Biology subjects

Maniezzi, C.

Publications and source records attributed to Maniezzi, C..

6 recordsLinked to original sources

bioRxiv2026

Species-Dependent Limitations of Murine Myocardium for Investigating the Combined Inotropic Effects of SERCA2a Stimulation and Myofilament Ca2+ Sensitization

Impaired sarcoplasmic reticulum Ca2+ handling and myofilament function both contribute to contractile dysfunction in heart failure. A previous study in failing human myocardium showed that combining the SERCA2a activator istaroxime (ISTA) with the Ca2+ sensitizer levosimendan (LEVO) produces greater positive inotropy than either drug alone. However, human multicellular preparations did not allow comprehensive investigation of the underlying cellular mechanisms. We therefore assessed contractile performance and Ca2+ dynamics in murine multicellular myocardial preparations and ventricular cardiomyocytes treated with ISTA (20 M), LEVO (0.5 M), or their combination. ISTA improved developed force, contraction-relaxation kinetics, and mechanical restitution. These effects were associated with increased Ca2+ transient amplitude, accelerated Ca2+ rise and decay, and enhanced sarcoplasmic reticulum reloading. Adding LEVO produced no further mechanical benefit and only minor changes in Ca2+ handling. LEVO alone elicited heterogeneous contractile responses and increased myofilament Ca2+ sensitivity in only a minority of cardiomyocytes, while consistently accelerating Ca2+ transient decay. This effect was reproduced by the phosphodiesterase-3 inhibitor cilostamide, after which LEVO caused no significant additional change, consistent with a contribution of downstream cAMP-PKA signaling to the acceleration of Ca2+ removal. Thus, limited murine responsiveness to LEVO-mediated myofilament sensitization prevented mechanistic reconstruction of the additive inotropic effect observed in human myocardium, highlighting a species-dependent limitation of the mouse model for studying this combined therapy.

physiology↗

bioRxiv2025

Cellular consequences of non-ablative radiotherapy, a novel approach to ventricular tachycardias

BackgroundRadiotherapy (RT) with a single focused application of ionizing radiation (STAR) has been suggested as a non-invasive alternative to radiofrequency in ablating ventricular tachycardia (VT). Emerging data reveal that STAR may suppress VT without substrate destruction, by enhancing impulse conduction instead, through increased expression of NaV1.5 channels and connexin 43. AimsTo investigate electrophysiology and intracellular Ca2+ dynamics in cardiomyocytes (CMs) from mice subjected to in-vivo RT. The emerging data led us to evaluate biochemical changes potentially linking electrophysiological response to ionizing irradiation. MethodsCMs isolated 2 weeks after RT with low-dose (15 Gy) or high-dose (25 Gy) were compared to those of sham-treated mice (CTRL). We evaluated: i) INaT and INasus properties; ii) AP parameters, including the prevalence of Early After-Depolarizations (EADs); iii) intracellular Ca2+ dynamics; iv) CaMKII phosphorylation and v) ROS content. Results25 Gy RT i) increased INaT and, to a larger extent, INasus (increased INasus/INaT ratio); ii) increased AP amplitude, +dV/dtmax and duration (APD) and facilitated EADs; iii) depressed intracellular Ca2+ dynamics. 15 Gy RT had similar but smaller effects (dose-dependency). 25 Gy RT reduced CaMKII phosphorylation but increased cell ROS content, thus providing a mechanism for INaL enhancement. ConclusionsThe results support the view that STAR may supress VT by increasing conduction velocity, with APD prolongation providing an additional mechanism. On the other hand, INasus enhancement (likely by ROS) and Ca2+ handling depression may impair electrical stability and contractility in the irradiated region.

physiology↗

bioRxiv2023

Early consequences of the phospholamban mutation PLN-R14del+/- in a transgenic mouse model

AimsThe heterozygous phospholamban (PLN) mutation R14del (PLN R14del+/-) is associated with a severe arrhythmogenic cardiomyopathy (ACM) developing in the adult. "Superinhibition" of SERCA2a by PLN R14del is widely assumed to underlie the pathogenesis, but alternative mechanisms such abnormal energy metabolism have also been reported. This work aims to 1) to evaluate Ca2+ dynamics and energy metabolism in a transgenic (TG) mouse model of the mutation prior to cardiomyopathy development; 2) to test whether they are causally connected. Methods and ResultsCa2+ dynamics, energy metabolism parameters, reporters of mitochondrial integrity, energy and redox homeostasis were measured in ventricular myocytes of 8-12 weeks-old, phenotypically silent, TG mice. Mutation effects were compared to pharmacological PLN antagonism and analysed during modulation of sarcoplasmic reticulum (SR) and cytosolic Ca2+ compartments. Transcripts and proteins of relevant signalling pathways were evaluated. The mutation was characterized by hyperdynamic Ca2+ handling, similar to that induced by PLN antagonism. Albeit all components of energy metabolism were depressed at rest, functional signs of mitochondrial damage or energy starvation were absent and cell energy charge was preserved. The response of mitochondrial O2 consumption to SERCA2a blockade was lost in mutant myocytes (SR-mitochondrial uncoupling) and ER-stress signalling was activated. Conclusions1) PLN R14del+/- loses its ability to inhibit SERCA2a, which argues against SERCA2a superinhibition as a mechanism of ACM; 2) depression of resting energy metabolism may at least partly reflect impairment of SR-mitochondrial coupling; 3) ER-stress may be an early factor in the pathogenesis.

physiology↗

bioRxiv2022

Optical modulation of excitation-contraction coupling in human induced pluripotent stem cell-derived cardiomyocytes

Non-genetic photostimulation is a novel and rapidly growing multidisciplinary field of research that aims to induce light sensitivity in living systems by exploiting exogeneous phototransducers. Here we propose a recently synthetized intramembrane photoswitch, based on an azobenzene derivative (Ziapin2), for optical pacing of human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). The light-mediated stimulation process has been studied by applying several characterization techniques to detect the effect on the cell properties. In particular, we recorded changes in membrane capacitance, in membrane potential (Vm), and modulation of intracellular Ca2+ dynamics. Finally, cell contractility was analyzed using a custom MATLAB algorithm. Photostimulation of intramembrane Ziapin2 causes a transient Vm hyperpolarization followed by a delayed depolarization and action potential firing. The observed initial electrical modulation nicely correlates with changes in Ca2+ dynamics and contraction rate. This work represents the proof of principle that Ziapin2 can modulate electrical activity and contractility in hiPSC-CMs, opening up a future development in cardiac physiology.

bioengineering↗

bioRxiv2020

SREBP2 delivery to striatal astrocytes normalizes transcription of cholesterol biosynthesis genes and ameliorates pathological features in Huntington's disease

Brain cholesterol is produced mainly by astrocytes and is important for neuronal function. Its biosynthesis is severely reduced in mouse models of Huntingtons Disease (HD). One possible mechanism is a diminished nuclear translocation of the transcription factor sterol regulatory element binding protein 2 (SREBP2) and, consequently, reduced activation of SREBP-controlled genes in the cholesterol biosynthesis pathway. Here we evaluated the efficacy of a gene therapy based on the unilateral intra-striatal injection of a recombinant adeno-associated virus 2/5 (AAV2/5) targeting astrocytes specifically and carrying the N-terminal fragment of human SREBP2 (hSREBP2). Robust hSREBP2 expression in striatal glial cells in HD mice activated the transcription of cholesterol biosynthesis pathway genes, restored synaptic transmission, reversed Drd2 transcript levels decline, cleared muHTT aggregates and attenuated behavioral deficits. We conclude that glial SREBP2 participates in HD brain pathogenesis in vivo and that AAV-based delivery of SREBP2 to astrocytes counteracts key features of HD.

neuroscience↗

bioRxiv2020

Dose-dependent and disease-modifying effects of striatal infusion of cholesterol in Huntington's disease

A variety of pathophysiological mechanisms are implicated in Huntingtons disease (HD). Among them, reduced cholesterol biosynthesis has been detected in the HD mouse brain from pre-symptomatic stages, leading to diminished cholesterol synthesis, particularly in the striatum. In addition, systemic injection of cholesterol-loaded brain-permeable nanoparticles ameliorates synaptic and cognitive function in a transgenic mouse model of HD. To identify an appropriate treatment regimen and gain mechanistic insights into the beneficial activity of exogenous cholesterol in the HD brain, we employed osmotic mini-pumps to infuse three escalating doses of cholesterol directly into the striatum of HD mice in a continuous and rate-controlled manner. All tested doses prevented cognitive decline, while amelioration of disease-related motor defects was dose-dependent. In parallel, we found morphological and functional recovery of synaptic transmission involving both excitatory and inhibitory synapses of striatal medium spiny neurons. The treatment also enhanced endogenous cholesterol biosynthesis and clearance of mutant Huntingtin aggregates. These results indicate that cholesterol infusion to the striatum can exert a dose-dependent, disease-modifying effect and may be therapeutically relevant in HD.

neuroscience↗