Shikonin Derivatives Inhibit Inflammation Processes and Modulate MAPK Signaling in Human Healthy and Osteoarthritis Chondrocytes

Shikonin hastens diabetic wound healing by inhibiting M1 macrophage polarisation through the MAPK signaling pathway

Diabetes is an endocrine disorder characterized by abnormally elevated blood glucose levels. Diabetic patients often exhibit impaired wound healing capabilities, particularly in the lower limbs, which is one of the numerous complications of diabetes. This is a significant factor leading to recurrent inflammation, disability, and even amputation. The primary objective of this study is to explore the mechanism by which shikonin accelerates diabetic wound healing by modulating macrophage phenotypes, particularly its role in the MAPK signaling pathway. To this end, we used a diabetic rat model and analyzed the effects of shikonin on the wound healing process and macrophage polarization in both in vivo and in vitro experiments. Additionally, we used immunofluorescence staining and Western blot techniques to detect the expression levels of macrophage polarization markers and proteins related to the MAPK signaling pathway. The results verify that shikonin significantly accelerated wound healing in diabetic rats and inhibited the polarization of M1 macrophages, reducing the expression of pro-inflammatory factors, while promoting the polarization of M2 macrophages, increasing the expression of anti-inflammatory factors. This process was accompanied by the regulation of the MAPK signaling pathway, indicating that shikonin accelerates diabetic wound healing by regulating the MAPK signaling pathway to inhibit the inflammatory phenotype of macrophages, showing significant clinical application prospects.

Myrislignan ameliorates the progression of osteoarthritis: An in vitro and in vivo study

Osteoarthritis (OA) is a prevalent disease of the musculoskeletal system that causes functional deterioration and diminished quality of life. Myrislignan (MRL) has a wide range of pharmacological characteristics, including an anti-inflammatory ability. Although inflammation is a major cause of OA, the role of MRL in OA treatment is still not well-understood. In this study, we analyze the anti-inflammatory and anti-ECM degradation effects of MRL both in vivo and in vitro. Rat primary chondrocytes were treated with interleukin-1β (IL-1β) to simulate inflammatory environmental conditions and OA in vitro. The in vivo OA rat model was established by anterior cruciate ligament transection (ACLT) on rat. Our investigation discovered that MRL lowers the IL-1β-activated tumor necrosis factor-α (TNF-α), cyclooxygenase-2 (COX2) and inducible nitric-oxide synthase (iNOS) expression in chondrocytes. Moreover, MRL effectively alleviates IL-1β-induced extracellular matrix (ECM) degradation and promotes ECM synthesis in chondrocytes by upregulating the mRNA level expression of collagen-II and aggrecan (ACAN), downregulating the expression of matrix metalloproteinases-3,-13 (MMP-3, MMP-13), and a disintegrin and metalloproteinase with thrombospondin motifs-5 (ADAMTS-5). Gene expression profiles of different groups identified DEGs that were mainly enriched in functions associated with NF-κB signaling pathway, and other highly enriched in functions related to TNF, IL-17, Rheumatoid arthritis and cytokine-cytokine receptor signaling pathways. Venn interaction of DEGs from the abovementioned five pathways showed that Nfkbia, Il1b, Il6, Nfkb1, Ccl2, Mmp3 were highly enriched DEGs. In addition, our research revealed that MRL suppresses NF-κB and modulates the Nrf2/HO-1/JNK signaling pathway activated by IL-1β in chondrocytes. In vivo research shows that MRL slows the progression of OA in rats. Our findings imply that MRL might be a viable OA therapeutic choice.

Shikonin alleviates asthma phenotypes in mice via an airway epithelial STAT3-dependent mechanism

Background

Asthma is an inflammatory disease where the balance between Th1/Th2 and Th17/Treg plays a crucial role in its pathogenesis. Shikonin is used to treat a variety of autoimmune diseases due to its good anti-inflammatory activity. However, the effect and mechanism of shikonin on asthma remain unknown.

Method

Mice were sensitized with ovalbumin (OVA)/house dust mite (HDM) and treated with shikonin. Lung inflammation was assessed histologically and via flow cytometry. Bronchoalveolar lavage fluid (BALF) was analyzed for cell counts and cytokines. Shikonin's impact on p-STAT3 was studied in vivo and in vitro.

Results

Shikonin inhibited OVA or HDM-induced inflammation and airway hyperresponsiveness. Upon treatment, a restoration of the Th1/Th2 and Th17/Treg balance was observed, evidenced by a reduction in IL-4 and IL-17A levels in BALF, alongside an elevation in interferon-gamma and IL-10. Furthermore, shikonin impeded the infiltration of eosinophils, neutrophils, macrophages, and lymphocytes into lung tissue. The observed decrease in STAT3 phosphorylation and diminished nuclear translocation of p-STAT3 confirmed that shikonin promotes the balance of Th1/Th2 and Th17/Treg by regulating airway epithelial STAT3.

Conclusion

Shikonin mitigates asthma symptoms through a STAT3-dependent mechanism, indicating its potential as an anti-asthmatic therapeutic agent.

Shikonin ameliorates depressive- and anxiogenic-like behaviors in rats via the suppression of inflammation in the hippocampus

Shikonin is an active naphthoquinone with antioxidative, anti-inflammatory, and anticancer properties. In this study, we investigated the effects of shikonin on depressive- and anxiety-like behaviors in lipopolysaccharide- (LPS-) induced depression and chronic unpredictable mild stress (CUMS) rat models and explored the potential mechanism. First, a 14-day intraperitoneal administration of shikonin (10 mg/kg) significantly decreased immobility time in forced swimming test (FST) and increased open arm entries in elevated plus maze (EPM) test, without affecting line crossings in open field test (OFT), indicating that shikonin has anti-depressant- and anxiolytic-like effects. Second, chronic shikonin administration (10 mg/kg) reversed depressive- and anxiety-like behaviors in LPS-induced and CUMS depression models, as shown in the sucrose preference test (SPT), FST, EPM, and novel object recognition test (NORT). Finally, shikonin significantly reduced the levels of interleukin-1β (IL-1β), IL-6, and tumor necrosis factor-α (TNF-α) in hippocampus, indicating that the anti-depressant- and anxiolytic-like effects of shikonin are related to the reduction of neuroinflammation in hippocampus. These findings suggest that shikonin exerts anti-depressant- and anxiolytic-like effects via an anti-inflammatory mechanism of shikonin in the hippocampus.

Based on network pharmacology and molecular docking to explore the potential mechanism of shikonin in periodontitis

OBJECTIVES

To investigate the potential mechanisms of shikonin in preventing and treating periodontitis using network pharmacology and molecular docking methods.

MATERIALS AND METHODS

The targets of shikonin were obtained in TCMSP and SEA databases, and targets of periodontitis were gathered from the OMIM, GeneCards and Drugbank Databases. The intersecting targets were entered into the DAVID database to obtain the relevant biological functions and pathways by GO and KEGG enrichment analysis. The obtained targets were analysed the protein-protein interaction (PPI) in STRING platform. In Cytoscape 3.8.0, the network analysis function with the MCODE plug-in were used to obtain the key targets, of shikonin and periodontitis. Molecular docking and molecular dynamics simulation (MD) were used to assess the affinity between the shikonin and the key targets.

RESULTS

Shikonin was screened for 22 targets and periodontitis was screened for 944 targets, the intersecting targets were considered as potential therapeutic targets. The targets played important roles in cellular response to hypoxia, response to xenobiotic stimulus and positive regulates of apoptotic process by GO enrichment analysis. 10 significant pathways were analyzed by KEGG, such as human cytomegalovirus infection and PI3K-Akt signaling pathway, etc. Cytoscape software screened the key genes including AKT1, CCL5, CXCR4, PPARG, PTEN, PTGS2 and TP53. Molecular docking and MD results showed that shikonin could bind stably to the targets.

CONCLUSIONS

The present study enriched the molecular mechanisms in periodontitis with shikonin, providing potential therapeutic targets for periodontitis.

Potential of natural products in inflammation: biological activities, structure-activity relationships, and mechanistic targets

A balance between the development and suppression of inflammation can always be found in the body. When this balance is disturbed, a strong inflammatory response can damage the body. It sometimes is necessary to use drugs with a significant anti-inflammatory effect, such as nonsteroidal anti-inflammatory drugs and steroid hormones, to control inflammation in the body. However, the existing anti-inflammatory drugs have many adverse effects, which can be deadly in severe cases, making research into new safer and more effective anti-inflammatory drugs necessary. Currently, numerous types of natural products with anti-inflammatory activity and distinct structural features are available, and these natural products have great potential for the development of novel anti-inflammatory drugs. This review summarizes 260 natural products and their derivatives with anti-inflammatory activities in the last two decades, classified by their active ingredients, and focuses on their structure-activity relationships in anti-inflammation to lay the foundation for subsequent new drug development. We also elucidate the mechanisms and pathways of natural products that exert anti-inflammatory effects via network pharmacology predictions, providing direction for identifying subsequent targets of anti-inflammatory natural products.

(2-Methylbutyryl)shikonin Naturally Occurring Shikonin Derivative Ameliorates the α-MSH-Induced Melanogenesis via ERK1/2 and p38 MAP Kinase-Mediated Down-Regulation of the MITF Transcription Factor

Cutaneous pigmentation is an important phenotypic trait whose regulation, despite recent advances, has yet to be completely elucidated. Melanogenesis, a physiological process of melanin production, is imperative for organism survival as it provides protection against the environmental insults that majorly involve sunlight-induced skin photodamage. However, immoderate melanin synthesis can cause pigmentation disorders associated with a psychosocial impact. In this study, the hypopigmentation effect of (2-methylbutyryl)shikonin, a natural product present in the root extract of Lithospermum erythrorhizon, and the underlying mechanisms responsible for the inhibition of melanin synthesis in α-MSH-stimulated B16F10 cells and C57BL/6J mice was studied. Non-cytotoxic concentrations of (2-methylbutyryl)shikonin significantly repressed cellular tyrosinase activity and melanin synthesis in both in vitro and in vivo models (C57BL/6J mice). (2-Methylbutyryl)shikonin remarkably abolished the protein expression of MITF, tyrosinase, tyrosinase-related protein 1, and tyrosinase-related protein 2, thereby blocking the production of pigment melanin via modulating the phosphorylation status of MAPK proteins, viz., ERK1/2 and p38. In addition, specific inhibition of ERK1/2 attenuated the inhibitory effects of (2-methylbutyryl)shikonin on melanin synthesis, whereas selective inhibition of p38 augmented the inhibitory effect of BSHK on melanin synthesis. Moreover, topical application of (2-methylbutyryl)shikonin on C57BL/6J mouse tails remarkably induced tail depigmentation. In conclusion, with these findings, we, for the first time, report the hypopigmentation effect of (2-methylbutyryl)shikonin via inhibition of cellular tyrosinase enzyme activity, subsequently ameliorating the melanin production, thereby indicating that (2-methylbutyryl)shikonin is a potential natural therapy for hyperpigmentation disorders.

Acetylshikonin induces necroptosis via the RIPK1/RIPK3-dependent pathway in lung cancer

Despite advances in therapeutic strategies, lung cancer remains the leading cause of cancer-related death worldwide. Acetylshikonin is a derivative of the traditional Chinese medicine Zicao and presents a variety of anticancer properties. However, the effects of acetylshikonin on lung cancer have not been fully understood yet. This study explored the mechanisms underlying acetylshikonin-induced cell death in non-small cell lung cancer (NSCLC). Treating NSCLC cells with acetylshikonin significantly reduced cell viability, as evidenced by chromatin condensation and the appearance of cell debris. Acetylshikonin has also been shown to increase cell membrane permeability and induce cell swelling, leading to an increase in the population of necrotic cells. When investigating the mechanisms underlying acetylshikonin-induced cell death, we discovered that acetylshikonin promoted oxidative stress, decreased mitochondrial membrane potential, and promoted G2/M phase arrest in lung cancer cells. The damage to NSCLC cells induced by acetylshikonin resembled results involving alterations in the cell membrane and mitochondrial morphology. Our analysis of oxidative stress revealed that acetylshikonin induced lipid oxidation and down-regulated the expression of glutathione peroxidase 4 (GPX4), which has been associated with necroptosis. We also determined that acetylshikonin induces the phosphorylation of receptor-interacting serine/threonine-protein kinase 1 (RIPK1)/RIPK3 and mixed lineage kinase domain-like kinase (MLKL). Treatment with RIPK1 inhibitors (necrostatin-1 or 7-Cl-O-Nec-1) significantly reversed acetylshikonin-induced MLKL phosphorylation and NSCLC cell death. These results indicate that acetylshikonin activated the RIPK1/RIPK3/MLKL cascade, leading to necroptosis in NSCLC cells. Our findings indicate that acetylshikonin reduces lung cancer cells by promoting G2/M phase arrest and necroptosis.

Natural Shikonin Potentially Alters Intestinal Flora to Alleviate Acute Inflammation

Shikonin, derived from the herb Lithospermum erythrorhizon (Purple Cromwell), is extensively utilized in traditional Chinese medicine as an anti-inflammatory agent; however, its effect on the intestinal flora is not yet known. Herein, we demonstrate that, compared to a blank control group, the intragastric administration of shikonin suppressed the swelling rate of ears in a mouse model of acute inflammation in a dose-dependent manner via animal experiments; furthermore, the 20 mg/kg shikonin treatment exhibited the highest inhibitory effect. In formal animal experimentation, we discovered that the inhibitory effect of shikonin with 20 mg/kg on inflammation was closely linked to the intestinal flora, whereby the microbiota phylum was altered in feces through a 16S rDNA sequencing analysis, implying that shikonin improves gut microbiota structures and compositions to counteract inflammation. Notably, using a real-time quantitative polymerase chain reaction (RT-qPCR), a Western blotting assay, and an immunohistochemistry (IHC) assay, we found that inflammatory cytokines such as TNF-α, IL-6, and IL-1β reduced in both the shikonin-administration group and the positive control group than those in the blank control group, as expected. To the best of our knowledge, this is the first study to outline the underlying mechanism through which shikonin acts on gut microbes to alleviate acute inflammation, providing an alternative mechanism for shikonin to become a preventive agent in countering inflammation.

Shikonin derivatives cause apoptosis and cell cycle arrest in human chondrosarcoma cells via death receptors and MAPK regulation

Background

Although chondrosarcoma is the second most common primary malignant bone tumor, treatment options are limited due to its extensive resistance to a chemo- and radiation therapy. Since shikonin has shown potent anticancer activity in various types of cancer cells, it represents a promising compound for the development of a new therapeutic approach.

Methods

The dose-relationships of shikonin and its derivatives acetylshikonin and cyclopropylshikonin on two human chondrosarcoma cell lines were measured using the CellTiter-Glo®. The changes in the cell cycle were presented by flow cytometry. Protein phosphorylation and expression apoptotic markers, MAPKs and their downstream targets were analyzed using western blotting and gene expression were evaluated using RT-qPCR.

Results

Chondrosarcoma cells showed a dose-dependent inhibition of cell viability after treatment with shikonin and its derivatives, with the strongest effect for shikonin and IC₅₀ values of 1.3 ± 0.2 µM. Flow cytometric measurements revealed a G₂/M arrest of the cells after treatment. Protein and gene expression analysis demonstrated a dose-dependent downregulation of survivin and XIAP, and an upregulation of Noxa, γH2AX, cleaved caspase-8, -9, -3, and -PARP. Furthermore, the expression of various death receptors was modulated. As MAPK signaling pathways play a key role in tumor biology, their phosphorylation pattern and their corresponding downstream gene regulation were analyzed. Treatment with shikonin derivatives caused an inhibition of pSTAT3 and an increase of pAKT and the MAPKs pERK, pJNK, and pp38 in a dose-dependent manner.

Conclusions

These data demonstrated the significant anti-tumorigenic effect of shikonin derivatives in chondrosarcoma and encourage further research.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-022-09857-x.