Dual effects of S-adenosyl-methyonine on PC12 cells exposed to the dopaminergic neurotoxin MPP.

OBJECTIVES: To investigate S-adenosyl-methyonine (SAM) effects on PC12 cells viability and neuritogenesis treated with MPP+ (1-methyl-4-phenylpyridinium). METHODS: PC12 cell viability test (MTT assay) in DMEM medium with SAM and/or MPP+; PC12 cell neuritogenesis test in F-12K medium with nerve growth factor (NGF); DNMT activity in PC12 cells (DNMT Activity Assay Kit) with SAM and/or MPP+. KEY FINDINGS: (1) MPP+ decreased cell viability; (2) SAM did not affect cell viability per se, but it increased MPP+ neurotoxicity when co-incubated with the neurotoxin, an effect abolished by DNA methyltransferases (DNMT) inhibitors; (3) pretreatment with SAM for 30 min or 24 h before MPP+ addition had no effect on cell viability. Neuritogenesis: Treatment with SAM for 30 min or 24 h (1) increased cell differentiation per se, (2) increased NGF differentiating effects (additive effect) and (3) blocked the neuritogenesis impairment induced by MPP+. SAM with MPP+ increased the DNMT activity, whereas SAM alone or MPP+ alone did not. CONCLUSIONS: (1) SAM might induce neurotoxic or neuroprotective effects on PC12 cells, depending on the exposure conditions; (2) DNMT inhibitors might attenuate the MPP+ exacerbation toxicity induced by SAM; (3) DNA methylation might be involved in the observed effects of SAM (needs further investigation).

The Antidiabetic Drug Liraglutide Minimizes the Non-Cholinergic Neurotoxicity of the Pesticide Mipafox in SH-SY5Y Cells.

Organophosphorus (OPs) compounds have been widely used in agriculture, industry, and household, and the neurotoxicity induced by them is still a cause of concern. The main toxic mechanism of OPs is the inhibition of acetylcholinesterase (AChE); however, the delayed neuropathy induced by OPs (OPIDN) is mediated by other mechanisms such as the irreversible inhibition of 70% of NTE activity (neuropathy target esterase) that leads to axonal degeneration. Liraglutide is a long-lasting GLP-1 analog clinically used as antidiabetic. Its neurotrophic and neuroprotective effects have been demonstrated in vitro and in experimental models of neurodegenerative diseases. As in OPIDN, axonal degeneration also plays a role in neurodegenerative diseases. Therefore, this study investigated the protective potential of liraglutide against the neurotoxicity of OPs by using mipafox as a neuropathic agent (at a concentration able to inhibit and age 70% of NTE activity) and a neuronal model with SH-SY5Y neuroblastoma cells, which express both esterases. Liraglutide protected cells against the neurotoxicity of mipafox by increasing neuritogenesis, the uptake of glucose, the levels of cytoskeleton proteins, and synaptic-plasticity modulators, besides decreasing the pro-inflammatory cytokine interleukin 1ß and caspase-3 activity. This is the first study to suggest that liraglutide might induce beneficial effects against the delayed, non-cholinergic neurotoxicity of OPs.

L- and T-type calcium channel blockers protect against the inhibitory effects of mipafox on neurite outgrowth and plasticity-related proteins in SH-SY5Y cells.

Some organophosphorus compounds (OP), including the pesticide mipafox, produce late onset distal axonal degeneration, known as organophosphorus-induced delayed neuropathy (OPIDN). The underlying mechanism involves irreversible inhibition of neuropathy target esterase (NTE) activity, elevated intracellular calcium levels, increased activity of calcium-activated proteases and impaired neuritogenesis. Voltage-gated calcium channels (VGCC) appear to play a role in several neurologic disorders, including OPIDN. Therefore, this study aimed to examine and compare the neuroprotective effects of T-type (amiloride) and L-type (nimodipine) VGCC blockers induced by the inhibitory actions of mipafox on neurite outgrowth and axonal proteins of retinoic-acid-stimulated SH-SY5Y human neuroblastoma cells, a neuronal model widely employed to determine the neurotoxicity attributed to OP. Both nimodipine and amiloride significantly blocked augmentation of intracellular calcium levels and activity of calpains, as well as decreased neurite length, number of differentiated cells, and lowered concentrations of growth-associated protein 43 (GAP-43) and synapsin induced by mipafox. Only nimodipine inhibited reduction of synaptophysin levels produced by mipafox. These findings demonstrate a role for calcium and VGCC in the impairment of neuronal plasticity mediated by mipafox. Data also demonstrated the neuroprotective potential of T-type and L-type VGCC blockers to inhibit OP-mediated actions, which may be beneficial to counteract cases of pesticide poisoning.

In vitro study of the neuropathic potential of the organophosphorus compounds trichlorfon and acephate.

Organophosphorus-induced delayed neuropathy (OPIDN) is a central and peripheral distal axonopathy characterized by ataxia and paralysis. Trichlorfon and acephate are two organophosphorus compounds (OPs) used worldwide as insecticide and which cause serious effects to non-target species. Despite that, the neuropathic potential of these OPs remains unclear. The present study addressed the neurotoxic effects and the neuropathic potential of trichlorfon and acephate in SH-SY5Y human neuroblastoma cells, by evaluating inhibition and aging of neuropathy target esterase (NTE), inhibition of acetylcholinesterase (AChE), neurite outgrowth, cytotoxicity and intracellular calcium. Additionally, the effects observed were compared to those of two well-studied OPs: mipafox (known as neuropathic) and paraoxon (known as non-neuropathic). Trichlorfon and mipafox presented the lowest percentage of reactivation of inhibited NTE and the lowest ratio IC50 NTE/IC50 AChE. Moreover, they caused inhibition and aging of at least 70% of the activity of NTE at sub-lethal concentrations. All these effects have been associated with induction of OPIDN. When assayed at these concentrations, trichlorfon and mipafox reduced neurite outgrowth and increased intracellular calcium, events implicated in the development of OPIDN. Acephate caused effects similar to those caused by paraoxon (non-neuropathic OP) and was only able to inhibit 70% of NTE activity at lethal concentrations. These findings suggest that trichlorfon is potentially neuropathic, whereas acephate is not.