Amyloid-β(25-35) induces a permanent phosphorylation of HSF-1, but a transitory and inflammation-independent overexpression of Hsp-70 in C6 astrocytoma cells

Mitochondrial chaperones in human health and disease

Molecular chaperones are a family of proteins that maintain cellular protein homeostasis through non-covalent peptide folding and quality control mechanisms. The chaperone proteins found within mitochondria play significant protective roles in mitochondrial biogenesis, quality control, and stress response mechanisms. Defective mitochondrial chaperones have been implicated in aging, neurodegeneration, and cancer. In this review, we focus on the two most prominent mitochondrial chaperones: mtHsp60 and mtHsp70. These proteins demonstrate different cellular localization patterns, interact with different targets, and have different functional activities. We discuss the structure and function of these prominent mitochondrial chaperone proteins and give an update on newly discovered regulatory mechanisms and disease implications.

Nicotinamide Ameliorates Amyloid Beta-Induced Oxidative Stress-Mediated Neuroinflammation and Neurodegeneration in Adult Mouse Brain

Alzheimer’s disease (AD) is the most predominant age-related neurodegenerative disease, pathologically characterized by the accumulation of aggregates of amyloid beta Aβ_1–42 and tau hyperphosphorylation in the brain. It is considered to be the primary cause of cognitive dysfunction. The aggregation of Aβ_1–42 leads to neuronal inflammation and apoptosis. Since vitamins are basic dietary nutrients that organisms need for their growth, survival, and other metabolic functions, in this study, the underlying neuroprotective mechanism of nicotinamide (NAM) Vitamin B3 against Aβ_1–42 -induced neurotoxicity was investigated in mouse brains. Intracerebroventricular (i.c.v.) Aβ_1–42 injection elicited neuronal dysfunctions that led to memory impairment and neurodegeneration in mouse brains. After 24 h after Aβ_1–42 injection, the mice were treated with NAM (250 mg/kg intraperitoneally) for 1 week. For biochemical and Western blot studies, the mice were directly sacrificed, while for confocal and “immunohistochemical staining”, mice were perfused transcardially with 4% paraformaldehyde. Our biochemical, immunofluorescence, and immunohistochemical results showed that NAM can ameliorate neuronal inflammation and apoptosis by reducing oxidative stress through lowering malondialdehyde and 2,7-dichlorofluorescein levels in an Aβ_1–42-injected mouse brains, where the regulation of p-JNK further regulated inflammatory marker proteins (TNF-α, IL-1β, transcription factor NF-kB) and apoptotic marker proteins (Bax, caspase 3, PARP1). Furthermore, NAM + Aβ treatment for 1 week increased the amount of survival neurons and reduced neuronal cell death in Nissl staining. We also analyzed memory dysfunction via behavioral studies and the analysis showed that NAM could prevent Aβ_1–42 -induced memory deficits. Collectively, the results of this study suggest that NAM may be a potential preventive and therapeutic candidate for Aβ_1–42 -induced reactive oxygen species (ROS)-mediated neuroinflammation, neurodegeneration, and neurotoxicity in an adult mouse model.

Associations between metabolic syndrome and type of dementia: analysis based on the National Health Insurance Service database of Gangwon province in South Korea

BACKGROUND

Metabolic syndrome is a cluster of conditions that occur together, increasing the risk of cardiovascular disease. However, the relationship between metabolic syndrome and dementia has remained controversial. Using nationwide population cohort data, we investigated the association between metabolic syndrome and dementia, according to the dementia type.

METHODS

We analyzed data of 84,144 individuals, in the aged group of more than 60 years, between January 1, 2009, to December 31, 2009, at Gangwon province by using the information of the (Korean) National Health Insurance Service. After eight years of gap, in 2017, we investigated the relationship between metabolic syndrome and dementia. We classified Dementia either as dementia of the Alzheimer type (AD) or vascular dementia (VD). AD and VD were defined as per the criteria of International Classification of Disease, Tenth Revision, Clinical Modification codes. Multiple logistic regression analyses examined the associations between metabolic syndrome or five metabolic syndrome components and dementia. Analyses included factors like age, sex, smoking, alcohol, physical inactivity, previous stroke, and previous cardiac disease.

RESULTS

Metabolic syndrome was associated with AD (OR = 11.48, 95% CI 9.03-14.59), not with VD. Each of five components of metabolic syndrome were also associated with AD. (high serum triglycerides: OR = 1.87, 95% CI 1.60-2.19; high blood pressure: OR = 1.85, 95% CI 1.55-2.21; high glucose: OR = 1.77, 95% CI 1.52-2.06; abdominal obesity: OR = 1.88, 95% CI 1.57-2.25; low serum high-density lipoprotein cholesterol: OR = 1.91, 95% CI 1.63-2.24) However, among components of metabolic syndrome, only the high glucose level was associated with VD. (OR = 1.26, 95% CI 1.01-1.56) body mass index (BMI), fasting glucose, and smoking were also associated with AD. (BMI: OR = 0.951, 95% CI 0.927-0.975; fasting glucose: OR = 1.003, 95% CI 1.001-1.005; smoking: OR = 1.020, 95% CI 1.003-1.039) A history of the previous stroke was associated with both AD and VD. (AD: OR = 1.827, 95% CI 1.263-2.644; VD: OR 2.775, 95% CI 1.747-4.406) CONCLUSIONS: Metabolic syndrome was associated with AD but not with VD. Patients with metabolic syndrome had an 11.48 times more likeliness to develop AD compared to those without metabolic syndrome. VD was associated only with several risk factors that could affect the vascular state rather than a metabolic syndrome. We suggested that the associations between metabolic syndrome and dementia would vary depending on the type of dementia.

Epicatechin Reduces Spatial Memory Deficit Caused by Amyloid-β25⁻35 Toxicity Modifying the Heat Shock Proteins in the CA1 Region in the Hippocampus of Rats

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by dementia and the aggregation of the amyloid beta peptide (Aβ). Aβ_25-35 is the most neurotoxic sequence, whose mechanism is associated with the neuronal death in the Cornu Ammonis 1 (CA1) region of the hippocampus (Hp) and cognitive damage. Likewise, there are mechanisms of neuronal survival regulated by heat shock proteins (HSPs). Studies indicate that pharmacological treatment with flavonoids reduces the prevalence of AD, particularly epicatechin (EC), which shows better antioxidant activity. The aim of this work was to evaluate the effect of EC on neurotoxicity that causes Aβ_25-35 at the level of spatial memory as well as the relationship with immunoreactivity of HSPs in the CA1 region of the Hp of rats. Our results show that EC treatment reduces the deterioration of spatial memory induced by the Aβ_25-35, in addition to reducing oxidative stress and inflammation in the Hp of the animals treated with EC + Aβ_25-35. Likewise, the immunoreactivity to HSP-60, -70, and -90 is lower in the EC + Aβ_25-35 group compared to the Aβ_25-35 group, which coincides with a decrease of dead neurons in the CA1 region of the Hp. Our results suggest that EC reduces the neurotoxicity induced by Aβ_25-35, as well as the HSP-60, -70, and -90 immunoreactivity and neuronal death in the CA1 region of the Hp of rats injected with Aβ_25-35, which favors an improvement in the function of spatial memory.

Alzheimer's disease and metabolic syndrome: A link from oxidative stress and inflammation to neurodegeneration

Alzheimer's disease (AD) is the most common cause of dementia and one of the most important causes of morbidity and mortality among the aging population. AD diagnosis is made post-mortem, and the two pathologic hallmarks, particularly evident in the end stages of the illness, are amyloid plaques and neurofibrillary tangles. Currently, there is no curative treatment for AD. Additionally, there is a strong relation between oxidative stress, metabolic syndrome, and AD. The high levels of circulating lipids and glucose imbalances amplify lipid peroxidation that gradually diminishes the antioxidant systems, causing high levels of oxidative metabolism that affects cell structure, leading to neuronal damage. Accumulating evidence suggests that AD is closely related to a dysfunction of both insulin signaling and glucose metabolism in the brain, leading to an insulin-resistant brain state. Four drugs are currently used for this pathology: Three FDA-approved cholinesterase inhibitors and one NMDA receptor antagonist. However, wide varieties of antioxidants are promissory to delay or prevent the symptoms of AD and may help in treating the disease. Therefore, therapeutic efforts to achieve attenuation of oxidative stress could be beneficial in AD treatment, attenuating Aβ-induced neurotoxicity and improve neurological outcomes in AD. The term inflammaging characterizes a widely accepted paradigm that aging is accompanied by a low-grade chronic up-regulation of certain pro-inflammatory responses in the absence of overt infection, and is a highly significant risk factor for both morbidity and mortality in the elderly.

Antioxidative stress effect of epicatechin and catechin induced by Aβ25-35 in rats and use of the electrostatic potential and the Fukui function as a tool to elucidate specific sites of interaction

Alzheimer's disease (AD) is a neurodegenerative disorder caused by the aggregation of the amyloid-beta peptide (Aβ) in senile plaques and cerebral vasculature. The Aβ_25-35 fraction has shown the most toxicity; its neurotoxic mechanisms are associated with the generation of oxidative stress and reactive astrogliosis that induce neuronal death and memory impairment. Studies indicate that pharmacological treatment with flavonoids reduces the rate of AD, in particular, it has been shown that antioxidants are compounds that could interact with this peptide due to their antioxidant proprieties. In this study, experimental and computational tools were used to calculate the molecular electrostatic potential and the Fukui function with the Gaussian 09 computational program, to predict the most reactive parts of these molecules and make the complex between Aβ_25-35 and two flavonoids (catechin and epicatechin) in the absolute gas-phase, where a possible interaction between them was observed. This is important for understanding the Aβ_25-35-Flavonoid (A-F) interaction as a therapeutic strategy to inhibit the neurotoxic effects that this peptide causes in AD, which currently is still considered an ambiguous process.

Protective Effects of Liquiritin on the Brain of Rats with Alzheimer's Disease

Background

Alzheimer's disease (AD) is a sort of nerve degenerative disease with clinical manifestation of memory damage and cognitive dysfunction. Its typical pathological change is the abnormal deposition of amyloid-beta (Aβ).

Method

In this study, a rat AD model with liquiritin (LQ) interference was established to observe the effects of LQ on the AD rats' behavioural memory and primary hippocampus cells.

Results

Liquiritin had the effect of improving the rats' learning and memory ability, enhancing the activity of catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) in rats' brain tissues, increasing the antioxidant ability, protecting the primary cultured hippocampal neurons and inhibiting the apoptosis induced by Aβ_25-35.

Conclusion

The protective effects of LQ can be related to the enhancement of antioxidase activity and clearance of oxygen radicals.

The synergistic effects of heat shock protein 70 and ginsenoside Rg1 against tert-butyl hydroperoxide damage model in vitro

Neural stem cells (NSCs) transplanted is one of the hottest research to treat Alzheimer's disease (AD), but cholinergic neurons from stem cells were also susceptible to cell death which Heat shock protein 70 (HSP70) was affirmed to reverse. Related to cognitive impairment, cholinergic nervous cells should be investigated and ginsenoside Rg1 (G-Rg1) was considered to increase them. We chose tert-butyl hydroperoxide (t-BHP) damage model to study in vitro. Functional properties of our recombination plasmid pEGFP-C2-HSP70 were affirmed by SH-SY5Y cells. To opposite the transitory appearance of HSP70, NSCs used as the vectors of HSP70 gene overexpressed HSP70 for at least 7 days in vitro. After transfection for 3 days, G-Rg1 pretreatment for 4 hours, and coculture for 3 days, the expression of acetylcholinesterase (ChAT), synaptophysin, and the ratio of NeuN and GFAP were assessed by western blot; Morphological properties were detected by 3D reconstruction and immunofluorescence. ChAT was markedly improved in the groups contained G-Rg1. In coculture system, the ratio of neurons/astrocytes and the filaments of neurons were increased; apoptosis cells were decreased, compared to monotherapy (P < 0.05). In conclusion, we demonstrated that, as a safe cotreatment affirmed in vitro, overexpression of HSP70 in NSCs plus G-Rg1 promoted nervous cells regeneration from chronic oxidative damage.

RIG-1 receptor expression in the pathology of Alzheimer's disease

BACKGROUND

Neuroinflammation plays a critical role in the pathogenesis of Alzheimer's disease (AD) and involves activation of the innate immune response via recognition of diverse stimuli by pattern recognition receptors (PRRs). The inflammatory inducers and precise innate signaling pathway contributing to AD pathology remain largely undefined.

RESULTS

In the present study we analyzed expression levels of innate immune proteins in temporal and occipital cortices from preclinical (no cognitive impairment, NCI, N = 22) to mild cognitive impairment (MCI, N = 20) associated with AD pathology (N = 20) and AD patients (N = 23). We found that retinoic acid-inducible gene-I (RIG-1) is significantly elevated in the temporal cortex and plasma in patients with MCI. In addition, primary human astrocytes stimulated with the RIG-1 ligand 5'ppp RNA showed increased expression of amyloid precursor protein (APP) and amyloid-β (Aβ), supporting the idea that RIG-1 is involved in the pathology of MCI associated with early progression to AD.

CONCLUSION

These findings suggest that RIG-1 may play a critical role in incipient AD.