RESUMO
Previous studies have reported that uric acid stimulates vascular smooth muscle cell (VSMC) proliferation in vitro. We hypothesized that uric acid may also have direct proinflammatory effects on VSMCs. Crystal- and endotoxin-free uric acid was found to increase VSMC monocyte chemoattractant protein-1 (MCP-1) expression in a time- and dose-dependent manner, peaking at 24 hours. Increased mRNA and protein expression occurred as early as 3 hours after uric acid incubation and was partially dependent on posttranscriptional modification of MCP-1 mRNA. In addition, uric acid activated the transcription factors nuclear factor-kappaB and activator protein-1, as well as the MAPK signaling molecules ERK p44/42 and p38, and increased cyclooxygenase-2 (COX-2) mRNA expression. Inhibition of p38 (with SB 203580), ERK 44/42 (with UO126 or PD 98059), or COX-2 (with NS398) each significantly suppressed uric acid-induced MCP-1 expression at 24 hours, implicating these pathways in the response to uric acid. The ability of both n-acetyl-cysteine and diphenyleneionium (antioxidants) to inhibit uric acid-induced MCP-1 production suggested involvement of intracellular redox pathways. Uric acid regulates critical proinflammatory pathways in VSMCs, suggesting it may have a role in the vascular changes associated with hypertension and vascular disease.
Assuntos
Quimiocina CCL2/biossíntese , Isoenzimas/fisiologia , Proteínas Quinases Ativadas por Mitógeno/fisiologia , Músculo Liso Vascular/metabolismo , Prostaglandina-Endoperóxido Sintases/fisiologia , Ácido Úrico/farmacologia , Animais , Células Cultivadas , Quimiocina CCL2/genética , Ciclo-Oxigenase 2 , Regulação da Expressão Gênica , Isoenzimas/genética , Proteína Quinase 1 Ativada por Mitógeno/fisiologia , Proteína Quinase 3 Ativada por Mitógeno , Músculo Liso Vascular/efeitos dos fármacos , Músculo Liso Vascular/enzimologia , NF-kappa B/metabolismo , Oxirredução , Prostaglandina-Endoperóxido Sintases/genética , RNA Mensageiro/biossíntese , Ratos , Fator de Transcrição AP-1/metabolismo , Regulação para Cima , Proteínas Quinases p38 Ativadas por MitógenoRESUMO
Cardiomyocytes of the failing heart undergo profound phenotypic and structural changes that are accompanied by variations in the genetic program and profile of calcium homeostatic proteins. The underlying mechanisms for these changes remain unclear. Because the mammalian counterpart of the fish calcium-regulating hormone stanniocalcin-1 (STC1) is expressed in the heart, we reasoned that STC1 might play a role in the adaptive-maladaptive processes that lead to the heart failure phenotype. We examined the expression and localization of STC1 in cardiac tissue of patients with advanced heart failure before and after mechanical unloading using a left ventricular assist device (LVAD), and we compared the results with those of normal heart tissue. STC1 protein is markedly upregulated in cardiomyocytes and arterial walls of failing hearts pre-LVAD and is strikingly reduced after LVAD treatment. STC1 is diffusely expressed in cardiomyocytes, although nuclear predominance is apparent. Addition of recombinant STC1 to the medium of cultured rat cardiomyocytes slows their endogenous beating rate and diminishes the rise in intracellular calcium with each contraction. Furthermore, using whole cell patch-clamp studies in cultured rat cardiomyocytes, we find that addition of STC1 to the bath causes reversible inhibition of transmembrane calcium currents through L-channels. Our data suggest differential regulation of myocardial STC1 protein expression in heart failure. In addition, STC1 may regulate calcium currents in cardiomyocytes and may contribute to the alterations in calcium homeostasis of the failing heart.
