Epidural injection of cyclooxygenase-2 inhibitor attenuates pain-related behavior following application of nucleus pulposus to the nerve root in the rat

Intervertebral disc degeneration and inflammatory microenvironment: expression, pathology, and therapeutic strategies

BACKGROUND

Intervertebral disc degeneration (IDD) is a leading cause of low back pain (LBP), posing a significant socioeconomic burden. Recent studies highlight the crucial role of inflammatory microenvironment in IDD progression.

METHOD

A keyword-based search was performed using the PubMed database for published articles.

RESULTS AND CONCLUSIONS

Dysregulated expression of inflammatory cytokines disrupts intervertebral disc (IVD) homeostasis, causing atrophy, fibrosis, and phenotypic changes in nucleus pulposus cells. Modulating the inflammatory microenvironment and restoring cytokine balance hold promise for IVD repair and regeneration. This comprehensive review systematically examines the expression regulation, pathological effects, therapeutic strategies, and future challenges associated with the inflammatory microenvironment and relevant cytokines in IDD. Key inflammatory cytokines, including interleukins (IL), tumor necrosis factor-alpha (TNF-α), and chemokines, exhibit significant pathological effects in IDD. Furthermore, major therapeutic modalities such as chemical antagonists, biologics, plant extracts, and gene transcription therapies are introduced to control and ameliorate the inflammatory microenvironment. These approaches provide valuable insights for identifying potential targets in future anti-inflammatory treatments for IDD.

Regulatory Effect of Inflammatory Mediators in Intervertebral Disc Degeneration

Intervertebral disc degeneration (IDD) is a major contributor to back, neck, and radicular pain. It is related to changes in tissue structure and function, including the breakdown of the extracellular matrix (ECM), aging, apoptosis of the nucleus pulposus, and biomechanical tissue impairment. Recently, an increasing number of studies have demonstrated that inflammatory mediators play a crucial role in IDD, and they are being explored as potential treatment targets for IDD and associated disorders. For example, interleukins (IL), tumour necrosis factor-α (TNF-α), chemokines, and inflammasomes have all been linked to the pathophysiology of IDD. These inflammatory mediators are found in high concentrations in intervertebral disc (IVD) tissues and cells and are associated with the severity of LBP and IDD. It is feasible to reduce the production of these proinflammatory mediators and develop a novel therapy for IDD, which will be a hotspot of future research. In this review, the effects of inflammatory mediators in IDD were described.

Effect of epidural polydeoxyribonucleotide in a rat model of lumbar foraminal stenosis

Background

We aimed to investigate the effect of epidural polydeoxyribonucleotide (PDRN) on mechanical allodynia and motor dysfunction in a rat model of lumbar foraminal stenosis (LFS).

Methods

This study was conducted in two stages, using male Sprague-Dawley rats. The rats were randomly divided into eight groups. In the first stage, the groups were as follows vehicle (V), sham (S), and epidural PDRN at 5 (P5), 8 (P8), and 10 (P10) mg/kg; and in the second stage, they were as follows intraperitoneal PDRN 8 mg/kg, epidural 3,7-dimethyl-1-propargilxanthine (DMPX) (0.1 mg/kg), and DMPX (0.1 mg/kg). The LFS model was established, except for the S group. After an epidural injection of the test solutions, von Frey and treadmill tests were conducted for 3 weeks. Subsequently, histopathologic examinations were conducted in the V, S, P5, and P10 groups.

Results

A total of 65 rats were included. The P8 and P10 groups showed significant recovery from mechanical allodynia and motor dysfunction at all time points after drug administration compared to the V group. These effects were abolished by concomitant administration of DMPX. On histopathological examination, no epineurial inflammation or fibrosis was observed in the epidural PDRN groups.

Conclusions

Epidural injection of PDRN significantly improves mechanical allodynia and motor dysfunction in a rat model of LFS, which is mediated by the spinal adenosine A_2A receptor. The present data support the need for further research to determine the role of epidural PDRN in spinal stenosis treatment.

Analgesic Effects of Two Types of Spinal Manipulation in Acute Lumbar Radiculopathy Model Rats

OBJECTIVE

To compare the analgesic effects of two types of spinal manipulation (SM) in acute lumbar radiculopathy (ALR) model rats induced by self-transplantation of autologous nucleus pulposus (ANP), and clarify the therapeutic mechanism.

METHODS

Totally 108 male Sprague-Dawley rats were randomly divided into 6 groups by a random number table (18 rats in each group), including a blank group with no interference, a sham operation group with a surgery by making a local soft tissue incision on the left side of L5-6 vertebral segment, a model group with ALR of L5 extraforaminal nerve by ANP self-transplantation without other interference, a sham manipulation (SMA) group with simulating physical rotation, as well as a mobilization (MOB) group with simulating low-velocity and variable-amplitude rotation and a manipulation (MAN) group with simulating high-velocity and low-amplitude rotation. The interventions in SMA, MOB, and MAN groups started 1 day after modeling followed by another 5 treatments at days 3, 5, 8, 10 and 12. Rats in the other 3 groups did not receive any special intervention. Behavioral pain tests of 50% mechanical pain withdrawal threshold (50% PWT) and paw withdrawal latency (PWL) were conducted 1 day before operation followed by another 10 tests on days 1-7, 10, 12 and 14. Immunohistochemical expression of nitric oxide synthase (NOS) was investigated on days 5 and 12 after operation.

RESULTS

After 3 experimental SM interventions, 50% PWT and PWL were higher in the MAN group than the SMA group on days 6 and 7, and higher on days 10, 12 and 14 postoperatively (P<0.05 or P<0.01), while the same indices were significantly higher in the MOB group than MAN group on days 1-4 (P<0.05 or P<0.01). The expression of NOS was lower in the MAN and MOB groups than SMA group on day 12 postoperatively (P<0.01).

CONCLUSIONS

Both manipulation and mobilization produced better results than sham interference in relieving pain by reducing neuroinflammation possibly. At the early period, compared with manipulation, mobilization presented less sensitive response to pain until later visit. SM may inhibit the overexpression of NOS, thereby alleviating severe radiculopathy.

Non-steroidal anti-inflammatory drugs (NSAIDs) for chronic non-cancer pain in children and adolescents

BACKGROUND

Pain is a common feature of childhood and adolescence around the world, and for many young people, that pain is chronic. The World Health Organization guidelines for pharmacological treatments for children's persisting pain acknowledge that pain in children is a major public health concern of high significance in most parts of the world. While in the past pain was largely dismissed and was frequently left untreated, views on children's pain have changed over time, and relief of pain is now seen as important.We designed a suite of seven reviews on chronic non-cancer pain and cancer pain (looking at antidepressants, antiepileptic drugs, non-steroidal anti-inflammatory drugs, opioids, and paracetamol) in order to review the evidence for children's pain utilising pharmacological interventions.As the leading cause of morbidity in the world today, chronic disease (and its associated pain) is a major health concern. Chronic pain (that is pain lasting three months or longer) can arise in the paediatric population in a variety of pathophysiological classifications (nociceptive, neuropathic, or idiopathic) from genetic conditions, nerve damage pain, chronic musculoskeletal pain, and chronic abdominal pain, as well as for other unknown reasons.Non-steroidal anti-inflammatory drugs (NSAIDs) are used to treat pain, reduce fever, and for their anti-inflammation properties. They are commonly used within paediatric pain management. Non-steroidal anti-inflammatory drugs are currently licensed for use in Western countries, however they are not approved for infants under three months old. The main adverse effects include renal impairment and gastrointestinal issues. Common side effects in children include diarrhoea, headache, nausea, constipation, rash, dizziness, and abdominal pain.

OBJECTIVES

To assess the analgesic efficacy and adverse events of NSAIDs used to treat chronic non-cancer pain in children and adolescents aged between birth and 17 years, in any setting.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) via the Cochrane Register of Studies Online, MEDLINE via Ovid, and Embase via Ovid from inception to 6 September 2016. We also searched the reference lists of retrieved studies and reviews, as well as online clinical trial registries.

SELECTION CRITERIA

Randomised controlled trials, with or without blinding, of any dose and any route, treating chronic non-cancer pain in children and adolescents, comparing any NSAID with placebo or an active comparator.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed studies for eligibility. We planned to use dichotomous data to calculate risk ratio and number needed to treat for one additional event, using standard methods. We assessed GRADE and created three 'Summary of findings' tables.

MAIN RESULTS

We included seven studies with a total of 1074 participants (aged 2 to 18 years) with chronic juvenile polyarthritis or chronic juvenile rheumatoid arthritis. All seven studies compared an NSAID with an active comparator. None of the studies were placebo controlled. No two studies investigated the same type of NSAID compared with another. We were unable to perform a meta-analysis.Risk of bias varied. For randomisation and allocation concealment, one study was low risk and six studies were unclear risk. For blinding of participants and personnel, three studies were low risk and four studies were unclear to high risk. For blinding of outcome assessors, all studies were unclear risk. For attrition, four studies were low risk and three studies were unclear risk. For selective reporting, four studies were low risk, two studies were unclear risk, and one study was high risk. For size, three studies were unclear risk and four studies were high risk. For other potential sources of bias, seven studies were low risk. Primary outcomesThree studies reported participant-reported pain relief of 30% or greater, showing no statistically significant difference in pain scores between meloxicam and naproxen, celecoxib and naproxen, or rofecoxib and naproxen (P > 0.05) (low-quality evidence).One study reported participant-reported pain relief of 50% or greater, showing no statistically significant difference in pain scores between low-dose meloxicam (0.125 mg/kg) and high-dose meloxicam (0.25 mg/kg) when compared to naproxen 10 mg/kg (P > 0.05) (low-quality evidence).One study reported Patient Global Impression of Change, showing 'very much improved' in 85% of ibuprofen and 90% of aspirin participants (low-quality evidence). Secondary outcomesAll seven studies reported adverse events. Participants reporting an adverse event (one or more per person) by drug were: aspirin 85/202; fenoprofen 28/49; ibuprofen 40/45; indomethacin 9/30; ketoprofen 9/30; meloxicam 18/47; naproxen 44/202; and rofecoxib 47/209 (very low-quality evidence).All seven studies reported withdrawals due to adverse events. Participants withdrawn due to an adverse event by drug were: aspirin 16/120; celecoxib 10/159; fenoprofen 0/49; ibuprofen 0/45; indomethacin 0/30; ketoprofen 0/30; meloxicam 10/147; naproxen 17/285; and rofecoxib 3/209 (very low-quality evidence).All seven studies reported serious adverse events. Participants experiencing a serious adverse event by drug were: aspirin 13/120; celecoxib 5/159; fenoprofen 0/79; ketoprofen 0/30; ibuprofen 4/45; indomethacin 0/30; meloxicam 11/147; naproxen 10/285; and rofecoxib 0/209 (very low-quality evidence).There were few or no data for our remaining secondary outcomes: Carer Global Impression of Change; requirement for rescue analgesia; sleep duration and quality; acceptability of treatment; physical functioning as defined by validated scales; and quality of life as defined by validated scales (very low-quality evidence).We rated the overall quality of the evidence (GRADE rating) for our primary and secondary outcomes as very low because there were limited data from studies and no opportunity for a meta-analysis.

AUTHORS' CONCLUSIONS

We identified only a small number of studies, with insufficient data for analysis.As we could undertake no meta-analysis, we are unable to comment about efficacy or harm from the use of NSAIDs to treat chronic non-cancer pain in children and adolescents. Similarly, we cannot comment on our remaining secondary outcomes: Carer Global Impression of Change; requirement for rescue analgesia; sleep duration and quality; acceptability of treatment; physical functioning; and quality of life.We know from adult randomised controlled trials that some NSAIDs, such as ibuprofen, naproxen, and aspirin, can be effective in certain chronic pain conditions.

Non-steroidal anti-inflammatory drugs (NSAIDs) for cancer-related pain in children and adolescents

BACKGROUND

Pain is a common feature of childhood and adolescence around the world, and for many young people, that pain is chronic. The World Health Organization (WHO) guidelines for pharmacological treatments for persisting pain in children acknowledge that pain in children is a major public health concern of high significance in most parts of the world. Views on children's pain have changed over time and relief of pain is now seen as important. In the past, pain was largely dismissed and was frequently left untreated, and it was assumed that children quickly forgot about painful experiences.We designed a suite of seven reviews in chronic non-cancer pain and cancer pain (looking at antidepressants, antiepileptic drugs, non-steroidal anti-inflammatory drugs, opioids, and paracetamol as priority areas) to review the evidence for children's pain using pharmacological interventions.As one of the leading causes of mortality and morbidity for children and adolescents in the world today, childhood cancer (and its associated pain) is a major health concern. Specific mortality and morbidity data relating to children are not currently identified. All childhood cancer rates are on the rise; for example, in the USA approximately 10,380 children aged under 15 years were expected to be diagnosed with cancer by the end of 2016. However, with survival rates also increasing, over 80% of paediatric cancer patients are expected to survive for five years or more, thus identifying the need to address pain management in this population.Cancer pain in infants, children, and adolescents is primarily nociceptive pain with negative long term effects. Cancer-related pain is generally caused directly by the tumour itself such as compressing on the nerve or inflammation of the organs. Cancer-related pain generally occurs as a result of perioperative procedures, nerve damage caused by radiation or chemotherapy treatments, or mucositis. However, this review focused on pain caused directly by the tumour itself such as nerve infiltration, external nerve compression, and other inflammatory events.Non-steroidal anti-inflammatory drugs (NSAIDs) are used to treat pain, reduce fever, and for their anti-inflammatory properties. They are commonly used within paediatric pain management. NSAIDs are currently licensed for use in western countries, however not approved for infants aged under three months. Primary adverse effects include gastrointestinal issues and possible renal impairment with long term use. Other adverse effects in children include diarrhoea, headache, nausea, constipation, rash, dizziness, and abdominal pain.

OBJECTIVES

To assess the analgesic efficacy, and adverse events, of non-steroidal anti-inflammatory drugs (NSAIDs) used to treat cancer-related pain in children and adolescents aged from birth and 17 years, in any setting.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) via the Cochrane Register of Studies Online, MEDLINE via Ovid, and Embase via Ovid from inception to 21 February 2017. We also searched the reference lists of retrieved studies and reviews, and searched online clinical trial registries.

SELECTION CRITERIA

Randomised, double-blind trials of any dose, and any route, treating cancer-related pain in children and adolescents, comparing NSAIDs with placebo or an active comparator.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed studies for eligibility. We planned to use dichotomous data to calculate risk ratio and number needed to treat for one additional event, using standard methods. We assessed GRADE (Grading of Recommendations Assessment, Development and Evaluation) and planned to create a 'Summary of findings' table.

MAIN RESULTS

No studies were eligible for inclusion in this review (very low quality evidence). We downgraded the quality of evidence by three levels due to the lack of data reported for any outcome.

AUTHORS' CONCLUSIONS

There is no evidence from randomised controlled trials that non-steroidal anti-inflammatory drugs (NSAIDs) reduce cancer-related pain in children and adolescents. This means that no reliance or conclusions can be made about efficacy or harm in the use of NSAIDs to treat chronic cancer-related pain in children and adolescents.

Oral nonsteroidal anti-inflammatory drugs for fibromyalgia in adults

BACKGROUND

Oral nonsteroidal anti-inflammatory drugs (NSAIDs) are widely used in the treatment of pain in fibromyalgia, despite being considered not to be effective.

OBJECTIVES

To assess the analgesic efficacy, tolerability (drop-out due to adverse events), and safety (serious adverse events) of oral nonsteroidal anti-inflammatory drugs for fibromyalgia in adults.

SEARCH METHODS

We searched CENTRAL, MEDLINE, and Embase for randomised controlled trials from inception to January 2017. We also searched the reference lists of retrieved studies and reviews, and online clinical trial registries.

SELECTION CRITERIA

We included randomised, double-blind trials of two weeks' duration or longer, comparing any oral NSAID with placebo or another active treatment for relief of pain in fibromyalgia, with subjective pain assessment by the participant.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data and assessed trial quality and potential bias. Primary outcomes were participants with substantial pain relief (at least 50% pain relief over baseline or very much improved on Patient Global Impression of Change scale (PGIC)) or moderate pain relief (at least 30% pain relief over baseline or much or very much improved on PGIC), serious adverse events, and withdrawals due to adverse events; secondary outcomes were adverse events, withdrawals due to lack of efficacy, and outcomes relating to sleep, fatigue, and quality of life. Where pooled analysis was possible, we used dichotomous data to calculate risk difference (RD) and number needed to treat for an additional beneficial outcome (NNT), using standard methods. We assessed the quality of the evidence using GRADE and created a 'Summary of findings' table.

MAIN RESULTS

Our searches identified six randomised, double-blind studies involving 292 participants in suitably characterised fibromyalgia. The mean age of participants was between 39 and 50 years, and 89% to 100% were women. The initial pain intensity was around 7/10 on a 0 to 10 pain scale, indicating severe pain. NSAIDs tested were etoricoxib 90 mg daily, ibuprofen 2400 mg daily, naproxen 1000 mg daily, and tenoxicam 20 mg daily; 146 participants received NSAID and 146 placebo. The duration of treatment in the double-blind phase varied between three and eight weeks.Not all studies reported all the outcomes of interest. Analyses consistently showed no significant difference between NSAID and placebo: substantial benefit (at least 50% pain intensity reduction) (risk difference (RD) -0.07 (95% confidence interval (CI) -0.18 to 0.04) 2 studies, 146 participants; moderate benefit (at least 30% pain intensity reduction) (RD -0.04 (95% CI -0.16 to 0.08) 3 studies, 192 participants; withdrawals due to adverse events (RD 0.04 (95% CI -0.02 to 0.09) 4 studies, 230 participants; participants experiencing any adverse event (RD 0.08 (95% CI -0.03 to 0.19) 4 studies, 230 participants; all-cause withdrawals (RD 0.03 (95% CI -0.07 to 0.14) 3 studies, 192 participants. There were no serious adverse events or deaths. Although most studies had some measures of health-related quality of life, fibromyalgia impact, or other outcomes, none reported the outcomes beyond saying that there was no or little difference between the treatment groups.We downgraded evidence on all outcomes to very low quality, meaning that this research does not provide a reliable indication of the likely effect. The likelihood that the effect could be substantially different is very high. This is based on the small numbers of studies, participants, and events, as well as other deficiencies of reporting study quality allowing possible risks of bias.

AUTHORS' CONCLUSIONS

There is only a modest amount of very low-quality evidence about the use of NSAIDs in fibromyalgia, and that comes from small, largely inadequate studies with potential risk of bias. That bias would normally be to increase the apparent benefits of NSAIDs, but no such benefits were seen. Consequently, NSAIDs cannot be regarded as useful for treating fibromyalgia.

Non‐steroidal anti‐inflammatory drugs (NSAIDs) for chronic non‐cancer pain in children and adolescents

This is a protocol for a Cochrane Review (Intervention). The objectives are as follows:

To assess the analgesic efficacy, and adverse events, of NSAIDs used to treat chronic non‐cancer pain in children and adolescents aged between birth and 17 years, in any setting.

Therapeutic effect of epidural hyaluronic acid in a rat model of foraminal stenosis

PURPOSE

Since receiving a warning from the US Food and Drug Administration (FDA) about injection of corticosteroids into the epidural space having serious adverse events, we have sought alternative medications for injection at this site. Hyaluronic acid (HA) has anti-adhesive, anti-inflammatory, and lubricating properties, so could potentially be useful for spinal pain. The exact mechanism by which spinal stenosis develops is not fully understood, but is likely to involve inflammation. Therefore, we hypothesized that HA could have a therapeutic effect in spinal stenosis. This study evaluated the effects of epidural administration of HA on alleviation of pain in a rat model of foraminal stenosis.

MATERIALS AND METHODS

After creating the animal model, HA (HA group) or saline solution (S group) was administered via an epidural catheter. The paw-withdrawal threshold to mechanical stimulation and motor dysfunction were monitored for up to 21 days. Tissue was collected to evaluate the degree of adhesion, inflammation in the perineural area, and chromatolysis in the dorsal root ganglion (DRG).

RESULTS

The mechanical withdrawal threshold was restored in the HA group but not in the S group (P < 0.001). The HA group also showed less fibrosis (P = 0.026) and less chromatolysis (P = 0.002) than the S group.

CONCLUSION

HA administered epidurally had a therapeutic effect on the allodynia and hyperalgesia induced by chronic compression of the DRG.

Mineralocorticoid Receptor, A Promising Target for Improving Management of Low Back Pain by Epidural Steroid Injections

AIM OF REVIEW

Low back pain is a major health problem in United States and worldwide. In this review, we aim to show that mineralocorticoid receptor (MR) activation has a critical role in the initiation of immune and inflammatory responses, which in turn can impact the effectiveness of the currently used steroids for epidural injections in low back pain management since most steroids activate MR in addition to the primary target, glucocorticoid receptor (GR). Moreover, we would like to determine some of the benefits of blocking the MR-induced negative effects. Overall, we propose a novel therapeutic approach for low back pain management by using a combination of a MR antagonist and a GR agonist in the epidural injections.

METHOD

We will first introduce the societal cost of low back pain and discuss how epidural steroid injections became a popular treatment for this condition. We will then describe several preclinical models used for the study of low back pain conditions and the findings with respect to the role of MR in the development of inflammatory low back pain.

RECENT FINDINGS

MR has pro-inflammatory effects in many tissues which can counteract the anti-inflammatory effects induced by GR activation. Blocking MR using the selective MR antagonist eplerenone can reduce pain and sensory neuron excitability in experimental models of low back pain. Moreover, combining the MR antagonist with clinically used steroids is more effective in reducing pain behaviors than using the steroids alone.

SUMMARY

MR antagonists are promising candidates to increase the effectiveness of currently used steroids. Since the activation of the MR is evident in preclinical models of low back pain, blocking its deleterious effects can be beneficial in managing inflammatory pain conditions.

A Novel Nitronyl Nitroxide with Salicylic Acid Framework Attenuates Pain Hypersensitivity and Ectopic Neuronal Discharges in Radicular Low Back Pain

Evidence has accumulated that reactive oxygen species and inflammation play crucial roles in the development of chronic pain, including radicular low back pain. Nonsteroid anti-inflammatory drugs (NSAIDs), for example, salicylic acid, aspirin, provided analgesic effects in various types of pain. However, long-term use of these drugs causes unwanted side effects, which limits their implication. Stable nitronyl (NIT) nitroxide radicals have been extensively studied as a unique and interesting class of new antioxidants for protection against oxidative damage. The present study synthesized a novel NIT nitroxide radical with salicylic acid framework (SANR) to provide synergistic effect of both antioxidation and antiinflammation. We demonstrated for the first time that both acute and repeated SANR treatment exerted dramatic analgesic effect in radicular low back pain mimicked by chronic compression of dorsal root ganglion in rats. This analgesic potency was more potent than that produced by classical NSAIDs aspirin and traditional nitroxide radical Tempol alone. Furthermore, SANR-induced behavioral analgesia is found to be mediated, at least in partial, by a reduction of ectopic spontaneous discharges in injured DRG neurons. Therefore, the synthesized NIT nitroxide radical coupling with salicylic acid framework may represent a novel potential therapeutic candidate for treatment of chronic pain, including radicular low back pain.

Reduced tonicity stimulates an inflammatory response in nucleus pulposus tissue that can be limited by a COX-2-specific inhibitor

In intervertebral disc herniation with nucleus pulposus (NP) extrusion, the elicited inflammatory response is considered a key pain mechanism. However, inflammatory cytokines are reported in extruded herniated tissue, even before monocyte infiltration, suggesting that the tissue itself initiates the inflammation. Since herniated tissue swells, we investigated whether this simple mechanobiological stimulus alone could provoke an inflammatory response that could cause pain. Furthermore, we investigated whether sustained-release cyclooxygenase-2 (COX2) inhibitor would be beneficial in such conditions. Healthy bovine NP explants were allowed to swell freely or confined. The swelling explants were treated with Celecoxib, applied either as a bolus or in sustained-release. Swelling explants produced elevated levels of interleukin-6 (IL-6) and prostaglandin E2 (PGE2 ) for 28 days, while confined explants did not. Both a high concentration bolus and 10 times lower concentration in sustained release completely inhibited PGE2 production, but did not affect IL-6 production. Swelling of NP tissue, without the inflammatory system response, can trigger cytokine production and Celecoxib, even in bolus form, may be useful for pain control in extruded disc herniation.

Oral nonsteroidal anti-inflammatory drugs for neuropathic pain

BACKGROUND

Although often considered to be lacking adequate evidence, nonsteroidal anti-inflammatory drugs (NSAIDs) are widely used in the management of neuropathic pain. Previous surveys found 18% to 47% of affected people reported using NSAIDs specifically for their neuropathic pain, although possibly not in the United Kingdom (UK).

OBJECTIVES

To assess the analgesic efficacy of oral NSAIDs for chronic neuropathic pain in adults, when compared to placebo or another active intervention, and the adverse events associated with its use in clinical trials.

SEARCH METHODS

We searched CENTRAL, MEDLINE, and EMBASE from inception to 29 May 2015, together with reference lists of retrieved papers and reviews, and an online trials registry.

SELECTION CRITERIA

We included randomised, double-blind studies of two weeks duration or longer, comparing any oral NSAID with placebo or another active treatment in chronic neuropathic pain.

DATA COLLECTION AND ANALYSIS

Two review authors independently searched for studies, extracted efficacy and adverse event data, and examined issues of study quality. We did not carry out any pooled analysis.

MAIN RESULTS

We included two studies involving 251 participants with chronic low back pain with a neuropathic component or postherpetic neuralgia; 209 of these participants were involved in a study of an experimental NSAID not used in clinical practice, and of the remaining 42, only 16 had neuropathic pain. This represented only third tier evidence, and was of very low quality. There was no indication of any significant pain reduction with NSAIDs. Adverse event rates were low, with insufficient events for any analysis.

AUTHORS' CONCLUSIONS

There is no evidence to support or refute the use of oral NSAIDs to treat neuropathic pain conditions.

Inflammation in intervertebral disc degeneration and regeneration

Intervertebral disc (IVD) degeneration is one of the major causes of low back pain, a problem with a heavy economic burden, which has been increasing in prevalence as populations age. Deeper knowledge of the complex spatial and temporal orchestration of cellular interactions and extracellular matrix remodelling is critical to improve current IVD therapies, which have so far proved unsatisfactory. Inflammation has been correlated with degenerative disc disease but its role in discogenic pain and hernia regression remains controversial. The inflammatory response may be involved in the onset of disease, but it is also crucial in maintaining tissue homeostasis. Furthermore, if properly balanced it may contribute to tissue repair/regeneration as has already been demonstrated in other tissues. In this review, we focus on how inflammation has been associated with IVD degeneration by describing observational and in vitro studies as well as in vivo animal models. Finally, we provide an overview of IVD regenerative therapies that target key inflammatory players.

Preclinical studies of low back pain

Chronic low back pain is a major cause of disability and health care costs. Current treatments are inadequate for many patients. A number of preclinical models have been developed that attempt to mimic aspects of clinical conditions that contribute to low back pain. These involve application of nucleus pulposus material near the lumbar dorsal root ganglia (DRG), chronic compression of the DRG, or localized inflammation of the DRG. These models, which are primarily implemented in rats, have many common features including behavioral hypersensitivity of the hindpaw, enhanced excitability and spontaneous activity of sensory neurons, and locally elevated levels of inflammatory mediators including cytokines. Clinically, epidural injection of steroids (glucocorticoids) is commonly used when more conservative treatments fail, but clinical trials evaluating these treatments have yielded mixed results. There are relatively few preclinical studies of steroid effects in low back pain models. One preclinical study suggests that the mineralocorticoid receptor, also present in the DRG, may have pro-inflammatory effects that oppose the activation of the glucocorticoid receptor. Although the glucocorticoid receptor is the target of anti-inflammatory steroids, many clinically used steroids activate both receptors. This could be one explanation for the limited effects of epidural steroids in some patients. Additional preclinical research is needed to address other possible reasons for limited efficacy of steroids, such as central sensitization or presence of an ongoing inflammatory stimulus in some forms of low back pain.

Evaluation of the Neurological Safety of Epidural Milnacipran in Rats

Background

Milnacipran is a balanced serotonin norepinephrine reuptake inhibitor with minimal side effects and broad safety margin. It acts primarily on the descending inhibitory pain pathway in brain and spinal cord. In many animal studies, intrathecal administration of milnacipran is effective in neuropathic pain management. However, there is no study for the neurological safety of milnacipran when it is administered neuraxially. This study examined the neurotoxicity of epidural milnacipran by observing behavioral and sensory-motor changes with histopathological examinations of spinal cords in rats.

Methods

Sixty rats were divided into 3 groups, with each group receiving epidural administration of either 0.3 ml (3 mg) of milnacipran (group M, n = 20), 0.3 ml of 40% alcohol (group A, n = 20), or 0.3 ml of normal saline (group S, n = 20).

Results

There were no abnormal changes in the behavioral, sensory-motor, or histopathological findings in all rats of groups M and S over a 3-week observation period, whereas all rats in group A had abnormal changes.

Conclusions

Based on these findings, the direct epidural administration of milnacipran in rats did not present any evidence of neurotoxicity in behavioral, sensory-motor and histopathological evaluations.

Modification of rat model of sciatica induced by lumber disc herniation and the anti-inflammatory effect of osthole given by epidural catheterization

One of the most treatable causes of lower back pain and associated sciatica is lumbar disc herniation (LDH), which is characterized by rupture of the hard outer wall (annulus fibrosis) in a lumbar intervertebral disc. In the current study, we aimed to: (1) develop and characterize a rat model of sciatica induced by LDH, while introducing a novel method of epidural catheterization; (2) use this model to evaluate the effect of osthole on pain due to LDH, and (3) gain insight into the mechanisms through which osthole affects sciatica induced by LDH. The results indicate that our newly developed rat model maintained mechanical allodynia for 28 days without reduction. Moreover, cyclooxygenase-2 (COX-2) and nitric oxide synthase (NOS) were overexpressed in the associated inflammatory response, which is consistent with clinical manifestations of the disease. We then used this model to study the effect and mechanisms through which osthole affected pain due to LDH. Our study suggests that osthole is capable of reversing hyperalgesia due to LDH, potentially through modulation of activity of COX-2 and NOS, two important proteins for the exacerbation of pain due to LDH. Finally, a molecular modeling simulation showed that osthole has unique binding capabilities to both NOS and COX-2. As the model-induced mechanical hyperalgesia response was consistent, and the position of the catheter tip and the extension/spreading of the drug in the epidural space were reliable, this study developed an improved model to study remedies for sciatic pain. Moreover, our studies demonstrate that osthole may be a feasible treatment for the reduction of pain due to hyperalgesia.

Evaluation of the neurological safety of epidurally-administered pregabalin in rats

Background

The primary site of action of pregabalin, i.e. the α-2-δ subunit of the voltage-dependent calcium channel, is located at the dorsal root ganglion and dorsal horn of the spinal cord. Therefore, the epidural administration of pregabalin could have advantages over oral administration. However, the possibility of its neurotoxicity should be excluded before any attempt at epidural administration. We evaluated the neuronal safety of epidurally-administered pregabalin by observing the sensory/motor changes and examining the histopathology of spinal cord in rats.

Methods

Sixty rats of 180-230 g were divided into three groups; 3 mg of pregabalin dissolved in 0.3 ml saline (group P, n = 20), 0.3 ml 40% alcohol (group A, n = 20), or 0.3 ml normal saline (group N, n = 20) was administered epidurally to the rats in each group. Pinch-toe test, motor function evaluation, and histopathologic examination of vacuolation, chromatolysis, meningeal inflammation, and neuritis were performed at the 1st, 3rd, 7th, and 21st day after each epidural administration.

Results

All rats enrolled in group P, like those in group N, showed neither sensory/motor dysfunction nor any histopathological abnormality over the 3-week observation period. In contrast, in group A, 80% of the rats showed abnormal response to the pinch-toe test and all rats showed decreased motor function during the entire evaluation period. In addition, all histopathologic findings of neurotoxicity were observed exclusively in group A.

Conclusions

The epidurally administered pregabalin (about 15 mg/kg) did not cause any neurotoxic evidence, in terms of both sensory/motor function evaluation and histopathological examination in rats.

Generalized deep-tissue hyperalgesia in patients with chronic low-back pain

Some chronic painful conditions including e.g. fibromyalgia, whiplash associated disorders, endometriosis, and irritable bowel syndrome are associated with generalized musculoskeletal hyperalgesia. The aim of the present study was to determine whether generalized deep-tissue hyperalgesia could be demonstrated in a group of patients with chronic low-back pain with intervertebral disc herniation. Twelve patients with MRI confirmed lumbar intervertebral disc herniation and 12 age and sex matched controls were included. Subjects were exposed to quantitative nociceptive stimuli to the infraspinatus and anterior tibialis muscles. Mechanical pressure (thresholds and supra-threshold) and injection of hypertonic saline (pain intensity, duration, distribution) were used. Pain intensity to experimental stimuli was assessed on a visual analogue scale (VAS). Patients demonstrated significantly higher pain intensity (VAS), duration, and larger areas of pain referral following saline injection in both infraspinatus and tibialis anterior. The patients rated significantly higher pain intensity to supra-threshold mechanical pressure stimulation in both muscles. In patients, the pressure pain-threshold was lower in the anterior tibialis muscle compared to controls. In conclusion, generalized deep-tissue hyperalgesia was demonstrated in chronic low-back pain patients with radiating pain and MRI confirmed intervertebral disc herniation, suggesting that this central sensitization should also be addressed in the pain management regimes.

Attenuation of inflammatory events in human intervertebral disc cells with a tumor necrosis factor antagonist

STUDY DESIGN

The inflammatory responses of primary human intervertebral disc (IVD) cells to tumor necrosis factor α (TNF-α) and an antagonist were evaluated in vitro.

OBJECTIVE

To investigate an ability for soluble TNF receptor type II (sTNFRII) to antagonize TNF-α-induced inflammatory events in primary human IVD cells in vitro.

SUMMARY OF BACKGROUND DATA

TNF-α is a known mediator of inflammation and pain associated with radiculopathy and IVD degeneration. sTNFRs and their analogues are of interest for the clinical treatment of these IVD pathologies, although information on the effects of sTNFR on human IVD cells remains unknown.

METHODS

IVD cells were isolated from surgical tissues procured from 15 patients and cultured with or without 1.4 nmol/L TNF-α (25 ng/mL). Treatment groups were coincubated with varying doses of sTNFRII (12.5-100 nmol/L). Nitric oxide (NO), prostaglandin E₂ (PGE₂), and interleukin-6 (IL6) levels in media were quantified to characterize the inflammatory phenotype of the IVD cells.

RESULTS

Across all patients, TNF-α induced large, statistically significant increases in NO, PGE₂, and IL6 secretion from IVD cells compared with controls (60-, 112-, and 4-fold increases, respectively; P < 0.0001). Coincubation of TNF-α with nanomolar doses of sTNFRII significantly attenuated the secretion of NO and PGE₂ in a dose-dependent manner, whereas IL6 levels were unchanged. Mean IC₅₀ values for NO and PGE₂ were found to be 35.1 and 20.5 nmol/L, respectively.

CONCLUSION

Nanomolar concentrations of sTNFRII were able to significantly attenuate the effects of TNF-α on primary human IVD cells in vitro. These results suggest this sTNFR to be a potent TNF antagonist with potential to attenuate inflammation in IVD pathology.

The neurological safety of epidural parecoxib in rats

Epidural injection of cyclooxygenase-2 inhibitors has been suggested as a useful therapeutic modality in pain management in animal studies and clinical settings. Direct epidural administration of parecoxib, a highly selective cyclooxygenase-2 inhibitor, may have advantages over its parenteral administration regarding required dose, side effects, and efficacy. However, no animal studies have been performed to investigate the possible neurotoxicity of epidurally injected parecoxib. Therefore, the present study was performed to assess the neurotoxicity of epidurally injected parecoxib in rats. Rats (n=45) were randomly divided into three groups: normal saline group (group N, n=15), ethanol group (group E, n=15), and parecoxib group (group P, n=15). 0.3 mL of epidural parecoxib (6 mg) and the same volume of epidural ethanol or normal saline were injected into the epidural space. Neurologic assessment was performed 3, 7 and 21 days after the injection by pinch toe testing. Histologic changes were evaluated for vacuolation of the dorsal funiculus, chromatolytic changes of the motor neurons, neuritis, and meningeal inflammation. All rats in groups N and P showed normal response to pinch-toe testing and had a normal gait at each observation point. Histological examination showed no evidence suggestive of neuronal body or axonal lesions, gliosis, or myelin sheet damage in group N or P at any time. However, all rats in group E showed sensory-motor dysfunction, behavioral change, or histopathological abnormalities. No neurotoxicity on the spinal cord or abnormalities in sensorimotor function or behavior was noted in rats that received epidural parecoxib.

The neurological safety of epidural pamidronate in rats

Background

Pamidronate is a potent inhibitor of osteoclast-mediated bone resorption. Recently, the drug has been known to relieve bone pain. We hypothesized that direct epidural administration of pamidronate could have various advantages over oral administration with respect to dosage, side effects, and efficacy. Therefore, we evaluated the neuronal safety of epidurally-administered pamidronate.

Methods

Twenty-seven rats weighing 250-350 g were equally divided into 3 groups. Each group received an epidural administration with either 0.3 ml (3.75 mg) of pamidronate (group P), 0.3 ml of 40% alcohol (group A), or 0.3 ml of normal saline (group N). A Pinch-toe test, motor function evaluation, and histopathologic examination of the spinal cord to detect conditions such as chromatolysis, meningeal inflammation, and neuritis, were performed on the 2nd, 7th, and 21st day following administration of each drug.

Results

All rats in group A showed an abnormal response to the pinch-toe test and decreased motor function during the entire evaluation period. Abnormal histopathologic findings, including neuritis and meningeal inflammation were observed only in group A rats. Rats in group P, with the exception of 1, and group N showed no significant sensory/motor dysfunction over a 3-week observation period. No histopathologic changes were observed in groups P and N.

Conclusions

Direct epidural injection of pamidronate (about 12.5 mg/kg) showed no neurotoxic evidence in terms of sensory/motor function evaluation and histopathologic examination.

The effects of punctured nucleus pulposus on lumbar radicular pain in rats: a behavioral and immunohistochemical study

OBJECT

Application of the nucleus pulposus (NP) to the nerve root has been developed as a model of lumbar radicular pain. The relationship between disc degeneration and the induction of radicular pain, however, has not yet been fully explored. The authors of this study investigated pain-related behaviors and expression of tumor necrosis factor-alpha (TNF-alpha) in the dorsal root ganglion (DRG) to evaluate the effects of punctured NP on lumbar radiculopathy.

METHODS

An anular needle puncture model of intervertebral disc degeneration in a rat tail was established. Normal and previously punctured NP tissues were obtained and placed on the L-5 nerve root following a hemilaminectomy. Behavioral tests including assessment of motor function, mechanical threshold, and thermal withdrawal latency were performed before and after surgery. The TNF-alpha immunoreactivity in L-5 DRG specimens was examined through immunohistochemical study.

RESULTS

The punctured discs showed significant degeneration 2 weeks after intervention. Application of both normal and punctured NP induced mechanical hyperalgesia in the ipsilateral paw for 10 days after surgery, but hyperalgesia was more severe in the punctured NP group. No statistically significant within-group changes in thermal withdrawal latency over time were found. A significant increase in the expression of TNF-alpha-positive neurons in DRG specimens was observed in both NP graft groups.

CONCLUSIONS

Needle puncture led to degenerative changes in the rat tail disc, and the degenerated NP enhanced mechanical hyperalgesia induced by application of the NP to the lumbar nerve root. This model of disc degeneration and lumbar radicular pain is appropriate for evaluating the efficacy of biological treatments for degenerative disc diseases.

Gene expression profile of dorsal root ganglion in a lumbar radiculopathy model

STUDY DESIGN

DNA array analysis of dorsal root ganglion (DRG) using a rat model with nerve root constriction.

OBJECTIVE

To determine the molecular changes in the DRG adjacent to the injured nerve root in a lumbar radiculopathy model.

SUMMARY OF BACKGROUND DATA

DNA array analysis in lumbar radiculopathy model has so far focused on the spinal dorsal horn. The molecular changes in the DRG adjacent to the injured nerve root in lumbar radiculopathy remain to be determined.

METHODS

Bilateral L5 DRGs were removed from 12 Sprague-Dawley rats on days 2, 7, 14, and 21 after nerve root ligation and on day 7 from 3 rats with sham operation. The aRNAs from the DRGs with nerve root ligation were labeled with Cy5 dye and those from the opposite side DRG (control) were labeled with Cy3 dye, and then hybridized to a 7793-spot Panorama Micro Array. It was considered to be significantly upregulated, when an average expression ratio of Cy5 to Cy3 was 2 or more. Genes upregulated were classified into early phase group (upregulated on day 2), midphase group (upregulated on days 7 and 14), and continuous group (upregulated from day 2 to 21). Seventeen genes were subjected to validation analysis with real-time quantitative PCR.

RESULTS

There were 16 upregulated genes in the early phase group, 56 genes in the midphase group, and 17 genes in the continuous group. Functional categorization revealed dominantly upregulated gene categories in each group; transcription/translation in the early phase group, enzyme/metabolism in the midphase group, and structure in the continuous group. Validation analysis of 17 genes demonstrated mean relative expression of 2.0 or more in all but 1 gene in the DRGs with nerve root ligation and none of them in the DRGs with sham operation.

CONCLUSION

The genes identified in this study, especially those involved in pain signaling and inflammation, serve as potential targets for molecular-based therapy for lumbar radiculopathy.

Effect of a nonprotein bioactive agent on the reduction of cyclooxygenase-2 and tumor necrosis factor–α in human intervertebral disc cells in vitro

Object

Neurotropin is a nonprotein extract from the inflamed skin of rabbits inoculated with vaccinia virus. In the present study the authors sought to clarify the focal antiinflammatory effects of Neurotropin in intervertebral disc cells, and these effects were compared with those induced by the selective cyclooxygenase (COX)–2 inhibitor 6-methoxy-2-naphthylacetic acid (nabumetone).

Methods

Six human intervertebral disc specimens were harvested during spinal surgery for lumbar disc herniation. Cells were stimulated with 500 pg/ml of interleukin (IL)–1β in the presence of various concentrations of Neurotropin (0, 10−5, 10−4, and 10−3Neurotropin Units/ml) or 50 μg/ml of nabumetone for 3 hours. The mRNA was extracted for polymerase chain reaction (PCR), and real-time PCR was used to quantify the mRNA levels of COX- 2, tumor necrosis factor (TNF)–α, and phospholipase A2. Cyclooxygenase-2, TNFα, and prostaglandin E2 (PGE2) protein concentrations were each determined by enzyme-linked immunosorbent assay.

Results

Neurotropin was found to significantly suppress the expression of COX-2 and TNFα at mRNA levels as well as the concentration of COX-2 at protein levels in a dose-dependent manner. Nabumetone was found to significantly increase COX-2 at mRNA levels but directly suppress the concentration of PGE2 in culture medium.

Conclusions

Results in this study suggest that Neurotropin has an analgesic effect through the suppression of COX-2 and TNFα in a focal area, and nabumetone shows this same effect through the suppression of PGE2 production. Thus, Neurotropin could decrease pain by blocking the central pain pathway or increasing focal antiinflammatory effects.

Up-regulation of acid-sensing ion channel 3 in dorsal root ganglion neurons following application of nucleus pulposus on nerve root in rats

STUDY DESIGN

Immunocytochemistry for acid-sensing ion channel 3 (ASIC3) in neurons of rat dorsal root ganglions (DRGs) from animals exposed to a model of lumbar disc herniation.

OBJECTIVE

To examine expression of ASIC3 in DRGs and the effect of a sodium channel blocker applied to the nerve root in a rat model of lumbar disc herniation.

SUMMARY OF BACKGROUND DATA

Radicular pain is a common symptom of lumbar disc herniation in human beings. A depolarizing sodium channel gated by protons during tissue acidosis, ASIC3, is specifically expressed in sensory neurons. It has been associated with cardiac ischemic and inflammatory pain. We often perform spinal nerve root block for radicular pain using a sodium channel blocker, such as lidocaine; however, it has been unclear whether the effective period of this treatment is usually longer than the expected duration of efficacy.

METHODS

For the lumbar disc herniation model, nucleus pulposus was harvested from the tail and applied to the L5 nerve root, and the nerve roots were pinched. We evaluated mechanical allodynia in sham-operated animals and a disc herniation model. Immunohistochemistry was used to examine ASIC3 expression in L5 DRGs. Finally, the effect of lidocaine on pain and ASIC3 expression in the disc herniation model was examined.

RESULTS

Animals exposed to the lumbar disc herniation model showed allodynia for 8 days, and ASIC3 immunoreactivity was up-regulated in DRG neurons. After administration of lidocaine to spinal nerve roots affected by disc herniation, ASIC3 immunoreactivity was down-regulated in DRG neurons, and the level of mechanical allodynia was significantly decreased for 8 days.

CONCLUSIONS

Our results suggest that ASIC3 in DRG neurons may play an important role in nerve root pain caused by lumbar disc herniation. Lidocaine decreased ASIC3 expression in DRG neurons and pain associated with the disc herniation model.

Pathophysiology of disk-related sciatica. I.--Evidence supporting a chemical component

Sciatica in patients with disk disease was long ascribed to pressure put on the sciatic nerve root by a herniated disk. However, a role for chemical factors acting in conjunction with this mechanical insult is suggested by a number of clinical observations: disk surgery does not consistently provide pain relief, large disk herniations are not always symptomatic, severe pain may be present in patients without imaging evidence of nerve root compression, the severity of symptoms and neurological signs is not well correlated with the size of the disk herniation, and conservative therapy is often effective. Experimental studies have provided further evidence for a chemical component: disk herniations can undergo spontaneous resorption, the intervertebral disk is immunogenic, and mediators for inflammation have been identified within intervertebral disk tissue. The current pathophysiological theory incriminates proinflammatory substances secreted by the nucleus pulposus (NP). When preexisting or concomitant mechanical injury to a nerve root occurs, these substances can cause nerve root pain. Animal experiments have established that the NP can induce functional and structural nerve root abnormalities in the absence of mechanical compression and that this effect is mediated by substances located at the surface of NP cells. Methylprednisolone, diclofenac, indomethacin, doxycycline, and cyclosporine induce variable inhibition of this effect. Available information points to tumor necrosis factor-alpha (TNF-alpha) as the main candidate among substances potentially responsible for nerve root pain. Therefore, trials of TNF-alpha antagonists in patients with disk-related sciatica are warranted.

Spinal neural cyclooxygenase-2 mediates pain caused in a rat model of lumbar disk herniation

Application of nucleus pulposus to nerve root generates radicular pain. We demonstrated that these animals showed allodynia for 2 weeks, and cyclooxygenase-2 (COX-2) immunoreactivities were up-regulated in the spinal dorsal horn. COX-2 immunoreactivities were shown in neurons; however, they were not in astrocytes. Intrathecal administration of an antibody to COX-2 decreased allodynia. Our results suggest that COX-2 in spinal cord might be a target for treatment of patients with nerve root pain caused by lumbar disk herniation.

PERSPECTIVE

Neural COX-2 might mediate nerve root pain in the spinal cord caused by lumbar disk herniation in rats.

Cyclooxygenase inhibition in nerve-injury- and TNF-induced hyperalgesia in the rat

After nerve injury, cyclooxygenase-2 (COX-2) is upregulated in spinal cord and peripheral nerve, the latter being dependent on tumor necrosis factor-alpha (TNF). Here we asked whether COX inhibitors attenuate pain behavior induced by chronic constrictive sciatic nerve injury (CCI) or intraneural injection of TNF (2.5 pg/ml). Rats received either 0.9% saline, the nonselective COX inhibitor ibuprofen (40 mg/kg) or the selective COX-2 inhibitor celecoxib (10 or 30 mg/kg) twice daily by gavage started 2 days before, 12 h or 7 days after surgery. Mechanical allodynia and thermal hyperalgesia induced by CCI was moderately, but consistently attenuated by early (day -2 or 12 h after CCI), but not late (7 days after CCI) ibuprofen and celecoxib treatment. Mechanical allodynia, but not thermal hyperalgesia induced by intraneural TNF, was reduced by ibuprofen, but not by celecoxib treatment 5 and 7 days after injection. Sciatic nerves, lumbar dorsal root ganglia (DRG) and spinal cords from rats with treatment started 12 h after surgery were analyzed for prostaglandin E2 (PGE2) levels 10 days after CCI. In injured nerves and ipsilateral DRG, PGE2 levels were increased. Ibuprofen treatment reversed PGE2 levels in injured nerves and DRG, whereas celecoxib blocked increased PGE2 levels only in nerves. In spinal cord, no change in PGE2 levels was observed. In contrast to the marked inhibition of nerve-injury-induced upregulation of PGE2 by COX inhibitors, the effect on pain behavior was modest. Nerve-injury- and TNF-induced pain-related behavior seem to be only partly dependent on peripheral prostaglandins.