Inhibition of Protein-Tyrosine Phosphatase PTP1B and LMPTP Promotes Palmitate/Oleate-Challenged HepG2 Cell Survival by Reducing Lipoapoptosis, Improving Mitochondrial Dynamics and Mitigating Oxidative and Endoplasmic Reticulum Stress

Abstract

Objectives: Non-alcoholic fatty liver disease (NAFLD) is considered a well-known pathology that is determined without using alcohol and has emerged as a growing public health problem. Lipotoxicity is known to promote hepatocyte death, which, in the context of NAFLD, is termed lipoapoptosis. The severity of NAFLD correlates with the degree of hepatocyte lipoapoptosis. Protein–tyrosine phosphatases (PTP) including PTP1B and Low molecular weight PTP (LMPTP), are negative regulators of the insulin signaling pathway and are considered a promising therapeutic target in the treatment of diabetes. In this study, we hypothesized that the inhibition of PTP1B and LMPTP may potentially prevent hepatocyte apoptosis, mitochondrial dysfunction and endoplasmic reticulum (ER) stress onset, following lipotoxicity induced using a free fatty acid (FFA) mixture. Methods: HepG2 cells were cultured in the presence or absence of two PTP inhibitors, namely MSI-1436 and Compound 23, prior to palmitate/oleate overloading. Apoptosis, ER stress, oxidative stress, and mitochondrial dynamics were then evaluated by either MUSE or RT-qPCR analysis. Results: The obtained data demonstrate that the inhibition of PTP1B and LMPTP prevents apoptosis induced by palmitate and oleate in the HepG2 cell line. Moreover, mitochondrial dynamics were positively improved following inhibition of the enzyme, with concomitant oxidative stress reduction and ER stress abrogation. Conclusion: In conclusion, PTP’s inhibitory properties may be a promising therapeutic strategy for the treatment of FFA-induced lipotoxicity in the liver and ultimately in the management of the NAFLD condition.

Efficacy and Mechanism of a Chinese Classic Prescription of Yueju in Treating Nonalcoholic Steatohepatitis and Protecting Hepatocytes from Apoptosis

“…Given that the cell viability was significantly decreased when the concentration of FFAs was over 400 μ M (see Figure 4(b) ), 2 mM FFAs were used to imitate the cytotoxicity of FFAs in vitro as previously described [ 30 ]. The apoptosis of the HepG2 cells was induced by 2 mM FFAs and treatment with 20, 100, and 500 μ g/mL YJP and 10 μ M FNF for 24 hr, respectively.…”

MSI-1436 improves EMS adipose derived progenitor stem cells in the course of adipogenic differentiation through modulation of ER stress, apoptosis, and oxidative stress

“…Dysfunctional adipose tissue remodeling contributes to insulin resistance, accelerates fibrosis and inflammation, and secretes wide range of adipokines, which worsens metabolic state of the organisms [ 4 ]. MSI-1436 action has been mostly investigated with HepG2 cells in vitro and in DIO models in vivo [ 29 ]. It was shown to improve insulin-stimulated tyrosine phosphorylation of insulin receptor (IR) β and enhance insulin sensitivity, suppress appetite, reduce body weight, and decrease leptin and insulin plasma levels [ 31 , 37 ].…”

“…Total metabolites were extracted from equine healthy and EMS ASCs cultured under either basal or adipogenic conditions according to the procedure described previously [ 29 ]. Briefly, cells from all tested groups were collected following 14 days of differentiation, washed three times with cold HBSS, and suspended in an extracting mixture comprising chloroform/methanol/water mixture in a ratio of 20:50:20.…”

“…The global analysis of adipogenic cells’ free fatty acid profile and quantity was performed according to Bourebaba et al’s [ 29 ] protocol. Briefly, crude lipid extract of adipogenic cells, with 30 μg of heptadecanoic acid methyl ester (Me.…”

“…The deterioration of ER functionality leads to increased accumulation of misfolded or unfolded peptides triggering the state of ER stress. Among proteins involved in the ER stress, inositol-requiring enzyme (IRE)-1, PKR-like ER-regulating kinase (PERK), and activating transcription factor (ATF)-6 play the key role [ 29 , 30 ]. These proteins trigger the activation of pathways that mitigate ER stress, through the unfolded protein response (UPR).…”