Excitatory and Inhibitory Actions of Isoprostanes in Human and Canine Airway Smooth Muscle 1 LUKE J. JANSSEN, MAHMOOD PREMJI, STUART NETHERTON, ADRIANNA CATALLI, GERARD COX, SHAF KESHAVJEE, and DENIS J. CRANKSHAW Asthma Research Group, Father Sean O’Sullivan Research Centre, Department of Medicine, McMaster University, Hamilton, Ontario, Canada (L.J.J., M.P., S.N., A.C., G.C.); Toronto Lung Transplant Program, Division of Thoracic Surgery, University of Toronto, Ontario, Canada (S.K.); and Department of Obstetrics and Gynecology, McMaster University, Hamilton, Ontario, Canada (D.J.C.) Accepted for publication July 11, 2000 This paper is available online at http://www.jpet.org ABSTRACT Isoprostanes are generated nonenzymatically during free radi- cal-mediated lipid peroxidation, and are used clinically and experimentally as markers of oxidative stress. However, their biological effects are poorly understood. We examined the effects of seven different 8-isoprostanes in human and canine airway smooth muscles. In large order airways (carina) of the human, several isoprostanes evoked powerful contractions, with 8-iso-prostaglandin (PG) E 2 , 8-iso-PGF 1 , and 8-iso- PGF 2 being the most efficacious (and with logEC 50 values of 7.0, 5.9, and 6.2 M, respectively). These contractions were sensitive to the prostanoid TP receptor antagonist ICI 192,605 (0.1–1 M), but not the EP prostanoid receptor antagonist AH-6809 (50 M), or the leukotriene receptor antagonists mon- teleukast or ICI 198,615 (both 1 M). Qualitatively similar results were obtained in small order human airways (2 mm o.d.), except that the isoprostanes were generally slightly less potent. None of the isoprostanes had any marked excitatory effect in canine airways. In carbachol-preconstricted tissues (pretreated with ICI 192,605 to block any potential contraction), several isoprostanes completely relaxed canine airways: 8-iso-PGE 1 , 8-iso-PGE 2 , and 8-iso-PGF 3 were the most potent, with logIC 50 values of 6.9, 6.9, and 5.7, respectively. Only 8-iso- PGF 3 relaxed human airways (logIC 50 = 4.9). Our results show that several 8-isoprostanes are highly biologically active in hu- man and canine airways, evoking both excitatory and/or inhib- itory effects, and that these effects are compound, species, and tissue dependent. The airways are continually exposed to a variety of free radicals and reactive oxygen species in inspired air (e.g., ozone) and liberated by inflammatory cells (e.g., peroxide, superoxide, hydroxyl radical). These agents can alter airway function, ranging from contraction in human airways (Rabe et al., 1995) to relaxation in canine airways (Gao and Van- houtte, 1992; Janssen et al., 2000b), but the underlying mechanisms are as yet unclear. It is now recognized that nonenzymatic peroxidation of arachidonic acid by free radicals and reactive oxygen species can give rise to isoprostanes (Morrow et al., 1990; Practico et al., 1995). Isoprostanes differ structurally from prostaglan- dins (PGs) by the cis-orientation at the cyclopentane ring junction compared with the trans-orientation in the classical prostanoids (Fig. 1). 8-Isoprostanes are present in substantial amounts even in normal plasma or urine (in which their levels can be several orders of magnitude higher than those of cyclooxygenase- derived PGs; Morrow et al., 1990), but they are further ele- vated in many states in which oxidative stress is a prominent feature. For example, they are elevated in smokers (Morrow et al., 1995; Pratico et al., 1995; Delanty et al., 1996; Reilly et al., 1996; Chiabrando et al., 1998; Pratico et al., 1998a); in patients with asthma (Montuschi et al., 1999a), chronic ob- structive pulmonary disease (Pratico et al., 1998b), intersti- tial lung disease (Montuschi et al., 1998), cystic fibrosis (Montuschi et al., 1999b), or acute chest syndrome (Klings et al., 1999); during exposure to allergen (Dworski et al., 1999), ozone (Hazbun et al.,1993), or hyperoxia (Vacchiano and Tempel, 1994); and during ventilated ischemia (Becker et al., 1998). Despite their prevalence in these disease states, the bio- logical effects of 8-isoprostanes in airways are very poorly understood. 8-iso-PGF 2 is a potent stimulant of vascular (Takahashi et al., 1992; Kang et al., 1993; Kromer and Tip- pins, 1996; Zhang et al., 1996; John and Valentin, 1997; Oliveira et al., 2000), intestinal (Elmhurst et al., 1997), and uterine (Crankshaw, 1995) smooth muscles where its effects are sensitive to selective prostanoid TP receptor antagonists. Consequently, the effects of 8-iso-PGF 2 are generally, al- though not exclusively, thought to be mediated by action at Received for publication April 4, 2000. 1 This study was supported by an operating grant and a Scientist Award from the Medical Research Council of Canada (to L.J.J.). ABBREVIATIONS: PG, prostaglandin; HUA, human umbilical artery; PSS, physiological salt solution. 0022-3565/00/2952-0506$03.00/0 THE JOURNAL OF PHARMACOLOGY AND EXPERIMENTAL THERAPEUTICS Vol. 295, No. 2 Copyright © 2000 by The American Society for Pharmacology and Experimental Therapeutics 2785/856035 JPET 295:506–511, 2000 Printed in U.S.A. 506 at ASPET Journals on May 29, 2017 jpet.aspetjournals.org Downloaded from