Thioredoxin domain containing 5 is involved in the hepatic storage of squalene into lipid droplets in a sex-specific way

Chitosan Nanoparticles, a Novel Drug Delivery System to Transfer Squalene for Hepatocyte Stress Protection

The Mediterranean diet is a well-known dietary pattern that has gained considerable popularity worldwide for its ability to prevent the progression of nonalcoholic fatty liver disease. This is largely attributed to the use of virgin olive oil as the primary source of fat, which contains a substantial amount of squalene, a natural antioxidant. In order to enhance the delivery of squalene and amplify its effects due to its highly hydrophobic nature, herein, squalene has been incorporated into chitosan nanoparticles. The characterization of the resulting nanoparticles was conducted via scanning electron microscopy, dynamic light scattering, ζ potential, Fourier transform infrared spectroscopy, and gas chromatography-mass spectrometry. Reactive oxygen species (ROS) generation and cell viability assays were conducted in oxidative and endoplasmic reticulum (ER) stress in AML12 and a TXNDC5-deficient AML12 cell line, which was generated by CRISPR/Cas9 technology. The results demonstrated that squalene was successfully encapsulated in chitosan nanoparticles and exhibited rapid and efficient cellular uptake at a 150 μM squalene concentration within 48 h. In conclusion, the encapsulation of squalene in chitosan nanoparticles, compared to the poly(d,l-lactide-co-glycolic acid) and ethanol drug carriers, significantly enhanced its cellular uptake. This allows the administration of higher doses, which improve hepatocyte viability and reduce ROS levels, effectively compensating for the adverse effects of TXNDC5 deficiency under the context of hepatocyte stress protection.

Squalene in Nanoparticles Improves Antiproliferative Effect on Human Colon Carcinoma Cells Through Apoptosis by Disturbances in Redox Balance

Squalene, a triterpene found in extra virgin olive oil, has therapeutic properties in diseases related to oxidative stress, such as cancer. However, its hydrophobic nature and susceptibility to oxidation limit its bioavailability outside of olive oil. To expand its applications, alternative delivery methods are necessary. The objective of the present study was to examine the impact of squalene encapsulated in PLGA (poly(lactic-co-glycolic) acid) nanoparticles (PLGA + Sq) on the proliferation of human colon carcinoma Caco-2 cells, as well as its underlying mechanism of action. The findings demonstrated that PLGA + Sq exert no influence on differentiated cells; however, it is capable of reducing the proliferation of undifferentiated Caco-2 cells through apoptosis and cell cycle arrest in the G1 phase. This effect was initiated by the release of cytochrome c into the cytoplasm and the subsequent activation of caspase-3. Furthermore, squalene exhibited pro-oxidant activity, as evidenced by an increase in intracellular ROS (reactive oxygen species) levels. The results of the squalene effect on genes associated with cell death, inflammation, and the cell cycle indicate that its antiproliferative effect may be post-transcriptional. In conclusion, PLGA + Sq demonstrate an antiproliferative effect on Caco-2 cells through apoptosis by altering redox balance, suggesting squalene's potential as a functional food ingredient for colorectal cancer prevention.

TXNDC5 Plays a Crucial Role in Regulating Endoplasmic Reticulum Activity through Different ER Stress Signaling Pathways in Hepatic Cells

The pathogenesis of non-alcoholic fatty liver disease (NAFLD) is influenced by a number of variables, including endoplasmic reticulum stress (ER). Thioredoxin domain-containing 5 (TXNDC5) is a member of the protein disulfide isomerase family and acts as an endoplasmic reticulum (ER) chaperone. Nevertheless, the function of TXNDC5 in hepatocytes under ER stress remains largely uncharacterized. In order to identify the role of TXNDC5 in hepatic wild-type (WT) and TXNDC5-deficient (KO) AML12 cell lines, tunicamycin, palmitic acid, and thapsigargin were employed as stressors. Cell viability, mRNA, protein levels, and mRNA splicing were then assayed. The protein expression results of prominent ER stress markers indicated that the ERN1 and EIF2AK3 proteins were downregulated, while the HSPA5 protein was upregulated. Furthermore, the ATF6 protein demonstrated no significant alterations in the absence of TXNDC5 at the protein level. The knockout of TXNDC5 has been demonstrated to increase cellular ROS production and its activity is required to maintain normal mitochondrial function during tunicamycin-induced ER stress. Tunicamycin has been observed to disrupt the protein levels of HSPA5, ERN1, and EIF2AK3 in TXNDC5-deficient cells. However, palmitic acid has been observed to disrupt the protein levels of ATF6, HSPA5, and EIF2AK3. In conclusion, TXNDC5 can selectively activate distinct ER stress pathways via HSPA5, contingent on the origin of ER stress. Conversely, the absence of TXNDC5 can disrupt the EIF2AK3 cascade.

Thioredoxin Domain Containing 5 (TXNDC5): Friend or Foe?

This review focuses on the thioredoxin domain containing 5 (TXNDC5), also known as endoplasmic reticulum protein 46 (ERp46), a member of the protein disulfide isomerase (PDI) family with a dual role in multiple diseases. TXNDC5 is highly expressed in endothelial cells, fibroblasts, pancreatic β-cells, liver cells, and hypoxic tissues, such as cancer endothelial cells and atherosclerotic plaques. TXNDC5 plays a crucial role in regulating cell proliferation, apoptosis, migration, and antioxidative stress. Its potential significance in cancer warrants further investigation, given the altered and highly adaptable metabolism of tumor cells. It has been reported that both high and low levels of TXNDC5 expression are associated with multiple diseases, such as arthritis, cancer, diabetes, brain diseases, and infections, as well as worse prognoses. TXNDC5 has been attributed to both oncogenic and tumor-suppressive features. It has been concluded that in cancer, TXNDC5 acts as a foe and responds to metabolic and cellular stress signals to promote the survival of tumor cells against apoptosis. Conversely, in normal cells, TXNDC5 acts as a friend to safeguard cells against oxidative and endoplasmic reticulum stress. Therefore, TXNDC5 could serve as a viable biomarker or even a potential pharmacological target.