Targeting protein neddylation with an NEDD8-activating enzyme inhibitor MLN4924 induced apoptosis or senescence in human lymphoma cells

Recent studies indicate that post-translational protein neddylation is required for the maintenance of cell viability in several lymphoma cell lines, while inhibition of the neddylation pathway with an NEDD8-activating enzyme (NAE) inhibitor MLN4924 induces apoptosis in lymphoma cells. However, the mechanism by which neddylation inhibition induces apoptosis in lymphoma cells has not been fully elucidated. Moreover, it is unknown whether neddylation inhibition triggers non-apoptotic cell-killing responses, such as cell senescence, in lymphoma cells. Here, we report that MLN4924 specifically inhibited protein neddylation, inactivated cullin-RING E3 ligase (CRL), the best-known neddylation substrate, and induced the accumulation of tumor-suppressive CRL substrates in lymphoma cells. Moreover, MLN4924 potently suppressed the growth of lymphoma cells by inducing G2 cell-cycle arrest, followed by apoptosis or senescence in a cell line-dependent manner. MLN4924-induced apoptosis was mediated by intrinsic apoptotic signaling with substantial up-regulation of pro-apoptotic Bik and Noxa as well as down-regulation of anti-apoptotic XIAP, c-IAP1 and c-IAP2, while senescence induction upon neddylation inhibition seemed dependent on the expression of tumor suppressor p21/p27. Together, these findings expand our understanding on how lymphoma cells respond to neddylation inhibition and support the development of neddylation inhibitors (e.g. MLN4924) for the treatment of lymphoma.

A Meta-analysis of Sequential Intravenous/Oral Moxifloxacin Monotherapy for Treatment of Skin and Skin Structure Infections

Moxifloxacin is widely recognized for the treatment of bacterial infections of the respiratory tract such as community acquired pneumonia, acute bacterial sinusitis and acute exacerbations of chronic bronchitis. However, the use of moxifloxacin for skin infections is much valued in recent years. This study is to compare the clinical efficacy and safety of moxifloxacin monotherapy among adults with skin and skin structure infections. The meta-analysis of RCTs is conducted by searching Medline, Embase, Pubmed and the Cochrane Library. 6 RCTs, involving a total of 2608 patients, were included in the meta-analysis. English and Chinese language papers were reviewed. The results of the meta-analysis showed that the moxifloxacin monotherapy has similar clinical cure rate, bacteriological success rates and mortality compared with the control group. The drug-related adverse of moxifloxacin was significantly higher than that in the control group, although the overall incidence of adverse events, serious adverse events, and serious drug-related adverse events were similar between the compared treatment groups. Through this meta-analysis, we can draw a conclusion that moxifloxacin monotherapy has similar effectiveness and relative safety as other recommended antibiotics for the treatment of SSSIs. At the same time, it possesses the superior bacteria eradication rate. The once-daily dosing of moxifloxacin monotherapy may be a useful alternative for other recommended antibiotic therapy.

B cells expressing CD11b effectively inhibit CD4+ T-cell responses and ameliorate experimental autoimmune hepatitis in mice

Increasing evidence in recent years has suggested that B cells act as a crucial regulator in autoimmune diseases. However, little is known about their role in autoimmune hepatitis (AIH) and the underlying regulatory mechanisms. In this study, we show that B cells ameliorated experimental AIH (EAH) by suppressing CD4+ T-cell responses and that CD11b expression on B cells was required for the regulatory function of B cells. In vitro studies reveal that the suppressive function of CD11b was mediated by the impairment of T-cell antigen receptor (TCR) signaling transduction and the promotion of TCR down-regulation. Moreover, we show that the increased CD11b expression on B cells was interleukin (IL)-10 dependent and that additional IL-10 stimulation promoted CD11b expression on B cells, thereby enhancing B-cell regulatory effects.

CONCLUSION

These findings reveal a previously unrecognized role for CD11b in B-cell regulatory function and its protective effect on EAH.

Morphological change of CD4(+) T cell during contact with DC modulates T-cell activation by accumulation of F-actin in the immunology synapse

BACKGROUND

The changes in T-cell morphology during immunological synapse (IS) formation are essential for T-cell activation. Previous researches have shown that T cell changed from spherical to elongated and/or flattened during in contact with B cell. As most powerful antigen presenting cell, dendritic cell (DC) has a strong ability to activate T cells. However, the morphological change of T cell which contacts DC and the relationship between morphological change and T-cell activation are not very clear. Thus, we studied the morphological change of CD4(+) T cell during contact with DC.

RESULTS

Using live-cell imaging, we discovered diversity in the T-cell morphological changes during contact with DCs. The elongation-flattening of CD4(+) T cells correlated with a low-level Ca(2+) response and a loss of T-cell receptor (TCR) signalling molecules in the IS, including zeta-chain associated protein kinase 70 (ZAP-70), phospholipase C-γ (PLC-γ) and protein kinase C-θ (PKC-θ), whereas rounding-flattening correlated with sufficient CD4(+) T-cell activation. Different morphological changes were correlated with the different amount of accumulated filamentous actin (F-actin) in the IS. Disruption of F-actin by cytochalasin D impaired the morphological change and the localisation of calcium microdomains in the IS and decreased the calcium response in CD4(+) T cells.

CONCLUSION

Our study discovered the diversity in morphological change of T cells during contacted with DCs. During this process, the different morphological changes of T cells modulate T-cell activation by the different amount of F-actin accumulation in the IS, which controls the distribution of calcium microdomains to affect T-cell activation.

Local immune compartments are related to the severity of dextran sodium sulphate induced colitis

Dextran sodium sulphate (DSS) induced colitis is commonly used to simulate human ulcerative colitis (UC). However, the mucosal immune responses related to the severity of disease have not been comprehensively documented. We used different concentration of DSS, induced various severities of colitis, and simultaneously examined the frequency of immune cells, antibodies and cytokine production. We found that T regulatory cells (Tregs), B cells, and IgA secretion increased on the recovery phase of mild colitis, accompanied by CD11b(+) cells, interleukin (IL)-6 and tumor necrosis factor (TNF)-α accumulated mildly. While during severe and irreversible colitis, the CD11b(+) cells, IL-6, and TNF-α infiltrated severely with Tregs, B cells, and IgA increased inconspicuously. These results demonstrate that Tregs, B cells, and IgA may play a significant role in maintaining the homeostasis of gut, by suppressing CD11b(+) cells and the pro-inflammatory cytokines.

Suppression of glioblastoma by targeting the overactivated protein neddylation pathway

BACKGROUND

The neddylation pathway has been recently identified as an attractive anticancer target, and MLN4924, a specific NEDD8-activating enzyme inhibitor, has been developed as a first-in-class anticancer agent. However, neither the status of the neddylation pathway in glioblastoma (GBM) nor the effect of MLN4924 against GBM has been systematically investigated yet.

METHODS

To measure the activation state of the neddylation pathway in GBM, expression of the NEDD8-activating enzyme (E1), NEDD8-conjugating enzyme (E2), and global protein neddylation in GBM tumor tissues versus adjacent tissues were examined by immunoblotting analysis and immunohistochemistry staining. To assess the therapeutic efficacy of neddylation inhibition in GBM, cell proliferation in vitro and tumor growth in vivo were determined upon neddylation inhibition by MLN4924, an investigational NEDD8-activating enzyme inhibitor.

RESULTS

The neddylation pathway was overactivated in a majority of GBM tumor tissues when compared with adjacent normal tissues. The upregulation of this pathway in GBM tissues was positively correlated with high-grade disease and postoperative recurrence but was negatively associated with patient overall survival. MLN4924 treatment inhibited cullin neddylation, inactivated cullin-RING E3 ligase, and led to the accumulation of tumor-suppressive cullin-RING E3 ligase substrates to trigger cell-cycle arrest and senescence or apoptosis in a cell-line dependent manner. Moreover, inhibition of neddylation by MLN4924 significantly suppressed tumor growth in an orthotopic xenograft model of human GBM.

CONCLUSION

Our study indicates that an overactivated neddylation pathway may be involved in GBM progression and that inhibition of this oncogenic pathway is a potentially new therapeutic approach for GBM.

Post-mortem assessment of the short and long-term effects of the trophic factor neurturin in patients with α-synucleinopathies

Substantial interest persists for developing neurotrophic factors to treat neurodegenerative diseases. At the same time, significant progress has been made in implementing gene therapy as a means to provide long-term expression of bioactive neurotrophic factors to targeted sites in the brain. Nonetheless, to date, no double-blind clinical trial has achieved positive results on its primary endpoint despite robust benefits achieved in animal models. A major issue with advancing the field is the paucity of information regarding the expression and effects of neurotrophic factors in human neurodegenerative brain, relative to the well-characterized responses in animal models. To help fill this information void, we examined post-mortem brain tissue from four patients with nigrostriatal degeneration who had participated in clinical trials testing gene delivery of neurturin to the putamen of patients. Each had died of unrelated causes ranging from 1.5-to-3-months (2 Parkinson's disease patients), to 4+-years (1 Parkinson's disease and 1 multiple-system atrophy-parkinsonian type patient) following gene therapy. Quantitative and immunohistochemical evaluation of neurturin, alpha-synuclein, tyrosine hydroxylase (TH) and an oligodendroglia marker (Olig 2) were performed in each brain. Comparable volumes-of-expression of neurturin were seen in the putamen in all cases (~15-22%; mean=18.5%). TH-signal in the putamen was extremely sparse in the shorter-term cases. A 6-fold increase was seen in longer-term cases, but was far less than achieved in animal models of nigrostriatal degeneration with similar or even far less NRTN exposure. Less than 1% of substantia nigra (SN) neurons stained for neurturin in the shorter-term cases. A 15-fold increase was seen in the longer-term cases, but neurturin was still only detected in ~5% of nigral cells. These data provide unique insight into the functional status of advanced, chronic nigrostriatal degeneration in human brain and the response of these neurons to neurotrophic factor stimulation. They demonstrate mild but persistent expression of gene-mediated neurturin over 4-years, with an apparent, time-related amplification of its transport and biological effects, albeit quite weak, and provide unique information to help plan and design future trials.

FcμR interacts and cooperates with the B cell receptor To promote B cell survival

The IgM FcR (FcμR) promotes B cell survival, but the molecular mechanism remains largely unknown. We show using FcμR(-/-) and wild-type mice that FcμR specifically enhanced B cell survival induced by BCR cross-linking with F(ab')2-anti-IgM Abs while having no effect on survival when the B cells were activated by CD40 ligation or LPS stimulation. FcμR expression was markedly upregulated by anti-IgM stimulation, which may promote enhanced FcμR signaling in these cells. Immunofluorescence and confocal microscopy analyses demonstrated that FcμR colocalized with the BCR on the plasma membrane of primary B cells. Coimmunoprecipitation analysis further revealed that FcμR physically interacted with the BCR complex. Because NF-κB plays a prominent role in B cell survival, we analyzed whether FcμR was involved in BCR-triggered NF-κB activation. FcμR did not affect BCR-triggered IκBα phosphorylation characteristic of the canonical NF-κB activation pathway but promoted the production of the noncanonical NF-κB pathway component p52. Consistent with the elevated p52 levels, FcμR enhanced BCR-triggered expression of the antiapoptotic protein BCL-xL. Importantly, FcμR stimulation alone in the absence of BCR signaling had no effect on either IκBα phosphorylation or the expression of p52 and BCL-xL. Therefore, FcμR relied on the BCR signal to activate the noncanonical NF-κB pathway and enhance B cell survival. These results reveal a cross-talk downstream of FcμR and BCR signaling and provide mechanistic insight into FcμR-mediated enhancement of B cell survival after BCR stimulation.

Multifaceted Modulation of SIRT1 in Cancer and Inflammation

SIRT1 is a highly conserved NAD+-dependent protein deacetylase that is involved in diverse cellular processes. SIRT1 can deacetylate not only histones, but also a growing number of nonhistone substrates involved in multiple signaling pathways. Accumulating evidence has indicated that SIRT1 is a key regulator of life span extension, DNA damage, metabolism stress, inflammation, and cancer. In inflammation, SIRT1 deacetylates several transcription factors and regulates the immune cell responses. In cancer, recent discoveries revealed opposite effects of SIRT1 as an oncoprotein or a tumor suppressor under different conditions. In the tumor microenvironment, both infiltrated immune cells and cancer cells can be affected by SIRT1. Understanding the proper cancer-related functions of SIRT1 in both systems may provide potential evidence for SIRT1-based therapies. Here, we discuss the current understanding of SIRT1 in regulating immune responses and tumorigenesis.

A Technique to Study Meloidogyne arenaria Resistance in Agrobacterium rhizogenes-Transformed Peanut

A reliable peanut root transformation system would be useful to study the functions of genes involved in root biology and disease resistance. The objective of this study was to establish an effective protocol to produce composite plants mediated by Agrobacterium rhizogenes transformation. In total, 75% of transformed peanut seedlings produced an average of 2.83 transgenic roots per plant. Peanut seed had the highest germination rate after treatment in a chlorine gas chamber for 8 h compared with 16 h in chlorine gas or Clorox and mercuric chloride immersion treatments. High transformation efficiency was achieved when the wound site for A. rhizogenes inoculation was covered with vermiculite instead of enclosing the whole plant in a high humidity chamber. On average, 2.5 galls from Meloidogyne arenaria infection were formed per transgenic root from susceptible genotype TifGP-2. These data indicate that A. rhizogenes-transformed roots can be used to phenotype the host response to nematode challenge. Transformation of RLP-2, a candidate resistance gene for M. arenaria integrated into a silencing construct, did not alter the resistance response of Tifguard, even though downregulation of endogenous RLP-2 expression was detected in transformed roots. It is likely that RLP-2 is not the gene conditioning M. arenaria resistance in peanut.

MicroRNA-7 sensitizes non-small cell lung cancer cells to paclitaxel

Paclitaxel (PTX) is the front-line chemotherapeutic agent against human non-small cell lung cancer (NSCLC). However, its therapeutic efficacy is restricted by the increasing frequency of chemotherapeutic resistance in NSCLC. Accumulating evidence has shown the potential role of microRNAs (miRNAs) in the chemotherapeutic sensitivity of cancer cells. Previously it was reported that microRNA-7 (miR-7) acts as an important tumor suppressor in NSCLC. Therefore, the present study was conducted to determine the regulatory role of miR-7 in PTX chemotherapy for NSCLC. Four NSCLC cell lines were used to analyze the correlation of the PTX-sensitivity and endogenoaus miR-7 expression. miR-7 expression was up- and downregulated using miR-7 mimics and inhibitors respectively, and the role of miR-7 in sensitizing NSCLC cells to PTX was assessed by cell viability and apoptosis assays. The molecular mechanism of PTX sensitivity was determined by quantitative polymerase chain reaction and western blotting. It was found that the sensitivity of NSCLC cells to PTX was dependent on endogenous miR-7. Upregulation of miR-7 enhanced the PTX-sensitivity of NSCLC cells by suppressing cell proliferation and promoting cell apoptosis, while the inhibition of miR-7 abrogated the antiproliferative proapoptotic effects of PTX. Pretreatment of miR-7 mimics enhanced the PTX-mediated downregulation of epidermal growth factor receptor (EGFR) in NSCLC cells. These results have identified miR-7 as a potential EGFR-targeting sensitizer in PTX therapy. These data may facilitate the development of novel chemotherapeutic approaches for NSCLC.

Dexamethasone potentiates myeloid-derived suppressor cell function in prolonging allograft survival through nitric oxide

Whereas GCs have been demonstrated to be beneficial for transplantation patients, the pharmacological mechanisms remain unknown. Herein, the role of GR signaling was investigated via a pharmacological approach in a murine allogeneic skin transplantation model. The GC Dex, a representative GC, significantly relieved allograft rejection. In Dex-treated allograft recipient mice, CD11b(+)Gr1(+) MDSCs prolonged graft survival and acted as functional suppressive immune modulators that resulted in fewer IFN-γ-producing Th1 cells and a greater number of IL-4-producing Th2 cells. In agreement, Dex-treated MDSCs promoted reciprocal differentiation between Th1 and Th2 in vivo. Importantly, the GR is required in the Dex-induced MDSC effects. The blocking of GR with RU486 significantly diminished the expression of CXCR2 and the recruitment of CD11b(+)Gr1(+) MDSCs, thereby recovering the increased MDSC-suppressive activity induced by Dex. Mechanistically, Dex treatment induced MDSC iNOS expression and NO production. Pharmacologic inhibition of iNOS completely eliminated the MDSC-suppressive function and the effects on T cell differentiation. This study shows MDSCs to be an essential component in the prolongation of allograft survival following Dex or RU486 treatment, validating the GC-GR-NO signaling axis as a potential therapeutic target in transplantation.

Systemic injection of TLR1/2 agonist improves adoptive antigen-specific T cell therapy in glioma-bearing mice

Adoptive immunotherapy is an attractive strategy for glioma treatment. However, some obstacles still need be overcome. In this study, GL261-bearing mice treated with adoptively transferred antigen-specific T cells and systemic injection of bacterial lipoprotein (BLP), a TLR1/2 agonist, got a long-term survival and even immune protection. By analyzing adoptive T cells, it was found that BLP maintained T cell survival, proliferation and anti-tumor efficacy in the brains of tumor-bearing hosts. Moreover, tumor microenvironment was modified by up-regulating IFN-γ-secreting CD8+ T cells and down-regulating MDSC, which might be related with high CXCL10 and low CCL2 expression. In addition, TLR2 deficiency abrogated therapeutic effect with increased MDSC accumulation and decreased IFN-γ-secreting CD8+ T cells in the brains. Thus, the systemic injection of BLP could improve the adoptive T cell therapy by maintaining T cell persistence, modifying the tumor microenvironment and even inducing systemic anti-tumor immunity, which might offer a clinically promising immunotherapeutic strategy for glioma.

Chemerin suppresses murine allergic asthma by inhibiting CCL2 production and subsequent airway recruitment of inflammatory dendritic cells

BACKGROUND

Chemerin has been implicated to play opposing roles, either pro-inflammatory or anti-inflammatory, in various tissue inflammation processes primarily through the regulation of tissue recruitment of immune cells. However, the effect of chemerin in allergic asthma has not yet been explored. We sought to investigate the role of chemerin in the murine model of allergic asthma and explore the underlying mechanism.

METHODS

We examined the effect of intranasal (i.n.) administration of chemerin during antigen challenge in murine models of asthma. Moreover, we examined whether administration of CCL2 or bone marrow-derived dendritic cells (BMDCs) transfer reversed the effects of chemerin on ovalbumin-induced asthma. We finally examined the effect of chemerin on CCL2 expression in activated lung epithelial cells in vitro.

RESULTS

The administration of chemerin attenuated allergic airway inflammation and airway hyperreactivity during antigen challenge. Chemerin treatment caused significant decreases in BALF CD4(+) T-cell accumulation and mRNA expression of Th2-attracting chemokines, CCL17 and CCL22, which was accompanied by significantly decreased BALF CD11c(+) CD11b(+) inflammatory DC accumulation and CCL2 production. Furthermore, airway administration of exogenous CCL2 or adoptive transfer of CD11c(+) CD11b(+) BMDCs abrogated the suppressive effects of chemerin on allergic asthma. Finally, in vitro study showed that chemerin inhibited CCL2 secretion by low-dose LPS-stimulated lung epithelial cells, which led to decreased chemotaxis of BMDCs.

CONCLUSIONS

Our study demonstrates that chemerin plays a protective role in allergic asthma by suppressing airway recruitment of inflammatory CD11c(+) CD11b(+) DCs through the inhibition of CCL2 secretion by active lung epithelial cells.

Overactivated neddylation pathway as a therapeutic target in lung cancer

BACKGROUND

A number of oncoproteins and tumor suppressors are known to be neddylated, but whether the neddylation pathway is entirely activated in human cancer remains unexplored.

METHODS

NEDD8-activating enzyme (NAE) (E1) and NEDD8-conjugating enzyme (E2) expression and global-protein neddylation were examined by immunohistochemistry, immunoblotting, and real-time polymerase chain reaction analysis. Cell proliferation, clonogenic survival, migration, and motility in vitro, as well as tumor formation and metastasis in vivo, were determined upon neddylation inhibition by MLN4924, an investigational NEDD8-activating enzyme inhibitor. Survival was analyzed with Kaplan-Meier methods and compared by the log-rank test. All statistical tests were two-sided.

RESULTS

The entire neddylation pathway, including NEDD8-activating enzyme E1, NEDD8-conjugating enzyme E2, and global-protein neddylation, is overactivated in both lung adenocarcinoma and squamous-cell carcinoma. Compared with lung adenocarcinoma patients with low expression, those with high expression had worse overall survival (NEDD8-activating enzyme E1 subunit 1 [NAE1]: hazard ratio [HR] = 2.07, 95% confidence interval [CI] = 0.95 to 4.52, P = .07; ubiquitin-conjugating enzyme E2M (UBC12): HR = 13.26, 95% CI = 1.77 to 99.35, P = .01; global protein neddylation: HR = 3.74, 95% CI = 1.65 to 8.47, P = .002). Moreover, inhibition of neddylation by the NAE inhibitor MLN4924 statistically significantly suppressed proliferation, survival, migration, and motility of lung cancer cells in vitro and tumor formation and metastasis in vivo. At the molecular level, MLN4924 inactivated Cullin-RING E3 ligases, led to accumulation of tumor-suppressive Cullin-RING E3 ligase substrates and induced phorbol-12-myristate-13-acetate-induced protein 1 (NOXA)-dependent apoptosis or cellular senescence.

CONCLUSIONS

Our study highlights the overactivated neddylation pathway in lung cancer development and as a promising therapeutic target.

Pseudomonas aeruginosa mannose-sensitive hemagglutinin promotes T-cell response via toll-like receptor 4-mediated dendritic cells to slow tumor progression in mice

Pseudomonas aeruginosa-mannose-sensitive hemagglutinin (PA-MSHA) as a drug may kill tumor cells and has been used clinically. However, the antitumor immune response of PA-MSHA is not completely understood. In this study, we found that treating Lewis lung carcinoma (3LL)-bearing mice with PA-MSHA plus 3LL antigen led to slower tumor progression and longer survival. After PA-MSHA treatment, T-cell number and dendritic cell maturation were both increased significantly at the tumor site. In addition, PA-MSHA in vitro stimulation resulted in the maturation of bone marrow-derived dendritic cells (BMDCs) from naive mice, showing higher costimulatory molecule expression, more cytokine secretion, lower endocytic activity, and stronger capacity to enhance T-cell activation. Toll-like receptor (TLR)4 but not TLR2 was required in the maturation process. More importantly, PA-MSHA-induced DCs were essential for PA-MSHA to enhance activation, expansion, and interferon (IFN)-γ secretion of TLR4-mediated T cells, which play a role in the antitumor effect of PA-MSHA. Thus, this study reveals PA-MSHA as a novel TLR4 agonist that elicits antitumor immune response to slow tumor progression.

Modulation of neutrophil development and homeostasis

Neutrophils are highly motile phagocytic cells that constitute the first line of defense of the innate immune system. Unlike the other innate immune cells, mature neutrophils fully equipped with an armory of granules are short lived cells which are differentiated and programmed from hematopoietic stem cells in the bone marrow. In blood, mature or nearly mature cells are devoid of proliferative potential. While the killing mechanisms of neutrophils have been the research focus in the past, attention was then directed toward granulocytopoiesis by the recent studies about the specific functional states and exact regulatory mechanisms in neutrophil development and homeostasis. Here, we focus on the recent findings regarding the mechanisms that control the generation and homeostasis of neutrophils.

Relative influence of heritability, environment and genetics on serum sclerostin

SUMMARY

We determined factors associated with serum sclerostin in 446 Afro-Caribbean family members. Age, weight, sex, diabetes and kidney function were associated with sclerostin. Sclerostin was heritable, and nine SNPs in the SOST gene region were associated with sclerostin. Variation in serum sclerostin is a heritable factor that is determined by both genetic and environmental factors.

INTRODUCTION

Sclerostin, encoded by the SOST gene, is a Wnt inhibitor that regulates bone mineralization and is a candidate gene locus for osteoporosis. However, little is known about the genetic and non-genetic sources of inter-individual variation in serum sclerostin levels.

METHODS

Serum sclerostin was measured in 446 Afro-Caribbean men and women aged 18+ from seven large, multigenerational families (mean family size, 64; 3,840 relative pairs). Thirty-six common single nucleotide polymorphisms (SNP) were genotyped within a 100 kb region encompassing the gene encoding sclerostin (SOST). Genetic and non-genetic factors were tested for association with serum sclerostin.

RESULTS

Mean serum sclerostin was 41.3 pmol/l and was greater in men than in women (P < 0.05). Factors associated with higher serum sclerostin were increased age and body weight, male sex, diabetes and decreased glomerular filtration rate, which collectively accounted for 25.4 % of its variation. Residual genetic heritability of serum sclerostin was 0.393 (P < 0.0001). Nine SNPs reached nominal significance with sclerostin. Three of those nine SNPs represented independent association signals (rs851056, rs41455049 and rs9909172), which accounted for 7.8 % of the phenotypic variation in sclerostin, although none of these SNPs surpassed a Bonferroni correction for multiple comparisons.

CONCLUSIONS

Serum sclerostin is a heritable trait that is also determined by environmental factors including age, sex, adiposity, diabetes and kidney function. Three independent common SNPs within the SOST region may collectively account for a significant proportion of the variation in serum sclerostin.

mTOR limits the recruitment of CD11b+Gr1+Ly6Chigh myeloid-derived suppressor cells in protecting against murine immunological hepatic injury

The mTOR pathway integrates diverse environmental inputs, including immune signals and metabolic cues, to direct the innate and adaptive immune responses. MDSCs are a heterogeneous cell population that plays a crucial regulatory effect in immune-related diseases. However, whether mTOR signaling affects the functions of MDSCs remains largely unknown. Here, we show that mTOR signaling is a pivotal negative determinant of MDSC recruitment in IMH disease. In the context of IMH, inhibition of mTOR with rapamycin in CD11b⁺Gr1⁺ MDSCs mediates protection against IMH and serves as a functional, suppressive immune modulator that results in increased CD11b⁺Gr1⁺Ly6C(high) MDSC recruitment to inflammatory sites. In agreement with this, mTOR down-regulation promotes CD11b⁺Gr1⁺Ly6C(high) MDSC migration in vitro and in vivo. Mechanistically, mTOR activity down-regulation in MDSCs induced iNOS expression and NO production. Pharmacologic inhibition of iNOS completely eliminated MDSC recruitment. This study identifies MDSCs as an essential component for protection against IMH following rapamycin treatment. Rapamycin treatment or mTOR inhibition promotes CD11b⁺Gr1⁺Ly6C(high) MDSC recruitment and is critically required for protection against hepatic injury. This study further validates the targeting of mTOR signaling as a potential therapeutic approach to IMH-related diseases.

Targeting S1P1 receptor protects against murine immunological hepatic injury through myeloid-derived suppressor cells

Although FTY720 may alter migration and homing of lymphocytes via sphingosine-1-phosphate (S1P) receptors, our recent studies indicated that FTY720 directly controls the differentiation of Th1 cells to regulatory T cells (Tregs) by targeting S1P1. However, the pharmacological function of FTY720 in immunological hepatic injury remains unknown. In this study, the role and regulatory signaling pathway of S1P receptor were investigated using a pharmacological approach in immune-mediated hepatic injury (IMH). In the context of IMH, FTY720 significantly ameliorated mortality and hepatic pathology. In FTY720-treated mice, recruited CD11b(+)Gr1(+) myeloid-derived suppressor cells (MDSCs) mediate protection against IMH and are functional suppressive immune modulators that result in fewer IFN-γ-producing Th1 cells and more Foxp3(+) Tregs. In agreement, FTY720-treated MDSCs promote the reciprocal differentiation between Th1 cells and Tregs in vitro and in vivo. Mechanistically, FTY720 treatment induced inducible NO synthase expression and NO production in MDSCs. Pharmacologic inhibition of inducible NO synthase completely eliminates MDSC suppressive function and eradicates their inducible effects on T cell differentiation. Finally, the mTOR inhibitor, rapamycin, photocopies the effects of FTY720 on MDSCs, implicating mTOR as a downstream effector of S1P1 signaling. This study identifies MDSCs as an essential component that provides protection against IMH following FTY720 or rapamycin treatment, validating the S1P1-mTOR signaling axis as a potential therapeutic target in hepatic injury.