Low back pain is a common ailment which can be debilitating and which becomes chronic in 30% of cases. Many patients fail to achieve adequate relief for such chronic pain conditions with current therapies. Inflammation of the lumbar dorsal root ganglia (DRG), e.g. secondary to an immune response to a ruptured disc, may contribute to some forms of low back pain. Because inflammation plays an important role in back pain, a common treatment involves local injections of anti-inflammatory corticosteroids. However, this treatment has been controversial. Randomized clinical trials of these treatments have had mixed results, and not all patients obtain relief from steroids. The nominal target of corticosteroid drugs is the glucocorticoid receptor (GR). However, recent in vitro studies show that many steroids clinically used for back pain injections (including 6-? methylprednisolone and triamcinolone) can also activate the mineralocorticoid receptor (MR) with similar potency. The MR is best known as the target of aldosterone, promoting sodium reabsorption in the kidney. However, this receptor is expressed in other cell types including cardiomyocytes, brain neurons, and DRG neurons. In many tissues MR plays a pro-inflammatory role which would be expected to counteract the anti-inflammatory effects of GR activation. Our hypothesis is that avoiding MR activation will increase the efficacy of steroids used in treatment of low back pain. We will test this hypothesis with three specific aims (SA), using two established preclinical models of low back pain. SA1. To further characterize effects of local MR activation in contributing to back pain and molecular correlates of inflammation. We will determine the effects of local mineralocorticoid blockade or activation, and MR receptor knockdown, in rat models of low back pain, examining pain behaviors, sensory neuron excitability, cytokine profile, and histochemical measures of inflammation and receptor activation. SA2. To test the hypothesis that clinically used glucocorticoids (GR agonists) also activate the mineralocorticoid receptor, reducing their ability to improve back pain and molecular correlates of inflammation. We will examine the effects of several steroids commonly used in low back pain injections (all of which activate the MR in vitro), a highly glucocorticoid selective steroid used in in other clinical settings, and the endogenous glucocorticoid corticosterone. SA3. To assess a novel therapeutic approach for back pain by combining GR agonists with MR antagonists to improve back pain and molecular correlates of inflammation. The steroids examined in SA2 will be tested in combination with mineralocorticoid antagonists or knockdown. Our long term goal is to establish the preclinical basis for clinical trials testing our hypothesis that mineralocorticoid antagonists may improve the response to locally injected steroids commonly used for low back pain treatment. Such trials are made more feasible by the fact that a selective mineralocorticoid antagonist, eplerenone, is already approved for use in the United States for heart failure and hypertension.

Public Health Relevance

We propose to establish the preclinical basis for clinical trials testing our hypothesis that mineralocorticoid antagonists may improve the response to locally injected steroids commonly used for low back pain treatment. Such trials are made more feasible by the fact that a selective mineralocorticoid antagonist, eplerenone, is already approved for use in the United States for heart failure and hypertension.

Agency
National Institute of Health (NIH)
Institute
National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS)
Type
Research Project (R01)
Project #
5R01AR068989-03
Application #
9517762
Study Section
Somatosensory and Chemosensory Systems Study Section (SCS)
Program Officer
Washabaugh, Charles H
Project Start
2016-07-15
Project End
2021-06-30
Budget Start
2018-07-01
Budget End
2019-06-30
Support Year
3
Fiscal Year
2018
Total Cost
Indirect Cost
Name
University of Cincinnati
Department
Anesthesiology
Type
Schools of Medicine
DUNS #
041064767
City
Cincinnati
State
OH
Country
United States
Zip Code
45221
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Strong, Judith A (2018) High-fat diet and post-operative pain: Why the hospital cafeteria may matter. Brain Behav Immun 74:45-46
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Li, Ai-Ling; Zhang, Jing-Dong; Xie, Wenrui et al. (2018) Inflammatory Changes in Paravertebral Sympathetic Ganglia in Two Rat Pain Models. Neurosci Bull 34:85-97
Xie, Wenrui; Strong, Judith A; Zhang, Jun-Ming (2017) Active Nerve Regeneration with Failed Target Reinnervation Drives Persistent Neuropathic Pain. eNeuro 4:
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Ibrahim, Shaimaa I A; Strong, Judith A; Zhang, Jun-Ming (2016) Mineralocorticoid Receptor, A Promising Target for Improving Management of Low Back Pain by Epidural Steroid Injections. J Anesth Perioper Med 3:177-184