Biology subjects

Karatsoreos, I. N.

Publications and source records attributed to Karatsoreos, I. N..

8 recordsLinked to original sources

bioRxiv2026

ThermoClock: A Novel Automated Temperature Regulation Device that Can Model Circadian Entrainment and Disruption in 2D and 3D in Vitro Models

Circadian rhythms are critical for maintaining homeostasis and regulating physiological functions, and consequentially impact disease progression; yet, they remain largely overlooked in in vitro models used in preclinical research. One major barrier to rigorously testing the role of circadian rhythms in these models is the lack of accessible tools that seamlessly integrate into standard culture setups and are capable of sustainably delivering time cues to cells and tissues in long term experiments. Here, we present the ThermoClock, a low-cost, Arduino-based automated temperature control system capable of delivering independent temperature programs to multiple cultures simultaneously. Using circadian reporter U2OS cell lines (Bmal1:Luc and Per2:Luc), we demonstrated that ThermoClock-driven temperature cycles (36{degrees}C/38.5{degrees}C, 12h:12h) produced significantly higher amplitude entrainment than a programmable incubator delivering identical temperature trajectories, suggesting that the ramp time to setpoint is a critical determinant of entrainment strength. We further applied ThermoClock to skin explants from keratinocyte-specific Dbp:Luc reporter mice, showing that circadian temperature cycles (T24: 12h:12h and T25: 12.5h:12.5h) extended synchronized circadian rhythms ex vivo, while a shortened T-cycle (T20: 10h:10h) induced rhythm disruptions. We also observed reduced cell migration in T20 temperature-entrained explants wounded ex vivo, closely recapitulating attenuated wound healing observed in T20 light-cycle-disrupted mice in vivo. Finally, we show that wounding can act as a phase-resetting cue but its efficacy depends on pre-injury entrainment state, with circadian entrained tissues (T25) resisting reset, while disrupted (T20) and unentrained tissues showed resetting sensitivity. These findings establish ThermoClock as a versatile platform for incorporating circadian regulation and, for the first time, disruption into 2D and 3D in vitro systems and demonstrate that peripheral clock disruption and its functional consequences can be modeled ex vivo.

bioengineering↗

bioRxiv2025

Endocannabinoid signaling is a critical link between circadian desynchronization and metabolic dysfunction

It is well documented that disruption of circadian rhythms can cause metabolic dysregulation, but the specific mechanisms involved remain unclear. Our findings demonstrate that the negative metabolic effects of environmental circadian desynchronization (ECD) are dependent upon the cannabinoid receptor 1 (CB1r). The endocannabinoid system has not previously been implicated in mediating the effects of circadian disruption. We showed that ECD induced a positive correlation between the levels of the endocannabinoids AEA and 2-AG in both plasma and liver. While global CB1r knockout protects against the metabolic effects of ECD, behavioral and physiological response to ECD was strikingly similar between WT and CB1r KO mice and could not account for their distinct metabolic outcomes. Using liver-specific CB1r KO mice, we further specified that the ECD-induced metabolic hormone disruption, but not weight gain, is mediated through liver CB1r signaling. Finally, we showed that ECD upregulated transcription of genes involved in oxidative phosphorylation in the liver of WT, but not liver-specific CB1r KO mice. In summary, ECD led to modular metabolic dysfunction through CB1r signaling in multiple tissues, with the liver playing a critical role.

physiology↗

bioRxiv2025

Perinatal circadian desynchronization disrupts sleep and prefrontal cortex function in adult offspring

Sleep and circadian (daily) rhythms impact nearly all aspects of physiology and are critical for optimal organismal function. Disruption of the clock can lead to significant metabolic disorders, neuropsychiatric illness, and cognitive dysfunction. Our lab has previously shown that environmental circadian desynchronization (ECD) in adults alters the anatomical structure and neurophysiological function of prefrontal cortex (PFC) neurons, PFC mediated behaviors, as well as sleep quality. As the PFC undergoes significant development in utero and early life, and maternal disturbances during this period can have significant long-term ramifications, we hypothesized that disrupting the circadian environment of dams during the perinatal period would alter sleep and PFC function in adult offspring. Using a mouse model of ECD we investigated how perinatal ECD (pECD) modulates sleep quality in adult offspring. We also determined how pECD impacts PFC neural function in adult offspring using ex vivo patch-clamp electrophysiology, exploring how pECD alters synaptic function and action potential dynamics. We found that male pECD mice trended toward increased total sleep during the inactive (light) period with shorter sleep bouts during the active (dark) period. pECD did not change sleep behavior in female mice. Independent of time of day, pECD altered post-synaptic dynamics of excitatory neurotransmitter release onto plPFC pyramidal neurons. There was also a loss of time-of-day effects on cell endogenous properties in male pECD mice. Thus, pECD clearly alters sleep behavior and PFC function in male mice. However, female mice appear protected against the effects of pECD in these measures. Together, these experiments form the foundation for future studies to understand the lifelong neurobehavioral impact of pECD.

neuroscience↗

bioRxiv2024

Acute and Chronic Neural and Glial Response to Mild Traumatic Brain Injury in the Hippocampus

Traumatic brain injury (TBI) is an established risk factor for developing neurodegenerative disease. However, how TBI leads from acute injury to chronic neurodegeneration is limited to post-mortem models. There is a lack of connections between in vitro and in vivo TBI models that can relate injury forces to both macroscale tissue damage and brain function at the cellular level. Needle-induced cavitation (NIC) is a technique that can produce small cavitation bubbles in soft tissues, which allows us to relate small strains and strain rates in living tissue to ensuing acute and chronic cell death, tissue damage, and tissue remodeling. Here, we applied NIC to mouse brain slices to create a new model of TBI with high spatial and temporal resolution. We specifically targeted the hippocampus, which is a brain region critical for learning and memory and an area in which injury causes cognitive pathologies in humans and rodent models. By combining NIC with patch-clamp electrophysiology, we demonstrate that NIC in the Cornu Ammonis (CA)3 region of the hippocampus dynamically alters synaptic release onto CA1 pyramidal neurons in a cannabinoid 1 receptor (CB1R)-dependent manner. Further, we show that NIC induces an increase in extracellular matrix proteins associated with neural repair that is mitigated by CB1R antagonism. Together, these data lay the groundwork for advanced approaches in understanding how TBI impacts neural function at the cellular level, and the development of treatments that promote neural repair in response to brain injury. SIGNIFICANCECurrent models of mild TBI (mTBI) cannot relate injury forces to both macroscale tissue damage and brain function at the cellular level. We combine a microscale injury model in ex vivo brain slices while simultaneously recording glutamatergic inputs onto CA1 hippocampal pyramidal neurons. Post-injury examination of chronic tissue regeneration by astrocytes allow us to connect acute neuronal signaling responses to chronic fibrosis after TBI. These studies provide a new tool for understanding the physiological and molecular responses to TBI and lay the groundwork for future experiments unraveling the synaptic mechanisms that mediate these responses seconds, minutes, and days following injury.

neuroscience↗

bioRxiv2022

Circadian regulation of glutamate release pathways shapes synaptic throughput in the brainstem nucleus of the solitary tract (NTS)

Circadian regulation of autonomic reflex pathways pairs physiological function with the daily light cycle. The brainstem nucleus of the solitary tract (NTS) is a key candidate for rhythmic control of the autonomic nervous system. Here we investigated circadian regulation of NTS neurotransmission and synaptic throughput using patch-clamp electrophysiology in brainstem slices from mice. We found that spontaneous quantal glutamate release on to NTS neurons showed strong circadian rhythmicity, with the highest rate of release during the light phase and the lowest in the dark, that were sufficient to drive day / night differences in constitutive postsynaptic action potential firing. In contrast, afferent-evoked action potential throughput was enhanced during the dark and diminished in the light. Afferent-driven synchronous release pathways showed a similar decrease in release probability that did not explain the enhanced synaptic throughput during the night. However, analysis of postsynaptic membrane properties revealed diurnal changes in conductance; which, when coupled with the circadian changes in glutamate release pathways, tuned synaptic throughput between the light and dark phases. These coordinated pre- / postsynaptic changes encode nuanced control over synaptic performance and pair NTS action potential firing and vagal throughput with time of day.

neuroscience↗

bioRxiv2022

Electrophysiological identification of daily rhythms in the prefrontal cortex

The prefrontal cortex (PFC) is heavily involved in cognitive and emotional processes, including working memory, cognition, stress responses, and fear associated behaviors. Many PFC-associated behaviors are time-of-day dependent, and disruption of daily rhythms negatively impacts these behavioral outputs, yet how the disruption of daily rhythms impacts the fundamental function of PFC neurons, and the mechanism(s) by which this occurs, remains unknown. Using a mouse model, we demonstrate that the activity and action potential dynamics of prelimbic PFC neurons are regulated by time-of-day in a sex specific manner. Further, we show that postsynaptic K+ channels play a central role in mediating these rhythms, suggesting an intrinsic gating mechanism mediating information throughput. Finally, we demonstrate that environmental circadian desynchronization alters the intrinsic functioning of these neurons in part by increasing sensitivity GIRK channel activation. These key discoveries demonstrate daily rhythms contribute to the mechanisms underlying the essential physiology of PFC circuits, and provide potential mechanisms by which circadian disruption may impact the fundamental properties of neurons. Significance StatementDisruption of circadian rhythms, such as shift work and jet lag, are associated with negative physiological and behavioral outcomes, including changes in affective state, cognitive function, learning and memory. The prefrontal cortex (PFC) plays a critical role in these functions, yet how daily rhythms and desynchronization of these rhythms impact the physiology of neurons in the PFC is unknown. Here we demonstrate that daily rhythms impact the physiological function of PFC neurons in a sex-dependent manner, and that environmental circadian desynchronization alters PFC function irrespective of time-of-day. These findings provide not only a physiological context to the neural and behavioral changes associated with circadian desynchronization, but also highlight the importance of considering the temporal dimension in studies of neural circuits.

neuroscience↗

bioRxiv2019

Daily rhythms in lactate metabolism in the medial prefrontal cortex of mouse: Effects of light and aging

Aging is associated with reduced circadian (daily) rhythm amplitude in physiology and behavior, and decreased function of the prefrontal cortex (PFC). Similar effects are seen in younger mice experiencing circadian desynchrony (CD) caused by exposure to 20h light-dark cycles (T20). Given changes in PFC structure/function, underlying metabolic functioning of the PFC may also occur. We aimed to determine whether there are similarities in neurometabolism between Aged and CD mice. Using enzymatic amperometric biosensors, we recorded lactate concentration changes in the medial PFC in freely-behaving mice. Young mice displayed a circadian rhythm of lactate, which was severely blunted by CD, while Aging only changed the rhythm in constant conditions. We simultaneously probed the relationship between arousal state and PFC lactate rhythms, showing relationships between arousal state and lactate concentration, and documenting changes that occurred in CD and aging. Finally, using RT-qPCR, we found changes in genes related to metabolism and plasticity in both Aged and CD mice. Together, these data suggest both Aging and light cycle manipulation can disrupt mPFC neurometabolism.\n\nHighlightsO_LILactate recordings were taken in Aged and circadian desynchronized (CD) mice.\nC_LIO_LILactate displayed a circadian rhythm in Control mice which was blunted in CD mice.\nC_LIO_LIThe sleep state/lactate relationship was influenced by Aging, CD, and light.\nC_LIO_LIBoth Aging and CD changed the expression of genes related to neurometabolism.\nC_LI

neuroscience↗

bioRxiv2018

Cell-autonomous regulation of astrocyte activation by the circadian clock protein BMAL1

Circadian clock dysfunction is a common symptom of aging and neurodegenerative diseases, though its impact on brain health is poorly understood. Astrocyte activation occurs in response to diverse insults, and plays a critical role in brain health and disease. We report that the core clock protein BMAL1 regulates astrogliosis in a synergistic manner via a cell-autonomous mechanism, and via a lesser non-cell-autonomous signal from neurons. Astrocyte-specific Bmal1 deletion induces astrocyte activation in vitro and in vivo, mediated in part by suppression of glutathione-s-transferase signaling. Functionally, loss of Bmal1 in astrocytes promotes neuronal death in vitro. Our results demonstrate that the core clock protein BMAL1 regulates astrocyte activation and function in vivo, elucidating a novel mechanism by which the circadian clock could influence many aspects of brain function and neurologic disease.

neuroscience↗