Thermal Cycling Stimulation via Nasal Inhalation Attenuates Aβ25–35-Induced Cognitive Deficits in C57BL/6 Mice

Alzheimer's disease (AD) remains a significant public health challenge, with current treatments limited partly due to the difficulty of delivering therapeutics across the blood-brain barrier (BBB). The nose-to-brain (N-2-B) pathway offers a promising alternative to circumvent the BBB, but no drugs have yet been clinically applied via this route for AD. Mild stress is thought to activate intrinsic protective mechanisms against neurodegeneration, but traditional methods lack specificity and practicality. To address this, we propose the inhalation of mildly heated air as thermal stimulation, which utilizes the N-2-B pathway to induce mild stress and stimulate cerebral activity. This study employs thermal cycling-hyperthermia (TC-HT) in developing thermal cycling-stimulation via nasal inhalation (TCSNI), providing cyclic stimulation to maintain pathway activity while minimizing thermal injury. In C57BL/6 mice, TCSNI showed no adverse olfactory effects. In β-amyloid (Aβ)-treated mice, TCSNI significantly enhanced cognitive performance in Y-maze and novel object recognition (NOR) assessments, suggesting cognitive improvement. Mice hippocampal protein analyses indicated a reduction in Aβ accumulation, alongside increased expression of heat shock protein 70 (HSP70), insulin-degrading enzyme (IDE), and phosphorylated Akt (p-Akt). These results suggest that N-2-B-delivered TCSNI effectively modulates protein expression and enhances cognitive function, highlighting its potential for further exploration in AD treatment.