Lipopolysaccharide and interleukin 1 augment the effects of hypoxia and inflammation in human pulmonary arterial tissue.

Abstract

The combined effects of hypoxia and interleukin 1, lipopolysaccharide, or tumor necrosis factor a on the expression of genes encoding endothelial constitutive and inducible nitric oxide synthases, endothelin 1, interleukin 6, and interleukin 8 were investigated in human primary pulmonary endothelial cells and whole pulmonary artery organoid cultures. Hypoxia decreased the expression of constitutive endothelial nitric oxide synthase (NOS-3) mRNA and NOS-3 protein as compared with normoxic conditions. The inhibition of expression of NOS-3 corresponded with a reduced production of NO. A combination of hypoxia with bacterial lipopolysaccharide, interleukin 113, or tumor necrosis factor a augmented both effects. In contrast, the combination of hypoxia and the inflammatory mediators superinduced the expression of endothelin 1, interleukin 6, and interleukin 8. Here, we have shown that inflammatory mediators aggravate the effect of hypoxia on the down-regulation of NOS-3 and increase the expression of proinflammatory cytokines in human pulmonary endothelial cells and whole pulmonary artery organoid cultures.The pathogenesis of pulmonary hypertension is unknown. However, both experimental and clinical evidence indicate that hypoxia or inflammation dramatically aggravates the extent of pulmonary hypertension, e.g., during acute bacterial infection in patients with chronic obstructive pulmonary disease. Experimental evidence suggests endothelial nitric oxide production as the main regulator ofvascular tone in pulmonary arteries. Nitric oxide (NO) is mainly produced by three isoforms of NO synthases (NOS 1-3), two of which are constitutively present in neuronal or endothelial cells (NOS-1 or NOS-3, respectively) (1). In human umbilical vein endothelial cells, hypoxia was found to be responsible for both a decrease of human NOS-3 and an increase of human endothelin 1 (ET-1) mRNA (2). Conversely, exposure of rat lungs to hypoxia for more than 1 week caused an increase of both NOS-3 mRNA and protein leading to a doubled production of NO (3). In short-term cultures using human aortic endothelial cells, inflammatory mediators have been demonstrated both to increase the mRNA of the inducible isoform of nitric oxide synthases (iNOS or NOS-2) and to decrease the amount of NOS-3 mRNA, which may imply a major influence of NOS-2 on the regulation of vascular tone during inflammatory states (4). NO has been shown to down-regulate the expression of vasoconstrictors and growth factors such as ET-1, interleukin 1 (IL-1), and platelet-derived growth factor in human umbilical vein endothelial cells (5). Similarly, proinflammatory cytokines were shown to induce the synthesis of NO, suggesting a crucial role of inflammatory mediators in the regulation of arterial tissues (6). Analogously, hypoxia stimulated the induction of major vascular growth factors such as ET-1 (5) and platelet-derived growth factor B (PDGF-B) (8). To evaluate the influence of inflammation and/or hypoxia on the regulation of NO biosynthesis, we characterized the...

Regulation of interleukin-8 expression by reduced oxygen pressure in human glioblastoma

“…It is also possible that in vivo in¯ammatory cells such as microglia or macrophages participate in IL-8 expression since anoxia can stimulate them to release IL-8 (Metinko et al, 1992). Tumor microvascular cells were not found to express IL-8, although endothelial cells can synthesize IL-8 in response to hypoxia (Karakurum et al, 1994;Stevens and Rodman, 1995;Ziesche et al, 1996). Despite the fact that hypoxia stimulates the release of IL-8 and facilitates polymorphonuclear leukocytes (PMN) transmigration (Colgan et al, 1996), PMN in®ltrates are rarely found in glioblastoma sections.…”

Hypoxic pulmonary vasoconstriction and pulmonary artery tissue cytokine expression are mediated by protein kinase C

“…Although it is not clear what role proinflammatory cytokine production from the PA plays, or the magnitude of cytokine production from the PA, these findings suggest that the local production of cytokines may effect direct changes in vascular reactivity. Indeed, previous studies have shown that inflammatory cytokines potentiate HPV (33). This could be compared with the relatively recent recognition that production of inflammatory mediators from cardiomyocytes may contribute to myocardial dysfunction following ischemia-reperfusion or other acute insults (14).…”

Active Stabilization of Human Endothelial Nitric Oxide Synthase mRNA by hnRNP E1 Protects against Antisense RNA and MicroRNAs

“…Under normal conditions, the eNOS mRNA is highly stable in human ECs, with a half-life in excess of 24 h, as assessed by actinomycin D transcription arrest experiments (8). Notably, we and others have shown that hypoxia significantly downregulates eNOS gene expression in ECs, with major contributions from the posttranscriptional downregulation of eNOS mRNA expression (9)(10)(11). In addition, models of proliferation/injury (12), tumor necrosis factor alpha (TNF-␣) treatment (13,14), and exposure to lipopolysaccharide (15) or high levels of oxidized low-density lipoprotein (16) all decrease eNOS steady-state mRNA expression in cultured ECs in a manner dependent, in major part, on changes in eNOS mRNA stability.…”