Preferential induction of TNF-alpha and IL-1beta and inhibition of IL-10 secretion by human peripheral blood monocytes by synthetic aza-alkyl lysophospholipids

Synthesis of ether lipids: natural compounds and analogues

Ether lipids are compounds present in many living organisms including humans that feature an ether bond linkage at the sn-1 position of the glycerol. This class of lipids features singular structural roles and biological functions. Alkyl ether lipids and alkenyl ether lipids (also identified as plasmalogens) correspond to the two sub-classes of naturally occurring ether lipids. In 1979 the discovery of the structure of the platelet-activating factor (PAF) that belongs to the alkyl ether class of lipids increased the interest in these bioactive lipids and further promoted the synthesis of non-natural ether lipids that was initiated in the late 60's with the development of edelfosine (an anticancer drug). More recently, ohmline, a glyco glycero ether lipid that modulates selectively SK3 ion channels and reduces in vivo the occurrence of bone metastases, and other glyco glycero ether also identified as GAEL (glycosylated antitumor ether lipids) that exhibit promising anticancer properties renew the interest in this class of compounds. Indeed, ether lipid represent a new and promising class of compounds featuring the capacity to modulate selectively the activity of some membrane proteins or, for other compounds, feature antiproliferative properties via an original mechanism of action. The increasing interest in studying ether lipids for fundamental and applied researches invited to review the methodologies developed to prepare ether lipids. In this review we focus on the synthetic method used for the preparation of alkyl ether lipids either naturally occurring ether lipids (e.g., PAF) or synthetic derivatives that were developed to study their biological properties. The synthesis of neutral or charged ether lipids are reported with the aim to assemble in this review the most frequently used methodologies to prepare this specific class of compounds.

Rituximab inhibits p38 MAPK activity in 2F7 B NHL and decreases IL-10 transcription: pivotal role of p38 MAPK in drug resistance

We have recently reported that Rituximab (anti-CD20) sensitizes drug-resistant 2F7 and 10C9 B Non-Hodgkin's lymphoma (NHL) cell lines to the apoptotic effects of various chemotherapeutic drugs by downregulation of IL-10 and Bcl-2 expression. The mechanism by which Rituximab induces downregulation of IL-10 was examined. We hypothesized that Rituximab may inhibit p38 MAPK activity that regulates IL-10 expression via Sp1. Treatment of 2F7 cells with Rituximab or the p38 inhibitor SB203580 inhibited the constitutive p38 MAPK activity and resulted in the inhibition of Sp1, IL-10, STAT3, and Bcl-2. Inhibition of the Src-family PTKs, Lyn, and Src-family PTKs upstream signaling molecules of the p38MAPK pathway, by PP2, a specific Src-family kinase inhibitor, resulted in the inhibition of p38MAPK and IL-10 expression. In addition to p38 MAPK, Rituximab also inhibited NF-kappaB activity. Inhibition of the Src PTKs, MAPK, and NF-kappaB activities by Rituximab or by specific chemical inhibitors sensitized the cells to CDDP-mediated apoptosis. The above signaling-mediated effects by Rituximab were observed with similar kinetics beginning at 1 h following treatment. Thus, altogether, these results demonstrate that signaling by Rituximab results in the inhibition of the p38MAPK pathway, which in turn inhibits the transcription of IL-10 via Sp1. Inhibition of the IL-10 autocrine/paracrine loop results in the inhibition of STAT3 activity and, consequently, inhibition of Bcl-2 expression and sensitization to drugs-apoptosis. Further, Rituximab-mediated signaling identifies several new intracellular targets in NHL that may be of potential therapeutic interest for the development of new drugs in the treatment of drug-refractory NHL tumor cells.

Induction of proinflammatory cytokines in human lung epithelial cells during Chlamydia pneumoniae infection

Chlamydia pneumoniae is an obligate intracellular human pathogen that causes acute respiratory diseases such as pneumonia and bronchitis. Previous studies have established that C. pneumoniae can induce cytokines in mouse and/or human cells, but little information is available on the cytokine response of respiratory epithelial cells, a first line of infection. In this study, heparin treatment of C. pneumoniae significantly reduced its ability to induce interleukin 8 (IL-8) and tumor necrosis factor alpha (TNF-alpha) mRNA in human lung carcinoma cells, indicating that cytadherence is an important early stimulus for induction of proinflammatory mediators. Although the IL-8, gamma interferon, and TNF-alpha message was consistently induced by infection of A549 cells not treated with heparin, only an elevation of IL-8 protein was detected in A549 supernatants. A549 IL-beta and IL-6 mRNA and supernatant protein profiles were not significantly changed by infection. Heat or UV inactivation of C. pneumoniae only partially reduced the cytokine response, and inhibition of C. pneumoniae protein or DNA synthesis did not affect its ability to induce cytokine gene expression. To prevent stress-induced cytokine release by the A549 cells, centrifugation was not utilized for infection experiments. These experiments establish the importance of cytadherence in cytokine release by cells of respiratory epithelial origin and suggest that further work in the area of cytokine mediators is warranted to gain valuable pathogenic and therapeutic insights.

Interleukin-1beta responses to Mycoplasma pneumoniae infection are cell-type specific

Interleukin-1beta (IL-1beta) is a major proinflammatory cytokine that is involved in many important cellular functions such as proliferation, differentiation, and activation of different cell types. Its mature form is released from the cells in response to various bacterial and viral infections, and it plays a significant role in host defense. Mycoplasma pneumoniae is a small bacterium without a cell wall that causes tracheobronchitis and atypical pneumonia in humans following attachment to respiratory epithelium, as well as extrapulmonary infections. Very little is known about the role of cytokines in pathogenesis or the response of target cells to M.pneumoniae attachment. The purpose of this study was to investigate the ability of M. pneumoniae to induce IL-1beta in human lung epithelial carcinoma A549 and in human monocytic U937 cell lines. Following M. pneumoniae infection, both IL-1beta mRNA and protein were induced in A549 cells vs. no induction in uninfected cells; however, the protein remained inside the A549 cells. Similarly, M. pneumoniae infection strongly increased mRNA and extracellular protein levels in U937 cells, which unlike A549 cells did exhibit baseline constitutive levels. De novo IL-1beta protein expression was verified by cycloheximide studies. M. pneumoniae infection did not affect constitutive caspase-1 mRNA or protein levels in either cell line. Reduced caspase-1 activity in A549 cell lysates suggests the presence of an endogenous caspase-1 inhibitory component in the A549 cells. These collective data confirm previous studies that show that M. pneumoniae is a potent inducer of cytokines following adherence to host target cells, and establish that IL-1beta release in response to M. pneumoniae infection is cell-type specific, thus emphasizing the importance of carefully considering multiple cell types in M. pneumoniae pathogenesis studies involving both immune cells and cytokine release patterns.

Regulation of proinflammatory cytokines in human lung epithelial cells infected with Mycoplasma pneumoniae

Mycoplasma pneumoniae is a small bacterium without a cell wall that causes tracheobronchitis and atypical pneumonia in humans. It has also been associated with chronic conditions, such as arthritis, and extrapulmonary complications, such as encephalitis. Although the interaction of mycoplasmas with respiratory epithelial cells is a critical early phase of pathogenesis, little is known about the cascade of events initiated by infection of respiratory epithelial cells by mycoplasmas. Previous studies have shown that M. pneumoniae can induce proinflammatory cytokines in several different study systems including cultured murine and human monocytes. In this study, we demonstrate that M. pneumoniae infection also induces proinflammatory cytokine expression in A549 human lung carcinoma cells. Infection of A549 cells resulted in increased levels of interleukin-8 (IL-8) and tumor necrosis factor alpha mRNA, and both proteins were secreted into culture medium. IL-1 beta mRNA also increased after infection and IL-1 beta protein was synthesized, but it remained intracellular. In contrast, levels of IL-6 and gamma interferon mRNA and protein remained unchanged or undetectable. Using protease digestion and antibody blocking methods, we found that M. pneumoniae cytoadherence is important for the induction of cytokines. On the other hand, while M. pneumoniae protein synthesis and DNA synthesis do not appear to be prerequisites for the induction of cytokine gene expression, A549 cellular de novo protein synthesis is responsible for the increased cytokine protein levels. These results suggest a novel role for lung epithelial cells in the pathogenesis of M. pneumoniae infection and provide a better understanding of M. pneumoniae pathology at the cellular level.