The biocompatibility and the metabolic impact of thermoresponsive, bile acid-based nanogels on auditory and macrophage cell lines

Deoxycholic acid (DCA), lithocholic acid (LCA), and ursodeoxycholic acid (UDCA) are bile acids that may serve as permeation enhancers when incorporated within the nanogel matrix for drug delivery in the inner ear. In this study, thermoresponsive nanogels were formulated with DCA, LCA and UDCA and their rheological properties and biocompatibility were assessed. The impact of nanogel on cellular viability was evaluated via cell viability assay, the impact of nanogels on cellular bioenergetic parameters was estimated by Seahorse mito-stress test and glycolysis-stress test, while the presence of intracellular free radicals was assessed by reactive oxygen species assay. Nanogels showed a high level of biocompatibility after 24-hour exposure to auditory and macrophage cell lines, with minimal cytotoxicity compared to untreated control. Incubation with nanogels did not alter cellular respiration and glycolysis of the auditory cell line but showed possible mitochondrial dysfunction in macrophages, suggesting tissue-dependent effects of bile acids. Bile acid-nanogels had minimal impact on intracellular reactive oxygen species, with LCA demonstrating the most pro-oxidative behaviour. This study suggests that thermoresponsive nanogels with bile acid, particularly DCA and UDCA, may be promising candidates for inner ear drug delivery.

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.

Lipid-Drug Conjugate for Enhancing Drug Delivery

Lipid-drug conjugates (LDCs) are drug molecules that have been covalently modified with lipids. The conjugation of lipids to drug molecules increases lipophilicity and also changes other properties of drugs. The conjugates demonstrate several advantages including improved oral bioavailability, improved targeting to the lymphatic system, enhanced tumor targeting, and reduced toxicity. Based on the chemical nature of drugs and lipids, various conjugation strategies and chemical linkers can be utilized to synthesize LDCs. Linkers and/or conjugation methods determine how drugs are released from LDCs and are critical for the optimal performance of LDCs. In this review, different lipids used for preparing LDCs and various conjugation strategies are summarized. Although LDCs can be administered without a delivery carrier, most of them are loaded into appropriate delivery systems. The lipid moiety in the conjugates can significantly enhance drug loading into hydrophobic components of delivery carriers and thus generate formulations with high drug loading and superior stability. Different delivery carriers such as emulsions, liposomes, micelles, lipid nanoparticles, and polymer nanoparticles are also discussed in this review.

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.