Palmatine improves cognitive dysfunction in Alzheimer's disease model rats through autophagy pathway and regulation of gut microbiota

Alzheimer's disease (AD) is a primary degenerative encephalopathy that first appeared as a decline in memory and learning skills. Over time, the condition's severity grew. Palmatine (Pal) alleviates Alzheimer's disease symptoms, which has neuroprotective benefits. Numerous investigations have demonstrated a close relationship among AD and gut structure changes. The aim of the research was investigating whether the improvement of Pal on AD is linked to regulating gut flora and autophagy. First, we used Aβ1-40 to induce apoptosis in HT22 cells. After Pal treatment, apoptosis can be improved. Then, We used bilateral intracranial hippocampal injection of Aβ1-40 for establishing the AD model, after treatment with Pal, the morris water maze experiment and eight-arm maze test demonstrated that Pal enhanced the AD rats' capacity for learning and memory, HE staining illustrated that Pal improved the morphological abnormalities of brain cells and gut tissue damage. Pal reduced the death of hippocampus neurons, as shown by Nissl staining. Pal substantially reduced Tau hyperphosphorylation and Aβ accumulation in the brain, according to immunohistochemical labelling. Pal improved the expression of LC3, Beclin 1, AMPK, and suppressed the expression of mTOR and P62, as validated by RT-qPCR and immunofluorescence labelling. This suggests that Pal's treatment of AD may be associated with the control of the AMPK/mTOR autophagy signalling system. 16S rRNA sequencing and short-chain fatty acids (SCFAs) content detection analysis illustrated that Pal has the potential to enhance the content of SCFAs, reverse the alterations in gut microorganisms. It has been showed by the study that Pal could improve AD by activating autophagy signaling pathway and improving gut barrier changes.