Biology subjects

Harvey, R. D.

Publications and source records attributed to Harvey, R. D..

3 recordsLinked to original sources

bioRxiv2025

Neuropeptide Y regulation of L-type Ca2+ channel activity is altered following chronic myocardial infarction

Neuropeptide Y (NPY) is a co-transmitter released from sympathetic neurons along with norepinephrine (NE). It has been observed that cardiac NPY levels are significantly elevated following myocardial infarction (MI), and this has been linked to an increase in ventricular arrhythmogenicity associated with elevated sympathetic tone. However, the effects that NPY has on the electrical activity of ventricular myocytes remain poorly understood. Previous studies have examined the influence of NPY alone on cardiac ion channel function, but not in the presence of NE, which is the situation expected in vivo. Furthermore, no one has examined the effects of NPY on ion channel activity following MI. The present study explored the impact of NPY on the L-type Ca2+ current in ventricular myocytes isolated from the hearts of normal healthy pigs and pigs subjected to MI. We found that NPY alone has a stimulatory effect on the Ca2+ current in myocytes isolated from healthy pigs. However, in the presence of NE, the effect of NPY was inhibitory. The stimulatory effect of NPY alone was blocked by the Y1 receptor antagonist BIBO3304, while the inhibitory effect observed in the presence of NE was blocked by the Y2 receptor antagonist BIIE0246. When the effects of NPY were examined using hearts from pigs following recovery from MI, the stimulatory effect of NPY was absent in myocytes obtained from both remote and border zone areas of infarcted hearts. The inhibitory effect of NPY observed in the presence of NE was also absent in myocytes from remote areas of the infarcted heart. However, the inhibitory effect of NPY observed in the presence of NE was intact in border zone cells. The implications of these results are discussed as they relate to the potential arrhythmogenic effects of NPY following MI. Graphical Abstract. NPY exerts bimodular, context dependent effects on LTCC. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=91 SRC="FIGDIR/small/690298v1_ufig1.gif" ALT="Figure 1"> View larger version (28K): org.highwire.dtl.DTLVardef@fb248borg.highwire.dtl.DTLVardef@1c3cd9org.highwire.dtl.DTLVardef@1def5b3org.highwire.dtl.DTLVardef@d4bfd5_HPS_FORMAT_FIGEXP M_FIG C_FIG Proposed signaling pathways for diverse effects of NPY in ventricular cardiac myocytes. Norepinephrine (NE) and neuropeptide Y (NPY) co-application results in a Y2/Gi-mediated reduction in {beta}-adrenergic ({beta}AR)/Gs enhanced ICaL, while NPY alone modestly enhances the current via Y1/Gq mechanism. These pathways are regionally altered following chronic MI.

pharmacology and toxicology↗

bioRxiv2025

Nuclear α1A-Adrenergic Receptor Regulation of cAMP Production by an Inside-Out MAP Kinase Signaling Pathway in Cardiac Myocytes

Sympathetic stimulation produces beneficial changes in cardiac function through {beta}-adrenergic receptor ({beta}AR) production of cAMP and subsequent alteration of electrical and mechanical activity. Long term activation of cAMP production also contributes to cardiac remodeling and detrimental changes associated with heart failure. However, sympathetic responses are mediated by the endogenous neurotransmitter norepinephrine (NE), which is also a potent 1-adrenergic receptor (1AR) agonist, and 1AR activation can produce significant effects on the heart as well. What is less clear is how 1- and {beta}-adrenergic responses interact with one another. Previous studies have demonstrated that 1AR activation can inhibit {beta}-adrenergic regulation of electrical and mechanical activity of cardiac myocytes, although the signaling mechanisms involved were not previously known. In the present study, we used FRET-based biosensors in adult rat ventricular myocytes to demonstrate that this crosstalk effect involves inhibition of cAMP production by nuclear 1AARs acting on {beta}ARs found on the plasma membrane. Furthermore, we established that this inside-out signaling mechanism involves a mitogen-activated protein kinase (MAPK) pathway that uncouples {beta}ARs from downstream signaling in a G protein coupled receptor kinase (GRK)/arrestin-dependent manner. These results reveal a novel, non-canonical signaling mechanism contributing to 1AR responses in the heart, and that this effect limits {beta}AR production of cAMP by NE. This mechanism may contribute to the cardioprotective effect previously ascribed to 1AAR activation. These findings also clearly demonstrate the importance of considering the contributions of 1 and {beta}ARs together when studying the influence of the sympathetic nervous system on the heart.

pharmacology and toxicology↗

bioRxiv2022

Absolute scattering length density profile of liposome bilayers obtained by SAXS combined with GIXOS - a tool to determine model biomembrane structure

Lipid membranes play an essential role in biology, acting as host matrices for biomolecules like proteins and facilitating their functions. Their structures, and structural responses to physiologically relevant interactions, i.e. with membrane proteins, provide key information for understanding biophysical mechanisms. Hence, there is a crucial need of methods to understand the effects of membrane host molecules on the lipid bilayer structure. Here, we present a purely experimental method for obtaining the absolute scattering length density (SLD) profile and the area per lipid of liposomal bilayers, by aiding the analysis of small angle X-ray scattering (SAXS) data with the volume of bare headgroups obtained from fast (20-120s) grazing incidence off-specular scattering (GIXOS) data from monolayers of the same model membrane lipid composition. The GIXOS data experimentally demonstrate that the variation of the bare headgroup volume upon lipid packing density change is small enough to allow its usage as a reference value without knowing the lipid packing stage in a bilayer. This approach also bares the advantage that the reference volume is obtained at the same aqueous environment as used for the model membrane bilayers. We demonstrate the validity of this method using several typical membrane compositions, as well as one example of a phospholipid membrane with an incorporated transmembrane peptide. This methodology allows to obtain absolute scale values rather than relative scale by using solely X-ray-based instrumentation, retaining a similar resolution of SAXS experiments. The presented method has high potential to understand structural effects of membrane proteins on the biomembrane structure.

biophysics↗