Urocortin 2 infusion in human heart failure

AIMS

To document the haemodynamic, neurohormonal, and renal responses to Urocortin 2 (UCN2) infused in human heart failure (HF).

METHODS AND RESULTS

Eight male patients with HF [left ventricular ejection fraction (LVEF) < 40%, NYHA class II-III] received placebo and 25 [low dose (LD)] and 100 microg [high dose (HD)] of UCN2 intravenously over 1 h in a single-blind, placebo-controlled, dose-escalation design. UCN2 increased cardiac output (CO) (mean peak increments +/- SEM; placebo 0.3 +/- 0.1; LD 1.0 +/- 0.3; HD 2.0 +/- 0.2 L/min; P < 0.001) and LVEF (0.0 +/- 1.5; LD 5.9 +/- 2.1; HD 14.1 +/- 2.7%; P = 0.001) and decreased mean arterial pressure (placebo 6.7 +/- 1.3; LD 11.4 +/- 1.7; HD 19.4 +/- 3.3 mmHg; P = 0.001), systemic vascular resistance (SVR) (placebo 104 +/- 37; LD 281 +/- 64; HD 476 +/- 79 dynes s/cm(5); P < 0.003), and cardiac work (CW) (placebo 48 +/- 12; LD 66 +/- 22; HD 94 +/- 13 mmHg/L/min; P < 0.001). No significant effect on vasoconstrictor/volume-retaining neurohormones was noted. UCN2 decreased urinary volume (P = 0.035) but not creatinine excretion (P = 0.962).

CONCLUSION

Intravenous UCN2 in HF induced increases in CO and LVEF with falls in SVR and CW. No hormone response occurred. The role of UCN2 in circulatory regulation and its potential therapeutic application in heart disease warrant further investigation.

Urocortin 2 infusion in healthy humans: hemodynamic, neurohormonal, and renal responses

OBJECTIVES

We sought to examine the effects of urocortin (UCN) 2 infusion on hemodynamic status, cardiovascular hormones, and renal function in healthy humans.

BACKGROUND

Urocortin 2 is a vasoactive and cardioprotective peptide belonging to the corticotrophin-releasing factor peptide family. Recent reports indicate the urocortins exert important effects beyond the hypothalamo-pituitary-adrenal axis upon cardiovascular and vasohumoral function in health and cardiac disease.

METHODS

We studied 8 healthy unmedicated men on 3 separate occasions 2 to 5 weeks apart. Subjects received placebo, 25-microg low-dose (LD), and 100-microg high-dose (HD) of UCN 2 intravenously over the course of 1 h in a single-blind, placebo-controlled, dose-escalation design. Noninvasive hemodynamic indexes, neurohormones, and renal function were measured.

RESULTS

The administration of UCN 2 dose-dependently increased cardiac output (mean peak increments +/- SEM) (placebo 0.5 +/- 0.2 l/min; LD 2.1 +/- 0.6 l/min; HD 5.0 +/- 0.8 l/min; p < 0.001), heart rate (placebo 3.3 +/- 1.0 beats/min; LD 8.8 +/- 1.8 beats/min; HD 17.8 +/- 2.1 beats/min; p < 0.001), and left ventricular ejection fraction (placebo 0.6 +/- 1.4%; LD 6.6 +/- 1.5%; HD 14.1 +/- 0.8%; p < 0.001) while decreasing systemic vascular resistance (placebo -128 +/- 50 dynes x s/cm(5); LD -407 +/- 49 dynes x s/cm(5); HD -774 +/- 133 dynes.s/cm(5); p < 0.001). Activation of plasma renin activity (p = 0.002), angiotensin II (p = 0.001), and norepinephrine (p < 0.001) occurred only with the higher 100-mug dose. Subtle decreases in urine volume (p = 0.012) and natriuresis (p = 0.001) were observed.

CONCLUSIONS

Brief intravenous infusions of UCN 2 in healthy humans induced pronounced dose-related increases in cardiac output, heart rate, and left ventricular ejection fraction while decreasing systemic vascular resistance. Subtle renal effects and activation of plasma renin, angiotensin II, and norepinephrine (at high-dose only) were observed. These findings warrant further investigation of the role of UCN 2 in circulatory regulation and its potential therapeutic application in heart disease.

Senescent and quiescent cell inhibitors of DNA synthesis. Membrane-associated proteins

Cytoplasts derived from senescent and quiescent human diploid cells inhibit DNA synthesis initiation when fused with cells capable of proliferation. When the cytoplasts were subjected to a variety of conditions (trypsin and cycloheximide treatment and growth on fibronectin), this inhibitory activity was lost, suggesting that the inhibitors involved were proteins associated with the surface membranes of the cells. We have studied the quiescent cell inhibitor in greater detail and determined that surface membrane-enriched preparations isolated from quiescent cells and proteins extracted from these membrane preparations have DNA synthesis-inhibitory activity.

Human placental (fetal) fibronectin: increased glycosylation and higher protease resistance than plasma fibronectin. Presence of polylactosamine glycopeptides and properties of a 44-kilodalton chymotryptic collagen-binding domain: difference from human plasma fibronectin

Human placental fibronectin was isolated from fresh term placenta by urea extraction and purified by gelatin affinity chromatography. A 44-kDa chymotryptic fragment, also purified by gelatin affinity chromatography, gave a broad, diffuse band on polyacrylamide gel electrophoresis, whereas the analogous 43-kDa fragment from human plasma fibronectin migrated as a defined, narrow band. Upon extended treatment with endo-beta-galactosidase from Escherichia freundii, the 44-kDa chymotryptic gelatin-binding fragment from placental fibronectin changed its behavior on gel electrophoresis and migrated as a narrower, more defined band. The carbohydrates on human placental fibronectin contained a large percentage of polylactosamine structures, part of which occurred on the gelatin-binding fragment, comprising almost twice as much carbohydrate as plasma fibronectin. NH2-terminal amino acid sequence analysis of the chymotryptic gelatin-binding fragments from both fibronectins showed the first 21 residues to be identical. Tryptic and chymotryptic peptide maps of the gelatin-binding fragment from placental fibronectin, however, showed differences including several protease-resistant domains not found in the analogous fragment from plasma fibronectin. Intact placental fibronectin contains 20,000 Da of carbohydrate, whereas plasma fibronectin contains 11,000 Da. Placental fibronectin is more protease-resistant than plasma fibronectin, possibly due to the additional carbohydrate. Polyclonal antibodies against either fibronectin completely cross-react with amniotic fluid fibronectin, placental fibronectin, and plasma fibronectin upon Ouchterlony immunodiffusion. Human fibronectins of putatively the same polypeptide structure are, therefore, glycosylated in a dramatically different fashion, depending on the tissue of expression. If the patterns of glycosylation comprise the only difference in the glycoprotein, this may confer the characteristic protease resistance found for each of the fibronectins.

Effect of aflatoxin B1 and major metabolites on phytohemeagglutinin-stimulated lymphoblastogenesis of bovine lymphocytes

Effects of aflatoxin B1 and three of its metabolites on cellular immune response were assessed with an assay based on inhibition of tritiated thymidine uptake by phytohemeagglutinin stimulated lymphocytes. In this in vitro system aflatoxin B1 and aflatoxin Q1 were strongly inhibitory (more than 50% inhibition) at concentrations of 10 mu/ml, whereas aflatoxicol and aflatoxin B2 alpha exhibited little inhibition at 10 micrograms/ml and only 45 to 50% inhibition at 25 micrograms/ml. Contrasts with single degrees of freedom and orthogonal polynomial analysis revealed that the pair of aflatoxin B1 and aflatoxin Q1 differed linearly and quadratically from the pair of aflatoxin B2 alpha and aflatoxicol, but within each pair there were no differences. Limited data with aflatoxin M1 revealed that it was slightly more active than aflatoxicol in the assay, but minimal replication prevented rigorous statistical testing. It may be theorized that the moderate to strong inhibition of blastogenesis by aflatoxin B1 and its metabolites could inhibit T lymphocyte functions, such as killer, helper, effector, or other immune processes, and thus compromise the immunological surveillance mechanism.