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.

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.

Hypolipidemic Effects of β-Glucans, Mannans, and Fucoidans: Mechanism of Action and Their Prospects for Clinical Application

The search for lipid-lowering drugs is important for clinical medicine. This review summarizes our research findings regarding the hypolipidemic activity of polysaccharides. There are several validated agents altering lipid levels which reduce the risk of atherosclerotic cardiovascular events. Nonetheless, for many people, the risk of such an event remains unacceptably high despite treatment with these agents. This situation has prompted the search for new therapies to reduce the residual cardiovascular risk. The lipid-lowering effect of β-glucans consumed with food was demonstrated in patients with atherosclerosis. The mechanism of the protective effect of β-glucans is poorly studied. The effects of β-glucans are mediated by Toll-like receptors, by dectin-1, and possibly by other receptors. Nevertheless, the mechanism of the protective action of β-glucan in lipemic mice has been studied insufficiently. This review will present up-to-date information regarding experimental hypolipidemic polysaccharide compounds that hold promise for medicine. Phagocyte-specific chitotriosidase in humans contributes to innate immune responses against chitin-containing fungi. This enzyme has been first described in patients with Gaucher disease and serves as an important diagnostic biomarker. It has been reported that, in mice, chitin particles of certain size are recognized by macrophages through Toll-like receptors, dectin-1, and to a lesser extent through mannose receptor.

Prolonged decrease in stress reactivity caused by dehydroepiandrosterone sulfate

In male rats exposed to repeated stress, the decrease in stress reactivity produced by subcutaneous injection of dehydroepiandrosterone sulfate (recorded by the decrease in stress-induced concentrations of corticosterone and adrenocorticotropic hormone in blood plasma) was observed 1-6 days postinjection and involved central regulatory mechanisms.

Ratio between the Contents of 11-Dehydrocorticosterone and Corticosterone after Acute and Repeated Stress: Effect of Dehydroepiandrosterone Sulfate

Acute stress was accompanied by reduction of 11-dehydrocorticosterone to corticosterone in male rats. The reverse reaction predominated during repeated stress and increased after administration of dehydroepiandrosterone sulfate. Treatment with mu-opioid receptor antagonist naltrexone in a dose of 0.1 mg/kg 20 min before administration of dehydroepiandrosterone sulfate abolished this effect.

Effects of Alternative Social Experience on the Sexual Function of Male Mice

The relevance of the social contact test "Wall" for evaluation of sexual motivation of male mice was tested and confirmed. Motivation of C57BL/6J male mice with alternative social experience (winners and victims in 10 and 20 daily male-male confrontations) was evaluated. Elevated primary sexual interest was detected in aggressive animals after 10 confrontations, while in submissive animals this interest was decreased; however after 20 confrontations sexual motivation in both groups was characterized by rapid exhaustion and low basal level of testosterone. Hence, the sexual function of male mice is inhibited under conditions of long social conflicts irrespective of previous experience of victories or defeats in male-male confrontations.

Stress-limiting effect of dehydroepiandrosterone sulfate and its mechanism

Dehydroepiandrosterone sulfate prevented the increase in corticosterone level in rats induced by repeated exposure to stress. The mu-opioid receptor blocker naltrexone administered in a dose of 0.1 mg/kg 20 min before treatment with dehydroepiandrosterone sulfate abolished the effect of this agent. Dehydroepiandrosterone sulfate and naltrexone had no effect on rats after acute stress.