TNF-alpha has been shown to induce matrix metalloproteinase-9 (MMP-9) expression, which, in turn, degrades extracellular matrix in the inflammatory responses. However, the inductive mechanisms of the MMP-9 by TNF-alpha remain unclear. In human tracheal smooth muscle cells, TNF-alpha induced MMP-9 expression and Akt phosphorylation in a time-dependent manner, which was attenuated by the inhibitors of Src (PP1), epidermal growth factor receptor (AG1478), PDGFR (AG1296), and PI3K (LY294002), respectively, revealed by reporter gene assay, RT-PCR, zymographic, and Western blot analyses. Transfection with the dominant negative mutants of c-Src (KM, K295M [kinase inactive mutant]), p85, and Akt (KA, K179A) also reduced MMP-9 expression. These findings indicated that MMP-9 expression was regulated by PI3K/Akt via the transactivation of growth factor receptors. Furthermore, LY294002 or wortmannin inhibited Akt phosphorylation but had no effect on NF-kappaB translocation, which was blocked by helenalin. Mutated NF-kappaB DNA binding element in the MMP-9 promoter and helenalin also attenuated MMP-9 expression, suggesting that PI3K/Akt and NF-kappaB independently regulated MMP-9 expression. To support this notion, immunofluorescence staining and immunoprecipitation were applied to characterize the transcription factors involved in these responses. The results showed that LY294002 and curcumin blocked Akt translocation into nucleus. In contrast, p300, acetyl-histone (H3), and NF-kappaB p65 were found to be coimmunoprecipitated with the phosphorylated Akt, indicating that these components associated with the MMP-9 promoter are revealed by chromatin immunoprecipitation assay. Thus, our study provides a new insight into the molecular mechanisms that TNF-alpha-stimulated Akt phosphorylation mediated through transactivation of Src and growth factor receptors may stimulate the recruitment of p300, assemble transcription factor (p65), and then lead to MMP-9 expression.

This study utilized a mass-resolved detection of ClOOCl to determine its photodissociation cross section, which is the product of the absorption cross section and dissociation quantum yield. An effusive molecular beam of ClOOCl was generated and its photodissociation probability was determined through measuring the decrease in the ClOOCl beam intensity upon laser irradiation. By comparing with a reference molecule, the absolute cross sections of ClOOCl were obtained without knowing its absolute concentration. The determined cross section of ClOOCl at 248.4 nm is (8.85+/-0.42)x10(-18) cm(2) at 200 K, significantly larger than previously reported values. The temperature dependence of the cross section was investigated at 248.4 nm in the range of 160-260 K; only a very small and negative temperature effect was observed. Because 248.4 nm is very close to the peak of the UV absorption band of ClOOCl, this work provides a new calibration point for normalizing relative absorption spectra of ClOOCl. In this work, the photodissociation cross section at 266 nm and 200 K was also reported to be (4.13+/-0.21)x10(-18) cm(2).

Recently, discrepancies in laboratory measurements of chlorine peroxide (ClOOCl) absorption cross sections have cast doubt on the validity of current photochemical models for stratospheric ozone degradation. Whereas previous ClOOCl absorption measurements all suffered from uncertainties due to absorption by impurities, we demonstrate here a method that uses mass-selected detection to circumvent such interference. The cross sections of ClOOCl were determined at two critical wavelengths (351 and 308 nanometers). Our results are sufficient to resolve the controversial issue originating from the ClOOCl laboratory cross sections and suggest that the highest laboratory estimates for atmospheric photolysis rates of ClOOCl, which best explain the field measurements via current chemical models, are reasonable.

Matrix metalloproteinases (MMPs) are responsible for degradation of extracellular matrix and play important roles in cell migration, proliferation, and tissue remodeling related to airway inflammation. Interleukin-1beta (IL-1beta) has been shown to induce MMP-9 production in many cell types and contribute to airway inflammatory responses. However, the mechanisms underlying MMP-9 expression induced by IL-1beta in human tracheal smooth muscle cells (HTSMCs) remain unclear. Here, we investigated the roles of p42/p44 MAPK, p38 MAPK, JNK, and NF-kappaB pathways for IL-1beta-induced MMP-9 production in HTSMCs. IL-1beta induced production of MMP-9 protein and mRNA in a time- and concentration-dependent manner determined by zymographic, Western blotting, and RT-PCR analyses, which was attenuated by inhibitors of MEK1/2 (U0126), p38 MAPK (SB202190), JNK (SP600125), and NF-kappaB (helenalin), and transfection with dominant negative mutants of MEK1/2, p38 and JNK, respectively. IL-1beta-stimulated phosphorylation of p42/p44 MAPK, p38 MAPK, and JNK was attenuated by pretreatment with U0126, SB202190, SP600125, or transfection with these dominant negative mutants of MEK, ERK, p38 and JNK, respectively. Furthermore, IL-1beta-stimulated translocation of NF-kappaB into the nucleus and degradation of IkappaB-alpha was blocked by helenalin. Finally, the reporter gene assay revealed that MAPKs and NF-kappaB are required for IL-1beta-induced MMP-9 luciferase activity in HTSMCs. MMP-9 promoter activity was enhanced by IL-1beta in HTSMCs transfected with MMP-9-Luc, which was inhibited by helenalin, U0126, SB202190, and SP600125. Taken together, the transcription factor NF-kappaB, p42/p44 MAPK, p38 MAPK, and JNK that are involved in MMP-9 expression in HTSMCs exposed to IL-1beta have now been identified.

Tumor necrosis factor-alpha (TNF-alpha) has been shown to induce the expression of adhesion molecules in airway resident cells and contribute to inflammatory responses. Here, the roles of mitogen-activated protein kinases (MAPKs) and NF-kappaB in TNF-alpha-induced expression of vascular cell adhesion molecule (VCAM)-1 were investigated in human tracheal smooth muscle cells (HTSMCs). TNF-alpha-enhanced expression of VCAM-1 protein and mRNA as well as phosphorylation of p42/p44 MAPK, p38, and JNK were significantly attenuated by inhibitors of MEK1/2 (U0126), p38 (SB202190), and JNK (SP600125). Transfection with dominant negative mutants of MEK1/2, ERK1, ERK2, p38, and JNK attenuated TNF-alpha-induced VCAM-1 expression. Furthermore, TNF-alpha-induced VCAM-1 expression was significantly blocked by a selective NF-kappaB inhibitor helenalin. TNF-alpha-stimulated translocation of NF-kappaB into the nucleus and degradation of IkappaB-alpha was blocked by helenalin, but not by U0126, SB202190, or SP600125. VCAM-1 promoter activity was enhanced by TNF-alpha in HTSMCs transfected with VCAM-1-Luc, which was inhibited by helenalin, U0126, SB202190, and SP600125. Most surprisingly, VCAM-1 expression was also significantly blocked by a selective inhibitor of p300, curcumin. NF-kappaB transcription factor and p300 were associated with the VCAM-1 promoter, which was dynamically linked to histone H3 acetylation stimulated by TNF-alpha, as determined by chromatin immunoprecipitation assay. Moreover, the resultant enhancement of VCAM-1 expression increased the adhesion of polymorphonuclear cells (PMNs) to monolayer of HTSMCs, which was blocked by helenalin, U0126, SB202190, or SP600125. These results suggest that in HTSMCs, activation of MAPK pathways, NF-kappaB, and p300 is essential for TNF-alpha-induced VCAM-1 expression.

Interleukin-1beta (IL-1beta) has been shown to induce the expression of adhesion molecules on airway epithelial and smooth cells and contributes to inflammatory responses. Here, the roles of mitogen-activated protein kinases (MAPKs) and nuclear factor-kappaB (NF-kappaB) pathways for IL-1beta-induced vascular cell adhesion molecule (VCAM)-1 expression were investigated in human tracheal smooth muscle cells (HTSMC). IL-1beta induced expression of VCAM-1 protein and mRNA in a time-dependent manner, which was significantly inhibited by inhibitors of MEK1/2 (U0126 and PD-98059), p38 (SB-202190), and c-Jun NH(2)-terminal kinase (JNK; SP-600125). Consistently, IL-1beta-stimulated phosphorylation of p42/p44 MAPK, p38, and JNK was attenuated by pretreatment with U0126, SB-202190, or SP-600125, respectively. IL-1beta-induced VCAM-1 expression was significantly blocked by the specific NF-kappaB inhibitors helenalin and pyrrolidine dithiocarbamate. As expected, IL-1beta-stimulated translocation of NF-kappaB into the nucleus and degradation of IkappaB-alpha were blocked by helenalin but not by U0126, SB-202190, or SP-600125. Moreover, the resultant enhancement of VCAM-1 expression increased the adhesion of polymorphonuclear cells to a monolayer of HTSMC, which was blocked by pretreatment with helenalin, U0126, SB-202190, or SP-600125 before IL-1beta exposure or by anti-VCAM-1 antibody. Together, these results suggest that in HTSMC, activation of p42/p44 MAPK, p38, JNK, and NF-kappaB pathways is essential for IL-1beta-induced VCAM-1 gene expression. These results provide new insight into the mechanisms of IL-1beta action that cytokines may promote inflammatory responses in airway disease.

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BACKGROUND AND PURPOSE Lipopolysaccharide (LPS)‐induced expression of cyclooxygenase‐2 (COX‐2) and cytosolic phospholipase A2 (cPLA2) has been implicated in several respiratory diseases. HuR is known to enhance the expression of genes by binding to 3′‐untranslated region (3′‐UTR) of mRNA and stabilizing mRNA. However, the exact mechanisms by which HuR affects the stability of mRNA and modulates LPS‐induced COX‐2 and cPLA2 expression in human tracheal smooth muscle cells (HTSMCs) are not known. EXPERIMENTAL APPROACH The expression of prostaglandin E2 (PGE2) was measured by ELISA, and pro‐inflammatory proteins were determined by use of a promoter assay, PCR or Western blot analysis. Overexpression of siRNAs to knock down the target components was used to manipulate the expression of HuR. Release of reactive oxygen species (ROS) was detected by fluorescence dye. The activation of signalling components was assessed by comparing phosphorylation levels, localization of protein kinases or coimmunoprecipitation assay. KEY RESULTS LPS induced COX‐2 and cPLA2 expression via post‐translational regulation of mRNA stabilization, which were attenuated by transfection with HuR siRNA in HTSMCs. In addition, LPS‐stimulated NADPH oxidase activation and ROS generation were attenuated by the NADPH oxidase inhibitors diphenyleneiodonium chloride (DPI) and apocynin (APO). Generation of ROS induced phosphorylation of p42/p44 mitogen‐activated protein kinase (MAPK), p38 MAPK and JNK1/2, which was attenuated by DPI and APO and the ROS scavenger N‐acetylcysteine. CONCLUSIONS AND IMPLICATIONS These results suggested that in HTSMCs, LPS‐induced COX‐2 and cPLA2 expression is mediated through NADPH oxidase/ROS‐dependent MAPKs associated with HuR accumulation in the cytoplasm. Activated MAPKs may regulate the nucleocytoplasmic shuttling of HuR, and thus induce the cytoplasmic accumulation of HuR.