Cardioprotection involves activation of NF-kappa B via PKC-dependent tyrosine and serine phosphorylation of I kappa B-alpha

Previous studies indicated that activation of PKC and Src tyrosine kinases by ischemic preconditioning (PC) may participate in the activation of NF-kappa B. However, the molecular mechanisms underlying activation of NF-kappa B during ischemic PC remain unknown. In the hearts of conscious rabbits, it was found that ischemic PC (6 cycles of 4-min coronary occlusion and 4-min reperfusion) significantly induced both tyrosine (+226.9 +/- 42%) and serine (+137.0 +/- 36%) phosphorylation of the NF-kappa B inhibitory protein I kappa B-alpha, concomitant with increased activation of the I kappa B-alpha kinases IKK alpha (+255.0 +/- 46%) and IKK beta (+173.1 +/- 35%). Furthermore, both tyrosine and serine phosphorylation of I kappa B-alpha were blocked by pretreatment with either the nonreceptor tyrosine kinase inhibitor lavendustin-A (LD-A) or the PKC inhibitor chelerythrine (Che) (both given at doses previously shown to block ischemic PC). Interestingly, Che completely abolished PC-induced activation of IKK alpha/beta, whereas LD-A had no effect. In addition, I kappa B-alpha protein level did not change during ischemic PC. Together, these data indicate that ischemic PC-induced activation of NF-kappa B occurs through both tyrosine and serine phosphorylation of I kappa B-alpha and is regulated by nonreceptor tyrosine kinases and PKC.     

Caveolin-1 null mice develop cardiac hypertrophy with hyperactivation of p42/44 MAP kinase in cardiac fibroblasts

Recently, development ofa caveolin-1-deficient (Cav-1 null) mouse model has allowed thedetailed analysis of caveolin-1's function in the context of awhole animal. Interestingly, we now report that the hearts ofCav-1 null mice are markedly abnormal, despite the fact that caveolin-1is not expressed in cardiac myocytes. However, caveolin-1 is abundantlyexpressed in the nonmyocytic cells of the heart, i.e., cardiacfibroblasts and endothelia. Quantitative imaging studies of Cav-1 nullhearts demonstrate a significantly enlarged right ventricular cavityand a thickened left ventricular wall with decreased systolic function.Histological analysis reveals myocyte hypertrophy withinterstitial/perivascular fibrosis. Because caveolin-1 is thought toact as a negative regulator of the p42/44 MAP kinase cascade, weperformed Western blot analysis with phospho-specific antibodies thatonly recognize activated ERK1/2. As predicted, the p42/44 MAP kinasecascade is hyperactivated in Cav-1 null heart tissue (i.e.,interstitial fibrotic lesions) and isolated cardiac fibroblasts. Inaddition, endothelial and inducible nitric oxide synthase levels aredramatically upregulated. Thus loss of caveolin-1 expression drivesp42/44 MAP kinase activation and cardiac hypertrophy.

     

Sequential unfolding of ankyrin repeats in tumor suppressor p16

The ANK repeat is a ubiquitous 33-residue motif that adopts a beta hairpin helix-loop-helix fold. Multiple tandem repeats stack in a linear manner to produce an elongated structure that is stabilized predominantly by short-range interactions between residues close in sequence. The tumor suppressor p16(INK4) consists of four repeats and represents the minimal ANK folding unit. We found from Phi value analysis that p16 unfolded sequentially. The two N-terminal ANK repeats, which are distorted from the canonical ANK structure in all INK4 proteins and which are important for functional specificity, were mainly unstructured in the rate-limiting transition state for folding/unfolding, while the two C-terminal repeats were fully formed. A sequential unfolding mechanism could have implications for the cellular fate of wild-type and cancer-associated mutant p16 proteins.     

粉防己碱拮抗豚鼠庆大霉素急性肾损伤的实验研究

目的 :探讨粉防己碱 (Tet)在庆大霉素 (GM)急性肾损伤中的拮抗作用。方法 :将豚鼠分为对照组、Tet组、GM组和Tet+GM组 ,于第 1 1d留取尿标本和肾组织 ,测定尿中NAG活性 ,观察肾组织学改变 ,用免疫组化技术测定Actin和TGF β1 在肾脏的表达。结果 :光镜和电镜显示Tet+GM组肾脏病理变化比GM组轻 ,细胞凋亡也明显少于GM组。Tet+GM组NAG活性比GM组低 (P <0 .0 1 ) ,而TGF β1 和Actin的表达在Tet +GM组高于GM组(P <0 .0 1 )。结论 :Tet能明显降低GM所致的急性肾损伤时NAG活性 ,减少Actin的破坏和细胞凋亡 ,诱导内源性TGF β1 蛋白表达水平上调 ,对GM急性肾损伤有拮抗作用     

高肺血流对大鼠肺血管结构及尾加压素Ⅱ表达的影响

目的：探讨新型血管活性肽人类尾加压素Ⅱ(hUⅡ)在高肺血流量所致肺动脉高压大鼠肺动脉中的表达及其作用。方法：对大鼠行腹主动脉-下腔静脉分流术。11周后,以右心导管法测肺动脉压力,观测肺血管显微结构的变化,以免疫组织化学方法检测肺动脉hUⅡ的表达。结果：分流术后11周,大鼠肺动脉高压形成,肺小血管肌化程度明显增强,肺中、小型肌型动脉相对中膜厚度明显增加。分流组大鼠肺动脉内皮细胞和平滑肌细胞hUⅡ蛋白表达上调,并且与肺动脉压力和肺血管结构的改变呈正相关。结论：肺动脉内皮细胞和平滑肌细胞hUⅡ的上调可能参与了高肺血流量所致肺血管结构重建和肺动脉高压的形成。     

脱氢紫堇碱对正常和低氧豚鼠心肌细胞内钙的影响

目的 :探讨脱氢紫堇碱 (dehydeocorydaline,DHC)及维拉帕米 (verapamil,Ver)对豚鼠心肌细胞内游离钙浓度([Ca2 + ] i)变化的影响。方法 :采用离体豚鼠心脏Langendorff法灌注 ,用荧光指示剂方法 (Fure 2 /AM)标记心肌([Ca2 + ] i)变化。观察低氧后心肌 [Ca2 + ] i 的变化。结果 :①正常氧状态心肌 [Ca2 + ] i 均值为 (1 2 0 .5± 8.3)nmol/L(n =2 0 ) ;②正常氧条件下 ,DHC、Ver均使心肌 [Ca2 + ] i 明显下降。 (3)低氧状态下 ,心肌 [Ca2 + ] i 增加与缺氧时间(程度 )直线相关 (r=0 .98)。④DHC对低氧后心肌 [Ca2 + ] i 增加明显减缓。结论 :DHC在正常氧、低氧条件下阻止心肌细胞内钙超载 ,我们认为DHC可能提高心肌细胞的自我保护作用     

Behavioral modification in choice process of<Emphasis Type="Italic">Drosophila</Emphasis>

In visual operant conditioning ofDrosophila at the flight simulator, only motor output of flies—yaw torque—is recorded, which is involved in the conditioning process. The current study used a newly-designed data analysis method to study the torque distribution ofDrosophila. Modification of torque distribution represents the effects of operant conditioning on flies’ behavioral mode. Earlier works^[10] showed that, when facing contradictory visual cues, flies could make choices based upon the relative weightiness of different cues, and it was demonstrated that mushroom bodies might play an important role in such choice behavior. The new “torque-position map” method was used to explore the CS-US associative learning and choice behavior inDrosophila from the aspect of its behavioral mode. Finally, this work also discussed various possible neural bases involved in visual associative learning, choice processing and modification processing of the behavioral mode in the visual operant conditioning ofDrosophila.     

CD28/B7 regulation of anti-CD3-mediated immunosuppression in vivo

FcR-binding "classical" anti-CD3 mAb is a potent immunosuppressive drug that alters CD4(+) and CD8(+) T cell function in vivo via anergy induction and programmed cell death (PCD). Anti-CD3-mediated PCD was Fas independent but was mediated by the mitochondria-initiated apoptosis that was abrogated in Bcl-x(L)-transgenic T cells. The PCD was more pronounced in CD28-deficient mice consistent with defective Bcl-x(L) up-regulation. Residual T cells isolated from anti-CD3-treated wild-type, CD28(-/-), and Bcl-x(L)-transgenic mice were hyporesponsive. The hyporesponsiveness was more pronounced in CD28(-/-) and wild-type mice treated with anti-B7-2, suggesting that CD28 interaction with B7-2 regulates T cell responsiveness in anti-CD3-treated animals. Finally, anti-CD3 treatment led to indefinite cardiac allograft survival in wild-type but not Bcl-x(L) animals. Together these results implicate CD28/B7 signaling in the regulation of both anti-CD3-induced T cell depletion and hyporesponsiveness in vivo, but T cell depletion, not hyporesponsiveness, appears to be critical for anti-CD3 mAb-mediated long-term immune regulation.     

Crystal structure of tabtoxin resistance protein complexed with acetyl coenzyme A reveals the mechanism for beta-lactam acetylation

Tabtoxin resistance protein (TTR) is an enzyme that renders tabtoxin-producing pathogens, such as Pseudomonas syringae, tolerant to their own phytotoxins. Here, we report the crystal structure of TTR complexed with its natural cofactor, acetyl coenzyme A (AcCoA), to 1.55A resolution. The binary complex forms a characteristic "V" shape for substrate binding and contains the four motifs conserved in the GCN5-related N-acetyltransferase (GNAT) superfamily, which also includes the histone acetyltransferases (HATs). A single-step mechanism is proposed to explain the function of three conserved residues, Glu92, Asp130 and Tyr141, in catalyzing the acetyl group transfer to its substrate. We also report that TTR possesses HAT activity and suggest an evolutionary relationship between TTR and other GNAT members.