Aβ Stress Research Articles

Lecanemab induces phenotypic change in glial and microglial cells in Alzheimer’s disease models: vitro and vivo evidences

AbstractBackgroundAlzheimer’s disease (AD) is characterized by the extracellular accumulation of senile plaques composed of beta‐amyloid (Aβ) and the intracellular deposition of neurofibrillary tangles composed of hyperphosphorylated tau (Tp). Aβ induces a chronic neuroinflammation that contributes to the neurite network disorganization and finally neuronal death.Lecanemab, a humanized monoclonal antibody (Ab) that recognizes protofibrils/oligomers and prevents Aβ deposition, is the first US approved Ab for AD. Its mode of action especially on inflammatory cells is still vague. We investigated Lecanemab’s effects in vitro in microglial cells and astrocytes phenotype after Aβ stress and in an aged mouse brains exposed to Aβ1‐42 (model of AD) and treated with LecanemabMethodPrimary rat cortical neurons, co‐cultured with microglia and astroglial cells were used. After 11 days of culture, cells were injured with Aβ up to 72h. Lecanemab was applied one hour before Aβ injury. After fixation, microglia and astroglia phenotype were analyzed. For both cell types, pro and anti‐inflammatory markers were assessed. Aged mice were stereotaxically infused with Aβ oligomeric fraction in CA1 hippocampal area. Animals were chronically treated with Lecanemab up to 4 weeks after the lesion. Histological analysis on brains was performed, inflammation markers were investigated.ResultApplication of Aβ induced a proliferation of astrocytes and microglial cells. In addition, a significant increase in M1 microglia was observed (TREM2/OX‐41 and Iba1) 72h after Aβ application followed with an increase of phagocytosis phenotype. A strong reduction of CD206 (M2 markers) was also detected. For astrocytes, a moderate astrogliosis was observed. Interestingly, Lecanemab treatment was able to increase number of S100A (+) cells (A2 population), associated with a moderate increase of GFAP area. In AD aged mice, cognition performances were improved and were associated with a significant reduction of brain amyloidic load in treated animals. Hippocampal section showed an increase of microglial activation (M1 and M2), and large astrogliosis.ConclusionLecanemab was able to decrease Aβ1‐42‐induced toxicity and modulated the Aβ1‐42‐induced neuroinflammatory response. These important and intriguing changes were observed both in vitro and in vivo. This study attempted to decipher the complex and unclear mode of action of Lecanemab.

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 alleviates neuroinflammatory responses.

A two-photon fluorescent probe sensitive to NADPH reveals metabolic aberrations in brain cells arising from mitochondrial dysfunction in Alzheimer’s disease

Mitochondrial dysfunction is implicated in the pathogenesis of numerous neurodegenerative disorders, including Alzheimer’s disease (AD). Nicotinamide adenine dinucleotide phosphate (NADPH) plays a crucial cofactor as a cofactor in diverse biological processes, with the interconversion between NADP+ and NADPH serving a pivotal function in intracellular reductive metabolism and redox homeostasis. Herein, we present a fast, ultrasensitive, two-photon fluorescent probe (NATP-3) with large Stokes shifts for real-time detection of NADPH levels in mitochondria of the brain cells and elucidate mitochondrial damage in AD. Significantly reduced levels of NAD(P)H in living brain cells under Aβ stress or in AD model animals such as C. elegans were intuitively observed, suggesting that cellular mitochondrial dysfunction and metabolic disorders in the brain are closely related to AD. Importantly, utilizing a high-throughput screening platform based on NATP-3, we identified apigenin as a promising candidate for mitigating mitochondrial dysfunction in AD. Notably, apigenin reinstates mitochondrial NAD(P)H production, thereby providing a potential entity molecule for intervening in mitochondrial damage during AD. This work provides a valuable tool for detecting and intervening in mitochondrial function and metabolic homeostasis associated with AD processes, emphasizing the importance of understanding the molecular mechanisms of mitochondrial dysfunction associated with neurodegenerative diseases.

Oxidative stress and death domain proteins in Alzheimer's disease

Signal-transduction pathways in the central nervous system provide key mechanisms for cellular responses to environmental stresses. Oxidative stresses are operative in the aging brain with infarction and Alzheimer's disease (AD). Mitogen-activated protein (MAP) kinases mediate these inputs to downstream targets, such as transcription factors. The result is either regeneration and protection, or cell death. AD, a multifactorial disease, results in death of selectively vulnerable neuronal subpopulations. Etiologic factors, including Aβ-oxidative stress, exert toxic effects through the MAP kinase signal transduction pathway. MAP kinases, including ERKs and stress-activated protein kinases especially c-Jun, N-terminal kinases (JNKs) and P38, are prime candidates for activation of c-Jun. Both ERKs and JNKs cause tau hyperphosphorylation potentially contributing to neurofibrillary tangle formation. Differentially expressed in neoplastic and non-neoplastic tissue (DENN)/mitogen-activated kinase activating death domain protein (MADD), a GDP/GTP exchange factor under basal conditions, interacts with JNK under Aβ stress through its JNK binding domain. As a death domain (DD)-bearing protein, DENN/MADD also interacts with other DD-proteins such as TNFR1. Our hypothesis is that DENN/MADD plays a potentially pivotal role in AD, in the cell death/survival process, via JNK. At a chronic level, DENN/MADD may modulate activation of the TNFR1 pathway by the pro-inflammatory cytokine, tumor necrosis factor-α, released by Aβ-activated macrophages and by JNK induction of FAS ligand which promote cell death via the FAS/TNFR pathway.