How to build a cognitive map.

Learning and interpreting the structure of the environment is an innate feature of biological systems, and is integral to guiding flexible behaviors for evolutionary viability. The concept of a cognitive map has emerged as one of the leading metaphors for these capacities, and unraveling the learning and neural representation of such a map has become a central focus of neuroscience. In recent years, many models have been developed to explain cellular responses in the hippocampus and other brain areas. Because it can be difficult to see how these models differ, how they relate and what each model can contribute, this Review aims to organize these models into a clear ontology. This ontology reveals parallels between existing empirical results, and implies new approaches to understand hippocampal-cortical interactions and beyond.

Phosphodiesterase 2A as a therapeutic target to restore cardiac neurotransmission during sympathetic hyperactivity.

Elevated levels of brain natriuretic peptide (BNP) are regarded as an early compensatory response to cardiac myocyte hypertrophy, although exogenously administered BNP shows poor clinical efficacy in heart failure and hypertension. We tested whether phosphodiesterase 2A (PDE2A), which regulates the action of BNP-activated cyclic guanosine monophosphate (cGMP), was directly involved in modulating Ca2+ handling from stellate ganglia (SG) neurons and cardiac norepinephrine (NE) release in rats and humans with an enhanced sympathetic phenotype. SG were also isolated from patients with sympathetic hyperactivity and healthy donor patients. PDE2A activity of the SG was greater in both spontaneously hypertensive rats (SHRs) and patients compared with their respective controls, whereas PDE2A mRNA was only high in SHR SG. BNP significantly reduced the magnitude of the calcium transients and ICaN in normal Wistar Kyoto (WKY) SG neurons, but not in the SHRs. cGMP levels stimulated by BNP were also attenuated in SHR SG neurons. Overexpression of PDE2A in WKY neurons recapitulated the calcium phenotype seen in SHR neurons. Functionally, BNP significantly reduced [3H]-NE release in the WKY rats, but not in the SHRs. Blockade of overexpressed PDE2A with Bay 60-7550 or overexpression of catalytically inactive PDE2A reestablished the modulatory action of BNP in SHR SG neurons. This suggests that PDE2A may be a key target in modulating the action of BNP to reduce sympathetic hyperactivity.

STING signalling: an emerging common pathway in autoimmunity and cancer.

The equipoise between the disease states of cancer and autoinflammation has perhaps been underappreciated in clinical practice and biomedical research. However, since the discover of STING (stimulator of interferon genes) as an integral regulator of innate immunity, a wealth of information has implicated this signaling pathway in both of these diseases. Under cellular homeostasis, STING serves to detect - and promote immune defense against - DNA viruses and intracellular bacteria, as described in its initial discovery. The role of STING has since been expanded to include tumor surveillance and immune responses to cancer; indeed, defective STING responses are associated with certain cancers. Conversely, constitutive activation of this pathway can result in autoinflammatory disease, whereby STING is over-stimulated by self-DNA. This review explores the current state of STING research, concluding that further elucidation of the details of the STING pathway may offer novel therapeutics for these diseases, which are of considerable clinical gravity.

Netrin-1 Reduces Monocyte and Macrophage Chemotaxis towards the Complement Component C5a.

Netrin-1, acting at its cognate receptor UNC5b, has been previously demonstrated to inhibit CC chemokine-induced immune cell migration. In line with this, we found that netrin-1 was able to inhibit CCL2-induced migration of bone marrow derived macrophages (BMDMs). However, whether netrin-1 is capable of inhibiting chemotaxis to a broader range of chemoattractants remains largely unexplored. As our initial experiments demonstrated that RAW264.7 and BMDMs expressed high levels of C5a receptor 1 (C5aR1) on their surface, we aimed to determine the effect of netrin-1 exposure on monocyte/macrophage cell migration induced by C5a, a complement peptide that plays a major role in multiple inflammatory pathologies. Treatment of RAW264.7 macrophages, BMDMs and human monocytes with netrin-1 inhibited their chemotaxis towards C5a, as measured using two different real-time methods. This inhibitory effect was found to be dependent on netrin-1 receptor signalling, as an UNC5b blocking antibody was able to reverse netrin-1 inhibition of C5a induced BMDM migration. Treatment of BMDMs with netrin-1 had no effect on C5aR1 proximal signalling events, as surface C5aR1 expression, internalisation and intracellular Ca2+ release following C5aR1 ligation remained unaffected after netrin-1 exposure. We next examined receptor distal events that occur following C5aR1 activation, but found that netrin-1 was unable to inhibit C5a induced phosphorylation of ERK1/2, Akt and p38, pathways important for cellular migration. Furthermore, netrin-1 treatment had no effect on BMDM cytoskeletal rearrangement following C5a stimulation as determined by microscopy and real-time electrical impedance sensing. Taken together these data highlight that netrin-1 inhibits monocyte and macrophage cell migration, but that the mechanism behind this effect remains unresolved. Nevertheless, netrin-1 and its cognate receptors warrant further investigation as they may represent a potential avenue for the development of novel anti-inflammatory therapeutics.