RESUMEN
Streptococcus pyogenes can be efficiently internalized by a variety of human epithelial cells. beta-lactam antibiotics, commonly used to treat S. pyogenes infections, do not readily permeate mammalian cells. There is growing evidence that the ability of streptococci to enter host cells contributes to the frequent failure of antibiotics to eradicate the organism from infected individuals. Recent studies have suggested that host cell entry requires the formation of a complex of a bacterial fibronectin (Fn) binding protein (e.g., M1 protein or protein F1/SfbI), human Fn, and the epithelial cell Fn receptor, integrin alpha5beta1. We report here that a low molecular weight, nonpeptide antagonist of integrin alpha5beta1, SJ755, can inhibit internalization of streptococci by primary human tonsillar epithelial cells and immortalized human epithelial (A549) cells, thus increasing the extent of bacterial killing by antibiotics. SJ755 blocked Fn binding by human tonsillar epithelial and A549 cells, suggesting that integrin alpha5beta1 is the major Fn receptor expressed by both cell types. SJ755 did not affect Fn binding by purified M1 protein or M1(+) bacteria. Purified M1 protein failed to associate with integrin alpha5beta1 unless the integrin had been prebound by Fn. Also, SJ755 blocked formation of alpha5beta1-Fn-M1 complexes in vitro. These results support the previous proposal that Fn functions as a molecular bridge between M1 protein and integrin alpha5beta1. Furthermore, these results suggest that integrin antagonists may enhance the efficacy of antibiotics in treatment of S. pyogenes infections.
Asunto(s)
Adhesinas Bacterianas , Antígenos Bacterianos , Proteínas de la Membrana Bacteriana Externa , Proteínas Bacterianas/metabolismo , Proteínas Portadoras/metabolismo , Células Epiteliales/microbiología , Fibronectinas/metabolismo , Integrinas/antagonistas & inhibidores , Receptores de Fibronectina/metabolismo , Streptococcus pyogenes/metabolismo , Bencimidazoles/farmacología , Adhesión Celular , Línea Celular , Relación Dosis-Respuesta a Droga , Ensayo de Inmunoadsorción Enzimática , Humanos , Modelos Biológicos , Tonsila Palatina/microbiología , Péptidos , Unión Proteica , Receptores de Fibronectina/antagonistas & inhibidores , Compuestos de Espiro/farmacologíaRESUMEN
Starting with lead compound 2, we sought to increase the selectivity for alpha(v)beta(3)-mediated cell adhesion by examining the effects of structural changes in both the guanidine mimetic and the substituent alpha to the carboxylate. To prepare some of the desired aminoimidazoles, a novel reductive amination utilizing a trityl-protected aminoimidazole was developed. It was found that guanidine mimetics with a wide range of pK(a)'s were potent antagonists of alpha(v)beta(3). In general, it appeared that an acylated 2-aminoimidazole guanidine mimetic imparted excellent selectivity for alpha(v)beta(3)-mediated adhesion versus alpha(IIb)beta(3)-mediated platelet aggregation, with selectivity of approximately 3 orders of magnitude observed for compounds 3g and 3h. It was also found in this series that the alpha-substituent was required for potent activity and that 2,6-disubstituted arylsulfonamides were optimal. In addition, the selective alpha(v)beta(3) antagonist 3h was found to be a potent inhibitor of alpha(v)beta(3)-mediated cell migration.
Asunto(s)
Isoxazoles/síntesis química , Receptores de Vitronectina/antagonistas & inhibidores , beta-Alanina/análogos & derivados , Adhesión Celular/efectos de los fármacos , Movimiento Celular/efectos de los fármacos , Quimiotaxis/efectos de los fármacos , Guanidinas/química , Humanos , Hiperplasia/metabolismo , Técnicas In Vitro , Isoxazoles/química , Isoxazoles/farmacología , Riñón/citología , Riñón/efectos de los fármacos , Riñón/metabolismo , Agregación Plaquetaria/efectos de los fármacos , Receptores de Vitronectina/biosíntesis , Estereoisomerismo , Relación Estructura-Actividad , Células Tumorales Cultivadas , Vitronectina/farmacología , beta-Alanina/síntesis química , beta-Alanina/química , beta-Alanina/farmacologíaRESUMEN
Five metabolites of actinomycete X-14881 were isolated from the fermentation broth and characterized. The major component was identified as [3R-(3 alpha,6a beta,7 beta,12 alpha,12a alpha)] or [3S-(3 beta,6a alpha, 7 alpha,12 beta,12a beta)]-6a, 7,12-trihydroxy-3,4,6a, 7,12, 12a-hexahydro-8-methoxy-3-methylbenz[a]-anthracen-1(2H)-one; the other four are closely related derivatives thereof.
Asunto(s)
Actinomycetales/metabolismo , Antibacterianos/biosíntesis , Benzo(a)Antracenos/metabolismo , Antibacterianos/aislamiento & purificación , Fenómenos Químicos , Química Física , Cristalización , Fermentación , Modelos MolecularesRESUMEN
Micromonospora echinospora strain X-14847 produces gentamicin A as the major antibiotic together with a new aminoglycoside, termed X-14847, and identified as a 2-amino-2-deoxy-alpha-D-glucopyranosyl myo-inositol. This report describes the taxonomy of the culture, fermentation conditions, the isolation and the identification of X-14847.