Effect of AmyTrap, an amyloid-β binding drug, on Aβ induced mitochondrial dysfunction and tau phosphorylation in cultured neuroblastoma cells

Metabolic and Cellular Compartments of Acetyl-CoA in the Healthy and Diseased Brain

The human brain is characterised by the most diverse morphological, metabolic and functional structure among all body tissues. This is due to the existence of diverse neurons secreting various neurotransmitters and mutually modulating their own activity through thousands of pre- and postsynaptic interconnections in each neuron. Astroglial, microglial and oligodendroglial cells and neurons reciprocally regulate the metabolism of key energy substrates, thereby exerting several neuroprotective, neurotoxic and regulatory effects on neuronal viability and neurotransmitter functions. Maintenance of the pool of mitochondrial acetyl-CoA derived from glycolytic glucose metabolism is a key factor for neuronal survival. Thus, acetyl-CoA is regarded as a direct energy precursor through the TCA cycle and respiratory chain, thereby affecting brain cell viability. It is also used for hundreds of acetylation reactions, including N-acetyl aspartate synthesis in neuronal mitochondria, acetylcholine synthesis in cholinergic neurons, as well as divergent acetylations of several proteins, peptides, histones and low-molecular-weight species in all cellular compartments. Therefore, acetyl-CoA should be considered as the central point of metabolism maintaining equilibrium between anabolic and catabolic pathways in the brain. This review presents data supporting this thesis.

OGDHL ameliorates cognitive impairment and Alzheimer's disease-like pathology via activating Wnt/β-catenin signaling in Alzheimer's disease mice

Alzheimer's disease (AD) is one of the most common neurodegenerative diseases related to several types of pathophysiological signs, including β-amyloid (Aβ) plaque accumulation, neuroinflammation, and neurofibrillary tangles. Similar to one of the three subunits of α-ketoglutarate dehydrogenase complex (KGDHC), oxoglutarate dehydrogenase-like (OGDHL) appears to be downregulated in triple-transgenic Alzheimer's (3 × Tg-AD) mice. KGDHC activity is specifically reduced in the brains of people with AD. However, the underlying mechanism of OGDHL in the cause of AD is still unknown. Herein, we confirmed the low expression of OGDHL in the brain of 3 × Tg-AD based on real-time quantitative PCR, Western blot, and immunohistochemistry. We also found that the upregulation of OGDHL can reduce the memory deficits of 3 × Tg-AD mice, thereby reminding its nervous system neuroprotective effect in AD. Next, we confirmed that the increase in OGDHL could reduce neuroinflammation, amyloid plaque load, and tau phosphorylation in 3 × Tg-AD mice. Additionally, we showed that the overexpression of OGDHL could activate Wnt/β-catenin signaling based on the expression of Wnt7B in vitro. Taken together, the results show that the rise of OGDHL reasonably improves the cognitive functions according to the activation of the Wnt/β-catenin signaling pathway. Therefore, this enzyme may be a potential strategy for AD treatment.

Formaldehyde toxicity in age-related neurological dementia

The primordial small gaseous molecules, such as: NO, CO, H₂S and formaldehyde (FA) are present in the brains. Whether FA as well as the other molecules participates in brain functions is unclear. Recently, its pathophysiological functions have been investigated. Notably, under physiological conditions, learning activity induces a transient generation of hippocampal FA, which promotes memory formation by enhancing N-methyl-D-aspartate (NMDA)-currents. However, ageing leads to FA accumulation in brain for the dysregulation of FA metabolism; and excessive FA directly impairs memory by inhibiting NMDA-receptor. Especially, in Alzheimer's disease (AD), amyloid-beta (Aβ) accelerates FA accumulation by inactivating alcohol dehydrogenase-5; in turn, FA promotes Aβ oligomerization, fibrillation and tau hyperphosphorylation. Hence, there is a vicious circle encompassing Aβ assembly and FA generation. Even worse, FA induces Aβ deposition in the extracellular space (ECS), which blocks the medicines (dissolved in the interstitial fluid) flowing into the damaged neurons in the deep cortex. However, phototherapy destroys Aβ deposits in the ECS and restores ISF flow. Coenzyme Q10, which scavenges FA, was shown to ameliorate Aβ-induced AD pathological phenotypes, thus suggesting a causative relation between FA toxicity and AD. These findings suggest that the combination of these two methods is a promising strategy for treating AD.

Opposite Roles of Co-enzyme Q10 and Formaldehyde in Neurodegenerative Diseases

Most of neurodegenerative diseases (NDD) have no cure. The common etiology of neurodegenerations is unclear. Air pollutant-gaseous formaldehyde is notoriously known to induce demyelination and cognitive impairments. Unexpectedly, an amount of formaldehyde has been detected in the brains. Multiple factors can induce the generation and accumulation of endogenous formaldehyde. Excessive formaldehyde can induce oxidative stress to generate H2O2; in turn, H2O2 promote formaldehyde production. Clinical investigations have shown that an abnormal high level of formaldehyde but low level of coenzyme Q10 (coQ10) was observed in patients with NDD. Further studies have proven that excessive formaldehyde directly inactivates coQ10, reduces the ATP generation, enhances oxidative stress, initiates inflammation storm, induces demyelination; subsequently, it results in neurodegeneration. Although the low water solubility of coQ10 limits its clinical application, nanomicellar water-soluble coQ10 exhibits positive therapeutical effects. Hence, nanopackage of coQ10 may be a promising strategy for treating NDD.