N-acetylcysteine amide preserves mitochondrial bioenergetics and improves functional recovery following spinal trauma

Abstract

Mitochondrial dysfunction is becoming a pivotal target for neuroprotective strategies following contusion spinal cord injury (SCI) and the pharmacological compounds that maintain mitochondrial function confer neuroprotection and improve long-term hindlimb function after injury. In the current study we evaluated the efficacy of cell-permeating thiol, N-acetylcysteineamide (NACA), a precursor of endogenous antioxidant glutathione (GSH), on mitochondrial function acutely, and long-term tissue sparing and hindlimb locomotor recovery following upper lumbar contusion SCI. Some designated injured adult female Sprague-Dawley rats (n=120) received either Vehicle or NACA (75, 150, 300 or 600 mg/kg) at 15min and 6hrs post-injury. After 24hr the total, synaptic, and non-synaptic mitochondrial populations were isolated from a single 1.5cm spinal cord segment (centered at injury site) and assessed for mitochondrial bioenergetics. Results showed compromised total mitochondrial bioenergetics following acute SCI that was significantly improved with NACA treatment in a dose-dependent manner, with maximum effects at 300 mg/kg (n=4/group). For synaptic and non-synaptic mitochondria, only 300 mg/kg NACA dosage showed efficacy. Similar dosage (300mg/kg) also maintained mitochondrial GSH near normal levels. Other designated injured rats (n=21) received continuous NACA (150 or 300mg/kg/day) treatment starting at 15min post-injury for one week to assess long-term functional recovery over 6 weeks post-injury. Locomotor testing and novel gait analyses showed significantly improved hindlimb function with NACA that were associated with increased tissue sparing at the injury site. Overall, NACA treatment significantly maintained acute mitochondrial bioenergetics and normalized GSH levels following SCI, and prolonged delivery resulted in significant tissue sparing and improved recovery of hindlimb function.

Neuroprotective effects of N-acetylcysteine amide on experimental focal penetrating brain injury in rats

“…For the 24 hour survival group, an additional bolus of 300 mg/kg was given after 4 hours. The dosage was chosen to deliver maximum CNS efficacy according to recent studies [20]. The rats were sacrificed by an overdose of pentobarbital, brains were snap frozen and cut into 14 lm coronal sections using a Microm HM560 cryostat (Thermo Fisher Scientific, Waltham, MA, USA).…”

“…In moderate TBI, NACA treatment improves mitochondrial bioenergetics, cognitive function, cortical tissue sparing and reduces lipid peroxidation product 4-hydroxynonenal compared to NAC or vehicle treated rats [19]. In acute spinal cord injury, NACA treatment improves mitochondrial bioenergetics, maintains mitochondrial glutathione and improves tissue sparing and hind limb function [20]. NACA also protects neurons and dopaminergic cells from oxidative stress in tissue cultures and lipid peroxidation in neuronal cell lines [21,22].…”

Comparative biochemical and motor function analysis of alpha lipoic acid and n-acetyl cysteine treatment on rats with experimental spinal cord injury

“…The literature review also turned up results where researchers recently emphasized the neuroprotective efficiency of NAC by using the amide derivative of NAC, which has a neutralized carboxylic group. The amide derivative of NAC becomes more lipophilic and willingly crosses blood brain barrier and cellular membranes as well (15,18).…”

“…Both Alpha Lipoic Acid (α-LA) and N-Acetyl Cysteine (NAC) are thiol derivatives and take part in regenerating GSH (18,20). α-LA and NAC may compose an imperative element of the antioxidant systems (15,20).…”

Mitochondrial-Based Therapeutics for the Treatment of Spinal Cord Injury: Mitochondrial Biogenesis as a Potential Pharmacological Target

“…N-acetylcysteineamide (NACA), a membrane-permeable U.S. Food and Drug Administration-approved thiolcontaining variant of the GSH precursor N-acetylcysteine, was observed to enhance GSH content, improving mitochondrial bioenergetics and correlating with functional recovery in rat models of both TBI and SCI when administered 15-30 minutes postinjury Patel et al, 2014). Although these results are undoubtedly encouraging, additional studies must be performed to assess the therapeutic window for treatment initiation, particularly considering that N-acetylcysteine was previously shown to be ineffective in rats if not given within 1 hour after TBI (Xiong et al, 1999).…”