**9.2. Etiology**

proteases HNE and proteinase-3. It is normally present at relatively high concentrations (1.5g/L) in the blood and is believed to play a prominent role in resolving inflammation un‐ der normal homeostasis. A1AD derived COPD is believed to be due to a protease/antipro‐ tease imbalance in which normal levels of HNE and proteinase-3 (P3) are uninhibited at sites of minor infection or inflammation. [66] The constitutively active HNE and P3 are left unencumbered to degrade extra-cellular matrix and begin a pro-inflammatory cascade of molecules that only further exacerbate the inflammation. Cigarette smoking is so destructive to those with A1AD because cigarette smoke directly inactivates A1AT, wreaking even fur‐ ther havoc on an already taxed system. The pathophysiology of A1AD is similar to that of

Very similar to the role they play in traditional COPD, PMNs are both effect and maintain inflammation seen in COPD. As producers of HNE they are responsible for the initial path‐ ology seen in the condition. [67]Under normal circumstances, A1AT is loosely bound to HNE, among other serine proteases. However, in the chronic inflammatory condition associ‐ ated with A1AD, HNE is constantly active and degrades the basement matrix. Furthermore, HNE has been shown to be capable of cleaving the inactive form of MMP-9, pro-MMP-9 to the active form, creating more protease stress on the system. MMP-9 and HNE are capable of degrading multiple matrix proteins present in the lung. This destruction of the basement collagen, elastin, etc. creates a "leaky" vasculature, only making it easier for other immune cells to move into the lung interstitium. [68] This movement of cells and proteins into the intracellular space brings with it fluid from the circulation and edema results. As the pro‐ ducers of HNE, neutrophils are integral to the pathogenesis and continuation of A1AD asso‐

Diagnosis of A1AD is only made in those cases of COPD where there is an unexplained cause of the condition. A1AT serum levels are measured using enzyme linked adsorbent as‐ says (ELISA), or more recently mass spectrometry. Like CF, there is a spectrum of pheno‐ types that are observed in the condition and they are categorized based upon the circulating levels of A1AT. Patients with the most severe phenotype are those individuals with concen‐

Because of the nature of the disease treatment of A1AD is very similar to that of traditional COPD, with one exception. Patients with a severe lung phenotype are treated with intrave‐ nous infusion of A1AT isolated from human serum. [70] Additionally, liver transplant has been utilized to address the absence of circulating A1AT. [71] In addition to these therapies, the common treatments for COPD mentioned previously are employed to address the spe‐

COPD and thus the underdiagnosis of this condition.

110 Oncogenesis, Inflammatory and Parasitic Tropical Diseases of the Lung

trations less than 15% of normal in their serum. [69]

**8.4. Role of neutrophils in A1AD**

ciated COPD.

**8.5. Diagnosis of A1AD**

**8.6. Treatment of A1AD**

cific symptoms of A1AD.

The development of asthma is thought to be associated with three major risk factors: genetic predisposition, and occupational and environmental factors. Although a precise list of genes associated with the atopic response in human has yet to be collated, GWAS studies in hu‐ man, and canines have revealed multiple loci related to the IgE response known to be im‐ portant in the etiology of asthma. [72],[73]

## **9.3. Pathophysiology**

Asthma begins in the airways with host contact of an allergen, following this, specific IGE antibodies are upregulated and initiate mast cell activation. Mast cell activation, in turn be‐ gins the early and late phase response. The early phase response is mediated by histamine, leukotriene C4, D4, and E4, and prostoglandin D2. After the early phase/hypersensitivity re‐ sponse, that late phase response begins. Eosinophils, basophils, neutrophils, and T cells are all recruited to the airway and produce inflammatory cytokines that propogate the allergic response that is a hallmark of asthma.

## **9.4. Role of neutrophils in neutrophilic and steroid-resistant asthma**

Asthma is typically thought of as an eosinophilic disease, yet there have been numerous studies reporting an increase in neutrophil number and activation in sputum collected from steroid-resistant asthma patients. There are reports of up to 50% of asthma cases that have an increase in IL-8 and neutrophil burden, separate from eosinophilic inflammation. [74], [75] Because of the variability seen in primary immune cell burden in asthma neutrophilic asthma has recently begun to be viewed as a specific sub-type of the condition. [76] Patients with neutrophilic asthma have a more severe progression of disease, respond poorly to ther‐ apy, and are burdened with much high health care costs than typical asthma patients. Un‐ fortunately, there is little, if any, established dogma regarding neutrophilic asthma. Studies have only been able to describe correlative relationships between neutrophil burden and the phenotypic profile observed in neutrophilic asthma patients. [77] There has been extensive work performed investigating the role of MMP-9 in the pathogenesis of asthma. In a report by Cundall et al the authors state that MMP-9 concentrations in BAL fluid correlate with eo‐ sinophils but not neutrophil or monocyte/macrophage counts. [78] They hypothesize that PMNs and macrophages release MMP-9 which breaks down the basement membrane, mak‐ ing it easier for the eosinophils to migrate into the airways. In another study, MMP-9 levels in BAL fluid were correlated significantly with decreases in FEV1 seen in asthma patients.

lized in extreme cases, but due to its expense and limited evidence of efficacy, its use is not widespread. Because of the lack of knowledge about the cellular and molecular etiology of neutrophilic asthma, current therapies are limited to those already employed in traditional asthma. As might be expected, these have limited efficacy in patients diagnosed with neu‐

New Frontiers in the Diagnosis and Treatment of Chronic Neutrophilic Lung Diseases

http://dx.doi.org/10.5772/53834

113

With better understanding of neutrophilic lung disease has come more advanced and target‐ ed therapeutics. Towards that end, recent work by the Blalock and Gaggar groups at the University of Alabama at Birmingham (UAB) has expanded the role of PMNs in multiple chronic inflammatory lung diseases, including COPD, CF, and BOS. They described a novel concept of neutrophils proteases producing a neutrophil chemokine from extra-cellular col‐ lagen that acted in a feed-forward mechanism of disease. Seminal papers by Weathington et al and Gaggar et al detail the step-wise manner in which IL-8 draws PMNs into the intersti‐ tium, upon activation they release MMP-8 and MMP-9 which perform an initial digestion of collagen from macromolecule size. Subsequently, neutrophils release prolyl endopeptidase (PE), a serine protease previously only known to be a processor of neuropeptides. PE per‐ forms the final digestion of collagen to the tri-peptide proline-glycine-proline (PGP) from the PPGP amino acid motif that is repeated over 40 times throughout a single collagen mole‐ cule. [84],[85] PGP binds to the same receptors as IL-8, CXCR1 and CXCR2 acting a neutro‐ phil chemoattractant and activator. [86] The authors showed that not only are the proteases responsible for PGP production present and elevated in BAL fluid collected from COPD and CF patients, both stable and in exacerbations, but PGP is also measurably elevated by mass spectrometry in the BAL fluid of such patients and correlates with PMN burden in disease. [39],[87],[88] These data indicate that not only is PGP a potential biomarker for chronic in‐ flammatory neutrophilic lung disease, but the system of proteases responsible for PGP's production, and the receptors upon which it acts are potential targets for the development of novel precise therapeutics. Furthermore, work by Hardison et al, and Braber et al have dem‐ onstrated that cigarette smoke and its constituents are capable of acetylating PGP into the more potent and stable n-terminal acetylated form, AcPGP. [89],[90] AcPGP has proven to be resistant to degradation by leukotriene A4 hydrolase (LTA4H), a hydrolase/amino-pepti‐ dase also produced a number of cells, including neutrophils. In a 2010 Science paper, Snel‐ grove et al described a novel function for the dual purpose enzyme in resolving acute neutrophilic inflammation in a mouse model of influenza. [91] It would be extremely useful to have pharmaco-interventions able to modulate the PGP system of neutrophil inflamma‐

**10. Novel therapeutics in neutrophilic lung diseases**

tion, either at the genesis (MMP, PE) or terminus (CXCR, LTA4H).

Although any therapeutics derived from such work may be years away from fruition, there are other recent advancements that are already making an impact on patient morbidity and mortality. Kalydeco, a drug produced by Vertex Pharmaceuticals is the first drug developed that addresses the underlying genetic cause of CF. First released on the market in January of 2012, it is effective in patients that carry the G115D amino acid change. [92] This is a class III

trophilic asthma.

HNE, another potent neutrophil derived protease, has also been correlated with symptoms of asthma. [79] Patients with allergic rhinitis has significantly elevated levels of HNE in their nasal lavage compared to control patients in which no rhinitis was observed. To add to the myriad of evidence that neutrophils are at the very least, associated with asthma, a study by Norzila et al demonstrated that myeloperoxidase (MPO), a neutrophil mediator of the oxi‐ dative burst, is elevated in induced sputum collected from certain asthma patients com‐ pared to control patients. [80] Because MPO, HNE, and MMP-9 are all contained in intracellular granules of the neutrophil it is evidence that neutrophils present in/around the lung in asthma patients are activated and degranulate.

#### **9.5. Diagnosis of asthma**

Diagnosis of asthma is made through evaluation of symptoms and pulmonary function test‐ ing (PFT) via spirometry. An increase in FEV of ≥15% in conjunction with reported wheez‐ ing, chest tightness, and coughing is diagnostic for asthma. A difficulty arises when patients present with normal spirometry results. To address this, home PFT devices are available to record lung function data over a period of time to encapsulate more data points. Additional‐ ly, controlled exacerbation of asthma attacks with methacholine in the clinician's office is a reliable method of eliciting the necessary response to confirm a diagnosis of asthma. [81]

#### **9.6. Traditional asthma therapeutics**

Similar to the other lung diseases discussed in this chapter, treatment of asthma is relegated to management of symptoms. Monitoring of frequency and severity of attacks is vital to ad‐ ministering correct dosages of medication. Patients are encouraged to keep records of at‐ tacks with information regarding date/time, location, duration, and triggers. The standard treatment of asthma is glucocorticoid (GC) inhaler with a long-acting β-agonist. [82] The GC treatment is directed at reducing the constant inflammatory state, whereas the β-agonist is a bronchodilator intended to ameliorate airway obstruction. So physicians will also prescribe the use of IgE inhibitors or neutralizing antibodies such as omaluzimab to combat the high levels of the pro-inflammatory molecule. [83] In neutrophil associated and steroid-resistant asthma, clinicians have fewer options with which to treat this potentially deadly condition. A patient's response to a two week trial of traditional asthma therapy will indicate whether or not they are a candidate for alternative asthma therapy. Because certain forms of asthma are refractory to GC therapy, the focus of treatment in such patients shifts to a more aggres‐ sive immunosuppressive approach. Treatment with cyclosporine, tacrolimus, and metho‐ trexate have been associated with some benefit, although the risk of side effects is significantly higher in these classes of medicines. Finally, IV immunoglobulin therapy is uti‐ lized in extreme cases, but due to its expense and limited evidence of efficacy, its use is not widespread. Because of the lack of knowledge about the cellular and molecular etiology of neutrophilic asthma, current therapies are limited to those already employed in traditional asthma. As might be expected, these have limited efficacy in patients diagnosed with neu‐ trophilic asthma.
