Systemic lupus erythematosus (SLE) is a prototypic autoimmune disease characterized by autoantibody production and immune complex mediated organ damage. One of the more profound features of SLE is females having a 9:1 prevalence of disease over men. The cause of this gender difference in SLE is multifactorial, including the sex hormones themselves and their receptors. Estrogen acts primarily via its receptors, estrogen receptor alpha and beta (ER?/ER?). Estrogen can also act, however, through non-receptor mediated mechanisms and, in kind, the ERs mediate physiologic functions independent of estrogen. In the previous funding period, we derived ER? and ER? knockout lupus prone MRL/lpr and NZM2410 mice. In both strains, the female ER? KOs developed significantly less proteinuria and pathologic renal disease and had significantly prolonged survival, despite increased serum levels of autoantibodies. These findings led us to postulate that the primary impact of ER? deficiency in lupus nephritis was on the response of the kidney to inflammation. We derived ER? KO and ER? KO mesangial cells from B6 mice and found that ER? KO mesangial cells had a marked blunted response to TLR 2, 3 and 7 ligands. ER? expression had no effect on mesangial cell responses as tested. Based on these findings, we hypothesize that the lack of ER? is renal protective in female lupus mice by blunting the response of mesangial cells to TLR3/7 induced inflammation. We believe this ER? protective effect is estrogen independent and mediated via TLR3/7 induced phosphorylation of ER?. To test this hypothesis, we propose the following Specific Aims: 1. Determine in vivo the effects of ER? deficiency on known mechanisms of lupus pathogenesis using sle1, sle3 and sle1/3 congenic mice and bone marrow transplantation of ER? KO and ER? WT mice. 2. Define the in vitro molecular mechanisms underlying TLR/ER? interactions that impact the inflammatory response in mesangial cells assessing the impact of ER? on the TLR3/7 activation pathways and TLR3/7 on ER? expression. 3. Define in vivo and in vitro the mechanisms by which ER? impacts TLR signaling utilizing mutant ER? knockin strains that affect specific ER? functions allowing delineation of specific ER? functions on the immune response. These studies will provide novel insight into the mechanisms by which ER? deficiency impacts lupus disease expression and further delineate the interaction between ER? and TLR induced inflammation that may partially underlie the female predominance in lupus.
Statement Lupus is a disease with increasing prevalence in the Veteran population. It is primarily a disease of women and minorities, who represent an increasing proportion of patients in VA clinics. Of increasing concern is, that despite recent advances in medical care, mortality rates and progression to renal failure continue to increase in lupus in minorities. This proposal addresses one of the key unanswered questions in lupus, that of the mechanism underlying the 9/1 female predominance in disease. We found that estrogen receptor alpha (ER?) is a key mediator of SLE in female lupus prone mice and that ER? mediates this effect, at least partially, by modulating the inflammatory response to specific TLR ligands implicated in lupus. Further defining the effect of ER? on SLE will provide new insight into mechanisms of disease and novel approaches to therapy.
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