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IgG antibodies form immune complexes (IC) that propagate inflammation and tissue damage in autoimmune diseases such as systemic lupus erythematosus. IgG IC engage Fcγ receptors (FcγR) on mononuclear phagocytes (MNP), leading to widespread changes in gene expression that mediate antibody effector function. Bromodomain and extra-terminal domain (BET) proteins are involved in governing gene transcription. We investigated the capacity of BET protein inhibitors (iBET) to alter IgG FcγR-mediated MNP activation. We found that iBET dampened IgG IC-induced pro-inflammatory gene expression and decreased activating FcγR expression on MNPs, reducing their ability to respond to IgG IC. Despite FcγR downregulation, iBET-treated macrophages demonstrated increased phagocytosis of protein antigen, IgG IC, and apoptotic cells. iBET also altered cell morphology, generating more amoeboid MNPs with reduced adhesion. iBET treatment impaired chemotaxis towards a CCL19 gradient in IC-stimulated dendritic cells (DC) in vitro , and inhibited IC-induced DC migration to draining lymph nodes in vivo , in a DC-intrinsic manner. Altogether, our data show that iBET modulates FcγR-mediated MNP activation and migration, revealing the therapeutic potential of BET protein inhibition in antibody-mediated diseases. [ABSTRACT FROM AUTHOR]

Proteases play a central role in regulating renal pathophysiology and are increasingly evaluated as actionable drug targets. Here, we review the role of proteolytic systems in inflammatory kidney disease. Inflammatory kidney diseases are associated with broad dysregulations of extracellular and intracellular proteolysis. As an example of a proteolytic system, the complement system plays a significant role in glomerular inflammatory kidney disease and is currently under clinical investigation. Based on two glomerular kidney diseases, lupus nephritis, and membranous nephropathy, we portrait two proteolytic pathomechanisms and the role of the complement system. We discuss how profiling proteolytic activity in patient samples could be used to stratify patients for more targeted interventions in inflammatory kidney diseases. We also describe novel comprehensive, quantitative tools to investigate the entirety of proteolytic processes in a tissue sample. Emphasis is placed on mass spectrometric approaches that enable the comprehensive analysis of the complement system, as well as protease activities and regulation in general. [ABSTRACT FROM AUTHOR]

Objectives: Bruton's tyrosine kinase (BTK) is a non-receptor tyrosine kinase required for intracellular signaling downstream of multiple immunoreceptors. We evaluated ABBV-105, a covalent BTK inhibitor, using in vitro and in vivo assays to determine potency, selectivity, and efficacy to validate the therapeutic potential of ABBV-105 in inflammatory disease. Methods: ABBV-105 potency and selectivity were evaluated in enzymatic and cellular assays. The impact of ABBV-105 on B cell function in vivo was assessed using mechanistic models of antibody production. Efficacy of ABBV-105 in chronic inflammatory disease was evaluated in animal models of arthritis and lupus. Measurement of BTK occupancy was employed as a target engagement biomarker. Results: ABBV-105 irreversibly inhibits BTK, demonstrating superior kinome selectivity and is potent in B cell receptor, Fc receptor, and TLR-9-dependent cellular assays. Oral administration resulted in rapid clearance in plasma, but maintenance of BTK splenic occupancy. ABBV-105 inhibited antibody responses to thymus-independent and thymus-dependent antigens, paw swelling and bone destruction in rat collagen induced arthritis, and reduced disease in an IFNa-accelerated lupus nephritis model. BTK occupancy in disease models correlated with in vivo efficacy. Conclusion: ABBV-105, a selective BTK inhibitor, demonstrates compelling efficacy in pre-clinical mechanistic models of antibody production and in models of rheumatoid arthritis and lupus. [ABSTRACT FROM AUTHOR]

Lupus is an autoimmune disease characterized by the development of antinuclear autoantibodies and immune complex-mediated tissue damage. T cells in lupus patients appear to undergo apoptosis at an increased rate, and this enhanced T cell apoptosis has been postulated to contribute to lupus pathogenesis by increasing autoantigen load. However, there is no direct evidence to support this hypothesis. In this study, we show that an Lck–cre transgene, which increases T cell apoptosis as a result of T cell-specific expression of cre recombinase, accelerates the development of autoantibodies and nephritis in lupus-prone (NZB × NZW)F1 mice. Although the enhanced T cell apoptosis in Lck–cre transgenic mice resulted in an overall decrease in the relative abundance of splenic CD4+ and CD8+ T cells, the proportion of activated CD4+ T cells was increased and no significant change was observed in the relative abundance of suppressive T cells. We postulate that the Lck–cre transgene promoted lupus by enhancing T cell apoptosis, which, in conjunction with the impaired clearance of apoptotic cells in lupus-prone mice, increased the nuclear antigen load and accelerated the development of anti-nuclear autoantibodies. Furthermore, our results also underscore the importance of including cre-only controls in studies using the cre-lox system. [ABSTRACT FROM AUTHOR]