Biology subjects

Namakkal-Soorappan, R.

Publications and source records attributed to Namakkal-Soorappan, R..

5 recordsLinked to original sources

bioRxiv2025

Early Transcriptomic Signatures of Reductive Stress Cardiomyopathy Reveal Insufficient HIF-1 Signaling

Chronic activation of Nrf2-regulated antioxidant pathways can lead to a pathological condition known as reductive stress (RS). While transient Nrf2 activation confers protection against oxidative stress, its sustained stimulation may provoke maladaptive responses in high-energy-demanding organs such as the heart. In this study, we employed a cardiac-specific constitutively active Nrf2 transgenic (CaNrf2-TG) mouse model to characterize early transcriptomic alterations associated with the transition from compensated cardiac function to pathological remodeling. Myocardial RNA sequencing at 12 weeks of age, a critical window preceding overt cardiac dysfunction, revealed widespread dysregulation of antioxidants, immune, metabolic, proteostasis, and stress-response pathways. Notably, genes related to HIF-1 signaling, PI3K-Akt, MAPK, and hypertrophic cardiomyopathy were significantly altered. Functional enrichment analysis highlighted upregulation of detoxification enzymes and stress response regulators, alongside downregulation of ER chaperones, calcium-handling proteins, and MHC-II immune mediators. Furthermore, perturbations in metabolic flexibility and sarcomeric gene expression suggest early disruption of structural and energy-regulating networks. These findings uncover early molecular signatures of Nrf2-driven RS cardiomyopathy and may aid in identifying potential therapeutic targets for mitigating disease progression.

biochemistry↗

bioRxiv2021

Proteome signatures of reductive stress cardiomyopathy

Nuclear factor erythroid 2-related factor 2 (NRF2), a redox sensor, is vital for cellular redox homeostasis. We reported that transgenic mice expressing constitutively active Nrf2 (CaNrf2-TG) exhibit reductive stress (RS). In this study, we identified novel protein biomarkers for RS-induced cardiomyopathy using Tandem Mass Tag (TMT) proteomic analysis in heart tissues of TG (CaNrf2-TG) and non-transgenic (NTg) mice at 6-7 months of age (N= 4/group). A total of 1105 proteins were extracted from 22544 spectra. Of note, about 560 proteins were differentially expressed in TG vs. NTg hearts, indicating a global impact of RS on myocardial proteome. From a closer analysis of the proteome datasets, we identified over 32 proteins that were significantly altered in response to RS. Among these, 20 were upregulated and 12 were downregulated in the hearts of TG vs. NTg mice, suggesting that these proteins could be putative signatures of RS. Scaffold analysis revealed a clear distinction between TG vs NTg hearts. Of note, we observed several proteins with redox (#185; cysteine residues), NEM-adducts (#81), methionine-loss (#21) and acetylation (#1) modifications in TG vs. NTg hearts due to chronic RS. The majority of the differentially expressed proteins (DEPs) that are significantly altered in RS mice were found to be involved in stress related pathways such as antioxidants, NADPH, protein quality control (PQC), etc. Interestingly, proteins that were involved in mitochondrial respiration, lipophagy and cardiac rhythm were dramatically decreased in TG hearts. Of note, we identified the glutathione family of proteins as the significantly changed subset of the proteome in TG heart. Surprisingly, our comparative analysis of NGS based transcriptome and TMT-proteome indicated [~]50% of the altered proteins in TG myocardium was found to be negatively correlated with their transcript levels. Modifications at cysteine/NEM-adducts (redox), methionine or lysine residues in multiple proteins in response to chronic RS might be associated with impaired PQC mechanisms, thus causing pathological cardiac remodeling. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=102 SRC="FIGDIR/small/460105v1_ufig1.gif" ALT="Figure 1"> View larger version (43K): org.highwire.dtl.DTLVardef@e5974borg.highwire.dtl.DTLVardef@12fe043org.highwire.dtl.DTLVardef@2c6e17org.highwire.dtl.DTLVardef@efb153_HPS_FORMAT_FIGEXP M_FIG Graphical Abstract C_FIG

cell biology↗

bioRxiv2020

Transcriptional regulation of structural and functional adaptations in a developing adulthood myocardium

The development of the heart follows a synergic action of several signaling pathways during gestational, pre- & postnatal stages. The current study aimed to investigate whether the myocardium experiences transcriptional changes during the transition from post-natal to adult hood stages. Herein, we used C57/Bl6/J mice at 4 (28-days; post-natal/PN) and 20 weeks (adulthood/AH) of ages and employed the next generation RNAseq (NGS) to profile the transcriptome and echocardiography analysis to monitor the structural/functional changes in the heart. NGS-based RNA-seq revealed that 1215 genes were significantly upregulated and 2549 were down regulated in the AH versus PN hearts, indicating a significant transcriptional change during this transition. A synchronized cardiac transcriptional regulation through cell cycle, growth hormones, redox homeostasis and metabolic pathways was noticed in both PN and AH hearts. Echocardiography reveals significant structural and functional (i.e. systolic/diastolic) changes during the transition of PN to adult stage. Particularly, a progressive decline in ejection fraction (EF) and cardiac output was observed in AH hearts. These structural adaptations are in line with critical signaling pathways that drive the maturation of heart during AH. Overall, we have presented a comprehensive transcriptomic analysis along with structural-functional relationship during the myocardial development in adult mice.

genomics↗

bioRxiv2019

Impaired Regulation of Redox Transcriptome during the Differentiation of iPSCs into Induced Cardiomyocytes (iCMs)

BackgroundReprogramming of somatic cells into pluripotent stem cells (iPSC) and subsequent differentiation into iPSC-derived cardiomyocytes (iCM) seems to be a promising strategy for cardiac regenerative therapy. However, recent failure or poor outcomes in cardiac cell therapy warrants further investigation focusing on the infarction/wound environment (site of healing) to improve the cardiac regenerative medicine. Here, using next generation sequencing (NGS), we analyzed the global transcriptome to discover the unidentified genes/pathways that are crucial for cell survival, cytoprotection and mitochondrial dynamics during the differentiation of iPSC into iCM.\n\nMethodsHigh throughput NGS was performed RNA from human iPSCs and iCMs (n=3/group) and analyzed the global changes in the transcriptome during differentiation. Furthermore, Ingenuity Pathway Analysis (IPA) and Gene Ontology (GO) for biological process were performed to understand the transcriptional networks that are involved during iCM differentiation. RNA-seq data were further validated by qRT-PCR analyses.\n\nResultsGlobal transcriptome analysis revealed that ~9,290 genes (log2 FC >2) were significantly altered in human iCMs compared to the parent iPSCs, in which 4,784 transcripts were substantially upregulated and 4,506 transcripts were down-regulated during differentiation. GO enrichment and IPA analyses revealed the top 10 regulatory networks (i.e. hierarchical order) involved in differentiation of iCMs including cardiomyocyte remodeling, integrin-linked kinase signaling, Rho family of GTPases, etc. Surprisingly, none of the top 10 pathways listed the genes liable for redox signaling networks that are crucial for the basal cellular redox homeostasis, Nrf2-dependent antioxidant defense, mitochondrial functions and cell survival. Our deeper and unbiased analysis of this data revealed that the genes involved in above canonical signaling pathways are found in the middle of the inverted vertical cone. Of note, although these pathways are significantly altered during the differentiation (of iPS into cardiomyocytes), a majority of them are ranked low in the hierarchical list (>150). Validation of the randomly selected genes representing various pathways real-time qPCR confirmed the global transcriptome changes observed in NGS.\n\nConclusionWe highlight the significance of Nrf2-redox and mitochondrial transcriptome during differentiation of iPSC into iCMs. Thus, targeting the redox signaling mechanisms in iCMs may enhance their efficiency for cell therapy and improved myocardial repair.

cell biology↗

bioRxiv2018

Evidence for hyper-reductive redox in a subset of heart failure patients

BackgroundOxidative stress has been linked to heart failure (HF) in humans. Antioxidant-based treatments are often ineffective. Therefore, we hypothesize that some of the HF patients might have a reductive stress (RS) condition. Investigating RS-related mechanisms will aid in personalized optimization of redox homeostasis for better outcomes among HF patients.\n\nMethodsBlood samples were collected from HF patients (n=54) and healthy controls (n=42) and serum was immediately preserved in -80{degrees}C for redox analysis. Malondialdehyde (MDA; lipid peroxidation) levels by HPLC, reduced glutathione (GSH) and its redox ratio (GSH/GSSG) using enzymatic-recycling assay in the serum of HF patients were measured. Further, the kinetics of key enzymatic-antioxidant enzymes was analyzed by UV-Vis spectrophotometry. Non-invasive echocardiography was used to relate circulating redox status with cardiac function and remodeling.\n\nResultsThe circulatory redox state (GSH/MDA ratio) was used to stratify the HF patients into normal redox (NR), hyper-oxidative (HO), and hyper-reductive (HR) groups. While the majority of the HF patients exhibited the HO (42%), 41% of them had a normal redox (NR) state. Surprisingly, a subset of HF patients (17%) belonged to the hyper-reductive group, suggesting a strong implication for RS in the progression of HF. In HF patients, SOD, GPx and catalase were significantly increased while GR activity was significantly reduced relative to healthy controls. Furthermore, echocardiography analyses revealed that 55% of HO patients had higher systolic dysfunction while 75% of the hyper-reductive patients had higher diastolic dysfunction.\n\nConclusionThese results suggest that RS may be associated with HF pathogenesis for a subset of cardiac patients. Thus, stratification of HF patients based on their circulating redox status may serve as a useful prognostic tool to guide clinicians designing personalized antioxidant therapies.

biochemistry↗