Silybin Alleviates Experimental Autoimmune Encephalomyelitis by Suppressing Dendritic Cell Activation and Th17 Cell Differentiation

Effective action of silymarin against ketamine-induced schizophrenia in male mice: Insight into the biochemical and molecular mechanisms of action

BACKGROUND

Neurochemical dysregulations resulting from N-methyl-D-aspartate hypofunction (NMDA), are exacerbated by neuroimmune and oxidative stress and are known risk factors for neuropsychiatric disorders like schizophrenia-like diseases. Here, we investigate the protective and curative effects, and mechanisms of silymarin, a polyphenolic flavonoid with neuroprotective functions in preventive-reversal model of ketamine, an NMDA antagonist in mice.

METHODS

Mice were grouped into 6 cohorts (n = 9). In the pre-treatment, groups 1 and 2 received saline (10 mL/kg/p.o.), groups 3 and 4 (silymarin, 50 and 100 mg/kg/p.o.), and group 5 (risperidone, 0.5 mg/kg/p.o.) consecutively for 14 days, then combined with ketamine (20 mg/kg/i.p.) injection in groups 2-5 from days 8-14. However, mice in reversal study received intraperitoneal injection of ketamine for 14 days before silymarin (50 and 100 mg/kg, p.o) and risperidone (0.5 mg/kg, p.o.) treatment between days 8-14. The consequences on schizophrenia-like behavior, neurochemistry, inflammation, and oxidative/nitrergic stress markers were evaluated in critical brain regions of the disease.

RESULTS

Silymarin prevented and reversed ketamine-induced increase in dopamine, 5-hydroxyltryptamine, acetylcholinesterase, malondialdehyde and nitrite levels in the striatum, prefrontal-cortex and hippocampus. These were accompanied by improvement in hyperlocomotion, stereotypy, memory, and social impairments, notably devoid of cataleptogenic potential. Complementarily, silymarin reduced myeloperoxidase, tumor-necrosis factor-α, and interleukin-6 concentrations relative to the ketamine group. Moreover, ketamine-induced decreased brain-derived neurotrophic factor, glutathione, catalase, superoxide-dismutase levels were normalized by silymarin in the brain regions relative to ketamine.

CONCLUSIONS

Overall, these findings suggest that silymarin's antipsychotic effect might be primarily associated, among other mechanisms, with the normalization of neurochemical and neurotrophic changes in the mice brains.

Silymarin and Inflammation: Food for Thoughts

Inflammation is a vital defense mechanism, creating hostile conditions for pathogens, preventing the spread of tissue infection and repairing damaged tissues in humans and animals. However, when inflammation resolution is delayed or compromised as a result of its misregulation, the process proceeds from the acute phase to chronic inflammation, leading to the development of various chronic illnesses. It is proven that redox balance disturbances and oxidative stress are among major factors inducing NF-κB and leading to over-inflammation. Therefore, the anti-inflammatory properties of various natural antioxidants have been widely tested in various in vitro and in vivo systems. Accumulating evidence indicates that silymarin (SM) and its main constituent silibinin/silybin (SB) have great potential as an anti-inflammation agent. The main anti-inflammatory mechanism of SM/SB action is attributed to the inhibition of TLR4/NF-κB-mediated signaling pathways and the downregulated expression of pro-inflammatory mediators, including TNF-α, IL-1β, IL-6, IL-12, IL-23, CCL4, CXCL10, etc. Of note, in the same model systems, SM/SB was able to upregulate anti-inflammatory cytokines (IL-4, IL-10, IL-13, TGF-β, etc.) and lipid mediators involved in the resolution of inflammation. The inflammatory properties of SM/SB were clearly demonstrated in model systems based on immune (macrophages and monocytes) and non-immune (epithelial, skin, bone, connective tissue and cancer) cells. At the same time, the anti-inflammatory action of SM/SB was confirmed in a number of in vivo models, including toxicity models, nonalcoholic fatty liver disease, ischemia/reperfusion models, stress-induced injuries, ageing and exercising models, wound healing and many other relevant model systems. It seems likely that the anti-inflammatory activities of SM/SB are key elements on the health-promoting properties of these phytochemicals.

Anti-inflammatory activities of flavonoid derivates

Background and purpose

Flavonoids are a group of phytochemicals found abundantly in various plants. Scientific evidence has revealed that flavonoids display potential biological activities, including their ability to alleviate inflammation. This activity is closely related to their action in blocking the inflammatory cascade and inhibiting the production of pro-inflammatory factors. However, as flavonoids typically have poor bioavailability and pharmacokinetic profile, it is quite challenging to establish these compounds as a drug. Nevertheless, progressive advancements in drug delivery systems, particularly in nanotechnology, have shown promising approaches to overcome such challenges.

Review approach

This narrative review provides an overview of scientific knowledge about the mechanism of action of flavonoids in the mitigation of inflammatory reaction prior to delivering a comprehensive discussion about the opportunity of the nanotechnology-based delivery system in the preparation of the flavonoid-based drug.

Key results

Various studies conducted in silico, in vitro, in vivo, and clinical trials have deciphered that the anti-inflammatory activities of flavonoids are closely linked to their ability to modulate various biochemical mediators, enzymes, and signalling pathways involved in the inflammatory processes. This compound could be encapsulated in nanotechnology platforms to increase the solubility, bioavailability, and pharmacological activity of flavonoids as well as reduce the toxic effects of these compounds.

Conclusion

In Summary, we conclude that flavonoids and their derivates have given promising results in their development as new anti-inflammatory drug candidates, especially if they formulate in nanoparticles.

Human Monocyte-Derived Dendritic Cells Are the Pharmacological Target of the Immunosuppressant Flavonoid Silibinin

Silibinin, a natural polyphenolic flavonoid, is known to possess anti-inflammatory, anticancer, antioxidant, and immunomodulatory properties. However, the effects of Silibinin on the maturation and immunostimulatory functions of human dendritic cells (DC) remain to be elucidated. In this study, we have attempted to ascertain whether Silibinin influences the maturation, cytokine production, and antigen-presenting capacity of human monocyte-derived DC. We show that Silibinin significantly suppresses the upregulation of costimulatory and MHC molecules in LPS-stimulated mature DC and inhibits lipopolysaccharide (LPS)-induced interleukin (IL)-12, IL-23, and TNF-α production. Furthermore, Silibinin impairs the proliferation response of the allogenic memory CD4 T lymphocytes elicited by LPS-matured DC and their Th1/Th17 profile. These findings demonstrate that Silibinin displays immunosuppressive activity by inhibiting the maturation and activation of human DC and support its potential application of adjuvant therapy in the treatment of autoimmune diseases.

Cinnamoyloxy-mammeisin, a coumarin from propolis of stingless bees, attenuates Th17 cell differentiation and autoimmune inflammation via STAT3 inhibition

T helper 17 (Th17) lymphocytes play a critical role in the pathogenesis of autoimmune diseases, mainly by producing the pro-inflammatory cytokine interleukin-17 (IL-17). Therefore, Th17 lymphocytes have been considered a strategic target for drug discovery and development. In this study, we investigated the activity and possible mechanisms of action of a 4-phenyl coumarin isolated from propolis, named cinnamoyloxy-mammeisin (CNM), in Th17 cell differentiation and the development of experimental Th17-dependent autoimmune encephalomyelitis (EAE). Our data showed that in vitro Th17 cell differentiation was attenuated by CNM treatment in a concentration-dependent manner (1, 3, and 10 μM). This was associated with a reduction in the release of IL-17 (35% inhibition) and interleukin-22 (IL-22, 51% inhibition). Th17-differentiated cells exposed to CNM also downregulated the expression of Th17 hallmarked cell genes, such as RAR-related orphan receptor c (Rorc, 51% inhibition), and interleukin-23 receptor (Il23r, 64% inhibition), indicating possible upstream molecular mechanisms. Mechanistically, CNM significantly reduced the phosphorylation of signal transducer and activator of transcription 3 (p-STAT3) during in vitro Th17 cell differentiation. In vivo treatment with CNM (100 μg/kg) reduced the clinical signs of EAE, which was associated with a reduction in Central Nervous System demyelination, neuroinflammation, and Th17 response in the spinal cord and inguinal lymph nodes. Consistent with this, CNM also effectively attenuated human Th17 differentiation in vitro. Collectively, our results highlight the potential of CNM as a new molecule that can modulate Th17 cells via inhibition of STAT3 signaling and, as a result, reduce autoimmune inflammation.

Silybin and its congeners: from traditional medicine to molecular effects

Covering: 2015 up to 2022 (Feb)Silymarin, an extract of milk thistle (Silybum marianum) fruits, has been used in various medicinal applications since ancient times. A major component of silymarin is the flavonolignan silybin and its relatives isosilybin, silychristin, silydianin, 2,3-dehydrosilybin, and some others. Except for silydianin, they occur in nature as two stereomers. This review focuses on recent developments in chemistry, biosynthesis, modern advanced analytical methods, and transformations of flavonolignans specifically reflecting their chirality. Recently described chemotypes of S. marianum, but also the newest findings regarding the pharmacokinetics, hepatoprotective, antiviral, neuroprotective, and cardioprotective activity, modulation of endocrine functions, modulation of multidrug resistance, and safety of flavonolignans are discussed. A growing number of studies show that the respective diastereomers of flavonolignans have significantly different activities in anisotropic biological systems. Moreover, it is now clear that flavonolignans do not act as antioxidants in vivo, but as specific ligands of biological targets and therefore their chirality is crucial. Many controversies often arise, mainly due to the non-standard composition of this phytopreparation, the use of various undefined mixtures, the misattribution of silymarin vs. silybin, and also the failure to consider the chemistry of the respective components of silymarin.