Countering xylazine damage with natural products targeting cholinergic receptors

About This Grant

SUMMARY This R21 application is in response to the NIH Notice of Special Interest (NOSI, NOT-DA-24-012) to understand xylazine misuse and consequences. Co-use of xylazine with opioids (frequently fentanyl) has become a major threat to human health in the United States. No FDA-approved medications, including the opioid overdose reversal medication naloxone, have efficacy in reversing xylazine’s effects. Although xylazine is a known non- selective agonist of α2-adrenergic receptors (α2-ARs), none of the α2-AR antagonists can effectively reverse all deleterious effects induced by xylazine, from central nervous system depression to severe skin lesions and infection, suggesting that most harmful manifestations of xylazine probably result from xylazine’s action on receptors other than α2-AR. The goal of this application is to fill a critical knowledge gap in understanding the pharmacological and pathological impact of xylazine and identify effective compounds that are proven "safe for human use" and can offset xylazine-caused damage. On which major receptors other than α2-AR does xylazine act? What are the functional consequences and immune responses due to xylazine’s actions? What compounds can effectively reverse damage induced by xylazine? We strive to answer these questions. Our preliminary studies show that xylazine inhibits α7 nicotinic acetylcholine receptors (α7nAChRs) and the inhibition can be offset by a class of natural products. Inhibiting Ca2+-conducting α7nAChRs is known to produce a broad spectrum of negative impacts because of the widespread expression of α7nAChRs across various cells in the human body. α7nAChRs play an important role in regulating the central and peripheral nervous systems as well as the cholinergic anti-inflammatory pathway. Here, we will investigate xylazine-induced functional changes of α7nAChR in different types of human cells and identify natural products that can effectively reverse the xylazine- induced functional consequences. We will also investigate xylazine-triggered cell death and inflammatory responses and determine how effectively the identified natural products reverse xylazine-caused damage. The influence of fentanyl on xylazine’s effects will be investigated to provide much needed insight into complications from xylazine-opioid misuse. Cell types to be investigated include human neural and skin cells that natively express α7nAChRs and opioid receptors and are clinically relevant to the organs and tissues linked to the deleterious effects of xylazine. The outcomes from the proposed studies will broaden the current understanding of xylazine misuse and lead to potential treatment strategies for rapid therapeutic deployment to xylazine/opioid users.