Heme Oxygenase-1/Carbon Monoxide Induces Vascular Endothelial Growth Factor Expression via p38 Kinase-dependent Activation of Sp1

Abstract

Heme oxygenase-1 (HO-1) is a stress-inducible enzyme catalyzing the oxidative degradation of heme to free iron, CO, and biliverdin. Previous studies demonstrated that HO-1 overexpression promoted VEGF expression and angiogenesis in the ischemic heart. However, the underlying mechanism remained elusive. Here we show that adenovirus-mediated HO-1 transduction of rat primary cardiomyocytes and H9C2 myocytes resulted in significant induction of VEGF expression, and a similar effect was seen in cells directly exposed to CO gas or a CO-releasing compound, tricarbonyldichlororuthenium (II) dimer. HO-1/CO-induced VEGF expression was significantly suppressed by pharmacological inhibition of p38 kinase, but not of AKT, activation. VEGF promoter-luciferase reporter assays, electrophoretic mobility shift assays, supershift assay, and chromatin immunoprecipitation showed that CO-induced VEGF promoter activation requires the binding of the Sp1 transcriptional factor to a cis-regulatory sequence located at the VEGF promoter. Western blot analysis and immunostaining experiments demonstrated that HO-1/CO induced p38-dependent phosphorylation of Sp1 at Thr-453 and Thr-739 both in vitro and in vivo. Overexpression of Sp1 protein with an alanine mutation at Thr-453 or Thr-739 suppressed CO-induced Sp1 binding to the VEGF promoter and its transcriptional activation. Collectively, these data suggest that p38-dependent phosphorylation of Sp1 at Thr-453/Thr-739 is crucial for HO-1/CO-induced VEGF expression in myocytes.

Lipopolysaccharide Decreases Single Immunoglobulin Interleukin-1 Receptor-related Molecule (SIGIRR) Expression by Suppressing Specificity Protein 1 (Sp1) via the Toll-like Receptor 4 (TLR4)-p38 Pathway in Monocytes and Neutrophils

“…In the present study, we also determined that LPSdependent SIGIRR down-regulation seems due to inhibition of Sp1-dependent SIGIRR basal expression in monocytic and neutrophilic cells by using primary cells and cell lines. Moreover, our findings emphasized that LPS-activated p38 contributes to suppress Sp1-dependent SIGIRR basal expression, although generally p38 have been assumed to be a positive regulator of Sp1 (23,24). Thus, our findings are the first to show a negative regulatory role of p38 on Sp1-dependent transcription.…”

Regulation of integrin αV subunit expression by sulfatide in hepatocellular carcinoma cells

“…The transcription expression of the integrin ␣ V subunit gene is commonly controlled by transcriptional factors, among which Sp1 has binding sites in the integrin ␣ V subunit gene promoter, and phosphorylation on threonine 739 was enhanced after sulfatide stimulation. Sp1 mediates its target genes and can change its activity by phosphorylation on threonine 739 ( 36 ). Regarding the integrin ␣ V subunit, Sp1 promoted its expression by enhanced binding activity to the promoter because Sp1 protein was phosphorylated and its expression was elevated.…”

“…This fi nding demonstrated that Erk1/2 signaling activation is important in Sp1 phosphorylation and integrin ␣ V subunit expression regulation by sulfatide. Activated p38 can also phosphorylate Sp1 on threonine 739 ( 36 ). Thus, activation of p38 contributes to the phosphorylation and activation of Sp1 as well, although the phosphorylation of p38 (T180/Y182) was not as robust as Erk1/2.…”

Repair and regeneration properties of Ginkgo biloba after ischemic brain injury

“…We have highly plausible explanations to establish the link between the two. For example, it is well known that HO1 is an inducer of vascular endothelial growth factor (VEGF) (Cisowski et al, 2005; Lin et al, 2011), which is not only a promoter of angiogenesis but also has neurogenic properties (Sun et al, 2003). Thus HO1 seems to act on the neurovascular niche that supports the newly formed neurons as well as the vasculature surrounding the network.…”