Salsolinol, a naturally occurring tetrahydroisoquinoline alkaloid, induces DNA damage and chromosomal aberrations in cultured Chinese hamster lung fibroblast cells

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.

In vivo protective effect of Uridine, a pyrimidine nucleoside, on genotoxicity induced by Levodopa/Carbidopa in mice

Parkinson's disease (PD) is a common neurodegenerative disorder that affects millions of people all over the world. Motor symptoms of PD are most commonly controlled by L-3,4-dihydroxyphenylalanine (Levodopa, L-DOPA), a precursor of dopamine, plus a peripherally-acting aromatic-L-amino-acid decarboxylase (dopa decarboxylase) inhibitor, such as carbidopa. However, chronic treatment with a combination of Levodopa plus carbidopa has been demonstrated to cause a major complication, namely abnormal involuntary movements. On the other hand, the effect of this treatment on bone marrow cells is unknown. Therefore, in this study, we aimed to investigate possible genotoxic effects of Levodopa and Carbidopa using male Balb/C mice. Our results showed that Levodopa alone or in combination with carbidopa caused genotoxicity in in vivo micronucleus test (mouse bone marrow) and Comet assay (blood cells). Furthermore, we showed that simultaneous administration of uridine, a pyrimidine nucleoside, reversed the genotoxic effect of Levodopa and Carbidopa in both assays. Our data show for the first time that Levodopa plus carbidopa combination causes genotoxicity which is reversed by uridine treatment. These findings might enhance our understanding for the complications of a common Parkinson's treatment and confer benefit in terms of reducing a possible genotoxic effect of this treatment.

Haplophytin-A induces caspase-8-mediated apoptosis via the formation of death-inducing signaling complex in human promyelocytic leukemia HL-60 cells

Haplophytin-A (10-methoxy-2,2-dimethyl-2,6-dihydro-pyrano[3,2-c]quinolin-5-one), a novel quinoline alkaloid, was isolated from the Haplophyllum acutifolium. In this study, we investigated the effect of haplophytin-A on the apoptotic activity and the molecular mechanism of action in human promyelocytic leukemia HL-60 cells. Treatment with haplophytin-A (50μM) induced classical features of apoptosis, such as, DNA fragmentation, DNA ladder formation, and the externalization of annexin-V-targeted phosphatidylserine residues in HL-60 cells. In addition, haplophytin-A triggered the activations of caspase-8, -9, and -3, and the cleavage of poly (ADP-ribose) polymerase (PARP) in HL-60 cells. In addition, haplophytin-A caused the loss of mitochondrial membrane potential (ΔΨ(m)) and the release of cytochrome c and Smac/DIABLO to the cytosol, and modulated the expression levels of Bcl-2 family proteins. We further demonstrated that knockdown of caspase-8 using its siRNA inhibited the mitochondrial translocation of tBid, the activations of caspase-9 and caspase-3, and subsequent DNA fragmentation by haplophytin-A. Furthermore, haplophytin-A-induced the formation of death-inducing signaling complex (DISC) and then activated caspase-8 in HL-60 cells. During haplophytin-A-induced apoptosis, caspase-8-stimulated tBid provide a link between the death receptor-mediated extrinsic pathway and the mitochondria- mediated intrinsic pathway. Taken together, these results suggest that the novel compound haplophytin-A play therapeutical role for leukemia via the potent apoptotic activity through the extrinsic pathway, involving the intrinsic pathway.

Neurotoxins and neurotoxicity mechanisms. an overview

Neurotoxins represent unique chemical tools, providing a means to 1) gain insight into cellular mechanisms of apopotosis and necrosis, 2) achieve a morphological template for studies otherwise unattainable, 3) specifically produce a singular phenotype of denervation, and 4) provide the starting point to delve into processes and mechanisms of nerve regeneration and sprouting. There are many other notable uses of neurotoxins in neuroscience research, and ever more being discovered each year. The objective of this review paper is to highlight the broad areas of neuroscience in which neurotoxins and neurotoxicity mechanism come into play. This shifts the focus away from neurotoxins per se, and onto the major problems under study today. Neurotoxins broadly defined are used to explore neurodegenerative disorders, psychiatric disorders and substance use disorders. Neurotoxic mechanisms relating to protein aggregates are indigenous to Alzheimer disease, Parkinson's disease. NeuroAIDS is a disorder in which microglia and macrophages have enormous import. The gap between the immune system and nervous system has been bridged, as neuroinflammation is now considered to be part of the neurodegenerative process. Related mechanisms now arise in the process of neurogenesis. Accordingly, the entire spectrum of neuroscience is within the purview of neurotoxins and neurotoxicity mechanisms. Highlights on discoveries in the areas noted, and on selective neurotoxins, are included, mainly from the past 2 to 3 years.

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

A group of naturally occurring isoquinoline alkaloids have been detected in certain regions of mammalian brain. One such compound is salsolinol (SAL; 1-methyl-6, 7-dihydroxy-1,2,3,4-tetrahydroisoquinoline). This endogenous isoquinoline derivative has been considered to be implicated in the pathophysiology of chronic alcoholism and Parkinsonism. The present study deals with the DNA strand scission induced by SAL in the presence of iron. Incubation of phiX174 DNA with SAL and ferric ion led to conversion of the supercoiled DNA to open circular and linear forms, which was inhibited by the iron chelator deferoxamine, catalase, and scavengers of reactive oxygen species. SAL in combination with Fe(III) also produced 8-hydroxydeoxyguanosine in calf thymus DNA. Exposure of PC12 cells to SAL produced concentration-dependent reduction in viability, which was exacerbated by iron and ameliorated by deferoxamine.

Oxidative DNA damage and cytotoxicity induced by copper-stimulated redox cycling of salsolinol, a neurotoxic tetrahydroisoquinoline alkaloid

A series of neurotoxic tetrahydroisoquinoline alkaloids has been detected in certain regions of mammalian brains. One such dopaminergic tetrahydroisoquinoline neurotoxin is salsolinol (SAL), which is suspected of being associated with the etiology of Parkinson's disease and neuropathology of chronic alcoholism. In the present study, we found that SAL in combination with Cu(II) induced strand scission in pBR322 and phiX174 supercoiled DNA, which was inhibited by the copper chelator, reactive oxygen species (ROS) scavengers, reduced glutathione, and catalase. SAL in the presence of Cu(II) caused hydroxylation of salicylic acid to produce 2,3- and 2,5-dihydroxybenzoic acids. Reaction of calf thymus DNA with SAL plus Cu(II) resulted in substantial oxidative DNA damage as determined by 8-hydroxydeoxyguanosine (8-OH-dG) formation. Blockade of the dihydroxy functional group of SAL abolished its capability to yield 8-OH-dG in the presence of Cu(II). The dehydro analog of SAL, 1-methyl-6,7-dihydroxy-3,4-dihydroisoquinoline, produced significantly high levels of 8-OH-dG when incubated with calf thymus DNA, even in the absence of Cu(II), which appears to be attributable to the tautomer formation by this compound. In another experiment, SAL exerted cytotoxicity when treated to rat pheochromocytoma (PC12) cells. Based on these findings, it seems likely that SAL undergoes redox cycling in the presence of Cu(II) with concomitant production of ROS, particularly hydroxyl radical, which could contribute to DNA damaging and cytotoxic properties of this neurotoxin.