Walther Schmiedt

Involvement of growth differentiation factor-15/macrophage inhibitory cytokine-1 (GDF-15/MIC-1) in oxLDL-induced apoptosis of human macrophages in vitro and in arteriosclerotic lesions.

Growth differentiation factor-15/macrophage inhibitory cytokine-1 (GDF-15/MIC-1) is a new member of the transforming growth factor beta (TGF-β) superfamily, which has most recently been found in activated macrophages (MΦ). We have now investigated GDF-15/MIC-1 in human MΦ after exposure to oxidized low-density lipoproteins (oxLDL) related mediators in vitro and in arteriosclerotic carotid arteries. Using RT-PCR and Western blotting a pronounced induction of GDF-15/MIC-1 expression by oxLDL, C6-ceramide, tumor necrosis factor (TNFα) and hydrogen peroxide (H2O2) was found in cultured human MΦ. In 11 human arteriosclerotic carotid arteries, immunohistochemical analyses supported by computer-assisted morphometry and regression analyses demonstrated a significant colocalization of GDF-15/MIC-1 immunoreactivity (IR) with oxLDL IR and manganese superoxide dismutase (MnSOD) IR in CD68 immunoreactive (ir) MΦ, which were also expressing AIF-IR (apoptosis-inducing factor), caspase-3-IR (CPP32), PARP-IR, c-Jun/AP-1-IR and p53-IR. Our data suggest that GDF-15/MIC-1 is inducible in human MΦ by oxLDL and its mediators in vitro and is supposed to contribute to oxidative stress dependent consequences in arteriosclerotic plaques, e.g. modulating apoptosis and inflammatory processes in activated MΦ.

Apoptosis caused by oxidized LDL is manganese superoxide dismutase and p53 dependent

Oxidized low density lipoprotein (oxLDL) induces apoptosis in human macrophages (MΦ), a significant feature in atherogenesis. We found that induction of apoptosis in MΦ by oxLDL, C2‐ceramide, tumor necrosis factor α (TNF‐α), and hydrogen peroxide (H2O2) was associated with enhanced expression of manganese superoxide dis‐mutase (MnSOD) and p53. Treatment of cells with p53 or MnSOD antisense oligonucleotides prior to stimulation with oxLDL, C2‐ceramide, TNF‐α, or H2O2 caused an inhibition of the expression of the respective protein together with a marked reduction of apoptosis. Exposure to N‐acetylcysteine before treatment with oxLDL, C2‐ceramide, TNF‐α, or H2O2 reversed a decrease in cellular glutathione concentrations as well as the enhanced production of p53 and MnSOD mRNA and protein. In apoptotic macrophages of human atherosclerotic plaques, colocalization of MnSOD and p53 immunoreactivity was found. These results indicate that in oxLDL‐induced apoptosis, a concomitant induction of p53 and MnSOD is critical, and suggest that it is at least in part due to an enhancement of the sphingomyelin/ ceramide pathway.—Kinscherf, R., Claus, R., Wagner, M., Gehrke, C., Kamencic, H., Hou, D., Nauen, O., Schmiedt, W., Kovacs, G., Pill, J., Metz, J., Deigner, H.‐P. Apoptosis caused by oxidized LDL is manganese superoxide dismutase and p53 dependent. FASEB J. 12, 461–467 (1998)

Complement C6 Deficiency Protects Against Diet-Induced Atherosclerosis in Rabbits

Low-density lipoprotein (LDL) can be transformed to an atherogenic moiety by nonoxidative, enzymatic degradation. Enzymatically degraded LDL induces macrophage foam cell formation, provokes release of cytokines, and also activates complement. To determine whether complement activation may contribute to atherogenesis, 6 pairs of homozygous C6-deficient rabbits and their non-C6-deficient heterozygous siblings were fed a cholesterol-rich diet for 14 weeks. Cholesterol levels and plasma lipoprotein profiles of the animals in the C6-competent and C6-deficient groups did not significantly differ, and the high density lipoprotein and LDL cholesterol ratios at the end of the experiment were 0.07+/-0.01 and 0.08+/-0.01 (SEM), respectively. However, differences in atherosclerotic plaque formation were discernible macroscopically, with extensive aortic lesions being visible in all C6-competent animals and absent in all C6-deficient animals. Aortas were sectioned from thorax to abdomen, and 10 sections were stained from each aorta. Quantification of atherosclerotic lesions and lumen stenosis with the use of computer-based morphometry documented a dramatic protective effect of C6 deficiency on the development of diet-induced atherosclerosis. We conclude that the terminal complement sequence is centrally involved in atherosclerotic lesion progression.

MRI Versus Helical CT for Endoleak Detection After Endovascular Aneurysm Repair

OBJECTIVE The objective of our study was to investigate the diagnostic accuracy of MRI and helical CT for endoleak detection. SUBJECTS AND METHODS Fifty-two patients underwent endovascular aneurysm repair with nitinol stent-grafts. Follow-up data sets included contrast-enhanced biphasic CT and MRI within 48 hr after the intervention; at 3, 6, and 12 months; and yearly thereafter. The endoleak size was categorized as < or = 3%, > 3% < or = 10%, > 10% < or = 30%, or > 30% of the maximum cross-sectional aneurysm area. A consensus interpretation of CT and MRI was defined as the standard of reference. RESULTS Of 252 data sets, 141 showed evidence for endoleaks. The incidence of types I, II, and III endoleaks and complex endoleaks was 3.2%, 40.1%, 8.7%, and 4.0%, respectively. The sensitivity for endoleak detection was 92.9%, 44.0%, 34.8%, and 38.3% for MRI, biphasic CT, uniphasic arterial CT, and uniphasic late CT, respectively. The corresponding negative predictive values were 91.7%, 58.4%, 54.7%, and 56.1%, respectively. The overall accuracy of endoleak detection and correct sizing was 95.2%, 58.3%, 55.6%, and 57.1% for MRI, biphasic CT, uniphasic arterial CT, and uniphasic late CT, respectively. CONCLUSION MRI is significantly superior to biphasic CT for endoleak detection and rating of endoleak size, followed by uniphasic late and uniphasic arterial CT scans. MRI shows a significant number of endoleaks in cases with negative CT findings and may help illuminate the phenomenon of endotension. Endoleak rates reported after endovascular aneurysm repair substantially depend on the imaging techniques used.

Ischemia-Reperfusion Injury

The term ischemia-reperfusion injury describes the experimentally and clinically prevalent finding that tissue ischemia with inadequate oxygen supply followed by successful reperfusion initiates a wide and complex array of inflammatory responses that may both aggravate local injury as well as induce impairment of remote organ function. Conditions under which ischemia-reperfusion injury is encountered include the different forms of acute vascular occlusions (stroke, myocardial infarction, limb ischemia) with the respective reperfusion strategies (thrombolytic therapy, angioplasty, operative revascularization) but also routine surgical procedures (organ transplantation, free-tissue-transfer, cardiopulmonary bypass, vascular surgery) and major trauma/shock. Since the first recognition of ischemia-reperfusion injury during the 1970s, significant knowledge has accumulated and the purpose of this review is to present an overview over the current literature on the molecular and cellular basis of ischemia-reperfusion injury, to outline the clinical manifestations and to compile contemporary treatment and prevention strategies. Although the concept of reperfusion injury is still a matter of debate, it is corroborated by recent and ongoing clinical trials that demonstrated ischemic preconditioning, inhibition of sodium-hydrogen-exchange and administration of adenosine to be effective in attenuating ischemia-reperfusion injury.

EFFECT OF ALTERATIONS OF BLOOD CHOLESTEROL LEVELS ON MACROPHAGES IN THE MYOCARDIUM OF NEW ZEALAND WHITE RABBITS

We investigated the effect of alterations of blood cholesterol levels on macrophages (mΦ) in the myocardium of New Zealand White (NZW) rabbits. Three groups of NZW rabbits were used: controls, rabbits fed a 0.5% cholesterol‐enriched diet (CH‐D) for 96 days, and rabbits fed a 0.5% CH‐D for 96 days followed by normal chow for 4 months. Immunohistochemical analysis by mAbs directed against mΦ (RAM‐11) and Mn superoxide dismutase (MnSOD) were quantified by computer‐assisted morphometry. Using cultured human and rabbit mΦ, a cross‐reaction of the human MnSOD mAbs was found as well as the predominant localization of MnSOD‐immunoreactivity (IR) in mitochondria, In group 1, only a very few RAM‐11‐immunoreactive (ir) mΦ occurred in the interstitial space of the myocardium. In group II blood cholesterol levels significantly increased in parallel with the numbers of mΦ, which often contained lipid droplets (foam cells). Although blood cholesterol concentrations regressed about 10‐fold in group III, mΦ in the myocardium were found to be reduced only about 20%. Most mΦ were also MnSOD‐ir. In atherosclerotic coronary arteries RAM‐11‐IR was located in mΦ and also extracellularly, whereas MnSOD‐IR was found only in mΦ. Drastically induced MnSOD in the mitochondria of mΦ is suggested as an indicator of increased oxidative stress caused by in vitro conditions or by phagocytosis of low‐density lipoprotein in vivo. Elevation of the cholesterol level leads to a long‐term increase and its regression results in a delayed reduction of such mΦ, which seem to play a key role in the atherogenesis of the coronary arteries as well. J. Leukoc. Biol. 62: 719–725; 1997.

Immune Response to Gelatin- and Collagen-Impregnated Aortic Dacron Grafts A Randomized Study

Dacron grafts are very common in vascular surgery. Primarily sealed grafts have been available for ten years. These improve handling and reduce intraoperative blood loss. Despite a widespread use all over the world, it has as yet not been clarified whether coating (sealing) substances might cause an immune response, especially in situations of fever or other unexplained events in the postoperative course after graft implantation. In this study, 37 patients with a gelatin-impregnated (Unigraft) and 33 with a collagen-impregnated (Hemashield) graft for aortic or aortoiliac replacement were compared. Serum samples were investigated for collagen antibodies at operation, one week and three months postoperatively. An enzyme-linked immunosorbent assay (ELISA) test could not demonstrate the development of antibodies against type I, II, or III collagen in the perioperative period or three months postoperatively.

Colocalization of oxidized low-density lipoprotein, caspase-3, cyclooxygenase-2, and macrophage migration inhibitory factor in arteriosclerotic human carotid arteries

Apoptotic and inflammatory processes occur in human arteriosclerotic lesions. We examined the hypothesis whether both processes are possibly associated by studying the colocalization of corresponding markers. In 11 human arteriosclerotic carotid arteries, proapoptotic markers (CPP32 (caspase-3), poly(ADP-ribose) polymerase, apoptosis-inducing factor, c-Jun/AP-1, and p53) and proinflammatory markers (macrophage migration inhibitory factor (MIF) and cyclooxygenase-2) were found in macrophages (MΦ) evaluated by computer-assisted immunohistomorphometry. Double-labeling studies demonstrated a colocalization of, both, proapoptotic and proinflammatory markers in these MΦ. Moreover, these MΦ also contained oxidized low-density lipoproteins (oxLDL). Exposure of cultured human MΦ to oxLDL, C6-ceramide, and tumor necrosis factor-alpha or H2O2 resulted in a significant increase of the apoptosis rate as well as of the MIF protein expression. Our study of MΦ in arteriosclerotic carotid arteries and in vitro experiments provide evidence that markers of apoptosis and inflammation are not only significantly increased but are also coexpressed. We conclude there are reciprocal modulatory interactions between apoptotic and inflammatory pathways in human plaque MΦ, which might importantly modify plaque progression or stability.

Efficacy of phosphodiesterase inhibitor enoximone in management of postcardiotomy cardiogenic shock

The efficacy of the phosphodiesterase inhibitor enoximone for reversal of severe postcardiotomy low cardiac output syndrome was investigated in 13 cases of cardiogenic shock refractory to conventional treatment consisting of beta-adrenergic agonists (n = 13) combined with vasodilators (n = 7), and intra-aortic balloon counterpulsation (n = 5). Following a bolus of 1 mg/kg enoximone, cardiac and stroke volume indices increased from 1.56 +/- 0.27 l/min/m2 and 16.3 +/- 3.3 ml/m2, respectively, to 2.72 +/- 0.67 and 27.8 +/- 7.1 (both p < 0.001). Mean arterial pressure fell, from 77 +/- 11 to 68 +/- 9 mmHg (p < 0.05), as did atrial filling pressures (LAP and RAP), LAP from 21.3 +/- 5.5 to 15.9 +/- 2.9 and RAP from 16.6 +/- 2.3 to 13.7 +/- 2.1 mmHg (both p < 0.01). The heart rate rose by only 5%. Enoximone therapy was maintained by a continuous infusion (5-7.5 micrograms/kg/min) for 40.6 +/- 8.6 hours (range 14-92). All hemodynamic parameters remained stable throughout treatment. Six patients died of sepsis and/or multiorgan failure but seven were discharged from hospital. Enoximone thus improved hemodynamic performance significantly in cardiogenic shock after open-heart surgery. It also has proved valuable in cardiac failure when conventional therapy was unsuccessful.