PET/MRI of hypoxia and vascular function in ER-positive breast cancer: correlations with immunohistochemistry

OBJECTIVES

To explore the relationship between indices of hypoxia and vascular function from 18F-fluoromisonidazole ([18F]-FMISO)-PET/MRI with immunohistochemical markers of hypoxia and vascularity in oestrogen receptor-positive (ER +) breast cancer.

METHODS

Women aged  > 18 years with biopsy-confirmed, treatment-naïve primary ER + breast cancer underwent [18F]-FMISO-PET/MRI prior to surgery. Parameters of vascular function were derived from DCE-MRI using the extended Tofts model, whilst hypoxia was assessed using the [18F]-FMISO influx rate constant, Ki. Histological tumour sections were stained with CD31, hypoxia-inducible factor (HIF)-1α, and carbonic anhydrase IX (CAIX). The number of tumour microvessels, median vessel diameter, and microvessel density (MVD) were obtained from CD31 immunohistochemistry. HIF-1α and CAIX expression were assessed using histoscores obtained by multiplying the percentage of positive cells stained by the staining intensity. Regression analysis was used to study associations between imaging and immunohistochemistry variables.

RESULTS

Of the lesions examined, 14/22 (64%) were ductal cancers, grade 2 or 3 (19/22; 86%), with 17/22 (77%) HER2-negative. [18F]-FMISO Ki associated negatively with vessel diameter (p = 0.03), MVD (p = 0.02), and CAIX expression (p = 0.002), whilst no significant relationships were found between DCE-MRI pharmacokinetic parameters and immunohistochemical variables. HIF-1α did not significantly associate with any PET/MR imaging indices.

CONCLUSION

Hypoxia measured by [18F]-FMISO-PET was associated with increased CAIX expression, low MVD, and smaller vessel diameters in ER + breast cancer, further corroborating the link between inadequate vascularity and hypoxia in ER + breast cancer.

KEY POINTS

• Hypoxia, measured by [18F]-FMISO-PET, was associated with low microvessel density and small vessel diameters, corroborating the link between inadequate vascularity and hypoxia in ER + breast cancer. • Increased CAIX expression was associated with higher levels of hypoxia measured by [18F]-FMISO-PET. • Morphologic and functional abnormalities of the tumour microvasculature are the major determinants of hypoxia in cancers and support the previously reported perfusion-driven character of hypoxia in breast carcinomas.

The potential of hyperpolarised 13C-MRI to target glycolytic tumour core in prostate cancer

Hyperpolarised [1-13C]pyruvate MRI (HP-13C-MRI) is an emerging metabolic imaging technique that has shown promise for evaluating prostate cancer (PCa) aggressiveness. Accurate tumour delineation on HP-13C-MRI is vital for quantitative assessment of the underlying tissue metabolism. However, there is no consensus on the optimum method for segmenting HP-13C-MRI, and whole-mount pathology (WMP) as the histopathological gold-standard is only available for surgical patients. Although proton MRI can be used for tumour delineation, this approach significantly underestimates tumour volume, and metabolic tumour segmentation based on HP-13C-MRI could provide an important functional metric of tumour volume. In this study, we quantified metabolism using HP-13C-MRI and segmentation approaches based on WMP maps, 1H-MRI-derived T2-weighted imaging (T2WI), and HP-13C-MRI-derived total carbon signal-to-noise ratio maps (TC-SNR) with an SNR threshold of 5.0. 13C-labelled pyruvate SNR, lactate SNR, TC-SNR, and the pyruvate-to-lactate exchange rate constant (kPL) were significantly higher when measured using the TC-SNR-guided approach, which also corresponded to a significantly higher tumour epithelial expression on RNAscope imaging of the enzyme catalysing pyruvate-to-lactate metabolism (lactate dehydrogenase (LDH)). However, linear regression and Bland-Altman analyses demonstrated a strong linear relationship between all three segmentation approaches, which correlated significantly with RNA-scope-derived epithelial LDH expression. These results suggest that standard-of-care T2WI and TC-SNR maps could be used as clinical reference tools for segmenting localised PCa on HP-13C-MRI in the absence of the WMP gold standard. The TC-SNR-guided approach could be used clinically to target biopsies towards highly glycolytic tumour areas and therefore to sample aggressive disease with higher precision. KEY POINTS: • T2WI- and TC-SNR-guided segmentations can be used in all PCa patients and do not explicitly require WMP maps. • Agreement between the three segmentation approaches is biologically validated by their strong relationship with epithelial LDH mRNA expression. • The TC-SNR-guided approach can potentially be used to identify occult disease on 1H-MRI and target the most glycolytically active regions.

POS0468 EXTRACELLULAR VESICLES FROM SERUM OF MYOSITIS PATIENTS AS CIRCULATING BIOMARKERS AND DISEASE MEDIATORS

Background

Inflammatory myopathies (IM) are a heterogeneous group of disorders characterized by autoimmune inflammatory destruction of skeletal muscles. It is many times associated with lung, skin and joint involvement. Identifying biomarkers that can differentiate IM from other muscle disorders may elucidate the pathophysiology of IM, guide novel therapies, monitor disease activity/response to treatments and predict prognosis. Exosomes are membrane-bound nanovesicles with diameters of 30-150 nm that contain multiple proteins, nucleic acid, lipids and other molecules in a tissue- and cell-specific manner. Exosomes are secreted by a large variety of cells, play major roles in cell-cell interactions, and have recently emerged as circulating biomarkers in a variety of pathological conditions, including several autoimmune diseases.

Objectives

To characterize exosomes from serum of IM patients, analyze protein expression and study their potential mediators of disease pathologies.

Methods

Serum was collected from patients suffering from IM(n=5) and from patients suffering from Becker (BMD) and Duchenne (DMD) muscular dystrophies (n=6). Exosomes were isolated by Exoquick precipitation and analyzed for size distribution and by nanoparticle tracking analysis (NTA) and by Western blot for exosome markers. The effects of the isolated EVs on human satellite cell proliferation and differentiation and macrophage activation were examined.

Results

Exosomes from IM patients decreased human satellite cell proliferation (51%, P<0.01) and inhibited their myogenic differentiation as indicated by lower fusion index (24% inhibition, P<0.01) and expression of myosin heavy chain (72% inhibition, P<0.001). Similar results were obtained also with exosomes derived from DMD and BMD patients; however, their inhibitory effect were more pronounced on MyoG expression. Treatment of macrophages with exosomes from IM patients significantly increased the expression of IL-10 (3-fold, P<0.001), compared to exosomes of healthy controls and DMD patients. Another significant difference was in the expression of signaling molecules: Thus, exosomes from BMD patients increased the phosphorylation of Erk and p38, whereas a smaller effect was induced by IM exosomes.

Conclusion

Exosomes from IM patients decrease satellite cell proliferation and myogenic differentiation compared to healthy exosomes. In addition, these exosomes increased the expression of IL-10 in macrophages. These effects are unique to exosomes of IM patients compared to muscular dystrophies. These promising results suggest that serum exosomes should be further investigated as a novel biomarker with potential therapeutic implications.

Disclosure of Interests

Shaye Kivity Speakers bureau: BI, Abbvie, Lilly, Pfizer, Janssen, Neopharm, Grant/research support from: Sobi, Haya Kravitz: None declared, Coral Cohen: None declared, Darya Margoulis: None declared, Moshe Amar: None declared, Gila Kazimirsky: None declared, David Ozeri Speakers bureau: Neopharm, Consultant of: Abbvie, Amir Dori Grant/research support from: Biogen, Chaya Brodie Grant/research support from: Biogen.

Divinylpyrimidine reagents generate antibody-drug conjugates with excellent in vivo efficacy and tolerability

The development of divinylpyrimidine (DVP) reagents for the synthesis of antibody-drug conjugates (ADCs) with in vivo efficacy and tolerability is reported. Detailed structural characterisation of the synthesised ADCs was first conducted followed by in vitro and in vivo evaluation of the ADCs' ability to safely and selectively eradicate target-positive tumours.

Psychiatric and psycho-social characteristics of suicide completers: a 13-year comprehensive evaluation of psychiatric case records and post-mortem findings

Currently, there are limited data comparing demographic and clinical characteristics of individuals who died by probable suicide and who did and did not previously attend mental health services (MHSs). This study compared demographic and clinical factors for both groups, in a Western region of Ireland over a 13-year period. Postmortem reports between January 1, 2006 and March 31, 2019 were reviewed for 400 individuals who died by probable suicide. Relevant sociodemographic and clinical data were extracted from individuals’ lifetime case notes. One hundred and fifty nine individuals (40%) had attended MHSs at some stage (“attendee”). Hanging was the most common method of suicide (61%), followed by drowning (18%) for both attendees and nonattendees of MHSs, with more violent methods utilized overall by nonattendees (p = 0.028). Sixty-eight percent of individuals who previously attempted hanging subsequently died utilizing this method. A higher proportion of attendees were female compared to nonattendees of MHSs (28.9 vs. 14.5%, p = 0.001). Recurrent depressive disorder (55%) was the most common diagnosed mental health disorder. For individuals with a diagnosis of schizophrenia, 39% had antipsychotic medications detectable in their toxicology reports. In conclusion, the majority of people who died by probable suicide had never had contact with MHSs, and nonattendees overall were more likely to utilize violent methods of suicide. Nonconcordance with psychotropic medications in psychotic patients and previous hanging attempt were highlighted as potential risk factors for death by probable suicide.

Hyperpolarised 13C-MRI identifies the emergence of a glycolytic cell population within intermediate-risk human prostate cancer

Hyperpolarised magnetic resonance imaging (HP 13C-MRI) is an emerging clinical technique to detect [1-13C]lactate production in prostate cancer (PCa) following intravenous injection of hyperpolarised [1-13C]pyruvate. Here we differentiate clinically significant PCa from indolent disease in a low/intermediate-risk population by correlating [1-13C]lactate labelling on MRI with the percentage of Gleason pattern 4 (%GP4) disease. Using immunohistochemistry and spatial transcriptomics, we show that HP 13C-MRI predominantly measures metabolism in the epithelial compartment of the tumour, rather than the stroma. MRI-derived tumour [1-13C]lactate labelling correlated with epithelial mRNA expression of the enzyme lactate dehydrogenase (LDHA and LDHB combined), and the ratio of lactate transporter expression between the epithelial and stromal compartments (epithelium-to-stroma MCT4). We observe similar changes in MCT4, LDHA, and LDHB between tumours with primary Gleason patterns 3 and 4 in an independent TCGA cohort. Therefore, HP 13C-MRI can metabolically phenotype clinically significant disease based on underlying metabolic differences in the epithelial and stromal tumour compartments.

Does Mode of Surgical Intervention Based on Oncotype DX Score Influence Disease Recurrence in Early Breast Cancer?

Introduction  Routine utilization of multigene assays to inform operative decision-making in early breast cancer (EBC) treatment is yet to be established. In this pilot study, we sought to establish the potential benefits of surgical intervention in EBC based on recurrence risk quantification using the Oncotype DX (ODX) assay.

Materials and Methods  Consecutive ODX tests performed over a 9-year period from October 2007 to May 2016 were evaluated. Oncotype scores were classified into high (≥31), medium (18–30), or low-risk (0–17) groups. The primary outcome was breast cancer recurrence. Subgroup analysis offered assessment of the recurrence effect of mode of surgical intervention for patient groups as defined by the oncotype score.

Results  In total 361 patients underwent ODX testing. The mean age and follow-up were 55.25 (± 10.58) years and 38.59 (± 29.1) months, respectively. The majority of patients underwent wide local excision (86.7%) with 8.9 and 4.4% patients having a mastectomy or wide local excision with completion mastectomy, respectively. Fifty-one percent of patients fell into the low risk ODX category with a further 40.2 and 8.5% deemed to be of intermediate and high risk. Five patients (1.38%) had disease recurrence. Comparative analysis of operative groups in each oncotype group revealed no difference in recurrence scores in the low- ( p  = 0.84) and high-risk groups ( p  = 0.92) with a statistically significant difference identified in the intermediate risk group ( p  = 0.002).

Conclusion  To date we have been unable to definitively identify a role for ODX in guiding surgical approach in EBC. There is, however, a need for larger studies to examine this hypothesis.

Author Correction: ARID1A influences HDAC1/BRD4 activity, intrinsic proliferative capacity and breast cancer treatment response

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

ARID1A influences HDAC1/BRD4 activity, intrinsic proliferative capacity and breast cancer treatment response

Using genome-wide clustered regularly interspaced short palindromic repeats (CRISPR) screens to understand endocrine drug resistance, we discovered ARID1A and other SWI/SNF complex components as the factors most critically required for response to two classes of estrogen receptor-alpha (ER) antagonists. In this context, SWI/SNF-specific gene deletion resulted in drug resistance. Unexpectedly, ARID1A was also the top candidate in regard to response to the bromodomain and extraterminal domain inhibitor JQ1, but in the opposite direction, with loss of ARID1A sensitizing breast cancer cells to bromodomain and extraterminal domain inhibition. We show that ARID1A is a repressor that binds chromatin at ER cis-regulatory elements. However, ARID1A elicits repressive activity in an enhancer-specific, but forkhead box A1-dependent and active, ER-independent manner. Deletion of ARID1A resulted in loss of histone deacetylase 1 binding, increased histone 4 lysine acetylation and subsequent BRD4-driven transcription and growth. ARID1A mutations are more frequent in treatment-resistant disease, and our findings provide mechanistic insight into this process while revealing rational treatment strategies for these patients.

Overcoming Autofluorescence (AF) and Tissue Variation in Image Analysis of In Situ Hybridization

Fluorescent detection of nucleic acid sequences such as DNA or RNA allows for multiplexing and visualization of an increased number of targets compared with chromogenic methods. This is due to the number of chromogens available as well as the ability of image analysis software platforms to distinguish between colors. Autofluorescence (AF) can be problematic during fluorescent imaging because the AF interferes with the detection of the specific fluorescent signals especially when the target signals are weak. AF has a broad emission spectrum leading to difficulty when performing image analysis due to masking of the specific signal across multiple wavelengths. Tissue sample variation can also affect levels of AF. In this chapter we share a method for overcoming the issues caused by sample variation and AF using HALO software on RNAscope in situ hybridization images.

Determination of Ochratoxin A in Currants, Raisins, Sultanas, Mixed Dried Fruit, and Dried Figs by Immunoaffinity Column Cleanup with Liquid Chromatography: Interlaboratory Study

An interlaboratory study was performed on behalf of the Food Standards Agency to evaluate the effectiveness of an affinity column cleanup liquid chromatographic (LC) method for the determination of ochratoxin A in a variety of dried fruit at European regulatory limits. To ensure homogeneity before analysis, laboratory samples are normally slurried with water in the ratio of 5 parts fruit to 4 parts water, and test materials in this form were used in the study. The test portion was extracted with acidified methanol. The extract was filtered, diluted with phosphate-buffered saline, and applied to an affinity column. The column was washed and ochratoxin A was eluted with methanol. Ochratoxin A was quantified by reversed-phase LC. The use of post-column pH shift to enhance the fluorescence of ochratoxin A by the addition of 1.1M ammonia solution to the column eluant is optional. Determination was by fluorescence. Currants, sultanas, raisins, figs, and mixed fruit (comprising dried pineapple, papaya, sultanas, prunes, dates, and banana chips), both naturally contaminated and blank (very low level), were sent to 24 collaborators in 7 European countries. Participants were asked to spike test portions of all test samples at a level equivalent to 5 ng/g ochra toxin A. Average recoveries ranged from 69 to 74%. Based on results for 5 naturally contaminated test samples (blind duplicates) the relative standard deviation for repeatability (RSDr) ranged from 4.9 to 8.7%, and the relative standard deviation for reproducibility (RSDR)rangedfrom14to28%. The method showed acceptable within-and be-tween-laboratory precision for all 5 matrixes, as evidenced by HORRAT values &lt;1.3.

Diffusion kurtosis MRI as a predictive biomarker of response to neoadjuvant chemotherapy in high grade serous ovarian cancer

This study assessed the feasibility of using diffusion kurtosis imaging (DKI) as a measure of tissue heterogeneity and proliferation to predict the response of high grade serous ovarian cancer (HGSOC) to neoadjuvant chemotherapy (NACT). Seventeen patients with HGSOC were imaged at 3 T and had biopsy samples taken prior to any treatment. The patients were divided into two groups: responders and non-responders based on Response Evaluation Criteria In Solid Tumours (RECIST) criteria. The following imaging metrics were calculated: apparent diffusion coefficient (ADC), apparent diffusion (Dapp) and apparent kurtosis (Kapp). Tumour cellularity and proliferation were quantified using histology and Ki-67 immunohistochemistry. Mean Kapp before therapy was higher in responders compared to non-responders: 0.69 ± 0.13 versus 0.51 ± 0.11 respectively, P = 0.02. Tumour cellularity correlated positively with Kapp (rho = 0.50, P = 0.04) and negatively with both ADC (rho = -0.72, P = 0.001) and Dapp (rho = -0.80, P < 0.001). Ki-67 expression correlated with Kapp (rho = 0.53, P = 0.03) but not with ADC or Dapp. In conclusion, Kapp was found to be a potential predictive biomarker of NACT response in HGSOC, which suggests that DKI is a promising clinical tool for use oncology and radiology that should be evaluated further in future larger studies.

Insulin increases H2O2-induced pancreatic beta cell death

Insulin resistance results, in part, from impaired insulin signaling in insulin target tissues. Consequently, increased levels of insulin are necessary to control plasma glucose levels. The effects of elevated insulin levels on pancreatic beta (β) cell function, however, are unclear. In this study, we investigated the possibility that insulin may influence survival of pancreatic β cells. Studies were conducted on RINm, RINm5F and Min-6 pancreatic β-cells. Cell death was induced by treatment with H(2)O(2), and was estimated by measurements of LDH levels, viability assay (Cell-Titer Blue), propidium iodide staining and FACS analysis, and mitochondrial membrane potential (JC-1). In addition, levels of cleaved caspase-3 and caspase activity were determined. Treatment with H(2)O(2) increased cell death; this effect was increased by simultaneous treatment of cells with insulin. Insulin treatment alone caused a slight increase in cell death. Inhibition of caspase-3 reduced the effect of insulin to increase H(2)O(2)-induced cell death. Insulin increased ROS production by pancreatic β cells and increased the effect of H(2)O(2). These effects were increased by inhibition of IR signaling, indicative of an effect independent of the IR cascade. We conclude that elevated levels of insulin may act to exacerbate cell death induced by H(2)O(2) and, perhaps, other inducers of apoptosis.

Clinicopathological significance of Borderline Nuclear Change - High Grade Dyskaryosis Not Excluded

During a recent discussion on classification of cervical cytology, the introduction of a 'Borderline Nuclear Change - High Grade Dyskaryosis Not Excluded' (BNCH) category was proposed. BNCH cases diagnosed prospectively were retrieved from laboratory records. Questionnaires were sent to referring practitioners regarding clinicopathological outcome. Cytopathological features resulting in the BNCH classification were recorded on slide review. A total of 103 reports on conventional cervical smears diagnosed as BNCH from 1999 to 2002 were retrieved, comprising 0.096% of 107 634 smears. Of 86/103 cases with clinical follow-up, CIN2 or worse was present in 30 (35%); 15 (17%) showed a borderline/low-grade abnormality and 41 (48%) were negative. No individual cytopathological feature was predictive of high-grade disease on follow-up. The yield of high-grade abnormalities on follow-up of BNCH supports the introduction of this terminology.

Regulation of cell apoptosis by protein kinase c delta

The isoforms of the PKC family are activated in response to mitogenic stimuli, to inflammatory stimuli, and to stress and play important roles in a variety of cellular functions including apoptosis. PKCdelta a member of the novel PKC subfamily, is actively involved in cell apoptosis in a stimulus and tissue specific manner; it both regulates the expression and function of apoptotic related proteins and is itself a target for caspases. Activation of PKCdelta by various apoptotic stimuli results in the translocation of PKCdelta to distinct cellular compartments such as mitochondria, golgi and nucleus, and the differential translocation contributes to its different effects. In addition, phosphorylation of PKCdelta on distinct tyrosine residues and its association with specific apoptotic related proteins such as c-Abl, DNA-PK, p73 and lamin B are pivotal to its function in cell apoptosis. Recent findings on these aspects of the PKCdelta cascades are the major focus of this review.

vFLIP protects PC-12 cells from apoptosis induced by Sindbis virus: implications for the role of TNF-alpha

Sindbis virus (SV) is an alphavirus used as a model for studying the pathogenesis of viral encephalitis. In this study we examined the effects and the mechanisms involved in the apoptosis induced by SV in PC-12 cells, and the role of a vFLIP in this process. Infection of PC-12 cells with a neurovirulent strain of SV, SVNI, induced cell apoptosis. Overexpression of vFLIP encoded by the HHV-8 or treatment with a caspase-8 inhibitor inhibited cell apoptosis. SVNI induced an increase in the expression of tumor necrosis factor alpha (TNF-alpha), and pre-treatment of the cells with an anti-TNF-alpha blocking antibody or with soluble TNF-alpha receptor abrogated the apoptotic effect of SVNI. Moreover, TNF-alpha R1 knockout mice were more resistant to the cytopathic effects of the virus as compared to control animals. Our results indicate that the apoptosis induced by SVNI is mediated by activation of caspase-8, and that TNF-alpha plays an important role in the apoptotic response.

Anaplastic and atypical meningiomas express high levels of Fas and undergo apoptosis in response to Fas ligation

In this study we characterized the expression of Fas and Fas ligand in different types of meningiomas and examined the effect of Fas ligation on the death of meningioma cells in culture. Using Western blot analysis, we found that extracts derived from anaplastic and atypical meningiomas expressed high levels of Fas, whereas benign meningiomas did not express detectable levels of this protein. All of the meningiomas examined expressed low levels of Fas ligand. Cultures of anaplastic meningiomas also expressed Fas and treatment of these cells with anti-Fas antibody induced cell death. The results of this study indicate that Fas is preferentially expressed in atypical and anaplastic meningiomas and suggest that it is involved in the increased apoptosis observed in these tumors.

Nerve growth factor regulates TNF-alpha production in mouse macrophages via MAP kinase activation

In this study, we examined the expression of nerve growth factor (NGF) and its receptors in mouse macrophages and the mechanisms involved in the effect of NGF on tumor necrosis factor (TNF)-alpha production. Macrophages expressed NGF and the NGF receptors TrkA and p75. Treatment of J744 cells or peritoneal macrophages with NGF induced a large increase in the production of TNF-alpha. In addition, NGF induced the secretion of nitric oxide in interferon-gamma-treated J774 cells or lipopolysaccharide-treated peritoneal macrophages. The induction of TNF-alpha production by NGF was blocked by K252a, an inhibitor of the TrkA receptor. NGF induced phosphorylation and activation of extracellular signal-regulated kinase, Erk1/Erk2 and c-Jun amino-terminal kinase, whereas it did not induce phosphorylation of p38 mitogen-activated protein kinase. Inhibition of the MAP kinase-Erk kinase pathway with PD 098059 decreased the secretion of TNF-alpha by NGF. Our results suggest that NGF has an important role in the activation of macrophages during inflammatory responses via activation of mitogen-activated protein kinases.

Protein kinase Calpha and protein kinase Cdelta play opposite roles in the proliferation and apoptosis of glioma cells

Protein kinase C (PKC) has been implicated in the proliferation and apoptosis of glial tumors, but the role of specific PKC isoforms remains unresolved. Comparing brain tumors differing in degree of malignancy, we found that malignant gliomas expressed higher levels of PKCalpha and lower levels of PKCdelta as compared with low-grade astrocytomas. Consistent with a mechanistic role for these differences, overexpression of PKCalpha in the human U87 glioma cell line resulted in enhanced cell proliferation and decreased glial fibrillary acidic protein (GFAP) expression as compared with controls. Reciprocally, overexpression of PKCdelta inhibited cell proliferation and enhanced GFAP expression. Using PKC chimeras, we found that the regulatory domains of PKCalpha and PKCdelta mediated their effects on cell proliferation and GFAP expression. PKCalpha and delta have been implicated as potential signaling molecules in apoptosis. Therefore, we examined the role of these isoforms in the resistance of glioma cells to apoptotic stimuli. In U87 cells, manipulation of PKCalpha levels had little effect on apoptosis in response to etoposide. In contrast, overexpression of PKCdelta rendered the U87 cells more sensitive to the apoptotic effect of etoposide, and PKCdelta was cleaved in these cells by a caspase-dependent process. Furthermore, the glioma cell line U373, which expresses endogenous PKCdelta, underwent apoptosis in response to etoposide, and the apoptotic response was blocked by the PKCdelta inhibitor rottlerin. Our results suggest that PKCalpha and PKCdelta play opposite roles in the proliferation and apoptosis of glioma cells.

Macrophages express neurotrophins and neurotrophin receptors. Regulation of nitric oxide production by NT-3

In this study we examined the expression of neurotrophins and their receptors in mouse macrophages and the effects of the neurotrophins on nitric oxide secretion. Macrophages expressed TrkB and TrkC but not BDNF, NT-3 or NT-4. LPS induced up-regulation of TrkB and TrkC and of BDNF and NT-3 expression. Treatment of macrophages with NT-3 increased the secretion of nitric oxide in LPS-treated macrophages and this increase was blocked by K252a, a Trk kinase inhibitor. In contrast, BDNF and NT-4 had no significant effects on the induction of nitric oxide. Our results suggest that NT-3 play important roles in the function of macrophages during inflammatory responses and in tissue repair.

Phosphorylation of protein kinase Cdelta on distinct tyrosine residues regulates specific cellular functions

Protein kinase Cdelta (PKCdelta) inhibits proliferation and decreases expression of the differentiation marker glutamine synthetase (GS) in C6 glioma cells. Here, we report that distinct, specific tyrosine residues on PKCdelta are involved in these two responses. Transfection of cells with PKCdelta mutated at tyrosine 155 to phenylalanine caused enhanced proliferation in response to 12-phorbol 12-myristate 13-acetate, whereas GS expression resembled that for the PKCdelta wild-type transfectant. Conversely, transfection with PKCdelta mutated at tyrosine 187 to phenylalanine resulted in increased expression of GS, whereas the rate of proliferation resembled that of the PKCdelta wild-type transfectant. The tyrosine phosphorylation of PKCdelta and the decrease in GS expression induced by platelet-derived growth factor (PDGF) were abolished by the Src kinase inhibitors PP1 and PP2. In response to PDGF, Fyn associated with PKCdelta via tyrosine 187. Finally, overexpression of dominant negative Fyn abrogated the decrease in GS expression and reduced the tyrosine phosphorylation of PKCdelta induced by PDGF. We conclude that the tyrosine phosphorylation of PKCdelta and its association with tyrosine kinases may be an important point of divergence in PKC signaling.

Differential regulation of Bcl-2 and Bax expression in cells infected with virulent and nonvirulent strains of sindbis virus

Sindbis virus is an alphavirus that infects cells in either lytic or persistent infection. In this study we examined the effects of Sindbis virus on cell apoptosis and on the expression of Bcl-2 and Bax. Of the two strains studied, SVA and SVNI, only the neurovirulent strain, SVNI, induced apoptosis of astrocytes and PC-12 cells. SVA, which infects cells in a persistent manner, induced up-regulation of bcl-2 mRNA and Bcl-2 protein, whereas SVNI induced an increase in Bax levels. Our results indicate a differential regulation of Bcl2 and Bax expression by SVA and SVNI, which may be associated with the apoptotic potential of the viruses.

Threonine phosphorylation diverts internalized epidermal growth factor receptors from a degradative pathway to the recycling endosome

Transregulation of the epidermal growth factor receptor (EGFR) by protein kinase C (PKC) serves as a model for heterologous desensitization of receptor tyrosine kinases, but the underlying mechanism remained unknown. By using c-Cbl-induced ubiquitination of EGFR as a marker for transfer from early to late endosomes, we provide evidence that PKC can inhibit this process. In parallel, receptor down-regulation and degradation are significantly reduced. The inhibitory effects of PKC are mediated by a single threonine residue (threonine 654) of EGFR, which serves as a major PKC phosphorylation site. Biochemical and morphological analyses indicate that threonine-phosphorylated EGFR molecules undergo normal internalization, but instead of sorting to lysosomal degradation, they recycle back to the cell surface. In conclusion, by sorting EGFR to the recycling endosome, heterologous desensitization restrains ligand-induced down-regulation of EGFR.

Differential regulation of neurotrophin expression by mitogens and neurotransmitters in mouse lymphocytes

In this study, we examined the expression of neurotrophins in mouse lymphocytes and the regulation of their expression by mitogens and neurotransmitters. We found that mixed splenocytes as well as T and B lymphocytes expressed mRNA for all the neurotrophins examined. Differential regulation of the neurotrophins was obtained upon stimulation of the cells. Thus, LPS increased the expression of NGF, BDNF and NT-3 in splenocytes and B cells, whereas Con-A increased the mRNA of NT-3 and NT-4 in T cells and NGF expression in splenocytes. The neurotransmitter substance P and the beta-adrenergic agonist, isoproterenol induced an increase in the expression of NGF. Our results suggest an important role for the different neurotrophins in the function of the immune system and point to a bi-directional interaction between neurotrophins and neurotransmitters in this system.

A single nucleotide change in the 5' noncoding region of Sindbis virus confers neurovirulence in rats

Two pairs of Sindbis virus (SV) variants that differ in their neuroinvasive and neurovirulent traits in mice have been isolated. Recently, we mapped the genetic determinants responsible for neuroinvasiveness in weanling mice. Here, we extend this study to newborn and adult rats and to rat neuronal cultures. Remarkably, certain aspects of the pathogenesis of these strains in rats were found to be quite distinct from the mouse model. Suckling rats were susceptible to all four isolates, and replication in the brain was observed after both intraperitoneal and intracranial (i.c.) inoculation. None of the isolates was neuroinvasive in adult rats, although all replicated after i.c. inoculation. For the isolate pair that was highly neurovirulent in mice, SVN and SVNI, only SVNI caused death after i.c. inoculation of adult rats. Similarly, only SVNI was cytotoxic for primary cultures of mature neurons. The genetic determinants responsible for the pathogenic properties of SVNI were mapped to the E2 glycoprotein and the 5' noncoding region (5'NCR). Substitution of two amino acids in SVN E2 with the corresponding residues of SVNI (Met-190 and Lys-260) led to paralysis in 3- and 5-week-old rats. More dramatically, a single substitution in the 5'NCR of SVN (G at position 8) transformed the virus into a lethal pathogen for 3-week-old rats like SVNI. In 5-week-old rats, however, this recombinant was attenuated relative to SVNI by 2 orders of magnitude. Combination of the E2 and 5'NCR determinants resulted in a recombinant with virulence properties indistinguishable from those of SVNI. These data indicate that the 5'NCR and E2 play an instrumental role in determining the age-dependent pathogenic properties of SV in rats.

Discoordinate regulation of different K channels in cultured rat skeletal muscle by nerve growth factor

We investigated the effects of nerve growth factor (NGF) on expression of K+ channels in cultured skeletal muscle. The channels studied were (1) charybdotoxin (ChTx)-sensitive channels by using a polyclonal antibody raised in rabbits against ChTx, (2) Kv1.5 voltage-sensitive channels, and (3) apamin-sensitive (afterhyperpolarization) channels. Crude homogenates were prepared from cultures made from limb muscles of 1-2-day-old rat pups for identification of ChTx-sensitive and Kv1.5 channels by Western blotting techniques. Apamin-sensitive K+ channels were studied by measurement of specific [125I]-apamin binding by whole cell preparations. ChTx-sensitive channels display a fusion-related increase in expression, and NGF downregulates these channels in both myoblasts and myotubes. Voltage-dependent Kv1.5 channel expression is low in myoblasts and increases dramatically with fusion; NGF induces early expression of these channels and causes expression after fusion to increase even further. NGF downregulates apamin-sensitive channels. NGF increases the rate of fall of the action potential recorded intracellularly from single myotubes with intracellular microelectrodes. The results confirm and extend those of previous studies in showing a functional role for NGF in the regulation of membrane properties of skeletal muscle. Moreover, the findings demonstrate that the different K+ channels in this preparation are regulated in a discoordinate manner. The divergent effects of NGF on expression of different K+ channels, however, do not appear sufficient to explain the NGF-induced increase in the rate of fall of the action potential. The changes during the falling phase may rather be due to increases in channel properties or may result from an increased driving force on the membrane potential secondary to the NGF-induced hyperpolarization.

Protein kinase C-epsilon plays a role in neurite outgrowth in response to epidermal growth factor and nerve growth factor in PC12 cells

In this study, we examined the role of specific protein kinase C (PKC) isoforms in the differentiation of PC12 cells in response to nerve growth factor (NGF) and epidermal growth factor (EGF). PC12 cells express PKC-alpha, -beta, -gamma, -delta, -epsilon, -mu, and -zeta. For PKC-delta, -epsilon, and -zeta, NGF and EGF exerted differential effects on translocation. Unlike overexpression of PKC-alpha and -delta, overexpression of PKC-epsilon caused enhanced neurite outgrowth in response to NGF. In the PKC-epsilon-overexpressing cells, EGF also dramatically induced neurite outgrowth, arrested cell proliferation, and induced a sustained phosphorylation of mitogen-activated protein kinase (MAPK), in contrast to its mitogenic effects on control cells or cells overexpressing PKC-alpha and -delta. The induction of neurite outgrowth by EGF was inhibited by the MAPK kinase inhibitor PD95098. In cells overexpressing a PKC-epsilon dominant negative mutant, NGF induced reduced neurite outgrowth and a more transient phosphorylation of MAPK than in controls. Our results suggest an important role for PKC-epsilon in neurite outgrowth in PC12 cells, probably via activation of the MAPK pathway.

Activation of Vav and Ras through the nerve growth factor and B cell receptors by different kinases

Engagement of the B-cell antigen receptor (BCR) or the nerve growth factor receptor (NGFR/TrkA) induces activation of multiple tyrosine kinases, resulting in phosphorylation of numerous intracellular substrates. We show that addition of NGF or anti-IgM antibody leads to the early tyrosine phosphorylation of p95(vav), which is expressed exclusively in hematopoietic cells; NGF, similar to crosslinking the BCR, also results in the rapid activation of Ras. The phosphorylation of Vav and activation of Ras triggered by NGF is mediated through Trk tyrosine kinase, whereas signaling through the BCR uses a different tyrosine kinase. We also show that NGF induces tyrosine phosphorylation of Shc and its association with Grb2. Vav and Ras with the adaptor proteins Shc and Grb2 appear to serve as a link between different receptor-mediated signaling pathways and, in human B cells, may play an important regulatory role in neuroimmune interactions.

Protein kinase C-independent selective induction of nitric oxide synthase activity in rat alveolar macrophages by staurosporine

The purpose of this study was to characterize the effect of the K-252a family of protein kinase inhibitors with emphasis on staurosporine (ST), on stimulation of the inducible nitric oxide synthase activity in rat alveolar NR8383 macrophages. We found that ST, but not K-252a, K-252b, KT-5720, and KT-5823, selectively enhanced the basal or the lipopolysaccharide (LPS)-induced nitric oxide production. ST-induced NO production was blocked by L-NAME, K-252a, and phosphatase inhibitors and could not be mimicked by other protein kinase C (PKC) inhibitors such as calphostine. An additive effect between ST and PMA on NO production was observed. LPS and PMA but not ST induced PKCbeta translocation from the cytosol to the membrane fraction. ST may induce and affect the state of phosphorylation of iNOS via PKC-independent mechanisms. ST provides an important pharmacological tool to investigate PKC-independent signal transduction pathways which regulate iNOS, induction, and activity in rat NR8383 macrophages.