Analysis of Heme oxygenase isomers in rat

Novel mutual prodrug of 5-fluorouracil and heme oxygenase-1 inhibitor (5-FU/HO-1 hybrid): design and preliminary in vitro evaluation

In this work, the first mutual prodrug of 5-fluorouracil and heme oxygenase1 inhibitor (5-FU/HO-1 hybrid) has been designed, synthesised, and evaluated for its in vitro chemical and enzymatic hydrolysis stability. Predicted in silico physicochemical properties of the newly synthesised hybrid (3) demonstrated a drug-like profile with suitable Absorption, Distribution, Metabolism, and Excretion (ADME) properties and low toxic liabilities. Preliminary cytotoxicity evaluation towards human prostate (DU145) and lung (A549) cancer cell lines demonstrated that 3 exerted a similar effect on cell viability to that produced by the reference drug 5-FU. Among the two tested cancer cell lines, the A549 cells were more susceptible for 3. Of note, hybrid 3 also had a significantly lower cytotoxic effect on healthy human lung epithelial cells (BEAS-2B) than 5-FU. Altogether our results served as an initial proof-of-concept to develop 5-FU/HO-1 mutual prodrugs as potential novel anticancer agents.

Development of new HO-1 inhibitors by a thorough scaffold-hopping analysis

HO-1 inhibition is considered a valuable anticancer approach. In fact, up-regulation of HO-1 had been repeatedly reported in many types of human malignancies, and in these clinical cases, poor outcomes are reported. To identify novel HO-1 inhibitors suitable for drug development, a scaffold-hopping strategy calculation was utilized to design novel derivatives. Different parts of the selected molecule were analyzed and the different series of novel compounds were virtually evaluated. The calculation for the linker moiety of the classical HO-1 inhibitors structure led us to compounds 5 and 6. A synthetic pathway for the two molecules was designed and the compounds were synthesized. The biological activity revealed an HO-1 inhibition of 0.9 and 54 μM for molecules 5 and 6 respectively. This study suggested that our scaffold-hopping approach was successful and these results are ongoing for further development.

Novel Structural Insight into Inhibitors of Heme Oxygenase-1 (HO-1) by New Imidazole-Based Compounds: Biochemical and In Vitro Anticancer Activity Evaluation

In this paper, the design, synthesis, and molecular modeling of a new azole-based HO-1 inhibitors was reported, using compound 1 as a lead compound, in which an imidazole moiety is linked to a hydrophobic group by means of an ethanolic spacer. The tested compounds showed a good inhibitor activity and possessed IC₅₀ values in the micromolar range. These results were obtained by targeting the hydrophobic western region. Molecular modeling studies confirmed a consolidated binding mode in which the nitrogen of the imidazolyl moiety coordinated the heme ferrous iron, meanwhile the hydrophobic groups were located in the western region of HO-1 binding pocket. Moreover, the new compounds were screened for in silico ADME-Tox properties to predict drug-like behavior with convincing results. Finally, the in vitro antitumor activity profile of compound 1 was investigated in different cancer cell lines and nanomicellar formulation was synthesized with the aim of improving compound's 1 water solubility. Finally, compound 1 was tested in melanoma cells in combination with doxorubicin showing interesting synergic activity.

Potholing of the hydrophobic heme oxygenase-1 western region for the search of potent and selective imidazole-based inhibitors

Here we report the design, synthesis, and molecular modeling of new potent and selective imidazole-based HO-1 inhibitors in which the imidazole nucleus and the hydrophobic groups are linked by a phenylethanolic spacer. Most of the tested compounds showed a good inhibitor activity with IC₅₀ values in the low micromolar range, with two of them (1b and 1j) exhibiting also high selectivity toward HO-2. These results were obtained by the idea of potholing the entire volume of the principal hydrophobic western region with an appropriate ligand volume. Molecular modeling studies showed that these molecules bind to the HO-1 in the consolidated fashion where the imidazolyl moiety coordinates the heme iron while the aromatic groups are stabilized by hydrophobic interaction in the western region of the binding pocket. Finally, the synthesized compounds were analyzed for in silico ADME-Tox properties to establish oral drug-like behavior and showed satisfactory results.

Phenotypic characterization of a novel HO-1 depletion model in the rat

Although the protective role of HO-1 induction in various forms of kidney disease is well established, mechanisms other than heme catabolism to biliverdin, bilirubin and carbon monoxide have recently been identified. Unraveling these mechanisms requires the generation of appropriate animal models. The present study describes the generation of a HO-1 deficient Hmox1 ^-/- rat model and characterizes its renal and extrarenal phenotype. Hmox1 ^-/- rats had growth retardation and splenomegaly compared to their Hmox1 ^+/+ littermates. Focal segmental glomerulosclerosis-type lesions and interstitial inflammatory infiltrates were prominent morphologic findings and were associated with increased blood urea nitrogen, serum creatinine and albuminuria. There was no increase in iron deposition in glomeruli, tubules or interstitium. Iron deposition in spleen and liver was reduced. Electron microscopic examination of glomeruli revealed edematous podocytes with scant areas of foot process effacement but otherwise well preserved processes and slit-diaphragms. Of the filtration barrier proteins examined, β-catenin expression was markedly reduced both in glomeruli and extrarenal tissues. Since the rat is the preferred laboratory animal in experimental physiology and pathophysiology, the rat model of HO-1 deficiency may provide a novel tool for investigation of the role of this enzyme in renal function and disease.

Heme oxygenase inhibition by 2-oxy-substituted 1-(1H-imidazol-1-yl)-4-phenylbutanes: effect of halogen substitution in the phenyl ring

A series of 2-oxy-substituted 1-(1H-imidazol-1-yl)-4-phenylbutanes comprising imidazole-ketones, imidazole-dioxolanes, and imidazole-alcohols substituted with halogens in the phenyl ring were synthesized and evaluated as novel inhibitors of heme oxygenase which are structurally distinct from metalloporphyrins. The entire library of compounds was found to be highly active, with the bromine- and iodine-substituted derivatives being the most potent. The imidazole-dioxolanes were all selective for the HO-1 isozyme (inducible) and exhibited substantially lower activity toward the HO-2 isozyme (constitutive). The corresponding imidazole-ketones and imidazole-alcohols showed selectivity toward HO-1 to a lesser degree than the similarly substituted imidazole-dioxolanes.

Heme regulation in traumatic brain injury: relevance to the adult and developing brain

Intracranial bleeding is one of the most prominent aspects in the clinical diagnosis and prognosis of traumatic brain injury (TBI). Substantial amounts of blood products, such as heme, are released because of traumatic subarachnoid hemorrhages, intraparenchymal contusions, and hematomas. Despite this, surprisingly few studies have directly addressed the role of blood products, in particular heme, in the setting of TBI. Heme is degraded by heme oxygenase (HO) into three highly bioactive products: iron, bilirubin, and carbon monoxide. The HO isozymes, in particular HO-1 and HO-2, exhibit significantly different expression patterns and appear to have specific roles after injury. Developmentally, differences between the adult and immature brain have implications for endogenous protection from oxidative stress. The aim of this paper is to review recent advances in the understanding of heme regulation and metabolism after brain injury and its specific relevance to the developing brain. These findings suggest novel clinical therapeutic options for further translational study.

Synthesis and evaluation of azalanstat analogues as heme oxygenase inhibitors

Several analogues based on the lead structure of azalanstat were synthesized and evaluated as novel inhibitors of heme oxygenase (HO). A number of these compounds, which are structurally distinct from metalloporphyrin HO inhibitors, were found to be selective for the HO-1 isozyme (stress induced), and had substantially less inhibitory activity on HO-2, the constitutive isozyme.