Suppression of the antigen-stimulated RBL-2H3 mast cell activation by Artekeiskeanol A

The Complexity of Sesquiterpene Chemistry Dictates Its Pleiotropic Biologic Effects on Inflammation

Sesquiterpenes (SQs) are volatile compounds made by plants, insects, and marine organisms. SQ have a large range of biological properties and are potent inhibitors and modulators of inflammation, targeting specific components of the nuclear factor-kappaB (NF-κB) signaling pathway and nitric oxide (NO) generation. Because SQs can be isolated from over 1600 genera and 2500 species grown worldwide, they are an attractive source of phytochemical therapeutics. The chemical structure and biosynthesis of SQs is complex, and the SQ scaffold represents extraordinary structural variety consisting of both acyclic and cyclic (mono, bi, tri, and tetracyclic) compounds. These structures can be decorated with a diverse range of functional groups and substituents, generating many stereospecific configurations. In this review, the effect of SQs on inflammation will be discussed in the context of their complex chemistry. Because inflammation is a multifactorial process, we focus on specific aspects of inflammation: the inhibition of NF-kB signaling, disruption of NO production and modulation of dendritic cells, mast cells, and monocytes. Although the molecular targets of SQs are varied, we discuss how these pathways may mediate the effects of SQs on inflammation.

Cytokine Storm Syndrome in SARS-CoV-2 Infections: A Functional Role of Mast Cells

Cytokine storm syndrome is a cascade of escalated immune responses disposing the immune system to exhaustion, which might ultimately result in organ failure and fatal respiratory distress. Infection with severe acute respiratory syndrome-coronavirus-2 can result in uncontrolled production of cytokines and eventually the development of cytokine storm syndrome. Mast cells may react to viruses in collaboration with other cells and lung autopsy findings from patients that died from the coronavirus disease that emerged in 2019 (COVID-19) showed accumulation of mast cells in the lungs that was thought to be the cause of pulmonary edema, inflammation, and thrombosis. In this review, we present evidence that a cytokine response by mast cells may initiate inappropriate antiviral immune responses and cause the development of cytokine storm syndrome. We also explore the potential of mast cell activators as adjuvants for COVID-19 vaccines and discuss the medications that target the functions of mast cells and could be of value in the treatment of COVID-19. Recognition of the cytokine storm is crucial for proper treatment of patients and preventing the release of mast cell mediators, as impeding the impacts imposed by these mediators could reduce the severity of COVID-19.

Twenty-first century mast cell stabilizers

Mast cell stabilizing drugs inhibit the release of allergic mediators from mast cells and are used clinically to prevent allergic reactions to common allergens. Despite the relative success of the most commonly prescribed mast cell stabilizer, disodium cromoglycate, in use for the preventative treatment of bronchial asthma, allergic conjunctivitis and vernal keratoconjunctivitis, there still remains an urgent need to design new substances that are less expensive and require less frequent dosing schedules. In this regard, recent developments towards the discovery of the next generation of mast cell stabilizing drugs has included studies on substances isolated from natural sources, biological, newly synthesized compounds and drugs licensed for other indications. The diversity of natural products evaluated range from simple phenols, alkaloids, terpenes to simple amino acids. While in some cases their precise mode of action remains unknown it has nevertheless sparked interest in the development of synthetic derivatives with improved pharmacological properties. Within the purely synthetic class of inhibitors, particular attention has been devoted to the inhibition of important signalling molecules including spleen TK and JAK3. The statin class of cholesterol-lowering drugs as well as nilotinib, a TK inhibitor, are just some examples of clinically used drugs that have been evaluated for their anti-allergic properties. Here, we examine each approach under investigation, summarize the test data generated and offer suggestions for further preclinical evaluation before their therapeutic potential can be realized.

Induction of IL-13 production and upregulation of gene expression of protease activated receptors in P815 cells by IL-6

Interleukin (IL)-6 is a multifunctional cytokine which has been showed to induce up-regulated expression of Fc epsilon RI receptor and histamine production in mast cells. However, little is known of its effects on Th2 cytokine secretion and protease activated receptor (PAR) expression in mast cells. In the present study, we examined potential influence of IL-6 on IL-13, IL-4 and IL-10 release from P815 cells and PAR expression on P815 cells by using flow cytometry analysis, quantitative real-time PCR, ELISA and cellular activation of signaling ELISA (CASE) techniques. The results showed that IL-6 induced up to 1.8-fold increase in IL-13, but not IL-4 or IL-10 release from P815 cells, and FSLLRY-NH(2) did not affect IL-6 induced IL-13 release. Tryptase elicited 2.0-fold increase in IL-13 release from P815 cells, which can be inhibited by IL-6. IL-6 elicited the up-regulated expression of PAR-1, PAR-2, PAR-3 and PAR-4 mRNAs, but had little effects on expression of PAR proteins. U0126, PD98059 and LY204002 abolished IL-6 induced IL-13 release when they were preincubated with P815 cells, indicating ERK and Akt cell signaling pathways may be involved in the event. In conclusion, IL-6 can stimulate IL-13 release from mast cells through an ERK and Akt cell signaling pathway dependent, but PAR independent mechanism.