Current Topics in Medicinal Chemistry - Volume 16, Issue 14, 2016

Chronic obstructive pulmonary disease (COPD) is a common and disabling disease and the third leading cause of global mortality behind ischemic heart disease and stroke. Acute exacerbations of COPD accelerate lung function decline affecting the quality of life of COPD patients and moreover, remain the major contributors to morbidity and mortality of these patients. Cardiovascular comorbidities are prevalent in COPD patients and of great importance since they have a negative impact on patients’ health status. During the past few years there is an increasing interest in potential molecules that can be measured accurately and reproducibly and that can be used in COPD as biomarkers to predict clinical important outcomes such as exacerbations, hospitalizations and mortality. Such molecules have been successfully used in cardiovascular diseases and therefore, cardiac biomarkers have attracted attention for their potential use in COPD. The present review summarizes the available evidence for the use of the most important cardiac biomarkers in the evaluation of COPD severity, outcomes and management.

Exhaled breath condensate (EBC) pH is a commonly studied biomarker which represents the acidity of the whole airway tract, including the lower and upper airways as well as oral cavity. Because neat, unprocessed EBC pH can be affected by environmental and end-tidal carbon dioxide, two further reproducible techniques have been developed to measure condensate acidity with several methodological, pathophysiological and environmental factors which may influence EBC pH. Airway acidification may contribute to various pathological features of asthma, therefore EBC pH may be a non-invasive, but unspecific clinical biomarker of this disorder. This review summarises the current knowledge on EBC pH in asthma focusing on methodological aspects and possible clinical applications.

Difficult asthma is a heterogeneous disease of the airways including various types of bronchial inflammation and various degrees of airway remodeling. Therapeutic response of severe asthmatics can be predicted by the use of biomarkers of Type2-high or Type2-low inflammation. Based on sputum cell analysis, four inflammatory phenotypes have been described. As induced sputum is timeconsuming and expensive technique, surrogate biomarkers are useful in clinical practice. Eosinophilic phenotype is likely to reflect ongoing adaptive immunity in response to allergen. Several biomarkers of eosinophilic asthma are easily available in clinical practice (blood eosinophils, serum IgE, exhaled nitric oxyde, serum periostin). Neutrophilic asthma is thought to reflect innate immune system activation in response to pollutants or infectious agents while paucigranulocytic asthma is thought to be not inflammatory and characterized by smooth muscle dysfunction. We currently lack of user-friendly biomarkers of neutrophilic asthma and airway remodeling. In this review, we summarize the biomarkers available for the management of difficult asthma.

Pulmonary surfactant is a highly surface-active mixture of proteins and lipids that is synthesized and secreted in the alveoli by type II epithelial cells and is found in the fluid lining the alveolar surface. The protein part of surfactant constitutes two hydrophilic proteins (SP-A and SP-D) that regulate surfactant metabolism and have immunologic functions, and two hydrophobic proteins (SP-B and SP-C), which play a direct role in the organization of the surfactant structure in the interphase and in the stabilization of the lipid layers during the respiratory cycle. Several studies have shown that cigarette smoke seems to affect, in several ways, both surfactant homeostasis and function. The alterations in surfactants’ biophysical properties caused by cigarette smoking, contribute to the development of several smoking related lung diseases. In this review we provide information on biochemical and physiological aspects of the pulmonary surfactant and on its possible association with the development of two major chronic diseases of the lung known to be related to smoking, i.e. chronic obstructive pulmonary disease (COPD) and idiopathic pulmonary fibrosis (IPF). Additional information on the possible role of surfactant protein alterations and/or dysfunction in the combination of these two conditions, recently described as combined pulmonary fibrosis and emphysema (CPFE) are also provided.

Asthma is a chronic inflammatory airways disorder mainly characterized by heterogeneity. A phenotype is defined as a group of patients that present similar clinically observable characteristics, without establishing a direct etiologic relationship with a distinct pathophysiologic mechanism. An endotype, on the other hand, describes a subgroup that shares the same pathophysiologic processes that lead to the development, the progression and the presentation of a disease. A biomarker has been defined as a characteristic that is objectively measured and evaluated as an indicator of normal biological processes, pathogenic processes or pharmacologic responses to a therapeutic intervention. Several inflammatory phenotypes have been identified by the use of biomarkers. Most of them are based on the predominant type of cells in different biological fluids with sputum to be remained the most representative one. Eosinophilia represents the major characteristic of what we called classic atopic asthma. This particular phenotype usually responds well to corticosteroids, except for a small subgroup of severe asthma where even in the presence of eosinophils the ICS seem to have a less responsive role. Neutrophilic phenotype driven by the presence of neutrophils shows inadequate response to corticosteroid treatment, even in mild asthma. The major approach in order to define an endotype is driven by three main parameters. The statistical clustering approach, use of advanced statistical mathematics to create distinct patient clusters, the specific targeted immune therapies and finally the application of omics’ approach. Both phenotypes and endotypes are trying to clarify mechanisms and processes that driven the complexity of asthma. Both concepts could identify approaches which could establish new targeted to specific biomarkers treatment therapies/strategies.

Idiopathic Pulmonary Fibrosis (IPF) is a chronic, progressive, debilitating disease of unknown etiology and a median survival from diagnosis of 3-5 years. Despite extensive research efforts, its etiology in humans still remains largely unknown, and no curative drug therapies are available. With a gradually increasing worldwide incidence, IPF still presents a major challenge in clinical research due to its appreciable heterogeneity among individual patients in disease course and the lack of easily reproducible surrogate markers for patient relevant outcomes. Currently clinicians and researchers apply a panel of functional, radiological and histopathological indices to stratify patients into distinct phenotypic patterns of disease progression. However, none of these indicators can reliably predict not only treatment responsiveness but more importantly disease behavior, thus allowing clinicians to promptly apply aggressive therapeutic approaches to prevent or ameliorate acute exacerbation. Furthermore, on the contrary to molecular biomarkers, physiologic prognosticators provide no insights into disease mechanism and thus are unlikely to identify distinct molecular phenotypes of the disease. In the dawn of the “fibromics” era the need for disease stratification based on molecular phenotypes and implementation of personalized medicine therapeutic approaches is still unmet. Molecular biomarkers lie in the core of personalized medicine and therefore represent the main focus of this review article. Limitations that hamper their widespread clinical applicability along with future perspectives on how to address these major caveats and launch IPF biomarkers to the same trajectory as to tumor biomarkers in oncology are also discussed.

Bronchial asthma and chronic obstructive pulmonary disease (COPD) remain a global health problem with significant morbidity and mortality. The changes in bronchial microvasculature that occurin asthma and COPD contribute to airway wall remodeling. Angiogenesis seems to be more prevalent in asthma and vasodilatation seemsmore relevant in COPD while vascular leak is present in both diseases. Recently, there has been increased interest in the vascular component of airway remodeling in chronic bronchial inflammation of asthma and COPD although its role in the progression of the diseases has not been fully elucidated. Various cells andmediators are involved in the vascular remodeling in asthma and COPD while proinflammatory cytokines and growth factors exert angiogenic and antiangiogenic effects. Vascular endothelial growth factor (VEGF) is a key regulator of blood vessel growth mainly in asthma but also in COPD. In asthmatic airways VEGF promotes proliferation and differentiation of endothelial cells and induces vascular leakage and permeability. It has also been involved in enhanced allergic sensitization, upregulated subsequent T-helper-2 type inflammatory responses, chemotaxis for monocytes and eosinophils, and airway oedema. Impaired VEGF signaling has been associated with emphysema in animal models. Studies on lung biopsies have shown a decreasing effect of anti-asthma drugs to the vascular component of airway remodeling. There is less available evidence on the effect of the currently used drugs on airway microvascular network in COPD. This review article explores the current knowledge regarding vascular biomarkers in asthma and COPD as well as the therapeutic implications of these mediators.

Breathomics, the multidimensional molecular analysis of exhaled breath, includes analysis of exhaled breath with gas-chromatography/mass spectrometry (GC/MS) and electronic noses (e-noses), and metabolomics of exhaled breath condensate (EBC), a non-invasive technique which provides information on the composition of airway lining fluid, generally by high-resolution nuclear magnetic resonance (NMR) spectroscopy or MS methods. Metabolomics is the identification and quantification of small molecular weight metabolites in a biofluid. Specific profiles of volatile compounds in exhaled breath and metabolites in EBC (breathprints) are potentially useful surrogate markers of inflammatory respiratory diseases. Electronic noses (e-noses) are artificial sensor systems, usually consisting of chemical cross-reactive sensor arrays for characterization of patterns of breath volatile compounds, and algorithms for breathprints classification. E-noses are handheld, portable, and provide real-time data. E-nose breathprints can reflect respiratory inflammation. E-noses and NMR-based metabolomics of EBC can distinguish patients with respiratory diseases such as asthma, COPD, and lung cancer, or diseases with a clinically relevant respiratory component including cystic fibrosis and primary ciliary dyskinesia, and healthy individuals. Breathomics has also been reported to identify patients affected by different types of respiratory diseases. Patterns of breath volatile compounds detected by e-nose and EBC metabolic profiles have been associated with asthma phenotypes. In combination with other -omics platforms, breathomics might provide a molecular approach to respiratory disease phenotyping and a molecular basis to tailored pharmacotherapeutic strategies. Breathomics might also contribute to identify new surrogate markers of respiratory inflammation, thus, facilitating drug discovery. Validation in newly recruited, prospective independent cohorts is essential for development of e-nose and EBC NMRbased metabolomics techniques.

Nitric oxide (NO), the first gas known to act as a biological messenger, is one of the most widely studied free radical/gas in medicine, both for its biological function and therapeutic applications. The measurement of endogenous NO in exhaled air is widely used in the evaluation of lung disorders. Partitioning of exhaled nitric oxide (eNO) is of increasing interest because of the additional information about lung pathology and distal lung inflammation that can be obtained. Specifically, measuring exhaled NO at multiple flow rates allows assessment of the flow-independent NO parameters: alveolar NO concentration (CalvNO), bronchial NO flux (JNO), bronchial wall NO concentration (CWNO), and bronchial diffusing capacity of NO (DNO). Several studies have reported that there were different patterns of those parameters in different airway diseases and/or in different severities of the same disease, mostly in asthma. Specifically, while JNO seems to provide the same information as FeNO50, alveolar NO concentration appears to be an independent parameter that is putatively associated with increased distal lung inflammation and more severe disease. However, despite much research interest in partitioning exhaled NO, clinical usefulness has yet to be established.