Lentinan has a beneficial effect on cognitive deficits induced by chronic Toxoplasma gondii infection in mice.

BACKGROUND: Toxoplasma gondii (T. gondii) is increasingly considered a risk factor for neurodegenerative diseases. However, there is only limited information on the development of drugs for T. gondii infection. Lentinan from Lentinula edodes is a bioactive ingredient with the potential to enhance anti-infective immunity. The present study aimed to investigate the neuroprotective effect of lentinan on T. gondii-associated cognitive deficits in mice. METHODS: A chronic T. gondii infection mouse model was established by administering 10 cysts of T. gondii by gavage. Lentinan was intraperitoneally administered 2 weeks before infection. Behavioral tests, RNA sequencing, immunofluorescence, transmission electron microscopy and Golgi-Cox staining were performed to assess the effect of lentinan on cognitive deficits and neuropathology in vivo. In vitro, the direct and indirect effects of lentinan on the proliferation of T. gondii tachyzoites were evaluated in the absence and presence of BV-2 cells, respectively. RESULTS: Lentinan prevented T. gondii-induced cognitive deficits and altered the transcriptome profile of genes related to neuroinflammation, microglial activation, synaptic function, neural development and cognitive behavior in the hippocampus of infected mice. Moreover, lentinan reduced the infection-induced accumulation of microglia and downregulated the mRNA expression of proinflammatory cytokines. In addition, the neurite and synaptic ultrastructural damage in the hippocampal CA1 region due to infection was ameliorated by lentinan administration. Lentinan decreased the cyst burden in the brains of infected mice, which was correlated with behavioral performance. In line with this finding, lentinan could significantly inhibit the proliferation of T. gondii tachyzoites in the microglial cell line BV2, although lentinan had no direct inhibitory effect on parasite growth. CONCLUSIONS: Lentinan prevents cognitive deficits via the improvement of neurite impairment and synaptic loss induced by T. gondii infection, which may be associated with decreased cyst burden in the brain. Overall, our findings indicate that lentinan can ameliorate T. gondii-related neurodegenerative diseases.

Lentinan alleviates diabetic cardiomyopathy by suppressing CAV1/SDHA-regulated mitochondrial dysfunction.

Diabetic cardiomyopathy (DCM), characterized by mitochondrial dysfunction and impaired energetics as contributing factors, significantly contributes to high mortality in patients with diabetes. Targeting key proteins involved in mitochondrial dysfunction might offer new therapeutic possibilities for DCM. Lentinan (LNT), a ß-(1,3)-glucan polysaccharide obtained from lentinus edodes, has demonstrated biological activity in modulating metabolic syndrome. In this study, the authors investigate LNT's pharmacological effects on and mechanisms against DCM. The results demonstrate that administering LNT to db/db mice reduces cardiomyocyte apoptosis and mitochondrial dysfunction, thereby preventing DCM. Notably, these effects are fully negated by Caveolin-1 (CAV1) overexpression both in vivo and in vitro. Further studies and bioinformatics analysis uncovered that CAV1 bound with Succinate dehydrogenase subunit A (SDHA), triggering the following ubiquitination and degradation of SDHA, which leads to mitochondrial dysfunction and mitochondria-derived apoptosis under PA condition. Silencing CAV1 leads to reduced apoptosis and improved mitochondrial function, which is blocked by SDHA knockdown. In conclusion, CAV1 directly interacts with SDHA to promote ubiquitination and proteasomal degradation, resulting in mitochondrial dysfunction and mitochondria-derived apoptosis, which was depressed by LNT administration. Therefore, LNT may be a potential pharmacological agent in preventing DCM, and targeting the CAV1/SDHA pathway may be a promising therapeutic approach for DCM.

Lentinan alleviates sciatic nerve injury by promoting autophagy to remove myelin fragments.

Lentinan, a natural drug with wide-ranging pharmacological activities, can regulate autophagy-the process through which Schwann cells (SCs) eliminate myelin fragments after peripheral nerve injury (PNI). However, the effect of lentinan after PNI and the role of accelerated myelin debris removal via autophagy in this process are unclear. This study examined the effect of lentinan on rat sciatic nerve repair following crush injury and the underlying mechanisms. After the successful establishment of the sciatic nerve compression injury model, group-specific treatments were performed. The treatment group received 20 mg/kg lentinan via intraperitoneal injection, while the model group was treated with normal saline. The recovery in each group was then evaluated. Further, a rat SC line (RSC96) was cultured in medium with/without lentinan after supplementation with homogenous myelin fractions to evaluate the removal of myelin particles. Our results showed that lentinan promotes autophagic flux in vivo via the AMPK/mTOR signaling pathway, accelerates the clearance of myelin debris by SCs, and inhibits neuronal apoptosis, thereby promoting neurological recovery. Similarly, in vitro experiments showed that lentinan promotes the phagocytosis of myelin debris by SCs. In conclusion, our results suggest that lentinan primarily promotes nerve regeneration by accelerating the autophagic clearance of myelin debris in SCs, and this process is likely regulated by the AMPK/mTOR signaling pathway. Therefore, this study provides compelling evidence that lentinan may be a cost-effective and natural treatment agent for PNI.

Supplementation with compound polysaccharides contributes to the development and metabolic activity of young rat intestinal microbiota.

Dietary intervention during early life has a significant impact on colonization of the gut microbiota. In addition, some polysaccharides have the potential to selectively stimulate the growth and metabolic activity of intestinal bacteria associated with health and well-being. However, less is known about the effect of polysaccharides on the development of gut microbiota in younger individuals. This study was conducted to investigate the health effects of supplementation with dietary compound polysaccharides (Lycium barbarum polysaccharides (LBP), Poria cocos polysaccharides (PCPs) and Lentinan, 1 : 1 : 1) on the intestinal microecosystem and metabolism of young rats. Male 21-day-old Sprague-Dawley rats received daily intragastric administration of either compound polysaccharides (three dosages, 6 g kg-1, 12 g kg-1 or 24 g kg-1) or saline for 28 consecutive days. 1H-NMR spectroscopy integrated with multi-variate pattern recognition analysis was applied to reveal the metabolism of the host and microflora, while 16S rRNA gene sequencing was used to monitor the dynamic changes in the gut microbiota. The relative concentrations of 35 urinary metabolites and 24 faecal metabolites were significantly changed compared with the control group. 16S rRNA analysis showed that the relative abundances of 4 bacterial genera (Bifidobacterium, Lactobacillus, Allobaculum and Oligella) significantly increased, whereas the relative abundance of 1 bacterial genus (Enterococcus) significantly declined in the compound polysaccharide-treated groups compared with the control group. Meanwhile, dietary compound polysaccharide treatment promoted the functional maturation of the gut bacterial community, characterised by increased basic metabolism (amino acid metabolism and energy metabolism), short chain fatty acid (SCFA)-related metabolism and nucleotide metabolism. These findings suggest that compound polysaccharides may help to promote the colonisation and functional maturation of infant intestinal microbiota and maintain the health of the intestinal microecosystem.

Lentinan degradation in the Lentinula edodes fruiting body during postharvest preservation is reduced by downregulation of the exo-ß-1,3-glucanase EXG2.

Lentinan from Lentinula edodes fruiting bodies (shiitake mushrooms) is a valuable ß-glucan for medical purposes based on its anticancer activity and immunomodulating activity. However, lentinan content in fruiting bodies decreases after harvesting and storage due to an increase in glucanase activity. In this study, we downregulated the expression of an exo-ß-1,3-glucanase, exg2, in L. edodes using RNA interference. In the wild-type strain, ß-1,3-glucanase activity in fruiting bodies remarkably increased after harvesting, and 41.7% of the lentinan content was lost after 4 days of preservation. The EXG2 downregulated strain showed significantly lower lentinan degrading activity (60-70% of the wild-type strain) in the fruiting bodies 2-4 days after harvesting. The lentinan content of fresh fruiting bodies was similar in the wild-type and EXG2 downregulated strains, but in the downregulated strain, only 25.4% of the lentinan was lost after 4 days, indicating that downregulation of EXG2 enables keeping the lentinan content high longer.

Inhibition of aflatoxin synthesis in Aspergillus flavus by three structurally modified lentinans.

The chemical properties of ß-glucans leading to their inhibition on aflatoxin (AF) production by Aspergillus flavus remain unclear. In this study, structurally modified lentinan derivatives were prepared by carboxymethylation, sulfation, and phosphorylation to explore their inhibition activity to AF synthesis. The results demonstrated that inhibitory activity of lentinan decreased at higher or lower concentrations than 200 µg/mL. Compared with lentinan, the sulphated derivatives only performed a reduced optimal inhibition rate at a higher concentration. The phosphorylated derivatives achieved complete inhibition of AF production at 50 µg/mL, but the inhibitory activity was attenuated with an increase of concentration. The minimum concentration of carboxymethylated derivatives to completely inhibit AF synthesis was the same as that of the original lentinan, whereas their inhibition activity was not reduced at the increasing concentration. RT-PCR analyses were conducted to understand the effects of lentinan and its carboxymethylated derivatives on the transcription of certain genes associated with AF biosynthesis. The results showed that lentinan delayed the transcription of aflQ, whereas its carboxymethylated derivatives promoted the transcriptions of all the tested genes. Our results revealed that some chemical group features apart from the ß-bond could play the vital role in the prevention of AF formation by polysaccharide, and highlighted the structural modifications which could promote its practicability in the control of aflatoxin contamination.

Dynamic high pressure microfluidization-assisted extraction and antioxidant activities of lentinan.

Dynamic high pressure microfluidization (DHPM) was applied to assist the lentinan extraction. Response surface methodology (RSM), based on Box-Behnken design, was employed to optimize the DHPM-assisted extraction conditions of lentinan. Three main independent variables (DHPM pressure, ratio of water to raw material, extraction temperature) were taken into consideration. A yield of 7.200% was obtained under a modified condition (ratio of water to raw material of 65 mL/g, DHPM pressure of 147 MPa, extraction temperature of 83 °C), which matched well with the predicted value of the model. The molecular weight of the DHPM-assisted extract and hot water extract was 913,329 and 965,361 Da, respectively. Compared to the traditional hot water extraction, the lentinan extracted by DHPM assisting had better scavenging capacity of hydroxyl radical, superoxide anion free radical, 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical and nitrite. It could be concluded that the DHPM was a promising method to enhance the yield and antioxidant activity of lentinan during extraction.

Lentinula edodes tlg1 encodes a thaumatin-like protein that is involved in lentinan degradation and fruiting body senescence.

Lentinan is an antitumor product that is purified from fresh Lentinula edodes fruiting bodies. It is a cell wall component, comprising beta-1,3-glucan with beta-1,6-linked branches, which becomes degraded during postharvest preservation as a result of increased glucanase activity. In this study, we used N-terminal amino acid sequence to isolate tlg1, a gene encoding a thaumatin-like (TL) protein in L. edodes. The cDNA clone was approximately 1.0 kb whereas the genomic sequence was 2.1 kb, and comparison of the two indicated that tlg1 contains 12 introns. The tlg1 gene product (TLG1) was predicted to comprise 240 amino acids, with a molecular mass of 25 kD and isoelectric point value of 3.5. The putative amino acid sequence exhibits approximately 40% identity with plant TL proteins, and a fungal genome database search revealed that these TL proteins are conserved in many fungi including the basidiomycota and ascomycota. Transcription of tlg1 was not detected in vegetative mycelium or young and fresh mushrooms. However, transcription increased following harvest. Western-blot analysis demonstrated a rise in TLG1 levels following harvest and spore diffusion. TLG1 expressed in Escherichia coli and Aspergillus oryzae exhibited beta-1,3-glucanase activity and, when purified from the L. edodes fruiting body, demonstrated lentinan degrading activity. Thus, we suggest that TLG1 is involved in lentinan and cell wall degradation during senescence following harvest and spore diffusion.

Characterization of the Lentinula edodes exg2 gene encoding a lentinan-degrading exo-beta-1,3-glucanase.

Lentinan, an antitumor substance purified from Lentinula edodes, is degraded during post-harvest preservation as a result of increased glucanase activity. We isolated an exo-beta-1,3-glucanase encoding gene, exg2, from L. edodes which is a homologue of an exo-glucanase-encoding gene conserved in ascomycetous fungi. The exg2 gene was cloned as an approximately 2.4-kbp cDNA, and as a genomic sequence of 3.9-kbp. The product of the exg2 gene is predicted to contain 759 amino acids with a molecular weight of 79 kDa and a pI value of 4.6. The putative N-terminus of EXG2 is identical to the N-terminal sequences of lentinan-degrading enzymes, GNase I and II, and a custom-made anti-EXG2 peptide anti-serum cross-reacted with purified GNase I and II. Transcription and translation of exg2 was low in the gills of mature fruiting bodies, but increased after harvesting. We conclude that the exg2 gene is a lentinan-degrading enzyme-encoding-gene in L. edodes.

Autolysis of lentinan, an antitumor polysaccharide, during storage of Lentinus edodes, shiitake mushroom.

The lentinan contents in the Lentinus edodes fruit body during storage were examined by ELISA method using anti-lentinan antibodies. The lentinan content (12.8 mg.g(-)(1) dw) before storage decreased to 3.7 mg.g(-)(1) dw over 7 days at 20 degrees C. However, it only slightly decreased at 1 degrees C and only decreased to 9.3 mg. g(-)(1) dw at 5 degrees C. Glucanase activity, which seems to be associated with lentinan degradation, increased more during storage of L. edodes at 20 degrees C than it did at lower temperatures. In addition, only glucose was detected as a degraded product from lentinan by the glucanase. This suggested that this enzyme would fit the profile of an exo-type glucanase. Also, polyphenol oxidase activity, known as an index of freshness reduction in the mushroom, increased approximately 2.7-fold (to 61.5 units.mg(-)(1)) over 7 days during storage at 20 degrees C. However, its activity changed little during storage at lower temperatures. These results indicate that the reduction during storage of the quality of L. edodes as a functional food is accompanied by the decrease of lentinan, and by browning, and that exo-glucanase plays an important role in the decrease of lentinan content.

In vitro and in vivo analysis of human leukocyte binding by the antitumor polysaccharide, lentinan.

Lentinan (LNT), a (1-->3)-beta-D-glucan with (1--6)-beta-D-glucopyranoside branches, has marked antitumor effects in syngeneic and autochtonous hosts. Clinically, LNT has proved effective with chemotherapeutic agents in patients with recurrent gastric and colorectal cancer. However, the mechanism that triggers subsequent immunologic reactions remains obscure. We hypothesized that LNT must first bind to the host cells. Accordingly, we analyzed LNT binding to host cells in healthy volunteers after incubating their cells under a variety of conditions as well as intravenously injecting LNT then subjecting them to flow cytometry and immunofluorescent staining using monoclonal antibody (anti-LNT mAb). LNT bound to monocytes and neutrophils, but not to lymphocytes in vitro. The most avid LNT binding was to monocytes. The percentage of LNT-bound monocytes after 60 min incubation at 4 degrees C was greater than that at 37 degrees C. The binding of LNT to monocytes was inhibited slightly by anti-iC3b receptor (anti-CR3) mAb, strongly by anti-C3b receptor (anti-CR1) mAb, and completely by anti-CR1 and anti-CR3 mAb together. The percentages of LNT-binding monocytes in the peripheral blood increased significantly 3 and 4 after 2 mg LNT-injection and returned to low levels 5 h later. However, no increase in LNT-binding neutrophils and lymphocytes was observed. We concluded that binding of LNT to human monocytes may initiate the influence of this compound on the immune system and differ between individuals. Its binding site may be similar to the C3b receptor.

[Fate of lentinan (antitumor polysaccharide) I : - fate of lentinan in mice, rats, and dogs (author's transl)].

Fate of lentinan, which is one of antitumor polysaccharides, was investigated with 3H-lentinan. 3H-lentinan was prepared by Wilzbach 3H gas exposure labeling, then purified by the gel filtration chromatography. 1) After a single intravenous injection of 3H-lentinan, radioactivity in plasma declined in a biphasic process. 2) There were urinary and fecal excretion, but expiratory excretion was a small proportion. 3) The radioactivity was predominantly incorporated into the liver and spleen, indicating selective retention of the lentinan in reticuloendothelial system cells. On the other hand the level of radioactivity in the lung and kidneys was dropped rapidly. 4) We can not find the selective incorporation of radioactivity into the tumor. 5) There was no species difference on the distribution of lentinan among mouse, rat and dog. 6) These results obtained were similar to other polysaccharides and immunologic antitumor agents.

[Fate of lentinan (antitumor polysaccharide) II : - fast of methyl lentinan in rats (author's transl)].

3H-labeled lentinan was prepared by methylation with 3H-dimethyl-sulfate. Blood level, distribution and excretion were studied in rats. After intravenous injection of [methyl-3H] -methyl lentinan, radioactivity rapidly disappeared from blood, lung and kidney, distributed mainly in liver, spleen and mesenteric lymph nodes. There was urinary excretion, but expiratory excretion was a small proportion. In the case of multi-injection of [methyl-3H] -methyl lentinan distribution of radioactivity was similar to a single injection, but retention of 3H was less than a single injection. Bile excretion and transport to fetuses and milk were in mere trace amounts. No substantial difference was found between two types of the 3H-labeled lentinan in either the distribution or excretion.