Taulipro rescues mitochondrial dysfunction and inhibits cGAS–STING neuroinflammation in Aβ-driven Alzheimer's disease models

Technical Summary: Taulipro Rescues Mitochondrial Dysfunction and Inhibits cGAS–STING Neuroinflammation in Aβ-Driven Alzheimer's Disease Models

Problem Statement
Alzheimer's disease (AD) remains a multifactorial neurodegenerative disorder lacking effective multitarget therapies. Current disease-modifying treatments, primarily anti-Aβ monoclonal antibodies, are limited by safety concerns (e.g., amyloid-related imaging abnormalities) and a narrow therapeutic window restricted to early-stage patients. A critical upstream pathogenic event in AD involves mitochondrial dysfunction, which precedes Aβ plaque deposition and tau phosphorylation. This dysfunction leads to the pathological opening of the mitochondrial permeability transition pore (mPTP), causing the leakage of mitochondrial DNA (mtDNA) into the cytoplasm. Once in the cytosol, mtDNA acts as a damage-associated molecular pattern (DAMP), activating the cGAS–STING innate immune signaling cascade. This activation drives the TBK1–IRF3–NF-κB pathway, resulting in the production of pro-inflammatory cytokines (TNFα, IL-18) and chronic neuroinflammation. To date, no therapeutic agent specifically targets the mtDNA leakage step to modulate this cGAS–STING axis.

Methodology
The study introduces Taulipro, a novel pharmaceutical co-crystal compound synthesized from taurine, lithium, and L-proline in a molar ratio of 1.5:1:1. The compound was characterized using ¹H NMR, Powder X-ray Diffraction (PXRD), Inductively Coupled Plasma Mass Spectrometry (ICP-MS), and Differential Scanning Calorimetry (DSC) to confirm its distinct crystalline structure and stoichiometry.

The efficacy of Taulipro was evaluated in two models:

1. In Vitro: SH-SY5Y neuronal cells challenged with Aβ42 oligomers. Cells were treated with Taulipro, taurine, LiCl, or a physical mixture of components. Parameters assessed included mitochondrial reactive oxygen species (ROS), membrane potential (JC-1 assay), mPTP opening, ATP levels, intracellular calcium (mitochondrial and cytosolic), and cytoplasmic mtDNA levels (via qPCR of ND1 sequences).
2. In Vivo: 5×FAD transgenic mice (carrying five human AD-related transgenes) received daily oral gavage of Taulipro, Li₂CO₃, taurine, or vehicle (ddH₂O) for 16 weeks. Outcomes included Aβ plaque burden (immunohistochemistry and Western blot), cGAS–STING pathway activation (Western blot for cGAS, p-STING, TBK1, IRF3), and downstream inflammatory markers (p-NFκB, TNFα, IL-18).

Key Contributions

• Novel Formulation: The development and characterization of Taulipro, a co-crystal designed to combine the mitochondria-stabilizing properties of taurine and the neuroprotective effects of lithium, while using L-proline to stabilize the coordination environment.
• Mechanistic Link: Establishing a direct mechanistic link between Aβ-induced mitochondrial dysfunction, cytoplasmic mtDNA leakage, and the subsequent activation of the cGAS–STING neuroinflammatory cascade in neuronal cells.
• Therapeutic Strategy: Proposing a multitarget approach that intervenes at the upstream level of mitochondrial integrity to prevent the initiation of neuroinflammation, rather than solely targeting downstream inflammatory cytokines or Aβ aggregation.

Results

• Characterization: PXRD, ¹H NMR, and DSC analyses confirmed that Taulipro is a distinct crystalline solid form, not a physical mixture of its components, with a defined taurine:lithium:L-proline ratio of 1.5:1:1.
• In Vitro Efficacy: In Aβ42-challenged SH-SY5Y cells, Taulipro significantly reversed mitochondrial dysfunction. It reduced ROS accumulation, restored mitochondrial membrane potential, inhibited mPTP opening, replenished ATP levels, and alleviated mitochondrial Ca²⁺ overload. Crucially, Taulipro substantially reduced cytoplasmic mtDNA levels, outperforming equimolar treatments with taurine, LiCl, or their physical mixture.
• In Vivo Efficacy: In 16-week treated 5×FAD mice, Taulipro reduced Aβ plaque burden in the dentate gyrus (DG), CA3, cortex, and thalamus more effectively than Li₂CO₃ or taurine monotherapy. It significantly suppressed the cGAS–STING–TBK1–IRF3 signaling axis and reduced downstream inflammatory markers (p-NFκB, TNFα, IL-18).
• Comparative Superiority: Across all measured parameters in both cell and animal models, Taulipro demonstrated superior efficacy compared to the individual components (taurine or lithium salts) and their physical mixtures, suggesting a synergistic effect conferred by the co-crystal architecture.

Significance and Claims
The authors claim that Taulipro represents a promising multitarget candidate for AD therapy. By rescuing mitochondrial function and preventing mtDNA leakage, Taulipro interrupts the cGAS–STING neuroinflammatory cascade at its source. This mechanism distinguishes it from current anti-Aβ monoclonal antibodies, which target a single downstream pathology and carry specific safety risks. The study posits that targeting mitochondrial dysfunction—a feature that precedes and persists beyond Aβ accumulation—offers a broader therapeutic window and a more durable, disease-modifying potential. The authors note that the co-crystal strategy may modulate lithium release kinetics to reduce toxicity while enhancing brain delivery via taurine transporters.

The paper concludes that while the results establish a strong correlative relationship and demonstrate therapeutic potential, further preclinical development is required. This includes definitive causality studies (e.g., genetic ablation of cGAS/STING), comprehensive pharmacokinetic profiling, formal toxicology studies, and cognitive behavioral assessments in additional AD models to fully validate the clinical translation of Taulipro.