Biology subjects

Culbert, B. M.

Publications and source records attributed to Culbert, B. M..

5 recordsLinked to original sources

bioRxiv2026

Transcriptional regulation of the rainbow trout spleen corticotropin-releasing factor system in response to inflammatory challenges: roles of NF-kB and cortisol

The corticotropin-releasing factor (CRF) system bidirectionally interacts with cytokines and other immune-related components in mammals. However, the nature of these interactions remains poorly characterized in other vertebrates, including teleost fishes. To gain insight into the relationship between immune responses and the CRF system in teleosts, we explored how CRF system components were transcriptionally regulated in immune organs of rainbow trout (Oncorhynchus mykiss). We first characterized the CRF system in the spleen and head kidney--two primary immune organs in teleosts--and found that many CRF system components were present in both tissues, but splenic expression was consistently greater. Changes in the abundance of splenic CRF system components following vaccination (which transiently stimulated inflammatory responses and cytokine production) indicated contrasting and time-dependent regulation of CRF receptor 1 (CRFR1; suppression) and CRFR2 (stimulation) activities in response to an inflammatory challenge. Using spleen explant cultures, we then evaluated whether these effects were mediated by either of nuclear factor kappa B (NF-{kappa}B; a pro-inflammatory transcription factor) or cortisol (an anti-inflammatory hormone). At baseline, cultured spleens increased cytokine production and exhibited transcriptional changes in CRF system components comparable to those observed following vaccination. Cortisol treatment and NF-{kappa}B inhibition both attenuated the rise in cytokine transcription; however, cortisol treatment generally affected transcripts influencing CRFR1 activity, while NF-{kappa}B inhibition reduced CRFR2 activity. Overall, our data provide novel insight into CRF system regulation in the spleen and suggest that cortisol and inflammatory cytokines differentially regulate CRFR1 and CRFR2 activity within this organ.

physiology↗

bioRxiv2026

Stressor- and tissue-specific regulation of the corticotropin-releasing factor system across epithelial tissues in rainbow trout

The corticotropin-releasing factor (CRF) system is a major neural regulator of stress responses in vertebrates. However, stress-related roles for the CRF system in other tissues--and whether these roles vary between stressor types--remain unclear. To address this gap, we first characterized the CRF system in the gills and intestine of rainbow trout (Oncorhynchus mykiss) and then evaluated how it is transcriptionally regulated following either an immune (vaccination) or osmotic (seawater transfer) stressor. Additionally, since the CRF system is involved in food intake regulation, we also evaluated whether feeding state affects the intestinal CRF system. Vaccination against Vibrio anguillarum reduced CRF system activity in the intestine--as indicated by elevations in CRF binding protein transcripts paired with reductions in ligand (crfa2) and receptor (crfr1b) transcripts--but did not affect the gill CRF system. In contrast, seawater transfer caused the abundance of most CRF system transcripts to increase in the middle (but not posterior) portion of the intestine, while transcript levels of CRF binding proteins and receptors in the gills declined. Finally, levels of CRF system transcripts in the intestine varied with feeding state in a region-specific manner. In the middle intestine, transcript levels of most components declined with fasting and increased when feeding was resumed, whereas the opposite pattern occurred in the posterior intestine. Overall, our results implicate the peripheral CRF system as a stressor- and epithelial tissue-specific modulator of immune and osmoregulatory functions in teleosts.

physiology↗

bioRxiv2024

Regulation of a unique neuroendocrine complex by environmental salinity in salmonid fishes

The caudal neurosecretory system (CNSS) is a fish-specific neuroendocrine complex whose function(s) remain uncertain despite 60+ years of research. Osmoregulatory roles for the CNSS have been hypothesized, but molecular regulation of the CNSS following changes in environmental salinity remains poorly characterized. Therefore, we performed transcriptomics on the CNSS of rainbow trout (Oncorhynchus mykiss) to establish: 1) how the CNSS responds following seawater (SW) transfer, and 2) which endocrine systems contribute to osmoregulatory responses in the CNSS. Responses following SW transfer varied at 24 h versus 168 h, with changes primarily affecting membrane transport and transcriptional processes at 24 h and neuronal processes at 168 h. Components of several osmoregulation-associated endocrine systems were affected (e.g., corticosteroids), including some which have not previously been identified in the CNSS (e.g., calcitonin). Additionally, transcript levels of corticotropin-releasing factor (CRF) peptides--which have osmoregulatory functions and were highly abundant in the CNSS--were [~]2-fold higher after 24 h in SW. Therefore, we performed additional experiments investigating CRF peptides in a more euryhaline salmonid, Atlantic salmon (Salmo salar). Smolts had up to 12-fold higher levels of CRF peptide transcripts than parr, but abundance declined following SW transfer. Additionally, CRF transcripts were lower 24 h following freshwater transfer of SW-acclimated salmon. These results suggest that CRF peptides acutely aid in coordinating physiological responses following fluctuations in environmental salinity via anticipatory and/or responsive mechanisms. Collectively, our data indicate that CNSS-mediated production of CRF peptides has osmoregulatory functions and provide a resource for investigations of novel CNSS functions.

zoology↗

bioRxiv2022

Social rank influences relationships between hormones and oxidative stress in a cichlid fish

An individuals social environment can have widespread effects on their physiology, including effects on oxidative stress and hormone levels. Many studies have posited that variation in oxidative stress experienced by individuals of different social ranks might be due to endocrine differences, however, few studies have evaluated this hypothesis. Here, we assessed whether a suite of markers associated with oxidative stress in different tissues (blood, plasma, liver, or gonads) had social rank-specific relationships with circulating testosterone or cortisol levels in males of a cichlid fish, Astatotilapia burtoni. Across all fish, blood DNA damage (a global marker of oxidative stress) and gonadal synthesis of reactive oxygen species (as indicated by NADPH-oxidase (NOX) activity) were lower when testosterone was high. High DNA damage in both the blood and gonads was associated with high cortisol in subordinates, but low cortisol in dominants. Additionally, high cortisol was associated with greater production of reactive oxygen species (greater NOX activity) in both the gonads (dominants only) and liver (dominants and subordinates). In general, high testosterone was associated with lower oxidative stress across both social ranks, whereas high cortisol was associated with lower oxidative stress in dominants and higher oxidative stress in subordinates. Taken together, our results show that differences in the social environment can lead to contrasting relationships between hormones and oxidative stress.

physiology↗

bioRxiv2019

Behavioral and physiological evidence that increasing group size ameliorates the impacts of social disturbance

Intra-group social stability is important for the long-term productivity and health of social organisms. We evaluated the effect of group size on group stability in the face of repeated social perturbations using a cooperatively breeding fish, Neolamprologus pulcher. In a laboratory study, we compared both the social and physiological responses of individuals from small versus large groups to the repeated removal and replacement of the most dominant group member (the breeder male). Individuals living in large groups were overall more resistant to instability but were seemingly slower to recover from perturbation. Members of small group were more vulnerable to instability but recovered faster. Breeder females in smaller groups also showed greater physiological preparedness for instability following social perturbations. In sum, we recover both behavioral and physiological evidence that living in larger groups helps to dampen the impacts of social instability in this system.\n\nSO_SCPLOWUMMARYC_SCPLOW SO_SCPLOWTATEMENTC_SCPLOWSocial stability is vital for group productivity and long-term persistence. Here, both behavioral and physiological evidence conveys that larger groups are less susceptible to social disturbance.

animal behavior and cognition↗