Neuroprotective Effect of Quercetin Encapsulated Liposomes: A Novel Therapeutic Strategy against Alzheimerʹs Disease

Problem statement: The prevalence of Alzheimerʹs disease is increasing but the efficacy of treatment is still very limited due to various factors including the blood brain barrier. Recent findings demonstrated the crucial role of oxidative stress on the pathophysiology of disease. In addition the burden of blood brain barrier can be overcome by nasal administration and vesicle-carrier mediated delivery system. Based on the potent antioxidant effect of quercetin and the burden of blood brain barrier, we hypothesized that the nasal administration of quercetin liposomes could protect against neurodegeneration in Alzheimerʹs disease. Approach: This study was designed to evaluate the effect and possible action of nasal administration of quercetin liposomes on neurodegeneration in animal model of Alzheimerʹs disease. Male Wistar rats were pretreated with quercetin liposomes, containing 0.5 mg of quercetin in 20 ^L via intranasal route once daily continually for 2 weeks before and 1 week after AF64A administration. After the quercetin liposomes treatment, the density of neurons and cholinergic neurons in hippocampus were assessed using histochemical and immunohistochemical techniques whereas the activities of Superoxide Dismutase (SOD), Catalase (CAT), Glutathione Peroxidase (GPx) and Malondialdehide (MDA), a lipid peroxidation product, were determined using biochemical assays. Results: Quercetin liposomes attenuated the degeneration of neurons and cholinergic neurons in hippocampus. The elevation of SOD, CAT and GPx activities and the reduction of MDA in hippocampus were also observed. Therefore, the neuroprotective of quercetin liposomes occurred partly via the reduction of oxidative stress. Conclusion: Our studies suggested that nasal administration of quercetin liposomes may be the potential novel therapeutic strategy against Alzheimerʹs disease. However, further researches are still essential.