Interactions between Yersinia pestis V-antigen (LcrV) and human Toll-like receptor 2 (TLR2) in a modelled protein complex and potential mechanistic insights.

BACKGROUND: Yersinia pestis, the etiological pathogen of plague, is capable of repressing the immune response of white blood cells to evade phagocytosis. The V-antigen (LcrV) was found to be involved in this process by binding to human Toll-like Receptor 2 (TLR2). The detailed mechanism behind this LcrV and TLR2 mediated immune response repression, however, is yet to be fully elucidated due to the lack of structural information. RESULTS: In this work, with protein structure modelling, we were able to construct a structure model of the heterotetramer of Y. pestis LcrV and human TLR2. Molecular dynamics simulation suggests the stability of this structure in aquatic environment. The LcrV model has a dumbbell-like structure with two globule domains (G1 at N-terminus and G2 away from membrane) connected with a coiled-coil linker (CCL) domain. The two horseshoe-shape TLR2 subunits form a V-shape structure, are not in direct contact with each other, and are held together by the LcrV homodimer. In this structure model, both the G1 and CCL domains are involved in the formation of LcrV homodimer, while all three domains are involved in LcrV-TLR2 binding. A mechanistic model was proposed based on this heterotetrameric structure model: The LcrV homodimer separates the TLR2 subunits to inhibit the dimerization of TLR2 and subsequent signal transfer for immune response; while LcrV could also inhibit the formation of heterodimers of TLR2 with other TLRs, and leads to immune response repression. CONCLUSIONS: A heterotetrameric structure of Y. pestis LcrV and human TLR2 was modelled in this work. Analysis of this modelled structure showed its stability in aquatic environments and the role of LcrV domains and residues in protein-protein interaction. A mechanistic model for the role of LcrV in Y. pestis pathogenesis is raised based on this heterotetrameric structure model. This work provides a hypothesis of LcrV function, with which further experimental validation may elucidate the role of LcrV in human immune response repression.

Discovery of a new autophagy inducer for A549 lung cancer cells.

Biological activities of a series of fluorescent compounds against human lung cancer cell line A549 were investigated. The results showed that (E)-1,3,3-trimethyl-2-(4-(piperidin-1-yl)styryl)-3H-indol-1-ium iodide (8) and (E)-2-(5,5-dimethyl-3-(4-(piperazin-1-yl)styryl)cyclohex-2-en-1-ylidene) malononitrile (11) could inhibit the growth of A549 cancer cells in a dose and time-dependent manner. Furthermore, compound 8 could trigger autophagy and apoptosis, but not obviously induce necrosis under the stimulatory condition. Therefore, 8 can be used as autophagy activator to investigate the regulatory mechanism of autophagy and may offer a new candidate for the treatment of lung cancer.

The promotion effect of novel magnetic nanoparticles on atherosclerotic plaque vulnerability in apolipoprotein E-/- mice.

Although manufactured magnetic nanoparticles (NPs) are currently used in many fields, NPs have potential toxicity on cardiovascular system especially atherosclerosis. In our previous study, we prepared novel Fe3O4 nanoparticles surface-coated with aminoguanidine (Fe3O4-AG NPs) which could remove acid dyes from aqueous solution efficiently. To understand its biocompatibility to atherosclerotic plaque vulnerability, we investigated the effects of the nanoparticles on human umbilical vein endothelial cells (HUVECs) in vitro and plaque stability in vivo. Fe3O4-AG NPs were taken up by HUVECs and induced HUVEC apoptosis. Fe3O4-AG NP injection remarkably promoted plaque vulnerability at low-dose (0.5 mg/kg) but not high-dose (5.0 mg/kg) in apolipoprotein E-/- (ApoE-/-) mice. Further study indicated that Fe3O4-AG NP-induced atherosclerotic plaque vulnerability was tightly linked to bioactivity of nitric oxide (NO). A significant decrease in NO production was induced which coincided with the inhibition of endothelial nitric oxide synthase (eNOS) activity in serum and endothelium of plaque in ApoE-/- mice injected with low-dose Fe3O4-AG NPs in vivo and HUVECs treated with low-dose Fe3O4-AG NPs in vitro. Thus, the low concentration of Fe3O4-AG NPs presented toxicity to atherosclerosis. Our results indicated that the use of Fe3O4-AG NPs to improve aqueous solution pollution should be cautious due to the potential toxicity.

The beneficial and deleterious role of dietary polyphenols on chronic degenerative diseases by regulating gene expression.

Dietary polyphenols, a natural component in many kinds of foods such as fruits and vegetables, play essential roles in a wide range of plant functions. Importantly, the discovery of the functions of polyphenols including anti-oxidant, anti-carcinogenic and anti-inflammatory has been appealing to researchers' attentions. Dietary polyphenols have shown protective effects on chronic degenerative diseases (CDD) such as cardiovascular diseases, cancers, and neurodegenerative diseases by regulating gene expression. Dietary polyphenols also affect the composition and activity of gut microbiota, in reverse, gut microbiota influences the bioavailability and physiological activity of dietary polyphenols. However, not all kinds of dietary polyphenols are beneficial for human health. The potential deleterious effects of several dietary polyphenols have been reported by inducing DNA damage and gene mutants. This review summarizes the potential therapeutic effects of dietary polyphenols on chronic degeneration diseases, the polyphenols-gut microbiota interactions, and the potential dangers of individual dietary polyphenols on human health.

A pH probe inhibits senescence in mesenchymal stem cells.

BACKGROUND: Bone marrow-derived mesenchymal stem cells (BMSCs) are gradually getting attention because of its multi-directional differentiation potential, hematopoietic support, and promotion of stem cell implantation. However, cultured BMSCs in vitro possess a very limited proliferation potential, and the presence of stem cell aging has substantially restricted the effect together with the efficiency in clinical treatment. Recently, increasing attention has been paid to the connection between cellular aging and lysosomal acidification as new reports indicated that vacuolar H+-ATPase (v-ATPase) activity was altered and lysosomal pH was dysregulated in the process of cellular aging. Therefore, promoting lysosomal acidification might contribute to inhibition of cell senescence. Our previous studies showed that a novel small molecule, 3-butyl-1-chloro imidazo [1, 5-a] pyridine-7-carboxylic acid (SGJ), could selectively and sensitively respond to acidic pH with fast response (within 3 min), but whether SGJ can promote lysosomal acidification and inhibit senescence in BMSCs is unknown. METHODS: Rat BMSCs were cultured based on our system that had been already documented. BMSCs were treated with SGJ and/or Bafilomycin-A1 (Baf-A1). The co-localization between SGJ and lysosomes was assessed by a confocal microscope. Acridine orange (AO) staining and the Lysosensor™ Green DND-189 reagents were used for indicating changes in lysosomal concentration of H+. Changes of senescence were detected by immunoblotting of p21 and senescence-associated beta-galactosidase (SA-ß-gal) staining as well as immunofluorescence assay of senescence-associated heterochromatin foci (SAHF). Changes of autophagy were detected by immunoblotting of MAP1LC3 (LC3B) and SQSTM1 (p62). Cell proliferation was determined by flow cytometry. Cell viability was calculated by sulforhodamine B assay (SRB). The V0 proton channel of v-ATPase was knocked down by transfecting with its small interfering RNA (si-ATP6V0C). RESULTS: Our work showed that SGJ can promote lysosomal acidification and inhibit senescence in BMSCs. Firstly, SGJ and lysosomes were well co-located in senescent BMSCs with the co-localization coefficient of 0.94. Secondly, SGJ increased the concentration of H+ and the protein expression of lysosome-associated membrane protein 1 (LAMP1) and lysosome-associated membrane protein 2 (LAMP2). Thirdly, SGJ suppressed the expression of p21 in the senescent BMSCs and reduced SA-ß-gal positive cells. Fourthly, SGJ promoted senescent BMSCs' proliferation and protein level of LC3B but reduced the p62/SQSTM1 protein level. Furthermore, experimental group pretreated with 20 µM SGJ showed a stronger red fluorescent intensity, thinner cell morphology, less SA-ß-gal positive cell, and less p21 protein level as well as higher cell viability in the presence of Baf-A1. Notably, ATP6V0C knockdown decreased the activity of v-ATPase and SGJ increased the concentration of H+. CONCLUSION: Our work showed that SGJ could inhibit senescence in BMSCs and protect lysosomes by promoting expression of LAMP1 and LAMP2. Meanwhile, SGJ could promote autophagy. Furthermore, our study also suggested that SGJ was a new Baf-A1 antagonist because SGJ could target and occupy the V0 proton channel of v-ATPase.

A small molecule targeting glutathione activates Nrf2 and inhibits cancer cell growth through promoting Keap-1 S-glutathionylation and inducing apoptosis.

The level of glutathione (GSH) is increased in many cancer cells. Consuming intracellular GSH by chemical small molecules that specifically target GSH is a new strategy to treat cancer. Recently, we synthesized and proved that a new compound 2-(7-(diethylamino)-2-oxo-2H-chromen-3-yl)cyclohexa-2,5-diene-1,4-dione (PBQC) could target to and consume intracellular GSH specifically, but, it is not clear if PBQC can affect cancer cell growth and the activity of the nuclear factor-erythroid 2-related factor 2 (Nrf2) which is a key factor involved in regulation of cancer cell growth. In this study, we addressed these questions. We found that PBQC suppressed cancer cell growth through increasing the activity of Nrf2, while it did not inhibit normal vascular endothelial cell growth. Furthermore, we demonstrated that PBQC can cause Keap-1 protein S-glutathionylation and promote Nrf2 nuclear translocation as well as the expression of pro-apoptosis genes. As a result, the cancer cells underwent apoptosis. Here, we provide a new Nrf2 activator, PBQC that can promote the expressions of pro-apoptosis genes downstream Nrf2. The data suggest that PBQC is a potential lead-compound for development of new anti-cancer drugs.