An Antibody-Drug Conjugate That Selectively Targets Human Monocyte Progenitors for Anti-Cancer Therapy.

As hematopoietic progenitors supply a large number of blood cells, therapeutic strategies targeting hematopoietic progenitors are potentially beneficial to eliminate unwanted blood cells, such as leukemic cells and immune cells causing diseases. However, due to their pluripotency, targeting those cells may impair the production of multiple cell lineages, leading to serious side effects such as anemia and increased susceptibility to infection. To minimize those side effects, it is important to identify monopotent progenitors that give rise to a particular cell lineage. Monocytes and monocyte-derived macrophages play important roles in the development of inflammatory diseases and tumors. Recently, we identified human monocyte-restricted progenitors, namely, common monocyte progenitors and pre-monocytes, both of which express high levels of CD64, a well-known monocyte marker. Here, we introduce a dimeric pyrrolobenzodiazepine (dPBD)-conjugated anti-CD64 antibody (anti-CD64-dPBD) that selectively induces the apoptosis of proliferating human monocyte-restricted progenitors but not non-proliferating mature monocytes. Treatment with anti-CD64-dPBD did not affect other types of hematopoietic cells including hematopoietic stem and progenitor cells, neutrophils, lymphocytes and platelets, suggesting that its off-target effects are negligible. In line with these findings, treatment with anti-CD64-dPBD directly killed proliferating monocytic leukemia cells and prevented monocytic leukemia cell generation from bone marrow progenitors of chronic myelomonocytic leukemia patients in a patient-derived xenograft model. Furthermore, by depleting the source of monocytes, treatment with anti-CD64-dPBD ultimately eliminated tumor-associated macrophages and significantly reduced tumor size in humanized mice bearing solid tumors. Given the selective action of anti-CD64-dPBD on proliferating monocyte progenitors and monocytic leukemia cells, it should be a promising tool to target cancers and other monocyte-related inflammatory disorders with minimal side effects on other cell lineages.

Estrogens decrease osteoclast number by attenuating mitochondria oxidative phosphorylation and ATP production in early osteoclast precursors.

Loss of estrogens at menopause is a major cause of osteoporosis and increased fracture risk. Estrogens protect against bone loss by decreasing osteoclast number through direct actions on cells of the myeloid lineage. Here, we investigated the molecular mechanism of this effect. We report that 17ß-estradiol (E2) decreased osteoclast number by promoting the apoptosis of early osteoclast progenitors, but not mature osteoclasts. This effect was abrogated in cells lacking Bak/Bax-two pro-apoptotic members of the Bcl-2 family of proteins required for mitochondrial apoptotic death. FasL has been previously implicated in the pro-apoptotic actions of E2. However, we show herein that FasL-deficient mice lose bone mass following ovariectomy indistinguishably from FasL-intact controls, indicating that FasL is not a major contributor to the anti-osteoclastogenic actions of estrogens. Instead, using microarray analysis we have elucidated that ERα-mediated estrogen signaling in osteoclast progenitors decreases "oxidative phosphorylation" and the expression of mitochondria complex I genes. Additionally, E2 decreased the activity of complex I and oxygen consumption rate. Similar to E2, the complex I inhibitor Rotenone decreased osteoclastogenesis by promoting osteoclast progenitor apoptosis via Bak/Bax. These findings demonstrate that estrogens decrease osteoclast number by attenuating respiration, and thereby, promoting mitochondrial apoptotic death of early osteoclast progenitors.

Different monocyte phenotypes result in proresolving macrophages in conjugated linoleic acid-induced attenuated progression and regression of atherosclerosis.

Monocytes/macrophages drive progression and regression of atherosclerosis. Conjugated linoleic acid (CLA), an anti-inflammatory lipid, mediates atheroprotective effects. We investigated how CLA alters monocyte/macrophage phenotype during attenuated progression and regression of atherosclerosis. Apolipoprotein E knockout (ApoE-/-) mice were fed a high-fat (60%) high-cholesterol (1%) diet (HFHCD) for 2 wk, followed by 6-wk 1% CLA 80:20 supplementation to investigate disease progression. Simultaneously, ApoE-/- mice were fed a 12-wk HFHCD with/without CLA for the final 4 wk to investigate regression. Aortic lesions were quantified by en face staining. Proteomic analysis, real-time quantitative PCR and flow cytometry were used to interrogate monocyte/macrophage phenotypes. CLA supplementation inhibited atherosclerosis progression coincident with decreased proinflammatory and increased anti-inflammatory macrophages. However, CLA-induced regression was associated with increased proinflammatory monocytes resulting in increased proresolving M2 bone marrow-derived macrophages, splenic macrophages, and dendritic cells in lesion-draining lymph nodes. Proteomic analysis confirmed regulation of a proinflammatory bone marrow response, which was abolished upon macrophage differentiation. Thus, in attenuation and regression of atherosclerosis, regardless of the monocyte signature, during monocyte to macrophage differentiation, proresolving macrophages prevail, mediating vascular repair. This study provides novel mechanistic insight into the monocyte/macrophage phenotypes in halted atherosclerosis progression and regression of atherosclerosis.-Bruen, R., Curley, S., Kajani, S., Lynch, G., O'Reilly, M. E., Dillon, E. T., Fitzsimons, S., Mthunzi, L., McGillicuddy, F. C., Belton, O. Different monocyte phenotypes result in proresolving macrophages in conjugated linoleic acid-induced attenuated progression and regression of atherosclerosis.

Hyaluronan preconditioning of monocytes/macrophages affects their angiogenic behavior and regulation of TSG-6 expression in a tumor type-specific manner.

Hyaluronan is a glycosaminoglycan normally present in the extracellular matrix in most tissues. Hyaluronan is a crucial player in many processes associated with cancer, such as angiogenesis, invasion, and metastasis. However, little has been reported regarding the action of hyaluronan on monocytes/macrophages (Mo/MØ) in tumor angiogenesis and its consequences on tumor development. In the present study, we investigated the effects of hyaluronan of different sizes on human Mo/MØ angiogenic behavior in colorectal and breast carcinoma. In vitro, the treatment of Mo/MØ with lysates and conditioned media from a breast but not from colorectal carcinoma cell line plus high-molecular weight hyaluronan induced: (a) an increased expression of angiogenic factors VEGF, IL-8, FGF-2, and MMP-2, (b) an increased endothelial cell migration, and (c) a differential expression of hyaluronan-binding protein TSG-6. Similar results were observed in Mo/MØ derived from breast cancer patients treated with tumor lysates. Besides, macrophages primed with high-molecular weight hyaluronan and inoculated in human breast cancer xenograft tumor increased blood vessel formation and diminished TSG-6 levels. In contrast, the effects triggered by high-molecular weight hyaluronan on Mo/MØ in breast cancer context were not observed in the context of colorectal carcinoma. Taken together, these results indicate that the effect of high-molecular weight hyaluronan as an inductor of the angiogenic behavior of macrophages in breast tumor context is in part consequence of the presence of TSG-6.

The role of autophagy in survival response induced by 27-hydroxycholesterol in human promonocytic cells.

Autophagy has been shown to be stimulated in advanced atherosclerotic plaques by metabolic stress, inflammation and oxidized lipids. The lack of published studies addressing the potential stimulation of pro-survival autophagy by oxysterols, a family of cholesterol oxidation products, has prompted our study. Thus, the goal of the current study is to elucidate the molecular mechanism of the autophagy induced by 27-hydroxycholesterol (27-OH), that is one of the most abundant oxysterols in advanced atherosclerotic lesions, and to assess whether the pro-oxidant effect of the oxysterol is involved in the given response. Here we showed that 27-OH, in a low micromolar range, activates a pro-survival autophagic response in terms of increased LC3 II/LC3 I ratio and Beclin 1, that depends on the up-regulation of extracellular signal-regulated kinase (ERK) and phosphoinositide 3-kinase (PI3K)/Akt pathways as a potential result of an intracellular reactive oxygen species increase provoked by the oxysterol in human promonocytic U937 cells. Moreover, 27-OH induced autophagy is dependent on the relation between nuclear factor erythroid 2 p45-related factor 2 (Nrf2)-dependent antioxidant response and p62. The data obtained highlight the involvement of cholesterol oxidation products in the pathogenesis of oxidative stress related chronic diseases like atherosclerosis. Therefore, deeply understanding the complex mechanism and generating synthetic or natural molecules targeting this survival mechanism might be very promising tools in the prevention of such diseases.

Nrf2 antioxidant defense is involved in survival signaling elicited by 27-hydroxycholesterol in human promonocytic cells.

Cholesterol oxidation products such as oxysterols are considered critical factors in the atherosclerotic plaque formation since they induce oxidative stress, inflammation and apoptotic cell death. 27-hydroxycholesterol (27-OH) is one of the most represented oxysterols in atherosclerotic lesions. We recently showed that relatively low concentrations of 27-OH generated a strong survival signaling through an early and transient increase of cellular ROS level, that enhanced MEK-ERK/PI3K-Akt phosphorylation, in turn responsible of a sustained quenching of ROS production. It remains to identify the link between ERK/Akt up-regulation and the consequent quenching effect on ROS intracellular level that efficiently and markedly delay the pro-apoptotic effect of the oxysterol. Here we report on the potent activation of Nrf2 redox-sensitive transcription factor by low micromolar amount of 27-OH added to U937 promonocytic cells. The 27-OH-exerted induction of Nrf2 and subsequently of the target genes, HO-1 and NQO-1, was proved to be: (i) dependent upon the activation of ERK and Akt pathways, (ii) directly responsible for the quenching of intracellular oxidative stress and by this way (iii) ultimately responsible for the observed oxysterol-induced pro-survival response.

ARHGEF3 controls HDACi-induced differentiation via RhoA-dependent pathways in acute myeloid leukemias.

Altered expression and activity of histone deacetylases (HDACs) have been correlated with tumorigenesis. Inhibitors of HDACs (HDACi) induce acetylation of histone and non-histone proteins affecting gene expression, cell cycle progression, cell migration, terminal differentiation and cell death. Here, we analyzed the regulation of ARHGEF3, a RhoA-specific guanine nucleotide exchange factor, by the HDACi MS275 (entinostat). MS275 is a well-known benzamide-based HDACi, which induces differentiation of the monoblastic-like human histiocytic lymphoma cell line U937 to monocytes/macrophages. Incubation of U937 cells with MS275 resulted in an up regulation of ARHGEF3, followed by a significant enhancement of the marker of macrophage differentiation CD68. ARHGEF3 protein is primarily nuclear, but MS275 treatment rapidly induced its translocation into the cytoplasm. ARHGEF3 cytoplasmic localization is associated with activation of the RhoA/Rho-associated Kinase (ROCK) pathway. In addition to cytoskeletal rearrangements orchestrated by RhoA, we showed that ARHGEF3/RhoA-dependent signals involve activation of SAPK/JNK and then Elk1 transcription factor. Importantly, MS275-induced CD68 expression was blocked by exposure of U937 cells to exoenzyme C3 transferase and Y27632, inhibitors of Rho and ROCK respectively. Moreover, ARHGEF3 silencing prevented RhoA activation leading to a reduction in SAPK/JNK phosphorylation, Elk1 activation and CD68 expression, suggesting a crucial role for ARHGEF3 in myeloid differentiation. Taken together, our results demonstrate that ARHGEF3 modulates acute myeloid leukemia differentiation through activation of RhoA and pathways directly controlled by small GTPase family proteins. The finding that GEF protein modulation by HDAC inhibition impacts on cell differentiation may be important for understanding the antitumor mechanism(s) by which HDACi treatment stimulates differentiation in cancer.

Nickel ions from a corroded cardiovascular stent induce monocytic cell apoptosis: Proposed impact on vascular remodeling and mechanism.

BACKGROUND/PURPOSE: Monocytes play important roles in inflammatory responses and vascular remodeling after vascular stenting. This research focused on impacts of nickel (Ni) ions released from a corroded cardiovascular stent on cytotoxicity and monocyte activation. METHODS: A human promonocytic (macrophage-like) cell line (U937) was exposed to graduated concentrations of Ni(2+)in vitro. Cells were observed and harvested at indicated times to determine the effects using histological and biochemical methods. RESULTS: Ni caused U937 cell death in dose- and time-dependent manners. In vitro, high concentrations of Ni(2+) (>240 µM) significantly induced cell apoptosis and increased terminal deoxynucleotidyl transferase (TdT) dUTP nick end labeling (TUNEL)-positive cells according to flow cytometric surveillance and triggered apoptotic cell death. Although no significant changes in Bcl-2 or Bax expressions were detected after 24 hours of Ni(2+) treatment, increasing cleavage of caspase-3 and -8 was present. Results showed that cleavage of caspase-8 was inhibited by the presence of the inhibitor, Z-IETD-FMK, and this suggested the presence of Ni(2+)-induced U937 cell death through a death receptor-mediated pathway. Simultaneously, when treated with a high concentration of Ni(2+) ions, expressions of the vascular remodeling factors, matrix metalloproteinases (MMP)-9 and -2, were activated in dose- and time-dependent manners. Secretion of the proliferative factor, monocyte chemoattractant protein (MCP)-1, significantly increased during the first 6 hours of incubation with 480 µM Ni(2+)-treated medium. CONCLUSION: Our results demonstrated that a high concentration of Ni ions causes apoptotic cell death of circulating monocytes. They may also play different roles in vascular remodeling during the corrosion process following implantation of Ni alloy-containing devices.

BMP-7 attenuates adverse cardiac remodeling mediated through M2 macrophages in prediabetic cardiomyopathy.

The main objective of this study was to determine whether or not monocyte infiltration occurs in the prediabetic (PD) heart and its role in PD cardiomyopathy. We hypothesized that the PD heart is significantly populated with monocytes and that bone morphogenetic protein (BMP)-7, a novel mediator of monocyte polarization, activates infiltrated monocytes into anti-inflammatory M2 macrophages, thereby inhibiting apoptosis and fibrosis and improving cardiac function. C57Bl6 mice were assigned to control, PD, or PD + BMP-7 groups. PD and PD + BMP-7 groups were administered streptozotocin (50 mg/kg), whereas control animals received sodium citrate buffer. Afterward, the PD + BMP-7 group was administered BMP-7 (200 µg/kg) for 3 days. Our data showed significantly increased infiltrated monocytes and associated pro-inflammatory cytokines, adverse cardiac remodeling, and heart dysfunction in the PD group (P < 0.05). Interestingly, M2 macrophage differentiation and associated anti-inflammatory cytokines were enhanced and there were reduced adverse cardiac remodeling and improved cardiac function in the PD + BMP-7 group (P < 0.05). In conclusion, our data suggest that PD cardiomyopathy is associated with increased monocyte infiltration and released proinflammatory cytokines, which contributes to adverse cardiac remodeling and cardiac dysfunction. Moreover, we report that BMP-7 possesses novel therapeutic potential in its ability to differentiate monocytes into M2 macrophages and confer cardiac protection in the PD heart.

Hematopoietic expression of oncogenic BRAF promotes aberrant growth of monocyte-lineage cells resistant to PLX4720.

UNLABELLED: Mutational activation of BRAF leading to expression of the BRAF(V600E) oncoprotein was recently identified in a high percentage of specific hematopoietic neoplasms in monocyte/histiocyte and mature B-cell lineages. Although BRAF(V600E) is a driver oncoprotein and pharmacologic target in solid tumors such as melanoma, lung, and thyroid cancer, it remains unknown whether BRAF(V600E) is an appropriate therapeutic target in hematopoietic neoplasms. To address this critical question, we generated a mouse model expressing inducible BRAF(V600E) in the hematopoietic system, and evaluated the efficacy of pathway-targeted therapeutics against primary hematopoietic cells. In this model, BRAF(V600E) expression conferred cytokine-independent growth to monocyte/macrophage-lineage progenitors leading to aberrant in vivo and in vitro monocyte/macrophage expansion. Furthermore, transplantation of BRAF(V600E)-expressing bone marrow cells promoted an in vivo pathology most notable for monocytosis in hematopoietic tissues and visceral organs. In vitro analysis revealed that MAP-ERK kinase inhibition, but not RAF inhibition, effectively suppressed cytokine-independent clonal growth of monocyte/macrophage-lineage progenitors. However, combined RAF and phosphoinositide 3-kinase (PI3K) inhibition effectively inhibited cytokine-independent colony formation, suggesting autocrine PI3K pathway activation. Taken together, these results provide evidence that constitutively activated BRAF(V600E) drives aberrant proliferation of monocyte-lineage cells. IMPLICATIONS: This study supports the development of pathway-targeted therapeutics in the treatment of BRAF(V600E)-expressing hematopoietic neoplasms in the monocyte/histiocyte lineage.

Recurring BALB/c mouse lung inflammatory responses to episodic allergen exposure.

This study detailed the sequence of recurring inflammatory events associated with episodic allergen exposures of mice resulting in airway hyperreactivity, sustained inflammation, goblet-cell hyperplasia, and fibrogenesis that characterize a lung with chronic asthma. Ovalbumin (OVA)-sensitized female BALB/c mice were exposed to saline-control or OVA aerosols for 1 h per day for episodes of 3 d/wk for up to 8 wk. Lung inflammation was assessed by inflammatory cell recoveries using bronchoalveolar lavages (BAL) and tissue collagenase dispersions. Cell accumulations were observed within airway submucosal and associated perivascular spaces using immunohistochemical and tinctorial staining methods. Airway responsiveness to methacholine aerosols were elevated after 2 wk and further enhanced to a sustained level after wk 4 and 8. Although by wk 8 diminished OVA-induced accumulations of eosinophils, neutrophils, and monocyte-macrophages were observed, suggesting diminished responsiveness, the BAL recovery of lymphocytes remained elevated. Airway but not perivascular lesions persisted with a proliferating cell population, epithelial goblet-cell hyperplasia, and evidence of enhanced collagen deposition. Examination of lung inflammatory cell content before the onset of the first, second, and fourth OVA exposure episodes demonstrated enhancements in residual BAL lymphocyte and BAL and tissue eosinophil recoveries with each exposure episode. Although tissue monocyte-macrophage numbers returned to baseline prior to each exposure episode, the greatest level of accumulation was observed after wk 4. These results provide the basis for establishing the inflammatory and exposure criteria by which episodic environmental exposures to allergen might result in the development of a remodeled lung in asthma.

Correlation between TGF-ß1 expression and proteomic profiling induced by severe acute respiratory syndrome coronavirus papain-like protease.

Severe acute respiratory syndrome (SARS) coronavirus (SARS-CoV) papain-like protease (PLpro), a deubiquitinating enzyme, demonstrates inactivation of interferon (IFN) regulatory factor 3 and NF-κB, reduction of IFN induction, and suppression of type I IFN signaling pathway. This study investigates cytokine expression and proteomic change induced by SARS-CoV PLpro in human promonocyte cells. PLpro significantly increased TGF-ß1 mRNA expression (greater than fourfold) and protein production (greater than threefold). Proteomic analysis, Western blot, and quantitative real-time PCR assays indicated PLpro upregulating TGF-ß1-associated genes: HSP27, protein disulfide isomerase A3 precursor, glial fibrillary acidic protein, vimentin, retinal dehydrogenase 2, and glutathione transferase omega-1. PLpro-activated ubiquitin proteasome pathway via upregulation of ubiquitin-conjugating enzyme E2-25k and proteasome subunit alpha type 5. Proteasome inhibitor MG-132 significantly reduced expression of TGF-ß1 and vimentin. PLpro upregulated HSP27, linking with activation of p38 MAPK and ERK1/2 signaling. Treatment with SB203580 and U0126 reduced PLpro-induced expression of TGF-ß1, vimentin, and type I collagen. Results point to SARS-CoV PLpro triggering TGF-ß1 production via ubiquitin proteasome, p38 MAPK, and ERK1/2-mediated signaling.

In vitro effects of pulmonary surfactant on macrophage morphology and function.

The effects of pulmonary surfactant on the morphology and functioning of young macrophages were studied on the model of monocyte/macrophage differentiation in vitro and on macrophages of the bronchial alveolar lavage fluid. Surfactant is not a differentiation inductor, but it stimulated the maturation and phagocytic activity of young macrophages. The stimulatory effect of surfactant on phagocytic activity of macrophages persisted even after its removal from the culture medium.

BET bromodomain inhibition as a novel strategy for reactivation of HIV-1.

The persistence of latent HIV-1 remains a major challenge in therapeutic efforts to eradicate infection. We report the capacity for HIV reactivation by a selective small molecule inhibitor of BET family bromodomains, JQ1, a promising therapeutic agent with antioncogenic properties. JQ1 reactivated HIV transcription in models of latent T cell infection and latent monocyte infection. We also tested the effect of exposure to JQ1 to allow recovery of replication-competent HIV from pools of resting CD4(+) T cells isolated from HIV-infected, ART-treated patients. In one of three patients, JQ1 allowed recovery of virus at a frequency above unstimulated conditions. JQ1 potently suppressed T cell proliferation with minimal cytotoxic effect. Transcriptional profiling of T cells with JQ1 showed potent down-regulation of T cell activation genes, including CD3, CD28, and CXCR4, similar to HDAC inhibitors, but JQ1 also showed potent up-regulation of chromatin modification genes, including SIRT1, HDAC6, and multiple lysine demethylases (KDMs). Thus, JQ1 reactivates HIV-1 while suppressing T cell activation genes and up-regulating histone modification genes predicted to favor increased Tat activity. Thus, JQ1 may be useful in studies of potentially novel mechanisms for transcriptional control as well as in translational efforts to identify therapeutic molecules to achieve viral eradication.

Zinc induces chemokine and inflammatory cytokine release from human promonocytes.

Our previous studies found that zinc oxide (ZnO) particles induced expression of intercellular adhesion molecule-1 (ICAM-1) protein in vascular endothelial cells via NF-κB and that zinc ions dissolved from ZnO particles might play the major role in the process. This study aimed to determine if zinc ions could cause inflammatory responses in a human promonocytic leukemia cell line HL-CZ. Conditioned media from the zinc-treated HL-CZ cells induced ICAM-1 protein expression in human umbilical vein endothelial cells (HUVEC). Zinc treatment induced chemokine and inflammatory cytokine release from HL-CZ cells. Inhibition of NFκB activity by over-expression of IκBα in HL-CZ cells did not block the conditioned medium-induced ICAM-1 protein expression in HUVEC cells. Zinc treatment induced activation of multiple immune response-related transcription factors in HL-CZ cells. These results clearly show that zinc ions induce chemokine and inflammatory cytokine release from human promonocytes, accompanied with activation of multiple immune response-related transcription factors. Our in vitro evidence in the zinc-induced inflammatory responses of vascular cells provides a critical linkage between zinc exposure and pathogenesis of those inflammatory vascular diseases.

Administration of zinc inhibits osteoclastogenesis through the suppression of RANK expression in bone.

Zinc (Zn) has been known to inhibit osteoclastic bone resorption and stimulate osteoblastic bone formation. However, the mechanisms responsible for these effects have not been well characterized in vivo. Here, the effects of a dietary administration of Zn on osteoclastogenesis and osteoblastogenesis were investigated in Zn-adequate rats. The administration of Zn decreased the activities of bone tartrate-resistant acid phosphatase (TRAP) and cathepsin K, without affecting the serum osteocalcin level. Histological analysis showed a decrease in the number of osteoclasts with a normal number of osteoblasts in the metaphysis of the proximal tibia. The mRNA levels of receptor for activation of NF-κB (RANK), c-fos, c-jun, TRAP and cathepsin K were significantly decreased, although those of RANK ligand, macrophage colony-stimulating factor and c-fms were unaltered. The gene expression of bone morphogenic protein-2, Runx2, Dlx5, osterix, alkaline phosphatase, osteocalcin and collagen was not affected. The level of the RANK protein decreased, while the levels of the Runx2 and ß-catenin proteins were unchanged. Further, the osteoclastic differentiation of precursor cells in vitro was suppressed. The suppressed osteoclastogenesis was associated with decreased levels of reactive oxygen species, extracellular signal-regulated kinase (ERK) activation and RANK expression. A lower lipid peroxide level and a higher glutathione level were also observed. These results suggested that Zn-administration did not affect osteoblastogenesis but decreased osteoclastogenesis by inhibiting RANK expression through suppression of the production of reactive oxygen species and ERK activation in Zn-adequate rats.

Intravenously delivered glucocorticoid liposomes inhibit osteoclast activity and bone erosion in murine antigen-induced arthritis.

UNLABELLED: The objective of this study was to determine the effect of systemic delivery of prednisolone phosphate (PLP) encapsulated within long circulating 'stealth' liposomes on bone erosion and osteoclast activity during experimental antigen-induced arthritis (AIA). Liposomal PLP strongly suppressed knee joint swelling, synovial infiltrate and bone erosion in antigen-induced arthritis. The number of active osteoclasts was not only suppressed in bone lesions near inflamed synovium, but also within the trabecular bone of the tibia, suggesting a systemic suppression of osteoclast activation. Furthermore, liposomal PLP directly blocked osteoclast differentiation and bone resorption in vitro while it also suppressed expression of osteoclast differentiation factors M-CSF and RANKL in the synovium. Targeting studies showed that liposomes are most efficiently phagocytosed by macrophages and early precursors of osteoclasts in the bone marrow rather than by mature osteoclasts, indicating a possible inhibition of osteoclast differentiation from an early stage. CONCLUSION: Liposomal glucocorticoid delivery rather than free PLP offers a more efficacious way to inhibit both inflammation and bone erosion in rheumatoid arthritis.

Hoxb8 conditionally immortalised macrophage lines model inflammatory monocytic cells with important similarity to dendritic cells.

We have examined the potential to generate bona fide macrophages (MØ) from conditionally immortalised murine bone marrow precursors. MØ can be derived from Hoxb8 conditionally immortalised macrophage precursor cell lines (MØP) using either M-CSF or GM-CSF. When differentiated in GM-CSF (GM-MØP) the resultant cells resemble GM-CSF bone marrow-derived dendritic cells (BMDC) in morphological phenotype, antigen phenotype and functional responses to microbial stimuli. In spite of this high similarity between the two cell types and the ability of GM-MØP to effectively present antigen to a T-cell hybridoma, these cells are comparatively poor at priming the expansion of IFN-γ responses from naïve CD4(+) T cells. The generation of MØP from transgenic or genetically aberrant mice provides an excellent opportunity to study the inflammatory role of GM-MØP, and reduces the need for mouse colonies in many studies. Hence differentiation of conditionally immortalised MØPs in GM-CSF represents a unique in vitro model of inflammatory monocyte-like cells, with important differences from bone marrow-derived dendritic cells, which will facilitate functional studies relating to the many 'sub-phenotypes' of inflammatory monocytes.

The significance of CD14+ monocytes in peripheral blood stem cells for the treatment of rat liver cirrhosis.

BACKGROUND AIMS: Circulating monocytes have been exploited as an important progenitor cell resource for hepatocytes in vitro and are instrumental in the removal of fibrosis. We investigated the significance of monocytes in peripheral blood stem cells (PBSC) for the treatment of liver cirrhosis. METHODS: Rat CD14+ monocytes in PBSC were mobilized with granulocyte-colony-stimulating factor (G-CSF) and harvested by magnetic cell sorting (MACS). Female rats with carbon tetrachloride (CCl4-induced liver cirrhosis were injected CM-DiI-labeled monocytes, CD14⁻ cells (1 x 107 cells/rat) or saline via the portal vein. RESULTS: Rat CD14+ and CD11b+ monocytes in PBSC were partly positive for CD34, CD45, CD44, Oct3/4 and Sox2, suggesting monocytes with progenitor capacity. Compared with CD14⁻ cell-infused and saline-injected rats, rats undergoing monocyte transplantation showed a gradually increased serum albumin level and decreased portal vein pressure, resulting in a significantly improved survival rate. Meanwhile, monocyte transplantation apparently attenuated liver fibrosis by analysis for fibronectin, α2-(1)-procollagen, α-smooth muscle aorta (SMA) and transforming growth factor (TGF)-ß. Transplanted monocytes mainly clustered in periportal areas of liver, in which 1.8% cells expressed hepatocyte marker albumin and CK18. The expression level of hepatocyte growth factor (HGF), TGF-α, extracellular matrix (EGF) and vascular endothelial growth factor (VEGF) increased, while monocyte transplantation enhanced hepatocyte proliferation. On the other hand, the activities and expression of matrix metalloproteinases (MMP) increased while tissue inhibitor of metalloproteinase (TIMP)-1 expression significantly reduced in monocyte-transplanted livers. Some transplanted monocytes expressed MMP-9 and -13. CONCLUSIONS: The data suggest that CD14+ monocytes in PBSC contribute to hepatocyte regeneration and extracellular matrix (ECM) remodeling in rat liver cirrhosis much more than CD14⁻ cells, and might offer a therapeutic alternative for patients with liver cirrhosis.