Transcriptional Inflammatory Signatures Differentiate Baseline Health from Acute Pain in Sickle Cell Disease Patients

Severe unpredictable acute pain and chronic daily pain causes significant morbidity for individuals with sickle cell disease (SCD). SCD is shown to be a chronic inflammatory disorder. Regulation of the immune response can potentially modulate the inflammatory impact on pain in SCD. We sought to determine the balance between patients’ inflammatory and immune regulatory response and examine whether this balance changes during acute SCD pain. We conducted a cross sectional analysis involving 3 cohorts: 16 SCD patients in baseline health, 27 SCD patients during acute pain and 45 healthy African American controls. Participant plasma was co-cultured with cryopreserved PBMCs from a healthy donor to induce transcription. We identified transcripts that differentiate SCD patients from healthy controls and retained ones differentially expressed that exhibit a fold change >1.4, ANOVA p-value of <0.05 and FDR <10%, thereby defining the disease-specific plasma-induced signature. Data were subjected to ontological analyses for quantitative interpretation with Database for Annotation, Visualization and Integrated Discovery (DAVID) and Ingenuity Pathway Analysis (IPA). For quantitative scoring we created a composite inflammatory index (I.I.com); average ratio between the mean log intensity of genes classified as “inflammatory” versus “regulatory”. Student's t-test was used to compare the mean I.I.com between cohorts. Quantitative scoring of plasma-induced signatures showed SCD patients had significantly higher mean I.I.com during baseline health compared to controls (0.713 vs. -1.235-12, p=5.4625-11). SCD patients during acute pain had significantly higher I.I.com than during baseline health (1.282 vs. 0.713, p=5.2051-8). Our novel assay that assesses inflammatory and immune regulatory gene expression allowed for determining the balance between these two states. We found distinct inflammatory signatures in SCD patients compared to controls and in SCD patients during acute pain as compared to baseline health. This imbalance between inflammation and immune regulation could contribute to the development of acute and chronic SCD pain. National Institutes of Health #1R61NS114954-01.