Background & Aims
Neuroimmune activity has been associated with pain, sleep and fatigue [1,2,5,6]. Compared to controls, we have previously reported higher cytokine levels in the cerebrospinal fluid (CSF) of patients suffering from degenerative disc disease (DDD), lumbar disc herniation (LDH) or osteoarthritis (OA) (n = 40/group) [5,6]. Here, we wanted to profit from these cohorts with well-defined chronic pain conditions to elucidate sleep disturbance and fatigue aspects. We were interested in whether the permeability of the blood-brain barrier (BBB) or systemic (serum) or central (cerebrospinal fluid, CSF) cytokines are associated with sleep disturbance and fatigue. Furthermore, we were interested in functional connections between 1) the cytokines that were associated with either symptom (before correction for multiple comparisons) and 2) jointly up- or downregulated cytokines as reported in previous studies [5,6].
Methods
Subjects completed questionnaires regarding pain intensity (visual analogue scale, VAS), sleep (Pittsburgh sleep quality index, PSQI), fatigue (multidimensional fatigue inventory, MFI), and mood (hospital anxiety and depression scale, HADS). The general fatigue subscale of MFI (MFI-GF) was used for analysis.
A 92-protein multiplex protein assay (OLINK) was used to assess the relative protein levels in serum and CSF. Albumin levels in serum and CSF were determined using ELISA.
Spearman’s correlation was used for univariate analyses, and correction for multiple comparisons was done using the Bonferroni method.
STRING was used to visualize functional interactions, with confidence level of evidence set to 0.90.
The linear regressions used PSQI and MFI_GF as dependent variables. Independent variables were sex, age, BMI, anxiety, depression, albumin quotient, pain during rest, and cytokines that were associated with the dependent variable following correction for multiple comparisons.
Results
Pain patients reported poorer sleep and more general fatigue than controls (both p < 0.001).
When all groups were analyzed together, six cytokines correlated with PSQI and 25 with MFI-GF at the p < 0.05 level. After correction for multiple comparisons, only serum levels of CDCP1, and CSF levels of CCL25 and CD244 remained significantly correlated with MFI-GF (all p < 0.001).
Functional clusters were visualized for 28 cytokines that were jointly upregulated in the CSF and for the 25 cytokines correlated with fatigue, yielding functional clusters of seven and six cytokines, respectively. The only common denominator was CXCL11, which was functionally linked to CCL25.
In multiple linear regressions, anxiety (p = 0.03), depression (p = 0.03) and pain during rest (p = 0.004) were associated with sleep disturbance. Independent variables associated with fatigue were CCL25 in CSF (p = 0.03), depressive symptoms (p < 0.001) and pain during rest (p = 0.02).
Conclusions
Functionally linked cytokines in CSF are jointly upregulated in all three pain cohorts. Similarly, we found functionally linked cytokines that correlate with levels of fatigue, but not sleep. Their common denominator, CXCL11, can be produced by astrocytes and microglia and has been linked to neuroprotection in animal studies [4]. CXCL11 is functionally linked to CCL25, a pro-inflammatory cytokine [3] with a significantly negative correlated to general fatigue. Although causality cannot be determined, the results suggest attenuating effects of neuroimmune alteration in chronic pain.
Fatigue and sleep disorders are common complaints in pain populations in general. We know from previous studies, that especially sleep has important implications for pain perception and that there is an intimate interaction between these two homeostatic systems. Fatigue, on the other hand, is generally considered part of the “sickness response” often seen in inflammatory conditions or in pain. However, the pathophysiological bases for these are not completely understood. The neuroimmune axis constitutes an interesting domain that remains poorly. Hence, research centered around the neuroimmune axis carries great promise of improving understood our understanding of how the brain communicates with the rest of the body, how neurons, glia cells and other immune cells communicate with one another, not only through electric signals, but also through chemical signals such as cytokines and neurotrophins.
References
[1] Bjurstrom MF, Irwin MR. Polysomnographic characteristics in nonmalignant chronic pain populations: A review of controlled studies. Sleep Med Rev 2016;26:74–86.
[2] Dantzer R, O’Connor JC, Freund GG, Johnson RW, Kelley KW. From inflammation to sickness and depression: when the immune system subjugates the brain. Nat Rev Neurosci 2008;9:46–56.
[3] Igaki K, Komoike Y, Nakamura Y, Watanabe T, Yamasaki M, Fleming P, Yang L, Soler D, Fedyk E, Tsuchimori N. MLN3126, an antagonist of the chemokine receptor CCR9, ameliorates inflammation in a T cell mediated mouse colitis model. International Immunopharmacology 2018;60:160–169.
[4] Müller M, Carter S, Hofer MJ, Campbell IL. Review: The chemokine receptor CXCR3 and its ligands CXCL9, CXCL10 and CXCL11 in neuroimmunity–a tale of conflict and conundrum. Neuropathol Appl Neurobiol 2010;36:368–387.
[5] Palada V, Ahmed AS, Freyhult E, Hugo A, Kultima K, Svensson CI, Kosek E. Elevated inflammatory proteins in cerebrospinal fluid from patients with painful knee osteoarthritis are associated with reduced symptom severity. J Neuroimmunol 2020;349:577391.
[6] Rosenström AHC, Ahmed AS, Kultima K, Freyhult E, Berg S, Bersellini Farinotti A, Palada V, Svensson CI, Kosek E. Unraveling the neuroimmune interface in chronic pain—the association between cytokines in the cerebrospinal fluid and pain in patients with lumbar disk herniation or degenerative disk disease. PAIN 2022:10.1097/j.pain.0000000000003175.
Presenting Author
Alexander Rosenström
Poster Authors
Alexander Rosenström
MSc
Department of surgical sciences, Uppsala university
Lead Author
Aisha Ahmed
Department of physiology and pharmacology, Karolinska Institute
Lead Author
Alex Bersellini Farinotti
PhD
Department of physiology and pharmacology, Karolinska Institute
Lead Author
Kim Kultima
PhD
Uppsala University
Lead Author
Svante Berg
Department of molecular medicine and surgery, Karolinska Institute
Lead Author
Martin Flores Bjurström
MD
Department of surgical sciences, Uppsala university
Lead Author
Camilla Svensson
Department of physiology and pharmacology, Karolinska Institute
Lead Author
Eva Kosek
Department of surgical sciences, Uppsala university
Lead Author
Topics
- Evidence, Clinical Trials, Systematic Review, Guidelines, and Implementation Science