Comparative analysis of early neurodegeneration signs in a mouse model of Alzheimer's disease-like pathology induced by two types of the central (Intracerebroventricular vs. Intrahippocampal) administration of Aβ25-35 oligomers

Animal models of Alzheimer's disease (AD) induced by intracerebroventricular (ICV) or intrahippocampal (IH) administration of amyloid-beta (Aβ) are widely used in current research. It remains unclear whether these models provide similar outcomes or mimic pathological mechanisms of AD equally. The aim of the work was to compare two models induced by ICV or IH administration of Aβ25-35 oligomers to C57BL/6 mice. Parameters characterizing cognitive function (passive avoidance test), protein expression (IBA1, Aβ, LC3-II) and expression of genes for neuroinflammation (Aif1, Lcn2, Nrf2), autophagy (Atg8, Becn1, Park2), or markers of neurodegeneration (Cst3, Insr, Vegfa) were analyzed. Сognitive deficits, amyloid accumulation, and neuroinflammatory response in the brain evaluated by the microglial activation were similar in both models. Thus, both ways of Aβ administration appear to be equally suitable for modelling AD-like pathology in mice. Our findings strongly support the key role of Aβ load and neuroinflammatory response in the hippocampus and frontal cortex for the progression of AD-like pathology and development of cognitive deficits. There were certain minor differences between the models in the mRNA level of genes involved in the processes of neuroinflammation, neurodegeneration, and autophagy. Modulating effects of the central administration of Aβ25-35 on the mRNA expression of Aif1, Lcn2, Park2, and Vegfa genes in different brain structures were revealed. The effects occurred to be more pronounced with the ICV method compared with the IH method. These findings give insight into the processes at initial stages of Aβ-induced pathology depending on a primary location of Aβ oligomers in the brain.

Modeling neurodegenerative disorders in zebrafish

Neurodegeneration is a major cause of Alzheimer's, Parkinson's, Huntington's, multiple and amyotrophic lateral sclerosis, pontocerebellar hypoplasia, dementia and other related brain disorders. Their complex pathogenesis commonly includes genetic and neurochemical deficits, misfolded protein toxicity, demyelination, apoptosis and mitochondrial dysfunctions. Albeit differing in specific underlying mechanisms, neurodegenerative disorders typically display evolutionarily conserved mechanisms across taxa. Here, we review the role of zebrafish models in recapitulating major human and rodent neurodegenerative conditions, demonstrating this species as a highly relevant experimental model for research on neurodegenerative diseases, and discussing how these fish models can further clarify the underlying genetic, neurochemical, neuroanatomical and behavioral pathogenic mechanisms.

Neuroprotective Effects of Ceftriaxone Involve the Reduction of Aβ Burden and Neuroinflammatory Response in a Mouse Model of Alzheimer's Disease

Ceftriaxone (CEF) is a safe and multipotent antimicrobial agent that possesses neuroprotective properties. Earlier, we revealed the restoration of cognitive function in OXYS rats with signs of Alzheimer's disease (AD)-like pathology by CEF along with its modulating the expression of genes related to the system of amyloid beta (Aβ) metabolism in the brain. The aim of this study was to determine the effects of CEF on behavior, Aβ deposition, and associated neuroinflammation using another model of an early AD-like pathology induced by Aβ. Mice were injected bilaterally i.c.v. with Aβ fragment 25-35 to produce the AD model, while the CEF treatment (100 mg/kg/day, i.p., 36 days) started the next day after the surgery. The open field test, T-maze, Barnes test, IntelliCage, and passive avoidance test were used for behavioral phenotyping. Neuronal density, amyloid accumulation, and the expression of neuroinflammatory markers were measured in the frontal cortex and hippocampus. CEF exhibited beneficial effects on some cognitive features impaired by Aβ neurotoxicity including complete restoration of the fear-induced memory and learning in the passive avoidance test and improved place learning in the IntelliCage. CEF significantly attenuated amyloid deposition and neuroinflammatory response. Thus, CEF could be positioned as a potent multipurpose drug as it simultaneously targets proteostasis network and neuroinflammation, as well as glutamate excitotoxicity, oxidative pathways, and neurotrophic function as reported earlier. Together with previous reports on the positive effects of CEF in AD models, the results confirm the potential of CEF as a promising treatment against cognitive decline from the early stages of AD progression.