Brain Activity of Thioctic Acid Enantiomers: In Vitro and in Vivo Studies in an Animal Model of Cerebrovascular Injury

Abstract

Oxidative stress is an imbalance between the production of free radicals and antioxidant defense mechanisms, potentially leading to tissue damage. Oxidative stress has a key role in the development of cerebrovascular and/or neurodegenerative diseases. This phenomenon is mainly mediated by an enhanced superoxide production by the vascular endothelium with its consequent dysfunction. Thioctic, also known as alpha-lipoic acid (1,2-dithiolane-3-pentanoic acid), is a naturally occurring antioxidant that neutralizes free radicals in the fatty and watery regions of cells. Both the reduced and oxidized forms of the compound possess antioxidant ability. Thioctic acid has two optical isomers designated as (+)- and (−)-thioctic acid. Naturally occurring thioctic acid is the (+)-thioctic acid form, but the synthetic compound largely used in the market for stability reasons is a mixture of (+)- and (−)-thioctic acid. The present study was designed to compare the antioxidant activity of the two enantiomers versus the racemic form of thioctic acid on hydrogen peroxide-induced apoptosis in a rat pheochromocytoma PC12 cell line. Cell viability was evaluated by MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay and free oxygen radical species (ROS) production was assessed by flow cytometry. Antioxidant activity of the two enantiomers and the racemic form of thioctic acid was also evaluated in spontaneously hypertensive rats (SHR) used as an in vivo model of increased oxidative stress. A 3-h exposure of PC12 cells to hydrogen peroxide (H2O2) significantly decreased cell viability and increased levels of intracellular ROS production. Pre-treatment with racemic thioctic acid or (+)-enantiomer significantly inhibited H2O2-induced decrease in cell viability from the concentration of 50 μmol/L and 20 μmol/L, respectively. Racemic thioctic acid and (+)-salt decreased levels of intracellular ROS, which were unaffected by (−)-thioctic acid. In the brain of SHR, the occurrence of astrogliosis and neuronal damage, with a decreased expression of neurofilament 200 kDa were observed. Treatment of SHR for 30 days with (+)-thioctic acid reduced the size of astrocytes and increased the neurofilament immunoreaction. The above findings could contribute to clarify the role played by thioctic acid in central nervous system injury related to oxidative stress. The more pronounced effect of (+)-thioctic acid observed in this study may have practical therapeutic implications worthy of being investigated in further preclinical and clinical studies.

Effect of treatment with the antioxidant alpha-lipoic (thioctic) acid on heart and kidney microvasculature in spontaneously hypertensive rats

“…This anti-inflammatory activity of alphalipoic acid can be related to its antioxidant property, by down-regulating the production of ROS. In fact, in a model of increased oxidative stress, in vitro, alpha-lipoic acid countered the ROS production (11,44,45). In addition, in SHR, alpha-lipoic acid reduced the oxidative stress decreasing the plasmatic malondyaldeyde levels and oxidative status of plasmatic protein (12).…”

“…The antioxidant activity of alpha-lipoic was investigated in an animal model of hypertension such as spontaneously hypertensive rats (SHR) (11,12). SHR has specific and uniform genetic predisposition to develop arterial hypertension (13), allowing to study causes, mechanisms, pathology and behavioral consequences of the disease.…”

Alpha-lipoic acid as a pleiotropic compound with potential therapeutic use in diabetes and other chronic diseases

“…In one study a hormonal admixture of ALA was used [65]. The same was noted in animal studies with different purposes [10, 56, 63, 64, 67–72] when the doses used were described as percentage [63] to doses described as mg/rat [68] or described as mg/kg which ranged from 20 to 100 mg/kg [10, 69, 70, 72]. As observed in in vitro studies, most of the in vivo studies did not give an information about which type of ALA was used.…”

Involvement of the N/OFQ-NOP system in rat morphine antinociceptive tolerance: Are astrocytes the crossroad?

“…The L4/L5 segments of the spinal cord were exposed from the lumbar vertebral column via laminectomy and identified by tracing the dorsal roots from their respective dorsal root ganglia (DRG). As previously described by (Di Cesare Mannelli et al, 2013; Di Cesare Mannelli et al, 2014; Tomassoni et al, 2013), formalin-fixed cryostat sections (7 μm) were washed 3 × phosphate-buffered saline (PBS), 0.3% Triton X-100 for 5 min and then were incubated, at room temperature, for 1 h in blocking solution (PBS, 0.3% Triton X-100, 5% albumin bovine serum; PBST). Slices were incubated overnight at 4°C in PBST containing rabbit primary antisera.…”