Novel Therapies for the Treatment of Neuropathic Pain: Potential and Pitfalls

Pain intensity and self-perceived burden mediate the relationship between family functioning and pain catastrophizing in patients with neuropathic pain

This cross-sectional study aimed to investigate the relationship between family functioning, pain intensity, self-perceived burden, and pain catastrophizing. Moreover, we also wanted to explore the multiple mediating roles of pain intensity and self-perceived burden. From October 2022 to March 2023, 252 Chinese people with neuropathic pain completed face-to-face questionnaires to assess family functioning, pain intensity, self-perceived burden, and pain catastrophizing. Data analysis was done using descriptive statistics and a structural equation model. The results showed better family functioning was significantly associated with more intense pain, less self-perceived burden, and less pain catastrophizing. Mediation analysis showed that family functioning could indirectly affect pain catastrophizing through pain intensity and self-perceived burden in addition to a direct effect on pain catastrophizing. Moreover, the mediating variable of pain intensity played a masking role. These findings suggest that good family functioning can effectively reduce the self-perceived burden and pain catastrophizing in patients with neuropathic pain. However, family functioning cannot show its maximum effectiveness, and it may be necessary to construct a model of family functioning suitable for patients with neuropathic pain in the future.

The dorsal root ganglion as a target for neurorestoration in neuropathic pain

Neuropathic pain is a severe and chronic condition widely found in the general population. The reason for this is the extensive variety of damage or diseases that can spark this unpleasant constant feeling in patients. During the processing of pain, the dorsal root ganglia constitute an important region where dorsal root ganglion neurons play a crucial role in the transmission and propagation of sensory electrical stimulation. Furthermore, the dorsal root ganglia have recently exhibited a regenerative capacity that should not be neglected in the understanding of the development and resolution of neuropathic pain and in the elucidation of innovative therapies. Here, we will review the complex interplay between cells (satellite glial cells and inflammatory cells) and factors (cytokines, neurotrophic factors and genetic factors) that takes place within the dorsal root ganglia and accounts for the generation of the aberrant excitation of primary sensory neurons occurring in neuropathic pain. More importantly, we will summarize an updated view of the current pharmacologic and nonpharmacologic therapies targeting the dorsal root ganglia for the treatment of neuropathic pain.

Stem cells and pain

Pain can be defined as an unpleasant sensory and emotional experience caused by either actual or potential tissue damage or even resemble that unpleasant experience. For years, science has sought to find treatment alternatives, with minimal side effects, to relieve pain. However, the currently available pharmacological options on the market show significant adverse events. Therefore, the search for a safer and highly efficient analgesic treatment has become a priority. Stem cells (SCs) are non-specialized cells with a high capacity for replication, self-renewal, and a wide range of differentiation possibilities. In this review, we provide evidence that the immune and neuromodulatory properties of SCs can be a valuable tool in the search for ideal treatment strategies for different types of pain. With the advantage of multiple administration routes and dosages, therapies based on SCs for pain relief have demonstrated meaningful results with few downsides. Nonetheless, there are still more questions than answers when it comes to the mechanisms and pathways of pain targeted by SCs. Thus, this is an evolving field that merits further investigation towards the development of SC-based analgesic therapies, and this review will approach all of these aspects.

Neuropathic pain: From actual pharmacological treatments to new therapeutic horizons

Neuropathic pain, caused by a lesion or disease affecting the somatosensory system, affects between 3 and 17% of the general population. The treatment of neuropathic pain is challenging due to its heterogeneous etiologies, lack of objective diagnostic tools and resistance to classical analgesic drugs. First-line treatments recommended by the Special Interest Group on Neuropathic Pain (NeuPSIG) and European Federation of Neurological Societies (EFNS) include gabapentinoids, tricyclic antidepressants (TCAs) and selective serotonin noradrenaline reuptake inhibitors (SNRIs). Nevertheless these treatments have modest efficacy or dose limiting side effects. There is therefore a growing number of preclinical and clinical studies aim at developing new treatment strategies to treat neuropathic pain with better efficacy, selectivity, and less side effects. In this review, after a brief description of the mechanisms of action, efficacy, and limitations of current therapeutic drugs, we reviewed new preclinical and clinical targets currently under investigation, as well as promising non-pharmacological alternatives and their potential co-use with pharmacological treatments.

Ion Channel Genes in Painful Neuropathies

Neuropathic pain (NP) is a typical symptom of peripheral nerve disorders, including painful neuropathy. The biological mechanisms that control ion channels are important for many cell activities and are also therapeutic targets. Disruption of the cellular mechanisms that govern ion channel activity can contribute to pain pathophysiology. The voltage-gated sodium channel (VGSC) is the most researched ion channel in terms of NP; however, VGSC impairment is detected in only <20% of painful neuropathy patients. Here, we discuss the potential role of the other peripheral ion channels involved in sensory signaling (transient receptor potential cation channels), neuronal excitation regulation (potassium channels), involuntary action potential generation (hyperpolarization-activated cyclic nucleotide-gated channels), thermal pain (anoctamins), pH modulation (acid sensing ion channels), and neurotransmitter release (calcium channels) related to pain and their prospective role as therapeutic targets for painful neuropathy.

Neuropathic Pain in the Emergency Setting: Diagnosis and Management

Neuropathic pain, traditionally considered a chronic condition, is increasingly encountered in the emergency department (ED), accounting for approximately 20% of patients presenting with pain. Understanding the physiology and key clinical presentations of neuropathic pain is crucial for ED physicians to provide optimal treatment. While diagnosing neuropathic pain can be challenging, emphasis should be placed on obtaining a comprehensive medical history and conducting a thorough clinical examination. Patients often describe neuropathic pain as a burning or shock-like sensation, leading them to seek care in the ED after ineffective relief from common analgesics such as paracetamol and NSAIDs. Collaboration between emergency medicine specialists, neurologists, and pain management experts can contribute to the development of evidence-based guidelines specifically tailored for the emergency department setting. This article provides a concise overview of the common clinical manifestations of neuropathic pain that may prompt patients to seek emergency care.

Pharmacological Proposal Approach to Managing Chronic Pain Associated with COVID-19

BACKGROUND

Post-COVID syndrome is widespread and chronic pain associated with this syndrome is increasingly being seen in pain clinics. Understanding and managing Chronic Post-COVID Pain (CPCoP) is essential in improving the quality of life of patients. Relevant sections: Identify the types of pain associated with post-COVID syndrome and look for ways to treat them.

RESULTS AND DISCUSSION

Based on our experience, we have identified five groups within CPCoP: (1) chronic pain post-hospitalization in intensive care or long hospitalizations, (2) pain associated with rehabilitation, (3) exacerbation of existing chronic pain pre-COVID-19 infection, (4) central and peripheral neuropathic pain post-COVID-19 infection, (5) chronic pain post vaccination. To fight against misinformation, we created an information capsule for doctors, nurses, and other health workers at a conference via the ECHO* program, delivered 2-3 times a year.

CONCLUSIONS

In pandemic and post-pandemic periods, it is important to determine the sequelae that a disease can leave in the general population, and to understand and treat them. The model proposed may serve as an inspiration to other pain centers to treat the increasing number of patients with CPCoP.

Recent Progress in Gels for Neuropathic Pain

Neuropathic pain is a complex and debilitating condition that affects millions of people worldwide. While several treatment options are available, they often have limited efficacy and are associated with adverse effects. In recent years, gels have emerged as a promising option for the treatment of neuropathic pain. Inclusion of various nanocarriers, such as cubosomes and niosomes, into gels results in pharmaceutical forms with higher drug stability and increased drug penetration into tissues compared to products currently marketed for the treatment of neuropathic pain. Furthermore, these compounds usually provide sustained drug release and are biocompatible and biodegradable, which makes them a safe option for drug delivery. The purpose of this narrative review was to provide a comprehensive analysis of the current state of the field and identify potential directions for future research in the development of effective and safe gels for the treatment of neuropathic pain, ultimately improving the quality of life for patients suffering from neuropathic pain.

Clinical characteristics of ankylosing spondylitis patients depending on neuropathic pain

Introduction

Neuropathic pain (NP) in ankylosing spondylitis (AS) is an important factor that complicates patients' everyday activities and leads to a decrease of life quality. Detection and diagnosis of NP can be facilitated by the use of screening instruments, and the comparative assessment of the sensitivity of different scales is important for improving the diagnosis and personalizing the treatment of AS.The aim of the study was to analyze prevalence of NP in patients with AS and clinical features of AS patients depending on the presence of NP.

Material and methods

We examined 94 patients with NP and 48 patients without pain in AS using the following questionnaires: LANSS, DN4, StEP, BASFI, BASMI, BASDAI, HAQ, ASAS HI/EF and BAS-G.

Results

The prevalence of NP according to LANSS was 51.7% in women and 32.7% in men (p = 0.048); according to DN4 - 58.6% and 32.7%, respectively (p = 0.010). Disease activity and functional disability of the patients were higher in the group of patients with NP than in the group of patients without NP according to the BASDAI, BASFI, BASMI, HAQ, ASAS HI/EF and BAS-G. Significance of differences between groups was at the level of p < 0.01.

Conclusions

The prevalence of NP in AS is alarmingly high. Even with low scores on screening scales, patients showed signs of NP, which may indicate higher prevalence of NP. Neuropathic pain is more associated with the activity of the disease, greater loss of functional capacity and a decrease in indicators of the general state of health, which allows it to be considered as an aggravating factor regarding these manifestations.

Methyl Ferulic Acid Alleviates Neuropathic Pain by Inhibiting Nox4-induced Ferroptosis in Dorsal Root Ganglia Neurons in Rats

Neuropathic pain is a disease that has become one of the major public health problems and a global burden. Nox4-induced oxidative stress can lead to ferroptosis and neuropathic pain. Methyl ferulic acid (MFA) can inhibit the Nox4-induced oxidative stress. This study aimed to estimate whether methyl ferulic acid alleviates neuropathic pain by inhibiting the expression of Nox4 and its induction of ferroptosis. Adult male Sprague-Dawley rats were subjected to spared nerve injury (SNI) model to induce neuropathic pain. After the establishment of the model, methyl ferulic acid was given 14 days by gavage. Nox4 overexpression was induced by microinjection of the AAV-Nox4 vector. All groups measured paw mechanical withdrawal threshold (PMWT), paw thermal withdrawal latency (PTWL), and paw withdrawal cold duration (PWCD). The expression of Nox4, ACSL4, GPX4, and ROS was investigated by Western blot and immunofluorescence staining. The changes in iron content were detected by a tissue iron kit. The morphological changes in mitochondria were observed by transmission electron microscopy. In the SNI group, the paw mechanical withdrawal threshold, the paw withdrawal cold duration decreased, the paw thermal withdrawal latency did not change, the Nox4, ACSL4, ROS, and iron content increased, the GPX4 decreased, and the number of abnormal mitochondria increased. Methyl ferulic acid can increase PMWT and PWCD but does not affect PTWL. Methyl ferulic acid can inhibit Nox4 protein expression. Meanwhile, ferroptosis-related protein ACSL4 expression was decreased, GPX4 expression was increased, ROS, iron content and abnormal mitochondrial number were decreased. By overexpressing Nox4, the PMWT, PWCD, and ferroptosis of rats were more severe than those of the SNI group, but they could be reversed after treatment with methyl ferulic acid. In conclusion, methyl ferulic acid can alleviate neuropathic pain, which is related to Nox4-induced ferroptosis.

Diagnosis and Management of Neuropathic Pain in Spine Diseases

Neuropathic pain is generally defined as a non-physiological pain experience caused by damage to the nervous system. It can occur spontaneously, as a reaction to a given stimulus, or independently of its action, leading to unusual pain sensations usually referred to as firing, burning or throbbing. In the course of spine disorders, pain symptoms commonly occur. According to available epidemiological studies, a neuropathic component of pain is often present in patients with spinal diseases, with a frequency ranging from 36% to 55% of patients. Distinguishing between chronic nociceptive pain and neuropathic pain very often remains a challenge. Consequently, neuropathic pain is often underdiagnosed in patients with spinal diseases. In reference to current guidelines for the treatment of neuropathic pain, gabapentin, serotonin and norepinephrine reuptake inhibitors and tricyclic antidepressants constitute first-line therapeutic agents. However, long-term pharmacologic treatment often leads to developing tolerance and resistance to used medications. Therefore, in recent years, a plethora of therapeutic methods for neuropathic pain have been developed and investigated to improve clinical outcomes. In this review, we briefly summarized current knowledge about the pathophysiology and diagnosis of neuropathic pain. Moreover, we described the most effective treatment approaches for neuropathic pain and discussed their relevance in the treatment of spinal pain.

Effect of Transcutaneous Spinal Direct Current Stimulation in Patients with Painful Polyneuropathy and Influence of Possible Predictors of Efficacy including BDNF Polymorphism: A Randomized, Sham-Controlled Crossover Study

Introduction: The neuromodulating effects of transcutaneous-spinal Direct Current Stimulation (tsDCS) have been reported to block pain signaling. For patients with chronic pain, tsDCS could be a potential treatment option. To approach this, we studied the effect of anodal tsDCS on patients with neuropathic pain approaching an optimal paradigm including the investigation of different outcome predictors. Methods: In this randomized, double-blinded, sham-controlled crossover study we recruited twenty patients with neurophysiologically evaluated neuropathic pain due to polyneuropathy (PNP). Variables (VAS; pain and sleep quality) were reported daily, one week prior to, and one week after the stimulation/sham period. Anodal tsDCS (2.5 mA, 20 min) was given once daily for three days during one week. BDNF-polymorphism, pharmacological treatment, and body mass index (BMI) of all the patients were investigated. Results: Comparing the effects of sham and real stimulation at the group level, there was a tendency towards reduced pain, but no significant effects were found. However, for sleep quality a significant improvement was seen. At the individual level, 30 and 35% of the subjects had a clinically significant improvement of pain level and sleep quality, respectively, the first day after the stimulation. Both effects were reduced over the coming week and these changes were negatively correlated. The BDNF polymorphism Val66Met was carried by 35% of the patients and this group was found to have a lower general level of pain but there was no significant difference in the tsDCS response effect. Neither pharmacologic treatment or BMI influenced the treatment effect. Conclusions: Short-term and sparse anodal thoracic tsDCS reduces pain and improves sleep with large inter-individual differences. Roughly 30% will benefit in a clinically meaningful way. The BDNF genotype seems to influence the level of pain that PNP produces. Individualized and intensified tsDCS may be a treatment option for neuropathic pain due to PNP.

Bibliometric and Visual Analysis of the Scientific Literature on Percutaneous Electrical Nerve Stimulation (PENS) for Pain Treatment

Background: Percutaneous electrical nerve stimulation (PENS) is a minimally invasive peripheral neuromodulation approach implemented against chronic neuropathic and mixed pain. This bibliometric study aims to quantitatively evaluate the output of PENS for pain treatment in the scientific literature. The main purpose is to stimulate research in the field and bridge potential scientific gaps. Methods: Articles were retrieved from the Web of Science (WOS) database. The search key term was “percutaneous electrical nerve stimulation (All Fields) and pain (All Fields)”. Year of publication, journal metrics (impact factor and quartile, Q), title, document type, topic, and citations were extracted. The join-point regression was implemented to assess differences in time points for the publication output. The software tool VOSviewer (version 1.6.17) was used for the visual analysis. Results: One thousand three hundred and eighteen articles were included in the knowledge visualization process. A linear upward trend for annual new publications was found. Almost two-thirds of the documents were published in top-ranked journals (Q1 and Q2). The topic “efficacy” was prevalent (12.81%). Concerning article type, the search strategy yielded 307 clinical investigations (23.3%). Articles were cited 36,610 times with a mean of 42.4 citations per article. Approximately one-half of the articles were cited less than 23 times in a range of 21 years. The semantic network analysis for keywords found eight clusters. The analysis of collaborative efforts among researchers showed five thematic clusters including 102 authors with a minimum of five documents produced in collaborations. Most partnerships involved the United States, England, and Germany. Conclusions: despite the upward trend in the number of publications on the subject and the publication of articles in top-ranked journals, there is a need to increase scientific collaborations between researchers and institutions from different countries.

A Review of the Therapeutic Targeting of SCN9A and Nav1.7 for Pain Relief in Current Human Clinical Trials

Introduction

There is a great need to find alternative treatments for chronic pain which have become a healthcare problem. We discuss current therapeutic targeting Nav1.7.

Areas Covered

Nav1.7 is a sodium ion channel protein that is associated with several human pain genetic syndromes. It has been found that mutations associated with Nav1.7 lead to the loss of the ability to perceive pain in individuals that are otherwise normal. Several therapeutic interventions are presently undergoing preclinical and research using the methodology of damping Nav1.7 expressions as a methodology to decrease the sensation of pain leading to analgesia.

Expert Opinion

It is our strong belief that there is a viable future in the targeting of protein of Nav1.7 for the relief of chronic pain in humans. The review will look at the genomics associated with SCN1A and proteomic of Nav1.7 as a foundation to explain the mechanism of the therapeutic interventions targeting Nav1.7, the human disease that are associated with Nav1.7, and the current development of treatment for chronic pain whether in preclinical or clinical trials targeting Nav1.7 expressions. The development of therapeutic antagonists targeting Nav1.7 could be a viable alternative to the current treatments which have led to the opioid crisis. Therefore, Nav1.7 targeted treatment has a major clinical significance that will have positive consequences as it relates to chronic pain interventions.