(Pro)renin receptor (PRR) contributes to regulating many physiological and pathological processes; however, the role of PRR-mediated signaling pathways in myocardial ischemia/reperfusion injury (IRI) remains unclear. In this study, we used an in vitro model of hypoxia/reoxygenation (H/R) to mimic IRI and carried out PRR knockdown by siRNA and PRR overexpression using cDNA in H9c2 cells. Cell proliferation activity was examined by MTT and Cell Counting Kit-8 (CCK-8) assays. Apoptosis-related factors, autophagy markers and β-catenin pathway activity were assessed by real-time PCR and western blotting. After 24 h of hypoxia followed by 2 h of reoxygenation, the expression levels of PRR, LC3B-I/II, Beclin1, cleaved caspase-3, cleaved caspase-9 and Bax were upregulated, suggesting that apoptosis and autophagy were increased in H9c2 cells. Contrary to the effects of PRR downregulation, the overexpression of PRR inhibited proliferation, induced apoptosis, increased the expression of pro-apoptotic factors and autophagy markers, and promoted activation of the β-catenin pathway. Furthermore, all these effects were reversed by treatment with the β-catenin antagonist DKK-1. Thus, we concluded that PRR activation can trigger H/R-induced apoptosis and autophagy in H9c2 cells through the β-catenin signaling pathway, which may provide new therapeutic targets for the prevention and treatment of myocardial IRI.
Atrial fibrillation is associated with atrial remodeling, in which connexin 43 (Cx43) and cell hypertrophy play important roles. In this study, apelin-13, an aliphatic peptide, was used to explore the protective effects of the adenosine monophosphate-activated protein kinase (AMPK)/mTOR signaling pathway on Cx43 expression and autophagy, using murine atrial HL-1 cells. The expression of Cx43, AMPK, B-type natriuretic peptide (BNP) and pathway-related proteins was detected by Western blot analysis. Cellular fluorescence imaging was used to visualize Cx43 distribution and the cytoskeleton. Our results showed that the Cx43 expression was significantly decreased in HL-1 cells treated with angiotensin II but increased in cells additionally treated with apelin-13. Meanwhile, apelin-13 decreased BNP expression and increased AMPK expression. However, the expression of Cx43 and LC3 increased by apelin-13 was inhibited by treatment with compound C, an AMPK inhibitor. In addition, rapamycin, an mTOR inhibitor, promoted the development of autophagy, further inhibited the protective effect on Cx43 expression and increased cell hypertrophy. Thus, apelin-13 enhances Cx43 expression and autophagy via the AMPK/mTOR signaling pathway, and serving as a potential therapeutic target for atrial fibrillation., Yifan Chen, Xi Qiao, Lijun Zhang, Xuewen Li, Qinghua Liu., and Obsahuje bibliografii
The acidic tumor microenvironment (TME) of pancreatic cancer affects the physiological function of pancreatic stellate cells (PSCs), which in turn promotes cancer progression. Acid-sensing ion channel 1a (ASIC1a) is responsible for acidosis-related physiopathological processes. In this study, we investigated the effect of acid exposure on the activation and autophagy of PSCs, and the role of ASIC1a in these events. The results showed that acidic medium upregulated the expression of ASIC1a, induced PSCs activation and autophagy, which can be suppressed by inhibiting ASIC1a using PcTx1 or ASIC1a knockdown, suggesting that ASIC1a involves these two processes. In addition, the acidinduced activation of PSCs was impaired after the application of autophagy inhibitor alone or in combination with ASIC1a siRNA, meaning a connection between autophagy and activation. Collectively, our study provides evidence for the involvement of ASIC1a in the acid-caused PSCs activation, which may be associated with autophagy induction.
We present data supporting the hypothesis that the lysosomalautophagy pathway is involved in the degradation of intracellular triacylglycerols in the liver. In primary hepatocytes cultivated in the absence of exogenous fatty acids (FFA), both inhibition of autophagy flux (asparagine) or lysosomal activity (chloroquine) decreased secretion of VLDL (very low density lipoproteins) and formation of FFA oxidative products while the stimulation of autophagy by rapamycine increased some of these parameters. Effect of rapamycine was completely abolished by inactivation of lysosomes. Similarly, when autophagic activity was influenced by cultivating the hepatocytes in “starving” (amino-acid poor medium) or “fed” (serum-supplemented medium) conditions, VLDL secretion and FFA oxidation mirrored the changes in autophagy being higher in starvation and lower in fed state. Autophagy inhibition as well as lysosomal inactivation depressed FFA and DAG (diacylglycerol) formation in liver slices in vitro. In vivo, intensity of lysosomal lipid degradation depends on the formation of autophagolysosomes, i.e. structures bringing the substrate for degradation and lysosomal enzymes into contact. We demonstrated that lysosomal lipase (LAL) activity in liver autophagolysosomal fraction was up-regulated in fasting and down-regulated in fed state together with the increased translocation of LAL and LAMP2 proteins from lysosomal pool to this fraction. Changes in autophagy intensity (LC3-II/LC3-I ratio) followed a similar pattern., V. Škop ... [et al.]., and Obsahuje seznam literatury
Animals use neutral lipids, particularly triacylglycerols (TAGs), to store energy. TAGs are universally organized into dynamic cytoplasmic structures called lipid droplets (LDs). In mammals TAG breakdown is catalysed by lipases, such as hormonesensitive lipase (HSL). LD membrane-resident proteins called perilipins (PLINs) regulate some of these lipases. The model organism Caenorhabditis elegans has a single known PLIN homologue and orthologues of most lipases including HSL. HOSL-1 (the HSL orthologue in C. elegans) is responsible for production of cryoprotective glycerol in cold conditions, in addition to its role in fasting-induced lipolysis. We employed this model of cold exposure to study the role of PLIN-1 in the regulation of HOSL-1. Our results suggest that both HOSL-1 and PLIN-1 are required for cold tolerance and for lipid breakdown in cold. However, the loss of PLIN-1 partially rescued the phenotype of hosl-1 null mutants exposed to cold, suggesting the presence of an alternative pathway generating glycerol via lipolysis. In early embryos, PLIN-1 knock-out results in accumulation of lipids and formation of cytoplasmic clusters of autophagic marker LGG-1, supporting the role of autophagy as an alternative lipolytic pathway in C. elegans, as is the case in mammals.
Mammalian Meckel´s cartilage is a temporary structure
associated with mandible development. Notably, its elimination is
not executed by apoptosis, and autophagy was suggested as the
major mechanism. Simultaneous reports point to pro-apoptotic
caspases as novel participants in autophagic pathways in general.
The aim of this research was to find out whether activation of
pro-apoptotic caspases (-2, -3, -6, -7, -8 and -9) was associated
with autophagy of the Meckel´s cartilage chondrocytes. Active
caspases were examined in serial histological sections of mouse
mandible using immunodetection and were correlated with
incidence of autophagy based on Beclin-1 expression. Caspase-2
and caspase-8 were found in Beclin-1 positive regions, whereas
caspase-3, -6, -7 and -9 were not present. Caspase-8 was further
correlated with Fas/FasL and HIF-1α, potential triggers for its
activation. Some Fas and FasL positivity was observed in the
chondrocytes but caspase-8 activation was found also in FasL
deficient cartilage. HIF-1α was abundantly present in the
hypertrophic chondrocytes. Taken together, caspase-8 activation
in the Meckel´s cartilage was demonstrated for the first time.
Caspase-8 and caspase-2 were the only pro-apoptotic caspases
detected in the Beclin-1 positive segment of the cartilage.
Activation of caspase-8 appears FasL/Fas independent but may
be switched on by HIF-1α.
Autophagy-lysosomal pathway is a cellular mechanism ensuring degradation of various macromolecules like proteins or triacylglycerols (TAG). Its disruption is related to many pathological states, including liver steatosis. We compared the effect of short- and long-established steatosis on the intensity of autophagy-lysosomal pathway in rat liver. The experiments were carried out on 3-month old Wistar rats fed standard (SD) or highfat diet for 2 (HF-2) or 10 (HF-10) weeks. HF diet administered animals accumulated an increased amount of TAG in the liver (HF-2→HF-10). Autophagy flux was up-regulated in HF-2 group but nearly inhibited after 10 weeks of HF administration. The expression of autophagy related genes was up-regulated in HF-2 but normal in HF-10. In contrast, total activities of two lysosomal enzymes, lysosomal lipase (LAL) and acid phosphatase, were unaffected in HF-2 but significantly increased in HF-10 groups. mRNA expression of lysosomal enzymes was not affected by the diet. We conclude that in a state of metabolic unbalance (steatosis), autophagy machinery and lysosomal enzymes expression are regulated independently. The accumulation of TAG in the liver is associated with the increase of total LAL activity and protein expression. In contrast, the autophagy response is bi-phasic and after rapid increase it is significantly diminished. This may represent an adaptive mechanism that counteracts the excessive degradation of substrate, i.e. TAG, and eliminate over-production of potentially hazardous lipiddegradation intermediates., Z. Papáčková, ... [et al.]., and Obsahuje seznam literatury
Activation of autophagy suppresses ovarian cancer (OC). This in vitro study investigated whether the anti-tumour effect of exendin-4 against OC involves modulation of autophagy and figured out the possible mechanisms of action. SKOV-3 and OVCAR-3 cells (1 × 105/ml) were cultured in DMEM medium and treated with exendin-4 in the presence or absence of chloroquine (CQ), an autophagy inhibitor. In some cases, cells were also treated with exendin- 4 with or without pre-treatment with compound C (CC), an AMPK inhibitor, or insulin-like growth factor (IGF-1), a PI3K/Akt activator. Exendin-4 increased expression of beclin-1 and LC3I/II, suppressed expression of p62, reduced cell survival, migration, and invasion, and increased cell apoptosis and LDH release in both SKOV-3 and OVCAR-3 cells. Besides, exendin-4 reduced phosphorylation of mTORC1, 6SK, 4E-BP1, and Akt but increased phosphorylation of AMPK in both cell lines. These effects were associated with down-regulation of Bcl-2, suppression of nuclear phosphorylation of NF-κB p65, and increased expression of Bax and cleaved caspases 3/8. Chloroquine completely prevented the inhibitory effects of exendin-4 on the cell survival, Bcl-2, NF-κB, and cell invasiveness and abolished its stimulation of cell apoptosis and LDH release. Moreover, only the combined treatment with IGF-1 and CC completely abolished the observed effect of exendin-4 on the expression of beclin-1, LC3I/II, p62, as well as on cell survival, apoptosis, and LDH release. Exendin-4 exhibits a potent anti-tumour cytotoxic effect in SKOV-3 and OVCAR-3 cells by activating the markers of autophagy, mediated by activation of AMPK and inhibition of Akt.
Autophagy can regulate cell growth, proliferation, and stability of
cell environment. Its dysfunction can be involved in a variety of
diseases. Hydrogen sulfide (H2S) is an important signaling
molecule that regulates many physiological and pathological
processes. Recent studies indicate that H2S plays an important
protective role in many diseases through influencing autophagy,
but its mechanism is not fully understood. This article reviewed
the progress about the effect of H2S on autophagy in diseases in
recent years in order to provide theoretical basis for the further
research on the interaction of H2S and autophagy and the
mechanisms involved.
Autophagy is the basic catabolic mechanism that involves degradation of dysfunctional cellular components through the action of lysosome as well as supplying energy and compounds for the synthesis of essential biomacromolecules. This process enables cells to survive stress from the external environment like nutrient deprivation. Autophagy is important in the breakdown of proteins, carbohydrates and lipids as well. Furthermore, recent studies have shown that autophagy is critical in wide range of normal human physiological processes, and defective autophagy is associated with diverse diseases, including lysosomal storage disease, myopathies, neurodegeneration and various metabolic disorders. This review summarizes the most up-to-date findings on what role autophagy plays in metabolism., Z. Papáčková, M. Cahová., and Obsahuje bibliografii