Biomedical subjects

Robert Langenbach

Publications and source records attributed to Robert Langenbach.

28 records · Page 2Linked to original sources

PubMed2004

Interleukin-1beta-induced mucin production in human airway epithelium is mediated by cyclooxygenase-2, prostaglandin E2 receptors, and cyclic AMP-protein kinase A signaling.

We reported recently that interleukin (IL)-1beta exposure resulted in a prolonged increase in MUC5AC mucin production in normal, well differentiated, human tracheobronchial epithelial (NHTBE) cell cultures, without significantly increasing MUC5AC mRNA (Am J Physiol 286:L320-L330, 2004). The goal of the present study was to elucidate the signaling pathways involved in IL-1beta-induced MUC5AC production. We found that IL-1beta increased cyclooxygenase-2 (COX-2) mRNA expression and prostaglandin (PG) E(2) production and that the COX-2 inhibitor celecoxib suppressed IL-1beta-induced MUC5AC production. Addition of exogenous PGE(2) to NHTBE cultures also increased MUC5AC production and IL-1beta-induced Muc5ac hypersecretion in tracheas from wild-type but not from COX-2-/- mice. NHTBE cells expressed all four E-prostanoid (EP) receptor subtypes and misoprostol, an EP2 and EP4 agonist, increased MUC5AC production, whereas sulprostone, an EP1 and EP3 agonist, did not. Furthermore, specific protein kinase A (PKA) inhibitors blocked IL-1beta and PGE(2)-induced MUC5AC production. However, neither inhibition of epidermal growth factor receptor (EGFR) activation with the tyrosine kinase inhibitor 4-(3-chloroanilino)-6,7-dimethoxyquinazoline HCl (AG-1478) or EGFR blocking antibody nor inhibition of extracellular signal-regulated kinase/P-38 mitogen activated protein kinases with specific inhibitors blocked IL-1beta stimulation of MUC5AC mucin production. We also observed that tumor necrosis factor (TNF)-alpha, platelet activating factor (PAF), and lipopolysaccharide (LPS) induced COX-2 and increased MUC5AC production that was blocked by celecoxib, suggesting a common signaling pathway of inflammatory mediator-induced MUC5AC production in NHTBE cells. We conclude that the induction of MUC5AC by IL-1beta, TNF-alpha, PAF, and LPS involves COX-2- generated PGE(2), activation of EP2 and/or EP4 receptor(s), and cAMP-PKA-mediated signaling.

Bronchi↗

PubMed2003

Genetic deficiency or pharmacological inhibition of cyclooxygenase-1 or -2 induces mouse keratinocyte differentiation in vitro and in vivo.

Previously we demonstrated that genetic deficiency of the cyclooxygenases (COX-1 or COX-2) altered keratinocyte differentiation in mouse skin [Tiano et. al. (2002) Cancer Res. 62, 3395-3401]. In this study, we show that topical application of SC-560 (a COX-1 selective inhibitor) or celecoxib (COX-2 selective) to TPA-treated wild-type skin caused fivefold increases in the number of basal keratinocytes expressing the early differentiation marker keratin 1 (K1). In contrast to skin, COX-2 not COX-1 was the major isoform expressed in cultured primary keratinocytes. COX-1 was predominantly expressed in detached, differentiated cells, whereas COX-2 was found in the attached, proliferating cells. High Ca++ medium induced K1 and COX-1 in wild-type keratinocytes but did not change COX-2 expression. As observed in skin, COX-1-/- and COX-2-/- primary keratinocytes expressed fivefold more K1 than wild-type cells. K1 levels in cultured wild-type keratinocytes were also increased by treatment with celecoxib and indomethacin. However, unlike its in vivo effect, SC-560, possibly due to low COX-1 expression in cultured mouse keratinocytes, did not increase K1 levels. Furthermore, no increases in apoptotic cell numbers were observed in COX-deficient keratinocytes or COX-inhibitor treated wild-type cells. Thus, a major effect of COX inhibitors and COX-deficiency is the induction of keratinocyte differentiation.

Animals↗

PubMed2003

Cooperation of cyclooxygenase 1 and cyclooxygenase 2 in intestinal polyposis.

Membrane arachidonic acid is converted by cyclooxygenase (COX) into prostaglandin (PG) G(2) and then to PGH(2) which is subsequently metabolized to PGE(2) by PGE synthase (PGES). Both COX-1 and COX-2 play critical roles in intestinal polyp formation, whereas COX-2 is also expressed in cancers of a variety of organs. Likewise, inducible microsomal PGES (mPGES-1) is expressed in several types of cancer, although its role in benign polyp formation has not been investigated. We demonstrated recently that most COX-2-expressing cells in the polyps are stromal fibroblasts. Here we show colocalization of COX-1, COX-2 and mPGES in the intestinal polyp stromal fibroblasts of Apc(Delta 716) mice, a model for familial adenomatous polyposis. Contrary to COX-2 that was induced only in polyps >1 mm in diameter, COX-1 was found in polyps of any size. In polyps >1 mm, not only COX-2 but also mPGES was induced in the stromal fibroblasts where COX-1 had already been expressed. Although polyp number and size were markedly reduced in COX-1 (-/-) or COX-2 (-/-) compound mutant Apc mice, both COX-2 and mPGES were induced in the COX-1 (-/-) polyps, whereas COX-1 was expressed in the COX-2 (-/-) polyps. We found also in human familial adenomatous polyposis polyps that COX-2 and mPGES were induced in the COX-1-expressing fibroblasts. On the basis of these results, we propose that COX-1 expression in the stromal cells secures the basal level of PGE(2) that can support polyp growth to approximately 1 mm, and that simultaneous inductions of COX-2 and mPGES support the polyp expansion beyond approximately 1 mm by boosting the stromal PGE(2) production.

Animals↗

PubMed2003

Accentuated T helper type 2 airway response after allergen challenge in cyclooxygenase-1-/- but not cyclooxygenase-2-/- mice.

Acute pharmacologic inhibition of cyclooxygenase (COX)-1 or -2 during allergen sensitization and exposure leads to enhanced T helper type 2 (Th2) airway responses. COX-1 and -2 play functionally distinct roles in lymphocyte development, and consequently, genetic deficiency of either enzyme, as opposed to acute pharmacologic inhibition, may modulate Th2-mediated allergic airway disease differently. An ovalbumin-induced mouse model of allergic airway disease was used. The immunophenotype of bronchoalveolar lavage lymphocytes was assessed by flow cytometry, bronchoalveolar lavage cytokines, and chemokines were measured by enzyme-linked immunosorbent assay, adhesion molecule expression was assessed by immunoblotting in combination with immunohistochemistry, and bronchoconstriction was assessed by whole body plethysmography. The airways of COX-1-/- mice contained increased numbers of CD4+ and CD8+ T cells, exaggerated levels of the Th2 cytokines interleukin-4, -5, and -13, and increased levels of eotaxin and thymus- and activation-regulated chemokine. Allergen-induced bronchoconstriction was also increased in COX-1-/- mice. Vascular cell adhesion molecule-1 and intercellular adhesion molecule-1 levels were increased in lungs of both COX-1-/- and COX-2-/- mice relative to wild type. These data suggest that genetic deficiency of COX-1 but not COX-2 modulates T cell recruitment, Th2 cytokine secretion, and lung function in the allergic airway.

Allergens↗

PubMed2003

Mechanism of cyclooxygenase-2 upregulation in late preconditioning.

Although the cardioprotection of late preconditioning (PC) is known to be mediated by both inducible NO synthase (iNOS) and cyclooxygenase-2 (COX-2), the signaling mechanism responsible for COX-2 upregulation and the interaction between iNOS and COX-2 remain unknown. A total of 122 mice were used to address this issue. In wild-type mice preconditioned with six cycles of 4-min coronary occlusion-4-min reperfusion, ischemic PC resulted in rapid activation of nuclear STAT1/3 through tyrosine phosphorylation (STAT1: 339 +/- 48% of control; STAT3: 389 +/- 46% of control) and increased STAT1/3-DNA binding activity (687 +/- 58% of control) at 30 min after PC, with subsequent upregulation of COX-2 protein (373 +/- 60% of control) and activity(increased myocardial levels of PGE2, PGF(2alpha), and 6-keto-PGF(1alpha)) at 24 h. However, COX-1 protein was not changed 24 h after ischemic PC. Pretreatment with the Janus tyrosine kinase (JAK) inhibitor AG-490 before the six occlusion-reperfusion cycles blocked both the tyrosine phosphorylation of STAT1/3 and the subsequent upregulation of COX-2 protein, demonstrating a necessary role of the JAK-STAT pathway in the induction of COX-2. Targeted disruption of the iNOS gene (iNOS-/-) did not block the increased expression of COX-2 protein 24 h after ischemic PC but completely blocked the increase in COX-2 activity, whereas targeted disruption of the COX-2 gene (COX-2-/-) did not alter ischemic PC-induced iNOS induction. Immunoprecipitation of preconditioned heart tissues with anti-COX-2 antibodies followed by immunoblotting with anti-iNOS antibodies revealed that the increased iNOS protein co-precipitated with COX-2. We conclude that (i) the upregulation of COX-2 protein expression after ischemic PC is mediated by a JAK1/2-STAT1/3-signaling cascade; (ii) COX-2 activity requires upregulated iNOS and iNOS-derived NO; and (iii) COX-2 forms complexes with iNOS, supporting a direct interaction between these two proteins. To our knowledge, this is the first evidence that myocardial COX-2 is upregulated via a JAK1/2-STAT1/3 pathway.

Animals↗

PubMed2002

Deficiency of either cyclooxygenase (COX)-1 or COX-2 alters epidermal differentiation and reduces mouse skin tumorigenesis.

Nonsteroidal anti-inflammatory drugs are widely reported to inhibit carcinogenesis in humans and in rodents. These drugs are believed to act by inhibiting one or both of the known isoforms of cyclooxygenase (COX). However, COX-2, and not COX-1, is the isoform most frequently reported to have a key role in tumor development. Here we report that homozygous deficiency of either COX-1 or COX-2 reduces skin tumorigenesis by 75% in a multistage mouse skin model. Reduced tumorigenesis was observed even though the levels of stable 7,12-dimethylbenz(a)anthracene-DNA adducts were increased about 2-fold in the COX-deficient mice compared with wild-type mice. The premature onset of keratinocyte terminal differentiation appeared to be the cellular event leading to the reduced tumorigenesis because keratin 1 and keratin 10, two keratins that indicate the commitment of keratinocytes to differentiate, were expressed 8-13-fold and 10-20-fold more frequently in epidermal basal cells of the COX-1-deficient and COX-2-deficient mice, respectively, than in wild-type mice. Papillomas on the COX-deficient mice also displayed the premature onset of keratinocyte terminal differentiation. However, loricrin, a late marker of epidermal differentiation, was not significantly altered, suggesting that it was the early stages of keratinocyte differentiation that were primarily affected by COX deficiency. Because keratin 5, a keratin associated with basal cells, was detected differently in papillomas of COX-1-deficient as compared with COX-2-deficient mice, it appears that the isoforms do not have identical roles in papilloma development. Interestingly, apoptosis, a cellular process associated with nonsteroidal anti-inflammatory drug-induced inhibition of tumorigenesis, was not significantly altered in the epidermis or in papillomas of the COX-deficient mice. Thus, both COX-1 and COX-2 have roles in keratinocyte differentiation, and we propose that the absence of either isoform causes premature terminal differentiation of initiated keratinocytes and reduced tumor formation.

9,10-Dimethyl-1,2-benzanthracene↗

PubMed2002

Susceptibility of cyclooxygenase-2-deficient mice to pulmonary fibrogenesis.

The cyclooxygenase (COX)-2 enzyme has been implicated as an important mediator of pulmonary fibrosis. In this study, the lung fibrotic responses were investigated in COX-1 or COX-2-deficient (-/-) mice following vanadium pentoxide (V(2)O(5)) exposure. Lung histology was normal in saline-instilled wild-type and COX-deficient mice. COX-2(-/-), but not COX-1(-/-) or wild-type mice, exhibited severe inflammatory responses by 3 days following V(2)O(5) exposure and developed pulmonary fibrosis 2 weeks post-V(2)O(5) exposure. Western blot analysis and immunohistochemistry showed that COX-1 protein was present in type 2 epithelial cells, bronchial epithelial cells, and airway smooth muscle cells of saline or V(2)O(5)-exposed wild-type and COX-2(-/-) mice. COX-2 protein was present in Clara cells of wild-type and COX-1(-/-) terminal bronchioles and was strongly induced 24 hours after V(2)O(5) exposure. Prostaglandin (PG) E(2) levels in the bronchoalveolar lavage (BAL) fluid from wild-type and COX-1(-/-) mice were significantly up-regulated by V(2)O(5) exposure within 24 hours, whereas PGE(2) was not up-regulated in COX-2(-/-) BAL fluid. Tumor necrosis factor-alpha was elevated in the BAL fluid from all genotypes after V(2)O(5) exposure, but was significantly and chronically elevated in the BAL fluid from COX-2(-/-) mice above wild-type or COX-1(-/-) mice. These findings indicate that the COX-2 enzyme is protective against pulmonary fibrogenesis, and we suggest that COX-2 generation of PGE(2) is an important factor in resolving inflammation.

Animals↗

PubMed2002

Phenotypes of the COX-deficient mice indicate physiological and pathophysiological roles for COX-1 and COX-2.

The development of mice deficient in either cyclooxygenase-1 (COX-1) or COX-2, as well as mice deficient in both COX isoforms, has provided models to elucidate the physiological and pathophysiological roles of these enzymes. The findings obtained with the COX-deficient mice suggest that COX-2 may be more important than COX-1 for supplying prostaglandins (PGs) to maintain tissue homeostasis. Furthermore, both isoforms may be involved in the development of diseases, such as inflammation and cancer. Therefore, the contribution of each isoform to the prevention or development of disease is more complex than originally described. Studies with the COX-deficient mice suggest that in addition to COX-2-selective inhibition, therapeutic advances may also be achieved with COX-1-selective inhibitors which lack gastrointestinal side effects.

Animals↗

PubMed2002

Cyclooxygenase-1-selective inhibition prolongs gestation in mice without adverse effects on the ductus arteriosus.

Preterm delivery is the leading cause of neonatal mortality and contributes significantly to infant morbidity. Classical cyclooxygenase (COX) inhibitors, such as indomethacin, which inhibit both COX-1 and COX-2, are effective for delaying premature labor, but their use is limited by serious complications to the fetus and neonate, including adverse effects on the ductus arteriosus (DA). Using isoform-selective inhibitors, we characterized the roles of the COX isoforms in the initiation of labor and the regulation of fetal and neonatal DA closure in mice. Chronic inhibition of COX-2 during pregnancy (gestation days 15-18) significantly increased neonatal mortality by preventing closure of the DA after birth, whereas acute COX-2 inhibition near the end of term (gestation day 18) constricted the fetal DA. In contrast, the inhibition of COX-1 during pregnancy lacked these prenatal and postnatal adverse effects on the DA and effectively delayed the initiation of full-term labor and LPS-induced preterm labor. These findings suggest that premature fetal DA closure or neonatal patent DA observed following indomethacin tocolysis in women may result from the inhibition of COX-2. Therefore, COX-1-selective inhibitors may provide effective treatment to delay preterm labor with fewer adverse effects on fetal or neonatal health than nonselective or COX-2-selective inhibitors.

Animals↗

PubMedDate not supplied

Cyclooxygenase enzymes in allergic inflammation and asthma.

The cyclooxygenase enzyme system produces eicosanoids which mediate many important physiological and pathological functions. Experimental and clinical data suggest a role for this enzyme system in the pathogenesis of allergic inflammation and asthma. This article focuses on the function of this pathway in the lung, reviews evidence implicating the involvement of this pathway in asthma and allergic airway inflammation, and discusses implications for the treatment of asthmatics with cyclooxygenase inhibitors.

Animals↗