Inadequate cytoplasmatic calcium signals in alveolar macrophages after cardiac surgery

Abstract

Patients undergoing cardiac surgery have an elevated risk for pulmonary complications. A dysfunction of alveolar macrophages (AM) might promote postoperative infections. Therefore intracellular calcium [Ca(2+)](i) as an important second messenger in cellular signaling was assessed in AM. Twelve patients undergoing elective coronary artery bypass graft surgery (CABG) were enrolled in this clinical trial. After anesthesia induction and 2 h after cardiopulomary bypass (CPB) declamping, the bronchoalveolar lavage (BAL) fluid was collected preoperatively from the right middle lobe and postoperatively from the left lingula of the lung. Cell subpopulations and [Ca(2+)](i) signals were assessed via flow cytometry. To express the changes of [Ca(2+)](i) signals the Fluo4/FuraRed-Ratio was used. After surgery the [Ca(2+)](i) baseline in unstimulated AMs were significantly reduced (p < 0.001). A significant signal reduction after fMLP (p = 0.021) and C5a (p = 0.028) stimulation was found in FSC high AMs after surgery, even though all populations showed a trend of less responsiveness. We suggest that the reduced [Ca(2+)](i) signaling in postoperative AMs is caused by a reduced coupling to membrane channels. These preliminary data suggest an inadequate [Ca(2+)](i) signal of AM after surgery, which may contribute to a local immune dysfunction in the lung.