Systemic lupus erythematosus (SLE) is one of many autoimmune diseases that disproportionately affects
females. Although many risk factors for lupus are identified: >170 genes including GPR174, myriad
environmental exposures, and aberrant X chromosome inactivation, none of these sufficiently explain the steep
rise in incidence of ADs at the time of puberty in a female-specific manner. Epidemiology suggests a major role
for sex hormones and their receptors in autoimmune diseases. We previously showed that female lupus-prone
mice, expressing only a short form of estrogen receptor alpha (ERa short), have significantly reduced renal
disease and increased survival. Determining the mechanism of this protective effect, which is estrogen
dependent, is the primary goal of this proposal. Of note, ERa-/- (null) lupus prone mice were not similarly
protected. Combined, our data suggest that the presence of the short form of ERa confers protection, not the
absence of full-length ERa. Others and we demonstrated a critical role for ERa in dendritic cell (DC) development
and endosomal Toll-like receptor (TLR) responsiveness. Interestingly, the ERa expressed in ERa short mice is
similar in structure to an endogenous ERa variant (ERa46) that lacks the same AF-1 domain, and differentially
regulates gene transcription compared to full length ERa. Overexpressing ERa46 in vitro also modulates TLR-
induced responses, relevant to this proposal. In the proposed study, we will further investigate the role of ERa
short variants in modulating TLR7-induced immune responses, and determine whether genomic and/or non-
genomic mechanisms of ERa short variant action are protective. Our overall hypothesis is that increasing
expression of ERa short or ERa46 in immune cells will be anti-inflammatory, and that the ratio of ERa46
to ERa66 is decreased in lupus patients versus healthy controls. We also hypothesize that targeting
immune cells with novel anti-inflammatory selective estrogen receptor modulators (SERMs) that alter ERa
membrane signaling and/or ERa-induced transcription will uncouple estrogen-mediated anti-inflammatory
responses from those impacting reproductive tissues. We will test our hypotheses by accomplishing these
Specific Aims: 1) Overexpress ERa short or treat immune cells with novel SERMs (OBHS, PaPE) that select for
anti-inflammatory properties of ERa and determine the effect on known TLR7-induced inflammatory endpoints,
2) Investigate effects of membrane-only ERa signaling vs. nuclear only ERa expression on TLR7-induced
pathways in mice, and 3) Identify ERa variants in human monocyte-derived dendritic cells (mo-DCs) and B cells
using droplet digital PCR and Iso-Seq technology, to determine whether ERa46 is differentially expressed in
lupus patients vs. controls, potentially explaining a biologic difference in females predisposed to autoimmunity.
These aims will allow us to determine if we can separate ERa's reproductive effects from its potentially modifiable
immune effects as a therapeutic strategy, which if successful, will provide novel approaches to immune
modulation in lupus and other immune mediated diseases, especially those with a significant sex bias.
