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

Discovery of neuroprotective Agents: Potent, brain Penetrating, lipoic acid derivatives for the potential treatment of ischemic stroke by regulating oxidative stress and inflammation - a Preliminary study

Stroke poses a serious risk to the physical and mental health of patients. Endogenous compounds are widely used to treat ischemic stroke. Lipoic acid, a naturally occurring (R)-5-(1,2-dithiolan-3-yl)pentanoic acid, has therapeutic potential for the treatment of ischemic stroke. However, the direct application of lipoic acid is limited by its relatively low efficacy and instability. Therefore, there is a need to modify the structure of lipoic acid to improve its pharmaceutical capabilities. Currently, 37 lipoic acid derivatives have been synthesized, and compound AA-9 demonstrated optimal therapeutic potential in an in vitro model of induced oxidative damage using tert-butyl hydroperoxide (t-BHP). In addition, in vitro experiments have shown that compound AA-9 has an excellent safety profile. Subsequently, the therapeutic effect of AA-9 was significant in the rat MCAO ischemic stroke model, which may be attributed to the antioxidant and anti-inflammatory effects of compound AA-9 by activating PGC-1α and inhibiting NLRP3. Notably, compound AA-9 exhibited higher stability and better bioavailability properties than ALA in plasma stability and pharmacokinetic properties. In conclusion, AA-9 may be a promising neuroprotective agent for the treatment of ischemic stroke and warrants further investigation.

Alpha lipoic acid ameliorates motor deficits by inhibiting ferroptosis in Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disease. Ferroptosis shares several features with PD pathophysiology, and anti-ferroptosis molecules are neuroprotective in PD animal models. As an antioxidant and iron chelating agent, alpha lipoic acid (ALA) has a neuroprotective effect on PD; however, the influence of ALA on ferroptosis in PD remains unclear. This study aimed to determine the mechanism of ALA in regulating ferroptosis in PD models. Results showed that ALA could ameliorate motor deficits in PD models and regulate iron metabolism by upregulating ferroportin (FPN) and ferritin heavy chain 1 (FTH1) and downregulating iron importer divalent metal transporter 1 (DMT1). Moreover, ALA decreased the accumulation of reactive oxygen species (ROS) and lipid peroxidation, rescued mitochondrial damage, and prevented ferroptosis effectively by inhibiting the downregulation of glutathione peroxidase 4 (GPX4) and cysteine/glutamate transporter (xCT) in PD. Mechanistic study indicated that the activation of SIRT1/NRF2 pathway was involved in the upregulation effect of GPX4 and FTH1. Thus, ALA ameliorates motor deficits in PD models by regulating iron metabolism and mitigating ferroptosis through the SIRT1/NRF2 signaling pathway.

Alpha lipoic acid treatment in late middle age improves cognitive function: Proteomic analysis of the protective mechanisms in the hippocampus

Alpha lipoic acid (ALA), a powerful antioxidant, has the potential to relieve age-related cognitive impairment and neurodegenerative disease. Clinical randomized controlled studies have demonstrated the cognitive improvement effects of lipoic acid in Alzheimer's disease (AD). In the present study, we examined the effects of ALA on cognitive function in ageing mice and its protective mechanisms. Eighteen-month-old male C57BL6/J mice received ALA or normal saline for 2 months. The Morris water maze test revealed improved cognitive function in animals that received ALA. Furthermore, tandem Mass Tags (TMT) based liquid chromotography with mass spectrometry/mass spectrometry (LC-MS/MS) was established to identify the target proteins. The results showed that 10 proteins were changed significantly. Gene Ontology (GO) analysis indicated that the upregulated proteins were enriched in terminal bouton, synaptic transmission and lipid transporter activity while the down-regulated proteins were involved in nuclear transcription factor-κB binding, apoptosis and mitogen-activated protein kinase binding. Based on the GO results, two upregulated proteins oxysterol-binding protein-related protein 10 (OSBPL10) and oligophrenin 1 (OPHN1), and one downregulated protein, CDK5 regulatory subunit-associated protein 3 (CDK5rap3), were validated through Western blotting. The results were consistent with the proteomic results. Modulation of synaptic transmission, lipid transporter activity and neuroinflammation appears to be the mechanisms of ALA in the aged brain.

SIRT1 pathway in Parkinson's disease: a faraway snapshot but so close

Silent information regulator (SIRT) has distinctive enzymatic activities and physiological functions to control cell-cycle progression, gene expression, and DNA stability by targeting histone and non-histone proteins. SIRT1 enhances synaptic formation and synaptic activity, and therefore, can reduce the progression of various degenerative brain diseases including Parkinson's disease (PD). SIRT1 activity is decreased by aging with a subsequent increased risk for the development of degenerative brain diseases. Inhibition of SIRT1 promotes inflammatory reactions since SIRT1 inhibits transcription of nuclear factor kappa B (NF-κB) which also inhibits SIRT1 activation via activation of microRNA and miR-34a which reduce NAD synthesis. SIRT1 is highly expressed in microglia as well as neurons, and has antioxidant and anti-inflammatory effects. Therefore, this review aimed to find the possible role of SIRT1 in PD neuropathology. SIRT1 has neuroprotective effects; therefore, downregulation of SIRT1 during aging promotes p53 expression and may increase the vulnerability of neuronal cell deaths. PD neuropathology is linked with the sequence of inflammatory changes and the release of pro-inflammatory cytokines due to the activation of inflammatory signaling pathways. In addition, oxidative stress, inflammatory disorders, mitochondrial dysfunction, and apoptosis contribute mutually to PD neuropathology. Thus, SIRT1 and SIRT1 activators play a crucial role in the mitigation of PD neuropathology through the amelioration of oxidative stress, inflammatory disorders, mitochondrial dysfunction, apoptosis, and inflammatory signaling pathways.

Sex-specific transcriptional rewiring in the brain of Alzheimer’s disease patients

Sex-specific differences may contribute to Alzheimer’s disease (AD) development. AD is more prevalent in women worldwide, and female sex has been suggested as a disease risk factor. Nevertheless, the molecular mechanisms underlying sex-biased differences in AD remain poorly characterized. To this end, we analyzed the transcriptional changes in the entorhinal cortex of symptomatic and asymptomatic AD patients stratified by sex. Co-expression network analysis implemented by SWItchMiner software identified sex-specific signatures of switch genes responsible for drastic transcriptional changes in the brain of AD and asymptomatic AD individuals. Pathway analysis of the switch genes revealed that morphine addiction, retrograde endocannabinoid signaling, and autophagy are associated with both females with AD (F-AD) and males with (M-AD). In contrast, nicotine addiction, cell adhesion molecules, oxytocin signaling, adipocytokine signaling, prolactin signaling, and alcoholism are uniquely associated with M-AD. Similarly, some of the unique pathways associated with F-AD switch genes are viral myocarditis, Hippo signaling pathway, endometrial cancer, insulin signaling, and PI3K-AKT signaling. Together these results reveal that there are many sex-specific pathways that may lead to AD. Approximately 20–30% of the elderly have an accumulation of amyloid beta in the brain, but show no cognitive deficit. Asymptomatic females (F-asymAD) and males (M-asymAD) both shared dysregulation of endocytosis. In contrast, pathways uniquely associated with F-asymAD switch genes are insulin secretion, progesterone-mediated oocyte maturation, axon guidance, renal cell carcinoma, and ErbB signaling pathway. Similarly, pathways uniquely associated with M-asymAD switch genes are fluid shear stress and atherosclerosis, FcγR mediated phagocytosis, and proteoglycans in cancer. These results reveal for the first time unique pathways associated with either disease progression or cognitive resilience in asymptomatic individuals. Additionally, we identified numerous sex-specific transcription factors and potential neurotoxic chemicals that may be involved in the pathogenesis of AD. Together these results reveal likely molecular drivers of sex differences in the brain of AD patients. Future molecular studies dissecting the functional role of these switch genes in driving sex differences in AD are warranted.