Role of HDL cholesterol in anthracycline-induced subclinical cardiotoxicity: a prospective observational study in patients with diffuse large B-cell lymphoma treated with R-CHOP.

OBJECTIVES: Anthracycline-induced cardiotoxicity is a debilitating cardiac dysfunction for which there are no effective treatments, making early prevention of anthracycline-induced subclinical cardiotoxicity (AISC) crucial. High-density lipoprotein cholesterol (HDL-C) plays a role in cardioprotection, but its impact on AISC remains unclear. Our study aims to elucidate the protective capacity of HDL-C in AISC in patients with diffuse large B-cell lymphoma (DLBCL) treated with R-CHOP (cyclophosphamide, vincristine, doxorubicin, prednisone and rituximab). DESIGN: Prospective observational study. SETTING: Conducted in China from September 2020 to September 2022. PARTICIPANTS: 70 chemotherapy-naïve patients newly diagnosed with DLBCL who were scheduled to receive the standard dose of R-CHOP; 60 participants included in a case-control study (DOI: 10.1186/s12885-022-10085-6). PRIMARY OUTCOME MEASURES: Serum biomarkers, 2D speckle tracking echocardiography and conventional echocardiography were measured at baseline, at the end of the third and sixth cycles of R-CHOP and 6 and 12 months after chemotherapy. RESULTS: 24 patients experienced AISC, while 10 did not. 36 patients were lost to follow-up and death. Cox regression analysis showed that higher levels of HDL-C were associated with a significantly lower risk of AISC (unadjusted HR=0.24, 95% CI 0.09 to 0.67, p=0.006; adjusted HR=0.27, 95% CI 0.09 to 0.79, p=0.017). Patients without AISC had a more stable and higher HDL-C level during the follow-up period. HDL-C levels significantly decreased from the end of the third cycle of chemotherapy to the end of the sixth cycle of chemotherapy in all patients (p=0.034), and particularly in the AISC group (p=0.003). The highest level of HDL-C was significantly higher in patients without AISC than in those with AISC (1.52±0.49 vs 1.22±0.29, p=0.034). CONCLUSIONS: Our study suggests that higher HDL-C levels may associate with lower AISC risk in patients with DLBCL treated with R-CHOP. HDL-C could be a cardioprotective target, but further research is needed to confirm its benefits and limitations. STUDY REGISTRATION NUMBER: Study registration number: ChiCTR2100054721.

Translation of paired box 6 (PAX6) mRNA is IRES-mediated and inhibited by cymarin in breast cancer cells.

Paired box 6 (PAX6) is a member of the PAX family and plays an essential role in cancer cell cycle progression, colony formation, proliferation and invasion. Its expression is upregulated in many cancers including breast cancer, but the process of PAX6 mRNA translation has rarely been studied. We found that PAX6 translation level increased in MCF-7 breast cancer cells treated with the chemotherapeutic drug adriamycin (ADM), which might be attributable to internal ribosome entry site (IRES)-mediated translation. By modifying a bicistronic luciferase plasmid that is widely used to examine IRES activity, we found that the 469-base 5'-UTR of PAX6 mRNA contains an IRES element and that core IRES activity is located between nucleotides 159 and 333. Moreover, PAX6 IRES activity was induced during ADM treatment, which may be the main reason for the elevated level of PAX6 protein. We also found that cymarin, a cardiac glycoside, acts as an inhibitor of PAX6 protein expression by impairing its IRES-mediated translation. Furthermore, MCF-7 cell proliferation was suppressed during treatment with cymarin. These results provide novel insights into the translation mechanism of PAX6 in breast cancer cells and suggest that cymarin is a promising candidate for the treatment of breast cancer via targeting the expression of PAX6.

Large-Scale Screening of Natural Products Transactivating Peroxisome Proliferator-Activated Receptor α Identifies 9S-Hydroxy-10E,12Z,15Z-Octadecatrienoic Acid and Cymarin as Potential Compounds Capable of Increasing Apolipoprotein A-I Transcription in Human Liver Cells.

Increasing apolipoprotein A-I (apoA-I), the predominant protein of high-density lipoprotein (HDL) particles, has favorable effects on atherogenic risk factors. Here, we investigated the effects of peroxisome proliferator-activated receptor α (PPARα) transactivating compounds on apoA-I transcription in HepG2 cells. A transient PPARα agonist transactivation assay was used to screen 2500 natural compounds. To analyze the effects on apoA-I transcription, human hepatocellular liver carcinoma (HepG2) were exposed to 0.1, 1, and 10 µg/mL of the natural PPARα transactivators. ApoA-I mRNA expression was determined by quantitative polymerase chain reaction. Extensive dose-response experiments were performed using compounds that increased apoA-I transcription by minimally 20%. Kelch-like ECH-associated protein 1 (KEAP) and carnitine palmitoyltransferase 1 alpha (CPT1α) expression were used respectively to confirm Bromodomain-containing protein 4 inhibition or PPARα activation. Twenty-eight natural compounds increased PPARα transactivation by at least twofold. Despite the increased CPT1α expression seen after the addition of most PPARα activating compounds, CPT1α expression and PPARα transactivation did not correlate. Addition of 0.05 µg/mL 9S-hydroxy-10E,12Z,15Z-octadecatrienoic acid (9(S)-HOTrE) increased apoA-I mRNA expression by 35%, whereas 10-25 µg/mL of cymarin increased apoA-I transcription by 37%. However, combining cymarin and 9(S)-HOTrE did not result in a synergistic effect, in contrast this combination even decreased apoA-I transcription. ApoA-I transcription involves multiple regulatory players, and PPARα transactivation alone is not sufficient. A search for natural compounds resembling the molecular structure of 9(S)-HOTrE or cymarin could aid to find additional components that increase apoA-I transcription.

Identification of cardiac glycoside molecules as inhibitors of c-Myc IRES-mediated translation.

Translation initiation is a fine-tuned process that plays a critical role in tumorigenesis. The use of small molecules that modulate mRNA translation provides tool compounds to explore the mechanism of translational initiation and to further validate protein synthesis as a potential pharmaceutical target for cancer therapeutics. This report describes the development and use of a click beetle, dual luciferase cell-based assay multiplexed with a measure of compound toxicity using resazurin to evaluate the differential effect of natural products on cap-dependent or internal ribosome entry site (IRES)-mediated translation initiation and cell viability. This screen identified a series of cardiac glycosides as inhibitors of IRES-mediated translation using, in particular, the oncogene mRNA c-Myc IRES. Treatment of c-Myc-dependent cancer cells with these compounds showed a decrease in c-Myc protein associated with a significant modulation of cell viability. These findings suggest that inhibition of IRES-mediated translation initiation may be a strategy to inhibit c-Myc-driven tumorigenesis.

A new pregnane glycoside and oligosaccharide from Parabarium huaitingii.

Two new compounds, along with two known compounds, were isolated from the barks of Parabarium huaitingii, and their structures were determined as 5α-pregn-6-ene-3ß,17α,20(S)-triol-20-O-ß-d-digitoxopyranoside (1), cymaropyranurolactone 4-O-ß-d-digitalopyranosyl-(1 â†’ 4)-O-ß-d-cymaropyranosyl-(1 â†’ 4)-O-ß-d-oleandropyranosyl-(1 â†’ 4)-O-ß-d-cymaropyranoside (2), 3ß,17α,20(S)-trihydroxy-5α-pregn-6-ene (3), and 5α-pregn-6-ene-3ß,17α,20(S)-triol-3-O-ß-d-digitalopyranoside (4) by spectroscopic methods.

Cardiotonic effect of Apocynum venetum L. extracts on isolated guinea pig atrium.

The effects on guinea-pig heart muscle of extracts of Apocynum venetum L. leaf, root, stem, old stem and Venetron--a polyphenol-rich extract of leaves--were studied by recording the mechanical activity and heart rate of isolated right atria. Cymarin--a cardiac glycoside--was also determined in A. venetum extracts by LC-MS/MS analysis. All extracts examined here showed a weak cardiotonic effect, i.e., induced a contractile response of the isolated atria and increased the pulse at a concentration of 1 mg/mL, which was not inhibited by propranolol (1 microM)-a beta-adrenoceptor blocker. The cymarin content in extracts of A. venetum was ranked as follows: old stem >> stem > root > leaf >> Venetron. Since the cardiotonic effects of A. venetum extracts did not reflect the cymarin content, a possible mechanism other than that of cardiac glycosides was investigated. The inhibitory effects on phosphodiesterase 3 (PDE3) were studied in a cell-free enzyme assay; all extracts of various parts of A. venetum inhibited PDE purified from human platelets. These results suggest that PDE3 inhibition may contribute to the cardiotonic effects of A. venetum extracts.

Inhibitory effect of Adonis amurensis components on tube-like formation of human umbilical venous cells.

Antiangiogenic activity-guided fractionation and isolation carried out on the methanol extract of Adonis amurensis led to the identification of three compounds, namely cymarin, cymarol, and cymarilic acid. Amongst the three compounds, cymarilic acid was isolated from this plant for the first time. This compound showed no significant cytotoxicity against tumor cell lines but was found to be strongly inhibitory toward tube formation induced by human umbilical venous endothelial (HUVE) cells. Cymarin and cymarol exhibited potent cytotoxicity against a human solid tumor cell line A549 (human lung carcinoma), while being inactive on murine leukemic cells (L1210).

Properties of palytoxin-induced whole cell current in single rat ventricular myocytes.

We examined the properties of the current induced by palytoxin in single ventricular cells of rats. The current was measured by a whole cell voltage clamp method. When the cell was held at -75 mV, palytoxin induced a sustained inward current in a concentration-dependent manner (2-100 pmol/l). The time-course of the inward current paralleled that of the depolarization. At a holding potential of +50 mV, it caused an outward current. Palytoxin-induced current reversed at 0 mV and its current-voltage relation was almost linear at either negative or positive voltage. Substitution of external NaCl with choline-Cl suppressed the palytoxin-induced inward current but not the outward current, by shifting the reversal potential to levels more negative than -50 mV. A cardiac glycoside, cymarin (10 and 100 mumol/l) partially inhibited the palytoxin-induced current without changing the reversal potential, only when applied before palytoxin. Palytoxin decreased the nicardipine-sensitive Ca2+ current. These data suggest that palytoxin-induced inward current is carried by extracellular Na+ and the outward current is carried mainly by intracellular K+, and that the inward current is responsible for the toxin's depolarizing action. The antagonism by cysmarin indicates that the site of action of palytoxin is in the vicinity of the binding site of cardiac glycosides.

[Determination of zimarin in urine]. / Opredelenie tsimarina v moche.

Private technique of extraction isolation and purification, chromatographic detection and photometric determination of zimarin in urine is suggested. Detection limit is 0.01 mg, determination limit is 0.1 mg of glycoside in 100 ml of urine. Method makes it possible to detect 66-80% of zimarin added to 100 ml of urine in quantities 0.5-0.1 mg.

Preparation and evaluation of technetium-99m labeled cardiac glycoside derivatives as potential myocardial imaging agent.

Three cardiac glycosides, two natural, cymarin and convallotoxin and one synthetic, strophanthidin-beta-D-glucoside were converted to their thiosemicarbazone and subsequently radiolabeled with 99mTc by chelation. The resulting radioactive chelate complexes were evaluated in animals to determine the suitability of this class of compounds for myocardial imaging. It was observed from the animal biodistribution data of the three radioactive compounds, there was a considerable variation in the heart to non-target organ uptake ratio. A possible explanation of this variation was offered in the light of their lipophilic character, protein binding ability and affinity towards non-target receptors. It is anticipated that this study may help to develop a 99mTc-cardiac glycoside complex with better distribution characteristics, and such a compound may offer a suitable alternative to 201Tl, which is at present used for myocardial imaging.

Absorption, metabolism and elimination of strophanthus glycosides in man.

In 33 healthy male volunteers, given a single oral and intravenous dose of cymarin (k-strophanthin-alpha), k-strophanthoside (k-strophanthin-gamma) and ouabain (g-strophanthin), enteral absorption and renal excretion of these glycosides and their metabolites were investigated by radioimmunoassay and HPLC. Cymarin was absorbed at 47% of the given dose. After intravenous injection 46% and after oral administration 21% of the given dose, i.e. the total amount as detected by radioimmunoassay which consisted of the unchanged glycoside and its metabolites, were excreted by the kidneys mainly as conjugated metabolites. The half-life of elimination, calculated from the total excreted amount was 13 h (i.v.) and 23 h (p.o.), respectively. k-Strophanthoside was absorbed at 16% of the given dose. After i.v.-injection 73% of the given dose was excreted by the kidneys with a half-life of elimination of 99 h. From this total amount about 70% was excreted as the unchanged drug, the remaining 30% as various metabolites. After oral administration 11% of the given dose were excreted with a half-life of elimination of 22 h. 80% of this amount consisted mainly of conjugated k-strophanthoside and conjugated metabolites as k-strophanthin-beta, cymarin, k-strophanthidin, cymarol and k-strophanthidol. Only 6% was excreted as the unchanged drug. Ouabain was absorbed after oral administration to a minimum of 1.4%. Given intravenously a total renal excretion of 33% of the given dose with a half-life of elimination of 23 h was measured. Of this 80% was unchanged ouabain.(ABSTRACT TRUNCATED AT 250 WORDS)

[Pharmacologic modification of diastolic ventricular function in patients with coronary heart disease]. / Pharmakologische Beeinflussung der diastolischen Ventrikelfunktion bei Patienten mit koronarer Herzkrankheit.

The influence of 2 different cardiac pharmaceutics on the diastolic ventricular function (VF) in patients with ischaemic heart disease was examined. Diltiazem, a calcium antagonist, and k-strophanthine led to a reduction of time constant T of the isovolumic relaxation from 49 +/- 9 to 39 +/- 7 msec (p less than 0.005), to an increase of the quotient dt/T from 2.4 +/- 0.5 to 3.0 +/- 0.6 msec (p less than 0.01), to an increase of the peak filling rate (PFR) from 2.08 +/- 0.65 EDV/sec to 2.34 +/- 0.67 EDV/sec (p less than 0.001), to an increase of the filling fraction (FF) from 30 +/- 12% to 33 +/- 15% (p less than 0.001). The ejection fraction (EF) and the maximum rise of pressure dp/dt did not change significantly. After k-strophanthine T was reduced from 49 +/- 7 to 46 +/- 11 msec (p less than 0.05). The increase of dt/T from 2.5 +/- 0.4 to 2.7 +/- 0.4 msec was not significant. The PFR with 2.16 +/- 0.7 and 2.08 +/- 0.8 EDV/sec and the FF with 32 +/- 14 and 34 +/- 18% did not show any significant changes. The EF rose from 52 +/- 15 to 55 +/- 16 (p less than 0.05) and dp/dt rose from 1855 +/- 468 to 2124 +/- 591 (p less than 0.05). Diltiazem improves the diastolic VF without deteriorating the systolic VF in patients with ischaemic heart disease. K-strophanthine improves the systolic VF and the velocity of the isovolumic relaxation. The other variables of the diastolic VF did not show any directed changes.

Mechanism whereby ouabain inhibits human T lymphocyte activation: effect on the interleukin 2 pathway.

Through the blockade of the Na-K-ATPase, ouabain inhibits several biochemical and biological events leading to the proliferation of activated lymphocytes. Since we already found that interleukin 1 production was not prevented by ouabain, we investigated by which mechanism this drug inhibits mitogen-induced human T lymphocyte activation, with respect to the interleukin 2 (IL 2) pathway. Our data revealed that at concentrations lower than 0.2 microM, IL 2 accumulation was not reduced in ouabain-treated cultures, even when cell proliferation was completely inhibited (0.1-0.2 microM ouabain). Moreover, in this concentration range, ouabain stimulated in a dose-dependent manner the accumulation of IL 2 in the supernatant of Con A-stimulated lymphocytes (optimum for 0.05 microM corresponding to half inhibition of lymphocyte proliferation). Such an effect, which appears correlated to the inhibition of Na-K-ATPase, suggests a failure of the cell to utilize IL 2. At concentrations higher than 0.3 microM, ouabain inhibited both lymphocyte proliferation and IL 2 production. These observations show that the glycosteroid interacts differently with the different cell populations involved in the cascade of reactions leading to cell proliferation, and suggest that the mitogenic inhibition resulting from the blockade of Na-K-ATPase is not related to the blockade of IL 2 production. On the other hand, we observed that: ouabain inhibited the expression of the receptors for IL 2, an obligatory step in lymphocyte proliferation; ouabain blocked the proliferation of an IL 2 sensitive human T cell line; in both cases the inhibition paralleled that of lymphocyte proliferation. Our data suggest that the essential steps of lymphocyte proliferation in which Na-K-ATPase-dependent K+ fluxes play a critical role are the expression of IL 2 receptors and the IL 2-dependent proliferative step.

Voltage dependence of the rheogenic Na+/K+ ATPase in the membrane of oocytes of Xenopus laevis.

Electrophysiological experiments were performed to analyze the Na+/K+-ATPase in full-grown prophase-arrested oocytes of Xenopus laevis. If the Na+/K+-ATPase is inhibited by dihydroouabain (DHO), the resting potential of the membrane of Na+-loaded oocytes may depolarize by nearly 50 mV. This hyperpolarizing contribution to the resting potential depends on the degree of activation of the Na+/K+-ATPase and varies with intracellular Na+ activity (aiNa) and extracellular K+ (K+o). It is concluded that variations of aiNa among different oocytes are primarily responsible for the variations of resting potentials measured in oocytes of X. laevis. Under voltage-clamp conditions, the DHO-sensitive current also exhibits dependence on aiNa that may be described by a Hill equation with a coefficient of 2. This current will be shown to be identical with the electrogenic current generated by the 3Na+/2K+ pump. The voltage dependence of the pump current was investigated at saturating values of aiNa (33 mmol/liter) and of K+o (3 mmol/liter) in the range from -200 to +100 mV. The current was found to exhibit a characteristic maximum at about +20 mV. This is taken as evidence that in the physiological range at least two steps within the cycle of the pump are voltage dependent and are oppositely affected by the membrane potential.

Activatory effect of two cardioglycosides on Cavia cobaya kidney Na+/K+-ATPase activity.

Ouabain and K-strophanthoside promote an enhancement of Na+/K+-ATPase activity in a range of cardioglycoside concentrations from 100 nM to 100 pM, with a maximum (+30%) between 10 and 4 nM. Binding experiments with [3H]ouabain show upward-curved Scatchard plots and evidence two intrinsic affinity constants for the ligand: (a) High-affinity constant: 350 nM (microsomes) and 15 nM (purified enzyme). (b) Low-affinity constant: 2100 nM (microsomes) and 890 nM (purified enzyme). The reaction velocity trend indicates that at ouabain concentrations higher than 20 nM but lower than the minimal inhibiting level, the enhanced reaction velocity is tending towards the control values.