Inhibitor Kappa B Kinase β, Modulated by DJ-1/p-VHL, Reduces Phosphorylated Tau (p-Tau) Accumulation via Autophagy in Alzheimer's Disease Model

Importance of DJ-1 in autophagy regulation and disease

Autophagy is a highly conserved biological process that has evolved across evolution. It can be activated by various external stimuli including oxidative stress, amino acid starvation, infection, and hypoxia. Autophagy is the primary mechanism for preserving cellular homeostasis and is implicated in the regulation of metabolism, cell differentiation, tolerance to starvation conditions, and resistance to aging. As a multifunctional protein, DJ-1 is commonly expressed in vivo and is associated with a variety of biological processes. Its most widely studied role is its function as an oxidative stress sensor that inhibits the production of excessive reactive oxygen species (ROS) in the mitochondria and subsequently the cellular damage caused by oxidative stress. In recent years, many studies have identified DJ-1 as another important factor regulating autophagy; it regulates autophagy in various ways, most commonly by regulating the oxidative stress response. In particular, DJ-1-regulated autophagy is involved in cancer progression and plays a key role in alleviating neurodegenerative diseases(NDS) and defective reperfusion diseases. It could serve as a potential target for the regulation of autophagy and participate in disease treatment as a meaningful modality. Therefore, exploring DJ-1-regulated autophagy could provide new avenues for future disease treatment.

Focus on Alzheimer's Disease: The Role of Fibroblast Growth Factor 21 and Autophagy

Alzheimer's disease (AD) is a disorder of the central nervous system that is typically marked by progressive cognitive impairment and memory loss. Amyloid β plaque deposition and neurofibrillary tangles with hyperphosphorylated tau are the two hallmark pathologies of AD. In mammalian cells, autophagy clears aberrant protein aggregates, thus maintaining proteostasis as well as neuronal health. Autophagy affects production and metabolism of amyloid β and accumulation of phosphorylated tau proteins, whose malfunction can lead to the progression of AD. On the other hand, defective autophagy has been found to induce the production of the neuroprotective factor fibroblast growth factor 21 (FGF21), although the underlying mechanism is unclear. In this review, we highlight the significance of aberrant autophagy in the pathogenesis of AD, discuss the possible mechanisms by which defective autophagy induces FGF21 production, and analyze the potential of FGF21 in the treatment of AD. The findings provide some insights into the potential role of FGF21 and autophagy in the pathogenesis of AD.

Deficiency of Parkinson's Related Protein DJ-1 Alters Cdk5 Signalling and Induces Neuronal Death by Aberrant Cell Cycle Re-entry

DJ-1 is a multifunctional protein involved in Parkinson disease (PD) that can act as antioxidant, molecular chaperone, protease, glyoxalase, and transcriptional regulator. However, the exact mechanism by which DJ-1 dysfunction contributes to development of Parkinson's disease remains elusive. Here, using a comparative proteomic analysis between wild-type cortical neurons and neurons lacking DJ-1 (data available via ProteomeXchange, identifier PXD029351), we show that this protein is involved in cell cycle checkpoints disruption. We detect increased amount of p-tau and α-synuclein proteins, altered phosphoinositide-3-kinase/protein kinase B (PI3K/AKT) and mitogen-activated protein kinase (MAPK) signalling pathways, and deregulation of cyclin-dependent kinase 5 (Cdk5). Cdk5 is normally involved in dendritic growth, axon formation, and the establishment of synapses, but can also contribute to cell cycle progression in pathological conditions. In addition, we observed a decrease in proteasomal activity, probably due to tau phosphorylation that can also lead to activation of mitogenic signalling pathways. Taken together, our findings indicate, for the first time, that aborted cell cycle re-entry could be at the onset of DJ-1-associated PD. Therefore, new approaches targeting cell cycle re-entry can be envisaged to improve current therapeutic strategies.

Molecular mechanisms of Alzheimer's disease: From therapeutic targets to promising drugs

Alzheimer's disease (AD) is a neurodegenerative disease characterized by cognitive impairment so widespread that it interferes with a person's ability to complete daily activities. AD is becoming increasingly common, and it is estimated that the number of patients will reach 152 million by 2050. Current treatment options for AD are symptomatic and have modest benefits. Therefore, considering the human, social, and economic burden of the disease, the development of drugs with the potential to alter disease progression has become a global priority. In this review, the molecular mechanisms involved in the pathology of AD were evaluated as therapeutic targets. The main aim of the review is to focus on new knowledge about mitochondrial dysfunction, oxidative stress, and neuronal transmission in AD, as well as a range of cellular signaling mechanisms and associated treatments. Important molecular interactions leading to AD were described in amyloid cascade and in tau protein function, oxidative stress, mitochondrial dysfunction, cholinergic and glutamatergic neurotransmission, cAMP-regulatory element-binding protein (CREB), the silent mating type information regulation 2 homolog 1 (SIRT-1), neuroinflammation (glial cells), and synaptic alterations. This review summarizes recent experimental and clinical research in AD pathology and analyzes the potential of therapeutic applications based on molecular disease mechanisms.

miR-129 Promotes the Proliferation of Alzheimer’s Neuronal Cells by Binding the 3′ Untranslated Regions (3′ UTR) of Amyloid Precursor Protein (APP)

Alzheimer’s disease (AD) is a neurodegenerative disease with memory loss and cognitive impairment. Short non-coding RNAs (miRNAs) are potential biomarkers and therapeutic targets for AD. This study aims to investigate miR-129’s role in AD. miR-129 and amyloid precursor protein (APP) expression was measured by Q-PCR, and LC3, p62, ATG5, Bcl-2, p-Tau and Caspase3 protein was detected by Western blot. Hydrogenase kits and DCFH-DA detected cell apoptosis, cytotoxicity and ROS generation. The interaction between APP and miR-129 was assessed by luciferase report experiment. HE staining and TUNEL assay evaluated hippocampal neuron damage. In AD patient serum, AD transgenic (TG) mouse brain tissue, and AB1-42-treated SH-SY5Y cells, miR-129 was downregulated but autophagy was increased. Overexpression of miR-129 reduced cell damage induced by AB1-42, and miR-129 can directly regulate APP expression by binding APP 3′-UTR. miR-129 inhibitors reversed the protective effect of shAPP on AB1-42-induced cell damage. In addition, miR-129 overexpression reduced neuronal damage through inhibiting autophagy in vivo. APP expression in AD patient and AD cell model was significantly increased compared to controls. Aβ-42 treatment caused up-regulation of APP expression, while APP knockdown inhibited neurons through autophagy. In conclusion, miR-129 overexpression can regulate autophagy by targeting APP5, thereby reducing neuronal damage in AD. These findings provide a new perspective for treating AD.

MicroRNA-155-5p Targets SKP2, Activates IKKβ, Increases Aβ Aggregation, and Aggravates a Mouse Alzheimer Disease Model

The nuclear factor kappa B (NF-κB) pathway and inhibitor of NF-κB kinase β (IKKβ) are involved in Alzheimer disease (AD) pathogenesis. This study explored the mechanisms underlying IKKβ-mediated Aβ aggregation and neuron regeneration in APP.PS1 mice. Adenoviral transduction particles were injected into the hippocampal CA1 region of the mice to knock down or inhibit target genes. Morris water maze was performed to evaluate the cognitive function of the mice. Aβ deposition was determined by histological examination. sh-IKKβ plasmids and microRNA (miR)-155-5p inhibitor were transfected into Aβ1-42-induced N2a cells. The expressions of AD-related proteins were detected by Western blot. The interaction between S-phase kinase-associated protein 2 (SKP2) and IKKβ was assessed by co-immunoprecipitation. IKKβ knockdown (KD) and miR-155-5p inhibition ameliorated cognitive impairment, improved neuron regeneration, and attenuated Aβ deposition in APP/PS1 mice. SKP2 KD aggravated cognitive impairment, inhibited neuron regeneration, and promoted Aβ deposition in the mice. SKP2 regulated the stability of IKKβ protein via ubiquitination. MiR-155-5p regulates Aβ deposition and the expression of Aβ generation-related proteins in N2a cells via targeting SKP2. These results indicate that the miR-155-5p/SKP2/IKKβ axis was critical for pathogenesis in this AD model and suggest the potential of miR-155-5p as a target for AD treatment.