The Influence of Betulin and Its Derivatives EB5 and ECH147 on the Antioxidant Status of Human Renal Proximal Tubule Epithelial Cells

The Influence of Betulin and Its Derivatives on Selected Colorectal Cancer Cell Lines' Viability and Their Antioxidant Systems

Oxidative stress is considered one of the main reasons for the development of colorectal cancer (CRC). Depending on the stage of the disease, variable activity of the main antioxidant enzymes, i.e., superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx), is observed. Due to limited treatment methods for CRC, new substances with potential antitumor activity targeting pathways related to oxidative stress are currently being sought, with substances of natural origin, including betulin, leading the way. The betulin molecule is chemically modified to obtain new derivatives with improved pharmacokinetic properties and higher biological activity. The aim of this study was to evaluate the effects of betulin and its new derivatives on viability and major antioxidant systems in colorectal cancer cell lines. The study showed that betulin and its derivative EB5 affect the antioxidant enzyme activity to varying degrees at both the protein and mRNA levels. The SW1116 cell line is more resistant to the tested compounds than RKO, which may be due to differences in the genetic and epigenetic profiles of these lines.

Redox homeostasis in human renal cells that had been treated with amphotericin B in combination with selected 1,3,4-thiadiazole derivatives

BACKGROUND

The use of amphotericin B (AmB) in the therapy of systemic mycosis is associated with strong side effects, including nephrotoxicity, and hepatotoxicity. Therefore, agents that can reduce the toxic effects of AmB while acting synergistically as antifungal agents are currently being sought. 1,3,4-thiadiazole derivatives are promising compounds that have an antifungal activity and act synergically with AmB. Such combinations might allow the dose of AmB, which is essential for preventing patients from having serious side effects, to be decreased. This might result from the antioxidant properties of 1,3,4-thiadiazoles. Thus, the aim of the study was to investigate redox homeostasis in human renal proximal tubule epithelial cells (RPTEC) after they had been treated with AmB in combination with 1,3,4-thiadiazole derivatives.

METHODS

Cellular redox homeostasis was assessed by investigating the total antioxidant capacity (TAC) of cells, the malondialdehyde (MDA) concentration, and the activity of antioxidant enzymes such as superoxide dismutase (SOD), glutathione peroxidase (GPX), and catalase (CAT). TAC was measured using an ABTS method. The MDA concentration, and the activity of SOD, GPX, and CAT were determined spectrophotometrically using commercially available assays. Additionally, the antioxidant defense system-related gene expression profile was determined using oligonucleotide microarrays (HG-U133A 2.0). Quantitative reverse transcription polymerase chain reaction (RT-qPCR) was used to confirm the microarray results.

RESULTS

Amphotericin B and selected 1,3,4-thiadiazole derivatives had a significant effect on the total antioxidant capacity of the RPTEC cells, and the activity of the antioxidant enzymes. We also revealed that the effect of thiadiazoles on the SOD and CAT activities is dependent on the treatment of RPTEC cells with AmB. At the transcriptional level, the expression of several genes was affected by the studied compounds and their combinations.

CONCLUSIONS

The results confirmed that thiadiazoles can stimulate the RPTEC cells to defend against the oxidative stress that is generated by AmB. In addition, together with the previously demonstrated synergistic antifungal activity, and low nephrotoxicity, these compounds have the potential to be used in new therapeutic strategies in the treatment of fungal infections.

Protective Effect of Betulin on Streptozotocin-Nicotinamide-Induced Diabetes in Female Rats

Type 2 diabetes is characterized by hyperglycemia and a relative loss of β-cell function. Our research investigated the antidiabetic potential of betulin, a pentacyclic triterpenoid found primarily in birch bark and, intriguingly, in a few marine organisms. Betulin has been shown to possess diverse biological activities, including antioxidant and antidiabetic activities; however, no studies have fully explored the effects of betulin on the pancreas and pancreatic islets. In this study, we investigated the effect of betulin on streptozotocin-nicotinamide (STZ)-induced diabetes in female Wistar rats. Betulin was prepared as an emulsion, and intragastric treatments were administered at doses of 20 and 50 mg/kg for 28 days. The effect of treatment was assessed by analyzing glucose parameters such as fasting blood glucose, hemoglobin A1C, and glucose tolerance; hepatic and renal biomarkers; lipid peroxidation; antioxidant enzymes; immunohistochemical analysis; and hematological indices. Administration of betulin improved the glycemic response and decreased α-amylase activity in diabetic rats, although insulin levels and homeostatic model assessment for insulin resistance (HOMA-IR) scores remained unchanged. Furthermore, betulin lowered the levels of hepatic biomarkers (aspartate aminotransferase, alanine aminotransferase, and alpha-amylase activities) and renal biomarkers (urea and creatine), in addition to improving glutathione levels and preventing the elevation of lipid peroxidation in diabetic animals. We also found that betulin promoted the regeneration of β-cells in a dose-dependent manner but did not have toxic effects on the pancreas. In conclusion, betulin at a dose of 50 mg/kg exerts a pronounced protective effect against cytolysis, diabetic nephropathy, and damage to the acinar pancreas and may be a potential treatment option for diabetes.

Synthesis, Pharmacological Properties, and Potential Molecular Mechanisms of Antitumor Activity of Betulin and Its Derivatives in Gastrointestinal Cancers

Gastrointestinal (GI) cancers are an increasingly common type of malignancy, caused by the unhealthy lifestyles of people worldwide. Limited methods of treatment have prompted the search for new compounds with antitumor activity, in which betulin (BE) is leading the way. BE as a compound is classified as a pentacyclic triterpene of the lupane type, having three highly reactive moieties in its structure. Its mechanism of action is based on the inhibition of key components of signaling pathways associated with proliferation, migration, interleukins, and others. BE also has a number of biological properties, i.e., anti-inflammatory, hepatoprotective, neuroprotective, as well as antitumor. Due to its poor bioavailability, betulin is subjected to chemical modifications, obtaining derivatives with proven enhanced pharmacological and pharmacokinetic properties as a result. The method of synthesis and substituents significantly influence the effect on cells and GI cancers. Moreover, the cytotoxic effect is highly dependent on the derivative as well as the individual cell line. The aim of this study is to review the methods of synthesis of BE and its derivatives, as well as its pharmacological properties and molecular mechanisms of action in colorectal cancer, hepatocellular carcinoma, gastric cancer, and esophageal cancer neoplasms.

The Influence of Betulin Derivatives EB5 and ECH147 on the Expression of Selected TGFβ Superfamily Genes, TGFβ1, GDF15 and BMP2, in Renal Proximal Tubule Epithelial Cells

Betulin derivatives are proposed to serve as an alternative to the drugs already established in oncologic treatment. Drug-induced nephrotoxicity leading to acute kidney injury frequently accompanies cancer treatment, and thus there is a need to research the effects of betulin derivatives on renal cells. The objective of our study was to assess the influence of the betulin derivatives 28-propynylobetulin (EB5) and 29-diethoxyphosphoryl-28-propynylobetulin (ECH147) on the expression of TGFβ1, BMP2 and GDF15 in renal proximal tubule epithelial cells (RPTECs) cultured in vitro. The changes in mRNA expression and copy numbers were assessed using real-time reverse transcription quantitative polymerase chain reaction (RT-qPCR) and the standard curve method, respectively. An enzyme-linked immunosorbent assay (ELISA) was used to evaluate the effect of the betulin derivatives on the protein concentration in the culture media's supernatant. The assessment of the betulin derivatives' influence on gene expression demonstrated that the mRNA level and protein concentration did not always correlate with each other. Each of the tested compounds affected the mRNA expression. The RT-qPCR analyses showed that EB5 and ECH147 induced effects similar to those of betulin or cisplatin and resulted in a decrease in the mRNA copy number of all the analyzed genes. The ELISA demonstrated that EB5 and ECH147 elevated the protein concentration of TGFβ1 and GDF15, while the level of BMP2 decreased. The concentration of the derivatives used in the treatment was crucial, but the effects did not always exhibit a simple linear dose-dependent relationship. Betulin and its derivatives, EB5 and ECH147, influenced the gene expression of TGFβ1, BMP2 and GDF15 in the renal proximal tubule epithelial cells. The observed effects raise the question of whether treatment with these compounds could promote the development of renal fibrosis.

Antiproliferative and Cytotoxic Properties of Propynoyl Betulin Derivatives against Human Ovarian Cancer Cells: In Vitro Studies

Due to the incidence of ovarian cancer (OC) and the limitations of available therapeutic strategies, it is necessary to search for novel therapeutic solutions. The aim of this study was to evaluate the cytotoxic effect of betulin 1 and its propynoyl derivatives 2-6 against ovarian cancer cells (SK-OV-3, OVCAR-3) and normal myofibroblasts (18Co). Paclitaxel was used as the reference compound. The propynoyl derivatives 2-6 exhibited stronger antiproliferative and cytotoxic activities compared to betulin 1. In both ovarian cancer cell lines, the most potent compound was 28-propynoylbetulin 2. In the case of compound 2, the calculated IC50 values were 0.2 µM for the SK-OV-3 cells and 0.19 µM for the OVCAR-3 cells. Under the same culture conditions, the calculated IC50 values for compound 6 were 0.26 µM and 0.59 µM, respectively. It was observed that cells treated with compounds 2 and 6 caused a decrease in the potential of the mitochondrial membrane and a significant change in cell morphology. Betulin 1, a diol from the group of pentacyclic triterpenes, has a confirmed wide spectrum of biological effects, including a significant anticancer effect. It is characterized by low bioavailability, which can be improved by introducing changes to its structure. The results showed that chemical modifications of betulin 1 only at position C-28 with the propynoyl group (compound 2) and additionally at position C-3 with the phosphate group (compound 3) or at C-29 with the phosphonate group (compound 6) allowed us to obtain compounds with greater cytotoxic activity than their parent compounds, which could be used to develop novel therapeutic systems effective in the treatment of ovarian cancer.

Pharmacological Potential of Betulin as a Multitarget Compound

Betulin is a natural triterpene, usually from birch bark, known for its potential wound-healing properties. Despite having a wide range of pharmacological targets, no studies have proposed betulin as a multitarget compound. Betulin has protective effects against cardiovascular and liver diseases, cancer, diabetes, oxidative stress, and inflammation. It reduces postprandial hyperglycemia by inhibiting α-amylase and α-glucosidase activity, combats tumor cells by inducing apoptosis and inhibiting metastatic proteins, and modulates chronic inflammation by blocking the expression of proinflammatory cytokines via modulation of the NFκB and MAPKs pathways. Given its potential to influence diverse biological networks with high target specificity, it can be hypothesized that betulin may eventually become a new lead for drug development because it can modify a variety of pharmacological targets. The summarized research revealed that the diverse beneficial effects of betulin in various diseases can be attributed, at least in part, to its multitarget anti-inflammatory activity. This review focuses on the natural sources, pharmacokinetics, pharmacological activity of betulin, and the multi-target effects of betulin on signaling pathways such as MAPK, NF-κB, and Nrf2, which are important regulators of the response to oxidative stress and inflammation in the body.

Effect of Modified Levopimaric Acid Diene Adducts on Mitochondrial and Liposome Membranes

This paper demonstrates the membranotropic effect of modified levopimaric acid diene adducts on liver mitochondria and lecithin liposomes. We found that the derivatives dose-dependently reduced the efficiency of oxidative phosphorylation of mitochondria due to inhibition of the activity of complexes III and IV of the respiratory chain and protonophore action. This was accompanied by a decrease in the membrane potential in the case of organelle energization both by glutamate/malate (complex I substrates) and succinate (complex II substrate). Compounds 1 and 2 reduced the generation of H₂O₂ by mitochondria, while compound 3 exhibited a pronounced antioxidant effect on glutamate/malate-driven respiration and, on the other hand, caused ROS overproduction when organelles are energized with succinate. All tested compounds exhibited surface-active properties, reducing the fluidity of mitochondrial membranes and contributing to nonspecific permeabilization of the lipid bilayer of mitochondrial membranes and swelling of the organelles. Modified levopimaric acid diene adducts also induced nonspecific permeabilization of unilamellar lecithin liposomes, which confirmed their membranotropic properties. We discuss the mechanisms of action of the tested compounds on the mitochondrial OXPHOS system and the state of the lipid bilayer of membranes, as well as the prospects for the use of new modified levopimaric acid diene adducts in medicine.