Inhibition of histone deacetylase 6 activity mitigates neurological impairment and post-hemorrhagic hydrocephalus after intraventricular hemorrhage by modulating pyroptosis and autophagy pathways

Background: Posthemorrhagic hydrocephalus (PHH) is a frequent and significant complication that impacts the prognosis of patients suffering from intraventricular hemorrhage (IVH). However, the underlying mechanism is uncertain. Neuronal Pyroptosis is characterized by neuronal lysis and destruction, along with the release of inflammatory factors. Autophagy is known to inhibit inflammation, and histone deacetylase-6 (HDAC6) is implicated in the regulation of both Autophagy and the NLRP3 inflammasome. However, the role of these proteins in the regulation of neuronal Pyroptosis in an IVH model has not been determined.

Methods: In this study, an IVH mouse (6-8 weeks) model was generated via the intracerebroventricular administration of autologous blood at a volume of 40 µL/animal. After the surgical operation, we monitored the mice at various time points, assessing ventricle size via MRI. Additionally, during both the acute (3 days) and chronic (28 days) phases post-surgery, we examined neuronal cell damage and ventricular cilia, as well as neurological function, using HE staining, Nissl staining, scanning electron microscopy, and behavioral experiments such as neurological function scoring and water maze tests. Finally, we detected activation of the Pyroptosis and Autophagy pathway through western blotting and immunofluorescence staining.

Results: Autophagy induction attenuated cerebral neuronal Pyroptosis caused by acute-phase autologous blood injection. HDAC6 was implicated in regulating Pyroptosis in the acute phase IVH through its influence on the transcription of nuclear factor kappa-B (NF-κB). Furthermore, HDAC6 regulates excessive autophagic activation in neurons in the chronic phase of IVH. Treatment with ricolinostat improved neurological deficits and ventricular damage during the acute phase of IVH. Moreover, it alleviated mood, memory, and learning deficits in the chronic phase of IVH while also improving PHH.

Conclusions: Enhanced Autophagy attenuates activation of the NOD-like Receptor protein 3 (NLRP3) inflammasome and inhibits neuronal Pyroptosis in the acute phase of IVH. HDAC6 plays an important role in regulating the interaction between Autophagy and Pyroptosis. Ricolinostat treatment significantly attenuated the upregulation of inflammatory factors and neurological impairments induced by Pyroptosis in the acute phase of IVH. In addition, ricolinostat effectively reduced excessive Autophagy and Apoptosis in neurons in the chronic phase and attenuated the formation of PHH.

Autophagy; HDAC6; Inflammation; Microglia; PHH; Pyroptosis.