Iron chelation acutely stimulates fetal human intestinal cell production of IL-6 and VEGF while decreasing HGF: the roles of p38, ERK, and JNK MAPK signaling

Tetrahydroberberrubine prevents peritoneal adhesion by suppressing inflammation and extracellular matrix accumulation

Peritoneal adhesion is a common abdominal surgical complication that induces abdominal haemorrhage, intestinal obstruction, infertility, and so forth. The high morbidity and recurrence rate of this disease indicate the need for novel therapeutic approaches. Here, we revealed the protective roles of tetrahydroberberrubine (THBru), a novel derivative of berberine (BBR), in preventing peritoneal adhesion and identified its underlying mechanism in vivo and in vitro. Abrasive surgery was used to create a peritoneal adhesion rat model. We found that THBru administration markedly ameliorated peritoneal adhesion, as indicated by a lowered adhesion score and ameliorated caecal tissue damage. By comparison, THBru exhibited more potent anti-adhesion effects than BBR at the same dose. Mechanistically, THBru inhibited inflammation and extracellular matrix (ECM) accumulation in the microenvironment of adhesion tissue. THBru suppressed the expression of inflammatory cytokines including interleukin-1β (IL-1β), IL-6, transforming growth factor β (TGF-β), tumor necrosis factor-α (TNF-α) and intercellular adhesion molecule-1 (ICAM-1), by regulating the transforming growth factor beta-activated kinase 1 (TAK1)/c-Jun N-terminal kinase (JNK) and TAK1/nuclear factor κB (NF-κB) signaling pathways. However, THBru promoted the activation of MMP-3 by directly blocking the TIMP-1 activation core and subsequently decreased collagen deposition. Taken together, this study identifies THBru as an effective anti-adhesion agent that regulates diverse mechanisms, thereby outlining its potential therapeutic implications for the treatment of peritoneal adhesion.

Cigarette Smoke Particle-Induced Lung Injury and Iron Homeostasis

It is proposed that the mechanistic basis for non-neoplastic lung injury with cigarette smoking is a disruption of iron homeostasis in cells after exposure to cigarette smoke particle (CSP). Following the complexation and sequestration of intracellular iron by CSP, the host response (eg, inflammation, mucus production, and fibrosis) attempts to reverse a functional metal deficiency. Clinical manifestations of this response can present as respiratory bronchiolitis, desquamative interstitial pneumonitis, pulmonary Langerhans’ cell histiocytosis, asthma, pulmonary hypertension, chronic bronchitis, and pulmonary fibrosis. If the response is unsuccessful, the functional deficiency of iron progresses to irreversible cell death evident in emphysema and bronchiectasis. The subsequent clinical and pathological presentation is a continuum of lung injuries, which overlap and coexist with one another. Designating these non-neoplastic lung injuries after smoking as distinct disease processes fails to recognize shared relationships to each other and ultimately to CSP, as well as the common mechanistic pathway (ie, disruption of iron homeostasis).

HCV-Induced Immunometabolic Crosstalk in a Triple-Cell Co-Culture Model Capable of Simulating Systemic Iron Homeostasis

Iron is crucial to the regulation of the host innate immune system and the outcome of many infections. Hepatitis C virus (HCV), one of the major viral human pathogens that depends on iron to complete its life cycle, is highly skilled in evading the immune system. This study presents the construction and validation of a physiologically relevant triple-cell co-culture model that was used to investigate the input of iron in HCV infection and the interplay between HCV, iron, and determinants of host innate immunity. We recorded the expression patterns of key proteins of iron homeostasis involved in iron import, export and storage and examined their relation to the iron regulatory hormone hepcidin in hepatocytes, enterocytes and macrophages in the presence and absence of HCV. We then assessed the transcriptional profiles of pro-inflammatory cytokines Interleukin-6 (IL-6) and interleukin-15 (IL-15) and anti-inflammatory interleukin-10 (IL-10) under normal or iron-depleted conditions and determined how these were affected by infection. Our data suggest the presence of a link between iron homeostasis and innate immunity unfolding among liver, intestine, and macrophages, which could participate in the deregulation of innate immune responses observed in early HCV infection. Coupled with iron-assisted enhanced viral propagation, such a mechanism may be important for the establishment of viral persistence and the ensuing chronic liver disease.

Genetically Predicted Serum Iron Status Is Associated with Altered Risk of Systemic Lupus Erythematosus among European Populations

BACKGROUND

Observational epidemiological studies have reported an inconsistent relation between iron status and risk of systemic lupus erythematosus (SLE). Moreover, it remains uncertain whether the observed association is causal or due to confounding or reverse causality.

OBJECTIVES

We aimed to investigate the association between serum iron status and risk of SLE using a 2-sample Mendelian randomization (MR) approach.

METHODS

Genetic instruments for iron status including serum iron, log-transformed ferritin, transferrin saturation, and transferrin were identified from a large-scale genome-wide association study (GWAS) performed by the Genetics of Iron Status Consortium among 48,972 individuals of European ancestry (55% female). Three independent single nucleotide polymorphisms (rs1800562, rs1799945, and rs855791) concordantly related with 4 iron status biomarkers were selected as instrumental variables. Summary statistics of SLE were obtained from a publicly available GWAS of 4036 patients with SLE and 6959 controls of European descent. The MR study was conducted using the inverse-variance weighted (IVW) method, supplemented with MR-Egger regression and simple- and weighted-median methods. Leave-one-out analysis was further performed to test the robustness of our findings. ORs with 95% CIs were calculated.

RESULTS

Genetically predicted iron status was associated with altered risk of SLE, with ORs of 0.79 (95% CI: 0.66, 0.94), 0.54 (95% CI: 0.34, 0.85), 0.82 (95% CI: 0.71, 0.94), and 1.36 (95% CI: 1.06, 1.76) per 1-SD increase in iron, log-transformed ferritin, transferrin saturation, and transferrin using the IVW method, respectively. MR-Egger regression did not indicate potential pleiotropic bias. Sensitivity analyses produced similar findings, suggesting the robustness of the association.

CONCLUSIONS

Our study suggested that high iron status may be associated with a reduced risk of SLE among European populations. Further studies are warranted to elucidate the mechanism underlying the protective role of iron against susceptibility to SLE.

Ozone Reacts With Carbon Black to Produce a Fulvic Acid-Like Substance and Increase an Inflammatory Effect

Exposure to ambient ozone has been associated with increased human mortality. Ozone exposure can introduce oxygen-containing functional groups in particulate matter (PM) effecting a greater capacity of the particle for metal complexation and inflammatory effect. We tested the postulate that (1) a fulvic acid-like substance can be produced through a reaction of a carbonaceous particle with high concentrations of ozone and (2) such a fulvic acid-like substance included in the PM can initiate inflammatory effects following exposure of respiratory epithelial (BEAS-2B) cells and an animal model (male Wistar Kyoto rats). Carbon black (CB) was exposed for 72 hours to either filtered air (CB-Air) or approximately 100 ppm ozone (CB-O₃). Carbon black exposure to high levels of ozone produced water-soluble, fluorescent organic material. Iron import by BEAS-2B cells at 4 and 24 hours was not induced by incubations with CB-Air but was increased following coexposures of CB-O₃ with ferric ammonium citrate. In contrast to CB-Air, exposure of BEAS-2B cells and rats to CB-O₃ for 24 hours increased expression of pro-inflammatory cytokines and lung injury, respectively. It is concluded that inflammatory effects of carbonaceous particles on cells can potentially result from (1) an inclusion of a fulvic acid-like substance after reaction with ozone and (2) changes in iron homeostasis following such exposure.

A Fulvic Acid-like Substance Participates in the Pro-inflammatory Effects of Cigarette Smoke and Wood Smoke Particles

We tested the postulates that (1) a fulvic acid (FA)-like substance is included in cigarette smoke and wood smoke particles (WSP) and (2) cell exposure to this substance results in a disruption of iron homeostasis, associated with a deficiency of the metal and an inflammatory response. The fluorescence excitation-emission matrix spectra of the water-soluble components of cigarette smoke condensate and WSP (Cig-WS and Wood-WS) approximated those for the standard reference materials, Suwanee River and Nordic fulvic acids (SRFA and NFA). Fourier transform infrared spectra for the FA fraction of cigarette smoke and WSP (Cig-FA and Wood-FA), SRFA, and NFA also revealed significant similarities (O-H bond in alcohols, phenols, and carboxylates, C═O in ketones, aldehydes, and carboxylates, and a significant carboxylate content). After exposure to Cig-WS and Wood-WS and the FA standards, iron was imported by respiratory epithelial cells, reflecting a functional iron deficiency. The release of pro-inflammatory mediators interleukin (IL)-8 and IL-6 by respiratory epithelial cells also increased following exposures to Cig-WS, Wood-WS, SRFA, and NFA. Co-exposure of the respiratory epithelial cells with iron decreased supernatant concentrations of the ILs relative to exposures to Cig-WS, Wood-WS, SRFA, and NFA alone. It is concluded that (1) a FA-like substance is included in cigarette smoke and WSP and (2) respiratory epithelial cell exposure to this substance results in a disruption of iron homeostasis associated with both a cell deficiency of the metal and an inflammatory response.

The toxicology of air pollution predicts its epidemiology

The epidemiologic investigation has successively delineated associations of air pollution exposure with non-malignant and malignant lung disease, cardiovascular disease, cerebrovascular disease, pregnancy outcomes, perinatal effects and other extra-pulmonary disease including diabetes. Defining these relationships between air pollution exposure and human health closely parallels results of an earlier epidemiologic investigation into cigarette smoking and environmental tobacco smoke (ETS), two other particle-related exposures. Humic-like substances (HULIS) have been identified as a chemical component common to cigarette smoke and air pollution particles. Toxicology studies provide evidence that a disruption of iron homeostasis with sequestration of host metal by HULIS is a fundamental mechanistic pathway through which biological effects are initiated by cigarette smoke and air pollution particles. As a result of a common chemical component and a shared mechanistic pathway, it should be possible to extrapolate from the epidemiology of cigarette smoking and ETS to predict associations of air pollution exposure with human disease, which are currently unrecognized. Accordingly, it is anticipated that the forthcoming epidemiologic investigation will demonstrate relationships of air pollution with COPD causation, peripheral vascular disease, hypertension, renal disease, digestive disease, loss of bone mass/risk of fractures, dental disease, eye disease, fertility problems, and extrapulmonary malignancies.

Prolyl hydroxylases positively regulated LPS-induced inflammation in human gingival fibroblasts via TLR4/MyD88-mediated AKT/NF-κB and MAPK pathways

OBJECTIVES

Prolyl hydroxylases (PHDs) play essential roles in oxygen-sensing system, whereas the effects of PHDs on inflammation have not been totally uncovered. Our study aimed to investigate the role of PHDs in lipopolysaccharide (LPS)-induced inflammation of human gingival fibroblasts (HGFs) and clarify the potential mechanisms.

MATERIALS AND METHODS

A pan hydroxylase inhibitor, dimethyloxallyl glycine (DMOG), and RNA interference were used to explore the role of PHDs in inflammation. Cytotoxic effect of DMOG was determined by cell-counting kit-8 and flow cytometry respectively. The secretion levels of IL-6 and IL-8 were assessed by ELISA. The mRNA levels of inflammatory cytokines, Toll-like receptor (TLR) 4 and MyD88 were evaluated by quantitative real-time PCR. The activation of NF-κB, mitogen-activated protein kinase (MAPK) and PI3K/AKT pathways were detected by western blot and the nuclear translocation of NF-κB p65 was examined by immunofluorescence. Downregulation of PHD1 and PHD2 was performed with siRNA transfection.

RESULTS

Dimethyloxallyl glycine inhibited LPS-induced inflammatory cytokine, TLR4 and MyD88 expression in gene level and the elevated secretion of IL-6 and IL-8 was also downregulated. Additionally, LPS-induced activation of NF-κB, MAPK and AKT pathways was abolished by DMOG treatment. Importantly, LPS-induced inflammatory cytokine expression was merely suppressed by PHD2 knockdown.

CONCLUSIONS

Prolyl hydroxylases acted as a positive regulator in LPS-induced inflammation of HGFs via TLR4/MyD88-mediated NF-κB, MAPK and AKT signalling pathways and PHD2 among three isoforms was principally responsible for the effects.

Epinephrine stimulates CXCL1 IL-1α, IL-6 secretion in isolated mouse limb muscle

Catecholamines stimulate interleukin‐6 (IL‐6) secretion in skeletal muscles. However, whether other cytokines are secreted is currently unknown. Skeletal muscle ex vivo preparations commonly used to study cytokine secretion have dealt with limitations including auto‐oxidation of catecholamines. The use of metal chelators could be an alternative to avoid auto‐oxidation and allow catecholamines to be used at physiological doses. We exposed isolated soleus muscles to 1 or 100 ng/mL epinephrine (EPI) and collected bath samples at 1 and 2 h for multiplex cytokine analysis. Keratinocyte chemoattractant (CXCL1), IL‐6, and IL‐1α were significantly elevated by 100 ng/mL exposure, but not by 1 ng/mL (median [CXCL1] (2 h) = 83 pg/mL; [IL‐6] = 19 pg/mL; IL‐1α = 7.5 pg/mL). CXCL1 and IL‐6 were highly correlated in each sample (P = 0.0001). A second experiment combined the metal chelator, deferoxamine mesylate (DFO), to prevent EPI autoxidation, with 2 ng/mL EPI and 10.5 ng/mL norepinephrine (NOREPI) to mimic peak exercise. Unexpectedly, DFO alone stimulated both IL‐6 and CXCL1 secretion, but together with EPI and NOREPI had no additional effects. Stimulation of cytokine secretory responses from skeletal muscle cells in response to DFO thus precludes its use as a chelating agent in ex vivo models. In conclusion, 100 ng/mL EPI stimulates a robust secretory CXCL1 response, which together with IL‐6 and IL‐1α, may constitute an adrenal‐muscle endocrine response system.

Human lung injury following exposure to humic substances and humic-like substances

Among the myriad particles the human respiratory tract is exposed to, a significant number are distinctive in that they include humic substances (HS) and humic-like substances (HULIS) as organic components. HS are heterogeneous, amorphous, organic materials which are ubiquitous occurring in all terrestrial and aqueous environments. HULIS are a complex class of organic, macromolecular compounds initially extracted from atmospheric aerosol particles which share some features with HS including an aromatic, polyacidic nature. As a result of having a variety of oxygen-containing functional groups, both HS and HULIS complex metal cations, especially iron. Following particle uptake by cells resident in the lung, host iron will be sequestered by HS- and HULIS-containing particles initiating pathways of inflammation and subsequent fibrosis. It is proposed that (1) human exposures to HS and HULIS of respirable size (<10 µm diameter) are associated with inflammatory and fibrotic lung disease and (2) following retention of particles which include HS and HULIS, the mechanism of cell and tissue injury involves complexation of host iron. Human inflammatory and fibrotic lung injuries following HS and HULIS exposures may include coal workers' pneumoconiosis, sarcoidosis, and idiopathic pulmonary fibrosis as well as diseases associated with cigarette smoking and exposures to emission and ambient air pollution particles.

Siderophore-mediated iron acquisition and modulation of host-bacterial interactions

Iron is an essential micronutrient for most life forms including the majority of resident bacteria of the microbiota and their mammalian hosts. Bacteria have evolved numerous mechanisms to competitively acquire iron within host environments, such as the secretion of small molecules known as siderophores that can solubilize iron for bacterial use. However, siderophore biosynthesis and acquisition is not a capability equally harbored by all resident bacteria. Moreover, the structural diversity of siderophores creates variability in the susceptibility to host mechanisms that serve to counteract siderophore-mediated iron acquisition and limit bacterial growth. As a result, the differential capabilities to acquire iron among members of a complex microbial community carry important implications for the growth and function of resident bacteria. Siderophores can also directly influence host function by modulating cellular iron homeostasis, further providing a mechanism by which resident bacteria may influence their local environment at the host-microbial interface. This review will explore the putative mechanisms by which siderophore production by resident bacteria in the intestines may influence microbial community dynamics and host-bacterial interactions with important implications for pathogen- and microbiota-driven diseases including infection, inflammatory bowel diseases and colorectal cancer.

Wnt5a is a key target for the pro-osteogenic effects of iron chelation on osteoblast progenitors

Iron overload due to hemochromatosis or chronic blood transfusions has been associated with the development of osteoporosis. However, the impact of changes in iron homeostasis on osteoblast functions and the underlying mechanisms are poorly defined. Since Wnt signaling is a critical regulator of bone remodeling, we aimed to analyze the effects of iron overload and iron deficiency on osteoblast function, and further define the role of Wnt signaling in these processes. Therefore, bone marrow stromal cells were isolated from wild-type mice and differentiated towards osteoblasts. Exposure of the cells to iron dose-dependently attenuated osteoblast differentiation in terms of mineralization and osteogenic gene expression, whereas iron chelation with deferoxamine promoted osteogenic differentiation in a time- and dose-dependent manner up to 3-fold. Similar results were obtained for human bone marrow stromal cells. To elucidate whether the pro-osteogenic effect of deferoxamine is mediated via Wnt signaling, we performed a Wnt profiler array of deferoxamine-treated osteoblasts. Wnt5a was amongst the most highly induced genes. Further analysis revealed a time- and dose-dependent induction of Wnt5a being up-regulated 2-fold after 48 h at 50 μM deferoxamine. Pathway analysis using specific inhibitors revealed that deferoxamine utilized the phosphatidylinositol-3-kinase and nuclear factor of activated T cell pathways to induce Wnt5a expression. Finally, we confirmed the requirement of Wnt5a in the deferoxamine-mediated osteoblast-promoting effects by analyzing the matrix mineralization of Wnt5a-deficient cells. The promoting effect of deferoxamine on matrix mineralization in wild-type cells was completely abolished in Wnt5a^-/- cells. Thus, these data demonstrate that Wnt5a is critical for the pro-osteogenic effects of iron chelation using deferoxamine.

L-mimosine increases the production of vascular endothelial growth factor in human tooth slice organ culture model

AIM

To assess the pro-angiogenic and pro-inflammatory capacity of the dentine-pulp complex in response to the prolyl hydroxylase inhibitor L-mimosine in a tooth slice organ culture model.

METHODOLOGY

Human teeth were sectioned transversely into 600-μm-thick slices and cultured in medium supplemented with serum and antibiotics. Then, pulps were stimulated for 48 h with L-mimosine. Pulps were subjected to viability measurements based on formazan formation in MTT assays. In addition, histological evaluation of pulps was performed based on haematoxylin and eosin staining. Culture supernatants were subjected to immunoassays for vascular endothelial growth factor (VEGF) to determine the pro-angiogenic capacity and to immunoassays for interleukin (IL)-6 and IL-8 to assess the pro-inflammatory response. Interleukin-1 served as pro-inflammatory control. Echinomycin was used to inhibit hypoxia-inducible factor-1 (HIF-1) alpha activity. Data were analysed using Student's t-test and Mann-Whitney U test.

RESULTS

Pulps within tooth slices remained vital upon L-mimosine stimulation as indicated by formazan formation and histological evaluation. L-mimosine increased VEGF production when normalized to formazan formation in the pulp tissue of the tooth slices (P < 0.05). This effect on VEGF was reduced by echinomycin (P < 0.01). Changes in normalized IL-6 and IL-8 levels upon treatment with L-mimosine did not reach the level of significance (P > 0.05), whilst treatment with IL-1, which served as positive control, increased IL-6 (P < 0.05) and IL-8 levels (P < 0.05).

CONCLUSIONS

The prolyl hydroxylase inhibitor L-mimosine increased VEGF production via HIF-1 alpha in the tooth slice organ culture model whilst inducing no prominent increase in IL-6 and IL-8. Pre-clinical studies will reveal if these in vitro effects translate into dental pulp regeneration.

Deferoxamine promotes osteoblastic differentiation in human periodontal ligament cells via the nuclear factor erythroid 2-related factor-mediated antioxidant signaling pathway

BACKGROUND AND OBJECTIVE

Recently it was reported that deferoxamine (DFO), an iron chelator, stimulates bone formation from MG63 and mesenchymal stem cells, but inhibits differentiation in rat calvarial cells; however, the effect of DFO on osteoblastic differentiation in human periodontal ligament cells (hPDLCs) has not been reported. The aim of this study was to investigate the effects and the possible underlying mechanism of DFO on osteoblastic differentiation of hPDLCs.

MATERIAL AND METHODS

The effect of DFO on osteoblast differentiation was determined by the staining intensity of calcium deposits with Alizarin red and by RT-PCR analysis of the expression of osteoblastic markers. Signal transduction pathways were analyzed by western blotting.

RESULTS

DFO increased osteogenic differentiation in a concentration-dependent manner by expression of the mRNA for differentiation markers and calcium nodule formation. Exposure of hPDLCs to DFO resulted in increases in the production of reactive oxygen species and in the levels of nuclear factor erythroid 2-related factor (Nrf2) protein in nuclear extractions, as well as a dose-dependent increase in the expression of Nrf2 target genes, including glutathione (GSH), glutathione S-transferase, γ-glutamylcysteine lygase, glutathione reductase and glutathione peroxidase. Pretreatment with Nrf2 small interfering RNA, GSH depletion by buthionine sulfoximine and diethyl maleate, and with antioxidants by N-acetylcysteine and vitamin E, blocked DFO-stimulated osteoblastic differentiation. Furthermore, pretreatment with GSH depletion and antioxidants blocked DFO-induced p38 MAPK, ERK, JNK and nuclear factor-kappaB pathways.

CONCLUSION

These data indicate, for the first time, that nontoxic DFO promotes osteoblastic differentiation of hPDLCs via modulation of the Nrf2-mediated antioxidant pathway.

Urotensin II stimulates vascular endothelial growth factor secretion from adventitial fibroblasts in synergy with angiotensin II

BACKGROUND

The adventitia plays an important role in and is considered to be the initiating site for vascular remodeling. Urotensin II (UII) and angiotensin II (Ang II) are the two most important vascular peptides involved in vascular remodeling in the adventitia. Nevertheless, little is known about their effect on the expression of vascular endothelial growth factor (VEGF). It was hypothesized that both UII and Ang II could induce VEGF expression in adventitial fibroblasts and VEGF may play a role in cell proliferation and collagen I synthesis induced by UII or Ang II.

METHODS AND RESULTS

Growth-arrested adventitial fibroblasts were incubated in serum-free medium with UII and/or Ang II and inhibitors of the mitogen-activated protein kinase (MAPK) pathway or VEGF-neutralizing antibodies. The VEGF expression was evaluated using enzyme-linked immunosorbent assay (ELISA), while the proliferation and collagen I synthesis were detected using methyl thiazol tetrazolium (MTT) assay and ELISA. It was found that: (1) both UII and Ang II could stimulate VEGF expression in adventitial fibroblasts and they had a synergistic effect; (2) MAPK pathway inhibitors could inhibit VEGF secretion induced by UII and/or Ang II; and (3) VEGF-neutralizing antibodies could inhibit UII/Ang II-induced cell proliferation and collagen synthesis in adventitial fibroblasts.

CONCLUSIONS

Induction of VEGF expression may be a new mechanism involved in vascular remodeling for UII and Ang II.

Prolyl hydroxylase inhibitors increase the production of vascular endothelial growth factor by periodontal fibroblasts

BACKGROUND AND OBJECTIVE

Pharmacological inhibitors of prolyl hydroxylases (PHDs) can induce a proangiogenic response that favors wound healing and bone regeneration. However, the response of periodontal cells to PHD inhibitors is unknown.

MATERIAL AND METHODS

To determine the effects of PHD inhibitors on periodontal cells, we exposed human fibroblasts from the gingiva and the periodontal ligament to dimethyloxallyl glycine, desferrioxamine, l-mimosine and CoCl(2). Viability, proliferation, and protein synthesis were assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), [(3)H]thymidine, and [(3)H]leucine incorporation, respectively. The levels of Ki67, hypoxia-inducible factor 1α (HIF-1α), p27, phosphorylated c-Jun N-terminal kinase (JNK) and phosphorylated p38 were determined by immunohistochemistry and western blotting. Vascular endothelial growth factor (VEGF) mRNA levels were measured by quantitative PCR. Protein levels of VEGF and interleukin (IL)-6 were evaluated by immunoassays.

RESULTS

We found that PHD inhibitors, while leaving cell viability unchanged, reduced proliferation and protein synthesis. This was paralleled by decreased Ki67 levels and increased p27 levels, suggesting that PHD inhibitors provoke growth arrest. Independently from this response, PHD inhibitors stabilized HIF-1α and increased the production of VEGF. This increase of VEGF was observed in the presence of proinflammatory IL-1 and pharmacological inhibitors of JNK and p38 signaling. Moreover, PHD inhibitors did not modulate expression of IL-6 and the phosphorylation of JNK and p38.

CONCLUSION

These results suggest that PHD inhibitors enhance the production of VEGF in periodontal fibroblasts, even in the presence of proinflammatory IL-1. The data further suggest that PHD inhibitors do not provoke a significant proinflammatory or anti-inflammatory response in this in vitro setting.

Proinflammatory stem cell signaling in cardiac ischemia

Cardiovascular disease remains a leading cause of mortality in developed nations, despite continued advancement in modern therapy. Progenitor and stem cell-based therapy is a novel treatment for cardiovascular disease, and modest benefits in cardiac recovery have been achieved in small clinical trials. This therapeutic modality remains challenged by limitations of low donor-cell survival rates, transient recovery of cardiac function, and the technical difficulty of applying directed cell therapy. Understanding the signaling mechanisms involved in the stem cell response to ischemia has revealed opportunities to modify directly aspects of these pathways to improve their cardioprotective abilities. This review highlights general considerations of stem cell therapy for cardiac disease, reviews the major proinflammatory signaling pathways of mesenchymal stem cells, and reviews ex vivo modifications of stem cells based on these pathways.

Ironing out the wrinkles in host defense: interactions between iron homeostasis and innate immunity

Iron is an essential micronutrient for both microbial pathogens and their mammalian hosts. Changes in iron availability and distribution have significant effects on pathogen virulence and on the immune response to infection. Recent advances in our understanding of the molecular regulation of iron metabolism have shed new light on how alterations in iron homeostasis both contribute to and influence innate immunity. In this article, we review what is currently known about the role of iron in the response to infection.

Stabilization of hepatocyte growth factor mRNA by hypoxia-inducible factor 1

Hypoxia regulates expression of hepatocyte growth factor (HGF) by increasing its transcription and by stabilizing its mRNA. Despite the pivotal role of hypoxia-inducible factor 1 (HIF-1) in transcriptional activation of hypoxia-responsive genes, it is not known whether HIF-1 mediates hypoxia-induced stabilization of HGF mRNA. We constructed adenoviral vectors expressing either the wild-type HIF-1alpha (Ad2/HIF-1alpha/FL), a constitutively stable hybrid form of HIF-1alpha (Ad2/HIF-1alpha/VP16), or no transgene (Ad2/CMVEV). In rat glioma (C6) cells, human glioma (U251) cells human cardiac, vascular smooth muscle, and endothelial cells, infection with Ad2/HIF-1alpha/VP16 or Ad2/HIF-1alpha/FL increased HGF expression at both the mRNA and protein levels. Under normoxic conditions, the half-life of HGF mRNA was 43 min in C6 and U251 cells. Hypoxia and Ad2/HIF-1alpha/VP16 increased the half-life of HGF mRNA to 3.2 and 2.8 h, respectively, while Ad2/CMVEV had no effect. These studies are the first to demonstrate that overexpression of HIF-1alpha increases HGF mRNA stability. Our results also suggest that stabilization of HGF mRNA by hypoxia is mediated, at least in part, by HIF-1.

VEGF signaling inhibitors: more pro-apoptotic than anti-angiogenic

The vascular endothelial growth factor (VEGF) family of polypeptide growth factors regulates a family of VEGF receptor (VEGFR) tyrosine kinases with pleiotropic downstream effects. Angiogenesis is the best known of these effects, but additional VEGF-dependent actions include increased vascular permeability, paracrine/autocrine growth factor release, enhancement of cell motility, and inhibition of apoptosis. In theory, therapeutic inhibition of angiogenesis should reduce tumor perfusion and thus increase tumor hypoxia and chemoresistance, but in clinical practice the VEGF antibody bevacizumab acts as a broad-spectrum chemosensitizer. Since VEGFR expression occurs in many tumor types, such chemosensitization is more readily explained by direct inhibition of tumor cell survival signals than by indirect stromal/vascular effects. The emerging model of anti-VEGF drug action being mediated primarily by tumoral (as distinct from endothelial) VEGFRs has clinically important implications for optimizing the anti-metastatic efficacy of this expanding drug class.