A profile of adult patients with major burns admitted to a Level 1 Trauma Centre and their functional outcomes at discharge: A retrospective review

Background: Patients with major burns suffer with pain, which impacts their physical function during hospitalisation.Objectives: To describe the demographics, burn characteristics, clinical course, physical function, complications developed after major burns and to establish predictors of non-independent physical function at hospital discharge.Method: Records of all consecutive adult burn admissions to a Level 1 Trauma Centre between 2015 and 2017 were screened retrospectively against our study criteria, using the Trauma Bank Data Registry. Anonymised data from included records were captured on specifically designed data extraction forms. Descriptive statistics were used to summarise findings. A regression analysis was undertaken to establish predictors of non-independent function at discharge.Results: Males represented 87.7% (n = 64) of included records (n = 73). Median age was 38 (interquartile range [IQR]: 22). Thermal burns were most reported (n = 47, 64.4%), followed by median total body surface area (TBSA) 31% and head and arms were most affected (60.3% and 71.2%). Injury severity was high with median intensive care unit (ICU) length of stay (LOS) of 17 (IQR: 34) and hospital LOS 44 (IQR: 31) days. Wound debridement was mostly performed (n = 27, 36.9%) with limb oedema as a common complication (n = 15, 21.7%). Muscle strength and functional performance improved throughout LOS. None of the variables identified were predictors of non-independent function at hospital discharge.Conclusion: Adults with major burns were predominantly male, in mid-life and sustained thermal injury with a high injury severity. Decreased range of motion (ROM) of affected areas, ‘fair’ muscle strength and independent function were recorded for most patients at hospital discharge.Clinical implications: These findings contribute to the limited body of evidence on the profile, clinical course and outcomes of South African adult burn patients.

Neuroinflammation: A Potential Risk for Dementia

Dementia is a neurodegenerative condition that is considered a major factor contributing to cognitive decline that reduces independent function. Pathophysiological pathways are not well defined for neurodegenerative diseases such as dementia; however, published evidence has shown the role of numerous inflammatory processes in the brain contributing toward their pathology. Microglia of the central nervous system (CNS) are the principal components of the brain’s immune defence system and can detect harmful or external pathogens. When stimulated, the cells trigger neuroinflammatory responses by releasing proinflammatory chemokines, cytokines, reactive oxygen species, and nitrogen species in order to preserve the cell’s microenvironment. These proinflammatory markers include cytokines such as IL-1, IL-6, and TNFα chemokines such as CCR3 and CCL2 and CCR5. Microglial cells may produce a prolonged inflammatory response that, in some circumstances, is indicated in the promotion of neurodegenerative diseases. The present review is focused on the involvement of microglial cell activation throughout neurodegenerative conditions and the link between neuroinflammatory processes and dementia.

Human Group IIA Phospholipase A2—Three Decades on from Its Discovery

Phospholipase A2 (PLA2) enzymes were first recognized as an enzyme activity class in 1961. The secreted (sPLA2) enzymes were the first of the five major classes of human PLA2s to be identified and now number nine catalytically-active structurally homologous proteins. The best-studied of these, group IIA sPLA2, has a clear role in the physiological response to infection and minor injury and acts as an amplifier of pathological inflammation. The enzyme has been a target for anti-inflammatory drug development in multiple disorders where chronic inflammation is a driver of pathology since its cloning in 1989. Despite intensive effort, no clinically approved medicines targeting the enzyme activity have yet been developed. This review catalogues the major discoveries in the human group IIA sPLA2 field, focusing on features of enzyme function that may explain this lack of success and discusses future research that may assist in realizing the potential benefit of targeting this enzyme. Functionally-selective inhibitors together with isoform-selective inhibitors are necessary to limit the apparent toxicity of previous drugs. There is also a need to define the relevance of the catalytic function of hGIIA to human inflammatory pathology relative to its recently-discovered catalysis-independent function.

Clathrin-mediated endocytosis-independent function of VAN3 ARF GTPase Activating Protein at the plasma membrane

ARF small GTPases in plants serve important cellular functions in subcellular trafficking and developmental functions in auxin-mediated patterning of the plant body. The Arabidopsis thaliana ARF regulator ARF-GAP VAN3 has been implicated to act at the plasma membrane (PM) and linked functionally to the clathrin- and dynamin-mediated endocytosis. Here we re-evaluated the localization of VAN3 at the PM and its function in endocytosis. Using Total Internal Reflection Fluorescence microscopy we observed remarkably transient associations of VAN3 to the PM at discrete foci, however, devoid of clathrin, the dynamin isoform DRP1A, or the ARF regulator GNOM, which is also involved in a developmental patterning function mediated from the PM. Clathrin-coated pits are abundant and endocytosis appears to proceed normally in van3-1 knockout mutant. In turn, post-translational silencing of clathrin expression indicates that the localization of VAN3 at the PM depends on clathrin function, presumably on clathrin-mediated endocytosis.

Dynein acts to cluster glutamate receptors and traffic the PIP5 kinase, Skittles, to regulate postsynaptic membrane organization at the neuromuscular junction

Cytoplasmic dynein is essential in motoneurons for retrograde cargo transport that sustains neuronal connectivity. Little, however, is known about dynein's function on the postsynaptic side of the circuit. Here we report distinct postsynaptic roles for dynein at neuromuscular junctions (NMJs). Intriguingly, we show that dynein punctae accumulate postsynaptically at glutamatergic synaptic terminals. Moreover, Skittles, a phosphatidylinositol 4-phosphate 5-kinase that produces PI(4,5)P2 to organize the spectrin cytoskeleton, also localizes specifically to glutamatergic synaptic terminals. Depletion of postsynaptic dynein disrupts the accumulation of Skittles, PI(4,5)P2 phospholipid, and organization of the spectrin cytoskeleton at the postsynaptic membrane. Coincidental with dynein depletion, we observe an increase in the clusters size of ionotropic glutamate receptor (iGluR), and an increase in the amplitude and frequency of mEJPs. However, PI(4,5)P2 levels do not affect iGluR clustering and dynein does not affect the protein levels of iGluR subunits at the NMJ, suggesting a separate, transport independent function for dynein in iGluR cluster organization. As dynein punctae closely associate with iGluR clusters, we propose that dynein physically tethers iGluR clusters at the postsynaptic membrane to ensure proper synaptic transmission.

A kinase-independent function of PAK is crucial for pathogen-mediated actin remodelling

The p21-activated kinase (PAK) family regulate a multitude of cellular processes, including actin cytoskeleton remodelling. Numerous bacterial pathogens usurp host signalling pathways that regulate actin reorganisation in order to promote Infection. Salmonella and pathogenic Escherichia coli drive actin-dependent forced uptake and intimate attachment respectively. We demonstrate that the pathogen-driven generation of both these distinct actin structures relies on the recruitment and activation of PAK. We show that the PAK kinase domain is dispensable for this actin remodelling, which instead requires the GTPase-binding CRIB and the central poly-proline rich region. PAK interacts with and inhibits the guanine nucleotide exchange factor β-PIX, preventing it from exerting a negative effect on cytoskeleton reorganisation. This kinase-independent function of PAK may be usurped by other pathogens that modify host cytoskeleton signalling and helps us better understand how PAK functions in normal and diseased eukaryotic cells.

A catalytic-independent function of human DNA polymerase Kappa controls the stability and abundance of the Checkpoint Kinase 1

DNA polymerase kappa (Pol κ) has been well documented thus far for its specialized DNA synthesis activity during translesion replication, progression of replication forks through regions difficult to replicate, restart of stalled forks and replication checkpoint efficiency. Pol κ is also required for the stabilization of stalled forks although the mechanisms are poorly understood. Here we unveiled an unexpected role for Pol κ in controlling the stability and abundance of Chk1, an important actor for the replication checkpoint and fork stabilization. We found that loss of Pol κ decreased the Chk1 protein level in the nucleus of four human cell lines. Pol κ and not the other Y‐family polymerase members is required to maintain the Chk1 protein pool all along the cell cycle. We showed that Pol κ depletion affected the protein stability of Chk1 and protected it from proteasome degradation. Importantly, we also observed that the fork restart defects observed in Pol κ-depleted cells could be overcome by the re-expression of Chk1. Strikingly, this new function of Pol κ does not require its catalytic activity. We propose that Pol κ could contribute to the protection of stalled forks through Chk1 stability.

PlzA is a bifunctional c-di-GMP biosensor that promotes tick and mammalian host-adaptation of Borrelia burgdorferi

In this study, we examined the relationship between c-di-GMP and its only known effector protein, PlzA, in Borrelia burgdorferi during the arthropod and mammalian phases of the enzootic cycle. Using a B. burgdorferi strain expressing a plzA point mutant (plzA-R145D) unable to bind c-di-GMP, we confirmed that the protective function of PlzA in ticks is c-di-GMP-dependent. Unlike ΔplzA spirochetes, which are severely attenuated in mice, the plzA-R145D strain was fully infectious, firmly establishing that PlzA serves a c-di-GMP-independent function in mammals. Contrary to prior reports, loss of PlzA did not affect expression of RpoS or RpoS-dependent genes, which are essential for transmission, mammalian host-adaptation and murine infection. To ascertain the nature of PlzA’s c-di-GMP-independent function(s), we employed infection models using (i) host-adapted mutant spirochetes for needle inoculation of immunocompetent mice and (ii) infection of scid mice with in vitro-grown organisms. Both approaches substantially restored ΔplzA infectivity, suggesting that PlzA enables B. burgdorferi to overcome an early bottleneck to infection. Furthermore, using a Borrelia strain expressing a heterologous, constitutively active diguanylate cyclase, we demonstrate that ‘ectopic’ production of c-di-GMP in mammals abrogates spirochete virulence and interferes with RpoS function at the post-translational level in a PlzA-dependent manner. Structural modeling and SAXS analysis of liganded- and unliganded-PlzA revealed marked conformational changes that underlie its biphasic functionality. This structural plasticity likely enables PlzA to serve as a c-di-GMP biosensor that in its respective liganded and unliganded states promote vector- and host-adaptation by the Lyme disease spirochete.