ABSTRACT
Heat exposure is an environmental stressor that has been associated with cognitive impairment. However, the neural mechanisms that underlie this phenomenon have yet to be extensively investigated. The Morris water maze test was utilized to assess cognitive performance. RNA sequencing was employed to discover the primary regulators and pathological pathways involved in cognitive impairment caused by heat. Before heat exposure in vivo and in vitro, activation of the sarco/endoplasmic reticulum (SR/ER) calcium (Ca2+)-ATPase (SERCA) was achieved by CDN1163. Hematoxylin-Eosin, Nissl staining, calcium imaging, transmission electron microscopy, western blot, and immunofluorescence were utilized to visualize histological changes, intracellular calcium levels, endoplasmic reticulum stress (ERS) markers, apoptosis, and synaptic proteins alterations. Heat stress (HS) significantly induced cognitive decline and neuronal damage in mice. By the transcriptome sequencing between control (n = 5) and heat stress (n = 5) mice in hippocampal tissues, we identified a reduction in the expression of the atp2a gene encoding SERCA, accompanied by a corresponding decrease in its protein level. Consequently, this dysregulation resulted in an excessive accumulation of intracellular calcium ions. Furthermore, HS exposure also activated ERS and apoptosis, as evidenced by the upregulation of p-PERK, p-eIF2α, CHOP, and caspase-3. Consistently, a reduction in postsynaptic density protein 95 (PSD95) and synaptophysin (SYN) expressions indicated modifications in synaptic function. Notably, the impacts on neurons caused by HS were found to be mitigated by CDN1163 treatment both in vivo and in vitro. Additionally, SERCA-mediated ERS-induced apoptosis was attenuated by GSK2606414 treatment via inhibiting PERK-eIF2α-CHOP axis that not only curtailed the level of caspase-3 but also elevated the levels of PSD95 and SYN. These findings highlight the significant impact of heat stress on cognitive impairment, and further elucidate the underlying mechanism involving SERCA/PERK/eIF2α pathway.
ABSTRACT
Heat stress will cause a series of response in the living system and the most significant impact is on brain functions. The aim of this article is to develop nutritional supplements that can alleviate cognitive decline caused by heat stress. In this article, we screen functional food factors which can prevent or relieve effects on heat stress injury based on bioinformatics. 129 function factors related to the crossover targets were obtained, and a food database related to the prevention of high-temperature impairment was constructed. After a series of scoring standards combined with food classification, two formulas-nutrition fortifier formula (tyrosine and multivitamin B) and plant compound formula (quercetin, proanthocyanidin, and naringin) were investigated using animal experiments to determine their ability to prevent cognitive impairment of heat-stressed animals. Our results demonstrated that certain functional food factors and our two designed formulations significantly prevent cognitive impairment of heat-stressed animals. Further mechanism was carried out by cell viability assay, reactive oxygen species assay, real-time quantitative PCR and Western blot. The results showed that the plant compound formula diluted 4000 times had the best relieving effect on HT22 after heat stress, and this concentration formula can significantly alleviate the elevated levels of reactive oxygen species caused by heat stress. This formula also can significantly down-regulate IL-1ß, IL-6, TNF-α, IL-10, iNOS and COX-2 expression. Likewise, Western blot results showed that the formula could activate the cAMP pathway and increase the expression of phosphorylated PKA and BDNF in hippocampal cells.
