Ketamine's mechanism of action with an emphasis on neuroimmune regulation: can the complement system complement ketamine's antidepressant effects?

Over 300 million people worldwide have major depressive disorder (MDD), but only 30-40% achieve remission with standard antidepressants. Ketamine offers rapid relief within hours, unlike weeks for conventional drugs. While many studies focus on ketamine's effects on glutamate, this review highlights its anti-inflammatory actions, especially through the complement system—a part of innate immunity involved in synaptic plasticity. The complement system is linked to depression, with increased complement component 3 (C3) expression found in the prefrontal cortex of suicidal individuals with depression. Given ketamine's anti-inflammatory properties and the complement system's role in glutamate modulation, the review suggests a common link between the complement system and ketamine's mechanism of action.

Study at a glance

Abstract

Over 300 million people worldwide suffer from major depressive disorder (MDD). Unfortunately, only 30-40% of patients with MDD achieve complete remission after conventional monoamine antidepressant therapy. In recent years, ketamine has revolutionized the treatment of MDD, with its rapid antidepressant effects manifesting within a few hours as opposed to weeks with conventional antidepressants. Many research endeavors have sought to identify ketamine's mechanism of action in mood disorders; while many studies have focused on ketamine's role in glutamatergic modulation, several studies have implicated its role in regulating neuroinflammation. The complement system is an important component of the innate immune response vital for synaptic plasticity. The complement system has been implicated in the pathophysiology of depression, and studies have shown increases in complement component 3 (C3) expression in the prefrontal cortex of suicidal individuals with depression. Given the role of the complement system in depression, ketamine and the complement system's abilities to modulate glutamatergic transmission, and our current understanding of ketamine's anti-inflammatory properties, there is reason to suspect a common link between the complement system and ketamine's mechanism of action. This review will summarize ketamine's anti- inflammatory roles in the periphery and central nervous system, with an emphasis on complement system regulation.