Baccharin and p-coumaric acid from green propolis mitigate inflammation by modulating the production of cytokines and eicosanoids.

ETHNOPHARMACOLOGICAL RELEVANCE: Green propolis is produced by Apis mellifera honeybees using Baccharis dracunculifolia D.C. (Asteraceae) as substrate. This Southern Brazilian native plant and green propolis have been used in traditional medicine to treat gastric diseases, inflammation and liver disorders. AIM OF THE STUDY: Investigate the effects of baccharin (Bac) or p-coumaric acid (pCA) isolated from B. dracunculifolia D.C. (Asteraceae) over the inflammation induced by lipopolysaccharide (LPS) in vivo. MATERIALS AND METHODS: Inflammation was induced by LPS injection into air-pouches in mice, which were subsequently treated with Bac or pCA. Lavage fluid was collected from air pouches for the quantification of cellular influx via microscopy, and quantification of inflammatory mediators via colorimetric methods, ELISA and liquid chromatography-tandem mass spectrometry (LC-MS/MS). RESULTS: LPS-induced inflammation increased cellular influx and increased the levels of parameters related to vascular permeability and edema formation, such as nitric oxide (NO) and protein extravasation. Moreover, LPS increased the levels of cytokines and eicosanoids in the air-pouches. Importantly, both Bac and pCA suppressed the infiltration of neutrophils, production of NO and protein extravasation. Notably, the compounds promote differential regulation of cytokine and eicosanoid production. CONCLUSIONS: Our results suggest that Bac from green propolis directly affects inflammation by inhibiting the production of cytokines and eicosanoids, while pCA may exert direct, but also indirect effects on inflammation by stimulating the production of regulatory effectors such as interkeukin-10 in vivo.

Crotoxin-Induced Mice Lung Impairment: Role of Nicotinic Acetylcholine Receptors and COX-Derived Prostanoids.

Respiratory compromise in Crotalus durissus terrificus (C.d.t.) snakebite is an important pathological condition. Considering that crotoxin (CTX), a phospholipase A2 from C.d.t. venom, is the main component of the venom, the present work investigated the toxin effects on respiratory failure. Lung mechanics, morphology and soluble markers were evaluated from Swiss male mice, and mechanism determined using drugs/inhibitors of eicosanoids biosynthesis pathway and autonomic nervous system. Acute respiratory failure was observed, with an early phase (within 2 h) characterized by enhanced presence of eicosanoids, including prostaglandin E2, that accounted for the increased vascular permeability in the lung. The alterations of early phase were inhibited by indomethacin. The late phase (peaked 12 h) was marked by neutrophil infiltration, presence of pro-inflammatory cytokines/chemokines, and morphological alterations characterized by alveolar septal thickening and bronchoconstriction. In addition, lung mechanical function was impaired, with decreased lung compliance and inspiratory capacity. Hexamethonium, a nicotinic acetylcholine receptor antagonist, hampered late phase damages indicating that CTX-induced lung impairment could be associated with cholinergic transmission. The findings reported herein highlight the impact of CTX on respiratory compromise, and introduce the use of nicotinic blockers and prostanoids biosynthesis inhibitors as possible symptomatic therapy to Crotalus durissus terrificus snakebite.

Paradoxical Effect of LTB4 on the Regulation of Stress-Induced Corticosterone Production.

Depression is a mental illness with a complex and multifactorial etiology, which has been associated with stress and inflammation. Infections, autoimmune diseases, envenomation, and trauma induce an inflammatory response that is characterized by increasing levels of circulating cytokines (e.g., IL-1ß) and lipid mediators [e.g., PGE2 and leukotrienes B4 (LTB4)]. Recently, we showed that LTB4 production by the 5-lipoxygenase (5-LO) pathway regulates IL-1ß and PGE2 release, reducing tissue damage in a model of sterile inflammation. Since IL-1ß and PGE2 increase in serum of stressed patients and potentially trigger depression, we used an animal model of chronic unpredictable stress (CUS) to investigate the potential impact of LTB4 over depression-like symptoms. At basal conditions, 5-LO deficiency (Alox5 -/-) reduces the preference for sucrose, while inducing a higher immobilization time on the tail suspension test when compared 129sv. Moreover, Alox5 -/- mice present increased caspase-1 expression and elevated levels of IL-1ß, IL-17 and PGE2 in the spleen, with increasing corticosterone levels in the frontal cortex but reducing systemic levels. Compared to 129sv mice, CUS induced higher levels of systemic, frontal cortex and hippocampal corticosterone, and also reduced sucrose preference, increased levels of splenic IL-1ß, IL-17 and PGE2 and reduced levels of LTB4. Interestingly, CUS exposure did not alter the reduced sucrose preference shown by Alox5 -/- mice but greatly enhanced splenic PGE2 production. Compared to Alox5 -/- mice at basal conditions, CUS exposure also increased levels of systemic corticosterone, which remained lower than those of CUS-129sv animals. We also observed that treatment with LTB4 decreased caspase-1 expression and systemic levels of corticosterone in CUS-Alox5 -/- mice but there was no significant impact on the reduced sucrose preference. Our results demonstrate that LTB4 controls the hypothalamic-pituitary-adrenal (HPA) axis by regulating levels of systemic corticosterone associated with the repression of caspase-1 expression and production of inflammatory mediators. One limitation of our study is that 129sv and Alox5 -/- mice were not littermates, not sharing, therefore, the same intra-uterine and preweaning environment. Even so, taken together our results indicate that 5-LO activity is critical for the regulation of stress-induced symptoms, suggesting that the Alox5 -/- mouse could be a natural model of corticosterone-independent reduced reward sensitivity.