Immunomodulatory effects of Santolina chamaecyparissus leaf extracts on human neutrophil functions

Phagocytosis, Degranulation and Extracellular Traps Release by Neutrophils-The Current Knowledge, Pharmacological Modulation and Future Prospects

Neutrophils are crucial elements of innate immune system, which assure host defense via a range of effector functions, such as phagocytosis, degranulation, and NET formation. The latest literature clearly indicates that modulation of effector functions of neutrophils may affect the treatment efficacy. Pharmacological modulation may affect molecular mechanisms activating or suppressing phagocytosis, degranulation or NET formation. In this review, we describe the role of neutrophils in physiology and in the course of bacterial and viral infections, illustrating the versatility and plasticity of those cells. This review also focus on the action of plant extracts, plant-derived compounds and synthetic drugs on effector functions of neutrophils. These recent advances in the knowledge can help to devise novel therapeutic approaches via pharmacological modulation of the described processes.

Unveiling the bioactive potential of the essential oil of a Portuguese endemism, Santolina impressa

ETHNOPHARMACOLOGICAL RELEVANCE

Santolina species are widely used in traditional medicine in the Mediterranean region for their anti-inflammatory, antimicrobial, antispasmodic, digestive, and analgesic properties. S. impressa, a Portuguese endemism, is traditionally recognized for its beneficial anti-inflammatory properties in several gastrointestinal affections and is also used in oropharyngeal infections.

AIM OF THE STUDY

The present study aims to characterize the essential oil of S. impressa growing in Portugal and validate its traditional uses by assessing the anti-inflammatory potential of its essential oil at concentrations without toxicity. The antifungal properties of the oil are also addressed, as well as, the putative mechanism of action underlying these effects.

MATERIAL AND METHODS

The essential oil was obtained in accordance with the European Pharmacopoeia and characterized by GC and GC-MS. The anti-inflammatory potential of the oil was assessed on LPS-stimulated macrophages, through the production of nitric oxide (NO) using the Griess reaction. Putative mechanisms of action included the role of the oil as a NO scavenger, as well as its effect on the expression of two key pro-inflammatory enzymes, iNOS and COX-2 by Western blot analysis. The antifungal effect of the oil was evaluated according to the CLSI guidelines on several yeast and filamentous strains and on two major virulence factors in Candida albicans, namely germ tubes and biofilms. Ultrastructural modifications on dermatophytes were also unveiled by transmission electron microscopy.

RESULTS

S. impressa essential oil was primarily characterized by the presence of monoterpene hydrocarbons and oxygenated monoterpenes, being the main compounds β-pinene (22.5%), 1,8-cineole (10.0%), limonene (9.1%), camphor (8.1%) and β-phellandrene (8.0%). A significant decrease (ca 60.0%) in nitrite levels was observed in LPS-stimulated macrophages treated with the oil without affecting cell viability. This effect could be explained by a great reduction on iNOS expression (85.0% inhibition), thus underpinning the anti-inflammatory potential of the oil. The oil also showed a fungicidal effect, being more active against Cryptococcus neoformans, Epidermophyton floccosum and Trichophytum rubrum. For these dermatophytes, significant ultrastructural modifications in cell wall structure were detected. Strikingly, for C. albicans, the oil showed a significant anti-infective potential (at 0.07 mg/mL for germ tube inhibition and 0.02 mg/mL for biofilm disruption) before fungal growth inhibition occurred.

CONCLUSIONS

Our results validate the main traditional use ascribed to S. impressa, namely its anti-inflammatory effect. In addition, an antifungal potential is pointed out, thus corroborating the antimicrobial uses and adding new value to an endemic species poorly recognized by the industry.