Pharmacokinetic study of lipoic acid in multiple sclerosis: comparing mice and human pharmacokinetic parameters

Antistress and Antiaging Potentials of Alpha-Lipoic Acid: Insights from Cell Culture-Based Experiments

Chronic stress has been linked to a large number of pathologies, including cancer, premature aging, and neurodegenerative diseases. The accumulation of molecular waste resulting from oxidative and heavy metal-induced stress has been ascribed as a major factor contributing to these diseases. With this in mind, we started by screening 13 small molecules to determine their antistress potential in heavy metal stress-exposed C6 glioblastoma and found that alpha-lipoic acid (ALA) (a natural antioxidant abundantly present in yeast, spinach, broccoli, and meat) was the most effective candidate. We then conducted molecular analyses to validate its mechanism of action. Dose-dependent toxicity assays of cells treated with two ALA enantiomers, R-ALA and S-ALA, showed that they are nontoxic and can be tolerated at relatively high doses. Cells exposed to heavy metal, heat, and oxidative stress showed better recovery when cultured in R-ALA-/S-ALA-supplemented medium, supported by reduction of reactive oxygen species (ROS), aggregated proteins, and mitochondrial and deoxyribonucleic acid (DNA) damage. Molecular analyses revealed protection against stress-induced apoptosis and induction of autophagy in R-ALA- and S-ALA-treated C6/U2OS cells. Consistent with these findings, normal human fibroblasts showed lifespan extension. Taken together, this study demonstrates that lipoic acid has antiaging and antistress potential and warrants further attention in laboratory and clinical studies.

Nature's Toolbox for Alzheimer's Disease: A Review on the Potential of Natural Products as Alzheimer's Disease Drugs

Numerous clinical trials involving natural products have been conducted to observe cognitive performances and biomarkers in Alzheimer's Disease (AD) patients. However, to date, no natural-based drugs have been approved by the FDA as treatments for AD. In this review, natural product-based compounds that were tested in clinical trials from 2011 to 2023, registered at www.clinicaltrials.gov were reviewed. Thirteen compounds, encompassing 7 different mechanisms of action were covered. Several observations were deduced, which are: i) several compounds showed cognitive improvement, but these improvements may not extend to AD, ii) compounds that are endogenous to the human body showed better outcomes, and iii) Docosahexaenoic acid (DHA) and cerebrolysin had the most potential as AD drugs among the 13 compounds. Based on the current findings, natural products may be more suitable as a supplement than AD drugs in most cases. However, the studies covered here were conducted in a relatively short amount of time, where compounds acting on AD pathways may take time to show any effect. Given the diverse pathways that these natural products are involved in, they may potentially produce synergistic effects that would be beneficial in treating AD. Additionally, natural products benefit from both physicochemical properties being in more favorable ranges and active transport playing a more significant role than it does for synthetic compounds.

Nephro-protective effects of alpha-lipoic acid in type I diabetes

Type 1 diabetes (T1D) is an insulin-dependent autoimmune condition. Short chain fatty acids (SCFAs) are volatile fatty acids with 1-6 carbon atoms that influence glucose storage in the body and can reduce appetite, potentially decreasing T1D risk. Alpha-lipoic acid (α-LA), a type of SCFA, has previously been used to treat diabetic neuropathy and inflammation due to its antioxidant properties. This study aims to assess α-LA's protective effects against T1D and associated kidney damage in rats induced with streptozotocin. Diabetic rats were treated with α-LA orally for 15 days, resulting in improved blood glucose (56% decrease) and kidney function markers like blood urea nitrogen, creatinine and uric acid. α-LA also showed significant antioxidant effects by decreasing LPO as well as improving activities of antioxidant enzymes like superoxide dismutase, catalase and glutathione-S transferase and alleviated kidney damage caused by diabetes. Docking experiments suggest that α-LA may regulate diabetes-related changes at the epigenetic level through interactions with the SIRT1 protein, indicating its potential as a target for future antidiabetic drug development.

Antioxidant effects of α-lipoic acid against epididymal oxidative damage in adult offspring rats exposed to maternal hypothyroidism stress

It is well known that the epididymis promotes post-testicular sperm maturation events. However, its malfunction during congenital hypothyroidism is relatively less understood as compared to the testis. The present study evaluated the probable effect of α-lipoic acid on epididymal oxidative stress parameters in rats exposed to antithyroid drug, carbimazole during fetal period. Time-mated pregnant rats in unexposed and carbimazole (1.35 mg/Kg body weight exposed were allowed to deliver pups and weaned. At postnatal day 100, the F1 male pups were assessed for epididymal endpoints. Among the epididymal regions, significant elevation of lipid peroxidation levels, superoxide anion, and hydrogen peroxide contents with a concomitant reduction in the activity levels of superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase and reduced glutathione levels were observed in cauda epididymis of carbimazole exposed rats over controls. Significant elevation in sperm DNA fragmentation (comet assay), accelerated cauda epididymal sperm transit time and reduction in epididymal sialic acid content was observed in carbimazole exposed rats. RT-qPCR studies revealed that embryonic exposure to carbimazole resulted in down regulation of androgen receptor, nuclear factor eryrthoid 2 like 2, 5α-reducatse 1 mRNA levels, while up regulation of caspase 3 mRNA was observed in epididymal regions of rats. In addition, fetal exposure to carbimazole resulted in disorganization of cauda epididymal architecture in rats. Conversely, supplementation of α-lipoic acid (70 mg/Kg bodyweight) during PND 3 to 14 restored epididymal functions in carbimazole exposed rats and the ameliorative effects of lipoic acid could be attributed to its antioxidant and steroidogenic effects.

The Effects of Antioxidant Nutraceuticals on Cellular Sulfur Metabolism and Signaling

Significance: Nutraceuticals are ingested for health benefits, in addition to their general nutritional value. These dietary supplements have become increasingly popular since the late 20th century and they are a rapidly expanding global industry approaching a half-trillion U.S. dollars annually. Many nutraceuticals are promulgated as potent antioxidants. Recent Advances: Experimental support for the efficacy of nutraceuticals has lagged behind anecdotal exuberance. However, accumulating epidemiological evidence and recent, well-controlled clinical trials are beginning to support earlier animal and in vitro studies. Although still somewhat limited, encouraging results have been suggested in essentially all organ systems and against a wide range of pathophysiological conditions. Critical Issues: Health benefits of "antioxidant" nutraceuticals are largely attributed to their ability to scavenge oxidants. This has been criticized based on several factors, including limited bioavailability, short tissue retention time, and the preponderance of endogenous antioxidants. Recent attention has turned to nutraceutical activation of downstream antioxidant systems, especially the Keap1/Nrf2 (Kelch like ECH associated protein 1/nuclear factor erythroid 2-related factor 2) axis. The question now becomes, how do nutraceuticals activate this axis? Future Directions: Reactive sulfur species (RSS), including hydrogen sulfide (H2S) and its metabolites, are potent activators of the Keap1/Nrf2 axis and avid scavengers of reactive oxygen species. Evidence is beginning to accumulate that a variety of nutraceuticals increase cellular RSS by directly providing RSS in the diet, or through a number of catalytic mechanisms that increase endogenous RSS production. We propose that nutraceutical-specific targeting of RSS metabolism will lead to the design and development of even more efficacious antioxidant therapeutic strategies. Antioxid. Redox Signal. 38, 68-94.

A novel approach to alpha-lipoic acid therapy in the treatment of diabetic peripheral neuropathy

Diabetic peripheral neuropathy (DPN) is a heterogenic disorder prevalent amongst patients suffering from diabetes mellitus (DM), with symptoms comprising neuropathic pain, paresthesia, and numbness in distal lower limbs. Alpha-lipoic acid (ALA) is proposed as a pathogenesis-oriented treatment option, targeting underlying causes of neural lesions such as hyperglycemia, metabolic and microvascular dysfunctions, and cellular oxidative stress. We performed a comprehensive review of controlled clinical trials demonstrating the clinical usefulness of ALA in the treatment of DPN, published in the last 5 years to determine the benefits of ALA monotherapy and combined treatments with other known antioxidants. We also investigated the differential efficacy of oral versus intravenous ALA administration. Clinical trials show the efficacy of ALA treatment, attributed to its anti-inflammatory, anti-hyperglycemic, and antioxidant properties, as well as its function in the endothelial activation and lipid metabolism parameters. ALA supplementation is associated with amelioration in nerve conduction velocity scores, clinically significant reduction of reported neuropathic pain, burning and paresthesia, as well as a decrease in serum triglycerides, improved insulin sensitivity, and quality of life.

Estimation of pharmacokinetic parameters of alpha-lipoic acid in the chicks model

Background and objective: Alpha-lipoic acid is a drug used to treat diabetic neuropathy, and it has other uses as a dietary supplement. The target of the study was to investigate the concentration of therapeutic doses of Alpha-lipoic acid in the blood plasma of broiler chicks to define the pharmacokinetic parameters. Methods: A randomized controlled study was performed on thirty-five healthy broiler chicks of seven days old, chicks were injected into the peritoneum with a single dose of analgesic ED50 80mg /kg b.wt, following injection of the drug, blood samples were collected at 0.25, 0.5, 1, 2, 4, 24 h (five chicks per time) from the jugular vein. Then the  blood plasma was obtained, the concentrations of Alpha-lipoic acid  in blood  plasma samples were determined utilizing UV Spectrometric Method, the pharmacokinetic parameters were determined by the PKSolver program. Time versus concentration curve for Alpha-lipoic acid was obtained from the program. The pharmacokinetic parameters were determined with non-compartmental models. Results: The concentration of Alpha-lipoic acid  in the blood plasma of chicks injected with Alpha lipoic at a dose (80 mg/kg) were 134.6±7.17, 178.5±4.10 ,192.4±7.83  ,158.5±11.05  ,147.1±10.16, 122.8±7.09  µg/ml at times   0.25, 0.5, 1, 2, 4, and 24 hours respectively. The maximum plasma concentration was 192.4µg/ml during a period of 1 hour of injection. The terminal elimination half-life was 65hours, the terminal phase elimination rate constant was 0.011 h-1 , the mean residence time was 94h, and the area under the curve from time 0 to infinity was 14960 µg.h/ml. Conclusions:  Our study concluded that the peak of the analgesic effect of alpha lipoic acid was one hour after treatment; furthermore, it is characterized by a long elimination half-life and a poor clearance from the chick’s body, which is reflected in the long effects of its pharmacological properties

Alpha-Lipoic Acid Attenuates MPTP/MPP+-Induced Neurotoxicity: Roles of SIRT1-Dependent PGC-1α Signaling Pathways

Accumulated oxidative damage plays key roles in the pathogenesis of Parkinson's disease (PD). Silent mating type information regulation 2 homolog 1 (SIRT1), a class III histone deacetylase, can directly activate peroxisome proliferator-activated receptor-c coactivator-1α (PGC-1α) and attenuate oxidative stress. Alpha-lipoic acid (ALA) is a natural antioxidant that has been demonstrated to protect PC12 cells against 1-methyl-4-phenylpyridinium (MPP⁺). However, the underlying mechanisms related to changes in cell signaling cascades are not fully understood. In the present study, the neuroprotective effect of ALA and the potential role of ALA in the SIRT1 pathway was investigated in vitro and in a mouse model of PD. A Cell Counting Kit-8 (CCK-8) assay was performed to detect the SY5Y-SH cell viability. Immunohistochemistry, quantitative real-time polymerase chain reaction and western blot assays were used to evaluate the expression of tyrosine hydroxylase (TH), SIRT1, and PGC-1α in vivo and in vitro. Intracellular reactive oxygen species (ROS) production and tissue SOD and MDA were detected by the corresponding assay kits. The results showed that ALA notably prevented oxidative stress and neurotoxicity in vivo and in vitro against 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP)/MPP⁺. Furthermore, ALA significantly increased the expression of SIRT1 and PGC-1α in vivo and in vitro in MPTP/MPP⁺-induced models, which was reversed by the SIRT1 inhibitor EX527. These results suggested that ALA prevented oxidative stress and that neurotoxicity was involved in the upregulation of SIRT1 and PGC-1α in PD mice.

Role of lipoic acid in multiple sclerosis

Lipoic acid (LA) is an endogenous antioxidant that exists widely in nature. Supplementation with LA is a promising approach to improve the outcomes of patients with multiple sclerosis (MS). This systematic review aimed to provide a comprehensive overview of both in vitro and in vivo studies describing the pharmacokinetics, efficacy, safety, and mechanism of LA in MS‐related experiments and clinical trials. A total of 516 records were identified by searching five databases, including PubMed, Web of Science, Embase, Scopus, and Cochrane Library. Overall, we included 20 studies reporting LA effects in cell and mouse models of MS and 12 studies reporting LA effects in patients with MS. Briefly, cell experiments revealed that LA protected neurons by inhibiting the expression of inflammatory mediators and activities of immune cells. Experimental autoimmune encephalomyelitis mouse experiments demonstrated that LA consistently reduced the number of infiltrating immune cells in the central nervous system and decreased the clinical disability scores. Patients with MS showed relatively stable Expanded Disability Status Scale scores and better walking performance with few adverse events after the oral administration of LA. Notably, heterogeneity of this evidence existed among modeling methods, LA usage, MS stage, and trial duration. In conclusion, this review provides evidence for the anti‐inflammatory and antioxidative effects of LA in both in vitro and in vivo experiments; therefore, patients with MS may benefit from LA administration. Whether LA can be a routine supplementary therapy warrants further study.

PHARMACOKINETICS OF SUBCUTANEOUS ALPHA LIPOIC ACID, A PROPOSED THERAPEUTIC AID FOR DOMOIC ACID INTOXICATION IN CALIFORNIA SEA LIONS (ZALOPHUS CALIFORNIANUS)

Domoic acid (DA) is a potent neurotoxin produced by certain marine algae that can cause neurologic and cardiac dysfunction by activating glutamate receptors. Glutamate receptor overexcitation results in continuous cellular activation, oxidative damage, and cell death. DA toxicosis causes disorientation and seizures, and antiseizure medications are the primary treatment. Alpha lipoic acid (ALA), a powerful antioxidant and glutathione precursor widely used in humans and dogs, can cross the blood-brain barrier to provide antioxidant availability to brain tissue. Hundreds of stranded California sea lions (CSL; Zalophus californianus) are diagnosed annually with DA toxicosis and thus are an appropriate animal in which to establish ALA dosing recommendations for treatment. The objective of this study was to determine the population pharmacokinetics of a single 10- or 20-mg/kg dose of ALA administered subcutaneously into the interscapular region to healthy rehabilitated CSL. Blood was collected at two time points between 15 min and 24 h after administration. Serum ALA concentrations were measured by liquid chromatography-mass spectrometry, and parameters were evaluated using a nonlinear mixed effects model. ALA was rapidly absorbed for each dose, peaking within 20 to 30 minutes, and t_1/2 of 40 and 32 min (10 and 20 mg/kg, respectively), followed by an initial steep distribution phase and prolonged elimination phase. Peak concentration (C_MAX) was 1,243 ng/ml (10-mg/ml dose) and 5,010 ng/ml (20-mg/ml dose). Serum from 13 CSLd with DA toxicosis treated with 10 mg/kg ALA for 1 to 9 d had measurable levels, and ALA was also measurable in cerebrospinal fluid from two treated CSLs. Therapeutic effects are noted with a C_MAX of 4,000 to 5,000 ng/ml in humans; thus in CSLs, 20 mg/kg administered subcutaneously once daily may be sufficient to achieve a therapeutic level in this species. Determination of efficacy and optimal dosing interval and duration require additional investigation.

Effects of Lipoic Acid on Ischemia-Reperfusion Injury

Ischemia-reperfusion (I/R) injury often occurred in some pathologies and surgeries. I/R injury not only harmed to physiological functions of corresponding organ and tissue but also induced multiple tissue or organ dysfunctions (even these in distant locations). Although the reperfusion of blood attenuated I/R injury to a certain degree, the risk of secondary damages was difficult to be controlled and it even caused failures of these tissues and organs. Lipoic acid (LA), as an endogenous active substance and a functional agent in food, owns better safety and effects in our body (e.g., enhancing antioxidant activity, improving cognition and dementia, controlling weight, and preventing multiple sclerosis, diabetes complication, and cancer). The literature searching was conducted in PubMed, Embase, Cochrane Library, Web of Science, and SCOPUS from inception to 20 May 2021. It had showed that endogenous LA was exhausted in the process of I/R, which further aggravated I/R injury. Thus, supplements with LA timely (especially pretreatments) may be the prospective way to prevent I/R injury. Recently, studies had demonstrated that LA supplements significantly attenuated I/R injuries of many organs, though clinic investigations were short at present. Hence, it was urgent to summarize these progresses about the effects of LA on different I/R organs as well as the potential mechanisms, which would enlighten further investigations and prepare for clinic applications in the future.

Failed, Interrupted, or Inconclusive Trials on Neuroprotective and Neuroregenerative Treatment Strategies in Multiple Sclerosis: Update 2015-2020

In the recent past, a plethora of drugs have been approved for the treatment of multiple sclerosis (MS). These therapeutics are mainly confined to immunomodulatory or immunosuppressive strategies but do not sufficiently address remyelination and neuroprotection. However, several neuroregenerative agents have shown potential in pre-clinical research and entered Phase I to III clinical trials. Although none of these compounds have yet proceeded to approval, understanding the causes of failure can broaden our knowledge about neuroprotection and neuroregeneration in MS. Moreover, most of the investigated approaches are characterised by consistent mechanisms of action and proved convincing efficacy in animal studies. Therefore, learning from their failure will help us to enforce the translation of findings acquired in pre-clinical studies into clinical application. Here, we summarise trials on MS treatment published since 2015 that have either failed or were interrupted due to a lack of efficacy, adverse events, or for other reasons. We further outline the rationale underlying these drugs and analyse the background of failure to gather new insights into MS pathophysiology and optimise future study designs. For conciseness, this review focuses on agents promoting remyelination and medications with primarily neuroprotective properties or unconventional approaches. Failed clinical trials that pursue immunomodulation are presented in a separate article.

Alpha-lipoic acid supplementation increases the efficacy of exercise- and diet-induced obesity treatment and induces immunometabolic changes in female mice and women

The decrease in the regulatory T cells (Tregs) population is highly involved in adipose tissue inflammation and insulin resistance in obesity. Tregs depend on fatty acids via β-oxidation for immunosuppressive function adapting their antioxidant systems to allow survival to oxidative stress. In this study, we have hypothesized that a dietary supplementation with alpha-lipoic acid (ALA), a powerful antioxidant, would improve immunometabolism when added to the classical strategy of obesity treatment. First, we showed by in vitro experiments that ALA favors the polarization of mice CD4 + T cells toward Tregs. Next, we have carried out a translational study where female obese mice and women were supplemented with ALA or vehicle/placebo (mice: 2.5 gALA /kgfood ; 6 weeks; women: 600 mgALA /day, 8 weeks) while following a protocol including regular exercise and a change in diet. Fatty acid oxidation potential and activity of nuclear erythroid-related factor 2 (NRF2) of mouse secondary lymphoid tissues were improved by ALA supplementation. ALA reduced visceral adipose tissue (VAT) mass and preserved Tregs in VAT in mice. In women, ALA supplementation induced significant metabolic changes of circulating CD4 + T cells including increased oxidative capacity and fatty acid oxidation, ameliorated their redox status, and improved the reduction of visceral fat mass. While appropriate biological markers are still required to be used in clinics to judge the effectiveness of long-term obesity treatment, further studies in female mice and women are needed to determine whether these immunometabolic changes would reduce VAT mass-associated risk for secondary health issues arising from obesity.

Development of a novel in vitro assay to screen for neuroprotective drugs against iatrogenic neurite shortening

This work tries to help overcome the lack of relevant translational screening assays, as a limitation for the identification of novel analgesics for neuropathic pain. Hyperexcitability and neurite shortening are common adverse effects of antiviral and antitumor drugs, leading to neuropathic pain. Now, as seen in the drug screening that we developed here, a high-content microscopy-based assay with immortalized dorsal root ganglia (DRG) neurons (differentiated F11 cells) allowed to identify drugs able to protect against the iatrogenic neurite shortening induced by the antitumor drug vincristine and the antiviral drug rilpivirine. We observed that vincristine and rilpivirine induced a significant reduction in the neurite length, which was reverted by α-lipoic acid. We had also evidenced protective effects of pregabalin and melatonin, acting through the α2δ-2 subunit of the voltage-dependent calcium channels and the MT1 receptor, respectively. Additionally, two hits originated from a previous primary screening aimed to detect inhibitors of hyperexcitability to inflammatory mediators in DRG neurons (nitrendipine and felodipine) also prevented neurite shortening in our model. In summary, in this work we developed a novel secondary assay for identifying hits with neuroprotective effect against iatrogenic neurite shortening, consistent with the anti-hyperexcitability action previously tested: highlighting nitrendipine and felodipine against iatrogenic damage in DRG neurons.

Orally Administered Alpha Lipoic Acid as a Treatment for Geographic Atrophy: A Randomized Clinical Trial

PURPOSE

Alpha lipoic acid (ALA) is a nutraceutical and potent antioxidant that has shown efficacy in the retina light damage mouse model and in humans for multiple sclerosis. Our objective was to evaluate the efficacy and safety of oral ALA for the treatment of geographic atrophy (GA).

DESIGN

Randomized, controlled, double-masked, multicenter phase 2 clinical trial of ALA versus placebo.

PARTICIPANTS

Participants with unilateral or bilateral GA from age-related macular degeneration.

METHODS

Participants were randomized to 1200 mg daily of ALA or placebo. Fundus autofluorescence, fundus color photography, and spectral-domain OCT were conducted and best-corrected visual acuity (BCVA) was obtained at baseline and every 6 months through month 18.

MAIN OUTCOME MEASURES

Annual rate of change over 18 months in square root-transformed area of GA in study eyes as measured on fundus autofluorescence. Secondary outcomes included the number of adverse events (AEs), change in BCVA, and annual rate of change in area of GA measured on color photographs.

RESULTS

Fifty-three participants (mean age, 80 years) were randomized (April 2016-August 2017). Twenty-seven participants (37 eyes) were in the placebo group, and 26 participants (36 eyes) were in the ALA group. Unadjusted mean (standard error) annual change in GA area was 0.28 (0.02) mm and 0.31 (0.02) mm for the placebo and ALA groups, respectively (difference, 0.04 mm; 95% confidence interval [CI], -0.03 to 0.11 mm; P = 0.30). Adjusting for baseline GA area, number of GA lesions, and presence of subfoveal GA, the mean annual change in GA area was 0.27 (0.04) mm and 0.32 (0.05) mm for the placebo and ALA groups, respectively (difference, 0.05 mm; 95% CI, -0.02 to 0.12 mm; P = 0.14). At 18 months, the percent of eyes losing 15 letters or more of BCVA was 22% (8 of 36) and 14% (5 of 36) in the placebo and ALA groups, respectively (P = 0.54). No difference was found in the percentage of participants with nonserious AEs (P = 0.96) or serious AEs (P = 0.28) between the placebo and ALA groups.

CONCLUSIONS

Results do not support ALA having beneficial effects on GA or BCVA. This trial design may be useful for other GA repurposing drug trials.

Are the beneficial effects of 'antioxidant' lipoic acid mediated through metabolism of reactive sulfur species?

The health benefits of lipoic acid (LA) are generally attributed to mitigating the harmful effects of reactive oxygen species (ROS). ROS are chemically similar to reactive sulfur species (RSS) and signal through identical mechanisms. Here we examined the effects of LA on RSS in HEK293 cells using H₂S and polysulfide (PS) specific fluorophores, AzMC and SSP4. We show that LA concentration-dependently increased both H₂S and PS. Physioxia (5% O₂) augmented the effects of LA on H₂S production but decreased PS production. Thiosulfate, a known substrate for reduced LA, and an intermediate in the catabolism of H₂S enhanced the effects of LA on H₂S and PS production. Inhibiting peroxiredoxins with conoidin A and gluraredoxins with tiopronin augmented the effects of LA on PS and H₂S, respectively while decreasing glutathione with buthionine-sulfoximine (BSO) or diethyl maleate (DEM) decreased the stimulatory effect of LA on H₂S production but augmented LA's effect on PS. Aminooxyacetate (AOA) and propargylglycine (PPG), inhibitors of H₂S production from cysteine partially inhibited LA augmentation of H₂S production and further decreased the LA effect when applied concurrently with BSO and DEM. The selective and cell-permeable H₂S scavenger, SS20, inhibited the effects of LA on cellular H₂S. Estimates of single-cell H₂S production suggest that 0.1-0.2% of O₂ consumption is used to metabolize H₂S and these requirements may increase to 1-2% with 1 mM LA. Collectively, these results suggest that LA rescues H₂S from irreversible oxidation and that the effects of LA on RSS directly confer antioxidant, anti-inflammatory and cytoprotective responses. They also suggest that TS may be an effective supplement to increase the efficacy of LA in clinical settings.

Lipoic Acid and Other Antioxidants as Therapies for Multiple Sclerosis

Oxidative stress (OS), when oxidative forces outweigh endogenous and nutritional antioxidant defenses, contributes to the pathophysiology of multiple sclerosis (MS). Evidence of OS is found during acute relapses, in active inflammatory lesions, and in chronic, longstanding plaques. OS results in both ongoing inflammation and neurodegeneration. Antioxidant therapies are a rational strategy for people with MS with all phenotypes and disease durations. PURPOSE OF REVIEW: To understand the function of OS in health and disease, to examine the contributions of OS to MS pathophysiology, and to review current evidence for the effects of selected antioxidant therapies in people with MS (PwMS) with a focus on lipoic acid (LA). RECENT FINDINGS: Studies of antioxidant interventions in both animal and in vivo models result in reductions in serum markers of OS and increases in levels and activity of antioxidant enzymes. Antioxidant trials in PwMS, while generally underpowered, detect short-term improvements in markers of OS and antioxidant defenses, and to a lesser extent, in clinical symptoms (fatigue, depression). The best evidence to date is a 2-year trial of LA in secondary progressive MS which demonstrated a significant reduction of whole-brain atrophy and trend toward improvement in walking speed. Antioxidant therapy is a promising approach to treat MS across the spectrum and duration of disease. Rigorous and well-powered trials are needed to determine their therapeutic benefits.

Nutritional intervention as an essential part of multiple sclerosis treatment?

Multiple sclerosis (MS) is a chronic inflammatory and demyelinating disease of the central nervous system. In addition to the genetic, epigenetic and immunological components, various other factors, e.g. unhealthy dietary habits, play a role in the MS pathogenesis. Dietary intervention is a highly appealing approach, as it presents a simple and relatively low risk method to potentially improve outcomes in patients with brain disorders in order to achieve remission and improvement of clinical status, well-being and life expectancy of patients with MS. The importance of saturated fat intake restriction for the clinical status improvement of MS patients was pointed for the first time in 1950s. Recently, decreased risk of first clinical diagnosis of CNS demyelination associated with higher intake of omega-3 polyunsaturated fatty acids particularly originating from fish was reported. Only few clinical trials have been performed to address the question of the role of dietary intervention, such is e.g. low saturated fat diet in MS treatment. This review summarizes current knowledge about the effect of different dietary approaches (diets low in saturated fat and dietary supplements such as fish oil, lipoic acid, omega-3 polyunsaturated fatty acids, seeds oils, high fiber diet, vitamin D, etc.) on neurological signs, patient's well-being, physical and inflammatory status. So far the results are not conclusive, therefore much more research is needed to confirm and to understand the effectiveness of these dietary interventions in the long term and well defined studies.

Early alpha-lipoic acid therapy protects from degeneration of the inner retinal layers and vision loss in an experimental autoimmune encephalomyelitis-optic neuritis model

Background

In multiple sclerosis (MS), neurodegeneration is the main reason for chronic disability. Alpha-lipoic acid (LA) is a naturally occurring antioxidant which has recently been demonstrated to reduce the rate of brain atrophy in progressive MS. However, it remains uncertain if it is also beneficial in the early, more inflammatory-driven phases. As clinical studies are costly and time consuming, optic neuritis (ON) is often used for investigating neuroprotective or regenerative therapeutics. We aimed to investigate the prospect for success of a clinical ON trial using an experimental autoimmune encephalomyelitis-optic neuritis (EAE-ON) model with visual system readouts adaptable to a clinical ON trial.

Methods

Using an in vitro cell culture model for endogenous oxidative stress, we compared the neuroprotective capacity of racemic LA with the R/S-enantiomers and its reduced form. In vivo, we analyzed retinal neurodegeneration using optical coherence tomography (OCT) and the visual function by optokinetic response (OKR) in MOG_35–55-induced EAE-ON in C57BL/6J mice. Ganglion cell counts, inflammation, and demyelination were assessed by immunohistological staining of retinae and optic nerves.

Results

All forms of LA provided equal neuroprotective capacities in vitro. In EAE-ON, prophylactic LA therapy attenuated the clinical EAE score and prevented the thinning of the inner retinal layer while therapeutic treatment was not protective on visual outcomes.

Conclusions

A prophylactic LA treatment is necessary to protect from visual loss and retinal thinning in EAE-ON, suggesting that a clinical ON trial starting therapy after the onset of symptoms may not be successful.

Electronic supplementary material

The online version of this article (10.1186/s12974-018-1111-y) contains supplementary material, which is available to authorized users.

Lipoic Acid Stimulates cAMP Production in Healthy Control and Secondary Progressive MS Subjects

Lipoic acid (LA) exhibits antioxidant and anti-inflammatory properties; supplementation reduces disease severity and T lymphocyte migration into the central nervous system in a murine model of multiple sclerosis (MS), and administration in secondary progressive MS (SPMS) subjects reduces brain atrophy compared to placebo. The mechanism of action (MOA) of LA's efficacy in suppression of MS pathology is incompletely understood. LA stimulates production of the immunomodulator cyclic AMP (cAMP) in vitro. To determine whether cAMP could be involved in the MOA of LA in vivo, we performed a clinical trial to examine whether LA stimulates cAMP production in healthy control and MS subjects, and whether there are differences in the bioavailability of LA between groups. We administered 1200 mg of oral LA to healthy control, relapsing remitting MS (RRMS) and SPMS subjects, and measured plasma LA and cAMP levels in peripheral blood mononuclear cells (PBMCs). There were no significant differences between the groups in pharmacokinetic (PK) parameters. Healthy and SPMS subjects had increased cAMP at 2 and 4 h post-LA treatment compared to baseline, while RRMS subjects showed decreases in cAMP. Additionally, plasma concentrations of prostaglandin E2 (PGE₂, a known cAMP stimulator) were significantly lower in female RRMS subjects compared to female HC and SPMS subjects 4 h after LA ingestion. These data indicate that cAMP could be part of the MOA of LA in SPMS, and that there is a divergent response to LA in RRMS subjects that may have implications in the efficacy of immunomodulatory drugs. This clinical trial, "Defining the Anti-inflammatory Role of Lipoic Acid in Multiple Sclerosis," NCT00997438, is registered at https://clinicaltrials.gov/ct2/show/record/NCT00997438 .

Lipoic acid in secondary progressive MS: A randomized controlled pilot trial

Objective:

To determine whether lipoic acid (LA), an endogenously produced antioxidant, slowed the whole-brain atrophy rate and was safe in secondary progressive MS (SPMS).

Methods:

Patients with SPMS aged 40–70 years enrolled in a single center, 2-year, double-blind, randomized trial of daily oral 1,200 mg LA vs placebo. Primary outcome was change in annualized percent change brain volume (PCBV). Secondary outcomes were changes in rates of atrophy of segmented brain, spinal cord, and retinal substructures, disability, quality of life, and safety. Intention-to-treat analysis used linear mixed models.

Results:

Participation occurred between May 2, 2011, and August 14, 2015. Study arms of LA (n = 27) and placebo (n = 24) were matched with mean age of 58.5 (SD 5.9) years, 61% women, mean disease duration of 29.6 (SD 9.5) years, and median Expanded Disability Status Score of 6.0 (interquartile range 1.75). After 2 years, the annualized PCBV was significantly less in the LA arm compared with placebo (−0.21 [standard error of the coefficient estimate (SEE) 0.14] vs −0.65 [SEE 0.10], 95% confidence interval [CI] 0.157–0.727, p = 0.002). Improved Timed 25-Foot Walk was almost but not significantly better in the LA than in the control group (−0.535 [SEE 0.358] vs 0.137 [SEE 0.247], 95% CI −1.37 to 0.03, p = 0.06). Significantly more gastrointestinal upset and fewer falls occurred in LA patients. Unexpected renal failure (n = 1) and glomerulonephritis (n = 1) occurred in the LA cohort. Compliance, measured by pill counts, was 87%.

Conclusions:

LA demonstrated a 68% reduction in annualized PCBV and suggested a clinical benefit in SPMS while maintaining favorable safety, tolerability, and compliance over 2 years.

ClinicalTrials.gov identifier:

NCT01188811.

Classification of evidence:

This study provides Class I evidence that for patients with SPMS, LA reduces the rate of brain atrophy.

Tolerability in the elderly population of high-dose alpha lipoic acid: a potential antioxidant therapy for the eye

Purpose

Alpha lipoic acid (ALA) is an antioxidant and iron-chelating supplement that has potential benefits for geographic atrophy in dry age-related macular degeneration as well as other eye diseases. The purpose of this study was to determine the tolerability of ALA in the elderly population.

Patients and methods

Fifteen subjects, age ≥65 years, took sequential ALA doses of 600, 800, and 1,200 mg. Each dose was taken once daily with a meal for 5 days. After each dose was taken by the subjects for 5 days, the subjects were contacted by phone, a review of systems was performed, and they were asked if they thought they could tolerate taking that dose of ALA for an extended period of time.

Results

The 600 mg dose was well tolerated. At the 800 mg dose, one subject had an intolerable flushing sensation. At the 1,200 mg dose, two subjects had intolerable upper gastrointestinal side effects and one subject had an intolerable flushing sensation. Subjects taking gastrointestinal prophylaxis medications had no upper gastrointestinal side effects.

Conclusion

High-dose ALA is not completely tolerated by the elderly. These preliminary data suggest that gastrointestinal prophylaxis may improve tolerability. (ClinicalTrials.gov, NCT02613572).

Determination of lipoic acid in biological samples

α-Lipoic acid (LA) is a unique antioxidant that is not only effective in affording protection against oxidative stress but also plays an essential role in metabolic processes of all living organisms. Therefore, the determination of LA and its metabolites content is crucial for understanding their physiological and pathophysiological functions. Most of the recently developed methods for the detection and determination of LA and its metabolites in various biological samples have focused on sample preparation procedures involving but not limited to sampling, extraction and storage. The main goal of this review is to summarize and critically evaluate the current state of the art of analytical procedures applied to the determination of LA and related compounds in biological samples.

Anti-inflammatory nutritional intervention in patients with relapsing-remitting and primary-progressive multiple sclerosis: A pilot study

The aim of this work was to assess the influence of nutritional intervention on inflammatory status and wellness in people with multiple sclerosis. To this end, in a seven-month pilot study we investigated the effects of a calorie-restricted, semi-vegetarian diet and administration of vitamin D and other dietary supplements (fish oil, lipoic acid, omega-3 polyunsaturated fatty acids, resveratrol and multivitamin complex) in 33 patients with relapsing-remitting multiple sclerosis and 10 patients with primary-progressive multiple sclerosis. At 0/3/6 months, patients had neurological examination, filled questionnaires and underwent anthropometric measurements and biochemical analyses. Serum fatty acids and vitamin D levels were measured as markers of dietary compliance and nutritional efficacy of treatment, whereas serum gelatinase levels were analyzed as markers of inflammatory status. All patients had insufficient levels of vitamin D at baseline, but their values did not ameliorate following a weekly administration of 5000  IU, and rather decreased over time. Conversely, omega-3 polyunsaturated fatty acids increased already after three months, even under dietary restriction only. Co-treatment with interferon-beta in relapsing-remitting multiple sclerosis was irrelevant to vitamin D levels. After six months nutritional treatment, no significant changes in neurological signs were observed in any group. However, serum levels of the activated isoforms of gelatinase matrix metalloproteinase-9 decreased by 59% in primary-progressive multiple sclerosis and by 51% in relapsing-remitting multiple sclerosis patients under nutritional intervention, including dietary supplements. This study indicates that a healthy nutritional intervention is well accepted by people with multiple sclerosis and may ameliorate their physical and inflammatory status.

Over-the-counter anti-oxidant therapies for use in multiple sclerosis: A systematic review

BACKGROUND

Anti-oxidant compounds that are found in over-the-counter (OTC) supplements and foods are gaining interest as treatments for multiple sclerosis (MS). They are widely used by patients, sometimes without a clear evidence base.

OBJECTIVE

We conducted a systematic review of animal and clinical research to determine the evidence for the benefits of OTC anti-oxidants in MS.

METHODS

Using predefined criteria, we searched key databases. Two authors scrutinized all studies against inclusion/exclusion criteria, assessed study risk-of-bias and extracted results.

RESULTS

Of the 3507 titles, 145 met criteria and included compounds, α(alpha)-lipoic acid (ALA), anti-oxidant vitamins, Ginkgo biloba, quercetin, resveratrol and epigallocatechin-3-gallate (ECGC). The strongest evidence to support OTC anti-oxidants was for compounds EGCG and ALA in animal models; both consistently showed anti-inflammatory/anti-oxidant effects and reduced neurological impairment. Only vitamin E, Ginkgo biloba and ALA were examined for efficacy in pilot clinical trials with either conflicting evidence or evidence of no benefit.

CONCLUSION

OTC anti-oxidants EGCG and ALA show the most consistent benefit, however only in preclinical studies. There is no evidence that they alter MS relapses or progression. Future work should focus on testing more of these therapies for clinical efficacy before recommending them to MS patients.

A randomized placebo-controlled pilot trial of omega-3 fatty acids and alpha lipoic acid in Alzheimer's disease

Oxidative stress, inflammation, and increased cholesterol levels are all mechanisms that have been associated with Alzheimer's disease (AD) pathology. Several epidemiologic studies have reported a decreased risk of AD with fish consumption. This pilot study was designed to evaluate the effects of supplementation with omega-3 fatty acids alone (ω-3) or omega-3 plus alpha lipoic acid (ω-3 + LA) compared to placebo on oxidative stress biomarkers in AD. The primary outcome measure was peripheral F2-isoprostane levels (oxidative stress measure). Secondary outcome measures included performance on: Mini-Mental State Examination (MMSE), Activities of Daily Living/Instrumental Activities of Daily Living (ADL/IADL), and Alzheimer Disease Assessment Scale-cognitive subscale (ADAS-cog). Thirty-nine AD subjects were randomized to one of three groups: 1) placebo, 2) ω-3, or 3) ω-3 + LA for a treatment duration of 12 months. Eighty seven percent (34/39) of the subjects completed the 12-month intervention. There was no difference between groups at 12 months in peripheral F2-isoprostane levels (p = 0.83). The ω-3 + LA and ω-3 were not significantly different than the placebo group in ADAS-cog (p = 0.98, p = 0.86) and in ADL (p = 0.15, p = 0.82). Compared to placebo, the ω-3 + LA showed less decline in MMSE (p < 0.01) and IADL (p = 0.01) and the ω-3 group showed less decline in IADL (p < 0.01). The combination of ω-3 + LA slowed cognitive and functional decline in AD over 12 months. Because the results were generated from a small sample size, further evaluation of the combination of omega-3 fatty acids plus alpha-lipoic acid as a potential treatment in AD is warranted.

Does lipoic acid consumption affect the cytokine profile in multiple sclerosis patients: a double-blind, placebo-controlled, randomized clinical trial

BACKGROUND

A limited amount of data exists regarding the effect of lipoic acid (LA), an oral antioxidant supplement, on cytokine profiles among multiple sclerosis (MS) patients.

OBJECTIVE

We aimed to assess the effect of daily consumption of LA on the cytokine profiles in MS patients.

METHODS

In this double-blind, placebo-controlled, randomized clinical trial, 52 relapsing-remitting MS patients with an age range of 18-50 years were recruited into 2 groups: LA consumption (1,200 mg/day) or placebo. Patients followed their prescribed supplements for 12 weeks. Fasting blood samples for cytokine profile measurement were collected at baseline and after the intervention. Anthropometric parameters were measured based on the standard guidelines.

RESULTS

INF-γ, ICAM-1, TGF-β and IL-4 were significantly reduced in the LA group compared to the placebo group [(INF-γ: 0.82 ± 0.2 vs. 0.2 ± 0.2 pg/ml, p < 0.0001), (ICAM-1: 20.2 ± 9.4 vs. 8 ± 10 ng/ml, p = 0.0001), (TGF-β: 103.1 ± 20.2 vs. 54.9 ± 26 ng/ml, p < 0.0001) and (IL-4: 0.1 ± 0.1 vs. 1.02 ± 1.7 ng/ml, p = 0.0112)]. No significant changes in TNF-α, IL-6, EDSS and MMP-9 were found between the LA and placebo groups (p = 0.6, p = 0.8, p = 0.09 and p = 0.8, respectively).

CONCLUSION

The results suggested that consumption of 1,200 mg LA per day beneficially affects several inflammatory cytokines including INF-γ, ICAM-1 TGF-β and IL-4. Further investigations are needed to verify the beneficial role of LA on other cytokine profiles among MS patients.

Pesticide-induced decrease in rat testicular steroidogenesis is differentially prevented by lipoate and tocopherol

We have previously demonstrated that the sub-chronic administration of low doses of Toc or α-Toc, glyphosate and zineb to rats (i.p. 1/250 LD50, three times a week for 5 weeks) provoked severe oxidative stress (OS) in testicles. These effects were also reflected in plasma. Lipoic acid (LA) and α-tocopherol are considered as antioxidants due to their ability to neutralize reactive oxygenated species (ROS) and reset endogenous antioxidant levels. To investigate the possible protective effect on reproductive function, LA and Toc (i.p. 25, 50 and 100mg/kg) were administered simultaneously with the pesticide mixture (PM) for 5 weeks. Both drugs prevented OS and the damage to proteins and lipids caused by PM in a dose-dependent manner. The PM-induced increase levels of prostaglandins E2 and F2α was completely restored by LA but not by Toc. Similarly, only LA was able to restore the inhibition of testosterone production, the decrease of 3β- and 17β-hydroxysteroid dehydrogenases activities, and the elevation of gonatropins (FSH and LH) levels produced by PM. Furthermore, LA was more efficient than Toc in normalizing the histological alterations produced by PM administration, suggesting that pesticides act though other mechanisms that generate oxidative stress. In our experimental model LA displayed a higher protective role against pesticide-induced damage than that observed by Toc administration. Our results suggest that LA administration is a promising therapeutic strategy for coping with disorders suspected to be caused by OS generators - such as pesticides - in male reproductive system.

Serum Dihydrolipoamide Dehydrogenase Is a Labile Enzyme

Dihydrolipoamide dehydrogenase (DLDH) is a multifunctional oxidoreductase and is well known as an essential component of four mammalian mitochondrial multienzyme complexes: pyruvate dehydrogenase, α-ketoglutarate dehydrogenase, branched chain α-keto acid dehydrogenase, and the glycine cleavage system. However, existence of extracellular DLDH in mammals, if any, has not been clearly defined. The present article reports identification and biochemical characterization of serum DLDH. Proteomic analysis of rat serum using blue native polyacrylamide gel electrophoresis (BN-PAGE) and mass spectrometry peptide sequencing led to generation of 6 tryptic peptides in one band that matched to mitochondrial DLDH, indicating the existence of DLDH in rat serum. Measurement of enzymatic activity also indicated the existence of DLDH in human and mouse serum. Further biochemical analysis of rat serum DLDH revealed that this enzyme lacked diaphorase activity and could not be detected on Western blots probed with antibodies that recognized mitochondrial DLDH. Moreover, both ammonium sulfate fractioning and gel filtration of serum samples rendered a great loss in DLDH activity, indicating that the enzyme activity of this serum protein, unlike that of mitochondrial DLDH, is very labile. When DTT was supplemented in the buffer used for gel filtration, DLDH activity was found to be largely preserved; indicating that serum DLDH is susceptible to air-implicated inactivation. Results of the present study indicate that serum DLDH differs from mitochondrial DLDH in that it is a very labile enzyme.

The influence of nutritional factors on the prognosis of multiple sclerosis

The effect of nutrition and dietary supplements on the course of multiple sclerosis (MS) is a topic of great interest to both patients and clinicians. In particular, vitamin D status has been shown to influence both the incidence and the course of MS. High vitamin D levels are probably protective against the development of MS, although the efficacy of vitamin D supplementation in slowing progression of MS remains to be established. The influence of polyunsaturated fatty acids (PUFAs) on the development and course of MS has also long been under investigation. Small clinical trials suggest a modest reduction in the severity and duration of relapses in patients with MS receiving PUFA supplements. Other nutritional factors have been evaluated for their effect on MS disease progression, including milk proteins, gluten, probiotics, antioxidants (uric acid, vitamins A, C and E, lipoic acid), polyphenols, Ginkgo biloba extracts and curcumin. However, further studies are needed to evaluate the effects of these dietary components on the relapse rate and progression of MS. This Review gives an overview of the literature on the nutritional factors most commonly implicated as having an effect on MS and discusses the biological rationale that is thought to underlie their influence.

Quantum-chemical investigation of the structure and the antioxidant properties of α-lipoic acid and its metabolites

Quantum-chemical computations were used to investigate the structure-antioxidant parameter relationships of α-lipoic acid and its natural metabolites bisnorlipoic acid and tetranorlipoic acid in their oxidized and reduced forms. The enantiomers of lipoic and dihydrolipoic acid were optimized using the B3LYP/6-311+G(3df,2p), B3LYP/aug-cc-pVDZ and MP2(full)/6-31+G(d,p) levels of theory as isolated molecules and in the presence of water. The geometries of the metabolites and the values of their antioxidant parameters (proton affinity, bond dissociation enthalpy, adiabatic ionization potential, spin density, and the highest occupied molecular orbital energy) were calculated at the B3LYP/6-311+G(3df,2p) level of theory. The results obtained reveal similarities between these structures: a pentatomic, nonaromatic ring is present in the oxidized forms, while an unbranched aliphatic chain (as found in saturated fatty acids) is present in both the oxidized and the reduced forms. Analysis of the spin density and the highest occupied molecular orbital energy revealed that the SH groups exhibited the greatest electron-donating activities. The values obtained for the proton affinity, bond dissociation enthalpy and adiabatic ionization potential indicate that the preferred antioxidant mechanisms for α-lipoic acid and its metabolites are sequential proton loss electron transfer in polar media and hydrogen atom transfer in vacuum.

Lipoic acid attenuates innate immune infiltration and activation in the visceral adipose tissue of obese insulin resistant mice

Visceral adipose inflammation mediated by innate and adaptive immune alterations plays a critical role in diet-induced obesity and insulin resistance (IR). The dietary supplement α-lipoic acid (αLA) has been shown to ameliorate inflammatory processes in macrophages, however the relative significance of these effects in the context of visceral adipose inflammation and IR remain unknown. In this study we investigated its effects via both intraperitoneal and oral administration in lean and obese transgenic mice expressing yellow fluorescent protein (YFP) under control of a monocyte specific promoter (c-fms(YFP+)). αLA significantly improved indices of insulin-resistance concomitant with a decrease in total (YFP(+)CD11b(+)) and activated (YFP(+)CD11b(+)CD11c(+)) visceral adipose tissue macrophages. Histologically, the visceral adipose tissue of obese mice receiving αLA had fewer "crown-like structures," a hallmark of adipose inflammation in murine obesity. Monocyte adhesion assessed by intravital microscopy of cremasteric venules was attenuated by αLA. In cultured WT and toll-like receptor 4 (TLR4) null primary mouse macrophages, αLA significantly decreased basal CCR-2, MCP-1 and TNF-α expression levels. LPS treatment resulted in increased TNFα, MCP-1, and IL-6 expression while αLA partially abrogated the LPS effect on MCP-1 and TNFα; Interestingly, CCR-2 was not coordinately regulated. AαLA prevented LPS-induced nuclear factor kappa B (NFκB) activation in the same cultured macrophages. These data suggest that αLA may modulate visceral adipose inflammation, a critical determinant of IR via TLR4 and NF-κB pathways.

May diet and dietary supplements improve the wellness of multiple sclerosis patients? A molecular approach

Multiple sclerosis is a complex and multifactorial neurological disease, and nutrition is one of the environmental factors possibly involved in its pathogenesis. At present, the role of nutrition is unclear, and MS therapy is not associated to a particular diet. MS clinical trials based on specific diets or dietary supplements are very few and in some cases controversial. To understand how diet can influence the course of MS and improve the wellness of MS patients, it is necessary to identify the dietary molecules, their targets and the molecular mechanisms involved in the control of the disease. The aim of this paper is to provide a molecular basis for the nutritional intervention in MS by evaluating at molecular level the effect of dietary molecules on the inflammatory and autoimmune processes involved in the disease.

Lipoic acid decreases inflammation and confers neuroprotection in experimental autoimmune optic neuritis

Lipoic acid (LA) is an antioxidant that is effective in treating experimental autoimmune encephalomyelitis (EAE), a model for multiple sclerosis (MS). C57BL/6 mice with EAE develop experimental autoimmune optic neuritis (EAON), which models acute optic neuritis in humans. Here we determined whether LA is therapeutically effective in EAON. We immunized C57BL/6 mice with MOG 35-55 peptide. Mice received either daily subcutaneous injections of LA (100mg/kg) or saline in early or late suppression paradigms. In the early suppression paradigm, optic nerve cross-sections showed 14.9±3.8% (mean±SEM) damage in mice receiving saline (n=7) and 2.0±0.4% damage in mice given LA (n=7, p=0.001). In the late suppression paradigm, optic nerve sections showed 24.6±3.5% damage in mice treated with saline (n=7) and 8.4±2.5% in mice treated with LA (n=7, p=0.004). Thus a dramatic reduction in axonal injury was seen after LA administration in both experimental paradigms. Compared with saline treated mice with EAON, optic nerves from mice receiving LA had significantly fewer CD4+ and CD11b+ cells in both paradigms. This study provides a rationale for investigating the therapeutic efficacy of LA in acute optic neuritis in humans.

Lipoic acid attenuates inflammation via cAMP and protein kinase A signaling

Background

Abnormal regulation of the inflammatory response is an important component of diseases such as diabetes, Alzheimer's disease and multiple sclerosis (MS). Lipoic acid (LA) has been shown to have antioxidant and anti-inflammatory properties and is being pursued as a therapy for these diseases. We first reported that LA stimulates cAMP production via activation of G-protein coupled receptors and adenylyl cyclases. LA also suppressed NK cell activation and cytotoxicity. In this study we present evidence supporting the hypothesis that the anti-inflammatory properties of LA are mediated by the cAMP/PKA signaling cascade. Additionally, we show that LA oral administration elevates cAMP levels in MS subjects.

Methodology/Principal Findings

We determined the effects of LA on IL-6, IL-17 and IL-10 secretion using ELISAs. Treatment with 50 µg/ml and 100 µg/ml LA significantly reduced IL-6 levels by 19 and 34%, respectively, in T cell enriched PBMCs. IL-17 levels were also reduced by 35 and 50%, respectively. Though not significant, LA appeared to have a biphasic effect on IL-10 production. Thymidine incorporation studies showed LA inhibited T cell proliferation by 90%. T-cell activation was reduced by 50% as measured by IL-2 secretion. Western blot analysis showed that LA treatment increased phosphorylation of Lck, a downstream effector of protein kinase A. Pretreatment with a peptide inhibitor of PKA, PKI, blocked LA inhibition of IL-2 and IFN gamma production, indicating that PKA mediates these responses. Oral administration of 1200 mg LA to MS subjects resulted in increased cAMP levels in PBMCs four hours after ingestion. Average cAMP levels in 20 subjects were 43% higher than baseline.

Conclusions/Significance

Oral administration of LA in vivo resulted in significant increases in cAMP concentration. The anti-inflammatory effects of LA are mediated in part by the cAMP/PKA signaling cascade. These novel findings enhance our understanding of the mechanisms of action of LA.