RESUMEN
Interleukin (IL)-24 has death-promoting effects on various proliferating cells including B-cells from chronic lymphocytic leukemia (CLL) and germinal center B-cells, but its molecular mechanisms are poorly understood. Using a B-cell differentiation model and mRNA profiling, we found that recombinant (r)IL-24 stimulated genes of the mitochondrial apoptotic pathway (Bax, Bid, Casp8, COX6C, COX7B) after 36 h, whereas the transcription of genes involved in DNA replication and metabolism was inhibited within 6 h. Unexpectedly, insulin-like growth factor 1 (IGF1), a hormone known to promote cell growth, was stimulated by IL-24. Activated B-cells express receptor for IGF1, to which they become sensitized and undergo apoptosis, a mechanism similar in this respect to IL-24-induced cell death. Furthermore, inhibition of the IGF1 pathway reversed the effects of IL-24. IL-24-mediated apoptosis was also antagonized by pifithrin-alpha, an inhibitor of p53 transactivation. Altogether, these results disclose sequential molecular signals generated by IL-24 in activated B-cells.
Asunto(s)
Apoptosis/efectos de los fármacos , Linfocitos B/efectos de los fármacos , Puntos de Control del Ciclo Celular/efectos de los fármacos , Interleucinas/farmacología , Mitocondrias/efectos de los fármacos , Transducción de Señal/efectos de los fármacos , Apoptosis/genética , Linfocitos B/citología , Linfocitos B/metabolismo , Proteína Proapoptótica que Interacciona Mediante Dominios BH3/genética , Proteína Proapoptótica que Interacciona Mediante Dominios BH3/metabolismo , Western Blotting , Caspasa 8/genética , Caspasa 8/metabolismo , Puntos de Control del Ciclo Celular/genética , Células Cultivadas , Niño , Preescolar , Complejo IV de Transporte de Electrones/genética , Complejo IV de Transporte de Electrones/metabolismo , Humanos , Factor I del Crecimiento Similar a la Insulina/genética , Factor I del Crecimiento Similar a la Insulina/metabolismo , Interleucinas/genética , Leucemia Linfocítica Crónica de Células B/genética , Leucemia Linfocítica Crónica de Células B/metabolismo , Leucemia Linfocítica Crónica de Células B/patología , Mitocondrias/genética , Mitocondrias/metabolismo , Análisis de Secuencia por Matrices de Oligonucleótidos , Proteínas Recombinantes/farmacología , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Transducción de Señal/genética , Factores de Tiempo , Transcriptoma/efectos de los fármacos , Transcriptoma/genética , Células Tumorales Cultivadas , Proteína p53 Supresora de Tumor/genética , Proteína p53 Supresora de Tumor/metabolismo , Proteína X Asociada a bcl-2/genética , Proteína X Asociada a bcl-2/metabolismoRESUMEN
The balance between extracellular inorganic phosphate (ePi) and extracellular inorganic pyrophosphate (ePPi) is controlled by four membrane proteins: the transporters ANK (exporting PPi outside the cells) and PiT-1 (importing ePi into the cells), and the enzymes PC-1 (generating ePPi from nucleotides) and Tissue Non-specific Alkaline Phosphatase (TNAP, hydrolyzing ePPi into ePi). TGF-ß1 was shown to stimulate ANK and PC-1 expression in articular chondrocytes, and subsequent ePPi level, as well as to increase ePi uptake by inducing PiT-1 expression in a chondrogenic cell line. Thus, we investigated the ability of ePi to modulate the effect of TGF-ß1 on the regulatory proteins of the ePi/ePPi balance in chondrocytes. In the pathophysiological range of 0.01-1 mM, ePi was inactive by itself but potentiated the stimulatory effects of TGF-ß1 on ANK, PC-1 or PiT-1 mRNA (RT-qPCR) and protein (Western blot) levels. PC-1 activity was also increased by TGF-ß1 and further potentiated by ePi supplementation. TNAP mRNA and activity became undetectable in response to TGF-ß1. These data suggest that ePi could increase ePPi level by changing the control of ANK and PC-1 expression by TGF-ß1, further highlighting an adaptative regulation of the Pi/PPi balance to prevent basic calcium phosphate deposition into the joints.