THE IMPACT OF THE NRF2 ACTIVATORS ARSENIC TRIOXIDE AND TERT BUTYLHYDROQUINONE ON B CELL FUNCTIONBy:Luca Marius KaiserB cells produce immunoglobulins and are essential for robust humoral host defense. B cell function is tightly regulated by interactions with other immune cells and antigens. B cells are subject to rapid clonal expansion and massive production of antibodies, which subjects them to oxidative stress. Many environmental toxicants, such as heavy metals and quinone-type food preservatives, are known to alter the function of other immune cells, such as T cells. The role of environmental toxicants on B cell function has received little investigation so far. Given the pivotal role of antibodies in the context of infection, autoimmunity, and allergy, it is gravely important to understand the impact environmental factors have on B cell function. The food additive tert-Butylhydroquinone and the heavy metal arsenic trioxide have been shown by our laboratory to alter T cell responses to infectious agents and alter cytokine production, partially due to the signaling of nuclear factor erythroid 2-related factor 2 (Nrf2). Due to the reciprocal relationship of B and T cells, this raises the question of the impact on B cell function. In these studies, we describe the impact of the Nrf2 activation compounds arsenic trioxide and tBHQ on human B cell function in vitro and on murine B cell function both in vivo and ex vivo. We isolated human peripheral blood mononuclear cells and exposed them to arsenic trioxide before a challenge with influenza A virus (IAV). After 96 hours, cells were harvested and analyzed using flow cytometry. Cells that were exposed to ATO showed less immunoglobulin surface expression, activation, and effector function. In rodents, we used an ex vivo activation model mimicking the T cell- B cell interaction to assess the role of tBHQ on B cell activation in a physiologically significant manner. In this model, we measured a decrease in IgG1 producing cells and a decrease in a variety of activation markers, indicating that tBHQ indeed altered B cell activation. Interestingly, we also observed a tBHQ dependent decrease in B cell clonal expansion and a diminished inhibition of negative regulators such as CD267. Finally, we measured the effect of tBHQ in vivo by exposing mice to 0.0014% tBHQ via their diet, a similar amount as found in commercially used rodent chow. These mice were then sensitized to chicken ovalbumin using a transdermal sensitization model mimicking the pathogenesis of human food allergies. Cells were harvested from lymph nodes to determine whether tBHQ had an impact on the development of allergies. The very early activation marker CD69 was inhibited, while CD25 was not. We also measured an increase in CD80 and CD138, and most importantly, an increase in the key atopic immunoglobulin IgE, both in serum and on the surface of B cells. Collectively, these data are the first descriptions of a change in B cell function upon exposure to NRF2 activating toxicants. Given the rise of atopic disease and the prevalence of infectious disease requiring immunoglobulin mediated immunity, further characterization of the impact of the toxiom on B cell function is urgently needed.
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