Arginase Inhibition Suppresses Native Low-Density Lipoprotein-Stimulated Vascular Smooth Muscle Cell Proliferation by NADPH Oxidase Inactivation

Lipotoxicity, glucotoxicity and some strategies to protect vascular smooth muscle cell against proliferative phenotype in metabolic syndrome

Metabolic syndrome (MetS) is a risk factor for the development of cardiovascular disease (CVD) and atherosclerosis through a mechanism that involves vascular smooth muscle cell (VSMC) proliferation, lipotoxicity and glucotoxicity. Several molecules found to be increased in MetS, including free fatty acids, fatty acid binding protein 4, leptin, resistin, oxidized lipoprotein particles, and advanced glycation end products, influence VSMC proliferation. Most of these molecules act through their receptors on VSMCs by activating several signaling pathways associated with ROS generation in various cellular compartments. ROS from NADPH-oxidase and mitochondria have been found to promote VSMC proliferation and cell cycle progression. In addition, most of the natural or synthetic substances described in this review, including pharmaceuticals with hypoglycemic and hypolipidemic properties, attenuate VSMC proliferation by their simultaneous modulation of cell signaling and their scavenging property due to the presence of a phenolic ring in their structure. This review discusses recent data in the literature on the role that several MetS-related molecules and ROS play in the change from contractile to proliferative phenotype of VSMCs. Hence the importance of proposing an appropriate strategy to prevent uncontrolled VSMC proliferation using antioxidants, hypoglycemic and hypolipidemic agents.

Chromatographic and mass spectrometric technologies for chemical analysis of Euodiae fructus: A review

INTRODUCTION

Euodiae fructus, also known as Evodiae fructus, is a popular Chinese herbal medicine derived from the dried, nearly ripe fruits of Tetradium ruticarpum (A. Juss.) T. G. Hartley. The main bioactive constituents of Euodiae fructus are alkaloids, limonoids, flavonoids, and anthraquinones. The contents of these compounds vary greatly between different plant species, geographic locations, and harvest times, which thus affect the therapeutic effects.

OBJECTIVES

We aimed to summarize the chromatographic and mass spectrometric technologies applied for chemical analysis and quality evaluation of Euodiae fructus. Moreover, we aimed to emphasize the diverse soft ionization techniques and mass analyzers of LC-MS methods for assessment of Euodiae fructus.

METHODOLOGY

A literature study was carried out by retrieving articles published between January 1988 and December 2021 from well-known databases, including PubMed, ASC, Elsevier, ScienceDirect, J·STAGE, Thieme, Taylor & Francis, Springer Link, Wiley Online Library, and CNKI. The chemical analysis methods were described in several categories in accordance with the used analytical techniques, including thin-layer chromatography (TLC), high-performance liquid chromatography (HPLC), high-performance liquid chromatography-mass spectrometry (HPLC-MS), gas chromatography-mass spectrometry (GC-MS), capillary electrophoresis (CE), and counter-current chromatography (CCC).

RESULTS

This review systematically summarizes the achievements in chemical analysis and quality evaluation of Euodiae fructus published in over three decades, covering the various chromatographic and mass spectrometric technologies applied for identification and quantification of phytochemical constituents.

CONCLUSION

The summary serves as an important basis for future phytochemical research and implementation of quality control methods in order to ensure the efficacy and safety of Euodiae fructus.

Arginase: shedding light on the mechanisms and opportunities in cardiovascular diseases

Arginase, a binuclear manganese metalloenzyme in the urea, catalyzes the hydrolysis of L-arginine to urea and L-ornithine. Both isoforms, arginase 1 and arginase 2 perform significant roles in the regulation of cellular functions in cardiovascular system, such as senescence, apoptosis, proliferation, inflammation, and autophagy, via a variety of mechanisms, including regulating L-arginine metabolism and activating multiple signal pathways. Furthermore, abnormal arginase activity contributes to the initiation and progression of a variety of CVDs. Therefore, targeting arginase may be a novel and promising approach for CVDs treatment. In this review, we give a comprehensive overview of the physiological and biological roles of arginase in a variety of CVDs, revealing the underlying mechanisms of arginase mediating vascular and cardiac function, as well as shedding light on the novel and promising therapeutic approaches for CVDs therapy in individuals.

Limonin stabilises SIRT6 by activating USP10 in cardiac hypertrophy

BACKGROUND AND PURPOSE

Limonin, a natural tetracyclic triterpenoid extract, exerts extensive pharmacological effects; however, its role in cardiac hypertrophy remains to be elucidated. We investigated the beneficial effects of limonin on cardiac hypertrophy and explored the potential mechanisms.

EXPERIMENTAL APPROACH

C57/BL6 male mice were subjected to aortic banding (AB) surgery and neonatal rat cardiac myocytes (NRCMs) were stimulated with phenylephrine (PE) to evaluate the effects of limonin on cardiac hypertrophy.

KEY RESULTS

Limonin markedly improved the cardiac function and heart weight in AB operation mice. In addition, limonin-treated mice and NRCMs produced fewer cardiac hypertrophy markers than those treated with the vehicle in hypertrophic groups. Sustained AB- or PE-stimulation impaired cardiac sirtuin 6 (SIRT6) protein levels, which were partially rescued by limonin and subsequently enhanced the activity of PPARα, and Sirt6 siRNA inhibited the anti-hypertrophic effects of limonin in vitro. Interestingly, limonin did not influence Sirt6 mRNA levels, but controlled its ubiquitin levels. Thus, the protein biosynthesis inhibitor, cycloheximide (CHX), and proteasome inhibitor, MG-132, were used to determine SIRT6 protein expression levels. Under PE stimulation, limonin increased SIRT6 protein levels in the presence of CHX, but it didn't influence SIRT6 expression in the presence of MG-132, suggesting that limonin promotes SIRT6 abundance by inhibiting its ubiquitination degradation. Furthermore, limonin inhibited the degradation of SIRT6 by activating ubiquitin-specific peptidase (Cuspidi et al.)-10, while USP10 siRNA abrogated the beneficial effects of limonin.

CONCLUSION AND IMPLICATIONS

Limonin mediates the ubiquitination and degradation of SIRT6 by activating USP10, providing an attractive therapeutic target for cardiac hypertrophy.

Angiopoietin-like proteins 8 knockout reduces intermittent hypoxia-induced vascular remodeling in a murine model of obstructive sleep apnea

OBJECTIVE

Obstructive sleep apnea (OSA) is a major risk factor for cardiovascular mortality. Apnea-induced chronic intermittent hypoxia (CIH) is a primary pathophysiological manifestation of OSA that promotes various cardiovascular alterations, such as aortic vascular remodeling. In this study, we investigated the association between angiopoietin-like proteins 8 (ANGPTL8) and CIH-induced aortic vascular remodeling in mice.

METHODS

C57BL/6J male mice were divided into four groups: Normoxia group, ANGPTL8^-/- group, CIH group, CIH + ANGPTL8^-/- group. Mice in the normoxia group and ANGPTL8^-/- group received no treatment, while mice in the CIH and CIH + ANGPTL8^-/- group were subjected to CIH (21%-5% O₂, 180 s/cycle, 10 h/day) for 6 weeks. At the end of the experiments, intima-media thickness (IMT), elastin disorganization, and aortic wall collagen abundance were assessed in vivo. Immunohistochemistry and Western-blot were used to detect endoplasmic reticulum stress (ERS) and aortic vascular smooth muscle cell proliferation. ANGPTL8 shRNA and ANGPL8 overexpression were used in aortic vascular smooth muscle cells to investigate the mechanism of ANGPTL8 in CIH.

RESULTS

Compared to the control group, CIH exposure significantly increased intima-media thickness (IMT), elastic fibers disorganization, and aortic wall collagen abundance. CIH also significantly increased blood pressure, induced hyperlipidemia, as well as the expression of ERS protein activating transcription factor-6 (ATF6) and aortic vascular smooth muscle cell proliferation. Contrary, ANGPTL8^-/- significantly mitigated the CIH-induced vascular remodeling; ANGPTL8^-/- decreased CIH-induced hypertension and hyperlipidemia, inhibited the protein expression of ATF6, and aortic vascular smooth muscle cell proliferation. Moreover, our in vitro study suggested that CIH could induce ANGPTL8 expression via hypoxia-inducible factor (HIF-1α); ANGPTL8 induced proliferation of aortic vascular smooth muscle cells via the ERS pathway.

CONCLUSION

ANGPTL8^-/- can prevent CIH-induced aortic vascular remodeling, probably through the inhibition of the ERS pathway. Therefore, ANGPTL8 might be a potential target in CIH-induced aortic vascular remodeling.

Limonin: A Review of Its Pharmacology, Toxicity, and Pharmacokinetics

Limonin is a natural tetracyclic triterpenoid compound, which widely exists in Euodia rutaecarpa (Juss.) Benth., Phellodendron chinense Schneid., and Coptis chinensis Franch. Its extensive pharmacological effects have attracted considerable attention in recent years. However, there is no systematic review focusing on the pharmacology, toxicity, and pharmacokinetics of limonin. Therefore, this review aimed to provide the latest information on the pharmacology, toxicity, and pharmacokinetics of limonin, exploring the therapeutic potential of this compound and looking for ways to improve efficacy and bioavailability. Limonin has a wide spectrum of pharmacological effects, including anti-cancer, anti-inflammatory and analgesic, anti-bacterial and anti-virus, anti-oxidation, liver protection properties. However, limonin has also been shown to lead to hepatotoxicity, renal toxicity, and genetic damage. Moreover, limonin also has complex impacts on hepatic metabolic enzyme. Pharmacokinetic studies have demonstrated that limonin has poor bioavailability, and the reduction, hydrolysis, and methylation are the main metabolic pathways of limonin. We also found that the position and group of the substituents of limonin are key in affecting pharmacological activity and bioavailability. However, some issues still exist, such as the mechanism of antioxidant activity of limonin not being clear. In addition, there are few studies on the toxicity mechanism of limonin, and the effects of limonin concentration on pharmacological effects and toxicity are not clear, and no researchers have reported any ways in which to reduce the toxicity of limonin. Therefore, future research directions include the mechanism of antioxidant activity of limonin, how the concentration of limonin affects pharmacological effects and toxicity, finding ways to reduce the toxicity of limonin, and structural modification of limonin—one of the key methods necessary to enhance pharmacological activity and bioavailability.

Resveratrol is an arginase inhibitor contributing to vascular smooth muscle cell vasoconstriction via increasing cytosolic calcium

The contractility of vascular smooth muscle cells (VSMCs) controls the lumen diameter of vessels, thus serving a role in regulating blood pressure and organ blood flow. Although arginases are known to have numerous effects in the biological activities of VSMCs, the effects of arginase II on the constriction of VSMCs has not yet been investigated. When conducting a natural products screen for an inhibitor against arginase, the present study identified that a relatively high concentration of resveratrol (RSV) exhibited arginase inhibitory activity. Therefore, the present study investigated whether RSV could regulate VSMCs contractions and the underlying mechanism. Arginase inhibition by RSV led to an increase in the concentration of the substrate L‑Arg and an accompanying increase in the cytosol Ca2+ concentration [(Ca2+)c] in VSMCs. The increased [Ca2+]c induced by RSV and L‑Arg treatments resulted in CaMKII‑dependent MLC20 phosphorylation. The effects of RSV on VSMCs were maintained even when VSMCs were pre‑treated with sirtinol, an inhibitor of Sirt proteins. In a vascular tension assay with de‑endothelialized aortic vessels, vasoconstrictor responses, which were measured using phenylephrine (PE), were significantly enhanced in the RSV‑ and L‑Arg‑treated vessels. Therefore, although arginase inhibition has exhibited beneficial effects in various diseases, care is required when considering administration of an arginase inhibitor to patients with vessels endothelial dysfunction as RSV can induce vessel contraction.