Variability in the Analgesic Response to Ibuprofen Is Associated With Cyclooxygenase Activation in Inflammatory Pain

Sex Differences in the Serum Proteomic Profile During Acute Low Back Pain-A Preliminary Study of the Relationship to Future Low Back Pain

The molecular processes driving the transition from acute to chronic low back pain (LBP) remain poorly understood and are likely to be sexually dimorphic. This study aimed to explore sex differences in the serum proteomic profile of people experiencing an acute LBP episode and determine if serum protein concentrations were associated with three-month outcome. Serum samples were collected through venepuncture from 30 female and 29 male participants experiencing an acute LBP episode. Serum samples underwent trypsin digestion and fractionation using hydrophobic interaction chromatography and were then analysed using mass-spectrometry. Mass-spectrometry spectra were searched in the Swissprot database for protein identification. Sex differences in protein abundance changes were evident upon inspection of fold changes. Multivariable data analysis identified 21 serum proteins during the acute episode that correctly classified 93% of males and 23 serum proteins that correctly classified 90% of females with ongoing LBP at 3 months. Pathway analysis suggested the differentially expressed proteins during acute LBP were frequently involved in immune, inflammatory, complement, or coagulation responses. This data provides preliminary evidence that biological processes during an acute LBP episode may contribute to the resolution, or persistence, of LBP symptoms at 3 months, however, these processes differ between males and females. PERSPECTIVE: Differential expression of serum proteins was observed between male and female participants during an acute LBP episode. This preliminary work provides a foundation for future research targeting distinct immune system processes in males and females that may interfere with the transition from acute to chronic LBP.

Clinical effects of different virtual reality presentation content on anxiety and pain: a randomized controlled trial

Many patients are frightened of or anxious about dental treatment. We have recently reported our use of virtual reality (VR) to alleviate the fear and anxiety experienced during oral surgical procedures However, the effectiveness of VR in alleviating anxiety varies greatly between individuals. We therefore investigated whether the content of the VR presentation made any difference to its effect in alleviating anxiety, and whether it had any analgesic effect. The study subjects experienced one of two different types of VR presentation and were asked to complete a questionnaire about any changes in their anxiety during the procedure, including a visual analog scale (VAS) score. As an objective evaluation, changes in pain threshold during the VR presentation were investigated using PainVision. For those patients who experienced a presentation showing a natural landscape, the change in VAS score was - 13.3 ± 28.7 mm, whereas for those who experienced a presentation showing a video game the change was - 22.2 ± 32.1 mm, an even greater reduction. In a pain questionnaire completed by individuals who had experienced the video game presentations, approximately 70% reported that their pain had diminished. An objective evaluation of pain threshold also showed that the pain threshold of individuals increased by around 3% while experiencing the natural landscape VR presentation, but that while experiencing the video game presentation, it increased significantly by around 15% compared with baseline. These results show that the content of the presentation affected not only the rate of decrease in anxiety, but also the pain threshold.

Prospective Blood Transcriptomics Study in a Motor Vehicle Collision Cohort Identified a Protective Function of the SAMD15 Gene Against Chronic Pain

Traumatic brain injuries following motor vehicle collisions (MVCs) are ubiquitous. Surprisingly, there are no correlates between concussion impact force and long-term pain outcomes. To study the molecular underpinnings of chronic pain after MVC, we assembled a prospective cohort of 36 subjects that experienced MVC and suffered documented mild traumatic brain injuries. For each participant, a first blood sample was drawn within 72 hours of the collision, then a second one at the 6-month mark. Pain was also assessed at the second blood draw to determine if pain became chronic or resolved. Blood samples enabled transcriptomics analyses for immune cells. At the transcriptome-wide level, we found that Sterile Alpha Motif Domain Containing 15 (SAMD15) mRNA was significantly upregulated with time in subjects who resolved their pain whereas unregulated in those with persistent pain. Using several large publicly available datasets, such as the UK Biobank and the GTeX portal, we then linked elevated SAMD15 gene expression, elevated neutrophils cell counts, and decreased risk for chronic pain to increased dosage of the T allele at SNP rs4903580, situated within SAMD15's gene locus. The causality between the components of our model was established and supported by Mendelian randomization. Overall, our results support the role of SAMD15 as a potential gene effector for neutrophil-dependent chronic pain development. PERSPECTIVE: This article highlights the potential protective role of the SAMD15 gene against chronic pain following a mild traumatic brain injury. The expression of the gene is associated with a SNP rs4903580, which is itself associated with neutrophils counts as well as chronic pain in large genetic studies.

Acute pain management and long term outcomes

PURPOSE OF REVIEW

The acute inflammatory reaction induced by tissue trauma causes pain but also promotes recovery. Recovery is highly variable among peoples. Effective acute pain (AP) management is very important but remains suboptimal what could affect long term outcomes. The review questions the impact of either failure or effectiveness of AP treatments and the choice of analgesic drugs on different long-term outcomes after tissue trauma.

RECENT FINDINGS

Pain control during mobilization is mandatory to reduce the risk of complications which exacerbate and prolong the inflammatory response to trauma, impairing physical recovery. Common analgesic treatments show considerable variability in effectiveness among peoples what argues for an urgent need to develop personalized AP management, that is, finding better responders to common analgesics and targeting challenging patients for more invasive procedures. Optimal multimodal analgesia to spare opioids administration remains a priority as opioids may enhance neuroinflammation, which underlies pain persistence and precipitates neurocognitive decline in frail patients. Finally, recent findings demonstrate that AP treatments which modulate nociceptive and inflammatory pain should be used with caution as drugs which inhibit inflammation like nonsteroidal antiinflammatory drugs and corticoids might interfere with natural recovery processes.

SUMMARY

Effective and safe AP management is of far greater importance than previously realized. Evidence of suboptimal AP management in many patients and recent reports pointing out the impact of current treatments on long term outcomes argue for further research in the field.

Sex-differences in prostaglandin signaling: a semi-systematic review and characterization of PTGDS expression in human sensory neurons

There is increasing evidence of sex differences in underlying mechanisms causing pain in preclinical models, and in clinical populations. There are also important disconnects between clinical pain populations and the way preclinical pain studies are conducted. For instance, osteoarthritis pain more frequently affects women, but most preclinical studies have been conducted using males in animal models. The most widely used painkillers, nonsteroidal anti-inflammatory drugs (NSAIDs), act on the prostaglandin pathway by inhibiting cyclooxygenase (COX) enzymes. The purpose of this study was to analyze the preclinical and clinical literature on the role of prostaglandins and COX in inflammation and pain. We aimed to specifically identify studies that used both sexes and investigate whether any sex-differences in the action of prostaglandins and COX inhibition had been reported, either in clinical or preclinical studies. We conducted a PubMed search and identified 369 preclinical studies and 100 clinical studies that matched our inclusion/exclusion criteria. Our analysis shows that only 17% of preclinical studies on prostaglandins used both sexes and, out of those, only 19% analyzed or reported data separated by sex. In contrast, 79% of the clinical studies analyzed used both sexes. However, only 6% of those reported data separated by sex. Interestingly, 14 out of 15 preclinical studies and 5 out of 6 clinical studies that analyzed data separated by sex have identified sex-differences. This builds on the increasing evidence of sex-differences in prostaglandin signaling and the importance of sex as a biological variable in data analysis. The preclinical literature identifies a sex difference in prostaglandin D2 synthase (PTGDS) expression where it is higher in female than in male rodents in the nervous system. We experimentally validated that PTGDS expression is higher in female human dorsal root ganglia (DRG) neurons recovered from organ donors. Our semi-systematic literature review reveals a need for continued inclusivity of both male and female animals in prostaglandins studies and data analysis separated by sex in preclinical and clinical studies. Our finding of sex-differences in neuronal PTGDS expression in humans exemplifies the need for a more comprehensive understanding of how the prostaglandin system functions in the DRG in rodents and humans.

Acute inflammatory response via neutrophil activation protects against the development of chronic pain

The transition from acute to chronic pain is critically important but not well understood. Here, we investigated the pathophysiological mechanisms underlying the transition from acute to chronic low back pain (LBP) and performed transcriptome-wide analysis in peripheral immune cells of 98 participants with acute LBP, followed for 3 months. Transcriptomic changes were compared between patients whose LBP was resolved at 3 months with those whose LBP persisted. We found thousands of dynamic transcriptional changes over 3 months in LBP participants with resolved pain but none in those with persistent pain. Transient neutrophil-driven up-regulation of inflammatory responses was protective against the transition to chronic pain. In mouse pain assays, early treatment with a steroid or nonsteroidal anti-inflammatory drug (NSAID) also led to prolonged pain despite being analgesic in the short term; such a prolongation was not observed with other analgesics. Depletion of neutrophils delayed resolution of pain in mice, whereas peripheral injection of neutrophils themselves, or S100A8/A9 proteins normally released by neutrophils, prevented the development of long-lasting pain induced by an anti-inflammatory drug. Analysis of pain trajectories of human subjects reporting acute back pain in the UK Biobank identified elevated risk of pain persistence for subjects taking NSAIDs. Thus, despite analgesic efficacy at early time points, the management of acute inflammation may be counterproductive for long-term outcomes of LBP sufferers.

Distribution of Opioid Prescribing and High-Risk Prescribing Among U.S. Dentists in 2019

INTRODUCTION

It is unknown whether certain dentists account for disproportionate shares of dental opioid prescriptions and high-risk prescriptions. Identifying and characterizing such dentists could inform the targeting of initiatives to improve the appropriateness and safety of dental opioid prescribing.

METHODS

In May 2021, the authors conducted a cross-sectional analysis using the IQVIA Longitudinal Prescription Database, which reports dispensing from 92% of U.S. pharmacies, and 2 provider databases (IQVIA OneKey, National Plan and Provider Enumeration System). Analyses included opioid prescriptions from dentists dispensed in 2019 to patients aged >12 years. High-risk prescriptions were those considered high risk by any of 3 metrics (prescriptions to opioid-naïve patients exceeding a 3-day supply, prescriptions with daily opioid dosage ≥50 morphine milligram equivalents, opioid prescriptions with benzodiazepine overlap). Among all prescriptions and high-risk prescriptions, the authors calculated the proportion accounted for by high-volume dentists -- those with prescription counts in the 95th percentile or higher. Using logistic regression, the characteristics associated with being a high-volume dentist were identified.

RESULTS

In 2019, a total of 141,345 dentists accounted for 10,736,743 opioid prescriptions dispensed to patients aged >12 years; 4,242,634 (39.5%) were high-risk prescriptions. The 7,079 high-volume dentists, a group representing 5.0% of the 141,345 dentists, accounted for 46.9% of all prescriptions and 47.5% of high-risk prescriptions. Male sex, younger age, non‒Northeast location, and specialization in oral and maxillofacial surgery were associated with a higher risk of being a high-volume dentist.

CONCLUSIONS

In 2019, high-volume dentists accounted for almost half of dental opioid prescriptions and high-risk prescriptions. Quality improvement initiatives targeting these dentists may be warranted.

Alternatives to opioids for acute pain management after dental procedures: A Department of Veterans Affairs consensus paper

BACKGROUND

Opioid misuse is a widespread public health problem, and opioids are often prescribed in the dental environment. These recommendations provide alternatives to opioids to reduce or eliminate dental procedure-related acute pain.

METHODS

A multidisciplinary working group developed these clinical recommendations to specifically address procedure-related acute pain. These recommendations, which are based on published peer-reviewed research and guidelines, include therapies used before, during, and after dental procedures. When evidence is not definitive, the best practices, which are based on experts' consensus, are included. The recommendations are not intended to be exhaustive.

RESULTS

These recommendations are a summary of the evidence and best practices for opioid alternatives to treat acute pain related to dental procedures.

CONCLUSIONS

Dental providers should prioritize opioid stewardship when managing procedure-related pain with strategies such as thorough preprocedure pain assessment, minimally invasive techniques, preemptive analgesia, intraprocedure pain management, and appropriately selected postprocedure pharmacologic therapy.

PRACTICAL IMPLICATIONS

These recommendations are a concise resource for clinical providers. It is important to address patients' procedure-related pain, using nonopioids whenever possible. Alternatives are outlined, allowing providers to make informed decisions.

Chemokines and Pain in the Trigeminal System

Chemotactic cytokines or chemokines are a large family of secreted proteins able to induce chemotaxis. Chemokines are categorized according to their primary amino acid sequence, and in particular their cysteine residues that form disulphide bonds to maintain the structure: CC, CXC, CX3C, and XC, in which X represents variable amino acids. Among their many roles, chemokines are known to be key players in pain modulation in the peripheral and central nervous systems. Thus, they are promising candidates for novel therapeutics that could replace current, often ineffective treatments. The spinal and trigeminal systems are intrinsically different beyond their anatomical location, and it has been suggested that there are also differences in their sensory mechanisms. Hence, understanding the different mechanisms involved in pain modulation for each system could aid in developing appropriate pharmacological alternatives. Here, we aim to describe the current landscape of chemokines that have been studied specifically with regard to trigeminal pain. Searching PubMed and Google Scholar, we identified 30 reports describing chemokines in animal models of trigeminal pain, and 15 reports describing chemokines involved in human pain associated with the trigeminal system. This review highlights the chemokines studied to date at different levels of the trigeminal system, their cellular localization and, where available, their role in a variety of animal pain models.

Preemptive use of intravenous ibuprofen to reduce postoperative pain after lower third molar surgery: a systematic review of randomized controlled trials

This study aimed to systematically review the literature to assess the effect of preemptive intravenous ibuprofen on pain reduction after lower third molar surgery. Nine databases (PubMed, Scopus, LILACS, SciELO, Embase, Web of Science, Cochrane, Open Gray, and Open Thesis) were used as sources of research, including "grey literature." The protocol was registered in PROSPERO. Only randomized clinical trials evaluating the effects of preemptive intravenous ibuprofen on pain during and immediately after the extraction of lower third molars were included, without restrictions of year and language. Two reviewers independently performed the study selection, data extraction, and assessment of the risk of bias. The "Joanna Briggs Institute for Randomized Controlled Trials" tool was used to assess the risk of bias. Each study was categorized according to the percentage of positive responses to the questions corresponding to the assessment instrument. The results were measured narratively/descriptively. The initial search resulted in 3,257 records, of which only three studies (n=150 participants) met the eligibility criteria and were included in the qualitative analysis. All studies were published in 2019. The risk of bias ranged from low to moderate. Two studies found significant pain reduction within 48 h after the procedure. In conclusion, the use of preemptive intravenous ibuprofen for extracting third molars reduces pain and analgesic consumption after the surgical procedure.

Multifocal Analysis of Acute Pain After Third Molar Removal

Background: To analyze the pain modulation capacity profile in a Brazilian population, the relationship between opioid receptor (OPRM1) and Catechol-O-methyltransferase (COMT) 1polymorphisms and pain modulation capacity was determined through preoperative pain modulation tests and acute postoperative pain control evaluation, swelling, and trismus in 200 volunteers undergoing lower third molar removal.

Methods: Psychologic and clinical parameters were measured. Patient DNA was sequenced for single nucleotide polymorphisms in OPRM1 and COMT, and the salivary concentration of interleukin (IL)-2 (IL)-6, interferon (IFN)-γ and tumor necrosis factor (TNF)-α was evaluated. Primary outcomes were the influence of all predictors on the fluctuation of pain intensity using a visual analogue scale (VAS), and swelling and trismus on the 2nd and 7th postoperative days. Preoperative pain modulation capacity (CPM), pain catastrophizing scale (PCS), body mass index (BMI), and surgery duration and difficulty were evaluated.

Results: Salivary concentration of IFN-γ and IL-2 as well as the duration of surgery influenced the fluctuation of postoperative pain in the VAS, and in the sum of the differences in pain intensity test at 8, 48, and 96 h. BMI influenced swelling, while both BMI and COMT haplotype influenced trismus on the 2nd postoperative day.

Conclusion: Polymorphisms in COMT, salivary concentrations of IL-2 and IFN-γ, BMI, and duration of surgery were predictors for pain fluctuation, swelling, and trismus on the 2nd day after lower third molar extraction. This therapy was effective in controlling inflammatory symptomatology after lower third molar extraction and ibuprofen was well tolerated by patients.

Clinical Trial Registration:www.ClinicalTrials.gov, identifier NCT03169127.

Effects of Morphologies of Thermosensitive Electrospun Nanofibers on Controllable Drug Release

Electrospun nanofibers is a promising and versatile avenue for building controlled drug release system because of the facile fabrication and the broad range of polymer materials. This research systematically studied the morphological effect of thermosensitive electrospun nanofibers, including porous and coaxial structures, on controllable drug release. Three types of drugs, nicotinamide, paracetamol, and ibuprofen, with different hydrophilicity were applied in this study. The data of drug release were all fitted to the first-order kinetic model regardless of the drug properties, and the release rates paralleled with their hydrophilicity. Sol-gel phase transition of the thermosensitive poly(N-isopropylacrylamide) (PNIPAAm) hydrogel led to slower drug release at 37°C compared with those at 25°C. Regarding morphology, coaxial nanofibers could provide higher loading efficiency and slower drug release rather than porous nanofibers. Our research highlighted the overall effects of compound property, temperature, and the morphological structures of thermosensitive electrospun nanofibers on the controlled drug release. Our results concluded that hydrophobic drug encapsulated in the core-shell PNIPAAm nanofibers could perform excellent sustained release and also controllable release under temperature stumuli. Impact statement The behaviors for the controlled release of drugs loaded in the thermosensitive electrospun nanofibers could be affected by various factors including the properties of loaded drug, morphologies of nanofibrous, and lower critical solution temperatures of thermosensitive hydrogels. However, few systematical investigations have been performed in this area. In this article, we designed and fabricated porous and coaxial thermosensitive poly(N-isopropylacrylamide) electrospun nanofibers with different drug loading to study the comprehensive effect. This study suggested when adopting thermosensitive electrospun hydrogel nanofibers as the controllable drug release carrier, the hydrophilicity of loaded compounds and the morphologies of nanofibers are necessary to be optimized.

Assessment of the impact of PTGS1, PTGS2 and CYP2C9 polymorphisms on pain, effectiveness and safety of NSAID therapies

Cyclooxygenase 1 and 2 (COX-1, COX-2) are enzymes that catalyze the first reaction in the arachidonic acid pathway. COXs are the therapeutic target for non-steroidal anti-inflammatory drugs. Inhibition of COX enzymatic activity has an analgesic, anti-inflammatory and sometimes antiplatelet effect. Single-nucleotide polymorphisms (SNPs) within genes encoding COX-1 and COX-2 (PTGS1, PTGS2) influence the risk of pain and their intensity in some diseases. They also affect the effectiveness of NSAID therapy in rheumatoid diseases. Moreover, the relationship between certain polymorphisms of PTGS2 and a higher risk of migraine and the development of aspirin resistance in the prophylaxis of cardiovascular diseases was demonstrated. The isoform of cytochrome P450, CYP2C9 has a significant influence on the efficacy and safety of NSAID use. It is responsible for the metabolism and speed of removal of these drugs. The occurrence of some of its polymorphic forms is associated with a decrease in CYP2C9 enzymatic activity, leading to changes in the pharmacokinetics and pharmacodynamics of NSAIDs. The prolonged half-life and decrease in clearance of these drugs lead to serious side effects such as hepatotoxicity, nephrotoxicity, anaphylactic reactions, cardiovascular or gastrointestinal incidents. Studies on polymorphisms of cyclooxygenases and CYP2C9 may improve the safety and efficacy of NSAIDs therapy by adjusting the dose to individual polymorphic variants, as well as expanding knowledge about the pathomechanism of inflammatory diseases.

Nonsteroidal Anti-Inflammatory Drugs and Opioids in Postsurgical Dental Pain

Postsurgical dental pain is mainly driven by inflammation, particularly through the generation of prostaglandins via the cyclooxygenase system. Thus, it is no surprise that numerous randomized placebo-controlled trials studying acute pain following the surgical extraction of impacted third molars have demonstrated the remarkable efficacy of nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen, naproxen sodium, etodolac, diclofenac, and ketorolac in this prototypic condition of acute inflammatory pain. Combining an optimal dose of an NSAID with an appropriate dose of acetaminophen appears to further enhance analgesic efficacy and potentially reduce the need for opioids. In addition to being on average inferior to NSAIDs as analgesics in postsurgical dental pain, opioids produce a higher incidence of side effects in dental outpatients, including dizziness, drowsiness, psychomotor impairment, nausea/vomiting, and constipation. Unused opioids are also subject to misuse and diversion, and they may cause addiction. Despite these risks, some dental surgical outpatients may benefit from a 1- or 2-d course of opioids added to their NSAID regimen. NSAID use may carry significant risks in certain patient populations, in which a short course of an acetaminophen/opioid combination may provide a more favorable benefit versus risk ratio than an NSAID regimen.

NSAID-Gut Microbiota Interactions

Nonsteroidal anti-inflammatory drugs (NSAID)s relieve pain, inflammation, and fever by inhibiting the activity of cyclooxygenase isozymes (COX-1 and COX-2). Despite their clinical efficacy, NSAIDs can cause gastrointestinal (GI) and cardiovascular (CV) complications. Moreover, NSAID use is characterized by a remarkable individual variability in the extent of COX isozyme inhibition, therapeutic efficacy, and incidence of adverse effects. The interaction between the gut microbiota and host has emerged as a key player in modulating host physiology, gut microbiota-related disorders, and metabolism of xenobiotics. Indeed, host-gut microbiota dynamic interactions influence NSAID disposition, therapeutic efficacy, and toxicity. The gut microbiota can directly cause chemical modifications of the NSAID or can indirectly influence its absorption or metabolism by regulating host metabolic enzymes or processes, which may have consequences for drug pharmacokinetic and pharmacodynamic properties. NSAID itself can directly impact the composition and function of the gut microbiota or indirectly alter the physiological properties or functions of the host which may, in turn, precipitate in dysbiosis. Thus, the complex interconnectedness between host-gut microbiota and drug may contribute to the variability in NSAID response and ultimately influence the outcome of NSAID therapy. Herein, we review the interplay between host-gut microbiota and NSAID and its consequences for both drug efficacy and toxicity, mainly in the GI tract. In addition, we highlight progress towards microbiota-based intervention to reduce NSAID-induced enteropathy.