Protective Activity of Aβ on Cell Cultures (PC12 and THP-1 after Differentiation) Preincubated with Lipopolysaccharide (LPS)

Activation of multifunctional DNA repair APE1/Ref-1 enzyme by the dietary phytochemical Ferulic acid protects human neuroblastoma SH-SY5Y cells against Aβ(25-35)-Induced oxidative stress and inflammatory responses

Alzheimer's disease (AD) is a multifactorial neurodegenerative disorder associated with the amyloid beta (Aβ) and tau hallmarks. The molecular insights into how neuroinflammation is initially triggered and how it affects neuronal cells are yet at the age of infancy. In this study, SH-SY5Y cells were used as a model for neurons by differentiating and were co-cultured with differentiated THP1 cells (microglia model) as well as treated with Aβ(25-35) and with antioxidant FA to study inflammatory, oxidative stress responses and their effects on co-cultured neurons. Neurons co-cultured with microglial cells showed pronounced increase in ROS levels, NOS expression, truncated N-terminal form (34 kDa) of APE1 expression and AIF's translocation in the nucleus. The pre-treatment of FA, on the other hand reversed these effects. It was further evaluated how FA/Aβ treatment altered microglial phenotype that in turn affected the neurons. Microglial cells showed M1 phenotype upon Aβ(25-35) stress, while FA induced M2 phenotype against Aβ stress, suggesting that FA alleviated Aβ induced phenotype and its associated effects in the co-cultured neurons by altering the phenotype of microglial cells and induced expression of full length (37 kDa) APE1 enzyme and inhibiting AIF's nuclear translocation, thus inhibiting apoptosis. This is the first study that revealed Aβ induced cleavage of APE1 enzyme in differentiated neurons, suggesting that APE1 may be the potential early target of Aβ that loses its function and exacerbates AD pathology. FA activated a fully functional form of APE1 against Aβ stress. The impaired function of APE1 could be the initial mechanism by which Aβ induces oxidative and inflammatory responses and dietary phytochemical FA can be a potential therapeutic strategy in managing the disease by activating APE1 that not only repairs oxidative DNA base damage but also maintains mitochondrial function and alleviate neuroinflammatory responses.

Diversity of amyloid beta peptide actions

Fibril formation by amyloidogenic proteins and peptides is considered the cause of a number of incurable diseases. One of the most known amyloid diseases is Alzheimer's disease (AD). Traditionally, amyloidogenic beta peptides Aβ40 and Aβ42 (Aβs) are considered as main causes of AD and the foremost targets in AD fight. The main efforts in pharmacology are aimed at reducing Aβs concentration to prevent their accumulation, aggregation, formation of senile plaques, neuronal death, and neurodegeneration. However, a number of publications have demonstrated certain beneficial physiological effects of Aβs. Simultaneously, it is indicated that the effects of Aβs turn into pathological due to the development of certain diseases in the body. The accumulation of C- and N-terminal truncated Aβs under diverse conditions is supposed to play a role in AD development. The significance of transformation of glutamate residue at positions 3 or 11 of Aβs catalyzed by glutaminyl cyclase making them more degradation resistant, hydrophobic, and prone to aggregation, as well as the participation of dipeptidyl peptidase IV in these transformations are discussed. The experimental data presented confirm the maintenance of physiological, nonaggregated state of Aβs by plant preparations. In conclusion, this review suggests that in the fight against AD, instead of removing Aβs, preference should be given to the treatment of common diseases. Glutaminyl cyclase and dipeptidyl peptidase IV can be considered as targets in AD treatment. Flavonoids and plant preparations that possess antiamyloidogenic propensity are proposed as beneficial neuroprotective, anticancer, and antidiabetic food additives.

Fraction of C. d. collilineatus venom containing crotapotin protects PC12 cells against MPP + toxicity by activating the NGF-signaling pathway

Background

Parkinson's disease (PD) is the second most prevalent neurodegenerative disease. There is no effective treatment for neurodegenerative diseases. Snake venoms are a cocktail of proteins and peptides with great therapeutic potential and might be useful in the treatment of neurodegenerative diseases. Crotapotin is the acid chain of crotoxin, the major component of Crotalus durissus collilineatus venom. PD is characterized by low levels of neurotrophins, and synaptic and axonal degeneration; therefore, neurotrophic compounds might delay the progression of PD. The neurotrophic potential of crotapotin has not been studied yet.

Methods

We evaluated the neurotrophic potential of crotapotin in untreated PC12 cells, by assessing the induction of neurite outgrowth. The activation of the NGF signaling pathway was investigated through pharmacological inhibition of its main modulators. Additionally, its neuroprotective and neurorestorative effects were evaluated by assessing neurite outgrowth and cell viability in PC12 cells treated with the dopaminergic neurotoxin MPP+ (1-methyl-4-phenylpyridinium), known to induce Parkinsonism in humans and animal models.

Results

Crotapotin induced neuritogenesis in PC12 cells through the NGF-signaling pathway, more specifically, by activating the NGF-selective receptor trkA, and the PI3K/Akt and the MAPK/ERK cascades, which are involved in neuronal survival and differentiation. In addition, crotapotin had no cytotoxic effect and protected PC12 cells against the inhibitory effects of MPP+ on cell viability and differentiation.

Conclusion

These findings show, for the first time, that crotapotin has neurotrophic/neuroprotective/neurorestorative potential and might be beneficial in Parkinson's disease. Additional studies are necessary to evaluate the toxicity of crotapotin in other cell models.

Neuroprotective Effects of Polysaccharides and Gallic Acid from Amauroderma rugosum against 6-OHDA-Induced Toxicity in SH-SY5Y Cells

The pharmacological activity and medicinal significance of Amauroderma rugosum (AR) have rarely been documented. We examined the antioxidant and neuroprotective effects of AR on 6-hydroxydopamine (6-OHDA)-induced neurotoxicity in an SH-SY5Y human neuroblastoma cell model of Parkinson's disease (PD) and explored the active ingredients responsible for these effects. The results showed that the AR aqueous extract could scavenge reactive oxygen species and reduce SH-SY5Y cell death induced by 6-OHDA. In addition, the AR aqueous extract increased the survival of Caenorhabditis elegans upon juglone-induced toxicity. Among the constituents of AR, only polysaccharides and gallic acid exhibited antioxidant and neuroprotective effects. The AR aqueous extract reduced apoptosis and increased the expression of phospho-Akt, phospho-mTOR, phospho-MEK, phospho-ERK, and superoxide dismutase-1 in 6-OHDA-treated SH-SY5Y cells. The polysaccharide-rich AR extract was slightly more potent than the aqueous AR extract; however, it did not affect the expression of phospho-Akt or phospho-mTOR. In conclusion, the AR aqueous extract possessed antioxidant and neuroprotective properties against 6-OHDA-induced toxicity in SH-SY5Y cells. The mechanism of action involves the upregulation of the Akt/mTOR and MEK/ERK-dependent pathways. These findings indicate the potential utility of AR and its active ingredients in preventing or treating neurodegenerative disorders associated with oxidative stress such as PD.

Does a pickle a day keep Alzheimer's away? Fermented food in Alzheimer's disease: A review

Fermented food is commonly viewed as healthy, mostly due to its probiotic and digestion-enhancing properties and recently it has been examined with regard to the development of new therapeutic and preventive measures for Alzheimer's disease. Fermented food has been shown to have anti-inflammatory and antioxidant properties and to alter the gut microbiota. However, the exact pathogenesis of Alzheimer's disease is still unknown and its connections to systemic inflammation and gut dysbiosis, as potential targets of fermented food, require further investigation. Therefore, to sum up the current knowledge, this article reviews recent research on the pathogenesis of Alzheimer's disease with emphasis on the role of the gut-brain axis and studies examining the use of fermented foods. The analysis of the fermented food research includes clinical and preclinical in vivo and in vitro studies. The fermented food studies have shown promising effects on amyloid-β metabolism, inflammation, and cognitive impairment in animals and humans. Fermented food has great potential in developing new approaches to Alzheimer's disease treatment.

Does Inflammation Play a Major Role in the Pathogenesis of Alzheimer's Disease?

Alzheimer's disease (AD) is a neurodegenerative disease leading to dementia for which no effective medicine exists. Currently, the goal of therapy is only to slow down the inevitable progression of the disease and reduce some symptoms. AD causes the accumulation of proteins with the pathological structure of Aβ and tau and the induction of inflammation of nerves in the brain, which lead to the death of neurons. The activated microglial cells produce pro-inflammatory cytokines that induce a chronic inflammatory response and mediate synapse damage and the neuronal death. Neuroinflammation has been an often ignored aspect of ongoing AD research. There are more and more scientific papers taking into account the aspect of neuroinflammation in the pathogenesis of AD, although there are no unambiguous results regarding the impact of comorbidities or gender differences. This publication concerns a critical look at the role of inflammation in the progression of AD, based on the results of our own in vitro studies using model cell cultures and other researchers.

Influence of 40 Hz and 100 Hz Vibration on SH-SY5Y Cells Growth and Differentiation-A Preliminary Study

(1) Background: A novel bioreactor platform of neuronal cell cultures using low-magnitude, low-frequency (LMLF) vibrational stimulation was designed to discover vibration influence and mimic the dynamic environment of the in vivo state. To better understand the impact of 40 Hz and 100 Hz vibration on cell differentiation, we join biotechnology and advanced medical technology to design the nano-vibration system. The influence of vibration on the development of nervous tissue on the selected cell line SH-SY5Y (experimental research model in Alzheimer’s and Parkinson’s) was investigated. (2) Methods: The vibration stimulation of cell differentiation and elongation of their neuritis were monitored. We measured how vibrations affect the morphology and differentiation of nerve cells in vitro. (3) Results: The highest average length of neurites was observed in response to the 40 Hz vibration on the collagen surface in the differentiating medium, but cells response did not increase with vibration frequency. Also, vibrations at a frequency of 40 Hz or 100 Hz did not affect the average density of neurites. 100 Hz vibration increased the neurites density significantly with time for cultures on collagen and non-collagen surfaces. The exposure of neuronal cells to 40 Hz and 100 Hz vibration enhanced cell differentiation. The 40 Hz vibration has the best impact on neuronal-like cell growth and differentiation. (4) Conclusions: The data demonstrated that exposure to neuronal cells to 40 Hz and 100 Hz vibration enhanced cell differentiation and proliferation. This positive impact of vibration can be used in tissue engineering and regenerative medicine. It is planned to optimize the processes and study its molecular mechanisms concerning carrying out the research.

Effect of amyloid-β on the redox system activity in SH-SY5Y cells preincubated with lipopolysaccharide or co-cultured with microglia cells

Amyloid deposits and hyperphosphorylation of the tau protein are still believed to be the two main causes of Alzheimer's disease. However, newer studies show the beneficial (including antiradical and antimicrobial) effects of amyloid at physiological concentrations. Therefore, this study aimed to investigate the impact of three amyloid fragments - 25-35, 1-40, and 1-42 at concentrations close to physiological levels on the oxidative stress induced by the administration of lipopolysaccharide (LPS) or co-culturing with microglia cells. Differentiated SH-SY5Y cells were used, constituting a model of neuronal cells that were preincubated with LPS or supernatant collected from THP-1 cell culture. The cells were treated with amyloid-β fragments at concentrations of 0.001, 0.1, and 1.0 µM, and then biological assays were carried out. The results of the study support the antioxidant properties of Aβ, which may protect neurons from the damaging effects of neuroinflammation. All tested amyloid-β fragments reduced oxidative stress and increased the levels of enzymatic stress parameters - the activity of SOD, GPx and catalase. In addition, the administration of amyloid-β at low physiological concentrations also increased reduced glutathione (GSH) levels and the ratio between reduced and oxidized glutathione (GSH/GSSG), which is considered a good indicator of maintaining cellular redox balance. Furthermore, a stronger antioxidant effect of 1-40 fragment was observed, occurring in a wider range of concentrations, compared to the other tested fragments 25-35 and 1-42.

Physiological Roles of Monomeric Amyloid-β and Implications for Alzheimer's Disease Therapeutics

Alzheimer's disease (AD) progressively inflicts impairment of synaptic functions with notable deposition of amyloid-β (Aβ) as senile plaques within the extracellular space of the brain. Accordingly, therapeutic directions for AD have focused on clearing Aβ plaques or preventing amyloidogenesis based on the amyloid cascade hypothesis. However, the emerging evidence suggests that Aβ serves biological roles, which include suppressing microbial infections, regulating synaptic plasticity, promoting recovery after brain injury, sealing leaks in the blood-brain barrier, and possibly inhibiting the proliferation of cancer cells. More importantly, these functions were found in in vitro and in vivo investigations in a hormetic manner, that is to be neuroprotective at low concentrations and pathological at high concentrations. We herein summarize the physiological roles of monomeric Aβ and current Aβ-directed therapies in clinical trials. Based on the evidence, we propose that novel therapeutics targeting Aβ should selectively target Aβ in neurotoxic forms such as oligomers while retaining monomeric Aβ in order to preserve the physiological functions of Aβ monomers.

The Role of the Microbiota-Gut-Brain Axis in the Development of Alzheimer's Disease

Along with the increase in life expectancy in the populations of developed and developing countries resulting from better access and improved health care, the number of patients with dementia, including Alzheimer’s disease (AD), is growing. The disease was first diagnosed and described at the beginning of the 20th century. However, to this day, there is no effective causal therapy, and symptomatic treatment often improves patients’ quality of life only for a short time. The current pharmacological therapies are based mainly on the oldest hypotheses of the disease—cholinergic (drugs affecting the cholinergic system are available), the hypothesis of amyloid-β aggregation (an anti-amyloid drug was conditionally approved by the FDA in 2020), and one drug is an N-methyl-D-aspartate receptor (NMDAR) antagonist (memantine). Hypotheses about AD pathogenesis focus on the nervous system and the brain. As research progresses, it has become known that AD can be caused by diseases that have been experienced over the course of a lifetime, which could also affect other organs. In this review, we focus on the potential association of AD with the digestive system, primarily the gut microbiota. The role of diet quality in preventing and alleviating Alzheimer’s disease is also discussed. The problem of neuroinflammation, which may be the result of microbiota disorders, is also described. An important aspect of the work is the chapter on the treatment strategies for changing the microbiota, potentially protecting against the disease and alleviating its course in the initial stages.

Impact of NMDA receptor activation on DNA damage in PC12 neuron-like cell cultures in the presence of β-amyloid peptides

OBJECTIVE

This study aimed to investigate the effect of low nanomolar concentrations of Aβ1-40 and Aβ25-35 on DNA double-strand breaks following NMDA activation of cells.

MATERIALS AND METHODS

After incubating the differentiated PC12 cells with Aβ_25-35, Aβ_1-40 or Aβ_1-42 for 24 h, the culture was washed and stimulated for 15 min with NMDA. Then, tests were performed at four-time intervals from stimulation to assess the viability of the culture, the level of oxygen free radicals, and the γH2AX and pATM kinase. NMDAR1 expression was also evaluated by performing immunocytochemical staining.

RESULTS

It was found that amyloid peptides in nanomolar concentrations reduce double-stranded DNA breaks after NMDA neuron activation. A slight antioxidant effect was also demonstrated when measured 120 min after NMDA cell activation.

CONCLUSION

The NMDA stimulation of PC12 cells led to a rapid increase in the number of double-stranded DNA breaks in the cells and is assumed to be the initial step in IEG activation and LTP induction. The effect of Aβ on the reduction of double-strand breaks after NMDA cell stimulation indicates that at concentrations similar to physiological amyloid peptides, it may reduce the mobilization of the neuronal response to stimuli, leading to inhibition of LTP induction and decreasing synaptic plasticity in the early stages of Alzheimer's disease.

MicroRNA-424 alleviates neurocyte injury by targeting PDCD4 in a cellular model of cerebral ischemic stroke

Cerebral ischemic stroke is the primary cause of stroke-associated mortality and disability, and current therapeutic options are limited and ineffective. The present study aimed to investigate the potential of apoptotic therapy and the role of microRNA (miR)-424 in cerebral ischemic stroke. PC12 cells, a cloned cell line from rat adrenal pheochromocytoma, were treated with CoCl₂ to construct a cellular ischemia model. mRNA and protein levels of programmed cell death protein 4 (PDCD4), Bcl-2, Bax, caspase-3, PI3K and AKT were evaluated using reverse transcription-quantitative PCR and western blot analyses, respectively. Cell Counting Kit-8 assays were performed to examine cell viability in the ischemia model. Flow cytometry was conducted to evaluate the apoptosis of ischemic cells. Furthermore, a luciferase assay was performed to verify the target gene of miR-424. It was revealed that the expression level of miR-424 was downregulated in the ischemia model, while the expression of PDCD4 was upregulated. Moreover, the expression of miR-424 was increased after treatment with miR-424 mimics. The mRNA and protein expression of PDCD4 was upregulated after transfection with pcDNA3.1-PDCD4. PDCD4 was predicted and demonstrated to be a target of miR-424. Notably, overexpression of miR-424 increased cell viability and inhibited apoptosis in the ischemia model, which was reversed by co-treatment with pcDNA3.1-PDCD4. Furthermore, overexpression of miR-424 regulated the expression of PDCD4, Bax, Bcl-2, phosphorylated-PI3K/AKT and caspase-3, which was restored after co-transfection with pcDNA3.1-PDCD4. Collectively, the results indicated that miR-424 regulated the progression of cerebral ischemic stroke in a cellular model by targeting PDCD4.

Anti-Inflammatory Properties of Statin-Loaded Biodegradable Lecithin/Chitosan Nanoparticles: A Step Toward Nose-to-Brain Treatment of Neurodegenerative Diseases

Nasal delivery has been indicated as one of the most interesting alternative routes for the brain delivery of neuroprotective drugs. Nanocarriers have emerged as a promising strategy for the delivery of neurotherapeutics across the nasal epithelia. In this work, hybrid lecithin/chitosan nanoparticles (LCNs) were proposed as a drug delivery platform for the nasal administration of simvastatin (SVT) for the treatment of neuroinflammatory diseases. The impact of SVT nanoencapsulation on its transport across the nasal epithelium was investigated, as well as the efficacy of SVT-LCNs in suppressing cytokines release in a cellular model of neuroinflammation. Drug release studies were performed in simulated nasal fluids to investigate SVT release from the nanoparticles under conditions mimicking the physiological environment present in the nasal cavity. It was observed that interaction of nanoparticles with a simulated nasal mucus decreased nanoparticle drug release and/or slowed drug diffusion. On the other hand, it was demonstrated that two antibacterial enzymes commonly present in the nasal secretions, lysozyme and phospholipase A2, promoted drug release from the nanocarrier. Indeed, an enzyme-triggered drug release was observed even in the presence of mucus, with a 5-fold increase in drug release from LCNs. Moreover, chitosan-coated nanoparticles enhanced SVT permeation across a human cell model of the nasal epithelium (×11). The nanoformulation pharmacological activity was assessed using an accepted model of microglia, obtained by activating the human macrophage cell line THP-1 with the Escherichia coli–derived lipopolysaccharide (LPS) as the pro-inflammatory stimulus. SVT-LCNs were demonstrated to suppress the pro-inflammatory signaling more efficiently than the simple drug solution (−75% for IL-6 and −27% for TNF-α vs. −47% and −15% at 10 µM concentration for SVT-LCNs and SVT solution, respectively). Moreover, neither cellular toxicity nor pro-inflammatory responses were evidenced for the treatment with the blank nanoparticles even after 36 h of incubation, indicating a good biocompatibility of the nanomedicine components in vitro. Due to their biocompatibility and ability to promote drug release and absorption at the biointerface, hybrid LCNs appear to be an ideal carrier for achieving nose-to-brain delivery of poorly water-soluble drugs such as SVT.

Can Control Infections Slow Down the Progression of Alzheimer's Disease? Talking About the Role of Infections in Alzheimer's Disease

Alzheimer’s disease as the most common age-related dementia affects more than 40 million people in the world, representing a global public health priority. However, the pathogenesis of Alzheimer’s disease (AD) is complex, and it remains unclear. Over the past decades, all efforts made in the treatments of AD, with targeting the pathogenic amyloid β (Aβ), neurofibrillary tangles, and misfolded tau protein, were failed. Recently, many studies have hinted that infection, and chronic inflammation that caused by infection are crucial risk factors for AD development and progress. In the review, we analyzed the role of infections caused by bacteria, viruses, and other pathogens in the pathogenesis of AD and its animal models, and explored the therapeutic possibility with anti-infections for AD. However, based on the published data, it is still difficult to determine their causal relationship between infection and AD due to contradictory results. We think that the role of infection in the pathogenesis of AD should not be ignored, even though infection does not necessarily cause AD, it may act as an accelerator in AD at least. It is essential to conduct the longitudinal studies and randomized controlled trials in humans, which can determine the role of infection in AD and clarify the links between infection and the pathological features of AD. Finding targeting infection drugs and identifying the time window for applying antibacterial or antiviral intervention may be more promising for future clinical therapeutic strategies in AD.

Effect of pyrrolo[3,4-d]pyridazinone derivatives in neuroinflammation induced by preincubation with lipopolysaccharide or coculturing with microglia-like cells

Alzheimer's disease is one of the most serious disorders of the 21st century. There is still no effective therapy for this condition. The study investigated the potential regenerative effect of four pyrrolo[3,4-d]pyridazinone derivatives in cultures of SH-SY5Y neuron-like cells preincubated with lipopolysaccharide (LPS) or cocultured with microglia-like cells. In addition to the traditional investigation of the effect on viability, the level of free radicals and nitric oxide, the average length of neurites was also measured. Via in silico studies, the possibility of penetration of the blood-brain barrier (BBB) by the tested compounds was assessed. The administration of LPS to the culture of SH-SY5Y cells as well as coculturing with microglia-like cells had a significant negative effect on the results of all the assays performed. The treatment with the tested derivatives in most cases significantly reduced this negative effect. The obtained results suggest that the compound L2 may have a beneficial impact on neuronal damage caused by LPS or proinflammatory cytokines secreted by microglia-like cells. Importantly, tested compounds can pass through the BBB, which allows them to enter the brain.

PC12 and THP-1 Cell Lines as Neuronal and Microglia Model in Neurobiological Research

Models based on cell cultures have become a useful tool in modern scientific research. Since primary cell lines are difficult to obtain and handle, neoplasm-derived lines like PC12 and THP-1 offer a cheap and flexible solution for neurobiological studies but require prior differentiation to serve as a neuronal or microglia model. PC12 cells constitute a suitable research model only after differentiation by incubation with nerve growth factor (NGF) and THP-1 cells after administering a differentiation factor such as phorbol 12-myristate-13-acetate (PMA). Still, quite often, studies are performed on these cancer cells without differentiation. The study aimed to assess the impact of PC12 or THP-1 cell differentiation on sensitivity to harmful factors such as Aβ25-35 (0.001–5 µM) (considered as one of the major detrimental factors in the pathophysiology of Alzheimer’s disease) or lipopolysaccharide (1–100 µM) (LPS; a pro-inflammatory factor of bacterial origin). Results showed that in most of the tests performed, the response of PC12 and THP-1 cells induced to differentiation varied significantly from the effect in undifferentiated cells. In general, differentiated cells showed greater sensitivity to harmful factors in terms of metabolic activity and DNA damage, while in the case of the free radicals, the results were heterogeneous. Obtained data emphasize the importance of proper differentiation of cell lines of neoplastic origin in neurobiological research and standardization of cell culture handling protocols to ensure reliable results.