Biology subjects

Ramirez, N.

Publications and source records attributed to Ramirez, N..

7 recordsLinked to original sources

bioRxiv2026

Sex-specific dichotomy of chronic mild stress effects on blood pressure and longitudinal measurements of renal sympathetic nerve activity: are females really protected?

Modulation of renal nerves to improve blood pressure (BP) control has become a topic of intense investigation over the last 10-15 years. Given that renal innervation is composed of mixed nerve fibers containing both afferent (sensory) and efferent (sympathetic) fibers, subsequent preclinical studies have been investigating their respective roles in hypertension pathobiology in different genetic and salt-sensitive rat models. Here we set out to investigate how renal afferent and efferent nerves regulate hypertension development in the chronic mild stress model (CMS). We show that in male CMS rats, ablation of afferent renal nerves (ARDNx) and all renal nerves (TRDNx) resulted in similar BP (104 {+/-} 2 mmHg vs. 101 {+/-} 3 mmHg, respectively), both reduced compared to the SHAM group (118 {+/-} 1 mmHg, p = 0.003 and p < 0.001, respectively) arguing for a prominent role of afferent renal nerves in CMS hypertension. Additionally, we show a reduction of vasopressin (AVP) V1b but not V1a receptor abundance in ARDNx CMS males but not females, suggesting that afferent renal nerves are involved in increase in BP via V1b AVP receptor. We additionally show that despite normal BP, female CMS rats display increased renal sympathetic nerve activity (RSNA; 2.39 {+/-} 0.23 bursts/beat vs. 1.44 {+/-} 0.12 bursts/beat, p < 0.005) measured directly with implanted telemetry in conscious rats over one week and aortic stiffness, as evidenced by increased aortic pulse wave velocity (173.2 {+/-} 50.9 mm/s vs. - 10.7 {+/-} 54.6 mm/s in controls, p = 0.0393). NEW & NOTEWORTHYWe show that renal denervation mitigates the rise in blood pressure (BP) in a model that is not genetic nor diet-dependent, the chronic mild stress model (CMS). Specifically, we demonstrate the role of afferent, rather than efferent, renal nerves in mediating the rise in BP in male CMS rats. Finally, we report that renal sympathetic nerve activity, but not BP, is elevated in female CMS rats measured by telemetry over seven days in conscious rats.

physiology↗

bioRxiv2024

Hypoxia disrupts circadian rhythms in astrocytes and causes synapse engulfment defects

Astrocytes are emerging as key regulators of neuronal synaptic network maturation and function, through control of synaptic pruning. This is important, because individuals with ASD have excess glutamatergic synapses in the cortex, but the biological mechanisms underlying this phenotype remain unclear. Here, we used human cortical organoids (hCO) derived from induced pluripotent stem cells (hiPSCs), to examine the effect of hypoxia on synapse engulfment in human astrocytes at postnatal-equivalent stages of development. We identified that hypoxia significantly inhibits the synaptosome phagocytosis, and that this phenotype is mediated through disruptions in the astrocytic circadian rhythm molecular pathway and subsequent decreased expression of MEGF10. Lastly, we demonstrated that circadian clock disruptions are sufficient to induce these observed phenotypes even in the absence of hypoxia, both in hCOs and within the mouse hippocampus in vivo. Our study uncovers a novel mechanistic link between hypoxia, circadian rhythms disruptions, and synapse pruning by astrocytes, and provides insight into the pathophysiology of ASD, and other neuropsychiatric diseases. Separately, the demonstration of the presence of circadian rhythms in hCOs opens an unprecedented opportunity to dissect the role of circadian clocks in normal brain development and how it contributes to specific diseases of environmental or genetic origin.

neuroscience↗

bioRxiv2022

Integrated Multi-omics Analyses of NFKB1 patients B cells points towards an up regula-tion of NF-κB network inhibitors

The transcription factor NF-{kappa}B plays a pivotal role in the adaptive immune response. Pathogenic variants in NFKB1 are the most common genetic etiology of common variable immunodeficiency (CVID). Patients frequently present with impaired terminal B cell differentiation, autoimmunity, and hyperinflammatory immune dysregulation. NF-{kappa}B signaling and target gene expression are expected to be dysregulated in NFKB1-mutated patients. Here, we performed a multi-omics characterization of B cells from a cohort of clinically affected and unaffected NFKB1 mutation carriers. Our analysis identified specific epigenetic dysregulation and gene expression differences on B cells from NFKB1-mutated patients. We observed an aberrant expression of negative regulators of NF-{kappa}B signaling in NFKB1 mutation carriers, which may be a key factor for the autoinflammatory phenotype of these patients. Moreover, our analysis points towards a dysregulation of XBP1 and BCL3, key players of B cell activation and proliferation at different stages of B cell differentiation. The reduced expression of negative regulators of the NF-{kappa}B network is likely to be one of several mechanisms responsible for the aberrant NF-{kappa}B signaling, which impairs the maintenance of a normal humoral immune response. In summary, our findings highlight epigenetic and gene expression changes in B cells associated with NFKB1 mutations. Our data give insight into future therapeutic opportunities for patients with NFKB1 (haplo)insufficiency.

immunology↗

bioRxiv2021

A novel α/β T-cell subpopulation defined by recognition of EPCR

T-cell self-recognition of antigen presenting molecules is led by antigen-dependent or independent mechanisms. The endothelial protein C receptor (EPCR) shares remarkable similarity with CD1d, including a lipid binding cavity. We have identified EPCR-specific /{beta} T-cells in the peripheral blood of healthy donors. The average frequency in the CD3+ leukocyte pool is comparable to other autoreactive T-cell subsets that specifically bind MHC-like receptors. Alteration of the EPCR lipid cargo, revealed by X-ray diffraction studies, points to a prevalent, yet not exclusive, lipid-independent self-recognition. In addition, we solve the EPCR lipidome, and detect species not yet described as EPCR ligands. These studies report, for the first time, novel recognition by circulating /{beta} T-cells and provide grounds for EPCR and lipid mediated T-cell restriction.

immunology↗

bioRxiv2021

Toxicity of 4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone (NKK) in early development: a wide-scope metabolomics assay in zebrafish embryos

The tobacco-specific nitrosamine 4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) is a carcinogenic and ubiquitous environmental pollutant which carcinogenic and cytotoxic activity has been thoroughly investigated in murine models and human tissues. However, its potential deleterious effects on vertebrate early development are yet poorly understood. In this work, we characterized the impact of NNK exposure during early developmental stages of zebrafish embryos, a known alternative model for mammalian toxicity studies. Embryos exposed to different NNK concentrations were monitored for lethality and for the appearance of malformations during the first five days after fertilization. LC/MS-based untargeted metabolomics was subsequently performed for a wide-scope assay of NNK-related metabolic alterations. Our results revealed the presence of not only the parental compound, but also of two NKK known metabolites, 4-Hydroxy-4-(3-pyridyl)-butyric acid (HPBA) and 4-(Methylnitrosamino)-1-(3-pyridyl-N-oxide)-1-butanol (NNAL-N-oxide) in exposed embryos likely resulting from active CYP450-mediated -hydroxylation and NNK detoxification pathways, respectively. This was paralleled by a disruption in purine and pyrimidine metabolisms and the activation of the base excision repair pathway. Our results confirm NNK as a harmful embryonic agent and demonstrate zebrafish embryos to be a suitable early development model to monitor NNK toxicity.

pharmacology and toxicology↗

bioRxiv2020

Reduced type-A carbohydrate-binding module interactions to cellulose leads to improved endocellulase activity

Dissociation of non-productively bound cellulolytic enzymes from cellulose is hypothesized to be a key rate-limiting factor impeding cost-effective biomass conversion to fermentable sugars. However, the role of carbohydrate-binding modules (CBMs) in enabling non-productive enzyme binding is not well understood. Here, we examine the subtle interplay of CBM binding and cellulose hydrolysis activity for three model Type-A CBMs (families 1, 3a, and 64) tethered to a multifunctional endoglucanase (CelE) on two distinct cellulose allomorphs (i.e., cellulose I and III). We generated a small-library of mutant CBMs with varying cellulose affinity, as determined by equilibrium binding assays, followed by monitoring cellulose hydrolysis activity of CelE-CBM fusion constructs. Finally, kinetic binding assays using quartz crystal microbalance with dissipation (QCM-D) were employed to measure CBM adsorption and desorption rate constants Kon and Koff, respectively, towards nanocrystalline cellulose derived from both allomorphs. Overall, our results indicate that reduced CBM equilibrium binding affinity towards cellulose I alone, resulting from increased desorption rates (Koff) and reduced effective adsorption rates (nKon), is correlated to overall improved endocellulase activity. Future studies could employ similar approaches to unravel the role of CBMs in non-productive enzyme binding and develop improved cellulolytic enzymes for industrial applications.Competing Interest StatementShishir P.S. Chundawat declares a conflict of interest and competing financial interest(s) having filed two patent applications on pretreatment processes to produce cellulose-III enriched cellulosic biomass for biofuels production (US20130244293A1and WO2011133571A2). All other authors declare that they have no competing interests.View Full Text

biochemistry↗

bioRxiv2020

Nucleolar disruption, activation of P53 and premature senescence in POLR3A-mutated Wiedemann-Rautenstrauch Syndrome fibroblasts

Recently, mutations in the RNA polymerase III subunit 3A (POLR3A) have been described as the cause of the neonatal progeria or Wiedemann-Rautenstrauch syndrome (WRS). POLR3A have important roles in the regulation of transcription of small RNAs, including tRNA, 5S rRNA and U6 snRNA. We aim to describe cellular and molecular features of WRS fibroblasts. Cultures of primary fibroblasts from one WRS patient [monoallelic POLR3A variant c.3772_3773delCT (p.Leu1258Glyfs*12)] and one control were grown. Mutation in POLR3A causes a decreased in the expression of POLR3A mRNA and protein and a sharp increased of mutant protein. In addition, there was an increased in its nuclear localization. These changes were associated to an increase number and area of nucleoli, a significantly larger nuclear area, and a high increased in the expression of pP53 and pH2AX. All these changes were associated to premature senescence. The present observations add to our understanding of the differences between HGPS and WRS, and opens new alternatives to study cell senesce and human aging.

cell biology↗