The Effect of Dichloronitrophenol on Amyloid Beta Toxicity and Steroid Levels

In Alzheimer's disease (AD), which is the most common cause of dementia, the accumulation of amyloid beta (AB) peptides has a causal role in the neurodegeneration process. AB peptides can induce synthesis of dehydroepiandrosterone (DHEA), which is a precursor of various steroids. Neurosteroids are modulators of neuronal survival and may have different effects depending on whether they are free or sulfa-conjugated. Nitrophenols can inhibit the aggregation of AB peptides at relatively low concentrations. 2,4-dichloro- 6-nitrophenol (DCNP) is a small water-soluble derivative of nitrophenols, and it is also known as the inhibitor of steroid sulfotransferase enzyme. However, the effects of DCNP on levels of distinct steroids and cell viability is not yet clearly known. This work aimed to investigate the effects of DCNP on various steroid levels and AB-induced cell death. SH-SY5Y cells were treated with DCNP (1 mu M) and aggregates of AB 1-42 peptides (10 mu M) for 72 hours. Cell viabilities were evaluated using MTT reduction and immune-fluorescence microscopy. The cellular changes of DHEA, DHEA sulfate, and sex steroids were determined using liquid chromatography-mass spectrometry (LC-MS/MS). The effect of DCNP on ultrastructure of AB aggregates was also examined with transmission electron microscopy. Seventy-two-hour treatment with DCNP significantly decreased DHEA sulfate and increased DHEA levels. Treatment with AB 1-42 aggregates decreased cell viability to approximately 50% and significantly changed DHEA and estradiol levels in SH-SY5Y cells. The ratio of cell death induced by AB 1-42 was reduced with DCNP treatment. When the AB aggregates were incubated in the aqueous solution with DCNP, the size of the aggregates became significantly smaller compared with the initial size. According to our literature knowledge, this is the first study to show the beneficial effects of DCNP on AB toxicity.