Sesamin Ameliorates Advanced Glycation End Products-Induced Pancreatic β-Cell Dysfunction and Apoptosis

Glycative stress inhibits hypertrophy and impairs cell membrane integrity in overloaded mouse skeletal muscle

BACKGROUND

Glycative stress, characterized by the formation and accumulation of advanced glycation end products (AGEs) associated with protein glycation reactions, has been implicated in inducing a decline of muscle function. Although the inverse correlation between glycative stress and muscle mass and strength has been demonstrated, the underlying molecular mechanisms are not fully understood. This study aimed to elucidate how glycative stress affects the skeletal muscle, particularly the adaptive muscle response to hypertrophic stimuli and its molecular mechanism.

METHODS

Male C57BL/6NCr mice were randomly divided into the following two groups: the bovine serum albumin (BSA)-treated and AGE-treated groups. Mice in the AGE-treated group were intraperitoneally administered AGEs (0.5 mg/g) once daily, whereas those in the BSA-treated group received an equal amount of BSA (0.5 mg/g) as the vehicle control. After 7 days of continuous administration, the right leg plantaris muscle of mice in each group underwent functional overload treatment by synergist ablation for 7 days to induce muscle hypertrophy. In in vitro studies, cultured C2C12 myocytes were treated with AGEs (1 mg/mL) to examine cell adhesion and cell membrane permeability.

RESULTS

Continuous AGE administration increased the levels of fluorescent AGEs, Nε-(carboxymethyl) lysine, and methylglyoxal-derived hydroimidazolone-1 in both plasma and skeletal muscle. Plantaris muscle weight, muscle fibre cross-sectional area, protein synthesis rate, and the number of myonuclei increased with functional overload in both groups; however, the increase was significantly reduced by AGE treatment. Some muscles of AGE-treated mice were destroyed by functional overload. Proteomic analysis was performed to explore the mechanisms of muscle hypertrophy suppression and myofibre destruction by AGEs. When principal component analysis was performed on 4659 data obtained by proteomic analysis, AGE treatment was observed to affect protein expression only in functionally overloaded muscles. Enrichment analysis of the 436 proteins extracted using the K-means method further identified a group of proteins involved in cell adhesion. Consistent with this finding, dystrophin-glycoprotein complex proteins and cell adhesion-related proteins were confirmed to increase with functional overload; however, this was attenuated by AGE treatment. Additionally, the treatment of C2C12 muscle cells with AGEs inhibited their ability to adhere and increased cell membrane permeability.

CONCLUSIONS

This study indicates that glycative stress may be a novel pathogenic factor in skeletal muscle dysfunctions by causing loss of membrane integrity and preventing muscle mass gain.

Sesamin ameliorates nonalcoholic hepatic steatosis by inhibiting CD36-mediated hepatocyte lipid accumulation in vitro and in vivo

Hepatic steatosis is a critical factor in the development of nonalcoholic steatohepatitis (NASH). Sesamin (Ses), a functional lignan isolated from Sesamum indicum, possesses hypolipidemic, liver-protective, anti-hypertensive, and anti-tumor properties. Ses has been found to improve hepatic steatosis, but the exact mechanisms through which Ses achieves this are not well understood. In this study, we observed the anti-hepatic steatosis effects of Ses in palmitate/oleate (PA/OA)-incubated primary mouse hepatocytes, AML12 hepatocytes, and HepG2 cells, as well as in high-fat, high-cholesterol diet-induced NASH mice. RNA sequencing analysis revealed that cluster of differentiation 36 (CD36), a free fatty acid (FA) transport protein, was involved in the Ses-mediated inhibition of hepatic fat accumulation. Moreover, the overexpression of CD36 significantly increased hepatic steatosis in both Ses-treated PA/OA-incubated HepG2 cells and NASH mice. Furthermore, Ses treatment suppressed insulin-induced de novo lipogenesis in HepG2 cells, which was reversed by CD36 overexpression. Mechanistically, we found that Ses ameliorated NASH by inhibiting CD36-mediated FA uptake and upregulation of lipogenic genes, including FA synthase, stearoyl-CoA desaturase 1, and sterol regulatory element-binding protein 1. The findings of our study provide novel insights into the potential therapeutic applications of Ses in the treatment of NASH.

Sesamin ameliorates nonalcoholic steatohepatitis through inhibiting hepatocyte pyroptosis in vivo and in vitro

Sesamin (Ses) is a natural lignan abundantly present in sesame and sesame oil. Pyroptosis, a newly identified type of pro-inflammatory programmed necrosis, contributes to the development of non-alcoholic steatohepatitis (NASH) when hepatocyte pyroptosis is excessive. In this study, Ses treatment demonstrated an improvement in hepatic damage in mice with high-fat, high-cholesterol diet-induced NASH and palmitate (PA)-treated mouse primary hepatocytes. Notably, we discovered, for the first time, that Ses could alleviate hepatocyte pyroptosis both in vivo and in vitro. Furthermore, treatment with phorbol myristate acetate, a protein kinase Cδ (PKCδ) agonist, increased PKCδ phosphorylation and attenuated the protective effects of Ses against pyroptosis in PA-treated mouse primary hepatocytes. Mechanistically, Ses treatment alleviated hepatocyte pyroptosis in NASH, which was associated with the regulation of the PKCδ/nod-like receptor family CARD domain-containing protein 4/caspase-1 axis. This study introduces a novel concept and target, suggesting the potential use of functional factors in food to alleviate liver damage caused by NASH.

Advanced glycation end products inhibit proliferation and primary cilia formation of myoblasts through receptor for advanced glycation end products pathway

The loss of skeletal muscle mass leads to various adverse conditions and shortened lifespan. The inhibition of myoblast proliferation is one of the causes that trigger muscle atrophy. Advanced glycation end products (AGEs) contribute to muscle atrophy. Since primary cilia are crucial organelles for proliferation, AGEs may inhibit primary cilia formation of myoblasts, thereby leading to impaired proliferation. Therefore, we aimed to clarify whether AGEs impeded the proliferation and formation of primary cilia of C2C12 skeletal muscle cells. AGE treatment inhibited the proliferation and formation of primary cilia. However, the inhibitor of the receptor for advanced glycosylation end products (RAGEs) abolished the inhibition of the proliferation and the primary cilia formation of C2C12 cells by AGEs, suggesting that AGEs cause these inhibitions through the RAGE pathway. In summary, our findings suggested that AGEs suppress the proliferation and formation of primary cilia of myoblasts through the RAGE pathway.

Protective effects of metformin on pancreatic β-cell ferroptosis in type 2 diabetes in vivo

Metformin (Met) is the recommended first-line therapeutic drug for type 2 diabetes mellitus (T2DM) and exerts protective effects on β-cell damage. Ferroptosis, a new form of cell death, is associated with pancreatic islet injury in patients with T2DM. However, the protective effects of Met treatment against β-cell damage through ferroptosis modulation remain under-reported. This study investigated the in vivo effects of Met treatment on pancreatic β-cell ferroptosis using two different diabetic mouse models, namely, low-dose streptozotocin (STZ) and high-fat diet (HFD)-induced diabetic mice and db/db mice. Met treatment significantly restored insulin release, reduced cell mortality, and decreased the overproduction of lipid-related reactive oxygen species in the islets of both STZ/HFD-induced diabetic mice and db/db mice. Administration of the Ras-selective lethal 3 injection significantly attenuated the antiferroptosis effects of Met. Mechanistically, Met treatment alleviated β-cell ferroptosis in T2DM, which was associated with the regulation of the GPX4/ACSL4 axis in the islets. In conclusion, our findings highlight the significance of ferroptosis in T2DM β-cell damage and provide novel insights into the protective effects of Met against islet β cells.

Sesamin: A Promising Therapeutic Agent for Ameliorating Symptoms of Diabetes

Diabetes is a chronic metabolic disease characterized by improperly regulating proteins, carbohydrates, and lipids due to insulin deficiency or resistance. The increasing prevalence of diabetes poses a tremendous socioeconomic burden worldwide, resulting in the rise of many studies on Chinese herbal medicines to discover the most effective cure for diabetes. Sesame seeds are among these Chinese herbal medicines that were found to contain various pharmacological activities, including antioxidant and anti-inflammatory properties, lowering cholesterol, improving liver function, blood pressure and sugar lowering, regulating lipid synthesis, and anticancer activities. These medicinal benefits are attributed to sesamin, which is the main lignan found in sesame seeds and oil. In this study, Wistar rat models were induced with type 2 diabetes using streptozotocin (STZ) and nicotinamide, and the effect of sesamin on the changes in body weight, blood sugar level, glycosylated hemoglobin (HbA1c), insulin levels, and the states of the pancreas and liver of the rats were evaluated. The results indicate a reduced blood glucose level, HbA1c, TG, and ALT and AST enzymes after sesamin treatment, while increased insulin level, SOD, CAT, and GPx activities were also observed. These findings prove sesamin's efficacy in ameliorating the symptoms of diabetes through its potent pharmacological activities.

Advanced Glycation End Products (AGEs) Inhibit Macrophage Efferocytosis of Apoptotic β Cells through Binding to the Receptor for AGEs

Pancreatic β cell apoptosis is important in the pathogenesis of type 2 diabetes mellitus (T2DM). Generally, apoptotic β cells are phagocytosed by macrophages in a process known as "efferocytosis." Efferocytosis is critical to the resolution of inflammation and is impaired in T2DM. Advanced glycation end products (AGEs), which are increased in T2DM, are known to suppress phagocytosis function in macrophages. In this study, we found that AGEs inhibited efferocytosis of apoptotic β cells by primary peritoneal macrophages in C57BL/6J mice or mouse macrophage cell line Raw264.7. Mechanistically, AGEs inhibit efferocytosis by blocking Ras-related C3 botulinum toxin substrate 1 activity and cytoskeletal rearrangement through receptor for advanced glycation end products/ras homolog family member A/Rho kinase signaling in macrophages. Furthermore, it was observed that AGEs decreased the secretion of anti-inflammatory factors and promoted the proinflammatory ones to modulate the inflammation function of efferocytosis. Taken together, our results indicate that AGEs inhibit efferocytosis through binding to receptor for advanced glycation end products and activating ras homolog family member A/Rho kinase signaling, thereby inhibiting the anti-inflammatory function of efferocytosis.

A SGLT2 Inhibitor Dapagliflozin Alleviates Diabetic Cardiomyopathy by Suppressing High Glucose-Induced Oxidative Stress in vivo and in vitro

Diabetic cardiomyopathy (DCM) is a serious complication of diabetes mellitus (DM). One of the hallmarks of the DCM is enhanced oxidative stress in myocardium. The aim of this study was to research the underlying mechanisms involved in the effects of dapagliflozin (Dap) on myocardial oxidative stress both in streptozotocin-induced DCM rats and rat embryonic cardiac myoblasts H9C2 cells exposed to high glucose (33.0 mM). In in vivo studies, diabetic rats were given Dap (1 mg/ kg/ day) by gavage for eight weeks. Dap treatment obviously ameliorated cardiac dysfunction, and improved myocardial fibrosis, apoptosis and oxidase stress. In in vitro studies, Dap also attenuated the enhanced levels of reactive oxygen species and cell death in H9C2 cells incubated with high glucose. Mechanically, Dap administration remarkably reduced the expression of membrane-bound nicotinamide adenine dinucleotide phosphate (NADPH) oxidase subunits gp91phox and p22phox, suppressed the p67phox subunit translocation to membrane, and decreased the compensatory elevated copper, zinc superoxide dismutase (Cu/Zn-SOD) protein expression and total SOD activity both in vivo and in vitro. Collectively, our results indicated that Dap protects cardiac myocytes from damage caused by hyperglycemia through suppressing NADPH oxidase-mediated oxidative stress.

Short Duration Alagebrium Chloride Therapy Prediabetes Does Not Inhibit Progression to Autoimmune Diabetes in an Experimental Model

Mechanisms by which advanced glycation end products (AGEs) contribute to type 1 diabetes (T1D) pathogenesis are poorly understood. Since life-long pharmacotherapy with alagebrium chloride (ALT) slows progression to experimental T1D, we hypothesized that acute ALT therapy delivered prediabetes, may be effective. However, in female, non-obese diabetic (NODShiLt) mice, ALT administered prediabetes (day 50-100) did not protect against experimental T1D. ALT did not decrease circulating AGEs or their precursors. Despite this, pancreatic β-cell function was improved, and insulitis and pancreatic CD45.1+ cell infiltration was reduced. Lymphoid tissues were unaffected. ALT pre-treatment, prior to transfer of primed GC98 CD8+ T cell receptor transgenic T cells, reduced blood glucose concentrations and delayed diabetes, suggesting islet effects rather than immune modulation by ALT. Indeed, ALT did not reduce interferon-γ production by leukocytes from ovalbumin-pre-immunised NODShiLt mice and NODscid recipients given diabetogenic ALT treated NOD splenocytes were not protected against T1D. To elucidate β-cell effects, NOD-derived MIN6N8 β-cell major histocompatibility complex (MHC) Class Ia surface antigens were examined using immunopeptidomics. Overall, no major changes in the immunopeptidome were observed during the various treatments with all peptides exhibiting allele specific consensus binding motifs. As expected, longer MHC Class Ia peptides were captured bound to H-2Db than H-2Kb under all conditions. Moreover, more 10-12 mer peptides were isolated from H-2Db after AGE modified bovine serum albumin (AGE-BSA) treatment, compared with bovine serum albumin (BSA) or AGE-BSA+ALT treatment. Proteomics of MIN6N8 cells showed enrichment of processes associated with catabolism, the immune system, cell cycling and presynaptic endocytosis with AGE-BSA compared with BSA treatments. These data show that short-term ALT intervention, given prediabetes, does not arrest experimental T1D but transiently impacts β-cell function.

Sesamin protects against DSS-induced colitis in mice by inhibiting NF-κB and MAPK signaling pathways

OBJECTIVE

To investigate the protective effects and mechanisms of sesamin (SES) on dextran sulfate sodium (DSS)-induced experimental colitis in mice.

METHODS

SES (50, 100, and 200 mg kg-1) were orally administered to C57BL/6 male mice after DSS instillation. The anti-inflammatory effect of SES on colonic damage was assessed by clinical, macroscopic, microscopic, and inflammatory signaling pathways.

RESULTS AND CONCLUSIONS

It could be found that bodyweight and colon length of mice treated with DSS was significantly decreased while that were increased by SES treatment. SES treatment reduced the DAI values and improved the histopathology of the colon in the DSS-treated mice. SES also reduced TNF-α, IL-1β and IL-6 production caused by DSS. We also measured the expression of the phosphorylation of p65, IκB, p38, ERK and JNK protein and found that SES can alleviate colon damage via the NF-κB and MAPK signaling pathways. The findings of this study suggested that SES had anti-inflammatory effects on intestinal inflammation and can be used as a new therapeutic candidate for inflammatory bowel disease.

Sesamin suppresses advanced glycation end products induced microglial reactivity using BV2 microglial cell line as a model

Neuroinflammation-mediated microglial reactivity is a major process, which explains the increased risk of Alzheimer's disease (AD) development in patients with Type 2 diabetes mellitus (T2DM). Advanced glycation end products (AGEs), formed by hyperglycemic condition in diabetes, is characterized as an intermediary of brain injury with diabetes through induction of microglial reactivity. Here, we explored the effect of AGEs on microglial reactivity using BV2 as a model. The NF-κB, p38 and JNK pathways were found to be important mechanism in AGEs-induced BV2 microglial reactivity. NF-κB inhibitor (BAY-11-7082), p38 inhibitor (SB203580) and JNK inhibitor (SP600125) exhibited the potential inhibition of AGEs-induced NO production. We also found that the sesamin, a major lignan found in sesame seed oils, exerts an anti-inflammatory effect under AGEs-induced microglial reactivity via suppressing the phosphorylation of NF-κB, p38 and JNK pathways. Moreover, sesamin also ameliorated AGEs-induced-receptor for advanced glycation end products (RAGE) expression. Taken together, sesamin may be a promising phytochemical compound to delay inflammatory progress by AGEs microglia function. Similarly, inhibition of AGEs-induced microglial reactivity might be potential therapeutic targets of neuroinflammation-based mechanisms in T2DM link progressive AD.

Immunomodulatory and anti-inflammatory effects of sesamin: mechanisms of action and future directions

Inflammation is associated with the development and progression of various disorders including atherosclerosis, diabetes mellitus and cancer. Sesamin, a fat-soluble lignan derived from Sesamum indicum seeds and oil, has received increased attention due to its wide array of pharmacological properties including its immunomodulatory and anti-inflammatory potential. To date, no review has been conducted to summarize or analyze the immunomodulatory and anti-inflammatory roles of sesamin. Herein, we provide a comprehensive review of experimental findings that were reported with regards to the ability of sesamin to modulate inflammation, cellular and humoral adaptive immune responses and Th1/Th2 paradigm. The potential influence of sesamin on the cytotoxic activity of NK cells against cancer cells is also highlighted. The molecular mechanisms and the signal transduction pathways underlying such effects are underscored. The metabolism, pharmacokinetics, absorption, tissue distribution and bioavailability of sesamin in different species, including humans, are reviewed. Moreover, we propose future preclinical and clinical investigations to further validate the potential preventive and/or therapeutic efficacy of sesamin against various immune-related and inflammatory conditions. We anticipate that sesamin may be employed in future therapeutic regimens to enhance the efficacy of treatment and dampen the adverse effects of synthetic chemical drugs currently used to alleviate immune-related and inflammatory conditions.

Sesamin alleviates diabetes-associated behavioral deficits in rats: The role of inflammatory and neurotrophic factors

Neuroinflammation and loss of neurotrophic support have key roles in the pathophysiology of diabetes-associated behavioral deficits (DABD). Sesamin (Ses), a major lignan of sesame seed and its oil, shows anti-hyperglycemic, anti-oxidative, and neuroprotective effects. The present study was designed to assess the potential protective effects of Ses against DABD and investigate the roles of inflammatory markers and neurotrophic factors in streptozotocin (STZ)-induced diabetic rats. After confirmation of diabetes, Ses (30 mg/kg/day; P.O.) or insulin (6 IU/rat/day; S.C.) was administered to rats for eight consecutive weeks. During the eighth-week period of the study, behavioral functions of the animals were evaluated by employing standard behavioral paradigms. Moreover, inflammation status, neurotrophic factors, and histological changes were assessed in the cerebral cortex and hippocampal regions of the rats. The results of behavioral tests showed that STZ-induced diabetes increased anxiety-/depression-like behaviors, decreased locomotor/exploratory activities, and impaired passive avoidance learning and memory. These DABD were accompanied by neuroinflammation, lack of neurotrophic support, and neuronal loss in both cerebral cortex and hippocampus of the rats. Intriguingly, chronic treatment with Ses improved all the above-mentioned diabetes-related behavioral, biochemical, and histological deficits, and in some cases, it was even more effective than insulin therapy. In conclusion, the results suggest that Ses was capable of improving DABD, which might be ascribed, at least partly, to the reduction of blood glucose level, inhibition of neuroinflammation, and potentiation of neurotrophic factors.

CG8005 Mediates Transit-Amplifying Spermatogonial Divisions via Oxidative Stress in Drosophila Testes

The generation of reactive oxygen species (ROS) widely occurs in metabolic reactions and affects stem cell activity by participating in stem cell self-renewal. However, the mechanisms of transit-amplifying (TA) spermatogonial divisions mediated by oxidative stress are not fully understood. Through genetic manipulation of Drosophila testes, we demonstrated that CG8005 regulated TA spermatogonial divisions and redox homeostasis. Using in vitro approaches, we showed that the knockdown of CG8005 increased ROS levels in S2 cells; the induced ROS generation was inhibited by NAC and exacerbated by H₂O₂ pretreatments. Furthermore, the silencing of CG8005 increased the mRNA expression of oxidation-promoting factors Keap1, GstD1, and Mal-A6 and decreased the mRNA expression of antioxidant factors cnc, Gclm, maf-S, ND-42, and ND-75. We further investigated the functions of the antioxidant factor cnc, a key factor in the Keap1-cnc signaling pathway, and showed that cnc mimicked the phenotype of CG8005 in both Drosophila testes and S2 cells. Our results indicated that CG8005, together with cnc, controlled TA spermatogonial divisions by regulating oxidative stress in Drosophila.

Health benefits of sesamin on cardiovascular disease and its associated risk factors

Sesamin, a major lignin isolated from sesame (Sesamum indicum) seeds and sesame oil, is known to possess antioxidant and anti-inflammatory properties. Several studies have revealed that oxidative stress and inflammation play a major role in a variety of cardiovascular diseases (CVDs). This comprehensive review summarizes the evidence on the effects of sesamin on CVD and its risk factors, principally due to its antioxidant properties. Specifically, this review highlights the mechanisms underlying the anti-hypertensive, anti-atherogenic, anti-thrombotic, anti-diabetic, and anti-obesity, lipolytic effects of sesamin both in vivo and in vitro, and identifies the signaling pathways targeted by sesamin and its metabolites. The data indicates that RAS/MAPK, PI3K/AKT, ERK1/2, p38, p53, IL-6, TNFα, and NF-κB signaling networks are all involved in moderating the various effects of sesamin on CVD and its risk factors. In conclusion, the experimental evidence suggesting that sesamin can reduce CVD risk is convincing. Thus, sesamin can be potentially useful as an adjuvant therapeutic agent to combat CVD and its multitude of risk factors.

Conversion of extracellular ATP into adenosine: a master switch in renal health and disease

ATP and its ultimate degradation product adenosine are potent extracellular signalling molecules that elicit a variety of pathophysiological functions in the kidney through the activation of P2 and P1 purinergic receptors, respectively. Extracellular purines can modulate immune responses, balancing inflammatory processes and immunosuppression; indeed, alterations in extracellular nucleotide and adenosine signalling determine outcomes of inflammation and healing processes. The functional activities of ectonucleotidases such as CD39 and CD73, which hydrolyse pro-inflammatory ATP to generate immunosuppressive adenosine, are therefore pivotal in acute inflammation. Protracted inflammation may result in aberrant adenosinergic signalling, which serves to sustain inflammasome activation and worsen fibrotic reactions. Alterations in the expression of ectonucleotidases on various immune cells, such as regulatory T cells and macrophages, as well as components of the renal vasculature, control purinergic receptor-mediated effects on target tissues within the kidney. The role of CD39 as a rheostat that can have an impact on purinergic signalling in both acute and chronic inflammation is increasingly supported by the literature, as detailed in this Review. Better understanding of these purinergic processes and development of novel drugs targeting these pathways could lead to effective therapies for the management of acute and chronic kidney disease.

Effects of Sesamin, the Major Furofuran Lignan of Sesame Oil, on the Amplitude and Gating of Voltage-Gated Na+ and K+ Currents

Sesamin (SSM) and sesamolin (SesA) are the two major furofuran lignans of sesame oil and they have been previously noticed to exert various biological actions. However, their modulatory actions on different types of ionic currents in electrically excitable cells remain largely unresolved. The present experiments were undertaken to explore the possible perturbations of SSM and SesA on different types of ionic currents, e.g., voltage-gated Na⁺ currents (I_Na), erg-mediated K⁺ currents (I_K(erg)), M-type K⁺ currents (I_K(M)), delayed-rectifier K⁺ currents (I_K(DR)) and hyperpolarization-activated cation currents (I_h) identified from pituitary tumor (GH₃) cells. The exposure to SSM or SesA depressed the transient and late components of I_Na with different potencies. The IC₅₀ value of SSM needed to lessen the peak or sustained I_Na was calculated to be 7.2 or 0.6 μM, while that of SesA was 9.8 or 2.5 μM, respectively. The dissociation constant of SSM-perturbed inhibition on I_Na, based on the first-order reaction scheme, was measured to be 0.93 μM, a value very similar to the IC₅₀ for its depressant action on sustained I_Na. The addition of SSM was also effective at suppressing the amplitude of resurgent I_Na. The addition of SSM could concentration-dependently inhibit the I_K(M) amplitude with an IC₅₀ value of 4.8 μM. SSM at a concentration of 30 μM could suppress the amplitude of I_K(erg), while at 10 μM, it mildly decreased the I_K(DR) amplitude. However, the addition of neither SSM (10 μM) nor SesA (10 μM) altered the amplitude or kinetics of I_h in response to long-lasting hyperpolarization. Additionally, in this study, a modified Markovian model designed for SCN8A-encoded (or Na_V1.6) channels was implemented to evaluate the plausible modifications of SSM on the gating kinetics of Na_V channels. The model demonstrated herein was well suited to predict that the SSM-mediated decrease in peak I_Na, followed by increased current inactivation, which could largely account for its favorable decrease in the probability of the open-blocked over open state of Na_V channels. Collectively, our study provides evidence that highlights the notion that SSM or SesA could block multiple ion currents, such as I_Na and I_K(M), and suggests that these actions are potentially important and may participate in the functional activities of various electrically excitable cells in vivo.

Excessive reactive oxygen species induce apoptosis via the APPL1-Nrf2/HO-1 antioxidant signalling pathway in trophoblasts with missed abortion

AIMS

Previous evidence has demonstrated that oxidative stress is related to the pathogenesis of missed abortion (MA), but the specific mechanism remains obscure. The adaptor protein APPL1 is one of the differential proteins in chorionic trophoblasts. Thus, this study aimed to assess the potential influence of APPL1 on oxidative stress responses as well the possible molecular mechanisms involving in MA.

MAIN METHODS

In the present study, the chorionic trophoblasts and the HTR-8/SVneo cell line were researched in vitro. Small interfering RNA (siRNA) was used to suppress the expression of APPL1. The fluorescent probes DHE and DCFH-DA were used to assess the intracellular reactive oxidative species (ROS). The activity of superoxide dismutase (SOD) was determined. Apoptosis was detected by TUNEL and flow cytometry. Cell viability was determined using Cell Counting Kit-8. Protein expression was detected by immunohistochemistry, western blotting, and reverse transcription-quantitative PCR.

KEY FINDINGS

The application of oxidant in normal chorionic trophoblasts induced cell death and overproduction of ROS, which was consistent with MA. In addition, knockdown of APPL1 in HTR-8/SVneo cells resulted in increased ROS and apoptosis, which could be rescued by pretreatment with antioxidants. Mechanistically, we report that overproduction of ROS in trophoblasts and disturbed SOD, APPL1 and Nrf2/HO-1 antioxidant responses constitute important contributors to apoptosis.

SIGNIFICANCE

Our results suggest that APPL1 has antioxidant properties that suppress oxidative stress and apoptosis via the Nrf2/HO-1 pathway. Moreover, antioxidant N-acetylcysteine (NAC) effectively restored the impaired antioxidative defense system elicited by excess ROS, as a potential therapeutic reagent for MA.

Advanced glycation end products enhance M1 macrophage polarization by activating the MAPK pathway

BACKGROUND

β-cell dysfunction is one of the core pathogenetic mechanisms of type 2 diabetes mellitus (T2DM). However, there are currently no effective therapeutic strategies to preserve β-cell mass and function. The role of islet macrophage phenotype reprogramming in β-cell dysfunction has attracted great attention. Given that advanced glycation end products (AGEs) are major pathogenic factors in T2DM, we investigated the effect of AGEs on macrophage activation and their role in β-cell dysfunction.

METHODS

We examined cytokine secretion, M1 and M2 macrophage-associated marker expression and MAPK phosphorylation levels in AGEs-stimulated macrophages. MIN6 cells were cocultured with AGEs-pretreated macrophages to study the effect of AGEs-induced macrophage activation on β-cell dysfunction.

RESULTS

We found that AGEs treatment significantly enhanced macrophage secretion of proinflammatory cytokines. The expression of M1 macrophage markers, such as iNOS and the surface marker CD11c, was significantly upregulated, whereas the expression of M2 macrophage markers, such as Arg1 and CD206, was reciprocally downregulated upon AGEs stimulation. AGEs treatment predominantly activated the MAPK pathway, and the inhibition of the MAPK pathway partially attenuated the AGEs-induced polarization of macrophages. In addition, coculture with AGEs-pretreated macrophages significantly inhibited the expression of molecules involved in β-cell function and was accompanied by the impairment of glucose-stimulated insulin secretion (GSIS) in MIN6 cells.

CONCLUSION

AGEs enhance the expression of proinflammatory molecules by activating the MAPK pathway. Moreover, these data imply that AGEs induce macrophage M1 phenotype polarization but restrain M2 polarization, which might contribute to β-cell dysfunction in the pathogenesis of T2DM.

LncRNA LEGLTBC Functions as a ceRNA to Antagonize the Effects of miR-34a on the Downregulation of SIRT1 in Glucolipotoxicity-Induced INS-1 Beta Cell Oxidative Stress and Apoptosis

Type 2 diabetes mellitus is a chronic metabolic disorder characterized by elevated blood glucose and/or high serum free fatty acids. Chronic hyperlipidemia causes the dysfunction of pancreatic beta cells, which is aggravated in the presence of hyperglycemia (glucolipotoxicity). Long noncoding RNAs (lncRNAs) have been suggested to play key roles in type 1 diabetes mellitus development. However, their roles in glucolipotoxicity-induced beta cell dysfunction are not fully understood. In the present study, we identified the differentially expressed lncRNAs in INS-1 cells exposed to high glucose and palmitate (HG/PA). Among the dysregulated lncRNAs, NONRATT003679.2 (low expression in glucolipotoxicity-treated beta cells (LEGLTBC)) was involved in glucolipotoxicity-evoked rat islet beta cell damage. LEGLTBC functioned as a molecular sponge of miR-34a in INS-1 cells. Additionally, SIRT1 was identified as a target of miR-34a and LEGLTBC promoted SIRT1 expression by sponging miR-34a. The upregulation of LEGLTBC attenuated HG/PA-induced INS-1 cell injury through the promotion of SIRT1-mediated suppression of ROS accumulation and apoptosis. This is the first study to comprehensively identify the lncRNA expression profiling of HG/PA-treated INS-1 beta cells and to demonstrate that LEGLTBC functions as a competing endogenous RNA and regulates miR-34a/SIRT1-mediated oxidative stress and apoptosis in INS-1 cells undergoing glucolipotoxicity.

Mitochondrial Pathway Is Involved in Advanced Glycation End Products-Induced Apoptosis of Rabbit Annulus Fibrosus Cells

STUDY DESIGN

Experimental study.

OBJECTIVE

The purposes of this study were to evaluate whether advanced glycation end-products (AGEs) induce annulus fibrosus (AF) cell apoptosis and further to explore the mechanism by which this process occurs.

SUMMARY OF BACKGROUND DATA

Recent studies revealed that AGEs accumulation is considered an important factor in diabetic intervertebral disc (IVD) degeneration. However, the effect of AGEs on intervertebral disc remains unclear.

METHODS

AF cells were treated with various concentrations of AGEs for 3 days. Cell viability and cell proliferation were measured by Cell Counting Kit-8 (CCK-8) and 5-ethynyl-2'-deoxyuridine (EdU) incorporation assays, respectively. Cell apoptosis was examined by Annexin V/PI apoptosis detection kit and Hoechst 33342. The expression of apoptosis-related proteins, including Bax, Bcl-2, cytochrome c, caspase-3, and caspase-9, was detected by western blotting. In addition, Bax and Bcl-2 mRNA expression levels were detected by real-time PCR (RT-PCR). Mitochondrial membrane potential (MMP) and intracellular reactive oxygen species (ROS) production of AF cell were examined by 5,5',6,6' -Tetrachloro-1,1',3,3'- tetraethyl-imidacarbocyanine iodide (JC-1) staining and 2',7'-Dichlorodihydrofluorescein diacetate (DCFH-DA) fluorescent probes, respectively.

RESULTS

Our results indicated that AGEs had inhibitory effects on AF cell proliferation and induced AF cell apoptosis. The molecular data showed that AGEs significantly up-regulated Bax expression and inhibited Bcl-2 expression. In addition, AGEs increased the release of cytochrome c into the cytosol and enhanced caspase-9 and caspase-3 activation. Moreover, treatment with AGEs resulted in a decrease in MMP and the accumulation of intracellular ROS in AF cells. The antioxidant N-acetyl-L-cysteine (NAC) significantly reversed AGE-induced MMP decrease and AF cell apoptosis.

CONCLUSION

These results suggested that AGEs induce rabbit AF cell apoptosis and mitochondrial pathway may be involved in AGEs-mediated cell apoptosis, which may provide a theoretical basis for diabetic IVD degeneration.

LEVEL OF EVIDENCE

N/A.

Sesamin Protects the Femoral Head From Osteonecrosis by Inhibiting ROS-Induced Osteoblast Apoptosis in Rat Model

Glucocorticoids intake has become the most common pathogenic factor for osteonecrosis of the femoral head (ONFH). Annually, tens of millions of patients suffer from pain related to ONFH. Researchers have proposed several underlying mechanisms of ONFH, including osteocyte apoptosis, cell differentiation disorder, and angiogenesis hindrance. Sesamin, isolated from Sesamum indicum seeds, was reported could affect osteocyte inflammation and differentiation in osteoarthritis and osteoporosis. We investigated the underlying influence of sesamin on ONFH rat model. Fifteen male Sprague-Dawley rats were randomly divided into three groups. The ONFH model group only received the methylprednisolone (MPS) and lipopolysaccharide (LPS) injection to promote the development of ONFH. The sesamin treatment group was injected with sesamin, MPS, and LPS. The control group was untreated. Rats from above groups were sacrificed 4 weeks later. The effect of sesamin on ONFH rats was validated by H&E staining. TUNEL staining showed that femoral head necrosis was attenuated by sesamin. Furthermore, the phosphorylation of Akt was increased and the downstream cellular apoptosis signal pathway was inhibited. Intracellular ROS level was decreased after sesamin treatment. In conclusion, our findings suggest that sesamin protects the femoral head from osteonecrosis by inhibiting ROS-induced osteoblast apoptosis.

Perinatal exposure to high dietary advanced glycation end products in transgenic NOD8.3 mice leads to pancreatic beta cell dysfunction

The contribution of environmental factors to pancreatic islet damage in type 1 diabetes remains poorly understood. In this study, we crossed mice susceptible to type 1 diabetes, where parental male (CD8+ T cells specific for IGRP206-214; NOD8.3) and female (NOD/ShiLt) mice were randomized to a diet either low or high in AGE content and maintained on this diet throughout pregnancy and lactation. After weaning, NOD8.3+ female offspring were identified and maintained on the same parental feeding regimen for until day 28 of life. A low AGE diet, from conception to early postnatal life, decreased circulating AGE concentrations in the female offspring when compared to a high AGE diet. Insulin, proinsulin and glucagon secretion were greater in islets isolated from offspring in the low AGE diet group, which was akin to age matched non-diabetic C57BL/6 mice. Pancreatic islet expression of Ins2 gene was also higher in offspring from the low AGE diet group. Islet expression of glucagon, AGEs and the AGE receptor RAGE, were each reduced in low AGE fed offspring. Islet immune cell infiltration was also decreased in offspring exposed to a low AGE diet. Within pancreatic lymph nodes and spleen, the proportions of CD4+ and CD8+ T cells did not differ between groups. There were no significant changes in body weight, fasting glucose or glycemic hormones. This study demonstrates that reducing exposure to dietary AGEs throughout gestation, lactation and early postnatal life may benefit pancreatic islet secretion and immune infiltration in the type 1 diabetic susceptible mouse strain, NOD8.3.

Activation of NLRP3 Inflammasome by Advanced Glycation End Products Promotes Pancreatic Islet Damage

Accumulation of advanced glycation end products (AGEs) contributes to ageing and age-related diseases, especially type 2 diabetes. The NLRP3 inflammasome, as a vital component of the innate immune system, is implicated in the pathogenesis of type 2 diabetes. However, the role of the NLRP3 inflammasome in AGE-induced pancreatic islet damage remains largely unclear. Results showed that administration of AGEs (120 mg/kg for 6 weeks) in C57BL/6J mice induced an abnormal response to glucose (as measured by glucose tolerance and insulin release), pancreatic β-cell ultrastructural lesion, and cell death. These effects were associated with an excessive superoxide anion level, significant increased protein expression levels for NADPH oxidase 2 (NOX2), thioredoxin-interacting protein (TXNIP), NLRP3, and cleaved IL-1β, enhanced caspase-1 activity, and a significant increase in the levels of TXNIP–NLRP3 protein interaction. Ablation of the NLRP3 inflammasome or treatment with antioxidant N-acetyl-cysteine (NAC) clearly ameliorated these effects. In conclusion, our results reveal a possible mechanism for AGE-induced pancreatic islet damage upon NLRP3 inflammasome activation.

Glucose-derived AGEs enhance human gastric cancer metastasis through RAGE/ERK/Sp1/MMP2 cascade

Advanced glycation end products (AGEs) have been reported to take part in many cancer processes. Whether AGEs contribute to gastric cancer (GC) course and the underlying mechanism are still unclear. Here, glucose-derived AGEs are detected to be accumulated in tumor tissues and blood of patients with GC. As the receptor for AGEs, RAGE is highly expressed in cancer tissues, and closely associated with the depth of cancer invasion, lymph node metastasis and TNM stage. Both in vivo and in vitro treatment of AGEs accelerate the tumor invasion and metastasis, with upregualtion of RAGE, Specificity Protein 1 (Sp1), and MMP2 protein expression, as well as enhancement of MMP2 activity. Either RAGE-blocking antibody or Sp1-knockdown can partially block the AGEs-induced effects. Moreover, AGEs increased the phosphorylation of ERK, and reducing the phosphorylation level of ERK by MEK1/2 inhibitor decreased the expression of Sp1. These results indicate that accumulation of glucose-derived AGEs may act as one of potential risk factors for GC progression and promote the invasion and metastasis of gastric cancer partially through the activation of RAGE/ERK/Sp1/MMP2 pathway.

Inhibition of tumor suppressor p53 preserves glycation-serum induced pancreatic beta-cell demise

Tumor suppressor p53 is a transcriptional factor that determines cell fate in response to multiple stressors, such as oxidative stress and endoplasmic reticulum stress, in the majority of cells. However, its role in pancreatic beta cells is not well documented. Our previous research has revealed that glycation-serum (GS) induced pancreatic beta-cell demise through the AGEs-RAGE pathway. In the present study, we investigated the role of p53 in GS-related beta-cell demise. Using pancreatic islets beta-cell line INS-1 cells, we found that with GS treatment, the transcriptional activity of p53 was significantly evoked due to the increased amount of nuclear p53 protein. Resveratrol (RSV) was capable of further enhancing this transcriptional ability and consequently increased the population of dead beta cells under GS exposure. In contrast, inhibiting this transcriptional activity via p53 interference greatly protected beta cells from the damage provoked by GS, as well as damage strengthened by RSV. However, the pharmacological activation of PPARγ with troglitazone (TRO) only suppressed GS-induced, not RSV-induced, p53 activity. Moreover, the activation of PPARγ greatly preserved beta cells from GS-induced death. This protective effect recurred due to improved mitochondrial function with Bcl2 overexpression. Further, p53 activation could induce cellular apoptosis in primary rat islets. Our findings explore the broader role of p53 in regulating pancreatic beta-cell demise in the presence of GS and may provide a therapeutic target for the treatment and prevention of diabetes.

Sesamin protects against renal ischemia reperfusion injury by promoting CD39-adenosine-A2AR signal pathway in mice

Ischemia reperfusion injury (IRI) is a leading cause of acute kidney injury with high morbidity and mortality due to limited therapy. Here, we examine whether sesamin attenuates renal IRI in an animal model and explore the underlying mechanisms. Male mice were subjected to right renal ischemia for 30 min followed by reperfusion for 24 h with sesamin (100 mg/kg) during which the left kidney was removed. Renal damage and function were assessed subsequently. The results showed that sesamin reduced kidney ischemia reperfusion injury, as assessed by decreased serum creatinine (Scr) and Blood urea nitrogen (BUN), alleviated tubular damage and apoptosis. In addition, sesamin inhibited neutrophils infiltration and pro-inflammatory cytokines tumor necrosis factor (TNF)-α and interleukin (IL)-1β production in IR-preformed kidney. Notably, sesamin promoted the expression of CD39, A2A adenosine receptor (A2AAR), and A2BAR mRNA and protein as well as adenosine production. Furthermore, CD39 inhibitor or A2AR antagonist abolished partly the protection of sesamin in kidney IRI. In conclusion, sesamin could effectively protect kidney from IRI by inhibiting inflammatory responses, which might be associated with promoting the adenosine-CD39-A2AR signaling pathway.

Sesamin Ameliorates High-Fat Diet-Induced Dyslipidemia and Kidney Injury by Reducing Oxidative Stress

The study explored the protective effect of sesamin against lipid-induced renal injury and hyperlipidemia in a rat model. An animal model of hyperlipidemia was established in Sprague-Dawley rats. Fifty-five adult Sprague-Dawley rats were divided into five groups. The control group was fed a standard diet, while the other four groups were fed a high-fat diet for 5 weeks to induce hyperlipidemia. Three groups received oral sesamin in doses of 40, 80, or 160 mg/(kg·day). Seven weeks later, the blood lipids, renal function, antioxidant enzyme activities, and hyperoxide levels in kidney tissues were measured. The renal pathological changes and expression levels of collagen type IV (Col-IV) and α-smooth muscle actin (α-SMA) were analyzed. The administration of sesamin improved the serum total cholesterol, triglyceride, low-density lipoprotein cholesterol, apolipoprotein-B, oxidized-low-density lipoprotein, and serum creatinine levels in hyperlipidemic rats, while it increased the high-density lipoprotein cholesterol and apolipoprotein-A levels. Sesamin reduced the excretion of 24-h urinary protein and urinary albumin and downregulated α-SMA and Col-IV expression. Moreover, sesamin ameliorated the superoxide dismutase activity and reduced malondialdehyde levels in kidney tissue. Sesamin could mediate lipid metabolism and ameliorate renal injury caused by lipid metabolism disorders in a rat model of hyperlipidemia.