Biology subjects

Lakatta, E. G.

Publications and source records attributed to Lakatta, E. G..

5 recordsLinked to original sources

bioRxiv2021

The Interaction of Angiotensin II and Milk Fat Globule Epidermal Growth Factor VIII in Proinflammatory Arterial Remodeling

BackgroundAngiotensin II (Ang II) and milk fat globule-epidermal growth factor VIII (MFG-E8) are involved in age-associated arterial remodeling; however, the inflammatory role of MFG-E8 in Ang II associated arterial remodeling with aging remains unknown. Methods and ResultsIn this study, 30-week-old MFG-E8 knock out (KO) and age-matched wild-type (WT) mice were infused with Ang II or saline. After infusion the with Ang II, the aortic molecular, cellular, and structural remodeling were observed in mice and compared to those infused with saline, but these effects were dependent on the expression of MFG-E8: (1) In the WT mice, Ang II infusion substantially increased intimal-medial thickness, elastic lamina degradation, collagen deposition, and the proliferation of VSMCs; in contrast, in the KO mice, these effects were significantly reduced; (2) In the WT mice, Ang II treatment significantly increased the activation and expression of MMP2, TGF-{beta}1, and its downstream signaling molecule p-SMAD2, and collagen type I production, however, in the KO mice, these molecular effects were significantly reduced; (3) In the WT mice, Ang II treatment increased inflammatory p-NF-{kappa}B p65, MCP1, TNF-, ICAM1, and VCAM1 molecular expression, while conversely, in the KO mice, no significant inflammatory changes were found; (4) Importantly, compared to untreated control mice with a wide range of age from 4-96 weeks, Ang II infused "younger" mice produced an "older" arterial inflammatory phenotype, which was alleviated by MFG-E8 deficiency. ConclusionsMFG-E8 mediates Ang II associated arterial inflammatory remodeling. Targeting MFG-E8 is a novel molecular approach to curb adverse arterial remodeling during aging and hypertension. CLINICAL PERSPECTIVEO_ST_ABSWhat Is New?C_ST_ABS* Both Ang II and MFG-E8 increases are involved in proinflammatory arterial remodeling mediating the molecular, cellular and tissue events in aging and hypertension. * MFG-E8 is essential for Ang II induced and age-associated adverse arterial remodeling via the increase of proinflammation, intimal medial thickening, elastin fragmentation, collagen deposition, and VSMC proliferation. What Are the Clinical Implications?Since MFG-E8 mediates Ang II induced proinflammation in arterial wall remodeling in aging and hypertension, targeting MFG-E8 is a potential molecular approach to curb inflammatory arterial remodeling, maintaining the health of the vascular system during aging and hypertension.

pathology↗

bioRxiv2020

Local calcium signals in pacemaker cells heart rate and body mass are self-similar from mice to humans

BackgroundTranslation of knowledge of sinoatrial nodal "SAN" automaticity gleaned from animal studies to human dysrhythmias, e.g. "Sick Sinus" Syndrome (SSS) requiring electronic pacemaker insertion has been sub-optimal, largely because heart rate (HR) varies widely across species. ObjectivesTo discover regulatory universal mechanisms of normal automaticity in SAN pacemaker cells that are self-similar across species. MethodSub-cellular Ca2+ releases, whole cell AP-induced Ca2+ transients and APs were recorded in isolated mouse, guinea-pig, rabbit and human SAN cells. Parametric Ca2+ and Vm Kinetic Transitions (PCVKT) during phases of AP cycles from their ignition to recovery were quantified. ResultsAlthough both action potential cycle lengths (APCL) and PCVKT during AP cycles differed across species by ten-fold, trans-species scaling of PCVKT during AP cycles and scaling, of PCVKT to APCL in cells in vitro, EKG RR intervals in vivo, and BM were self-similar (obeyed power laws) across species. Thus, APCL in vitro, HR in vivo, and BM of any species can be predicted by PCVKT during AP cycles in SAN cells measured in any single species in vitro. ConclusionsIn designing optimal HR to match widely different BM and energy requirements from mice to humans, nature did not "reinvent pacemaker cell wheels", but differentially scaled kinetics of gears that regulate the rates at which the "wheels spin". This discovery will facilitate the development of novel pharmalogic therapies and biologic pacemakers featuring a normal, wide-range rate regulation in animal models and the translation of these to humans to target recalcitrant human SSS. Condensed AbstractStudies in animal models are an important facet of cardiac arrhythmia research. Because HR differs by over ten-fold between some animals and humans, translation of knowledge about regulatory mechanisms of SAN normal automaticity gleaned from studies in animal models to target human SSS has been sub-optimal. Our findings demonstrating that trans-species self-similarity of sub-cellular and cellular mechanisms that couple Ca2+ to Vm during AP cycles can predict heart rate in vivo from mice to humans will inform on the design of novel studies in animal models and facilitate translation of this knowledge to target human disease.

physiology↗

bioRxiv2020

MFG-E8 Signaling Promotes Elastolysis and Calcification in the Aging Aortic Wall

Milk fat globule-EGF factor 8 (MFG-E8) protein increases with age and is mainly secreted by vascular smooth muscle cells in the arterial wall. Here, we investigated the role of MFG-E8 signaling during proinflammation, elastolysis, fibrosis, and calcification within the aging arterial wall. In vivo studies indicated that (1) Elastic lamina breaks collagen deposition and calcium-phosphorus products were markedly increased in the aging arterial wall of rats; (2) MFG-E8 protein abundance was markedly increased while intact tropoelastin (TPELN), an element of repair of the elastic fibers, was markedly decreased in the aging arterial wall of rats; (3) The absence of MFG-E8 markedly alleviated age-associated increases in elastic lamina breaks, collagen deposition and calcium-phosphorus products in mice; and (4) MFG-E8 deficiency significantly decreased age-associated increases in matrix metalloproteinase type II (MMP-2) activation, alkaline phosphatase, and runt-related transcription factor 1 (Runx1) expression in the aortic walls of mice. The in vitro studies demonstrated that (1) treating either young or old rat VSMCs with recombinant human MFG-E8 protein (rhMFG-E8) significantly reduced TPELN levels while MFG-E8 gene silencing significantly increased TPELN levels; (2) rhMFG-E8 treatment activated MMP-2 levels in both young and old VSMCs; and (3) MMP-2 bound to and cleaved TPELN secreted from VSMCs. Thus, these findings suggest that MFG-E8 signaling promotes age-associated adverse structural remodeling, including elastolysis, fibrosis, and calcification; however, MFG-E8 deficiency markedly mitigates these adverse effects in mice.

pathology↗

bioRxiv2020

Self-similar action potential cycle-to-cycle variability of Ca2+ and current oscillators in cardiac pacemaker cells

Ca2+ and Vm transitions occurring throughout AP cycles in sinoatrial nodal (SAN) cells are cues that: (1) not only regulate activation states of molecules operating within criticality (Ca2+ domain) and limit-cycle (Vm domain) mechanisms of a coupled-clock system that underlies SAN cell automaticity; (2) but are also regulated by the activation states of the clock molecules they regulate. In other terms, these cues are both causes and effects of clock molecular activation (recursion). Recently, we demonstrated that Ca2+ and Vm transitions during AP cycles in single SAN cells isolated from mice, guinea pigs, rabbits and humans are self-similar (obey a power law) and are also self-similar to trans-species AP firing intervals of these cells in vitro, to heart rate in vivo, and to body mass. Neurotransmitter stimulation of {beta} adrenergic receptor or cholinergic receptor initiated signaling in SAN cells modulates their AP firing rate and rhythm by impacting on the degree to which SAN clocks couple to each other, creating the broad physiologic range of SAN cell mean AP firing intervals and firing interval variabilities. Here we show that Ca2+ and Vm domain kinetic transitions (time to AP ignition in diastole and 90% AP recovery) occurring within given AP, the mean AP firing intervals, and AP firing interval variabilities within time-series of APs in 230 individual SAN cells are self-similar (obey power laws). In other terms, these long-range correlations inform on self-similar distributions of order among SAN cells across the entire broad physiologic range of SAN AP firing intervals, regardless of whether autonomic receptors of these cells are stimulated or not, and regardless of the type (adrenergic or cholinergic) of autonomic receptor stimulation. These long-range correlations among distributions of Ca2+ and Vm kinetic functions that regulate SAN cell clock coupling during each AP cycle in different individual, isolated SAN cells not in contact with each other. Our numerical model simulations further extended our perspectives to the molecular scale and demonstrated that many ion currents also behave self-similar across autonomic states. Thus, to ensure rapid flexibility of AP firing rates in response to different types and degrees of autonomic input, nature "did not reinvent molecular wheels within the coupled-clock system of pacemaker cells", but differentially engaged or scaled the kinetics of gears that regulate the rate and rhythm at which the "wheels spin" in a given autonomic input context.

biophysics↗

bioRxiv2020

Synchronized cardiac impulses emerge from multi-scale, heterogeneous local calcium signals within and among cells of heart pacemaker tissue

ABSTRACTBackground The current paradigm of Sinoatrial Node (SAN) impulse generation: (i) is that full-scale action potentials (APs) of a common frequency are initiated at one site and are conducted within the SAN along smooth isochrones; and (ii) does not feature fine details of Ca2+ signalling present in isolated SAN cells, in which small subcellular, subthreshold local Ca2+ releases (LCRs) self-organize to generate cell-wide APs.Objectives To study subcellular Ca2+ signals within and among cells comprising the SAN tissue.Methods We combined immunolabeling with a novel technique to detect the occurrence of LCRs and AP-induced Ca2+ transients (APCTs) in individual pixels (chonopix) across the entire mouse SAN images.Results At high magnification, Ca2+ signals appeared markedly heterogeneous in space, amplitude, frequency, and phase among cells comprising an HCN4+/CX43- cell meshwork. The signalling exhibited several distinguishable patterns of LCR/APCT interactions within and among cells. Apparently conducting rhythmic APCTs of the meshwork were transferred to a truly conducting HCN4-/CX43+ network of straited cells via narrow functional interfaces where different cell types intertwine, i.e. the SAN anatomical/functional unit. At low magnification, the earliest APCT of each cycle occurred within a small area of the HCN4 meshwork and subsequent APCT appearance throughout SAN pixels was discontinuous.Conclusions We have discovered a novel, microscopic Ca2+ signalling paradigm of SAN operation that has escaped detection using low-resolution, macroscopic tissue isochrones employed in prior studies: APs emerge from heterogeneous subcellular subthreshold Ca2+ signals, resembling multiscale complex processes of impulse generation within clusters of neurons in neuronal networks.Condensed abstract By combining immunolabeling with a novel optical technique we detected markedly heterogenous Ca2+signals within and among cell clusters of an HCN4+/CX43- meshwork in mouse sinoatrial node. These Ca2+ signals self-organized and transferred, throughout the node, to projections from an HCN4-/CX43+ network connected to a highly organized, rapidly conducting part of the CX43+ network. Thus, APs emerge from heterogeneous, subthreshold Ca2+ signaling not detected in low-resolution macroscopic isochrones. Our discovery requires a fundamental paradigm shift from concentric impulse propagation initiated within a leading site, to a multiscale/complex process, resembling the emergence of organized signals from heterogeneous local signals within neuronal networks.Competing Interest StatementThe authors have declared no competing interest.Abbreviations listAPaction potentialAPCTAP-induced Ca2+ transientChronopixchrono-pixelCX43Connexin 43 (Gap junction alpha-1 protein)FFTFast Fourier TransformHCN4Hyperpolarization-Activated Cyclic Nucleotide-Gated Channel 4ICaLL-type Ca2+ currentICaTT-type Ca2+ currentIVCInferior Vena CavaLCRLocal Ca2+ ReleaseNCXNa+/Ca2+ exchangerPBSPhosphate-Buffered SalinepreBötCpreBötzinger ComplexROIRegion of InterestSANSinoatrial NodeSVCSuperior Vena CavaView Full Text

physiology↗