Microbiome Depletion Increases Fentanyl Self-Administration and Alters the Striatal Proteome Through Short-Chain Fatty Acids

Abstract

Opioid use disorder (OUD) is a public health crisis currently being exacerbated by increased rates of use and overdose of synthetic opioids, primarily fentanyl. Therefore, the identification of novel biomarkers and treatment strategies to reduce problematic fentanyl use and relapse to fentanyl taking is critical. In recent years, there has been a growing body of work demonstrating that the gut microbiome can serve as a potent modulator of the behavioral and transcriptional responses to both stimulants and opioids. Here, we advance this work to define how manipulations of the microbiome drive fentanyl intake and fentanyl-seeking in a translationally relevant drug self-administration model. Depletion of the microbiome of male rats with broad spectrum antibiotics leads to increased drug administration on increased fixed ratio, progressive ratio, and drug seeking after abstinence. Utilizing 16s sequencing of microbiome contents from these animals, specific populations of bacteria from the gut microbiome correlate closely with levels of drug taking. Additionally, global proteomic analysis of the nucleus accumbens following microbiome manipulation and fentanyl administration to define how microbiome status alters the functional proteomic landscape in this key limbic substructure. These data demonstrate that an altered microbiome leads to marked changes in the synaptic proteome in response to repeated fentanyl treatment. Finally, behavioral effects of microbiome depletion are reversible by supplementation of the microbiome derived short-chain fatty acid metabolites. Taken together, these findings establish clear relevance for gut-brain signaling in models of OUD and lay foundations for further translational work in this space.Significance StatementThere is a growing understanding that the resident bacteria in the gut, collectively the gut microbiome, play a role in regulating brain and behavior. Previous work showed that the microbiome can mediate place preference for opioids and can alter gene expression in response to repeated drug exposure. Here, using a self-administration and drug seeking model, we see that depletion of the microbiome enhances motivation to take and seek fentanyl and shifts the dose-response curve for the drug. Additionally, we utilize quantitative global proteomics methods to define how the microbiome alters the synaptic proteome following fentanyl exposure. These studies provide important mechanistic insights to the growing literature on gut-brain signaling in substance use disorders.

Escalation of intravenous fentanyl self-administration and assessment of withdrawal behavior in male and female mice

“…The current study builds upon previous findings and demonstrates that 2 hours of access to 2.5 µg/kg/infusion of fentanyl over 14 days is sufficient to establish escalation of fentanyl intake and result in withdrawal symptoms in mice. Previous literature has investigated rodent models of opioid dependence, including morphine (47)(48)(49), oxycodone (10,12,50,51), heroin (6,(52)(53)(54), remifentanil (34,(55)(56)(57)(58), and fentanyl (24,33,36,38,(59)(60)(61)(62)(63)(64)(65)(66), using various routes of administration, with the majority of studies done in rats. IVSA of fentanyl has been widely studied in rats (24,25,(59)(60)(61)(62)(67)(68)(69)(70)(71), with findings demonstrating mixed results on the development of dependence and withdrawal signs.…”

“…Previous literature has investigated rodent models of opioid dependence, including morphine (47)(48)(49), oxycodone (10,12,50,51), heroin (6,(52)(53)(54), remifentanil (34,(55)(56)(57)(58), and fentanyl (24,33,36,38,(59)(60)(61)(62)(63)(64)(65)(66), using various routes of administration, with the majority of studies done in rats. IVSA of fentanyl has been widely studied in rats (24,25,(59)(60)(61)(62)(67)(68)(69)(70)(71), with findings demonstrating mixed results on the development of dependence and withdrawal signs. One previous study reported that rats undergoing 14 days IVSA of fentanyl for 6 hours per day maintained a consistent rate of self-administration (62).…”

“…One previous study reported that rats undergoing 14 days IVSA of fentanyl for 6 hours per day maintained a consistent rate of self-administration (62). Another study found that rats self-administering fentanyl for 3 hours per day over 10 days exhibited a trend towards increasing reward-associated lever presses (59). A separate study showed that when compared to a short access self-administration period, 12-hour self-administration of fentanyl resulted in escalation of fentanyl intake (25).…”

Long access heroin self-administration significantly alters gut microbiome composition and structure

“…Exposure to morphine during pregnancy (35) or in newborn rats (36) induces a dysbiosis that persists from the neonatal period into adulthood. Other opioids, including oxycodone (37)(38)(39), fentanyl (40,41), and heroin (22), have also been shown to cause dysbiosis in the gut microbiome. The interactions of opioid drugs with the gut microbiome have been also described in numerous review articles (10,(42)(43)(44)(45)(46)(47)(48)(49).…”