ASM-024, a piperazinium compound, promotes the in vitro relaxation of ß2-adrenoreceptor desensitized tracheas.

Inhaled ß2-adrenoreceptor agonists are widely used in asthma and chronic obstructive pulmonary disease (COPD) for bronchoconstriction relief. ß2-Adrenoreceptor agonists relax airway smooth muscle cells via cyclic adenosine monophosphate (cAMP) mediated pathways. However, prolonged stimulation induces functional desensitization of the ß2-adrenoreceptors (ß2-AR), potentially leading to reduced clinical efficacy with chronic or prolonged administration. ASM-024, a small synthetic molecule in clinical stage development, has shown activity at the level of nicotinic receptors and possibly at the muscarinic level and presents anti-inflammatory and bronchodilator properties. Aerosolized ASM-024 reduces airway resistance in mice and promotes in-vitro relaxation of tracheal and bronchial preparations from animal and human tissues. ASM-024 increased in vitro relaxation response to maximally effective concentration of short-acting beta-2 agonists in dog and human bronchi. Although the precise mechanisms by which ASM-024 promotes airway smooth muscle (ASM) relaxation remain unclear, we hypothesized that ASM-024 will attenuate and/or abrogate agonist-induced contraction and remain effective despite ß2-AR tachyphylaxis. ß2-AR tachyphylaxis was induced with salbutamol, salmeterol and formoterol on guinea pig tracheas. The addition of ASM-024 relaxed concentration-dependently intact or ß2-AR desensitized tracheal rings precontracted with methacholine. ASM-024 did not induce any elevation of intracellular cAMP in isolated smooth muscle cells; moreover, blockade of the cAMP pathway with an adenylate cyclase inhibitor had no significant effect on ASM-024-induced guinea pig trachea relaxation. Collectively, these findings show that ASM-024 elicits relaxation of ß2-AR desensitized tracheal preparations and suggest that ASM-024 mediates smooth muscle relaxation through a different target and signaling pathway than ß2-adrenergic receptor agonists. These findings suggest ASM-024 could potentially provide clinical benefit when used adjunctively with inhaled ß2-adrenoreceptor agonists in those patients exhibiting a reduced response to their chronic use.

Modulation of eosinophil activation in vitro by a nicotinic receptor agonist.

Nicotinic receptor agonists decreased the infiltration of eosinophils into the lung and airways in a mouse model of asthma. To better understand the mechanisms implicated in this anti-inflammatory phenomenon, the expression of nicotinic acetylcholine receptors (nAChRs) and the effect of dimethylphenylpiperazinium (DMPP), a nonselective nAChR agonist, on human blood eosinophils were studied. The expression of alpha-3, -4, and -7 nAChR subunits on human blood eosinophils was measured by cell ELISA and immunocytochemistry. mRNA expression for all three subunits was evaluated by quantitative RT-PCR. The effect of DMPP on leukotriene C4 (LTC4) and matrix metalloproteinase-9 (MMP-9) production, eosinophil migration, and intracellular calcium mobilization was measured. The results show that the alpha-3, -4, and -7 nAChR subunits and mRNAs are expressed by blood eosinophils. In vitro treatment of these cells with various concentrations of DMPP reduced platelet-activating factor (PAF)-induced LTC4 production significantly. DMPP (160 microM) decreased eotaxin, and 5-oxo-6,8,11,14-eicosatetranoic acid induced eosinophil migration through Matrigel by 40.9% and 55.5%, respectively. This effect was reversed by the nAChR antagonist mecamylamine. In addition, DMPP reduced MMP-9 release and the inositol 1,4,5-triphosphate-dependent intracellular calcium increase provoked by PAF. Taken together, these results indicate that functional nAChRs are expressed on eosinophils and that nAChR agonists down-regulate eosinophil function in vitro. These anti-inflammatory effects could be of interest in the treatment of allergic asthma.

Sensitization to airborne molds and its health effects in peat moss processing plant workers.

The goal of this study was to evaluate the incidence of sensitization to the major molds found in peat dust in workers exposed to stored peat moss and the health impact of this sensitization. Air samples from each plant were obtained to measure the levels of airborne molds, bacteria, and dust. There were 189 workers from 14 peat moss processing plants (3 all-year mixing plants and 11 seasonal plants) recruited for the study. The subjects completed a symptoms questionnaire, underwent spirometric measurements and skin-prick tests, and gave venous blood samples. Blood samples from 43 nonexposed control subjects were also taken. A similar percentage of smokers from both plant types was observed. Twenty-eight percent of the workers tested had a positive serum reaction to at least one of the tested molds. The percentage of positive workers varied from plant to plant, going from none in 4 plants to 14 out of 21 for 1 plant. This variability was not correlated with the airborne levels of molds. FEV tended to be lower in the workers with positive antibodies compared with seronegative workers. IgG positive frequency was higher for those workers employed in the all-year plants, and workers from those plants had lower FEV/FVC than seasonal plant workers. Seasonal plants were more contaminated with molds than all-year mixing plants, suggesting that the duration of exposure may trigger more sensitization than the level of exposure. We conclude that there is a high incidence of mold sensitization in peat moss factory workers and that this sensitization may have a negative respiratory health impact.

Dimethyphenylpiperazinium, a nicotinic receptor agonist, downregulates inflammation in monocytes/macrophages through PI3K and PLC chronic activation.

Activation of nicotinic acetylcholine receptors (nAChRs) on inflammatory cells induces anti-inflammatory effects. The intracellular mechanisms that regulate this effect are still poorly understood. In neuronal cells, nAChRs are associated with phosphatidylinositol 3-kinase (PI3K). This enzyme, which can activate phospholipase C (PLC), is also present in monocytes. The aim of this study was to assess the role of these proteins in the signaling pathways involved in the anti-inflammatory effect of dimethylphenylpiperazinium (DMPP), a synthetic nAChR agonist, on monocytes and macrophages. The results indicate that PI3K is associated with alpha3, -4, and -5 nAChR subunits in monocytes. The PI3K inhibitors wortmannin and LY294002 abrogated the inhibitory effect of DMPP on LPS-induced TNF release by monocytes. Treatment with DMPP for 24 and 48 h provoked a mild PLC phosphorylation, which was blocked by the nAChR antagonist mecamylamine and reversed by PI3K inhibitors. Treatment of monocytes and alveolar macrophages with DMPP reduced the inositol 1,4,5-trisphosphate (IP3)-dependent intracellular calcium mobilization induced by platelet-activating factor (PAF), an effect that was reversed by mecamylamine in alveolar macrophages. DMPP did not have any effect on PAF receptor expression. DMPP also inhibited the thapsigargin-provoked calcium release, indicating that the endoplasmic reticulum calcium stores might be depleted by treatment with the nAChR agonist. Taken together, these results suggest that PI3K and PLC activation is involved in the anti-inflammatory effect of DMPP. PLC limited, but constant activation could induce, the depletion of intracellular calcium stores, leading to the anti-inflammatory effect of DMPP.

Adiposity affects human response to inhaled organic dust.

BACKGROUND: Swine containment facilities are often highly contaminated with organic dusts that often contain varying levels of endotoxins and other microbial products. This study was performed to evaluate the effect of obesity on the inflammatory response induced by chronic or acute exposure to swine confinement buildings (SCB). METHODS: Two separate studies were performed; Study I included 36 SCB long-time workers and a control group of 35 matched male hospital workers never exposed to SCB. In Study II, 14 naïve healthy young subjects (8 overweight and 6 lean) volunteered to be acutely exposed to a SCB environment for 5 hr. Markers of sub-clinical inflammation linked to obesity (C-reactive protein (CRP), interleukin 6 (IL-6)) or to active inflammation (soluble adhesion molecules, IL-8, TNF) were measured. RESULTS: In the first study, positive correlations were found between girth circumference and serum levels of IL-6 (r = 0.57, P = 0.0003) and CRP (r = 0.62, P < 0.0001) in the control group. These correlations were however blunted or lost in the SCB workers group who showed positive correlations between girth circumference and soluble l-selectin (r = 0.34, P = 0.04), TNFalpha (r = 0.37, P = 0.03), ICAM-1 (r = 0.61, P < 0.0001). In the second study involving acute SCB exposure of naïve volunteers, no significant differences were observed between normal weight and overweight subjects for white blood cells, nasal lavage cell counts, and IL-8 levels. However, higher levels of CRP, TNF, and IL-6 were detected in overweight volunteers compared to those who were lean. CONCLUSIONS: In pig farmers (Study I), environmentally induced chronic inflammation appears to blunt the sub-clinical inflammation linked to obesity, whereas in naïve volunteers of Study II, environmentally induced acute inflammation seems to have a potentiating effect on obesity-related inflammatory markers.

Pathogenesis of hypersensitivity pneumonitis.

PURPOSE OF REVIEW: Hypersensitivity pneumonitis is a group of immunologically mediated diseases caused by an abnormal response to a wide variety of inhaled antigens. Its pathogenesis is complex and involves many immunological concepts. This review discusses recent advances in our understanding of the pathogenesis of hypersensitivity pneumonitis. RECENT FINDINGS: Over the last 3 years, several studies on the pathogenesis of hypersensitivity pneumonitis have been published. New antigens have been identified. We now have a better understanding of the role of inflammatory cells and mediators, and promoting and protective factors have been suggested. SUMMARY: Most of the mechanisms involved in the pathogenesis of hypersensitivity pneumonitis remain incompletely understood. Current and future findings will not only help our understanding of the disease and its prevention, but also improve its treatment.

Inhibitory effect of nicotine on experimental hypersensitivity pneumonitis in vivo and in vitro.

The incidence of hypersensitivity pneumonitis (HP) is lower in smokers than in nonsmokers. Because nicotine is immunosuppressive, we hypothesized that it could have a protective effect on HP induction in vivo. HP was induced in mice that were treated with nicotine either intraperitoneally (IP) (0.5 to 2.0 mg/kg/day) or intranasally (IN) (0.025 to 2.0 mg/kg/day). Both IP- and IN-treated animals had fewer bronchoalveolar lavage total cells and lymphocytes and a decreased lung tissue inflammation. IFN-gamma but not interleukin-10 mRNA expression was reduced in lung tissue of 2.0-mg/kg IN-treated animals. To test the effect of nicotine on alveolar macrophages, AMJ2-C11 cells were treated with nicotine and stimulated with lipopolysaccharide or Saccharopolyspora rectivirgula, a causative agent of HP. Nicotine reduced tumor necrosis factor release and tumor necrosis factor, interleukin-10, and IFN-gamma mRNA expression after stimulation and decreased CD80 expression by 55% in lipopolysaccharide-stimulated cells and by 41% in S. rectivirgula-stimulated cells. We conclude that nicotine could be, at least in part, responsible for the protection observed in smokers against HP. The inhibitory effect of nicotine on alveolar macrophages could be one of the mechanisms involved.

Chronic inflammation induced by organic dust and related metabolic cardiovascular disease risk factors.

OBJECTIVE: Chronic inflammation is now considered a risk factor for cardiovascular diseases. Exposure to organic dust induces an inflammatory response. This study was done to verify whether inflammation caused by exposure to organic dust increases the metabolic risk factors for cardiovascular diseases. METHODS: Thirty-six nonsmoking men who worked in a swine confinement building and 35 unexposed matched controls were studied. Each person was evaluated for inflammatory markers, including white blood cell counts, cell-bound (CD11b, CD18, CD31, CD62L) and circulating soluble adhesion molecule levels (sICAM-1, sPECAM-1, sL, sE, and sP selectins), serum CRP (C-reactive protein), fibrinogen, and interleukin-6 (IL-6). Cardiovascular risk factors [the serum lipid profile, apoprotein B (Apo B)] and insulin levels were also assessed. RESULTS: The groups were similar with respect to age, physical characteristics, and blood cell counts. The expression of adhesion molecules (P-values <0.01) and serum levels of sL-selectin (P<0.0001) were higher for the workers than for the controls, while neutrophils and interleukin-6 were slightly higher for the workers (P=0.05). No differences in CRP, fibrinogen, lipid profile, Apo B, or insulin levels were observed. CONCLUSIONS: Exposure to contaminated organic dust induces a chronic inflammation that is not associated with increased metabolic or acute-phase cardiovascular risk factors; this finding suggests that chronic inflammation per se may not be a cardiovascular risk factor in this group of pig farmers.