Biology subjects

Felth, L.

Publications and source records attributed to Felth, L..

4 recordsLinked to original sources

bioRxiv2025

Dynamic flexibility of the gut microbiota to morphine disturbance enables escape from the stable dysbiosis associated with addiction-like behavior

Although opioids are effective analgesics, they can lead to problematic drug use behaviors that underlie opioid use disorder (OUD). Opioids also drive gut microbiota dysbiosis which is linked to altered opioid responses tied to OUD. To interrogate the role of the gut microbiota in a mouse model of OUD, we used a longitudinal paradigm of voluntary oral morphine self-administration to capture multiple facets of drug seeking and preserve both individual behavioral response and gut microbiota variation to examine associations between these two variables. After prolonged morphine consumption, only a subset of mice transitioned to a state we define statistically as compulsive. In compulsive mice, morphine fragmented the microbiota networks which subsequently reorganized to form robust novel connections. In contrast, the communities of non-compulsive mice also changed but were highly interconnected during morphine disturbance and maintained more continuity post morphine suggesting dynamic flexibility. Compulsive mice displayed a greater loss of functional diversity and a shift towards a new stable state dominated by potential pathobionts, whereas non-compulsive mice better preserved genera associated with gut health and broader functional diversity. These findings highlight how persistent and stable gut microbiota dysbiosis aligns with long-term behavioral changes underlying OUD, potentially contributing to relapse.

microbiology↗

bioRxiv2024

Gut dysbiosis was inevitable, but tolerance was not: temporal responses of the murine microbiota that maintain its capacity for butyrate production correlate with sustained antinociception to chronic voluntary morphine

The therapeutic benefits of opioids are compromised by the development of analgesic tolerance, which necessitates higher dosing for pain management thereby increasing the liability for drug dependence and addiction. Rodent models indicate opposing roles of the gut microbiota in tolerance: morphine-induced gut dysbiosis exacerbates tolerance, whereas probiotics ameliorate tolerance. Not all individuals develop tolerance which could be influenced by differences in microbiota, and yet no study design has capitalized upon this natural variation. We leveraged natural behavioral variation in a murine model of voluntary oral morphine self-administration to elucidate the mechanisms by which microbiota influences tolerance. Although all mice shared similar morphine-driven microbiota changes that largely masked informative associations with variability in tolerance, our high-resolution temporal analyses revealed a divergence in the progression of dysbiosis that best explained sustained antinociception. Mice that did not develop tolerance maintained a higher capacity for production of the short-chain fatty acid (SCFA) butyrate known to bolster intestinal barriers and promote neuronal homeostasis. Both fecal microbial transplantation (FMT) from donor mice that did not develop tolerance and dietary butyrate supplementation significantly reduced the development of tolerance independently of suppression of systemic inflammation. These findings could inform immediate therapies to extend the analgesic efficacy of opioids.

systems biology↗

bioRxiv2023

Deletion of arrestin-3 does not alter compulsive morphine-seeking behavior in an oral operant self-administration paradigm

Opioid drugs are potent analgesics that mimic the endogenous opioid peptides, endorphins and enkephalins, by activating the {micro}-opioid receptor. Opioid use is limited by side effects, including significant risk of opioid use disorder. Improvement of the effect/side effect profile of opioid medications is a key pursuit of opioid research, yet there is no consensus on how to achieve this goal. One hypothesis is that the degree of arrestin-3 recruitment to the {micro}-opioid receptor impacts therapeutic utility. However, it is not clear whether increased or decreased interaction of the {micro}-opioid receptor with arrestin-3 would reduce compulsive drug-seeking. To examine this question, we utilized three genotypes of mice with varying abilities to recruit arrestin-3 to the {micro}-opioid receptor in response to morphine in a novel longitudinal operant self-administration model. We demonstrate that arrestin-3 knockout and wild type mice have highly variable drug-seeking behavior with few genotype differences. In contrast, in mice where the {micro}-opioid receptor strongly recruits arrestin-3, drug-seeking behavior is much less varied. We created a quantitative method to define compulsivity in drug-seeking and found that mice lacking arrestin-3 were more likely to meet the criteria for compulsivity whereas mice with enhanced arrestin-3 recruitment did not develop a compulsive phenotype. Our data suggest that opioids that engage both G protein and arrestin-3, recapitulating the endogenous signaling pattern, will reduce abuse liability.

animal behavior and cognition↗

bioRxiv2020

Kinetic-Mechanistic Evidence for Which E. coli RNA Polymerase-{lambda}PR Open Promoter Complex Initiates and for Stepwise Disruption of Contacts in Bubble Collapse

In transcription initiation, specific contacts between RNA polymerase (RNAP) and promoter DNA are disrupted as the RNA-DNA hybrid advances into the cleft, resulting in escape of RNAP. From the pattern of large and small rate constants for steps of initiation at {lambda}PR promoter at 19{degrees}C, we proposed that in-cleft interactions are disrupted in extending 3-mer to 5-mer RNA, -10 interactions are disrupted in extending 6-mer to 9-mer, and -35 interactions are disrupted in extending 10-mer to 11-mer, allowing RNAP to escape. Here we test this mechanism and determine enthalpic and entropic activation barriers of all steps from kinetic measurements at 25{degrees}C and 37{degrees}C. Initiation at 37{degrees}C differs significantly from expectations based on lower-temperature results. At low concentration of the second iNTP (UTP), synthesis of full-length RNA at 37{degrees}C is slower than at 25{degrees}C and no transient short RNA intermediates are observed, indicating a UTP-dependent bottleneck step early in the 37{degrees}C mechanism. Analysis reveals that the 37{degrees}C {lambda}PR OC (RPO) cannot initiate and must change conformation to a less-stable initiation complex (IC) capable of binding the iNTP. We find that IC is the primary {lambda}PR OC species below 25{degrees}C, and therefore conclude that IC must be the I3 intermediate in RPO formation. Surprisingly, Arrhenius activation energy barriers to five steps where RNAP-promoter in-cleft and -10 contacts are disrupted are much smaller than for other steps, including a negative barrier for the last of these steps. We interpret these striking effects as enthalpically-favorable, entropically-unfavorable, stepwise bubble collapse accompanying disruption of RNAP contacts. SignificanceTranscription initiation is highly regulated. To understand regulation, mechanisms of initiation and escape of RNA polymerase (RNAP) from the promoter must be understood. RNAP forms a highly-stable open complex (RPO) with {lambda}PR promoter at 37{degrees}C. From experiments determining effects of temperature on rate constants for each step of RNA synthesis, we find that RPO cannot bind the initiating nucleotides, that the I3 intermediate and not RPO is the initiation complex, and that contacts of RNAP with single-stranded DNA of the discriminator and -10 region and with -35 duplex DNA are disrupted stepwise as the RNA-DNA hybrid moves into the cleft. Evidence is obtained for stepwise bubble collapse and base stacking accompanying disruption of interactions of the single-stranded discriminator and -10 regions with RNAP.

biochemistry↗