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CRITICAL CARE AND TRAUMA

Cyclooxygenase Inhibitors Attenuate Bradykinin-Induced Vasoconstriction in Septic Isolated Rat Lungs

Lars G. Fischer, MD^*,, Markus W. Hollmann, MD, Damian J. Horstman, PhD, and George F. Rich, MD, PhD

*Klinik und Poliklinik für Anästhesiologie und operative Intensivmedizin, Westfälische-Wilhelms-Universität Münster, Germany; and University of Virginia Health System, Department of Anesthesiology, Charlottesville, Virginia

Address correspondence and reprint requests to George F. Rich, MD, PhD, University of Virginia Health System, Department of Anesthesiology, PO Box 800710, Charlottesville, VA 22908-0710.

Cyclooxygenase (COX) products play an important role in modulating sepsis and subsequent endothelial injury. We hypothesized that COX inhibitors may attenuate endothelial dysfunction during sepsis, as measured by receptor-mediated bradykinin (BK)-induced vasoconstriction and/or receptor-independent hypoxic pulmonary vasoconstriction (HPV). Rats were administered intraperitoneally a nonselective COX inhibitor (indomethacin, 5 or 10 mg/kg) or a selective COX-2 inhibitor (NS-398, 4 or 8 mg/kg) 1 h before lipopolysaccharide (LPS, 15 mg/kg), or saline (control). Three hours later, the rats were anesthetized, the lungs were isolated, and pulmonary vasoreactivity was assessed with BK (0.3, 1.0, and 3.0 µg) and HPV (3% O₂). Perfusion pressure was monitored as an index of vasoconstriction. To investigate what receptor-subtype is mediating BK responses, the BK₁-receptor antagonist des-Arg⁹-[Leu⁸]-BK, the BK₂-receptor antagonist HOE-140, or the thromboxane A₂-receptor antagonist SQ 29548 (all at 1 µM) were added to the perfusate. BK-induced vasoconstriction was significantly increased in LPS lungs (1.4–5.2 mm Hg) compared with control (0.1–1.1 mm Hg). In LPS lungs, indomethacin 10 mg/kg significantly decreased BK vasoconstriction by 78% ± 9%, whereas 5 mg/kg did not. NS-398, 4 mg/kg, significantly attenuated BK vasoconstriction at 0.3 µg (71% ± 7%) and 1.0 µg (56% ± 12%), whereas 8 mg/kg attenuated 0.3 µg BK (57% ± 14%), compared with LPS lungs. HPV was increased in LPS lungs (21.5 ± 2 mm Hg) compared with control lungs (9.8 ± 0.6 mm Hg). Indomethacin 5 mg/kg increased HPV in LPS lungs; otherwise, HPV was not altered by COX inhibition. BK-induced vasoconstriction was prevented by BK₂, but not BK₁ or thromboxane A₂-receptor antagonism. This study suggests that nonselective COX inhibition, and possibly inhibition of the inducible isoform COX-2, may attenuate sepsis-induced, receptor-mediated vasoconstriction in rats.

Implications: This study demonstrated that, in an isolated rat lung model, nonselective inhibition of the cyclooxygenase pathway, and possibly selective inhibition of the inducible cyclooxygenase-2 isoform, may attenuate sepsis-induced endothelial dysfunction.

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