Heme oxygenase-1: unleashing the protective properties of heme

Heme Oxygenase-1 Induction by Blood-Feeding Arthropods Controls Skin Inflammation and Promotes Disease Tolerance

Hematophagous vectors lacerate host skin and capillaries to acquire a blood meal, resulting in leakage of red blood cells (RBCs) and inflammation. Here, we show that heme oxygenase-1 (HO-1), a pleiotropic cytoprotective isoenzyme that mitigates heme-mediated tissue damage, is induced after bites of sand flies, mosquitoes, and ticks. Further, we demonstrate that erythrophagocytosis by macrophages, including a skin-residing CD163⁺CD91⁺ professional iron-recycling subpopulation, produces HO-1 after bites. Importantly, we establish that global deletion or transient inhibition of HO-1 in mice increases inflammation and pathology following Leishmania-infected sand fly bites without affecting parasite number, whereas CO, an end product of the HO-1 enzymatic reaction, suppresses skin inflammation. This indicates that HO-1 induction by blood-feeding sand flies promotes tolerance to Leishmania infection. Collectively, our data demonstrate that HO-1 induction through erythrophagocytosis is a universal mechanism that regulates skin inflammation following blood feeding by arthropods, thus promoting early-stage disease tolerance to vector-borne pathogens.

Interactive and independent effects of early lipopolysaccharide and hyperoxia exposure on developing murine lungs

Bronchopulmonary dysplasia (BPD)-associated pulmonary hypertension (PH) is a chronic infantile lung disease that lacks curative therapies. Infants with BPD-associated PH are often exposed to hyperoxia and additional insults such as sepsis that contribute to disease pathogenesis. Animal models that simulate these scenarios are necessary to develop effective therapies; therefore, we investigated whether lipopolysaccharide (LPS) and hyperoxia exposure during saccular lung development cooperatively induce experimental BPD-PH in mice. C57BL/6J mice were exposed to normoxia or 70% O₂ (hyperoxia) during postnatal days (PNDs) 1-5 and intraperitoneally injected with varying LPS doses or a vehicle on PNDs 3-5. On PND 14, we performed morphometry, echocardiography, and gene and protein expression studies to determine the effects of hyperoxia and LPS on lung development, vascular remodeling and function, inflammation, oxidative stress, cell proliferation, and apoptosis. LPS and hyperoxia independently and cooperatively affected lung development, inflammation, and apoptosis. Growth rate and antioxidant enzyme expression were predominantly affected by LPS and hyperoxia, respectively, while cell proliferation and vascular remodeling and function were mainly affected by combined exposure to LPS and hyperoxia. Mice treated with lower LPS doses developed adaptive responses and hyperoxia exposure did not worsen their BPD phenotype, whereas those mice treated with higher LPS doses displayed the most severe BPD phenotype when exposed to hyperoxia and were the only group that developed PH. Collectively, our data suggest that an additional insult such as LPS may be necessary for models utilizing short-term exposure to moderate hyperoxia to recapitulate human BPD-PH.

CD163 as a Biomarker in Colorectal Cancer: The Expression on Circulating Monocytes and Tumor-Associated Macrophages, and the Soluble Form in the Blood

The macrophage-associated molecule CD163 has been reported as a prognostic biomarker in different cancer types, but its role in colorectal cancer (CRC) is unclear. We studied CD163 in the tumor microenvironment and circulation of patients with CRC in relation to clinicopathological parameters. An enzyme-linked immunosorbent assay (ELISA) was used to measure the serum sCD163 levels and multiparameter flow cytometry was used to study the peripheral blood monocytes and their CD163 expression in CRC patients (N = 78) and healthy donors (N = 50). The distribution of tumor-associated macrophages (TAMs) was studied in primary colorectal tumors with multiplex immunofluorescence. We showed that CRC patients with above-median sCD163 level had a shorter overall survival (OS, p = 0.035) as well as disease-free survival (DFS, p = 0.005). The above-median sCD163 remained significantly associated with a shorter DFS in the multivariate analysis (p = 0.049). Moreover, a shorter OS was observed in CRC patients with an above-median total monocyte percentage (p = 0.007). The number and phenotype of the stromal and intraepithelial TAMs in colorectal tumors were not associated with clinical outcome. In conclusion, sCD163 and monocytes in the circulation may be potential prognostic biomarkers in CRC patients, whereas TAMs in the tumor showed no association with clinical outcome. Thus, our results emphasize the importance of the innate systemic immune response in CRC disease progression.

Effect of nifedipine, a calcium channel blocker, on the generation of nitric oxide and interleukin-1β by murine macrophages activated by lipopolysaccharide from Prevotella intermedia

Nifedipine, a calcium channel blocker, has been reported to possess anti-inflammatory and immunosuppressive effects. The current study was undertaken to explore the influence of nifedipine on the generation of proinflammatory mediators by murine macrophages activated by lipopolysaccharide (LPS) prepared from Prevotella intermedia, a putative periodontal pathogen, and associated mechanisms of action as well. LPS was purified by employing phenol-water extraction protocol. Culture supernatants were analyzed for nitric oxide (NO) and interleukin (IL)-1β. Real-time PCR and immunoblotting were conducted to quantify mRNA and protein expression, respectively. NF-κB-dependent secreted embryonic alkaline phosphatase (SEAP) levels were estimated by reporter assay. Nifedipine markedly suppressed the generation of iNOS-derived NO and IL-1β together with their mRNA expressions in murine macrophages activated by P. intermedia LPS. LPS-stimulated cells exposed to nifedipine notably increased the mRNA levels of Arg-1, Ym-1, FIZZ1, and TGF-β, which are typical markers for M2 macrophage polarization. Nifedipine induced HO-1 at both gene and protein levels in cells challenged with P. intermedia LPS, and the nifedipine-mediated inhibition of NO generation was significantly abrogated by adding SnPP, an HO-1 inhibitor. Nifedipine inhibited LPS-evoked generation of NO and IL-1β in a PPAR-γ-independent manner. In addition, NF-κB activation as well as phosphorylation of STAT1/3 induced by P. intermedia LPS was suppressed by nifedipine. Nifedipine is an inhibitor of P. intermedia LPS-evoked production of NO and IL-1β in murine macrophages and encourages macrophage polarization toward the M2 phenotype. Nifedipine possibly has potential to be used for host modulation of periodontal disease and is worth being further researched.

Genome-Wide Association Study Using Individual Single-Nucleotide Polymorphisms and Haplotypes for Erythrocyte Traits in Alpine Merino Sheep

Adaptation to high-altitude hypoxia is essential for domestic animals, such as yak, Tibetan chicken, and Tibetan sheep, living on high plateaus, as it ensures efficient oxygen absorption and utilization. Red blood cells are the primary medium for transporting oxygen in the blood. However, little is known about the genetic mechanism of erythrocyte traits. Genome-wide association studies (GWASs) based on single markers or haplotypes have identified potential mechanisms for genetic variation and quantitative traits. To identify loci associated with erythrocyte traits, we performed a GWAS based on the method of the single marker and haplotype in 498 Alpine Merino sheep for six erythrocyte traits: red blood cell count (RBC), hemoglobin (HGB), hematocrit (HCT), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), and RBC volume distribution width coefficient of variation (RWD_CV). Forty-two significant single-nucleotide polymorphisms (SNPs) associated with the six erythrocyte traits were detected by means of a single-marker GWAS, and 34 significant haplotypes associated with five erythrocyte traits were detected by means of haplotype analysis. We identified six genes (DHCR24, SPATA9, FLI1, PLCB1, EFNB2, and SH2B3) as potential genes of interest via gene function annotations, location, and expression variation. In particular, FLI1 and PLCB1 were associated with hematopoiesis and erythropoiesis, respectively. These results provide a theoretical basis for analyzing erythrocyte traits and high-altitude hypoxia adaptation in Alpine Merino sheep and will be a useful reference for future studies of plateau-dwelling livestock.

Anti-Inflammatory Effects of Ribes diacanthum Pall Mediated via Regulation of Nrf2/HO-1 and NF-κB Signaling Pathways in LPS-Stimulated RAW 264.7 Macrophages and a TPA-Induced Dermatitis Animal Model

Ribes diacanthum Pall (RDP) is a Mongolian traditional medicine used to treat renal inflammation. In the present study, we initially investigated the anti-inflammatory effects and mechanisms of action of ethylacetate extract of RDP (EARDP) in RAW 264.7 macrophages stimulated by lipopolysaccharide (LPS) and 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced dermatitis in mice. We demonstrated that EARDP protected against LPS-induced cell death by inhibiting intracellular reactive oxygen species (ROS) and malondialdehyde (MDA) production, as well as the synthesis of pro-inflammatory mediators and cytokines, such as nitric oxide (NO), tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and IL-1β. EARDP inhibited the phosphorylation and degradation of inhibitory κB-α (IκB-α) and the activation of nuclear factor (NF)-κB, indicating that the anti-inflammatory effect of EARDP was mediated via the suppression of NF-κB nuclear translocation. In addition, EARDP induced the heme oxygenase-1 (HO-1) expression and nuclear translocation of nuclear factor-E2-related factor 2 (Nrf2), indicating that EARDP induced HO-1 via the Nrf2 pathway in RAW 264.7 cells. Furthermore, EARDP significantly suppressed the protein expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) in LPS-stimulated RAW 264.7 macrophages. However, ZnPP, a specific inhibitor of HO-1, reversed the EARDP-mediated inhibition of NO and TNF-α production in LPS-stimulated RAW 264.7 macrophages. EARDP blocked the phosphorylation of mitogen-activated protein kinase (MAPK) and Akt in LPS-stimulated RAW 264.7 cells. In the in vivo animal model, EARDP significantly and dose-dependently reduced TPA-induced secretion of TNF-α and IL-6 in mouse ear. Based on these results, EARDP represents a promising natural compound, protective against oxidative stress and inflammatory diseases.

Heme oxygenase promotes B-Raf-dependent melanosphere formation

Biosynthesis and degradation of heme, an iron-bound protoporphyrin molecule utilized by a wide variety of metabolic processes, are tightly regulated. Two closely related enzymes, heme oxygenase 1 (HMOX1) and heme oxygenase 2 (HMOX2), degrade free heme to produce carbon monoxide, Fe²⁺ , and biliverdin. HMOX1 expression is controlled via the transcriptional activator, NFE2L2, and the transcriptional repressor, Bach1. Transcription of HMOX1 and other NFE2L2-dependent genes is increased in response to electrophilic and reactive oxygen species. Many tumor-derived cell lines have elevated levels of NFE2L2. Elevated expression of NFE2L2-dependent genes contributes to tumor growth and acquired resistance to therapies. Here, we report a novel role for heme oxygenase activity in melanosphere formation by human melanoma-derived cell lines. Transcriptional induction of HMOX1 through derepression of Bach1 or transcriptional activation of HMOX2 by oncogenic B-Raf^V600E results in increased melanosphere formation. Genetic ablation of HMOX1 diminishes melanosphere formation. Further, inhibition of heme oxygenase activity with tin protoporphyrin markedly reduces melanosphere formation driven by either Bach1 derepression or B-Raf^V600E expression. Global transcriptome analyses implicate genes involved in focal adhesion and extracellular matrix interactions in melanosphere formation.

Hematoma Resolution In Vivo Is Directed by Activating Transcription Factor 1

RATIONALE

The efficient resolution of tissue hemorrhage is an important homeostatic function. In human macrophages in vitro, heme activates an AMPK (AMP-activated protein kinase)/ATF1 (activating transcription factor-1) pathway that directs Mhem macrophages through coregulation of HO-1 (heme oxygenase-1; HMOX1) and lipid homeostasis genes.

OBJECTIVE

We asked whether this pathway had an in vivo role in mice.

METHODS AND RESULTS

Perifemoral hematomas were used as a model of hematoma resolution. In mouse bone marrow-derived macrophages, heme induced HO-1, lipid regulatory genes including LXR (lipid X receptor), the growth factor IGF1 (insulin-like growth factor-1), and the splenic red pulp macrophage gene Spic. This response was lost in bone marrow-derived macrophages from mice deficient in AMPK (Prkab1^-/-) or ATF1 (Atf1^-/-). In vivo, femoral hematomas resolved completely between days 8 and 9 in littermate control mice (n=12), but were still present at day 9 in mice deficient in either AMPK (Prkab1^-/-) or ATF1 (Atf1^-/-; n=6 each). Residual hematomas were accompanied by increased macrophage infiltration, inflammatory activation and oxidative stress. We also found that fluorescent lipids and a fluorescent iron-analog were trafficked to lipid-laden and iron-laden macrophages respectively. Moreover erythrocyte iron and lipid abnormally colocalized in the same macrophages in Atf1^-/- mice. Therefore, iron-lipid separation was Atf1-dependent.

CONCLUSIONS

Taken together, these data demonstrate that both AMPK and ATF1 are required for normal hematoma resolution. Graphic Abstract: An online graphic abstract is available for this article.

Human Cytomegalovirus Interleukin 10 Homologs: Facing the Immune System

Human Cytomegalovirus (HCMV) can cause a variety of health disorders that can lead to death in immunocompromised individuals and neonates. The HCMV lifecycle comprises both a lytic (productive) and a latent (non-productive) phase. HCMV lytic infection occurs in a wide range of terminally differentiated cell types. HCMV latency has been less well-studied, but one characterized site of latency is in precursor cells of the myeloid lineage. All known viral genes are expressed during a lytic infection and a subset of these are also transcribed during latency. The UL111A gene which encodes the viral IL-10, a homolog of the human IL-10, is one of these genes. During infection, different transcript isoforms of UL111A are generated by alternative splicing. The most studied of the UL111A isoforms are cmvIL-10 (also termed the "A" transcript) and LAcmvIL-10 (also termed the "B" transcript), the latter being a well-characterized latency associated transcript. Both isoforms can downregulate MHC class II, however they differ in a number of other immunomodulatory properties, such as the ability to bind the IL10 receptor and induce signaling through STAT3. There are also a number of other isoforms which have been identified which are expressed by differential splicing during lytic infection termed C, D, E, F, and G, although these have been less extensively studied. HCMV uses the viral IL-10 proteins to manipulate the immune system during lytic and latent phases of infection. In this review, we will discuss the literature on the viral IL-10 transcripts identified to date, their encoded proteins and the structures of these proteins as well as the functional properties of all the different isoforms of viral IL-10.

Translocator protein (18 kDa) (TSPO) ligands activate Nrf2 signaling and attenuate inflammatory responses and oxidative stress in human retinal pigment epithelial cells

Degeneration of the retinal pigment epithelium (RPE) is a hallmark of atrophic age-related macular degeneration (AMD). Microglia mediated inflammatory responses and oxidative stress are critical pathophysiological processes in the onset and progression of RPE degeneration. Given the central role of the RPE, strategies to protect these cells from damage caused by oxidative stress and inflammation present a promising therapeutic approach to mitigate AMD. Ligands for the translocator protein (18 kDa) (TSPO) have been shown to confer protection against retinal inflammatory responses and neurodegeneration by acting primarily through retinal glia. However, despite RPE cells demonstrating strong TSPO expression, it remains unclear whether TSPO ligands could also inhibit inflammatory responses of RPE cells. Here, we investigated the influence of three different TSPO ligands XBD173, PK11195 and Ro5-4864 on inflammatory responses in human ARPE-19 cells triggered by supernatants from reactive human microglial cells and the lysosomal destabilizer, LLOMe. Our findings revealed that TSPO ligands significantly inhibited proinflammatory gene expression, inflammasome-mediated caspase-1 activation, lipid accumulation and intracellular ROS levels in stressed ARPE-19 cells. Notably, TSPO ligands induced activation of Nrf2 pathway and its downstream regulated genes in ARPE-19 cells, with Hmox-1 being the most strongly upregulated gene. Collectively, our study indicates that TSPO ligands can enhance the Nrf2 antioxidant pathway in RPE cells and protect them from cellular damage resulting from inflammation and oxidative stress.

Therapeutic approaches to diabetic cardiomyopathy: Targeting the antioxidant pathway

The global epidemic of cardiovascular disease continues unabated and remains the leading cause of death both in the US and worldwide. We hereby summarize the available therapies for diabetes and cardiovascular disease in diabetics. Clearly, the current approaches to diabetic heart disease often target the manifestations and certain mediators but not the specific pathways leading to myocardial injury, remodeling and dysfunction. Better understanding of the molecular events determining the evolution of diabetic cardiomyopathy will provide insight into the development of specific and targeted therapies. Recent studies largely increased our understanding of the role of enhanced inflammatory response, ROS production, as well as the contribution of Cyp-P450-epoxygenase-derived epoxyeicosatrienoic acid (EET), Peroxisome Proliferator-Activated Receptor Gamma Coactivator-1α (PGC-1α), Heme Oxygenase (HO)-1 and 20-HETE in pathophysiology and therapy of cardiovascular disease. PGC-1α increases production of the HO-1 which has a major role in protecting the heart against oxidative stress, microcirculation and mitochondrial dysfunction. This review describes the potential drugs and their downstream targets, PGC-1α and HO-1, as major loci for developing therapeutic approaches beside diet and lifestyle modification for the treatment and prevention of heart disease associated with obesity and diabetes.

Synergistic effect of fasting-mimicking diet and vitamin C against KRAS mutated cancers

Fasting-mimicking diets delay tumor progression and sensitize a wide range of tumors to chemotherapy, but their therapeutic potential in combination with non-cytotoxic compounds is poorly understood. Here we show that vitamin C anticancer activity is limited by the up-regulation of the stress-inducible protein heme-oxygenase-1. The fasting-mimicking diet selectivity reverses vitamin C-induced up-regulation of heme-oxygenase-1 and ferritin in KRAS-mutant cancer cells, consequently increasing reactive iron, oxygen species, and cell death; an effect further potentiated by chemotherapy. In support of a potential role of ferritin in colorectal cancer progression, an analysis of The Cancer Genome Atlas Database indicates that KRAS mutated colorectal cancer patients with low intratumor ferritin mRNA levels display longer 3- and 5-year overall survival. Collectively, our data indicate that the combination of a fasting-mimicking diet and vitamin C represents a promising low toxicity intervention to be tested in randomized clinical trials against colorectal cancer and possibly other KRAS mutated tumors.

Fasting diets are emerging as an approach to delay tumor progression and improve cancer therapies. Here, the authors show that the combination of fasting-mimicking diet with vitamin C decreases tumor development and increases chemotherapy efficacy in KRAS-mutant cancer.

Copper-imidazo[1,2-a]pyridines induce intrinsic apoptosis and modulate the expression of mutated p53, haem-oxygenase-1 and apoptotic inhibitory proteins in HT-29 colorectal cancer cells

Metastatic colorectal cancer responds poorly to treatment and is a leading cause of cancer related deaths. Worldwide, chemotherapy of metastatic colorectal cancer remains plagued by poor efficacy, development of resistance and serious adverse effects. Copper-imidazo[1,2-a]pyridines were previously shown by our group to be selectively active against several cancer cell lines, with three complexes, JD46(27), JD47(29), and JD88(21), showing IC₅₀ values between 0.8 and 1.8 μM against HT-29 cells. Here, we report that treatment with the copper complexes resulted in fragmented nuclei suggestive of apoptotic cell death, which was confirmed by increased annexin V binding and caspase-3/7 activity. The copper complexes caused a loss of mitochondrial membrane potential and increased caspase-9 activity. The absence of caspase-8 activity indicated activation of the intrinsic pathway. Proteomic analysis revealed that copper-imidazo[1,2-a]pyridines decreased the expression of phosphorylated forms of p53 [phospho-p53(S15), phospho-p53(S46) and phospho-p53(S392)]. The expression of inhibitor of apoptosis proteins, XIAP, cIAP1, livin, and the antiapoptotic proteins, Bcl-2 and Bcl-x, was decreased. HO/HMOX/HSP32, expression was notably increased, which suggested the accumulation of reactive oxygen species. Increased expression of TRAIL-R2/DR5 death receptor indicated the possible dual activation of both the extrinsic and intrinsic apoptotic pathways; however, caspase-8 activation could not be demonstrated. In conclusion, the copper-imidazo[1,2-a]pyridines were effective inducers of apoptotic cell death at low micromolar concentrations and changed the expression levels of proteins important for cell survival and cell death. These copper complexes may be useful tools to better understand the complexity of signalling networks in cancer cell death in response to cell stress.

Activation of the Nrf2/HO-1 Pathway by Amomum villosum Extract Suppresses LPS-Induced Oxidative Stress In Vitro and Ex Vivo

Despite its deleterious effects on living cells, oxidative stress plays essential roles in normal physiological processes and provides signaling molecules for cell growth, differentiation, and inflammation. Macrophages are equipped with antioxidant mechanisms to cope with intracellular ROS produced during immune response, and Nrf2 (NF-E2-related factor 2)/HO-1 (heme oxygenase-1) pathway is an attractive target due to its protective effect against ROS-induced cell damage in inflamed macrophages. We investigated the effects of ethanol extract of A. villosum (AVEE) on lipopolysaccharide- (LPS-) stimulated inflammatory responses generated via the Nrf2/HO-1 signaling pathway in murine peritoneal macrophages and RAW 264.7 cells. AVEE was found to suppress the NF-κB signaling pathway, thus, to reduce proinflammatory cytokine, nitric oxide, and prostaglandin levels in peritoneal macrophages and Raw 264.7 cells treated with LPS, and to enhance HO-1 expression by activating Nrf2 signaling. Furthermore, these anti-inflammatory effects of AVEE were diminished when cells were pretreated with SnPP (a HO-1 inhibitor). HPLC analysis revealed AVEE contained quercetin, a possible activator of the Nrf2/HO-1 pathway. These results show A. villosum ethanol extract exerts anti-inflammatory effects by activating the Nrf2/HO-1 pathway in LPS-stimulated macrophages.

HO-1 overexpression alleviates senescence by inducing autophagy via the mitochondrial route in human nucleus pulposus cells

Intervertebral disc degeneration (IDD) is closely associated with aging. Our previous studies have confirmed that heme oxygenase-1 (HO-1) can inhibit nucleus pulposus (NP) cell apoptosis. However, whether or not HO-1 is involved in NP cell senescence and autophagy is unclear. Our results indicated that HO-1 expression was reduced in IDD tissues and replicative senescent NP cells. HO-1 overexpression using a lentiviral vector reduced the NP cell senescence level, protected mitochondrial function, and promoted NP cell autophagy through the mitochondrial pathway. Autophagy inhibitor 3-MA pretreatment reversed the anti-senescent and protective effects on the mitochondrial function of HO-1, which promoted the degradation of the extracellular matrix (ECM) in the intervertebral disc. In vivo, HO-1 overexpression inhibited IDD and enhanced autophagy. In summary, these results suggested that HO-1 overexpression alleviates NP cell senescence by inducing autophagy via the mitochondrial route.

Transcriptional Regulation of HMOX1 Gene in Hezuo Tibetan Pigs: Roles of WT1, Sp1, and C/EBPα

Heme oxygenase 1 (HMOX1) is a stress-inducing enzyme with multiple cardiovascular protective functions, especially in hypoxia stress. However, transcriptional regulation of swine HMOX1 gene remains unclear. In the present study, we first detected tissue expression profiles of HMOX1 gene in adult Hezuo Tibetan pig and analyzed the gene structure. We found that the expression level of HMOX1 gene was highest in the spleen of the Hezuo Tibetan pig, followed by liver, lung, and kidney. A series of 5’ deletion promoter plasmids in pGL3-basic vector were used to identify the core promoter region and confirmed that the minimum core promoter region of swine HMOX1 gene was located at −387 bp to −158 bp region. Then we used bioinformatics analysis to predict transcription factors in this region. Combined with site-directed mutagenesis and RNA interference assays, it was demonstrated that the three transcription factors WT1, Sp1 and C/EBPα were important transcription regulators of HMOX1 gene. In summary, our study may lay the groundwork for further functional study of HMOX1 gene.

Human Heme Oxygenase-1 Induced by Interleukin-6 via JAK/STAT3 Pathways Is a Tumor Suppressor Gene in Hepatoma Cells

Heme oxygenase-1 (HO-1) has several important roles in hepatocytes in terms of anti-inflammation, anti-apoptosis, and antioxidant properties. Interleukin-6 (IL-6) is a pleiotropic cytokine associated with liver regeneration and protection against injury. The aim of this study was to determine the potential crosstalk between HO-1 and IL-6, and to elucidate the signaling pathways involved in the induction of HO-1 by IL-6 in human hepatoma cells. Ectopic overexpression of HO-1 not only attenuated cell proliferation in vitro and in vivo, but also blocked the reactive oxygen species (ROS) induced by H₂O₂ and the pyocyanin in HepG2 or Hep3B cells. IL-6 expression was negatively regulated by HO-1, while IL-6 induced signal transducer and activator of transcription 3 (STAT3) phosphorylation and HO-1 gene expression in HepG2 cells. The co-transfected HO-1 reporter vector and a protein inhibitor of the activated STAT3 (PIAS3) expression vector blocked the IL-6-induced HO-1 reporter activity. Both interferon γ and interleukin-1β treatments induced STAT1 but not STAT3 phosphorylation, which had no effects on the HO-1 expression. Treatments of AG490 and luteolin blocked the JAK/STAT3 signaling pathways which attenuated IL-6 activation on the HO-1 expression. Our results indicated that HO-1 is the antitumor gene induced by IL-6 through the IL-6/JAK/STAT3 pathways; moreover, a feedback circuit may exist between IL-6 and HO-1 in hepatoma cells.

Association of heme oxygenase-1 single nucleotide polymorphisms with susceptibility to tuberculosis in Chinese Han population

Background

Tuberculosis (TB) is an infectious disease, caused by mycobacterium tuberculosis infection, which is associated with oxidative stress and the induction of host antioxidants to counteract this response. The heme oxygenase‐1 (HO‐1) single nucleotide polymorphisms have been reported to be associated with many critical diseases. Our purpose was to investigate the association of HO‐1 single nucleotide polymorphisms with the susceptibility to tuberculosis in Chinese Han population.

Methods

A case‐control study was performed on Chinese Han population, and a group of 638 TB patients was compared to 610 healthy controls. Three single nucleotide polymorphisms (SNPs) including rs2071746, rs5995098, and rs8140669 were genotyped using the MassARRAY platform. The genotype frequency was compared between TB patients and healthy controls. The association between the three genetic models of the three SNPs and TB risk was further investigated.

Results

The results showed that, in the case of additive model, there was significant difference of the genotype frequencies of SNP rs8140669 between the TB patients and control groups (P = .038). In the case of dominant model, the genotype frequencies of SNP rs8140669 may have difference between the two cohorts (P = .051), while the allele frequency and genotype distribution for other two SNPs showed no significant difference between the two groups (P > .05).

Conclusion

HO‐1 polymorphism was associated with TB susceptibility in Chinese Han population.

Carbon Monoxide Inhibits T Cell Proliferation by Suppressing Reactive Oxygen Species Signaling

Aims: Carbon monoxide (CO) confers antiproliferative effects on T cells; however, how these effects are produced remains unclear. Reactive oxygen species (ROS) have recently emerged as important modulators of T cell proliferation. In this study, we aimed to determine whether the inhibitory effects of CO on T cell proliferation are dependent on the inhibition of ROS signaling. Results: Pretreatment with CO-releasing molecule-2 (CORM-2) had potent inhibitory effects on mouse T cell proliferation stimulated by anti-CD3/CD28 antibodies. Interestingly, CORM-2 pretreatment markedly suppressed intracellular ROS generation as well as the activity of NADPH oxidase and mitochondrial complexes I-IV in T cells after stimulation. The inhibitory effects of CORM-2 on both ROS production and T cell proliferation were comparable with those produced by the use of antioxidant N-acetylcysteine or a combined administration of mitochondrial complex I-IV inhibitors. Moreover, increasing intracellular ROS via hydrogen peroxide supplementation largely reversed the inhibitory effect of CORM-2 on the proliferation of T cells. The inhibitory effects of CORM-2 on both cell proliferation and intracellular ROS production were also shown in a T cell proliferation model involving stimulation by allogeneic dendritic cells or phorbol 12-myristate 13-actetate/ionomycin, as well as in spontaneous cell proliferation models in EL-4 and RAW264.7 cells. In addition, CORM-2 treatment significantly inhibited T cell activation in vivo and attenuated concanavalin A-induced autoimmune hepatitis. Innovation: CO inhibits T cell proliferation via suppression of intracellular ROS production. Conclusion: The study could supply a general mechanism to explain the inhibitory effects of CO on T cell activation and proliferation, favoring its future application in T cell-mediated diseases.

A Role of the Heme Degradation Pathway in Shaping Prostate Inflammatory Responses and Lipid Metabolism

The molecular mechanisms of prostate inflammation are unclear. We hypothesized that heme oxygenase 1 (HMOX1; HO-1), an enzyme responsible for degradation of heme to carbon monoxide, bilirubin, and iron, is an important regulator of inflammation and epithelial responses in the prostate. Injection of non-uropathogenic Escherichia coli (MG1655 strain) or phosphate-buffered saline into the urethra of mice led to increased numbers of CD45⁺ leukocytes and mitotic markers (phosphorylated histone H₃ and phosphorylated ERK1/2) in the prostate glands. Leukocyte infiltration was elevated in the prostates harvested from mice lacking HO-1 in myeloid compartment. Conversely, exogenous carbon monoxide (250 ppm) increased IL-1β levels and suppressed cell proliferation in the prostates. Carbon monoxide did not affect the number of infiltrating CD45⁺ cells in the prostates of E. coli- or phosphate-buffered saline-treated mice. Interestingly, immunomodulatory effects of HO-1 and/or carbon monoxide correlated with early induction of the long-chain acyl-CoA synthetase 1 (ACSL1). ACSL1 levels were elevated in response to E. coli treatment, and macrophage-expressed ACSL1 was in part required for controlling of IL-1β expression and prostate cancer cell colony growth in soft agar. These results suggest that HO-1 and/or carbon monoxide might play a distinctive role in modulating prostate inflammation, cell proliferation, and IL-1β levels in part via an ACSL1-mediated pathway.

Heme-Derived Metabolic Signals Dictate Immune Responses

Heme is one of the most abundant molecules in the body acting as the functional core of hemoglobin/myoglobin involved in the O2/CO2 carrying in the blood and tissues, redox enzymes and cytochromes in mitochondria. However, free heme is toxic and therefore its removal is a significant priority for the host. Heme is a well-established danger-associated molecular pattern (DAMP), which binds to toll-like receptor 4 (TLR4) to induce immune responses. Heme-derived metabolites including the bile pigments, biliverdin (BV) and bilirubin (BR), were first identified as toxic drivers of neonatal jaundice in 1800 but have only recently been appreciated as endogenous drivers of multiple signaling pathways involved in protection from oxidative stress and regulators of immune responses. The tissue concentration of heme, BV and BR is tightly controlled. Heme oxygenase-1 (HO-1, encoded by HMOX1) produces BV by heme degradation, while biliverdin reductase-A (BLVR-A) generates BR by the subsequent conversion of BV. BLVR-A is a fascinating protein that possesses a classical protein kinase domain, which is activated in response to BV binding to its enzymatic site and initiates the downstream mitogen-activated protein kinases (MAPK) and phosphatidylinositol 3-kinase (PI3K) pathways. This links BLVR-A activity to cell growth and survival pathways. BLVR-A also contains a bZip DNA binding domain and a nuclear export sequence (NES) and acts as a transcription factor to regulate the expression of immune modulatory genes. Here we will discuss the role of heme-related immune response and the potential for targeting the heme system for therapies directed toward hepatitis and cancer.

Why some organ allografts are tolerated better than others: new insights for an old question

PURPOSE OF REVIEW

There is great variability in how different organ allografts respond to the same tolerance induction protocol. Well known examples of this phenomenon include the protolerogenic nature of kidney and liver allografts as opposed to the tolerance-resistance of heart and lung allografts. This suggests there are organ-specific factors which differentially drive the immune response following transplantation.

RECENT FINDINGS

The specific cells or cell products that make one organ allograft more likely to be accepted off immunosuppression than another are largely unknown. However, new insights have been made in this area recently.

SUMMARY

The current review will focus on the organ-intrinsic factors that contribute to the organ-specific differences observed in tolerance induction with a view to developing therapeutic strategies to better prevent organ rejection and promote tolerance induction of all organs.

Redox Epiphospholipidome in Programmed Cell Death Signaling: Catalytic Mechanisms and Regulation

A huge diversification of phospholipids, forming the aqueous interfaces of all biomembranes, cannot be accommodated within a simple concept of their role as membrane building blocks. Indeed, a number of signaling functions of (phospho)lipid molecules has been discovered. Among these signaling lipids, a particular group of oxygenated polyunsaturated fatty acids (PUFA), so called lipid mediators, has been thoroughly investigated over several decades. This group includes oxygenated octadecanoids, eicosanoids, and docosanoids and includes several hundreds of individual species. Oxygenation of PUFA can occur when they are esterified into major classes of phospholipids. Initially, these events have been associated with non-specific oxidative injury of biomembranes. An alternative concept is that these post-synthetically oxidatively modified phospholipids and their adducts with proteins are a part of a redox epiphospholipidome that represents a rich and versatile language for intra- and inter-cellular communications. The redox epiphospholipidome may include hundreds of thousands of individual molecular species acting as meaningful biological signals. This review describes the signaling role of oxygenated phospholipids in programs of regulated cell death. Although phospholipid peroxidation has been associated with almost all known cell death programs, we chose to discuss enzymatic pathways activated during apoptosis and ferroptosis and leading to peroxidation of two phospholipid classes, cardiolipins (CLs) and phosphatidylethanolamines (PEs). This is based on the available LC-MS identification and quantitative information on the respective peroxidation products of CLs and PEs. We focused on molecular mechanisms through which two proteins, a mitochondrial hemoprotein cytochrome c (cyt c), and non-heme Fe lipoxygenase (LOX), change their catalytic properties to fulfill new functions of generating oxygenated CL and PE species. Given the high selectivity and specificity of CL and PE peroxidation we argue that enzymatic reactions catalyzed by cyt c/CL complexes and 15-lipoxygenase/phosphatidylethanolamine binding protein 1 (15LOX/PEBP1) complexes dominate, at least during the initiation stage of peroxidation, in apoptosis and ferroptosis. We contrast cell-autonomous nature of CLox signaling in apoptosis correlating with its anti-inflammatory functions vs. non-cell-autonomous ferroptotic signaling facilitating pro-inflammatory (necro-inflammatory) responses. Finally, we propose that small molecule mechanism-based regulators of enzymatic phospholipid peroxidation may lead to highly specific anti-apoptotic and anti-ferroptotic therapeutic modalities.

Bioluminescence imaging of carbon monoxide in living cells based on a selective deiodination reaction

Modification of a heavy iodine atom for d-Luciferin was explored as a “turn-on” transduction scheme for CO detection. This new probe could image exogenous and endogenous CO in the luciferase-transfected cancer cells.

Autophagy: Multiple Mechanisms to Protect Skin from Ultraviolet Radiation-Driven Photoaging

Autophagy is an essential cellular process that maintains balanced cell life. Restriction in autophagy may induce degenerative changes in humans. Natural or pathological aging of susceptible tissues has been linked with reduced autophagic activity. Skin photoaging is an example of such pathological condition caused by ambient solar UV radiation exposure. The UV-induced production of reaction oxygen species (ROS) has been linked to the promotion and progression of the photoaging process in exposed tissues. Accordingly, it has been suggested that autophagy is capable of delaying the skin photoaging process caused by solar ultraviolet (UV), although the underlying mechanism is still under debate. This review highlights several plausible mechanisms by which UV-induced ROS activates the cellular signaling pathways and modulates the autophagy. More specifically, the UV-mediated regulation of autophagy and age-related transcription factors is discussed to pinpoint the contribution of autophagy to antiphotoaging effects in the skin. The outcome of this review will provide insights into design intervention strategies for delaying the phenomenon of sunlight-induced photodamage, photoaging, and other aging-related chronic diseases based on factors that activate the autophagy process in the skin.

MicroRNA-155 and microRNA-181a, via HO-1, participate in regulating the immunotoxicity of cadmium in the kidneys of exposed Cyprinus carpio

Cadmium (Cd) is a nonessential metal that is a contaminant in aquatic ecosystems. Cd can accumulate in aquatic animals, leading to detrimental effects in tissues, and Cd exposure can induce immunotoxicity in fish. MicroRNAs (miRNAs) play critical roles in immune responses, yet the participation of miRNAs in Cd-induced immunotoxicity remains poorly understood. The present study evaluated the effects of Cd exposure on the immune responses and the mRNAs and miRNAs expressions of immune-related genes in Cyprinus carpio (C. carpio). Then, microRNA-155 (miR-155) was overexpressed and microRNA-181a (miR-181a) was knocked down to determine which miRNA plays a key role in the immune response to Cd. The results showed that 0.5 mg/L Cd²⁺ significantly decreased the activity of alkaline phosphatase (AKP) and acid phosphatase (ACP) in the kidneys of C. carpio. Cd exposure upregulated the mRNA expressions of interleukin (IL)-1β, IL-8, nuclear factor-kappa B (NF-κB), tumour necrosis factor-α (TNF-α), and Toll-like receptor 4(TLR-4) and downregulated those of IL-10 and heme oxygenase-1 (HO-1) in C. carpio kidneys. Cd exposure also led to upregulation of miR-155 and miR-181a expressions. Furthermore, AKP and ACP activity in the kidneys was markedly changed after intraperitoneal injection of C. carpio with miR-155 agomir and miR-181a antagomir. All detected mRNA expressions were significantly decreased after injection of miR-155 agomir, and IL-10, NF-κB, TNF-α, and HO-1 mRNA expressions were markedly increased after injection of miR-181a antagomir. The results of this study demonstrate that Cd exposure can immunocompromise C. carpio by targeting HO-1 through miR-155 and miR-181a. This is the first study to reveal that Cd exposure induces immunotoxicity through miR-155 and miR-181a in the kidneys of C. carpio.

The hepatoprotective effect of sitagliptin against hepatic ischemia reperfusion-induced injury in rats involves Nrf-2/HO-1 pathway

BACKGROUND

Oxidative stress and inflammation play a key role in the development of hepatic ischemia reperfusion (HIR)-induced injury. Nuclear factor-erythroid 2-related factor-2 (Nrf-2) is a main regulator of numerous genes, encoding cytoprotective molecules including heme oxygenase-1 (HO-1). Sitagliptin (Sit) is an incretin enhancer acting via inhibition of dipeptidyl peptidase-4 (DPP-4) enzyme. This study was undertaken to investigate the ability of Sit to prevent the hepatic pathological changes of HIR induced injury and to modify Nrf-2 and its target HO-1.

METHODS

Pringle's maneuver was used to induce total HIR in adult male rats that were randomly assigned into 4 groups. Group1 (sham-operated control), Group 2 (sham-operated + Sit-control group), Group 3 (HIR non-treated), and Group 4 (HIR + Sit). Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities together with hepatic contents of malondialdhyde (MDA), nitric oxide (NO) and reduced glutathione (GSH) and superoxide dismutase (SOD) activity were evaluated. Hepatic tissue mRNA of Nrf-2 and protein content of HO-1 along with histopathological examination and scoring of hepatic injury were performed.

RESULTS

Sit caused a significant reduction in ALT and AST activities together with attenuation of HIR-induced histopathological liver injury. Effect of Sit was associated with decreased hepatic level of MDA and NO with increased GSH level and SOD activity. Non-treated rats with HIR showed an increase in Nrf-2 mRNA expression and HO-1 content in hepatic tissue which was further increased by Sit treatment.

CONCLUSIONS

These results indicate that hepatoprotective activity of Sit against HIR is attributed at least in part to modulation of Nrf-2/ HO-1 signaling pathway.

Ameliorative effects of silymarin on HCl-induced acute lung injury in rats; role of the Nrf-2/HO-1 pathway

OBJECTIVES

Aspiration is a common cause of acute lung injury (ALI), which lacks an effective treatment. Inflammation and oxidative stress play key roles in ALI development. Silymarin is an active extract of Silybum marianum plant seeds (milk thistle). Silymarin has potent anti-inflammatory and antioxidant effects; however its role in aspiration induced ALI has not been investigated. The aim of this study is to investigate the role of silymarin in the treatment of hydrochloric acid (HCl) aspiration induced ALI and explores its mechanisms of action.

MATERIALS AND METHODS

The study included three groups of rats: Control non-treated group, ALI group (intra-tracheal HCl injected), and silymarin treated ALI group. White blood cells (WBCs) with differential count, oxidative stress parameters, B-cell lymphoma 2 (Bcl-2), transforming growth factor-beta (TGF-β), cyclooxygenase 2 (COX-2), nuclear factor erythroid 2-related factor-2 (Nrf-2), and heme oxygenase-1 (HO-1) were investigated. Lung tissue histopathology and immunohistochemical expression of survivin and proliferating cell nuclear antigen (PCNA) were also examined.

RESULTS

The results of the study showed that HCL caused histopathological changes in ALI with leukocytopenia and increased oxidative stress biomarkers. It increased TGF-β, up-regulated mRNA expression of COX-2, Nrf-2, and HO-1 and increased survivin and PCNA but decreased Bcl-2. Silymarin ameliorated the histopathological lung injury with further up-regulation of Nrf-2 and HO-1 mRNA and decreased the inflammatory and fibrotic parameters together with up-regulation of the anti-apoptotic and the proliferation parameters.

CONCLUSION

The protective effect of silymarin against ALI is mediated by Nrf-2/HO-1 pathway with subsequent antioxidant, anti-inflammatory, antiapoptotic, and proliferating activities.

MhuD from Mycobacterium tuberculosis: Probing a Dual Role in Heme Storage and Degradation

The Mycobacterium tuberculosis (Mtb) heme oxygenase MhuD liberates free iron by degrading heme to the linear tetrapyrrole mycobilin. The MhuD dimer binds up to two hemes within the active site of each monomer. Binding the first solvent-exposed heme allows heme degradation and releases free iron. Binding a second heme renders MhuD inactive, allowing heme storage. Native-mass spectrometry revealed little difference in binding affinity between solvent-exposed and solvent-protected hemes. Hence, diheme-MhuD is formed even when a large proportion of the MhuD population is in the apo form. Apomyoglobin heme transfer assays showed MhuD-diheme dissociation is far slower than monoheme dissociation at ∼0.12 min^-1 and ∼0.25 s^-1, respectively, indicating that MhuD has a strong affinity for diheme. MhuD has not evolved to preferentially occupy the monoheme form and, through formation of a diheme complex, it functions as part of a larger network to tightly regulate both heme and iron levels in Mtb.

Heme oxygenase-1/carbon monoxide as modulators of autophagy and inflammation

Heme oxygenase-1 (HO-1) catalyzes heme degradation to generate biliverdin-IXα, carbon monoxide (CO), and iron. The HO-1/CO system confers cytoprotection in animal models of organ injury and disease, via modulation of inflammation and apoptosis. Recent studies have uncovered novel anti-inflammatory targets of HO-1/CO including regulation of the autophagy and inflammasome pathways. Autophagy is a lysosome-dependent program for the turnover of cellular organelles such as mitochondria, proteins, and pathogens; which may downregulate inflammatory processes. Therapeutic modulation of autophagy by CO has been demonstrated in models of sepsis. The nucleotide-binding domain, leucine-rich-containing family, pyrin domain-containing-3 (NLRP3) inflammasome regulates the maturation of pro-inflammatory cytokines. CO can regulate NLRP3 inflammasome activation and associated pro-inflammatory cytokines production and promote the resolution of inflammation by upregulating the synthesis of specialized pro-resolving mediators (SPMs). Mitochondria may represent a proximal target of HO-1/CO action. HO-1 may localize to mitochondria in response to stress, while CO can moderate mitochondrial dysfunction and regulate mitochondrial autophagy (mitophagy) and biogenesis. The interplay between mitochondrial autophagy, mitochondrial dysfunction, and the regulation and resolution of inflammation may make important contributions to the protection afforded by HO-1/CO in cellular and organ injury models. Recent studies have continued to explore the potential of CO for clinical applications.

Role of Heme Oxygenase as a Modulator of Heme-Mediated Pathways

The heme oxygenase (HO) system is essential for heme and iron homeostasis and necessary for adaptation to cell stress. HO degrades heme to biliverdin (BV), carbon monoxide (CO) and ferrous iron. Although mostly beneficial, the HO reaction can also produce deleterious effects, predominantly attributed to excessive product formation. Underrated so far is, however, that HO may exert effects additionally via modulation of the cellular heme levels. Heme, besides being an often-quoted generator of oxidative stress, plays also an important role as a signaling molecule. Heme controls the anti-oxidative defense, circadian rhythms, activity of ion channels, glucose utilization, erythropoiesis, and macrophage function. This broad spectrum of effects depends on its interaction with proteins ranging from transcription factors to enzymes. In degrading heme, HO has the potential to exert effects also via modulation of heme-mediated pathways. In this review, we will discuss the multitude of pathways regulated by heme to enlarge the view on HO and its role in cell physiology. We will further highlight the contribution of HO to pathophysiology, which results from a dysregulated balance between heme and the degradation products formed by HO.

Protective Effects of Aqueous Extract of Mentha suaveolens against Oxidative Stress-Induced Damages in Human Keratinocyte HaCaT Cells

Mentha suaveolens is an aromatic herb that has a wide range of biological activities, including antimicrobial, antifungal, anti-inflammatory, and hepatoprotective properties. Although there are a few reports on the antioxidant property of M. suaveolens, its cytoprotective activity against oxidative stress has not been reported yet. The objective of this study was to determine the protective activity of M. suaveolens aqueous extract (MSAE) against hydrogen peroxide- (H₂O₂-) induced oxidative stress and apoptosis in human keratinocyte HaCaT cells. MSAE pretreatment decreased H₂O₂-induced cytotoxicity and suppressed H₂O₂-induced intracellular ROS generation. Furthermore, MSAE suppressed expression levels of H₂O₂-induced apoptotic genes such as cleaved caspase-3, caspase-9, and cleaved poly (ADP-ribose) polymerase (PARP). Pretreatment with MSAE induced expression of phase II enzyme such as HO-1 through translocation of NF-E2-related factor (Nrf2) upon H₂O₂ exposure. These results revealed that the cytoprotective effect of MSAE against oxidative stress-induced cell death was associated with activation of Nrf2-mediated phase II enzyme expression.

HO-1 overexpression and underexpression: Clinical implications

In this review we examine the effects of both over- and under-production of heme oxygenase-1 (HO-1) and HO activity on a broad spectrum of biological systems and on vascular disease. In a few instances e.g., neonatal jaundice, overproduction of HO-1 and increased HO activity results in elevated levels of bilirubin requiring clinical intervention with inhibitors of HO activity. In contrast HO-1 levels and HO activity are low in obesity and the HO system responds to mitigate the deleterious effects of oxidative stress through increased levels of bilirubin (anti-inflammatory) and CO (anti-apoptotic) and decreased levels of heme (pro-oxidant). Site specific HO-1 overexpression diminishes adipocyte terminal differentiation and lipid accumulation of obesity mediated release of inflammatory molecules. A series of diverse strategies have been implemented that focus on increasing HO-1 and HO activity that are central to reversing the clinical complications associated with diseases including, obesity, metabolic syndrome and vascular disease.

Dietary supplementation with sulforaphane attenuates liver damage and heme overload in a sickle cell disease murine model

Sickle cell disease (SCD) is a recessively inherited blood disorder caused by abnormal β-globin production. The β-globin mutation changes erythrocyte morphology into a sickle shape and increases erythrocyte vulnerability to hemolysis. Oxidative stress and concomitant inflammation eventually result in damage to multiple organs. Nrf2 is a master regulator of the oxidative stress response, homeostasis, and metabolism. Keap1 modulates Nrf2 protein levels; Nrf2 inducers alter nuclear Nrf2 levels by interacting with Keap1. Genetic modification of Keap1 helps to reduce inflammation and tissue damage in SCD model mice through Nrf2 induction. Here, we investigated the benefits of a mild and safe Nrf2 agonist, sulforaphane (SFN), in ameliorating SCD pathology in a murine model. SFN is a phytochemical and is found in cruciferous vegetables as its inert precursor, glucoraphanin. We found that dietary SFN administration for 14 days or 2 months increased the expression of Nrf2-dependent cytoprotective genes, but SFN uptake did not have deleterious effects on the food consumption and growth of SCD model mice. SFN ameliorated the liver damage of SCD mice, which could be validated by the rescue of liver function and the significantly reduced liver necrotic area. SFN administration also helped to eliminate heme released from lysed sickle cells. These results indicate that dietary supplementation with SFN relieves SCD symptoms by inducing Nrf2 and support our contention that SFN is a potential drug for the long-term treatment of children with SCD.

Cardiac expression of HMOX1 and PGF in sickle cell mice and haem-treated wild type mice dominates organ expression profiles via Nrf2 (Nfe2l2)

Haemolysis is a major feature of sickle cell disease (SCD) that contributes to organ damage. It is well established that haem, a product of haemolysis, induces expression of the enzyme that degrades it, haem oxygenase-1 (HMOX1). We have also shown that haem induces expression of placental growth factor (PGF), but the organ specificity of these responses has not been well-defined. As expected, we found high level expression of Hmox1 and Pgf transcripts in the reticuloendothelial system organs of transgenic sickle cell mice, but surprisingly strong expression in the heart (P < 0·0001). This pattern was largely replicated in wild type mice by intravenous injection of exogenous haem. In the heart, haem induced unexpectedly strong mRNA responses for Hmox1 (18-fold), Pgf (4-fold), and the haem transporter Slc48a1 (also termed Hrg1; 2·4-fold). This was comparable to the liver, the principal known haem-detoxifying organ. The NFE2L2 (also termed NRF2) transcription factor mediated much of the haem induction of Hmox1 and Hrg1 in all organs, but less so for Pgf. Our results indicate that the heart expresses haem response pathway genes at surprisingly high basal levels and shares with the liver a similar transcriptional response to circulating haem. The role of the heart in haem response should be investigated further.

Intravenous Heme Arginate Induces HO-1 (Heme Oxygenase-1) in the Human Heart

Objective- HO-1 (heme oxygenase-1) induction may prevent or reduce ischemia-reperfusion injury. We previously evaluated its in vivo induction after a single systemic administration of heme arginate in peripheral blood mononuclear cells. The current trial was designed to assess the pharmacological tissue induction of HO-1 in the human heart with heme arginate in vivo. Approach and Results- Patients planned for conventional aortic valve replacement received placebo (n=8), 1 mg/kg (n=7) or 3 mg/kg (n=9) heme arginate infused intravenously 24 hours before surgery. A biopsy of the right ventricle was performed directly before aortic cross-clamping and after cross-clamp release. In addition, the right atrial appendage was partially removed for analysis. HO-1 protein and mRNA concentrations were measured in tissue samples and in peripheral blood mononuclear cells before to and up to 72 hours after surgery. No study medication-related adverse events occurred. A strong, dose-dependent effect on myocardial HO-1 mRNA levels was observed (right ventricle: 7.9±5.0 versus 88.6±49.1 versus 203.6±148.7; P=0.002 and right atrium: 10.8±8.8 versus 229.8±173.1 versus 392.7±195.7; P=0.001). This was paralleled by a profound increase of HO-1 protein concentration in atrial tissue (8401±3889 versus 28 585±10 692 versus 29 022±8583; P<0.001). Surgery and heme arginate infusion significantly increased HO-1 mRNA concentration in peripheral blood mononuclear cells ( P<0.001). HO-1 induction led to a significant increase of postoperative carboxyhemoglobin (1.7% versus 1.4%; P=0.041). No effect on plasma HO-1 protein levels could be detected. Conclusions- Myocardial HO-1 mRNA and protein can be dose-dependently induced by heme arginate. Protective effects of this therapeutic strategy should be evaluated in upcoming clinical trials. Clinical Trial Registration- URL: http://www.clinicaltrials.gov . Unique identifier: NCT02314780.

Carbon Monoxide Releasing Molecule-2-Upregulated ROS-Dependent Heme Oxygenase-1 Axis Suppresses Lipopolysaccharide-Induced Airway Inflammation

The up-regulation of heme oxygenase-1 (HO-1) is mediated through nicotinamaide adenine dinucleotide phosphate (NADPH) oxidases (Nox) and reactive oxygen species (ROS) generation, which could provide cytoprotection against inflammation. However, the molecular mechanisms of carbon monoxide-releasing molecule (CORM)-2-induced HO-1 expression in human tracheal smooth muscle cells (HTSMCs) remain unknown. Here, we found that pretreatment with CORM-2 attenuated the lipopolysaccharide (LPS)-induced intercellular adhesion molecule (ICAM-1) expression and leukocyte count through the up-regulation of HO-1 in mice, which was revealed by immunohistochemistrical staining, Western blot, real-time PCR, and cell count. The inhibitory effects of HO-1 by CORM-2 were reversed by transfection with HO-1 siRNA. Next, Western blot, real-time PCR, and promoter activity assay were performed to examine the HO-1 induction in HTSMCs. We found that CORM-2 induced HO-1 expression via the activation of protein kinase C (PKC)α and proline-rich tyrosine kinase (Pyk2), which was mediated through Nox-derived ROS generation using pharmacological inhibitors or small interfering ribonucleic acids (siRNAs). CORM-2-induced HO-1 expression was mediated through Nox-(1, 2, 4) or p47^phox, which was confirmed by transfection with their own siRNAs. The Nox-derived ROS signals promoted the activities of extracellular signal-regulated kinase 1/2 (ERK1/2). Subsequently, c-Fos and c-Jun-activator protein-1 (AP-1) subunits-were up-regulated by activated ERK1/2, which turned on transcription of the HO-1 gene by regulating the HO-1 promoter. These results suggested that in HTSMCs, CORM-2 activates PKCα/Pyk2-dependent Nox/ROS/ERK1/2/AP-1, leading to HO-1 up-regulation, which suppresses the lipopolysaccharide (LPS)-induced airway inflammation.

Differential modulatory effects of Propofol and Sevoflurane anesthesia on blood monocyte HLA-DR and CD163 expression during and after cardiac surgery with cardiopulmonary bypass: a preliminary randomized flow cytometry study

INTRODUCTION

The increase of the anti-inflammatory CD163^highHLA-DR^low blood monocyte subset is one of the mechanisms dampening inflammation during cardiac surgery with cardiopulmonary bypass. We evaluated the effect of two different anesthetic protocols, intravenous Propofol infusion or Sevoflurane-gas administration, on the perioperative frequency of this subset.

METHODS

Blood from patients (Propofol = 11, Sevoflurane = 13) undergoing minimally invasive mitral valve surgery was drawn preoperatively (T1), before declamping (T2), at 6 (T3), 24 (T4), 48 (T5), and 72 hours (T6) after declamping. C-reactive protein, haptoglobin, and lactate dehydrogenase were measured. A hemolytic index, as C-reactive protein/haptoglobin ratio, was introduced. Monocyte expression of HLA-DR, CD163, and the CD163^highHLA-DR^low subset fraction was quantified by flow cytometry. Baseline-referred variations of plasmatic and cellular data at T2 were normalized for clamping times. Subsequent time-point variations were normalized for the final cardiopulmonary bypass times.

RESULTS

Variations of hemolytic index and lactate dehydrogenase were higher with Propofol at T3 (p = 0.004 and p = 0.02, respectively) when compared with Sevoflurane. At T2, the down-modulation of CD163 was higher with Propofol (p = 0.005). Starting from T3, the up-regulatory trend of CD163 was basically higher with Propofol, although not significantly. Propofol induced higher increments of HLA-DR low fractions, at T2 (p = 0.04) and, to a lesser extent, at T4 (p = 0.06). Starting from T3, the CD163^highHLA-DR^low subset variations were higher with Propofol, especially at T4 and T6.

CONCLUSION

Propofol seems to induce a higher postoperative fraction of the CD163^highHLA-DR^low monocyte subset. This could represent either a compensatory mechanism dampening the higher inflammatory condition observed with Propofol at T2 or a consequence of a higher postoperative Propofol-induced hemolysis.

Gene expression profiling and identification of hub genes in Nellore cattle with different marbling score levels

The marbling rate evaluation is difficult and expensive, requiring slaughter of the animal or ultrasound measurement. Thus, this trait is generally not included in animal breeding programs. The use of molecular techniques to elucidate intramuscular fat deposition may help improve this trait. In this respect, transcriptome studies and differential gene expression analysis by RNA-Seq can contribute to advances in this area. The objective of this study was to use RNA-Seq to identify differentially expressed genes (DEGs) in muscle tissue (longissimus thoracis) of Nellore cattle divergently ranked on marbling, in order to increase our understanding of genes involved in the expression of this trait. The results revealed 49 DEGs and three hub genes (CISH, UFM1, TSHZ1), all of them involved in insulin and diabetes mellitus metabolism. These results indicating key genes and pathways, which may help to develop strategies designed to select animals with greater marbling.

CO-Releasing Materials: An Emphasis on Therapeutic Implications, as Release and Subsequent Cytotoxicity Are the Part of Therapy

The CO-releasing materials (CORMats) are used as substances for producing CO molecules for therapeutic purposes. Carbon monoxide (CO) imparts toxic effects to biological organisms at higher concentration. If this characteristic is utilized in a controlled manner, it can act as a cell-signaling agent for important pathological and pharmacokinetic functions; hence offering many new applications and treatments. Recently, research on therapeutic applications using the CO treatment has gained much attention due to its nontoxic nature, and its injection into the human body using several conjugate systems. Mainly, there are two types of CO insertion techniques into the human body, i.e., direct and indirect CO insertion. Indirect CO insertion offers an advantage of avoiding toxicity as compared to direct CO insertion. For the indirect CO inhalation method, developers are facing certain problems, such as its inability to achieve the specific cellular targets and how to control the dosage of CO. To address these issues, researchers have adopted alternative strategies regarded as CO-releasing molecules (CORMs). CO is covalently attached with metal carbonyl complexes (MCCs), which generate various CORMs such as CORM-1, CORM-2, CORM-3, ALF492, CORM-A1 and ALF186. When these molecules are inserted into the human body, CO is released from these compounds at a controlled rate under certain conditions or/and triggers. Such reactions are helpful in achieving cellular level targets with a controlled release of the CO amount. However on the other hand, CORMs also produce a metal residue (termed as i-CORMs) upon degradation that can initiate harmful toxic activity inside the body. To improve the performance of the CO precursor with the restricted development of i-CORMs, several new CORMats have been developed such as micellization, peptide, vitamins, MOFs, polymerization, nanoparticles, protein, metallodendrimer, nanosheet and nanodiamond, etc. In this review article, we shall describe modern ways of CO administration; focusing primarily on exclusive features of CORM's tissue accumulations and their toxicities. This report also elaborates on the kinetic profile of the CO gas. The comprehension of developmental phases of CORMats shall be useful for exploring the ideal CO therapeutic drugs in the future of medical sciences.

Protective effects of two novel nitronyl nitroxide radicals on heart failure induced by hypobaric hypoxia

AIMS

Hypobaric hypoxia (HH), linked to oxidative stress, impairs cardiac function. We synthesized a novel nitronyl nitroxide radical, an HPN derivative (HEPN) and investigated the protective effects of HEPN and HPN against HH-induced heart injury in mice and the underlying mechanisms of action.

MAIN METHODS

Mice were administered with HPN (200 mg/kg) or HEPN (200 mg/kg) 30 min before exposed to HH. The cardiac function was measured. Serum AST, CK, LDH and cTnI were estimated. Heart tissue oxidase activity, SOD, CAT, GSH-Px, ROS and MDA were estimated. ATP content, Na⁺/K⁺-ATPase and Ca²⁺/Mg²⁺-ATPase activity was measured. The expression of HIF-1, VEGF, Nrf2, HO-1, Bax, Bcl-2, Caspase-3 was estimated.

KEY FINDINGS

Results showed that pretreatment with HEPN or HPN led to a dramatic decrease in the activity of biochemical markers AST, CK, LDH and cTnI in murine serum. They increased the activity of SOD, CAT and GSH-Px and reduced the level of ROS and MDA in the hearts of mice. HEPN and HPN could increase the expression of Nrf2 and OH-1. They could maintain the ATPase activity. The Bax and Caspase-3 expression as well as the ratio of Bax/Bcl-2 were significantly downregulated and the Bcl-2 expression was upregulated by HPN or HEPN compared to the HH group. They may attenuate the HH-induced oxidant stress via free radical scavenging activity.

SIGNIFICANCE

The present study showed that the nitronyl nitroxide radical HEPN and HPN may be potential therapeutic agents for treatment of HH-induced cardiac dysfunction.

Similarities and Distinctions in the Effects of Metformin and Carbon Monoxide in Immunometabolism

Immunometabolism, defined as the interaction of metabolic pathways with the immune system, influences the pathogenesis of metabolic diseases. Metformin and carbon monoxide (CO) are two pharmacological agents known to ameliorate metabolic disorders. There are notable similarities and differences in the reported effects of metformin and CO on immunometabolism. Metformin, an anti-diabetes drug, has positive effects on metabolism and can exert anti-inflammatory and anti-cancer effects via adenosine monophosphate-activated protein kinase (AMPK)-dependent and AMPK-independent mechanisms. CO, an endogenous product of heme oxygenase-1 (HO-1), can exert anti-inflammatory and antioxidant effects at low concentration. CO can confer cytoprotection in metabolic disorders and cancer via selective activation of the protein kinase R-like endoplasmic reticulum (ER) kinase (PERK) pathway. Both metformin and CO can induce mitochondrial stress to produce a mild elevation of mitochondrial ROS (mtROS) by distinct mechanisms. Metformin inhibits complex I of the mitochondrial electron transport chain (ETC), while CO inhibits ETC complex IV. Both metformin and CO can differentially induce several protein factors, including fibroblast growth factor 21 (FGF21) and sestrin2 (SESN2), which maintain metabolic homeostasis; nuclear factor erythroid 2-related factor 2 (Nrf2), a master regulator of the antioxidant response; and REDD1, which exhibits an anticancer effect. However, metformin and CO regulate these effects via different pathways. Metformin stimulates p53- and AMPK-dependent pathways whereas CO can selectively trigger the PERK-dependent signaling pathway. Although further studies are needed to identify the mechanistic differences between metformin and CO, pharmacological application of these agents may represent useful strategies to ameliorate metabolic diseases associated with altered immunometabolism.

Effects of heme oxygenase-1 upregulation on isoproterenol-induced myocardial infarction

The present study was designed to examine the effect of heme oxygenase-1 (HO-1) induction by cobalt protoporphyrin (CoPP) on the cardiac functions and morphology, electrocardiogram (ECG) changes, myocardial antioxidants (superoxide dismutase [SOD] and glutathione [GSH]), and expression of heat shock protein (Hsp) 70 and connexin 43 (Cx-43) in myocardial muscles in isoproterenol (ISO) induced myocardial infarction (MI). Thirty two adult male Sprague Dawely rats were divided into 4 groups (each 8 rats): normal control (NC) group, ISO group: received ISO at dose of 150 mg/kg body weight intraperitoneally (i.p.) for 2 successive days; ISO + Trizma group: received (ISO) and Trizma (solvent of CoPP) at dose of 5 mg/kg i.p. injection 2 days before injection of ISO, with ISO at day 0 and at day 2 after ISO injections; and ISO + CoPP group: received ISO and CoPP at a dose of 5 mg/kg dissolved in Trizma i.p. injection as Trizma. We found that, administration of ISO caused significant increase in heart rate, corrected QT interval, ST segment, cardiac enzymes (lactate dehydrogenase, creatine kinase-muscle/brain), cardiac HO-1, Hsp70 with significant attenuation in myocardial GSH, SOD, and Cx-43. On the other hand, administration of CoPP caused significant improvement in ECG parameters, cardiac enzymes, cardiac morphology; antioxidants induced by ISO with significant increase in HO-1, Cx-43, and Hsp70 expression in myocardium. In conclusions, we concluded that induction of HO-1 by CoPP ameliorates ISO-induced myocardial injury, which might be due to up-regulation of Hsp70 and gap junction protein (Cx-43).

CO-Releasing Molecule-2 Induces Nrf2/ARE-Dependent Heme Oxygenase-1 Expression Suppressing TNF-α-Induced Pulmonary Inflammation

The upregulation of heme oxygenase-1 (HO-1) by the carbon monoxide-releasing molecule (CORM)-2 may be mediated through the activation of nicotinamide adenine dinucleotide phosphate (NADPH) oxidases [Nox] and reactive oxygen species (ROS) generation, which could provide cytoprotection against various cellular injuries. However, the detailed mechanisms of CORM-2-induced HO-1 expression in human pulmonary alveolar epithelial cells (HPAEpiCs) remain largely unknown. Therefore, we dissected the mechanisms underlying CORM-2-induced HO-1 expression in HPAEpiCs. We found that the administration of mice with CORM-2 attenuated the tumor necrosis factor-alpha (TNF-α)-induced intercellular adhesion molecule-1 (ICAM-1) expression and leukocyte count as revealed by immunohistochemical staining, western blot, real-time polymerase chain reaction (PCR), and cell count. Furthermore, TNF-α-induced ICAM-1 expression associated with monocyte adhesion to HPAEpiCs was attenuated by infection with adenovirus (adv)-HO-1 or incubation with CORM-2. These inhibitory effects of HO-1 were reversed by pretreatment with hemoglobin (Hb). Moreover, CORM-2-induced HO-1 expression was mediated via the phosphorylation of p47^phox, c-Src, epidermal growth factor receptor (EGFR), Akt, and NF-E2-related factor 2 (Nrf2), which were inhibited by their pharmacological inhibitors, including diphenyleneiodonium (DPI) or apocynin (APO), ROS [N-acetyl-L-cysteine (NAC)], PP1, AG1478, PI3K (LY294002), or Akt (SH-5), and small interfering RNAs (siRNAs). CORM-2-enhanced Nrf2 expression, and anti-oxidant response element (ARE) promoter activity was also inhibited by these pharmacological inhibitors. The interaction between Nrf2 and AREs was confirmed with a chromatin immunoprecipitation (ChIP) assay. These findings suggest that CORM-2 increases the formation of the Nrf2 and AREs complex and binds with ARE-binding sites via Src, EGFR, and PI3K/Akt, which further induces HO-1 expression in HPAEpiCs. Thus, the HO-1/CO system might suppress TNF-α-mediated inflammatory responses and exert a potential therapeutic strategy in pulmonary diseases.

Alternate and Additional Functions of Erythrocyte Hemoglobin

The review discusses pleiotropic effects of erythrocytic hemoglobin (Hb) and their significance for human health. Hemoglobin is mostly known as an oxygen carrier, but its biochemical functions are not limited to this. The following aspects of Hb functioning are examined: (i) catalytic functions of the heme component (nitrite reductase, NO dioxygenase, monooxygenase, alkylhydroperoxidase) and of the apoprotein (esterase, lipoxygenase); (ii) participation in nitric oxide metabolism; (iii) formation of membrane-bound Hb and its role in the regulation of erythrocyte metabolism; (iv) physiological functions of Hb catabolic products (iron, CO, bilirubin, peptides). Special attention is given to Hb participation in signal transduction in erythrocytes. The relationships between various erythrocyte metabolic parameters, such as oxygen status, ATP formation, pH regulation, redox balance, and state of the cytoskeleton are discussed with regard to Hb. Hb polyfunctionality can be considered as a manifestation of the principle of biochemical economy.