Biomedical subjects

Qing-Hua Liu

Publications and source records attributed to Qing-Hua Liu.

12 recordsLinked to original sources

PubMed2006

Two distinct signaling pathways for regulation of spontaneous local Ca2+ release by phospholipase C in airway smooth muscle cells.

Spontaneous local Ca(2+) release events have been observed in airway smooth muscle cells (SMCs), but the underlying mechanisms are largely unknown. Considering that each type of SMCs may use its own mechanisms to regulate local Ca(2+) release events, we sought to investigate the signaling pathway for spontaneous local Ca(2+) release events in freshly isolated mouse airway SMCs using a laser scanning confocal microscope. Application of ryanodine to block ryanodine receptors (RyRs) abolished spontaneous local Ca(2+) release events, indicating that these events are RyR-mediated Ca(2+) sparks. Inhibition of inositol 1,4,5-triphosphate receptors (IP(3)Rs) by 2-aminoethoxydiphenyl-borate (2-APB) or xestospongin-C significantly blocked the activity of Ca(2+) sparks. Under patch clamp conditions, dialysis of IP(3) to activate IP(3)Rs increased the activity of local Ca(2+) events in control cells but had no effect in ryanodine-pretreated cells. The RyR agonist caffeine augmented the frequency of Ca(2+) sparks in cells pretreated with and without 2-APB or xestospongin-C. The specific phospholipase C (PLC) blocker U73122 decreased the activity of Ca(2+) sparks and prevented xestospongin-C from producing the inhibitory effect. The protein kinase C (PKC) activator 1-oleoyl-2-acetyl-glycerol or phorbol-12-myristate-13-acetate inhibited Ca(2+) sparks, whereas the PKC inhibitor chelerythrine, PKCvarepsilon inhibitory peptide, or PKCvarepsilon gene knockout produced an opposite effect. Collectively, our data suggest that the basal activation of PLC regulates the activity of RyR-mediated, spontaneous Ca(2+) sparks in airway SMCs through two distinct signaling pathways: a positive IP(3)-IP(3)R pathway and a negative diacylglycerol-PKCvarepsilon pathway.

Alkaloids↗

PubMed2006

Mitochondrial ROS-PKCepsilon signaling axis is uniquely involved in hypoxic increase in [Ca2+]i in pulmonary artery smooth muscle cells.

The molecular mechanisms underlying hypoxic responses in pulmonary and systemic arteries remain obscure. Here we for the first time report that acute hypoxia significantly increased total PKC and PKCepsilon activity in pulmonary, but not mesenteric arteries, while these two tissues showed comparable PKCepsilon protein expression and activation by the PKC activator phorbol 12-myristate 13-acetate. Hypoxia induced an increase in intracellular reactive oxygen species (ROS) generation in isolated pulmonary artery smooth muscle cells (PASMCs), but not in mesenteric artery SMCs. Inhibition of mitochondrial ROS generation with rotenone, myxothiazol, or glutathione peroxidase-1 overexpression prevented hypoxia-induced increases in total PKC and PKCepsilon activity in pulmonary arteries. The inhibitory effects of rotenone were reversed by exogenous hydrogen peroxide. A PKCepsilon translocation peptide inhibitor or PKCepsilon gene deletion decreased hypoxic increase in [Ca(2+)](i) in PASMCs, whereas the conventional PKC inhibitor GO6976 had no effect. These data suggest that acute hypoxia may specifically increase mitochondrial ROS generation, which subsequently activates PKC, particularly PKCepsilon, contributing to hypoxia-induced increase in [Ca(2+)](i) and contraction in PASMCs.

Animals↗

PubMed2006

Adhesion- and degranulation-promoting adapter protein is required for efficient thymocyte development and selection.

Adhesion- and degranulation-promoting adapter protein (ADAP) is required in TCR-induced activation and proliferation of peripheral T cells. Loss of ADAP also impairs TCR-initiated inside-out activation of the integrin LFA-1 (CD11a/CD18, alphaLbeta2). In this study, we demonstrate that ADAP-deficient CD4/CD8 double-positive (DP) cells have a diminished ability to proliferate, and that these DP thymocytes up-regulate CD69 poorly in vivo. Moreover, in both MHC class I- and class II-restricted TCR transgenic models, loss of ADAP interferes with both positive and negative selection. ADAP deficiency also impairs the ability of transgene-bearing DP thymocytes to form conjugates with Ag-loaded presenting cells. These findings suggest that ADAP is critical for thymocyte development and selection.

Adaptor Proteins, Signal Transducing↗

PubMed2006

Lignan oligosaccharide esters from Eritrichium rupestre.

Three new lignan oligosaccharide esters, rupestrin A (1), rupestrin B (2), and rupestrin C (3), were isolated from the ethanol extract of Eritrichium rupestre. Their structures were elucidated on the basis of spectroscopic and chemical evidence.

Boraginaceae↗

PubMed2005

Distinct calcium channels regulate responses of primary B lymphocytes to B cell receptor engagement and mechanical stimuli.

Intracellular Ca(2+) plays a central role in controlling lymphocyte function. Nonetheless, critical gaps remain in our understanding of the mechanisms that regulate its concentration. Although Ca(2+)-release-activated calcium (CRAC) channels are the primary Ca(2+) entry pathways in T cells, additional pathways appear to be operative in B cells. Our efforts to delineate these pathways in primary murine B cells reveal that Ca(2+)-permeant nonselective cation channels (NSCCs) operate in a cooperative fashion with CRAC. Interestingly, these non-CRAC channels are selectively activated by mechanical stress, although the mechanism overlaps with BCR-activated pathways, suggesting that they may operate in concert to produce functionally diverse Ca(2+) signals. NSCCs also regulate the membrane potential, which activates integrin-dependent binding of B cells to extracellular matrix elements involved in their trafficking and localization within secondary lymphoid organs. Thus, CRAC and distinct Ca(2+) permeant NSCCs are differentially activated by the BCR and mechanical stimuli and regulate distinct aspects of B cell physiology.

Animals↗

PubMed2004

Suppressive effects of 17beta-estradiol on hepatic fibrosis in CCl4-induced rat model.

AIM: To investigate the pathway via which 17beta-estradiol (beta-Est) exerts suppressive effects on rat hepatic fibrosis. METHODS: In vivo study was done in CCl4-induced female hepatofibrotic rats. Fibrosis-suppressive effect of beta-Est (20 microg/kg/d) was evaluated in intact and ovariectomized rat models. Six weeks after the treatment, all the rats were sacrificed and specimens of serum or liver tissue were collected for the studies. Serum liver enzymes, fibrosis markers and estradiol levels were determined by standard enzymatic methods, ELISA and RIA, respectively. Degrees of fibrosis and areas of hepatic stellate cells (HSCs) positive for alpha-smooth muscle actin (alpha-SMA) in the liver were determined by van Gieson (VG) stain and immunohistochemistry. In vitro studies, HSCs were isolated by a combination of pronase-collagenase perfusion and density gradient centrifugation. First-passage HSCs were randomly divided into 10 groups, and different concentrations of beta-Est, 2-hydroxyestradiol (2OHE) or 2-methoxyestradiol (2MeOE) were separately added to the cell groups. After incubation for 72 h, the degree of cell proliferation, collagen production, alpha-SMA or estrogen receptor (ER) expression was determined by MTT assay, ELISA and immunohistochemistry, respectively. RESULTS: Beta-Est treatment reduced aspartate aminotransferase (AST), alanine aminotransferase (ALT), hyaluronic acid (HA) and type IV collagen (C IV) in sera, suppressed hepatic collagen content, decreased the areas of HSCs positive for alpha-SMA significantly in both intact and ovariectomized female hepatofibrotic rats. There was a negative correlation between the percentage of fibrotic area of liver tissue and the serum estradiol level; the calculated correlation coefficient was -0.57 (P<0.01). Beta-Est and its metabolites concentration-dependently (10(-9) mol/L-10(-7) mol/L) inhibited HSC proliferation and collagen synthesis. At the concentration of 10(-7) mol/L, they could inhibit alpha-SMA expression. The order of potency was 2MeOE>2OHE>beta-Est. CONCLUSION: Beta-Est may suppress hepatic fibrosis probably via its biologically active metabolites.

Animals↗

PubMed2004

Chemokine receptor utilization and macrophage signaling by human immunodeficiency virus type 1 gp120: Implications for neuropathogenesis.

Human immunodeficiency virus type 1 (HIV-1) uses the chemokine receptors CCR5 and CXCR4 for entry. Macrophages and microglia (M/M) are the principal productively infected brain cells in HIV encephalopathy (HIVE), and neuronal injury is believed to result both from direct effects of viral proteins and indirect effects mediated by macrophage activation and secretion of neurotoxic products. In vitro, direct injury by the viral envelope glycoprotein gp120 can be mediated by neuronal CXCR4, but most HIV-1 isolates from the central nervous system (CNS) studied to date use CCR5 (R5 strains) rather than CXCR4 (X4 or R5X4 strains). Additionally, it remains unknown how HIV induces M/M activation and neurotoxin secretion. To address these issues, the authors analyzed a CNS-derived primary isolate, TYBE, and showed that it uses CXCR4 only and replicates efficiently in macrophages through CXCR4-mediated entry. The authors also showed that both R5 and X4 gp120 activate intracellular signals in macrophages through CCR5 and CXCR4, including calcium elevations; K+, Cl- and nonselective cation channel activation; phosphorylation of the nonreceptor tyrosine kinase Pyk2; and activation of p38 and SAPK/JNK mitogen-activated protein kinases (MAPKs). Finally, the authors showed that macrophages stimulated with gp120 produce soluble factors through MAPK-dependent pathways, including beta-chemokines implicated in HIVE pathogenesis. The findings emphasize that both X4 and R5 HIV-1 isolates may contribute to HIVE pathogenesis, and that gp120/chemokine receptor interactions in M/M trigger specific signal transduction pathways that may affect M/M function and provide a mechanism underlying CNS injury.

AIDS Dementia Complex↗

PubMed2004

A new alkaloid and its artificial derivative with an indazole ring from Nigella glandulifera.

A new compound, nigeglanine (1), and its new artificial derivative (1a), were isolated from the seeds of Nigella glandulifera, together with a known aporphine alkaloid, fuzitine (2). Their structures were established by spectral analysis, including two-dimensional (2D)-NMR spectroscopy. Nigeglanine (1) is the third natural product determined to contain an indazole nucleus.

Alkaloids↗

PubMed2003

Macrophage activation through CCR5- and CXCR4-mediated gp120-elicited signaling pathways.

Macrophages are major targets for infection by human immunodeficiency virus type 1 (HIV-1). In addition to their role as productive viral reservoirs, inappropriate activation of infected and uninfected macrophages appears to contribute to pathogenesis. HIV-1 infection requires initial interactions between the viral envelope surface glycoprotein gp120, the cell-surface protein CD4, and a chemokine receptor CCR5 or CXCR4. Besides their role in HIV-1 entry, CCR5 and CXCR4 are G protein-coupled receptors that can activate multiple intracellular signaling pathways. HIV-1 gp120 has been shown to activate signaling pathways through the chemokine receptors in several cell types including lymphocytes, neurons, and astrocytes. In some cell types, these consequences may cause cellular injury. In this review, we highlight our data demonstrating diverse signaling events that occur in primary human macrophages in response to gp120/chemokine receptor interactions. These responses include K+, Cl-, and nonselective cation currents, intracellular Ca2+ increases, and activation of several kinases including the focal adhesion-related tyrosine kinase Pyk2, mitogen-activated protein kinases (MAPK), and phosphoinositol-3 kinase. Activation of the MAPK leads to gp120-induced expression of chemokines such as monocyte chemoattractant protein-1 and macrophage-inflammatory protein-1beta and the proinflammatory cytokine tumor necrosis factor alpha. These responses establish a complex cytokine network, which may enhance or suppress HIV-1 replication. In addition, dysregulation of macrophage function by gp120/chemokine receptor signaling may contribute to local inflammation and injury and further recruit additional inflammatory and/or target cells. Targeting these cellular signaling pathways may have benefit in controlling inflammatory sequelae of HIV infection such as in neurological disease.

Calcium Signaling↗

PubMed2003

Regulation of T cell activation and tolerance by phospholipase C gamma-1-dependent integrin avidity modulation.

Ag receptor engagement without costimulation induces a tolerant state in CD4(+) T cells termed anergy. Anergic CD4(+) T cells are primarily characterized by the inability to produce IL-2, but the biochemical basis for this functional defect is not completely understood. We demonstrate that primary CD4(+) T cells anergized by costimulatory blockade exhibit impaired TCR-coupled phospholipase C (PLC)gamma-1 activation. This defect is associated with the marked reduction of multiple downstream signaling events required for IL-2 transcription, including mobilization of intracellular Ca(2+) and activation of the mitogen-activated protein kinase cascade. We also found that primary anergic CD4(+) T cells fail entirely to modulate their integrin binding avidity in response to TCR stimulation. Integrin avidity modulation is required for full T cell activation and effector function, and as we show in this study, is completely dependent upon PLCgamma-1 activity. Finally, analogs that mimic the actions of diacylglycerol and inositol 1,4,5-triphosphate, the immediate products of PLCgamma-1 activity, restored integrin avidity modulation and IL-2 production by anergic T cells. Thus, deficient coupling of PLCgamma-1 to the TCR appears to be a central biochemical defect that could potentially account for the failure of multiple functional responses in primary anergic CD4(+) T cells.

Animals↗

PubMed2003

HIV-1 gp120 chemokine receptor-mediated signaling in human macrophages.

The chemokine receptors CCR5 and CXCR4 serve as the cellular receptors in conjunction with CD4 for HIV-1 entry and infection of target cells. Although the virus has subverted these molecules for its own use, their natural function is to respond to activation and migration signals delivered by extracellular chemokines. A principal research objective of our laboratory is to understand the consequences of virus-chemokine receptor interactions for cellular function, as well as for entry and infection. We hypothesized that CXCR4-using (X4) and CCR5-using (R5) HIV-1 strains might elicit signals through the chemokine receptors that result in aberrant function and/or regulate virus entry or postentry steps of infection. We have focused on primary human macrophages, which express both CXCR4 and CCR5, because macrophages are a principal target for HIV-1 in vivo, inappropriate macrophage activation appears to play a major role in the pathogenesis of certain sequelae of AIDS, such as HIV encephalopathy, and macrophage infection is regulated at several steps subsequent to entry in ways that are linked to envelope- receptor interactions. This review summarizes our recent findings regarding the mechanisms of chemokine-receptor signaling in macrophages, the role of viral envelope glycoproteins in eliciting macrophage signals, and how these activation pathways may participate in macrophage infection and affect cell functions apart from infection.

HIV Envelope Protein gp120↗

PubMed2002

Modulation of Kv channel expression and function by TCR and costimulatory signals during peripheral CD4(+) lymphocyte differentiation.

Ionic signaling pathways, including voltage-dependent potassium (Kv) channels, are instrumental in antigen-mediated responses of peripheral T cells. However, how Kv channels cooperate with other signaling pathways involved in T cell activation and differentiation is unknown. We report that multiple Kv channels are expressed by naive CD4(+) lymphocytes, and that the current amplitude and kinetics are modulated by antigen receptor-mediated stimulation and costimulatory signals. Currents expressed in naive CD4(+) lymphocytes are consistent with Kv1.1, Kv1.2, Kv1.3, and Kv1.6. Effector CD4(+) cells generated by optimal TCR and costimulation exhibit only Kv1.3 current, but at approximately sixfold higher levels than naive cells. CD4(+) lymphocytes anergized through partial stimulation exhibit similar Kv1.1, Kv1.2, and/or Kv1.6 currents, but approximately threefold more Kv1.3 current than naive cells. To determine if Kv channels contribute to the distinct functions of naive, effector, and anergized T cells, we tested their role in immunoregulatory cytokine production. Each Kv channel is required for maximal IL-2 production by naive CD4(+) lymphocytes, whereas none appears to play a role in IL-2, IL-4, or IFN-gamma production by effector cells. Interestingly, Kv channels in anergized lymphocytes actively suppress IL-4 production, and these functions are consistent with a role in regulating the membrane potential and calcium signaling.

Animals↗