Relationship Between Blood Cytokine Levels, Psychological Comorbidity, and Widespreadness of Pain in Chronic Pelvic Pain

The role of cytokines in acute and chronic postsurgical pain after major musculoskeletal surgeries in a quaternary pediatric center

STUDY OBJECTIVE

To determine if baseline cytokines/chemokines and their changes over postoperative days 0-2 (POD0-2) predict acute and chronic postsurgical pain (CPSP) after major surgery.

DESIGN

Prospective, observational, longitudinal nested study.

SETTING

University-affiliated quaternary children's hospital.

PATIENTS

Subjects (≥8 years old) with idiopathic scoliosis undergoing spine fusion or pectus excavatum undergoing Nuss procedure.

MEASUREMENTS

Demographics, surgical, psychosocial measures, pain scores, and opioid use over POD0-2 were collected. Cytokine concentrations were analyzed in serial blood samples collected before and up to two weeks after surgery, using Luminex bead arrays. After data preparation, relationships between pre- and post-surgical cytokine concentrations with acute (% time in moderate-severe pain over POD0-2) and chronic (pain score > 3/10 beyond 3 months post-surgery) post-surgical pain were analyzed using univariable and multivariable regression analyses with adjustment for covariates and mixed effects models were used to associate longitudinal cytokine concentrations with pain outcomes.

MAIN RESULTS

Analyses included 3,164 repeated measures of 16 cytokines/chemokines from 112 subjects (median age 15.3, IQR 13.5-17.0, 54.5 % female, 59.8 % pectus). Acute postsurgical pain was associated with higher baseline concentrations of GM-CSF (β = 0.95, SE 0.31; p = 0.003), IL-1β (β = 0.84, SE 0.36; p = 0.02), IL-2 (β = 0.78, SE 0.34; p = 0.03), and IL-12 p70 (β = 0.88, SE 0.40; p = 0.03) and longitudinal postoperative elevations in GM-CSF (β = 1.38, SE 0.57; p = 0.03), IFNγ (β = 1.36, SE 0.6; p = 0.03), IL-1β (β = 1.25, SE 0.59; p = 0.03), IL-7 (β = 1.65, SE 0.7; p = 0.02), and IL-12 p70 (β = 1.17, SE 0.58; p = 0.04). In contrast, CPSP was associated with lower baseline concentration of IL-8 (β = -0.39, SE 0.17; p = 0.02), and the risk of developing CPSP was elevated in patients with lower longitudinal postoperative concentrations of IL-6 (β = -0.57, SE 0.26; p = 0.03), IL-8 (β = -0.68, SE 0.24; p = 0.006), and IL-13 (β = -0.48, SE 0.22; p = 0.03). Covariates female (vs. male) sex and surgery type (pectus surgery vs. spine) were associated with higher odds for CPSP in baseline adjusted cytokine-CPSP association models for IL-2, IL-4, IL-5, IL-6, IL-8, IL-10, TNFα, and IL-8, IL-10, respectively.

CONCLUSION

We identified pro-inflammatory cytokine profiles associated with higher risk of acute postoperative pain. Interestingly, pleiotropic cytokine IL-6, chemokine IL-8 (which promotes neutrophil infiltration and monocyte differentiation), and monocyte-released anti-inflammatory cytokine IL-13, were associated with lower CPSP risk. Our results suggest heterogenous outcomes of cytokine/chemokine signaling that can both promote and protect against post-surgical pain. These may serve as predictive and prognostic biomarkers of pain outcomes following surgery.

The Role of Cytokines in Acute and Chronic Postsurgical Pain in Pediatric Patients after Major Musculoskeletal Surgeries

Study Objective

To determine if baseline cytokines and their changes over postoperative days 0-2 (POD0-2) predict acute and chronic postsurgical pain (CPSP) after major surgery.

Design

Prospective, observational, longitudinal nested study.

Setting

University-affiliated quaternary children's hospital.

Patients

Subjects (≥8 years old) with idiopathic scoliosis undergoing spine fusion or pectus excavatum undergoing Nuss procedure.

Measurements

Demographics, surgical, psychosocial measures, pain scores, and opioid use over POD0-2 were collected. Cytokine concentrations were analyzed in serial blood samples collected before and after (up to two weeks) surgery, using Luminex bead arrays. After data preparation, relationships between pre- and post-surgical cytokine concentrations with acute (% time in moderate-severe pain over POD0-2) and chronic (pain score>3/10 beyond 3 months post-surgery) pain were analyzed. After adjusting for covariates, univariate/multivariate regression analyses were conducted to associate baseline cytokine concentrations with postoperative pain, and mixed effects models were used to associate longitudinal cytokine concentrations with pain outcomes.

Main Results

Analyses included 3,164 measures of 16 cytokines from 112 subjects (median age 15.3, IQR 13.5-17.0, 54.5% female, 59.8% pectus). Acute postsurgical pain was associated with higher baseline concentrations of GM-CSF (β=0.95, SE 0.31; p=.003), IL-1β (β=0.84, SE 0.36; p=.02), IL-2 (β=0.78, SE 0.34; p=.03), and IL-12 p70 (β=0.88, SE 0.40; p=.03) and longitudinal postoperative elevations in GM-CSF (β=1.38, SE 0.57; p=.03), IFNγ (β=1.36, SE 0.6; p=.03), IL-1β (β=1.25, SE 0.59; p=.03), IL-7 (β=1.65, SE 0.7, p=.02), and IL-12 p70 (β=1.17, SE 0.58; p=.04). In contrast, CPSP was associated with lower baseline concentration of IL-8 (β= -0.39, SE 0.17; p=.02), and the risk of developing CPSP was elevated in patients with lower longitudinal postoperative concentrations of IL-6 (β= -0.57, SE 0.26; p=.03), IL-8 (β= -0.68, SE 0.24; p=.006), and IL-13 (β= -0.48, SE 0.22; p=.03). Furthermore, higher odds for CPSP were found for females (vs. males) for IL-2, IL-4, IL-5, IL-6, IL-8, IL-10, and TNFα, and for pectus (vs. spine) surgery for IL-8 and IL-10.

Conclusion

We identified pro-inflammatory cytokines associated with increased acute postoperative pain and anti-inflammatory cytokines associated with lower CPSP risk, with potential to serve as predictive and prognostic biomarkers.

Autonomic Nervous System Dysfunction Is Related to Chronic Prostatitis/Chronic Pelvic Pain Syndrome

Chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS) is a common and non-lethal urological condition with painful symptoms. The complexity of CP/CPPS's pathogenesis and lack of efficient etiological diagnosis results in incomplete treatment and recurrent episodes, causing long-term mental and psychological suffering in patients. Recent findings indicate that the autonomic nervous system involves in CP/CPPS, including sensory, sympathetic, parasympathetic, and central nervous systems. Neuro-inflammation and sensitization of sensory nerves lead to persistent inflammation and pain. Sympathetic and parasympathetic alterations affect the cardiovascular and reproductive systems and the development of prostatitis. Central sensitization lowers pain thresholds and increases pelvic pain perception in chronic prostatitis. Therefore, this review summarized the detailed processes and mechanisms of the critical role of the autonomic nervous system in developing CP/CPPS. Furthermore, it describes the neurologically relevant substances and channels or receptors involved in this process, which provides new perspectives for new therapeutic approaches to CP/CPPS.

Links between brain neuroimaging and blood inflammatory markers in urological chronic pelvic pain syndrome

Urological chronic pelvic pain syndrome (UCPPS) is a debilitating painful condition with unclear etiology. Prior researchers have indicated that compared to healthy controls, patients with UCPPS demonstrated altered brain activity. Researchers have also shown that in UCPPS, several blood inflammatory markers relate to clinical variables of pain, fatigue, and pain widespreadness. However, how altered brain function in patients with UCPPS relates to blood inflammation remains unknown. To extend and connect prior findings of altered brain function and inflammatory factors in UCPPS, we conducted a secondary analysis of data from a cohort of UCPPS patients (N = 29) and healthy controls (N = 31) who provided both neuroimaging and blood data (National Institute of Health MAPP Research Network publicly available dataset). In our present study, we aimed to evaluate relationships between a priori-defined brain neuroimaging markers and inflammatory factors of interest and their relationships to pain-psychological variables. We hypothesized that two brain alterations of interest (i.e., PCC - left hippocampus functional connectivity and PCC - bilateral amygdala functional connectivity) would be correlated with four cytokine markers of interest: interleukin (IL) - 6, tumor necrosis factor-alpha (TNF-a), IL-8, and granulocyte-macrophage colony-stimulating factor (GM-CSF). In the UCPPS cohort, we identified a significant PCC - left hippocampus functional connectivity relationship with IL-6 (p = 0.0044). Additionally, in the UCPPS cohort, we identified a PCC - amygdala functional connectivity relationship with GM-CSF which did not meet our model's threshold for statistical significance (p = 0.0665). While these data are preliminary and cross-sectional, our findings suggest connections between brain function and levels of low-grade systemic inflammation in UCPPS. Thus, while further study is needed, our data indicate the potential for advancing the understanding of how brain functional circuits may relate to clinical symptoms and systemic inflammation.

How Can Experimental Endotoxemia Contribute to Our Understanding of Pain? A Narrative Review

The immune system and the central nervous system exchange information continuously. This communication is a prerequisite for adaptive responses to physiological and psychological stressors. While the implicate relationship between inflammation and pain is increasingly recognized in clinical cohorts, the underlying mechanisms and the possibilities for pharmacological and psychological approaches aimed at neuro-immune communication in pain are not fully understood yet. This calls for preclinical models which build a bridge from clinical research to laboratory research. Experimental models of systemic inflammation (experimental endotoxemia) in humans have been increasingly recognized as an approach to study the direct and causal effects of inflammation on pain perception. This narrative review provides an overview of what experimental endotoxemia studies on pain have been able to clarify so far. We report that experimental endotoxemia results in a reproducible increase in pain sensitivity, particularly for pressure and visceral pain (deep pain), which is reflected in responses of brain areas involved in pain processing. Increased levels of blood inflammatory cytokines are required for this effect, but cytokine levels do not always predict pain intensity. We address sex-dependent differences in immunological responses to endotoxin and discuss why these differences do not necessarily translate to differences in behavioral measures. We summarize psychological and cognitive factors that may moderate pain sensitization driven by immune activation. Together, studying the immune-driven changes in pain during endotoxemia offers a deeper mechanistic understanding of the role of inflammation in chronic pain. Experimental endotoxemia models can specifically help to tease out inflammatory mechanisms underlying individual differences, vulnerabilities, and comorbid psychological problems in pain syndromes. The model offers the opportunity to test the efficacy of interventions, increasing their translational applicability for personalized medical approaches.

Stimulated whole-blood cytokine/chemokine responses are associated with interstitial cystitis/bladder pain syndrome phenotypes and features of nociplastic pain: a multidisciplinary approach to the study of chronic pelvic pain research network study

ABSTRACT

Interstitial cystitis/bladder pain syndrome (IC/BPS) is a common and debilitating disease with poor treatment outcomes. Studies from the multidisciplinary approach to the study of chronic pelvic pain research network established that IC/BPS patients with chronic overlapping pain conditions (COPCs) experience poorer quality of life and more severe symptoms, yet the neurobiological correlates of this subtype are largely unknown. We previously showed that ex vivo toll-like receptor 4 (TLR4) cytokine/chemokine release is associated with the presence of COPCs, as well as widespread pain and experimental pain sensitivity women with IC/BPS. Here, we attempt to confirm these findings in the multisite multidisciplinary approach to the study of chronic pelvic pain Symptom Patterns Study using TLR4-stimulated whole blood (female IC/BPS patients with COPC n = 99; without n = 36). Samples were collected in tubes preloaded with TLR4 agonist, incubated for 24 hours, and resulting supernatant assayed for 7 cytokines/chemokines. These were subject to a principal components analysis and the resulting components used as dependent variables in general linear models. Controlling for patient age, body mass index, and site of collection, we found that greater ex vivo TLR4-stimulated cytokine/chemokine release was associated with the presence of COPCs ( P < 0.01), extent of widespread pain ( P < 0.05), but not experimental pain sensitivity ( P > 0.05). However, a second component of anti-inflammatory, regulatory, and chemotactic activity was associated with reduced pain sensitivity ( P < 0.01). These results confirm that the IC/BPS + COPCs subtype show higher levels of ex vivo TLR4 cytokine/chemokine release and support a link between immune priming and nociplastic pain in IC/BPS.

Inflammatory Blood Signature Related to Common Psychological Comorbidity in Chronic Pain

Chronic pain is characterized by high psychological comorbidity, and diagnoses are symptom-based due to a lack of clear pathophysiological factors and valid biomarkers. We investigate if inflammatory blood biomarker signatures are associated with pain intensity and psychological comorbidity in a mixed chronic pain population. Eighty-one patients (72% women) with chronic pain (>6 months) were included. Patient reported outcomes were collected, and blood was analyzed with the Proseek Multiplex Olink Inflammation Panel (Bioscience Uppsala, Uppsala, Sweden), resulting in 77 inflammatory markers included for multivariate data analysis. Three subgroups of chronic pain patients were identified using an unsupervised principal component analysis. No difference between the subgroups was seen in pain intensity, but differences were seen in mental health and inflammatory profiles. Ten inflammatory proteins were significantly associated with anxiety and depression (using the Generalized Anxiety Disorder 7-item scale (GAD-7) and the Patient Health Questionnaire (PHQ-9): STAMBP, SIRT2, AXIN1, CASP-8, ADA, IL-7, CD40, CXCL1, CXCL5, and CD244. No markers were related to pain intensity. Fifteen proteins could differentiate between patients with moderate/high (GAD-7/PHQ-9 > 10) or mild/no (GAD-7/PHQ-9 < 10) psychological comorbidity. This study further contributes to the increasing knowledge of the importance of inflammation in chronic pain conditions and indicates that specific inflammatory proteins may be related to psychological comorbidity.

The Role of Neuro-Immune Interactions in Chronic Pain: Implications for Clinical Practice

Chronic pain remains a public health problem and contributes to the ongoing opioid epidemic. Current pain management therapies still leave many patients with poorly controlled pain, thus new or improved treatments are desperately needed. One major challenge in pain research is the translation of preclinical findings into effective clinical practice. The local neuroimmune interface plays an important role in the initiation and maintenance of chronic pain and is therefore a promising target for novel therapeutic development. Neurons interface with immune and immunocompetent cells in many distinct microenvironments along the nociceptive circuitry. The local neuroimmune interface can modulate the activity and property of the neurons to affect peripheral and central sensitization. In this review, we highlight a specific subset of many neuroimmune interfaces. In the central nervous system, we examine the interface between neurons and microglia, astrocytes, and T lymphocytes. In the periphery, we profile the interface between neurons in the dorsal root ganglion with T lymphocytes, satellite glial cells, and macrophages. To bridge the gap between preclinical research and clinical practice, we review the preclinical studies of each neuroimmune interface, discuss current clinical treatments in pain medicine that may exert its action at the neuroimmune interface, and highlight opportunities for future clinical research efforts.