alpha-lipoic acid prevents the induction of iNOS gene expression through destabilization of its mRNA in proinflammatory cytokine-stimulated hepatocytes

An updated systematic review and dose-response meta-analysis of the randomized controlled trials on the effects of Alpha-Lipoic acid supplementation on inflammatory biomarkers

Data about the effects of alpha-lipoic acid (ALA) supplementation on inflammatory markers are inconsistent. This systematic review and dose-response meta-analysis of randomized controlled trials was performed to summarize the effects of ALA supplementation on inflammatory markers such as C-reactive protein (CRP), interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) in adults. A comprehensive literature search was conducted in the electronic databases of PubMed, Web of Science, ProQuest, Embase, and SCOPUS from inception to February 2020. Among all of the eligible studies, 20 articles were selected. The weighted mean differences (WMD) and 95% confidence intervals (CI) were calculated to evaluate the pooled effect size. Between-study heterogeneity was evaluated using Cochran's Q test and I². Subgroup analysis was done to evaluate the potential sources of heterogeneity. The dose-response relationship was evaluated using fractional polynomial modeling. Twenty eligible studies with a total sample size of 947 participants were included in the current meta-analysis. The findings of the meta-analysis showed that ALA supplementation significantly reduced CRP (WMD: -0.69 mg/L, 95% CI: -1.13, -0.26, P=0.002), IL-6 (WMD: -1.83 pg/ml, 95% CI: -2.90, -0.76, P=0.001), and TNF-α concentrations (WMD: -0.45 pg/ml, 95% CI: -0.85, -0.04, P=0.032). No evidence of departure from linearity was observed between dose and duration of the ALA supplementation on serum CRP, IL-6 and TNF-α concentration. In subgroup analysis, ALA dosage, baseline concentrations of the parameter, sample size, and gender were considered as possible sources of heterogeneity. In summary, ALA supplementation improves inflammatory markers without any evidence of non-linear association to dose or duration of the trial.

Protective Effect and Mechanism of α-Lipoic Acid on Partial Hepatic Ischemia-Reperfusion Injury in Adult Male Rats

In order to reduce tissue damage caused by ischemia-reperfusion injury, this study aims to investigate the protective effect and mechanism of α-lipoic acid on hepatic ischemia-reperfusion injury in rats. The bloodstream of rats was blocked in the left middle and left lateral liver lobes of the liver. Forty rats were randomly divided into two groups: treatment group and injury group. Rats were injected with either 25 mg/1 ml of α-lipoic acid (treatment group) or 1 ml of saline (injury group) into the caudal vein 15 min before hepatic ischemia-reperfusion. Rat serum alanine aminotransferase (GPT), glutathione (GSH) and superoxide dismutase (SOD) levels were examined at various time points (1, 3, 6 and 12 h) in both groups. Changes in nuclear factor kappa B P65 (NF-κB P65) expression in ischemia-reperfusion liver at various time points after reperfusion (1, 3, 6 and 12 h) were evaluated through immunohistochemistry assay. Changes in macrophage inflammatory protein-2 (MIP-2) mRNA and inducible nitric oxide synthase (iNOS) mRNA expression in ischemic reperfused rat livers were detected by RT-PCR. Serum GPT level was significantly higher in the injury group than in the treatment group (P<0.01). NF-κB P65, MIP-2 mRNA and iNOS mRNA expression in ischemic reperfused rat livers were significantly higher in the injury group than in the treatment group (P<0.01). Serum GSH and SOD levels were higher in the treatment group than in the injury group (P<0.01). Alpha-lipoic acid significantly reduced ischemia-reperfusion injury in rat livers. This may be associated to the direct scavenging of oxygen-free radicals, increased GSH production, and the activation of downstream media due to decreased NF-κB and GSH consumption.

α-lipoic acid in patients with autosomal dominant polycystic kidney disease

OBJECTIVES

Autosomal dominant polycystic kidney disease (ADPKD) is the most common genetic kidney disease characterized by multiple and bilateral cystic dilation of renal tubules. Hypertension, endothelial dysfunction, systemic inflammation, and accelerated atherosclerosis are alterations found at a very early stage of the disease and are responsible for increasing both cardiovascular risks and progression toward end-stage renal disease. The aim of the study was to evaluate the effects of the use of 1.6 g α-lipoic acid (ALA) daily for 3 and 6 on the main markers of systemic inflammation, endothelial dysfunction, and atherosclerosis, as well as on nutritional, cardiovascular, and psychocognitive parameters, in ADPKD patients with CKD stage G2/G3 Kidney Disease Improving Global Outcomes chronic kidney disease (KDIGO) compared to controls.

METHODS

This was a controlled, longitudinal, prospective, interventional study with 59 patients with ADPKD. Of the patients, 33 were treated with ALA (1.6 g/d) for 6 mo and 26 were controls. Clinical, laboratory (inflammation and metabolic indexes), instrumental parameters (intima media thickness (IMT), renal resistive index (RRI), flow-mediated dilation (FMD), ankle-brachial index (ABI), and psycho-cognitive tests (Mini-Mental State Examination [MMSE], Hamilton Depression Rating Scale [HAM-D], Beck Depression Inventory-II [BDI-II]) were evaluated at baseline (T0), 3 mo (T1), and 6 mo (T2).

RESULTS

Patients treated with ALA at T1 and T2 showed a significant reduction in serum glucose, insulin, homeostatic model assessment-insulin resistance, and serum uric acid (P = 0.013, P = 0.002, P = 0.002, P <0.001; respectively) and significantly higher values of base excess (P < 0.001), compared with the control group. Moreover, the results showed a significant increase in bicarbonates (P = 0.009) and FMD (P < 0.001), and a significant reduction of C-reactive protein (P <0.001) and RRI (P = 0.013). On the other hand, we did not assess a significant difference in IMT and ABI at T1 and T2. Psychocognitive tests (BDI-II, HAM-D, and MMSE) were significantly improved (P = 0.007, P < 0.001, P < 0.001; respectively) in patients treated with ALA for 6 mo compared with the control group. A significant difference in nicotinamide adenine dinucleotide phosphate oxidase 2 concentrations was observed between T0 and T2 only in ADPKD patients treated with ALA (P = 0.039, P = 0.039; respectively), although we did not find a significant difference in interleukin-6, interleukin -1β, and tumor necrosis factor-α concentrations in either group.

CONCLUSIONS

We suggest an early and careful monitoring of traditional and non-traditional cardiovascular risk factors in patients with ADPKD. Moreover, we suggest the use of ALA, an anti-inflammatory and antioxidant nutraceutical with few side effects. Additionally, it is important to evaluate the cognitive abilities, psychological health, and quality of life of patients with ADPKD, especially at the early stage of disease.

Alpha-lipoic acid (ALA) supplementation effect on glycemic and inflammatory biomarkers: A Systematic Review and meta- analysis

BACKGROUND & AIMS

Several randomized clinical trials (RCTs) have investigated the effect of Alpha - Lipoic Acid (ALA) supplementation on metabolic parameters, with conflicting results. Therefore, the present study assessed the effect of ALA on some glycemic and inflammatory parameters.

METHODS

A comprehensive literature search was conducted up from inception to July 2018 on PubMed, Scopus, Cochrane databases, Google Scholar, ProQuest, Web of Science, and Embase. From among eligible trials, 41 articles were selected for the meta-analysis. Two reviewers independently assessed the risk of bias and extracted data from the included studies. Meta-analyses using the random-effects model were performed to analyze the data.

RESULTS

Based on the Cochrane risk of bias tool, 19 articles had a good quality, 16 trials had a poor quality and 6 trials had a fair quality. The results demonstrated the significant effect of ALA on Fasting Blood Sugar (FBS) (weighted mean difference (WMD)) = -6.57, 95% confidence interval (CI: -11.91 to -1.23, P = 0.016), Hemoglobin A1c (HbA1c) (WMD = -0.35, 95% CI: -0.55 to -0.15, P = 0.004), Tumor Necrosis Factor Alpha (TNF-α) (WMD = -1.57, 95% CI: -2.29 to -0.85, P < 0.05), Interleukin 6 levels (IL-6) (WMD = -1.15, 95% CI: -1.58 to -0.72, P < 0.001), and C-reactive protein (CRP) (WMD = -0.31, 95% CI: -0.47 to -0.16, P > 0.001). No effect was detected for ALA on insulin and the homeostatic model assessment of insulin resistance (HOMA-IR).

CONCLUSIONS

These findings suggest that ALA is a viable supplement to improve some of the glycemic and inflammatory biomarkers.

Curcumin-carrying nanoparticles prevent ischemia-reperfusion injury in human renal cells

Renal ischemia-reperfusion injury (IRI) is a major complication in clinical practice. However, despite its frequency, effective preventive/treatment strategies for this condition are scarce. Curcumin possesses antioxidant properties and is a promising potential protective agent against renal IRI, but its poor water solubility restricts its application. In this study, we constructed curcumin-carrying distearoylphosphatidylethanolamine-polyethylene glycol nanoparticles (Cur-NPs), and their effect on HK-2 cells exposed to IRI was examined in vitro. Curcumin encapsulated in NPs demonstrated improved water solubility and slowed release. Compared with the IRI and Curcumin groups, Cur-NP groups displayed significantly improved cell viability, downregulated protein expression levels of caspase-3 and Bax, upregulated expression of Bcl-2 protein, increased antioxidant superoxide dismutase level, and reduced apoptotic rate, reactive oxygen species level, and malondialdehyde content. Results clearly showed that Cur-NPs demonstrated good water solubility and slow release, as well as exerted protective effects against oxidative stress in cultured HK-2 cells exposed to IRI.

Elental® amino acid component has protective effects on primary cultured hepatocytes and a rat model of acute liver injury

Amino acids can exert protective effects on the liver either when administered as a medication or following an operation. In this study, we examined the protective effects of amino acids on the liver using in vitro and in vivo models by studying their influence on the induction of inducible nitric oxide synthase (iNOS) and nitric oxide production as a liver injury marker in cultured hepatocytes and liver-protective effects in d-galactosamine and lipopolysaccharide (GalN/LPS)-treated rats, respectively. Primary cultured rat hepatocytes were treated with interleukin (IL)-1β in the presence or absence of Elental® amino acid component (EleAA; 17 amino acids). Rats were pretreated with either EleAA or a diet containing selected amino acids followed by GalN/LPS injection. Survival rate and mRNA expression were analyzed. EleAA inhibited iNOS induction through reduction of mRNA synthesis and stability in cultured hepatocytes, indicating prevention of liver injury, but did not show a liver-protective effect in GalN/LPS rats. Among EleAA, Lys, Trp, His, and Arg (4AA) markedly decreased nitric oxide production and inhibited nuclear factor-κB (NF-κB) activation. In GalN/LPS rats, 4AA (3% of each amino acid in diet) increased survival rate by 50% and decreased mRNA expression of iNOS, tumor necrosis factor-α, and cytokine-induced neutrophil chemoattractant-1 in the liver. 4AA reduced NF-κB activation induced by GalN/LPS. 4AA inhibited the expression of inflammatory mediators, in part through inhibition of NF-κB activation in cultured hepatocytes and GalN/LPS-treated rats. The results suggest that EleAA has therapeutic potential for organ injuries including liver.

New progress in roles of nitric oxide during hepatic ischemia reperfusion injury

Hepatic ischemia reperfusion injury (HIRI) is a clinical condition which may lead to cellular injury and organ dysfunction. The role of nitric oxide (NO) in HIRI is complicated and inconclusive. NO produced by endothelial nitric oxide synthase (eNOS) activation plays a protective role during early HIRI. But eNOS overexpression and the resulting excessive NO bioavailability can aggravate liver injury. NO induced by inducible nitric oxide synthase (iNOS) may have either a protective or a deleterious effect during the early phase of HIRI, but it may protect the liver during late HIRI. Here, we reviewed the latest findings on the role of NO during HIRI: (1) NO exerts a protective effect against HIRI by increasing NO bioavailability, downregulating p53 gene expression, decreasing inflammatory chemokines, reducing ROS via inhibiting the mitochondrial respiratory chain, activating sGC-GTP-cGMP signal pathway to reduce liver cell apoptosis, and regulating hepatic immune functions; (2) eNOS protects against HIRI by increasing NO levels, several eNOS/NO signal pathways (such as Akt-eNOS/NO, AMPK-eNOS/NO and HIF-1α-eNOS/NO) participating in the anti-HIRI process, and inhibiting over-expression of eNOS also protects against HIRI; and (3) the inhibition of iNOS prevents HIRI. Thus, the adverse effects of NO should be avoided, but its positive effect in the clinical treatment of diseases associated with HIRI should be recognized.

Alpha-lipoic acid prevents endotoxic shock and multiple organ dysfunction syndrome induced by endotoxemia in rats

Alpha-lipoic acid (ALA), a naturally occurring disulfide derivative of octanoic acid, serves as a strong antioxidant and has been reported to possess anti-inflammatory effects. The aim of the present study is to investigate the preventive and therapeutic effects of ALA on multiple organ dysfunction syndrome (MODS) caused by endotoxemia in rats. Male Wistar rats were intravenously infused with lipopolysaccharide (LPS) (10 mg/kg) to induce endotoxemia. Alpha-lipoic acid 10, 20, or 40 mg/kg was administered intravenously 60 min before (pretreatment) LPS challenge, and ALA 40 mg/kg was administered intravenously 30 min after (posttreatment) LPS challenge. Pretreatment and posttreatment with ALA significantly improved the deleterious hemodynamic changes 8 h after LPS challenge, including hypotension and bradycardia. Alpha-lipoic acid reduced the plasma levels of glutamic pyruvic transaminase, blood urea nitrogen, lactate dehydrogenase, tumor necrosis factor-α, nitric oxide metabolites, and thrombin-antithrombin complex, which increased markedly after LPS challenge. The induction of inducible nitric oxide synthase both in the liver and the lung and vascular superoxide anion production were also significantly suppressed by ALA. Moreover, ALA significantly attenuated LPS-induced caspase-3 activation in cardiomyocytes and improved survival rate. In conclusion, ALA effectively attenuated LPS-induced acute inflammatory response and improved MODS. The antioxidant and anti-inflammatory effects of ALA may contribute to these beneficial effects. Alpha-lipoic acid might be considered as a novel therapeutic strategy in the prevention of sepsis-induced MODS and inflammatory vascular diseases.

Alpha-lipoic acid exerts anti-inflammatory effects on lipopolysaccharide-stimulated rat mesangial cells via inhibition of nuclear factor kappa B (NF-κB) signaling pathway

Sepsis is often initiated by invasive infection, characterized by overwhelming induction of pro-inflammatory cytokines. The incidence and mortality of sepsis and the associated development of acute kidney injury (AKI) remain high, and lines of research into potential treatments are needed. This study was conducted to investigate effects of alpha-lipoic acid (ALA) on septic AKI in vitro. ALA of 200 or 400 μM was used to pretreat rat HBZY-1 mesangial cells before commencement of 1 μg/mL lipopolysaccharide (LPS). Our data indicated that ALA pretreatment reduced LPS-stimulated release of inflammatory cytokines, such as tumor necrosis factor alpha (TNF-α), interleukin (IL)-1 beta (IL-1β), as well as IL-6, in HBZY-1 cell supernatant. Moreover, LPS-induced expression of cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) was inhibited by ALA pretreatment, and consequently, the secretion levels of their respective enzymatic products prostaglandin E2 (PGE2) and nitric oxide (NO) were significantly decreased. LPS-enhanced phosphorylation of nuclear factor kappa B (NF-κB) inhibitor alpha (IκBα) and IκB kinase alpha/beta (IKKα/β) and nuclear translocation of NF-κB subunit p65 in HBZY-1 cells were inhibited by ALA pretreatment. Additionally, the NF-κB inhibitor N-acetylcysteine (NAC) exerted similar inhibitory effects as ALA on COX-2 and iNOS expression. In summary, our study demonstrates that ALA mitigates LPS-induced inflammatory responses in rat mesangial cells probably via inhibition of NF-κB signaling pathway, suggesting a therapeutic potential of ALA in AKI related to sepsis.

Co-administration of α-lipoic acid and glutathione is associated with no significant changes in serum bilirubin, alkaline phosphatase or γ-glutamyltranspeptidase levels during the treatment of neuroborreliosis with intravenous ceftriaxone

BACKGROUND

While pharmacotherapy with intravenous ceftriaxone, a third-generation cephalosporin, is a potential treatment of Lyme neuroborreliosis, there is concern that it can cause the formation of biliary sludge, leading to hepatobiliary complications such as biliary colic, jaundice and cholelithiasis, which are reflected in changes in serum levels of bilirubin and markers of cholestatic liver injury (alkaline phosphatase and γ-glutamyltranspeptidase). It has been suggested that the naturally occurring substances α-lipoic acid and glutathione may be helpful in preventing hepatic disease. α-Lipoic acid exhibits antioxidant, anti-inflammatory and anti-apoptotic activities in the liver, while glutathione serves as a sulfhydryl buffer. The aim of this study was to determine whether co-administration of α-lipoic acid and glutathione is associated with significant changes in serum levels of bilirubin, alkaline phosphatase and γ-glutamyltranspeptidase during the treatment of Lyme neuroborreliosis with long-term intravenous ceftriaxone.

METHODS

Serum levels of bilirubin, alkaline phosphatase and γ-glutamyltranspeptidase were measured in 42 serologically positive Lyme neuroborreliosis patients before and after long-term treatment with intravenous ceftriaxone (2-4 g daily) with co-administration of oral/intravenous α-lipoic acid (600 mg daily) and glutathione (100 mg orally or 0.6-2.4 g intravenously daily).

RESULTS

None of the patients developed biliary colic and there were no significant changes in serum bilirubin, alkaline phosphatase or γ-glutamyltranspeptidase levels over the course of the intravenous ceftriaxone treatment (mean length 75.0 days).

CONCLUSIONS

Co-administration of α-lipoic acid and glutathione is associated with no significant changes in serum bilirubin, alkaline phosphatase or γ-glutamyltranspeptidase levels during the treatment of neuroborreliosis with intravenous ceftriaxone.

Alpha-lipoic acid affects the oxidative stress in various brain structures in mice with methionine and choline deficiency

Deficiency in methionine or choline can induce oxidative stress in various organs such as liver, kidney, heart, and brain. This study was to examine the effects of alpha-lipoic acid (LA) on oxidative stress induced by methionine and choline deficiency (MCD) in several brain structures. Male mice C57BL/6 (n = 28) were divided into four groups: (1) control - continuously fed with standard chow; (2) LA - fed with standard chow and receiving LA; (3) MCD2 - fed with MCD diet for two weeks, and (4) MCD2+LA - fed with MCD diet for two weeks and receiving LA (100 mg/kg/day intraperitonealy [i.p.]). Brain tissue (cortex, hypothalamus, striatum and hippocampus) was taken for determination of oxidative stress parameters. MCD diet induced a significant increase in malondialdehyde and NOx concentration in all brain regions, while LA restored their content to normal values. Similar to this, in MCD2 group, activity of total SOD, MnSOD, and Cu/ZnSOD was reduced by MCD diet, while LA treatment improved their activities in all brain structures. Besides, in MCD2 group a decrease in catalase activity in cortex and GSH content in hypothalamus was evident, while LA treatment induced an increase in catalase activity in cortex and striatum and GSH content in hypothalamus. LA treatment can significantly reduce lipid peroxidation and nitrosative stress, caused by MCD diet, in all brain regions by restoring antioxidant enzymes activities, predominantly total SOD, MnSOD, and Cu/ZnSOD, and to a lesser extent by modulating catalase activity and GSH content. LA supplementation may be used in order to prevent brain oxidative injury induced by methionine and choline deficiency.

THE COMBINATION OF α-LIPOIC ACID INTAKE WITH ECCENTRIC EXERCISE MODULATES ERYTHROPOIETIN RELEASE

The generation of reactive nitrogen/oxygen species (RN/OS) represents an important mechanism in erythropoietin (EPO) expression and skeletal muscle adaptation to physical and metabolic stress. RN/OS generation can be modulated by intense exercise and nutrition supplements such as α-lipoic acid, which demonstrates both anti- and pro-oxidative action. The study was designed to show the changes in the haematological response through the combination of α-lipoic acid intake with running eccentric exercise. Sixteen healthy young males participated in the randomised and placebo-controlled study. The exercise trial involved a 90-min run followed by a 15-min eccentric phase at 65% VO₂max (-10% gradient). It significantly increased serum concentrations of nitric oxide (NO), hydrogen peroxide (H₂O₂) and pro-oxidative products such as 8-isoprostanes (8-iso), lipid peroxides (LPO) and protein carbonyls (PC). α-Lipoic acid intake (Thiogamma: 1200 mg daily for 10 days prior to exercise) resulted in a 2-fold elevation of serum H₂O₂ concentration before exercise, but it prevented the generation of NO, 8-iso, LPO and PC at 20 min, 24 h, and 48 h after exercise. α-Lipoic acid also elevated serum EPO level, which highly correlated with NO/H₂O₂ ratio (r = 0.718, P < 0.01). Serum total creatine kinase (CK) activity, as a marker of muscle damage, reached a peak at 24 h after exercise (placebo 732 ± 207 IU · L^-1, α-lipoic acid 481 ± 103 IU · L^-1), and correlated with EPO (r = 0.478, P < 0.01) in the α-lipoic acid group. In conclusion, the intake of high α-lipoic acid modulates RN/OS generation, enhances EPO release and reduces muscle damage after running eccentric exercise.

Alpha-lipoic acid attenuates renal injury in rats with obstructive nephropathy

This study was established to determine the possible protective effects of alpha-lipoic acid (ALA), a powerful antioxidant, on renal injury in obstructive nephropathy. Male Sprague-Dawley rats were assigned into sham-operated unilateral ureteral obstruction (UUO) and UUO treated with ALA groups. ALA 60 mg/kg was injected intraperitoneally 2 days before UUO induction and continued afterward for 7 days. Renal function, oxidative stress markers, nitric oxide, transforming growth factor-1 (TGF-β1), and histological changes were evaluated at the end of the experiment. Obstruction of the ureter resulted in renal dysfunction as indicated by significant increases in blood urea nitrogen and serum creatinine. Nonobstructed contralateral kidneys in all groups examined did not show any morphological or biochemical alterations. In untreated UUO group, the obstructed kidney developed marked hydronephrosis, leukocyte infiltration, and severe interstitial fibrosis. These functional and structural changes were associated with significant increases in tissue levels of malondialdehyde, nitric oxide, and TGF-β1 but decreases in reduced glutathione and total antioxidant capacity. Pretreatment with ALA significantly minimized all the changes elicited by ureteral obstruction. These findings demonstrate that ALA supplementation attenuates renal injury in rats with obstructive nephropathy and further suggest that oxidative stress inhibition is likely to be involved in the beneficial effects of this compound.

α-Lipoic acid reduces infarct size and preserves cardiac function in rat myocardial ischemia/reperfusion injury through activation of PI3K/Akt/Nrf2 pathway

Background

The present study investigates the effects and mechanisms of α-Lipoic acid (LA) on myocardial infarct size, cardiac function and cardiomyocyte apoptosis in rat hearts subjected to in vivo myocardial ischemia/reperfusion (MI/R) injury.

Methodology/Principal Findings

Male adult rats underwent 30 minutes of ischemia followed by 3, 24, or 72 h of reperfusion. Animals were pretreated with LA or vehicle before coronary artery ligation. The level of MI/R- induced LDH and CK release, infarct size, cardiomyocyte apoptosis and cardiac functional impairment were examined and compared. Western blot analysis was performed to elucidate the mechanism of LA pretreatment. The level of inflammatory cytokine TNF-α released to serum and accumulated in injured myocardium as well as neutrophil accumulation in injured myocardium were also examined after MI/R injury. Our results reveal that LA administration significantly reduced LDH and CK release, attenuated myocardial infarct size, decreased cardiomyocytes apoptosis, and partially preserved heart function. Western blot analysis showed that LA pretreatment up-regulated Akt phosphorylation and Nrf2 nuclear translocation while producing no impact on p38MAPK activation or nitric oxide (NO) production. LA pretreatment also increased expression of HO-1, a major target of Nrf2. LA treatment inhibited neutrophil accumulation and release of TNF-α. Moreover, PI3K inhibition abolished the beneficial effects of LA.

Conclusions/Significance

This study indicates that LA attenuates cardiac dysfunction by reducing cardiomyoctyes necrosis, apoptosis and inflammation after MI/R. LA exerts its action by activating the PI3K/Akt pathway as well as subsequent Nrf2 nuclear translocation and induction of cytoprotective genes such as HO-1.

A kavalactone derivative inhibits lipopolysaccharide-stimulated iNOS induction and NO production through activation of Nrf2 signaling in BV2 microglial cells

Neuroinflammation and oxidative stress are involved in the pathogenesis of neurodegenerative diseases such as Alzheimer's diseases and Parkinson's disease. Naturally derived kavalactones isolated from Piper methysticum (Piperaceae) have been shown to exhibit neuroprotective effects. We have previously reported that a chemically synthesized kavalactone derivative, 2',6'-dichloro-5-methoxymethyl-5,6-dehydrokawain (compound 1) protects against oxidative stress-induced neuronal cell death through activation of Nrf2 signaling. In the present study, we examined the effect of compound 1 on neuroinflammation. In BV2 microglial cells, compound 1 strongly inhibited LPS-stimulated iNOS induction and NO production, but did not affect LPS-stimulated induction of COX2. At 6h after LPS challenge, when iNOS induction was not clearly seen, treatment with LPS or compound 1 alone increased expression of heme oxygenase 1 (HO-1) whose transcription is regulated by Nrf2. When treated with both, compound 1 enhanced LPS-stimulated HO-1 induction, which was more evident at 24h after LPS treatment. Furthermore, LPS-stimulated activation of Nrf2 signaling and nuclear translocation of Nrf2 were potentiated by compound 1. The mechanism by which compound 1 activated Nrf2 signaling was supposed to be a covalent modification of the sulfhydryl groups of Keap1 by an α,β-unsaturated carbonyl group present in the compound 1. Treatment with hemin, a HO-1 inducer, and with [Ru(CO)₃Cl₂]₂, a CO donor, decreased LPS-stimulated iNOS induction and NO production. In contrast, siRNA-mediated knockdown of HO-1 expression reduced the inhibitory effect of compound 1 on LPS-stimulated iNOS induction and NO production. The compound 1 inhibited LPS-stimulated ERK phosphorylation after LPS treatment. Finally, compound 1 suppressed LPS/IFN-γ-stimulated NO production in primary microglial cells. These results suggest that compound 1 is capable of inhibiting LPS-stimulated iNOS induction and NO production via activation of Nrf2 signaling and HO-1 induction in microglial cells. Taken together, compound 1 has a potential to reduce neuroinflammation as well as oxidative stress in neurodegenerative diseases through activation of Nrf2 signaling.

Lipoic acid inhibits adiponectin production in 3T3-L1 adipocytes

Lipoic acid (LA) is a naturally occurring compound with antioxidant properties. Recent attention has been focused on the potential beneficial effects of LA on obesity and related metabolic disorders. Dietary supplementation with LA prevents insulin resistance and upregulates adiponectin, an insulin-sensitizing adipokine, in obese rodents. The aim of this study was to investigate the direct effects of LA on adiponectin production in cultured adipocytes, as well as the potential signaling pathways involved. For this purpose, fully differentiated 3T3-L1 adipocytes were treated with LA (1-500 μM) during 24 h. The amount of adiponectin secreted to media was detected by ELISA, while adiponectin mRNA expression was determined by RT-PCR. Treatment with LA induced a dose-dependent inhibition on adiponectin gene expression and protein secretion. Pretreatment with the PI3K inhibitor LY294002 inhibited adiponectin secretion and mRNA levels, and significantly potentiated the inhibitory effect of LA on adiponectin secretion. The AMPK activator AICAR also reduced adiponectin production, but surprisingly, it was able to reverse the LA-induced inhibition of adiponectin. The JNK inhibitor SP600125 and the MAPK inhibitor PD98059 did not modify the inhibitory effect of LA on adiponectin. In conclusion, our results revealed that LA reduces adiponectin secretion in 3T3-L1 adipocytes, which contrasts with the stimulation of adiponectin described after in vivo supplementation with LA, suggesting that an indirect mechanism or some in vivo metabolic processing is involved.

Physical activity and alpha-lipoic acid modulate inflammatory response through changes in thiol redox status

α-Lipoic acid (αLA), as an inductor of hydrogen peroxide (H2O2) and nitrogen oxide (NO) generation and modulator of thiol redox status, plays an important role in cell signalling pathways. The study was designed to observe the effect of αLA on inflammatory response through changes in H2O2 and NO levels as well as thiol redox status. Sixteen physically active males were randomly assigned to one of two groups: placebo or αLA (1,200 mg d(-1) for 10 days prior to exercise). The exercise trial involved a 90-min run at 65% VO2max (0% gradient) followed by 15-min eccentric phase at 65% VO2max (-10% gradient). Blood samples were collected before the exercise trial and then again 20 min, 24, and 48 h after. αLA significantly elevated H2O2 but reduced NO generation before or after exercise. Thiol redox status (GSHtotal-2GSSG/GSSG) increased by >50% after αLA and exercise (ANOVA, P < 0.05) and correlated with changes in cytokines interleukin-6 (IL-6) (r = -0.478, P < 0.05) and IL-10 (r = -0.455, P < 0.05). This was caused by strong effect of αLA on GSSG concentration. αLA elevated IL-6 and IL-10 levels at 20 min after exercise and decreased in interleukin-1β and tumor necrosis factor α before and after exercise. This enhanced the regeneration of injured muscles. Creatine kinase activity tended to lower values after αLA intake. The study suggests that the combination of intense exercise with α-lipoic acid intake might be useful to improve the skeletal muscle regeneration through changes in inflammatory response which are associated with H2O2 and NO generation as well as thiol redox status.