Decreased PGC-1α Expression Research Articles

The critical role of P2XR/PGC-1α signalling pathway in hypoxia-mediated pyroptosis and M1/M2 phenotypic differentiation of mouse microglia.

Microglia are endogenous immune cells in the brain, and their pyroptosis and phenotype dichotomy are proved to play roles in neurodegenerative diseases. We investigated whether and how hypoxia affected pyroptosis and phenotype polarization in mouse microglia. Primary mouse microglia and BV2 microglia were exposed to hypoxia. Pyroptosis and M1/M2 phenotype were assessed by measuring gasdermin D truncation and M1/M2 surface marker expression. Mechanisms including purinergic ionotropic receptor (P2XR), peroxisome proliferator-activated receptor coactivator-1α (PGC-1α) and NOD-like receptor protein 3 (NLRP3) inflammasome were investigated. We reported hypoxia (90% N2, 5% O2 and 5% CO2) induced pyroptosis and promoted M1 phenotype polarization in primary mouse microglia and BV2 microglia, and the effect appeared after 6h exposure. Although hypoxia (90% N2, 5% O2 and 5% CO2, 6h) had no effect on P2X1R and P2X7R expression, it increased P2X4R expression and decreased PGC-1α expression. Interestingly, blockade of P2X4R or P2X7R abolished hypoxia-modulated PGC-1α expression, pyroptosis and M1 polarization. PGC-1α overexpression or overactivation alleviated hypoxia-induced pyroptosis and M1 polarization, while PGC-1α knockdown or deactivation promoted pyroptosis and M1 polarization under normoxic situation. Further, hypoxia induced NLRP3 expression and activated caspase-1 and induced the phosphorylation of NF-κB and reduced the phosphorylation of STAT3/6. NLRP3 inhibitor and caspase-1 inhibitor abolished hypoxia-induced pyroptosis, while NF-κB inhibitor and STAT phosphorylation inducer ameliorated hypoxia-induced M1 polarization. In addition, NF-κB activator and STAT3/6 inhibitor caused microglia M1 polarization under normoxic situation. We concluded in cultured mouse microglia, hypoxia may induce pyroptosis via P2XR/PGC-1α/NLRP3/caspase-1 pathway and trigger M1 polarization through P2XR/PGC-1α/NF-κB/STAT3/6 pathway.

PM2.5 induces cardiac defects via AHR-SIRT1-PGC-1α mediated mitochondrial damage

Recent evidence indicates that PM2.5 poses a risk for congenital heart diseases, but the mechanisms remain unclear. We hypothesized that AHR activated by PM2.5 might cause mitochondrial damage via PGC-1α dysregulation, leading to heart defects. We initially discovered that the PGC-1α activator ZLN005 counteracted cardiac defects in zebrafish larvae exposed to EOM (extractable organic matter) from PM2.5. Moreover, ZLN005 attenuated EOM-induced PGC-1α downregulation, mitochondrial dysfunction/biogenesis, and apoptosis. EOM exposure not only decreased PGC-1α expression levels, but suppressed its activity via deacetylation, and SIRT1 activity is required during both processes. We then found that SIRT1 expression levels and NAD+/NADH ratio were reduced in an AHR-dependent way. We also demonstrated that AHR directly suppressed the transcription of SIRT1 while promoted the transcription of TiPARP which consumed NAD+. In conclusion, our study suggests that PM2.5 induces mitochondrial damage and heart defects via AHR/SIRT1/PGC-1α signal pathway.

MiR-871-5p / PGC1α regulates aging-induced lipid deposition in hepatocytes through fatty acid β-oxidation.

This study investigated the role of the miR-871-5p/proliferator-activated receptor α (PGC1α) pathway in ameliorating hepatic steatosis. We examined miR-871-5p expression in liver tissues of ageing mice and AML12 senescent cells co-induced by low serum and palmitic acid (PA). Bioinformatics and multiple experiments were employed to validate the expression level of the target gene PGC1α for miR-871-5p. In this study, we aimed to investigate the potential role of miR-871-5p in regulating hepatic lipid deposition associated with ageing. To do so, we performed in vitro transfection of both miR-871-5p mimic and inhibitor into senescent hepatocytes. Our results showed that miR-871-5p could inhibit PGC1α expression and cause lipid deposition in the liver due to ageing. MiR-871-5p controls this process by regulating PGC1α / fatty acid β oxidation. H&E staining displayed the appearance of fat vacuoles in the livers of ageing mice, and fatty acid β oxidation-related genes (acyl-coenzyme A oxidase 1 carnitine palmitoyl transferase 1α (ACOX1), and peroxisome proliferator-activated receptor α (PPARα)) expression was significantly reduced. Lipogenic genes (sterol regulatory element binding protein 1C (SREBP-1C), fatty acid synthase (FASN)) expression level was increased in the livers of ageing mice. In AML12 cells co-induced by low serum and PA, miR-871-5p mimics decreased PGC1α expression and increased lipid droplet accumulation in senescent hepatocytes. Conversely, miR-871-5p inhibitor promoted PGC1α expression and reduced lipid deposition in senescent hepatocytes. Our findings suggest that inhibiting miR-871-5p could be crucial in ameliorating aging-associated hepatic steatosis. These findings offer valuable insights into the molecular mechanisms driving hepatic steatosis in ageing.

NUCLEOLIN PROTECTS CARDIOMYOCYTES BY UPREGULATING PGC-1α AND PROMOTING MITOCHONDRIAL BIOGENESIS IN LPS-INDUCED MYOCARDIAL INJURY.

Background: Lipopolysaccride-induced myocardial injury was characterized by frequent mitochondrial dysfunction. Our previous studies found that nucleolin (NCL) played important protective roles in myocardial ischemia-reperfusion injury. Recently, it has been found that NCL has a protective effect on LPS-induced myocardial injury in vivo . However, the exact underlying mechanisms that how NCL protects myocardium against the LPS-induced myocardial injury remains unclear. Objective: The aim of the study is to investigate the protective role of NCL in LPS-induced myocardial injury from the aspect of mitochondrial biogenesis. Methods: The cardiac-specific NCL-knockout (NCL -/- ) or NCL f/f mice were injected with LPS (10 mg/kg) to induce LPS-induced myocardial injury. The supernatant generated after LPS stimulation of macrophages was used as the conditioned medium to stimulate H9C2 and established the injured cell model. Analysis of mRNA stability, RNA-binding protein immunoprecipitation assay, and luciferase reporter assay were performed to detect the mechanism by which NCL regulated the expression of PGC-1α. Results: The expression of NCL and PGC-1α was elevated in cardiac tissue and cardiomyocytes during LPS-induced myocardial injury. The cardiac-specific NCL-knockout decreased PGC-1α expression, inhibited mitochondrial biogenesis, and increased cardiomyocytes death during LPS-induced myocardial injury in vitro and in vivo . In contrast, the overexpression of NCL could improve mitochondrial biogenesis in H9C2 cells. Moreover, the analysis of mRNA stability and luciferase reporter assay revealed that the interaction between NCL and PGC-1α significantly promoted the stability of PGC-1α mRNA, thereby upregulating the expression of PGC-1α and exerting a cardioprotective effect. In addition, the activation of PGC-1α diminished the detrimental effects of NCL knockdown on mitochondrial biogenesis in vitro and in vivo . Conclusions: Nucleolin upregulated the gene expression of PGC-1α by directly binding to the 5'-UTR of PGC-1α mRNA and increasing its mRNA stabilities, then promoted mitochondrial biogenesis, and played protective effect on cardiomyocytes during LPS-induced myocardial injury. Taken together, all these data showed that NCL activated PGC-1α to rescue cardiomyocytes from LPS-induced myocardial injury insult, suggesting that the cardioprotective role of NCL might be a promising prospect for clinical treatment of patients with endotoxemia.

Resveratrol improves diabetic cardiomyopathy by preventing asymmetric dimethylarginine-caused peroxisome proliferator-activated receptor-γ coactivator-1α acetylation

ObjectivesCardiac protection of resveratrol is related to the improvement of mitochondrial function through sirtuin1 (SIRT1) activation and peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) deacetylation. Asymmetric dimethylarginine (ADMA) as an endogenous inhibitor of nitric oxide synthases is associated with diabetic cardiovascular complications and has a cross-talk with lysine acetylation. This study was to determine whether resveratrol reverses ADMA's pathogenic role in diabetic cardiomyopathy and elucidate the underlying mechanisms in type 2 diabetic (T2DM) rats and cardiomyocytes. MethodsT2DM Rats were induced by high-fat diet plus small-dose streptozotocin injection (35 mg/kg). Resveratrol was given by gavage (50 mg/kg/d) to some rats for 16w. Cardiac function was measured by echocardiography, and PGC-1α acetylation was detected by immunoprecipitation. Mitochondrial DNA and ATP contents were analyzed to evaluate mitochondrial biogenesis and function. ResultsEndogenous ADMA accumulation and its signal disorders were associated with cardiac and mitochondrial dysfunctions in accompany with increased PGC-1α acetylation and decreased PGC-1α expression in the myocardium of T2DM rats compared with control rats. Resveratrol treatment attenuated ADMA accumulation, cardiac and mitochondrial dysfunctions in parallel with reversing altered PGC-1α expression and acetylation in the myocardium of T2DM rats. Exogenous ADMA not only reproduced mitochondrial dysfunction and cardiac hypertrophy but also reduced PGC-1α expression and enhanced PGC-1α acetylation in accompany of down-regulating SIRT1 and up-regulating acetyltransferase expression, all of which could be prevented by resveratrol pretreatment in cardiomyocytes. ConclusionsThese results indicate that ADMA promotes PGC-1α acetylation as a potential therapeutic target for resveratrol of management diabetic cardiomyopathy in T2DM rats.

Persistent diastolic dysfunction in chronically ischemic hearts following coronary artery bypass graft

ObjectiveA porcine model was used to study diastolic dysfunction in hibernating myocardium (HM) and recovery with coronary artery bypass surgery (CABG). MethodsHM was induced in Yorkshire–Landrace juvenile swine (n = 30) by placing a c-constrictor on left anterior descending artery causing chronic myocardial ischemia without infarction. At 12 weeks, animals developed the HM phenotype and were either killed humanely (HIB group; n = 11) or revascularized with CABG and allowed 4 weeks of recovery (HIB+CABG group; n = 19). Control pigs were matched for weight, age, and sex to the HIB group. Before the animals were killed humanely, cardiac magnetic resonance imaging (MRI) was done at rest and during a low-dose dobutamine infusion. Tissue was obtained for histologic and proinflammatory biomarker analyses. ResultsDiastolic peak filling rate was lower in HIB compared with control (5.4 ± 0.7 vs 6.7 ± 1.4 respectively, P = .002), with near recovery with CABG (6.3 ± 0.8, P = .06). Cardiac MRI confirmed preserved global systolic function in all groups. Histology confirmed there was no transmural infarction but showed interstitial fibrosis in the endomysium in both the HIB and HIB+CABG groups compared with normal myocardium. Alpha-smooth muscle actin stain identified increased myofibroblasts in HM that were less apparent post-CABG. Cytokine and proteomic studies in HM showed decreased peroxisome proliferator-activator receptor gamma coactivator 1-alpha (PGC1-α) expression but increased expression of granulocyte-macrophage colony-stimulating factor and nuclear factor kappa-light-chain enhancer of activated B cells (NFκB). Following CABG, PGC1-α and NFκB expression returned to control whereas granulocyte-macrophage colony-stimulating factor, tumor necrosis factor-α, and interferon gamma remained increased. ConclusionsIn porcine model of HM, increased NFκB expression, enhanced myofibroblasts, and collagen deposition along with decreased PGC1-α expression were observed, all of which tended toward normal with CABG. Estimates of impaired relaxation with MRI within HM during increased workload persisted despite CABG, suggesting a need for adjuvant therapies during revascularization.

Transcriptional coactivator PGC-1α contributes to decidualization by forming a histone-modifying complex with C/EBPβ and p300

We previously reported that CCAAT/enhancer-binding protein beta (C/EBPβ) is the pioneer factor inducing transcription enhancer mark H3K27 acetylation (H3K27ac) in the promoter and enhancer regions of genes encoding insulin-like growth factor–binding protein-1 (IGFBP-1) and prolactin (PRL) and that this contributes to decidualization of human endometrial stromal cells (ESCs). Peroxisome proliferator–activated receptor gamma coactivator 1-alpha (PGC-1α; PPARGC1A) is a transcriptional coactivator known to regulate H3K27ac. However, although PGC-1α is expressed in ESCs, the potential role of PGC-1α in mediating decidualization is unclear. Here, we investigated the involvement of PGC-1α in the regulation of decidualization. We incubated ESCs with cAMP to induce decidualization and knocked down PPARGC1A to inhibit cAMP-induced expression of IGFBP-1 and PRL. We found cAMP increased the recruitment of PGC-1α and p300 to C/EBPβ-binding sites in the promoter and enhancer regions of IGFBP-1 and PRL, corresponding with increases in H3K27ac. Moreover, PGC-1α knockdown inhibited these increases, suggesting PGC-1α forms a histone-modifying complex with C/EBPβ and p300 at these regions. To further investigate the regulation of PGC-1α, we focused on C/EBPβ upstream of PGC-1α. We found cAMP increased C/EBPβ recruitment to the novel enhancer regions of PPARGC1A. Deletion of these enhancers decreased PGC-1α expression, indicating that C/EBPβ upregulates PGC-1α expression by binding to novel enhancer regions. In conclusion, PGC-1α is upregulated by C/EBPβ recruitment to novel enhancers and contributes to decidualization by forming a histone-modifying complex with C/EBPβ and p300, thereby inducing epigenomic changes in the promoters and enhancers of IGFBP-1 and PRL.

Effect of 12-wk Training in Ovariectomised Rats on PGC-1α, NRF-1 and Energy Substrates.

Metabolic diseases are associated with hypoestrogenism owing to their lower energy expenditure and consequent imbalance. Physical training promotes energy expenditure through PGC-1α and NRF-1, which are muscle proteins of the oxidative metabolism. However, the influence of physical training on protein expression in individuals with hypoestrogenism remains uncertain. Thus, the aim of this study is to determine the effect of 12 weeks of moderate-intensity swimming training on the muscle expression of PGC-1α, NRF-1, glycogen and triglyceride in ovariectomised rats. OVX and OVX+TR rats were subjected to ovariectomy. The trained animals swam for 30 minutes, 5 days/week, at 80% of the critical load intensity. Soleus was collected to quantify PGC-1α and NRF-1 expressions, while gastrocnemius and gluteus maximus were collected to measure glycogen and triglyceride. Blood glucose was also evaluated. Whereas ovariectomy decreased PGC-1α expression (p<0.05) without altering NRF-1 (p=0.48), physical training increased PGC-1α (p<0.01) and NRF-1 (p<0.05). Ovariectomy reduced glycogen (p<0.05) and triglyceride (p<0.05), whereas physical training increased glycogen (p<0.05) but did not change triglyceride (p=0.06). Ovariectomy increased blood glucose (p<0.01), while physical training reduced it (p<0.01). In summary, 12 weeks of individualized and moderate-intensity training were capable of preventing muscle metabolic consequences caused by ovariectomy.

Protective effects of HIIT vs. CET exercise training on high-fat-high-fructose diet-induced hyperglycemia, hyperlipidemia, and histopathology of liver in rats: regulation of SIRT1/PGC-1α

Disruption of the function of sirtuin1 (SIRT1) has been reported to link with diabetes and metabolic disorders. The aim of this study was to investigate the effect of a modified high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) or continuous endurance training (CET) program on Sirt1 and PGC-1α mRNA gene expression in hepatocytes of high-fat/high-fructose diet-induced diabetes in rats. Twenty-eight male Wistar rats (220 ± 20 g) were randomly divided into four groups of non-diabetic (NDC), diabetic control (received high fat high-fructose diet (HFHFD-DC)), CET (HFHFD-CET), and HIIT (HFHFD-HIIT). Diabetes was induced by feeding rats a high-fat (30%) high-fructose (20%) diet for 25 weeks. Following confirmed hyperglycemia, both HFHFD-CET (60–65% Vo2max) and HFHFD-HIIT (85–90% Vo2max) rats underwent treadmill exercise for 30 min, 5 days/week at 10 m/min for 8 weeks. Thereafter, blood and liver samples were obtained for biochemical studies. For histological analysis, the liver was fixed in 10% formalin, embedded in paraffin, and sectioned (5 μm thickness) for H&E staining. SIRT-1 and PGC-1α mRNA expression were measured by RT-PCR from the liver sample (frizzed sample). All data were presented as mean ± standard error mean and compared the differences by one-way analysis of variances. The alpha level was set at 0.05 (p < 0.05) for statistical difference. The results show that HIIT was more effective than CET to reduce vesicular steatosis. HIIT significantly enhanced the expression of SIRT-1 compared to the HFHFD-DC group (fold change: 1.47, p < 0.047). However, HIIT decreased PGC-1α expression compared to the HFHFD-DC group, but it was not significant (fold change: 1.32 and p < 0.247). HIIT was more effective than CET in SIRT-1 expression augmentation in high-fat, high-fructose diabetic rats which suggests a possible treatment strategy in the context of type 2 diabetes.

Anti-TWEAK Antibody Alleviates Renal Interstitial Fibrosis by Increasing PGC-1α Expression in Lupus Nephritis.

PurposeCurrent studies on the mechanism of tumor necrosis factor-like weak inducer of apoptosis (TWEAK) in lupus nephritis (LN) mainly focus on the inflammatory pathway. Herein, we aimed to determine whether TWEAK could promote the progression of renal interstitial fibrosis by regulating peroxisome proliferator-activated receptor-gamma coactivator-1α (PGC-1α) expression and intervening in lipid metabolism in LN.Materials and MethodsMRL/lpr mice, an animal model of lupus, were treated with the anti-TWEAK antibody or co-treated with adeno-associated virus-mediated PGC-1α short hairpin RNA (shRNA). In addition, human proximal tubular epithelial cells (HK2 cells) were treated with recombinant human TWEAK (rhTWEAK) or ammonium pyrrolidine dithiocarbamate (PDTC) in vitro.ResultsThe renal contents of free fatty acids and triglycerides were higher in MRL/lpr mice than in MRL/MpJ mice; however, these contents were decreased by treatment with the anti-TWEAK antibody. Based on immunofluorescence staining, the expression of PGC-1α was markedly more in the renal tubules of MRL/MpJ mice than in the glomeruli. However, treatment with anti-TWEAK antibody increased the levels of PGC-1α and its downstream target genes, which were remarkably lower in MRL/lpr mice than in MRL/MpJ mice. Anti-TWEAK antibody effectively eased renal interstitial fibrosis, which manifested as a decrease in the deposition of collagen fibers and the inhibition of type I collagen and fibronectin expression. However, the therapeutic effects of the anti-TWEAK antibody were abolished by PGC-1α shRNA. Treatment with rhTWEAK decreased PGC-1α expression in both dose- and time-dependent manners in HK2 cells in vitro. PDTC, an inhibitor of IκBα phosphorylation, suppressed the decrease in the PGC-1α protein level induced by rhTWEAK treatment.ConclusionOur results suggest that TWEAK prevents renal tubular PGC-1α expression by promoting NF-κB activation, resulting in a deficiency in lipid metabolism and the progress of renal interstitial fibrosis. The upregulation of renal tubular PGC-1α expression to improve lipid metabolism is one of the mechanisms employed by the anti-TWEAK antibody to treat renal interstitial fibrosis.

Mitochondrial biogenesis factor PGC-1α suppresses spinal morphine tolerance by reducing mitochondrial superoxide

Opioid use disorders (OUDs) have reached an epidemic level in the United States. The opioid epidemic involves illicit opioid use, prescription opioids for analgesia, counterfeit opioids, new psychoactive substances, and diverted opioids. Opioids remain the last option for the treatment of intractable clinical pain, but chronic use of opioids are limited in part due to antinociceptive/analgesic tolerance. Peroxisome proliferator-activated receptor (PPAR)-gamma coactivator-1alpha (PGC-1α), a mitochondrial biogenesis factor can reduce toxic reactive oxygen species (ROS) that play a role in morphine tolerance (MT). Decreased PGC-1α expression has been shown to contribute to various metabolic disorders or neurodegeneration diseases through increasing ROS. We examined the relationship of PGC-1α and ROS in MT. To induce MT, adult Sprague-Dawley rats received intrathecal morphine for 7 days. Mechanical threshold was measured using the von Frey test and thermal latency was examined using the heat plate test. Expression of PGC-1α in the spinal cord dorsal horn (SCDH) was examined using RT-PCR and western blots. Mitochondrial superoxide was detected using MitoSox Red, a mitochondrial superoxide indicator. The antinociceptive effect of recombinant PGC-1α (rPGC-1α) or Mito-Tempol (a mitochondria-targeted superoxide scavenger) was determined using the von Frey test and hot plate test. Furthermore, we examined the effect of rPGC-1α on mitochondrial superoxide using cultured neurons. Our findings include that: (i) spinal MT decreased the expression of spinal PGC-1α in the SCDH neurons; (ii) rPGC-1α increased mechanical threshold and thermal latency in MT animals; (iii) Mito-Tempol reduced MT behavioral response; (iv) rPGC-1α reduced MT-induced mitochondria-targeted superoxide; and (v) cultured neuronal cells treated with TNFα increased mitochondria-targeted superoxide that can be inhibited by rPGC-1α. The present findings suggest that spinal PGC-1α reduce MT through decreasing mitochondria-targeted superoxide in the SCDH.

SIRT3-Mediated SOD2 and PGC-1α Contribute to Chemoresistance in Colorectal Cancer Cells.

Anticancer drugs generate excessive reactive oxygen species (ROS), which can cause cell death. Cancer cells can resist this oxidative stress, but the mechanism of resistance and associations with chemoresistance are unclear. Here, we focused on Sirtuin 3 (SIRT3), a deacetylating mitochondrial enzyme, in oxidative stress resistance in colorectal cancer (CRC). To evaluate SIRT3-related changes in mitochondrial function, ROS (mtROS) induction, and apoptosis, we used the human CRC cell lines HT29 and HCT116 transfected with short-hairpin RNA targeting SIRT3 and small interfering RNAs targeting superoxide dismutase 2 mitochondrial (SOD2) and peroxisome proliferator-activated receptor γ coactivator-1 (PGC-1α). In 142 clinical specimens from patients with CRC, we also assessed the association of SIRT3 protein levels (high/low) and prognosis. SIRT3 expression correlated with mtROS generation and apoptosis induction in cells treated with anticancer agents. Suppressing SIRT3 increased mtROS levels and cell sensitivity to anticancer agents. SIRT3 knockdown decreased SOD2 expression and activity, and suppressing SOD2 also improved sensitivity to anticancer drugs. In addition, SIRT3 was recruited with PGC-1α under oxidative stress, and suppressing SIRT3 decreased PGC-1α expression and mitochondrial function. PGC-1α knockdown decreased mitochondrial activity and increased apoptosis in cells treated with anticancer drugs. In resected CRC specimens, high vs low SIRT3 protein levels were associated with significantly reduced cancer-specific survival. SIRT3 expression affected CRC cell chemoresistance through SOD2 and PGC-1α regulation and was an independent prognostic factor in CRC. SIRT3 may be a novel target for CRC therapies and a predictive marker of sensitivity to chemotherapy.

Effect of forkhead box O1 in renal tubular epithelial cells on endotoxin-induced acute kidney injury.

Mitochondrial damage in renal tubular epithelial cells (RTECs) is a hallmark of endotoxin-induced acute kidney injury (AKI). Forkhead box O1 (FOXO1) is responsible for regulating mitochondrial function and is involved in several kidney diseases. Here, we investigated the effect of FOXO1 on endotoxin-induced AKI and the related mechanism. In vivo, FOXO1 downregulation in mouse RTECs and mitochondrial damage were found in endotoxin-induced AKI. Overexpression of FOXO1 by kidney focal adeno-associated virus (AAV) delivery improved renal function and reduced mitochondrial damage. Peroxisome proliferator-activated receptor-γ coactivator 1-α (PGC1-α), a master regulator of mitochondrial biogenesis and function, was reduced in endotoxin-induced AKI, but the reduction was reversed by FOXO1 overexpression. In vitro, exposure to LPS led to a decline in HK-2 cell viability, mitochondrial fragmentation, and mitochondrial superoxide accumulation, as well as downregulation of FOXO1, PGC1-α, and mitochondrial complex I/V. Moreover, overexpression of FOXO1 in HK-2 cells increased HK-2 cell viability and PGC1-α expression, and it alleviated the mitochondrial injury and superoxide accumulation induced by LPS. Meanwhile, inhibition of FOXO1 in HK-2 cells by siRNA treatment decreased PGC1-α expression and HK-2 cell viability. Chromatin immunoprecipitation assays and PCR analysis confirmed that FOXO1 bound to the PGC1-α promoter in HK-2 cells. In conclusion, downregulation of FOXO1 in RTECs mediated endotoxin-induced AKI and mitochondrial damage. Overexpression of FOXO1 could improve renal injury and mitochondrial dysfunction, and this effect occurred at least in part as a result of PGC1-α signaling. FOXO1 might be a potential target for the prevention and treatment of endotoxin-induced AKI.

Thioredoxin protects mitochondrial structure, function and biogenesis in myocardial ischemia-reperfusion via redox-dependent activation of AKT-CREB- PGC1α pathway in aged mice.

Aging is an independent risk factor for cardiovascular diseases, such as myocardial infarction due to ischemia-reperfusion injury (I/R) of the heart. Cytosolic thioredoxin (Trx) is a multifunctional redox protein which has antioxidant and protein disulfide reducing properties. We hypothesized that high levels of Trx will protect against multifactorial disease such as myocardial infarction due to I/R injury in aged mice. Aged mice overexpressing human Trx (Trx-Tg), mice expressing redox-inactive mutant of human Trx (dnTrx-Tg) and non-transgenic litter-mates (NT) were subjected to I/R (60/30 min), and cardiac function, mitochondrial structure and function, and biogenesis involving PGC1α pathway were evaluated in these mice. While aged Trx-Tg mice were protected from I/R-induced reduction in ejection fraction (EF) and fractional shortening (FS), had smaller infarct with decreased apoptosis and preserved mitochondrial function, aged dnTrx-Tg mice showed enhanced myocardial injury and mitochondrial dysfunction. Further, Trx-Tg mice were protected from I/R induced loss of PGC1α, ACO2, MFN1 and MFN2 in the myocardium. The dnTrx-Tg mice were highly sensitive to I/R induced apoptosis. Overall, our study demonstrated that the loss of Trx redox balance in I/R in aged NT or dnTrx-Tg mice resulted in decreased PGC1α expression that decreased mitochondrial gene expression with increased myocardial apoptosis. High levels of Trx, but not mitochondrial thioredoxin (Trx-2) maintained Trx redox balance in I/R resulting in increased PGC1α expression via AKT/CREB activation upregulating mitochondrial gene expression and protection against I/R injury.

PPRC1, but not PGC-1α, levels directly correlate with expression of mitochondrial proteins in human dermal fibroblasts.

The XPC protein, which is mutated in xeroderma pigmentosum (XP) complementation group C (XP-C), is a lesion recognition factor in NER, but it has also been shown to interact with and stimulate DNA glycosylases, to act as transcriptional co-activator and on energy metabolism adaptation. We have previously demonstrated that XP-C cells show increased mitochondrial H2O2 production with a shift between respiratory complexes I and II, leading to sensitivity to mitochondrial stress. Here we report a marked decrease in expression of the transcriptional co-activator PGC-1α, a master regulator of mitochondrial biogenesis, in XP-C cells. A transcriptional role for XPC in PGC-1α expression was discarded, as XPC knockdown did not downregulate PGC-1α expression and XPC-corrected cells still showed lower PGC-1α expression. DNA methylation alone did not explain PGC-1α silencing. In four different XP-C cell lines tested, reduction of PGC-1α expression was detected in three, all of them carrying the c.1643_1644delTG mutation (ΔTG) in XPC. Indeed, all cell lines carrying XPC ΔTG mutation, whether homozygous or heterozygous, presented decreased PGC-1α expression. However, this alteration in gene expression was not exclusive to XPC ΔTG cell lines, for other non-related cell lines also showed altered PGC-1α expression. Moreover, PGC1-α expression did not correlate with expression levels of TFAM and SDHA, known PGC-1α target-genes. In turn, PPRC1, another member of the PGC family of transcription co-activators controlling mitochondrial biogenesis, displayed a good correlation between its expression in 10 cell lines and TFAM and SDHA. Nonetheless, PGC-1α knockdown led to a slight decrease of its target-gene protein level, TFAM, and subsequently of a mtDNA-encoded gene, MT-CO2. These results indicate that PGC-1α and PPRC1 cooperate as regulators of mitochondrial biogenesis and maintenance in fibroblasts.

Sirtuin 1 Regulates Mitochondrial Biogenesis and Provides an Endogenous Neuroprotective Mechanism Against Seizure-Induced Neuronal Cell Death in the Hippocampus Following Status Epilepticus.

Status epilepticus may decrease mitochondrial biogenesis, resulting in neuronal cell death occurring in the hippocampus. Sirtuin 1 (SIRT1) functionally interacts with peroxisome proliferator-activated receptors and γ coactivator 1α (PGC-1α), which play a crucial role in the regulation of mitochondrial biogenesis. In Sprague-Dawley rats, kainic acid was microinjected unilaterally into the hippocampal CA3 subfield to induce bilateral seizure activity. SIRT1, PGC-1α, and other key proteins involving mitochondrial biogenesis and the amount of mitochondrial DNA were investigated. SIRT1 antisense oligodeoxynucleotide was used to evaluate the relationship between SIRT1 and mitochondrial biogenesis, as well as the mitochondrial function, oxidative stress, and neuronal cell survival. Increased SIRT1, PGC-1α, and mitochondrial biogenesis machinery were found in the hippocampus following experimental status epilepticus. Downregulation of SIRT1 decreased PGC-1α expression and mitochondrial biogenesis machinery, increased Complex I dysfunction, augmented the level of oxidized proteins, raised activated caspase-3 expression, and promoted neuronal cell damage in the hippocampus. The results suggest that the SIRT1 signaling pathway may play a pivotal role in mitochondrial biogenesis, and could be considered an endogenous neuroprotective mechanism counteracting seizure-induced neuronal cell damage following status epilepticus.

Nobiletin ameliorates hepatic ischemia and reperfusion injury through the activation of SIRT-1/FOXO3a-mediated autophagy and mitochondrial biogenesis

Hepatic ischemia and reperfusion injury are characterized by impaired autophagy, mitochondrial dysfunction, and subsequent compromise of cellular homeostasis following hepatic surgery or transplantation. Nobiletin, a natural flavonoid, is a beneficial antioxidant that possesses anti-inflammatory and anti-cancer activities. We investigated the effect of nobiletin on hepatic IR injury and described the underlying mechanisms. C57BL/6 mice were subjected to 60 min of partial hepatic ischemia, treated with nobiletin (5 mg/kg) or vehicle at the start of reperfusion, and killed at 5 h of reperfusion. Hepatic ischemia and reperfusion increased hepatocellular oxidative damage, inflammation, and cell death, but these changes were alleviated upon nobiletin treatment. Nobiletin increased the expression of proteins that control autophagy, mitochondrial dynamics, and biogenesis. Specifically, the SIRT-1/FOXO3a and PGC-1α pathways were activated by nobiletin. IR-induced AKT activation was associated with FOXO3a phosphorylation, which resulted in a significant reduction in the nuclear FOXO3a levels and potentially attenuated autophagy-regulatory gene expression. Nobiletin increased FOXO3a expression and its nuclear translocation via the inhibition of AKT. Specific inhibition of SIRT-1 abolished the protective effect of nobiletin, causing decreased FOXO3a expression, followed by autophagy induction and decreased PGC-1α expression and mitochondrial dynamics. Taken together, our data indicate that SIRT-1 directly mediates the protective effect of nobiletin against hepatic ischemia and reperfusion injury. The activation of autophagy and mitochondrial function through the SIRT-1/FOXO3a and PGC-1α pathways indicate that nobiletin could have therapeutic potential for treating hepatic ischemia and reperfusion injury.

The SMILE transcriptional corepressor inhibits cAMP response element–binding protein (CREB)–mediated transactivation of gluconeogenic genes

Under fasting conditions, activation of several hepatic genes sets the stage for gluconeogenesis in the liver. cAMP response element-binding protein (CREB), CREB-regulated transcription coactivator 2 (CRTC2), and peroxisome proliferator-activated receptor γ coactivator 1-alpha (PGC-1α) are essential for this transcriptional induction of gluconeogenic genes. PGC-1α induction is mediated by activation of a CREB/CRTC2 signaling complex, and recent findings have revealed that small heterodimer partner-interacting leucine zipper protein (SMILE), a member of the CREB/ATF family of basic region-leucine zipper (bZIP) transcription factors, is an insulin-inducible corepressor that decreases PGC-1α expression and abrogates its stimulatory effect on hepatic gluconeogenesis. However, the molecular mechanism whereby SMILE suppresses PGC-1α expression is unknown. Here, we investigated SMILE's effects on the CREB/CRTC2 signaling pathway and glucose metabolism. We found that SMILE significantly inhibits CREB/CRTC2-induced PGC-1α expression by interacting with and disrupting the CREB/CRTC2 complex. Consequently, SMILE decreased PGC-1α-induced hepatic gluconeogenic gene expression. Furthermore, SMILE inhibited CREB/CRTC2-induced phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase (G6Pase) gene expression by directly repressing the expression of these genes and by indirectly inhibiting the expression of PGC-1α via CREB/CRTC2 repression. Indeed, enhanced gluconeogenesis and circulating blood glucose levels in mice injected with an adenovirus construct containing a constitutively active CRTC2 variant (CRTC2-S171A) were significantly reduced by WT SMILE, but not by leucine zipper-mutated SMILE. These results reveal that SMILE represses CREB/CRTC2-induced PGC-1α expression, an insight that may help inform potential therapeutic approaches targeting PGC-1α-mediated regulation of hepatic glucose metabolism.

High-fat diet inhibits PGC-1α suppressive effect on NFκB signaling in hepatocytes.

The peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α) regulates the expression of genes implicated in fatty acid oxidation and oxidative phosphorylation. Its role in liver steatosis is well established, since mice with liver-specific deletion of PGC-1α exhibit lipid accumulation and high-fat diet reduces hepatic PGC-1α expression in mice. In this study, we investigated the role of PGC-1α in the inflammatory changes observed in steatohepatitis induced by high-fat diet. C57black/6 mice were fed a high-fat diet containing 30% fat for 10weeks. After euthanasia, liver morphology was examined by HE staining and inflammation was determined by IL-6, TNF-α, and IL-1β quantification. Liver gene expression of PGC-1 isoforms was evaluated by real-time PCR and p65 NFκB nuclear translocation by Western blotting. HepG2 cells were treated with linoleic acid overload for 72h to create an in vitro model of steatohepatitis. RNA interference (RNAi) was used to evaluate the involvement of PGC-1α on inflammatory mediators' production by hepatocytes. The high-fat diet led to a state of nonalcoholic steatohepatitis, associated with increased deposits of intra-abdominal fat, hyperglycemia and hyperlipidemia. Mice liver also exhibited increased proinflammatory cytokines' levels, decreased PGC-1α expression, and marked increase in p65 NFκB nuclear translocation. Linoleic acid treated cells also presented increased expression of proinflammatory cytokines and decreased PGC-1α expression. The knockdown of PGC-1α content caused an increase in IL-6 expression and release via enhanced IκBα phosphorylation and subsequent increase of p65 NFκB nuclear translocation. High-fat diet induces liver inflammation by inhibiting PGC-1α expression and its suppressive effect in NFκB pathway.

Supranutritional selenium intake from enriched milk casein impairs hepatic insulin sensitivity via attenuated IRS/PI3K/AKT signaling and decreased PGC-1α expression in male Sprague–Dawley rats

Selenium (Se)-enriched milk provides antioxidant benefits and has therapeutic potential against cancer. However, both antidiabetic and prodiabetic effects have been attributed to Se. Our objective was to evaluate the effect of Se-enriched milk casein on insulin sensitivity in rats when given at the requirement of 0.25 ppm Se and supranutritionally on both low- and high-fat diets. Two hundred sixteen male Sprague–Dawley rats were fed low- or high-fat diets containing one, two or eight times the Se requirement in a randomized block design. After 7 weeks, 72 rats were subjected to the hyperinsulinemic–euglycemic clamp with [3-3H]glucose infusion to estimate glucose fluxes. Tissues were collected from the remaining 144 rats 8 min after ip saline or insulin injection. During hyperinsulinemic–euglycemic clamps, glucose infusion rate was 22% lower (P=.058), and endogenous glucose production was 76% higher (P=.054) when Se content increased from one to eight times the requirement on low-fat diets, indicating impaired hepatic insulin sensitivity. Se also decreased the ability for insulin to stimulate Akt phosphorylation at Thr308. Hepatic oxidation state and expression of selenoprotein P and glutathione peroxidase-1 were unaffected while expression of insulin receptor substrate (IRS)-1 and−2 and PPARγ coactivator-1α (PGC-1α) decreased with supranutritional Se and high-fat intake. In addition, hepatic expression of regulatory and catalytic subunits of phosphatidylinositol 3-kinase (PI3K) decreased with supranutritional intake of Se. Se intake from enriched casein up to eight times the requirement impairs hepatic insulin sensitivity in a mechanism similar to fat feeding, via attenuated IRS/PI3K/Akt signaling and decreased PGC-1α expression.