Neuroprotective effects of microRNA-211-5p on chronic stress-induced neuronal apoptosis and depression-like behaviours

From Perspective of Hippocampal Plasticity: Function of Antidepressant Chinese Medicine Xiaoyaosan

The hippocampus is one of the most commonly studied brain regions in the context of depression. The volume of the hippocampus is significantly reduced in patients with depression, which severely disrupts hippocampal neuroplasticity. However, antidepressant therapies that target hippocampal neuroplasticity have not been identified as yet. Chinese medicine (CM) can slow the progression of depression, potentially by modulating hippocampal neuroplasticity. Xiaoyaosan (XYS) is a CM formula that has been clinically used for the treatment of depression. It is known to protect Gan (Liver) and Pi (Spleen) function, and may exert its antidepressant effects by regulating hippocampal neuroplasticity. In this review, we have summarized the association between depression and aberrant hippocampal neuroplasticity. Furthermore, we have discussed the researches published in the last 30 years on the effects of XYS on hippocampal neuroplasticity in order to elucidate the possible mechanisms underlying its therapeutic action against depression. The results of this review can aid future research on XYS for the treatment of depression.

Levomilnacipran ameliorates lipopolysaccharide-induced depression-like behaviors and suppressed the TLR4/Ras signaling pathway

Levomilnacipran, a serotonin and norepinephrine reuptake inhibitor, has been reported to have anti-depressive effects. However, the detailed mechanisms underlying these effects are still unclear. This study aimed to investigate the antidepressant mechanisms of levomilnacipran to discover new perspectives on the treatment of depression in male rats. Intraperitoneal injection of lipopolysaccharide (LPS) was used to induce depressive behaviors in rats. Activation of microglia and apoptosis of neurons verified by immunofluorescence. Inflammatory related proteins and neurotrophic related proteins were verified by immunoblotting. The mRNA expression of apoptosis markers was verified by real-time quantitative PCR. Finally, electron microscopy analysis was used to observe the ultrastructural pathology of neuron. Here, we found that the anti-depression and anti-anxiety effects of levomilnacipran in the LPS-induced rat model of depression was resulted from the suppression of neuroinflammation and neuronal apoptosis within prefrontal cortex of rats. Furthermore, we found that levomilnacipran could decrease the number of microglia and suppress its activation in prefrontal cortex of rats. This effect may be mediated by suppressing the TLR4/NF-κB and Ras/p38 signaling pathways. In addition, levomilnacipran plays a neuroprotective role by increasing the expression of neurotrophic factors. Taken together, these results suggest that levomilnacipran exerts antidepressant effects by attenuating neuroinflammation to inhibit the damage in central nervous system and plays a neuroprotective role to improve depressive behaviors. These findings suggest that suppression of neuroinflammation in prefrontal cortex could ameliorate depressive behavioral disorder of rats induced by LPS, which provided a new perspective for the treatment of depression.

Upregulation of KLK8 contributes to CUMS-induced hippocampal neuronal apoptosis by cleaving NCAM1

Neuronal apoptosis has been well-recognized as a critical mediator in the pathogenesis of depressive disorders. Tissue kallikrein-related peptidase 8 (KLK8), a trypsin-like serine protease, has been implicated in the pathogenesis of several psychiatric disorders. The present study aimed to explore the potential function of KLK8 in hippocampal neuronal cell apoptosis associated with depressive disorders in rodent models of chronic unpredictable mild stress (CUMS)-induced depression. It was found that depression-like behavior in CUMS-induced mice was associated with hippocampal KLK8 upregulation. Transgenic overexpression of KLK8 exacerbated, whereas KLK8 deficiency attenuated CUMS-induced depression-like behaviors and hippocampal neuronal apoptosis. In HT22 murine hippocampal neuronal cells and primary hippocampal neurons, adenovirus-mediated overexpression of KLK8 (Ad-KLK8) was sufficient to induce neuron apoptosis. Mechanistically, it was identified that the neural cell adhesion molecule 1 (NCAM1) may associate with KLK8 in hippocampal neurons as KLK8 proteolytically cleaved the NCAM1 extracellular domain. Immunofluorescent staining exhibited decreased NCAM1 in hippocampal sections obtained from mice or rats exposed to CUMS. Transgenic overexpression of KLK8 exacerbated, whereas KLK8 deficiency largely prevented CUMS-induced loss of NCAM1 in the hippocampus. Both adenovirus-mediated overexpression of NCAM1 and NCAM1 mimetic peptide rescued KLK8-overexpressed neuron cells from apoptosis. Collectively, this study identified a new pro-apoptotic mechanism in the hippocampus during the pathogenesis of CUMS-induced depression via the upregulation of KLK8, and raised the possibility of KLK8 as a potential therapeutic target for depression.

The role of microRNAs in depression

Major depressive disorder (MDD) is a psychiatric disorder with increasing prevalence worldwide. It is a leading cause of disability and suicide, severely affecting physical and mental health. However, the study of depression remains at an exploratory stage in terms of diagnostics and treatment due to the complexity of its pathogenesis. MicroRNAs are endogenous short-stranded non-coding RNAs capable of binding to the 3’untranslated region of mRNAs. Because of their ability to repress translation process of genes and are found at high levels in brain tissues, investigation of their role in depression has gradually increased recently. This article summarizes recent research progress on the relationship between microRNAs and depression. The microRNAs play a regulatory role in the pathophysiology of depression, involving dysregulation of monoamines, abnormalities in neuroplasticity and neurogenesis, hyperactivity of the HPA axis, and dysregulation of inflammatory responses. These microRNAs might provide new clue for the diagnosis and treatment of MDD, and the development of antidepressant drugs.

Empagliflozin alleviates endoplasmic reticulum stress and augments autophagy in rotenone-induced Parkinson's disease in rats: Targeting the GRP78/PERK/eIF2α/CHOP pathway and miR-211-5p

Empagliflozin, a selective sodium-glucose co-transporter-2 inhibitor, has been demonstrated to provide additional non-glycemic benefits, including neuroprotection. Endoplasmic reticulum (ER) stress is a key player in neurodegeneration and occurs at the crossroads of other pathologic mechanisms; however, its role in the pathogenesis of Parkinson's disease (PD) is still elusive. miR-211-5p regulates neuronal differentiation and viability and was predicted to target CHOP, a downstream effector in the ER stress pathway. For the first time, this study investigated the possible neuroprotective effect of empagliflozin in a rotenone-induced rat model of PD from the perspective of ER stress. Rotenone (1.5 mg/kg) was administered subcutaneously every other day for 3 weeks. Meanwhile, the treated group received empagliflozin 10 mg/kg/day orally for 15 consecutive days post-PD induction. On the molecular level, the ER stress pathway components; GRP78, total and phosphorylated PERK, eIF2α and CHOP, along with miR-211-5p expression were upregulated in the striatum of rotenone-injected rats. Concurrently, the untreated rats showed elevated striatal α-synuclein levels along with diminished autophagy and the proteasome system as evidenced by reduced beclin-1 protein and ELF2/NERF mRNA expression levels. The rotenone-induced striatal oxidative stress and neuroinflammation were expressed by reduced catalase activity and elevated interleukin (IL)-1β levels. miR-211-5p was positively correlated with PERK/eIF2α/CHOP, IL-1β and α-synuclein, while negatively correlated with ELF2/NERF, beclin-1 and catalase activity. Empagliflozin treatment showed a restorative effect on all biochemical alterations and improved the motor function of rats tested by open field, grip strength and footprint gait analysis. In the histopathological examination, empagliflozin increased the intact neuron count and attenuated astrogliosis and microgliosis by reducing the glial fibrillary protein and ionized calcium-binding adaptor protein 1 immunostaining. Conclusively, these results emphasize the neurotherapeutic impact of empagliflozin in PD by moderating the GRP78/PERK/eIF2α/CHOP ER stress pathway, downregulating miR-211-5p, resolving oxidative stress, lessening astrocyte/microglial activation and neuroinflammation, along with augmenting autophagy.

Elevation of N-acetyltransferase 10 in hippocampal neurons mediates depression- and anxiety-like behaviors

Major depressive disorder (MDD) is one of the most debilitating and severe mental diseases globally. Increasing evidence has shown that epigenetics is critical for understanding brain function and brain disorders, including MDD. N-acetyltransferase 10 (NAT10), acting on histones, mRNA and other substrates, has been reported to be involved in epigenetic events, including histone acetylation and mRNA modifications. NAT10 is highly expressed in the brain. However, the potential effects of NAT10 on MDD are still unknown. Here, we exploited chronic mild stress (CMS) to induce anxiety- and depression-like behaviors in mice and found that the expression of NAT10 in the mouse hippocampus was upregulated after CMS treatment. Inhibition of NAT10 by pharmacological methods produced anxiolytic- and antidepressant-like effects. Neuron-specific overexpression of NAT10 in the hippocampus resulted in anxiety- and depression-like behaviors, accompanied by higher SIRT1 protein levels, and lower dendritic spine densities. Overall, it was found that elevation of NAT10 in hippocampal neurons is involved in the occurrence of anxiety- and depression-like behaviors, suggesting that NAT10 could be a potential new target for developing anxiolytics and antidepressants.

MiR-410-3p facilitates Angiotensin II-induced cardiac hypertrophy by targeting Smad7

MicroRNAs (miRNAs) have emerged as important regulators in the development of cardiovascular diseases. miR-410-3p was shown to play a protective or detrimental role in the progression in cardiovascular events. However, the exact role and the underlying mechanism of miR-410-3p in cardiac hypertrophy have not been documented. The current work was aimed to determine the role and underlying mechanism of miR-410-3p on Angiotensin II (Ang II) induced cardiac hypertrophy. FITC-phalloidin staining was used for determination of cardiomyocyte surface area. Quantitative reverse transcription polymerase chain reaction (qRT-PCR) was performed to identify mRNA expression level of hypertrophic markers. Smad7 protein expression level was analyzed using Western blot. Dual-luciferase reporter assay was used to examine the regulatory function of miR-410-3p on Smad7. MiR-410-3p was found significantly up-regulated in Ang II–induced cardiac hypertrophy. MiR-410-3p inhibitor remarkably alleviated cardiomyocyte hypertrophic changes. Dual-luciferase reporter assay result indicated that miR-410-3p directly targeted Smad7 and miR-410-3p inhibitor effectively prevented Ang II triggered down-regulation of Smad7. Moreover, Smad7 overexpression significantly reversed the pro-hypertrophic effect of miR-410-3p. In summary, our findings revealed that miR-410-3p mediated Ang II–induced cardiac hypertrophy via targeting inhibition of Smad7.

Neuroprotective effects of microRNA-211-5p on chronic stress-induced neuronal apoptosis and depression-like behaviours

Findings from recent studies have revealed that microRNAs (miRNAs) are related to numerous neurological disorders. However, whether miRNAs regulate neuronal anomalies involved in the pathogenesis of depression remain unclear. In the present study, we screened miRNA expression profiles in the CA1 hippocampus of a rat model of depression and found that a specific miRNA, microRNA-211-5p, was significantly down-regulated in depressed rats. When miR-211-5p was up-regulated in these rats, neuronal apoptosis within the CA1 area was suppressed, effects which were accompanied with an amelioration of depression-like behaviours in these rats. These neuroprotective effects of miR-211-5p in depressed rats appear to result through suppression of the Dyrk1A/ASK1/JNK signalling pathway within the CA1 area. In further support of this proposal are the findings that knock-down of miR-211-5p within the CA1 area of normal rats activated the Dyrk1A/ASK1/JNK pathway, resulting in the promotion of neuronal apoptosis and display of depression-like behaviours in these rats. Taken together, these results demonstrate that deficits in miR-211-5p contribute to neuronal apoptosis and thus depression-like behaviours in rats. Therefore, the miR-211-5p/Dyrk1A pathway may be critically involved in the pathogenesis of depression and serve as a potential therapeutic target for the treatment of depression.