Biology subjects

Nieman, M. L.

Publications and source records attributed to Nieman, M. L..

3 recordsLinked to original sources

bioRxiv2023

HuR inhibition reduces post-ischemic cardiac remodeling by dampening acute inflammatory gene expression and the innate immune response

Myocardial ischemia/reperfusion (I/R) injury and the resulting cardiac remodeling is a common cause of heart failure. The RNA binding protein Human Antigen R (HuR) has been previously shown to reduce cardiac remodeling following both I/R and cardiac pressure overload, but the full extent of the HuR-dependent mechanisms within cells of the myocardium have yet to be elucidated. In this study, we applied a novel small molecule inhibitor of HuR to define the functional role of HuR in the acute response to I/R injury and gain a better understanding of the HuR-dependent mechanisms during post-ischemic myocardial remodeling. Our results show an early (two hours post-I/R) increase in HuR activity that is necessary for early inflammatory gene expression by cardiomyocytes in response to I/R. Surprisingly, despite the reductions in early inflammatory gene expression at two hours post-I/R, HuR inhibition has no effect on initial infarct size at 24-hours post-I/R. However, in agreement with previously published work, we do see a reduction in pathological remodeling and preserved cardiac function at two weeks post-I/R upon HuR inhibition. RNA-sequencing analysis of neonatal rat ventricular myocytes (NRVMs) at two hours post-LPS treatment to model damage associated molecular pattern (DAMP)-mediated activation of toll like receptors (TLRs) demonstrates a broad HuR-dependent regulation of pro-inflammatory chemokine and cytokine gene expression in cardiomyocytes. We show that conditioned media from NRVMs pre-treated with HuR inhibitor loses the ability to induce inflammatory gene expression in bone marrow derived macrophages (BMDMs) compared to NRVMs treated with LPS alone. Functionally, HuR inhibition in NRVMs also reduces their ability to induce endocrine migration of peripheral blood monocytes in vitro and reduces post-ischemic macrophage infiltration to the heart in vivo. In summary, these results suggest a HuR-dependent expression of pro-inflammatory gene expression by cardiomyocytes that leads to subsequent monocyte recruitment and macrophage activation in the post-ischemic myocardium.

molecular biology↗

bioRxiv2022

Single-cell transcriptomic profiling of kidney fibrosis identifies a novel specific fibroblast marker and putative disease target

BackgroundPersistent kidney fibroblast activation and tubular epithelial cell (TEC) injury are key contributors to CKD. However, transcriptional and cellular identities of advanced kidney disease, along with renal fibroblast specific markers and molecular targets contributing to persistent tubular injury, remain elusive. MethodsWe performed single-cell RNA sequencing with two clinically relevant murine kidney fibrosis models. Day 28 post-injury was chosen to ensure advanced fibrotic disease. Identified gene expression signatures were validated using multiple quantitative molecular analyses. ResultsWe revealed comprehensive single cell transcriptomic profiles of two independent kidney fibrosis models compared to normal control. Both models exhibited key CKD characteristics including renal blood flow decline, inflammatory expansion and proximal tubular loss. We identified novel populations including "secretory", "migratory" and "contractile" activated fibroblasts, specifically labelled by newly identified fibroblast-specific Gucy1a3 expression. Fibrotic kidneys elicited elevated embryonic and pro-fibrotic signaling, including separate "Embryonic" and "Pro-fibrotic" TEC clusters. Also, fibrosis caused enhanced cell-to-cell crosstalk, particularly between activated fibroblasts and pro-fibrotic TECs. Analysis of factors mediating mesenchymal phenotype in the injured epithelium identified persistent elevation of Ahnak, previously reported in AKI, in both CKD models. AHNAK knockdown in primary human renal proximal tubular epithelial cells induced a pro-fibrotic phenotype and exacerbated TGF{beta} response via p38, p42/44, pAKT, BMP and MMP signaling. ConclusionsOur study comprehensively examined kidney fibrosis in two independent models at the singe-cell resolution, providing a valuable resource for the field. Moreover, we newly identified Gucy1a3 as a kidney activated fibroblast specific marker and validated AHNAK as a putative disease target. Significance StatementMechanistic understanding of kidney fibrosis is principal for mechanistic understanding and developing targeted strategies against CKD. However, specific markers and molecular targets of key effector cells - activated kidney fibroblasts and injured tubular epithelial cells - remain elusive. Here, we created comprehensive single cell transcriptomic profiles of two clinically relevant kidney fibrosis models. We revealed "secretory", "contractile" and "migratory" fibroblasts and identified Gucy1a3 as a novel marker selectively labelling all three populations. We revealed that kidney fibrosis elicited remarkable epithelial-to-stromal crosstalk and pro-fibrotic signaling in the tubular cells. Moreover, we mechanistically validated AHNAK as a putative novel kidney injury target in a primary human in vitro model of epithelial-to-mesenchymal transition. Our findings advance understanding of and targeted intervention in fibrotic kidney disease.

molecular biology↗

bioRxiv2021

Adipocyte deletion of the RNA binding protein HuR induces cardiac hypertrophy and fibrosis

Adipose tissue continues to gain appreciation for its broad role as an endocrine organ, and disruptions in adipose tissue homeostasis plays a central role in cardiovascular physiology. We have previously shown that expression of the RNA binding protein HuR in adipose tissue mediates energy expenditure, but the potential cardiovascular impacts of this finding have not been explored. We show here that adipose tissue-specific deletion of HuR (Adipo-HuR-/-) is sufficient to induce the spontaneous development of cardiac hypertrophy and fibrosis. Hearts from Adipo-HuR-/- mice have increased left ventricular (LV) ejection fraction, rate of pressure generation, and LV posterior wall thickness that is accompanied by an increase in LV/body weight ratio and hypertrophic gene expression. Furthermore, Adipo-HuR-/- hearts display increased fibrosis by picrosirius red staining and periostin expression. To identify underlying mechanisms, we applied both RNA-seq and weighted gene co-expression network analysis (WGCNA) to define HuR-dependent changes in gene expression as well as significant relationships between adipose tissue gene expression and LV mass. RNA-seq results demonstrate a significant increase in pro-inflammatory gene expression in the subcutaneous white adipose tissue (scWAT) from Adipo-HuR-/- mice that is accompanied by an increase in serum levels of both TNF- and IL-6. WGCNA identified a significant enrichment in inflammation, apoptosis/cell death, and vesicle-mediated transport genes among those whose expression most significantly associated with CVD in Adipo-HuR-/-. In conclusion, we demonstrate that the loss of HuR expression in adipose tissue promotes the development of cardiac hypertrophy and fibrosis, potentially through modulation of inflammation and vesicle-mediated transport in scWAT. NEW AND NOTEWORTHYThis work demonstrates the spontaneous development of cardiac hypertrophy and fibrosis upon adipose tissue-specific deletion of the RNA binding protein HuR that appears to be mechanistically driven by HuR-dependent changes in inflammatory and extracellular vesicle transport mediating genes in the subcutaneous white adipose tissue. These results suggest that loss of HuR expression in adipose tissue in obesity, as demonstrated in mouse and humans by our group and others, may contribute to obesity-mediated CVD.

physiology↗