Activation of metalloproteinases and their association with integrins: an auxiliary apoptotic pathway in human endothelial cells

Anchorage of cells to the extracellular matrix and integrin-mediated signals play crucial roles in cell survival. We have previously shown that during growth factor deprivation-induced apoptosis in human umbilical vein endothelial cells (HUVECs), key molecules in focal adhesions and adherens junctions are cleaved by caspases. In this study we provide evidence for a selective upregulation of cell-associated matrix metalloproteinases (MMPs). We observe a physical association of MMP2 with beta1 and alphav integrins, which increased three- to fourfold during apoptosis and is dependent upon integrin beta1 levels and activation state. Both enforced activation of beta1 integrin by a specific antibody and inhibition of MMPs protect HUVECs from apoptosis. We hypothesize that, prior to the commitment to apoptosis, 'inside-out' signals initiated by the apoptotic stimulus alter cell shape together with the activation states and/or the availability of integrins, which promote matrix-degrading activity around dying cells. This 'auxiliary' apoptotic pathway may interrupt ECM-mediated survival signaling, and thus accelerate the efficient execution of the cell death program.

Measurement of systemic oxygen uptake during low-flow anaesthesia with a standard technique vs. a novel method

We assessed agreement between measurement of systemic oxygen uptake using the Fick-derived method, and a novel method described by Biro, based on the difference in oxygen concentrations of the delivered fresh gas and the gas circulating in the circle system. Twenty-nine patients undergoing elective cardiac surgery were studied during stable haemodynamic and ventilatory conditions. Systemic oxygen uptake was measured using the two methods in each patient before and after cardiopulmonary bypass. Limits of agreement were found to be wide (-162 to 311 ml.min-1 before bypass, and -257 to 401 ml.min-1 after bypass), indicating poor agreement between the methods. No significant difference was found between the pre- and post cardiopulmonary bypass values for each method. We conclude that the Biro method, although attractive in terms of its simplicity, is an unreliable measure of systemic oxygen uptake under these conditions.

Expression of the ATP-binding cassette transporter gene ABCG1 (ABC8) in Tangier disease

Several members of the ATP-binding cassette (ABC) transporter family are involved in cholesterol efflux from cells. A defect in one member, ABCA1, results in Tangier disease, a condition characterized by cholesterol accumulation in macrophages and virtual absence of mature circulating high-density lipoproteins. Expression of a second member, ABCG1, is increased by cholesterol-loading in human macrophages. We now show that ABCG1, which we identified by differential display RT-PCR in foamy macrophages, is overexpressed in macrophages from patients with Tangier disease compared to control macrophages. On examination by confocal laser scanning microscopy, ABCG1 was present in perinuclear structures within the cell. In addition, a combination of in situ hybridization and indirect immunofluorescence microscopy revealed that ABCG1 is expressed in foamy macrophages within the atherosclerotic plaque. These data indicate that not only ABCA1 but also ABCG1 may play a role in the cholesterol metabolism of macrophages in vitro and in the atherosclerotic plaque.

Validity and reliability of a postoperative quality of recovery score: the QoR-40

Quality of recovery after anaesthesia is an important measure of the early postoperative health status of patients. We attempted to develop a valid, reliable and responsive measure of quality of recovery after anaesthesia and surgery. We studied 160 patients and asked them to rate postoperative recovery using three methods: a 100-mm visual analogue scale (VAS), a nine-item questionnaire and a 50-item questionnaire; the questionnaires were repeated later on the same day. From these results, we developed a 40-item questionnaire as a measure of quality of recovery (QoR-40; maximum score 200). We found good convergent validity between QoR-40 and VAS (r = 0.68, P < 0.001). Construct validity was supported by a negative correlation with duration of hospital stay (rho = -0.24, P < 0.001) and a lower mean QoR-40 score in women (162 (SD 26)) compared with men (173 (17)) (P = 0.002). There was also good test-retest reliability (intra-class ri = 0.92, P < 0.001), internal consistency (Cronbach's alpha = 0.93, P < 0.001) and split-half coefficient (alpha = 0.83, P < 0.001). The standardized response mean, a measure of responsiveness, was 0.65. The QoR-40 was completed in less than 6.3 (4.9) min. We believe that the QoR-40 is a good objective measure of quality of recovery after anaesthesia and surgery. It would be a useful end-point in perioperative clinical studies.

Human macrophages synthesize type VIII collagen in vitro and in the atherosclerotic plaque

Type VIII collagen is a short-chain collagen that is present in increased amounts in atherosclerotic lesions. Although the physiological function of this matrix protein is unclear, recent data suggest an important role in tissue remodeling. Type VIII collagen in the atherosclerotic lesion is mainly derived from smooth muscle cells. We now show that macrophages in the atherosclerotic vessel wall and monocytes in adjacent mural thrombi also express type VIII collagen. We demonstrated this using a novel combined fluorescence technique that simultaneously stains, within the same tissue section, specific RNAs by in situ hybridization and proteins by indirect immunofluorescence. In culture, human monocyte/macrophages expressed type VIII collagen at all time points from 1 h to 3 wk after isolation. Western blotting and immunoprecipitation also revealed secretion of type VIII collagen into the medium of 14-day-old macrophages. Because this is the first report of secretion of a collagen by macrophages, we tested the effect of lipopolysaccharide (LPS) and interferon gamma, substances that stimulate macrophages to secrete lytic enzymes, on macrophage expression of type VIII collagen. LPS and interferon gamma decreased expression of type VIII collagen. By contrast, secretion of matrix metalloproteinase 1 (MMP 1) was increased, indicating a switch from a collagen-producing to a degradative phenotype. Double in situ hybridization studies of expression of type VIII collagen and MMP 1 in human coronary arteries showed that in regions important for plaque stability, the ratio of MMP 1 RNA to macrophage type VIII collagen RNA varies widely, indicating that the transition from one phenotype to the other that we observed in vitro may also occur in vivo.

Projectin-thin filament interactions and modulation of the sensitivity of the actomyosin ATPase to calcium by projectin kinase

The insect muscle protein projectin (900 kDa) belongs to a novel family of cytoskeleton-associated protein kinases (titin, twitchin, and projectin) that are members of the immunoglobulin superfamily. The functions of these kinases are still unknown although recent data suggest a role in modulating muscle activity and generating passive elasticity. An important question is what are the in vivo substrates for these enzymes. We found a thin filament-associated 30 kDa protein that acts as an in vitro substrate for projectin kinase from Locusta migratoria. However, we did not find activators for projectin kinase. Neither calcium, calcium with calmodulin, nor cAMP activated the in vitro activity of projectin kinase. Binding studies revealed a strong interaction between projectin and thin filaments comparable with that of the projectin-myosin interaction. That an interaction might be possible in vivo is suggested by immunological studies showing that projectin is attached to the surface of myosin filaments. Since the molecular weights indicate that the 30 kDa protein might be troponin I, which is known to play a central role in modulating cardiac contractile activity, we studied whether phosphorylation of this protein by projectin changes the calcium sensitivity of the actomyosin ATPase. We found a significant increase in the calcium sensitivity. Thus, our results indicate the existence of a novel mechanism of regulation of muscle activity by a cytoskeleton-associated kinase.