Respiratory syncytial virus infection increases chlorine-induced airway hyperresponsiveness

Countermeasures against Pulmonary Threat Agents

Inhaled toxicants are used for diverse purposes, ranging from industrial applications such as agriculture, sanitation, and fumigation to crowd control and chemical warfare, and acute exposure can induce lasting respiratory complications. The intentional release of chemical warfare agents (CWAs) during World War I caused life-long damage for survivors, and CWA use is outlawed by international treaties. However, in the past two decades, chemical warfare use has surged in the Middle East and Eastern Europe, with a shift toward lung toxicants. The potential use of industrial and agricultural chemicals in rogue activities is a major concern as they are often stored and transported near populated areas, where intentional or accidental release can cause severe injuries and fatalities. Despite laws and regulatory agencies that regulate use, storage, transport, emissions, and disposal, inhalational exposures continue to cause lasting lung injury. Industrial irritants (e.g., ammonia) aggravate the upper respiratory tract, causing pneumonitis, bronchoconstriction, and dyspnea. Irritant gases (e.g., acrolein, chloropicrin) affect epithelial barrier integrity and cause tissue damage through reactive intermediates or by direct adduction of cysteine-rich proteins. Symptoms of CWAs (e.g., chlorine gas, phosgene, sulfur mustard) progress from airway obstruction and pulmonary edema to acute lung injury (ALI) and acute respiratory distress syndrome (ARDS), which results in respiratory depression days later. Emergency treatment is limited to supportive care using bronchodilators to control airway constriction and rescue with mechanical ventilation to improve gas exchange. Complications from acute exposure can promote obstructive lung disease and/or pulmonary fibrosis, which require long-term clinical care. SIGNIFICANCE STATEMENT: Inhaled chemical threats are of growing concern in both civilian and military settings, and there is an increased need to reduce acute lung injury and delayed clinical complications from exposures. This minireview highlights our current understanding of acute toxicity and pathophysiology of a select number of chemicals of concern. It discusses potential early-stage therapeutic development as well as challenges in developing countermeasures applicable for administration in mass casualty situations.

CPAP-induced airway hyper-reactivity in mice is modulated by hyaluronan synthase-3

BACKGROUND

Continuous positive airway pressure (CPAP) is a primary mode of respiratory support for preterm infants. Animal studies have shown long-term detrimental effects on lung/airway development, particularly airway (AW) hyper-reactivity, as an unfortunate consequence of neonatal CPAP. Since the hyaluronan (HA) synthesizing enzyme hyaluronan synthase-3 (HAS3) is involved in various adult pulmonary disorders, the present study used a neonatal mouse model to investigate the role of HAS3 in CPAP-induced AW hyper-reactivity.

METHODS

Male and female neonatal mice were fitted with a custom-made mask for delivery of daily CPAP 3 h/day for 7 days. At postnatal day 21 (2 weeks after CPAP ended), airway (AW) hyper-reactivity and HAS3 expression were assessed with and without in vitro HAS3 siRNA treatment.

RESULTS

MRIs of 3-day-old mice confirmed that CPAP increased lung volume with incrementing inflation pressures. CPAP increased AW reactivity in both male and female mice, which was associated with increased airway smooth muscle and epithelial HAS3 immunoreactivity. CPAP did not affect HA accumulation, but HAS3 siRNA reversed CPAP-induced AW hyper-reactivity and reduced HAS3 expression.

CONCLUSIONS

These data in mice implicate a role for HAS3 in long-term effects of CPAP in the developing airway in the context of preterm birth and CPAP therapy.

IMPACT

Neonatal CPAP increases airway smooth muscle and epithelial HAS3 expression in mice. CPAP-induced airway hyper-reactivity is modulated by HAS3. These data enhance our understanding of the role mechanical forces play on lung development. These data are a significance step toward understanding CPAP effects on developing airway. These data may impact clinical recognition of the ways that CPAP may contribute to wheezing disorders of former preterm infants.

Halogen-Induced Chemical Injury to the Mammalian Cardiopulmonary Systems

The halogens chlorine (Cl₂) and bromine (Br₂) are highly reactive oxidizing elements with widespread industrial applications and a history of development and use as chemical weapons. When inhaled, depending on the dose and duration of exposure, they cause acute and chronic injury to both the lungs and systemic organs that may result in the development of chronic changes (such as fibrosis) and death from cardiopulmonary failure. A number of conditions, such as viral infections, coexposure to other toxic gases, and pregnancy increase susceptibility to halogens significantly. Herein we review their danger to public health, their mechanisms of action, and the development of pharmacological agents that when administered post-exposure decrease morbidity and mortality.

Transient receptor potential channels in pulmonary chemical injuries and as countermeasure targets

The lung is highly sensitive to chemical injuries caused by exposure to threat agents in industrial or transportation accidents, occupational exposures, or deliberate use as weapons of mass destruction (WMD). There are no antidotes for the majority of the chemical threat agents and toxic inhalation hazards despite their use as WMDs for more than a century. Among several putative targets, evidence for transient receptor potential (TRP) ion channels as mediators of injury by various inhalational chemical threat agents is emerging. TRP channels are expressed in the respiratory system and are essential for homeostasis. Among TRP channels, the body of literature supporting essential roles for TRPA1, TRPV1, and TRPV4 in pulmonary chemical injuries is abundant. TRP channels mediate their function through sensory neuronal and nonneuronal pathways. TRP channels play a crucial role in complex pulmonary pathophysiologic events including, but not limited to, increased intracellular calcium levels, signal transduction, recruitment of proinflammatory cells, neurogenic inflammatory pathways, cough reflex, hampered mucus clearance, disruption of the integrity of the epithelia, pulmonary edema, and fibrosis. In this review, we summarize the role of TRP channels in chemical threat agents-induced pulmonary injuries and how these channels may serve as medical countermeasure targets for broader indications.

Hyaluronan and halogen-induced airway hyperresponsiveness and lung injury

Chlorine (Cl2 ) and bromine (Br2 ) are produced in large quantities throughout the world and used in the industry and the sanitation of water. These halogens can pose a significant threat to public health when released into the atmosphere during transportation and industrial accidents, or as acts of terrorism. In this review, we discuss the evidence showing that the activity of Cl2 and Br2 , and of products formed by their interaction with biomolecules, fragment high-molecular-weight hyaluronan (HMW-HA), a key component of the interstitial space and present in epithelial cells, to form proinflammatory, low-molecular-weight hyaluronan fragments that increase intracellular calcium (Ca2+ ) and activate RAS homolog family member A (RhoA) in airway smooth muscle and epithelial and microvascular cells. These changes result in airway hyperresponsiveness (AHR) to methacholine and increase epithelial and microvascular permeability. The increase in intracellular Ca2+ is the result of the activation of the calcium-sensing receptor by Cl2 , Br2 , and their by-products. Posthalogen administration of a commercially available form of HMW-HA to mice and to airway cells in vitro reverses the increase of Ca2+ and the activation of RhoA, and restores AHR to near-normal levels of airway function. These data have established the potential of HMW-HA to be a countermeasure against Cl2 and Br2 toxicity.

Pulmonary function analysis in cotton rats after respiratory syncytial virus infection

The cotton rat (Sigmodon hispidus) is an excellent small animal model for human respiratory viral infections such as human respiratory syncytial virus (RSV) and human metapneumovirus (HMPV). These respiratory viral infections, as well as other pulmonary inflammatory diseases such as asthma, are associated with lung mechanic disturbances. So far, the pathophysiological effects of viral infection and allergy on cotton rat lungs have not been measured, although this information might be an important tool to determine the efficacy of vaccine and drug candidates. To characterize pulmonary function in the cotton rat, we established forced oscillation technique in uninfected, RSV infected and HDM sensitized cotton rats, and characterized pulmonary inflammation, mucus production, pulmonary edema, and oxygenation. There was a gender difference after RSV infection, with females demonstrating airway hyper-responsiveness while males did not. Female cotton rats 2dpi had a mild increase in pulmonary edema (wet: dry weight ratios). At day 4 post infection, female cotton rats demonstrated mild pulmonary inflammation, no increase in mucus production or reduction in oxygenation. Pulmonary function was not significantly impaired after RSV infection. In contrast, cotton rats sensitized to HDM demonstrated airway hyper-responsiveness with a significant increase in pulmonary inflammation, increase in baseline tissue damping, and a decrease in baseline pulmonary compliance. In summary, we established baseline data for forced oscillation technique and other respiratory measures in the cotton rat and used it to analyze respiratory diseases in cotton rats.

[Characteristics of pulmonary function in infants and young children with pertussis-like coughing]

OBJECTIVE

To study the characteristics of pulmonary function in children with pertussis-like coughing caused by different pathogen infections.

METHODS

The data on etiology and tidal breathing pulmonary function were collected from 95 hospitalized infants and young children with pertussis-like coughing. The tidal breathing pulmonary function was compared between these children and 67 healthy children. According to the type of pathogen, the children with pertussis-like coughing were classified to 6 groups: pertussis (n=17), viral infection (n=23), tuberculosis infection (n=6), Mycoplasma infection (n=9), other bacterial infection (n=8), and unknown pathogen (n=32).

RESULTS

Among the 95 children with pertussis-like coughing, 15 (16%) had mild obstructive ventilatory dysfunction, 30 (32%) had moderate obstructive ventilatory dysfunction, and 22 (23%) had severe obstructive ventilatory dysfunction. Compared with the normal control group, the children with pertussis-like coughing had significant reductions in inspiratory-to-expiratory time ratio, ratio of time to peak tidal expiratory flow to total expiratory time (tPF%tE), and ratio of volume to peak tidal expiratory flow to total expiratory volume (vPF%vE) (P<0.05). The tuberculosis infection and Mycoplasma infection groups had a significantly lower tidal volume than the normal control group (P<0.05). All pathogen infection groups except the tuberculosis infection group had significantly lower tPF%tE and vPF%vE than the normal control group (P<0.05). The pertussis group had significantly lower tPF%tE and vPF%vE than the other infection groups (P<0.05).

CONCLUSIONS

Most of children with pertussis-like coughing have abnormal pulmonary functions. The children with Bordetella pertussis infection have the most severe pulmonary function impairment. Tidal breathing pulmonary function test may provide a reference for pathogen analysis of children with pertussis-like coughing.

[Characteristics of pulmonary function in infants and young children with pertussis-like coughing]

OBJECTIVE

To study the characteristics of pulmonary function in children with pertussis-like coughing caused by different pathogen infections.

METHODS

The data on etiology and tidal breathing pulmonary function were collected from 95 hospitalized infants and young children with pertussis-like coughing. The tidal breathing pulmonary function was compared between these children and 67 healthy children. According to the type of pathogen, the children with pertussis-like coughing were classified to 6 groups: pertussis (n=17), viral infection (n=23), tuberculosis infection (n=6), Mycoplasma infection (n=9), other bacterial infection (n=8), and unknown pathogen (n=32).

RESULTS

Among the 95 children with pertussis-like coughing, 15 (16%) had mild obstructive ventilatory dysfunction, 30 (32%) had moderate obstructive ventilatory dysfunction, and 22 (23%) had severe obstructive ventilatory dysfunction. Compared with the normal control group, the children with pertussis-like coughing had significant reductions in inspiratory-to-expiratory time ratio, ratio of time to peak tidal expiratory flow to total expiratory time (tPF%tE), and ratio of volume to peak tidal expiratory flow to total expiratory volume (vPF%vE) (P<0.05). The tuberculosis infection and Mycoplasma infection groups had a significantly lower tidal volume than the normal control group (P<0.05). All pathogen infection groups except the tuberculosis infection group had significantly lower tPF%tE and vPF%vE than the normal control group (P<0.05). The pertussis group had significantly lower tPF%tE and vPF%vE than the other infection groups (P<0.05).

CONCLUSIONS

Most of children with pertussis-like coughing have abnormal pulmonary functions. The children with Bordetella pertussis infection have the most severe pulmonary function impairment. Tidal breathing pulmonary function test may provide a reference for pathogen analysis of children with pertussis-like coughing.

Changes in the Th9 cell population and related cytokines in the peripheral blood of infants with recurrent wheezing

Introduction

T helper type 9 (Th9) cells have been shown to play a key role in initiating allergic reactions and promoting airway inflammation. However, to the best of our knowledge, their role has not been analyzed in infants with recurrent wheezing.

Material and methods

We performed a case-control study including 34 infants with recurrent wheezing and the same number of healthy infants as controls; all subjects were aged 1- to 3-years-old. The Th9 cell populations in the peripheral blood of these subjects were analyzed using flow cytometry, along with the assessment of Th9- and Th2-related plasma cytokine levels, including interleukin (IL)-1β, IL-4, IL-5, IL-9, IL-10, IL-13, IL-17A, and IL-33, and transforming growth factor β1 (TGF-β1) using a Luminex 200 immunoassay.

Results

Our results indicatedthat infants with recurrent wheezing had higher percentages of Th9 cells (median, 0.69%; range, 0.46-1.08%) as compared to healthy infants (median, 0.25%, range, 0.13-0.36%; p < 0.05). In addition, infants with recurrent wheezing also exhibited higher plasma levels of cytokines IL-4, IL-9, IL-10, IL-33, and TGF-β1. Furthermore, the percentage of Th9 cells was positively correlated with the levels of IL-4 (r = 0.408, p < 0.05) and IL-9 (r = 0.644, p < 0.05) in the peripheral blood of wheezing infants.

Conclusions

Our findings suggest that the percentage of Th9 cells is increased in infants with recurrent wheezing; thus, Th9 cells may play an important role in the pathogenesis of recurrent wheezing.

One-Week Nebulization of Mycobacterium vaccae Can Protect Against Pulmonary Respiratory Syncytial Virus Infection in Balb/c Mice

Background: Respiratory syncytial virus (RSV) infection is the most common cause of acute lower respiratory tract infection in children, leading to their death. Currently, no effective prevention and treatment methods for RSV infection are available. RSV and many other unknown viruses pose a serious threat to human health. Our previous study demonstrated that Mycobacterium vaccae nebulization can protect against allergic asthma. As RSV infection and asthma are closely related, we hypothesized that M. vaccae could protect against pulmonary RSV infection. Therefore, we evaluated the effect of M. vaccae on RSV infection in Balb/c mice. Methods: The mice were randomized into three groups: normal, RSV, and M. vaccae. One week before the RSV infection model was established, the mice in the M. vaccae group were nebulized with M. vaccae. On the fourth day after RSV infection, airway responsiveness, airway inflammation, pulmonary RSV infection, mRNA levels of pulmonary toll-like receptor (TLR) 7 and TLR8, and pulmonary NF09, acetylcholine, and epidermal growth factor regulator (EGFR) expression levels in all mice were measured. Results: The airway inflammation in the M. vaccae group was alleviated compared with that in the RSV group. In the M. vaccae group, the pulmonary mRNA level of RSV and the pulmonary expression levels of NF09, acetylcholine, and EGFR were decreased considerably, whereas the mRNA levels of TLR7 and TLR8 were increased significantly. Conclusions: One-week nebulization of M. vaccae can protect against RSV infection in Balb/c mice. The mechanism involves the regulation of neurotransmitters and expression of TLR7, TLR8, and EGFR.

Toxic effects of chlorine gas and potential treatments: a literature review

Chlorine gas is one of the highly produced chemicals in the USA and around the world. Chlorine gas has several uses in water purification, sanitation, and industrial applications; however, it is a toxic inhalation hazard agent. Inhalation of chlorine gas, based on the concentration and duration of the exposure, causes a spectrum of symptoms, including but not limited to lacrimation, rhinorrhea, bronchospasm, cough, dyspnea, acute lung injury, death, and survivors develop signs of pulmonary fibrosis and reactive airway disease. Despite the use of chlorine gas as a chemical warfare agent since World War I and its known potential as an industrial hazard, there is no specific antidote. The resurgence of the use of chlorine gas as a chemical warfare agent in recent years has brought speculation of its use as weapons of mass destruction. Therefore, developing antidotes for chlorine gas-induced lung injuries remains the need of the hour. While some of the pre-clinical studies have made substantial progress in the understanding of chlorine gas-induced pulmonary pathophysiology and identifying potential medical countermeasure(s), yet none of the drug candidates are approved by the U.S. Food and Drug Administration (FDA). In this review, we summarized pathophysiology of chlorine gas-induced pulmonary injuries, pre-clinical animal models, development of a pipeline of potential medical countermeasures under FDA animal rule, and future directions for the development of antidotes for chlorine gas-induced lung injuries.

High molecular weight hyaluronan ameliorates allergic inflammation and airway hyperresponsiveness in the mouse

Allergic asthma is a major cause of morbidity in both pediatric and adult patients. Recent research has highlighted the role of hyaluronan (HA), an extracellular matrix glycosaminoglycan, in asthma pathogenesis. Experimental allergic airway inflammation and clinical asthma are associated with an increase of shorter fragments of HA (sHA), which complex with inter-α-inhibitor heavy chains (HCs) and induce inflammation and airway hyperresponsiveness (AHR). Importantly, the effects of sHA can be antagonized by the physiological counterpart high molecular weight HA (HMWHA). We used a mouse model of house dust mite-induced allergic airway inflammation and demonstrated that instilled HMWHA ameliorated allergic airway inflammation and AHR, even when given after the establishment of allergic sensitization and after challenge exposures. Furthermore, instilled HMWHA reduced the development of HA-HC complexes and the activation of Rho-associated, coiled-coil containing protein kinase 2. We conclude that airway application of HMWHA is a potential treatment for allergic airway inflammation.

TNF-stimulated gene 6 promotes formation of hyaluronan-inter-α-inhibitor heavy chain complexes necessary for ozone-induced airway hyperresponsiveness

Exposure to pollutants, such as ozone, exacerbates airway inflammation and hyperresponsiveness (AHR). TNF-stimulated gene 6 (TSG-6) is required to transfer inter-α-inhibitor heavy chains (HC) to hyaluronan (HA), facilitating HA receptor binding. TSG-6 is necessary for AHR in allergic asthma, because it facilitates the development of a pathological HA-HC matrix. However, the role of TSG-6 in acute airway inflammation is not well understood. Here, we hypothesized that TSG-6 is essential for the development of HA- and ozone-induced AHR. TSG-6^-/- and TSG-6^+/+ mice were exposed to ozone or short-fragment HA (sHA), and AHR was assayed via flexiVent. The AHR response to sHA was evaluated in the isolated tracheal ring assay in tracheal rings from TSG-6^-/- or TSG-6^+/+, with or without the addition of exogenous TSG-6, and with or without inhibitors of Rho-associated, coiled-coil-containing protein kinase (ROCK), ERK, or PI3K. Smooth-muscle cells from mouse tracheas were assayed in vitro for signaling pathways. We found that TSG-6 deficiency protects against AHR after ozone (in vivo) or sHA (in vitro and in vivo) exposure. Moreover, TSG-6^-/- tracheal ring non-responsiveness to sHA was reversed by exogenous TSG-6 addition. sHA rapidly activated RhoA, ERK, and Akt in airway smooth-muscle cells, but only in the presence of TSG-6. Inhibition of ROCK, ERK, or PI3K/Akt blocked sHA/TSG-6-mediated AHR. In conclusion, TSG-6 is necessary for AHR in response to ozone or sHA, in part because it facilitates rapid formation of HA-HC complexes. The sHA/TSG-6 effect is mediated by RhoA, ERK, and PI3K/Akt signaling.

Mechanisms and Treatment of Halogen Inhalation-Induced Pulmonary and Systemic Injuries in Pregnant Mice

Inhalation of oxidant gases has been implicated in adverse outcomes in pregnancy, but animal models to address mechanisms and studies to identify potential pregnancy-specific therapies are lacking. Herein, we show that inhalation of bromine at 600 parts per million for 30 minutes by pregnant mice on the 15th day of embryonic development results in significantly lower survival after 96 hours than an identical level of exposure in nonpregnant mice. On the 19th embryonic day, bromine-exposed pregnant mice have increased systemic blood pressure, abnormal placental development, severe fetal growth restriction, systemic inflammation, increased levels of circulating antiangiogenic short fms-like tyrosine kinase-1, and evidence of pulmonary and cardiac injury. Treatment with tadalafil, an inhibitor of type 5 phosphodiesterase, by oral gavage 1 hour post-exposure and then once daily thereafter, attenuated systemic blood pressures, decreased inflammation, ameliorated pulmonary and cardiac injury, and improved maternal survival (from 36% to 80%) and fetal growth. These pathological changes resemble those seen in preeclampsia. Nonpregnant mice did not exhibit any of these pathological changes and were not affected by tadalafil. These findings suggest that pregnant women exposed to bromine may require particular attention and monitoring for signs of preeclampsia-like symptoms.

An Official American Thoracic Society Workshop Report: Chemical Inhalational Disasters. Biology of Lung Injury, Development of Novel Therapeutics, and Medical Preparedness

This report is based on the proceedings from the Inhalational Lung Injury Workshop jointly sponsored by the American Thoracic Society (ATS) and the National Institutes of Health (NIH) Countermeasures Against Chemical Threats (CounterACT) program on May 21, 2013, in Philadelphia, Pennsylvania. The CounterACT program facilitates research leading to the development of new and improved medical countermeasures for chemical threat agents. The workshop was initiated by the Terrorism and Inhalational Disasters Section of the Environmental, Occupational, and Population Health Assembly of the ATS. Participants included both domestic and international experts in the field, as well as representatives from U.S. governmental funding agencies. The meeting objectives were to (1) provide a forum to review the evidence supporting current standard medical therapies, (2) present updates on our understanding of the epidemiology and underlying pathophysiology of inhalational lung injuries, (3) discuss innovative investigative approaches to further delineating mechanisms of lung injury and identifying new specific therapeutic targets, (4) present promising novel medical countermeasures, (5) facilitate collaborative research efforts, and (6) identify challenges and future directions in the ongoing development, manufacture, and distribution of effective and specific medical countermeasures. Specific inhalational toxins discussed included irritants/pulmonary toxicants (chlorine gas, bromine, and phosgene), vesicants (sulfur mustard), chemical asphyxiants (cyanide), particulates (World Trade Center dust), and respirable nerve agents.

Emerging concepts in smooth muscle contributions to airway structure and function: implications for health and disease

Airway structure and function are key aspects of normal lung development, growth, and aging, as well as of lung responses to the environment and the pathophysiology of important diseases such as asthma, chronic obstructive pulmonary disease, and fibrosis. In this regard, the contributions of airway smooth muscle (ASM) are both functional, in the context of airway contractility and relaxation, as well as synthetic, involving production and modulation of extracellular components, modulation of the local immune environment, cellular contribution to airway structure, and, finally, interactions with other airway cell types such as epithelium, fibroblasts, and nerves. These ASM contributions are now found to be critical in airway hyperresponsiveness and remodeling that occur in lung diseases. This review emphasizes established and recent discoveries that underline the central role of ASM and sets the stage for future research toward understanding how ASM plays a central role by being both upstream and downstream in the many interactive processes that determine airway structure and function in health and disease.