Pro-Inflammatory Action of MIF in Acute Myocardial Infarction via Activation of Peripheral Blood Mononuclear Cells

Objectives

Macrophage migration inhibitory factor (MIF), a pro-inflammatory cytokine, has been implicated in the pathogenesis of multiple inflammatory disorders. We determined changes in circulating MIF levels, explored the cellular source of MIF, and studied the role of MIF in mediating inflammatory responses following acute myocardial infarction (MI).

Methods and Results

We recruited 15 patients with MI, 10 patients with stable angina and 10 healthy volunteers and measured temporal changes of MIF in plasma. Expression of MIF, matrix metalloproteinase-9 (MMP-9) and interleukin-6 (IL-6) in cultured peripheral blood mononuclear cells (PBMCs) and the media were measured by ELISA or real-time PCR. Compared to controls, plasma levels of MIF and IL-6 were significantly elevated at admission and 72 h post-MI. In contrast, expression of MIF, MMP-9 and IL-6 by PBMCs from MI patients was unchanged at admission, but significantly increased at 72 h. Addition of MIF activated cultured PBMCs by upregulating expression of inflammatory molecules and also synergistically enhanced stimulatory action of IL-1β which were inhibited by anti-MIF interventions. In a mouse MI model we observed similar changes in circulating MIF as seen in patients, with reciprocal significant increases in plasma MIF and reduction of MIF content in the infarct myocardium at 3 h after MI. MIF content in the infarct myocardium was restored at 72 h post-MI and was associated with robust macrophage infiltration. Further, anti-MIF intervention significantly reduced inflammatory cell infiltration and expression of monocyte chemoattractant protein-1 at 24 h and incidence of cardiac rupture in mice post-MI.

Conclusion

MI leads to a rapid release of MIF from the myocardium into circulation. Subsequently MIF facilitates PBMC production of pro-inflammatory mediators and myocardial inflammatory infiltration. Attenuation of these events, and post-MI cardiac rupture, by anti-MIF interventions suggests that MIF could be a potential therapeutic target following MI.     

Breakdown of self-incompatibility in the perennial Arabidopsis lyrata (Brassicaceae) and its genetic consequences

Mating systems in plants are known to be highly labile traits, with frequent transitions from outcrossing to selfing. The genetic basis for breakdown in self-incompatibility (SI) systems has been studied, but data on variation in selfing rates in species for which the molecular basis of SI is known are rare. This study surveyed such variation in Arabidopsis lyrata (Brassicaceae), which is often considered an obligately outcrossing species, to examine the causes and genetic consequences of changes in its breeding system. Based on controlled self-pollinations in the greenhouse, three populations from the Great Lakes region of North America included a minority of self-compatible (SC) individuals, while two showed larger proportions of SC individuals and all populations contained some individuals capable of setting selfed seeds. Loss of SI was not associated with particular haplotypes at the S-locus (as estimated by alleles amplified at the SRK locus, the gene controlling female specificity) and all populations contained similar numbers of SRK alleles, suggesting that some other genetic factor is responsible for modifying the SI reaction. The loss of SI has resulted in an effective shift in the mating system, as the two populations with a high frequency of SC individuals showed significantly lower microsatellite-based multilocus outcrossing rates and higher inbreeding coefficients than the other populations. Based on microsatellites, observed heterozygosities and genetic diversity were also significantly depressed in these populations. These findings provide the unique opportunity to examine in detail the consequences of mating system changes within a species with a well-characterized SI system.     

Recruitment of the cell cycle checkpoint kinase ATR to chromatin during S-phase

The ataxia telangiectasia-mutated (ATM) and Rad3-related kinase (ATR) is a central component of the cell cycle checkpoint machinery required to induce cell cycle arrest in response to DNA damage. Accumulating evidence suggests a role for ATR in signaling DNA damage during S-phase. Here we show that ATR is recruited to nuclear foci induced by replication fork stalling in a manner that is dependent on the single stranded binding protein replication protein A (RPA). ATR associates with chromatin in asynchronous cell cultures, and we use a variety of approaches to examine the association of ATR with chromatin in the absence of agents that cause genotoxic stress. Under our experimental conditions, ATR exhibits a decreased affinity for chromatin in quiescent cells and cells synchronized at mitosis but an increased affinity for chromatin as cells re-enter the cell cycle. Using centrifugal elutriation to obtain cells enriched at various stages of the cell cycle, we show that ATR associates with chromatin in a cell cycle-dependent manner, specifically during S-phase. Cell cycle association of ATR with chromatin mirrors that of RPA in addition to claspin, a cell cycle checkpoint protein previously shown to be a component of the replication machinery. Furthermore, association of ATR with chromatin occurs in the absence of detectable DNA damage and cell cycle checkpoint activation. These data are consistent with a model whereby ATR is recruited to chromatin during the unperturbed cell cycle and points to a role of ATR in monitoring genome integrity during normal S-phase progression.     

The RustPuccinia abruptavar.partheniicola,a Potential Biocontrol Agent of Parthenium Weed: Environmental Requirements for Disease Progress

The rust fungusPuccinia abruptavar.partheniicola,a potential biological control agent of parthenium weed (Parthenium hysterophorus), was evaluated under controlled environmental conditions. A range of spore germination temperatures as well as dew period durations and temperatures were investigated to determine some of the environmental requirements for disease establishment and disease progress. Plants were inoculated with urediniospores and exposed to dew periods between 3 to 12 h at temperatures of 10, 15, or 20°C. For disease expression, the inoculated plants were then grown in a glasshouse at one of two temperature regimes (30/26°C or 18/13°C; day/night). Urediniospores germinated best at 12 ± 1°C, with lower germination rates at 5°C or above 20°C. No infection occurred when the plants were exposed to dew periods of ≤3 h, regardless of the incubation temperature. The disease progressed most rapidly when plants were inoculated and incubated for a dew period of at least 12 h at a temperature of 15 ± 1°C. The disease progressed most slowly following inoculation at dew periods of 6 h or less. Disease progress was more rapid when the plants were exposed to a cool-temperature regime (18/13°C) than when exposed to a warm-temperature regime (30/26°C). This suggests that good infection of parthenium weed could be obtained when the urediniospores arrive on the plants during the afternoon in the cooler months of the central Queensland autumn when relatively long dew periods are expected.     

A population-based study of Helicobacter pylori infection in Chinese children resident in Hong Kong: prevalence and potential risk factors

Background: Data of Helicobacter pylori prevalence in children and its risk factors provide clues to the health authority to estimate burden of H. pylori‐associated diseases usually encountered in adulthood and facilitate healthcare planning. Materials and Methods: A cross‐sectional population‐based study was conducted in Chinese children in elementary and high schools. Schools were selected from all three major areas of Hong Kong. H. pylori infection was defined by a positive ¹³C‐urea breath test. Study subjects were stratified into six age groups for estimation of prevalence. Potential risk factors were analyzed from data of self‐administered questionnaires. Results: A total of 2480 children (aged 6–19, male: 47.3%) participated in the study. Overall, 324 (13.1%) were positive for H. pylori. There was no difference in prevalence between sexes, and no statistical trend in the prevalence across the six age groups. Multivariate logistic regression identified lack of formal education of mother (OR = 2.43, 95%CI 1.36–4.34), family history of gastric cancer (OR = 2.19, 95%CI 1.09–4.41), and household member > 5 (OR = 1.57, 95%CI 1.12–2.19) to be positively associated with H. pylori infection in our children. Conclusions: The H. pylori prevalence of Hong Kong children is comparable to the data of developed countries. The association with family history of gastric cancer justifies further study to investigate the cost‐benefit of community screening program for such children to decrease the incidence of gastric cancer in adulthood.     

Gonadal Mosaicism Induced by Chemical Treatment of Sperm in Drosophila melanogaster

Accurate interpretation of forward genetic screens of chromosomes exposed in mature spermatozoa to a mutagenic chemical requires understanding—incomplete to date—of how exposed chromosomes and their replicas proceed through early development stages from the fertilized ovum to establishment of the germline of the treated male’s offspring. We describe a model for early embryonic development and establishment of the germline of Drosophila melanogaster and a model-validating experiment. Our model proposes that, barring repair, DNA strands modified by treatment with alkylating agents are stable and mutagenic. Each replication of an alkylated strand can result in misreplication and a mutant-bearing daughter nucleus. Daughter nuclei thenceforth replicate faithfully and their descendants comprise the embryonic syncytium. Of the 256 nuclei present after the eighth division, several migrate into the polar plasm at the posterior end of the embryo to found the germline. Based upon distribution of descendants of the alkylated strands, the misreplication rate, and the number of nuclei selected as germline progenitors, the frequency of gonadal mosaicism is predictable. Experimentally, we tracked chromosomes 2 and 3 from EMS-treated sperm through a number of generations, to characterize autosomal recessive lethal mutations and infer gonadal genetic content of the sons of treated males. Over 50% of 106 sons bore germlines that were singly, doubly, or triply mosaic for chromosome 2 or chromosome 3. These findings were consistent with our model, assuming a rate of misreplication between 0.65 and 0.80 at each replication of an alkylated strand. Crossing treated males to mismatch-repair-deficient females had no apparent effect on mutation rate.