C-reactive protein augments hypoxia-induced apoptosis through mitochondrion-dependent pathway in cardiac myocytes

C-reactive protein (CRP) is an important predictive factor for cardiac disorders including acute myocardial infarction. Therapeutic inhibition of CRP has been shown to be a promising new approach to cardioprotection in acute myocardial infarction in rat models, but the direct effects of CRP on cardiac myocytes are poorly defined. In this study, we investigated the effects of CRP on cardiac myocytes and its molecular mechanism involved. Neonatal rat cardiac myocytes were exposed to hypoxia for 8 h. Hypoxia induced myocyte apoptosis under serum-deprived conditions, which was accompanied by cytochrome c release from mitochondria into cytosol, as well as activation of Caspase-9, Caspase-3. Hypoxia also increased Bax and decreased Bcl-2 mRNA and protein expression, thereby significantly increasing Bax/Bcl-2 ratio. Cotreatment of CRP (100 μg/ml) under hypoxia significantly increased the percentage of apoptotic myocytes, translocation of cytochrome c, Bax/Bcl-2 ratio, and the activity of Caspase-9 and Caspase-3. However, no effects were observed on myocyte apoptosis when cotreatment of CRP under normoxia. Furthermore, Bcl-2 overexpression significantly improved cellular viability through inhibition of hypoxia or cotreatment with CRP induced Bax/Bcl-2 ratio changes and cytochrome c release from mitochondria to cytosol, and significantly blocked the activity of Caspase-9 and Caspase-3. The present study demonstrates that CRP could enhance apoptosis in hypoxia-stimulated myocytes through the mitochondrion-dependent pathway but CRP alone has no effects on neonatal rat cardiac myocytes under normoxia. Bcl-2 overexpression might prevent CRP-induced apoptosis by inhibiting cytochrome c release from the mitochondria and block activation of Caspase-9 and Caspase-3. Jin Yang and Junhong Wang contributed equally to this work.     

NEDDylation antagonizes ubiquitination of proliferating cell nuclear antigen and regulates the recruitment of polymerase η in response to oxidative DNA damage

NEDDylation has been shown to participate in the DNA damage pathway, but the substrates of neural precursor cell expressed developmentally downregulated 8 (NEDD8) and the roles of NEDDylation involved in the DNA damage response (DDR) are largely unknown. Translesion synthesis (TLS) is a damage-tolerance mechanism, in which RAD18/RAD6-mediated monoubiquitinated proliferating cell nuclear antigen (PCNA) promotes recruitment of polymerase η (polη) to bypass lesions. Here we identify PCNA as a substrate of NEDD8, and show that E3 ligase RAD18-catalyzed PCNA NEDDylation antagonizes its ubiquitination. In addition, NEDP1 acts as the deNEDDylase of PCNA, and NEDP1 deletion enhances PCNA NEDDylation but reduces its ubiquitination. In response to H₂O₂ stimulation, NEDP1 disassociates from PCNA and RAD18-dependent PCNA NEDDylation increases markedly after its ubiquitination. Impairment of NEDDylation by Ubc12 knockout enhances PCNA ubiquitination and promotes PCNA-polη interaction, while up-regulation of NEDDylation by NEDD8 overexpression or NEDP1 deletion reduces the excessive accumulation of ubiquitinated PCNA, thus inhibits PCNA-polη interaction and blocks polη foci formation. Moreover, Ubc12 knockout decreases cell sensitivity to H₂O₂-induced oxidative stress, but NEDP1 deletion aggravates this sensitivity. Collectively, our study elucidates the important role of NEDDylation in the DDR as a modulator of PCNA monoubiquitination and polη recruitment.     

微生态调节剂Microbe FA9102对仔猪及肉用仔鸡的饲养试验

Ｍｉｃｒｏｂｅ ＦＡ９１０２是我们新近研制的一种富含蛋白质的微生态调节剂。本试验研究了它对断乳仔猪及肉用仔猪的增重及饲料利用率的可能影响,Ｍｉｃｒｏｂｅ ＦＡ９１０２在它们的基础日粮中的添加量是５％。在断乳仔猪生长育肥试验中,Ｍｉｃｒｏｂｅ ＦＡ９１０２使仔猪的增重率显著提高（相对提高２５．８７％,Ｐ〈０．０５）,饲料消耗显著降低（相对降低１１．５％,Ｐ〈０．０５）,且较对照组提前３５天达到９０ｋ     

Mechanism of cancer: Oncohistones in action

Oncohistones are histones with high-frequency point mutations that are associated with tumorigenesis. Although each histone variant is encoded by multiple genes, a single mutation in one allele of one gene seems to have a dominant effect over global histone H3 methylation level at the relevant amino acid residue. These oncohistones are highly tumor type specific. For example, H3K27M and H3G34V/R mutations occur only in pediatric brain cancers, whereas H3K36M and H3G34W/L have only been found in pediatric bone tumors. H1 mutations also seem to be exclusively linked to lymphomas. In this review, we discuss the occurrence, frequency and potential functional mechanisms of each oncohistone in tumorigenesis of its relevant cancer. We believe that further investigation into the mechanism regarding their tumor type specificity and cancer-related functions will shed new light on their application in cancer diagnosis and targeted therapy development.     

Characterization and abolishment of the cyclopiazonic acids produced by Aspergillus oryzae HMP-F28

Extracellular alkalinization and H₂O₂ production are important early events during induced resistance establishment in plants. In a screen for metabolites as plant resistance activators from 98 fungal isolates associated with marine sponge Hymeniacidon perleve, the cyclopiazonic acids (CPAs) produced by Aspergillus oryzae HMP-F28 induced significant extracellular alkalinization coupled with augmented H₂O₂ production in tobacco cell suspensions. Bioassay-guided fractionation led to the isolation and structural elucidation of a new CPA congener (4, 3-hydroxysperadine A) and three known ones (1–3). To construct a mutasynthetic strain to generate unnatural CPA analogues, a hybrid pks-nrps gene (cpaS) was disrupted to abolish the production of the critical precursor of cyclo-acetoacetyl-L-tryptophan (cAATrp) and all the downstream CPA products. Elimination of cAATrp will allow cAATrp mimics being processed by the CPA biosynthetic machinery to produce CPA derivatives with designed structural features.     

The Rtt109-Vps75 histone acetyltransferase complex acetylates non-nucleosomal histone H3

Acetylation of lysine 56 of histone H3 (H3-Lys-56) occurs in S phase and disappears during G(2)/M phase of the cell cycle. However, it is not clear how this modification is regulated during the progression of the cell cycle. We and others have shown that the histone acetyltransferase (HAT) Rtt109 is the primary HAT responsible for acetylating H3-Lys-56 in budding yeast. Here we show that Rtt109 forms a complex with Vps75 and that both recombinant Rtt109-Vps75 complexes and native complexes purified from yeast cells acetylate H3 present in H3/H4/H2A/H2B core histones but not other histones. In addition, both recombinant and native Rtt109-Vps75 HAT complexes exhibited no detectable activity toward nucleosomal H3, suggesting that H3-Lys-56 acetylation is at least in part regulated by the inability of Rtt109-Vps75 complexes to acetylate nucleosomal H3 during G(2)/M phase of the cell cycle. Further, Rtt109 bound mutant H3/H4 tetramers composed of histones lacking their N-terminal tail domains less efficiently than wild-type H3/H4 tetramers, and Rtt109-Vps75 complexes displayed reduced HAT activity toward these mutant H3/H4 tetramers. Thus, the N termini of H3/H4 tetramers are required for efficient acetylation of H3 by the Rtt109-Vps75 complex. Taken together, these studies provide insights into how H3-Lys-56 acetylation is regulated during the cell cycle.     

Identification of early salt stress response genes in tomato root by suppression subtractive hybridization and microarray analysis

High salinity is one of the most serious threats to crop production. To understand the molecular basis of plant responses to salt stress better, suppression subtractive hybridization (SSH) and microarray approaches were combined to identify the potential important or novel genes involved in the early stage of tomato responses to severe salt stress. First, SSH libraries were constructed for the root tissue of two cultivated tomato (Solanum lycopersicum) genotypes: LA2711, a salt-tolerant cultivar, and ZS-5, a salt-sensitive cultivar, to compare salt treatment and non-treatment plants. Then a subset of clones from these SSH libraries were used to construct a tomato cDNA array and microarray analysis was carried out to verify the expression changes of this set of clones upon a high concentration of salt treatment at various time points compared to the corresponding non-treatment controls. A total of 201 non-redundant genes that were differentially expressed upon 30 min of severe salt stress either in LA2711 or ZS-5 were identified from microarray analysis; most of these genes have not previously been reported to be associated with salt stress. The diversity of the putative functions of these genes indicated that salt stress resulted in a complex response in tomato plants.     

Acupuncture pretreatment protects heart from injury in rats with myocardial ischemia and reperfusion via inhibition of the beta(1)-adrenoceptor signaling pathway

Our previous study showed that a cardioprotective effect was produced by pretreatment with acupuncture at bilateral Neiguan acupoints (PC6) and the effect of EA was diminished by propranolol, a nonspecific antagonist of beta-adrenoceptors (beta-ARs) which are the most powerful cardiac receptors, indicating an involvement of beta-ARs. The present study explored further the signaling mechanism underlying the cardioprotective effect of acupuncture pretreatment in rats subjected to myocardial ischemia and reperfusion (MIR). Myocardial ischemia was achieved by ligating the left anterior descending coronary artery and reperfusion by releasing the ligation. Adult rats were divided into three groups, namely, a normal control (NC) group, a group subjected to ischemia and reperfusion (IR) only, and a group given electro-acupuncture (EA) before IR. For EA, bilateral Neiguan points (PC6) of the rats were stimulated for 30 min once a day for 3 consecutive days. The ST segment of ECG, the ratio of infarct size over risk zone, and the contents of beta(1)-adrenoceptor (beta(1)-AR), Gsalpha protein and cAMP in ischemic myocardium were compared among the three groups. IR increased the elevation of ECG ST segment, myocardial infarct size, contents of beta(1)-AR, Gsalpha protein and cAMP. These effects were attenuated by EA pretreatment at bilateral Neiguan acupoints. In conclusion, the present results indicate that EA produces cardioprotective effect against IR which may be mediated via the beta(1)-AR-Gs-protein-cAMP pathway.