Mehdi Khosravi

Asthma, Chronic Obstructive Pulmonary Disease, and Mortality in the U.S. Population

Background: COPD and asthma are common diseases in the U.S. population and can coexist. Our goal was to determine the prevalence of self-reported, physician-diagnosed asthma and COPD in a sample of the U.S. population and their association with lung function impairment and mortality. Methods: We used baseline data from NHANES III and the follow-up mortality data. We used logistic regression and Cox Proportional Hazards models, adjusting for age, sex, race/ethnicity, education level, smoking status, and disease stage. Results: The sample consisted of 15,203 subjects, of whom 4,542 died during the follow-up period. Coexisting COPD and asthma was reported by 357 (2.7%), COPD by 815 (5.3%), and asthma by 709 (5.3%). Subjects with both conditions had a higher proportion of obstruction (30.9%) than those with COPD (24.3%), asthma (13.3%), or no lung disease (5.4%). In survival models adjusting for all factors except baseline lung function, coexisting COPD and asthma had the highest risk for mortality (Hazard Ratio [HR] 1.83, 95% confidence interval [CI] 1.34, 2.49), followed by COPD only (HR 1.44, 95% CI 1.28, 1.62), and asthma only (HR 1.16, 95% CI 0.94, 1.42). These affects were attenuated after controlling for baseline lung function: coexisting asthma and COPD (HR 1.45, 95% CI 1.06, 1.98), COPD only (1.28, 95% CI 1.13, 1.45), and asthma only (HR 1.04, 95% CI 0.85, 1.27). Conclusion: In this analysis, subjects who report coexisting asthma and COPD have a higher risk of obstruction on spirometry and a higher risk of death during follow-up.

Bronchoconstriction Triggered by Breathing Hot Humid Air in Patients with Asthma Role of Cholinergic Reflex

RATIONALE Hyperventilation of hot humid air induces transient bronchoconstriction in patients with asthma; the underlying mechanism is not known. Recent studies showed that an increase in temperature activates vagal bronchopulmonary C-fiber sensory nerves, which upon activation can elicit reflex bronchoconstriction. OBJECTIVES This study was designed to test the hypothesis that the bronchoconstriction induced by increasing airway temperature in patients with asthma is mediated through cholinergic reflex resulting from activation of these airway sensory nerves. METHODS Specific airway resistance (SR(aw)) and pulmonary function were measured to determine the airway responses to isocapnic hyperventilation of humidified air at hot (49°C; HA) and room temperature (20-22°C; RA) for 4 minutes in six patients with mild asthma and six healthy subjects. A double-blind design was used to compare the effects between pretreatments with ipratropium bromide and placebo aerosols on the airway responses to HA challenge in these patients. MEASUREMENTS AND MAIN RESULTS SR(aw) increased by 112% immediately after hyperventilation of HA and by only 38% after RA in patients with asthma. Breathing HA, but not RA, triggered coughs in these patients. In contrast, hyperventilation of HA did not cause cough and increased SR(aw) by only 22% in healthy subjects; there was no difference between their SR(aw) responses to HA and RA challenges. More importantly, pretreatment with ipratropium completely prevented the HA-induced bronchoconstriction in patients with asthma. CONCLUSIONS Bronchoconstriction induced by increasing airway temperature in patients with asthma is mediated through the cholinergic reflex pathway. The concomitant increase in cough response further indicates an involvement of airway sensory nerves, presumably the thermosensitive C-fiber afferents.

Children and Adults With Frequent Hospitalizations for Asthma Exacerbation, 2012-2013: A Multicenter Observational Study.

BACKGROUND Earlier studies reported that many patients were frequently hospitalized for asthma exacerbation. However, there have been no recent multicenter studies to characterize this patient population with high morbidity and health care utilization. OBJECTIVE To examine the proportion and characteristics of children and adults with frequent hospitalizations for asthma exacerbation. METHODS A multicenter chart review study of patients aged 2 to 54 years who were hospitalized for asthma exacerbation at 1 of 25 hospitals across 18 US states during the period 2012 to 2013 was carried out. The primary outcome was frequency of hospitalizations for asthma exacerbation in the past year (including the index hospitalization). RESULTS The cohort included 369 children (aged 2-17 years) and 555 adults (aged 18-54 years) hospitalized for asthma exacerbation. Over the 12-month period, 36% of the children and 42% of the adults had 2 or more (frequent) hospitalizations for asthma exacerbation. Among patients with frequent hospitalizations, guideline-recommended outpatient management was suboptimal. For example, among adults, 32% were not on inhaled corticosteroids at the time of index hospitalization and 75% had no evidence of a previous evaluation by an asthma specialist. At hospital discharge, among adults with frequent hospitalizations who had used no controller medications previously, 37% were not prescribed inhaled corticosteroids. Likewise, during a 3-month postdischarge period, 64% of the adults with frequent hospitalizations were not referred to an asthma specialist. Although the proportion of patients who did not receive these guideline-recommended outpatient care appeared higher in adults, these preventive measures were still underutilized in children; for example, 38% of the children with frequent hospitalizations were not referred to asthma specialist after the index hospitalization. CONCLUSIONS This multicenter study of US patients hospitalized with asthma exacerbation demonstrated a disturbingly high proportion of patients with frequent hospitalizations and ongoing evidence of suboptimal longitudinal asthma care.

Underuse of guideline-recommended long-term asthma management in children hospitalized to the intensive care unit: a multicenter observational study

BACKGROUND Despite the significant burden of childhood asthma, little is known about prevention-oriented management before and after hospitalizations for asthma exacerbation. OBJECTIVE To investigate the proportion and characteristics of children admitted to the intensive care unit (ICU) for asthma exacerbation and the frequency of guideline-recommended outpatient management before and after the hospitalization. METHODS A 14-center medical record review study of children aged 2 to 17 years hospitalized for asthma exacerbation during 2012-2013. Primary outcome was admission to the ICU; secondary outcomes were 2 preventive factors: inhaled corticosteroid (ICS) use and evaluation by asthma specialists in the pre- and posthospitalization periods. RESULTS Among 385 children hospitalized for asthma, 130 (34%) were admitted to the ICU. Risk factors for ICU admission were female sex, having public insurance, a marker of chronic asthma severity (ICS use), and no prior evaluation by an asthma specialist. Among children with ICU admission, guideline-recommended outpatient management was suboptimal (eg, 65% were taking ICSs at the time of index hospitalization, and 19% had evidence of a prior evaluation by specialist). At hospital discharge, among children with ICU admission who had not previously used controller medications, 85% were prescribed ICSs. Furthermore, 62% of all children with ICU admission were referred to an asthma specialist during the 3-month posthospitalization period. CONCLUSION In this multicenter study of US children hospitalized with asthma exacerbation, one-third of children were admitted to the ICU. In this high-risk group, we observed suboptimal pre- and posthospitalization asthma care. These findings underscore the importance of continued efforts to improve prevention-oriented asthma care at all clinical encounters.

A synergistic effect of simultaneous TRPA1 and TRPV1 activations on vagal pulmonary C-fiber afferents

Transient receptor potential ankyrin type 1 (TRPA1) and vanilloid type 1 (TRPV1) receptors are coexpressed in vagal pulmonary C-fiber sensory nerves. Because both these receptors are sensitive to a number of endogenous inflammatory mediators, it is conceivable that they can be activated simultaneously during airway inflammation. This study aimed to determine whether there is an interaction between these two polymodal transducers upon simultaneous activation, and how it modulates the activity of vagal pulmonary C-fiber sensory nerves. In anesthetized, spontaneously breathing rats, the reflex-mediated apneic response to intravenous injection of a combined dose of allyl isothiocyanate (AITC, a TRPA1 activator) and capsaicin (Cap, a TRPV1 activator) was ∼202% greater than the mathematical sum of the responses to AITC and Cap when they were administered individually. Similar results were also observed in anesthetized mice. In addition, the synergistic effect was clearly demonstrated when the afferent activity of single vagal pulmonary C-fiber afferents were recorded in anesthetized, artificially ventilated rats; C-fiber responses to AITC, Cap and AITC + Cap (in combination) were 0.6 ± 0.1, 0.8 ± 0.1, and 4.8 ± 0.6 impulses/s (n = 24), respectively. This synergism was absent when either AITC or Cap was replaced by other chemical activators of pulmonary C-fiber afferents. The pronounced potentiating effect was further demonstrated in isolated vagal pulmonary sensory neurons using the Ca(2+) imaging technique. In summary, this study showed a distinct positive interaction between TRPA1 and TRPV1 when they were activated simultaneously in pulmonary C-fiber sensory nerves.

Lung transplantation in patients with coal workers’ pneumoconiosis

Hayes D Jr., Diaz‐Guzman E, Davenport DL, Zwischenberger JB, Khosravi M, Absher KJ, Hoopes CW. Lung transplantation in patients with coal workers’ pneumoconiosis.

Interaction between TRPA1 and TRPV1: Synergy on pulmonary sensory nerves

Transient receptor potential ankyrin type 1 (TRPA1) and vanilloid type 1 (TRPV1) receptors are co-expressed in vagal pulmonary C-fiber sensory nerves. Because both these ligand-gated non-selective cation channels are sensitive to a number of endogenous inflammatory mediators, it is highly probable that they can be activated simultaneously during airway inflammation. Studies were carried out to investigate whether there is an interaction between these two polymodal transducers upon simultaneous activation, and how it modulates the activity of vagal pulmonary C-fiber sensory nerves. Our studies showed a distinct potentiating effect induced abruptly by simultaneous activations of TRPA1 and TRPV1 by their respective selective agonists, allyl isothiocyanate (AITC) and capsaicin (Cap), at near-threshold concentrations. This synergistic effect was demonstrated in the studies of single-unit recording of vagal bronchopulmonary C-fiber afferents and the reflex responses elicited by activation of these afferents in intact animals, as well as in the isolated nodose and jugular bronchopulmonary sensory neurons. This potentiating effect was absent when either AITC or Cap was replaced by non-TRPA1 and non-TRPV1 chemical activators of these neurons, demonstrating the selectivity of the interaction between these two TRP channels. Furthermore, the synergism was dependent upon the extracellular Ca(2+), and the rapid onset of the action further suggests that the interaction probably occurred locally at the sites of these channels. These findings suggest that the TRPA1-TRPV1 interaction may play an important role in regulating the function and excitability of pulmonary sensory neurons during airway inflammation, but the mechanism underlying this positive interaction is not yet fully understood.

Breathing hot humid air induces airway irritation and cough in patients with allergic rhinitis

We studied the respiratory responses to an increase in airway temperature in patients with allergic rhinitis (AR). Responses to isocapnic hyperventilation (40% of maximal voluntary ventilation) for 4min of humidified hot air (HA; 49°C) and room air (RA; 21°C) were compared between AR patients (n=7) and healthy subjects (n=6). In AR patients, cough frequency increased pronouncedly from 0.10±0.07 before to 2.37±0.73 during, and 1.80±0.79coughs/min for the first 8min after the HA challenge, but not during the RA challenge. In contrast, neither HA nor RA had any significant tussive effect in healthy subjects. The HA challenge also caused respiratory discomfort (mainly throat irritation) measured by the handgrip dynamometry in AR patients, but not in healthy subjects. Bronchoconstriction was not detected after the HA challenge in either group of subjects. In conclusion, hyperventilation of HA triggered vigorous cough response and throat irritation in AR patients, indicating the involvement of sensory nerves innervating upper airways.

Enhanced Generation of Suppressor T Cells in Patients with Asthma Taking Oral Contraceptives

Introduction. A dysregulation of regulatory T cells (Tregs) could play a major role in the pathogenesis of bronchial asthma. Sex-dependent differences as well as the impact of hormonal changes in the incidence and severity of asthma are widely recognized. Emerging evidence suggests that asthma symptoms are alleviated in female patients taking hormone oral contraceptives (OCs). The impact of OCs on the generation of induced Tregs (iTregs) was assessed in a cohort of female patients with asthma. Methods. Thirteen patients were included in this pilot study. During three distinct phases of their menstrual cycles, we measured exhaled nitric oxide (eNO) levels, forced expiratory volume at 1 second (FEV1s), asthma control test (ACT) score, sex steroid hormone levels in serum, natural Tregs in peripheral blood, and the ability of CD4+ T cells to generate iTregs ex vivo. Results. The luteal serum levels of estradiol and progesterone negatively correlated with the proportion of iTregs generated ex vivo in patients not taking OCs. In addition, physiological doses of estradiol and progesterone prevented the acquisition of a suppressor T cell phenotype in vitro. Interestingly, patients taking OCs had reduced serum sex hormone levels associated with higher iTreg induction, a better ACT score, and a tendency toward lower eNO levels. Conclusions. Our results identify an impact of sex hormones on the capacity of T cells to polarize towards a regulatory phenotype and suggest the regulation of peripheral T cell lineage plasticity as a potential mechanism underlying the beneficial effects of OCs in women with asthma.

Cough and expiration reflexes elicited by inhaled irritant gases are intensified in ovalbumin-sensitized mice

This study was designed to determine the effect of active sensitization with ovalbumin (Ova) on cough responses to inhaled irritant gases in mice. Conscious mice moved freely in a recording chamber, while the pressure change in the chamber and audio and video signals of the mouse movements were recorded simultaneously to measure the frequencies of cough reflex (CR) and expiration reflex (ER). To further verify the accuracy of cough analysis, the intrapleural pressure was also recorded by a telemetry sensor surgically implanted in the intrapleural space in a subgroup of mice. During the irritant gas inhalation challenge, sulfur dioxide (SO2; 200 and 400 ppm) or ammonia (NH3; 0.1% and 0.2%) was drawn into the chamber at a constant flow rate for 8 min. Ova sensitization and sham sensitization with vehicle (Veh) were performed over a 25-day period in separate groups of mice. Our results showed that 1) both SO2 and NH3 inhalation challenges increased CR and ER frequencies in a concentration-dependent manner before Ova sensitization; 2) the baseline CR frequency was significantly elevated after Ova sensitization, accompanied by pronounced airway inflammation; and 3) Ova sensitization also markedly augmented the responses of CR and ER to both SO2 and NH3 inhalation challenges; in sharp contrast, the cough responses did not change after sham sensitization in the Veh group. In conclusion, Ova sensitization caused distinct and lingering increases in baseline cough frequency, and also intensified both CR and ER responses to inhaled irritant gases, which probably resulted from an allergic inflammation-induced hypersensitivity of airway sensory nerves.