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We examined whether haem oxygenase-1 (HO-1) could enhance the immunosuppressive effects of bone marrow mesenchymal stem cells (BMMSCs) on the rejection of transplanted liver allografts in rats. The animals were divided into three groups: the normal saline (NS) group, BMMSC group and HO-1/BMMSCs group. In vitro, the extraction, culture and HO-1 transfection of BMMSCs were performed. Mixed lymphocyte response (MLR) analysis of HO-1/BMMSCs efficacy was performed. The rejection model of orthotopic liver transplantation in rats was established when BMMSCs and HO-1/BMMSCs were transfused via the portal vein. To reduce research bias, we established an isogenic Liver transplantation model of (LEW → LEW) and (BN → BN), which can achieve tolerance. Changes in histopathology and liver function in the transplanted liver and changes in regulatory T cell (Tregs), natural killer (NK) cells and cytokines after transplantation were observed in the different groups. The severe acute rejection after liver transplantation on postoperative Day 10 was observed in the NS group. The BMMSC group showed strong protective effects against rejection within the first 10 days after transplantation, while HO-1/BMMSCs showed stronger effects on rejection than BMMSCs alone. In addition, the activity of natural killer (NK) cells decreased significantly, the levels of regulatory T cells (Tregs), interleukin-10 (IL-10) and transforming growth factor-β (TGF-β) increased significantly and the levels of interleukin-2 (IL-2), interleukin-6 (IL-6), interleukin-17 (IL-17), interleukin-23 (IL-23), tumour necrosis factor-α (TNF-α) and interferon-γ (IFN-γ) decreased significantly in the HO-1/BMMSC group compared with the BMMSC group. HO-1/BMMSCs showed better immunosuppressive effects after liver transplantation than the other treatments. Our findings reveal that HO-1 can enhance the effects of BMMSCs on inhibiting acute rejection in orthotopic liver transplantation in rats., (© 2022. The Author(s).)

Nephrotoxicity is an indication for the damage of kidney-specific detoxification and excretion mechanisms by exogenous or endogenous toxicants. Exposure to vancomycin predominantly results in renal damage and losing the control of body homeostasis. Vancomycin-treated rats (200 mg/kg/once daily, for seven consecutive days, i.p.) revealed significant increase in serum pivotal kidney function, oxidative stress, and inflammatory biomarkers. Histologically, vancomycin showed diffuse acute tubular necrosis, denudation of epithelium and infiltration of inflammatory cells in the lining tubular epithelium in cortical portion. In the existing study, the conservative consequences of scopoletin against vancomycin nephrotoxicity was investigated centering on its capacity to alleviate oxidative strain and inflammation through streamlining nuclear factor (erythroid-derived-2) like 2 (Nrf2)/heme oxygenase-1 (HO-1) signaling and prohibiting the nuclear factor kappa B (NF-κB)/mitogen-activated protein kinase (p38 MAPK) pathway. With respect to vancomycin group, scopoletin pretreatment (50 mg/kg/once daily, i.p.) efficiently reduced kidney function, oxidative stress biomarkers and inflammatory mediators. Moreover, histological and immunohistochemical examination of scopoletin-treated group showed remarkable improvement in histological structure and reduced vancomycin-induced renal expression of iNOS, NF-κB and p38 MAPK. In addition, scopoletin downregulated (Kelch Like ECH Associated Protein1) Keap1, P38MAPK and NF-κB expression levels while upregulated renal expression levels of regulatory protein (IκBα), Nrf2 and HO-1. Furthermore, molecular docking and network approach were constructed to study the prospect interaction between scopoletin and the targeted proteins that streamline oxidative stress and inflammatory pathways. The present investigations elucidated that scopoletin co-treatment with vancomycin may be a rational curative protocol for mitigation of vancomycin-induced renal intoxication., (Copyright © 2021. Published by Elsevier B.V.)

This review examines the beneficial effects of ultraviolet radiation on systemic autoimmune diseases, including multiple sclerosis and type I diabetes, where the epidemiological evidence for the vitamin D-independent effects of sunlight is most apparent. Ultraviolet radiation, in addition to its role in the synthesis of vitamin D, stimulates anti-inflammatory pathways, alters the composition of dendritic cells, T cells, and T regulatory cells, and induces nitric oxide synthase and heme oxygenase metabolic pathways, which may directly or indirectly mitigate disease progression and susceptibility. Recent work has also explored how the immune-modulating functions of ultraviolet radiation affect type II diabetes, cancer, and the current global pandemic caused by SARS-CoV-2. These diseases are particularly important amidst global changes in lifestyle that result in unhealthy eating, increased sedentary habits, and alcohol and tobacco consumption. Compelling epidemiological data shows increased ultraviolet radiation associated with reduced rates of certain cancers, such as colorectal cancer, breast cancer, non-Hodgkins lymphoma, and ultraviolet radiation exposure correlated with susceptibility and mortality rates of COVID-19. Therefore, understanding the effects of ultraviolet radiation on both vitamin D-dependent and -independent pathways is necessary to understand how they influence the course of many human diseases., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Background: Current treatments of lipopolysaccharide (LPS)-induced acute lung injury (ALI) are unsatisfactory due to the insufficient understanding of the pathogenesis of LPS-induced ALI. The NLRP3 inflammasome is an essential part of the innate protection system and is involved in LPS-induced ALI; however, comprehensive understanding of molecular pathogenesis of the disease is lacking. Our study explored the effect of heme oxygenase-1 (HO-1) on NLRP3 inflammasomes in vitro., Methods: Alveolar macrophages (NR8383) were preincubated with high-mobility group box-1 (HMGB1) or HO-1 CRISPR plasmids before LPS stimulation. Then, we detected the effect of HO-1 on NLRP3 inflammasomes., Results: Our study demonstrates that the activation of HO-1 represses the level of NLRP3 inflammasomes and the subsequent increases of the level of IL-1β. Moreover, NLRP3 inflammasome activation was sensitive to the HMGB1 activity, and HO-1 was able to reduce the amount of HMGB1 released. Furthermore, downregulation of NLRP3 inflammasomes was related to NADPH quinone oxidoreductase 1 (an HO-1-related gene)., Conclusions: Our study clarifies the constrained coordination of the HO-1 signal in the HMGB1-mediated activation of NLRP3 inflammasomes in NR8383 alveolar macrophages after LPS stimulation., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Objective: Chicoric acid (CA) is a natural product with promising antioxidant and anti-inflammatory properties; however, its protective effect on methotrexate (MTX)-induced acute kidney injury (AKI) hasn't been reported. We investigated the effect of CA on MTX-induced AKI in rats, pointing to the role of NF-κB/NLRP3 inflammasome and Nrf2/ARE/HO-1 signaling., Materials and Methods: Wistar rats received 25 mg/kg and 50 mg/kg CA for 15 days and a single injection of MTX at day 16. At day 19, the rats were killed, and samples were collected for analyses., Results: MTX induced a significant increase in serum creatinine and urea, and kidney Kim-1, reactive oxygen species (ROS), malondialdehyde and nitric oxide levels. In addition, MTX-induced rats exhibited multiple histopathological alterations, diminished antioxidant defenses, and decreased expression of Nrf2, NQO-1 and HO-1. CA prevented histological alterations, ameliorated kidney function markers, attenuated ROS production and lipid peroxidation, and boosted antioxidant defenses. CA suppressed the expression of NF-κB p65, NLRP3, caspase-1 and IL-1β in the kidney of MTX-induced rats. Furthermore, CA inhibited MTX-induced apoptosis as evidenced by the decreased expression of BAX and caspase-3, and increased Bcl-2 gene expression., Conclusions: CA prevented MTX-induced AKI through activation of Nrf2/ARE/HO-1 signaling, and attenuation of ROS-induced activation of NF-κB/NLRP3 inflammasome signaling.

Background: Idiopathic inflammatory myopathies (IIM) are a group of autoimmune diseases characterized by muscle disorders. We conducted this study to detect whether NF-E2-related factor 2 (Nrf2) pathway inhibit inflammatory infiltration by macrophage in experimental autoimmune myositis (EAM) rat model., Methods: CD163 levels were examined by immunohistochemistry (IHC), while serum creatine kinase (CK), reactive oxygen species (ROS), and serum monocyte chemoattractant protein-1 (MCP-1), tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) levels were determined by enzyme linked immunosorbnent assay (ELISA), both in IIM patients and EAM rat. We also detected MCP-1, TNF-α, IL-6, and Nrf2 levels by Realtime quantitative PCR (RT-PCR) in patients' muscles, and MCP-1, TNF-α, IL-6, and Nrf2, HO-1, NQO-1 levels by RT-PCR and Western blot in EAM rats' muscles. EAM macrophages were separated, and Nrf2 over-expression macrophages were constructed. ROS level and cell migration were detected by flow cytometer and transwell assay respectively. Then, levels of MCP-1, TNF-α, IL-6, Nrf2, Heme oxygenase-1 (HO-1) and NAD(P)H: quinine oxidoreductase 1 (NQO-1) were detected by RT-PCR and Western blot., Results: Results showed that EAM rats were histopathologically inflammatory cell infiltration. Levels of CD163, serum CK and ROS, serum/muscle MCP-1, TNF-α and IL-6 increased and muscle Nrf2 level decreased in IIM patients and EAM rats. Cell migration ability and levels of ROS, MCP-1, TNF-α, IL-6, and plasma Nrf2 were down-regulated, and total/nucleus Nrf2, HO-1, NQO-1 were up-regulated notably when Nrf2 over-expressed., Conclusion: Nrf2 inhibited EAM macrophage infiltration by activating Nrf2/ARE pathway which could induce ROS degradation and inhibit pro-inflammatory factors expression., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Carbon monoxide (CO) is an anti-inflammatory gaseous molecule produced endogenously by heme oxygenases (HOs) HO-1 and HO-2. However, the mechanisms underlying the anti-inflammatory effects of CO in the human bronchial epithelium are still not fully understood. In this study, the cationic peptide poly-l-arginine (PLA) was utilized to induce bronchial epithelial damage and subsequent pro-inflammatory cytokine release in the human bronchial epithelial cell line 16HBE14o-. Expression of both HO-1 and HO-2 after PLA exposure was examined. The polarized secretion of two pro-inflammatory cytokines, interleukin (IL)-6 and IL-8, was determined by ELISA. The anti-inflammatory effects of CO liberated from CO-releasing molecules (CORMs) were examined by both ELISA and western blot analysis. Our results indicate that PLA exposure leads to upregulation of HO-1 expression and p65 NF-κB phosphorylation, as well as IL-6 and IL-8 release. HO-1 induction by hemin or CORMs significantly suppressed IL-6 and IL-8 release. In addition, HO-1 knockdown further increased IL-6 and IL-8 release under basal and PLA-stimulated conditions. Our results thereby demonstrate that the HO-1/CO axis exerts significant anti-inflammatory activity during bronchial epithelial damage caused by cationic protein., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

The heme oxygenase (HO) system is an important regulatory arm of the intrinsic cytoprotective and anti-inflammatory system. HO-2 plays an important role in regulating inflammation following injury. The aim of this study was to evaluate the effect of HO-2 overexpression on inflammatory responses. A skin transplantation model, involving the application of skin grafts from wild-type or HO-2 overexpressing mice to BALB/c mice, was used for investigation. HO-2 overexpression suppressed the production of pro-inflammatory cytokines (IL-1β, TNF-α, and IL-6) in macrophages compared to that in macrophages obtained from control mice. HO-2 overexpression also significantly prolonged the survival of allografted skin. Our findings suggest that HO-2 attenuates inflammatory responses and effectively prolongs skin graft survival., (Copyright © 2018 Elsevier B.V. All rights reserved.)

The present study was carried out to investigate the anti-arthritic activity of Berberis aristata hydroalcoholic extract (BAHE) in formaldehyde-induced arthritis and adjuvant-induced arthritis (AIA) model. Arthritis was induced by administration of either formaldehyde (2% v/v) or CFA into the subplantar surface of the hind paw of the animal. In formaldehyde-induced arthritis and AIA, treatment of BAHE at doses 50, 100 and 200 mg/kg orally significantly decreased joint inflammation as evidenced by decrease in joint diameter and reduced inflammatory cell infiltration in histopathological examination. BAHE treatment demonstrated dose-dependent improvement in the redox status of synovium (decrease in GSH, MDA, and NO levels and increase in SOD and CAT activities). The beneficial effect of BAHE was substantiated with decreased expression of inflammatory markers such as IL-1β, IL-6, TNF-R1, and VEGF by immunohistochemistry analysis in AIA model. BAHE increased HO-1/Nrf-2 and suppressed NF-κB mRNA and protein expression in adjuvant immunized joint. Additionally, BAHE abrogated degrading enzymes, as there was decreased protein expression of MMP-3 and -9 in AIA. In conclusion, we demonstrated the anti-arthritic activity of Berberis aristata hydroalcoholic extract via the mechanism of inhibition of NF-κB and activation of Nrf-2/HO-1.

Induction of mammalian heme oxygenase (HO)-1 and exposure of animals to carbon monoxide (CO) ameliorates experimental colitis. When enteric bacteria, including Escherichia coli, are exposed to low iron conditions, they express an HO-like enzyme, chuS, and metabolize heme into iron, biliverdin and CO. Given the abundance of enteric bacteria residing in the intestinal lumen, our postulate was that commensal intestinal bacteria may be a significant source of CO and those that express chuS and other Ho-like molecules suppress inflammatory immune responses through release of CO. According to real-time PCR, exposure of mice to CO results in changes in enteric bacterial composition and increases E. coli 16S and chuS DNA. Moreover, the severity of experimental colitis correlates positively with E. coli chuS expression in IL-10 deficient mice. To explore functional roles, E. coli were genetically modified to overexpress chuS or the chuS gene was deleted. Co-culture of chuS-overexpressing E. coli with bone marrow-derived macrophages resulted in less IL-12p40 and greater IL-10 secretion than in wild-type or chuS-deficient E. coli. Mice infected with chuS-overexpressing E. coli have more hepatic CO and less serum IL-12 p40 than mice infected with chuS-deficient E. coli. Thus, CO alters the composition of the commensal intestinal microbiota and expands populations of E. coli that harbor the chuS gene. These bacteria are capable of attenuating innate immune responses through expression of chuS. Bacterial HO-like molecules and bacteria-derived CO may represent novel targets for therapeutic intervention in inflammatory conditions., (© 2015 The Societies and Wiley Publishing Asia Pty Ltd.)

Cochlear inflammatory diseases, such as tympanogenic labyrinthitis, are associated with acquired sensorineural hearing loss. Although otitis media is extremely frequent in children, tympanogenic labyrinthitis is not commonly observed, which suggests the existence of a potent anti-inflammatory mechanism modulating cochlear inflammation. In this study, we aimed to determine the molecular mechanism involved in cochlear protection from inflammation-mediated tissue damage, focusing on IL-10 and hemoxygenase-1 (HMOX1) signaling. We demonstrated that IL-10Rs are expressed in the cochlear lateral wall of mice and rats, particularly in the spiral ligament fibrocytes (SLFs). The rat SLF cell line was found to inhibit nontypeable Haemophilus influenzae (NTHi)-induced upregulation of monocyte chemotactic protein-1 (MCP-1; CCL2) in response to IL-10. This inhibition was suppressed by silencing IL-10R1 and was mimicked by cobalt Protoporphyrin IX and CO-releasing molecule-2. In addition, IL-10 appeared to suppress monocyte recruitment through reduction of NTHi-induced rat SLF cell line-derived chemoattractants. Silencing of HMOX1 was found to attenuate the inhibitory effect of IL-10 on NTHi-induced MCP-1/CCL2 upregulation. Chromatin immunoprecipitation assays showed that IL-10 inhibits NTHi-induced binding of p65 NF-κB to the distal motif in the promoter region of MCP-1/CCL2, resulting in suppression of NTHi-induced NF-κB activation. Furthermore, IL-10 deficiency appeared to significantly affect cochlear inflammation induced by intratympanic injections of NTHi. Taken together, our results suggest that IL-10/HMOX1 signaling is involved in modulation of cochlear inflammation through inhibition of MCP-1/CCL2 regulation in SLFs, implying a therapeutic potential for a CO-based approach for inflammation-associated cochlear diseases., (Copyright © 2015 by The American Association of Immunologists, Inc.)

Smoke inhalation injury represents a major cause of mortality in burn patients and is associated with a high incidence of pulmonary complications. Glutamine (GLN) is considered a conditionally essential amino acid during critical illness and injury. However, whether GLN could attenuate lung injury caused by smoke inhalation is still unknown. The purpose of this study is to investigate whether GLN has a beneficial effect on smoke inhalation induced lung injury. In our present work, rats were equally randomized into three groups: Sham group (ambient air inhalation plus GLN treatment), Control group (smoke inhalation plus physiological saline) and GLN treatment group (smoke inhalation injury plus GLN treatment). At sampling, bronchoalveolar lavage fluid was performed to determine total protein concentration and pro-inflammatory cytokine levels. Lung tissues were collected for wet/dry ratio, histopathology, hydroxyproline and Western blotting measurement. Our results exhibited that GLN attenuated the lung histopathological alterations, improved pulmonary oxygenation, and mitigated pulmonary edema. At 28days post-injury, GLN mitigated smoke inhalation-induced excessive collagen deposition as evidence by Masson-Goldner trichrome staining and hydroxyproline content. GLN mitigated smoke inhalation-induced lung inflammatory response, and further prevented the activity of NF-kappa-B. More importantly, results from Western blotting and Immunohistochemistry exhibited that GLN enhanced the expression of HSF-1, HSP-70 and HO-1 in lung tissues. Our data demonstrated that GLN protected rats against smoke inhalation-induced lung injury and its protective mechanism seems to involve in inhibition inflammatory response and enhancing HSP expression., (Crown Copyright © 2013. Published by Elsevier B.V. All rights reserved.)

The anti-inflammatory effects of globular adiponectin (gAcrp) are mediated by IL-10/heme oxygenase 1 (HO-1)-dependent pathways. Although full-length (flAcrp) adiponectin also suppresses LPS-induced pro-inflammatory signaling, its signaling mechanisms are not yet understood. The aim of this study was to examine the differential mechanisms by which gAcrp and flAcrp suppress pro-inflammatory signaling in macrophages. Chronic ethanol feeding increased LPS-stimulated TNF-α expression by Kupffer cells, associated with a shift to an M1 macrophage polarization. Both gAcrp and flAcrp suppressed TNF-α expression in Kupffer cells; however, only the effect of gAcrp was dependent on IL-10. Similarly, inhibition of HO-1 activity or siRNA knockdown of HO-1 in RAW264.7 macrophages only partially attenuated the suppressive effects of flAcrp on MyD88-dependent and -independent cytokine signatures. Instead, flAcrp, acting via the adiponectin R2 receptor, potently shifted the polarization of Kupffer cells and RAW264.7 macrophages to an M2 phenotype. gAcrp, acting via the adiponectin R1 receptor, was much less effective at eliciting an M2 pattern of gene expression. M2 polarization was also partially dependent on AMP-activated kinase. flAcrp polarized RAW264.7 macrophages to an M2 phenotype in an IL-4/STAT6-dependent mechanism. flAcrp also increased the expression of genes involved in oxidative phosphorylation in RAW264.7 macrophages, similar to the effect of flAcrp on hepatocytes. In summary, these data demonstrate that gAcrp and flAcrp utilize differential signaling strategies to decrease the sensitivity of macrophages to activation by TLR4 ligands, with flAcrp utilizing an IL-4/STAT6-dependent mechanism to shift macrophage polarization to the M2/anti-inflammatory phenotype.

Objective: Systemic inflammatory response following ischemia-reperfusion injury (IRI) to a specific organ may cause injuries in multiple remote organs. The emergence of ischemic postconditioning (IPO) provides a potential method for experimentally and clinically attenuating various types of organ postischemic injuries. We have shown that IPO can attenuate lung IRI by up-regulating the protein expression of heme oxygenase-1(HO-1). This study tested the hypothesis that IPO attenuates systemic inflammatory responses following lung IRI by activating HO-1., Methods: Anaesthetized and mechanically ventilated adult Sprague-Dawley rats were randomly assigned to one of the following groups (n = 8 each): the sham-operated control group, the ischemia-reperfusion (IR) group (40 min of left-lung ischemia and 120 min of reperfusion), the IPO group (three successive cycles of 30-s reperfusion per 30-s occlusion before restoring full perfusion), and the zinc protoporphyrin IX (ZnP) plus IPO group (ZnP, an inhibitor of HO-1, was injected intraperitoneally at 20 mg/kg 24 h prior to the experiment, and the rest of the procedures were similar to that of the IPO group). Lung injury was assessed by arterial blood gas analysis, wet-to-dry lung weight ratio and tissue histologic and biochemical changes. The lung tissue and plasma levels of lipid peroxidation were determined by measuring the contents of malondialdehyde (MDA) production. Protein expression of HO-1 was determined by Western blotting. Pulmonary neutrophil was counted. Lung tissue myeloperoxidase (MPO) activity as well as plasma levels of proinflammatory cytokines tumor necrosis factor-α (TNF-α), interleukines 6 and 8 (IL-6, IL-8) were determined by spectrophotography., Results: Lung ischemia-reperfusion led to severe lung pathologic morphologic changes and increased pulmonary MDA production, neutrophil count, and MPO activity and reduced arterial oxygen partial pressure (all P < 0.05 IR versus sham), accompanied with a compensatory increase in HO-1 protein and activity. Plasma levels of TNF-α, IL-6, and IL-8 were increased in the IR group (all P < 0.05 versus sham). IPO attenuated or prevented all the above changes, except that it further increased lung HO-1 activity. Treatment with ZnP abolished all the protective effects of postconditioning., Conclusion: Postconditioning attenuated pulmonary neutrophil accumulation and activation and lung IRI and reduced systemic inflammatory responses by activating HO-1., (Copyright © 2011 Elsevier Inc. All rights reserved.)

Background: Heme oxygenase (HO)-1 protects transplanted organs from ischemia reperfusion injury and immune rejection. This study sought to investigate whether persistent overexpression of HO-1 in donor livers could improve the survival by expanding T regulatory cells in a rat model of orthotopic liver transplantation., Methods: Livers of Dark Agouti rats were intraportally perfused with an AAV expression vector encoding rat HO-1 (AAV-HO-1), and then transplanted into Lewis rats. The survival, HO-1 activity, Banff rejection activity index, serum levels of IL-2 and TNF-α, infiltration of CD4(+), CD8(+), and T(reg) (CD4(+)CD25(+)Foxp3(+)) cells into donor livers, and expression of Foxp3, TGF-β, and IL-10 were examined. A mixed lymphocyte reaction (MLR) was performed., Results: Intraportal delivery of AAV-HO-1 resulted in persistent expression of HO-1 and increased activity of HO-1 in transplanted livers, leading to prolonged survival of recipients. Overexpression of HO-1 reduced the Banff rejection activity index, and production of IL-2 and TNF-α, inhibited infiltration of CD4(+) and CD8(+) cells, and increased infiltration of T(reg) cells, into donor livers. The spleens of recipients expressed higher levels of Foxp3, TGF-β, and IL-10 than those of control rats, and the transplanted livers expressed higher levels of Foxp3 and TGF-β. Splenocytes from the tolerant recipients had higher percentages of T(reg) cells, and responded poorly to the allogeneic donor splenocytes., Conclusions: Persistent expression of HO-1 in donor livers by intraportal delivery of AAV-HO-1 improves the survival by expanding T(reg) cells. HO-1-based therapies, as described herein, promise new strategies to prevent the rejection of liver transplants., (Copyright © 2011 Elsevier Inc. All rights reserved.)

The synthetic triterpenoid, CDDO-Me, has potent antiproliferative and antioxidant properties. However, its immunomodulatory effects in the context of LPS challenge are incompletely defined. Pretreatment with oral CDDO-Me significantly improved survival following lethal-dose LPS challenge in mice. To define this protection further, we measured effects of CDDO-Me pretreatment on splenocyte populations and cytokine production following LPS challenge, using low-level LPS pretreatment as an in vivo control for reducing cytokine production. Despite similar decreases in levels of LPS-inducible, circulating proinflammatory cytokines (IL-12p70, IFN-gamma, IL-6, IL-17, and IL-23) and increases in heme oxygenase 1 (HO-1) protein expression, low-dose LPS and CDDO-Me pretreatments markedly differed in their overall response profiles. Splenocytes from LPS-pretreated mice contained reduced numbers of dendritic cells, increased percentages of Th17 and T-regulatory cells, lower levels of TLR-inducible IL-6, and higher levels of TLR-inducible IL-10. In contrast, CDDO-Me protection against LPS challenge had no impact on absolute numbers or distribution of splenocyte subsets, despite attenuating in vivo induction of proinflammatory cytokines in an IL-10-independent manner. Together, these results suggest that CDDO-Me pretreatment uniquely confers protection against LPS challenge by modulating the in vivo immune response to LPS. Thus, CDDO-Me potentially represents a novel oral agent for use in LPS-mediated inflammatory diseases.

Having previously demonstrated that heme oxygenase (HO) is expressed on invasive trophoblast within the human placental bed, we have now further hypothesised that HO may play a role in trophoblast invasion. To begin to test this hypothesis we have used a well characterised in vitro model of trophoblast invasion to determine whether antibodies raised against HO-1 and HO-2, or selective inhibition of HO with the HO inhibitor zinc protoporhyrin-9 (Zn PP-9), would affect the invasive ability of trophoblast cells. Cytotrophoblast cells were purified from term human placenta then cultured on Matrigel-coated chambers in the presence or absence of HO antibodies or Zn PP-9. The HO-1 antibody had no effect on invasion whereas the presence of the HO-2 antibody significantly inhibition invasion (p<0.05). The presence of Zn PP-9 resulted in a significant reduction in invasion (p<0.05) whereas the vehicle alone had no effect. Taken together these results suggest, that at least in vitro, HO-2 may be important in controlling trophoblast invasion.

Accommodation refers to the condition in which an organ transplant functions normally by acquiring resistance to immune-mediated injury (especially), despite the presence of anti-transplant antibodies in the recipient. This status is associated with several modifications in the recipient as well as in the graft, such as previous depletion of anti-graft antibodies and their slow return once the graft is placed; expression of several protective genes in the graft; a Th2 immune response in the recipient; and inhibition of the membrane attack complex of complement.

Gut mucosal injury observed during ischemia-reperfusion is believed to trigger a systemic inflammatory response leading to multiple organ failure. It should be interesting to demonstrate this relationship between gut and multiple organ failure in a sepsis model. Intestinal preconditioning (PC) can be used as a tool to assess the effect of intestinal ischemia in inflammatory response after LPS challenge. The aim of this study was to investigate the protective effect of PC against LPS-induced systemic inflammatory and intestinal heme oxygenase-1 (HO-1) expression. ES was performed with LPS (10 mg/kg iv) with or without PC, which was done before LPS. Rats were first subjected to sham surgery or PC with four cycles of 1 min ischemia and 4 min of reperfusion 24 h before LPS challenge or saline administration. PC significantly reduced fluid requirements, lung edema, intestinal lactate production, and intestinal injury. Inflammatory mRNA expressions for intestine and lung ICAM and TNF were significantly reduced after PC, and these effects were significantly abolished by zinc-protoporphyrin (a specific HO-1 activity inhibitor) and mimicked by bilirubin administration. Intestinal PC selectively increased HO-1 mRNA expression in intestine, but we have observed no expression in lungs. These findings demonstrate that intestinal injury is a important event for inflammatory response and multiple organ injury after LPS challenge. Intestinal HO-1 expression attenuates LPS-induced multiple organ failure by modulating intestine injury and its consequences on inflammatory response. Identification of the exact mechanisms responsible for intestine HO-1 induction may lead to the development of new pharmacological interventions.

Heme oxygenase-1 (HO-1) is an intracellular enzyme that degrades heme and inhibits immune responses and inflammation in vivo. In most cell types, HO-1 is inducible by inflammatory stimuli and oxidative stress. Here we demonstrate that human monocyte-derived immature dendritic cells (iDCs) and several but not all freshly isolated rat splenic DC subsets and rat bone marrow-derived iDCs, spontaneously express HO-1. HO-1 expression drastically decreases during human and rat DC maturation induced in vitro. In human tissues, iDCs also express HO-1, whereas mature DCs do not. Induction of HO-1 expression with cobalt protoporphyrin (CoPP) in human and rat DCs inhibits lipopolysaccharide (LPS)-induced phenotypic maturation and secretion of proinflammatory cytokines, resulting in the inhibition of alloreactive T-cell proliferation. CoPP-treated DCs, however, retain the ability to produce the anti-inflammatory cytokine interleukin 10 (IL-10). Reactive oxygen species induced by LPS in DCs were inhibited by induction of HO-1. In conclusion, we identify, for the first time, the capacity of HO-1 to block maturation of DCs and to inhibit proinflammatory and allogeneic immune responses while preserving IL-10 production. This novel immune function for HO-1 may be of interest for the inhibition of immune responses in autoimmune diseases, transplantation, and other conditions involving activation of the immune system.

Haem-oxygenase-1 (HO-1) has been shown to exert anti-inflammatory, anti-apoptotic and anti-proliferative effects. We investigated HO-1 expression in patients with inflammatory bowel disease (IBD) and could demonstrate a scattered expression of HO-1 in the intestinal epithelium of severely inflamed colonic mucosa of patients with IBD compared to control specimens such as diverticulitis, suggesting dysregulated expression in IBD. To further analyse potential mechanisms of HO-1 induction in the intestine we employed an in vitro epithelial cell apoptosis model and an experimental colitis model. In vitro induction of HO-1 by the HO-1 inducer cobalt protoporphyrin (CoPP) resulted in a dose-dependent down-regulation of caspase-3 activation in HT-29 cells, indicating an anti-apoptotic function of HO-1 in the intestine. In vivo, preventive HO-1 induction by CoPP in acute dextran sodium sulphate (DSS)-induced colitis led to a significant down-regulation of colonic inflammation (P < 0.01) with a concomitant reduction in interferon (IFN)-gamma - but unaffected interleukin (IL)-10-secretion by isolated mesenteric lymph nodes (P < 0.01). Additionally, TUNEL staining of colonic sections demonstrated fewer apoptotic epithelial cells in the colon of CoPP treated animals. No beneficial effects were observed if HO-1 was induced by CoPP after the onset of acute colitis or in chronic DSS-induced colitis. In conclusion, the data suggest a protective role of HO-1 if it is induced before the onset of inflammation. However, as shown by the lack of effects in established acute or in chronic colitis, the induction of HO-1 may not be a promising approach for the treatment of IBD.

There is accumulating evidence that haem oxygenase (HO)-1 plays a protective role in various disorders. The beneficial efficacy of HO-1 induction therapy has been shown in renal diseases such as glomerulonephritis, interstitial nephritis and drug induced nephrotoxicity. However, involvement of HO-1 in the development of autoimmune renal diseases remains uncertain. To assess the clinical efficacy of HO-1 induction therapy for lupus glomerulonephritis, MRL/lpr mice were intraperitoneally injected with 100 micromol/kg hemin, a potent HO-1 inducer, or PBS as controls, once a week from 6 weeks of age to 21-24 weeks-old. We found that treatment with hemin led to a significant reduction of proteinuria and remarkable amelioration of glomerular lesions accompanied by decreased immune depositions. In addition, the circulating IgG anti-double-stranded DNA antibody level was significantly decreased in hemin treated mice when compared with controls. A single intraperitoneal injection with hemin resulted in reduction of inducible nitric oxide synthase expression in the kidney and spleen, and serum interferon-gamma level. Our results suggest that HO-1 induction therapy ameliorates lupus nephritis by suppressing nitric oxide (NO) dependent inflammatory responses and attenuating production of pathogenic autoantibodies.

Antioxidant enzymes, including heme oxygenase (HO)-1, are an important line of defense against oxidant-mediated liver injury. Because hepatitis C virus (HCV) infection appears to increase the production of oxidants, we evaluated levels of antioxidant enzymes and HO-1 in liver-biopsy samples from HCV-infected patients by immunoblot and semiquantitative reverse-transcriptase polymerase chain reaction. In HCV-infected liver samples, levels of immunoreactive HO-1 and HO-1 mRNA were >4-fold lower than levels in control samples, but levels of superoxide dismutase and catalase were unaffected. Immunohistochemical results confirmed the decreased expression of HO-1 in hepatocytes from liver samples from HCV-infected patients but not in those from patients with other chronic liver diseases. The expression of HO-1 was also reduced in cell lines that stably express HCV core protein, which suggests that core gene products are capable of regulating the expression of HO-1.

Inflammation and oxidative stress play important roles in cystic fibrosis (CF) lung disease. Inflammatory/oxidant-mediated induction of heme oxygenase-1 (HO-1) is believed to be a cytoprotective response. This study examined HO-1 expression in lung samples from patients with CF using immunohistochemistry and quantitative reverse transcription-polymerase chain reaction. In addition, we evaluated myeloperoxidase staining as a marker of acute inflammation and potentially an increase in oxidant stress and Prussian blue and ferritin staining to assess iron status of the lung. Macrophage HO-1 staining was increased in diseased lungs as compared with normal control subjects and correlated with myeloperoxidase staining. Quantitative reverse transcription-polymerase chain reaction further supported an increase in HO-1 expression in CF lung disease. Although iron staining was minimal, ferritin staining was increased in diseased lungs in concert with HO-1 staining. To determine whether HO-1 induction was cytoprotective, we evaluated a CF airway epithelial cell line, IB3.1, in response to Pseudomonas aeruginosa-induced injury/apoptosis in cells overexpressing HO-1 by either transient or stable transfection of pcDNA3.1/HO-1 construct. Overexpression of HO-1 resulted in protection against P. aeruginosa-induced injury/apoptosis. This suggests that the induction of HO-1 in patients with CF is a cytoprotective event and that augmenting its expression is a potential therapy against bacterial injury.

Heme-oxygenase 1 (HO-1) is a stress-response protein with anti-inflammatory activity. This study has examined the regulation of HO-1 expression by the anti-inflammatory factor, interleukin (IL)-10 and whether HO-1 could account for the function of the cytokine. IL-10-induced expression of HO-1 required the activation of signal transducer and activator of transcription (STAT)-3 but not p38 mitogen-activated protein kinase. However, expression of HO-1 also required the activation of the phosphatidylinositol-3 kinase pathway, a signaling mechanism not required for the anti-inflammatory activity of IL-10. Moreover, induction of HO-1 expression was not restricted to IL-10, as IL-6, a cytokine known to activate STAT-3, could also induce the protein. In human macrophages, lipopolysaccharide inhibited HO-1 expression induced by IL-10. Also, inhibition of HO-1 activity by the specific inhibitor zinc-II-protoporphyrin-IX had no effect on the anti-inflammatory function of IL-10. In summary, although IL-10 does regulate HO-1 expression, it does not appear to play a significant role in the anti-inflammatory activity of the cytokine.

Acute graft-versus-host disease (aGVHD) remains one of the main obstacles after allogeneic bone marrow transplantation (BMT). Using a well-established mouse BMT model in which aGVHD is induced across a haploidentical mismatch, we show that the expression of heme oxygenase-1 (HO-1) can be induced by cobalt-protoporphyrin IX (CoPP) in aGVHD target organs such as liver and bowel and that the induction of HO-1 before BMT results in improved overall survival and reduced aGVHD. Serum levels of proinflammatory cytokines were markedly reduced in CoPP-treated animals. Recipients displayed less damage to the intestinal mucosa, and this resulted in reduced serum lipopolysaccharide levels at day 6 after transplantation. Peritoneal cells and CD45(+) liver cells isolated from mice that received transplants strongly expressed HO-1 and displayed a reduction in the expression of activation markers such as CD11b, CD80, and major histocompatibility complex class I. This resulted in reduced T-cell activation ex vivo. These results demonstrate that the induction of HO-1 before high-dose conditioning protects the host in multiple ways and effectively ameliorates aGVHD.

Heme oxygenase (HO) degrades heme to carbon monoxide (CO), ferrous ions, and the bile pigment biliverdin, which is subsequently reduced to the other important bile pigment, bilirubin, by biliverdin reductase. Fe2+ liberated from the heme molecule upregulates ferritin production, and bile pigments are potent endogenous antioxidants. The HO enzyme exists in three isophorms: HO-1 is expressed at low levels under physiological conditions, but is induced by numerous factors, including oxidative stress, inflammation, nitric oxide, an elevated level of substrate, and hypoxia. HO-2 is a constitutive enzyme involved in the baseline production of CO in the cardiovascular and nervous systems, whereas HO-3 is also ubiquitously expressed, but possesses low catalytic activity. Like nitric oxide, CO activates soluble guanylate cyclase and elevates cGMP in target tissues, which dilates blood vessels. It also does this by directly activating potassium channels in vascular smooth muscle cells. In addition, CO inhibits platelet aggregation and proliferation of vascular smooth muscle cells, inhibits apoptosis, and stimulates angiogenesis. Both deficiency, and excess of HO-1 may be involved in the pathogenesis of arterial hypertension. Induction of HO-1 attenuates atherosclerosis and myocardial ischemia-reperfusion injury. Pharmacological and genetic induction of HO-1 as well as the delivery of exogenous CO are promising therapeutic strategies for the treatment of cardiovascular diseases.

Interleukin-10 (IL-10), originally identified as an inhibitor of pro-inflammatory cytokine production, exerts multiple immunomodulatory functions. Its ability to inhibit a Th1 response has been used in clinical trials for the treatment of inflammatory diseases including psoriasis. However, little is known about the molecular mechanisms of IL-10 functions. We aimed at identifying possible mediators of in vitro IL-10 treatment in monocytes by gene chip technology using Hu95a Affymetrix mRNA arrays with 12,000 genes. To prove relevance of the identified genes for the clinical situation we compared these in vitro results with genes being regulated by IL-10 in peripheral blood mononuclear cells from psoriatic patients undergoing IL-10 therapy. A high proportion of the 1,600 genes up-regulated and 1,300 genes down-regulated in vitro was found to be similarly regulated in vivo. Some genes, which were previously unknown to be regulated by IL-10, can be assigned to known IL-10 functions like e.g. the increase of pathogen clearance. Other new potentially immunomodulating genes have been identified to be regulated by IL-10, but their impact needs to be experimentally evaluated. We could confirm a recently reported up-regulation of heme oxygenase-1 (HO-1). However, we demonstrate that the anti-inflammatory mechanisms of IL-10 remain functional even when HO-1 is irreversibly inhibited.

Heme oxygenase (HO)-1 catabolizes heme into three products: carbon monoxide (CO), biliverdin (which is rapidly converted to bilirubin) and free iron (which leads to the induction of ferritin, an iron-binding protein). HO-1 serves as a "protective" gene by virtue of the anti-inflammatory, anti-apoptotic and anti-proliferative actions of one or more of these three products. Administration of CO, biliverdin, bilirubin or iron-binding compounds is protective in rodent disease models of ischemia-reperfusion injury, allograft and xenograft survival, intimal hyperplasia following balloon injury or as seen in chronic graft rejection and others. We suggest that the products of HO-1 action could be valuable therapeutic agents and speculate that HO-1 functions as a "therapeutic funnel", mediating the beneficial effects attributed to other molecules, such as interleukin-10 (IL-10), inducible nitric oxide synthase (NOS2; iNOS) and prostaglandins. This Review is the third in a series on the regulation of the immune system by metabolic pathways.

Vascular tissues express heme oxygenase (HO), which metabolizes heme to form carbon monoxide (CO). CO relaxes vascular smooth muscle but inhibits nitric oxide (NO) formation. Decreased NO synthesis may contribute to salt-induced hypertension in Dahl salt-sensitive (DS) rats. The current study examines the hypothesis that elevated levels of endogenous CO contribute to NO dysfunction in salt-induced hypertensive DS rats. Male DS rats were placed on high-salt (8% NaCl, HS) or low-salt (0.3% NaCl, LS) diets for 4 weeks. With respect to the LS group, the HS group's blood pressure and carboxyhemoglobin levels were elevated, and abdominal aortas showed 6-fold higher HO-1 protein levels. Experiments used isolated pressurized first-order gracilis muscle arterioles superfused with oxygenated modified Krebs buffer. An inhibitor of NO synthase, Nomega-nitro-L-arginine methyl ester (L-NAME), caused concentration-dependent vasoconstriction in both groups, with attenuated responses in HS arterioles. HS arterioles also showed attenuated vasodilatory responses to an endothelium-dependent vasodilator, acetylcholine. Acute pretreatment with an inhibitor of HO, chromium mesoporphyrin, enhanced vascular responses to L-NAME and acetylcholine in both groups but abolished the differences between HS and LS arterioles. These data show that HO-1 protein levels and CO production are increased in HS rats. Arteriolar responses to L-NAME and acetylcholine are impaired in HS rats compared with LS animals, and this difference can be abolished by an inhibitor of endogenous CO production. These results suggest that elevated levels of endogenous CO contribute to arteriolar NO dysfunction in DS rats with salt-induced hypertension.

This study examined the role of bilirubin in heme oxygenase (HO)-1-mediated amelioration of mast cell (MC)-elicited inflammatory responses. Pretreatment of rats with an intraperitoneal injection of hemin, an inducer of HO-1, evolved a marked induction of the enzyme in MCs. Intravital videomicroscopy revealed that hemin pretreatment attenuated compound 48/80-elicited degranulation of MCs and resultant leukocyte adhesion in venules. Superfusion with biliverdin or bilirubin, but not with carbon monoxide (CO), another product of the HO reaction, mimicked suppressive actions of the HO-1 induction on both the cell degranulation and leukocyte adhesion elicited by the stimulus, suggesting a requirement of the enzyme reaction to generate bilirubin in the inhibitory mechanisms. Such MC-desensitizing actions of bilirubin were observed in primary-cultured MCs and reproduced irrespective of the choice of stimuli, such as compound 48/80, calcium ionophore, and anti-IgE serum. Furthermore, MC-stabilizing effects of HO-1 were reproduced by the gene transfection of the enzyme into mastocytoma cell line RBL2H3. These results suggest that bilirubin generated through HO-1 serves as an anti-inflammatory substance that desensitizes MCs and ameliorates leukocyte recruitment.

Background: Ischemia/reperfusion (I/R) injury remains an important clinical problem that affects both early and later allograft outcome. This study was designed to analyze the role of T cells and CD154-CD40 T- cell costimulation pathway in a mouse liver I/R model., Methods and Results: Ninety minutes of warm ischemia followed by 4 h of reperfusion in wild-type (WT) mice resulted in a significant hepatic damage, as assessed by liver function (serum alanine aminotransferase [sALT] levels), local neutrophil accumulation (myeloperoxidase activity), and histology (Suzuki's score). In contrast, T-cell deficiency (in T-cell deficient [nu/nu] mice), disruption of the CD154 signaling (in knockout [KO] mice), or its blockade in WT recipients (after MR1 monoclonal antibody [mAb] treatment), virtually prevented hepatic I/R insult. Unlike CD154-deficient T cells, adoptive transfer of WT spleen cells fully restored hepatic I/R injury in nu/nu mice. Finally, the improved hepatic function in CD154 KO recipients, WT mice treated with CD154 mAb, or nu/nu mice infused with CD154-deficient cells resulted in consistently enhanced expression of heme oxygenase-1 (HO-1), a heat-shock protein with cytoprotective functions., Conclusion: This study confirms the importance of T cells, and documents for the first time the role of CD154 costimulation signals in the mechanism of hepatic I/R injury. We also show that CD154 blockade-mediated cytoprotection results and depends on HO-1 overexpression. Our data provide the rationale for human trials to target CD154-CD40 costimulation in hepatic I/R injury, particularly in the transplant patient.

Endothelial cells (EC) play a pivotal role in regulating inflammatory reactions such as those involved in the rejection of transplanted organs. This occurs through the expression of a series of pro- and anti-inflammatory genes that are associated with the activation of these cells. Presumably, the expression of pro-inflammatory genes promotes events that lead to graft rejection, while expression of anti-inflammatory (protective) genes suppresses those events and thus contributes in sustaining graft survival. Understanding how the expression of these genes is regulated and their mechanism of action are important issues for the development of new therapeutic strategies to suppress graft rejection. We have studied this phenomenon using experimental models of transplantation in rats. We discuss here data that supports the concept that grafts can express anti-inflammatory (protective) genes that mitigate inflammatory reactions leading to graft rejection. The data reviewed focus on the role of one of such genes, the stress responsive gene heme oxygenase-1, and of its byproduct carbon monoxide, which can suppress graft rejection and lead to long-term graft survival.

Hemeoxygenase 1 (HO-1) has been implicated in the protection of lung tissue against exogenous oxidant exposure. However, the expression and cellular distribution of HO-1 in human lung continue to be poorly characterized. The localization of HO-1 was studied in histopathologically healthy lung from nonsmoking patients with a carcinoid or other lung tumor (5 cases), pulmonary sarcoidosis (13 cases), and chronic interstitial pneumonias (9 cases, usual interstitial pneumonia; 10 cases, desquamative interstitial pneumonia). Immunostaining was graded from 0 (no immunoreactivity) to +++ (intense immunoreactivity). In healthy lung, HO-1 was localized to alveolar macrophages with reactivity varying from moderate to intense, and in bronchial epithelium, alveolar epithelium, endothelium, and interstitium, the immunoreactivity was not detectable or was very low. Sarcoidosis and interstitial pneumonias showed intense HO-1 immunoreactivity in alveolar macrophages in most of the cases and weak to intense immunoreactivity in the granulomas of sarcoidosis. The immunoreactivity of interstitium was negative or weak in the fibrotic areas of the lung and also in the samples of bronchoalveolar lavage fluid obtained from the patients with UIP. Western blotting indicated that HO-1 is up-regulated by exposure of monocytes to formylated peptide, fMLP, which causes respiratory burst in the cells, and that inhibition of HO-1 by tin protoporphyrin potentiates the injury of fMLP-exposed cells. In conclusion, these data show differential distribution of HO-1 in human lung cells and strongly suggest the importance of HO-1, especially in the defense of alveolar macrophages in normal human lung and in the inflammatory, but not in the fibrotic, stage of interstitial lung disorders., (Copyright 2001 by W.B. Saunders Company)

Various pathologic conditions, such as hemorrhage, hemolysis and cell injury, are characterized by the release of large amounts of heme. Recently, it was demonstrated that heme oxygenase (HO), the heme-degrading enzyme, and heme are able to modulate adhesion molecule expression in vitro. In the present study, the effects of heme and HO on inflammation in mice were analyzed by monitoring the biodistribution of radiolabeled liposomes and leukocytes in conjunction with immunohistochemistry. Small liposomes accumulate in inflamed tissues by diffusion because of locally enhanced vascular permeability, whereas leukocytes actively migrate into inflammatory areas through specific adhesive interactions with the endothelium and chemotaxis. Exposure to heme resulted in a dramatic increase in liposome accumulation in the pancreas, but also intestines, liver, and spleen exhibited significantly increased vascular permeability. Similarly, intravenously administered heme caused an enhanced influx of radiolabeled leukocytes into these organs. Immunohistochemical analysis showed differential up-regulation of the adhesion molecules ICAM-1, P-selectin, and fibronectin in liver and pancreas in heme-treated animals. Heme-induced adhesive properties were accompanied by a massive influx of granulocytes into these inflamed tissues, suggesting an important contribution to the pathogenesis of inflammatory processes. Moreover, inhibition of HO activity exacerbated heme-induced granulocyte infiltration. Here it is demonstrated for the first time that heme induces increased vascular permeability, adhesion molecule expression, and leukocyte recruitment in vivo, whereas HO antagonizes heme-induced inflammation possibly through the down-modulation of adhesion molecules.

Preliminary studies showed that the inducible form of heme oxygenase (HO-1) was induced and played a protective role in the process of inflammation. The present study investigated the possible role of HO-1 in 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced colitis in rats. We measured HO-1 activity in TNBS-induced colitis in rats and analyzed the severity of colitis along with altered HO activity by assessing lesion area and myeloperoxidase activity. HO-1 mRNA and protein expressions were determined at different time points after TNBS induction. Free radical production and inducible nitric oxide synthase (iNOS), which participate in oxidative injury, were also assayed. HO activity and HO-1 gene expression increased markedly after TNBS induction. Administration with tin mesoporphyrin (SnMP), a HO inhibitor, potentiated the colonic damage along with a reduction in HO-1 activity. Furthermore, the reduction of HO-1 expression by SnMP also enhanced reactive oxygen species and iNOS expression, both of which were dramatically increased after the TNBS enema. L-Arginine pretreatment further aggravated the injurious action of SnMP. Our results indicate that HO-1 plays a protective role in the colonic damage induced by the TNBS enema, and the preventive effects probably result from decreased free radical production and inhibition of iNOS expression in colonic tissues.

Recent evidence suggests that carbon monoxide (CO) may be a neurotransmitter, similar to nitric oxide (NO) in the enteric nervous system. The distribution of haem oxygenase (HO), the biosynthetic enzyme for CO, has been determined in the enteric nervous system of animals, but little is known about the distribution of HO in human gastrointestinal tract. The present study investigated the expression of HO and its colocalization with NO synthase (NOS), the biosynthetic enzyme for NO, in human antrum and jejunum. HO isoforms were identified using immunohistochemistry and NOS was identified by immunohistochemistry or NADPH-d histochemistry. HO-2 immunoreactive (IR) cell bodies in enteric ganglia and nerve fibres in longitudinal and circular muscle were found in both antrum and jejunum. Co-localization of HO-2 and NOS was about 40% in HO-2 containing cell bodies of myenteric ganglia and only 10% or less in cell bodies of submucous ganglia. HO-1 immunoreactivity was not detected in antrum or jejunum. The results suggest that CO is produced in human enteric ganglion neurones and indicate a possible role of CO as a neurotransmitter and possible interaction between HO and NOS pathways in inhibitory neurotransmission in the human gastrointestinal tract.

In the present study the localization of heme oxygenase-2 (HO-2) in developing and mature olfactory epithelium of the bovine is investigated using immunohistochemistry and post embedding immunogold labelling. HO-2 immunoreactivity is first seen in epithelial cells localized along the luminal surface of the olfactory pit. Up to midgestation the number of HO-2 immunoreactive cells increases throughout all layers of the developing olfactory epithelium. From midgestation through adulthood immunostaining is restricted to perinuclear cytoplasm and axons of mature olfactory receptor neurons localized in intermediate epithelial regions. The temporal and spatial expression patterns of HO-2 immunohistochemistry support the notion that CO plays a role in neuronal differentiation while its presence in mature neurons might be functionally related to olfactory transduction.

A double antibody capture ELISA for the HO-1 protein has been developed to separately quantitate HO-1 protein. The use of 2.5% NP40 detergent greatly assists in freeing HO-1 protein from membranes and/or other cellular entities and increased the amount of HO-1 protein found in rat liver whole homogenates as well as the nuclear, mitochondrial and microsomal fractions. Use of the detergent NP40 did not substantially change HO-1 protein standard curves. The ELISA assay for HO-1 has been shown to be reproducible over (i) a 4-day trial period as well as (ii) almost 1 year of general laboratory use. Excellent specificity for the HO-1 isoform is shown by the failure of either the human HO-2 protein or HO-2 peptide (at concentrations as high as 1000 ng/ml) to generate any signal above background. At least a 300-fold greater signal comes from HO-1 protein as compared to the HO-2 protein. The EC(50) is about 200 ng/ml for HO-1, and the minimum detectable level of the HO-1 protein is about 1 ng/ml. The ELISA assay for the HO-1 protein requires a total of 6 h to complete. Of the total cellular HO-1 protein, 20, 19, 9 and 3% appeared in the nuclear, microsomal, mitochondrial and high speed supernatant fractions, respectively. As expected, the highest concentration of HO-1 protein per total protein in a subcellular fraction was found in the microsomes. For many research projects utilizing this ELISA assay for HO-1 protein concentration, use of the whole homogenate will be an excellent choice, rather than use of the postmitochondrial or microsomal fractions. Much higher HO-1 protein levels were found in tissues of rats rather than mice. This may be because the capture antibody and secondary antibody were both raised against the rat and not the mouse forms of the HO-1 protein. In rats the HO-1 concentrations were 1067, 364, 194, 31, 28 19, 5 and 2 ng/g tissue in whole homogenates from testes, brain, liver, lung, spleen, kidney, small intestines and urinary bladder, respectively. The ELISA assay for HO-1 described here will be useful for HO-1 research studies in tissues and cell cultures of rats and mice. This ELISA for HO-1 may also work with human tissues and cells.

Experimental thiamine deficiency (TD) is a model of impaired oxidative metabolism associated with region-selective neuronal loss in the brain. Oxidative stress is a prominent feature of TD neuropathology, as evidenced by the accumulation of heme oxygenase-1 (HO-1), ferritin, reactive iron and superoxide dismutase in microglia, nitrotyrosine and 4-hydroxynonenal in neurons, as well as induction of endothelial nitric oxide synthase within the vulnerable areas. Dietary restriction (DR) reduces oxidative stress in several organ systems including the brain. DR increases lifespan and reduces neurodegeneration in a variety of models of neuronal injury. The possibility that DR can protect vulnerable neurons against TD-induced oxidative insults has not been tested. The current studies tested whether approximately 3 months of DR (60% of ad libitum intake) altered the response to TD. Six month-old ad libitum-fed or dietary restricted C57BL/6 mice received a thiamine-deficient diet either ad libitum, or under a DR regimen respectively for eleven days. The TD mice also received daily injections of the thiamine antagonist pyrithiamine. Control ad libitum-fed or DR mice received an unlimited amount, or 60% of ad libitum intake, respectively, of thiamine-supplemented diet. As in past studies, TD produced region-selective neuronal loss (-60%), HO-1 induction, and IgG extravasation in the thalamus of ad libitum-fed mice. DR attenuated the TD-induced neuronal loss (-30%), HO-1 induction and IgG extravasation in the thalamus. These studies suggest that oxidative damage is critical to the pathogenesis of TD, and that DR modulates the extent of free radical damage in the brain. Thus, TD is an important model for studying the relationship between aging, oxidative stress and nutrition.

The aim of the present study was to investigate the expression and distribution patterns of heme oxygenase (HO)-1 and HO-2 in human placental villi at term and in the first trimester of pregnancy using reverse transcription-polymerase chain reaction (RT-PCR), Western blotting, and immunohistochemistry. RT-PCR detected mRNA for HO-1 and HO-2 in human placental villi during gestation. Western blotting also revealed the expression of the two distinct HO proteins throughout gestation. HO-1 was constitutively expressed, while HO-2 expression was apparently greater at term than in early pregnancy. Immunohistochemistry showed that distribution of the two HO isoforms had distinct topographic patterns: HO-1 was observed in villous trophoblastic cells, while HO-2 was found in endothelial cells and smooth muscle cells of blood vessels of placental villi. These results may provide a microtopographic basis for elucidating the mechanism of carbon monoxide (CO)-mediated vasodilatation, and it is suggested that the CO/HO system may be involved in the control of placental vascular function and may protect the syncytiotrophoblast and endothelium against oxidative injury., (Copyright 2000 Academic Press.)

The enzyme heme oxygenase-1 (HO-1) is reducing heme to the gaseous mediator carbon monoxide, to iron and the antioxidant biliverdin. The inducible expression of HO-1 is considered a protective cellular mechanism against reactive oxygen intermediates. Further, carbon monoxide (CO) is a regulator of cGMP synthesis, of NO-synthetases and cyclooxygenases, thereby indirectly modulating reactive processes. Here we report expression of HO-1 in rat experimental autoimmune encephalomyelitis (EAE) and neuritis (EAN). With both models, similar results were obtained: HO-1 was localized predominantly to infiltrating, monocytic, but only rarely to ramified microglial cells or astrocytes surrounding the inflammatory lesions. Prominent expression by monocytic cells was seen from day 11 after immunization correlating with the development of neurologic disease. Further, local expression is persistent for long after cessation of neurologic signs. Thus, HO-1 could be considered a factor in the formation and resolution of inflammatory autoimmune lesions of the nervous system.

We investigated whether application of non-distending hydrostatic pressure facilitates gene transfer into vein grafts. An external jugular vein was placed in a chamber with 100 microl adenovirus solution at a titer of 10(10) pfu/ml and was pressurized to up to 8 atm above ambient pressure for 10 min. Histochemical analysis demonstrated a positive transgene expression in all layers of the vessel wall. Gene transfer with 8 atm pressurization resulted in an approximately 50 times higher transgene expression than that without pressurization. Under 8 atm pressurization, the efficiency of gene transfer reached a plateau at 7.5 min. The application of hydrostatic pressure may improve the effectiveness of intraoperative genetic engineering of vein grafts.

Background: Carbon monoxide (CO) has recently emerged as an endogenously produced gaseous mediator that, like nitric oxide (NO), appears to be involved in both upper and lower airway inflammation. In healthy subjects a large part of the exhaled NO seems to originate from the nasal airways, and the paranasal sinuses have been described as a dominating site for NO production., Objective: The current study was designed to investigate whether CO could also be produced in the nose and paranasal sinuses., Methods: The occurrence in the nasal mucosa of the enzyme heme oxygenase, the rate limiting step for CO production, was analyzed with use of immunocytochemistry. CO in exhaled and sampled air was measured with an infrared analyzer. Forty-two healthy subjects and two patients with a tracheostoma volunteered for the study., Results: Heme oxygenase-like immunoreactivity was seen in the respiratory epithelium, in connection with seromucous glands and in the vascular smooth muscle of the nose. When CO was continuously sampled from one nostril during normal breathing through the mouth, stable levels of CO could be measured within 40 seconds in all subjects tested (n = 33). Repeated measurements indicated only minor variations in the values obtained. Sampling through a drainage tube inserted into the maxillary sinus revealed CO levels comparable to the levels obtained by sampling through the nose (n = 6). Breathing through the nose increased the CO levels obtained in the exhaled air (n = 33, P <. 001)., Conclusion: These results imply that the nose and paranasal sinuses contribute to the CO production of the human airways.

Previous in vitro studies have shown that increases in endogenous carbon monoxide (CO) generation via activation of the enzyme heme oxygenase (HO) within the rat hypothalamus are associated with the reduced release of the neuropeptides, vasopressin (AVP) and oxytocin, while evidence concerning corticotrophin-releasing hormone (CRH) is controversial. The present study investigated whether there is also a functional relationship between the HO-CO pathway and AVP and corticosterone (Cort) in vivo. Male Wistar rats were challenged with bacterial lipopolysaccharide (LPS) at doses producing significant activation of the hypothalamo-pituitary-adrenal (HPA) axis. LPS was given alone or after pretreatment with the HO inhibitor Sn-protoporphyrin-9 (SnPP9). The latter was injected either intraperitoneally (i.p.) or by intracerebroventricular (i.c.v.) route. SnPP9 given i.p. failed to modify either basal or LPS-stimulated levels of AVP and Cort. On the contrary, i.c.v. SnPP9 strongly potentiated LPS-induced AVP release and significantly enhanced basal serum Cort levels, although it failed to potentiate stimulation by LPS. The LPS + i.c.v. SnPP9 also significantly reduced the hypothalamic stores of AVP compared to controls, correlating with increased circulating levels of AVP. Taken collectively, these data are in concordance with previous in vitro observations showing that the HO-CO pathway acts centrally to attenuate endotoxin-stimulated AVP release, while having less effects on the pituitary-adrenal axis.

This study was performed to examine the differences in expression of heme oxygenase protein with age using immunocytochemistry. We compared the contents of HO-1 and HO-2 between young and aged rats using immunocytochemical methods. Stronger HO-1 expression was detected in the internal layer of the median eminence (ME) of aged than of young rats. Moreover, the cells expressing HO-1 were larger in the aged than the young animals. Electron microscopy indicated these cells with HO-1-like immunoreactivity (HO-1-LI) to be astrocytes. These findings suggested that the expression of HO-1 increased in the ME with age. The significance of this increased expression of HO-1 with age will be discussed briefly.

Background: Carbon monoxide (CO), like nitric oxide (NO), is a putative gaseous neurotransmitter. CO is produced by the enzyme heme oxygenase (HO) acting on a family of heme-containing compounds. Two isomers of HO have been characterized (HO-1, HO-2). In the CNS and in peripheral ganglia HO-2 occurs in a majority of neurons. NO and CO function as transmitters of enteric neurons but the relative distribution of enteric neurons utilizing these gaseous transmitters is unknown in rodent. We have studied the distribution of HO-2 immunoreactivity and NO synthase (NOS) activity within the rat ileum., Methods: Tissue sections and primary neuronal cell cultures were incubated with a HO-2 specific antibody, and then assessed or reprocessed for NOS activity using NADPH-dependent diaphorase staining., Results: HO-2 immunoreactivity was expressed in subpopulations of myenteric and submucosal neurons. Approximately 45% of the ganglion cells in tissue section were HO-2 positive. This was similar in proportion to those found to stain for NOS activity, and 10% of HO-2 positive neurons also contained NOS. HO-2 immunoreactivity was also found in epithelial cells within the villi, and in interstitial cells around the myenteric plexus and within the smooth muscle. In culture, the distribution and colocalisation of HO-2 and NOS positive neurons was similar to that in tissue sections. We identified labelled neurons as either Dogiel Type I or II; only Type II cells colocalized NOS and HO-2., Conclusion: Neurons, endocrine-like cells and interstitial cells with the capacity for CO production are distributed throughout the ileum and some neurons have the capacity to synthesize both NO and CO as gaseous messengers.

Background: Modification of the aminoacid sequence of peptides derived from the HLA class I heavy chain in combination with computer rational design resulted in the development of a peptide, RDP1258, with enhanced immunosuppressive activity., Methods: We evaluated the activity of this peptide, analyzing infiltrate by immunohistology and cytokine transcripts by reverse transcriptase-polymerase chain reaction method, in a hamster-to-rat xenograft model where recipients were treated with cobra venom factor (CVF) and peptide., Results: Although CVF or peptide alone had no effect, a combination of CVF/peptide RDP1258 resulted in a significant prolongation of graft survival (7.9+/-1 vs. 4.5+/-0 and 3.5+/-0 days, P<0.001). This effect was associated with an increased expression of heme oxygenase 1 (HO-1) in spleen, a significant reduced graft infiltrate, and a decrease of tumor necrosis factor-alpha mRNA transcripts (P<0.05) compared with CVF-treated recipients (1.6+/-0.07 vs. 3.3+/-0.3%, P=0.001) on day 3 after transplantation., Conclusion: These observations are consistent with the observation that up-regulation of HO-1 results in inhibition of immune effector functions and suggest that the peptide acts, at least partially, through HO-1 regulation.

Objectives: a) To evaluate in vivo, in rat liver, heme oxygenase-1 (HO-1) messenger RNA (mRNA) expression level and the regulation of 3',5'-cyclic guanosine monophosphate (cGMP) production during hepatic regeneration, localized inflammation, and systemic inflammation; and b) to investigate the effect of the induction of cytochrome P-450 and nitric oxide synthase (NOS) inhibition on HO-1 mRNA level and cGMP production in the liver., Design: Experimental, comparative study., Setting: Biochemical and molecular biology laboratory., Subjects: Six-wk-old male Sprague-Dawley rats (n = 60)., Interventions: We randomly divided the rats into four groups: a) saline controls; b) animals receiving lipopolysaccharide (600 microg/kg) for systemic inflammation; c) animals receiving turpentine oil (5 mL/kg) for localized inflammation obtained by sterile abscess; and d) partially hepatectomized animals (two-thirds removal of the parenchyma) for hepatic regeneration., Measurements and Main Results: Hepatic regeneration induced HO-1 mRNA expression, as shown by quantitative reverse transcription-polymerase chain reaction analysis. The time course of liver HO-1 mRNA induction after partial hepatectomy and localized and systemic inflammation showed a similar and gradual increase, with a maximum at 6 hrs and a return to a minimal level 48 hrs after treatments. Liver HO-1 mRNA was overexpressed during localized vs. systemic inflammation. This overexpression was not correlated with either serum IL-6 or corticosterone concentrations, but is related to increased cGMP production. The administration of phenobarbital, a cytochrome P-450 inducer and of nitro-L-arginine methyl ester, a NOS inhibitor, prevented cGMP production and abolished the overexpression of HO-1 mRNA., Conclusions: The results of this study indicate that HO-1 mRNA is induced during hepatic regeneration with a similar time course to that observed during acute inflammation. In addition, we demonstrated that: a) HO-1 mRNA is overexpressed during localized vs. systemic inflammation; b) this overexpression is not correlated with IL-6 or corticosterone concentrations but is related to intrahepatic cGMP production; c) induction of cytochromes P-450 and/or inhibition of NOS both reduce liver cGMP production and HO-1 mRNA expression. These results suggest that in rat liver, a cGMP-transducing pathway may control HO-1 mRNA expression. Thus, there may be a role for HO-1 mRNA in the modulation of the hepatic stress response.