Chemo-sensitizing activity of natural cadinanes from Heterotheca inuloides in human uterine sarcoma cells and their in silico interaction with ABC transporters

Flavonoids and phenols from the stems of Ephedra equisetina

Twelve undescribed compounds, including five flavonoids and seven phenols, were isolated from the stems of Ephedra equisetina Bunge. Their structures were elucidated by spectroscopic methods, including NMR spectroscopy and HRESIMS analysis. Their absolute configurations were elucidated by comparing their experimental and calculated ECD spectra. In the in vitro bioactive assay, all compounds were tested for their anti-asthmatic activities by releasing β-Hex in C48/80-induced RBL-2H3 cells. The β-Hex release rates of compounds 3, 8, 10, and 11 were 0.8502 ± 0.0231, 0.8802 ± 0.0805, 0.7850 ± 0.0593, and 0.8361 ± 0.0728, respectively, suggesting that compounds 3, 8, 10, and 11 have potential anti-asthmatic activities.

Evaluation of selected natural sesquiterpenes as sensitizing agents of β-lactam-resistant bacterial strains

AIMS

To evaluate the capacity of fourteen sesquiterpenes to enhance the action of known antibiotics against two β-lactam resistant strains, and to determine a possible mechanism of antibiotic sensitization by assessing their ability to inhibit a β-lactamase enzyme.

METHODS AND RESULTS

The broth microdilution method was used to determine the minimum inhibitory concentration (MIC) of β-lactams cefuroxime (CEFM) and cefepime (CPM) against Staphylococcus aureus 23MR and Escherichia coli 82MR strains in the absence and presence of subinhibitory concentrations of fourteen natural sesquiterpenes. (1R,4R)-4H-1,2,3,4-tetrahydro-1-hydroxycadalen-15-oic acid (5), xerantolide (8), estafiatin (11), and ambrosin (12) exhibited the best sensitizing effects in both strains. These compounds were able to reduce the MIC of CEFM by 2-fold (from 15.0 to 7.5 µg/mL) and CPM by 15-fold (from 0.9 to 0.06 µg/mL) in S. aureus 23MR. For E. coli 82MR, the MIC of CEFM was reduced up to 8-fold (from 120.0 to 15.0 µg/mL). In this strain, the activity of 8 and 11 surpassed that of clavulanic acid (positive reference), which reduced the MIC of CEFM from 120.0 to 60.0 µg/mL. To elucidate a possible mechanism of antibiotic sensitization, molecular docking studies were conducted with β-lactamases. These studies revealed an affinity with the enzymes (energies > -4.93 kcal/mol) by the formation of hydrogen bonds with certain conserved amino acid residues within the active sites. However, the in vitro results indicated only marginal inhibition, with percentages <50%.

CONCLUSIONS

The bioevaluations indicate that nine of fourteen sesquiterpenes enhance the action of CEFM and CPM against the β-lactam resistant strains, and these compounds displayed moderate activity as inhibitors of β-lactamase.

Drug Transporters in the Kidney: Perspectives on Species Differences, Disease Status, and Molecular Docking

The kidneys are a pair of important organs that excretes endogenous waste and exogenous biological agents from the body. Numerous transporters are involved in the excretion process. The levels of these transporters could affect the pharmacokinetics of many drugs, such as organic anion drugs, organic cationic drugs, and peptide drugs. Eleven drug transporters in the kidney (OAT1, OAT3, OATP4C1, OCT2, MDR1, BCRP, MATE1, MATE2-K, OAT4, MRP2, and MRP4) have become necessary research items in the development of innovative drugs. However, the levels of these transporters vary between different species, sex-genders, ages, and disease statuses, which may lead to different pharmacokinetics of drugs. Here, we review the differences of the important transports in the mentioned conditions, in order to help clinicians to improve clinical prescriptions for patients. To predict drug-drug interactions (DDIs) caused by renal drug transporters, the molecular docking method is used for rapid screening of substrates or inhibitors of the drug transporters. Here, we review a large number of natural products that represent potential substrates and/or inhibitors of transporters by the molecular docking method.

Design and application of hybrid cyclic-linear peptide-doxorubicin conjugates as a strategy to overcome doxorubicin resistance and toxicity

Doxorubicin (Dox) is used for breast cancer, leukemia, and lymphoma treatment as an effective chemotherapeutic agent. However, Dox use is restricted due to inherent and acquired resistance and an 8-fold increase in the risk of potentially fatal cardiotoxicity. Hybrid cyclic-linear peptide [R₅K]W₇A and linear peptide R₅KW₇A were conjugated with Dox through a glutarate linker to afford [R₅K]W₇A-Dox and R₅KW₇A-Dox conjugates to generate Dox derivatives. Alternatively, [R₅K]W₇C was conjugated with Dox via a disulfide linker to generate [R₅K]W₇C-S-S-Dox conjugate, where S-S is a disulfide bond. Comparative antiproliferative assays between conjugates [R₅K]W₇A-Dox, [R₅K]W₇C-S-S-Dox, linear R₅KW₇A-Dox, the corresponding physical mixtures of the peptides, and Dox were performed in normal and cancer cells. [R₅K]W₇A-Dox conjugate was 2-fold more efficient than R₅KW₇A-Dox, and [R₅K]W₇C-S-S-Dox conjugates in inhibiting the cell proliferation of human leukemia cells (CCRF-CEM). Therefore, hybrid cyclic-linear [R₅K]W₇A-Dox conjugate was selected for further studies and inhibited the cell viability of CCRF-CEM (84%), ovarian adenocarcinoma (SK-OV-3, 39%), and gastric carcinoma (AGS, 73%) at a concentration of 5 μM after 72 h of incubation, which was comparable to Dox (5 μM) efficacy (CCRF-CEM (85%), SK-OV-3 (33%), and AGS (87%)). While [R₅K]W₇A-Dox had a significant effect on the viability of cancer cells, it exhibited minimal cytotoxicity to normal kidney (LLC-PK1, 5-7%) and heart cells (H9C2, <9%) at concentrations of 5-10 μM (compared to free Dox at 5 μM that reduced the viability of kidney and heart cells by 85% and 44%, respectively). The fluorescence microscopy images were consistent with the cytotoxicity studies, indicating minimal uptake of the cyclic-linear [R₅K]W₇A-Dox (5 μM) in H9C2 cells. In comparison, Dox (5 μM) showed significant uptake, reduced cell viability, and changed the morphology of the cells after 24 h. [R₅K]W₇A-Dox showed 16-fold and 9.5-fold higher activity against Dox-resistant cells MDA231R and MES-SA/MX2 (lethal dose for 50% cell death or LC₅₀ of 2.3 and 4.3 μM, respectively) compared to free Dox (LC₅₀ of 36-41 μM, respectively). These data, along with the results obtained from the cell viability tests, indicate comparable efficiency of [R₅K]W₇A-Dox to free Dox in leukemia, ovarian, and gastric cancer cells, significantly reduced toxicity in normal kidney LLC-PK1 and heart H9C2 cells, and significantly higher efficiency in Dox-resistant cells. A number of endocytosis inhibitors did not affect the cellular uptake of [R₅K]W₇A-Dox.

Targeting Drug Chemo-Resistance in Cancer Using Natural Products

Cancer is one of the leading causes of death globally. The development of drug resistance is the main contributor to cancer-related mortality. Cancer cells exploit multiple mechanisms to reduce the therapeutic effects of anticancer drugs, thereby causing chemotherapy failure. Natural products are accessible, inexpensive, and less toxic sources of chemotherapeutic agents. Additionally, they have multiple mechanisms of action to inhibit various targets involved in the development of drug resistance. In this review, we have summarized the basic research and clinical applications of natural products as possible inhibitors for drug resistance in cancer. The molecular targets and the mechanisms of action of each natural product are also explained. Diverse drug resistance biomarkers were sensitive to natural products. P-glycoprotein and breast cancer resistance protein can be targeted by a large number of natural products. On the other hand, protein kinase C and topoisomerases were less sensitive to most of the studied natural products. The studies discussed in this review will provide a solid ground for scientists to explore the possible use of natural products in combination anticancer therapies to overcome drug resistance by targeting multiple drug resistance mechanisms.