A Special Extract of Bacopa monnieri (CDRI-08)-Restored Memory in CoCl2-Hypoxia Mimetic Mice Is Associated with Upregulation of Fmr-1 Gene Expression in Hippocampus

Rett Syndrome and Fragile X Syndrome: Different Etiology With Common Molecular Dysfunctions

Rett syndrome (RTT) and Fragile X syndrome (FXS) are two monogenetic neurodevelopmental disorders with complex clinical presentations. RTT is caused by mutations in the Methyl-CpG binding protein 2 gene (MECP2) altering the function of its protein product MeCP2. MeCP2 modulates gene expression by binding methylated CpG dinucleotides, and by interacting with transcription factors. FXS is caused by the silencing of the FMR1 gene encoding the Fragile X Mental Retardation Protein (FMRP), a RNA binding protein involved in multiple steps of RNA metabolism, and modulating the translation of thousands of proteins including a large set of synaptic proteins. Despite differences in genetic etiology, there are overlapping features in RTT and FXS, possibly due to interactions between MeCP2 and FMRP, and to the regulation of pathways resulting in dysregulation of common molecular signaling. Furthermore, basic physiological mechanisms are regulated by these proteins and might concur to the pathophysiology of both syndromes. Considering that RTT and FXS are disorders affecting brain development, and that most of the common targets of MeCP2 and FMRP are involved in brain activity, we discuss the mechanisms of synaptic function and plasticity altered in RTT and FXS, and we consider the similarities and the differences between these two disorders.

miR-302a-3p targets FMR1 to regulate pyroptosis of renal tubular epithelial cells induced by hypoxia-reoxygenation injury

NEW FINDINGS

What is the central question of this study? How does miR-302a-3p play a role in hypoxia-reoxygenation-induced pyroptosis of renal tubular epithelial cells? What is the main finding and its importance? Hypoxia-reoxygenation treatment upregulated the expression of miR-302a-3p in HK-2 cells, and then inhibited the transcription of FMRP translational regulator 1 (FMR1), so as to promote the activation of the NLRP3 inflammasome and aggravate the pyroptosis of HK-2 cells. miR-302a-3p was used as a molecular target in this study, which provides a new theoretical basis for the treatment of renal failure.

ABSTRACT

Hypoxia-reoxygenation (H/R) induction can affect miRNA expression and then control NLR family pyrin domain containing 3 (NLRP3) inflammasome-mediated pyroptosis. This study investigated the mechanism of miR-302a-3p in H/R-induced renal tubular epithelial cell (RTEC) pyroptosis. Human HK-2 RTECs were induced by H/R. Lactate dehydrogenase content, cell activity and pyroptosis, and levels of NLRP3, GSDMD-N, caspase-1, interleukin (IL)-1β, IL-18, superoxide dismutase, and malondialdehyde were detected to verify the effect of H/R on HK-2 cells. The NLRP3 inflammasome action was evaluated after H/R-induced HK-2 cells were treated with BAY11-7082, an inflammasome inhibitor. After inhibiting miR-302a-3p expression, the changes of pyroptosis were observed. The binding relation between miR-302a-3p and FMRP translational regulator 1 (FMR1) was verified. A function-rescue experiment verified the role of FMR1 in the regulation of pyroptosis. H/R-induced HK-2 cells showed significant pyroptosis injury, and the NLRP3 inflammasome was activated. After inhibiting the NLRP3 inflammasome, H/R-induced apoptosis was inhibited. After H/R treatment, miR-302a-3p in HK-2 cells was increased, and miR-302a-3p downregulation limited H/R-induced NLRP3 inflammasome-mediated pyroptosis. FMR1 is the target of miR-302a-3p. Inhibition of FMR1 alleviated the inhibition of H/R-induced HK-2 cell pyroptosis by miR-302a-3p inhibitor. Collectively, inhibiting miR-302a-3p can weaken its targeted inhibition on FMR1, thereby inhibiting the activation of NLRP3 inflammasomes and reducing caspase-1-dependent pyroptosis in HK-2 cells.

Insights Into the Molecular Aspects of Neuroprotective Bacoside A and Bacopaside I

Bacopa monnieri, commonly known as Brahmi, has been extensively used as a neuromedicine for various disorders such as anxiety, depression and memory loss. Chemical characterization studies revealed the major active constituents of the herb as the triterpenoid saponins, bacosides. Bacoside A, the vital neuroprotective constituent, is composed of four constituents viz., bacoside A3, bacopaside II, jujubogenin isomer of bacopasaponin C (bacopaside X) and bacopasaponin C. B. monnieri extracts as well as bacosides successfully establish a healthy antioxidant environment in various tissues especially in the liver and brain. Free radical scavenging, suppression of lipid peroxidation and activation of antioxidant enzymes by bacosides help to attain a physiological state of minimized oxidative stress. The molecular basis of neuroprotective activity of bacosides is attributed to the regulation of mRNA translation and surface expression of neuroreceptors such as AMPAR, NMDAR and GABAR in the various parts of the brain. Bioavailability as well as binding of neuroprotective agents (such as bacosides) to these receptors is controlled by the Blood Brain Barrier (BBB). However, nano conversion of these drug candidates easily resolves the BBB restriction and carries a promising role in future therapies. This review summarizes the neuroprotective functions of B. monnieri extracts as well as its active compounds (bacoside A, bacopaside I) and the molecular mechanisms responsible for these pharmacological activities.

Bacopa monnieri extract improves novel object recognition, cell proliferation, neuroblast differentiation, brain-derived neurotrophic factor, and phosphorylation of cAMP response element-binding protein in the dentate gyrus

Bacopa monnieri is a medicinal plant with a long history of use in Ayurveda, especially in the treatment of poor memory and cognitive deficits. In the present study, we hypothesized that Bacopa monnieri extract (BME) can improve memory via increased cell proliferation and neuroblast differentiation in the dentate gyrus. BME was administered to 7-week-old mice once a day for 4 weeks and a novel object recognition memory test was performed. Thereafter, the mice were euthanized followed by immunohistochemistry analysis for Ki67, doublecortin (DCX), and phosphorylated cAMP response element-binding protein (CREB), and western blot analysis of brain-derived neurotrophic factor (BDNF). BME-treated mice showed moderate increases in the exploration of new objects when compared with that of familiar objects, leading to a significant higher discrimination index compared with vehicle-treated mice. Ki67 and DCX immunohistochemistry showed a facilitation of cell proliferation and neuroblast differentiation following the administration of BME in the dentate gyrus. In addition, administration of BME significantly elevated the BDNF protein expression in the hippocampal dentate gyrus, and increased CREB phosphorylation in the dentate gyrus. These data suggest that BME improves novel object recognition by increasing the cell proliferation and neuroblast differentiation in the dentate gyrus, and this may be closely related to elevated levels of BDNF and CREB phosphorylation in the dentate gyrus.

Ethanolic Extract of Opuntia ficus-indica var. saboten Ameliorates Cognitive Dysfunction Induced by Cholinergic Blockade in Mice

The stem of Opuntia ficus-indica var. saboten is edible and has been used as a medicinal herb on Jeju Island in Korea. We previously reported that the butanolic extract of O. ficus-indica var. saboten exerts the enhancement of long-term memory in mice. However, the antiamnesic effects of O. ficus-indica var. saboten and its mode of action has not been clearly elucidated. In the present study, we explored the effects of the ethanolic extract of stems of O. ficus-indica var. saboten (EOFS) on cognitive performance in mouse and attempted to delineate its mechanism of action. We used the passive avoidance, Y-maze, and novel object recognition tests to assess its effects on cognitive functions in scopolamine-induced memory-impaired mice. We observed that EOFS (100, 200, and 400 mg/kg) ameliorated scopolamine-induced cognitive dysfunction. We also explored its mechanism of action by conducting an acetylcholinesterase (AChE) activity assay using the mouse whole brain and Western blot using the mouse hippocampal tissue. Western blot analysis and the ex vivo study revealed that EOFS increased the levels of phosphorylated extracellular signal-regulated kinase and cAMP response element-binding protein (CREB) and the levels of brain-derived neurotrophic factor (BDNF) expression in the hippocampus. It also inhibited AChE activity in the brain. Our findings suggest that EOFS would be useful for the treatment of cholinergic blockade-induced cognitive dysfunction.

Effect of Metformin on Adult Hippocampal Neurogenesis: Comparison with Donepezil and Links to Cognition

Recent studies have uncovered evidence suggesting that interference with hippocampal adult neurogenesis contributes to neurodegeneration in Alzheimer's disease (AD). Evidence supporting that AD is a metabolic disease with derangements in brain glucose utilization implies the use of anti-diabetics as an alternate therapeutic strategy. The present study drew comparison between the pro-neurogenic potential of metformin and donepezil in AlCl₃-induced mouse model of neurodegeneration. Morris water maze task and subsequent immunohistochemical evaluation for NeuN was conducted. Expression of neurogenesis markers and hippocampal proteome analysis was determined by qRT-PCR and SDS-PAGE, respectively, followed by ESI-QTOFF MS/MS identification. The results demonstrated impaired spatial memory and differential expression of eight proteins in the AlCl₃ group as compared to the controls. Interestingly, treatment with metformin normalized the proteome profile and expression levels of neurogenesis markers along with improvement in the spatial memory. Moreover, as compared to donepezil, metformin-treated mice exhibited an enhanced number of post-mitotic NeuN-positive neurons. It is suggested that underlying molecular mechanisms of metformin-mediated adult hippocampal neurogenesis may have implications in treatment of neurodegenerative disorders.

Alterations in Hippocampal Oxidative Stress, Expression of AMPA Receptor GluR2 Subunit and Associated Spatial Memory Loss by Bacopa monnieri Extract (CDRI-08) in Streptozotocin-Induced Diabetes Mellitus Type 2 Mice

Bacopa monnieri extract has been implicated in the recovery of memory impairments due to various neurological disorders in animal models and humans. However, the precise molecular mechanism of the role of CDRI-08, a well characterized fraction of Bacopa monnieri extract, in recovery of the diabetes mellitus-induced memory impairments is not known. Here, we demonstrate that DM2 mice treated orally with lower dose of CDRI-08 (50- or 100 mg/kg BW) is able to significantly enhance spatial memory in STZ-DM2 mice and this is correlated with a significant decline in oxidative stress and up regulation of the AMPA receptor GluR2 subunit gene expression in the hippocampus. Treatment of DM2 mice with its higher dose (150 mg/kg BW or above) shows anti-diabetic effect in addition to its ability to recover the spatial memory impairment by reversing the DM2-induced elevated oxidative stress and decreased GluR2 subunit expression near to their values in normal and CDRI-08 treated control mice. Our results provide evidences towards molecular basis of the memory enhancing and anti diabetic role of the Bacopa monnieri extract in STZ-induced DM2 mice, which may have therapeutic implications.