High doses of digitalis increase the myocardial production of proinflammatory cytokines and worsen myocardial injury in viral myocarditis: a possible mechanism of digitalis toxicity.

Results of recent studies suggest that proinflammatory cytokines cause myocardial contractile dysfunction, and that the drugs used to treat heart failure modulate the production of cytokines. This study was designed to examine the effects of digoxin in a murine model of heart failure induced by viral myocarditis. Four-week-old inbred DBA/2 mice were inoculated intraperitoneally with encephalomyocarditis virus (EMCV). Digoxin was given orally in doses of 0.1, 1 or 10 mg/kg daily from the day of virus inoculation. Interleukin (IL)-1beta, IL-6 and tumor necrosis factor (TNF)-alpha production in the heart were measured on day 5 after EMCV inoculation by enzyme-linked immunosorbent assay. The 14-day mortality tended to be increased in mice treated with 1 mg/kg, and was significantly increased in the group treated with 10 mg/kg per day. Myocardial necrosis and cellular infiltration on day 6 were significantly more severe in the high-dose digoxin group than in the control group. In the animals treated with 1 mg/kg digoxin, IL-1beta was significantly higher than in the control group. Intracardiac TNF-alpha levels were increased in a dose-dependent manner. These results suggest that digoxin worsens viral myocarditis, and that its use in high doses should be avoided in patients suffering from heart failure due to viral myocarditis.

Prevention of myocardial reperfusion injury in rats by an antibody against monocyte chemotactic and activating factor/monocyte chemoattractant protein-1.

MCAF (monocyte chemotactic and activating factor)/MCP-1 (monocyte chemoattractant protein-1) is an important mediator of monocyte recruitment to inflammatory sites. However, its pathophysiologic role in myocardial reperfusion injury remains unknown. Male Wistar rats were anesthetized, and the left anterior descending coronary artery was ligated for an hour, after which the ligature was released. Northern blotting analysis revealed that MCAF/MCP-1 mRNA expression increased 16-fold in the reperfused region at 12 hours after reperfusion. MCAF/MCP-1 concentration in plasma and the heart was already elevated after hour of ischemia in this model. Goat polyclonal antibodies were prepared by repeated immunization of animals with purified, recombinant rat MCAF/MCP-1, and the neutralizing activities of this antibody were confirmed by monocyte chemotaxis assay and administration to rats with crescentic glomerulonephritis. Intravenous injection of anti-MCAF/MCP-1 antibody significantly reduced the infarct size at 24 hours after reperfusion compared with the injection of control IgG (33.9 +/- 5.1% vs 49.4 +/- 2.7% of ischemic area, mean +/- SEM). Administration of this antibody markedly decreased the intercellular adhesion molecule-1 mRNA expression and infiltration of macrophages, which suggested the pathophysiologic role of MCAF/MCP-1. Neutralization of MCAF/MCP-1 is beneficial by preventing reperfusion injury in a rat model of myocardial ischemia and reperfusion.

Modulation of cytokine production and protection against lethal endotoxemia by the cardiac glycoside ouabain.

BACKGROUND: Recent studies have shown that cytokines are capable of modulating cardiovascular function and that some drugs used in the treatment of heart failure variably modulate the production of cytokines. To examine whether cardiac glycosides also modulate cytokine production, we evaluated the effects of ouabain on the production of cytokines in vitro and in vivo. METHODS AND RESULTS: Human peripheral blood mononuclear cells (PBMC) were obtained from healthy volunteers. PBMC were cultured with or without ouabain in the presence or absence of lipopolysaccharide (LPS). Ouabain induced the production of interleukin (IL)-1beta, IL-6, and tumor necrosis factor (TNF)-alpha in PBMC and induced mRNA of these cytokines, an induction apparently at the transcriptional level. Amiloride, staurosporin, and genistein inhibited cytokine production, and protein kinase C and tyrosine kinase appeared to be involved in the modulation of cytokine production induced by ouabain. However, when PBMC were stimulated with LPS, ouabain suppressed the production of IL-6 and TNF-alpha. To investigate whether ouabain modulates cytokine production in vivo, we evaluated the effects of ouabain in LPS-treated mice. Ouabain was found to protect against LPS-induced lethal toxicity in mice and decreased circulating IL-6 and TNF-alpha levels in vivo. CONCLUSIONS: These previously unrecognized immunomodulating effects of a cardiac glycoside may explain either the beneficial or the detrimental effects of these drugs in heart failure patients.

Augmentation and suppression of the excitatory and inhibitory neuromuscular transmission induced by the ionophores, X-537A and A23187, in the red muscle of carp, Cyprinus carpio.

The effects of the ionophores, X-537A and A23187, on excitatory junction potentials (ejp), inhibitory junction potentials (ijp), diphasic junction potentials (diphasic jp) composed of ejp and ijp, and miniature excitatory junction potentials (mejp) were examined in the red muscles of carp, Cyprinus carpio. When 25 microM X-537A and 5 microM A23187 were applied, the amplitude of ejp and ijp increased transiently, then decreased gradually, and finally disappeared. The duration of ejp and ijp was little affected by the ionophores. The ionophores induced a transient increase in the frequency of mejp, which then decreased gradually after the maximum increase was attained, and finally fell below the control level. The ionophores had little effect on the resting membrane potential, membrane resistance of the muscle fiber, and amplitude of the compound action potential recorded from nerve bundles innervating this muscle. The ionophores caused ACh-evoked potentials to decrease gradually and finally disappear. These results suggest that the increase in the amplitude of ejp and ijp and in the frequency of mejp might be mainly due to the augmentation of ACh release from nerve terminals caused by an elevation of the intracellular Ca2+ concentration. On the other hand, the decrease and the abolition in the amplitude of ejp and ijp and in the frequency of mejp might be mainly due to the desensitization of the postsynaptic membrane.

Effects of a new histamine H2-receptor antagonist, Z-300, on gastric secretion and gastro-duodenal lesions in rats: comparison with roxatidine.

We examined the effects of a new compound, N-[3-[3-(piperidinomethyl)phenoxy]-propyl]-2-(2-hydroxyethyl-1- thio)acetamido.2-(4-hydroxy benzoyl)benzoate (Z-300), on the histamine H2-receptor, gastric secretion in rats and dogs, and acute gastro-duodenal lesions or chronic gastric ulcers in rats. Roxatidine acetate hydrochloride (roxatidine), a known histamine H2-receptor antagonist, was used as a reference compound. The pA2 values for Z-300 and roxatidine for the isolated guinea pig atrium were 6.8 and 7.0, respectively. These agents at less than 10(-5) M did not affect the contraction of guinea pig ileum in response to carbachol. Z-300, administered either orally or parenterally, significantly inhibited the basal and histamine-stimulated gastric acid secretion in rats. Gastric acid secretion stimulated by histamine, pentagastrin or carbachol in Heidenhain pouch dogs was also significantly inhibited by the compound. The effect persisted for greater than 7 hr in the case of histamine-stimulation. Oral Z-300 significantly protected the gastric mucosa from water-immersion stress-, indomethacin-, aspirin- and HCl.ethanol-induced lesions and protected the duodenal mucosa against mepirizole- and cysteamine-induced ulcers. These effects on gastric secretion and lesion formation were, as a whole, stronger than those observed with roxatidine. Z-300, but not roxatidine, significantly accelerated the spontaneous healing of acetic acid ulcers induced in rats and prevented the delay in ulcer healing caused by indomethacin. The mechanism of action of Z-300 on acute lesions and chronic ulcers appears to be mostly related to its potent antisecretory and mucosal-protective activities.

[Discovery and development of the proton pump inhibitor].

Gastric (H+/K+)-ATPase, the proton pump of the parietal cell, is responsible for the final step of acid secretion in the stomach. In 1981, picoprazole, a substituted benzimidazole, was found to inhibit (H+/K+)-ATPase. It was reported in 1983 that omeprazole has the most potent efficacy among the substituted benzimidazoles and today, omeprazole has been used for treatment of gastroduodenal disease. Recently, lansoprazole, similar to omeprazole in chemical structure, was developed in Japan, and several other compounds, such as pantoprazole, E-3810 and NC-1300-O-3, have also been reported to suppress acid secretion through inhibition of (H+/K+)-ATPase. In the present paper the background of the discovery of (H+/K+)-ATPase and development of proton pump inhibitors is reviewed.

[Detection of immune complex by C1q solid phase enzyme immunoassay].

We have developed a new and improved method for detecting immune complexes (IC) by C1q solid-phase enzyme immunoassay (CSP-EIA). The sensitivity of this method was between 0.62 micrograms/ml and 1.25 micrograms/ml, and values in normal individuals were 1.8 micrograms/ml and less. The positive rate of IC of sera in which abnormal values were detected by autoimmune disease associated laboratory examinations was 50.0% in RA (2+), 20.4% in ANA (+), 60.0% in CH50 (less than 10), 41.7% in LE latex (+). In sera of RA (2+), the higher the value of CRP detected by a semi-quantitative analysis was, the higher the frequency having abnormal high IC values was. The number of IC positive sera, in which enzyme-linked immunoglobulins were detected, was 18 of 68 (positive rate 26.5%). The number of IC positive samples in asymptomatic carriers of sera, whose titer of anti-HTLV-I antibody was positive by gelatin particle agglutination assay (PA), was 14 of 67 (pos. rate 18.4%). All of these 14 samples were high positivity of anti-HTLV-I antibody (titer greater than or equal to 256 times). In urine of some patients with urogenital diseases, IC-like substances to show positive reaction by our CSP-EIA were detected. However, any positive reaction was not detected either by an anti-C1q- or an anti-C3d method. Studies are in progress to elucidate detailed characterization of the IC-like substances.

Synthesis and structure-activity relationships of N-substituted 2-[(2-imidazolylsulfinyl)methyl]anilines as a new class of gastric H+/K(+)-ATPase inhibitors.

A series of N-substituted 2-[(2-imidazolylsulfinyl)methyl]anilines (3) was synthesized and evaluated for its biological activity against gastric H+/K(+)-ATPase prepared from rabbit stomach and gastric acid secretions in Heidenhain pouch dogs. Monoalkyl substituents on the nitrogen atom of the aniline moiety markedly inhibited the enzyme activity to the same degree as omeprazole, a representative H+/K(+)-ATPase inhibitor. Most of these compounds, administered at 3 mg/kg i.v. inhibited histamine-stimulated gastric acid secretion. The inhibitory activity of these derivatives on the enzymes at pH 6.0 was more potent than that at pH 7.4, and was distinctly correlated to stability in aqueous solution at pH 5.0.

[Effects of IT-066, a new histamine H2-receptor antagonist, on gastric acid secretion and experimental gastric ulcers in rats and dogs].

We examined the effects of a new histamine H2-receptor antagonist, 3-amino-4-(4-[4-(1-piperidinomethyl)-2-pyridyloxy]-cis-2- butenylamino)-3- cyclobutene-1,2-dione hydrochloride (IT-066), on gastric acid secretion and the healing process of experimental ulcers in rats and dogs. Famotidine, a well-established H2-receptor antagonist, was used as the reference drug. Male Donryu rats (240-260 g) and Beagle dogs of both sexes (8-10 kg), having Heidenhain pouches, were used. IT-066 dose-dependently inhibited the basal gastric acid secretion of rats, and this inhibition significantly persisted for 12 hr. In addition, the agent significantly inhibited histamine-stimulated acid secretion in both normal rats and rats with acetic acid ulcers. IT-066, given p.o. twice daily for 2 and 3 weeks after ulceration, significantly accelerated both spontaneous and delayed healing (with indomethacin) of acetic acid-induced gastric ulcers in rats. The effects of IT-066 on acid secretion and ulcer healing were almost the same or slightly more potent than those observed with famotidine. IT-066, when given i.v. or p.o., dose-dependently inhibited the gastric acid secretion stimulated by histamine, pentagastrin, or carbachol in dogs. The antisecretory effects of the agent on histamine-stimulated acid secretion significantly persisted for more than 6 hr. These results indicate that IT-066 appears to be a promising antisecretory and anti-ulcer agent.