OBJECTIVE  To investigate the effect of bs-5-YHEDA iron chelating peptide combined with semaglutide on the cognitive ability and pathological characteristics of D-Gal-induced Alzheimer's disease(AD) model mice.

METHODS  Forty mice were randomly divided into 5 groups, namely the healthy control group, PBS group, bs-5-YHEDA iron chelating peptide group, combined treatment group and positive control group, with 8 mice in each group, half of each sex. Except for the healthy control group, D-galactose was injected to induce the AD mice model for 6 weeks. For 3 consecutive weeks starting from the 4th week, the bs-5-YHEDA iron chelating peptide group was injected with bs-5-YHEDA(1 mg·mL^–1) once every other day at 200 µL in the tail vein; the bs-5-YHEDA iron chelating peptide(1 mg·mL^–1) and semaglutide(25 nmol·kg^–1·d^–1) were given alternately once a day in the combination treatment group; the positive control group was given memantine(3.3 mg·kg^–1·d^–1) by gavage every other day. The healthy control group and PBS group were injected with the equal dose of PBS. At the end of treatment, the learning memory ability of mice was detected by the Morris water maze method, whole brain and whole blood were dissected, and pathological changes in hippocampal region were observed by HE staining, and Aβ expression and Tau protein phosphorylation levels were detected by immunohistochemistry, enzyme-linked immunosorbent assay and immunoblotting.

RESULTS  In the Morris water maze spatial exploration experiment, the differences in the number of times the mice traversed the platform, the ratio of swimming distance to the target quadrant, and the time ratio were statistically significant in each group(P<0.05); compared with the PBS group, the ratio of swimming distance to the target quadrant increased in the combined treatment group, and the differences were statistically significant(P<0.05). The results of HE staining showed that compared with the healthy control mice, the hippocampal area in the PBS group showed reduced levels of pyramidal cells, disorganized arrangement, cell edema, and deep staining of nuclei consolidation. Cellular disorganization, deep staining of nuclei and apoptosis in the hippocampus were significantly improved in each treatment group after drug treatment. Immunohistochemistry and Western blotting results showed that the Aβ expression levels and Tau protein phosphorylation levels were significantly higher in the PBS-administered mice compared with the healthy control mice, and the Aβ expression levels and Tau protein phosphorylation levels were reduced in each group after drug treatment, with statistically significant differences(P<0.01 or P<0.001 ).

CONCLUSION  The combination of bs-5-YHEDA iron chelating peptide and semaglutide can effectively improve the learning and memory ability and pathological characteristics of AD mice, but from the results of immunohistochemistry and immunoblotting experiments, the improvement of pathological characteristics of AD mice in the combination treatment group is not obvious compared with the single bs-5-YHEDA iron chelating peptide group, suggesting that there may be a threshold effect of our designed dual-target combination treatment on the cognitive improvement of AD mice, and the optimization and validation of the effect of multi-target combination treatment need further study.