Dendropanax morbifera Léveille extract ameliorates D-galactose-induced memory deficits by decreasing inflammatory responses in the hippocampus

Extracts from Dendropanax morbifera leaves ameliorates cerebral ischemia-induced hippocampal damage by reducing oxidative damage in gerbil

AIM

In this study, we investigated the effects of Dendropanax morbifera extract (DME) on neuroprotection against ischemic damage in gerbils.

METHODS

DME (100 or 300 mg/kg) was orally administered to gerbils for three weeks, and 2 h after the last DME treatment, transient forebrain ischemia in the common carotid arteries was induced for 5 min. The forebrain ischemia-related cognitive impairments were assessed by spontaneous motor activity and passive avoidance test one and four days after ischemia, respectively. In addition, surviving and degenerating neurons were morphologically confirmed by neuronal nuclei immunohistochemical staining and Fluoro-Jade C staining, respectively, four days after ischemia. Changes of glial morphology were visualized by immunohistochemical staining for each marker such as glial fibrillary acidic protein and ionized calcium-binding protein. Oxidative stress was determined by measurements of dihydroethidium, O2· (formation of formazan) and malondialdehyde two days after ischemia. In addition, glutathione redox system such as reduced glutathione, oxidized glutathione levels, glutathione peroxidase, and glutathione reductase activities were measured two days after ischemia.

RESULTS

Spontaneous motor activity monitoring and passive avoidance tests showed that treatment with 300 mg/kg DME, but not 100 mg/kg, significantly alleviated ischemia-induced memory impairments. In addition, approximately 67 % of mature neurons survived and 29.3 % neurons were degenerated in hippocampal CA1 region four days after ischemia, and ischemia-induced morphological changes in astrocytes and microglia were decreased in the CA1 region after 300 mg/kg DME treatment. Furthermore, treatment with 300 mg/kg DME significantly ameliorated ischemia-induced oxidative stress, such as superoxide formation and lipid peroxidation, two days after ischemia. In addition, ischemia-induced reduction of the glutathione redox system in the hippocampus, assessed two days after the ischemia, was ameliorated by treatment with 300 mg/kg DME. These suggest that DME can potentially reduce ischemia-induced neuronal damage through its antioxidant properties.

The Neuroprotective Effects of Dendropanax morbifera Water Extract on Scopolamine-Induced Memory Impairment in Mice

This study investigated the neuroprotective effects of Dendropanax morbifera leaves and stems (DMLS) water extract on scopolamine (SCO)-induced memory impairment in mice. First, we conducted experiments to determine the protective effect of DMLS on neuronal cells. Treatment with DMLS showed a significant protective effect against neurotoxicity induced by Aβ(25-35) or H2O2. After confirming the neuroprotective effects of DMLS, we conducted animal studies. We administered DMLS orally at concentrations of 125, 250, and 375 mg/kg for 3 weeks. In the Y-maze test, SCO decreased spontaneous alternation, but treatment with DMLS or donepezil increased spontaneous alternation. In the Morris water-maze test, the SCO-treated group showed increased platform reach time and decreased swim time on the target platform. The passive avoidance task found that DMLS ingestion increased the recognition index in short-term memory. Furthermore, memory impairment induced by SCO reduced the ability to recognize novel objects. In the Novel Object Recognition test, recognition improved with DMLS or donepezil treatment. In the mouse brain, except for the cerebellum, acetylcholinesterase activity increased in the SCO group and decreased in the DMLS and donepezil groups. We measured catalase and malondialdehyde, which are indicators of antioxidant effectiveness, and found that oxidative stress increased with SCO but was mitigated by DMLS or donepezil treatment. Thus, our findings suggest that ingestion of DMLS restored memory impairment by protecting neuronal cells from Aβ(25-35) or H2O2-induced neurotoxicity, and by reducing oxidative stress.

Purpurin ameliorates D-galactose-induced aging phenotypes in mouse hippocampus by reducing inflammatory responses

Purpurin, an anthraquinone, has potent anti-oxidant and anti-inflammatory effects in various types of brain damage. In a previous study, we showed that purpurin exerts neuroprotective effects against oxidative and ischemic damage by reducing pro-inflammatory cytokines. In the present study, we investigated the effects of purpurin against D-galactose-induced aging phenotypes in mice. Exposure to 100 mM D-galactose significantly decreased cell viability in HT22 cells, and purpurin treatment significantly ameliorated the reduction of cell viability, formation of reactive oxygen species, and lipid peroxidation in a concentration-dependent manner. Treatment with 6 mg/kg purpurin significantly improved D-galactose-induced memory impairment in the Morris water maze test in C57BL/6 mice and alleviated the reduction of proliferating cells and neuroblasts in the subgranular zone of the dentate gyrus. In addition, purpurin treatment significantly mitigated D-galactose-induced changes of microglial morphology in the mouse hippocampus and the release of pro-inflammatory cytokines such as interleukin-1β, interleukin-6, and tumor necrosis factor-α. In addition, purpurin treatment significantly ameliorated D-galactose-induced phosphorylation of c-Jun N-terminal kinase and cleavage of caspase-3 in HT22 cells. These results suggest that purpurin can delay aging by reducing the inflammatory cascade and phosphorylation of the c-Jun N-terminal in the hippocampus.

Dendropanax Morbiferus and Other Species from the Genus Dendropanax: Therapeutic Potential of Its Traditional Uses, Phytochemistry, and Pharmacology

The Dendropanax genus is a kind of flowering plant in the family of Araliaceae that encompasses approximately 91 to 95 species. Several Dendropanax species are used as traditional medicinal plants, extensively used Korea and South America and other parts of the world. Almost every part of the plant, including the leaves, bark, roots, and stems, can be used as traditional medicine for the prevention and management of a broad spectrum of health disorders. This paper sought to summarizes the ethnopharmacological benefits, biological activities, and phytochemical investigations of plants from the genus Dendropanax, and perhaps to subsequently elucidate potential new perspectives for future pharmacological research to consider. Modern scientific literature suggests that plants of the Dendropanax genus, together with active compounds isolated from it, possess a wide range of therapeutic and pharmacological applications, including antifungal, anti-complement, antioxidant, antibacterial, insect antifeedant, cytotoxic, anti-inflammatory, neuroprotective, anti-diabetic, anti-cancer, and anti-hypouricemic properties. The botanical descriptions of approximately six to 10 species are provided by different scientific web sources. However, only six species, namely, D. morbiferus, D. gonatopodus, D. dentiger, D. capillaris, D. chevalieri, and D. arboreus, were included in the present investigation to undergo phytochemical evaluation, due to the unavailability of data for the remaining species. Among these plant species, a high concentration of variable bioactive ingredients was identified. In particular, D. morbifera is a traditional medicinal plant used for the multiple treatment purposes and management of several human diseases or health conditions. Previous experimental evidence supports that the D. morbifera species could be used to treat various inflammatory disorders, diarrhea, diabetes, cancer, and some microbial infections. It has recently been reported, by our group and other researchers, that D. morbifera possesses a neuroprotective and memory-enhancing agent. A total of 259 compounds have been identified among six species, with 78 sourced from five of these species reported to be bioactive. However, there is no up-to-date information concerning the D. morbifera, its different biological properties, or its prospective benefits in the enhancement of human health. In the present study, we set out to conduct a comprehensive analysis of the botany, traditional medicinal history, and medicinal resources of species of the Dendropanax genus. In addition, we explore several phytochemical constituents identified in different species of the Dendropanax genus and their biological properties. Finally, we offer comprehensive analysis findings of the phytochemistry, medicinal uses, pharmacological actions, and a toxicity and safety evaluation of the D. morbifera species and its main bioactive ingredients for future consideration.

High fat diet accelerates and exacerbates microgliosis and neuronal damage/death in the somatosensory cortex after transient forebrain ischemia in gerbils

Obesity has been known as an independent risk factor for stroke. Effects of high-fat diet (HFD)-induced obesity on neuronal damage in the somatosensory cortex of animal models of cerebral ischemia have not been studied yet. In this study, HFD-induced obesity was used to study the impact of obesity on neuronal damage/loss and microgliosis in the somatosensory cortex of a gerbil model of 5-min transient forebrain ischemia. We used gerbils fed normal diet (ND) and HFD and chronologically examined microgliosis (microglial cell activation) by ionized calcium-binding adapter molecule 1 (Iba-1) immunohistochemistry. In addition, we examined neuronal damage or death by using neuronal nuclear protein (NeuN, a neuronal marker) immunohistochemistry and Fluoro-Jade B (F-J B, a marker for neuronal degeneration) histofluorescence staining. We found that ischemia-induced microgliosis in ND-fed gerbils was increased from 2 days post-ischemia; however, ischemia-mediated microgliosis in HFD-fed gerbils increased from 1 day post-ischemia and more accelerated with time than that in the ND-fed gerbils. Ischemia-induced neuronal death/loss in the somatosensory cortex in the ND-fed gerbils was apparently found at 5 days post-ischemia. However, in the HFD-fed gerbils, neuronal death/loss was shown from 2 days post-ischemia and progressively exacerbated at 5 days post-ischemia. Our findings indicate that HFD can evoke earlier microgliosis and more detrimental neuronal death/loss in the somatosensory cortex after transient ischemia than ND evokes.

D-galactose: a model of accelerated ageing sufficiently sensitive to reflect preventative efficacy of an antioxidant treatment

Considering that the phenomenon of accelerated ageing contributes to early onset of various chronic diseases, modelling of the relevant dysregulated systems or responses is vital for research aimed at identification of potential therapeutic targets. Here, we aimed to establish a model capable of simulating the redox and inflammatory changes of accelerated ageing-specifically, the aim was early phase accelerated ageing, which would allow therapeutic intervention in a preventative approach prior to clinical disease manifestation. A secondary aim was to evaluate the sensitivity of the model to reflect preventative treatment efficacy. Daily D-galactose injections (250 mg/kg body mass/day) for 8 weeks in 9-week-old male Wistar rats induced a model of early accelerated ageing (decreased plasma FRAP; P < 0.05 and altered inflammatory signalling) and an aged profile in lymph node ultrastructure, but did not yet result in telomere shortening. Preventative daily oral antioxidant administration (grape seed-derived polyphenol, 100 mg/kg body mass) prevented tissue ageing, beneficially modulated the inflammatory response, including neutrophil chemokinetic capacity, and tended to increase absolute telomere length. Data suggests that using a mild model of D-galactose administration than those employed to induce neurodegeneration, simulated the point where oxidative stress starts to overwhelm the endogenous antioxidant response and where a pro-inflammatory phenotype switch manifests. Furthermore, despite the expected small effect size, the model was sufficiently sensitive to reflect benefits of preventative antioxidant treatment in the context of ageing. This model presents a practical model for use in drug discovery, particularly in the context of preventative medicine aimed at limiting oxidative stress-associated ageing. Since this starting point of accelerated ageing as illustrated by current data, is not expected to reflect major ageing-associated changes yet, we recommend that future preventative drug discovery studies employ a longitudinal study design in order to clearly demonstrate the delay of this starting point by preventative strategies.

Changes of fat-mass and obesity-associated protein expression in the hippocampus in animal models of high-fat diet-induced obesity and D-galactose-induced aging

Fat-mass and obesity-associated protein (Fto) is highly expressed in the brain including, the hippocampus, and its expression is significantly decreased in the brain of Alzheimer’s disease patients. In the present study, we measured Fto immunoreactivity and protein levels in the hippocampus of obese and aged mice, which were induced by high-fat diet for 12 weeks and D-galactose treatment for 10 weeks, respectively. The obesity and aging phenotypes were assessed by physiological parameters and Morris water maze test, respectively. High fat diet fed mice showed significant increases in body weight and blood glucose levels compared to that in the control or D-galactose-induced aged mice. In addition, treatment with D-galactose significantly decreased the spatial memory. Fto immunoreactivity in the control group was mainly detected in the pyramidal cells of the CA1 and CA3 regions and in the granule cells of the dentate gyrus. In the hippocampus of high-fat diet-fed mice, Fto immunoreactive structures were similarly found in the hippocampus compared to that in the control group, but Fto immunoreactivity in high-fat diet-fed mice was also found in the stratum oriens and radiatum of the CA1 and CA3 regions and the polymorphic layer of the dentate gyrus. In the hippocampus of D-galactose-induced aged mice, fewer Fto immunoreactive structures were detected in the granule cell layer of the dentate gyrus compared to the control group. Fto mRNA and protein levels based on quantitative real-time polymerase chain reaction and western blot assays were slightly increased in the hippocampus of high-fat diet-fed mice compared to that in control mice. In addition, Fto mRNA and protein levels were significantly decreased in the aged hippocampus compared to that in the control group. Fto protein levels are susceptible to the aging process, but not in the hippocampus of high-fat diet-induced obesity. The reduction of Fto in aged mice may be associated with reduced memory impairment in mice.

Leaf extracts from Dendropanax morbifera Léveille mitigate mercury-induced reduction of spatial memory, as well as cell proliferation, and neuroblast differentiation in rat dentate gyrus

Background

The brain is susceptible to methylmercury toxicity, which causes irreversible damage to neurons and glia and the leaf extract Dendropanax morbifera Léveille (DML) has various biological functions in the nervous system. In this study, we examined the effects of DML on mercury-induced proliferating cells and differentiated neuroblasts.

Methods

Dimethylmercury (5 μg/kg) and galantamine (5 mg/kg) was administered intraperitoneally and/or DML (100 mg/kg) was orally to 7-week-old rats every day for 36 days. One hour after the treatment, novel object recognition test was examined. In addition, spatial probe tests were conducted on the 6th day after 5 days of continuous training in the Morris swim maze. Thereafter, the rats were euthanized for immunohistochemical staining analysis with Ki67 and doublecortin and measurement for acetylcholinesterase (AChE) activity.

Results

Dimethylmercury-treated rats showed reduced discrimination index in novel object recognition test and took longer to find the platform than did control group. Compared with dimethylmercury treatment alone, supplementation with DML or galatamine significantly ameliorated the reduction of discrimination index and reduced the time spent to find the platform. In addition, the number of platform crossings was lower in the dimethylmercury-treated group than in controls, while the administration of DML or galantamine significantly increased the number of crossings than did dimethylmercury treatment alone. Proliferating cells and differentiated neuroblasts, assessed by Ki67 and doublecortin immunohistochemical staining was significantly decreased in the dimethylmercury treated group versus controls. Supplementation with DML or galantamine significantly increased the number of proliferating cells and differentiated neuroblasts in the dentate gyrus. In addition, treatment with dimethylmercury significantly increased AChE activity in hippocampal homogenates, while treatment with dimethylmercury+DML or dimethylmercury+galantamine significantly ameliorated this increase.

Conclusions

These results suggest that DML may be a functional food that improves dimethylmercury-induced memory impairment and ameliorates dimethylmercury-induced reduction in proliferating cells and differentiated neuroblasts, and demonstrates corresponding activation of AChE activity in the dentate gyrus.