Occupational risk factors and asthma among health care professionals

Peripheral mechanisms I: plasticity of peripheral pathways

Cough plays a vital role in protecting the lower airways from inhaled irritants, pollutants, and infectious agents. The cough reflex exhibits remarkable plasticity, such that in the context of infectious or inflammatory respiratory diseases such as asthma, chronic bronchitis, and idiopathic pulmonary fibrosis the cough reflex can become dysregulated, leading to a chronic cough. A chronic, nonproductive (dry) cough can rob sufferers of quality of life. Plasticity of the cough reflex likely involves multiple intersecting pathways within the airways, the peripheral nerves that supply them, and the central nervous system. While further studies are needed to determine the presence and relevance of many of these specific pathways in cough associated with chronic respiratory disease, the last decade has yielded unprecedented insight into the molecular identity of the ion channels and associated proteins that initiate and conduct action potentials in the primary sensory nerves involved in reflexes such as cough. We now know, for instance, that members of the transient receptor potential superfamily of nonselective cation channels function as transducers that convert specific external stimuli into neuronal activation. We also know that certain Na+ and K+ channels play specialized roles in regulating action potential discharge in irritant-sensing afferent nerves. In this chapter, we summarize the available information regarding factors that may modulate afferent neuron function acutely, via posttranslational modifications and over the longer term through neurotrophin-dependent alterations of the transcriptional programs of adult sensory neurons.

Occupational exposures and adult asthma

Occupational exposures can cause a new onset of asthma in a subset of susceptible workers on the basis of sensitization to a specific work agent or a high-level irritant exposure. Epidemiologic studies give insight into the natural history of occupational asthma, including host factors and environmental factors leading to the development of occupational asthma, the progression, and the potential role of preventive measures. Work-exacerbated asthma has been a focus of studies only recently but is recognized as common among asthmatic workers and is a potential cause of significant morbidity and socioeconomic impact.

Impact of depression and anxiety on quality of life, health behaviors, and asthma control among adults in the United States with asthma, 2006

BACKGROUND

Psychological factors such as anxiety and depression are increasingly being recognized as influencing the onset and course of asthma.

METHODS

We obtained Patient Health Questionnaire 8 depression data from 41 states and territories using the 2006 Behavioral Risk Factor Surveillance System. Heath risk behaviors, social and emotional support, life satisfaction, disability, and four health-related quality-of-life (HRQOL) questions were available for all states and territories (n = 18,856 with asthma). Five additional HRQOL questions were asked in three states (n = 1345 persons with asthma), and questions assessing asthma control were available for nine states (n = 3943 persons with asthma).

RESULTS

Persons with asthma were significantly more likely than those without asthma to have current depression (19.4% vs. 7.7%), a lifetime diagnosis of depression (30.6% vs. 14.4%), and anxiety (23.5% vs. 10.2%). For most domains examined, there was a dose-response relationship between level of depression severity and mean number of days of impaired HRQOL in the past 30 days, as well as an increased prevalence of life dissatisfaction, inadequate social support, disability, and risk behaviors, such as smoking, physical inactivity, and obesity, among those with asthma. Moreover, depression and anxiety were associated with a decreased level of asthma control, including more visits to the doctor or emergency room, inability to do usual activities, and more days of symptoms compared to those without depression or anxiety.

CONCLUSION

This research indicates that a multidimensional, integrative approach to health care should be considered when assessing patients with asthma.

Prostaglandin-induced activation of nociceptive neurons via direct interaction with transient receptor potential A1 (TRPA1)

Inflammation contributes to pain hypersensitivity through multiple mechanisms. Among the most well characterized of these is the sensitization of primary nociceptive neurons by arachidonic acid metabolites such as prostaglandins through G protein-coupled receptors. However, in light of the recent discovery that the nociceptor-specific ion channel transient receptor potential A1 (TRPA1) can be activated by exogenous electrophilic irritants through direct covalent modification, we reasoned that electrophilic carbon-containing A- and J-series prostaglandins, metabolites of prostaglandins (PG) E(2) and D(2), respectively, would excite nociceptive neurons through direct activation of TRPA1. Consistent with this prediction, the PGD(2) metabolite 15-deoxy-Delta(12,14)-prostaglandin J(2) (15dPGJ(2)) activated heterologously expressed human TRPA1 (hTRPA1-HEK), as well as a subset of chemosensitive mouse trigeminal neurons. The effects of 15dPGJ(2) on neurons were blocked by both the nonselective TRP channel blocker ruthenium red and the TRPA1 inhibitor (HC-030031), but unaffected by the TRPV1 blocker iodo-resiniferatoxin. In whole-cell patch-clamp studies on hTRPA1-HEK cells, 15dPGJ(2) evoked currents similar to equimolar allyl isothiocyanate (AITC) in the nominal absence of calcium, suggesting a direct mechanism of activation. Consistent with the hypothesis that TRPA1 activation required reactive electrophilic moieties, A- and J-series prostaglandins, and the isoprostane 8-iso-prostaglandin A(2)-evoked calcium influx in hTRPA1-HEK cells with similar potency and efficacy. It is noteworthy that this effect was not mimicked by their nonelectrophilic precursors, PGE(2) and PGD(2), or PGB(2), which differs from PGA(2) only in that its electrophilic carbon is rendered unreactive through steric hindrance. Taken together, these data suggest a novel mechanism through which reactive prostanoids may activate nociceptive neurons independent of prostaglandin receptors.

The associations between smoking, physical inactivity, obesity, and asthma severity in the general US population

The purpose of this study was to examine the associations between smoking, physical inactivity, obesity, and asthma severity among US adults. The magnitude of these associations was very strong. For example, those who visited an emergency room in the past year were 60% more likely than those who did not to smoke; those who used an inhaler > or =15 times in the past month (versus those who did not use an inhaler) were 90% more likely to be physically inactive; and those who had asthma symptoms all the time in the past 30 days (versus those with no symptoms) were 80% more likely to be obese.