Neuroprotective role of L-carnitine in the 3-nitropropionic acid induced neurotoxicity

The correlation between carbamazepine and valproic acid monotherapy with serum adiponectin and carnitine

Antiepileptic drugs may cause systemic and metabolic side effects. The aim of our study was to investigate the effects of valproic acid and carbamazepine monotherapy used in the treatment of epilepsy patients on serum adiponectin and carnitine levels. The study included 60 patients, of which 30 patients receiving valproic acid monotherapy and 30 patients receiving carbamazepine monotherapy, who were followed up by the epilepsy outpatient clinic with the diagnosis of idiopathic epilepsy, and 30 healthy volunteers. Patients, who used drugs for at least 6 months, were selected. Venous blood samples were collected from the patients and healthy volunteers after their consent was obtained. Serum carnitine and adiponectin levels in the collected samples were measured using the ELISA method. Serum carnitine levels were 5166.55 ng/ml (± 1954.92) in patients receiving carbamazepine, 4224.56 ng/ml (± 2055.54) in patients using valproic acid, and 5802.64 ng/ml (± 3422.57) in the control group. Serum adiponectin levels were 13,606.51 ng/ml (± 5915.92) in patients using carbamazepine, 11,986.58 ng/ml (± 5367.82) in patients receiving valproic acid, and 14,033.43 ng/ml (± 5646.34) in the control group. In both groups, both serum carnitine and serum adiponectin levels were lower than the control group. There was a negative but insignificant correlation between the duration and dose of carbamazepine and valproic acid drug use and serum adiponectin and carnitine levels. There is a need for more extensive studies with larger sample size to investigate the effect of antiepileptic drugs used on serum adiponectin and carnitine levels.

A pioneer study on human 3-nitropropionic acid intoxication: Contributions from metabolomics

The neurotoxin 3-nitropropionic acid (3-NPA) is an inhibitor of succinate dehydrogenase, an enzyme participating both in the citric acid cycle and the mitochondrial respiratory chain. In human intoxications, it produces symptoms such as vomiting and stomach ache in mild cases, and dystonia, coma, and sometimes death in severe cases. We report the results from a liquid chromatography-Orbitrap mass spectrometry metabolomics study mapping the metabolic impacts of 3-NPA intoxication in plasma, urine, and cerebrospinal fluid (CSF) samples of a Norwegian boy initially suspected to suffer from a mitochondrial disease. In addition to the identification of 3-NPA, our findings included a large number of annotated/identified altered metabolites (80, 160, and 62 in plasma, urine, and CSF samples, respectively) belonging to different compound classes, for example, amino acids, fatty acids, and purines and pyrimidines. Our findings indicated protective mechanisms to attenuate the toxic effects of 3-NPA (e.g., decreased oleamide), occurrence of increased oxidative stress in the patient (such as increased free fatty acids and hypoxanthine) and energy turbulence caused by the intoxication (e.g., increased succinate). To our knowledge, this is the first case of 3-NPA intoxication reported in Norway and the first published metabolomics study of human 3-NPA intoxication worldwide. The unexpected identification of 3-NPA illustrates the importance for health care providers to consider intake-related intoxications during diagnostic evaluations, treatment and follow-up examinations for neurotoxicity and a wide range of metabolic derangements.

Effects of Dietary L-Carnitine Supplementation on Platelets and Erythrogram of Dairy Cows with Special Emphasis on Parturition

During late gestation and early lactation, many proliferative processes and metabolic adaptions are involved in homeorhesis. An adjusted supply of oxygen is a precondition for an optimized cellular energy metabolism whereby erythrocytes play a central role. Endogenous L-carnitine modulates the mitochondrial fatty acid utilization for generating adenosine triphosphate (ATP). As it might be insufficient around calving due to increased need, L-carnitine supplementation is frequently recommended. Thus, the present study addressed the interplay between the red hemogram, platelets, oxidative stress indices, and L-carnitine supplementation of dairy cows around calving. German Holstein cows were assigned to a control (n = 30) and an L-carnitine group (n = 29, 25 g of rumen-protected L-carnitine per cow and per day), and blood samples were taken from day 42 ante partum (ap) until day 110 postpartum (pp), with a higher sampling frequency during the first three days pp. The time courses of the erythrogram parameters reflected the physiological adaptations to the oxygen need without being influenced by L-carnitine supplementation. Erythrocytic antioxidative enzymatic defence paralleled the relative development of polycythemia ap, while non-enzymatic total plasma antioxidative capacity continuously increased pp. In contrast to erythrocytes, the platelet counts of the L-carnitine supplemented cows varied at significantly higher levels. This can be interpreted as a result of a membrane-stabilizing effect of L-carnitine.

Neuroprotective efficacy of nano-CoQ against propionic acid toxicity in rats: Role of BDNF and CREB protein expressions

Propionic acid (PRA) is used as a food preservative. This study was aimed to investigate the neuroprotective effect of acetyl-l-carnitine (ALC) and nano-Coenzyme Q (N-CoQ) on brain intoxication induced by PRA in rats. Rats were divided into five groups: group I: control; group II: received PRA; group III: received ALC; group IV: received N-CoQ; and group V: received ALC and N-CoQ for 5 days. The antioxidants in question markedly ameliorated serum interleukin-1β and tumor necrosis factor-α, and brain NO, lipid peroxide, glutathione, and superoxide dismutase levels as well as protein expression of brain-derived neurotrophic factor (BDNF) and P-cyclic-AMP response element-binding protein (CREB) that were altered by a toxic dose of PRA, as well as histopathological alterations, including improvement of the cerebellum architecture. Interestingly, the combination therapy of ALC and N-CoQ achieved the most neuroprotective effect compared with monotherapies. The current study established that N-CoQ is considered as a useful tool to prevent brain injury induced by PRA. BDNF and CREB proteins are involved in both PRA neurotoxicity and treatment.

Exogenous L-Carnitine Promotes Plant Growth and Cell Division by Mitigating Genotoxic Damage of Salt Stress

L-carnitine is a fundamental ammonium compound responsible for energy metabolism in all living organisms. It is an oxidative stress regulator, especially in bacteria and yeast and lipid metabolism in plants. Besides its metabolic functions, l-carnitine has detoxification and antioxidant roles in the cells. Due to the complex interrelationship of l-carnitine between lipid metabolism and salinity dependent oxidative stress, this study investigates the exogenous l-carnitine (1 mM) function on seed germination, cell division and chromosome behaviour in barley seeds (Hordeum vulgare L. cv. Bulbul-89) under different salt stress concentrations (0, 0.25, 0.30 and 0.35 M). The present work showed that l-carnitine pretreatment could not be successful to stimulate cell division on barley seeds under non-stressed conditions compared to stressed conditions. Depending on increasing salinity without pretreatment with l-carnitine, the mitotic index significantly decreased in barley seeds. Pretreatment of barley seeds with l-carnitine under salt stress conditions was found promising as a plant growth promoter and stimulator of mitosis. In addition, pretreatment of barley seeds with l-carnitine alleviated detrimental effects of salt stress on chromosome structure and it protected cells from the genotoxic effects of salt. This may be caused by the antioxidant and protective action of the l-carnitine. Consequently, this study demonstrated that the exogenous application of 1 mM l-carnitine mitigates the harmful effects of salt stress by increasing mitosis and decreasing DNA damage caused by oxidative stress on barley seedlings.

L-carnitine regulated Nrf2/Keap1 activation in vitro and in vivo and protected oxidized fish oil-induced inflammation response by inhibiting the NF-κB signaling pathway in Rhynchocypris lagowski Dybowski

Nrf2/Keap1 pathway is associated with oxidative stress. l-carnitine is currently under preclinical evaluation as a antioxidant, but the use of l-carnitine in aquaculture has been poorly evaluated and so far no mechanism has been demonstrated. Here, we explored the effects of l-carnitine in vitro and in vivo and discussed the possible molecular mechanisms involved. Firstly, Nrf2-siRNA significantly knocked down the mRNA level of Nrf2 in FHM cells. Thus, the activities of antioxidant enzymes (T-SOD, CAT, GSH-PX) and the level of antioxidant substance (GSH) and the level of MDA showed that Nrf2-siRNA pretreatment weakened the protective effect of l-carnitine. Moreover, the mRNA levels of Keap1, Nrf2, Maf and HO-1 indicated that l-carnitine regulated Nrf2/Keap1 activation. Furthermore, oxidized fish oil remarkably suppressed growth in Rhynchocypris lagowski Dybowski, and the lower antioxidant capacity was also observed in liver. According to the results of immune related indexes (the levels of IL-1β, TNF-α, LZM, AKP) in serum and the mRNA levels of immune related genes (NF-κB, IL-1β, TNF-α, IL-8, IL-10 and TGF-β) in liver, oxidized fish oil also induced inflammatory response in fish. Also, l-carnitine supplementation can relieve this bad condition. In conclusion, l-carnitine regulated Nrf2/Keap1 activation in vitro and in vivo and protected oxidized fish oil-induced inflammation response by inhibiting the NF-κB signaling pathway in Rhynchocypris lagowski Dybowski.

The effect of L-carnitine on inflammatory mediators: a systematic review and meta-analysis of randomized clinical trials

AIM AND BACKGROUND

Reducing inflammation by nutritional supplements may help to reduce the risk of many chronic diseases. Our aim in this meta-analysis was to determine the effect of L-carnitine on inflammatory mediators including C-reactive protein (CRP), tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6).

METHODS

Our systematic search to find relevant randomized clinical trials (RCTs) was performed up to October 2018 using ISI Web of Science, Google Scholar, PubMed/Medline, and SCOPUS. In this meta-analysis, the weighted mean differences (WMD) with standard errors (SE) were used to pool the data. WMD was calculated by subtracting change-from-baseline mean values in the control group from change-from-baseline mean values in the intervention group in each study. To identify heterogeneity among studies, the I² statistic was employed. The protocol was registered with PROSPERO (No. CRD42019116695).

RESULTS

Thirteen articles were included in our systematic review and meta-analysis. The results of the meta-analysis indicated that L-carnitine supplementation was significantly associated with lower levels of CRP in comparison to controls (WMD = -1.23 mg/L; 95% CI: -1.73, -0.72 mg/dL; P < 0.0001). Also, a slight but statistically significant decrease was observed in IL-6 and TNF-α levels (WMD = -0.85 pg/dL; 95% CI: -1.38, -0.32 pg/dL; P = 0.002 and WMD = -0.37 pg/dL; 95% CI: -0.68, -0.06 pg/dL; P = 0.018, respectively).

CONCLUSION

Our results indicate that L-carnitine reduced inflammatory mediators, especially in studies with a duration of more than 12 weeks. Further studies with different doses and intervention durations and separately in men and women are necessary.

Effects of levetiracetam and valproic acid treatment on liver function tests, plasma free carnitine and lipid peroxidation in childhood epilepsies

BACKGROUND AND AIMS

The relationship between anti-epileptic usage and oxidative damage has not yet been clearly understood. In our study, we investigated oxidative stress parameters, carnitine levels, liver function tests (LFT) and their relationship in epileptic children treated with valproic acid or levetiracetam.

METHOD

LFTs, serum free carnitine and oxidative damage markers and their relations with each other were determined in patients who are on valproic acid or levetiracetam treatment at least for 6 months. 25 patients on therapeutic doses of valproic acid, 26 patients on therapeutic doses of levetiracetam and 26 healthy volunteers as controls were included. LFTs, ammonia, carnitine, lipid peroxidation biomarker malondialdehyde (MDA) and a sensitive marker of DNA damage, 8-hydroxy-2-deoxyguanosine (8-OHdG) levels were measured. Results of patients are compared to healthy controls. The data is evaluated with IBM SPSS Statistics 22.0.

RESULTS

Ammonia and MDA levels were elevated in patients using levetiracetam; 8-OHdG levels were elevated in both patient groups. Carnitine levels were significantly low in patients under valproic acid therapy, however they were not found to be correlated with MDA, 8-OHdG or LFTs. MDA showed positive correlation with ammonia and 8-OHdG in the levetiracetam group.

CONCLUSION

We did not observe hepatotoxicity in patients under therapeutic doses of valproic acid. However, epileptic children under therapeutic doses of levetiracetam showed significantly elevated levels of MDA and 8-OHdG, which is supportive for oxidative damage under levetiracetam therapy. This result was observed for the first time in childhood epilepsies and further studies are needed to understand its mechanism.

The effects of concurrent Coenzyme Q10, L-carnitine supplementation in migraine prophylaxis: A randomized, placebo-controlled, double-blind trial

Purpose

The present study aimed to determine the effects of combined supplementation of Coenzyme Q10 with L-carnitine on mitochondrial metabolic disorders marker and migraine symptoms among migraine patients.

Methods

A total of 56 men and women, between 20–40 years of age with migraine headache, participated in this randomized, double-blind, placebo-controlled, parallel study. The subjects were randomly assigned to receive either 30 mg/day Coenzyme Q10 and 500 mg/day L-carnitine at the same time and/or placebo tablets for 8 weeks. The measurements were completed at the beginning and end of the study. The primary outcome was severity of headache attacks. The secondary outcomes included duration, frequency of headache attacks, the headache diary results (HDR), and serum levels of lactate.

Results

A significant reduction was obtained in serum levels of lactate (−2.28 mg/dl, 95% CI: −3.65, −0.90; p = 0.002), severity (−3.03, 95% CI: −3.65, −2.40; p ≤ 0.001), duration (−7.67, 95% CI: −11.47, −3.90; p ≤ 0.001), frequency (−5.42, 95% CI: −7.31, −3.53; p ≤ 0.001) and HDR (−103.03, 95% CI: −145.76, −60.29; p ≤ 0.001) after 8 weeks.

Conclusion

This double-blind parallel study provides evidences supporting the beneficial effects of Coenzyme Q10 and L-carnitine supplements on serum levels of lactate and migraine symptoms.

Trial registration

IRCT20121216011763N21.

L-Carnitine and extendin-4 improve outcomes following moderate brain contusion injury

There is a need for pharmaceutical agents that can reduce neuronal loss and improve functional deficits following traumatic brain injury (TBI). Previous research suggests that oxidative stress and mitochondrial dysfunction play a major role in neuronal damage after TBI. Therefore, this study aimed to investigate two drugs known to have antioxidant effects, L-carnitine and exendin-4, in rats with moderate contusive TBI. L-carnitine (1.5 mM in drinking water) or exendin-4 (15 µg/kg/day, ip) were given immediately after the injury for 2 weeks. Neurological function and brain histology were examined (24 h and 6 weeks post injury). The rats with TBI showed slight sensory, motor and memory functional deficits at 24 h, but recovered by 6 weeks. Both treatments improved sensory and motor functions at 24 h, while only exendin-4 improved memory. Both treatments reduced cortical contusion at 24 h and 6 weeks, however neither affected gliosis and inflammatory cell activation. Oxidative stress was alleviated and mitochondrial reactive oxygen species was reduced by both treatments, however only mitochondrial functional marker protein transporter translocase of outer membrane 20 was increased at 24 h post injury. In conclusion, L-carnitine and exendin-4 treatments immediately after TBI can improve neurological functional outcome and tissue integrity by reducing oxidative stress.

L-carnitine protects C2C12 cells against mitochondrial superoxide overproduction and cell death

AIM

To identify and characterize the protective effect that L-carnitine exerted against an oxidative stress in C2C12 cells.

METHODS

Myoblastic C2C12 cells were treated with menadione, a vitamin K analog that engenders oxidative stress, and the protective effect of L-carnitine (a nutrient involved in fatty acid metabolism and the control of the oxidative process), was assessed by monitoring various parameters related to the oxidative stress, autophagy and cell death.

RESULTS

Associated with its physiological function, a muscle cell metabolism is highly dependent on oxygen and may produce reactive oxygen species (ROS), especially under pathological conditions. High levels of ROS are known to induce injuries in cell structure as they interact at many levels in cell function. In C2C12 cells, a treatment with menadione induced a loss of transmembrane mitochondrial potential, an increase in mitochondrial production of ROS; it also induces autophagy and was able to provoke cell death. Pre-treatment of the cells with L-carnitine reduced ROS production, diminished autophagy and protected C2C12 cells against menadione-induced deleterious effects.

CONCLUSION

In conclusion, L-carnitine limits the oxidative stress in these cells and prevents cell death.

Oxidative stress controlling agents are effective for small intestinal injuries induced by non-steroidal anti-inflammatory drugs

BACKGROUND AND AIM

Video-capsule endoscopy (VCE) has shown that intestinal ulcers are common in non-steroidal anti-inflammatory drugs (NSAIDs) users, although the mechanisms and management have not been clearly defined. To explore the contribution of oxidative stress and potential of anti-oxidants for NSAIDs-induced intestinal ulcers, we assessed human serum oxidative stress balance and the effect of anti-oxidants using a mouse model.

METHODS

A total of 30 NSAIDs users (17 aspirin and 13 non-aspirin users) received VCE. Serum reactive oxygen metabolite (d-ROM) and antioxidative OXY-adsorbent test (OXY) were measured. The indomethacin (IND)-induced mouse intestinal ulcer model was used to assess the effect of anti-oxidants. Eight-week-old mice were divided into four groups; control diet and diet including IND (N group), IND and L-carnitine (NC group), and IND and vitamin E (NE group).

RESULTS

Serum OXY levels among non-aspirin users were lower in the mucosal injuries positive group than the negative group (P < 0.05). In the mouse models, the degree of mucosal injuries was lower in NC and NE than N (P < 0.01). Serum d-ROM levels were lower in NC and NE than N (P < 0.01), and OXY levels were higher in NC than N and NE (P < 0.01). The degeneration of intestinal mitochondria was mild in NC and NE. The serum KC/CXCL-1 level and hepatic expression of the anti-oxidant molecule Gpx4 were lower in NC than N.

CONCLUSIONS

Non-aspirin NSAID-induced intestinal ulcers are related to decreased anti-oxidative stress function. Anti-oxidants, especially L-carnitine, are good candidates for intestinal ulcers.

Effect of Acetyl-L-Carnitine on Antioxidant Status, Lipid Peroxidation, and Oxidative Damage of Arsenic in Rat

Arsenic (As) is a widespread environmental contaminant present around the world in both organic and inorganic forms. Oxidative stress is postulated as the main mechanism for As-induced toxicity. This study was planned to examine the protective effect of acetyl-L-carnitine (ALC) on As-induced oxidative damage in male rats. Animals were randomly divided into four groups of control (saline), sodium arsenite (NaAsO2, 20 mg/kg), ALC (300 mg/kg), and NaAsO2 plus ALC. Animals were dosed orally for 28 successive days. Blood and tissue samples including kidney, brain, liver, heart, and lung were collected on the 28th day and evaluated for oxidative damage and histological changes. NaAsO2 exposure caused a significant lipid peroxidation as evidenced by elevation in thiobarbituric acid-reactive substances (TBARS). The activity of antioxidant enzymes such as glutathione-S-transferase (GST), catalase (CAT), superoxide dismutase (SOD), as well as sulfhydryl group content (SH group) was significantly suppressed in various organs following NaAsO2 treatment (P < 0.05). Furthermore, NaAsO2 administration increased serum values of alanine aminotransferase (ALT), aspartate aminotransferase (AST), lactate dehydrogenase (LDH), and bilirubin. Our findings revealed that co-administration of ALC and NaAsO2 significantly suppressed the oxidative damage induced by NaAsO2. Tissue histological studies have confirmed the biochemical findings and provided evidence for the beneficial role of ALC. The results concluded that ALC attenuated NaAsO2-induced toxicity, and this protective effect may result from the ability of ALC in maintaining oxidant-antioxidant balance.

Potential protective effects of l-carnitine against neuromuscular ischemia-reperfusion injury: From experimental data to potential clinical applications

BACKGROUND & AIM

Ischemia-reperfusion (I/R) injury plays important role in morbidity and mortality in several pathologies, including myocardial infarction, ischemic stroke, acute kidney injury, trauma, and circulatory arrest. An imbalance in metabolic supply and tissue's demand during ischemia results in profound tissue hypoxia and microvascular dysfunction. Subsequently, reperfusion further results in activation of immune responses and cell death programs. l-carnitine and its derivatives have been administered to improve tolerance against I/R injury in various tissues. Anti-ischemic properties of l-carnitine and its derivative in neuromuscular organs will be reviewed here at the light of pertinent results from basic and clinical researches.

METHOD

All available in vitro and in vivo studies, patents, clinical trials, and meeting abstracts in English language that examined the protective effects of l-carnitine against I/R induced injury in neuromuscular organs were reviewed. Materials were obtained by searching ELSEVIER, web of knowledge, PubMed, Scopus, clinical trials, and Cochrane database of systematic reviews.

CONCLUSION

Although animal studies on central nervous system and some human studies on muscular system were in favors of effects of l-carnitine against I/R injury, however, more clinical trials are needed to clarify the clinical importance of l-carnitine as a treatment option to manage I/R-induced injury of neuromuscular system.

Antiinflammatory effects of L-carnitine supplementation (1000 mg/d) in coronary artery disease patients

OBJECTIVE

Inflammation mediators have been recognized as risk factors for the pathogenesis of coronary artery disease (CAD). The purpose of this study was to investigate the effect of L-carnitine supplementation (LC, 1000 mg/d) on inflammation markers in patients with CAD.

METHODS

We enrolled 47 patients with CAD in the study. The patients with CAD were identified by cardiac catheterization as having <50% stenosis of one major coronary artery. The patients were randomly assigned to the placebo (n = 24) and LC (n = 23) groups and the intervention was administered for 12 wk. The levels of LC, antioxidant status (malondialdehyde and antioxidant enzymes activities), and inflammation markers (C-reactive protein [CRP], interleukin [IL]-6, and tumor necrosis factor [TNF]-α) were measured.

RESULTS

Thirty-nine participants completed the study (19 placebo; 20 LC). After LC supplementation, the levels of inflammation markers were significantly reduced compared with the baseline (CRP, P < 0.01; IL-6, P = 0.03; TNF-α, P = 0.07) and those in the placebo group (CRP, P < 0.05; IL-6, P = 0.04; TNF-α, P = 0.03). The levels of inflammation markers were significantly negatively correlated with the levels of LC and antioxidant enzymes activities (P < 0.05).

CONCLUSIONS

We suggest that LC supplementation, due to its antioxidant effects, may have potential utility to reduce inflammation in CAD.

Modulatory effects of l-carnitine on tamoxifen toxicity and oncolytic activity

The aim of this study was to investigate the protective effect of l-carnitine (l-CAR) in tamoxifen (TAM)-induced toxicity and antitumor activity. Adult female rats were randomly divided into four groups. Group I was served as control, groups II and III were treated with TAM (10 mg/kg, periorally) and l-CAR (300 mg/kg, intraperitoneally), respectively, while group IV was treated with both compounds. The treatment continued daily for 28 days. Administration of TAM resulted in significant increase in serum lipid profiles, liver enzymes, and bilirubin level. TAM produced a significant increase in lipid peroxides (LPO) level and nonsignificant change in nitrogen oxide (NO( x)) level accompanied with significant decrease in superoxide dismutase (SOD) activity of hepatic and uterus tissues and significant decrease in glutathione (GSH) content of uterus tissue. Administration of l-CAR for 1 h prior to TAM treatment decreased serum lipids and liver enzymes significantly and significantly increased SOD activity in liver and uterus tissues compared with TAM-treated group. Furthermore, it restored LPO and GSH levels and increased NO( x) level in uterus tissue. DNA fragmentation and the apoptotic marker, caspase-3, were not detected in the liver of all treated groups. Histopathologically, alterations in the liver and uterus structures after TAM treatment, which was attenuated after l-CAR administration. The antitumor effect and survival of the combined treatment of Ehrlich ascites carcinoma (EAC)-bearing mice was less than each one alone. l-CAR interestingly increased survival rate of EAC-bearing mice more than TAM-treated group. In conclusion, l-CAR has beneficial effects regarding TAM toxicity; however, it interferes with its antitumor effect.

The protective effect of L-carnitine against hippocampal damage due to experimental formaldehyde intoxication in rats

We investigated the protective effects of L-carnitine on hippocampus tissue damage in rats during experimental formaldehyde (FA) intoxication. Male Wistar albino rats were assigned into four groups: (1) control (C), (2) formaldehyde (FA), (3) formaldehyde + 0.5 g/kg of L-carnitine (FA + 0.5 LC) (4) formaldehyde + 1 g/kg L-carnitine (FA + 1 LC). At the end of the 14 day trial period, animals were sacrificed by decapitation under anesthesia. The hippocampus tissue samples were extracted to measure MDA, GSH and SOD activity. Neuronal degeneration was assessed based on histopathological (hematoxylin and eosin) and immunohistochemical (anti-ubiquitin) examination. To detect oxidative stress, specimens were reacted with anti-Cu/Zn-SOD antibody. After administering L-carnitine with FA to the animals, the activities of SOD and GSH increased, but the levels of MDA decreased in hippocampus tissue. Neuronal degeneration was observed in the FA group. L-carnitine administration reduced neuronal degeneration and histological structure was similar to controls. After FA application, degenerated hippocampus neurons were stained with anti-ubiquitin and Cu/Zn-SOD antibodies; weakly positive staining was observed in L- carnitine-treated groups. L-carnitine may be useful for preventing oxidative damage in the hippocampus tissue due to formaldehyde intoxication.

L-carnitine supplementation as a potential antioxidant therapy for inherited neurometabolic disorders

In recent years increasing evidence has emerged suggesting that oxidative stress is involved in the pathophysiology of a number of inherited metabolic disorders. However the clinical use of classical antioxidants in these diseases has been poorly evaluated and so far no benefit has been demonstrated. l-Carnitine is an endogenous substance that acts as a carrier for fatty acids across the inner mitochondrial membrane necessary for subsequent beta-oxidation and ATP production. Besides its important role in the metabolism of lipids, l-carnitine is also a potent antioxidant (free radical scavenger) and thus may protect tissues from oxidative damage. This review addresses recent findings obtained from patients with some inherited neurometabolic diseases showing that l-carnitine may be involved in the reduction of oxidative damage observed in these disorders. For some of these diseases, reduced concentrations of l-carnitine may occur due to the combination of this compound to the accumulating toxic metabolites, especially organic acids, or as a result of protein restricted diets. Thus, l-carnitine supplementation may be useful not only to prevent tissue deficiency of this element, but also to avoid oxidative damage secondary to increased production of reactive species in these diseases. Considering the ability of l-carnitine to easily cross the blood-brain barrier, l-carnitine supplementation may also be beneficial in preventing neurological damage derived from oxidative injury. However further studies are required to better explore this potential.

The effect of L-carnitine on oxidative stress responses of experimental contrast-induced nephropathy in rats

This study was conducted to investigate the prophylactic effects of carnitine against contrast-induced nephropathy (CIN) and its relation to oxidant/antioxidant status in kidney, liver, heart, spleen and lung tissues in a CIN rat model. Twenty-eight adult male Wistar rats were divided into 4 groups, the control, contrast media (CM), carnitine and contrast media+carnitine (CM+carnitine) groups. Animals were placed in individual metabolism cages, and on the 2nd day, rats were deprived of water for 24 hr. On the 3rd day, contrast media were administered to groups CM and CM+carnitine. L-carnitine was administered on days 2, 3 and 4. Histopathological changes were evaluated in the right kidney after euthanization. Superoxide dismutase (SOD) and catalase (CAT) activities and glutathione (GSH) and malondialdehyde (MDA) levels were measured in renal, liver, heart, spleen and lung tissues. The SOD activities in the renal (P<0.05), liver (P<0.001) and spleen (P<0.05) tissues were increased in the carnitine group. The CAT activities in the spleen tissue were decreased (P<0.01) only in the CM group. Renal (P<0.05), liver (P<0.001), spleen (P<0.001) and lung tissue (P<0.01) GSH levels were found to be higher in the carnitine group. In renal, liver and lung tissues, the MDA levels increased in the CM group (P<0.001). The histopathological findings showed that L-carnitine may have a preventative effect in alleviating the negative effects of CIN. Similar to this, L-carnitine may play a major role in the stability of the antioxidant status in the kidney, liver, spleen and lung of the CIN rat model.

Protective effect of L-carnitine against H(2)O(2)-induced neurotoxicity in neuroblastoma (SH-SY5Y) cells

OBJECTIVES

4-N-trimethylammonium-3-hydroxybutyric acid (L-carnitine) is an endogenous mitochondrial membrane compound and some studies have reported that L-carnitine could effectively protect various cells against oxidative injury both in vitro and in vivo. In the present study, we used the human neuroblastoma SH-SY5Y cell line as an in vitro model and assessed the effect of L-carnitine on hydrogen peroxide (H(2)O(2))-mediated oxidative stress and neurotoxicity.

METHODS

Cells in culture were treated with different concentrations of H(2)O(2) alone or pretreated with L-carnitine. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assays, transmission electron microscopy, agarose gel electrophoresis, biochemical methods, and Western blotting were employed in the present study.

RESULTS

Pretreatment with L-carnitine for 3 hours inhibited H(2)O(2)-induced cell viability loss, morphological changes, intracellular reactive oxygen species generation, and lipid peroxidation in a concentration-dependent manner. Endogenous anti-oxidant defense components including total anti-oxidative capacity, glutathione peroxidase, catalase, and superoxide dismutase were also promoted by L-carnitine. Meanwhile, H(2)O(2)-induced down-regulation of Bcl-2, up-regulation of Bax, and DNA damage and apoptosis were also inhibited in the presence of L-carnitine.

DISCUSSION

Taken together, these results suggest that L-carnitine may function as an anti-oxidant to inhibit H(2)O(2)-induced oxidative stress as well as regulation of Bcl-2 family and prevent the apoptotic death of neuronal cells, which might be beneficial for the treatment of oxidative stress in neurodegenerative diseases.

Endogenous antioxidants and radical scavengers

All living organisms are constantly exposed to oxidant agents deriving from both endogenous and exogenous sources capable to modify biomolecules and induce damages. Free radicals generated by oxidative stress exert an important role in the development of tissue damage and aging. Reactive species (RS) derived from oxygen (ROS) and nitrogen (RNS) pertain to free radicals family and are constituted by various forms of activated oxygen or nitrogen. RS are continuosly produced during normal physiological events but can be removed by antioxidant defence mechanism: the imbalance between RS and antioxidant defence mechanism leads to modifications in cellular membrane or intracellular molecules. In this chapter only endogenous antioxidant molecules will be critically discussed, such as Glutathione, Alpha-lipoic acid, Coenzyme Q, Ferritin, Uric acid, Bilirubin, Metallothioneine, L-carnitine and Melatonin.

L-Carnitine supplementation reduces oxidized LDL cholesterol in patients with diabetes

BACKGROUND

Patients with type 2 diabetes are under high oxidative stress, and levels of hyperglycemia correlate strongly with levels of LDL oxidation. Carnitine favorably modulates oxidative stress.

OBJECTIVE

This objective of this study was to evaluate the efficacy of L-carnitine on the reduction of oxidized LDL cholesterol in patients with type 2 diabetes.

DESIGN

Eighty-one patients with diabetes were randomly assigned to 1 of 2 treatment groups for 3 mo. The 2 groups received either 2 g L-carnitine once daily (n = 41) or placebo (n = 40). The following variables were assessed at baseline, after washout, and at 1, 2, and 3 mo of treatment: body mass index, fasting plasma glucose, glycosylated hemoglobin, total cholesterol, LDL cholesterol, HDL cholesterol, triglycerides, apolipoprotein A1, apolipoprotein B-100, oxidized LDL cholesterol, thiobarbituric acid-reactive substances, and conjugated dienes.

RESULTS

At the end of the study period, the L-carnitine-treated patients showed significant improvements compared with the placebo group in the following markers: oxidized LDL levels decreased by 15.1 compared with 3.0 U/L (P < 0.001); LDL cholesterol decreased by 0.45 compared with 0.16 mmol/L (P < 0.05); triglycerides decreased by 1.02 compared with 0.09 mmol/L (P < 0.001); apolipoprotein A1 concentrations decreased by 0.12 compared with 0.03 mg/dL (P < 0.05); apolipoprotein B-100 concentrations decreased by 0.13 compared with 0.04 mg/dL (P < 0.05); thiobarbituric acid-reactive substance concentrations decreased by 1.92 compared with 0.05 (P < 0.001), and conjugated diene concentrations decreased by 0.72 compared with 0.11 in the placebo group (P < 0.001).

CONCLUSION

Our study indicates that oral administration of L-carnitine reduces oxidized LDL cholesterol levels in patients with type 2 diabetes.

Depressive-like behavior in mice recently recovered from motor disorders after 3-nitropropionic acid intoxication

OBJECTIVE

Striatum may be involved in depressive disorders according to the neuroimaging analysis and clinical data. However, no animal model at present supported the possible role of striatum in the pathogenesis of depression. In the present study, we have investigated the depressive-like behavior in mice recently intoxicated with 3-nitropropionic acid (3-NP), a widely known toxin that selectively damages the striatum in the brain.

METHODS

Mouse model was made with subacute systemic 3-NP treatment, and the depressive-like behavior was measured using the duration of immobility during forced swimming test (FST).

RESULTS

When the mice at day 15 post-intoxication just totally recovered from motor deficits, the duration of immobility in FST was significantly longer than that in controls. The depressive-like behavior was not due to the fatigue or general sickness following 3-NP intoxication and could be reversed by the antidepressant, desipramine hydrochloride. In two successive FST in 24 h interval, the depressive-like behavior could be observed again in subsequent FST (at day 16 post-intoxication), and the mice presented a normal "learned helplessness".

CONCLUSION

A novel depression animal model could be established in mice during the initial period of recovery from 3-NP intoxication. The depression-like behavior might occur independently without involvement of cognitive defects, and the striatal lesions may underlie the depression-like behavior attributable to 3-NP intoxication.

Lipid peroxidation, mitochondrial dysfunction and neurochemical and behavioural deficits in different neurotoxic models: protective role of S-allylcysteine

Experimental evidence on the protective properties of S-allylcysteine (SAC) was collected from three models exerting striatal toxicity. In the first model, SAC (120 mg kg(-1)x5) prevented lipoperoxidation (LP) and mitochondrial dysfunction (MD) in synaptosomal fractions from 1-methyl-4-phenyl-1,2,3,6-tetrahydropiridinium-treated mice (30 mg kg(-1)), but without complete restoration of dopamine levels. In the second model, SAC (300 mg kg(-1)x 3), prevented LP and MD in synaptosomes from rats infused with 6-hydroxydopamine (8 microg microl(-1)) into the substantia nigra pars compacta, but again, without total reversion of depleted dopamine levels. In the third model, SAC (100 mg kg(-1)x 1) prevented MD in synaptosomes from rats injected with 3-nitropropionic acid (10 mg kg(-1)), but in contrast to the other models, it failed to prevent LP. SAC also prevented the aberrant motor activity patterns evoked by the three toxins. Altogether, the results suggest that the antioxidant properties of SAC are responsible for partial or total preservation of neurochemical, biochemical and behavioural markers, indicating that pro-oxidant reactions underlie the neurotoxicity in these models.

Valproate and acetyl-L-carnitine prevent methamphetamine-induced behavioral sensitization in mice

This study deals with the possible inhibitory role played by acetyl-l-carnitine (ALC) against methamphetamine (METH)-induced behavioral sensitization. Because valproate (VAL) inhibits the behavioral sensitization exerted by different psychostimulants, we investigated ALC's potential to prevent the amplification of METH-mediated psychomotor effects. We therefore evaluated the locomotor effects of VAL or ALC alone or in combination with METH after acute (day 1) as well as repeated (day 7) drug challenge. Finally, to assess the induction of behavioral sensitization, we also recorded the METH-mediated locomotor response after 7 days of drug suspension (day 15). Results showed that both VAL and ALC prevented the METH-induced sensitization. Another interesting observation was the significantly higher METH-induced hyperactivity at day 15 (after a 7-day drug-free period), indicating that behavioral sensitization developed during the washout period. Results also showed that both the acute and repeated coadministration of METH with either VAL or ALC inhibited METH-induced hyperactivity. We present different hypotheses concerning similar but also peculiar mechanisms that might underlie the preventive action of VAL and ALC. These data add to a growing body of literature that illustrates the potential of ALC in protecting against the insult of dysfunctional mitochondrial metabolism and psychostimulant-mediated neurotoxicity. By demonstrating an in vivo action against one of the most abused drugs, these results raise the possibility of beneficial effects of ALC in abuse behavior.

Excitotoxic damage, disrupted energy metabolism, and oxidative stress in the rat brain: antioxidant and neuroprotective effects of L-carnitine

Excitotoxicity and disrupted energy metabolism are major events leading to nerve cell death in neurodegenerative disorders. These cooperative pathways share one common aspect: triggering of oxidative stress by free radical formation. In this work, we evaluated the effects of the antioxidant and energy precursor, levocarnitine (L-CAR), on the oxidative damage and the behavioral, morphological, and neurochemical alterations produced in nerve tissue by the excitotoxin and free radical precursor, quinolinic acid (2,3-pyrindin dicarboxylic acid; QUIN), and the mitochondrial toxin, 3-nitropropionic acid (3-NP). Oxidative damage was assessed by the estimation of reactive oxygen species formation, lipid peroxidation, and mitochondrial dysfunction in synaptosomal fractions. Behavioral, morphological, and neurochemical alterations were evaluated as markers of neurotoxicity in animals systemically administered with L-CAR, chronically injected with 3-NP and/or intrastriatally infused with QUIN. At micromolar concentrations, L-CAR reduced the three markers of oxidative stress stimulated by both toxins alone or in combination. L-CAR also prevented the rotation behavior evoked by QUIN and the hypokinetic pattern induced by 3-NP in rats. Morphological alterations produced by both toxins (increased striatal glial fibrillary acidic protein-immunoreactivity for QUIN and enhanced neuronal damage in different brain regions for 3-NP) were reduced by L-CAR. In addition, L-CAR prevented the synergistic action of 3-NP and QUIN to increase motor asymmetry and depleted striatal GABA levels. Our results suggest that the protective properties of L-CAR in the neurotoxic models tested are mostly mediated by its characteristics as an antioxidant agent.

Acute administration of 3-nitropropionic acid, a reactive oxygen species generator, boosts ethanol-induced locomotor stimulation. New support for the role of brain catalase in the behavioural effects of ethanol

The antioxidant enzyme catalase by reacting with H(2)O(2), forms the compound known as compound I (catalase-H(2)O(2)). This compound is able to oxidise ethanol to acetaldehyde in the CNS. It has been demonstrated that 3-nitropropionic acid (3-NPA) induces the activity of the brain catalase-H(2)O(2) system. In this study, we tested the effect of 3-NPA on both the brain catalase-H(2)O(2) system and on the acute locomotor effect of ethanol. To find the optimal interval for the 3-NPA-ethanol interaction mice were treated with 3-NPA 0, 45, 90 and 135min before an ethanol injection (2.4mg/kg). In a second study, 3-NPA (0, 15, 30 or 45mg/kg) was administered SC to animals 90min before saline or several doses of ethanol (1.6 or 2.4g/kg), and the open-field behaviour was registered. The specificity of the effect of 3-NPA (45mg/kg) was evaluated on caffeine (10mg/kg IP) and cocaine (4mg/kg)-induced locomotion. The prevention of 3-NPA effects on both ethanol-induced locomotion and brain catalase activity by L-carnitine, a potent antioxidant, was also studied. Nitropropionic acid boosted ethanol-induced locomotion and brain catalase activity after 90min. The effect of 3-NPA was prevented by l-carnitine administration. These results indicate that 3-NPA enhanced ethanol-induced locomotion by increasing the activity of the brain catalase system.

l-Carnitine protects mammalian cells from chromosome aberrations but not from inhibition of cell proliferation induced by hydrogen peroxide

L-carnitine is a small essential molecule indispensable in fatty acid metabolism and required in several biological pathways regulating cellular homeostasis. Despite considerable progress in understanding of L-carnitine biosynthesis and metabolism, very few data are reported concerning the protective role of L-carnitine from oxidative stress-induced DNA damage that is known to be a factor in cell transformation and tumourigenesis. In order to detect the capability of L-carnitine to protect mammalian cells from oxidative stress-induced chromosomal effects, we analysed chromosome aberrations in mitotic CHO cells, which represent an appropriate cytogenetic model to study compounds that enhance cell protection against externally induced DNA damage. We chose H2O2 as an inducer of oxidative stress. Our results demonstrate for the first time a marked and reproducible reduction of H2O2-induced chromosome damage involving an L-carnitine-mediated capacity to buffer intracellular formation of reactive oxygen species (ROS). Furthermore, by studying the mitotic index and cell cycle progression, we also demonstrated that this protective effect is highly specific, since L-carnitine itself was not able to prevent the inhibition of cell growth caused by H2O2.

Antioxidant and antiradical activities of L-carnitine

L-carnitine plays an important regulatory role in the mitochondrial transport of long-chain free fatty acids. In this study, the antioxidant activity of L-carnitine was investigated as in vitro. The antioxidant properties of the L-carnitine were evaluated by using different antioxidant assays such as 1, 1-diphenyl-2-picryl-hydrazyl free radical (DPPH.) scavenging, total antioxidant activity, reducing power, superoxide anion radical scavenging, hydrogen peroxide scavenging and metal chelating activities. Total antioxidant activity was measured according to ferric thiocyanate method. alpha-tocopherol and trolox, a water-soluble analogue of tocopherol, were used as the reference antioxidant compounds. At the concentrations of 15, 30 and 45 microg/mL, l-carnitine showed 94.6%, 95.4% and 97.1% inhibition on lipid peroxidation of linoleic acid emulsion, respectively. On the other hand, 45 microg/mL of standard antioxidant such as alpha-tocopherol and trolox indicated an inhibition of 88.8% and 86.2% on peroxidation of linoleic acid emulsion, respectively. In addition, L-carnitine had an effective DPPH. scavenging, superoxide anion radical scavenging, hydrogen peroxide scavenging, total reducing power and metal chelating on ferrous ions activities. Also, those various antioxidant activities were compared to alpha-tocopherol and trolox as references antioxidants.

Protective effect of melatonin on 3-nitropropionic acid-induced oxidative stress in synaptosomes in an animal model of Huntington's disease

The effect of melatonin (1 mg/kg BW i.p./day) on the oxidative changes produced by 3-nitropropionic acid (20 mg/kg BW/day for 4 days) in rat striatal and cortical synaptosomes was investigated. The effects of 3-nitropropionic acid were evaluated as changes in the quantity of lipid peroxidation products, protein carbonyl groups and superoxide dismutase and succinate dehydrogenase activities. 3-Nitropropionic acid caused a rise in lipid peroxidation levels and protein carbonyls content whereas it induced a reduction in the activity of succinate dehydrogenase and triggered an enhancement in superoxide dismutase activity. These changes were prevented by previous administration of melatonin. Our results reveal: (i) 3-nitropropionic acid induces a status of oxidative stress in some brain regions of the Wistar rat; (ii) melatonin prevents the deleterious effects induced by the acid. In conclusion, the results show the ability of melatonin to modify the neural response to 3-nitropropionic acid with the protective mechanism likely involving the antioxidative processes of melatonin.

Neuroprotective effect of l-carnitine in the 3-nitropropionic acid (3-NPA)-evoked neurotoxicity in rats

A plant and fungal toxin, 3-NPA, acts as an inhibitor of mitochondrial function via irreversible inactivation of the mitochondrial inner membrane enzyme, succinate dehydrogenase (SDH). Inhibition of SDH disturbs electron transport and leads to cellular energy deficits and neuronal injury. We have shown that pretreatment with l-carnitine, while not significantly attenuating SDH inhibition, prevented hypothermia and oxidative stress-associated increased activity of free radical-scavenging enzymes. Here, a neurohistological method was applied to examine the effect of carnitine pretreatment against 3-NPA-induced neurotoxicity. Twenty adult male Sprague-Dawley rats were randomly divided into two groups (n = 10/group). Rats in the first group were injected twice with 3-NPA at 30 mg/kg s.c., 2 days apart, and the second group of animals received l-carnitine pretreatment at 100 mg/kg 30-40 min before 3-NPA administration. Rats in both groups were perfused 7 days later and their brains harvested. Degenerating neurons were identified and localized via the fluorescent marker Fluoro-Jade B. In the three animals that survived 3-NPA dosing, one exhibited no pathology, one exhibited moderate unilateral damage to the striatum, and the third exhibited extensive bilateral neuronal degeneration in multiple forebrain regions. In the seven surviving animals that received l-carnitine prior to 3-NPA insult, six exhibited no lesions, while one exhibited a modest unilateral lesion in the striatum. It appears that l-carnitine is protective against 3-NPA-induced toxicity, as reflected by both reduced mortality and significantly reduced neuronal degeneration.

Effect of glucocorticoids on 3-nitropropionic acid-induced oxidative stress in synaptosomes

The present study with rat striatal and cortical synaptosomes evaluated the effect of dexamethasone (300 microg/kg i.p./day) with and without simultaneous adrenalectomy on the oxidative stress induced by 3-nitropropionic acid (20 mg/kg/day for 4 days). Adrenalectomy enhanced the oxidative stress induced by 3-nitropropionic acid. These changes were prevented by previous and simultaneous administration of dexamethasone. Adrenalectomy alone induced oxidative stress with decreases in succinate dehydrogenase activity. Our results revealed that adrenal glucocorticoids, and especially dexamethasone (synthetic glucocorticoid), have a protective effect against oxidative stress induced by 3-nitropropionic acid in some brain regions of the Wistar rat.

The influence of L-carnitine on methanol biotransformation in rats

There persists a need for potent and safe inhibitors of alcohol dehydrogenase (ADH), to effectively treat methanol poisoning by slowing its rate of biotransformation to there toxic products, formaldehyde and formic acid. Only a few former papers have reported on the significant effectiveness of L-carnitine in treating ethanol poisoning as well as alcohol abuse. As are no reports on the effectiveness of L-carnitine in treating methanol poisoning till now, the current studies were conducted to investigate the influence of L-carnitine on both oxydative metabolism and elimination of methanol in rats. Male Sprague-Dawley rats, aged 3 months with the body weight of 200-230 g were divided into 6 groups at random, with two of the groups considered to be control. Rats were given drinking water (control) or methanol in two different doses of 3220 mg/kg b.m. or 6440 mg/kg b.m. intragastrically and 0.9% NaCl (control) or 6.2 mmol/kg b.m. of L-carnitine intraperitionelly. Within 96 hours after the administration of methanol and 0.9% NaCl or L-carnitine, the urine was collected and then the animals were decapitated. To determine methanol there were taken blood samples for clot, and to determine carnitine and its derivatives blood was taken into heparinized test tubes. During the autopsy liver was also secured. In all the experimental time points stated the methanol concentrations in blood, urine and liver homogenate were determined by a head-space gas chromatography.

Optic nerve atrophy in propionic acidemia

OBJECTIVE

Propionic acidemia is a rare metabolic disorder that is diagnosed in the early neonatal period. The disorder is characterized by life-threatening ketoacidosis, lethargy, failure to thrive, and developmental delay. Herein we report the ocular findings in a prospective series of six patients with propionic acidemia.

DESIGN

Prospective case series.

PARTICIPANTS

Six children (three male and three female) between the ages of 2 and 10 years with propionic acidemia who were examined at Children's Hospital Los Angeles.

METHODS

A complete ophthalmic examination was performed on each of the six children. The examination included visual acuity testing, ocular motility, anterior segment examination, and funduscopic evaluation. Emphasis was placed on the function of the optic nerve and on the appearance of the optic disc, looking for possible atrophic changes.

MAIN OUTCOME MEASURES

The clinical appearance of the optic disc and evidence of optic neuropathy.

RESULTS

Optic nerve atrophy was present exclusively in all of the male patients in the series; none of the female patients demonstrated any detectable impairment of optic nerve function. The optic nerve atrophy was symmetric and age dependent and varied from moderate to severe. There were no other anterior or posterior segment abnormalities, other than one case of unilateral morning glory syndrome, diagnosed at birth. There was no correlation between metabolic control and the development and progression of optic nerve atrophy.

CONCLUSIONS

Males with propionic acidemia have moderate to severe bilateral optic atrophy.

Type I glutaric aciduria, part 2: a model of acute striatal necrosis

Type I glutaric aciduria (GA1) is an inborn error of organic acid metabolism that is associated with acute neurological crises, typically precipitated by an infectious illness. The neurological crisis coincides with swelling, metabolic depression, and necrosis of basal ganglia gray matter, especially the putamina and can be visualized as focal, stroke-like, signal hyperintensity on MRI. Here we focus on the stroke-like nature of striatal necrosis and its similarity to brain injury that occurs in infants after hypoxia-ischemia or systemic intoxication with 3-nitropropionic acid (NPA). These conditions share several features including abrupt onset, preferential effect in the striatum and age-specific susceptibility. The pathophysiology of the conditions is reviewed and a model proposed herein. We encourage investigators to test this model in an appropriate experimental system.

Neuroprotective effects of L-carnitine in induced mitochondrial dysfunction

The neuroprotective action of l-carnitine (LC) in the rat model of 3-nitropropionic acid (3-NPA)-induced mitochondrial dysfunction was examined. 3-NPA is known to produce decreases in neuronal ATP levels via inhibition of the succinate dehydrogenase (SDH) at complex II of the mitochondrial electron transport chain. SDH is involved in reactions of the Krebs cycle and oxidative phosphorylation, and its inhibition leads to both necrosis and apoptosis. LC enhances mitochondrial metabolism and, together with its acetylated form, acetyl-l-carnitine (ALC), via the LC-ALC-mediated transfer of acetyl groups, plays an important modulatory role in neurotransmitter signal transduction pathways and gene expression in neuronal cells. In the study described here, adult male Sprague-Dawley rats were injected with 3-NPA alone or treated with LC prior to 3-NPA administration. Pretreatment with LC totally prevented the 3-NPA-induced decrease in brain temperature measured using temperature probes implanted intracranially. It appears that the protective effects of LC against 3-NPA-induced neurotoxicity are achieved via compensatory enhancement of several pathways of mitochondrial energy metabolism. The results of this and previous studies conducted by our division in the 3-NPA model of mitochondrial dysfunction demonstrate that 3-NPA may be employed in vivo to evaluate enhancers of mitochondrial function that might exert neuroprotective effects.

3-nitropropionic acid inhibition of succinate dehydrogenase (complex II) activity in cultured Chinese hamster ovary cells: antagonism by L-carnitine

3-Nitropropionic acid (3-NPA) is an inhibitor of the mitochondrial enzyme succinate dehydrogenase (SDH, a part of complex II) that links the tricarboxylic acid (TCA) cycle to the respiratory electron transport chain. 3-NPA inactivates SDH by covalently and irreversibly binding to its active site. We previously examined the effects of 3-NPA on the histochemical activity of SDH in vivo, by using the reduction of a yellow tetrazolium dye (nitro blue tetrazolium) to a blue formazan as an indicator. In studies of cultured cells, the related dye methylthiazoletetrazolium (MTT) has commonly been used as an indicator of the presence and number of viable cells; that is cells that are capable of producing energy via the TCA cycle. Here we observed that doses of 3-NPA as low as 10(-8) M inhibited formazan production in an in vitro model system using CHO cells. This effect was antagonized by l-carnitine, which greatly increased the production of formazan, indicating a considerable improvement in energy production by the cultured cells. CHO cells appear to be a convenient model for the evaluation of therapeutic compounds that may modulate cellular bioenergetics.

Possible mechanism for the neuroprotective effects of L-carnitine on methamphetamine-evoked neurotoxicity

Some of the damage to the CNS that is observed following amphetamine and methamphetamine (METH) administration is known to be linked to increased formation of free radicals. This increase could be, in part, related to mitochondrial dysfunction and/or cause damage to the mitochondria, thereby leading to a failure of cellular energy metabolism and an increase in secondary excitotoxicity. The actual neuronal damage that occurs with METH-induced toxicity seems to affect dopaminergic cells in particular. METH-induced toxicity is related to an increase in the generation of both reactive oxygen (hydroxyl, superoxide, peroxide) and nitrogen (nitric oxide) species. Peroxynitrite (ONOO(-)), which is a reaction product of either superoxide or nitric oxide, is the most damaging radical. It can be reduced by antioxidants such as selenium, melatonin, and the selective nNOS inhibitor, 7-nitroindazole. METH-induced toxicity has been previously shown to increase production of the peroxynitrite stress marker, 3-nitrotyrosine (3-NT), in vitro, in cultured PC12 cells, and also in vivo, in the striatum of adult male mice. Pre- and post-treatment of mice with l-carnitine (LC) significantly attenuated the production of 3-NT in the striatum after METH exposure. LC is a mitochondriotropic compound in that it carries long-chain fatty acyl groups into mitochondria for beta-oxidation. It was shown also to play a protective role against various mitochondrial toxins, such as 3-nitropropionic acid. The protective effects of LC against METH-induced toxicity could be related to its prevention of possible metabolic compromise produced by METH and the resulting energy deficits. In particular, LC may be maintaining the mitochondrial permeability transition (MPT) and modulating the activation of the mitochondrial permeability transition pores (mPTP), especially the cyclosporin-dependent mPTP. The possible neuroprotective mechanism of LC against METH-toxicity and the role of the mitochondrial respiratory chain and the generation of free radicals and their subsequent action on the MPT and mPTP are also being examined using an in vitro model of NGF-differentiated pheochromocytoma cells (PC12). In preliminary experiments, the pretreatment of PC12 cells with LC (5 mM), added 10 min before METH (500 micro M), indicated that LC enhances METH-induced DA depletion. The role of LC in attenuating METH-evoked toxicity is still under investigation and promises to reveal information regarding the underlying mechanisms and role of mitochondria in the triggering of cell death.