Dexamethasone pretreatment provides antiinflammatory and myocardial protection in neonatal arterial switch operation.

BACKGROUND: This prospective double-blinded randomized study tested the hypothesis that preoperative treatment with dexamethasone would attenuate inflammatory priming of the myocardium, reduce the systemic inflammatory reaction upon cardiac operation, and provide organ protection in neonates. METHODS: Twenty neonates (age, 8 to 21 days) with transposition of the great arteries scheduled for arterial switch operation were included. Nine received dexamethasone (1 mg/kg body weight) 4 hours before cardiopulmonary bypass, and 11 received natrium chloride. We studied intramyocardial messenger RNA expression of interleukin (IL)-6, IL-8, IL-1ß, and tumor necrosis factor-α (TNF-α), as well as IL-10 and expression of TNF-α on protein level in right atrial tissue taken before institution of CPB. We measured plasma levels of IL-6, IL-10, lipopolysaccharide binding protein, and cardiac troponin T. Cytokine expression was related to postoperative outcome. RESULTS: Pretreatment with dexamethasone led to a significant decrease in myocardial expression of IL-6, IL-8, IL-1ß, and TNF-α messenger RNA and to a decrease in protein synthesis of TNF-α. Plasma concentrations of IL-6 were significantly lower and those of IL-10 significantly higher in pretreated patients. This was associated with lower cardiac troponin T values and lower dobutamine requirement. Levels of lipopolysaccharide binding protein were significantly higher postoperatively in pretreated neonates. CONCLUSIONS: Dexamethasone administration before arterial switch operation leads to a shift in the myocardial and systemic cytokine expression profile in neonates with transposition of the great arteries, with downregulation of proinflammatory and upregulation of antiinflammatory cytokines. Lower myocardial cell damage and lower catecholamine requirement suggest myocardial protection in treated patients.

Expression profile of the transient receptor potential (TRP) family in neutrophil granulocytes: evidence for currents through long TRP channel 2 induced by ADP-ribose and NAD.

An early key event in the activation of neutrophil granulocytes is Ca(2+) influx. Members of the transient receptor potential (TRP) channel family may be held responsible for this. The aim of the present study is to analyse the expression pattern of TRP mRNA and identify characteristic currents unambiguously attributable to particular TRP channels. mRNA was extracted from human neutrophils, isolated by gradient centrifugation and also by magnetically labelled CD15 antibodies. The presence of mRNA was demonstrated using reverse transcriptase-PCR in neutrophils (controlled to be CD5-negative) as well as in human leukaemic cell line 60 (HL-60) cells, for the following TRP species: the long TRPC2 (LTRPC2), the vanilloid receptor 1, the vanilloid receptor-like protein 1 and epithelial Ca(2+) channels 1 and 2. TRPC6 was specific for neutrophils, whereas only in HL-60 cells were TRPC1, TRPC2, TRPC3, melastatin 1 and melastatin-related 1 found. Patch-clamp measurements in neutrophils revealed non-selective cation currents evoked by intracellular ADP-ribose and by NAD(+). Both these modes of activation have been found to be characteristic of LTRPC2. Furthermore, single-channel activity was resolved in neutrophils and it was indistinguishable from that in LTRPC2-transfected HEK-293 cells. The results provide evidence that LTRPC2 in neutrophil granulocytes forms an entry pathway for Na(+) and Ca(2+), which is regulated by ADP-ribose and the redox state.

Activation of the cation channel long transient receptor potential channel 2 (LTRPC2) by hydrogen peroxide. A splice variant reveals a mode of activation independent of ADP-ribose.

LTRPC2 is a cation channel recently reported to be activated by adenosine diphosphate-ribose (ADP-ribose) and NAD. Since ADP-ribose can be formed from NAD and NAD is elevated during oxidative stress, we studied whole cell currents and increases in the intercellular free calcium concentration ([Ca(2+)](i)) in long transient receptor potential channel 2 (LTRPC2)-transfected HEK 293 cells after stimulation with hydrogen peroxide (H(2)O(2)). Cation currents carried by monovalent cations and Ca(2+) were induced by H(2)O(2) (5 mm in the bath solution) as well as by intracellular ADP-ribose (0.3 mm in the pipette solution) but not by NAD (1 mm). H(2)O(2)-induced currents developed slowly after a characteristic delay of 3-6 min and receded after wash-out of H(2)O(2). [Ca(2+)](i) was rapidly increased by H(2)O(2) in LTRPC2-transfected cells as well as in control cells; however, in LTRPC2-transfected cells, H(2)O(2) evoked a second delayed rise in [Ca(2+)](i). A splice variant of LTRPC2 with a deletion in the C terminus (amino acids 1292-1325) was identified in neutrophil granulocytes. This variant was stimulated by H(2)O(2) as the wild type. However, it did not respond to ADP-ribose. We conclude that activation of LTRPC2 by H(2)O(2) is independent of ADP-ribose and that LTRPC2 may mediate the influx of Na(+) and Ca(2+) during oxidative stress, such as the respiratory burst in granulocytes.