Imidazole−Dioxolane Compounds as Isozyme-Selective Heme Oxygenase Inhibitors

Vlahakis, Jason Z.; Kinobe, Robert T.; Bowers, Raymond J.; Brien, James F.; Nakatsu, Kanji; Szarek, Walter A.

doi:10.1021/jm0511435

Cited by 67 publications

(61 citation statements)

References 25 publications

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“…In previous reports, we described the selective inhibitory effects of imidazole-dioxolane compounds on HO (QC-1 and QC-13) and HO-1 (QC-13) in vitro Vlahakis et al, 2006). The calculated logP values for these inhibitors (QC-1 ϭ 3.97; QC-13 ϭ 3.27) suggested that they should cross membrane barriers and be effective in intact cell preparations as well as in vivo.…”

Section: Discussionmentioning

confidence: 90%

Effectiveness of Novel Imidazole-Dioxolane Heme Oxygenase Inhibitors in Renal Proximal Tubule Epithelial Cells

Kinobe¹,

Ji²,

Vlahakis³

et al. 2007

J Pharmacol Exp Ther

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To enhance our understanding of the physiological roles of heme oxygenase (HO) isozymes, HO-1 (inducible) and HO-2 (constitutive), we developed novel imidazole-based HO inhibitors. Unlike the metalloporphyrins, these imidazole-dioxolane compounds are selective for the in vitro inhibition of HO with minimal effects on other heme-dependent enzymes such as nitric oxide synthase and soluble guanylyl cyclase. In the current study, we tested the hypothesis that these novel HO inhibitors are effective in intact cells by extending their application to cultured, renal proximal tubule epithelial cells (LLC-PK 1 ). HO-1 and HO-2 protein expression was enhanced by pretreatment of cells with hemin, transduction with adenovirus encoding human HO-1, and transfection with cDNA for HO-2, respectively. Total HO activity was measured by determining the formation of carbon monoxide (CO), whereas cell viability and apoptosis were measured by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and the expression of activated caspase-3. Gliotoxin/tumor necrosis factor-␣ (TNF-␣) produced cytotoxicity in wild-type LLC-PK 1 cells (P Ͻ 0.05) but not in HO-1 and HO-2 overexpressing or wild type cells pretreated with hemin (10 M). The presence of imidazole-dioxolane HO inhibitors (2-25 M) decreased cell viability (P Ͻ 0.05). A CO-releasing molecule reversed, in a dose-dependent manner, the cytotoxic effects and caspase-3 activation induced by the combination of gliotoxin/TNF-␣ and the HO inhibitors, suggesting an important role for CO in protection against renal toxicity. These data demonstrate a protective role of both HO-1 and HO-2 against gliotoxin/TNF-␣-induced cytotoxicity in LLC-PK 1 cells. The novel imidazole-dioxolane compounds can be used as effective inhibitors of HO activity in cell culture.

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Section: Discussionmentioning

confidence: 90%

Effectiveness of Novel Imidazole-Dioxolane Heme Oxygenase Inhibitors in Renal Proximal Tubule Epithelial Cells

Kinobe¹,

Ji²,

Vlahakis³

et al. 2007

J Pharmacol Exp Ther

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“…32 We have performed in vivo studies using azalanstat, a dioxolane compound, and found that it can inhibit in vivo HO activity, but only at a high dose (500 mmol kg À1 body weight), and also can induce HO-1. 34 Because these compounds were first designed as inhibitors of cholesterol production by lanosterol 14-a-demethylase, the effects of inhibiting this important pathway may preclude their use in a developing newborn, and as such have been proposed as only pharmacological tools for studying HO-1 and CO. 32,33 Although major differences exist between HO-1 and HO-2, each isoenzyme is evolutionarily conserved in the primary amino-acid and nucleotide sequences, with homology between HO-1 and HO-2 being B42%. As mentioned above, the Hmox1 gene responds to all types of stimuli, many of which have in common the association with oxidative stress; in contrast, HO-2 is responsive mainly to adrenal glucocorticoids.…”

Section: Discussionmentioning

confidence: 99%

In vitro inhibition of heme oxygenase isoenzymes by metalloporphyrins

et al. 2011

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Objective: Neonatal jaundice results from an increased bilirubin production and decreased hepatic bilirubin conjugation and excretion. Severe hyperbilirubinemia is currently treated with phototherapy or exchange transfusion; however, its prevention by inhibiting bilirubin formation is a more logical strategy. Heme oxygenase (HO), with inducible (HO-1) and constitutive (HO-2) isoenzymes, is the rate-limiting enzyme in heme catabolism, producing equimolar amounts of bilirubin and carbon monoxide (CO). Metalloporphyrins (Mps) are heme derivatives that competitively inhibit HO and thereby suppress hyperbilirubinemia. No systematic studies have been reported evaluating whether the HO isoenzymes are inhibited differentially by various Mps. Identification of Mps that selectively inhibit the inducible HO-1 without affecting the 'housekeeping' HO-2 isoenzyme might be desirable in the clinical setting of hemolytic disease, in which the Hmox1 gene is greatly induced. Although bilirubin production is due to the activity of both HO-1 and HO-2, the inhibition of HO-1 with a relative sparing of HO-2 activity might provide the most selective approach for the treatment of hemolytic disease.Study Design: We determined for the deutero-, proto-, meso-and bisglycol porphyrins with zinc, tin and chromium as central atoms, respectively, the concentration needed for 50% inhibition (I 50 ) of HO-1 and HO-2 activities in rat spleen and brain tissue.Result: For a given Mp, HO-1 activity was less inhibited than that of HO-2. The order of inhibitor potency of each Mp was nearly identical for both isoenzymes. Tin mesoporphyrin was the most potent inhibitor for both isoenzymes. HO-2 selectivity was greatest for tin protoporphyrin. Conversely, the Zn compounds were least inhibitory toward HO-2. No Mp preferentially inhibited HO-1. Conclusion:Mps that produce a less inhibitory effect on HO-2, while limiting the response of the inducible HO-1, such as ZnPP, may be a useful clinical tool.

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“…[44][45][46] Heme oxygenase inhibitors developed more recently include the imidazole-dioxolanes which have been shown to selectively inhibit the mammalian HO-1 (inducible) versus the HO-2 (constitutive) isoform. 47 The dioxolane inhibitors were developed by synthetic modification of the lead compound azalanstat, an inhibitor of lanosterol 14R-demethylase, a fungal CYP and a critical enzyme in the lanosterol biosynthetic pathway. 48 While these inhibitors are selective in that inhibition of sGC, NOS, and the CYP isoforms 3A1/3A2 and CYP2E1 were not observed in vitro, it is hypothesized that by focusing on developing small-molecule inhibitors that bind specifically to the apoprotein rather than compounds that coordinate to the heme iron, we can further increase the selectivity toward HO.…”

Section: Discussionmentioning

confidence: 99%

Inhibition of the Bacterial Heme Oxygenases from Pseudomonas aeruginosa and Neisseria meningitidis: Novel Antimicrobial Targets

et al. 2007

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The final step in heme utilization and iron acquisition in many pathogens is the oxidative cleavage of heme by heme oxygenase (HO), yielding iron, biliverdin, and carbon monoxide. Thus, the essential requirement for iron suggests that HO may provide a potential therapeutic target for antimicrobial drug development. Computer-aided drug design (CADD) combined with experimental assays identified small-molecule inhibitors of the Neisseria meningitidis HO (nm-HO). CADD virtual screening applied to 800 000 compounds identified 153 for biological assay. Several of the compounds were shown to have K D values in the micromolar range for nm-HO and the Pseudomonas aeruginosa HO (pa-HO). The compounds also inhibited the growth of P. aeruginosa as well as biliverdin formation in E. coli cells overexpressing nm-HO. Thus, CADD combined with experimental analysis has been used to identify novel inhibitors of the bacterial heme oxygenases that can cross the cell membrane and specifically inhibit HO activity.

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Imidazole−Dioxolane Compounds as Isozyme-Selective Heme Oxygenase Inhibitors

Cited by 67 publications

References 25 publications

Effectiveness of Novel Imidazole-Dioxolane Heme Oxygenase Inhibitors in Renal Proximal Tubule Epithelial Cells

Effectiveness of Novel Imidazole-Dioxolane Heme Oxygenase Inhibitors in Renal Proximal Tubule Epithelial Cells

In vitro inhibition of heme oxygenase isoenzymes by metalloporphyrins

Inhibition of the Bacterial Heme Oxygenases from Pseudomonas aeruginosa and Neisseria meningitidis: Novel Antimicrobial Targets

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