Biology subjects

al-Abed, Y.

Publications and source records attributed to al-Abed, Y..

4 recordsLinked to original sources

bioRxiv2025

Longitudinal Characterization of Compound Action Potentials in Chronic Vagus Nerve Recordings in Mice

The vagus nerve (VN) mediates bidirectional communication between the body and brain to maintain physiological homeostasis; likewise, alterations in ongoing vagal signaling may be indicators of disease and/or contribute to disease pathogenesis. Even though extensively documented in acute experiments, ongoing vagal activity has not been characterized longitudinally, over days or weeks, in mice, a preferred preclinical model. In addition, even though many VN recordings in mice occur during anesthesia, the effects of anesthesia on vagal signaling are unknown. This study uses a chronic implant mouse model to record vagal activity in anesthetized and awake, behaving animals for an average of 10 weeks and up to 6 months. Individual compound action potentials (CAPs) are tracked across multiple days by quantifying comparisons in features, including firing rates, waveform shape, inter-CAP interval histograms, and phase-locking to cardiac and respiratory signals while demonstrating long-term electrode-nerve interface viability and stable signal-to-noise ratios. Additionally, cytokine challenge experiments produced detectable CAP responses up to 3 months after electrode implantation. Lastly, awake recordings incorporated video analysis to identify and remove motion artifacts to preserve and extract neural and cardiac recordings during behavior. Results reveal diverse CAP populations with diverse physiological coupling and firing rates modulated by anesthesia. This work highlights the potential of chronic VN recordings to assess long-term changes in vagal activity in health and disease, with implications in discovery of autonomic markers of disease and closed-loop VNS stimulation strategies.

neuroscience↗

bioRxiv2025

Endogenous CGRP activates NRF2 signaling via non-electrophilic mechanisms

The transcription factor nuclear factor erythroid 2-related factor 2 (NRF2) is crucial for regulating cellular responses to oxidative stress, making it a significant target for therapeutic interventions. While exogenous NRF2 activators offer significant therapeutic potential, their predominantly electrophilic nature poses considerable challenges for clinical use; the heightened electrophilic reactivity required to achieve therapeutic efficacy raises potential safety concerns. Calcitonin gene-related peptide (CGRP) has shown protective effects against oxidative stress and is involved in NRF2 activation; however, the underlying mechanisms are not fully understood. This study explores the mechanisms underlying endogenous CGRP-mediated NRF2 upregulation by inducing acute or chronic CGRP release through diving reflex (DR) in male Sprague-Dawley rats. Brain tissue proteomics confirmed the upregulation of NRF2-dependent antioxidant transcripts-- predominantly glutathione-related genes--without concurrent elevation of oxidative stress markers in both acute and chronic CGRP exposure paradigms. CGRP potently activated NRF2 in brain and peripheral tissues, evidenced by elevated nuclear and phosphorylated NRF2, increased nuclear:cytosolic NRF2 ratios, and enhanced antioxidant gene transcription--effects substantially attenuated by CGRP antagonism. Reduced glutathione levels increased without concurrent elevations in lipid peroxidation, protein oxidation, or evidence of tissue damage, suggesting CGRP avoids side effects characteristic of electrophilic NRF2 activators. Furthermore, our findings suggest that CGRP-mediated NRF2 activation primarily occurs via non-electrophilic mechanisms, with the p62-KEAP1-NRF2 pathway predominantly active in peripheral organs (lung and kidney), and the AMPK-NRF2 pathway more pronounced in the brain, highlighting the organ-specific nature of the response. Time-dependent variations in CGRP-mediated NRF2 activation were also observed, influencing both the response to CGRP and its impact on oxidative stress resistance. These results suggest that targeting NRF2 with endogenous CGRP may offer a promising therapeutic approach for managing oxidative stress-related diseases, both acute and chronic, across multiple organs, by avoiding electrophilic stress. HighlightsO_LIEndogenous CGRP triggers a potent and non-electrophilic activation of NRF2 signaling. C_LIO_LICGRP increases reduced glutathione levels following both acute and chronic exposures, in contrast to the effects of exogenous electrophilic NRF2 activators. C_LIO_LIIn peripheral organs, CGRP predominantly activates the KEAP1-dependent p62-KEAP1-NRF2 pathway. C_LIO_LIIn the brain, CGRP primarily activates the KEAP1-independent AMPK-NRF2 pathway. C_LIO_LICGRP exhibits time-dependent patterns, where acute exposure leads to a more significant upregulation of NRF2-targeted antioxidative gene expression and chronic exposure confers increased resistance to oxidative stress. C_LI Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=166 SRC="FIGDIR/small/650677v1_ufig8.gif" ALT="Figure 8"> View larger version (44K): org.highwire.dtl.DTLVardef@ae52a3org.highwire.dtl.DTLVardef@b35d1eorg.highwire.dtl.DTLVardef@1a68f31org.highwire.dtl.DTLVardef@31234_HPS_FORMAT_FIGEXP M_FIG C_FIG

molecular biology↗

bioRxiv2024

Intrinsic diving reflex induces potent antioxidative response by activation of NRF2 signaling

AimsThis study aims to elucidate the underlying mechanisms of diving reflex, a powerful endogenous mechanism supporting underwater mammalian survival. Antioxidative responses, observed in marine mammals, may be contributing factors. Using a multi-organ approach, this study assesses whether acute and chronic diving reflex activate nuclear factor-erythroid-2-related factor 2 (NRF2) signaling pathways, which regulate cellular antioxidant responses. MethodsMale Sprague-Dawley rats (n=38) underwent either a single diving session to elicit acute diving reflex, or daily diving sessions for 4-weeks to produce chronic diving reflex. NRF2 (total, nuclear, phosphorylated), NRF2-downstream genes, and malondialdehyde were assessed via Western blot, immunofluorescence, RT-PCR, and ELISA in brain, lung, kidney, and serum. ResultsDiving reflex increased nuclear NRF2, phosphorylated NRF2, and antioxidative gene expression, in an organ-specific and exposure time-specific manner. Comparing organs, the brain had the highest increase of phosphorylated NRF2 expression, while kidney had the highest degree of nuclear NRF2 expression. Comparing acute and chronic sessions, phosphorylated NRF2 increased the most with chronic diving reflex, but acute diving reflex had the highest antioxidative gene expression. Notably, calcitonin gene-related peptide appears to mediate diving reflex effects on NRF2 activation. ConclusionsAcute and chronic diving reflex activate potent NRF2 signaling in the brain and peripheral organs. Interestingly, acute diving reflex induces higher expression of downstream antioxidative genes compared to chronic diving reflex. This result contradicts previous assumptions requiring chronic exposure to diving for induction of antioxidative effects and implies that the diving reflex has a strong translational potential during preconditioning and postconditioning therapies. Key PointsO_LIDiving reflex activates potent NRF2 signaling via multiple mechanisms, including phosphorylation, nuclear translocation, and KEAP1 downregulation with both acute and chronic exposure. C_LIO_LIDiving reflex activates NRF2 via differential pathways in the brain and other organs; phosphorylated NRF2 increases more in the brain, while nuclear NRF2 increases more in the peripheral organs. C_LIO_LIAcute diving reflex exposure induces a more pronounced antioxidative effect than chronic diving reflex exposure, indicating that the antioxidative response activated by diving reflex is not dependent upon chronic adaptive responses and supports diving reflex as both a preconditioning and postconditioning treatment. C_LI

physiology↗

bioRxiv2023

Ultrasound neuromodulation of an anti-inflammatory pathway at the spleen produces sustained improvement of experimental pulmonary hypertension

BackgroundInflammation is pathogenically implicated in pulmonary arterial hypertension (PAH); however, it has not been adequately targeted therapeutically. We investigated whether neuromodulation of an anti-inflammatory neuroimmune pathway involving the splenic nerve using noninvasive, focused ultrasound stimulation of the spleen (sFUS) can improve experimental pulmonary hypertension (PH). MethodsPH was induced in rats either by SU5416 (20 mg/kg SQ) injection, followed by 21 (or 35) days of hypoxia (SuHx model), or by monocrotaline (60 mg/kg IP) injection (MCT model). Animals were randomized to receive either daily, 12-min-long sessions of sFUS or sham stimulation, for 14 days. Catheterizations, echocardiography, indices of autonomic function, lung and heart histology and immunohistochemistry, spleen flow cytometry and lung single-cell-RNA sequencing were performed after treatment to assess the effects of sFUS. ResultsSplenic denervation right before induction of PH results in a more severe phenotype. In both SuHx and MCT models of PH, sFUS treatment reduces right ventricular (RV) systolic pressure by 25-30% compared to sham therapy, without affecting systemic pressure, and improves RV function and autonomic indices. sFUS reduces wall thickness, apoptosis, and proliferation in small pulmonary arterioles, suppresses CD3+ and CD68+ cell infiltration in lungs and RV fibrosis and hypertrophy and lowers brain natriuretic peptide. Beneficial effects persist for weeks after sFUS discontinuation and are more robust with early and longer treatment. Splenic denervation abolishes sFUS therapeutic benefits. sFUS partially normalizes CD68+ and CD8+ T-cells cell counts in the spleen and downregulates several inflammatory genes and pathways in nonclassical and classical monocytes, and macrophages in the lung. Differentially expressed genes in those cell types are significantly enriched for human PAH-associated genes. ConclusionssFUS causes dose-dependent, sustained improvement of hemodynamic, autonomic, laboratory and pathological manifestations in two models of experimental PH. Mechanistically, sFUS normalizes immune cell populations in the spleen and downregulates inflammatory genes and pathways in the lung, many of which are relevant in human disease.

neuroscience↗