Substance P exacerbation of staphylococcal bone damage

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Project Summary Bone disorders such as osteomyelitis that result from bacterial infection are associated with severe inflammation and progressive bone loss. Staphylococcus aureus is the most common causative agent of osteomyelitis and the incidence and severity of staphylococcal osteomyelitis appears to be increasing despite improvements in prophylaxis and diagnosis. Dysregulation of osteoclast formation and activity results in bone destruction and/or abnormal bone remodeling at sites of infection, and osteoblasts play an essential role in the regulation of these bone-resorbing cells. In addition, bacterially infected osteoblasts and osteoclasts are capable of producing an array of immune mediators that could promote the recruitment and activation of inflammatory leukocytes in bone tissue. The neuropeptide substance P (SP) is increasingly recognized to exacerbate inflammation in a range of tissues including the gut, skin, and central nervous system. Given the extensive innervation of bone tissue with SP- containing nerve fibers, the functional expression of the specific receptor for SP (NK-1R) by bone cells, and previous evidence that this neuropeptide can modulate bone cell responses, we suggest that SP/NK-1R interactions exacerbate inflammation in osteomyelitis. In this application, we propose a comprehensive preclinical evaluation of the ability of this neuropeptide to augment inflammation in isolated murine and human resident bone cells and an established in vivo animal model of staphylococcal osteomyelitis. This work builds upon our prior work and will test the hypothesis that inhibition of SP/NK-1R interactions attenuates the immune and osteolytic responses of resident bone cells to bacteria. Furthermore, these studies represent an essential step in evaluating the therapeutic potential of repurposing clinically approved NK-1R antagonists as an adjunctive therapy to limit staphylococcal osteomyelitis-associated inflammatory bone loss and/or abnormal bone remodeling, and may point to neurogenic input as a therapeutic target for the treatment of inflammatory bone disorders in general.