Dentin phosphoprotein inhibits lipopolysaccharide-induced macrophage activation independent of its serine/aspartic acid-rich repeats

OBJECTIVE

The objective of this study was to investigate the effects of dentin phosphoprotein (DPP) on lipopolysaccharide-induced inflammatory responses of macrophages in vitro.

DESIGN

Wildtype and mutant recombinant dentin phosphoprotein (rDPP) proteins were generated using a mammalian expression system. Macrophages, phorbol 12-myristate 13-acetate-differentiated THP-1 cells, were stimulated with lipopolysaccharide in the absence or presence of rDPP proteins. After the 24-hr incubation, the inflammatory gene expression levels were examined by quantitative reverse-transcription polymerase chain reaction and the amount of secreted TNF-α protein was evaluated by enzyme-linked immunosorbent assay. Furthermore, the subcellular localization of exogenously added rDPP was examined by immunocytochemistry, and the direct binding of rDPP to lipopolysaccharide was quantified by solid-phase binding assay.

RESULTS

rDPP dose-dependently reduced the expression of lipopolysaccharide-induced inflammatory genes, such as TNFα, IL-1β, and IL-8, and TNF-α protein secretion from the macrophages. Furthermore, mutant rDPP having a shortened serine/aspartic acid-rich repeats (SDrr) was also able to inhibit lipopolysaccharide-induced inflammatory responses of macrophages. rDPP was localized adjacent to the cellular membrane rather than in the cytoplasm, and rDPP was able to bind to lipopolysaccharide. These results suggested that rDPP inhibited lipopolysaccharide-induced inflammatory responses by binding to lipopolysaccharide.

CONCLUSIONS

In addition to the well-known functions of DPP for dentin mineralization that depend on the SDrr, we demonstrated that DPP possesses anti-inflammatory effects on lipopolysaccharide-stimulated macrophages that are independent of the SDrr.

Nanaomycin K, a new epithelial-mesenchymal transition inhibitor produced by the actinomycete "Streptomyces rosa subsp. notoensis" OS-3966

A new nanaomycin analog, nanaomycin K, was isolated from a cultured broth of actinomycete strain "Streptomyces rosa subsp. notoensis" OS-3966. Nuclear magnetic resonance (NMR) analyses revealed that the planar structure of nanaomycin K had an ergothioneine moiety. To determine the absolute configuration, nanaomycin K was semisynthesized using standards of nanaomycin E and l-ergothioneine. The natural and semisynthetic nanaomycin K were identified as the same compounds based on retention time, mass spectrometry, ¹H NMR, and optical rotation data. Nanaomycin K showed cytotoxicity against Madin-Darby canine kidney (MDCK) cells undergoing transforming growth factor (TGF) β1-induced epithelial-mesenchymal transition.

Synthesis of Poly(N-vinylpyrrolidone)-Based Polymer Bottlebrushes by ATRPA and RAFT Polymerization: Toward Drug Delivery Application

Atom transfer radical polyaddition (ATRPA) was utilized herein to synthesize a specific functional polyester. We conducted ATRPA of 4-vinylbenzyl 2-bromo-2-phenylacetate (VBBPA) inimer and successfully obtained a linear type poly(VBBPA) (PVBBPA) polyester with benzylic bromides along the backbone. To obtain a novel amphiphilic polymer bottlebrush, however, the lateral ATRP chain extension of PVBBPA with N-vinyl pyrrolidone (NVP) met the problem of quantitative dimerization. By replacing the bromides to xanthate moieties efficiently, we thus observed a pseudo linear first order reversible addition-fragmentation chain transfer (RAFT) polymerization to obtain novel poly(4-vinylbenzyl-2-phenylacetate)-g-poly(NVP) (PVBPA-g-PNVP) amphiphilic polymer bottlebrushes. The critical micelle concentration (CMC) and particle size of the amphiphilic polymer bottlebrushes were characterized by fluorescence spectroscopy, dynamic light scattering (DLS), and scanning electron microscopy (SEM) (CMCs < 0.5 mg/mL; particle sizes = ca. 100 nm). Toward drug delivery application, we examined release profiles using a model drug of Nile red at different pH environments (3, 5, and 7). Eventually, low cytotoxicity and well cell uptake of the Madin-Darby Canine Kidney Epithelial (MDCK) for the polymer bottlebrush micelles were demonstrated.

Photoactivatable Hydrogel Interfaces for Resolving the Interplay of Chemical, Mechanical, and Geometrical Regulation of Collective Cell Migration

Collective migration is the mechanobiological interplay within migrating cell clusters and against extracellular matrixes (ECMs) underneath, mediating various physiological and pathological processes. Therefore, it is crucial to develop a robust platform on which collective migration can be studied under standardized conditions to understand how cells migrate differently between normal and disease states. We herein demonstrated phtotoactivatable hydrogel interfaces as suitable candidates for such applications. The substrate was composed of a poly(acrylamide) (PAAm) hydrogel whose surface was sequentially functionalized with poly-d-lysine (PDL) and photocleavable poly(ethylene glycol) (PEG). On the surface of the gel substrates, cell clusters with any given geometries can be prepared by controlling the irradiation patterns (geometrical cue), and their collective migration can be induced by the subsequent irradiation of the surrounding regions. Moreover, the substrate mechanical properties can be controlled by changing the composition of the PAAm hydrogel (mechanical cue), and the chemical properties were controlled by changing the amount of immobilized PDL, thereby altering the adsorbed amount of ECM proteins (chemical cue). The photoactivatable gel substrates were characterized by fluorescence microscopy, ζ-potential measurements, and the protein adsorption test. Through the study of the interplay of chemical, mechanical, and geometrical cues in the regulation of collective characteristics, we found additive effects of chemical and mechanical cues on the suppression of circular expansion by up-regulating the epithelial morphology. Also, the impact of geometrical cues became more significant by decreasing the chemical cue. We believe the present platform will be a useful research tool for the comprehensive mechanobiological analysis of collective cell migration.

Heparin-LL37 complexes are less cytotoxic for human dental pulp cells and have undiminished antimicrobial and LPS-neutralizing abilities

AIM

To investigate whether glycosaminoglycans (GAGs) binding to high-dose LL37 eliminates its cytotoxicity to dental pulp cells (hDPCs) whilst retaining undiminished antimicrobial and LPS-neutralizing abilities.

METHODOLOGY

hDPCs were stimulated with varying concentrations of LL37, and their cell viability was analysed by MTT. Then, high-dose LL37 (10 μmol L^-1 ) was bound to varying concentrations of three GAGs, heparin, chondroitin sulphate and hyaluronic acid, and their cytotoxic effects on hDPCs and antimicrobial effects were evaluated and compared. Furthermore, the LPS-neutralizing ability of heparin (5 μg mL^-1 )-LL37 (10 μmol L^-1 ) complexes, which were found to be less cytotoxic for hDPCs with undiminished antimicrobial ability, was investigated. Statistical analysis was performed using one-way analysis of variance (anova), followed by Dunnett's test. P values below 0.05 were considered significant.

RESULTS

LL37 significantly reduced the cell viability of hDPCs in a dose-dependent manner (P < 0.01). LL37 (10 μmol L^-1 ) binding to heparin within a limited concentration range (2~6 μg mL^-1 ) eliminated the cytotoxicity for hDPCs (P < 0.01) whilst exerting potent antimicrobial effects against Streptococcus mutans, Streptococcus sobrinus, Streptococcus salivarius, Aggegatibacter actinomycetemcomitans and Escherichia coli. LL37 (10 μmol L^-1 ) binding to chondroitin sulphate exhibited similar functions (P < 0.01); however, the effective chondroitin sulphate concentration was highly restricted (3 μg mL^-1 ). LL37 (10 μmol L^-1 ) binding to hyaluronic acid was unable to abrogate the cytotoxicity of LL37 even at higher concentrations (10 and 100 μg mL^-1 ). Moreover, exogenous addition of LPS dose-dependently reduced the amount of LL37 precipitated with the heparin-LL37 agarose beads (P < 0.01), and the released LL37 simultaneously neutralized the pro-inflammatory ability of LPS in macrophages (P < 0.01).

CONCLUSIONS

Heparin-LL37 complexes generated at suitable concentration ratios are easy to make, are less cytotoxic and are broad-range antimicrobial materials that can neutralize LPS by providing LL37 in accordance with the amount of free LPS. They may be a potential treatment to save dental pulp tissue from the acute inflammation exacerbated by invading bacteria and the LPS they release.

Modulation of Mesenchymal Stem Cells Mechanosensing at Fluid Interfaces by Tailored Self-Assembled Protein Monolayers

Mechanical cues of cellular microenvironments can modulate cell functions including cell spreading and differentiation. Most studies of cellular functions are performed using a solid substrate, and it is thought that cells cannot spread on fluid substrates because of rapid relaxation, which cannot resist against actomyosin-based cell contractility. Here, the spreading and growth of anchorage-dependent cells such as human mesenchymal stem cells at the liquid interface between a perfluorocarbon fluid and the culture medium are observed. It is demonstrated that a monomolecular protein nanosheet self-assembled at a fluid interface is sufficiently rigid to support cell spreading without additional treatment. Fine tuning of the packing of these proteins at the liquid interface permits tailoring of the mechanics of the protein layer, ultimately allowing for the regulation of cell spreading. The greater stiffness of the protein nanosheets triggers cell spreading, adhesion growth, and yes-associated protein nuclear translocation. Cell behavior at the fluid interface is explained within the framework of the molecular clutch model. In addition, the freestanding ultrathin protein nanosheets are extremely flexible, easily deformed, and perceived by cells as being much softer. The findings are expected to provide a new perspective for insights into cell-material interactions.

Nanaomycin I and J: New nanaomycins generated by mycothiol-mediated compounds from "Streptomyces rosa subsp. notoensis" OS-3966

Two new nanaomycin analogs, nanaomycin I and J, were isolated from a cultured broth of an actinomycete strain, "Streptomyces rosa subsp. notoensis" OS-3966. In our previous study, we have confirmed the occurrence of nanaomycin I (m/z = 482 [M + H]⁺) that lacks a pseudo-disaccharide from the mycothiol of nanaomycin H under same culture condition. In this study, to confirm the structure of nanaomycin I, the strain "S. rosa subsp. notoensis" OS-3966 was re-cultured and the target compound with m/z = 482 [M + H]⁺ was isolated. Furthermore, we discovered another new analog, designated as nanaomycin J in isolating nanaomycin I. The NMR analyses revealed that the structures of nanaomycin I and J are N-acetylcysteine S-conjugates without a pseudo-disaccharide and N-acetylcysteine S-conjugates without a myo-inositol of nanaomycin H, respectively. The relative configurations of the tetrahydropyrane moiety of nanaomycin I and J were determined by rotating-frame overhauser effect spectroscopy (ROESY) analysis. Absolute configurations of the N-acetylcysteine moiety of nanaomycin I and J were determined by advanced Marfey's analyses for acid hydrolysis of de-sulfurized nanaomycin I and J with Raney nickel. Nanaomycin I and J showed moderate cytotoxicity against several human tumor cell lines.

An Application of Photoactivatable Substrate for the Evaluation of Epithelial-mesenchymal Transition Inhibitors

Epithelial-mesenchymal transition (EMT), phenotypic changes in cell adhesion and migration, is involved in cancer invasion and metastasis, hence becoming a target for anti-cancer drugs. In this study, we report a method for the evaluation of EMT inhibitors by using a photoactivatable gold substrate, which changes from non-cell-adhesive to cell-adhesive in response to light. The method is based on the geometrical confinement of cell clusters and the subsequent migration induction by controlled photoirradiation of the substrate. As a proof-of-concept experiment, a known EMT inhibitor was successfully evaluated in terms of the changes in cluster area or leader cell appearance, in response to biochemically and mechanically induced EMT. Furthermore, an application of the present method for microbial secondary metabolites identified nanaomycin H as an EMT inhibitor, potentially killing EMTed cells in disseminated conditions. These results demonstrate the potential of the present method for screening new EMT inhibitors.

Genome-wide identification of chromatin-enriched RNA reveals that unspliced dentin matrix protein-1 mRNA regulates cell proliferation in squamous cell carcinoma

Chromatin-enriched noncoding RNAs (ncRNAs) have emerged as key molecules in epigenetic processes by interacting with chromatin-associated proteins. Recently, protein-coding mRNA genes have been reported to be chromatin-tethered, similar with ncRNA. However, very little is known about whether chromatin-enriched mRNA is involved in the chromatin modification process. Here, we comprehensively examined chromatin-enriched RNA in squamous cell carcinoma (SQCC) cells by RNA subcellular localization analysis, which was a combination of RNA fractionation and RNA-seq. We identified 11 mRNAs as highly chromatin-enriched RNAs. Among these, we focused on the dentin matrix protein-1 (DMP-1) gene because its expression in SQCC cells has not been reported. Furthermore, we clarified that DMP-1 mRNA was retained in chromatin in its unspliced form in SQCC in vitro and in vivo. As the inhibition of the unspliced DMP-1 mRNA (unspDMP-1) expression resulted in decreased cellular proliferation in SQCC cells, we performed ChIP-qPCR to identify cell cycle-related genes whose expression was epigenetically modified by unspDMP-1, and found that the CDKN1B promoter became active in SQCC cells by inhibiting unspDMP-1 expression. This result was further validated by the increased CDKN1B gene expression in the cells treated with siRNA for unspDMP-1 and by restoration of the decreased cellular proliferation rate by simultaneously inhibiting CDKN1B expression in SQCC cells. Further, to examine whether unspDMP-1 was able to associate with the CDKN1B promoter region, SQCC cells stably expressing PP7-mCherry fusion protein were transiently transfected with the unspDMP-1 fused to 24 repeats of the PP7 RNA stem loop (unspDMP-1-24xPP7) and we found that unspDMP-1-24xPP7 was efficiently precipitated with the antibody against mCherry and was significantly enriched in the CDKN1B promoter region. Thus, unspDMP-1 is a novel chromatin-enriched RNA that epigenetically regulates cellular proliferation of SQCC.

Suppression of Myogenic Differentiation of Mammalian Cells Caused by Fluidity of a Liquid-Liquid Interface

There is growing evidence to suggest that the prevailing physical microenvironment and mechanical stress regulate cellular functions, including adhesion, proliferation, and differentiation. Moreover, the physical microenvironment determines the stem-cell lineage depending on stiffness of the substrate relative to biological tissues as well as the stress relaxation properties of the viscoelastic substrates used for cell culture. However, there is little known regarding the biological effects of a fluid substrate, where viscoelastic stress is essentially absent. Here, we demonstrate the regulation of myogenic differentiation on fluid substrates by using a liquid-liquid interface as a scaffold. C2C12 myoblast cells were cultured using water-perfluorocarbon (PFC) interfaces as the fluid microenvironment. We found that, for controlled in vitro culture at water-PFC interfaces, expression of myogenin, myogenic regulatory factors (MRF) family gene, is remarkably attenuated even when myogenic differentiation was induced by reducing levels of growth factors, although MyoD was expressed at the usual level (MyoD up-regulates myogenin under an elastic and/or viscoelastic environment). These results strongly suggest that this unique regulation of myogenic differentiation can be attributed to the fluid microenvironment of the interfacial culture medium. This interfacial culture system represents a powerful tool for investigation of the mechanisms by which physical properties regulate cellular adhesion and proliferation as well as their differentiation. Furthermore, we successfully transferred the cells cultured at such interfaces using Langmuir-Blodgett (LB) techniques. The combination of the interfacial culture system with the LB approach enables investigation of the effects of mechanical compression on cell functions.

Estradiol-tethered micropatterned surfaces for the study of estrogenic non-genomic pathways

Besides its well-known hormonal effects initiated in the nucleus, estradiol (E2) also activates non-nuclear pathways through interactions with receptors located on the cell plasma membrane. Micropatterned substrates consisting of gold dots bearing tethered E2 distributed on a cell-adhesive substrate were prepared and shown to trigger specifically E2 non-genomic effects in cells grown on the substrates.

Reduced adhesive ligand density in engineered extracellular matrices induces an epithelial-mesenchymal-like transition

A synergistic effect of biochemical and mechanical cues emanating from the extracellular matrix (ECM) on inducing malignant transformation of epithelial cells has been observed recently. However, the effect of quantitative changes in biochemical stimuli on cell phenotype, without changes in ECM component and rigidity, remains unknown. To determine this effect, we grew Madin-Darby canine kidney epithelial cells (MDCK) on gold surfaces immobilized with varying densities of cyclic arginine-glycine-aspartate (cRGD) peptide and analyzed cell morphology, cell migration, cytoskeletal organization, and protein expression. Cells grown on a surface presenting a higher density of cRGD displayed an epithelial morphology and grew in clusters, while those grown on a diluted cRGD surface transformed into an elongated, fibroblast-like form with extensive scattering. Time-lapse imaging of cell clusters grown on the concentrated cRGD surface revealed collective migration with intact cell-cell contacts accompanied by the development of cortical actin. In contrast, cells migrated individually and formed stress fibers on the substrate with sparse cRGD. These data point towards transdifferentiation of epithelial cells to mesenchymal-like cells when plated on a diluted cRGD surface. Supporting this hypothesis, immunofluorescence microscopy and western blot analysis revealed increased membrane localization and total expression of N-cadherin and vimentin in cells undergoing mesenchymal-like transition. Taken together, these results suggest a possible role of decreased biochemical stimuli from the ECM in regulating epithelial phenotype switching.

STATEMENT OF SIGNIFICANCE

Epithelial-mesenchymal transition (EMT) is a process where adherent epithelial cells convert into individual migratory mesenchymal phenotype. It plays an important role both in physiological and pathological processes. Recent studies demonstrate that the program is not only governed by soluble factors and gene expressions, but also modulated by biochemical and mechanical cues in ECMs. In this study, we developed chemically defined surfaces presenting controlled ECM ligand densities and studied their impact on the EMT progression. Morphological and biochemical analyses of epithelial cells cultured on the surfaces indicate the cells undergo an EMT-like transition on the diluted cRGD surface while retaining epithelial characteristics on the cRGD-rich substrate, suggesting an important role of the ECM ligand density in epithelial phenotype switching.

Dynamic control of cell adhesion on a stiffness-tunable substrate for analyzing the mechanobiology of collective cell migration

A photoactivatable gel substrate with defined mechanical properties was developed to study the mechanobiology of collective cell migration.

Facile preparation of a photoactivatable surface on a 96-well plate: a versatile and multiplex cell migration assay platform

A novel photoactivatable 96-well plate based on photocleavable PEG and poly-d-lysine serves as a useful high-throughput cell migration assay platform.

Colorimetric microchip assay using our own whole blood collected by a painless needle for home medical care

We have developed a colorimetric measurement chip that measures triglycerides, total cholesterol, and high-density lipoprotein in 6 μL of whole blood collected with a painless needle. The chip can be used by patients to self-monitor certain health conditions at home. This chip contains a sharp 150 μm diameter stainless steel (SUS) needle that collects blood painlessly. The chip consists of three layers of injection-molded poly(methyl methacrylate) bonded together with two double-sided tapes. Two commercial reagents are used, and the volume ratio of plasma to reagent is doubled from the reagent specification to reduce the optical absorption length (and chip mass) by half. Centrifugal force separates the plasma from the blood, and then weighs out and mixes the plasma and reagents. A zigzag channel allows mixing of the plasma with the reagents mainly by vortex motion due to the centrifugal force generated at the corners of the channel. The measured values correlated well with conventionally tested values.