Ventricular Arrhythmias and Fibrosis in Mice

Is interstitial fibrosis a contributor, among other factors, in the prognosis for patients at high risk for arrhythmias? Yes, according to a new study by Nguyen et al. In this podcast Deputy Editor Merry Lindsey (University of Mississippi Medical Center) interviews lead author Xiao-Jun Du (Baker IDI Heart and Diabetes Institute) about his lab’s latest work exploring the interplay between ventricular arrhythmias, cardiac fibrosis, and the resulting functional consequences. Using a transgenic mouse model of spontaneous ventricular tachyarrhythmias and employing detailed telemetry data analysis, Du and colleagues connected the increase in collagen content and collagen cross-linking with an increase over time in arrhythmia episodes. Is connexin 43 upregulated via cardiomyocytes or fibroblasts? Do interventions using antioxidative stress, such as treating with relaxin, reduce fibrosis and therefore reduce the incidents of arrhythmias? Listen to find out.

My-Nhan Nguyen, Helen Kiriazis, Diego Ruggiero, Xiao-Ming Gao, Yidan Su, Anne Jian, Li-Ping Han, Julie R McMullen, Xiao-Jun Du Spontaneous ventricular tachyarrhythmias in β2-adrenoceptor transgenic mice in relation to cardiac interstitial fibrosis Am J Physiol Heart Circ Physiol, published online June 26, 2015, DOI: 10.1152/ajpheart.00405.2015.

Listen Now:

Voluntary Exercise in Heart Failure Rats

Exercise guidelines exist for the management and treatment of patients with most cardiovascular diseases, but where does pulmonary arterial hypertension fit into the exercise training therapy picture? In this podcast Guest Editor Shawn Bender interviews lead author Ed White (University of Leeds) and content expert Daphne Merkus (Erasmus MC, Netherlands) about the work by Natali and co-authors, which used an innovative rat model of voluntary wheel running to determine whether exercise training could be beneficial in the treatment of pulmonary artery hypertension (PAH) and right ventricular failure. The authors found that, while wheel running did not prevent the development of PAH, it did significantly delay the median time to heart failure. Will the work by White and collaborators lead to new “off the shelf” exercise training treatments, which could be utilized by clinicians in the treatment of human patients with PAH? Listen and find out.

Antonio José Natali, Ewan Douglas Fowler, Sarah Calaghan, Ed White Voluntary exercise delays heart failure onset in rats with pulmonary artery hypertension Am J Physiol Heart Circ Physiol, published August 1, 2015, DOI: 10.1152/ajpheart.00262.2015.

Listen Now:

Post-Heat Stress Cardiovascular Dysregulation

If core temperature is not the primary determinant of heat stroke severity, what is? In this latest podcast, Guest Editor Michael Falvo (VA NJ Health Care System; Rutgers New Jersey Medical School) interviews authors Gerald Audet and Nisha Charkoudian (both of US Army Research Institute of Environmental Medicine), along with content expert Robert Matthew Brothers (University of Texas at Austin), about the innovative work by Quinn et al centered on a unique rat model seeking to identify the failures of the cardiovascular system after heat stroke, rather than during heat stroke. What role do reactive oxygen species and the systemic inflammatory cascade play in governing heart rate and arterial pressure responses observed by the authors? How does this experimental model translate to patient populations, such as the elderly or workers doing physical labor, whose cardiovascular reserves are already taxed when heat stress or heat stroke occurs? Listen and learn.

Carrie M. Quinn, Gerald N. Audet, Nisha Charkoudian, Lisa R. Leon Cardiovascular and thermoregulatory dysregulation over 24 h following acute heat stress in rats Am J Physiol Heart Circ Physiol, published August 15, 2015, DOI: 10.1152/ajpheart.00918.2014.

Listen Now:

Optical Projection Tomography for Infarct Assessment

Is optical projection tomography (OPT) useful for producing more than just beautiful images? Yes, according to Zhao et al, who employed the innovative OPT methodology to quantify infarct size experimentally. In this podcast, Associate Editor Ajay Shah (King's College London) interviews lead author Gillian Gray (University of Edinburgh) and content expert Michael Marber (The Rayne Institute, St. Thomas' Hospital, King’s College London) about how Gray and colleagues used OPT to image the heart and capture 3-dimensional measurement of infarct volume. How does OPT stack up against standard histology and MRI? What exactly is giving rise to the autofluorescence signal when using OPT? Is there a future for OPT as a method of measuring infarct volume to transcend biological variations and the limitations of measuring individual sections of infarcted tissue? Listen to find out.

Xiaofeng Zhao, Junxi Wu, Calum D. Gray, Kieran McGregor, Adriano G Rossi, Harris Morrison, Maurits A Jansen, Gillian A Gray Optical projection tomography permits efficient assessment of infarct volume in the murine heart post-myocardial infarction Am J Physiol Heart Circ Physiol, published online June 12, 2015, DOI: 10.1152/ajpheart.00233.2015.

Listen Now:

Exercise and Chemoreflex Control of Renal Blood Flow in Chronic Heart Failure

It is well known that reduced kidney function in chronic heart failure (CHF) patients leads to morbidity and mortality in a significant proportion of this clinical population. So how does exercise training fit into the picture? In this podcast, Deputy Editor Merry Lindsey (University of Mississippi Medical Center) interviews lead author Noah Marcus (Des Moines University) and content expert Timothy Musch (Kansas State University) about the innovative work by Marcus and colleagues utilizing a unique rabbit exercise training experimental model of poor renal function in CHF with reduced renal perfusion. We tackle a number of intriguing questions in this author interview! Does enhanced carotid body chemoreceptor activity mediate tonic and/or hypoxia-induced reductions in renal blood flow in heart failure? Can exercise training be used as a non-pharmacological treatment to improve renal blood flow in heart failure patients? Do rabbits really run on a treadmill? Listen to find out.

Noah J. Marcus, Carolin Pügge, Jai Mediratta, Alicia M. Schiller, Rodrigo Del Rio, Irving H. Zucker, Harold D. Schultz Exercise training attenuates chemoreflex-mediated reductions of renal blood flow in heart failure Am J Physiol Heart Circ Physiol, published July 15, 2015, DOI: 10.1152/ajpheart.00268.2015.

Listen Now:

Angiotensin II and Reflex Vasoconstriction with Age

What are the key age-related differences in the reflex vasoconstrictor response in skin microvessels, and how are angiotensin II and Rho-kinase activation involved? These questions and more are answered in our latest podcast on the work by Lang and Kolb. Listen as Associate Editor Debra Diz (Wake Forest University School of Medicine) interviews lead author James Lang (Des Moines University) and content expert Caitlin Thompson-Torgerson (Anne Arundel Community College) about this intriguing work which has clear thermoregulatory ramifications for older adults. Is there a potential upstream role for reactive oxygen species in upregulating Angiotensin II? How can the primary effects of aging in a healthy older adult cohort be extrapolated to disease states such as diabetes? Listen to find out.

James A. Lang , Kelsey E. Kolb Angiotensin II type I receptor blockade attenuates reflex cutaneous vasoconstriction in aged but not young skin Am J Physiol Heart Circ Physiol, published May 15, 2015, DOI: 10.1152/ajpheart.00017.2015.

Listen Now:

Environmentally Persistent Free Radicals Increase Post Ischemic Dysfunction

What is the role of environmentally persistent free radicals (EPFRs) in increasing cardiac vulnerability to subsequent myocardial infarction ischemia/reperfusion injury? Guest Editor Loren Wold (The Ohio State University) interviews lead author Kurt Varner (Louisiana State University Health Sciences Center New Orleans) and content expert Kevin Lord (University of the Incarnate Word) in this lively and engaging podcast which explores the work by Burn et al. Using a nose-only inhalation technique, Burn and Varner sought to mimic “real world” air pollution exposure to EPRFs and reduce any potential inflammation response from intratracheal installation of particulate matter. Which components of particulate matter contribute most to oxidative stress? How does the work by Burn and Varner fit into next-generation tobacco products, such as e-cigarettes? Listen to find out.

Brendan R. Burn , Kurt J. Varner Environmentally persistent free radicals compromise left ventricular function during ischemia/reperfusion injury Am J Physiol Heart Circ Physiol, published May 1, 2015, DOI: 10.1152/ajpheart.00891.2014.

Listen Now:

Mechanotransduction and Redox Signals

Why cover only one article in a podcast, when we can discuss five articles at once? In this podcast on a unique Review article, Associate Editor Nancy Kanagy (University of New Mexico) interviews senior author and symposium organizer Shampa Chatterjee (University of Pennsylvania) and leading expert Mark Nelson (University of Vermont) about five reports presented at the 1st Pan American Congress of Physiological Sciences: Physiology Without Borders held in August 2014 in Iguassu Falls, Brazil. Under the umbrella topic of mechanosignaling and downstream redox-dependent responses, what links the mechanical forces at the cell membrane to the intracellular responses? Several key new findings were presented at the meeting. Among them, researchers have found that numerous elements on the cytoskeleton, such as PECAM and caveolae (caveolin-1), work together to form a mechanosome. Is the key to understanding the response to mechanosensing defining the machinery within the multifarious mechanosomes? How do we translate observations in cultured cells to responses in intact tissues and animals? Listen and learn.

Shampa Chatterjee, Keigi Fujiwara, Nestor G. Perez, Masuko Ushio-Fukai, Aron B. Fisher Mechanosignaling in the Vasculature: Emerging Concepts in Sensing, Transduction and Physiological Responses Am J Physiol Heart Circ Physiol, published online April 11, 2015, DOI: 10.1152/ajpheart.00105.2015.

Listen Now:

TTD Reverses Human Cardiac Myofibroblast Activation

How does Tetrandrine (TTD) directly affect human cardiac fibroblasts, and can it benefit heart failure patients? In this new podcast, Deputy Editor Merry Lindsey (University of Mississippi Medical Center) interviews lead author Paul Fedak (University of Calgary) and content expert Jason Gardner (Louisiana State University Health Sciences Center) about the exciting new work by Teng et al which investigates the potential therapeutic agent TTD, a calcium channel blocker with anti-fibrotic effects in human patients. In addition to in vivo studies, Fedak and co-authors used a unique micro gel technique to isolate a single human fibroblast and identify its influence on local matrix remodeling. Given that the primary dysfunction associated with heart failure with preserved ejection fraction (HFPEF) is reduced relaxation due to extensive fibrosis, the results shown by Fedak and colleagues are particularly interesting. TTD was shown in their animal model to reverse fibrosis and restore cardiac compliance in vivo, but had little effect on fibroblast production of collagen. What is next in this fascinating story? Listen to find out.

Guoqi Teng, Daniyil Svystonyuk, Holly E.M. Mewhort, Jeannine D. Turnbull, Darrell D. Belke, Henry J. Duff, Paul W.M. Fedak Tetrandrine reverses human cardiac myofibroblast activation and myocardial fibrosis Am J Physiol Heart Circ Physiol, published online April 11, 2015, doi: 10.1152/ajpheart.00126.2015.

Listen Now:

MSNA and Trigeminal Nerve Stimulation

Ever wonder how the impressive diving reflex seen in seals might be related to human physiology? In this engaging podcast, Guest Editor Nisha Charkoudian (U.S. Army Research Institute of Environmental Medicine) interviews lead author James P. Fisher (University of Birmingham, United Kingdom) and Zeljko Dujic (University of Split School of Medicine, Croatia) about a fascinating new study by Fisher and colleagues designed to investigate whether the sympathetic effects of the trigeminal nerve reflex have additive effects with the reflexes due to exercise. The authors used ice packs applied the face to stimulate the trigeminal nerve, and added handgrip exercise to evaluate whether excessive sympathoexcitation could result. What was the response of muscle sympathetic nerve activity when hand-grip exercise was added to the facial cooling-stimulation of the diving reflex? What implications does this study have for elite breath-hold divers, for recreational divers, or for patient populations who want to participate in water sports? Listen and find out.

James P. Fisher, Igor A. Fernandes, Thales C. Barbosa, Eliza Prodel, John H. Coote, Antonio Claudio L. Nóbrega, Lauro C. Vianna Diving and exercise: The interaction of trigeminal receptors and muscle metaboreceptors on muscle sympathetic nerve activity in humans Am J Physiol Heart Circ Physiol, published March 1, 2105, DOI: 10.1152/ajpheart.00728.2014.

Listen Now: