Heme oxygenase-1 induction prevents neuronal damage triggered during mitochondrial inhibition: role of CO and bilirubin

Serum bilirubin levels are associated with poor functional outcomes in patients with acute ischemic stroke or transient ischemic attack

BACKGROUND

The prognostic value of serum bilirubin in stroke is controversial, since bilirubin has both neuroprotective and neurotoxic properties. We aimed to investigate the association between serum bilirubin, including total bilirubin (TBIL), direct bilirubin (DBIL) and indirect bilirubin (IBIL) and poor functional outcomes in patients with acute ischemic stroke (AIS) or transient ischemic attack (TIA).

METHODS

All patients with AIS or TIA were recruited from the Third China National Stroke Registry. The poor functional outcomes included modified Rankin Scale (mRS) score 2-6 and 3-6 at 3 months and 1 year. Multivariable logistic regression was used to investigate the associations of TBIL, DBIL, and IBIL with poor functional outcomes.

RESULTS

Among 11,121 enrolled patients, the median (interquartile range) of TBIL, DBIL, and IBIL was 13.30 (9.90-17.70), 3.80 (2.70-5.30), and 9.30 (6.70-12.80) µmol/L. After adjustment for conventional confounding factors, patients in the highest TBIL quartile had the highest proportion of mRS score 2-6 at 3 months (odds ratio [OR], 1.37; 95 % confidence interval [CI], 1.19-1.59) and 1 year (OR, 1.31; 95 % CI, 1.13-1.52), and mRS score 3-6 at 3 months (OR, 1.33; 95 % CI, 1.11-1.59) and 1 year (OR, 1.28; 95 % CI, 1.07-1.53), when compared to patients in the lowest TBIL quartile. Similar results were observed for DBIL and IBIL. We also found J-shaped associations between serum bilirubin levels and each outcome.

CONCLUSIONS

Elevated levels of serum bilirubin were significantly associated with poor functional outcomes in patients with AIS or TIA at 3 months and 1 year.

Transcriptomic Changes Associated with Loss of Cell Viability Induced by Oxysterol Treatment of a Retinal Photoreceptor-Derived Cell Line: An In Vitro Model of Smith-Lemli-Opitz Syndrome

Smith–Lemli–Opitz Syndrome (SLOS) results from mutations in the gene encoding the enzyme DHCR7, which catalyzes conversion of 7-dehydrocholesterol (7DHC) to cholesterol (CHOL). Rats treated with a DHCR7 inhibitor serve as a SLOS animal model, and exhibit progressive photoreceptor-specific cell death, with accumulation of 7DHC and oxidized sterols. To understand the basis of this cell type specificity, we performed transcriptomic analyses on a photoreceptor-derived cell line (661W), treating cells with two 7DHC-derived oxysterols, which accumulate in tissues and bodily fluids of SLOS patients and in the rat SLOS model, as well as with CHOL (negative control), and evaluated differentially expressed genes (DEGs) for each treatment. Gene enrichment analysis and compilation of DEG sets indicated that endoplasmic reticulum stress, oxidative stress, DNA damage and repair, and autophagy were all highly up-regulated pathways in oxysterol-treated cells. Detailed analysis indicated that the two oxysterols exert their effects via different molecular mechanisms. Changes in expression of key genes in highlighted pathways (Hmox1, Ddit3, Trib3, and Herpud1) were validated by immunofluorescence confocal microscopy. The results extend our understanding of the pathobiology of retinal degeneration and SLOS, identifying potential new druggable targets for therapeutic intervention into these and other related orphan diseases.

The Role of Bilirubin and the Other "Yellow Players" in Neurodegenerative Diseases

Bilirubin is a yellow endogenous derivate of the heme catabolism. Since the 1980s, it has been recognized as one of the most potent antioxidants in nature, able to counteract 10,000× higher intracellular concentrations of H2O2. In the recent years, not only bilirubin, but also its precursor biliverdin, and the enzymes involved in their productions (namely heme oxygenase and biliverdin reductase; altogether the "yellow players"-YPs) have been recognized playing a protective role in diseases characterized by a chronic prooxidant status. Based on that, there is an ongoing effort in inducing their activity as a therapeutic option. Nevertheless, the understanding of their specific contributions to pathological conditions of the central nervous system (CNS) and their role in these diseases are limited. In this review, we will focus on the most recent evidence linking the role of the YPs specifically to neurodegenerative and neurological conditions. Both the protective, as well as potentially worsening effects of the YP's activity will be discussed.

Astrocytes Are More Vulnerable than Neurons to Silicon Dioxide Nanoparticle Toxicity in Vitro

Some studies have shown that silicon dioxide nanoparticles (SiO₂-NPs) can reach different regions of the brain and cause toxicity; however, the consequences of SiO₂-NPs exposure on the diverse brain cell lineages is limited. We aimed to investigate the neurotoxic effects of SiO₂-NP (0–100 µg/mL) on rat astrocyte-rich cultures or neuron-rich cultures using scanning electron microscopy, Attenuated Total Reflection-Fourier Transform Infrared spectroscopy (ATR-FTIR), FTIR microspectroscopy mapping (IQ mapping), and cell viability tests. SiO₂-NPs were amorphous particles and aggregated in saline and culture media. Both astrocytes and neurons treated with SiO₂-NPs showed alterations in cell morphology and changes in the IR spectral regions corresponding to nucleic acids, proteins, and lipids. The analysis by the second derivative revealed a significant decrease in the signal of the amide I (α-helix, parallel β-strand, and random coil) at the concentration of 10 µg/mL in astrocytes but not in neurons. IQ mapping confirmed changes in nucleic acids, proteins, and lipids in astrocytes; cell death was higher in astrocytes than in neurons (10–100 µg/mL). We conclude that astrocytes were more vulnerable than neurons to SiO₂-NPs toxicity. Therefore, the evaluation of human exposure to SiO₂-NPs and possible neurotoxic effects must be followed up.

Serum bilirubin level correlates with mortality in patients with traumatic brain injury

As a catabolic product of hemoglobin, bilirubin has been confirmed playing an important role in the development of various central nervous system disease. The aim of this study is to explore the correlation between serum bilirubin level and mortality in patients with traumatic brain injury (TBI).Patients admitted with traumatic brain injury (TBI) in our hospital between January 2015 and January 2018 were enrolled in this study. Clinical and laboratory data of 361 patients were retrospectively collected to explore the independent risk factors of mortality.The comparison of baseline characteristics showed that non-survivors had lower Glasgow Coma Scale (GCS) (P < .001) and higher level of serum total bilirubin (TBIL) (P < .001) and direct bilirubin (DBIL) (P < .001). We found that only GCS (P < .001), glucose (P < .001), lactate dehydrogenase (LDH) (P = .042) and DBIL (P = .005) were significant risk factors in multivariate logistic regression analysis. GCS and DBIL had comparable AUC value (0.778 vs 0.750, P > .05) on predicting mortality in TBI patients. The AUC value of the combination of GCS and DBIL is higher than the single value of these two factors (P < .05). Moreover, predictive model 1 consisted of GCS, glucose, LDH and DBIL had the highest AUC value of 0.894.DBIL is a significant risk factor of mortality in TBI patients. Assessing the level of DBIL is beneficial for physicians to evaluate severity and predict outcome for TBI patients.

Bilirubin: a novel predictor of hemorrhagic transformation and symptomatic intracranial hemorrhage after mechanical thrombectomy

BACKGROUND AND PURPOSE

The role of bilirubin in patients treated with mechanical thrombectomy (MT) is unknown. We investigated the relationship between admission bilirubin levels and hemorrhagic complication in acute ischemic stroke (AIS) patients treated with MT and detailed the roles of direct bilirubin (DB), indirect bilirubin (IDB), and total bilirubin (TB).

METHODS

Consecutive AIS patients treated with MT were enrolled from two stroke centers. Outcome measures included hemorrhagic transformation (HT) and symptomatic intracranial hemorrhage (sICH) within 48 h. An independent association of bilirubin with outcomes was identified by multivariate logistic regression analysis. The accuracies of bilirubin in predicting outcome were evaluated using receiver operating characteristic curve analysis.

RESULTS

Of the 153 enrolled patients, 64 (41.8%) were diagnosed with HT, of which 28 (18.3%) had sICH. In univariate analyses, DB, IDB, and TB were higher in patients with HT and sICH than in patients without. After adjustment for potential confounders, DB (odds ratio [OR], 1.364; 95% confidence interval [CI], 1.133-1.641; p = 0.001), IDB (OR, 1.143; 95% CI, 1.052-1.242; p = 0.002), and TB (OR, 1.106; 95% CI, 1.041-1.175; p = 0.001) were independently associated with HT. IDB (OR, 1.177; 95% CI, 1.064-1.303; p = 0.002) and TB (OR, 1.102; 95% CI, 1.027-1.182; p = 0.007) were independently associated with sICH. Receiver operating characteristic curve analysis showed no significant difference between the three indicators of predicting HT and sICH.

CONCLUSIONS

Elevated admission bilirubin is an independent predictor of HT and sICH in AIS patients treated with MT.

The MLN4924 inhibitor exerts a neuroprotective effect against oxidative stress injury via Nrf2 protein accumulation

It was explored the cytoprotective and antioxidant effect of MLN4924, a specific inhibitor of Nedd8-activating enzyme (NAE), against hydrogen peroxide (H₂O₂)-induced damage in cerebellar granule neurons (CGNs). Primary cultures of CGNs were exposed to H₂O₂ after preincubation with MLN4924. The compounds were removed, and CGNs were incubated in culture medium for 24 h in order to determine cell viability by 3-[4,5-dimethylthiazol-2-yl)]-2,5-diphenyl-tetrazolium bromide (MTT) and fluorescein diacetate (FDA) assays. It was demonstrated that MLN4924 remarkably attenuated H₂O₂-induced cell damage. Meanwhile reactive oxygen species (ROS) production was evaluated with the fluorescent probe dihydroethidium (DHE). Interestingly H₂O₂-induced ROS production was inhibited by pretreatment with MLN4924. MLN4924 treatment in CGNs resulted in nuclear factor E2-related factor 2 (Nrf2) protein accumulation. Intriguingly this effect was observed in the cytosolic and nuclear compartments of the CGNs. The cytoprotective effect of MLN4924 was associated with its ability to diminish ROS production induced by H₂O₂ and the accumulation of Nrf2 protein levels in the cytoplasm and nucleus of the CGNs.

•

MLN4924 attenuates H₂O₂-induced neuronal damage.

•

MLN4924 attenuates H₂O₂-induced ROS production in neurons.

•

MLN4924 promotes both nuclear and cytoplasmic accumulation of Nrf2.

Curcumin pretreatment induces Nrf2 and an antioxidant response and prevents hemin-induced toxicity in primary cultures of cerebellar granule neurons of rats

Curcumin is a bifunctional antioxidant derived from Curcuma longa. This study identifies curcumin as a neuroprotectant against hemin-induced damage in primary cultures of cerebellar granule neurons (CGNs) of rats. Hemin, the oxidized form of heme, is a highly reactive compound that induces cellular injury. Pretreatment of CGNs with 5–30 μM curcumin effectively increased by 2.3–4.9 fold heme oxygenase-1 (HO-1) expression and by 5.6–14.3-fold glutathione (GSH) levels. Moreover, 15 μM curcumin attenuated by 55% the increase in reactive oxygen species (ROS) production, by 94% the reduction of GSH/glutathione disulfide (GSSG) ratio, and by 49% the cell death induced by hemin. The inhibition of heme oxygenase system or GSH synthesis with tin mesoporphyrin and buthionine sulfoximine, respectively, suppressed the protective effect of curcumin against hemin-induced toxicity. These data strongly suggest that HO-1 and GSH play a major role in the protective effect of curcumin. Furthermore, it was found that 24 h of incubation with curcumin increases by 1.4-, 2.3-, and 5.2-fold the activity of glutathione reductase, glutathione S-transferase and superoxide dismutase, respectively. Additionally, it was found that curcumin was capable of inducing nuclear factor (erythroid-derived 2)-like 2 (Nrf2) translocation into the nucleus. These data suggest that the pretreatment with curcumin induces Nrf2 and an antioxidant response that may play an important role in the protective effect of this antioxidant against hemin-induced neuronal death.

Dietary resveratrol supplementation normalizes gene expression in the hippocampus of streptozotocin-induced diabetic C57Bl/6 mice

Diabetes is associated with cognitive impairment and brain aging, with alterations in hippocampal neurogenesis and synaptic plasticity implicated in these changes. As the prevalence of diabetes continues to rise, readily implemented strategies are increasingly needed in order to protect the brain's cognitive functions. One possibility is resveratrol (RES) (3,5,4- trihydroxystilbene), a polyphenol of the phytoalexin family that has been shown to be protective in a number of neuropathology paradigms. In the present study, we sought to determine whether dietary supplementation with RES has potential for the protection of cognitive functions in diabetes. Diabetes was induced using streptozotocin, and once stable, animals received AIN93G rodent diet supplemented with RES for 6 weeks. Genome-wide expression analysis was conducted on the hippocampus and genes of interest were confirmed by quantitative, real-time polymerase chain reaction. Genome-wide gene expression analysis of the hippocampus revealed that RES supplementation of the diabetic group resulted in 481 differentially expressed genes compared to non-supplemented diabetic mice. Intriguingly, gene expression that was previously found significantly altered in the hippocampus of diabetic mice, and that is implicated in neurogenesis and synaptic plasticity (Hdac4, Hat1, Wnt7a, ApoE), was normalized following RES supplementation. In addition, pathway analysis revealed Jak-Stat signaling was the most significantly enriched pathway. The Jak-Stat pathway induces a pro-inflammatory signaling cascade, and we found most genes involved in this cascade (e.g. Il15, Il22, Socs2, Socs5) had significantly lower expression following RES supplementation. These data indicate RES could be neuroprotective and beneficial for the maintenance of cognitive function in diabetes.

Increase of oxidative stress by a novel PINK1 mutation, P209A

Mutation in the human PTEN-induced protein kinase 1 (PINK1) gene is responsible for the second most common form of recessive Parkinson disease (PD). We have identified a single heterozygous PINK1 mutation, P209A, from a cohort of 68 patients with early onset PD. From age 31, this patient developed an asymmetric bradykinesia with rigidity that was L-DOPA responsive. An [(18)F]-fluorodopa PET scan showed reduced DOPA uptake in the bilateral basal ganglia. The H2O2-induced cell death, ROS production, and caspase-3 activation in SH-SY5Y cells were enhanced by the transfection of the PINK1 P209A mutant. The heme oxygenase-1 (HO-1) induction in response to H2O2 and MPP(+) treatment was impaired by the overexpression of the PINK1 P209A mutant. In addition, SOD2 induction after TNFα treatment was also inhibited by the PINK1 P209A mutation. Akt and ERK are involved in HO-1 induction after oxidative stress. The phosphorylation of Akt and ERK after exposure to H2O2 or MPP(+) was also inhibited in PINK1 P209A mutant cells compared with empty-vector-transfected cells. These results indicate a novel pathway by which the P209A defect in the PINK1 kinase domain inhibits oxidative stress-induced HO-1 and SOD2 induction, which may accelerate the neurodegeneration in PD with PINK1 defect.

Antagonizing effects of soybean isoflavones on β-amyloid peptide-induced oxidative damage in neuron mitochondria of rats

Soybean isoflavone (SIF) has been demonstrated to have neuroprotective effects induced by β-amyloid peptides (Aβ) through suppressing oxidative stress; however, the explicit mechanisms still remain uncovered. In the present study, 32 Wistar rats were randomly divided into four groups: an Aβ1-42-treated group, a SIF + Aβ1-42 group, a SIF-treated group and a control group. We measured the protein content of 8-hydroxydeoxyguanosine (8-OhdG) and mRNA expression of 8-oxoguanine DNA glycosylase (OGG1). The protein expression of OGG1, Bcl-xl, Bad, beta subunit of ATP synthase (ATPB) and pyruvate dehydrogenase (PDH) in brain was also measured. The results showed that the level of 8-OHdG in both SIF groups was significantly decreased compared to the Aβ1-42-treated group (p < 0.05), while the mRNA and protein expression of OGG1 in the SIF + Aβ1-42 groups were up-regulated compared with the Aβ1-42-treated groups (p < 0.05). The expression of Bcl-xl was up-regulated in the SIF-treated group compared with the Aβ1-42-treated groups (p < 0.05), while the expression of Bad was down-regulated in the two SIF-treated groups (p < 0.05). Aβ1-42 significantly down-regulated the expression of ATPase and PDH proteins compared with the control group (p < 0.05). SIF reversed the down-regulation effects on the mitochondrial energy metabolic enzymes induced by Aβ1-42 (p < 0.05) in the rats. These results suggest that SIF alleviate the oxidative stress in neurons and mitochondria of rat brains mediated by Aβ1-42, and these protective effects might be associated with the regulation of OGG1, Bad, Bcl-xl, ATPB and PDH.

The heme oxygenase 1 inducer (CoPP) protects human cardiac stem cells against apoptosis through activation of the extracellular signal-regulated kinase (ERK)/NRF2 signaling pathway and cytokine release

Intracoronary delivery of c-kit-positive human cardiac stem cells (hCSCs) is a promising approach to repair the infarcted heart, but it is severely limited by the poor survival of donor cells. Cobalt protoporphyrin (CoPP), a well known heme oxygenase 1 inducer, has been used to promote endogenous CO generation and protect against ischemia/reperfusion injury. Therefore, we determined whether preconditioning hCSCs with CoPP promotes CSC survival. c-kit-positive, lineage-negative hCSCs were isolated from human heart biopsies. Lactate dehydrogenase release assays demonstrated that preconditioning CSCs with CoPP markedly enhanced cell survival after oxidative stress induced by H(2)O(2), concomitant with up-regulation of heme oxygenase 1, COX-2, and anti-apoptotic proteins (BCL2, BCL2-A1, and MCL-1) and increased phosphorylation of NRF2. Apoptotic cytometric assays showed that pretreatment of CSCs with CoPP enhanced the cells' resistance to apoptosis induced by oxidative stress. Conversely, knocking down HO-1, COX-2, or NRF2 by shRNA gene silencing abrogated the cytoprotective effects of CoPP. Further, preconditioning CSCs with CoPP led to a global increase in release of cytokines, such as EGF, FGFs, colony-stimulating factors, and chemokine ligand. Conditioned medium from cells pretreated with CoPP conferred naive CSCs remarkable resistance to apoptosis, demonstrating that cytokines released by preconditioned cells play a key role in the anti-apoptotic effects of CoPP. Preconditioning CSCs with CoPP also induced an increase in the phosphorylation of Erk1/2, which are known to modulate multiple pro-survival genes. These results potentially provide a simple and effective strategy to enhance survival of CSCs after transplantation and, therefore, their efficacy in repairing infarcted myocardium.

Selective brain cooling in rats ameliorates intracerebral hemorrhage and edema caused by penetrating brain injury: possible involvement of heme oxygenase-1 expression

Brain edema formation associated with trauma-induced intracerebral hemorrhage (ICH) is a clinical complication with high mortality. Studies have shown that heme oxygenase-1 (HO-1) plays an important role in ICH-induced brain edema. In order to understand the role of HO-1 in the protective effect of selective brain cooling (SBC), we investigated the time course of HO-1 changes following penetrating ballistic-like brain injury (PBBI) in rats. Samples were collected from injured and control animals at 6, 24, 48, and 72 h, and 7 days post-injury to evaluate HO-1 expression, heme concentration, brain water content, and immunohistochemistry (IHC). Following a 10% frontal PBBI, HO-1 mRNA and protein was increased at all time points studied, reaching maximum expression levels at 24-48 h post-injury. An increase in the heme concentration and the development of brain edema coincided with the upregulation of HO-1 mRNA and protein during the 7-day post-injury period. SBC significantly decreased PBBI-induced heme concentration, attenuated HO-1 upregulation, and concomitantly reduced brain water content. These results suggest that the neuroprotective effects of SBC may be partially mediated by reducing the heme accumulation, which reduced injury-mediated upregulation of HO-1, and in turn ameliorated edema formation. Collectively, these results suggest a potential value of HO-1 as a diagnostic and/or therapeutic biomarker in hemorrhagic brain injury.

Signaling pathways activated by the phytochemical nordihydroguaiaretic acid contribute to a Keap1-independent regulation of Nrf2 stability: Role of glycogen synthase kinase-3

Defense against oxidative stress is executed by an antioxidant program that is tightly controlled by the transcription factor Nrf2. The stability of Nrf2 involves the interaction of two degradation domains, designated Neh2 and Neh6, with the E3 ubiquitin ligase adaptors, Keap1 and β-TrCP, respectively. The regulation of Nrf2 through the Neh6 degron remains largely unexplored but requires GSK-3 to form a phosphodegron. In this study, the cancer-chemopreventive agent nordihydroguaiaretic acid (NDGA) increased the level of Nrf2 protein and expression of heme oxygenase-1 (HO-1) in kidney-derived LLC-PK1 and HEK293T cells and in wild-type mouse embryo fibroblasts (MEFs). However, NDGA did not induce HO-1 in Nrf2(-/-) MEFs, indicating that Nrf2 is required for induction. The relevance of the Nrf2/HO-1 axis to antioxidant protection was further demonstrated by the finding that the HO-1 inhibitor stannous-mesoporphyrin abolished protection against hydrogen peroxide conferred by NDGA. NDGA increased Nrf2 and HO-1 protein levels in Keap1(-/-) MEFs, implying that Keap1-independent mechanisms regulate Nrf2 stability. Mutants of the Neh2 or Nrh6 domain and chimeric proteins comprising cyan fluorescent protein fused to Neh2 and green fluorescent protein fused to Neh6 exhibited longer half-lives in the presence of NDGA, demonstrating that NDGA targets both the Neh2 and the Neh6 degrons. In common with other chemopreventive agents, NDGA activated the ERK1/2, p38, JNK, and PI3K pathways. By using selective kinase inhibitors we found that PI3K, JNK, and p38 were responsible for the stabilization of Nrf2 and induction of HO-1 by NDGA. To explain how NDGA might up-regulate Nrf2 in a Keap1-independent manner we explored the participation of GSK-3β because it controls the Neh6 phosphodegron. Importantly, NDGA caused inhibitory phosphorylation of GSK-3β at Ser9 and at Thr390, and this was associated with a substantial reduction in Neh6 phosphorylation. Our study demonstrates that NDGA activates Nrf2 through multiple signaling cascades and identifies GSK-3β as an integrator of these signaling pathways and a gatekeeper of Nrf2 stability at the level of the Neh6 phosphodegron.

Celastrol inhibits aminoglycoside-induced ototoxicity via heat shock protein 32

Hearing loss is often caused by death of the mechanosensory hair cells of the inner ear. Hair cells are susceptible to death caused by aging, noise trauma, and ototoxic drugs, including the aminoglycoside antibiotics and the antineoplastic agent cisplatin. Ototoxic drugs result in permanent hearing loss for over 500 000 Americans annually. We showed previously that induction of heat shock proteins (HSPs) inhibits both aminoglycoside- and cisplatin-induced hair cell death in whole-organ cultures of utricles from adult mice. In order to begin to translate these findings into a clinical therapy aimed at inhibiting ototoxic drug-induced hearing loss, we have now examined a pharmacological HSP inducer, celastrol. Celastrol induced upregulation of HSPs in utricles, and it provided significant protection against aminoglycoside-induced hair cell death in vitro and in vivo. Moreover, celastrol inhibited hearing loss in mice receiving systemic aminoglycoside treatment. Our data indicate that the major heat shock transcription factor HSF-1 is not required for celastrol-mediated protection. HSP32 (also called heme oxygenase-1, HO-1) is the primary mediator of the protective effect of celastrol. HSP32/HO-1 inhibits pro-apoptotic c-Jun N-terminal kinase (JNK) activation and hair cell death. Taken together, our data indicate that celastrol inhibits aminoglycoside ototoxicity via HSP32/HO-1 induction.

Melatonin synergistically increases resveratrol-induced heme oxygenase-1 expression through the inhibition of ubiquitin-dependent proteasome pathway: a possible role in neuroprotection

Melatonin is an indoleamine secreted by the pineal gland as well as a plant-derived product, and resveratrol (RSV) is a naturally occurring polyphenol synthesized by a variety of plant species; both molecules act as a neuroprotector and antioxidant. Recent studies have demonstrated that RSV reduced the incidence of Alzheimer's disease and stroke, while melatonin supplementation was found to reduce the progression of the cognitive impairment in AD. The heme oxygenase-1 (HO-1) is an inducible and redox-regulated enzyme that provides tissue-specific antioxidant effects. We assessed whether the co-administration of melatonin and RSV shows synergistic effects in terms of their neuroprotective properties through HO-1. RSV significantly increased the expression levels of HO-1 protein in a concentration-dependent manner both in primary cortical neurons and in astrocytes, while melatonin per se did not. Melatonin + RSV showed a synergistic increase in the expression levels of HO-1 protein but not in the HO-1 mRNA level compared to either melatonin or RSV alone, which is mediated by the activation of PI3K-Akt pathway. Treatment of melatonin + RSV significantly attenuated the neurotoxicity induced by H(2) O(2) in primary cortical neurons and also in organotypic hippocampal slice culture. The blockade of HO-1 induction by shRNA attenuated HO-1 induction by melatonin + RSV and hindered the neuroprotective effects against oxidative stress induced by H(2) O(2) . The treatment of MG132 + RSV mimicked the effects of melatonin + RSV, and melatonin + RSV inhibited ubiquitination of HO-1. These data suggest that melatonin potentiates the neuroprotective effect of RSV against oxidative injury, by enhancing HO-1 induction through inhibiting ubiquitination-dependent proteasome pathway, which may provide an effective means to treat neurodegenerative disorders.

Angiotensin II increases mRNA levels of all TGF-beta isoforms in quiescent and activated rat hepatic stellate cells

AII (angiotensin II) is a vasoactive peptide that plays an important role in the development of liver fibrosis mainly by regulating profibrotic cytokine expression such as TGF-beta (transforming growth factor-beta). Activated HSCs (hepatic stellate cells) are the major cell type responsible for ECM (extracellular matrix) deposition during liver fibrosis and are also a target for AII and TGF-beta actions. Here, we studied the effect of AII on the mRNA levels of TGF-beta isoforms in primary cultures of rat HSCs. Both quiescent and activated HSCs were stimulated with AII for different time periods, and mRNA levels of TGF-beta1, TGF-beta2 and TGF-beta3 isoforms were evaluated using RNaseI protection assay. The mRNA levels of all TGF-beta isoforms, particularly TGF-beta2and TGF-beta3, were increased after AII treatment in activated HSCs. In addition, activated HSCs were able to produce active TGF-beta protein after AII treatment. The mRNA expression of TGF-beta isoforms induced by AII required both ERK1/2 and Nox (NADPH oxidase) activation but not PKC (protein kinase C) participation. ERK1/2 activation induced by AII occurs via AT1 receptors, but independently of either PKC and Nox activation or EGFR (epidermal growth factor receptor) transactivation. Interestingly, AII has a similar effect on TGF-beta expression in quiescent HSCs, although it has a smaller but significant effect on ERK1/2 activation in these cells.

Induction of heme oxygenase-1 with hemin attenuates hippocampal injury in rats after acute carbon monoxide poisoning

Carbon monoxide (CO) poisoning is a major cause of brain injury and mortality; delayed neurological syndrome (DNS) is encountered in survivors of acute CO exposure. The toxic effects of CO have been attributed to oxidative stress induced by hypoxia. Heme oxygenase-1 (HO-1) is the inducible heme oxygenase isoform, and its induction acts as an important cellular defense mechanism against oxidative stress, cellular injury and disease. In this study, we examined the functional roles of HO-1 induction in a rat model of CO-exposured hippocampal injury. We report that acute CO exposure produces severe hippocampal injury in rats. However, hemin pretreatment reduced both the CO-induced rise in hippocampal water content and levels of neuronal damage in the hippocampus; survival rates at 24 h were significantly improved. Upregulation of HO-1 by hemin pretreatment resulted in a significant decrease in hippocampal levels of malondialdehyde (MDA), a marker of oxidative stress; levels of pro-apoptotic caspase-3 were also reduced. In contrast, inhibition of HO activity by administration of tin protoporphyrin IX (SnPP, a specific inhibitor of HO) abolished the neuroprotective effects of HO-1 induction. These data suggested that the upregulation of endogenous HO-1 expression therefore plays a pivotal protective role in CO neurotoxicity. Though the precise mechanisms underlying hemin-mediated HO-1 induction and neuroprotection are not known, these may involve the anti-oxidant and anti-apoptotic effects of HO-1 enzyme activity.