Increased production of nitric oxide stimulated by interferon-gamma from peripheral blood monocytes in patients with complex regional pain syndrome

Successful treatment of complex regional pain syndrome with topical ambroxol: a case series

AIM

The secretolytic drug ambroxol may be useful for the treatment of neuropathic pain due to its multiple modes of action. We hypothesized that ambroxol may be a treatment option for complex regional pain syndrome (CRPS).

METHODS

Additional to standard therapy, eight CRPS-patients with symptoms of less than 12 months were treated with topical 20% ambroxol cream. Clinical courses were assessed using detailed anamnesis and clinical examination.

RESULTS

Following treatment we found a reduction of spontaneous pain (6 patients), pain on movement (6 patients), edema (seven patients), allodynia (six patients), hyperalgesia (seven patients), reduction of skin reddening (four patients), improvement of motor dysfunction (six patients) and improvement of skin temperature (four patients).

CONCLUSION

Topical treatment with ambroxol cream may ameliorate symptoms of CRPS.

Regulation of proinflammatory genes by the circulating microRNA hsa-miR-939

Circulating microRNAs are beneficial biomarkers because of their stability and dysregulation in diseases. Here we sought to determine the role of miR-939, a miRNA downregulated in patients with complex regional pain syndrome (CRPS). Hsa-miR-939 is predicted to target several proinflammatory genes, including IL-6, VEGFA, TNFα, NFκB2, and nitric oxide synthase 2 (NOS2A). Binding of miR-939 to the 3' untranslated region of these genes was confirmed by reporter assay. Overexpression of miR-939 in vitro resulted in reduction of IL-6, NOS2A and NFκB2 mRNAs, IL-6, VEGFA, and NOS2 proteins and NFκB activation. We observed a significant decrease in the NOS substrate l-arginine in plasma from CRPS patients, suggesting reduced miR-939 levels may contribute to an increase in endogenous NOS2A levels and NO, and thereby to pain and inflammation. Pathway analysis showed that miR-939 represents a critical regulatory node in a network of inflammatory mediators. Collectively, our data suggest that miR-939 may regulate multiple proinflammatory genes and that downregulation of miR-939 in CRPS patients may increase expression of these genes, resulting in amplification of the inflammatory pain signal transduction cascade. Circulating miRNAs may function as crucial signaling nodes, and small changes in miRNA levels may influence target gene expression and thus disease.

Arterialization of Venous Blood for Differentiation of Sickle Cell Subjects in Vaso-occlusive Crisis

These studies were designed as two experiments. Experiment 1 was performed to validate the hypothesis that oxygen saturation of the venous blood may be a marker for vaso-occlusive crisis (VOC) in sickle cell patients undergoing hydroxyurea (HU) treatments. Experiment 2 was performed to test the hypothesis that an acute increase in the blood nitric oxide (NO) concentration by administering HU modulates the perception of pain in sickle cell subjects in VOC. The percent saturations of oxyhemoglobin (%O<PRE>2</PRE>Hb), reduced hemoblogin (%RHb), carboxy-hemoglobin (%COHb), met-hemoglobin (%MHb), fetal hemoglobin (HbF), and nitric oxide metabolites were measured in venous blood samples collected from sickle cell disease (SCD) who were on and off HU and O<PRE>2</PRE> at steady state and during VOC. The results showed the ratio of %O<PRE>2</PRE>Hb/RHb in VOC+HU was significantly higher than patients in the steady state who were on and off of HU (p<0.05). The %COHb was higher in all SCD groups, %COHb values were significantly different in SCD at steady state who were on HU. HU and O<PRE>2</PRE> treatment did not play important role on venous blood %O<PRE>2</PRE>Hb and pain scores in SCD during VOC. A single oral dose of HU was associated with a significant increase in the venous concentration of nitric oxide metabolites (NOx), p<0.05. These findings suggest that the ratio %O<PRE>2</PRE>Hb/RHb in venous blood and pain scores differentiate HU-untreated and HU-treated at steady state subjects from HU-treated subjects in VOC; however, the acute increase in venous NOx produced by administering HU to HU-treated subjects in VOC does not explain this difference.

Nitric oxide synthase modulates CFA-induced thermal hyperalgesia through cytokine regulation in mice

Background

Although it has been largely demonstrated that nitric oxide synthase (NOS), a key enzyme for nitric oxide (NO) production, modulates inflammatory pain, the molecular mechanisms underlying these effects remain to be clarified. Here we asked whether cytokines, which have well-described roles in inflammatory pain, are downstream targets of NO in inflammatory pain and which of the isoforms of NOS are involved in this process.

Results

Intraperitoneal (i.p.) pretreatment with 7-nitroindazole sodium salt (7-NINA, a selective neuronal NOS inhibitor), aminoguanidine hydrochloride (AG, a selective inducible NOS inhibitor), L-N(G)-nitroarginine methyl ester (L-NAME, a non-selective NOS inhibitor), but not L-N(5)-(1-iminoethyl)-ornithine (L-NIO, a selective endothelial NOS inhibitor), significantly attenuated thermal hyperalgesia induced by intraplantar (i.pl.) injection of complete Freund's adjuvant (CFA). Real-time reverse transcription-polymerase chain reaction (RT-PCR) revealed a significant increase of nNOS, iNOS, and eNOS gene expression, as well as tumor necrosis factor-alpha (TNF), interleukin-1 beta (IL-1β), and interleukin-10 (IL-10) gene expression in plantar skin, following CFA. Pretreatment with the NOS inhibitors prevented the CFA-induced increase of the pro-inflammatory cytokines TNF and IL-1β. The increase of the anti-inflammatory cytokine IL-10 was augmented in mice pretreated with 7-NINA or L-NAME, but reduced in mice receiving AG or L-NIO. NNOS-, iNOS- or eNOS-knockout (KO) mice had lower gene expression of TNF, IL-1β, and IL-10 following CFA, overall corroborating the inhibitor data.

Conclusion

These findings lead us to propose that inhibition of NOS modulates inflammatory thermal hyperalgesia by regulating cytokine expression.

Role of inflammation gene polymorphisms on pain severity in lung cancer patients

Many of the same inflammatory factors that promote tumor growth are also hypothesized to function as pain modulators. There is substantial interindividual variation in pain severity in cancer patients. Therefore, we evaluated 59 single nucleotide polymorphisms in 37 inflammation genes in newly diagnosed non-Hispanic Caucasian lung cancer patients (n = 667) and assessed their association with pain severity. Patients rated their pain "during the past week" on an 11-point numeric scale (0 = "no pain" and 10 = "pain as bad as you can imagine") at presentation before initiating cancer therapy. Reported analgesic use was abstracted from charts and converted to morphine equivalent daily dose. Results showed that 16% of the patients reported severe pain (score > or = 7). Advanced stage of disease [odds ratio (OR), 2.34; 95% confidence interval (95% CI), 1.50-3.65; P = 0.001], age < or = 50 years (OR, 2.10; 95% CI, 1.32-3.30; P = 0.002), reports of depressed mood (OR, 3.68; 95% CI, 1.96-6.93; P = 0.001), fatigue (OR, 3.72; 95% CI, 2.36-5.87; P = 0.001), and morphine equivalent daily dose (OR, 1.02; 95% CI, 1.01-1.03) were significantly correlated with severe pain. Controlling for these nongenetic covariates, we found that patients with CC genotypes for PTGS2 exon10+837T>C (rs5275) were at lower risk for severe pain (OR, 0.33; 95% CI, 0.11-0.97) and an additive model for TNFalpha -308GA (rs1800629; OR, 1.67; 95% CI, 1.08-2.58) and NFKBIA Ex6+50C>T (rs8904) was predictive of severe pain (OR, 0.64; 95% CI, 0.43-0.93). In a multigene analysis, we found a gene-dose effect, with each protective genotype reducing the risk for severe pain by as much as 38%. This study suggests the importance of inflammation gene polymorphisms in modulating pain severity. Additional studies are needed to validate our findings.

Insights from experimental studies into allodynia and its treatment

Migraine is a common disorder that often is accompanied by cutaneous allodynia. Cutaneous allodynia on the head has been linked to sensitization of neurons in the trigeminal nucleus caudalis in animal models of migraine. In addition, migraine with allodynia is refractory to acute treatment with triptans. Understanding the mechanisms of allodynia, preventing its development, and finding effective treatments have become a priority in headache research. This paper reviews recent research on the pathogenesis of headache and the generation of allodynia. We discuss the regions of the nervous system that are involved in generating and maintaining headache pain and allodynia. We also discuss recent advances in the treatment of migraine based on translation research.

Vasodilative effect of isosorbide dinitrate ointment in complex regional pain syndrome type 1

BACKGROUND

In complex regional pain syndrome type 1 (CRPS1) vascular changes occur from the initial, inflammatory event onto the trophic signs during chronicity of the disease, resulting in blood flow disturbances and marked temperature changes. Pharmacotherapeutic treatment is generally inadequate.

AIM

To determine whether local application of the nitric oxide donor isosorbide dinitrate (ISDN) could cause vasodilation and thereby improve tissue blood distribution in the affected extremity.

METHODS

In a pilot study, 5 female patients with CRPS1 in one hand were treated with ISDN ointment 4 times daily during 10 weeks. As a primary objective videothermography was used to monitor changes in blood distribution in both the involved and contralateral extremities.

RESULTS

Patients treated with ISDN showed an increase of 4 degrees C to 6 degrees C in mean skin temperature of the cold CRPS1 hands, reaching values similar to that of the contralateral extremities within 2 to 4 weeks time, suggesting normalization of blood distribution. This was confirmed by an improvement in skin color. In 3 patients the Visual Analog Scale pain declined, whereas in the other 2 patients the Visual Analog Scale pain was unchanged over time.

CONCLUSIONS

In this pilot study, topical application of ISDN seems to be beneficial to improve symptoms for patients with cold type CRPS1, but further study is needed.

Autoimmunity in complex-regional pain syndrome

Complex regional pain syndrome (CRPS) is an etiologically unclear syndrome with the main symptoms being pain, trophic and autonomic disturbances, and functional impairment that develops after limb trauma or operation and is located at the distal site of the affected limb. Because autoantibodies against nervous system structures have been described in these patients, an autoimmune etiology of CRPS is discussed. These autoantibodies bind to the surface of peripheral autonomic neurons. Using a competitive binding assay, it can be shown that at least some of the CRPS sera bind to the same neuronal epitope. Autoimmune etiology of CRPS is a new pathophysiological concept and may have severe impact on the treatment of this often chronic disease.

Transcriptional activity of genes encoding interferon gamma (IFNgamma) and its receptor assessed in peripheral blood mononuclear cells in patients with cardiac syndrome X

BACKGROUND

Cardiac syndrome X is typically characterized by effort induced anginal pain with ST segment depression suggestive of myocardial ischemia and normal coronary arteries at angiography. The possible mechanism that may participate in the pathology of CSX is a microvascular dysfunction related to inflammatory process affecting endothelium. Interferon gamma (IFN-gamma) is an important cytokine in inflammatory reaction. It acts through its specific receptor composed of 2 subunits IFN-gamma R1 (ligand binding) and R2 (signal transduction). The expression and proportion of these subunits influences IFN-gamma activity. The aim of the study was to assess the gene expression of IFN-gamma and its receptors in peripheral blood mononuclear cells (PBMC) from patients with syndrome X.

METHODS

The study was carried out in 36 patients aged 44-77 (average 57 years old) with cardiac syndrome X and 23 sex- and age-matched healthy subjects (control group). To evaluate gene expression of IFNgamma and its receptor total mRNA was extracted from peripheral blood mononuclear cells (PBMC) and the number of mRNA copies were assessed by quantitive reverse transcriptase polymerase chain reaction (QRT-PCR).

RESULTS

We have not observed statistically significant differences in INFgamma gene expression between studied group and control. Genes encoding IFNgamma receptor subunits showed higher expression in PBMCs from patients with cardiac syndrome X vs control subjects (IFNgammaR1, 97,244 +/- 26,956 c/microg vs 12,120 +/- 2,940 c/microg, p < 0.005, respectively and IFNgammaR2, 129,153 +/- 36,883 c/microg vs 16,445 +/- 2,923 c/microg, p < 0.005, respectively).

CONCLUSION

Variation in transcriptional activity of genes encoding INF-gamma receptor subunits may affect function of microvasculature and thereby participate in the pathology of cardiac syndrome X.

Ibudilast (AV-411)

The treatment of neuropathic pain is a major unresolved medical challenge. Present pharmacotherapies only have modest efficacy and numerous side effects. The use of opioid analgesics is additionally coupled with dependence and withdrawal syndromes. Ibudilast (AV-411) is a non-selective phosphodiesterase inhibitor that is also known to suppress glial cell activation. It has been used clinically for other indications with a good safety profile. As glial cell activation is considered to crucially contribute to neuropathic pain as well as opioid dependence and withdrawal, the authors conceived that ibudilast may be useful for treating these conditions. Preclinical data indicate that ibudilast crosses the blood-brain barrier, is well tolerated, is active on oral administration, reduces glial activation and attenuates pain symptoms in diverse rat models of neuropathic pain. In addition, it enhances acute morphine analgesia and attenuates morphine tolerance and withdrawal. Thus ibudilast may improve opioid efficacy and is a promising therapeutic candidate for neuropathic pain, with a novel mechanism of action.

Applied information retrieval and multidisciplinary research: new mechanistic hypotheses in complex regional pain syndrome

Background

Collaborative efforts of physicians and basic scientists are often necessary in the investigation of complex disorders. Difficulties can arise, however, when large amounts of information need to reviewed. Advanced information retrieval can be beneficial in combining and reviewing data obtained from the various scientific fields. In this paper, a team of investigators with varying backgrounds has applied advanced information retrieval methods, in the form of text mining and entity relationship tools, to review the current literature, with the intention to generate new insights into the molecular mechanisms underlying a complex disorder. As an example of such a disorder the Complex Regional Pain Syndrome (CRPS) was chosen. CRPS is a painful and debilitating syndrome with a complex etiology that is still unraveled for a considerable part, resulting in suboptimal diagnosis and treatment.

Results

A text mining based approach combined with a simple network analysis identified Nuclear Factor kappa B (NFκB) as a possible central mediator in both the initiation and progression of CRPS.

Conclusion

The result shows the added value of a multidisciplinary approach combined with information retrieval in hypothesis discovery in biomedical research. The new hypothesis, which was derived in silico, provides a framework for further mechanistic studies into the underlying molecular mechanisms of CRPS and requires evaluation in clinical and epidemiological studies.

Increased endothelin-1 and diminished nitric oxide levels in blister fluids of patients with intermediate cold type complex regional pain syndrome type 1

Background

In complex regional pain syndrome type 1 (CRPS1) pro-inflammatory mediators and vascular changes play an important role in the sustained development and outcome of the disease. The aim of this study was to determine the involvement of vasoactive substances endothelin-1 (ET-1) and nitric oxide (NO) during early chronic CRPS1.

Methods

Included were 29 patients with CRPS 1 who were diagnosed during the acute stage of their disease and observed during follow-up visits. Disease activity and impairment were determined and artificial suction blisters were made on the CRPS1 and the contralateral extremities for measurements of IL-6, TNF-α, ET-1 and nitrate/nitrite (NOx).

Results

The levels of IL-6, TNF-α and ET-1 in blister fluid in the CRPS1 extremity versus the contralateral extremity were significantly increased and correlated with each other, whereas NOx levels were decreased.

Conclusion

The NOx/ET-1 ratio appears to be disturbed in the intermediate stage of CRPS, resulting in vasoconstriction and consequently in a diminished tissue blood distribution.

Leukocytes in Complex Regional Pain Syndrome Type I

OBJECTIVE

The pathophysiology of Complex Regional Pain Syndrome type I (CRPS I) is unclear. An inflammatory reaction may cause the syndrome in which leukocytes may play an important role.

MATERIALS AND METHODS

In this pilot study of six patients with acute warm CRPS I, we performed radiolabeled autologous leukocyte scans of both hands, in order to assess leukocyte accumulation. Comparison was made with the unaffected limb, and with three control patients with a Colles fracture without CRPS I.

RESULTS

Images of the CRPS I patients obtained 4 h after leukocyte injection provided the clearest results. At 4 h post-injection, there was clear, asymmetrical leukocyte accumulation in the affected extremity with a mean ratio of 1.49+/-0.19. In control patients, no asymmetry was observed between hands (mean ratio 1.09+/-0.06), indicating the absence of specific leukocyte accumulation. There was a statistically significant difference between CRPS I and control subjects 4 h post injection (p=0.012).

CONCLUSION

We found a significantly increased accumulation of leukocytes in patients with CRPS I. This is the first study to show a possible role for leukocytes in the pathophysiology of acute CRPS I.

Pathophysiology of complex regional pain syndrome

Complex regional pain syndrome (CRPS) most often follows injury to peripheral nerves or their endings in soft tissue. A combination of prostanoids, kinins and cytokines cause peripheral nociceptive sensitization. In time, the Mg(2+) block of the N-methyl-D-aspartate receptor is removed, pain transmission neurons (PTN) are altered by an influx of Ca(2+) that activates kinases for excitation and phosphatases for depression, activity-dependent plasticity that alters the firing of PTN. In time, these neurons undergo central sensitization that lead to a major physiological change of the autonomic, pain and motor systems. The role of the immune system and the sickness response is becoming clearer as microglia are activated following injury and can induce central sensitization while astrocytes may maintain the process.

Changes in cerebrospinal fluid levels of pro-inflammatory cytokines in CRPS

Complex Regional Pain Syndrome (CRPS) Types I and II are characterized by various combinations of sensory, autonomic and motor abnormalities. Pain disproportionate to the severity and duration of the inciting event is the most devastating symptom. In animal studies, conditions resulting in exaggerated pain states demonstrate elevated pro-inflammatory cytokines. In addition, pro-inflammatory cytokines have been shown to induce or increase neuropathic and inflammatory pain. Utilizing high sensitivity enzyme linked immunosorbent assay (ELISA), we compared the levels of the pro-inflammatory cytokines interleukin-1beta (IL-1beta), interleukin-6 (IL-6) and Tumor Necrosis Factor-alpha (TNF-alpha) in the cerebrospinal fluid (CSF) of patients afflicted with CRPS to CSF levels found in other patients with and without painful conditions. The results from this study demonstrated significant increases in IL-1beta and IL-6, but not TNF-alpha in the CSF of individuals afflicted with CRPS as compared to controls. CSF cytokine levels in controls with painful conditions did not differ from levels in controls without pain. These increases showed no correlation with the patient's gender or weight. These results are consistent with studies that suggest that the pathogenesis of CRPS is due in part to central neuroimmune activation.

Plasma nitric oxide level in familial Mediterranean fever and its modulations by Immuno-Guard

Familial Mediterranean fever (FMF) is a recessively inherited inflammatory disorder, characterised by recurrent attacks of fever and serositis. Since nitric oxide (NO) is an important mediator of inflammation, the production of NO (assessed as the accumulation of nitrate and nitrite and measured by capillary electrophoresis) in blood plasma of FMF patients during acute attacks (active) and attack-free periods (inactive) of the disease has been determined and compared with NO levels found in healthy volunteers (control group C). Thirty-six FMF patients were involved in a placebo-controlled double-blind study (group A received the drug, group B the placebo) of the effects of Immuno-Guard, a novel herbal preparation which relieves the severity and longevity of FMF attacks on NO blood levels. Thirty-two FMF patients (group D) being permanently treated with colchicine were also examined with respect to their NO blood level. No significant differences were found between the NO levels in blood of inactive FMF patients and those of control group C, or between inactive colchicine-treated group D patients and inactive patients of groups A and B, a finding which is atypical for chronic inflammatory disorders. Significantly lower plasma NO levels were found in active FMF patients in groups A and B compared with inactive patients in those groups (p=0.031 and 0.036, respectively) and with patients of group D and the control group C (p=0.0235 and 0.0453, respectively). The decrease of NO in blood of FMF patients may trigger the generation of fever by initiating the production of pro-inflammatory IL-6. Plasma NO levels in inactive FMF patients were significantly increased during attack-free periods following treatment with Immuno-Guard. The preparation has a normalising effect both on NO and IL-6 blood levels in FMF patients during attacks, demonstrating a relationship between the beneficial effect of Immuno-Guard in reducing the severity of inflammatory attacks in FMF patients and the increase in NO blood levels.

Complex regional pain syndrome--diagnostic, mechanisms, CNS involvement and therapy

Complex regional pain syndromes (CRPS, formerly reflex sympathetic dystrophy and causalgia) are neuropathic pain conditions of one extremity developing inadequately after a trauma. The initiating trauma affects primarily the extremity, but can also be a central lesion (e.g., spinal cord injury, stroke). CRPS is clinically characterized by sensory, autonomic and motor disturbances. Pathophysiologically there is evidence for functional changes within the central nervous system and for involvement of peripheral inflammatory processes. The sympathetic nervous system plays a key role in maintaining pain and autonomic dysfunction in the affected extremity. After a primary central lesion, secondary peripheral changes in the paretic extremity are suggested to be important in initiating a CRPS. Though there is no diagnostic gold standard, careful clinical evaluation and additional test procedures should lead to an adequate diagnosis. An early diagnosis and an interdisciplinary approach are important for optimal and successful treatment.

Opioids: a review

Recent discoveries in opioid pharmacology help explain the enormous variability in clinical responses to these powerful analgesics. Although there is only one m opioid receptor gene, splice variants of that gene's expression result in a panoply of different functioning receptors. Other sources of variable response include polymorphisms in the m opioid receptor regulatory region, and pharmacokinetic differences because of cytochrome P-450 mono-oxygenase heterogeneity. Analgesic tolerance is likely the key phenomenon limiting the benefit of opioids. A plethora of intracellular pathways affects this. Among them are the N-methyl-D-aspartate receptor, protein kinase C gamma activity, nitric oxide synthase, and GM1 ganglioside content of the neuronal membrane. Clinical studies undercut the routine use of meperidine in most settings. Other studies have shown better ways to diminish opioid side effects.