Pathways to healing: Plants with therapeutic potential for neurodegenerative diseases

Some of the greatest challenges in medicine are the neurodegenerative diseases (NDs), which remain without a cure and mostly progress to death. A companion study employed a toolkit methodology to document 2001 plant species with ethnomedicinal uses for alleviating pathologies relevant to NDs, focusing on its relevance to Alzheimer's disease (AD). This study aimed to find plants with therapeutic bioactivities for a range of NDs. 1339 of the 2001 plant species were found to have a bioactivity from the literature of therapeutic relevance to NDs such as Parkinson's disease, Huntington's disease, AD, motor neurone diseases, multiple sclerosis, prion diseases, Neimann-Pick disease, glaucoma, Friedreich's ataxia and Batten disease. 43 types of bioactivities were found, such as reducing protein misfolding, neuroinflammation, oxidative stress and cell death, and promoting neurogenesis, mitochondrial biogenesis, autophagy, longevity, and anti-microbial activity. Ethno-led plant selection was more effective than random selection of plant species. Our findings indicate that ethnomedicinal plants provide a large resource of ND therapeutic potential. The extensive range of bioactivities validate the usefulness of the toolkit methodology in the mining of this data. We found that a number of the documented plants are able to modulate molecular mechanisms underlying various key ND pathologies, revealing a promising and even profound capacity to halt and reverse the processes of neurodegeneration.

The satiating hormone amylin enhances neurogenesis in the area postrema of adult rats

OBJECTIVE

Adult neurogenesis in the subgranular zone and subventricular zone is generally accepted, but its existence in other brain areas is still controversial. Circumventricular organs, such as the area postrema (AP) have recently been described as potential neurogenic niches in the adult brain. The AP is the major site of action of the satiating hormone amylin. Amylin has been shown to promote the formation of neuronal projections originating from the AP in neonatal rodents but the role of amylin in adult neurogenesis remains unknown.

METHODS

To test this, we first performed an RNA-sequencing of the AP of adult rats acutely injected with either amylin (20 μg/kg), amylin plus the amylin receptor antagonist AC187 (500 μg/kg) or vehicle. Second, animals were subcutaneously equipped with minipumps releasing either amylin (50 μg/kg/day) or vehicle for 3 weeks to assess cell proliferation and differentiation with the 5'-bromo-2-deoxyuridine (BrdU) technique.

RESULTS

Acute amylin injections affected genes involved in pathways and processes that control adult neurogenesis. Amylin consistently upregulated NeuroD1 transcript and protein in the adult AP, and this effect was blocked by the co-administration of AC187. Further, chronic amylin treatment increased the number of newly proliferated AP-cells and significantly promoted their differentiation into neurons rather than astrocytes.

CONCLUSION

Our findings revealed a novel role of the satiating hormone amylin in promoting neurogenesis in the AP of adult rats.

Tauroursodeoxycholic acid increases neural stem cell pool and neuronal conversion by regulating mitochondria-cell cycle retrograde signaling

The low survival and differentiation rates of stem cells after either transplantation or neural injury have been a major concern of stem cell-based therapy. Thus, further understanding long-term survival and differentiation of stem cells may uncover new targets for discovery and development of novel therapeutic approaches. We have previously described the impact of mitochondrial apoptosis-related events in modulating neural stem cell (NSC) fate. In addition, the endogenous bile acid, tauroursodeoxycholic acid (TUDCA) was shown to be neuroprotective in several animal models of neurodegenerative disorders by acting as an anti-apoptotic and anti-oxidant molecule at the mitochondrial level. Here, we hypothesize that TUDCA might also play a role on NSC fate decision. We found that TUDCA prevents mitochondrial apoptotic events typical of early-stage mouse NSC differentiation, preserves mitochondrial integrity and function, while enhancing self-renewal potential and accelerating cell cycle exit of NSCs. Interestingly, TUDCA prevention of mitochondrial alterations interfered with NSC differentiation potential by favoring neuronal rather than astroglial conversion. Finally, inhibition of mitochondrial reactive oxygen species (mtROS) scavenger and adenosine triphosphate (ATP) synthase revealed that the effect of TUDCA is dependent on mtROS and ATP regulation levels. Collectively, these data underline the importance of mitochondrial stress control of NSC fate decision and support a new role for TUDCA in this process.

p38α controls self-renewal and fate decision of neurosphere-forming cells in adult hippocampus

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Neural stem cells (NSC) from the adult hippocampus easily lose their activity in vitro.

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Inhibition of p38α enables successful long-term culture of adult hippocampus NSC.

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Inhibition of p38α can maintain a high neurogenic capacity for NSC.

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Neurogenic competence-related microRNAs are upregulated in NSC by p38α inhibition.

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In vitro expanded NSC by p38α inhibition are beneficial against brain damage.

Neural stem cells (NSC) from the adult hippocampus easily lose their activity in vitro. Efficient in vitro expansion of adult hippocampus-derived NSC is important for generation of tools for research and cell therapy. Here, we show that a single copy disruption or pharmacological inhibition of p38α enables successful long-term neurosphere culture of adult mouse hippocampal cells. Expanded neurospheres with high proliferative activity differentiated into the three neuronal lineages under differentiating conditions. Thus, inhibition of p38α can maintain adult hippocampal NSC activity in vitro.

Ameliorating effects of traditional Chinese medicine preparation, Chinese materia medica and active compounds on ischemia/reperfusion-induced cerebral microcirculatory disturbances and neuron damage

Ischemic stroke and ischemia/reperfusion (I/R) injury induced by thrombolytic therapy are conditions with high mortality and serious long-term physical and cognitive disabilities. They have a major impact on global public health. These disorders are associated with multiple insults to the cerebral microcirculation, including reactive oxygen species (ROS) overproduction, leukocyte adhesion and infiltration, brain blood barrier (BBB) disruption, and capillary hypoperfusion, ultimately resulting in tissue edema, hemorrhage, brain injury and delayed neuron damage. Traditional Chinese medicine (TCM) has been used in China, Korea, Japan and other Asian countries for treatment of a wide range of diseases. In China, the usage of compound TCM preparation to treat cerebrovascular diseases dates back to the Han Dynasty. Even thousands of years earlier, the medical formulary recorded many classical prescriptions for treating cerebral I/R-related diseases. This review summarizes current information and underlying mechanisms regarding the ameliorating effects of compound TCM preparation, Chinese materia medica, and active components on I/R-induced cerebral microcirculatory disturbances, brain injury and neuron damage.