Vitamin K modulates cardiac action potential by blocking sodium and potassium ion channels

Nanoparticle Polymers Influence on Cardiac Health: Good or Bad for Cardiac Physiology?

Cardiovascular diseases (CVD) are one of the leading causes of death and morbidity worldwide. Lifestyle modifications, medications, and addressing epidemiological factors have long been at the forefront of targeting therapeutics for CVD. Treatments can be further complicated given the intersection of gender, age, unique comorbidities, and healthcare access, among many other factors. Therefore, expanding treatment and diagnostic modalities for CVD is absolutely necessary. Nanoparticles and nanomaterials are increasingly being used as therapeutic and diagnostic modalities in various disciplines of biomedicine. Nanoparticles have multiple ways of interacting with the cardiovascular system. Some of them alter cardiac physiology by impacting ion channels, whereas others influence ions directly or indirectly, improving cellular death via decreasing oxidative stress.  While embedding nanoparticles into therapeutics can help enhance healthy cardiovascular function in other scenarios, they can also impair physiology by increasing reactive oxidative species and leading to cardiotoxicity. This review explores different types of nanoparticles, their effects, and the applicable dosages to create a better foundation for understanding the current research findings.

Characterizing the Severe Reactions of Parenteral Vitamin K1

Parenteral vitamin K1 (phytonadione) is used for anticoagulant reversal, and a boxed warning exists with intravenous and intramuscular administration due to the possibility of severe reactions, including fatalities. These reactions resemble hypersensitivity or anaphylaxis, including anaphylactoid reaction, and have led to shock and cardiac and/or respiratory arrest. The objective of this review is to summarize the available literature detailing the anaphylactic/anaphylactoid reactions with parenteral vitamin K1 in order to better characterize the reaction and provide a more in-depth understanding of its importance. A comprehensive literature search of MEDLINE (1946 to June 2016) and EMBASE (1947 to June 2016) was conducted using the terms vitamin K1, phytonadione, phytomenadione, vitamin K group, anaphylaxis, polyoxyethylated castor oil, and cremophor. A total of 2 retrospective surveillance studies, 2 retrospective cohort studies, and 17 case reports were identified for inclusion and assessment. Based on a review of the literature, use of parenteral vitamin K1 may result in severe hypotension, bradycardia or tachycardia, dyspnea, bronchospasm, cardiac arrest, and death. These reactions are most consistent with a nonimmune-mediated anaphylactoid mechanism. It appears that intravenous administration is more frequently associated with these reactions and occurs at an incidence of 3 per 10 000 doses of intravenous vitamin K1. The solubilizer may also increase the risk of adverse reactions, which occurred in patients with and without previous exposure to vitamin K1. Although there are known factors that increase the risk of an adverse drug event occurring, reactions have been reported despite all precautions being properly followed.

Ischemic, genetic and pharmacological origins of cardiac arrhythmias: the contribution of the Quebec Heart Institute

Research in the field of basic electrophysiology at the Quebec Heart Institute (Laval Hospital, Quebec City, Quebec) has evolved since its beginning in the 1990s. Interests were focused on cardiac arrhythmias induced by drugs, allelic variants and metabolic factors produced during ischemia. The results have contributed to the creation of new standards in drug development, more specifically, testing all new drugs for their potential effects on cardiac potassium currents, which could produce life-threatening proarrhythmic effects. In a French-Canadian population, three heterozygous single nucleotide polymorphisms in hK(v)1.5, a gene encoding for a major atrial repolarizing current, were found. These variants affect the expression level of the hK(v)1.5 channel and change the inactivation process in the presence of its accessory beta subunit. Because these effects could shorten atrial action potential, their presence was tested in postcoronary bypass patients and a higher prevalence was found in patients with postoperative atrial fibrillation. Finally, three potentially proarrhythmic factors characteristic of ischemia were identified: pH decrease; oxygen free radicals, which both increase the flow of K(+) ions through human ether-a-go-go-related gene and hK(v)1.5, producing a reduction in action potential duration, frequently leading to cardiac arrhythmias; and lysophosphatidylcholine, a metabolite involved in the production of cardiac arrhythmias early during ischemia that was shown to be a major cause of electrical uncoupling. Over the past decade, the Quebec Heart Institute has provided a significant amount of original data in the field of basic cardiac electrophysiology, specifically concerning arrhythmias originating from pharmacological agents, genetic background and cardiac ischemia.

HERG binding specificity and binding site structure: evidence from a fragment-based evolutionary computing SAR study

We describe the application of genetic programming, an evolutionary computing method, to predicting whether small molecules will block the HERG cardiac potassium channel. Models based on a molecular fragment-based descriptor set achieve an accuracy of 85-90% in predicting whether the IC(50) of a 'blind' set of compounds is <1 microM. Analysis of the models provides a 'meta-SAR', which predicts a pharmacophore of two hydrophobic features, one preferably aromatic and one preferably nitrogen-containing, with a protonatable nitrogen asymmetrically situated between them. Our experience of the approach suggests that it is robust, and requires limited scientist input to generate valuable predictive results and structural understanding of the target.