Background/Objectives: Beneficial effects of neurosteroid dehydroepiandrosterone sulphate (DHEAS) on cognition, emotions and behavior have been previously reported, suggesting its potential in the prevention and treatment of various neuropsychiatric and neurodegenerative disorders, including Alzheimer’s disease (AD). This study aimed to investigate the potential neuroprotective actions of DHEAS against Aβ toxicity in both cellular and animal models of AD. Methods: After optimizing the AD model in vitro, we investigated the DHEAS effects on the viability and death of primary mouse neurons exposed to toxic Aβ₄₂ oligomers for 24 h. In order to extend our research to an in vivo study, we further tested the acute effects of intraperitoneal DHEAS administration on the Aβ plaque density in different brain regions of 3xTg-AD mice, an animal model of AD. Results: In cell culture, DHEAS hampered the decrease in the neuronal viability caused by toxic Aβ oligomers, primarily by influencing mitochondrial function and apoptosis. DHEAS also counteracted the increase in the mRNA expression of selected genes (PI3K, Akt, Bcl2, Bax), induced in neuronal culture by treatment with Aβ₄₂ oligomers. Obtained data suggested the involvement of mitochondria, caspases 3 and 7, as well as the PI3K/Akt and Bcl2 signaling network in the antiapoptotic properties of DHEAS in neurons. Forty-eight hours after DHEAS treatment, a significantly lower number of Aβ plaques was observed in the motor cortex but not in other brain areas of 3xTg-AD mice. Conclusions: Results indicated potential neuroprotective effects of DHEAS against Aβ toxicity and accumulation, suggesting that DHEAS supplementation should be further studied as a novel option for AD prevention and/or treatment.

Background: Posttraumatic stress disorder (PTSD) is a mental illness in which central stress-regulating regions, including locus coeruleus (LC) and paraventricular nucleus of hypothalamus (PVN), play key roles. Clonidine, a central sympatholytic drug, can inhibit LC activity and reduce PTSD-related symptoms, suggesting noradrenergic involvement. Glia-driven immune mechanisms may link LC activity to PVN responses. Since TRPA1 ion channel is implicated in both neuroinflammation and stress adaptation, we aimed to determine whether its presence modulates the function of brain structures contributing to PTSD-related alteration in central stress adaptation. Methods: Foot shock PTSD model was applied to Trpa1 wild-type (WT) and knockout (KO) mice, and outcomes were assessed four weeks later. Immunohistochemistry was used to evaluate tyrosine hydroxylase (TH) levels in the LC and glial activation in the PVN. Behavioral effects of clonidine and circulating corticosterone levels were also examined. Results: Stress increased LC/TH immunoreactivity and PVN glial activation. Trpa1 deletion exaggerated LC/TH responses but reduced PVN astrocyte activation. Clonidine increased freezing and decreased jumping (a hyperarousal marker). KO mice showed enhanced jumping and did not respond to clonidine. Corticosterone levels remained unchanged. Conclusions: TRPA1 may support stress adaptation in PTSD by regulating LC noradrenergic output and PVN neuroinflammation, independently of α₂-adrenergic signaling.

Alzheimer's disease (AD) is an increasing health and social problem worldwide with prevalent cholinergic cell involvement. To reveal the details of the exact mechanisms, further preclinical studies in animals are needed. Our aim was to create a mouse model that represents the progression of AD with easy cholinergic manipulation. The 3xTg-AD and ChAT-Cre strains were crossbred. After serial genotyping, a colony, homozygote for all four genes (PSEN1, APPSwe, tauP301L and Cre; 3xAD-ChAT-Cre) was established. The presence of amyloid-β (Aβ) plaques and phosphor-Tau (pTau) aggregates was confirmed by immunohistochemistry. To test the functionality of the Cre enzyme, a stimulating DREADD virus (AAV8-hSyn-DIO-hM3Dq-mCherry) was injected unilaterally into the nucleus basalis magnocellularis, and clozapine-N-oxide-induced c-Fos activation was compared between the two hemispheres. Behavioral characterization was performed using the Y-maze, social discrimination (SDT), single pellet reaching (SPR), fox odor (FOT), and splash tests (ST). Food, water consumption and body weight change were investigated. Immunostaining and RNAscope confirmed the expression of Cre in ChAT-positive cells and the progressive appearance of pathological hallmarks (Aβ and pTau). The c-Fos activity was significantly increased in the virus-injected hemisphere. Compared with control mice, 3xAD-ChAT-Cre mice showed decreased locomotion (Y-maze, SDT, FOT), increased anxiety (FOT, ST) and weaker fine motor skills (SPR). In conclusion, newly created animals have a functional Cre recombinase enzyme in cholinergic cells. Additionally, the animals presented the pathophysiological hallmarks of AD in specific brain areas and maintained the typical behavioral alterations previously reported in 3xTg-AD mice. Thus, this strain seems to be appropriate for further studies.