Biology subjects

Costello, H. M.

Publications and source records attributed to Costello, H. M..

3 recordsLinked to original sources

bioRxiv2022

Defining the age-dependent and tissue-specific circadian transcriptome in male mice

Cellular circadian clocks direct a daily transcriptional program that supports homeostasis and resilience. Emerging evidence supports age-associated changes in circadian functions. To define age-dependent changes at the systems level, we profiled the circadian transcriptome in the hypothalamus, lung, heart, kidney, skeletal muscle, and adrenal gland in 3 age groups. We found age-dependent and tissue-specific clock output changes. Aging reduced the number of rhythmically expressed genes (REGs), indicative of weakened circadian control. Many genes gained rhythmicity in old tissues, reflecting an adaptive response. REGs were enriched for the hallmarks of aging, adding a new dimension to our understanding of aging. Differential gene expression analysis found that there were temporally distinct clusters of genes in tissue-specific manner. Increased daily gene expression variability is a common feature of aged tissues. This novel analysis extends the landscape of the understanding of aging and highlights the impact of aging on circadian clock function and temporal changes in gene expression. HIGHLIGHTS- Rhythmically expressed genes (REGs) in Young, but not Old mice, are enriched for the aging hallmarks across all tissues. - The numbers of REGs decline across all tissues with age implicating the circadian clock in altered homeostasis. - Age- and tissue-specific differentially expressed genes (DEGs) cluster at specific times of the day. - Increase in gene expression variability over a day is a common feature of aging tissues.

genomics↗

bioRxiv2022

High salt intake activates the hypothalamic-pituitary-adrenal axis, amplifies the stress response, and alters tissue glucocorticoid exposure in mice

High salt intake is common and contributes to poor cardiovascular health. Sustained cortisol excess also induces an adverse cardiovascular profile. Urinary cortisol excretion positively correlates with urinary sodium excretion. We hypothesised that this was due to hypothalamic-pituitary-adrenal axis activation by high salt intake. In male C57BL6/J mice, 2 weeks of high salt intake increased Crh and Pomc mRNA abundance in the hypothalamus and anterior pituitary, respectively and caused a sustained rise in plasma corticosterone. Plasma copeptin and anterior pituitary V1b receptor mRNA expression was elevated, which may contribute to basal HPA axis activation. Additionally, high salt intake amplified glucocorticoid response to restraint stress, indicative of enhanced HPA axis sensitivity. In the periphery, high salt intake reduced the binding capacity of corticosteroid-binding globulin, enhancing glucocorticoid bioavailability. Within several tissues, the expression of glucocorticoid-regenerating enzyme, 11{beta}-hydroxysteroid dehydrogenase type 1, was increased and the glucocorticoid receptor downregulated. Overall, high salt intake increased glucocorticoid exposure in the hippocampus, anterior pituitary and liver. Chronic high salt intake amplifies basal and stress-induced glucocorticoid levels and resets glucocorticoid biology centrally, peripherally and within cells. This shows direct connectivity between salt homeostasis and HPA axis function. The cumulative effect is likely maladaptive and may contribute to the long-term health consequences of a high salt diet.

physiology↗

bioRxiv2021

Synchronization Temperature Determines the Location of RSV Fusion During Entry in Cultured Cells

Respiratory syncytial virus (RSV) is the most frequent cause of bronchiolitis in children under five years of age. No vaccines against this virus are currently available. RSV infection of a cell is initiated by fusion between the virion membrane and a cellular membrane, but it is not clear if the fusion process takes place at the plasma membrane or within an endosome. Most such experiments have been initiated at the traditional synchronization temperature of 4{degrees}C, an abnormal temperature for animal cells and one at which cellular homeostasis may be negatively affected. We have compared two synchronization temperatures (4{degrees}C and 22{degrees}C) to determine the kinetics of RSV entry into human bronchial epithelial cells. Following inoculation, virus entry was halted at different times by the addition of neutralizing antibody or temperature reduction to 4{degrees}C. We engineered a virus that encodes an extra viral gene, beta-lactamase fused to the viral phosphoprotein (P), to enable rapid detection after infection initiation. We found that the synchronization temperature used during inoculation determines the site of fusion. Transition from 4{degrees}C to 37{degrees}C resulted in RSV entry via the endosomal pathway but also induced F-actin disruption and plasma membrane blebbing, whether the cells were inoculated with RSV or not. Transition from 22{degrees}C to 37{degrees}C resulted in RSV entry by fusion at the plasma membrane and without the F-actin and plasma membrane disruptions. These results suggest that RSV normally enters cells by fusion at the plasma membrane and that the induction of endocytosis by infection synchronization at 4{degrees}C may be an artefact caused by distortion of the plasma membrane-supporting cytoskeleton. Author SummaryIn order to understand the overall mechanism driving infection, it is important to determine how the virus enters cells. The pathway that RSV uses to infect cells is unclear. It is a common practice to attach the virions at 4{degrees}C to synchronize the viral infection. In this report, we found that warming up primary cultures of undifferentiated normal human bronchial epithelial cells to 37{degrees}C from 4{degrees}C triggered dramatic changes in their cell membrane and cytoskeleton totally unrelated to the presence of the virions. The assessment of viral content delivery to the cytoplasm using RSV engineered to express BlaM allowed us to find that the virions attached at 4{degrees}C or 22{degrees}C fused their envelope with endosome or plasma membrane, respectively. Consequently, the entry via endosome after attachment at 4{degrees}C is an experimental artefact and RSV infects by fusing its envelope with the plasma membrane. The implications go beyond RSV since the entry of several virus species have been explored by synchronizing the infection after attachment at 4{degrees}C.

microbiology↗