The Role of Chemokine Signaling in Sickle Cell Pain

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 DESCRIPTION (provided by applicant): The overall goal of this project is to determine the contribution of the chemokine CCL2 to the sensation of pain in Sickle Cell Disease (SCD). SCD is a common genetic disorder that involves crippling pain during acute vaso-occlusive crises; moreover, approximately 50% of patients develop chronic pain by adulthood. This pain has elements of both neuropathic and inflammatory pain, and patients report pronounced hypersensitivity to both touch and cold. Previous evidence has shown that the chemokine CCL2 is elevated both during and between crises in sickle patients. Importantly, CCL2 has been linked to both cold and mechanical hypersensitivity in other animal models of neuropathic pain. However, there has been little research investigating how inflammatory mediators such as CCL2 may contribute to SCD pain. Thus, this proposal will explore mechanisms through which inflammatory mediators influence the generation and maintenance of pain in SCD. To achieve this goal, these studies will use a mouse model of sickle cell disease that closely mimics the human SCD pain phenotype. Just as human patients with SCD report cold pain and sensitized cold thresholds, sickle mice exhibit behavioral cold hypersensitivity and the sensory neurons from sickle mice are sensitized to cold. Aim 1 will determine whether the chemokine CCL2 acting at CCR2 is responsible for the increased cold sensitization in SCD. Previous research has also noted a strong mechanical hypersensitivity in sickle mice. Aim 2 will determine whether CCL2 drives the mechanical sensitization observed in SCD. To achieve these aims, patch clamp electrophysiology and teased nerve fiber recordings will be performed, along with calcium imaging and behavioral assays. These interrelated aims provide a directed, yet multifaceted, approach to address the role of CCL2 in the complex pain syndromes associated with SCD. By addressing the mechanisms underlying the frequent and severe pain of sickle cell disease, this proposal's aims align with the mission of the NINDS to reduce the burden of neurological and painful diseases.