Protein kinase C-mediated calcium signaling as the basis for cardiomyocyte plasticity

Quantal size increase induced by the endocannabinoid 2-arachidonoylglycerol requires activation of CGRP receptors in mouse motor synapses

In mouse motor synapses, the exogenous application of the endocannabinoid (EC) 2-arachidonoylglycerol (2-AG) increases acetylcholine (ACh) quantal size due to the activation of CB1 receptors and the stimulation of ACh vesicular uptake. In the present study, microelectrode recordings of miniature endplate potentials (MEPP) revealed that this effect of 2-AG is independent of brain-derived neurotrophic factor (BDNF) signaling but involves the activation of calcitonin gene-related peptide (CGRP) receptors along with CB1 receptors. Potentiation of MEPP amplitude in the presence of 2-AG was prevented by blockers of CGRP receptors and ryanodine receptors (RyR) and by inhibitors of phospholipase C (PLC) and Ca2+ /calmodulin-dependent protein kinase II (CaMKII). Therefore, we suggest a hypothetical chain of events, which starts from the activation of presynaptic CB1 receptors, involves PLC, RyR, and CaMKII, and results in CGRP release with the subsequent activation of presynaptic CGRP receptors. Activation of CGRP receptors is probably a part of a complex molecular cascade leading to the 2-AG-induced increase in ACh quantal size and MEPP amplitude. We propose that the same chain of events may also take place if 2-AG is endogenously produced in mouse motor synapses, because the increase in MEPP amplitude that follows after prolonged tetanic muscle contractions (30 Hz, 2 min) was prevented by the blocking of CB1 receptors. This work may help to unveil the previously unknown aspects of the functional interaction between ECs and peptide modulators aimed at the regulation of quantal size and synaptic transmission.

Role of Ca2+ in healthy and pathologic cardiac function: from normal excitation-contraction coupling to mutations that cause inherited arrhythmia

Calcium (Ca²⁺) ions are a key second messenger involved in the rhythmic excitation and contraction of cardiomyocytes throughout the heart. Proper function of Ca²⁺-handling proteins is required for healthy cardiac function, whereas disruption in any of these can cause cardiac arrhythmias. This comprehensive review provides a broad overview of the roles of Ca²⁺-handling proteins and their regulators in healthy cardiac function and the mechanisms by which mutations in these proteins contribute to inherited arrhythmias. Major Ca²⁺ channels and Ca²⁺-sensitive regulatory proteins involved in cardiac excitation-contraction coupling are discussed, with special emphasis on the function of the RyR2 macromolecular complex. Inherited arrhythmia disorders including catecholaminergic polymorphic ventricular tachycardia, long QT syndrome, Brugada syndrome, short QT syndrome, and arrhythmogenic right-ventricular cardiomyopathy are discussed with particular emphasis on subtypes caused by mutations in Ca²⁺-handling proteins.

Research Progress on the Mechanism of Reducing Toxicity and Increasing the Efficacy of Sini Decoction Compatibility

Sini Decoction (SND) is the main prescription for treating Shaoyin disease in Zhang Zhongjing's Treatise on Typhoid Diseases in Han Dynasty. It is composed of Aconitum carmichaeli Debeaux, Glycyrrhiza uralensis Fisch ex DC and Zingiber officinale Roscoe. It has the effects of warming middle-jiao to dispel cold and revive the yang for resuscitation. Nowadays, it is mainly used in diseases in cardiovascular system, nervous system, digestive system and so on. In this paper, the effect and mechanism of the compatibility of Aconitum carmichaelii, Glycyrrhiza uralensis Fisch ex DC and Zingiber officinale Roscoe in SND were described. The results showed that SND performed remarkbly on strengthening heart, promoting blood circulation as well as inhibiting cardiomyocyte apoptosis, anti-inflammatory and anti-hypothyroidism. The toxic effect of Aconitum carmichaelii was relieved by the combination of Glycyrrhiza uralensis Fisch ex DC and Zingiber officinale Roscoe. The mechanism of increasing efficiency and reducing toxicity after the compatibility of medicines in SND was discussed from the perspective of changes in biological effects and chemical compositions. In terms of biological effects, the mechanism of SND in treating heart failure, myocardial ischemia, myocardial hypertrophy and hypothyroidism and protecting cell injury were discussed. As to chemical composition changes, most studies have compared the changes of main components in Aconitum carmichaelii, Glycyrrhiza uralensis Fisch ex DC and Zingiber officinale Roscoe with the whole prescription, drug pair and single Decoction, which further confirmed the effect of Glycyrrhiza uralensis Fisch ex DC on the detoxification of Aconitum carmichaelii and the significance of compatibility efficiency of SND. For the application of differently processed varieties of Aconitum carmichaelii in SND, the treatment of different diseases has siginificant tendencies and differences in the selections of Aconitum carmichaelii processed varieties. This paper will lay a foundation on clarifying the mechanism of drug compatibility of SND and in the future, provide a reference for the proper selection of differently processed products of Aconitum carmichaelii in SND in order to exert better effects in clinical pratices.