Knockdown of ribosome RNA processing protein 15 suppresses migration of hepatocellular carcinoma through inhibiting PATZ1-associated LAMC2/FAK pathway.

BACKGROUND: Ribosomal RNA processing protein 15 (RRP15) has been found to regulate the progression of hepatocellular carcinoma (HCC). Nevertheless, the extent to which it contributes to the spread of HCC cells remains uncertain. Thus, the objective of this research was to assess the biological function of RRP15 in the migration of HCC. METHODS: The expression of RRP15 in HCC tissue microarray (TMA), tumor tissues and cell lines were determined. In vitro, the effects of RRP15 knockdown on the migration, invasion and adhesion ability of HCC cells were assessed by wound healing assay, transwell and adhesion assay, respectively. The effect of RRP15 knockdown on HCC migration was also evaluated in vivo in a mouse model. RESULTS: Bioinformatics analysis showed that high expression of RRP15 was significantly associated with low survival rate of HCC. The expression level of RRP15 was strikingly upregulated in HCC tissues and cell lines compared with the corresponding controls, and TMA data also indicated that RRP15 was a pivotal prognostic factor for HCC. RRP15 knockdown in HCC cells reduced epithelial-to-mesenchymal transition (EMT) and inhibited migration in vitro and in vivo, independent of P53 expression. Mechanistically, blockade of RRP15 reduced the protein level of the transcription factor POZ/BTB and AT hook containing zinc finger 1 (PATZ1), resulting in decreased expression of the downstream genes encoding laminin 5 subunits, LAMC2 and LAMB3, eventually suppressing the integrin ß4 (ITGB4)/focal adhesion kinase (FAK)/nuclear factor κB kappa-light-chain-enhancer of activated B cells (NF-κB) signaling pathway. CONCLUSIONS: RRP15 promotes HCC migration by activating the LAMC2/ITGB4/FAK pathway, providing a new target for future HCC treatment.

Prognostic factors of sarcomas occurring in bone and joint: A SEER based study.

To clarify the epidemiology, treatment, and prognosis of sarcomas occurring in the bones and joints. The surveillance, epidemiology, and end results (SEER) 18 registries, comprising sarcoma diagnoses made between 2008 and 2014, were queried for sarcomas arising in bones or joints. Kaplan-Meier analysis, multivariate logistic regression analysis, Cox proportional hazards model, and nomograms were used to identify prognostic factors. 2794 patients aged from 1 to 99 (55.8% male) with microscopically confirmed diagnosed as sarcomas (including osteosarcoma, chondrosarcoma, Ewing sarcoma, and soft tissue sarcomas) which primary site limited to bone and joint were identified. Eight independent factors, including age, race, sex, tumor site, histology, pathology grade, tumor size, and total number of malignant tumors (TNOMT), were associated with tumor metastasis. Nine independent prognostic factors, including age (>=60 year, hazard ratio [HR] = 4.145, 95% confidence interval [CI], P < .001), sex (female, HR = 0.814, 95%CI, P = .007), tumor site (spine, HR = 2.527, 95%CI, P < .001), histology, pathology grade (undifferentiated, HR = 5.816, 95%CI, P < .001), tumor size (>=20 cm, HR = 3.043, 95%CI, P < .001), tumor extent (distant, HR = 4.145, 95%CI, P < .001), surgery (no performed, HR = 2.436, 95%CI, P < .001), and TNOMT (1, HR = 0.679, 95%CI, P < .001, were identified and incorporated to construct a nomogram for 2- and 5-year overall survival (OS). The calibration curve for the probability of survival showed good agreement between prediction by the nomogram and actual observation. The C-index of the nomogram for survival prediction was 0.814. Patients who received chemotherapy had a significantly decreased risk of death only for Ewing sarcoma, poorly differentiated tumors, undifferentiated tumors, and distant tumor invasion (P < .05). However, radiotherapy did not show significant differences in OS. This study presents population-based estimates of prognosis for patients with bone sarcomas and demonstrates the impact of age, race, sex, tumor site, histology, pathology grade, tumor size, tumor extent, surgery, radiotherapy, chemotherapy, and the TNOMT on OS. Moreover, the nomogram resulted in a more accurate prognostic prediction. However, in our study, radiotherapy showed no survival benefit, perhaps because detailed data on treatment factors were unavailable and which may have influenced the results.

Effects of natural 24-epibrassinolide on inducing apoptosis and restricting metabolism in hepatocarcinoma cells.

BACKGROUND: 24-epibrassinolide (EBR) is a ubiquitous steroidal phytohormone with anticancer activity. Yet the cytotoxic effects and mechanism of EBR on hepatocarcinoma (HCC) cells remain elusive. METHODS: Cell counting kit-8 (CCK-8) assay was performed to evaluate cell viability. Real-time cell analysis (RTCA) technology and colony formation assays were used to evaluate cell proliferation. The apoptosis ratio was measured by flow cytometry. Seahorse XFe96 was applied to detect the effects of EBR on cellular bioenergetics. RNA-seq analysis was performed to investigate differences in gene expression profiles. Western blot and qRT-PCR were used to detect the changes in target molecules. RESULTS: EBR induced apoptosis and caused energy restriction in HCC, both of which were related to insulin-like growth factor-binding protein 1 (IGFBP1). EBR rapidly and massively induced IGBFP1, part of which was transcribed by activating transcription factor-4 (ATF4). The accumulation of secreted and cellular IGFBP1 had different important roles, in which secreted IGFBP1 affected cell energy metabolism by inhibiting the phosphorylation of Akt, while intracellular IGFBP1 acted as a pro-survival factor to resist apoptosis. Interestingly, the extracellular signal-regulated kinase (ERK) inhibitor SCH772984 and MAP/ERK kinase (MEK) inhibitor PD98059 not only attenuated the EBR-induced IGFBP1 expression but also the basal expression of IGFBP1. Thus, the treatment of cells with these inhibitors further enhances the cytotoxicity of EBR. CONCLUSION: Taken together, these findings suggested that EBR can be considered as a potential therapeutic compound for HCC due to its pro-apoptosis, restriction of energy metabolism, and other anti-cancer properties. Meanwhile, the high expression of IGFBP1 induced by EBR in HCC contributes to our understanding of the role of IGFBP1 in drug resistance.

Synthetic oleanane triterpenoid derivative CDDO-Me disrupts cellular bioenergetics to suppress pancreatic ductal adenocarcinoma via targeting SLC1A5.

To investigate the potential antitumor activity of synthetic triterpenoid, methyl-2-cyano-3,12-dioxooleana-1,9(11)-dien-28-oate (CDDO-Me) in pancreatic ductal adenocarcinoma (PDAC), MTT cytotoxicity assay, and xenograft nude mice assay were performed to evaluate tumor growth in vitro and in vivo. Seahorse XFe96 bioenergetics analyzer was applied to determine aerobic glycolysis and mitochondrial respiration. Western blot and quantitative reverse transcription-polymerase chain reactions are used to detect protein and messenger RNA transcripts of SLC1A5 and metabolic enzymes. We confirmed the strong antitumor activity of CDDO-Me in suppressing PDAC growth. Mechanistically, we demonstrated CDDO-Me induced mitochondrial respiration and aerobic glycolysis dysfunction. We also verified CDDO-Me downregulated glutamine transporter SLC1A5, resulting in excessive reactive oxygen species (ROS) levels that suppressed tumor growth. Moreover, we confirmed that SLC1A5 depletion reduced the ratio of glutathione/oxidized glutathione. We also found CDDO-Me could inhibit N-linked glycosylation of SLC1A5, which promotes protease-mediated degradation. Finally, we confirmed SLC1A5 was significantly overexpressed in PDAC and closely correlated with the poor prognosis of PDAC patients. Our work uncovers CDDO-Me is effective at suppressing PDAC cell growth in vitro and in vivo and illuminates CDDO-Me caused excessive ROS and cellular bioenergetics disruption which contributed to CDDO-Me inhibited PDAC growth. Our data highlights CDDO-Me could be considered a potential compound for PDAC therapy, and SLC1A5 could be a novel biomarker for PDAC patients.

A Novel Defined Hypoxia-Related Gene Signature for Prognostic Prediction of Patients With Ewing Sarcoma.

The therapeutic strategy of Ewing sarcoma (EWS) remains largely unchanged over the past few decades. Hypoxia is reported to have an impact on tumor cell progression and is regarded as a novel potential therapeutic target in tumor treatment. This study aimed at developing a prognostic gene signature based on hypoxia-related genes (HRGs). EWS patients from GSE17674 in the GEO database were analyzed as a training cohort, and differently expressed HRGs between tumor and normal samples were identified. The univariate Cox regression, Least Absolute Shrinkage and Selection Operator (LASSO) and multivariate Cox regression analyses were used in this study. A total of 57 EWS patients from the International Cancer Genome Consortium (ICGC) database were set as the validation cohort. A total of 506 differently expressed HRGs between tumor and normal tissues were identified, among which 52 were associated with the prognoses of EWS patients. Based on 52 HRGs, EWS patients were divided into two molecular subgroups with different survival statuses. In addition, a prognostic signature based on 4 HRGs (WSB1, RXYLT1, GLCE and RORA) was constructed, dividing EWS patients into low- and high-risk groups. The 2-, 3- and 5-years area under the receiver operator characteristic curve of this signature was 0.913, 0.97 and 0.985, respectively. It was found that the survival rates of patients in the high-risk group were significantly lower than those in the low-risk group (p < 0.001). The risk level based on the risk score could serve as an independent clinical factor for predicting the survival probabilities of EWS patients. Additionally, antigen-presenting cell (APC) related pathways and T cell co-inhibition were differently activated in two risk groups, which may result in different prognoses. CTLA4 may be an effective immune checkpoint inhibitor to treat EWS patients. All results were verified in the validation cohort. This study constructed 4-HRGs as a novel prognostic marker for predicting survival in EWS patients.

6-methoxydihydroavicine, the alkaloid extracted from Macleaya cordata (Willd.) R. Br. (Papaveraceae), triggers RIPK1/Caspase-dependent cell death in pancreatic cancer cells through the disruption of oxaloacetic acid metabolism and accumulation of reactive oxygen species.

BACKGROUND: Many extracts and purified alkaloids of M. cordata (Papaveraceae family) have been reported to display promising anti-tumor effects by inhibiting cancer cell growth and inducing apoptosis in many cancer types. However, no evidence currently exists for anti-pancreatic cancer activity of alkaloids extracted from M. cordata, including a novel alkaloid named 6­methoxy dihydrosphingosine (6-Methoxydihydroavicine, 6-ME) derived from M. cordata fruits. PURPOSE: The aim of this study was to investigate the anti-tumor effects of 6-ME on PC cells and the underlying mechanism. METHODS: CCK-8, RTCA, and colony-formation assays were used to analyze PC cell growth. Cell death ratios, changes in MMP and ROS levels were measured by flow cytometry within corresponding detection kits. A Seahorse XFe96 was employed to examine the effects of 6-ME on cellular bioenergetics. Western blot and q-RT-PCR were conducted to detect changes in target molecules. RESULTS: 6-ME effectively reduced the growth of PC cells and promoted PCD by activating RIPK1, caspases, and GSDME. Specifically, 6-ME treatment caused a disruption of OAA metabolism and increased ROS production, thereby affecting mitochondrial homeostasis and reducing aerobic glycolysis. These responses resulted in mitophagy and RIPK1-mediated cell death. CONCLUSION: 6-ME exhibited specific anti-tumor effects through interrupting OAA metabolic homeostasis to trigger ROS/RIPK1-dependent cell death and mitochondrial dysfunction, suggesting that 6-ME could be considered as a highly promising compound for PC intervention.

A Novel Mechanism of Cannabidiol in Suppressing Hepatocellular Carcinoma by Inducing GSDME Dependent Pyroptosis.

Cannabidiol (CBD), a phytochemical derived from Cannabis sativa L., has been demonstrated to exhibit promising anti-tumor properties in multiple cancer types. However, the effects of CBD on hepatocellular carcinoma (HCC) cells remain unknown. We have shown that CBD effectively suppresses HCC cell growth in vivo and in vitro, and induced HCC cell pyroptosis in a caspase-3/GSDME-dependent manner. We further demonstrated that accumulation of integrative stress response (ISR) and mitochondrial stress may contribute to the initiation of pyroptotic signaling by CBD. Simultaneously, CBD can repress aerobic glycolysis through modulation of the ATF4-IGFBP1-Akt axis, due to the depletion of ATP and crucial intermediate metabolites. Collectively, these observations indicate that CBD could be considered as a potential compound for HCC therapy.

Dimethyl Fumarate Induces Metabolic Crisie to Suppress Pancreatic Carcinoma.

Dimethyl fumarate (DMF) is an approved drug used in the treatment of multiple sclerosis (MS) and psoriasis therapy. Multiple studies have demonstrated other pharmacological activities of DMF such as an anti-cancer agent. In particular, studies have shown that DMF can modulate the NRF2/HO1/NQO1 antioxidant signal pathway and inactivate NF-κB to suppress the growth of colon and breast cancer cells, and induce cell death. In this study, we aimed to evaluate the anti-tumor activities of DMF in pancreatic cancer (PC) focusing on cell death as the predominant mechanism of response. We showed that both mitochondrial respiration and aerobic glycolysis were severely depressed following treatment with DMF and the effects could be abrogated by treatment with L-cysteine and N-acetyl-L-cysteine (NAC). Importantly, we verified that DMF induced metabolic crisis and that cell death was not related to alterations in ROS. Our data implied that MTHFD1 could be a potential downstream target of DMF identified by molecular docking analysis. Finally, we confirmed that MTHFD1 is up-regulated in PC and overexpression of MTHFD1 was negatively related to outcomes of PC patients. Our data indicate that DMF induces metabolic crisie to suppress cell growth and could be a potential novel therapy in the treatment of PC.

A benzene-bridged divanadium complex-early transition metal catalyst for alkene alkylarylation with PhI(O2CR)2via decarboxylation.

The synthesis, structure and catalytic activity of a benzene-bridged divanadium complex were comprehensively studied. The reduction of (Nacnac)VCl2 (1) (Nacnac = (2,6-iPr2C6H3NCMe)2HC) supported by ß-diketiminate with potassium graphite (KC8) by employing benzene as the solvent allows access to the benzene-bridged inverted-sandwich divanadium complex (µ-η6:η6-C6H6)[V(Nacnac)]2 (2a), which can catalyze alkene alkylarylation with hypervalent iodine(iii) reagents (HIRs) via decarboxylation to generate regioselectively diverse indolinones. Furthermore, the mild nature of this reaction was amenable to a wide range of functionalities on alkenes and HIRs. Mechanistic studies revealed a relay sequence of decarboxylative radical alkylation/radical arylation/oxidative re-aromatization.

Elevated Serum Matrix Metalloproteinase-9, Interleukin-6, Hypersensitive C-Reactive Protein, and Homocysteine Levels in Patients with Epilepsy.

Neuroinflammation contributes to the occurrence and development of epilepsy. However, several inflammatory factors that are important for facilitating the diagnosis to reduce or prevent seizures need to be further studied. This study is aimed to explore serum levels of matrix metalloproteinase-9 (MMP-9), interleukin-6 (IL-6), hypersensitive C-reactive protein (hs-CRP), and homocysteine (HCY) in epilepsy patients and the relationship of them with epilepsy. Epilepsy patients (n = 101) in the Second Xiangya Hospital from January 2017 to August 2018 were allocated to the epilepsy groups, which were divided into idiopathic epilepsy group (n = 43) and symptomatic epilepsy group (n = 58) according to the pathogeny. Healthy individuals (n = 50) were allocated to the control group. The concentrations of serum MMP-9, IL-6, hs-CRP, and HCY in all samples were detected by enzyme-linked immunosorbent assay, chemiluminescence method, latex-enhanced immunoturbidimetry, and enzyme circulation method. The levels of serum MMP-9, IL-6, hs-CRP, and HCY in epilepsy patients were higher than those in the control group (P < 0.05, P < 0.01, P < 0.01, and P < 0.01, respectively). The levels of serum MMP-9, IL-6, hs-CRP, and HCY in the symptomatic epilepsy group were higher than those in the control group (P < 0.01 or P < 0.05, respectively). The levels of serum MMP-9, IL-6, and hs-CRP in idiopathic epilepsy patients were higher than those in the control group (P < 0.01 or P < 0.05, respectively). The serum HCY level in the idiopathic epilepsy group was lower than that in the symptomatic epilepsy group (P < 0.01). MMP-9, IL-6, hs-CRP, and HCY may be recommended as the state biomarker to distinguish etiology of epilepsy. We hope our study could provide help in some ways for clinical diagnosis and treatment.

Extended exenatide administration enhances lipid metabolism and exacerbates pancreatic injury in mice on a high fat, high carbohydrate diet.

This study expanded upon a previous study in mice reporting a link between exenatide treatment and exocrine pancreatic injury by demonstrating temporal and dose responses and providing an initial mechanistic hypothesis. The design of the present study included varying lengths of exenatide exposure (3, 6 weeks to 12 weeks) at multiple concentrations (3, 10, or 30 µg/kg) with multiple endpoints (histopathology evaluations, immunoassay for cytokines, immunostaining of the pancreas, serum chemistries and measurement of trypsin, amylase, and, lipase, and gene expression profiles). Time- and dose-dependent exocrine pancreatic injury was observed in mice on a high fat diet treated with exenatide. The morphological changes identified in the pancreas involved acinar cell injury and death (autophagy, apoptosis, necrosis, and atrophy), cell adaptations (hypertrophy and hyperplasia), and cell survival (proliferation/regeneration) accompanied by varying degrees of inflammatory response leading to secondary injury in pancreatic blood vessels, ducts, and adipose tissues. Gene expression profiles indicated increased signaling for cell survival and altered lipid metabolism in exenatide treated mice. Immunohistochemistry supported gene expression findings that exenatide caused and/or exacerbated pancreatic injury in a high fat diet environment potentially by further increasing high fat diet exacerbated lipid metabolism and resulting oxidative stress. Further investigation is required to confirm these findings and determine their relevance to human disease.

S5a binds to death receptor-6 to induce THP-1 monocytes to differentiate through the activation of the NF-κB pathway.

Analyses of supernatants from apoptotic cells have helped in the identification of many signals that modulate the states of cell activation and differentiation. However, the current knowledge about the soluble factors that are released during apoptosis is rather limited. Previous studies have shown that S5a and angiocidin (both encoded by PSMD4) induce human acute monocytic leukemia cells (THP-1 cells) to differentiate into macrophages, but the cell-surface receptor of S5a has not been identified. In this study, we show that apoptotic THP-1 cells release endogenous S5a that binds to death receptor-6 (DR6, also known as TNFRSF1), which was identified as an orphan receptor, to induce THP-1 cells to differentiate. Furthermore, we found that the NF-κB pathway is activated, and that the transcription factors WT1 (Wilms' tumor 1) and c-myb mediate S5a-induced THP-1 differentiation. We also show that differentiation is blocked by anti-DR6 antibody, DR6 siRNA, DR6-Fc, NF-κB inhibitor or WT1 siRNA treatment. Our findings indicate that the interaction between cells can determine their differentiation, and we provide evidence for a functional interaction between S5a and DR6, which provides a novel potential mechanism to induce the differentiation of cancer cells, especially during biotherapy for leukemia.

Benzene toxicity: The role of the susceptibility factor NQO1 in bone marrow endothelial cell signaling and function.

The homozygous NQO1*2 polymorphism results in a null NQO1 phenotype and is a susceptibility factor for occupational benzene poisoning. NQO1 plays an important role in detoxification of benzene-derived quinones but plays a role in numerous other non-metabolic cellular functions. NQO1 is expressed in endothelial cells of bone marrow which form the vascular stem cell niche important in stem cell homing and mobilization. We therefore employed a transformed human bone marrow endothelial cell (HBMEC) line to define the effects of compromising NQO1 on endothelial function. Either inhibition or knockdown of NQO1 led to decreased expression of the adhesion molecules E-selectin, VCAM-1 and ICAM-1 and decreased functional adhesion of CD34+ progenitor cells after TNFα stimulation. Suicide inhibition or knockdown of NQO1 decreased NFκB p105 precursor and NFκB p50 subunit levels as well as leading to decreased nuclear levels of NFκB phospho-p65. An additional function of endothelial cells is tube formation and angiogenesis which was inhibited by the benzene metabolite hydroquinone suggesting that endothelial function may be affected at multiple levels after exposure of NQO1*2 polymorphic individuals to benzene. These data demonstrate that NQO1 plays an upstream role in NFκB signaling and adhesion molecule expression in HBMEC and that NQO1 has important regulatory effects in its own right in addition to being a marker for Nrf-2 activation. Metabolic susceptibility factors such as NQO1 have roles in addition to detoxification of reactive intermediates and interrogation of these novel roles can inform both mechanisms of toxicity and human risk assessment.

NAD(P)H:quinone oxidoreductase 1-compromised human bone marrow endothelial cells exhibit decreased adhesion molecule expression and CD34+ hematopoietic cell adhesion.

NAD(P)H:quinone oxidoreductase 1 (NQO1) deficiency resulting from a homozygous NQO1*2 polymorphism has been associated with an increased risk of benzene-induced myeloid toxicity and a variety of de novo and therapy-induced leukemias. Endothelial cells in human bone marrow form one of the two known hematopoietic stem cell microenvironments and are one of the major cell types that express NQO1 in bone marrow. We have used a transformed human bone marrow endothelial cell (TrHBMEC) line to study the potential impact of a lack of NQO1 activity on adhesion molecule [endothelial leukocyte adhesion molecule 1 (E-selectin), vascular cell adhesion molecule (VCAM)-1, and intercellular adhesion molecule (ICAM)-1] expression and functional adhesion to bone marrow progenitor cells. We used both 5-methoxy-1,2-dimethyl-3-[(4-nitrophenoxy)methyl]indole-4,7-dione (ES936), a mechanism-based inhibitor of NQO1, and anti-NQO1 small interfering RNA to abrogate NQO1 activity. Real-time reverse transcription-polymerase chain reaction data demonstrated a significant inhibition of tumor necrosis factor (TNF)alpha-induced E-selectin mRNA levels after ES936 pretreatment. Immunoblot assays demonstrated a significant reduction in TNFalpha-stimulated E-selectin, VCAM-1, and ICAM-1 proteins after inhibition or knockdown of NQO1. The mechanisms underlying this effect remain undefined, but modulation of nuclear factor-kappaB (p65), c-Jun, and activating transcription factor 2, transcriptional regulators of adhesion molecules, were observed after inhibition or knockdown of NQO1. Decreased level of E-selectin, VCAM-1, and ICAM-1 also resulted in a functional deficit in adhesion. A parallel plate flow chamber study demonstrated a marked reduction in CD34(+) cell (KG1a) adhesion to NQO1-deficient TrHBMECs relative to controls. The reduced adhesive ability of TrHBMECs may affect the function of the vascular stem cell niche and also may contribute to the increased susceptibility of polymorphic individuals lacking NQO1 to leukemias and hematotoxicants such as benzene.

Relationships between metabolic and non-metabolic susceptibility factors in benzene toxicity.

Reactive metabolites formed from benzene include benzene oxide, trans,trans muconaldehyde, quinones, thiol adducts, phenolic metabolites and oxygen radicals. Susceptibility to the toxic effects of benzene has been suggested to occur partly because of polymorphisms in enzymes involved in benzene metabolism which include cytochrome P450 2E1, epoxide hydrolases, myeloperoxidase, glutathione-S-transferases and quinone reductases. However, susceptibility factors not directly linked to benzene metabolism have also been associated with its toxicity and include p53, proteins involved in DNA repair, genomic stability and expression of cytokines and/or cell adhesion molecules. In this work, we examine potential relationships between metabolic and non-metabolic susceptibility factors using the enzyme NAD(P)H:quinone oxidoreductase (NQO1) as an example. NQO1 may also impact pathways in addition to metabolism of quinones due to protein-protein interactions or other mechanisms related to NQO1 activity. NQO1 has been implicated in stabilizing p53 and in maintaining microtubule integrity. Inhibition or knockdown of NQO1 in bone marrow endothelial cells has been found to lead to deficiencies of E-selectin, ICAM-1 and VCAM-1 adhesion molecule expression after TNFalpha stimulation. These examples illustrate how the metabolic susceptibility factor NQO1 may influence non-metabolic susceptibility pathways for benzene toxicity.

Benzene metabolite hydroquinone up-regulates chondromodulin-I and inhibits tube formation in human bone marrow endothelial cells.

Bone marrow is a major target of benzene toxicity, and NAD-(P)H:quinone oxidoreductase (NQO1), an enzyme protective against benzene toxicity, is present in human bone marrow endothelial cells, which form the hematopoietic stem cell vascular niche. In this study, we have employed a transformed human bone marrow endothelial cell (TrHBMEC) line to study the adverse effects induced by the benzene metabolite hydroquinone. Hydroquinone inhibited TrHBMEC tube formation at concentrations that were not overtly toxic, as demonstrated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide or sulforhodamine B analysis. Hydroquinone was found to up-regulate chondromodulin-I (ChM-I), a protein that promotes chondrocyte growth and inhibits endothelial cell growth and tube formation. Recombinant human ChM-I protein inhibited tube formation in TrHBMECs, suggesting that up-regulation of ChM-I may explain the ability of hydroquinone to inhibit TrHB-MEC tube formation. To explore this possibility further, anti-ChM-I small interfering RNA (siRNA) was used to deplete ChM-I mRNA and protein. Pretreatment with anti-ChM-I siRNA markedly abrogated hydroquinone-induced inhibition of tube formation in TrHBMECs. Overexpression of the protective enzyme NQO1 in TrHBMECs inhibited the up-regulation of ChM-I and abrogated the inhibition of tube formation induced by hydroquinone. In summary, hydroquinone treatment up-regulated ChM-I and inhibited tube formation in TrHBMECs; NQO1 inhibited hydroquinone-induced up-regulation of ChM-I in TrHB-MECs and protected cells from hydroquinone-induced inhibition of tube formation. This study demonstrates that ChM-I up-regulation is one of the underlying mechanisms of inhibition of tube formation and provides a mechanism that may contribute to benzene-induced toxicity at the level of bone marrow endothelium.

4-HNE inhibits tube formation and up-regulates chondromodulin-I in human endothelial cells.

The aim of the present study was to investigate the effects of 4-hydroxy-2-nonenal (4-HNE) on tube formation by human bone marrow endothelial cells (HBMEC). We found that 4-HNE at physiologically achievable concentrations (5 and 10 microM) inhibited the formation of tubes. Western blot analysis revealed that inhibition of tube formation by 4-HNE was associated with increased expression of chondromodulin-I (CHM-I), a protein with well-known anti-angiogenic properties. Cell viability assays showed that 4-HNE at concentrations of 10 microM or less did not cause HBMEC cell death. Luciferase reporter assays did not show any inducing effect of 4-HNE on the promoter activity of human CHM-I gene indicating that post-transcriptional or post-translational modifications may account for the up-regulation of CHM-I. Collectively, the results of the present study show for the first time that 4-HNE inhibits tube formation by HBMECs indicating a potential anti-angiogenic activity of 4-HNE. This inhibition occurs at least in part via 4-HNE-induced CHM-I protein expression.