Accumulating evidence indicates that oxidative and nitrosative stress (O&NS) pathways play a key role in the pathophysiology of bipolar disorder (BD) and major depressive disorder (MDD). However, only a handful of studies have directly compared alterations in O&NS pathways among patients with MDD and BD types I (BPI) and BPII. Thus, the current study compared superoxide dismutase (SOD1), lipid hydroperoxides (LOOH), catalase, nitric oxide metabolites (NOx), malondialdehyde (MDA), and advanced oxidation protein products (AOPP) between mood disorder patients in a clinically remitted state. To this end 45, 23, and 37 participants with BPI, BPII, and MDD, respectively, as well as 54 healthy controls (HCs) were recruited. Z-unit weighted composite scores were computed as indices of reactive oxygen species (ROS) production and nitro-oxidative stress driving lipid or protein oxidation. SOD1, NOx, and MDA were significantly higher in MDD than in the other three groups. AOPP was significantly higher in BPI than in HCs and BPII patients. BPII patients showed lower SOD1 compared to all other groups. Furthermore, MDD was characterized by increased indices of ROS and lipid hydroperoxide production compared to BPI and BPII groups. Indices of nitro-oxidative stress coupled with aldehyde production or protein oxidation were significantly different among the three patient groups (BDII > BDI > MDD). Finally, depressive symptom scores were significantly associated with higher LOOH and AOPP levels. In conclusion, depression is accompanied by increased ROS production, which is insufficiently dampened by catalase activity, thereby increasing nitro-oxidative damage to lipids and aldehyde production. Increased protein oxidation with formation of AOPP appeared to be hallmark of MDD and BPI. In addition, patients with BPII may have protection against the damaging effects of ROS including lipid peroxidation and aldehyde formation. This study suggests that biomarkers related to O&NS could aid in the differentiation of MDD, BPI, and BPII.

Evidence indicates that major depression is accompanied by increased translocation of gut commensal Gram-negative bacteria (leaky gut) and consequent activation of oxidative and nitrosative (O&NS) pathways. This present study examined the associations among chronic apical periodontitis (CAP), root canal endotoxin levels (lipopolysaccharides, LPS), O&NS pathways, depressive symptoms, and quality of life. Measurements included advanced oxidation protein products (AOPP), nitric oxide metabolites (NOx), lipid peroxides (LOOH), -sulfhydryl (SH) groups, total radical trapping antioxidant parameter (TRAP), and paraoxonase (PON)1 activity in participants with CAP, with and without depression, as well as healthy controls (no depression, no CAP). Root canal LPS levels were positively associated with CAP, clinical depression, severity of depression (as measured with the Hamilton Depression Rating Scale (HDRS) and the Beck Depression Inventory) and O&NS biomarkers, especially NOx and TRAP. CAP-related depression was accompanied by increased levels of NOx, LOOH, AOPP, and TRAP. In CAP participants, there was a strong correlation (r = 0.734, p < 0.001) between root canal LPS and the HDRS score. There were significant and positive associations between CAP or root canal endotoxin with the vegetative and physio-somatic symptoms of the HDRS as well as a significant inverse association between root canal endotoxin and quality of life with strong effects on psychological, environmental, and social domains. It is concluded that increased root canal LPS accompanying CAP may cause depression and a lowered quality of life, which may be partly explained by activated O&NS pathways, especially NOx thereby enhancing hypernitrosylation and thus neuroprogressive processes. Dental health and "leaky teeth" may be intimately linked to the etiology and course of depression, while significantly impacting quality of life.

Accumulating evidence shows that nitro-oxidative pathways play an important role in the pathophysiology of major depressive disorder (MDD) and bipolar disorder (BD) and maybe anxiety disorders. The current study aims to examine superoxide dismutase (SOD1), catalase, lipid hydroperoxides (LOOH), nitric oxide metabolites (NOx), advanced oxidation protein products (AOPP), malondialdehyde (MDA), glutathione (GSH), paraoxonase 1 (PON1), high-density lipoprotein cholesterol (HDL), and uric acid (UA) in participants with and without generalized anxiety disorder (GAD) co-occurring or not with BD, MDD, or tobacco use disorder. Z unit-weighted composite scores were computed as indices of nitro-oxidative stress driving lipid and protein oxidation. SOD1, LOOH, NOx, and uric acid were significantly higher and HDL and PON1 significantly lower in participants with GAD than in those without GAD. GAD was more adequately predicted by increased SOD + LOOH + NOx and lowered HDL + PON1 composite scores. Composite scores of nitro-oxidative stress coupled with aldehyde and AOPP production were significantly increased in participants with comorbid GAD + MDD as compared with all other study groups, namely MDD, GAD + BD, BD, GAD, and healthy controls. In conclusion, GAD is characterized by increased nitro-oxidative stress and lipid peroxidation and lowered lipid-associated antioxidant defenses, while increased uric acid levels in GAD may protect against aldehyde production and protein oxidation. This study suggests that increased nitro-oxidative stress and especially increased SOD1 activity, NO production, and lipid peroxidation as well as lowered HDL-cholesterol and PON1 activity could be novel drug targets for GAD especially when comorbid with MDD.

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Lowered levels of IgM responses to MDA during pregnancy are accompanied by a reduced regulation of nitro-oxidative processes thereby explaining increased oxidative and nitrosative stress biomarkers in association with DPSS. IgM responses to NO adducts, which reflect nitrosylation as a consequence of increased NO production, regulate DPSS symptoms at the end of term and are a trait marker of major depression. IgM responses to MDA are a key part of the compensatory anti-inflammatory responses system.