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Department of Physiology, University of Kentucky, Lexington, Kentucky 40536-0084
ABSTRACT
INTRODUCTION
METHODS
RESULTS
DISCUSSION
ACKNOWLEDGEMENTS
FOOTNOTES
REFERENCES
ABSTRACT 
Hong, Ju-Lun, and Lu-Yuan Lee. Cigarette smoke-induced
bronchoconstriction: causative agents and role of thromboxane receptors. J. Appl. Physiol. 81(5):
2053-2059, 1996.
Inhalation of cigarette smoke induces a biphasic
bronchoconstriction in guinea pigs: the first phase is induced by a
combination of cholinergic reflex and tachykinins, whereas the second
phase involves cyclooxygenase metabolites (J.-L. Hong, I. W. Rodger,
and L.-Y. Lee. J. Appl. Physiol. 78:
2260-2266, 1995
[Medline]
). This study was carried out to further determine
the causative agents in the smoke and the types of prostanoid receptors
and endogenous prostanoids mediating the bronchoconstriction. Inhalation of 10 ml of high-nicotine cigarette smoke consistently elicited the biphasic bronchoconstriction in anesthetized and artificially ventilated guinea pigs. Pretreatment with hexamethonium (10 mg/kg iv) significantly reduced the first-phase bronchoconstriction but did not have any measurable effect on the second-phase response. In
sharp contrast, gas-phase smoke did not elicit any bronchoconstrictive effect. Furthermore, when the animals were challenged with low-nicotine cigarette smoke, only a single second-phase response was evoked, accompanied by increases in thromboxane (Tx)
B2 (a stable metabolite of
TxA2), prostaglandin (PG)
D2,
PGF2
in the bronchoalveolar lavage fluid. The bronchoconstrictive response induced by low-nicotine smoke was completely prevented by pretreatment with SQ-29548 (0.3 mg/kg
iv), a TxA2-receptor antagonist.
These results indicate that 1)
nicotine is the primary causative agent responsible for the first-phase
bronchoconstriction and 2)
nonnicotine smoke particulates evoke the release of
TxA2,
PGD2, and
PGF2, which act on
TxA2 receptors on airway smooth
muscles and induce the second-phase response to cigarette smoke.
hexamethonium; SQ-29548; tachykinins; guinea pigs; prostaglandins
INTRODUCTION INHALATION OF CIGARETTE SMOKE has repeatedly been shown
to induce acute bronchoconstriction in various species including humans (9, 15, 20). In a previous study, Hong et al. (9) have reported that inhalation of cigarette smoke in guinea pigs induces an
acute bronchoconstriction consisting of two distinct phases that are
different in both the time course and the underlying mechanism; the
first phase is induced by a combination of cholinergic reflex and
tachykinin release, whereas the second phase is inhibited by a
pretreatment with indomethacin, suggesting the involvement of
arachidonic acid metabolites of the cyclooxygenase pathway. Several
questions regarding the smoke-induced bronchoconstriction remained
unanswered in that study. First, although nicotine has been shown to be
the major causative agent in cigarette smoke responsible for activating
bronchopulmonary sensory afferents and for inducing an immediate
bronchoconstriction via the cholinergic reflex in dogs (8, 11, 14), the
smoke constituent(s) responsible for the release of tachykinins and
cyclooxygenase metabolites in guinea pigs has not yet been identified.
Second, two types of prostanoid receptors, thromboxane (Tx)
A2-sensitive (TP) receptors and
one subtype of prostaglandin (PG)
E2-sensitive (EP1)
receptors (3, 18) that are known to mediate bronchoconstriction, have been identified in the guinea pig airways; the receptor types and the
bronchoconstrictive prostanoids responsible for the smoke-induced bronchoconstriction have not been elucidated.
Therefore, the purposes of this study were
1) to identify the cigarette smoke
constituents that induce the first- and second-phase responses and
2) to determine the types of
prostanoid receptors and endogenous prostanoids involved in the
smoke-induced second-phase bronchoconstriction.
METHODS Male Hartley guinea pigs, ranging from 330 to 580 g body weight, were
anesthetized with an intraperitoneal injection of Transpulmonary pressure (Ptp) was measured as the difference between
the tracheal pressure (Ptr) and the intrapleural pressure with a
differential pressure transducer (Validyne MP-45-28, range ±50
cmH2O) positioned between a side
arm of the tracheal cannula and the intrapleural cannula. Respiratory
flow was measured with a pneumotachograph and a differential pressure
transducer (Validyne MP-45-14, range ±2
cmH2O) and was integrated to give
VT; the pneumotachograph had a
linear flow-pressure relationship in the range of 0-20 ml/s and a
flow resistance of 0.046 cmH2O · ml Two types of cigarettes, high (HN) and low nicotine (LN) (University of
Kentucky series 2R1 and 4A1, respectively), were used in this study;
the nicotine content in the latter (0.17 mg/cigarette) was
approximately one-fifteenth of that in the former (2.45 mg/cigarette), with negligible differences in other smoke constituents (5). The
methods of generating and delivering cigarette smoke were the same as
those described in a previous report (15). Briefly, whole smoke (WS)
was generated directly from the midportion of a lighted cigarette by a
smoke machine (7), whereas gas-phase smoke (GPS) was obtained by
passing the WS through a standard glass-fiber Cambridge filter that
removed all (>99%) nicotine and smoke particulates from the WS (28).
Ten milliliters of either WS or GPS were then delivered into the
airways via the inspiratory line of the respirator over three
consecutive respirator cycles. The lungs were hyperinflated (3 × VT) periodically and also
before each smoke challenge to maintain a constant volume history and
to avoid atelectasis (19).
Bronchoalveolar lavage fluid (BALF) was collected from guinea pigs
prepared in the same manner as described above. Ten milliliters of 0.1 M phosphate buffer (pH 7.25) containing 10 µg/ml of meclofenamate, a
cyclooxygenase inhibitor, were injected into the lungs via the tracheal
cannula in each animal, withdrawn immediately, and reinjected; after
the procedure was repeated three times, the recovered BALF was filtered
through surgical gauze to remove the mucus, centrifuged to remove
cells, and stored at Experimental Protocol
-chloralose (100 mg/kg) and urethan (500 mg/kg). The trachea was cannulated below the
larynx via a tracheostomy with a tracheal cannula through which the
animal was ventilated with a respirator (Harvard model 683) at a
constant rate of 44 breaths/min. Tidal volume
(VT) was adjusted according to
the body weight (8 ml/kg) and was kept constant in each experiment. The
jugular vein and carotid artery were cannulated for intravenous
injections and for arterial blood pressure measurement with a pressure
transducer (Statham P23AA), respectively. A catheter for measuring
intrapleural pressure was inserted into the right intrapleural space
between the fifth and sixth ribs via a surgical incision that was
subsequently sutured and further sealed airtight with silicone jelly.
The pneumothorax produced by this procedure was corrected by a brief
opening of the intrapleural catheter to the ambient air during a held
hyperinflation (3 × VT).
The animals were paralyzed with an intravenous injection of pancuronium bromide (30 µg/kg) during the experiment to prevent the animals' spontaneous breathing. Each time when the effect of pancuronium bromide
wore off (~1 h) and before additional pancuronium bromide was given,
the depth of anesthesia was checked and additional doses of
anesthetics, if necessary, were administered to abolish the pain
reflex. A heating pad was placed under the animal, which was lying in a
supine position, to maintain the body temperature at 36-37°C
during the experiment.
1 · s.
All signals were recorded on a chart recorder (Grass model 7), and
total pulmonary resistance
(RL) and dynamic lung
compliance (Cdyn) were analyzed by an on-line computer on a
breath-by-breath basis (13); RL
was determined by dividing the difference between the transpulmonary
pressures by the sum of the flows at equal lung volumes on inspiration
and expiration.
80°C until the assay. Concentrations of
prostanoids in the BALF were measured with the enzyme immunoassay method (Vmax kinetic microplate reader, Molecular Devices). Because PGE2 is rapidly converted in the
lungs to its 13,14-dihydro-15-keto metabolite that is also unstable and
undergoes further degradation to PGA products, these
PGE2 metabolites were first
converted to stable bicyclo-PGE2
before the assay. For a similar reason,
PGD2 was first converted to a
stable methoxime (MOX) derivative
(PGD2-MOX) before the assay. All
samples were tested in duplicate. Results are expressed in picograms
per milliliter of BALF; the detection limits for
bicyclo-PGE2,
TxB2,
PGD2-MOX, and
PGF2 measurements were 2, 7, 10, and 30 pg/ml, respectively.
Study series 2. To examine the possible role of smoke particulates, the responses of RL and Cdyn to HN-WS and GPS generated from the same cigarette were compared in the same animals (n = 6) separated by 30 min. The sequence of delivery of HN-WS and GPS was altered among animals to achieve a balanced design.
Study series 3. To investigate the reproducibility of the bronchoconstrictive response to WS generated from LN cigarettes (LN-WS), the responses of RL and Cdyn to LN-WS were studied twice, separated by 30 min, in each animal (n = 5).
Study series 4. Because a tachyphylaxis of the response to LN-WS was found in study series 3, the role of TP receptors in mediating the second-phase response was studied in two separate groups. In the control group (n = 6), animals without any pharmacological pretreatment were challenged with LN-WS. In the other group (n = 6), responses to LN-WS were measured 15 min after a bolus injection of SQ-29548 (0.3 mg/kg iv), a selective TP-receptor antagonist (21). To examine any possible effect caused by the vehicle, the response to LN-WS was studied after a bolus injection of the same volume of the vehicle solution for SQ-29548 in two additional animals.
Study series 5. To determine the types
of endogenous prostanoids released during the second-phase response,
the concentrations of PGE2
metabolites, TxB2,
PGD2, and
PGF2 in BALF collected from
both control animals (n = 6) and those
challenged with 10 ml of LN-WS (n = 6)
were measured; in the latter group, BALF was obtained ~1.5 min after
the smoke challenge when the Ptr reached its plateau.
Materials
A mixture of 2%-chloralose (Sigma Chemical) and 10%
urethan (Sigma Chemical) was dissolved in a 2% borax (Sigma Chemical) solution. Pancuronium bromide (2 mg/ml; Elkins-Sinn Pharmaceuticals) was diluted in a 1:30 ratio in saline. Hexamethonium bromide (Sigma Chemical) was dissolved in saline. SQ-29548 (Cayman Chemical) was
dissolved in ethanol and diluted with 0.02%
Na2CO3;
this solution was further diluted in saline on the day of use to a
concentration of 0.33 mg/ml (ethanol-0.02%
Na2CO3-saline = 0.5:9.5:20, vol/vol). The enzyme immunoassay kits were purchased from
Cayman Chemical.
Statistical Analysis
Unless otherwise mentioned, a two-way analysis of variance (ANOVA) was used for the statistical analysis of data. One factor of the two-way ANOVA was the effect of smoke challenge in all study series; the other factor was the effect of hexamethonium in study series 1, effect of removing particulate matter in study series 2, effect of the number of challenges in study series 3, and effect of SQ 29548 in study series 4. When the two-way ANOVA showed a significant interaction, pairwise comparisons were made with a post hoc analysis (Fisher's least significant difference test). In each animal, we averaged the six consecutive breaths immediately before the smoke challenge as the baseline, the six consecutive breaths with the maximum increase in RL that occurred within the first 20 breaths after the smoke inhalation as the first-phase response, and breaths 75-80 (last six breaths in Figs. 1, 2, 3, 4) as the second-phase response.
,
Control responses; 
, responses to smoke 15 min after pretreatment
with hexamethonium (10 mg/kg iv) in the same animals. Cigarette smoke
was delivered by respirator between the 2 arrows. Data are means ± SE.
) and gas-phase
smoke () generated from high-nicotine cigarettes (10 ml for both) in
the same anesthetized guinea pigs (n = 6). A: RL.
B: Cdyn. Cigarette smoke was delivered
by respirator between the 2 arrows. Sequence of challenges with these 2 different types of cigarette smoke was altered among animals. Data are
means ± SE.
) and 2nd () smoke inhalation
challenges to allow both RL
(A) and Cdyn
(B) to return to their baselines. Data are means ± SE.
, Responses in control
group (n = 6); , responses in a
matching group (n = 6) pretreated with SQ-29548 (0.3 mg/kg iv) 15 min before smoke challenge. Cigarette smoke
was delivered by respirator between the 2 arrows. Data are means ± SE.
RESULTS
Study Series 1: Effect of Hexamethonium on Bronchoconstriction Induced by HN-WS
Inhalation of 10 ml of HN-WS induced an immediate increase in RL from a baseline of 0.22 ± 0.03 cmH2O · ml1 · s
to a peak of 1.69 ± 0.35 cmH2O · ml1 · s
in 10-15 breaths (P < 0.01;
Fig. 1, Table 1).
RL then gradually declined
toward the baseline but remained moderately elevated for a sustained
period of time (>1.5 min), although it did not reach a significant
level (Fig. 1, Table 1). Cdyn decreased from a baseline of 0.48 ± 0.05 to 0.19 ± 0.05 ml/cmH2O
(P < 0.01) within 10-15 breaths
after the smoke challenge and remained significantly lower than the
baseline (P < 0.01) for the rest of
the recording period (Table 1, Fig. 1). These responses were similar to
those described in a previous study (9) and could be divided into two
distinct phases after appropriate pharmacological interventions: the
first phase reached a peak rapidly within 20 breaths after the smoke
inhalation and the second-phase response developed slowly and reached
its plateau at ~1.5 min after the smoke challenge. Pretreatment with
hexamethonium did not change the baselines of either
RL or Cdyn, but it significantly
reduced the first-phase response in
RL and Cdyn by 86 (P < 0.01) and 50%
(P < 0.01), respectively (Fig. 1).
However, hexamethonium pretreatment did not significantly affect the
second-phase response of either
RL or Cdyn (Fig. 1, Table 1).
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Cigarette smoke also induced a distinct cardiovascular response. The mean arterial blood pressure (MABP) first decreased transiently from a baseline of 55 ± 4 to 36 ± 2 mmHg (P < 0.01), concomitant with the first-phase response in RL and Cdyn. MABP then returned toward the baseline before a more sustained decrease (35 ± 4 mmHg; P < 0.01) slowly developed. After the smoke challenge, heart rate (HR) did not change initially but then gradually decreased from a baseline of 286 ± 11 beats/min to a steady state of 243 ± 8 beats/min after ~40 breaths (P < 0.01). Pretreatment with hexamethonium significantly reduced the baseline MABP to 30 ± 3 mmHg (P < 0.01) and decreased the baseline HR to 216 ± 6 beats/min (P < 0.01); furthermore, it completely abolished the changes in MABP and HR after the smoke challenge (Fig. 1).
Study Series 2: Effect of Removing Particulates from Cigarette Smoke on Bronchoconstriction
In sharp contrast to the response induced by HN-WS, the same volume of GPS did not elicit any detectable changes in RL or Cdyn during either the first or second phase (Table 1, Fig. 2). Similarly, GPS challenge did not cause significant changes in MABP or HR.Study Series 3: Bronchoconstriction Induced by LN-WS
Inhalation of LN-WS induced a single delayed bronchoconstriction without any detectable first-phase response (Fig. 3). The time course of this delayed response was very similar to the second-phase response to HN-WS (9): beginning 15-25 breaths after the smoke inhalation, RL gradually increased and Cdyn gradually decreased from their baselines (RL, 0.16 ± 0.01 cmH2O · ml1 · s;
Cdyn, 0.64 ± 0.05 ml/cmH2O)
and reached a steady state (RL, 0.37 ± 0.02 cmH2O · ml1 · s,
P < 0.01; Cdyn, 0.20 ± 0.04 ml/cmH2O,
P < 0.01) ~50 breaths after the
challenge (Fig. 3). Surprisingly, the response to the second LN-WS
challenge was consistently smaller than that to the first one in all
five animals tested (Fig. 3). However, the responses of
RL (0.22 ± 0.02 cmH2O · ml1 · s)
and Cdyn (0.35 ± 0.06 ml/cmH2O) to the second challenge were still significantly higher than the baseline
RL (0.15 ± 0.01 cmH2O · ml1 · s;
P < 0.05) and lower than the
baseline Cdyn (0.58 ± 0.06 ml/cmH2O;
P < 0.01), respectively. In
addition, a third LN-WS challenge was given in four of these animals,
and the response was not significantly different from that to the
second one.
Study Series 4: Effect of SQ-29548 on Bronchoconstriction Induced by LN-WS
In the control group, LN-WS induced a delayed response (Fig. 4). In the animals receiving the pretreatment with SQ-29548, the delayed bronchoconstriction induced by LN-WS was completely prevented; the RL and Cdyn ~1.5 min after the smoke challenge were not significantly different from the baseline RL and Cdyn (Fig. 4, Table 1). In the two animals pretreated with the vehicle solution for SQ-29548, the responses of RL and Cdyn to LN-WS were similar to those obtained in the control group. To determine whether lung atelectasis was involved in the second-phase response, we tested the effect of a held hyperinflation (4 × VT for 5 s) on RL and Cdyn in four additional animals. When the delayed response induced by LN-WS reached its plateau [change in (
) RL = 118 ± 2% of the baseline, P < 0.05;
Cdyn = 74 ± 3%, P < 0.05, one-way ANOVA] ~1.5 min after the smoke challenge,
hyperinflation of the lungs twice effectively reversed the
bronchoconstriction (e.g., Fig. 5);
RL = 31 ± 3% of the
baseline, P > 0.05; Cdyn = 9 ± 2%, P > 0.05 (one-way ANOVA).
; inspiratory flow: positive).
Cigarette smoke was delivered by respirator between the 2 arrows.
Hyperinflation of lungs was produced by occluding expiratory line of
respirator for 4 consecutive cycles and then maintained for 5 s by
turning off respirator.
Study Series 5: Effect of LN-WS on Prostanoid Levels in BALF
The concentration of TxB2 in the BALF of the control group was 75.7 ± 22.2 pg/ml; it was elevated to 1,143.1 ± 255.3 pg/ml (P < 0.01, t-test) in the guinea pigs challenged with LN-WS. The concentration of PGD2 was below the detection limit (<10 pg/ml) in five of the six control animals and 67.8 pg/ml in the remaining one; it was significantly higher in animals challenged with LN-WS (120.0 ± 6.8 pg/ml; P < 0.01, Wilcoxon rank sum test). The concentration of PGF2 was undetectable (<30
pg/ml) in all six control animals and 61.4 ± 7.0 pg/ml in the smoke
group (P < 0.01, Wilcoxon rank sum
test). The concentration of PGE2
was 12.2 ± 3.9 pg/ml in the control group, and no significant
difference was found in the smoke group (18.5 ± 2.2 pg/ml;
P > 0.05, t-test).
DISCUSSION
Constituents in cigarette smoke can be classified into two major categories based on their physical nature: those in the particulate phase (including nicotine) and those in the gas phase. Previous studies have suggested that nicotine is the major bronchoconstrictive agent in the cigarette smoke that causes immediate bronchoconstriction in dogs (8, 11, 14). However, the relative role of nicotine in the cigarette smoke-induced first- and second-phase bronchoconstriction in guinea pigs (9) was not known. Although hexamethonium, a nicotinic acetylcholine-receptor antagonist, prevented the first-phase bronchoconstrictive response, it had no effect on the second phase (Fig. 1, Table 1), indicating that nicotine was only responsible for evoking the first-phase response. This finding is not surprising because a previous study (9) has shown that the first-phase response to cigarette smoke is mediated by a combination of cholinergic reflex and tachykinin release; both of these mechanisms are presumably evoked by activation of bronchopulmonary C-fiber endings, and nicotine is known to be a potent stimulant of these afferent endings (11, 14). The previous finding that the stimulatory effect of nicotine on bronchopulmonary C-fiber endings is also blocked by pretreatment with hexamethonium lends additional support to this conclusion (14).
Results of the present study further suggest that the nonnicotine particulate matter is the primary causative agent producing the second-phase response to cigarette smoke because the response persisted even after hexamethonium pretreatment (Fig. 1, Table 1), whereas GPS failed to evoke any detectable effect (Fig. 2, Table 1). Additionally, LN-WS did not elicit any measurable first-phase bronchoconstriction but induced a clear second-phase response (Fig. 3, Table 1). The particulate matter of cigarette smoke consists of thousands of identifiable chemical components, and the specific causative agent(s) cannot be identified in this study.
It has been demonstrated that the second-phase bronchoconstrictive
response to smoke persists even after the first-phase
bronchoconstriction is completely blocked by a combination of atropine
and tachykinin antagonists (9), suggesting that the second-phase
response is not caused by the recirculation of the same agents that
evoke the first-phase response (12). Furthermore, the second-phase response is completely inhibited by indomethacin pretreatment (9),
indicating a role of cyclooxygenase metabolites. Indeed, the levels of
several prostanoids (e.g., TxA2
and PGF2) and their
metabolites in BALF and/or serum have been shown to increase after inhalation of a larger volume of cigarette smoke (24, 25, 29). In
addition, two types of prostanoid receptors, TP receptors and
EP1 receptors that are involved in
prostanoid-induced bronchoconstriction, have been identified in guinea
pig airways (3, 18). Therefore, the exact types of prostanoids and
their receptors mediating the second-phase bronchoconstriction remain to be determined. SQ-29548 is a potent and selective TP-receptor antagonist and does not block
PGE2-induced tracheal contraction in guinea pigs (21). Our results demonstrated that the second-phase response to LN-WS was completely prevented by pretreatment with SQ-29548 (Fig. 4, Table 1), indicating that TP-receptor activation was
responsible for the second-phase bronchoconstriction. Interestingly, the TP receptor is also the primary receptor mediating
prostanoid-induced constriction of human airways (1). Although TP
receptors are more sensitive to
TxA2, as is demonstrated by its
higher sensitivity to U-46619, a
TxA2 mimetic, than to other
prostanoids, some other prostanoids such as
PGD2 and
PGF2 may also activate TP
receptors to some extent and induce airway smooth muscle contraction
(21, 26). Therefore, we assayed four naturally occurring prostanoids or
their metabolites in the BALF of both control animals and animals challenged with LN-WS to determine the types of prostanoids that may
have a role in the activation of TP receptors after smoke challenge.
Although our data showed that the concentrations of all three major
bronchoconstrictive prostanoids
(TxA2,
PGD2, and PGF2) increased after smoke
challenge, the much higher increase in
TxB2 in the BALF in conjunction
with the high sensitivity of TP receptors to
TxA2 suggests an important role of
TxA2 in mediating the second-phase
response to cigarette smoke. Several prostanoids, including
TxA2 and
PGF2, have been shown to
increase pulmonary vascular pressure, vascular permeability, and
transvascular filtration rate in the lungs, which may then lead to
pulmonary edema and reduced lung compliance (17). However, the fact
that hyperinflation of the lungs at the plateau of the second-phase
response immediately reversed the increased
RL and the decreased Cdyn (Fig.
5) suggests that constriction and/or closure of small airways,
followed by regional atelectasis instead of lung edema, is the primary
cause of the observed changes.
The mechanism underlying the attenuated response to the second LN-WS challenge is not completely understood. U-46619 (2 µg/kg iv; Cayman Chemical), a selective TP-receptor agonist, evoked bronchoconstriction at an intensity similar to that caused by LN-WS but did not cause any tachyphylaxis in two consecutive challenges in three animals tested (Hong and Lee, unpublished observations). Thus a reduced sensitivity of TP receptors of airway smooth muscles during the second smoke challenge cannot account for the tachyphylaxis. It seems plausible that the difference between the two responses may be due to a reduced synthesis of prostanoids. It has been reported that nicotine in vitro selectively inhibits TxA2 synthesis in macrophage-like cells (6), platelets, and lung tissues (25); whether the first cigarette smoke inhalation challenge inhibited TxA2 synthase and led to a smaller amount of TxA2 being released in response to the second challenge is not known. Alternatively, substrate-induced (suicide) inactivation of cyclooxygenase (27) and Tx synthase (10) may also play a role in the observed tachyphylaxis. Coincidently, when the systemic infusion of acid solution that triggered the release of TxA2 from platelets was repeated in 1.5-h intervals in anesthetized cats, a smaller amount of TxA2 was released and, consequently, less intense pulmonary hypertensive and hyperventilatory responses were elicited during the second and third challenges (23).
In addition to bronchoconstriction, cardiovascular changes in the reflex response elicited by activation of pulmonary C fibers include transient hypotension and bradycardia in dogs, cats, and rats (4). In anesthetized spontaneous-breathing guinea pigs, however, stimulation of pulmonary C fibers by intravenous capsaicin, a selective C-fiber stimulant, elicits hypotension without significant changes in HR (22). Similar cardiovascular responses (transient hypotension without accompanying bradycardia) were also observed immediately after the HN-WS inhalation into the airways of anesthetized and artificially ventilated guinea pigs in this study, coinciding with the first-phase bronchoconstriction (Fig. 1) that stems partially from vagal cholinergic reflex (9). The fact that pretreatment with hexamethonium completely prevented the transient hypotension seems to support the notion that nicotine in the cigarette smoke is responsible for activating bronchopulmonary C fibers (11, 13). Alternatively, because systemic administration of hexamethonium also blocks the ganglionic transmission of the autonomic nervous system, the hypotensive response elicited by activating other afferents or evoked by smoke constituents other than nicotine will also be blocked. The mechanisms underlying the delayed and prolonged hypotension and bradycardia induced by cigarette smoke could not be determined in our study. Activation of bronchopulmonary C fibers by cigarette smoke triggers the release of calcitonin gene-related peptide (15), a potent vasodilator, which is colocalized in and coreleased from these endings with tachykinins (16). Furthermore, a direct negative inotropic effect of nicotine on the guinea pig heart has been reported, and this effect is also blocked by hexamethonium (2).
In conclusion, our present study demonstrates that nicotine is the
primary agent responsible for triggering the first-phase bronchoconstrictive response to cigarette smoke, whereas nonnicotine smoke particulates play a major role in the second-phase response in
guinea pigs. Additionally, these results suggest that smoke particulates induce the second-phase response by releasing
bronchoconstrictive prostanoids
TxA2,
PGD2, and
PGF2 that act on TP receptors of airway smooth muscles and cause a constriction and/or
closure of peripheral airways.
ACKNOWLEDGEMENTS
The authors are grateful to Dr. Hsin-Hsiung Tai for helpful advice and to Dr. Timothy McClintock for making the Vmax kinetic microplate reader available for the enzyme immunoassay experiment. The authors also thank Dr. Mary K. Rayens for statistical consultation and Robert Morton for technical assistance.
FOOTNOTES
Address reprint requests to L.-Y. Lee.
Received 14 December 1995; accepted in final form 12 July 1996.
REFERENCES
| 1. | Armour, C. L., P. R. L. Johnson, M. L. Alfredson, and J. L. Black. Characterization of contractile prostanoid receptors on human airway smooth muscle. Eur. J. Pharmacol. 165: 215-222, 1989. |
| 2. | Becker, B. F., and E. Gerlach. Acute effects of nicotine on hemodynamic and metabolic parameters of isolated, perfused hearts of guinea pigs and rats. Klin. Wochenschr. 62: 58-66, 1984. |
| 3. | Coleman, R. A., and I. Kennedy. Characterization of the prostanoid receptors mediating contraction of guinea pig isolated trachea. Prostaglandins 29: 363-375, 1985. |
| 4. | Dawes, G. S., and J. H. Comroe, Jr. Chemoreflexes from the heart and lungs. Physiol. Rev. 34: 167-201, 1954. |
| 5. | Diana, J. N., and A. Vaught. Research Cigarettes. Lexington: Univ. of Kentucky Printing Services, 1990. |
| 6. | Goerig, M., V. Ullrich, G. Schettler, C. Foltis, and A. Habenicht. A new role for nicotine: selective inhibition of thromboxane formation by direct interaction with thromboxane synthase in human promyelocytic leukemia cells differentiating into macrophages. Clin. Investig. 70: 239-243, 1992. |
| 7. | Griffith, R. B., and R. Hancock. Simultaneous mainstream-sidestream smoke exposure systems. I. Equipment and procedures. Toxicology 34: 123-138, 1985. |
| 8. | Hartiala, J. J., C. Mapp, R. A. Mitchell, and W. M. Gold. Nicotine-induced respiratory effects of cigarette smoke in dogs. J. Appl. Physiol. 59: 64-71, 1985. |
| 9. | Hong, J.-L., I. W. Rodger, and L.-Y. Lee. Cigarette smoke-induced bronchoconstriction: cholinergic mechanisms, tachykinins, and cyclooxygenase products. J. Appl. Physiol. 78: 2260-2266, 1995. |
| 10. | Jones, D. A., and F. A. Fitzpatrick. "Suicide" inactivation of thromboxane A2 synthase. J. Biol. Chem. 265: 20166-20171, 1990. |
| 11. | Kou, Y. R., D. T. Frazier, and L.-Y. Lee. The stimulatory effect of nicotine on vagal pulmonary C-fibers in dogs. Respir. Physiol. 76: 347-356, 1989. |
| 12. | Lauzon, A.-M., G. Dechman, and J. H. T. Bates. Time course of respiratory mechanics during histamine challenge in the dog. J. Appl. Physiol. 73: 2643-2647, 1992. |
| 13. | Lee, B. P., R. F. Morton, and L.-Y. Lee. Acute effects of acrolein on breathing: role of vagal bronchopulmonary afferents. J. Appl. Physiol. 72: 1050-1056, 1992. |
| 14. | Lee, L.-Y., Y. R. Kou, D. T. Frazier, E. R. Beck, T. E. Pisarri, H. M. Coleridge, and J. C. G. Coleridge. Stimulation of vagal pulmonary C-fibers by a single breath of cigarette smoke in dogs. J. Appl. Physiol. 66: 2032-2038, 1989. |
| 15. | Lee, L.-Y., Y.-P. Lou, J.-L. Hong, and J. M. Lundberg. Cigarette smoke-induced bronchoconstriction and release of tachykinins in guinea pig lungs. Respir. Physiol. 99: 173-181, 1995. |
| 16. | Lundberg, J. M., and A. Saria. Polypeptide-containing neurons in airway smooth muscle. Annu. Rev. Physiol. 40: 557-572, 1987. |
| 17. | Malik, A. B., M. B. Perlman, J. A. Cooper, T. Noonan, and R. Bizios. Pulmonary microvascular effects of arachidonic acid metabolites and their role in lung vascular injury. Federation Proc. 44: 36-42, 1995. |
| 18. | McKenniff, M., I. W. Rodger, P. Norman, and P. J. Gardiner. Characterisation of receptors mediating the contractile effects of prostanoids in guinea-pig and human airways. Eur. J. Pharmacol. 153: 149-159, 1988. |
| 19. | Mead, J., and C. Collier. Relation of volume history of lungs to respiratory mechanics in anesthetized dogs. J. Appl. Physiol. 14: 669-678, 1959. |
| 20. | Nadel, J. A., and J. H. Comroe, Jr. Acute effects of inhalation of cigarette smoke on airway conductance. J. Appl. Physiol. 16: 713-716, 1961. |
| 21. | Ogletree, M. L., D. N. Harris, R. Greenberg, M. F. Haslanger, and M. Nakane. Pharmacological actions of SQ 29,548, a novel selective thromboxane antagonist. J. Pharmacol. Exp. Ther. 234: 435-441, 1985. |
| 22. | Pórszász, R., and J. Szolcsányi. Circulatory and respiratory effects of capsaicin and resiniferatoxin on guinea pigs. Acta Biochim. Biophys. Hung. 26: 131-138, 1991. |
| 23. | Shams, H., B. A. Peskar, and P. Scheid. Acid infusion elicits thromboxane A2 -mediated effects on respiration and pulmonary hemodynamics in the cat. Respir. Physiol. 71: 169-183, 1988. |
| 24. |
Tanizawa, H.,
T. Iwanaga,
and
H.-H. Tai.
Increase in thromboxane B2 and decrease in prostaglandin E2 and 6-keto-prostaglandin F1 release into rat bronchoalveolar fluid as a consequence of cigarette smoking.
Prostaglandins Leukot. Med.
28:
195-201,
1987.
|
| 25. | Toivanen, J., O. Ylikorkala, and L. Viinikka. Effects of smoking and nicotine on human prostacyclin and thromboxane production in vivo and in vitro. Toxicol. Appl. Pharmacol. 82: 301-306, 1986. |
| 26. |
Underwood, D. C.,
R. M. Muccitelli,
M. A. Luttmann,
D. W. P. Hay,
T. J. Torphy,
and
M. A. Wasserman.
Differential antagonism of airway contractile responses to prostaglandin (PG)D2 and 9, 11 -PGF2 by atropine, SK&F 88046 and SQ 29,548 in the guinea pig.
J. Pharmacol. Exp. Ther.
268:
304-310,
1994.
|
| 27. | Varfolomeyev, S. D., and A. T. Mevkh. Prostaglandin H synthase as a limiting enzyme of prostaglandin synthesis: substrate-induced inactivation as a new kind of enzyme activity regulation. Biotechnol. Appl. Biochem. 17: 291-304, 1993. |
| 28. | Wartman, W. B., E. C. Cogbill, and E. S. Harlow. Determination of particulate matter in concentrated aerosols. Application of analysis of cigarette smoke. Anal. Chem. 31: 1705-1709, 1959. |
| 29. | Zijlstra, F. J., J. E. Vincent, W. M. Mol, H. C. Hoogsteden, P. T. W. Van Hal, and R. C. Jongejan. Eicosanoid levels in bronchoalveolar lavage fluid of young female smokers and non-smokers. Eur. J. Clin. Invest. 22: 301-306, 1992. |
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