Investigation into the distinct subcellular effects of docosahexaenoic acid loaded low-density lipoprotein nanoparticles in normal and malignant murine liver cells

Abstract

Background Recent studies have shown that low density lipoproteins reconstituted with the natural omega 3 fatty acid docosahexaenoic acid (LDL-DHA) is selectively cytotoxic to liver cancer cells over normal hepatocytes. To date, little is known about the subcellular events which transpire following LDL-DHA treatment. Methods Herein, murine noncancer and cancer liver cells, TIB-73 and TIB-75 respectively, were investigated utilizing confocal microscopy, flow cytometry and viability assays to demonstrate differential actions of LDL-DHA nanoparticles in normal versus malignant cells. Results Our studies first showed that basal levels of oxidative stress are significantly higher in the malignant TIB-75 cells compared to the normal TIB-73 cells. As such, upon entry of LDL-DHA into the malignant TIB-75 cells, DHA is rapidly oxidized precipitating global and lysosomal lipid peroxidation along with increased lysosomal permeability. This leakage of lysosomal contents and lipid peroxidation products trigger subsequent mitochondrial dysfunction and nuclear injury. The cascade of LDL-DHA mediated lipid peroxidation and organelle damage was partially reversed by the administration of the antioxidant, N-acetylcysteine, or the iron-chelator, deferoxamine. LDL-DHA treatment in the normal TIB-73 cells was well tolerated and did not elicit any cell or organelle injury. Conclusion These studies have shown that LDL-DHA is selectively cytotoxic to liver cancer cells and that increased levels of ROS and iron catalyzed reactions promote the peroxidation of DHA which lead to organelle dysfunction and ultimately the demise of the cancer cell. General significance LDL-DHA selectively disrupts lysosomal, mitochondrial and nuclear function in cancer cells as a novel pathway for eliminating cancer cells.

<p>Nanomedicine-based formulations containing &omega;-3 polyunsaturated fatty acids: potential application in cardiovascular and neoplastic diseases</p>

“…A relevant approach was used by the Corbin group. 12,[27][28][29] They created low-density lipoprotein (LDL)-based nanoparticles with DHA as bioactive cargo (Table 2; Figure 2A), and tested them on a normal mouse liver cell line, as well as on mice, 12,28 rats, 29 or human liver cancer cell lines. 27 Interestingly, this DHA nanoformulation was successfully employed by the same group of authors also for the delivery of DHA to the brain.…”

“…[32][33][34] Indeed, one particularly interesting feature of these engineered nanoparticles was their ability to be selectively cytotoxic to hepatocarcinoma cells, over the nonmalignant counterparts. 12,28 This specificity for cancer cells is highly advantageous for antineoplastic agents, and, presumably, it was related to the fact that high concentrations of the cell growth inhibitor DHA were achieved only inside the cancer cells. Particularly, the selective growth-inhibitory effect of the LDL-DHA nanoparticles in liver cancer cells was explained on the basis of the specific and powerful anti-inflammatory and pro-resolving properties of the ω-3 PUFAs and their bioactive derivatives.…”

Low-density lipoprotein docosahexaenoic acid nanoparticles induce ferroptotic cell death in hepatocellular carcinoma

“…Formulating DHA into the LDL nanoparticles directs DHA along the endolysosomal pathway in the cell, in contrast, unesterified DHA enters the cell by diffusion or facilitative transporters. 19 This unique transport and processing of DHA along the endolysosomal pathway (which induces lysosome membrane permeability, mitochondrial dysfunction and nuclear injury) 9 , results in alternate cell death pathways such as ferroptosis.…”

“…Upon entry into the cell LDL-DHA disrupts lysosomal and mitochondrial function such that the cancer cell’s redox balance further favors oxidative metabolism. 9 Under this oxidative stress LDL-DHA undergoes disintegrative free radical peroxidation and cellular GSH levels are subsequently depleted. This in turn leads to the inactivation of GPX4, which allows further lipid peroxidation to proceed unabated.…”

“…Several small-molecule cell death inhibitor assays were performed but neither apoptosis, autophagy nor necroptosis inhibitors were able to prevent LDL-DHA mediated killing of HCC cells. 9 More recently a new iron-dependent form of regulated non-apoptotic cell death called ferroptosis was described. 10 It is characterized by increased lipid peroxidation and lethal accumulation of ROS derived from iron metabolism.…”