PROJECT SUMMARY
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.
