Enabling SDN in VANETs: What is the Impact on Security?

The demand for safe and secure journeys over roads and highways has been growing at a tremendous pace over recent decades. At the same time, the smart city paradigm has emerged to improve citizens' quality of life by developing the smart mobility concept. Vehicular Ad hoc NETworks (VANETs) are widely recognized to be instrumental in realizing such concept, by enabling appealing safety and infotainment services. Such networks come with their own set of challenges, which range from managing high node mobility to securing data and user privacy. The Software Defined Networking (SDN) paradigm has been identified as a suitable solution for dealing with the dynamic network environment, the increased number of connected devices, and the heterogeneity of applications. While some preliminary investigations have been already conducted to check the applicability of the SDN paradigm to VANETs, and its presumed benefits for managing resources and mobility, it is still unclear what impact SDN will have on security and privacy. Security is a relevant issue in VANETs, because of the impact that threats can have on drivers' behavior and quality of life. This paper opens a discussion on the security threats that future SDN-enabled VANETs will have to face, and investigates how SDN could be beneficial in building new countermeasures. The analysis is conducted in real use cases (smart parking, smart grid of electric vehicles, platooning, and emergency services), which are expected to be among the vehicular applications that will most benefit from introducing an SDN architecture.

The cervical vertebrae maturation (CVM) method cannot predict craniofacial growth in girls with Class II malocclusion.

INTRODUCTION: The cervical vertebrae maturation (CVM) method is used to determine the timing of treatment of Class II malocclusion. Because its performance has not been tested in patients with Class II, the objective of this study was to evaluate the effectiveness of the CVM method in predicting craniofacial growth in Class II malocclusion. METHODS: Twenty-nine untreated girls with Class II malocclusion were identified among participants of the Nijmegen Growth Study. Each girl had a series of cephalograms taken semi-annually from 9 to 14 years of age. The CVM status was established by five observers on a cephalogram taken at 9 years; mandibular and maxillary length and anterior face height were assessed on all available cephalograms. Method error was evaluated with kappa statistics and Bland-Altman (BA) plots. Regression analysis was used to determine if CVM grade can predict the amount of facial growth. RESULTS: The mean kappa for intra-rater agreement during grading with CVM was 0.36 (fair agreement). BA plots demonstrated acceptable agreement for cephalometric measurements. The regression analysis demonstrated that the only chronologic age was associated with the facial growth. The largest effect of age was for condylion-gnathion (Cd-Gn) and articulare-gnathion (Ar-Gn)-for every additional 6 months the Cd-Gn increases by 1.8mm [95 per cent confidence interval (CI): 1.7, 1.9, P < 0.001] and Ar-Gn increases by 1.59mm (95 per cent CI: 1.52, 1.67, P < 0.001). The CVM grade could not predict the change of cephalometric variables. CONCLUSIONS: There is no evidence to support the hypothesis that the CVM method can predict the amount of craniofacial growth in girls with Class II malocclusion.

Digital Staining of White Blood Cells With Confidence Estimation.

Chemical staining of the blood smears is one of the crucial components of blood analysis. It is an expensive, lengthy and sensitive process, often prone to produce slight variations in colour and seen structures due to a lack of unified protocols across laboratories. Even though the current developments in deep generative modeling offer an opportunity to replace the chemical process with a digital one, there are specific safety-ensuring requirements due to the severe consequences of mistakes in a medical setting. Therefore digital staining system would profit from an additional confidence estimation quantifying the quality of the digitally stained white blood cell. To this aim, during the staining generation, we disentangle the latent space of the Generative Adversarial Network, obtaining separate representation s of the white blood cell and the staining. We estimate the generated image's confidence of white blood cell structure and staining quality by corrupting these representations with noise and quantifying the information retained between multiple outputs. We show that confidence estimated in this way correlates with image quality measured in terms of LPIPS values calculated for the generated and ground truth stained images. We validate our method by performing digital staining of images captured with a Differential Inference Contrast microscope on a dataset composed of white blood cells of 24 patients. The high absolute value of the correlation between our confidence score and LPIPS demonstrates the effectiveness of our method, opening the possibility of predicting the quality of generated output and ensuring trustworthiness in medical safety-critical setup.

Apolipoprotein E induces antiinflammatory phenotype in macrophages.

OBJECTIVE: Apolipoprotein E (apoE) exerts potent antiinflammatory effects. Here, we investigated the effect of apoE on the functional phenotype of macrophages. METHODS AND RESULTS: Human apoE receptors very-low-density lipoprotein receptor (VLDL-R) and apoE receptor-2 (apoER2) were stably expressed in RAW264.7 mouse macrophages. In these cells, apoE downregulated markers of the proinflammatory M1 phenotype (inducible nitric oxide synthase, interleukin [IL]-12, macrophage inflammatory protein-1α) but upregulated markers of the antiinflammatory M2 phenotype (arginase I, SOCS3, IL-1 receptor antagonist [IL-1RA]). In addition, M1 macrophage responses (migration, generation of reactive oxygen species, antibody-dependent cell cytotoxicity, phagocytosis), as well as poly(I:C)- or interferon-γ-induced production of proinflammatory cytokines; cyclooxygenase-2 expression; and activation of nuclear factor-κB, IκB, and STAT1, were suppressed in VLDL-R- or apoER2-expressing cells. Conversely, the suppression of the M2 phenotype and the enhanced response to poly(I:C) were observed in apoE-producing bone marrow macrophages derived from VLDL-R-deficient mice but not wild-type or low-density lipoprotein receptor-deficient mice. The modulatory effects of apoE on macrophage polarization were inhibited in apoE receptor-expressing RAW264.7 cells exposed to SB220025, a p38 mitogen-activated protein kinase inhibitor, and PP1, a tyrosine kinase inhibitor. Accordingly, apoE induced tyrosine kinase-dependent activation of p38 mitogen-activated protein kinase in VLDL-R- or apoER2-expressing macrophages. Under in vivo conditions, apoE-/- mice transplanted with apoE-producing wild-type bone marrow showed increased plasma IL-1RA levels, and peritoneal macrophages of transplanted animals were shifted to the M2 phenotype (increased IL-1RA production and CD206 expression). CONCLUSIONS: ApoE signaling via VLDL-R or apoER2 promotes macrophage conversion from the proinflammatory M1 to the antiinflammatory M2 phenotype. This effect may represent a novel antiinflammatory activity of apoE.

Multi-Task Multi-Domain Learning for Digital Staining and Classification of Leukocytes.

This paper addresses digital staining and classification of the unstained white blood cell images obtained with a differential contrast microscope. We have data coming from multiple domains that are partially labeled and partially matching across the domains. Using unstained images removes time-consuming staining procedures and could facilitate and automatize comprehensive diagnostics. To this aim, we propose a method that translates unstained images to realistically looking stained images preserving the inter-cellular structures, crucial for the medical experts to perform classification. We achieve better structure preservation by adding auxiliary tasks of segmentation and direct reconstruction. Segmentation enforces that the network learns to generate correct nucleus and cytoplasm shape, while direct reconstruction enforces reliable translation between the matching images across domains. Besides, we build a robust domain agnostic latent space by injecting the target domain label directly to the generator, i.e., bypassing the encoder. It allows the encoder to extract features independently of the target domain and enables an automated domain invariant classification of the white blood cells. We validated our method on a large dataset composed of leukocytes of 24 patients, achieving state-of-the-art performance on both digital staining and classification tasks.

Change in out-of-hospital 12-lead ECG diagnostic classification following resuscitation from cardiac arrest.

INTRODUCTION: We evaluated the incidence of change in serial 12-lead electrocardiogram (ECG) diagnostic classifications in patients resuscitated from out-of-hospital (OH) cardiac arrest (OHCA) comparing OH to emergency department (ED) ECGs. METHODS: This retrospective case series included: 1) adults (≥ 18 years old), 2) resuscitated from OHCA, 3) ≥ 1 OH and 1 ED ECG/patient, and 4) emergency medical services (EMS) transport to the study hospital. OH and ED ECGs were classified as: 1) STEMI (ST-segment Elevation Myocardial Infarction), 2) Ischemic, and 3) Non-ischemic. Two ED physicians and one cardiologist independently classified all ECGs, then generated a consensus opinion classification for each ECG based on American Heart Association's 2018 Expert Consensus criteria. The most ischemic OH ECG classification was compared with the last ED ECG classification. RESULTS: From 7/27/12 to 7/18/19, 176 patients were entered with a mean age of 61.2 ± 16.6 years; 102/176 (58%) were male. Overall, 504 OH and ED 12-lead ECGs were acquired (2.9 ECGs/patient). ECG classification inter-rater reliability kappa score was 0.63 ± 0.02 (substantial agreement). Overall, 86/176 (49%) changed ECG classification from the OH to ED setting; 69/86 (80%) of these ECGs changed from more to less ischemic classifications. Of 49 OH STEMI ECG classifications, 33/49 (67%) changed to a less ischemic (non-STEMI) ED ECG classification. CONCLUSIONS: Change in 12-lead ECG classification from OH to ED setting in patients resuscitated from OHCA was common (49%). The OH STEMI classification changed to a less ischemic (non-STEMI) ED classification in 67% of cases.

SLC37A4-CDG: Mislocalization of the glucose-6-phosphate transporter to the Golgi causes a new congenital disorder of glycosylation.

Loss-of-function of the glucose-6-phosphate transporter is caused by biallelic mutations in SLC37A4 and leads to glycogen storage disease Ib. Here we describe a second disease caused by a single dominant mutation in the same gene. The mutation abolishes the ER retention signal of the transporter and generates a weak Golgi retention signal. Intracellular mislocalization of the transporter leads to a congenital disorder of glycosylation instead of glycogen storage disease.

Knotless anatomic double-layer double-row rotator cuff repair: a novel technique re-establishing footprint and shape of full-thickness tears.

The standard technique for restoring footprint after full-thickness tears of the rotator cuff includes double-row or transosseous-equivalent techniques. However, the anatomically typical bird's beak shape and profile of tendon insertion may not be originally restored and biomechanics may be altered. In this report, the authors describe a technique that involves creating two intratendinous stitches at different levels of the torn tendon. The first passes through the bursal-side layer, the second stitch through the joint-side layer. Both stitches may be performed in mattress suture configuration. The anchorage is performed by knotless anchors in order to avoid knots lying within the insertion area. The footprint is restored first medially then laterally by the use of double-row principles. The joint-side suture is anchored within the medially placed anchor. The bursal-side suture is anchored by a laterally placed anchor. The anatomic insertion and restoration of the shape and profile may be enabled by the described double-layer suture technique. Using a double-layer double-row repair may potentially improve functional results of rotator cuff repair constructs.

Arthroscopic reduction and subchondral support of reverse Hill-Sachs lesions with a bioabsorbable interference screw.

Traumatic posterior dislocation of the shoulder is frequently associated with an osteochondral defect on the anterior articular surface of the humeral head (so-called reverse Hill-Sachs lesion). Possible treatment options are either filling or elevation of the osseous defect. Previously, an open technique has been described using a bioabsorbable interference screw. On the basis of a 64-year-old patient presenting with a reverse Hill-Sachs lesion after epileptic seizure, we describe an arthroscopic technique in which the defect is reconstructed under arthroscopic and fluoroscopic control and supported by a bioabsorbable interference screw.

End tidal CO2 and cerebral oximetry for the prediction of return of spontaneous circulation during cardiopulmonary resuscitation.

BACKGROUND: End Tidal CO2 (ETCO2) is a reasonable predictor of Return of Spontaneous Circulation (ROSC) in cardiac arrest (CA), though with many limitations. Cerebral Oximetry (CerOx) non-invasively measures brain O2 saturation and correlates with flow. OBJECTIVES: This study compares ETCO2 and CerOx for ROSC prediction during both out of hospital (OHCA) and emergency department cardiac arrests (EDCA). METHODS: We conducted a prospective study on CA patients resuscitated in the ED. ETCO2 and CerOx simultaneously measured during ED CPR. Data was analyzed with logistic regression modeling and area under the curve (AUC). RESULTS: 176 patients were analyzed, 66.7% were witnessed, 52.8% had bystander CPR. EMS alert to ED arrival was 27.0 ± 10.6 min. Initial rhythm was 31.8% asystole, 27.8% PEA, 25.6% VF/VT with 26.1% achieving ROSC. AUC predictors of ROSC were: last 5 min trend [CerOx = 0.82 ; ETCO2 = 0.74], delta first to last [CerOx = 0.86 ; ETCO2 = 0.73], the penultimate minute [CerOx = 0.81 ; ETCO2 = 0.76], and final minute [CerOx = 0.89 ; ETCO2 = 0.77]. AUC comparison of simultaneous measurements (n = 125) revealed: last 5 min trend [CerOx = 0.80 ; ETCO2 = 0.79], delta first to last [CerOx = 0.83 ; ETCO2 = 0.75], penultimate minute [CerOx = 0.83 ETCO2 = 0.74], and final minute [CerOx = 0.89 ; ETCO2 = 0.75]. CONCLUSIONS: Our data shows, both ETCO2 and rSO2 are good predictors of ROSC. We found CerOx superior to ETCO2 in predicting ROSC.

The surgical approach for locking plate osteosynthesis of displaced proximal humeral fractures influences the functional outcome.

This study evaluated the influence of the surgical approach for locking plate osteosynthesis in proximal humeral fractures during a 1-year period. We performed a comparative study in 83 patients to evaluate possible benefits for an early functional result for function, pain, activity levels, radiographic evaluation, and complications. In 39 cases, the extended anterolateral deltoid-splitting approach was used (group DS); in 44 cases, the deltopectoral approach was used (group DP). The clinical and radiologic follow-up took place 3, 6, and 12 months after the operation. The functional results in the adjusted Constant score after 3 months showed higher values for group DS of 57.9% vs group DP with 49.6%. After 6 months, no significant differences were seen, with 69.4% for group DS and 71.4% for group DP. Finally, after 12 months, group DP showed higher results at 81% compared with 73.1% for DS. In the subgroups of the Constant score, abduction and active anterior elevation showed particularly higher values in group DP. The duration of the operation was 67 minutes in group DS and 86 minutes in group DP. One case of avascular necrosis was observed in group DS and 3 in group DP. We conclude that the choice of approach for exposure of the proximal humerus region may influence the functional outcome. Stable osteosynthesis is important, but the outcome of operatively treated proximal humerus fractures is dependent on soft tissue management as well.

Expression of ATP binding cassette-transporter ABCG1 prevents cell death by transporting cytotoxic 7beta-hydroxycholesterol.

Oxysterols result from cholesterol by enzymatic or oxidative processes. Some exert cytotoxic effects leading to necrosis or apoptosis. Detoxification of these compounds mainly occurs in the liver and requires transport from peripheral tissues towards it. Some ATP-binding cassette transporters are involved in export of cytotoxic compounds. In the current study, we investigated whether ABC transporter family member G1 (ABCG1) may be involved in oxysterol transport, since its gene expression is highly responsive to oxysterol loading. TetOff HeLa cells stably expressing ABCG1 showed decreased mass uptake of 7beta-hydroxycholesterol (7beta-HC) whereas that of other physiologically relevant oxysterols was unaffected. Application of 7beta-HC to ABCG1 expressing cells induced hyperpolarization of mitochondrial membrane potential and production of reactive oxygen species, indicating energy consumption by the ATP-binding cassette transporter when it is activated by its correct substrate. Our study points to detoxification as one of potential cellular functions of ABCG1. We assume that ABCG1 protects against 7beta-HC-induced cell death, an important role in prevention of neurodegenerative and cardiovascular disease.

Countercurrent distribution of two distinct SNARE complexes mediating transport within the Golgi stack.

Genetic and biochemical evidence has established that a SNARE complex consisting of syntaxin 5 (Sed5)-mYkt6 (Ykt6)-GOS28 (Gos1)-GS15 (Sft1) is required for transport of proteins across the Golgi stack in animals (yeast). We have utilized quantitative immunogold labeling to establish the cis-trans distribution of the v-SNARE GS15 and the t-SNARE subunits GOS28 and syntaxin 5. Whereas the distribution of the t-SNARE is nearly even across the Golgi stack from the cis to the trans side, the v-SNARE GS15 is present in a gradient of increasing concentration toward the trans face of the stack. This contrasts with a second distinct SNARE complex, also required for intra-Golgi transport, consisting of syntaxin 5 (Sed5)-membrin (Bos1)-ERS24 (Sec22)-rBet1 (Bet1), whose v-(rBet1) and t-SNARE subunits (membrin and ERS24), progressively decrease in concentration toward the trans face. Transport within the stack therefore appears to utilize countercurrent gradients of two Golgi SNAREpins and may involve a mechanism akin to homotypic fusion.

Expression and functional characterization of ABCG1 splice variant ABCG1(666).

The ATP-binding cassette transporter ABCG1 mediates the transport of excess cholesterol from macrophages and other cell types to high density lipoprotein (HDL) but not to lipid-depleted apolipoprotein AI. Several splice variants which may have different functions have been identified in mammals. In the current study, we characterized the human splice variant ABCG1(666), which differs from full-length ABCG1(678) by absence of an internal segment of 12 amino acids (VKQTKRLKGLRK). Accordingly spliced ABCG1 transcripts were detected in macrophages and liver in approximately twofold higher amounts than the alternatively spliced ABCG1 form encoding full-length ABCG1. We used transient and stable expression of ABCG1(666) fusion proteins to characterize glycosylation, subcellular localization, molecular interaction and functions of this ABCG1 variant. It could be demonstrated that ABCG1(666) is located at the cell surface and has the ability to form cholesterol transport competent homodimers which affect cellular cholesterol export in a similar manner as previously characterized forms of ABCG1. Our results support that ABCG1(666) may in fact be the most prominent form of functional ABCG1 expressed in the human.

Polyunsaturated fatty acids and acetoacetate downregulate the expression of the ATP-binding cassette transporter A1.

Low HDL cholesterol is a frequent cardiovascular risk factor in diabetes. Because of its pivotal role for the regulation of HDL plasma levels, we investigated in vivo and in vitro regulation of the ATP-binding cassette transporter A1 (ABCA1) by insulin and metabolites accumulating in diabetes. Compared with euglycemic control mice, ABCA1 gene expression was severely decreased in the liver and peritoneal macrophages of diabetic mice. Treatment with insulin restored this deficit. Incubation of cultivated HepG2 hepatocytes and RAW264.7 macrophages with unsaturated fatty acids or acetoacetate, but not with insulin, glucose, saturated fatty acids, or hydroxybutyrate, downregulated ABCA1 mRNA and protein. The suppressive effect of unsaturated fatty acids and acetoacetate became most obvious in cells stimulated with oxysterols or retinoic acid but was independent of the expression of the thereby regulated transcription factors liver-X-receptor alpha (LXRalpha) and retinoid-X-receptor alpha (RXRalpha), respectively. Unsaturated fatty acids and acetoacetate also reduced ABCA1 promotor activity in RAW264.7 macrophages that were transfected with a 968-bp ABCA1 promotor/luciferase gene construct. As the functional consequence, unsaturated fatty acids and acetoacetate inhibited cholesterol efflux from macrophages. Downregulation of ABCA1 by unsaturated fatty acids and acetoacetate may contribute to low HDL cholesterol and increased cardiovascular risk of diabetic patients.

Cloning, cellular localization, genomic organization, and tissue-specific expression of the TGFbeta1-inducible SMAP-5 gene.

SMAP-5 is a member of the five-pass transmembrane protein family localizing in the Golgi apparatus and the endoplasmic reticulum. These proteins have been implicated in intracellular trafficking, in secretion and in vesicular transport. Phylogenetic analyses revealed that SMAP-5 is a member of a small Rab GTPase interacting factor protein family. The human SMAP-5 gene spans about 12.5 kb and comprises 6 exons on chromosomal locus 5q32. The proximal 5'-flanking region of the gene lacks a TATA box and is highly GC rich. Consistent with this, the SMAP-5 gene is expressed in all tissues. The highest level of expression was found in coronary smooth muscle cells, in which expression of the SMAP-5 gene was induced by transforming growth factor beta1, thus indicating that this protein may play an important role in inflammation.

Pharmacological regulation of cholesterol efflux in human monocyte-derived macrophages in the absence of exogenous cholesterol acceptors.

Cholesterol efflux from human monocyte-derived macrophages in the absence of exogenous acceptors has been described, but is unclear in mechanism. We investigated this process in relation to the expression of relevant genes, intracellular cholesterol storage and apoE secretion using drugs affecting different aspects of cholesterol metabolism. Both natural (22R-hydroxycholesterol/9-cis-retinoic acid) and synthetic (T0901317 and RO264456) LXR/RXR ligands increased ABCA1 and ABCG1 mRNAs in native macrophages and in cells loaded with acetylated LDL (acLDL). The ACAT inhibitor avasimibe increased only ABCG1 mRNA, whereas no treatment affected apoE mRNA. Avasimibe, progesterone, and natural but not synthetic LXR/RXR ligands prevented cholesterol esterification after acLDL-loading. Cholesterol efflux into acceptor-free medium was increased only by synthetic LXR/RXR ligands and avasimibe in acLDL-loaded cells. ApoE secretion was reduced by drugs affecting cholesterol trafficking but enhanced by LXR/RXR ligands. Incubation with an anti-apoE antibody virtually removed immunodetectable apoE from the medium, significantly increasing cholesterol storage and decreasing efflux. These findings indicate that in human macrophages spontaneous cholesterol efflux: (i) is not necessarily promoted by increasing intracellular free cholesterol, (ii) is increased by compounds that activate ABCA1 and, to a greater extent, ABCG1 and (iii) is only partially correlated with secretion of endogenous apoE, which acted as a cholesterol acceptor.

ADP-ribosylation factor (ARF)-like 7 (ARL7) is induced by cholesterol loading and participates in apolipoprotein AI-dependent cholesterol export.

Here, we identify ADP-ribosylation factor (ARF)-like 7 (ARL7) as the only ARF- and ARL-family member whose mRNA-expression is induced by liver X-receptor/retinoid X-receptor agonists or cholesterol loading in human macrophages. Moreover, subcellular distribution of mutant and wild type ARL7-enhanced green fluorescent protein (EGFP) supports that ARL7 may be involved in a vesicular transport step between a perinuclear compartment and the plasma membrane. Therefore, we investigated the effect of ARL7 over-expression on the cholesterol secretory pathway. We found that expression of wild type and dominant active ARL7-EGFP stimulated the rate of apolipoprotein AI-specific cholesterol efflux 1.7- and 2.8-fold. In contrast, expression of the dominant negative form of ARL7-EGFP led to approximately 50% inhibition of cholesterol efflux. This data is consistent with a model in which ARL7 is involved in transport between a perinuclear compartment and the plasma membrane apparently linked to the ABCA1-mediated cholesterol secretion pathway.

Electrical power generation characteristics of piezoelectric generator under quasi-static and dynamic stress conditions.

The electrical characteristics of a piezoelectric power generator are investigated under quasi-static (duration > 100 ms) and dynamic (stress duration < 10 ms) stress applications. The electromechanical model of piezoelectric generator is presented and used to explain the effects of the two stress conditions. A computer simulation of the piezoelectric generator is used to compare the theoretical and experimental results. The simulation predicts that a quasi-static stress will produce a bidirectional generator output voltage, and a dynamic stress will produce a unidirectional output voltage. The simulation also predicts that, when equal stresses are applied to the generator, the dynamic stress will generate a 10X higher output voltage than the quasi-static stress, contradicting results reported by other investigators. The output voltage is different for the two cases because of the generator's resistive capacitive (RC) time constant. The dynamic stress is applied in a time that is less than the generator's RC time constant, and the quasi-static stress is applied in a time greater than the generator's RC time constant. The piezoelectric capacitance has enough time to charge in the quasi-static case, resulting in the lower output voltage. The simulation results are experimentally verified for leaded zirconia titanate PZT 5H and PZT 5A materials. Simulated and experimental results are shown to be in good agreement.

3ß,5α,6ß-Cholestanetriol and 25-hydroxycholesterol accumulate in ATP-binding cassette transporter G1 (ABCG1)-deficiency.

OBJECTIVE: Oxysterols are oxidized derivatives of sterols that have cytotoxic effects and are potent regulators of diverse cellular functions. Efficient oxysterol removal by the sub-family G member 1 of the ATP-binding cassette transporters (ABCG1) is essential for cell survival and control of cellular processes. However, the specific role of ABCG1 in the transport of various oxysterol species has been not systematically investigated to date. Here, we examined the involvement of ABCG1 in the oxysterol metabolism by studying oxysterol tissue levels in a mouse model of Abcg1-deficiency. METHODS AND RESULTS: Analysis of lung tissue of Abcg1(-/-) mice on a standard diet revealed that 3ß,5α,6ß-cholestanetriol (CT) and 25-hydroxycholesterol (HC) accumulated at more than 100-fold higher levels in comparison to wild-type mice. 24S-HC and 27-HC levels were also elevated, but were minor constituents. A radiolabeled assay employing regulable ABCG1-expressing HeLa cell lines revealed that 25-HC export to albumin was dependent on functional ABCG1 expression and could be blocked by an excess of unlabeled 25-HC or 27-HC. In this cell line, 25-HC at low doses triggered mitochondrial membrane potential, and reactive oxygen species production, which are both indirect indicators of cellular energy expenditure. CONCLUSION: Our results suggest that 25-HC and CT are physiologic substrates for ABCG1. Excessive accumulation of these oxysterols may explain the increased rate of cell death and the inflammatory phenotype observed in Abcg1-deficient animals and cells.