β‐Caryophyllene Ameliorates STZ‐Induced Alzheimer's Disease‐Like Conditions in Rats via Modulation of Brain‐Derived Neurotrophic Factor, Synaptic Plasticity, and Neuroinflammation

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by cognitive decline, synaptic dysfunction, and neuroinflammation. Synaptic plasticity and neuroinflammation are hallmarks of AD, with their dysregulation forming a self-reinforcing cycle that aggravates neurodegeneration. Proinflammatory cytokines impair synaptic signaling by suppressing brain-derived neurotrophic factor (BDNF) expression and neuroplasticity markers, further compromising synaptic plasticity. β-Caryophyllene (BCP), a natural bicyclic sesquiterpene with anti-inflammatory and neuroprotective properties, may counteract these pathological processes. This study evaluated the effect of BCP in mitigating streptozotocin (STZ)-induced AD-like conditions in male Sprague-Dawley rats. Two doses of STZ (3 mg/kg) on Days 1 and 3 were administered intracerebroventricularly to induce AD-like pathology. Rats received BCP (10, 20 mg/kg, i.p.) or rivastigmine (2.5 mg/kg) for 28 days. Cognitive performance was assessed using the Barnes maze and novel object recognition tests. Hippocampal tissues were analyzed for BDNF expression, synaptic plasticity markers (e.g., synaptophysin, neural cell adhesion molecule [NCAM], and ciliary neurotrophic factor [CNTF]), neuroinflammatory markers (e.g., IL-1β, TNF-α, IL-6, COX2, and NF-κB), and oxidative stress markers. Histological (hematoxylin and eosin) and Golgi-Cox staining techniques were employed to evaluate neuronal integrity and synaptic organization. STZ-induced rats exhibited significant cognitive deficits, synaptic loss, and increased neuroinflammation. BCP treatment improved spatial learning and memory retention, increased BDNF expression, and restored synaptic plasticity markers. Furthermore, BCP attenuated neuroinflammation by reducing proinflammatory cytokine levels. Histopathology confirms normal hippocampal neuronal architecture in BCP-treated groups. These findings highlight the ability of BCP to modulate BDNF signaling, synaptic plasticity, and neuroinflammatory pathways, underscoring its potential as a multitarget therapeutic candidate for AD.