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D Stengel

Publications and source records attributed to D Stengel.

At least 37 records · Page 2Linked to original sources
PubMed2003

A likelihood ratio approach to meta-analysis of diagnostic studies.

OBJECTIVE: To develop a clinically and methodologically sound approach to diagnostic meta-analysis. METHODS: Two-step model was used involving four fictitious sets of 10 studies each with varying sensitivity and specificity; this was followed by the application of the method to data from a published systematic review of emergency ultrasound. Multidimensional test characteristics (relating to the detection or exclusion of the condition of interest) were described by likelihood ratio scatterplots and pooled likelihood ratios. Likelihood ratios summarise the ability of a test to revise the prior probability of disease. They can be summarised by established fixed-effects and random-effects methods. RESULTS: Likelihood ratios precisely describe both directions of test performance. By plotting positive against negative likelihood ratios, together with their 95% confidence intervals, a multidimensional forest plot is obtained that can be interpreted in analogy to therapeutic meta-analyses. There are accepted threshold values of positive and negative likelihood ratios (i.e. 10.0 and 0.1) to recommend a test for clinical use. In the matrix space, distinct test characteristics can even be assessed by eyeballing. With regard to data from the real meta-analysis, the suggested high discriminatory power of ultrasound was only partially qualified by likelihood ratios. The positive value confirms the reliability of a positive scan, whereas the negative value questions a normal sonogram. CONCLUSIONS: A full characterisation of test performance requires multidimensional effect measures. Likelihood ratios are recommended descriptors of the two dimensions of diagnostic research evidence and provide a convenient means to visualise and to communicate results as weighted summary estimates of a diagnostic meta-analysis.

Diagnosis↗
PubMed2002

A phase II study of topotecan plus gemcitabine in the treatment of patients with relapsed ovarian cancer after failure of first-line chemotherapy.

BACKGROUND: Second-line chemotherapy for patients with ovarian cancer who failed platinum and paclitaxel treatment remains a therapeutic challenge. We investigated the toxicity profile and therapeutic efficacy of a novel combination regimen, topotecan plus gemcitabine, in a clinical phase II study. PATIENTS AND METHODS: Women with relapsed epithelial ovarian cancer after platinum and paclitaxel treatment were eligible to participate in this trial. Topotecan was given at an initial dose of 0.5 mg/m(2) daily (days 1-5), combined with gemcitabine 800 mg/m(2) and 600 mg/m(2) on days 1 and 8, respectively. Precluding good tolerability, this protocol facilitated subsequent dose increases of topotecan up to 1.0 mg/m(2). The primary objective was to determine the dose-limiting toxicity, whereas secondary objectives comprised measurable and CA-125 response rates, disease-free and overall survival. RESULTS: The twenty-one patients (median age 57 years, range 37-70 years) who were allocated to this trial received a total of 94 courses of chemotherapy. Median follow-up was 20.5 months. Topotecan dosage could be escalated to 0.75 mg/m(2) in nine patients and 1 mg/m(2) in another two patients. Dose reduction was not necessary in any case. There were no episodes of neutropenic fever, sepsis or chemotherapy-related fatalities. Only one patient developed CTC grade 4 leukopenia after the first treatment cycle, whereas three patients showed grade 3/4 anaemia. Five patients experienced thrombocytopenia grade 4 without clinical sequelae. Non-hematological toxicities were mild and rare. Eleven patients could be evaluated for clinical tumour response, with three complete, and four partial remissions. Two patients each had stable and progressive diseases. The median progression-free survival rate was 8.8 months [95% confidence interval (CI) 6.3-13.4 months]. The median overall survival rate was 21.1 months (95% CI 14.8-22.1 months). CONCLUSIONS: Topotecan combined with gemcitabine has a favourable toxicity profile and encouraging efficacy in patients with recurrent ovarian cancer.

Adult↗
PubMed2001

Adenovirus-mediated gene transfer of human platelet-activating factor-acetylhydrolase prevents injury-induced neointima formation and reduces spontaneous atherosclerosis in apolipoprotein E-deficient mice.

BACKGROUND: Atherosclerosis is characterized by an early inflammatory response involving proinflammatory mediators such as platelet-activating factor (PAF)-like phospholipids, which are inactivated by PAF-acetylhydrolase (PAF-AH). The effect of adenovirus-mediated expression of PAF-AH on injury-induced neointima formation and spontaneous atherosclerosis was studied in apolipoprotein E-deficient mice. METHODS AND RESULTS: Intravenous administration of an adenovirus (5 x 10(8) plaque-forming units) directing liver-specific expression of human PAF-AH resulted in a 3.5-fold increase of plasma PAF-AH activity at day 7 (P<0.001); this was associated with a 2.4- and 2.3-fold decrease in malondialdehyde-modified LDL autoantibodies and the lysophosphatidylcholine/phosphatidylcholine ratio, respectively (P<0.001 for both). Non-HDL and HDL cholesterol levels in PAF-AH-treated mice were similar to those of control virus-treated mice. Seven days after virus injection, endothelial denudation of the common left carotid artery was induced with a guidewire. Neointima formation was assessed 18 days later. PAF-AH gene transfer reduced oxidized lipoproteins by 82% (P<0.001), macrophages by 69% (P=0.006), and smooth muscle cells by 84% (P=0.002) in the arterial wall. This resulted in a 77% reduction (P<0.001) of neointimal area. Six weeks after adenovirus-mediated gene transfer, spontaneous atherosclerotic lesions in the aortic root were analyzed. PAF-AH gene transfer reduced atherosclerotic lesions by 42% (P=0.02) in male mice, whereas a nonsignificant 14% reduction was observed in female mice. Basal and PAF-AH activity after gene transfer were higher in male mice than in female mice (P=0.01 and P=0.04, respectively). CONCLUSIONS: Gene transfer of PAF-AH inhibited injury-induced neointima formation and spontaneous atherosclerosis in apolipoprotein E-deficient mice. Our data indicate that PAF-AH, by reducing oxidized lipoprotein accumulation, is a potent protective enzyme against atherosclerosis.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗
PubMed2001

Shed L-selectin (sCD62L) load in trauma patients.

BACKGROUND: Low circulating plasma concentrations of the leukocyte adhesion molecule L-selectin (sCD62L) were found to be associated with an increased risk for subsequent lung failure and case fatality after severe trauma. The objective of this study was to determine the robustness of soluble L-selectin, correcting for a broad spectrum of physiological variables. METHODS: Patients with suspected multiple and/or trunk injuries were enrolled into this study over a 1-year period. Plasma samples were obtained on hospital presentation, and circulating soluble L-selectin was measured with a commercially available ELISA kit. Study records comprised all relevant clinical and laboratory data. Thirty-day survival rate, subsequent acute lung failure, and nosocomial pneumonia were defined as study endpoints. Statistical analysis was performed using multivariate logistic regression models. RESULTS: Seventy patients with a mean age of 35.51 years (range, 10-87 years) and a mean ISS score of 36.61 (95% CI, 31.08-42.14) entered the study. Eleven patients died, leading to an attributable mortality of 15.70%. L-Selectin levels did not differ between survivors and nonsurvivors. Five patients progressed to acute lung injury, whereas 11 patients developed hospital-acquired pneumonia. Lower L-selectin levels indicated patients at risk for lung injury with a relative odds estimated at 4.43 (P = 0.017). Statistical significance diminished in the multivariate model. In contrast, plasma concentrations of circulating sCD62L were significantly decreased in patients developing nosocomial pneumonia (P = 0.023), with a twofold increased relative odds (OR, 1.96; 95% CI, 0.51-7.50). No effect modification was observed by the included covariables. CONCLUSIONS: The results of this study highlight the independent predictive value of initially decreased soluble L-selectin levels for the identification of patients susceptible to subsequent respiratory complications after severe trauma.

Adolescent↗
PubMed2001

Systematic review and meta-analysis of antibiotic therapy for bone and joint infections.

We set out to evaluate the clinical efficacy of individual antibiotic agents for bone and joint infections in adults. Published and unpublished controlled trials reported between 1966 and 2000 were reviewed to determine if they involved random or quasi-random allocation to systemically administered antimicrobials or local antibiotic therapy for osteomyelitis and septic arthritis. Quiescence of infection after 1 year of follow-up was defined as the primary outcome measure. 22 trials containing 927 patients were eligible for final analysis. Varying proportions of the entire study population could be evaluated with respect to primary and secondary endpoints. Methodological quality was poor among most studies, and interpretability of results was further limited by small sample sizes, missing descriptions of patient populations and disease characteristics, and the frequent application of concomitant antibiotics. A trend towards improved, long-lasting infection control was observed in favour of a rifampicin-ciprofloxacin combination versus ciprofloxacin monotherapy for the treatment of staphylococcal infections related to orthopaedic devices (absolute risk difference [ARD] 28-9%; 95% CI -0.7 to 54.4%). Obviously unbalanced comparative studies showed some benefit of ticarcillin for bone infections caused by Pseudomonas species. No significant differences in therapeutic efficacy were found among trials comparing oral fluoroquinolones with intravenous beta-lactam drugs for both end-of-treatment (OR 0.8; 0.5 to 1.4) and long-term results (OR 1.3; 0.8 to 2.1). A variety of drugs was used as controls, thereby leading to inconsistent findings of drug-related side effects. Only one randomised trial was suitable to investigate the impact of polymethylmethacrylate gentamicin bead chains compared with parenteral antibiotics for skeletal infections, although this study was biased by patients receiving both combined local and systemic antibiotic therapy. Whereas intention-to-treat evaluation suggested a therapeutic advantage of systemic over local therapy, this trend diminished in the per-protocol analysis (1-year follow-up ARD -2.3;-17.5 to 10.8%). There exists little high-quality evidence on antibiotic therapy for osteomyelitis and septic arthritis. The observed heterogeneity among patient populations and medical and surgical treatment concepts preclude reliable inferences from the available data.

Anti-Bacterial Agents↗
PubMed2001

Systematic review and meta-analysis of emergency ultrasonography for blunt abdominal trauma.

BACKGROUND: How precise and reliable is ultrasonography as a primary tool for injury assessment in blunt abdominal trauma? METHODS: A systematic review and meta-analysis were conducted of prospective clinical trials of ultrasonography for blunt abdominal trauma. Publications were retrieved by structured searching among databases, review articles and major text books. Authors and experts in the field were contacted for original and unpublished data. For statistical analysis, summary receiver operating characteristic curves (SROCs) were computed using weighted and robust regression models, with Q* denoting the shoulder of the curve. Post-test probabilities were calculated as a function of pooled likelihood ratios (LRs). RESULTS: Thirty of 123 trials enrolling 9047 patients were eligible for final analysis. With respect to targeting organ lesions, ultrasonography showed a summary Q* value of 0.91 (inverse variance weights, 95 per cent confidence interval (c.i.) 0.76-1.07); negative predictive values ranged from 0.72 to 0.99. A similar SROC slope was calculated for screening for free fluid (Q* = 0.89 (95 per cent c.i. 0.73-1.05)). Ultrasonography detects the presence of organ lesions, but fails to exclude abdominal injuries (random effects negative LR 0.23 (95 per cent c.i. 0.18-0.28)). Given a pretest probability of 50 per cent for blunt abdominal injury, a post-test probability of nearly 25 per cent remains in the case of a negative sonogram. CONCLUSION: Despite its high specificity, ultrasonography has an unexpectedly low sensitivity for the detection of both free fluid and organ lesions. In clinically suspected abdominal trauma, another assessment (e.g. helical computed tomography) must be performed regardless of the initial ultrasonographic findings.

Abdominal Injuries↗
PubMed2001

Oxidized low density lipoproteins downregulate LPS-induced platelet-activating factor receptor expression in human monocyte-derived macrophages: implications for LPS-induced nuclear factor-kappaB binding activity.

Monocytes/macrophages play a key role in atherogenesis due to their inflammatory properties including formation of lipid mediators such as platelet-activating-factor (PAF). We investigated the effect of oxidized low-density lipoprotein (oxLDL) on lipopolysaccharide (LPS)-induced PAF receptor (PAF-R) expression in human macrophages and the implication of the nuclear factor (NF)-kappaB in this regulation. LPS-treatment (1 microg.mL(-1)) of macrophages increased PAF binding and PAF-R mRNA expression by 56% (P < 0.05) and twofold (P < 0.01), respectively. In contrast, highly oxidized low-density lipoprotein [ox24hLDL; 100 microg.mL(-1); thiobarbituric acid reacting substances: 31 +/- 3 nmol equiv. malondialdehyde (MDA).mg protein LDL-1] diminished PAF-R expression (-69%; P < 0.05) and mRNA level (- 45%; P < 0.01). LPS pretreatment induced the activated form of p65 in the nuclear compartment of macrophages (detected by Western blotting) and NF-kappaB binding activity (by electrophoretic mobility shift assay). Treatment of macrophages with ox24hLDL suppressed the LPS-induced binding of NF-kappaB to DNA. In addition, treatment of macrophages with lysophosphatidylcholine (2 and 10 microM), a major component of oxLDL, inhibited the LPS-induced NF-kappaB binding to DNA and reduced PAF binding by 30 and 70%, respectively. In conclusion, oxLDL may downregulate PAF-R expression in human macrophages by inhibiting LPS-induced NF-kappaB binding to DNA.

Arteriosclerosis↗
PubMed2001

Discriminatory power of 3.5 MHz convex and 7.5 MHz linear ultrasound probes for the imaging of traumatic splenic lesions: a feasibility study.

BACKGROUND: Ultrasound is a powerful tool for recognition of free fluid after blunt abdominal trauma, whereas its role for detection of organ lesions remains to be defined. The objective of this study was to determine the diagnostic value of different ultrasound transducers for the precise detection of visceral damage rather than its surrogates in case of splenic injury. METHODS: After a standardized focused abdominal sonogram for trauma protocol to screen for hemoperitoneum, 37 slim, hemodynamically stable subjects with suspected torso trauma were investigated for the extent of parenchymal lesions of the spleen using a 3.5 MHz curved array and a 7.5 MHz linear device. Helical computed tomographic scanning was carried out as the reference standard in all cases. RESULTS: Twenty patients presented splenic damage. The 7.5 MHz transducer showed higher accuracy than the lower frequency probe for the detection of tissue irregularities (difference in proportions, 16.2%; 95% confidence interval, -1.9%-33.5%). A similar trend was observed for 13 lacerations subsequently progressing to two-timed splenic rupture that required surgery (absolute risk reduction, 8.1%; 95% confidence interval, -7.6%-23.9%). With an observed prevalence of 54% for the presence of splenic injury, organ lacerations could be excluded more confidently using the linear probe (posttest probability, 16% vs. 36%). CONCLUSION: In slim patients, higher frequency linear ultrasound probes can provide therapy-relevant information on the integrity of splenic parenchyma after blunt abdominal trauma.

Abdominal Injuries↗
PubMed2001

Arg123-Tyr166 domain of human ApoA-I is critical for HDL-mediated inhibition of macrophage homing and early atherosclerosis in mice.

Atherosclerosis was studied in apolipoprotein E (apoE) knockout mice expressing human apolipoprotein A-I (apoA-I) or an apoA-I/apolipoprotein A-II (apoA-II) chimera in which the Arg123-Tyr166 central domain of apoA-I was substituted with the Ser12-Ala75 segment of apoA-II. High density lipoprotein (HDL) cholesterol levels were identical in apoA-I and apoA-I/apoA-II mice, but at 4 months, plaques were 2.7-fold larger in the aortic root of the apoA-I/apoA-II mice (P<0.01). The macrophage-to-smooth muscle cell ratio of lesions was 2.1-fold higher in apo-I/apoA-II mice than in apoA-I mice (P<0.01). This was due to a 2.7-fold higher (P<0.001) in vivo macrophage homing in the aortic root of apoA-I/apoA-II mice. Plasma platelet-activating factor acetyl hydrolase activity was lower (P<0.01) in apoA-I/apoA-II mice, resulting in increased oxidative stress, as evidenced by the higher titer of antibodies against oxidized low density lipoprotein (P<0.01). Increased oxidative stress resulted in increased stimulation of ex vivo macrophage adhesion by apoA-I/apoA-II beta-very low density lipoprotein and decreased inhibition of beta-very low density lipoprotein-induced adhesion by HDL from apoA-I/apoA-II mice. The cellular cholesterol efflux capacity of HDL from apoA-I/apoA-II mice was very similar to that of apoA-I mice. Thus, the Arg123-Tyr166 central domain of apoA-I is critical for reducing oxidative stress, macrophage homing, and early atherosclerosis in apoE knockout mice independent of its role in HDL production and cholesterol efflux.

Animals↗
PubMed2001

N-linked glycosylation of macrophage-derived PAF-AH is a major determinant of enzyme association with plasma HDL.

Human plasma PAF-AH (platelet-activating factor-acetylhydrolase) is a Ca(2)+-independent phospholipase A2 of hematopoietic origin associated with LDL and HDL; it degrades PAF and oxidizes phospholipids. We show that human macrophages synthesize PAF-AH as a premedial Golgi precursor containing high mannose N-linked glycans. Secreted PAF-AH possesses a molecular mass of approximately 55 kDa and contains mature N-linked glycans. Secreted PAF-AH activity (90 +/- 4% of the total) bound to a wheat germ lectin column and could be eluted with N-acetylglucosamine, whereas digestion with N-acetylneuraminidase II completely abolished enzyme absorption. Tunicamycin significantly reduced cell-associated PAF-AH activity and inhibited enzyme secretion; but it did not alter the ratio of secreted to cell-associated enzyme (1.8 at 6 h and 3.1 at 24 h), suggesting that glycosylation is not essential for PAF-AH secretion. Digestion of cell-associated PAF-AH or secreted PAF-AH with peptide N-glycosidase F affected neither catalytic activity nor its resistance to proteolysis with trypsin or proteinase K; in addition, it did not affect PAF-AH association with LDL, but significantly increased its association with HDL. We suggest that macrophage-derived PAF-AH contains heterogeneous asparagine-conjugated sugar chain(s) involving sialic acid, which hinders its association with HDL but does not influence the secretion, catalytic activity, or resistance of PAF-AH to proteases.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗
PubMed2000

Expression of platelet-activating factor receptor in human carotid atherosclerotic plaques: relevance to progression of atherosclerosis.

BACKGROUND: Human monocyte-derived macrophages synthesize numerous proinflammatory and prothrombotic substances, including lipid mediators, such as platelet-activating factor (PAF), which may play a major role in the onset and perpetuation of atherosclerotic lesions. In addition, both monocytes and macrophages express PAF receptors (PAF-R). The expression of PAF-R is transcriptionally downregulated by oxidized LDL in in vitro primary cultures of monocyte/macrophages. In this study, we evaluated the expression of PAF-R in human carotid plaque tissue, in foam cells isolated from human carotid plaques, and in primary cultures of umbilical smooth muscle cells (SMCs). METHODS AND RESULTS: We show that PAF-R was expressed at low levels in foam cells compared with monocyte/macrophages in plaques, as assessed by immunohistochemical staining and in situ hybridization. In addition, low levels of mRNA were also detected by RT-PCR in isolated human carotid foam cells. A prominent finding of our study was the demonstration that contractile SMCs were positive for PAF-R, and its mRNA was extracted from primary cultures of umbilical SMCs. CONCLUSIONS: As macrophages loose their inflammatory phenotype on transformation into foam cells, they may equally loose their capacity of defense against aggression. We postulate that the diminished expression of PAF-R may be deleterious in the context of plaque formation and progression. The observation that arterial SMCs of contractile phenotype express PAF-R opens new avenues concerning the migration of these cells from media to intima and atherosclerotic plaque formation.

Antigens, Differentiation↗
PubMed2000

Cloning and expression of human adenylyl cyclase type VI in normal thyroid tissues.

The adenylyl cyclase type VI gene expressed in human normal thyroid tissue was cloned and sequenced. The cDNA sequence (6463 nt) is susceptible to code for a 1168 aa protein. Northern blots using specific probes showed that the expression of adenylyl cyclase type VI gene was significantly higher in one hyperfunctioning thyroid tumor than in normal thyroid tissue, in one follicular cold adenoma or in one papillary carcinoma.

Adenoma↗
PubMed2000

HDL-associated PAF-AH reduces endothelial adhesiveness in apoE-/- mice.

Macrophage infiltration into the subendothelial space at lesion prone sites is the primary event in atherogenesis. Inhibition of macrophage homing might therefore prevent atherosclerosis. Since HDL levels are inversely correlated with cardiovascular risk, their effect on macrophage homing was assessed in apoE-deficient (apoE-/-) mice. Overexpression of human apolipoprotein AI in apoE-/- mice increased HDL levels 3-fold and reduced macrophage accumulation in an established assay of leukocyte homing to aortic root endothelium 3.2-fold (P<0.005). This was due to reduced in vivo betaVLDL oxidation, reduced betaVLDL triggered endothelial cytosolic Ca2+ signaling through PAF-like bioactivity, lower ICAM-1 and VCAM-1 expression, and diminished ex vivo leukocyte adhesion. Adenoviral gene transfer of human PAF-acetylhydrolase (PAF-AH) in apoE-/- mice increased PAF-AH activity 1.5-fold (P<0.001), reduced betaVLDL-induced ex vivo macrophage adhesion 3.5-fold (P<0.01), and reduced in vivo macrophage homing 2.6-fold (P<0.02). These inhibitory effects were observed in the absence of increased HDL cholesterol levels. In conclusion, HDL reduces macrophage homing to endothelium by reducing oxidative stress via its associated PAF-AH activity. This protective mechanism is independent of the function of HDL as cholesterol acceptor. Modulation of lipoprotein oxidation by PAF-AH may prevent leukocyte recruitment to the vessel wall, a key feature in atherogenesis.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗
PubMed2000

Primary mucinous adenocarcinoma of the appendix: a rare entity in the differential diagnosis of ovarian cancer.

We report a 58-year-old female patient with the suspected diagnosis of ovarian cancer. Upon surgical exploration, examination of the appendix revealed the histological diagnosis of primary mucinous adenocarcinoma. This is an unusual consideration in the differential diagnosis of the ovarian cancer. We discuss the diagnosis, classification and treatment of the cancer of the appendix in relation to ovarian cancer.

Adenocarcinoma, Mucinous↗
PubMed2000

Effect of overexpression of human apo A-I in C57BL/6 and C57BL/6 apo E-deficient mice on 2 lipoprotein-associated enzymes, platelet-activating factor acetylhydrolase and paraoxonase. Comparison of adenovirus-mediated human apo A-I gene transfer and human apo A-I transgenesis.

Various mechanisms may contribute to the antiatherogenic potential of apolipoprotein A-I (apo A-I) and high density lipoproteins (HDLs). Therefore, the effect of adenovirus-mediated human apo A-I gene transfer or human apo A-I transgenesis on platelet-activating factor acetylhydrolase (PAF-AH) and arylesterase/paraoxonase (PON1) was studied in C57BL/6 and C57BL/6 apo E(-/-) mice. Human apo A-I transgenesis in C57BL/6 mice resulted in a 4.2-fold (P<0.0001) increase of PAF-AH and a 1.7-fold (P=0.0012) increase of PON1 activity. The apo E deficiency was associated with a 1.6-fold (P=0.008) lower PAF-AH and a 2.0-fold (P=0.012) lower PON1 activity. Human apo A-I transgenesis in C57BL/6 apo E(-/-)mice increased PAF-AH and PON1 activity by 2.1-fold (P=0.01) and 2.5-fold (P=0.029), respectively. After adenovirus-mediated gene transfer of human apo A-I into C57BL/6 apo E(-/-)mice, a strong correlation between human apo A-I plasma levels and PAF-AH activity was observed at day 6 (r=0.92, P<0.0001). However, PON1 activity failed to increase, probably as a result of cytokine-mediated inhibition of PON 1 expression. In conclusion, this study indicates that overexpression of human apo A-I increases HDL-associated PAF-AH activity. PON1 activity was also increased in human apo A-I transgenic mice, but not after human apo A-I gene transfer, a result that was probably related to cytokine production induced in the liver by the adenoviral vectors. Increased levels of these HDL-associated enzymes may contribute to the anti-inflammatory and antioxidative potential of HDL and thereby to the protection conferred by HDL against atherothrombosis.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗
PubMed2000

Mildly oxidized LDL induces expression of group IIa secretory phospholipase A(2) in human monocyte-derived macrophages.

Phospholipase A(2)s (PLA(2)s) constitute a family of enzymes that hydrolyze fatty acids of membrane phospholipids, thus initiating the synthesis of proinflammatory mediators. Various PLA(2)s have been detected in human atherosclerotic arteries (advanced lesions); however, only the secretory group of PLA(2) has been shown to specifically hydrolyze low density lipoprotein (LDL)-associated phospholipids and, as such, may play a potential role in atherogenesis. In the present study, we investigated the expression pattern of group IIa, IV, and V PLA(2)s in human macrophages, which are the key cells involved in the onset and perpetuation of atherosclerosis. Immunohistochemical staining by double labeling showed that the secretory nonpancreatic PLA(2) (snpPLA(2)) is detectable in macrophages in the intima of early atherosclerotic lesions. Reverse transcription-polymerase chain reaction analysis of RNA extracted from human monocytes clearly showed that expression of group IV PLA(2) was enhanced during differentiation into macrophages, with an onset of induction at days 2 to 3 of differentiation. Group V snpPLA(2) was constitutively expressed on differentiation, whereas the detection of group IIa snpPLA(2) was dependent on both differentiation and subsequent stimulation of macrophages. Indeed, the transcription of group IIa snpPLA(2) in macrophages was induced by treatment with minimally modified or mildly oxidized LDL, whereas native, extensively oxidized, or acetylated LDL had no effect. To our knowledge, this is the first report describing induction of group IIa snpPLA(2) expression in human monocyte-derived macrophages. The mRNA levels of cytosolic PLA(2) group IV and snpPLA(2) group V remained unchanged on LDL treatment. Thus, our results show that the expression of distinct PLA(2) enzymes is regulated not only during differentiation of monocytes into macrophages but also on exposure of macrophages to distinct LDL species. Consequently, our results indicate a potential role for both cytosolic and secretory PLA(2) enzymes in inflammation and in macrophage functions related to atherosclerosis, with a specific role for group IIa snpPLA2 in LDL scavenging.

Arteriosclerosis↗
PubMed1998

Inhibition of LPL expression in human monocyte-derived macrophages is dependent on LDL oxidation state: a key role for lysophosphatidylcholine.

The regulation of macrophage lipoprotein lipase (LPL) secretion and mRNA expression by atherogenic lipoproteins is of critical relevance to foam cell formation. LPL is present in arterial lesions and constitutes a bridging ligand between lipoproteins, proteoglycans, and cell receptors, thus favoring macrophage lipoprotein uptake and lipid accumulation. We investigated the effects of native and of oxidized lipoproteins on the expression of LPL in an in vitro human monocyte-macrophage system. Exposure of mature macrophages (day 12) to highly copper-oxidized human low density lipoprotein (LDL) (100 microg protein per milliliter) led to marked reduction in the expression of LPL activity (-62%, P<0.01) and mRNA level (-47%, P<0.05); native LDL, acetylated LDL, and LDL oxidized for <6 hours were without effect. The reduction in LPL activity became significant at a threshold of 6 hours of LDL oxidation (-31%, P<0.05). Among the biologically active sterols formed during LDL oxidation, only 7beta-hydroxycholesterol (5 microg/mL) induced a minor reduction in macrophage LPL activity, whereas 25-hydroxycholesterol was without effect. By contrast, lysophosphatidylcholine, whose LDL content increased in parallel with the degree of oxidation, induced significant reductions in LPL activity and mRNA levels at concentrations of 2 to 20 micromol/L (-34% to -53%, P<0.01). Our results demonstrate that highly oxidized LDL (>6-hour oxidation) exerts negative feedback on LPL secretion in human monocytes-macrophages via a reduction in mRNA levels. By contrast, native LDL and mildly oxidized LDL (<6-hour oxidation) did not exert a feedback effect on LPL expression. We speculate that the content of lysophosphatidylcholine and, to a lesser degree, of 7beta-hydroxycholesterol in oxidized LDLs is responsible for the downregulation of LPL activity and mRNA abundance in human monocyte-derived macrophages and may therefore modulate LPL-mediated pathways of lipoprotein uptake during conversion of macrophages to foam cells.

Cells, Cultured↗