Radiation-induced DNA Damage and Repair in Lens Epithelial Cells of both Ptch1(+/-) and Ercc2(+/-) Mutated Mice.

Epidemiological studies suggest an increased incidence and risk of cataract after low-dose (<2 Gy) ionizing radiation exposures. However, the biological mechanism(s) of this process are not fully understood. DNA damage and repair are thought to have a contributing role in radiation-induced cataractogenesis. Recently we have reported an inverse dose-rate effect, as well as the low-dose response, of DNA damage and repair in lens epithelial cells (LECs). Here, we present further initial findings from two mutated strains (Ercc2+/- and Ptch1+/-) of mice, both reportedly susceptible to radiation-induced cataract, and their DNA damage and repair response to low-dose and low-dose-rate gamma rays. Our results support the hypothesis that the lens epithelium responds differently to radiation than other tissues, with reported radiation susceptibility to DNA damage not necessarily translating to the LECs. Genetic predisposition and strain(s) of mice have a significant role in radiation-induced cataract susceptibility.

Lens Epithelial Cell Proliferation in Response to Ionizing Radiation.

Lens epithelial cell proliferation and differentiation are naturally well regulated and controlled, a characteristic essential for lens structure, symmetry and function. The effect of ionizing radiation on lens epithelial cell proliferation has been demonstrated in previous studies at high acute doses, but the effect of dose and dose rate on proliferation has not yet been considered. In this work, mice received single acute doses of 0.5, 1 and 2 Gy of radiation, at dose rates of 0.063 and 0.3 Gy/min. Eye lenses were isolated postirradiation at 30 min up until 14 days and flat-mounted. Then, cell proliferation rates were determined using biomarker Ki67. As expected, radiation increased cell proliferation 2 and 24 h postirradiation transiently (undetectable 14 days postirradiation) and was dose dependent (changes were very significant at 2 Gy; P = 0.008). A dose-rate effect did not reach significance in this study (P = 0.054). However, dose rate and lens epithelial cell region showed significant interactions (P < 0.001). These observations further our mechanistic understanding of how the lens responds to radiation.

Radiation-Induced Lens Opacity and Cataractogenesis: A Lifetime Study Using Mice of Varying Genetic Backgrounds.

Recent epidemiological findings and reanalysis of historical data suggest lens opacities resulting from ionizing radiation exposures are likely induced at lower doses than previously thought. These observations have led to ICRP recommendations for a reduction in the occupational dose limits for the eye lens, as well as subsequent implementation in EU member states. The EU CONCERT LDLensRad project was initiated to further understand the effects of ionizing radiation on the lens and identify the mechanism(s) involved in radiation-induced cataract, as well as the impact of dose and dose-rate. Here, we present the results of a long-term study of changes to lens opacity in male and female adult mice from a variety of different genetic (radiosensitive or radioresistant) backgrounds, including mutant strains Ercc2 and Ptch1, which were assumed to be susceptible to radiation-induced lens opacities. Mice received 0.5, 1 and 2 Gy 60Co gamma-ray irradiation at dose rates of 0.063 and 0.3 Gy min-1. Scheimpflug imaging was used to quantify lens opacification as an early indicator of cataract, with monthly observations taken postirradiation for an 18-month period in all strains apart from 129S2, which were observed for 12 months. Opacification of the lens was found to increase with time postirradiation (with age) for most mouse models, with ionizing radiation exposure increasing opacities further. Sex, dose, dose rate and genetic background were all found to be significant contributors to opacification; however, significant interactions were identified, which meant that the impact of these factors was strain dependent. Mean lens density increased with higher dose and dose rate in the presence of Ercc2 and Ptch1 mutations. This project was the first to focus on low (<1 Gy) dose, multiple dose rate, sex and strain effects in lens opacification, and clearly demonstrates the importance of these experimental factors in radiobiological investigations on the lens. The results provide insight into the effects of ionizing radiation on the lens as well as the need for further work in this area to underpin appropriate radiation protection legislation and guidance.

The experience of clinical supervision for nurses and healthcare assistants in a secure adolescent service: Affecting service improvement.

WHAT IS KNOWN ON THE SUBJECT?: Regular and effective clinical supervision for mental health nurses and healthcare assistants (HCAs) is an important tool in helping to reduce stress and burnout, and in ensuring safe, effective and high-quality mental health care. Previous studies of clinical supervision within secure mental health environments have found both a low availability of clinical supervision, and a low level of staff acceptance of its value, particularly for HCAs. WHAT DOES THIS PAPER ADD TO EXISTING KNOWLEDGE?: In previous studies, the understanding shown by HCAs and nurses around the benefits of clinical supervision may have been limited by the methods used. This study was specifically designed to help them best express their views. In contrast to previous studies, both nurses and HCAs showed a good understanding of the function and value of clinical supervision. Significant improvements in the experience of, and access to, clinical supervision for nurses and HCAs working in secure mental health services may be achieved by raising staff awareness, demonstrating organizational support and increasing monitoring of clinical supervision. WHAT ARE THE IMPLICATIONS FOR PRACTICE?: Organizations should consider reviewing their approach to supervision to include raising staff awareness, multidisciplinary supervision, group supervision, and recording and tracking of supervision rates. Organizations should be mindful of the need to provide effective clinical supervision to HCAs as well as nurses. ABSTRACT: Introduction Studies have found a low availability and appreciation of clinical supervision, especially for healthcare assistants (HCAs). Qualitative research is needed to further understand this. Aims Increase understanding of nurses' and HCAs' experiences of, and access to, clinical supervision. Identify nurses' and HCAs' perceptions of the value and function of clinical supervision. Assess how interventions affect staff's experiences of clinical supervision. Methods In 2013, HCAs and nurses in a secure adolescent service were surveyed about clinical supervision. Forty-nine HCAs and 20 nurses responded. In 2014, interventions to facilitate supervision were introduced. In 2016, the study was repeated. Forty HCAs and 30 nurses responded. Responses were analysed using a mixed methods approach. Results Significantly more HCAs found supervision to be a positive experience in 2016, and both nurses and HCAs reported significantly fewer challenges in accessing supervision. HCAs and nurses understood the value of clinical supervision. Discussion Significant improvements in the experience of clinical supervision were achieved following increased staff awareness, multidisciplinary and group supervision, and recording supervision rates. HCAs and nurses understood the consequences of inadequate supervision. Implications for practice Organizations could adopt the interventions to facilitate clinical supervision. Supervision should not be overlooked for HCAs.

Pheochromocytoma of the Organ Zuckerkandl.

INTRODUCTION: Pheochromocytomas (PCCs);, or intra-adrenal paragangliomas (PGLs);, are neuroendocrine tumors arising within the adrenal medulla. Extra-adrenal paragangliomas may arise in the sympathetic or parasympathetic paraganglia and more rarely in other organs. One of the most common extra-adrenal sites is in the organ of Zuckerkandl, a collection of chromaffin cells near the origin of the inferior mesenteric artery or near the aortic bifurcation. The following is a case of a patient with resistant hypertension secondary to an extra-adrenal paraganglioma in the organ of Zuckerkandl. CASE: The patient is a 43 year old man with a history of depression, type 2 diabetes mellitus, and hypertension who was sent to the emergency department by his primary care physician for severely elevated blood pressures. Patient also had diaphoresis, tachycardia, and a new, fine tremor of his left hand. Upon presentation, the patient's blood pressure was 260/120 mmHg with a heart rate of 140 beats per minute. Plasma fractionated metanephrines sent on admission revealed significantly elevated levels of total plasma metanephrines (2558 pg/mL);, free metanephrine (74 pg/ml); and free normetanephrine (2484pg/mL);. An I-123 metaiodobenzylguanidine (MIBG); scan showed abnormal uptake in the lower abdomen at the level of the aortic bifurcation. Patient was started on alpha-blockade, with subsequent addition of a beta-blocker prior to surgery. Patient underwent surgical removal of the tumor with pathology consistent with a paraganglioma. DISCUSSION: Pheochromocytomas and paragangliomas are responsible for approximately 0.5 percent of cases of secondary hypertension. Many different biochemical markers have been used to aid in the diagnosis of PCC/PGL including plasma catecholamines, plasma metanephrines, urine fractionated metanephrines, urine catecholamines, total metanephrines and vanillymandellic acid. Definitive management of a PCC and PGL involves surgical removal of the tumor. Finally, there should be a discussion with each patient to determine if he or she should undergo genetic testing, as studies show that approximately 25 percent of catecholamine producing PCCs and PGLs are due to heritable genetic mutations.

Additive effects of oxytocin receptor gene polymorphisms on reward circuitry in youth with autism.

Several common alleles in the oxytocin receptor gene (OXTR) are associated with altered brain function in reward circuitry in neurotypical adults and may increase risk for autism spectrum disorders (ASD). Yet, it is currently unknown how variation in the OXTR relates to brain functioning in individuals with ASD, and, critically, whether neural endophenotypes vary as a function of aggregate genetic risk. Here, for we believe the first time, we use a multi-locus approach to examine how genetic variation across several OXTR single-nucleotide polymorphisms (SNPs) affect functional connectivity of the brain's reward network. Using data from 41 children with ASD and 41 neurotypical children, we examined functional connectivity of the nucleus accumbens (NAcc) - a hub of the reward network - focusing on how connectivity varies with OXTR risk-allele dosage. Youth with ASD showed reduced NAcc connectivity with other areas in the reward circuit as a function of increased OXTR risk-allele dosage, as well as a positive association between risk-allele dosage and symptom severity, whereas neurotypical youth showed increased NAcc connectivity with frontal brain regions involved in mentalizing. In addition, we found that increased NAcc-frontal cortex connectivity in typically developing youth was related to better scores on a standardized measure of social functioning. Our results indicate that cumulative genetic variation on the OXTR impacts reward system connectivity in both youth with ASD and neurotypical controls. By showing differential genetic effects on neuroendophenotypes, these pathways elucidate mechanisms of vulnerability versus resilience in carriers of disease-associated risk alleles.

Acclimation to decompression sickness in rats.

Protection against decompression sickness (DCS) by acclimation to hyperbaric decompression has been hypothesized but never proven. We exposed rats to acclimation dives followed by a stressful "test" dive to determine whether acclimation occurred. Experiments were divided into two phases. Phase 1 rats were exposed to daily acclimation dives of hyperbaric air for 30 min followed by rapid decompression on one of the following regimens: 70 ft of seawater (fsw) for 9 days (L70), 70 fsw for 4 days (S70), 40 fsw for 9 days (L40), 40 fsw for 4 days (S40), or unpressurized sham exposure for 9 days (Control). On the day following the last exposure, all were subjected to a "test" dive (175 fsw, 60 min, rapid decompression). Both L70 and S70 rats had significantly lower incidences of DCS than Control rats (36% and 41% vs. 62%, respectively). DCS incidences for the other regimens were lower than in Control rats but without statistical significance. Phase 2 used the most protective regimen from phase 1 (L70); rats were exposed to L70 or a similar regimen with a less stressful staged decompression. Another group was exposed to a single acclimation dive (70 fsw/30 min) on the day before the test dive. We observed a nonsignificant trend for the rapidly decompressed L70 dives to be more protective than staged decompression dives (44% vs. 51% DCS incidence). The single acclimation dive regimen did not provide protection. We conclude that protection against DCS can be attained with acclimating exposures that do not themselves cause DCS. The deeper acclimation dive regimens (70 fsw) provided the most protection.

Immune effects of decreasing low-molecular weight hemoglobin components of hemoglobin-based oxygen carriers (HBOC) in a swine model of severe controlled hemorrhagic shock.

Hemoglobin-based oxygen carriers (HBOCs) show potential as safe, efficacious, pre-hospital resuscitation fluids. The major criticism of HBOC-201 is its vasoactive property, attributed partially to low-molecular weight (low-MW) tetrameric/dimeric (TD) hemoglobin (Hb) in HBOC solution. Here we sought to determine whether resuscitation with decreasing concentrations of low-MW Hb component of HBOC affects immune responses in hemorrhagic swine. 28 anesthetized swine underwent a soft muscle crush and controlled hemorrhage of 55% blood volume, followed by resuscitation with HBOC containing 31%, 2%, or 0.4% low-MW Hb in four 10 ml/kg infusions at 20, 30, 45 and 60 minutes before hospital arrival at 75 minutes. IL-10, cell activation and adhesion markers and CD4:CD8 ratio remained unchanged in all 3 groups compared to baseline. Leukocyte apoptosis was equally elevated across all groups. Purification from 31% to 0.4% low-MW Hb in HBOC solution did not alter immune effects in a swine model of severe controlled hemorrhagic shock.

Innate immune responses in Swine resuscitated from severe traumatic hemorrhagic shock with hemoglobin-based oxygen carrier-201.

Hemoglobin-based oxygen carrier-201 transports oxygen and improves survival in swine with hemorrhagic shock, but has potential to be immune activating. Herein, we evaluated HBOC-201's immune effects in swine with more severe hemorrhagic shock due to soft tissue injury and 55% blood volume catheter withdrawal over 15 minutes followed by fluid resuscitation at 20 minutes with HBOC-201, Hextend, or no treatment (NON) before hospital arrival. Survival rates were similar with HBOC-201 and Hextend (p > 0.05), but were higher than in (p = 0.007). There were no significant group differences in blood cell count, percentages of leukocyte sub-populations and immunophenotype (CD4:CD8 ratio), adhesion markers expression (neutrophil CD11b; monocyte or neutrophil CD49d) and apoptosis. There was a trend to higher plasma IL-10 in HBOC-201 and groups vs. Hextend. We conclude that in swine with severe controlled HS and soft tissue injury, immune responses are similar with resuscitation with HBOC-201 and Hextend.

Coagulation patterns following haemoglobin-based oxygen carrier resuscitation in severe uncontrolled haemorrhagic shock in swine.

Massive blood loss due to penetrating trauma and internal organ damage can cause severe haemorrhagic shock (HS), leading to a severely compromised haemostatic balance. This study evaluated the effect of bovine polymerized haemoglobin (Hb) (Hb-based oxygen carrier, HBOC) resuscitation on haemostasis in a swine model of uncontrolled HS. Following liver injury/HS, swine received HBOC (n= 8), Hextend (HEX) (n= 8) or no resuscitation (NON) (n= 8). Fluids were infused to increase mean arterial pressure above 60 mmHg and to reduce heart rate to baseline. At 4 h, the animals were eligible for blood transfusions. Prothrombin time (PT), activated partial thromboplastin time, fibrinogen, thromboelastography (TEG) and platelet function analyser closure time (PFA-CT) were compared by using mixed statistical model. At 4 h, blood loss (% estimated blood volume) was comparable for HBOC (65.5 +/- 18.5%) and HEX (80.8 +/- 14.4%) and less for NON (58.7 +/- 10.1%; P < 0.05). Resuscitation-induced dilutional coagulopathy was observed with HBOC and HEX, as indicated by reduced haematocrit, platelets and fibrinogen (P < 0.05). At 4 h, PT was higher in HEX than in HBOC groups (P < 0.01). In the early hospital phase, a trend to increased TEG reaction time and PFA-CT indicates that dilutional effects persist in HBOC and HEX groups. PFA-CT returned to baseline later with HBOC than with HEX (48 vs. 24 h) following blood transfusion. At 4 h, all surviving HEX animals (n= 3) required transfusion, in contrast to no HBOC (n= 7) or NON (n= 1) animals. In this severe uncontrolled HS model, successful resuscitation with HBOC produced haemodilutional coagulopathy less than or similar to that produced by resuscitation with HEX.

Endothelial-mediated regulation of cerebral microcirculation.

Vascular endothelial cells are important not only for maintaining homeostasis, but also in pathogenesis of vascular disorders. Cerebral capillary and microvascular endothelial cells play an active role in maintaining cerebral blood flow, microvascular tone and blood brain barrier functions. Factors produced and released by endothelial cells, other brain cells and circulating blood cells participate in these regulatory functions. In particular, endothelin-1 (ET-1) and nitric oxide (NO) are known to contribute to the functional vascular changes under pathological conditions (e.g., hypertension, arteriosclerosis, and stroke). This report describes the involvement of endothelial cell mediators in the post-ischemic hypoperfusion induced by brain ischemia and in vitro endothelial responses (Ca(2+) mobilization and cytoskeletal rearrangements) to ET-1 and its interactions with NO or 2-AG. The capacity of NO and endocannabinoids to counteract ET-1-induced cerebral capillary and microvascular endothelial responses indicates that they may actively participate in EC function and implicates them in physiological and pathophysiological conditions.

ET-1- and NO-mediated signal transduction pathway in human brain capillary endothelial cells.

Previous studies have demonstrated that functional interaction between endothelin (ET)-1 and nitric oxide (NO) involves changes in Ca(2+) mobilization and cytoskeleton in human brain microvascular endothelial cells. The focus of this investigation was to examine the possible existence of analogous interplay between these vasoactive substances and elucidate their signal transduction pathways in human brain capillary endothelial cells. The results indicate that ET-1-stimulated Ca(2+) mobilization in these cells is dose-dependently inhibited by NOR-1 (an NO donor). This inhibition was prevented by ODQ (an inhibitor of guanylyl cyclase) or Rp-8-CPT-cGMPS (an inhibitor of protein kinase G). Treatment of endothelial cells with 8-bromo-cGMP reduced ET-1-induced Ca(2+) mobilization in a manner similar to that observed with NOR-1 treatment. In addition, NOR-1 or cGMP reduced Ca(2+) mobilization induced by mastoparan (an activator of G protein), inositol 1,4,5-trisphosphate, or thapsigargin (an inhibitor of Ca(2+)-ATPase). Interestingly, alterations in endothelial cytoskeleton (actin and vimentin) were associated with these effects. The data indicate for the first time that the cGMP-dependent protein kinase colocalizes with actin. These changes were accompanied by altered levels of phosphorylated vasodilator-stimulated phosphoprotein, which were elevated in endothelial cells incubated with NOR-1 and significantly reduced by ODQ or Rp-8-CPT-cGMPS. The findings indicate a potential mechanism by which the functional interrelationship between ET-1 and NO plays a role in regulating capillary tone, microcirculation, and blood-brain barrier function.

Antioxidant properties of the vasoactive endocannabinoid, 2-arachidonoyl glycerol (2-AG).

Reactive oxygen species (ROS) were shown to play a role in altering blood-brain barrier (BBB) permeability and formation of brain edema induced by trauma and/or ischemia. 2-arachidonoyl glycerol (2-AG), a novel, potent vasodilatory and cytoprotective endocannabinoid has been implicated to act as an antioxidative agent. This study examines: 1) the possible 2-AG modulation of BBB injury and edema formation induced by closed head injury (CHI); and 2) comparable effects between 2-AG and 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl (TPL), a known antioxidant nitroxide on endothelial Ca2+ and cytoskeletal responses to H2O2 (ROS). 2-AG treatment reduced the CHI-induced increase in BBB permeability and brain edema. The endothelial H2O2-stimulated Ca2+ mobilization and cytoskeleton (vimentin) rearrangement was modified by either 2-AG or TPL. These findings provide evidence of 2-AG antioxidant activity and are consistent with the involvement of ROS in the pathomechanism of CHI-induced BBB injury and brain edema.

Examination of several potential mechanisms for the negative outcome in a clinical stroke trial of enlimomab, a murine anti-human intercellular adhesion molecule-1 antibody: a bedside-to-bench study.

BACKGROUND AND PURPOSE: Enlimomab, a murine monoclonal anti-human intercellular adhesion molecule (ICAM)-1 antibody, had a negative outcome in a multicenter acute-stroke trial. We did a bedside-to-bench study in standardized rat stroke models to explore mechanisms for these untoward results. METHODS: After focal brain ischemia in Wistar rats and spontaneously hypertensive rats (SHR), we administered murine anti-rat ICAM-1 antibody (1A29), subclass-matched murine immunoglobulin (IgG1), or vehicle intravenously. To examine whether rat anti-mouse antibodies were generated against the mouse protein and whether these were deleterious, we sensitized Wistar rats with 1A29 or vehicle 7 days before surgery. Infarct volume, tissue myeloperoxidase activity, neutrophil CD11b expression, and microvascular E-selectin, P-selectin, and ICAM-1 expression were examined 48 hours after surgery. Complement activation was serially assessed for 2 hours after a single injection of either 1A29 or vehicle. RESULTS: 1A29 treatment did not significantly reduce infarct size in either strain. 1A29 sensitization augmented infarct size and generated rat anti-mouse antibodies. Although 1A29 inhibited neutrophil trafficking shown by reduction in brain myeloperoxidase activity, circulating neutrophils were activated and displayed CD11b upregulation. Complement was activated in 1A29-sensitized Wistar rats and 1A29-treated SHR. E-selectin (SHR), endothelial P-selectin (Wistar and SHR), and ICAM-1 (SHR) were upregulated in animals treated with 1A29. CONCLUSIONS: Administration to rats of a murine antibody preparation against ICAM-1, 1A29, elicits the production of host antibodies against the protein, activation of circulating neutrophils, complement activation, and sustained microvascular activation. These observations provide several possible mechanisms for central nervous system-related clinical deterioration that occurred when Enlimomab was given in acute ischemic stroke.

Screening for cerebroprotective agents using an in vivo model of cerebral reversible depolarization in awake rats.

The need to screen cerebroprotective compounds without anesthetic interference prompted the development of a model using hypoxic rats. In this model two outcome measures were used: (1) the time to reach isoelectric electroencephalogram (iEEG), caused by nitrogen gas inhalation in the test chamber, and (2) the time for behavioral recovery measuring the latency of restoration of the head-withdrawal reflex upon vibrissae stimulation. We report here data of blood chemistry, cerebral tissue oxygen measurements, a definition of a proposed scoring system, and the pharmacological results of RGH-2202. The findings with RGH-2202 are used here to show the utility of the screening method. Events during hypoxia: Arterial and venous pO(2), pCO(2), and pH, and brain tissue pO(2)significantly declined. Significant correlations were established among the pO(2)of cerebral tissue, blood, and the test chamber. RGH-2202 significantly and dose-dependently shortened the iEEG time; the compound's Effective Dose(30)was 227.8 mg kg(-1). Events during recovery: Immediately after the iEEG, when the atmosphere in the chamber was replaced with room air, the arterial, venous and brain tissue pO(2)increased above the control level and subsequently recovered to baseline levels. Behavioral recovery occurred before blood chemistry was otherwise normalized. RGH-2202 significantly and dose-dependently shortened the recovery time; the Effective Dose(30)was 8.71 mg kg(-1). The available data define and support the physiological basis of this practicable rat-screening model.

Increased CD8(+) T cells associated with Chlamydia pneumoniae in symptomatic carotid plaque.

BACKGROUND AND PURPOSE: The presence of Chlamydia pneumoniae has been reported in carotid atheroma, but its causative effect in the activation of an atherosclerotic plaque to a prothrombotic state remains unproved. Antigen- mediated activation of T lymphocytes within plaque may represent a mechanism by which infection can result in plaque conversion. The goal of the present study was to characterize the T-cell subtype profile related to the presence of C pneumoniae in patients with symptomatic versus asymptomatic carotid atherosclerosis. METHODS: We studied 14 plaques (5 symptomatic and 9 asymptomatic) positive for C pneumoniae confirmed by polymerase chain reaction and 14 plaques (6 symptomatic and 8 asymptomatic) from age- and stenosis-matched patients negative for C pneumoniae by polymerase chain reaction. T-cell subpopulations of T-helper, T-cytotoxic, and T-memory lymphocytes were identified through indirect enzyme immunohistochemistry with anti-CD3+, anti-CD4+, anti-CD8+, and anti-CD45RO+ monoclonal antibodies, respectively. Results are expressed as the number of positive cells per millimeter squared. RESULTS: In the absence of C pneumoniae, symptomatic plaques had a modest but significant increase of CD3+ (89.6 versus 55.3, P=0.013), CD4+ (57.3 versus 32.7, P=0.01), and CD45RO+ (82.8 versus 43.7, P=0.007), but not CD8+ T cells (28.5 versus 25.5, P=0.245) compared with asymptomatic. However, in the presence of C pneumoniae, there was significant increase of all T-lymphocyte subtypes in symptomatic plaques, including CD8+ (76.8 versus 30.3, P=0.03), CD3+ (192.1 versus 80.4, P=0.004), CD4+ (111.9 versus 37.9, P=0.003), and CD45RO+ (120.2 versus 72.9, P=0.003) cells compared with asymptomatic plaques. With use of 2-way ANOVA, both the presence of chlamydia and symptoms were associated with significantly higher T-cell counts (P<0.005 for all subtypes). CONCLUSIONS: Although all patients with symptomatic disease show a modest elevation in the concentration of intraplaque lymphocytes, a preferential increase in CD8+ class I-restricted T cells is observed in symptomatic carotid plaque positive for C pneumoniae. These data provide incentive to further explore the role of Chlamydia in the modification of immune-mediated mechanisms in active atherosclerotic plaque.

Proinflammatory cytokine expression contributes to brain injury provoked by chronic monocyte activation.

BACKGROUND: We have proposed that an increased interaction between monocyte/macrophages and blood vessel endothelium predisposes subjects to strokes. The effect of chronic monocyte activation on the development of cerebral infarcts was thus studied in rats after provocation of a modified local Swartzman reaction, in brain vasculature. MATERIALS AND METHODS: Two weeks after an IV bolus of bacillus Calmette-Guérin (BCG), we studied spontaneous superoxide production, integrin expression, endothelial adhesion of monocytes and the neurological symptoms, brain histology, and cytokine immunoreactivity after a provocative dose of LPS (30-300 microg/rat i.c.v.). RESULTS: Monocyte migration into the brain was stimulated by BCG priming. The incidence of paralysis and death in response to LPS was markedly increased in BCG-primed rats. Histological evaluation of the brains of neurologically impaired and moribund animals revealed intravascular thrombosis and pale and hemorrhagic infarcts. Infiltrates of leukocytes expressing immunoreactive IL-1:, IL-6, and TNF-alpha were found around blood vessels, cerebral ventricles, and meninges, and were accompanied by a profound microglial expression of IL1P, endothelial expression of IL-6, and expression of TNF-alpha and TNF-R 1 in glia and neurons of cortex and hippocampus. Treatment (2 x 100 microg/10 ,I, i.c.v.) with recombinant human (rh-)TNF 55kDa receptor completely prevented, and treatment with rh-IL- I receptor antagonist significantly decreased the incidence of paralysis and death in response to BCG + LPS. The improvement of neurological symptoms was accompanied by reduced histological damage and supppression of IL-1P/ expression in the brain tissue. CONCLUSIONS: The data demonstrate that chronic monocyte activation predisposes subjects to thrombosis and hemorrhage via an exaggerated release of proinflammatory cytokines.