Hepatic Arterial Infusion of Low-Density Lipoprotein Docosahexaenoic Acid Nanoparticles Selectively Disrupts Redox Balance in Hepatoma Cells and Reduces Growth of Orthotopic Liver Tumors in Rats.

BACKGROUND & AIMS: Dietary intake of the natural omega-3 fatty acid docosahexaenoic acid (DHA) has been implicated in protecting patients with viral hepatitis B or C from developing hepatocellular carcinoma (HCC). Little is known about the effects of DHA on established solid tumors. Here we describe a low-density lipoprotein-based nanoparticle that acts as a transporter for unesterified DHA (LDL-DHA) and demonstrates selective cytotoxicity toward HCC cells. We investigated the ability of LDL-DHA to reduce growth of orthotopic hepatomas in rats. METHODS: AxC-Irish (ACI) rats were given intrahepatic injections of rat hepatoma cells (H4IIE); 24 tumor-bearing rats (mean tumor diameter, ∼1 cm) were subject to a single hepatic artery injection of LDL nanoparticles (2 mg/kg) loaded with DHA (LDL-DHA), triolein (LDL-TO), or sham surgery controls. Tumor growth was measured by magnetic resonance imaging and other methods; tumor, liver, and serum samples were collected and assessed by histochemical, immunofluorescence, biochemical, and immunoblot analyses. RESULTS: Three days after administration of LDL-TO or sham surgery, the control rats had large, highly vascularized tumors that contained proliferating cells. However, rats given LDL-DHA had smaller, pale tumors that were devoid of vascular supply and >80% of the tumor tissue was necrotic. Four to 6 days after injection of LDL-DHA, the tumors were 3-fold smaller than those of control rats. The liver tissue that surrounded the tumors showed no histologic or biochemical evidence of injury. Injection of LDL-DHA into the hepatic artery of rats selectively deregulated redox reactions in tumor tissues by increasing levels of reactive oxygen species and lipid peroxidation, depleting and oxidizing glutathione and nicotinamide adenine dinucleotide phosphate, and significantly down-regulating the antioxidant enzyme glutathione peroxidase-4. Remarkably, the redox balance in the surrounding liver was not disrupted. CONCLUSION: LDL-DHA nanoparticle selectively kills hepatoma cells and reduces growth of orthotopic liver tumors in rats. It induces tumor-specific necrosis by selectively disrupting redox balance within the cancer cell.

Mitochondrial metabolism mediates oxidative stress and inflammation in fatty liver.

Mitochondria are critical for respiration in all tissues; however, in liver, these organelles also accommodate high-capacity anaplerotic/cataplerotic pathways that are essential to gluconeogenesis and other biosynthetic activities. During nonalcoholic fatty liver disease (NAFLD), mitochondria also produce ROS that damage hepatocytes, trigger inflammation, and contribute to insulin resistance. Here, we provide several lines of evidence indicating that induction of biosynthesis through hepatic anaplerotic/cataplerotic pathways is energetically backed by elevated oxidative metabolism and hence contributes to oxidative stress and inflammation during NAFLD. First, in murine livers, elevation of fatty acid delivery not only induced oxidative metabolism, but also amplified anaplerosis/cataplerosis and caused a proportional rise in oxidative stress and inflammation. Second, loss of anaplerosis/cataplerosis via genetic knockdown of phosphoenolpyruvate carboxykinase 1 (Pck1) prevented fatty acid-induced rise in oxidative flux, oxidative stress, and inflammation. Flux appeared to be regulated by redox state, energy charge, and metabolite concentration, which may also amplify antioxidant pathways. Third, preventing elevated oxidative metabolism with metformin also normalized hepatic anaplerosis/cataplerosis and reduced markers of inflammation. Finally, independent histological grades in human NAFLD biopsies were proportional to oxidative flux. Thus, hepatic oxidative stress and inflammation are associated with elevated oxidative metabolism during an obesogenic diet, and this link may be provoked by increased work through anabolic pathways.

Low-density lipoprotein-mediated delivery of docosahexaenoic acid selectively kills murine liver cancer cells.

AIM: The natural omega-3 polyunsaturated fatty acid, docosahexaenoic acid (DHA), has recently been credited for possessing anticancer properties. Herein, we investigate the cytotoxic actions of DHA-loaded low-density lipoprotein (LDL) nanoparticles in normal and liver cancer cells. MATERIALS & METHODS: LDL-DHA nanoparticles were prepared and subjected to extensive biophysical characterization. The therapeutic utility of LDL-DHA nanoparticles was evaluated in normal and malignant murine hepatocyte cell lines, TIB-73 and TIB-75, respectively. RESULTS & DISCUSSION: The engineered LDL-DHA nanoparticles possessed enhanced physical and oxidative stabilities over native LDL and free DHA. Dose-response studies showed that therapeutic doses of LDL-DHA nanoparticles that completely killed TIB-75 were innocuous to TIB-73. The selective induction of lipid peroxidation and reactive oxygen species in the cancer cells was shown to play a central role in LDL-DHA nanoparticle-mediated cytotoxicity. CONCLUSION: In summary, these findings indicate that LDL-DHA nanoparticles show great promise as a selective anticancer agent against hepatocellular carcinoma.