Deciphering the Role of Bacterial Polyphosphates in Intestinal Immune Networks

About This Grant

Project Summary: The gastrointestinal tract hosts a substantial microbiota reservoir that supports processes like nutrition, metabolism, immune development, and defense against pathogens. However, an imbalance in the microbiota that favors pathobionts can augment inflammation, tissue injury, and pathologies such as inflammatory bowel disease (IBD). IBD affects ~3 million people in the United States, impacting ~1 in every 100 individuals. The mechanisms governing host mucosal immune cell interactions with pathogens in IBD pathobiology are not fully elucidated. Bacterial polyphosphates are long-chain polymers (≥700 phosphate residues) with pleiotropic roles in prokaryotic metabolism, virulence, and host evasion. Recently, our group has reported that bacterial polyphosphates interfere with bone marrow-derived macrophage responses to promote lethality of Escherichia coli sepsis in mice. Emerging evidence also suggests that the IBD therapeutic, mesalamine, lowers the amount of bacterial polyphosphates in the colon and thus the colonization of the inflamed tissue. Our preliminary studies show that mice monocolonized with E. coli deficient in polyphosphate kinase (Δppk), the enzyme mediating polyphosphate synthesis, have lowered inflammation versus mice monocolonized with wild type E. coli. Notably, in experimental colitis, mice showed more weight loss, severe colitis, and reduced survival after receiving polyphosphate-exposed T cells vs non-exposed T cells from colonic lamina propria. In addition, polyphosphates decreased IL-27 expression and blocked STAT1 phosphorylation, supporting a central role for polyphosphates in altering JAK1/STAT1-dependent IL-27 signaling pathways. In metagenomic analyses, ppk was more abundant in IBD patients than controls. Here, we propose to elucidate the role of polyphosphates in exacerbating intestinal inflammation and IBD through three aims: (1) To characterize how microbiota-derived polyphosphates modulate intestinal immune cell networks with a focus on JAK1/STAT pathways (in vivo). We will also perform immunophenotyping on the effect of polyphosphates on JAK/STAT signaling pathways and IL- 12 family cytokines during intestinal inflammation through ‘omics’ approaches. (2) To characterize the effects of polyphosphates on IL-27 release and its activation of JAK/STAT signaling (in vitro). We will investigate the mechanistic effects of polyphosphates on IL-27 production and JAK1/STAT1 signaling in mononuclear phagocytes and T cells. (3) To study the involvement of polyphosphates in human diseases (IBD). For translational studies, we will characterize the abundance of ppk in blood samples and fecal metagenomics data from human IBD patients. Furthermore, we plan to investigate the therapeutic potential of polyphosphate neutralization in T cell-transfer colitis in mice. Overall, we anticipate that findings from our studies will enhance insights into the role of bacterial polyphosphates in maladaptive mucosal immune immunity, which may help define new therapeutic strategies .