New approaches to anti-inflammatory therapy for asthma

Screening 5-lipoxygenase inhibitors from selected traditional Chinese medicines and isolation of the active compounds from Polygoni Cuspidati Rhizoma by an on-line bioactivity evaluation system

To identify natural products as new prototypes for 5-lipoxygenase (5-LOX), 12 traditional Chinese medicines (TCMs), were selected for screening their 5-LOX inhibition activities. The results showed that all of the methanol extracts of 12 selected TCMs possessed inhibitory activities of 5-LOX at 200 μg/mL, of which six extracts of the TCMs showed significant inhibitory effects with IC₅₀ values ranged from 33.2 ± 1.4 μg/mL to 153.5 ± 1.7 μg/mL, and the extract of Polygoni Cuspidati Rhizoma (RPC) was the most active sample. An on-line UPLC-PDA-MSⁿ -5-LOX-FLD method was applied to further identify the potential 5-LOX inhibitory constituents in RPC extracts, which resulted in the identification of 7 components with 5-LOX-binding activities. Finally, four compounds (polydatin, resveratrol, emodin-8-O-glucoside and emodin) were successfully purified from RPC extracts. The 5-LOX inhibition action was assayed in vitro, and the results showed that these compounds possessed potent inhibitory effects against 5-LOX with IC₅₀ values of 15.3 ± 2.1, 4.5 ± 1.2, 23.8 ± 0.4 and 11.8 ± 1.5 μg/mL, respectively. This was the first study to reveal the 5-LOX inhibitory constituents of RPC, and the present investigation might provide a valuable approach for the rapid discovery of natural inhibitors from TCMs.

Peroxisomes in Dermatology. Part II

Background:

Peroxisomes are small cellular organelles that were almost ignored for years because they were believed to play only a minor role in cellular functions. However, it is now known that peroxisomes play an important role in regulating cellular proliferation and differentiation as well as in the modulation of inflammatory mediators. In addition, peroxisomes have broad effects on the metabolism of lipids, hormones, and xenobiotics. Through their effects on lipid metabolism, peroxisomes also affect cellular membranes and adipocyte formation, as well as insulin sensitivity, and peroxisomes play a role in aging and tumorigenesis through their effects on oxidative stress.

Objective:

To review genetically determined peroxisomal disorders, especially those that particularly affect the skin, and some recent information on the specific genetic defects that lead to some of these disorders. In addition, we present some of the emerging knowledge of peroxisomal proliferator activator receptors (PPARs) and how ligands for these receptors modulate different peroxisomal functions. We also present information on how the discovery of PPARs, and the broad and diverse group of ligands that activate these members of the superfamily of nuclear binding transcription factors, has led to development of new drugs that modulate the function of peroxisomes.

Conclusion:

PPAR expression and ligand modulation within the skin have shown potential uses for these ligands in a number of inflammatory cutaneous disorders, including acne vulgaris, cutaneous disorders with barrier dysfunction, cutaneous effects of aging, and poor wound healing associated with altered signal transduction, as well as for side effects induced by the metabolic dysregulation of other drugs.

Role of cysteinyl leukotriene receptor-1 antagonists in treatment of experimentally induced mammary tumor

It has been reported that a leukotriene (LT)-D4 receptor (i.e. cysteinyl LT1 receptor; CysLT1R) has an important role in carcinogenesis. The current study was carried out to assess the possible antitumor effects of montelukast (MON), a CysLT1R antagonist, in a mouse mammary carcinoma model, that is, a solid Ehrlich carcinoma (SEC). Effects of MON on tumor-induced immune dysfunction and the possibility that MON may modulate the antitumor and immunomodulatory effects of doxorubicin (DOX) were also studied. The effects in tumor-bearing hosts of several dosings with MON (10 mg/kg, per os), with and without the added presence of DOX (2 mg/kg, intraperitoneal), were investigated in vivo; end points evaluated included assessment of tumor volume, splenic lymphocyte profiles/functionality, tumor necrosis factor-α content, as well as apoptosis and expression of nuclear factor-κB (NF-κB) among the tumor cells. The data indicate that MON induced significant antitumor activity against the SEC. MON treatments also significantly mitigated both tumor- and DOX-induced declines in immune parameters assessed here. Moreover, MON led to decreased NF-κB nuclear expression and, in doing so, appeared to chemosensitize these tumor cells to DOX-induced apoptosis.

Synthesis and evaluation of benzoxazole derivatives as 5-lipoxygenase inhibitors

5-Lipoxygenase (5-LOX) is important enzyme in the biosynthesis of leukotrienes, and is a potential target in the treatment of asthma and allergy. We designed and synthesized a series of benzoxazoles and benzothiazoles as 5-LOX inhibitors. Fourteen compounds prepared showed the inhibition of LTC4 formation with IC(50) value of 0.12-23.88 μM. Also two compounds 2d and 2g showed improved airway hypersensitiveness.

Relationship between cysteinyl-leukotriene-1 receptor and human transitional cell carcinoma in bladder

OBJECTIVES

To investigate the leukotriene (LT) D(4) (LTD(4)) receptor (cysteinyl-LT(1) receptor [CysLT(1)R]) expression in transitional cell carcinoma (TCC) of the bladder, as well as the effects of the CysLT(1)R antagonist on cell proliferation in TCC cell lines. The metabolism of arachidonic acid by either cyclooxygenase or lipoxygenase is thought to play an important role in carcinogenesis. LTD(4) is a pro-inflammatory mediator derived from arachidonic acid through various enzymatic steps, and 5-lipoxygenase is an important factor in generating LTD(4).

METHODS

CysLT(1)R expression in TCC tissue and normal bladder tissue was examined. CysLT(1)R expression was detected using immunohistochemistry. The effects of the CysLT(1)R antagonist on TCC cell growth were examined by 3-(4,5-dimethylthiazol-2-thiazolyl)-2,5-diphenyltetrazolium bromide assay and reverse transcriptase-polymerase chain reaction. Flow cytometry was used to determine whether the CysLT(1)R antagonist induced apoptosis.

RESULTS

Initially, only slight CysLT(1)R expression was detected in normal bladder tissues and marked CysLT(1)R expression was detected in the TCC tissues. CysLT(1)R expression was greater in high-grade cancer than in low-grade cancer. Furthermore, CysLT(1)R expression was also greater in advanced-stage cancer than in early-stage cancer. Finally, the CysLT(1)R antagonist caused marked inhibition of TCC cells by inducing early apoptosis.

CONCLUSIONS

CysLT(1)R was induced in TCC. The results suggest that the CysLT(1)R antagonist might mediate potent antiproliferative effects on TCC cells. Thus, the target of the CysLT(1)R is potentially a new therapy in the treatment of TCC.

Peroxisome proliferator-activated receptors (PPARs) and the human skin: importance of PPARs in skin physiology and dermatologic diseases

Peroxisome proliferator-activated receptors (PPARs) are members of the nuclear receptor superfamily that regulate lipid, glucose, and amino acid metabolism. More recently, PPARs and corresponding ligands have been shown in skin and other organs to regulate important cellular functions, including cell proliferation and differentiation, as well as inflammatory responses. These new functions identify PPARs and corresponding ligands as potential targets for the treatment of various skin diseases and other disorders. It has been shown that in inflammatory skin disorders, including hyperproliferative psoriatic epidermis and the skin of patients with atopic dermatitis, the expression of both PPARalpha and PPARgamma is decreased. This observation suggests the possibility that PPARalpha and PPARgamma activators, or compounds that positively regulate PPAR gene expression, may represent novel NSAIDs for the topical or systemic treatment of common inflammatory skin diseases such as atopic dermatitis, psoriasis, and allergic contact dermatitis. Moreover, recent findings indicate that PPAR-signaling pathways may act as a promising therapeutic target for the treatment of hyperproliferative skin diseases including skin malignancies. Studies in non-diabetic patients suggest that oral thiazolidinediones, which are synthetic ligands of PPARgamma, not only exert an antidiabetic effect but also may be beneficial for moderate chronic plaque psoriasis by suppressing proliferation and inducing differentiation of keratinocytes; furthermore, they may even induce cell growth arrest, apoptosis, and terminal differentiation in various human malignant tumors. It has been reported that PPARalpha immunoreactivity is reduced in human keratinocytes of squamous cell carcinoma (SCC) and actinic keratosis (AK), while PPARdelta appears to be upregulated. Additionally, the microvessel density is significantly higher in AK and SCC that express high levels of PPARdelta. PPARdelta has been demonstrated to have an anti-apoptotic role and to maintain survival and differentiation of epithelial cells, whereas PPARalpha and PPARgamma activators induce differentiation and inhibit proliferation and regulate apoptosis. In melanoma, the growth inhibitory effect of PPARgamma activation is independent of apoptosis and seems to occur primarily through induction of cell cycle arrest in the G1 phase of the cell cycle or induction of re-differentiation. PPARalpha activation causes inhibition of migration of melanoma cells and anchorage-independent growth, whereas primary tumor growth remains unaltered. In clinical trials of gemfibrozil, a PPARalpha ligand, significantly fewer patients treated with this lipid-lowering drug were diagnosed with melanoma as compared to those in the control group. In conclusion, an increasing body of evidence indicates that PPAR signaling pathways may represent interesting therapeutic targets for a broad variety of skin disorders, including inflammatory skin diseases such as psoriasis and atopic dermatitis, and skin malignancies.

Asthma and pregnancy

Asthma complicates 4-8% of pregnancies. Mild and well-controlled moderate asthma can be associated with excellent maternal and perinatal pregnancy outcomes. Severe and poorly controlled asthma may be associated with increased prematurity, need for cesarean delivery, preeclampsia, growth restriction, other perinatal complications, as well as maternal morbidity and mortality. Optimal management of asthma during pregnancy includes objective monitoring of lung function, avoiding or controlling asthma triggers, patient education, and individualized pharmacologic therapy. Those with persistent asthma should be monitored by peak expiratory flow rate, spirometry to measure the forced expiratory volume in 1 second, or both. Step-care therapeutic approach uses the least amount of drug intervention necessary to control a patient's severity of asthma. Inhaled corticosteroids are the preferred treatment for the management of all levels of persistent asthma during pregnancy. It is safer for pregnant women with asthma to be treated with asthma medications than it is for them to have asthma symptoms and exacerbations. The ultimate goal of asthma therapy is maintaining adequate oxygenation of the fetus by prevention of hypoxic episodes in the mother. Asthma exacerbations should be aggressively managed, with a goal of alleviating asthma symptoms and attaining peak expiratory flow rate or forced expiratory volume in 1 second of 70% predicted or more. Pregnancies complicated by moderate or severe asthma may benefit from ultrasound for fetal growth and accurate dating and antenatal assessment of fetal well-being. Asthma medications should be continued during labor, and parturients should be encouraged to breastfeed.

Synthesis and biological evaluation of new phenidone analogues as potential dual cyclooxygenase (COX-1 and COX-2) and human lipoxygenase (5-LOX) inhibitors

A new series of potential human 5-LOX inhibitors structurally related to the 1-phenyl-3-pyrazolidinone (phenidone, 2) has been synthesized and the activity against COX-1, COX-2, and human 5-LOX enzymes has been evaluated. In contrast with literature data, we observed that phenidone resulted to be inactive against human 5-LOX, while retains its activity against cyclooxygenases in a micromolar range. The present results suggest that the substitution of the amino function at the 4-position is detrimental in terms of activity toward COX-1 and COX-2, while the presence of a double bond at the 4,5-position does not alter the biological profile against COX. The absence of activity vs. human 5-LOX strongly suggests a re-consideration of phenidone and its analogs as 5-LOX inhibitors in humans.

Pharmacology of airway inflammation in asthma and COPD

The current asthma therapies are not cures and symptoms return soon after treatment is stopped even after long term treatment. Although inhaled glucocorticoids are highly effective in controlling airway inflammation in asthma, they are ineffective in the small group of patients with glucocorticoid-dependent and -resistant asthma. With very few exceptions, COPD is caused by tobacco smoking, and smoking cessation is the only truly effective treatment of COPD available. Current pharmacological treatment of COPD is unsatisfactory, as it does not significantly influence the severity of the disease or its natural course. Glucocorticoids are scarcely effective in COPD patients without concomitant asthma. Bronchodilators improves symptoms and quality of life, in COPD patients, but, with the exception of tiotropium, they do not significantly influence the natural course of the disease. Theophylline is the only drug which has been demonstrated to have a significant effect on airway inflammation in patients with COPD. Here we review the pharmacology of currently used antiinflammatory therapies for asthma and COPD and their proposed mechanisms of action. Recent understanding of disease mechanisms in severe steroid-dependent and -resistant asthma and in COPD, has lead to the development of novel compounds, which are in various stages of clinical development. We review the current status of some of these new potential drugs.

Dual inhibition of cyclooxygenase-2 (COX-2) and 5-lipoxygenase (5-LOX) as a new strategy to provide safer non-steroidal anti-inflammatory drugs

Dual COX/5-LOX (cyclooxygenase/5-lipoxygenase) inhibitors constitute a valuable alternative to classical non-steroidal anti-inflammatory drugs (NSAIDs) and selective COX-2 inhibitors for the treatment of inflammatory diseases. Indeed, these latter present diverse side effects, which are reduced or absent in dual-acting agents. In this review, COX and 5-LOX pathways are first described in order to highlight the therapeutic interest of designing such compounds. Various structural families of dual inhibitors are illustrated.

Colchicine as an oral corticosteroid sparing agent for asthma

BACKGROUND

Oral corticosteroids are used as a treatment for asthma, but they are often associated with serious side effects. Colchicine is an anti-inflammatory, immuno modulating agent, which could potentially have a beneficial effect in the treatment of asthma as well as act as a steroid-sparing agent.

OBJECTIVES

To determine the effectiveness of colchicine as an oral corticosteroid sparing agent for in the treatment of chronic asthma.

SEARCH STRATEGY

We searched the Cochrane Airways Group trials register (November 2002), SIGLE (1980 to 2001) and reference lists of potential articles. We also contacted researchers in the field.

SELECTION CRITERIA

Randomised controlled trials investigating the addition of colchicine compared to placebo in stable steroid dependent asthmatics.

DATA COLLECTION AND ANALYSIS

No trials were found that met the inclusion criteria.

MAIN RESULTS

We were unable to perform any meta-analyses. Two small studies have assessed the efficacy of colchicine subsequent to inhaled steroid withdrawal and as a tapering agent in inhaled steroids. Both studies failed to detect a significant difference between colchicine and placebo.

REVIEWER'S CONCLUSIONS

No relevant trials have been published, so there is no evidence to indicate that colchicine is beneficial or otherwise in the management of steroid-dependent asthmatic patients. There is a need for well designed randomised controlled trials to be performed.

Treatment of disseminated granuloma annulare with a 5-lipoxygenase inhibitor and vitamin E

Histologically, granuloma annulare (GA) is a common non-infectious necrobiotic granulomatous reaction pattern that correlates with a number of different, but relatively specific clinical presentations. The cause or causes of GA are unknown: when localized, it is usually self-limiting, but it may be persistent when disseminated. We present three women who had had disseminated GA for more than 1 year. One patient had previously been treated with isotretinoin with no response. All three patients were treated with vitamin E 400 IU daily and zileuton 2400 mg daily. All responded within 3 months with complete clinical clearing. The anti-inflammatory and immune regulatory effects of vitamin E and zileuton may be an effective treatment in some patients with prolonged disseminated/generalized GA.

Leukotriene receptor antagonists--a novel therapeutic approach in atopic dermatitis?

Cysteinyl leukotrienes have been shown to be important in the pathogenesis of both asthma and rhinitis. Improvement of skin manifestations in atopic dermatitis has been reported with leukotriene receptor antagonists. This article reviews current data on the experimental evidence and clinical efficacy of leukotriene receptor antagonists in the treatment of atopic dermatitis.

Effects of pranlukast on chemical mediators in induced sputum on provocation tests in atopic and aspirin-intolerant asthmatic patients

BACKGROUND

Leukotrienes (LTs) are important in asthma, and LT modifiers modulate antigen-induced asthma. Overproduction of LT by suppression of cyclooxygenase activity is involved in patients with aspirin-intolerant asthma (AIA).

METHODS

House dust mite (HDM) inhalation provocation tests were performed in HDM-sensitive asthmatic inpatients without AIA (HDM group; n = 6), and aspirin oral provocation tests were performed in AIA patients (ASA group; n = 7). Tests were repeated using the same regimen after 7 days of treatment with pranlukast, an LT receptor antagonist (LTRA). The effects of pranlukast on changes in sputum LTC(4)-LTD(4), eosinophil cationic protein (ECP), eosinophil count, urinary LTE(4)/creatinine, 11-dehydrothromboxane B(2) (11-dhTXB(2))/creatinine, serum LTC(4)-LTD(4), ECP, and peripheral blood eosinophil count, during immediate asthmatic reaction (IAR) and late asthmatic reaction (LAR) in the HDM group and during IAR in the ASA group for each test, were compared in each group.

RESULTS

In the HDM group, IAR and LAR were observed. Sputum LTC(4)-LTD(4) and urinary LTE(4)/creatinine increased significantly both during IAR and LAR. Sputum ECP increased during IAR and further increased during LAR. Eosinophil count in the sputum did not increase during IAR but significantly increased during LAR. Pranlukast suppressed the fall in FEV(1) both during IAR and LAR (73.8% and 51.9%, respectively) and inhibited the increase in sputum eosinophil count during LAR and sputum ECP during IAR and LAR. In the ASA group, aspirin-induced IAR was associated with a fall in urinary 11-dhTXB(2)/creatinine, increased the levels of sputum LTC(4)-LTD(4) and ECP and urinary LTE(4)/creatinine. Pranlukast suppressed IAR and inhibited the increase of the level of sputum ECP, but failed to change aspirin-induced LT production in the sputum and urine. The levels of sputum LTC(4)-LTD(4) and urinary LTE(4)/creatinine in the stable phase in the ASA group were significantly greater than those in the HDM group.

CONCLUSION

Our results indicated that HDM-provoked asthma is associated with overproduction of LT with an antigen-antibody reaction, while AIA is associated with overproduction of LT with a shift to the 5-lipoxygenase series of the arachidonate cascade. LTRA may be useful against both types of asthma through inhibition of LT activity and eosinophilic inflammation of the airways.

Leukotrienes: new therapies and their influence on asthma

Leukotriene receptor antagonists (LTRAs) are new therapies in asthma management which act to block the naturally occurring leukotrienes and improve lung function. It is clear from past research that many asthmatics dislike taking both oral and inhaled steroids and may probably welcome these new drugs simply because they are not steroid preparations. The oral route of LTRAs may be helpful for particular groups of patients, although LTRAs will not be suitable for all asthmatics. Their use so far has been largely as 'add-on' therapies for mild-to-moderate asthma with results that are promising in some patients but have been disappointing in others. Fewer side-effects may well improve medication compliance which has caused both unnecessary morbidity and has been linked to mortality in the past.

Drugs affecting the respiratory system

Differences in the disposition of drugs among exotic animals is a well-recognized hurdle when treating disease. Differences exist in pharmacokinetics, pharmacodynamics, and disease processes. This article focuses on the principles of treating respiratory tract diseases, with the recognition that not all drugs are indicated for use in all exotic species. The discussion begins with a description of respiratory physiology as it pertains to response to drugs, using the mammalian lung as a template. The role of respiratory defense mechanisms in airway protection and disease is addressed. Drugs used to treat the respiratory tract include the bronchodilators and anti-inflammatory drugs, drugs that modify respiratory secretions (e.g., mucolytics, mucokinetics, and expectorants), antitussive drugs, and decongestants. Aerosolization is an important adjuvant for respiratory therapy as long as precautions are met. Infectious diseases are among the more common respiratory diseases encountered, and the discussion includes a focus on the use of antibiotics for treating respiratory tract infections.

Anti-leukotrienes in asthma: yet to arrive

Inflammation plays a predominant role in the pathogenesis of asthma. The leukotrienes (LTs) exert their actions by binding to and activating various receptors. Leukotrienes B4, C4, D4, and E4 have been shown experimentally to play a role in inflammatory mechanisms, producing the pathologic changes seen in asthma. Antileukotrienes represent a new class of anti-asthma drugs with anti-inflammatory role. In asthma management, LT modifiers from the groups of 5 lipoxygenase inhibitor and Cys LT1 receptor antagonists are found useful. LAs are of main use in mild to moderate chronic asthma. Their usefulness is also observed in allergic rhinitis and even in severe chronic cases of asthma which are resistant to steroids. In chronic asthma they are required to be used for prolonged periods with other agents viz. inhaled steroids and beta 2 agonists. These agents are essentially safe. Except for Montelukast, which can be used in children above six years of age, the paediatric use of other agents is yet to be established. LAs are gradually becoming available in increasing number of countries. In India, we have to presumably wait for sometime before these drugs reach the market. The cost of LAs is reasonably high. Thus, India awaits arrival of LAs, may be for good, as more concrete information from various trials will permit us to practice more evidence based medicine.

Role for cysteinyl leukotriene receptor antagonist therapy in asthma and their potential role in allergic rhinitis based on the concept of "one linked airway disease"

OBJECTIVE

This review focuses on the shared pathophysiology of asthma and allergic rhinitis. The similarities illustrate the "one linked airway disease" concept, a unifying theory of these upper and lower airway inflammatory disorders. Since leukotrienes are mediators in both conditions, studies have been performed to assess the potential therapeutic role of cysteinyl leukotriene antagonists. The purpose of this paper is to provide an overview of the accumulating data concerning these agents in treating asthma and allergic rhinitis.

DATA SOURCES

Relevant publications obtained from a literature review.

STUDY SELECTION

Relevant publications on the topics of leukotrienes, leukotriene receptor antagonists, asthma, and allergic rhinitis were critically evaluated.

RESULTS AND CONCLUSIONS

Studies to date have documented the efficacy of cysteinyl leukotriene receptor antagonists for asthma. The pathophysiology of allergic rhinitis and its similarities to asthma suggest that these agents could play a significant therapeutic role in managing this upper airway disorder. Because the leukotriene antagonists are oral agents, they may be valuable in treating not only either condition but also both at the same time when they coexist. They appear to be beneficial when prescribed as the initial medicine and when used in conjunction with other therapies.

cDNA cloning of 15-lipoxygenase type 2 and 12-lipoxygenases of bovine corneal epithelium

Bovine corneal epithelium contains arachidonate 12- and 15-lipoxygenase activity, while human corneal epithelium contains only 15-lipoxygenase activity. Our purpose was to identify the corneal 12- and 15-lipoxygenase isozymes. We used cDNA cloning to isolate the amino acid coding nucleotide sequences of two bovine lipoxygenases. The translated sequence of one lipoxygenase was 82% identical with human 15-lipoxygenase type 2 and 75% identical with mouse 8-lipoxygenase, whereas the other translated nucleotide sequence was 87% identical with human 12-lipoxygenase of the platelet type. Expression of 15-lipoxygenase type 2 and platelet type 12-lipoxygenase mRNAs were detected by Northern analysis. In addition to these two lipoxygenases, 12-lipoxygenase of leukocyte (tracheal) type was detected by polymerase chain reaction (PCR), sequencing, and Northern analysis. Finally, PCR and sequencing suggested that human corneal epithelium contains 15-lipoxygenase types 1 and 2.