Epigenetic downregulation of the antibody and autoantibody response Epigenetic marks include DNA methylation, histone modifications and microRNAs. As we have contended, these "interact" with genetic programs to regulate B cell functions, such as class switch DNA recombination (CSR), somatic hypermutation (SHM) and plasma cell differentiation, thereby informing the antibody response. Epigenetic dysregulation can result in aberrant antibody responses to exogenous antigens, such as those on viruses and bacteria, or self-antigens, such as chromatin, histones and dsDNA in lupus. We hypothesize that the epigenetic modulators histone deacetylase (HDAC) inhibitors (HDIs) inhibit the B cell intrinsic functions CSR/SHM and plasma cell differentiation, thereby blunting antibody and autoantibody responses. We further argue that HDIs inhibit these B cell functions by upregulating selected microRNAs, including miR-155, miR-181b and miR-361 to downregulate AID (Aicda gene, critical for CSR/SHM), as well as miR-23b, miR-30a and miR-125 to downregulate Blimp1 (Prdm1 gene, critical for plasma cell differentiation). Our hypotheses uniquely focus on B cells and are supported by our compelling data using purified human and mouse B cells in vitro, and in vivo in normal mice responding to T-dependent and T- independent antigens, and prevention of disease and "treatment" of lupus-prone mice by HDI. Our strengths in B cell biology, molecular CSR/SHM mechanisms and autoimmunity, and our cutting-edge epigenetic tools and approaches make us uniquely poised to test our hypotheses. We will:
(Aim 1) analyze the impact of HDIs (valproic acid, butyrate and SAHA) on CSR/SHM and plasma cell differentiation, and on specific T-dependent and T-independent antibody responses in normal C57BL/6 and Balb/c mice and autoantibody responses in lupus-prone MRL/Faslpr/lpr and B6.NZM/Sle1.Sle2.Sle3 mice;
(Aim 2) use molecular biology, biochemistry and high-throughput/bioinformatics tools to analyze HDI-mediated upregulation of miR-155, miR-181b, miR-361, miR-23b, miR-30a and miR-125b in B cells through enhanced histone acetylation and transcription of the microRNA "host genes", address downregulation of AID and Blimp1 by these microRNAs, and construct microRNA in vivo targeting maps of Aicda and Prdm1 3'UTRs using Ago HITS-CLIP;
(Aim 3) prove the critical role of B cell microRNAs in mediating HDI suppression of antibody and autoantibody responses using a three-prong integrated in vivo approach involving construction of new knockin mice lacking specific microRNA targeting sites in Aicda or Prdm1 3'UTR, B cell conditional Dicer or Drosha KO mice, and mice expressing "sponge" inhibitors specific for miR-155, miR-181b and miR-361 (targeting Aicda) and/or for miR-23b, miR-30a and miR-125b (targeting Prdm1) in B cells. Our proposal is highly innovative and exquisitely translational. It will provide mechanistic insights and future directions in epigenetics and immunoregulation, including the critical role of B cell microRNAs in antibody/autoantibody responses and epigenetic tools as new therapeutics in autoimmunity.
This proposal addresses the epigenetic modification in antibody and autoantibody responses, and inhibition of autoantibody response by histone deacetylase inhibitors (HDIs) in autoimmune diseases. Epigenetic marks interact with genetic programs to regulate B cell functions, such as immunoglobulin (antibody) gene class switch DNA recombination (CSR), somatic hypermutation (SHM) and plasma cell differentiation, thereby informing the antibody response. Epigenetic dysregulation can result in aberrant antibody responses, and would compound genetic susceptibility to mediate autoimmunity, including systemic lupus (SLE), in which heavily mutated and class-switched (mainly IgG) autoantibodies to nuclear antigens, as secreted by large numbers of plasma cells, produce widespread tissue and organ injury. In our study, we use FDA-approved and widely-used HDI compounds to selectively inhibit CSR, SHM and plasma cell differentiation, and abrogate the generation of pathogenic autoantibodies and prevent, treat and even cure lupus. The proposed research addresses core autoimmune mechanisms of lupus and will have sustained impact on the fields of epigenetics, immunoregulation and autoimmunity. Finally, it is exquisitely translational, as it provides a sound mechanistic basis for use of inexpensive and available epigenetic modulators as therapeutics in autoimmune diseases.
|Lam, Tonika; Kulp, Dennis V; Wang, Rui et al. (2016) Small Molecule Inhibition of Rab7 Impairs B Cell Class Switching and Plasma Cell Survival To Dampen the Autoantibody Response in Murine Lupus. J Immunol 197:3792-3805|
|Pone, Egest J; Lam, Tonika; Lou, Zheng et al. (2015) B cell Rab7 mediates induction of activation-induced cytidine deaminase expression and class-switching in T-dependent and T-independent antibody responses. J Immunol 194:3065-78|
|Zan, Hong; Casali, Paolo (2015) Editorial: Epigenetics of B Cells and Antibody Responses. Front Immunol 6:656|
|Zan, Hong; Casali, Paolo (2015) Epigenetics of Peripheral B-Cell Differentiation and the Antibody Response. Front Immunol 6:631|
|Lou, Zheng; Casali, Paolo; Xu, Zhenming (2015) Regulation of B Cell Differentiation by Intracellular Membrane-Associated Proteins and microRNAs: Role in the Antibody Response. Front Immunol 6:537|
|Pone, Egest J; Lou, Zheng; Lam, Tonika et al. (2015) B cell TLR1/2, TLR4, TLR7 and TLR9 interact in induction of class switch DNA recombination: modulation by BCR and CD40, and relevance to T-independent antibody responses. Autoimmunity 48:1-12|
|Shen, Tian; Sanchez, Helia N; Zan, Hong et al. (2015) Genome-Wide Analysis Reveals Selective Modulation of microRNAs and mRNAs by Histone Deacetylase Inhibitor in B Cells Induced to Undergo Class-Switch DNA Recombination and Plasma Cell Differentiation. Front Immunol 6:627|
|White, Clayton A; Pone, Egest J; Lam, Tonika et al. (2014) Histone deacetylase inhibitors upregulate B cell microRNAs that silence AID and Blimp-1 expression for epigenetic modulation of antibody and autoantibody responses. J Immunol 193:5933-50|
|Morgado, Pedro; Sudarshana, Dattanand M; Gov, Lanny et al. (2014) Type II Toxoplasma gondii induction of CD40 on infected macrophages enhances interleukin-12 responses. Infect Immun 82:4047-55|
|Zan, Hong; Tat, Connie; Casali, Paolo (2014) MicroRNAs in lupus. Autoimmunity 47:272-85|
Showing the most recent 10 out of 18 publications