Montelukast, a selective cysteinyl leukotriene receptor 1 antagonist, reduces cerulein-induced pancreatic injury in rats

Inhibition of sepsis-induced pancreatic injury by leukotriene receptor antagonism via modulation of oxidative injury, and downregulation of inflammatory markers in experimental rats

The purpose of this study is to investigate the effect of montelukast on lipopolysaccharide (LPS)-induced pancreatitis. Adult male Wistar rats were divided into 5 groups: normal control, control montelukast, LPS group, and two LPS + montelukast-treated groups. Acute pancreatitis (AP) was induced by a single dose of LPS (6 mg/kg, i.p.), while montelukast was given in two different doses (10 and 20 mg/kg/day) for 3 consecutive days prior to the injection of LPS. AP was demonstrated by significant increases in serum levels of lactate dehydrogenase (LDH) and pancreatic enzymes lipase and amylase. Proinflammatory response activation was evident by elevated serum levels of nitric oxide (NO) and increased pancreatic concentrations of tumor necrosis factor-α (TNF-α), interleukin-1 (IL-1β), and intercellular adhesion molecule-1 (ICAM-1). The activity of myeloperoxidase (MPO), a neutrophil infiltration marker, has also been increased. Oxidative stress was confirmed by significant increases in the concentrations of lipid peroxides measured as thiobarbituric acid reactive substances (TBARS) and decreases in the concentrations of reduced glutathione (GSH) in the pancreatic tissues of animals treated with LPS. Histological examination confirmed the biochemical alterations. Montelukast treatment reversed all these biochemical indices and histopathological changes that LPS induced. Montelukast reduced the increase in serum levels of lipase, amylase, LDH, total nitrite/nitrate, TNF-α, IL-1β, and ICAM-1. MPO activities and TBARS concentrations were also suppressed while GSH content was increased in pancreatic tissues. These results show that montelukast may be a beneficial pharmacological agent in protection against LPS-induced oxidative pancreatic injury by inhibiting neutrophil infiltration, counteracting oxidative stress, and suppressing inflammatory mediators.

The Effect of Oral Montelukast Administration in Cholesteatoma Development and Inflammation: An Experimental Animal Model

HYPOTHESIS

We hypothesized that oral montelukast treatment could inhibit cholesteatoma formation in an experimental animal model.

BACKGROUND

Inflammation and excessive proliferation have been described in the histopathology of cholesteatoma. The aim of this study was to determine the effect of oral montelukast on cholesteatoma development.

METHODS

Eighteen healthy female Wistar albino rats weighing 250 g were chosen for the study. The animals were divided into two groups: group 1 received montelukast and group 2 was the control group. Intratympanic propylene glycol injection was administered into the left ears and physiologic serum was instilled into the right ears of the animals on the first, eighth, and fifteenth days. The effects of montelukast administration were evaluated by histological examination of the tympanic membrane and middle ear.

RESULTS

Group 1 (montelukast group) showed significant differences in terms of cholesteatoma formation, granulation, epithelial invagination, and inflammation. Cholesteatoma formation in the left ear was observed in 2 (22%) and 8 (89%) rats in groups 1 and 2, respectively (p = 0.015).

CONCLUSION

Development of cholesteatoma and inflammation was significantly lower in the montelukast-administered group. Thus, oral montelukast was found effective in preventing cholesteatoma formation.

Is there any effect of montelukast on prevention of myringosclerosis after myringotomy in a rat model?

OBJECTIVES

In this study, our aim was to identify the possible effects of montelukast sodium (ML) on the prevention of experimentally induced myringosclerosis.

MATERIALS AND METHODS

Twenty-eight female Wistar albino rats were used and they were divided into four groups randomly. Tympanic membranes (TM) of all animals were perforated and then group 1 received no treatment (control group), group 2 was treated with a topical saline solution, group 3 received topically ML and group 4 received orally ML. On the 15th day, all animals were euthanized. Tympanic membranes were evaluated otomicroscopically and histopathologically.

RESULTS

The histopathological findings, compared against a control and saline groups, showed the topically and orally ML groups had statistically significant differences of degree of myringosclerosis (p < 0.002) and median thickness of the TMs (p < 0.001). Suppression of inflammation was statistically significant only in the oral ML treatment group (p < 0.002).

CONCLUSION

Oral and topically administration of ML reduced myringosclerosis formation in myringotomies rats.

Mechanisms underlying the protective effect of montelukast in prevention of endometrial hyperplasia in female rats

OBJECTIVE

To study the possible protective role of montelukast in endometrial hyperplesia (EH) rat model, induced by estradiol valerate (EV).

METHODS/MATERIALS

Thirty six female albino Wistar rats were classified into 7 groups: normal control, EV (2 mg/kg/day, p.o.), montelukast (10 mg/kg/day, p.o.), montelukast (1 mg/kg/day, p.o.) + EV (2 mg/kg/day, p.o.), montelukast (10 mg/kg/day, p.o.) + EV (2 mg/kg/day, p.o.), montelukast (20 mg/kg/day, p.o.) + EV (2 mg/kg/day, p.o.) groups. Uterine malondialdehyde (MDA), superoxide dismutase (SOD), total nitrites (NO) and serum total antioxidant capacity (TAC) were determined. Uterine, serum total cholesterol, high density lipoprotein (HDL) and tumor necrosis factor (TNF)-α were measured. Histopathological examination of the uterine tissue was also done. In addition, immunohistochemistry was done using Phosphatase and tensin homolog (PTEN) and inducible nitric oxide synthase (iNOS) antibodies.

RESULTS

Our results showed that montelukast in dose dependant manner improves oxidative stress, lipids profile and TNF α which were affected by EV. Moreover, immunohistochemical examination revealed that montelukast markedly reduced iNOS expression, while expression of PTEN was markedly enhanced, as compared to EV group. The protective effects of montelukast were also verified histopathologically.

CONCLUSIONS

Montelukast in dose dependant manner provided biochemical and histo-pathological improvement in EV induced EH, through its anti-inflammatory, antioxidant activity and inhibition of iNOS expression with induction of PTEN expression.

5-Lipoxygenase: Its involvement in gastrointestinal malignancies

Lipoxygenases (LOXs) are dioxygenases that catalyze the peroxidation of linoleic acid (LA) or arachidonic acid (AA), in the presence of molecular oxygen. The existence of inflammatory component in the tumor microenvironment intimately links the LOXs to gastrointestinal (GI) cancer progression. Amongst the six-different human LOX-isoforms, 5-LOX is the most vital enzyme for leukotriene (LT) biosynthesis, which is the main inflammation intermediaries. As recent investigations have shown the association of 5-LOX with tumor metastasis, there has also been significant progress in discovering the function of 5-LOX pathway in GI cancer. Studies on GI cancer cells using the pharmacological drugs targeting 5-LOX pathway have shown antiproliferative and proapoptotic effects. Pharmacogenetic discoveries in other diseases have revealed strong heritable basis for the leukotriene pathway, which helps in exploring the mechanistic source of genetic alteration within the leukotriene pathway and offer insights into GI cancer pathogenesis and future prospects for treatment and prevention. This review recapitulates the current research status of 5-LOX activity in GI malignancies.

Effects of Montelukast in an Experimental Model of Acute Pancreatitis

Background

We evaluated the hematological, biochemical, and histopathological effects of Montelukast on pancreatic damage in an experimental acute pancreatitis model created by cerulein in rats before and after the induction of pancreatitis.

Materials/Methods

Forty rats were divided into 4 groups with 10 rats each. The study groups were: the Cerulein (C) group, the Cerulein + early Montelukast (CMe) group, the Cerulein + late Montelukast (CMl) group, and the Control group. The pH, pO2, pCO2, HCO3, leukocyte, hematocrit, pancreatic amylase, and lipase values were measured in the arterial blood samples taken immediately before rats were killed.

Results

There were statistically significant differences between the C group and the Control group in the values of pancreatic amylase, lipase, blood leukocyte, hematocrit, pH, pO2, pCO2, HCO3, and pancreatic water content, and also in each of the values of edema, inflammation, vacuolization, necrosis, and total histopathological score (P<0.05). When the CMl group and C group were compared, no statistically significant differences were found in any parameter analyzed. When the CMe group was compared with the C group, pancreatic amylase, lipase, pH, PO2, pCO2, HCO3, pancreatic water content, histopathological edema, inflammation, and total histopathological score values were significantly different between the groups (P<0.05). Finally, when the CMe group and the Control group were compared, significant differences were found in all except 2 (leukocyte and pO2) parameters (P<0.05).

Conclusions

Leukotriene receptor antagonists used in the late phases of pancreatitis might not result in any benefit; however, when they are given in the early phases or prophylactically, they may decrease pancreatic damage.

Effects of Myrtus communis extract treatment in bile duct ligated rats

BACKGROUND

The aim of our study was to investigate the antifibrotic and antioxidant effects of Myrtus communis subsp. communis (MC) extract against liver injury and fibrosis occurring in rats with biliary obstruction.

MATERIALS AND METHODS

The rats were randomized into four groups (n = 8). Control group (C), MC-administrated group (MC), the bile duct ligation (BDL), and BDL + MC groups. MC was administered at a dose of 50 mg/kg a day orally for 28 days. In blood samples, total bilirubin, direct bilirubin, alanine aminotransferase, aspartate aminotransferase levels, tumor necrosis factor-α, and interleukin-1β measurement were measured. Oxidative injury was examined by measuring luminol and lucigenin chemiluminescence, malondialdehyde and glutathione levels, superoxide dismutase and myeloperoxidase activities. Transforming growth factor-beta and hydroxyproline levels were measured for analyzing fibrosis. The hepatic injury was also analyzed microscopically.

RESULTS

Plasma total bilirubin, direct bilirubin, alanine aminotransferase, aspartate aminotransferase, tumor necrosis factor-α, and interleukin-1β levels were found significantly high in the BDL group, while these values significantly decreased in the BDL group treated with MC. On the other hand, the glutathione and superoxide dismutase values significantly decreased in the BDL group compared to the control group but increased markedly in BDL + MC group compared to the BDL group. Malondialdehyde levels, myeloperoxidase activity, tissue luminol, lucigenin, transforming growth factor-beta, and hydroxyproline levels when compared with the control group increased dramatically in the BDL group and reduced the MC + BDL group.

CONCLUSIONS

Our results suggest that MC protects the liver tissues against oxidative damage following BDL via its radical scavenging and antioxidant activities, which appear to involve the inhibition of tissue neutrophil infiltration.

Effects of phloretin on oxidative and inflammatory reaction in rat model of cecal ligation and puncture induced sepsis

BACKGROUND

Sepsis is a debilitating systemic disease and described as a severe and irregular systemic inflammatory reaction syndrome (SIRS) against infection. We employed CLP (Cecal Ligation and Puncture) model in rats to investigate anti-inflammatory and antioxidant effects of phloretin, as a natural antioxidant agent, and its protective effect on liver tissue damage caused by sepsis.

METHODS

Male Wistar albino rats were randomly divided into three groups: sham group, CLP induced sepsis group and phloretin treated CLP group. Sepsis was induced by CLP method. 50 mmol/kg Phloretin was administered intraperitoneally in two equal doses immediately after surgery.

RESULTS

It was observed that blood urea nitrogen (BUN) and tumor necrosis factor alpha (TNF-α) levels were dramatically increased in the CLP induced sepsis group (43.88 ± 1.905 mg/dl, 37.63 ± 1.92, respectively) when compared to the sham group. Moreover, tissue Glutathione (GSH) and liver nuclear factor ĸB (NF-ĸB p65) transcription factor values were higher in CLP induced sepsis group. This elevation was considerably reduced in the phloretin treated CLP group. No significant differences were observed in serum creatinine and creatinine phosphokinase levels.

CONCLUSIONS

The present study suggested that phloretin, as a natural protective agent, act against tissue damages introduced following the experimental sepsis induced model, likely caused by free oxygen radicals.

Factors Affecting the Efficacy of Nonsteroidal Anti-inflammatory Drugs in Preventing Post-Endoscopic Retrograde Cholangiopancreatography Pancreatitis: A Systematic Review and Meta-analysis

OBJECTIVES

To identify the factors affecting the efficacy of nonsteroidal anti-inflammatory drugs (NSAIDs) in preventing post-endoscopic retrograde cholangiopancreatography (ERCP) pancreatitis (PEP).

METHODS

We systematically searched databases for relevant studies published from inception to November 2013.

RESULTS

A meta-analysis of 11 randomized trials (n = 2497) revealed a significant reduction in PEP in patients who received NSAIDs compared with that in patients who received placebo (relative risk [RR], 0.59; 95% confidence interval [CI], 0.41-0.85; P = 0.005). In subgroup analysis by treatment type, indomethacin had no significant effect (RR, 0.66; 95% CI, 0.38-1.15; P = 0.14), whereas other NSAIDs showed significant benefit (RR, 0.51; 95% CI, 0.29-0.91; P = 0.02). Only rectal administration significantly reduced the incidence of PEP (RR, 0.43; 95% CI, 0.32-0.58; P < 0.00001). The risk for PEP was the lowest among patients who received NSAIDs before ERCP (RR, 0.48; 95% CI, 0.29-0.78; P = 0.003). NSAIDs did not significantly reduce the risk of PEP in men (RR, 0.61; 95% CI, 0.34-1.09), patients with sphincter of Oddi dysfunction (RR, 0.98; 95% CI, 0.38-2.54), or patients with pancreatic duct injection (RR, 0.64; 95% CI, 0.35-1.18).

CONCLUSIONS

Rectal administration of NSAIDs (especially diclofenac), before ERCP, seemed to be the most effective strategy for preventing PEP.

The apoptosis of peripheral blood lymphocytes promoted by hyperbaric oxygen treatment contributes to attenuate the severity of early stage acute pancreatitis in rats

The aim of this study was to investigate the immunoregulatory effects of hyperbaric oxygen (HBO) via promoting the apoptosis of peripheral blood lymphocytes (PBLs) to attenuate the severity of early stage acute pancreatitis (AP) in rats. Additionally, the persistence of the HBO treatment effects was evaluated. One hundred and twenty male Wistar rats were randomized into four groups: sham, AP, AP + normobaric oxygen (NBO), and AP + HBO. Each group consisted of 30 rats. Four hours after the induction of AP, the 30 rats in the AP + NBO group were given normobaric oxygen treatment with 100 % oxygen at 1 atm for 90 min. The 30 rats in the AP + HBO group received 100 % oxygen at 2.5 atm for 90 min, with a compression/decompression time of 15 min. The 30 rats in the AP group remained untreated. At 6, 12, and 24 h after the induction of AP, surviving rats from each group were sacrificed, and the blood and tissue samples were collected for the following measurements: the partial pressure of oxygen (PaO2) and oxygen saturation (SaO2) of the arterial blood, the levels of serum amylase, lipase, interleukin-2 (IL-2), interferon-γ (IFN-γ), interleukin-10 (IL-10), hepatocyte growth factor (HGF), and reactive oxygen species (ROS), and the mitochondrial membrane potential (∆Ψm) of the PBLs. The expression levels of procaspase-3, caspase-3, procaspase-9, and caspase-9 were also evaluated in the PBLs. Additionally, the apoptosis of PBLs was assessed, and the pancreatic tissues were subjected to a histopathological analysis by pathological grading and scoring. The histopathology of the lung, liver, kidney, duodenum, and heart was also analyzed at 12 h after the induction of AP. Significant differences were found at 6 and 12 h after AP induction. The HBO treatment significantly elevated the PaO2 and SaO2 levels, and the ROS levels in the PBLs. Additionally, HBO downregulated the levels of amylase and lipase. The HBO treatment also reduced the ∆Ψm levels, upregulated the expression of caspase-3 and caspase-9, and increased the apoptosis rate of the PBLs. Moreover, the HBO treatment decreased the serum concentrations of IL-2, IFN-γ and HGF, and reduced the pathological scores of the pancreatic tissue. The histopathological changes of the lung, liver, kidney, duodenum, and heart were also improved. A significant elevation of IL-10 occurred only at the 12-h time point. However, no obvious differences were found at the 24-h time point. This study demonstrated that the HBO treatment can promote the apoptosis of PBLs via a mitochondrial-dependent pathway and inhibit the inflammatory response. These immunoregulatory effects may play an important therapeutic role in attenuating the severity of early stage AP. The repeated administration of HBO or the use of HBO in combination with other approaches may further improve outcomes.

Cysteinyl leukotriene receptor 1 mediates LTD4-induced activation of mouse microglial cells in vitro

AIM

To investigate the roles of cysteinyl leukotriene receptors CysLT1R and CysLT2R in leukotriene D4 (LTD4)-induced activation of microglial cells in vitro.

METHODS

Mouse microglial cell line BV2 was transfected with pcDNA3.1(+)-hCysLT1R or pcDNA3.1(+)-hCysLT2R. The expression of relevant mRNAs and proteins in the cells was detected using RT-PCR and Western blotting, respectively. Phagocytosis was determined with flow cytometry analysis. The release of interleukin-1β (IL-1β) from the cells was measured using an ELISA assay.

RESULTS

The expression of CysLT1R or CysLT2R was considerably increased in the transfected BV2 cells, and the receptors were mainly distributed in the plasma membrane and cytosol. Treatment of the cells expressing CysLT1R or CysLT2R with CysLT receptor agonist LTD4 (0.1-100 nmol/L) concentration-dependently enhanced the phagocytosis, and increased mRNA expression and release of IL-1β. Moreover, the responses of hCysLT1R-BV2 cells to LTD4 were significantly larger than those of hCysLT2R-BV2 or WT-BV2 cells. Pretreatment of hCysLT1R-BV2 cells with the selective CysLT1R antagonist montelukast (1 μmol/L) significantly blocked LTD4-induced phagocytosis as well as the mRNA expression and release of IL-1β, whereas the selective CysLT2R antagonist HAMI 3379 (1 μmol/L) had no such effects.

CONCLUSION

CysLT1R mediates LTD4-induced activation of BV2 cells, suggesting that CysLT1R antagonists may exert anti-inflammatory activity in brain diseases.

A case of montelukast induced hypercholesterolemia, severe hypertriglyceridemia and pancreatitis

Montelukast sodium is a leukotriene inhibitor, and competitively antagonizes cys-LT1 receptor and used widely and effectively in treating allergic rhinitis, bronchial asthma and allied respiratory conditions. This case report outlines a rare case of montelukast induced hypercholesterolemia, severe hypertriglyceridemia and acute pancreatitis in a 22 years old male patient. The patient was taking 10 mg oral montelukast daily for allergic rhinitis. Although his symptoms improved considerably, after 2 months of therapy, he experienced unusual weight gain and got admitted with severe pain abdomen. Clinical and other relevant investigation findings revealed the presence of acute pancreatitis with associated hypercholesterolemia and severe hypertriglyceridemia. There were no evidences of any other possible hereditary, surgical, metabolic, infective, organic or other pathologic causes giving rise to these conditions. De-challenge was done and the patient was treated conservatively resulting in reversal of the diseased state. Naranjo adverse drug reaction probability scale suggested that it was 'probable' that oral administration of montelukast was responsible for the acute pancreatitis associated with hypercholesterolemia and severe hypertriglyceridemia. There is only a singular and confirmed reported case of montelukast induced hypertriglyceridemia from India. For patients taking montelukast for a long duration, routine lipid profile monitoring should be done, and if these patients present with symptoms of epigastric and periumbilical pain with vomiting, provisions for screening acute pancreatitis might be warranted.

Montelukast inhibits caspase-3 activity and ameliorates oxidative damage in the spinal cord and urinary bladder of rats with spinal cord injury

Spinal cord injury (SCI) leads to an inflammatory response that generates substantial secondary damage within the tissue besides the primary damage. Leukotrienes are biologically active 5-lipoxygenase products of arachidonic acid metabolism that are involved in the mediation of various inflammatory disorders including SCI. In this study, we investigated the possible protective effects of montelukast, a leukotriene receptor blocker, on SCI-induced oxidative damage. Wistar albino rats (n=24) were divided randomly as control, vehicle- or montelukast (10mg/kg, ip)-treated SCI groups. To induce SCI, a standard weight-drop method that induced a moderately severe injury at T10 was used. Vehicle or montelukast were administered to the injured animals 15 min after injury. At seven days post-injury, neurological examination was performed and rats were decapitated. Blood samples were taken to evaluate leukotriene B4 levels, and pro-inflmamatory cytokines (TNF-α, IL-1β) while in spinal cord and urinary bladder samples malondialdehyde (MDA), glutathione (GSH), luminol chemiluminescence (CL) levels and myeloperoxidase (MPO) and caspase-3 activities were determined. Tissues were also evaluated histologically. SCI caused significant decreases in tissue GSH, which were accompanied with significant increases in luminol CL and MDA levels and MPO and caspase-3 activities, while pro-inflammatory cytokines in the plasma were elevated. On the other hand, montelukast treatment reversed these parameters and improved histological findings. In conclusion, SCI caused oxidative tissue injury through the activation of pro-inflammatory mediators and by neutrophil infiltration into tissues, and the neuroprotective and antiapoptotic effects of montelukast are mediated by the inhibition of lipid peroxidation, neutrophil accumulation and pro-inflammatory cytokine release. Moreover, montelukast does not only exert antioxidant and antiapoptotic effects on the spinal cord, but it has a significant impact on the bladder tissue damage secondary to SCI.

Protective effects of lycopene on cerulein-induced experimental acute pancreatitis in rats

BACKGROUND

The purpose of our study was to evaluate the protective effect of the strong antioxidant and anti-inflammatory agent, lycopene, on oxidative stress in a rat model of cerulein-induced acute edematous pancreatitis.

METHODS

Sprague-Dawley rats were pretreated with lycopene (50 mg/kg, i.p.) or saline 15 min before cerulein was given 20 μg/kg (i.p.) at 1-h intervals within 4 h. Twelve hours after cerulein or saline injections, the animals were killed by decapitation. Blood samples were collected to analyze amylase, lipase, and proinflammatory cytokines (TNF-α and IL-1ß). Pancreatic tissues were taken for the determination of tissue glutathione (GSH) and malondialdehyde (MDA) levels, Na(+)/K(+)-ATPase, and myeloperoxidase (MPO) activities. Tissue samples were also examined histologically.

RESULTS

Acute pancreatitis caused significant decrease in tissue GSH levels and Na(+)/K(+)-ATPase activity, while pancreatic MDA levels and MPO activity were increased. Furthermore, TNF-α, IL-1ß, and amylase lipase levels were also significantly increased. On the other hand, lycopene pretreatment reserved all these biochemical indices as well as histopathologic alterations that were induced by cerulein.

CONCLUSIONS

According to the results, lycopene protects the pancreatic tissues from oxidative damage induced by cerulein, and this effect possibly involves the inhibition of neutrophil infiltration and lipid peroxidation. These results suggest that high dietary intake of tomatoes may have protective effects against acute pancreatitis.

Molecular mechanisms of pancreatic injury

PURPOSE OF REVIEW

Despite being a subject of much scientific scrutiny, the pathogenesis of acute pancreatitis is still not well understood. This article reviews recent advances in our understanding of acute pancreatitis.

RECENT FINDINGS

Zymogen activation, observed within acini early during acute pancreatitis for a long time, was shown to be sufficient to induce acute pancreatitis. Another key early event, NFκB activation, has previously been shown to induce acute pancreatitis. The relationship between these two key early steps is beginning to be clarified. Mechanisms of zymogen activation - pathologic calcium signaling, pH changes, colocalization and autophagy, and of NFκB activation have been investigated intensively along with potential therapeutic targets both upstream and downstream of these key events. Additional key findings have been elucidation of the role of bioenergetics and the dual role of oxidative stress in acute pancreatitis, recognition of endoplasmic reticulum stress as an early step and the status of duct cells as important entities in pancreatic injury.

SUMMARY

Current findings have provided further insight into the roles and mechanisms of zymogen activation and inflammatory pathways in pancreatic injury. Future studies, which will be of great importance in identifying therapeutic targets, are being undertaken to establish the relative contributions of these pathways during acute pancreatitis.

Effects of cysteinyl-leukotriene receptors' antagonism by montelukast on lung mechanics and olfactory system histology in healthy mice

CONTEXT

At variance with steroid administration, the possible effects of leukotrienes inhibition on basal respiratory mechanics and olfactory system function are still unclear.

OBJECTIVE

To investigate if interference with the leukotrienes activity may influence basal lung mechanics in healthy mammals, as well as the olfactory system.

MATERIALS AND METHODS

We measured lung mechanics by the end-inflation occlusion method in control and in montelukast i.p. treated anaesthetised healthy mice (10 mg/kg/die for a week). A study of olfactory system histology was also conducted.

RESULTS

Elastance and resistive properties of the lung were not affected by montelukast, while a significant increment of lung hysteresis was observed. The analysis of olfactory system histology revealed no significant effects of montelukast compared to controls.

DISCUSSION AND CONCLUSIONS

Leukotrienes' antagonism does not affect respiratory mechanics in basal conditions, except for a hysteresis increment, which might counteract the increase in expiratory flow in asthmatic subjects assuming montelukast.