Synthesis, Structure-Activity Relationship, and Mechanistic Investigation of Lithocholic Acid Amphiphiles for Colon Cancer Therapy

The anticancer activity of bile acids in drug discovery and development

Bile acids (BAs) constitute essential components of cholesterol metabolites that are synthesized in the liver, stored in the gallbladder, and excreted into the intestine through the biliary system. They play a crucial role in nutrient absorption, lipid and glucose regulation, and the maintenance of metabolic homeostasis. In additional, BAs have demonstrated the ability to attenuate disease progression such as diabetes, metabolic disorders, heart disease, and respiratory ailments. Intriguingly, recent research has offered exciting evidence to unveil their potential antitumor properties against various cancer cell types including tamoxifen-resistant breast cancer, oral squamous cell carcinoma, cholangiocarcinoma, gastric cancer, colon cancer, hepatocellular carcinoma, prostate cancer, gallbladder cancer, neuroblastoma, and others. Up to date, multiple laboratories have synthesized novel BA derivatives to develop potential drug candidates. These derivatives have exhibited the capacity to induce cell death in individual cancer cell types and display promising anti-tumor activities. This review extensively elucidates the anticancer activity of natural BAs and synthetic derivatives in cancer cells, their associated signaling pathways, and therapeutic strategies. Understanding of BAs and their derivatives activities and action mechanisms will evidently assist anticancer drug discovery and devise novel treatment.

Recent developments in membrane targeting antifungal agents to mitigate antifungal resistance

Fungal infections cause severe and life-threatening complications especially in immunocompromised individuals. Antifungals targeting cellular machinery and cell membranes including azoles are used in clinical practice to manage topical to systemic fungal infections. However, continuous exposure to clinically used antifungal agents in managing the fungal infections results in the development of multi-drug resistance via adapting different kinds of intrinsic and extrinsic mechanisms. The unique chemical composition of fungal membranes presents attractive targets for antifungal drug discovery as it is difficult for fungal cells to modify the membrane targets for emergence of drug resistance. Here, we discussed available antifungal drugs with their detailed mechanism of action and described different antifungal resistance mechanisms. We further emphasized structure-activity relationship studies of membrane-targeting antifungal agents, and classified membrane-targeting antifungal agents on the basis of their core scaffold with detailed pharmacological properties. This review aims to pique the interest of potential researchers who could explore this interesting and intricate fungal realm.

Mechanism of Bile Acid-Induced Programmed Cell Death and Drug Discovery against Cancer: A Review

Bile acids are major signaling molecules that play a significant role as emulsifiers in the digestion and absorption of dietary lipids. Bile acids are amphiphilic molecules produced by the reaction of enzymes with cholesterol as a substrate, and they are the primary metabolites of cholesterol in the body. Bile acids were initially considered as tumor promoters, but many studies have deemed them to be tumor suppressors. The tumor-suppressive effect of bile acids is associated with programmed cell death. Moreover, based on this fact, several synthetic bile acid derivatives have also been used to induce programmed cell death in several types of human cancers. This review comprehensively summarizes the literature related to bile acid-induced programmed cell death, such as apoptosis, autophagy, and necroptosis, and the status of drug development using synthetic bile acid derivatives against human cancers. We hope that this review will provide a reference for the future research and development of drugs against cancer.

N-methyl Benzimidazole Tethered Cholic Acid Amphiphiles Can Eradicate S. aureus-Mediated Biofilms and Wound Infections

Infections associated with Gram-positive bacteria like S. aureus pose a major threat as these bacteria can develop resistance and thereby limit the applications of antibiotics. Therefore, there is a need for new antibacterials to mitigate these infections. Bacterial membranes present an attractive therapeutic target as these membranes are anionic in nature and have a low chance of developing modifications in their physicochemical features. Antimicrobial peptides (AMPs) can disrupt the microbial membranes via electrostatic interactions, but the poor stability of AMPs halts their clinical translation. Here, we present the synthesis of eight N-methyl benzimidazole substituted cholic acid amphiphiles as antibacterial agents. We screened these novel heterocyclic cholic acid amphiphiles against different pathogens. Among the series, CABI-6 outperformed the other amphiphiles in terms of bactericidal activity against S. aureus. The membrane disruptive property of CABI-6 using a fluorescence-based assay has also been investigated, and it was inferred that CABI-6 can enhance the production of reactive oxygen species. We further demonstrated that CABI-6 can clear the pre-formed biofilms and can mitigate wound infection in murine models.

In vitro protoscolicidal effects of lithocholic acid on protoscoleces of Echinococcus granulosus and its mechanism

Surgery has been found to be the best choice of treatment for hydatidosis. However, leakage of cyst contents during surgery is the foremost reason for recurrence of hydatidosis. In this study, we investigated the in vitro efficacy of lithocholic acid (LCA) against Echinococcus granulosus protoscoleces. The protoscoleces were divided into a control group, an albendazole (ABZ) positive control group and LCA intervention groups at concentrations of 0.5, 1, 2, and 3 mmol/L and stained with 0.1% eosin for observation using an inverted microscope; the protoscolecal ultrastructure was examined with SEM and TEM; the activities of ROS, SOD, and caspase-3 were investigated using an ROS kit, SOD kit, and caspase-3 kit, respectively; the contents of HO-1 and NQO-1 were analyzed by enzyme-linked immunosorbent assay; and the expression level of cytochrome c (Ctyc) was analyzed by western blotting. Results: As the concentration of LCA increased, the survival rate of protoscoleces gradually decreased. The microstructure shows that the external shape and internal structure were gradually deformed and collapse. SOD, GSH, HO-1 and NQO-1 decreased more significantly in the 3 mmol/L LCA group. However, ROS levels gradually increased. LCA treatment for 3 days at all concentrations significantly increased caspase-3 activity and expression in a dose-dependent manner. LCA decreased the level of Ctyc protein in vitro. LCA demonstrated a parasiticidal effect on the protoscoleces of Echinococcus granulosus in vitro. LCA may induce apoptosis of E. granulosus protoscoleces by oxidative stress and mitochondrial pathways.

Synthesis of New Cisplatin Derivatives from Bile Acids

A series of bile acid derived 1,2- and 1,3-diamines as well as their platinum(II) complexes were designed and synthesized in hope to get a highly cytotoxic compound by the combination of two bioactive moieties. All complexes obtained were subjected to cytotoxicity assays in vitro and some hybrid molecules showed an expected activity.

Role of bile acids in colon carcinogenesis

Bile acids (BAs) are cholesterol derivatives synthesized in the liver and then secreted into the intestine for lipid absorption. There are numerous scientific reports describing BAs, especially secondary BAs, as strong carcinogens or promoters of colon cancers. Firstly, BAs act as strong stimulators of colorectal cancer (CRC) initiation by damaging colonic epithelial cells, and inducing reactive oxygen species production, genomic destabilization, apoptosis resistance, and cancer stem cells-like formation. Consequently, BAs promote CRC progression via multiple mechanisms, including inhibiting apoptosis, enhancing cancer cell proliferation, invasion, and angiogenesis. There are diverse signals involved in the carcinogenesis mechanism of BAs, with a major role of epidermal growth factor receptor, and its down-stream signaling, involving mitogen-activated protein kinase, phosphoinositide 3-kinase/Akt, and nuclear factor kappa-light-chain-enhancer of activated B cells. BAs regulate numerous genes including the human leukocyte antigen class I gene, p53, matrix metalloprotease, urokinase plasminogen activator receptor, Cyclin D1, cyclooxygenase-2, interleukin-8, and miRNAs of CRC cells, leading to CRC promotion. These evidence suggests that targeting BAs is an efficacious strategies for CRC prevention and treatment.

Programmed 'triple-mode' anti-tumor therapy: Improving peritoneal retention, tumor penetration and activatable drug release properties for effective inhibition of peritoneal carcinomatosis

Peritoneal carcinomatosis (PC) is a fatal condition arising in the gastrointestinal tract. PC patients administered drugs locally in the tumor region, such as in intraperitoneal chemotherapy (IPCh), suffer from low drug retention time and tumor penetration. Herein, we synthesized a lithocholic acid (LCA)-conjugated disulfide-linked polyethyleneimine (ssPEI) micelle (LAPMi) nanoconstruct by covalently conjugating ssPEI and LCA, thereby forming positive charged nanomicellar structures loaded with paclitaxel (PTX) (LAPMi-PTX) for IPCh. The incorporation of a positive surface charge aided in prolonging the peritoneal retention time, presumably via ascites-induced protein corona formation, and the subsequent size expansion caused resistance against undesired clearance through lymphatic openings. Furthermore, preferential tumor penetration by LAPMi-PTX is attributable to the permeation-enhancing properties of LCA, and the subsequent tumor activatable drug release was induced by the presence of disulfide linkages. By integrating these properties, LAPMi exhibited prolonged peritoneal residence time, enhanced tumor permeation and chemotherapeutic effect evidenced by in vitro, tumor spheroid and in vivo studies. Importantly, our strategy enabled significant PC inhibition and increased the overall survival rate of tumor-bearing mice. In conclusion, we provided a new paradigm of intractable PC treatment by enabling the prolonged residence time of the nanoconstruct, thereby enhancing tumor penetration and anti-tumor therapy.

Deciphering the role of hydrophobic and hydrophilic bile acids in angiogenesis using in vitro and in vivo model systems

Bile acids have emerged as strong signaling molecules capable of influencing various biological processes like inflammation, apoptosis, cancer progression and atherosclerosis depending on their chemistry. In the present study, we investigated the effect of major hydrophobic bile acids lithocholic acid (LCA) and deoxycholic acid (DCA) and hydrophilic bile acids cholic acid (CA) and chenodeoxycholic acid (CDCA) on angiogenesis. We employed human umbilical vein endothelial cells (HUVECs) and zebrafish embryos as model systems for studying the role of bile acids in angiogenesis. Our studies revealed that the hydrophilic CDCA enhanced ectopic vessel formation as observed by the increase in the number of sub-intestinal vessels (SIVs) in the zebrafish embryos. The pro-angiogenic role of CDCA was further corroborated by in vitro vessel formation studies performed with human umbilical vein endothelial cells (HUVECs), whereas the hydrophobic LCA reduced tubulogenesis and was toxic to the zebrafish embryos. We validated that CDCA enhances angiogenesis by increasing the expression of vascular growth factor receptors (VEGFR1 and VEGFR2) and matrix metalloproteinases (MMP9) and by decreasing the expression of adhesion protein vascular endothelial cadherin (VE-cadherin). Our work implicates that the nature of bile acids plays a critical role in dictating their biological functions and in regulating angiogenesis.

The synthesis and antitumor activity of lithocholic acid and its derivatives

In this paper, a new and concise synthetic route of lithocholic acid (LCA) using commercially available steroid source deoxycholic acid is reported. A series of amide derivatives of LCA were also synthesized and investigated for their activity against the growth of MCF-7 and MCF-7/ADR cells using the sulforhodamine B assay. For MCF-7, the most potent compound 20 showed a 20-fold higher antitumor activity than LCA. For MCF-7/ADR, the most potent compound 24 showed a 22-fold higher antitumor activity than LCA. The transwell migration assay of 20 was evaluated on MDA-MB-231 cells. The colony formation and apoptosis assays of 20 were performed on MCF-7 and MCF-7/ADR cell lines.

Lithocholic Acid Hydroxyamide Destabilizes Cyclin D1 and Induces G0/G1 Arrest by Inhibiting Deubiquitinase USP2a

USP2a is a deubiquitinase responsible for stabilization of cyclin D1, a crucial regulator of cell-cycle progression and a proto-oncoprotein overexpressed in numerous cancer types. Here we report that lithocholic acid (LCA) derivatives are inhibitors of USP proteins, including USP2a. The most potent LCA derivative, LCA hydroxyamide (LCAHA), inhibits USP2a, leading to a significant Akt/GSK3β-independent destabilization of cyclin D1, but does not change the expression of p27. This leads to the defects in cell-cycle progression. As a result, LCAHA inhibits the growth of cyclin D1-expressing, but not cyclin D1-negative cells, independently of the p53 status. We show that LCA derivatives may be considered as future therapeutics for the treatment of cyclin D1-addicted p53-expressing and p53-defective cancer types.

Protoscolicidal effects of chenodeoxycholic acid on protoscoleces of Echinococcus granulosus

Dissemination of protoscoleces-rich fluid during surgical operation for cystic echinococcosis is a major cause of its recurrence. Instillation of a scolicidal agent into hydatid cysts to reduce the risk of spillage of viable protoscoleces is an integral part of the surgical technique employed by many surgeons. In this study, the protoscolicidal effect of chenodeoxycholic acid (CDCA) was investigated. Freshly isolated protoscoleces were subjected to CDCA treatment (500, 1000, 2000, and 3000 μmol/L), and the effects on protoscoleces were investigated with the help of 0.1% eosin staining, electron microscopy, and colorimetric assay of caspase-3 like activity. Dose-dependent mortality of Echinococcus granulosus protoscoleces was observed within a few days of CDCA treatment. The treated protoscoleces showed loss of viability, and morphological changes such as contraction of the soma region, formation of blebs, rostellar disorganization, loss of hooks, destruction of microtriches, and formation of vesicles, lipid droplets, and lamellar bodies. Apoptosis was evident in the treated protoscoleces, as compared to the control group, which were cultivated for nearly 3 months. Our study indicates a therapeutic potential for CDCA as a protoscolicidal agent against E. granulosus. However, further studies are needed to test the long-term effects of CDCA in animal models.

Cross-talk between bile acids and gastrointestinal tract for progression and development of cancer and its therapeutic implications

Increasing incidences of gastrointestinal (GI) cancer are linked to changes in lifestyle with excess of red meat/fat consumption, and elevated secretion of bile acids. Bile acids are strong signaling molecules that control various physiological processes. Failure in bile acid regulation has detrimental effects, often linked with development and promotion of cancer of digestive tract including esophagus, stomach, liver, and intestine. Excessive concentration of bile acids especially lipophillic secondary bile acids are cytotoxic causing apoptosis and reactive oxygen species-mediated damage to the cells. Resistance to this apoptosis and accumulation of mutations leads to progression of cancer. Cytotoxicity of bile acids is contingent on their chemical structure. In this review, we discuss the chemistry of bile acids, bile acid mediated cellular signaling processes, their role in GI cancer progression, and therapeutic potential of synthetic bile acid derivatives for cancer therapy.

Nature of the charged head group dictates the anticancer potential of lithocholic acid-tamoxifen conjugates for breast cancer therapy

Anticancer drug Tamoxifen is modified to charged lithocholic acid derived amphiphile for enhanced cytotoxicity against breast cancer cells.