Crystal arthritides - gout and calcium pyrophosphate arthritis : Part 3: Treatment

The treatment of gout is based on several principles. Symptom control and termination of the inflammatory process are important early goals, whereas the urate level should be lowered in the long term to prevent further gout attacks and complications. The non-pharmacological approach is based on individually informing the patient on dietary measures and changes of life style. Besides physical measures, such as cold applications on the affected joint, various medications are available for treatment of an acute gout attack. The choice of drug depends on the individual risk profile. If non-steroidal anti-inflammatory drugs (NSAID) and coxibs are chosen it should be taken into account that the use is restricted in patients with renal insufficiency. Moreover, these drugs may have gastrointestinal side effects and are associated with increased cardiovascular morbidity and mortality. Colchicine has gastrointestinal side effects at high dosages but can also be used for differential diagnostics if there is a quick response to treatment. Steroids are an effective alternative and can be given orally or parenterally in patients with dysphagia. Moreover, steroids can be used in cases of renal insufficiency. After symptoms of the acute attack have subsided, urate lowering therapy should be initiated to prevent further attacks. Low-dose urate lowering therapy can be started during an acute gout attack when acute therapy is initiated. Allopurinol is still the medication of choice but its use is restricted in patients with renal insufficiency. A rare but serious side effect is allopurinol hypersensitivity syndrome. Febuxostat can be an alternative in patients who do not tolerate allopurinol. In February 2016, lesinurad, an URAT-1 and OAT-4 inhibitor, was approved in combination with allopurinol or febuxostat. Data on the effectiveness and safety of synthetic uricases and biologicals are still sparse for elderly patients. These substances are reserved for severe cases of gout.

[Combination of biologics : where do we stand?]

INTRODUCTION

Data with respect to safety and therapeutic efficacy for the combination of biological DMARDs is scarce and inhomogeneous in order to make final conclusions. To this end, data to biologic combinations is disappointing due to relatively low therapeutic efficacy and partially enhanced rates of severe infectious events.

METHODS

Combining biologics is an option only in very special situations (RTX plus TNFi). In addition, the relation of financial effort to therapeutic efficacy is questionable, especially in the situation of numerous drug options (anti-cytokine principle, T-cell inhibition, B-cell depletion) and therapeutic strategies of combining biologics with DMARDs. Generally speaking, combinations of biological should only be used in clinical trials. New drugs influencing intracellular signaling pathways (small molecules) are going to be approved or are already approved by the drug agencies, thus, adding to the existing armamentarium. Furthermore, combinations with these new molecules are going to be interesting.

CONCLUSIONS

This review summarizes the available studies concerning combination of biologicals in a tabular fashion.

[Screening and early diagnosis of psoriasis arthritis]

Psoriasis arthritis (PsA) encompasses many diverse clinical symptoms. Epidemiological data about the prevalence in general, predisposed age groups, prevalence of joint, spine, enthesis, and extra-articular manifestations are very heterogeneous. Even for the PsA specialist the clinical picture is not always easy to differentiate from other overlapping or clinically similar disease entities. This paper tries to give some guidance on how to screen for and how to detect PsA early in the population of psoriasis patients on the basis of the Mainz PsA screening and early diagnosis algorithm.

[Ultrasound-guided joint injections in patients with rheumatic diseases]

Joint and soft tissue injections are routinely performed in daily rheumatology practice to establish the diagnosis or as part of the treatment in patients suffering from rheumatic diseases. Consequently, joint injections have been included in the rheumatology further training curriculum. Despite numerous studies demonstrating a poor accuracy and outcome of joint injections guided only by clinical examination, most of the injection procedures are still performed in a "blind" fashion based on clinical judgment. Ultrasound has evolved as an established imaging method in rheumatology within the past decade and is considered the preferred imaging modality for joint interventions due to its availability and lack of radiation exposure. In this article the indications and important aspects of the practical management of ultrasound-guided injections performed in daily rheumatology practice are summarized.

Serum BAFF strongly correlates with PsA activity in male patients only--is there a role for sex hormones?

OBJECTIVES

To determine the relationship between serum levels of B cell activating factor belonging to the TNF family (BAFF) and disease activity (DAS28) in psoriatic arthritis (PsA) patients.

METHODS

Twenty-two male and 31 female psoriasis patients fulfilling the CASPAR criteria for PsA were recruited for the study. Disease activity was recorded using the disease activity score for 28 joints (DAS28). Whole blood and serum samples were analysed for serum BAFF, estradiol, and testosterone levels.

RESULTS

Serum BAFF levels were positively correlated with DAS28 only in male PsA patients (r=0.669, p<0.001). In male but not female patients, serum testosterone was negatively correlated with DAS28 (r=-0.632, p=0.002), and serum BAFF (r=-0.520, p=0.018), respectively. The serum BAFF/ serum testosterone (B/T) ratio showed a strong correlation with DAS28 in male patients (r=0.743, p<0.0001) and, again, no correlation was found in female participants (r=0.019, p=0.93). A linear regression analysis showed that the B/T is a good predictor of DAS28 (r2=0.586, p<0.001). On the other hand, estradiol levels did neither correlate with PsA activity in male nor female patients in our study population.

CONCLUSIONS

Even though a role for B cells in the pathogenesis of PsA has not been established, BAFF levels correlate with disease activity in male PsA patients. Furthermore, serum testosterone in male patients negatively correlates with disease activity and BAFF, respectively. The serum BAFF/serum testosterone ratio might be used as predictor of disease activity in male PsA patients.

[Treatment of osteoarthritis with drugs and other modalities]

There is an increasing incidence in osteoarthritis, particularly following the 5th life-decade. However, also young people may suffer from severe osteoarthritis, which is estimated to be the most common cause of disability in adults resulting in substantial economic burden. To this end, effective therapies are needed. Therapeutic options are very comprehensive, which are presented in this review as non-pharmacological, pharmacological and surgical treatment modalities. Treatment efficacy will be discussed with regard to alleviation of symptoms and potential prevention of disease progression according to the given evidence.

Lack of dehydroepiandrosterone in type I and II hereditary angioedema and role of danazol in steroid hormone conversion

BACKGROUND

Hereditary angioedema (HAE) is successfully treated with danazol, a therapeutic steroid compound. To investigate hormones of the hypothalamic-pituitary-adrenal (HPA) and hypothalamic-pituitary-gonadal (HPG) axis in patients with HAE with and without danazol.

METHODS

We included 16 patients with type I HAE, nine patients with type II HAE, and 16 healthy subjects. Serum levels of adrenocorticotropic hormone (ACTH), cortisol, androstenedione, dehydroepiandrosterone (DHEA), free testosterone, and 17beta-oestradiol were measured.

RESULTS

Serum levels of ACTH were markedly decreased in patients with type II HAE compared to the other groups (P < 0.001). Serum cortisol was similar between groups but danazol treatment decreased cortisol levels, particularly in women (P = 0.019). Serum levels of DHEA were significantly decreased in all patients with type I and II HAE compared to controls (P < 0.05), which was only partly dependent on prior danazol therapy as patients without danazol had also decreased serum levels of DHEA (P < 0.05). Furthermore, free testosterone serum levels were markedly increased in patients under danazol (P < 0.005) and the ratio of 17beta-oestradiol/free testosterone was significantly decreased in these patients (P < 0.005).

CONCLUSIONS

This study demonstrated decreased DHEA in patients with type I and II HAE independent of danazol therapy, which was particularly evident in women. It also demonstrates that danazol induced a marked up-regulation of free testosterone in relation to precursors and downstream 17beta-oestradiol. In HAE, there seems to be a primary lack of the adrenal androgen DHEA.

The role of the sympathetic nervous system in intestinal inflammation

The nervous system in the intestine controls motility, secretion, sensory perception, and immune function. Peptidergic neurones with neurotransmitters such as substance P and nerve growth factors have been the main focus of neuroimmunomodulation research in the gut. This review summarises the present knowledge concerning the role of the sympathetic nervous system (SNS) in modulating intestinal inflammation. The role of the SNS for gut inflammation is compared with its role in rheumatoid arthritis which demonstrates notable similarities. Nerve fibres of the SNS not only enter the enteric plexuses but also innervate the mucosa and gut associated lymphoid tissue (GALT). The SNS has pro- and anti-inflammatory functions. Neurotransmitters such as norepinephrine, adenosine, and others can evoke remarkably different opposing effects depending on concentration (presence of sympathetic nerve fibres and extent of neurotransmitter release), receptor affinity at different receptor subtypes, expression of adrenoceptors, availability of cotransmitters, and timing of SNS activity in relation to the inflammatory course. This review attempts to integrate the different perspectives of the pro- and anti-inflammatory effects of the SNS on inflammatory disease of the gut.

Key role of the sympathetic microenvironment for the interplay of tumour necrosis factor and interleukin 6 in normal but not in inflamed mouse colon mucosa

BACKGROUND

In the intestinal tract, the role of sympathetic neurotransmitters has been largely ignored in mucosal neuroimmunology.

AIM

Our aim was to investigate the influence of the sympathetic microenvironment on the mucosal interplay of tumour necrosis factor (TNF) and interleukin 6 (IL-6).

METHODS

Colon strips of normal and colitic BALB/c mice were superfused in vitro. Tissue was electrically stimulated to investigate the influence of endogenous norepinephrine (NE) on secretion of IL-6, with or without anti-TNF antibodies (anti-TNF) and adrenoceptor antagonists. IL-6 was secreted from macrophages.

RESULTS

Superfusion with anti-TNF stimulated IL-6 secretion in normal but not in colitic colon (p<0.005). Parallel superfusion with a beta-adrenergic antagonist abrogated this phenomenon. Anti-TNF increased release of NE from normal colonic strips (p<0.05), which demonstrates TNF induced inhibition of preterminal NE release. In colitic mice, anti-TNF did not change NE release. In the presence of anti-TNF, exogenous and endogenous NE stimulated colonic IL-6 secretion via beta-adrenoceptors in normal (p<0.001) but not in colitic mice. In the absence of anti-TNF, endogenous and exogenous NE inhibited IL-6 secretion via the beta-adrenoceptor in normal but not in colitic mice (p<0.01). Colitic mice demonstrated loss of sympathetic nerve fibres.

CONCLUSIONS

Modulation of mucosal IL-6 is largely dependent on the sympathetic microenvironment and availability of local TNF in normal but not in colitic mice. Anti-TNF strategies may lead to an increase in the proinflammatory cytokine depending on adrenergic tone. This would be relevant with normal sympathetic innervation, which is lost in colitic mice. We present a model of sympathetic regulation of colonic macrophage TNF and IL-6 secretion.

Increase of sympathetic outflow measured by neuropeptide Y and decrease of the hypothalamic-pituitary-adrenal axis tone in patients with systemic lupus erythematosus and rheumatoid arthritis: another example of uncoupling of response systems

OBJECTIVE

To study in parallel the outflow of the sympathetic nervous system (SNS) and the hypothalamic-pituitary adrenal (HPA) axis tone in systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA).

METHODS

32 patients with SLE, 62 with RA, and 65 healthy subjects (HS) were included. To measure the tone of the HPA axis, plasma ACTH and serum cortisol were determined. Serum neuropeptide Y (NPY) was used to evaluate the sympathetic outflow.

RESULTS

Patients with SLE had increased NPY levels in comparison with HS, irrespective of prior prednisolone treatment (p<0.001). For patients with RA, only those with prednisolone treatment had increased NPY levels in comparison with HS (p = 0.016). Daily prednisolone dose correlated positively with serum NPY in RA (R(Rank) = 0.356, p = 0.039). In contrast, plasma ACTH levels were generally decreased significantly in comparison with HS in SLE with prednisolone, and in RA with/without prednisolone. Similarly, serum cortisol levels were also decreased in SLE with/without prednisolone, and in RA with prednisolone. The NPY/ACTH ratio was increased in SLE and RA, irrespective of prior prednisolone treatment. The NPY/cortisol ratio was increased in SLE with/without prednisolone, and in RA with prednisolone. Twelve weeks' anti-TNF antibody treatment with adalimumab did not decrease NPY levels in RA, irrespective of prednisolone treatment.

CONCLUSIONS

An increased outflow of the SNS was shown and a decreased tone of the HPA axis in patients with SLE and RA. Low levels of cortisol in relation to SNS neurotransmitters may be proinflammatory because cooperative anti-inflammatory coupling of the two endogenous response axes is missing.

Predictive and potentially predictive factors in early arthritis: a multidisciplinary approach

OBJECTIVES

Rheumatoid arthritis (RA) is characterized by variable degrees of joint inflammation, joint destruction, progressive disability and premature death. Destruction of joint cartilage and bone may occur early during disease, as was shown in longitudinal studies of RA, and there is increasing consent among rheumatologists that early diagnosis and early initiation of therapy with disease-modifying anti-rheumatic drugs (DMARDs) can limit the severity of RA. Unfortunately, the currently used diagnostic and predictive indicators (clinical, laboratory and radiological) are of limited value for making an early diagnosis and prognosis of the disease course at the individual level, thus reducing optimal benefit from present and emerging therapies. Therefore, this review focuses on the multidisciplinary aspects of neuroendocrine-immune changes in RA.

METHODS

A Medline search was performed using the search terms 'androgens', 'estrogens', 'sympathetic nervous system', 'sensory nervous system', 'prognosis', 'early rheumatoid arthritis', 'arthritis' and 'studies' in various combinations. For the tabular overview, we only listed clinical studies focusing on endocrine and neuronal aspects.

RESULTS

In addition to the currently used predictive indicators, there is an abundant body of literature describing changes of the neuronal, endocrine and immune parameters during inflammatory diseases. Unfortunately, no longitudinal studies concerning neuroendocrine aspects have been done up to now.

CONCLUSION

Parameters of the neuroendocrine system should be included in anticipated longitudinal clinical studies to find their true predictive value in early RA.

Successful treatment of psoriatic onycho-pachydermo periostitis (POPP) with adalimumab

Psoriatic onycho-pachydermo periostitis (POPP) is recognized as a rare subset of psoriatic arthritis, characterized by psoriatic onychodystrophy, connective tissue thickening above the distal phalanx, and a periosteal reaction. Therapy for this rare disease is based on treatments used for psoriatic arthritis, but traditional disease-modifying antirheumatic drugs, such as sulfasalazine and methotrexate, have shown inconsistent and unsatisfactory results. We report herein a successful therapeutic approach for POPP using the fully human anti-tumor necrosis factor (TNF) antibody adalimumab in a 42-year-old male patient. After 4 months of anti-TNF treatment, a remarkable normalization of the clinical appearance was achieved and magnetic resonance imaging showed complete resolution of the initial inflammatory lesions. Therefore, we consider a TNF-blocking strategy as promising for treatment of POPP.

Possible role of leptin in hypoandrogenicity in patients with systemic lupus erythematosus and rheumatoid arthritis

BACKGROUND

Hypoandrogenicity is common in obesity and in chronic inflammatory diseases such as systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA). Adrenal androgens such as androstenedione (ASD) and dehydroepiandrosterone (DHEA) sulphate are low, which partly depends on the influence of TNF in chronic inflammatory diseases. Leptin is stimulated by TNF and is associated with hypoandrogenicity in non-inflammatory conditions.

OBJECTIVE

To study the interrelation between serum levels of leptin and adrenal steroids in SLE and RA.

METHODS

In a retrospective study, serum levels of leptin, ASD, DHEA, and 17-hydroxyprogesterone (17OHP) were measured by ELISA, and serum levels of cortisol by radioimmunoassay in 30 patients with RA, 32 with SLE, and 54 healthy control subjects (HS).

RESULTS

In SLE and RA but not HS, serum levels of ASD correlated negatively with serum levels of leptin (p<0.01) independently of prior prednisolone treatment in patients with SLE (p = 0.013) and tended to be independent of prednisolone in patients with RA (p = 0.067). In a partial correlation analysis, this interrelation remained significant after controlling for daily prednisolone dose in both patient groups. In both patient groups, serum leptin levels correlated negatively with the molar ratio of serum ASD/serum cortisol and serum ASD/serum 17OHP, and positively with the molar ratio of serum DHEA/serum ASD.

CONCLUSIONS

The negative correlation of serum leptin and ASD or, particularly, ASD/17OHP, together with its known anti-androgenic effects indicate that leptin is also involved in hypoandrogenicity in patients with SLE and RA. Leptin may be an important link between chronic inflammation and the hypoandrogenic state.

No alterations of serum levels of adrenal and gonadal hormones in patients with ankylosing spondylitis

Ankylosing spondylitis (AS) is a chronic inflammatory disease with a marked preponderance of affected males compared to females of approximately 6 to 1. During the last two decades, this circumstance stimulated several research groups to investigate serum levels of gonadal and adrenal sex hormones. From available results of cross-sectional studies, there seems to be no particular defect in secretion or production of adrenal, gonadal, and pituitary hormones. This is in striking contrast to diseases such as rheumatoid arthritis and other chronic inflammatory diseases. In the latter diseases, low serum levels of dehydroepiandrosterone (DHEA), DHEA sulphate (DHEAS), and testosterone have been described in an advanced chronic disease stage, whereas estrogen serum levels remain normal. Although AS is an inflammatory disease with signs of systemic inflammation such as elevated erythrocyte sedimentation rate or increased circulating proinflammatory cytokines, serum levels of adrenal and gonadal androgens are normal. It is unclear whether this can be considered as unexpected. It may be that inflammation does not reach the pituitary, adrenal, and gonadal glands or does not alter the aromatase complex in peripheral tissue. Furthermore, the inflammation-induced changes may be subtle so that only specific endocrine examination of these axes may reveal signs of alterations. In conclusion, current data on sex steroid hormones provide no straightforward explanation for the male predominance in AS. At the moment, there is no rationale to treat AS patients with sex steroid hormones.

Expression of human and macaque type I IFN transgenes interferes with HSV-1 replication at the transcriptional and translational levels: IFN-beta is more potent than IFN-alpha 2

A study was undertaken to compare the efficacy of plasmid constructs encoding human IFN-alpha 2 and IFN-beta and macaque IFN-beta against herpes simplex virus type 1 in transfected cells. All type I IFN transgenes significantly reduced viral titers in transfected cells by 3 logs. Human IFN-alpha 2-transfected cells produced significantly more IFN (2274 pg/ml) in comparison to IFN-beta-transfected cells (134-165 pg/ml). Viral lytic gene transcript and viral protein levels were lower in IFN-beta- versus IFN-alpha 2-transfected cells, which coincided with elevated PKR and OAS transcript levels and increased total STAT1 and phosphorylated STAT1 (Y701) protein levels in the IFN-beta-transfected cells. Although comparable viral titers were recovered in IFN-alpha 2 and IFN-beta plasmid-transfected cells, IFN-alpha 2 plasmid-transfected cells exhibited significantly more cytopathic effect compared to the IFN-beta transgene-transfected cells. In addition, IFN-alpha 2 transgene-transfected, infected cells displayed a cell cycle profile similar to that of vector-transfected, infected cells, whereas IFN-beta plasmid-transfected cells displayed a profile similar to uninfected control. Collectively, the results indicate that human IFN-beta is superior to IFN-alpha 2 in antagonizing herpes simplex virus type 1 infection.

The immune response to ocular herpes simplex virus type 1 infection

Herpes simplex virus type 1 (HSV-1) is a prevalent microbial pathogen infecting 60% to 90% of the adult world population. The co-evolution of the virus with humans is due, in part, to adaptations that the virus has evolved to aid it in escaping immune surveillance, including the establishment of a latent infection in its human host. A latent infection allows the virus to remain in the host without inducing tissue pathology or eliciting an immune response. During the acute infection or reactivation of latent virus, the immune response is significant, which can ultimately result in corneal blindness or fatal sporadic encephalitis. In fact, HSV-1 is one of the leading causes of infectious corneal blindness in the world as a result of chronic episodes of viral reactivation leading to stromal keratitis and scarring. Significant inroads have been made in identifying key immune mediators that control ocular HSV-1 infection and potentially viral reactivation. Likewise, viral mechanisms associated with immune evasion have also been identified and will be discussed. Lastly, novel therapeutic strategies that are currently under development show promise and will be included in this review. Most investigators have taken full advantage of the murine host as a viable working in vivo model of HSV-1 due to the sensitivity and susceptibility to viral infection, ease of manipulation, and a multitude of developed probes to study changes at the cellular and molecular levels. Therefore, comments in this review will primarily be restricted to those observations pertaining to the mouse model and the assumption (however great) that similar events occur in the human condition.

ICAM-1 is required for resistance to herpes simplex virus type 1 but not interferon-alpha1 transgene efficacy

The purpose of this study was to determine the role of ICAM-1 in ocular herpes simplex virus type 1 (HSV-1) infection. Wild-type and ICAM-1 knockout mice were assessed for resistance to ocular HSV-1 infection in the presence of naked DNA plasmid vector or plasmid DNA encoding interferon-alpha1 topically applied to the cornea of the mice. Wild-type mice showed greater resistance to HSV-1 infection compared to ICAM-1 knockout mice as measured by cumulative survival. The absence of ICAM-1 did not affect the efficacy of the interferon-alpha1 transgene against ocular HSV-1. Both ICAM-1 and wild-type mice treated with the transgene showed a reduction in viral load and antigen expression in the trigeminal ganglion compared to the plasmid vector-treated counterparts. In contrast, the presence of the transgene reduced the number of infiltrating cells into the cornea in comparison to plasmid vector DNA controls in the wild-type mice but not in the ICAM-1 knockout mice. Collectively, these results suggest that the IFN-alpha1 transgene can restore resistance against HSV-1 infection in ICAM-1-deficient mice.

The application of a plasmid DNA encoding IFN-alpha 1 postinfection enhances cumulative survival of herpes simplex virus type 2 vaginally infected mice

Using a hormonally induced susceptibility mouse model to investigate vaginal HSV type 2 (HSV-2) infection, a study was undertaken to determine the efficacy of a plasmid DNA encoding IFN-alpha1 introduced into the vaginal lumen postinfection (PI). Mice infected with HSV-2 intravaginally and treated intravaginally 24 h later with 100 microg DNA encoding IFN-alpha1 showed enhanced survival (10/15) in comparison to mice treated with 100 microg plasmid DNA vector alone (3/10) or vehicle (4/27). In contrast, mice receiving recombinant IFN-alphaA (5-500 U/vagina) 24 h PI showed no significant survival in comparison to the vehicle (saline)-treated group. The protective effect was time dependent in that mice receiving the IFN-alpha1 transgene 48 h PI succumbed at a rate similar to the plasmid DNA vector-treated group. The increase in cumulative survival elicited by the transgene corresponded with a reduction in viral replication and Ag expressed in the vaginal epithelium early (i.e., 3 days PI) during acute infection and replicating virus recovered in the spinal cord day 7 PI. By day 7 PI, HSV-2 glycoprotein B transcript expression was no longer detectable in vaginal tissue from the IFN-alpha1 transgene-treated group (0/8) compared with levels expressed in plasmid vector-treated controls (4/6 mice surveyed were positive). Collectively, these results suggest the application of DNA encoding type I IFN is an effective and alternative approach to currently prescribed therapies in controlling vaginal HSV-2 infection by antagonizing viral replication.

Release of [3H]acetylcholine in human isolated bronchi. Effect of indomethacin on muscarinic autoinhibition

Receptor-mediated regulation of acetylcholine release in the airways, particularly in humans, remains unclear. In the present study, the tissue content of acetylcholine and release of [3H]acetylcholine were measured in freshly dissected human bronchi obtained at thoracotomy. Large (main and lobar bronchi) and small (segmental and subsegmental bronchi) airways contained considerable amounts of endogenous acetylcholine (300 +/- 50 pmol/100 mg wet weight), whereas significantly less was found in lung parenchyma (60 +/- 30 pmol/100 mg). Isolated small bronchi incubated in an organ bath with the precursor [3H]choline synthesized significant amounts of [3H]acetylcholine (26,000 +/- 4,000 dpm/100 mg). Subsequent transmural stimulation (four 20 s trains at 15 Hz) of radiolabeled bronchi caused an enhanced tritium outflow that was abolished by removal of extracellular calcium or by tetrodotoxin. HPLC analysis of the medium collected before, during, and after transmural stimulation showed that the electrically stimulated tritium outflow represented exclusively [3H]acetylcholine, whereas the outflow of [3H]choline and [3H]phosphorylcholine was not affected by electrical stimulation. Oxotremorine (0.1 and 1 mumol/L) inhibited evoked [3H]acetylcholine release in a concentration-related manner, whereas atropine (0.03 mumol/L) enhanced evoked [3H]acetylcholine release. Inactivation of cyclooxygenase activity by 3 mumol/L of indomethacin did not impair the inhibitory effect of 0.1 or 1 mumol/L of oxotremorine. In conclusion, the present experiments indicate a considerable cholinergic innervation of human large and small airways.