Angiotensin II stimulates peptide leukotriene production by guinea pig airway via the AT1 receptor pathway

PROSTAGLANDINSLEUKOTRIENES AND ESSENTIALFATTYACIDS ProstaglandinsLeukotrienesand Essential Fatty Acids (1995) 52, 241-244 © Pearson ProfessionalLtd 1995

Angiotensin II Stimulates Peptide Leukotriene Production by Guinea Pig Airway via the AT1 Receptor Pathway H. Kanazawa, N. Kurihara, K. Hirata, S. Kudoh, T. Fujii, S. Tanaka and T. Takeda

1st Department of Internal Medicine, Osaka City University Medical School, 1-5-7, Asahi-machi, Abenoku, Osaka, Japan 545 (Reprint requests to HK) ABSTRACT. Angiotensin II (Ang II) regulates a variety of physiological functions, including contraction of smooth muscle. Peptide leukotrienes (LTs) have recently been reported to be potent bronchoconstrictors and may play a role in the pathogenesis of airway inflammation. However, the possibility that Ang II and peptide LTs interact in the control of airway function has not been studied. In this study, we showed that Ang II receptors are present on guinea pig airway, and that they are of the ATa subtype. We showed the possibility that Ang U induced the release of peptide LTs from guinea pig airway by activation of the ATa receptor pathway. Our findings thus suggest that interaction between Ang II and peptide LTs might increase airway inflammation in the guinea pig.

INTRODUCTION

The results of one study of specific receptor antagonists have suggested that peptide LTs play a role in the immediate bronchoconstriction which follows allergen challenge in asthmatic patients (9). The present study was designed to determine whether Ang II stimulates synthesis of peptide LTs in guinea pig airway in vivo, and whether Ang II receptor-mediated LT formation occurs via AT 1 receptor pathways.

Angiotensin II (Ang II) regulates a variety of physiological functions, including blood pressure, water and salt intake, and contraction of smooth muscle. Regulation is initiated by the interaction of Ang II with specific receptors located on the plasma membrane of target cells. Notably, however, there is evidence that Ang II receptors on many types of cells are heterogenous (1). Evidence for the existence of Ang II receptor subtypes has been obtained in studies with non-peptide Ang II receptor antagonists (2), prototypes of which include DUP753 and PD123319. Receptors of the Ang ILl subtype (ATe) have high affinity for DUP753, while those of the Ang II-2 subtype (AT2) have high affinity for PD123319. Leukotrienes ( L T s ) are recently discovered arachidonic acid (AA) metabolites of the lipoxygenase pathway which axe associated with slow-reacting substance of anaphylaxis (SRS-A) (3). LTC 4 and LTD4 have recently been reported to be potent bronchoconstrictors in several species, including humans (4). They also increase vascular permeability and induce mucosal edema (5). These findings suggest that LTs may be involved in the pathogenesis of allergic inflammation. FPL-55712, a LT receptor antagonist, has been reported to antagonize all the peptide LTs (6). ONO-1078 is representative of yet another class of orally active peptide LT receptor antagonists which have recently been described (7, 8).

METHODS Male Hartley guinea pigs weighing 400-500 g each were used. Under sodium pentobarbital anesthesia (50 mg/kg, i.p, Abbott Laboratories), artificial ventilation was performed through a tracheal cannula connected to a constant-volume ventilator (Model 680, Harvard Apparatus Co.) at a rate of 60 breaths/min. The tidal volume was set at 6 ml/kg. Airflow was monitored continuously with a pneumotachograph (TV-241T, Nihon Kohden Co.) connected to a differential pressure transducer (TP602T, Nihon Kohden Co.). The tidal volume was calculated by electrical integration of airflow. A fluid-filled polyethylene catheter was introduced into the esophagus to measure esophageal pressure as an approximation of pleural pressure. Intratracheal pressure was measured using a polyethylene catheter inserted into a short tube connecting the tracheal cannula to the pneumotachograph. Transpulmonary pressure (defined as the difference between the intratracheal and the esophageal pressure) was measured with a differential pressure transducer.

Date received 30 J u n e 1994 Date accepted 29 A u g u s t 1994 241

242

Prostaglandins Leukotrienes and Essential Fatty Acids

Total pulmonary resistance (RE) was calculated using methods previously described (10, 11). All agents used in this study were aerosolized with an ultrasonic nebulizer and delivered to the airways using a ventilator. In the first set of experiments, to determine the effect of Ang II (Sigma Chemical, St. Louis, MO) and LTC 4 or LTD 4 (ONO Pharamaceutical Co., Osaka, Japan) on airway responses in vivo, they were administered in aerosol form using the method described above. In the next set of experiments, we attempted to determine whether exposure to Ang II receptor antagonists influences Ang II-induced airway responses in guinea pigs. Animals were exposed to an AT1 antagonist (DUP753, a gift from Du Pont Merck Pharmaceuticals Co.) in one group and an AT2 antagonist (PD123319, a gift from Warner-Lambert Co.) in a second group. The effect of the peptide LT antagonist, ONO-1078 (ONO Pharmaceutical Co., Osaka, Japan) on Ang II-induced airway responses was also examined. The effect of aerosol administration of Ang II on pulmonary resistance was determined 30 rain after the administration of ONO1078. Results were expressed as means + SD and analyzed with Student's t-test. Findings o f p < 0.05 were taken to indicate statistical significance.

RESULTS LTC 4 and LTD 4 tested separately induced bronchoconstriction 10rain after inhaled administration in guinea pig. This contractile response to the peptide LTs was completely inhibited by ONO-1078 (Fig. 1). ONO-1078 itself had no effect on guinea pig airway

~RL

[%]

200-

200 -

100-

100-

LTC4(10 'M)

LTC4(10 "M) + ONO-1078(10 ~M)

(data not shown). Airway resistance was markedly increased 60 min after the inhalational administration of Ang II. If pretreatment with AT1 receptor antagonist was performed, the Ang II-induced contractile response was completely inhibited; however, pretreatment with AT2 receptor antagonist did not inhibit the Ang IIinduced contractile response. ONO-1078, on the other hand, significantly attenuated this response (Fig. 2). Ang H-induced bronchoconstriction increased in a timedependent fashion, but in the presence of ONO-1078, bronchoconstriction was significantly inhibited 50 rain and 60 rain after inhaled administration of Ang II. These findings suggest that Ang II may have induced production of peptide LTs via the AT1 receptor pathway 50 rain after inhaled administration (Fig. 3). Ang IImediated bronchoconstriction was inhibited by ONO1078 in a dose-dependent fashion. Inhaled Ang II directly constricted guinea pig airway, but a portion of this contractile response was induced by peptide LTs (Table).

P < 0,01 NS I P < 0.01

I

1

400 -

300

200

-

7///:

~.(/,,

-

100 -

,

Ang I](10 ~M)

LTD4(10 'M) + ONO-1078(10 ~M)

Fig. 1 The effect of leukotriene receptor antagonist ONO-1078 (10 -5 M, 60 breaths) on aerosolized LTC 4 or LTD 4 (10-4 M, 30 breaths) mediated bronchoconstriction (n = 5).

I

°~RL [%)

LTD4(!0 'M)

Ang I](10-~M) + DUP753(10 'M)

Ang rl(10 'M) + PD123319(10'M)

Ang I](10 ~'M)

+ ONO-1078(10 ~M)

Fig. 2 The effect of AT 1 receptor antagonist DUP753 (10 3 M, 30 breaths), AT 2 receptor antagonist PD123319 ( 1 ~ 3 M, 30 breaths) and leukotriene antagonist ONO-1078 (10 5 M, 60 breaths) on airway resistance (RL) 60 min after administration of aerosolized Ang II (105 M, 30 breaths) (n = 5).

Angiotensin II Stimulates Peptide Leukotriene Production by Guinea Pig Airway via the AT 1 Receptor Pathway P < 0.05

I

I

NS

I NS

%RL

I P < 0.01

P < 0.01

I---3

[%] 400-

~ ' ~ Ang IIUO ~M) ~-]

300-

Ang rf(lO ~M) + ONO- 1078(10 ~M)

200-

100-

30

40

50

60

[mini

Fig. 3 Time course of effect of aerosolized Ang II (10 5 M, 30 breaths) on airway resistance (RL) in the presence of leukotriene antagonist ONO-1078 (10 `5 M, 60 breaths) (n = 5).

Table

% Inhibition Ang Ang Ang Ang

II II II II

(10 .5 M) (104 M) + ONO - 1078 (10 -5 M) (10.5 M) + ONO - 1078 (10 4 M) (10 5 M) + ONO - 1078 (10 -7 M)

62 -+ 15 40 -+ 20 15 + 5

Dose response effect of leukotriene antagonist ONO-1078 (10 -5 M, 60 breaths) on airway resistance (RL) 60 min after administration of aerosolized Ang II (10 .5 M, 30 breaths) (n = 5). Ang II (10 .5 M) vs Ang II (10.5 M) + ONO-1078 (10.5 M): p < 0.01 Ang II (10 s M) vs Ang II (10 -5 M) + ONO-1078 (10 -6 M): p < 0.01 Ang II (10.5 M) vs Ang II (10 -5 M) + ONO-1078 (10 7 M): p < 0.05

DISCUSSION

Airway inflammation is reported to be strictly related to the development of non-specific bronchial hyperreactivity. When alveolar capillary permeability is increased during related airway inflammation, leakage of Ang II into the airspace may affect airway function. The findings of the present study show that Ang II receptors on guinea pig airway are functionally coupled to bronchoconstriction. Since the response to Ang II binding was inhibited by DUP753 (an ATl-selective antagonist), but not by PD123319 (an AT2-selective antagonist), these receptors appear to be of AT~ subtype. The closely related cysteinyl-containing LTs LTC 4 and LTD4, are proposed mediators of bronchial asthma and airway inflammation. They are potent constrictors of human airways (12) and mediators of allergen-induced bronchial contraction in vitro (13). They are quite potent, and have a longer lasting effect on the human bronchus than do histamine and methacholine (14). Furthermore, studies in asthmatic patients have shown that specific anti-LT receptor antagonists attenuate airway obstruction induced by several triggers of bronchial asthma, including allergens and exercise (15, 16). It has also been convincingly shown that asthmatic patients release LTs when provoked by non-specific airway irritants (17). In addition to their effects on human bronchus, LTC 4 and LTD 4

243

increase vascular permeability and stimulate mucous secretion in the airway (18). Therefore, peptide LTs appear to induce all the phenomena contributing to airflow obstruction during airway inflammation, including bronchospasm, mucosal edema, and hypersecretion. However, the fashion in which Ang II and peptide LTs interact in control of airway function has not been studied. Recent studies have shown that Ang II can induce the release of AA metabolites in the lung of rats and dogs. Lefer et al have shown that calcium ionophore and PAF potently stimulate the formation and release of peptide LTs by lung in cats, guinea pigs, and rats (19). In the present study, the results suggest that Ang II induced the release of peptide LTs. Our findings suggest that interaction between Ang II and peptide LTs might increase airway inflammation in the guinea pig. In conclusion, the findings of this study suggest that peptide LT antagonism may provide a new therapeutic strategy for the treatment of airway inflammation. While there is some evidence that AT 1 receptor antagonists may also antagonize Ang II-mediated physiological functions, further studies will be required to establish that they have anti-inflammatory properties.

References i. Chiu A T, Herbtin W F, McCall D E et al. Identification of angiotensin II receptor subtypes. Biochem. Biophys. Res. Commun. 1989; 165: 196-203. 2. Timmermans P B M W N, Wong P C, Chin A T, Herblin W F. Nonpeptide angiotensin II receptor antagonists. Trends Pharmacol. Sci. 1991; 12: 55-67. 3. Hanna C J, Bach M K, Pare P D, Schellenberg R R. Slowreacting substances (leukotrienes) contract human airway and pulmonary vascular smooth muscle in vitro. Nature 1981; 290: 343-344. 4. Smith L J, Greenberrger P A, Patterson R, Krell R D, Bernstein P R. The effect of inhaled leukotriene D 4 in humans. Am. Rev. Respir. Dis. 1985; 131: 368-372. 5. Soter N A, Lewis R A, Corey E J, Austen K F. Local effect of synthetic leukotrienes (LTC4, LTD4, LTE4 and LTB4) in human skin. J. Invest. Dermatol. 1983; 80: 115-119. 6. Augstein J, Farmer J B, Lee T B, Sheard P, Tattersall M L. Selective inhibitor of slow-reacting substance of anaphylaxis. Nature 1973; 245: 215-216. 7. Obata T, Katsube N, Miyamoto T. New antagonists of leukotrienes: ONO-RS-411 and ONO-RS-347. Adv. Prostaglandin Thromboxane Leukot. Res. 1985; 15: 229-231. 8. Fujiwara H, Kurihara N, Ohta K et al. Effect of a new leukotriene receptor antagonist, ONO-1078, on human bronchial smooth muscle in vitro. Prostaglandins Leukot Essent. Fatty Acids 1993; 48: 241-246. 9. Taylor I K, O'Shanghnessy K M, Fuller R W, Dollery C T. Effect of cysteinyMeukotriene receptor antagonist ICI204219 on allergen-induced bronchoconstriction and airway hypen'eactivity in atopic subjects. Lancet 1991; 337: 690-694. 10. Frossard N, Muller F. Epithelial modulation of tracheal smooth muscle responses to antigenic stimulation. J. Appl. Physiol. 1986; 61: 1449-1456. 11. Kanazawa H, Kmihara N, Hirata K, Fujiwara H, Matsushita H, Takeda T. Low concentration endothelin-1 enhanced histamine-mediated bronchial contractions of guinea pigs in vivo. Biochem. Biophys. Res. Commun. 1992; 187: 717-721. 12. Dahlen S-E, Hedqvist P, Hammarstr6n S, Samuellsson B.

244

Prostaglandins Leukotrienes and Essential Fatty Acids

Leukotrienes are potent constrictors of human bronchi. Nature 1980; 288: 484-486. 13. Dahlen S-E, Hansson G, Hedqvist P, Bjtirck T, Granstr6m E, Dahle B. Allergen challenge of lung tissue from asthmatics elicits bronchial contraction that correlates with the release of leukotrienes C4, D4 and E 4. Proc. Natl. Acad. Sci. USA 1983; 80: 1712-1716. 14. Weiss J W, Drazen J M, McFadden E R. Airway constriction in normal humans produced by inhalation of leukotriene D4: Potency, time course, and effect of aspirin therapy. JAMA 1983; 249: 2814-2817. 15. Taylor I K, O'Shaughnessy K M, Fuller R W, Dollery C T. Effect of cysteinyl-leukotriene receptor antagonist ICI204219 on allergen-induced bronchoconstriction and airway hypperreactivity in atopic subjects. Lancet 1991; 337: 690-694.

16. Manning P J, Watson R M, Margolskee D J, Williams V C, Schwartz J I, O'Byrne P M. Inhibition of exerciseinduced bronchoconstriction by MK-571: A potent leukotriene D 4 receptor antagonist. N. Engl. J. Med. 1990; 323: 1736-1739. 17. Knapp H R, Sladek K, Fitzgerald G A. Increased excretion of lenkotriene E 4 during aspirin-induced asthma. J. Lab. Clin. Med. 1992; 119: 48-51. 18. Marom Z, Shelhamer J H, Bach M K, Morton D R, Kaliner M. Slow reacting substances, leukotriene C4 and D 4 increase the release of mucous from human airway in vitro. Am. Rev. Respir. Dis. 1982; 126: 449-451. 19. Lefer A M, Roth D M, Lefer D J, Smith J B. Potentiation of leukotriene formation in pulmonary and vascular tissue. Naunyn-Schmiedeberg's Arch. Pharmacol. 1984; 326: 186-189.