A novel synthetic derivative of melatonin, 5-hydroxy-2'-isobutyl-streptochlorin (HIS), inhibits inflammatory responses via regulation of TRIF-dependent signaling and inflammasome activation.

Melatonin is substantially reported to possess anti-inflammatory properties. In the present study, we synthesized a novel melatonin derivative, 5-hydroxy-2'-isobutyl-streptochlorin (HIS), which displayed superior anti-inflammatory properties to its parent compound. Further, we explored its underlying mechanisms in cellular and experimental animal models. Lipopolysaccharide was used to induce in vitro inflammatory responses in RAW 264.7 macrophages. LPS-primed macrophages were pulsed with biologically unrelated toxic molecules to evaluate the role of HIS on inflammasome activation. In vivo verifications were carried out using acute lung injury (ALI) and Escherichia coli-induced septic shock mouse models. HIS inhibited the production of proinflammatory mediators and cytokines such as nitric oxide, cyclooxygenase 2, IL-1ß, IL-6 and TNF-α in LPS-stimulated RAW 264.7 macrophages. HIS suppressed the infiltration of immune cells into the lung and the production of pro-inflammatory cytokines such as IL-6 and TNF-α in broncho-alveolar lavage fluid in the ALI mouse model. Mechanistic studies revealed that the inhibitory effects of HIS were mediated through the regulation of the TIR domain-containing, adaptor-inducing, interferon-ß (TRIF)-dependent signaling pathway from toll-like receptors. Further, HIS attenuated IL-1ß secretion via the inhibition of NLRP3 inflammasome activation independent of mitochondrial ROS production. Furthermore, HIS suppressed IL-1ß, IL-6 and interferon-ß production in peritoneal lavage in the Escherichia coli-induced sepsis mouse model. In conclusion, HIS exerted potent anti-inflammatory effects via the regulation of TRIF-dependent signaling and inflammasome activation. Notably, the superior anti-inflammatory properties of this derivative compared with its parent compound could be a promising lead for treating various inflammatory-mediated diseases.

Lysimachia clethroides Duby extract attenuates inflammatory response in Raw 264.7 macrophages stimulated with lipopolysaccharide and in acute lung injury mouse model.

ETHNOPHARMACOLOGICAL RELEVANCE: Lysimachia clethroides Duby (LC) is a traditional medicinal herb used to treat edema, hepatitis and inflammatory diseases in China and other Asian countries. In this study, the anti-inflammatory effects of LC extract and the mechanisms underlying were explored in both in vitro cell lines and acute lung injury (ALI) animal model of inflammation in vivo. MATERIALS AND METHODS: Lipopolysaccharide (LPS)-stimulated Raw 264.7 murine macrophages were used to study the regulatory effects of LC extract on inflammatory mediators such as nitric oxide (NO) and proinflammatory cytokine expression. Western blotting or ELISA techniques were employed to estimate protein levels. RT-PCR was used for analyzing the interferon (IFN)-ß production. LPS-induced ALI mouse model in vivo was employed to study the effect of LC extract. Further high-performance liquid chromatography (HPLC) fingerprinting technique was used to evaluate the active constituents present in LC extract, compared with reference standards. RESULTS: Pre-treatment with LC extract inhibited the LPS-stimulated NO release, interleukin (IL)-1ß and IL-6 production in Raw 264.7 cells dose dependently. LC extract inhibited the LPS-stimulated IRF3 and STAT1 phosphorylation. Further, in vivo experiments revealed that LC extract suppressed the infiltration of immune cells into the lung and proinflammatory cytokine production in broncho-alveolar lavage fluid (BALF) in the LPS-induced ALI mouse model. CONCLUSIONS: Our results indicate that LC extract attenuates LPS-stimulated inflammatory responses in macrophages via regulating the key inflammatory mechanisms, providing a scientific support for its traditional use in treating various inflammatory diseases.