OBJECTIVE

Hetastarch is an artificial colloid widely used intraoperatively in fluid-replacement regimens. Previous studies have found that the intraoperative administration of hetastarch may increase the risk of postoperative bleeding in patients who undergo coronary artery bypass graft surgery with cardiopulmonary bypass. Previous published reports have not examined this risk in patients who underwent coronary artery bypass grafting without cardiopulmonary bypass.

METHODS

In a randomized clinical trial, 156 patients undergoing off-pump coronary artery bypass grafting were assigned to receive either 1 liter of hetastarch or 1 liter of albumin as part of intraoperative volume replacement. Sample recruitment was halted in a review per protocol by the study's Data Safety Monitoring Committee. We assessed the rate of postoperative bleeding by monitoring the number of units of blood products transfused in the first 24 postoperative hours in the intensive care unit and the hourly chest tube drainage in the first 12 postoperative hours.

RESULTS

Intraoperative administration of 1 liter of hetastarch was associated with statistically significant increases in 3 measures: transfusion requirements on postoperative day 1 (red blood cells, 1.14 vs 0.40 units, P = .017; fresh-frozen plasma, 0.57 vs 0.15, P = .009; platelets, 0.35 vs 0.10, P = .013); the overall likelihood of receiving transfusion on postoperative day 1 (46.2% vs 25.6%, P = .012); and the volume of chest tube drainage in the first 12 hours postoperatively (732.0 vs 563.6 mL, P < .001).

CONCLUSION

In patients undergoing off-pump coronary artery bypass, the intraoperative administration of hetastarch increases the postoperative transfusion requirement and the volume of blood drained postoperatively.

Intact alveolar barrier function is associated with better outcomes in acute lung injury patients; however, the regulation of alveolar epithelial paracellular transport during lung injury has not been extensively investigated. This study was undertaken to determine whether changes in tight junction claudin expression affect alveolar epithelial barrier properties and to determine the mechanisms of altered expression. In anesthetized mice exposed to ventilator-induced lung injury, claudin-4 was specifically induced among tight junction structural proteins. Real-time PCR showed an eightfold increase in claudin-4 expression in the lung injury model. To examine the role of this protein in barrier regulation, claudin-4 function was inhibited with small interfering RNA (siRNA) and a blocking peptide derived from the binding domain of Clostridium perfringens enterotoxin (CPE(BD)). Inhibition of claudin-4 decreased transepithelial electrical resistance but did not alter macromolecule permeability in primary rat and human epithelial cells. In mice, CPE(BD) decreased air space fluid clearance >33% and resulted in pulmonary edema during moderate tidal volume ventilation that did not induce edema in control peptide-treated mice. In vitro phorbol ester induced a ninefold increase in claudin-4 expression that was dependent on PKC activation and the JNK MAPK pathway. These data establish that changes in alveolar epithelial claudin expression influence paracellular transport, alveolar fluid clearance rates, and susceptibility to pulmonary edema. We hypothesize that increased claudin-4 expression early in acute lung injury represents a mechanism to limit pulmonary edema and that the regulation of alveolar epithelial claudin expression may be a novel target for acute lung injury therapy.

BACKGROUND

Although the MMP-2 promoter lacks a canonical progesterone response element (PRE), the hormone inhibits MMP-2 expression and is part of treatment protocols in gynecological invasive pathologies, including endometriosis and endometrial hyperplasia. This study aimed to explore the mechanism by which progesterone inhibits MMP-2 expression.

METHODS

The effect of progesterone on MMP-2 expression in the JAR human choriocarcinoma cell line was analyzed by gelatin zymography. MMP-2 transcript expression was studied using Northern blot and semi-quantitative RT-PCR. Rat promoter deletion analysis, electrophoretic mobility shift and chromatin immuno-precipitation assays were performed in order to locate the DNA binding site and the transcription factors involved in MMP-2 regulation.

RESULTS

Progesterone significantly decreased secretion of pro-MMP-2 and MMP-2 transcript expression level in a dose-dependent manner. Progesterone (1 microM) significantly decreased both human and rat MMP-2 promoter activity (80.1% +/- 0.3 and 81.3% +/- 0.23, respectively). Progesterone acts through the SP1 family transcription factors-binding site, located between -1433 and -1342 bp region from the transcriptional start site of the rat MMP-2 promoter, which are present in the orthologous human MMP-2 promoter. Progesterone receptor (PR), SP2, SP3 and SP4 proteins are constitutively bound to this consensus sequence.

CONCLUSION

Progesterone reduces PR and SP4 binding to the MMP-2 promoter, thereby suppressing transcription. Progesterone also promotes SP4 degradation. These novel mechanisms of MMP-2 regulation by progesterone provide the biological rationale for the use of progesterone in clinical settings associated with increased MMP-2 expression.