Hypoxia potentiates LPS-induced inflammatory response and increases cell death by promoting NLRP3 inflammasome activation in pancreatic β cells

Hypoxia and islet inflammation are involved in β-cell failure in type 2 diabetes (T2D). Elevated plasma LPS levels have been verified in patients with T2D, and hypoxia occurs in islets of diabetic mice. Activation of inflammasomes in ischemic or hypoxic conditions was identified in various tissues. Here, we investigated whether hypoxia activates the inflammasome in β cells and the possible mechanisms involved. In mouse insulinoma cell line 6 (MIN6), hypoxia (1% O₂) primes the NLRP3 inflammasome along with NF-κB signaling activation. Our results demonstrate that hypoxia can activate the NLRP3 inflammasome in LPS-primed MIN6 to result in initiating the β cell inflammatory response and cell death in vitro. Reactive oxygen species (ROS) and the thioredoxin-interacting protein (TXNIP) are up-regulated in response to hypoxia. Finally, the role of the ROS-TXNIP axis in mediating the activation of the NLRP3 inflammasome and cell death was characterized by pretreating with the ROS scavenger N-acetylcysteine (NAC) and performing TXNIP knockdown experiments in MIN6. Our data indicate for the first time that the inflammasome is involved in the inflammatory response and cell death in hypoxia-induced β cells through the ROS-TXNIP-NLRP3 axis in vitro. This provides new insight into the relationship between hypoxia and inflammation in T2D.     

不同氧浓度对骨髓源内皮祖细胞分泌促血管新生相关生长因子的影响

目的:观察培养环境不同氧浓度对骨髓源内皮祖细胞分泌促血管新生相关生长因子的影响。方法:利用密度梯度离心技术分离SD大鼠骨髓单个核细胞,向内皮祖细胞进行诱导分化、扩增、培养和鉴定。然后在不同氧浓度(1%,5%,21%)的环境中培养,于第3天,7天,10天采用酶联免疫吸附试验检测内皮祖细胞分泌血管内皮生长因子(Vascular endothelial growth factor,VEGF)、基质细胞衍生因子-1α(Stromal-derived factor-1α, SDF-1α)、胰岛素样生长因子I(Insulin-like growth factor-I, IGF-I)等生长因子的水平。结果:第3天,不同氧浓度下各组EPC分泌VEGF、SDF-1α、IGF-I无明显差异(P均0.05)。第7天和第10天,各组EPC分泌IGF-I无明显差异(P均0.05);但是和21%氧浓度相比,相对低氧浓度(1%和5%)能够明显增强EPC分泌VEGF和SDF-1α(P均0.001)。结论:适当时间的低氧环境培养能够显著刺激内皮祖细胞分泌VEGF和SDF-1α,进而增强其促血管新生能力。     

Isoform-specific induction of PKC-epsilon by high glucose protects heart-derived H9c2 cells against hypoxic injury

We investigated which PKC isoforms are involved in high glucose-induced protection against hypoxic injury. Treatment for 48 h with high glucose (22 mM) markedly increased the expression of PKC- epsilon in the particulate fraction (213+/-22.1% of the control) but had no effect on other types of PKC isoforms, suggesting that the high glucose-induced increase in PKC expression is isoform-specific. The mRNA level for PKC- epsilon was also substantially increased, reaching its peak after 4h of high glucose treatment. The high glucose increased PKC-epsilon activity in the particulate fraction up to 183+/-32.2% of the control. During hypoxia, the amount of PKC-epsilon in the particulate fraction was remarkably diminished in the low glucose-treated cells, but remained at a higher level in high glucose-treated cells. The treatment with epsilon V1-2 (10 microM), a specific inhibitor of PKC epsilon, abolished the protective effect of high glucose against hypoxia. These results suggest that isoform-specific induction of PKC-epsilon is involved in high glucose-induced protection against hypoxic injury in heart-derived H9c2 cells.     

Biogenic Amine-Stimulated Cyclic Adenosine-3'',5''-Monophosphate Formation in the Rat Carotid Body

The subcutaneous injection of isoprenaline, salbutamol, histamine, and adrenaline to rats, which were subsequently killed by microwave irradiation, resulted in a rapid increase in the cyclic AMP content of the carotid body. On the other hand, noradrenaline, dopamine, adenosine, and 5-hydroxytryptamine, at doses at least 100 times greater than that of isoprenaline, did not significantly alter the cyclic nucleotide content in vivo. The response to isoprenaline was dose related, with an ED50 of 15 micrograms X kg-1, and reached a peak level 1-1.5 min after injection. Incubation of intact carotid bodies with isoprenaline (10(-5) M) in vitro also resulted in a 10-fold increase in cyclic AMP content. The in vivo response to isoprenaline could be blocked stereo-selectively by propranolol, and ICI 118.551, a beta 2-selective antagonist, blocks the isoprenaline-elicited increase in cyclic AMP completely at a dose of 30 micrograms X kg-1; whereas betaxolol, a beta 1-selective antagonist, was ineffective, even at a dose of 300 micrograms X kg-1. Hypoxia (5% oxygen in 95% N2) did not result in a significant increase in the cyclic AMP content, nor did it significantly alter the isoprenaline-stimulated increase in the cyclic AMP content of the rat carotid body. These results suggest that some catecholamines may stimulate cyclic AMP formation by interacting with a beta 2-adrenoceptor in the rat carotid body.     

Effects of intracerebroventricular administration of aminophylline on hyperbaric-induced increase in carotid blood flow

Carotid blood flow was measured in rats by implanted transit-time ultrasonic flowprobes during hyperbaric experiments at up to 70 bar (7 MPa) using an helium-oxygen hyperoxic (partial pressure of O₂ = 400 mbar) mixture. Before the hyperbaric experiment, an intracerebroventricular injection of phosphate saline buffered solution (PBS) or aminophylline, an adenosine receptor blocker, in PBS was given. Throughout the hyperbaric experiment carotid blood flow increased with ambient pressure in both PBS, i.e. control, and aminophylline treated rats. The increase in carotid blood flow was significantly attenuated in aminophylline treated rats. Additional experiments showed that the increased carotid blood flow was independent of hyperoxia as well as of temperature. The hypothesis that the hyperbaric dependent increase in carotid blood flow was mediated by brain adenosine receptors and its implication regarding a cerebral vasodilatation are discussed.     

HIF-1alpha信号通路在肿瘤细胞调控中的研究进展

缺氧诱导因子（HIF-1alpha）是肿瘤细胞生长过程中重要的调控因子,研究其作用机制有利于实现对肿瘤细胞增殖的抑制作用。 HIF-1alpha可引起多种基因转录,使肿瘤细胞耐受低氧环境,进而使癌症患者在治疗过程中产生耐受反应,最终影响治疗效果,甚至 放弃治疗。因此,以HIF-1alpha为靶点是治疗肿瘤的重要手段和方法。本文对HIF-1alpha的基本概况及其主要信号通路（PI3K 通路、 HSP90 通路及MAPK通路）以及不同通路抑制剂（如LY294002、17AAG、PD98059、U0126、SB203580、SP600125 等）进行综述,并 对HIF-1alpha的应用前景进行展望。     

Hypoxia reduces MAX expression in endothelial cells by unproductive splicing

The MYC–MAX–MXD network is involved in the regulation of cell differentiation and proliferation. Hypoxia affects the expression levels of several members of this network, but changes specific to MAX expression have so far not been shown. We found that in endothelial cells, hypoxia induces alternative splicing of MAX, thereby increasing the expression of two MAX isoforms that differ from the wild type in their 3′ end. Isoform C is degraded by nonsense-mediated decay and isoform E encodes a highly unstable protein. The instability of isoform E is conferred by 36 isoform-specific amino acids, which have the capacity to destabilize heterologous proteins. Both splicing events are therefore unproductive and serve the purpose to downregulate the wild type protein.