An ion channel hypothesis to explain divergent cardiovascular safety of cyclooxygenase-2 inhibitors: the answer to a hotly debated puzzle?

Potential Therapeutic Targets for Hypotension in Duchenne Muscular Dystrophy

Duchenne Muscular Dystrophy (DMD) is marked by genetic mutations occurring in the DMD gene, which is widely expressed in the cardiovascular system. In addition to developing cardiomyopathy, patients with DMD have been reported to be susceptible to the development of symptomatic hypotension, although the mechanisms are unclear. Analysis of single-cell RNA sequencing data has identified potassium voltage-gated channel subfamily Q member 5 (KCNQ5) and possibly ryanodine receptor 2 (RyR2) as potential candidate hypotension genes whose expression is significantly upregulated in the vascular smooth muscle cells of DMD mutant mice. We hypothesize that heightened KCNQ5 and RyR2 expression contributes to decreased arterial blood pressure in patients with DMD. Exploring pharmacological approaches to inhibit the KCNQ5 and RyR2 channels holds promise in managing the systemic hypotension observed in individuals with DMD. This avenue of investigation presents new prospects for improving clinical outcomes for these patients.

Identification of Novel Gene Regulatory Networks for Dystrophin Protein in Vascular Smooth Muscle Cells by Single-Nuclear Transcriptome Analysis

Duchenne muscular dystrophy is an X-linked recessive disease caused by mutations in dystrophin proteins that lead to heart failure and respiratory failure. Dystrophin (DMD) is not only expressed in cardiomyocytes and skeletal muscle cells, but also in vascular smooth muscle cells (VSMCs). Patients with DMD have been reported to have hypotension. Single nuclear RNA sequencing (snRNA-seq) is a state-of-the-art technology capable of identifying niche-specific gene programs of tissue-specific cell subpopulations. To determine whether DMD mutation alters blood pressure, we compared systolic, diastolic, and mean blood pressure levels in mdx mice (a mouse model of DMD carrying a nonsense mutation in DMD gene) and the wide-type control mice. We found that mdx mice showed significantly lower systolic, diastolic, and mean blood pressure than control mice. To understand how DMD mutation changes gene expression profiles from VSMCs, we analyzed an snRNA-seq dataset from the muscle nucleus of DMD mutant (DMDmut) mice and control (Ctrl) mice. Gene Ontology (GO) enrichment analysis revealed that the most significantly activated pathways in DMDmut-VSMCs are involved in ion channel function (potassium channel activity, cation channel complex, and cation channel activity). Notably, we discovered that the DMDmut-VSMCs showed significantly upregulated expression of KCNQ5 and RYR2, whereas the most suppressed pathways were transmembrane transporter activity (such as anion transmembrane transporter activity, inorganic anion transmembrane transporter activity, import into cell, and import across plasma membrane). Moreover, we analyzed metabolic pathways from the Kyoto Encyclopedia of Genes and Genomes (KEGG) using "scMetabolism" R package. DMDmut-VSMCs exhibited dysregulation of pyruvate metabolism and nuclear acid metabolism. In conclusion, via the application of snRNA-seq, we (for the first time) identify the potential molecular regulation by DMD in the upregulation of the expression of KCNQ5 genes in VSMCs, which helps us to understand the mechanism of hypotension in DMD patients. Our study potentially offers new possibilities for therapeutic interventions in systemic hypotension in DMD patients with pharmacological inhibition of KCNQ5.

Vectors and strategies for nonviral cancer gene therapy

INTRODUCTION

This review presents recent developments in the use of nonviral vectors and transfer technologies in cancer gene therapy. Tremendous progress has been made in developing cancer gene therapy in ways that could be applicable to treatments. Numerous efforts are focused on methods of attacking known and novel targets more efficiently and specifically. In parallel to progress in nonviral vector design and delivery technologies, important achievements have been accomplished for suicide, gene replacement, gene suppression and immunostimulatory therapies. New nonviral cancer gene therapies have been developed based on emerging RNAi (si/shRNA-, miRNA) or ODN.

AREAS COVERED

This review provides an overview of recent gene therapeutic strategies in which nonviral vectors have been used experimentally and in clinical trials. Furthermore, we present current developments in nonviral vector systems in association with important chemical and physical gene delivery technologies and their potential for the future.

EXPERT OPINION

Nonviral gene therapy has maintained its position as an approach for treating cancer. This is reflected by the fact that more than 17% of all gene therapy trials employ nonviral approaches. Thus, nonviral vectors have emerged as a clinical alternative to viral vectors for the appropriate expression and delivery of therapeutic genes.

Structural and functional screening in human induced-pluripotent stem cell-derived cardiomyocytes accurately identifies cardiotoxicity of multiple drug types

Safety pharmacology studies that evaluate new drug entities for potential cardiac liability remain a critical component of drug development. Current studies have shown that in vitro tests utilizing human induced pluripotent stem cell-derived cardiomyocytes (hiPS-CM) may be beneficial for preclinical risk evaluation. We recently demonstrated that an in vitro multi-parameter test panel assessing overall cardiac health and function could accurately reflect the associated clinical cardiotoxicity of 4 FDA-approved targeted oncology agents using hiPS-CM. The present studies expand upon this initial observation to assess whether this in vitro screen could detect cardiotoxicity across multiple drug classes with known clinical cardiac risks. Thus, 24 drugs were examined for their effect on both structural (viability, reactive oxygen species generation, lipid formation, troponin secretion) and functional (beating activity) endpoints in hiPS-CM. Using this screen, the cardiac-safe drugs showed no effects on any of the tests in our panel. However, 16 of 18 compounds with known clinical cardiac risk showed drug-induced changes in hiPS-CM by at least one method. Moreover, when taking into account the Cmax values, these 16 compounds could be further classified depending on whether the effects were structural, functional, or both. Overall, the most sensitive test assessed cardiac beating using the xCELLigence platform (88.9%) while the structural endpoints provided additional insight into the mechanism of cardiotoxicity for several drugs. These studies show that a multi-parameter approach examining both cardiac cell health and function in hiPS-CM provides a comprehensive and robust assessment that can aid in the determination of potential cardiac liability.

Celecoxib and ion channels: a story of unexpected discoveries

Celecoxib (Celebrex), a highly popular selective inhibitor of cyclooxygenase-2, can modulate ion channels and alter functioning of neurons and myocytes at clinically relevant concentrations independently of cyclooxygenase inhibition. In experimental systems varying from Drosophila to primary mammalian and human cell lines, celecoxib inhibits many voltage-activated Na(+), Ca(2+), and K(+) channels, including NaV1.5, L- and T-type Ca(2+) channels, KV1.5, KV2.1, KV4.3, KV7.1, KV11.1 (hERG), while stimulating other K(+) channels-KV7.2-5 and, possibly, KV11.1 (hERG) channels under certain conditions. In this review, we summarize the information currently available on the effects of celecoxib on ion channels, examine mechanistic aspects of drug action and the concomitant changes at the cellular and organ levels, and discuss these findings in the therapeutic context.

Characteristics and molecular basis of celecoxib modulation on K(v)7 potassium channels

BACKGROUND AND PURPOSE

Celecoxib is a selective cyclooxygenase-2 (COX-2) inhibitor used for the treatment of pain and inflammation. Emerging and accumulating evidence suggests that celecoxib can affect cellular targets other than COX, such as ion channels. In this study, we characterized the effects of celecoxib on K(v)7 K(+) channels and compared its effects with the well-established K(v)7 channel opener retigabine.

EXPERIMENTAL APPROACH

A perforated whole-cell patch technique was used to record K(v)7currents expressed in HEK 293 cells and M-type currents from rat superior cervical ganglion neurons.

KEY RESULTS

Celecoxib enhanced K(v)7.2-7.4, K(v)7.2/7.3 and K(v)7.3/7.5 currents but inhibited K(v)7.1 and K(v)7.1/KCNE1 currents and these effects were concentration dependent. The IC(50) value for inhibition of K(v)7.1 channels was approximately 4 µM and the EC(50) values for activation of K(v)7.2-7.4, K(v)7.2/K(v)7.3 and K(v)7.3/K(v)7.5 channels were approximately 2-5 µM. The effects of celecoxib were manifested by increasing current amplitudes, shifting the voltage-dependent activation curve in a more negative direction and slowing the deactivation of K(v)7 currents. 2,5-Dimethyl-celecoxib, a celecoxib analogue devoid of COX inhibition activity, has similar but greater effects on K(v)7currents. K(v)7.2(A235T) and K(v) 7.2(W236L) mutant channels, which have greatly attenuated responses to retigabine, showed a reversed response to celecoxib, from activation to inhibition.

CONCLUSIONS AND IMPLICATIONS

These results suggest that K(v)7 channels are targets of celecoxib action and provide new mechanistic evidence for understanding the effects of celecoxib. They also provide a new approach to developing K(v)7 modulators and for studying the structure-function relationship of K(v)7 channels.

Genome-wide association study of blood pressure response to methylphenidate treatment of attention-deficit/hyperactivity disorder

OBJECTIVE

We conducted a genome-wide association study of blood pressure in an open-label study of the methylphenidate transdermal system (MTS) for the treatment of attention-deficit/hyperactivity disorder (ADHD).

METHOD

Genotyping was conducted with the Affymetrix Genome-Wide Human SNP Array 6.0. Multivariate association analyses were conducted using the software package PLINK. After data cleaning and quality control we tested 316,934 SNPs in 140 children with ADHD.

RESULTS

We observed no genome-wide statistically significant findings, but a SNP in a K(+)-dependent Na(+)/Ca(2+) exchanger expressed in vascular smooth muscle (SLC24A3) was included in our top associations at p<1E-04. Genetic enrichment analyses of genes with ≥1 SNP significant at p<0.01, implicated several functional categories (FERM domain, p=5.0E-07; immunoglobulin domain, p=8.1E-06; the transmembrane region, p=4.4E-05; channel activity, p=2.0E-04; and type-III fibronectins, p=2.7E-05) harboring genes previously associated with related cardiovascular phenotypes.

CONCLUSIONS

The hypothesis generating results from this study suggests that polymorphisms in several genes consistently associated with cardiovascular diseases may impact changes in blood pressure observed with methylphenidate pharmacotherapy in children with ADHD.

Nonsteroidal Anti-Inflammatory Drugs and the Kidney

Non-steroidal anti-inflammatory drugs (NSAIDs) inhibit the isoenzymes COX-1 and COX-2 of cyclooxygenase (COX). Renal side effects (e.g., kidney function, fluid and urinary electrolyte excretion) vary with the extent of COX-2-COX-1 selectivity and the administered dose of these compounds. While young healthy subjects will rarely experience adverse renal effects with the use of NSAIDs, elderly patients and those with co-morbibity (e.g., congestive heart failure, liver cirrhosis or chronic kidney disease) and drug combinations (e.g., renin-angiotensin blockers, diuretics plus NSAIDs) may develop acute renal failure. This review summarizes our present knowledge how traditional NSAIDs and selective COX-2 inhibitors may affect the kidney under various experimental and clinical conditions, and how these drugs may influence renal inflammation, water transport, sodium and potassium balance and how renal dysfunction or hypertension may result.