The protective effect of RES against DOX-induced cardiomyocyte apoptosis is associated with the up-regulation of SIRT1-mediated p53 deacetylation.

No abstract

The objective of this study was to evaluate the negative regulatory role of heat shock protein 70 (HSP70) on endotoxin-induced activation of inflammatory cytokine signaling pathways in a macrophage cell line. Our studies show that elevation of HSP70 either by activation of the heat shock response (HSR) or through forced expression of the hsp70.1 gene downregulates cytokine expression. Our experiments showed that activation of the HSR and HSP70 overexpression could inhibit LPS-mediated expression of the proinflammatory cytokines TNF-alpha and IL-1 at the mRNA and protein levels. We also investigated the effects of HSP70 elevation on signaling pathways downstream of LPS and its receptors, including the NF-kappaB and mitogen-activated protein kinase (MAPK) pathways. The effects of HSP70 on cytokine expression were correlated with its effects on activation of NF-kappaB, a known activator of the tnfalpha and Il-1 genes. Overexpression of HSP70 inhibited the nuclear translocation of p65, the transcriptionally active component of the NF-kappaB complex, and prevented the degradation of IkappaBalpha, the regulator of NF-kappaB activity. However, HSP70 elevation did not markedly inhibit signaling through the MAPK arm of the LPS-induced pathway, suggesting that the effects of HSP70 are mediated primarily through the NF-kappaB cascade. Our experiments therefore suggested that elevated levels of HSP70 inhibit LPS-induced production of inflammatory cytokines by a mechanisms involving inactivation of NF-kappaB but cast doubt on significant role for the MAPK pathway in these effects.

Proangiogenesis is generally regarded as an effective approach for treating ischemic heart disease. Vascular endothelial growth factor (VEGF)‐A is a strong and essential proangiogenic factor. Reactive oxygen species (ROS), endoplasmic reticulum (ER) stress, and autophagy are implicated in the process of angiogenesis. This study is designed to clarify the regulatory mechanisms underlying VEGF‐A, ROS, ER stress, autophagy, and angiogenesis in acute myocardial infarction (AMI). A mouse model of AMI was successfully established by occluding the left anterior descending coronary artery. Compared with the sham‐operated mice, the microvessel density, VEGF‐A content, ROS production, expression of vascular endothelial cadherin, positive expression of 78 kDa glucose‐regulated protein/binding immunoglobulin protein (GRP78/Bip), and LC3 puncta in CD31‐positive endothelial cells of the ischemic myocardium were overtly elevated. Moreover, VEGF‐A exposure predominantly increased the expression of beclin‐1, autophagy‐related gene (ATG) 4, ATG5, inositol‐requiring enzyme‐1 (IRE‐1), GRP78/Bip, and LC3‐II/LC3‐I as well as ROS production in the human umbilical vein endothelial cells (HUVECs) in a dose and time‐dependent manner. Both beclin‐1 small interfering RNA and 3‐methyladenine treatment predominantly mitigated VEGF‐A‐induced tube formation and migration of HUVECs, but they failed to elicit any notable effect on VEGF‐A‐increased expression of GRP78/Bip. Tauroursodeoxycholic acid not only obviously abolished VEGF‐A‐induced increase of IRE‐1, GRP78/Bip, beclin‐1 expression, and LC3‐II/LC3‐I, but also negated VEGF‐A‐induced tube formation and migration of HUVECs. Furthermore, N‐acetyl‐ l‐cysteine markedly abrogated VEGF‐A‐increased ROS production, IRE‐1, GRP78/Bip, beclin‐1 expression, and LC3‐II/LC3‐I in the HUVECs. Taken together, our data demonstrated that increased spontaneous production of VEGF‐A may induce angiogenesis after AMI through initiating ROS–ER stress‐autophagy axis in the vascular endothelial cells.

In response to inflammatory stimuli (e.g., endotoxin, proinflammatory cytokines) or oxidative stress, macrophages actively release a ubiquitous nuclear protein, high-mobility group box 1 (HMGB1), to sustain an inflammatory response to infection or injury. In this study, we demonstrated mild heat shock (e.g., 42.5°C, 1 h), or enhanced expression of heat shock protein (Hsp) 72 (by gene transfection) similarly rendered macrophages resistant to oxidative stress-induced HMGB1 cytoplasmic translocation and release. In response to oxidative stress, cytoplasmic Hsp72 translocated to the nucleus, where it interacted with nuclear proteins including HMGB1. Genetic deletion of the nuclear localization sequence (NLS) or the peptide binding domain (PBD) from Hsp72 abolished oxidative stress-induced nuclear translocation of Hsp72-ΔNLS (but not Hsp72-ΔPBD), and prevented oxidative stress-induced Hsp72-ΔPBD-HMGB1 interaction in the nucleus. Furthermore, impairment of Hsp72-ΔNLS nuclear translocation, or Hsp72-ΔPBD-HMGB1 interaction in the nucleus, abrogated Hsp72-mediated suppression of HMGB1 cytoplasmic translocation and release. Taken together, these experimental data support a novel role for nuclear Hsp72 as a negative regulator of oxidative stress-induced HMGB1 cytoplasmic translocation and release.