Antinociceptive properties of shikonin: in vitro and in vivo studies

Pharmacological Significance of Boraginaceae with Special Insights into Shikonin and Its Potential in the Food Industry

Shikonin is a naphthoquinone pigment present in the hairy roots of the plant species from the Boraginaceae family. The compound has been well investigated for its highly efficient medicinal, antioxidant, and antimicrobial properties. Various extraction methodologies have been employed to maximise yield while minimising waste production of shikonin and its derivatives. Despite substantial research on shikonin and Boraginaceae plants, a research gap persists in the food industry and extraction technologies. This review addresses crucial aspects of shikonin deserving of further exploration. It begins by elucidating the attributes of the Boraginaceae plants and their medicinal traits in folklore. It proceeds to focus on the roots of the plant and its medicinal properties, followed by extraction procedures explored in the last fifteen years, emphasising the novel technologies that have been chosen to improve the yield extract while minimising extraction times. Furthermore, this review briefly outlines studies employing cell culture techniques to enhance in vitro shikonin production. Lastly, attention is directed towards research in the food industry, particularly on shikonin-loaded biodegradable films and the antioxidant activity of shikonin. This review concludes by summarising the future potential in food science and prominent research gaps in this field.

Shikonin alleviates doxorubicin-induced cardiotoxicity via Mst1/Nrf2 pathway in mice

Doxorubicin (DOX) is a popular and potent anticancer drug, but its cardiotoxicity limits its clinical application. Shikonin has a wide range of biological functions, including antioxidant and anti-inflammatory effects. The aim of this study was to investigate the effects of shikonin on DOX-induced cardiac injury and to identify the underlying mechanisms. Mice receiving shikonin showed reduced cardiac injury response and enhanced cardiac function after DOX administration. Shikonin significantly attenuated DOX-induced oxidative damage, inflammation accumulation and cardiomyocyte apoptosis. Shikonin protects against DOX-induced cardiac injury by inhibiting Mammalian sterile 20-like kinase 1 (Mst1) and oxidative stress and activating the nuclear factor erythroid 2-related factor 2 (Nrf2) pathway. In conclusion, shikonin alleviates DOX-induced cardiotoxicity by inhibiting Mst1 and activating Nrf2. Shikonin may be used to treat DOX-induced cardiac injury.

Therapeutics for Chemotherapy-Induced Peripheral Neuropathy: Approaches with Natural Compounds from Traditional Eastern Medicine

Chemotherapy-induced peripheral neuropathy (CIPN) often develops in patients with cancer treated with commonly used anti-cancer drugs. The symptoms of CIPN can occur acutely during chemotherapy or emerge after cessation, and often accompany long-lasting intractable pain. This adverse side effect not only affects the quality of life but also limits the use of chemotherapy, leading to a reduction in the survival rate of patients with cancer. Currently, effective treatments for CIPN are limited, and various interventions are being applied by clinicians and patients because of the unmet clinical need. Potential approaches to ameliorate CIPN include traditional Eastern medicine-based methods. Medicinal substances from traditional Eastern medicine have well-established analgesic effects and are generally safe. Furthermore, many substances can also improve other comorbid symptoms in patients. This article aims to provide information regarding traditional Eastern medicine-based plant extracts and natural compounds for CIPN. In this regard, we briefly summarized the development, mechanisms, and changes in the nervous system related to CIPN, and reviewed the substances of traditional Eastern medicine that have been exploited to treat CIPN in preclinical and clinical settings.

"Shikonin inhibits microglia activation and reduces CFA-induced mechanical hyperalgesia in an animal model of pain"

Shikonin is an ointment produced from Lithospermun erythrorhizon which has been used in traditional medicine both in Europe and Asia for wound healing and is associated with anti-inflammatory properties. The goal of this work is to assess the analgesic properties of Shikonin in the CFA-induced inflammation model of pain. Rats were subjected to inflammation of the hind paw by CFA injection with a preventive injection of Shikonin and compared to either a control group or to a CFA-inflamed group with the vehicle drug solution. Inflammation of the hind paw by CFA was assessed by measurement of the dorsal to plantar diameter. Mechanical thresholds were established by means of the Von Frey filaments which are calibrated filaments that exert a defined force. Finally, the spinal cord of the studied animals was extracted to analyse the microglia population through immunohistochemistry using the specific marker Iba-1. Our results show that Shikonin reduces the paw oedema caused by CFA inflammation. Subsequently, there is a concomitant restoration of the mechanical thresholds reduced by CFA hind paw injection. Additionally, spinal microglia is activated after CFA-induced inflammation. Our results show that microglia is inhibited by Shikonin and has concomitant restoration of the mechanical thresholds. Our findings demonstrate for the first time that Shikonin inhibits microglia morphological changes and thereby ameliorates pain-like behaviour elicited by mechanical stimulation.

Shikonin induces apoptosis and autophagy via downregulation of pyrroline-5-carboxylate reductase1 in hepatocellular carcinoma cells

Shikonin(SK) is a natural small molecule naphthoquinone compound, which has anti-cancer activity in various human malignant tumors. Pyrroline-5-carboxylate reductase 1(PYCR1) is involved in tumorigenesis and regulates various cellular processes, including growth, invasion, migration, and apoptosis. However, the effect of SK and PYCR1 on apoptosis and autophagy in hepatocellular carcinoma are unclear. Our goal is to determine the internal molecular mechanism of the interaction between SK and PYCR1 and its role in the occurrence and development of liver cancer. The CCK8 assay, wound healing assay, and transwell assays show that SK and siPYCR1(gene silence PYCR1) inhibited the malignant phenotype of HCC cells, including cell viability, colony formation, migration, and invasion, respectively. The flow cytometry assays and immunofluorescence show that SK and siPYCR1 activated apoptosis and autophagy, respectively. SK induces apoptosis and autophagy in a dose-dependent manner. In addition, HCC cells were transfected with small interference fragment PYCR1 siRNA to construct siPYCR1 and SK single treatment group and co-treatment group to verify the interaction between SK and PYCR1. The Western blot identified that PI3K/Akt/mTOR signal pathway protein expression was significantly downregulated in HCC cells treated with SK and siPYCR1 together. Collectively, SK may induce apoptosis and autophagy by reducing the expression of PYCR1 and suppressing PI3K/Akt/mTOR. Thus, SK may be a promising antineoplastic drug in Hepatocellular carcinoma (HCC). SK downregulating PYCR1 might supply a theoretical foundation for the potential therapeutic application in hepatocellular carcinoma.

Shikonin, a naphthalene ingredient: Therapeutic actions, pharmacokinetics, toxicology, clinical trials and pharmaceutical researches

BACKGROUND

Shikonin is one of the major phytochemical components of Lithospermum erythrorhizon (Purple Cromwell), which is a type of medicinal herb broadly utilized in traditional Chinese medicine. It is well established that shikonin possesses remarkable therapeutic actions on various diseases, with the underlying mechanisms, pharmacokinetics and toxicological effects elusive. Also, the clinical trial and pharmaceutical study of shikonin remain to be comprehensively delineated.

PURPOSE

The present review aimed to systematically summarize the updated knowledge regarding the therapeutic actions, pharmacokinetics, toxicological effects, clinical trial and pharmaceutical study of shikonin.

METHODS

The information contained in this review article were retrieved from some authoritative databases including Web of Science, PubMed, Google scholar, Chinese National Knowledge Infrastructure (CNKI), Wanfang Database and so on, till August 2021.

RESULTS

Shikonin exerts multiple therapeutic efficacies, such as anti-inflammation, anti-cancer, cardiovascular protection, anti-microbiomes, analgesia, anti-obesity, brain protection, and so on, mainly by regulating the NF-κB, PI3K/Akt/MAPKs, Akt/mTOR, TGF-β, GSK3β, TLR4/Akt signaling pathways, NLRP3 inflammasome, reactive oxygen stress, Bax/Bcl-2, etc. In terms of pharmacokinetics, shikonin has an unfavorable oral bioavailability, 64.6% of the binding rate of plasma protein, and enhances some metabolic enzymes, particularly including cytochrome P450. In regard to the toxicological effects, shikonin may potentially cause nephrotoxicity and skin allergy. The above pharmacodynamics and pharmacokinetics of shikonin have been validated by few clinical trials. In addition, pharmaceutical innovation of shikonin with novel drug delivery system such as nanoparticles, liposomes, microemulsions, nanogel, cyclodextrin complexes, micelles and polymers are beneficial to the development of shikonin-based drugs.

CONCLUSIONS

Shikonin is a promising phytochemical for drug candidates. Extensive and intensive explorations on shikonin are warranted to expedite the utilization of shikonin-based drugs in the clinical setting.

Shikonin inhibits migration and invasion of triple-negative breast cancer cells by suppressing epithelial-mesenchymal transition via miR-17-5p/PTEN/Akt pathway

Background: Triple-negative breast cancer (TNBC) is a great threat to global women's health due to its high metastatic potential. Epithelial-to-mesenchymal transition (EMT) is considered as a key event in the process of metastasis. So the pharmacological targeting of EMT might be a promising strategy in improving the therapeutic efficacy of TNBC. Here, we investigated the effect of shikonin exerting on EMT and consequently the metastasis of TNBC cells and its underlying mechanism. Methods: The invasive and migratory capacities of MDA-MB-231 and BT549 cells were tested using transwell invasion and wound healing assay. MiR-17-5p expression was examined by qRT-PCR. MiR-17-5p targeted genes were predicted with different bioinformatic algorithms from four databases (TargetScan, miRanda, PITA and picTar) and further screened by Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis. The differential expressions of predicted genes and their correlations with miR-17-5p were identified in breast cancer patients based on The Cancer Genome Atlas (TCGA) database. The interaction between phosphatase and tensin homolog deleted on chromosome ten (PTEN) and miR-17-5p was analyzed by luciferase reporter assay. The overexpression vector and small interfering RNA were constructed to investigate the role PTEN played in metastasis and EMT regulation. The expressions of EMT markers, protein kinase B (Akt) and phospho-Akt (p-Akt) were evaluated by western blot. Results: Shikonin suppressed the migration and invasion of MDA-MB-231 and BT549 cells and meanwhile the corresponding alterations of EMT biomarkers were observed in shikonin treated MDA-MB-231 cells. Shikonin inhibited the expression of miR-17-5p, which was upregulated in breast cancer. The 3'-untranslated region (3'-UTR) of PTEN was found to be direct binding target of miR-17-5p by luciferase reporter assays. PTEN functioned as a suppressor both in the metastasis and EMT of TNBC cells. Moreover, Akt and p-Akt (Ser473) were involved in the process of inhibition in cancer cell migration, invasion and EMT by shikonin. Conclusions: Shikonin inhibits migration and invasion of TNBC cells by suppressing EMT via miR-17-5p/PTEN/Akt pathway. This suggests shikonin as a promising therapeutic agent to counteract metastasis in the TNBC patients.

Shikonin relieves osteoporosis of ovariectomized mice by inhibiting RANKL-induced NF-κB and NFAT pathways

Postmenopausal osteoporosis is very common in women. Currently, many kinds of new drugs are being developed for this disease. Postmenopausal osteoporosis is closely related to overactivity of osteoclasts in body. Shikonin is purple red naphthoquinone pigment extracted from lithospermum, which has anti-inflammation, antivirus, anticancer and other bioactivities. At the same time, it has been proved that shikonin can promote the proliferation and differentiation of osteoblasts, but its influence on osteoclasts and molecular mechanism are unknown. Our study showed that shikonin could inhibit the activity and formation of RANKL-mediated osteoclasts depending on dose without affecting the activity of bone marrow macrophages (BMM). In addition, we have also found that shikonin can inhibit the expression of specific marker gene of osteoclasts, including nuclear factor of activated T cells cytoplasmic 1 (NFATc1), cathepsin K (Ctsk), tartrate resistant acid phosphatase (TRAcP) and calcitonin receptor. Shikonin also could promote the proliferation of MC3T3-E1, increasing the expression of mRNA related to osteogenesis, like the expression of bone morphogenetic protein-2 (BMP-2), alkaline phosphatase (ALP), runt-related transcription factor 2 (Runx2) and osteocalcin (OCN). Luciferase reporter gene assay and Western blot analysis further indicated that shikonin could inhibit the activity of RANKL-induced NF-κB and NFAT receptors. Moreover, shikonin can also slow down bone loss of ovariectomized (OVX) mice by inhibiting the activity of osteoclasts. This work explains the molecular mechanism of shikonin in RANKL-mediated formation of osteoclasts, and reveals the potential of further developing shikonin into a new drug for prevention and treatment of postmenopausal osteoporosis.

The inhibitory effects of shikonin and β,β-dimethylacrylshikonin on tramadol metabolism in vitro and in vivo

OBJECTIVES

The objective of this study was to investigate the possible interaction of shikonin and β,β-dimethylacrylshikonin (DSK) with tramadol.

METHODS

Human liver microsome (HLM) and rat liver microsome (RLM) incubation experiments were carried out to assess the half-maximal inhibitory concentration (IC₅₀ ) and inhibitory mechanism of shikonin and DSK on tramadol metabolism in vitro. And pharmacokinetics experiments containing low and high doses of shikonin and DSK were performed to confirm the inhibitory effects on tramadol metabolism in vivo.

KEY FINDINGS

The IC₅₀ of shikonin on tramadol metabolism was 5.66 ± 1.2 μmol/l in HLM and 3.35 ± 1.1 μmol/l in RLM, while that of DSK on tramadol metabolism was 14.33 ± 1.1 μmol/l in HLM and 8.24 ± 1.26 μmol/l in RLM. Moreover, shikonin and DSK showed non-competitive inhibition of the cytochrome P450 enzyme in both HLM and RLM. Oral administration of 10 and 30 mg/kg shikonin inhibited tramadol metabolism in a dose-dependent manner. Furthermore, a dose of 30 mg/kg DSK inhibited the metabolism of tramadol in rats, while the lower dose of 10 mg/kg showed no inhibitory effect.

CONCLUSIONS

The results of this study suggest that shikonin and DSK can inhibit tramadol metabolism both in vitro and in vivo.