(NOS), is an important mediator of lung inflammation in allergic asthma. Asymmetric dimethylarginine (ADMA), a competitive endogenous inhibitor of NOS, is metabolized by the enzyme dimethylarginine dimethylaminohydrolase (DDAH). Elevated ADMA has been shown to affect lung function in mice, and by inhibiting NOS it alters NO and reactive oxygen species production in mouse lung epithelial cells. However, the effects of altered ADMA levels during lung inflammation have not been explored. A model of allergen-induced airway inflammation was utilized in combination with the modulation of endogenous circulating ADMA levels in mice. Airway inflammation was assessed by quantifying inflammatory cell infiltrates in lung lavage and by histology. Lung DDAH expression was assessed by quantitative PCR and immunohistochemistry. Nitrite levels were determined in lung lavage fluid as a measure of NO production. iNOS expression was determined by immunohistochemistry, immunofluorescence, Western blot, and quantitative PCR. NF-B binding activity was assessed by a transcription factor binding assay. Allergen-induced lung inflammation was potentiated in mice with elevated circulating ADMA and was reduced in mice overexpressing DDAH. Elevated ADMA reduced nitrite levels in lung lavage fluid in both allergenchallenged and control animals. ADMA increased iNOS expression in airway epithelial cells in vivo following allergen challenge and in vitro in stimulated mouse lung epithelial cells. ADMA also increased NF-B binding activity in airway epithelial cells in vitro. These data support that ADMA may play a role in inflammatory airway diseases such as asthma through modulation of iNOS expression in lung epithelial cells. airway; dimethylarginine dimethylaminohydrolase; inducible nitric oxide synthase ONE OF THE KEY PATHOGENIC features of asthma is the infiltration and activation of inflammatory cells in the airways (6,17,21,22). Lung inflammation in allergic asthma is induced by a cascade of reactions involving several mediators including nitric oxide (NO) (55). NO is a highly reactive radical formed by the metabolism of the semi-essential amino acid L-arginine by nitric oxide synthase (NOS) (29). There are three predominant NOS isoforms. The constitutive isoforms of NOS (cNOS) are expressed mainly in nonadrenergic noncholinergic nerves (nNOS), in endothelial cells (eNOS), and in airway epithelium (nNOS and eNOS) (2,19,29,62), and are involved in the physiological regulation of the airway by local production of small amounts of NO. The third isoform (iNOS) is induced following exposure to proinflammatory cytokines and is expressed in epithelial and inflammatory cells of the airway (57). Although it is known that NO plays a role in asthma by contributing to pulmonary inflammation after allergen challenge (49, 69), the contribution of each of the NOS isoforms to inflammation in the airway is unclear. Pharmacological inhibitors of NOS have been used to study the role of specific NOS isoforms in asthma and have provided support for iNOSmediate...

Our recent ultrastructural studies of amyloid angiopathy in biopsy specimens from Alzheimer's disease patients showed that perivascular cells and perivascular microglia are involved in the production of amyloid fibrils. Further examination of the walls of the vessels with and without amyloid deposits presented in this report reveals numerous mononuclear cells with a broad spectrum of morphological appearances. Some of these cells produce amyloid in the vascular wall and migrate into the neuropil. Others do not produce amyloid in this location but also migrate through the vascular basal lamina and position themselves on the external surface of basal lamina or in the neuropil outside the vascular astrocytic end-feet processes. The presence of clusters or rows of six or more of these cells in the position of perivascular microglial cells suggests their proliferation in the perivascular region. After leaving the perimeter of the vessel wall, perivascular cells become the perivascular, neuropil, and satellite microglia cells. Migrating perivascular cells become the microglia, which are engaged in amyloid fibril formation and development of classical and primitive plaques.

There is increasing evidence that the endogenous nitric oxide synthase (NOS) inhibitor asymmetric dimethyl-arginine (ADMA) is involved in the pathogenesis of chronic lung diseases. One important regulator of this molecule is the ADMA-metabolizing enzyme dimethyl-arginine dimethyl-aminohydrolase (DDAH). The objective of this study was to determine whether perturbation of the ADMA-DDAH pathway contributes to lung inflammation following exposure to cigarette smoke (CS). For these studies, wild-type and DDAH transgenic mice were sham or CS-exposed. Serum ADMA levels were determined by mass spectrometry. ADMA content and DDAH expression were also visualized in mouse lung tissue by immunohistochemistry. DDAH expression was determined by real-time quantitative PCR (qPCR). Inflammation was assessed by H&E staining and analyses of total cell counts and fluid tumor necrosis factor (TNF)-levels (using ELISA) in lung lavage fluid. NF-B binding activity in mouse lung epithelial (LA-4) cells was assessed by a transcription factor-binding assay. The results indicated that the concentration of serum ADMA was increased following exposure to CS, and this corresponded with increased ADMA content in bronchial epithelial cells in lung tissue. Total lung DDAH expression was significantly decreased in lung tissue and cultured LA-4 cells following CS exposure. Addition of exogenous ADMA increased CSE-mediated NF-B binding activity and TNFa production in LA-4 cells more than 2-fold compared to that in CSE-exposed controls. CS-mediated lung inflammation was significantly attenuated in DDAH transgenic mice compared to in wild-type controls. These findings demonstrated that lung ADMA metabolism was altered in mice following CS exposure and suggested that ADMA played a role in CS-mediated inflammation through increasing the presence of inflammatory mediators in lung epithelial cells.

No abstract

No abstract