Mechanism Of Heme Oxygenase-1 Research Articles

The role and mechanism of heme oxygenase-1 in arrhythmias.

The global incidence and prevalence of arrhythmias are continuously increasing. However, the precise mechanisms of underlying arrhythmogenesis and the optimal measures for effective treatment remain incompletely understood. The inducible form of heme oxygenase, known as heme oxygenase-1 (HO-1), is recognized as a potent antioxidant molecule capable of exerting anti-inflammatory and anti-apoptotic effects. Recent research indicates that HO-1 plays a role in preventing arrhythmias by mitigating cardiac remodeling, including electrical remodeling, ion remodeling, and structural remodeling. This review aimed to consolidate current knowledge regarding the involvement of HO-1 in arrhythmias and elucidate its underlying mechanisms of action.

Activation of heme oxygenase-1 by laminar shear stress ameliorates high glucose-induced endothelial cell and smooth muscle cell dysfunction.

High glucose (HG)-induced endothelial cell (EC) and smooth muscle cell (SMC) dysfunction is critical in diabetes-associated atherosclerosis. However, the roles of heme oxygenase-1 (HO-1), a stress-response protein, in hemodynamic force-generated shear stress and HG-induced metabolic stress remain unclear. This investigation examined the cellular effects and mechanisms of HO-1 under physiologically high shear stress (HSS) in HG-treated ECs and adjacent SMCs. We found that exposure of human aortic ECs to HSS significantly increased HO-1 expression; however, this upregulation appeared to be independent of adenosine monophosphate-activated protein kinase, a regulator of HO-1. Furthermore, HSS inhibited the expression of HG-induced intercellular adhesion molecule-1, vascular cell adhesion molecule-1, and reactive oxygen species (ROS) production in ECs. In an EC/SMC co-culture, compared with static conditions, subjecting ECs close to SMCs to HSS and HG significantly suppressed SMC proliferation while increasing the expression of physiological contractile phenotype markers, such as α-smooth muscle actin and serum response factor. Moreover, HSS and HG decreased the expression of vimentin, an atherogenic synthetic phenotypic marker, in SMCs. Transfecting ECs with HO-1-specific small interfering (si)RNA reversed HSS inhibition on HG-induced inflammation and ROS production in ECs. Similarly, reversed HSS inhibition on HG-induced proliferation and synthetic phenotype formation were observed in co-cultured SMCs. Our findings provide insights into the mechanisms underlying EC-SMC interplay during HG-induced metabolic stress. Strategies to promote HSS in the vessel wall, such as continuous exercise, or the development of HO-1 analogs and mimics of the HSS effect, could provide an effective approach for preventing and treating diabetes-related atherosclerotic vascular complications.

Elevation of HO-1 expression protects the intestinal mucosal barrier in severe acute pancreatitis via inhibition of the MLCK/p-MLC signaling pathway

In severe acute pancreatitis (SAP), intestinal mucosal barrier damage can cause intestinal bacterial translocation and induce or aggravate systemic infections. Heme oxygenase-1 (HO-1) is a validated antioxidant and cytoprotective agent. This research aimed to investigate the effect and mechanism of HO-1 on SAP-induced intestinal barrier damage in SAP rats. Healthy adult male Sprague-Dawley rats were randomly separated into the sham-operated group, SAP group, SAP + Hemin group, and SAP + Znpp group. The rat model of SAP was established by retrograde injection of sodium taurocholate (5%) into the biliopancreatic duct. Hemin (a potent HO-1 activator) and Znpp (a competitive inhibitor of HO-1) were injected intraperitoneally in the selected groups 24 h before SAP. Serum and intestinal tissue samples were collected for analysis after 24 h in each group. Hemin pretreatment significantly reduced systemic inflammation, intestinal oxidative stress, and intestinal epithelial apoptosis in SAP by increasing HO-1 expression. Meanwhile, pretreatment with Hemin abolished the inhibitory effect on the expression of the tight junction proteins and significantly inhibited the activation of the MLCK/P-MLC signaling pathway. Conversely, ZnPP completely reversed these effects. Our study indicates that upregulation of HO-1 expression attenuates the intestinal mucosal barrier damage in SAP. The protective effect of HO-1 on the intestine is attributed to MLCK/p-MLC signaling pathway inhibition.

Heme oxygenase-1 reduces inflammatory response by inhibiting thioredoxin interacting protein/NOD-like receptor protein 3 inflammasome activation in RAW264.7 cells

To investigate the inhibitory effect and mechanism of heme oxygenase-1 (HO-1) on the inflammatory response of macrophages. Mouse macrophage strain RAW264.7 was cultured in vitro, and the cells in the logarithmic growth phase were used for the experiment. The RAW264.7 cells were divided into four groups. In blank control group, the cells were continuously incubated and received no treatment (cultured at 37 centigrade, 95% air, 5% CO2). In lipopolysaccharide (LPS) model group, 1 mg/L LPS was added to the medium to prepare LPS challenge model. In HO-1 inducer group, the cells were incubated with 30 μmol/L HO-1 inducer hemin for 1 hour, and then 1 mg/L LPS was added for incubation. In HO-1 inhibition group, the cells were incubated with 5 μmol/L HO-1 specific antagonist Zinc protoporphyrin IX (ZnPPIX) for 0.5 hour, and then 1 mg/L LPS was added for incubation. After 48 hours of incubation with LPS, the supernatant of each group was taken, and the protein expressions of HO-1, tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), thioredoxin interacting protein (TXNIP), NOD-like receptor protein 3 (NLRP3) and mitochondrial autophagy marker microtubule-associated protein 1 light chain 3B (LC-3B) were detected by Western blotting. The expression of reactive oxygen species (ROS) was detected by immunofluorescence staining. Compared with the blank control group, the cells in the LPS model group had a certain stress response, and autophagy occurred in mitochondria, but the expression of some inflammatory factors was restricted, which was related to the impairment of cell function. The protein expressions of HO-1, IL-1β, LC-3B, ROS were significantly increased, the protein expressions of TNF-α, TXNIP, and NLRP3 were decreased significantly, indicating that the cells were seriously injured after LPS challenge, and the model was successfully established. Compared with the LPS model group, HO-1 protein expression in the HO-1 inducer group was significantly increased (HO-1/GAPDH: 0.31±0.03 vs. 0.22±0.03, P < 0.05), the protein expressions of TNF-α, IL-1β, TXNIP, NLRP3, LC-3B and ROS were significantly inhibited [TNF-α protein (TNF-α/GAPDH): 0.08±0.01 vs. 0.45±0.05, IL-1β protein (IL-1β/GAPDH): 0.50±0.01 vs. 0.82±0.03, TXNIP protein (TXNIP/GAPDH): 0.21±0.02 vs. 0.28±0.02, NLRP3 protein (NLRP3/GAPDH): 0.11±0.01 vs. 0.17±0.02, LC-3B protein (LC-3B/GAPDH): 0.67±0.04 vs. 0.92±0.12, ROS (fluorescence intensity): 80.9±12.5 vs. 94.1±19.5, all P < 0.05], indicating that HO-1 could inhibit inflammatory response and oxidative stress, and reduce mitochondrial autophagy. Antagonizing HO-1 could increase inflammatory response, oxidative stress and mitochondrial autophagy, the inhibitory degree of TNF-α and IL-1β expression was significantly reduced as compared with the HO-1 inducer group [TNF-α protein (TNF-α/GAPDH): 0.26±0.02 vs. 0.08±0.01, IL-1β protein (IL-1β/GAPDH): 0.76±0.01 vs. 0.50±0.01, both P < 0.05], the protein expressions of TXNIP, NLRP3, LC-3B and ROS were significantly increased as compared with the LPS model group [TXNIP protein (TXNIP/GAPDH): 0.43±0.02 vs. 0.28±0.02, NLRP3 protein (NLRP3/GAPDH): 0.24±0.02 vs. 0.17±0.02, LC-3B protein (LC-3B/GAPDH): 1.12±0.07 vs. 0.92±0.12, ROS (fluorescence intensity): 112.0±17.0 vs. 94.1±19.5, all P < 0.05]. HO-1 can reduce the inflammatory response by inhibiting the activation of TXNIP/NLRP3 inflammasome and reducing the release of inflammatory mediators.

Role and Potential Mechanism of Heme Oxygenase-1 in Intestinal Ischemia-Reperfusion Injury.

Intestinal ischemia-reperfusion (IR) injury is a complex, multifactorial, and pathophysiological condition with high morbidity and mortality, leading to serious difficulties in treatment, especially in humans. Heme oxygenase (HO) is the rate-limiting enzyme involved in heme catabolism. HO-1 (an inducible form) confers cytoprotection by inhibiting inflammation and oxidation. Furthermore, nuclear factor-erythroid 2-related factor 2 (Nrf2) positively regulates HO-1 transcription, whereas BTB and CNC homolog 1 (Bach1) competes with Nrf2 and represses its transcription. We investigated the role and potential mechanism of action of HO-1 in intestinal IR injury. Intestinal ischemia was induced for 45 min followed by 4 h of reperfusion in wild-type, Bach1-deficient, and Nrf2-deficient mice, and a carbon monoxide (CO)-releasing molecule (CORM)-3 was administered. An increase in inflammatory marker levels, nuclear factor-κB (NF-κB) activation, and morphological impairments were observed in the IR-induced intestines of wild-type mice. These inflammatory changes were significantly attenuated in Bach1-deficient mice or those treated with CORM-3, and significantly exacerbated in Nrf2-deficient mice. Treatment with an HO-1 inhibitor reversed this attenuation in IR-induced Bach1-deficient mice. Bach1 deficiency and treatment with CORM-3 resulted in the downregulation of NF-κB activation and suppression of adhesion molecules. Together, Bach1, Nrf2, and CO are valuable therapeutic targets for intestinal IR injury.

Heme Oxygenase-1 Inhibits the Proliferation of Hepatic Stellate Cells by Activating PPARγ and Suppressing NF-κB.

Background Hepatic stellate cells (HSCs) are reported to play significant roles in the development of liver fibrosis. Heme oxygenase-1 (HO-1) is a key rate-limiting enzyme, which could decrease collagen synthesis and liver damage. Nevertheless, it was yet elusive towards the function and mechanism of HO-1. Methods An HO-1 inducer Hemin or an HO-1 inhibitor ZnPP-IX was used to treat the activated HSC-T6, respectively. MTT assay was adopted to detect cell proliferation. Immunocytochemical staining was employed to test the levels of alpha-smooth muscle actin (α-SMA), peroxisome proliferator-activated receptor-γ (PPARγ), and nuclear factor-kappa B (NF-kappa B) levels in HSC-T6. HO-1, PPARγ, and NF-κB expression levels were measured by qRT-PCR and Western blotting. ELISA was then used to detect the levels of transforming growth factor- (TGF-) beta 1 (TGF-β1), interleukin-6 (IL-6), serum hyaluronic acid (HA), and serum type III procollagen aminopeptide (PIIIP). Results HSC-T6 proliferation was inhibited in Hemin-treated HSCs. The levels of α-SMA, HA, and PIIIP and the production of ECM were lower in Hemin-treated HSCs, whereas those could be rescued by ZnPP-IX. NF-κB activation was decreased, but PPARγ expression was increased after HO-1 upregulation. Furthermore, the levels of TGF-β1 and IL-6, which were downstream of activated NF-κB in HSC-T6, were reduced. The PPAR-specific inhibitor GW9662 could block those mentioned effects. Conclusions Our data demonstrated that HO-1 induction could inhibit HSC proliferation and activation by regulating PPARγ expression and NF-κB activation directly or indirectly, which makes it a promising therapeutic target for liver fibrosis.

Study on the role and possible mechanism of hemeoxygenase-1/carbon monoxide system in protection of quercetin against ethanol-induced hepatocytes oxidative injury

Objective: To study the protective effect and potential mechanism of heme oxygenase (HO-1)/carbon monoxide (CO)-mediated quercetin on alcoholic oxidative damage of primary rat hepatocytes. Methods: Primary rat hepatocytes were isolated and cultured by two-step collagenase technique. Ethanol exposed primary rat hepatocytes were simultaneously added with quercetin (100 μmol/L) and/or hemoglobin (100 μmol/L) or different doses of CO-releasing molecules (CORM-2, 5-50 μmol/L) for their combined action. After polling, LDH, AST activities and MDA and GSH levels were measured in the supernatant of cell culture. The alone or combined effects of quercetin, CORM-2, hemoglobin and zinc protoporphyrin IX exposed to ethanol were detected by the activity of CYP2E1 in liver microsomes. Statistical analysis of data was performed by analysis of variance (ANOVA) and intergroup comparison was done by SNK-test. Results: Simultaneous addition of 100 μmol/L quercetin had significantly reduced ethanol-induced AST and LDH release, and GSH consumption and MDA elevation extent. Moreover, quercetin had not only lost the hemoglobin (CO blocker) protective effect but also had further exacerbated ethanol-induced lipid peroxidation. CORM-2 had reduced ethanol-induced AST and LDH release, and GSH consumption and MDA production in liver cells, and thus had dose-dependent protective effect. Ethanol had increased significantly CYP2E1 activity. Quercetin or CORM-2 had inhibited CYP2E1 activity, while hemoglobin or protoporphyrin IX had eliminated quercetin inhibitory effect and had increased the CYP2E1 activity. Quercetin, and CYP2E1 activity was constant as compared to ethanol group when CORM-2, zinc protoporphyrin IX and ethanol were incubated with hepatocytes, but the CYP2E1 activity was significantly decreased (P < 0.05), and the differences were statistically significant. Conclusion: CO/HO-1 metabolite mediates the protective effect of quercetin on alcoholic oxidative damage of hepatocytes, which may be related to the inhibition of CYP2E1 activity.

1718-P: Heme Oxygenase-1 Promotes Hepatic Glucose Production via Increasing the Intracellular Ferrous Iron

The heme oxygenase-1 (HO1) catalyzes the degradation of heme into biliverdin, ferrous iron and carbon monoxide (CO). Although HO1 has long been considered as an anti-inflammatory molecule, recent studies showed that HO1 disrupts the mitochondrial function in hepatocytes, as well as drives inflammation and insulin resistance in mice and humans. Such different findings from the historical view impelled us to further investigate the roles of HO1 in glucose metabolism. In the present study, we found that overexpression of HO1 promoted hepatic glucose production (HGP) in hepatocytes from the wild type (WT) mice, which was comparable to the treatment of glucagon. Since the regulatory roles of the transcription factor forkhead box O1 (Foxo1) in HGP have been well recognized, we then generated the liver-specific Foxo1 knockout (L-FKO) mice to study the contribution of Foxo1 in mediating the effects of HO1. We found that HO1 overexpression did not have a significant effect in promoting HGP in hepatocytes from the L-FKO mice, suggesting HO1 improved HGP dependent on Foxo1. Besides, HO1 overexpression improved the mRNA levels of Foxo1-targeted gluconeogenic genes and increased the phosphorylation of Foxo1 at Ser273, which is a phosphorylation site integrating into the glucagon signaling. We also found that HO1 overexpression activated p38α and p65/NF-κB in hepatocytes. Further study using siRNA or specific inhibitor demonstrated that p65/NF-κB, but not p38α, mediated the HO1-induced pFoxo1-S273 and HGP in hepatocytes. We then explored the role of HO1-induced ferrous iron in activating p65/NF-κB and promoting HGP. We found that HO1 overexpression in hepatocytes substantially increased the intracellular ferrous iron. The pretreatment of iron chelator deferoxamine mesylate diminished the effects of HO1 overexpression on p65/NF-κB, pFoxo1-S273, and HGP. Taken together, results from this study revealed the mechanisms of HO1 in driving HGP, which is through the generation of ferrous iron. Disclosure W. Liao: None. W. Yang: None. Q. Pan: None. Z. Shen: None. W. Ai: None. S. Guo: None. Funding National Institutes of Health (R01DK120968)

Heme oxygenase-1 inhibition mediates Gas6 to enhance bortezomib-sensitivity in multiple myeloma via ERK/STAT3 axis.

Chemoresistance is still a critical challenge for efficient treatment of multiple myeloma (MM) during the bortezomib-based chemotherapy. Recent studies have suggested that heme oxygenase-1 (HO-1) is involved in apoptosis, proliferation and chemoresistance in cancer cells. Here we aim to investigate the role and mechanism of HO-1 in bortezomib-sensitivity to myeloma cells. In the study population, we found that HO-1 was highly expressed in CD138+ primary myeloma cells, which was positively associated with Gas6 expression and Gas6 plasma levels in MM patients. Downregulation of HO-1 using pharmacological inhibitor ZnPPIX or siRNA knockdown significantly enhanced myeloma cell sensitivity to bortezomib in human primary CD138+ cells, U266 and RPMI8226 cell lines. Mechanistically, HO-1 regulated Gas6 production via ERK/STAT3 axis. Combination with HO-1 inhibition increased bortezomib-induced apoptosis and antiproliferative effects via suppressing Gas6 production. These findings suggest that combination of bortezomib and HO-1 inhibitor may serve as a promising therapeutic target against bortezomib-resistant MM.

Protective properties of heme oxygenase-1 expressed in umbilical cord mesenchymal stem cells help restore the ovarian function of premature ovarian failure mice through activating the JNK/Bcl-2 signal pathway-regulated autophagy and upregulating the circulating of CD8+CD28\u2212 T cells

BackgroundUmbilical cord-derived mesenchymal stem cell (UCMSCs) transplantation has been widely studied in premature ovarian failure (POF). However, the underlying mechanism remains elusive. This study aims to investigate the protective properties and mechanisms of heme oxygenase-1 (HO-1) expressed in UCMSCs in restoring the ovarian function of POF mice.MethodsIn in vitro and in vivo experiments, mice were treated with the presence or absence of the HO-1/shHO-1-transfected UCMSCs, and the administration of SP600125 or anisomycin, the inhibitor or activator of JNK. The viability and apoptosis of granulosa cells (GCs) at different time points of co-cultivation were assessed in vitro. In in vivo experiments, mouse ovarian function was assessed by detecting the serum levels of hormone and observing the ovarian morphological changes. Multiple molecular indices of JNK/Bcl-2 signal pathway were performed. And the autophagy changes in GCs were assessed by detecting the associated cytokines and observing the intracellular autophagosome accumulation. Additionally, the spleen levels of CD8+CD28− T cells and serum levels of interleukin 10 (IL-10) were tested to evaluate the immune mechanisms involved.ResultsUCMSCs transfected with shHO-1 or treated with SP600125 inhibited GCs’ viability and promoted its apoptosis in a time-dependent manner in vitro. In in vivo experiments, mice in both groups showed little therapeutic efficiency which presented as the increased extent of ovarian fibrosis with decreased number of functional follicles, and disordered hormone production. Additionally, the JNK/Bcl-2-associated cytokines were obviously declined. The inhibited autophagy-related cytokines, the chromatin condensation and abound vacuolar autophagosome in GCs, and weakened fluorescence intensity by MDC were observed. The downregulated levels of CD8+CD28− T cells and serum levels of IL-10 were also detected. The damages above can be alleviated with HO-1-MSCs treatment or anisomycin administration.ConclusionsHO-1 expressed in UCMSCs is critical in restoring the ovarian function in POF mice with UCMSC transplantation, which is mediated by the activation of JNK/Bcl-2 signal pathway-regulated autophagy and upregulating the circulating of CD8+CD28− T cells.

Research on the anti-oxidative effect and mechanism of heme oxygenase-1 on lung injury after cardiopulmonary bypass

Research on the anti-oxidative effect and mechanism of heme oxygenase-1 on lung injury after cardiopulmonary bypass

Hemeoxygenase-1 Suppresses IL-1β-Induced Apoptosis Through the NF-κB Pathway in Human Degenerative Nucleus Pulposus Cells

Background/Aims: Nucleus pulposus cell (NPC) apoptosis is the main factor in intervertebral disc degeneration (IDD); thus, inhibiting the excessive apoptosis of nucleus pulposus cells may be a potential way to alleviate IDD. The effect of Hemeoxygenase-1 (HO-1) on human NPC apoptosis has never been reported. Our study aimed to investigate the effect and mechanism of HO-1 on apoptosis in human degenerative NPCs. Methods: Nucleus pulposus tissues were collected from patients with lumbar vertebral fracture (LVF) and IDD. The expression of HO-1 and P65 in intervertebral discs was determined using immunohistochemistry and western blot analysis. Apoptosis of human nucleus pulposus cells was quantified by flow cytometric analysis. A recombinant lentiviral vector overexpressing HO-1 and HO-1-siRNA was used to promote or silence the expression of HO-1 in nucleus pulposus cells. The NF-κB inhibitor PDTC was used to inhibit the NF-κB pathway. Results: Our study demonstrated that compared with normal samples, IDD samples showed down-regulation of HO-1 expression and up-regulation of P65 expression. Overexpression of HO-1 inhibited the increase in nucleus pulposus cell apoptosis after IL-1β treatment and simultaneously inhibited the expression of p-P65. Furthermore, after treatment with PDTC, the number of apoptotic cells was significantly decreased with or without overexpression of HO-1. Conclusion: HO-1 might play a significant role in IDD, and HO-1 protected degenerative human NPCs against apoptosis induced by IL-1β through the NF-κB pathway. These findings would aid in the development of novel therapeutic approaches for IDD treatment.

Spinal Heme Oxygenase-1 (HO-1) Exerts Antinociceptive Effects Against Neuropathic Pain in a Mouse Model of L5 Spinal Nerve Ligation.

Heme oxygenase-1 (HO-1) exerts protective effects against ischemia and inflammation in the central nervous system. However, its role in neuropathic pain is still unclear. This study was undertaken to explore the distribution and possible mechanism of HO-1 in a mouse model of peripheral nerve injury. The experiment was conducted using a mouse model of L5 spinal nerve ligation (SNL). Mice received repeated intraperitoneal injection of Carbon monoxide-releasing molecule-2 (CO-RM-2), HO-1 inducer cobalt protoporphyrin IX (CoPP) or single intraspinal injection of lentivirus (LV) over-expressing HO-1. The behavior analyses were conducted. The distribution and expression of HO-1 in the spinal cord were analyzed. HO-1 but not HO-2 was upregulated in spinal cord microglia cells after nerve injury, and the repeated intraperitoneal administration of CORM-2 (10 mg/kg/d) or CoPP (5 mg/kg/d) both significantly reduced the mechanical allodynia and thermal hyperalgesia induced by SNL (P < 0.01). Intraspinal injection of LV-HO-1 persistently suppresses SNL-induced neuropathic pain (P < 0.01 or P < 0.05), significantly induced the spinal HO-1 protein content (P < 0.01) and inhibited the microglia activation (P < 0.01) 7 days after SNL. HO-1 upregulation could elicit potent analgesic effects against neuropathic pain, which might partly be attributed to inhibition of spinal microglia activation. HO-1 signaling pathway may present a novel strategy for the treatment of neuropathic pain.

Effect and mechanism of heme oxygenase-1 alleviating rat bile duct ischemia-reperfusion injury

Objective To explore the effect and mechanism of heme oxygenase-1 (HO-1) in rat bile duct ischemia-reperfusion injury.Methods 128 SD rats were randomly divided into a saline group (Saline),empty virus group (Adv),induced group (Adv-HO-1),and inhibition group (HO-1 siR-NA).Rats were injected using 0.5ml of saline,empty adenovirus,HO-1 adenovirus,and siRNA adenovirus (2× 109 TU/rat) via the dorsal penile vein 24 h before surgery.Liver function and bile composition was analyzed at 1 h,24 h,7d,and 14 d after reperfusion.The liver's histopathological changes and infiltration of inflammatory cells to the bile duct were examined,and the expression of HO-1,multidrug resistance protein (Mrp2),sodium taurocholate cotransporting polypeptide (Ntcp),and bile salt export pump (Bsep) protein were detected.Results Liver function was significantly reduced in the induced group after surgery,and hepatocytes and bile duct injury was attenuated.In comparison to the Adv-HO-1 group,abundant inflammatory cells and irregular configuration of bile ducts were seen in liver tissues of the HO-1 siRNA group.The expression of HO-1,Mrp2,Ntcp,and Bsep were significantly higher in the induced group than the suppressed group.However,serum conjugated bile salts,total bilirubin,and bile salt/phospholipid in the suppressed group was significantly higher than that in the induced group.Conclusions HO-1 can prevent biliary ischemia-reperfusion injury and reduce the accumulation of inflammatory cells around the bile duct.The inhibition of HO-1 enhanced the bile salt/phospholipid ratio aggravating cholangitis and cholestasis. Key words: Heme oxygenase-1; Biliary tract; Reperfusion injury

P-0016 - High Expression of Heme Oxygenase-1 is Associated with Tumor Invasion in Gastric Cancer Through Sonic Hedgehog Signaling Pathway

Background: Heme oxygenase-1 (HO-1), a rate-limiting enzyme in heme catabolism, is known to play a role in the protection of cells against oxidative stress, inflammation, and influences tumor growth and metastasis. Gastric cancer (GC) is one of the most common cancers and a major cause of cancer-related death worldwide. As yet, the role and mechanism of HO-1 in gastric cancer development and metastasis remains unclear. Sonic hedgehog signaling pathway is very related to tumor growth, apoptosis and invasion.

Antidiabetic Potential of the Heme Oxygenase-1 Inducer Curcumin Analogues

Although there is a therapeutic treatment to combat diabetes, the identification of agents that may deal with its more serious aspects is an important medical field for research. Diabetes, which contributes to the risk of cardiovascular disease, is associated with a low-grade chronic inflammation (inflammatory stress), oxidative stress, and endoplasmic reticulum (ER) stress. Because the integration of these stresses is critical to the pathogenesis of diabetes, agents and cellular molecules that can modulate these stress responses are emerging as potential targets for intervention and treatment of diabetic diseases. It has been recognized that heme oxygenase-1 (HO-1) plays an important role in cellular protection. Because HO-1 can reduce oxidative stress, inflammatory stress, and ER stress, in part by exerting antioxidant, anti-inflammatory, and antiapoptotic effects, HO-1 has been suggested to play important roles in pathogenesis of diabetes. In the present review, we will explore our current understanding of the protective mechanisms of HO-1 in diabetes and present some emerging therapeutic options for HO-1 expression in treating diabetic diseases, together with the therapeutic potential of curcumin analogues that have their ability to induce HO-1 expression.

Effects and mechanisms of heme oxygenase-1 on rats with postresuscitation myocardial dysfunction

To explore the effects and mechanisms of heme oxygenase-1 on rats with postresuscitation myocardial dysfunction. Male Sprague-Dawley rats were asphyxiated for 9 minutes and resuscitated. They were randomly divided into 4 groups: sham-operated, cardiopulmonary resuscitation (CPR), hemin and hemin + ZnPP (zinc protoporphyrin IX). Resuscitated groups had 2 observation points: 6 and 24 hours post-CPR (n = 8 for each time point). And the sham-operated group of 12 rats were divided in two observation points, according to 6 or 24 hours post-operation (n = 6 each). Hemodynamic was observed. The expression of heme oxygenase-1 (HO-1) in cardiac tissue was detected by Western blot. And the activity of cardiac homogenate superoxide dismutase (SOD) was determined by xanthine oxidase method and the level of malondialdehyde (MDA) measured by the thiobarbituric acid method. Nitrotyrosine protein expression in cardiac tissue was analyzed by immunohistochemistry. (1) The mean blood pressure (MAP) significantly decreased in resuscitated groups after resuscitation (all P < 0.05). No difference existed between the subgroups. The scores of dP/dt40 and -dP/dt significantly decreased in CPR and hemin + ZnPP groups after resuscitation (all P < 0.05). But dP/dt40 in hemin group did not differ significantly after resuscitation and -dP/dt decreased only 0.5 hour and 1 hour post-resuscitation (3341.60 ± 524.85 and 3711.40 ± 502.39 vs 4284.20 ± 800.87, all P < 0.05). The scores of dP/dt40 and -dP/dt in hemin group at all time points post-resuscitation were significantly higher than those in CPR and hemin + ZnPP groups (all P < 0.05). (2) Compared with the sham-operated group, the HO-1 expression, MDA level and nitrotyrosine protein expression significantly increased while the activities of SOD decreased after resuscitation in the CPR, hemin and hemin + ZnPP groups (all P < 0.05). Compared with the CPR and hemin + ZnPP groups, the expression of HO-1 and the activity of SOD increased, while MDA level and nitrotyrosine protein expression were decreased in group hemin (all P < 0.05). No difference existed in the above indices between the CPR and hemin + ZnPP groups. HO-1 can reduce myocardial oxidative stress injury after cardiopulmonary resuscitation and effectively improve post-resuscitation myocardial function in rats.

The Anti-inflammatory Mechanism of Heme Oxygenase-1 Induced by Hemin in Primary Rat Alveolar Macrophages

Alveolar macrophages (AMs) can initiate lung inflammation by producing pro-inflammatory cytokines and chemokines, but they participate actively in the prevention of inflammation during acute lung injury (ALI). Heme oxygenase-1 (HO-1) is mainly expressed in AMs and has anti-inflammatory properties in ALI, but the anti-inflammatory mechanisms of HO-1 are largely unknown. In this study, AMs were treated with saline, LPS (1μg/ml), hemin (10μM), zinc protoporphyrin (ZnPP; 10μM, 1h prior to LPS and hemin), SB203580 (10μM, 1h prior to LPS and hemin), or their combination up to 24h. The specific HO-1 inhibitor ZnPP and SB203580 were used to inhibit the effects of HO-1 and the phosphorylated p38 mitogen-activated protein kinase (MAPK), respectively. The protein levels of HO-1 and p38 MAPK were analyzed by western blotting; arginase activity was measured in lysates obtained from cultured cells; nitric oxide production in the extracellular medium of AMs cultured for 24h was monitored by assessing nitrite levels; the phagocytic ability of macrophage was measured by neutral red uptake. IL-10 of culture supernatants in AMs was determined by enzyme-linked immunosorbent assay. The results indicated that HO-1 induced by hemin increased arginase activity and phagocytic ability and decreased iNOS activity via p38 MAPK pathway in primary rat AMs. These changes and p38 MAPK may be the anti-inflammatory mechanism of HO-1 induced by hemin in primary rat AMs.

Heme Oxygenase-1 Alleviates Mouse Hepatic Failure through Suppression of Adaptive Immune Responses

Heme oxygenase-1 (HO-1) has protective effects on liver damage induced by noxious stimuli. The mechanism of action of HO-1 is not well understood. In the present study, we investigate the effect of HO-1 in a model of fulminant hepatic failure induced by Propionibacterium acnes and lipopolysaccharide (LPS). The expression of HO-1 mRNA and protein in the liver was increased after repeated administration of the HO-1 inducer cobalt protoporphyrin IX. We found that HO-1 protected mice from acute liver damage induced by P. acnes/LPS and prolonged survival. On the contrary, administration of the HO-1 inhibitor zinc protoporphyrin IX increased liver damage induced by P. acnes/LPS. Subsequently, to investigate the underlying mechanisms of HO-1 in the acute liver injury model, we primed mice with P. acnes only. We found that the expression of HO-1 mRNA and protein in dendritic cells (DCs) was increased after the administration of cobalt protoporphyrin IX. HO-1 decreased the mature markers major histocompatibility complex II and CD80 on liver DCs. The expression of CCR7, CCL2, and CCL22 mRNA, which are expressed by mature DCs, was also reduced. These liver DCs could not efficiently stimulate CD4+ T cell activation and proliferation. Consequently, HO-1 inhibited the activation, proliferation, and T helper 1 polarization of liver-infiltrating CD4+ T cells and reduced the production of serum alanine aminotransferase and proinflammatory cytokines such as interferon-γ and tumor necrosis factor-α. Taken together, our data suggest that HO-1 alleviates P. acnes/LPS-induced fulminant hepatic failure, probably by inhibiting DC-induced adaptive responses.

Abstract 5300: Study heme oxygenase and imaging liver cancer in mice

Abstract Liver cancer is the fifth most common cancer caused deaths worldwide and its incidence is increasing. The factors that influence the liver cancer progression are not clear. Recent reports show heme oxygenase-1 (HO-1) plays an important role in tumor progression and metastasis. Therefore, study the mechanism of HO-1 in liver cancer could potentially understand the liver cancer development and metastasis. We established two liver cancer cell lines that either contains wild- or mutant-type HO-1 gene to study the role of HO-1 in liver cancer metastasis. Matrigel invasion chambers assay was used to determine the invasion and migration of cells. The expression of IL-6, which is the key regulator of HO-1, was analyzed by real-time RT-PCR and ELISA for mRNA and protein, respectively. Two target-specific MMP and RGD peptides imaging agents were synthesized to follow up the liver cancer growth. Imaging studies were performed in cancer cells and xenograft models. In vivo imaging studies (n=10) were performed with peptide imaging agents and 18F fluoro-deoxy-glucose (18F-FDG) using optical, CT and PET scanning. The data demonstrated that overexpression of HO-1 significantly decreased the invasion ability of the liver cancer cells (P&amp;lt;0.05). Furthermore, the expression of IL-6 was also significantly decreased (P&amp;lt;0.05) in the wild-type HO-1 cells. The overexpression of mutant HO-1 significantly increased invasion ability (P&amp;lt;0.05) and the expression level of IL-6 (P&amp;lt;0.05). Cells treated by IL-6 siRNA down regulate the expression of IL-6 and decreased the invasion ability (P&amp;lt;0.05). The MMP peptide imaging agent, but not the free dye, bound to liver tumor cells in vitro and was internalized into the cells. Both cell and animal data confirmed that MMP imaging agent is taken up by liver cancer cells. RGD imaging agent was used to display blood vessel formation in the tumor regions. 18F-FDG PET imaging exhibited glucose metabolic stage in the disease site. It is found that the molecular imaging agents had different distributions in the body and differentially internalized into liver cancer cells. All target-specific agents yielded high tumor-to-background ratios after injection. In conclusion, HO-1 inhibited the invasion and migration of human hepatocellular cancer cell lines by regulating the expression of IL-6. Target-specific molecular imaging agents can be used to study liver cancer in vitro and in vivo. Noninvasive imaging with multi-target-specific molecular imaging agents could provide a tool for simultaneously studying multiple disease components. *CZ, WW: These authors contributed equally to this work. Grant support: DoD W81XWH-08-1-0489 (SK, WW), Department of Radiology research fund (SK, WW, MEM), National Science Foundation of China Grants 81000933 (CZ), Major State Basic Research Development Program of China 973 Program 2009CB521702 (XG). Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5300. doi:10.1158/1538-7445.AM2011-5300