RESUMEN
INTRODUCTION: Hepatocellular carcinoma is the most common form of primary hepatic carcinoma. A new N(2)S(2) tetradentate ligand, N-[2-(triphenylmethyl)thioethyl]-3-aza-19-ethyloxycarbonyl-3-[2-(triphenylmethyl)thioethyl]octadecanoate (H(3)MN-16ET), was introduced and labeled with (188)Re to create (188)Re-MN-16ET in the Lipiodol phase. The potential of (188)Re-MN-16ET/Lipiodol for hepatoma therapy was evaluated in a hepatocellular carcinoma animal model of Sprague-Dawley rats implanted with the N1S1 cell line. METHODS: Synthesis of H(3)MN-16ET was described, and characterization was identified by infrared, nuclear magnetic resonance and mass spectra. We compared the effects of transchelating agents (glucoheptonate or tartaric acid) and a reducing agent (stannous chloride) on the complexing of (188)Re-perrhenate and H(3)MN-16ET. Twenty-four rats implanted with hepatoma were injected with 3.7 MBq/0.1 ml of (188)Re-MN-16ET/Lipiodol or (188)Re-MN-16ET via transcatheter arterial embolization. Biodistribution experiments and single-photon emission computed tomography imaging were performed to investigate tumor accumulation. RESULTS: H(3)MN-16ET was proved to easily conjugate with the Re isotope and showed good solubility in Lipiodol. The radiochemical purity of (188)Re-MN-16ET/Lipiodol with 10 mg tartaric acid and stannous chloride was shown to be more than 90%. The major distribution sites of (188)Re-MN-16ET in Sprague-Dawley rats were hepatoma and the liver. However, the radioactivity at the tumor site postadministered with (188)Re-MN-16ET was quickly decreased from 9.15±0.23 (at 1 h) to 2.71%±0.18% of injected dose/g (at 48 h). The biodistribution and micro-single-photon emission computed tomography/computed tomography image data showed that (188)Re-MN-16ET/Lipiodol was selectively retained at the tumor site, with 11.55±1.44, 13.16±1.46 and 10.67%±0.95% of injected dose/g at 1, 24 and 48 h postinjection, respectively. The radioactivity in normal liver tissue was high but significantly lower than that of the tumors. CONCLUSION: H(3)MN-16ET is a suitable tetradentate ligand for (188)Re labeling. From the animal data, we suggest that (188)Re-MN-16ET/Lipiodol has the potential to be a therapeutic radiopharmaceutical for hepatoma treatment.
Asunto(s)
Carcinoma Hepatocelular/radioterapia , Complejos de Coordinación/síntesis química , Complejos de Coordinación/uso terapéutico , Aceite Etiodizado/química , Glicina/análogos & derivados , Neoplasias Hepáticas/radioterapia , Ácidos Palmíticos/síntesis química , Ácidos Palmíticos/uso terapéutico , Radioisótopos/uso terapéutico , Renio/uso terapéutico , Estearatos/síntesis química , Estearatos/uso terapéutico , Animales , Carcinoma Hepatocelular/diagnóstico por imagen , Carcinoma Hepatocelular/metabolismo , Línea Celular Tumoral , Complejos de Coordinación/química , Complejos de Coordinación/farmacocinética , Modelos Animales de Enfermedad , Glicina/síntesis química , Glicina/química , Glicina/farmacocinética , Glicina/uso terapéutico , Neoplasias Hepáticas/diagnóstico por imagen , Neoplasias Hepáticas/metabolismo , Masculino , Ácidos Palmíticos/química , Ácidos Palmíticos/farmacocinética , Radioquímica , Ratas , Estearatos/química , Estearatos/farmacocinética , Tomografía Computarizada de Emisión de Fotón ÚnicoRESUMEN
N-Acylethanolamines, including N-palmitoyl-ethanolamine (PEA), are hydrolyzed to the corresponding fatty acids and ethanolamine by fatty acid amide hydrolase (FAAH). Recently, N-acylethanolamine-hydrolyzing acid amidase (NAAA) was identified as being able to specifically hydrolyze PEA. In order to find selective and effective inhibitors of this enzyme, we synthesized and screened several amides, retroamides, esters, retroesters and carbamates of palmitic acid (1-21) and esters with C15 and C17 alkyl chains (22-27). Cyclopentylhexadecanoate (13) exhibited the highest inhibitory activity on NAAA (IC(50)=10.0 microM), without inhibiting FAAH up to 50 microM. Compound 13 may become a useful template to design new NAAA inhibitors.