Ionizing radiation‐induced long‐term expression of senescence markers in mice is independent of p53 and immune status

Exposure to IR has been shown to induce the formation of senescence markers, a phenotype that coincides with lifelong delayed repair and regeneration of irradiated tissues. We hypothesized that IR‐induced senescence markers could persist long‐term in vivo, possibly contributing to the permanent reduction in tissue functionality. Here, we show that mouse tissues exposed to a sublethal dose of IR display persistent (up to 45 weeks, the maximum time analyzed) DNA damage foci and increased p16^INK4a expression, two hallmarks of cellular senescence and aging. BrdU‐labeling experiments revealed that IR‐induced damaged cells are preferentially eliminated, at least partially, in a tissue‐dependent manner. Unexpectedly, the accumulation of damaged cells was found to occur independent from the DNA damage response modulator p53, and from an intact immune system, as their levels were similar in wild‐type and Rag2^?/? γC^?/? mice, the latter being deficient in T, B, and NK cells. Together, our results provide compelling evidence that exposure to IR induces long‐term expression of senescence markers in vivo, an effect that may contribute to the reduced tissue functionality observed in cancer survivors.     

Below-ground herbivory promotes soil nutrient transfer and root growth in grassland

Extremely little is known about the ecosystem-level implications of below-ground herbivory, which often represents the dominant form of consumption of primary productivity. We provide the first empirical evidence that low levels of below-ground herbivory may promote soil nutrient flux and root growth of both host plants and companion plants. Low levels of white clover ( Trifolium repens L.) root infection by clover cyst nematodes ( Heterodera trifolii Goffart) increased root growth by 141% and 219% in the host plant and the uninfected neighbouring grass ( Lolium perenne L.), respectively. Root infection increased the size of the soil microbial biomass in the root zone and the transfer of ¹⁵N from the host plant to soil and the neighbouring grass. These data suggest that low amounts of below-ground herbivory may increase the transfer of plant carbon and nitrogen below-ground, leading to increases in root growth and soil nutrient recycling in grasslands. Presumably, such interactions will influence the competitive interactions between plant species, altering plant community structure in grasslands.     

DNA damage, p14ARF, Nucleophosmin (NPM/B23), and cancer

The p53/p14ARF/mdm2 stress response pathway plays a central role in mediating cellular responses to oncogene activation, genome instability, and therapy-induced DNA damage. Abrogation of the pathway occurs in most if not all cancers, and may be essential for tumor development. The high frequency with which the pathway is disabled in cancer and the fact that the pathway appears to be incompatible with tumor cell growth, has made it an important point of focus in cancer research and therapeutics development. Recently, Nucleophosmin (NPM, B23, NO38 and numatrin), a multifunctional nucleolar protein, has emerged as a p14ARF binding protein and regulator of p53. While complex formation between ARF and NPM retains ARF in the nucleolus and prevents ARF from activating p53, DNA damaging treatments promote a transient subnuclear redistribution of ARF to the nucleoplasm, where it interacts with mdm2 and promotes p53 activation. The results add support to a recently proposed model in which the nucleolus serves as a p53-uspstream sensor of stress, and where ARF links nucleolar stress signals to nucleoplasmic effectors of the stress response. A better understanding of ARF’s nucleolar interactions could further elucidate the regulation of the p53 pathway and suggest new therapeutic approaches to restore p53 function.     

DNA repair mechanisms in dividing and non-dividing cells

DNA damage created by endogenous or exogenous genotoxic agents can exist in multiple forms, and if allowed to persist, can promote genome instability and directly lead to various human diseases, particularly cancer, neurological abnormalities, immunodeficiency and premature aging. To avoid such deleterious outcomes, cells have evolved an array of DNA repair pathways, which carry out what is typically a multiple-step process to resolve specific DNA lesions and maintain genome integrity. To fully appreciate the biological contributions of the different DNA repair systems, one must keep in mind the cellular context within which they operate. For example, the human body is composed of non-dividing and dividing cell types, including, in the brain, neurons and glial cells. We describe herein the molecular mechanisms of the different DNA repair pathways, and review their roles in non-dividing and dividing cells, with an eye toward how these pathways may regulate the development of neurological disease.     

Effect of H4R antagonist N-(2-aminoethyl)-5-chloro-1H-indol-2-carboxamides and 5-chloro-2-(piperazin-1-ylmethyl)-1H-benzimidazole on histamine and 4-methylhistamine-induced mast cell response

Context: The histamine plays a decisive role in acute and chronic inflammatory responses and is regulated through its four types of distinct receptors designated from H1 to H4. Recently histamine 4 receptor (H4R) antagonists have been reported to possess various pharmacological effects against various allergic diseases.

Objective: To investigate the inhibitory effect of N-(2-aminoethyl)-5-chloro-1H-indol-2-carboxamide (Compound A) and 5-chloro-2-(piperazin-1-ylmethyl)-1H-benzimidazole (Compound L) on H4R-mediated calcium mobilization, cytokine IL-13 production, ERK1/2, Akt and NF-κB activation in human mastocytoma cells-1 (HMC-1).

Materials and methods: Compounds A and L were synthesized chemically and their inhibitory effect on intracellular calcium release was analyzed by Fluo-4 calcium assay, cytokine measurement through ELISA and activation of signaling molecules by western blot.

Results: Pre-treatment with compounds A and L significantly reduced the H4R-mediated intracellular calcium release. Histamine and 4-methylhistamine (4-MH) induced Th2 cytokine IL-13 production in HMC-1 cells, was inhibited by compound A (77.61%, 74.25% at 1?μM concentration) and compound L (79.63%, 81.70% at 1?μM concentration). Furthermore, histamine induced the phosphorylation of ERK1/2, Akt and NF-κB was suppressed by compounds A and L at varying levels, ERK1/2 (88%, 86%), Akt (88%, 89%) and NF-κB (89%, 87%) in HMC-1 cells.

Discussion and conclusions: Taken together these data demonstrate that compound A and compound L may block H4R-mediated downstream signaling events.     

Muscle damage and repair in voluntarily running mice: strain and muscle differences

Summary Soleus, extensor digitorum longus and tibialis anterior muscles of mice voluntarily running in wheels for periods of 5 to 120 days were studied in spaced serial and serial cross-sections. Shortly after the onset of running and during the next 2 weeks, degeneration, necrosis, phagocytosis and regeneration of muscle fibers, satellite cell proliferation and cellular infiltration were found in soleus muscles of mice from all strains investigated (CBA/J, NMRI, C57b, NIH, SWS and Balb/c). Tibialis anterior but not extensor digitorum longus muscles were also damaged. Predominantly high-oxidative fibers were affected (both slow-oxidative and fast oxidative glycolytic in soleus, fast-oxidative glycolytic in tibialis anterior). Denervated soleus muscles that had been passively stretched during running were not damaged. Evidence was found that, during the early period of running, split fibers form by myogenesis within (regeneration) or outside (satellite cell proliferation) necrotic muscle fiber segments. Split fibers persisted in solei of long-term (2 to 3 months) exercised CBA/J but not NMRI mice. In 6 out of 20 solei of CBA/J runners exercised for 2 months or longer, fiber-type grouping was observed in the areas where extensive damage usually occurred in the early periods. The results show that different muscles are damaged and repaired to varying degrees and that marked interstrain and inter-individual differences are present. It appears that acute muscle injury occurring upon onset of voluntary running is a usual event in the adaptation of muscles to altered use.     

Non‐recombinogenic roles for Rad52 in translesion synthesis during DNA damage tolerance

DNA damage tolerance relies on homologous recombination (HR) and translesion synthesis (TLS) mechanisms to fill in the ssDNA gaps generated during passing of the replication fork over DNA lesions in the template. Whereas TLS requires specialized polymerases able to incorporate a dNTP opposite the lesion and is error‐prone, HR uses the sister chromatid and is mostly error‐free. We report that the HR protein Rad52—but not Rad51 and Rad57—acts in concert with the TLS machinery (Rad6/Rad18‐mediated PCNA ubiquitylation and polymerases Rev1/Pol ζ) to repair MMS and UV light‐induced ssDNA gaps through a non‐recombinogenic mechanism, as inferred from the different phenotypes displayed in the absence of Rad52 and Rad54 (essential for MMS‐ and UV‐induced HR); accordingly, Rad52 is required for efficient DNA damage‐induced mutagenesis. In addition, Rad52, Rad51, and Rad57, but not Rad54, facilitate Rad6/Rad18 binding to chromatin and subsequent DNA damage‐induced PCNA ubiquitylation. Therefore, Rad52 facilitates the tolerance process not only by HR but also by TLS through Rad51/Rad57‐dependent and ‐independent processes, providing a novel role for the recombination proteins in maintaining genome integrity.     

高致病性冠状病毒感染导致宿主免疫应答异常

近二十多年,全球范围内先后爆发了由严重急性呼吸综合征冠状病毒（severe acute respiratory syndrome coronavirus,SARS-CoV）、中东呼吸综合征冠状病毒（middle east respiratory syndrome coronavirus,MERS-CoV）和严重急性呼吸综合征冠状病毒2（severe acute respiratory syndrome coronavirus 2,SARS-CoV-2）3种高致病性冠状病毒导致的疫情。这3种高致病性冠状病毒感染通常伴随着免疫系统功能失调,临床表现有淋巴细胞减少症、细胞因子风暴、急性呼吸系统窘迫综合征,甚至多器官衰竭而导致死亡。揭示高致病性冠状病毒在免疫应答中的作用机制,对于预防与控制冠状病毒感染具有重要意义。本文总结了SARS-CoV、MRES-CoV和SARS-CoV-2的进入机制和受体特征、固有免疫应答和适应性免疫应答失调方面的研究进展,强调了高致病性冠状病毒与宿主免疫应答之间的复杂相互作用,以期为防治冠状病毒感染提供参考。     

ARPE-19 conditioned medium promotes neural differentiation of adipose-derived mesenchymal stem cells

BACKGROUNDAdipose-derived stem cells (ASCs) have been increasingly explored for cell-based medicine because of their numerous advantages in terms of easy availability, high proliferation rate, multipotent differentiation ability and low immunogenicity. In this respect, they have been widely investigated in the last two decades to develop therapeutic strategies for a variety of human pathologies including eye disease. In ocular diseases involving the retina, various cell types may be affected, such as Müller cells, astrocytes, photoreceptors and retinal pigment epithelium (RPE), which plays a fundamental role in the homeostasis of retinal tissue, by secreting a variety of growth factors that support retinal cells.AIMTo test ASC neural differentiation using conditioned medium (CM) from an RPE cell line (ARPE-19).METHODSASCs were isolated from adipose tissue, harvested from the subcutaneous region of healthy donors undergoing liposuction procedures. Four ASC culture conditions were investigated: ASCs cultured in basal Dulbecco''s Modified Eagle Medium (DMEM); ASCs cultured in serum-free DMEM; ASCs cultured in serum-free DMEM/F12; and ASCs cultured in a CM from ARPE-19, a spontaneously arising cell line with a normal karyotype derived from a human RPE. Cell proliferation rate and viability were assessed by crystal violet and MTT assays at 1, 4 and 8 d of culture. At the same time points, ASC neural differentiation was evaluated by immunocytochemistry and western blot analysis for typical neuronal and glial markers: Nestin, neuronal specific enolase (NSE), protein gene product (PGP) 9.5, and glial fibrillary acidic protein (GFAP).RESULTSDepending on the culture medium, ASC proliferation rate and viability showed some significant differences. Overall, less dense populations were observed in serum-free cultures, except for ASCs cultured in ARPE-19 serum-free CM. Moreover, a different cell morphology was seen in these cultures after 8 d of treatment, with more elongated cells, often showing cytoplasmic ramifications. Immunofluorescence results and western blot analysis were indicative of ASC neural differentiation. In fact, basal levels of neural markers detected under control conditions significantly increased when cells were cultured in ARPE-19 CM. Specifically, neural marker overexpression was more marked at 8 d. The most evident increase was observed for NSE and GFAP, a modest increase was observed for nestin, and less relevant changes were observed for PGP9.5. CONCLUSIONThe presence of growth factors produced by ARPE-19 cells in tissue culture induces ASCs to express neural differentiation markers typical of the neuronal and glial cells of the retina.     

曲美他嗪对大鼠放射性心肌损伤后TNF-α表达的影响

目的:放射性心肌损伤是纵膈及胸腔等部位恶性肿瘤放射治疗后发生的严重并发症,目前尚无有效防治方法,而本实验拟探索曲美他嗪对放射性心肌损伤的保护作用。方法:将45只SD大鼠随机分为正常对照组(C组)、单纯照射组(X组)、曲美他嗪治疗组(T组),每组15只,其中X组、T组予以10 Gy/d,共3天。大鼠照射完毕处死后测定血清cTnI浓度,心肌组织TNF-αmRNA及蛋白的表达。结果:1.X组与C组相比,血清cTnI浓度,心肌组织TNF-αmRNA及蛋白的表达均明显升高(P0.05);2.T组与C组相比,血清cTnI浓度,心肌组织TNF-αmRNA及蛋白的表达均明显升高(P0.05);3.T组与X组相比,血清cTnI浓度,心肌组织TNF-αmRNA及蛋白的表达均明显降低(P0.05)。结论:曲美他嗪能够通过减少心肌组织TNF-αmRNA及蛋白的表达,从而有效减轻大鼠放射后心脏炎症反应,以减轻心肌损伤。