Iron enhancement of oxidative DNA damage and neuronal cell death induced by salsolinol

Salsolinol Induces Parkinson's Disease Through Activating NLRP3-Dependent Pyroptosis and the Neuroprotective Effect of Acteoside

Endogenous neurotoxin 1-methyl-6,7-dihydroxy-1,2,3,4-tetrahydroiso-quinoline (Salsolinol, SAL) is a dopamine metabolite that is toxic to dopaminergic neurons in vitro and in vivo, and is involved in the pathogenesis of Parkinson's disease (PD). However, the molecular mechanism by which SAL induces neurotoxicity in PD remains challenging for future investigations. This study found that SAL induced neurotoxicity in SH-SY5Y cells and mice. RNA sequencing (RNAseq) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis were used to detect differentially expressed genes in SAL-treated SH-SY5Y cells. We found that NLR family pyrin domain-containing 3 (NLRP3)-dependent pyroptosis was enriched by SAL, which was validated by in vitro and in vivo SAL models. Further, NLRP3 inflammasome-related genes (ASC, NLRP3, active caspase 1, IL-1β, and IL-18) were increased at the mRNA and protein level. Acteoside mitigates SAL-induced neurotoxicity by inhibiting NLRP3 inflammasome-related pyroptosis in in vitro and in vivo PD models. In summary, the present study suggests for the first time that NLRP3-dependent pyroptosis plays a role in the pathogenesis of SAL-induced PD, and acteoside mitigates SAL-induced pyroptosis-dependent neurotoxicity in in vitro and in vivo PD models. The present results demonstrated a new mechanism whereby SAL mediates neurotoxicity by activating NLRP3-dependent pyroptosis, further highlighting SAL-induced pyroptosis-dependent neurotoxicity as a potential therapeutic target in PD.

The Regulatory Effects and the Signaling Pathways of Natural Bioactive Compounds on Ferroptosis

Natural bioactive compounds abundantly presented in foods and medicinal plants have recently received a remarkable attention because of their various biological activities and minimal toxicity. In recent years, many natural compounds appear to offer significant effects in the regulation of ferroptosis. Ferroptosis is the forefront of international scientific research which has been exponential growth since the term was coined. This type of regulated cell death is driven by iron-dependent phospholipid peroxidation. Recent studies have shown that numerous organ injuries and pathophysiological processes of many diseases are driven by ferroptosis, such as cancer, arteriosclerosis, neurodegenerative disease, diabetes, ischemia-reperfusion injury and acute renal failure. It is reported that the initiation and inhibition of ferroptosis plays a pivotal role in lipid peroxidation, organ damage, neurodegeneration and cancer growth and progression. Recently, many natural phytochemicals extracted from edible plants have been demonstrated to be novel ferroptosis regulators and have the potential to treat ferroptosis-related diseases. This review provides an updated overview on the role of natural bioactive compounds and the potential signaling pathways in the regulation of ferroptosis.

The Mechanism of Action of Salsolinol in Brain: Implications in Parkinson's Disease

1-Methyl-1,2,3,4-tetrahydroisoquinoline-6,7-diol, commonly known as salsolinol, is a compound derived from dopamine. It was first discovered in 1973 and has gained attention for its role in Parkinson's disease. Salsolinol and its derivatives were claimed to play a role in the pathogenesis of Parkinson's disease as a neurotoxin that induces apoptosis of dopaminergic neurons due to its structural similarity to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and its ability to induce Parkinsonism. In this article, we discussed the biosynthesis, distribution and blood-brain barrier permeability of salsolinol. The roles of salsolinol in a healthy brain, particularly the interactions with enzymes, hormone and catecholamine, were reviewed. Finally, we discussed the involvement of salsolinol and its derivatives in the pathogenesis of Parkinson's disease.

Oxidative modification of human ceruloplasmin induced by a catechol neurotoxin, salsolinol

Salsolinol (SAL), a compound derived from dopamine metabolism, is the most probable neurotoxin involved in the pathogenesis of Parkinson's disease (PD). In this study, we investigated the modification and inactivation of human ceruloplasmin (hCP) induced by SAL. Incubation of hCP with SAL increased the protein aggregation and enzyme inactivation in a dose-dependent manner. Reactive oxygen species scavengers and copper chelators inhibited the SAL-mediated hCP modification and inactivation. The formation of dityrosine was detected in SAL-mediated hCP aggregates. Amino acid analysis post the exposure of hCP to SAL revealed that aspartate, histidine, lysine, threonine and tyrosine residues were particularly sensitive. Since hCP is a major copper transport protein, oxidative damage of hCP by SAL may induce perturbation of the copper transport system, which subsequently leads to deleterious conditions in cells. This study of the mechanism by which ceruloplasmin is modified by salsolinol may provide an explanation for the deterioration of organs under neurodegenerative disorders such as PD.

Salsolinol, a catechol neurotoxin, induces oxidative modification of cytochrome c

Methyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline (salsolinol), an endogenous neurotoxin, is known to perform a role in the pathogenesis of Parkinson’s disease (PD). In this study, we evaluated oxidative modification of cytochrome c occurring after incubation with salsolinol. When cytochrome c was incubated with salsolinol, protein aggregation increased in a dosedependent manner. The formation of carbonyl compounds and the release of iron were obtained in salsolinol- treated cytochrome c. Salsolinol also led to the release of iron from cytochrome c. Reactive oxygen species (ROS) scavengers and iron specific chelator inhibited the salsolinol-mediated cytochrome c modification and carbonyl compound formation. It is suggested that oxidative damage of cytochrome c by salsolinol might induce the increase of iron content in cells, subsequently leading to the deleterious condition which was observed. This mechanism may, in part, provide an explanation for the deterioration of organs under neurodegenerative disorders such as PD. [BMB Reports 2013; 46(2): 119-123]

Oxidative modification of neurofilament-L and neuronal cell death induced by the catechol neurotoxin, tetrahydropapaveroline

Tetrahydropapaveroline (THP), which is an endogenous neurotoxin, has been suspected to be associated with dopaminergic neurotoxicity of l-DOPA. In this study, we examined oxidative modification of neurofilament-L (NF-L) and neuronal cell death induced by THP. When disassembled NF-L was incubated with THP, protein aggregation was increased in a time- and THP dose-dependent manner. The formation of carbonyl compounds and dityrosine were observed in the THP-mediated NF-L aggregates. Radical scavengers reduced THP-mediated NF-L modification. These results suggest that the modification of NF-L by THP may be due to oxidative damage resulting from the generation of reactive oxygen species (ROS). When THP exposed NF-L was subjected to amino acid analysis, glutamate, proline and lysine residues were found to be particularly sensitive. We also investigated the effects of copper ions on THP-mediated NF-L modification. At a low concentration of THP, copper ions enhanced the modification of NF-L. Treatment of C6 astrocyte cells with THP led to a concentration-dependent reduction in cell viability. When these cells were treated with 100μM THP, the levels of ROS increased 3.5-fold compared with control cells. Furthermore, treatment of cells with THP increased NF-L aggregate formation, suggesting the involvement of NF-L modification in THP-induced cell damage.

Differential effects of dopaminergic neurotoxins on DNA cleavage

AIMS

Environmental and endogenous toxins are considered to increase the risk of dopaminergic neurodegeneration. Parkinson's disease is a neurological disorder occurring due to the death of dopaminergic neurons in substantia nigra. The present study investigated the effect of parkinsonian neurotoxins salsolinol and rotenone on plasmid and genomic DNA.

MAIN METHODS

Salsolinol or rotenone (0-1000 μM) alone or in presence of divalent metals (copper or iron) was incubated with plasmid DNA pBR322 (1 μg) or calf thymus DNA (1 μg). In order to study their effects on restriction endonuclease sites, the plasmid DNA was incubated with the neurotoxins (salsolinol or rotenone), extracted and subjected to restriction enzyme digestion (BamHI, EcoRV, HindIII, SalI).

KEY FINDINGS

Exposure of rotenone or salsolinol alone to the plasmid or calf thymus DNA did not induce any strand scission or damage. However, salsolinol in the presence of divalent copper induced strand scission and damage in both plasmid and genomic DNA. All of the tested restriction endonucleases linearized the plasmid DNA pre-treated with salsolinol or rotenone suggesting that these neurotoxins did not selectively damage the restriction enzyme sites in the DNA.

SIGNIFICANCE

The above observations suggest that salsolinol and rotenone differentially interact with DNA in inducing damage in the presence of copper, and behave similarly in their binding to DNA by not damaging the selected restriction endonuclease cleavage sites.

CONCLUSION

Risk for neuronal degeneration can be significantly augmented by the environmental and endogenous toxins in the presence of various metals due to their deleterious effects on DNA.

Salsolinol, a catechol neurotoxin, induces modification of ferritin: Protection by histidine dipeptide

1-Methyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline (salsolinol), an endogenous neurotoxin present in the mammalian brain, is known to perform a role in the pathogenesis of Parkinson's disease. In this study, we evaluated oxidative modifications of ferritin occurring after incubation with salsolinol. When ferritin was incubated with salsolinol, protein aggregation increased in a time-dependent manner. Free radical scavengers inhibited this salsolinol-mediated ferritin modification. The exposure of ferritin to salsolinol also results in the generation of protein carbonyl compounds and the formation of dityrosine. The results of this study show that free radicals may perform a pivotal role in salsolinol-mediated ferritin modification. Histidine dipeptides, such as carnosine, have been proposed to function as antioxidant agents in vivo. In this study, we also attempted to determine whether the histidine dipeptides, carnosine and N-acetyl-carnosine, could prevent salsolinol-mediated oxidative modification of ferritin. Our results showed that both carnosine and N-acetyl-carnosine significantly reduced ferritin aggregation. Both compounds effectively inhibited the formation of both carbonyl compounds and dityrosine. These results suggest that carnosine derivatives can, indeed, protect against salsolinol-mediated ferritin modification, as the consequence of free radical-scavenging activity.

Salsolinol, a tetrahydroisoquinoline catechol neurotoxin, induces human Cu,Zn-superoxidie dismutase modificaiton

The endogenous neurotoxin, 1-methyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline (salsolinol), has been considered a potential causative factor for the pathogenesis of Parkinsonos disease (PD). In the present study, we examined the pattern of human Cu,Zn-superoxide dismutase (SOD) modification elicited by salsolinol. When Cu,Zn-SOD was incubated with salsolinol, some protein fragmentation and some higher molecular weight aggregates were occurred. Salsolinol led to inactivation of Cu,Zn-SOD in a concentration-dependent manner. Free radical scavengers and catalase inhibited the salsolinolmediated Cu,Zn-SOD modificaiton. Exposure of Cu,Zn-SOD to salsolinol led also to the generation of protein carbonyl compounds. The deoxyribose assay showed that hydroxyl radicals were generated during the oxidation of salsolinol in the presence of Cu,Zn-SOD. Therefore, the results indicate that free radical may play a role in the modification and inactivation of Cu,Zn-SOD by salsolinol.

1-Benzyl-1,2,3,4-tetrahydroisoquinoline passes through the blood–brain barrier of rat brain: An in vivo microdialysis study

Previous work has established that 1-benzyl-1,2,3,4-tetrahydroisoquinoline (1-BnTIQ) causes a parkinsonian syndrome in rats. The present study reports the blood-brain barrier (BBB) permeability of 1-BnTIQ in freely moving rats with the aid of in vivo microdialysis-based measurements. The microdialysis probe was implanted in the frontal cortex of rat brain. Brain dialysate samples were analyzed using an HPLC-MS/MS assay. 1-BnTIQ, when administered i.p., dose-dependently appeared in brain extracellular fluid (ECF), reaching a maximum concentration after about 40 min. Two other tetrahydroisoquinoline derivatives, 1,2,3,4-tetrahydroisoquinoline (TIQ) and 6,7-dihydroxy-1-methyl-1,2,3,4-tetrahydroisoquinoline [salsolinol (SAL)], served as positive and negative controls, respectively. The results confirmed an earlier report that SAL does not reach the brain after i.p. administration. In contrast, TIQ readily passed through the BBB. The brain dialysate concentration of 1-BnTIQ was about 24% that of TIQ when administered i.p. at the same dose. Both of them decreased quickly with a half-life of about 50 min.

Chiral CE Separation of Dopamine-Derived Neurotoxins

An enantiomeric separation of dopamine-derived neurotoxins by capillary electrophoresis has been developed. Tetrahydroisoquinoline (TIQ), dopamine (DA), (R/S)-1-benzyl-TIQ (BTIQ), (R/S)-6,7-dihydroxy-1-methyl-TIQ (salsolinol, Sal), and (R/S)-6,7-dihydroxy-1, 2-dimethyl-TIQ (N-methyl-salsolinol, NMSal) were studied as model compounds. The CE running buffer (50 mM phosphate buffer at pH 3.0) contained 1.5 M urea and 12 mM beta-CD as a chiral selector. During separation, the (R)-enantiomers formed more stable inclusion complexes with beta-CD, and thus had a longer migration time than their optical antipodes. It was noticed that the recovery rates of these TIQ derivatives were very poor (< 15%) during protein precipitation, a procedure widely used for cleaning up biological samples. The recovery was significantly improved by pre-mixing the sample with a surfactant (e.g., sodium hexanesulfonate or Triton X-100) to reduce the co-precipitation. The present method in combination with electrospray ionization tandem mass spectrometry (ESI-MS/MS) was applied to study samples obtained from in vitro incubation of two catecholamines, dopamine and epinine, with aldehydes forming neurotoxins including (S)- and (R)-NMSal enantiomers. The later is known to induce Parkinsonism in rats.

2-Hydroxyestradiol induces oxidative DNA damage and apoptosis in human mammary epithelial cells

Catechol estrogens, the hydroxylated metabolites of 17beta-estradiol (E2), have been considered to be implicated in estrogen-induced carcinogenesis. 2-Hydroxyestradiol (2-OHE2), a major oxidized metabolite of E2 formed preferentially by cytochrome P-450 1A1, reacts with DNA to form stable adducts and exerts genotoxicity. 2-OHE2 can be oxidized to quinone, which is accompanied by generation of reactive oxygen species (ROS). In the present study, 2-OHE2 induced strand scission in phiX174 phage DNA and oxidative base modifications in calf thymus DNA in the presence of cupric ion. In cultured human mammary epithelial (MCF-10A) cells, 2-OHE2 treatment produced ROS accumulation, 8-oxo-7,8-dihydroxy-2'-deoxyguanosine formation, cytotoxicity, and disruption of mitochondrial transmembrane potential, all of which were prevented by N-acetylcysteine. These findings, taken together, suggest that 2-OHE2-induced oxidative DNA damage and apoptosis in MCF-10A cells might be mediated by ROS generated via the redox cycling of this catechol estrogen.

Salsolinol, a dopamine-derived tetrahydroisoquinoline, induces cell death by causing oxidative stress in dopaminergic SH-SY5Y cells, and the said effect is attenuated by metallothionein

The endogenous neurotoxin, 1-methyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline (salsolinol), has been considered a potential neurotoxin in the etiology of Parkinson's disease (PD). Salsolinol and N-methyl(R)-salsolinol were identified in the brains and cerebrospinal fluid (CSF) of PD patients. Oxidative stress is known to be one of the major contributing factors in the cascade that may finally leads to the cell death in PD. The present study was undertaken to understand the role of salsolinol in oxidative-mediated neuronal toxicity in dopaminergic SH-SY5Y cells, and the neuroprotective effects of metallothionein (MT) against salsolinol toxicity in MT overexpressing (MT(trans)) fetal mesencephalic cells. Salsolinol increased the production of reactive oxygen species (ROS) and significantly decreased glutathione (GSH) levels and cell viability in SH-SY5Y cells. Salsolinol also decreased intracellular ATP levels and induced nuclear condensation in these cells. Salsolinol-induced depletion in cell viability was completely prevented by N-acetylcysteine in SH-SY5Y cells, and also prevented by MT in MT(trans) fetal mesencephalic cells compared to control(wt) cells. The extent of nuclear condensation and caspase activation was also less in MT(trans) cells than control(wt) cells. These results suggest that salsolinol causes oxidative stress by decreasing the levels of GSH and by increasing ROS production, and these events may lead to the death of dopaminergic cell. Furthermore, MT overexpression may protect dopaminergic neurons against salsolinol-induced neurotoxicity, most probably by the inhibition of oxidative stress and apoptotic pathways including caspase-3 activation.

Brain sites of movement disorder: genetic and environmental agents in neurodevelopmental perturbations

In assessing and assimilating the neurodevelopmental basis of the so-called movement disorders it is probably useful to establish certain concepts that will modulate both the variation and selection of affliction, mechanisms-processes and diversity of disease states. Both genetic, developmental and degenerative aberrations are to be encompassed within such an approach, as well as all deviations from the necessary components of behaviour that are generally understood to incorporate "normal" functioning. In the present treatise, both conditions of hyperactivity/hypoactivity, akinesia and bradykinesia together with a constellation of other symptoms and syndromes are considered in conjunction with the neuropharmacological and brain morphological alterations that may or may not accompany them, e.g. following neonatal denervation. As a case in point, the neuroanatomical and neurochemical points of interaction in Attention Deficit and Hyperactivity disorder (ADHD) are examined with reference to both the perinatal metallic and organic environment and genetic backgrounds. The role of apoptosis, as opposed to necrosis, in cell death during brain development necessitates careful considerations of the current explosion of evidence for brain nerve growth factors, neurotrophins and cytokines, and the processes regulating their appearance, release and fate. Some of these processes may possess putative inherited characteristics, like alpha-synuclein, others may to greater or lesser extents be endogenous or semi-endogenous (in food), like the tetrahydroisoquinolines, others exogenous until inhaled or injested through environmental accident, like heavy metals, e.g. mercury. Another central concept of neurodevelopment is cellular plasticity, thereby underlining the essential involvement of glutamate systems and N-methyl-D-aspartate receptor configurations. Finally, an essential assimilation of brain development in disease must delineate the relative merits of inherited as opposed to environmental risks not only for the commonly-regarded movement disorders, like Parkinson's disease, Huntington's disease and epilepsy, but also for afflictions bearing strong elements of psychosocial tragedy, like ADHD, autism and Savantism.