Mechanical effects of liriodenine on the left ventricular-arterial coupling in Wistar rats: pressure-stroke volume analysis

Screening an In-House Isoquinoline Alkaloids Library for New Blockers of Voltage-Gated Na+ Channels Using Voltage Sensor Fluorescent Probes: Hits and Biases

Voltage-gated Na⁺ (Na_V) channels are significant therapeutic targets for the treatment of cardiac and neurological disorders, thus promoting the search for novel Na_V channel ligands. With the objective of discovering new blockers of Na_V channel ligands, we screened an In-House vegetal alkaloid library using fluorescence cell-based assays. We screened 62 isoquinoline alkaloids (IA) for their ability to decrease the FRET signal of voltage sensor probes (VSP), which were induced by the activation of Na_V channels with batrachotoxin (BTX) in GH3b6 cells. This led to the selection of five IA: liriodenine, oxostephanine, thalmiculine, protopine, and bebeerine, inhibiting the BTX-induced VSP signal with micromolar IC₅₀. These five alkaloids were then assayed using the Na⁺ fluorescent probe ANG-2 and the patch-clamp technique. Only oxostephanine and liriodenine were able to inhibit the BTX-induced ANG-2 signal in HEK293-hNa_V1.3 cells. Indeed, liriodenine and oxostephanine decreased the effects of BTX on Na⁺ currents elicited by the hNa_V1.3 channel, suggesting that conformation change induced by BTX binding could induce a bias in fluorescent assays. However, among the five IA selected in the VSP assay, only bebeerine exhibited strong inhibitory effects against Na⁺ currents elicited by the hNav1.2 and hNav1.6 channels, with IC₅₀ values below 10 µM. So far, bebeerine is the first BBIQ to have been reported to block Na_V channels, with promising therapeutical applications.

Pyridoxamine protects against mechanical defects in cardiac ageing in rats: studies on load dependence of myocardial relaxation

New Findings

Our team demonstrated in the past that pyridoxamine attenuated arterial stiffening by targeting the pathogenic formation of glycated collagen cross-links in aged rats. Herein, we examined whether pyridoxamine therapy can protect against mechanical defects in myocardial relaxation by improving arterial wave properties and cardiac contractile performance in senescent animals. Fifteen-month-old male Fisher 344 rats were treated daily with pyridoxamine (1 g l⁻¹ in drinking water) for 5 months and compared with age-matched untreated control animals (20 months old). Arterial wave properties were characterized by wave transit time (τ_w) and wave reflection factor (R_f). We measured the contractile status of the myocardium in an intact heart as the left ventricular (LV) end-systolic elastance (E_es). Myocardial relaxation was described according to the time constant of the LV isovolumic pressure decay (τ_e). Pyridoxamine therapy prevented the age-associated prolongation in LV τ_e and the diminished E_es in senescent rats. The drug also attenuated the age-related augmentation in afterload imposed on the heart, as evidenced by the increased τ_w and decreased R_f. We found that the LV τ_e was significantly influenced by both the arterial τ_w and R_f (τ_e = 16.3902 + 8.3123 × R_f − 0.4739 × τ_w; r = 0.7048, P < 0.005). In the meantime, the LV τ_e and the LV E_es showed a significant inverse linear correlation (τ_e = 13.9807 − 0.0068 × E_es; r = 0.6451, P < 0.0005). All these findings suggested that long-term treatment with pyridoxamine might ameliorate myocardial relaxation rate, at least partly through its ability to enhance myocardial contractile performance, increase wave transit time and decrease wave reflection factor in aged rats.

Ethnobotany, phytochemistry and pharmacology of Stephania rotunda Lour

ETHNOPHARMACOLOGICAL RELEVANCE

Stephania rotunda Lour. (Menispermaceae) is an important traditional medicinal plant that is grown in Southeast Asia. The stems, leaves, and tubers have been used in the Cambodian, Lao, Indian and Vietnamese folk medicine systems for years to treat a wide range of ailments, including asthma, headache, fever, and diarrhoea.

AIM OF THE REVIEW

To provide an up-to-date, comprehensive overview and analysis of the ethnobotany, phytochemistry, and pharmacology of Stephania rotunda for its potential benefits in human health, as well as to assess the scientific evidence of traditional use and provide a basis for future research directions.

MATERIAL AND METHODS

Peer-reviewed articles on Stephania rotunda were acquired via an electronic search of the major scientific databases (Pubmed, Google Scholar, and ScienceDirect). Data were collected from scientific journals, theses, and books.

RESULTS

The traditional uses of Stephania rotunda were recorded in countries throughout Southeast Asia (Cambodia, Vietnam, Laos, and India). Different parts of Stephania rotunda were used in traditional medicine to treat about twenty health disorders. Phytochemical analyses identified forty alkaloids. The roots primarily contain l-tetrahydropalmatine (l-THP), whereas the tubers contain cepharanthine and xylopinine. Furthermore, the chemical composition differs from one region to another and according to the harvest period. The alkaloids exhibited approximately ten different pharmacological activities. The main pharmacological activities of Stephania rotunda alkaloids are antiplasmodial, anticancer, and immunomodulatory effects. Sinomenine, cepharanthine, and l-stepholidine are the most promising components and have been tested in humans. The pharmacokinetic parameters have been studied for seven compounds, including the three most promising compounds. The toxicity has been evaluated for liriodenine, roemerine, cycleanine, l-tetrahydropalmatine, and oxostephanine.

CONCLUSION

Stephania rotunda is traditionally used for the treatment of a wide range of ailments. Pharmacological investigations have validated different uses of Stephania rotunda in folk medicine. The present review highlights the three most promising compounds of Stephania rotunda, which could constitute potential leads in various medicinal fields, including malaria and cancer.

Aminoguanidine prevents fructose-induced deterioration in left ventricular-arterial coupling in Wistar rats

BACKGROUND AND PURPOSE

Aminoguanidine (AG), an inhibitor of advanced glycation endproducts, has been identified as a prominent agent that prevents the fructose-induced arterial stiffening in male Wistar rats. Our aims were to examine whether AG produced benefits on the left ventricular (LV)-arterial coupling in fructose-fed (FF) animals in terms of the ventricular and arterial chamber properties.

EXPERIMENTAL APPROACH

Rats given 10% fructose in drinking water (FF) were daily treated with AG (50 mg x kg(-1), i.p.) for 2 weeks and compared with the untreated FF group. In anaesthetised rats, LV pressure and ascending aortic flow signals were recorded to calculate LV end-systolic elastance (E(es), an indicator of myocardial contractility) and effective arterial volume elastance (E(a)). The optimal afterload (Q(load)) determined by the ratio of E(a) to E(es) was used to measure the coupling efficiency between the left ventricle and its vasculature.

KEY RESULTS

There was a significant interaction between fructose and AG in their effects on E(a). Fructose loading significantly elevated E(a) and AG prevented the fructose-derived deterioration in arterial chamber elastance. Both fructose and AG affected E(es) and Q(load), and there was an interaction between fructose and AG for these two variables. Both E(es) and Q(load) exhibited a decline with fructose feeding but showed a significant rise after AG treatment in the FF rats.

CONCLUSIONS AND IMPLICATIONS

AG prevented not only the contractile dysfunction of the heart caused by fructose loading, but also the fructose-induced deterioration in matching left ventricular function to the arterial system.

Aminoguanidine prevents age-related deterioration in left ventricular-arterial coupling in Fisher 344 rats

In recent studies, aminoguanidine (AG), an inhibitor of advanced glycation endproducts, has been identified as a prominent agent that can prevent the age-related aortic stiffening and cardiac hypertrophy. The aim of this study was to determine whether AG had effects on the left ventricular (LV)-arterial coupling in aged Fisher 344 rats in terms of the ventricular and arterial chamber properties. Normotensive rats were treated from 18 to 24 months with AG (1 g l(-1) in drinking water) and compared with a control group. LV pressure and ascending aortic flow signals were recorded to construct the ventricular and arterial end-systolic pressure-stroke volume relationships to calculate LV end-systolic elastance (Ees) and effective arterial volume elastance (Ea), respectively. The optimal afterload (Qload) determined by the ratio of Ea to Ees was used to measure the efficiency of mechanical energy transferred from the left ventricle to the arterial system. In comparison with the 6-month-old rats, the 24-month-old animals had decreased Ees, at 567.4 +/- 26.7 vs 639.0 +/- 20.7 mmHg ml(-1), decreased Ea, at 411.5 +/- 18.6 vs 577.9 +/- 15.7 mmHg ml(-1), and decreased Q(load), at 0.9428 +/- 0.0024 vs 0.9962 +/- 0.0014. Treatment with AG for 6 months did not significantly affect Ees; however, when normalized to LV weight (i.e., Eesn = Ees/LV weight), Eesn showed a significant rise of 22.8%, suggesting that AG may retard the aging process on the intrinsic contractility of the left ventricle. On the other hand, the decrease in Ea in aging rats was prevented by AG, as reflected in the increase of 19.7% in this variable (P < 0.05). The 24-month-old treated rats also exhibited a significant rise of 21.6% in Ea/Ees, causing an increase of 5.2% in Qload (P < 0.05). We conclude that in healthy older Fisher 344 rats without diabetes, long-term treatment with AG may improve both the arterial and ventricular function and optimize the matching condition for the left ventricular-arterial coupling.

Activation of peroxisome proliferator-activated receptors in human airway smooth muscle cells has a superior anti-inflammatory profile to corticosteroids: relevance for chronic obstructive pulmonary disease therapy

Airway smooth muscle is actively involved in the inflammatory process in diseases such as chronic obstructive pulmonary disease and asthma by 1) contributing to airway narrowing through hyperplasia and hypertrophy and 2) the release of GM-CSF and G-CSF, which promotes the survival and activation of infiltrating leukocytes. Thus, the identification of novel anti-inflammatory pathways in airway smooth muscle will have important implications for the treatment of inflammatory airway disease. This study identifies such a pathway in the activation of peroxisome proliferator-activated receptors (PPARs). PPAR ligands are known therapeutic agents in the treatment of diabetes; however, their role in human airway disease is unknown. We demonstrate, for the first time, that human airway smooth muscle cells express PPAR alpha and -gamma subtypes. Activation of PPAR gamma by natural and synthetic ligands inhibits serum-induced cell growth more effectively than does the steroid dexamethasone, and induces apoptosis. Moreover, PPAR gamma activation, like dexamethasone, inhibits the release of GM-CSF. However, PPAR gamma ligands, but not dexamethasone, similarly inhibits G-CSF release. These results reveal a novel anti-inflammatory pathway in human airway smooth muscle, where PPAR gamma activation has additional anti-inflammatory effects to those of steroids. Hence, PPAR ligands might act as potential treatments in human respiratory diseases.