Overwhelming evidence links inflammation to the pathogenesis of smoking-related pulmonary diseases, especially chronic obstructive pulmonary disease (COPD). Despite an increased understanding of the disease pathogenesis, mechanisms initiating smoking-induced inflammatory processes remain incompletely understood.To investigate the mechanisms that initiate and propagate smoke-induced inflammation, we used a wellcharacterised mouse model of cigarette smoke exposure, mice deficient for interleukin (IL)-1α, IL-1β and Toll-like receptor 4, and antibodies blocking granulocyte-macrophage colony-stimulating factor (GM-CSF). Studies were also pursued using intranasal delivery of human oxidised low-density lipoprotein (hOxLDL), a source of oxidised lipids, to investigate the inflammatory processes associated with impaired lipid homeostasis.We found that cigarette smoke exposure rapidly led to lipid accumulation in pulmonary macrophages, a defining feature of foam cells, which in turn released high levels of IL-1α. In smoke-exposed IL-1α-deficient mice, phospholipids accumulated in the bronchoalveolar lavage, a phenomenon also observed when blocking GM-CSF. Intranasal administration of hOxLDL led to lipid accumulation in macrophages and initiated an inflammatory process that mirrored the characteristics of cigarette smoke-induced inflammation.These findings identify a link between lipid accumulation in macrophages, inflammation and damaged surfactant, suggesting that the response to damaged pulmonary surfactant is a central mechanism that drives cigarette smoke-induced inflammation. Further investigations are required to explore the role of distorted lipid homeostasis in the pathogenesis of COPD. @ERSpublications Lipid accumulation in pulmonary macrophages drives cigarette smoke-induced lung inflammation

Formation of pulmonary tertiary immune structures is a characteristic feature of advanced COPD. In the current study, we investigated the mechanisms of tertiary lymphoid tissue (TLT) formation in the lungs of cigarette smoke-exposed mice. We found that cigarette smoke exposure led to TLT formation that persisted following smoking cessation. TLTs consisted predominantly of IgM positive B cells, while plasma cells in close proximity to TLTs expressed IgM, IgG, and IgA. The presence of TLT formation was associated with anti-nuclear autoantibody (ANA) production that also persisted following smoking cessation. ANAs were observed in the lungs, but not the circulation of cigarette smoke-exposed mice. Similarly, we observed ANA in the sputum of COPD patients where levels correlated with disease severity and were refractory to steroid treatment. Both ANA production and TLT formation were dependent on interleukin-1 receptor 1 (IL-1R1) expression. Contrary to TLT and ANA, lung neutrophilia resolved following smoking cessation. These data suggest a differential regulation of innate and B cell-related immune inflammatory processes associated with cigarette smoke exposure. Moreover, our study further emphasizes the importance of interleukin-1 (IL-1) signaling pathways in cigarette smoke-related pulmonary pathogenesis.

Emerging evidence suggests that autoimmune processes are implicated in the pathogenesis of chronic obstructive pulmonary disease (COPD). In this study, we assessed the expression of B‐cell activating factor (BAFF) in smokers, and investigated the functional importance of BAFF in the induction and maintenance of cigarette smoke‐induced pulmonary antinuclear antibodies (ANA) and tertiary lymphoid tissues (TLTs) using a preclinical mouse model. We observed that BAFF levels were elevated in smokers and mice exposed to cigarette smoke. In mice, BAFF expression was rapidly induced in the lungs following 4 days of cigarette smoke exposure and remained elevated following 8 and 24 weeks of exposure. Alveolar macrophages were the major source of BAFF. Blockade of BAFF using a BAFF receptor‐Fc (BAFFR‐Fc) construct prevented pulmonary ANA and TLT formation when delivered concurrent with cigarette smoke exposure. Under these conditions, no impact on lung inflammation was observed. However, administration of BAFFR‐Fc following smoking cessation markedly reduced the number of TLTs and ANA levels and, of note, reduced pulmonary neutrophilia. Altogether, this study shows for the first time a central role of BAFF in the induction and maintenance of cigarette smoke‐induced pulmonary ANA and suggests that BAFF blockade following smoking cessation could have beneficial effects on persistent inflammatory processes.In this study, we assessed the expression of B‐cell activating factor (BAFF) in smokers, and investigated the functional importance of BAFF in the induction and maintenance of cigarette smoke‐induced pulmonary antinuclear antibodies (ANA) and tertiary lymphoid tissues (TLTs) using a preclinical mouse model. Data presented show that BAFF plays a central role in the induction and maintenance of cigarette smoke‐induced pulmonary ANA and suggest a therapeutic potential for BAFF blockade in limiting autoimmune processes associated with smoking.

Streptococcus pneumoniae is a leading cause of invasive bacterial infections, with nasal colonization an important first step in disease. While cigarette smoking is a strong risk factor for invasive pneumococcal disease, the underlying mechanisms remain unknown. This is partly due to a lack of clinically relevant animal models investigating nasal pneumococcal colonization in the context of cigarette smoke exposure. We present a model of nasal pneumococcal colonization in cigarette smoke-exposed mice and document, for the first time, that cigarette smoke predisposes to invasive pneumococcal infection and mortality in an animal model. Cigarette smoke increased the risk of bacteremia and meningitis without prior lung infection. Mechanistically, deficiency in interleukin 1␣ (IL-1␣) or platelet-activating factor receptor (PAFR), an important host receptor thought to bind and facilitate pneumococcal invasiveness, did not rescue cigarette smoke-exposed mice from invasive pneumococcal disease. Importantly, we observed cigarette smoke to attenuate nasal inflammatory mediator expression, particularly that of neutrophil-recruiting chemokines, normally elicited by pneumococcal colonization. Smoking cessation during nasal pneumococcal colonization rescued nasal neutrophil recruitment and prevented invasive disease in mice. We propose that cigarette smoke predisposes to invasive pneumococcal disease by suppressing inflammatory processes of the upper respiratory tract. Given that smoking prevalence remains high worldwide, these findings are relevant to the continued efforts to reduce the invasive pneumococcal disease burden.

Chronic obstructive pulmonary disease (COPD) is characterised by a state of chronic pulmonary inflammation punctuated by microbial exacerbations. Despite advances in treatment options, COPD remains difficult to manage. In this study, we investigated the potential of peroxisome proliferator-activated receptor (PPAR)γ activation as a new therapy against cigarette smoke-induced inflammation and its associated bacterial exacerbation. C57BL/6 mice were exposed to room air or cigarette smoke for either 4 days or 4 weeks and treated either prophylactically or therapeutically with rosiglitazone. The impact of rosiglitazone on cigarette smoke-induced exacerbated response to the bacterial pathogen nontypeable Haemophilus influenzae (NTHi) was studied using the therapeutic treatment protocol. We found that rosiglitazone was able to reduce cigarette smoke-induced neutrophilia both when administered prophylactically or therapeutically. Therapeutic intervention with rosiglitazone was also effective in preventing cigarette smoke-induced neutrophilia exacerbation following NTHi infection. Moreover, the anti-inflammatory effects of rosiglitazone did not lead to an increase in the pulmonary bacterial burden, unlike dexamethasone. Altogether, our data suggest that pharmacological activation of PPARγ may be an effective therapeutic approach to improve COPD management, as it is able to reduce cigarette smoke-induced inflammation and decrease the magnitude of bacterial exacerbations, without compromising the ability of the immune system to control the infection.

Estradiol (E2) is a sex hormone which has shown to be protective against sexually transmitted infections such as herpes simplex virus 2 (HSV-2). However, few studies have examined the underlying mechanisms by which this occurs. Here, we investigated the effect of E2 on the establishment of memory T cells post-intranasal immunization with HSV-2. CD4+ T cell responses first appeared in the upper respiratory tract (URT) within 3 days post-immunization, before being detected in the female reproductive tract (FRT) at 7 days. E2 treatment resulted in greater and earlier Th17 responses, which preceded augmented Th1 responses in these sites. The CD4+ T cells persisted in the URT for up to 28 days, and E2 treatment resulted in higher frequencies of memory T cells. Intranasal immunization also led to the establishment of CD4+ tissue-resident memory T cells (TRM cells) in the FRT, and E2 treatment resulted in increased Th1 and Th17 TRM cells. When the migration of circulating T cells into the FRT was blocked by FTY720, immunized E2-treated mice remained completely protected against subsequent genital HSV-2 challenge compared to non-E2 controls, confirming that TRM cells alone are adequate for protection in these mice. Finally, the enhanced vaginal Th1 TRM cells present in E2-treated mice were found to be modulated through an IL-17-mediated pathway, as E2-treated IL-17A deficient mice had impaired establishment of Th1 TRM cells. This study describes a novel role for E2 in enhancing CD4+ memory T cells and provides insight on potential strategies for generating optimal immunity during vaccination. IMPORTANCE Herpes simplex virus 2 (HSV-2) is a highly prevalent sexually transmitted infection for which there is currently no vaccine available. Interestingly, the female sex hormone estradiol has been shown to be protective against HSV-2. However, the underlying mechanisms by which this occurs remains relatively unknown. Our study demonstrates that under the influence of estradiol treatment, intranasal immunization with an attenuated strain of HSV-2 leads to enhanced establishment of anti-viral memory T cell responses in the upper respiratory tract and female reproductive tract. In these sites, estradiol treatment leads to greater Th17 memory cells, which precede enhanced Th1 memory responses. Consequently, the T cell responses mounted by tissue-resident memory cells in the female reproductive tract of estradiol-treated mice are sufficient to protect mice against vaginal HSV-2 challenge. This study offers important insights regarding the regulation of mucosal immunity by hormones and on potential strategies for generating optimal immunity during vaccination.

BackgroundChronic cigarette smoke exposure is known to activate the adaptive immune system; however, the functional role of these processes is currently unknown. Given the role of oxidized lipids in driving innate inflammatory responses to cigarette smoke, we investigated whether an adaptive immune response against damaged lipids was induced following chronic cigarette smoke exposure.Methods and resultsUsing a well-established mouse model, we showed that cigarette smoke exposure led to a progressive increase in pulmonary antibodies against oxidized low-density lipoprotein (OxLDL). Functionally, we found that intranasal delivery of an antibody against oxidized phosphatidylcholine (anti-OxPC; clone E06) increased lipid and particle uptake by pulmonary macrophages without exacerbating cigarette smoke-induced neutrophilia. We also found that anti-OxPC treatment increased particle uptake following smoking cessation. Finally, the frequency of pulmonary macrophages with internalized particles was increased after prolonged smoke exposure, at which time lung anti-OxPC responses were highest.ConclusionsAltogether, this is the first report to demonstrate a non-pathogenic, and possibly protective, function of a newly identified autoantibody induced by chronic cigarette smoke exposure.

RationaleThe accumulation of macrophages in the airways and the pulmonary interstitium is a hallmark of cigarette smoke-associated inflammation. Notably, pulmonary macrophages are not a homogenous population but consist of several subpopulations. To date, the manner in which cigarette smoke exposure affects the relative composition and functional capacity of macrophage subpopulations has not been elucidated.MethodsUsing a whole-body cigarette smoke exposure system, we investigated the impact of cigarette smoke on macrophage subpopulations in C57BL/6 mice using flow cytometry-based approaches. Moreover, we used bromodeoxyuridine labelling plus Il1a-/- and Il1r1-/- mice to assess the relative contribution of local proliferation and monocyte recruitment to macrophage accumulation. To assess the functional consequences of altered macrophage subpopulations, we used a model of concurrent bleomycin-induced lung injury and cigarette smoke exposure to examine tissue remodelling processes.Main ResultsCigarette smoke exposure altered the composition of pulmonary macrophages increasing CD11b+ subpopulations including monocyte-derived alveolar macrophages (Mo-AM) as well as interstitial macrophages (IM)1, -2 and -3. The increase in CD11b+ subpopulations was observed at multiple cigarette smoke exposure timepoints. Bromodeoxyuridine labelling and studies in Il1a-/- mice demonstrated that increased Mo-AM and IM3 turnover in the lungs of cigarette smoke-exposed mice was IL-1α dependent. Compositional changes in macrophage subpopulations were associated with impaired induction of fibrogenesis including decreased α-smooth muscle actin positive cells following intratracheal bleomycin treatment. Mechanistically, in vivo and ex vivo assays demonstrated predominant macrophage M1 polarisation and reduced matrix metallopeptidase 9 activity in cigarette smoke-exposed mice.ConclusionCigarette smoke exposure modified the composition of pulmonary macrophage by expanding CD11b+ subpopulations. These compositional changes were associated with attenuated fibrogenesis, as well as predominant M1 polarisation and decreased fibrotic activity. Overall, these data suggest that cigarette smoke exposure altered the composition of pulmonary macrophage subpopulations contributing to impaired tissue remodelling.