Melatonin modulates TLR4/MyD88/NF-κB signaling pathway to ameliorate cognitive impairment in sleep-deprived rats.

Sleep deprivation (SD) is commonplace in today's fast-paced society. SD is a severe public health problem globally since it may cause cognitive decline and even neurodegenerative disorders like Alzheimer's disease. Melatonin (MT) is a natural chemical secreted by the pineal gland with neuroprotective effects. The purpose of this study was to investigate the protective effect and mechanism of MT on chronic sleep deprivation-induced cognitive impairment. A 3-week modified multi-platform method was used to create the SD rat model. The Morris water maze test (MWM), Tissue staining (including Hematoxylin and Eosin (H & E) staining, Nissl staining, and immunofluorescence), Western blot, Enzyme-linked immunosorbent assay (ELISA), and Quantitative real-time polymerase chain reaction (qPCR) were used to investigate the protective effect and mechanism of MT in ameliorating cognitive impairment in SD rats. The results showed that MT (50 and 100 mg/kg) significantly improved cognitive function in rats, as evidenced by a shortening of escape latency and increased time of crossing the platform and time spent in the quadrant. Additionally, MT therapy alleviated hippocampus neurodegeneration and neuronal loss while lowering levels of pathogenic factors (LPS) and inflammatory indicators (IL-1ß, IL-6, TNF-α, iNOS, and COX2). Furthermore, MT treatment reversed the high expression of Aß42 and Iba1 as well as the low expression of ZO-1 and occludin, and inhibited the SD-induced TLR4/MyD88/NF-κB signaling pathway. In summary, MT ameliorated spatial recognition and learning memory dysfunction in SD rats by reducing neuroinflammation and increasing neuroprotection while inhibiting the TLR4/MyD88/NF-κB signaling pathway. Our study supports the use of MT as an alternate treatment for SD with cognitive impairment.

Mechanism of Salvia miltiorrhiza Bunge extract to alleviate Chronic Sleep Deprivation-Induced cognitive dysfunction in rats.

BACKGROUND: Bidirectional communication between the gut microbiota and the brain may play an essential role in the cognitive dysfunction associated with chronic sleep deprivation(CSD). Salvia miltiorrhiza Bunge (Danshen, DS), a famous Chinese medicine and functional tea, is extensively used to protect learning and memory capacities, although the mechanism of action remains unknown. PURPOSE: The purpose of this research was to explore the efficacy and the underlying mechanism of DS in cognitive dysfunction caused by CSD. METHODS: DS chemical composition was analyzed by UPLC-QTOF-MS/MS. Forty rats were randomly assigned to five groups (n = 8): control (CON), model (MOD), low- (1.35 g/kg, DSL), high-dose (2.70 g/kg, DSH) DS group, and Melatonin(100 mg/kg, MT) group. A CSD rat model was established over 21 days. DS's effects and the underlying mechanism were explored using the open-field test(OFT), Morris water-maze(MWM), tissue staining(Hematoxylin and Eosin Staining, Nissl staining, Alcian blue-periodic acid SCHIFF staining, and Immunofluorescence), enzyme-linked immunosorbent assay, Western blot, quantitative real-time polymerase chain reaction(qPCR), and 16S rRNA sequencing. RESULTS: We demonstrated that CSD caused gut dysbiosis and cognitive dysfunction. Furthermore, 16S rRNA sequencing demonstrated that Firmicutes and Proteobacteria were more in fecal samples from model group rats, whereas Bacteroidota and Spirochaetota were less. DS therapy, on the contrary hand, greatly restored the gut microbial community, consequently alleviating cognitive impairment in rats. Further research revealed that DS administration reduced systemic inflammation via lowering intestinal inflammation and barrier disruption. Following that, DS therapy reduced Blood Brain Barrier(BBB) and neuronal damage, further decreasing neuroinflammation in the hippocampus(HP). Mechanistic studies revealed that DS therapy lowered lipopolysaccharide (LPS) levels in the HP, serum, and colon, consequently blocking the TLR4/MyD88/NF-κB signaling pathway and its downstream pro-inflammatory products(IL-1ß, IL-6, TNF-α, iNOS, and COX2) in the HP and colon. CONCLUSION: DS treatment dramatically improved spatial learning and memory impairments in rats with CSD by regulating the composition of the intestinal flora, preserving gut and brain barrier function, and reducing inflammation mediated by the LPS-TLR4 signaling pathway. Our findings provide novel insight into the mechanisms by which DS treats cognitive dysfunction caused by CSD.

Tanshinone IIA Ameliorates Spatial Learning and Memory Deficits by Inhibiting the Activity of ERK and GSK-3ß.

BACKGROUND: Alzheimer disease (AD) is the most common type of dementia which is becoming a primary problem in the present society, but it lacks effective treatment methods and means of AD. Tanshinone IIA (Tan IIA) has been reported to have neuroprotective effects to restrain the Aß25-35-mediated apoptosis. However, few studies try to understand how Aß1-42 affects hyperphosphorylation of tau and how Tan IIA regulates this process at the molecular level. METHODS: Fifty male Sprague-Dawley rats were randomly divided into 5 groups and infused through the lateral ventricle with Aß1-42 except the control group. Then the rats were treated with Tan IIA through intragastric administration for 4 weeks. After the ability of learning and memory being measured, histomorphological examination and Western blot were used to detect the possible mechanism in the AD-associated model rats. RESULTS: We observed that Aß1-42 infusion could induce spatial learning and memory deficits in rats. Simultaneously, Aß1-42 also could reduce the neuron in cornu ammonis 1 and dentate gyrus of hippocampus, as well as increase the levels of cleaved caspase 3, hyperphosphorylated tau at the sites Ser396, Ser404, and Thr205 with enhancing staining of black granules in brain. We also found that Aß1-42 could increase the activity of extracellular signal-regulated protein kinase (ERK) and glycogen synthase kinase-3ß (GSK-3ß). Meanwhile, these phenomena could be ameliorated when Tan IIA was used. CONCLUSION: We concluded that Tan IIA might have neuroprotective effect and improving learning and memory ability to be a viable candidate in AD therapy with mechanisms involving the ERK and GSK-3ß signal pathway.