Project description:To investigate the functional significance of myocardial ferritin heavy chain (FtH) in a model of acute myocardial infarction (MI). FtH was deleted using FtH floxed mice and Sm-22 Cre mice on a C57/bl6 background At 3 hours following 45 minutes of ischemia induced via ligation of left ant. decsending coronary artery, ischemic regions were identified, dissected, and total RNA was isolated fand gene expression profiling analysis using data obtained from RNA-seq of 3 different animals. RNA Total RNA isolated from left ventricle under homeostatic (bseline conditions) served as negative ctr. (n=3/group)
Project description:HO-1 cells denote the cultured rat mesangial cells with heme oxygenase-1 knocked down by RNA interference (using lentiviral vector). GFP cells denote the cultured rat mesangial cells that are transfected with empty lentiviral vector containing GFP cassette. Cells are treated with hydrogen peroxide 100 micromolar for 2 hours, or without. RNA are then harvested for array analysis. Biological replicates are performed (two independent experiment sets). GFP cell and HO-1 cell are untreated, or treated with hydrogen peroxide (100 micromolar for 2 hours).
Project description:Heme regulatory motifs (HRMs) are found in a variety of proteins that are involved in diverse biological functions. In the C-terminal tail region of human heme oxygenase-2 (HO2), there are two HRMs whose cysteines form a disulfide bond; when reduced, these cysteines are available to bind Fe3+-heme. Heme binding to the HRMs is independent of the HO2 catalytic active site in the core of the protein, where heme binds with high affinity and is degraded to biliverdin. Here, we describe the reversible, protein-mediated transfer of heme between the HRMs and the core of HO2. Using HDX-MS to monitor the dynamics of HO2 with and without Fe3+-heme bound to the HRMs and to the core, we detected conformational changes in the catalytic core only in one state of the catalytic cycle – when Fe3+-heme is bound to the HRMs and the core is in the apo state. The conformational changes detected are consistent with transfer of heme between binding sites. Indeed, Fe3+-heme bound to the HRMs is transferred to the apo-core upon either independently expressing the core and a construct spanning the HRM-containing tail or after single turnover of heme at the core. In addition, we observed transfer of heme from the core to the HRMs and equilibration of heme between the core and HRMs. We thus propose a Fe3+-heme transfer model in which heme bound to the HRMs is readily transferred to the catalytic site for degradation to facilitate turnover but can also equilibrate between the sites to maintain heme homeostasis.
Project description:HO-1 cells denote the cultured rat mesangial cells with heme oxygenase-1 knocked down by RNA interference (using lentiviral vector). GFP cells denote the cultured rat mesangial cells that are transfected with empty lentiviral vector containing GFP cassette. Cells are treated with hydrogen peroxide 100 micromolar for 2 hours, or without. RNA are then harvested for array analysis. Biological replicates are performed (two independent experiment sets).
Project description:Tumor-Associated Macrophages (TAMs) contribute to the maintenance of a strong immunosuppressive environment, supporting tumor progression and resistance to treatment. To date, the mechanisms that drive acquisition of these immunosuppressive features are still poorly defined. Heme oxygenase-1 (HO-1) is the rate-limiting enzyme that catabolizes free heme. It displays important cytoprotective, anti-inflammatory and antioxidant properties. A growing body of evidence suggests that HO-1 may also promote tumor development. Herein, we show that HO-1 is highly expressed in monocytic cells in the tumor microenvironment (TME) once they differentiate into TAMs. Deletion of HO-1 in the myeloid compartment enhances the beneficial effects of a therapeutic antitumor vaccine by restoring CD8 T-cell proliferation and cytotoxicity. We further show that induction of HO-1 plays a major role on monocyte education by tumor cells by modulating their transcriptional and epigenetic programs. These results identify HO-1 as a valuable therapeutic target to reprogram the TME and synergize with current cancer therapies to facilitate antitumoral response.
Project description:Tumor-Associated Macrophages (TAMs) contribute to the maintenance of a strong immunosuppressive environment, supporting tumor progression and resistance to treatment. To date, the mechanisms that drive acquisition of these immunosuppressive features are still poorly defined. Heme oxygenase-1 (HO-1) is the rate-limiting enzyme that catabolizes free heme. It displays important cytoprotective, anti-inflammatory and antioxidant properties. A growing body of evidence suggests that HO-1 may also promote tumor development. Herein, we show that HO-1 is highly expressed in monocytic cells in the tumor microenvironment (TME) once they differentiate into TAMs. Deletion of HO-1 in the myeloid compartment enhances the beneficial effects of a therapeutic antitumor vaccine by restoring CD8 T-cell proliferation and cytotoxicity. We further show that induction of HO-1 plays a major role on monocyte education by tumor cells by modulating their transcriptional and epigenetic programs. These results identify HO-1 as a valuable therapeutic target to reprogram the TME and synergize with current cancer therapies to facilitate antitumoral response.
Project description:Acute kidney injury (AKI) is a major public health concern with significant attributable morbidity and mortality with no current FDA approved treatments other than supportive care through dialysis. Several pre-clinical studies have suggested that heme-oxygenase-1 (HO-1), an enzyme that catalyzes the breakdown of heme, has promise as a potential therapeutic target for AKI. Clinical trials involving HO-1 products (biliverdin, carbon monoxide, and iron), however, have not progressed beyond the Phase 1/2 level. We have identified small molecule inducers of HO-1 that enable us to exploit the full therapeutic potential of HO-1, the combination of its products, and as-yet-undefined effects of the enzyme system. Through cell-based, high throughput screens for induction of HO-1 through the human HO-1 promoter/enhancer, we identified two novel small molecules and broxaldine, an FDA approved antiprotozoal, for further consideration as candidate compounds exhibiting Emax ≥ 70% of 5 µM hemin and EC50<10 µM. RNA sequencing identified shared binding motifs to NRF-2, a transcription factor known to regulate antioxidant genes, including HO-1. siRNA knockdown of NRF-2 confirmed the role of NRF-2 in induction of HO-1. In vitro, cytoprotective function of the candidates was assessed against cisplatin-induced cytotoxicity and apoptosis. In vivo, delivery of candidate compounds induced HO-1 expression in the kidneys of mice. This study serves as the basis for further development of small molecule HO-1 inducers as preventative or therapeutic interventions for a variety of pathologies, including AKI.
Project description:Sepsis-associated acute kidney injury (SA-AKI) is a key contributor to the life threatening sequalae attributed to sepsis. Mechanistically, SA-AKI is a consequence of unabated myeloid cell activation and oxidative stress that induces tubular injury. Iron mediates inflammatory pathways directly and through regulating the expression of myeloid-derived ferritin, an iron storage protein comprised of ferritin light (FtL) and ferritin heavy chain (FtH) subunits. Previous work revealed myeloid FtH deletion leads to a compensatory increase in intracellular and circulating FtL and is associated with amelioration of SA-AKI. We designed this study to test the hypothesis that loss of myeloid FtL and subsequently, circulating FtL will exacerbate the sepsis-induced inflammatory response and worsen SA-AKI. We generated a novel myeloid-specific FtL knockout mouse (FtLLysM-/-) and induced sepsis via cecal ligation and puncture or lipopolysaccharide endotoxemia. As expected, serum ferritin levels were significantly lower in the knockout mice, suggesting that myeloid cells dominantly contribute to circulating ferritin. Interestingly, while sepsis induction led to a marked production of pro- and anti-inflammatory cytokines, there was no statistical difference between the genotypes. There was a similar loss of kidney function, as evident by a rise in serum creatinine and cystatin C, and renal injury identified by expression of kidney injury molecule-1 and neutrophil gelatinase associated lipocalin. Finally, RNA sequencing revealed upregulation of pathways for cell cycle arrest and autophagy post-sepsis, but no significant differences were observed between genotypes, including in key genes associated with ferroptosis, an iron-mediated form of cell death. The loss of FtL did not impact sepsis-mediated activation of NFkB or HIF-1a signaling, key inflammatory pathways associated with dysregulated host response. Taken together, while FtL overexpression was shown to be protective against sepsis, loss of FtL did not influence sepsis pathogenesis.