RESUMEN
Hemolysis-induced acute kidney injury (AKI) is attributed to heme-mediated proximal tubule epithelial cell (PTEC) injury and tubular cast formation due to intratubular protein condensation. Megalin is a multiligand endocytic receptor for proteins, peptides, and drugs in PTECs and mediates the uptake of free hemoglobin and the heme-scavenging protein α1-microglobulin. However, understanding of how megalin is involved in the development of hemolysis-induced AKI remains elusive. Here, we investigated the megalin-related pathogenesis of hemolysis-induced AKI and a therapeutic strategy using cilastatin, a megalin blocker. A phenylhydrazine-induced hemolysis model developed in kidney-specific mosaic megalin knockout (MegKO) mice confirmed megalin-dependent PTEC injury revealed by the co-expression of kidney injury molecule-1 (KIM-1). In the hemolysis model in kidney-specific conditional MegKO mice, the uptake of hemoglobin and α1-microglobulin as well as KIM-1 expression in PTECs was suppressed, but tubular cast formation was augmented, likely due to the nonselective inhibition of protein reabsorption in PTECs. Quartz crystal microbalance analysis revealed that cilastatin suppressed the binding of megalin with hemoglobin and α1-microglobulin. Cilastatin also inhibited the specific uptake of fluorescent hemoglobin by megalin-expressing rat yolk sac tumor-derived L2 cells. In a mouse model of hemolysis-induced AKI, repeated cilastatin administration suppressed PTEC injury by inhibiting the uptake of hemoglobin and α1-microglobulin and also prevented cast formation. Hemopexin, another heme-scavenging protein, was also found to be a novel ligand of megalin, and its binding to megalin and uptake by PTECs in the hemolysis model were suppressed by cilastatin. Mass spectrometry-based semiquantitative analysis of urinary proteins in cilastatin-treated C57BL/6J mice indicated that cilastatin suppressed the reabsorption of a limited number of megalin ligands in PTECs, including α1-microglobulin and hemopexin. Collectively, cilastatin-mediated selective megalin blockade is an effective therapeutic strategy to prevent both heme-mediated PTEC injury and cast formation in hemolysis-induced AKI. © 2024 The Pathological Society of Great Britain and Ireland.
Asunto(s)
Lesión Renal Aguda , Hemólisis , Túbulos Renales Proximales , Proteína 2 Relacionada con Receptor de Lipoproteína de Baja Densidad , Ratones Noqueados , Animales , Proteína 2 Relacionada con Receptor de Lipoproteína de Baja Densidad/metabolismo , Proteína 2 Relacionada con Receptor de Lipoproteína de Baja Densidad/genética , Lesión Renal Aguda/metabolismo , Lesión Renal Aguda/patología , Túbulos Renales Proximales/metabolismo , Túbulos Renales Proximales/patología , Túbulos Renales Proximales/efectos de los fármacos , Hemoglobinas/metabolismo , Ratones , Cilastatina/farmacología , Modelos Animales de Enfermedad , Fenilhidrazinas , Ratones Endogámicos C57BL , Masculino , Receptor Celular 1 del Virus de la Hepatitis A/metabolismo , alfa-Globulinas/metabolismo , HumanosAsunto(s)
Alquenos/química , Diterpenos/química , Diterpenos/síntesis química , Compuestos Heterocíclicos de 4 o más Anillos/síntesis química , Factor de Activación Plaquetaria/antagonistas & inhibidores , Alcanos/química , Compuestos Heterocíclicos de 4 o más Anillos/química , Factor de Activación Plaquetaria/químicaRESUMEN
A new cytotoxic bis-indole alkaloid, hyrtinadine A (1), with a pyrimidine moiety has been isolated from an Okinawan marine sponge Hyrtios sp., and the structure was elucidated on the basis of spectroscopic data.
Asunto(s)
Antineoplásicos/aislamiento & purificación , Alcaloides Indólicos/aislamiento & purificación , Poríferos/química , Animales , Antineoplásicos/química , Antineoplásicos/farmacología , Ensayos de Selección de Medicamentos Antitumorales , Humanos , Alcaloides Indólicos/química , Alcaloides Indólicos/farmacología , Concentración 50 Inhibidora , Células KB , Biología Marina , Estructura MolecularRESUMEN
Two 26-membered macrolides, amphidinolides B6 ( 2) and B7 ( 1), have been isolated from a marine symbiotic dinoflagellate Amphidinium sp., and the structures were elucidated on the basis of detailed analyses of 2D NMR data. The relative and absolute configurations for 1 and 2 were assigned by comparison of NMR data and CD data with those of known amphidinolides.
Asunto(s)
Dinoflagelados/química , Macrólidos/aislamiento & purificación , Macrólidos/farmacología , Animales , Dicroismo Circular , Macrólidos/química , Estructura Molecular , Resonancia Magnética Nuclear BiomolecularRESUMEN
To obtain insight into how the cyclization pathway is controlled, the mechanism of diterpene synthase reactions (the putative phomactatriene synthase and taxadiene synthases) involving the same intermediate was investigated in detail. The mechanism of the initial transformation of GGDP to verticillen-12-yl cation (A+) was proposed based on the labelling pattern of phomactatriene (9a) obtained in the feeding experiments with 13C-labelled acetates. To obtain information on the reaction pathway of A+ to 9a and taxadiene, reactions of verticillol with various acids were conducted. Structural determination of products allowed us to propose a reaction pathway via cations A+, D+, E+, F+ and G+. Identification of hydrocarbons in mycelial extracts of phomactin-producing fungus supported the proposed reaction mechanism. Based on the results of ab initio calculations for highly flexible cation intermediates, a mechanism is proposed.