Truncating mutations in FLNC caused an overlapping phenotype of dilated and left-dominant arrhythmogenic cardiomyopathies complicated by frequent premature sudden death. Prompt implantation of a cardiac defibrillator should be considered in affected patients harboring truncating mutations in FLNC.

The fibrinolytic system includes a broad spectrum of proteolytic enzymes with physiological and pathophysiological functions in several processes, such as haemostatic balance, tissue remodeling, tumor invasion, angiogenesis and reproduction. The main enzyme of the plasminogen activator system is plasmin, which is responsible for the degradation of fibrin into soluble degradation products. The activation of plasminogen into plasmin is mediated by two types of activators, urokinase-type plasminogen activator (uPA) and tissue-type plasminogen activator (tPA). The activity of both is regulated by specific plasminogen activator inhibitors (PAIs). There are 3 types of PAIs described so far but the most important fibrinolytic inhibitor in vivo is PAI type 1 (PAI-1). Among others, the presence of metabolic syndrome and the -675 4G/5G promoter polymorphism are known to be modulators of PAI-1 levels. Besides their fibrinolytic profile, plasmin and plasminogen activators are implicated in tissue proliferation and cellular adhesion, as they can proteolytically degrade the extracellular matrix and regulate the activation of both growth factors and matrix metalloproteinases. By all these means, the fibrinolytic system is also involved in physiological processes, and in pathological situations such as thrombosis, arteriosclerosis, endometriosis and cancer. PAI 1 has been studied in different settings with thrombotic pathophysiology, such as coronary artery disease and ischaemic stroke. Controversial results have been published and concerns about study designs or presence of confounders have been claimed to be responsible of them. Recently, its involvement in adverse thrombotic events related to the modern drug-eluting coronary stents has renewed the interest of its study. PAI-1 also plays an important role in signal transduction, cell adherence, and migration. Indeed, studies of several types of cancers, including breast cancer, have shown that increased uPA and PAI-1 levels are associated with aggressive tumor behavior and poor prognosis. Endometriosis is defined by the presence of endometrial glands and stroma outside the uterus with marked ability to attach and invade the peritoneum. It is one of the most frequent benign gynecological diseases that affect women with pelvic pain or infertility during their reproductive age. Immune system disorders, genetic predisposition, altered peritoneal environment and endometrial alterations are believed to increase the susceptibility to endometriosis. The plasminogen activator system may be involved in this process, where local extracellular proteolysis plays a crucial role. Altered expression of several components of the fibrinolytic system in both eutopic and ectopic endometrium and peritoneal fluid of women with the disease has been implicated not only in the onset, but also in the progression of the endometriotic lesions.

Background Catecholaminergic Polymorphic Ventricular Tachycardia (CPVT) is characterized by stress-triggered syncope and sudden death. CPVT patients manifest sino-atrial node (SAN) dysfunction, the mechanisms of which remain unexplored. Methods and Results We investigated SAN [Ca2+]i handling in mice carrying the CPVT-linked mutation of ryanodine receptor (RyR2R4496C) and on their wild-type (WT) littermates. In vivo telemetric recordings showed impaired SAN automaticity in RyR2R4496C mice following Isoproterenol (ISO) injection, analogous to what was observed in CPVT patients after exercise. Pacemaker activity was explored by measuring spontaneous [Ca2+]i transients in SAN cells within the intact SAN by confocal microscopy. RyR2R4496C SAN presented significantly slower pacemaker activity and impaired chronotropic response under β-adrenergic stimulation, accompanied by the appearance of pauses (in spontaneous [Ca2+]i transients and action potentials) in 75% of the cases. Ca2+ spark frequency was increased by 2-fold in RyR2R4496C SAN. Whole-cell patch-clamp experiments performed on isolated RyR2R4496C SAN cells showed that L-type Ca2+ current (ICa,L) density was reduced by ~50%, an effect blunted with internal Ca2+ buffering. ISO dramatically increased the frequency of Ca2+ sparks and waves by ~5 and ~10-fold, respectively. Interestingly, the sarcoplasmic reticulum (SR) Ca2+ content was significantly reduced in RyR2R4496C SAN cells in the presence of ISO, which may contribute to stopping the “Ca2+-clock” rhythm generation, originating SAN pauses. Conclusions The increased activity of RyR2R4496C in SAN leads to an unanticipated decrease on SAN automaticity by Ca2+-dependent decrease of ICa,L and SR Ca2+ depletion during diastole, identifying subcellular pathophysiologic alterations contributing to the SAN dysfunction in CPVT patients.