Airway Inflammation Before and After Bronchial Thermoplasty in Severe Asthma

Figures & data

Figure 1 Study design. Three weeks before BT treatment baseline data were collected: BALF from the lingula and brushes from the left lower lobe. Six months after BT treatment BALF and brushes were collected from the treated lingula and left lower lobe, and untreated middle lobe. (Figure created with BioRender.com).

Abbreviations: BT, bronchial thermoplasty; BALF, bronchoalveolar lavage fluid.

Table 1 Patient Characteristics at Baseline

Characteristics	Data
Number of patients	28
Sex (male/female)	6/22
Age (years)	45 (± 12)
BMI (kg/m^2)	28.2 (± 4.8)
Dose of LABA (μg/day salmeterol equivalents)	136 (± 35)
Dose of ICS (μg/day fluticasone equivalents)	1158 (± 501)
Number of patients on maintenance use of OCS	9
Dose of oral prednisone (mg/day) in OCS users	13 (± 6)
Number of patients on omalizumab	3
Pre-short-acting bronchodilator FEV1 (% predicted)	86 (± 24)
Post-short-acting bronchodilator FEV1 (% predicted)	100 (± 19)
FEV1 reversibility (%)	14 (± 15)
PC20 (mg/mL)	0.35 (0.03–2.92 IQR) (N=27)
FeNO	17.5 (12.8–41.8 IQR) (N=25)
Number of patients with a positive skin prick test	15 (54%)
Total serum IgE (kU/L)	51.95 (17.05–210.25 IQR)
Blood eosinophil count (10^9/L)	0.14 (0.06–0.29 IQR)

Notes: Data are presented as absolute numbers, mean ± standard deviation) or median with interquartile range (IQR).

Abbreviations: BMI, body mass index; LABA, long-acting β₂-agonist; ICS, Inhaled corticosteroids; OCS, oral corticosteroids; FEV1, forced expiratory volume in 1 second; PC20, methacholine provocation test; FeNO, fraction exhaled nitric oxide; IgE, Immunoglobulin E.

Table 2 Gene Set Enrichment Analysis (GSEA) Showing the List of Differentially Expressed Gene Sets

Gene Set Name [# Genes (K)]	Description	# Genes in Overlap (k)	p-value	FDR q-value
HALLMARK_TNFA_SIGNALING_VIA_NFKB [200]	Genes regulated by NG-kB in response to TNF [GeneID=7124].	37	2.61 e^−37	1.31 e^−35
HALLMARK_MYC_TARGETS_V1 [200]	A subgroup of genes regulated by MYC - version 1 (v1).	24	5.56 e^−20	1.41 e^−18
HALLMARK_HYPOXIA [200]	Genes up-regulated in response to low oxygen levels (hypoxia).	18	4.06 e⁻¹³	6.77 e^−12
HALLMARK_UV_RESPONSE_UP [158]	Genes up-regulated in response to ultraviolet (UV) radiation.	14	2.07 e^−10	2.59 e^−9
HALLMARK_P53_PATHWAY [200]	Genes involved in p53 pathways and networks.	15	4.9 e^−10	4.9 e^−9
HALLMARK_OXIDATIVE_PHOSPHORYLATION [200]	Genes encoding proteins involved in oxidative phosphorylation.	13	3.9 e^−8	3.25 e^−7
HALLMARK_APOPTOSIS [161]	Genes mediating programmed cell death (apoptosis) by activation of caspases.	11	2.63 e^−7	1.88 e^−6
HALLMARK_GLYCOLYSIS [200]	Genes encoding proteins involved in glycolysis and gluconeogenesis.	12	3.09 e^−7	1.93 e^−6
HALLMARK_FATTY_ACID_METABOLISM [158]	Genes encoding proteins involved in metabolism of fatty acids.	10	1.85 e^−6	1.03 e^−5
HALLMARK_ALLOCGRAFT_REJECTION [200]	Genes up-regulates during transplant rejection.	10	1.49 e^−5	5.74 e⁻^5

Figure 2 Differentially expressed gene sets before and after BT treatment. (A) (upper panel: baseline (pre BT) versus after treatment (post BT)). Heatmaps of inflammatory genes for bronchial epithelial cells showing a non-significant difference between the baseline (pre BT) and treated airways (post BT). (A) (lower panel: untreated versus treated (after treatment)). Heatmaps of inflammatory genes for bronchial epithelial cells after BT showing a significant downregulation of the treated lobe compared to the untreated middle lobe. (B) (After treatment). Z-scores from heatmaps showing a significant difference between untreated middle lobe and treated lobes after BT (p<0.0001 = ****). There were no significant differences between responders (green dots) and non-responders (red dots). (C) (baseline versus after treatment). Z-scores from heatmaps showing a non-significant difference between the baseline (pre-BT) and treated airways (post-BT).

Figure 3 Differentially expressed inflammatory and glycolysis gene sets in the responder and non-responder groups. (A) After treatment: Heatmaps of inflammatory genes for bronchial epithelial cells are downregulated in treated airways compared to the untreated (middle) lobe. No differences between responders and non-responders were seen. (B and C) at baseline: Glycolysis gene expression in responders and non-responders. (B) Heatmaps of genes representing glycolysis showing that glycolysis genes are downregulated in responders. (C) Z-scores from glycolysis genes showing a significant difference between responders and non-responders.

Figure 4 Differences at baseline between responders and non-responders. Mann–Whitney U-test analyses showed (A) difference in blood eosinophil count (p=0.006), (B) difference in BALF eosinophil count (p=0.02) and (C) difference between serum IgE (p=0.02) between responders and non-responders. * = p < 0.05.

Abbreviations: AQLQ, asthma quality of life questionnaire; BALF, bronchoalveolar lavage; IgE, Immunoglobulin E.

Figure 5 Proposed interaction between BT and inflammation. Inflammatory genes are downregulated after BT, whereas the expression of oxidative phosphorylation genes and glucocorticoid receptors is increased after BT, as described in other studies.^41,42 *Described in study of Ravi et al⁴¹ **Described in study of Papakonstantinou et al⁴² (Figure created with BioRender.com).

Abbreviation: BT, bronchial thermoplasty.

Ravi A, Goorsenberg AWM, Dijkhuis A, et al. Metabolic differences between bronchial epithelium from healthy individuals and patients with asthma and the effect of bronchial thermoplasty. J Allergy Clin Immunol. 2021;148(5):1236–1248. doi:10.1016/j.jaci.2020.12.653

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Papakonstantinou E, Koletsa T, Zhou L, et al. Bronchial thermoplasty in asthma: an exploratory histopathological evaluation in distinct asthma endotypes/phenotypes. Respir Res. 2021;22(1):186. doi:10.1186/s12931-021-01774-0

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