The Study On The New Mechanism For ALD-DNA Induced SLE: Macrophage Polarization And Its Role In SLE

The study on the new mechanism for ALD-DNA induced SLE:macrophage polarization and its role in SLESystemic lupus erythematosus (SLE) is a potentially fatal disease characterized by the prototypic autoimmune syndrome with heterogeneous manifestations frequently including autoimmunity, vasculitis, arthritis, and glomerulonephritis. In the United States, the number of patients with SLE exceeds 250,000. The 90 percent of SLE patients are women of childbearing age. Recently, the 5-y survival rate of patients with lupus glomerulonephritis increased from 44%in the 1950s to 82%. Despite great advances in the treatment of this autoimmune disease, the mean age of death of patients dying from systemic lupus erythematosus is 44 y. To the clinician, SLE is important because it is a potentially fatal disease that is easily confused with many other disorders. To the immunologist, lupus is intriguing because all the key components of the immune system are involved in the underlying mechanisms of the SLE disease.The anti-dsDNA autoantibody, which is a serological hallmark of SLE, has been proved to be pathogenic and could cause subsequent tissue deposition of immune complexes (IC) and tissue damage. Anti-dsDNA antibodies are highly specific for SLE and levels of anti-dsDNA antibodies in serum tend to reflect disease activity. Genetic studies in SLE patients revealed that anti-dsDNA autoantibodies, which generally belong to IgG subtype with high-affinity binding to dsDNA, differ from the germ line due to somatic mutations. Generally, mammalian DNA gains poor immunogenicity and could not trigger the immune response. Accumulating data indicated that undigested DNA released from apoptotic cells could induce macrophage activation and trigger a set of immune response, thus producing autoantibodies to self-DNA, which occurs commonly in SLE patients. In this study, we utilized the SLE murine model established by our group previously through immunizing syngeneic female BALB/c mice with a self-DNA released from apoptotic lymphocytes which termed as activated lymphocyte-derived DNA. A series of SLE syndrome including highly anti-dsDNA antibodies, proteinuria, immune complex deposition, and glomerulonephritis were developed in our murine model, which resembles human SLE syndrome accompanied with abundant self-DNA released from unremoved apoptotic cells. Thereby the ALD-DNA immunized mice could be used as an ideal murine lupus model to explore the potential cellular and molecular immunological mechanisms responsible for SLE disease.SLE syndrome is generally considered to be autoantibody-mediated systemic inflammation and tissue damage triggered by aggressive T and B cell responses of the adaptive immune system. Yet, the underlying cellular and molecular mechanisms for onset and progression of SLE are still poorly understood. It was reported that markedly activated macrophages and other myeloid cells which infiltrated in lymphoid tissues and kidneys, mediated the onset and propagation of an aggressive adaptive immune response, thereby leading to SLE pathogenesis in mice. Accumulating data demonstrated that F4/80+macrophages represented the major inflammatory infiltrated cells and played a crucial pathogenic role in the development of SLE nephritis. However, It is still unclear whether the activated macrophages found in the kidneys have a pathogenic or protective role. Furthermore, macrophages display remarkable plasticity and can change their physiology in response to exposure to various microenvironmental signals. Functional macrophage polarization represents different extremes of a continuum ranging from M1, M2a (alternatively activated macrophages, AAMΦs), M2b (type-II), to M2c. The concrete phenotype and mechanism for functional macrophage polarization in SLE remains unclear.PART ONE:Induction of inflammatory and immune responses by macrophages stimulated with ALD-DNA:implications for the pathogenesis of SLEUndigested DNA released from apoptotic cells could trigger a set of immune response, thus producing autoantibodies to self-DNA, which occurs commonly in SLE patients. But the role of macrophages in the pathogenesis of SLE remains largely unknown. In this study, we report that in the SLE murine model generated by immunization with ALD-DNA, the nephritic tissues were found infiltrated with activated macrophages. ALD-DNA could induce the secretion of TNF-α, IL-1β, IL-6, and IL-10 and the expression of activation markers including MHC class-II, CD40, CD80, and CD86 in macrophages in vitro and in vivo. However, DNA derived from un-activated lymphocytes (UnALD-DNA) could not. Furthermore, activated macrophages were found to be involved in the ALD-DNA induced autoimmune response via promoting the cytokine production by T cells and autoantibody production by B cells when stimulated with ALD-DNA. More importantly, macrophage depletion could decrease the urine protein and induce the remission of established lupus nephritis in SLE murine model. Our findings suggest that ALD-DNA activates macrophages and, thereby, may crucially contribute to the pathogenesis of SLE.PART TWO:Blockade of Notchl signaling alleviates murine lupus via blunting macrophage activation and M2b polarizationSystemic lupus erythematosus (SLE) patients are found to be accompanied with innate immunity dysregulation including abnormally macrophage activation. But the concrete phenotype and the mechanism for functional polarization of the activated macrophages during pathogenesis of SLE remains unknown. As an important local cellular interaction mechanism responsible for cell fate determination, Notch signaling is reported to exert crucial functions in the development and differentiation of various immunocytes, whereas its role in macrophage polarization is not fully understood. Herein, in the SLE murine model generated by immunization with activated lymphocyte-derived DNA (ALD-DNA), the nephritic tissues were found infiltrated with M2b-polarized macrophages. Notchl signaling activity was significantly up-regulated in the ALD-DNA induced M2b macrophages in vitro and in vivo. Furthermore, ALD-DNA induced M2b polarization was found to be dependent on enhanced Notchl signaling through accelerating NF-κB p50 translocation into nucleus mediated by PI3K and MAPK pathways. Moreover, blockade of Notchl signaling with y-secretase inhibitor (GSI) treatment could ameliorate murine lupus through impeding macrophage M2b polarization. Our results implied that Notchl signaling dependent M2b-polarized macrophages might play a pivotal role in the pathogenesis of SLE, which could provide Notchl signaling blockade as a potential therapeutic approach for SLE disease.PART THREE:Notchl engagement by Jaggedl bias the M2 functional differentiation of activated macrophagesFollowing activation by antigen, macrophages execute distinct genetic programs that result in their differentiation toward the type 1 or type 2 macrophages (M1 or M2) phenotype. Although the differentiation and function of these macrophage subsets has been well studied, little is known about the contribution to these differentiation events of cell surface receptors other than those for soluble cytokines, such as IFN-y or IL-4. Here, we provide direct evidence that the Jaggedl interaction with Notchl on macrophages transduces signals, promoting development toward the M2 phenotype. The positive role of Notch signaling in effector cell differentiation was dose dependent, with high levels of Jaggedl stimulation resulting in increased macrophage M2 polarization. Our data revealed a clear contribution of Notchl pathways engaged by Jaggedl to M2 versus M1 fate decisions, while also providing insight into another mechanism for inhibition of macrophage M2 activation.PART FOUR:Serum amyloid P component ameliorates murine lupus via biasing macrophage activation to the alternative pathwaySerum amyloid P component (SAP) has been reported to activate macrophage-mediated phagocytosis of nuclear debris, whereas its role in the pathogenesis of systemic lupus erythematosus (SLE) is not fully understood. Herein, decreased serological ratios of SAP to DNA were found to be negatively correlated with the titers of anti-dsDNA antibodies in SLE patients and lupus murine model. SAP was shown to promote macrophage-mediated DNA uptake through binding to DNA. Furthermore, type-Ⅱpolarized macrophages induced by DNA could be switched to alternatively activated macrophages (AAMΦs) by SAP-DNA complex in vitro. IL-10 secreted by AAMΦs was found to predominantly impede DNA induced macrophage type-II activation and promote DNA phagocytosis. More importantly, reinforced SAP level in vivo could efficiently ameliorate glomerulonephritis through inducing renal macrophage alternative activation in lupus murine model. Taken together, our results reveal a protective role of SAP in lupus, which suggest that enhanced SAP level could alleviate SLE syndrome via switching the polarized phenotype of macrophages from pro-immune type-II activation to anti-immune alternative activation. This might provide SAP as a potential therapeutic approach for SLE disease.