Inhibition of kinin B1 receptors attenuates pulmonary hypertension and vascular remodeling.

This study examined whether the kinin B1 receptor is involved in the pathogenesis of pulmonary hypertension, and whether its inhibition could reduce inflammation, pulmonary hypertension, vascular remodeling, and right heart dysfunction. Male Wistar rats underwent left pneumonectomy. Seven days later, the rats were injected subcutaneously with monocrotaline (60 mg/kg). The rats were then randomly assigned to receive treatment with vehicle or with BI113823 (a selective B1 receptor antagonist, 30 mg/kg, twice per day) via oral gavage from the day of monocrotaline injection to day 28. By day 28, BI113823-treated rats had significantly lower mean pulmonary artery pressure, less right ventricular hypertrophy, and pulmonary arterial neointimal formation than that of the vehicle-treated rats. Real-time polymerase chain reaction revealed that there was a significant increase in mRNA expression of B1 receptors in the lungs of monocrotaline-challenged pneumonectomized rats. Treatment with BI113823 significantly reduced macrophage recruitment, as measured via bronchoalveolar lavage. It also markedly reduced CD-68 positive macrophages and proliferating cell nuclear antigen positive cells in the perivascular areas, reduced expression of inducible nitric oxide synthase, matrix metalloproteinase 2 and 9, and B1 receptors compared with measurements in vehicle-treated rats. These findings demonstrate that kinin B1 receptors represent a novel therapeutic target for pulmonary arterial hypertension.

Des-Arg9-bradykinin causes kinin B1 receptor mediated endothelium-independent contractions in endotoxin-treated porcine coronary arteries.

This study examined responses of isolated pig coronary arteries after kinin B1 receptor induction by endotoxin. Des-Arg9-bradykinin (DBK) induced concentration-dependent, endothelium-independent contractions in lipopolysaccharide (LPS)-treated but not untreated arterial rings. The B1-receptor antagonist SSR240612, but not the B2-receptor antagonist HOE140, prevented the endothelium-independent contractions to DBK. The DBK-induced contractions were blocked by indomethacin (nonselective cyclooxygenase [COX] inhibitor), celecoxib (selective COX-2 inhibitor), and terbogrel (thromboxane-prostanoid [TP] receptor antagonist) but not valeryl salicylate (selective COX-1 inhibitor), AH6809 (an E prostanoid [EP] and PGD2 receptor [DP1] receptor antagonist), AL 8810 (a selective PGF2α [FP] receptor antagonist), or RO1138452 (a selective I prostanoid [IP] receptor antagonist). They were attenuated by N-(p-amylcinnamoyl) anthranilic acid (ACA), and by DETCA plus tiron but not by l-NAME. Quantitative RT-PCR revealed excessive up-regulations of mRNA expressions of B1 receptors, COX-2, and thromboxane A synthase 1 (TBXAS1) following LPS incubation, but not of B2 receptors or COX-1. The present data demonstrate that B1 receptors are coupled to COX-2 in causing endothelium-independent contractions in endotoxin-treated pig coronary arteries. Accordingly, kinin B1 receptor induction during inflammation may have a pathological significance in the vasculature, particular in coronary arteries with dysfunctional endothelial cells.

COX-2 mediated induction of endothelium-independent contraction to bradykinin in endotoxin-treated porcine coronary artery.

This study examined the vascular effects of bradykinin in health and vascular inflammation comparing responses of isolated pig coronary arteries in the absence and presence of endotoxins. Bradykinin induced contractions in lipopolysaccharide-treated, but not untreated, arterial rings without endothelium. The B2-receptor antagonist HOE140, but not the B1-receptor inhibitor SSR240612, blocked these endothelium-independent contractions in response to bradykinin. The bradykinin-induced contractions were blocked by indomethacin, celecoxib, and terbogrel but not valeryl salicylate, AH6809, AL 8810, or RO1138452. They were attenuated by N-(p-amylcinnamoyl) anthranilic acid, and by diethyldithiocarbamate plus tiron but not by L-NAME. Quantitative reverse-transcription polymerase chain reaction revealed significant upregulations of messenger RNA expressions of B1 receptors, COX-2, and thromboxane A synthase 1 (TBXAS1) following lipopolysaccharide incubation but not of B2 receptors or COX-1. The present data demonstrate that bradykinin induces contractions mediated by the COX-2 pathway in endotoxin-treated pig coronary arteries. These results support differential roles of bradykinin in health and disease.

Caspase-8 and Apaf-1-independent caspase-9 activation in Sendai virus-infected cells.

Apoptotic cell death is of central importance in the pathogenesis of viral infections. Activation of a cascade of cysteine proteases, i.e. caspases, plays a key role in the effector phase of virus-induced apoptosis. However, little is known about pathways leading to the activation of initiator caspases in virus-infected host cells. Recently, we have shown that Sendai virus (SeV) infection triggers apoptotic cell death by activation of the effector caspase-3 and initiator caspase-8. We now investigated mechanisms leading to the activation of another initiator caspase, caspase-9. Unexpectedly we found that caspase-9 cleavage is not dependent on the presence of active caspases-3 or -8. Furthermore, the presence of caspase-9 in mouse embryonic fibroblast (MEF) cells was a prerequisite for Sendai virus-induced apoptotic cell death. Caspase-9 activation occurred without the release of cytochrome c from mitochondria and was not dependent on the presence of Apaf-1 or reactive oxygen intermediates. Our results therefore suggest an alternative mechanism for caspase-9 activation in virally infected cells beside the well characterized pathways via death receptors or mitochondrial cytochrome c release.