Protective effect of L-carnitine against bilirubin-induced neuronal cell death

The Alteration of L-Carnitine Transport and Pretreatment Effect under Glutamate Cytotoxicity on Motor Neuron-Like NSC-34 Lines

L-Carnitine (LC) is essential for transporting fatty acids to the mitochondria for β-oxidation. This study was performed to examine the alteration of the LC transport system in wild type (WT, NSC-34/hSOD1^WT) and mutant type (MT, NSC-34/hSOD1^G93A) amyotrophic lateral sclerosis (ALS) models. The uptake of [³H]L-carnitine was dependent on time, temperature, concentration, sodium, pH, and energy in both cell lines. The Michaelis–Menten constant (K_m) value as well as maximum transport velocity (V_max) indicated that the MT cell lines showed the higher affinity and lower capacity transport system, compared to that of the WT cell lines. Additionally, LC uptake was inhibited by organic cationic compounds but unaffected by organic anions. OCTN1/slc22a4 and OCTN2/slc22a5 siRNA transfection study revealed both transporters are involved in LC transport in NSC-34 cell lines. Additionally, slc22a4 and slc22a5 was significantly decreased in mouse MT models compared with that in ALS WT littermate models in the immune-reactivity study. [³H]L-Carnitine uptake and mRNA expression pattern showed the pretreatment of LC and acetyl L-carnitine (ALC) attenuated glutamate induced neurotoxicity in NSC-34 cell lines. These findings indicate that LC and ALC supplementation can prevent the neurotoxicity and neuro-inflammation induced by glutamate in motor neurons.

Molecular Physiology and Pathophysiology of Bilirubin Handling by the Blood, Liver, Intestine, and Brain in the Newborn

Bilirubin is the end product of heme catabolism formed during a process that involves oxidation-reduction reactions and conserves iron body stores. Unconjugated hyperbilirubinemia is common in newborn infants, but rare later in life. The basic physiology of bilirubin metabolism, such as production, transport, and excretion, has been well described. However, in the neonate, numerous variables related to nutrition, ethnicity, and genetic variants at several metabolic steps may be superimposed on the normal physiological hyperbilirubinemia that occurs in the first week of life and results in bilirubin levels that may be toxic to the brain. Bilirubin exists in several isomeric forms that differ in their polarities and is considered a physiologically important antioxidant. Here we review the chemistry of the bilirubin molecule and its metabolism in the body with a particular focus on the processes that impact the newborn infant, and how differences relative to older children and adults contribute to the risk of developing both acute and long-term neurological sequelae in the newborn infant. The final section deals with the interplay between the brain and bilirubin and its entry, clearance, and accumulation. We conclude with a discussion of the current state of knowledge regarding the mechanism(s) of bilirubin neurotoxicity.

Evaluation of carnitine deficit in very low birth weight preterm newborns small for their gestational age

OBJECTIVE

To verify whether small-for-gestational-age (SGA) preterm newborns represent a special risk group for carnitine deficiency. Secondary outcome includes assessment of longitudinal differences of total carnitine (TC), free carnitine (FC) and acylcarnitines between SGA and appropriate-for-gestational-age (AGA).

METHODS

A retrospective study to evaluate carnitine and acylcarnitines profile on 144 very-low-birth weight newborns (VLBW), classified as AGA (n = 73) and SGA (n = 71), was performed by tandem mass spectrometry, during their first 5 weeks of life. Carnitine deficiency was defined as FC <40 µmol/L and FC/TC <0.7.

RESULTS

Carnitine deficiency was observed in the two study groups throughout the monitoring period (maximum FC: 36.05 µmol/L in AGA and 32.24 µmol/L in SGA). FC/TC remains under 0.7 in both with progressive improvement. Unlike expected, a comparatively higher value of TC, FC and total acylcarnitines (tAC) was found in SGA during the first 2 weeks, with significant relevance on day 3-5, especially for tAC (p < 0.001). The only acylcarnitine with persistently lower value in SGA is C5 (p < 0.05 in first 2 weeks).

CONCLUSIONS

A carnitine deficiency was demonstrated in all VLBW. Although birth weight restriction has been suggested as a risk factor for impaired carnitine status, in our study, SGA was not related with higher carnitine deficiency.

Treatment with Carnitine Enhances Bone Fracture Healing under Osteoporotic and/or Inflammatory Conditions

The aim of this study was to examine the effects of carnitine on bone healing in ovariectomy (OVX) and inflammation (INF)-induced osteoporotic rats. The rats were randomly divided into nine groups (n = 8 animals per group): sham-operated (Group 1: SHAM); sham + magnesium silicate (Mg-silicate) (Group 2: SHAM + INF); ovariectomy (Group 3: OVX); ovariectomy + femoral fracture (Group 4: OVX + FRC); ovariectomy + femoral fracture + Mg-silicate (Group 5: OVX + FRC + INF); ovariectomy + femoral fracture + carnitine 50 mg/kg (Group 6: OVX + FRC + CAR50); ovariectomy + femoral fracture + carnitine 100 mg/kg (Group 7: OVX + FRC + CAR100); ovariectomy + femoral fracture + Mg-silicate + carnitine 50 mg/kg (Group 8: OVX + FRC + INF + CAR50); and ovariectomy + femoral fracture + Mg-silicate + carnitine 100 mg/kg (Group 9: OVX + FRC + INF + CAR100). Eight weeks after OVX, which allowed for osteoporosis to develop, INF was induced with subcutaneous Mg-silicate. On day 80, all of the rats in groups 4-9 underwent fracture operation on the right femur. Bone mineral density (BMD) showed statistically significant improvements in the treatment groups. The serum markers of bone turnover (osteocalcin and osteopontin) and pro-inflammatory cytokines (tumour necrosis factor α, interleukin 1β and interleukin 6) were decreased in the treatment group. The X-ray images showed significantly increased callus formation and fracture healing in the groups treated with carnitine. The present results show that in a rat model with osteoporosis induced by ovariectomy and Mg-silicate, treatment with carnitine improves the healing of femur fractures.

Neuroprotective effects of L-carnitine against oxygen-glucose deprivation in rat primary cortical neurons

Purpose

Hypoxic-ischemic encephalopathy is an important cause of neonatal mortality, as this brain injury disrupts normal mitochondrial respiratory activity. Carnitine plays an essential role in mitochondrial fatty acid transport and modulates excess acyl coenzyme A levels. In this study, we investigated whether treatment of primary cultures of rat cortical neurons with L-carnitine was able to prevent neurotoxicity resulting from oxygen-glucose deprivation (OGD).

Methods

Cortical neurons were prepared from Sprague-Dawley rat embryos. L-Carnitine was applied to cultures just prior to OGD and subsequent reoxygenation. The numbers of cells that stained with acridine orange (AO) and propidium iodide (PI) were counted, and lactate dehydrogenase (LDH) activity and reactive oxygen species (ROS) levels were measured. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and the terminal uridine deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling assay were performed to evaluate the effect of L-carnitine (1 µM, 10 µM, and 100 µM) on OGD-induced neurotoxicity.

Results

Treatment of primary cultures of rat cortical neurons with L-carnitine significantly reduced cell necrosis and prevented apoptosis after OGD. L-Carnitine application significantly reduced the number of cells that died, as assessed by the PI/AO ratio, and also reduced ROS release in the OGD groups treated with 10 µM and 100 µM of L-carnitine compared with the untreated OGD group (P<0.05). The application of L-carnitine at 100 µM significantly decreased cytotoxicity, LDH release, and inhibited apoptosis compared to the untreated OGD group (P<0.05).

Conclusion

L-Carnitine has neuroprotective benefits against OGD in rat primary cortical neurons in vitro.

L-carnitine protects against nickel-induced neurotoxicity by maintaining mitochondrial function in Neuro-2a cells

Mitochondrial dysfunction is thought to be a part of the mechanism underlying nickel-induced neurotoxicity. L-carnitine (LC), a quaternary ammonium compound biosynthesized from the amino acids lysine and methionine in all mammalian species, manifests its neuroprotective effects by improving mitochondrial energetics and function. The purpose of this study was to investigate whether LC could efficiently protect against nickel-induced neurotoxicity. Here, we exposed a mouse neuroblastoma cell line (Neuro-2a) to different concentrations of nickel chloride (NiCl₂) (0.25, 0.5, 1, and 2 mM) for 24 h, or to 0.5 mM and 1 mM NiCl₂ for various periods (0, 3, 6, 12, or 24 h). We found that nickel significantly increased the cell viability loss and lactate dehydrogenase (LDH) release in Neuro-2a cells. In addition, nickel exposure significantly elevated reactive oxygen species (ROS) and malondialdehyde (MDA) levels, disrupted the mitochondrial membrane potential (ΔΨ(m)), reduced adenosine-5'-triphosphate (ATP) concentrations and decreased mitochondrial DNA (mtDNA) copy numbers and mtRNA transcript levels. However, all of the cytotoxicities and mitochondrial dysfunctions that were triggered by nickel were efficiently attenuated by pretreatment with LC. These protective effects of LC may be attributable to its role in maintaining mitochondrial function in nickel-treated cells. Our results suggest that LC may have great pharmacological potential in protecting against the adverse effects of nickel in the nervous system.