Br. J. clin. Pharmac. (1991), 32, 713-716
Effect of enalapril on allergen-induced cutaneous hypersensitivity reaction J. R. SNYMAN & De K. SOMMERS Department of Pharmacology, University of Pretoria, PO Box 2034, Pretoria 0001, South Africa
1 To test the hypothesis that the in vivo inhibition of angiotensin converting enzyme in a patient who presents atopy, results in a significant increase in cutaneous bradykinin and prostaglandin production, the effect of enalapril on the cutaneous hypersensitivity reaction was examined in 10 atopic volunteers. 2 A crossover study design was used and volunteers were randomly allocated to treatment with either enalapril (10 mg) alone, or in combination with indomethacin (75 mg), with and without ketotifen (1 mg). Drugs were administered twice daily for 2 days. 3 Allergen (Southern Grass Mix) was administered intradermally 2 h after last drug dosage and the surface areas of the immediate wheal-and-flare-reactions were measured 15 min later. The late phase of the cutaneous response was evaluated 6 h later by determining skinfold thickness and surface area. 4 Enalapril alone had no effect on any of the parameters measured. 5 The cutaneous hypersensitivity reaction was significantly reduced with regard to both immediate and late cutaneous responses when the indomethacin and ketotifen combination was added to enalapril therapy. 6 When only indomethacin was added to enalapril pretreatment the flare reaction was significantly reduced, but whealing was unaffected. 7 This study presents further evidence that mast cell mediators other than prostaglandins are involved in the cutaneous hypersensitivity reaction. Furthermore, that endogenous bradykinin production after enalapril pretreatment either never reaches the supraphysiological concentrations used in previous experiments, or that bradykinin is rapidly and effectively broken down to inactive peptides by other carboxypeptidase enzymes.
Keywords enalapril indomethacin
cutaneous hypersensitivity reaction
ketotifen
Introduction
The angiotensin converting enzyme (ACE) is a nonspecific kininase II, responsible for the conversion of angiotensin I to angiotensin II, as well as the degradation of bradykinin to inactive peptides (Sheikh & Kaplan, 1986a,b). It is inhibited by enalapril, captopril, ramipril etcetera (McAreavey & Robertson, 1990; Studdy et al., 1983), and part of the antihypertensive effect of these ACE inhibitors has been postulated to result from an increase in tissue bradykinin, with the secondary production of vasodilatory prostaglandins (Williams, 1988; Zusman, 1984). These autacoids have been implicated in some ACE inhibitor side effects such as the dry cough and angioedema, and have even been claimed to be responsible for the worsening of bronchial asthma in
one patient treated with enalapril (Semple & Herd, 1986; Wood & Mann, 1987). Exogenous bradykinin administration has been used experimentally to induce
vasodilatation, cough, bronchoconstriction and cutaneous wheal-and-flare reactions in order to elucidate bradykinin's role in the above mentioned effects (Dixon et al., 1987; Ferner et al., 1987, 1989, 1990; Fuller et al., 1987a,b; Heavey et al., 1985; McAlpine & Thomson, 1989). In some experiments augmentation of bradykinin effects after ACE inhibition was demonstrated (Ferner et al., 1987, 1989, 1990; Fuller et al., 1987b; McAlpine & Thomson, 1989), while other authors failed to do this (Dixon et al., 1987; Fuller et al., 1987a). To test the hypothesis that the in vivo inhibition of
Correspondence: Dr J. R. Snyman, Department of Pharmacology, University of Pretoria, PO Box 2034, Pretoria 0001, South Africa
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kininase II results in a significantly increased production of bradykinin and secondarily prostaglandins, the present experiment examines the possible contribution of these two substances to the cutaneous hypersensitivity reaction. Both bradykinin and prostaglandins have been shown to be implicated in the hypersensitivity response to antigens in vivo (Atkins et al., 1987; De Shazo et al., 1979; Proud et al., 1983).
Methods
Ten volunteers manifesting atopy (four female and six male subjects, aged 20-27 years) took part in this study after ethical approval and informed consent were obtained. They were all healthy and had no history of any dermatological abnormalities i.e. eczema, angioneurotic oedema or dermatographism. Strict inclusion criteria were applied and only volunteers allergic to grass pollens, and who gave a history of allergic rhinitis and/or conjunctivitis, or asthma during the pollen season, were admitted to the study. They were on no medication for at least 1 month prior to testing. The volunteers were selected on the basis of a modified prick test, using histamine and glycero-saline controls. They all manifested an immediate wheal reaction more or less equal to that of the positive histamine control, followed by a late phase reaction after skin prick test with the Southern Grass Mix (Bayer Miles). A crossover study design was used; the volunteers and the experimenters being blinded. The tablets, including placebo, were randomly assigned and administered by a colleague not participating in the experiment. Volunteers were allocated to four treatment modalities: (a) Placebo: to detect baseline values of reaction. (b) Enalapril (Logos) 10 mg, an ACE inhibitor (Ferner et al., 1987, 1990). (c) Enalapril 10 mg and 75 mg indomethacin, a nonsteroidal anti-inflammatory drug (Logos). The latter was added to suppress the formation of prostaglandins in the reaction (McAlpine & Thomson, 1989). (d) Enalapril 10 mg, and indomethacin 75 mg were given with 1 mg ketotifen, a known histamine1 receptor antagonist as well as a mast cell membrane stabilizer (Grant et al., 1990; Huston et al., 1986). This combination would tend to inhibit the contribution of both prostaglandin and histamine to the reaction. All tablets were taken 12 hourly for 48 h and the skin tests were initiated 2 h after the last drug administration.
The late phase of the cutaneous hypersensitivity reaction was evaluated by determining the induration of the skin at 6 h. The skin fold thickness was measured with a modified Harpenden calliper before and 6 h after antigen administration. The calliper was modified by removing one spring in order to reduce pressure executed on the skinfold (Humphreys & Schuster, 1990). The difference in skinfold thickness was an indication of the oedema at that time. The perimeters of the late phase reactions were calculated as for the wheal-and-flare reactions. Each test was separated by at least a 3 week washout period and alternate arms were used at each time. The paired t-test was used to detect any significant change in blood pressure readings taken before and after treatment on each occasion (P c 0.05). The cutaneous hypersensitivity reactions were compared intraindividually on each of the four occasions using Friedmans two-way-analysis of variance test followed by a multiple comparative procedure (Miller, 1966) and P < 0.0083 was taken as being statistically significant throughout.
Results
Figures 1 and 2 shows the cutaneous hypersensitivity response to intradermally administered allergen after pretreatment with combinations of enalapril, indomethacin and ketotifen. The immediate hyperensitivity reaction caused whealand-flare reactions after 15 min which differed as follows at 15 min: (i) Pretreatment with enalapril, ketotifen and indomethacin (B) significantly reduced the immediate wheal-and-flare reaction when compared with treatment with placebo (A), enalapril (D) or enalapril and indomethacin (C), respectively. (ii) The flare reaction after enalapril and indomethacin (C) was significantly reduced when compared with pretreatment with enalapril alone (D), but compared Wheal (cm2)
Flare (cm2)
(n= 10)
*#
.*
The skin tests The immediate wheal-and-flare reactions were measured 15 min after antigen administration, i.e. aliquots of 5 PNU/0.05 ml of the southern grass mix were administered intra-dermally with a 27 gauge needle on the volare aspect of the forearms of the volunteers. The perimeters of both the wheal-and-flare reactions were transferred to transparent plastic sheets and the surface areas measured with digitised computer planimetry (Humphreys & Shuster, 1990).
8
6
30
40
50
Figure 1 Wheal-and-flare reactions at 15 min (mean ± s.d.). *Pretreatment with enalapril (10 mg), ketotifen (1 mg) and indomethacin (75 mg) (B, 1) significantly reduced the immediate cutaneous hypersensitivity response when compared with placebo (A, U), enalapril (D, U) or enalapril and indomethacin (C, U) pretreatment. **Pretreatment with C reduced only the flare reaction significantly when compared with D.
Enalapril and cutaneous hypersensitivity reaction Skin thickness (mm)
Area (cm2)
(n= 10) -Hd
-H
i*
=s M%s'S
.rr
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i6A
=M ElaIs
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Figure 2 Late phase of the cutaneous hypersensitivity reaction (6 h) (mean ± s.d.). *Pretreatment with enalapril (10 mg), ketotifen (1 mg) and indomethacin (75 mg) (B, 1) significantly reduced the surface areas of the late responses when compared to those after pretreatment with placebo (A, H) and enalapril (D, M) but did not differ significantly from those after enalapril and indomethacin (C, U) pretreatment. None of the other parameters was significantly reduced.
with placebo (A) this marked reduction did not reach significance at the 5% level. The wheal response was not influenced by the enalapril and indomethacin combination (C). The late phase of the hypersensitivity reaction showed no significant change in skinfold thickness when the different regimens were compared. Only the surface areas of this late response (6 h) were reducd by enalapril, indomethacin and ketotifen pretreatment (B) when compared with the placebo (A), and enalapril (D) regimens respectively. Pretreatment with enalapril and indomethacin (C) caused a non-significant reduction in this response when compared with both placebo (A) and enalapril alone (D). The cutaneous response after pretreatment with enalapril alone (D) did not differ significantly from placebo (A) in any of the parameters investigated. Enalapril (D) alone and in combination (B,C) resulted in a slight (i.e. 4,5%) drop in mean blood pressure. However, the changes in blood pressure on the different treatment modalities was not significant. Side effects When indomethacin was added to the treatment regimens three volunteers complained of a frontal headache and dizziness. Two complained of sedation while on ketotifen treatment. No other side effects were noted.
Discussion
Antigen challenge releases bradykinin (Atkins et al., 1987; De Shazo et al., 1979; Proud et al., 1983) and cutaneous response to intradermally administered bradykinin is known to be increased by ACE inhibition (Ferner et al., 1987, 1989, 1990; Fuller et al., 1987b; McAlpine & Thomson, 1989). Prostaglandins have been shown to be responsible for some of the vascular effects observed
715
with ACE inhibition (Swartz & Williams, 1982), and also, to be partially responsible for bronchoconstriction with intravenously administered bradykinin (Ichinose et al., 1990). Synergism was also demonstrated by an increased wheal-and-flare reaction when bradykinin and prostaglandins were simultaneously injected intradermally (Williams, 1979). However, prostaglandindependence of bradykinin reactions was not demonstrated with cutaneous reactions (Crossman & Fuller, 1988), pulmonary reactions (Fuller et al., 1987a; Ichinose et al., 1990), and after the administration of the cyclo-oxygenase inhibitor, indomethacin (McAlpine & Thomson, 1989). The latter is in contrast to the finding by Ferner et al. (1990) that another cyclo-ogenase inhibitor, sulindac, blunts whealing with intradermal bradykinin. The present study failed to demonstrate that ACE inhibition augments the cutaneous hypersensitivity reaction to intradermal antigen administration. This is in contrast with the finding, in human volunteers, by Warren et al. (1988) that the flare response, although not whealing, was increased, and the demonstration by Lindgren etal. (1987) in guinea pigs that both immediate and late cutaneous hypersensitivity reactions was augmented. In this study indomethacin was administered to eliminate the prostaglandin-mediated contribution to cutaneous reactions. The mast cell stabilizer, ketotifen (Grant et al., 1990; Huston et al., 1986) was added to prevent mast cell degranulation and the resultant release of the proteolytic ezymes responsible for bradykinin production (Proud et al., 1985; Swartz, 1988). The addition of both ketotifen and indomethacin to enalapril pretreatment reduced both the immediate wheal-andflare reaction (at 15 min) and the late phase reaction (at 6 h), suggesting that prostaglandins and other mast cell mediators are responsible for the cutaneous hypersensitivity reactions. This is in accordance with previous findings (Grant et al., 1990; Robinson, 1988; Schwartz, 1988). Indomethacin alone significantly reduced the flare reaction, but had no significant effect on whealing. This supports earlier work demonstrating that cyclooxygenase inhibition attenuates mostly the flare response, which is an a axon reflex caused by neuropeptides (Chapman & Loring, 1977), while the wheal response is virtually unchanged (Fuller et al., 1987c). We conclude that either endogenous bradykinin production during the cutaneous hypersensitivity reaction never reaches the exogenously administered supra-physiological concentrations used in previous experiments (Ferner et al., 1987, 1989, 1990; Fuller et al., 1987b; McAlpine & Thompson, 1987) where wheal and flare reactions were strictly dose related, or that bradykinin is rapidly and effectively broken down to inactive peptides by other carboxypeptidase enzymes (Sheikh & Kaplan, 1986a,b). In our experiments the attenuation of the cutaneous hypersensitivity reaction may probably be ascribed to the effect of ketotifen and indomethacin. The possibility of significantly increased tissue bradykinin levels are unlikely seeing that no reaction was augmented by ACE inhibition. Patients who develop angioedema after ACE inhibition may have another factor responsible for their abnormally increased kinin response, e.g. a carboxypeptidase N deficiency (Mathews et al., 1980; Schapira et al., 1983).
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References Atkins, P. C., Miragliotta, G., Talbot, S. F., Zweiman, B. & Kaplan, A. P. (1987). Activation of plasma hageman factor and kallikrein in ongoing allergic reactions in the skin. J. Immunol., 139, 2744-2748. Chapman, L. F. & Loring, F. (1977). Mechanisms of the flare reactions in human skin. J. invest. Dermatol., 69, 88-97. Choudry, N., McEwan, J. R. & Fuller, R. W. (1989). The effect of sulindac on the cough associated with angiotensin converting ezyme inhibitor therapy. Br. J. clin. Pharmac., 27, 657P-658P. Crossman, D. C. & Fuller, R. W. (1988). Bradykinin induced wheal and flare is not mediated by histamine release or cyclooxygenase products. Br. J. clin. Pharmac., 26, 113-115. De Shazo, R. D., Levinson, A. I., Dvorak, H. F. & Davis, R. W. (1979). The late phase skin reaction: evidence for activation of the coagulation system in an IgE-Dependent reaction in man. J. Immunol., 122, 692-698. Dixon, C. M. S., Fuller, R. W. & Barnes, P. J. (1987). The effect of an angiotensin converting enzyme inhibitor, ramipril, on bronchial responses to inhaled histamine and bradykinin in asthmatic subjects. Br. J. clin. Pharmac., 23, 91-93. Ferner, R. E., Simpson, J. M. & Rawlins, M. D. (1987). Effects of intradermal bradykinin after inhibition of angiotensin converting enzyme. Br. med. J., 294, 1119-1120. Ferner, R. E., Wilson, D., Paterson, J. R., Wilkinson, R. & Rawlins, M. D. (1989). The effects of intradermal bradykinin are potentiated by angiotensin converting enzyme inhibitors in hypertensive patients. Br. J. clin. Pharmac., 27, 337-342. Ferner, R. E., Kamali, F. & Rawlins, M. D. (1990). The effect of sulindac on dermal responses to bradykinin in normal subjects given an angiotensin converting enzyme inhibitor. Br. J. clin. Pharmac., 29, 363-365. Fuller, R. W., Conradson, T. B., Dixon, C. M. S., Crossman, D. C. & Barnes, P. J. (1987c). Sensory neuropeptide effects in human skin. Br. J. Pharmac., 92, 781-788. Fuller, R. W., Dixon, C. M. S., Cuss, M. C. & Barnes, P. J. (1987a). Bradykinin-induced bronchoconstriction in humans. Am. Rev. resp. Dis., 135, 176-180. Fuller, R. W., Warren, J. B., McCusker, M. & Dollery, C. T. (1987b). Effect of enalapril on the skin response to bradykinin in man. Br. J. clin. Pharmac., 23, 88-90. Grant, S. M., Goa, K. L., Filton, A. & Sorkin, E. M. (1990). Ketotifen: A Review of its pharmacodynamic and pharmacokinetic properties, and therapeutic use in asthma and allergic disorders. Drugs, 40, 412-448. Heavey, D. J., Barrow, S. E., Hickling, N. E. & Ritter, J. M. (1985). Aspirin causes short-lived inhibition of bradykinin-stimulated prostacyclin production in man. Nature, 318, 186-188. Humphreys, F. & Shuster, S. (1990). The effect of indomethacin on the kinetics of histamine, 48/80 and antigen whealing. Br. J. clin. Pharmac., 29, 195-199. Huston, D. P., Bressler, R. B., Kaliner, M., Sowell, L. K. & Baylor, M. W. (1986). Prevention of mast-cell degranulation by ketotifen in patients with physical urticarias. Ann. intern. Med., 104, 507-510. Ichinose, M., Belvisi, M. G. & Bames, P. J. (1990). Bradykinininduced bronchoconstriction in guinea pig in vivo: role of neural mechanisms. J. Pharmac. exp. Ther., 253, 594-599. Lindgren, B. R., Anderson, C. D. & Anderson, R. G. G. (1987). Potentiation of inflammatory reaction in guinea-pig skin by an angiotensin converting enzyme inhibitor (MK422). Eur. J. Pharmac., 135, 383-387. Mathews, K. P., Pan, P. M., Gardner, N. J. & Hugli, T. E.
(1980). Familial carboxypeptidase N deficiency. Ann. intern Med., 93, 443-445. McAlpine, L. G. & Thomson, N. C. (1989). The effect of indomethacin and enalapril on the cutaneous response to bradykinin. Br. J. clin. Pharmac., 27, 870-872. McAreavey, D. & Robertson, J. I. S. (1990). Angiotensin converting enzyme inhibitors and moderate hypertension. Drugs, 40, 326-345. Miller, R. G. (1966). Simultaneous statistical inference, pp 173-174. New York: McGraw-Hill. Proud, D., Maglashan, D W., Newball, H. H., Schulmans, A. & Lichtenstein, L. M. (1985). Immunoglobulin E mediated release of a kininogenase from purified human lung mast cells. Am. Rev. resp. Dis., 132, 405-406. Proud, D., Togias, A., Naclerio, R. M., Crush, S. A., Norman, P. S. & Lichtenstein, L. M. (1983). Kinins are generated in vivo following nasal airway challenge of allergic individuals with allergen. J. clin. Invest, 72, 1678-1685. Robinson, C. (1988). Mast cells and newly-generated lipid mediators. In Mast cells, mediators and disease, Holgate, S. T., pp. 149-174. London: Kluwer Academic Publishers. Schapira, M., Silver, L. D., Scott, C. F., Schmaier, A. H., Prograis, L. J., Curd, J. G. & Colman, R. W. (1983). Prekallikrein activation and high-molecular weight kininogen consumption in hereditory angioedema. New Engl. J. Med., 308, 1050-1053. Schwartz, L. B. (1988). Preformed mediators of human mast cells and basophils. In Mast cells, mediators and disease, Holgate, S. T., pp. 129-147. London: Kluwer Academic Publishers. Semple, P. F. & Herd, G. W. (1986). Cough and wheeze caused by inhibitors of angiotensin-converting enzyme. New Engl. J. Med., 314, 61. Sheikh, I. A. & Kaplan, A. P. (1986a). Studies of the digestion of bradykinin, lysyl bradykinin and kinin-degradation products by carboxypeptides A, B, and N. Biochem. Pharmac., 35, 1957-1963. Sheikh, I. A. & Kaplan, A. P. (1986b). Studies of the digestion of bradykinin, lys-bradykinin, and des-arg-bradykinin by angiotensin converting enzyme. Biochem. Pharmac., 35, 1951-1956. Studdy, P. R., Lapworth, R. & Bird, R. (1983). Angiotensinconverting enzyme and its clinical significance - a review. J. clin. Path., 36, 938-947. Swartz, S. L. & Williams, G. H. (1982). Angiotensin-converting enzyme inhibition and prostaglandins. Am. J. Cardiol., 49, 1405-1409. Warren, J. B., Newman, C. M. H., Pixley, F. J., Fuller, R. W. & Dollery, C. T. (1988). The importance of bradykinin and histamine in the skin response to antigen. Br. J. clin. Pharmac., 26, 803-805. Williams, G. H. (1988). Converting-enzyme inhibitors in the treatment of hypertension. New Engl. J. Med., 319, 1517-1525. Williams, T. J. (1979). Prostaglandin E2, prostaglandin 12 and the changes of inflammation. Br. J. Pharmac., 65, 517-524. Wood, S. M. & Mann, R. D. (1987). Angio-oedema and urticaria associated with angiotensin converting enzyme inhibitors. Br. med. J., 294, 91-92. Zusman, R. M. (1984). Renin- and non-renin-mediated antihypertensive actions of converting enzyme inhibitor. Kidney International, 25, 969-983.
(Received 9 April 199], accepted 3 July 1991)
Effect of enalapril on allergen-induced cutaneous hypersensitivity reaction J. R. SNYMAN & De K. SOMMERS Department of Pharmacology, University of Pretoria, PO Box 2034, Pretoria 0001, South Africa
1 To test the hypothesis that the in vivo inhibition of angiotensin converting enzyme in a patient who presents atopy, results in a significant increase in cutaneous bradykinin and prostaglandin production, the effect of enalapril on the cutaneous hypersensitivity reaction was examined in 10 atopic volunteers. 2 A crossover study design was used and volunteers were randomly allocated to treatment with either enalapril (10 mg) alone, or in combination with indomethacin (75 mg), with and without ketotifen (1 mg). Drugs were administered twice daily for 2 days. 3 Allergen (Southern Grass Mix) was administered intradermally 2 h after last drug dosage and the surface areas of the immediate wheal-and-flare-reactions were measured 15 min later. The late phase of the cutaneous response was evaluated 6 h later by determining skinfold thickness and surface area. 4 Enalapril alone had no effect on any of the parameters measured. 5 The cutaneous hypersensitivity reaction was significantly reduced with regard to both immediate and late cutaneous responses when the indomethacin and ketotifen combination was added to enalapril therapy. 6 When only indomethacin was added to enalapril pretreatment the flare reaction was significantly reduced, but whealing was unaffected. 7 This study presents further evidence that mast cell mediators other than prostaglandins are involved in the cutaneous hypersensitivity reaction. Furthermore, that endogenous bradykinin production after enalapril pretreatment either never reaches the supraphysiological concentrations used in previous experiments, or that bradykinin is rapidly and effectively broken down to inactive peptides by other carboxypeptidase enzymes.
Keywords enalapril indomethacin
cutaneous hypersensitivity reaction
ketotifen
Introduction
The angiotensin converting enzyme (ACE) is a nonspecific kininase II, responsible for the conversion of angiotensin I to angiotensin II, as well as the degradation of bradykinin to inactive peptides (Sheikh & Kaplan, 1986a,b). It is inhibited by enalapril, captopril, ramipril etcetera (McAreavey & Robertson, 1990; Studdy et al., 1983), and part of the antihypertensive effect of these ACE inhibitors has been postulated to result from an increase in tissue bradykinin, with the secondary production of vasodilatory prostaglandins (Williams, 1988; Zusman, 1984). These autacoids have been implicated in some ACE inhibitor side effects such as the dry cough and angioedema, and have even been claimed to be responsible for the worsening of bronchial asthma in
one patient treated with enalapril (Semple & Herd, 1986; Wood & Mann, 1987). Exogenous bradykinin administration has been used experimentally to induce
vasodilatation, cough, bronchoconstriction and cutaneous wheal-and-flare reactions in order to elucidate bradykinin's role in the above mentioned effects (Dixon et al., 1987; Ferner et al., 1987, 1989, 1990; Fuller et al., 1987a,b; Heavey et al., 1985; McAlpine & Thomson, 1989). In some experiments augmentation of bradykinin effects after ACE inhibition was demonstrated (Ferner et al., 1987, 1989, 1990; Fuller et al., 1987b; McAlpine & Thomson, 1989), while other authors failed to do this (Dixon et al., 1987; Fuller et al., 1987a). To test the hypothesis that the in vivo inhibition of
Correspondence: Dr J. R. Snyman, Department of Pharmacology, University of Pretoria, PO Box 2034, Pretoria 0001, South Africa
713
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J. R. Snyman & De K. Sommers
kininase II results in a significantly increased production of bradykinin and secondarily prostaglandins, the present experiment examines the possible contribution of these two substances to the cutaneous hypersensitivity reaction. Both bradykinin and prostaglandins have been shown to be implicated in the hypersensitivity response to antigens in vivo (Atkins et al., 1987; De Shazo et al., 1979; Proud et al., 1983).
Methods
Ten volunteers manifesting atopy (four female and six male subjects, aged 20-27 years) took part in this study after ethical approval and informed consent were obtained. They were all healthy and had no history of any dermatological abnormalities i.e. eczema, angioneurotic oedema or dermatographism. Strict inclusion criteria were applied and only volunteers allergic to grass pollens, and who gave a history of allergic rhinitis and/or conjunctivitis, or asthma during the pollen season, were admitted to the study. They were on no medication for at least 1 month prior to testing. The volunteers were selected on the basis of a modified prick test, using histamine and glycero-saline controls. They all manifested an immediate wheal reaction more or less equal to that of the positive histamine control, followed by a late phase reaction after skin prick test with the Southern Grass Mix (Bayer Miles). A crossover study design was used; the volunteers and the experimenters being blinded. The tablets, including placebo, were randomly assigned and administered by a colleague not participating in the experiment. Volunteers were allocated to four treatment modalities: (a) Placebo: to detect baseline values of reaction. (b) Enalapril (Logos) 10 mg, an ACE inhibitor (Ferner et al., 1987, 1990). (c) Enalapril 10 mg and 75 mg indomethacin, a nonsteroidal anti-inflammatory drug (Logos). The latter was added to suppress the formation of prostaglandins in the reaction (McAlpine & Thomson, 1989). (d) Enalapril 10 mg, and indomethacin 75 mg were given with 1 mg ketotifen, a known histamine1 receptor antagonist as well as a mast cell membrane stabilizer (Grant et al., 1990; Huston et al., 1986). This combination would tend to inhibit the contribution of both prostaglandin and histamine to the reaction. All tablets were taken 12 hourly for 48 h and the skin tests were initiated 2 h after the last drug administration.
The late phase of the cutaneous hypersensitivity reaction was evaluated by determining the induration of the skin at 6 h. The skin fold thickness was measured with a modified Harpenden calliper before and 6 h after antigen administration. The calliper was modified by removing one spring in order to reduce pressure executed on the skinfold (Humphreys & Schuster, 1990). The difference in skinfold thickness was an indication of the oedema at that time. The perimeters of the late phase reactions were calculated as for the wheal-and-flare reactions. Each test was separated by at least a 3 week washout period and alternate arms were used at each time. The paired t-test was used to detect any significant change in blood pressure readings taken before and after treatment on each occasion (P c 0.05). The cutaneous hypersensitivity reactions were compared intraindividually on each of the four occasions using Friedmans two-way-analysis of variance test followed by a multiple comparative procedure (Miller, 1966) and P < 0.0083 was taken as being statistically significant throughout.
Results
Figures 1 and 2 shows the cutaneous hypersensitivity response to intradermally administered allergen after pretreatment with combinations of enalapril, indomethacin and ketotifen. The immediate hyperensitivity reaction caused whealand-flare reactions after 15 min which differed as follows at 15 min: (i) Pretreatment with enalapril, ketotifen and indomethacin (B) significantly reduced the immediate wheal-and-flare reaction when compared with treatment with placebo (A), enalapril (D) or enalapril and indomethacin (C), respectively. (ii) The flare reaction after enalapril and indomethacin (C) was significantly reduced when compared with pretreatment with enalapril alone (D), but compared Wheal (cm2)
Flare (cm2)
(n= 10)
*#
.*
The skin tests The immediate wheal-and-flare reactions were measured 15 min after antigen administration, i.e. aliquots of 5 PNU/0.05 ml of the southern grass mix were administered intra-dermally with a 27 gauge needle on the volare aspect of the forearms of the volunteers. The perimeters of both the wheal-and-flare reactions were transferred to transparent plastic sheets and the surface areas measured with digitised computer planimetry (Humphreys & Shuster, 1990).
8
6
30
40
50
Figure 1 Wheal-and-flare reactions at 15 min (mean ± s.d.). *Pretreatment with enalapril (10 mg), ketotifen (1 mg) and indomethacin (75 mg) (B, 1) significantly reduced the immediate cutaneous hypersensitivity response when compared with placebo (A, U), enalapril (D, U) or enalapril and indomethacin (C, U) pretreatment. **Pretreatment with C reduced only the flare reaction significantly when compared with D.
Enalapril and cutaneous hypersensitivity reaction Skin thickness (mm)
Area (cm2)
(n= 10) -Hd
-H
i*
=s M%s'S
.rr
..
i6A
=M ElaIs
i-
e=
1 ;x _i. i
L2 20
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b.
A
40
60
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Figure 2 Late phase of the cutaneous hypersensitivity reaction (6 h) (mean ± s.d.). *Pretreatment with enalapril (10 mg), ketotifen (1 mg) and indomethacin (75 mg) (B, 1) significantly reduced the surface areas of the late responses when compared to those after pretreatment with placebo (A, H) and enalapril (D, M) but did not differ significantly from those after enalapril and indomethacin (C, U) pretreatment. None of the other parameters was significantly reduced.
with placebo (A) this marked reduction did not reach significance at the 5% level. The wheal response was not influenced by the enalapril and indomethacin combination (C). The late phase of the hypersensitivity reaction showed no significant change in skinfold thickness when the different regimens were compared. Only the surface areas of this late response (6 h) were reducd by enalapril, indomethacin and ketotifen pretreatment (B) when compared with the placebo (A), and enalapril (D) regimens respectively. Pretreatment with enalapril and indomethacin (C) caused a non-significant reduction in this response when compared with both placebo (A) and enalapril alone (D). The cutaneous response after pretreatment with enalapril alone (D) did not differ significantly from placebo (A) in any of the parameters investigated. Enalapril (D) alone and in combination (B,C) resulted in a slight (i.e. 4,5%) drop in mean blood pressure. However, the changes in blood pressure on the different treatment modalities was not significant. Side effects When indomethacin was added to the treatment regimens three volunteers complained of a frontal headache and dizziness. Two complained of sedation while on ketotifen treatment. No other side effects were noted.
Discussion
Antigen challenge releases bradykinin (Atkins et al., 1987; De Shazo et al., 1979; Proud et al., 1983) and cutaneous response to intradermally administered bradykinin is known to be increased by ACE inhibition (Ferner et al., 1987, 1989, 1990; Fuller et al., 1987b; McAlpine & Thomson, 1989). Prostaglandins have been shown to be responsible for some of the vascular effects observed
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with ACE inhibition (Swartz & Williams, 1982), and also, to be partially responsible for bronchoconstriction with intravenously administered bradykinin (Ichinose et al., 1990). Synergism was also demonstrated by an increased wheal-and-flare reaction when bradykinin and prostaglandins were simultaneously injected intradermally (Williams, 1979). However, prostaglandindependence of bradykinin reactions was not demonstrated with cutaneous reactions (Crossman & Fuller, 1988), pulmonary reactions (Fuller et al., 1987a; Ichinose et al., 1990), and after the administration of the cyclo-oxygenase inhibitor, indomethacin (McAlpine & Thomson, 1989). The latter is in contrast to the finding by Ferner et al. (1990) that another cyclo-ogenase inhibitor, sulindac, blunts whealing with intradermal bradykinin. The present study failed to demonstrate that ACE inhibition augments the cutaneous hypersensitivity reaction to intradermal antigen administration. This is in contrast with the finding, in human volunteers, by Warren et al. (1988) that the flare response, although not whealing, was increased, and the demonstration by Lindgren etal. (1987) in guinea pigs that both immediate and late cutaneous hypersensitivity reactions was augmented. In this study indomethacin was administered to eliminate the prostaglandin-mediated contribution to cutaneous reactions. The mast cell stabilizer, ketotifen (Grant et al., 1990; Huston et al., 1986) was added to prevent mast cell degranulation and the resultant release of the proteolytic ezymes responsible for bradykinin production (Proud et al., 1985; Swartz, 1988). The addition of both ketotifen and indomethacin to enalapril pretreatment reduced both the immediate wheal-andflare reaction (at 15 min) and the late phase reaction (at 6 h), suggesting that prostaglandins and other mast cell mediators are responsible for the cutaneous hypersensitivity reactions. This is in accordance with previous findings (Grant et al., 1990; Robinson, 1988; Schwartz, 1988). Indomethacin alone significantly reduced the flare reaction, but had no significant effect on whealing. This supports earlier work demonstrating that cyclooxygenase inhibition attenuates mostly the flare response, which is an a axon reflex caused by neuropeptides (Chapman & Loring, 1977), while the wheal response is virtually unchanged (Fuller et al., 1987c). We conclude that either endogenous bradykinin production during the cutaneous hypersensitivity reaction never reaches the exogenously administered supra-physiological concentrations used in previous experiments (Ferner et al., 1987, 1989, 1990; Fuller et al., 1987b; McAlpine & Thompson, 1987) where wheal and flare reactions were strictly dose related, or that bradykinin is rapidly and effectively broken down to inactive peptides by other carboxypeptidase enzymes (Sheikh & Kaplan, 1986a,b). In our experiments the attenuation of the cutaneous hypersensitivity reaction may probably be ascribed to the effect of ketotifen and indomethacin. The possibility of significantly increased tissue bradykinin levels are unlikely seeing that no reaction was augmented by ACE inhibition. Patients who develop angioedema after ACE inhibition may have another factor responsible for their abnormally increased kinin response, e.g. a carboxypeptidase N deficiency (Mathews et al., 1980; Schapira et al., 1983).
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(Received 9 April 199], accepted 3 July 1991)
