During neuroinflammation, activated microglial cells migrate toward dying neurons, where they exacerbate local cell damage. The signaling molecules that trigger microglial cell migration are poorly understood. In this paper, we show that pathological overstimulation of neurons by glutamate plus carbachol dramatically increases the production of the endocannabinoid 2-arachidonylglycerol (2-AG) but only slightly increases the production of anandamide and does not affect the production of two putative endocannabinoids, homo-␥-linolenylethanolamide and docosatetraenylethanolamide. We further show that pathological stimulation of microglial cells with ATP also increases the production of 2-AG without affecting the amount of other endocannabinoids. Using a Boyden chamber assay, we provide evidence that 2-AG triggers microglial cell migration. This effect of 2-AG occurs through CB2 and abnormal-cannabidiolsensitive receptors, with subsequent activation of the extracellular signal-regulated kinase 1/2 signal transduction pathway. It is important to note that cannabinol and cannabidiol, two nonpsychotropic ingredients present in the marijuana plant, prevent the 2-AG-induced cell migration by antagonizing the CB2 and abnormal-cannabidiol-sensitive receptors, respectively. Finally, we show that microglial cells express CB2 receptors at the leading edge of lamellipodia, which is consistent with the involvement of microglial cells in cell migration. Our study identifies a cannabinoid signaling system regulating microglial cell migration. Because this signaling system is likely to be involved in recruiting microglial cells toward dying neurons, we propose that cannabinol and cannabidiol are promising nonpsychotropic therapeutics to prevent the recruitment of these cells at neuroinflammatory lesion sites.

Recent studies suggest that the CREB-CRE transcriptional pathway is pivotal in the formation of some types of long-term memory. However, it has not been demonstrated that stimuli that induce learning and memory activate CRE-mediated gene expression. To address this issue, we used a mouse strain transgenic for a CRE-lac Z reporter to examine the effects of hippocampus-dependent learning on CRE-mediated gene expression in the brain. Training for contextual conditioning or passive avoidance led to significant increases in CRE-dependent gene expression in areas CA1 and CA3 of the hippocampus. Auditory cue fear-conditioning, which is amygdala dependent, was associated with increased CRE-mediated gene expression in the amygdala, but not the hippocampus. These data demonstrate that learning in response to behavioral conditioning activates the CRE transcriptional pathway in specific areas of brain.

It is well documented that estrogen can activate rapid signaling pathways in a variety of cell types. These non-classical effects of estrogen have been reported to be important for cell survival after exposure to a variety of neurotoxic insults. Since direct evidence of the ability of the estrogen receptors (ERs) a and/or b to mediate such responses is lacking, the hippocampal-derived cell line HT22 was stably transfected with either ERa (HTERa) or ERb (HTERb). In HTERa and HTERb cells, but not untransfected cells, an increase in ERK2 phosphorylation was measured within 15 min of 17b-estradiol treatment. The ER antagonist ICI 182, 780 (1 lM) and the MEK inhibitor, PD98059 (50 lM) blocked this increase in ERK2 phosphorylation. Treatment of HT22, HTERa and HTERb cells with the b-amyloid peptide (25-35) (10 lM) resulted in a significant decrease in cell viability. Pre-treatment for 15 min with 10 nM 17b-estradiol resulted in a 50% increase in the number of living cells in HTERa and HTERb cells, but not in HT22 cells. Finally, ICI 182, 780 and PD98059 prevented 17b-estradiol-mediated protection. This study demonstrates that both ERa and ERb can couple to rapid signaling events that mediate estrogen-elicited neuroprotection.

The ability of estrogen to rapidly initiate a variety of signal transduction cascades is increasingly recognized as playing an important role in a number of tissue-specific transcriptional actions of the hormone. In vivo, estrogen rapidly elicits phosphorylation of cAMP response element-binding protein (CREB). We have previously shown that both ER alpha and ER beta are capable of activating the MAPK pathway in response to a low dose of 17beta-estradiol. In the present study, the ability of estrogen to act through both ER alpha and ER beta to increase CREB phosphorylation was evaluated in an immortalized hippocampal cell line stably expressing either receptor. Estrogen treatment promoted rapid CREB phosphorylation, reaching a maximum by 15 min. This activation is completely blocked by the antiestrogen ICI 182,780, suggesting an estrogen receptor-dependent mechanism. The addition of the mitogen/ERK kinase-1 inhibitor, PD98059, also blocked the ability of estrogen to signal to CREB phosphorylation. Estrogen also caused an increase in p90Rsk activity, a critical mediator of MAPK effects. Surprisingly, blockade of the protein kinase A pathway in cells treated with estrogen did not affect estrogen-mediated CREB phosphorylation. Thus, MAPK and p90Rsk appear to be the primary mediators of estrogen-induced gene transcription through ER alpha and ER beta.

Prostate carcinogenesis is influenced by genetic alterations resulting in a biochemical condition that favors cell proliferation and survival. Studies of prostate carcinoma using comparative genomic hybridization and cDNA microarray analysis indicate that numerous biochemical processes may be affected during cellular transformation and progression to an invasive phenotype. Among the consistently observed tumor-associated changes are alterations in fatty acid metabolism that influence diverse cellular activities such as signaling, energy utilization, and membrane fluidity. Increases in fatty acid synthase (FAS) levels have been shown to be one of the earliest and most frequent molecular alterations in prostate carcinogenesis. We sought to identify tumor-associated changes in the expression of genes with functional roles associated with lipid metabolism. Defined populations of normal and neoplastic prostate epithelium were acquired by laser capture microdissection and transcript levels were measured by cDNA microarray hybridization. We determined that stearoylCoA desaturase (SCD) transcripts were downregulated in cancer relative to normal epithelium. These results were confirmed by quantitative PCR. Further analysis by immunohistochemical evaluation of radical prostatectomy samples employed a quantitative scoring system with a range of 0 -300. The median SCD expression levels were 150, 45 and 10 for normal, PIN and carcinoma samples, respectively. Statistically significant differential SCD expression between normal and cancerous epithelium was determined at the p ‫؍‬ 0.001 level, and between PIN and prostate carcinoma at the p ‫؍‬ 0.03 level. Of these cases, 92% overexpressed fatty acid synthase (FAS) in cancerous cells and 84.7% exhibited the signature of FAS overexpression and SCD loss in prostate carcinoma as compared to normal prostate epithelium. These results indicate that loss of SCD expression is a frequent event in prostate adenocarcinoma, and further supports a role for altered lipid metabolism as a factor in the process of carcinogenesis.