New Papers on Neuroendocrine and Reproductive Effects of PBDEs

Two new papers discuss how PBDE congeners can cross blood–placenta and blood–brain barriers, causing subtle changes in some parameters of neurobehavior, changes in circulating thyroid hormone levels, and changes in reproductive endpoints. Some of these effects appear to be irreversible. Please let Rebecca know if you would like a pdf of either of these papers.

1) Kodavanti PRS, Curras-Collazo MC (2010); Neuroendocrine actions of organohalogens: Thyroid hormones, arginine vasopressin, and neuroplasticity, Front. Neuroendocrinol. doi:10.1016/j.yfrne.2010.06.005
2) Karpeta A, Gregoraszczuk E (2010) Mixture of dominant PBDE congeners (BDE-47, -99, -100 and -209) at levels noted in human blood greatly enhances progesterone secretion by ovarian follicles. Endocr Regul 44(2):49-55

1) A new review by Kodavanti and Curras-Collazo discusses the body of literature on PBDEs in regard to their actions as neuroendocrine disruptors for the thyroid hormone and arginine vasopressin (AVP) systems.

Effects on Thyroid Hormones:
In vivo studies show reductions in serum T4 levels following exposure to PBDEs, both after acute and sub-acute exposure and after developmental exposure. PBDEs also interfere with TH receptor (TR) mediated TH signaling. The PBDE effects on TR would have physiological implications such as alterations in the development of neuronal cells.

Effects on AVP System:
-An important role of AVP is in several types of learned behaviors such as active or passive avoidance conditioning and social recognition. Several PBDE congeners have been shown to disrupt behavior when given to animals during development or adulthood. These effects include reduced learning and memory and reduced habituation and are similar to effects seen after AVP inactivation or receptor blockade.
-Penta-BDE congeners and mixtures have been shown to disrupt osmotically stimulated somatodendritic AVP secretion and have complementary effects on osmoregulatory outcomes. Such effects are shown over two years after exposure, suggesting that PBDE exposure during development produces permanent functional deficits within the hypothalamo-neurohypophysial system.

2) Karpeta and Gregoraszczuk recently evaluated the in vitro effect of the mixture of the four most abundant PBDE congeners (BDE-47, -99, -100, -209) on the secretion of gonad hormones by ovarian follicles in pigs.
-Short-term exposure increased secretion of all investigated steroids (progesterone, testosterone, and estradiol) was noted only with small dose.

-With longer-term exposure, stimulation of estradiol and testosterone secretion was observed with low and medium doses while increases in progesterone secretion were noted with low, medium, and high doses

-The increase of progesterone:testosterone ratio with a parallel decrease of testosterone:estradiol ratio was found suggesting preterm luteinization in antral follicles followed by the disruption of ovulation and it was not possible to reverse the steroidogenic effects of PBDEs mixture by removing reagents from the cell cultures.