Use of a soluble epoxide hydrolase inhibitor in smoke-induced chronic obstructive pulmonary disease

Abstract

Tobacco smoke-induced chronic obstructive pulmonary disease (COPD) is a prolonged inflammatory condition of the lungs characterized by progressive and largely irreversible airflow limitation attributable to a number of pathologic mechanisms, including bronchitis, bronchiolitis, emphysema, mucus plugging, pulmonary hypertension, and small-airway obstruction. Soluble epoxide hydrolase inhibitors (sEHIs) demonstrated anti-inflammatory properties in a rat model after acute exposure to tobacco smoke. We compared the efficacy of sEHI t-TUCB (trans-4-{4-[3-(4-trifluoromethoxy-phenyl)-ureido]-cyclohexyloxy}-benzoic acid) and the phosphodiesterase-4 (PDE4) inhibitor Rolipram (Biomol International, Enzo Life Sciences, Farmingdale, NY) to reduce lung injury and inflammation after subacute exposure to tobacco smoke over a period of 4 weeks. Pulmonary physiology, bronchoalveolar lavage, cytokine production, and histopathology were analyzed to determine the efficacy of sEHI and Rolipram to ameliorate tobacco smoke-induced inflammation and injury in the spontaneously hypertensive rat. Both t-TUCB and Rolipram inhibited neutrophil elevation in bronchoalveolar lavage. sEHI t-TUCB suppressed IFN-γ, while improving lung function by reducing tobacco smoke-induced total respiratory resistance and tissue damping (small-airway and peripheral tissue resistance). Increases in tobacco smoke-induced alveolar airspace size were attenuated by t-TUCB. Rolipram inhibited the production of airway mucus. Both t-TUCB and Rolipram inhibited vascular remodeling-related growth factor. These findings suggest that sEHI t-TUCB has therapeutic potential for treating COPD by improving lung function and attenuating the lung inflammation and emphysematous changes caused by tobacco smoke. To the best of our knowledge, this is the first report to demonstrate that sEHI exerts significant protective effects after repeated, subacute tobacco smoke-induced lung injury in a rat model of COPD.

Figure 1.

Effects of trans-4-{4-[3-(4-trifluoromethoxy-phenyl)-ureido]-cyclohexyloxy}-benzoic acid (t-TUCB) and Rolipram on tobacco smoke (TS) exposure–induced weight loss in spontaneously hypertensive (SH) rats. Body weight measurements were taken before and after smoke exposure each week. The weekly mean weights measured before smoke exposure each week are reported. The time course is presented for body weight changes of age-matched, non–TS-exposed animals as controls (open circles), TS-exposed animals treated with vehicle (solid squares), TS-exposed animals treated with soluble epoxide hydrolase inhibitors (sEHI) t-TUCB (solid triangles), and TS-exposed animals treated with Rolipram (open diamonds). Data are expressed as means ± SEM for 4–8 animals/group. wk, weeks. *P < 0.05, TS-exposed groups were significantly different from the control group. ^†P < 0.05, treatment group with sEHI t-TUCB was significantly different from the TS vehicle group.

Figure 2.

Effects of t-TUCB and Rolipram on leukocyte profile in bronchoalveolar lavage. (A) Percent of mononuclear cells (including macrophages, monocytes, and lymphocytes). (B) Percentages of neutrophils in the bronchoalveolar lavage (BAL). Data are expressed as means ± SEM for 4–8 animals/group. *P < 0.05, TS-exposed groups were significantly different from control group. ^†P < 0.05, treatment group with sEHI t-TUCB was significantly different from the TS vehicle group. ^‡P < 0.05, treatment group with Rolipram was significantly different from the TS vehicle group.

Figure 3.

Effects of t-TUCB and Rolipram on pulmonary inflammatory cytokines. Inflammatory cytokine (A) IL-1β, (B) IL-6, (C) IFN-γ, and (D) IL-12p70 concentrations in whole-lung homogenate are reported. Data are expressed as mean ± SEM for 4–8 animals/group. *P < 0.05, TS-exposed groups were significantly different from the control group. ^†P < 0.05, treatment group with sEHI t-TUCB was significantly different from the TS vehicle group.

Figure 4.

Effects of t-TUCB and Rolipram on vascular endothelial growth factor (VEGF) in the lung. Data are expressed as means ± SEM for 4–8 animals/group. *P < 0.05, TS-exposed groups were significantly different from the control group. ^†P < 0.05, treatment group with sEHI t-TUCB was significantly different from the TS vehicle group. ^‡P < 0.05, treatment group with Rolipram was significantly different from the TS vehicle group.

Figure 5.

Effects of t-TUCB and Rolipram on pulmonary function in the lung. (A) Total respiratory resistance (R) and (B) elastance (E), (C) compliance (C), (D) central airway resistance (Rn), (E) tissue damping (G), and (F) elastance (H) are shown. Data are expressed as means ± SEM for 4–8 animals/group. *P < 0.05, TS–exposed groups were significantly different from the control group. ^†P < 0.05, treatment group with sEHI t-TUCB was significantly different from the TS vehicle group. ^‡P < 0.05, treatment group with Rolipram was significantly different from the TS vehicle group.

Figure 6.

Effects of t-TUCB and Rolipram on oxylipins in the lung. (A) Major oxylipins prostaglandin E2 (PGE2), (B) 13-hydroxyoctadecadienoic acid, and (C) 5-oxo-6,8,11,14-eicosatetraenoic acid and (D) the epoxyeicosatrienoic acids (EETs)/diols ratio are shown. Data are expressed as means ± SEM for 4–8 animals/group. *P < 0.05, TS-exposed groups were significantly different from the control group. ^†P < 0.05, treatment group with sEHI t-TUCB was significantly different from the TS vehicle group. ^‡P < 0.05, treatment group with Rolipram was significantly different from the TS vehicle group.

Figure 7.

Effects of t-TUCB and Rolipram on TS exposure–induced mucin production. (A) Sections of the bronchial wall from filtered air (Control), TS-exposed SH rats with vehicle treatment (TS vehicle), sEHI treatment (TS sEHI), or Rolipram treatment (TS Rolipram) stained with alcian blue/periodic acid–Schiff for the detection of mucous glycoconjugate. (B) Blinded quantification of intraepithelial mucosubstances. *P < 0.05, TS-exposed groups were significantly different from the control group. ^‡P < 0.05, treatment group with Rolipram was significantly different from the TS vehicle group.

Figure 8.

Effects of t-TUCB and Rolipram on TS exposure–induced airspace enlargement. (A) Sections of the parenchyma from filtered air (Control), TS-exposed SH rats with vehicle treatment (TS vehicle), sEHI treatment (TS sEHI), or Rolipram treatment (TS Rolipram) were stained with hematoxylin and eosin. (B) Blinded quantification of mean linear intercept. *P < 0.05, TS-exposed groups were significantly different from the control group. ^†P < 0.05, treatment group with sEHI t-TUCB was significantly different from the TS vehicle group.