PL201, a Reported Rhamnoside Against Alzheimer's Disease Pathology, Alleviates Neuroinflammation and Stimulates Nrf2 Signaling.

Neuroinflammation induced by overactivated glia cells is believed to be a major hallmark of Alzheimer's disease (AD) and a hopeful target against AD. A rhamnoside PL201 was previously reported to promote neurogenesis and ameliorate AD, and in this study, we revealed that PL201 also significantly reduced accumulation of the activated microglia and proinflammatory cytokines in APP/PS1 mice. In vitro, PL201 consistently suppressed the microglia induction of proinflammatory cytokines after stimulation with lipopolysaccharides and Aß42. Further mechanistic studies demonstrated that PL201 considerably enhanced the expression level and the nuclear translocation of Nrf2, a key regulator of neuroinflammation. Moreover, PL201 effectively stimulated Nrf2 signaling cascade, including upregulation of HO-1 and downregulation of NF-κB pathway. Thus, our findings indicated the anti-neuroinflammatory effect by PL201 in vivo and suggested that PL201 or the like, with multiple functions such as neurogenesis, mitochondria maintenance, and anti-neuroinflammation, could be a promising candidate in AD treatment.

A Newly Synthesized Rhamnoside Derivative Alleviates Alzheimer's Amyloid-ß-Induced Oxidative Stress, Mitochondrial Dysfunction, and Cell Senescence through Upregulating SIRT3.

Oxidative stress-induced mitochondrial dysfunction and cell senescence are considered critical contributors to Alzheimer's disease (AD), and oxidant/antioxidant imbalance has been a therapeutic target in AD. SIRT3 is a mitochondrial protein regulating metabolic enzyme activity by deacetylation and its downregulation is associated with AD pathology. In the present study, we showed that a newly synthesized rhamnoside derivative PL171 inhibited the generation of reactive oxidant species (ROS) induced by amyloid-ß 42 oligomers (Aß 42O), major AD pathological proteins. Moreover, the reduction of mitochondrial membrane potential (MMP) and the impairment of mitochondrial oxygen consumption triggered by Aß 42O were also prevented by PL171. Further experiments demonstrated that PL171 reduced the acetylation of mitochondrial proteins, and particularly the acetylation of manganese superoxide dismutase (MnSOD) and oligomycin-sensitivity-conferring protein (OSCP), two mitochondrial SIRT3 substrates, was suppressed by PL171. Mechanism studies revealed that PL171 upregulated SIRT3 and its upstream peroxisome proliferator-activated receptor-γ coactivator 1α (PGC-1α) under basal and Aß 42O-treated conditions. The inhibition of SIRT3 activity could eliminate the protective effects of PL171. Further, long-term treatment with Aß 42O increased the number of senescent neuronal cell, which was also alleviated by PL171 in a SIRT3-dependent manner. Taken together, our results indicated that PL171 rescued Aß 42O-induced oxidative stress, mitochondrial dysfunction, and cell senescence via upregulating SIRT3 and might be a potential drug candidate against AD.

Synthesis and cytotoxic activity of G3 PAMAM-NH(2) dendrimer-modified digoxin and proscillaridin A conjugates in breast cancer cells.

The objective of this study was to determine the cytotoxicity, antiproliferative activity, and apoptosis induction activity of two modified glycosides - digoxin and proscillaridin A - conjugated to a generation 3 polyamidoamine dendrimer (G3 PAMAM-NH(2)) in human breast cancer cells. The results suggest that conjugation with the G3 PAMAM-NH(2) dendrimer enhances the cytotoxicity of modified digoxin and proscillaridin Aboth in MCF-7 and in MDA-MB-231 breast cancer cells. Additionally, the conjugate-induced apoptosis was significantly greater than apoptosis evoked by free modified digoxin and proscillaridin A.

Cardiac glycoside-induced elevation of intracellular Na+ ion concentration in human erythrocytes studied by 23Na NMR spectroscopy: relationship between inotropy speed and elevation rate of intracellular Na+ ion concentration.

Elevation of intracellular sodium ion concentration in human erythrocyte induced by the cardiac glycoside, proscillaridin, and its four derivatives was measured using 23Na NMR spectrometry. In this examination, there was a significant correlation between the time to half maximum inotropic effect and the time to maximum of Na+ concentrations in human erythrocyte, determined by 23Na NMR.

[Studies on cardiac ingredients of plants. X. Preparation of nitrates of tetrahydroproscillaridin and their pharmacological activities].

To reduce the vascular contracting effect of the hydrogenated cardiac glycosides, 20-(R)- and 20-(S)-tetrahydroproscillaridins (THPs, 1a, 1b), and to extend the concentration-dependent range, mono- and dinitrates of THPs were prepared. The pharmacological activities of the nitrates of THP were evaluated by use of isolated guinea-pig papillary muscle preparations and Na+,K(+)-adenosine triphosphatase preparations from dog kidney. Furthermore, the effect for smooth muscle was examined using the helical strips isolated from 13-week-old spontaneously hypertensive rat. The positive inotropic effects of mononitrates (11a, 11b, 2a, 2b, 8a, and 8b) were more potent than those of THPs. Nitration of the sugar moiety in THPs resulted in a vascular relaxing effect unobserved in the case of THPs.

Studies on cardiac ingredients of plants. IX. Chemical transformation of proscillaridin by utilizing its 1,4-cycloadducts as key compounds and biological activities of their derivatives.

Three aromatic compounds (2-4) possessing a carbomethoxyl group or a dimethoxyphthaloyl group, prepared by the Diels-Alder reaction of the cardiac glycoside, proscillaridin (1), with dimethyl acetylenedicarboxylate and methyl propiolate, were transformed into alcohols, carboxylic acids and amides. The biological activities of the resulting derivatives were evaluated by the use of Na+, K(+)-adenosine triphosphatase (Na+,K(+)-ATPase) from dog kidney and isolated guinea-pig papillary muscle. Although the biological activities of the resulting derivatives were less potent than that of 1, a para-substituted benzylalcohol (5), methylbenzamides (9a and 10a), and ethylbenzamides (9b and 10b) inhibited the activity of Na+,K(+)-ATPase almost as potently as naturally occurring cardiac glycosides such as digoxin and digitoxin.

Studies on cardiac ingredients of plants. VII: Chemical transformation of proscillaridin by means of the Diels-Alder reaction and biological activities of its derivatives.

The Diels-Alder reactions of a cardiac glycoside, proscillaridin (1), with some dienophiles were investigated. The reaction of 1 with alkenes such as methyl vinyl ketone and methyl acrylate afforded 3-oxo-2-oxabicyclo[2.2.2]oct-7-enes (2-5) and para-substituted benzene derivatives (6 and 7), while 1 reacted with alkynes (3-butyn-2-one, methyl propiolate) to yield para- or meta-substituted benzene derivatives (6-9). The biological activities of the resulting derivatives were evaluated by the use of isolated guinea-pig papillary muscle preparations and Na+,K(+)-adenosine triphosphatase (ATPase) preparation from dog kidney. Among the proscillaridin derivatives, compounds 4 and 7 moderately inhibited Na+,K(+)-ATPase activity. Furthermore, the concentration range of 7 over which its positive inotropic effect on guinea-pig papillary muscle preparations, increased from 5% to 95% of maximum was broader than that of 1, i.e., concentration dependency was maintained over a greater range of concentration.

The bioavailability of methylepoxyproscillaridin (P35): a new semisynthetic cardiac glycoside.

The pharmacokinetic data of methylepoxyproscillaridin (3'-methyl-4'-5'-epoxyproscillaridin) (P35) after 1 mg i.v. or oral administration in two different galenic preparations (hard and soft gelatin capsules) in randomized succession were studied in 9 healthy volunteers, showing a bioavailability of 88 +/- 10.5% (soft gelatin capsule) and 81 +/- 12% (hard gelatin capsule). The half-life of P35 was calculated to be 80 +/- 13.3 h.

Hemodynamic effect of methylepoxyproscillaridin (P35) in patients with congestive myocardiopathy.

The hemodynamic effect of methylepoxyproscillaridin (3'-methyl-4'-5'-epoxy-proscillaridin) (P35) was studied according to the Swan Ganz thermodilution method in 6 patients with latent cardiac insufficiency. Both at rest and under ergometer exercise, the stroke volume and the systolic blood pressures increased under P35. Moreover, under physical exercise the heart rate decreased significantly, while cardiac output increased. The hemodynamic effect of P35 can therefore be regarded as typical of cardiac glycosides.

[Studies on cardiac ingredients of plants (IV). Effect of reduced proscillaridins on guinea-pig hearts].

Five hydrogenated proscillaridins (bufa-4,20-dienolide (PH21), bufa-4,20 (22)-dienolide (PH22), 20R-bufa-4-enolide (PH4-R), 20S-bufa-4-enolide (PH4-S), chola-4-enoate (PH4-E) ) were prepared semi-synthetically, and their pharmacological effect was studied using guinea pigs. The positive inotropic effect (PIE) was examined in papillary muscles isolated from guinea-pig hearts. These compounds produced PIE, dose-dependently; the Dose-PIE curve was characterized by a faster PIE development than that by the parent compound proscillaridin (PS). The concentrations at which half maximum PIE just developed (pD2) were as follows: PS, 7.4; PH22, 6.2; PH21, 5.8; PH4-R, 5.3; PH4-E, 5.0; and PH4-S, 4.9. The time required to the half maximum effect (T50) at a given concentration of pD2 was measured in min: PS, 33; PH4-E, 22; PH22, 15; PH21, 7; PH4-S, 7; and PH4-R, 2. The speeds of inotropy of these compounds depended on the position of lactone ring reduction, though they have the same lipophilicity (Rm). Concentration-PIE curves of reduced PS-compounds were characterized by a decrease in potency and an increase in efficacy. PH21 and PH4-R produced PIE over wider range of concentrations than those of the other compounds. When PH21 at the dose of 11.9 mg/kg, an equivalent dose of 4.4 times the pD2 values, was administrated intravenously by bolus injection into guinea pigs, no arrhythmias were observed on the ECG.(ABSTRACT TRUNCATED AT 250 WORDS)

A comparative dose-effect study with cardiac glycosides assessing cardiac and extracardiac responses in normal subjects.

We tested the hypothesis that differences exist in the pharmacodynamic pattern of different cardiac glycosides. We conducted a randomized, placebo-controlled study in normal volunteers and evaluated the effects of weekly increased oral dosing of digoxin (n = 10; from 0.25 to 1.0 mg/day), meproscillarin (n = 10; from 0.5 to 2.0 mg/day), and placebo (n = 5). To determine the glycoside effects, corrected electromechanical systole (QS2c) was used to measure inotropy and the PQ interval to test dromotropy. Red-green discrimination and critical flicker fusion (CFF) assessed visual functions. Subjective complaints were collected using rating lists. Both glycosides dose dependently shortened QS2c and prolonged PQ interval. PQ prolongations over +20 ms occurred in seven of 10 digoxin subjects, in two of 10 meproscillarin, and in one of five placebo. Equi-inotropic response, identified at 12 ms mean QS2c shortening, revealed the relative potency of digoxin to be 2.4 times higher than meproscillarin; this ratio increased to sevenfold for equi-effective negative dromotropic effects at 12 ms mean PQ prolongation. Each drug was associated with a dominant subjective complaint: digoxin with anergy and meproscillarin with diarrhea. Red-green discrimination was better under meproscillarin and CFF was depressed by digoxin. The results indicate that pharmacodynamic differences exist between cardiac glycosides. A differential use of various glycosides should be considered and tested clinically.

[Plasma concentration and elimination behavior of the cardiac glycoside meproscillarin in patients with liver cirrhosis]. / Plasmakonzentration und Eliminationsverhalten des Herzglykosids Meproscillarin bei Patienten mit Leberzirrhose.

During a one week period patients with liver cirrhosis and a control group were treated with a repeated dosage of the new heart glcoside Meproscillarin. After achieving a steady state in plasma level the same Meproscillarin plasma levels were found among both groups. Compared with the control group no difference was detected in the elimination rate of Meproscillarin in patients with liver cirrhosis, which means a complex disturbed liver function. Nevertheless the greater variance of the Meproscillarin plasma levels in the patients with liver cirrhosis in comparison with the controls means a diminished predictability of the therapeutic success in the cirrhosis group. With this limitation Meproscillarin can be used therapeutically in patients with liver cirrhosis, because a toxic accumulation is not to be expected.

[Threshold of action of meproscillarin following intravenous administration]. / Wirkungseintritt von Meproscillarin nach intravenöser Applikation.

A placebo-controlled double-blind trial was conducted, to determine the onset of effect of Meproscillarin (injected intravenously). 28 days apart six healthy volunteers were given double-blind 1,0 mg Meproscillarin or placebo and 60 days later 0,6 mg Digoxin, each drug as short infusion over four minutes. The total electromechanical systole corrected for heart rate (QS2c), was used as criterion of the inotropic effect of the glycoside. After placebo there no changes were observed over a period of two hours. Both glycosides shortened QS2c for about--16 ms. From Meproscillarin a 40% higher dosis was required, to achieve the same effect as with digoxin. After use of Meproscillarin the peak effect was reached after ten minutes; after digoxin a period of 60--120 minutes were required. The results show that intravenously given Meproscillarin is a fast acting glycoside.

[Meproscillarin in patients with renal failure and concomitant heart failure (author's transl)]. / Meproscillarin bei gleichzeitiger Nieren- und Herzinsuffizienz. Wirkungund Plasmakonzentration bei Dauernwendung.

Meproscillarin is a glycoside with a high bioavailability (about 70%) and an elimination independent of the renal function. It was to be investigated whether a good cardiac effectiveness can be demonstrated during oral long-term application of meproscillarin to patients with renal failure. 29 patients with renal failure of varying degree and concomitant heart failure were daily given an oral dose of 0.75 mg of meproscillarin over 14 days. The effectiveness of the glycoside was measured as change of the electromechanical systole (QS2c) and the quotient of the diameter of heart and thorax (C/T) from the 1st--15th day. The plasma levels of the glycoside were determined on the 1st, 8th, and 15th day. There was a significant shortening of QS2c (by mean = 27 ms, P less than 0.005) and a marked decrease in the size of the heart (P less than 0.0025); heart rate and PQ-interval were only insignificantly influenced. Plasma levels of 0.95 ng/ml were found after 8 days of treatment compared to 1.25 ng/ml after 15 days. As the pharmacokinetics of the glycoside is practically not influenced by the renal function, meproscillarin represents an alternative in the treatment of patients with heart failure and impaired renal function.

[14,15-beta-oxido analog of proscillaridin (HOE 040). A new cardiac glycoside with low arrhythmic activity and greater absorption ratio]. / Das 14,15-beta-Oxido-Analoge des Proscillaridins (HOE 040) Ein neues Herzglykosid mit geringer Arrhythmie-Wirkung und hoher Resorptionsquote.

The 14,15-beta-oxido analogue of proscillaridin A (HOE 040), in a dose 4 times higher showed equally positive-inotropic effect on the isolated guinea pig heart as did proscillaridin A. In the dog in vivo HOE 040 was equally positive-inotropic, as measured by the increase of dp/dt of the left ventricle of the heart, as proscillaridin A. In combination with aconitine, HOE 040 also in 4fold higher dose caused less cardiac fibrillation on the isolated guinea pig heart than did proscillaridin A. The dose of HOE 040 which by infusion in the guinea pig in vivo precipitates cardiac arrhythmias was 4 times higher than that of proscillaridin A, the lethal dose was 5 times higher. In dogs in vivo the dose of HOE 040 by infusion causing prolongation of PQ or cardiac arrhythmias, resp., was twice the dose necessary of proscillaridin A, the lethal dose was nearly 5 times higher. The decrease of cardiac activity in Rhesus monkeys amounted to 69% in 24 h, whereas proscillaridin A decreased cardiac activity only by 41% in 24 h. The absorption of HOE 040 from the duodenum of dogs anesthetized with pentobarbital amounted to 72%, whereas proscillaridin A is observed by only between 14 and 25%. The concentration of the drug HOE 040 in hearts of rats was twice, in the hearts of dogs 3 fold that of proscillaridin A. The concentrations of both drugs in the brain of rats and dogs were not different. In the biochemical test system in vitro the blocking effect of both drugs on the Na+K+-ATPase of ox brain was not different.

[Effect of proscillaridin-4'-methylether on pressure rise velocity in the left ventricle of patients with coronary heart disease (author's transl)]. / Die Wirkung von Proscillaridin-4'-methyläther auf die maximale Druckanstiegsgeschwindigkeit im linken Ventrikel von Patienten mit Coronarinsuffizienz.

In a randomized, controlled, double-blind study 2 groups of 7 patients each with coronary heart disease received either 1 mg methylproscillaridin (MP) a cardiac glycoside of the squill intravenously, or placebo to test the inotropic effect of MP. Pressures and dp/dt max were measured in the left ventricle before and after coronary angiography after an average of 62 min (60 to 70 min). There was a significant (p less than 0.05) increase of dp/dt max in the MP-group (Wilcoxon-Mann-Whitney test). Left ventricular enddiastolic pressure was decreased from 16.1 to 13.6 mm Hg in the MP-group, and increased in theplacebo group from 12 to 13.7 mm Hg (mean values). Thus, a positive inotropic effect of the glycoside may be assumed.

Stability in vitro of methylproscillaridin.

The in vitro stability of methylproscillaridin has been compared with that of proscillaridin, the activities of the glycosides being assayed by the 86Rb-technique. After incubation in gastric juice at pH 1,2, and 3, the activity half life of each glycoside was proportional to pH and was approximately 0.25 h, 2.5 h, and 25 h, respectively. The inactivation rate in pure hydrochloric acid at pH 2 did not differ from that in gastric juice of the same pH. The glycosides were stable in bile and enteric juice. In faeces, methylproscillaridin was stable and proscillaridin was inactivated with a half life of 32 h. It is concluded that the difference in biological availability between the two glycosides cannot be explained by differences in gastrointestinal stability.

Pharmacokinetics and pharmacodynamics of methyl proscillaridin in healthy man.

The aim of this study was to obtain data about the pharmacological properties of a new glycoside derivative in man. Plasma concentrations and ECG parameters were measured after oral and intravenous administration of a single dose of 1.2 mg methyl proscillaridin in 16 healthy volunteers, using a strictly randomized, two-period change-over design. Glycoside concentrations were measured using a modified 86Rb-erythrocyte-assay. QT-duration, corrected for frequency (QTc), was the principal variable measured in the ECG. By either route, there was a maximum plasma level after 1 hour, which had decreased to a minimum at 3 hours, followed by a second peak at 4 to 10 hours (orally greater than iv). From 10 to 72 hours the concentrations decreased with a median t 1/2 of 23.3 hours (iv) and 33.0 hours (orally). Comparison of the ratio of plasma concentrations following oral and iv administration resulted in a bioavailability of 69% using the 48 hour plasma levels, and 59% using the areas under the concentration-time curves. The mean QTc was maximally shortened to 28 msec at 1 hour after iv and to 19 msec at 10 hours after the oral dose. A distinct similarity between time-concentration and time-QTc curves was seen after the initial distribution phase, both after oral and intravenous administration. The new derivative shows a rapid elimination. Its bioavailability is reasonably high.