Delineation of the pathogenesis of systemic lupus erythematosus by using murine models

Effects of AS2819899, a novel selective PI3Kδ inhibitor, in a NZB/W F1 mouse lupus-like nephritis model

Phosphoinositide 3-kinases generate lipid-based second messengers that control an array of intracellular signaling pathways. In particular, phosphoinositide 3-kinases delta (PI3Kδ) is expressed primarily in hematopoietic cells and plays an important role in B-cell development and function. B cells play a critical role in autoimmune diseases by producing autoantibodies. Studies have therefore increasingly focused on PI3Kδ as a therapeutic target for the treatment of inflammatory and autoimmune diseases. One such autoimmune disease is systemic lupus erythematosus (SLE). SLE is a chronic systemic autoimmune disease with repeated recurrence and remission, and autoantibodies play an important role in its pathogenesis. Here, we examined the pharmacological profile of the novel PI3Kδ selective inhibitor AS2819899 and investigated its therapeutic potential against SLE in a NZB/W F1 mouse lupus-like nephritis model, a widely-used SLE mouse model. AS2819899 prevented B and T cell activation in vitro, and inhibited antibody production in a T-cell independent de novo antibody production mouse model. In the spontaneous NZB/W F1 mouse model, AS2819899 treatment significantly reduced anti-dsDNA antibody titers and improved kidney dysfunction. Further, AS2819899 inhibited the memory recall reaction in a T-cell dependent antibody production mouse model, suggesting that AS2819899 can potentially maintain remission of SLE. Moreover, we identified a pharmacodynamics marker for AS2819899 that may be useful in clinical studies. These results indicate that AS2819899 may be an attractive therapeutic candidate for SLE, including the maintenance of remission.

Phosphoinositide 3-kinases in health and disease

In the last decade, the availability of genetically modified animals has revealed interesting roles for phosphoinositide 3-kinases (PI3Ks) as signaling platforms orchestrating multiple cellular responses, both in health and pathology. By acting downstream distinct receptor types, PI3Ks nucleate complex signaling assemblies controlling several biological process, ranging from cell proliferation and survival to immunity, cancer, metabolism and cardiovascular control. While the involvement of these kinases in modulating immune reactions and neoplastic transformation has long been accepted, recent progress from our group and others has highlighted new and unforeseen roles of PI3Ks in controlling cardiovascular function. Hence, the view is emerging that pharmacological targeting of distinct PI3K isoforms could be successful in treating disorders such as myocardial infarction and heart failure, besides inflammatory diseases and cancer. Currently, PI3Ks represent attractive drug targets for companies interested in the development of novel and safe treatments for such diseases. Numerous hit and lead compounds are now becoming available and, for some of them, clinical trials can be envisaged in the near future. In the following sections, we will outline the impact of specific PI3K isoforms in regulating different cellular contexts, including immunity, metabolism, cancer and cardiovascular system, both in physiological and disease conditions.

PI3Ks-drug targets in inflammation and cancer

Phosphoinositide 3-kinases (PI3Ks) control cell growth, proliferation, cell survival, metabolic activity, vesicular trafficking, degranulation, and migration. Through these processes, PI3Ks modulate vital physiology. When over-activated in disease, PI3K promotes tumor growth, angiogenesis, metastasis or excessive immune cell activation in inflammation, allergy and autoimmunity. This chapter will introduce molecular activation and signaling of PI3Ks, and connections to target of rapamycin (TOR) and PI3K-related protein kinases (PIKKs). The focus will be on class I PI3Ks, and extend into current developments to exploit mechanistic knowledge for therapy.

Identification of candidate IgG biomarkers for Alzheimer's disease via combinatorial library screening

The adaptive immune system is thought to be a rich source of protein biomarkers, but diagnostically useful antibodies remain unknown for a large number of diseases. This is, in part, because the antigens that trigger an immune response in many diseases remain unknown. We present here a general and unbiased approach to the identification of diagnostically useful antibodies that avoids the requirement for antigen identification. This method involves the comparative screening of combinatorial libraries of unnatural, synthetic molecules against serum samples obtained from cases and controls. Molecules that retain far more IgG antibodies from the case samples than the controls are identified and subsequently tested as capture agents for diagnostically useful antibodies. The utility of this method is demonstrated using a mouse model for multiple sclerosis and via the identification of two candidate IgG biomarkers for Alzheimer's disease.

PI3K inhibition in inflammation: Toward tailored therapies for specific diseases

In the past decade, the availability of genetically modified animals has enabled the discovery of interesting roles for phosphatidylinositol 3-kinase-gamma (PI3Kgamma) and -delta (PI3Kdelta) in different cell types orchestrating innate and adaptive immune responses. Therefore, these PI3K isoforms appear to be attractive drug targets for the treatment of diseases caused by unrestrained immune reactions. Currently, pharmacological targeting of PI3Kgamma and/or PI3Kdelta represents one of the most promising challenges for companies interested in the development of novel safe treatments for inflammatory diseases. In this review we provide a general outline of PI3Kgamma- and PI3Kdelta-specific functions in distinct subsets of inflammatory cells. We also discuss the therapeutic impact of novel compounds targeting PI3Kgamma, PI3Kdelta or both, in mouse models of autoimmune disorders (systemic lupus erythematosus (SLE) and rheumatoid arthritis), respiratory diseases (allergic asthma and chronic obstructive pulmonary disease) and cardiovascular dysfunctions (atherosclerosis and myocardial infarction).

Spontaneous class switching and B cell hyperactivity increase autoimmunity against intracellular self antigen in Lyn-deficient mice

IgG autoantibodies cause pathology due to their ability to bind self antigens. However, the extent to which the initial B cell activation and isotype switching is antigen-driven is unclear and it has been widely proposed that intrinsic B cell hyperactivity may be a contributing factor. To explore this issue we generated mice with B cell hyperactivity secondary to deficiency in the src kinase Lyn that also expressed a gene-targeted anti-hen egg lysozyme Ig construct (VDJkappa) capable of class switching to all isotypes. The B cell hyperactivity caused spontaneous hypersecretion of antibodies and class switching to IgM, IgA, IgG1 and IgG3 isotypes in the absence of self antigen, and this persisted as an autoimmune phenomenon in the presence of intracellularly expressed hen egg lysozyme. Exaggerated class switching was also unaffected by antigen in vitro. These findings show that systemic high-avidity intracellular self antigens do not induce self tolerance in the face of B cell hyperactivity. Under these circumstances, spontaneous activation of hyperactive B cells leads to isotype switching and the development of high titres of IgG autoantibodies against intracellular proteins.