Calpeptin improves the cognitive function in Alzheimer's disease-like complications of diabetes mellitus rats by regulating TXNIP/NLRP3 inflammasome.

ABSTRACT

AIMS: Diabetes mellitus (DM) is closely associated with Alzheimer's disease (AD), and is considered an accelerator of AD. Our previous study has confirmed that the Calpain inhibitor Calpeptin may alleviate AD-like complications of diabetes mellitus. This work further investigated its underlying mechanism. MATERIALS AND METHODS: Diabetes mellitus rat model was constructed by a high-fat and high-sugar diet combined with streptozotocin, followed by the administration of Calpeptin. Moreover, rats were micro-injected with LV-TXNIP-OE/vector into the CA1 region of the hippocampus one day before streptozotocin injection. The Morris water maze test assessed the spatial learning and memory ability of rats. Immunohistochemistry and western blotting detected the expression of the pericyte marker PDGFRß, tight junction proteins occludin and ZO-1, calpain-1, calpain-2, APP, Aß, Aß-related, and TXNIP/NLRP3 inflammasome-related proteins. Immunofluorescence staining examined the blood vessel density and neurons in the hippocampus. Evans blue extravasation and fluorescence detected the permeability of the blood-brain barrier (BBB) in rats. Additionally, the oxidative stress markers and inflammatory-related factors were assessed by enzyme-linked immunosorbent assay. RESULTS: Calpeptin effectively reduced the expression of Calpain-2 and TXNIP/NLRP3 inflammasome-related proteins, improved the decreased pericyte marker (PDGFR-ß) and cognitive impairment in hippocampus of DM rats. The neuronal loss, microvessel density, permeability of BBB, Aß accumulation, inflammation, and oxidative stress injury in the hippocampus of DM rats were also partly rescued by calpeptin treatment. The influence conferred by calpeptin treatment was reversed by TXNIP overexpression. CONCLUSIONS: These data demonstrated that calpeptin treatment alleviated AD-like symptoms in DM rats through regulating TXNIP/NLRP3 inflammasome. Thus, calpeptin may be a potential drug to treat AD-like complications of diabetes mellitus.