thromboxane-a2 and Peritonitis

In humans, LL-37 and eicosanoids are important mediators of inflammation and immune responses. Here we report that LL-37 promotes leukotriene B4 (LTB4) and thromboxane A2 (TXA2) generation by human monocyte-derived macrophages (HMDMs). LL-37 evokes calcium mobilization apparently via the P2X7 receptor (P2X7R), activation of ERK1/2 and p38 MAPKs, as well as cytosolic phospholipase A2 (cPLA2) and 5-lipoxygenase in HMDMs, leading to an early (1 h) release of LTB4. Similarly, TXA2 production at an early time involved the same signaling sequence along an LL-37-P2X7R-cPLA2-cyclooxygenase-1 (COX-1) axis. However, at later (6-8 h) time points, internalized LL-37 up-regulates COX-2 expression, promoting TXA2 production. Furthermore, intraperitoneal injection of mice with murine cathelicidin-related antimicrobial peptide (mCRAMP) induces significantly higher levels of LTB4 and TXA2 in mouse ascites rich in macrophages. Conversely, cathelicidin-deficient (Cnlp(-/-)) mice produce much less LTB4 and TXB2 in vivo in response to TNF-α compared with control mice. We conclude that LL-37 elicits a biphasic release of eicosanoids in macrophages with early, Ca(2+)-dependent formation of LTB4 and TXA2 followed by a late peak of TXA2, generated via induction of COX-2 by internalized LL-37, thus allowing eicosanoid production in a temporally controlled manner. Moreover, our findings provide evidence that LL-37 is an endogenous regulator of eicosanoid-dependent inflammatory responses in vivo.

Topics: Amino Acid Sequence; Animals; Antimicrobial Cationic Peptides; Arachidonate 5-Lipoxygenase; Calcium Signaling; Cathelicidins; Cells, Cultured; Eicosanoids; Humans; Inflammation; Leukotriene B4; Macrophages; Male; MAP Kinase Signaling System; Mice; Mice, Inbred C57BL; Molecular Sequence Data; Peritonitis; Phospholipases A2, Cytosolic; Phosphorylation; Prostaglandin-Endoperoxide Synthases; Protein Kinase Inhibitors; Protein Processing, Post-Translational; Receptors, Purinergic P2X7; Recombinant Proteins; Thromboxane A2; Tumor Necrosis Factor-alpha

Visceral microcirculatory insufficiency has been demonstrated in sepsis despite a hyperdynamic systemic circulation. This study examines the effect of the cyclo-oxygenase inhibitor indomethacin and the thromboxane synthetase inhibitor imidazole on septic hemodynamics and visceral perfusion in a septic rat model of cecal ligation and puncture. Animals received either indomethacin (INDO), imidazole (IMID), or saline intramuscularly at t = 0, 6, and 12 hr of peritonitis. Thermodilution cardiac output, mean arterial pressure, heart rate, hematocrit, effective hepatic blood flow, effective renal plasma flow, and arterial and mixed venous blood gases were determined at 15 hr. Both INDO and IMID improved effective hepatic blood flow in the septic animals to virtually sham, nonseptic levels without significantly altering systemic hemodynamics. This study suggests that the reduction in hepatic perfusion in sepsis may be mediated by thromboxane, the synthesis of which is suppressed by both INDO and IMID.

Topics: Animals; Female; Hemodynamics; Imidazoles; Indomethacin; Liver Circulation; Peritonitis; Rats; Rats, Inbred Strains; Renal Circulation; Thromboxane A2

This study investigates the role of prostaglandins (PG) in hyperdynamic sepsis. Thirteen chronically instrumented dogs were rendered septic by implanting in the peritoneal cavity a fibrin clot containing viable Escherichia coli. One day later, cardiac output (CO) increased from 2.80 +/- 0.22 to 3.72 +/- 0.32 l/min (p = 0.011); heart rate (HR) increased from 122 +/- 8 to 147 +/- 6 beats/min (p = 0.005); mean pulmonary artery pressure (PAP) increased from 15 +/- 1 to 19 +/- 1 mmHg (p = 0.003); mean systemic arterial pressure (MAP) decreased from 120 +/- 5 to 107 +/- 7 mmHg; and systemic vascular resistance (SVR) decreased from 44.1 +/- 2.6 to 29.3 +/- 1.9 mmHg/l/min (p less than 0.001). Sixty minutes after intravenous injection of indomethacin (2 mg/kg) or ibuprofen (25 mg/kg), CO decreased to 2.60 +/- 0.21 l/min (p less than 0.001); HR decreased to 118 +/- 5 beats/min (p less than 0.001); PAP decreased to 17 +/- 1 mmHg (p = 0.021); and SVR increased to 43.7 mmHg/l/min (p less than 0.001). In seven control dogs, laparotomy alone did not significantly affect any of these parameters. Infusion of indomethacin caused a slight increase in MAP (106 +/- 4 to 116 +/- 4 mmHg, p = 0.035) but otherwise did not alter hemodynamics. It is concluded that administration of indomethacin or ibuprofen restores normal hemodynamics in a canine model of high-output sepsis, probably by inhibiting PG synthesis.

Topics: 6-Ketoprostaglandin F1 alpha; Animals; Disease Models, Animal; Dogs; Escherichia coli Infections; Female; Hemodynamics; Ibuprofen; Indomethacin; Male; Oxygen Consumption; Peritonitis; Prostaglandin Antagonists; Prostaglandins; Sepsis; Shock, Septic; Thromboxane A2

We investigated the effects of the thromboxane synthetase inhibitor 7-(1-imidazolyl)heptanoic acid (7-IHA) and the fatty acid cyclooxygenase inhibitors indomethacin or ibuprofen in the treatment of fecal peritonitis in the rat. The effects of gentamicin alone and in combination with reduction of arachidonic acid metabolism by either treatment with indomethacin or essential fatty acid deficiency was also investigated. 7-IHA (60 mg/kg), administered i.p. 30 min before i.p. instillation of a fecal suspension, significantly reduced the plasma levels of immunoreactive (i) TxB2 from 1066 +/- 194 pg/ml (N = 14) to nondetectable (less than 200 pg/ml; N = 9) (P less than .01) at 1 hr and from 1695 +/- 218 (N = 16) to 508 +/- 56 pg/ml (N = 6) (P less than .01) at 4 hr after instillation of feces. In contrast, the levels of i6-keto-prostaglandin (PG)F1 alpha, the stable metabolite of prostacyclin, were significantly elevated by 7-IHA pretreatment from vehicle-treated septic control levels of 3777 +/- 414 (N = 16) to 5185 +/- 467 pg/ml (N = 9) (P less than .05) at 1 hr. Plasma i6-keto-PGF1 alpha at 4 hr in 7-IHA-treated rats (5503 +/- 665 pg/ml) (N = 6) was not different from vehicle-treated controls. Survival associated with fecal peritonitis was not altered by 7-IHA pretreatment. Indomethacin (10 mg/kg) or ibuprofen (5 mg/kg) administered i.p. 30 min before the fecal suspension significantly decreased both iTxB2 and i6-keto-PGF1 alpha, plasma levels when measured at 4 hr and prolonged survival time (P less than .05). Fibrinogen/fibrin degradation products were elevated (P less than .01) during fecal peritonitis and were reduced by indomethacin (P less than .01) or 7-IHA (P less than .05). Gentamicin significantly increased mean survival time from 8.6 +/- 0.2 (N = 50) to 23.8 +/- 2.6 hr (N = 16) (P less than .01). Gentamicin in combination with indomethacin or essential fatty acid deficiency further improved mean survival time and resulted in long-term survivals (greater than 48 hr) of 35 (N = 17) and 30% (N = 7), respectively (P less than .01 compared with gentamicin). Gentamicin pretreatment did not significantly alter plasma iTxB2 levels, but decreased i6-keto-PGF1 alpha from 9465 +/- 792 (N = 7) to 3096 +/- 1,174 pg/ml (N = 5; P less than .01) at 6 hr after induction of fecal peritonitis. These studies raise the possibility that inhibition of fatty acid cyclooxygenase may be a useful adjunct to antibiotic therapy in the treatment of septic shock.

Topics: Animals; Epoprostenol; Fatty Acids, Essential; Female; Fibrin Fibrinogen Degradation Products; Gentamicins; Ibuprofen; Imidazoles; Indomethacin; Macrophages; Male; Peritonitis; Prostaglandins; Prostaglandins F; Rats; Shock, Septic; Thromboxane A2; Thromboxane B2; Thromboxanes

We investigated a rat fecal peritonitis model of acute intraabdominal sepsis in order to evaluate the potential role of arachidonic acid metabolites in septic shock. Immunoreactive TxB2, the stable metabolite of thromboxane A2, and i6-keto-PGF1 alpha, the stable metabolite of prostacyclin, were measured by radioimmunoassay. Plasma levels of iTxB2 rapidly increased from nondetectable (ND less than 200 pg/ml) to 1,052 +/- 208 pg/ml, one hour after feces injection. iTxB2 then increased to 1,681 +/- 248 pg/ml at four hours and remained unchanged through six hours. Plasma i6-keto-PGF1 alpha increased from ND to 3,848 +/- 489 pg/ml a one hour. Four hours after feces, i6-keto-PGF1 alpha levels rose to 7, 450 +/- 933 pg/ml then continued to rise to 9,465 +/- 792 pg/ml at six hours. Either essential fatty acid deficiency (arachidonic acid depletion) or indomethacin treatment (cyclo-oxygenase inhibition) significantly decreased (P less than 0.01) the elevation of plasma iTxB2 and i6-keto-PGF1 alpha associated with fecal peritonitis. Thrombocytopenia occurred within six hours after injection of feces and was significantly improved (P less than 0.05) by indomethacin. Elevated fibrin degradation products at six hours (18 +/- 3 micrograms/ml) were significantly reduced in essential fatty acid-deficient (7 +/- 2 micrograms/ml; P less than 0.05) and indomethacin-treated (4 +/- 0.7 micrograms/ml; P less than 0.01) rats. Survival time (8.6 +/- 0.2 hours) was significantly enhanced by essential fatty acid-deficiency (10.2 +/- 0.4 hours; P less than 0.01) or indomethacin treatment (13.3 +/- 0.6 hours; P less than 0.01). These studies show that fecal peritonitis is associated with increased synthesis of thromboxane A2 and prostacyclin and suggest that these arachidonic acid metabolites may play a role in the pathophysiology of septic shock.

Topics: 6-Ketoprostaglandin F1 alpha; Animals; Epoprostenol; Fatty Acids, Essential; Female; Fibrin Fibrinogen Degradation Products; Indomethacin; Peritonitis; Prostaglandins; Rats; Rats, Inbred Strains; Shock, Septic; Thrombocytopenia; Thromboxane A2; Thromboxanes; Time Factors