Metabolic Activation of Militarine In Vitro and In Vivo

Effect fraction of Bletilla striata (Thunb.) Reichb.f. alleviates LPS-induced acute lung injury by inhibiting p47phox/NOX2 and promoting the Nrf2/HO-1 signaling pathway

BACKGROUND & AIMS

The effect fraction of Bletilla striata (Thunb.) Reichb.f. (EFBS), a phenolic-rich extract, has significant protective effects on lipopolysaccharide (LPS)-induced acute lung injury (ALI), but its composition and molecular mechanisms are unclear. This study elucidated its chemical composition and possible protective mechanisms against LPS-induced ALI from an antioxidant perspective.

METHODS

EFBS was prepared by ethanol extraction, enriched by polyamide column chromatography, and characterized using ultra-performance liquid chromatography/time-of-flight mass spectrometry. The LPS-induced ALI model and the RAW264.7 model were used to evaluate the regulatory effects of EFBS on oxidative stress, and transcriptome analysis was performed to explore its possible molecular mechanism. Then, the pathway by which EFBS regulates oxidative stress was validated through inhibitor intervention, flow cytometry, quantitative PCR, western blotting, and immunofluorescence techniques.

RESULTS

A total of 22 compounds in EFBS were identified. The transcriptome analyses of RAW264.7 cells indicated that EFBS might reduce reactive oxygen species (ROS) production by inhibiting the p47phox/NADPH oxidase 2 (NOX2) pathway and upregulating the nuclear factor erythroid 2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1) pathway. Both in vitro and in vivo data confirmed that EFBS significantly inhibited the expression and phosphorylation of p47phox protein, thereby weakening the p47phox/NOX2 pathway and reducing ROS production. EFBS significantly increased the expression of Nrf2 in primary peritoneal macrophages and lung tissue and promoted its nuclear translocation, dose-dependent increase in HO-1 levels, and enhancement of antioxidant activity. In vitro, both Nrf2 and HO-1 inhibitors significantly reduced the scavenging effects of EFBS on ROS, further confirming that EFBS exerts antioxidant effects at least partially by upregulating the Nrf2/HO-1 pathway.

CONCLUSIONS

EFBS contains abundant phenanthrenes and dibenzyl polyphenols, which can reduce ROS production by inhibiting the p47phox/NOX2 pathway and enhance ROS clearance activity by upregulating the Nrf2/HO-1 pathway, thereby exerting regulatory effects on oxidative stress and improving LPS-induced ALI.

Advances in militarine: Pharmacology, synthesis, molecular regulation and regulatory mechanisms

Militarine is the lead member of secondary metabolites found in multiple medicinal plants of the orchid family. It acts as not only an important inhibitor on plant growth, but also functions as the quality marker for medicinal materials. In addition, Militarine has been shown to possess remarkably medicinal value, with a definite potential for finding widespread adoption of treating various diseases, including lung injury, brain nerve injury, cognitive impairment, aging, tumors, inflammation, peptic ulcers, and more. Thus, it can serve as a material carrier for pharmacophore upon, so much so that it probes as natural source of lead compounds in the research and development of medication. The study reported herein makes an overview on the physicochemical properties and pharmacological mechanisms of Militarine compounds, summarizes the biogenic pathways of Militarine and organically integrates the biological characteristics of Militarine with multiple omics techniques. Besides, this review also constructs a regulatory system for the biological accumulation of Militarine around its precursor compounds, characteristic gene elements, key enzymes, important metabolic products, and critical steps and links. Exceptionally, emphasis on the biosynthesis of Militarine under both abiotic and biotic stress, as well as an elaboration of the signaling pathways and critical regulatory mechanisms that govern the metabolic flow of Militarine have been represented accordingly in this paper. These findings are expected to provide reference schemes and theoretical foundations for acquiring high-quality resources of Militarine and advancing its large-scale industrial production, drug development, and clinical applications to comprehensively elucidate the biosynthetic and metabolic pathways.