Zongfang Li

Angiotensin II Induces Angiogenic Factors Production Partly Via AT1/JAK2/STAT3/SOCS3 Signaling Pathway in MHCC97H Cells

Angiotensin II (Ang II) has been shown to function as a key role in neovascularization of hepatocellular carcinoma (HCC), but little is known its underlying mechanisms. The aim of this study was to explore the role of Janus kinase/signal transducer and activator of transcription (JAK/STAT) signaling pathway in Ang II-induced HCC angiogenic factors production. Herein, we found that Ang II upregulated angiogenic factors production such as vascular endothelial growth factor (VEGF), angiopoietin-2 (Ang-2) and Tie-2 in MHCC97H cells in a time- and concentration-dependent manner. And VEGF and Ang-2 caused a significant increase in angiogenic tube formation. Especially, Ang II-induced angiogenic tube formation was blunted by VEGF small interfering RNA (siRNA) and Ang-2 siRNA, respectively. The JAK2 inhibitor AG490 partly attenuated the effects of Ang II. Moreover, Ang II- induced JAK2 and STAT3 phosphorylation was significantly suppressed by losartan but not PD123319. Meanwhile, STAT3 phosphorylation and suppressor of cytokine signaling 3 (SOCS3) expression induced by Ang II were evidently impaired by AG490. More importantly, SOCS3 siRNA remarkably reinforced Ang II-induced VEGF, Ang-2 and Tie-2 generation in MHCC97H cells. Taken together, the present study demonstrates that Ang II induces angiogenic factors production partly via AT1/ JAK2/STAT3/SOCS3 signaling pathway in MHCC97H cells. These findings may provide important insights into the potential mechanism with respect to the AT1/ JAK2/ STAT3/SOCS3 signaling pathway associated with Ang II-induced angiogenesis in the pathogenesis of HCC.

Expression and regulation of complement receptors by human natural killer cells

Integration of cellular and humoral arms of the innate immune response is fundamental to the development of powerful effector functions in host defence as well as aberrant immune responses. Here, we provide evidence in support of the relationship between complement activation and NK cell functional modulation. We demonstrate that human NK cells and both CD56(bright)CD16(-) and CD56(dim)CD16(+) populations express receptors known to detect the biologically active peptides C3a and C5a (i.e. C3aR, C5aR, C5L2) and the covalently-bound fragments C3b and metabolites iC3b and C3d which serve in immune adhesion (e.g. CR3, CR4). We also show that several pathogen- or tumour/inflammation-related stimuli differentially regulated those complement receptor expression. Furthermore, our results suggest that C3 fragments (C3a, iC3b) have a negative regulatory effect on IFN-γ production in NK cells. This work provides extensive information of human complement receptors relevant to the integrated actions of complement and NK cells which has been suggested by animal studies. The observations may act as a resource that allows further understanding and exploitation of role of complement in human health and immune mediated diseases.

Angiotensin II Enhances Proliferation and Inflammation through AT1/PKC/NF-κB Signaling Pathway in Hepatocellular Carcinoma Cells.

Background/Aims: The pathogenesis of hepatocellular carcinoma (HCC) is mainly characterized by persistent cycles of liver injury, inflammation, and compensatory hepatocyte proliferation. Angiotensin II (Ang II) behaves as an endogenous pro-inflammatory molecule playing a significant role in HCC, however, the molecular link between Ang II, proliferation and inflammation remains unclear. Methods: Human HCC cell lines (HepG-2, SMMC-7721, MHCC97-H) were incubated with Ang II at the indicated concentrations for 24, 48, 72 h. MTT, BrdU ELISA, plate colony formation assay, immunohistochemistry, ELISA, small-interfering RNA(siRNA) transfection, quantitative real-time PCR and western blot were applied to assess their functional, morphological and molecular mechanisms in HCC cell lines. Results: High expression of Ang II type 1 receptor (AT1) and low expression of AT2 in HCC cells and tissues were found. Next, Ang II could significantly enhance cell growth and proliferation. Albeit Ang II slightly increased the percentage of HCC cells in the G0/G1 phase using flow cytometry analysis, no statistically significant alterations were shown. Further studies suggested that Ang II could directly induce proliferation associated proteins C-myc and proliferating cell nuclear antigen (PCNA) expressions, and inflammatory cytokines tumor necrosis factor-alpha (TNF-α) and C-reactive protein (CRP) productions in HCC cells. Interestingly, blocking AT1 and AT1 siRNA evidently inhibited Ang II-induced cell proliferation and inflammatory responses in HCC cells. More importantly, these effects may be mediated by AT1/PKC/NF-κB signaling pathway in HCC cell lines. Conclusions: The results propose that Ang II/AT1/PKC/NF-κB signaling pathway is necessary for proliferation and inflammation of HCC cells, which increases our understanding of the pathogenesis and provides clues for developing new strategies against Ang II-related progress of HCC.

Modulation of LPS-mediated inflammation by fenofibrate via the TRIF-dependent TLR4 signaling pathway in vascular smooth muscle cells.

Lipopolysaccharide (LPS) induced-vascular inflammation plays a central role in vasculitis and atherosclerosis. The stimulation of toll-like receptor 4 (TLR4) by LPS elicits the release of major proinflammatory cytokines that aggravates cardiovascular disorders. Peroxisome proliferator- activated receptor Α (PPARΑ) agonists have been shown to reduce cardiovascular events by controlling lipid metabolism as well as inflammation. However, the role of PPARΑ agonist fenofibrate in modulating LPS-mediated inflammatory responses in vascular smooth muscle cells (VSMCs) remains elusive. The present study demonstrated that fenofibrate exerted a potent anti-inflammatory action through reducing interleckin-1(IL-18), tissue inhibitor of metalloproteinase-1(TIMP-1), TLR4 and enhancing PPARΑ in LPS-stimulated VSMCs. Additionally, treatment of VSMCs with the TLR4 inhibition or TLR4 small-interfering RNA illustrated that the modulatory effects of fenofibrate on LPS-mediated inflammatory responses in VSMCs were reliant on TLR4. Especially, the results suggested that beneficial effects of fenofibrate on LPS-stimulated inflammatory responses in VSMCs were mediated through interference of TLR4 and its downstream signaling components such as Toll-interleckin-1(IL-1) receptor domain- containing adaptor inducing interferon-Β (TRIF), interferon regulatory factor 3 (IRF3) and interferon-gamma inducible protein 10 (IP-10). In conclusion, PPARΑ agonist fenofibrate exerts anti-inflammatory property by antagonizing LPS-mediated inflammatory responses in VSMCs. More importantly, the modulation of the TRIF-dependent signaling pathway (TLR4/TRIF/IRF3/IP-10) might be a useful and novel anti-inflammatory strategy of fenofibrate.

Activation of endogenous anti-inflammatory mediator cyclic AMP attenuates acute pyelonephritis in mice induced by uropathogenic Escherichia coli.

The pathogenesis of pyelonephritis caused by uropathogenic Escherichia coli (UPEC) is not well understood. Here, we show that besides UPEC virulence, the severity of the host innate immune response and invasion of renal epithelial cells are important pathogenic factors. Activation of endogenous anti-inflammatory mediator cAMP significantly attenuated acute pyelonephritis in mice induced by UPEC. Administration of forskolin (a potent elevator of intracellular cAMP) reduced kidney infection (ie, bacterial load, tissue destruction); this was associated with attenuated local inflammation, as evidenced by the reduction of renal production of proinflammatory mediators, renal infiltration of inflammatory cells, and renal myeloperoxidase activity. In primary cell culture systems, forskolin not only down-regulated UPEC-stimulated production of proinflammatory mediators by renal tubular epithelial cells and inflammatory cells (eg, monocyte/macrophages) but also reduced bacterial internalization by renal tubular epithelial cells. Our findings clearly indicate that activation of endogenous anti-inflammatory mediator cAMP is beneficial for controlling UPEC-mediated acute pyelonephritis in mice. The beneficial effect can be explained at least in part by limiting excessive inflammatory responses through acting on both renal tubular epithelial cells and inflammatory cells and by inhibiting bacteria invasion of renal tubular epithelial cells.

Direct Detection of FoxP3 Expression in Thymic Double-Negative CD4 − CD8 − Cells by Flow Cytometry

Foxp3 expression is a marker of regulatory T cells (Treg), but how early it is expressed in the thymus is still not fully defined. In this study, we examined Foxp3 expression in double-negative (DN) CD4−CD8− T cell precursors in the thymus by flow cytometry. By increasing the number of collected cells from the conventional 104 cells up to more than 106 cells during flow cytometry, we found that DN cells exhibited higher Foxp3 expression than double-positive (DP) CD4+CD8+ and single-positive (SP) CD4+ or CD8+ (SP) T cells. CD44+ expression positively correlated with Foxp3 in thymic DN cells. Furthermore, TCR-β−CD25+ DN cells exhibited the highest frequency of Foxp3-expressing cells. Almost all Foxp3+ cells expressed CD25in DN cells. These results suggest that Foxp3 expression in DN cells can directly be detected by flow cytometry and it was positively corelated with CD25 and CD44 in DN cells.

Mice with Hepatic Loss of the Desmosomal Protein γ-Catenin Are Prone to Cholestatic Injury and Chemical Carcinogenesis

γ-Catenin, an important component of desmosomes, may also participate in Wnt signaling. Herein, we dissect the role of γ-catenin in liver by generating conditional γ-catenin knockout (KO) mice and assessing their phenotype after bile duct ligation (BDL) and diethylnitrosamine-induced chemical carcinogenesis. At baseline, KO and wild-type littermates showed comparable serum biochemistry, liver histology, and global gene expression. β-Catenin protein was modestly increased without any change in Wnt signaling. Desmosomes were maintained in KO, and despite no noticeable changes in gene expression, differential detergent fractionation revealed quantitative and qualitative changes in desmosomal cadherins, plaque proteins, and β-catenin. Enhanced association of β-catenin to desmoglein-2 and plakophilin-3 was observed in KO. When subjected to BDL, wild-type littermates showed specific changes in desmosomal protein expression. In KO, BDL deteriorated baseline compensatory changes, which manifested as enhanced injury and fibrosis. KO also showed enhanced tumorigenesis to diethylnitrosamine treatment because of Wnt activation, as also verified in vitro. γ-Catenin overexpression in hepatoma cells increased its binding to T-cell factor 4 at the expense of β-catenin-T-cell factor 4 association, induced unique target genes, affected Wnt targets, and reduced cell proliferation and viability. Thus, γ-catenin loss in liver is basally well tolerated. However, after insults like BDL, these compensations at desmosomes fail, and KO show enhanced injury. Also, γ-catenin negatively regulates tumor growth by affecting Wnt signaling.

C5aR1 promotes acute pyelonephritis induced by uropathogenic E. coli

C5a receptor 1 (C5aR1) is a G protein–coupled receptor for C5a and also an N-linked glycosylated protein. In addition to myeloid cells, C5aR1 is expressed on epithelial cells. In this study, we examined the role of C5aR1 in bacterial adhesion/colonization of renal tubular epithelium and addressed the underlying mechanisms of this role. We show that acute kidney infection was significantly reduced in mice with genetic deletion or through pharmacologic inhibition of C5aR1 following bladder inoculation with uropathogenic E. coli (UPEC). This was associated with reduced expression of terminal α-mannosyl residues (Man; a ligand for type 1 fimbriae of E. coli) on the luminal surface of renal tubular epithelium and reduction of early UPEC colonization in these mice. Confocal microscopy demonstrated that UPEC bind to Man on the luminal surface of renal tubular epithelium. In vitro analyses showed that C5a stimulation enhances Man expression in renal tubular epithelial cells and subsequent bacterial adhesion, which, at least in part, is dependent on TNF-α driven by C5aR1-mediated intracellular signaling. Our findings demonstrate a previously unknown pathogenic role for C5aR1 in acute pyelonephritis, proposing a potentially novel mechanism by which C5a/C5aR1 signaling mediates upregulation of carbohydrate ligands on renal tubules to facilitate UPEC adhesion.

Complement Receptor 3 Has Negative Impact on Tumor Surveillance through Suppression of Natural Killer Cell Function

Complement receptor 3 (CR3) is expressed abundantly on natural killer (NK) cells; however, whether it plays roles in NK cell-dependent tumor surveillance is largely unknown. Here, we show that CR3 is an important negative regulator of NK cell function, which has negative impact on tumor surveillance. Mice deficient in CR3 (CD11b−/− mice) exhibited a more activated NK phenotype and had enhanced NK-dependent tumor killing. In a B16-luc melanoma-induced lung tumor growth and metastasis model, mice deficient in CR3 had reduced tumor growth and metastases, compared with WT mice. In addition, adaptive transfer of NK cells lacking CR3 (into NK-deficient mice) mediated more efficient suppression of tumor growth and metastases, compared with the transfer of CR3 sufficient NK cells, suggesting that CR3 can impair tumor surveillance through suppression of NK cell function. In vitro analyses showed that engagement of CR3 with iC3b (classical CR3 ligand) on NK cells negatively regulated NK cell activity and effector functions (i.e. direct tumor cell killing, antibody-dependent NK-mediated tumor killing). Cell signaling analyses showed that iC3b stimulation caused activation of Src homology 2 domain-containing inositol-5-phosphatase-1 (SHIP-1) and JNK, and suppression of ERK in NK cells, supporting that iC3b mediates negative regulation of NK cell function through its effects on SHIP-1, JNK, and ERK signal transduction pathways. Thus, our findings demonstrate a previously unknown role for CR3 in dysregulation of NK-dependent tumor surveillance and suggest that the iC3b/CR3 signaling is a critical negative regulator of NK cell function and may represent a new target for preserving NK cell function in cancer patients and improving NK cell-based therapy.