Biology subjects

Vallejo-Illarramendi, A.

Publications and source records attributed to Vallejo-Illarramendi, A..

4 recordsLinked to original sources

bioRxiv2025

Disrupting the Feed-Forward Cycle of RyR1 Calcium Leak and Oxidative Stress Mitigates Doxorubicin-Induced Skeletal Myopathy

Doxorubicin (DOX), a highly effective and widely used chemotherapeutic agent used to treat various types of cancer. Unfortunately, DOX also has some undesirable and off-target effects, particularly debilitating muscle weakness and fatigue. The mechanism behind this DOX-induced skeletal myotoxicity (DISM) remains unclear. Here, we show that acute DOX exposure, at clinically relevant concentrations, impairs isometric force production and accelerates fatigue in ex vivo murine flexor digitorum brevis (FDB) muscles. Mechanistically, we found that DOX increases the open probability of single RyR1 and disrupts calcium (Ca2+)-dependent inactivation (CDI). This results in a persistent sarcoplasmic reticulum (SR) Ca2+ leak, elevated basal cytosolic Ca2+, and abnormal Ca2+ release during action potentials. This abnormal intracellular Ca2+ handling ultimately leads to increased mitochondrial reactive oxygen species (ROS) production, which, in turn, exacerbates the functional instability of RyR1. Interestingly, the cytosolic basal Ca2+ elevation precedes ROS generation, suggesting that it initiates a destructive cross-talk between Ca2+ dysregulation and oxidative stress. Notably, pharmacological stabilization of the RyR1-FKBP12 complex with novel triazole compounds, MP-001 and MP-034, normalizes RyR1 function, Ca2+ and ROS homeostasis, as well as muscle force and fatigue resistance. Our findings indicate that DISM is initiated by DOX destabilization of the RyR1-FKBP12 complex (abnormal SR Ca2+ leak) and then exacerbated by the Ca-ROS vicious cycle. Limiting RyR1-mediated Ca2+ leak with MP-001 represents a promising therapeutic strategy for anti-DISM, aiming to normalize muscle function in patients undergoing DOX chemotherapy.

physiology↗

bioRxiv2025

Assessment of the pharmacological and safety profile of the small molecule MP-004 after topical eye drops administration

MP-004 is a novel small molecule under development as a non-invasive therapeutic for inherited retinal dystrophies (IRDs), including retinitis pigmentosa. Here, we evaluated its ocular concentration and safety profile following topical administration in three animal species --mouse, rabbit, and pig--. MP-004 formulation with 0.3% hyaluronic acid significantly enhanced retinal concentration in mice compared to non-formulated compound (6.67 vs 1.27 {micro}g/g at 4 h). MP-004 reached therapeutically relevant retinal concentrations in all species tested, with minimal systemic exposure: in mice, levels detected in serum were lower than 5 ng/mL while in rabbits, the compound was undetectable in blood and peripheral tissues 12 h post-dose. Seven-day repeated-dose toxicity studies in mice and rabbits showed no systemic or ocular toxicity. In rabbits, only transient ocular redness was observed post-administration, with no evidence of corneal damage or systemic adverse effects. Hematological and biochemical parameters in both species remained within normal limits. Importantly, retinal and optic nerve concentrations remained detectable in rabbits 7 days after final dosing, while the compound was eliminated systemically, supporting prolonged target tissue retention. These findings demonstrate that MP-004 is well tolerated and achieves effective retinal concentrations via topical delivery, overcoming a major barrier in retinal drug development. The favorable pharmacokinetic and safety profile across species, including anatomically relevant models, supports MP-004s advancement toward regulatory preclinical studies and clinical translation as a non-invasive therapy for IRDs.

pharmacology and toxicology↗

bioRxiv2024

Topical administration of novel FKBP12 ligand MP-004 improves retinal function and structure in retinitis pigmentosa models.

PurposeThis study evaluates the therapeutic potential of MP-004, a novel FKBP12 ligand, in the treatment of inherited retinal dystrophies (IRDs). MP-004 targets FKBP12/RyR interaction, which is disrupted in several neurological disorders with underlying oxidative stress. MethodsThe toxicity and efficacy of MP-004 were examined in vitro in 661W cells. Efficacy was evaluated in phototoxic and H2O2-induced damage using impedance assays, calcium igaing and in situ PLA. In vivo, MP-004 efficacy was evaluated in the rd10 mouse model of retinitis pigmenetosa (RP) by topical ocular instillation. Retinal function was assessed by electroretinography (ERG), visual acuity was measured using a water maze test, and retinal structure was analyzed morphometrically. ResultsMP-004 exhibited low toxicity (LD50: 1.22 mM) and effectively protected 661W cells from phototoxicity (EC50: 30.6 nM). Under oxidative stress conditions, MP-004 preserved FKBP12.6/RyR2 interaction, partially restored endoplasmic reticulum calcium stores and prevented cell death. In vivo, MP-004 significantly preserved retinal function in rd10 mice, with ERG wave amplitude increases of up to 50% in scotopic and 71% in photopic conditions, corresponding to rod and cone functions, respectively. Additionally, MP-004 improved visual acuity for low spatial frequency patterns, and preserved retinal structure with a 23% increase in outer nuclear layer thickness, and preservation in the number of rods and cones and their segment length. ConclusionsMP-004 shows promise as a therapeutic agent for RP, preserving retinal structure and function, likely through modulation of FKBP12.6/RyR2 interaction. Further studies are needed to explore its pharmacokinetics and efficacy in other IRD models.

neuroscience↗

bioRxiv2024

Novel FKBP12 ligand promotes functional improvement in SOD1-G93A ALS mice

Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disease with limited treatment options. ALS pathogenesis involves intricate processes within motor neurons (MNs), characterized by dysregulated Ca2+ influx and buffering in early ALS-affected MNs. This study proposes the modulation of ryanodine receptors (RyRs), key mediators of intracellular Ca2+, as a therapeutic target. A novel class of novel FKBP12 ligands that show activity as cytosolic calcium modulators through stabilizing RyR channel activity, were tested in the SOD1G93A mouse model of ALS. Different outcomes were used to assess treatment efficacy including electrophysiology, histopathology, neuromuscular function, and survival. Among the novel FKBP12 ligands, MP-010 was chosen for its central nervous system availability. Chronic administration of MP-010 to SOD1G93A mice produced a dose-dependent preservation of motor nerve conduction, with the 61 mg/kg dose significantly delaying the onset of motor impairment. This was accompanied by improved motor coordination, increased innervated endplates, and significant preservation of MNs in the spinal cord of treated mice. Notably, MP-010 treatment significantly extended lifespan by an average of 10 days compared to vehicle. In conclusion, FKBP12 ligands, particularly MP-010, exhibit promising neuroprotective effects in ALS, highlighting their potential as novel therapeutic agents. Further investigations into the molecular mechanisms and clinical translatability of these compounds are needed for their application in ALS treatment.

neuroscience↗