Human monocyte-derived insulin-like growth factor-2 enhances the infection of human arterial endothelial cells by Chlamydia pneumoniae

It has been shown that infection of human endothelial cells by Chlamydia pneumoniae is enhanced by co-culturing endothelial cells with human monocytes and is mediated by monocyte-derived soluble factors. This study was conducted to identify the infectivity-enhancing factor. Serum-free conditioned medium of human monocytic cells was fractionated by ultrafiltration. The enhancing activity was found in the fraction in the molecular mass range between 5000 and 10,000 kDa. Recombinant human insulin-like growth factor (IGF)-1 or -2, with a molecular mass of 7500 kDa, was added to the culture medium of human endothelial cells for growing C. pneumoniae. Only IGF-2 enhanced C. pneumoniae growth. Pretreatment of the conditioned medium with a monoclonal antibody against IGF-2 blocked the enhancing activity. This suggests that the infectivity-enhancing factor is IGF-2 and that paracrine interactions between monocytes and endothelial cells in vivo can induce secretory products and sustain infection with C. pneumoniae within atherosclerotic lesions.     

Interactions of Chlamydia pneumoniae with human endothelial cells

In order to fulfill the "biological plausibility" criterion of a role for infection with Chlamydia pneumoniae in the pathogenesis of human atherosclerosis, detailed studies on the interaction of this organism with the cell types involved are necessary. This article summarizes the current knowledge on the interaction of C. pneumoniae with human endothelial cells. In vitro, C. pneumoniae can infect human endothelial cells and induce the expression of many molecules that are important mediators of atherogenesis including cytokines, adhesion molecules, chemokines, and molecules with procoagulant activity.     

Monocyte-endothelial cell coculture enhances infection of endothelial cells with Chlamydia pneumoniae

To determine the mechanism(s) by which Chlamydia pneumoniae homes to and establishes persistent infection in atheromatous lesions, the effect of the interaction of monocytes/macrophages (U937 cells) with human umbilical vein endothelial cells (HUVECs) and transformed human arterial endothelial cells (HMEC-1s) on the susceptibility of endothelial cells to infection with C. pneumoniae was investigated. Infection was enhanced 4.7-fold (HUVECs) and 4.4-fold (HMEC-1s) after coculture at monocyte-to-endothelial cell ratios of 5 and 2.5, respectively. U937 cells also directly transmitted infection to the endothelial cells, and addition of U937 cell-conditioned media dose-dependently enhanced the infectivity 2.0- to 2.5-fold. The stimulation of infectivity was specific to endothelial cells, because coculturing of monocytes with epithelial cells did not enhance the susceptibility of epithelial cells to infection. The susceptibility of endothelial cells to infection with C. trachomatis and C. psittaci was not enhanced by the monocyte-derived factor(s).     

Atherogenetically relevant cells support continuous growth of Chlamydia pneumoniae

The obligate intracellular bacterium Chlamydia pneumoniae has been implicated in the pathogenesis of atherosclerosis since viable pathogen has been recovered from plaques. Chlamydiae are epithelial pathogens notorious for causing persistent infection. Atherosclerosis, however, is a chronic inflammatory disease involving mesenchymal cells of the vascular wall. A bacterial contribution to atherosclerosis appears more relevant if the resident mesenchymal cells of the vascular wall that constitute the plaque can support chlamydial infection continuously. Therefore we inoculated immortalized and primary mesenchymal cells with a vascular and a respiratory Chlamydia pneumoniae isolate. Primary human coronary artery endothelial and smooth muscle cells, primary human embryonic fibroblasts as well as the immortalized cell lines were permissive for continuous growth of both strains. Thus, the resident vascular cells that produce the atheromatous plaque can acquire permanent productive. Chlamydia pneumoniae infection. Immortalized monocytic cells and peripheral blood monocytes also supported chlamydial growth, though productive infection ceased after 5 passages. Monocytes/macrophages are not resident cells of the vascular wall but have an active role in plaque formation. Systemic circulation and transendothelial migration makes them a potential vector system for chlamydial distribution. These findings add further plausibility to the hypothesis of a chronic infectious component in the multifactorial condition of atherosclerosis. Further studies must precisely define chlamydial target cells in vivo and differentiate infection in resident cells of the vascular wall from a presence limited to migrating macrophages. Endovascular infection might provide an explanation for unclear phenomena of atherogenesis like mesenchymal cell proliferation and its distinct inflammatory component.     

Detection of Chlamydia pneumoniae in arterial tissues

In literature in which detection of Chlamydia pneumoniae in the artery is described, the methods used were immunocytochemistry (ICC), polymerase chain reaction (PCR), electron microscopy, and isolation. These studies demonstrated the presence of the organism in atheromatous lesions. The organism was detected frequently by ICC and PCR in atheromatous tissues (approximately 50% of subjects) but rarely in normal arteries (approximately 1% of subjects). There has been poor correlation between detection and serology. Detection studies have been used to assess the etiologic role of C. pneumoniae in atherosclerosis and to determine whether C. pneumoniae infection contributes to acute cardiovascular events. Although these studies produced suggestive evidence of an etiologic role, the use of observational studies to obtain a definitive answer is difficult. Therefore, investigators are increasingly concentrating their efforts on studies that use animal models, in vitro cultured arterial cells, and therapeutic trials in humans to determine the pathogenic role of the organism in atherosclerosis.     

特异性p38蛋白激酶抑制剂SB203580对小鼠感染肺炎衣原体后细胞因子变化的影响

目的 探讨特异性p38蛋白激酶(p38 MAPK)抑制剂SB203580对小鼠感染肺炎衣原体后细胞因子变化.方法 使用TLR4基因缺失(C3H/HeJ)小鼠90只,随机分为正常组、感染组和SB203580组,每组再分别按0、1、4、7、14 d分成5小组.正常组鼻内接种二磷酸蔗糖缓冲液,感染组鼻内接种肺炎衣原体约4.0×106 IFU/ml,SB203580组在感染肺炎衣原体后腹腔注射SB203580(100 mg/kg).分别在接种后第0天,第1天、第4天、第7天、第14天预定的时间处死小鼠,取肺组织分别采用Western blot法测p38 MAPK蛋白的表达,用酶联免疫吸附法检测肺组织中肿瘤坏死因子α(TNF-α)、白介素1(IL-1)的表达,同时观察各组小鼠肺组织病理变化.结果 感染组肺组织中TNF-α、IL-1的表达水平在各时间点均高于正常组(P＜0.05或P＜0.01),并在第4天出现高峰,14天以后开始下降.SB203580组肺组织中细胞因子TNF-α、IL-1的表达水平在各时间点均低于感染组(P＜0.05或P＜0.01).同时,SB203580组p38 MAPK蛋白表达强度弱于感染组.结论 p38 MAPK参与小鼠感染肺炎衣原体的炎症反应,特异性p38 MAPK抑制剂SB203580能抑制小鼠感染肺炎衣原体后的细胞因子表达,减轻炎症反应.     

Placental infection with Chlamydia pneumoniae and intrauterine growth restriction

BACKGROUND: The concept that low birth weight infants are more predisposed to coronary artery disease (CAD) in adulthood has been studied extensively. Although many infectious agents have been associated with intrauterine growth restriction (IUGR), Chlamydia pneumoniae an organism implicated in CAD has not been investigated. It was our aim to assess whether C. pneumoniae DNA is present in placental tissue and whether its detection is associated with IUGR. METHODS: Fifty-nine pregnant women were studied: 32 women had an uncomplicated pregnancy with no antenatal or post-natal evidence of IUGR. Twenty-seven women had pregnancies with ultrasonographically demonstrated IUGR, defined as foetal abdominal circumference measuring less than 2 S.D.s from the mean for gestational age. At the time of delivery, maternal blood and placental tissue samples were obtained. Placental samples were taken from four sites centrally and peripherally on the maternal and foetal side of the placentas and tested by nested polymerase chain reaction for C. pneumoniae DNA. IgG antibodies to C. pneumoniae were measured using microimmunfluorescence. RESULTS: C. pneumoniae DNA was detected in 44% of the placental tissue but there was no difference in the prevalence of bacterial DNA between the control and the low birth weight group (P=0.58). Additionally C. pneumoniae seropositivity did not differ between the index and control groups (78 vs. 70%, P=0.44). CONCLUSIONS: C. pneumoniae is present in placental tissue. Its presence however does not correlate with IUGR. Similarly, maternal C. pneumoniae seropositivity is not related to low birth weight. Thus C. pneumoniae infection is unlikely to play a role in the pathogenesis of IUGR.     

Detection of Chlamydia pneumoniae within peripheral blood monocytes of patients with unstable angina or myocardial infarction

Because individual diagnoses of vascular infection with Chlamydia pneumoniae depend entirely on surgically removed tissues, a better assay to predict vascular infection is needed. Polymerase chain reaction detection of chlamydial DNA was applied to CD14-positive cells collected from 238 patients with angiographically identified unstable angina or acute myocardial infarction. C. pneumoniae was detected in 52 (28%) of 188 persons with unstable angina and in 13 (26%) of 50 persons with myocardial infarction. Differences between groups were not significant. C. pneumoniae is present in monocytes/macrophages of a significant proportion of persons with progressive coronary artery disease. Infarction is not accompanied by a rise in chlamydial detection rates. The potential role of chlamydiae in coronary atherosclerosis may therefore be more related to acceleration of disease or systemic effects by persistent infection than to sudden initiation of infarction by acute infection.     

Lithium enhances growth of human leukaemia cells in vitro

Lithium is known to cause leucocytosis in normal humans, and lithium salts have been used therapeutically in attenuating leucopenia in patients undergoing chemotherapy. Recent reports also described leukaemia development during lithium treatment. We have investigated the effect of lithium chloride on the proliferation of human myeloid, erythroblastic, and T- and B-lymphoblast leukaemia cells in vitro. Colony formation by cells of the myeloid leukaemia lines HL-60 and KG-1 was enhanced by lithium chloride, and maximal stimulation was seen at 5 x 10⁻⁴ M. Lithium also increased the proliferation of KG-1a cells, a subline of KG-1 cells that does not respond to colony-stimulating factor, indicating a direct growth-promoting effect on myeloid leukaemia cells. Lithium was found to enhance colony formation by the T-lymphoblast cell line MOLT 4 and the B-lymphoblast line IM-9 at concentrations between 10⁻⁶ and 10⁻³ M. The addition of lithium chloride to murine Friend or human K-562 erythroleukaemia cells also caused an augmentation in colony formation. These observations may have relevance to the therapeutic use of lithium in patients with haematological malignancies.     

Human herpesvirus 8 enhances human immunodeficiency virus replication in acutely infected cells and induces reactivation in latently infected cells

Human herpesvirus 8 (HHV-8) is etiologically associated with Kaposi sarcoma (KS), the most common AIDS-associated malignancy. Previous results indicate that the HHV-8 viral transactivator ORF50 interacts synergistically with Tat protein in the transactivation of human immunodeficiency virus (HIV) long terminal repeat (LTR), leading to increased cell susceptibility to HIV infection. Here, we analyze the effect of HHV-8 infection on HIV replication in monocyte-macrophage and endothelial cells, as potential targets of coinfection. Primary or transformed monocytic and endothelial cells were infected with a cell-free HHV-8 inoculum and subsequently infected with lymphotropic or monocytotropic strains of HIV. The results show that HHV-8 coinfection markedly increases HIV replication in both cell types. HHV-8 infection induces also HIV reactivation in chronically infected cell lines and in peripheral blood mononuclear cells (PBMCs) from patients with asymptomatic HIV, suggesting the possibility that similar interactions might take place also in vivo. Furthermore, coinfection is not an essential condition, since contiguity of differently infected cells is sufficient for HIV reactivation. The results suggest that HHV-8 might be a cofactor for HIV progression and that HHV-8-infected endothelial cells might play a relevant role in transendothelial HIV spread.     

Infection and activation of airway epithelial cells by Chlamydia pneumoniae

The activation of primary human airway epithelial cells (HAECs) and of the bronchial epithelial cell line BEAS-2B by Chlamydia pneumoniae, an important respiratory pathogen, was characterized. A time-dependent enhanced release of interleukin (IL)-8 and prostaglandin-E(2) and an increased expression of the epithelial adhesion molecule intercellular adhesion molecule-1 (ICAM-1), followed by subsequent transepithelial migration of polymorphonuclear neutrophils (PMN), were also demonstrated. The transepithelial PMN migration could be blocked by an anti-ICAM-1 monoclonal antibody (MAb) but not by MAbs against IL-8. In addition, there was an enhanced C. pneumoniae-mediated activation of NF-kappaB within 30-60 min in HAECs and BEAS-2B, which was followed by increases in mRNA synthesis of IL-8, ICAM-1, and cyclooxygenase-2, with maximal effects occurring 2 h after infection. Thus, C. pneumoniae infects and activates HAECs and BEAS-2B and therefore may be able to trigger a cascade of pro- and anti-inflammatory reactions during chlamydial infections.     

Evidence for persistent Chlamydia pneumoniae infection of human coronary atheromas

To date, structures representing developmental stages of Chlamydia pneumoniae, especially persistent forms of this intracellular bacteria, have not been described in human atherosclerotic tissues using specific antibody labeling and transmission electron microscopy.Staining of atherosclerotic tissue from five patients seeking heart transplantation with gold-labeled antibodies specific for up-regulated chlamydial heat shock proteins, GroEL and GroES, and visualisation via transmission electron microscopy revealed intracellular, atypical, round to oval structures of variable diameter. These structures resembled reticulate bodies of Chlamydia, were surrounded by membranes and were located within smooth muscle cells, macrophages or fibroblasts. By using double immunogold electron microscopy technique (GroEL and GroES in combination with chlamydial LPS/MOMP antibodies), we demonstrated these structures were of chlamydial origin.In the current study, we demonstrated the presence of aberrant bodies of C. pneumoniae in vivo in archival coronary atheromatous heart tissues by the immunogold electron microscopy technique.     

Comparison of sensitivity of Hep-2 cells with that of HL cells against Chlamydia pneumoniae]

We compared the growth of Chlamydia pneumoniae, reference strain TW183 and an isolate from a Japanese infant, AC43 in HeLa229, HL and Hep-2 cells. The mean number of inclusion-forming units was significantly higher on HL cells than HeLa229 cells, when the cells were not pretreated with DEAE-dextran. When the cells were not pretreated with DEAE-dextran, Hep-2 cells had a higher mean number of inclusion-forming units and a higher yield than other cell lines. Iscove's modified Dulbecco medium enhanced growth of strain TW183 in HeLa229 cells but had a low yield of strain AC43 in Hep-2 cells.     

Stimulation of plasminogen activator inhibitor activity in human monocytes infected with dengue virus

Human monocytes, in an essentially serum-free culture medium, were infected with dengue 2 virus in the presence of sub-neutralizing concentrations of antibody. Changes in procoagulant activity (PCA), in the plasminogen activator urokinase (UK), and the plasminogen activator inhibitor-2 (PAI-2) were quantitated. One day after exposure to dengue virus, the cell-associated PAI-2 activity in the infected monocytes was 562 +/- 9 mU/10(6) cells (mean +/- SE) compared to 206 +/- 56 mU/10(6) cells for uninfected monocytes. Supernatants of the infected cells also showed greater than 2-fold increase in PAI-2 activity. This increase in cell-associated and supernatant PAI-2 activity was maintained during 4 days of culture. UK activity was not detected in control and infected cells nor in their supernatants. PCA activity was the same in control and dengue virus infected monocytes when measured during 4 days of culture. These data suggest that dengue infected monocytes may affect fibrinolysis at a localized level through increased production of PAI-2.     

Release of nerve growth factor from cultured aortic smooth-muscle cells.

Conditioned medium from cultured aortic smooth-muscle cells from rat aorta yielded neurite-extending effects on sensory and sympathetic ganglia of chick embryos. These effects were blocked by adding specific antiserum against 2.5S nerve growth factor (NGF), suggesting that NGF might be released from vascular smooth-muscle cells.