Regulation of pro-inflammatory responses by lipoxygenases via intracellular reactive oxygen species in vitro and in vivo

Association between genetic variations of the transforming growth factor ß receptor type III and asthma in a Korean population

Transforming growth factor-beta (TGF-ß) and its receptors have been suggested to play key roles in the pathogenesis of asthma. The aim of this study was to evaluate the effects of genetic variations in the TGF-ß receptor type III (TGFBR3) on asthma and on its related phenotypes in the general population. A cohort of 2,118 subjects aged from 10 to 18 years responded to a questionnaire concerning asthma symptoms and risk factors. Methacholine airway hyperresponsiveness (AHR), skin test responses to common aeroallergens, and serum total IgE levels were evaluated in the cohort. A total of 19 SNPs for TGFBR3 were found using direct re-sequencing in 24 healthy adults. Of these, informative SNPs [+44T>C (S15F) and +2753G>A at 3'UTR] were selected and scored using the high throughput single base extension method. Atopy was identified in subjects with 44T>C allele [P=0.04, OR (95% CI)=0.79 (0.62-0.99)] and in subjects with Ht1 (CG) more frequently than in subjects with other haplotypes [P=0.04, OR (95% CI)=1.27 (1.01-1.59)]. The A allele in 2753G>A was more common in subjects with non-atopic asthma [OR (95% CI)=1.76 (1.01-3.05)]. A significant association was found between non-atopic asthma and 44T_2753A [OR (95% CI) =2.16 (1.22-3.82)]. Genetic variations in TGFBR3 appear to be associated with a genetic predisposition to development of asthma and to phenotypes of asthma. Also, the minor allele 2753G and the haplotype TA in the TGFBR3 gene were associated with a pathogenesis of non-atopic asthma.

Mono(2-ethylhexyl) phthalate induces both pro- and anti-inflammatory responses in rat alveolar macrophages through crosstalk between p38, the lipoxygenase pathway and PPARalpha

Airway inflammation is important in asthma pathogenesis. Recent epidemiological data have indicated an association between asthma symptoms in children and exposure to di(2-ethylhexyl) phthalate (DEHP). Thus, we have studied inflammatory responses in primary rat alveolar macrophages (AMs) after exposure to mono(2-ethylhexyl) phthalate (MEHP), the major primary metabolite of DEHP. First, we show that MEHP induces a dose-dependent release of the pro-inflammatory tumour necrosis factor-alpha (TNF-alpha) in AMs, giving a maximal (5-fold) increase at 0.7 mM. This concentration also induced some cell death. MEHP also induced phosphorylation of MAPK p38, while the p38 inhibitor SB 202190 reduced MEHP-induced TNF-alpha, suggesting a p38-dependent cytokine production. Next, we elucidated possible effects of MEHP on the 5-lipoxygenase (5-LO) pathway and found that MEHP caused increased leukotriene (LTB(4)) release. Further, we found that the 5-LO inhibitor nordihydrogualaretic acid (NDGA) significantly reduced both MEHP-induced TNF-alpha release and MEHP-induced formation of reactive oxygen species (ROS), supporting an involvement of the 5-LO pathway in MEHP induced inflammatory reactions. Last, we found that MK-886, a known inhibitor of peroxisome proliferator-activated receptor alpha (PPARalpha), increased the MEHP-induced TNF-alpha response. This indicates that MEPH-PPARalpha binding mediates an anti-inflammatory signal.

Upregulation of xCT by KSHV-encoded microRNAs facilitates KSHV dissemination and persistence in an environment of oxidative stress

Upregulation of xCT, the inducible subunit of a membrane-bound amino acid transporter, replenishes intracellular glutathione stores to maintain cell viability in an environment of oxidative stress. xCT also serves as a fusion-entry receptor for the Kaposi's sarcoma-associated herpesvirus (KSHV), the causative agent of Kaposi's sarcoma (KS). Ongoing KSHV replication and infection of new cell targets is important for KS progression, but whether xCT regulation within the tumor microenvironment plays a role in KS pathogenesis has not been determined. Using gene transfer and whole virus infection experiments, we found that KSHV-encoded microRNAs (KSHV miRNAs) upregulate xCT expression by macrophages and endothelial cells, largely through miR-K12-11 suppression of BACH-1-a negative regulator of transcription recognizing antioxidant response elements within gene promoters. Correlative functional studies reveal that upregulation of xCT by KSHV miRNAs increases cell permissiveness for KSHV infection and protects infected cells from death induced by reactive nitrogen species (RNS). Interestingly, KSHV miRNAs simultaneously upregulate macrophage secretion of RNS, and biochemical inhibition of RNS secretion by macrophages significantly reduces their permissiveness for KSHV infection. The clinical relevance of these findings is supported by our demonstration of increased xCT expression within more advanced human KS tumors containing a larger number of KSHV-infected cells. Collectively, these data support a role for KSHV itself in promoting de novo KSHV infection and the survival of KSHV-infected, RNS-secreting cells in the tumor microenvironment through the induction of xCT.

A cell-based assay for screening lipoxygenase inhibitors

Lipoxygenases (LOX) form a family of lipid peroxidizing enzymes within the plant and animal kingdoms. In humans, six functional lipoxygenase isoforms have been identified. 5-LOX, "platelet-type" 12-LOX (p12-LOX) and 15-LOX type 1 (15-LOX1), originally identified in leukocytes, platelets, and reticulocytes, respectively, generate lipid mediators involved in host cellular functions and in the pathophysiology of asthma, cardiovascular diseases, and cancer. The pharmaceutical industry has reinvigorated their programs to develop novel LOX inhibitors in view of recent findings. However, high throughput LOX screening assays to test novel agents against these intracellular enzymes are limited. We describe a cell-based 96-well microplate fluorescence assay tested against several existing LOX inhibitors, and validate the assay by comparing known IC(50) values and HPLC analysis, which may provide a useful screen for novel LOX inhibitors.