Maleylated-BSA suppresses lipopolysaccharide-induced IL-6 production by activating the ERK-signaling pathway in murine RAW264.7 cells

Anti-inflammatory chemical constituents of Flos Chrysanthemi Indici determined by UPLC-MS/MS integrated with network pharmacology

Flos Chrysanthemi Indici (FCI), the flower of Chrysanthemum indicum L., is a common functional food and a well-known traditional Chinese medicine (TCM) for the treatment of inflammatory diseases. Previous studies have revealed that FCI has anti-inflammatory activity, but little is known about its anti-inflammatory chemical profile. In this study, the potential anti-inflammatory constituents of FCI were investigated by ultra-high-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF/MS) combined with the network pharmacology approach, and further confirmed on a LPS activated RAW264.7 macrophage model. As a result, a total of forty-two compounds, including thirty-two flavonoids, nine phenolic acids and one sesquiterpene, were identified. Among them, fourteen compounds including eight flavonoids (11, 17, 24, 28, 32, 39, 41 and 42) and six caffeoylquinic acids (3, 4, 5, 13, 15 and 20) were recognized as potential key anti-inflammatory constituents of FCI through network pharmacology analysis, because they accounted for 92% of the relative peak area in the UPLC-Q-TOF/MS chromatogram and acted on 87 of 97 the inflammatory targets of FCI. However, only 16 targets were shared between the flavonoids and caffeoylquinic acids, indicative of both acting on more different targets. Further the anti-inflammatory effects of the fourteen constituents were validated with the decreased levels of NO, TNF-α, IL-6 and PGE2 in RAW264.7 macrophage cells treated with LPS. Our results indicated that both flavonoids and caffeoylquinic acids were responsible for the anti-inflammatory effect of FCI through synergetic actions on multi-targets. Moreover, 3,5-dicaffeoylquinic acid (15), luteolin (24) and linarin (28) were the most important active constituents of FCI and could be selected as chemical markers for quality control of FCI. Overall, the findings not only explore the anti-inflammatory chemical constituents of FCI, but also provide novel insights into the effective constituents and mechanism of TCMs.

Mutant glucocorticoid receptor binding elements on the interleukin-6 promoter regulate dexamethasone effects

Background

Glucocorticoids (GCs) have been extensively used as essential modulators in clinical infectious and inflammatory diseases. The GC receptor (GR) is a transcription factor belonging to the nuclear receptor family that regulates anti-inflammatory processes and releases pro-inflammatory cytokines, such as interleukin (IL)-6.

Results

Five putative GR binding sites and other transcriptional factor binding sites were identified on theIL-6 promoter, and dexamethasone (DEX) was noted to reduce the lipopolysaccharide (LPS)-induced IL-6 production. Among mutant transcriptional factor binding sites, nuclear factor-kappa B (NF-κB), activator protein (AP)-1, and specificity protein (Sp)1–2 sites reduced basal and LPS-induced IL-6 promoter activities through various responses. The second GR binding site (GR2) was noted to play a crucial role in both basal and inducible promoter activities in LPS-induced inflammation.

Conclusions

We concluded that selective GR2 modulator might exert agonistic and antagonistic effects and could activate crucial signaling pathways during the LPS-stimulated inflammatory process.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12865-021-00413-z.

A high concentration of fatty acids induces TNF-α as well as NO release mediated by the P2X4 receptor, and the protective effects of puerarin in RAW264.7 cells

Circulating levels of free fatty acids (FFAs) are often found to be increased in patients with type 2 diabetes mellitus (T2DM) and metabolic syndrome (MS). High plasma FFA levels may give rise to maladaptive macrophage activation and promote inflammatory responses, which has been proposed as a potential mechanism for the development of DM and MS. P2X4 receptor (P2X4R), a ligand-gated cation channel activated by extracellular adenosine triphosphate (ATP), plays a primary role in the regulation of inflammatory responses. Puerarin has been reported to possess potential anti-inflammatory activity. However, the anti-inflammatory activity of puerarin and the underlying molecular mechanisms in a setting of a high concentration of FFAs remain unknown. In this study, we found that a high concentration of FFAs increased the expression of P2X4R, cytosolic Ca²⁺ concentration and the phosphorylation of extracellular signal-regulated kinase (ERK) and induced the expression of tumor necrosis factor (TNF)-α and inducible nitric oxide synthase (iNOS) mRNA and the release of TNF-α and nitric oxide (NO) in RAW264.7 macrophages. Such a high concentration FFA-induced inflammation may be reversed by the P2X4R selective antagonist 5-BDBD, which manifests the important role of P2X4R in the TNF-α and NO release caused by the high concentration of FFAs in RAW264.7 cells. Molecular docking data showed that puerarin could interfere with the activation of P2X4R by forming hydrogen bonding towards residue Arg267, an important residue essential for the canonical activation of P2X4R. Treatment with puerarin dose-dependently reduced high concentration FFA-elevated P2X4R expression and inhibited P2X4R-mediated inflammatory signalling, including high concentration FFA-evoked [Ca²⁺]_i, ERK phosphorylation, expression of TNF-α and iNOS mRNA and release of TNF-α and NO. Our findings emphasize the critical role of P2X4R in high concentration FFA-induced TNF-α and NO release of RAW264.7 macrophages. Puerarin notably counteracts these high concentration FFA-induced adverse effects through its inhibition of P2X4R expression and P2X4R-mediated inflammatory signalling.

Intranasal Immunization with DOTAP Cationic Liposomes Combined with DC-Cholesterol Induces Potent Antigen-Specific Mucosal and Systemic Immune Responses in Mice

Despite the progress made by modern medicine, infectious diseases remain one of the most important threats to human health. Vaccination against pathogens is one of the primary methods used to prevent and treat infectious diseases that cause illness and death. Vaccines administered by the mucosal route are potentially a promising strategy to combat infectious diseases since mucosal surfaces are a major route of entry for most pathogens. However, this route of vaccination is not widely used in the clinic due to the lack of a safe and effective mucosal adjuvant. Therefore, the development of safe and effective mucosal adjuvants is key to preventing infectious diseases by enabling the use of mucosal vaccines in the clinic. In this study, we show that intranasal administration of a cationic liposome composed of 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) and 3β-[N-(N',N'-dimethylaminoethane)-carbamoyl] (DC-chol) (DOTAP/DC-chol liposome) has a potent mucosal adjuvant effect in mice. Intranasal vaccination with ovalbumin (OVA) in combination with DOTAP/DC-chol liposomes induced the production of OVA-specific IgA in nasal tissues and increased serum IgG1 levels, suggesting that the cationic DOTAP/DC-chol liposome leads to the induction of a Th2 immune response. Additionally, nasal-associated lymphoid tissue and splenocytes from mice treated with OVA plus DOTAP/DC-chol liposome showed high levels of IL-4 expression. DOTAP/DC-chol liposomes also enhanced OVA uptake by CD11c+ dendritic cells in nasal-associated lymphoid tissue. These data demonstrate that DOTAP/DC-chol liposomes elicit immune responses via an antigen-specific Th2 reaction. These results suggest that cationic liposomes merit further development as a mucosal adjuvant for vaccination against infectious diseases.

Nucleolin is a receptor for maleylated-bovine serum albumin on macrophages

Scavenger receptors have a broad range of functions that include pathogen clearance, and identification of the scavenger receptor family has been of great benefit to the field of physiology. The shuttling-protein nucleolin has recently been shown to possess scavenger receptor-like activity. We therefore investigated whether or not nucleolin is a receptor for maleylated-bovine serum albumin (maleylated-BSA), which is a common ligand for scavenger receptors. Binding and phagocytosis of native control-BSA by thioglycollate-elicited mouse peritoneal macrophages was weak, but that of maleylated-BSA was strong. Surface plasmon-resonance analysis revealed that nucleolin strongly associated with maleylated-BSA but not control-BSA or maleic anhydride. Further, co-treatment of macrophages with anti-nucleolin antibody, but not control-immunoglobulin G, inhibited binding of maleylated-BSA. In addition, antineoplastic guanine rich oligonucleotide (AGRO), a nucleolin-specific oligonucleotide aptamer, inhibited binding of maleylated-BSA. Further, binding of maleylated-BSA to nucleolin-transfected HEK293 cells was higher than that by control HEK cells. These results indicate that nucleolin is a receptor that enables macrophages to recognize maleylated-BSA.