Autophagy induction plays a protective role against hypoxic stress in human dental pulp cells

MiR-143-5p regulates the proangiogenic potential of human dental pulp stem cells by targeting HIF-1α/RORA under hypoxia: A laboratory investigation in pulp regeneration

AIM

Angiogenesis is a key event in the successful healing of pulp injuries, and hypoxia is the main stimulator of pulpal angiogenesis. In this study, we investigated the effect of hypoxia on the proangiogenic potential of human dental pulp stem cells (hDPSCs) and the role of miR-143-5p in the process.

METHODOLOGY

Human dental pulp stem cells were isolated, cultured and characterized in vitro. Cobalt chloride (CoCl2) was used to induce hypoxia in hDPSCs. CCK-8 and Transwell assays were used to determine the effect of hypoxia on hDPSCs proliferation and migration. Quantitative real-time polymerase chain reaction (qRT-PCR), Western blotting (WB) and ELISA were performed to assess the mRNA and protein levels of HIF-1α and angiogenic cytokines in hDPSCs. The effect of hypoxia on hDPSCs proangiogenic potential was measured in vitro using Matrigel tube formation and chick chorioallantoic membrane (CAM) assays. Recombinant lentiviral vectors were constructed to stably overexpress or inhibit miR-143-5p in hDPSCs, and the proangiogenic effects were assessed using qRT-PCR, WB, and tube formation assays. miR-143-5p target genes were identified and verified using bioinformatics prediction tools, dual-luciferase reporter assays and RNA pull-down experiments. Finally, a subcutaneous transplantation model in nude mice was used to determine the effects of hypoxia treatment and miR-143-5p overexpression/inhibition in hDPSCs in dental pulp regeneration.

RESULTS

Hypoxia promotes hDPSCs proliferation, migration and proangiogenic potential. The in vivo experiments showed that hypoxia treatment (50 and 100 μM CoCl2) promoted pulp angiogenesis and dentine formation. In contrast to the levels of proangiogenic factors, miR-143-5p levels decreased with increasing CoCl2 concentration. miR-143-5p inhibition significantly promoted proangiogenic potential of hDPSCs, whereas miR-143-5p overexpression inhibited angiogenesis in vitro. Dual-luciferase reporter assay identified retinoic acid receptor-related orphan receptor alpha (RORA) as an miR-143-5p target gene in hDPSCs. RNA pull-down experiments demonstrated that HIF-1α and RORA were pulled down by biotin-labelled miR-143-5p, and the levels of HIF-1α and RORA bound to miR-143-5p in the hypoxia group were lower than those in the normoxia group. Inhibition of miR-143-5p expression in hDPSCs promoted ectopic dental pulp tissue regeneration.

CONCLUSIONS

CoCl2-induced hypoxia promotes hDPSCs-driven paracrine angiogenesis and pulp regeneration. The inhibition of miR-143-5p upregulates the proangiogenic potential of hDPSCs under hypoxic conditions by directly targeting HIF-1α and RORA.

Autophagy induced by hypoxia in pulpitis is mediated by HIF-1α/BNIP3

OBJECTIVE

Hypoxia-inducible factor-1α (HIF-1α) and its downstream factor, 19 kDa BCL-2 interacting protein 3 (BNIP3), promote cellular autophagy under hypoxic conditions. However, their roles in pulpitis are unclear. Therefore, the changes in inflammatory response and autophagy levels caused by hypoxia during pulpitis were evaluated. Additionally, the regulatory mechanism of HIF-1α/BNIP3 in cellular autophagy in pulpitis was explored.

DESIGN

Pulp from dental pulp tissues of healthy individuals and patients with pulpitis (n = 10) were exposed and combined with a low oxygen simulation chamber to construct pulpitis (n = 6), hypoxia (n = 6), and hypoxia+pulpitis (n = 6) rat models. Hematoxylin and eosin and immunohistochemical staining were used to detect the localization and expression levels of HIF-1α, BNIP3, and autophagy marker protein, LC3B. Transmission electron microscopy was used to confirm autophagosome formation. An in vitro hypoxic model of human dental pulp cells was established, and HIF-1α chemical inhibitor 3-(5'-hydroxymethyl-2'-furyl)- 1-benzylindazole (YC-1) was administered. Immunofluorescence and western blotting were used to detect the localization and protein levels of HIF-1α, BNIP3, and LC3B.

RESULTS

Autophagy is significantly increased and HIF-1α and BNIP3 are elevated in inflamed dental pulp tissue. Both pulp exposure and hypoxia intervention cause inflammatory reactions in rat dental pulp tissue, accompanied by the autophagy activation. Hypoxia significantly enhances HIF-1α/BNIP3 and autophagy activation. BNIP3 downregulates and autophagy reduces after treatment with YC-1.

CONCLUSIONS

In pulpitis, activation of the HIF-1α/BNIP3 signaling pathway driven by hypoxia leads to increased autophagy. This provides a new molecular explanation for autophagy activation in apical periodontitis and new insights into the pathogenesis of the disease.

Investigating the Association between the Autophagy Markers LC3B, SQSTM1/p62, and DRAM and Autophagy-Related Genes in Glioma

High-grade gliomas are extremely fatal tumors, marked by severe hypoxia and therapeutic resistance. Autophagy is a cellular degradative process that can be activated by hypoxia, ultimately resulting in tumor advancement and chemo-resistance. Our study aimed to examine the link between autophagy markers' expression in low-grade gliomas (LGGs) and high-grade gliomas (HGGs). In 39 glioma cases, we assessed the protein expression of autophagy markers LC3B, SQSTM1/p62, and DRAM by immunohistochemistry (IHC) and the mRNA expression of the autophagy genes PTEN, PI3K, AKT, mTOR, ULK1, ULK2, UVRAG, Beclin 1, and VPS34 using RT-qPCR. LC3B, SQSTM1/p62, and DRAM expression were positive in 64.1%, 51.3%, and 28.2% of glioma cases, respectively. The expression of LC3B and SQSTM1/p62 was notably higher in HGGs compared to LGGs. VPS34 exhibited a significant differential expression, displaying increased fold change in HGGs compared to LGGs. Additionally, it exhibited robust positive associations with Beclin1 (rs = 0.768), UVRAG (rs = 0.802), and ULK2 (rs = 0.786) in HGGs. This underscores a potential association between autophagy and the progression of gliomas. We provide preliminary data for the functional analysis of autophagy using a cell culture model and to identify potential targets for therapeutic interventions.

TPPU inhibits inflammation-induced excessive autophagy to restore the osteogenic differentiation potential of stem cells and improves alveolar ridge preservation

Inflammation-induced autophagy is a double-edged sword. Dysfunction of autophagy impairs the differentiation capacity of mesenchymal stem cells and enhances inflammation-induced bone loss. Tooth extraction with periodontal and/or endodontic lesions exacerbates horizontal and vertical resorption of alveolar bone during the healing period. Alveolar socket preservation (ASP) procedure following tooth extraction has important clinical implications for future prosthodontic treatments. Studies have shown that epoxyeicosatrienoic acids (EETs) have significant anti-inflammatory effects and participate in autophagy. However, whether EETs can minimize alveolar bone resorption and contribute to ASP by regulating autophagy levels under inflammatory conditions remain elusive. Here, we figured out that LPS-induced inflammatory conditions increased the inflammatory cytokine and inhibited osteogenic differentiation of human dental pulp stem cells (hDPSCs), and led to excessive autophagy of hDPSCs. Moreover, we identified that increased EETs levels using TPPU, a soluble epoxide hydrolase inhibitor, reversed these negative outcomes. We further demonstrated the potential of TPPU to promote early healing of extraction sockets and ASP, and speculated that it was related to autophagy. Taken together, these results suggest that targeting inhibition of soluble epoxide hydrolase using TPPU plays a protective role in the differentiation and autophagy of mesenchymal stem cells and provides potential feasibility for applying TPPU for ASP, especially under inflammatory conditions.

A critical analysis of research methods and experimental models to study pulpitis

Pulpitis is the inflammatory response of the dental pulp to a tooth insult, whether it is microbial, chemical, or physical in origin. It is traditionally referred to as reversible or irreversible, a classification for therapeutic purposes that determines the capability of the pulp to heal. Recently, new knowledge about dental pulp physiopathology led to orientate therapeutics towards more frequent preservation of pulp vitality. However, full adoption of these vital pulp therapies by dental practitioners will be achieved only following better understanding of cell and tissue mechanisms involved in pulpitis. The current narrative review aimed to discuss the contribution of the most significant experimental models developed to study pulpitis. Traditionally, in vitro two(2D)- or three(3D)-dimensional cell cultures or in vivo animal models were used to analyse the pulp response to pulpitis inducers at cell, tissue or organ level. In vitro 2D cell cultures were mainly used to decipher the specific roles of key actors of pulp inflammation such as bacterial by-products, pro-inflammatory cytokines, odontoblasts or pulp stem cells. However, these simple models did not reproduce the 3D organisation of the pulp tissue and, with rare exceptions, did not consider interactions between resident cell types. In vitro tissue/organ-based models were developed to better reflect the complexity of the pulp structure. Their major disadvantage is that they did not allow the analysis of blood supply and innervation participation. On the contrary, in vivo models have allowed researchers to identify key immune, vascular and nervous actors of pulpitis and to understand their function and interplay in the inflamed pulp. However, inflammation was mainly induced by iatrogenic dentine drilling associated with simple pulp exposure to the oral environment or stimulation by individual bacterial by-products for short periods. Clearly, these models did not reflect the long and progressive development of dental caries. Lastly, the substantial diversity of the existing models makes experimental data extrapolation to the clinical situation complicated. Therefore, improvement in the design and standardization of future models, for example by using novel molecular biomarkers, databased models and artificial intelligence, will be an essential step in building an incremental knowledge of pulpitis in the future.

LPS-induced autophagy in human dental pulp cells is associated with p38

Lipopolysaccharides (LPS), which are components of the cell wall of Gram-negative bacteria, are among the important factors that induce inflammation, including pulpitis. Autophagy in human dental pulp cells (hDPCs) acts as a protective mechanism that promotes cell survival under adverse conditions through different signaling pathways. In this study, we examined whether LPS increases autophagy in hDPCs and investigated the role of mitogen-activated protein kinases signaling and nuclear factor κB (NF-κB) in this process. We found that stimulation of hDPCs with 0.1 µg/mL LPS increased the protein and mRNA levels of autophagy markers, beclin1 and microtubule associated protein light chain 3II (LC3II). In addition, acridine orange staining and transmission electron microscopy demonstrated the induction of autophagy upon the treatment of LPS. Furthermore, LPS affected phosphorylation of p38, extracellular signal-regulated kinase (ERK), and c-Jun N-terminal kinase (JNK), and the nuclear translocation of NF-κB. While p38 inhibitor suppressed the LPS-induced increase in protein levels of beclin1 and LC3-II. Our results suggest that LPS induced autophagy in hDPCs and affected the phosphorylation of p38, ERK, and JNK, as well as the nuclear translocation of NF-κB. Phosphorylation of p38 may be involved in LPS-induced autophagy in hDPCs.

Autophagy upregulates inflammatory cytokines in gingival tissue of patients with periodontitis and lipopolysaccharide-stimulated human gingival fibroblasts

Background

Periodontitis is an inflammatory disease caused by multiple disease‐associated bacterial species in periodontal tissues. Autophagy is known to modulate various inflammation‐driven diseases and inflammatory responses, but the role of autophagy related to the pathogenesis of periodontitis is not fully established. We investigated whether autophagic flux regulated the expression of inflammatory cytokines in the gingiva of periodontitis patients and lipopolysaccharide (LPS)‐stimulated human gingival fibroblasts (HGFs) and the underlying mechanism.

Methods

The mRNA and protein expression of proinflammatory cytokines was assessed in human gingival tissues collected from patients with periodontitis and HGFs treated with LPS. The expression of signaling molecules related to autophagy was evaluated by immunofluorescence and Western blot analyses.

Results

The expression of interleukin (IL)‐6, tumor necrosis factor‐α (TNF‐α), cyclooxygenase‐2 (COX‐2), and intercellular adhesion molecule‐1 (ICAM‐1) was increased in the gingival tissues of patients with periodontitis. LC3B‐positive cells, a typical autophagic marker, were increased in the gingival tissues of periodontitis patients and LPS‐treated HGFs. The conversion ratio of LC3‐I to LC3‐II was higher in the gingival tissues associated with periodontitis and LPS‐treated HGFs compared to the controls. The autophagy inhibitor 3‐methyladenine (3MA) significantly abrogated the LPS‐sustained inflammatory effect by reducing the expression of IL‐6, TNF‐α, COX‐2, and ICAM‐1 in HGFs. The phosphorylation of protein kinase B (AKT) and protein S6K1 (S6), signals involved in the mTOR‐dependent mechanism, was decreased in gingiva derived from periodontitis patients and LPS‐treated HGFs.

Conclusions

Autophagy augmented the production of inflammatory cytokines by mTOR inactivation via the AKT signaling pathway in the gingival tissues of patients with periodontitis and LPS‐stimulated HGFs. These findings would provide a better understanding of the mechanism by which autophagy regulates the inflammatory response associated with periodontal pathogenesis.

A Key Pathway to Cancer Resilience: The Role of Autophagy in Glioblastomas

There are no effective strategies for the successful treatment of glioblastomas (GBM). Current therapeutic modalities effectively target bulk tumor cells but leave behind marginal GBM cells that escape from the surgical margins and radiotherapy field, exhibiting high migratory phenotype and resistance to all available anti-glioma therapies. Drug resistance is mostly driven by tumor cell plasticity: a concept associated with reactivating transcriptional programs in response to adverse and dynamic conditions from the tumor microenvironment. Autophagy, or "self-eating", pathway is an emerging target for cancer therapy and has been regarded as one of the key drivers of cell plasticity in response to energy demanding stress conditions. Many studies shed light on the importance of autophagy as an adaptive mechanism, protecting GBM cells from unfavorable conditions, while others recognize that autophagy can kill those cells by triggering a non-apoptotic cell death program, called 'autophagy cell death' (ACD). In this review, we carefully analyzed literature data and conclude that there is no clear evidence indicating the presence of ACD under pathophysiological settings in GBM disease. It seems to be exclusively induced by excessive (supra-physiological) stress signals, mostly from in vitro cell culture studies. Instead, pre-clinical and clinical data indicate that autophagy is an emblematic example of the 'dark-side' of a rescue pathway that contributes profoundly to a pro-tumoral adaptive response. From a standpoint of treating the real human disease, only combinatorial therapy targeting autophagy with cytotoxic drugs in the adjuvant setting for GBM patients, associated with the development of less toxic and more specific autophagy inhibitors, may inhibit adaptive response and enhance the sensibility of glioma cells to conventional therapies.

Autophagy in tooth: Physiology, disease and therapeutic implication

Autophagy is an evolutionarily conserved cellular process, in which damaged organelles and proteins are engulfed in autophagic vesicles and subsequently fuse with lysosomes for degradation. Autophagy is widely involved in different physiologic or pathologic processes in human. Accumulating evidence indicates that autophagy operates as a critical quality control mechanism to maintain pulp homeostasis and structural integrity of the dentin-pulp complex. Autophagy is activated during stresses and is involved in the pathogenesis of pulpitis and periapical infection. Recent discoveries have also provided intriguing insights into the roles of autophagy in tooth development, pulp aging and stress adaptation. In this review, we provide an update on the multifaceted functions of autophagy in physiology and pathophysiology of tooth. We also discuss the therapeutic implications of autophagy modulation in diseases and the regeneration of dentin-pulp complex.

Microenvironment Influences Odontogenic Mesenchymal Stem Cells Mediated Dental Pulp Regeneration

Dental pulp as a source of nutrition for the whole tooth is vulnerable to trauma and bacterial invasion, which causes irreversible pulpitis and pulp necrosis. Dental pulp regeneration is a valuable method of restoring the viability of the dental pulp and even the whole tooth. Odontogenic mesenchymal stem cells (MSCs) residing in the dental pulp environment have been widely used in dental pulp regeneration because of their immense potential to regenerate pulp-like tissue. Furthermore, the regenerative abilities of odontogenic MSCs are easily affected by the microenvironment in which they reside. The natural environment of the dental pulp has been proven to be capable of regulating odontogenic MSC homeostasis, proliferation, and differentiation. Therefore, various approaches have been applied to mimic the natural dental pulp environment to optimize the efficacy of pulp regeneration. In addition, odontogenic MSC aggregates/spheroids similar to the natural dental pulp environment have been shown to regenerate well-organized dental pulp both in preclinical and clinical trials. In this review, we summarize recent progress in odontogenic MSC-mediated pulp regeneration and focus on the effect of the microenvironment surrounding odontogenic MSCs in the achievement of dental pulp regeneration.

[Role of autophagy in lipopolysaccharide-induced apoptosis of odontoblasts]

OBJECTIVE

To investigate the role of autophagy in lipopolysaccharide (LPS)-induced apoptosis of murine odontoblasts.

METHODS

Murine odontoblasts (mDPC-23 cells) were treated with 5 μg/mL LPS for 6, 12 and 24 h, and the changes in cell viability was examined using CCK8 kit and cell apoptosis was detected by TUNEL staining. The changes in the protein levels of LC3, Beclin1, Atg5, AKT, p-AKT, mTOR and p-mTOR were detected using Western blotting. The effect of 3-MA treatment for 24 h on LPS-induced apoptosis of mDPC-23 cells was evaluated by detecting the expressions of apoptosis-related proteins caspase-3 and Bax using Western blotting.

RESULTS

Stimulation with LPS for 6 and 12 h did not cause significant changes in the proliferation or apoptosis of mDPC-23 cells, but LPS treatment for 24 h significantly suppressed cell proliferation (P < 0.05) and promoted cell apoptosis as shown by TUNEL assay (P < 0.05). Stimulation with LPS for 24 significantly increased the expression levels of LC3, Beclin1 and Atg5, decreased the expressions of p-AKT and p-mTOR (P < 0.05), and obviously upregulated the expressions of caspase-3 and Bax (P < 0.05). Treatment with 3-MA markedly lowered caspase-3 and Bax protein expressions in LPS-stimulated cells (P < 0.05).

CONCLUSIONS

LPS stimulation induces autophagy to promote apoptosis of mDPC-23 cells, and suppression of autophagy attenuates LPS-induced apoptosis. Autophagy may play an important role in the injury of inflamed pulp tissues.

Inhibition of autophagy enhances cadmium-induced apoptosis in duck renal tubular epithelial cells

Increasing evidence indicates autophagy and apoptosis are involved in the toxicity mechanism of heavy metals. Our previous studies showed that cadmium (Cd) could induce autophagy and apoptosis in duck kidneys in vivo, nevertheless, the interaction between them has yet to be elucidated. Herein, the cells were either treated with 3CdSO₄·8H₂O (0, 1.25, 2.5, 5.0 μM Cd) or/and 3-methyladenine (3-MA) (2.5 μM) for 12 h and the indictors related autophagy and apoptosis were detected to assess the correlation between autophagy and apoptosis induced by Cd in duck renal tubular epithelial cells. The results demonstrated that Cd exposure notably elevated intracellular and extracellular Cd contents, the number of autophagosomes and LC3 puncta, up-regulated LC3A, LC3B, Beclin-1, Atg5 mRNA levels, and Beclin-1 and LC3II/LC3I protein levels, down-regulated mTOR, p62 and Dynein mRNA levels and p62 protein level. Additionally, autophagy inhibitor 3-MA decreased Beclin-1, LC3II/LC3I protein levels and increased p62 protein level. Moreover, co-treatment with Cd and 3-MA could notably elevate Caspase-3, Cyt C, Bax, and Bak-1 mRNA levels, Caspase-3 and cleaved Caspase-3 protein levels, and cell apoptotic rate as well as cell damage, decreased mitochondrial membrane potential (MMP), Bcl-2 mRNA level and the ratio of Bcl-2 to Bax compared to treatment with Cd alone. Overall, these results indicate Cd exposure can induce autophagy in duck renal tubular epithelial cells, and inhibition of autophagy might aggravate Cd-induced apoptosis through mitochondria-mediated pathway.

Exploring the molecular disorder and dysfunction mechanism of human dental pulp cells under hypoxia by comprehensive multivariate analysis

Dental pulp cells (DPCs) are multipotent cells, which can differentiate into various tissues and have the potential to treat many diseases. However, little is known about the molecular disorder mechanism. To explore the mechanism of molecular disorders and dysfunction of DPCs under hypoxia, we investigated the molecular effects of two hypoxic time lengths on DPCs. Differential analysis, protein interaction network (PPI), enrichment analysis and coupling analysis were further synthesized to identify human dental pulp cell dysfunction modules under hypoxic conditions. Based on the module aggregation of 579 genes, 13 dental pulp cell dysfunction modules were obtained. Importantly, we found that up to 12 modules were significantly involved in positive regulation of neurogenesis, positive regulation of nervous system development. Based on the predictive analysis of regulators, we identified a series of ncRNAs (including CRNDE, MALAT1, microRNA-140-5p, microRNA-300 and microRNA-30a-5p) and transcription factors (including E2F1). Based on the comprehensive functional module analysis, we identified the dysfunction module of human dental pulp cells (HDPCs) under hypoxia. The results suggest that nerve regulation plays an important role in regulating the dysfunction module of DPCs. These prominent pivotal regulators in the module were used as an important part of the molecular disorders of DPCs, may be an important part of the subnetwork of the manipulation module and affect the molecular dysregulation mechanism of DPCs. This study provides new directions and potential targets for further research.

Induction of autophagy protects human dental pulp cells from lipopolysaccharide-induced pyroptotic cell death

The NOD-like receptor protein 3/caspase-1 inflammasome can be activated in human dental pulp tissue and fibroblasts; however, the underlying mechanisms are poorly understood. In the present study, lipopolysaccharide (LPS) was used to treat dental pulp cells to establish an inflammation model. Cell viability was examined by sulforhodamine B assay. Interleukin (IL)-1β, caspase-1, microtubule-associated protein-1 light chain 3-II/I and p62 were determined by western blotting and ELISA. The phosphorylation (p-) levels of NF-κB and NF-κB inhibitor (IκB)α protein were observed by western blotting. The results demonstrated that LPS induced pyroptotic cell death in cultured dental pulp cells, which was supported by the increased levels of IL-1β, IL-18 and caspase-1. Rapamycin and 3-methyladenine (3-MA) were used to activate and inhibit autophagy, and it was observed that LPS increased autophagy and rapamycin reduced LPS-induced dental pulp cell pyroptosis. However, 3-MA aggravated LPS-induced dental pulp cell pyroptosis. In addition, LPS inhibited the expression of IκBα, but increased the expression of p-NF-κB. Compared with the LPS group, 3-MA further inhibited the expression of IκBα but promoted the expression of p-NF-κB. However, rapamycin produced the opposite results to LPS. Under LPS treatment, the NF-κB pathway inhibitor BAY11-7082 further enhanced the inhibitory effects of rapamycin, but inhibited the promoting effects of 3-MA on the protein expression levels of IL-1β and caspase-1. The results of the present study demonstrated that there is an important crosstalk between autophagy, pyroptosis and the NF-κB pathway, and that the modulation of pyroptosis in dental pulp cells may be a promising strategy to pulpitis therapy.

Molecular insights into an ancient form of Paget's disease of bone

We identify an ancient and atypical form of Paget’s disease of bone (PDB) in a collection of medieval skeletons exhibiting unusually extensive pathological changes, high disease prevalence, and low age-at-death estimations. Proteomic analysis of ancient bone-preserved proteins combined with analysis of small RNAs supports a retrospective diagnosis of PDB. Remains affected by other skeletal disorders may therefore hold a chemical memory amenable to similar molecular interrogation. Abnormalities in a contemporary PDB-linked protein detected in ancient tooth samples indicate that dentition may represent an unexplored storehouse for the study of skeletal disorders. Our work provides insights into the natural history of PDB and prompts a similar revaluation of other archaeological collections.

Paget’s disease of bone (PDB) is a chronic skeletal disorder that can affect one or several bones in individuals older than 55 y of age. PDB-like changes have been reported in archaeological remains as old as Roman, although accurate diagnosis and natural history of the disease is lacking. Six skeletons from a collection of 130 excavated at Norton Priory in the North West of England, which dates to medieval times, show atypical and extensive pathological changes resembling contemporary PDB affecting as many as 75% of individual skeletons. Disease prevalence in the remaining collection is high, at least 16% of adults, with age at death estimations as low as 35 y. Despite these atypical features, paleoproteomic analysis identified sequestosome 1 (SQSTM1) or p62, a protein central to the pathological milieu of PDB, as one of the few noncollagenous human sequences preserved in skeletal samples. Targeted proteomic analysis detected >60% of the ancient p62 primary sequence, with Western blotting indicating p62 abnormalities, including in dentition. Direct sequencing of ancient DNA excluded contemporary PDB-associated SQSTM1 mutations. Our observations indicate that the ancient p62 protein is likely modified within its C-terminal ubiquitin-associated domain. Ancient miRNAs were remarkably preserved in an osteosarcoma from a skeleton with extensive disease, with miR-16 expression consistent with that reported in contemporary PDB-associated bone tumors. Our work displays the use of proteomics to inform diagnosis of ancient diseases such as atypical PDB, which has unusual features presumably potentiated by yet-unidentified environmental or genetic factors.

Ganoderic acid A alleviates hypoxia-induced apoptosis, autophagy, and inflammation in rat neural stem cells through the PI3K/AKT/mTOR pathways

Effects of ganoderic acid A (GAA), a lanostane triterpene, on hypoxia-ischemia encephalopathy (HIE) remain unclear. We aimed to figure out the specific role of GAA in hypoxia-treated neural stem cells (NSCs) as well as the regulatory mechanisms. Primary rat NSCs were incubated under hypoxia to simulate HIE. Viability and apoptosis of hypoxia-injured NSCs were measured by cell counting kit-8 and flow cytometry assays, respectively. Proteins related to apoptosis, autophagy, and the PI3K/AKT/mTOR pathways were evaluated by Western blot analysis. LY294002 and rapamycin were added to inhibit the PI3K/AKT pathway and mTOR pathway, respectively. Enzyme-linked immunosorbent assay was carried out to test the release of proinflammatory cytokines. We found that hypoxia-induced decrease of cell viability, increases of apoptotic cells and autophagy, and the release of IL-6, IL-1β, and TNF-α were all attenuated by GAA stimulation. Activation of caspases induced by hypoxia was alleviated by GAA. Furthermore, we found that inhibition of the PI3K/AKT pathway eliminated the effects of GAA on apoptosis and proinflammatory cytokines release in hypoxia-injured NSCs. Meanwhile, inhibition of the mTOR pathway abrogated the effects of GAA on cell autophagy in hypoxia-injured NSCs. In conclusion, GAA alleviated hypoxia-induced injury in NSCs might be through activating the PI3K/AKT and mTOR pathways.

Diet Modulation Restores Autophagic Flux in Damaged Skeletal Muscle Cells

OBJECTIVES

Autophagy is a physiological and highly regulated mechanism, crucial for cell homeostasis maintenance. Its impairment seems to be involved in the onset of several diseases, including muscular dystrophies, myopathies and sarcopenia. According to few papers, chemotherapeutic drug treatment is able to trigger side effects on skeletal muscle tissue and, among these, a defective autophagic activation, which leads to the persistence of abnormal organelles within cells and, finally, to myofiber degeneration. The aim of this work is to find a strategy, based on diet modulation, to prevent etoposide-induced damage, in a model of in vitro skeletal muscle cells.

METHODS

Glutamine supplementation and nutrient deprivation have been chosen as pre-treatments to counteract etoposide effect, a chemotherapeutic drug known to induce oxidative stress and cell death. Cell response has been evaluated by means of morpho-functional, cytofluorimetric and molecular analyses.

RESULTS

Etoposide treated cells, if compared to control, showed dysfunctional mitochondria presence, ER stress and lysosomal compartment damage, confirmed by molecular investigations.

CONCLUSIONS

Interestingly, both dietary approaches were able to rescue myofiber from etoposide-induced damage. Glutamine supplementation, in particular, seemed to be a good strategy to preserve cell ultrastructure and functionality, by preventing the autophagic impairment and partially restoring the normal lysosomal activity, thus maintaining skeletal muscle homeostasis.

Autophagy pathways in drug abusers after forensic autopsy: LC3B, ph-mTOR and p70S6K analysis

INTRODUCTION

Autophagy plays a role in various central nervous system diseases. Little is known about its molecular activation in drug addiction. Our aim was to investigate the signalling pathways of autophagy in brain tissues from drug abusers.

METHODS

Twenty-five drug abusers with acute lethal intoxication and 10 controls were medico-legally autopsied. Brain-tissue samples from the parietal cortex and cerebellum were obtained. Expression of LC3B, phospho-mTOR (ph-mTOR) and phospho70S6 Kinase (p70S6K) was identified in tissue microarrays, with three tissue spots per case. Blood, urine or vitreous humour were tested in all cases to identify the acute intoxication. Hair analysis was performed in 14 cases to confirm chronic intoxication; the remaining cases had a documented medical history of chronic abuse.

RESULTS

The autophagy marker LC3B was always positive on both the cortex and the cerebellum, stratified as strongly in 18 (72%) cases and weakly positive in seven (28%) cases. ph-mTOR was negative in all cases. The p70S6K molecule showed positivity in 14 (56%) cases on cortex tissue. The cerebellum was always negative, except for Purkinje cells. Drug abusers had statistically more double positive cases (LC3B-p70S6K) than controls ( p=0.0094).

CONCLUSION

Autophagy pathways were activated in our series, and 56% of drug abusers showed simultaneous LC3B-p70S6K immunoexpression on tissue from the parietal cortex and cerebellum. This may be of value in autopsy practice as an indicator of brain damage due to drug abuse and could serve as alternative or additional double sensitive diagnostic method to detect drug-related deaths using a tissue-based rationale.

HIF-1α/Beclin1-Mediated Autophagy Is Involved in Neuroprotection Induced by Hypoxic Preconditioning

Hypoxic preconditioning (HPC) exerts a protective effect against hypoxic/ischemic brain injury, and one mechanism explaining this effect may involve the upregulation of hypoxia-inducible factor-1 (HIF-1). Autophagy, an endogenous protective mechanism against hypoxic/ischemic injury, is correlated with the activation of the HIF-1α/Beclin1 signaling pathway. Based on previous studies, we hypothesize that the protective role of HPC may involve autophagy occurring via activation of the HIF-1α/Beclin1 signaling pathway. To test this hypothesis, we evaluated the effects of HPC on oxygen-glucose deprivation/reperfusion (OGD/R)-induced apoptosis and autophagy in SH-SY5Y cells. HPC significantly attenuated OGD/R-induced apoptosis, and this effect was suppressed by the autophagy inhibitor 3-methyladenine and mimicked by the autophagy agonist rapamycin. In control SH-SY5Y cells, HPC upregulated the expression of HIF-1α and downstream molecules such as BNIP3 and Beclin1. Additionally, HPC increased the LC3-II/LC3-I ratio and decreased p62 levels. The increase in the LC3-II/LC3-I ratio was inhibited by the HIF-1α inhibitor YC-1 or by Beclin1-short hairpin RNA (shRNA). In OGD/R-treated SH-SY5Y cells, HPC also upregulated the expression levels of HIF-1α, BNIP3, and Beclin1, as well as the LC3-II/LC3-I ratio. Furthermore, YC-1 or Beclin1-shRNA attenuated the HPC-mediated cell viability in OGD/R-treated cells. Taken together, our results demonstrate that HPC protects SH-SY5Y cells against OGD/R via HIF-1α/Beclin1-regulated autophagy.

Oxygen concentration modulates cellular senescence and autophagy in human trophoblast cells

PROBLEM

We investigated the effect of oxygen concentrations on cellular senescence and autophagy and examined the role of autophagy in human trophoblast cells.

METHOD OF STUDY

Human first-trimester trophoblast cells (Sw.71) were incubated under 21%, 5%, or 1% O₂ concentrations for 24 hours. We examined the extent of senescence caused using senescence-associated β-galactosidase (SA-β-Gal) and senescence-associated secretory phenotype (SASP) as markers. Moreover, we examined the role of autophagy in causing cellular senescence using an autophagy inhibitor (3-methyladenine, 3MA).

RESULTS

Physiological normoxia (5% O₂ ) decreased SA-β-Gal-positive cells and SASP including interleukin-6 (IL-6) and IL-8 compared with cultured cells in 21% O₂ . Pathophysiological hypoxia (1% O₂ ) caused cytotoxicity, including extracellular release of ATP and lactate dehydrogenase, and decreased senescence phenotypes. 3MA-treated trophoblast cells significantly suppressed senescence markers (SA-β-Gal-positive cells and SASP secretion) in O₂ -independent manner.

CONCLUSION

We conclude that O₂ concentration modulates cellular senescence phenotypes regulating autophagy in the human trophoblast cells. Moreover, inhibiting autophagy suppresses cellular senescence, suggesting that autophagy contributes to oxygen stress-induced cellular senescence.