Mammalian target of rapamycin (mTOR)/nitric oxide system possibly modulate antidepressant-like effect of 17α-ethinyl estradiol in ovariectomized mice

Ginseng total saponins and Fuzi total alkaloids exert antidepressant-like effects in ovariectomized mice through BDNF-mTORC1, autophagy and peripheral metabolic pathways

BACKGROUND

Shenfu decoction (SFD) is a classic Chinese medicine prescription that has a strong cardiotonic effect. The combination of ginseng (the dried root of Panax ginseng C. A. Meyer) and Fuzi (processed product of sub-root of Aconitum carmichaeli Debx), the main constituents of SFD, has been reported to improve the pharmacological effect of each other. Moreover, research has shown that the main active components of SFD, ginseng total saponins (GTS) and Fuzi total alkaloids (FTA), have antidepressant activity. However, the effects of these ingredients on depressive-like behavior induced by ovariectomy, a model of menopausal depression, have not been studied.

PURPOSE

Our research aims to elucidate the antidepressant-like effects of GTS and FTA compatibility (GF) in ovariectomized mice and the potential mechanisms.

METHODS

To elucidate the antidepressant-like effects of GF in mice in ovariectomy condition, behavioral tests were performed after 7 days of intragastric administration of different doses of GF. Underlying molecular mechanisms of CREB-BDNF, BDNF-mTORC1 and autophagy signaling were detected by western blotting, serum metabolites were examined by UPLC-QE plus-MS and dendritic spine density was determined by Golgi-Cox staining.

RESULTS

GF remarkably decreased the immobility time in the forced swim test. GF also increased levels of pCREB/CREB, BDNF, Akt, mTORC1 and p62 in the prefrontal cortex and hippocampus, as well as decreased LC3-II/LC3-I in the prefrontal cortex and hippocampus of ovariectomized mice. Furthermore, 15 serum differential metabolites (9 of which are lipids and lipid molecules) were identified by metabonomics. Next, the antidepressant-like effects of GF was blocked by rapamycin, an inhibitor of mTORC1. The antidepressant actions of GF on levels of pCREB, mTORC1, LC3-Ⅱ/LC3-Ⅰ and p62 in the prefrontal cortex and the levels of BDNF, Akt, mTORC1 and p62 in the hippocampus were inhibited by rapamycin, and the dendritic spines density was also regulated.

CONCLUSION

GF has antidepressant effects in ovariectomized mice, and like other antidepressants, these effects involve activation of BDNF-mTORC1, autophagy regulation and consequent effects on hippocampal synaptic plasticity. Moreover, metabolomic results suggest that GF also has effects on peripheral lipid profiles that may provide potential biomarkers for these antidepressant-like effects. These results indicate that GF is worthy of further exploration as a promising pharmaceutical treatment for depression. This study provides a new direction for the development of new indications for traditional Chinese medicine compounds.

The Role of Sildenafil in Treating Brain Injuries in Adults and Neonates

Sildenafil is a recognized treatment for patients suffering from erectile dysfunction and pulmonary hypertension. However, new evidence suggests that it may have a neuroprotective and a neurorestorative role in the central nervous system of both adults and neonates. Phosphodiesterase type 5-the target of sildenafil-is distributed in many cells throughout the body, including neurons and glial cells. This study is a comprehensive review of the demonstrated effects of sildenafil on the brain with respect to its function, extent of injury, neurons, neuroinflammation, myelination, and cerebral vessels.

Early-life stress induces emotional and molecular alterations in female mice that are partially reversed by cannabidiol

Gender is considered as a pivotal determinant of mental health. Indeed, several psychiatric disorders such as anxiety and depression are more common and persistent in women than in men. In the past two decades, impaired brain energy metabolism has been highlighted as a risk factor for the development of these psychiatric disorders. However, comprehensive behavioural and neurobiological studies in brain regions relevant to anxiety and depression symptomatology are scarce. In the present study, we summarize findings describing cannabidiol effects on anxiety and depression in maternally separated female mice as a well-established rodent model of early-life stress associated with many mental disorders. Our results indicate that cannabidiol could prevent anxiolytic- and depressive-related behaviour in early-life stressed female mice. Additionally, maternal separation with early weaning (MSEW) caused long-term changes in brain oxidative metabolism in both nucleus accumbens and amygdalar complex measured by cytochrome c oxidase quantitative histochemistry. However, cannabidiol treatment could not revert brain oxidative metabolism impairment. Moreover, we identified hyperphosphorylation of mTOR and ERK 1/2 proteins in the amygdala but not in the striatum, that could also reflect altered brain intracellular signalling related with to bioenergetic impairment. Altogether, our study supports the hypothesis that MSEW induces profound long-lasting molecular changes in mTOR signalling and brain energy metabolism related to depressive-like and anxiety-like behaviours in female mice, which were partially ameliorated by CBD administration.

APOE4 genotype exacerbates the impact of menopause on cognition and synaptic plasticity in APOE-TR mice

The impact of sex and menopausal status in Alzheimer's disease remains understudied despite increasing evidence of greater female risk, particularly in APOE4 carriers. Utilizing female APOE-TR mice maintained on a high-fat diet background we induced ovarian failure through repeated VCD injections, to mimic human menopause. At 12 months of age, recognition memory and spatial memory were assessed using object recognition, Y-maze spontaneous alternation, and Barnes maze. A VCD*genotype interaction reduced the recognition memory (P < .05), with APOE4 VCD-treated animals unable to distinguish between novel and familiar objects. APOE4 mice displayed an additional 37% and 12% reduction in Barnes (P < .01) and Y-maze (P < .01) performance, indicative of genotype-specific spatial memory impairment. Molecular analysis indicated both VCD and genotype-related deficits in synaptic plasticity with BDNF, Akt, mTOR, and ERK signaling compromised. Subsequent reductions in the transcription factors Creb1 and Atf4 were also evident. Furthermore, the VCD*genotype interaction specifically diminished Ephb2 expression, while Fos, and Cnr1 expression reduced as a consequence of APOE4 genotype. Brain DHA levels were 13% lower in VCD-treated animals independent of genotype. Consistent with this, we detected alterations in the expression of the DHA transporters Acsl6 and Fatp4. Our results indicate that the combination of ovarian failure and APOE4 leads to an exacerbation of cognitive and neurological deficits.

Activity Dependent Mammalian Target of Rapamycin Pathway and Brain Derived Neurotrophic Factor Release Is Required for the Rapid Antidepressant Effects of Puerarin

Puerarin is a traditional Chinese medicine with beneficial effects of reduced depression-like behaviors in mice with stress. Previous studies also show that puerarin can produce neuroprotective effect via activating the Akt or increased brain-derived neurotrophic factor (BDNF) expression. Interestingly, BDNF and Akt downstream target, mammalian target of rapamycin (mTOR) mediate the fast-acting antidepressant properties of ketamine. Until now, the involvement of the mTOR signaling pathway or BDNF on puerarin-induced antidepressant effect remains unknown. We aimed to investigate whether the antidepressant-like effect induced by puerarin would associate mTOR signaling pathway and BDNF release. The antidepressant-like effects of puerarin were evaluated using the forced swim test. The activation of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionaic acid receptor (AMPAR)-mTOR signaling pathway and release of BDNF in the prefrontal cortex were determined. We also investigated the effect of puerarin on AMPAR trafficking through measuring the PKA phosphorylation of AMPAR subunit GluR1. Our present results show that puerarin exerted antidepressant-like responses that was mediated by AMPAR-induced mTOR signaling pathway and associated with increased BDNF release. Moreover, a significant increase in the GluR1 phosphorylation at its PKA site was noted following puerarin treatment. Our findings are the first to demonstrate that the antidepressant-like actions of puerarin require AMPAR-mTOR signaling pathway activation, are associated with an increased BDNF level and facilitate AMPAR membrane insertion. These findings provide preclinical evidence that puerarin may possess antidepressant property which is mediated by the glutamatergic system.

Pathologic role of nitrergic neurotransmission in mood disorders

Mood disorders are chronic, recurrent mental diseases that affect millions of individuals worldwide. Although over the past 40 years the biogenic amine models have provided meaningful links with the clinical phenomena of, and the pharmacological treatments currently employed in, mood disorders, there is still a need to examine the contribution of other systems to the neurobiology and treatment of mood disorders. This article reviews the current literature describing the potential role of nitric oxide (NO) signaling in the pathophysiology and thereby the treatment of mood disorders. The hypothesis has arisen from several observations including (i) altered NO levels in patients with mood disorders; (ii) antidepressant effects of NO signaling blockers in both clinical and pre-clinical studies; (iii) interaction between conventional antidepressants/mood stabilizers and NO signaling modulators in several biochemical and behavioral studies; (iv) biochemical and physiological evidence of interaction between monoaminergic (serotonin, noradrenaline, and dopamine) system and NO signaling; (v) interaction between neurotrophic factors and NO signaling in mood regulation and neuroprotection; and finally (vi) a crucial role for NO signaling in the inflammatory processes involved in pathophysiology of mood disorders. These accumulating lines of evidence have provided a new insight into novel approaches for the treatment of mood disorders.

Neurodevelopmental Disorders and Environmental Toxicants: Epigenetics as an Underlying Mechanism

The increasing prevalence of neurodevelopmental disorders, especially autism spectrum disorders (ASD) and attention deficit hyperactivity disorder (ADHD), calls for more research into the identification of etiologic and risk factors. The Developmental Origin of Health and Disease (DOHaD) hypothesizes that the environment during fetal and childhood development affects the risk for many chronic diseases in later stages of life, including neurodevelopmental disorders. Epigenetics, a term describing mechanisms that cause changes in the chromosome state without affecting DNA sequences, is suggested to be the underlying mechanism, according to the DOHaD hypothesis. Moreover, many neurodevelopmental disorders are also related to epigenetic abnormalities. Experimental and epidemiological studies suggest that exposure to prenatal environmental toxicants is associated with neurodevelopmental disorders. In addition, there is also evidence that environmental toxicants can result in epigenetic alterations, notably DNA methylation. In this review, we first focus on the relationship between neurodevelopmental disorders and environmental toxicants, in particular maternal smoking, plastic-derived chemicals (bisphenol A and phthalates), persistent organic pollutants, and heavy metals. We then review studies showing the epigenetic effects of those environmental factors in humans that may affect normal neurodevelopment.