Neuroprotective Effects of Valproic Acid in a Rat Model of Cauda Equina Injury

Valproic acid ameliorates morpho-dysfunctional effects triggered by Ischiatic nerve crush injury-induced by compression model in mice: nerve regeneration and immune-modulatory pathway

Peripheral nerve injuries are extremely severe and may lead to permanent disability, despite the regenerative capacity of the peripheral nervous system (PNS). To date, there is no established pharmacological therapy capable of predicting functional recovery and alleviation of trauma-related symptoms such as neuropathic pain, inflammation and weakness, which are the main targets for current therapies. In this work we provide new evidence for a therapeutic use of valproic acid (VPA) upon ischiatic nerve injury. Ischiatic nerve-injured mice treated with VPA after lesion, displayed an improvement in pain and motor function associated with an increase in the number of myelinated nerve fibers, and exhibited a more organized microenvironment during regeneration. In addition, VPA treatment also promoted an immunomodulatory capacity, leading to a significant enhancement of neutrophils in the peritoneal cavity, suggesting its role on the sensory and motor recovery after ischiatic nerve injury. This highlights the physiological role of VPA during ischiatic nerve regeneration and contributes to the characterization of innovative pharmacological epigenetic therapy capable of accelerating peripheral nerve regeneration with critical impacts on the clinical practice.

Valproic acid ameliorates cauda equina injury by suppressing HDAC2-mediated ferroptosis

INTRODUCTION

Persistent neuroinflammatory response after cauda equina injury (CEI) lowers nociceptor firing thresholds, accompanied by pathological pain and decreasing extremity dysfunction. Histone deacetylation has been considered a key regulator of immunity, inflammation, and neurological dysfunction. Our previous study suggested that valproic acid (VPA), a histone deacetylase inhibitor, exhibited neuroprotective effects in rat models of CEI, although the underlying mechanism remains elusive.

METHODS

The cauda equina compression surgery was performed to establish the CEI model. The Basso, Beattie, Bresnahan score, and the von Frey filament test were carried out to measure the animal behavior. Immunofluorescence staining of myelin basic protein and GPX4 was carried out. In addition, transmission electron microscope analysis was used to assess the effect of VPA on the morphological changes of mitochondria. RNA-sequencing was conducted to clarify the underlying mechanism of VPA on CEI protection.

RESULTS

In this current study, we revealed that the expression level of HDAC1 and HDAC2 was elevated after cauda equina compression model but was reversed by VPA treatment. Meanwhile, HDAC2 knockdown resulted in the improvement of motor functions and pathologic pain, similar to treatment with VPA. Histology analysis also showed that knockdown of histone deacetylase (HDAC)-2, but not HDAC1, remarkably alleviated cauda equina injury and demyelinating lesions. The potential mechanism may be related to lowering oxidative stress and inflammatory response in the injured region. Notably, the transcriptome sequencing indicated that the therapeutic effect of VPA may depend on HDAC2-mediated ferroptosis. Ferroptosis-related genes were analyzed in vivo and DRG cells further validated the reliability of RNA-sequencing results, suggesting HDAC2-H4K12ac axis participated in epigenetic modulation of ferroptosis-related genes.

CONCLUSION

HDAC2 is critically involved in the ferroptosis and neuroinflammation in cauda equina injury, and VPA ameliorated cauda equina injury by suppressing HDAC2-mediated ferroptosis.

Thymoquinone could be protective against valproic acid-induced testicular toxicity by antioxidant and anti-inflammatory mechanisms

Although valproic acid (VPA) is a low-cost and effective drug, it is known to cause organ toxicity via oxidative stress and related process. In present study, we aimed to evaluate the possible protective effects of thymoquinone (TMQ) on VPA-induced testicular toxicity. Male Sprague-Dawley rats were divided into three as control, VPA (500 mg kg^-1  day^-1 ) for 14 days and VPA plus TMQ (50 mg kg^-1  day^-1 for 14 days) with seven rats in. Spermatic and interstitial degenerations induced by VPA were ameliorated with TMQ. In VPA group, increased TOS and OSI levels, and decreased TAS level were seen. TMQ reversed these oxidative stress parameters significantly. In Western analysis, VPA was found to increase the expressions of phospho-nuclear factor kappa beta (p-Nf-kB) and Caspase-3. These expressions were decreased by TMQ significantly. Intense immunostaining for p-Nf-kB, Caspase-3 and NADPH oxidase 2 induced by VPA were transformed to moderate immunostaining by TMQ. VPA-induced inflammation and apoptosis that were developed mainly by p-Nf-kB pathway were attenuated by TMQ. TMQ can be a candidate supportive treatment for patients who need long-term and high-dose VPA therapy. TMQ inhibits the Nf-kB activation, and in addition to antioxidant property, it shows anti-inflammatory feature on VPA-induced testicular toxicity.

Valproic Acid Promotes Survival of Facial Motor Neurons in Adult Rats After Facial Nerve Transection: a Pilot Study

Valproic acid (VPA), a medication primarily used to treat epilepsy and bipolar disorder, has been applied to the repair of central and peripheral nervous system injury. The present study investigated the effect of VPA on functional recovery, survival of facial motor neurons (FMNs), and expression of proteins in rats after facial nerve trunk transection by functional measurement, Nissl staining, TUNEL, immunofluorescence, and Western blot. Following facial nerve injury, all rats in group VPA showed a better functional recovery, which was significant at the given time, compared with group NS. The Nissl staining results demonstrated that the number of FMNs survival in group VPA was higher than that in group normal saline (NS). TUNEL staining showed that axonal injury of facial nerve could lead to neuronal apoptosis of FMNs. But treatment of VPA significantly reduced cell apoptosis by decreasing the expression of Bax protein and increased neuronal survival by upregulating the level of brain-derived neurotrophic factor (BDNF) and growth associated protein-43 (GAP-43) expression in injured FMNs compared with group NS. Overall, our findings suggest that VPA may advance functional recovery, reduce lesion-induced apoptosis, and promote neuron survival after facial nerve transection in rats. This study provides an experimental evidence for better understanding the mechanism of injury and repair of peripheral facial paralysis.