Stabilizing the neural barrier - A novel approach in pain therapy.

Chronic and neuropathic pain are a widespread burden. Incomplete understanding of underlying pathomechanisms is one crucial factor for insufficient treatment. Recently, impairment of the blood nerve barrier (BNB) has emerged as one key aspect of pain initiation and maintenance. In this narrative review, we discuss several mechanisms and putative targets for novel treatment strategies. Cells such as pericytes, local mediators like netrin-1 and specialized proresolving mediators (SPMs), will be covered as well as circulating factors including the hormones cortisol and oestrogen and microRNAs. They are crucial in either the BNB or similar barriers and associated with pain. While clinical studies are still scarce, these findings might provide valuable insight into mechanisms and nurture development of therapeutic approaches.

Bortezomib induced peripheral neuropathy and single nucleotide polymorphisms in PKNOX1.

We analyzed single nucleotide polymorphisms (SNPs) in PKNOX1 (rs2839629) and in the intergenic region between PKNOX1 and CBS (rs915854) by Sanger sequencing in 88 patients with multiple myeloma treated with bortezomib. All patients (n = 13) harboring a homozygous mutation in PKNOX1 (rs2839629) also had a homozygous mutated rs915854 genotype. Homozygous mutated genotypes of rs2839629 and rs915854 were significantly enriched in patients with painful peripheral neuropathy (PNP) (P < 0.0001), and homozygous mutated rs2839629 genotype was significantly enriched in patients with pain compared to patients with no pain (P = 0.04). In summary, both SNPs rs2839629 and/or rs915854 may be potential biomarkers predicting an increased risk to develop painful PNP under bortezomib.

Systemic inflammatory markers in patients with polyneuropathies.

Introduction: In patients with peripheral neuropathies (PNP), neuropathic pain is present in 50% of the cases, independent of the etiology. The pathophysiology of pain is poorly understood, and inflammatory processes have been found to be involved in neuro-degeneration, -regeneration and pain. While previous studies have found a local upregulation of inflammatory mediators in patients with PNP, there is a high variability described in the cytokines present systemically in sera and cerebrospinal fluid (CSF). We hypothesized that the development of PNP and neuropathic pain is associated with enhanced systemic inflammation. Methods: To test our hypothesis, we performed a comprehensive analysis of the protein, lipid and gene expression of different pro- and anti-inflammatory markers in blood and CSF from patients with PNP and controls. Results: While we found differences between PNP and controls in specific cytokines or lipids, such as CCL2 or oleoylcarnitine, PNP patients and controls did not present major differences in systemic inflammatory markers in general. IL-10 and CCL2 levels were related to measures of axonal damage and neuropathic pain. Lastly, we describe a strong interaction between inflammation and neurodegeneration at the nerve roots in a specific subgroup of PNP patients with blood-CSF barrier dysfunction. Conclusion: In patients with PNP systemic inflammatory, markers in blood or CSF do not differ from controls in general, but specific cytokines or lipids do. Our findings further highlight the importance of CSF analysis in patients with peripheral neuropathies.

Neurofilament light chain levels indicate acute axonal damage under bortezomib treatment.

INTRODUCTION: Bortezomib (BTZ) is a selective and reversible proteasome inhibitor and first line treatment for multiple myeloma (MM). One of the side effects is BTZ-induced peripheral neuropathy (BIPN). Until now there is no biomarker which can predict this side effect and its severity. Neurofilament light chain (NfL) is a neuron specific cytoskeletal protein, of which higher levels can be detected in peripheral blood in case of axon damage. In this study, we aimed to evaluate the relationship between NfL serum levels and characteristics of BIPN. METHODS: We performed a first interim analysis of a monocentric, non-randomized, observational clinical trial including 70 patients (DRKS00025422) diagnosed with MM in the inclusion period of June 2021 until March 2022. Two groups of patients-one with ongoing BTZ treatment at the time of recruiting, and one with BTZ treatment in the past-were compared to controls. NfL in serum was analyzed via the ELLA™ device. RESULTS: Both patients with previous and ongoing BTZ treatment had higher serum NfL levels than controls, and patients with ongoing BTZ treatment had higher NfL levels than patients with BTZ treatment in the past. Serum NfL levels correlated with electrophysiological measures of axonal damage in the group with ongoing BTZ treatment. CONCLUSION: Elevated NfL levels indicate acute axonal damage under BTZ in MM patients.

Molecular and clinical markers of pain relief in complex regional pain syndrome: An observational study.

BACKGROUND: Complex regional pain syndrome (CRPS) is marked by disproportionate pain after trauma. Whilst the long-term outcome is crucial to patients, predictors or biomarkers of the course of pain or CRPS symptoms are still lacking. In particular, microRNAs, such as miR-223, decreased in CRPS, have been described only in cross-sectional studies. METHODS: In this study, we characterised CRPS patients over a course of 2.5 years of standard treatment. The patient underwent clinical examination including pain measurement, symptom questionnaires, quantitative sensory testing (QST) and blood sampling. Exosomal microRNA levels were measured via qPCR. After follow-up, patients were stratified into 'pain relief' (mean pain reduced by ≥2 numeric rating scale) or 'persistence' (mean pain unchanged or worsened). The primary outcome was miR-223 and miR-939 expression, secondary outcomes were differences in clinical parameters between groups and time points. RESULTS: Thirty-nine patients were included, 33 of whom qualified for stratification. Overall, patients reported lower pain and improved clinical characteristics after 2.5 years, but no significant changes in QST or miR-223 and miR-939 expression levels. 16 patients met the criteria for pain relief. This was associated with stable exosomal miR-223 expression, whilst levels further decreased in pain persistence. Clinically, pain relief was marked by shorter disease duration and correlated positively with high initial pain. CONCLUSION: We identified progressively reduced miR-223 as a putative biomarker of chronic CRPS pain. Clinically, this study underlines the importance of early diagnosis and treatment showing that high initial pain does not predict an unfavourable outcome. Finally, pain relief and recovery of sensory disturbances seem independent processes.

Community-level prevalence of epilepsy and of neurocysticercosis among people with epilepsy in the Balaka district of Malawi: A cross-sectional study.

BACKGROUND: Epilepsy and neurocysticercosis (NCC) prevalence estimates in sub-Saharan Africa are still scarce but show important variation due to the population studied and different screening and diagnosis strategies used. The aims of this study were to estimate the prevalence of epileptic seizures and epilepsy in the sampled population, and the proportion of NCC among people with epilepsy (PWE) in a large cross-sectional study in a rural district of southern Malawi. METHODS: We conducted a community-based door-to-door screening study for epileptic seizures in Balaka, Malawi between October and December 2012. Past epileptic seizures were reported through a 15-item questionnaire answered by at least one person per household generating five major criteria. People who screened positive were further examined by a neurologist to establish diagnosis. Patients diagnosed with epilepsy were examined and offered Taenia solium cyst antigen and antibody serological tests, and a CT scan for the diagnosis of NCC. RESULTS: In total, screening information on 69,595 individuals was obtained for lifetime occurrence of epileptic seizures. 3,100 (4.5%) participants screened positive, of whom 1,913 (62%) could be followed-up and underwent further assessment. Lifetime prevalence was 3.0% (95% Bayesian credible interval [CI] 2.8 to 3.1%) and 1.2% (95%BCI 0.9 to 1.6%) for epileptic seizures and epilepsy, respectively. NCC prevalence among PWE was estimated to be 4.4% (95%BCI 0.8 to 8.5%). A diagnosis of epilepsy was ultimately reached for 455 participants. CONCLUSION: The results of this large community-based study contribute to the evaluation and understanding of the burden of epilepsy in the population and of NCC among PWE in sub-Saharan Africa.

MicroRNA-21-5p functions via RECK/MMP9 as a proalgesic regulator of the blood nerve barrier in nerve injury.

Both nerve injury and complex regional pain syndrome (CRPS) can result in chronic pain. In traumatic neuropathy, the blood nerve barrier (BNB) shielding the nerve is impaired-partly due to dysregulated microRNAs (miRNAs). Upregulation of microRNA-21-5p (miR-21) has previously been documented in neuropathic pain, predominantly due to its proinflammatory features. However, little is known about other functions. Here, we characterized miR-21 in neuropathic pain and its impact on the BNB in a human-murine back translational approach. MiR-21 expression was elevated in plasma of patients with CRPS as well as in nerves of mice after transient and persistent nerve injury. Mice presented with BNB leakage, as well as loss of claudin-1 in both injured and spared nerves. Moreover, the putative miR-21 target RECK was decreased and downstream Mmp9 upregulated, as was Tgfb. In vitro experiments in human epithelial cells confirmed a downregulation of CLDN1 by miR-21 mimics via inhibition of the RECK/MMP9 pathway but not TGFB. Perineurial miR-21 mimic application in mice elicited mechanical hypersensitivity, while local inhibition of miR-21 after nerve injury reversed it. In summary, the data support a novel role for miR-21, independent of prior inflammation, in elicitation of pain and impairment of the BNB via RECK/MMP9.

Microvascular Barrier Protection by microRNA-183 via FoxO1 Repression: A Pathway Disturbed in Neuropathy and Complex Regional Pain Syndrome.

Blood nerve barrier disruption and edema are common in neuropathic pain as well as in complex regional pain syndrome (CRPS). MicroRNAs (miRNA) are epigenetic multitarget switches controlling neuronal and non-neuronal cells in pain. The miR-183 complex attenuates hyperexcitability in nociceptors, but additional non-neuronal effects via transcription factors could contribute as well. This study explored exosomal miR-183 in CRPS and murine neuropathy, its effect on the microvascular barrier via transcription factor FoxO1 and tight junction protein claudin-5, and its antihyperalgesic potential. Sciatic miR-183 decreased after CCI. Substitution with perineural miR-183 mimic attenuated mechanical hypersensitivity and restored blood nerve barrier function. In vitro, serum from CCI mice und CRPS patients weakened the microvascular barrier of murine cerebellar endothelial cells, increased active FoxO1 and reduced claudin-5, concomitant with a lack of exosomal miR-183 in CRPS patients. Cellular stress also compromised the microvascular barrier which was rescued either by miR-183 mimic via FoxO1 repression or by prior silencing of Foxo1. PERSPECTIVE: Low miR-183 leading to barrier impairment via FoxO1 and subsequent claudin-5 suppression is a new aspect in the pathophysiology of CRPS and neuropathic pain. This pathway might help untangle the wide symptomatic range of CRPS and nurture further research into miRNA mimics or FoxO1 inhibitors.

[COVID-19 in obstetric anesthesia : Prospective surveillance of peripartum infections with SARS-CoV-2 and peripartum course of disease in affected women]. / COVID-19 in der geburtshilflichen Anästhesie : Prospektive Erfassung von SARS-CoV-2-Infektionen zum Zeitpunkt der Geburt sowie des peripartalen Verlaufs SARS-CoV-2-positiver Schwangerer.

BACKGROUND: In the current pandemic regarding the infection with the SARS-CoV-2-virus and COVID-19 as the disease, concerns about pregnant women, effects on childbirth and the health of the newborn remain high. Initially, due to the early manifestation of the disease in younger patients, high numbers of COVID-19 patients in women needing peripartum care were expected. OBJECTIVE: This article aims to provide a general overview over the beginning of the pandemic as well as the second wave of infections in Germany and Switzerland, regarding SARS-CoV­2 positive pregnant women hospitalized for childbirth. We therefore launched a registry to gain timely information over the dynamic situation during the SARS-CoV­2 pandemic in Germany. MATERIAL AND METHODS: As part of the COVID-19-related Obstetric Anesthesia Longitudinal Assessment (COALA) registry, centers reported weekly birth rates, numbers of suspected SARS-CoV­2 cases, as well as the numbers of confirmed cases between 16 March and 3 May 2020. Data acquisition was continued from 18 October 2020 till 28 February 2021. The data were analyzed regarding distribution of SARS-CoV­2 positive pregnant women hospitalized for childbirth between centers, calendar weeks and birth rates as well as maternal characteristics, course of disease and outcomes of SARS-CoV­2 positive pregnant women. RESULTS: A total of 9 German centers reported 2270 deliveries over 7 weeks during the first wave of infections including 3 SARS-CoV­2 positive cases and 9 suspected cases. During the second survey period, 6 centers from Germany and Switzerland reported 41 positive cases out of 4897 deliveries. One woman presented with a severe and ultimately fatal course of the disease, while another one needed prolonged ECMO treatment. Of the women 28 presented with asymptomatic infections and 6 neonates were admitted to a neonatal intensive care unit for further treatment. There was one case of neonatal SARS-CoV­2 infection. CONCLUSION: The number of pregnant women infected with SARS-CoV­2 was at a very low level at the time of delivery, with only sporadic suspected or confirmed cases. Due to the lack of comprehensive testing in the first survey period, however, a certain number of asymptomatic cases are to be assumed. Of the cases 68% presented as asymptomatic or as mild courses of disease but the data showed that even in young healthy patients without the presence of typical risk factors, serious progression can occur. These outcomes should raise awareness for anesthesiologists, obstetricians, pediatricians and intensive care physicians to identify severe cases of COVID-19 in pregnant women during childbirth and to take the necessary precautions to ensure the best treatment of mother and neonate. The prospective acquisition of data allowed a timely assessment of the highly dynamic situation and gain knowledge regarding this vulnerable group of patients.

[Pregnancy and Irreversible Loss of Brain Functions - Case Report]. / Intensivtherapie bei Schwangerer mit irreversiblem Hirnfunktionsausfall.

A 29-year-old woman suffered major traumatic brain injury caused by a car accident. As diagnostic measures had revealed an early pregnancy (9th week), treatment on the intensive care unit was continued for 5 months, after unfavourable cerebral prognosis was followed by an irreversible loss of brain function in the 10th week of pregnancy. After assisted vaginal delivery of a healthy child in the 31th week of pregnancy on the critical care unit, organ procurement took place according to the presumed will of the patient. The article presents the details of the critical care therapy and discusses the supportive medical measures. Those measures served primarily to uphold the pregnancy und support the healthy development and delivery of the fetus and only in second instance the organ preservation aiming on organ donation. Necessary measures included maintenance of vital functions, hemostasis of electrolytes, nutrition, treatment of infection, prevention of adverse effects on the fetus, substitution of hormones and vitamins as well as the preparation of a planned or an unplanned delivery.

[Ethical, Psychosocial and Legal Aspects of the Treatment of Pregnant Patients with Brain Death]. / Ethische, psychosoziale und rechtliche Aspekte der Behandlung hirntoter Schwangerer.

The therapy of brain-dead pregnant women is an extreme example not only of the possibilities in current critical care, but also of resulting ethical, social and legal controversies, an area not familiar to most clinicians. Based on the case of a patient with fatal traumatic brain injury, a previously unknown early pregnancy and stated will to donate organs, we will discuss several aspects using published case reports: therapeutic goals, especially palliative care vs. continuation; implications of brain death diagnosis; considerations on legal care; involvement of relatives, especially the child's father; dynamics within the care team; and finally the issue of putative organ donation. This complex case once more depicts that even facing such highly unfavourable framework and seemingly irreconcilable factors, pregnancy can prevail. The researched facts and considerations in this article are intended to give an overview of potential dilemmas and might serve as a starting point in similar situations.

Getting hit by the bus around the world - a global perspective on goal directed treatment of massive hemorrhage in trauma.

PURPOSE OF REVIEW: Major trauma remains one of the leading causes of death worldwide with traumatic brain injury and uncontrolled traumatic bleeding as the main determinants of fatal outcome. Interestingly, the therapeutic approach to trauma-associated bleeding and coagulopathy shows differences between geographic regions, that are reflected in different guidelines and protocols. RECENT FINDINGS: This article summarizes main principles in coagulation diagnostics and compares different strategies for treatment of massive hemorrhage after trauma in different regions of the world. How would a bleeding trauma patient be managed if they got hit by the bus in the United States, United Kingdom, Germany, Switzerland, Austria, Denmark, Australia, or in Japan? SUMMARY: There are multiple coexistent treatment standards for trauma-induced coagulopathy in different countries and different trauma centers. Most of them initially follow a protocol-based approach and subsequently focus on predefined clinical and laboratory targets.

[Placebo Effect - The Benefit of "Nothingness" in Pain Therapy]. / Der Placeboeffekt ­ der Nutzen des "Nichts" am Beispiel der Schmerztherapie.

For a long time considered ineffective, placebos nowadays have an accepted role in studies as well as clinical practice. The identification of psychological as well as neurophysiological mechanisms helped to conceptualize and legitimize the placebo effect. Moreover, studies have even proven a therapeutic value. Consequently, the benefits of a thoughtfully applied placebo effect are increasingly being exploited. This article reviews the concept and current understanding of the placebo effect and depicts its use in the field of pain management.

Vaginal delivery in the 30+4 weeks of pregnancy and organ donation after brain death in early pregnancy.

A 28-year-old woman suffered a traffic accident resulting in severe head injuries with deleterious prognosis. Diagnostics further revealed a hitherto unknown pregnancy, at suspected week 9. Based on the patient's wish to donate organs, brain death protocol confirmed irreversible loss of brain function. Yet, vital pregnancy rendered organ transplantation impossible. Multiple ethical and legal issues arose, from invalidation of established legal care after brain death to the delivery of a healthy child after trauma and long-term critical care. After medicolegal and ethical counselling, pregnancy was sustained, and the goal of organ donation postponed. Critical care focused on foetal homeostasis. At 30+4 weeks, a viable girl was born via assisted vaginal delivery. Postpartal organ donation resulted in heart, kidney and pancreas transplantation. The case emphasises the medical, legal and ethical challenges to combine two apparently diametrical goals: the successful full-term pregnancy and the fulfilment of a patient's wish to donate organs.

What is normal trauma healing and what is complex regional pain syndrome I? An analysis of clinical and experimental biomarkers.

Complex regional pain syndrome (CRPS) typically develops after fracture or trauma. Many of the studies so far have analyzed clinical and molecular markers of CRPS in comparison with healthy or pain controls. This approach, however, neglects mechanisms occurring during physiological trauma recovery. Therefore, we compared the clinical phenotype, sensory profiles, patient-reported outcomes, and exosomal immunobarrier microRNAs (miRs) regulating barrier function and immune response between CRPS and fracture controls (FCs) not fulfilling the CRPS diagnostic criteria. We included upper-extremity FCs, acute CRPS I patients within 1 year after trauma, a second disease control group (painful diabetic polyneuropathy), and healthy controls. Fracture controls were not symptoms-free, but reported some pain, disability, anxiety, and cold pain hyperalgesia in quantitative sensory testing. Patients with CRPS had higher scores for pain, disability, and all patient-reported outcomes. In quantitative sensory testing, ipsilateral and contralateral sides differed significantly. However, on the affected side, patients with CRPS were more sensitive in only 3 parameters (pinprick pain and blunt pressure) when compared to FCs. Two principal components were identified in the cohort: pain and psychological parameters distinguishing FC and CPRS. Furthermore, the immunobarrier-protective hsa-miR-223-5p was increased in plasma exosomes in FCs with normal healing, but not in CRPS and healthy controls. Low hsa-miR-223-5p was particularly observed in subjects with edema pointing towards barrier breakdown. In summary, normal trauma healing includes some CRPS signs and symptoms. It is the combination of different factors that distinguish CRPS and FC. Fracture control as a control group can assist to discover resolution factors after trauma.

Tissue plasminogen activator and neuropathy open the blood-nerve barrier with upregulation of microRNA-155-5p in male rats.

The blood-nerve barrier (BNB) consisting of the perineurium and endoneurial vessels is sealed by tight junction proteins. BNB alterations are a crucial factor in the pathogenesis of peripheral neuropathies. However, barrier opening, e.g. by tissue plasminogen activator (tPA), can also facilitate topical application of analgesics. Here, we examined tPA both in the pathophysiology of neuropathy-induced BNB opening or via exogenous application and its effect on the cytoplasmatic tight junction protein anchoring protein, zona occludens-1 (ZO-1), the adherens molecule JAM-C and microRNA(miR)-155-5p. Specifically, we investigated whether tPA alone and barrier opening lead to pain behavioral changes, i.e. hyperalgesia, or whether these effects require further factors. Male Wistar rats underwent chronic constriction injury (CCI) or were treated by a single perisciatic application of recombinant (r)tPA. CCI elicited mechanical allodynia, tPA mRNA upregulation, macrophage invasion, BNB leakage for large molecule tracers, downregulation of ZO-1 and JAM-C mRNA/protein, and a loss of immunoreactivity of both in perineurium and endoneurial cells. Similarly, after perisciatic rtPA injection, ZO-1 and JAM-C mRNA as well as cytosolic/membrane protein and ZO-1 immunoreactivity were downregulated, and the BNB was opened. Neither mechanical hypersensitivity nor macrophage infiltration was observed after rtPA in contrast to CCI. Mechanistically, miR-155-5p, which is known to destabilize barriers and tight junction proteins like claudin-1 and ZO-1, was increased in CCI and to lesser extent after rtPA application. In summary, tPA transiently opens the BNB possibly via miR-155-5p. However, tPA does not provoke allodynia in the absence of a neuropathic stimulus like a ligation or inflammation.

Quantitative and Microstructural Changes of the Blood-Nerve Barrier in Peripheral Neuropathy.

Peripheral neuropathy is accompanied by changes in the neuronal environment. The blood-nerve barrier (BNB) is crucial in protecting the neural homeostasis: Tight junctions (TJ) seal paracellular spaces and thus prevent external stimuli from entering. In different models of neuropathic pain, the BNB is impaired, thus contributing to local damage, immune cell invasion and, ultimately, the development of neuropathy with its symptoms. In this study, we examined changes in expression and microstructural localization of two key tight junction proteins (TJP), claudin-1 and the cytoplasmic anchoring ZO-1, in the sciatic nerve of mice subjected to chronic constriction injury (CCI). Via qPCR and analysis of fluorescence immunohistochemistry, a marked downregulation of mRNA as well as decreased fluorescence intensity were observed in the nerve for both proteins. Moreover, a distinct zig-zag structure for both proteins located at cell-cell contacts, indicative of the localization of TJs, was observed in the perineurial compartment of sham-operated animals. This microstructural location in cell-cell-contacts was lost in neuropathy as semiquantified via computational analysis, based on a novel algorithm. In summary, we provide evidence that peripheral neuropathy is not only associated with decrease in relevant TJPs but also exhibits alterations in TJP arrangement and loss in barrier tightness, presumably due to internalization. Specifically, semiquantification of TJP in cell-cell-contacts of microcompartments could be used in the future for routine clinical samples of patients with neuropathy.

Analgesic drug delivery via recombinant tissue plasminogen activator and microRNA-183-triggered opening of the blood-nerve barrier.

The peripheral nerve contains three barriers which include the blood-nerve barrier consisting of endoneurial vessels and the perineurium as well as autotypic junctions in Schwann cells. The perineurium prevents diffusion of perineurally injected drugs that can be used for selective regional pain control. It is composed of a basal membrane and layers of perineurial cells sealed by tight junction proteins like claudin-1. Claudin-1 expression and barrier function are regulated via low-density lipoprotein receptor-related protein (LRP-1). Perisciatic application of recombinant tissue plasminogen activator (rtPA) or the catalytically inactive rtPAi - both agonists of LRP-1 - reduced claudin-1 mRNA and protein expression in the rat nerve. This facilitated an increase of nociceptive thresholds after local application of hydrophilic opioids or the voltage gated sodium channel blocker (NaV1.7) ProToxin-II without apparent nerve toxicity. RtPA-induced barrier opening was mediated by LRP-1 and intracellularly by Erk phosphorylation. In silico, microRNA (miR)-rno-29b-2-5p and rno-miR-183-5p were identified as potential regulators of claudin-1 transcription in the rat. RtPA application increased miR-183-5p in the sciatic nerve. MiR-183-5p mimics functionally opened the perineurium and downregulated claudin-1 expression in vivo. In vitro, hsa-miR-183-3p mimics reduced claudin-1 expression in human HT-29/B6 cells. Overall, rtPA regulates perineurial barrier tightness via LRP-1, Erk phosphorylation and miR-183-5p/3p. This mechanism might serve as a new principle to facilitate drug delivery to peripheral nerves in humans.