Chitosan and solid lipid nanoparticles enhance the efficiency of alpha-lipoic acid against experimental neurotoxicity

Alpha-lipoic acid (α-LA) is characterized by its unpleasant odor, poor bioavailability and stability. Nanotechnology was applied to overcome this limitation. So we aimed in this study to formulate α-LA in two different forms of chitosan nanoparticles (CsNPs) and solid lipid nanoparticles (SLNPs) and characterize them in terms of physical properties and biological activities against aluminum chloride (AlCl₃)-induced neurotoxicity in rats. The vivo study was processed on 50 rats divided into 5 groups as follow: control, neurotoxic, treated α-LA, treated α-lipoic acid-loaded chitosan nanoparticles (α-LA-CsNPs) and treated α-lipoic acid-loaded solid lipid nanoparticles (α-LA-SLNPs) groups. The result was depicted by transmission electron microscopy (TEM) revealed that α-LA-SLNPs had a regular spherical shape while α-LA-CsNPs showed an irregular spherical form. Dynamic light scattering (DLS) analysis showed that the average particle size for α-LA-SLNPs was about 71 nm and for α-LA-CsNPs was about 126 nm. After the experimental period, we observed that AlCl₃ administration significantly increased oxidative stress, neuroinflammation and apoptosis and decreased brain fatty acid contentsand brain-derived neurotrophic factor,while α-LA, α-LA-CsNPs and α-LA-SLNPs were able to ameliorate these negative changes in the neurotoxic rats. However, the effect of the α-LA-loaded NPs was more prominent than that of pristine α-LA but the α-LA-SLNPs group was almost close to the control group. Conclusion: α-LA can attenuate neurotoxicity induced by AlCl3, attributed to its anti-inflammatory, antioxidant and anti-apoptotic activities in addition to the effectiveness of the encapsulation technique that can increase the efficiency and stability of α-LA. Moreover, α-LA-SLNPs are more efficient than α-LA-CsNPs.

GLRX5-associated [Fe-S] cluster biogenesis disorder: further characterisation of the neurological phenotype and long-term outcome

Background

Identification and characterisation of monogenic causes of complex neurological phenotypes are important for genetic counselling and prognostication. Bi-allelic pathogenic variants in the gene encoding GLRX5, a protein involved in the early steps of Fe-S cluster biogenesis, are rare and cause two distinct phenotypes: isolated sideroblastic anemia and a neurological phenotype with variant non-ketotic hyperglycinemia. In this study, we analysed the evolution of clinical and MRI findings and long-term outcome of patients with GLRX5 mutations.

Methods

Four patients from three Australian families of Lebanese descent were identified. All patients presented in childhood and were followed up into adult life through multiple clinical assessments. All were prescribed sodium benzoate.

Results

All patients (all females, age range 18–56 years) showed a complex neurological phenotype characterised by varying combinations of spastic paraparesis, length-dependent motor/sensory-motor axonal polyneuropathy, and psychiatric disturbances with variable intellectual disability. All had non-ketotic hyperglycinemia and a homozygous pathogenic c.151_153delAAG (p.K51del) change in GLRX5. Motor disability gradually progressed reaching moderate disability during adolescence and moderately severe disability during adult life. The major MRI finding was the upper cervical spinal cord signal changes with contrast enhancement noted in all and additional leukoencephalopathy in one. On follow up MRI, the white matter lesions diminished on a subsequent scan and then remained static over time. The spinal cord showed gliotic changes. Two patients have previously demonstrated low pyruvate dehydrogenase complex deficiency but none had plasma lactate elevation, nor biochemical evidence of branch-chain keto-dehydrogenase deficiency. Glycine levels reduced in patients that tolerated sodium benzoate, possibly stabilising clinical manifestations.

Conclusions

This report demonstrates that the p.K51del GLRX5 variant causes a distinct and predictable neurological phenotype. The clinical assessments spanning from childhood to adult life enable physicians to infer the natural history of GLRX5 related neurological disorder. There may be widespread metabolic consequences, and optimal management is unknown.

Lipoic acid. Kinetics and pluripotent biological properties and derivatives

Lipoic acid (LA) is globally known and its supplements are widely used. Despite its importance for the organism it is not considered a vitamin any more. The multiple metabolic forms and the differences in kinetics (absorption, distribution and excretion), as well as the actions of its enantiomers are analysed in the present article together with its biosynthetic path. The proteins involved in the transfer, biotransformation and activity of LA are mentioned. Furthermore, the safety and the toxicological profile of the compound are commented, together with its stability issues. Mechanisms of lipoic acid intervention in the human body are analysed considering the antioxidant and non-antioxidant characteristics of the compound. The chelating properties, the regenerative ability of other antioxidants, the co-enzyme activity and the signal transduction by the implication in various pathways will be discussed in order to be elucidated the pleiotropic effects of LA. Finally, lipoic acid integrating analogues are mentioned under the scope of the multiple pharmacological actions they acquire towards degenerative conditions.

Biochemical Approaches to Probe the Role of the Auxiliary Iron-Sulfur Cluster of Lipoyl Synthase from Mycobacterium Tuberculosis

Lipoic acid is an essential sulfur-containing cofactor used by several multienzyme complexes involved in energy metabolism and the breakdown of certain amino acids. It is composed of n-octanoic acid with sulfur atoms appended at C6 and C8. Lipoic acid is biosynthesized de novo in its cofactor form, in which it is covalently bound in an amide linkage to a target lysyl residue on a lipoyl carrier protein (LCP). The n-octanoyl moiety of the cofactor is derived from type 2 fatty acid biosynthesis and is transferred to an LCP to afford an octanoyllysyl amino acid. Next, lipoyl synthase (LipA in bacteria) catalyzes the attachment of the two sulfur atoms to afford the intact cofactor. LipA is a radical S-adenosylmethionine (SAM) enzyme that contains two [4Fe-4S] clusters. One [4Fe-4S] cluster is used to facilitate a reductive cleavage of SAM to render the highly oxidizing 5'-deoxyadenosyl 5'-radical needed to abstract C6 and C8 hydrogen atoms to allow for sulfur attachment. By contrast, the second cluster is the sulfur source, necessitating its destruction during turnover. In Escherichia coli, this auxiliary cluster can be restored after each turnover by NfuA or IscU, which are two iron-sulfur cluster carrier proteins that are implicated in iron-sulfur cluster biogenesis. In this chapter, we describe methods for purifying and characterizing LipA and NfuA from Mycobacterium tuberculosis, a human pathogen for which endogenously synthesized lipoic acid is essential. These studies provide the foundation for assessing lipoic acid biosynthesis as a potential target for the design of novel antituberculosis agents.

New cellulose-collagen-alginate materials incorporated with quercetin, anthocyanins and lipoic acid

Herein we present a new biomaterial based on cellulose, collagen and sodium alginate which served as a matrix for the incorporation of bioactive substances with antioxidant properties. Compared with pure cellulose hydrogels, the compressive strength and the elastic modulus of cellulose-collagen-alginate hydrogels were significantly enhanced, thus the compressive strength increased from 0.256 kPa to 6.91 kPa, while the elastic modulus increased from 0.0023 kPa to 0.115 kPa at 30% strain level. The release kinetic of all drugs through matrix components was done according to the Korsmeyer-Peppas model with a Fickian diffusion. The presence of bioactive principles, quercetin, lipoic acid and anthocyanins, gives biomaterials an antioxidant capacity on average 30% higher compared to the base matrix. The mechanical resistance, mucoadhesiveness, bioadhesiveness, release kinetic, and antioxidant capacity of active principles, recommend these biomaterials for the manufacture of transdermal drug delivery devices.

Htd2 deficiency-associated suppression of α-lipoic acid production provokes mitochondrial dysfunction and insulin resistance in adipocytes

Mitochondria harbor a unique fatty acid synthesis pathway (mtFAS) with mysterious functions gaining increasing interest, while its involvement in metabolic regulation is essentially unknown. Here we show that 3-Hydroxyacyl-ACP dehydratase (HTD2), a key enzyme in mtFAS pathway was primarily downregulated in adipocytes of mice under metabolic disorders, accompanied by decreased de novo production of lipoic acid, which is the byproduct of mtFAS pathway. Knockdown of Htd2 in 3T3-L1 preadipocytes or differentiated 3T3-L1 mature adipocytes impaired mitochondrial function via suppression of complex I activity, resulting in enhanced oxidative stress and impaired insulin sensitivity, which were all attenuated by supplement of lipoic acid. Moreover, lipidomic study revealed limited lipid alterations in mtFAS deficient cells which primarily presenting accumulation of triglycerides, attributed to mitochondrial dysfunction. Collectively, the present study highlighted the pivotal role of mtFAS pathway in regulating mitochondrial function and adipocytes insulin sensitivity, demonstrating supportive evidence for lipoic acid being potential effective nutrient for improving insulin resistance and related metabolic disorders.

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3-Hydroxyacyl-ACP dehydratase is decreased in adipocytes under diabetic condition.

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Deficient of 3-Hydroxyacyl-ACP dehydratase (HTD2) triggers mitochondrial dysfunction.

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Deficient of HTD2 promotes insulin resistance in adipocytes.

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Supplement of lipoic acid ameliorates deleterious effects of HTD2 deficiency.

Effects of lipoic acid supplementation on age- and iron-induced memory impairment, mitochondrial DNA damage and antioxidant responses

PURPOSE

To investigate the effects of lipoic acid (LA) supplementation during adulthood combined with supplementation later in life or LA administration only at old age on age-induced cognitive dysfunction, mitochondrial DNA deletions, caspase 3 and antioxidant response enzymes expression in iron-treated rats.

METHODS

Male rats were submitted to iron treatment (30 mg/kg body wt of Carbonyl iron) from 12 to 14th post-natal days. Iron-treated rats received LA supplementation (50 mg/kg, daily) in adulthood and old age or at old age only for 21 days. Memory, mitochondrial DNA (mtDNA) complex I deletions, caspase 3 mRNA expression and antioxidant response enzymes mRNA expression were analyzed in the hippocampus.

RESULTS

LA administration in adulthood combined with treatment later in life was able to reverse age-induced effects on object recognition and inhibitory avoidance memory, as well as on mtDNA deletions, nuclear factor (erythroid-derived 2)-like 2 (Nrf2) expression, and antioxidant enzymes disruption induced by iron in aged rats. LA treatment only at old age reversed iron-induced effects to a lesser extent when compared to the combined treatment.

CONCLUSION

The present findings support the view that LA supplementation may be considered as an adjuvant against mitochondrial damage and cognitive decline related to aging and neurodegenerative disorders.

Plasmodium falciparum LipB mutants display altered redox and carbon metabolism in asexual stages and cannot complete sporogony in Anopheles mosquitoes

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Apicoplast LipB deletion leads to changed antioxidant expression that precedes and coincides with accelerated differentiation.

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3D7 Plasmodium exhibits changes in glycolysis and tricarboxylic acid cycle activity after deletion of apicoplast LipB.

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When LipB is deleted from NF54 Plasmodium, the resulting parasites cannot complete their development in mosquitoes.

Malaria is still one of the most important global infectious diseases. Emergence of drug resistance and a shortage of new efficient antimalarials continue to hamper a malaria eradication agenda. Malaria parasites are highly sensitive to changes in the redox environment. Understanding the mechanisms regulating parasite redox could contribute to the design of new drugs. Malaria parasites have a complex network of redox regulatory systems housed in their cytosol, in their mitochondrion and in their plastid (apicoplast). While the roles of enzymes of the thioredoxin and glutathione pathways in parasite survival have been explored, the antioxidant role of α-lipoic acid (LA) produced in the apicoplast has not been tested. To take a first step in teasing a putative role of LA in redox regulation, we analysed a mutant Plasmodium falciparum (3D7 strain) lacking the apicoplast lipoic acid protein ligase B (lipB) known to be depleted of LA. Our results showed a change in expression of redox regulators in the apicoplast and the cytosol. We further detected a change in parasite central carbon metabolism, with lipB deletion resulting in changes to glycolysis and tricarboxylic acid cycle activity. Further, in another Plasmodium cell line (NF54), deletion of lipB impacted development in the mosquito, preventing the detection of infectious sporozoite stages. While it is not clear at this point if the observed phenotypes are linked, these findings flag LA biosynthesis as an important subject for further study in the context of redox regulation in asexual stages, and point to LipB as a potential target for the development of new transmission drugs.

Improved gene delivery to K-562 leukemia cells by lipoic acid modified block copolymer micelles

Although there has been substantial progress in the research field of gene delivery, there are some challenges remaining, e.g. there are still cell types such as primary cells and suspension cells (immune cells) known to be difficult to transfect. Cationic polymers have gained increasing attention due to their ability to bind, condense and mask genetic material, being amenable to scale up and highly variable in their composition. In addition, they can be combined with further monomers exhibiting desired biological and chemical properties, such as antioxidative, pH- and redox-responsive or biocompatible features. By introduction of hydrophobic monomers, in particular as block copolymers, cationic micelles can be formed possessing an improved chance of transfection in otherwise challenging cells. In this study, the antioxidant biomolecule lipoic acid, which can also be used as crosslinker, was incorporated into the hydrophobic block of a diblock copolymer, poly{[2-(dimethylamino)ethyl methacrylate]101-b-[n-(butyl methacrylate)124-co-(lipoic acid methacrylate)22]} (P(DMAEMA101-b-[nBMA124-co-LAMA22])), synthesized by RAFT polymerization and assembled into micelles (LAMA-mic). These micelles were investigated regarding their pDNA binding, cytotoxicity mechanisms and transfection efficiency in K-562 and HEK293T cells, the former representing a difficult to transfect, suspension leukemia cell line. The LAMA-mic exhibited low cytotoxicity at applied concentrations but demonstrated superior transfection efficiency in HEK293T and especially K-562 cells. In-depth studies on the transfection mechanism revealed that transfection efficiency in K-562 cells does not depend on the specific oncogenic fusion gene BCR-ABL alone. It is independent of the cellular uptake of polymer-pDNA complexes but correlates with the endosomal escape of the LAMA-mic. A comparison of the transfection efficiency of the LAMA-mic with structurally comparable micelles without lipoic acid showed that lipoic acid is not solely responsible for the superior transfection efficiency of the LAMA-mic. More likely, a synergistic effect of the antioxidative lipoic acid and the micellar architecture was identified. Therefore, the incorporation of lipoic acid into the core of hydrophobic-cationic micelles represents a promising tailor-made transfer strategy, which can potentially be beneficial for other difficult to transfect cell types.

Chromone-lipoic acid conjugate: Neuroprotective agent having acceptable butyrylcholinesterase inhibition, antioxidant and copper-chelation activities

PURPOSE

Alzheimer's disease (AD) is a multifaceted neurodegenerative disease. To target simultaneously multiple pathological processes involved in AD, natural-origin compounds with unique characteristics are promising scaffolds to develop novel multi-target compounds in the treatment of different neurodegenerative disease, especially AD. In this study, novel chromone-lipoic acid hybrids were prepared to find a new multifunctional lead structure for the treatment of AD.

METHODS

Chromone-lipoic acid hybrids were prepared through click reaction and their neuroprotection and anticholinesterase activity were fully evaluated. The anti-amyloid aggregation, antioxidant and metal-chelation activities of the best compound were also investigated by standard methods to find a new multi-functional agent against AD.

RESULTS

The primary biological screening demonstrated that all compounds had significant neuroprotection activity against H2O2-induced cell damage in PC12 cells. Compound 19 as the most potent butyrylcholinesterase (BuChE) inhibitor (IC50 = 7.55 μM) having significant neuroprotection activity as level as reference drug was selected for further biological evaluations. Docking and kinetic studies revealed non-competitive mixed-type inhibition of BuChE by compound 19. It could significantly reduce formation of the intracellular reactive oxygen species (ROS) and showed excellent reducing power (85.57 mM Fe+2), comparable with quercetin and lipoic acid. It could also moderately inhibit Aβ aggregation and selectively chelate with copper ions in 2:1 M ratio.

CONCLUSION

Compound 19 could be considered as a hopeful multifunctional agent for the further development gainst AD owing to the acceptable neuroprotective and anti-BuChE activity, moderate anti-Aβ aggregation activity, outstanding antioxidant activity as well as selective copper chelation ability. A new chromone-lipoic acid hybrid was synthesized as anti-Alzheimer agent with BuChE inhibitory activity, anti-Aβ aggregation, metal-chelation and antioxidant properties.

Whole exome sequencing identifies a novel homozygous MECR mutation in a Chinese patient with childhood-onset dystonia and basal ganglia abnormalities, without optic atrophy

Childhood-onset dystonia with optic atrophy and basal ganglia abnormalities is an extremely rare autosomal recessive mitochondrial disease caused by biallelic mutations in MECR. Using whole-exome sequencing, we identified a novel homozygous MECR mutation (c.910G > T, p.Asp304Tyr) in a Chinese patient with childhood-onset dystonia and basal ganglia abnormalities, without optic atrophy. With lipoic acid treatment, the disease progression was under control, and neither visual impairment nor optic atrophy was observed. To our knowledge, this is the first study about MECR-related mitochondrial disease in a Chinese patient and the first to report that supplementation with lipoic acid is a possible effective therapeutic strategy for this disease.

[The protective effects of α-lipoic acid on fluoride-induced reproductive lesion in rats via oxidative stress-mediated endoplasmic reticulum stress]

Objective: To determine the oxidative stress and endoplasmic reticulum stress and their changes after α-lipoic acid (α-LA) intervention, and to explore the effect and mechanism of fluoride-induced reproductive lesion. Methods: A total of 40 male Sprague-Dawley (SD) rats were randomly divided into four groups, control group(0.9% sodium chloride), α-LA group(100 mg/kg α-LA), NaF group(25 mg/kg NaF), and NaF+α-LA group(25 mg/kg NaF+100 mg/kg α-LA). Each group was treated in the way of intragastric administration for eight weeks. Sperm quality and the content of NaF in testis were analyzed. The morphologic changes of the testis were observed with the use of HE staining and the apoptosis was detected by the TUNEL assay. Biochemical method was used to measure oxidative stress. Western blot was used to detect the expression of endoplasmic reticulum stress markers, such as GRP78, PERK, and CHOP. Results: Compared with the control group, the NaF group had a low level in sperm density [(5.99±1.45)×10(6)/ml to (10.96±1.83)×10(6)/ml, P<0.01] and sperm vitality [(33.40±2.71)% vs (66.41±3.33)%, P<0.01], but a high level in sperm abnormality rate [(26.43±2.43)% vs (11.44±1.55)%, P<0.01]. Compared with the NaF group,the NaF+α-LA group had a high level in both sperm density [(8.47±0.82)×10(6)/ml vs (5.99±1.45)×10(6)/ml, P<0.05] and sperm vitality [(49.97±3.51)% vs (33.40±2.71)%, P<0.05], but a low level in sperm abnormality rate [(22.69±2.39)% vs (26.43±2.43)%, P<0.05].There was a significantly higher content of NaF in testis in the NaF group [(11.14±0.77) μg/g vs (5.78±0.28) μg/g, P<0.01] than the control group. Optical microscope was used to observe the morphologic changes of the testis, and it was showed that loose structure appeared both in spermatogenic cells and mature sperm cells while the amount of them decreased. However, after the administration of α-LA, there were complete organelles structure and exfoliated cells in the lumen ameliorated. TUNEL assay found that the apoptotic cells were in a high level in the NaF group [(61.32±7.14)% vs (6.99±2.17)%, P<0.01], while α-LA significantly suppressed the percentage of apoptotic cells in the NaF+α-LA group compared with the Naf group [(45.96±5.31)% vs (61.32±7.14)%, P<0.01].Oxidative stress assays showed that there were higher express of Malondialdehyde(MDA) content [(5.46±0.30) nmol/mgprot vs (3.24±0.58) nmol/mgprot, P<0.01], the activity of Superoxide Dismutase(SOD) [(6.04±0.71) U/mgprot vs (7.19±0.52) U/mgprot, P<0.01] and Glutathione peroxidase(GSH-Px) [(23.67±0.99) U/mgprot vs (26.91±1.67) U/mgprot, P<0.01] in the NaF group than the control group. To compared with the NaF group, the counterpart in the NaF+a-LA group of MDA content was less [(4.66±0.70) nmol/mgprot vs (5.46±0.30) nmol/mgprot, P<0.05] and the GSH-Px activity was high [(25.90±1.93) U/mgprot vs (23.67±0.99) U/mgprot, P<0.05]. Towards the detection of endoplasmic reticulum stress, we found that there were all in higher level in the NaF group that the expression of GRP78 [(0.79±0.05) vs (0.45±0.09), P<0.01], PERK [(0.71±0.04) vs (0.40±0.05), P<0.01], and CHOP[(0.79±0.09) vs (0.19±0.08), P<0.01] than the control group, and to compared with the NaF group, α-LA significantly supressed the expression of GRP78 [(0.46±0.06) vs (0.79±0.05), P<0.01] and CHOP[(0.52±0.09) vs (0.79±0.09), P<0.01]. Conclusion: α-lipoic acid plays a protective role in fluoride-induced reproductive lesion in rats by oxidative stress-mediated endoplasmic reticulum stress.

Effect of alpha-lipoic acid supplementation on the lipid profile and lipid ratios in women with gestational diabetes mellitus: A clinical trial study

BACKGROUND

Evidence suggests that Oxidative stress has been shown to plays an important role in gestational diabetes mellitus (GDM) etiology. On the other hand, women with GDM are at an increased risk for complications such as endothelial dysfunction and cardiovascular diseases.

OBJECTIVE

To investigate the effects of alpha-lipoic acid (ALA) on the maternal circulating values of lipid profile and lipid ratios in women with GDM.

MATERIALS AND METHODS

Sixty women with GDM were participated in the present study. The ALA group (n = 30) received ALA (100 mg/day) and the placebo group (n = 30) received cellulose acetate (100 mg/day) for eight wk. The maternal circulating values of hemoglobin A1C, triglyceride (TG), total cholesterol, high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol, triglyceride-glucose (TyG) index, atherogenic index of plasma (AIP), non-HDL-C, and lipid ratios were assessed before and after the intervention. P-value < 0.05 was considered as statistically significant.

RESULTS

The values of TyG index (p < 0.001), TG (p = 0.006), TG/HDL-C (p = 0.003), and AIP (p = 0.005) decreased significantly in the ALA group after the intervention.

CONCLUSION

Maternal circulating values of TyG index, TG, TG/HDL, AIP decreased after eight wk of ALA supplementation in women with GDM.

Acetic acid transporter-mediated, oral, multifunctional polymer liposomes for oral delivery of docetaxel

Nanoparticle-structuring aimed at the acetic acid (A) transporter on intestinal epithelial cells and tumor cells is a new potential strategy to enhance oral bioavailability and anti-tumor efficacy. In this study, chitosan (CS) was modified with hydrophilic A and hydrophobic lipoic acid (L), to produce ACSL. A novel ACSL-modified multifunctional liposomes (Lip) loaded with docetaxel (DTX; DTX-ACSL-Lip) was then prepared and characterized. DTX-ACSL-Lip recorded higher pH sensitivity and slower release than DTX-Lip and showed dithiothreitol (DTT) response release. DTX-ACSL-Lip uptake by Caco-2 cells was also significantly enhanced mainly viaA transporters compared with DTX-Lip. ACSL modification of DTX-Lip also improved oral bioavailability by 10.70-folds, with a 3.45-fold increase in C_max and a 1.19-fold prolongation in retention time of DTX in the blood. Moreover, the grafting degree of A significantly affected cell uptake and oral bioavailability. They also showed a significant (1.33-fold) increase in drug intratumoral distribution, as well as an increase in tumor growth inhibition rate from 54.34% to 87.51% without weight loss, compared with DTX-Lip. Therefore, modification of DTX-Lip with ACSL can significantly enhance the oral bioavailability and anti-tumor efficacy of DTX without obvious toxicity, confirming the potential of the dual strategy of targeting A transporter and controlled drug release in tumor cells in oral therapy of tumor.

Design, synthesis and pharmacological evaluation of ester-based quercetin derivatives as selective vascular KCa1.1 channel stimulators

Quercetin represents one of the most studied dietary flavonoids; it exerts a panel of pharmacological activities particularly on the cardiovascular system. Stimulation of vascular K_Ca1.1 channels contributes to its vasorelaxant activity, which is, however, counteracted in part by its concomitant stimulation of Ca_V1.2 channels. Therefore, several quercetin hybrid derivatives were designed and synthesized to produce a more selective K_Ca1.1 channel stimulator, then assessed both in silico and in vitro. All the derivatives interacted with the K_Ca1.1 channel with similar binding energy values. Among the selected derivatives, 1E was a weak vasodilator, though displaying an interesting Ca_V1.2 channel blocking activity. The lipoyl derivatives 1F and 3F, though showing pharmacological and electrophysiological features similar to those of quercetin, seemed to be more effective as K_Ca1.1 channel stimulators as compared to the parent compound. The strategy pursued demonstrated how different chemical substituents on the quercetin core can change/invert its effect on Ca_V1.2 channels or enhance its K_Ca1.1 channel stimulatory activity, thus opening new avenues for the synthesis of efficacious vasorelaxant quercetin hybrids.

Liquid crystalline nanodispersion functionalized with cell-penetrating peptides improves skin penetration and anti-inflammatory effect of lipoic acid after in vivo skin exposure to UVB radiation

In this study, the development and the performance of a new targeted liquid crystalline nanodispersion (LCN) by the attachment of cell-penetrating peptides (CPP) onto their surfaces to improve skin delivery of lipoic acid (LA) were evaluated. For that, the synthesis and characterization of this new platform as well as its spatiotemporal analysis from in vitro and in vivo topical application were explored and extensively discussed in this paper. The TAT or D4 peptides were chosen as CPP due to specific target strategies by the charge grouping on the skin surface or target the overexpressed epidermal growth factor receptor (EGFR) of cell membrane of keratinocytes, respectively. Thus, the nanoparticle characterization results when taken together suggested that designed LCNs maintained their hexagonal phase structure, nanoscale particle size, and low polydispersity index even after drug, lipopolymers, and peptide additions, which are proved to be favorable for topical skin delivery. There were no statistical differences among the LCNs investigated, except for superficial charge of LCN conjugated with TAT which may have altered the LCN zeta potential due to cationic charge of TAT amino acid sequence compared with D4. The cumulative amounts of LA retained into the skin were determined to be even higher coming from the targeted LCNs. Moreover, the exogenous antioxidant application of the LA from the LCNs can prevent ROS damage, which was demonstrated by this study with the less myeloperoxidase (MPO) activity and decrease in cytokine levels (TNF-alpha and IL-1β) generated by the oxidative stress modulation. Together, the data presented highlights the potential of these targeted LCNs, and overall, opens new frontiers for preclinical trials.

Lipoic Acid and Fish Oil Combination Potentiates Neuroinflammation and Oxidative Stress Regulation and Prevents Cognitive Decline of Rats After Sepsis

Sepsis causes organ dysfunction due to an infection, and it may impact the central nervous system. Neuroinflammation and oxidative stress are related to brain dysfunction after sepsis. Both processes affect microglia activation, neurotrophin production, and long-term cognition. Fish oil (FO) is an anti-inflammatory compound, and lipoic acid (LA) is a universal antioxidant substance. They exert neuroprotective roles when administered alone. We aimed at determining the effect of FO+LA combination on microglia activation and brain dysfunction after sepsis. Microglia cells from neonatal pups were co-treated with lipopolysaccharide (LPS) and FO or LA, alone or combined, for 24 h. Cytokine levels were measured. Wistar rats were subjected to sepsis by cecal ligation and perforation (CLP) and treated orally with FO, LA, or FO+LA. At 24 h after surgery, the hippocampus, prefrontal cortex, and total cortex were obtained and assayed for levels of cytokines, myeloperoxidase (MPO) activity, protein carbonyls, superoxide dismutase (SOD), and catalase (CAT) activity. At 10 days after surgery, brain-derived neurotrophic factor (BDNF) levels were determined and behavioral tests were performed. The combination diminished in vitro levels of pro-inflammatory cytokines. The combination reduced TNF-α in the cortex, IL-1β in the prefrontal cortex, as well as MPO activity, and decreased protein carbonyls formation in all structures. The combination enhanced catalase activity in the prefrontal cortex and hippocampus, elevated BDNF levels in all structures, and prevented behavioral impairment. In summary, the combination was effective in preventing cognitive damage by reducing neuroinflammation and oxidative stress and increasing BDNF levels.

Cancer and Alzheimer's disease: intracellular pH scales the metabolic disorders

Alzheimer's disease (AD) and cancer have much in common than previously recognized. These pathologies share common risk factors (inflammation and aging), with similar epidemiological and biochemical features such as impaired mitochondria. Metabolic reprogramming occurs during aging and inflammation. We assume that inflammation is directly responsible of the Warburg effect in cancer cells, with a decreased oxidative phosphorylation and a compensatory highthroughput glycolysis (HTG). Similarly, the Warburg effect in cancer is thought to support an alkaline intracellular pH (pHi), a key component of unrelenting cell growth. In the brain, inflammation results in increased secretion of lactate by astrocytes. The increased uptake of lactic acid by neurons results in the inverse Warburg effect, such as seen in AD. The neuronal activity is dampened by a fall of pHi. Pronounced cytosol acidification results in decreased mitochondrial energy yield as well as apoptotic cell death. The link between AD and cancer is reinforced by the fact that treatment aiming at restoring the mitochondrial activity have been experimentally shown to be effective in both diseases. Low carb diet, lipoic acid, and/or methylene blue could then appear promising in both sets of these clinically diverse diseases.

Core-crosslinked nanomicelles based on crosslinkable prodrug and surfactants for reduction responsive delivery of camptothecin and improved anticancer efficacy

As an important DNA topoisomerase I inhibitor in oncotherapy, camptothecin (CPT) with traditional formulation only shows a limited clinical application mainly because of its poor solubility. In this study, a novel redox responsive nanoscaled delivery system was developed to overcome the inherent defect of CPT. Firstly, a CPT prodrug (CPT-LA) and two crosslinkable surfactants (SO-LA and MPEG-LA) was synthesized, all of which contained the same lipoic acid (LA) structure. In the preparation, highly core-crosslinked structure was formed by adding a thiol crosslinker, which can induce LA ring opening polymerization and disulfide crosslinking. The resulting CPT-LA core-crosslinked nanomicelles (CPT-LA CNM) were formulated with a highly crosslinked core and a PEG hydrophilic shell. Dynamic light scattering (DLS) characterization indicated that CPT-LA CNM possessed a narrow size distribution (184.6 ± 3.6 nm) and negatively charged zeta potential (-3.5 ± 1.2 mV). The storage and physiological stabilities showed that the size distribution of CPT-LA CNM was relatively stable in both conditions which were neutral PBS at 4 °C (1 week period) and PBS containing 10% serum at 37 °C (24 h period). Moreover, the effective CPT release behavior of CPT-LA CNM was confirmed in the reducing circumstances containing dithiothreitol (DTT). Under confocal laser scanning microscopy (CLSM), CPT-LA CNM demonstrated a rapid cellular uptake behavior against cancer cells when compared to CPT suspension. Finally, the enhanced anticancer efficacy of CPT-LA CNM was also detected by in vitro cytotoxicity and cell apoptosis assay. In summary, the core-crosslinked CPT-LA CNM could be a promising CPT delivery system because of high stability, effectively controlled release as well as improved anticancer activity.

Novel α-Lipoic Acid/3-n-Butylphthalide Conjugate Enhances Protective Effects against Oxidative Stress and 6-OHDA Induced Neuronal Damage

Neurodegenerative diseases are irreversible conditions that result in progressive degeneration and death of nerve cells. Although the underlying mechanisms may vary, oxidative stress is considered to be one of the major causes of neuronal loss. Importantly, there are still no comprehensive treatments to completely cure these diseases. Therefore, protecting neurons from oxidative damage may be the most effective therapeutic strategy. Here we report a neuroprotective effects of a novel hybrid compound (dlx-23), obtained by conjugating α-lipoic acid (ALA), a natural antioxidant agent, and 3-n-butylphthalide (NBP), a clinical anti-ischemic drug. Dlx-23 protected against neuronal death induced by both H₂O₂ induced oxidative stress in Cath.-a-differentiated (CAD) cells and 6-OHDA, a toxin model of Parkinson's disease (PD) in SH-SY5Y cells. These activities proved to be more potent than the parent compound (ALA) alone. Dlx-23 scavenged free radicals, increased glutathione levels, and prevented mitochondria damage. In addition, live imaging of primary cortical neurons demonstrated that dlx-23 protected against neuronal growth cone damage induced by H₂O₂. Taken together these results suggest that dlx-23 has substantial potential to be further developed into a novel neuroprotective agent against oxidative damage and toxin induced neurodegeneration.

Lipoic acid alleviates schistosomiasis-induced liver fibrosis by upregulating Drp1 phosphorylation

Lipoic acid (LA) has been shown to possess protective effects against liver fibrosis mainly by induction of apoptosis of activated hepatic stellate cells, but the mechanism of LA activity in liver fibrosis has yet to be completely explained. LA occurs naturally in mitochondria as a coenzyme. In this study, we used mice with schistosomiasis-induced liver fibrosis and mouse hepatocarcinoma cell line 1C1C7 as models to investigate the mitochondrial mechanism of LA treatment for liver fibrosis. Western blot, real-time PCR and oxygen consumption rate (OCR) test were used. In the livers of mice with liver fibrosis, the mRNA levels of LA synthetic pathway enzymes, including MCAT, OXSM, MECR, and LIAS, were significantly reduced. Livers of mice with liver fibrosis showed degenerative signs, such as mitochondrial edema, a reduced mitochondrial crest and matrix density, or vacuolation; the activities of mitochondrial complexes I, II, IV, and V were also decreased in these livers. The expression of phosphorylation Drp1 (p-Drp1) was decreased in the livers of mice with liver fibrosis, indicating increased mitochondrial fission activity, whereas OPA1 and MFN1 expression was reduced, denoting decreased activity of mitochondrial fusion. To understand the mitochondrial mechanism of LA treatment for liver fibrosis, p-Drp1, OPA1, and MFN1 expression were detected at the protein level in mouse hepatocarcinoma cell line 1C1C7 stimulated by LA. OPA1 and MFN1 were not significantly altered, but p-Drp1 was significantly increased. The results suggest that LA may alleviate liver fibrosis through upregulating p-Drp1. This study provides a new insight into the mechanism of the protective effect of LA against schistosomiasis-induced liver fibrosis, which demonstrates that LA is required for the maintenance of mitochondrial function by upregulating p-Drp1 expression to inhibit mitochondrial fission.

Solanum lycopersicum (tomato) possesses mitochondrial and plastidial lipoyl synthases capable of increasing lipoylation levels when expressed in bacteria

Lipoic acid (LA) and its reduced form (dihydrolipoic acid, DHLA) have unique antioxidant properties among such molecules. Moreover, after a process termed lipoylation, LA is an essential prosthetic group covalently-attached to several key multi-subunit enzymatic complexes involved in primary metabolism, including E2 subunits of pyruvate dehydrogenase (PDH). The metabolic pathway of lipoylation has been extensively studied in Escherichia coli and Arabidopsis thaliana in which protein modification occurs via two routes: de novo synthesis and salvage. Common to both pathways, lipoyl synthase (LIP1 in plants, LipA in bacteria, EC 2.8.1.8) inserts sulphur atoms into the molecule in a final, activating step. However, despite the detection of LA and DHLA in other plant species, including tomato (Solanum lycopersicum), no plant LIP1s have been characterised to date from species other than Arabidopsis. In this work, we present the identification and characterisation of two LIPs from tomato, SlLIP1 and SlLIP1p. Consistent with in silico data, both are widely-expressed, particularly in reproductive organs. In line with bioinformatic predictions, we determine that yellow fluorescent protein tagged versions of SlLIP1 and SlLIP1p are mitochondrially- and plastidially-localised, respectively. Both possess the molecular hallmarks and domains of well-characterised bacterial LipAs. When heterologously-expressed in an E. coli lipA mutant, both are capable of complementing specific growth phenotypes and increasing lipoylation levels of E2 subunits of PDH in vivo, demonstrating that they do indeed function as lipoyl synthases.

Simultaneous nanoencapsulation of lipoic acid and resveratrol with improved antioxidant properties for the skin

Cutaneous aging is intimately related to redox imbalance, which is mainly caused by ultraviolet radiation exposure. The aim of the present investigation was to develop lipid-core nanocapsules for the co-nanoencapsulation of resveratrol and lipoic acid aiming to improve the chemical stability and photostability of the compounds, as well as their antioxidant properties. Lipid-core nanocapsules were developed and characterized according to their mean size, size distribution, zeta potential, pH value, drug content, encapsulation efficiency, release profile, stability under storage, photostability and skin permeation profile. In vitro antioxidant activity was analyzed by lipid peroxidation method and the in vitro cytotoxicity by MTT assay and cellular count, using BALB/c-3T3 fibroblasts. It was possible to co-nanoencapsulate resveratrol and lipoic acid into particles of average diameter close to 200 nm, low polydispersity index and encapsulation efficiencies around 90 %. Nanoencapsulation increased the substances stability under storage and photostability under UVA light exposure, besides controlling substances release. The actives were able to permeate a skin model membrane when nanoencapsulated, with a faster permeation of lipoic acid. The antioxidant activity was potentiated by the co-nanoencapsulation of resveratrol and lipoic acid, without signs of cytotoxicity to fibroblasts. Therefore, the co-nanoencapsulation of resveratrol and lipoic acid is promising for application in topical formulations aiming antioxidant effects.

Expanding the phenotype of mitochondrial disease: Novel pathogenic variant in ISCA1 leading to instability of the iron-sulfur cluster in the protein

We report a patient carrying a novel pathogenic variant p.(Tyr101Cys) in ISCA1 leading to MMDS type 5. He initially presented a psychomotor regression with loss of gait and language skills and a tetrapyramidal spastic syndrome. Biochemical analysis of patient fibroblasts revealed impaired lipoic acid synthesis and decreased activities of complex I and II of respiratory chain. While ISCA1 is involved in the mitochondrial machinery for iron-sulfur cluster biogenesis, these dysfunctions are secondary to impaired maturation of mitochondrial proteins containing the [4Fe-4S] clusters. Expression and purification of the human ISCA1 showed a decreased stability of the [2Fe-2S] cluster in the mutated protein.

Overexpression of endogenous lipoic acid synthase attenuates pulmonary fibrosis induced by crystalline silica in mice

Oxidative stress and inflammatory processes are proposed to mediate the development of silicosis. However, antioxidant therapy has not produced consistent results during the treatment of silicosis. α-Lipoic acid synthesized by lipoic acid synthase is a powerful anti-oxidant and helps protect mitochondria. Thus far, the effect of endogenous α-Lipoic acid on silicosis has not been elucidated yet. We established an experimental model of silicosis with wildtype and Lias^H/H mice, a new antioxidant mouse model which has overexpressed Lias gene (∼150 %) relative to its wild type counterpart. We systemically examined main pathological changes of pulmonary fibrosis, and explored α-lipoic acid effects on oxidative stress, inflammatory and pulmonary fibrosis biomarkers in silica-instillated mice. In Lias^H/H mice over-expression of lipoic acid alleviated the severity of major pathological alterations in the early stage of pulmonary fibrosis induced by silica compared with wild type mice. Silica significantly increased oxidative stress in both wild type and Lias^H/H mice. The antioxidant defense was strengthen including increased NRF2 and LIAS production in Lias^H/H mice. Relieved oxidative stress resulted in decreased inflammatory response and secretion of chemokines. Lias^H/H mice reduced chronic inflammatory response and inhibition of NF-κB activity after silica instillation. The Lias^H/H mouse model overexpression of lipoic acid synthase gene retarded the development of silica-induced pulmonary fibrosis. Strengthen antioxidant defense by increased lipoic acid synthase is a potential strategy for protection against silica-induced pulmonary fibrosis.