Nele Heulens

Antielastin B-cell and T-cell immunity in patients with chronic obstructive pulmonary disease

Rationale Antielastin autoimmunity has been hypothesised to drive disease progression in chronic obstructive pulmonary disease (COPD). The proposed mechanism is currently disputed by conflicting data. The authors aimed to explore antibody responses against elastin in a large and extensively characterised COPD population and to assess elastin-specific peripheral T-cell reactivity in a representative subgroup. Methods Antielastin antibodies were analysed with indirect ELISA on the plasma of 320 patients with COPD (Global Initiative for Chronic Obstructive Lung Disease 1–4) and 143 smoking controls. In a second group of 40 patients with COPD and smoking controls, T-cell responses against extracellular matrix (elastin, collagen I and collagen V) were determined with enzyme-linked immunosorbent spot (EliSpot) (interferon γ (IFNγ) and interleukin-2) on peripheral blood mononuclear cells and compared with the responses of 11 never-smoking controls. Results Antielastin antibody titres were not elevated in patients with COPD compared with smoking controls and even decreased significantly with increasing severity of COPD (p<0.001). Lower antielastin antibody titres were also found in a subgroup of patients with CT-proven emphysema. Elastin-specific INFγ-mediated T helper 1 responses could not be revealed in smoking subjects with and without COPD. Collagen I-mediated T-cell responses were also absent, which contrasted with a significant increased anticollagen V response in the smoking controls and patients with COPD compared with the never smokers (p=0.008). Collagen V-mediated T-cell responses could not discriminate between patients with COPD and smoking controls. Conclusion A systemic immune response against elastin could not be identified in patients with COPD. By contrast, collagen V-mediated autoimmunity was increased in the subgroup of smokers and may potentially contribute to the pathogenesis of COPD.

1,25-Dihydroxyvitamin D Modulates Antibacterial and Inflammatory Response in Human Cigarette Smoke-Exposed Macrophages

Cigarette smoking is associated with increased inflammation and defective antibacterial responses in the airways. Interestingly, vitamin D has been shown to suppress inflammation and to improve antibacterial defense. However, it is currently unknown whether vitamin D may modulate inflammation and antibacterial defects in human cigarette smoke (CS)-exposed airways. To explore these unresolved issues, alveolar macrophages obtained from non-smoking and smoking subjects as well as human cigarette smoke extract (CSE)-treated THP-1 macrophages were stimulated with 1,25-dihydroxyvitamin D (1,25(OH)2D) to address inflammatory and antibacterial responses. Although basal levels of inflammatory cytokines and chemokines did not differ between non-smoking and smoking subjects, 1,25(OH)2D did reduce levels of IL-6, TNF-α and MCP-1 in alveolar macrophages in response to LPS/IFN-γ, although not statistically significant for TNF-α and IL-6 in smokers. CSE did not significantly alter vitamin D metabolism (expression levels of CYP24A1 or CYP27B1) in THP-1 macrophages. Furthermore, stimulation with 1,25(OH)2D reduced mRNA expression levels and/or protein levels of IL-8, TNF-α and MCP-1 in CSE-treated THP-1 macrophages. 1,25(OH)2D did not improve defects in phagocytosis of E. coli bacteria or the oxidative burst response in CSE-treated THP-1 macrophages or alveolar macrophages from smokers. However, 1,25(OH)2D significantly enhanced mRNA expression and/or protein levels of the antimicrobial peptide cathelicidin in alveolar macrophages and THP-1 macrophages, independently of CS exposure. In conclusion, our results provide the first evidence that vitamin D could be a new strategy for attenuating airway inflammation and improving antibacterial defense in CS-exposed airways.

Innate Immune Modulation in Chronic Obstructive Pulmonary Disease: Moving Closer toward Vitamin D Therapy

Chronic obstructive pulmonary disease (COPD) is one of the most common respiratory diseases and a major cause of morbidity and mortality worldwide. Disturbed innate immune processes characterize the pathogenesis of COPD. Vitamin D deficiency is very common in COPD patients and has been associated with disease severity. Interestingly, mechanistic evidence from animal and in vitro studies has demonstrated important innate immunomodulatory functions of vitamin D, including anti-inflammatory, antioxidative, and antimicrobial functions. This review discusses in detail how the innate immunomodulatory functions of vitamin D may have therapeutic potential in COPD patients. The remaining challenges associated with vitamin D therapy in COPD patients are also discussed.

Interaction between Physical Activity and Smoking on Lung, Muscle, and Bone in Mice

Physical inactivity is an important contributor to skeletal muscle weakness, osteoporosis, and weight loss in chronic obstructive pulmonary disease. However, the effects of physical inactivity, in interaction with smoking, on lung, muscle, and bone are poorly understood. To address this issue, male mice were randomly assigned to an active (daily running), moderately inactive (space restriction), or extremely inactive group (space restriction followed by hindlimb suspension to mimic bed rest) during 24 weeks and simultaneously exposed to either cigarette smoke or room air. The effects of different physical activity levels and smoking status and their respective interaction were examined on lung function, body composition, in vitro limb muscle function, and bone parameters. Smoking caused emphysema, reduced food intake with subsequent loss of body weight, and fat, lean, and muscle mass, but increased trabecular bone volume. Smoking induced muscle fiber atrophy, which did not result in force impairment. Moderate inactivity only affected lung volumes and compliance, whereas extreme inactivity increased lung inflammation, lowered body and fat mass, induced fiber atrophy with soleus muscle dysfunction, and reduced exercise capacity and all bone parameters. When combined with smoking, extreme inactivity also aggravated lung inflammation and emphysema, and accelerated body and muscle weight loss. This study shows that extreme inactivity, especially when imposed by absolute rest, accelerates lung damage and inflammation. When combined with smoking, extreme inactivity is deleterious for muscle bulk, bone, and lungs. These data highlight that the consequences of physical inactivity during the course of chronic obstructive pulmonary disease should not be neglected.

Vitamin D deficiency impairs skeletal muscle function in a smoking mouse model

Chronic obstructive pulmonary disease (COPD) is associated with skeletal muscle dysfunction. Vitamin D plays an important role in muscle strength and performance in healthy individuals. Vitamin D deficiency is highly prevalent in COPD, but its role in skeletal muscle dysfunction remains unclear. We examined the time-course effect of vitamin D deficiency on limb muscle function in mice with normal or deficient vitamin D serum levels exposed to air or cigarette smoke for 6, 12 or 18 weeks. The synergy of smoking and vitamin D deficiency increased lung inflammation and lung compliance from 6 weeks on with highest emphysema scores observed at 18 weeks. Smoking reduced body and muscle mass of the soleus and extensor digitorum longus (EDL), but did not affect contractility, despite type II atrophy. Vitamin D deficiency did not alter muscle mass but reduced muscle force over time, downregulated vitamin D receptor expression, and increased muscle lipid peroxidation but did not alter actin and myosin expression, fiber dimensions or twitch relaxation time. The combined effect of smoking and vitamin D deficiency did not further deteriorate muscle function but worsened soleus mass loss and EDL fiber atrophy at 18 weeks. We conclude that the synergy of smoking and vitamin D deficiency in contrast to its effect on lung disease, had different, independent but important noxious effects on skeletal muscles in a mouse model of mild COPD.

The effects of smoking on whisker movements: A quantitative measure of exploratory behaviour in rodents

Nicotine, an important component of cigarette smoke, is a neurotransmitter that contributes to stress, depression and anxiety in smokers. In rodents, it increases anxiety and reduces exploratory behaviours. However, so far, the measurements of exploratory behaviour in rodents have only been semi-quantitative and lacking in sufficient detail to characterise the temporal effect of smoking cessation. As rodents, such as mice and rats, primarily use whiskers to explore their environment, we studied the effect of 3 months smoking with 1 and 2 weeks smoking cessation on whisker movements in mice, using high-speed video camera footage and image analysis. Both protraction and retraction whisker velocities were increased in smoking mice (p<0.001) and returned to normal following just one week of smoking cessation. In addition, locomotion speeds were decreased in smoking mice, and returned to normal following smoking cessation. Lung function was also impacted by smoking and remained impaired even following smoking cessation. We suggest that the increased whisker velocities in the smoking mice reflect reduced exploration and impeded tactile performance. The increase in whisker velocity with smoking, and its reduction following smoking cessation, also lends support to acetylcholine being involved in awareness, attention and alertness pathways. It also shows that smoking-induced behavioural changes can be reversed with smoking cessation, which may have implications for human smokers.