Mechanisms of viral entry: sneaking in the front door

Recent developments in methods to study virus internalisation are providing clearer insights into mechanisms used by viruses to enter host cells. The use of dominant negative constructs, specific inhibitory drugs and RNAi to selectively prevent entry through particular pathways has provided evidence for the clathrin-mediated entry of hepatitis C virus (HCV) as well as the caveolar entry of Simian Virus 40. Moreover, the ability to image and track fluorescent-labelled virus particles in real-time has begun to challenge the classical plasma membrane entry mechanisms described for poliovirus and human immunodeficiency virus. This review will cover both well-documented entry mechanisms as well as more recent discoveries in the entry pathways of enveloped and non-enveloped viruses. This will include viruses which enter the cytosol directly at the plasma membrane and those which enter via endocytosis and traversal of internal membrane barrier(s). Recent developments in imaging and inhibition of entry pathways have provided insights into the ill-defined entry mechanism of HCV, bringing it to the forefront of viral entry research. Finally, as high-affinity receptors often define viral internalisation pathways, and tropism in vivo, host membrane proteins to which viral particles specifically bind will be discussed throughout

Peripheral blood mononuclear cells from patients with rheumatoid arthritis spontaneously secrete vascular endothelial growth factor (VEGF): specific up-regulation by tumour necrosis factor-alpha (TNF-α) in synovial fluid

This study was designed to investigate VEGF production from peripheral blood mononuclear cells (PBMC) from patients with rheumatoid arthritis (RA) compared with healthy controls and to identify the predominant cellular source in PBMC isolated from RA patients. The regulation of PBMC VEGF production by cytokines and synovial fluid (SF) was studied. PBMC were isolated from RA patients and healthy controls and stimulated with lipopolysaccharide (LPS), IL-1β, IL-4, IL-6, IL-8, IL-10, TNF-α and transforming growth factor-beta (TGF-β) isoforms for varying time points up to 72 h at 37°C/5% CO2. The effect of SF on VEGF secretion by PBMC was also studied. Supernatant VEGF levels were measured using a flt-1 receptor capture ELISA. RA patients had significantly higher spontaneous production of VEGF compared with controls, and monocytes were identified as the predominant cellular source. RA PBMC VEGF production was up-regulated by TGF-β isoforms and TNF-α and down-regulated by IL-4 and IL-10, with no effect observed with IL-1β, IL-6 and IL-8. Antibody blocking experiments confirmed that TNF-α and not TGF-β isoforms in SF increased VEGF secretion by RA PBMC. These results emphasize the importance of monocytes as a source of VEGF in the pathophysiology of RA. Several cytokines known to be present in SF can modulate the level of VEGF secretion, but the predominant effect of SF in VEGF up-regulation is shown to be dependent on TNF-α

Cannabidiol Attenuates the Appetitive Effects of Δ9-Tetrahydrocannabinol in Humans Smoking Their Chosen Cannabis

Worldwide cannabis dependence is increasing, as is the concentration of Δ9-tetrahydrocannabinol (THC) in street cannabis. At the same time, the concentration of the second most abundant cannabinoid in street cannabis, cannabidiol (CBD), is decreasing. These two cannabinoids have opposing effects both pharmacologically and behaviorally when administered in the laboratory. No research has yet examined how the ratio of these constituents impacts on the appetitive/reinforcing effects of cannabis in humans. A total of 94 cannabis users were tested 7 days apart, once while non-intoxicated and once while acutely under the influence of their own chosen smoked cannabis on dependence-related measures. Using an unprecedented methodology, a sample of cannabis (as well as saliva) was collected from each user and analyzed for levels of cannabinoids. On the basis of CBD : THC ratios in the cannabis, individuals from the top and bottom tertiles were directly compared on indices of the reinforcing effects of drugs, explicit liking, and implicit attentional bias to drug stimuli. When intoxicated, smokers of high CBD : THC strains showed reduced attentional bias to drug and food stimuli compared with smokers of low CBD : THC. Those smoking higher CBD : THC strains also showed lower self-rated liking of cannabis stimuli on both test days. Our findings suggest that CBD has potential as a treatment for cannabis dependence. The acute modulation of the incentive salience of drug cues by CBD may possibly generalize to a treatment for other addictive disorders