Comparative cytotoxicity of gambierol versus other marine neurotoxins.

Many microalgae produce compounds that exhibit potent biological activities. Ingestion of marine organisms contaminated with those toxins results in seafood poisonings. In many cases, the lack of toxic material turns out to be an obstacle to make the toxicological investigations needed. In this study, we evaluate the cytotoxicity of several marine toxins on neuroblastoma cells, focusing on gambierol and its effect on cytosolic calcium levels. In addition, we compared the effects of this toxin with ciguatoxin, brevetoxin, and gymnocin-A, with which gambierol shares a similar ladder-like backbone, as well as with polycavernoside A analogue 5, a glycosidic macrolide toxin. For this purpose, different fluorescent dyes were used: Fura-2 to monitor variations in cytosolic calcium levels, Alamar Blue to detect cytotoxicity, and Oregon Green 514 Phalloidin to quantify and visualize modifications in the actin cytoskeleton. Data showed that, while gambierol and ciguatoxin were successful in producing a calcium influx in neuroblastoma cells, gymnocin-A was unable to modify this parameter. Nevertheless, none of the toxins induced morphological changes or alterations in the actin assembly. Although polycavernoside A analogue 5 evoked a sharp reduction of the cellular metabolism of neuroblastoma cells, gambierol scarcely reduced it, and ciguatoxin, brevetoxin, and gymnocin-A failed to produce any signs of cytotoxicity. According to this, sharing a similar polycyclic ether backbone is not enough to produce the same effects on neuroblastoma cells; therefore, more studies should be carried out with these toxins, whose effects may be being underestimated.

Inhibition of lung natural killer cell activity by smoking: the role of alveolar macrophages.

BACKGROUND: It is known that natural killer (NK) cell activity in the lung of smokers (SM) is lower than in non-smokers (NS). However, little is known about the underlying mechanisms. OBJECTIVE: The purpose of this work was to investigate the mechanisms of the inhibition of NK cell activity by alveolar macrophages (AM) in SM. METHODS: Lung effector cells and AM were obtained using bronchoalveolar lavage. The NK cell activity was assayed by 51Cr release method after incubation of 4 and 24 h, using K562 as target cell. AM were added at a concentration of 25% to effector cells. RESULTS: Following 24-hour culture, NK cell activity significantly increased in the NS but not in the SM. Lung NK cell activity was significantly augmented by interleukin-2 in the NS but not in the SM. Addition of AM to the NK cell preparation from SM exerted a significantly greater suppressive effect on autologous blood NK cell activity than in the NS. Indomethacin, catalase or thiourea did not prevent AM-mediated suppression of NK cell activity, in contrast to superoxide dismutase. CONCLUSIONS: These results suggest that the suppression of NK cell activity by AM in SM may be caused by O2- release rather than by prostaglandins, H2O2 or OH release from AM.

Lung deflation impairs alveolar epithelial fluid transport in ischemic rabbit and rat lungs.

BACKGROUND: Because the fluid transport capacity of the alveolar epithelium after lung ischemia with and without lung deflation has not been well studied, we carried out experimental studies to determine the effect of lung deflation on alveolar fluid clearance. METHODS: After 1 or 2 hr of ischemia, we measured alveolar fluid clearance using 125I-albumin and Evans blue-labeled albumin concentrations in in vivo rabbit lungs in the presence of pulmonary blood flow and in ex vivo rat lungs in the absence of any pulmonary perfusion, respectively. RESULTS: The principal results were: (1) lung deflation decreased alveolar fluid clearance while inflation of the lungs during ischemia preserved alveolar fluid clearance in both in vivo and ex vivo studies; (2) alveolar fluid clearance was normal in the rat lungs inflated with nitrogen (thus, alveolar gas composition did not affect alveolar fluid clearance); (3) amiloride-dependent alveolar fluid clearance was preserved when the lungs were inflated during ischemia; (4) terbutaline-simulated alveolar fluid clearance was preserved in the hypoxic rat lungs inflated with nitrogen; (5) lecithinized superoxide dismutase, a scavenger of superoxide anion, and N(omega)-nitro-L-arginine methyl ester, an inhibitor of nitric oxide, preserved normal alveolar fluid clearance in the deflated rat lungs. CONCLUSION: Lung deflation decreases alveolar fluid clearance by superoxide anion- and nitric oxide-dependent mechanisms.