Mitotic Activity in Glioblastoma Correlates with Estimated Extravascular Extracellular Space Derived from Dynamic Contrast-Enhanced MR Imaging

BACKGROUND AND PURPOSE

A number of parameters derived from dynamic contrast-enhanced MR imaging and separate histologic features have been identified as potential prognosticators in high-grade glioma. This study evaluated the relationships between dynamic contrast-enhanced MRI-derived parameters and histologic features in glioblastoma multiforme.

MATERIALS AND METHODS

Twenty-eight patients with newly presenting glioblastoma multiforme underwent preoperative imaging (conventional imaging and T1 dynamic contrast-enhanced MRI). Parametric maps of the initial area under the contrast agent concentration curve, contrast transfer coefficient, estimate of volume of the extravascular extracellular space, and estimate of blood plasma volume were generated, and the enhancing fraction was calculated. Surgical specimens were used to assess subtype and were graded (World Health Organization classification system) and were assessed for necrosis, cell density, cellular atypia, mitotic activity, and overall vascularity scores. Quantitative assessment of endothelial surface area, vascular surface area, and a vascular profile count were made by using CD34 immunostaining. The relationships between MR imaging parameters and histopathologic features were examined.

RESULTS

High values of contrast transfer coefficient were associated with the presence of frank necrosis (P = .005). High values of the estimate of volume of the extravascular extracellular space were associated with a fibrillary histologic pattern (P < .01) and with increased mitotic activity (P < .05). No relationship was found between mitotic activity and histologic pattern, suggesting that the correlation between the estimate of volume of the extravascular extracellular space and mitotic activity was independent of the histologic pattern.

CONCLUSIONS

A correlation between the estimate of volume of the extravascular extracellular space and mitotic activity is reported. Further work is warranted to establish how dynamic contrast-enhanced MRI parameters relate to more quantitative histologic measurements, including markers of proliferation and measures of vascular endothelial growth factor expression.

Increased drug resistance is associated with reduced glucose levels and an enhanced glycolysis phenotype

BACKGROUND AND PURPOSE

The testing of anticancer compounds in vitro is usually performed in hyperglycaemic cell cultures, although many tumours and their in vivo microenvironments are hypoglycaemic. Here, we have assessed, in cultures of tumour cells, the effects of reduced glucose levels on resistance to anticancer drugs and investigated the underlying cellular mechanisms.

EXPERIMENTAL APPROACH

PIK3CA mutant (AGS, HGC27), and wild-type (MKN45, NUGC4) gastric cancer cells were cultured in high-glucose (HG, 25 mM) or low-glucose (LG, 5 mM) media and tested for sensitivity to two cytotoxic compounds, 5-fluorouracil (5-FU) and carboplatin, the PI3K/mTOR inhibitor, PI103 and the mTOR inhibitor, Ku-0063794.

KEY RESULTS

All cells had increased resistance to 5-FU and carboplatin when cultured in LG compared with HG conditions despite having similar growth and cell cycle characteristics. On treatment with PI103 or Ku-0063794, only the PIK3CA mutant cells displayed increased resistance in LG conditions. The PIK3CA mutant LG cells had selectively increased p-mTOR, p-S6, p-4EBP1, GLUT1 and lactate production, and reduced reactive oxygen species, consistent with increased glycolysis. Combination analysis indicated PI103 and Ku-0063794 were synergistic in PIK3CA mutant LG cells only. Synergism was accompanied by reduced mTOR signalling and increased autophagy.

CONCLUSIONS AND IMPLICATIONS

Hypoglycaemia increased resistance to cytotoxic agents, especially in tumour cells with a high dependence on glycolysis. Dual inhibition of the PI3K/mTOR pathway may be able to attenuate such hypoglycaemia-associated resistance.

The refinement of topics for systematic reviews: lessons and recommendations from the Effective Health Care Program

OBJECTIVES

The Agency for Healthcare Research and Quality (AHRQ) Effective Health Care Program conducts systematic reviews of health-care topics nominated by stakeholders. Topics undergo refinement to ensure relevant questions of appropriate scope and useful reviews. Input from key informants, experts, and a literature scan informs changes in the nominated topic. AHRQ convened a work group to assess approaches and develop recommendations for topic refinement.

STUDY DESIGN AND SETTING

Work group members experienced in topic refinement generated a list of questions and guiding principles relevant to the refinement process. They discussed each issue and reached agreement on recommendations.

RESULTS

Topics should address important health-care questions or dilemmas, consider stakeholder priorities and values, reflect the state of the science, and be consistent with systematic review research methods. Guiding principles of topic refinement are fidelity to the nomination, relevance, research feasibility, responsiveness to stakeholder inputs, reduced investigator bias, transparency, and suitable scope. Suggestions for stakeholder engagement, synthesis of input, and reporting are discussed. Refinement decisions require judgment and balancing guiding principles. Variability in topics precludes a prescriptive approach.

CONCLUSION

Accurate, rigorous, and useful systematic reviews require well-refined topics. These guiding principles and methodological recommendations may help investigators refine topics for reviews.

Screening for and treatment of suicide risk relevant to primary care: a systematic review for the U.S. Preventive Services Task Force

BACKGROUND

In 2009, suicide accounted for 36 897 deaths in the United States.

PURPOSE

To review the accuracy of screening instruments and the efficacy and safety of screening for and treatment of suicide risk in populations and settings relevant to primary care.

DATA SOURCES

Citations from MEDLINE, PsycINFO, the Cochrane Central Register of Controlled Trials, and CINAHL (2002 to 17 July 2012); gray literature; and a surveillance search of MEDLINE for additional screening trials (July to December 2012).

STUDY SELECTION

Fair- or good-quality English-language studies that assessed the accuracy of screening instruments in primary care or similar populations and trials of suicide prevention interventions in primary or mental health care settings.

DATA EXTRACTION

One investigator abstracted data; a second checked the abstraction. Two investigators rated study quality.

DATA SYNTHESIS

Evidence was insufficient to determine the benefits of screening in primary care populations; very limited evidence identified no serious harms. Minimal evidence suggested that screening tools can identify some adults at increased risk for suicide in primary care, but accuracy was lower in studies of older adults. Minimal evidence limited to high-risk populations suggested poor performance of screening instruments in adolescents. Trial evidence showed that psychotherapy reduced suicide attempts in high-risk adults but not adolescents. Most trials were insufficiently powered to detect effects on deaths.

LIMITATION

Treatment evidence was derived from high-risk rather than screening-detected populations. Evidence relevant to adolescents, older adults, and racial or ethnic minorities was limited.

CONCLUSION

Primary care-feasible screening tools might help to identify some adults at increased risk for suicide but have limited ability to detect suicide risk in adolescents. Psychotherapy may reduce suicide attempts in some high-risk adults, but effective interventions for high-risk adolescents are not yet proven.

PRIMARY FUNDING SOURCE

Agency for Healthcare Research and Quality.

Primary care-relevant interventions for tobacco use prevention and cessation in children and adolescents: a systematic evidence review for the U.S. Preventive Services Task Force

BACKGROUND

Interventions to prevent smoking uptake or encourage cessation among young persons might help prevent tobacco-related illness.

PURPOSE

To review the evidence for the efficacy and harms of primary care-relevant interventions that aim to reduce tobacco use among children and adolescents.

DATA SOURCES

Three systematic reviews that collectively covered the relevant literature; MEDLINE, PsycINFO, the Cochrane Central Register of Controlled Trials, and the Database of Abstracts of Reviews of Effects through 14 September 2012; and manual searches of reference lists and gray literature.

STUDY SELECTION

Two investigators independently reviewed 2453 abstracts and 111 full-text articles. English-language trials of behavior-based or medication interventions that were relevant to primary care and reported tobacco use, health outcomes, or harms were included.

DATA EXTRACTION

One investigator abstracted data from good- and fair-quality trials into an evidence table, and a second checked these data.

DATA SYNTHESIS

19 trials (4 good-quality and 15 fair-quality) that were designed to prevent tobacco use initiation or promote cessation (or both) and reported self-reported smoking status or harms were included. Pooled analyses from a random-effects meta-analysis suggested a 19% relative reduction (risk ratio, 0.81 [95% CI, 0.70 to 0.93]; absolute risk difference, -0.02 [CI, -0.03 to 0.00]) in smoking initiation among participants in behavior-based prevention interventions compared with control participants. Neither behavior-based nor bupropion cessation interventions improved cessation rates. Findings about the harms related to bupropion use were mixed.

LIMITATIONS

No studies reported health outcomes. Interventions and measures were heterogeneous. Most trials examined only cigarette smoking. The body of evidence was largely published 5 to 15 years ago.

CONCLUSION

Primary care-relevant interventions may prevent smoking initiation over 12 months in children and adolescents.

Evaluation of patient-centered electronic health record to overcome digital divide

Advances and wide acceptance of information and communication technology (ICT) have made development and implementation of web-based electronic personal health records (PHRs) more feasible than ever before, and previous studies have demonstrated some of its potential and promises. However, this type of ICT-dependent approach inherits its own vulnerabilities of exposing the society to digital divide, commonly described as the gap that exists among individuals and communities with regards to the haves and have-nots of information and modern communications technologies. To address these concerns and improve healthcare outcomes, we have developed and customized a web-based patient-centered electronic PHR, named the Personal Health Information Management System (PHIMS), and evaluated the system at the Everett Housing Authority, which provides housings for low-income ncome families and elderly or disabled populations. A preliminary study demonstrates that 92% of the participating residents are satisfied with the PHIMS system in general. Some of the residents found PHIMS records very useful for their clinic visits.

Evaluation of patient-centered electronic health record to overcome digital divide

Advances and wide acceptance of information and communication technology (ICT) have made development and implementation of web-based electronic personal health records (PHRs) more feasible than ever before, and previous studies have demonstrated some of its potential and promises. However, this type of ICT-dependent approach inherits its own vulnerabilities of exposing the society to "digital divide", commonly described as the gap that exists among individuals and communities with regards to the 'haves' and 'have-nots' of information and modern communications technologies. To address these concerns and improve healthcare outcomes, we have developed and customized a web-based patient-centered electronic PHR, named the Personal Health Information Management System (PHIMS), and evaluated the system at the Everett Housing Authority, which provides housings for low-income families and elderly or disabled populations. A preliminary study demonstrates that 92% of the participating residents are satisfied with the PHIMS system in general. Some of the residents found PHIMS records very useful for their clinic visits.

The concepts, diagnosis and management of early imaging changes after therapy for glioblastomas

Since postoperative radiotherapy plus concomitant temozolomide followed by adjuvant temozolomide has become standard treatment for glioblastoma, the phenomenon of early post-treatment enlargement of the imaged tumour volume, usually without clinical deterioration, has become widely recognised. The term pseudoprogression has been used to describe a poorly understood pathophysiological process. In this review, the pathophysiological concepts, relevance, diagnosis and management of patients with 'pseudoprogression' and 'pseudoresponse' are discussed. Guidelines are given with respect to radiological imaging modality, mode and frequency. Further biological and clinical insights into these phenomena require carefully designed prospective studies.

Enhancing fraction in glioma and its relationship to the tumoral vascular microenvironment: A dynamic contrast-enhanced MR imaging study

BACKGROUND AND PURPOSE

EnF is a newly described measure of proportional tumor enhancement derived from DCE-MR imaging. The aim of this study was to assess the relationship between EnF and the more established DCE-MR imaging parameters: K(trans), v(e), and v(p).

MATERIALS AND METHODS

Forty-two patients with 43 gliomas (16 grade II, 3 grade III, and 24 grade IV) were studied. Imaging included pre- and postcontrast T1-weighted sequences through the lesion and T1-weighted DCE-MR imaging. Parametric maps of EnF, K(trans), v(e), and v(p) were generated. Voxels were classified as enhancing if the IAUC was positive (EnF(IAUC)(60>0)). A threshold of IAUC > 2.5 mmol.s was used to generate EnF(IAUC)(60>2.5). Both measures of EnF were compared with the DCE-MR imaging parameters (K(trans), v(e), and v(p)).

RESULTS

In grade II gliomas, EnF(IAUC60>0) and EnF(IAUC60>2.5) correlated with v(p) (R(2) = 0.6245, P < .0005; and R(2) = 0.4727, P = .003) but not with K(trans) or v(e). In grade IV tumors, both EnF(IAUC60>0) and EnF(IAUC60>2.5) correlated with K(trans) (R(2) = 0.3501, P = .001; and R(2) = 0.4699, P < .0005) and v(p) (R(2) = 0.1564, P = .01; and R(2) = 0.2429, P = .007), but not with v(e). Multiple regression analysis showed K(trans) as the only independent correlate of both EnF(IAUC60>0) and EnF(IAUC60>2.5) for grade IV tumors.

CONCLUSIONS

This study suggests that in grade II tumors, EnF reflects v(p) and varies due to changes in vascular density. In grade IV gliomas, EnF is affected by K(trans) with secondary associated changes in v(p).

Candidate biomarkers of extravascular extracellular space: a direct comparison of apparent diffusion coefficient and dynamic contrast-enhanced MR imaging--derived measurement of the volume of the extravascular extracellular space in glioblastoma multiforme

BACKGROUND AND PURPOSE

ADC measurements have been shown to have an inverse relationship with tumor cell density. DCE-MR imaging modeling techniques can produce a measurement of the v(e), which would also be expected to have an inverse relationship with cell density. The objective of this study was to test the hypothesis that areas of increased cellularity, and therefore low ADC, would be expected to have a small EES (low v(e)).

MATERIALS AND METHODS

Nineteen patients with GBM were recruited. All imaging was performed before surgery on a 3T MR imaging scanner. Imaging included diffusion tensor imaging, T1-weighted DCE-MR imaging, and anatomic sequences. Tumor VOIs were defined on the anatomic images and modified to contain only enhancing voxels. Parametric maps of ADC and v(e) were generated. Statistical analysis of ADC and v(e) was performed on both a voxel-by-voxel basis and comparison of median values.

RESULTS

No correlation was demonstrated between ADC and v(e) in either a voxel-by-voxel analysis or comparison of median values (P = .124).

CONCLUSIONS

This study failed to demonstrate a correlation between ADC and v(e). This is important because it suggests that though the mechanisms underlying these parameters are theoretically similar, they actually reflect different aspects of tumor microenvironment. Consequently ADC and v(e) should be considered to provide independent information about the properties of the EES.

A randomized, double-blind, placebo-controlled, phase IIIb trial (ATLAS) comparing bevacizumab (B) therapy with or without erlotinib (E) after completion of chemotherapy with B for first-line treatment of locally advanced, recurrent, or metastatic non-small cell lung cancer (NSCLC)

LBA8002

Background: B when added to chemotherapy, and E alone, each lead to improved survival in the treatment of patients (pts) with NSCLC (Sandler et al, NEJM 2006, 355:2542–2550; Shepherd et al, NEJM 2005, 353:123–132). Pre-clinical and clinical data (Herbst, J Clin Oncol 2007, 25: 4743–4750) suggest that the combination of B and E may improve the efficacy of NSCLC treatment. This potential was demonstrated in the BETA (B in combination with E compared with E alone for treatment of advanced NSCLC after failure of standard first-line chemotherapy) trial, a phase III trial in which progression free survival (PFS) was improved for patients treated with B + E (Hainsworth, Thoracic Oncol 2008, 3(11) Supp. 4:S302). Methods: The ATLAS study was designed to evaluate B + E (150 mg daily) versus B alone, following B + platin-containing doublet chemotherapy, in pts with stage IIIb/IV NSCLC. Enrolled pts were B-eligible, including pts with treated brain metastases, and pts anticoagulated with low molecular weight heparin(s). Pts with peripheral and/or extra-thoracic squamous tumors were also eligible. Pts received 4 cycles of B (15 mg/kg every 3 weeks) with chemotherapy. Pts who had not experienced disease progression (DP) or significant toxicity were then randomized to receive B + E or B + placebo (P). The primary objective of ATLAS was to compare PFS in pts receiving B + E versus B + placebo. Secondary objectives included the assessment of safety, and overall survival. A data safety monitoring committee (DSMC) monitored safety and efficacy. Results: 1,160 patients were enrolled and 768 randomized from May 2005 to May 2008. The DSMC recommended stopping the trial at the second planned interim efficacy analysis, because it met the primary endpoint. The median PFS after randomization was 4.8 mos for (B + E) vs. 3.7 mos for (B + P), HR= 0.722 (95% CI: 0.592–0.881), p = 0.0012. The safety profile for B + E was consistent with known profiles for B and E. Conclusions: E added to B treatment after chemotherapy with B significantly improves the PFS of patients treated in the first-line setting for locally advanced, recurrent, or metastatic NSCLC.

[Table: see text]

A PDA-Based ECG Beat Detector for Home Cardiac Care

Recent rapid growth in mobile computing technologies enables telemedicine applications to operate on mobile devices. Our focus is on the design of an integrated electrocardiogram (ECG) beat detector on a Personal Digital Assistant (PDA) platform for the health screening process. The ECG beat detector module will be supported by the PDA version of Personal Health Information Management System (PHIMS) and Facilitated Accurate Referral Management System (FARMS) through wireless network infrastructure as a home-based mobile cardiac monitoring solution.

Feature extraction based on mel-scaled wavelet transform for heart sound analysis

To provide a robust representation of heart sound signal in an automatic heart disease diagnosis system, a melscaled wavelet transform has been developed. It combines the advantages of linear perceptual scale by mel mapping with the suitability of analyzing non-stationary signals by wavelet transform. The heart sound signal is firstly divided into windowing frames. A set of mel-scaled filterbank is then used to calculate the mel-warped spectrum, which is followed by a wavelet transform to extract the mel-scaled wavelet features. The performance of the proposed algorithm is evaluated for heart sound analysis using clean and noisy data, and compared with the standard mel-frequency cepstral coefficients. Results show that the proposed approach provides a robust representation of heart sound signal in noisy environment.

First heart sound detection for phonocardiogram segmentation

This paper presents an algorithm for accurate and improved detection of the first heart sound S<inf>1</inf>for heart sound cardiac cycle segmentation under noisy environments. The proposed algorithm integrates an S<inf>1</inf>/S<inf>2</inf>selection step and an S<inf>1</inf>identification step. An adaptive sub-level tracking algorithm based on wavelet transform is proposed to separate the S<inf>1</inf>and S<inf>2</inf>from other components such as murmurs and noises. This is followed by a detection procedure based on Shannon energy to reject the overlapping interference so that the peaks of S<inf>1</inf>and S<inf>2</inf>can be detected. Criteria of time interval, energy and phonocardiogram (PCG) collecting position are used to identify S<inf>1</inf>with respect to the beginning of each cardiac cycle. Experimental results show that the proposed algorithm leads to an efficient segmentation of PCG cycle. Due to its simplicity and fast implementation, the method can be deployed clinically for further analysis and eventual use.

Follow-up of intracranial aneurysms treated with matrix detachable coils: a single-center experience

BACKGROUND AND PURPOSE

Matrix coils are polymer-coated bioactive coils used in treatment of intracranial aneurysms. The current study is aimed at evaluating the efficacy and safety of these coils in treatment of ruptured and unruptured aneurysms.

METHODS

Seventy-seven consecutive patients with 84 aneurysms were included in the study. Forty-six aneurysms were treated with Matrix coils alone, and 38 were treated with Matrix coils in combination with other coils/devices. Angiographic follow-up was available in 64 patients with 70 aneurysms. Length of follow-up ranged from 6 to 28 months with mean of 10 months. Both postembolization and follow-up angiograms were graded on a 3-point Raymond scale. Aneurysms were classified as stable, improved, or recanalized based on the follow-up angiograms. Recanalization was considered major if it was saccular and its size would theoretically permit retreatment with coils.

RESULTS

At the end of the initial procedure, 47 (56.0%) aneurysms showed complete occlusion (Raymond 1), 20 (23.8%) showed contrast filling the neck of the aneurysm (Raymond 2), and 16 (19.0%) showed contrast filling the sac of the aneurysm (Raymond 3). Of the 70 aneurysms in which follow-up angiograms were available, 55.7% remained stable in appearance, 20.0% showed improved occlusion, and 24.3% demonstrated recanalization; 8.6% demonstrated major recanalization. There were 2 aneurysm rebleeds (both incompletely packed); one resulted in death.

CONCLUSION

Matrix coils are safe to use and the recanalization rate of aneurysms treated with these coils appears to be at least comparable with historical studies with Guglielmi detachable coils.

Reversible delayed posthypoxic leukoencephalopathy

Hypoxic ischemic encephalopathy may cause early deep white matter abnormalities on MR imaging that usually progress to include gray matter and basal ganglia change. Toxic leukoencephalopathy due to heroin inhalation predominantly causes cerebellar and posterior cerebral radiologic change. Both conditions rarely present clinically and radiologically in a delayed manner with subsequent recovery. We report a case of reversible delayed posthypoxic/toxic leukoencephalopathy with no clinical or radiologic evidence of gray matter insult.

In-vivo measurement of brain relaxation after lobectomies

Very little data exists on the visco-elastic properties of the living human brain tissue and collection of such data is vital for mechanical modelling. The purpose of this study was to measure the rate of relaxation of brain that has been compressed by tumour after surgical decompression. Seven patients who underwent a lobectomy for an intracranial space occupying lesion were included in the study. All underwent two CT scans within the first 24 h after the surgery. Volumes of the residual void on the serial CT scan were calculated using tools in the image acquisition software. There was a rapid expansion of the brain to fill up the void space in the first 24 h after surgery. The average rate of relaxation of the compressed brain is 2.25(0.76 - 6.64) ml/h. The graphs plotted for the volume of the void space against the time after surgery when the CT scans were done can be used to further explore the dynamics of brain relaxation. The rate of brain relaxation in the first 24 h after removal of a mass lesion averages 2.25(0.76 - 6.64) ml/h in this study. Further studies using more frequent data collection would allow for more accurate definition of the rate of relaxation.

Reversible cytotoxic cerebral edema in cerebral fat embolism

We present a case of cerebral fat embolism (CFE) that demonstrated evidence of diffuse white matter cytotoxic edema on diffusion-weighted magnetic resonance imaging, in addition to punctate hyperintensities on T2-weighted and diffusion-weighted imaging. The case suggests that CFE represents a combination of occlusive arteriolar disease and secondary neurotoxicity.

The human endoplasmic reticulum molecular chaperone BiP is an autoantigen for rheumatoid arthritis and prevents the induction of experimental arthritis

Rheumatoid arthritis (RA) is the most common, crippling human autoimmune disease. Using Western blotting and tandem mass spectroscopy, we have identified the endoplasmic reticulum chaperone BiP, a 78-kDa glucose-regulated protein, as a possible autoantigen. It preferentially stimulated increased proliferation of synovial T cells from patients with RA but not from patients with other arthritides. Mice with established collagen- or pristane-induced arthritis developed IgG Abs to BiP. Although BiP injected in CFA failed to induce arthritis in several strains of rats and mice, including HLA-DR4(+/-)- and HLA-DR1(+/+)-transgenic animals, it completely inhibited the development of arthritis when given i.v. 1 wk before the injection of type II collagen arthritis. Preimmunization with BiP suppressed the development of adjuvant arthritis in Lewis rats in a similar manner. This is the first report of a mammalian chaperone that is an autoantigen in human RA and in experimental arthritis and that can also prevent the induction of experimental arthritis. These findings may stimulate the development of new immunotherapies for the treatment of RA.

In vivo resistance to corticosteroids in bronchial asthma is associated with enhanced phosyphorylation of JUN N-terminal kinase and failure of prednisolone to inhibit JUN N-terminal kinase phosphorylation

BACKGROUND

Corticosteroid-resistant (CR) asthma is associated with increased in vitro activity of the proinflammatory transcription factor activating peptide (AP)-1 in PBMCs resulting from increased c-FOS synthesis. Increased AP-1 may sequester the glucocorticoid receptor to produce a CR state. Using the tuberculin-induced inflammatory responses in the skin, we have previously demonstrated that a therapeutically effective dose of prednisolone suppressed T-cell, macrophage, and eosinophil infiltration into purified protein derivative-induced lesional skin of corticosteroid-sensitive (CS), but not CR, individuals.

OBJECTIVE

Skin biopsy specimens from a tuberculin-induced model of dermal inflammation have been evaluated for the effect of corticosteroids in regulating components of AP-1 in vivo.

METHODS

Immunohistochemical analysis of the tuberculin-mediated cutaneous response has been performed on 9 subjects with CS asthma and 6 subjects with CR asthma for the regulatory components of AP-1 before and after 9 days of either 40 mg prednisolone or placebo.

RESULTS

Significantly greater expression of c-FOS, phosphorylated c-JUN, and phosphorylated JUN N-terminal kinase (JNK) protein has been identified in CR than in CS subjects. Corticosteroids suppressed phosphorylation of c-JUN and JNK in the CS Group (P =.004 for both) but enhanced phosphorylation of c-JUN and JNK in the CR group (P =.031 for both).

CONCLUSION

Resistance to corticosteroids in asthmatic subjects may be caused, at least in part, by failure to suppress JNK phosphorylation, leading to failure to suppress c-JUN N-phosphorylation. Increased JNK may be one of the mechanisms central to the mechanism of CR asthma.

Structure/activity relationship of leukotriene B4 and its structural analogues in chemotactic, lysosomal-enzyme release and receptor-binding assays

The biological activities of chemically synthesized leukotriene B4 and eight structural analogues have been studied using chemotaxis, lysosomal-enzyme release and receptor-binding assays on human neutrophils. The results show that increasing the number of double bonds between C14 and C20, having triple bonds at C6 or C14, substitution of the primary carboxyl group at C1, changing the geometry of the double bond at C6 from the cis to trans configuration and changing the chirality of the hydroxyl group at C12 from the R to the S configuration result in substantial loss of both biological activity and the capacity to bind to the LTB4 recognition site in parallel. We suggest that the functional epitopes of 5S,12R-dihydroxy-6,14-cis-8,10-trans-icosatetraenoic acid (LTB4) are either the same, or reside in the same domain as the binding site for the LTB4 receptor. Development of LTB4 antagonists to the high-affinity LTB4 receptor, based on the structure of LTB4, is unlikely to be successful.

Effects of exogenous eicosapentaenoic acid on generation of leukotriene C4 and leukotriene C5 by calcium ionophore-activated human eosinophils in vitro

Exogenous eicosapentaenoic acid (EPA) has been compared with exogenous arachidonic acid (AA) for its ability to modulate the oxidative metabolism of membrane-derived arachidonic acid by the 5-lipoxygenase pathway in ionophore-activated human eosinophils, and for its suitability as a parallel substrate in this pathway. Products were quantitated by specific RIA and tetraene and pentaene leukotrienes (LT) were separated by reverse-phase HPLC. Eosinophils were preincubated with control buffer, exogenous EPA or AA and stimulated optimally with 10 microM calcium ionophore (A23187) for 15 min. Mean generation of LTC4 in the absence of fatty acid was 6.0 = 1.1 ng/10(6) eosinophils (mean = SEM, n = 5). In the presence of EPA, the amount of LTC4 generated rose to peak at 16.5 +/- 1.9 ng/10(6) eosinophils at 10 micrograms/ml EPA and then fell to 8.3 +/- 3.1 ng/10(6) cells at 40 micrograms/ml EPA. The EPA derivative, LTC5 was first detectable at 5 micrograms/ml EPA with 4.8 +/- 1.2 ng/10(6) cells and gradually rose with increasing dose of EPA to be maximal at 40 micrograms/ml with 12.7 +/- 2.2 ng/10(6) cells. Identity of the LTC5 was confirmed by an identical retention time to synthetic LTC5 standard, immunoreactivity to a specific antibody against LTC4 and LTC5 and a typical UV absorbance spectrum. When eosinophils were preincubated with AA and similarly stimulated, LTC4 generation gradually increased from a baseline of 6.7 +/- 0.7 ng/10(6) cells in the absence of fatty acid to reach a maximum of 12.9 +/- 0.8 ng/10(6) cells at 40 micrograms/ml of AA. Total LTC generation was nearly twofold more with cells incubated with EPA than with cells incubated with AA (p &lt; 0.05). Thus, EPA does not suppress LTC generation from eosinophils but stimulates it at lower doses and is a substrate for LTC5 generation.

Effects of exogenous eicosapentaenoic acid on generation of leukotriene C4 and leukotriene C5 by calcium ionophore-activated human eosinophils in vitro

Exogenous eicosapentaenoic acid (EPA) has been compared with exogenous arachidonic acid (AA) for its ability to modulate the oxidative metabolism of membrane-derived arachidonic acid by the 5-lipoxygenase pathway in ionophore-activated human eosinophils, and for its suitability as a parallel substrate in this pathway. Products were quantitated by specific RIA and tetraene and pentaene leukotrienes (LT) were separated by reverse-phase HPLC. Eosinophils were preincubated with control buffer, exogenous EPA or AA and stimulated optimally with 10 microM calcium ionophore (A23187) for 15 min. Mean generation of LTC4 in the absence of fatty acid was 6.0 = 1.1 ng/10(6) eosinophils (mean = SEM, n = 5). In the presence of EPA, the amount of LTC4 generated rose to peak at 16.5 +/- 1.9 ng/10(6) eosinophils at 10 micrograms/ml EPA and then fell to 8.3 +/- 3.1 ng/10(6) cells at 40 micrograms/ml EPA. The EPA derivative, LTC5 was first detectable at 5 micrograms/ml EPA with 4.8 +/- 1.2 ng/10(6) cells and gradually rose with increasing dose of EPA to be maximal at 40 micrograms/ml with 12.7 +/- 2.2 ng/10(6) cells. Identity of the LTC5 was confirmed by an identical retention time to synthetic LTC5 standard, immunoreactivity to a specific antibody against LTC4 and LTC5 and a typical UV absorbance spectrum. When eosinophils were preincubated with AA and similarly stimulated, LTC4 generation gradually increased from a baseline of 6.7 +/- 0.7 ng/10(6) cells in the absence of fatty acid to reach a maximum of 12.9 +/- 0.8 ng/10(6) cells at 40 micrograms/ml of AA. Total LTC generation was nearly twofold more with cells incubated with EPA than with cells incubated with AA (p < 0.05). Thus, EPA does not suppress LTC generation from eosinophils but stimulates it at lower doses and is a substrate for LTC5 generation.

Cutaneous histamine metabolism in chronic urticaria

Impaired metabolism of histamine in the skin of patients with chronic idiopathic urticaria (CIU) might explain the observed enhanced and prolonged skin responses to intradermal histamine. Histamine metabolism was measured in homogenates from unaffected forearm skin in nine patients with CIU and in skin of age- and sex-matched control subjects with a radiochromatographic assay, and the results are expressed as nanograms of histamine metabolized per milligram of protein per hour. Endogenous histamine content was determined by RIA. There was a highly significant increase in endogenous histamine content in the skin of patients with urticaria (407.8 +/- 188.3 ng/mg of protein) compared with that in skin of control subjects (240.0 +/- 73.0 ng/mg of protein) (mean +/- 1 SD; p less than 0.02), which suggests either an increase in mast cell number or histamine concentration per cell. No significant difference was observed in the metabolism of histamine between patient and control group; therefore, an alternative mechanism may underlie differences in skin reactivity to histamine.