Decoding depression: stress-derived formaldehyde initiates depressive symptoms in mouse and human

Area of Science:

• Neuroscience
• Biochemistry
• Psychiatry

Background:

• Stress is a significant risk factor for major depressive disorder (MDD), often associated with hippocampal damage and neurotransmitter imbalances.
• While exogenous formaldehyde (FA) can induce depressive symptoms, its role in endogenous depression remains unclear.

Purpose of the Study:

• To investigate whether stress-derived endogenous formaldehyde promotes the onset of depression.
• To explore the mechanisms by which formaldehyde affects neuronal function and contributes to depressive behaviors.

Main Methods:

• Quantified endogenous formaldehyde levels in mice and humans under stress using a FA-sensitive fluorescence probe.
• Utilized patch clamp electrophysiology, mass spectrometry, spectrophotometry, and MRI to assess FA's impact on hippocampal CA1 neurons, monoamine levels, and brain structure.
• Analyzed biochemical data from MDD patients and employed bioinformatics and metabolomics to link FA accumulation with depression severity and pathways.

Main Results:

• Stress, particularly involving glutamic acid, triggers formaldehyde production in hippocampal CA1 neurons in cellular and mouse models.
• Excessive formaldehyde buildup leads to depressive behaviors by decreasing extracellular serotonin, dopamine, and melatonin, and by deactivating these monoamines.
• Formaldehyde-induced damage to hippocampal CA1 structure and reduced neuroexcitability were observed, mirroring findings in adolescent MDD patients with hippocampal atrophy and monoamine deficiencies.

Conclusions:

• Stress-derived formaldehyde is a critical trigger for depression onset.
• Formaldehyde inactivates essential monoamine neurotransmitters and impairs hippocampal function, contributing to MDD.
• Blood formaldehyde levels may serve as a predictive biomarker for depression severity.