Pusan National University Researchers Identify the Brain Enzyme That Drives Nicotine Addiction and Smoking Dependence

Researchers uncover how overlooked glial cells regulate nicotine-dependent behavior, pointing toward future smoking cessation-related research

BUSAN, South Korea, Dec. 4, 2025 /PRNewswire/ -- Nicotine addiction remains one of the most persistent global health challenges, yet the cellular mechanisms underlying it are less explored. Now, researchers have discovered that astrocytes, glial cells in the brain thought to play only a passive role, actively contribute to the brain changes triggered by repeated nicotine exposure. The findings provide insights into nicotine-induced changes in the brain by an enzyme that regulates a key glutamate-related pathway linked to sensitized behavior.

Nicotine addiction remains one of the most persistent public health challenges worldwide, driven by changes in the brain that reinforce repeated use and make quitting extremely difficult. For decades, scientists have focused primarily on neurons to explain how these changes occur. But growing evidence suggests that other brain cells may play a far more active role in shaping addictive behavior than previously thought.

Building on this shift in understanding, a team of researchers led by Professor Eun Sang Choe from the Department of Biological Sciences, Pusan National University, Republic of Korea, has uncovered how astrocytes actively contribute to nicotine-induced brain changes, revealing a previously overlooked mechanism involving astrocytic glutamine synthetase (GS). GS is an essential enzyme for regulating glutamate, the brain's primary excitatory neurotransmitter. The study was published online in the journal of Acta Pharmaceutica Sinica B on 25 September 2025.

"Most of the studies on nicotine addiction traditionally focus on neurons, while neglecting the role of glial cells. Our innovative study demonstrates that astrocytes interact with neurons within the brain's reward system to regulate nicotine-dependent behavior, advancing the current understanding of nicotine addiction," says Prof. Choe.

In this study, researchers repeatedly injected rat models with nicotine and found that nicotine exposure stimulated α7 nicotinic acetylcholine receptors on astrocytes of the caudate and putamen region of brain, initiating a surge in intracellular calcium. This rise in calcium led to activation of phosphorylated c-Jun N-terminal kinase (pJNK), a signaling molecule known to respond to cellular stress and drug exposure. Once activated, JNK further interacted with the metabotropic glutamate receptor 1a (mGluR1a), boosting GS activity and activating the glutamate-glutamine pathway, leading to enhanced locomotor sensitization.

A custom-designed inhibitory peptide was used to block the interaction between pJNK and mGluR1a. When this peptide was administered directly into the caudate and putamen of rats repeatedly exposed to nicotine, the usual increase in GS activity was significantly reduced. Behaviorally, this intervention dampened locomotor sensitization, demonstrating that astrocytic signaling is a key driver of nicotine-induced changes in the brain.

These findings open new directions for addiction research by highlighting the importance of neuron and glia communication. Although nicotine dependence is widely recognized as a disorder of disrupted glutamate signaling, this study shows that astrocytes participate in the molecular processes that reinforce repeated nicotine use. While the work is preclinical, the implications for long-term research are significant.

"While clinical translation of this research will take time and direct human application is uncertain, this work deepens our understanding of nicotine addiction, paving the way for development of therapeutic strategies ultimately supporting smoking-cessation efforts," concludes Prof. Choe.

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