Central and peripheral interactions between endocannabinoids and steroids, and implications for drug dependence

Role of Steroids on the Membrane Binding Ability of Fatty Acid Amide Hydrolase

Background: Fatty acid amide hydrolase (FAAH) is a membrane-bound homodimeric enzyme that gets in contact with a lipophilic substrate in the lipid bilayer, and then cleaves it into water soluble products. FAAH plays a critical role in modulating in vivo content and biological activity of endocannabinoids (eCBs), and its function is affected by membrane lipids. Increasing evidence suggests that also steroids can modulate endocannabinoid signaling, both in the central nervous system and at the periphery.

Methods: In this study, we interrogated the effect of six steroids with relevant biological activity (testosterone, hydrocortisone, estradiol, pregnenolone, progesterone, and cortisone) on the membrane binding ability of rat FAAH. The experimental data analysis obtained by Fluorescence Resonance Energy Transfer Spectroscopy was paralleled by computational docking analysis.

Results: Our data revealed distinct effects of the different steroids on the interaction of rat FAAH with model membranes. Among them, pregnenolone was found to be the most effective in raising rat FAAH affinity for model membranes. A possible binding pocket for steroid molecules was identified by docking analysis in the membrane-embedded region of the enzyme; such a pocket could account for the observed increase of the membrane affinity in the presence of the tested molecules.

Conclusions: Overall, the results point to steroids as new regulators of FAAH interaction with membranes, which may impact the biological activity of eCBs.

Interplay between endocannabinoids, steroids and cytokines in the control of human reproduction

The use of marijuana, which today is the most used recreational drug, has been demonstrated to affect adversely reproduction. Marijuana smokers, both men and women, show impaired fertility, owing to defective signalling pathways, aberrant hormonal regulation, or wrong timing during embryo implantation. Anandamide (N-arachidonoylethanolamine, AEA) and 2-arachidonoylglycerol (2-AG) mimic Delta(9)-tetrahydrocannabinol (THC), the psychoactive principle of Cannabis sativa, by binding to both the brain-type (CB(1)) and the spleen-type (CB(2)) cannabinoid receptors. These 'endocannabinoids' exert several actions either in the central nervous system or in peripheral tissues, and are metabolised by specific enzymes that synthesise or hydrolyse them. In this review, we shall describe the elements that constitute the endocannabinoid system (ECS), in order to put in a better perspective the role of this system in the control of human fertility, both in females and males. In addition, we shall discuss the interplay between ECS, sex hormones and cytokines, which generates an endocannabinoid-hormone-cytokine array critically involved in the control of human reproduction.

Modulation of the endocannabinoid system by focal brain ischemia in the rat is involved in neuroprotection afforded by 17beta-estradiol

Endogenous levels of the endocannabinoid anandamide, and the activities of the synthesizing and hydrolyzing enzymes, i.e. N-acylphosphatidylethanolamine-hydrolyzing phospholipase D and fatty acid amide hydrolase, respectively, were determined in the cortex and the striatum of rats subjected to transient middle cerebral artery occlusion. Anandamide content was markedly increased ( approximately 3-fold over controls; P < 0.01) in the ischemic striatum after 2 h of middle cerebral artery occlusion, but not in the cortex, and this elevation was paralleled by increased activity of N-acylphosphatidylethanolamine-hydrolyzing phospholipase D ( approximately 1.7-fold; P < 0.01), and reduced activity ( approximately 0.6-fold; P < 0.01) and expression ( approximately 0.7-fold; P < 0.05) of fatty acid amide hydrolase. These effects of middle cerebral artery occlusion were further potentiated by 1 h of reperfusion, whereas anandamide binding to type 1 cannabinoid and type 1 vanilloid receptors was not affected significantly by the ischemic insult. Additionally, the cannabinoid type 1 receptor antagonist SR141716, but not the receptor agonist R-(+)-WIN55,212-2, significantly reduced (33%; P < 0.05) cerebral infarct volume detected 22 h after the beginning of reperfusion. A neuroprotective intraperitoneal dose of 17beta-estradiol (0.20 mg x kg(-1)) that reduced infarct size by 43% also minimized the effect of brain ischemia on the endocannabinoid system, in an estrogen receptor-dependent manner. In conclusion, we show that the endocannabinoid system is implicated in the pathophysiology of transient middle cerebral artery occlusion-induced brain damage, and that neuroprotection afforded by estrogen is coincident with a re-establishment of anandamide levels in the ischemic striatum through a mechanism that needs to be investigated further.

Distinct molecular mechanisms underlying clinically relevant subtypes of breast cancer: gene expression analyses across three different platforms

Background

Gene expression profiling has been used to define molecular phenotypes of complex diseases such as breast cancer. The luminal A and basal-like subtypes have been repeatedly identified and validated as the two main subtypes out of a total of five molecular subtypes of breast cancer. These two are associated with distinctly different gene expression patterns and more importantly, a significant difference in clinical outcome. To further validate and more thoroughly characterize these two subtypes at the molecular level in tumors at an early stage, we report a gene expression profiling study using three different DNA microarray platforms.

Results

Expression data from 20 tumor biopsies of early stage breast carcinomas were generated on three different DNA microarray platforms; Applied Biosystems Human Genome Survey Microarrays, Stanford cDNA Microarrays and Agilent's Whole Human Genome Oligo Microarrays, and the resulting gene expression patterns were analyzed. Both unsupervised and supervised analyses identified the different clinically relevant subtypes of breast tumours, and the results were consistent across all three platforms. Gene classification and biological pathway analyses of the genes differentially expressed between the two main subtypes revealed different molecular mechanisms descriptive of the two expression-based subtypes: Signature genes of the luminal A subtype were over-represented by genes involved in fatty acid metabolism and steroid hormone-mediated signaling pathways, in particular estrogen receptor signaling, while signature genes of the basal-like subtype were over-represented by genes involved in cell proliferation and differentiation, p21-mediated pathway, and G1-S checkpoint of cell cycle-signaling pathways. A minimal set of 54 genes that best discriminated the two subtypes was identified using the combined data sets generated from the three different array platforms. These predictor genes were further verified by TaqMan^® Gene Expression assays.

Conclusion

We have identified and validated the two main previously defined clinically relevant subtypes, luminal A and basal-like, in a small set of early stage breast carcinomas. Signature genes characterizing these two subtypes revealed that distinct molecular mechanisms might have been pre-programmed at an early stage in different subtypes of the disease. Our results provide further evidence that these breast tumor subtypes represent biologically distinct disease entities and may require different therapeutic strategies. Finally, validated by multiple gene expression platforms, including quantitative PCR, the set of 54 predictor genes identified in this study may define potential prognostic molecular markers for breast cancer.