| 2020 | Acylhydrazones as isoniazid derivatives with multi-target profiles for the treatment of Alzheimer's disease: Radical scavenging, myeloperoxidase/acetylcholinesterase inhibition and biometal chelation. | Bioorg Med Chem | Acylhydrazones 1a-o, derived from isoniazid, were synthesized and evaluated for Myeloperoxidase (MPO) and Acetylcholinesterase (AChE) inhibition, as well as their antioxidant and metal chelating activities, with the purpose of investigating potential multi-target profiles for the treatment of Alzheimer's disease. Synthesized compounds were tested using the 2,2-diphenyl-2-picrylhydrazyl (DPPH) method and 1i, 1j and 1 m showed radical scavenging ability. Compounds 1b, 1 h, 1i, 1 m and 1o inhibited MPO activity (10 μM) at 96.1 ± 5.5%, 90 ± 2.1%, 100.3 ± 1.7%, 80.1 ± 9.4% and 82.2 ± 10.6%, respectively, and only compound 1 m was able to inhibit 54.2 ± 1.7% of AChE activity (100 μM). Docking studies of the most potent compound 1 m were carried out, and the computational results provided the theoretical basis of enzyme inhibition. Furthermore, compound 1 m was able to form complexes with Fe and Zn ions in a 2:1 ligand:metal ratio according to the Job Plot method. |
| 2014 | Ordered cleavage of myeloperoxidase ester bonds releases active site heme leading to inactivation of myeloperoxidase by benzoic acid hydrazide analogs. | Arch Biochem Biophys | Myeloperoxidase (MPO) catalyzes the breakdown of hydrogen peroxide and the formation of the potent oxidant hypochlorous acid. We present the application of the fluorogenic peroxidase substrate 10-acetyl-3,7-dihydroxyphenoxazine (ADHP) in steady-state and transient kinetic studies of MPO function. Using initial kinetic parameters for the MPO system, we characterized under the same conditions a number of gold standards for MPO inhibition, namely 4-amino benzoic acid hydrazide (4-ABAH), isoniazid and NaN3 before expanding our focus to isomers of 4-ABAH and benzoic acid hydrazide analogs. We determined that in the presence of hydrogen peroxide that 4-ABAH and its isomer 2-ABAH are both slow-tight binding inhibitors of MPO requiring at least two steps, whereas NaN3 and isoniazid-based inhibition has a single observable step. We also determined that MPO inhibition by benzoic acid hydrazide and 4-(trifluoromethyl) benzoic acid hydrazide was due to hydrolysis of the ester bond between MPO heavy chain Glu 242 residue and the heme pyrrole A ring, freeing the light chain and heme b fragment from the larger remaining MPO heavy chain. This new mechanism would essentially indicate that the benzoic acid hydrazide analogs impart inhibition through initial ejection of the heme catalytic moiety without prior loss of the active site iron. |
| Metabolism of isoniazid by activated leukocytes. Possible role in drug-induced lupus. | Drug Metab Dispos | The tuberculostatic agent isoniazid has been implicated in inducing various idiosyncratic reactions including drug-induced lupus. The mechanism is unknown but may involve a reactive metabolite of the drug. Isoniazid was oxidized by activated leukocytes to isonicotinic acid. Myeloperoxidase is likely the enzyme in the leukocyte involved, since the oxidation was inhibited by azide, which inhibits myeloperoxidase, and by catalase, which catalyzes the breakdown of hydrogen peroxide. The same metabolic profile was observed when isoniazid was incubated with purified myeloperoxidase and hydrogen peroxide. The rate of the reaction was increased in the presence of chloride. Hypochlorous acid was also able to oxidize isoniazid to isonicotinic acid. Isoniazid, or an oxidative product, inhibited the reaction when high initial substrate concentrations were used. Isoniazid is oxidized by activated leukocytes, possibly to a reactive intermediate, which may have implications for isoniazid-induced lupus. |