Hirudin Promotes Peripheral Nerve Repair by Enhancing Mitophagy to Suppress NLRP3 Inflammasome Activation

Peripheral nerve injuries — such as crush or laceration injuries — often leave patients with lasting loss of sensation or movement, and there are very few drugs that speed up repair. This study asks whether hirudin, an anticoagulant compound originally derived from medicinal leeches, might do more than thin the blood: specifically, whether it can protect the energy-producing compartments of nerve-support cells (mitochondria) and, by doing so, dampen a damaging inflammatory cascade. The researchers used rats with a standardised sciatic nerve crush injury and also tested the compound in cultured Schwann cells — the glial cells that wrap nerve fibres and are essential for regeneration. They found that hirudin appeared to boost a cellular 'mitochondrial clean-up' process called mitophagy, which removes damaged mitochondria before they can leak signals that trigger inflammation. This in turn seemed to suppress a well-studied inflammatory assembly called the NLRP3 inflammasome, reducing a form of inflammatory cell death called pyroptosis. In living rats, hirudin-treated animals showed better leg function, less muscle wasting in the calf, and more signs of nerve fibre regrowth and re-myelination. When the researchers chemically blocked mitophagy, most of these benefits disappeared — supporting the idea that the mitophagy pathway is central to hirudin's effects. The authors caution that the work is preliminary and that further in vivo validation is needed before clinical implications can be drawn.

• In LPS/nigericin-challenged RSC96 Schwann cells, hirudin preserved mitochondrial membrane potential and reduced mitochondrial reactive oxygen species, with downstream suppression of NLRP3/caspase-1/GSDMD activation; specific quantitative effect sizes were not reported in the abstract.
• In the rat sciatic nerve crush model, hirudin improved the sciatic functional index (a standardised gait-based measure of hindlimb function) and mitigated gastrocnemius muscle atrophy, alongside histological markers consistent with axonal regeneration, myelin presence, and vascular remodelling.
• Co-administration of the autophagy inhibitor 3-methyladenine attenuated hirudin's functional and histological benefits, while the selective NLRP3 inhibitor MCC950 produced a comparable anti-inflammatory profile — together supporting a mitophagy → NLRP3 suppression mechanistic axis.
• Network pharmacology analysis prioritised the NOD-like receptor pathway and identified GSDMD and IL-1β as candidate effectors, providing a target landscape consistent with the observed experimental findings.
• The overall mechanistic model proposed is: hirudin enhances mitophagy → reduced mitochondrial ROS and preserved membrane potential → attenuated NLRP3 inflammasome assembly → less caspase-1 activation → less GSDMD-mediated pyroptosis → improved Schwann cell survival and nerve regeneration.

The in vivo component used a rat sciatic nerve crush injury model with systemic hirudin administration; sample sizes and dosing regimens are not specified in the available abstract. In vitro experiments employed RSC96 Schwann cells stimulated with lipopolysaccharide plus nigericin to activate the NLRP3 inflammasome, with hirudin co-treatment and pharmacological probes (3-methyladenine to inhibit autophagy; MCC950 to inhibit NLRP3). Outcome measures spanned functional indices, electrophysiology-adjacent histology, mitochondrial membrane potential, mitochondrial ROS, mitophagy marker expression, and inflammasome component levels. Statistical comparisons used two-sample t-tests or one-way ANOVA with Tukey's post hoc correction; the study is posted as a preprint on Research Square (2025) and has not yet undergone formal peer review.

Because this is a preprint, key methodological details — including exact animal numbers, hirudin doses, treatment duration, and follow-up time points — are unavailable from the abstract alone, making effect-size interpretation and reproducibility assessment difficult. The in vitro inflammasome activation paradigm (LPS + nigericin in an immortalised Schwann cell line) is a pharmacological model that may not fully recapitulate the complex cellular milieu of an in vivo crush injury, and the cellular sources of NLRP3 activation in the nerve microenvironment remain uncharacterised. The study does not demonstrate direct PINK1/Parkin pathway engagement or confirm autophagic flux through LC3-II turnover assays, leaving the precise molecular entry point of hirudin's mitophagy effect unresolved. The logical next experiments would be conditional knockout or siRNA silencing of key mitophagy mediators (e.g., PINK1, Parkin, or BNIP3L) in vivo, combined with more clinically translatable nerve injury models and longer follow-up periods to assess sustained functional recovery.

This study extends [§115], which showed that dexmedetomidine attenuates LPS-induced acute lung injury through mitochondrial autophagy activation, by applying an analogous mitophagy-centred logic to peripheral nerve repair — demonstrating that the mitophagy → NLRP3 suppression axis operates across tissue types and injury modalities. It parallels [§30] in positioning NLRP3 inflammasome suppression as a tractable therapeutic endpoint, although that work addresses diabetic nephropathy rather than neurological injury, suggesting the pathway may be broadly conserved across inflammatory disease contexts. The work also parallels [§134], which interrogates PINK1/Parkin-linked mitophagy in obesity-related cardiomyopathy, in that both studies use pharmacological modulation of mitophagy flux to infer pathway causality, though neither definitively maps the upstream molecular target of their respective interventions. Finally, the neuronal-context mitochondrial biology examined here complements [§99], which investigates mitochondrial RNA release as an inflammation trigger during ageing-related senescence, together suggesting that multiple mitochondrial damage-associated molecular patterns converge on inflammatory amplification in post-mitotic and slowly-regenerating cell types.

• Dexmedetomidine attenuates LPS-induced acute lung injury via activation of mitochondrial autophagy
  Closest mechanistic parallel in this corpus: dexmedetomidine activates mitophagy to suppress NLRP3-driven inflammatory injury (in lung), allowing direct comparison of how mitophagy enhancement translates to inflammasome control across different organs and injury triggers.
• Cardiomyocyte BMAL1 deficiency worsens obesity-related cardiomyopathy with heightened PINK1/Parkin-linked mitophagy and mitochondrial dysfunction
  Both studies use pharmacological perturbation of the PINK1/Parkin mitophagy axis to argue for pathway causality in tissue injury, but in divergent disease contexts (obesity-related cardiomyopathy vs. nerve crush), making this a useful cross-tissue validity check.
• Mitigating Mitochondrial RNA Release During Aging to Control Inflammation and Senescence
  Offers a complementary upstream perspective: while the hirudin study focuses on mitophagy preventing ROS-driven NLRP3 activation, this article examines mitochondrial RNA release as an independent inflammation-initiating signal during ageing — together they map distinct routes from mitochondrial dysfunction to sterile inflammation.
• Exercise hormone irisin alleviates rheumatoid arthritis by removing dysfunctional mitochondria
  Irisin alleviates rheumatoid arthritis by clearing dysfunctional mitochondria in a musculoskeletal context, providing a comparator for how mitophagy-promoting interventions of different chemical classes (peptide hormone vs. anticoagulant protein) achieve anti-inflammatory outcomes in connective-tissue-adjacent cell types.
• Heterogeneous Mitochondrial Gene Expression in SH-SY5Y Cells Following ERRa and ERRy Depletion Reveals Divergent Stress Responses
  Examines mitochondrial gene expression and stress responses specifically in a neuronal cell line (SH-SY5Y), making it a direct neuronal-context counterpart to the Schwann-cell-focused hirudin study and highlighting whether mitochondrial stress responses differ between neurons and glia.