Periodontitis promotes bacterial extracellular vesicle-induced neuroinflammation in the brain and trigeminal ganglion.

Gram-negative bacteria derived extracellular vesicles (EVs), also known as outer membrane vesicles, have attracted significant attention due to their pathogenic roles in various inflammatory diseases. We recently demonstrated that EVs secreted by the periodontopathogen Aggregatibacter actinomycetemcomitans (Aa) can cross the blood-brain barrier (BBB) and that their extracellular RNA cargo can promote the secretion of proinflammatory cytokines, such as IL-6 and TNF-α, in the brain. To gain more insight into the relationship between periodontal disease (PD) and neuroinflammatory diseases, we investigated the effect of Aa EVs in a mouse model of ligature-induced PD. When EVs were administered through intragingival injection or EV-soaked gel, proinflammatory cytokines were strongly induced in the brains of PD mice. The use of TLR (Toll-like receptor)-reporter cell lines and MyD88 knockout mice confirmed that the increased release of cytokines was triggered by Aa EVs via TLR4 and TLR8 signaling pathways and their downstream MyD88 pathway. Furthermore, the injection of EVs through the epidermis and gingiva resulted in the direct retrograde transfer of Aa EVs from axon terminals to the cell bodies of trigeminal ganglion (TG) neurons and the subsequent activation of TG neurons. We also found that the Aa EVs changed the action potential of TG neurons. These findings suggest that EVs derived from periodontopathogens such as Aa might be involved in pathogenic pathways for neuroinflammatory diseases, neuropathic pain, and other systemic inflammatory symptoms as a comorbidity of periodontitis.

Differential expression and sorting of exosomal microRNAs upon activation of the human monocyte-like cell line U937.

Extracellular vesicles such as exosomes in eukaryotes have drawn scrutiny due to their various roles in intercellular communication. Small RNAs, including microRNAs (miRNAs), are more abundant among the cargo of exosomes than other RNA types. MiRNAs loaded in secreted exosomes (or extracellular microRNAs) can be transported to recipient cells and may play a regulatory role although the miRNA loading (or sorting) mechanism in exosomes has not been clearly elucidated. Therefore, this study analyzed exosomal miRNA sequencing data from human myeloid U937 cells treated with phorbol 12-myristate 13-acetate (PMA) and compared it with data from PMA-untreated U937 cells. MiR-24 was highly expressed in the cytoplasm and exosomes of PMA-treated U937 cells. Also, miRNA pull-down and mass spectrophotometry analysis of PMA-treated U937 cells revealed that miR-24 was specifically associated with α-tubulin and hnRNP-E1 proteins. Furthermore, exosomal miR-24 was dramatically reduced when those proteins were inactivated with siRNAs, whereas cellular miR-24 showed no significant effect. We conclude that miR-24 is transported into exosomes from activated macrophages with the support of α-tubulin and hnRNP-E1.

Differential Angiogenic Potential of 3-Dimension Spheroid of HNSCC Cells in Mouse Xenograft.

The experimental animal model is still essential in the development of new anticancer drugs. We characterized mouse tumors derived from two-dimensional (2D) monolayer cells or three-dimensional (3D) spheroids to establish an in vivo model with highly standardized conditions. Primary cancer-associated fibroblasts (CAFs) were cultured from head and neck squamous cell carcinoma (HNSCC) tumor tissues and co-injected with monolayer cancer cells or spheroids into the oral mucosa of mice. Mice tumor blood vessels were stained, followed by tissue clearing and 3D Lightsheet fluorescent imaging. We compared the effect of exosomes secreted from 2D or 3D culture conditions on the angiogenesis-related genes in HNSCC cells. Our results showed that both the cells and spheroids co-injected with primary CAFs formed tumors. Interestingly, vasculature was abundantly distributed inside the spheroid-derived but not the monolayer-derived mice tumors. In addition, cisplatin injection more significantly decreased spheroid-derived but not monolayer-derived tumor size in mice. Additionally, exosomes isolated from co-culture media of FaDu spheroid and CAF upregulated angiogenesis-related genes in HNSCC cells as compared to exosomes from FaDu cell and CAF co-culture media under in vitro conditions. The mouse tumor xenograft model derived from 3D spheroids of HNSCC cells with primary CAFs is expected to produce reliable chemotherapy drug screening results given the robust angiogenesis and lack of necrosis inside tumor tissues.

Extracellular RNAs in periodontopathogenic outer membrane vesicles promote TNF-α production in human macrophages and cross the blood-brain barrier in mice.

Among the main bacteria implicated in the pathology of periodontal disease, Aggregatibacter actinomycetemcomitans (Aa) is well known for causing loss of periodontal attachment and systemic disease. Recent studies have suggested that secreted extracellular RNAs (exRNAs) from several bacteria may be important in periodontitis, although their role is unclear. Emerging evidence indicates that exRNAs circulate in nanosized bilayered and membranous extracellular vesicles (EVs) known as outer membrane vesicles (OMVs) in gram-negative bacteria. In this study, we analyzed the small RNA expression profiles in activated human macrophage-like cells (U937) infected with OMVs from Aa and investigated whether these cells can harbor exRNAs of bacterial origin that have been loaded into the host RNA-induced silencing complex, thus regulating host target transcripts. Our results provide evidence for the cytoplasmic delivery and activity of microbial EV-derived small exRNAs in host gene regulation. The production of TNF-α was promoted by exRNAs via the TLR-8 and NF-κB signaling pathways. Numerous studies have linked periodontal disease to neuroinflammatory diseases but without elucidating specific mechanisms for the connection. We show here that intracardiac injection of Aa OMVs in mice showed successful delivery to the brain after crossing the blood-brain barrier, the exRNA cargos increasing expression of TNF-α in the mouse brain. The current study indicates that host gene regulation by microRNAs originating from OMVs of the periodontal pathogen Aa is a novel mechanism for host gene regulation and that the transfer of OMV exRNAs to the brain may cause neuroinflammatory diseases like Alzheimer's.-Han, E.-C., Choi, S.-Y., Lee, Y., Park, J.-W., Hong, S.-H., Lee, H.-J. Extracellular RNAs in periodontopathogenic outer membrane vesicles promote TNF-α production in human macrophages and cross the blood-brain barrier in mice.

Inhibition of streptococcal biofilm formation by Aronia by extracellular RNA degradation.

BACKGROUND: The accumulation of oral bacterial biofilms is one of the primary etiological factors for oral diseases. Aronia melanocarpa extracts display general health benefits, including antimicrobial activities. This study evaluates the inhibitory effect of Aronia juice on oral streptococcal biofilm formation. RESULTS: Exposure to 1/10-diluted Aronia juice for 1 min significantly decreased in vitro streptococcal biofilm formation (P < 0.001). No remarkable difference was noted in streptococcal growth by Aronia under the same conditions. Interestingly, 1 week of oral rinse with diluted Aronia juice led to significantly fewer salivary streptococcal colony-forming units (CFUs) relative to oral rinsing with tap water (P < 0.05). Furthermore, Aronia exerted an extracellular RNA-degrading effect, and RNase inhibitor alleviated Aronia-dependent streptococcal biofilm inhibition. CONCLUSION: Aronia might inhibit initial biofilm formation by decomposing extracellular RNA, which plays an important role in bacterial biofilm formation. Our data suggest that oral rinsing with Aronia juice will aid in treating oral biofilm-dependent diseases easily and efficiently. © 2019 Society of Chemical Industry.

Microbe-Host Communication by Small RNAs in Extracellular Vesicles: Vehicles for Transkingdom RNA Transportation.

Extracellular vesicles (EVs) are evolutionary well-conserved nano-sized membranous vesicles that are secreted by both prokaryotic and eukaryotic cells. Recently, they have gained great attention for their proposed roles in cell-to-cell communication, and as biomarkers for human disease. In particular, small RNAs (sRNAs) contained within EVs have been considered as candidate interspecies-communication molecules, due to their demonstrated capacity to modulate gene expression in multiple cell types and species. While research into this field is in its infancy, elucidating the mechanisms that underlie host⁻microbe interactions and communications promises to impact many fields of biological research, including human health and medicine. Thus, this review discussed the results of recent studies that have examined the ways in which EVs and sRNAs mediate 'microbe⁻host' and 'host⁻microbe' interspecies communication.

Early Growth Response 1-Dependent Downregulation of Matrix Metalloproteinase 9 and Mouse Double Minute 2 Attenuates Head and Neck Squamous Cell Carcinoma Metastasis.

BACKGROUND/AIMS: The functional relevance of early growth response-1 (EGR1) on cancer invasion remains controversial. The effect of EGR1 on the expression of MMP9, which is important for HNSCC invasion, is still disputed. There is no previous data showing the effect of EGR1 on mouse double minute 2 (MDM2), an enhancer of matrix metalloproteinase 9 (MMP9) expression. Our aim is to clarify the negative correlation between EGR1 expression and head and neck squamous cell carcinoma (HNSCC) metastasis. METHODS: EGR1 mRNA and protein expressions were compared in normal and HNSCC tissues using The Cancer Genome Atlas (TCGA) dataset analysis or immunohistochemistry (IHC), respectively. In vitro cell invasion was evaluated Matrigel invasion assay. EGR1-dependent inhibition of MDM2 transcription was assessed by promoter-luciferase assay and chromatin immunoprecipitation (ChIP). RESULTS: TCGA data showed that EGR1 mRNA levels are significantly higher in normal oral tissues as compared with HNSCC tumor tissues (adjusted P = 1.64x10-16). In addition, nonmetastatic HNSCC tissues showed significantly higher EGR1 mRNA levels as compared with metastatic tissues (adjusted P = 0.023). IHC analysis showed that primary tumor tissues expressed significantly higher levels of nuclear EGR1 compared with paired metastatic lymph node tissues (P < 0.05). EGR1 overexpression downregulated MMP9 and MDM2 protein expression. Consistent with these observations, TCGA data analysis found significantly fewer metastatic patients among a subgroup of population presenting higher EGR1 expressions with lower MMP9 and/or MDM2. CONCLUSION: Our data suggests that EGR1 prevents HNSCC metastasis through downregulation of MMP9 and MDM2. EGR1 might be a potential candidate to attenuate HNSCC metastasis.

Oxytocin inhibits head and neck squamous cell carcinoma cell migration by early growth response-1 upregulation.

The effect of oxytocin (OXT) on cancer invasion is controversial. Few studies have examined the effect of early growth response-1 (EGR1) on the invasion of head and neck squamous cell carcinoma (HNSCC). Here, we evaluated how EGR1 affects HNSCC cell migration through the molecular mechanism of OXT in exerting anti-invasion activity. Matrigel invasion and wound-healing assays were used to measure the in-vitro cell migration. The molecular mechanism of OXT was assessed by knockdown or overexpression of EGR1 in HNSCC cells. Three-dimensional (3-D) spheroids formation, followed by the image analysis for quantification was performed. OXT at 500 nmol/l increased mRNA and protein expression of E-cadherin without cytotoxicity. OXT upregulated mRNA and protein expression of EGR1 in 6 h. p53, phosphatase and tensin, and p21 expression was increased in an EGR1-dependent manner with OXT treatment. In addition, OXT significantly downregulated 3-D spheroids' formation according to spheroids' number and size. Our data showed that OXT downregulated HNSCC cell migration by EGR1 upregulation. OXT inhibited spheroids' formation of HNSCC cells under 3-D culture conditions.

Comparison of gene expression between mandibular and iliac bone-derived cells.

OBJECTIVES: The purpose of this study is to investigate the differences in gene expression between the human mandibular and iliac bone-derived cells (BCs) for better understanding of the site-specific characteristics of bones. METHODS: Primary cells were obtained from mandibular and iliac bones from six healthy, elderly donors. To investigate site-specific differences, gene expression profile of mandibular and iliac BC from the same donors were compared via cDNA microarray analysis. RESULTS: A comparison of the gene expression profiles revealed that 82 genes were significantly upregulated and 66 genes were downregulated with 1.5 fold or greater in mandibular versus iliac BCs. The most significantly differentially regulated genes were associated with skeletal system development or morphogenesis (SIX1, MSX1, MSX2, HAND2, PRRX1, OSR2, HOX gene family, PITX2). Especially, upregulated genes in mandibular BC were related with tooth morphogenesis, originated from the ectomesenchyme. Microarray analysis revealed that Msx1 was 2.03-fold and Msx2 was 1.99-fold upregulated in mandibular versus iliac BCs (both p < 0.01). Furthermore, in mandibular BCs, all members of the HOX gene family that were analyzed were downregulated (p < 0.01) and osteopontin was also downregulated by 2.84-fold (p < 0.01). CONCLUSIONS: Site-specific differences between jaw and long bones can be explained by the differences in gene expression patterns. Our results suggest that bone cell-derived cells maintain the genetic characteristics of their embryological origin. CLINICAL RELEVANCE: This study revealed fundamental differences in gene expression between the mandibular and iliac bone in humans. These differences could be important for understanding jaw bone-specific development of bisphosphonate-related osteonecrosis of the jaw.

Bone healing with oxytocin-loaded microporous ß-TCP bone substitute in ectopic bone formation model and critical-sized osseous defect of rat.

AIM: This study investigated the efficacy of the hypothalamic nonapeptide oxytocin (OT) by direct delivery to local defects using a microporous ß-tricalcium phosphate (TCP) as the carrier for the future applications as a method to achieve predictable bone regeneration of large osseous defects requiring sinus bone graft and guided bone regeneration procedures for implant placement. MATERIAL AND METHODS: Both the ectopic and new bone formation induced by the OT-loaded microporous ß-TCP powder was histomorphometrically compared with unloaded ß-TCP in a subcutaneous ectopic bone formation model and calvarial critical-sized defects (CSDs) in 45 rats. RESULTS: The OT-loaded ß-TCP clearly enhanced ectopic bone formation compared with the unloaded control group. A High initial OT dose (250 µg) significantly increased ectopic bone formation at an early healing time-point compared with a lower OT dose (50 µg). The OT-loaded samples displayed greater new bone formation in the rat calvarial CSDs. Extensive new bone formation was achieved in the calvarial CSDs with the higher OT dose. CONCLUSION: These results suggest that local OT delivery to bone substitute promotes new bone formation via an osteoinductive mode of action.

Flavonoid gossypetin protects alveolar bone and limits inflammation in ligature-induced periodontitis in mice.

BACKGROUND: Bacterial-induced inflammation instigates the destruction of hard and soft tissues surrounding teeth in periodontitis. In severe cases, the increased number and activity of osteoclasts induces the resorption of alveolar bones, ultimately leading to tooth loss. Because of their diverse chemical structures and bioactivities, natural compounds are often suggested to treat a wide variety of diseases, including inflammatory disorders. METHODS: In the present study, we demonstrated an inhibitory effect of gossypetin, a hexahydroxy flavone, on osteoclast differentiation and bone resorption using in vitro culture of osteoclasts from mouse bone marrow macrophage (BMM) precursors and in vivo model of ligature-induced periodontitis in mice. RESULTS: Gossypetin significantly reduced the differentiation of osteoclasts from mouse BMM precursors in the presence of the receptor activator of nuclear factor κB ligand (RANKL). In vitro, gossypetin inhibited critical signaling events downstream of RANKL including the auto-amplification of nuclear factor of activated T-cells, cytoplasmic 1, Ca2+ oscillations, and the generation of reactive oxygen species. In a mouse ligature-induced periodontitis model, the administration of gossypetin significantly reduced osteoclastogenesis and alveolar bone resorption. Furthermore, gossypetin prevented the ligature-induced increase in macrophages and T cells and reduced the production of tumor necrosis factor-α and interleukin-6. CONCLUSION: Taken together, these results show anti-osteoclastogenic and anti-inflammatory effects of gossypetin, suggesting the potential use of this natural compound in periodontitis.

Differential effect of cancer-associated fibroblast-derived extracellular vesicles on cisplatin resistance in oral squamous cell carcinoma via miR-876-3p.

Rationale: Platinum-based chemotherapy is commonly used for treating solid tumors, but drug resistance often limits its effectiveness. Cancer-associated fibroblast (CAF)-derived extracellular vesicle (EV), which carry various miRNAs, have been implicated in chemotherapy resistance. However, the molecular mechanism through which CAFs modulate cisplatin resistance in oral squamous cell carcinoma (OSCC) is not well understood. We employed two distinct primary CAF types with differential impacts on cancer progression: CAF-P, representing a more aggressive cancer-promoting category, and CAF-D, characterized by properties that moderately delay cancer progression. Consequently, we sought to investigate whether the two CAF types differentially affect cisplatin sensitivity and the underlying molecular mechanism. Methods: The secretion profile was examined by utilizing an antibody microarray with conditioned medium obtained from the co-culture of OSCC cells and two types of primary CAFs. The effect of CAF-dependent factors on cisplatin resistance was investigated by utilizing conditioned media (CM) and extracellular vesicle (EVs) derived from CAFs. The impacts of candidate genes were confirmed using gain- and loss-of-function analyses in spheroids and organoids, and a mouse xenograft. Lastly, we compared the expression pattern of the candidate genes in tissues from OSCC patients exhibiting different responses to cisplatin. Results: When OSCC cells were cultured with conditioned media (CM) from the two different CAF groups, cisplatin resistance increased only under CAF-P CM. OSCC cells specifically expressed insulin-like growth factor binding protein 3 (IGFBP3) after co-culture with CAF-D. Meanwhile, IGFBP3-knockdown OSCC cells acquired cisplatin resistance in CAF-D CM. IGFBP3 expression was promoted by GATA-binding protein 1 (GATA1), a transcription factor targeted by miR-876-3p, which was enriched only in CAF-P-derived EV. Treatment with CAF-P EV carrying miR-876-3p antagomir decreased cisplatin resistance compared to control miRNA-carrying CAF-P EV. On comparing the staining intensity between cisplatin-sensitive and -insensitive tissues from OSCC patients, there was a positive correlation between IGFBP3 and GATA1 expression and cisplatin sensitivity in OSCC tissues from patients. Conclusion: These results provide insights for overcoming cisplatin resistance, especially concerning EVs within the tumor microenvironment. Furthermore, it is anticipated that the expression levels of GATA1 and miR-876-3p, along with IGFBP3, could aid in the prediction of cisplatin resistance.

Bone marrow oxytocin mediates the anabolic action of estrogen on the skeleton.

Estrogen uses two mechanisms to exert its effect on the skeleton: it inhibits bone resorption by osteoclasts and, at higher doses, can stimulate bone formation. Although the antiresorptive action of estrogen arises from the inhibition of the MAPK JNK, the mechanism of its effect on the osteoblast remains unclear. Here, we report that the anabolic action of estrogen in mice occurs, at least in part, through oxytocin (OT) produced by osteoblasts in bone marrow. We show that the absence of OT receptors (OTRs) in OTR(-/-) osteoblasts or attenuation of OTR expression in silenced cells inhibits estrogen-induced osteoblast differentiation, transcription factor up-regulation, and/or OT production in vitro. In vivo, OTR(-/-) mice, known to have a bone formation defect, fail to display increases in trabecular bone volume, cortical thickness, and bone formation in response to estrogen. Furthermore, osteoblast-specific Col2.3-Cre(+)/OTR(fl/fl) mice, but not TRAP-Cre(+)/OTR(fl/fl) mice, mimic the OTR(-/-) phenotype and also fail to respond to estrogen. These data attribute the phenotype of OTR deficiency to an osteoblastic rather than an osteoclastic defect. Physiologically, feed-forward OT release in bone marrow by a rising estrogen concentration may facilitate rapid skeletal recovery during the latter phases of lactation.

MicroRNA profiling in the mouse hypothalamus reveals oxytocin-regulating microRNA.

Oxytocin (Oxt), produced in the hypothalamic paraventricular and supraoptic nuclei for transport to and release from the posterior pituitary, was originally discovered through its role in lactation and parturition. Oxt also plays important roles in the central nervous system by influencing various behaviors. MicroRNAs (miRNAs), endogenous regulators of many genes, are a class of small non-coding RNAs that mediate post-transcriptional gene silencing. We performed miRNA expression profiling of the mouse hypothalamus by deep sequencing. Among the sequenced and cross-mapped small RNAs, expression of known miRNAs and unknown miRNAs candidates were analyzed. We investigated in detail one miRNA, miR-24, and found that it is a novel regulator of Oxt and controls both transcript and peptide levels of Oxt. These results provide insights into potential neurohypophysial hormone regulation mediated by miRNAs.

2-Hydroxycinnamaldehyde inhibits the epithelial-mesenchymal transition in breast cancer cells.

Since epithelial-mesenchymal transition (EMT) plays a critical role in cancer progression and in maintaining cancer stem cell properties, EMT is emerging as a therapeutic target for inhibiting the metastatic progression of cancer cells. 2'-Hydroxycinnamaldehyde (HCA) and its derivative, 2'-benzoyloxycinnamaldehyde, have recently been suggested as promising therapeutic candidates for cancer treatment. The purpose of this study is to investigate the anti-metastatic effect of HCA on breast cancer and the molecular mechanisms by which HCA regulates the transcriptional program during EMT. HCA induces epithelial reversion at nanomolar concentrations by suppressing Snail via the nuclear translocalization of GSK-3ß, which results in the transcriptional upregulation of E-cadherin. HCA also activates the transcription factor KLF17, which suppresses Id-1, indicating that HCA inhibits EMT by multiple transcriptional programs. Further, HCA treatment significantly inhibits lung metastasis in a mouse orthotopic breast cancer model. This study demonstrates the anti-metastatic effect of the non-toxic natural compound HCA through attenuation of EMT in a breast cancer model.

Identification of microRNA-size, small RNAs in Escherichia coli.

Noncoding small regulatory RNA molecules control gene expression and microRNAs provide one of the best examples in eukaryotes. However, bacterial RNAs of comparable size to eukaryotic microRNAs have received little attention. Here, we demonstrate the existence of microRNA-size, small RNAs (msRNAs) in the model bacterium Escherichia coli. We examined the small RNAs in E. coli using a deep sequencing approach, and analyzed 33.2 million small RNA clone reads after size fractionation. Bioinformatic analysis of the whole set revealed more than 400 individual msRNA species. The cellular contents of selected highly expressed msRNAs were verified by quantitative RT-PCR and northern blotting. Although, the functional significance of these RNAs is unclear, their high abundance suggests that they may play specialized roles in bacteria, analogous to miRNAs in eukaryotes.

Up-regulation of microRNA* strands by their target transcripts.

During microRNA (miRNA) biogenesis, one strand of a 21-23 nucleotide RNA duplex is preferentially selected for entry into an RNA-induced silencing complex (RISC). The other strand, known as the miRNA* species, is typically thought to be degraded. Previous studies have provided miRNA* selection models, but it remains unclear how the dominance of one arm arises during the biogenesis of miRNA. Using miRNA sponge-like methods, we cloned four tandem target sequences (artificial target) of miR-7b* and then measured miR-7b* expression levels after transfection of the artificial target. miR-7b* levels were found to significantly increase after transfection of the artificial target. We postulate that the abundance of target transcripts drives miRNA arm selection.

TRPA1-like channels enhance glycinergic transmission in medullary dorsal horn neurons.

The effect of icilin, a potent agonist of transient receptor potential ankyrin 1 (TRPA1) and TRPM8, on glycinergic transmission was examined in mechanically isolated rat medullary dorsal horn neurons by use of the conventional whole-cell patch-clamp technique. Icilin increased the frequency of glycinergic spontaneous miniature inhibitory post-synaptic currents (mIPSCs) in a dose-dependent manner. Either allyl isothiocyanate(AITC) or cinnamaldehyde, other TRPA1 agonists, also increased mIPSC frequency, but the extent of facilitation induced by AITC or cinnamaldehyde was less than that induced by icilin. However, menthol, a TRPM8 agonist, had no facilitatory effect on glycinergic mIPSCs. The icilin-induced increase in mIPSC frequency was significantly inhibited by either HC030031, a selective TRPA1 antagonist, or ruthenium red, a non-selective transient receptor potential channel blocker. Icilin failed to increase glycinergic mIPSC frequency in the absence of extracellular Ca(2+), suggesting that the icilin-induced increase in mIPSC frequency is mediated by the Ca(2+) influx from the extracellular space. In contrast, icilin still increased mIPSC frequency either in the Na(+) -free external solution or in the presence of Cd(2+), a general voltage-dependent Ca(2+) channel blocker. The present results suggest that icilin acts on pre-synaptic TRPA1-like ion channels, which are permeable to Ca(2+), to enhance glycinergic transmission onto medullary dorsal horn neurons. The TRPA1-like channel-mediated enhancement of glycinergic transmission in medullary dorsal horn neurons would contribute to the regulation of pain information from the peripheral tissues.