Evidence for a Novel Endocrine Disruptor: The Pesticide Propanil Requires the Ovaries and Steroid Synthesis to Enhance Humoral Immunity

Abstract

Steroid hormones are known to affect the humoral immune response to a variety of antigens. However, the mechanisms regulating these effects are poorly understood. The immunotoxic chemical propanil and estrogen have similar effects on the immune system including augmentation of humoral immune responses. Propanil enhances the number of phosphorylcholine (PC)-specific IgG2b, IgG3, and IgM antibody-secreting cells (ASCs) in the spleen four- to sixfold 7 days after vaccination of female C57BL/6 mice with heat-killed Streptococcus pneumoniae. Several experiments were performed to test the hypothesis that propanil increases the response via an estrogenic pathway. Ovariectomy abrogated the effect of propanil on the PC-specific ASC response. Both in vitro and in vivo assays indicate that propanil does not bind either estrogen receptor (ER) alpha or beta. Exogenous estradiol administration in ovariectomized mice failed to restore the effect of propanil on the PC response. Treatment of female mice with a pure ER antagonist, ICI 182,780, or the progesterone antagonist RU486 did not inhibit the increase in ASCs. These data suggest that estrogen and progesterone do not regulate the effect of propanil. However, complete inhibition of steroid synthesis with the gonadotropin-releasing hormone (GnRH) antagonist antide abrogated the increased response in propanil-treated mice, indicating a necessary role for steroid synthesis. Experiments in male mice demonstrated that propanil increased the number of ASCs comparable to female mice. However, orchiectomy did not inhibit this effect, suggesting that androgens do not regulate the amplification of the humoral response. These data suggest a novel role for the ovarian hormones in the regulation of the PC-specific antibody response.

The XX Sex Chromosome Complement is Required in Male and Female Mice for Enhancement of Immunity Induced by Exposure to 3,4‐Dichloropropionanilide

“…A preliminary experiment demonstrated that propanil exposure in XY male C57BL/6J mice did not enhance the immune response to HKSP, similar to the results with the XYM FCG mice. XX female C57BL/6J mice had an enhanced immune response after exposure to propanil that was comparable to previous results in Hilltop female mice that was dependent on the ovaries (data not shown and reference 28). Additional studies are necessary to determine if C57BL/6 substrains from different colonies have developed subtle differences in the Y chromosome that affect their responses.…”

“…The first was that XXF females, in contrast to previous studies using wild type C57BL/6 XX females 28 , did not require the ovaries for the enhanced response induced by exposure to propanil. The second was that exposure to propanil did not enhance the immune response in either the XYF or XYM mice, in contrast to wild type C57BL/6 XY males ( 28 and Figure 2). Interestingly, a study on juvenile social behavior also demonstrated that the differences in behavior were different in FCG mice compared to C57BL/6 mice 37 .…”

“…Previous studies demonstrated that propanil acts as a novel endocrine disrupter to enhance the immune response to HKSP vaccination in C57BL/6 female and male mice and that the ovaries were required for the enhanced response in females, but the testes were not required in males 28 . Although gonadal hormones are known to influence immune responses, the effect of propanil was not influenced by treatment of females with estrogen or progesterone agonists, or by manipulations of levels of androgens by castration of males 28 .…”

“…HKSP elicits a robust antibody response to the immunodominant T-independent type 2 polysaccharide phosphorylcholine (PC) 27 . When propanil is administered to mice simultaneously with HKSP, the number of splenic antibody secreting cells (ASC) specific for PC is increased significantly over controls 28 . Interestingly, the increased response in females is primarily dependent on the ovaries, while the testes are not required for the enhanced response in males.…”

Development of novel IC-ELISA as a primary high throughput screening for various estrogen molecules

“…Upon the exposure to humans or animals, they may alter the hormone systems and disrupt their physiological functions [8][9][10] , such as, the decline of reproductive functions in males, the increasing incidence of breast cancer in young women, the alterations of thyroid function, and neurobehavioral diseases. In general, wastewater treatment plants permanently receive complex mixture of industrial, domestic and agricultural wastewater containing lots of synthetic or natural chemical compounds and hormonally active agents [11][12][13][14] .…”