Internal thoracic artery graft failure and recurrence of symptoms following single-vessel coronary artery bypass graft surgery.

OBJECTIVES: Coronary events and disease recurrence following coronary artery bypass (CABG) surgery could derive from either failure in the internal thoracic artery (ITA) graft, failure in other conduits or progressive disease in the coronaries. We aim to estimate the contribution of ITA graft failure to the recurrence of symptoms after CABG surgery. METHODS: Within the Swedish Web System for Enhancement and Development of Evidence-Based Care in Heart Disease Evaluated According to Recommended Therapies registry, we identified patients who had coronary artery bypass grafting from 1997 to 2020 with a single-vessel ITA graft bypass. Deaths, postoperative incidence of coronary angiography and the presence of a failed graft at the time of the angiography were recorded. RESULTS: The study population consisted of 1939 patients with a mean follow-up time (SD) of 17.2 (5.6) years. The cumulative incidence (95% CI) at 20 years for a first clinically-driven postoperative angiography was 38.6% (36.2-41.1). A failed ITA graft was reported in 16.4% of the angiographies. CONCLUSIONS: A substantial part of recurrent symptoms of coronary artery disease do not seem to be related to ITA failure. Disease progression in the native coronary vessels may instead be the main driver of symptom recurrence.

Symptomatic late saphenous vein graft failure in coronary artery bypass surgery.

OBJECTIVES: Coronary artery bypass grafting for advanced coronary artery disease is a well-established procedure with excellent long-term results. The issue of saphenous vein graft (SVG) performance and its relation to clinical symptoms and thereby the potential for improvement by using superior grafts are still not fully understood. We aim to estimate the contribution of late SVG failure to the long-term outcome. METHODS: A study population operated between 1997 and 2020, with an internal thoracic artery with a single distal anastomosis and 1, 2 or 3 distal SVG anastomoses, was isolated from the Swedish Web System for Enhancement and Development of Evidence-Based Care in Heart Disease Evaluated According to Recommended Therapies registry. Data regarding postoperative clinically driven coronary angiography and status of bypass grafts were collected. RESULTS: The study population consisted of 44 951 patients. Clinically driven angiography occurred in 10.1% (9.5-10.8), 7.9% (7.6-8.3) and 7.1% (6.7-7.5), respectively, of patients within 3 years and 23.6% (22.6-24.5), 20.0% (19.5-20.6) and 17.5% (16.9-18.2), respectively, of patients within 10 years after surgery. Excluding the first 3 postoperative years, no failed SVGs were found in >75%, 60% and 45%, respectively, of cases when an angiography was performed in the first 10 years after surgery. CONCLUSIONS: The results suggest that the risk of symptomatic graft failure due to vein graft disease during the first 10 years after surgery is in the range of 1-2% for every grafted coronary vessel and provide an estimate for the upper limit of the improvements in results that could be achieved by replacing SVGs with superior grafts.

Intermediate outcomes following arch reconstruction with frozen elephant trunk, a single centre study.

BACKGROUND: Surgery on the aortic arch and proximal descending thoracic aorta can be lifesaving but is also associated with significant morbidity, ranging from minor infections to severe neurological impairments as well as a substantial risk of mortality. The aim of this study is to clinically assess outcomes, with special regards to neurologic injury, as well as to seek to identify predictors of in-hospital mortality in two patient groups with different underlying aortic pathology, aneurysms and dissections, undergoing arch/descending aortic repair. METHODS: 34 patients (17 aneurysms, 17 dissections) underwent surgery involving the arch and/or descending aorta, using the Thoraflex or E-Vita frozen elephant trunk graft. 40% were female. Subgroup analysis of aneurysms compared to dissections were performed. Mean follow-up time was 53.9 months and mean age 63.5 years. RESULTS: In-hospital mortality was 18%. Survival was comparable between aneurysms and dissections. Incidence of spinal cord injury was 9% and stroke 9%. 67% suffered any form of neurological affection, when also cognitive afflictions were included. Perioperative reoperation rate was 29% (bleeding 21%, visceral ischemia 6%, infection 2%), the need for postoperative dialysis was 11% and a series of other minor complications such as atrial fibrillation and pleurocentesis were common. CONCLUSION: Postoperative dialysis was found to be a predictor of in-hospital mortality, while both dialysis as well as reoperation due to bleeding and/or visceral ischemia increased the risk for overall mortality, irrespective of preoperative diagnosis. Previous or current smoking appeared to be associated with negative outcomes regarding both in-hospital and overall mortality during follow-up. Trial registration Retrospectively enrolled.

Extracorporeal Cardiopulmonary Resuscitation Guided by End-Tidal Carbon Dioxide-a Porcine Model.

Extracorporeal membrane cardiopulmonary resuscitation (ECPR) during cardiopulmonary resuscitation (CPR) for selected cases and end-tidal carbon dioxide (ETCO2) could be used to guide initiation of ECPR. Ventricular fibrillation was induced in 12 pigs and CPR was performed until ETCO2 fell below 10 mmHg; then, ECPR was performed. Animals were divided into group short (GShort) and group long (GLong), according to time of CPR. Carotid blood flow was higher (p = 0.02) and mean arterial blood pressure lower in GLong during CPR (p < 0.05). B-Lactate was lower and pH higher in GShort (p < 0.01). In microdialysis lactate-pyruvate ratio, glycerol and glutamate increased in both groups during CPR, but considerably in GLong (p < 0.01). No difference could be seen in histopathology of the brain or kidney post-ECPR. No apparent histological differences of tissue damage in brains or levels of S100B in plasma were detected between groups. This might suggest that ETCO2 could be used as a marker for brain injury following ECPR.

Mechanical Reperfusion Following Prolonged Global Cerebral Ischemia Attenuates Brain Injury.

Previous experiments demonstrated improved outcome following prolonged cerebral ischemia given controlled brain reperfusion using extracorporeal circulation. The current study further investigates this. Young adult pigs were exposed to 30 min of global normothermic cerebral ischemia, achieved through intrathoracic clamping of cerebral arteries, followed by 20 min of isolated mechanical brain reperfusion. Leukocyte-filtered blood was delivered by a roller-pump at fixed pressure and flow. One experimental group additionally had a custom-made buffer solution delivered at 1:8 ratio with the blood. Hemodynamics including intracranial pressure were monitored. Blood gases were from peripheral arteries and the sagittal sinus, and intraparenchymal brain microdialysis was performed. The brains were examined by a neuropathologist. The group with the added buffer showed lower intracranial pressure as well as decreased intraparenchymal glycerol and less signs of excitotoxicity and ischemia, although histology revealed similar degrees of injury. A customized mechanical reperfusion improves multiple parameters after prolonged normothermic global cerebral ischemia. Graphical Abstract The current study investigates if it possible to improve neurological outcomes following prolonged global brain ischemia. The results indicate that a customized mechanical reperfusion protocol can attenuate neurological injury.

Detection of Changes in Immunohistochemical Stains Caused by Postmortem Delay and Fixation Time.

In this study, we have systematically assessed the influence of postmortem delay (PMD) and fixation time (FT) on the immunohistochemical (IHC) staining outcome. The IHC method is frequently applied on surgical and postmortem samples in diagnostics and research. To replicate the routine situation, brain tissues from pigs were exposed to either storage in a refrigerator (+8°C), that is, PMD (1 to 168 h), or fixed in 10% buffered formalin, that is, FT (18 to 94 d). Subsequently, the tissue was routinely processed into paraffin blocks to enable construction of tissue microarrays (TMA). Sections cut from the TMA blocks were stained applying 13 different antibodies directed against neuronal and glial antigens. Immunoreactivity applying 5 antibodies was influenced by prolonged PMD and applying 2 antibodies by prolonged FT. None of the staining outcomes related to the PMD or FT were predictable. Loss of TMA cores during processing was primarily influenced by pretreatment and by tissue characteristics (gray/white matter). The test model described here confirmed that these 2 variables, PMD and FT, indeed influence the IHC outcome. The PMD and FT are particularly of importance while assessing tissue samples obtained at autopsy. The result above is also of importance while comparing the IHC outcomes seen in the postmortem setting (various PMD/FT) with surgical samples or with IHC outcome seen in experimental animal setting (controlled PMD/FT). Thus, we suggest that the test model described here is considered when assessing the reliability of the IHC outcome when analyzing tissues with various characteristics.

Protein Profiling in Serum and Cerebrospinal Fluid Following Complex Surgery on the Thoracic Aorta Identifies Biological Markers of Neurologic Injury.

Surgery on the arch or descending aorta is associated with significant risk of neurological complications. As a consequence of intubation and sedation, early neurologic injury may remain unnoticed. Biomarkers to aid in the initial diagnostics could prove of great value as immediate intervention is critical. Twenty-three patients operated in the thoracic aorta with significant risk of perioperative neurological injury were included. Cerebrospinal fluid (CSF) and serum were obtained preoperatively and in the first and second postoperative days and assessed with a panel of 92 neurological-related proteins. Three patients suffered spinal cord injury (SCI), eight delirium, and nine hallucinations. There were markers in both serum and CSF that differed between the affected and non-affected patients (SCI; IL6, GFAP, CSPG4, delirium; TR4, EZH2, hallucinations; NF1). The study identifies markers in serum and CSF that reflect the occurrence of neurologic insults following aortic surgery, which may aid in the care of these patients.

Graft failure and recurrence of symptoms after coronary artery bypass grafting.

OBJECTIVES: Saphenous vein grafts (SVGs) most often used in coronary artery bypass grafting (CABG) are subject to graft disease and have poor long-term patency, however the clinical implication of this is not completely known. We aim to assess the influence of graft failure on the postoperative recurrence of coronary artery disease (CAD) symptoms in relation to the contribution from progression of atherosclerosis in the native coronary vessels. DESIGN: Within the SWEDEHEART registry we identified 46,663 CABG cases between 2001 and 2015 with patient age 40-80 years where single internal mammary artery (IMA) anastomosis (IMA), single IMA with one (1SVG) or multiple SVG anastomoses (2+ SVG) had been performed. Clinical characteristics as well as mortality and postoperative incidence of coronary angiography were recorded and multivariable adjusted hazard ratios were calculated. Indications for the angiographies and occurrence of graft failure were also registered. RESULTS: The adjusted hazard ratio for death was similar for the three groups. The adjusted hazard ratio for being submitted to angiography as compared to 2+ SVG was (95% CI) 1.24 (1.06-1.46) for IMA and 1.21 (1.15-1.28) for 1SVG. Failed grafts were found at the first postoperative angiography with preceding CAD symptoms in 21.4% of patients in the IMA group, 41.6% in the 1SVG group and 61.1% in the 2+ SVG group. CONCLUSIONS: A substantial amount of angiographies occur in patients without any graft failure and a large part of postoperative recurrence of CAD symptoms and are likely attributed to IMA failure or progression of atherosclerosis in the native coronary arteries.

Hyperglycemia Alters Expression of Cerebral Metabolic Genes after Cardiac Arrest.

BACKGROUND: Survivors of cardiac arrest often experience neurologic deficits. To date, treatment options are limited. Associated hyperglycemia is believed to further worsen the neurologic outcome. The aim with this study was to characterize expression pathways induced by hyperglycemia in conjunction with global brain ischemia. METHODS: Pigs were randomized to high or normal glucose levels, as regulated by glucose and insulin infusions with target levels of 8.5-10 mM and 4-5.5 mM, respectively. The animals were subjected to 5-minute cardiac arrest followed by 8 minutes of cardiopulmonary resuscitation and direct-current shock to restore spontaneous circulation. Global expression profiling of the cortex using microarrays was performed in both groups. RESULTS: A total of 102 genes differed in expression at P < .001 between the hyperglycemic and the normoglycemic pigs. Several of the most strongly differentially regulated genes were involved in transport and metabolism of glucose. Functional clustering using bioinformatics tools revealed enrichment of multiple biological processes, including membrane processes, ion transport, and glycoproteins. CONCLUSIONS: Hyperglycemia during cardiac arrest leads to differential early gene expression compared with normoglycemia. The functional relevance of these expressional changes cannot be deduced from the current study; however, the identified candidates have been linked to neuroprotective mechanisms and constitute interesting targets for further studies.

No improvements in long-term outcome after coronary artery bypass grafting with arterial grafts as a second conduit: a Swedish nationwide registry study.

OBJECTIVES: Coronary artery bypass grafting using saphenous vein grafts (SVGs) in addition to the left internal mammary artery (IMA) graft is vitiated by poor long-term patency of the vein grafts. Hypothetically, the increased use of arterial grafts could confer even better outcomes. Our goal was to evaluate results after coronary artery bypass grafting in Sweden, where arterial grafts were used as a second conduit. METHODS: Within the Swedish Web System for Enhancement and Development of Evidence-Based Care in Heart Disease Evaluated According to Recommended Therapies (SWEDEHEART) registry, we identified patients who had coronary artery bypass grafting from 2001 to 2015 using the IMA and the SVG, the radial artery (RA) or the additional IMA [bilateral IMA (BIMA)] as a second conduit. Deaths, postoperative incidence of coronary angiography and need for reintervention were recorded, and multivariable adjusted hazard ratios were calculated for different types of grafts. RESULTS: The study population comprised 46 343 cases of IMA + SVG, 1036 cases of IMA + RA and 862 cases of BIMA. The mean follow-up time (SD) was 9.3 (4.2) years for IMA + SVG, 10.7 (4.1) years for IMA + RA grafts and 5.5 (5.0) years for the BIMA graft. The adjusted hazard ratio for death was (95% confidence interval) 1.01 (0.89-1.14) for IMA + RA and 0.87 (0.72-1.06) for BIMA grafts compared with IMA + SVG. The adjusted hazard ratio for the first angiographic examination was (95% confidence interval) 0.96 (0.84-1.10) for IMA + RA and 1.13 (0.95-1.35) for BIMA grafts. The adjusted hazard ratio for the need for reintervention was (95% confidence interval) 0.91 (0.75-1.09) for IMA + RA and 1.26 (1.00-1.58) for BIMA grafts. CONCLUSIONS: Patients who had arterial grafts as second conduits did not demonstrate a better outcome in any of the studied end-points. Radial artery grafts seem to be preferable to BIMA grafts as an alternative to an SVG.

Mechanical reperfusion with leucocyte-filtered blood does not prevent injury following global cerebral ischaemia.

Objectives: Prolonged global cerebral ischaemia leads to irreversible injury, often with lethal outcome. Brain injuries are partly caused by the uncontrolled reperfusion that occurs once the circulation is re-established. Recent animal experiments suggest that controlled reperfusion following lengthy ischaemia might prevent severe brain injury. This study aimed at further exploring cerebral alterations and outcome following prolonged global cerebral ischaemia and mechanically manipulated reperfusion. Methods: Three groups of pigs were included; one sham operated ( n = 3) and two that underwent 30-min global cerebral ischaemia. All vessels that supply the brain were isolated intrathoracically, after which they were occluded for 30 min in the ischaemic groups. In one of the ischaemic groups uncontrolled reperfusion was applied (URep, n = 6), i.e. normal circulation was restored 30 min after arrested cerebral circulation. The second ischaemic group received mechanical reperfusion (MRep, n = 6) with leucocyte-filtered blood at constant flow and pressure for 20 min using extracorporeal circulation following the 30-min ischaemia, after which normal blood flow resumed. All animals were monitored for 3 h after start of uncontrolled reperfusion. Haemodynamic parameters, arterial and sagittal sinus blood gases, cerebral oxygen extraction rates and intraparenchymal biomarkers using microdialysis were measured. Brain histology was performed post-mortem. Results: Global brain ischaemia led to the same extent of severe morphological changes at the level of light microscopy in the two ischaemic experimental groups, regardless of reperfusion protocol. Furthermore, no significant differences were found between the URep and MRep groups regarding cerebral blood gases or microdialysis biomarkers. Conclusions: Mechanical reperfusion following the current protocol does not modify brain alterations caused by 30 min of arrested cerebral circulation.

Blood Flow Quantitation by Positron Emission Tomography During Selective Antegrade Cerebral Perfusion.

BACKGROUND: Perfusion strategies during aortic surgery usually comprise hypothermic circulatory arrest (HCA), often combined with selective antegrade cerebral perfusion (SACP) or retrograde cerebral perfusion. Cerebral blood flow (CBF) is a fundamental parameter for which the optimal level has not been clearly defined. We sought to determine the CBF at a pump flow level of 6 mL/kg/min, previously shown likely to provide adequate SACP at 20°C in pigs. METHODS: Repeated positron emission tomography (PET) scans were used to quantify the CBF and glucose metabolism throughout HCA and SACP including cooling and rewarming. Eight pigs on cardiopulmonary bypass were assigned to either HCA alone (n = 4) or HCA+SACP (n = 4). The CBF was measured by repeated [15O]water PET scans from baseline to rewarming. The cerebral glucose metabolism was examined by [18F]fluorodeoxyglucose PET scans after rewarming to 37°C. RESULTS: Cooling to 20°C decreased the cortical CBF from 0.31 ± 0.06 at baseline to 0.10 ± 0.02 mL/cm3/min (p = 0.008). The CBF was maintained stable by SACP of 6 mL/kg/min during 45 minutes. After rewarming to 37°C, the mean CBF increased to 0.24 ± 0.07 mL/cm3/min, without significant differences between the groups at any time-point exclusive of the HCA period. The net cortical uptake (Ki) of [18F]fluorodeoxyglucose after rewarming showed no significant difference between the groups. CONCLUSIONS: Cooling autoregulated the CBF to 0.10 mL/cm3/min, and 45 minutes of SACP at 6 mL/kg/min maintained the CBF in the present model. Cerebral glucose metabolism after rewarming was similar in the study groups.

Complement Receptor 2 is increased in cerebrospinal fluid of multiple sclerosis patients and regulates C3 function.

Besides its vital role in immunity, the complement system also contributes to the shaping of the synaptic circuitry of the brain. We recently described that soluble Complement Receptor 2 (sCR2) is part of the nerve injury response in rodents. We here study CR2 in context of multiple sclerosis (MS) and explore the molecular effects of CR2 on C3 activation. Significant increases in sCR2 levels were evident in cerebrospinal fluid (CSF) from both patients with relapsing-remitting MS (n=33; 6.2ng/mL) and secondary-progressive MS (n=9; 7.0ng/mL) as compared to controls (n=18; 4.1ng/mL). Furthermore, CSF sCR2 levels correlated significantly both with CSF C3 and C1q as well as to a disease severity measure. In vitro, sCR2 inhibited the cleavage and down regulation of C3b to iC3b, suggesting that it exerts a modulatory role in complement activation downstream of C3. These results propose a novel function for CR2/sCR2 in human neuroinflammatory conditions.

Outcomes following the implementation of a quality control campaign to decrease sternal wound infections after coronary artery by-pass grafting.

BACKGROUND: Coronary artery by-pass grafting (CABG) remains the optimal strategy in achieving complete revascularization in patients with complex coronary artery disease. However, sternal wound infections (SWI), especially deep SWI are potentially severe complications to the surgery. At the department of cardiothoracic surgery in Uppsala University Hospital a gradual increase in all types of SWI occurred, which peaked in 2009. This prompted an in-depth revision of the whole surgical process. To monitor the frequency of post-operative infections all patients receive a questionnaire that enquires whether any treatment for wound infection has been carried out. METHODS: All patients operated with isolated CABG between start of 2006 and end of 2012 were included in the study. 1515 of 1642 patients answered and returned the questionnaire (92.3 %). The study period is divided into the time before the intervention program was implemented (2006-early 2010) and the time after the intervention (early 2010- end 2012). To assess whether potential differences in frequency of SWI were a consequence of change in the characteristics of the patient population rather than an effect of the intervention a retrospective assessment of medical records was performed, where multiple of the most known risk factors for developing SWI were studied. RESULTS: We noticed a clear decrease in the frequency of SWI after the intervention. This was not a consequence of a healthier population. CONCLUSIONS: Our results from implementing the intervention program are positive in that they reduce the number of SWI. As several changes in the perioperative care were introduced simultaneously we cannot deduce which is the most effective.

Dissecting ventricular pseudoaneurysm after perimyocarditis-a case report.

BACKGROUND: The current case describes the fast development of a pseudoaneurysm in a patient that presented with signs of systemic inflammation and generally deranged blood work. CASE PRESENTATION: The pseudoaneurysm appeared within one week of disease onset. The anatomic extent of the pseudoaneurysm was unusual, as it dissected intramurally beneath the septum, inferior to the right ventricle and had effect on the RV filling. The etiology could not be definitely defined, since in adults the most common cause for pseudoaneurysm development is recent myocardial infarction, but in this patient the coronary arteries were healthy. Instead it could have been a consequence of an aggressive perimyocarditis. CONCLUSIONS: Due to the unpredictable nature of pseudoaneurysms we advocate early contact with a center with cardiothoracic surgery expertise for rapid surgical intervention.

Complement receptor 2 is up regulated in the spinal cord following nerve root injury and modulates the spinal cord response.

BACKGROUND: Activation of the complement system has been implicated in both acute and chronic states of neurodegeneration. However, a detailed understanding of this complex network of interacting components is still lacking. METHODS: Large-scale global expression profiling in a rat F2(DAxPVG) intercross identified a strong cis-regulatory influence on the local expression of complement receptor 2 (Cr2) in the spinal cord after ventral root avulsion (VRA). Expression of Cr2 in the spinal cord was studied in a separate cohort of DA and PVG rats at different time-points after VRA, and also following sciatic nerve transection (SNT) in the same strains. Consequently, Cr2 (-/-) mice and Wt controls were used to further explore the role of Cr2 in the spinal cord following SNT. The in vivo experiments were complemented by astrocyte and microglia cell cultures. RESULTS: Expression of Cr2 in naïve spinal cord was low but strongly up regulated at 5-7 days after both VRA and SNT. Levels of Cr2 expression, as well as astrocyte activation, was higher in PVG rats than DA rats following both VRA and SNT. Subsequent in vitro studies proposed astrocytes as the main source of Cr2 expression. A functional role for Cr2 is suggested by the finding that transgenic mice lacking Cr2 displayed increased loss of synaptic nerve terminals following nerve injury. We also detected increased levels of soluble CR2 (sCR2) in the cerebrospinal fluid of rats following VRA. CONCLUSIONS: These results demonstrate that local expression of Cr2 in the central nervous system is part of the axotomy reaction and is suggested to modulate subsequent complement mediated effects.

Complement component C3 and butyrylcholinesterase activity are associated with neurodegeneration and clinical disability in multiple sclerosis.

Dysregulation of the complement system is evident in many CNS diseases but mechanisms regulating complement activation in the CNS remain unclear. In a recent large rat genome-wide expression profiling and linkage analysis we found co-regulation of complement C3 immediately downstream of butyrylcholinesterase (BuChE), an enzyme hydrolyzing acetylcholine (ACh), a classical neurotransmitter with immunoregulatory effects. We here determined levels of neurofilament-light (NFL), a marker for ongoing nerve injury, C3 and activity of the two main ACh hydrolyzing enzymes, acetylcholinesterase (AChE) and BuChE, in cerebrospinal fluid (CSF) from patients with MS (n = 48) and non-inflammatory controls (n = 18). C3 levels were elevated in MS patients compared to controls and correlated both to disability and NFL. C3 levels were not induced by relapses, but were increased in patients with ≥9 cerebral lesions on magnetic resonance imaging and in patients with progressive disease. BuChE activity did not differ at the group level, but was correlated to both C3 and NFL levels in individual samples. In conclusion, we show that CSF C3 correlates both to a marker for ongoing nerve injury and degree of disease disability. Moreover, our results also suggest a potential link between intrathecal cholinergic activity and complement activation. These results motivate further efforts directed at elucidating the regulation and effector functions of the complement system in MS, and its relation to cholinergic tone.

Variability in C-type lectin receptors regulates neuropathic pain-like behavior after peripheral nerve injury.

INTRODUCTION: Neuropathic pain is believed to be influenced in part by inflammatory processes. In this study we examined the effect of variability in the C-type lectin gene cluster (Aplec) on the development of neuropathic pain-like behavior after ligation of the L5 spinal nerve in the inbred DA and the congenic Aplec strains, which carries seven C-type lectin genes originating from the PVG strain. RESULTS: While both strains displayed neuropathic pain behavior early after injury, the Aplec strain remained sensitive throughout the whole study period. Analyses of several mRNA transcripts revealed that the expression of Interleukin-1ß, Substance P and Cathepsin S were more up-regulated in the dorsal part of the spinal cord of Aplec rats compared to DA, indicating a stronger inflammatory response. This notion was supported by flow cytometric analysis revealing increased infiltration of activated macrophages into the spinal cord. In addition, macrophages from the Aplec strain stimulated in vitro displayed higher expression of inflammatory cytokines compared to DA cells. Finally, we bred a recombinant congenic strain (R11R6) comprising only four of the seven Aplec genes, which displayed similar clinical and immune phenotypes as the Aplec strain. CONCLUSION: We here for the first time demonstrate that C-type lectins, a family of innate immune receptors with largely unknown functions in the nervous system, are involved in regulation of inflammation and development of neuropathic pain behavior after nerve injury. Further experimental and clinical studies are needed to dissect the underlying mechanisms more in detail as well as any possible relevance for human conditions.

Unbiased expression mapping identifies a link between the complement and cholinergic systems in the rat central nervous system.

The complement system is activated in a wide spectrum of CNS diseases and is suggested to play a role in degenerative phenomena such as elimination of synaptic terminals. Still, little is known of mechanisms regulating complement activation in the CNS. Loss of synaptic terminals in the spinal cord after an experimental nerve injury is increased in the inbred DA strain compared with the PVG strain and is associated with expression of the upstream complement components C1q and C3, in the absence of membrane attack complex activation and neutrophil infiltration. To further dissect pathways regulating complement expression, we performed genome-wide expression profiling and linkage analysis in a large F2(DA × PVG) intercross, which identified quantitative trait loci regulating expression of C1qa, C1qb, C3, and C9. Unlike C1qa, C1qb, and C9, which all displayed distinct coregulation with different cis-regulated C-type lectins, C3 was regulated in a coexpression network immediately downstream of butyrylcholinesterase. Butyrylcholinesterase hydrolyses acetylcholine, which exerts immunoregulatory effects partly through TNF-α pathways. Accordingly, increased C3, but not C1q, expression was demonstrated in rat and mouse glia following TNF-α stimulation, which was abrogated in a dose-dependent manner by acetylcholine. These findings demonstrate new pathways regulating CNS complement expression using unbiased mapping in an experimental in vivo system. A direct link between cholinergic activity and complement activation is supported by in vitro experiments. The identification of distinct pathways subjected to regulation by naturally occurring genetic variability is of relevance for the understanding of disease mechanisms in neurologic conditions characterized by neuronal injury and complement activation.