Pain is the leading cause of emergency department visits, hospitalizations, and daily suffering in individuals with sickle cell disease (SCD). The pathologic mechanisms leading to the perception of pain during acute RBC sickling episodes and development of chronic pain remain poorly understood and ineffectively treated. We provide the first study that explores nociceptor sensitization mechanisms that contribute to pain behavior in mice with severe SCD. Sickle mice exhibit robust behavioral hypersensitivity to mechanical, cold, and heat stimuli. Mechanical hypersensitivity is further exacerbated when hypoxia is used to induce acute sickling. Behavioral mechanical hypersensitivity is mediated in part by enhanced excitability to mechanical stimuli at both primary afferent peripheral terminal and sensory membrane levels. In the present study, inhibition of the capsaicin receptor transient receptor potential vanilloid 1 (TRPV1) with the selective antagonist A-425619 reversed the mechanical sensitization at both primary afferent terminals and isolated somata, and markedly attenuated mechanical behavioral hypersensitivity. In contrast, inhibition of TRPA1 with HC-030031 had no effect on mechanical sensitivity. These results suggest that the TRPV1 receptor contributes to primary afferent mechanical sensitization and a substantial portion of behavioral mechanical hypersensitivity in SCD mice. Therefore, TRPV1-targeted compounds that lack thermoregulatory side effects may provide relief from pain in patients with SCD. (Blood. 2011;118(12):3376-3383) IntroductionSickle cell disease (SCD) is a major health care and socioeconomic problem that affects millions of people worldwide. In the United States alone, SCD affects Ͼ 80 000 people, the majority of whom are African American. Pain is the hallmark symptom of SCD and the leading cause of emergency department visits, hospitalizations, and daily suffering. 1 Patients suffer unpredictable, incapacitating acute pain episodes that are believed to result from red blood cell (RBC) sickling and "vaso-occlusion." However, many features of this pain are not explained by hemoglobin polymerization and vascular obstruction. Furthermore, individuals with SCD often develop chronic pain syndromes that are poorly understood and ineffectively treated. 1,2 The frequency and severity of pain is associated with increased mortality and profoundly erodes patients' quality of life. 3 Because they are often from minority and lower socioeconomic groups, SCD patients are commonly underserved and suboptimally treated.The pathologic mechanisms leading to the perception of pain during RBC sickling episodes and the transition from acute to chronic pain remain poorly understood. 1,2 Patient descriptors of SCD pain include neuropathic pain attributes such as "aching," "shooting," and "stabbing," as well as nociceptive pain qualities such as "sharp," "throbbing," and "pounding." These descriptors depict spontaneous pain or nonstimulus-evoked pain. 2,4 Furthermore, increased hospital admissions and reports of...

Background: Neuropathic pain is associated with poor health-related quality of life (HRQL) in pain conditions other than sickle cell disease (SCD); this relationship in SCD is unknown. We investigated this relationship and hypothesized neuropathic pain is associated with poor HRQL in adolescents with SCD. Methods: We conducted a cross-sectional study of patients with SCD ages 13-18 years during baseline health. Primary outcome was HRQL, assessed by the PedsQL SCD Module (child self-report, parent proxy report). PedsQL is scored from 0 to 100, with higher scores indicating better HRQL. Neuropathic pain was assessed using the painDETECT questionnaire (scored 0-38); higher scores indicated greater likelihood of neuropathic pain. All completed both PedsQL SCD Module and painDETECT questionnaire. Descriptive statistics were used and associations between painDETECT and PedsQL Total Score, Pain Impact, Pain and Hurt, and Pain Management and Control Scores were determined via Pearson correlation. Significance was P < .05. Results: Twelve patients were enrolled. Median (interquartile range [IQR]) age was 15 (14-16.5) years, 75% were female, and 83% were on hydroxyurea. Higher painDETECT scores were significantly associated with lower PedsQL SCD Module child self-report Pain and Hurt Scores (r = −0.68, P = .01). Higher painDETECT scores were also significantly associated with lower PedsQL parent proxy-report Total Scores (r = −0.64, P = .03) and Pain and Hurt Scores (r = −0.67, P = .02). Conclusions: These data suggest that adolescents with SCD and neuropathic pain have poor HRQL even in their baseline state of health. Prospective, larger studies are needed to confirm this preliminary finding and explore a multimodal approach for pain assessment in SCD. K E Y W O R D S health-related quality of life, neuropathic pain, sickle cell disease Abbreviations: HRQL, health-related quality of life; IQR, interquartile range; PedsQL, pediatric quality-of-life inventory; PRO, patient-reported outcome; SCD, sickle cell disease 1 INTRODUCTION Sickle cell disease (SCD) is an inherited hemoglobinopathy affecting ∼100 000 people in the United States. 1,2 The hallmark complication of

A novel hemoglobin-binding peptide reduces cellfree hemoglobin in murine hemolytic anemia.