Neoechinulin A Protects PC12 Cells against MPP+-induced Cytotoxicity

Abstract

Neoechinulin A, an alkaloid from Eurotium rubrum, can protect neuronal PC12 cells against cytotoxicity of a potent oxidant, peroxynitrite. Because involvement of peroxynitrite has been suggested in the pathogenesis of Parkinson's disease, we assessed whether this alkaloid could also protect PC12 cells from the cytocidal action of 1-methyl-4-phenylpyridine (MPP ϩ ), a Parkinson's disease, which affects 0.1% of the population over the age of 40 years, is characterized by a progressive loss of dopaminergic neurons in the substantia nigra [3,4]. Currently, no cure is available that can impede neuronal cell death. Except for some inherited cases, causative factors for the vast majority of cases remain elusive. The environmental toxin hypothesis has gained attention since the identification of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), a by-product of illegal heroin synthesis, as a causative agent for an acute Parkinson's-like disorder among drug abusers [5]. In the brain, MPTP is oxidized to 1-methyl-4-phenylpyridine (MPP ϩ ; Fig. 1), which is then taken up by neurons of the substantia nigra via the dopamine transporter [3]. In cells, MPP ϩ accumulates in mitochondria and binds to complex I of the electron transport chain, resulting in the production of reactive oxygen species (ROS) by the organelle, a decline in ATP biosynthesis, and eventually the demise of the cells [6,7]. A few insecticides and herbicides that also target mitochondrial complex I have been demonstrated to induce Parkinsonism in animal models, supporting the role of environmental toxins in the neurodegeneration [4]. MPTP and MPP ϩ have been widely used in studies of Parkinson's disease in rodents and in cultured cells, respectively. As peroxynitrite has been suggested to be involved in the pathogenesis of Parkinson's disease as well as MPP ϩ cytotoxicity in animals and cultured cells [3,8,9], we

Neoechinulin A Impedes the Progression of Rotenone-Induced Cytotoxicity in PC12 Cells

“…Thus, the requirement of the simultaneous presence of the alkaloid with the neurotoxin for cytoprotection is consistent with the case of MPP ϩ -induced cytotoxicity. 16) These results suggest that antioxidant activity 14) and/or interaction of an unknown cellular target molecule with neoechinulin A plays a role in the cytoprotective action of neoechinulin A against rotenone.…”

“…In contrast to neoechinulin A, preechinulin showed no cytoprotection. The results demonstrate that in addition to MPP ϩ -induced cytotoxicity, 16) neoechinulin A is also effective against rotenone-induced cytotoxicity and that the presence of the C8/C9 double bond, which gives rise to a conjugated system across the indole moiety to the diketo- (A) Dependency of rotenone cytotoxicity on glucose availability in the culture medium. NGF-differentiated PC12 cells in 96-well plates were treated with the indicated concentrations of rotenone in either 50 ml or 100 ml of culture medium for 25 h, and viability was determined by the LDH assay.…”

“…[13][14][15] Subsequently, we found that neoechinulin A can also protect PC12 cells from MPP ϩ by ameliorating downstream lethal events resulting from mitochondrial complex I inactivation. 16) Although the cytoprotective mechanism of neoechinulin A remains unclear, it is probably not a single mechanism; while cytoprotection against SIN-1 can be afforded by pretreatment of cells with neoechinulin A at least for 12 h before SIN-1 challenge, 13) protection against MPP ϩ toxicity does not require pretreatment but its co-presence during the neurotoxin treatment. 16) The present study was aimed at clarifying the cytoprotective mechanism of neoechinulin A in mitochondrial dysfunction-induced cell death.…”

“…16) Although the cytoprotective mechanism of neoechinulin A remains unclear, it is probably not a single mechanism; while cytoprotection against SIN-1 can be afforded by pretreatment of cells with neoechinulin A at least for 12 h before SIN-1 challenge, 13) protection against MPP ϩ toxicity does not require pretreatment but its co-presence during the neurotoxin treatment. 16) The present study was aimed at clarifying the cytoprotective mechanism of neoechinulin A in mitochondrial dysfunction-induced cell death. By using rotenone, we demonstrate here that neoechinulin A can also protect PC12 cells from rotenone cytotoxicity while paradoxically lowering cellular ATP levels.…”

Neoechinulin A Imparts Resistance to Acute Nitrosative Stress in PC12 Cells: A Potential Link of an Elevated Cellular Reserve Capacity for Pyridine Nucleotide Redox Turnover with Cytoprotection

“…Previously, we found that the treatment of differentiated PC12 cells with neoechinulin A can render the cells resistant to oxidative/nitrosative stress derived from the superoxide (O 2 − ) and nitric oxide (NO) cogenerator 3-morpholinosydnonimine (SIN-1). 2,7,8) Subsequent studies also demonstrated that neoechinulin A can also impede the progression of PC12 cell death induced by 1-methyl-4-phenylpyridinium (MPP + ) 9) and rotenone, 10) both of which are well-established Parkinson disease-inducing neurotoxins. However, the cytoprotective mechanisms against SIN-1 and neurotoxins are probably different.…”