[Therapeutic effect and mechanism of Xiaoyao Kangai Jieyu Recipe on mice with breast cancer related depression through regulating COX pathway].

This study aimed to investigate the intervention effect and mechanism of Xiaoyao Kangai Jieyu Recipe(XKJR) on hip-pocampal microglia and neuronal damage in mice with breast cancer related depression. The mouse model of breast cancer related depression was established by inoculation of 4T1 breast cancer cells in axilla and subcutaneous injection of corticosterone(30 mg·kg~(-1)). The successfully modeled mice were randomly divided into a model group, a positive drug group(capecitabine 60 mg·kg~(-1)+fluoxetine 19.5 mg·kg~(-1)), and XKJR group(19.5 mg·kg~(-1) crude drug), with 6 in each group. Another 6 normal mice were taken as a normal group. The administration groups were given corresponding drugs by gavage, while the normal and model groups were given an equal volume of distilled water, once a day for 21 consecutive days. The depressive behavior of mice was assessed by glucose consumption test, open field test and novelty-suppressed feeding test. Hematoxylin and eosin(HE) staining and tumor suppression rate were used to evaluate the changes of axillary tumors. The mRNA expressions and the relative protein expressions of interleukin-1ß(IL-1ß), interleukin-18(IL-18), cyclooxyganese-2(COX-2) and glutamyl-prolyl-tRNA synthetase(EPRs) in the hippocampus of mice were determined by quantitative real-time polymerase chain reaction(qRT-PCR) and immunohistochemistry, respectively. Immunofluorescence was performed to detect the mean fluorescence intensity of CD11b, a marker of hippocampal microglia activation. Nissler staining and transmission electron microscopy were employed to observe the morphological changes and the ultramorphological changes of hippocampal neurons, respectively. The experimental results indicated that compared with the normal group, the model group had reduced glucose consumption and lowered number of total activities in open field test(P<0.05, P<0.01), prolonged first feeding latency in no-velty-suppressed feeding test(P<0.01), and significant depression-like behavior; the contents of IL-1ß, IL-18, COX-2, and EPRs in hippocampus were increased(P<0.05, P<0.01), with hippocampal microglia activation and obvious neuronal damage. Compared with the model group, the positive drug group and the XKJR group presented an improvement in depressive behaviors, a decrease in the contents of IL-1ß, IL-18, COX-2 and EPRs in hippocampus, and an alleviation in the activation of hippocampal microglia and neuronal damage; the tumor suppression rates of positive drug and XKJR were 40.32% and 48.83%, respectively, suggesting a lower tumor growth rate than that of the model group. In summary, XKJR may improve hippocampal microglia activation and neuronal damage in mice with breast cancer related depression through activating COX signaling pathway.

Sleep deprivation leads to further impairment of hippocampal synaptic plasticity by suppressing melatonin secretion in the pineal gland of chronically unpredictable stress rats.

There has been ample research showing that insomnia is a potential trigger of depression as well as a symptom of depression. These two factors contribute to behavioural problems and are closely related to the plasticity of hippocampal synapses. Although depression and insomnia impair hippocampal synaptic plasticity, the mechanism by which this happens remains a mystery. This study aimed to investigate the pathogenesis of insomnia comorbidity in depression and the regulatory effect of venlafaxine combined with melatonin on hippocampal synaptic plasticity in chronic unpredictable mild stress (CUMS) with sleep deprivation (SD) rats. Thus, rats were subjected to 14 days of chronic mild unpredictable stress, gradually acclimated to sleep deprivation on days 12-14. Followed by 21 consecutive days of sleep deprivation, 18 h per day, with daily gavage of venlafaxine (13.5 mg/kg) + melatonin (72 mg/kg) on days 15-36. Venlafaxine + melatonin treatment improves depression-like behaviour, pentobarbital sodium experimental sleep latency, and sleep duration in CUMS +SD rats. In addition to improving depressive-like behaviors, sleep deprivation also upregulates the expression of caspase-specific cysteine protein 3 (Caspase 3) in the pineal glial cells of chronic mild rats, as well as in hippocampal microglia. Expression of ionic calcium-binding adaptor 1 (iba-1), downregulates the secretion of several synaptic plasticity-related proteins, notably cAMP response element binding protein (CREB), glial cell line-derived neurotrophic factor (GDNF), and the synaptic scaffolding protein Spinophiline (Spinophiline). Hematoxylin-eosin staining showed that the structure of the pineal gland and hippocampus was damaged, and Golgi staining showed that the dendrites and spines in the DG area of the hippocampus were destroyed, vaguely aggregated or even disappeared, and the connection network could not be established. Western blot analysis further revealed a positive correlation between low melatonin levels and reduced Spinophiline protein. Interestingly, venlafaxine + melatonin reversed these events by promoting hippocampal synaptic plasticity by regulating melatonin secretion from the pineal gland. Therefore, it exerted an antidepressant effect in sleep deprivation combined with CUMS model rats. Overall, the results of this study suggest that the pathophysiology of depressive insomnia comorbidity is mediated by impaired pineal melatonin secretion and impaired hippocampal synaptic plasticity. In addition, these responses are associated with melatonin secretion from the pineal gland.

The molecular mechanism underlying mitophagy-mediated hippocampal neuron apoptosis in diabetes-related depression.

Diabetes-related depression (DD) is a major complication of diabetes mellitus. Our previous studies indicated that glutamate (Glu) and hippocampal neuron apoptosis are key signal and direct factor leading to diabetes-related depression, respectively. However, the accurate pathogenesis remains to be unclear. We hypothesized that diabetes-related depression might be associated with the mitophagy-mediated hippocampal neuron apoptosis, triggered by aberrant Glu-glutamate receptor2 (GluR2)-Parkin pathway. To testify this hypothesis, here the rat model of DD in vivo and in vitro were both established so as to uncover the potential mechanism of DD based on mitophagy and apoptosis. We found that DD rats exhibit an elevated glutamate levels followed by monoamine neurotransmitter deficiency and depressive-like behaviour, and DD modelling promoted autophagosome formation and caused mitochondrial impairment, eventually leading to hippocampal neuron apoptosis via aberrant Glu-GluR2-Parkin pathway. Further, in vitro study demonstrated that the simulated DD conditions resulted in an abnormal glutamate and monoamine neurotransmitter levels followed by autophagic flux increment, mitochondrial membrane potential reduction and mitochondrial reactive oxygen species and lactic dehydrogenase elevation. Interestingly, both GluR2 and mammalian target of rapamycin (mTOR) receptor blocker aggravated mitophagy-induced hippocampal neuron apoptosis and abnormal expression of apoptotic protein. In contrast, both GluR2 and mTOR receptor agonist ameliorated those apoptosis in simulated DD conditions. Our findings revealed that mitophagy-mediated hippocampal neuron apoptosis, triggered by aberrant Glu-GluR2-Parkin pathway, is responsible for depressive-like behaviour and monoamine neurotransmitter deficiency in DD rats. This work provides promising molecular targets and strategy for the treatment of DD.

GR/NF-κB signaling pathway regulates hippocampal inflammatory responses in diabetic rats with chronic unpredictable mild stress.

Clinical studies have shown that diabetes can present with underlying depression, and a combination of the two can lead to emotional, memory and cognitive disorders, closely associated with hippocampal neuroinflammation. However, the mechanism underlying the development of hippocampal neuroinflammation under the above condition remains elusive. The aims of this study were to explore the pathogenesis of diabetes combined with depression, and the effect of dexamethasone (Dex), a glucocorticoid receptor (GR) agonist, on hippocampal neuroinflammation in diabetic rats with chronic unpredictable mild stress (CUMS). Therefore, rats were intragastrically fed on a high-fat diet (10% cholesterol 10 ml/kg) for 14 days and thereafter injected with 38 mg/kg of streptozotocin on the 15th day to induce diabetes. Dex treatment of the diabetic and CUMS rats ameliorated the depression-associated behavior in the respective rats. Apart from enhanced depressive behavior, diabetes-depressed condition also up-regulated the expression of hippocampus microglia chemokine Ⅰ receptor (CX3CR1) and secretion of several pro-inflammatory factors, in particular, interleukin 1ß (IL-1ß), interleukin-6 (IL-6), interleukin-8 (IL-8) and tumor necrosis factor - α (TNF-α). Hematoxylin-eosin staining revealed inflammatory damages in the hippocampus. Western blot analysis further revealed repression of GR proteins converse to the nuclear factor kappa-B (NF-κB) proteins, which were up-regulated. Intriguingly, Dex reversed the above events by inhibiting inflammatory reactions in the hippocampus. Consequently, played an antidepressant effect in diabetic and CUMS model rats. Overall, findings of this research suggest that the physiopathology of diabetes with stress cormobity are mediated by inflammatory reactions in the hippocampus. In particular, the responses are associated with regulation of GR/NF-κB signaling pathway.

Abnormal Glu/mGluR2/3/PI3K pathway in the hippocampal neurovascular unit leads to diabetes-related depression.

Our previous studies have shown that glutamate and hippocampal neuron apoptosis are key signals and direct factors associated with diabetes-related depression, and structural and functional damage to the hippocampal neurovascular unit has been associated with diabetes-related depression. However, the underlying mechanism remains unclear. We hypothesized that diabetes-related depression might be associated with the glutamate (Glu)/metabotropic glutamate receptor2/3 (mGluR2/3)/phosphoinositide 3-kinase (PI3K) pathway, activated by glucocorticoid receptors in the hippocampal neurovascular unit. To test this hypothesis, rat hippocampal neurovascular unit models, containing hippocampal neurons, astrocytes, and brain microvascular endothelial cells, were treated with 150 mM glucose and 200 µM corticosterone, to induce diabetes-related depression. Our results showed that under conditions of diabetes complicated by depression, hippocampal neurovascular units were damaged, leading to decreased barrier function; elevated Glu levels; upregulated glucocorticoid receptor, vesicular glutamate transporter 3 (VGLUT-3), and metabotropic glutamate receptor 2/3 (mGluR2/3) expression; downregulated excitatory amino acid transporter 1 (EAAT-1) expression; and alteration of the balance of key proteins associated with the extracellular signal-regulated kinase (ERK)/glial cell-derived neurotrophic factor (GDNF)/PI3K signaling pathway. Moreover, the viability of neurons was dramatically reduced in the model of diabetes-related depression, and neuronal apoptosis, and caspase-3 and caspase-9 expression levels, were increased. Our results suggest that the Glu/mGluR2/3/PI3K pathway, induced by glucocorticoid receptor activation in the hippocampal neurovascular unit, may be associated with diabetes-related depression. This study was approved by the Laboratory Animal Ethics Committee of The First Hospital of Hunan University of Chinese Medicine, China (approval No. HN-ZYFY-2019-11-12) on November 12, 2019.

Structural and functional damage to the hippocampal neurovascular unit in diabetes-related depression.

Previous studies have shown that models of depression exhibit structural and functional changes to the neurovascular unit. Thus, we hypothesized that diabetes-related depression might be associated with damage to the hippocampal neurovascular unit. To test this hypothesis, neurons, astrocytes and endothelial cells were isolated from the brain tissues of rat embryos and newborn rats. Hippocampal neurovascular unit co-cultures were produced using the Transwell chamber co-culture system. A model of diabetes-related depression was generated by adding 150 mM glucose and 200 µM corticosterone to the culture system and compared with the neuron + astrocyte and astrocyte + endothelial cell co-culture systems. Western blot assay was used to measure levels of structural proteins in the hippocampal neurovascular unit co-culture system. Levels of basic fibroblast growth factor, angiogenic factor 1, glial cell line-derived neurotrophic factor, transforming growth factor ß1, leukemia inhibitory factor and 5-hydroxytryptamine in the hippocampal neurovascular unit co-culture system were measured by enzyme-linked immunosorbent assay. Flow cytometry and terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick end labeling staining was used to assess neuronal apoptosis in the hippocampal neurovascular unit. The neurovascular unit triple cell co-culture system had better barrier function and higher levels of structural and secretory proteins than the double cell co-culture systems. In comparison, in the model of diabetes-related depression, the neurovascular unit was damaged with decreased barrier function, poor structural integrity and impaired secretory function. Moreover, neuronal apoptosis was markedly increased, and 5-hydroxytryptamine levels were reduced. These results suggest that diabetes-related depression is associated with structural and functional damage to the neurovascular unit. Our findings provide a foundation for further studies on the pathogenesis of diabetes-related depression.