Sp family of transcription factors is involved in iron-induced collagen alpha1(I) gene expression

The purpose of this study was to identify the cis-acting elements and the trans-acting factors involved in the iron-induced expression of the collagen alpha1(I) (COL1aI) gene. Rat hepatic stellate cells were cultured in the presence of 50 microM ferric chloride, 50 microM ascorbic acid, and 250 microM citric acid (Fe/AA/CA), and the effects on collagen gene expression and the binding of nuclear proteins to the COL1aI promoter were measured. The Fe/AA/CA treatment induced a time- and dose-dependent increase in the cellular levels of COL1aI mRNA that was abrogate by pretreating cells with cycloheximide, antioxidants, and inhibitors of aldehyde-protein adduct formation. Transient transfection experiments showed that Fe/AA/CA exerted its effect through regulatory elements located between -220 and -110 bp of the COL1aI promoter. Gel retardation assays showed that Fe/AA/CA increased the binding of nuclear proteins to two elements located between -161 and -110 bp of the COL1aI promoter. These bindings were blocked by unlabeled consensus Sp1 oligonucleotide and supershifted with Sp1 and Sp3 antibodies. Finally, Fe/AA/CA increased cellular levels of the Sp1 and Sp3 proteins and Sp1 mRNA. Treatment with Fe/AA/CA stimulates COL1aI gene expression by inducing the synthesis of Sp1 and Sp3 and their binding to two regulatory elements located between -161 and -110 bp of the COL1aI promoter.     

Progesterone potentiates calcium release through IP3 receptors by an Akt-mediated mechanism in hippocampal neurons

Progesterone (P4) is a steroid hormone that plays multiple roles in the central nervous system (CNS) including promoting neuroprotection. However, the precise mechanisms involved in its neuroprotective effects are still unknown. Given that the regulation of the intracellular calcium (Ca²⁺) concentration is critical for cell survival, we determined if inositol 1, 4, 5-trisphosphate receptors (IP₃Rs) are relevant targets of P4. Using primary hippocampal neurons, we tested the hypothesis that P4 controls the gain of IP3R-mediated intracellular Ca²⁺ signaling in neurons and characterized the subcellular distribution and phosphorylation of potential signaling intermediates involved in P4s actions. Our results reveal that P4 treatment altered the intensity and distribution of IP3R immunoreactivity and induced the nuclear translocation of phosphorylated Akt. Further, P4 potentiated IP₃R-mediated intracellular Ca²⁺ responses. These results suggest a potential involvement of P4 in particular and of steroid hormone signaling pathways in general in the control of intracellular Ca²⁺ signaling and its related functions.     

TRIM59 expression is regulated by Sp1 and Nrf1 in LPS-activated macrophages through JNK signaling pathway

Activated macrophages play an important role in many inflammatory diseases including septic shock and atherosclerosis. TRIM59 has been showed to participate in many pathological processes, such as inflammation, cytotoxicity and tumorigenesis. However, the molecular mechanisms controlling its expression in activated macrophages are not fully understood. Here we report that TRIM59 expression is regulated by Sp1 and Nrf1 in LPS-activated macrophages. TRIM59 is highly expressed in macrophages, and markedly decreased by LPS stimuli in vivo and in vitro. TRIM59 promoter activity is also significantly suppressed by LPS and further analysis demonstrated that Sp1 and Nrf1 directly bound to the proximal promoter of TRIM59 gene. LPS treatment significantly decreased Sp1 expression, nuclear translocation and reduced its binding to the promoter, whereas increased Nrf1 expression, nuclear translocation and enhanced its binding to the promoter. Moreover, LPS-decreased TRIM59 expression was reversed by JNK inhibitor. Finally, TRIM59 level is significantly decreased during atherosclerosis progression. Taken together, our results demonstrated that TRIM59 expression was precisely regulated by Sp1 and Nrf1 in LPS-activated macrophages, which may be dependent on the activation of JNK signaling pathway and TRIM59 may be a potential therapeutic target for inflammatory diseases such as atherosclerosis.     

Myocardial hypoxia-inducible HIF-1alpha, VEGF, and GLUT1 gene expression is associated with microvascular and ICAM-1 heterogeneity during endotoxemia

The systemic inflammatory response to infection is the leading cause of mortality in North American intensive-care units. Although much is known about inflammatory mediators, the relationships between microregional inflammation, microvascular heterogeneity, hypoxia, hypoxia-inducible gene expression, and myocardial dysfunction are unknown. Male Sprague-Dawley rats were injected intraperitoneally with LPS to test the hypothesis that sepsis-induced local inflammation and increased microvascular heterogeneity are spatially and temporally associated with hypoxia, hypoxia-inducible gene expression, and decreased left-ventricular contractility. Using a combination of three-dimensional microvascular imaging, tissue Po(2), and pressure-volume conductance measurements, we found that 5 h after LPS, minimum oxygen-diffusion distances increased (P < 0.05), whereas tissue oxygenation and contractility both decreased (P < 0.05) in the left ventricle. Real-time RT-PCR analysis revealed that the hypoxia-inducible genes hypoxia-inducible factor (HIF)-1alpha, VEGF, and glucose transporter (GLUT) 1 were all upregulated (P < 0.05) in the left ventricle. Tissue regions expressing ICAM-1, obtained by using laser-capture microdissection, had increased HIF-1alpha and GLUT1 (P < 0.05) gene expression. VEGF gene expression was more diffuse. In LPS rats, GLUT1 gene expression correlated (P < 0.05) with left-ventricular contractility. In 5-h hypoxic cardiomyocytes, we found strong transient HIF-1alpha, weak VEGF, and greater prolonged GLUT1 gene expression. By comparison, the HIF-1alpha-GLUT1 gene-induction pattern was reversed in the left ventricle of LPS rats. Together, these results show that LPS induces hypoxia in the left ventricle associated with increased microvascular heterogeneity and decreased contractility. HIF-1alpha and GLUT1 gene induction are related to a heterogeneous ICAM-1 expression and may be cardioprotective during the onset of septic injury.