Search

Antibiotic usage promotes intestinal colonization of antibiotic-resistant bacteria. However, whether resistant bacteria gain dominance in enteric microflora or disseminate to extraintestinal viscera remains unclear. Our aim was to investigate temporal diversity changes in microbiota and transepithelial routes of bacterial translocation after antibiotic-resistant enterobacterial colonization. Mice drinking water with or without antibiotics were intragastrically gavaged with ampicillin-resistant (Amp-r) nonpathogenic Escherichia coli (E. coli) and given normal water afterward. The composition and spatial distribution of intestinal bacteria were evaluated using 16S rDNA sequencing and fluorescence in situ hybridization. Bacterial endocytosis in epithelial cells was examined using gentamicin resistance assay and transmission electromicroscopy. Paracellular permeability was assessed by tight junctional immunostaining and measured by tissue conductance and luminal- to-serosal dextran fluxes. Our results showed that antibiotic treatment enabled intestinal colonization and transient dominance of orally acquired Amp-r E. coli in mice. The colonized Amp-r E. coli peaked on day 3 postinoculation and was competed out after 1 wk, as evidenced by the recovery of commensals, such as Escherichia, Bacteroides, Lachnospiraceae, Clostridium, and Lactobacillus. Mucosal penetration and extraintestinal dissemination of exogenous and endogenous enterobacteria were correlated with abnormal epithelial transcytosis but uncoupled with paracellular tight junctional damage. In conclusion, antibiotic-induced enteric dysbiosis predisposes to exogenous infection and causes systemic dissemination of both antibiotic- resistant and commensal enterobacteria through transcytotic routes across epithelial layers. These results may help explain the susceptibility to sepsis in antibiotic-resistant enteric bacterial infection. [ABSTRACT FROM AUTHOR]

Abstract: The highly toxic monomer 12-deoxyphorbol 13-palmitate (G) was extracted from the roots of Euphorbia fischeriana. Our experimental data confirmed studies showing that 12-deoxyphorbol 13-palmitate had certain antitumor activities. The MTT method, soft agar experiments, and nude mouse tumor experiments proved that 12-deoxyphorbol 13-palmitate inhibited the growth of BGC823 cells. We found that the drug could induce cell cycle arrest at the G2-M checkpoint in BGC823 cells. The compound also induced apoptosis as assayed by Annexin-V-FITC/PI dual labeling, AO/EB dyeing, and caspase-3 and caspase-9 activity. The reduction in expression of cyclin B1 protein and the increased activity of reactive oxygen species were observed in BGC823 cells treated with 12-deoxyphorbol 13-palmitate for 24 h. In addition, we found down-regulation of cdc2/cyclin B, cyclin A and p-chk1 in tumor cells. There was also up-regulation of Bax, p53, p21, and IκB-α and down-regulation of Bcl-2 and NF-κB by WB. Our studies may define a novel mechanism by which 12-deoxyphorbol 13-palmitate inhibits tumor cell growth and induces apoptosis. The results of our current studies provided strong experimental evidence for the use of 12-deoxyphorbol 13-palmitate as a potential preventive and/or therapeutic agent in cancer. [Copyright &y& Elsevier]

Brain-derived neurotrophic factor (BDNF) plays important roles in cell survival, neural plasticity, learning, and stress regulation. However, whether the recently found human BDNF Val66Met (BDNFMet) polymorphism could alter stress vulnerability remains controversial. More importantly, the molecular and structural mechanisms underlying the interaction between the BDNFMet polymorphism and stress are unclear. We found that heterozygous BDNF+/Met mice displayed hypothalamic-pituitary-adrenal axis hyperreactivity, increased depressive-like and anxiety-like behaviors, and impaired working memory compared withWTmice after 7 d restraint stress. Moreover,BDNF+/Met mice exhibited more prominent changes in BDNF levels and apical dendritic spine density in the prefrontal cortex and amygdala after stress, which correlated with the impaired working memory and elevated anxiety-like behaviors. Finally, the depressive-like behaviors in BDNF+/Met mice could be selectively rescuedbyacute administration ofdesipraminebutnotfluoxetine.Thesedata indicate selective behavioral, molecular,andstructural deficits resulting from the interaction between stress and the human genetic BDNFMet polymorphism. Importantly, desipramine but not fluoxetine has antidepressant effects onBDNF+/Met mice, suggesting that specific classes of antidepressantmaybe a more effective treatment option for depressive symptoms in humans with this genetic variant BDNF. [ABSTRACT FROM AUTHOR]

Abstract: LIM domain-containing proteins mediate protein–protein interactions and play regulatory roles in various physiopathological processes. The mRNA of Crip2, a LIM-only gene, has been detected abundantly in developing and adult hearts but its cell-type specific expression profile has not been well characterized. In this study, we showed that Crip2 is highly expressed in the myocardium, moderately expressed in the endocardium and absent from the epicardium of the developing mouse heart. Interestingly, Crip2 expression is present in the endocardial cells that line both endocardial cushions, whereas it is markedly reduced in the cushion mesenchymes during valve leaflet formation. In the developing vascular system, Crip2 is detected in the endothelial cells of both blood and lymphatic vessels. Consistent with the expression pattern observed in embryos, Crip2 is also highly expressed in the myocardium, endocardium and coronary vascular endothelial cells of the adult heart. In the cardiomyocytes, Crip2 is colocalized with cardiac troponin T in the thin-filaments of sarcomeres. Nonetheless, experimental studies revealed that the expression level of Crip2 is not altered in the isoproterenol (ISO) induced hypertrophic heart. Moreover, Crip2 is detected in endothelial cells of the neovasculature during wound healing and tumor growth. The persistence of Crip2 expression in cardiovascular tissues implies that Crip2 might exert an important impact on the cardiovascular development, maintenance and homeostasis. [Copyright &y& Elsevier]

AbstractMicroRNAs play important regulatory roles in many physiological processes. This study investigated potential involvement of microRNAs in hepatic ischemia/reperfusion injury and ischemic preconditioning in mice. MicroRNAs with significant changes in expression in the livers upon ischemic preconditioning following ischemia/reperfusion injury were detected by microRNA microarrays. Seventy-eight microRNAs (40 down/38 up) exhibiting more than twofold differences were identified in the livers upon ischemia/reperfusion injury. Among these microRNAs, four microRNAs were further significantly downregulated by ischemic preconditioning in comparison to nonpreconditioned controls. These included mmu-miR-23a, mmu-miR-326, mmu-miR-346_MM1, and mmu-miR-370, all of which were positively correlated with the severity of ischemic injury. The expression of mmu-miR-326 was further confirmed by quantitative real-time RT-PCR, and CCAAT/enhancer binding protein alpha was predicted by computer-aided algorithms to be a downstream target of this microRNA. In summary, our study showed a distinctive miRNA expression pattern in mouse livers in response to ischemic preconditioning following ischemia/reperfusion injury. Further studies on the miRNAs identified herein may enhance the understanding of miRNA-based mechanisms of hepatic ischemia/reperfusion injury and ischemic preconditioning. [ABSTRACT FROM AUTHOR]

Autophagy is essential for maintaining both survival and health of cells. Autophagy is normally suppressed by amino acids and insulin. It is unclear what happens to the autophagy activity in the presence of insulin resistance and hyperinsulinemia. In this study, we examined the autophagy activity in the presence of insulin resistance and hyperinsulinemia and the associated mechanism. Insulin resistance and hyperinsulinemia were induced in mice by a high fat diet, followed by measurements of autophagy markers. Our results show that autophagy was suppressed in the livers of mice with insulin resistance and hyperinsulinemia. Transcript levels of some key autophagy genes were also suppressed in the presence of insulin resistance and hyperinsulinemia. Conversely, autophagy activity was increased in the livers of mice with streptozotocin-induced insulin deficiency. Levels of vps34, atg12, and gabarapil transcripts were elevated in the livers of mice with insulin deficiency. To study the mechanism, autophagy was induced by nutrient deprivation or glucagon in cultured hepatocytes in the presence or absence of insulin. Autophagy activity and transcript levels of vps34, atg12, and gabarapli genes were reduced by insulin. The effect of insulin was largely prevented by overexpression of the constitutive nuclear form of FoxO1. Importantly, autophagy of mitochondria (mitophagy) in cultured cells was suppressed by insulin in the presence of insulin resistance. Together, our results show that autophagy activity and expression of some key autophagy genes were suppressed in the presence of insulin resistance and hyperinsulinemia. Insulin suppression of autophagy involves FoxO1-mediated transcription of key autophagy genes. [ABSTRACT FROM AUTHOR]

MicroRNAs are a group of small non-coding RNAs with modulator activity of gene expression. Recent studies have uncovered a profound role of microRNAs in liver diseases. This study aimed to investigate a potential relationship between microRNA-223 (miR-223) expression and hepatic ischemia/reperfusion injury in mice. Quantitative RT-PCR analysis showed that miR-223 expression levels were greatly up-regulated in the livers after 75 min ischemia followed by 120 min reperfusion when compared to sham controls (2.59 +/- 0.23 vs. 0.83 +/- 0.15; P < 0.01). Correlation analysis also revealed that hepatic miR-223 expression level was significantly positively correlated with serum markers of ischemic injury. By prediction assay of miRNA targets mRNA, acyl-CoA synthetase long-chain family member 3, ephrin A1, and ras homolog gene family member B were predicted to be downstream targets of miR-223. Thus, we conclude that hepatic ischemia/reperfusion injury might be another form of liver disease that is associated with alteration in miR-223 expression. [ABSTRACT FROM AUTHOR]

Subjects with type 1 diabetes mellitus (T1DM) eventually develop insulin resistance and other features of T2DM such as cardiovascular disorders. The exact mechanism has been not been completely understood. In this study, we tested the hypothesis that excessive or inappropriate exposure to insulin is a primary mediator of insulin resistance in T1DM. We found that continuous exposure of mice with non-obese diabetes to insulin detemir, which is similar to some current conventional treatment of human T1DM, induced severe insulin resistance, whereas untreated hyperglycemia for the same amount of time (2 weeks) did not cause obvious insulin resistance. Insulin resistance was accompanied by decreased mitochondrial production as evaluated by mitochondrial DNA and levels of transcripts and proteins of mitochondrion-associated genes, increased ectopic fat accumulation in liver and skeletal muscle (gastrocnemius) evaluated by measurements of triglyceride content, and elevated oxidative stress detected by the GSH/GSSG ratio. Prolonged exposure of cultured hepatocytes to insulin induced significant insulin resistance, whereas the same length of exposure to a high level of glucose (33 mM) did not cause obvious insulin resistance. Furthermore, our results showed that prolonged exposure to insulin caused oxidative stress, and blockade of mitochondrion-derived oxidative stress by overexpression of manganese-superoxide dismutase prevented insulin resistance induced by the prolonged exposure to insulin. Together, our results show that excessive exposure to insulin is a primary inducer of insulin resistance in T1DM in mice. [ABSTRACT FROM AUTHOR]

A majority of subjects with insulin resistance and hyperinsulinemia can maintain their blood glucose levels normal for the whole life presumably through protein kinase B (Akt)-dependent insulin signaling. In this study, we found that the basal Akt phosphorylation level was increased in liver and gastrocnemius of mice under the high-fat diet (HFD). Levels of mitochondrial DNA and expression of some mitochondrion-associated genes were decreased by the HFD primarily in liver. Triglyceride content was increased in both liver and gastrocnemius by the HFD. Oxidative stress was induced by the HFD in both liver and gastrocnemius. Insulin sensitivity was decreased by the HFD. All of these changes were largely or completely reversed by treatment of animals with the phosphatidylinositol 3-kinase inhibitor LY-294002 during the time when animals usually do not eat. Consequently, the overall insulin sensitivity was increased by treatment with LY-294002. Together, our results indicate that increased basal Akt-dependent insulin signaling suppresses mitochondrial production, increases ectopic fat accumulation, induces oxidative stress, and desensitizes insulin signaling in subjects with insulin resistance and hyperinsulinemia. [ABSTRACT FROM AUTHOR]

Phellinus Liteus is a perennial fungus which is selectively parasitic on Morus rubra. This fungus is know as the Chinese medicine, Souou, and rich with polysaccharide and polysaccharide-protein complex. The aim of this study was to determine Phellinus Liteus is anti-tumor effect in a murine model of hepatocellular carcinoma (HCC). Eight weeks old male SCID mice were transplanted with Hep3B cells, followed by dairly Phellinus Liteus administration for 8 weeks. Phellinus Liteus administration induced a significant reduction in tumor size, improved survival rate, and was association with a significant increase in splenocytes. There was no significant difference between groups was noted in any of the other serum cytokine level. However, Phellinus Liteus administration induces a significant suppression of human HCC. This effect is mediated by induction of natural killer cell activation, along with direct inhibition of tumor growth. [ABSTRACT FROM AUTHOR]

Ganoderma lucidum has been widely used in traditional Chinese medicines for preventing and treating various diseases. The spores of Ganoderma lucidum have higher bioactivities than those of the fruiting bodies of Ganoderma lucidum. This study examined the cytokine profiles after administration spores of Ganoderma lucidum in BALB/C mice for 8 weeks. The mice divided into control group and experiment group (administration 1750 and 3500 mg spores of Ganoderma lucidum / Kg BW). Compared the control group and experiment group, CD4+and NK cells number had a significant increase in experiment group. Our data revealed that both IFN-£∧and TNF-£\ were expressed at high level in experiment group, which are know marker of activated T helper 1 lymphocytes. Furthermore, IL-4, IL-10, two key cytokines of the TH2 pathway, were expressed at higher levels in experiment group. These observations support the potential implication of the spores of Ganoderma lucidum could be a mediator of host immune defense and immune response modulator in both TH1 and TH2 pathways. [ABSTRACT FROM AUTHOR]

Citrus fruits are thought to have inhibitory effects on oxidative stress, thereby attenuating the onset and progression of cancer and cardiovascular disease; however, there are few reports assessing their effect on vascular remodeling. Here, we investigated the effect of drinking the juice of two different citrus fruits on vascular neointima formation using a cuff-induced vascular injury mouse model. Male C57BL6 mice were divided into five groups as follows: 1) Control (water) (C), 2) 10% Citrus unshiu (CU) juice (CU10), 3) 40% CU juice (CU40), 4) 10% Citrus iyo (CI) juice (CI10), and 5) 40% CI juice (CI40). After drinking them for 2 weeks from 8 weeks of age, cuff injury was induced by polyethylene cuff placement around the femoral artery. Neointima formation was significantly attenuated in CU40, CI10 and CI40 compared with C; however, no remarkable preventive effect was observed in CU10. The increases in levels of various inflammatory markers including cytokines such as monocyte chemotactic protein-1, interleukin-6 (IL-6), IL-1β, and tumor necrosis factor-α in response to vascular injury did not differ significantly between C, CU10 and CI10. The increases in cell proliferation and superoxide anion production were markedly attenuated in CI10, but not in CU10 compared with C. The increase in phosphorylated ERK expression was markedly attenuated both in CU10 and CI10 without significant difference between CU10 and CI10. Accumulation of immune cells did not differ between CU10 and CI10. These results indicate that drinking citrus fruit juice attenuates vascular remodeling partly via a reduction of oxidative stress. Interestingly, the preventive efficacy on neointima formation was stronger in CI than in CU at least in part due to more prominent inhibitory effects on oxidative stress by CI. [ABSTRACT FROM AUTHOR]

Abstract: Adiponectin and its receptors are expressed in bone marrow-derived osteoblasts. Previous studies in vivo and in vitro have produced controversial results. The purpose of this study was to use porcine adiponectin receptor 1 transgenic mice (pAdipoR1) as a model to evaluate the role of AdipoR1 on bone physiology at different ages. pAdipoR1 transgenic mice had higher bone mineral density than wild-type mice in both genders at 56weeks of age. The bone volume and trabecular number, measured by micro-computed tomography (μCT) was significantly greater in transgenic than in wild-type female mice at both 8 and 56weeks of age. ELISA analysis revealed that both serum osteocalcin and osteoprotegerin (OPG) were significantly increased in 8-week old pAdipoR1 transgenic mice of both genders. Furthermore, serum OPG was elevated at 32 and 56weeks of age in female and male pAdipoR1 transgenic mice. Serum TRAP5b concentration was reduced in 8 and 56weeks old male pAdipoR1 mice compared with wild-type male mice. Knock-down of AdipoR1 significantly decreased gene expression of osteocalcin, OPG, alkaline phosphatase and msh homeobox 2 and the mineralization in MC3T3-E1 cells and mesenchymal stem cells. In addition, pathscan analysis and real-time PCR analysis suggest AdipoR1 regulates osteoblast differentiation through GSK-3 β and β-Catenin signaling. Consequently, the lack of AdipoR1 impaired osteoblast differentiation and bone formation. We conclude that AdipoR1 is a critical factor for the osteoblast differentiation and bone homeostasis. [Copyright &y& Elsevier]

Abstract: Type 2 diabetes mellitus (T2DM) is known to be associated with increased risk of cognitive impairment including Alzheimer disease. Recent studies have suggested an interaction between angiotensin II and N-methyl-d-aspartic acid (NMDA) glutamate receptors. We previously reported that stimulation of the angiotensin II type 2 (AT2) receptor exerts brain protective effects. A newly developed AT2 receptor agonist, compound 21 (C21), has enabled examination of the direct effect of AT2 receptor stimulation in vivo. Accordingly, we examined the possible synergistic effect of C21 and memantine on cognitive impairment in T2DM mice, KKAy. KKAy were divided into four groups; (1) control, (2) treatment with C21 (10μg/kg/day), (3) treatment with memantine (20mg/kg/day), and (4) treatment with both for 4 weeks, and subjected to Morris water maze tasks. Treatment with C21 or memantine alone at these doses tended to shorten escape latency compared to that in the control group. C21 treatment increased cerebral blood flow (CBF), but memantine did not influence CBF. Treatment with C21 or C21 plus memantine increased hippocampal field-excitatory postsynaptic potential (f-EPSP). Moreover, treatment with memantine or C21 increased acetylcholine level, which was lower in KKAy than in wild-type mice, and C21 plus memantine treatment enhanced memantine or C21-induced acetylcholine secretion. This study provides an insight into new approaches to understand the interaction of angiotensin II and neurotransmitters. We can anticipate a new therapeutic approach against cognitive decline using C21 and memantine. [Copyright &y& Elsevier]

Background: Recent studies of Giardia lamblia outbreaks have indicated that 40-80% of infected patients experience long-lasting functional gastrointestinal disorders after parasitic clearance. Our aim was to assess changes in the intestinal barrier and spatial distribution of commensal bacteria in the post-clearance phase of Giardia infection. Methods: Mice were orogastrically inoculated with G. lamblia trophozoites (strain GS/M) or pair-fed with saline and were sacrificed on post-infective (PI) days 7 (colonization phase) and 35 (post-clearance phase). Gut epithelial barrier function was assessed by Western blotting for occludin cleavage and luminal-to-serosal macromolecular permeability. Gut-associated, superficial adherent, and mucosal endocytosed bacteria were measured by agar culturing and were examined by fluorescence in situ hybridization. Intracellular bacteria cultured from isolated mucosal cells were characterized by 16S rDNA sequencing. Neutrophil-specific esterase staining, a myeloperoxidase activity assay, and enzyme-linked immunosorbent assays for cytokine concentrations were used to verify intestinal tissue inflammation. Results: Tight junctional damage was detected in the intestinal mucosa of Giardia-infected mice on PI days 7 and 35. Although intestinal bacterial overgrowth was evident only during parasite colonization (PI day 7), enhanced mucosal adherence and endocytosis of bacteria were observed on PI days 7 and 35. Multiple bacterial strains, including Bacillus, Lactobacillus, Staphylococcus, and Phenylobacterium, penetrated the gut mucosa in the post-infective phase. The mucosal influx of bacteria coincided with increases in neutrophil infiltration and myeloperoxidase activity on PI days 7 and 35. Elevated intestinal IFN?, TNFα, and IL-1β levels also were detected on PI day 35. Conclusions: Giardia-infected mice showed persistent tight junctional damage and bacterial penetration, accompanied by mucosal inflammation, after parasite clearance. These novel findings suggest that the host's unresolved immune reactions toward its own microbiota, due to an impaired epithelial barrier, may partly contribute to the development of post-infective gut disorders. [ABSTRACT FROM AUTHOR]

Seroepidemiological studies imply a correlation between Epstein-Barr virus (EBV) reactivation and the development of nasopharyngeal carcinoma (NPC). N-nitroso compounds, phorbols, and butyrates are chemicals found in food and herb samples collected from NPC high-risk areas. These chemicals have been reported to be risk factors contributing to the development of NPC, however, the underlying mechanism is not fully understood. We have demonstrated previously that low dose N-methyl-N'-nitro-N-nitrosoguanidine (MNNG, 0.1 µmg/ml) had a synergistic effect with 12-O-tetradecanoylphorbol- 13-acetate (TPA) and sodium butyrate (SB) in enhancing EBV reactivation and genome instability in NPC cells harboring EBV. Considering that residents in NPC high-risk areas may contact regularly with these chemical carcinogens, it is vital to elucidate the relation between chemicals and EBV and their contributions to the carcinogenesis of NPC. In this study, we constructed a cell culture model to show that genome instability, alterations of cancer hallmark gene expression, and tumorigenicity were increased after recurrent EBV reactivation in NPC cells following combined treatment of TPA/SB and MNNG. NPC cells latently infected with EBV, NA, and the corresponding EBV-negative cell, NPC-TW01, were periodically treated with MNNG, TPA/SB, or TPA/SB combined with MNNG. With chemically-induced recurrent reactivation of EBV, the degree of genome instability was significantly enhanced in NA cells treated with a combination of TPA/SB and MNNG than those treated individually. The Matrigel invasiveness, as well as the tumorigenicity in mouse, was also enhanced in NA cells after recurrent EBV reactivation. Expression profile analysis by microarray indicates that many carcinogenesis-related genes were altered after recurrent EBV reactivation, and several aberrations observed in cell lines correspond to alterations in NPC lesions. These results indicate that cooperation between chemical carcinogens can enhance the reactivation of EBV and, over recurrent reactivations, lead to alteration of cancer hallmark gene expression with resultant enhancement of tumorigenesis in NPC. [ABSTRACT FROM AUTHOR]

The primary player that induces insulin resistance has not been established. Here, we studied whether or not fat can cause insulin resistance in the presence of insulin deficiency. Our results showed that high-fat diet (HFD) induced insulin resistance in C57BL/6 (B6) mice. The HFD-induced insulin resistance was prevented largely by the streptozotocin (STZ)-induced moderate insulin deficiency. The STZ-induced insulin deficiency prevented the HFD-induced ectopic fat accumulation and oxidative stress in liver and gastrocnemius. The STZ-induced insulin deficiency prevented the HFD- or insulin-induced increase in hepatic expression of long-chain acyl-CoA synthetases (ACSL), which are necessary for fatty acid activation. HFD increased mitochondrial contents of long-chain acyl-CoAs, whereas it decreased mitochondrial ADP/ATP ratio, and these HFD-induced changes were prevented by the STZ-induced insulin deficiency. In cultured hepatocytes, we observed that expressions of ACSL1 and -5 were stimulated by insulin signaling. Results in cultured cells also showed that blunting insulin signaling by the PI3K inhibitor LY-294002 prevented fat accumulation, oxidative stress, and insulin resistance induced by the prolonged exposure to either insulin or oleate plus sera that normally contain insulin. Finally, knockdown of the insulin receptor prevented the oxidative stress and insulin resistance induced by the prolonged exposure to insulin or oleate plus sera. Together, our results show that insulin and insulin signaling are required for fat induction of insulin resistance in mice and cultured mouse hepatocytes. [ABSTRACT FROM AUTHOR]

The IC53 gene was reported to be upregulated in the colon adenocarcinoma cell line SW480. Here, we show that the expression level of IC53 is positively correlated with the grade and depth of invasion in adenocarcinoma of the colon. Injection of IC53 stably transfected HCT-116 cells into athymic nude mice promoted tumor growth. Furthermore, overexpression of IC53 increased cell invasive growth, which could be dramatically prevented by knocking down IC53 with siRNA. The effects of IC53 on cellinvasive growth were mediated by upregulation of integrins, activation of phosphatidylinositol 3-kinase and phosphorylation of Akt. A single-nucleotide polymorphism rs2737 in the IC53 gene created a potential microRNA379 target site, and microRNA379 expression inhibited IC53 translation. Among 222 patients with colorectal cancer, the C/C rs2737 genotype was associated with late onset of colorectal cancer (median age 63.0 versus 55.3 years, P = 0.003). The frequency of the C/C rs2737 genotype was much lower in patients who developed colorectal cancer below the age of 45 years than in individuals over age 45 years (10.8% versus 26.6%, P = 0.039). These data indicated that IC53 is a positive mediator for colon cancer progression, and IC53-rs2737 may serve as protection from the onset of colorectal cancer. [ABSTRACT FROM AUTHOR]

Mesenchymal stem cells (MSCs) are characterized by their hematopoiesis-supporting and immunosuppressive capacity, while osteoclasts are main cell components in the endosteal hematopoietic stem cell niche and pivotal players in osteoimmunology. To clarify the association of these 2 kinds of cells, mouse CD11bmonocytes were cultured onto MSC layers in the presence or absence of macrophage colony-stimulating factor (M-CSF) and receptor activator of NF-B ligand (RANKL). The results showed that MSCs independently supported osteoclast development and this effect was enhanced by M-CSF and RANKL. Interestingly, tumor necrosis factor- (TNF-)–stimulated MSCs turned to inhibit osteoclast formation and protect tusk slices from osteoclastic resorption. Real-time PCR and ELISA assays demonstrated that osteoprotegerin expression at both mRNA and protein levels in TNF-–stimulated MSCs was up-regulated, at least partially by activating the mitogen-activated protein kinase pathway. Furthermore, TNF-–stimulated MSCs maintained their immunophenotypic, multipotential differentiation and immunosuppressive characteristics. Moreover, MSCs treated with synovial fluid from rheumatoid arthritis patients modulated osteoclast generation in close relation with the TNF- levels. This study suggests that MSCs exhibit dual modulatory function on osteoclasts and the result might shed light on understanding the involvement of MSCs in the inflammatory diseases. [ABSTRACT FROM AUTHOR]