Nicorandil attenuates high glucose-induced insulin resistance by suppressing oxidative stress-mediated ER stress PERK signaling pathway

ATF4-dependent and independent mitokine secretion from OPA1 deficient skeletal muscle in mice is sexually dimorphic

Introduction

Reducing Optic Atrophy 1 (OPA1) expression in skeletal muscle in male mice induces Activation Transcription Factor 4 (ATF4) and the integrated stress response (ISR). Additionally, skeletal muscle secretion of Fibroblast Growth Factor 21 (FGF21) is increased, which mediates metabolic adaptations including resistance to diet-induced obesity (DIO) and glucose intolerance in these mice. Although FGF21 induction in this model can be reversed with pharmacological attenuation of ER stress, it remains to be determined if ATF4 is responsible for FGF21 induction and its metabolic benefits in this model.

Methods

We generated mice with homozygous floxed Opa1 and Atf4 alleles and a tamoxifen-inducible Cre transgene controlled by the human skeletal actin promoter to enable simultaneous depletion of OPA1 and ATF4 in skeletal muscle (mAO DKO). Mice were fed high fat (HFD) or control diet and evaluated for ISR activation, body mass, fat mass, glucose tolerance, insulin tolerance and circulating concentrations of FGF21 and growth differentiation factor 15 (GDF15).

Results

In mAO DKO mice, ATF4 induction is absent. Other indices of ISR activation, including XBP1s, ATF6, and CHOP were induced in mAO DKO males, but not in mOPA1 or mAO DKO females. Resistance to diet-induced obesity was not reversed in mAO DKO mice of both sexes. Circulating FGF21 and GDF15 illustrated sexually dimorphic patterns. Loss of OPA1 in skeletal muscle increases circulating FGF21 in mOPA1 males, but not in mOPA1 females. Additional loss of ATF4 decreased circulating FGF21 in mAO DKO male mice, but increased circulating FGF21 in female mAO DKO mice. Conversely, circulating GDF15 was increased in mAO DKO males and mOPA1 females, but not in mAO DKO females.

Conclusion

Sex differences exist in the transcriptional outputs of the ISR following OPA deletion in skeletal muscle. Deletion of ATF4 in male and female OPA1 KO mice does not reverse the resistance to DIO. Induction of circulating FGF21 is ATF4 dependent in males, whereas induction of circulating GDF15 is ATF4 dependent in females. Elevated GDF15 in males and FGF21 in females could reflect activation by other transcriptional outputs of the ISR, that maintain mitokine-dependent metabolic protection in an ATF4-independent manner.

Nicorandil mitigates arsenic trioxide-induced lung injury via modulating vital signalling pathways SIRT1/PGC-1α/TFAM, JAK1/STAT3, and miRNA-132 expression

BACKGROUND AND PURPOSE

Nicorandil, a selective opener of potassium channels, used to treat angina, has drawn attention for its potential in mitigating lung injury, positioning it as a promising therapeutic approach to treat drug-induced lung toxicity. This study aimed to explore the protective role of nicorandil in arsenic trioxide (ATO)-induced lung injury and to elucidate the underlying mechanistic pathways.

EXPERIMENTAL APPROACH

We assessed the effects of nicorandil (15 mg·kg-1, p.o.) in a rat model of pulmonary injury induced by ATO (5 mg·kg-1, i.p.). The assessment included oxidative stress biomarkers, inflammatory cytokine levels, and other biomarkers, including sirtuin-1, sirtuin-3, STAT3, TFAM, and JAK in lung tissue. Histological examination using H&E staining and molecular investigations using western blotting and PCR techniques were conducted.

KEY RESULTS

In our model of lung injury, treatment with nicorandil ameliorated pathological changes as seen with H&E staining, reduced tissue levels of toxicity markers, and exerted significant antioxidant and anti-inflammatory actions. On a molecular level, treatment with nicorandil down-regulated JAK, STAT3, PPARγ, Nrf2, VEGF, p53, and micro-RNA 132 while up-regulating Sirt1, 3, TFAM, AMPK, and ERR-α in lung tissue.

CONCLUSIONS AND IMPLICATIONS

The results presented here show nicorandil as a significant agent in attenuating lung injury induced by ATO in a rodent model. Nonetheless, further clinical studies are warranted to strengthen these findings.

ZBTB7A interferes with the RPL5-P53 feedback loop and reduces endoplasmic reticulum stress-induced apoptosis of pancreatic cancer cells

Endoplasmic reticulum (ER) stress is a primary mechanism leading to cell apoptosis, making it of great research interests in cancer management. This study delves into the function of ribosomal protein L5 (RPL5) in ER stress within pancreatic cancer (PCa) cells and investigates its regulatory mechanisms. Bioinformatics predictions pinpointed RPL5 as an ER stress-related gene exhibiting diminished expression in PCa. Indeed, RPL5 was found to be poorly expressed in PCa tissues and cells, with this reduced expression correlating with an unfavorable prognosis. Moreover, RPL5 overexpression led to heightened levels of p-PERK, p-eIF2α, and CHOP, bolstering the proapoptotic effect of Tunicamycin, an ER stress activator, on PCa cells. Additionally, the RPL5 overexpression curbed cell proliferation, migration, and invasion. Tunicamycin enhanced the binding between RPL5 and murine double minute 2 (MDM2), thus suppressing MDM2-mediated ubiquitination and degradation of P53. Consequently, P53 augmentation intensified ER stress, which further enhanced the binding between RPL5 and MDM2 through PERK-dependent eIF2α phosphorylation, thereby establishing a positive feedback loop. Zinc finger and BTB domain containing 7A (ZBTB7A), conspicuously overexpressed in PCa samples, repressed RPL5 transcription, thereby reducing P53 expression. Silencing of ZBTB7A heightened ER stress and subdued the malignant attributes of PCa cells, effects counteracted upon RPL5 silencing. Analogous outcomes were recapitulated in vivo employing a xenograft tumor mouse model, where ZBTB7A silencing dampened the tumorigenic potential of PCa cells, an effect reversed by additional RPL5 silencing. In conclusion, this study suggests that ZBTB7A represses RPL5 transcription, thus impeding the RPL5-P53 feedback loop and mitigating ER-induced apoptosis in PCa cells.

Microplastics induced endoplasmic reticulum stress to format an inflammation and cell death in hepatocytes of carp (Cyprinus carpio)

Microplastics (MPs) are a serious threat to the living environment of aquatic organisms. However, there are fewer studies on the toxicity of microplastics to freshwater organisms. This study aimed to establish a polystyrene microplastics (PS-MPs) model by feeding carp (Cyprinus carpio) PS-MP (1000 ng/L) particles 8 μm in size. HE staining revealed a mass of inflammatory cells infiltrated in the carp hepatopancreas. The activities of alkaline phosphatase (AKP), aspartate transaminase (AST), lactate dehydrogenase (LDH), and alanine transaminase (ALT) were strengthened considerably, suggesting that PS-MPs cause injury to the hepatopancreas of carp. Real-Time polymerase chain reaction and western blotting results indicated increased levels of glucose-regulated protein 78 (GRP78), (PKR)-like ER kinase (PERK), eukaryotic translation initiation Factor 2α (EIF2α) and activating transcription Factor 4 (ATF4) genes and increased levels of inflammatory factors downstream of endoplasmic reticulum stress (ERs) thioredoxin-interacting protein (TXNIP), NOD-like receptor protein 3 (NLRP3), interleukin-18 (IL-18), interleukin-1β (IL-1β), and caspase 1. Increased expression of microtubule-associated protein-2 (LC3II), autophagy-related 5 (ATG5) and autophagy-related 12 (ATG12) genes revealed that PS-MPs promoted autophagy in carp hepatocytes. The enhanced expression of the Caspase 12, Caspase 3, and Bax genes suggested that PS-MPs led to the apoptosis of carp hepatocytes. These results suggest that PS-MPs result in serious injury to the hepatopancreas of carp. The present study of PS-MPs in freshwater fish from the aspect of endoplasmic reticulum stress was conducted to provide references and suggestions for toxicological studies of PS-MPs in freshwater environments.

Advanced glycation end products induce skeletal muscle atrophy and insulin resistance via activating ROS-mediated ER stress PERK/FOXO1 signaling

Skeletal muscle atrophy is often found in patients with type 2 diabetes mellitus (T2DM), which is characterized by insulin resistance. As the largest tissue in the body, skeletal muscle plays important roles in insulin resistance. Advanced glycation end products (AGEs) are a type of toxic metabolite that are representative of multiple pathophysiological changes associated with T2DM. Mice were exposed to AGEs. Forkhead box O1 (FOXO1) was silenced by using a constructed viral vector carrying siRNA. Skeletal muscle atrophy was evaluated by using hematoxylin-eosin (H&E), oil red O, myosin skeletal heavy chain (MHC), and laminin immunofluorescent stains. Reactive oxygen species (ROS) generation was assessed by using the dihydroethidium (DHE) stain. Western blotting was used to evaluate protein expression and phosphorylation. Insulin resistance was monitored via the insulin tolerance test and the glucose infusion rate (GIR). Mice exposed to AGEs showed insulin resistance, which was evidenced by reduced insulin tolerance and GIR. H&E and MHC immunofluorescent stains suggested reduced cross-sectional muscle fiber area. Laminin immunofluorescent and oil red O stains indicated increased intramuscular fibrosis and lipid deposits, respectively. Exposure to AGEs induced ROS generation, increased phosphorylation of protein kinase RNA-like endoplasmic reticulum kinase (PERK) and FOXO1, facilitated FOXO1 nuclear translocation, and elevated expression of muscle atrophy F-box (MAFbx) in gastrocnemius muscle. foxo1 silencing significantly suppressed skeletal muscle atrophy and insulin resistance without affecting ROS production. AGEs exacerbated skeletal muscle atrophy and insulin resistance by activating the PERK/FOXO1 signaling pathway in skeletal muscle.NEW & NOTEWORTHY In this study, we proposed a molecular mechanism underlying the skeletal muscle atrophy-associated insulin resistance in type 2 diabetes mellitus (T2DM). Our investigation suggests that exposure to AGEs, which are characteristic metabolites of T2DM pathology, induces the activation of reactive oxygen species (ROS)-mediated endoplasmic reticulum (ER) stress, leading to the upregulation of the protein kinase RNA-like ER kinase (PERK)/forkhead box O1 (FOXO1)/muscle atrophy F-box pathway and subsequent skeletal muscle atrophy, ultimately resulting in insulin resistance.

Effect of Insulin and Pioglitazone on Protein Phosphatase 2A Interaction Partners in Primary Human Skeletal Muscle Cells Derived from Obese Insulin-Resistant Participants

Skeletal muscle insulin resistance is a major contributor to type-2 diabetes (T2D). Pioglitazone is a potent insulin sensitizer of peripheral tissues by targeting peroxisome proliferator-activated receptor gamma. Pioglitazone has been reported to protect skeletal muscle cells from lipotoxicity by promoting fatty acid mobilization and insulin signaling. However, it is unclear whether pioglitazone increases insulin sensitivity through changes in protein-protein interactions involving protein phosphatase 2A (PP2A). PP2A regulates various cell signaling pathways such as insulin signaling. Interaction of the catalytic subunit of PP2A (PP2Ac) with protein partners is required for PP2A specificity and activity. Little is known about PP2Ac partners in primary human skeletal muscle cells derived from lean insulin-sensitive (Lean) and obese insulin-resistant (OIR) participants. We utilized a proteomics method to identify PP2Ac interaction partners in skeletal muscle cells derived from Lean and OIR participants, with or without insulin and pioglitazone treatments. In this study, 216 PP2Ac interaction partners were identified. Furthermore, 26 PP2Ac partners exhibited significant differences in their interaction with PP2Ac upon insulin treatments between the two groups. Multiple pathways and molecular functions are significantly enriched for these 26 interaction partners, such as nonsense-mediated decay, metabolism of RNA, RNA binding, and protein binding. Interestingly, pioglitazone restored some of these abnormalities. These results provide differential PP2Ac complexes in Lean and OIR in response to insulin/pioglitazone, which may help understand molecular mechanisms underpinning insulin resistance and the insulin-sensitizing effects of pioglitazone treatments, providing multiple targets in various pathways to reverse insulin resistance and prevent and/or manage T2D with less drug side effects.

Endoplasmic Reticulum Stress-Related Signature for Predicting Prognosis and Immune Features in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) with cancer cells under endoplasmic reticulum (ER) stress has a poor prognosis. This study is aimed at discovering credible biomarkers for predicting the prognosis of HCC based on ER stress-related genes (ERSRGs). We constructed a novel four-ERSRG prognostic risk model, including PON1, AGR2, SSR2, and TMCC1, through a series of bioinformatic approaches, which can accurately predict survival outcomes in HCC patients. Higher risk scores were linked to later grade, recurrence, advanced TNM stage, later T stage, and HBV infection. In addition, 20 fresh frozen tumors and normal tissues from HCC patients were collected and used to validate the genes expressed in the signature by qRT-PCR and immunohistochemical (IHC) assays. Moreover, we found the ER stress-related signature could reflect the infiltration levels of different immune cells in the tumor microenvironment (TME) and forecast the efficacy of immune checkpoint inhibitor (ICI) treatment. Finally, we created a nomogram incorporating this ER stress-related signature. In conclusion, our constructed four-gene risk model associated with ER stress can accurately predict survival outcomes in HCC patients, and the model's risk score is associated with the poor clinical classification.

Roles and Therapeutic Implications of Endoplasmic Reticulum Stress and Oxidative Stress in Cardiovascular Diseases

In different pathological states that cause endoplasmic reticulum (ER) calcium depletion, altered glycosylation, nutrient deprivation, oxidative stress, DNA damage or energy perturbation/fluctuations, the protein folding process is disrupted and the ER becomes stressed. Studies in the past decade have demonstrated that ER stress is closely associated with pathogenesis of obesity, insulin resistance and type 2 diabetes. Excess nutrients and inflammatory cytokines associated with metabolic diseases can trigger or worsen ER stress. ER stress plays a critical role in the induction of endothelial dysfunction and atherosclerosis. Signaling pathways including AMP-activated protein kinase and peroxisome proliferator-activated receptor have been identified to regulate ER stress, whilst ER stress contributes to the imbalanced production between nitric oxide (NO) and reactive oxygen species (ROS) causing oxidative stress. Several drugs or herbs have been proved to protect against cardiovascular diseases (CVD) through inhibition of ER stress and oxidative stress. The present article reviews the involvement of ER stress and oxidative stress in cardiovascular dysfunction and the potential therapeutic implications.