Post-ischemic ubiquitination at the postsynaptic density reversibly influences the activity of ischemia-relevant kinases

Ubiquitin modifications alter protein function and stability, thereby regulating cell homeostasis and viability, particularly under stress. Ischemic stroke induces protein ubiquitination at the ischemic periphery, wherein cells remain viable, however the identity of ubiquitinated proteins is unknown. Here, we employed a proteomics approach to identify these proteins in mice undergoing ischemic stroke. The data are available in a searchable web interface ( https://hochrainerlab.shinyapps.io/StrokeUbiOmics/ ). We detected increased ubiquitination of 198 proteins, many of which localize to the postsynaptic density (PSD) of glutamatergic neurons. Among these were proteins essential for maintaining PSD architecture, such as PSD95, as well as NMDA and AMPA receptor subunits. The largest enzymatic group at the PSD with elevated post-ischemic ubiquitination were kinases, such as CaMKII, PKC, Cdk5, and Pyk2, whose aberrant activities are well-known to contribute to post-ischemic neuronal death. Concurrent phospho-proteomics revealed altered PSD-associated phosphorylation patterns, indicative of modified kinase activities following stroke. PSD-located CaMKII, PKC, and Cdk5 activities were decreased while Pyk2 activity was increased after stroke. Removal of ubiquitin restored kinase activities to pre-stroke levels, identifying ubiquitination as the responsible molecular mechanism for post-ischemic kinase regulation. These findings unveil a previously unrecognized role of ubiquitination in the regulation of essential kinases involved in ischemic injury.

Post-ischemic ubiquitination at the postsynaptic density reversibly influences the activity of ischemia-relevant kinases

Ubiquitin modifications alter protein function and stability, thereby regulating cell homeostasis and viability, particularly under stress. Ischemic stroke induces protein ubiquitination at the ischemic periphery, wherein cells remain viable, however the identity of ubiquitinated proteins is unknown. Here, we employed a proteomics approach to identify these proteins in mice undergoing ischemic stroke. The data are available in a searchable web interface ( https://hochrainerlab.shinyapps.io/StrokeUbiOmics/ ). We detected increased ubiquitination of 198 proteins, many of which localize to the postsynaptic density (PSD) of glutamatergic neurons. Among these were proteins essential for maintaining PSD architecture, such as PSD95, as well as NMDA and AMPA receptor subunits. The largest enzymatic group at the PSD with elevated post-ischemic ubiquitination were kinases, such as CaMKII, PKC, Cdk5, and Pyk2, whose aberrant activities are well-known to contribute to post-ischemic neuronal death. Concurrent phospho-proteomics revealed altered PSD-associated phosphorylation patterns, indicative of modified kinase activities following stroke. PSD-located CaMKII, PKC, and Cdk5 activities were decreased while Pyk2 activity was increased after stroke. Removal of ubiquitin restored kinase activities to pre-stroke levels, identifying ubiquitination as the responsible molecular mechanism for post-ischemic kinase regulation. These findings unveil a previously unrecognized role of ubiquitination in the regulation of essential kinases involved in ischemic injury.

Abstract WMP110: Cerebral Ischemia-Reperfusion Alters Postsynaptic Kinase Activities Through Ubiquitination

Background: Aberrant activity of the postsynaptic density (PSD)-associated kinases CaMKII, PKC, Pyk2 and Cdk5 contributes to post-ischemic neuronal death. However, the mechanism(s) leading to altered activity after ischemia have not been discovered. We investigated the role of ubiquitination in post-ischemic PSD kinase activity regulation.

Methods: Cerebral ischemia was induced in male C57BL6 mice by middle cerebral artery occlusion (MCAO), followed by 1-hour reperfusion. Ubiquitinated and phosphorylated proteins in the ischemic neocortex were identified by nanoLC-MS/MS and analyzed for GO enrichment. PSD isolation was carried out by detergent extraction. Kinase ubiquitination was confirmed by co-immunoprecipitation with ubiquitin. Protein phosphorylation was assessed with phospho-specific antibodies and kinase activities were measured by transfer of γ 32 P to peptide substrates. Removal of ubiquitin from PSD lysates was achieved by addition of USP2 deubiquitinase.

Results: MS analysis revealed that MCAO increases ubiquitination of proteins associated with the PSD (p=5.14x10 -33 , n=60/group). This is also evidenced by biochemical detection of ubiquitin at the synapse and PSD but not cytosol of cortical MCAO extracts (p<0.001, n=6/group). Interestingly, a significant number of ubiquitinated PSD proteins exhibit kinase activity (p=1.02x10 -23 , n=60/group) and include the kinases CaMKII, PKC, Pyk2 and Cdk5, which were biochemically verified (n=3/group). Concurrent with ubiquitination, MCAO also changes the phosphorylation state of PSD-associated proteins (p=3.66x10 -13 , n=60/group). Pyk2 and Cdk5 target sites are hyper-phosphorylated in post-ischemic PSD extracts, while CaMKII and PKC targets show decreased phosphorylation (p<0.05, n=5/group). In line with this, post-ischemic CaMKII (-69±6% of sham, p<0.001, n=9/group) and PKC (-63±8% of sham, p<0.001, n=6/group) activities are severely suppressed at the PSD, which is restored by de-ubiquitination (CaMKII: 105.8±23% of sham, n=6/group; PKC: 101.4±11% of sham, n=4/group).

Conclusions: Ubiquitination is a potent and reversible modulator of kinase activity at the PSD that could impact tissue outcome and, as such, may open new avenues for the treatment of ischemic stroke.

Stroke affects intestinal immune cell trafficking to the central nervous system

Stroke is an acute neurological disease with a strong inflammatory component that can be regulated by the intestinal microbiota and intestinal immune cells. Although stroke has been shown to alter immune cell populations in the gut, the dynamics of cell trafficking have not been elucidated. To study the trafficking of gut-derived immune cells after stroke, we used mice expressing the photoconvertible protein Kikume Green-Red, which turns form green to red when exposed to violet light. Mice underwent laparotomy and the small intestine was exposed to violet laser light. Immune cells were isolated from the small intestine immediately after photoconversion and 2 days later. Percentage of immune cells (CD45⁺KikR⁺) that expressed the red variant of the protein (KikR) was higher immediately after photoconversion than 2 days later, indicating cell egress from the small intestine. To investigate whether intestinal immune cells traffic to the periphery and/or the central nervous system (CNS) after stroke, we analyzed KikR⁺ immune cells (2 days after photoconversion) in peripheral lymphoid organs, meninges and brain, 3 and 14 days after transient occlusion of the middle cerebral artery (tMCAo) or sham-surgery. Although migration was observed in naïve and sham animals, stroke induced a higher mobilization of gut KikR⁺ immune cells, especially at 3 days after stroke, to all the organs analyzed. Notably, we detected a significant migration of CD45^hi immune cells from the gut to the brain and meninges at 3 days after stroke. Comparison of cell trafficking between organs revealed a significant preference of intestinal CD11c⁺ cells to migrate from the small intestine to brain and meninges after stroke. We conclude that stroke increases immune cell trafficking from the small intestine to peripheral lymphoid organs and the CNS where they might contribute to post-stroke inflammation.

Elevated post-ischemic ubiquitination results from suppression of deubiquitinase activity and not proteasome inhibition

Cerebral ischemia-reperfusion increases intraneuronal levels of ubiquitinated proteins, but the factors driving ubiquitination and whether it results from altered proteostasis remain unclear. To address these questions, we used in vivo and in vitro models of cerebral ischemia-reperfusion, in which hippocampal slices were transiently deprived of oxygen and glucose to simulate ischemia followed by reperfusion, or the middle cerebral artery was temporarily occluded in mice. We found that post-ischemic ubiquitination results from two key steps: restoration of ATP at reperfusion, which allows initiation of protein ubiquitination, and free radical production, which, in the presence of sufficient ATP, increases ubiquitination above pre-ischemic levels. Surprisingly, free radicals did not augment ubiquitination through inhibition of the proteasome as previously believed. Although reduced proteasomal activity was detected after ischemia, this was neither caused by free radicals nor sufficient in magnitude to induce appreciable accumulation of proteasomal target proteins or ubiquitin-proteasome reporters. Instead, we found that ischemia-derived free radicals inhibit deubiquitinases, a class of proteases that cleaves ubiquitin chains from proteins, which was sufficient to elevate ubiquitination after ischemia. Our data provide evidence that free radical-dependent deubiquitinase inactivation rather than proteasomal inhibition drives ubiquitination following ischemia-reperfusion, and as such call for a reevaluation of the mechanisms of post-ischemic ubiquitination, previously attributed to altered proteostasis. Since deubiquitinase inhibition is considered an endogenous neuroprotective mechanism to shield proteins from oxidative damage, modulation of deubiquitinase activity may be of therapeutic value to maintain protein integrity after an ischemic insult.

Endothelium-Macrophage Crosstalk Mediates Blood-Brain Barrier Dysfunction in Hypertension

Hypertension is a leading cause of stroke and dementia, effects attributed to disrupting delivery of blood flow to the brain. Hypertension also alters the blood-brain barrier (BBB), a critical component of brain health. Although endothelial cells are ultimately responsible for the BBB, the development and maintenance of the barrier properties depend on the interaction with other vascular-associated cells. However, it remains unclear if BBB disruption in hypertension requires cooperative interaction with other cells. Perivascular macrophages (PVM), innate immune cells closely associated with cerebral microvessels, have emerged as major contributors to neurovascular dysfunction. Using 2-photon microscopy in vivo and electron microscopy in a mouse model of Ang II (angiotensin II) hypertension, we found that the vascular segments most susceptible to increased BBB permeability are arterioles and venules >10 µm and not capillaries. Brain macrophage depletion with clodronate attenuates, but does not abolish, the increased BBB permeability in these arterioles where PVM are located. Deletion of AT1R (Ang II type-1 receptors) in PVM using bone marrow chimeras partially attenuated the BBB dysfunction through the free radical-producing enzyme Nox2. In contrast, downregulation of AT1R in cerebral endothelial cells using a viral gene transfer-based approach prevented the BBB disruption completely. The results indicate that while endothelial AT1R, mainly in arterioles and venules, initiate the BBB disruption in hypertension, PVM are required for the full expression of the dysfunction. The findings unveil a previously unappreciated contribution of resident brain macrophages to increased BBB permeability of hypertension and identify PVM as a putative therapeutic target in diseases associated with BBB dysfunction.

Distinct Commensal Bacterial Signature in the Gut Is Associated With Acute and Long-Term Protection From Ischemic Stroke

Background and Purpose- Commensal gut bacteria have a profound impact on stroke pathophysiology. Here, we investigated whether modification of the microbiota influences acute and long-term outcome in mice subjected to stroke. Methods- C57BL/6 male mice received a cocktail of antibiotics or single antibiotic. After 4 weeks, fecal bacterial density of the 16S rRNA gene was quantitated by qPCR, and phylogenetic classification was obtained by 16S rRNA gene sequencing. Infarct volume and hemispheric volume loss were measured 3 days and 5 weeks after middle cerebral artery occlusion, respectively. Neurological deficits were tested by the Tape Test and the open field test. Results- Mice treated with a cocktail of antibiotics displayed a significant reduction of the infarct volume in the acute phase of stroke. The neuroprotective effect was abolished in mice recolonized with a wild-type microbiota. Single antibiotic treatment with either ampicillin or vancomycin, but not neomycin, was sufficient to reduce the infarct volume and improved motorsensory function 3 days after stroke. This neuroprotective effect was correlated with a specific microbial population rather than the total bacterial density. In particular, random forest analysis trained for the severity of the brain damage revealed that Bacteroidetes S24.7 and the enzymatic pathway for aromatic metabolism discriminate between large versus small infarct size. Additionally, the microbiota signature in the ampicillin-treated mice was associated with a reduced gut inflammation, long-term favorable outcome shown by an amelioration of the stereotypic behavior, and a reduction of brain tissue loss in comparison to control and was predictive of a regulation of short-chain fatty acids and tryptophan pathways. Conclusions- The findings highlight the importance of the intestinal microbiota in short- and long-term outcomes of ischemic stroke and raises the possibility that targeted modification of the microbiome associated with specific microbial enzymatic pathways may provide a preventive strategy in patients at high risk for stroke. Visual Overview- An online visual overview is available for this article.

Abstract 050: Essential Role of Cerebral Endothelial AT1 Receptors in the Blood-Brain Barrier Disruption Induced by Angiotensin-II Hypertension

The blood-brain barrier (BBB) controls the molecular exchange between blood and brain and is critical for maintaining brain health. Although hypertension (HTN) is well known to disrupt the BBB, the underlying cellular bases and the susceptible cerebrovascular segments(s) remain unclear. Here, we addressed these open questions in male mice in which HTN was induced by angiotensin II (Ang II; 600ng/kg/min s.c.; n=9-14/group) for 14 days. HTN increased BBB permeability to 3000 MW FITC-dextran, measured spectrophotometrically in brain extracts (30 ± 1 vs 18 ± 0.5 ng/g in controls; p<0.01). In vivo 2-photon microscopy revealed that dextran leaks out more from microvessels >10ϒm (+38%; p<0.05) than cerebral capillaries (+7%; p>0.05). Electron microscopy showed that HTN induces tight junction remodeling (length -25%; complexity: -11%), and increases endothelial transcytosis (capillaries 1.9 and arterioles 3.5 folds; p<0.05), which is consistent with the downregulation of tight junction proteins (occludin: -17%; claudin-5: -30%) and of the transcytosis inhibitor Msfd2a (-43%). Since AT1 receptors (AT1R) on brain perivascular macrophages (PVM) mediate the deleterious cerebrovascular effects of Ang II HTN (JCI 126:4674), we tested if PVM also mediate the BBB dysfunction. However, PVM depletion (icv clodronate) or deletion of AT1R on PVM (bone marrow chimeras), attenuated the BBB dysfunction only partially (-60% and -49%, respectively; p<0.05), whereas AT1R-/- mice harboring AT1R+ PVM were completely protected (19 ± 1 ng/g; p>0.05 vs control), pointing to a key role of endothelial AT1R. Consistent with this prediction, cerebral endothelial AT1R deletion using a cerebral endothelial specific AAV-BR1-iCre in AT1R floxed mice prevented the BBB disruption completely (21 ± 1 ng/g; p>0.05 vs control). We conclude that AT1 signaling in cerebral endothelial cells initiates the BBB opening induced by Ang II HTN by increasing both paracellular and vesicular transport mainly in arterioles and venules, and that AT1 signaling in PVM, presumably from circulating Ang II crossing the BBB, amplifies the dysfunction. Such increase in BBB permeability to circulating agents may contribute to the cerebrovascular and cognitive dysfunction associated with HTN.

AGO CLIP Reveals an Activated Network for Acute Regulation of Brain Glutamate Homeostasis in Ischemic Stroke

Post-transcriptional regulation by microRNAs (miRNAs) is essential for complex molecular responses to physiological insult and disease. Although many disease-associated miRNAs are known, their global targets and culminating network effects on pathophysiology remain poorly understood. We applied Argonaute (AGO) crosslinking immunoprecipitation (CLIP) to systematically elucidate altered miRNA-target interactions in brain following ischemia and reperfusion (I/R) injury. Among 1,190 interactions identified, the most prominent was the cumulative loss of target regulation by miR-29 family members. Integration of translational and time-course RNA profiles revealed a dynamic mode of miR-29 target de-regulation, led by acute translational activation and a later increase in RNA levels, allowing rapid proteomic changes to take effect. These functional regulatory events rely on canonical and non-canonical miR-29 binding and engage glutamate reuptake signals, such as glial glutamate transporter (GLT-1), to control local glutamate levels. These results uncover a miRNA target network that acts acutely to maintain brain homeostasis after ischemic stroke.

Abstract 31: CaMKII-alpha Ubiquitination Induced by Cerebral Ischemia-Reperfusion Injury Reversibly Inhibits Post-Ischemic CaMKII Activity at the Post-Synaptic Density

Background: Brain calcium-calmodulin-dependent protein kinase II (CaMKII) is exclusively expressed in neurons, where it localizes to the post-synaptic density (PSD) to link calcium signals to changes in synaptic activity. Independent studies suggest that deregulation of CaMKII contributes to neuronal death associated with cerebral ischemia and could be a target for stroke therapy. However, the molecular events underlying CaMKII activity modification after ischemia are not understood. Cerebral ischemia induces ubiquitination of PSD proteins, raising the possibility that post-ischemic CaMKII function is modulated by ubiquitination. Here we investigate a novel link between CaMKIIα subunit ubiquitination and post-ischemic CaMKII regulation.

Methods: Cerebral ischemia was induced in male C57BL6 mice by middle cerebral artery occlusion (MCAO) for 35 min. Whole tissue extracts as well as cytosolic, membrane and PSD fractions were prepared at different times after ischemia to assess CaMKIIα ubiquitination, protein levels and activity. Ubiquitination was reverted with recombinant USP2cc de-ubiquitinase.

Results: MCAO induces CaMKIIα ubiquitination specifically in the neocortical PSD fraction peaking at 1-hour reperfusion. The ubiquitination is accompanied by translocation of CaMKIIα from cytosol/membrane to PSD (cytosol/membrane: 61±4%; PSD: 190±6% of sham, P<0.001, n=9/group), while total CaMKIIα protein levels are not affected (98±1% of sham, P=0.767, n=3/group). In the cytosol CaMKII activity normalized to protein content is not changed post-stroke (91±19% of sham; P<0.001, n=9/group), however at the PSD it is severely suppressed (31±6% of sham, P<0.001, n=9/group). De-ubiquitination leads to restoration of PSD-associated CaMKII activity (347±59% of untreated, P<0.001, n=6/group), identifying ubiquitination as reversible repressor of CaMKII activity at the PSD.

Conclusions: CaMKIIα ubiquitination induced by cerebral ischemia-reperfusion constitutes a previously unappreciated mechanism of post-ischemic CaMKII regulation that may be important for modulating the ischemic outcome. Better understanding of how post-ischemic CaMKIIα ubiquitination is controlled may help to identify a new therapeutic stroke target.

The prolyl 4-hydroxylase inhibitor GSK360A decreases post-stroke brain injury and sensory, motor, and cognitive behavioral deficits

There is interest in pharmacologic preconditioning for end-organ protection by targeting the HIF system. This can be accomplished by inhibition of prolyl 4-hydroxylase (PHD). GSK360A is an orally active PHD inhibitor that has been previously shown to protect the failing heart. We hypothesized that PHD inhibition can also protect the brain from injuries and resulting behavioral deficits that can occur as a result of surgery. Thus, our goal was to investigate the effect of pre-stroke surgery brain protection using a verified GSK360A PHD inhibition paradigm on post-stroke surgery outcomes. Vehicle or an established protective dose (30 mg/kg, p.o.) of GSK360A was administered to male Sprague-Dawley rats. Initially, GSK360A pharmacokinetics and organ distribution were determined, and then PHD-HIF pharmacodynamic markers were measured (i.e., to validate the pharmacological effects of the GSK360A administration regimen). Results obtained using this validated PHD dose-regimen indicated significant improvement by GSK360A (30mg/kg); administered at 18 and 5 hours prior to transient middle cerebral artery occlusion (stroke). GSK360A exposure and plasma, kidney and brain HIF-PHD pharmacodynamics endpoints (e.g., erythropoietin; EPO and Vascular Endothelial Growth Factor; VEGF) were measured. GSK360A provided rapid exposure in plasma (7734 ng/ml), kidney (45–52% of plasma level) and brain (1–4% of plasma level), and increased kidney EPO mRNA (80-fold) and brain VEGF mRNA (2-fold). We also observed that GSK360A increased plasma EPO (300-fold) and VEGF (2-fold). Further assessments indicated that GSK360A reduced post-stroke surgery neurological deficits (47–64%), cognitive dysfunction (60–75%) and brain infarction (30%) 4 weeks later. Thus, PHD inhibition using GSK360A pretreatment produced long-term post-stroke brain protection and improved behavioral functioning. These data support PHD inhibition, specifically by GSK360A, as a potential strategy for pre-surgical use to reduce brain injury and functional decline due to surgery-related cerebral injury.

Abstract T P205: Thrombopoietin Reduces Brain Injury and Cognitive Impairment in Rodent Cerebrovascular Disease Models

Objectives: Thrombopoietin (TPO) reduces brain injury and sensory-motor deficits following stroke in the rat. TPO brain protection is mediated by vascular protection. TPO reduces stroke-induced inflammatory cytokines, matrix metalloproteinase’s and blood brain barrier injury. Here we demonstrate that TPO protects the brain and reduces vascular cognitive impairment in: [1] rat embolic stroke (+/- tissue plasminogen activator; tPA), [2] mouse suture-focal stroke, and [3] mouse chronic carotid stenosis-induced forebrain hypoperfusion.

Methods: Rats (Wistar) underwent embolic middle cerebral artery occlusion (MCAO). Vehicle, tPA (10 mg/kg, iv), TPO (0.1 μg/kg, iv) or TPO plus tPA were administered 2 hours post-stroke. Mice (C57Bl/6) underwent suture-MCAO or carotid artery stenosis-induced forebrain hypoperfusion and then received Vehicle or TPO (0.3 or 0.1 μg/kg, iv) at 1 hr or 1 day after surgery. Neurological deficits, complex learning and hemispheric infarct size were measured for 1-21 days post-surgery.

Results: In rat embolic stroke, tPA or TPO plus tPA improved stroke-induced neurological deficits significantly. Significant post-stroke-induced deficits in APA cognitive performance were improved 87.2±16.4% by TPO or 69.4±9.7% by TPO plus tPA, but not by tPA alone. In mouse suture-focal stroke, brain infarcts were reduced by 64.5±7.7% and neurological deficits were reduced by 90.3±6.4%. In mouse carotid artery stenosis-induced forebrain hypoperfusion a single administration of TPO 1 day after surgery improved APA performance 84.8+3.1% 3 weeks later (all p<0.01).

Conclusions: We have demonstrated TPO long-term protection and safety with and without tPA. TPO exhibits protection in mouse suture-focal and in mouse forebrain hypoperfusion-induced complex learning deficits. These data present multiple model and species work that supports the potential “multiple use” of TPO in the future.

Long-term post-stroke changes include myelin loss, specific deficits in sensory and motor behaviors and complex cognitive impairment detected using active place avoidance

Persistent neurobehavioral deficits and brain changes need validation for brain restoration. Two hours middle cerebral artery occlusion (tMCAO) or sham surgery was performed in male Sprague-Dawley rats. Neurobehavioral and cognitive deficits were measured over 10 weeks included: (1) sensory, motor, beam balance, reflex/abnormal responses, hindlimb placement, forepaw foot fault and cylinder placement tests, and (2) complex active place avoidance learning (APA) and simple passive avoidance retention (PA). Electroretinogram (ERG), hemispheric loss (infarction), hippocampus CA1 neuronal loss and myelin (Luxol Fast Blue) staining in several fiber tracts were also measured. In comparison to Sham surgery, tMCAO surgery produced significant deficits in all behavioral tests except reflex/abnormal responses. Acute, short lived deficits following tMCAO were observed for forelimb foot fault and forelimb cylinder placement. Persistent, sustained deficits for the whole 10 weeks were exhibited for motor (p<0.001), sensory (p<0.001), beam balance performance (p<0.01) and hindlimb placement behavior (p<0.01). tMCAO produced much greater and prolonged cognitive deficits in APA learning (maximum on last trial of 604±83% change, p<0.05) but only a small, comparative effect on PA retention. Hemispheric loss/atrophy was measured 10 weeks after tMCAO and cross-validated by two methods (e.g., almost identical % ischemic hemispheric loss of 33.4±3.5% for H&E and of 34.2±3.5% for TTC staining). No visual dysfunction by ERG and no hippocampus neuronal loss were detected after tMCAO. Fiber tract damage measured by Luxol Fast Blue myelin staining intensity was significant (p<0.01) in the external capsule and striatum but not in corpus callosum and anterior commissure. In summary, persistent neurobehavioral deficits were validated as important endpoints for stroke restorative research in the future. Fiber myelin loss appears to contribute to these long term behavioral dysfunctions and can be important for cognitive behavioral control necessary for complex APA learning.

Poor predictive value of cytomegalovirus (CMV)-specific T cell assays for the development of CMV retinitis in patients with AIDS

BACKGROUND

We examined the potential clinical utility of using a cytomegalovirus (CMV)-specific T cell immunoassay to determine the risk of developing new-onset CMV retinitis (CMVR) in patients with acquired immunodeficiency syndrome (AIDS).

METHODS

CMV-specific T cell assays were performed by multiparameter flow cytometry using stored peripheral blood mononuclear cells that had been obtained in an observational study 2-6 months before new-onset CMVR was diagnosed in case patients (at a study visit during which a dilated ophthalmologic examination revealed no evidence of CMVR) and at the same study visit in control subjects (matched by absolute CD4(+) T cell count at entry) who did not subsequently develop retinitis during 1-6 years of study follow-up.

RESULTS

There were no significant differences in CMV-specific CD4(+) or CD8(+) T cell interferon-gamma or interleukin-2 expression in peripheral blood mononuclear cells from case patients and control subjects. Although there were trends toward lower percentages and absolute numbers of CMV-specific, cytokine-expressing CD8(+) T cells with a "late memory" phenotype (CD27(-)CD28(-)) as well as with an "early memory" phenotype (CD27(+)CD28(+)CD45RA(+)) in case patients than in control subjects, these differences were not statistically significant.

CONCLUSIONS

Many studies have reported that CMV-specific CD4(+) and CD8(+) T cell responses distinguish patients with active CMVR (i.e., who lack CMV-protective immunity) from those with inactive CMVR after immune restoration by antiretroviral treatment (i.e., who have CMV-protective immunity). However, the multiple CMV-specific immune responses we measured do not appear to have clinical utility for predicting the risk for patients with AIDS of developing new-onset CMVR with sufficient accuracy to be used in guiding therapeutic management.

Factors affecting knee cartilage volume in healthy men

OBJECTIVES

To understand the factors that influence joint cartilage in health and disease as they are important for the prevention and management of osteoarthritis.

METHODS

We conducted a cross-sectional study to determine factors influencing knee cartilage volume in 45 males aged (mean+/-S.D.) 52.5+/-13.2 yr.

RESULTS

Total and medial tibial volumes were inversely associated with age, body mass index (BMI) and amount of physical activity and positively associated with total bone content. BMI explained the largest amount of the variation in tibial cartilage volume (18.7%). There were similar findings at the lateral tibial cartilage, but for age and total bone content this did not reach statistical significance. There was a positive association with serum testosterone at all tibial cartilage sites, but this only reached statistical significance for medial tibial cartilage, where serum testosterone explained up to 8% of the variation in cartilage volume.

CONCLUSIONS

Modifiable risk factors of osteoarthritis also appear to be significant determinants of tibial cartilage volume. Serum testosterone may provide one possible explanation for gender differences in tibial cartilage volume and prevalence of tibiofemoral osteoarthritis. The proposed link between osteoarthritis and knee cartilage volume and the effect of testosterone will need to be confirmed in longitudinal studies.

Effects of calcitriol or calcium on bone mineral density, bone turnover, and fractures in men with primary osteoporosis: a two-year randomized, double blind, double placebo study

Osteoporosis in men is an emerging public health problem. As calcitriol reduces the rate of vertebral fractures in osteoporotic postmenopausal women, we conducted a prospective study of this treatment in men with primary osteoporosis. Our study was a 2-yr, randomized, double masked, double placebo-controlled trial of calcitriol (0.25 microg twice daily) or calcium (500 mg twice daily) in 41 men with primary osteoporosis and at least 1 baseline fragility fracture. Thirty-three men (85%) completed the study. There were no differences in baseline characteristics. Spinal and femoral neck bone mineral densities at 2 yr were unchanged in both groups. Serum osteocalcin decreased in both groups by 30% (P < 0.05), whereas urine N-telopeptide cross-links decreased only in the calcium group by 30% (P < 0.05). After 2 yr, fractional calcium absorption increased by 34% (P < 0.01) in the calcitriol group. Nineteen incident fragility fractures occurred (14 vertebral and 5 nonvertebral) in 7 men. Over 2 yr, the number of men with vertebral fractures (6 vs. 1; P = 0.097) was similar in both groups. In conclusion, the efficacy of calcitriol remains unproven as a single agent for the treatment of osteoporosis in men.

Overexpression of macrophage colony-stimulating factor receptor on microglial cells induces an inflammatory response

Microglia are important in the inflammatory response in Alzheimer's disease (AD). We showed previously that macrophage colony-stimulating factor receptor (M-CSFR), encoded by the c-fms protooncogene, is overexpressed on microglia surrounding amyloid beta (Abeta) deposits in the APP(V717F) mouse model for AD. The M-CSFR is also increased on microglia after experimental brain injury and in AD. To determine the relevance of these findings, we transiently expressed M-CSFR on murine BV-2 and human SV-A3 microglial cell lines using an SV40-promoted c-fms construct. M-CSFR overexpression resulted in microglial proliferation and increased expression of inducible nitric-oxide synthase, the proinflammatory cytokines interleukin-1alpha, macrophage inflammatory protein 1-alpha, and interleukin-6 and of macrophage colony-stimulating factor (M-CSF) itself. Antibody neutralization of M-CSF showed that the M-CSFR-induced proinflammatory response was dependent on M-CSF in the culture media. By using a co-culture of c-fms-transfected murine microglia and rat organotypic hippocampal slices and a species-specific real time reverse transcriptase-polymerase chain reaction assay and enzyme-linked immunosorbent assay, we showed that M-CSFR overexpression on exogenous microglia induced expression of interleukin-1alpha by the organotypic culture. These results show that increased M-CSFR expression induces microglial proliferation, cytokine expression, and a paracrine inflammatory response, suggesting that in APP(V717F) mice increased M-CSFR on microglia could be an important factor in Abeta-induced inflammatory response.

DNA hypomethylation perturbs the function and survival of CNS neurons in postnatal animals

DNA methyltransferase I (Dnmt1), the maintenance enzyme for DNA cytosine methylation, is expressed at high levels in the CNS during embryogenesis and after birth. Because embryos deficient for Dnmt1 die at gastrulation, the role of Dnmt1 in the development and function of the nervous system could not be studied by using this mutation. We therefore used the cre/loxP system to produce conditional mutants that lack Dnmt1 in neuroblasts of embryonic day 12 embryos or in postmitotic neurons of the postnatal animal. Conditional deletion of the Dnmt1 gene resulted in rapid depletion of Dnmt1 proteins, indicating that the enzyme in postmitotic neurons turns over quickly. Dnmt1 deficiency in postmitotic neurons neither affected levels of global DNA methylation nor influenced cell survival during postnatal life. In contrast, Dnmt1 deficiency in mitotic CNS precursor cells resulted in DNA hypomethylation in daughter cells. Whereas mutant embryos carrying 95% hypomethylated cells in the brain died immediately after birth because of respiratory distress, mosaic animals with 30% hypomethylated CNS cells were viable into adulthood. However, these mutant cells were eliminated quickly from the brain within 3 weeks of postnatal life. Thus, hypomethylated CNS neurons were impaired functionally and were selected against at postnatal stages.

A Porphyromonas gingivalis genetic locus encoding a heme transport system

Porphyromonas gingivalis has been implicated in the onset and progression of periodontitis and the availability of hemin for in vitro growth has been associated with virulence of the bacterium in animal models. We report here the cloning and sequence analysis of a P. gingivalis TonB-linked outer membrane receptor gene tlr. This gene was previously identified as a TonB-linked adhesin gene tla and shown to be essential for growth at low concentrations of hemin. The tlr gene is immediately downstream of four open reading frames (htrABCD) that encode a putative ATP binding cassette transport system with sequence similarlity to heme transport systems of other bacteria. Analysis of P. gingivalis W50 mRNA revealed that the htrABCD genes are cotranscribed similar to hemin transport genes of other bacteria.

Placebo-controlled trial assessing the use of oral midazolam as a premedication to conscious sedation for pediatric endoscopy

BACKGROUND

This study was performed to evaluate the effect of midazolam, as premedication before intravenous conscious sedation, on preprocedural, procedural, and post-procedural patient comfort and anxiety in children undergoing endoscopy.

METHODS

A placebo-controlled, double-blind, randomized study was conducted in 123 children (age 7.75 +/- 4.46 years, 56% male) using oral midazolam (0.5 mg/kg, maximum 20 mg) as a premedication before insertion of an intravenous access device (i.v.) and upper endoscopy. Patients were evaluated with regard to changes in vital signs, level of sedation during i.v. placement, level of pre- and post-procedure conscious sedation, ease of separation from parents, ease and duration of procedure, recovery time, and amnesia to objects shown before i.v. placement and immediately before the start of the procedure.

RESULTS

A significant difference was noted in the study group for the following parameters: level of sedation for i.v. placement (p < 0.0001), pre-procedural sedation (p < 0.001), ease of i.v. insertion (p < 0.003), ease of separation from parents (p = 0.022), and ease of the nursing personnel's ability to monitor the patient during the procedure (p = 0.0012). The patient's amnesia to an object shown immediately before beginning the endoscopy was increased (p < 0.001). Patients and parents were also more satisfied with the procedure process (p < 0.05). No significant difference was noted with regard to the length or performance of the procedure or recovery time or in the dose of i.v. medication required for successful completion of the endoscopy.

CONCLUSION

Oral midazolam is an effective and safe premedication for children undergoing upper endoscopy and should be used in all anxious children and in patients previously judged to be difficult to sedate.

The prognostic value of thyrotropin receptor antibody measurement in the early stages of treatment of Graves' disease with antithyroid drugs

In most trials, at least 50% of patients with Graves' disease treated with antithyroid drugs (ATD) relapse after achieving euthyroidism. At present, there are no definitive prognostic parameters available early in treatment to indicate those likely to achieve long-term remission. Because thyrotropin receptor antibodies (TRAb) are specific for Graves' disease, the possibility that their rate of change early in treatment (0 to 6 months) might be such an indicator was explored. TRAb were measured both as thyrotropin binding inhibitory immunoglobulins (TBII) and as thyroid-stimulating antibodies (TSAb) in 85 patients with untreated Graves' disease at 6-month intervals throughout their ATD treatment. The patients in the study were treated for a minimum period of 12 months and were categorized retrospectively into two groups depending on whether or not they remained in remission after ATD treatment. Remission was deemed as reached in patients who remained euthyroid for a minimum period of 15 months after cessation of ATD. The mean initial TBII and TSAb values in the nonremission group were significantly higher than in the remission group (p < 0.001 for both parameters). The rates of fall in mean TBII levels were similar for each group in the first 6 months of treatment, but while they continued to fall in the remission group over the next 6 to 12 months, mean values for the nonremission group plateaued and failed to fall to control levels within that period. These results indicate that changes in TRAb levels, measured either as TBII or TSAb, occur more rapidly in the second 6 months of treatment in patients who ultimately achieve remission than those who do not. If TBII fall to control levels by 12 months, the patient has at least a 70% chance of ultimately achieving remission with ATD treatment alone.

Studies of the surgical scrub

BACKGROUND

To evaluate the effectiveness of various scrub techniques in reducing bacterial skin flora, the present study was developed in three stages.

METHODS

Each stage involved fingertip bacterial colony counts measured before, immediately after and 30 min after a variety of handwashing techniques using 10% povidone iodine solution. The first compared 1, 2 or 3 non-timed washes from fingertips to elbows in 10 volunteers. The second compared two volunteers scrubbing for equal durations with or without friction rubbing, while the third involved 15 volunteers who each scrubbed for different time intervals.

RESULTS

The first stage showed that a single wash episode failed to provide lasting bacterial colony count reductions on fingertip cultures. The second showed that enduring colony count reductions occur whether friction rubbing of the hands was used or not, and the third showed that a 30 s wash was as effective as washing for longer periods in reducing fingertip flora.

CONCLUSIONS

These findings suggest that prolonged vigorous pre-operative scrubbing is unnecessary, although more than a cursory wash is required to produce lasting fingertip antisepsis.

A placebo-controlled trial using intravenous atropine as an adjunct to conscious sedation in pediatric esophagogastroduodenoscopy

BACKGROUND

The usefulness of intravenous atropine as an adjunct to conscious sedation in pediatric esophagogastroduodenoscopy remains an unresolved issue.

METHODS

This prospective, double-blind, randomized study examined 101 patients, who were randomized to receive either intravenous atropine 0.02 mg/kg (maximum 0.4 mg) or a placebo of normal saline solution prior to the procedure.

RESULTS

The mean maximum heart rate during the procedure and the percentage of time that the heart rate was more than 1 standard deviation above mean for age was significantly greater in the atropine group as compared to the placebo group (p < 0.0005). There was no significant difference between groups in the amount of secretions noted, gastric motility, retching or vomiting, facial flushing, or dysphoria. There were no causes of significant bradycardia or hypotension in either group. There was a significant number of patients greater than 5 years of age and receiving meperidine and atropine (as compared with meperidine and placebo) whose arterial oxygen saturation dropped below 90% during the procedure (p = 0.0485).

CONCLUSIONS

We found that the use of atropine when used as an adjunct to conscious sedation in children undergoing upper endoscopy did not increase the safety of the procedure or provide significant benefits. We do not recommend the routine use of atropine for upper endoscopy in pediatric patients.

Specific effects of radioiodine treatment on TSAb and TBAb levels in patients with Graves' disease

Radioactive iodine (RAI)-induced changes in the levels of antibodies to the thyroid-stimulating hormone (TSH) receptor (TRAb) in patients undergoing treatment for autoimmune thyroid disease have been well documented. Previous studies have reported effects on the overall level of the antibodies present, TSH-binding inhibitory immunoglobulins (TBII), without detailed studies of specific effects on the levels of thyroid-stimulating (TSAb) or thyroid-blocking antibodies (TBAb). More detailed studies have been reported only in individual cases. In this study, the values of TSAb, TBAb, and TBII were measured longitudinally in 33 patients (27 females and 6 males) who received RAI. The bioassays for TSAb and TBAb were performed in JPO9 cells. Following RAI, there were significant and immediate effects on the values of TBII in 70% of patients. TBII levels fell in 7 patients (20%) (Group 1), rose in 16 patients (48%) (Group 2) or remained unchanged but elevated in 10 patients (32%) (Group 3). In the Group 1 patients, only TSAb were detectable and none of these patients became hypothyroid after treatment. In the 16 patients in Group 2, increases in TBII were attributable to specific increases in TSAb in 7 (44%), in TBAb in 3 (19%), and in both TSAb and TBAb in 3 (19%). There were 3 patients (19%) in this group in whom there was no detectable TSAb or TBAb activity despite the increase in TBII. Six patients from this group became hypothyroid within 6 months of RAI treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Apparatus for studying fretting fatique in vacuum

Recent investigations on the mechanism of fretting fatigue have indicated that mechanical damage, not chemical corrosion, has the largest effect in decreasing structural component life. Since there is no general agreement on the mechanism of fretting fatigue, an experiment has been designed to evaluate statistically the relative role of the mechanical process and the chemical process in reducing fatigue life. An initial step was to develop an apparatus that allows fretting fatigue tests to be performed in both laboratory air and vacuum environments. A detailed discussion of the experimental apparatus and experimental procedure are presented in this paper. Also typical test results are presented. It is found that fretting fatigue in vacuum is about ten times slower than that in laboratory air. Fractographic analysis of the wear surface indicated that less severe fretting damage occurred in the vacuum environment.