Biology subjects

Racine, J.

Publications and source records attributed to Racine, J..

3 recordsLinked to original sources

bioRxiv2024

Torsion-Induced Traumatic Optic Neuropathy (TITON): A Physiologically Relevant Animal Model of Traumatic Optic Neuropathy

Traumatic optic neuropathy (TON) is a common cause of irreversible blindness following head injury. TON is characterized by axon damage in the optic nerve followed by retinal ganglion cell death in the days and weeks following injury. At present, no therapeutic or surgical approach has been found to offer any benefit beyond observation alone. This is due in part to the lack of translational animal models suitable for understanding mechanisms and evaluating candidate treatments. In this study, we developed a rat model of TON in which the eye is rapidly rotated, inflicting mechanical stress on the optic nerve and leading to significant visual deficits. These functional deficits were thoroughly characterized up to one week after injury using electrophysiology and immunohistochemistry. The photopic negative response (PhNR) of the light adapted full field electroretinogram (LA ffERG) was significantly altered following injury. This correlated with increased biomarkers of retinal stress, axon disruption, and cell death. Together, this evidence suggests the utility of our model for mimicking clinically relevant TON and that the PhNR may be an early diagnostic for TON. Future studies will utilize this animal model for evaluation of candidate treatments.

bioengineering↗

bioRxiv2024

Ibudilast Protects Retinal Bipolar Cells from Excitotoxic Retinal Damage and Activates the mTOR Pathway

Ibudilast, an inhibitor of macrophage migration inhibitory factor (MIF) and phosphodiesterase (PDE), has been recently shown to have neuroprotective effects in a variety of neurologic diseases. We utilize a chick excitotoxic retinal damage model to investigate ibudilasts potential to protect retinal neurons. Using single cell RNA-sequencing (scRNA-seq), we find that MIF, putative MIF receptors CD74 and CD44, and several PDEs are upregulated in different retinal cells during damage. Intravitreal ibudilast is well tolerated in the eye and causes no evidence of toxicity. Ibudilast effectively protects neurons in the inner nuclear layer from NMDA-induced cell death, restores retinal layer thickness on spectral domain optical coherence tomography, and preserves retinal neuron function, particularly for the ON bipolar cells, as assessed by electroretinography. PDE inhibition seems essential for ibudilasts neuroprotection, as AV1013, the analogue that lacks PDE inhibitor activity, is ineffective. scRNA-seq analysis reveals upregulation of multiple signaling pathways, including mTOR, in damaged Muller glia (MG) with ibudilast treatment compared to AV1013. Components of mTORC1 and mTORC2 are upregulated in both bipolar cells and MG with ibudilast. The mTOR inhibitor rapamycin blocked accumulation of pS6 but did not reduce TUNEL positive dying cells. Additionally, through ligand-receptor interaction analysis, crosstalk between bipolar cells and MG may be important for neuroprotection. We have identified several paracrine signaling pathways that are known to contribute to cell survival and neuroprotection and might play essential roles in ibudilast function. These findings highlight ibudilasts potential to protect inner retinal neurons during damage and show promise for future clinical translation. Graphical AbstractO_ST_ABSMain PointsC_ST_ABS- Ibudilast, a MIF and PDE inhibitor, preserves the form and function of the retina, especially bipolar cells, during excitotoxic damage - Ibudilast upregulates multiple signaling pathways, including mTOR, in damaged Muller glia and bipolar cells O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=88 SRC="FIGDIR/small/585556v1_ufig1.gif" ALT="Figure 1"> View larger version (41K): org.highwire.dtl.DTLVardef@18d9916org.highwire.dtl.DTLVardef@13db1b2org.highwire.dtl.DTLVardef@15d3d8dorg.highwire.dtl.DTLVardef@742b0c_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2023

PINK1 Deficiency Alters Muscle Stem Cell Fate Decision And Muscle Regenerative Capacity.

Maintenance of optimal mitochondrial function plays a crucial role in the regulation of muscle stem cell (MuSC) behavior, but the underlying maintenance mechanisms remain ill defined. In this study, we explored the importance of mitophagy, as a mitochondrial quality control regulator, in MuSCs and the role this process plays in maintaining optimal muscle regenerative capacity. Here we show that MuSCs exhibit dynamic alterations in mitophagy under different physiological myogenic states. In particular, quiescent MuSCs exhibit high levels of PINK1/Parkin-dependent mitophagy, which is rapidly decreased upon transition to an early activation state. Genetic disruption of this pathway using Pink1 knockout mice reduced mitophagy in quiescent MuSCs, which was accompanied by increased mitochondrial ROS release and mitochondrial network fragmentation. These abnormalities led to hampered self-renewal of MuSCs which ultimately translated in a progressive loss of muscle regeneration following repetitive injury. However, proliferation and differentiation capacity were unaltered in the absence of PINK1, indicating that altered fate decisions is the main mechanism underlying impaired muscle regeneration. Impaired fate decisions in PINK1 deficient MuSCs could be restored by scavenging excess mitochondrial ROS. Together, these data shed new light on the regulation of mitophagy during MuSC state transitions and position the PINK1-dependent pathway as an important regulator of MuSC mitochondrial properties and fate decisions.

cell biology↗