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Diabetic peripheral neuropathy (DPN) is a common complication of diabetes mellitus (DM). Schwann cell (SC) apoptosis contributes to the occurrence and development of DPN. Effective drugs to prevent SC apoptosis are required to relieve and reverse peripheral nerve injury caused by DM. Oltipraz [4-methyl-5-(2-pyrazinyl)-1,2-dithiole-3-thione], an agonist of nuclear factor erythroid derived-2-related factor 2 (Nrf2), exerts strong effect against oxidative stress in animal models or clinical patients in certain diseases, including heart failure, acute kidney injury, and liver injury. The aim of the present study was to determine the effectiveness of oltipraz in preventing SC apoptosis induced by high glucose levels. RSC96 cells pretreated with oltipraz were cultured in high-glucose medium (50 mM glucose) for 24 h, and cells cultured in medium containing 5 mM glucose were used as the control. Flow cytometry was used to evaluate the degree of apoptosis. A Cell Counting Kit-8 assay was used to assess cell viability. The mitochondrial membrane potential was assessed using JC-1 staining, and reactive oxygen species (ROS) generation was measured using 20,70-dichlorodihydrofluorescein diacetate staining. In addition, the levels of malondialdehyde (MDA) and superoxide dismutase (SOD) levels were also evaluated using the corresponding kits. Flow cytometry was subsequently used to detect apoptosis, and western blotting was used to measure the expression levels of nuclear factor erythroid derived-2-related factor 2 and NADPH quinone oxidoreductase 1. The results showed that high glucose concentration increased oxidative stress and apoptosis in RSC96 cells. Oltipraz improved cell viability and reduced apoptosis of RSC96 cells in the high glucose environment. Additionally, oltipraz exhibited a significant antioxidative effect, as shown by the decrease in MDA levels, increased SOD levels, and reduced ROS generation in RSC96 cells. The results of the present study suggest that oltipraz exhibits potential as an effective drug for treatment with DPN., Competing Interests: The authors declare that they have no competing interests., (Copyright © 2020 Zengxin Jiang et al.)

Diabetes mellitus (DM) contributes to intervertebral disc degeneration (IDD). The long non‑coding RNA MALAT1 has been revealed to play an important role in diabetes‑associated complications. However, the specific role of MALAT1 in diabetes‑associated IDD has not been determined. The aim of the present study was to evaluate the roles of MALAT1 in the apoptosis of cartilage endplate (CEP) cells induced by high glucose and to explore the mechanisms underlying this effect. Rat CEP cells were cultured in high‑glucose medium (25 mM glucose) for 24 or 72 h. Cells cultured in medium containing 5 mM glucose were used as a control. Flow cytometry was used to detect the degree of apoptosis. Reverse transcription‑quantitative PCR was used to measure the expression of MALAT1 mRNA. In addition, CEP cells were treated with different conditions (high glucose, high glucose + MALAT1 negative control, high glucose + MALAT1 RNAi, normal control) for 72 h. Flow cytometry was subsequently used to detect apoptosis and western blotting was used to measure the expression levels of total and phosphorylated p38. The results revealed that high glucose concentration promoted apoptosis and enhanced expression of MALAT1 in CEP cells. Furthermore, MALAT1 knockout decreased the expression levels of total and phosphorylated p38 and reduced the apoptosis of rat CEP cells. The results obtained in the present study indicated that MALAT1 may serve as an important therapeutic target for curing or delaying IDD in patients with diabetes.

ABSTRACT: Diabetes mellitus (DM) is an important factor in intervertebral disc degeneration (IDD). Apoptosis of cartilage endplate (CEP) cells is one of the initiators of IDD. However, the effects of high glucose on CEP cells are still unknown. Therefore, we conducted the present study to evaluate the effects of high glucose on CEP cells and to identify the mechanisms of those effects. Rat CEP cells were isolated and cultured in 10% foetal bovine serum (FBS, normal control) or high‐glucose medium (10% FBS + 0.1 M glucose or 10% FBS + 0.2 M glucose, experimental conditions) for 1 or 3 days. In addition, CEP cells were treated with 0.2 M glucose for 3 days in the presence or absence of alpha‐lipoic acid (ALA, 0.15 M). Flow cytometry was performed to identify and quantify the degree of apoptosis. The expression of reactive oxygen species (ROS) was assessed by flow cytometry, and mitochondrial damage (mitochondrial membrane potential) was assessed by fluorescence microscopy. Furthermore, the expression levels of cleaved caspase‐3, cleaved caspase‐9, Bcl‐2, Bax, and cytochrome c were evaluated by Western blotting. High glucose significantly increased apoptosis and ROS accumulation in CEP cells in a dose‐ and time‐dependent manner. Meanwhile, a disrupted mitochondrial membrane potential was detected in rat CEP cells cultured in the two high glucose concentrations. Incubating in high glucose enhanced the expression levels of cleaved caspase‐3, cleaved caspase‐9, Bax, and cytochrome c but decreased the level of the anti‐apoptotic protein Bcl‐2. ALA inhibited the expression of cleaved caspase‐3, cleaved caspase‐9, Bax, and cytochrome c but enhanced the expression of Bcl‐2. ALA also prevented disruption of the mitochondrial membrane potential in CEP cells. This study demonstrates that high glucose‐induced excessive reactive oxygen species promote mitochondrial damage, thus causing apoptosis in rat CEP cells in a dose‐ and time‐dependent manner. ALA could prevent mitochondrial damage and apoptosis caused by high glucose in CEP cells. The results suggest that appropriate blood glucose control may be the key to preventing IDD in diabetic patients. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2476–2483, 2018. [ABSTRACT FROM AUTHOR]