Association of the PPARγ/PI3K/Akt pathway with the cardioprotective effects of tacrolimus in myocardial ischemic/reperfusion injury

Recombinant human erythropoietin upregulates PPARγ through the PI3K/Akt pathway to protect neurons in rats subjected to oxidative stress

In vitro cell experiments have suggested that recombinant human erythropoietin (rhEPO) and peroxisome proliferator activated receptor γ (PPARγ) activation exert protective effects on neurons. This study observed the learning and memory ability, antioxidant capacity and the ratio of apoptotic cells after rhEPO intervention and investigated the relationship among rhEPO, PI3K/Akt and PPARγ in the anti-neural oxidative stress injury process in vivo. The results showed that rhEPO significantly improved the learning and memory abilities of rats subjected to oxidative stress, enhanced the antioxidant capacity of cells, and reduced neuronal apoptosis. Then, the PI3K/Akt and PPARγ pathways were inhibited, and TUNEL staining were used to observe the changes in the effect of rhEPO. After the PI3K/Akt and PPARγ pathways were inhibited, the effect of rhEPO on rats subjected to oxidative stress was significantly weakened, suggesting that both the PI3K/Akt and PPARγ pathways are involved in the process by which rhEPO protects neurons. Finally, Western blotting and immunofluorescence staining were used to observe the changes in PI3K/Akt and PPARγ signalling proteins in the neurons after the rhEPO intervention and to explore the relationship among the three. The results showed that rhEPO significantly increased the levels of the p-Akt and PPARγ proteins and the level of the PPARγ protein in the nucleus, indicating that the PI3K/Akt pathway was located upstream of and regulates PPARγ. In conclusion, this study suggested that rhEPO activates the PI3K/Akt to upregulate PPARγ, enhance the cellular antioxidant capacity, and protect neurons in rats subjected to oxidative stress.

rhEPO Upregulates the PPARγ Pathway in Long-term Cultured Primary Nerve Cells via PI3K/Akt to Delay Cell Senescence

Previous studies have confirmed that both recombinant human erythropoietin (rhEPO) and peroxisome proliferator-activated receptors γ (PPARγ) activator pioglitazone can protect senescent nerve cells, and their mechanisms involve enhancing cell antioxidant capacity and reducing cell apoptosis. However, whether the PPARγ pathway is involved in the rhEPO anti-aging process in neuronal cells is still unclear. In this study, to explore the relationship between rhEPO and the PPARγ pathway at the cellular level, primary nerve cells cultured for 22 days were used to simulate the natural aging process of nerve cells. Starting on the 11th day of culture, rhEPO, LY294002, and GW9662 were added for treatment. Immunochemical methods and SA-β-gal staining were used to observe the changes in cellular antioxidant capacity and the fraction of senescent cells. The results showed that PPARγ blockade retarded the effect of rhEPO on the cellular antioxidant capacity and altered the fraction of senescent cells. It was confirmed that PPARγ was involved in rhEPO's anti-aging process in neuronal cells. Real-time fluorescent quantitative RT-PCR, Western blotting, and immunofluorescence staining were used to observe the changes in PPARγ pathway-related factors in nerve cells after rhEPO treatment. The results showed that rhEPO significantly upregulated the expression of PPARγ coactivator-1α (PGC-1α), PPARγ, and nuclear PPARγ in cells but did not affect the level of phosphorylated PPARγ protein, confirming that rhEPO has the ability to upregulate the PPARγ pathway. PI3K/Akt and PPARγ pathway blockade experiments were used to explore the relationships among rhEPO, PI3K/Akt, and PPARγ. The results showed that after PPARγ blockade, rhEPO had no significant effect on the PI3K/Akt pathway-related factor p-Akt, while after PI3K/Akt blockade, rhEPO's effects on PPARγ-related factors (PGC-1α, PPARγ, and nuclear PPARγ) were significantly decreased. It is suggested that rhEPO delays the PI3K/Akt pathway in the process of neuronal senescence, which is located upstream of PPARγ regulation. In conclusion, this study confirmed that rhEPO can upregulate the expression of PGC-1α and PPARγ in cells and the level of PPARγ protein in the nucleus to enhance the antioxidant capacity of cells and delay the senescence of nerve cells through the PI3K/Akt pathway. These findings will provide ideas for finding new targets for neuroprotection research and will also provide a theoretical basis and experimental evidence for rhEPO anti-aging research in neural cells.

[PI3K/Akt signaling pathway mediates the protective effect of endomorphin-1 postconditioning against myocardial ischemia-reperfusion injury in rats]

OBJECTIVE

To investigate the role of PI3K/Akt signaling pathway in mediating the protective effect of endomorphin-1 against myocardial ischemia-reperfusion (IR) injury.

OBJECTIVE

Fifty SD male rats were randomly divided into sham operation group, myocardial IR group, endomorphin-1 post-treatment group (EM50 group), endomorphin-1+wortmannin (a PI3K/Akt signaling pathway inhibitor) treatment group (EM50+Wort group), and wortmannin treatment group (Wort group). Rat models of myocardial IR injury were established by ligation of the left anterior descending coronary artery for 30 min followed by reperfusion for 120 min. The heart rate and mean arterial pressure were monitored during the experiment. Plasma levels of LDH, CK-MB, cTnI, IL-6, TNF-α, SOD and MDA were measured after reperfusion. The mRNA expression of Bax and Bcl-2 was detected using RT-PCR, and the expression of apoptosis-related protein cleaved caspase-3, phosphorylated Akt protein and total Akt protein in myocardial tissue was detected using Western blotting.

OBJECTIVE

Myocardial IR injury significantly decreased heart rate and blood pressure of the rats in comparison with the sham operation (P < 0.05). Compared with those in the IR group, the rats in EM50 group showed significantly increased heart rate and blood pressure (P < 0.05) with decreased plasma LDH, CK-MB, cTnI, IL-6, TNF-α and MDA levels (P < 0.05), increased SOD activity (P < 0.05), increased expression of p-Akt protein and Bcl-2 mRNA (P < 0.05), and decreased expression of Bax mRNA and cleaved caspase-3 protein (P < 0.05). In EM50+Wort group, the heart rate and blood pressure were significantly lowered (P < 0.05), plasma LDH, CK-MB, cTnI, IL-6, TNF-α and MDA levels increased (P < 0.05), SOD activity decreased (P < 0.05), the expression of p-Akt protein and Bcl-2 mRNA was reduced (P < 0.05), and the expression of Bax mRNA and cleaved caspase-3 protein increased (P < 0.05) as compared with those in EM50 group.

OBJECTIVE

EM-1 postconditioning can regulate cardiac myocyte apoptosis and reduce myocardial IR injury in rats. The PI3K/Akt signaling pathway may play a role in mediating the myocardial protective effects of EM-1 postconditioning.

Role of Oxidative Stress in Reperfusion following Myocardial Ischemia and Its Treatments

Myocardial ischemia is a disease with high morbidity and mortality, for which reperfusion is currently the standard intervention. However, the reperfusion may lead to further myocardial damage, known as myocardial ischemia/reperfusion injury (MI/RI). Oxidative stress is one of the most important pathological mechanisms in reperfusion injury, which causes apoptosis, autophagy, inflammation, and some other damage in cardiomyocytes through multiple pathways, thus causing irreversible cardiomyocyte damage and cardiac dysfunction. This article reviews the pathological mechanisms of oxidative stress involved in reperfusion injury and the interventions for different pathways and targets, so as to form systematic treatments for oxidative stress-induced myocardial reperfusion injury and make up for the lack of monotherapy.

Telmisartan Inhibits the NLRP3 Inflammasome by Activating the PI3K Pathway in Neural Stem Cells Injured by Oxygen-Glucose Deprivation

Angiotensin II receptor blockers (ARBs) have been shown to exert neuroprotective effects by suppressing inflammatory and apoptotic responses. In the present study, the effects of the ARB telmisartan on the NLRP3 inflammasome induced by oxygen-glucose deprivation (OGD) in neural stem cells (NSCs) were investigated, as well as their possible association with the activation of the PI3K pathway. Cultured NSCs were treated with different concentrations of telmisartan and subjected to various durations of OGD. Cell counting, lactate dehydrogenase, bromodeoxyuridine, and colony-forming unit assays were performed to measure cell viability and proliferation. In addition, the activity of intracellular signaling pathways associated with the PI3K pathway and NLRP3 inflammasome was evaluated. Telmisartan alone did not affect NSCs up to a concentration of 10 μM under normal conditions but showed toxicity at a concentration of 100 μM. Moreover, OGD reduced the viability of NSCs in a time-dependent manner. Nevertheless, treatment with telmisartan increased the viability and proliferation of OGD-injured NSCs. Furthermore, telmisartan promoted the expression of survival-related proteins and mRNA while inhibiting the expression of death-related proteins induced by OGD. In particular, telmisartan attenuated OGD-dependent expression of the NLRP3 inflammasome and its related signaling proteins. These beneficial effects of telmisartan were blocked by a PI3K inhibitor. Together, these results indicate that telmisartan attenuated the activation of the NLRP3 inflammasome by triggering the PI3K pathway, thereby contributing to neuroprotection.

miR-27a promotes osteogenic differentiation in glucocorticoid-treated human bone marrow mesenchymal stem cells by targeting PI3K

MicroRNA-27a (miR-27a) modulates osteogenic differentiation (OD); however, the mechanism by which it influences osteoclastic activity in the glucocorticoid (GC)-elicited osteoporotic bone is still unclear. Bone marrow was obtained from the proximal femur of patients (n = 3) with a femoral neck fracture and those (n = 3) with steroid-related osteonecrosis of the femoral head (ONFH). GC was applied to an established ONFH cell model from human bone marrow mesenchymal stem cells (hBMSCs). The miR-27a expression profiles were found to be downregulated in ONFH samples and GC-induced hBMSCs using microarray analysis and real-time quantitative polymerase chain reaction, whereas the OD capacity of hBMSCs was significantly reduced in the GC group compared with the control group. Subsequent transfection of an miR-27a mimic in hBMSCs revealed that the OD capacity of cells was remarkably strengthened in the GC group compared with the miR-control group. Bioinformatics software (TargetScan) predicted that phosphoinositide 3-kinase (PI3K) might be a potential miR-27a target, which was indicated by dual-luciferase reporter assay. Compared with the control group, the GC group exhibited a significantly downregulated protein expression level of PI3K and its downstream protein kinase B (Akt) and mammalian target of rapamycin (mTOR) expression. Furthermore, administration of 10 μM 740 Y-P, a cell-permeable phosphopeptide activator of PI3K, to hBMSCs increased the expression of Akt and mTOR. Treatment with 740 Y-P reversed the effect of miR-27a on OD in hBMSCs. In conclusion, miR-27a is thought to relieve ONFH and the OD repression in GC-induced hBMSCs by targeting the PI3K/Akt/mTOR pathway.

Gastrodin prevents homocysteine-induced human umbilical vein endothelial cells injury via PI3K/Akt/eNOS and Nrf2/ARE pathway

In this study, we investigated the protective effects of gastrodin (Gas) against homocysteine‐induced human umbilical vein endothelial cell (HUVEC) injury and the role of the phosphoinositide 3‐kinase (PI3K)/threonine kinase 1 (Akt)/endothelial nitric oxide synthase (eNOS) and NF‐E2‐related factor 2 (Nrf2)/antioxidant response element (ARE) pathways. We stimulated cells with homocysteine (1 mmol/L, 24 hours) and tested the effects of gastrodin (200‐800 μg/mL) on cell viability and the production of malondialdehyde (MDA), lactate dehydrogenase (LDH) and reactive oxygen species (ROS). Then, Nrf2 distribution in the cytoplasm and nucleus as well as the expression of enzymes downstream of Nrf2 was determined. Furthermore, we analysed the expression of bax, bcl‐2 and cleaved caspase3, and assessed the involvement of the PI3K/Akt/eNOS pathway by Western blots. Finally, we tested the vasoactive effect of gastrodin in thoracic aortic rings. The results showed that gastrodin decreased MDA, LDH and ROS production and increased cell viability, NO production and relaxation of thoracic aortic rings. Moreover, the protective effects of Gas on NO production and relaxation of thoracic aortic rings were blocked by L‐NAME but enhanced by Cav‐1 knockdown, and MK‐2206 treatment abolished the effect of Gas on the ROS. In addition, treatment with gastrodin increased Nrf2 nuclear translocation, thus enhancing the expression of downstream enzymes. Finally, gastrodin increased the expression of PI3K, p‐Akt, and eNOS and decreased Cav‐1 protein expression. In conclusion, our study suggested that gastrodin may protect HUVECs from homocysteine‐induced injury, and the PI3K/Akt/eNOS and Nrf2/ARE pathways may be responsible for the efficacy of gastrodin.

Sulodexide attenuates endoplasmic reticulum stress induced by myocardial ischaemia/reperfusion by activating the PI3K/Akt pathway

Acute myocardial ischaemia/reperfusion (MI/R) injury causes severe arrhythmias with a high rate of lethality. Extensive research focus on endoplasmic reticulum (ER) stress and its dysfunction which leads to cardiac injury in MI/R Our study evaluated the effects of sulodexide (SDX) on MI/R by establishing MI/R mice models and in vitro oxidative stress models in H9C2 cells. We found that SDX decreases cardiac injury during ischaemia reperfusion and decreased myocardial apoptosis and infarct area, which was paralleled by increased superoxide dismutase and reduced malondialdehyde in mice plasm, increased Bcl‐2 expression, decreased BAX expression in a mouse model of MI/R. In vitro, SDX exerted a protective effect by the suppression of the ER stress which induced by tert‐butyl hydroperoxide (TBHP) treatment. Both of the in vivo and in vitro effects were involved in the phosphatidylinositol 3‐kinase (PI3K)/Akt signalling pathway. Inhibition of PI3K/Akt pathway by specific inhibitor, LY294002, partially reduced the protective effect of SDX. In short, our results suggested that the cardioprotective role of SDX was related to the suppression of ER stress in mice MI/R models and TBHP‐induced H9C2 cell injury which was through the PI3K/Akt signalling pathway.

Tetramethylpyrazine exerts a protective effect against injury from acute myocardial ischemia by regulating the PI3K/Akt/GSK-3β signaling pathway

Objective

We investigated the protective effect of tetramethylpyrazine (TMP) on injury related to acute myocardial ischemia (AMI) induced by isoproterenol (ISO).

Materials and methods

Rats were randomly assigned to five groups: control, ISO, ISO + propranolol (10 mg/kg), ISO + TMP (10 mg/kg) and ISO + TMP (20 mg/kg). The rats in the three ISO + groups were pretreated with propranolol or TMP, while the rats in the control and ISO groups were pretreated with an equal volume of saline. Afterwards, the rats in the four administration groups were subcutaneously injected with ISO for two consecutive days. The levels of creatine kinase (CK), lactate dehydrogenase (LDH), superoxide dismutase (SOD), malondialdehyde (MDA), tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) and IL-1β in the serum were measured using ELISA. The expressions of B-cell lymphoma-associated X-2 (Bax-2), B-cell lymphoma-2 (Bcl-2), phosphoinositide-3-kinase (PI3K), protein kinase B (Akt), glycogen synthase kinase 3β (GSK-3β), MDA5 and SOD1 were determined using western blotting assay. The phosphorylation of PI3K, Akt and GSK-3β were also determined using western blotting assay. The left ventricles of the rats were extracted and stained using hematoxylin and eosin (H&E). The ST segment was recorded using electrocardiograms (ECGs).

Results

Administration of TMP (10, 20 mg/kg) reduced the levels of MDA and CK and the activities of SOD and LDH in the serum. Pretreatment with TMP significantly reduced the levels of pro-inflammatory cytokines, including IL-1β, IL-6 and TNF-α. Treatment with TMP also improved the histopathological alteration and decreased the ST elevation. Furthermore, TMP ameliorated the expressions of Cu, SOD1, MDA5, Bax-2, Bcl-2, p-PI3K, p-Akt and p-GSK-3β in ISO-induced rats.

Conclusions

Tetramethylpyrazine protected against injury due to AMI by regulating the PI3K/Akt /GSK-3β signaling pathway.