RESUMO
Diamond-Blackfan anemia (DBA) is a congenital pure red cell aplasia often associated with skeletal malformations. Mutations in ribosomal protein coding genes, mainly in RPS19, account for the majority of DBA cases. The molecular mechanisms underlying DBA pathogenesis are still not completely understood. Alternative spliced isoforms of FLVCR1 (feline leukemia virus subgroup C receptor 1) transcript coding for non-functional proteins have been reported in some DBA patients. Consistently, a phenotype very close to DBA has been described in animal models of FLVCR1 deficiency. FLVCR1 gene codes for two proteins: the plasma membrane heme exporter FLVCR1a and the mitochondrial heme exporter FLVCR1b. The coordinated expression of both FLVCR1 isoforms regulates an intracellular heme pool, necessary for proper expansion and differentiation of erythroid precursors. Here, we investigate the role of FLVCR1 isoforms in a cellular model of DBA. RPS19-downregulated TF1 cells show reduced FLVCR1a and FLVCR1b mRNA levels associated with heme overload. The downregulation of FLVCR1 isoforms affects cell cycle progression and apoptosis in differentiating K562 cells, a phenotype similar to DBA. Taken together, these data suggest that alteration of heme metabolism could play a role in the pathogenesis of DBA.
Assuntos
Regulação Leucêmica da Expressão Gênica , Heme/biossíntese , Proteínas de Membrana Transportadoras/genética , RNA Mensageiro/genética , Receptores Virais/genética , Proteínas Ribossômicas/genética , Processamento Alternativo , Anemia de Diamond-Blackfan/genética , Anemia de Diamond-Blackfan/metabolismo , Anemia de Diamond-Blackfan/patologia , Apoptose , Ciclo Celular , Linhagem Celular Tumoral , Membrana Celular/metabolismo , Heme/agonistas , Heme/antagonistas & inibidores , Humanos , Células K562 , Proteínas de Membrana Transportadoras/metabolismo , Mitocôndrias/metabolismo , Modelos Biológicos , Mutação , Isoformas de Proteínas/antagonistas & inibidores , Isoformas de Proteínas/genética , Isoformas de Proteínas/metabolismo , RNA Mensageiro/antagonistas & inibidores , RNA Mensageiro/metabolismo , RNA Interferente Pequeno/genética , RNA Interferente Pequeno/metabolismo , Receptores Virais/antagonistas & inibidores , Receptores Virais/metabolismo , Proteínas Ribossômicas/antagonistas & inibidores , Proteínas Ribossômicas/metabolismoRESUMO
Infectious diseases that cause hemolysis are among the most threatening human diseases, because of severity and/or global distribution. In these conditions, hemeproteins and heme are released, but whether heme affects the inflammatory response to microorganism molecules remains to be characterized. Here, we show that heme increased the lethality and cytokine secretion induced by LPS in vivo and enhanced the secretion of cytokines by macrophages stimulated with various agonists of innate immune receptors. Activation of nuclear factor κB (NF-κB) and MAPKs and the generation of reactive oxygen species were essential to the increase in cytokine production induced by heme plus LPS. This synergistic effect of heme and LPS was blocked by a selective inhibitor of spleen tyrosine kinase (Syk) and was abrogated in dendritic cells deficient in Syk. Moreover, inhibition of Syk and the downstream molecules PKC and PI3K reduced the reactive oxygen species generation by heme. Our results highlight a mechanism by which heme amplifies the secretion of cytokines triggered by microbial molecule activation and indicates possible pathways for therapeutic intervention during hemolytic infectious diseases.
Assuntos
Heme/imunologia , Imunidade Inata/fisiologia , Peptídeos e Proteínas de Sinalização Intracelular/imunologia , Lipopolissacarídeos/imunologia , Macrófagos Peritoneais/imunologia , Proteínas Tirosina Quinases/imunologia , Espécies Reativas de Oxigênio/imunologia , Animais , Citocinas/imunologia , Citocinas/metabolismo , Células Dendríticas/imunologia , Células Dendríticas/metabolismo , Heme/agonistas , Heme/metabolismo , Heme/farmacologia , Humanos , Imunidade Inata/efeitos dos fármacos , Peptídeos e Proteínas de Sinalização Intracelular/antagonistas & inibidores , Peptídeos e Proteínas de Sinalização Intracelular/genética , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Lipopolissacarídeos/agonistas , Lipopolissacarídeos/farmacologia , Macrófagos Peritoneais/metabolismo , Camundongos , Camundongos Knockout , NF-kappa B/genética , NF-kappa B/imunologia , NF-kappa B/metabolismo , Fosfatidilinositol 3-Quinases/genética , Fosfatidilinositol 3-Quinases/imunologia , Fosfatidilinositol 3-Quinases/metabolismo , Inibidores de Fosfoinositídeo-3 Quinase , Proteína Quinase C/genética , Proteína Quinase C/imunologia , Proteína Quinase C/metabolismo , Inibidores de Proteínas Quinases/farmacologia , Proteínas Tirosina Quinases/antagonistas & inibidores , Proteínas Tirosina Quinases/genética , Proteínas Tirosina Quinases/metabolismo , Espécies Reativas de Oxigênio/metabolismo , Quinase SykRESUMO
Nitric oxide formation is impaired in chronic renal failure. The renoprotective effects of a nonhypotensive dose of HMR1766, a direct activator of the heme enzyme soluble guanylyl cyclase was studied in comparison to an ACE-i in the remnant kidney model. Male Sprague-Dawley rats were subtotally nephrectomized (SNX) or sham operated (sham) and left untreated or started on treatment with HMR1766 or ACE-i in non-hypotensive doses. BP, albumin excretion and parameters of renal damage were analyzed. After a 12-week study, urinary albumin excretion was significantly higher in untreated SNX than in sham; this increase was prevented by ACE-i and ameliorated by HMR1766. Relative kidney and left ventricular weight were significantly higher in untreated SNX compared to sham; these changes were completely prevented by HMR1766. In untreated SNX, glomerulosclerosis (1.02 +/- 0.13) was significantly higher than in sham (0.12 +/- 0.04), SNX+HMR1766 (0.27 +/- 0.04) and SNX+ACE-i (0.46 +/- 0.06). Tubulointerstitial changes went in parallel. Increased glomerular cell number after SNX (71.5 +/- 14 vs. 60 +/- 7.3 in sham) was prevented by HMR1766 (55.7 +/- 7.3), but not by ACE-i (66.6 +/- 9). The results document beneficial BP-independent HMR1766 effects on kidney structure and urinary albumin excretion in a noninflammatory model of renal failure and may argue for a novel therapeutic principle.