Considering the high metastatic potential of colorectal cancer (CRC), the inhibition of metastasis is important for anti-CRC therapy. Agrimonia pilosa Ledeb (A. pilosa) is a perennial herbaceous plant that is widely distributed in Asia. The extracts of A. pilosa have shown diverse pharmacological properties, such as antimicrobial, anti-inflammatory, and antitumor activities. In the present study, the antimetastatic activity of A. pilosa was evaluated. Methanol extraction from the roots of A. pilosa was performed by high-performance liquid chromatography (HPLC) and 12 fractions were obtained. Among these, fraction 4 showed the most potent inhibitory effect on the migration of colon cancer cells. Using LC-HR MS analysis, quercetin and quercitrin were identified as flavonoids contained in fraction 4. Like fraction 4, quercetin and quercitrin effectively inhibited the migration and invasion of RKO cells. While the level of E-cadherin was increased, the levels of N-cadherin and vimentin were decreased by the same agents. Although they all activate the p38, JNK, and ERK signaling pathways, only SP600125, an inhibitor of the JNK pathway, specifically inhibited the effect of fraction 4, quercetin, and quercitrin on cell migration. An in vivo experiment also confirmed the antitumor activity of quercetin and quercitrin. Collectively, these results suggest that A. pilosa and its two flavonoids, quercetin and quercitrin, are candidates for the antimetastatic treatment of CRC.

Homeostasis in the level of reactive oxygen species (ROS) in cardiac myocytes plays a critical role in regulating their physiological functions. Disturbance of balance between generation and removal of ROS is a major cause of cardiac myocyte remodeling, dysfunction, and failure. Cardiac myocytes possess several ROS-producing pathways, such as mitochondrial electron transport chain, NADPH oxidases, and nitric oxide synthases, and have endogenous antioxidation mechanisms. Cardiac Ca²⁺-signaling toolkit proteins, as well as mitochondrial functions, are largely modulated by ROS under physiological and pathological conditions, thereby producing alterations in contraction, membrane conductivity, cell metabolism and cell growth and death. Mechanical stresses under hypertension, post-myocardial infarction, heart failure, and valve diseases are the main causes for stress-induced cardiac remodeling and functional failure, which are associated with ROS-induced pathogenesis. Experimental evidence demonstrates that many cardioprotective natural antioxidants, enriched in foods or herbs, exert beneficial effects on cardiac functions (Ca²⁺ signal, contractility and rhythm), myocytes remodeling, inflammation and death in pathological hearts. The review may provide knowledge and insight into the modulation of cardiac pathogenesis by ROS and natural antioxidants.

ATP is a major energy source in the mammalian cells, but it is an extracellular chemical messenger acting on P2 purinergic receptors. A line of evidence has shown that ATP is released from many different types of cells including neurons, endothelial cells, and muscle cells. In this review, we described the distribution of P2 receptor subtypes in the cardiac cells and their physiological and pathological roles in the heart. So far, the effects of external application of ATP or its analogues, and those of UTP on cardiac contractility and rhythm have been reported. In addition, specific genetic alterations and pharmacological agonists and antagonists have been adopted to discover specific roles of P2 receptor subtypes including P2X4-, P2X7-, P2Y2- and P2Y6-receptors in cardiac cells under physiological and pathological conditions. Accumulated data suggest that P2X4 receptors may play a beneficial role in cardiac muscle function, and that P2Y2- and P2Y6-receptors can induce cardiac fibrosis. Recent evidence further demonstrates P2Y1 receptor and P2X4 receptor as important mechanical signaling molecules to alter membrane potential and Ca²⁺ signaling in atrial myocytes and their uneven expression profile between right and left atrium.

Changes in heart rate affect Ca²⁺ signalling and contractility in ventricular muscle, but the effects on atrial Ca²⁺ signalling are poorly understood. Here, we explored how increased stimulation frequency affects right atrial (RA) and left atrial (LA) local Ca²⁺ signalling and underlying cellular mechanisms. We used two‐dimensional confocal Ca²⁺ imaging, patch clamping, immunocytochemistry and western blotting in isolated rat atrial myocytes. Centripetal Ca²⁺ waves were common in both RA and LA myocytes. Increasing the stimulation frequency from 1 to 3 Hz reduced local Ca²⁺ transients in LA but not in RA myocytes. LA myocytes consistently exhibited threefold faster centripetal Ca²⁺ propagation than RA myocytes. RA myocytes had a faster Ca²⁺ decay rate at higher frequencies. Most LA myocytes displayed fast release sites in the interior upon depolarization and significant transverse–axial tubules (TATs) that were partly co‐localized with junctophilin‐2, unlike RA myocytes. Increased frequency similarly reduced the Ca²⁺ current (I_Ca) in both cell types, but I_Ca was larger in RA cells. At increased frequencies, sarcoplasmic reticulum (SR) Ca²⁺ loading and fractional release (FR) remained stable in RA cells, while peripheral SR content and FR decreased in LA cells. RA cells had higher levels of peripheral SERCA2 and protein expressions of phospholamban (PLB) and phosphorylated PLB. Our data and integrative modelling suggest that LA myocytes may contract faster than RA myocytes due to TAT‐associated faster central Ca²⁺ release. However, LA Ca²⁺ signalling is more prone to maladaptation to frequency increases due to less effective SR Ca²⁺ uptake and a smaller trigger I_Ca. image Key points: Changes in heart rate affect Ca²⁺ signalling and contractility in ventricular muscle, but the effects on atrial Ca²⁺ signalling are less well understood. Here we determine how increased electrical stimulation frequency affects right (RA) and left atrial (LA) local Ca²⁺ signalling and underlying cellular mechanisms. We demonstrate that, during depolarization, centripetal Ca²⁺ propagation occurs approximately threefold faster in LA myocytes compared to RA myocytes possibly due to fast releases in the interior, associated with transverse–axial tubules, and less peripheral sarcoplasmic reticulum Ca²⁺ pumps. Increasing stimulation frequency more readily compromises peripheral sarcoplasmic reticulum Ca²⁺ loading in LA myocytes, thereby impairing local Ca²⁺ releases, unlike in RA myocytes. The lower peripheral density of sarcoplasmic reticulum Ca²⁺ pumps, along with reduced levels of phospholamban monomer and phosphorylated phospholamban, in LA myocytes compared to RA myocytes underlies the defective Ca²⁺ signalling adaptation to increased frequency in the left atrium.

Ko TH, et al. Korean Circ J. 2024 Oct;55:e7. https://doi.org/10.4070/kcj.2024.0179

Shear stress induces atrial Ca²⁺ waves via connexin43 (Cx43)-mediated ATP release. Here, we examined whether ventricular myocytes release ATP under shear stress, and the underlying and regulatory mechanisms. A bioluminescence assay and the ‘sniffer patch’ were used to measure ATP release from multiple and single murine ventricular myocytes, respectively, in combination with laminar flow or micro-puffing. Shear stress (∼16 dyn/cm²) induced transient ATP release from myocyte batches, peaking at ~7 mol/cm²-membrane within 2 s. This response was abolished by the application of La³⁺ but was not affected by Gap19 treatment or zero external Ca²⁺. In addition, shear-induced ATP release was not different between control and cardiac-specific Cx43-conditional knockout (Cx43-cKO) ventricular cells, suggesting no role for Cx43. Shear-induced ATP release was suppressed by probenecid, low concentrations of carbenoxolone, or the pannexin (Panx) 1 inhibitory peptide ¹⁰Panx1 by 60−75%, suggesting a major role for Panx. Pharmacological screening further revealed a partial (30−40%) role of 9‐anthracenecarboxylic acid-sensitive, tamoxifen-insensitive Cl^- channels in ATP release. The sniffer patch, using a P2X7 receptor-overexpressing HEK293 cell positioned at a local region of the ventricular cell, showed a rapid development of shear-induced currents, approximated to be ∼1−10 μM ATP. The Cx43-cKO did not affect these sniffer cell currents. This shear response was suppressed by mitochondrial uncoupling or inhibition of the electron transport chain by 70-80% but was rather enhanced by Mito-TEMPO. Our data suggest that shear stress induces ATP release from murine ventricle cells mainly via Panx and that mitochondrial oxidative phosphorylation may be required for this response.