Endocrine Abstracts

Phthalates are man-made chemicals that are used in many different types of products. The main use is as plasticizers, but they can also be added to, for example, cosmetics, drug coatings, and perfumes. One of the most commonly used phthalates is di-butyl phthalate (DBP), which has been detected in both food and drinking water globally. Once ingested, DBP is rapidly metabolized to its main metabolite, mono-butyl phthalate (MBP), which is frequently detected in human plasma and urine. Studies suggest that DBP has anti-androgenic potential and that it can induce reproductive and developmental effects. However, the molecular mechanisms behind these effects are unknown. We used the human adrenocortical cell line H295R to investigate how DBP and MBP may affect steroid hormone synthesis. After 48-h exposure, samples were collected and the supernatant analyzed by mass spectrometry and cell pellet by western blot to measure the levels of several steroid hormones and key steroidogenic enzymes, respectively. The results demonstrated that DBP induced a dose-dependent decrease in testosterone levels, and a similar decrease was detected for the precursor androstenedione. The corticosterone level also decreased after DBP-exposure, while cortisol increased. MBP induced similar effects as DBP, but with a lower effect size. However, MBP-exposure caused a decrease in cortisol, thereby indicating that there are differences in the mechanism of action between the two compounds. In addition, it was discovered that the decreases in steroid hormone levels are potentiated when the cells are co-treated with dibuturyl-cyclicAMP, which mimics endogenous stimulation of adrenal cells by adrenocorticotropic hormone to increase production of steroid hormones. The results also revealed that the levels of several steroidogenic enzymes were altered, with similar differences between MBP and DBP exposure as for the hormone concentrations. To conclude, these findings suggest that MBP is less potent than its parent compound, that the effects of phthalate exposure on the steroidogenesis are more profound during stimulation, and that both compounds affect steroid hormone production by alterations to the steroidogenic enzymes.