Baicalein, 7,8-Dihydroxyflavone and Myricetin as Potent Inhibitors of Human Ornithine Decarboxylase

Preventing Cancer by Inhibiting Ornithine Decarboxylase: A Comparative Perspective on Synthetic vs. Natural Drugs

This perspective delves into the investigation of synthetic and naturally occurring inhibitors, their patterns of inhibition, and the effectiveness of newly utilized natural compounds as inhibitors targeting the Ornithine decarboxylase enzyme. This enzyme is known to target the MYC oncogene, thereby establishing a connection between polyamine metabolism and oncogenesis in both normal and cancerous cells. ODC activation and heightened polyamine activity are associated with tumor development in numerous cancers and fluctuations in ODC protein levels exert a profound influence on cellular activity for inhibition or suppressing tumor cells. This perspective outlines efforts to develop novel drugs, evaluate natural compounds, and identify promising inhibitors to address gaps in cancer prevention, highlighting the potential of newly designed synthetic moieties and natural flavonoids as alternatives. It also discusses natural compounds with potential as enhanced inhibitors.

Baicalein improves the chemoresistance of ovarian cancer through regulation of CirSLC7A6

PURPOSE

The present study aimed to investigate whether baicalein improves the sensitivity of resistant ovarian cancer cells to cisplatin.

METHODS

Transcriptomic sequencing and bioinformatics analysis were used to screen differentially expressed CirSLC7A6 in A2780 and A2780/CDDP cells. RT-qPCR was performed to examine the expression levels of CirSLC7A6, miR-2682-5p, and SLC7A6. Cell proliferation and apoptosis were examined using a Cell Counting Kit-8 assay and flow cytometry, and cell migration and invasion were analyzed using wound healing and Transwell assays. Cell suspensions were inoculated into the subcutaneous tissues of the bilateral interscapular region of nude mice. Saline, cisplatin, baicalein and cisplatin plus baicalein were intraperitoneally injected to observe the effects on tumor growth. Toxicity analyses in the liver and kidney were performed using H&E staining. RT-qPCR and immunohistochemistry were used to detect the expression of CirSLC7A6, miR-2682-5p, and SLC7A6 in tumor tissues, and western blot analysis was carried out to measure protein expression levels.

RESULTS

CirSLC7A6 was markedly upregulated in A2780/CDDP cells compared with the A2780 cells. CirSLC7A6 knockdown notably increased the expression of miR-2682-5p and decreased SLC7A6 expression. The rates of inhibition and apoptosis in the group treated with a combination of cisplatin and baicalein were significantly higher than those of the cisplatin and baicalein groups of A2780/CDDP shCirSLC7A6 cells. In A2780/CDDP shCirSLC7A6 cells, migration and invasion were significantly higher in the cisplatin and baicalein groups, compared with the combined treatment group. In the A2780/CDDP shCirSLC7A6 cell xenograft, the tumor weight of the combined treatment group was significantly lower than that of the cisplatin and baicalein groups. In addition, the combination of cisplatin and baicalein did not induce higher levels of toxicity in the liver or kidney. Baicalein alone and in combination with cisplatin notably reduced the expression of CirSLC7A6 and SLC7A6, and increased the expression of miR-2682-5p in the A2780/CDDP shCirSLC7A6 cell xenograft. In A2780/CDDP shCirSLC7A6 cells, the expression levels of P-Akt, P-mTOR, P-Erk, Bcl-2 and MMP2 were lower in the combined treatment group than in the control group.

CONCLUSIONS

Treatment with baicalein improved the sensitivity of ovarian cancer cells to cisplatin and inhibited cell proliferation, metastasis and tumor growth.

Triptolide attenuates irritable bowel syndrome via inhibiting ODC1

BACKGROUND

Irritable bowel syndrome (IBS) is a chronic disorder of the gut-brain axis with significant morbidity. Triptolide, an active compound extracted from Tripterygium wilfordii Hook F (TwHF), has been widely used as a major medicinal herb in the treatment of inflammatory disease.

METHODS

The chronic-acute combined stress (CAS) stimulation was used to establish IBS rat model. The model rats were then gavaged with triptolide. Forced swimming, marble-burying, fecal weight and abdominal withdrawal reflex (AWR) score were recorded. Pathologic changes in the ileal and colonic tissues were validated by hematoxylin and eosin staining. The inflammatory cytokines and Ornithine Decarboxylase-1 (ODC1) in the ileal and colonic tissues were performed by ELISA and WB.

RESULTS

Triptolide didn't have antidepressant- and antianxiety- effects in rats caused by CAS, but decreased fecal weight and AWR score. In addition, Triptolide reduced the release of IL-1, IL-6, and TNF-α and the expression of ODC1 in the ileum and colon.

CONCLUSION

The therapeutic efficacy of triptolide for IBS induced by CAS was revealed in this study, which may be related to the reduction of ODC1.

Some Nanocarrier's Properties and Chemical Interaction Mechanisms with Flavones

Flavones such as 7,8-dihydroxyflavone (tropoflavin), 5,6,7-trihydroxyflavone (baicalein), 3',4',5,6-tetrahydroxyflavone (luteolin), 3,3',4',5,5',7-hexahydroxyflavone (myricetin), 4',5,7-trihydroxyflavone (apigenin), and 5,7-dihydroxyflavone (chrysin) are important both for their presence in natural products and for their pharmacological applications. However, due to their chemical characteristics and their metabolic processes, they have low solubility and low bioavailability. Knowledge about the physicochemical properties of nanocarriers and the possible mechanisms of covalent and non-covalent interaction between nanoparticles (NPs) and drugs is essential for the design of nanocarriers to improve the bioavailability of molecules with pharmacological potential, such as tropoflavin, baicalein, luteolin, myricetin, apigenin, and chrysin. The parameters of characterization of some NPs of these flavones, such as size, polydispersity index (PDI), zeta potential, encapsulation efficiency (EE), and % release/time, utilized in biomedical applications and the covalent and non-covalent interactions existing between the polymeric NPs and the drug were analyzed. Similarly, the presence of functional groups in the functionalized carbon nanotubes (CNTs), as well as the effect of pH on the % adsorption of flavonoids on functionalized multi-walled carbon nanotubes (MWCNT-COOH), were analyzed. Non-covalent interaction mechanisms between polymeric NPs and flavones, and covalent interaction mechanisms that could exist between the NPs and the amino and hydroxyl functional groups, are proposed.

An anti-leishmanial compound 4',7-dihydroxyflavone elicits ROS-mediated apoptosis-like death in Leishmania parasite

The treatment for leishmaniasis is currently plagued by side effects such as toxicity and the emergence of drug resistance to the available repertoire of drugs, as well as the expense of these drugs. Considering such rising concerns, we report the anti-leishmanial activity and mechanism of a flavone compound 4',7-dihydroxyflavone (TI 4). Four flavanoids were initially screened for anti-leishmanial activity and cytotoxicity. The results showed that the compound TI 4 exhibited higher activity and selectivity index at the same time as maintaining low cytotoxicity. Preliminary microscopic studies and fluorescence-activated cell sorting analysis reported that the parasite underwent apoptosis on TI 4 treatment. Further in-depth studies revealed high reactive oxygen species (ROS) production and thiol levels in the parasites, suggesting ROS-mediated apoptosis in the parasites upon TI 4 treatment. Other apoptotic indicators such as intracellular Ca²⁺ and mitochondrial membrane potential also indicated the onset of apoptosis in the treated parasites. The mRNA expression levels signified that the redox metabolism genes were upregulated by two-fold along with the apoptotic genes. In summary, the use of TI 4 on Leishmania parasites induces ROS-mediated apoptosis; therefore, the compound has immense potential to be an anti-leishmanial drug. However, in vivo studies would be required to ascertain its safety and efficacy before we can exploit the compound against the growing leishmaniasis crisis.

Molecular Pathways Involved in the Anti-Cancer Activity of Flavonols: A Focus on Myricetin and Kaempferol

Natural compounds have always represented valuable allies in the battle against several illnesses, particularly cancer. In this field, flavonoids are known to modulate a wide panel of mechanisms involved in tumorigenesis, thus rendering them worthy candidates for both cancer prevention and treatment. In particular, it was reported that flavonoids regulate apoptosis, as well as hamper migration and proliferation, crucial events for the progression of cancer. In this review, we collect recent evidence concerning the anti-cancer properties of the flavonols myricetin and kaempferol, discussing their mechanisms of action to give a thorough overview of their noteworthy capabilities, which are comparable to those of their most famous analogue, namely quercetin. On the whole, these flavonols possess great potential, and hence further study is highly advised to allow a proper definition of their pharmaco-toxicological profile and assess their potential use in protocols of chemoprevention and adjuvant therapies.

Ornithine decarboxylase functions in both autophagy and apoptosis in response to ultraviolet B radiation injury

We present a mechanism for how ornithine decarboxylase (ODC) regulates the crosstalk between autophagy and apoptosis. In cancer cells, low-intensity ultraviolet B (UVB_L ) induces autophagy while high-intensity UVB (UVB_H ) induces apoptosis. Overexpression of ODC decreases UVB_L -induced autophagy by inhibiting Atg5-Atg12 conjugation and suppressing the expression of autophagy markers LC3, Atg7, Atg12, and BECN1 proteins. In contrast, when ODC-overexpressing cells are exposed to UVB_H radiation, the levels of LC3-II, Atg5-Atg12 conjugate, BECN1, Atg7, and Atg12 increase, while the apoptosis marker cleaved-PARP proteins decrease, indicating that ODC overexpression induced UVB_H -induced autophagy but inhibited UVB_H -induced cellular apoptosis. Additionally, when exposed to UVB_H radiation, silencing BECN1, Atg5, and Atg12 genes results in a decrease in the level of LC3-II proteins but an increase in the level of cleaved-PARP proteins, and apoptotic bodies were significantly increased while autophagosomes were significantly decreased. These findings imply that ODC inhibits apoptosis in cells via the autophagy pathway. The role of Atg12 in ODC-overexpressing cells exposed to UVB_H radiation is investigated using site-directed mutagenesis. Our results indicate that the Atg12-D111S mutant has increased cell survival. The Atg12-ΔG186 mutant impairs autophagy and enhances apoptosis. We demonstrate that when ODC-overexpressing cells are silenced for the Atg12 protein, autophagy and apoptosis are strongly affected, and ODC-induced autophagy protects against UVB_H -induced apoptosis via the Atg12 protein.