Montelukast versus Dexamethasone Treatment in a Guinea Pig Model of Chronic Pulmonary Neutrophilic Inflammation

Figures & data

Figure 1. Schedule of the study: Chronic (9 exposures, 48 hours apart) exposure (60 min) to nebulized lipopolysaccharides (LPS) (30 μg/ml) or vehicle (pathogen-free saline) of conscious guinea pigs, with and without Montelukast or dexamethasone treatment. Airway hyperreactivity (AHR) was measured at 48 hours after the final exposure to LPS, bronchoalveolar lavage fluid (BALF) was conducted for cellular analysis and tumor necrosis factor (TNF) α level measurement. Lungs for malondialdehyde, histone deacetylase activity and histological analysis) were collected at 48 hours. Test drugs were administered every day, usually 30 minutes before exposure on days of LPS challenge.

Figure 2. Effect of oral treatment with Montelukast (10 and 30 mg/kg) and dexamethasone on airway function of conscious guinea pigs during base line, after first exposure and after chronic exposure (9 times) to LPS (30 mg/ml) or vehicle (saline) inhalation, for 1 hour, 48 hours apart. Drug treatment started 1 day before LPS exposure and continued daily for 20 days. Airway function was expressed as specific airway resistance (sRaw). Each point represents the mean ± S.E.M. (n = 6). Significance of differences from saline exposure (*, p < 0.05), significance of differences from LPS exposures (#, p < 0.05) and significance of differences from dexamethasone treatment ($, p < 0.05) were determined by analysis of variance (single factor), followed by Newman–Keuls Multiple Comparison Test.

Table 1. Effect of pretreatment with montelukast and dexamethasone on airway hyperresponsiveness (AHR) to methacholine (Mch) in chronic LPS exposed guinea pigs

	Specific airway resistance (means ± S.E.M) induced by gradual increasing doses of inhaled methacholine (mg/ml)
Groups (n = 6)	0.125	0.25	0.5	1.0	2.0	4.0
Naïve	4.04 ± 0.17	4.61 ± 0.24	5.27 ± 0.19	5.67 ± 0.22	6.26 ± 0.14	8.12 ± 0.17
Saline	4.2 ± 0.17	4.88 ± 0.2	5.43 ± 0.14	6.12 ± 0.12	6.8 ± 0.11	9.41 ± 0.06
LPS	5.67 ± 0.34*	6.45 ± 0.15*	7.77 ± 0.46*	9.19 ± 0.21*	11.57 ± 0.27*	21.02 ± 0.46*
Montelukast (10 mg/kg)	4.47 ± 0.15#	5.27 ± 0.19#	6.58 ± 0.14#	7.51 ± 0.23#	9.64 ± 0.2#	18.18 ± 0.34#
Montelukast (30 mg/kg)	4.23 ± 0.11#	4.61 ± 0.2#	5.67 ± 0.18#	6.52 ± 0.17#$	8.18 ± 0.18#$	13.21 ± 0.3#$
Dexamethasone	4.51 ± 0.14#	6.32 ± 0.14#	6.96 ± 0.07#	8.85 ± 0.1#	9.79 ± 0.21#	20.1 ± 0.21#

The effects of gradual increasing doses of inhaled methacholine (mg/ml) on specific airway resistance in chronic LPS exposed guinea pigs with and without daily (oral) Montelukast (10 and 30 mg/ kg), or dexamethasone (20 mg/ kg). Each value represents the mean ± S.E.M. (n = 6) Significance of differences from saline values ($, p < 0.05), Significance of differences from LPS exposures (#, p < 0.05), and Significance of differences from dexamethasone treatment ($, p < 0.05) was determined by analysis of variance (single factor), followed by Newman–Keuls Multiple Comparison Test, respectively.

Figure 3. Effect of oral treatment with Montelukast (10 and 30mg/kg) and dexamethasone on airway hyperreactivity (AHR). AHR was examined 48 hours after the 9th exposure to LPS with increasing concentration of methacholine. Airway hyperreactivity is expressed as PC100 (the methacholine dose, in mg/kg, at which 100% bronchoconstriction was induced. Values given are means ± S.E.M. (n = 6). Significance of differences from saline exposure (*, p < 0.05), significance of differences from LPS exposures (#, p < 0.05) and significance of differences from dexamethasone treatment ($, p < 0.05) were determined by analysis of variance (single factor), followed by Newman–Keuls Multiple Comparison Test.

Table 2. Effect of oral treatment with montelukast or dexamethasone on airway influx of inflammatory cells (leukocytes count) after chronic exposure to LPS or saline

Cells per Bronchoalveolar Lavage Sample (×10^6)
Groups	Naïve	Chronic saline	Chronic LPS	Chronic LPS and montelukast (10mg/kg)	Chronic LPS and montelukast (30mg/kg)	Chronic LPS and dexamethasone
Measurements
Total Cell Count	7.06 ± 0.09	4.42 ± 0.1	31.78 ± 1.17	19.25 ± 0.28	17.68 ± 0.3	14.28 ± 0.2
% Change from LPS				–39.43%^#	–44.37%^#	–55.07%^#
% Change from dexamethasone				+25.82%$	+19.23%$
Macrophages	6.48 ± 0.11	3.58 ± 0.05	16.62 ± 0.12	9. 8 ± 0.07	8.45 ± 0.1	6.82 ± 0.12
% Change from LPS				–41.03%^#	–49.16%^#	–58.1%^#
% Change from dexamethasone				+43.7%$	+23.9%$
Eosinophils	0.3 ± 0.02	0.62 ± 0.05	2.8 ± 0.1	0.98 ± 0.03	0.59 ± 0.02	0.35 ± 0.01
% Change from LPS				–65%^#	–78.93%^#	–87.5%^#
% Change from dexamethasone				+64.29%$	+39.8%$
Neutrophils	0.0 ± 0.0	0.07 ± 0.01	12.30 ± 1.3	9.12 ± 0.05	8.17 ± 0.12	6.68 ± 0.08
% Change from LPS				–25.85%^#	–33.58%^#	–45.69%^#
% Change from dexamethasone				+36.53%$	+16.34%

Total and differential cell counts (macrophages, eosinophils, and neutrophils) were made in bronchoalveolar lavage fluid removed from guinea pigs 48 hour after chronic (9) exposures (1 hour, 48 hours apart) to LPS (30 mg/ml) or vehicle (saline) by inhalation. Values represent the mean ± S.E.M. (n = 6) of the cells per sample (×10⁶). Significance of differences from LPS exposures #, p < 0.05) and significance of differences from dexamethasone treatment ($, p < 0.05) were determined by analysis of variance (single factor), followed by the Newman–Keuls Multiple Comparison Test.

Figure 4. Effect of oral treatment with Montelukast (Mont) (10 and 30 mg/kg) and dexamethasone (Dex) on release of A: Tumor necrosis factor-α. B: Leukotriene B4 in BALF 48 hours after the 9th exposure to LPS in guinea pigs. Each column shows means ± S.E.M. (n = 6). Significance of differences from saline exposure (*, p < 0.05), significance of differences from LPS exposures (#, p < 0.05) and significance of differences from dexamethasone treatment ($, p < 0.05) were determined by analysis of variance (single factor), followed by Newman–Keuls Multiple Comparison Test.

Figure 5. Effect of oral treatment with Montelukast (10 and 30 mg/kg) and dexamethasone on A: MDA (malondialdehyde) level and B: HDAC (Histone deacetylase) activity in lung tissue homogenate 48 hours after the 9th exposure to LPS in guinea pigs. Each column shows means ± S.E.M. (n = 6). Significance of differences from saline exposure (*, p < 0.05), significance of differences from LPS exposures (#,p < 0.05) and significance of differences from dexamethasone treatment ($, p < 0.05) were determined by analysis of variance (single factor), followed by the Newman–Keuls Multiple Comparison Test.

Figure 6. Effect of oral treatment with Montelukast (10 and 30 mg/kg) and dexamethasone on average number of inflammatory cells in 10 randomly chosen fields (500-μm squares) measured from 10 randomly selected lines passing through the lung in H & E stained sections taken 48 hours after the 9th exposure to LPS. Each column represents means ± S.E.M. (n = 6). Significance of differences from saline exposure (*, p < 0.05), and significance of differences from LPS exposures (#, p < 0.05) were determined by analysis of variance (single factor), followed by the Newman–Keuls Multiple Comparison Test.

Chaney MO, Froelich LL, Gapinski DM, Mallett BE, Jackson WT. Characterization of the spatial arrangement of the 2 acid-binding sites on the human neutrophil ltb (4) receptor. Receptor 1992; 2:169–179.

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