Enhanced microglial activity in FAAH(-/-) animals.

AIMS: Several lines of evidence suggest that the endocannabinoid system is involved in the regulation of glial activity. Enhanced levels of the endocannabinoid N-arachidonoyl ethanolamine (AEA, also referred to as anandamide) as well as non-cannabinoid lipids like palmitoylethanolamine (PEA) due to genetic deletion or pharmacologic blockade of its degrading enzyme fatty acid amide hydrolase (FAAH) reduced neuroinflammatory changes in models of neurodegeneration. Now we addressed the question if genetic deletion of FAAH also influences age-related neuroinflammation. MAIN METHODS: To answer this question we compared the number and size of microglia in young and old wild-type and FAAH(-/-) mice and analysed the distribution of microglia sizes in the four groups. Additionally, we analysed IL-6 and IL-1ß levels with ELISA and astrocyte activities as ratio of GFAP-positive areas in the hippocampus. KEY FINDINGS: Ageing was associated with an increased number and activity of microglia, elevated IL-6 and IL-1ß levels and enhanced area covered by astrocytes in wild-type animals. Unexpectedly, in FAAH(-/-) animals the number of microglia and the ratio of activated microglia and IL-1ß level were already higher in young animals than in age-matched wild-type controls. There was no further age-related increase in these inflammation markers in the knockout line. SIGNIFICANCE: Our results suggest that AEA is involved in the regulation of microglia activity. Life-long elevation of AEA levels disturbs microglial regulation and leads to pro-inflammatory changes.

The cannabinoid CB2 receptor-selective phytocannabinoid beta-caryophyllene exerts analgesic effects in mouse models of inflammatory and neuropathic pain.

The widespread plant volatile beta-caryophyllene (BCP) was recently identified as a natural selective agonist of the peripherally expressed cannabinoid receptor 2 (CB2). It is found in relatively high concentrations in many spices and food plants. A number of studies have shown that CB2 is critically involved in the modulation of inflammatory and neuropathic pain responses. In this study, we have investigated the analgesic effects of BCP in animal models of inflammatory and neuropathic pain. We demonstrate that orally administered BCP reduced inflammatory (late phase) pain responses in the formalin test in a CB2 receptor-dependent manner, while it had no effect on acute (early phase) responses. In a neuropathic pain model the chronic oral administration of BCP attenuated thermal hyperalgesia and mechanical allodynia, and reduced spinal neuroinflammation. Importantly, we found no signs of tolerance to the anti-hyperalgesic effects of BCP after prolonged treatment. Oral BCP was more effective than the subcutaneously injected synthetic CB2 agonist JWH-133. Thus, the natural plant product BCP may be highly effective in the treatment of long lasting, debilitating pain states. Our results have important implications for the role of dietary factors in the development and modulation of chronic pain conditions.

Smad-interacting protein 1 affects acute and tonic, but not chronic pain.

BACKGROUND: Smad-interacting protein 1 (also named Zeb2 and Zfhx1b) is a transcription factor that plays an important role in neuronal development and, when mutated, causes Mowat-Wilson syndrome (MWS). A corresponding mouse model carrying a heterozygous Zeb2 deletion was comprehensively analysed in the German Mouse Clinic. The most prominent phenotype was the reduced pain sensitivity. In this study, we investigated the role of Zeb2 in inflammatory and neuropathic pain. METHODS: For this, we tested mutant Zeb2 animals in different models of inflammatory pain like abdominal constriction, formalin and carrageenan test. Furthermore, we studied the pain reactivity of the mice after peripheral nerve ligation. To examine the nociceptive transmission of primary sensory dorsal root ganglia (DRG) neurons, we determined the neuronal activity in the spinal dorsal horn after the formalin test using staining of c-Fos. Next, we characterized the neuronal cell population in the DRGs and in the sciatic nerve to study the effect of the Zeb2 mutation on peripheral nerve morphology. RESULTS: The present data show that Zeb2 is involved in the development of primary sensory DRG neurons, especially of C- and Aδ fibres. These alterations contribute to a hypoalgesic phenotype in inflammatory but not in neuropathic pain in these Zeb2(+/-) mice. CONCLUSION: Our data suggest that the under-reaction to pain observed in MWS patients results from a reduced responsivity to nociceptive stimulation rather than an inability to communicate discomfort.

Near real time confocal microscopy of amelanotic tissue: dynamics of aceto-whitening enable nuclear segmentation.

High resolution, in vivo confocal imaging of amelanotic epithelial tissue may offer a clinically useful adjunct to standard histopathologic techniques. Application of acetic acid has been shown to enhance contrast in confocal images of these tissues. In this study, we record the time course of aceto-whitening at the cellular level and determine whether the contrast provided enables quantitative feature analysis. Confocal images and videos of cervical specimens were obtained throughout the epithelium before, during and post-acetic acid after the application of 6% acetic acid. Aceto-whitening occurs within seconds after the application. The confocal imaging system resolved sub-cellular detail throughout the entire epithelial thickness and provided sufficient contrast to enable quantitative feature analysis.