Physical and functional interaction between CB1 cannabinoid receptors and ��2-adrenoceptors

Background and purpose:

The CB₁ cannabinoid receptor and the β₂-adrenoceptor are G protein-coupled receptors (GPCRs) co-expressed in many tissues. The present study examined physical and functional interactions between these receptors in a heterologous expression system and in primary human ocular cells.

Experimental approach:

Physical interactions between CB₁ receptors and β₂-adrenoceptors were assessed using bioluminescence resonance energy transfer (BRET). Functional interactions between these receptors were evaluated by examining receptor trafficking, as well as extracellular signal-regulated kinase (ERK) and cyclic AMP response element binding protein (CREB) signalling.

Key results:

Physical interactions between CB₁ receptors and β₂-adrenoceptors were demonstrated using BRET. In human embryonic kidney (HEK) 293H cells, co-expression of β₂-adrenoceptors tempered the constitutive activity and increased cell surface expression of CB₁ receptors. Co-expression altered the signalling properties of CB₁receptors, resulting in increased Gα_i-dependent ERK phosphorylation, but decreased non-Gα_i-mediated CREB phosphorylation. The CB₁ receptor inverse agonist AM251 (N-(piperidin-1-yl)-5-(4-iodophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide) attenuated β₂-adrenoceptor-pERK signalling in cells expressing both receptors, while the CB₁ receptor neutral antagonist O-2050 ((6aR,10aR)-3-(1-methanesulfonylamino-4-hexyn-6-yl)-6a,7,10,10a-tetrahydro-6,6,9-trimethyl-6H-dibenzo[b,d]pyran) did not. The actions of AM251 and O-2050 were further examined in primary human trabecular meshwork (HTM) cells, which are ocular cells endogenously co-expressing CB₁ receptors and β₂-adrenoceptors. In HTM cells, as in HEK 293H cells, AM251 but not O-2050, altered the β₂-adrenoceptor–pERK response.

Conclusion and implications:

A complex interaction was demonstrated between CB₁ receptors and β₂-adrenoceptors in HEK 293H cells. As similar functional interactions were also observed in HTM cells, such interactions may affect the pharmacology of these receptors in tissues where they are endogenously co-expressed.This article is part of a themed issue on Cannabinoids. To view the editorial for this themed issue visit http://dx.doi.org/10.1111/j.1476-5381.2010.00831.x     

Guidelines for reporting experiments involving animals: the ARRIVE guidelines

British Journal of Pharmacology (BJP) is pleased to publish a new set of guidelines for reporting research involving animals, simultaneously with several other journals; the ‘ARRIVE’ guidelines (Animals in Research: Reporting In Vivo Experiments). This editorial summarizes the background to the guidelines, gives our view of their significance, considers aspects of specific relevance to pharmacology, re-states BJP''s guidelines for authors on animal experiments and indicates our commitment to carrying on discussion of this important topic. We also invite feedback via the British Pharmacological Society website.     

Large normal and reduced penetrance alleles in Huntington disease: instability in families and frequency at the laboratory,at the clinic and in the population

Sequeiros J, Ramos EM, Cerqueira J, Costa MC, Sousa A, Pinto‐Basto J, Alonso I. Large normal and reduced penetrance alleles in Huntington disease: instability in families and frequency at the laboratory, at the clinic and in the population. Large normal (‘intermediate’) alleles may produce de novo expansions in Huntington disease; nevertheless, there is very little evidence about their population prevalence and impact in daily practice, and there are conflicting reports about the extent of their instability. We estimated the frequency of large normal alleles (27–35 CAGs) and of reduced penetrance alleles (36–39 CAGs), as well as the frequency of genotypes carrying them, in (i) a diagnostic laboratory, (ii) a genetic counselling clinic and (iii) the general population. Large normal alleles were present in 6% of a large control sample, 7% of consultands who took pre‐symptomatic testing and 7% of samples in the laboratory. Reduced penetrance alleles were found in 1 of 1772 control chromosomes (0.1% of individuals), 5% of 146 pre‐symptomatic testees and over 2% of 1214 diagnostic samples (350 families). All 16 alleles sized 27–32 CAGs seemed to be transmitted stably; alleles ≥ 36 repeats were unstable in five families. Seven small full penetrance alleles contracted into the reduced penetrance range, but none into the large normal range. Evidence showed that large normal alleles are relatively frequent and that those with reduced penetrance are not a rare event, either at the laboratory or the clinic. This reinforces the need to understand the genomic context of repeat instability in each family and population.     

Effect of low doses of cannabidiolic acid and ondansetron on LiCl-induced conditioned gaping (a model of nausea-induced behaviour) in rats

Background and Purpose

To determine the minimally effective dose of cannabidiolic acid (CBDA) that effectively reduces lithium chloride (LiCl)-induced conditioned gaping reactions (nausea-induced behaviour) in rats and to determine if these low systemic doses of CBDA (5–0.1 μg·kg⁻¹) relative to those of CBD could potentiate the anti-nausea effects of the classic 5-hydroxytryptamine 3 (5-HT₃) receptor antagonist, ondansetron (OND).

Experimental Approach

We investigated the efficacy of low doses of CBDA to suppress acute nausea, assessed by the establishment of conditioned gaping to a LiCl-paired flavour in rats. The potential of threshold and subthreshold doses of CBDA to enhance the reduction of nausea-induced conditioned gaping by OND were then determined.

Key Results

CBDA (at doses as low as 0.5 μg·kg⁻¹) suppressed nausea-induced conditioned gaping to a flavour. A low dose of OND (1.0 μg·kg⁻¹) alone reduced nausea-induced conditioned gaping, but when it was combined with a subthreshold dose of CBDA (0.1 μg·kg⁻¹) there was an enhancement in the suppression of LiCl-induced conditioned gaping.

Conclusions and Implications

CBDA potently reduced conditioned gaping in rats, even at low doses and enhanced the anti-nausea effect of a low dose of OND. These findings suggest that combining low doses of CBDA and OND will more effectively treat acute nausea in chemotherapy patients.     

Patient preference and satisfaction in hospital-at-home and usual hospital care for COPD exacerbations: Results of a randomised controlled trial

Background

In the absence of clear differences in effectiveness and cost-effectiveness between hospital-at-home schemes and usual hospital care, patient preference plays an important role. This study investigates patient preference for treatment place, associated factors and patient satisfaction with a community-based hospital-at-home scheme for COPD exacerbations.

Methods

The study is part of a larger randomised controlled trial. Patients were randomised to usual hospital care or early assisted discharge which incorporated discharge at day 4 and visits by a home care nurse until day 7 of treatment (T + 4 days). The hospital care group received care as usual and was discharged from hospital at day 7. Patients were followed for 90 days (T + 90 days). Patient preference for treatment place and patient satisfaction (overall and per item) were assessed quantitatively and qualitatively using questionnaires at T + 4 days and T + 90 days. Factors associated with patient preference were analysed in the early assisted discharge group.

Results

139 patients were randomised. No difference was found in overall satisfaction. At T + 4 days, patients in the early assisted discharge group were less satisfied with care at night and were less able to resume normal daily activities. At T + 90 days there were no differences for the separate items. Patient preference for home treatment at T + 4 days was 42% in the hospital care group and 86% in the early assisted discharge group and 35% and 59% at T + 90 days. Patients’ mental state was associated with preference.

Conclusion

Results support the wider implementation of early assisted discharge for COPD exacerbations and this treatment option should be offered to selected patients that prefer home treatment.     

A modeling approach to evaluate long-term outcome of prophylactic and on demand treatment strategies for severe hemophilia A

Background

Severe hemophilia requires life-long treatment with expensive clotting factor concentrates; studies comparing effects of different therapeutic strategies over decades are very difficult to perform. A simulation model was developed to evaluate the long-term outcome of on demand, prophylactic and mixed treatment strategies for patients with severe hemophilia A.

Design and Methods

A computer model was developed based on individual patients’ data from a Dutch cohort study in which intermediate dose prophylaxis was used and a French cohort study in which on demand treatment was used, and multivariate regression analyses. This model simulated individual patients’ life expectancy, onset of bleeding, life-time joint bleeds, radiological outcome and concentrate use according to the different treatment strategies.

Results

According to the model, life-time on demand treatment would result in an average of 1,494 joint bleeds during the hemophiliac’s life, and consumption of 4.9 million IU of factor VIII concentrate. In contrast, life-time intermediate dose prophylaxis resulted in a mean of 357 joint bleeds and factor consumption of 8.3 million IU. A multiple switch strategy (between prophylactic and on demand treatment based on bleeding pattern) resulted in a mean number of 395 joint bleeds and factor consumption of 6.6 million IU. The estimated proportion of patients with Pettersson scores over 28 points was 32% for both the prophylactic and the multiple switching strategies, compared to 76% for continuous on demand treatment.

Conclusions

The present model allows evaluation of the impact of various treatment strategies on patients’ joint bleeds and clotting factor consumption. It may be expanded with additional data to allow more precise estimates and include economic evaluations of treatment strategies.