter and number measured via Eosin & Hematoxylin, phosphorylated and total TFE3 protein levels via western blot, mTORC1 and Calcineurin mRNA levels via real-time PCR. ResultsAgeing occurred with increased pTFE3/TFE3total protein (BF=579), declined mTORC1 mRNA (BF=3.99), and muscle diameter (BF=87), signifying sarcopenia and potential contributors. Conversely, Calcineurin mRNA (BF=0.67) and muscle fibre number (BF=0.31) remained unaltered during ageing. Exercise elicited acute responses, reducing pTFE3/TFE3total protein (BF=306), elevating mTORC1 (BF=1.57) and Calcineurin mRNA levels (BF=3.19). Three weeks of endurance training further decreased resting pTFE3/TFE3total protein (BF=174) while increasing Calcineurin mRNA (BF=12) and muscle fibre diameter (BF=126), with no changes in mTORC1 mRNA levels (BF=0.46) and muscle fibre number. Post-exercise, trained rats sustained decreased pTFE3/TFE3total protein (BF=56) and elevated mTORC1 mRNA (BF=1.16). ConclusionThis study underscores the involvement of TFE3, MTORC1, and Calcineurin in sarcopenia, proposing endurance training as an effective strategy to mitigate age-related changes and enhance muscle function in aged rats. Additionally, it suggests impairments in TFE3 possibly contribute to sarcopenia. key pointO_LIGiven the pivotal role lysosomes play in multiple homeostatic processes, investigating mTORC1, Calcineurin, and TFE3, an overlooked lysosome biogenesis factor involved in the metabolic effects of exercise, could help understand the metabolic state of sarcopenia and the role exercise plays. C_LIO_LIThrough eosin & hematoxylin, western blotting and real-time PCR, we found Ageing results in sarcopenia, reduced TFE3 activity and mTORC1 gene expression. C_LIO_LIWe saw a single bout of Endurance training elicited a response by increasing TFE3 protein activation, mTORC1, and Calcineurin gene expression, which is directed to improved sarcopenia. C_LIO_LIThree weeks of endurance training improved sarcopenia and was accompanied by elevated resting levels of TFE3 protein activation, and Calcineurin gene expression. C_LIO_LIEndurance training was still able to elicit post exercise response in TFE3 protein activation, and Calcineurin gene expression. C_LIO_LIEndurance training is a beneficial for sarcopenia, and TFE3 protein is a major player in inducing its effects. C_LI

cell biology↗

bioRxiv2024

Monitoring transcription of miR-15a and miR-124 in mesenchymal stem cells from adipose tissue origin differentiated into pancreatic beta-cells

MicroRNAs are small noncoding pieces of nucleic acid with the potential to control mRNA translation. These sequences participate in the regulation of cell dynamic growth and differentiation. In this study, the expression of miR-15a and miR-124 was monitored in adipose-derived tissue stem cells committed to pancreatic {beta} cells in vitro over 28 days. In the current experiment, adipose-derived mesenchymal stem cells were incubated in an induction medium to accelerate differentiation toward endocrine pancreatic lineage for 28 days with a three-stage protocol. To confirm the efficient trans-differentiation of stem cells into pancreatic {beta} cells, we performed a Dithizone staining, a zinc chelating agent, and pancreas-specific hormones (insulin and C peptide) examination via electrochemiluminescence. Real-time PCR analysis was done to assess the expression of miR-15a and miR-124. Dithizone staining confirmed a successful orientation of adipose-derived mesenchymal stem cells into pancreatic {beta} cells indicating with red to strong brown appearance compared to negative control stem cells, indicating insulin positivity in differentiating cells. These effects were prominent by time and reached maximum level at day 28. Concurrently, the expression of both miR-15a and miR-124 was induced and reached a peak expression level at the end stage of the experiment compared to the stem cells (p<0.05). ConclusionThe dynamic of distinct miRNAs, in particular, miR-15a and miR-124 was induced during pancreatic {beta} cells derivation of adipose-derived mesenchymal stem cells.

cell biology↗

bioRxiv2020

Hunting with catapults: the predatory strike of the dragonfly larva

Dragonfly larvae capture their prey with a strongly modified -extensible- mouthpart using a biomechanically unique but not yet understood mechanism. The current opinion of hydraulic pressure being the driving force of the predatory strike can be refuted by our manipulation experiments and reinterpretation of former studies. On this fact, we present evidence for a synchronized dual-catapult system powered by two spring-loaded catapults. The power output of the system exceeds generally the maximum power achievable by musculature. Energy for the movement is stored by straining a resilin-containing structure at each joint and possibly the surrounding cuticle which is preloaded by muscle contraction. To achieve the precise timing required to catch fast-moving prey, accessory structures are used to lock and actively trigger the system, ensuring the synchronisation of both catapults. As a proof of concept, we developed a bio-inspired robotic arm resembling the morphology and functional principle of the extensible mouthpart. Our study elucidates the predatory strike of dragonfly larvae by proposing a novel mechanism, where two synchronized catapults power the ballistic movement of prey capturing in dragonfly larvae – a so-called synchronized dual-catapult system. Understanding this complex biomechanical system may further our understanding in related fields of bio inspired robotics and biomimetics.One Sentence Summary The synchronized dual-catapult, a biomechanically novel mechanism for the ballistic movement of prey capturing in dragonfly larvaeCompeting Interest StatementThe authors have declared no competing interest.View Full Text

zoology↗

bioRxiv2020

A ballistic pollen dispersal strategy hidden in stylar oscillation

Asteraceae, the most successful flowering plant family, is adapted to the vast range of ecological niches. Their adaptability is partially based on their strong ability of reproduction. The initial, yet challenging, step for plant reproduction is to transport pollen to flower-visiting pollinators. Using quantitative experiments and numerical simulations, here we show that the common floral feature of Asteraceae, a pollen-bearing style, serves as a ballistic lever for catapulting pollen grains to pollinators. This is likely to be a pollination strategy to propel pollen to blind spots of pollinators bodies, which are beyond the physical reach of the styles. Our results suggest that the specific morphology and length of the floret, as well as the pollen adhesion, avoid pollen waste by catapulting pollen within a certain range equal to the size of a flowerhead. The insights into the functional floral oscillation may shed light on the superficially unremarkable, but ubiquitous functional floral design of Asteraceae.

plant biology↗