Digestive characteristics of extracellular polysaccharide from Lactiplantibacillus plantarum T1 and its regulation of intestinal microbiota.

This study assessed the potential prebiotic characteristics of the previously reported Lactiplantibacillus plantarum extracellular polysaccharide (EPS-T1) with immunological activity. EPS-T1 was a novel heteropolysaccharide composed of glucose and galactose (1.00:1.21), with a molecular weight of 1.41 × 106 Da. The monosaccharide composition, molecular weight, fourier transform infrared, and 1H NMR analysis showed that EPS-T1 was well tolerated in the simulated oral cavity, gastric fluid, and small intestinal fluid environments, and was not easily degraded. Meanwhile, EPS-T1 could effectively be used as a carbon source to promote the growth of beneficial Lactobacillus species (Lactobacillus delbrueckii ssp. Bulgaricus, Streptococcus thermophilus, Lacticaseibacillus rhamnose GG, Lactiplantibacillus plantarum, Lacticaseibacillus paracasei and Lactobacillus reuteri). After 24 h of fecal fermentation, EPS-T1(5 mg/mL) effectively reduced the relative abundance of harmful bacteria such as the Escherichia-Shigella, Citrobacter, Fusobacterium, Parasutterella, and Lachnoclostridium. While, the level content of beneficial flora (Bacteroides, Blautia, Phascolarctobacterium, Bifidobacterium, Parabacteroides, and Subdoligranulum) were significantly increased. In addition, EPS-T1 was able to significantly promote the enrichment of short-chain fatty acids such as acetic acid, propionic acid and butyric acid. These results provide some basis for the functional application of EPS-T1 as a potential prebiotic.

A novel HMGA2::KITLG fusion in a dedifferentiated liposarcoma with amplification of MDM2 and HMGA2.

High-mobility group AT-hook 2 (HMGA2) is rearranged in various types of mesenchymal tumors, particularly lipomas. HMGA2 is also co-amplified with mouse double minute 2 (MDM2) in well-differentiated liposarcoma/dedifferentiated liposarcoma (WDLPS/DDLPS). We report a case of relapsed DDLPS with a novel in-frame fusion between HMGA2 and KITLG, which encodes the ligand for KIT kinase, a critical protein involved in gametogenesis, hematopoiesis, and melanogenesis. The HMGA2 breakpoint is in intron 3, a commonly observed location for HMGA2 rearrangements, while the KITLG breakpoint is in intron 2, leading to a fusion protein that contains almost the entire coding sequence of KITLG. By immunohistochemical staining, tumor cells expressed KIT and showed phosphorylated MAPK, a major KIT downstream target. We suggest an oncogenic mechanism that involves the overexpression of KITLG caused by its rearrangement with HMGA2, leading to the constitutive activation of KIT kinase. While MDM2 amplification was observed in both the primary tumor and the relapsed tumor, the HMGA2::KITLG was only present in the relapsed tumor, indicating the role of HMGA2::KITLG in disease progression.

Effects of Lacticaseibacillus paracasei SNB-derived postbiotic components on intestinal barrier dysfunction and composition of gut microbiota.

The bacterial surface components are considered as effector molecules and show the potential to support intestinal health, but the detailed mechanism of how the gut microbiota changes after the intervention of surface molecules is still unknown. In the present study, capsular polysaccharide (B-CPS) and surface layer protein (B-SLP) were extracted from Lacticaseibacillus paracasei S-NB. The protective effect of direct administration of B-CPS (100 µg/mL) and B-SLP (100 µg/mL) on intestinal epithelial barrier dysfunction was verified based on the LPS-induced Caco-2 cell model. Additionally, the B-CPS and B-SLP could be utilized as carbon source and nitrogen source for the growth of several Lactobacillus strains, respectively. The postbiotic potential of B-CPS and B-SLP was further evaluated by in vitro fermentation with fecal cultures. The B-CPS and a combination of B-CPS and B-SLP regulated the composition of gut microbiota by increasing the relative abundances of Bacteroides, Bifidobacterium, Phascolarctobacterium, Parabacteroides, Subdoligranulum and Collinsella and decreasing the abundance of pathogenic bacteria like Escherichia-Shigella, Blautia, Citrobacter and Fusobacterium. Meanwhile, the total short-chain fatty acid production markedly increased after fermentation with either B-CPS individually or in combination with B-SLP. These results provided an important basis for the application of B-CPS and B-SLP as postbiotics to improve human intestinal health.

Roles of luxS in regulation of probiotic characteristics and inhibition of pathogens in Lacticaseibacillus paracasei S-NB.

Lactic acid bacteria (LAB) have excellent tolerance to the gastrointestinal environment and high adhesion ability to intestinal epithelial cells, which could be closely related to the LuxS/AI-2 Quorum sensing (QS) system. Here, the crucial enzymes involved in the synthesis of AI-2 was analyzed in Lacticaseibacillus paracasei S-NB, and the luxS deletion mutant was constructed by homologous recombination based on the Cre-lox system. Afterwards, the effect of luxS gene on the probiotic activities in L. paracasei S-NB was investigated. Notably, the tolerance of simulated gastrointestinal digestion, AI-2 production, ability of auto-aggregation and biofilm formation significantly decreased (p < 0.05 for all) in the S-NB△luxS mutant. Compared to the wild-type S-NB, the degree of reduction in the relative transcriptional level of the biofilm -related genes in Escherichia coli ATCC 25922 and Staphylococcus aureus ATCC 25923 was diminished when co-cultured with S-NB△luxS. Furthermore, the inhibitory effect of S-NB△luxS on the adhesion (competition, exclusion and displacement) of E. coli ATCC 25922 and S. aureus ATCC 25923 to Caco-2 cells markedly decreased. Therefore, comprehensive analysis of the role by luxS provides an insight into the LuxS/AI-2 QS system of L. paracasei S-NB in the regulation of strain characteristics and inhibition of pathogens.

The interaction among Kluyveromyces marxianus G-Y4, Lacticaseibacillus paracasei GL1, and Lactobacillus helveticus SNA12 and signaling molecule AI-2 participate in the formation of biofilm.

In this study, two strains of lactic acid bacteria (Lacticaseibacillus paracasei GL1 and Lactobacillus helveticus SNA12) and one yeast strain of Kluyveromyces marxianus G-Y4 (G-Y4) isolated from Tibetan kefir grains were co-cultured. It was found that the addition of G-Y4 could not only promote the growth of lactic acid bacteria, but also increase the release of metabolites (lactic acid, ethanol, and amino nitrogen). Furthermore, the addition of live cells and cell-free fermentation supernatant (CFS) of G-Y4 could increase the ability of biofilm formation. Morever, the surface characteristics results showed that the addition of G-Y4 live cells could enhance the aggregation ability and hydrophobicity of LAB. Meanwhile, adding live cells and CFS of G-Y4 could promote the release of signaling molecule AI-2 and enhance the expression of the LuxS gene related to biofilm formation. In addition, Fourier-transform infrared spectroscopy and chemical composition analysis were used to investigate the composition of the biofilm, and the results indicated that the biofilm was mainly composed of a small amount of protein but it was rich in polysaccharides including glucose, galactose, and mannose with different ratios. Finally, the formation of biofilm could delay the decline of the number of viable bacteria in storage fermented milk.

Controlled release of Lactiplantibacillus plantarum by colon-targeted adhesive pectin microspheres: Effects of pectin methyl esterification degrees.

The aim of this study is to report the preparation of pectin microspheres by varying degrees of methyl esterification (DM) cross-linked with divalent cationic calcium to encapsulate Lactiplantibacillus plantarum STB1 and L. plantarum LJ1, respectively. Scanning electron microscopy revealed the compact and smooth surface of pectin of DM 28 %, and the stochastic distribution of L. plantarum throughout the gel reticulation. And the pectin of DM 28 % considerably increased probiotics tolerance after continuous exposure to stimulated gastrointestinal tract conditions, with viable counts exceeding 109 CFU/mL. This data indicated that low methoxy-esterification pectin was more efficient to improve the targeted delivery of probiotics in GIT. Additionally, the controlled release of microspheres was dependent on various pH levels. At pH 7.4, the release rates of L. plantarum STB1 and L. plantarum LJ1 reached up to 97.63 % and 95.33 %, respectively. Finally, the Caco-2 cell adhesion model was used to evaluate the cell adhesion rate after encapsulation, which exhibited better adhesion at DM of 60 %.

Co-cultivation effects of Lactobacillus helveticus SNA12 and Kluveromyces marxiensis GY1 on the probiotic properties, flavor, and digestion in fermented milk.

This study aimed to evaluate inoculating the lactic acid bacteria Lactobacillus helveticus SNA12 and the yeast Kluyveromyces marxiensis GY1 as starter cultures on milk fermentation. In this study, the probiotic properties of L. helveticus SNA12, K. marxiensis GY1 and co-culture of these two strains (L. helveticus SNA12-K. marxiensis GY1) were investigated, and the results showed that K. marxiensis GY1 had better gastrointestinal tolerance, aggregation, and cell adhesion properties than L. helveticus SNA12. After the co-cultivation of two strains, the presence of K. marxiensis GY1 significantly increased the gastrointestinal tolerance, aggregation, and adhesion characteristics of L. helveticus SNA12. In order to investigate the flavor changes, digestive characteristics, and antioxidant properties following co-cultivation fermentation, the optimal fermentation ratio of 8 %-2% (v/v) and fermentation temperature (37 °C) of L. helveticus SNA12-K. marxiensis GY1 were determined. The results of the electronic nose and electronic tongue showed that L. helveticus SNA12-K. marxiensis GY1 could increase the aroma components of fermented milk, such as terpenes and aromatic substances. Meanwhile, dynamic in vitro rat stomach-duodenum model was used to analyse the changes in the digestion of proteins and peptides (<10 kDa), and the results indicated that co-cultivation fermented milk could be digested faster compared to a single fermentation. Furthermore, the antioxidant capacity of co-cultivation fermented milk was higher than that of single fermentation.

Advanced structural characterization and in vitro fermentation prebiotic properties of cell wall polysaccharide from Kluyveromyces marxianus.

Through previous study, the three yeast α-mannans (MPS) from various sources of Kluyveromyces marxianus (LZ-MPS, MC-MPS, and G-MPS) were preliminarily characterized. In this study, the advanced structural characterization and the in vitro human fecal fermentation behavior of the three MPS were investigated. According to the results of this study, the polysaccharide molecules of the three MPS were aggregated in solution, supporting their branched chain structure. After in vitro fermentation, the molecular weight and pH of fermentation broth decreased significantly, indicating that the three MPS could be utilized by human gut microbiota. Meanwhile, the production of total short-chain fatty acids (SCFAs) of the three MPS was promoted, especially the production of propionic acid was 45.55, 38.23, and 38.87 mM, respectively. In particular, the three MPS have the ability to alter the composition of human gut microbiota, especially to promote the proliferation of Bacteroidetes, suggesting that the bioactivities of the three MPS can be significantly influenced by intestine Bacteroidetes. In terms of metabolism, all MPS can promote cofactors, vitamins, amino acid metabolism, and glycan biosynthesis and metabolism of bacteria. In consequence, the three MPS were confirmed to regulate the human gut microbiota, increase the level of SCFAs, promote the metabolisms of bacteria on amino acid and glycan, and improve the intestinal health.

Effects of genes required for exopolysaccharides biosynthesis in Lacticaseibacillus paracasei S-NB on cell surface characteristics and probiotic properties.

The cell surface of lactic acid bacteria (LAB) plays an essential role in cell-cell and cell-host interactions. Exopolysaccharides (EPSs) are produced on the cell surface of LAB or in the surrounding medium and are considered to be in favor of the strain- specific probiotic surface characteristics. In this work, the structure features of EPS from Lacticaseibacillus paracasei S-NB were analyzed preliminarily, and the genes involved in EPS biosynthesis of S-NB strain were hypothesized and annotated, and their role in phenotypic characteristics were demonstrated by gene deletion analysis. Four mutant strains with deletion of crucial genes involved in EPS synthesis were analyzed for strain characteristics that are closely related to their ability to interact with the host intestinal epithelium cells, including strain surface characteristics and viability under the gastrointestinal stress conditions (both acid and bile stress). Furthermore, the adherence and immunomodulatory properties of wild-type S-NB and its mutant strains were compared using Caco-2 and RAW 264.7 cell lines, respectively. Taken together, the results indicated the importance of genes associated with EPS biosynthesis in L. paracasei S-NB as a determinant in strain surface characteristics and cell-host interaction, especially for S-NB_2176 (responsible for EPS polymerization) and S-NB_2175 (responsible for CpsD/CapB family tyrosine-protein kinase).

Structural and prebiotic activity analysis of the polysaccharide produced by Lactobacillus helveticus SNA12.

Exopolysaccharide (EPS) isolated from Lactobacillus helveticus SNA12 were purified, and one fraction (SNA12-EPS) was obtained. The structure of SNA12-EPS was proposed using Fourier-transform infrared spectroscopy, gas chromatography-mass spectrometry, and nuclear magnetic resonance. Results showed that SNA12-EPS was rich in galactose and glucose with the molar ratios of 2.1:1.0, and SNA12-EPS possessed the repeat units of →3)-ß-D-Glcp-(1→3)-ß-D-Glcp-(1→4)-ß-D-Galp-(1→ with an average molecular weight of 3.81 × 105 Da. The scanning electron microscope results showed that SNA12-EPS had a tight structure with a smooth and uneven surface. Furthermore, the prebiotic potential of SNA12-EPS was performed using in vitro simulated digestion with human faecal fermentation. SNA12-EPS was not digested by digestive juice, and it could markedly regulate the gut microbiota composition by increasing the relative abundances of Parabacteroides and Blautia and decreasing the abundance of pathogenic bacteria of Fusobacterium. Additionally, SNA12-EPS improved the ability of gut microbiota to produce short-chain fatty acids.

Lactobacillus plantarum Lp3a improves functional constipation: evidence from a human randomized clinical trial and animal model.

Background: Functional constipation (FC) is a common gastrointestinal (GI) disorder characterized by symptoms of constipation without a clear physiologic or anatomic cause. Gut microbiome dysbiosis has been postulated to be a factor in the development of FC, and treatment with probiotic regimens, including strains of Lactobacillus plantarum (L. plantarum), has demonstrated efficacy in managing symptoms. To further understand the role of L. plantarum in GI health, we conducted an animal study and a randomized, double-blind, placebo-controlled clinical trial to evaluate the effect of a specific sub-strain, Lp3a, on FC. Methods: For the animal study, male Kunming mice were treated with doses of L. plantarum Lp3a ranging from 0.67 to 2.00 g/kg or an equivalent amount of placebo for 15 days prior to the induction of constipation via 20 mL/kg of 25% diphenoxylate solution. GI motility parameters including intestinal motion and stool amount were then assessed. In the human study, 120 patients with FC were randomized to treatment [L. plantarum Lp3a; 2×1.0×1010 (colony forming units; CFU) ×7 days] or control groups (n=60 each). The primary endpoint was survey information on FC signs/symptoms. Participants and observers were blinded to group allocation. A subset of 20 Lp3a treated patients underwent pre- and post-treatment 16 s ribosomal ribonucleic acid (rRNA) gene sequencing. Whole genome sequencing (WGS) of L. plantarum Lp3a was also performed. Results: Lp3a-treated mice showed significantly improved intestinal motion, reduced time to first defecation, and increased stool amounts. Similarly, patients in the treatment group (n=59) reported significant improvements in FC signs/symptoms compared to controls (n=58; all P<0.05). Although 16 s rRNA sequencing revealed no significant variations between pre- and post-treatment samples, WGS of Lp3a itself revealed several biological pathways that may underlie the relief of FC symptoms in animals and humans, including methane and fatty acid metabolism and bile acid biosynthesis. Conclusions: We found that the use of the novel probiotic sub-strain, L. plantarum Lp3a, led to clinically significant improvements in FC in both mice and humans, and identified the potential biological mechanisms underlying this activity.

A Novel Probiotic Formula, BIOCG, Protects Against Alzheimer's-Related Cognitive Deficits via Regulation of Dendritic Spine Dynamics.

BACKGROUND: The brain-gut-microbiome axis has emerged as an important pathway through which perturbations in the gut and/or microbial microenvironment can impact neurological function. Such alterations have been implicated in a variety of neuropsychiatric disorders, including depression, anxiety, and Alzheimer's Disease (AD) and the use of probiotics as therapy for these diseases remains promising. However, the mechanisms underlying the gut microenvironment's influence on disease pathogenesis and therapy remain unclear. OBJECTIVE: The objective of this study is to investigate the effect of a novel probiotic formula, BIOCG, on cognitive function and pathobiological mechanisms, including amyloid processing and dendritic spine dynamics, in a mouse model of AD. METHODS: BIOCG was administered for 3 months to 3xTg or 3xTg; Thy1-YFP AD mice and functional outcomes were assessed via behavioral testing and electrophysiology. Mechanisms relevant to AD pathogenesis including dendritic spine morphology and turnover, Amyloid Precursor Protein (APP) processing and microglial phenotype were also evaluated. Finally, we sequenced fecal samples following probiotic treatment to assess the impact on gut microbial composition and correlate the changes with the above described measures. RESULTS: Mice treated with BIOCG demonstrated preserved cognitive abilities and stronger Long- Term Potentiation (LTP), spontaneous Excitatory Postsynaptic Currents (sEPSC), and glutamate-induced LTPs, indicative of functional and electrophysiological effects. Moreover, we observed attenuated AD pathogenesis, including reduced Amyloid Beta (Aß) burden, as well as more mature dendritic spines in the BIOCG-treated. Our finding of changes in microglial number and phenotype in the treatment group suggests that this formulation may mediate its effects via attenuation of neuroinflammation. Sequencing data confirmed that the gut microbiome in treated mice was more varied and harbored a greater proportion of "beneficial" bacteria. CONCLUSION: Overall, our results indicate that treatment with BIOCG enhances microbial diversity and, through gut-brain axis interactions, attenuates neuroinflammation to produce histologic and functional improvement in AD pathogenesis.

Joint Detection of Serum IgM/IgG Antibody Is an Important Key to Clinical Diagnosis of SARS-CoV-2 Infection.

BACKGROUND: This study was aimed to investigate the application of SARS-CoV-2 IgM and IgG antibodies in diagnosis of COVID-19 infection. METHOD: This study enrolled a total of 178 patients at Huangshi Central Hospital from January to February 2020. Among them, 68 patients were SARS-CoV-2 infected, confirmed with nucleic acid test (NAT) and CT imaging. Nine patients were in the suspected group (NAT negative) with fever and other respiratory symptoms. 101 patients were in the control group with other diseases and negative to SARS-CoV-2 infection. After serum samples were collected, SARS-CoV-2 IgG and IgM antibodies were tested by chemiluminescence immunoassay (CLIA) for all patients. RESULTS: The specificity of serum IgM and IgG antibodies to SARS-CoV-2 was 99.01% (100/101) and 96.04% (97/101), respectively, and the sensitivity was 88.24% (60/68) and 97.06% (66/68), respectively. The combined detection rate of SARS-CoV-2 IgM and IgG antibodies was 98.53% (67/68). CONCLUSION: Combined detection of serum SARS-CoV-2 IgM and IgG antibodies had better sensitivity compared with single IgM or IgG antibody testing, which can be used as an important diagnostic tool for SARS-CoV-2 infection and a screening tool of potential SARS-CoV-2 carriers in clinics, hospitals, and accredited scientific laboratories.

Isolation, purification, characterization and immunostimulatory activity of an exopolysaccharide produced by Lactobacillus pentosus LZ-R-17 isolated from Tibetan kefir.

In this study, three strains of lactic acid bacteria isolated from Tibetan kefir grains, including two strains of Lactobacillus pentosus LZ-R-17 and L. helveticus LZ-R-5, and one strain of Lactococcus lactis subsp. lactis LZ-R-12. The ability of three strains to produce exopolysaccharide (EPS) was tested, and L. pentosus LZ-R-17 was found to have the highest EPS yield. One EPS (R-17-EPS) was isolated from the fermented milk by L. pentosus LZ-R-17 and purified by DEAE-52 anion exchange chromatography. Furthermore, R-17-EPS preliminary structure and macrophage immunomodulatory activity in vitro were investigated. On the basis of the analytical results of ultraviolet-visible spectrum, Fourier transform-infrared spectrum, monosaccharide composition analysis and one-dimensional and two-dimensional nuclear magnetic resonance (NMR) spectra, R-17-EPS was found to have an average molecular weight of 1.20 × 106 Da and was composed of galactose and glucose residues with a molar ratio of 1.00:3.15. NMR analysis revealed that the R-17-EPS was a linear hetero-galactoglucan containing repeating units of →2)-α-D-Galp-(1 â†’ 4)-ß-D-Glcp-(1 â†’ 4)-ß-D-Glcp-(1 â†’ 4)-ß-D-Glcp-(1→. In addition, R-17-EPS could effectively enhanced the proliferation, phagocytosis, nitric oxide and cytokines production of RAW264.7 cells, suggesting that R-17-EPS had potent immunostimulatory activity and could be explored as immunomodulator in functional food and/or medicine fields.

Structural characterization and immunomodulatory activity of an exopolysaccharide produced by Lactobacillus helveticus LZ-R-5.

Exopolysaccharide (R-5-EPS) was isolated from the fermented milk of Lactobacillus helveticus LZ-R-5 and purified by DEAE-52 cellulose anion-exchange column, and characterization of the structure was conducted. Results showed that R-5-EPS was a heteropolysaccharide containing linear repeating units of →6)-ß-D-Galp-(1→3)-ß-D-Glcp-(1→3)-ß-D-Glcp-(1→3)-ß-D-Glcp-(1→3)-ß-D-Glcp-(1→ with an average Mw of 5.41 × 105 Da. Furthermore, at a cellular level, R-5-EPS showed immunostimulatory activity due to its strong effect on increasing proliferation of RAW264.7 macrophages and enhancing phagocytosis, acid phosphatase activity, nitric oxide production and cytokines production in macrophages. These results suggest that R-5-EPS have a potent immunostimulatory activity and may be explored as a potential immunomodulatory agent.

A Review of the Brain-Gut-Microbiome Axis and the Potential Role of Microbiota in Alzheimer's Disease.

Alzheimer's disease (AD) is a neurodegenerative process characterized by loss of neurons in the hippocampus and cerebral cortex, leading to progressive cognitive decline. Pathologically, the hallmark of AD is accumulation of "senile" plaques composed of amyloid-ß (Aß) protein surrounding neurons in affected regions. Despite extensive research into AD pathogenesis and therapeutic targets, there remains no breakthroughs in its management. In recent years, there has been a spark of interest in the connection between the brain and gastrointestinal tract, referred to as the brain-gut axis, and its potential implications for both metabolic and neurologic disease. Moreover, the gastrointestinal flora, referred to as the microbiome, appears to exert significant influence over the brain-gut axis. With the need for expanded horizons in understanding and treating AD, many have turned to the brain-gut-microbiome axis for answers. Here we provide a review of the brain-gut-microbiome axis and discuss the evidence supporting alterations of the axis in the pathogenesis of AD. Specifically, we highlight the role for the microbiome in disruption of Aß metabolism/clearance, increased permeability of the blood-brain barrier and modulation of the neuroinflammatory response, and inhibition of hippocampal neurogenesis. The majority of the above described findings are the result of excellent, albeit basic and pre-clinical studies. Therefore, we conclude with a brief description of documented clinical support for brain-gut-microbiome axis alteration in AD, including potential microbiome-based therapeutics for AD. Collectively, these findings suggest that the brain-gut-microbiome axis may be a "lost link" in understanding and treating AD and call for future work.

Microcystin-leucine-arginine induced neurotoxicity by initiating mitochondrial fission in hippocampal neurons.

Microcystin-leucine-arginine (MC-LR) can cross the blood-brain barrier (BBB) and demonstrate potent acute hippocampal neurotoxicity. Chronic exposure to MC-LR has been confirmed to cause learning and memory deficits in mice, but the potential molecular mechanism of MC-LR-caused neurotoxicity is still unclear. In this research, we observed that MC-LR induced oxidative stress, mitochondrial fission and apoptosis in HT-22 hippocampal neurons. Moreover, further studies identified that MC-LR induced mitochondrial fragmentation via activating Dynamin-related protein 1 (Drp1) and Mitochondrial fission factor (Mff), contributing to apoptosis of hippocampal neuronal cells. The observed effects were associated with increased intracellular Ca2+ and reduced activity of protein phosphatases 2A (PP2A) as results of MC-LR exposure in hippocampal neuron cells. Ca2+ activates CaMK II and Akt to enhance phosphorylation of Drp1 at Ser616 residue. Inhibition of PP2A activity increased AMPK activity to mediate phosphorylation of Mff. Our data proved that MC-LR can cause mitochondrial fragmentation in hippocampal neurons, which provides novel perception to explore the underlying molecular mechanism associated with MC-LR-induced neurotoxicity and Alzheimer's disease-like changes.

Blood-brain barrier disruption and inflammation reaction in mice after chronic exposure to Microcystin-LR.

Microcystin-leucine-arginine (MC-LR), which produced by toxic cyanobacteria and widely present in eutrophic waters, has been shown to have potent acute hepatotoxicity. MC-LR has been revealed to inflict damage to brain, while the neurotoxicity of chronic exposure to MC-LR and mechanisms underlying it are still confusing. Here, the mice were exposed to MC-LR dissolved in drinking water at dose of 1, 7.5, 15, and 30 µg/L for consecutive 180 days. MC-LR accumulated in mouse brains and impaired the blood-brain barrier by inducing the expression of matrix metalloproteinase-8 (MMP-8), which was regulated by NF-κB, c-Fos and c-Jun. Furthermore, MC-LR exposure induced microglial and astrocyte activation and resultant neuroinflammatory response. This study highlights the risks to human health of the current microcystin exposure.

Learning and memory deficits and alzheimer's disease-like changes in mice after chronic exposure to microcystin-LR.

Previous studies have demonstrated that toxins produced by toxic cyanobacterial blooms are hazardous materials. Although microcystin-LR (MC-LR) has been revealed to inflict damage to the brain, the mechanisms underlying its neurotoxicity as a result of chronic exposure to MC-LR are not fully described. In this study, the mice were exposed to MC-LR dissolved in drinking water at doses of 1, 7.5, 15, or 30 µg/L for 180 days. MC-LR accumulated mostly in the mouse hippocampus (55 ng/g dry weight) followed by cortex (28 ng/g dry weight) after exposure to MC-LR at 30 µg/L. MC-LR exposure at this concentration induced dysfunction of learning and memory, accompanied with apoptosis of neuronal cells (with 10% reduction of the neurons in the CA1 region and 15% in the CA2 region), reduction of spine density, accumulation of ß-amyloid plaques 1-42 (Aß1-42), and enhanced phosphorylation of tau (p-tau) in the brain, which is characteristic of Alzheimer's disease (AD). These data indicate that MC-LR may induce AD-like pathology. Following prolonged exposure, MC-LR significantly upregulated the ratio of proBDNF to BDNF by downregulating the tPA levels, thereby activating downstream signaling pathways to improve the expression of p-JNK, and c-Jun while to inhibit the expression of p-Creb and p-PKC. This study uncovered new molecular mechanisms that account for neurotoxicity after chronic exposure to MC-LR, which has wide-ranging implications for public health.