While most studies assessed the acute toxicity of saxitoxin (STX), fewer studies focus on the long-term degenerative effects of STX on the central nervous system. We investigated the cognitive impairment and hippocampal damages of 6 months' exposure of low-dose STX to C57BL/6NJ mice with behavioral tests, H&E staining, and Western blots, and the possible mechanism (Ppp1C, YAP1, tau-phosphorylation) underlies the pathological changes. Furthermore, we discussed the specific localization of YAP1 in N2a cells induced by STX and the effect of inactivated Ppp1C on its downstream protein YAP1 in the Hippo signal pathway. We found STX intoxicated mice showed declined cognitive performance in both NOR test and MWM test, degenerations in the CA1 area of hippocampi. STX induced up-regulation expression of Ppp1C and YAP1 in hippocampus and N2a cells. Meanwhile, STX treatment induced cell apoptosis and Tau protein hyperphosphorylation. In addition, STX treatment promoted YAP1 cytoplasmic retention that indicates the activation of Hippo pathway, while depletion of Ppp1C inactivate YAP1 during the treatment of STX. Our results highlight the role of Ppp1C and YAP1 cytoplasmic retention in chronic low-dose STX intoxication.

Lipophilic shellfish toxins (LSTs) can cause human illness and therefore represent a serious threat to public health. Shellfish are the main dietary source of LSTs, but very few studies have appraised dietary exposure to LSTs through shellfish consumption in China. We measured levels of multiple LSTs in shellfish samples sold in the principal wholesale seafood market in the southern coastal city of Shenzhen, and we estimated the potential for acute and chronic LST exposure of the Shenzhen population via ingestion of shellfish. LST contamination data were obtained from a total of 14 species of 188 commercial samples. Eleven individual LSTs, namely okadaic acid (OA), dinophysis toxin-1 and -2 (DTX1 and DTX2), pectenotoxin-2 (PTX2), yessotoxin and homo yessotoxin (YTX and hYTX), azaspiracid-1, -2 and -3 (AZA1, AZA2, AZA3), spirolides (SPXs), and gymnodimine (GYM), were determined using liquid chromatography electrospray-ionization tandem mass spectrometry (LC-ESI-MS/ MS). More than two thirds of samples showed undetectable LSTs, while the detection rates (the proportion of samples with detectable LSTs) of individual LSTs ranged from 0% to 45.7%. Most shellfish samples had lower levels of LST contamination than the corresponding limits of detection (LODs), while some samples had levels of hYTX and GYM that exceeded the limits of quantification (LOQs). Overall, levels of LSTs in the 188 samples were below the regulatory limits set by most countries. Acute and chronic exposures of LST were estimated by a pointestimate modeling method that combined sample contamination data with consumption data from dietary survey of Shenzhen residents and consumption figures proposed by EFSA, the European Food Safety Authority. Seasonal variations in LST concentrations were noted in some instances. Overall, the estimated acute exposure to LSTs based on consumption of large-size shellfish portions and the maximum LSTs contamination level were below the provisional acute reference doses (ARfDs) proposed by the EFSA. Chronic exposure estimates based on mean and 99th percentile consumption of shellfish by Shenzhen residents and mean LSTs contamination levels in the collected samples were from 2452 to 74 times lower than those associated with estimated acute exposure levels.

Saxitoxin (STX), as a type of paralytic shellfish poisoning (PSP), is gaining widespread attention due to its long existence in edible shellfish. However, the mechanism underlying STX chronic exposure-induced effect is not well understood. Here, we evaluated the neurotoxicity effects of long-term low-dose STX exposure on C57/BL mice by behavioral tests, pathology analysis, and hippocampal proteomics analysis. Several behavioral tests showed that mice were in a cognitive deficiency after treated with 0, 0.5, 1.5, or 4.5 μg STX equivalents/kg body weight in the drinking water for 3 months. Compared with control mice, STX-exposed mice exhibited brain neuronal damage characterized by decreasing neuronal cells and thinner pyramidal cell layers in the hippocampal CA1 region. A total of 29 proteins were significantly altered in different STX dose groups. Bioinformatics analysis showed that protein phosphatase 1 (Ppp1c) and arylsulfatase A (Arsa) were involved in the hippo signaling pathway and sphingolipid metabolism pathway. The decreased expression of Arsa indicates that long-term low doses of STX exposure can cause neuronal inhibition, which is a process related to spatial memory impairment. Taken together, our study provides a new understanding of the molecular mechanisms of STX neurotoxicity.

The coronavirus disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has become a worldwide health emergency. Patients infected with SARS-CoV-2 present with diverse symptoms related to the severity of the disease. Determining the proteomic changes associated with these diverse symptoms and in different stages of infection is beneficial for clinical diagnosis and management. Here, we performed a tandem mass tag-labeling proteomic study on the plasma of healthy controls and COVID-19 patients, including those with asymptomatic infection (NS), mild syndrome, and severe syndrome in the early phase and the later phase. Although the number of patients included in each group is low, our comparative proteomic analysis revealed that complement and coagulation cascades, cholesterol metabolism, and glycolysis-related proteins were affected after infection with SARS-CoV-2. Compared to healthy controls, ELISA analysis confirmed that SOD1, PRDX2, and LDHA levels were increased in the patients with severe symptoms. Both gene set enrichment analysis and receiver operator characteristic analysis indicated that SOD1 could be a pivotal indicator for the severity of COVID-19. Our results indicated that plasma proteome changes differed based on the symptoms and disease stages and SOD1 could be a predictor protein for indicating COVID-19 progression. These results may also provide a new understanding for COVID-19 diagnosis and treatment.

Alzheimer's disease (AD) is the most common neurodegenerative disease characterized by progressive memory loss and neuropsychiatric symptoms. Environmental enrichment (EE), a non-pharmacological intervention, has been reported to counteract pathological signs in models of AD. In this study, we investigated the effects of long-term EE treatment on cognitive and emotional behavior of triple transgenic AD (3xTg-AD) mice. We treated 3 month-old male 3xTg-AD mice with EE for 10 months. Our results from open field test, elevated plus maze and light/dark box showed that long-term EE treatment can alleviate anxiety-related behavior of 3xTg-AD mice. Forced swim test and tail suspension test demonstrated that EE helped to relieve depression behavior. Meanwhile, Y maze and step-down avoidance test showed that EE can slightly lessen memory impairment of 3xTg-AD mice. Our data suggested that long-term EE treatment exerted protective effects against anxiety, depression and memory deficit in 3xTg-AD mice. This work was supported by NSFC (the National Natural Science Foundation of China) (81102154), Medical Scientific Research Foundation of Guangdong Province (A2013598), Shenzhen Scheme of Science and Technology (Medicine and Health) (201302148), Shenzhen Special Fund Project on Strategic Emerging Industry Development (JCYJ20130329103949650, JCYJ20120616144140857).