BackgroundThe granulocyte colony-stimulating factor receptor (G-CSFR) plays a critical role in maintaining homeostatic levels of circulating neutrophils (PMN). The mechanisms modulating G-CSFR surface expression to prevent chronic neutrophilia are poorly understood. Here, we report that neutrophil elastase (NE) proteolytically cleaves the G-CSFR on human PMN and blocks G-CSFR-mediated granulopoiesis in vitro.MethodsHuman peripheral blood PMN isolated from healthy donors were incubated with NE. Expression of the G-CSFR was analyzed by flow cytometry and western blot analyses. Detection of G-CSFR cleavage products from the culture supernatants was also performed. Human bone marrow mononuclear cells were also cultured in the presence or absence of NE to determine its effects on the proliferation of granulocyte-macrophage colony forming units (CFU-GM).ResultsTreatment of PMN with NE induced a time-dependent decrease in G-CSFR expression that correlated with its degradation and the appearance of proteolytic cleavage fragments in conditioned media. Immunoblot analysis confirmed the G-CSFR was cleaved at its amino-terminus. Treatment of progenitor cells with NE prior to culture inhibited the growth of granulocyte-macrophage colony forming units.ConclusionsThese findings indicate that in addition to transcriptional controls and ligand-induced internalization, direct proteolytic cleavage of the G-CSFR by NE also downregulates G-CSFR expression and inhibits G-CSFR-mediated granulopoiesis in vitro. Our results suggest that NE negatively regulates granulopoiesis through a novel negative feedback loop.

BackgroundIL-6 is a pro-inflammatory cytokine that signals via binding to a soluble or membrane bound receptor, while nitric oxide (NO), an oxidative stress molecule, diffuses through the cell membrane without a receptor. Both mediators signal through different mechanisms, yet they are dependent on NFκB. We proposed that both mediators are co-induced and co-regulated in inflamed mammary epithelial cells.MethodsSCp2 mammary epithelial cells were treated with bacterial endotoxin (ET) for different time periods and analyzed for induction of IL-6 secretion and NO production by ELISA and Griess reaction, respectively. The expression of IL-6 and induced NO synthase (iNOS) was assayed by real time PCR and/or western immunoblots, and the activation of NFκB was assayed by immunobinding assay. To investigate the role of mammary cell microenvironment (cell-substratum or interaction of mammary epithelial cell types; critical to mammary development, function, and disease) in modulation of the inflammatory response, SCp2 cells were cultured with or without extracellular matrix (EHS) or in coculture with their myoepithelial counterpart (SCg6), and assayed for ET-induced IL-6 and NO.ResultsEndotoxin induced NFκB activation at 1 h after ET application. IL-6 secretion and NO production were induced, but with unexpected delay in expression of mRNA for iNOS compared to IL-6. NFκB/p65 activation was transient but NFκB/p50 activation persisted longer. Selective inhibition of NFκB activation by Wedelolactone reduced ET-induced expression of IL-6 mRNA and protein but not iNOS mRNA or NO production, suggesting differences in IL-6 and iNOS regulation via NFκB. SCp2 cells in coculture with SCg6 but not in presence of EHS dramatically induced IL-6 secretion even in the absence of ET. ET-induced NO production was blunted in SCp2/SCg6 cocultures compared to that in SCp2 alone.ConclusionsThe differential regulation of IL-6 and iNOS together with the differential activation of different NFκB dimers suggest that IL-6 and iNOS are regulated by different NFκB dimers, and differentially regulated by the microenvironment of epithelial cells. The understanding of innate immune responses and inflammation in epithelia and linkage thereof is crucial for understanding the link between chronic inflammation and cancer in epithelial tissues such as the mammary gland.

BackgroundPrevious studies in our lab have identified Pre-B-cell colony enhancing factor (PBEF) as a novel biomarker in acute lung injury (ALI). The molecular mechanism of PBEF involvement in the pathogenesis of ALI is still incompletely understood. This study examined the role of PBEF in regulating pulmonary alveolar epithelial cell IL-8 expression and permeability.MethodsHuman pulmonary alveolar epithelial cells (cell line and primary cells) were transfected with human PBEF cDNA or PBEF siRNA and then cultured in the presence or absence of TNFα. PBEF and IL-8 expression were analyzed by RT-PCR and Western blotting. In addition, changes in pulmonary alveolar epithelial and artery endothelial cell barrier regulation with altered PBEF expression was evaluated by an in vitro cell permeability assay.ResultsOur results demonstrated that, in human pulmonary alveolar epithelial cells, the overexpression of PBEF significantly augmented basal and TNFα-stimulated IL-8 secretion by more than 5 to 10-fold and increased cell permeability by >30%; the knockdown of PBEF expression with siRNA significantly inhibited basal and TNFα-stimulated IL-8 secretion by 70% and IL-8 mRNA levels by 74%. Further, the knockdown of PBEF expression also significantly attenuated TNFα-induced cell permeability by 43%. Similar result was observed in human pulmonary artery endothelial cells.ConclusionThese results suggest that PBEF may play a vital role in basal and TNFα-mediated pulmonary inflammation and pulmonary epithelial barrier dysfunction via its regulation of other inflammatory cytokines such as IL-8, which could in part explain the role of PBEF in the susceptibility and pathogenesis of ALI. These results lend further support to the potential of PBEF to serve as a diagnostic and therapeutic target to ALI.

BackgroundBee venom therapy has been used to treat inflammatory diseases including rheumatoid arthritis in humans and in experimental animals. We previously found that bee venom and melittin (a major component of bee venom) have anti-inflammatory effect by reacting with the sulfhydryl group of p50 of nuclear factor-kappa B (NF-κB) and IκB kinases (IKKs). Since mitogen activated protein (MAP) kinase family is implicated in the NF-κB activation and inflammatory reaction, we further investigated whether activation of MAP kinase may be also involved in the anti-inflammatory effect of melittin and bee venom.MethodsThe anti-inflammatory effects of melittin and bee venom were investigated in cultured Raw 264.7 cells, THP-1 human monocytic cells and Synoviocytes. The activation of NF-κB was investigated by electrophoretic mobility shift assay. Nitric oxide (NO) and prostaglandin E2 (PGE2) were determined either by Enzyme Linked Immuno Sorbent Assay or by biochemical assay. Expression of IκB, p50, p65, inducible nitric oxide synthetase (iNOS), cyclooxygenase-2 (COX-2) as well as phosphorylation of MAP kinase family was determined by Western blot.ResultsMelittin (0.5–5 μg/ml) and bee venom (5 and 10 μg/ml) inhibited lipopolysaccharide (LPS, 1 μg/ml) and sodium nitroprusside (SNP, 200 μM)-induced activation of c-Jun NH2-terminal kinase (JNK) in RAW 264.7 cells in a dose dependent manner. However, JNK inhibitor, anthra [1,9-cd]pyrazole-6 (2H)-one (SP600215, 10–50 μM) dose dependently suppressed the inhibitory effects of melittin and bee venom on NF-κB dependent luciferase and DNA binding activity via suppression of the inhibitory effect of melittin and bee venom on the LPS and SNP-induced translocation of p65 and p50 into nucleus as well as cytosolic release of IκB. Moreover, JNK inhibitor suppressed the inhibitory effects of melittin and bee venom on iNOS and COX-2 expression, and on NO and PGE2 generation.ConclusionThese data show that melittin and bee venom prevent LPS and SNP-induced NO and PGE2 production via JNK pathway dependent inactivation of NF-κB, and suggest that inactivation of JNK pathways may also contribute to the anti-inflammatory and anti-arthritis effects of melittin and bee venom.

BackgroundThe recruitment of mononuclear cells has important implications for tissue inflammation. Previous studies demonstrated enhanced CCR1 and CCR5 expression and decreased CCR2 expression during in vitro monocyte to macrophage differentiation. To date, no study examined the in vivo differences in chemokine receptor expression between human peripheral blood monocytes and alveolar macrophages.MethodsWe examined the expression of these receptors in human peripheral blood monocytes and alveolar macrophages using microarray analysis, reverse-transcriptase PCR, flow cytometry and migration analyses.ResultsIn contrast to peripheral blood monocytes, alveolar macrophages did not express the CCL2 receptor, CCR2, and did not migrate toward CCL2. In contrast, monocytes and freshly isolated resident alveolar macrophages both migrated towards CCL3. However, up to 6-fold more monocytes migrated toward equivalent concentrations of CCL3 than did alveolar macrophages from the same donor. While peripheral blood monocytes expressed the CCL3 receptor, CCR1, alveolar macrophages expressed the alternate CCL3 receptor, CCR5. The addition of anti-CCR5 blocking antibodies completely abrogated CCL3-induced migration in alveolar macrophages, but did not affect the migration of peripheral blood monocytes.ConclusionThese data support the specificity of CCL2 to selectively drive monocyte, but not alveolar macrophage recruitment to the lung and CCR5 as the primary macrophage receptor for CCL3.

BackgroundSerum sialic acid and C reactive protein are the markers for inflammation. The main objective of this study was to determine the sialic acid level in Caribbean type 2 diabetic patients with and without microvascular complications and its relationship with metabolic and anthropometric variables.Research design and methodsThe Caribbean subjects aged 15–60 years with type 2 diabetes were recruited for the study. Fasting venous blood samples were collected from 162 subjects of which 44 were healthy individuals, 44 were of type 2 diabetes, 44 were of type 2 diabetes with nephropathy and 30 were of diabetes with retinopathy. Simultaneously urine samples were also collected from each of the subjects. All the blood samples were processed for lipid profile, glucose, HbA1C, C-reactive protein and sialic acid. The urine samples were analysed for sialic acid and microalbumin.ResultsSerum sialic acid concentrations were significantly higher among diabetic subjects (66.0 ± 11.7 mg %) as compared to controls (55.2 ± 8.3 mg %). There was a significantly increasing trend of serum sialic acid with severity of nephropathy (71.6 ± 23.6 mg %) and degree of urinary albumin excretion (794.3 ± 805.9). The diabetic retinopathy patients also demonstrated significantly higher values of serum sialic acid (77.9 ± 29.0) and urine microalbumin (351.1 ± 559.9). Elevated serum sialic acid microalbumin concentrations were associated with cardiovascular risk factors such as hypertension, increased waist to hip ratios. (P < 0.05). Sialic acid had no correlation with CRP or any component of the lipid profile.ConclusionThe increased serum sialic acid and microalbumin were strongly related to the presence of microvascular complications like diabetic nephropathy and diabetic retinopathy and cardiovascular risk factors like hypertension and waist to hip ratios in Caribbean type-2 diabetic patients. The serum sialic acid may be used as an inflammatory marker and possible indicator of microvascular complications in type-2 diabetic patients.

BackgroundNurr1 is an orphan member of the nuclear receptor superfamily; these orphan receptors are a group for which a ligand has yet to be identified. Nurr1 has been shown to regulate the expression of a small number of genes as a monomeric, constitutively active receptor. These Nurr1 regulated genes are primarily associated with dopamine cell maturation and survival. However, previous reports have shown an increased expression of Nurr1 in the synovium of patients with rheumatoid arthritis (RA) suggesting a pro-inflammatory role for Nurr1 in RA. In this study we investigate the potential pro-inflammatory role of Nurr1 by monitoring Nurr1 dependent gene expression in an immortalised synoviocyte cell line, K4IM.MethodsWe overexpressed the wild type and a dominant negative form of the orphan nuclear receptor Nurr1, in a model synoviocyte cell line. Using the Affymetrix HG-U133 Genechips we demonstrate the effects on the transcriptome by the receptor. Further evidence of gene expression change was demonstrated using quantitative RT-PCR and ELISA analysis.ResultsWe show that Nurr1 regulates transcription of a small number of genes for pro-inflammatory modulators of which the most significant is interleukin-8 (IL-8). We also demonstrate increased synthesis and secretion of IL-8 further supporting a role for Nurr1 in inflammatory signalling pathways.ConclusionUsing microarray analysis we show that elevated levels of Nurr1 leads to increased gene expression of pro-inflammatory genes: IL-8, Amphiregulin and Kit ligand in a model cell line. This data provides further evidence for an additional role for Nurr1 in inflammation and may play a role in the pathogenesis of rheumatoid arthritis.

Based on the hypothesis that 26 kD membrane-bound rumor necrosis factor precursor (proTNF) may act as a principle regulator to maintain homeostasis in an adult, we tried to examine whether proTNF shows bidirectional regulation in specific cellular response. We focused on production of 17 kD mature TNF by acute monocytic leukemia cells THP-1 after stimulation by lipopolysaccharide. ProTNF of primed THP-1 cells had been shown to act as a positive regulator for production of mature TNF by homologous cells (primed THP-1) after LPS stimulation, whereas when THP-1 cells were co-cultivated with NIH3T3 which expressed pro-TNF, production of mature TNF by THP-1 by LPS was significantly suppressed. These results suggested that pro-TNF was really involved in bidirectional feedback regulation for TNF production by THP-1 cells themselves through cell to cell contact.

Signals triggered by tumor necrosis factor (TNF) are mediated by its two receptors: the 55 kDa TNF receptor one (TNF-R1) and the 75 kDa TNF receptor two (TNF-R2). Activation of TNF-R1 induces cell death, NF-kappa B activation, inflammatory response and anti-viral activity, while TNF-R2 mainly stimulates cell proliferation and NF-kappa B activation. The TNF-R2-associated factor TRAF2 has been shown to mediate activation of NF-kappa B by TNF-R2 and CD40. The human TNF-R1-associated death domain protein (TRADD) induces cell death and NF-kappa B activation when overexpressed. Here we describe the cloning and gene structure of the mouse homolog of TRADD. Mouse TRADD shares 75% overall amino acid sequence identity with human TRADD, suggesting high conservation of function. Mouse TRADD specifically interacts with wild type TNF-R1 but not with a truncated mutant TNF-R1 lacking its C-terminal 20 amino acids. Like human TRADD, mouse TRADD also induces activation of NF-kappa B and cell death. The expression of TRADD in mouse embryo appears developmentally regulated. The mTRADD gene contains four exons, with the fourth exon encoding all of the death domain. The mouse TRADD gene was localized to the distal region of chromosome 8.

Acute inflammatory lung injury is a common clinical occurrence following blood loss and trauma, and is characterized by massive neutrophil infiltration into the lung. In order to better examine cell trafficking that may contribute to lung injury in this setting, we investigated in vivo mRNA levels and immunohistochemically determined expression of the adhesion molecules P-selectin and the intercellular adhesion molecule (ICAM)-1 in murine lungs over the 3-day period following hemorrhage and resuscitation. Significant increases in P-selectin mRNA levels were present in lungs obtained 3 days after hemorrhage. ICAM-1 mRNA levels were significantly increased 6 and 72 hr after hemorrhage. Immunohistochemical staining for P-selectin was enhanced on pulmonary vascular endothelium in all visible vessels at 6, 24, and 72 hr after hemorrhage. ICAM-1 immunoreactivity was significantly increased on the alveolar epithelium at 6 and 72 hr post-hemorrhage. These results suggest that increased expression of adhesion molecules in the lung at early post-hemorrhage timepoints may contribute to neutrophil infiltration into the lungs and the frequent development of acute lung injury following blood loss and trauma.