Year in review 2011: asthma, chronic obstructive pulmonary disease and airway biology

Nontypeable Haemophilus influenzae-Induced MyD88 Short Expression Is Regulated by Positive IKKβ and CREB Pathways and Negative ERK1/2 Pathway

Airway diseases such as asthma and chronic obstructive pulmonary disease (COPD) are characterized by excessive inflammation and are exacerbated by nontypeable Haemophilus influenzae (NTHi). Airway epithelial cells mount the initial innate immune responses to invading pathogens and thus modulate inflammation. While inflammation is necessary to eliminate a pathogen, excessive inflammation can cause damage to the host tissue. Therefore, the inflammatory response must be tightly regulated and deciphering the signaling pathways involved in this response will enhance our understanding of the regulation of the host inflammatory response. NTHi binds to TLR2 and signal propagation requires the adaptor molecule myeloid differentiation factor 88 (MyD88). An alternative spliced form of MyD88 is called MyD88 short (MyD88s) and has been identified in macrophages and embryonic cell lines as a negative regulator of inflammation. However, the role of MyD88s in NTHi-induced inflammation in airway epithelial cells remains unknown. Here we show that NTHi induces MyD88s expression and MyD88s is a negative regulator of inflammation in airway epithelial cells. We further demonstrate that MyD88s is positively regulated by IKKβ and CREB and negatively regulated by ERK1/2 signaling pathways. Taken together these data indicate that airway inflammation is controlled in a negative feedback manner involving MyD88s and suggest that airway epithelial cells are essential to maintain immune homeostasis.

CXCR2 Antagonist MK-7123. A Phase 2 Proof-of-Concept Trial for Chronic Obstructive Pulmonary Disease

RATIONALE

An antagonist (MK-7123) of the cytokine receptor CXCR2 reduces neutrophil chemotaxis and thus may alleviate airway inflammation in chronic obstructive pulmonary disease (COPD).

OBJECTIVES

To assess the efficacy, safety, and tolerability of three dose levels of MK-7123, compared with placebo, in patients with moderate to severe COPD.

METHODS

This 6-month, double-blind study randomized patients with moderate to severe COPD (already on standard therapy) to daily MK-7123 at 10, 30, or 50 mg or placebo. The primary endpoint was change from baseline in post-bronchodilator FEV1.

MEASUREMENTS AND MAIN RESULTS

A total of 616 patients (71% male; mean age, 63 yr; 45% current smokers; baseline FEV1 [SD], 1.43 L [0.45]; mean FEV1 percent predicted, 43.9%) were randomized. Only MK-7123 50 mg led to significant improvement in FEV1 over placebo (mean difference [SE], 67 ml [32]). Reduced sputum neutrophil count was observed among the 122 patients examined; P = 0.003 (3 mo) and P = 0.092 (6 mo) (MK-7123 50 mg vs. placebo). The stratum of current smokers, but not that of nonsmokers, showed significant improvement versus placebo in FEV1 (168 ml) and time-to-first exacerbation, and showed numerical improvement in St. George's Respiratory Questionnaire for COPD score. MK-7123 caused a dose-dependent decrease in absolute neutrophil count (ANC) and reduced inflammatory biomarkers matrix metallopeptidase-9 and myeloperoxidase in plasma and sputum; ANC lower than 1.5 × 10(9)/L led to discontinuations with higher doses of MK-7123 (18% in the MK-7123 50-mg group vs. 1% in placebo). Plasma C-reactive protein and fibrinogen increased with MK-7123 treatment. Rates of infections at 6 months were similar in all groups.

CONCLUSIONS

Treatment with MK-7123 50 mg versus placebo led to significant improvement in FEV1 in patients with COPD, suggesting clinically important antiinflammatory effects with CXCR2 antagonism, although dose-related discontinuations were observed because of ANC decreases with MK-7123. Greater response was observed in smokers versus ex-smokers. Clinical trial registered with www.clinicaltrials.gov (NCT 01006616).

Differential activation of killer cells in the circulation and the lung: a study of current smoking status and chronic obstructive pulmonary disease (COPD)

BACKGROUND

CD8(+) T-lymphocytes, natural killer T-like cells (NKT-like cells, CD56(+)CD3(+)) and natural killer cells (NK cells, CD56(+)CD3(-)) are the three main classes of human killer cells and they are implicated in the pathogenesis of chronic obstructive pulmonary disease (COPD). Activation of these cells can initiate immune responses by virtue of their production of inflammatory cytokines and chemokines that cause lung tissue damage, mucus hypersecretion and emphysema. The objective of the current study was to investigate the activation levels of human killer cells in healthy non-smokers, healthy smokers, ex-smokers with COPD and current smokers with COPD, in both peripheral blood and induced sputum.

METHODS/PRINCIPAL FINDINGS

After informed consent, 124 participants were recruited into the study and peripheral blood or induced sputum was taken. The activation states and receptor expression of killer cells were measured by flow cytometry. In peripheral blood, current smokers, regardless of disease state, have the highest proportion of activated CD8(+) T-lymphocytes, NKT-like cells and NK cells compared with ex-smokers with COPD and healthy non-smokers. Furthermore, CD8(+) T-lymphocyte and NK cell activation is positively correlated with the number of cigarettes currently smoked. Conversely, in induced sputum, the proportion of activated killer cells was related to disease state rather than current smoking status, with current and ex-smokers with COPD having significantly higher rates of activation than healthy smokers and healthy non-smokers.

CONCLUSIONS

A differential effect in systemic and lung activation of killer cells in COPD is evident. Systemic activation appears to be related to current smoking whereas lung activation is related to the presence or absence of COPD, irrespective of current smoking status. These findings suggest that modulating killer cell activation may be a new target for the treatment of COPD.