Modulation of ER Stress and Inflammation by S-Ketamine, R-Ketamine, and Their Metabolites in Human Microglial Cells: Insights into Novel Targets for Depression Therapy.
Marta Jóźwiak-Bębenista, Anna Wiktorowska-Owczarek, Małgorzata Siatkowska, Piotr Komorowski, Aneta Włodarczyk, Edward Kowalczyk, Paulina Sokołowska
Cells June 3, 2025 DOI: 10.3390/cells14110831 (opens in new tab)
Study at a glance
AI-extracted from the abstract| Characteristics | In vitro study Peer reviewed |
|---|---|
| Population | Human microglial cells (HMC3 cell line) |
| Interventions | S-ketamine R-ketamine 2S 6S-hydroxynorketamine 2R 6R-hydroxynorketamine |
| Topics | Depression Ketamine Esketamine |
| Keywords | Chop Er stress Grp78 Upr pathway Antidepressants Ketamine metabolites Depression treatment Ketamine therapy Neuroinflammation Molecular psychiatry Stress response proteins |
| Citations | 4 |
| Key points | Ketamine enantiomers and their metabolites reduce CHOP and GRP78 expression under ER stress and decrease IL-6 and IL-8 levels in activated microglia. |
Abstract
Despite affecting millions worldwide, major depressive disorder (MDD) remains a therapeutic challenge, with approximately one-third of patients failing to respond to standard treatments. The need for innovative, molecularly driven therapies has turned attention to ketamine and its enantiomers. While S-ketamine is clinically approved for treatment-resistant depression (TRD), it has various psychoactive side effects and potential for abuse. Hence, it is necessary to identify alternative compounds, such as R-ketamine, and their metabolites (e.g., 2S,6S-hydroxynorketamine and 2R,6R-hydroxynorketamine, collectively referred to as HNKs). Emerging evidence suggests that the pathophysiology of MDD involves two processes regulated by the unfolded protein response (UPR): endoplasmic reticulum (ER) stress and neuroinflammation. As such, they represent promising therapeutic targets. The study provides the first direct comparison of ketamine enantiomers and their metabolites in modulating ER stress and inflammatory signaling in human microglial cells (HMC3), which play key roles in neuroimmune communication. Both S-ketamine and R-ketamine, along with their metabolites, significantly reduced both the expression and protein levels of CHOP and GRP78-two critical UPR components-under tunicamycin-induced ER stress conditions. Additionally, the compounds significantly decreased IL-6 levels and, to a lesser extent, IL-8 levels in lipopolysaccharide (LPS)-stimulated microglia, indicating anti-inflammatory potential. Taken together, these findings highlight a novel glia-targeted mechanism by which ketamine and its metabolites modulate ER stress and neuroinflammation. CHOP and GRP78 appear to be stress-responsive molecular markers within the UPR pathway. These results justify further in vivo validation and support the development of antidepressants with fewer psychoactive effects.
Comparable studies
Other preclinical and animal studies on esketamine for depression, most cited first.