Biology subjects

Nieman, M.

Publications and source records attributed to Nieman, M..

4 recordsLinked to original sources

bioRxiv2025

Modulating Cardiac-Gut Microbiome Interaction Post-Myocardial Infarction with Engineered Bacteria

The gut microbiome plays a critical role in the pathophysiology of acute myocardial infarction (MI). MI events significantly impact intestinal integrity which results in leakage of bacterial products into the systemic circulation. We demonstrate that MI not only compromises intestinal integrity, leading to systemic leakage of bacterial products like LPS, but also results in the translocation and colonization of live, intact gut bacteria in the MI heart - a novel aspect of the heart-gut axis. Our initial findings with natural murine gut microbiome were substantiated using orally administered E. coli Nissle 1917 (EcN), as a tracer bacterium. Furthermore, we engineered EcN to express the microbial anti-inflammatory molecule (MAM) derived from the probiotic Faecalibacterium prausnitzii. Treatment with this engineered strain, EcN-MAM, led to significantly improved survival and cardiac function in MI mice. This was attributed to enhanced gut barrier integrity, resulting in reduced systemic bacterial permeation and subsequent inflammation. These findings shed light on a previously unrecognized dimension of the heart-gut axis and highlight the potential of microbiome-based interventions in MI management.

synthetic biology↗

bioRxiv2024

MCM2 mediates post-MI cardioprotection by promoting the pro-angiogenic cardiosome signaling

AbstractO_ST_ABSBackgroundC_ST_ABSIn the past decade, induced cardiac rejuvenation has emerged as a leading approach to repair cardiac injury. Recent studies demonstrate that promoting cell cycle reentry in adult cardiomyocytes (CM) enhances cardiac rejuvenation by influencing paracrine signaling. We previously demonstrated that the inhibition of two cell cycle inhibitors, Retinoblastoma 1 (Rb1) and Meis homeobox 2 (Meis2), in the adult CM enhances angiogenesis and cardiac function following ischemic injury, but the underlying mechanisms have yet to be elucidated. The goal of this study is to determine the mechanisms by which inhibition of Rb1 and Meis2 promotes cardiac rejuvenation in a mouse model of myocardial infarction. MethodsMyocardial infarction was induced in adult C57/Bl6 mice via permanent LAD occlusion followed by direct injection of either control or Rb1+Meis2 siRNA cocktail to the ischemic myocardium. MCM2 overexpression done via direct myocardial injection of an MCM2-plasmid DNA expression cassette. Cardiac function and LV wall motion was assessed via echocardiography, and fibrosis and CM hypertrophy were assessed via histology. RNA-sequencing was performed on isolated adult murine CMs with siRNA-mediated Rb1+Meis2 knockdown to delineate the downstream mechanisms. Further identification of Rb1, Meis2, and MCM2-dependent mechanisms were done using in vitro techniques in isolated CMs and HUVEC cells. ResultsWe show that siRNA-mediated knockdown of Rb1 and Meis2 in vivo reduces pathological LV remodeling and preserves cardiac structure and function in adult mouse hearts post-MI. RNA-seq analyses revealed MCM2 as a potential downstream target of Rb1/Meis2 to enhance protective paracrine signaling in primary adult CMs. Indeed, re-expression of MCM2, which is developmentally lost from neonatal to adult CM in the heart, improves cardiac function and LV wall motion while reducing myocyte hypertrophy and fibrotic scar size post-MI. Mechanistically, re-expression of MCM2 promotes the secretion of pro- angiogenic factors from adult CM, and transfer of conditioned media from MCM2 expressing CM induced vasculogenesis in HUVEC cells. Proteomic analysis of the MCM2 interactome confirmed a significant enrichment of angiogenic mediators and suggests an MCM2-dependent protein packaging of pro- angiogenic factors in CM-derived small extracellular vesicles (cardiosomes). ConclusionRe-expression of MCM2 in adult CM promotes the secretion of pro-angiogenic cardiosomes that induce paracrine revascularization of endothelial cells and mitigates cardiac injury post-MI. SUMMARY DIAGRAM O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=193 SRC="FIGDIR/small/628232v1_ufig1.gif" ALT="Figure 1"> View larger version (60K): org.highwire.dtl.DTLVardef@17eaeforg.highwire.dtl.DTLVardef@40f0f5org.highwire.dtl.DTLVardef@18b7664org.highwire.dtl.DTLVardef@109cb1c_HPS_FORMAT_FIGEXP M_FIG C_FIG

physiology↗

bioRxiv2024

The Plasmodium falciparum NCR1 membrane protein is a novel antimalarial target that exports cholesterol to maintain membrane homeostasis

Malaria is an extremely devastating parasitic infection that kills over half a million people each year. It is the leading cause of death in many developing countries, in part, due to a lack of resources and readily available therapeutics. Unfortunately, the most prevalent and deadliest causative agent of malaria, Plasmodium falciparum, has developed resistance to nearly all currently available antimalarial drugs. The P. falciparum Niemann-Pick Type C1-related (PfNCR1) transporter has been identified as a druggable target, as it is required for membrane homeostasis of the parasite. However, the structure and detailed molecular mechanism of this membrane protein are not yet available. Here we present three structures of PfNCR1 both in the absence and presence of the functional inhibitor MMV009108 at resolutions between 2.98 [A] and 3.81 [A] using single-particle cryo-electron microscopy (cryo-EM). The data suggest that PfNCR1 binds cholesterol and forms a cholesterol transport tunnel to modulate the composition of the parasite plasma membrane. Cholesterol efflux assays substantiate this as they show that PfNCR1 is an exporter capable of extruding cholesterol from the membrane. Additionally, the inhibition mechanism of MMV009108 appears to be due to a direct blockage of PfNCR1, preventing this transporter from shuttling cholesterol.

biochemistry↗

bioRxiv2024

Fast skeletal myosin binding protein-C expression exacerbates dysfunction in heart failure

During heart failure, gene and protein expression profiles undergo extensive compensatory and pathological remodeling. We previously observed that fast skeletal myosin binding protein-C (fMyBP-C) is upregulated in diseased mouse hearts. While fMyBP-C shares significant homology with its cardiac paralog, cardiac myosin binding protein-C (cMyBP-C), there are key differences that may affect cardiac function. However, it is unknown if the expression of fMyBP-C expression in the heart is a pathological or compensatory response. We aim to elucidate the cardiac consequence of either increased or knockout of fMyBP-C expression. To determine the sufficiency of fMyBP-C to cause cardiac dysfunction, we generated cardiac-specific fMyBP-C over-expression mice. These mice were further crossed into a cMyBP-C null model to assess the effect of fMyBP-C in the heart in the complete absence of cMyBP-C. Finally, fMyBP-C null mice underwent transverse aortic constriction (TAC) to define the requirement of fMyBP-C during heart failure development. We confirmed the upregulation of fMyBP-C in several models of cardiac disease, including the use of lineage tracing. Low levels of fMyBP-C caused mild cardiac remodeling and sarcomere dysfunction. Exclusive expression of fMyBP-C in a heart failure model further exacerbated cardiac pathology. Following 8 weeks of TAC, fMyBP-C null mice demonstrated greater protection against heart failure development. Mechanistically, this may be due to the differential regulation of the myosin super-relaxed state. These findings suggest that the elevated expression of fMyBP-C in diseased hearts is a pathological response. Targeted therapies to prevent upregulation of fMyBP-C may prove beneficial in the treatment of heart failure. Significance StatementRecently, the sarcomere - the machinery that controls heart and muscle contraction - has emerged as a central target for development of cardiac therapeutics. However, there remains much to understand about how the sarcomere is modified in response to disease. We recently discovered that a protein normally expressed in skeletal muscle, is present in the heart in certain settings of heart disease. How this skeletal muscle protein affects the function of the heart remained unknown. Using genetically engineered mouse models to modulate expression of this skeletal muscle protein, we determined that expression of this skeletal muscle protein in the heart negatively affects cardiac performance. Importantly, deletion of this protein from the heart could improve heart function suggesting a possible therapeutic avenue.

physiology↗