Acute Monocytic Leukemia Cell Line Research Articles

Effect of phospholipomannan of Candida albicans on the production of interleukin 6 and interleukin 8 in monocytes

To investigate whether Candida albicans-native phospholipomannan (PLM) induce an inflammation response through Toll-like receptor(TLRé2 in human acute monocytic leukemia cell line (THP-1) cells. Human THP-1 monocytes were challenged with PLM in vitro. The mRNA expressions of TLR2, TLR4, proinflammatory cytokine [interleukin(IL)-6], and chemokine (IL-8) were assayed by real time reverse transcription polymerase chain reaction. The secretions of IL-6 and IL-8 were measured by enzyme-linked immunosorbent assay. The expression of TLR2 was analyzed with Western blot. PLM increased the mRNA expressions and secretions of proinflammatory cytokines (IL-6) and chemokines (IL-8) in THP-1 cells (all P=0.0000). PLM up-regulated the mRNA and protein levels of TLR2 (P=0.0000), whereas the mRNA level of TLR4 was not altered. PLM hydrolyzed with β-D-mannoside manno hydrolase failed to induce gene and protein expressions of TLR2, IL-6, and IL-8. Anti-TLRS-neutralizing antibody blocked the PLM-induced secretions of IL-6 and IL-8 in THP-1 cells (P = 0.0003, P = 0.0010). Canidada albicans-native PLM may contribute to the inflammatory responses during Candida infection in a TLR2-dependent manner.

Antioxidant capacity and anti-inflammatory effect of the ethyl acetate fraction of dried persimmon (Diospyros kaki Thumb.) on THP-1 human acute monocytic leukemia cell line

Antioxidant capacity and anti-inflammatory effect of ethyl acetate (EtOAc) fraction of phenolic extract from dried persimmon (Diospyros kaki Thumb.) were investigated on THP-1 human acute monocytic leukemia cells. Phenolic extract of dried persimmon was sequentially fractionized using five different solvents, hexane, chloroform, EtOAc, butanol, and water, among which EtOAc fraction showed the highest antioxidant capacity. Cytotoxicity of THP-1 cells pretreated with the EtOAc fraction and curcumin was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Curcumin and the EtOAc fraction showed respective cytotoxicities at 30 and 100 μg/mL. Expression level of proinflammatory tumor necrosis factor-α (TNF-α) was quantified by enzyme-linked immunosorbent assay. TNF-α production was significantly inhibited by curcumin and the EtOAc fraction at 20 and 50 μg/mL, respectively. These results showed that phenolic compounds of dried persimmon alleviated the augmentation of TNF-α level induced by lipopolysaccharide in THP-1 cells, suggesting that dietary uptake of dried persimmon may be beneficial to promote anti-inflammation.

Anthracycline treatment of the human monocytic leukemia cell line THP-1 increases phosphatidylserine exposure and tissue factor activity

Introduction Cancer associated thrombosis is a well-recognized phenomenon that results in considerable patient morbidity and mortality. Malignancy conveys an increased risk for thrombosis and chemotherapy further elevates this risk. The pathophysiological mechanisms underlying this process remain poorly defined. Materials and Methods A human acute monocytic leukemia cell line (THP-1) was treated with commonly used anthracycline chemotherapeutics at concentrations similar to those found in the plasma of cancer patients. Cells were analyzed for tissue factor (TF) mRNA, protein, and activity. Microparticle (MP) TF activity was also measured. Phosphatidylserine (PS) exposure on cells and MPs was analyzed by flow cytometry. PS levels on MPs was also evaluated in an annexin V capture assay. Results Anthracycline treatment of THP-1 cells resulted in a concentration-dependent increase in cellular TF activity without a change in TF protein, which was associated with increased PS exposure on the cell surface and apoptosis. The increase in TF activity was abolished by annexin V or lactadherin indicating that PS exposure was required. Anthracycline treatment of THP-1 cells also increased the number of TF-positive MPs. Conclusion Treatment of THP-1 cells with anthracyclines induces apoptosis and increases cellular TF activity. The increased activity required an increase in exposure of PS. Additionally, anthracyclines increase the release of TF-positive MPs from THP-1 cells. We propose that the increase in cellular TF activity in circulating leukemic cells, combined with increased numbers of TF-positive MPs, may contribute to thrombosis in cancer patients receiving chemotherapy.

Tumour necrosis factor-like weak inducer of apoptosis (TWEAK), an important mediator of endothelial inflammation, is associated with the pathogenesis of Henoch–Schonlein purpura

Tumour necrosis factor-like weak inducer of apoptosis (TWEAK), a member of the tumour necrosis factor (TNF) family, has been implicated as a proinflammatory cytokine in many types of autoimmune and infectious diseases. However, information about TWEAK in dermatological diseases is limited. Herein, we investigated the role of TWEAK in patients with Henoch-Schonlein purpura (HSP) and the ability of TWEAK on chemokine production in the human dermal microvascular endothelial cell line (HMEC-1). Serum TWEAK levels in patients with HSP, together with patients with psoriasis vulgaris (PV) and atopic dermatitis (AD), were detected by enzyme-linked immunosorbent assay (ELISA). HMEC-1 cells were treated with TWEAK at concentrations ranging from 1 ng/ml to 100 ng/ml. Serum levels of TWEAK were elevated in patients with HSP in the acute stage but not in patients with PV or AD. Moreover, TWEAK levels were correlated with the severity of HSP. TWEAK markedly induced CCL5 and CXCL8 production at both mRNA and protein levels in HMEC-1 cells. In addition, TWEAK-stimulated HMEC-1 supernatant enhanced HL-60 or human acute monocytic leukaemia cell line (THP-1) cell migration. Finally, Western blot data revealed that TWEAK can induce rapid phosphorylation of inhibitor of κB-α (IκBα) in HMEC-1 cells. In conclusion, we show that serum levels of TWEAK were elevated in patients with acute stage HSP. TWEAK may act as a regulator of nuclear factor-κB (NF-κB) activation and chemokine production in human dermal microvascular endothelial cells, thus promoting leucocyte migration in cutaneous vasculitis.

Ubiquitination is associated with lysosomal degradation of cell surface-resident ATP-binding cassette transporter A1 (ABCA1) through the endosomal sorting complex required for transport (ESCRT) pathway

ATP-binding cassette transporter A1 (ABCA1) plays an essential role in the biogenesis of high-density lipoprotein in liver and in the prevention of foam cell formation in macrophages by mediating the efflux of cellular cholesterol and phospholipids to apolipoprotein A-I (apoA-I). Our current study investigated the mechanism of degradation of cell surface-resident ABCA1, focusing on ubiquitination. A coimmunoprecipitation study indicated the presence of ubiquitinated ABCA1 in the plasma membrane of the human hepatoma cell line, HuH-7, of cells from mouse liver, and of macrophages differentiated from the human acute monocytic leukemia cell line, THP-1 (THP-1 macrophages). In HuH-7 cells, degradation of cell surface-resident ABCA1 was inhibited by the overexpression of a dominant-negative form of ubiquitin. Moreover, the disruption of the endosomal sorting complex required for transport (ESCRT) pathway, a dominant mechanism for ubiquitination-mediated lysosomal degradation, by the knockdown of hepatocyte growth factor-regulated tyrosine kinase substrate (HRS), significantly delayed the degradation of cell surface-resident ABCA1. This was accompanied by an increase in ABCA1 expression as well as in apoA-I-mediated [3H]-cholesterol efflux function. The effect of HRS knockdown was also observed after calpain inhibitor treatment, which is reported to retard ABCA1 degradation. The induction of ABCA1 by HRS knockdown was confirmed in THP-1 macrophages. Together with the fact that lysosomal inhibitor treatments increased ABCA1 expression in HuH-7 and THP-1 macrophages, these results suggest that ubiquitination mediates the lysosomal degradation of cell surface-resident ABCA1 through the ESCRT pathway, and thereby controls the expression and cholesterol efflux function of ABCA1. This mechanism seems to mediate ABCA1 degradation independently of the calpain-involving pathway. The modulation of ABCA1 ubiquitination could thus be a potential new therapeutic target for antiatherogenic drugs.

CD300F Blocks Both MyD88 and TRIF-Mediated TLR Signaling through Activation of Src Homology Region 2 Domain-Containing Phosphatase 1

CD300F is known to exhibit inhibitory activity in myeloid cells through its intracellular ITIM. To investigate the effect of CD300F stimulation on TLR signaling, the human acute monocytic leukemia cell line THP-1 was treated with CD300F-specific mAbs or two synthetic peptides that represented the ITIM-like domains of CD300F. Treatment with these agents blocked TLR2-, 3-, 4-, and 9-mediated expression of proinflammatory mediators such as IL-8 and matrix metalloproteinase-9. The luciferase reporter assay in 293T cells and Western blot analysis of THP-1 cells revealed that these inhibitory actions were effective in pathways involving MyD88 and/or TRIF of TLR signaling and associated with marked suppression of IκB kinase activation, phosphorylation/degradation of IκB, and subsequent activation of NF-κB. Use of specific inhibitors and immunoprecipitation analysis further indicated that the inhibitory effects were mediated by Src homology 2 domain-containing phosphatase-1, a protein tyrosine phosphatase with inhibitory activity in hematopoietic cells. These data indicate that CD300F is an active regulator of TLR-mediated macrophage activation through its association with Src homology 2 domain-containing phosphatase-1 and that the synthetic peptides can be applied for the regulation of immune responses that are induced by TLRs.

American Journal of Physiology-Cell Physiology theme: ion channels and transporters in cancer

in this issue, the American Journal of Physiology-Cell Physiology initiates the publication of a new Theme series of review articles that focus on the pathogenic role of ion channels and transporters in cancer. Ion channels, as an important family of membrane proteins that are highly expressed in

Porphyrin-magnetite nanoconjugates for biological imaging

BackgroundThe use of silica coated magnetic nanoparticles as contrast agents has resulted in the production of highly stable, non-toxic solutions that can be manipulated via an external magnetic field. As a result, the interaction of these nanocomposites with cells is of vital importance in understanding their behaviour and biocompatibility. Here we report the preparation, characterisation and potential application of new "two-in-one" magnetic fluorescent nanocomposites composed of silica-coated magnetite nanoparticles covalently linked to a porphyrin moiety.MethodThe experiments were performed by administering porphyrin functionalised silica-coated magnetite nanoparticles to THP-1 cells, a human acute monocytic leukaemia cell line. Cells were cultured in RPMI 1640 medium with 25 mM HEPES supplemented with heat-inactivated foetal bovine serum (FBS).ResultsWe have synthesised, characterised and analysed in vitro, a new multimodal (magnetic and fluorescent) porphyrin magnetic nanoparticle composite (PMNC). Initial co-incubation experiments performed with THP-1 macrophage cells were promising; however the PMNC photobleached under confocal microscopy study. β-mercaptoethanol (β-ME) was employed to counteract this problem and resulted not only in enhanced fluorescence emission, but also allowed for elongated imaging and increased exposure times of the PMNC in a cellular environment.ConclusionOur experiments have demonstrated that β-ME visibly enhances the emission intensity. No deleterious effects to the cells were witnessed upon co-incubation with β-ME alone and no increases in background fluorescence were recorded. These results should present an interest for further development of in vitro biological imaging techniques.

Involvement of IRAKs and TRAFs in anti-β2GPI/β2GPI-induced tissue factor expression in THP-1 cells

Our previous study has shown that Toll-like receptor 4 (TLR4) and its signalling pathway contribute to anti-β₂-glycoprotein I/β₂-glycoprotein I (anti-β₂GPI/β₂GPI)-induced tissue factor (TF) expression in human acute monocytic leukaemia cell line THP-1 and annexin A2 (ANX2) is involved in this pathway. However, its downstream molecules have not been well explored. In this study, we have established that interleukin-1 receptor-associated kinases (IRAKs) and tumour necrosis factor receptor-associated factors (TRAFs) are crucial downstream molecules of anti-β₂GPI/β₂GPI-induced TLR4 signaling pathway in THP-1 cells and explored the potential mechanisms of their self-regulation. Treatment of THP-1 cells with anti-β₂GPI/β₂GPI complex induced IRAKs and TRAFs expression and activation. Anti-β₂GPI/β₂GPI complex firstly induced expression of IRAK4 and IRAK1, then IRAK1 phosphorylation and last IRAK3 upregulation. In addition, anti-β₂GPI/β₂GPI complex simultaneously and acutely enhanced mRNA levels of TRAF6, TRAF4 and zinc finger protein A20 (A20), while chronically increased A20 protein level. Moreover, anti-β₂GPI/β₂GPI complex-induced IRAKs and TRAFs expression and activation were attenuated by knockdown of ANX2 by infection with ANX2-specific RNA interference lentiviruses (LV-RNAi-ANX2) or by treatment with paclitaxel, which inhibits TLR4 as an antagonist of myeloid differentiation protein 2 (MD-2) ligand. Furthermore, both IRAK1/4 inhibitor and a specific proteasome inhibitor MG-132 could attenuate TRAFs expression as well as TF expression induced by anti-β₂GPI/β₂GPI complex. In conclusion, our results indicate that IRAKs and TRAFs play important roles in anti-β₂GPI/β₂GPI-stimulated TLR4/TF signaling pathway in THP-1 cells and contribute to the pathological processes of antiphospholipid syndrome (APS).

HOXA4 protein levels and localization in the aorta and in human abdominal aortic aneurysms

This report presents evidence for the specificities of select commercially available HOXA4 antibodies in regards to concerns about the specificity of the HOXA4 antibody used by Lillvis et al. (Regional expression of HOXA4 along the aorta and its potential role in human abdominal aortic aneurysms. BMC Physiol 2011, 11:9). Using an antibody characterized extensively by us, Lillvis et al. report detecting HOXA4 at a size of 33 kDa despite our previous reports that HOXA4 is detected at ~37-39 kDa and that the ~30-33 kDa band is non-specific. Using small interfering RNA targeting HOXA4, forced expression of full-length HOXA4 and HOXA4-positive and -negative ovarian cancer cell lines, we confirm our previous findings that the ~30-33 kDa band is non-specific and that HOXA4 is detected at ~37-39 kDa. Moreover, we demonstrate that HOXA4 small interfering RNA reduces the ~37-39 kDa HOXA4 band, but not the ~30-33 kDa non-specific band, in a human acute monocytic leukemia cell line used by Lillvis et al. Western blot analysis performed with two additional commercially available HOXA4 antibodies also detected HOXA4 at ~37-39 kDa. Lastly, immunofluorescent staining of a HOXA4-negative ovarian cancer cell line with the antibody used by Lillvis et al. yields strong perinuclear staining, similar to that observed by Lillvis et al., which cannot be attributed to HOXA4. Our results highlight and briefly discuss the importance of careful antibody validation and selection for use in various applications.

Endothelial Argininosuccinate Synthetase 1 Regulates Nitric Oxide Production and Monocyte Adhesion under Static and Laminar Shear Stress Conditions

Laminar shear stress (LSS) is known to increase endothelial nitric oxide (NO) production, which is essential for vascular health, through expression and activation of nitric oxide synthase 3 (NOS3). Recent studies demonstrated that LSS also increases the expression of argininosuccinate synthetase 1 (ASS1) that regulates the provision of L-arginine, the substrate of NOS3. It was thus hypothesized that ASS1 might contribute to vascular health by enhancing NO production in response to LSS. This hypothesis was pursued in the present study by modulating NOS3 and ASS1 levels in cultured endothelial cells. Exogenous expression of either NOS3 or ASS1 in human umbilical vein endothelial cells increased NO production and decreased monocyte adhesion stimulated by tumor necrosis factor-α (TNF-α). The latter effect of overexpressed ASS1 was reduced when human umbilical vein endothelial cells were co-treated with small interfering RNAs (siRNAs) for ASS1 or NOS3. SiRNAs of NOS3 and ASS1 attenuated the increase of NO production in human aortic endothelial cells stimulated by LSS (12 dynes·cm(-2)) for 24 h. LSS inhibited monocyte adhesion to human aortic endothelial cells stimulated by TNF-α, but this effect of LSS was abrogated by siRNAs of NOS3 and ASS1 that recovered the expression of vascular cell adhesion molecule-1. The current study suggests that the expression of ASS1 harmonized with that of NOS3 may be important for the optimized endothelial NO production and the prevention of the inflammatory monocyte adhesion to endothelial cells.

Peoniflorin suppresses tumor necrosis factor-α induced chemokine production in human dermal microvascular endothelial cells by blocking nuclear factor-κB and ERK pathway

Peoniflorin (PF) extracted from the root of Paeonia lactiflora pall displays anti-inflammation and antioxidant properties in several animal models. Chemokines are vital for directing the movement of circulating leukocytes to the sites of inflammation and are involved in the pathogenesis of various inflammatory skin diseases. Herein, we investigated the effects and potential mechanisms of PF on tumor necrosis factor-α (TNF-α) induced chemokine production in human dermal microvascular endothelial cells. Human dermal microvascular endothelial cell line (HMEC-1) was treated by TNF-α with or without PF. PF markedly attenuated TNF-α-induced chemokines (including CCL2, CCL5, CCL20, CXCL8, CXCL16 and CX3CL1) mRNA expression in HMEC-1. PF also reduced the secretion of these chemokines in culture supernatants. In addition, endothelial activation in the presence of PF markedly blocked the chemotactic activities of TNF-α-stimulated HMEC-1 supernatant on promyelocytic leukemia cell line (HL-60) or the acute mature monocytic leukemia cell line (THP-1) cell migration. Furthermore, Western blot data revealed TNF-α upregulated phosphorylation of inhibitor of κB-α (IκBα) and phosphorylation of extracellular signal-regulated kinase (ERK)1/2, which was almost completely reversed by PF. Finally, PF inhibited nuclear factor-κB (NF-κB) nuclear translocation to the nucleus. Taken together, our data provide the first evidence that PF has an anti-inflammatory ability against TNF-α-induced chemokine production and leukocyte migration, which may be at least partly related to the inhibition of NF-κB and ERK pathway. PF may be a candidate medicine for the treatment of inflammatory skin diseases.

MMP-2 and MMP-9 Secreted by Leukemic Cells Increase the Permeability of Blood-Brain Barrier by Disrupting Tight Junction Proteins In Central Nervous System Leukemia

AbstractAbstract 2694Recurrence of acute leukemia (AL) in the central nervous system (CNS) confers a poor prognosis. However, little is known about the the underlying mechanisms of leukemic cell infiltration into the CNS. The blood brain barrier (BBB) makes CNS become a refugee to leukemic cells and serves as a resource of cells that seed extraneural sites. Tight junction in brain microvessel endothelial cells (HMECs) constituted by tight junction proteins is an important structure of BBB. Except the well known role of degrading extracellular matrix in metastasis of cancer cells, here we identify matrix metalloproteinase 2 (MMP-2) and MMP-9 secreted by leukemic cells are also associated with BBB opening by degrading tight junction proteins. We have successfully established an animal model of CNS leukemia by using a highly invasive human acute monocytic leukemia cell line SHI-1 in nude mice. Multiple organs including skull and brain were sectioned and determined histopathologically for leukemia cell infiltration. The fact that the down- regulation of ZO-1, Claun-5 and Occludin accompanied with up-regulation of MMP-2 and MMP-9 was correlated with BBB breakdown in mice with CNS leukemia was found when examined by laser scanning fluorescence confocal microscopy and gelatin in situ zymography. The treatment with MMP-inhibitor GM6001 could significantly reverse these changes in tight junction proteins. In an in vitro monolayer BBB model made by human encephalo-microvessel endothelial cells and matreil gel, MMP-2 and MMP-9 specifically down-regulated ZO-1, Claun-5 and Occludin. Knock-down or inhibition of MMP-2 and MMP-9 expression protected ZO-1, Claun-5 and occludin from degradation and alleviated the permeability of BBB. Our findings suggest that the degradation of tight junction proteins ZO-1, Claun-5 and Occludin by MMP-2 and MMP-9 secreted by leukemic cells constitutes an important mechanism in BBB breakdown in CNS leukemia. These studies provide a potent evidence for future pharmacological treatment to inhibit the CNS involvement in acute leukemia. Disclosures:No relevant conflicts of interest to declare.

Acetyl-11-keto-beta-boswellic acid and arsenic trioxide regulate the productions and activities of matrix metalloproteinases in human skin fibroblasts and human leukemia cell line THP-1

In order to reveal the treatment mechanism of Chinese medicine with the effect of activating blood and resolving putridity, we selected acetyl-11-keto-beta-boswellic acid (AKBA) and arsenic trioxide (ATO), the main monomeric components of frankincense and arsenolite which are two most commonly used Chinese medicine with effect of activating blood and resolving putridity. We combined AKBA and ATO as a compound, and explored its regulatory role in productions and activities of matrix metalloproteinase (MMP)-1, MMP-2 and MMP-9 in human skin fibroblasts (HSFbs) and human acute monocytic leukemia cell line THP-1 in inflammatory state. In order to simulate the inflammatory micro-environment of chronic wounds, we established 3 cell models: HSFb model activated by tumor necrosis factor-alpha (TNF-α), THP-1 cell model activated by phorbol-12-myristate-13-acetate (PMA) and HSFb-THP-1 cell coculture system. AKBA and ATO were cocultured with these cell models. Enzyme-linked immunosorbent assay (ELISA), gelatin zymography assay and reverse transcription-polymerase chain reaction (RT-PCR) were used to test the secretions, activities and mRNA expressions of MMP-1, MMP-2 and MMP-9. In the study of the regulatory mechanism of AKBA and ATO on MMPs, AKBA and ATO were cocultured with the cell models. ELISA was used to test the secretions of TNF-α and interleukin-1beta (IL-β) and Western blot was used to test the phosphorylation levels of extracellular signal-regulated kinases 1 and 2 (ERK1/2) and p38 mitogen-activated proteinkinase (p38MAPK). Compound of AKBA and ATO inhibited MMP-1, MMP-2 and MMP-9 mRNA expressions, secretions and activities respectively in HSFbs and THP-1 cells in inflammatory state (P<0.05, P<0.01). Also compound of AKBA and ATO inhibited secretions of TNF-α and IL-1β in THP-1 cells and cell coculture system (P<0.01). It also decreased the phosphorylation of ERK1/2 and p38 MAPK in HSFbs and THP-1 cells (P<0.05, P<0.01). The combined use of AKBA and ATO which in line with the rule of activating blood and resolving putridity inhibits fibroblasts and inflammatory cells in producing MMPs in inflammatory state through inhibiting the release of inflammatory factors and MAPK cascade pathway.

Ellagic acid inhibits oxidized LDL-mediated LOX-1 expression, ROS generation, and inflammation in human endothelial cells

LOX-1, a lectin-like receptor on endothelial cells, facilitates the uptake of oxidized low-density lipoprotein (oxLDL). Expression of LOX-1 is involved in the pathobiological effects of oxLDL in endothelial cells, including reactive oxygen species (ROS) generation, suppression of endothelial nitric oxide synthase (eNOS) activity, and leukocytic adhesion. Moderate consumption of phenolic-enriched food may have a protective effect against the development of atherosclerosis via the antioxidant capacity of phenolic compounds at the endothelial level. In this study, we determined whether ellagic acid, a polyphenolic compound widely distributed in fruits and nuts, protects against oxLDL-induced endothelial dysfunction by modulating the LOX-1-mediated signaling pathway. Human umbilical vein endothelial cells (HUVECs) were pretreated with ellagic acid at doses of 5, 10, 15, and 20 μM for 2 hours and then incubated with oxLDL (150 μg/mL) for an additional 24 hours. LOX-1 protein expression was markedly lower after exposure to oxLDL in HUVECs pretreated with ellagic acid or diphenyleneiodonium, a well-known inhibitor of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, than in HUVECs exposed to oxLDL alone, suggesting that ellagic acid deactivates NADPH oxidase. We also found that oxLDL activated the membrane assembly of p47phox, Rac1, gp91 and p22phox, and the subsequent induction of ROS generation; however, ROS generation was markedly suppressed in cells pretreated with ellagic acid or anti-LOX-1 monoclonal antibody. In addition, oxLDL down-regulated eNOS and up-regulated inducible NO synthase (iNOS), thereby augmenting the formation of NO and protein nitrosylation. Furthermore, oxLDL induced the phosphorylation of p38 mitogen-activated protein kinase, activated the NF-κB-mediated inflammatory signaling molecules interleukin-(IL) 6 and IL-8 and the adhesion molecules intercellular adhesion molecule-1, vascular cell adhesion molecule-1, and E-selectin, and stimulated the adherence of THP-1 (a human acute monocytic leukemia cell line) to HUVECs. Pretreatment with ellagic acid, however, exerted significant cytoprotective effects in all events. Findings from this study may provide insight into a possible molecular mechanism by which ellagic acid inhibits LOX-1-induced endothelial dysfunction. Our data indicate that ellagic acid exerts its protective effects by inhibiting NADPH oxidase-induced overproduction of superoxide, suppressing the release of NO by down-regulating iNOS, enhancing cellular antioxidant defenses, and attenuating oxLDL-induced LOX-1 up-regulation and eNOS down-regulation.

The functional expression of calcium-sensing receptor in the differentiated THP-1 cells

The expression and function of calcium-sensing receptor (CaSR) in differentiated THP-1 (human acute monocytic leukemia cell line) cells are unknown currently. This study investigated above-mentioned issues using TRAP staining, immunofluorescence staining, Western blotting, ELISA, and Laser Confocal Scanning Microscopy techniques. We found that CaSR protein was expressed, and mainly located in the membrane and cytoplasm in differentiated THP-1 cells. Elevated extracellular calcium or GdCl(3) (an agonist of CaSR) raised intracellular calcium concentration. And this increase was inhibited or abolished by NPS2390 (an inhibitor of CaSR), U73122 (a specific inhibitor of phospholipase C, PLC) or thapsigargin (a Ca(2+)-ATPase inhibitor). The extracellular GdCl(3) elevation stimulated both of IL-1beta and TNFalpha release, and this effect of GdCl(3) was inhibited by NPS2390. In conclusion, CaSR is functionally expressed in differentiated THP-1 cells, and the activated CaSR contributes to intracellular calcium increment through Gq-PLC- inositol triphosphate (IP3) pathway and commits to cytokine secretion. These results suggest that CaSR might be involved in a variety of pathological processes mediated by activated monocyte-macrophages.

Identification of CD44 as a senescence-induced cell adhesion gene responsible for the enhanced monocyte recruitment to senescent endothelial cells

The mechanism that is responsible for progression of atherosclerosis seen with increasing age remains controversial. This issue was addressed in the present study, by searching for genes that are uniquely expressed in senescent endothelial cells and functionally involved in inflammatory leukocyte adhesion recognized as a critical step in the initiation of atherogenesis. Senescent human umbilical vein endothelial cells (HUVECs) prepared by continuous subculturing in vitro showed higher binding affinity for monocytes (THP-1 cells, human acute monocytic leukemia cell line) compared with young cells. Gene expression profiles between young and senescent endothelial cells were compared by the cDNA microarray method, and CD44 was identified as one of the "senescence-induced cell adhesion genes" whose expression was upregulated in senescent cells and whose gene ontology annotation indicated their role in cell adhesion. The enhanced gene expression of CD44 in senescent endothelial cells was verified both at the mRNA and protein levels. Adhesion of monocytes to senescent endothelial cells was significantly reduced following pretreatment of endothelial cells with the CD44 antibody or small-interfering RNA, thus reinforcing the critical role of CD44 in the inflammatory event. Exogenous expression of CD44 in young HUVECs and in human aortic endothelial cells led to an increase in monocyte adhesion. CD44 expression levels in the rat aorta endothelium were found to increase in an age-dependent manner, as determined by immunohistochemistry and Western blotting. CD44 and other senescence-induced cell adhesion genes identified in this study may provide the novel targets for the prevention of inflammatory leukocyte adhesion leading to the development atherosclerosis.

Identification of novel target genes for the prevention of inflammatory monocytes adhesion to senescent endothelial cells

The mechanism for enhanced atherosclerosis with increasing age remains controversial. This study addressed this issue at the cellular level, by searching for genes uniquely expressed in senescent endothelial cells and functionally involved in inflammatory leukocytes adhesion, a critical initiation step of atherogenesis. Senescent human umbilical vein endothelial cells prepared by continuous sub‐culturing in vitro showed higher binding affinity for monocytes (THP‐1 cells, human acute monocytic leukemia cell line) compared with young cells. Comparing gene expression profiles between young and senescent endothelial cells by the cDNA microarray method, CD44 was identified as one of the ‘senescence‐induced cell adhesion genes’ whose expression was up‐regulated in senescent cells and whose gene ontology annotation indicated their role in cell adhesion. The enhanced gene expression of CD44 in senescent endothelial cells was verified at the mRNA and protein levels. Adhesion of monocytes to senescent endothelial cells was significantly reduced when endothelial cells were pretreated with CD44 antibody or small interfering RNA, supporting the critical role of CD44 in the inflammatory event. CD44 and other ‘senescence‐induced cell adhesion genes’ identified in this study may provide the novel targets for the prevention of inflammatory leukocytes adhesion leading to the development atherosclerosis.

The essential roles of matrix metalloproteinase-2, membrane type 1 metalloproteinase and tissue inhibitor of metalloproteinase-2 in the invasive capacity of acute monocytic leukemia SHI-1 cells

The frequency of extramedullary infiltration (EMI) in acute myeloblastic leukemia (AML) is reported up to 40% and most prevalent in myelo-monoblastic and monoblastic subtypes of AML (M4 and M5 according to FAB classification). The majority of patients with EMI suffered poor prognosis. To explore mechanism underlying EMI, we analyzed SHI-1 cells, a highly invasive human acute monocytic leukemia cell line, and found their strong expression of matrix metalloproteinase 2 (MMP-2), membrane type 1 MMP (MT1-MMP) and tissue inhibitor of metalloproteinase 2 (TIMP-2). SHI-1 cells showed higher invasive ability to traverse reconstituted basement membranes (Matrigel) and stronger activation of proMMP-2 than other leukemia cell line such as NB4, K562, U937 and THP-1 cells. When co-cultured with bone marrow stromal cells (BMSCs), the invasive capacity and proMMP-2 activation of SHI-1 cells enhanced remarkably. Furthermore, the inhibition of MMP-2, MT1-MMP, or TIMP-2 by small interfering RNA (siRNA) substantially impaired SHI-1 cells invasion and decreased proMMP-2 activation. In the contrast, up-regulated expression of TIMP-2 for 2–3 folds level increased cell invasion and proMMP-2 activation. These results demonstrated that constitutively high expression of MMP-2, MT1-MMP and TIMP-2 in SHI-1 cells facilitated cell invasion by promoting proMMP-2 activation. Moreover, up-regulation of TIMP-2 exhibited not a repressive but an activating effect on SHI-1 cells invasion. Our study indicated that increasing TIMP-2 in AML patients with EMI may potentially cause adverse effects, particularly in patients containing high levels of MMP-2 and MT1-MMP.

TLR4‐dependent induction of vascular adhesion molecule‐1 in rheumatoid arthritis synovial fibroblasts: Roles of cytosolic phospholipase A2α/cyclooxygenase‐2

Lipopolysaccharide (LPS)/Toll-like receptor 4 (TLR4)-mediated signaling pathways have caught the attention of strategies designed for rheumatoid arthritis (RA). In this study, we identified that cPLA(2)alpha acted as a modulator of LPS-induced VCAM-1 expression and THP-1 (human acute monocytic leukemia cell line) adherence. Treatment of RA synovial fibroblasts (RASFs) with LPS, a TLR4 agonist, promoted the VCAM-1 expression and THP-1 adherence which were decreased by pretreatment with a selective cytosolic phospholipase A(2) (cPLA(2)) inhibitor (AACOCF(3)), implying the involvement of cPLA(2)alpha in these responses. This notion was further confirmed by knockdown of cPLA(2)alpha expression by transfection with cPLA(2)alpha small interfering RNA (siRNA) leading to a decrease in VCAM-1 expression and THP-1 adherence induced by LPS. Subsequently, the LPS-stimulated cPLA(2)alpha phosphorylation was attenuated by pretreatment with a MEK1/2 inhibitor (U0126), suggesting that LPS-stimulated cPLA(2)alpha phosphorylation and activity are mediated through an ERK-dependent mechanism. Moreover, COX-2-derived PGE(2) production appeared to involve in LPS-induced VCAM-1 expression which was attenuated by pretreatment with selective COX-2 inhibitors (NS-398 and celecoxib), transfection with COX-2 siRNA, or PGE(2) receptor antagonists. In addition, pretreatment with ecosapentaenoic acid (EPA), a substrate competitor of arachidonic acid (AA), also blocked LPS-induced VCAM-1 mRNA and protein expression, and THP-1 adherence. Collectively, these results suggest that LPS-induced VCAM-1 expression and adhesion of THP-1 cells are mediated through the TLR4/ERK/cPLA(2)alpha phosphorylation and COX-2 expression/PGE(2) synthesis in RASFs.