DNA mismatch repair (MMR) deficiency has been associated with a higher risk of developing colorectal, endometrial, and ovarian cancer, and confers resistance in conventional chemotherapy. In addition to the lack of treatment options that work efficaciously on these MMR-deficient cancer patients, there is a great need to discover new drug leads for this purpose. In this study, we screened through a library of commercial and semisynthetic natural compounds to identify potential synthetic lethal drugs that may selectively target MLH1 mutants using MLH1 isogenic colorectal cancer cell lines and various cancer cell lines with known MLH1 status. We identified a novel diarylpentanoid analogue, 2-benzoyl-6-(2,3-dimethoxybenzylidene)-cyclohexenol, coded as AS13, that demonstrated selective toxicity toward MLH1-deficient cancer cells. Subsequent analysis suggested AS13 induced elevated levels of oxidative stress, resulting in DNA damage where only the proficient MLH1 cells were able to be repaired and hence escaping cellular death. While AS13 is modest in potency and selectivity, this discovery has the potential to lead to further drug development that may offer better treatment options for cancer patients with MLH1 deficiency.
Limonene oxidation products (LOPs) have gained interest on their harmful health effects over time. Recently, studies have shown that the selected LOPs: 4-oxopentanal (4-OPA), 3-isopropenyl-6-oxo-heptanal (IPOH) and 4-acetyl-1-methylcyclohexene (4-AMCH) have sensory irritation effects in mice and inflammatory effects in human lung cells. This study was therefore undertaken to investigate the potential capacity of 4-OPA, IPOH and 4-AMCH to cause cell membrane damage, oxidative stress and inflammation in human bronchial (16HBE14o-) and alveolar (A549) epithelial cell lines. Overall results suggest that 4-OPA, IPOH have cytotoxic effects on human lung cells that might be mediated by ROS: the highest concentration applied of IPOH [500 μM] enhanced ROS generation by 100-fold ± 7.7 (A549) and 230-fold ± 19.9 (16HBE14o-) compared to the baseline. 4-OPA [500 μM] increased ROS levels by 1.4-fold ± 0.3 (A549) and by 127-fold ± 10.5 (16HBE14o-), while treatment with 4-AMCH [500 μM] led to 0.9-fold ± 0.2 (A549) and 49-fold ± 12.8 (16HBE14o-) increase. IPOH [500 μM] caused a decrease in the thiol-state balance (e.g. after 2 h, GSH:GSSG was reduced by 37% compared to the untreated 16HBE14o-cells). 4-OPA [500 μM] decreased the GSH:GSSG by 1.3-fold change in A549 cells and 1.4-fold change in 16HBE14o-cells. No statistically significant decrease in the GSH:GSSG in A549 and 16HBE14o-cell lines was observed for 4-AMCH [500 μM]. In addition, IPOH and 4-OPA [31.2 μM] increased the amount of the inflammatory markers: RANTES, VEGF and EGF. On the other hand, 4-AMCH [31.2 μM] did not show inflammatory effects in A549 or 16HBE14o-cells. The 4-OPA, IPOH and 4-AMCH treatment concentration and time-dependently induce oxidative stress and/or alteration of inflammatory markers on human bronchial and alveolar cell lines.
Micro-emulsions and sometimes nano-emulsions are well known candidates to deliver drugs locally. However, the poor rheological properties are marginally affecting their acceptance pharmaceutically. This work aimed to modify the poor flow properties of a nano-scaled emulsion comprising palm olein esters as the oil phase and ibuprofen as the active ingredient for topical delivery. Three Carbopol ® resins: 934, 940 and Ultrez 10, were utilized in various concentrations to achieve these goals. Moreover, phosphate buffer and triethanolamine solutions pH 7.4 were used as neutralizing agents to assess their effects on the gel-forming and swelling properties of Carbopol ® 940. The addition of these polymers caused the produced nano-scaled emulsion to show a dramatic droplets enlargement of the dispersed globules, increased intrinsic viscosity, consistent zeta potential and transparent-to-opaque change in appearance. These changes were relatively influenced by the type and the concentration of the resin used. Carbopol ® 940 and triethanolamine appeared to be superior in achieving the proposed tasks compared to other materials. The higher the pH of triethanolamine solution, the stronger the flow-modifying properties of Carbopol ® 940. Transmission electron microscopy confirmed the formation of a well-arranged gel network of Carbopol ® 940, which was the major cause for all realized changes. Later in vitro permeation studies showed a significant decrease in the drug penetration, thus further modification using 10% w/w menthol or limonene as permeation promoters was performed. This resulted in in vitro and in vivo pharmacodynamics properties that are comparably higher than the reference chosen for this study.