Author ORCID Identifier

https://orcid.org/0000-0002-6801-8085

Date Available

7-30-2024

Year of Publication

2024

Degree Name

Doctor of Philosophy (PhD)

Document Type

Doctoral Dissertation

College

Medicine

Department/School/Program

Pharmacology and Nutritional Sciences

First Advisor

Analia Loria

Abstract

Opioid use disorder (OUD), one of the greatest public health threats in the US, requires urgent attention. In 2022, the CDC reported 107,941 overdose deaths, over 70% attributed to synthetic opioids such as fentanyl (FEN). An alarming increase in opioid use disorder (OUD) diagnoses in pregnant people resulted in a 5-fold rise in cases of neonatal opioid withdrawal syndrome (NOWS). This condition elicits sympathetic overactivity, neural hyperexcitability, and a stress reaction characterized by tachycardia and hypertension. Whether prenatal exposure to fentanyl induces cardiovascular dysfunction in the offspring remains undetermined, impeding the timely development of strategies to mitigate OUD-related health risks in this vulnerable population.

In the general population, OUD doubles the risk of developing cardiovascular disease, metabolic-like syndrome, dyslipidemia, and atherogenesis while increasing the risk of coronary artery disease by 16%. Preclinical reports have shown that opiates and the endogenous opioid system (EOS), which comprises opioid receptors (mu, delta, Kappa) and endogenous opioid peptides (enkephalins, dynorphins, endorphins), are critical modulators of cardiovascular and metabolic function in both normotensive and hypertensive states. In the fetus, natural and synthetic opioids can cross the placenta and blood-brain barrier, exposing infants to short and long-term health risks, including premature or still-births, NOWS, and altered neurodevelopment. However, the transplacental effects of opioids on the offspring's cardiometabolic outcomes are poorly understood in the clinical and non-clinical literature. Therefore, this body of work aimed to develop preclinical OUD paradigms to investigate the effects of prenatal opioid exposure on the cardiometabolic outcomes of the offspring, identify potential underlying mechanisms, and test therapeutic approaches.

First, we developed an animal model exposing Sprague Dawley dams with ramping doses of morphine (MOR), a typical mu-opioid receptor agonist, using 5-20mg/kg/day. A single MOR injection (5mg/kg/day, s.c.) from gestational day 1 (GD1-3) and increasing 5 mg/kg/day every 5 days from GD4 to 19. Prenatally, MOR-exposed adult female and male rats showed increased conscious mean arterial pressure (MAP) and sympathetic index, which were measured using arterial catheters, impaired vascular function, insulin resistance, glucose intolerance, increased low-density lipoprotein, and reduced renal function.

Second, we developed a FEN self-administration (SA-FEN) paradigm to enhance further the translatability of the prenatal OUD model, where dams develop opioid dependence prior to conception and FEN-SA is continued until GD 14. Pups were video-recorded from postnatal days (PND) 1, 3, and 5. Somatic withdrawal signs were quantified to determine the global withdrawal score (GWS). The panel included body curls and stretching, foreleg, hindleg, and head movements, locomotion, spasms, and quietness. GWS was increased in FEN-exposed offspring up to postnatal day 5. Treatment with buprenorphine (1-0.2 mg/kg, s.c., 0.2 decrement/day, PND 1-5) trend to reduce GWS in FEN-exposed offspring. The cephalization index, a marker for brain development and is linked to an increased risk of neurodevelopmental disorders, was significantly higher in FEN-exposed offspring compared to VEH-exposed. FEN-exposed offspring displayed increased MAP and sympathetic activity. Additionally, Proenkephalin (PENK), a neurotransmitter that shows inhibitory effects on neuronal activation, protein levels were decreased in brain areas involved in blood pressure regulation. Thus, long-term PENK reduction could potentially contribute to impairing the mechanisms controlling pressor responses.

Third, we tested the effect of prenatal opioid exposure in well-characterized opioid-mediated responses in the adult offspring. Overall, we found that prenatal opioid exposure reduced tolerance development to the hypoactive effect of morphine on locomotion, increased latency of thermal nociception, and increased FEN plasma levels in response to an acute FEN dose, without changes in FEN clearance. Altogether, our data suggest that prenatal opioid exposure permanently alters the response to opioids and pain threshold.

Using these models, we determined that prenatal exposure to opioids increases signs of withdrawal, blood pressure and sympathetic tone, metabolic dysfunction, renal damage, differences in their response to analgesics, molecular changes in cardiovascular regulation, and dysregulation of PENK. Our study identifies the dysregulation of EOS components as a potential link between prenatal opioid exposure and cardiovascular and metabolic dysfunction. Further, we showed that the model developed can serve as a unique tool to test traditional medications used for OUD, and novel non-opioid therapeutic alternatives to improve pregnancy outcomes and offspring health.

Digital Object Identifier (DOI)

https://doi.org/10.13023/etd.2024.343

Funding Information

This study was supported by the Centers of Biomedical Research Excellence (P20 GM1035, Dr. 27-06, Pilot), the Alliance for Diabetes and Obesity Research, Pilot, Substance Use Priority Research Area to Nermin Ahmed, Pilot, the Neuroscience Research Priority Area, Pilot and the Department of Pharmacology and Nutritional Sciences at the University of Kentucky

Download

Share

COinS