Potential Protective Effects of Equol (Soy Isoflavone Metabolite) on Coronary Heart Diseases—From Molecular Mechanisms to Studies in Humans

Equol, a soy isoflavone-derived metabolite of the gut microbiome, may be the key cardioprotective component of soy isoflavones. Systematic reviews have reported that soy isoflavones have no to very small effects on traditional cardiovascular disease risk factors. However, the potential mechanistic mode of action of equol on non-traditional cardiovascular risk factors has not been systematically reviewed. We searched the PubMed through to July 2021 by using terms for equol and each of the following markers: inflammation, oxidation, endothelial function, vasodilation, atherosclerosis, arterial stiffness, and coronary heart disease. Of the 231 records identified, 69 articles met the inclusion criteria and were summarized. Our review suggests that equol is more lipophilic, bioavailable, and generally more potent compared to soy isoflavones. Cell culture, animal, and human studies show that equol possesses antioxidative, anti-inflammatory, and vasodilatory properties and improves arterial stiffness and atherosclerosis. Many of these actions are mediated through the estrogen receptor β. Overall, equol may have a greater cardioprotective benefit than soy isoflavones. Clinical studies of equol are warranted because equol is available as a dietary supplement

Novel PDE4 inhibitors derived from Chinese medicine forsythia.

Cyclic adenosine monophosphate (cAMP) is a crucial intracellular second messenger molecule that converts extracellular molecules to intracellular signal transduction pathways generating cell- and stimulus-specific effects. Importantly, specific phosphodiesterase (PDE) subtypes control the amplitude and duration of cAMP-induced physiological processes and are therefore a prominent pharmacological target currently used in a variety of fields. Here we tested the extracts from traditional Chinese medicine, Forsythia suspense seeds, which have been used for more than 2000 years to relieve respiratory symptoms. Using structural-functional analysis we found its major lignin, Forsynthin, acted as an immunosuppressant by inhibiting PDE4 in inflammatory and immune cell. Moreover, several novel, selective small molecule derivatives of Forsythin were tested in vitro and in murine models of viral and bacterial pneumonia, sepsis and cytokine-driven systemic inflammation. Thus, pharmacological targeting of PDE4 may be a promising strategy for immune-related disorders characterized by amplified host inflammatory response

Forsythin is an inhibitor of PDE4.

<p><b>A–C.</b> The chemical structure of Forsythin extracted from <i>Forsythia suspensa</i> seeds. Forsythin is an o-linked β-D-glucopyranosylated lignin that can be hydrolyzed (Red line). <b>D.</b> Predicted docking site of Forsythin with PDE4. <b>E.</b> Predicted residue electrostatic and van der Waals interactions between PDE4 amino acids and Forsythin. Using ZINCPharmer <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0115937#pone.0115937-Koes1" target="_blank">[24]</a>, a pharmacophore model was generated (upper left) and used to screen the lead compounds from an 18.3 million purchasable compound library.</p

Tested compounds reduce TNF secretion in LPS stimulated mouse RAW264.7 and human PBMCs.

<p><b>A.</b> 5×10⁵ RAW264.7 cells were seeded in 96 wells for 18 h. Cells were primed with compounds at different concentration for 3 h before treated with LPS (1 ng/ml) for additional 8 h. TNF cytokine releases were monitored by ELISA. <b>B.</b> PBMC (0.2 ml at 1×10⁵/ml) were primed with compounds at different concentration for 3 h before treated with LPS (1 ng/ml) for additional 8 h. TNF cytokine releases were monitored by ELISA. % of TNF secretion were calculated and graphed. <b>C.</b> Summary of compound IC₅₀. The data represent <i>n</i> = 3–6 experiments.</p

Tested compounds exhibit high potency and selectivity towards PDE4.

<p>For the PDE activity assay, all test compounds were diluted in DMSO with final concentrations in each assay of 100, 10, 1, 0.1, 0.01, 0.001, 0.0001 µM. For the PDE4 activity assay, 10 mU of purified PDE4 (Millipore) was used per reaction. Compounds 6, 7, 9 and 13 (blue underline) were further tested in PDE3, 5, 7, 10 activity assays in which 25 mU of purified enzyme was used per reaction. Summary of compound IC₅₀ in lower right corner.</p

PDE4 inhibitors lessen cytokine storm induced by LPS septic shock.

<p>C57/BL6 mice were administered i.p. nothing (CON), vehicle, 10 ug/kg, 100 ug/kg, 1 mg/kg or 10 mg/kg of compounds 6, 7 or 9. Mice were given LPS (<i>E. coli,</i> 100 µg) 10 min later through an i.p. injection. 2 h later mice were euthanized using pentobarbital and blood was collected for IL-6 and TNF measurements. Shown in panel <b>A–B</b> is the % inhibition of cytokine levels as a function of drug dose. The data represent <i>n</i> = 3 mice/group at each dose. C57/BL6 mice were also pretreated with compound 5, 6, 7 or 9 at 1 mg/kg. Mice were given LPS (<i>E. coli,</i> 100 µg) 18 h later through an i.p. injection. 2 h later the mice were euthanized using pentobarbital and blood was collected for IL-6 and TNF measurements (<b>C–D</b>). The data represent <i>n</i> = 4–6 mice/group, *<i>P</i><0.05 versus vehicle.</p

PDE4 inhibitors reduce H1N1 influenza-induced lung injury.

<p>C57/BL6 mice were challenged with H1N1 (10⁵ pfu/mouse, i.t.) for up to 6 days. For compound treatment, a stock solution (5 mg/ml) was added to the drinking water (containing 2% sucrose) to a final concentration of 30 µg/ml. <b>A.</b> Survival studies of mice administered i.t. with H1N1 (10⁵ pfu/mouse, <i>n</i> = 6 mice/group). Mice were then euthanized using pentobarbital and lungs were lavaged with saline, harvested, and then homogenized. Cell counts and lavage protein were measured (<b>B, C</b>). Lavage cytokine secretions were measured (<b>D, E</b>). Serum samples were also collected and cytokine levels were measured (<b>F, G</b>). <b>H.</b> H&E staining was performed on lung samples. Original magnification, ×60. The data represent <i>n</i> = 4–6 mice/group, *<i>P</i><0.05 versus vehicle.</p

PDE4 inhibitors ameliorate LPS induced lung injury.

<p>C57/BL6 mice were challenged with LPS <i>(E.coli</i>, 3 mg/kg, i.t.) followed by i.p. administration of vehicle, 1 mg/kg of compound 2, 6, 7 or 9. Mice were then euthanized 18 h later using pentobarbital, and lungs were lavaged with saline, harvested, and then homogenized. Lavage cytokine secretion (<b>A–C</b>), protein concentrations (<b>D</b>) and cell counts (<b>E</b>) were measured. <b>F.</b> H&E staining was performed on lung samples. Original magnification, ×20. The data represent <i>n</i> = 4–6 mice/group, *<i>P</i><0.05 versus vehicle.</p