PI3K are a family of lipid kinase enzymes that are involved in a broad spectrum of cellular, physiological and pathological processes. Notably, PI3K dysfunction is associated with cancer, inflammation and metabolism. The PI3K family consists of three classes, Class I, Class II and Class III, which are defined according to their structure, function and lipid specificity. Class I is further subdivided into Class IA, which consists of p110α, p110β and p110δ, and Class IB, which consists of p110γ. Both p110α and p110β are ubiquitously expressed. Conversely, p110δ and p110γ have a restricted tissue distribution, limited mainly to leukocytes, where they are highly enriched. In this work, we have focused on understanding the role of p110δ in macrophages and specifically, on gaining insight into its role in genome-wide transcriptional regulation. Our results suggest that the contribution of p110δ activity to transcriptional regulation in growing primary macrophages is very limited. Genetic or pharmacological inactivation of p110δ resulted in differential regulation of less than twenty-five unique genes. Interestingly, at the level of genome-wide transcription, we have observed a significant difference between the effects of pharmacological and genetic inactivation. Indeed, none of the genes identified were differentially regulated as a result of both pharmacological and genetic inactivation of p110δ. We discovered that the majority of the genes differentially regulated in p110δ KI macrophages are located within close proximity to the Pik3cd gene. We propose that the differential regulation of these genes represents an artefact of the genetic engineering strategy employed to generate the p110δ KI mice. We have confirmed that genetic inactivation of p110δ results in reduced expression of Rab6b, a gene which is not linked to Pik3cd. We have confirmed that this does translate into a reduced level of rab6b protein in p110δ KI macrophages.

Macrophages (M?) are widely distributed immune cells and can be phenotypically polarised by microenvironment to mount specific functional programs. M? polarised in vitro can be broadly classified in two main groups: classically activated (or Ml), and alternatively activated (or M2) M?. M1 exhibit potent microbicidal properties and induce pro-inflammatory responses, whilst M2 play a role in resolution of inflammation and reduce pro-inflammatory responses.

Background: Microglial cells can be regarded as the macrophages of the central nervous system. Their activation has protective functions in the destruction of pathogens, removal of debris and release of neurotrophic factors, but excessive activation can exacerbate the effects of inflammation contributing to neurodegenerative conditions such as Alzheimers disease. The cannabinoids have a variety of anti-inflammatory properties and the main aim of this project is to determine the role of cannabinoids in modulation of microglial cell function using in vitro approaches, and to investigate the molecular mechanisms underlying such modulation. Methods: BV-2 murine microglial and primary murine microglial cells were activated using bacterial lipopolysaccharide (LPS). Nitric oxide (NO) was determined with a Griess assay. Western blotting was used to measure the expression of NFκB p65, Ikβα, inducible nitric oxide synthase (iNOS), COX-2, and total and phosphorylated forms of the MAP kinases, p38, JNK1/2 and ERK1/2; blots were analysed with an Odyssey imaging system (Li-Cor Bioscience), Expression of GPR55 mRNA was determined by RT-PCR. Phagocytosis was assessed in BV-2, HAPI and primary murine microglial cells and in RAW 264.7 monocyte/macrophages using fluorescent latex beads and the cells viewed by confocal microscopy. Fluorescent bead accumulation was quantified on consecutive image and rate phagocytic was calculated by normalizing the number of beads to the number of cells in each field. Western blotting was used to measure the expression of the receptor channels TRPV2 and TRPV1 and AKT. Immunocytochemistry was used to investigate the translocation of TRPV2, and the involvement of MLC11, PLCγ2, PKCα, ε in phagocytosis. Fura-2-based Ca2+ imaging of microglia was undertaken and migration was assessed using a novel “Compass” device. Result: BV-2 cells did not express CB1 or CB2 receptor mRNA; however, the cannabinoid receptor agonist CP55-940, the CB1 antagonist AM251and the non-psychoactive cannabinoid cannabidiol (CBD) all at 10μM produced significant inhibitions of lipopolysaccharide (LPS; 100ng/ml)-stimulated nitric oxide (NO) formation. The putative GPR55 receptor agonists VSN16R and O1916 (were without effect, as was the endogenous GPR55 agonist lysophosphatidylinositol (LPI). A number of other cannabinoid receptor agonists and antagonists and the phytocannabinoids (CBG, CBDV, THCV, CBDA and CBGA (Pertwee, 2008) (all 10 µM) were without. Cannabidiol inhibited LPS-enhancement of both iNOS and COX-2 expression. LPS significantly induced phosphorylation of the MAP kinases ERK 1/2, p38 and JNK and CBD inhibited both LPS-induced p38 and JNK phosphorylation but was without effect on phosphorylation of ERK1/2. The p38 inhibitor SB203580 (10 µM) also significantly reduced iNOS expression after 24 hours of LPS stimulation. LPS increased NF-KB p65 expression and this was significantly attenuated by CBD. LPS also stimulated NF-KB p65 translocation to the nucleus whereas CBD inhibited the effect. CBD-induced phagocytosis of BSA latex beads was similarly induced in HAPI, RAW264.7 and primary murine microglial cells. Inhibitors of Rho kinase (Y27632) and PI (3)kinase (wortmannin) inhibited basal but not CBD-enhanced phagocytosis. CBD increased intracellular calcium in BV-2 cells and the TRP channel blocker ruthenium red reversed CBD-induced phagocytosis. CBD increased expression of TRPV2 protein and mRNA and caused a translocation to the cell membrane. This was abolished in presence of cycloheximide and PI3K inhibitor. Other cannabinoids and phytocannabinoids (CBG, CBDV, THCV, CBDA and CBGA) were without effect. CBD also increased BV-2 cell migration. Conclusion: The data presented demonstrate that CBD, despite inhibiting NO formation, mediated by reduction of NF-kβ P38 MAPK, JNK and ROS activity, enhances microglial migration and phagocytosis. The mechanism of action appears to involve TRPV2 channel activation accompanied by increased protein synthesis and translocation to the cell membrane. Therefore, CBD might be developed as a useful treatment for neurodegenerative disease.

Human macrophages are one of the main targets for HIV-1 infection, despite their moderately low surface expression levels of the main HIV-1 receptor, CD4. The site of HIV-1 fusion can occur at the surface or following uptake through an endosomal pathway and it might be anticipated that the site would affect the progress of HIV-1 through the cell to the nucleus. Previous pharmacological studies provide one line of evidence for an endosomal entry route which is dependent on Detergent Resistant Membranes (DRMs). However, these findings need confirmation using a genetic approach, as small molecules may have multiple non-specific effects. For this study, a novel genetic approach was developed to manipulate sub-cellular CD4 distribution and investigate whether it determines the HIV-1 entry pathway in macrophages. This was achieved by transducing human embryonic stem cells (hESC) with lentiviral vectors and differentiating these cells into homogeneous genetically modified macrophages. This cellular system by-passes the challenges posed by the refractoriness to direct genetic manipulation of heterogeneous primary macrophages. Firstly, as proof of principle, a short hairpin RNA targeting CD4 was expressed in hESC-macrophages, resulting in knockdown of CD4 and, as anticipated, strong inhibition of HIV-1 infection. Secondly, expression of LCK in hESC-macrophages effectively tethered CD4 at the cell surface, and sequestered HIV-1 into an unproductive pathway, presumably through surface fusion, rather than progressing successfully to the nucleus. Thirdly, endogenous CD4 was substituted with CD4 mutants designed to be excluded from DRMs, which resulted in reduced successful HIV-1 entry versus substituted control CD4. The results support the model in which the productive entry pathway of HIV-1 in macrophages occurs via fusion after a raft-dependent endocytic uptake pathway, and requires CD4 localization to lipid rafts.