Vesicular translocation of PARP-1 to cytoplasm causes ADP-ribosylation and disassembly of vimentin filaments during microglia activation induced by LPS.

ADP-ribosylation plays a significant role in various biological processes including genomic stability maintenance, transcriptional regulation, energy metabolism, and cell death. Using macrodomain pull-down assay with microglia lysates and MALDI-TOF-MS analysis, we identified vimentin as a major protein highly ADP-ribosylated by the poly(ADP-ribose) polymerases-1 (PARP-1) in response to LPS. ABT-888, a potent inhibitor of PARP-1/2 blocks the disassembly and ADP-ribosylation of vimentin. PARP-1 is a highly abundant nuclear protein. Its nuclear functions in repairing DNA damages induced by various stress signals, such as inflammatory stresses, have been well studied. In contrast, limited studies have been done on the cytoplasmic role(s) of PARP-1. Our study focuses on the cytoplasmic role of PARP-1 during microglia activation. Using immunofluorescence microscopy and Western blotting, we showed that a significant amount of PARP-1 is present in the cytosol of microglia cells stimulated and activated by LPS. Live cell imaging showed the translocation of nuclear PARP-1-EGFP to the cytoplasm in vesicular structures upon LPS stimulation. ABT-888 and U0126 can block this translocation. Immunofluorescence staining with various organelle marker antibodies revealed that PARP-1 vesicles show colocalization with Lamin A/C, suggesting they might be derived from the nuclear envelope through nuclear envelope budding. In conclusion, we demonstrated that PARP-1 is translocated from the nucleus to cytoplasm via vesicles upon LPS stimulation and that cytoplasmic PARP-1 causes ADP-ribosylation and disassembly of vimentin filaments during microglia activation induced by LPS.

Ticagrelor or Clopidogrel as Antiplatelet Agents in Patients with Chronic Kidney Disease and Cardiovascular Disease: A Meta-analysis.

INTRODUCTION: The worldwide prevalence of chronic kidney disease (CKD) has significantly increased in the past decades. Scientific reports have shown CKD to be an enhancing risk factor for the development of cardiovascular disease (CVD), which is the leading cause of premature death in patients with CKD. Clinical practice guidelines are ambiguous in view of the use of antiplatelet drugs in patients with CKD because patients with moderate-to-severe CKD were often excluded from clinical trials evaluating the efficacy and safety of anticoagulants and antiplatelet agents. In this analysis, we aimed to systematically assess the adverse cardiovascular and bleeding outcomes that were observed with ticagrelor versus clopidogrel use in patients with CKD and cardiovascular disease. METHODS: Electronic databases including Web of Science, Google Scholar, http://www. CLINICALTRIALS: gov , Cochrane database, EMBASE, and MEDLINE were carefully searched for English-based articles comparing ticagrelor with clopidogrel in patients with CKD. Adverse cardiovascular outcomes and bleeding events were the endpoints in this study. The latest version of the RevMan software (version 5.4) was used to analyze the data. Risk ratios (RR) with 95% confidence intervals (CI) were used to represent the data post analysis. RESULTS: A total of 15,664 participants were included in this analysis, whereby 2456 CKD participants were assigned to ticagrelor and 13,208 CKD participants were assigned to clopidogrel. Our current analysis showed that major adverse cardiac events (MACEs) (RR: 0.85, 95% CI: 0.71-1.03; P = 0.09), all-cause mortality (RR: 0.82, 95% CI: 0.57- 1.18; P = 0.29), cardiovascular death (RR: 0.83, 95% CI: 0.56-1.23; P = 0.35), myocardial infarction (RR: 0.87, 95% CI: 0.70-1.07; P = 0.19), ischemic stroke (RR: 0.80, 95% CI: 0.58-1.11; P = 0.18), and hemorrhagic stroke (RR: 1.06, 95% CI: 0.38-2.99; P = 0.91) were not significantly different in CKD patients who were treated with ticagrelor versus clopidogrel. Thrombolysis in myocardial infarction (TIMI)-defined minor (RR: 0.89, 95% CI: 0.52-1.53; P = 0.68) and TIMI major bleeding (RR: 1.10, 95% CI: 0.69-1.76; P = 0.67) were also not significantly different. However, bleeding defined according to the academic research consortium (BARC) bleeding type 1 or 2 (RR: 1.95, 95% CI: 1.13-3.37; P = 0.02) and BARC bleeding type 3 or 5 (RR: 1.70, 95% CI: 1.17-2.48; P = 0.006) were significantly higher with ticagrelor. CONCLUSIONS: When compared with clopidogrel, even though ticagrelor was not associated with higher risk of adverse cardiovascular outcomes in these patients with CKD, it was associated with significantly higher BARC bleeding. Therefore, the safety outcomes of ticagrelor still require further evaluation in patients with CKD. Nevertheless, this hypothesis should only be confirmed with more powerful results that could usually only be achieved using large-scale randomized trials.

Functional Dissection of Genes Encoding DNA Polymerases Based on Conditional Mutants in the Heterocyst-Forming Cyanobacterium Anabaena PCC 7120.

The filamentous cyanobacterium Anabaena sp. PCC 7120 develops N2-fixing heterocyst cells under condition of combined-nitrogen deprivation and constitutes an excellent model for studying cell differentiation. The mechanism of heterocyst development has been extensively investigated and a network of regulating factors has been identified. A few studies have showed that the process of heterocyst differentiation relates with cell cycle events, but further investigation is still required to understand this relationship. In a previous study, we created a conditional mutant of PolI encoding gene, polA, by using a CRISPR/Cpf1 gene-editing technique. Here, we were able to create another conditional mutant of a PolIII encoding gene dnaENI using a similar strategy and subsequently confirmed the essential roles of both polA and dnaENI in DNA replication. Further investigation on the phenotype of the mutants showed that lack of PolI caused defects in chromosome segregation and cell division, while lack of DnaENI (PolIII) prevented bulk DNA synthesis, causing significant loss of DNA content. Our findings also suggested the possible existence of a SOS-response like mechanism operating in Anabaena PCC 7120. Moreover, we found that heterocyst development was differently affected in the two conditional mutants, with double heterocysts/proheterocysts found in PolI conditional mutant. We further showed that formation of such double heterocysts/proheterocysts are likely caused by the difficulty in nucleoids segregation, resulting delayed, or non-complete closure of the septum between the two daughter cells. This study uncovers a link between DNA replication process and heterocyst differentiation, paving the way for further studies on the relationship between cell cycle and cell development.

Expanding the Potential of CRISPR-Cpf1-Based Genome Editing Technology in the Cyanobacterium Anabaena PCC 7120.

CRISPR systems, such as CRISPR-Cas9 and CRISPR-Cpf1, have been successfully used for genome editing in a variety of organisms. Although the technique of CRISPR-Cpf1 has been applied in cyanobacteria recently, its use was limited without exploiting the full potential of such a powerful genetic system. Using the cyanobacterium Anabaena PCC 7120 as a model strain, we improved the tools and designed genetic strategies based on CRISPR-Cpf1, which enabled us to realize genetic experiments that have been so far difficult to do in cyanobacteria. The development includes: (1) a "two-spacers" strategy for single genomic modification, with a success rate close to 100%; (2) rapid multiple genome editing using editing plasmids with different resistance markers; (3) using sacB, a counter-selection marker conferring sucrose sensitivity, to enable the active loss of the editing plasmids and facilitate multiple rounds of genetic modification or phenotypic analysis; (4) manipulation of essential genes by the creation of conditional mutants, using as example, polA encoding the DNA polymerase I essential for DNA replication and repair; (5) large DNA fragment deletion, up to 118 kb, from the Anabaena chromosome, corresponding to the largest bacterial chromosomal region removed with CRISPR systems so far. The genome editing vectors and the strategies developed here will expand our ability to study and engineer cyanobacteria, which are extensively used for fundamental studies, biotechnological applications including biofuel production, and synthetic biology research. The vectors developed here have a broad host range, and could be readily used for genetic modification in other microorganisms.

Signaling Pathways Controlling Microglia Chemotaxis.

Microglia are the primary resident immune cells of the central nervous system (CNS). They are the first line of defense of the brain's innate immune response against infection, injury, and diseases. Microglia respond to extracellular signals and engulf unwanted neuronal debris by phagocytosis, thereby maintaining normal cellular homeostasis in the CNS. Pathological stimuli such as neuronal injury induce transformation and activation of resting microglia with ramified morphology into a motile amoeboid form and activated microglia chemotax toward lesion site. This review outlines the current research on microglial activation and chemotaxis.