Effects of N-acetylcysteine and acetyl-L-carnitine on acute PTZ-induced seizures in larval and adult zebrafish.

BACKGROUND: Epilepsy is a prevalent neurological disease, affecting approximately 1-2% of the global population. The hallmark of epilepsy is the occurrence of epileptic seizures, which are characterized by predictable behavioral changes reflecting the underlying neural mechanisms of the disease. Unfortunately, around 30% of patients do not respond to current pharmacological treatments. Consequently, exploring alternative therapeutic options for managing this condition is crucial. Two potential candidates for attenuating seizures are N-acetylcysteine (NAC) and Acetyl-L-carnitine (ALC), as they have shown promising neuroprotective effects through the modulation of glutamatergic neurotransmission. METHODS: This study aimed to assess the effects of varying concentrations (0.1, 1.0, and 10 mg/L) of NAC and ALC on acute PTZ-induced seizures in zebrafish in both adult and larval stages. The evaluation of behavioral parameters such as seizure intensity and latency to the crisis can provide insights into the efficacy of these substances. RESULTS: Our results indicate that both drugs at any of the tested concentrations were not able to reduce PTZ-induced epileptic seizures. On the other hand, the administration of diazepam demonstrated a notable reduction in seizure intensity and increased latencies to higher scores of epileptic seizures. CONCLUSION: Consequently, we conclude that, under the conditions employed in this study, NAC and ALC do not exhibit any significant effects on acute seizures in zebrafish.

Non-micronized and micronized curcumin do not prevent the behavioral and neurochemical effects induced by acute stress in zebrafish.

BACKGROUND: Curcumin, a polyphenol extracted from the rhizome of Curcuma longa L. (Zingiberaceae), presents neuroprotective properties and can modulate neuronal pathways related to mental disorders. However, curcumin has low bioavailability, which can compromise its use. The micronization process can reduce mean particle diameter and improve this compound's bioavailability and therapeutic potential. METHODS: We compared the behavioral (open tank test, OTT) and neurochemical (thiobarbituric acid reactive substances (TBARS) and non-protein thiols (NPSH) levels) effects of non-micronized curcumin (CUR, 10 mg/kg, ip) and micronized curcumin (MC, 10 mg/kg, ip) in adult zebrafish subjected to a 90-min acute restraint stress (ARS) protocol. RESULTS: ARS increased the time spent in the central area and the number of crossings and decreased the immobility time of the animals in the OTT. These results suggest an increase in locomotor activity and a decrease in thigmotaxis behavior. Both CUR and MC were not able to prevent these effects. Furthermore, ARS also induced oxidative damage by increasing TBARS and decreasing NPSH levels. Both CUR and MC did not prevent these effects. CONCLUSION: ARS-induced behavioral and biochemical effects were not blocked by any curcumin preparation. Therefore, we conclude that curcumin does not have acute anti-stress effects in zebrafish.

Effects of N-acetylcysteine amide on anxiety and stress behavior in zebrafish.

Anxiety disorders are highly prevalent and a leading cause of disability worldwide. Their etiology is related to stress, an adaptive response of the organism to restore homeostasis, in which oxidative stress and glutamatergic hyperactivity are involved. N-Acetylcysteine (NAC) is a multitarget approved drug proved to be beneficial in the treatment of various mental disorders. Nevertheless, NAC has low membrane permeability and poor bioavailability and its limited delivery to the brain may explain inconsistencies in the literature. N-Acetylcysteine amide (AD4) is a synthetic derivative of NAC in which the carboxyl group was modified to an amide. The amidation of AD4 improved lipophilicity and blood-brain barrier permeability and enhanced its antioxidant properties. The purpose of this study was to investigate the effects of AD4 on behavioral and biochemical parameters in zebrafish anxiety models. Neither AD4 nor NAC induced effects on locomotion and anxiety-related parameters in the novel tank test. However, in the light/dark test, AD4 (0.001 mg/L) increased the time spent in the lit side in a concentration 100 times lower than NAC (0.1 mg/L). In the acute restraint stress protocol, NAC and AD4 (0.001 mg/L) showed anxiolytic properties without meaningful effects on oxidative status. The study suggests that AD4 has anxiolytic effects in zebrafish with higher potency than the parent compound. Additional studies are warranted to characterize the anxiolytic profile of AD4 and its potential in the management of anxiety disorders.

N-acetylcysteine protects against motor, optomotor and morphological deficits induced by 6-OHDA in zebrafish larvae.

BACKGROUND: Parkinson's disease (PD) is the second most common neurodegenerative disorder. In addition to its highly debilitating motor symptoms, non-motor symptoms may precede their motor counterparts by many years, which may characterize a prodromal phase of PD. A potential pharmacological strategy is to introduce neuroprotective agents at an earlier stage in order to prevent further neuronal death. N-acetylcysteine (NAC) has been used against paracetamol overdose hepatotoxicity by restoring hepatic concentrations of glutathione (GSH), and as a mucolytic in chronic obstructive pulmonary disease by reducing disulfide bonds in mucoproteins. It has been shown to be safe for humans at high doses. More recently, several studies have evidenced that NAC has a multifaceted mechanism of action, presenting indirect antioxidant effect by acting as a GSH precursor, besides its anti-inflammatory and neurotrophic effects. Moreover, NAC modulates glutamate release through activation of the cystine-glutamate antiporter in extra-synaptic astrocytes. Its therapeutic benefits have been demonstrated in clinical trials for several neuropsychiatric conditions but has not been tested in PD models yet. METHODS: In this study, we evaluated the potential of NAC to prevent the damage induced by 6-hydroxydopamine (6-OHDA) on motor, optomotor and morphological parameters in a PD model in larval zebrafish. RESULTS: NAC was able to prevent the motor deficits (total distance, mean speed, maximum acceleration, absolute turn angle and immobility time), optomotor response impairment and morphological alterations (total length and head length) caused by exposure to 6-OHDA, which reinforce and broaden the relevance of its neuroprotective effects. DISCUSSION: NAC acts in different targets relevant to PD pathophysiology. Further studies and clinical trials are needed to assess this agent as a candidate for prevention and adjunctive treatment of PD.

Effects of N-acetylcysteine on amphetamine-induced sensitization in mice

Objective: N-acetylcysteine (NAC) is beneficial in psychiatric conditions, including schizophrenia. Patients with schizophrenia exhibit mesolimbic dopamine hyperfunction consequent to an endogenous sensitization process. This sensitization can be modeled in rodents by repeated exposure to psychostimulants, provoking an enduring amplified response at subsequent exposure. The aim of this study was to investigate the effects of NAC on amphetamine sensitization in mice. Methods: D-amphetamine was administered to C57BL/6 mice three times a week for 3 weeks; the dose was increased weekly from 1 to 3 mg/kg. NAC (60 mg/kg) or saline was administered intraperitoneally before saline or amphetamine during the second and third weeks. After a 4-week washout period, latent inhibition (LI) and the locomotor response to amphetamine 2 mg/kg were assessed. Results: Sensitization disrupted LI and amplified the locomotor response; NAC disrupted LI in control mice. In sensitized animals, NAC attenuated the enhanced locomotion but failed to prevent LI disruption. Conclusion: NAC warrants consideration as a candidate for early intervention in ultra-high risk subjects due to its safety profile and the relevance of its mechanism of action. Supplementing this proposition, we report that NAC attenuates sensitization-induced locomotor enhancement in mice. The finding that NAC disrupted LI incites a cautionary note and requires clarification.

Effects of N-acetylcysteine on amphetamine-induced sensitization in mice.

OBJECTIVE: N-acetylcysteine (NAC) is beneficial in psychiatric conditions, including schizophrenia. Patients with schizophrenia exhibit mesolimbic dopamine hyperfunction consequent to an endogenous sensitization process. This sensitization can be modeled in rodents by repeated exposure to psychostimulants, provoking an enduring amplified response at subsequent exposure. The aim of this study was to investigate the effects of NAC on amphetamine sensitization in mice. METHODS: D-amphetamine was administered to C57BL/6 mice three times a week for 3 weeks; the dose was increased weekly from 1 to 3 mg/kg. NAC (60 mg/kg) or saline was administered intraperitoneally before saline or amphetamine during the second and third weeks. After a 4-week washout period, latent inhibition (LI) and the locomotor response to amphetamine 2 mg/kg were assessed. RESULTS: Sensitization disrupted LI and amplified the locomotor response; NAC disrupted LI in control mice. In sensitized animals, NAC attenuated the enhanced locomotion but failed to prevent LI disruption. CONCLUSION: NAC warrants consideration as a candidate for early intervention in ultra-high risk subjects due to its safety profile and the relevance of its mechanism of action. Supplementing this proposition, we report that NAC attenuates sensitization-induced locomotor enhancement in mice. The finding that NAC disrupted LI incites a cautionary note and requires clarification.

Anxiolytic properties of N-acetylcysteine in mice.

Anxiety disorders are highly prevalent and often result in poor quality of life. Available anxiolytics show significant adverse effects as well as partial efficacy in a sizable part of patients. Innovative treatments with more favorable risk-benefit ratio are sorely needed. A growing body of clinical data indicates the benefits of N-acetylcysteine (NAC) in psychiatric conditions. NAC modulates antioxidant, glutamatergic, inflammatory and neurotrophic pathways in the central nervous system, all of which are relevant to anxiety pathology. We evaluated the effects of NAC in mice models commonly used to characterize anxiolytic compounds. Male adult CF1 or BALB/c mice were treated (i.p.) acutely or subacutely (4 consecutive days) with NAC (60-150mg/kg) 60min before open field, light/dark, hole-board, social interaction, elevated T-maze or stress-induced hyperthermia tests. Diazepam (2mg/kg) was used as positive control. We found that NAC presents anxiolytic effects in all models, except for the elevated T-maze. Subacute treatments resulted in lower effective doses in comparison to acute treatment. The anxiolytic effects of NAC were comparable to diazepam. NAC is a safe and low cost medicine with suggested benefits in psychiatric conditions often presenting co-morbidity with anxiety. This study contributes evidence to support the validity of clinical trials with NAC in the context of anxiety disorders, especially considering the safety profile in comparison to the limitations of diazepam for long term treatment.

Effects of N-acetylcysteine and imipramine in a model of acute rhythm disruption in BALB/c mice.

Circadian rhythm disturbances are among the risk factors for depression, but specific animal models are lacking. This study aimed to characterize the effects of acute rhythm disruption in mice and investigate the effects of imipramine and N-acetylcysteine (NAC) on rhythm disruption-induced changes. Mice were exposed to 12:12-hour followed by 10:10-hour light:dark cycles (LD); under the latter, mice were treated with saline, imipramine or NAC. Rhythms of rest/activity and temperature were assessed with actigraphs and iButtons, respectively. Hole-board and social preference tests were performed at the beginning of the experiment and again at the 8th 10:10 LD, when plasma corticosterone and IL-6 levels were also assessed. Actograms showed that the 10:10 LD schedule prevents the entrainment of temperature and activity rhythms for at least 13 cycles. Subsequent light regimen change activity and temperature amplitudes showed similar patterns of decline followed by recovery attempts. During the 10:10 LD schedule, activity and temperature amplitudes were significantly decreased (paired t test), an effect exacerbated by imipramine (ANOVA/SNK). The 10:10 LD schedule increased anxiety (paired t test), an effect prevented by NAC (30 mg/kg). This study identified mild but significant behavioral changes at specific time points after light regimen change. We suggest that if repeated overtime, these subtle changes may contribute to lasting behavioral disturbancess relevant to anxiety and mood disorders. Data suggest that imipramine may contribute to sustained rhythm disturbances, while NAC appears to prevent rhythm disruption-induced anxiety. Associations between sleep/circadian disturbances and the recurrence of depressive episodes underscore the relevance of potential drug-induced maintenance of disturbed rhythms.

N-acetylcysteine prevents increased amphetamine sensitivity in social isolation-reared mice.

Treating individuals at risk to develop schizophrenia may be strategic to delay or prevent transition to psychosis. We verified the effects of N-acetylcysteine (NAC) in a neurodevelopmental model of schizophrenia. C57 mice were reared in isolation or social groups and treated with NAC from postnatal day 42-70; the locomotor response to amphetamine was assessed at postnatal day 81. NAC treatment in isolated mice prevented the hypersensitivity to amphetamine, suggesting neuroprotection relevant to striatal dopamine. Considering its safety and tolerability profile, complementary studies are warranted to further evaluate the usefulness of NAC to prevent conversion to schizophrenia in at-risk individuals.