Sickle Cell Disease Associated Changes in the Gut Microbiome Contribute to Persistent Pain

Many patients with sickle cell disease (SCD) suffer from chronic pain, the underlying causes of which are unclear. Recent 16s ribosomal RNA sequencing studies revealed differences in the number and types of bacteria in the gastrointestinal tract of patients and mouse models of SCD relative to controls, but it is unclear if or how these changes contribute to symptomology. In these experiments, we used transgenic SCD mice to determine the extent to which disease related gut dysbiosis contributes to persistent pain. Reflexive pain behaviors were first measured in SCD mice following longitudinal probiotic or antibiotic treatment. Vehicle-treated SCD mice displayed significant mechanical allodynia relative to vehicle-treated wildtype mice, and antibiotic treatment further exacerbated mechanical allodynia in both genotypes. In contrast, probiotic treatment completely reversed persistent touch hypersensitivity in SCD mice. Persistent touch pain was also transiently reversed in SCD mice following fecal material transplant from healthy mice. In complementary experiments, wildtype recipient mice developed cold and touch hypersensitivity that persisted for several weeks after fecal material transplant from SCD donors. Using whole-cell patch clamp recordings, we further determined that these behavioral observations were accompanied by altered intrinsic plasticity in a select class of nodose ganglia sensory neurons, the peripheral terminals of which are well positioned to detect sensory information in the gut. Nodose ganglia neurons isolated from animals that received sickle cell fecal material transplants were hyperexcitable relative to those isolated from animals that received control fecal material transplants. These data are the first to suggest that disease-related gut dysbiosis induces pain through changes in vagal nerve activity. Ongoing studies are examining specific bacterial populations and/or metabolites responsible for these functional changes in order to develop novel therapeutics for chronic SCD pain management. Grant support from National Institutes of Health grants K99HL155791 and R01NS070711.