Hypoxia induces expression of the chemokines monocyte chemoattractant protein-1 (MCP-1) and IL-8 in human dermal fibroblasts

Analyzing the Prevalence of Depression and Its Influencing Factors in Elderly Patients With Obstructive Sleep Apnea: A Machine Learning Approach

Objective: Depressive symptoms are prevalent and detrimental in elderly patients with obstructive sleep apnea (OSA). Understanding the factors influencing these symptoms is crucial. This study aims to use machine learning algorithms to identify the contributing factors in this population. Method: The National Health and Nutrition Examination Survey database provided the data for this study. The study includes elderly patients who are eligible for diagnostic evaluation for OSA. Logistic regression was used to screen their influencing factors, and random forest (RF), extreme gradient boosting (XGB), artificial neural network (ANN), and support vector machine (SVM) were utilized to 4 algorithms were used to construct depressive symptoms classification models, and the best model performance was selected for feature importance ranking. Influential factors included demographics (age, gender, education, etc.), chronic disease status (diabetes, hypertension, etc.), and laboratory findings (white blood cells, C-reactive protein, cholesterol, etc.). Result: Ultimately, we chose 1538 elderly OSA patients for the study, out of which 528 (34.4%) suffered from depressive symptoms. Logistic regression initially identified 17 influencing factors and then constructed classification models based on those 17 using RF, XGB, ANN, and SVM. We selected the best-performing SVM model [area under the curve (AUC) = 0.746] based on the AUC values of 0.73, 0.735, 0.742, and 0.746 for the 4 models. We ranked the variables in order of importance: General health status, sleep disorders, gender, frequency of urinary incontinence, liver disease, physical activity limitations, education, moisture, eosinophils, erythrocyte distribution width, and hearing loss. Conclusion: Elderly OSA patients experience a high incidence of depressive symptoms, influenced by various objective and subjective factors. The situation is troubling, and healthcare institutions and policymakers must prioritize their mental health. We should implement targeted initiatives to improve the mental health of high-risk groups in multiple dimensions.

Hypoxia-induced miR-210-3p expression in lung adenocarcinoma potentiates tumor development by regulating CCL2 mediated monocyte infiltration

In most cancers, tumor hypoxia downregulates the expression of C-C motif chemokine 2 (CCL2), and this downregulation has been implicated in monocyte infiltration and tumor progression; however, the molecular mechanism is not yet clear. We compared noncancerous and lung-adenocarcinoma human samples for hypoxia-inducible factor 1-alpha (HIF-1A), microRNA-210-3p (mir-210-3p), and CCL2 levels. Mechanistic studies were performed on lung adenocarcinoma cell lines and 3D tumor spheroids to understand the role of hypoxia-induced miR-210-3p in the regulation of CCL2 expression and macrophage polarization. HIF-1Α stabilization increases miR-210-3p levels in lung adenocarcinoma and impairs monocyte infiltration by inhibiting CCL2 expression. Mechanistically, miR-210-3p directly binds to the 3'untranslated region (UTR) of CCL2 mRNA and silences it. Suppressing miR-210-3p substantially downregulates the effect of hypoxia on CCL2 expression. Monocyte migration is significantly hampered in miR-210-3p mimic-transfected HIF-1A silenced cancer cells. In contrast, inhibition of miR-210-3p in HIF-1A-overexpressed cells markedly restored monocyte migration, highlighting a direct link between the miR-210-3p level and tumor monocyte burden. Moreover, miR-210-3p inhibition in 3D tumor spheroids promotes monocyte recruitment and skewing towards an antitumor M1 phenotype. Anti-hsa-miR-210-3p-locked nucleic acid (LNA) delivery in a lung tumor xenograft zebrafish model caused tumor regression, suggesting that miR-210-3p could be a promising target for immunomodulatory therapeutic strategies against lung adenocarcinoma.

Hypoxia exacerbates intestinal injury and inflammatory response mediated by myeloperoxidase during Salmonella Typhimurium infection in mice

BACKGROUND

High-altitude exposure can cause oxidative stress damage in the intestine, which leads to increased intestinal permeability and bacterial translocation, resulting in local and systemic inflammation. Control of infection is critically dependent on the host's ability to kill pathogens with reactive oxygen species (ROS). Myeloperoxidase (MPO) targets ROS in pathogens. This study aimed to investigate the effects of hypoxia on the colonic mucosal barrier and myeloperoxidase (MPO)-mediated innate immune response in the colon.

METHODS AND RESULTS

Genetically engineered mice were exposed to a hypobaric oxygen chamber for 3 days and an inflammation model was established using Salmonella Typhimurium infection. We found that hypoxic exposure caused the development of exacerbated bacterial colitis and enhanced bacterial dissemination in MPO-deficient mice. Infection and disease severity were associated with significantly increased Ly6G+ neutrophil and F4/80+ macrophage counts in infected tissues, which is consistent with elevated proinflammatory cytokines and chemoattractant molecules. Hypoxia restrained antioxidant ability and MPO deficiency aggravated the respiratory burst in the colon.

CONCLUSION

Hypoxia can damage the colonic mucosa. MPO mediates the innate immune response and regulates the mucosal and systemic inflammatory responses to Salmonella infection during hypoxia.

Evaluation of Inflammation and Oxidative Stress Markers in Patients with Obstructive Sleep Apnea (OSA)

Background: The identification of circulating markers of oxidative stress and systemic inflammation might enhance risk stratification in obstructive sleep apnea (OSA). We investigated the association between specific haematological parameters, as easily measurable markers of oxidative stress and inflammation, and the degree of hypoxia during polysomnography using the apnea hypopnea index (AHI), oxygen desaturation index (ODI), and oxygen saturation (SpO₂), in OSA patients. Methods: Associations between polysomnographic parameters and demographic, clinical, and laboratory characteristics were assessed in a consecutive series of patients with OSA attending the Respiratory Disease Unit of the University Hospital of Sassari, north Sardinia (Italy), between 2015 and 2019. Results: In 259 OSA patients (195 males and 64 females), the body mass index (BMI) was significantly and positively associated with the AHI and ODI, and negatively associated with the mean SpO₂. No haematological parameter was independently associated with the AHI or ODI. By contrast, albumin, neutrophil, and monocyte counts, and the systemic inflammatory response index (SIRI) were independently associated with a lower SpO₂. Conclusions: Our results suggest that albumin and specific haematological parameters are promising markers of reduced oxygen saturation in OSA.

Macrophage-Orbital Fibroblast Interaction and Hypoxia Promote Inflammation and Adipogenesis in Graves' Orbitopathy

The inflammatory eye disease Graves' orbitopathy (GO) is the main complication of autoimmune Graves' disease. In previous studies we have shown that hypoxia plays an important role for progression of GO. Hypoxia can maintain inflammation by attracting inflammatory cells such as macrophages (MQ). Herein, we investigated the interaction of MQ and orbital fibroblasts (OF) in context of inflammation and hypoxia. We detected elevated levels of the hypoxia marker HIF-1α, the MQ marker CD68, and inflammatory cytokines TNFα, CCL2, CCL5, and CCL20 in GO biopsies. Hypoxia stimulated GO tissues to release TNFα, CCL2, and CCL20 as measured by multiplex enzyme-linked immunosorbent assay (ELISA). Further, TNFα and hypoxia stimulated the expression of HIF-1α, CCL2, CCL5, and CCL20 in OF derived from GO tissues. Immunofluorescence confirmed that TNFα-positive MQ were present in the GO tissues. Thus, interaction of M1-MQ with OF under hypoxia also induced HIF-1α, CCL2, and CCL20 in OF. Inflammatory inhibitors etanercept or dexamethasone prevented the induction of HIF-1α and release of CCL2 and CCL20. Moreover, co-culture of M1-MQ/OF under hypoxia enhanced adipogenic differentiation and adiponectin secretion. Dexamethasone and HIF-1α inhibitor PX-478 reduced this effect. Our findings indicate that GO fat tissues are characterized by an inflammatory and hypoxic milieu where TNFα-positive MQ are present. Hypoxia and interaction of M1-MQ with OF led to enhanced secretion of chemokines, elevated hypoxic signaling, and adipogenesis. In consequence, M1-MQ/OF interaction results in constant inflammation and tissue remodeling. A combination of anti-inflammatory treatment and HIF-1α reduction could be an effective treatment option.

The downregulation of NADPH oxidase Nox4 during hypoxia in hemangioendothelioma cells: a possible role of p22phox on Nox4 protein stability

NADPH oxidase (Nox) 4 produces H₂O₂ by forming a heterodimer with p22^phox and is involved in hemangioendothelioma development through monocyte chemoattractant protein-1 (MCP-1) upregulation. Here, we show that Nox4 protein levels were maintained by p22^phox in hemangioendothelioma cells and Nox4 protein stability was dependent on p22^phox coexpression. Conversely, the degradation of Nox4 monomer was enhanced by p22^phox knockdown. Under hypoxic conditions in hemangioendothelioma cells, p22^phox was downregulated at the mRNA and protein levels. Downregulation of p22^phox protein resulted in the enhanced degradation of Nox4 protein in hypoxia-treated hemangioendothelioma cells. In contrast, Nox2, a Nox isoform, was not altered at the protein level under hypoxic conditions. Nox2 exhibited a higher affinity for p22^phox compared with Nox4, suggesting that when coexpressed with Nox4 in the same cells, Nox2 acts as a competitor. Nox2 knockdown restored Nox4 protein levels partially reduced by hypoxic treatment. Thus, Nox4 protein levels were attenuated in hypoxia-treated cells resulting from p22^phox depletion. MCP-1 secretion was decreased concurrently with hypoxia-induced Nox4 downregulation compared with that under normoxia.

MMP9 secreted from mononuclear cell quality and quantity culture mediates STAT3 phosphorylation and fibroblast migration in wounds

Introduction

Intractable ulcers may ultimately lead to amputation. To promote wound healing, researchers developed a serum-free ex vivo peripheral blood mononuclear cell quality and quantity culture (MNC-QQc) as a source for cell therapy. In mice, pigs, and even humans, cell therapy with MNC-QQc reportedly yields a high regenerative efficacy. However, the mechanism of wound healing by MNC-QQc cells remains largely unknown. Hence, using an in vitro wound healing model, this study aimed to investigate MNC-QQc cells and the migratory potential of dermal fibroblasts.

Methods

After separation from a 50 mL blood sample from healthy individuals, mononuclear cells were cultured for 7 days in a serum-free ex vivo expansion system with five different cytokines (MNC-QQc method). The effects of MNC-QQc cells on human dermal fibroblast migration were observed by scratch assay. An angiogenesis array screened the MNC-QQc cell supernatant for proteins related to wound healing. Finally, fibroblast migration was confirmed by observing the intracellular signal transduction pathways via Western blot.

Results

The migration of fibroblasts co-cultured with MNC-QQc cells increased by matrix metallopeptidase-9 (MMP9) secretion, as suggested by the angiogenesis array. Furthermore, the phosphorylation of signal transducer and activator of transcription 3 (STAT3) in fibroblast/MNC-QQc cell co-culture and fibroblast culture with added recombinant human MMP9 protein increased. When fibroblasts were cultured with either an MMP9 inhibitor or a STAT3 inhibitor, both fibroblast migration and STAT3 phosphorylation were significantly suppressed.

Conclusions

MNC-QQc cells promote wound healing by the secretion of MMP9, which induces fibroblast migration via the STAT3 signaling pathway.

The Effect of Hypoxia on the Expression of CXC Chemokines and CXC Chemokine Receptors-A Review of Literature

Hypoxia is an integral component of the tumor microenvironment. Either as chronic or cycling hypoxia, it exerts a similar effect on cancer processes by activating hypoxia-inducible factor-1 (HIF-1) and nuclear factor (NF-κB), with cycling hypoxia showing a stronger proinflammatory influence. One of the systems affected by hypoxia is the CXC chemokine system. This paper reviews all available information on hypoxia-induced changes in the expression of all CXC chemokines (CXCL1, CXCL2, CXCL3, CXCL4, CXCL5, CXCL6, CXCL7, CXCL8 (IL-8), CXCL9, CXCL10, CXCL11, CXCL12 (SDF-1), CXCL13, CXCL14, CXCL15, CXCL16, CXCL17) as well as CXC chemokine receptors—CXCR1, CXCR2, CXCR3, CXCR4, CXCR5, CXCR6, CXCR7 and CXCR8. First, we present basic information on the effect of these chemoattractant cytokines on cancer processes. We then discuss the effect of hypoxia-induced changes on CXC chemokine expression on the angiogenesis, lymphangiogenesis and recruitment of various cells to the tumor niche, including myeloid-derived suppressor cells (MDSCs), tumor-associated macrophages (TAMs), tumor-associated neutrophils (TANs), regulatory T cells (T_regs) and tumor-infiltrating lymphocytes (TILs). Finally, the review summarizes data on the use of drugs targeting the CXC chemokine system in cancer therapies.

Cytokine-, Neurotrophin-, and Motor Rehabilitation-Induced Plasticity in Parkinson's Disease

Neuroinflammation and cytokine-dependent neurotoxicity appear to be major contributors to the neuropathology in Parkinson's disease (PD). While pharmacological advancements have been a mainstay in the treatment of PD for decades, it is becoming increasingly clear that nonpharmacological approaches including traditional and nontraditional forms of exercise and physical rehabilitation can be critical adjunctive or even primary treatment avenues. Here, we provide an overview of preclinical and clinical research detailing the biological role of proinflammatory molecules in PD and how motor rehabilitation can be used to therapeutically modulate neuroinflammation, restore neural plasticity, and improve motor function in PD.

Hypoxia Alters the Expression of CC Chemokines and CC Chemokine Receptors in a Tumor-A Literature Review

Hypoxia, i.e., oxygen deficiency condition, is one of the most important factors promoting the growth of tumors. Since its effect on the chemokine system is crucial in understanding the changes in the recruitment of cells to a tumor niche, in this review we have gathered all the available data about the impact of hypoxia on β chemokines. In the introduction, we present the chronic (continuous, non-interrupted) and cycling (intermittent, transient) hypoxia together with the mechanisms of activation of hypoxia inducible factors (HIF-1 and HIF-2) and NF-κB. Then we describe the effect of hypoxia on the expression of chemokines with the CC motif: CCL1, CCL2, CCL3, CCL4, CCL5, CCL7, CCL8, CCL11, CCL13, CCL15, CCL16, CCL17, CCL18, CCL19, CCL20, CCL21, CCL22, CCL24, CCL25, CCL26, CCL27, CCL28 together with CC chemokine receptors: CCR1, CCR2, CCR3, CCR4, CCR5, CCR6, CCR7, CCR8, CCR9, and CCR10. To better understand the effect of hypoxia on neoplastic processes and changes in the expression of the described proteins, we summarize the available data in a table which shows the effect of individual chemokines on angiogenesis, lymphangiogenesis, and recruitment of eosinophils, myeloid-derived suppressor cells (MDSC), regulatory T cells (T_reg), and tumor-associated macrophages (TAM) to a tumor niche.

Association between urinary biomarkers and disease progression in adults with autosomal dominant polycystic kidney disease

Background

Height-adjusted total kidney volume (htTKV) is considered as the best predictor of kidney function in patients with autosomal dominant polycystic kidney disease (ADPKD), but its limited predictive capacity stresses the need to find new biomarkers of ADPKD progression. The aim of this study was to investigate urinary biomarkers of ADPKD progression.

Methods

This observational study included ADPKD patients, and two comparator groups of ischaemic and non-ischaemic kidney injury: benign nephroangiosclerosis patients and non-ischaemic chronic kidney disease (CKD) patients. Proteinuria, htTKV and urinary levels of molecules are associated with ischaemia and/or tubular injury. The slope of estimated glomerular filtration rate (eGFR) was used as a dependent variable in univariate and multivariate models of kidney function decline.

Results

The study included 130 patients with ADPKD, 55 with nephroangiosclerosis and 40 with non-ischaemic CKD. All patients had increased urinary concentrations of biomarkers associated with tubular lesions (liver fatty acid-binding protein, kidney injury molecule-1, β2-microglobulin) and molecules overexpressed under ischaemic conditions [hypoxia-inducible factor-1α, vascular endothelial growth factor (VEGF) and monocyte chemoattractant protein-1 (MCP-1)]. These biomarkers correlated positively with htTKV and negatively with the eGFR slope. htTKV was the single best predictor of the eGFR slope variability in univariate analyses. However, a multivariate model including urinary levels of β2-microglobulin, MCP-1 and VEGF improved the capacity to predict the decline of eGFR in ADPKD patients compared with htTKV alone.

Conclusions

The urinary levels of molecules associated with either renal ischaemia (VEGF and MCP-1) or tubular damage (β2-microglobulin) are associated with renal function deterioration in ADPKD patients, and are, therefore, candidates as biomarkers of ADPKD progression.

Decoding the secreted inflammatory response of primary human hepatocytes to hypoxic stress in vitro

Background

The cellular and molecular response of liver cells to hypoxic stress is not fully understood. We used computational modeling to gain insights into the inflammatory response of primary human hepatocytes (HC) to hypoxic stress in vitro.

Methods

Primary HC from cancer patients were exposed to hypoxia (1% O₂) or normoxia (21% O₂) for 1-48 h, and the cell supernatants were assayed for 21 inflammatory mediators. Data were analyzed by Two-Way ANOVA, Dynamic Bayesian Network (DBN) inference, Dynamic Network Analysis (DyNA), and Time-interval Principal Component Analysis (TI-PCA).

Results

The chemokines MCP-1/CCL2 and IP-10/CXCL10, along with the cytokines interleukin (IL)-2 and IL-15 were altered significantly over time in hypoxic vs. normoxic HC. DBN inference suggested central, coordinating roles for MCP-1 and IL-8 in regulating a largely conserved inflammatory program in both hypoxic and normoxic HC. DyNA likewise suggested similar network trajectories of decreasing complexity over time in both hypoxic and normoxic HC, though with differential connectivity of MCP-1, IP-10, IL-8, and Eotaxin. TI-PCA pointed to IL-1β as a central characteristic of inflammation in hypoxic HC across all time intervals, along with IL-15 and IL-10, vs. Eotaxin, IL-7, IL-10, IL-15, and IL-17A in normoxic HC.

Conclusions

Thus, diverse human HC appear to respond in a largely conserved fashion to cell culture stress, with distinct characteristics based on the presence or absence of hypoxia.

Polyriboinosinic-polyribocytidylic acid facilitates interleukin-6, and interleukin-8 secretion in human dermal fibroblasts via the JAK/STAT3 and p38 MAPK signal transduction pathways

Polyriboinosinic-polyribocytidylic acid (polyI:C) is a viral dsRNA analoguethat promotes wounds healing, accelerates re-epithelialization, granulation and neovascularization, and induces pro-inflammatory cytokine release. Little is known about polyI:C mediated induction of inflammatory mediators in human dermal fibroblast (HDFs), which form the primary scaffold for epithelial cells covering the wound. Here, we found that polyI:C enhances IL-6 and IL-8 mRNA expression and induces of IL-6 and IL-8 production in a concentration-dependent and time-dependent manner in HDFs. PolyI:C treatment rapidly increased phosphorylation level of both STAT3 and p38 mitogen-activated protein kinase (MAPK). Moreover, pretreatment with AG490, a Janus kinase (JAK) inhibitor, inhibited polyI:C-induced STAT3 phosphorylation and subsequent IL-6 and IL-8 release. Conversely, pretreatment with SB203580, a selective inhibitor of p38 MAPK, blocked p38 MAPK phosphorylation and IL-6 and IL-8 expression. In conclusion, polyI:C induces IL-6 and IL-8 production in HDFs via the JAK/STAT3 and p38 MAPK signaling pathways.

Lack of Evidence for Vasoactive and Inflammatory Mediators in the Promotion of Macular Edema Associated with Epiretinal Membranes

The development of symptoms in patients with epiretinal membranes (ERMs) often corresponds with the accumulation of interstitial fluid in the retina [i.e., the development of macular edema, (ME)]. To explore the potential value of pharmacologic therapeutic options to treat ME in patients with ERMs, we examine here the expression of vasoactive and inflammatory mediators in the vitreous of patients with idiopathic ERMs. We observed that vitreous concentrations of classic vasoactive factors (e.g., vascular endothelial growth factor) were similar in ERM patients with ME compared to controls. Using an array assessing the expression of 102 inflammatory cytokines we similarly did not observe a marked difference in cytokine expression in the vitreous of most ERM patients with ME compared to control patients. While the array data did implicate a group of inflammatory cytokines that were elevated in a subset of ERM patients who had severe ME (central subfield thickness ≥450 μm on spectral domain optical coherence tomography), expression of 3 of these inflammatory cytokines, all previously implicated in the promotion of ME in ischemic retinal disease, were not elevated by quantitative enzyme-linked immunosorbent assay. We conclude that therapies modulating vasoactive mediators or inflammatory cytokines may not affect ME in ERM patients.

Hypoxia-induced CCL28 promotes recruitment of regulatory T cells and tumor growth in liver cancer

Tumor cells craft microenvironment to overcome growth disadvantages and adjust to escape the immunosurveillance during tumorigenesis and metastasis. The evolving adaption to the changing microenvironment is exemplified by the development of strategies to deal with hypoxia resulted from fast proliferation of the tumor cells. In this study, we found that hypoxia hepatocellular carcinoma (HCC) cells recruited Regulatory T cells (Tregs) and expressed more Chemokine (C-C motif) ligand 28 (CCL28). Deletion of CCL28 inhibited Treg recruitment. Furthermore, overexpression of CCL28 promoted tumor growth and Treg infiltration in vivo. Enhanced angiogenesis and VEGF expression was also observed. Moreover, inhibition of HIF1α reversed hypoxia-induced CCL28 upregulation. Taken together, our results demonstrate that HCC recruits Tregs to promote angiogenesis under hypoxic condition by upregulating CCL28 expression. These findings establish a link between Tregs and hypoxia in HCC growth and may provide a new potential therapeutic target for treating HCC.

Folic Acid Represses Hypoxia-Induced Inflammation in THP-1 Cells through Inhibition of the PI3K/Akt/HIF-1α Pathway

Though hypoxia has been implicated as a cause of inflammation, the underlying mechanism is not well understood. Folic acid has been shown to provide protection against oxidative stress and inflammation in patients with cardiovascular disease and various models approximating insult to tissue via inflammation. It has been reported that hypoxia-induced inflammation is associated with oxidative stress, upregulation of hypoxia-inducible factor 1-alpha (HIF-1α), and production of pro-inflammatory molecules. Whether folic acid protects human monocytic cells (THP-1 cells) against hypoxia-induced damage, however, remains unknown. We used THP-1 cells to establish a hypoxia-induced cellular injury model. Pretreating THP-1 cells with folic acid attenuated hypoxia-induced inflammatory responses, including a decrease in protein and mRNA levels of interleukin (IL)-1β and tumor necrosis factor-alpha (TNF-α), coupled with increased levels of IL-10. Folic acid also reduced hypoxia-induced Akt phosphorylation and decreased nuclear accumulation of HIF-1α protein. Both LY294002 (a selective inhibitor of phosphatidyl inositol-3 kinase, PI3K) and KC7F2 (a HIF-1α inhibitor) reduced levels of hypoxia-induced inflammatory cytokines. We also found that insulin (an Akt activator) and dimethyloxallyl glycine (DMOG, a HIF-1α activator) induced over-expression of inflammatory cytokines, which could be blocked by folic acid. Taken together, these findings demonstrate how folic acid attenuates the hypoxia-induced inflammatory responses of THP-1 cells through inhibition of the PI3K/Akt/HIF-1α pathway.

Hypoxia increases the expression of enamel genes and cytokines in an ameloblast-derived cell line

The aim of this study was to investigate the effect of hypoxic conditions on the expression of enamel genes and on the secretion of alkaline phosphatase (ALP), lactate dehydrogenase (LDH), cytokines, and interleukins by an ameloblast-derived cell line. Murine ameloblast-derived cells (LS-8 cells) were exposed to 1% oxygen for 24 and 48 h and harvested after 1, 2, 3, and 7 d. The effect of culture in hypoxic conditions on the expression of structural enamel matrix genes and on the secretion of cytokines and interleukins, as well as ALP and LDH, into the cell-culture medium was calculated relative to the expression and secretion of these factors by untreated cells (controls) at each time point. Hypoxia increased expression of the structural enamel matrix genes amelogenin (Amelx), ameloblastin (Ambn), and enamelin (Enam), and the enamel protease matrix metalloproteinase-20 (Mmp20). Expression of hypoxia-inducible factor 1-alpha (Hif1α), and secretion of several vascularization factors and pro-inflammatory factors, were increased after 24 and 48 h of hypoxia. The ALP activity was reduced after 24 and 48 h of hypoxia, whereas the LDH level in the cell-culture medium was higher after 24 h of hypoxic conditions compared with 48 h. In conclusion, hypoxic exposure may disrupt the controlled fine-tuned expression and processing of enamel genes, and promote the secretion of pro-inflammatory factors.

Annexin A1 mimetic peptide controls the inflammatory and fibrotic effects of silica particles in mice

BACKGROUND AND PURPOSE

Endogenous glucocorticoids are pro-resolving mediators, an example of which is the endogenous glucocorticoid-regulated protein annexin A1 (ANXA1). Because silicosis is an occupational lung disease characterized by unabated inflammation and fibrosis, in this study we tested the therapeutic properties of the N-terminal ANXA1-derived peptide annexin 1-(2-26) (Ac2-26) on experimental silicosis.

EXPERIMENTAL APPROACH

Swiss-Webster mice were administered silica particles intranasally and were subsequently treated with intranasal peptide Ac2-26 (200 μg per mouse) or dexamethasone (25 μg per mouse) for 7 days, starting 6 h post-challenge. Ac2-26 abolished the leukocyte infiltration, collagen deposition, granuloma formation and generation of pro-inflammatory cytokines evoked by silica; these variables were only partially inhibited by dexamethasone.

KEY RESULTS

A clear exacerbation of the silica-induced pathological changes was observed in ANXA1 knockout mice as compared with their wild-type (WT) littermate controls. Incubation of lung fibroblasts from WT mice with Ac2-26 in vitro reduced IL-13 or TGF-β-induced production of CCL2 (MCP-1) and collagen, but this peptide did not affect the production of CCL2 (MCP-1) by stimulated fibroblasts from formyl peptide receptor type 1 (FPR1) knockout mice. Ac2-26 also inhibited the production of CCL2 (MCP-1) from fibroblasts of FPR2 knockout mice.

CONCLUSIONS AND IMPLICATIONS

Collectively, our findings reveal novel protective properties of the ANXA1 derived peptide Ac2-26 on the inflammatory and fibrotic responses induced by silica, and suggest that ANXA1 mimetic agents might be a promising strategy as innovative anti-fibrotic approaches for the treatment of silicosis.

A small molecule approach to engineering vascularized tissue

The repertoire of growth factors determines the biological engagement of human mesenchymal stromal cells (hMSCs) in processes such as immunomodulation and tissue repair. Hypoxia is a strong modulator of the secretome and well known stimuli to increase the secretion of pro-angiogenic molecules. In this manuscript, we employed a high throughput screening assay on an hMSCs cell line in order to identify small molecules that mimic hypoxia. Importantly, we show that the effect of these small molecules was cell type/species dependent, but we identified phenanthroline as a robust hit in several cell types. We show that phenanthroline induces high expression of hypoxia-target genes in hMSCs when compared with desferoxamine (DFO) (a known hypoxia mimic) and hypoxia incubator (2% O(2)). Interestingly, our microarray and proteomics analysis show that only phenanthroline induced high expression and secretion of another angiogenic cytokine, interleukin-8, suggesting that the mechanism of phenanthroline-induced hypoxia is distinct from DFO and hypoxia and involves the activation of other signaling pathways. We showed that phenanthroline alone was sufficient to induce blood vessel formation in a Matrigel plug assay in vivo paving the way to its application in ischeamic-related diseases.

Low oxygen tension positively influences cardiomyocyte progenitor cell function

Previously we observed that cardiomyocyte progenitor cells (hCMPCs) isolated from the human heart differentiate spontaneously into cardiomyocytes and vascular cells when transplanted after myocardial infarction (MI) in the ischemic heart. After MI, deprivation of oxygen is the first major change in the cardiac environment. How cells handle hypoxia is highly cell type dependent. The effect of hypoxia on cardiac stem or progenitor cells remains to be elucidated. Here, we show for the first time that short- and long-term hypoxia have different effects on hCMPCs. Short-term hypoxia increased the migratory and invasive capacities of hCMPCs likely via mesenchymal transformation. Although long-term exposure to low oxygen levels did not induce differentiation of hCMPCs into mature cardiomyocytes or endothelial cells, it did increase their proliferation, stimulated the secretome of the cells which was shifted to a more anti-inflammatory profile and dampened the migration by altering matrix metalloproteinase (MMP) modulators. Interestingly, hypoxia greatly induced the expression of the extracellular matrix modulator thrombospondin-2 (TSP-2). Knockdown of TSP-2 resulted in increased proliferation, migration and MMP activity. In conclusion, short exposure to hypoxia increases migratory and invasive capacities of hCMPCs and prolonged exposure induces proliferation, an angiogenic secretion profile and dampens migration, likely controlled by TSP-2.

Renal tubulointerstitial hypoxia: cause and consequence of kidney dysfunction

1. Intrarenal oxygen availability is the balance between supply, mainly dependent on renal blood flow, and demand, determined by the basal metabolic demand and the energy-requiring tubular electrolyte transport. Renal blood flow is maintained within close limits in order to sustain stable glomerular filtration, so increased intrarenal oxygen consumption is likely to cause tissue hypoxia. 2. The increased oxygen consumption is closely linked to increased oxidative stress, which increases mitochondrial oxygen usage and reduces tubular electrolyte transport efficiency, with both contributing to increased total oxygen consumption. 3. Tubulointerstitial hypoxia stimulates the production of collagen I and α-smooth muscle actin, indicators of increased fibrogenesis. Furthermore, the hypoxic environment induces epithelial-mesenchymal transdifferentiation and aggravates fibrosis, which results in reduced peritubular blood perfusion and oxygen delivery due to capillary rarefaction. 4. Increased oxygen consumption, capillary rarefaction and increased diffusion distance due to the increased fibrosis per se further aggravate the interstitial hypoxia. 5. Recently, it has been demonstrated that hypoxia simulates the infiltration and maturation of immune cells, which provides an explanation for the general inflammation commonly associated with the progression of chronic kidney disease. 6. Therapies targeting interstitial hypoxia could potentially reduce the progression of chronic renal failure in millions of patients who are otherwise likely to eventually present with fully developed end-stage renal disease.

Vascular changes in bleomycin-induced scleroderma

Systemic sclerosis (SSc) is characterized by vascular injury, immunological abnormalities, and fibrosis of the skin as well as various internal organs. Vascular impairment is the early manifestation and plays a fundamental role in the pathogenesis of SSc. Recent studies suggest that complex interactions among the endothelial cells, pericytes, smooth muscle cells, and fibroblasts are involved in the systemic vasculopathy in SSc, and histological feature of proliferation of vascular wall is seen in the lesional scleroderma skin at the late stage of disease. One of the most representative mouse models for scleroderma is the bleomycin-induced scleroderma; however, aspects of vascular alteration have not been described in detail so far. A number of studies have shown that bleomycin stimulates endothelial cells and fibroblasts to induce proinflammatory and fibrogenic cytokines, apoptosis, reactive oxygen species, and so on. This paper makes a focus on the vascular involvement in the bleomycin-induced murine scleroderma.

Hypoxia reduces the response of human adipocytes towards TNFα resulting in reduced NF-κB signaling and MCP-1 secretion

OBJECTIVE

Obesity is associated with adipose tissue hypoxia, and is thought to be linked to the chronic low-grade inflammation of adipose tissue, although the precise mechanism has remained unclear. In this study, we investigated the effect of a prominent hypoxia on human primary adipocyte secretion and tumor necrosis factor alpha (TNFα)-induced nuclear factor-κB (NF-κB) signaling.

RESULTS

Using cytokine array and ELISA analysis, we compared the secretion patterns of normoxic and hypoxic (1% O(2)) adipocytes and observed various alterations in adipokine release. We could reproduce known alterations like an induction of interleukin (IL)-6, vascular endothelial growth factor, leptin and a reduction in adiponectin release under hypoxia. Interestingly, we observed a significant reduction in the secretion of macrophage chemotactic protein (MCP)-1 and other NF-κB-related genes, such as growth-regulated oncogene-α, eotaxin and soluble TNF-Receptor1 (TNF-R1) under hypoxia. TNFα stimulation of hypoxic adipocytes resulted in a significantly reduced phosphorylation of NF-κB and its inhibitor IκBα compared with normoxic cells. Furthermore, chronic treatment of hypoxic adipocytes with TNFα resulted in an expected higher secretion of the chemokines MCP-1 and IL-8, but under hypoxia, the secretion level was substantially lower than that under normoxia. This reduction in protein release was accompanied by a reduced mRNA expression of MCP-1, whereas IL-8 mRNA expression was not altered. Additionally, we observed a significantly reduced expression of the TNF-receptor TNF-R1, possibly being one cause for the reduced responsiveness of hypoxic adipocytes towards TNFα stimulation.

CONCLUSION

In conclusion, human primary adipocytes show a basal and TNFα-induced reduction of MCP-1 release under hypoxia. This effect may be due to a reduced expression of TNF-R1 and therefore attenuated TNFα-induced NF-κB signaling. These observations demonstrate a reduced responsiveness of hypoxic adipocytes towards inflammatory stimuli like TNFα, which may represent an adaptation process to maintain adipose tissue function under hypoxia and inflammatory conditions.

Lipopolysaccharide and hypoxia significantly alters interleukin-8 and macrophage chemoattractant protein-1 production by human fibroblasts but not fibrosis related factors

Besides extracellular matrix production, fibroblasts are able to produce various cytokines. Their ubiquitous position makes fibroblasts appropriate cells for sensing various noxious stimuli and for attracting immune cells in the affected area. In the present study the effect of lipopolysaccharide (LPS) and cobalt chloride (CoCl(2)) on the above fibroblasts functions were evaluated in primary human skin fibroblasts cultures. Collagen, matrix metalloproteinase-1, tissue inhibitor of metalloproteinases-1, transforming growth factor-β1, interleukin-8 (IL-8) and macrophage chemoattractant protein-1 (MCP-1) were measured in fibroblasts culture supernatants. Fibroblasts proliferation and viability were assessed as well. Hypoxia inducible factor-1α and the phosphorylated p65 portion of NF-κB were assessed in fibroblasts protein extracts. LPS and CoCl(2) had a minor effect on fibrosis related factors in human primary fibroblasts, possibly due to the absence of interplay with other cell types in the used experimental system. On the contrary both LPS and CoCl(2) increased significantly IL-8. LPS also increased considerably MCP-1, but CoCl(2) decreased it. Thus LPS and CoCl(2) induce a sentinel, nevertheless not identical, phenotype in primary human fibroblasts. The last disparity could result in different body response to infectious or hypoxic noxious stimuli.

Fibroblast activation in vascular inflammation

Vascular inflammation is implicated in both local and systemic inflammatory conditions. Endothelial activation and leukocyte extravasation are key events in vascular inflammation. Lately, the role of the stromal microenvironment as a source of proinflammatory stimuli has become increasingly appreciated. Stromal fibroblasts produce cytokines, growth factors and proteases that trigger and maintain acute and chronic inflammatory conditions. Fibroblasts have been associated with connective tissue pathologies such as scar formation and fibrosis, but recent research has also connected them with vascular dysfunctions. Fibroblasts are able to modulate endothelial cell functions in a paracrine manner, including proinflammatory activation and promotion of angiogenesis. They are also able to activate and attract leukocytes. Stromal fibroblasts can thus cause a proinflammatory switch in endothelial cells, and promote leukocyte infiltration into tissues. New insights in the role of adventitial fibroblasts have further strengthened the link between stromal fibroblasts and proinflammatory vascular functions. This review focuses on the role of fibroblasts in inducing and maintaining vascular inflammation, and describes recent findings and concepts in the field, along with examples of pathologic implications.

Autoimmune mechanisms of scleroderma and a role of oxidative stress

Scleroderma is a fibrotic condition characterized by immunological abnormalities, vascular injury and increased accumulation of extracellular matrix proteins in the skin. Although the etiology of scleroderma has not yet been fully elucidated, a growing body of evidence suggests that extracellular matrix overproduction by activated fibroblasts results from complex interactions among endothelial cells, lymphocytes, macrophages and fibroblasts via a number of mediators, such as cytokines, chemokines and growth factors. Recent investigations have further suggested that reactive oxygen species (ROS) are involved and play a role of autoimmunology in scleroderma. In this review, current findings on the autoimmune mechanisms in the pathophysiology of scleroderma are described.

Hypoxia and hypoxia-inducible factors: master regulators of metastasis

Hypoxia is a common condition found in a wide range of solid tumors and is often associated with poor prognosis. Hypoxia increases tumor glycolysis, angiogenesis, and other survival responses, as well as invasion and metastasis by activating relevant gene expressions through hypoxia-inducible factors (HIF). HIF-1α and HIF-2α undergo oxygen-dependent regulation, and their overexpression is frequently associated with metastasis and poor clinical outcomes. Recent studies show that each step of the metastasis process, from the initial epithelial-mesenchymal transition to the ultimate organotropic colonization, can potentially be regulated by hypoxia, suggesting a master regulator role of hypoxia and HIFs in metastasis. Furthermore, modulation of cancer stem cell self-renewal by HIFs may also contribute to the hypoxia-regulated metastasis program. The hypoxia-induced metastatic phenotype may be one of the reasons for the modest efficacy of antiangiogenic therapies and may well explain the recent provocative findings that antiangiogenic therapy increased metastasis in preclinical models. Multiple approaches to targeting hypoxia and HIFs, including HIF inhibitors, hypoxia-activated bioreductive prodrugs, and gene therapies may become effective treatments to prevent or reduce metastasis.

Importance of CCL2-CCR2A/2B signaling for monocyte migration into spheroids of breast cancer-derived fibroblasts

A considerable fraction of tumor-associated macrophages (TAM) is located in the fibroblast-rich stromal compartment of desmoplastic breast carcinoma. We analyzed the migratory activity of blood monocytes (MO), the precursor cells of TAM, into 3-D cultures of carcinoma cells and fibroblasts from breast tumor origin. MO migration into breast tumor spheroids was highly variable: Hs578T spheroids showed high MO infiltration rates, T47D cultures were intermediate, whereas BT549, BT474 and MCF-7 spheroids were poorly infiltrated. MO infiltration was also high in tumor-derived fibroblast spheroids; however, no MO subpopulation with specific infiltrative potential was identified by CD14/CD16 expression profile. The infiltration of MO could be inhibited by pre-exposure to pertussis and cholera toxins, but only pertussis toxin, which blocks G(i) protein function, entirely inhibited MO migration. The G(i) coupled CCL2 receptor CCR2A/2B was expressed on roughly all MO. Furthermore, highly infiltrated tumor-derived fibroblast and Hs578T spheroids secreted considerable amounts of CCL2. In line with this, the infiltration of MO into fibroblast spheroids was suppressed by either addition of recombinant CCL2 to disturb the CCL2 gradient or by pre-incubation of MO with a CCR2A/2B blocking antibody. MO infiltration of Hs578T spheroids, however, could not be inhibited by CCL2 receptor blockade. Our study clearly shows that the CCL2-CCR2A/2B pathway is crucial for the recruitment of blood MO into tumor fibroblastic areas, whereas additional factors may be relevant for the migration of MO into tumor cell sites.

Tubular epithelial cells transfected with hHGF counteracts monocyte chemotactic protein-1 up-regulation after hypoxia/reoxygenation insult

Acute kidney injury (AKI) which is mainly produced by nephrotoxic or ischemic insults is correlated with a high mortality and morbidity. Proximal tubular epithelial cells (PTEC) play a major role. They are the main target of ischemia/reperfusion injury. PTECs have also been proposed as the effectors of AKI reversibility, but also as the creator of the inflammatory milieu: cytokine, chemokine, and complement expression. An important chemokine implicated in this process is monocyte chemotactic protein-1 (MCP-1) due to its ability to recruit and activate monocytes. Hepatocyte growth factor (HGF) is a pleiotropic factor with mitogenic, anti-apoptotic, and proliferative effects which has recently been studied for its anti-inflammatory and antifibrogenic effects. Our aim was to evaluate the potential inflammatory effect of hypoxia and reoxygenation on rat PTECs. We created a stable human HGF (hHGF) expressing PTEC line that emulated in vivo transfection and analyzed the role of this cell type in the induction and reversibility of AKI. Our results showed the efficiency of transfection with the hHGF gene to promote sustained expression of the protein in the medium (7627.13 +/- 1144.078 to 8211.3 +/- 795.37 pg/mL). When rat PTECs were under a hypoxia/reoxygenation insult, MCP-1 was highly overexpressed (4479.3 +/- 154.3 pg/mL of protein and 5.099 +/- 1.23 times control gene expression). Transfected cells abrogated this effect (288.7 +/- 13.5 pg/mL and 1.169 +/- 0.0759 times control). In conclusion, we observed that the hypoxia/reoxygenation insult stimulated MCP-1 protein secretion in PTECs and that PTECs which were stably transfected and overexpressing hHGF abrogated the inflammatory reaction mediated by hypoxia/reoxygenation, being a suitable model for later studies.

Mediators of neovascularization and the hypoxic cornea

The maintenance of corneal avascularity is essential to vision. The mechanisms by which the cornea becomes vascularized in response to inflammation or hypoxic stress are beginning to be elucidated. A detailed understanding of the molecular responses of the cornea to hypoxia is critical for prevention and development of novel treatments for neovascularization in a range of disease states. Here, we have examined the current literature on the major mediators of angiogenesis, which have previously been reported during hypoxia in the cornea in order to better understand the mechanisms by which corneal angiogenesis occurs in circumstances where the available oxygen is reduced. The normal cornea produces angiogenic factors that are regulated by the production of anti-angiogenic molecules. The various cell types of the cornea respond differentially to inflammatory and hypoxic stimuli. An understanding of the factors that may predispose patients to development of corneal blood vessels may provide an opportunity to develop novel prophylactic strategies. The difficulties with extrapolating data from other cell types and animal models to the cornea are also examined.

Activated nuclear factor kappa B and airway inflammation after smoke inhalation and burn injury in sheep

In a recent study, we have shown a rapid inflammatory cell influx across the glandular epithelium and strong proinflammatory cytokine expression at 4 hours after inhalation injury. Studies have demonstrated a significant role of nuclear factor kappa B in proinflammatory cytokine gene transcription. This study examines the acute airway inflammatory response and immunohistochemical detection of p65, a marker of nuclear factor kappa B activation, in sheep after smoke inhalation and burn injury. Pulmonary tissue from uninjured sheep and sheep at 4, 8, 12, 24, and 48 hours after inhalation and burn injury was included in the study. Following immunostaining for p65 and myeloperoxidase, the cell types and the percentage of bronchial submucosal gland cells staining for p65 and the extent of myeloperoxidase stained neutrophils in the bronchial submucosa were determined. Results indicate absence of detection of P65 before 12 hours after injury. At 12 hours after injury, strong perinuclear staining for p65 was evident in bronchial gland epithelial cells, macrophages, and endothelial cells. Bronchial submucosal gland cells showed a significant increase in the percentage of cells stained for p65 compared with uninjured animals and earlier times after injury, P < .05. At 24 and 48 hours after injury, p65 expression was evident in the bronchiolar epithelium, Type II pneumocytes, macrophages, and endothelial cells. Quantitation of the neutrophil influx into the bronchial submucosa showed a significant increase compared with uninjured tissue at 24 and 48 hours after injury, P < .05. In conclusion, immunohistochemical detection of activated p65 preceded the overall inflammatory response measured in the lamina propria. However, detection of p65 did not correlate with a recent study showing rapid emigration of neutrophils at 4 hours postinjury. Together, these results suggest that p65 immunostaining may identify cells that are activated to produce proinflammatory cytokines after injury; however, the immunoexpression may not adequately reflect the temporal activation of gene transcription that may occur with proinflammatory cytokine production with inhalation injury.

Regulation of chemokine gene expression by hypoxia via cooperative activation of NF-kappaB and histone deacetylase

Hypoxia is a microenvironmental factor frequently associated with tumors and inflammation. This study addresses the question of how hypoxia modulates the basal and IL-1 beta-induced production of cytokines and aims to identify the underlying mechanism of hypoxic transcriptional repression. We found that despite the similarities of the promoter structures of IL-8 and MCP-1, these chemokines were differently regulated by hypoxia (an increase in IL-8, but a decrease in MCP-1 mRNA and protein expression). Such differences were not observed in a reporter gene assay, in which both of the promoters were activated by hypoxia. The difference in the response to hypoxia between MCP-1 expression and the promoter assay was not due to mRNA instability. Using proteosome inhibitor MG132 and I kappaB overexpression we demonstrated that an NF-kappaB-dependent mechanism was involved in both the activation of IL-8 and the repression of MCP-1 mRNA expression in response to hypoxia. The histone deacetylase inhibitor Trihostatin A abolished the inhibitory actions of hypoxia on IL-1 beta-induced MCP-1 gene expression. Furthermore, hypoxia induced histone deacetylase activity in the nuclear extracts. Although stimulation with IL-1 beta and/or hypoxia increased the acetylation of histones H3 and H4 in the presence of Trihostatin A, histone acetylation remained unchanged when the cells were treated without histone deacetylase inhibitor. Collectively, our findings suggest that transiently transfected promoters are not subject to the same NF-kappaB regulatory mechanisms as their chromatinized counterparts. NF-kappaB, activated by hypoxia, can act as a transcriptional repressor via a mechanism that involves deacetylation of histones.

Evaluation of a near-senescent human dermal fibroblast cell line and effect of amelogenin

BACKGROUND

Fibroblast senescence may delay healing of chronic wounds.

OBJECTIVES

To characterize a chronic human dermal fibroblast cell line (CRL-7815) with near-senescent properties, cell proliferation and production of wound-healing modulating cytokines, and biosynthesis and remodelling of collagen were compared with normal human dermal fibroblasts. Also, the response of CRL-7815 fibroblasts to the extracellular matrix protein amelogenin that is beneficial in the treatment of stalled chronic wounds was studied.

METHODS

Fibroblast proliferation was monitored by time-resolved growth curves and factors secreted into the culture medium containing 10% fetal bovine serum were measured by enzyme-linked immunosorbent assays. Fibroblast-mediated reorganization was examined in three-dimensional type I collagen matrices.

RESULTS

Cell proliferation over 9 days was significantly (P < 0.01) slower for CRL-7815 than for normal fibroblasts. Amelogenin at 1 mg mL(-1) increased (P < 0.01) CRL-7815 proliferation to the level of the normal fibroblasts. The neutrophil chemoattractant interleukin (IL)-8 was low while the constitutive production of monocyte chemoattractant protein (MCP)-1 was highly elevated in medium from cultured CRL-7815 fibroblasts. Amelogenin augmented IL-8 but attenuated MCP-1 secretion in CRL-7815 fibroblasts. The elevated vascular endothelial growth factor production in CRL-7815 fibroblasts was further increased with amelogenin while increased type I collagen synthesis by CRL-7815 was reduced with 0.1 mg mL(-1) amelogenin. The dramatically impaired collagen matrix remodelling with CRL-7815 fibroblasts (P < 0.001) was slightly improved with amelogenin (P = 0.0011).

CONCLUSIONS

The near-senescent cell line CRL-7815 shares functional anomalies with fibroblasts isolated from nonhealing chronic cutaneous wounds. Amelogenin has the capacity to switch chronic fibroblasts into an acute-like phenotype.

An age-old paradigm challenged: old baboons generate vigorous humoral immune responses to LcrV, a plague antigen

Immune senescence in the elderly results in decreased immunity with a concomitant increase in susceptibility to infection and diminished efficacy of vaccination. Nonhuman primate models have proven critical for testing of vaccines and therapeutics in the general population, but a model using old animals has not been established. Toward that end, immunity to LcrV, a protective Ag from Yersinia pestis, was tested in young and old baboons. Surprisingly, there was no age-associated loss in immune competence; LcrV elicited high-titer, protective Ab responses in the older individuals. The primary responses in the younger baboons were lower, but they did show boosting upon secondary immunization to the levels achieved in the old animals. The LcrV Ag was also tested in mice and, as expected, age-associated loss of immunity was seen; older animals responded with lower-titer Abs and, as a result, were more susceptible to Yersinia challenge. Thus, although age-related loss in immune function has been observed in humans, rodents, and some nonhuman primates, baboons appear to be unusual; they age without losing immune competence.

The immunobiology of systemic sclerosis

OBJECTIVES

Systemic sclerosis (SSc) is a chronic connective tissue disease characterized by vascular damage, autoimmunity, and excessive collagen deposition. Despite advances in disease-specific treatment of other rheumatologic diseases, disease-targeted treatment in SSc continues to be elusive. In this review, our goal was to place the contemporary immunobiology of SSc in the perspective of clinical medicine.

METHODS

We performed a PubMed search for the period from 1989 to 2007, using the keyword, "systemic sclerosis," resulting in a total of 9099 publications, including 1252 reviews. Articles were then selected based on their discussion of recent advances in the elusive pathogenesis of SSc. A final total of 259 articles were chosen for the review.

RESULTS

The SSc hallmarks of vascular damage, immunologic activation, and collagen deposition can be traced to 4 major factors: T-cells, fibroblasts, B-cells, and cytokines/chemokines. T-cells are a major component of the infiltrate in skin and lung, exhibiting increased expression of activation markers and showing signs of antigen-driven expansion. Preliminary data indicate that induction of oral tolerance with collagen, a target of SSc T-cell responses, is associated with clinical benefits. Although this suggests that T-cells participate in the pathogenesis of SSc, their precise role and antigen specificity largely remain to be elucidated. Defective numbers and functions of certain T-cell subsets, such as natural killer and gammadelta T-cells, may be involved in the failure to maintain tolerance. Other data suggest that gammadelta T-cells may themselves be effector cells in endothelial cell cytotoxicity. There are several lines of evidence for a pathogenic role of B-cells in SSc, in particular, through the production of autoantibodies. Antibody-dependent cell-mediated cytotoxicity is a primary pathogenic event in an animal model of SSc and is likely to be involved in human SSc. Nonetheless, there is as yet no convincing evidence for the pathogenicity of SSc-specific antibodies. SSc fibroblasts exhibit a specific phenotype characterized not only by excessive collagen production but also by increased responsiveness to and production of cytokines and chemokines. This phenotype is induced by a complex network of cytokines and chemokines but appears to be maintained in the absence of exogenous stimuli via the autocrine production of some of these factors by SSc fibroblasts themselves, particularly transforming growth factor, platelet-derived growth factor, monocyte chemoattractant protein 1, and interleukin-1.

CONCLUSIONS

Significant variations in laboratory data among patients suggest that the pathology reflects a heterogeneous disease. Nonetheless, the possibility of achieving clinical benefits by inducing oral tolerance highlights the importance of characterizing SSc T-cell antigens. It is hoped that the identification of some of the key players in the induction and maintenance of the SSc fibroblast phenotype may yield new disease-targeted treatment regimens for patients with SSc.

CXCR2 agonists in ADPKD liver cyst fluids promote cell proliferation

Autosomal dominant polycystic kidney disease (ADPKD) is a highly prevalent genetic disease that results in cyst formation in kidney and liver. Cytokines and growth factors secreted by the cyst-lining epithelia are positioned to initiate autocrine/paracrine signaling and promote cyst growth. Comparative analyses of human kidney and liver cyst fluids revealed disparate cytokine/growth factor profiles. CXCR2 agonists, including IL-8, epithelial neutrophil-activating peptide (ENA-78), growth-related oncogene-alpha (GRO-alpha), are potent proliferative agents that were found at high levels in liver but not kidney cyst fluids. Liver cysts are lined by epithelial cells derived from the intrahepatic bile duct (i.e., cholangiocytes). In polarized pkd2(WS25/-) mouse liver cyst epithelial monolayers, CXCR2 agonists were released both apically and basally, indicating that they may act both on the endothelial and epithelial cells within or lining the cyst wall. IL-8 and human liver cyst fluid induced cell proliferation of HMEC-1 cells, a human microvascular endothelial cell line, and Mz-ChA1 cells, a human cholangiocyte cell model. IL-8 expression can be regulated by specific stresses. Hypoxia and mechanical stretch, two likely stressors acting on the liver cyst epithelia, significantly increased IL-8 secretion and promoter activity. AP-1, c/EBP, and NF-kappaB were required but not sufficient to drive the stress-induced increase in IL-8 transcription. An upstream element between -272 and -1,481 bp allowed for the stress-induced increase in IL-8 transcription. These studies support the hypothesis that CXCR2 signaling promotes ADPKD liver cyst growth.

Synovial proliferation differentially affects hypoxia in the joint cavities of rheumatoid arthritis and osteoarthritis patients

This study was performed to investigate whether synovial proliferation (SP) differentially affects hypoxia in the joint cavities of rheumatoid arthritis (RA) and osteoarthritis (OA) patients. Thirty RA and 42 OA patients who underwent synovitis assessment were classified into two groups based on the presence or absence of SP, as revealed by musculoskeletal ultrasonography. Synovial fluids (SFs) from the knee joints were analyzed for interleukin (IL)-8, pO(2), and white blood cell counts and blood samples were analyzed for erythrocyte sedimentation rate (ESR). No difference was found between the OA patients with and without SP in terms of SF oxygen tension (SF pO(2)) or IL-8 level, whereas the RA patients had significantly lower SF pO(2) levels in their knee joints than did the OA patients with SP, and the RA patients had higher levels of IL-8 in their joints than did the OA patients. The counts of infiltrated immune cells in the SF and tissues were much higher for patients with RA and SP than for those with OA and SP. The ESRs were not found to be correlated with SP in OA patients but were negatively correlated with SF pO(2) levels in RA patients. We conclude that ultrasonographically detected SP in OA patients does not generate a more hypoxic SF than that found in OA patients without SP. The SFs from RA patients with SP are hypoxic, which indicates that SP may have different impacts on hypoxia in the joint cavities of RA and OA patients.

Intrarenal oxygenation in chronic renal failure

In chronic renal failure (CRF), renal impairment correlates with tubulointerstitial fibrosis characterized by inflammation, interstitial expansion with accumulation of extracellular matrix (ECM), tubular atrophy and vascular obliteration. Tubulointerstitial injury subsequent to glomerular sclerosis may be induced by proteinuria, leakage of glomerular filtrate or injury to the post-glomerular peritubular capillaries (hypoxia). In vivo data in animal models suggest that CRF is associated with hypoxia, with the decline in renal Po2 preceding ECM accumulation. Chronic renal failure is characterized by loss of microvascular profiles but, in the absence of microvascular obliteration, hypoxia can occur by a variety of complementary mechanisms, including anaemia, decreased capillary flow, increased vasoconstriction, increased metabolic demand and increased diffusion distances due to ECM deposition. Hypoxia regulates a wide array of genes, including many fibrogenic factors. Hypoxia-inducible factors (HIF) are the major, but not the sole, transcriptional regulators in the hypoxic response. In CRF, hypoxia may play a role in the sustained inflammatory response. In vitro studies in tubulointerstitial cells suggest that hypoxia can induce profibrogenic changes in proximal tubular epithelial cells and interstitial fibroblasts consistent with changes observed in CRF in vivo. The effect of hypoxia on renal microvascular cells warrants investigation. Hypoxia may play a role in the recruitment, retention and differentiation of circulating progenitor cells to the kidney contributing to the disease process and may also affect intrinsic stem cell populations. Chronic hypoxia in CRF fails to induce a sustained angiogenic response. Therapeutic manipulation of the hypoxic response may be of benefit in slowing progression of CRF. Potential therapies include correction of anaemia, inhibition of the renin-angiotensin system, administration of exogenous pro-angiogenic factors to protect the microvasculature, activation of HIF and hypoxia-mediated targeting of engineered progenitor cells.

Hypoxia-induced mitogenic factor has proangiogenic and proinflammatory effects in the lung via VEGF and VEGF receptor-2

From a mouse model of hypoxia-induced pulmonary hypertension, we previously found a highly upregulated protein in the lung that we named hypoxia-induced mitogenic factor (HIMF), also known as found in inflammatory zone 1 (FIZZ1), and resistin-like molecule alpha (RELMalpha). However, the mechanisms of HIMF in the pulmonary vascular remodeling remain unknown. We now demonstrate that HIMF promoted cell proliferation, migration, and the production of vascular endothelial growth factor (VEGF) and monocyte chemotactic protein-1 (MCP-1) in pulmonary endothelial cells as well as the production of reactive oxygen species in murine monocyte/macrophage cells. HIMF-induced CD31-positive cell infiltrate in in vivo Matrigel plugs was significantly suppressed by VEGF receptor-2 (VEGFR2) blockade. In ex vivo studies, HIMF stimulated the production of VEGF, MCP-1, and stromal cell-derived factor-1 (SDF-1) in the lung resident cells, and VEGFR2 neutralization significantly suppressed HIMF-induced MCP-1 and SDF-1 production. Furthermore, intravenous injection of HIMF showed marked increase of CD68-positive inflammatory cells in the lungs, and these events were attenuated by VEGFR2 neutralization. Intravenous injection of HIMF also downregulated the expression of VEGFR2 in the lung. These results suggest that HIMF plays critical roles in pulmonary inflammation as well as angiogenesis.

Chemokines and Chemokine Receptors in Scleroderma

Scleroderma is a connective tissue disease with unknown etiology characterized by excessive deposition of extracellular matrix in the skin. Cellular infiltrates of certain immune cells and proinflammatory mediators are suggested to play a crucial role in cutaneous fibrosis, forming complicated networks between fibroblasts and immune cells via cell-cell communications. Tissue-selective trafficking of leukocytes is mediated by combinations of adhesion molecules and chemokines. Recent studies have shown that an increase in proinflammatory chemokines has been associated with the initiation and/or development of skin fibrosis/sclerosis, suggesting that chemokines and their receptors may be important mediators of inflammation and fibrosis in scleroderma. This review will focus on the roles of chemokines and their receptors during the process of cutaneous sclerosis and will also provide a current insight into the potential mechanisms of scleroderma.

Regulation of monocyte chemoattractant protein 1 (MCP-1) release by explants of human visceral adipose tissue

BACKGROUND

Monocyte chemoattractant protein-1 (MCP-1) is a chemokine involved in monocyte recruitment during inflammation whose plasma level is elevated in obesity.

OBJECTIVE

The present studies were designed to examine the release of MCP-1 in primary culture by explants of visceral adipose tissue from morbidly obese women.

RESULTS

Most of the MCP-1 released by adipose tissue explants was derived from the nonfat cells in adipose tissue. The release of MCP-1 by adipose tissue explants was upregulated almost five-fold between 3 and 48 h of incubation. Approximately half of this upregulation was due to the release of endogenous tumor necrosis factor alpha (TNFalpha) and IL-1beta based on the ability of a combination of a soluble TNFalpha receptor (etanercept) and a blocking antibody against IL-1beta to reduce MCP-1 release. The release of MCP-1 over 48 h was unaffected by insulin or dexamethasone but significantly reduced by the combination of both agents. MCP-1 release was reduced by 60% in the presence of an inhibitor of the nuclear factor kappaB (NF-kappaB) pathway. There were no significant effects of inhibitors of p44/42 mitogen-activated protein kinase (ERK), Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase (p38 MAPK) pathways on MCP-1 release. However, inhibition of MCP-1 release in the presence of inhibitors of both the p38 MAPK and NF-kappaB pathways was greater than that seen with only the NF-kappaB inhibitor.

DISCUSSION

The present data shows that MCP-1 formation is upregulated over a 48-h incubation of primary explants of visceral adipose tissue. Half of this upregulation is dependent upon endogenous TNFalpha and Il-1beta and involves the p38 MAPK and NF-kappaB pathways.

Angiogenic transcriptome of human microvascular endothelial cells: Effect of hypoxia, modulation by atorvastatin

Hypoxia changes expression of angiogenic genes. Statins were also reported to affect blood vessel formation. However, data on the effects of statins on endothelial cells in hypoxia are limited. Here, effect of hypoxia and atorvastatin was assessed in human microvascular endothelial cells (HMEC-1). Hypoxia (1% O2) up-regulated vascular endothelial growth factor-A (VEGF-A) but, unexpectedly, it decreased interleukin-8 (IL-8) and placenta growth factor (PlGF) expression. Atorvastatin (0.1-1 microM) attenuated PlGF in HMEC-1 in normoxia while it decreased VEGF-A and IL-8 production both in normoxia and hypoxia. Notably, the expression of VEGF-D, macrophage scavenger receptor-1 (MSR1), transforming growth factor beta receptor III (TGFbetaR3) and inhibitor of DNA binding 3 (ID3) was augmented by atorvastatin in cells cultured in normoxia, while in hypoxia the statin attenuated their expression. These data showed that hypoxia influenced in the opposite way the expression of major endothelial genes, augmenting VEGF-A and decreasing IL-8 and PlGF. The influence of atorvastatin on angiogenic gene expression is complex, and final pro- or anti-angiogenic outcome of statin therapy remains to be established for numerous angiogenesis-related diseases.

The bleomycin-induced scleroderma model: what have we learned for scleroderma pathogenesis?

Scleroderma is a fibrotic condition characterized by immunologic abnormalities, vascular injury and increased accumulation of extracellular matrix (ECM) proteins in the skin. Although the etiology of scleroderma has not yet been fully elucidated, a growing body of evidence suggests that ECM overproduction by activated fibroblasts results from complex interactions among endothelial cells, lymphocytes, macrophages and fibroblasts, via a number of mediators, such as cytokines, chemokines and growth factors. For a better understanding of the pathophysiology of scleroderma, animal models are important tools. We established a murine model of cutaneous sclerosis by local treatment of bleomycin. This model reproduces several histological as well as biochemical aspects of human scleroderma. However, it must be emphasized that studying animal models cannot answer all the problems of human scleroderma. In this review, we introduce current insights into the pathogenesis of bleomycin-induced scleroderma, and discuss its contribution to our understanding of the pathogenesis of, and treatments for, human scleroderma.

Fas activation of a proinflammatory program in rheumatoid synoviocytes and its regulation by FLIP and caspase 8 signaling

OBJECTIVE

The expansion of an aggressive population of fibroblast-like synoviocytes (FLS) in rheumatoid arthritis (RA) synovium occurs despite their expression of functional death receptors and exposure to death receptor ligands. FLS can survive Fas challenge because of the constitutive expression of FLIP apoptosis inhibitor. We investigated whether Fas signaling plays a pathogenetic role by activating a nonapoptotic proinflammatory program in RA FLS.

METHODS

Cultured RA FLS were stimulated with an agonistic anti-Fas antibody in the presence or absence of the caspase inhibitor Z-VAD-FMK or after RNA interference with a short hairpin RNA expression plasmid directed against FLIP. NF-kappaB and activator protein 1 (AP-1) activation was studied by electrophoretic mobility shift assays and p65 immunofluorescence analysis, and expression of messenger RNA (mRNA) for monocyte chemoattractant protein 1, interleukin-8, IkappaB alpha, and matrix metalloproteinases (MMPs) 1, 9, and 13 was examined by reverse transcription-polymerase chain reaction. Chemotactic activity of Fas-activated FLS-conditioned media was studied in Transwell migration assays.

RESULTS

Fas stimulation activated NF-kappaB and AP-1, and this response required caspase activity, since Z-VAD-FMK inhibitor precluded it. FLIP was processed to p43 protein after Fas stimulation in a caspase-dependent manner, and inhibition of FLIP expression resulted in reduced Fas-triggered NF-kappaB activation. Fas stimulation increased expression of mRNA for IkappaB alpha, MMPs, and chemokines, and Fas-activated RA FLS displayed increased chemotactic activity for monocytic cells.

CONCLUSION

Fas triggering may contribute to the proinflammatory features of RA FLS by activating NF-kappaB and AP-1 and by expression of relevant target genes, such as MMPs and chemokines. Fas proinflammatory signaling is dependent upon caspase activity and FLIP expression. These data implicate FLIP as a potentially important molecular switch that turns the Fas signaling away from apoptosis and toward induction of a proinflammatory phenotype in RA FLS.

Induction of interleukin-8 secretion and activation of ERK1/2, p38 MAPK signaling pathways by thrombin in dermal fibroblasts

It was reported that thrombin could induce IL-8 secretion from human dermal fibroblasts (HDFs) through activation of proteinase activated receptor (PAR)-1. However, little is known of intracellular signaling pathways involved in the event. In the present study, expression of PARs in primarily cultured HDFs was determined by flow cytometry analysis and reverse transcription polymerase chain reaction (RT-PCR), levels of IL-8 were determined by using ELISA and signaling pathways were examined by using Western blot. It was found that HDFs express PAR-1 and PAR-3, and thrombin induces approximately 7.4-fold increase in IL-8 secretion from HDFs. Hirudin and a PAR-1 blocking antibody completely abolish the action of thrombin. It was also found that PD98059, a mitogen-activated protein kinase (MAPK) pathway inhibitor and U0126, an inhibitor of extracellular signal-regulated kinase (ERK) blocks thrombin-induced phosphorylation of ERK1/2 and IL-8 secretion, indicating the involvement of MAPK/ERK signaling pathway in thrombin-induced IL-8 secretion. p38 MAPK pathway appears also being involved as SB203580, a selective inhibitor of p38 MAPK inhibit phosphorylation of p38 MAPK and thrombin-induced IL-8 secretion. Furthermore, Janus kinase (JAK)/signal transducer and activator of transcription 3 (STAT3) pathway, but not phosphotidylinositol 3-kinase (PI3K)/Akt signaling pathway may also be activated by thrombin. In conclusion, thrombin potently induce IL-8 release via PAR-1 from HDFs. Thrombin elicited IL-8 release is predominantly conducted through MAPK/ERK and p38 MAPK signaling pathways. Discovery of the signaling pathways of thrombin in HDFs may help to understand the role of thrombin in inflammation and tissue remodeling.