Xianzhong Xiao

HSF1 is required for extra‐embryonic development, postnatal growth and protection during inflammatory responses in mice

HSF1 is the major heat shock transcriptional factor that binds heat shock element (HSE) in the promoter of heat shock proteins (Hsps) and controls rapid Hsp induction in cells subjected to various environmental stresses. Although at least four members of the vertebrate HSF family have been described, details of their individual physiological roles remain relatively obscure. To assess whether HSF1 exhibited redundant or unique in vivo functions, we created Hsf1−/− deficient mice. We demonstrate that homozygous Hsf1−/− mice can survive to adulthood but exhibit multiple phenotypes including: defects of the chorioallantoic placenta and prenatal lethality; growth retardation; female infertility; elimination of the ‘classical’ heat shock response; and exaggerated tumor necrosis factor alpha production resulting in increased mortality after endotoxin challenge. Because basal Hsp expression is not altered appreciably by the HSF1 null mutation, our findings suggest that this factor, like Drosophila Hsf protein, might be involved in regulating other important genes or signaling pathways. Our results establish direct causal effects for the HSF1 transactivator in regulating critical physiological events during extra‐embryonic development and under pathological conditions such as sepsis to modulate pro‐inflammatory responses, indicating that these pathways have clinical importance as therapeutic targets in humans.

Hydrogen peroxide stimulates macrophages and monocytes to actively release HMGB1.

High mobility group box 1 (HMGB1) can be actively secreted by macrophages/monocytes in response to exogenous and endogenous inflammatory stimuli (such as bacterial endotoxin, TNF‐α, IL‐1, and IFN‐γ) or passively released by necrotic cells and mediates innate and adaptive inflammatory responses to infection and injury. Here, we demonstrated that a reactive oxygen species, hydrogen peroxide (H2O2), induces active and passive HMGB1 release from macrophage and monocyte cultures in a time‐ and dose‐dependent manner. At nontoxic doses (e.g., 0.0125–0.125 mM), H2O2 induced HMGB1 cytoplasmic translocation and active release within 3–24 h. At higher concentrations (e.g., 0.25 mM), however, H2O2 exhibited cytotoxicity to macrophage and monocyte cell cultures and consequently, triggered active and passive HMGB1 release. In addition, H2O2 stimulated potential interaction of HMGB1 with a nuclear export factor, chromosome region maintenance (CRM1), in macrophage/monocyte cultures. Inhibitors specific for the JNK (SP600125) and MEK (PD98059), but not p38 MAPK (SB203580), abrogated H2O2‐induced, active HMGB1 release. Together, these data establish an important role for oxidative stress in inducing active HMGB1 release, potentially through a MAPK‐ and CRM1‐dependent mechanism.

Mouse heat shock transcription factor 1 deficiency alters cardiac redox homeostasis and increases mitochondrial oxidative damage

In this study, using heat shock factor 1 (Hsf1) knockout mice as a model, we tested the hypothesis that HSF1‐dependent regulation of heat shock proteins (Hsps) is required to maintain redox state and attenuate oxidative damage in the normal heart. Here we report that, in mice, HSF1 deficiency reduces cardiac expression of Hsp25, αB‐crystallin and Hsp70, but not Hsp60 and Hsp90. Consistent with the downregulation of Hsp25, for example, a significantly lower glutathione (GSH)/glutathione disulfate (GSSG) ratio was associated with the decreased activity, but not protein content, of glucose 6‐phosphate dehydrogenase. Con sequently, superoxide was generated at a higher rate, and several mitochondrial proteins, including adenine nucleotide translocase 1 (ANT1), were more oxidized by HSF1 deficiency in vivo. Oxidative damage to ANT1 protein, a structural component of the mitochondrial permeability transition pore (MPTP), decreases its catalytic activity and increases MPTP opening, respectively. Taken together, our results indicate for the first time that constitutive expression of HSP chaperones requires HSF1 activity, and that such HSF1‐dependent requirements are directly and functionally linked to maintain redox homeostasis and antioxidative defenses at normal (37°C) temperature.

Resveratrol attenuates doxorubicin-induced cardiomyocyte apoptosis in mice through SIRT1-mediated deacetylation of p53

AIMS Doxorubicin (DOX) is an anthracycline drug with a wide spectrum of clinical antineoplastic activity, but increased apoptosis has been implicated in its cardiotoxicity. Resveratrol (RES) was shown to harbour major health benefits in diseases associated with oxidative stress. In this study, we aimed to determine the effect of RES on DOX-induced myocardial apoptosis in mice. METHODS AND RESULTS Male Balb/c mice were randomized to one of the following four treatments: saline, RES, DOX, or RES plus DOX (10 mice in each group). DOX treatment markedly depressed cardiac function, decreased the heart weight, the body weight, and the ratio of heart weight to body weight, but inversely increased the level of protein carbonyl, malondialdehyde, and serum lactate dehydrogenase, and induced mitochondrial cytochrome c release and cardiomyocyte apoptosis. However, these effects of DOX were ameliorated by its combination with RES. Further studies with a co-immunoprecipitation assay revealed an interaction between p53 and Sirtuin 1 (SIRT1). It was found by western blot and electrophoretic mobility shift assay that DOX treatment increased p53 protein acetylation and cytochrome c release from mitochondria, activated p53 binding at the Bax promoter, and up-regulated Bax expression, but supplementation with RES could weaken all these effects. CONCLUSION The protective effect of RES against DOX-induced cardiomyocyte apoptosis is associated with the up-regulation of SIRT1-mediated p53 deacetylation.

MicroRNA Expression Abnormalities in Limited Cutaneous Scleroderma and Diffuse Cutaneous Scleroderma

Scleroderma (systemic sclerosis, SSc) is a complex autoimmune disease caused by progressive fibrotic replacement of normal tissue architecture, a progressive and ultimately fatal process that currently has no cure. Although dysregulation of microRNAs (miRNAs) is known to be involved in a variety of pathophysiologic processes, the role of miRNAs in SSc is unclear. In comparison with the normal skin tissues, miRNAs were aberrantly expressed in limited cutaneous scleroderma and diffuse cutaneous scleroderma skin tissues. We also identified miRNAs whose expressions were correlated with SSc fibrosis: miR-21, miR-31, miR-146, miR-503, miR-145, and miR-29b were predicted to be involved. This study further confirmed that miR-21 was increased whereas miR-145 and miR-29b were decreased both in the skin tissues and fibroblasts. As predicted target genes, SMAD7, SAMD3, and COL1A1 were regulated by these miRNAs. After stimulation with transforming growth factor β, the expression of miR-21 was increased and that of SMAD7 mRNA was decreased. MiR-145 was upregulated whereas the mRNA level of SMAD3 was downregulated. The downregulation of miR-29b was correlated with the upregulation of COL1A1 mRNA. MiRNAs might play an important role in the pathogenesis of SSc and suggest a potential therapy.

Heat shock pretreatment inhibited the release of Smac/DIABLO from mitochondria and apoptosis induced by hydrogen peroxide in cardiomyocytes and C2C12 myogenic cells

Abstract Oxidative stress may cause apoptosis of cardiomyocytes in ischemia-reperfused myocardium, and heat shock pretreatment is thought to be protective against ischemic injury when cardiac myocytes are subjected to ischemia or simulated ischemia. However, the detailed mechanisms responsible for the protective effect of heat shock pretreatment are currently unclear. The aim of this study was to determine whether heat shock pretreatment exerts a protective effect against hydrogen peroxide(H2O2)–induced apoptotic cell death in neonatal rat cardiomyocytes and C2C12 myogenic cells and whether such protection is associated with decreased release of second mitochondria-derived activator of caspase–direct IAP binding protein with low pI (where IAP is inhibitor of apoptosis protein) (Smac/DIABLO) from mitochondria and the activation of caspase-9 and caspase-3. After heat shock pretreatment (42 ± 0.3°C for 1 hour, recovery for 12 hours), cardiomyocytes and C2C12 myogenic cells were exposed to H2O2 (0.5 mmol/L) for 6, 12, 24, and 36 hours. Apoptosis was evaluated by Hoechst 33258 staining and DNA laddering. Caspase-9 and caspase-3 activities were assayed by caspase colorimetric assay kit and Western analysis. Inducible heat shock proteins (Hsp) were detected using Western analysis. The release of Smac/DIABLO from mitochondria to cytoplasm was observed by Western blot and indirect immunofluorescence analysis. (1) H2O2 (0.5 mmol/L) exposure induced apoptosis in neonatal rat cardiomyocytes and C2C12 myogenic cells, with a marked release of Smac/DIABLO from mitochondria into cytoplasm and activation of caspase-9 and caspase-3, (2) heat shock pretreatment induced expression of Hsp70, Hsp90, and αB-crystallin and inhibited H2O2-mediated Smac/DIABLO release from mitochondria, the activation of caspase-9, caspase-3, and subsequent apoptosis. H2O2 can induce the release of Smac/DIABLO from mitochondria and apoptosis in cardiomyocytes and C2C12 myogenic cells. Heat shock pretreatment protects the cells against H2O2-induced apoptosis, and its mechanism appears to involve the inhibition of Smac release from mitochondria.

Quercetin Prevents LPS-Induced High-Mobility Group Box 1 Release and Proinflammatory Function

The pathogenesis of sepsis is mediated in part by the pathogen-associated molecular pattern molecule bacterial endotoxin, which stimulates macrophages to sequentially release early (e.g., TNF-alpha, IL-1beta) and late (e.g., high-mobility group box [HMGB] 1 protein) proinflammatory mediators. The recent discovery of HMGB1 as a late mediator of lethal sepsis has prompted investigation into development of several new experimental therapeutics that limit release, either blocking HMGB1 itself or its nominal receptors. Quercetin was recently identified as an experimental therapeutic that significantly protects against oxidative injury. Here, we report that quercetin attenuates lethal systemic inflammation caused by endotoxemia, even if treatment is started after the early TNF response. Quercetin treatment reduced circulating levels of HMGB1 in animals with established endotoxemia. In macrophage cultures, quercetin inhibited release as well as the cytokine activities of HMGB1, including limiting the activation of mitogen-activated protein kinase and NF-kappaB, two signaling pathways that are critical for HMGB1-induced subsequent cytokine release. Quercetin and autophagic inhibitor, wortmannin, inhibited LPS-induced type-II microtubule-associated protein 1A/1B-light chain 3 production and aggregation, as well as HMGB1 translocation and release, suggesting a potential association between autophagy and HMGB1 release. Quercetin delivery, a strategy to pharmacologically inhibit HMGB1 release that is effective at clinically achievable concentrations, now warrants further evaluation in sepsis and other systemic inflammatory disorders.

The inhibition of LPS-induced production of inflammatory cytokines by HSP70 involves inactivation of the NF-κB pathway but not the mapk pathways

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-&agr; 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-&kgr;B and mitogen-activated protein kinase (MAPK) pathways. The effects of HSP70 on cytokine expression were correlated with its effects on activation of NF-&kgr;B, a known activator of the tnf&agr; and Il-1 genes. Overexpression of HSP70 inhibited the nuclear translocation of p65, the transcriptionally active component of the NF-&kgr;B complex, and prevented the degradation of I&kgr;B&agr;, the regulator of NF-&kgr;B 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-&kgr;B cascade. Our experiments therefore suggested that elevated levels of HSP70 inhibit LPS-induced production of inflammatory cytokines by a mechanisms involving inactivation of NF-&kgr;B but cast doubt on significant role for the MAPK pathway in these effects.

Exogenous hydrogen sulfide protects against global cerebral ischemia/reperfusion injury via its anti-oxidative, anti-inflammatory and anti-apoptotic effects in rats

The present study was undertaken to study the effects of exogenous hydrogen sulfide (H(2)S) on global cerebral ischemia-reperfusion(I/R) and the underlying mechanisms. After a 24h I/R, administration of NaHS, an exogenous donor for H(2)S, at the dose of 0.2 or 0.4 μmol/kg significantly decreased the apoplexy index, neurological symptom scoring, and brain infarcted area as compared to the I/R group in a dose dependent manner. At the same time, NaHS-treated rats displayed significant reduction of MDA content, and striking increase of SOD activity in the brain tissues compared with I/R group. The up-regulated mRNA levels of p47(phox) and gp91(phox) subunits of NADPH oxidase were also suppressed by NaHS treatment. In this study, the pro-inflammatory markers TNF-α and MCP-1 in I/R group were markedly increased by 24h I/R, which were significantly attenuated by NaHS in a dose-dependent manner. In contrast, the anti-inflammatory factor IL-10 was markedly induced by NaHS administration. In addition, the expression of the anti-apoptotic protein Bcl-2 was significantly decreased in I/R group compared with the sham-operated group. This reduction was significantly blunted in NaHS-treated group. On the contrary, the pro-apoptotic protein Bax content in brain tissues of I/R group was markedly elevated compared with sham-operated animals. And such an induction of Bax content was significantly ameliorated by NaHS. Taken together, our results suggest that hydrogen sulfide has potent protective effect against a severe cerebral injury induced by a global I/R possibly through the inhibition of oxidative stress, inflammation and apoptosis.

MicroRNA-21 in Scleroderma Fibrosis and its Function in TGF-β- Regulated Fibrosis-Related Genes Expression

Uncontrolled fibrosis in multiple organs is the main cause of death in systemic sclerosis (SSc), and transforming growth factor-β (TGF-β) activation plays a fundamental role in the process. Our previous study demonstrated that miR-21 was significantly up-regulated in SSc fibroblasts. Here, we found that TGF-β regulated the expression of miR-21 and fibrosis-related genes, and decreased Smad7 expression. Over-expression of miR-21 in fibroblasts decreased the levels of Smad7, whereas knockdown of miR-21 increased its expression. Further study using a reporter gene assay demonstrated Smad7 was a direct target of miR-21. Similar to human SSc, the expression of miR-21 increased in the bleomycin induced skin fibrosis. Inhibition of fibrosis by treatment with anti-fibrosis drug bortezomib restored the levels of miR-21 and Smad7. MiR-21 may function in an amplifying circuit to enhance TGF-β signaling events in SSc fibrosis, and suggesting that miR-21 may act as a potential therapeutic target.Uncontrolled fibrosis in multiple organs is the main cause of death in systemic sclerosis (SSc), and transforming growth factor-β (TGF-β) activation plays a fundamental role in the process. Our previous study demonstrated that miR-21 was significantly up-regulated in SSc fibroblasts. Here, we found that TGF-β regulated the expression of miR-21 and fibrosis-related genes, and decreased Smad7 expression. Over-expression of miR-21 in fibroblasts decreased the levels of Smad7, whereas knockdown of miR-21 increased its expression. Further study using a reporter gene assay demonstrated Smad7 was a direct target of miR-21. Similar to human SSc, the expression of miR-21 increased in the bleomycin induced skin fibrosis. Inhibition of fibrosis by treatment with anti-fibrosis drug bortezomib restored the levels of miR-21 and Smad7. MiR-21 may function in an amplifying circuit to enhance TGF-β signaling events in SSc fibrosis, and suggesting that miR-21 may act as a potential therapeutic target.