CTGF Increases IL-6 Expression in Human Synovial Fibroblasts through Integrin-Dependent Signaling Pathway

Background

Connective tissue growth factor (CTGF; also known as CCN2) is an inflammatory mediator, and shows elevated levels in regions of severe injury and inflammatory diseases. CTGF is abundantly expressed in osteoarthritis (OA). However, the relationship between CTGF and IL-6 in OA synovial fibroblasts (OASFs) is mostly unknown.

Methodology/Principal Findings

OASFs showed significant expression of CTGF, and expression was higher than in normal SFs. OASFs stimulation with CTGF induced concentration-dependent increases in IL-6 expression. CTGF mediated IL-6 production was attenuated by αvβ5 integrin neutralized antibody and apoptosis signal-regulating kinase 1 (ASK1) shRNA. Pretreatment with p38 inhibitor (SB203580), JNK inhibitor (SP600125), AP-1 inhibitors (Curcumin and Tanshinone IIA), and NF-κB inhibitors (PDTC and TPCK) also inhibited the potentiating action of CTGF. CTGF-mediated increase of NF-κB and AP-1 luciferase activity was inhibited by SB203580 and SP600125 or ASK1 shRNA or p38 and JNK mutant.

Conclusions/Significance

Our results suggest that CTGF increased IL-6 production in OASFs via the αvβ5 integrin, ASK1, p38/JNK, and AP-1/NF-κB signaling pathways.     

Salusin-β, but Not Salusin-α, Promotes Human Umbilical Vein Endothelial Cell Inflammation via the p38 MAPK/JNK-NF-κB Pathway

Objective

Recently, salusin-β has been reported to have pro-atherosclerotic effects, but salusin-α has anti-atherosclerotic effects. Our previous study has shown that salusin-β but not salusin-α promotes vascular inflammation in apoE-deficient mice. However, the underlying mechanism remains unknown. In this study, we observed the effect of salusins on inflammatory responses and the MAPK-NF-κB signaling pathway in human umbilical vein endothelial cells (HUVECs).

Methods and Results

HUVECs were incubated with different concentrations of salusin-α and salusin-β. The levels of interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) were determined using enzyme-linked immunosorbent assay (ELISA). The mRNA expressions of vascular cell adhesion molecule-1 (VCAM-1) and monocyte chemoattractant protein-1 (MCP-1) were quantified using quantitative real-time polymerase chain reaction (PCR). The protein expressions of VCAM-1, MCP-1, I-κBα, NF-κB, p-JNK and p-p38 MAPK were measured using western blotting analysis. Our results showed that in HUVECs, salusin-β could up-regulate the levels of IL-6, TNF-α, VCAM-1 and MCP-1, promote I-κBα degradation and NF-κB activation, and increase the phosphorylation of JNK and p38 MAPK. These effects could be inhibited by p38 MAPK inhibitor SB203580 and/or JNK inhibitor SP600125. In contrast, salusin-α could selectively decrease VCAM-1 protein, but did not show any effect on the expressions of VCAM-1 mRNA, TNF-α, IL-6, MCP-1, I-κBα, NF-κB, p-JNK or p-p38 MAPK.

Conclusion

Salusin-β was able to promote inflammatory responses in HUVECs via the p38 MAPK-NF-κB and JNK-NF-κB pathways. In contrast, salusin-α failed to show any significant effects on the inflammatory responses in HUVECs. These results provide further insight into the mechanisms behind salusins in vascular inflammation and offer a potential target for the prevention and treatment of atherosclerosis.     

Increased C-C Chemokine Receptor 2 Gene Expression in Monocytes of Severe Obstructive Sleep Apnea Patients and under Intermittent Hypoxia

Background

Obstructive sleep apnea (OSA) is known to be a risk factor of coronary artery disease. The chemotaxis and adhesion of monocytes to the endothelium in the early atherosclerosis is important. This study aimed to investigate the effect of intermittent hypoxia, the hallmark of OSA, on the chemotaxis and adhesion of monocytes.

Methods

Peripheral blood was sampled from 54 adults enrolled for suspected OSA. RNA was prepared from the isolated monocytes for the analysis of C-C chemokine receptor 2 (CCR2). The effect of intermittent hypoxia on the regulation and function of CCR2 was investigated on THP-1 monocytic cells and monocytes. The mRNA and protein expression levels were investigated by RT/real-time PCR and western blot analysis, respectively. Transwell filter migration assay and cell adhesion assay were performed to study the chemotaxis and adhesion of monocytes.

Results

Monocytic CCR2 gene expression was found to be increased in severe OSA patients and higher levels were detected after sleep. Intermittent hypoxia increased the CCR2 expression in THP-1 monocytic cells even in the presence of TNF-α and CRP. Intermittent hypoxia also promoted the MCP-1-mediated chemotaxis and adhesion of monocytes to endothelial cells. Furthermore, inhibitor for p42/44 MAPK or p38 MAPK suppressed the activation of monocytic CCR2 expression by intermittent hypoxia.

Conclusions

This is the first study to demonstrate the increase of CCR2 gene expression in monocytes of severe OSA patients. Monocytic CCR2 gene expression can be induced under intermittent hypoxia which contributes to the chemotaxis and adhesion of monocytes.     

The role of the p38 MAPK signaling pathway in high glucose-induced epithelial-mesenchymal transition of cultured human renal tubular epithelial cells

Background

Epithelial-mesenchymal transition of tubular epithelial cells, which is characterized by a loss of epithelial cell characteristics and a gain of ECM-producing myofibroblast characteristics, is an essential mechanism that is involved in tubulointerstitial fibrosis, an important component of the renal injury that is associated with diabetic nephropathy. Under diabetic conditions, p38 MAPK activation has been reported in glomeruli and mesangial cells; however, studies on p38 MAPK in TECs are lacking. In this study, the role of p38 MAPK in AP-1 activation and in the EMT in the human proximal tubular epithelial cell line (HK-2) under high glucose concentration conditions is investigated.

Methodology/Principal Findings

A vector for small interfering RNA that targets p38 MAPK was constructed; the cells were then either transfected with p38 siRNA or pretreated with a chemical inhibitor of AP-1 and incubated with low glucose plus TGF-β1 or high glucose for 48 h. Cells that were not transfected or pretreated and were exposed to low glucose with or without TGF-β1 or high glucose for 48 h were considered to be the controls. We found that high glucose induced an increase in TGF-β1. And high glucose-induced p38 MAPK activation was inhibited by p38 siRNA (P<0.05). A significant decline in E-cadherin and CK expression and a notable increase in vimentin and α-SMA were detected when exposed to low glucose with TGF-β1 or high glucose, and a significant raise of secreted fibronectin were detected when exposed to high glucose; whereas these changes were reversed when the cells were treated with p38 siRNA or AP-1 inhibitor (P<0.05). AP-1 activity levels and Snail expression were up-regulated under high glucose conditions but were markedly down-regulated through knockdown of p38 MAPK with p38 siRNA or pretreatment with AP-1 inhibitor (P<0.05).

Conclusion

This study suggests that p38 MAPK may play an important role in the high glucose-induced EMT by activating AP-1 in tubular epithelial cells.     

CCL5 and CCR5 interaction promotes cell motility in human osteosarcoma

Background

Osteosarcoma is characterized by a high malignant and metastatic potential. CCL5 (previously called RANTES) was originally recognized as a product of activated T cells, and plays a crucial role in the migration and metastasis of human cancer cells. It has been reported that the effect of CCL5 is mediated via CCR receptors. However, the effect of CCL5 on migration activity and integrin expression in human osteosarcoma cells is mostly unknown.

Methodology/Principal Findings

Here we found that CCL5 increased the migration and expression of αvβ3 integrin in human osteosarcoma cells. Stimulation of cells with CCL5 increased CCR5 but not CCR1 and CCR3 expression. CCR5 mAb, inhibitor, and siRNA reduced the CCL5-enhanced the migration and integrin up-regulation of osteosarcoma cells. Activations of MEK, ERK, and NF-κB pathways after CCL5 treatment were demonstrated, and CCL5-induced expression of integrin and migration activity was inhibited by the specific inhibitor and mutant of MEK, ERK, and NF-κB cascades. In addition, over-expression of CCL5 shRNA inhibited the migratory ability and integrin expression in osteosarcoma cells.

Conclusions/Significance

CCL5 and CCR5 interaction acts through MEK, ERK, which in turn activates NF-κB, resulting in the activations of αvβ3 integrin and contributing the migration of human osteosarcoma cells.     

Altered PI3-Kinase/Akt Signalling in Skeletal Muscle of Young Men with Low Birth Weight

Background

Low birth weight (LBW) is associated with increased future risk of insulin resistance and type 2 diabetes mellitus. The underlying molecular mechanisms remain poorly understood. We have previously shown that young LBW men have reduced skeletal muscle expression of PI3K p85α regulatory subunit and p110β catalytic subunit, PKCζ and GLUT4 in the fasting state. The aim of this study was to determine whether insulin activation of the PI3K/Akt and MAPK signalling pathways is altered in skeletal muscle of young adult men with LBW.

Methods

Vastus lateralis muscle biopsies were obtained from 20 healthy 19-yr old men with BW</ = 10^th percentile for gestational age (LBW) and 20 normal birth weight controls (NBW), matched for physical fitness and whole-body glucose disposal, prior to (fasting state) and following a 4-hr hyperinsulinemic euglycemic clamp (insulin stimulated state). Expression and phosphorylation of selected proteins was determined by Western blotting.

Principal Findings

Insulin stimulated expression of aPKCζ (p<0.001) and Akt1 (p<0.001) was decreased in muscle of LBW men when compared to insulin stimulated controls. LBW was associated with increased insulin stimulated levels of IRS1 (p<0.05), PI3K p85α (p<0.001) and p110β (p<0.05) subunits, while there was no significant change in these proteins in insulin stimulated control muscle. In addition LBW had reduced insulin stimulated phospho-Akt (Ser 473) (p<0.01), indicative of reduced Akt signalling. Insulin stimulated expression/phosphorylation of all the MAPK proteins studied [p38 MAPK, phospho-p38 MAPK (Thr180/Tyr182), phospho-ERK (Thr 202/Tyr204), JNK1, JNK2 and phospho-JNK (Thr 183/Tyr185)] was not different between groups.

Conclusions

We conclude that altered insulin activation of the PI3K/Akt but not the MAPK pathway precedes and may contribute to development of whole-body insulin resistance and type 2 diabetes in men with LBW.     

TNF-α Mediates PKCδ/JNK1/2/c-Jun-Dependent Monocyte Adhesion via ICAM-1 Induction in Human Retinal Pigment Epithelial Cells

Retinal inflammatory diseases induced by cytokines, such as tumor necrosis factor-α (TNF-α) are associated with an up-regulation of intercellular adhesion molecule-1 (ICAM-1) in the retinal pigment epithelial cells (RPECs). Retinal pigment epithelium (RPE) is a monolayer of epithelial cells that forms the outer blood-retinal barrier in the posterior segment of the eye, and is also implicated in the pathology of, such as neovascularization in age-related macular degeneration (AMD). However, the detailed mechanisms of TNF-α-induced ICAM-1 expression are largely unclear in human RPECs. We demonstrated that in RPECs, TNF-α could induce ICAM-1 protein and mRNA expression and promoter activity, and monocyte adhesion. TNF-α-mediated responses were attenuated by pretreatment with the inhibitor of PKCs (Ro318220), PKCδ (Rottlerin), MEK1/2 (U0126), JNK1/2 (SP600125), or AP-1 (Tanshinone IIA) and transfection with siRNA of TNFR1, TRAF2, JNK2, p42, or c-Jun. We showed that TNF-α could stimulate the TNFR1 and TRAF2 complex formation. TNF-α-stimulated JNK1/2 was also reduced by Rottlerin or SP600125. However, Rottlerin had no effect on TNF-α-induced p42/p44 MAPK phosphorylation. We observed that TNF-α induced c-Jun phosphorylation which was inhibited by Rottlerin or SP600125. On the other hand, TNF-α-stimulated ICAM-1 promoter activity was prominently lost in RPECs transfected with the point-mutated AP-1 ICAM-1 promoter plasmid. These results suggest that TNF-α-induced ICAM-1 expression and monocyte adhesion is mediated through a TNFR1/TRAF2/PKCδ/JNK1/2/c-Jun pathway in RPECs. These findings concerning TNF-α-induced ICAM-1 expression in RPECs imply that TNF-α might play an important role in ocular inflammation and diseases.     

Protein Kinase C ε Expression in Platelets from Patients with Acute Myocardial Infarction

Objective

Platelets play crucial roles in the pathophysiology of thrombosis and myocardial infarction. Protein kinase C ε (PKCε) is virtually absent in human platelets and its expression is precisely regulated during human megakaryocytic differentiation. On the basis of what is known on the role of platelet PKCε in other species, we hypothesized that platelets from myocardial infarction patients might ectopically express PKCε with a pathophysiological role in the disease.

Methods and Results

We therefore studied platelet PKCε expression from 24 patients with myocardial infarction, 24 patients with stable coronary artery disease and 24 healthy subjects. Indeed, platelets from myocardial infarction patients expressed PKCε with a significant frequency as compared to both stable coronary artery disease and healthy subjects. PKCε returned negative during patient follow-up. The forced expression of PKCε in normal donor platelets significantly increased their response to adenosine diphosphate-induced activation and adhesion to subendothelial collagen.

Conclusions

Our data suggest that platelet generations produced before the acute event retain PKCε-mRNA that is not down-regulated during terminal megakaryocyte differentiation. Results are discussed in the perspective of peri-infarctual megakaryocytopoiesis as a critical component of myocardial infarction pathophysiology.     

Down-regulation of PKCζ in renal cell carcinoma and its clinicopathological implications

Background

Metastatic renal cell carcinoma (RCC) is highly resistant to systemic chemotherapy. Unfortunately, nearly all patients die of the metastatic and chemoresistant RCC. Recent studies have shown the atypical PKCζ is an important regulator of tumorigenesis. However, the correlation between PKCζ expression and the clinical outcome in RCC patients is unclear. We examined the level of PKCζ expression in human RCC.

Methods

PKCζ mRNA and protein expressions were examined by real-time polymerase chain reaction (PCR) and immunohistochemistry (IHC) respectively in RCC tissues of 144 patients. Cellular cytotoxicity and proliferation were assessed by MTT.

Results

PKCζ expression was significantly higher in normal than in cancerous tissues (P < 0.0001) by real-time PCR and IHC. Similarly, PKCζ expression was down-regulated in four renal cancer cell lines compared to immortalized benign renal tubular cells. Interestingly, an increase of PKCζ expression was associated with the elevated tumor grade (P = 0.04), but no such association was found in TNM stage (P = 0.13). Tumors with higher PKCζ expression were associated with tumor size (P = 0.048). Expression of higher PKCζ found a poor survival in patients with high tumor grade. Down-regulation of PKCζ showed the significant chemoresistance in RCC cell lines. Inactivation of PKCζ expression enhanced cellular resistance to cisplatin and paclitaxel, and proliferation in HK-2 cells by specific PKCζ siRNA and inhibitor.

Conclusions

PKCζ expression was associated with tumorigenesis and chemoresistance in RCC.     

Angiotensin II Upregulates Endothelial Lipase Expression via the NF-Kappa B and MAPK Signaling Pathways

Background

Angiotensin II (AngII) participates in endothelial damage and inflammation, and accelerates atherosclerosis. Endothelial lipase (EL) is involved in the metabolism and clearance of high density lipoproteins (HDL), the serum levels of which correlate negatively with the onset of cardiovascular diseases including atherosclerosis. However, the relationship between AngII and EL is not yet fully understood. In this study, we investigated the effects of AngII on the expression of EL and the signaling pathways that mediate its effects in human umbilical vein endothelial cells (HUVECs).

Methods and Findings

HUVECs were cultured in vitro with different treatments as follows: 1) The control group without any treatment; 2) AngII treatment for 0 h, 4 h, 8 h, 12 h and 24 h; 3) NF-κB activation inhibitor pyrrolidine dithiocarbamate (PDTC) pretreatment for 1 h before AngII treatment; and 4) mitogen-activated protein kinase (MAPK) p38 inhibitor (SB203580) pretreatment for 1 h before AngII treatment. EL levels in each group were detected by immunocytochemical staining and western blotting. HUVECs proliferation was detected by MTT and proliferating cell nuclear antigen (PCNA) immunofluorescence staining. NF-kappa B (NF-κB) p65, MAPK p38, c-Jun N-terminal kinase (JNK), extracellular signal-regulated kinase (ERK) and phosphorylated extracellular signal-regulated kinase (p-ERK) expression levels were assayed by western blotting. The results showed that the protein levels of EL, NF-κB p65, MAPK p38, JNK, and p-ERK protein levels, in addition to the proliferation of HUVECs, were increased by AngII. Both the NF-kB inhibitor (PDTC) and the MAPK p38 inhibitor (SB203580) partially inhibited the effects of AngII on EL expression.

Conclusion

AngII may upregulate EL protein expression via the NF-κB and MAPK signaling pathways.     

Differential effects of cytokines and corticosteroids on Toll-like receptor 2 expression and activity in human airway epithelia

Background

The recognition of microbial molecular patterns via Toll-like receptors (TLRs) is critical for mucosal defenses.

Methods

Using well-differentiated primary cultures of human airway epithelia, we investigated the effects of exposure of the cells to cytokines (TNF-α and IFN-γ) and dexamethasone (dex) on responsiveness to the TLR2/TLR1 ligand Pam3CSK4. Production of IL-8, CCL20, and airway surface liquid antimicrobial activity were used as endpoints.

Results

Microarray expression profiling in human airway epithelia revealed that first response cytokines markedly induced TLR2 expression. Real-time PCR confirmed that cytokines (TNF-α and IFN-γ), dexamethasone (dex), or cytokines + dex increased TLR2 mRNA abundance. A synergistic increase was seen with cytokines + dex. To assess TLR2 function, epithelia pre-treated with cytokines ± dex were exposed to the TLR2/TLR1 ligand Pam3CSK4 for 24 hours. While cells pre-treated with cytokines alone exhibited significantly enhanced IL-8 and CCL20 secretion following Pam3CSK4, mean IL-8 and CCL20 release decreased in Pam3CSK4 stimulated cells following cytokines + dex pre-treatment. This marked increase in inflammatory gene expression seen after treatment with cytokines followed by the TLR2 ligand did not correlate well with NF-κB, Stat1, or p38 MAP kinase pathway activation. Cytokines also enhanced TLR2 agonist-induced beta-defensin 2 mRNA expression and increased the antimicrobial activity of airway surface liquid. Dex blocked these effects.

Conclusion

While dex treatment enhanced TLR2 expression, co-administration of dex with cytokines inhibited airway epithelial cell responsiveness to TLR2/TLR1 ligand over cytokines alone. Enhanced functional TLR2 expression following exposure to TNF-α and IFN-γ may serve as a dynamic means to amplify epithelial innate immune responses during infectious or inflammatory pulmonary diseases.     

β1-Adrenoceptor Autoantibodies from DCM Patients Enhance the Proliferation of T Lymphocytes through the β1-AR/cAMP/PKA and p38 MAPK Pathways

Background

Autoantibodies against the second extracellular loop of the β₁-adrenergic receptor (β₁-AA) not only contribute to increased susceptibility to heart failure, but also play a causative role in myocardial remodeling through their sympathomimetic-like effects that are induced upon binding to the β₁-adrenergic receptor. However, their role in the function of T lymphocytes has never been previously investigated. Our present study was designed to determine whether β₁-AA isolated from the sera of dilated cardiomyopathy (DCM) patients caused the proliferation of T cells and the secretion of cytokines.

Methods

Blood samples were collected from 95 DCM patients as well as 95 healthy subjects, and β₁-AA was detected using ELISA. The CD3⁺T lymphocytes were selected separately through flow cytometry and the effect of β₁-AA on T lymphocyte proliferation was examined by CCK-8 kits and CFSE assay. Western blotting was used to analyze the expressions of phospho-VASP and phospho-p38 MAPK.

Results

β₁-AA enhanced the proliferation of T lymphocytes. This effect could be blocked by the selective β₁-adrenergic receptor antagonist metoprolol, PKA inhibitor H89, and p38 MAPK inhibitor SB203580. Furthermore, the expression of the phosphorylated forms of phospho-VASP and phospho-p38 MAPK were markedly increased in the presence of β₁-AA. β₁-AA also inhibited the secretion of interferon-γ (IFN-γ) while promoting an increase in interleukin-4 (IL-4) levels.

Conclusions

These results demonstrate that β₁-AA isolated from DCM patients binds to β₁-AR on the surface of T cells, causing changes in T-cell proliferation and secretion through the β₁-AR/cAMP/PKA and p38 MAPK pathways.     

Differential involvement of PKC-dependent MAPKs activation in lipopolysaccharide-induced AP-1 expression in human tracheal smooth muscle cells

Lipopolysaccharide (LPS) has been shown to up-regulate the expression of vascular cell adhesion molecule (VCAM)-1 which contributes to the occurrence of airway inflammatory diseases. Genetic analysis reveals the existence of activator protein-1 (AP-1) binding site on VCAM-1 promoter region. However, the role of AP-1 in LPS-induced VCAM-1 expression in human tracheal smooth muscle cells (HTSMCs) is not known. Here, we show that LPS increased VCAM-1 expression and adhesiveness of HTSMCs through AP-1, since pretreatment with an AP-1 inhibitor tanshinone attenuated LPS-induced VCAM-1 expression and leukocytes adhesion. The implication of AP-1 in LPS-induced VCAM-1 expression was confirmed by animal studies showing that pretreatment of mice with tanshinone attenuated LPS-induced VCAM-1 mRNA expression in airway tissues and accumulation of leukocytes in bronchoalveolar lavage. By using the pharmacological inhibitors and transfection with siRNA of PKC, p42, p38, or JNK2, LPS-induced expression of c-Fos was mediated through protein kinase C (PKC), p42/p44 MAPK and p38 MAPK. While, c-Jun expression was mediated through PKC and mitogen-activated protein kinases (MAPKs, p42/p44 MAPK, p38 MAPK and JNK) in HTSMCs. Pretreatment with the inhibitors of PKCs or MAPKs attenuated LPS-stimulated nuclear translocation and VCAM-1 promoter binding abilities of AP-1, which attenuated promoter activity and gene expression of VCAM-1 and the adhesiveness between HTSMCs and leukocytes. These results indicated that differential regulation of AP-1 through PKCs-dependent MAPKs activation plays central roles in LPS-induced VCAM-1 expression. The altered modulation of this axis with inhibitors or siRNAs may contribute to the improvement of airway inflammatory diseases.     

Regulation of IL-17A responses in human airway smooth muscle cells by Oncostatin M

Background

Regulation of human airway smooth muscle cells (HASMC) by cytokines contributes to chemotactic factor levels and thus to inflammatory cell accumulation in lung diseases. Cytokines such as the gp130 family member Oncostatin M (OSM) can act synergistically with Th2 cytokines (IL-4 and IL-13) to modulate lung cells, however whether IL-17A responses by HASMC can be altered is not known.

Objective

To determine the effects of recombinant OSM, or other gp130 cytokines (LIF, IL-31, and IL-6) in regulating HASMC responses to IL-17A, assessing MCP-1/CCL2 and IL-6 expression and cell signaling pathways.

Methods

Cell responses of primary HASMC cultures were measured by the assessment of protein levels in supernatants (ELISA) and mRNA levels (qRT-PCR) in cell extracts. Activation of STAT, MAPK (p38) and Akt pathways were measured by immunoblot. Pharmacological agents were used to assess the effects of inhibition of these pathways.

Results

OSM but not LIF, IL-31 or IL-6 could induce detectable responses in HASMC, elevating MCP-1/CCL2, IL-6 levels and activation of STAT-1, 3, 5, p38 and Akt cell signaling pathways. OSM induced synergistic action with IL-17A enhancing MCP-1/CCL-2 and IL-6 mRNA and protein expression, but not eotaxin-1 expression, while OSM in combination with IL-4 or IL-13 synergistically induced eotaxin-1 and MCP-1/CCL2. OSM elevated steady state mRNA levels of IL-4Rα, OSMRβ and gp130, but not IL-17RA or IL-17RC. Pharmacologic inhibition of STAT3 activation using Stattic down-regulated OSM, OSM/IL-4 or OSM/IL-13, and OSM/IL-17A synergistic responses of MCP-1/CCL-2 induction, whereas, inhibitors of Akt and p38 MAPK resulted in less reduction in MCP-1/CCL2 levels. IL-6 expression was more sensitive to inhibition of p38 (using SB203580) and was affected by Stattic in response to IL-17A/OSM stimulation.

Conclusions

Oncostatin M can regulate HASMC responses alone or in synergy with IL-17A. OSM/IL-17A combinations enhance MCP-1/CCL2 and IL-6 but not eotaxin-1. Thus, OSM through STAT3 activation of HASMC may participate in inflammatory cell recruitment in inflammatory airway disease.

Electronic supplementary material

The online version of this article (doi:10.1186/s12931-014-0164-4) contains supplementary material, which is available to authorized users.     

UDP-glucose dehydrogenase modulates proteoglycan synthesis in articular chondrocytes: its possible involvement and regulation in osteoarthritis

Introduction

The objective of this study was to investigate the possible role of UDP-glucose dehydrogenase (UGDH) in osteoarthritis (OA) and uncover whether, furthermore how interleukin-1beta (IL-1β) affects UGDH gene expression.

Methods

UGDH specific siRNAs were applied to determine the role of UGDH in proteoglycan (PG) synthesis in human articular chondrocytes. Protein levels of UGDH and Sp1 in human and rat OA cartilage were detected. Then, human primary chondrocytes were treated with IL-1β to find out whether and how IL-1β could regulate the gene expression of UGDH and its trans-regulators, that is Sp1, Sp3 and c-Krox. Finally, p38 mitogen-activated protein kinase (MAPK) inhibitor SB203580 and stress-activated protein kinase/c-Jun N-terminal kinase (SAP/JNK) inhibitor SP600125 were used to pick out the pathway that mediated the IL-1β-modulated PGs synthesis and gene expression of UGDH, Sp1, Sp3 and c-Krox.

Results

UGDH specific siRNAs markedly inhibited UGDH mRNA and protein expression, and thus led to an obvious suppression of PGs synthesis in human articular chondrocytes. UGDH protein level in human and rat OA cartilage were much lower than the corresponding controls and negatively correlated to the degree of OA. Decrease in Sp1 protein level was also observed in human and rat OA cartilage respectively. Meanwhile, IL-1β suppressed UGDH gene expression in human articular chondrocytes in the late phase, which also modulated gene expression of Sp1, Sp3 and c-Krox and increased both Sp3/Sp1 and c-Krox/Sp1 ratio. Moreover, the inhibition of SAP/JNK and p38 MAPK pathways both resulted in an obvious attenuation of the IL-1β-induced suppression on the UGDH gene expression.

Conclusions

UGDH is essential in the PGs synthesis of articular chondrocytes, while the suppressed expression of UGDH might probably be involved in advanced OA, partly due to the modulation of p38 MAPK and SAP/JNK pathways and its trans-regulators by IL-1β.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-014-0484-2) contains supplementary material, which is available to authorized users.