Iloprost inhalation in mild asthma

Prostacyclin Regulation of Allergic Inflammation

Prostacyclin is a metabolic product of the cyclooxygenase pathway that is constitutively expressed and can be induced during inflammatory conditions. While prostacyclin and its analogs have historically been considered effective vasodilators and used in treating pulmonary hypertension, prostacyclin has demonstrated potent anti-inflammatory effects in animal models of allergic airway inflammation. In vitro studies reveal that prostacyclin directly inhibits type 2 cytokine production from CD4+ Th2 cells and ILC2 and reduces the ability of dendritic cells to generate Th2 cytokine production from CD4+ T cells in an antigen-specific manner. Thus, there is strong evidence that prostacyclin may be an additional therapeutic target for treating allergic inflammation and asthma in human subjects.

Prostaglandins in asthma and allergic diseases

Prostaglandins are synthesized through the metabolism of arachidonic acid via the cyclooxygenase pathway. There are five primary prostaglandins, PGD₂, PGE₂, PGF₂, PGI₂, and thromboxane B₂, that all signal through distinct seven transmembrane, G-protein coupled receptors. The receptors through which the prostaglandins signal determines their immunologic or physiologic effects. For instance, the same prostaglandin may have opposing properties, dependent upon the signaling pathways activated. In this article, we will detail how inhibition of cyclooxygenase metabolism and regulation of prostaglandin signaling regulates allergic airway inflammation and asthma physiology. Possible prostaglandin therapeutic targets for allergic lung inflammation and asthma will also be reviewed, as informed by human studies, basic science, and animal models.

Prostanoids in Asthma and COPD: Actions, Dysregulation, and Therapeutic Opportunities

Pathophysiologic gaps in the actions of currently available treatments for asthma and COPD include neutrophilic inflammation, airway remodeling, and alveolar destruction. All of these processes can be modulated by cyclic adenosine monophosphate-elevating prostaglandins E2 and I2 (also known as prostacyclin). These prostanoids have long been known to elicit bronchodilation and to protect against bronchoconstriction provoked by a variety of stimuli. Much less well known is their capacity to inhibit inflammatory responses involving activation of lymphocytes, eosinophils, and neutrophils, as well as to attenuate epithelial injury and mesenchymal cell activation. This profile of actions identifies prostanoids as attractive candidates for exogenous administration in asthma. By contrast, excessive prostanoid production and signaling might contribute to both the increased susceptibility to infections that drive COPD exacerbations and the inadequate alveolar repair that characterizes emphysema. Inhibition of endogenous prostanoid synthesis or signaling, thus, has therapeutic potential for these types of patients. By virtue of their pleiotropic capacity to modulate numerous pathophysiologic processes relevant to the expression and natural history of airway diseases, prostanoids emerge as attractive targets for therapeutic manipulation.

The role of prostaglandins in allergic lung inflammation and asthma

Prostaglandins (PGs) are products of the COX pathway of arachidonic acid metabolism. There are five primary PGs, PGD₂, PGE₂, PGF₂, PGI₂ and thromboxane A₂, all of which signal through distinct seven transmembrane, G-protein coupled receptors. Some PGs may counteract the actions of others, or even the same PG may have opposing physiologic or immunologic effects, depending on the specific receptor through which it signals. In this review, we examine the effects of COX activity and the various PGs on allergic airway inflammation and physiology that is associated with asthma. We also highlight the potential therapeutic benefit of targeting PGs in allergic lung inflammation and asthma based on basic science, animal model and human studies.

Lipid mediators and allergic diseases

OBJECTIVE

To review the basic science and translational relevance of lipid mediators in the pathobiology of allergic diseases.

DATA SOURCES

PubMed was searched for articles using the key terms lipid mediator, prostaglandin, prostanoid, leukotriene, thromboxane, asthma, and allergic inflammation.

STUDY SELECTIONS

Articles were selected based on their relevance to the goals of this review. Articles with a particular focus on clinical and translational aspects of basic science discoveries were emphasized.

RESULTS

Lipid mediators are bioactive molecules generated from cell membrane phospholipids. They play important roles in many disease states, particularly in inflammatory and immune responses. Lipid mediators and their receptors are potentially useful as diagnostic markers of disease and therapeutic targets.

CONCLUSIONS

Several useful therapeutic agents have been developed based on a growing understanding of the lipid mediator pathways in allergic disease, notably the cysteinyl leukotriene receptor type 1 antagonists and the 5-lipoxygenase inhibitor, zileuton. Additional receptor agonists and antagonists relevant to these pathways are in development, and it is likely that future pharmacologic treatments for allergic disease will become available as our understanding of these molecules continues to evolve.