Effect of Flavonoids on MCP-1 Expression in Human Coronary Artery Endothelial Cells and Impact on MCP-1-Dependent Migration of Human Monocytes

The monocyte chemoattractant protein-1 (MCP-1), also known as chemokine (CC motif) ligand 2 (CCL2), is involved in the formation, progression, and destabilization of atheromatous plaques. Flavonoids, found in fruits and vegetables, have been associated with various health-promoting properties, including antioxidant, anti-inflammatory, and cardioprotective effects. In the present study, the flavonoids quercetin, kaempferol, and luteolin, but not cannflavin A, were shown to substantially inhibit interleukin (IL)-1β-induced MCP-1 mRNA and protein expression in human coronary artery endothelial cells (HCAEC). At the functional level, conditioned medium (CM) from IL-1β-stimulated HCAEC caused an increase in the migration of THP-1 monocytes compared with CM from unstimulated HCAEC. However, this induction was suppressed when IL-1β-treated HCAEC were coincubated with quercetin, kaempferol, or luteolin. The functional importance of MCP-1 in IL-1β-induced monocyte migration was supported by experiments showing that neutralization of MCP-1 in the CM of IL-1β-treated HCAEC led to a significant inhibition of migration. In addition, a concentration-dependent induction of monocyte migration in the presence of recombinant MCP-1 was demonstrated. Collectively, the flavonoids quercetin, kaempferol, and luteolin were found to exert potential antiatherogenic effects in HCAEC, challenging further studies with these compounds.

Extracellular vesicles from the trematodes Fasciola hepatica and Dicrocoelium dendriticum trigger different responses in human THP-1 macrophages

Extracellular vesicles (EVs) released by the helminths Dicrocoelium dendriticum and Fasciola hepatica are important modulators of the host immune response, contributing to the establishment of the infection. Monocytes and, in particular, macrophages are major regulators of the inflammatory response and are likely responsible for the phagocytosis of most of the parasite EVs. In this study, we isolated EVs from F. hepatica (FhEVs) and D. dendriticum (DdEVs) by size exclusion chromatography (SEC) and characterized them by nanoparticle tracking analysis, transmission electron microscopy and LC-MS/MS, and analyzed the cohort of proteins. The treatment of monocytes/macrophages with FhEVs, DdEVs or EV-depleted fractions from SEC, demonstrated species-specific effects of the EVs. In particular, FhEVs reduce the migratory capacity of monocytes and the analysis of the cytokine profile showed that they induce a mixed M1/M2 response, exerting anti-inflammatory properties in Lipopolysaccharide-activated macrophages. In contrast, DdEVs do not affect monocyte migration and seem to have pro-inflammatory properties. These results correlate with the differences in the life cycle of both parasites, suggesting different host immune responses. Only F. hepatica migrates to the bile duct through the liver parenchyma, driving the host immune response to heal deep erosions. Furthermore, the proteomic analysis of the macrophages upon FhEV treatment identified several proteins that might be involved in FhEV-macrophage interactions.

Anti-Inflammatory Potential of Fucoidan for Atherosclerosis: In Silico and In Vitro Studies in THP-1 Cells

Several diseases, including atherosclerosis, are characterized by inflammation, which is initiated by leukocyte migration to the inflamed lesion. Hence, genes implicated in the early stages of inflammation are potential therapeutic targets to effectively reduce atherogenesis. Algal-derived polysaccharides are one of the most promising sources for pharmaceutical application, although their mechanism of action is still poorly understood. The present study uses a computational method to anticipate the effect of fucoidan and alginate on interactions with adhesion molecules and chemokine, followed by an assessment of the cytotoxicity of the best-predicted bioactive compound for human monocytic THP-1 macrophages by lactate dehydrogenase and crystal violet assay. Moreover, an in vitro pharmacodynamics evaluation was performed. Molecular docking results indicate that fucoidan has a greater affinity for L-and E-selectin, monocyte chemoattractant protein 1 (MCP-1), and intercellular adhesion molecule-1 (ICAM-1) as compared to alginate. Interestingly, there was no fucoidan cytotoxicity on THP-1 macrophages, even at 200 µg/mL for 24 h. The strong interaction between fucoidan and L-selectin in silico explained its ability to inhibit the THP-1 monocytes migration in vitro. MCP-1 and ICAM-1 expression levels in THP-1 macrophages treated with 50 µg/mL fucoidan for 24 h, followed by induction by IFN-γ, were shown to be significantly suppressed as eight- and four-fold changes, respectively, relative to cells treated only with IFN-γ. These results indicate that the electrostatic interaction of fucoidan improves its binding affinity to inflammatory markers in silico and reduces their expression in THP-1 cells in vitro, thus making fucoidan a good candidate to prevent inflammation.

Atorvastatin Inhibits Endothelial PAI-1-Mediated Monocyte Migration and Alleviates Radiation-Induced Enteropathy

Intestinal injury is observed in cancer patients after radiotherapy and in individuals exposed to radiation after a nuclear accident. Radiation disrupts normal vascular homeostasis in the gastrointestinal system by inducing endothelial damage and senescence. Despite advances in medical technology, the toxicity of radiation to healthy tissue remains an issue. To address this issue, we investigated the effect of atorvastatin, a commonly prescribed hydroxy-3-methylglutaryl-coenzyme A reductase inhibitor of cholesterol synthesis, on radiation-induced enteropathy and inflammatory responses. We selected atorvastatin based on its pleiotropic anti-fibrotic and anti-inflammatory effects. We found that atorvastatin mitigated radiation-induced endothelial damage by regulating plasminogen activator inhibitor-1 (PAI-1) using human umbilical vein endothelial cells (HUVECs) and mouse model. PAI-1 secreted by HUVECs contributed to endothelial dysfunction and trans-endothelial monocyte migration after radiation exposure. We observed that PAI-1 production and secretion was inhibited by atorvastatin in irradiated HUVECs and radiation-induced enteropathy mouse model. More specifically, atorvastatin inhibited PAI-1 production following radiation through the JNK/c-Jun signaling pathway. Together, our findings suggest that atorvastatin alleviates radiation-induced enteropathy and supports the investigation of atorvastatin as a radio-mitigator in patients receiving radiotherapy.

Punicalagin Regulates Key Processes Associated with Atherosclerosis in THP-1 Cellular Model

Atherosclerosis may lead to cardiovascular diseases (CVD), which are the primary cause of death globally. In addition to conventional therapeutics for CVD, use of nutraceuticals that prevents cholesterol deposition, reduce existing plaques and hence anti-atherosclerotic effects of nutraceuticals appeared to be promising. As such, in the present study we evaluated the beneficial effects of punicalagin, a phytochemical against an atherosclerotic cell model in vitro. Cytotoxicity assays were examined for 10 µM concentration of punicalagin on THP-1 macrophages. Real-time-polymerase chain reaction (RT-PCR) was used to analyze monocyte chemoattractant protein-1 (MCP-1) and Intercellular adhesion molecule (ICAM-1) expressions. Monocyte migration and cholesterol efflux assays were performed to investigate punicalagin's further impact on the key steps of atherosclerosis. Cytotoxicity assays demonstrated no significant toxicity for punicalagin (10 µM) on THP-1 macrophages. Punicalagin inhibited the IFN-γ-induced overexpression of MCP-1 and ICAM-1 in macrophages by 10 fold and 3.49 fold, respectively, compared to the control. Punicalagin also reduced the MCP-1- mediated migration of monocytes by 28% compared to the control. Percentages of cellular cholesterol efflux were enhanced in presence or absence of IFN-γ by 88% and 84% compared to control with 58 %and 62%, respectively. Punicalagin possesses anti-inflammatory and anti-atherosclerotic effects. Punicalagin also did not exhibit any cytotoxicity and therefore can be considered a safe and potential candidate for the treatment and prevention of atherosclerosis.

Post-transcriptional regulation of C-C motif chemokine ligand 2 expression by ribosomal protein L22 during LPS-mediated inflammation

Monocyte infiltration to the site of pathogenic invasion is critical for inflammatory response and host defence. However, this process demands precise regulation as uncontrolled migration of monocytes to the site delays resolution of inflammation and ultimately promotes chronic inflammation. C-C motif chemokine ligand 2 (CCL2) plays a key role in monocyte migration, and hence, its expression should be tightly regulated. Here, we report a post-transcriptional regulation of CCL2 involving the large ribosomal subunit protein L22 (RPL22) in LPS-activated, differentiated THP-1 cells. Early events following LPS treatment include transcriptional upregulation of RPL22 and its nuclear accumulation. The protein binds to the first 20 nt sequence of the 5'UTR of ccl2 mRNA. Simultaneous nuclear translocation of up-frameshift-1 protein and its interaction with RPL22 results in cytoplasmic degradation of the ccl2 mRNA at a later stage. Removal of RPL22 from cells results in increased expression of CCL2 in response to LPS causing disproportionate migration of monocytes. We propose that post-transcriptional regulation of CCL2 by RPL22 fine-tunes monocyte infiltration during a pathogenic insult and maintains homeostasis of the immune response critical to resolution of inflammation. DATABASES: Microarray data are available in NCBI GEO database (Accession No GSE126525).

The Role of Butyrate on Monocyte Migration and Inflammation Response in Patient with Type 2 Diabetes Mellitus

Type 2 Diabetes Mellitus (T2DM) is a very serious global problem. In Indonesia, this disease attacks at the most productive age; consequently, it can reduce economic status and life expectancy. The pathogenesis of T2DM is very closely related to inflammation and macrophage accumulation. However, no anti-inflammatory agent has been proven to play a role in the management of T2DM. Butyrate is a short chain fatty acid produced from resistant starch fermentation in the intestinal lumen. It is able to bind to GPR41 and GPR43 receptors on monocytes, so that it can change the pattern of cytokine expression, activation, migration and cell differentiation. Hence, it is interesting to examine the anti-inflammation effect of butyrate and the effect on monocyte migration. A total of 37 subjects were examined in this study. They were divided into two groups, with and without butyrate treatment. We analyzed two pro-inflammatory cytokines (Tumor Necrosis Factor TNF-α and Interleukin IL-6) and one anti-inflammatory cytokine, IL 10. Monocytes were isolated in type 1 collagen gel for migration testing using the µ-slide chemotaxis IBIDI. Image analysis used ImageJ and Chemotaxis tool software. There was a significant difference in the TNFα/IL 10 ratio between healthy groups and T2DM. Butyrate also appears to suppress TNFα cytokine production and increase IL10 production. It also decreases the accumulation distance of monocyte migration in T2DM.

HIV-1-Induced miR-146a Attenuates Monocyte Migration by Targeting CCL5 in Human Primary Macrophages

MicroRNAs (miRNAs) are widely involved in immune regulation during virus infection. Several studies showed that the expression of miR-146a was increased in human immunodeficiency virus type I (HIV-1)-infected cells, but the definitive function of miR-146a in HIV-1 infection remains obscure. The production of chemokine (C-C motif) ligand 5 (CCL5) in macrophages has been reported to play an important role in HIV/AIDS-associated pathogenesis. In this study, we examined the effects of miR-146a on CCL5 regulation in HIV-1-infected macrophages. Gain and loss of function studies showed that CCL5 might be one of the miR-146a targets, as miR-146a mimic reduced, while miR-146a inhibitor increased CCL5 production in HIV-1-infected macrophages. In addition, we demonstrated that miR-146a reduced CCL5-induced monocyte migration. Our study provided evidence that miR-146a targets CCL5 3' untranslated regions, downregulates its release from macrophages, and affects monocyte migration consequently. These findings drew a novel layer of posttranscriptional control of the chemokine CCL5 by miR-146a during HIV infection, which might contribute to HIV pathogenesis.

Heterogeneity of Bovine Peripheral Blood Monocytes

Peripheral blood monocytes of several species can be divided into different subpopulations with distinct phenotypic and functional properties. Herein, we aim at reviewing published work regarding the heterogeneity of the recently characterized bovine monocyte subsets. As the heterogeneity of human blood monocytes was widely studied and reviewed, this work focuses on comparing bovine monocyte subsets with their human counterparts regarding their phenotype, adhesion and migration properties, inflammatory and antimicrobial functions, and their ability to interact with neutrophilic granulocytes. In addition, the differentiation of monocyte subsets into functionally polarized macrophages is discussed. Regarding phenotype and distribution in blood, bovine monocyte subsets share similarities with their human counterparts. However, many functional differences exist between monocyte subsets from the two species. In contrast to their pro-inflammatory functions in human, bovine non-classical monocytes show the lowest phagocytosis and reactive oxygen species generation capacity, an absent ability to produce the pro-inflammatory cytokine IL-1β after inflammasome activation, and do not have a role in the early recruitment of neutrophils into inflamed tissues. Classical and intermediate monocytes of both species also differ in their response toward major monocyte-attracting chemokines (CCL2 and CCL5) and neutrophil degranulation products (DGP) in vitro. Such differences between homologous monocyte subsets also extend to the development of monocyte-derived macrophages under the influence of chemokines like CCL5 and neutrophil DGP. Whereas the latter induce the differentiation of M1-polarized macrophages in human, bovine monocyte-derived macrophages develop a mixed M1/M2 macrophage phenotype. Although only a few bovine clinical trials analyzed the correlation between changes in monocyte composition and disease, they suggest that functional differences between human and bovine monocyte subsets are also reflected in their different clinical relevance for distinct diseases. In opposite to the human system, where higher blood cell number of non-classical monocytes was widely correlated with several human infectious and non-infectious diseases, higher counts of bovine intermediate monocytes are suggested as a potential biomarker for inflammatory responses postpartum.

Contracting C2C12 myotubes release CCL2 in an NF-κB-dependent manner to induce monocyte chemoattraction

Muscle inflammation following exercise is characterized by expression of inflammatory cytokines and chemokines. Exercise also increases muscle macrophages derived from circulating monocytes. However, it is unknown whether muscle cells themselves attract circulating monocytes, or what is the underlying mechanism. We used an in vitro system of electrical stimulation (ES) causing C2C12 myotube contraction to explore whether monocyte chemoattraction ensues and investigated the mediating chemoattractants. Conditioned medium from ES-contracted myotubes caused robust chemoattraction of THP-1 monocytes across Boyden chambers. Following ES, expression of several known monocyte chemokines [C-C motif ligand 2 (CCL2) and C-X-C motif ligand (CXCL)1, -2, and -5] was elevated, but of these, only recombinant CCL2 effectively reproduced monocyte migration. Electrically stimulated myotubes secreted CCL2, and neutralization of CCL2 in conditioned medium or antagonizing the CCL2 receptor (CCR2) in THP-1 monocytes inhibited ES-induced monocyte migration. N-benzyl-p-toluene sulfonamide (BTS), a myosin II-ATPase inhibitor, prevented ES-induced myotube contraction but not CCL2 gene expression and secretion. The membrane-permeant calcium chelator BAPTA-AM reduced ES-induced CCL2 secretion. Hence, electrical depolarization, rather than mechanical contraction, drives the rise in CCL2, with partial calcium input. ES activated the NF-κB pathway; NF-κB inhibitors reduced ES-induced CCL2 gene expression and secretion and repressed ES-induced THP-1 chemoattraction. Thus, electrically stimulated myotubes chemoattract monocytes through NF-κB-regulated CCL2 secretion.

IVIG inhibits TNF-α-induced MMP9 expression and activity in monocytes by suppressing NF-κB and P38 MAPK activation

Matrix metalloproteinase-9 (MMP9) has been involved in inflammatory and pathologic processes of coronary artery lesions (CAL) in Kawasaki disease (KD). Intravenous immunoglobulin (IVIG), a traditional treatment for Kawasaki disease, could decrease the expressions of MMP9. The purpose of this study was to investigate the protective effect of IVIG in chemotactic migration of monocyte and the regulation of MMP9 induced by tumor necrosis factor-α (TNF-α) in U937s. Studies were carried out with real time polymerase chain reaction (RT-PCR), zymographic, Western blotting and immunofluorescence. U937s' migration was enhanced by TNF-α stimulation, while was inhibited by IVIG pretreatment. MMP9 expression and activity in U937s were also significantly enhanced by TNF-α and inhibited by IVIVG pretreatment. During inflammatory stimulus, nuclear factor kappa B (NF-κB) and P38 Mitogenactivated protein kinase (P38 MAPK) pathways play a significant role in regulating MMP9 gene expression. TNF-α induced nuclear translocation of NF-κB and P38 MAPK activation in U937s were inhibited significantly by IVIG. Furthermore, we clarified that nuclear NF-κB and P38 MAPK pathways play pivotal roles in regulating U937s' migration and MMP9 expressions using PDTC and SB203580, which were specific inhibitors of NF-κB and p38 MAPK pathways. IVIG displays striking biological effects, notably promoting monocyte migration. These effects involve the NF-κB and p38 pathways, and increased MMP9 activity. It might be a crucial mechanism of IVIG reducing the occurrence of CAL that IVIG inhibited monocytes expressing MMP9 and decreased chemotactic migration of monocyte.

Inflammation-induced chemokine expression in uveal melanoma cell lines stimulates monocyte chemotaxis

PURPOSE

Uveal melanoma (UM) is the most common primary intraocular tumor in adults and the presence of infiltrating leucocytes is associated with a poor prognosis. Little is known how infiltrating leucocytes influence the tumor cells. The purpose of this study was to investigate the effect of activated T cells on the expression of chemotactic cytokines in UM cells. Furthermore, we examined the ability of stimulated UM cells to attract monocytes.

METHODS

We used an in vitro coculture system in which UM cell lines and T cells were cultured together, but separated by a membrane. Uveal melanoma gene expression was quantified using a microarray. Protein expression in the supernatant was quantified with ELISA or cytometric bead array. For the monocyte migration assay, a transwell plate was used.

RESULTS

Gene-expression analysis of UM cell lines showed that coculture with activated T cells resulted in an upregulation of chemokines such as CXCL8, CXCL9, CXCL10, CXCL11, CCL2, CCL5, VEGF, intracellular adhesion molecule 1 (ICAM1), and granulocyte-macrophage colony-stimulating factor (GM-CSF). The upregulation of these molecules was confirmed at the protein level. This increase of chemokines coincided with an increased chemotactic capacity of the supernatant toward monocytes.

CONCLUSIONS

Cytokines derived from activated T cells shifted the UM cell transcriptome toward a more inflammatory state, including upregulation of several chemokines, which led to an increased migration of monocytes. Therefore, UM cells might actively participate in generating a tumor-promoting inflammatory microenvironment.

Inflammatory response of prostate epithelial cells to stimulation by Trichomonas vaginalis

BACKGROUND

Trichomonas vaginalis is known as the most common cause of sexually transmitted infection. However, its prevalence may have been underestimated. Trichomonads are detected in prostatic tissue in benign prostatic hyperplasia, prostatitis, and prostate cancer. Our objective was to investigate whether T. vaginalis could induce an inflammatory response in prostate epithelium.

METHODS

The cytokine production by human prostate epithelial cell (RWPE-1) activated with T. vaginalis was determined by ELISA and real-time PCR. Intracellular ROS was evaluated by flow cytometry or spectrofluorometry. The protein levels of MAP kinase, NF-κB were analyzed by Western blot. The migration of neutrophil and monocyte were performed in 24-well microplates with filter insert.

RESULTS

Incubation of cells of a human prostate epithelial cell line with a live T. vaginalis T016 isolate increased expression of the inflammatory mediators IL-1β, CCL2, and CXCL8. In addition, ROS, MAPK, and NF-κB activities increased, while inhibitors of ROS, ERK, and NF-κB reduced IL-1β production. Medium conditioned by incubation of RWPE-1 cells with T. vaginalis contained IL-1β and stimulated the migration of human neutrophils and monocytes (THP-1 cell line).

CONCLUSIONS

We conclude that T. vaginalis may increase IL-1β expression in human prostate epithelium through activation of ROS, ERK, and NF-κB, and this in turn may induce the migration of neutrophils and monocytes and lead to an inflammatory response. This research is the first attempt to confirm inflammatory reaction caused by T. vaginalis in prostate epithelial cell.

MCP-1 binds to oxidized LDL and is carried by lipoprotein(a) in human plasma

Lipoprotein oxidation plays an important role in pathogenesis of atherosclerosis. Oxidized low density lipoprotein (OxLDL) induces profound inflammatory responses in vascular cells, such as production of monocyte chemoattractant protein-1 (MCP-1) [chemokine (C-C motif) ligand 2], a key chemokine in the initiation and progression of vascular inflammation. Here we demonstrate that OxLDL also binds MCP-1 and that the OxLDL-bound MCP-1 retains its ability to recruit monocytes. A human MCP-1 mutant in which basic amino acids Arg-18 and Lys-19 were replaced with Ala did not bind to OxLDL. The MCP-1 binding to OxLDL was inhibited by the monoclonal antibody E06, which binds oxidized phospholipids (OxPLs) in OxLDL. Because OxPLs are carried by lipoprotein(a) [Lp(a)] in human plasma, we tested to determine whether Lp(a) binds MCP-1. Recombinant wild-type but not mutant MCP-1 added to human plasma bound to Lp(a), and its binding was inhibited by E06. Lp(a) captured from human plasma contained MCP-1 and the Lp(a)-associated endogenous MCP-1 induced monocyte migration. These results demonstrate that OxLDL and Lp(a) bind MCP-1 in vitro and in vivo and that OxPLs are major determinants of the MCP-1 binding. The association of MCP-1 with OxLDL and Lp(a) may play a role in modulating monocyte trafficking during atherogenesis.

Lysophosphatidylcholine activates a novel PKD2-mediated signaling pathway that controls monocyte migration

OBJECTIVE

Monocyte activation and migration are crucial events in the development of atherosclerosis and other inflammatory diseases. This study examined the role of protein kinase D (PKD) in monocyte migration. Method and Results- PKD2 is the predominant isoform of PKD expressed in monocytic THP-1 cells and primary human monocytes. Lysophosphatidylcholine (lysoPC), a prominent component of oxidized low-density lipoprotein, induces rapid and marked PKD activation in these cells. Using multiple approaches, including dominant-negative mutants and small interfering RNA knock-down, we found that lysoPC-induced PKD2 activation was required for the activation of both ERK and p38 MAPK. p38 MAPK mediation of lysoPC-induced monocytic cell migration was reported previously; our results reveal that the lysoPC-induced PKD2-p38 pathway controls monocyte migration.

CONCLUSIONS

This study provides the first evidence that (1) lysoPC activates PKD, (2) PKD2 has a novel role in p38 activation, and (3) the PKD2-activated p38 pathway is responsible for lysoPC-induced migration of THP-1 cells and human monocytes. Thus, PKD is a novel and functional intracellular regulator in both lysoPC signaling and monocyte migration. These results suggest a new role for PKD2 in the development of atherosclerosis and other inflammatory diseases.

Monocyte-chemoattractant-protein-1-mediated migration of human monocytes towards blasts from patients with acute myeloid leukemia

PURPOSE

In the present study the possible clinical relevance of monocyte chemoattractant protein (MCP)-1 in patients with acute myeloid leukemia (AML) was established.

METHODS

The pattern of migration of human monocytes towards the supernatants of blasts from 15 patients with AML was studied and the role of MCP-1, produced by these blasts, was assessed.

RESULTS

In 4 patients (group 1) the amount of monocyte migration was low and not inhibited by the addition of anti-hMCP-1. In 11 patients, the amount of monocyte migration was high; after addition of anti-hMCP-1, monocyte migration was either completely (8 patients, group 2), or partly or not (3 patients, group 3) inhibited to the level of chemokinesis. In groups 1 and 2, there was a good correlation (r = 0.67) between the concentration of MCP-1 in the supernatants and the amount of monocyte migration. In group 3, such a correlation was not evident, suggesting that another chemokine might be involved or MCP-1 function was impaired by an unknown substance. Finally, measurements of MCP-1 during culture of AML blasts showed that the time at which maximal amounts of MCP-1 are produced differs between the AML samples.

CONCLUSIONS

AML blasts produce different amounts of MCP-1, which plays an important role in monocyte migration towards most AML blasts. Therefore, in the context of adoptive immunotherapy, MCP-1 might be involved in future tumor vaccination programmes using autologous MCP-1-transfected irradiated AML blasts.