The voltage-gated L-type calcium channel (LTCC) is essential for multiple cellular processes. In the heart, calcium influx through LTCC plays an important role in cardiac electrical excitation. Mutations in LTCC genes, including CACNA1C, CACNA1D, CACNB2 and CACNA2D, will induce the dysfunctions of calcium channels, which result in the abnormal excitations of cardiomyocytes, and finally lead to cardiac arrhythmias. Nevertheless, the newly found mutations in LTCC and their functions are continuously being elucidated. This review summarizes recent findings on the mutations of LTCC, which are associated with long QT syndromes, Timothy syndromes, Brugada syndromes, short QT syndromes, and some other cardiac arrhythmias. Indeed, we describe the gain/loss-of-functions of these mutations in LTCC, which can give an explanation for the phenotypes of cardiac arrhythmias. Moreover, we present several challenges in the field at present, and propose some diagnostic or therapeutic approaches to these mutation-associated cardiac diseases in the future.

Myeloma bone disease (MBD) can cause bone destruction and increase the level of Ca2+ concentration in the bone marrow microenvironment by stimulating osteoclastic differentiation. Nevertheless, the relationships between MBD and highly efficient stimuli of Ca2+ in multiple myeloma (MM) progression, and possible regulatory mechanisms are poorly defined. Here, we reported that the nonselective cation channel transient receptor potential vanilloid 2 (TRPV2) plays a functional role in Ca2+ oscillations and osteoclastogenesis. To investigate the expression of TRPV2 in MM, we analyzed publicly available MM data sets and performed immunohistochemistry in MM patients. The correlations between TRPV2 expression levels and osteoclast-related cytokines were analyzed. Fluo-4 staining and ELISA assays were used to assess the regulated function of TRPV2 in intracellular Ca2+ and cytokines. Western blotting and Chromatin immunoprecipitation (ChIP) assays were performed to explore the signaling pathway of TRPV2-induced osteoclastic differentiation. Real-time PCR, Western blotting, ELISA and tartrate-resistant acid phosphatase (TRAP) staining were performed to detect the biological effects of TRPV2 inhibitor on osteoclastogenesis. The functional expression of TRPV2, involved in the osteolysis through gating the calcium influx, was changed in the MM cells cultured in a high Ca2+ environment. Mechanistically, TRPV2 modulates nuclear factor-κB ligand (RANKL)-dependent osteoclastic differentiation through the Ca2+-calcineurin-NFAT signaling pathway. Of clinical relevance, systemic administration with SKF96365 could attenuate the MM-induced osteoclast formation in vitro. Our study uncovers the possible roles of TRPV2, which enhances MBD, suggesting that targeting osteocyte-MM cells interactions through blockade of TRPV2 channel may provide a promising treatment strategy in MM.

Formononetin (FMN) is a phytoestrogen member of the flavonoid family, which has the pharmacological effects of antioxidative, antihypertensive, antitumor, and anti-infective. FMN demonstrates potential in the prevention and treatment of diseases, specifically neurological diseases, such as traumatic brain injury (TBI), spinal cord injury (SCI), ischemic stroke, cerebral ischemia-reperfusion, Alzheimer’s disease, and nerve tumor. Herein, a literature search is conducted to provide information on the signaling pathways of neuroprotection of formononetin based on the neuroprotective study. The significant neuroprotective function of FMN makes it a novel candidate for the development of drugs targeting the central nervous system.

Calcium influx from activated voltage-gated calcium channel Ca _V 1.2 in vascular smooth muscle cells is indispensable for maintaining myogenic tone and blood pressure. The function of Ca _V 1.2 channel can be optimized by alternative splicing, one of post-transcriptional modification mechanisms. The splicing factor Rbfox2 is known to regulate the Ca _V 1.2 pre-mRNA alternative splicing events during neuronal development. However, Rbfox2’s roles in modulating the key function of vascular Ca _V 1.2 channel and in the pathogenesis of hypertension remain elusive. Here, we report that the proportion of Ca _V 1.2 channels with alternative exon 9* is increased by 10.3%, whereas that with alternative exon 33 is decreased by 10.5% in hypertensive arteries. Surprisingly, the expression level of Rbfox2 is increased ≈3-folds, presumably because of the upregulation of a dominant-negative isoform of Rbfox2. In vascular smooth muscle cells, we find that knockdown of Rbfox2 dynamically increases alternative exon 9*, whereas decreases exon 33 inclusion of Ca _V 1.2 channels. By patch-clamp studies, we show that diminished Rbfox2-induced alternative splicing shifts the steady-state activation and inactivation curves of vascular Ca _V 1.2 calcium channel to hyperpolarization, which makes the window current potential to more negative. Moreover, siRNA-mediated knockdown of Rbfox2 increases the pressure-induced vascular myogenic tone of rat mesenteric artery. Taken together, our data indicate that Rbfox2 modulates the functions of vascular Ca _V 1.2 calcium channel by dynamically regulating the expressions of alternative exons 9* and 33, which in turn affects the vascular myogenic tone. Therefore, our work suggests a key role for Rbfox2 in hypertension, which provides a rational basis for designing antihypertensive therapies.

Background: L-type Ca²⁺ channel Ca_V1.2 is essential for cardiomyocyte excitation, contraction and gene transcription in the heart, and abnormal functions of cardiac Ca_V1.2 channels are presented in diabetic cardiomyopathy. However, the underlying mechanisms are largely unclear. The functions of Ca_V1.2 channels are subtly modulated by splicing factor-mediated alternative splicing (AS), but whether and how Ca_V1.2 channels are alternatively spliced in diabetic heart remains unknown. Methods: Diabetic rat models were established by using high-fat diet in combination with low dose streptozotocin. Cardiac function and morphology were assessed by echocardiography and HE staining, respectively. Isolated neonatal rat ventricular myocytes (NRVMs) were used as a cell-based model. Cardiac Ca_V1.2 channel functions were measured by whole-cell patch clamp, and intracellular Ca²⁺ concentration was monitored by using Fluo-4 AM. Results: We find that diabetic rats develop diastolic dysfunction and cardiac hypertrophy accompanied by an increased Ca_V1.2 channel with alternative exon 9* (Ca_V1.2_E9*), but unchanged that with alternative exon 8/8a or exon 33. The splicing factor Rbfox2 expression is also increased in diabetic heart, presumably because of dominate-negative (DN) isoform. Unexpectedly, high glucose cannot induce the aberrant expressions of Ca_V1.2 exon 9* and Rbfox2. But glycated serum (GS), the mimic of advanced glycation end-products (AGEs), upregulates Ca_V1.2_E9* channels proportion and downregulates Rbfox2 expression in NRVMs. By whole-cell patch clamp, we find GS application hyperpolarizes the current-voltage curve and window currents of cardiac Ca_V1.2 channels. Moreover, GS treatment raises K⁺-triggered intracellular Ca²⁺ concentration ([Ca²⁺]_i), enlarges cell surface area of NRVMs and induces hypertrophic genes transcription. Consistently, siRNA-mediated knockdown of Rbfox2 in NRVMs upregulates Ca_V1.2_E9* channel, shifts Ca_V1.2 window currents to hyperpolarization, increases [Ca²⁺]_i and induces cardiomyocyte hypertrophy. Conclusions: AGEs, not glucose, dysregulates Rbfox2 which thereby increases Ca_V1.2_E9* channels and hyperpolarizes channel window currents. These make the channels open at greater negative potentials and lead to increased [Ca²⁺]_i in cardiomyocytes, and finally induce cardiomyocyte hypertrophy in diabetes. Our work elucidates the underlying mechanisms for Ca_V1.2 channel regulation in diabetic heart, and targeting Rbfox2 to reset the aberrantly spliced Ca_V1.2 channel might be a promising therapeutic approach in diabetes-induced cardiac hypertrophy.