CD300f immunoreceptor is associated with major depressive disorder and decreased microglial metabolic fitness.

A role for microglia in neuropsychiatric diseases, including major depressive disorder (MDD), has been postulated. Regulation of microglial phenotype by immune receptors has become a central topic in many neurological conditions. We explored preclinical and clinical evidence for the role of the CD300f immune receptor in the fine regulation of microglial phenotype and its contribution to MDD. We found that a prevalent nonsynonymous single-nucleotide polymorphism (C/T, rs2034310) of the human CD300f receptor cytoplasmic tail inhibits the protein kinase C phosphorylation of a threonine and is associated with protection against MDD, mainly in women. Interestingly, CD300f-/- mice displayed several characteristic MDD traits such as augmented microglial numbers, increased interleukin 6 and interleukin 1 receptor antagonist messenger RNA, alterations in synaptic strength, and noradrenaline-dependent and persistent depressive-like and anhedonic behaviors in females. This behavioral phenotype could be potentiated inducing the lipopolysaccharide depression model. RNA sequencing and biochemical studies revealed an association with impaired microglial metabolic fitness. In conclusion, we report a clear association that links the function of the CD300f immune receptor with MDD in humans, depressive-like and anhedonic behaviors in female mice, and altered microglial metabolic reprogramming.

Antidepressant-like effect of guanosine involves activation of AMPA receptor and BDNF/TrkB signaling.

Guanosine is a purine nucleoside that has been shown to exhibit antidepressant effects, but the mechanisms underlying its effect are not well established. We investigated if the antidepressant-like effect induced by guanosine in the tail suspension test (TST) in mice involves the modulation of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor, voltage-dependent calcium channel (VDCC), and brain-derived neurotrophic factor (BDNF)/tropomyosin receptor kinase B (TrkB) pathway. We also evaluated if the antidepressant-like effect of guanosine is accompanied by an acute increase in hippocampal and prefrontocortical BDNF levels. Additionally, we investigated if the ability of guanosine to elicit a fast behavioral response in the novelty suppressed feeding (NSF) test is associated with morphological changes related to hippocampal synaptogenesis. The antidepressant-like effect of guanosine (0.05 mg/kg, p.o.) in the TST was prevented by DNQX (AMPA receptor antagonist), verapamil (VDCC blocker), K-252a (TrkBantagonist), or BDNF antibody. Increased P70S6K phosphorylation and higher synapsin I immunocontent in the hippocampus, but not in the prefrontal cortex, were observed 1 h after guanosine administration. Guanosine exerted an antidepressant-like effect 1, 6, and 24 h after its administration, an effect accompanied by increased hippocampal BDNF level. In the prefrontal cortex, BDNF level was increased only 1 h after guanosine treatment. Finally, guanosine was effective in the NSF test (after 1 h) but caused no alterations in dendritic spine density and remodeling in the ventral dentate gyrus (DG). Altogether, the results indicate that guanosine modulates targets known to be implicated in fast antidepressant behavioral responses (AMPA receptor, VDCC, and TrkB/BDNF pathway).

NLRP3 inflammasome-driven pathways in depression: Clinical and preclinical findings.

Over the past three decades, an intricate interaction between immune activation, release of pro-inflammatory cytokines and changes in brain circuits related to mood and behavior has been described. Despite extensive efforts, questions regarding when inflammation becomes detrimental or how we can target the immune system to develop new therapeutic strategies for the treatment of psychiatric disorders remain unresolved. In this context, novel aspects of the neuroinflammatory process activated in response to stressful challenges have recently been documented in major depressive disorder (MDD). The Nod-like receptor pyrin containing 3 inflammasome (NLRP3) is an intracellular multiprotein complex responsible for a number of innate immune processes associated with infection, inflammation and autoimmunity. Recent data have demonstrated that NLRP3 activation appears to bridge the gap between immune activation and metabolic danger signals or stress exposure, which are key factors in the pathogenesis of psychiatric disorders. In this review, we discuss both preclinical and clinical evidence that links the assembly of the NLRP3 complex and the subsequent proteolysis and release of the pro-inflammatory cytokines interleukin-1ß (IL-1ß) and interleukin-18 (IL-18) in chronic stress models and patients with MDD. Importantly, we also focus on the therapeutic potential of targeting the NLRP3 inflammasome complex to improve stress resilience and depressive symptoms.

Preventive Effect of Cecropia pachystachya Against Ketamine-Induced Manic Behavior and Oxidative Stress in Rats.

Cecropia species are widely used in traditional medicine by its anti-diabetic, anti-hypertensive and anti-inflammatory properties. In the present study, we investigated the neuroprotective and antioxidant effects of the crude aqueous extract from Cecropia pachystachya leaves in a rat model of mania induced by ketamine. The results indicated that ketamine treatment (25 mg/kg i.p., for 8 days) induced hyperlocomotion in the open-field test and oxidative damage in prefrontal cortex and hippocampus, evaluated by increased lipid peroxidation, carbonyl protein formation and decreased total thiol content. Moreover, ketamine treatment reduced the activity of the antioxidant enzymes superoxide dismutase and catalase in hippocampus. Pretreatment of rats with C. pachystachya aqueous extract (200 and 400 mg/kg p.o., for 14 days) or with lithium chloride (45 mg/kg p.o., for 14 days, used as a positive control) prevented both behavioral and pro-oxidant effects of ketamine. These findings suggest that C. pachystachya might be a useful tool for preventive intervention in bipolar disorder, reducing the episode relapse and the oxidative damage associated with the manic phase of this disorder .

Sex-dependent role of CD300f immune receptor in generalized anxiety disorder.

Generalized Anxiety Disorder (GAD) presents a high prevalence in the population, leading to distress and disability. Immune system alterations have been associated with anxiety-related behaviors in rodents and GAD patients. CD300f immune receptors are highly expressed in microglia and participate not only in the modulation of immune responses but also in pruning and reshaping synapses. It was recently demonstrated that CD300f might be influential in the pathogenesis of depression in a sex-dependent manner. Here, we evaluated the role of CD300f immune receptor in anxiety, using CD300f knockout mice (CD300f-/-) and patients with GAD. We observed that male CD300f-/- mice had numerous behavioral changes associated with a low-anxiety phenotype, including increased open field central locomotion and rearing behaviors, more exploration in the open arms of the elevated plus-maze test, and decreased latency to eat in the novelty suppressed feeding test. In a cross-sectional population-based study, including 1111 subjects, we evaluated a common single-nucleotide polymorphism rs2034310 (C/T) in the cytoplasmatic tail of CD300f gene in individuals with GAD. Notably, we observed that the T allele of the rs2034310 polymorphism conferred protection against GAD in men, even after adjusting for confounding variables. Overall, our data demonstrate that CD300f immune receptors are involved in the modulation of pathological anxiety behaviors in a sex-dependent manner. The biological basis of these sex differences is still poorly understood, but it may provide significant clues regarding the neuropathophysiological mechanisms of GAD and can pave the way for future specific pharmacological interventions.

Depression and peripheral inflammatory profile of patients with obesity.

This narrative review will present and discuss clinical data from 16 cross-sectional and 6 longitudinal studies examining the relationship between body mass index (BMI), symptoms of depression and peripheral inflammation. Our aim is to determine which of obesity and depression contributes best to the peripheral low-grade inflammation frequently associated to both conditions. Studies including a complete evaluation of inflammatory markers are scarce and high levels of interleukin-6 (IL-6) and C-reactive protein (CRP) are the most consistent findings associated with obesity and symptoms of depression. Among the cross-sectional studies, seven studies, including a total of 9421 individuals, pointed to BMI as the major factor associated with systemic low-grade inflammation. However, in four studies, including 16,837 individuals, CRP levels remained associated with the symptoms of depression even after correction for BMI, suggestion that in the absence of overweight or obesity other sources of peripheral inflammation might contribute to presence of depressive symptoms. Additionally, another five studies, including 5569 individuals failed to find an association between depression and peripheral inflammation, reinforcing the heterogeneity of this condition. In the longitudinal data, changes in BMI were associated with a reduction in depressive scores at follow-up, after bariatric surgery or after diet. In four longitudinal studies, high levels of CRP were found to be associated with depression even after adjustment for BMI and weight loss, further corroborating the idea that other sources of peripheral inflammation might contribute to depressive symptoms. Thus it seems that both obesity and depressive symptoms can contribute to peripheral inflammation, and once installed the presence of inflammation can contribute to several behavioral alterations that reinforce the cyclic pattern of co-occurrence observed in patients with obesity and MDD. Future clinical studies should focus on strategic efforts to collect new data and to improve or standardize methods for the evaluation of depression, body composition and a more complete inflammatory profile. These approaches are essential for the development of pharmacological and/or non-pharmacological strategies designed to break this cyclic pattern of co-occurrence.

Cognitive psychotherapy treatment decreases peripheral oxidative stress parameters associated with major depression disorder.

INTRODUCTION: Studies have already pointed out the contribution of oxidative stress in the pathophysiology of major depressive disorder (MDD). The aim of the present study was to investigate the oxidative-antioxidative systems in MDD and in response to cognitive psychotherapies. Oxidative stress were analyzed in 49 MDD patients at baseline, post-treatment, and follow-up; and 49 control subjects without history of psychiatric disorders. RESULTS: MDD subjects presented an increase in oxidative damage related to control subjects for thiobarbituric acid reactive species (TBARS), nitric oxide, and a decrease in total thiol content. Cognitive psychotherapies were able to counteract peripheral oxidative stress in MDD patients, reducing TBARS levels (p<0.001) in the follow-up, nitric oxide (p<0.001) in the post-treatment and follow-up, and increasing the total thiol content (p<0.01) in the post-treatment and follow-up. CONCLUSION: Oxidative stress was associated with MDD and the regulation of these parameters might represent an important mechanism associated with the clinical improvement of cognitive psychotherapy.

Neuroprotective and antioxidant effects of curcumin in a ketamine-induced model of mania in rats.

Bipolar disorder (BD) is a chronic and debilitating illness characterized by recurrent manic and depressive episodes. Our research investigates the protective effects of curcumin, the main curcuminoid of the Indian spice turmeric, in a model of mania induced by ketamine administration in rats. Our results indicated that ketamine treatment (25 mg/kg, for 8 days) induced hyperlocomotion in the open-field test and oxidative damage in prefrontal cortex (PFC) and hippocampus (HP), evaluated by increased lipid peroxidation and decreased total thiol content. Moreover, ketamine treatment reduced the activity of the antioxidant enzymes superoxide dismutase and catalase in the HP. Pretreatment of rats with curcumin (20 and 50 mg/kg, for 14 days) or with lithium chloride (45 mg/kg, positive control) prevented behavioral and pro-oxidant effects induced by ketamine. These findings suggest that curcumin might be a good compound for preventive intervention in BD, reducing the episode relapse and the oxidative damage associated with the manic phase of this disorder.