Cellular Radiosensitivity: How much better do we understand it?

Purpose: Ionizing radiation exposure gives rise to a variety of lesions in DNA that result in genetic instability and potentially tumorigenesis or cell death. Radiation extends its effects on DNA by direct interaction or by radiolysis of H2O that generates free radicals or aqueous electrons capable of interacting with and causing indirect damage to DNA. While the various lesions arising in DNA after radiation exposure can contribute to the mutagenising effects of this agent, the potentially most damaging lesion is the DNA double strand break (DSB) that contributes to genome instability and/or cell death. Thus in many cases failure to recognise and/or repair this lesion determines the radiosensitivity status of the cell. DNA repair mechanisms including homologous recombination (HR) and non-homologous end-joining (NHEJ) have evolved to protect cells against DNA DSB. Mutations in proteins that constitute these repair pathways are characterised by radiosensitivity and genome instability. Defects in a number of these proteins also give rise to genetic disorders that feature not only genetic instability but also immunodeficiency, cancer predisposition, neurodegeneration and other pathologies. Conclusions: In the past fifty years our understanding of the cellular response to radiation damage has advanced enormously with insight being gained from a wide range of approaches extending from more basic early studies to the sophisticated approaches used today. In this review we discuss our current understanding of the impact of radiation on the cell and the organism gained from the array of past and present studies and attempt to provide an explanation for what it is that determines the response to radiation

Autoimmune and autoinflammatory mechanisms in uveitis

The eye, as currently viewed, is neither immunologically ignorant nor sequestered from the systemic environment. The eye utilises distinct immunoregulatory mechanisms to preserve tissue and cellular function in the face of immune-mediated insult; clinically, inflammation following such an insult is termed uveitis. The intra-ocular inflammation in uveitis may be clinically obvious as a result of infection (e.g. toxoplasma, herpes), but in the main infection, if any, remains covert. We now recognise that healthy tissues including the retina have regulatory mechanisms imparted by control of myeloid cells through receptors (e.g. CD200R) and soluble inhibitory factors (e.g. alpha-MSH), regulation of the blood retinal barrier, and active immune surveillance. Once homoeostasis has been disrupted and inflammation ensues, the mechanisms to regulate inflammation, including T cell apoptosis, generation of Treg cells, and myeloid cell suppression in situ, are less successful. Why inflammation becomes persistent remains unknown, but extrapolating from animal models, possibilities include differential trafficking of T cells from the retina, residency of CD8(+) T cells, and alterations of myeloid cell phenotype and function. Translating lessons learned from animal models to humans has been helped by system biology approaches and informatics, which suggest that diseased animals and people share similar changes in T cell phenotypes and monocyte function to date. Together the data infer a possible cryptic infectious drive in uveitis that unlocks and drives persistent autoimmune responses, or promotes further innate immune responses. Thus there may be many mechanisms in common with those observed in autoinflammatory disorders

Hyperhomocysteinemia is independently associated with albuminuria in the population-based CoLaus study

<p>Abstract</p> <p>Background</p> <p>Increased serum levels of homocysteine and uric acid have each been associated with cardiovascular risk. We analyzed whether homocysteine and uric acid were associated with glomerular filtration rate (GFR) and albuminuria independently of each other. We also investigated the association of <it>MTHFR </it>polymorphisms related to homocysteine with albuminuria to get further insight into causality.</p> <p>Methods</p> <p>This was a cross-sectional population-based study in Caucasians (<it>n </it>= 5913). Hyperhomocysteinemia was defined as total serum homocysteine ≥ 15 μmol/L. Albuminuria was defined as urinary albumin-to-creatinine ratio > 30 mg/g.</p> <p>Results</p> <p>Uric acid was associated positively with homocysteine (r = 0.246 in men and r = 0.287 in women, <it>P </it>< 0.001). The prevalence of albuminuria increased across increasing homocysteine categories (from 6.4% to 17.3% in subjects with normal GFR and from 3.5% to 14.5% in those with reduced GFR, <it>P </it>for trend < 0.005). Hyperhomocysteinemia (OR = 2.22, 95% confidence interval: 1.60-3.08, <it>P </it>< 0.001) and elevated serum uric acid (OR = 1.27, 1.08-1.50, per 100 μmol/L, <it>P </it>= 0.004) were significantly associated with albuminuria, independently of hypertension and type 2 diabetes. The 2-fold higher risk of albuminuria associated with hyperhomocysteinemia was similar to the risk associated with hypertension or diabetes. <it>MTHFR </it>alleles related to higher homocysteine were associated with increased risk of albuminuria.</p> <p>Conclusions</p> <p>In the general adult population, elevated serum homocysteine and uric acid were associated with albuminuria independently of each other and of renal function.</p

Chemical Addressability of Ultraviolet-Inactivated Viral Nanoparticles (VNPs)

. Thus, inactivation of the virus RNA genome is important for biosafety considerations, however the surface characteristics and chemical reactivity of the particles must be maintained in order to preserve chemical and structural functionality. were shown to maintain particle structure and chemical reactivity, and cellular binding properties were similar to CPMV-WT. applications

H5N1 and 1918 Pandemic Influenza Virus Infection Results in Early and Excessive Infiltration of Macrophages and Neutrophils in the Lungs of Mice

Fatal human respiratory disease associated with the 1918 pandemic influenza virus and potentially pandemic H5N1 viruses is characterized by severe lung pathology, including pulmonary edema and extensive inflammatory infiltrate. Here, we quantified the cellular immune response to infection in the mouse lung by flow cytometry and demonstrate that mice infected with highly pathogenic (HP) H1N1 and H5N1 influenza viruses exhibit significantly high numbers of macrophages and neutrophils in the lungs compared to mice infected with low pathogenic (LP) viruses. Mice infected with the 1918 pandemic virus and a recent H5N1 human isolate show considerable similarities in overall lung cellularity, lung immune cell sub-population composition and cellular immune temporal dynamics. Interestingly, while these similarities were observed, the HP H5N1 virus consistently elicited significantly higher levels of pro-inflammatory cytokines in whole lungs and primary human macrophages, revealing a potentially critical difference in the pathogenesis of H5N1 infections. These results together show that infection with HP influenza viruses such as H5N1 and the 1918 pandemic virus leads to a rapid cell recruitment of macrophages and neutrophils into the lungs, suggesting that these cells play a role in acute lung inflammation associated with HP influenza virus infection. In addition, primary macrophages and dendritic cells were also susceptible to 1918 and H5N1 influenza virus infection in vitro and in infected mouse lung tissue

Calcium-Activated Potassium Channels BK and IK1 Are Functionally Expressed in Human Gliomas but Do Not Regulate Cell Proliferation

Gliomas are morbid brain tumors that are extremely resistant to available chemotherapy and radiology treatments. Some studies have suggested that calcium-activated potassium channels contribute to the high proliferative potential of tumor cells, including gliomas. However, other publications demonstrated no role for these channels or even assigned them antitumorogenic properties. In this work we characterized the expression and functional contribution to proliferation of Ca2+-activated K+ channels in human glioblastoma cells. Quantitative RT-PCR detected transcripts for the big conductance (BK), intermediate conductance (IK1), and small conductance (SK2) K+ channels in two glioblastoma-derived cell lines and a surgical sample of glioblastoma multiforme. Functional expression of BK and IK1 in U251 and U87 glioma cell lines and primary glioma cultures was verified using whole-cell electrophysiological recordings. Inhibitors of BK (paxilline and penitrem A) and IK1 channels (clotrimazole and TRAM-34) reduced U251 and U87 proliferation in an additive fashion, while the selective blocker of SK channels UCL1848 had no effect. However, the antiproliferative properties of BK and IK1 inhibitors were seen at concentrations that were higher than those necessary to inhibit channel activity. To verify specificity of pharmacological agents, we downregulated BK and IK1 channels in U251 cells using gene-specific siRNAs. Although siRNA knockdowns caused strong reductions in the BK and IK1 current densities, neither single nor double gene silencing significantly affected rates of proliferation. Taken together, these results suggest that Ca2+-activated K+ channels do not play a critical role in proliferation of glioma cells and that the effects of pharmacological inhibitors occur through their off-target actions

Human Genetics in Rheumatoid Arthritis Guides a High-Throughput Drug Screen of the CD40 Signaling Pathway

Although genetic and non-genetic studies in mouse and human implicate the CD40 pathway in rheumatoid arthritis (RA), there are no approved drugs that inhibit CD40 signaling for clinical care in RA or any other disease. Here, we sought to understand the biological consequences of a CD40 risk variant in RA discovered by a previous genome-wide association study (GWAS) and to perform a high-throughput drug screen for modulators of CD40 signaling based on human genetic findings. First, we fine-map the CD40 risk locus in 7,222 seropositive RA patients and 15,870 controls, together with deep sequencing of CD40 coding exons in 500 RA cases and 650 controls, to identify a single SNP that explains the entire signal of association (rs4810485, P = 1.4×10(−9)). Second, we demonstrate that subjects homozygous for the RA risk allele have ∼33% more CD40 on the surface of primary human CD19+ B lymphocytes than subjects homozygous for the non-risk allele (P = 10(−9)), a finding corroborated by expression quantitative trait loci (eQTL) analysis in peripheral blood mononuclear cells from 1,469 healthy control individuals. Third, we use retroviral shRNA infection to perturb the amount of CD40 on the surface of a human B lymphocyte cell line (BL2) and observe a direct correlation between amount of CD40 protein and phosphorylation of RelA (p65), a subunit of the NF-κB transcription factor. Finally, we develop a high-throughput NF-κB luciferase reporter assay in BL2 cells activated with trimerized CD40 ligand (tCD40L) and conduct an HTS of 1,982 chemical compounds and FDA–approved drugs. After a series of counter-screens and testing in primary human CD19+ B cells, we identify 2 novel chemical inhibitors not previously implicated in inflammation or CD40-mediated NF-κB signaling. Our study demonstrates proof-of-concept that human genetics can be used to guide the development of phenotype-based, high-throughput small-molecule screens to identify potential novel therapies in complex traits such as RA

Imaging findings in noncraniofacial childhood rhabdomyosarcoma

Rhabdomyosarcoma (RMS) is the most common soft-tissue sarcoma of childhood. This paper is focuses on imaging for diagnosis, staging, and follow-up of noncraniofacial RMS