MerTK expressing hepatic macrophages promote the resolution of inflammation in acute liver failure.

OBJECTIVE: Acute liver failure (ALF) is characterised by overwhelming hepatocyte death and liver inflammation with massive infiltration of myeloid cells in necrotic areas. The mechanisms underlying resolution of acute hepatic inflammation are largely unknown. Here, we aimed to investigate the impact of Mer tyrosine kinase (MerTK) during ALF and also examine how the microenvironmental mediator, secretory leucocyte protease inhibitor (SLPI), governs this response. DESIGN: Flow cytometry, immunohistochemistry, confocal imaging and gene expression analyses determined the phenotype, functional/transcriptomic profile and tissue topography of MerTK+ monocytes/macrophages in ALF, healthy and disease controls. The temporal evolution of macrophage MerTK expression and its impact on resolution was examined in APAP-induced acute liver injury using wild-type (WT) and Mer-deficient (Mer-/-) mice. SLPI effects on hepatic myeloid cells were determined in vitro and in vivo using APAP-treated WT mice. RESULTS: We demonstrate a significant expansion of resolution-like MerTK+HLA-DRhigh cells in circulatory and tissue compartments of patients with ALF. Compared with WT mice which show an increase of MerTK+MHCIIhigh macrophages during the resolution phase in ALF, APAP-treated Mer-/- mice exhibit persistent liver injury and inflammation, characterised by a decreased proportion of resident Kupffer cells and increased number of neutrophils. Both in vitro and in APAP-treated mice, SLPI reprogrammes myeloid cells towards resolution responses through induction of a MerTK+HLA-DRhigh phenotype which promotes neutrophil apoptosis and their subsequent clearance. CONCLUSIONS: We identify a hepatoprotective, MerTK+, macrophage phenotype that evolves during the resolution phase following ALF and represents a novel immunotherapeutic target to promote resolution responses following acute liver injury

Repeated PTZ Treatment at 25-Day Intervals Leads to a Highly Efficient Accumulation of Doublecortin in the Dorsal Hippocampus of Rats

BACKGROUND: Neurogenesis persists throughout life in the adult mammalian brain. Because neurogenesis can only be assessed in postmortem tissue, its functional significance remains undetermined, and identifying an in vivo correlate of neurogenesis has become an important goal. By studying pentylenetetrazole-induced brain stimulation in a rat model of kindling we accidentally discovered that 25±1 days periodic stimulation of Sprague-Dawley rats led to a highly efficient increase in seizure susceptibility. METHODOLOGY/PRINCIPAL FINDINGS: By EEG, RT-PCR, western blotting and immunohistochemistry, we show that repeated convulsive seizures with a periodicity of 25±1 days led to an enrichment of newly generated neurons, that were BrdU-positive in the dentate gyrus at day 25±1 post-seizure. At the same time, there was a massive increase in the number of neurons expressing the migratory marker, doublecortin, at the boundary between the granule cell layer and the polymorphic layer in the dorsal hippocampus. Some of these migrating neurons were also positive for NeuN, a marker for adult neurons. CONCLUSION/SIGNIFICANCE: Our results suggest that the increased susceptibility to seizure at day 25±1 post-treatment is coincident with a critical time required for newborn neurons to differentiate and integrate into the existing hippocampal network, and outlines the importance of the dorsal hippocampus for seizure-related neurogenesis. This model can be used as an in vivo correlate of neurogenesis to study basic questions related to neurogenesis and to the neurogenic mechanisms that contribute to the development of epilepsy

HBV DNA Integration and Clonal Hepatocyte Expansion in Chronic Hepatitis B Patients Considered Immune Tolerant

BACKGROUND & AIMS: Chronic hepatitis B virus (HBV) infection is characterized clinically by progression through disease phases. The first, labeled immune tolerant (IT), is perceived to lack disease activity. Here, we examined HBV-DNA integration, clonal hepatocyte expansion, HBV antigen expression and HBV-specific immunity in patients considered IT to assess whether this designation is appropriate, or if pathological changes may be present. METHODS: HBV-DNA integration, clonal hepatocyte expansion, HBsAg and HBcAg expression were studied in liver tissue from CHB patients, (age 14–39 years; median=24.5). These included 9 HBeAg(+) IT patients. Ten HBeAg(+) and 7 HBeAg(−) age-matched patients with active disease served as controls. HBV-specific T cells were quantified in paired peripheral blood lymphocytes. RESULTS: HBV antigen expression differed between the patient groups. However, unexpectedly high numbers of HBV-DNA integrations, randomly distributed across most chromosomes, were detectable in all patient groups. Patients considered IT also displayed significant clonal hepatocyte expansion, potentially in response to active HBV-specific T cell immunity. HBV-specific T cell responses were also confirmed in the periphery of these patients. CONCLUSIONS: A high level of HBV DNA integration and clonal hepatocyte expansion in patients considered IT suggests that events in hepatocarcinogenesis are underway even in the early stages of CHB. The concept that the IT phase is devoid of markers of disease progression and is immunologically inert is unsupported; instead, we propose that high replicative low inflammatory (HRLI) CHB more accurately reflects this early disease phase. The timing of therapeutic intervention to minimize further genetic damage to the hepatocyte population should be reconsidered

Fingolimod and tumor-infiltrating lymphocytes in checkpoint-inhibitor treated cancer patients

Immune checkpoint inhibitors (ICIs) are emerging as the new standard of care for treating various metastatic cancers. It is known that effective anti-tumor immune responses are associated with a stronger presence of tumor-infiltrating lymphocytes (TILs) in solid tumor tissue. Cancer patients with relapsing-remitting multiple sclerosis (RRMS) are often under continuous treatment with fingolimod, an immune-modulating drug that inhibits lymphocyte egress from secondary lymphatic organs. Little is known about the effect of fingolimod on ICI cancer therapy, as fingolimod may limit the number of TILs. Here we present three patients with RRMS, who developed various cancers during fingolimod treatment. Histology of all tumors consistently showed low numbers of TILs. A second biopsy taken from one of the tumors, a melanoma, revealed a significant increase of TILs after stopping fingolimod and starting pembrolizumab, indicating a surge in the number and re-invigoration of T cells. Our study suggests that fingolimod limits the number of TILs in solid tumors and may, thus, inhibit anti-cancer immune responses

Diagrams.

<p>(<i>Upper panel</i>): Flow diagram of Exp. #1 regarding times and type of treatment with pentylenetetrazole. <i>(Lower panel):</i> Schematic diagram of the distribution of proliferative (BrdU-positive) cells in the brain at day 25 after a single administration of a convulsive dose of PTZ. Note the change from a widespread distribution (<b>A</b>) to a more restricted distribution at 25 days post-seizure (<b>B</b>). In control rats, there were only a few BrdU-positive cells, often in a duplex, mitosis-like state (<b>C, D, E</b>). Many proliferative cells in PTZ-treated animals appeared to enter the brain from the circulation via leptomeningeal blood vessels (<b>F</b>, arrow points to a mitosis-like state). (<b>G</b>, <b>H</b>): Quantitation of BrdU-positive cells. One episode of convulsive seizure causes, at day 3, dramatically increased BrdU-positive cell numbers in the hippocampus (15-fold over controls; p = 0.001) (<b>G</b>) and temporal neocortex (22.5-fold over controls; p = 0.001) (<b>H</b>). Although the numbers of BrdU-positive cells decreased dramatically by day 25, their number remained, nonetheless, at relatively high levels in the hippocampus (4.8-fold; p = 0.001)(<b>G</b>) and temporal neocortex (5.6-fold; p = 0.001) (<b>H</b>) over control levels. N = 15 rats for each timepoint. <i>Abbreviations</i>: <i>Te-II</i>, temporal neocortex layer II; <i>Ent</i>, entorhinal neocortex; <i>HC</i>, hippocampus; <i>lep</i>, leptomeninx. Bars: (<b>C, D, E</b>), 20 µm; (<b>F</b>), 30 µm.</p

Number and phenotyping of BrdU-positive cells after seizure activity.

<p>Each PTZ treatment led to an accumulation of BrdU⁺ cells in the dentate gyrus of the kindled rats (9-fold, p = 0.0001; <b>A</b>). (<b>B–E</b>): 3D projections of confocal BrdU(red)/NeuN(green) double-labeled images from PTZ-treated animals. A single episode of seizure activity led to the appearance of BrdU-positive cells in the polymorphic layer that were in a mitosis-like state (<b>B</b>). Occasionally some neurons in layers II and III of the temporal neocortex also displayed BrdU⁺ cells in close apposition to neurons (<b>B</b>, insets). After 2× PTZ some BrdU-positive cells have differentiated into neurons, particularly in the granule cell layer (<b>C</b>, arrows). In addition, some BrdU-positive nuclei were detected in the walls of large blood vessels (<b>C</b>, inset). The number of double-labeled BrdU(red)/NeuN(green) increased with the number of PTZ injections and reached a maximum in the granule cells layer of kindled animals (<b>D</b>, low power; <b>E</b>, higher power). <i>Abbreviations</i>: <i>Te</i>, temporal neocortex; <i>GCL</i>, granule cell layer; <i>BV</i>, Blood Vessel.</p

Localization and quantification of DCX in the rat brain during kindling development.

<p>(<b>A, B</b>) Overview of DCX staining in the ventral (<b>A,</b> arrows) and dorsal (<b>B,</b> arrows) hippocampal hilus of the kindled animals. The dorsal hippocampus of kindled animals, was highly significant (p = 0.001) enriched in DCX⁺-cells (<b>C</b>). Note that the DCX antigens were localized both in cell bodies and extensions penetrating the densely packed granule cell neurons (<b>D</b>, arrows). (<b>E-F</b>): Phenotyping of DCX-cells. After 2× PTZ some DCX⁺ positive cells (green) in the dorsal hippocampus along the hilar border with the granule cell layer had a NeuN nucleus (red) (<b>E</b>, arrows). In kindled animals some of the DCX (green)/BrdU (red) double-labeled cells had a clonal appearance (<b>F</b>, inset, 3D-image) while other DCX⁺ cells (green) sometimes displayed a fragmented BrdU-positivity (<b>F</b>, arrow). By quantitative RT-PCR there was a 3-fold increase (p = 0.01) in the relative amount of DCX transcripts in kindled animals over that of controls (<b>G</b>). Note that the number of DCX⁺ cells also is maximal when PTZ is administered every 25^th day (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0039302#pone-0039302-g004" target="_blank">Fig. 4</a>H, filled circles) as opposed to every 30^th day (<b>H</b>, open circles). <i>Abbreviations</i>: <i>gcl</i>, granule cell layer; <i>hl</i>, hilus; <i>pml</i>, polymorphic layer. Bars: (<b>A,B</b>), 200 µm; (<b>D</b>), 100 µm.</p