Androgen receptor signaling protects male mice from the development of immune response to peanut.

Am J Clin Exp Immunol 2023;12(4):60-71 www.ajcei.us /ISSN:2164-7712/AJCEI0150900 Original Article Androgen receptor signaling protects male mice from the development of immune response to peanut Sunanda Rajput*, McKenna S Vininski*, Leigh-Anne Lehmann, Nicholas J Hobbs, Joseph J Dolence Department of Biology, University of Nebraska at Kearney, Kearney, NE, USA. *Equal contributors. Received April 24, 2023; Accepted July 9, 2023; Epub August 20, 2023; Published August 30, 2023 Abstract: Objectives: Peanut (PN) allergy is a major public health concern. Recent research has brought clarity about how individuals become sensitized to PN allergen with routes known through the skin, as well as the airway. Still unclear, however, is the role of sex hormones on the development of allergic immune responses to PN. This study examines the role of androgen receptor (AR) signaling in regulating PN-specific immune responses. Methods: We utilized a 4-week inhalation mouse model of PN allergy that is known to drive the production of PN-specific antibodies and elicit systemic anaphylaxis following PN challenge. Wildtype (WT) male, female, and androgen receptor-deficient testicular feminization mutant (ARTfm) male mice were examined using this model to document sex differences in PN allergy. To determine if sex differences also existed in the cellular immune response, this study utilized a 3-day inhalation mouse model of PN to examine the response of group 2 innate lymphoid cells (ILC2s). WT male and female mice were examined using this model to document sex differences in ILC2 response within the lungs. Results: AR use is critical in regulating PN-specific antibody levels. We found that ARTfm males have a higher antibody response and significantly worse anaphylactic response following PN challenge relative to WT males. WT males also exhibit a less severe anaphylactic response compared to ARTfm male and female mice. Lastly, we discovered that lung ILC2s from female mice respond more robustly to PN compared to ILC2s within WT male mice. Conclusions: Taken together, this study suggests that male sex hormones, namely androgens, negatively regulate allergic immune responses to PN. Keywords: Peanut (PN) allergy, androgen receptor, ARTfm (androgen receptor-deficient) male, PN-specific antibodies, systemic anaphylaxis, group 2 innate lymphoid cells (ILC2s) Introduction Peanut (PN) allergy is a major medical problem as it remains one of the most common, severe, and persistent food allergies, and its prevalence is increasing rapidly [1-6]. Although progress has been made in the last decade to better understand PN allergy, our knowledge of the immunological mechanisms involved in the initial development of the disease remains incomplete. Specifically, how sex hormones regulate the immune pathways associated with the development of PN allergy is unknown. An examination of food allergies revealed that under the age of 18, males are almost twice as likely to have a food allergy compared to females [7]. In adulthood, however, the ratio dramatically shifts as females are more likely to have a food allergy (female to male ratio of 1:0.53) [8]. Post-menopause, males and females appear evenly impacted [7]. The sex reversals during puberty and following menopause suggest that sex hormones impact the development of food allergy [7, 8]. PN allergy also displays a clinical sex bias. An analysis of US adults allergic to PN showed that female adults were twice as likely to develop PN allergy during their childhoods than males [9]. The twofold difference favoring females with PN allergy was maintained into adulthood in the US and Mexico [9, 10]. Collectively, these data strongly suggest that allergic reactions to foods like PN are sensitive to sex hormones and that studying the immune mechanisms impacted by sex hormones are clinically relevant. Recent clinical trials have provided strong evidence that eating PN early in life allows the development of an oral tolerance that protects children from developing allergic responses to Androgens protect against peanut allergy PN [11, 12]. Studies using mouse models and human cell-based systems have shown that sensitization to PN via the airways is a likely route of sensitization [13]. PN is commonly found in household dust and is biologically active [14-16]. We were the first to show that PN exposure through the airways elicited PN sensitization in mice, and upon PN challenge, anaphylaxis occurs [17]. While we discuss in greater detail the known mechanisms of peanut allergy in a recent review [18], we and others showed that following inhalation of PN, IL-1α stimulates type 2 innate lymphoid cells (ILC2s) to secrete IL-13 to activate dendritic cells (DCs) that work to trigger a T follicular helper (Tfh) cell-mediated, PN-specific IgE antibody response that sensitizes the mice [17, 19]. Of note, a recent study showed that sensitization to PN via the airways can be inhibited by oral exposure to PN prior to inhalation [20]. The significance of these discoveries is that for the first time in an animal model, sensitization via inhalation of PN was reported and this sensitization can be blocked by oral tolerance, mirroring what was observed in the Learning Early About Peanut Allergy study [11, 12]. Sex hormones have been shown to modulate airway inflammation. Estrogen has been shown in multiple studies to drive airway inflammation (reviewed in 22), while testosterone was shown to reduce airway inflammation in murine models of airway inflammation. Interestingly, this decrease was linked to the ability of testosterone to negatively regulate group 2 innate lymphoid cells (ILC2s), as well as stabilizing the suppressive function of T regulatory cells [2125]. Knowledge about how sex hormones influence the development of allergic immune responses to PN initiated within the airways remains unclear. The goal of this study was twofold. First, we wanted to document whether androgens impact the development of PN allergy. Second, we examined how androgens impact allergic immune responses to PN. To accomplish this, we exposed WT male, WT female, and androgen receptor-deficient testicular feminization mutant (ARTfm) male mice, to PN using established inhalation models [17, 19]. ARTfm male mice lack both functional ARs and the ability to produce endogenous testosterone [26-28]. To assess whether differences existed in the ability of the mice to become sen- 61 sitized to PN, plasma was examined for the presence of PN-specific antibodies and mice were challenged with PN to induce systemic anaphylaxis. Using these methods, we identified that WT female and ARTfm male mice developed worse PN-induced anaphylactic reactions and that ARTfm males developed higher PNspecific antibody responses than WT mice. We also investigated the response of ILC2s in the lungs of mice exposed to PN. We found that the ILC2 response in female mice is more robust than their male counterparts. These data suggest t (...truncated)