Bisphenol A Diglycidyl Ether (BADGE) and Bisphenol Analogs, but Not Bisphenol A (BPA), Activate the CatSper Ca2+ Channel in Human Sperm

Abstract

Aim: Evidence suggests that bisphenol A diglycidyl ether (BADGE), bisphenol A (BPA), and BPA analogs can interfere with human male fertility. However, the effect directly on human sperm function is not known. The CatSper Ca 2+ channel in human sperm controls important sperm functions and is necessary for normal male fertility. Environmental chemicals have been shown to activate CatSper and thereby affect Ca 2+ signaling in human sperm. BPA has previously been investigated for effects on Ca 2+ signaling human sperm, whereas the effects of other BPA analogs are currently unknown. The aim of this study is thus to characterize the effect of BADGE, BPA, and the eight analogs BPG, BPAF, BPC, BPB, BPBP, BPE, BPF, BPS on Ca 2+ signaling, and CatSper in human sperm. Methods: Direct effects of the bisphenols on Ca 2+ signaling in human sperm cells were evaluated using a Ca 2+ fluorimetric assay measuring changes in intracellular Ca 2+. Effects via CatSper were assessed using the specific CatSper inhibitor RU1968. Effects on human sperm function was assessed using an image cytometry-based acrosome reaction assay and the modified Kremer's sperm-mucus penetration assay. Results: At 10 µM the bisphenols BPG, BPAF, BPC, BADGE, BPB, and BPBP induced Ca 2+ signals in human sperm cells, whereas BPE, BPF, BPS, and BPA had no effect. The efficacy of the chemicals at 10 µM is BPG > BPAF > BPC > BADGE > BPB > BPBP. Dose-response relations of BPG, BPAF, BPC, BADGE, BPB, and BPBP yielded EC50-values in the nM-µM range. The induced Ca 2+ signals were almost completely abolished using the CatSper inhibitor RU1968, indicating an effect of the bisphenols on CatSper. All bisphenols, except BPBP, were found to dose-dependently inhibit progesterone-induced Ca 2+ signals, with BPG and BPAF displaying inhibition even in low µM doses. BPG and BPAF were shown to affect human sperm function in a progesterone-like manner. Rehfeld et al. Bisphenols Activate Human CatSper Conclusion: Our results show that the bisphenols BPG, BPAF, BPC, BADGE, BPB, and BPBP can affect Ca 2+ signaling in human sperm cells through activation of CatSper. This could potentially disrupt human sperm function by interfering with normal CatSpersignaling and thus be a contributing factor in human infertility, either alone or in mixtures with other chemicals.

Bisphenol A Diglycidyl Ether (BADGE) and Progesterone Do Not Induce Ca2+ Signals in Boar Sperm Cells

“…In line with this, the very large Ca 2+ signal induced by the Ca 2+ -ionophores ionomycin ( Figure 1 ) and A23187 ( Figure 2 ) indicates that, at the moment of adding the ionophones to the sperm cells, a large proportion of the sperm cells must have been viable, as unviable sperm cells cannot maintain their Ca 2+ gradient across the cell membrane. Our findings therefore do not support our hypothesis that exposure of boar sperm cells to BADGE leads to reproductive failure in sows ( Nerin et al, 2014 ) through an effect on Ca 2+ signaling in boar sperm cells, similar to the effect that we have recently shown for BADGE on human sperm cells ( Rehfeld et al, 2020 ).…”

“…Intriguingly, no effects were found on routine boar sperm parameters, including motility and viability, or on in vitro fertilization tests, but only on in vivo fertility rates in sows ( Nerin et al, 2014 ). We speculated that the reproductive failure could be due to effects on Ca 2+ signaling through an action on CatSper in the boar sperm cells, as CatSper has been shown to be expressed in boar sperm cells ( Song et al, 2011 ; Vicente-Carrillo et al, 2017 ), has been suggested to be functional through the use of CatSper-inhibitors ( Vicente-Carrillo et al, 2017 ; Machado et al, 2019 ), and as we have recently found that BADGE in μM concentrations can interfere with Ca 2+ signaling through an action on CatSper in human sperm cells ( Rehfeld et al, 2020 ). Our results here, however, showed that addition of the exact same solutions of BADGE to the sperm cells, induced transient biphasic Ca 2+ signals in the human sperm cells, but failed to do so both in non-capacitated and capacitated boar sperm cells ( n ≥ 3) ( Figure 1 ), similar to after addition of 5 μM progesterone.…”

“…Recently, a study found that BADGE could leach from plastic bags used for storage of boar semen and that exposure of boar sperm cells to BADGE led to reproductive failure in sows ( Nerin et al, 2014 ), however, without any clear mode of action identified. As we have shown that BADGE in μM concentrations can induce transient biphasic Ca 2+ signals via an activation of CatSper in human sperm cells ( Rehfeld et al, 2020 ), we hypothesized that a similar mechanism in the boar sperm cells could be responsible for the reproductive failure in sows. Here we set out to test this hypothesis, by investigating whether BADGE could interfere with Ca 2+ signaling in boar sperm cells through an examination of the effect of both BADGE and the endogenous ligand of human CatSper, progesterone, on human and boar sperm cells side-by-side using a Ca 2+ fluorimetric assay.…”

Bisphenol A and Its Analogues Deteriorate the Hormones Physiological Function of the Male Reproductive System: A Mini-Review

“…Furthermore, these chemicals also have the ability to disturb gene expression, such as Kiss1 and CYP19A1, which are involved in the HPG axis and steroidogenesis, respectively [ 63 ]. Recently, the effects of BPA and its analogues on these three significant pathways, in the form of the HPG axis [ 56 , 59 , 62 , 64 , 65 , 66 , 67 , 68 , 69 , 70 , 71 , 72 , 73 , 74 , 75 , 76 , 77 ], steroidogenesis [ 55 , 56 , 59 , 64 , 65 , 66 , 67 , 68 , 69 , 70 , 74 , 75 , 76 , 77 , 78 , 79 ], and spermatogenesis outcomes [ 64 , 65 , 66 , 67 , 68 , 69 , 70 , 75 , 76 , 77 , 80 , 81 , 82 , 83 , 84 , 85 ]...…”

Evaluation of a panel of spermatological methods for assessing reprotoxic compounds in multilayer semen plastic bags

“…The results obtained in the present study could help to understand the interaction of potentially toxic compounds with spermatozoa, as seen by other authors 25,26 . For example, in human sperm, BADGE may lead to an activation of specific Ca 2+ channels (CatSper) 27 that could influence important sperm functions.…”