Poly(ADP-ribose) polymerase (PARP) plays an important role in tissue injury in conditions associated with oxidative stress and inflammation. Because asthma is a chronic inflammatory disorder of the airways, we designed the present experimental study to evaluate the effects of PARP inhibition on allergeninduced asthma-like reaction in ovalbumin-sensitized guinea pigs. Cough and dyspnea in response to ovalbumin aerosol were absent in naive guinea pigs, whereas they became severe in the sensitized animals. In the latter ones, ovalbumin aerosol also induced a rapid increase in PARP activity, bronchiolar constriction, pulmonary air space inflation, mast cell degranulation, poly(ADP-ribose) and nitrotyrosine immunostaining, myeloperoxidase activity, and malondialdehyde in lung tissue, as well as a rise in the amounts of nitrites and tumor necrosis factor-␣ in bronchoalveolar lavage fluid. Pretreatment with the PARP inhibitors 3-aminobenzamide (10 mg/kg b.wt.) or 5-aminoisoquinolinone (0.5 mg/kg b.wt.) given i.p. 3 h before ovalbumin challenge significantly reduced the severity of cough and the occurrence of dyspnea and delayed the onset of respiratory abnormalities. Both PARP inhibitors were also able to prevent the above morphological and biochemical changes of lung tissue or bronchoalveolar lavage fluid induced by ovalbumin challenge. Conversely, p-aminobenzoic acid, the inactive analog of 3-aminobenzamide, had no effects.Poly(ADP-ribose) polymerase (PARP; E.C.2.4.2.30) identifies a family of ubiquitous nuclear enzymes involved in many physiological and pathophysiological events, whose best studied member is PARP-1 (molecular mass 113 kDa) (Shieh et al

Inducible nitric oxide synthase (iNOS) is expressed in a variety of cell types, in particular in inflammatory cells, in response to diverse pro-inflammatory stimuli. This process requires critical levels of arachidonic acid (AA), generated by constitutive phospholipase A(2) (PLA(2)), promoting tyrosine kinase-dependent phosphorylation, and inhibition, of constitutive NOS. Lowering basal NO levels is indeed critical for the activation of nuclear factor-kappaB (NF-kappaB), and thus for the expression of genes (e.g. iNOS) regulated by this transcription factor. It is interesting to note that NO and AA, two small lipid soluble molecules, rapidly cross the plasma membrane thereby allowing the triggering of the above responses in distal cells. That is, constitutive NO might inhibit NF-kappaB activity in the same cells (e.g. astrocytes) in which it is generated, as well as in other cells that do not express constitutive NOS (e.g. microglia). NO from cells unable to respond to pro-inflammatory stimuli (e.g. neurons) will also contribute to these effects. Along the same line, AA released by pro-inflammatory molecules in specific cell types (e.g. astrocytes) might suppress constitutive NOS activity in the same cells as well as in other cells (e.g. neurons). Thus, AA produced at the very early stages of the inflammatory response is a likely critical signal switching the regulation of the "NO tone" from physiological (i.e. mediated by constitutive NOS) to pathological (i.e. mediated by iNOS). This second phase of the inflammatory response is often accompanied by the onset of deleterious effects in the tissue in which a critical role is played by iNOS-derived NO (directly or indirectly, i.e. via formation of peroxynitrite) as well as by products of the AA cascade. In summary, we suggest that the relative amounts of NO and AA, released by their constitutive enzymes, produce autocrine and paracrine effects regulating the onset of an inflammatory response in which, in addition to other factors, NO and AA are extensively released by their inducible enzymes.

In this study, we have evaluated the effects of the polyphenol epigallocatechin-3-gallate (EGCG), an antioxidant molecule that also enhances constitutive nitric-oxide synthase (NOS) activity, on antigen-induced asthma-like reaction in sensitized guinea pigs. For comparison, we used epicatechin, which shares antioxidant but not NOS-modulating properties with EGCG. Ovalbumin-sensitized guinea pigs placed in a respiratory chamber were challenged with ovalbumin. EGCG (25 mg/kg b.wt.) or epicatechin (25 mg/kg b.wt.) was given i.p. 20 min before ovalbumin challenge. We analyzed latency time for the onset of respiratory abnormalities, cough severity, duration of dyspnea, lung tissue histopathology, mast cell activation (by granule release), leukocyte/eosinophilic infiltration (by major basic protein and myeloperoxidase), oxygen free radical-mediated injury (by nitrotyrosine and 8-hydroxy-2-deoxyguanosine and superoxide dismutase), NOS activity, and bronchial inflammatory response [by tumor necrosis factor-␣ in bronchoalveolar lavage (BAL)]. In the sensitized animals, severe respiratory abnormalities appeared soon after the antigen challenge, accompanied by bronchoconstriction, alveolar inflation, and a marked increase in the assayed parameters of inflammatory cell recruitment, free radical lung injury, and release of proinflammatory molecules in BAL fluid. This was associated with marked depression of constitutive NOS activity. Pretreatment with EGCG, but not epicatechin, significantly reduced all the above parameters and sustained endothelial-type NOS activity. These findings provide evidence that EGCG, probably by modulating NOS activity, can counteract allergic asthma-like reaction in sensitized guinea pigs and suggest its possible future use for the treatment of asthma.Asthma is a common inflammatory airway disease whose prevalence is ever-increasing, especially among children (Kitch et al., 2000), and whose major pathophysiological hallmarks are mast cell activation, increased endothelial expression of adhesion molecules, and enhanced leukocyte recruitment (Maddox and Schwartz, 2002). The therapy mainly relies on ␤ 2 -agonists for acute episodes and glucocorticoids for long-term treatment (Von Mutius, 2000). Understanding the factors regulating transition between acute and chronic asthma and airway remodeling, or perpetuation of any of these states, may help identification of new targets for asthma therapy.In many cell types, nitric oxide (NO) is generated by three NO synthase (NOS) isoenzymes. The neuronal-type (nNOS) and the endothelial-type (eNOS) isoforms are Ca 2ϩ /calmodulin-dependent and expressed constitutively. The inducible NOS (iNOS) is Ca 2ϩ /calmodulin-independent and is expressed mainly on inflammation (Moncada et al., 1991). Induction of iNOS transcription is mediated by early events, including the activation of nuclear factor B by lipopolysaccharide, interleukin 1␤, and tumor necrosis factor (TNF)-␣, as well as of signal transducer and activator of transcription 1 by interferon-␥. Constitut...

Extensive DNA damage leads to the activation of poly(ADP-ribose) polymerase and subsequently to the formation of poly(ADP-ribose). When the damage is severe or leads to cell death, poly(ADP-ribose) may leak into the blood circulation. The metabolism of poly(ADP-ribose) in the bloodstream is not well understood. Thus, in the present study, the metabolism of 32 P-labeled poly(ADP-ribose) was followed in mice after injection of this labeled compound into the tail vein. The results showed that 5 min after injection more than half of the radioactivity was concentrated in acid-soluble fractions, namely in low molecular weight compounds in the blood, liver, and kidneys. Most of this radioactivity was in the form of inorganic phosphate, detected 5 min post-injection in the blood, kidneys, and urine. By contrast, the metabolites ADP-ribose and phosphoribosyl-AMP were not detected in any of the tissues nor in blood or urine. Taken together, these findings suggest that once poly(ADP-ribose) enters the bloodstream it is rapidly degraded, thereby preventing its accumulation in the blood.