Background: Pu'er tea, a type of post-fermented tea made from Camellia sinensis leaves, has long been widely used in East Asian countries. It is mainly produced in southern China and is effective in preventing obesity due to its ability to break down fat. However, the effects of Pu'er tea on cognitive impairment or neuroinflammation by endotoxin have not yet been studied.
Purpose: Here, we assessed the inhibitory activity of Pu'er tea hot water extract (PTW) on neuroinflammation and cognitive impairment and explored its mechanism.
Study design: The ability of PTW to inhibit cognitive impairment was investigated in a mouse model of lipopolysaccharide (LPS)-induced neuroinflammation and murine microglia BV2 cells.
Methods: We examined whether oral administration of PTW prevented cognitive impairment and LPS-induced neuroinflammation using behavioral tests, Nissl staining, immunohistochemistry, western blotting, real-time reverse transcription-polymerase chain reaction (real-time RT-PCR), Griess assay, and enzyme-linked immunosorbent assay (ELISA).
Results: First, Morris water maze (MWM) and passive avoidance (PA) tests demonstrated that oral administration of PTW effectively attenuated LPS-induced spatial memory loss and inhibited neuronal damage of mouse brains. Histopathological analysis showed that PTW repressed LPS-induced expression of the activation markers ionized calcium-binding adaptor molecule-1 (Iba-1) and glial fibrillary acidic protein (GFAP). Furthermore, PTW inhibited the expression of amyloidogenesis proteins such as amyloid-β precursor protein (APP), C99, and β-secretase-1 (BACE-1); production of inflammatory proteins such as Iba-1, GFAP, inducible nitric oxide synthase (iNOS), and cyclooxygenase (COX)-2; activation of inflammatory pathways; and expression of inflammatory mediator mRNAs in hippocampal tissue. In cultured microglia, PTW treatment inhibited the generation of various inflammatory factors activated by LPS.
Conclusion: Our results in vivo and in vitro demonstrate that PTW effectively prevents cognitive impairment caused by neuroinflammation and is, therefore, a potential candidate for the development of a therapeutic agent for neurodegenerative diseases.
Keywords: Pu'er tea; amyloidogenesis; cognitive impairment; neuroinflammation; neuronal protection.
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