The inhibitory effect of shikonin on the agonist-induced regulation of vascular contractility

Structure-based discovery of potent myosin inhibitors to guide antiparasite drug development

Monogenea, a prevalent parasite in aquaculture, poses significant threats to the industry, leading to substantial losses. Current preventive measures have proven insufficient, necessitating the development of novel and effective anti-parasitic drugs. In this investigation, we obtained the full-length myosin cDNA sequence by analyzing three-generation transcriptome data, revealing a 5817-base sequence encoding 1938 amino acids. Subsequently, we modeled and analyzed the characteristics of the secondary and tertiary of myosin, pinpointing the crucial functional region within the motor domain (amino acids 1-768). The prokaryotic expression of this domain yielded a protein of 87.44 kDa, confirmed as myosin by Western Blotting. Molecular docking identified ASN439 as the key amino acid residue involved in arctigenin and myosin binding, a result corroborated by site-directed mutagenesis, affirming the active cavity of this interaction. Chalcone and shikonin were chosen from a virtual sieve of molecular library of natural drugs based on the active cavity. Chalcone and shikonin exhibited EC50 values of 1.085 mg/L and 0.371 mg/L, respectively, with corresponding IC50 values for myosin of 0.44 mM and 0.14 mM. Given its superior activity and structure, shikonin was selected for further optimization of drug molecule design, culminating in the discovery of 1,4-naphthoquinone as a potent antiparasitic agent. This compound demonstrated an EC50 of 0.047 mg/L, LC50 of 0.23 mg/L, and a TI index of 4.893. These findings collectively highlight the potential of shikonin and 1,4-naphthoquinone as alternative compounds to control Gyrodactylus infections. Further optimization of medicinal chemistry holds promise for the development of more potent 1,4-naphthoquinone analogues, offering prospects for future anthelmintic control through combinatorial or replacement strategies.

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 Exerts Cytotoxic Effects in Human Colon Cancers by Inducing Apoptotic Cell Death via the Endoplasmic Reticulum and Mitochondria-Mediated Pathways

The apoptotic effects of shikonin (5,8-dihydroxy-2-[(1R)-1-hydroxy-4-methylpent-3-enyl]naphthalene-1,4-dione) on the human colon cancer cell line SNU-407 were investigated in this study. Shikonin showed dose-dependent cytotoxic activity against SNU-407 cells, with an estimated IC₅₀ value of 3 µM after 48 h of treatment. Shikonin induced apoptosis, as evidenced by apoptotic body formation, sub-G₁ phase cells, and DNA fragmentation. Shikonin induced apoptotic cell death by activating mitogen-activated protein kinase family members, and the apoptotic process was mediated by the activation of endoplasmic reticulum (ER) stress, leading to activation of the PERK/elF2α/CHOP apoptotic pathway, and mitochondrial Ca²⁺ accumulation. Shikonin increased mitochondrial membrane depolarization and altered the levels of apoptosis-related proteins, with a decrease in B cell lymphoma (Bcl)-2 and an increase in Bcl-2-associated X protein, and subsequently, increased expression of cleaved forms of caspase-9 and -3. Taken together, we suggest that these mechanisms, including MAPK signaling and the ER-and mitochondria-mediated pathways, may underlie shikonin-induced apoptosis related to its anticancer effect.