Cardiac hormones eliminate some human squamous lung carcinomas in athymic mice.

BACKGROUND: Four cardiac hormones synthesized by the same gene, i.e. atrial natriuretic peptide, vessel dilator, long acting natriuretic peptide and kaliuretic peptide, have anticancer effects in vitro. MATERIALS AND METHODS: These cardiac hormones were infused subcutaneously for 28 days with weekly fresh hormones at 0.3 nM kg(-1) body weight in athymic mice bearing human squamous cell carcinomas. RESULTS: Vessel dilator, atrial natriuretic peptide and kaliuretic peptide each eliminated one in six (17%) of the human squamous cell lung carcinomas. Long-acting natriuretic peptide, although it did not eliminate any of the human squamous cell lung carcinomas did decrease the volume of one carcinoma to only 2% (P < 0.0001) of the untreated carcinomas. The squamous cell lung carcinomas that were not eliminated, with the exception of the one LANP-treated tumour that decreased to only 2% of the volume of the untreated cancers, grew rapidly but their growth velocity compared to controls decreased by 76%, 40%, 38% and 25% in the vessel dilator, atrial natriuretic peptide, kaliuretic peptide and long-acting natriuretic peptide groups respectively (P < 0.05). CONCLUSIONS: Three of four cardiac hormones synthesized by the atrial natriuretic peptide gene can eliminate human squamous cell lung carcinomas in athymic mice when treated subcutaneously for 4 weeks. The 4th cardiac hormone, i.e. long-acting natriuretic peptide, decreased the volume of one squamous cell lung carcinoma to 2% of that of untreated animals, suggesting that it, too, has beneficial effects on squamous cell lung cancers.

Biotin enhances guanylate cyclase activity.

Biotin and its analog, (+)-biotin-p-nitrophenyl ester enhanced guanylate cyclase activity two- to threefold in rat liver, kidney, colon, cerebellum, and heart. Dose-response relationships revealed that at concentrations as low as 1 micromolar, both biotin and its analog caused maximal augmentation of guanylate cyclase activity. These data suggest a role for the activation of guanylate cyclase in the mechanism of action of this vitamin.

Bee venom enhances guanylate cyclase activity.

Bee venom and phospholipase A2 extracted from bee venom enhanced guanylate cyclase (E.C. 4.6.1.2) activity two- to threefold in rat liver, lung, heart, kidney, ileum, and cerebellum. Dose-response relationships revealed that bee venom at concentrations as low as 1 microgram per milliliter and phospholipase A2 at 1 microunit per milliliter caused a maximal enhancement of guanylate cyclase.

Calcium requirement for melanophore-stimulating hormone action on melanophores.

The calcium ion is specifically required for the action of melanophorestimulating hormone on melanosome dispersion within lizard (Anolis carolinensis) melanophores in vitro. The response to this hormone is directly related to the concentration of the Ca(2+) ion. Lithium, choline, rubidium, and cesium will replace the sodium and potassium of Ringer solution if Ca(2+) is present. Calcium ions are not required for melanosome dispersion itself, since theophylline or dibutyryl cyclic adenosine monophosphate reversibly darkens lizard skins in the absence of calcium.

Cardiac hormones activate ERK 1/2 kinases in human fibroblasts.

Two cardiac hormones, vessel dilator and kaliuretic peptide, localize to fibroblasts with immunohistochemistry. Vessel dilator and kaliuretic peptide were investigated in dose-response and time-sequenced experiments for their cell signaling of extracellular signal-regulated kinases 1/2 in human fibroblasts to test the hypothesis that these two cardiovascular hormones contribute to fibroblast proliferation by activating extracellular signal-regulated kinases 1/2. Vessel dilator at 10 pM (physiological range) enhanced the phosphorylation of extracellular signal-regulated kinases 1/2 by 188+/-9% (p<0.001) in 10 min and, maximally, by 200+/-10% in 15 min (p<0.001). Vessel dilator at 10 nM enhanced the phosphorylation of extracellular signal-regulated kinases 1/2 by 107+/-5% (p<0.01) in 10 min. Kaliuretic peptide at 10 pM enhanced the activation of extracellular signal-regulated kinases 1/2 by 389+/-19% in 10 min (p<0.001). Kaliuretic peptide at 10 nM enhanced the phosphorylation of extracellular signal-regulated kinases 1/2 by 82+/-4% (p<0.01). Our results show that both cardiac hormones activate extracellular signal-regulated kinases 1/2 in human fibroblasts, suggesting that they may have a role in enhancing fibroblast proliferation.

Phosphatidylinositol 3-kinase/Akt signaling mediates interleukin-6 protection against p53-induced apoptosis in M1 myeloid leukemic cells.

M1 myeloid leukemic cells were used to dissect the molecular mechanisms of myeloid cell survival and apoptosis. A salient feature of M1 cells is that they respond to the physiological survival factor interleukin-6 (IL-6), yet lack the tumor suppressor gene p53. Functional wild-type activation of temperature-sensitive p53 protein (p53 val) at permissive temperature in M1-t-p53 cells results in rapid apoptosis, which is blocked by IL-6. How p53 induces M1 apoptosis and how IL-6 protects against p53-induced apoptosis are not fully understood. Here it is shown that p53-mediated apoptosis of M1 cells involves rapid activation of the proapoptotic Fas/CD95 death pathway, which activates caspases 8 and 10. Functional p53 also targets the mitochondria, causing upregulation of proapoptotic Bax, downregulation of prosurvival Bcl-2 and activation of caspase 9. IL-6 was found to protect against p53-induced apoptosis via activation of the PI3K/Akt survival pathway, which in turn counters both the Fas/CD95 and mitochondrial apoptotic pathways and activates the prosurvival transcription factor nuclear factor-kappaB (NF-kappaB). Taken together, this work supports a novel model for leukemic progression where cells that acquire the ability to produce an autocrine survival factor, such as IL-6, can bypass normal p53 surveillance function by targeting Akt, which in turn can exert effects on the regulators of apoptosis, such as the Fas/CD95 pathway, the mitochondria and NF-kappaB.

Cardiac and kidney hormones cure up to 86% of human small-cell lung cancers in mice.

BACKGROUND: Four cardiac hormones synthesized by the same gene, i.e. atrial natriuretic peptide, vessel dilator, long acting natriuretic peptide and kaliuretic peptide, and the kidney hormone urodilatin have anticancer effects in vitro. MATERIALS AND METHODS: These cardiac hormones and urodilatin were infused subcutaneously for 28 days with weekly fresh hormones since they lose biological effects at body temperature for more than a week at 0.3 nm kg(-1) body weight in athymic mice bearing human small-cell lung carcinomas. RESULTS: Long acting natriuretic peptide, vessel dilator, kaliuretic peptide, atrial natriuretic peptide and urodilatin eliminated 86%, 71%, 57%, 43% (P < 0.001 for the cardiac hormones) and 25% (P < 0.05; urodilatin) of the human small-cell lung carcinomas. The treated small-cell lung carcinomas that were not cured grew rapidly, similar to the untreated controls, whose volume was 7 fold larger in 1 week, 18-fold increased in 2 weeks, 39-fold increased in 3 weeks, 63-fold increased in 1 month and 97-fold increased in volume in 6 weeks. One vessel dilator treated small-cell lung carcinoma animal developed a large tumour (8428 mm3 volume) on treatment and this tumour was eliminated with utilizing atrial natriuretic peptide and then long acting natriuretic peptide sequentially. CONCLUSIONS: Four cardiac hormones eliminate up to 86% of human small-cell lung carcinomas in athymic mice. Urodilatin can also eliminate small-cell lung carcinomas but at a lower cure rate of 25%. Unresponsive lesions can be eliminated by utilizing different hormones synthesized by the atrial natriuretic peptide gene in a sequential manner.

Circadian distribution of hematology variables in subjects with multiple sclerosis.

Hematology variables were measured in blood samples obtained every 3h (8/24h) from 10 multiple sclerosis (MS) patients and 34 healthy subjects and analyzed for circadian characteristics using the population multiple-components method. Red blood cell (RBC) and hemoglobin levels as well as hematocrits exhibited circadian rhythms with minimal amplitudes in healthy individuals and insignificant variability in the smaller group of MS patients. In contrast the total white blood cell (WBC) and platelet counts for MS patients and healthy individuals both showed significant circadian characteristics while the mean 24h WBC and platelet levels did not significantly differ between the two groups. When the different WBC subsets were examined independently, statistically significant circadian rhythms were seen for lymphocytes and eosinophils for both MS patients and healthy individuals and for neutrophils only in the latter. Moreover, the 24h mean levels of lymphocytes, basophils, and eosinophils were significantly higher for the healthy controls while those of monocytes were higher for the MS patients. However, of all the variables tested with significant circadian rhythms in both groups of individuals, only those of lymphocyte numbers exhibited different patterns with somewhat higher amplitude in healthy individuals and a peak level occurring over an hour after that of MS patients. These changes may be the reflection of a disturbance in the regulation of patterns of lymphocyte activity and migration in MS patients. In addition, the elevation in circulating monocytes in MS patients is consistent with the inflammatory nature of the disease.

Activation of guanylate cyclase by streptozotocin and 1-methyl-1-nitrosourea.

Streptozotocin has been shown to induce the production of a variety of tumors in rats. The present report demonstrates that streptozotocin and 1-methyl-1-nitrosourea, a component of the streptozotocin molecule and a known carcinogen, stimulate the enzyme guanylate cyclase which catalyzes the production of guanosine 3',5'-monophosphate. At a maximal concentration of 3 mg/ml, these agents activated guanylate cyclase approximately 30-fold in liver, 20-fold in kidney, 15-fold in cerebellum. 15- to 30-fold in cerebrum, 4- to 20-fold inheart, 12-fold in brain stem, 10-fold in lung, and 2-fold in pancreas. Since recent evidence suggests a role for guanosine 3',5'-monophosphate in malignant transformation, the data may help explain the tumor-inducing capacity of these agents.

Decreased rat hepatic guanylate cyclase activity in streptozotocin-induced diabetes mellitus.

Guanylate cyclase is found in virtually all cells, but its physiologic role and the effect of hormones on its activity have not been clarified. Hepatic soluble guanylate cyclase activity (37,000 g supernatant) in rats with diabetes-mellitus-like syndrome induced by streptozotocin, 65 mg./kg. i.v., was 140 +/- 8 pmoles accumulated/mg. protein/10 min. (n = 13 rats) as against 279 +/- 16 pmoles accumulated/mg. protein/10 min. (n = 12 rats) in normal rats. The average blood sugar for the 12 normal rats was 100 +/- 4 mg./100 ml. and 546 +/- 32 mg./100 ml. for 13 diabetic rats. The decreased soluble hepatic guanylate cyclase activity in diabetic rats was completely restored to normal with 10 U. regular insulin, i.p. The maximum increase in guanylate cyclase activity was observed as early as five minutes and as late as two hours after insulin administration. Insulin restoration of guanylate cyclase was dose-related over a range of 1 U. to 10 U., i.p. Hepatic cyclic GMP levels in vivo paralleled in-vitro guanylate cyclase activity, being 29 +/- 0.4 pmoles/gm. wet weight in normals, 17 +/- 0.4 pmoles/gm. wet weight in streptozotocin-diabetic rats, and 38 +/- 0.4 pmoles/gm. wet weight two hours after the injection of 10 U. regular insulin. We conclude that rat hepatic guanylate cyclase is decreased in streptozotocin-induced diabetes and that insulin modulates this enzyme. The administration of exogenous insulin in normal animals did not further augment hepatic guanylate cyclase activity.

Acute renal failure in insulin-dependent diabetics: episodes secondary to intravenous pyelography.

Diabetic patients with chronic renal failure are known to be at risk for exacerbation of renal failure if they undergo intravenous pyelography (IVP). The present report demonstrates that diabetic patients with normal serum creatinine levels can sustain irreversible renal failure following an IVP. The experiences with this case suggest that, if the creatinine clearance is decreased in an insulin-dependent patient irrespective of the serum creatinine value, one must be aware of the possible hazard of acute renal failure and irreversible renal damage following the IVP. This would appear to be especially true if the diabetic patient has proteinuria in combination with the decreased creatinine clearance.

Somogyi effect in patient with hypopituitarism.

A patient with diabetes mellitus and hypopituitarism developed the Somogyi effect that was characterized by insulin-induced hypoglycemia and rebound insulin-resistant hypoglycemia. This compensatory insulin-resistant hyperglycemia has generally been ascribed to the release of anterior hypophyseal hormones; however, our findings suggest that factors other than anterior hypophyseal hormones are involved.

Congestive heart failure: increased cardiac and extracardiac atrial natriuretic peptide gene expression.

OBJECTIVES: The present investigation was designed to determine if atrial natriuretic peptide (ANP) gene expression increases in extracardiac as well as within the heart in congestive heart failure. METHODS: Congestive heart failure (CHF) was induced by producing cardiac hypertrophy secondary to an aortocaval fistula in Sprague-Dawley rats. To characterize this model, control and CHF rats had cardiac catheterizations and transthoracic echocardiography. ANP messenger RNA was measured by RNAase protection analysis in atria, ventricles, liver, colon, and stomach of CHF and sham rats and quantitated by 2-D scanning. The product of ANP gene expression was determined in each of these tissues with high performance-gel permeation chromatography. To help determine if increased degradation of atrial natriuretic peptides occur in congestive heart failure, the circulating concentrations and the excretion of the atrial natriuretic peptides into urine were measured by specific radioimmunoassays. RESULTS: ANP steady-state mRNA increased 4.2 +/- 0.05 and 4.3 +/- 0.06-fold, respectively, in the antrum of the stomach and within the heart ventricle of CHF rats compared with age-matched sham rats. ANP gene expression was present but not increased in atria, liver, and gastrointestinal tract of the CHF rats. High-performance gel permeation chromatography revealed that the product of this ANP gene expression within the stomach and heart ventricle in CHF animals was the ANP prohormone. There was not any decrease in the metabolism of these peptides by the kidney in CHF. CONCLUSIONS: ANP steady-state mRNA increases in extracardiac (i.e., stomach antrum) tissue as well as in the ventricle of the heart in CHF. The product of the ANP gene expression, i.e., the ANP prohormone is the same in the extracardiac tissues as within the heart. Whether the increased extracardiac ANP steady-state mRNA and its resultant increased atrial natriuretic peptides helps prevent bowel wall edema in CHF needs to be elucidated.

Adrenomedullin, endothelin, neuropeptide Y, atrial, brain, and C-natriuretic prohormone peptides compared as early heart failure indicators.

OBJECTIVES: The present investigation was designed to determine the best endogenous plasma marker of early congestive heart failure (CHF). METHODS: Forty volunteers with mild CHF (New York Heart Association Class I, n = 12), moderate (Class II, n = 8), or severe (Class III and Class IV, each = n of 5) and 10 age-matched healthy individuals had the simultaneous evaluation of their respective plasma samples by the following radioimmunoassays: atrial natriuretic peptide, ANP; three N-terminal ANP prohormone assays, i.e., proANPs 1-30, 31-67, and 79-98 with the numbers referring to their amino acid (a.a.) sequences in their 126 a.a. prohormone; brain (BNP) and C-natriuretic peptides; N-terminal BNP prohormone; adrenomedullin; neuropeptide Y and endothelin. RESULTS: ProANPs 31-67, 1-30 and 79-98 had 100% (P = 0.01), 83% (P = 0.09) and 50% (P = 0.74) sensitivity in differentiating Class I CHF subjects from healthy subjects. The ANP, BNP, NT-proBNP, CNP, adrenomedullin, neuropeptide Y, and endothelin assays could not differentiate mild CHF subjects from healthy individuals. Logistic regression analysis revealed that only proANP 31-67 significantly (P = 0.0001) discriminated between early CHF (5226 +/- 377 pg/ml) and healthy individuals (1595 +/- 157 pg/ml). The positive and negative predicative values of proANP 31-67 were excellent (100% for each). The peptides measured in these assays were found to be independent markers of CHF with respect to left ventricular ejection fraction. CONCLUSIONS: ProANPs 31-67 is the most sensitive marker in discriminating NYHA Class I CHF subjects from healthy individuals. The ANP, BNP, NT-proBNP, CNP, adrenomedullin, neuropeptide Y and endothelin radioimmunoassays cannot discern mild CHF. These peptides are independent of left ventricular ejection fraction.

Bromocriptine enhances guanylate cyclase activity.

Bromocriptine and its parent compound alpha-ergocryptine were investigated with respect to their ability to interact with the guanylate cyclase (E.C.4.6.1.2)-cyclic GMP system in vitro in the rat pituitary and ovary. Both bromocriptine and alpha-ergocryptine enhanced guanylate cyclase two- to threefold in both of these tissues over a concentration range of 1 nM to 1 microM. Since bromocriptine is thought to be a dopamine agonist in the pituitary, dopamine's effects on guanylate cyclase were also tested. Dopamine caused a twofold enhancement of guanylate cyclase activity in the pituitary and ovary. When bromocriptine and dopamine were used in combination, bromocriptine had to be in equal or a greater concentration with respect to dopamine in vitro to enhance guanylate cyclase activity. These findings suggest that bromocriptine's effect at the level of the pituitary and ovary may be mediated through enhancement of guanylate cyclase activity.

Kaliuretic peptide: the most potent inhibitor of Na(+)-K+ ATPase of the atrial natriuretic peptides.

The present investigation was designed to determine whether atrial natriuretic peptides consisting of amino acids 1-30 (i.e. long-acting natriuretic peptide), 31-67 (vessel dilator), 79-98 (kaliuretic peptide), and 99-126 [atrial natriuretic factor (ANF)] of the 126 amino acid ANF prohormone inhibit sodium-potassium-ATPase as part of their mechanism(s) of action for producing a natriuresis and/or kaliuresis. Kaliuretic peptide, long-acting natriuretic peptide, vessel dilator and ANF at their 10(-11) M concentrations inhibited Na(+)-K(+)-ATPase 39.5%, 27.8%, 19.2%, and 4% respectively, in bovine renal medulla, whereas their inhibition in renal cortical membranes was 37.5%, 27.5%, 20%, and 0%, respectively. Ouabain (0.5 mM) inhibited kidney medullary Na(+)-K(+)-ATPase 45% and in the cortex, 38%. There was no additive effect of any of these peptides with ouabain suggesting that they are interacting with the same site on the Na(+)-K(+)-ATPase as ouabain. To help elucidate the mechanism of these peptides' interaction with Na(+)-K(+)-ATPase, naproxen (0.5 mM), an inhibitor of prostaglandin synthesis, and direct measurement of prostaglandin E2 by RIA were used. Naproxen completely blocked the inhibition of Na(+)-K(+)-ATPase by kaliuretic peptide, long-acting natriuretic peptide, and vessel dilator suggesting that their inhibition of Na(+)-K(+)-ATPase in both the kidney medulla and cortex are mediated by prostaglandins. Direct measurement of prostaglandin E2 revealed that kaliuretic peptide > long-acting natriuretic peptide > vessel dilator increased prostaglandin E2 synthesis, whereas ANF did not have any effect. Of interest, angiotensin II and ouabain inhibition of Na(+)-K(+)-ATPase were also completely blocked by naproxen.

Estrogens and progesterone increase fetal and maternal guanylate cyclase activity.

Since both estrogens and cyclic guanosine 3',5'-monophosphate stimulate protein synthesis, the objective of the present investigation was to determine if estrogens and their precursors might have part of their mechanism of action through stimulation of guanylate cyclase (E.C.4.6.1.2), the enzyme that catalyzes the conversion of guanosine triphosphate to cyclic guanosine 3',5'-monophosphate. The precursors of estrogen synthesis originate from cholesterol. Cholesterol itself had no effect on guanylate cyclase activity. The precursors of estrogen synthesis generated from cholesterol, namely, progesterone, 17 alpha-OH-progesterone, androstenedione, pregnenolone, 17 alpha-OH-pregnenolone, and dehydroepinandrosterone, however, caused a 2- to 3-fold enhancement of fetal and maternal guinea pig hepatic and uterine guaynlate cyclase activity at a concentration of 1 microM. In comparative studies, similar effects were seen on immature female Sprague-Dawley rat hepatic and uterine guanylate cyclase activity. Estrone, estradiol-17 beta, estriol, and the synthetic estrogen, diethylstilbestrol, enhanced guanylate cyclase activity in the same tissues 2- to 3- fold at the 1 microM concentration. Dose-response relationships revealed that these estrogens and their precursors had their maximal effect at 0.001 microM. Estradiol-17 alpha also enhanced uterine guanylate cyclase activity, but a 1000-fold greater concentration compared to the other estrogens was necessary to show any significant effect. The data in this investigation suggest that guanylate cyclase may play a role in the mechanism of action of estrogens and their precursors.

Cimetidine partially blocks gastrin's activation of gastric mucosal guanylate cyclase.

The objective of the present investigation was to determine if gastrin at physiological concentrations has part of its mechanism(s) of action through stimulation of guanylate cyclase (EC 4.6.1.2). Human gastrin (I), pentagastrin, tetragastrin, and gastrin-related tetrapeptide all increased cyclic GMP levels and guanylate cyclase activity in rat gastric mucosa, whole stomach, and duodenum. Maximal stimulation was seen at 1 microM with all of the above. There was no further enhancement of guanylate cyclase with increasing the concentration to the millimolar range. The ED50 for human gastrin and pentagastrin was 0.01 microM, whereas the ED50 was 0.1 microM for tetragastrin and the tetrapeptide. No enhancement of guanylate cyclase activity was seen with decreasing the concentration to 1 nM of the respective gastrins. Cimetidine utilized at 1 microM or 1 mM concentrations partially blocked the augmentation by gastrin suggesting that part of this enhancement was through the histamine 2 receptor which has been shown to be important in pentagastrin-stimulated gastric acid release. Since the block was only partial these data would also indicate that some part of gastrin's activation of this enzyme is not mediated through the histamine 2 receptor.

Plant growth-promoting hormones activate mammalian guanylate cyclase activity.

In vivo injections of plant growth-promoting hormones increase the growth of animals as well as plants. Plant growth-promoting hormones and positive plant growth regulators are known to increase RNA and protein synthesis. Since cyclic GMP also increases RNA and protein synthesis, the object of the present investigation was to determine whether physiological levels of plant growth-promoting hormones and positive plant growth regulators have part of their mechanism(s) of action through stimulation of the guanylate cyclase (EC 4.6.1.2)-cyclic GMP system. Representatives of the three classes of growth-promoting hormones were investigated. Thus, auxins (indole-3-acetic acid, indole-3-butyric acid, beta-naphthoxyacetic acid, and 2,4,5-trichlorophenoxy acetic acid), gibberellins (gibberellic acid), and cytokinins [N6-benzyl adenine, kinetin (6-furfuryl aminopurine), and beta-(2-furyl) acrylic acid] all increased rat lung, small intestine, liver, and renal cortex guanylate cyclase activity 2- to 4-fold at the 1 microM concentration. Dose response curves revealed that maximal stimulation of guanylate cyclase by these plant growth regulators was at 1 microM; there was no augmented cyclase activity at 1 nM. The guanylate cyclase cationic cofactor manganese was not essential for augmentation of guanylate cyclase by these plant growth-promoting regulators. The antioxidant butylated hydroxytoluene did not block the enhancement of guanylate cyclase by these plant growth-promoting factors. These data suggest that guanylate cyclase may play a role in the mechanism of action of plant growth-promoting hormones and even of positive plant regulators at the cellular level.

Epidermal growth factor enhances guanylate cyclase activity in vivo and in vitro.

Epidermal growth factor (EGF) increases DNA synthesis and cell division both in vivo and in vitro. The mechanism by which EGF increases growth and DNA synthesis is unknown. Since the intracellular messenger cGMP stimulates DNA synthesis, the present investigation was designed to determine if EGF might have part of its mechanism of action through activating guanylate cyclase [EC 4.6.1.2], the enzyme that catalyzes the formation of cGMP. EGF enhanced soluble and particulate guanylate cyclase activities as well as cGMP levels 2- to 3-fold in hypophysectomized and nonhypophysectomized tissues both in vivo and in vitro. EGF increased guanylate cyclase activity 0.5 h after ip injection in mice, and this increased activity was still present 12 h later. Guanylate cyclase activity was increased to a greater extent secondary to EGF in hypophysectomized cecum compared to nonhypophysectomized cecum. Dose-response curves revealed that maximal stimulation of guanylate cyclase by EGF occurred at 1 nM. There was no augmented guanylate cyclase activity when the concentration of EGF was decreased to 0.01 nM. The data in this investigation suggest that guanylate cyclase may play a role in the mechanism of action of EGF.