Stephens, A. | bioRxiv Science

bioRxiv2025

Brain cholesterol metabolites cause significant neurodegeneration in human iPSC-derived neurons

Disrupted cholesterol metabolism is increasingly recognised as a contributing factor in neurodegeneration; however, the specific effects of key brain-derived cholesterol metabolites, 24S-hydroxycholesterol (24S-HC) and 27-hydroxycholesterol (27-HC), remain poorly understood. Using human iPSC-derived i3 cortical neurons, we demonstrate that both 24S-HC and 27-HC significantly impair neuronal calcium signalling by elevating resting calcium levels, reducing spike amplitude, and disrupting network synchrony. These functional deficits are accompanied by widespread organelle dysfunction. Both oxysterols induce mitochondrial fragmentation, decrease spare respiratory capacity, and impair lysosomal degradation. Notably, 27-HC uniquely triggers lysosomal swelling and membrane permeabilisation. Additional signs of cellular stress, including axonal swellings and elevated endoplasmic reticulum calcium levels, were also observed. Furthermore, both 24S-HC and 27-HC were found to directly interact with alpha-synuclein (aSyn), promoting its accumulation in cellular models. In contrast, cholesterol itself had minimal impact, highlighting the distinct toxicity of its hydroxylated metabolites. Together, these findings reveal a mechanistic link between oxysterol accumulation and neuronal dysfunction, supporting the hypothesis that elevated levels of 24S-HC and 27-HC, commonly observed in Parkinsons and Alzheimers disease, may actively drive neurodegenerative processes. Targeting oxysterol metabolism may therefore represent a promising therapeutic avenue for intervention in neurodegenerative disorders.

neuroscience↗

bioRxiv2022

Route of oxytetracycline administration differentially impacts the growth and gut microbiome of pigs co-infected with Bordetella bronchiseptica and Pasteurella multocida

Along with judicious antibiotic use, there is great interest in how the dose regimen of an antibiotic affects the animal gut microbiota. This study evaluated the impact of experimental respiratory infection alone or respiratory infection followed by oxytetracycline (oxytet) treatment on the animals health and its fecal microbiome. Piglets of approximately three weeks-of-age were separated into four groups (n=20 per group). One group remained non-infected and administered non-medicated feed and the other three groups were infected with Bordetella bronchiseptica (day 0) and Pasteurella multocida (day 4), with one group receiving non- medicated feed and the remaining two groups receiving oxytetr starting on day 7 by injection or in-feed (day 7-14). Infection with B. bronchiseptica and P. multocida negatively impacted piglet growth and induced mild pneumonia. Infection alone had minimal effect on the fecal microbiota community. When oxytet was administered either by injection or in-feed to treat the respiratory infections, both routes had minimal effect on clearing B. bronchiseptica and P. multocida in the animal. However, both routes appeared to limit lung lesion severity, and injected oxytet reduced the negative impact of infection on weight gain. Both routes had limited impact on the animals overall gut microbiome, including relative abundances of bacterial taxa and antibiotic resistance genes tet32, tetW, and aph2. Overall, oxytet administered by either route did not clear the respiratory infection, but oxytet administration minimized the negative health impacts of infection and had minor impact on the pig gut microbiome. ImportanceEfforts to address antibiotic resistance calls for improved antibiotic stewardship, including considering antibiotic administration route. While our previous study found in-feed oxytet had greater impact on the gut microbiome of healthy piglets than injected oxytet, it remained unknown if oxytet treatments would have the same impact on the microbiota of infected piglets. We evaluated the impact of respiratory infection alone or respiratory infection followed by oxytet treatment on the animals health and their gut microbiome profile. Respiratory infection negatively affected piglets health, but infection alone had minimal impact on the gut community. When oxytet was administered either in-feed or by injection to treat the respiratory infection, neither route of administration led to the clearance of the respiratory pathogens. However, oxytet minimized the negative health impacts of infection, and had minor impact on the pig gut microbiome. These findings are informative for disease management in food animals while integrating antibiotic stewardship practices.

microbiology↗