Shenoda Botros B, Alexander Guillermo M, Ajit Seena K
Pharmacology and Physiology, Drexel University College of Medicine, 245 North 15th Street, Mail Stop 488, Philadelphia, PA, 19102, USA.
Neurology, Drexel University College of Medicine, Philadelphia, USA.
J Transl Med. 2016 Mar 3;14:64. doi: 10.1186/s12967-016-0820-1.
Ketamine provides relief for a subset of patients with complex regional pain syndrome (CRPS). The poor responders had a lower body mass index (BMI) relative to responders. Regulation of proopiomelanocortin (POMC) expression is crucial in normal body weight homeostasis. The main objectives of this study were to investigate the mechanisms underlying lower BMI characterizing CRPS patients responding poorly to intravenous ketamine therapy and identify potential biomarkers for predicting response.
We investigated POMC transcript levels in blood from CRPS patients grouped as responders and poor responders to ketamine therapy. Plasma levels of β-endorphin, ACTH and α-MSH were measured by ELISA. We previously identified differential expression of small noncoding microRNA hsa-miR-34a in blood between responders and poor responders. We investigated whether a 11-fold downregulation of hsa-miR-34a in poor responders relative to responders is contributing to the differences in POMC levels by targeting POMC regulator CRHR1. Binding of miR-34a to CRHR1 was assessed using reporter assay; changes in mRNA and protein levels of CRHR1 were used to determine the regulation of CRHR1 by miR-34a. RNA from blood of CRPS and control subjects were used for quantitative PCR for CRHR1.
Though ketamine treatment did not alter POMC expression, poor responders had higher levels of POMC mRNA than responders, both before and after treatment. Corticotropin-releasing hormone (CRH) is a key regulator of POMC expression and the biological effects are mediated through its receptor corticotrophin releasing hormone receptor 1 (CRHR1). We show that hsa-miR-34a is a negative regulator of CRHR1; overexpression of hsa-miR-34a in Jurkat cells resulted in reduction of CRH-mediated POMC expression. Poor responders had higher expression of CRHR1 transcripts than responders, indicating a regulatory role for miR-34a. In addition, we found positive correlations between the pretreatment levels of miR-34a to BMI and response to ketamine therapy.
Our findings indicate a mechanism by which hsa-miR-34a can regulate the CRH/CRHR1/POMC axis and may influence BMI. Studies in larger patient cohorts are required to confirm the biomarker utility of circulating hsa-miR-34a levels in predicting treatment response to ketamine therapy.
氯胺酮可为一部分复杂性区域疼痛综合征（CRPS）患者缓解疼痛。相对于有反应者，无反应者的体重指数（BMI）较低。阿片促黑素皮质激素原（POMC）表达的调节在正常体重稳态中至关重要。本研究的主要目的是探讨CRPS患者对静脉注射氯胺酮治疗反应不佳时BMI较低的潜在机制，并确定预测反应的潜在生物标志物。
我们研究了氯胺酮治疗反应者和无反应者分组的CRPS患者血液中POMC转录水平。通过酶联免疫吸附测定（ELISA）测量血浆β-内啡肽、促肾上腺皮质激素（ACTH）和α-促黑素（α-MSH）水平。我们之前已确定反应者和无反应者血液中小非编码微小RNA hsa-miR-34a的差异表达。我们研究了相对于反应者，无反应者中hsa-miR-34a下调11倍是否通过靶向POMC调节因子促肾上腺皮质激素释放激素受体1（CRHR1）导致POMC水平的差异。使用报告基因测定评估miR-34a与CRHR1的结合；通过CRHR1的mRNA和蛋白质水平变化来确定miR-34a对CRHR1的调节作用。CRPS患者和对照受试者血液中的RNA用于CRHR1的定量聚合酶链反应（PCR）。
尽管氯胺酮治疗未改变POMC表达，但无论治疗前还是治疗后，无反应者的POMC mRNA水平均高于反应者。促肾上腺皮质激素释放激素（CRH）是POMC表达的关键调节因子，其生物学效应通过其受体促肾上腺皮质激素释放激素受体1（CRHR1）介导。我们发现hsa-miR-34a是CRHR1的负调节因子；在Jurkat细胞中过表达hsa-miR-34a导致CRH介导的POMC表达降低。无反应者的CRHR1转录本表达高于反应者，表明miR-34a具有调节作用。此外，我们发现miR-34a预处理水平与BMI及氯胺酮治疗反应之间存在正相关。
我们的研究结果表明hsa-miR-34a可调节CRH/CRHR1/POMC轴并可能影响BMI的一种机制。需要在更大的患者队列中进行研究，以确认循环hsa-miR-34a水平在预测氯胺酮治疗反应中的生物标志物效用。
