Is urologist burnout different on the other side of the pond? A European perspective

The rate of burnout among physicians appears to be on the rise and urologist are no exception. In fact, urology appears to be one of the specialties most affected, with European urologists reporting burnout rates of up to 54% and those working in the United States up to 68%.Herein, we review the relatively few studies looking at burnout in European urologists to estimate its prevalence and discuss what could be done to reverse the trend. A total of seven studies were identified assessing burnout in urologists in Europe and Turkey. While the rates vary (9.3-68%), they indicate that burnout is prevalent within urology, with data from other studies suggesting there is a rising trend. Although the topic has been studied for many years, with an increased focus in the last decade, little seems to have been done to improve the situation.

Presenting features of COVID-19 in older people: relationships with frailty, inflammation and mortality

PURPOSE

To describe the clinical features of COVID-19 in older adults, and relate these to outcomes.

METHODS

A cohort study of 217 individuals (median age 80, IQR 74-85 years; 62% men) hospitalised with COVID-19, followed up for all-cause mortality, was conducted. Secondary outcomes included cognitive and physical function at discharge. C-reactive protein and neutrophil:lymphocyte ratio were used as measures of immune activity.

RESULTS

Cardinal COVID-19 symptoms (fever, dyspnoea, cough) were common but not universal. Inflammation on hospitalisation was lower in frail older adults. Fever, dyspnoea, delirium and inflammation were associated with mortality. Delirium at presentation was an independent risk factor for cognitive decline at discharge.

CONCLUSIONS

COVID-19 may present without cardinal symptoms as well as implicate a possible role for age-related changes in immunity in mediating the relationship between frailty and mortality.

Outcomes from COVID-19 across the range of frailty: excess mortality in fitter older people

PURPOSE

Our aim was to quantify the mortality from COVID-19 and identify any interactions with frailty and other demographic factors.

METHODS

Hospitalised patients aged ≥ 70 were included, comparing COVID-19 cases with non-COVID-19 controls admitted over the same period. Frailty was prospectively measured and mortality ascertained through linkage with national and local statutory reports.

RESULTS

In 217 COVID-19 cases and 160 controls, older age and South Asian ethnicity, though not socioeconomic position, were associated with higher mortality. For frailty, differences in effect size were evident between cases (HR 1.02, 95% CI 0.93-1.12) and controls (HR 1.99, 95% CI 1.46-2.72), with an interaction term (HR 0.51, 95% CI 0.37-0.71) in multivariable models.

CONCLUSIONS

Our findings suggest that (1) frailty is not a good discriminator of prognosis in COVID-19 and (2) pathways to mortality may differ in fitter compared with frailer older patients.

Sequence homology between human PARP14 and the SARS-CoV-2 ADP ribose 1'-phosphatase

•There is amino acid sequence homology between the ADP-ribose binding sites of human PARP14 and SARS-CoV-2 ADRP. •This homology is even more pronounced in bat species. •The model proposed highlights the potential of the PARP axis to yield druggable targets for the treatment of COVID-19.

The eIF4A inhibitor silvestrol sensitizes T-47D ductal breast carcinoma cells to external-beam radiotherapy

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Treatment of T-47D breast cancer cells with silvestrol sensitised them to radiation.

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1 nM silvestrol caused a 34% reduction in cells exposed to 2 Gy.

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Clonogenic assays revealed silvestrol had a dose modifying factor of 1.4.

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Radiation was delivered to the tissue culture plate using a clinical LINAC machine.

Purpose

eIF4A is an RNA helicase that forms part of the machinery of translation initiation.

Proteomic analysis demonstrated eIF4A expression to be at least two-fold greater in a radioresistant derivative of T-47D breast cancer cells compared to parental cells.

Inhibition of eIF4A has previously been shown to re-sensitize lymphomas to chemotherapeutic agents that cause DNA damage.

The objective of this work is to investigate whether inhibition of eIF4A using silvestrol sensitizes breast cancer cells to radiotherapy in tissue culture, using T-47D as a model system.

Methods and materials

T-47D cells were incubated in medium containing 0 nM to 1 nM silvestrol either for 24 h prior to irradiation at 0 Gy to 10 Gy, delivered by linear accelerator (LINAC) or continually for six days post irradiation. MTT viability and clonogenic assays were used to quantify response.

Results

Pre-treatment of T-47D cells with 1 nM silvestrol caused a 34% reduction (p = 0.014) in viability on irradiation at 2 Gy compared to treatment with a DMSO control, as assessed by MTT assay.

Maintenance of cells in 1 nM silvestrol for six days following irradiation at 2 Gy caused a 58% reduction (p = <0.001) in tumor cell viability.

Clonogenic assays performed on cells maintained in 1 nM silvestrol following irradiation showed a dose modifying factor (DMF) of 1.4 (p = <0.001, one-way ANOVA).

Conclusions

Low concentrations of silvestrol sensitize T-47D breast cancer cells to radiation with minimal effects on unirradiated cells. This highlights the possible usefulness of eIF4A inhibition in potentiating radiation-induced damage at the tumor site without causing systemic toxicity.

Exploitation of Antibiotic Resistance as a Novel Drug Target: Development of a β-Lactamase-Activated Antibacterial Prodrug

Expression of β-lactamase is the single most prevalent determinant of antibiotic resistance, rendering bacteria resistant to β-lactam antibiotics. In this article, we describe the development of an antibiotic prodrug that combines ciprofloxacin with a β-lactamase-cleavable motif. The prodrug is only bactericidal after activation by β-lactamase. Bactericidal activity comparable to ciprofloxacin is demonstrated against clinically relevant E. coli isolates expressing diverse β-lactamases; bactericidal activity was not observed in strains without β-lactamase. These findings demonstrate that it is possible to exploit antibiotic resistance to selectively target β-lactamase-producing bacteria using our prodrug approach, without adversely affecting bacteria that do not produce β-lactamase. This paves the way for selective targeting of drug-resistant pathogens without disrupting or selecting for resistance within the microbiota, reducing the rate of secondary infections and subsequent antibiotic use.

Uninformed Reform: The Attempt to Abolish the Hospital Managers' Section 23 Discharge Power Under the Mental Health Act 1983

Under section 23 of the Mental Health Act 1983 a person can be discharged by the managers of the hospital from compulsory care. The limited evidence indicates that the section 23 power is normally delegated to a specially appointed panel who hold a hearing. Unfortunately, notwithstanding the implications for the liberty, autonomy, and dignity of the compelled person, very little is known about how this process operates. Nonetheless, since 1996 there has been a sustained effort to abolish the power. In view of this, the proposal to reform the 1983 Act contained in the Queen's Speech January 2017, and the subsequent establishment of the Independent Review of the Mental Health Act in October 2017, I critique the claims made in the abolition debate, and establish the conceptual gaps therein. I argue that a much more developed understanding of the power is required before any change is made to the law in this area.

Trends in UK regional cancer mortality 1991-2007

Background:

Until 1990, there was an upward trend in mortality from breast, lung, prostate, and colon cancers in the United Kingdom. With improvements in cancer treatment there has, in general, been a fall in mortality over the last 20 years. We evaluate regional cancer mortality trends in the United Kingdom between 1991 and 2007.

Methods:

We analysed mortality trends for breast, lung, prostate, and colon cancers using data obtained from the EUREG cancer database. We have described changes in age-standardised rates (using European standard population) per 100 000 for cancer mortality and generated trends in mortality for the 11 regions using Joinpoint regression.

Results:

Across all regions in the United Kingdom there was a downward trend in mortality for the four most common cancers in males and females. Overall, deaths from colon cancer decreased most rapidly and deaths from prostate cancer decreased at the slowest rate. Similar downward trends in mortality were observed across all regions of the United Kingdom with the data for lung cancer exhibiting the greatest variation.

Conclusions:

Mortality from the four most common cancers decreased across all regions of the United Kingdom; however, the rate of decline varied between cancer type and in some instances by region.

Asthma and allergy development: contrasting influences of yeasts and other fungal exposures

BACKGROUND

Infancy is a developmental stage with heightened susceptibility to environmental influences on the risk of chronic childhood disease. Few birth cohort studies have detailed measures of fungal diversity data in infants' bedrooms, limiting the potential to measure long-term associations of these complex exposures with development of asthma or allergy.

OBJECTIVE

We evaluated the relation of home fungal levels in infancy to repeated measures of wheeze and development of asthma and rhinitis by age 13, and sensitization by age 12 years.

METHODS

In the Epidemiology of Home Allergens and Asthma prospective birth cohort study, we recruited 408 children with family history of allergic disease or asthma. When children were aged 2-3 months, we measured culturable fungi in bedroom air and dust, and in outdoor air. Main outcomes included ascertainment of symptoms/disease onset by questionnaire from birth through age 13. We estimated hazard ratios and, for wheeze and sensitization, odds ratios for an interquartile increase in log-transformed fungal concentrations, adjusting for other outcome predictors and potential confounders.

RESULTS

Elevated levels of yeasts in bedroom floor dust were associated with reduced: i) wheeze at any age; ii) fungal sensitization; and iii) asthma development by age 13 (hazard ratio (HR) = 0.86; 95% confidence interval (CI), [0.75 to 0.98]). Outdoor airborne Cladosporium and dustborne Aspergillus predicted increased rhinitis. Risk of fungal sensitization by age 12, in response to environmental Alternaria and Aspergillus, was elevated in children with a maternal history of fungal sensitization.

CONCLUSIONS AND CLINICAL RELEVANCE

Despite the irritant and allergenic properties of fungi, early-life elevated dust yeast exposures or their components may be protective against allergy and asthma in children at risk for these outcomes. Ascertainment of fungal components associated with immunoprotective effects may have therapeutic relevance for asthma.

An internal ribosome entry site in the 5' untranslated region of epidermal growth factor receptor allows hypoxic expression

The expression of epidermal growth factor receptor (EGFR/ERBB1/HER1) is implicated in the progress of numerous cancers, a feature that has been exploited in the development of EGFR antibodies and EGFR tyrosine kinase inhibitors as anti-cancer drugs. However, EGFR also has important normal cellular functions, leading to serious side effects when EGFR is inhibited. One damaging characteristic of many oncogenes is the ability to be expressed in the hypoxic conditions associated with the tumour interior. It has previously been demonstrated that expression of EGFR is maintained in hypoxic conditions via an unknown mechanism of translational control, despite global translation rates generally being attenuated under hypoxic conditions. In this report, we demonstrate that the human EGFR 5′ untranslated region (UTR) sequence can initiate the expression of a downstream open reading frame via an internal ribosome entry site (IRES). We show that this effect is not due to either cryptic promoter activity or splicing events. We have investigated the requirement of the EGFR IRES for eukaryotic initiation factor 4A (eIF4A), which is an RNA helicase responsible for processing RNA secondary structure as part of translation initiation. Treatment with hippuristanol (a potent inhibitor of eIF4A) caused a decrease in EGFR 5′ UTR-driven reporter activity and also a reduction in EGFR protein level. Importantly, we show that expression of a reporter gene under the control of the EGFR IRES is maintained under hypoxic conditions despite a fall in global translation rates.

eIF4A inhibition allows translational regulation of mRNAs encoding proteins involved in Alzheimer's disease

Alzheimer's disease (AD) is the main cause of dementia in our increasingly aging population. The debilitating cognitive and behavioral symptoms characteristic of AD make it an extremely distressing illness for patients and carers. Although drugs have been developed to treat AD symptoms and to slow disease progression, there is currently no cure. The incidence of AD is predicted to increase to over one hundred million by 2050, placing a heavy burden on communities and economies, and making the development of effective therapies an urgent priority. Two proteins are thought to have major contributory roles in AD: the microtubule associated protein tau, also known as MAPT; and the amyloid-beta peptide (A-beta), a cleavage product of amyloid precursor protein (APP). Oxidative stress is also implicated in AD pathology from an early stage. By targeting eIF4A, an RNA helicase involved in translation initiation, the synthesis of APP and tau, but not neuroprotective proteins, can be simultaneously and specifically reduced, representing a novel avenue for AD intervention. We also show that protection from oxidative stress is increased upon eIF4A inhibition. We demonstrate that the reduction of these proteins is not due to changes in mRNA levels or increased protein degradation, but is a consequence of translational repression conferred by inhibition of the helicase activity of eIF4A. Inhibition of eIF4A selectively and simultaneously modulates the synthesis of proteins involved in Alzheimer's disease: reducing A-beta and tau synthesis, while increasing proteins predicted to be neuroprotective.

Lack of TAR-DNA binding protein-43 (TDP-43) pathology in human prion diseases

AIMS

TAR-DNA binding protein-43 (TDP-43) is the major ubiquitinated protein in the aggregates in frontotemporal dementia with ubiquitin-positive, tau-negative inclusions and motor neurone disease. Abnormal TDP-43 immunoreactivity has also been described in Alzheimer's disease, Lewy body diseases and Guam parkinsonism-dementia complex. We therefore aimed to determine whether there is TDP-43 pathology in human prion diseases, which are characterised by variable deposition of prion protein (PrP) aggregates in the brain as amyloid plaques or more diffuse deposits.

MATERIAL AND METHODS

TDP-43, ubiquitin and PrP were analysed by immunohistochemistry and double-labelling immunofluorescence, in sporadic, acquired and inherited forms of human prion disease.

RESULTS

Most PrP plaques contained ubiquitin, while synaptic PrP deposits were not associated with ubiquitin. No abnormal TDP-43 inclusions were identified in any type of prion disease case, and TDP-43 did not co-localize with ubiquitin-positive PrP plaques or with diffuse PrP aggregates.

CONCLUSIONS

These data do not support a role for TDP-43 in prion disease pathogenesis and argue that TDP-43 inclusions define a distinct group of neurodegenerative disorders.

The diverse series of recombinant P2Y purinoceptors

A cDNA encoding a P2Y purinoceptor was originally cloned from chick brain and the bovine and human homologues have recently been obtained. These are seven-transmembrane-domain polypetides, i.e. G protein-coupled receptors. When activated by agonists, this P2Y receptor mobilizes intracellular Ca2+ and has been shown to be coupled to inositol-1,4,5-trisphosphate formation. Its pharmacology has been established in several expression systems, using both ligand binding and functional responses: 2-methylthioATP has the highest potency of nucleotides and derivatives tested, while UTP and alpha, beta-methylene ATP are inactive. This was hence assigned as a new subtype of the pharmacologically defined P2Y receptors, P2Y1. P2Y1 receptors are exceptionally abundant in the brain. A P2U receptor reported by others can be designated P2Y2. Another P2 receptor subtype, P2Y3, now cloned as a cDNA from the brain and expressed in oocytes and in transfected cells, shows a quite different ligand potency profile to the first two. A fourth subtype is expressed primarily in certain haemopoietic cells and in cardiac muscle. A putative fifth subtype is expressed only in T lymphocytes, upon activation. Yet other P2Y subtypes are indicated by recent cloning studies. The amino acid sequences of all of these P2 receptors, while displaying some homology, are strikingly diverse: they form a separate and unusual new family in the G protein-coupled receptor main superfamily.

Crisis of faith vs. spiritual cry of distress

Traumatic events radiate shock waves that impact the totality of an individual: the physical, cognitive, emotional, behavioral and spiritual aspects of a person. Symptoms of distress appear horizontally in relationships with family, friends, and co-workers and vertically in relationship with God. People who have a faith relationship with God will often use religious language to express their anguish and despair regarding a traumatic event. The challenge of any crisis interventionist is to be able to hear accurately the cry of the distressed individual and respond so as to connect with and instill hope in the traumatized individual.

Aroma components of an oil-based grill flavoring by direct thermal desorption-gas chromatography-olfactometry and sample dilution analysis

Grill flavorings are a convenient way for food processors to impart grill-like flavor to meat products that have not been grilled. In this study a commercially available oil-based processed grill flavoring was analyzed by direct thermal desorption (DTD)-gas chromatography-olfactometry (GCO) and DTD-GC-mass spectrometry (MS). Sample mass dilution analysis-GCO was used to indicate which compounds had the greatest impact on the overall aroma of the sample. Major aroma contributors included 1-octen-3-one, 2-methoxyphenol, and (E)-2-nonenal. Minor contributors were (E)-2-decenal and 2,4-decadienal. Other major contributors, characterized as having grill aroma notes, were unidentified. Excluding the possibility of artifact formation from the thermal degradation of fatty acid hydroperoxides, DTD functioned well as a GCO technique, but poorly as a qualitative GC-MS technique.

Mechanisms of P2 receptor-evoked DNA synthesis in thyroid FRTL-5 cells

The expression of the P2 receptors and their functional responses were studied in rat thyroid FRTL-5 cells. RT-PCR analysis revealed transcripts for the G protein-coupled P2Y(2), P2Y(4) and P2Y(6) receptors, and for the transmitter-gated ion channel P2X(3), P2X(4) and P2X(5) subunits. In Fura-2-loaded cells, UTP, ATP, ATPgammaS or UDP increased [Ca(2+)](i), and behaved as potent full agonists, while 2-Methylthio-ATP (2-MeSATP), alpha,beta-methylene-ATP (alpha,beta-meATP) and pure ADP were weak agonists. The agonist-mediated [Ca(2+) ](i) increases were diminished in Ca(2+) -free buffer, and by pertussis toxin (PTX) or suramin treatments. ATP, UTP, UDP and ATPgammaS increased (3)H-thymidine incorporation into DNA and expression of the protooncogenes c-Fos and c-Jun, while 2-MeSATP was ineffective, and alpha,beta-meATP gave a response only at 100-microM dose. The ATP-stimulated expression of c-Fos and c-Jun was dependent on Ca(2+), and protein kinase C, but not on calmodulin or Ca(2+)/calmodulin-dependent protein kinase II. Extracellular signal-regulated kinases (ERK1 and ERK2) are also involved as the MEK inhibitor, PD98059, reduced both ATP-evoked (3)H-thymidine incorporation and c-Fos and c-Jun expression. These results indicate that multiple P2Y receptor subtypes and at least the P2X(5) subtype are functionally expressed in FRTL-5 cells, and that nucleotides acting via P2 receptors are involved in the regulation of DNA-synthesis.

Staying the course in stormy seas: establishing a central Critical Incident Stress Management team in the Navy Marine Corps environment

Crisis response teams are becoming a standard operating procedure for most United States military organizations and for many military organizations outside the U.S. This paper describes the establishment of one specific Critical Incident Stress Management (CISM) team designed to provide psychological support during crisis, disasters, traumas, and other critical incidents that may be encountered in a Navy Marine Corps environment.

Pharmacological characterisation of pyrimidinoceptor responses in NG108-15 cells

In the present study, the P2Y receptor(s) mediating the effects of the pyrimidines UTP and UDP on phospholipase C activation in the mouse neuroblastoma x rat glioma hybrid cell line NG108-15 was investigated. Reverse Transcriptase-Polymerase Chain Reaction (RT-PCR) analysis detected transcripts for the P2Y(6) and P2Y(2) receptors, but not for P2Y(1) and P2Y(4.) UTP and UDP were equipotent agonists and their effects were partially additive. Suramin, reactive blue 2 and pyridoxal phosphate-6-azophenyl-2',4'disulfonic acid (PPADS) antagonised the phospholipase C response to both UTP and UDP. High micromolar concentrations of adenosine, 2-p-(2-carboxyethyl)phenethylamino-5'-N-ethylcarboxamidoadenosine (CGS-21680), 2',3'-O-isopropylideneadenosine (iPAdo) and adenosine 3':5'-cyclic monophosphate (3',5'-cAMP) were able to antagonise the effect of UTP on phospholipase C but not that of UDP. The additivity of the UTP and UDP responses, novel P2 receptor antagonist profile and the distinguishing action of adenosine may indicate the expression of a pyrimidine selective P2Y receptor in addition to the P2Y(6) type in these cells.

Assessing a crisis of faith and making a pastoral crisis intervention

Evaluating the spiritual impact of a critical incident upon an individual is a vital aspect of restoring an individual to functioning in their relationships and work responsibilities. Being able to recognize and respond to spiritual symptoms of critical incident stress will allow crisis interventionists to address crisis recovery issues that are often central to an individual's identity and purpose for living. Spiritual symptoms of traumatic stress issue from the defining identity of an individual. With an understanding of the nature of a crisis of faith crisis interventionists can employ critical incident stress management skills to support a person in spiritual as well as psychological trauma.

Evidence that rat hepatocytes co-express functional P2Y1 and P2Y2 receptors

Previous studies have indicated the expression of multiple P2Y receptors by rat hepatocytes although they have not been identified. Here we show by reverse transcriptase-polymerase chain reaction (RT - PCR) that rat hepatocytes express mRNA encoding all of the four cloned rat P2Y receptors (P2Y(1), P2Y(2), P2Y(4) and P2Y(6)). The effects of UTP have been examined on single aequorin-injected rat hepatocytes. The [Ca(2+)](i) transients induced by UTP were indistinguishable from those induced by ATP in the same cell. The modulatory effects of elevated intracellular cyclic AMP concentration were the same on both UTP- and ATP-induced [Ca(2+)](i) transients. UDP, an agonist at the P2Y(6) receptor, failed to induce transients in hepatocytes, indicating that functional P2Y(6) receptors coupled to increased [Ca(2+)](i) are not expressed. The transients evoked by ADP were more sensitive to inhibition by suramin than those induced by either ATP or UTP. Within an individual cell, the transients induced by ATP and UTP were inhibited by the same concentration of suramin. This sensitivity of ATP and UTP responses to suramin suggests action through P2Y(2) rather than P2Y(4) receptors. Co-application of 30 microM pyridoxalphosphate-6-azophenyl-2',4'-disulphonic acid (PPADS) caused a decrease in frequency and amplitude of transients induced by ADP. ATP- and UTP-induced transients also displayed a decrease in amplitude in response to addition of PPADS, but this was accompanied by an increase in frequency of transients. In conclusion the data presented here are consistent with the co-expression of P2Y(1) and P2Y(2) receptors by rat hepatocytes.

Only pyrimidinoceptors are functionally expressed in mouse neuroblastoma cell lines

The ability of UTP, UDP, ATP, and ADP to influence inositol phospholipid hydrolysis in neuroblastoma origin cell lines was assessed. The mouse neuroblastoma lines N1E 115, Neuro 2a, and NB4 1A3 and the rat glioma/mouse neuroblastoma hybrid line NG108-15 gave robust responses to both UTP and UDP, which were essentially equipotent. Thus a range of cell lines of mouse neuroblastoma origin express a pyrimidine-selective P2Y receptor. The NG108-15 cells were the only cell type tested at which ATP and ADP displayed activity with EC50 values of greater than 100 microM, compared with values of 0.58 and 1.25 microM for UTP and UDP, respectively. In contrast to the cell lines derived from mouse neuroblastoma, the human neuroblastoma lines SH-SY5Y and SK-N-SH did not respond to any nucleotides, although both responded well to carbachol.

Dual coupling of heterologously-expressed rat P2Y6 nucleotide receptors to N-type Ca2+ and M-type K+ currents in rat sympathetic neurones

1. The P2Y6 receptor is a uridine nucleotide-specific G protein-linked receptor previously reported to stimulate the phosphoinositide (PI) pathway. We have investigated its effect in neurones, by micro-injecting its cRNA into dissociated rat sympathetic neurones and recording responses of N-type Ca2+ (I(Ca(N))) and M-type K+ (I(K(M))) currents. 2. In P2Y6 cRNA-injected neurones, UDP or UTP produced a voltage-dependent inhibition of I(Ca(N)) by approximately 53% in whole-cell (disrupted-patch) mode and by 73% in perforated-patch mode; no inhibition occurred in control cells. Mean IC50 values (whole-cell) were: UDP, 5.9+/-0.3 nM; UTP, 20+/-1 nM. ATP and ADP (1 microM) had no significant effect. Pertussis toxin (PTX) substantially (approximately 60%) reduced UTP-mediated inhibition in disrupted patch mode but not in perforated-patch mode. 3. Uridine nucleotides also inhibited I(K(M)) in P2Y6 cRNA-injected cells (by up to 71% at 10 microM UTP; perforated-patch). Mean IC50 values were: UDP, 30+/-3 nM; UTP, 115+/-12 nM. ATP (10 microM) again had no effect. No significant inhibition occurred in control cells. Inhibition was PTX-resistant. 4. Thus, the P2Y6 receptor, like the P2Y2 subtype studied in this system, couples to both of these two neuronal ion channels through at least two different G proteins. However, the P2Y6 receptor displays a much higher sensitivity to its agonists than the P2Y2 receptor in this expression system and higher than previously reported using other expression methods. The very high sensitivity to both UDP and UTP suggests that it might be preferentially activated by any locally released uridine nucleotides.

Molecular cloning and characterization of the rat P2Y4 receptor

Degenerate PCR was used to amplify DNAs encoding members of the P2Y receptor family from rat brain RNA. A full-length sequence obtained for one novel clone (R5) contained an intronless open reading frame that encoded a polypeptide of 361 amino acids, sharing 84% sequence identity with the human P2Y4 receptor. When R5 was stably expressed in Jurkat cells, calcium fluxes resulting from stimulation of the receptor showed that UDP, ADP, 2-methylthio-ATP, and diadenosine tetraphosphate were inactive, whereas UTP and ATP were both full agonists with similar potency. At the human receptor, ATP has significantly lower potency than UTP. The R5 transcript was not detected in brain by northern hybridization. Therefore, its tissue distribution was assessed by PCR, and the mRNA was found to be widely distributed at a low abundance, being present in brain, spinal cord, and a variety of peripheral organs. Localization of the receptor transcript in adult rat brain sections by in situ hybridization indicated that it is expressed at highest levels in the pineal gland and ventricular system. It is presumed that R5 is a species orthologue of the human P2Y4 receptor but with this significant difference in agonist pharmacology.

Phenotype changes of the vascular smooth muscle cell regulate P2 receptor expression as measured by quantitative RT-PCR

Studies using selective agonists have suggested that the contractile effect of extracellular nucleotides, such as ATP and UTP, in blood vessels is mediated mainly by P2X1 receptors with a smaller contribution of P2Y receptors while the mitogenic effect is mediated by P2Y (P2Y1, P2Y2, P2Y4, and P2Y6) receptors with no effect of P2X1 receptors. This indicates a difference in P2 receptor expression between the contractile and the synthetic phenotype of the SMC. To measure the expression of mRNA for these receptors a competitive RT-PCR assay was developed that utilised synthetic RNA-competitors allowing determination of the number of mRNA copies for each receptor in the samples. In the synthetic phenotype the mitogenic P2Y1 and P2Y2 receptor transcripts were upregulated by 342- and 8-fold, respectively, while the contractile P2X1 receptor is totally downregulated and the P2Y4 and P2Y6 receptors were unchanged. This plasticity of the receptor expression may be important in the transition from the contractile to the synthetic SMC phenotype.

P2Y2 nucleotide receptors expressed heterologously in sympathetic neurons inhibit both N-type Ca2+ and M-type K+ currents

The P2Y2 receptor is a uridine/adenosine triphosphate (UTP/ATP)-sensitive G-protein-linked nucleotide receptor that previously has been reported to stimulate the phosphoinositide signaling pathway. Messenger RNA for this receptor has been detected in brain tissue. We have investigated the coupling of the molecularly defined rat P2Y2 receptor to neuronal N-type Ca2+ channels and to M-type K+ channels by heterologous expression in rat superior cervical sympathetic (SCG) neurons. After the injection of P2Y2 cRNA, UTP inhibited the currents carried by both types of ion channel. As previously reported [Filippov AK, Webb TE, Barnard EA, Brown DA (1997) Inhibition by heterologously expressed P2Y2 nuerones. Br J Pharmacol 121:849-851], UTP inhibited the Ca2+ current (ICa(N)) by up to 64%, with an IC50 of approximately 0.5 microM. We now find that UTP also inhibited the K+M current (IK(M)) by up to 61%, with an IC50 of approximately 1.5 microM. UTP had no effect on either current in neurons not injected with P2Y2 cRNA. Structure-activity relations for the inhibition of ICa(N) and IK(M) in P2Y2 cRNA-injected neurons were similar, with UTP >/= ATP > ITP >> GTP,UDP. However, coupling to these two channels involved different G-proteins: pretreatment with Pertussis toxin (PTX) did not affect UTP-induced inhibition of IK(M) but reduced inhibition of ICa(N) by approximately 60% and abolished the voltage-dependent component of this inhibition. In unclamped neurons, UTP greatly facilitated depolarization-induced action potential discharges. Thus, the single P2Y2 receptor can couple to at least two G-proteins to inhibit both Ca2+N and K+M channels with near-equal facility. This implies that the P2Y2 receptor may induce a broad range of effector responses in the nervous system.

Regional distribution of [35S]2'-deoxy 5'-O-(1-thio) ATP binding sites and the P2Y1 messenger RNA within the chick brain

The distribution of the P2Y1 receptor protein and transcript in the one-day-old chick brain were determined by quantitative in vitro ligand autoradiography and in situ hybridization histochemistry. We have previously used [35S]2'-deoxy 5'-O-(1-thio) ATP as a radioligand for the recombinant P2Y1 receptor transiently expressed in COS-7 cells and have also shown that such sites are present at high density (Bmax: approximately 37 pmol radioligand bound/mg protein) in chick brain membranes. Here we report the macroscopic localization of these [35S]2'-deoxy 5'-O-(1-thio) ATP binding sites within the chick brain. They were found to be widely distributed there (within the range of 0.047 +/- 0.012 to 0.309 +/- 0.035 pmol bound/mg wet tissue). The affinities of P2 agonists and antagonists at these binding sites was comparable to that found previously for the recombinant P2Y1 receptor. In parallel experiments, the regional and cellular localization of the P2Y1 receptor messenger RNA was examined by in situ hybridization. The transcript was also found to be widely distributed throughout the brain. High levels of hybridization were detected in the cortex piriformis, ectostriatum, hippocampus, cerebellum and in a range of discrete nuclei throughout the brain, including the ovoidalis, isthmo-opticus and spiriformis lateralis nuclei. Localization at cellular level indicates that this receptor transcript is expressed in neurons and also at non-neuronal sites. Furthermore, the distribution of the P2Y1 transcript and the [35S]2'-deoxy 5'-O-(1-thio) ATP binding sites matched in a number of the regions and structures mentioned above. The present study clarifies the anatomical distribution of the P2Y1 receptor within the chick brain. Its broad distribution coupled with its neuronal expression suggest an important role for this type of metabotropic nucleotide receptor within the brain.

Evidence that P2Y4 nucleotide receptors are involved in the regulation of rat aortic smooth muscle cells by UTP and ATP

1. Previous studies have shown that ATP and UTP are able to stimulate phospholipase C (PLC) and proliferation in cultured aortic smooth muscle cells. Here we set out to characterize the receptor responsible, and investigate a possible role for p42 and p44 mitogen activated protein kinase (MAPK) in the proliferative response. 2. The phospholipase C response of spontaneously hypertensive rat (SHR) derived aortic smooth muscle cells in culture showed that the response to ATP was partial compared to the response to UTP. 3. Further studies characterized the responses of the SHR derived cells. UTP was the only full agonist with the SHR cells; UDP gave a partial response while ADP, 2-methythio-ATP and alpha,beta-methylene ATP were essentially ineffective. The response to UDP was almost lost in the presence of hexokinase, consistent with this being due to extracellular conversion to UTP. These observations are inconsistent with the response being mediated by either P2Y1 or P2Y6 receptors. 4. When increasing concentrations of ATP were present with a maximally effective concentration of UTP, the size of the response diminished, consistent with UTP and ATP acting at a single population of receptors for which ATP was a partial agonist. This is inconsistent with a response mainly at P2Y2 receptors. 5. 1321N1 cells transfected with human P2Y4 receptors gave a similar agonist response profile, with ATP being partial compared to UTP, loss of response to UDP with hexokinase treatment, and with the response to UTP diminishing in the presence of increasing concentrations of ATP. 6. Use of the reverse transcriptase-polymerase chain reaction confirmed the presence of mRNA encoding P2Y4 receptors in SHR derived vascular smooth muscle cells. Transcripts for P2Y2, P2Y4 and P2Y6 receptors, but not P2Y1 receptors, were detected. 7. Stimulation of SHR derived cells with UTP enhanced the tyrosine phosphorylation of both p42 and p44 MAPK, and the incorporation of [3H]-thymidine into DNA. Both these responses were diminished in the presence of an inhibitor of activation of MAPK. 8 These results lead to the conclusion that in SHR derived cultured aortic smooth muscle cells, PLC responses to extracellular UTP and ATP are predominantly at P2Y4 receptors, and suggest that these receptors are coupled to mitogenesis via p42/p44 MAPK.

Stimulation of P2Y receptors activates c-fos gene expression and inhibits DNA synthesis in cultured cardiac fibroblasts

OBJECTIVES

The aims of this study were to determine (1) whether neonatal rat cardiac fibroblasts (CAFB) express P2Y receptors; (2) whether CAFB respond to extracellular ATP by inducing expression of c-fos mRNA; and (3) whether extracellular ATP modulates norepinephrine (NE)-stimulated cell growth in CAFB.

METHODS

Expression of P2Y1 and P2Y2 receptors and induction of c-fos were examined by Northern blot analysis. CAFB growth was assessed by measuring [3H]thymidine incorporation and DNA content. P2Y receptor pharmacology was studied using various ATP analogues.

RESULTS

Northern blot analysis of polyA enriched RNA confirmed that at least 2 subtypes of P2Y receptors (P2Y1 and P2Y2) are expressed in cultured CAFB. Extracellular ATP induced the expression of c-fos mRNA through a pathway that was sensitive to inhibitors of protein kinase C (PKC), but not to inhibitors of intracellular Ca2+ signaling. Extracellular ATP inhibited the NE-stimulated increases in DNA content and in [3H]thymidine incorporation into DNA. Whereas the potency order for stimulation of c-fos expression was ATP = UTP > ADP > adenosine, the potency order to inhibit the NE-induced increase of [3H]thymidine incorporation into DNA was ATP > ADP > UTP > adenosine.

CONCLUSIONS

These data demonstrate that CAFB express both P2Y1 and P2Y2 receptor mRNA and that CAFB respond to P2Y receptor stimulation by induction of c-fos and inhibition of DNA synthesis. These findings suggest that the effects of ATP on [3H]thymidine incorporation into DNA and on expression of c-fos mRNA are exerted via distinct P2Y receptor subtypes.

Nucleotide receptors in the nervous system. An abundant component using diverse transduction mechanisms

Extracellular nucleotides achieve their role as cell-to-cell communicators by acting at cell surface transmembrane receptors-the P2 receptors. Before molecular cloning led to the isolation of any P2-receptor sequence, a small number of receptor types had been proposed on the basis of pharmacological evidence. The application of molecular biology to this field of receptor research has indicated that a great underestimation of the number of receptor subtypes and of their abundance had occurred. There are now known to be seven characterized P2Y (G protein linked) receptors and the same number again of P2X receptors of the transmitter-gated ion channel type. In this review, we discuss the properties of these cloned receptors, their distribution within the nervous system, and their methods of signal transduction.

Distribution of [35S]dATP alpha S binding sites in the adult rat neuraxis

Highly abundant, saturable and specific binding sites for [35S]2'-deoxyadenosine 5'-O-(1-thio) triphosphate ([35S]dATP alpha S, Kd: 9 +/- 2 nM; Bmax: 39 +/- 8 pmol/mg protein) are present in adult rat brain membranes and have characteristics consistent with those expected for a P2Y1 receptor. The anatomical distribution of these binding sites in the brain and spinal cord was examined using in vitro autoradiography. The [35S]dATP alpha S binding sites showed a widespread distribution throughout the brain and spinal cord. They could be displaced by a large excess (100 microM) of 2-methylthioATP (2MeS-ATP) but not by uridine-5'-triphosphate (UTP) or alpha,beta-methyleneATP (alpha,beta-meATP). Within the cortical regions labelling was of equal medium density. However, discrete structures and nuclei within the olfactory bulb, subcortical telencephalon, hippocampal complex, thalamic regions and mesencephalon displayed a variety of densities. Within the spinal cord, gray matter was labelled at a greater density than the funiculi. The present study clarifies the anatomical distribution of P2Y1 and closely related receptors within the central nervous system of rat and extends the evidence that those receptors are abundant and widely distributed within the neuraxis.

Inhibition by heterologously-expressed P2Y2 nucleotide receptors of N-type calcium currents in rat sympathetic neurones

The P2Y2 nucleotide receptor has previously been shown to stimulate phosphoinositide breakdown. We now show that, when P2Y2 receptors are heterologously expressed by cRNA injection into dissociated rat sympathetic neurones, activation of these receptors by uridine 5'-triphosphate (UTP) or adenosine 5'-triphosphate (ATP) inhibits the N-type voltage-gated calcium current by approximately 65%, with an IC50 of 0.5 microM. Thus, the same molecular species of nucleotide receptor can link to two different effector pathways.

The P2Y purinoceptor in rat brain microvascular endothelial cells couple to inhibition of adenylate cyclase

1. B10 cells, a clonal line of rat brain capillary endothelial cells, exhibit a single P2 purinoceptor, activation of which leads to increases in free intracellular calcium. In the current study the identity of this P2Y receptor was determined by its binding parameters for a range of purinoceptor ligands and by its complementary DNA (cDNA) sequence. The signal transduction mechanism activated by this receptor was also investigated. 2. The radioligand [35S]-dATP alpha S bound with high affinity (Kd = 9.8 nM) to the P2Y purinoceptor expressed on B10 cells, which was found to be extremely abundant (Bmax = 22.5 pmol mg-1 protein). The calculated Ki values of a range of P2 purinoceptor agonists which competitively displaced binding of [35S]-dATP alpha S led to the rank order of affinity: dATP alpha S (Ki 3.4 nM) > 2-chloroATP (2-ClATP) (13 nM), ATP (22 nM) > ATP gamma S (43 nM) > 2-methylthioATP (2-MeSATP) (88 nM) > ADP (368 nM) > > UTP, L-beta,gamma-methyleneATP (both > 10,000 nM). The P2 purinoceptor antagonists, Reactive blue 2 and suramin, were also able to displace binding, with Ki values of 833 and 1358 nM respectively. In contrast pyridoxal-phosphate-6-azophenyl-2',4'-disulphonic acid 4-sodium (PPADS) was able to displace only 20% of [35S]-dATP alpha S binding at a concentration of 100 microM. 3. 2-ClATP (EC50 = 0.22 microM), 2-MeSATP (0.54 microM), ADP (7.9 microM) and ATP (a partial agonist), but not UTP, inhibited the cyclic AMP formation stimulated by cholera toxin, in a manner that was prevented by pertussis toxin. The purinoceptor antagonist, PPADS, was found to be inactive at a concentration of 100 microM. 4. A P2Y receptor cDNA was derived from mRNA from B10 cells and from C6-2B, a rat glioma cell line known to possess a P2Y receptor that is coupled to the inhibition of adenylate cyclase. Sequence analysis of the entire coding region revealed that both were 100% identical to the rat P2Y1 purinoceptor cDNA. No other P2Y-type receptor mRNA could be detected in B10 cells. Exactly the same sequence was isolated from rat brain cortical astrocytes, where 2-MeSATP has been shown to increase phospholipase C activity. 5. Since the receptor responsible for the transduction shares with the aforementioned binding site significant pharmacological features, including a strong activity of 2-MeSATP (characteristic of P2Y1 receptors alone among all known P2Y purinoceptors) and an unusual insensitivity to PPADS, and since abundant mRNA is present of the P2Y1 receptor but not of any other type resembling the known P2Y receptors, it is concluded that a P2Y1 receptor on rat brain microvascular endothelial cells can account for all of the observations. This single P2Y1 receptor, therefore, appears to couple in different native cell types to either adenylate cyclase inhibition or to phospholipase C activation.

Molecular biology of P2Y purinoceptors: expression in rat heart

1. Application of molecular biology to the study of P2Y purinoceptors has led to the identification of seven such receptors. Here we briefly review their properties and investigate qualitatively the expression of four rat receptor transcripts in heart. 2. The reverse transcriptase-polymerase chain reaction was used to ascertain whether the rat P2Y1, P2Y2, P2Y4 and P2Y6 receptor transcripts were expressed in whole heart, neonatal cardiac fibroblasts, neonatal cardiac myocytes and adult cardiac myocytes. 3. All receptor sequences could be amplified from neonatal rat whole heart, with P2Y6 appearing the most abundant transcript of the four. P2Y1 is expressed at higher levels in comparison to P2Y2, P2Y4 and P2Y6 in the neonatal myocyte. In the adult myocyte P2Y1, P2Y2 and P2Y6 could be amplified but P2Y4 could not be detected. In the neonatal fibroblast, P2Y1 and P2Y6 appear to be expressed at higher levels than P2Y2 and P2Y4. 4. In summary, it is concluded that multiple P2Y receptor subtypes are expressed in heart and that the expression in myocytes changes from the neonate to the adult.

Molecular cloning of a novel P2 purinoceptor from human erythroleukemia cells

Screening of a human erythroleukemia cell cDNA library with radiolabeled chicken P2Y3 cDNA at low stringency revealed a cDNA clone encoding a novel G protein-coupled receptor with homology to P2 purinoceptors. This receptor, designated P2Y7, has 352 amino acids and shares 23-30% amino acid identity with the P2Y1-P2Y6 purinoceptors. The P2Y7 cDNA was transiently expressed in COS-7 cells: binding studies thereon showed a very high affinity for ATP (37 +/- 6 nM), much less for UTP and ADP (approximately 1300 nM), and a novel rank order of affinities in the binding series studied of 8 nucleotides and suramin. The P2Y7 receptor sequence appears to denote a different subfamily from that of all the other known P2Y purinoceptors, with only a few of their characteristic sequence motifs shared. The P2Y7 receptor mRNA is abundantly present in the human heart and the skeletal muscle, moderately in the brain and liver, but not in the other tissues tested. The P2Y7 receptor mRNA was also abundantly present in the rat heart and cultured neonatal rat cardiomyocytes. The P2Y7 receptor is functionally coupled to phospholipase C in COS-7 cells transiently expressing this receptor. The P2Y7 gene was shown to be localized to human chromosome 14. We have thus cloned a unique member of the P2Y purinoceptor family which probably plays a role in the regulation of cardiac muscle contraction.

A novel G protein-coupled P2 purinoceptor (P2Y3) activated preferentially by nucleoside diphosphates

A partial cDNA was isolated by hybridization screening of an embryonic chick brain library for P2Y purinoceptors. After extension to full length, it revealed an open reading frame that encoded a protein, P2Y3, of 328 amino acids that is nearest in sequence identity to the G protein-coupled P2 purinoceptors obtained by DNA cloning. Expression of P2Y3 in cRNA-injected Xenopus oocytes confirmed that this cDNA encodes a member of the metabotropic purinoceptor family, with a novel order for the relative activities of nucleotides. At 100 microM concentrations, ADP gave the highest activity, and UTP and UDP were also strongly active. When expressed in the human T cell line Jurkat, P2Y3 mediated transient increases in intracellular Ca2+ in response to various nucleotides. Again, an unusual agonist rank order was revealed, with uridine nucleotides being more potent than adenosine nucleotides and UDP being the most potent agonist tested (half-maximal concentration, 0.13 microM) and 10-fold more potent than UTP. 2-Methylthlo-ATP was of relatively low activity in both systems. The receptor transcript is expressed in brain, spinal cord, kidney, and lung and is highly abundant in the spleen but not in other peripheral tissues that we tested. The results indicated that P2Y3 is a previously unknown P2 purinoceptor subtype with a preference for nucleoside diphosphates.

Identification of 6H1 as a P2Y purinoceptor: P2Y5

We have determined the identity of the orphan G-protein coupled receptor cDNA, 6H1, present in activated chicken T cells, as a subtype of P2Y purinoceptor. This identification is based on first on the degree of sequence identity shared with recently cloned members of the P2Y receptor family and second on the pharmacological profile. Upon transient expression in COS-7 cells the 6H1 receptor bound the radiolabel [35S]dATP alpha S specifically and with high affinity (Kd, 10 nM). This specific binding could be competitively displaced by a range of ligands active at P2 purinoceptors, with ATP being the most active (K (i)), 116 nM). Such competition studies have established the following rank order of activity: ATP ADP 2-methylthioATP alpha, beta-methylene ATP, UTP, thus confirming 6H1 as a member of the growing family of P2Y purinoceptors. As the fifth receptor of this type to be identified we suggest that it be named P2Y5.

Evaluation of oncofetal protein-related mRNA transport activity as a potential early cancer marker in dogs with malignant neoplasms

A 55-kd protein with mRNA transport activity found in fetal rat liver cells and plasma from mice, rats, and human beings with malignant neoplasms has been designated oncofetal protein 55 (OFP55). Monoclonal antibody produced to rat OFP55 cross-reacts with human OFP55. Using this monoclonal antibody in a bioassay measuring mRNA transport stimulated by OFP55, we tested the plasma from 19 dogs with a variety of malignant neoplasms, including carcinomas, sarcomas, lymphomas, and melanomas, and compared the results with plasma from 20 clinically normal dogs without evidence of neoplasia. The mean mRNA transport activity from the group of dogs with malignant neoplasms was 0.43 +/- 0.28%/mg of protein. Mean transport activity from the group of control dogs was 0.04 +/- 0.02%/mg of protein. These means were significantly different (P < 0.0001). The degree of overlap between these 2 groups in their OFP55-related mRNA transport activity was minimal, and measurement of this protein appears to have potential for the early detection of malignant neoplasms in dogs.

Characterisation of a recombinant P2Y purinoceptor

We have previously cloned a cDNA encoding a G-protein-coupled P2 purinoceptor from chick brain and designated this as a P2Y1 purinoceptor (Webb, T.E., J. Simon, B.J. Krishek, A.N. Bateson, T.G. Smart, B.J. King, G. Bumstock and E.A. Barnard, 1993, FEBS Lett. 324, 219). Here, we describe the further characterisation of this recombinant receptor expressed in both simian kidney endothelial (COS-7) cells and Xenopus oocytes. In transfected COS-7 cell membranes, the recombinant receptor showed a high level of expression (Bmax = 7.9 +/- 2.2. pmol [35S]dATP alpha S bound/mg protein) and affinity (Kd = 6.6 +/- 0.3 nM). In these COS-7 cells, the activation of the implanted purinoceptor induced a suramin-sensitive formation of inositol 1,4,5-triphosphatic (1,4,5InsP3). Upon expression in Xenopus oocytes, ATP was the only natural nucleoside triphosphate to elicit a Ca(2+)-activated chloride current. The P2 purinoceptor antagonists suramin and Reactive Blue-2 were both able to inhibit this evoked current. Utilizing both expression systems, the binding affinity profile and the functional pharmacological profile of the agonists, the common series found was: 2-methylthioATP (2-MeSATP) > or = ATP > ADP beta S > ADP. These two agonist series and the lack of activity of adenosine, alpha, beta-methyleneATP (alpha, beta-meATP), 3'-O-(4-benzoyl) benzoyl-ATP (Bz-ATP) and UTP, together confirmed that this receptor is a specific subtype of the P2Y purinoceptors.

Cloning and characterisation of a bovine P2Y receptor

Using a chick P2Y1 receptor cDNA probe we have isolated a mammalian P2Y receptor clone from a bovine aortic endothelial cell library. The sequence has a high degree of similarity to the chick P2Y1 clone. When transfected into the Jurkat cell line, the cDNA conferred sensitivity to purinoceptor agonists. Using fura-2 loaded cells the potency order at the receptor was found to be 2-methylthioadenosine 5' triphosphate = adenosine 5' diphosphate > adenosine 5' triphosphate >> alpha,beta-methyleneadenosine 5' triphosphate and uridine 5' triphosphate. This corresponds to the agonist potency order expected for the bovine aortic endothelial cell P2Y receptor.

Relative efficacy of glucarate on the initiation and promotion phases of rat mammary carcinogenesis

The independent effects of the potential cancer chemopreventive agent calcium glucarate (CGT) when fed (128 mmol/kg diet) during the initiation (I), promotion (P) or (I+P) phases of 7,12-dimethylbenzanthracene-induced rat mammary carcinogenesis, was compared to that of the known chemopreventive agent N-(4-hydroxyphenyl) retinamide (4-HPR) fed (2.0 mmol/kg diet) during these same phases. CGT and especially 4-HPR both significantly increased tumor latency when fed during the P-phase. When fed during I, P or I+P phases mammary tumor incidence was reduced compared to the controls 33%, 42% and 67% by 4-HPR and 18%, 42% and 50% by CGT. Similarly, tumor multiplicity was significantly reduced by either agent. For example, as compared to the corresponding control, when fed during the I, P or I+P phases 4-HPR reduced tumor multiplicity 63, 34 and 63%, while CGT reduced tumor multiplicity 28, 42 and 63% respectively. CGT, like 4-HPR, acts on both the I and P phases with the effect being maximal when fed during P and I+P phases.

Characterization of a P2Y purinoceptor in the brain

Little has been known of the abundance in the brain of any of the G protein coupled P2 purinoceptors nor their pharmacology. Here we show that [35S]dATP alpha S is a suitable radioligand for investigating these receptors and hence that they are exceptionally abundant both in one-day-old chick (Bmax: 37 pmol agonist sites/mg protein) and adult rat brain membranes (Bmax: 39 pmol/mg protein). [35S]dATP alpha S (which is selective for P2Y over the P2X types of purinoceptor) binds with high affinity to these sites in the chick (Kd: 13.3 nM) and in the rat brain membranes (Kd: 9.1 nM). The rank order of potency of purinoceptor-active agonists and antagonists displacing [35S]dATP alpha S binding is: dATP alpha S > (3'-deoxyATP, 2-methylthioATP, ATP alpha S, ATP) > 2'-deoxyATP > 2-methylthioADP > ADP >> suramin, Reactive Blue-2 >> UTP, L-beta,gamma-methyleneATP, adenosine; this defines these binding sites as P2Y subtypes of the P2 purinoceptors. This pharmacological profile of purinergic ligands is in excellent agreement with the potency order established for the recombinant P2Y1 purinoceptor from chick brain, identifying the great majority of the brain P2 purinoceptors as identical or very similar to the native P2Y1 receptor.

Transient expression of the recombinant chick brain P2y1 purinoceptor and localization of the corresponding mRNA

Extracellular ATP acts at specific cell surface purinoceptors to elicit a wide range of physiological responses. We have recently isolated a cDNA for a G-protein-coupled P2 purinoceptor (P2y1) from chick brain. It has been defined as a P2Y-like purinoceptor by the rank order of potency of P2 purinoceptor ligands, determined electrophysiologically in the Xenopus oocyte expression system. Here, we examine the ligand selectivity of this recombinant receptor, expressed transiently in COS-7 cells. The regional distribution of the P2y1 purinoceptor transcript within the one-day-post-hatch chick brain was also determined. It is widely expressed in the cerebellum and telencephalon and in specific nuclei of the mesencephalon and diencephalon, suggesting a neuronal localization of the P21 purinoceptor.

Pharmacokinetics relevant to the anti-carcinogenic and anti-tumor activities of glucarate and the synergistic combination of glucarate:retinoid in the rat

Alone and in synergistic combination with retinoids, dietary glucarate inhibits both the chemical induction and growth of rat mammary tumors. To investigate the pharmacokinetics of glucarate, [14C]glucarate was synthesized, converted to the calcium salt, and administered to rats bearing primary mammary tumors. When given by gavage, [14C]glucarate, as the calcium salt, showed a biphasic response in the blood. After peaking within 1 hr of administration at a level of 0.4 mumol/mL (normal endogenous level is approximately 0.04 mumol/mL), its plasma concentration dropped to 0.1 mumol/mL at 3 hr. In the second phase, there was a semilog increase to 0.6 mumol/mL at 15 hr, followed by a slow rise to 0.75 mumol/mL at 24 hr. Of the 38% of the administered glucarate that was recovered, 38% was excreted in the urine, and 30% remained in the gastrointestinal tract at 24 hr. Glucarate was concentrated 3- to 4-fold in the liver and intestinal mucosa, compared to the level in serum. With minor exception, the pharmacokinetics of [14C]13-cis-retinoic acid administered by gavage to rats was similar or not the semipurified diets were supplemented with 64 mmol/kg of calcium glucarate. During the interval between 5 and 10 hr post-administration of [14C]13-cis-retinoid, there was a transient 35-50% rise in the plasma level in rats on the glucarate-supplemented diet. This rise had no observable effect on the level of retinoid in major organs or in the tumor. A glucarate-binding protein was detected in the tumor cytosol. This potential receptor had a Ka of 1.49 x 10(7) M-1.

Activity of D-glucarate analogues: synergistic antiproliferative effects with retinoid in cultured human mammary tumor cells appear to specifically require the D-glucarate structure

D-Glucarate has shown modest chemopreventive and synergistic chemopreventive effects with retinoids in a number of tumor models as well as a similar antiproliferative effect in MCF-7 human tumor cells in culture. It has been postulated that D-glucarate exerts some of its effects by equilibrium conversion to D-glucarolactone, a potent beta-glucuronidase inhibitor. In the present study, D-glucarate and a number of its analogues, including D-glucarolactone, were evaluated as antiproliferatives in the MCF-7 model with and without added retinoid. Results suggest that the effects of glucarate are reasonably specific for its structure and may not require conversion to glucarolactone.