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Objective: To assess the efficacy of the heme oxygenase inhibitor, tin mesoporphyrin (SnMP), to reduce total bilirubin (TB) levels. Study Design: Masked, SnMP (4.5 mg kg −1 ), placebo-controlled, multicenter trial of single intramuscular injection to newborns ⩾35 weeks gestational age whose predischarge screening transcutaneous bilirubin (TcB) was >75th percentile. Results: Two hundred and thirteen newborns (median age 30 h) were randomized to treatment with SnMP ( n =87) or ‘sham’ ( n =89). We found that the duration of phototherapy was halved. Within 12 h of SnMP administration, the natural TB trajectory was reversed. At age 3 to 5 days, TB in the SnMP-treated group was +8% but sixfold lower than the 47% increase in the sham-treated group ( P <0.001). At age 7 to 10 days, mean TB declined 18% ( P <0.001) compared with a 7.1% increase among controls. No short-term adverse events from SnMP treatment were noted other than photoreactivity due to inadvertent exposure to white light phototherapy. Conclusion: Early, predischarge SnMP administration decreased the duration of phototherapy, reversed TB trajectory and reduced the severity of subsequent hyperbilirubinemia.

Drug targets for kidney cancer Inherited mutations in fumarate hydratase (FH), an enzyme in the tricarboxylic acid cycle — which links many of the metabolic reactions in aerobic cellular respiration — can lead to malignancies including kidney cancer. Frezza et al . now observe a metabolic pathway in FH-deficient cells that converts glutamine into bilirubin through the synthesis and degradation of haem. This renders FH-deficient cells sensitive to inhibition of haem oxygenase, a key enzyme in this pathway. Haem oxygenase might therefore be a therapeutic target in patients with tumours associated with FH loss. Fumarate hydratase (FH) is an enzyme of the tricarboxylic acid cycle (TCA cycle) that catalyses the hydration of fumarate into malate. Germline mutations of FH are responsible for hereditary leiomyomatosis and renal-cell cancer (HLRCC) 1 . It has previously been demonstrated that the absence of FH leads to the accumulation of fumarate, which activates hypoxia-inducible factors (HIFs) at normal oxygen tensions 2 , 3 , 4 . However, so far no mechanism that explains the ability of cells to survive without a functional TCA cycle has been provided. Here we use newly characterized genetically modified kidney mouse cells in which Fh1 has been deleted, and apply a newly developed computer model of the metabolism of these cells to predict and experimentally validate a linear metabolic pathway beginning with glutamine uptake and ending with bilirubin excretion from Fh1 -deficient cells. This pathway, which involves the biosynthesis and degradation of haem, enables Fh1 -deficient cells to use the accumulated TCA cycle metabolites and permits partial mitochondrial NADH production. We predicted and confirmed that targeting this pathway would render Fh1 -deficient cells non-viable, while sparing wild-type Fh1 -containing cells. This work goes beyond identifying a metabolic pathway that is induced in Fh1 -deficient cells to demonstrate that inhibition of haem oxygenation is synthetically lethal when combined with Fh1 deficiency, providing a new potential target for treating HLRCC patients.

The development of the field of nanotechnology has revolutionized various aspects in the fields of modern sciences. Nano-medicine is one of the primary fields for the application of nanotechnology techniques. The current study sheds light on the reno-protective impacts of gold nano-particles; nanogold (AuNPs) against 5-flurouracil (5-FU)-induced renal toxicity. Indeed, the use of 5-FU has been associated with kidney injury which greatly curbs its therapeutic application. In the current study, 5-FU injection was associated with a significant escalation in the indices of renal injury, i.e., creatinine and urea. Alongside this, histopathological and ultra-histopathological changes confirmed the onset of renal injury. Both gene and/or protein expression of nuclear factor erythroid 2–related factor 2 (Nrf-2) and downstream antioxidant enzymes revealed consistent paralleled anomalies. AuNPs administration induced a significant renal protection on functional, biochemical, and structural levels. Renal expression of the major sensor of the cellular oxidative status Nrf-2 escalated with a paralleled reduction in the renal expression of the other contributor to this axis, known as Kelch-like ECH-associated protein 1 (Keap-1). On the level of the effector downstream targets, heme oxygenase 1 (HO-1) and gamma-glutamylcysteine synthetase (γ-GCS) AuNPs significantly restored their gene and protein expression. Additionally, combination of AuNPs with 5-FU showed better cytotoxic effect on MCF-7 cells compared to monotreatments. Thus, it can be inferred that AuNPs conferred reno-protective impact against 5-FU with an evident modulatory impact on Nrf-2/Keap-1 and its downstream effectors, HO-1 and γ-GCS, suggesting its potential use in 5-FU regimens to improve its therapeutic outcomes and minimize its underlying nephrotoxicity.

To determine whether or not the antioxidants N-acetylcysteine (NAC) and allopurinol (ALP) confer synergistic cardioprotection against myocardial ischemia/reperfusion (MI/R) injury by stabilizing hypoxia inducible factor 1α (HIF-1α)/heme oxygenase 1 (HO-1) signaling in diabetic myocardium. Control or diabetic [streptozotocin (STZ)-induced] Sprague Dawley rats received vehicle or NAC, ALP or their combination for four weeks starting one week after STZ injection. The animals were then subjected to thirty minutes of coronary artery occlusion followed by two hours reperfusion in the absence or presence of the selective HO-1 inhibitor, tin protoporphyrin-IX (SnPP-IX) or the HIF-1α inhibitor 2-Methoxyestradiol (2ME2). Cardiomyocytes exposed to high glucose were subjected to hypoxia/re-oxygenation in the presence or absence of HIF-1α and HO-1 achieved by gene knock-down with related siRNAs. Myocardial and plasma levels of 15-F2t-isoprostane, an index of oxidative stress, were significantly increased in diabetic rats while cardiac HO-1 protein and activity were reduced; this was accompanied with reduced cardiac protein levels of HIF-1α, and increased post-ischemic myocardial infarct size and cellular injury. NAC and ALP given alone and in particular their combination normalized cardiac levels of HO-1 and HIF-1α protein expression and prevented the increase in 15-F2t-isoprostane, resulting in significantly attenuated post-ischemic myocardial infarction. NAC and ALP also attenuated high glucose-induced post-hypoxic cardiomyocyte death in vitro. However, all the above protective effects of NAC and ALP were cancelled either by inhibition of HO-1 or HIF-1α with SnPP-IX and 2ME2 in vivo or by HO-1 or HIF-1α gene knock-down in vitro. NAC and ALP confer synergistic cardioprotection in diabetes via restoration of cardiac HIF-1α and HO-1 signaling.

Background. Endotoxin-associated acute kidney injury (AKI), a disease characterized by marked oxidative stress and inflammation disease, is a major cause of mortality in critically ill patients. Mitochondrial fission and pyroptosis often occur in AKI. However, the underlying biological pathways involved in endotoxin AKI remain poorly understood, especially those related to mitochondrial dynamics equilibrium disregulation and pyroptosis. Previous studies suggest that heme oxygenase- (HO-) 1 confers cytoprotection against AKI during endotoxic shock, and PTEN-induced putative kinase 1 (PINK1) takes part in mitochondrial dysfunction. Thus, in this study, we examine the roles of HO-1/PINK1 in maintaining the dynamic process of mitochondrial fusion/fission to inhibit pyroptosis and mitigate acute kidney injury in rats exposed to endotoxin. Methods. An endotoxin-associated AKI model induced by lipopolysaccharide (LPS) was used in our study. Wild-type (WT) rats and PINK1 knockout (PINK1KO) rats, respectively, were divided into four groups: the control, LPS, Znpp+LPS, and Hemin+LPS groups. Rats were sacrificed 6 h after intraperitoneal injecting LPS to assess renal function, oxidative stress, and inflammation by plasma. Mitochondrial dynamics, morphology, and pyroptosis were evaluated by histological examinations. Results. In the rats with LPS-induced endotoxemia, the expression of HO-1 and PINK1 were upregulated at both mRNA and protein levels. These rats also exhibited inflammatory response, oxidative stress, mitochondrial fission, pyroptosis, and decreased renal function. After upregulating HO-1 in normal rats, pyroptosis was inhibited; mitochondrial fission and inflammatory response to oxidative stress were decreased; and the renal function was improved. The effects were reversed by adding Znpp (a type of HO-1 inhibitor). Finally, after PINK1 knockout, there is no statistical difference in the LPS-treated group and Hemin or Znpp pretreated group. Conclusions. HO-1 inhibits inflammation response and oxidative stress and regulates mitochondria fusion/fission to inhibit pyroptosis, which can alleviate endotoxin-induced AKI by PINK1.

The mechanisms underlying the action of the potent anti-inflammatory interleukin-10 (IL-10) are poorly understood. Here we show that, in murine macrophages, IL-10 induces expression of heme oxygenase-1 (HO-1), a stress-inducible protein with potential anti-inflammatory effect, via a p38 mitogen-activated protein kinase-dependent pathway. Inhibition of HO-1 protein synthesis or activity significantly reversed the inhibitory effect of IL-10 on production of tumor necrosis factor-α induced by lipopolysaccharide (LPS). Additional experiments revealed the involvement of carbon monoxide, one of the products of HO-1-mediated heme degradation, in the anti-inflammatory effect of IL-10 in vitro . Induction of HO-1 by IL-10 was also evident in vivo . IL-10-mediated protection against LPS-induced septic shock in mice was significantly attenuated by cotreatment with the HO inhibitor, zinc protoporphyrin. The identification of HO-1 as a downstream effector of IL-10 provides new possibilities for improved therapeutic approaches for treating inflammatory diseases.

The tumor microenvironment (TME) is highly heterogeneous and can dictate the success of therapeutic interventions. Identifying TMEs that are susceptible to specific therapeutic interventions paves the way for more personalized and effective treatments. In this study, using a spontaneous murine model of breast cancer, we characterize a TME that is responsive to inhibitors of the heme degradation pathway mediated by heme oxygenase (HO), resulting in CD8+ T cell- and NK cell-dependent tumor control. A hallmark of this TME is a chronic type I interferon (IFN) signal that is directly involved in orchestrating the antitumor immune response. Importantly, we identify that similar TMEs exist in human breast cancer that are associated with patient prognosis. Leveraging these observations, we demonstrate that combining a STING agonist, which induces type I IFN responses, with an HO inhibitor produces a synergistic effect leading to superior tumor control. This study highlights HO activity as a potential resistance mechanism for type I IFN responses in cancer, supporting a therapeutic rationale for targeting the heme degradation pathway to enhance the efficacy of STING agonists.

Carbon monoxide (CO) produced by heme oxygenase (HO)-1 and HO-2 or released from the CO-donor, tricarbonyldichlororuthenium (II) dimer (CORM-2) causes vasodilation, with unknown efficacy against stress-induced gastric lesions. We studied whether pretreatment with CORM-2 (0.1–10 mg/kg oral gavage (i.g.)), RuCl3 (1 mg/kg i.g.), zinc protoporphyrin IX (ZnPP) (10 mg/kg intraperitoneally (i.p.)), hemin (1–10 mg/kg i.g.) and CORM-2 (1 mg/kg i.g.) combined with NG-nitro-l-arginine (l-NNA, 20 mg/kg i.p.), 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ, 10 mg/kg i.p.), indomethacin (5 mg/kg i.p.), SC-560 (5 mg/kg i.g.), and celecoxib (10 mg/kg i.g.) affects gastric lesions following 3.5 h of water immersion and restraint stress (WRS). Gastric blood flow (GBF), the number of gastric lesions and gastric CO and nitric oxide (NO) contents, blood carboxyhemoglobin (COHb) level and the gastric expression of HO-1, HO-2, hypoxia inducible factor 1α (HIF-1α), tumor necrosis factor α (TNF-α), cyclooxygenase (COX)-2 and inducible NO synthase (iNOS) were determined. CORM-2 (1 mg/kg i.g.) and hemin (10 mg/kg i.g.) significantly decreased WRS lesions while increasing GBF, however, RuCl3 was ineffective. The impact of CORM-2 was reversed by ZnPP, ODQ, indomethacin, SC-560 and celecoxib, but not by l-NNA. CORM-2 decreased NO and increased HO-1 expression and CO and COHb content, downregulated HIF-1α, as well as WRS-elevated COX-2 and iNOS mRNAs. Gastroprotection by CORM-2 and HO depends upon CO’s hyperemic and anti-inflammatory properties, but is independent of NO.

Previously, we reported that isorhamnentin, a 3′- O -methylated metabolite of quercetin, reduced inducible nitric oxide synthase (iNOS) expression and NO production. The present study further investigated the underlying mechanism of anti-inflammatory and antioxidant effects of isorhamnentin. Administration of isorhamnetin decreased the number of cyclooxygenase-2 (COX-2) positive cells in rats with carrageenan-induced paw edema. Isorhamnetin also suppressed lipopolysaccharide (LPS)-induced expression of COX-2 in cells. It is well known that LPS-induced reactive oxygen species (ROS) production leads to COX-2 induction. Isorhamnetin decreased LPS-induced ROS production and apoptosis. In addition, the basal expression of heme oxygenase-1 (HO-1) was increased by isorhamnetin treatment in agreement with the increase in nuclear translocation of NF-E2-related factor-2 (Nrf2), an essential transcription factor for the regulation of HO-1 expression. Moreover, pretreatment of tin protoporphyrin IX (SnPP), a chemical inhibitor of HO-1, reversed the ability of isothamnetin to inhibit COX-2 expression. These results demonstrate that induction of HO-1 by isorhamnetin leads to a reduction in ROS production and its antioxidant property might contribute to the inhibition of COX-2 expression in response to inflammation.

Triptolide is a bioactive component of Chinese herbal plant Tripterygium wilfordii Hook F that has recently been noted to attenuate hepatic and cerebral ischemia/reperfusion (I/R) injuries in rodents. To investigate whether triptolide could protect against myocardial I/R injuries, triptolide (25, 50 or 100 μg/kg) was administrated in Wistar rats that underwent left anterior descending coronary artery ligation in this study. Our data showed that triptolide pretreatment could attenuate myocardial infarction, increase the fractional shortening and left ventricular systolic pressure and decrease the left ventricular end-diastolic pressure in ischemic rats. Also, triptolide was noted to inhibit the activities of lactate dehydrogenase and creatine kinase in I/R rats. Moreover, triptolide administration suppressed macrophage infiltration, inhibited the overproduction of tumor necrosis factor-α, interleukin (IL)-1β, IL-6 and malondialdehyde (MDA) in reperfused myocardium tissues and upregulated the activities of antioxidative superoxide dismutase (SOD), glutathione (GSH) and glutathione peroxidase (GPx). In addition, nuclear accumulation of nuclear factor erythroid 2-related factor 2 (Nrf2) and the activity of its downstream target Heme oxygenase-1 (HO-1) in ischemic myocardium tissues were enhanced by triptolide pretreatment. In addition, the HO-1 inhibitor, zinc protoporphyrin-IX, abrograted the cardiac protection mediated by triptolide. Our study reveals a novel cardioprotective effect of triptolide in rats with I/R injuries, wherein the activation of Nrf2/HO-1 signaling was involved.