Splenic rupture complicating periinterventional glycoprotein IIb/IIIa antagonist therapy for myocardial infarction in polycythemia vera

Polycythemia vera is a myeloproliferative disorder predisposing to thromboembolic and bleeding complications. We report the case of a patient with polyglobuly, leukocytosis, and thrombocytosis, who suffered from acute ST-segment elevation myocardial infarction due to thrombotic high-grade pre-stent stenosis two months after percutaneous coronary intervention for complex coronary one vessel disease. Following re-PTCA and stent implantation in conjunction with periinterventional GP IIb/IIIa antagonist treatment, the patient was initially symptom free for about two hours before rapidly developing signs of a hemorrhagic shock. An abdominal CT scan showed splenic rupture with massive intraabdominal hemorrhage as a consequence of secondary bleeding into multiple pre-existing splenic infarctions. The patient's condition stabilized after emergency splenectomy. Subsequent bone marrow biopsy revealed the presence of polycythemia vera. Post-operatively, the patient was treated with the anti-platelet agents aspirin and clopidogrel to prevent subacute stent thrombosis. Additionally, cyto-reductive therapy with hydroxyurea was initiated because of a further increase in the platelet count. In patients with polycythemia vera, the indication for treatment with GP IIb/IIIa antagonists should be carefully weighed against the potentially serious bleeding complications. Should treatment be established, a risk stratification using abdominal sonography and bleeding time testing is recommended, while during treatment red blood count, platelet count, coagulation tests, and hemodynamic parameters should be closely monitored.

Role of phosphoinositide 3-kinase in monocyte recruitment under flow conditions

Chemokines such as the monocyte chemol attractant protein-1 (MCP-1) convert monocyte rolling to firm arrest under physiological flow conditions via integrin activation and simultaneously activate phosphoinositide 3-kinase (PI3K). Here we used adenoviral gene transfer and biochemical inhibitors to manipulate PI3K-dependent pathways in human monocytes. In in vitro lipid kinase assays from purified human monocytes, we showed that MCP-1 activates the "classical" PI3Kalpha pathway and not PI3Kgamma, a PI3K isoform thought to be activated only by the betagamma complex of heterotrimeric G proteins. The activity of PI3Kalpha in purified human monocytes was evident within 30 s. MCP-1-induced monocyte arrest was significantly inhibited both by wortmannin (n = 4; p < 0.01) and LY294002 (n = 4; p < 0.01) with restoration of the rolling phenotype (p < 0.05 for both inhibitors, compared with rolling of control monocytes after MCP-1 treatment). To test the hypothesis that activation of PI3K is sufficient to induce monocyte adhesion, we transduced the monocytic THP-1 cell line with a recombinant adenovirus (Ad) carrying a constitutively active mutant of PI3K (Ad.BD110). We examined the ability of these cells to adhere to human vascular endothelium (HUVEC) transduced with adenoviruses carrying E-selectin, intercellular adhesion molecule-1 (ICAM-1), and VCAM-1. Under flow conditions, ICAM-1- and VCAM-1-dependent firm adhesion of Ad.BD110-transduced THP-1 cells was enhanced compared with THP-1 cells infected with control Ad (n = 4; p < 0.01 for both). Adhesion augmented by constitutive PI3K activation was entirely abrogated by pretreatment with wortmannin (n = 3; p < 0.01). In contrast, a constitutively active Akt construct had no effect on THP-1 adhesion (n = 3; p = NS). We conclude that PI3K activation is necessary and sufficient to enhance monocytic adhesion under physiological flow conditions. BD110-expressing THP-1 cells should provide a useful tool for identifying the signaling pathways downstream of PI3K that are necessary for monocyte recruitment relevant to a variety of human vascular pathologies.

Contribution of the endothelin system to the renal hypoperfusion associated with experimental congestive heart failure

The objective of this study was to define further the local activation of endothelin-1 (ET-1) and the ETA receptor as well as the functional consequences of activated ET-1 for renal hypoperfusion associated with experimental congestive heart failure (CHF). We studied eight rabbits permanently instrumented with Doppler flow probes around the renal arteries before and after the induction of epinephrine-induced CHF. CHF was characterized by left-ventricular dysfunction (fractional shortening 34+/-2% vs. 46+/-3%; p < or = 0.05) and dilatation (LVEDd 13.6+/-0.3 vs. 11.5+/-0.4 mm; p < or = 0.05), decreased mean arterial pressure (59.4+/-2.9 vs. 74.6+/-3.7 mm Hg; p < or = 0.05), increased heart rate (236+/-11 vs. 216+/-8 beats/min; p < or = 0.05) and renal vasoconstriction (vascular resistance 49.65 +/-8.55 vs. 24.61+/-5.85 U; p < 0.05; blood flow velocity, 1.58+/-0.21 vs. 3.63+/-0.31 kHz; p < 0.05). ET-1 concentrations were significantly increased not only in plasma (7.67+/-0.47 vs. 4.56 +/-0.69 pg/ml; p < 0.05) but also in renal tissue (4.8+/-0.5 vs. 3.5 +/-0.64 pg/mg; p < 0.05). Northern analysis revealed an unchanged expression of ETA receptor messenger RNA (0.79+/-0.05 vs. 0.77+/-0.04 arbitrary units; NS) in renal tissue, whereas expression of prepro-ET-1 was below the range of detection. In CHF, selective ETA-receptor antagonism with BQ-123 (1 mg/ kg bolus, i.v.) significantly increased renal blood flow velocity (3.07+/-0.38 vs. 1.33+/-0.19 kHz; p < 0.05) and reduced renal vascular resistance (29.63+/-6.22 vs. 58.17+/-8.75 U; p < 0.05) without significant effects on mean arterial pressure or heart rate. These studies demonstrate activation of the renal ET system, unaltered gene expression, and functional integrity of the renal ETA receptor in CHF. They indicate a principal functional role for the ETA receptor in renal vasoconstriction and suggest blockade of the renal ETA receptor as an important strategy to attenuate renal hypoperfusion in CHF.

Modulation of renal blood flow by endogenous endothelin-1 in conscious rabbits with left ventricular dysfunction

The current study addresses the functional status and role of the endothelin ET(A) receptor for renal vascular function in rabbits with and without heart failure (epinephrine-induced cardiomyopathy). Under baseline conditions, the ET(A) receptor antagonist BQ-123 did not change basal renal hemodynamics, but completely prevented endothelin-1 (ET-1)-induced renal vasoconstriction. In heart failure, in the presence of elevated plasma ET-1 concentrations (P < .05), renal vasoconstriction in response to exogenous ET-1 was intact. Unlike under baseline conditions, ET(A) receptor antagonism markedly increased renal blood flow (P <.05) and decreased renal vascular resistance (P < .05) in heart failure. The current study provides new insight into the pathophysiology of renal vasoconstriction associated with heart failure and the specific role of the renal ET(A) receptor in this pathophysiologic adaptation.