The Phytophthora parasitica effector AVH195 interacts with ATG8, attenuates host autophagy, and promotes biotrophic infection

BACKGROUND

Plant pathogens secrete effector proteins into host cells to suppress immune responses and manipulate fundamental cellular processes. One of these processes is autophagy, an essential recycling mechanism in eukaryotic cells that coordinates the turnover of cellular components and contributes to the decision on cell death or survival.

RESULTS

We report the characterization of AVH195, an effector from the broad-spectrum oomycete plant pathogen, Phytophthora parasitica. We show that P. parasitica expresses AVH195 during the biotrophic phase of plant infection, i.e., the initial phase in which host cells are maintained alive. In tobacco, the effector prevents the initiation of cell death, which is caused by two pathogen-derived effectors and the proapoptotic BAX protein. AVH195 associates with the plant vacuolar membrane system and interacts with Autophagy-related protein 8 (ATG8) isoforms/paralogs. When expressed in cells from the green alga, Chlamydomonas reinhardtii, the effector delays vacuolar fusion and cargo turnover upon stimulation of autophagy, but does not affect algal viability. In Arabidopsis thaliana, AVH195 delays the turnover of ATG8 from endomembranes and promotes plant susceptibility to P. parasitica and the obligate biotrophic oomycete pathogen Hyaloperonospora arabidopsidis.

CONCLUSIONS

Taken together, our observations suggest that AVH195 targets ATG8 to attenuate autophagy and prevent associated host cell death, thereby favoring biotrophy during the early stages of the infection process.

Dual Immunofluorescence of γH2AX and 53BP1 in Human Peripheral Lymphocytes

Double strand breaks (DSBs) are one of the most severe lesions that can occur in cell nuclei, and, if not repaired, they can lead to severe outcomes, including cancer. The cell is, therefore, provided with complex mechanisms to repair DSBs, and these pathways involve histone H2AX in its phosphorylated form at Ser-139 (namely γH2AX) and p53 binding protein 1 (53BP1). As both proteins can form foci at the sites of DSBs, identification of these markers is considered a suitable method to study both DSBs and their kinetics of repair. According to the molecular processes that lead to the formation of γH2AX and 53BP1 foci, it could be more useful to investigate their co-localization near the DSBs in order to set up an alternative approach that allows quantifying DSBs by the simultaneous detection of two DNA damage markers. Thus, this protocol aims to assess the genomic damage induced in human lymphocytes by the radiomimetic agent bleomycin through the presence of γH2AX and 53BP1 foci in a dual immunofluorescence. Using this methodology, we also delineated the variation in the number of γH2AX and 53BP1 foci over time, as a preliminary attempt to study the repair kinetics of bleomycin-induced DSBs.

Oxidative and DNA damage in obese patients undergoing bariatric surgery: A one-year follow-up study

The pathogenesis of obesity and related comorbidities has long been associated with oxidative stress. The excess of adipose tissue contributes to the production of free radicals that sustain both a local and a systemic chronic inflammatory state, whereas its reduction can bring to an improvement in inflammation and oxidative stress. In our work, using the fluorescent lipid probe BODIPY® 581/591 C11 and the γH2AX foci assay, a well-known marker of DNA double strand breaks (DSB), we evaluated the extent of cell membrane oxidation and DNA damage in peripheral blood lymphocytes of normal weight (NW) controls and obese patients sampled before and after bariatric surgery. Compared to NW controls, we observed a marked increase in both the frequencies of oxidized cells or nuclei exhibiting phosphorylation of histone H2AX in preoperatory obese patients. After bariatric surgery, obese patients, resampled over one-year follow-up, improved oxidative damage and reduced the presence of DSB. In conclusion, the present study highlights the importance for obese patients undergoing bariatric surgery to also monitor these molecular markers during their postoperative follow-up.

High level of γH2AX phosphorylation in the cord-blood cells of large-for-gestational-age (LGA) newborns

Newborns can experience adverse effects as a consequence of maternal or in utero exposure, altered growth of the fetus, or placental dysfunctions. Accurate characterization of gestational age allows monitoring of fetal growth, identification of deviations from the normal growth trajectory, and classification of babies as adapted, small, or large for gestational age (AGA, SGA, or LGA). The aim of this work was to evaluate nuclear and oxidative damage in umbilical cord-blood cells of newborns (sampled at birth), by applying the γH2AX assay and the fluorescent probe BODIPY^581/591 C¹¹, to detect DNA DSB and cell membrane oxidation, respectively. No statistically significant differences were observed in the proportion of oxidized cord-blood cells among the groups of newborns, although the LGA group showed the highest value. With regard to genome damage, elevated levels of γH2AX foci were detected in the cell nuclei from LGA newborns as compared to AGA or SGA babies, whose values did not differ from each other. Considering that the observed DNA damage, although still repairable, can represent a risk factor for obesity, metabolic diseases, or other pathologies, monitoring genome and cell integrity at birth can provide useful information for prevention of diseases later in life.

UCTD and SLE patients show increased levels of oxidative and DNA damage together with an altered kinetics of DSB repair

Immunological tolerance is a critical feature of the immune system; its loss might lead to an abnormal response of lymphocytes causing autoimmune diseases. One of the most important groups belonging to autoimmune disorders is the connective tissue diseases (CTD). CTD are classified among systemic rheumatic diseases and include pathologies such as systemic lupus erythematosus (SLE), and undifferentiated CTD (UCTD). In this study, we evaluated oxidative and genome damage in peripheral blood lymphocytes from patients with SLE and UCTD, further classified on the basis of disease activity and the presence/absence of a serological profile. Oxidative damage was evaluated in cell membrane using the fluorescent fatty acid analogue BODIPY 581/591 C11. The percentage of oxidised lymphocytes in both SLE and UCTD patients was higher than in the control group, and the oxidative stress correlated positively with both disease activity and autoantibody profile. The γH2AX focus assay was used to quantify the presence of spontaneous double strand breaks (DSBs), and to assess the abilities of DSBs repair system after T cells were treated with mitomycin C (MMC). Subjects with these autoimmune disorders showed a higher number of γH2AX foci than healthy controls, but no correlation with diseases activity and presence of serological profile was observed. In addition, patients displayed an altered response to MMC-induced DSBs, which led their peripheral cells to greatly increase apoptosis. Taken together our results confirmed an interplay among oxidative stress, DNA damage and impaired DNA repair, which are directly correlated to the aggressiveness and clinical progression of the diseases. We propose the evaluation of these molecular markers to better characterize SLE and UCTD, aiming to improve the treatment plan and the quality of the patients' life.

Clinical approach on challenge and desensitization procedures with aspirin in patients with ischemic heart disease and nonsteroidal anti-inflammatory drug hypersensitivity

BACKGROUND

Hypersensitivity to acetylsalicylic acid (ASA) constitutes a serious problem for subjects with coronary artery disease. In such subjects, physicians have to choose the more appropriate procedure between challenge and desensitization. As the literature on this issue is sparse, this study aimed to establish in these subjects clinical criteria for eligibility for an ASA challenge and/or desensitization.

METHODS

Collection and analysis of data on ASA challenges and desensitizations from 10 allergy centers, as well as consensus among the related physicians and an expert panel.

RESULTS

Altogether, 310 subjects were assessed; 217 had histories of urticaria/angioedema, 50 of anaphylaxis, 26 of nonimmediate cutaneous eruptions, and 17 of bronchospasm related to ASA/nonsteroidal anti-inflammatory drugs (NSAID) intake. Specifically, 119 subjects had index reactions to ASA doses lower than 300 mg. Of the 310 subjects, 138 had an acute coronary syndrome (ACS), 101 of whom underwent desensitizations, whereas 172 suffered from a chronic ischemic heart disease (CIHD), 126 of whom underwent challenges. Overall, 163 subjects underwent challenges and 147 subjects underwent desensitizations; 86 of the latter had index reactions to ASA doses of 300 mg or less. Ten subjects reacted to challenges, seven at doses up to 500 mg, three at a cumulative dose of 110 mg. The desensitization failure rate was 1.4%.

CONCLUSIONS

In patients with stable CIHD and histories of nonsevere hypersensitivity reactions to ASA/NSAIDs, an ASA challenge is advisable. Patients with an ACS and histories of hypersensitivity reactions to ASA, especially following doses lower than 100 mg, should directly undergo desensitization.

Vincristine-induced bystander effect in human lymphocytes

Bystander effect is a known radiobiological effect, widely described using ionizing radiations and which, more recently, has also been related to chemical mutagens. In this study, we aimed to assess whether or not a bystander response can be induced in cultured human peripheral lymphocytes by vincristine, a chemotherapeutic mutagen acting as spindle poison, and by mitomycin-C, an alkylating agent already known to induce this response in human lymphoblastoid cells. Designing a modified ad hoc protocol for the cytokinesis blocked micronucleus (MN) assay, we detected the presence of a dose-dependent bystander response in untreated cultures receiving the conditioned medium (CM) from mitomycin-C (MMC) or vincristine (VCR) treated cultures. In the case of MMC, MN frequencies, expressed as micronucleated binucleates, were: 13.5±1.41 at 6μM, 22±2.12 at 12μM or 28.25±5.13 at 15μM vs. a control value of 4.75±1.59. MN levels for VCR, expressed as micronucleated mononucleates were: 2.75±0.88 at 0.0μM, 27.25±2.30 at 0.4μM, 46.25±1.94 at 0.8μM, 98.25±7.25 at 1.6μM. To verify that no mutagen residual was transferred to recipient cultures together with the CM, we evaluated MN levels in cultures receiving the medium immediately after three washings following the chemical treatment (unconditioned medium). We further confirmed these results using a cell-mixing approach where untreated lymphocytes were co-cultured with donor cells treated with an effect-inducing dose of MMC or VCR. A distinct production pattern of both reactive oxygen species and soluble mediator proteins by treated cells may account for the differences observed in the manifestation of the bystander effect induced by VCR. In fact, we observed an increased level of ROS, IL-32 and TGF-β in the CM from VCR treated cultures, not present in MMC treated cultures.

Classification and practical approach to the diagnosis and management of hypersensitivity to nonsteroidal anti-inflammatory drugs

Hypersensitivity reactions to aspirin (acetylsalicylic acid) and other nonsteroidal anti-inflammatory drugs (NSAIDs) constitute only a subset of all adverse reactions to these drugs, but due to their severity pose a significant burden to patients and are a challenge to the allergist. In susceptible individuals, NSAIDs induce a wide spectrum of hypersensitivity reactions with various timing, organ manifestations, and severity, involving either immunological (allergic) or nonimmunological mechanisms. Proper classification of reactions based on clinical manifestations and suspected mechanism is a prerequisite for the implementation of rational diagnostic procedures and adequate patient management. This document, prepared by a panel of experts from the European Academy of Allergy and Clinical Immunology Task Force on NSAIDs Hypersensitivity, aims at reviewing the current knowledge in the field and proposes uniform definitions and clinically useful classification of hypersensitivity reactions to NSAIDs. The document proposes also practical algorithms for the diagnosis of specific types of NSAIDs hypersensitivity (which include drug provocations, skin testing and in vitro testing) and provides, when data are available, evidence-based recommendations for the management of hypersensitive patients, including drug avoidance and drug desensitization.

Skin test concentrations for systemically administered drugs -- an ENDA/EAACI Drug Allergy Interest Group position paper

Skin tests are of paramount importance for the evaluation of drug hypersensitivity reactions. Drug skin tests are often not carried out because of lack of concise information on specific test concentrations. The diagnosis of drug allergy is often based on history alone, which is an unreliable indicator of true hypersensitivity.To promote and standardize reproducible skin testing with safe and nonirritant drug concentrations in the clinical practice, the European Network and European Academy of Allergy and Clinical Immunology (EAACI) Interest Group on Drug Allergy has performed a literature search on skin test drug concentration in MEDLINE and EMBASE, reviewed and evaluated the literature in five languages using the GRADE system for quality of evidence and strength of recommendation. Where the literature is poor, we have taken into consideration the collective experience of the group.We recommend drug concentration for skin testing aiming to achieve a specificity of at least 95%. It has been possible to recommend specific drug concentration for betalactam antibiotics, perioperative drugs, heparins, platinum salts and radiocontrast media. For many other drugs, there is insufficient evidence to recommend appropriate drug concentration. There is urgent need for multicentre studies designed to establish and validate drug skin test concentration using standard protocols. For most drugs, sensitivity of skin testing is higher in immediate hypersensitivity compared to nonimmediate hypersensitivity.

Aspirin challenge/desensitisation before coronary stenting in subjects with history of hypersensitivity. A pragmatic approach

BACKGROUND

Aspirin hypersensitivity may represent a major problem in patients with ischemic coronary disease who need a stenting procedure. In those patients, clinically unsettled reasonably quick desensitisation procedures are needed. In our study we attempted to select the most suitable procedure on the basis of characteristics and severity of ASA hypersensitivity.

METHODS

Thirty patients with a history of mild reactions to anti-inflammatory doses of aspirin (> 325 mg) were considered at low risk and underwent a tolerance test in 5 steps. Thirty-one patients, with a history of severe reactions to anti-platelet doses of aspirin 0 mg) underwent a slow desensitisation in 12 steps, reaching a cumulative dose of 150 mg ASA in 220 minutes.

RESULTS

In the first group, 29 patients tolerated the challenge. One developed urticaria, thus underwent challenge/desensitisation and achieved tolerance. In the second group, 3 patients did not tolerate the procedure and had to discontinue. CONCLUSION. Our approach to aspirin hypersensitivity in patients needing coronary stenting, based on a severity stratification, allowed to achieve an effective tolerance to aspirin in the majority of subject in a reasonable short time.