The human microbiome is the sum of microbes that live in or on the human body, and it contributes to both health and disease. Our previous work has established that nitric oxide (NO) generated by gut microbiota acts as a language of inter-species communication between the microbiome and its host by changing fundamental host functions. Altered gut microbiota has also been implicated as an important risk factor in the etiology of inflammatory bowel diseases such as Crohn?s disease (CD). While excess NO generated by overexpression of nitric oxide synthase (NOS) in the host gut has been observed in CD, the role of the NO derived from gut microbiota has not been investigated or considered. NO signals in large part by post-translationally modifying proteins via S-nitrosylation, the covalent attachment of NO to the thiol side-chain of specific cysteine residues to form S-nitrosothiols (SNOs), altering protein function. Here we will test the hypothesis that communication between gut microbiota and mammalian host via host protein S-nitrosylation impacts health in normal mice and in a mouse model of CD. To do this, we will first characterize the extent to which microbiota-derived NO mediates host S-nitrosylation of gut proteins including known CD-associated proteins, and demonstrate that host gut proteins are highly regulated by microbiotal-NO/SNO. Further, we will show that gut microbiota-derived NO is not limited to affecting just adjacent gut tissue but may have far-reaching systemic effects within the host, by identifying host organs beyond the gut where endogenous protein S-nitrosylation and consequently organ functions are impacted by gut microbiota-derived NO, in both healthy and CD mice. This will establish an organ- specific, gut microbial NO-dependent SNO-proteome atlas at baseline, to compare and identify alterations found in the SNO-proteome in the CD mouse model. This will also allow identification of specific host proteins in CD whose S-nitrosylation depends significantly on NO derived from gut microbiota, enabling investigation of the role of specific alterations in patients with CD. Additionally, the microbial-NO dependent S-nitrosylation signature in gut and beyond will be helpful towards the diagnosis and treatment of CD. Using our CD mouse model, we will also test the use of a specific class of aminoquinoline-based inhibitors that selectively target bacterial-NOS?but not mammalian-NOSs?as a treatment option of CD. Furthermore, the establishment of this gut microbiota-NO- dependent SNO-proteome atlas in different major organs (gut, liver, heart, lung, kidney, brain) will be very useful in studying its perturbations across different mice models of human disease in the future. In addition, we will identify the mechanism(s) by which NO is transported from the gut to distant organs. The proposed work will, for the first time, determine: the effect of gut microbiota-derived NO on mammalian host physiology via S- nitrosylation, the mechanism of transport of bioactive SNOs from the gut to other organs, and the role of gut microbiota-derived NO/SNO in normal physiology and in disease conditions, particularly CD. Altogether, our work promises new understanding of means of communication between microbes and host.
Inflammatory bowel diseases (IBD) affect nearly 1.5 million people in the US alone. Since many aspects of the disease pathology are not entirely understood, it is no surprise that many patients either do not respond to symptom-focused therapies or suffer a relapse of the disease after initial success. This proposal focuses on an unexplored facet of IBD: the contribution of nitric oxide generated by gut microbiota as a contributor to the pathophysiology of these diseases in the host, and may identify novel therapeutic targets and treatment strategies for IBD.
