N-acetylcysteine treatment mitigates loss of cortical parvalbumin-positive interneuron and perineuronal net integrity resulting from persistent oxidative stress in a rat TBI model

A comparison of the antiepileptogenic efficacy of two rationally chosen multitargeted drug combinations in a rat model of posttraumatic epilepsy

Post-traumatic epilepsy (PTE) is a recurrent and often drug-refractory seizure disorder caused by traumatic brain injury (TBI). No single drug treatment prevents PTE, but preventive drug combinations that may prophylax against PTE have not been studied. Based on a systematic evaluation of rationally chosen drug combinations in the intrahippocampal kainate (IHK) mouse model of acquired epilepsy, we identified two multi-targeted drug cocktails that exert strong antiepileptogenic effects. The first, a combination of levetiracetam (LEV) and topiramate, only partially prevented spontaneous recurrent seizures in the model. We therefore added atorvastatin (ATV) to the therapeutic cocktail (TC) to increase efficacy, forming "TC-001". The second cocktail - a combination of LEV, ATV, and ceftriaxone, termed "TC-002" - completely prevented epilepsy in the mouse IHK model. In the present proof-of-concept study, we tested whether the two drug cocktails prevent epilepsy in a rat PTE model in which recurrent electrographic seizures develop after severe rostral parasagittal fluid percussion injury (FPI). Following FPI, rats were either treated over 3-4 weeks with vehicle or drug cocktails, starting either 1 or 4-6 h after the injury. Using mouse doses of TC-001 and TC-002, no significant antiepileptogenic effect was obtained in the rat PTE model. However, when using allometric scaling of drug doses to consider the differences in body surface area between mice and rats, PTE was prevented by TC-002. Furthermore, the latter drug cocktail partially prevented the loss of perilesional cortical parvalbumin-positive GABAergic interneurons. Plasma and brain drug analysis showed that these effects of TC-002 occurred at clinically relevant levels of the individual TC-002 drug components. In silico analysis of drug-drug brain protein interactions by the STITCH database indicated that TC-002 impacts a larger functional network of epilepsy-relevant brain proteins than each drug alone, providing a potential network pharmacology explanation for the observed antiepileptogenic and neuroprotective effects observed with this combination.

Defects of parvalbumin-positive interneurons are implicated in psychiatric disorders

Psychiatric disorders are a common cause of severe long-term disability and socioeconomic burden worldwide. Although our understanding of these disorders has advanced substantially over the last few years, little has changed the standards of care for these illnesses. Fast-spiking parvalbumin-positive interneurons (PVIs), a subpopulation of gamma-aminobutyric acid (GABA)ergic interneurons, are widely distributed in the hippocampus and have been reported to play an important role in various mental disorders. However, the mechanisms underlying the regulation of the molecular networks relevant to depression and schizophrenia (SCZ) are unknown. Here, we discuss the functions of PVIs in psychiatric disorders, including depression and SCZ. After reviewing several studies, we concluded that dysfunction in PVIs could cause depression-like behavior, as well as cognitive categories in SCZ, which might be mediated in large part by greater synaptic variability. In summary, this scientific review aims to discuss the current knowledge regarding the function of PVIs in depression and SCZ. Moreover, we highlight the importance of neurogenesis and synaptic plasticity in the pathogenesis of depression and SCZ, which seem to be mediated by PVIs activity. These findings provide a better understanding of the role of PVIs in psychiatric disorders.

Reciprocal regulation of oxidative stress and mitochondrial fission augments parvalbumin downregulation through CDK5-DRP1- and GPx1-NF-κB signaling pathways

Loss of parvalbumin (PV) expressing neurons (PV neurons) is relevant to the underlying mechanisms of the pathogenesis of neurological and psychiatric diseases associated with the dysregulation of neuronal excitatory networks and brain metabolism. Although PV modulates mitochondrial morphology, volume and dynamics, it is largely unknown whether mitochondrial dynamics affect PV expression and what the molecular events are responsible for PV neuronal degeneration. In the present study, L-buthionine sulfoximine (BSO, an inhibitor of glutathione synthesis) did not degenerate PV neurons under physiological condition. However, BSO-induced oxidative stress decreased PV expression and facilitated cyclin-dependent kinase 5 (CDK5) tyrosine (Y) 15 phosphorylation, dynamin-related protein 1 (DRP1)-mediated mitochondrial fission and glutathione peroxidase-1 (GPx1) downregulation in PV neurons. Co-treatment of roscovitine (a CDK5 inhibitor) or mitochondrial division inhibitor-1 (Mdivi-1, an inhibitor of mitochondrial fission) attenuated BSO-induced PV downregulation. WY14643 (an inducer of mitochondrial fission) reduced PV expression without affecting CDK5 Y15 phosphorylation. Following status epilepticus (SE), CDK5 Y15 phosphorylation and mitochondrial fission were augmented in PV neurons. These were accompanied by reduced GPx1-mediated inhibition of NF-κB p65 serine (S) 536 phosphorylation. N-acetylcysteine (NAC), roscovitine and Mdivi-1 ameliorated SE-induced PV neuronal degeneration by mitigating CDK5 Y15 hyperphosphorylation, aberrant mitochondrial fragmentation and reduced GPx1-mediated NF-κB inhibition. Furthermore, SN50 (a NF-κB inhibitor) alleviated SE-induced PV neuronal degeneration, independent of dysregulation of mitochondrial fission, CDK5 hyperactivation and GPx1 downregulation. These findings provide an evidence that oxidative stress may activate CDK5-DRP1- and GPx1-NF-κB-mediated signaling pathways, which would be possible therapeutic targets for preservation of PV neurons in various diseases.

Targeting Circadian Protein Rev-erbα to Alleviate Inflammation, Oxidative Stress, and Enhance Functional Recovery Following Brain Trauma

Traumatic brain injury (TBI) is a significant cause of morbidity and mortality worldwide, and its pathophysiology is characterized by oxidative stress and inflammation. Despite extensive research, effective treatments for TBI remain elusive. Recent studies highlighted the critical interplay between TBI and circadian rhythms, but the detailed regulation remains largely unknown. Motivated by the observed sustained decrease in Rev-erbα after TBI, we aimed to understand the critical role of Rev-erbα in the pathophysiology of TBI and determine its feasibility as a therapeutic target. Using a mouse model of TBI, we observed that TBI significantly downregulates Rev-erbα levels, exacerbating inflammatory and oxidative stress pathways. The regulation of Rev-erbα with either the pharmacological activator or inhibitor bidirectionally modulated inflammatory and oxidative events, which in turn influenced neurobehavioral outcomes, highlighting the protein's protective role. Mechanistically, Rev-erbα influences the expression of key oxidative stress and inflammatory regulatory genes. A reduction in Rev-erbα following TBI likely contributes to increased oxidative damage and inflammation, creating a detrimental environment for neuronal survival and recovery which could be reversed via the pharmacological activation of Rev-erbα. Our findings highlight the therapeutic potential of targeting Rev-erbα to mitigate TBI-induced damage and improve outcomes, especially in TBI-susceptible populations with disrupted circadian regulation.

N-Acetylcysteine and Probenecid Adjuvant Therapy for Traumatic Brain Injury

N-Acetylcysteine (NAC) has shown promise as a putative neurotherapeutic for traumatic brain injury (TBI). Yet, many such promising compounds have limited ability to cross the blood-brain barrier (BBB), achieve therapeutic concentrations in brain, demonstrate target engagement, among other things, that have hampered successful translation. A pharmacologic strategy for overcoming poor BBB permeability and/or efflux out of the brain of organic acid-based, small molecule therapeutics such as NAC is co-administration with a targeted or nonselective membrane transporter inhibitor. Probenecid is a classic ATP-binding cassette and solute carrier inhibitor that blocks transport of organic acids, including NAC. Accordingly, combination therapy using probenecid as an adjuvant with NAC represents a logical neurotherapeutic strategy for treatment of TBI (and other CNS diseases). We have completed a proof-of-concept pilot study using this drug combination in children with severe TBI-the Pro-NAC Trial (ClinicalTrials.gov NCT01322009). In this review, we will discuss the background and rationale for combination therapy with probenecid and NAC in TBI, providing justification for further clinical investigation.

Effect of N-Acetylcysteine on Sleep: Impacts of Sex and Time of Day

Non-rapid eye movement sleep (NREMS) is accompanied by a decrease in cerebral metabolism, which reduces the consumption of glucose as a fuel source and decreases the overall accumulation of oxidative stress in neural and peripheral tissues. Enabling this metabolic shift towards a reductive redox environment may be a central function of sleep. Therefore, biochemical manipulations that potentiate cellular antioxidant pathways may facilitate this function of sleep. N-acetylcysteine increases cellular antioxidant capacity by serving as a precursor to glutathione. In mice, we observed that intraperitoneal administration of N-acetylcysteine at a time of day when sleep drive is naturally high accelerated the onset of sleep and reduced NREMS delta power. Additionally, N-acetylcysteine administration suppressed slow and beta electroencephalographic (EEG) activities during quiet wake, further demonstrating the fatigue-inducing properties of antioxidants and the impact of redox balance on cortical circuit properties related to sleep drive. These results implicate redox reactions in the homeostatic dynamics of cortical network events across sleep/wake cycles, illustrating the value of timing antioxidant administration relative to sleep/wake cycles. A systematic review of the relevant literature, summarized herein, indicates that this "chronotherapeutic hypothesis" is unaddressed within the clinical literature on antioxidant therapy for brain disorders such as schizophrenia. We, therefore, advocate for studies that systematically address the relationship between the time of day at which an antioxidant therapy is administered relative to sleep/wake cycles and the therapeutic benefit of that antioxidant treatment in brain disorders.

Inhibition of spinal ferroptosis-like cell death alleviates hyperalgesia and spontaneous pain in a mouse model of bone cancer pain

Bone cancer pain (BCP) impairs patients' quality of life. However, the underlying mechanisms are still unclear. This study investigated the role of spinal interneuron death using a pharmacological inhibitor of ferroptosis in a mouse model of BCP. Lewis lung carcinoma cells were inoculated into the femur, resulting in hyperalgesia and spontaneous pain. Biochemical analysis revealed that spinal levels of reactive oxygen species and malondialdehyde were increased, while those of superoxide dismutase were decreased. Histological analysis showed the loss of spinal GAD65+ interneurons and provided ultrastructural evidence of mitochondrial shrinkage. Pharmacologic inhibition of ferroptosis using ferrostatin-1 (FER-1, 10 mg/kg, intraperitoneal for 20 consecutive days) attenuated ferroptosis-associated iron accumulation and lipid peroxidation and alleviated BCP. Furthermore, FER-1 inhibited the pain-associated activation of ERK1/2 and COX-2 expression and prevented the loss of GABAergic interneurons. Moreover, FER-1 improved analgesia by the COX-2 inhibitor Parecoxib. Taken together, this study shows that pharmacological inhibition of ferroptosis-like cell death of spinal interneurons alleviates BCP in mice. The results suggest that ferroptosis is a potential therapeutic target in patients suffering on BCP and possibly other types of pain.